JP7645219B2 - Polarizing plate and image display device - Google Patents

Description

The present invention relates to a polarizing plate and an image display device.

Conventionally, image display devices have adopted a method of placing a circular polarizer on the viewing side of the image display panel to suppress the decrease in visibility due to reflection of external light.

A circular polarizer is a laminate of a linear polarizer and a retardation plate. In a circular polarizer, external light heading toward the image display panel is converted into linearly polarized light by the linear polarizer, and then converted into circularly polarized light by the subsequent retardation plate. Although the circularly polarized external light is reflected by the surface of the image display panel, the direction of rotation of the polarization plane is reversed during this reflection, and the light is converted into linearly polarized light by the retardation plate, and then blocked by the subsequent linear polarizer. As a result, the emission of external light to the outside is significantly suppressed.

A retardation plate having a retardation layer containing a cured liquid crystal compound is known (for example, Patent Documents 1 and 2). With such a configuration, it is possible to make the retardation plate thinner.

JP 2015-163935 A JP 2019-91030 A

In retardation plates having multiple retardation layers containing a cured liquid crystal compound, prioritizing thinning can cause problems such as damage to the retardation layers, especially those close to the substrate being peeled off, due to the peeling force applied when peeling off the substrate.

The present invention aims to provide a polarizing plate having a retardation plate with multiple retardation layers containing a cured product of a liquid crystal compound, and which has excellent durability against the peeling force applied when peeling off the substrate.

The present invention provides the following polarizing plate.
[1] A polarizing plate including a linear polarizing plate, a first bonding layer, and a retardation plate laminated in this order,
The retardation plate is
A first retardation layer and a second retardation layer are included,
The first retardation layer and the second retardation layer include a cured product of a liquid crystal compound,
The puncture elastic modulus is 70 g/mm or more,
The first attachment layer has a tensile modulus of elasticity of 1.0×10 ⁸ Pa or less at a temperature of 23° C. and a relative humidity of 55%.
[2] The polarizing plate according to [1], in which the product of the thickness (m) and the tensile modulus (Pa) of the first bonding layer is 500 or less. [3] The retardation plate according to [1] or [2], in which the retardation plate has only an alignment film between the first retardation layer and the second retardation layer, or has no other intervening layer.
[4] The linear polarizing plate has a polarizer,
The polarizing plate according to any one of items [1] to [3], wherein the polarizer has a thickness of 15 μm or less.
[5] The linear polarizing plate has a protective film provided on a surface of the polarizer opposite to the first attachment layer,
The polarizing plate according to [4], wherein the protective film has a thickness of 30 μm or less.
[6] The polarizing plate according to any one of [1] to [5], wherein the first retardation layer is a λ/4 layer having reverse dispersion.
[7] The polarizing plate according to any one of [1] to [6], wherein the second retardation layer is a positive C plate.

The present invention provides a polarizing plate that has excellent durability against the peeling force applied when peeling off the substrate.

FIG. 1 is a schematic cross-sectional view illustrating an example of a polarizing plate according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing a specific example of a retardation plate. FIG. 2 is a schematic cross-sectional view showing a specific example of a retardation plate. 1 is a schematic cross-sectional view showing an example of an image display device according to an embodiment of the present invention.

Below, an embodiment of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiment. In all of the drawings below, the scale of each component has been appropriately adjusted to make it easier to understand, and the scale of each component shown in the drawings does not necessarily match the scale of the actual component.

[Polarizing plate]
Fig. 1 is a schematic cross-sectional view showing an example of the polarizing plate of the present embodiment. As shown in Fig. 1, the polarizing plate 1 includes a linear polarizing plate 10, a first bonding layer 21, and a retardation plate 30 laminated in this order from the front side. The retardation plate 30 has a first retardation layer 31 and a second retardation layer 32. The polarizing plate 1 may be a circular polarizing plate. In this specification, the term polarizing plate also includes a circular polarizing plate.

The retardation film 30 has a piercing elastic modulus of 70 g/mm or more. The piercing elastic modulus is a value measured by a method according to the method described in the examples. The piercing elastic modulus of the retardation film 30 is preferably 140 g/mm or less, more preferably 120 g/mm or less, and may be 110 g/mm or less. The retardation film 30 may or may not include a substrate that is intended to be peeled off from the polarizing plate, and the piercing elastic modulus of the retardation film 30 referred to in this specification means the piercing elastic modulus of the layer structure of the portion of the retardation film 30 that does not include the substrate that is intended to be peeled off from the polarizing plate. In the retardation film 30, there may or may not be another layer interposed between the first retardation layer 31 and the second retardation layer 32.

In the retardation plate 30, when the first phase difference layer 31 and the second phase difference layer 32 are bonded together via a bonding layer (hereinafter referred to as the "third bonding layer"), the puncture modulus depends on the hardness of the third bonding layer, but when the third bonding layer is a layer made of an adhesive, the puncture modulus tends to be low and may be less than 70 g/mm. On the other hand, when the third bonding layer is a layer made of an adhesive, the puncture modulus tends to be high and may be 70 g/mm or more. In the retardation plate 30, when the first phase difference layer 31 and the second phase difference layer 32 are laminated without a bonding layer interposed therebetween, the puncture modulus of the retardation plate 30 tends to be high and is usually 70 g/mm or more. In the retardation plate 30, examples of a configuration in which the first retardation layer 31 and the second retardation layer 32 are laminated without a bonding layer include a configuration in which only an alignment film is present between the first retardation layer 31 and the second retardation layer 32, or a configuration in which no other layers are present.

The present inventors have found that a polarizing plate using a retardation plate with a high piercing elasticity has low durability against the peeling force applied when the substrate is peeled off. On the other hand, if the piercing elasticity of the retardation plate is reduced, the peeling force of the substrate becomes lighter and the substrate is likely to float. The present inventors have further conducted intensive research and have found that even if a polarizing plate using a retardation plate with a piercing elasticity of 70 g/mm or more is used, the first bonding layer 21 interposed between the linear polarizing plate 10 and the retardation plate 30 can be made of a pressure-sensitive adhesive having a tensile elasticity of 1.0×10 ⁸ Pa or less at a temperature of 23° C. and a relative humidity of 55%, thereby making it possible to obtain a polarizing plate with excellent durability against the peeling force applied when the substrate is peeled off, and have arrived at the present invention. In addition, by having such a configuration, the present invention can suppress the occurrence of cracks caused by heat shock or polishing. The tensile modulus of the adhesive forming the first bonding layer 21 at a temperature of 23° C. and a relative humidity of 55% is preferably 1.0×10 ⁷ Pa or less, more preferably 1.0×10 ⁶ Pa or less, preferably 1.0×10 ³ Pa or more, and more preferably 1.0×10 ⁵ Pa or more. The product of the thickness (m) and the tensile modulus (Pa) of the adhesive forming the first bonding layer 21 is preferably 500 or less, more preferably 50 or less, and even more preferably 5 or less. The product of the thickness (m) and the tensile modulus (Pa) of the adhesive forming the first bonding layer 21 is preferably 0.005 or more, and more preferably 0.5 or more. By setting it to this numerical range, the durability against peeling force can be improved.

The polarizing plate according to the present invention has high durability against the peeling force applied when the substrate is peeled off, and more specifically, it is possible to suppress damage to the retardation layer of the retardation plate when the substrate is peeled off from a polarizing plate having a retardation plate with a substrate. When the retardation layer of the retardation plate is a layer containing a cured product of a liquid crystal compound, it is thin and easily damaged when the substrate is peeled off, and the retardation layer closer to the substrate is particularly prone to damage, but the polarizing plate according to the present invention can suppress such damage. The substrate can be the substrate used in the manufacturing process of the retardation plate.

The tensile modulus of the adhesive forming the first lamination layer 21 at a temperature of 23°C and a relative humidity of 55% can be measured by the following procedure. The adhesive composition is applied to the release-treated surface of a release-treated polyethylene terephthalate film (hereinafter sometimes referred to as "PET film") using an applicator. The film is then pre-dried for 30 minutes at room temperature, and then dried for 5 minutes at a temperature of 100°C, to thoroughly volatilize the solvent contained in the adhesive composition applied to the PET film. Finally, a predetermined curing process (heating process, ultraviolet irradiation process, etc.) is performed to prepare an adhesive layer on the PET film, and the PET film is peeled off to obtain an adhesive layer, which is used as a measurement sample, and the tensile modulus can be measured by the method described in the Examples below.

[First bonding layer]
The first bonding layer 21 is a layer that bonds the linear polarizer 10 and the retarder 30. Examples of the adhesive having a tensile modulus of elasticity of 1.0×10 ⁸ Pa or less at a temperature of 23° C. and a relative humidity of 55% include a pressure-sensitive adhesive and an adhesive. A pressure-sensitive adhesive is preferably used as the first bonding layer 21.

Specific examples of adhesives used in the first bonding layer 21 include those that use acrylic polymers, silicone polymers, polyesters, polyurethanes, polyethers, or the like as base polymers. Among them, it is preferable to select and use an adhesive that has excellent optical transparency, moderate wettability and cohesive strength, excellent adhesion to the substrate, weather resistance, heat resistance, and the like, and does not cause peeling problems such as lifting or peeling under heating or humidifying conditions, such as acrylic polymers. In the case of acrylic polymers, an acrylic copolymer having a weight average molecular weight of 100,000 or more, which is prepared by blending an alkyl ester of acrylic acid having an alkyl group with 20 or less carbon atoms, such as a methyl group, an ethyl group, or a butyl group, with a functional group-containing acrylic monomer such as (meth)acrylic acid or hydroxyethyl (meth)acrylate, so that the glass transition temperature is preferably 25°C or less, more preferably 0°C or less, is useful as the base polymer.

The acrylic polymer is not particularly limited, but (meth)acrylic acid ester-based base polymers such as butyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate, and copolymer-based base polymers using two or more of these (meth)acrylic acid esters are preferably used. In addition, polar monomers may be copolymerized in these base polymers. Examples of polar monomers include monomers having polar functional groups such as carboxyl groups, hydroxyl groups, amide groups, amino groups, and epoxy groups, such as (meth)acrylic acid, 2-hydroxypropyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, (meth)acrylamide, 2-N,N-dimethylaminoethyl (meth)acrylate, and glycidyl (meth)acrylate.

Although these acrylic polymers can be used alone as adhesives, crosslinking agents are usually blended into adhesives. Examples of crosslinking agents include divalent or polyvalent metal ions that form metal carboxylates with carboxyl groups, polyamine compounds that form amide bonds with carboxyl groups, polyepoxy compounds or polyol compounds that form ester bonds with carboxyl groups, and polyisocyanate compounds that form amide bonds with carboxyl groups. Of these, polyisocyanate compounds are widely used as organic crosslinking agents.

In this embodiment, the means for adjusting the tensile modulus of the adhesive forming the first bonding layer is not particularly limited, but a suitable example is a method of blending an oligomer, specifically a urethane acrylate oligomer, with the above-mentioned adhesive components. Furthermore, an adhesive blended with such a urethane acrylate oligomer may be irradiated with energy rays and cured. Adhesives blended with urethane acrylate oligomers, or adhesives with separators that are coated on a support film (separator) and cured with ultraviolet light, are well known and can be obtained from adhesive manufacturers.

In addition to the above-mentioned base polymer, crosslinking agent, and oligomer, the adhesive may contain appropriate additives such as natural or synthetic resins, tackifying resins, antioxidants, UV absorbers, dyes, pigments, defoamers, corrosion inhibitors, and photopolymerization initiators to adjust the adhesive strength, cohesive strength, viscosity, elastic modulus, glass transition temperature, etc., of the adhesive as needed. UV absorbers include salicylic acid ester compounds, benzophenone compounds, benzotriazole compounds, cyanoacrylate compounds, and nickel complex salt compounds.

The thickness of the first adhesive layer 21 is determined according to its adhesive strength, but is usually in the range of 1 to 40 μm. It is preferable to set the thickness of the adhesive layer to 3 to 25 μm or 20 μm or less, as this maintains good processability and shows high durability. Furthermore, by having a thickness in the above range, durability against peeling force can be further improved.

Specific examples of adhesives used in the first bonding layer 21 include adhesives other than pressure-sensitive adhesives (adhesives), such as water-based adhesives and active energy ray-curable adhesives.

An example of a water-based adhesive is an adhesive in which a polyvinyl alcohol resin is dissolved or dispersed in water. There are no particular limitations on the drying method when using a water-based adhesive, but for example, a drying method using a hot air dryer or an infrared dryer can be used.

Examples of active energy ray-curable adhesives include solvent-free active energy ray-curable adhesives that contain a curable compound that cures when exposed to active energy rays such as ultraviolet light, visible light, electron beams, and X-rays. By using a solvent-free active energy ray-curable adhesive, it is possible to improve the adhesion between layers.

The active energy ray curable adhesive preferably contains either one or both of a cationic polymerizable curable compound and a radically polymerizable curable compound, since these exhibit good adhesive properties. The active energy ray curable adhesive may further contain a cationic polymerization initiator, such as a photocationic polymerization initiator, for initiating the curing reaction of the curable compound, or a radical polymerization initiator.

Examples of cationic polymerizable curable compounds include epoxy-based compounds such as alicyclic epoxy compounds having an epoxy group bonded to an alicyclic ring, polyfunctional aliphatic epoxy compounds having two or more epoxy groups and no aromatic ring, monofunctional epoxy compounds having one epoxy group (excluding those included in alicyclic epoxy compounds), polyfunctional aromatic epoxy compounds having two or more epoxy groups and an aromatic ring; oxetane compounds having one or more oxetane rings in the molecule; and combinations of these.

Examples of radically polymerizable curable compounds include (meth)acrylic compounds (compounds having one or more (meth)acryloyloxy groups in the molecule), other vinyl compounds having radically polymerizable double bonds, or combinations of these.

The active energy ray curable adhesive may contain a sensitizer such as a photosensitizer assistant, if necessary. The use of a sensitizer improves reactivity, and the mechanical strength and adhesive strength of the adhesive layer can be further improved. Any known sensitizer can be used as appropriate. When a sensitizer is added, the amount of the sensitizer added is preferably in the range of 0.1 to 20 parts by mass per 100 parts by mass of the total amount of the active energy ray curable adhesive.

The active energy ray curable adhesive may contain additives such as ion trapping agents, antioxidants, chain transfer agents, tackifiers, thermoplastic resins, fillers, flow control agents, plasticizers, defoamers, antistatic agents, leveling agents, and solvents, as necessary.

When an active energy ray curing adhesive is used, the adhesive layer can be formed by irradiating the adhesive coating layer with active energy rays such as ultraviolet rays, visible light, electron beams, or X-rays to cure the adhesive layer. As the active energy ray, ultraviolet rays are preferred, and in this case, the light source can be a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultra-high pressure mercury lamp, a chemical lamp, a black light lamp, a microwave excited mercury lamp, a metal halide lamp, etc.

When an adhesive is used as the first bonding layer 21, its thickness is determined according to its adhesive strength, but is usually in the range of 0.02 to 10 μm. From the viewpoint of further improving durability against external forces, it is preferable to make the thickness of the adhesive layer 1 to 4 μm.

[Linear polarizing plate]
The linear polarizing plate 10 may be any film having a polarizing function that obtains linearly polarized light from transmitted light. Examples of the film include a stretched film adsorbed with a dye having absorption anisotropy, or a film including a film coated with a dye having absorption anisotropy as a polarizer. Examples of the dye having absorption anisotropy include a dichroic dye. Examples of the film coated with a dye having absorption anisotropy that is used as a polarizer include a stretched film adsorbed with a dye having absorption anisotropy, or a film having a liquid phase layer obtained by applying a composition containing a dichroic dye having liquid crystal properties or a composition containing a dichroic dye and a polymerizable liquid crystal.

<Linear polarizing plate having a stretched film as a polarizer>
A linear polarizing plate having a stretched film adsorbed with a dye having absorption anisotropy as a polarizer will be described. The stretched film adsorbed with a dye having absorption anisotropy, which is a polarizer, is usually manufactured through a process of uniaxially stretching a polyvinyl alcohol-based resin film, a process of dyeing the polyvinyl alcohol-based resin film with a dichroic dye to adsorb the dichroic dye, a process of treating the polyvinyl alcohol-based resin film adsorbed with the dichroic dye with a boric acid aqueous solution, and a process of washing with water after the treatment with the boric acid aqueous solution. Such a polarizer may be used as it is as a linear polarizing plate, or a polarizer having a transparent protective film attached to at least one surface thereof may be used as a linear polarizing plate.

The thickness of the polarizer obtained by uniaxially stretching the polyvinyl alcohol resin film, dyeing it with a dichroic dye, treating it with boric acid, washing it with water, and drying it is preferably 5 to 40 μm, more preferably 15 μm or less, and even more preferably 10 μm or less.

The material of the protective film to be attached to one or both sides of the polarizer is not particularly limited, but examples thereof include films known in the art, such as cyclic polyolefin resin films, cellulose acetate resin films made of resins such as triacetyl cellulose and diacetyl cellulose, polyester resin films made of resins such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate, polycarbonate resin films, (meth)acrylic resin films, and polypropylene resin films. From the viewpoint of thinning, the thickness of the protective film is usually 300 μm or less, preferably 200 μm or less, more preferably 30 μm or less, and usually 5 μm or more, and may be 10 μm or more. If the thickness of the protective film is 30 μm or less, or the tensile modulus at a temperature of 23° C. is 2000 MPa or more, the protective film does not easily function as a relaxation layer for the force applied when the substrate is peeled off, so that the durability against substrate peeling is reduced, and problems such as damage to the retardation layer close to the substrate to be peeled off are likely to occur. Additionally, the protective film on the viewing side may or may not have a phase difference.

The protective film can be attached to one or both sides of the polarizer via an attachment layer (hereinafter referred to as the "second attachment layer").

<Linear polarizing plate equipped with a film having a liquid crystal layer as a polarizer>
A linear polarizing plate having a film having a liquid crystal layer as a polarizer will be described. Examples of the film coated with a dye having absorption anisotropy used as a polarizer include a composition containing a dichroic dye having liquid crystal properties, or a film obtained by coating a composition containing a dichroic dye and a liquid crystal compound. The film may be used alone as a linear polarizing plate, or may be used as a linear polarizing plate with a protective film on one or both sides. Examples of the protective film include the same film as the linear polarizing plate having the above-mentioned stretched film as a polarizer. The protective film can be attached to one or both sides of the polarizer via a second attachment layer.

The film coated with the dye having absorption anisotropy is preferably thin, but if it is too thin, the strength decreases and the processability tends to be poor. The thickness of the film is usually 20 μm or less, preferably 15 μm or less, more preferably 5 μm or less, and even more preferably 0.5 μm or more and 3 μm or less.

Specific examples of films coated with a dye having the above-mentioned absorption anisotropy include the films described in JP 2013-33249 A and the like.

One embodiment of the linear polarizing plate is one in which a protective film is provided on the surface of the linear polarizing plate opposite the first bonding layer.

<Frontmost layer>
The linear polarizing plate 10 may have an antireflection layer on the front surface. The antireflection layer has a function of preventing reflected light of external light from being visible on the surface or inside of the linear polarizing plate 10, and can be formed by a conventional method for forming an antireflection layer or the like, i.e., a coating method, a sputtering method, a vacuum deposition method, or the like. The antireflection layer may be formed in advance on the front side of a protective film provided on the front side of the linear polarizing plate 10, and the linear polarizing plate with an antireflection layer may be constituted using such a protective film, or may be provided separately from the protective film.

The linear polarizing plate 10 may have a surface treatment layer other than the anti-reflection layer on the front surface. Examples of such surface treatment layers include a hard coat layer, an anti-sticking layer, an anti-glare layer, a diffusion layer, etc.

[Retardation Plate]
The retardation plate 30 has a first retardation layer 31 and a second retardation layer 32, and the first retardation layer 31 and the second retardation layer 32 contain a cured product of a liquid crystal compound, and are not limited as long as they have a puncture elastic modulus of 70 g/mm or more. The retardation plate 30 may have a third retardation layer. The first retardation layer, the second retardation layer, and the third retardation layer may each be composed of two or more layers. The retardation plate 30 may have a substrate on the surface opposite to the linear polarizer 10 side. The substrate may be a substrate for forming a retardation layer, and may be peelable from the retardation layer.

The retardation plate 30 preferably has optical characteristics represented by formulas (1) and (2). In order for the retardation plate 30 to have such optical characteristics, the first retardation layer 31, the second retardation layer 32, or the third retardation layer may have the optical characteristics represented by formulas (1) and (2), or at least two selected from the first retardation layer 31, the second retardation layer 32, and the third retardation layer may be combined to exhibit the optical characteristics represented by formulas (1) and (2).
Re(450)/Re(550)≦1.00 (1)
1.00≦Re(650)/Re(550) (2)

In this specification, Re(450) represents the in-plane retardation value at a wavelength of 450 nm, Re(550) represents the in-plane retardation value at a wavelength of 550 nm, and Re(650) represents the in-plane retardation value at a wavelength of 650 nm.

<Retardation Layer>
Examples of the retardation layer include a layer formed by polymerizing a polymerizable liquid crystal and a stretched film. The optical properties of the retardation layer can be adjusted by the orientation state of the polymerizable liquid crystal or the stretching method of the stretched film. The layer formed by polymerizing the polymerizable liquid crystal contains a cured product of a liquid crystal compound. In the retardation plate 30, from the viewpoint of thinning, at least the first retardation layer 31 and the second retardation layer 32 are layers containing a cured product of a liquid crystal compound.

(Layer formed by polymerizing polymerizable liquid crystal)
In this specification, the optical axis of the polymerizable liquid crystal is defined as being aligned horizontally to the substrate plane as horizontal alignment, and the optical axis of the polymerizable liquid crystal is defined as being aligned perpendicularly to the substrate plane as vertical alignment. The optical axis refers to the direction in which a cross section cut in a direction perpendicular to the optical axis of an index ellipsoid formed by the orientation of the polymerizable liquid crystal is a circle, that is, the direction in which the refractive indexes in the three directions are all equal.

Polymerizable liquid crystals include rod-shaped polymerizable liquid crystals and disk-shaped polymerizable liquid crystals. When rod-shaped polymerizable liquid crystals are aligned horizontally or vertically to the substrate, the optical axis of the polymerizable liquid crystal coincides with the long axis direction of the polymerizable liquid crystal. When disk-shaped polymerizable liquid crystals are aligned, the optical axis of the polymerizable liquid crystal exists in a direction perpendicular to the disk surface of the polymerizable liquid crystal.

The direction of the slow axis of a stretched film varies depending on the stretching method, and the slow axis and optical axis are determined according to the stretching method, such as uniaxial, biaxial, or oblique stretching.

In order for the layer formed by polymerizing the polymerizable liquid crystal to exhibit in-plane retardation, the polymerizable liquid crystal may be aligned in an appropriate direction. When the polymerizable liquid crystal is rod-shaped, the optical axis of the polymerizable liquid crystal is aligned horizontally to the substrate plane to exhibit in-plane retardation. In this case, the optical axis direction and the slow axis direction are the same. When the polymerizable liquid crystal is disc-shaped, the optical axis of the polymerizable liquid crystal is aligned horizontally to the substrate plane to exhibit in-plane retardation. In this case, the optical axis and the slow axis are perpendicular to each other. The alignment state of the polymerizable liquid crystal can be adjusted by combining an alignment film with the polymerizable liquid crystal.

The in-plane retardation value of the retardation layer can be adjusted by the thickness of the retardation layer. Since the in-plane retardation value is determined by the formula (10), in order to obtain a desired in-plane retardation value (Re(λ)), Δn(λ) and the film thickness d may be adjusted.
Re(λ)=d×Δn(λ) (10)
In the formula, Re(λ) represents the in-plane retardation value at a wavelength of λ nm, d represents the film thickness, and Δn(λ) represents the birefringence at a wavelength of λ nm.

The birefringence Δn (λ) is obtained by measuring the in-plane retardation value and dividing it by the thickness of the retardation layer. In a specific measurement method, the actual characteristics of the retardation layer can be measured by measuring a film formed on a substrate that does not have an in-plane retardation in the substrate itself, such as a glass substrate.

In this specification, the refractive indices in three directions in the index ellipsoid formed by the orientation of the polymerizable liquid crystal or the stretching of the film are represented as nx, ny, and nz. nx represents the principal refractive index in the direction parallel to the film plane in the index ellipsoid formed by the retardation layer. ny represents the refractive index in the direction parallel to the film plane and perpendicular to the direction of nx in the index ellipsoid formed by the retardation layer. nz represents the refractive index in the direction perpendicular to the film plane in the index ellipsoid formed by the retardation layer.

When the optical axis of the rod-shaped polymerizable liquid crystal is aligned horizontally to the substrate plane, the refractive index relationship of the resulting retardation layer is nx>ny≒nz (positive A plate), and the axis of the nx direction in the refractive index ellipsoid coincides with the slow axis.

In addition, when the optical axis of the disc-shaped polymerizable liquid crystal is oriented horizontally to the substrate plane, the refractive index relationship of the resulting retardation layer is nx < ny ≒ nz (negative A plate), and the axis in the ny direction of the refractive index ellipsoid coincides with the slow axis.

In order for the layer formed by polymerizing the polymerizable liquid crystal to exhibit retardation in the thickness direction, the polymerizable liquid crystal may be oriented in an appropriate direction. In the present invention, the expression of retardation in the thickness direction is defined as a characteristic in which Rth (retardation value in the thickness direction) is negative in formula (20). Rth can be calculated from the retardation value (R ₄₀ ) measured by inclining the in-plane fast axis at 40 degrees as the tilt axis, and the in-plane retardation value (Re). That is, Rth can be calculated by determining nx, ny, and nz from Re, R ₄₀ , d (thickness of retardation layer), and n0 (average refractive index of retardation layer) according to the following formulas (21) to (23), and substituting them into formula (20).
Rth=[(nx+ny)/2-nz]×d (20)
Re = (nx-ny)×d (21)
R ₄₀ = (nx-ny') x d/cos(φ) (22)
(nx+ny+nz)/3=n0 (23)
Where:
φ=sin ^-1 [sin (40°)/n0]
ny'=ny×nz/[ny ² ×sin ² (φ)+nz ² ×cos ² (φ)] ^1/2
Additionally, nx, ny and nz are defined as above.

When the polymerizable liquid crystal is rod-shaped, the optical axis of the polymerizable liquid crystal is oriented perpendicular to the substrate plane to produce a phase difference in the thickness direction. When the polymerizable liquid crystal is disc-shaped, the optical axis of the polymerizable liquid crystal is oriented horizontally to the substrate plane to produce a phase difference in the thickness direction. In the case of disc-shaped polymerizable liquid crystal, the optical axis of the polymerizable liquid crystal is parallel to the substrate plane, so when Re is determined, the thickness is fixed and Rth is uniquely determined, but in the case of rod-shaped polymerizable liquid crystal, the optical axis of the polymerizable liquid crystal is perpendicular to the substrate plane, so Rth can be adjusted by adjusting the thickness of the retardation layer without changing Re.

When the optical axis of the rod-shaped polymerizable liquid crystal is oriented perpendicular to the substrate plane, the refractive index relationship of the resulting retardation layer is nx ≒ ny < nz (positive C plate), and the axis of the nz direction in the refractive index ellipsoid coincides with the slow axis direction.

In addition, when the optical axis of the disc-shaped polymerizable liquid crystal is oriented parallel to the substrate plane, the refractive index relationship of the resulting retardation layer is nx < ny ≒ nz (negative A plate), and the axis of the ny direction in the refractive index ellipsoid coincides with the slow axis direction.

<Polymerizable Liquid Crystal>
The polymerizable liquid crystal is a compound having a polymerizable group and liquid crystallinity. The polymerizable group means a group involved in a polymerization reaction, and is preferably a photopolymerizable group. Here, the photopolymerizable group means a group that can be involved in a polymerization reaction by an active radical or an acid generated from a photopolymerization initiator described later. Examples of the polymerizable group include a vinyl group, a vinyloxy group, a 1-chlorovinyl group, an isopropenyl group, a 4-vinylphenyl group, an acryloyloxy group, a methacryloyloxy group, an oxiranyl group, and an oxetanyl group. Among them, an acryloyloxy group, a methacryloyloxy group, a vinyloxy group, an oxiranyl group, and an oxetanyl group are preferable, and an acryloyloxy group is more preferable. The liquid crystallinity of the polymerizable liquid crystal may be a thermotropic liquid crystal or a lyotropic liquid crystal, and when the thermotropic liquid crystal is classified according to the degree of order, it may be a nematic liquid crystal or a smectic liquid crystal.

Examples of rod-shaped polymerizable liquid crystals include compounds represented by the following formula (A) and compounds containing a group represented by the following formula (X). As rod-shaped polymerizable liquid crystals, liquid crystals having a T-shaped or H-shaped mesogen structure that is oriented perpendicular to the molecular axis direction and has birefringence are preferred from the viewpoint of wavelength dispersion expression, and T-shaped liquid crystals are more preferred from the viewpoint of obtaining stronger dispersion. Specific examples of the structure of T-shaped liquid crystals include compounds represented by the following formula (A).

(Compound represented by formula (A))
Formula (A) is as follows: Hereinafter, the compound represented by formula (A) may be referred to as polymerizable liquid crystal (A).

In formula (A), Ar represents a divalent aromatic group which may have a substituent. The divalent aromatic group preferably contains at least one of a nitrogen atom, an oxygen atom, and a sulfur atom. When the divalent group Ar contains two or more aromatic groups, the two or more aromatic groups may be bonded to each other via a divalent bonding group such as a single bond, -CO-O-, or -O-.
G ¹ and G ² each independently represent a divalent aromatic group or a divalent alicyclic hydrocarbon group, wherein a hydrogen atom contained in the divalent aromatic group or the divalent alicyclic hydrocarbon group may be substituted with a halogen atom, an alkyl group having 1 to 4 carbon atoms, a fluoroalkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a cyano group, or a nitro group, and a carbon atom constituting the divalent aromatic group or the divalent alicyclic hydrocarbon group may be substituted with an oxygen atom, a sulfur atom, or a nitrogen atom.
L ¹ , L ² _, B ¹ and B ² each independently represent a single bond or a divalent linking group.
k and l each independently represent an integer of 0 to 3, and satisfy the relationship of 1≦k+l, where, when 2≦k+l, B ¹ and B ² , and G ¹ and G ² may be the same or different from each other.
^E1 and ^E2 each independently represent an alkanediyl group having 1 to 17 carbon atoms, in which a hydrogen atom contained in the alkanediyl group may be substituted with a halogen atom, and _-CH2- contained in the alkanediyl group may be substituted with -O-, -S- or -COO-, and when there are a plurality of -O-, -S- or -COO-, they are not adjacent to each other. ^P1 and ^P2 each independently represent a polymerizable group or a hydrogen atom, and at least one of them is a polymerizable group.

G ¹ and G ² are each independently preferably a 1,4-phenylenediyl group which may be substituted with at least one substituent selected from the group consisting of a halogen atom and an alkyl group having 1 to 4 carbon atoms, or a 1,4-cyclohexanediyl group which may be substituted with at least one substituent selected from the group consisting of a halogen atom and an alkyl group having 1 to 4 carbon atoms, more preferably a 1,4-phenylenediyl group substituted with a methyl group, an unsubstituted 1,4-phenylenediyl group, or an unsubstituted 1,4-trans-cyclohexanediyl group, and particularly preferably an unsubstituted 1,4-phenylenediyl group, or an unsubstituted 1,4-trans-cyclohexanediyl group.
At least one of a plurality of ^G1 and ^G2 is preferably a divalent alicyclic hydrocarbon group, and it is more preferable that at least one of ^G1 and ^G2 bonded to ^L1 or ^L2 is a divalent alicyclic hydrocarbon group.

^L1 and ^L2 are each independently preferably a single bond, an alkylene group having 1 to 4 carbon atoms, -O-, -S-, -R ^a1 OR ^a2 -, -R ^a3 COOR ^a4 -, -R ^a5 OCOR ^a6 -, R ^a7 OC=OOR ^a8 -, -N=N-, -CR ^c =CR ^d -, or C≡C-, where R ^a1 to R ^a8 are each independently a single bond or an alkylene group having 1 to 4 carbon atoms, and R ^c and R ^d are an alkyl group having 1 to 4 carbon atoms or a hydrogen atom. L ¹ and L ² are each independently more preferably a single bond, -OR ^a2-1 -, -CH ₂ -, -CH ₂ CH ₂ -, -COOR ^a4-1 -, or OCOR ^a6-1 -. Here, R ^a2-1 , R ^a4-1 , and R ^a6-1 each independently represent a single bond, -CH ₂ -, or -CH ₂ CH ₂ -. ^{L 1} and L ² are each independently more preferably a single bond, -O-, -CH ₂ CH ₂ -, -COO-, -COOCH ₂ CH ₂ -, or OCO-.

B ¹ and B ² are each independently preferably a single bond, an alkylene group having 1 to 4 carbon atoms, -O-, -S-, -R ^a9 OR ^a10 -, -R ^a11 COOR ^a12 -, -R ^a13 OCOR ^a14 -, or R ^a15 OC═OOR ^a16 -. Here, R ^a9 to R ^a16 are each independently a single bond, or an alkylene group having 1 to 4 carbon atoms. ^{B 1} and B ² are each independently more preferably a single bond, -OR ^a10-1 -, -CH ₂ -, -CH ₂ CH ₂ -, -COOR ^a12-1 -, or OCOR ^a14-1 -. Here, R ^a10-1 , R ^a12-1 and R ^a14-1 each independently represent a single bond, -CH ₂ - or -CH ₂ CH ₂ -. ^{B 1} and B ² each independently represent more preferably a single bond, -O-, -CH ₂ CH ₂ -, -COO-, -COOCH ₂ CH ₂ -, -OCO- or OCOCH ₂ CH ₂ -.

From the viewpoint of expressing reverse wavelength dispersion, k and l are preferably in the range of 2≦k+l≦6, preferably k+l=4, and more preferably k=2 and l=2. k=2 and l=2 are preferable because they result in a symmetrical structure.

E ¹ and E ² each independently preferably represent an alkanediyl group having 1 to 17 carbon atoms, and more preferably an alkanediyl group having 4 to 12 carbon atoms.

Examples of the polymerizable group represented by ^P1 or ^P2 include an epoxy group, a vinyl group, a vinyloxy group, a 1-chlorovinyl group, an isopropenyl group, a 4-vinylphenyl group, an acryloyloxy group, a methacryloyloxy group, an oxiranyl group, and an oxetanyl group. Among these, an acryloyloxy group, a methacryloyloxy group, a vinyloxy group, an oxiranyl group, and an oxetanyl group are preferred, and an acryloyloxy group is more preferred.

It is preferable that Ar has at least one selected from an aromatic hydrocarbon ring which may have a substituent, an aromatic heterocycle which may have a substituent, and an electron-withdrawing group. Examples of the aromatic hydrocarbon ring include a benzene ring, a naphthalene ring, and an anthracene ring, and a benzene ring and a naphthalene ring are preferable. Examples of the aromatic heterocycle include a furan ring, a benzofuran ring, a pyrrole ring, an indole ring, a thiophene ring, a benzothiophene ring, a pyridine ring, a pyrazine ring, a pyrimidine ring, a triazole ring, a triazine ring, a pyrroline ring, an imidazole ring, a pyrazole ring, a thiazole ring, a benzothiazole ring, a thienothiazole ring, an oxazole ring, a benzoxazole ring, and a phenanthroline ring. Among them, it is preferable that Ar has a thiazole ring, a benzothiazole ring, or a benzofuran ring, and it is more preferable that Ar has a benzothiazole group. In addition, when Ar contains a nitrogen atom, it is preferable that the nitrogen atom has π electrons.

In formula (A), the total number Nπ of π electrons contained in the divalent aromatic group represented by _Ar is preferably 8 or more, more preferably 10 or more, even more preferably 14 or more, and particularly preferably 16 or more. Also, it is preferably 30 or less, more preferably 26 or less, and even more preferably 24 or less.

Suitable examples of aromatic groups represented by Ar include the following groups:

In formulae (Ar-1) to (Ar-23), the mark * represents a linking portion, and Z ⁰ , Z ¹ and Z ² each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms, a cyano group, a nitro group, an alkylsulfinyl group having 1 to 12 carbon atoms, an alkylsulfonyl group having 1 to 12 carbon atoms, a carboxyl group, a fluoroalkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an alkylthio group having 1 to 12 carbon atoms, an N-alkylamino group having 1 to 12 carbon atoms, an N,N-dialkylamino group having 2 to 12 carbon atoms, an N-alkylsulfamoyl group having 1 to 12 carbon atoms, or an N,N-dialkylsulfamoyl group having 2 to 12 carbon atoms.

Q ¹ , Q ² and Q ³ each independently represent -CR ^2' R ^3' -, -S-, -NH-, -NR ^2' -, -CO- or O-, and R ^2' and R ^3' each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

J ¹ and J ² each independently represent a carbon atom or a nitrogen atom.

Y ¹ , Y ² and Y ³ each independently represent an aromatic hydrocarbon group or an aromatic heterocyclic group which may be substituted.

W ¹ and W ² each independently represent a hydrogen atom, a cyano group, a methyl group, or a halogen atom; m represents an integer of 0 to 6.

Examples of the aromatic hydrocarbon group in ^Y1 , ^Y2 , and ^Y3 include aromatic hydrocarbon groups having 6 to 20 carbon atoms, such as a phenyl group, a naphthyl group, an anthryl group, a phenanthryl group, and a biphenyl group, with a phenyl group and a naphthyl group being preferred, and a phenyl group being more preferred. Examples of the aromatic heterocyclic group include aromatic heterocyclic groups having 4 to 20 carbon atoms and containing at least one heteroatom, such as a nitrogen atom, an oxygen atom, or a sulfur atom, such as a furyl group, a pyrrolyl group, a thienyl group, a pyridinyl group, a thiazolyl group, and a benzothiazolyl group, with a furyl group, a thienyl group, a pyridinyl group, a thiazolyl group, and a benzothiazolyl group being preferred.

^Y1 , ^Y2 and ^Y3 may each independently be an optionally substituted polycyclic aromatic hydrocarbon group or polycyclic aromatic heterocyclic group. The polycyclic aromatic hydrocarbon group refers to a condensed polycyclic aromatic hydrocarbon group or a group derived from an aromatic ring assembly. The polycyclic aromatic heterocyclic group refers to a condensed polycyclic aromatic heterocyclic group or a group derived from an aromatic ring assembly.

Z ⁰ , Z ¹ and Z ² are each preferably independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms, a cyano group, a nitro group, or an alkoxy group having 1 to 12 carbon atoms, Z ⁰ is more preferably a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, or a cyano group, and Z ¹ and Z ² are more preferably a hydrogen atom, a fluorine atom, a chlorine atom, a methyl group, or a cyano group.

Q ¹ , Q ² and Q ³ are preferably -NH-, -S-, -NR ^2' - or -O-, and R ^2' is preferably a hydrogen atom, with -S-, -O- and -NH- being particularly preferred.

Among the formulae (Ar-1) to (Ar-23), the formulae (Ar-6) and (Ar-7) are preferred from the viewpoint of molecular stability.
In formulae (Ar-16) to (Ar-23), Y ¹ may form an aromatic heterocyclic group together with the nitrogen atom to which it is bonded and Z ^0. Examples of the aromatic heterocyclic group include those described above as aromatic heterocyclic rings that Ar may have, such as a pyrrole ring, an imidazole ring, a pyrroline ring, a pyridine ring, a pyrazine ring, a pyrimidine ring, an indole ring, a quinoline ring, an isoquinoline ring, a purine ring, and a pyrrolidine ring. This aromatic heterocyclic group may have a substituent. In addition, Y ¹ may be, together with the nitrogen atom to which it is bonded and Z ⁰ , the aforementioned polycyclic aromatic hydrocarbon group or polycyclic aromatic heterocyclic group which may be substituted. Examples include a benzofuran ring, a benzothiazole ring, and a benzoxazole ring.

(Compound containing a group represented by formula (X))
Formula (X) is as follows: Hereinafter, a compound containing a group represented by formula (X) may be referred to as polymerizable liquid crystal (B).
P11-B11-E11-B12-A11-B13- (X)

In formula (X), P11 represents a polymerizable group.
A11 represents a divalent alicyclic hydrocarbon group or a divalent aromatic hydrocarbon group. A hydrogen atom contained in the divalent alicyclic hydrocarbon group and the divalent aromatic hydrocarbon group may be substituted with a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a cyano group, or a nitro group, and a hydrogen atom contained in the alkyl group having 1 to 6 carbon atoms and the alkoxy group having 1 to 6 carbon atoms may be substituted with a fluorine atom.
B11 represents -O-, -S-, -CO-O-, -O-CO-, -O-CO-O-, -CO-NR ¹⁶ -, -NR ¹⁶ -CO-, -CO-, -CS- or a single bond, and R ¹⁶ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.
B12 and B13 each independently represent -C≡C-, -CH=CH-, -CH ₂ -CH ₂ -, -O-, -S-, -C(=O)-, -C(=O)-O-, -O-C(=O)-O-, -CH=N-, -N=CH-, -N=N-, -C(=O)-NR ¹⁶ -, -NR 16 -C(=O)-, -OCH ^{2 -, -OCF 2} -, -CH ₂ O-, -CF _{2 O-} , -CH=CH-C(=O)-O-, -O-C(=O)-CH=CH- or _a single bond.
E11 represents an alkanediyl group having 1 to 12 carbon atoms, a hydrogen atom contained in the alkanediyl group may be substituted with an alkoxy group having 1 to 5 carbon atoms, and a hydrogen atom contained in the alkoxy group may be substituted with a halogen atom. In addition, -CH ₂ - constituting the alkanediyl group may be replaced with -O- or -CO-.]

The number of carbon atoms in the aromatic hydrocarbon group and alicyclic hydrocarbon group of A11 is preferably in the range of 3 to 18, more preferably in the range of 5 to 12, and particularly preferably 5 or 6. A11 is preferably a cyclohexane-1,4-diyl group or a 1,4-phenylene group.

E11 is preferably a linear alkanediyl group having 1 to 12 carbon atoms. --CH ₂ -- constituting the alkanediyl group may be replaced with --O--.
Specific examples of such alkyl groups include linear alkanediyl groups having 1 to 12 carbon atoms, such as a methylene group, an ethylene group, a propane-1,3-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diyl group, a heptane-1,7-diyl group, an octane-1,8-diyl group, a nonane-1,9-diyl group, a decane-1,10-diyl group, an undecane-1,11 _- diyl group, and a dodecane-1,12-diyl group; -CH ₂ -CH _{2 -O} -CH ₂ -CH ₂ -, -CH ₂ -CH 2 -O-CH ₂ -CH _{2 -O} -CH _{2 -CH 2 - and -CH 2} -CH ₂ -O-CH ₂ -CH ₂ -O-CH ₂ -CH ₂ -O-CH ₂ Examples include —CH ₂ —.
As B11, --O--, --S--, --CO--O-- and --O--CO-- are preferable, and among them, --CO--O-- is more preferable.
As B12 and B13, each independently is preferably -O-, -S-, -C(=O)-, -C(=O)-O-, -O-C(=O)- or -O-C(=O)-O-, and among these, -O- or -O-C(=O)-O- is more preferable.

As the polymerizable group represented by P11, a radically polymerizable group or a cationic polymerizable group is preferred because of its high polymerization reactivity, particularly photopolymerization reactivity. In addition, the polymerizable group is preferably a group represented by the following formulae (P-11) to (P-15), because it is easy to handle and the liquid crystal compound itself is easy to manufacture.

［式（Ｐ－１１）～（Ｐ－１５）中、
Ｒ^１７～Ｒ^２１はそれぞれ独立に、炭素数１～６のアルキル基または水素原子を表わす。］

[In formulas (P-11) to (P-15),
R ¹⁷ to R ²¹ each independently represent an alkyl group having 1 to 6 carbon atoms or a hydrogen atom.]

Specific examples of the groups represented by formulas (P-11) to (P-15) include the groups represented by the following formulas (P-16) to (P-20).

P11 is preferably a group represented by formula (P-14) to formula (P-20), and more preferably a vinyl group, a p-stilbene group, an epoxy group or an oxetanyl group.
The group represented by P11-B11- is more preferably an acryloyloxy group or a methacryloyloxy group.

The polymerizable liquid crystal (B) may be a compound represented by formula (I), formula (II), formula (III), formula (IV), formula (V) or formula (VI).
P11-B11-E11-B12-A11-B13-A12-B14-A13-B15-A14-B16-E12-B17-P12 (I)
P11-B11-E11-B12-A11-B13-A12-B14-A13-B15-A14-F11 (II)
P11-B11-E11-B12-A11-B13-A12-B14-A13-B15-E12-B17-P12 (III)
P11-B11-E11-B12-A11-B13-A12-B14-A13-F11 (IV)
P11-B11-E11-B12-A11-B13-A12-B14-E12-B17-P12 (V)
P11-B11-E11-B12-A11-B13-A12-F11 (VI)
(Wherein,
A12 to A14 each independently have the same meaning as A11, B14 to B16 each independently have the same meaning as B12, B17 has the same meaning as B11, and E12 has the same meaning as E11.
F11 represents a hydrogen atom, an alkyl group having 1 to 13 carbon atoms, an alkoxy group having 1 to 13 carbon atoms, a cyano group, a nitro group, a trifluoromethyl group, a dimethylamino group, a hydroxy group, a methylol group, a formyl group, a sulfo group ( _-SO3H ), a carboxy group, an alkoxycarbonyl group having 1 to 10 carbon atoms, or a halogen atom, and _-CH2- constituting the alkyl group and the alkoxy group may be replaced by -O-.

Specific examples of polymerizable liquid crystals (B) include compounds having a polymerizable group among those described in "3.8.6 Network (fully cross-linked type)" and "6.5.1 Liquid crystal materials b. Polymerizable nematic liquid crystal materials" in Liquid Crystal Handbook (edited by Liquid Crystal Handbook Editorial Committee, published by Maruzen Co., Ltd. on October 30, 2000), and the polymerizable liquid crystals described in JP-A Nos. 2010-31223, 2010-270108, 2011-6360, and 2011-207765.

Specific examples of the polymerizable liquid crystal (B) include compounds represented by the following formulas (I-1) to (I-4), (II-1) to (II-4), (III-1) to (III-26), (IV-1) to (IV-26), (V-1) to (V-2), and (VI-1) to (VI-6). In the following formulas, k1 and k2 each independently represent an integer from 2 to 12. These polymerizable liquid crystals (B) are preferred in terms of ease of synthesis or availability.

An example of a disc-shaped polymerizable liquid crystal is a compound containing a group represented by formula (W) (hereinafter sometimes referred to as polymerizable liquid crystal (C)).

［式（Ｗ）中、Ｒ^４０は、下記式（Ｗ－１）～（Ｗ－５）を表わす。

In formula (W), R ⁴⁰ represents any one of the following formulae (W-1) to (W-5).

X ⁴⁰ and Z ⁴⁰ each represent an alkanediyl group having 1 to 12 carbon atoms, and a hydrogen atom contained in the alkanediyl group may be substituted with an alkoxy group having 1 to 5 carbon atoms, and a hydrogen atom contained in the alkoxy group may be substituted with a halogen atom. In addition, -CH ₂ - constituting the alkanediyl group may be replaced with -O- or -CO-.

Specific examples of polymerizable liquid crystals (C) include the compounds described in "6.5.1 Liquid crystal materials b. Polymerizable nematic liquid crystal materials Figure 6.21" in Liquid Crystal Handbook (edited by Liquid Crystal Handbook Editorial Committee, published by Maruzen Co., Ltd. on October 30, 2000), and the polymerizable liquid crystals described in JP-A-7-258170, JP-A-7-30637, JP-A-7-309807, and JP-A-8-231470.

The retardation plate 30 having the optical properties represented by formulas (1) and (2) can be obtained by polymerizing a polymerizable liquid crystal having a specific structure, by stretching a polymer film having a specific structure, or by combining a layer having the optical properties represented by formulas (4), (6), and (7) with a layer having the optical properties represented by formulas (5), (6), and (7) in a specific slow axis relationship.
Re(450)/Re(550)≦1.00 (1)
1.00≦Re(650)/Re(550) (2)
100nm<Re(550)<160nm (4)
200nm<Re(550)<320nm (5)
Re(450)/Re(550)≧1.00 (6)
1.00≧Re(650)/Re(550) (7)

The retardation plate 30 preferably has the optical characteristics expressed by formulas (1) and (2). When the retardation plate 30 has the optical characteristics expressed by formulas (1) and (2), uniform polarization conversion characteristics can be obtained for light of each wavelength in the visible light range, and light leakage during black display of a display device such as an organic EL display device can be suppressed.

The polymerizable liquid crystal having the specific structure can be, for example, the polymerizable liquid crystal (A).By aligning the polymerizable liquid crystal (A) so that the optical axis is horizontal to the substrate plane, a retardation layer having the optical properties represented by formula (1) and formula (2) can be obtained, and further, by adjusting the film thickness according to formula (10), a retardation layer having a desired in-plane retardation value such as the optical properties represented by formula (4) can be obtained.
100nm<Re(550)<160nm (4)

Examples of a method for combining a layer having the optical properties represented by formulas (4), (6), and (7) with a layer having the optical properties represented by formulas (5), (6), and (7) in a specific slow axis relationship include well-known methods.
For example, Japanese Patent Application Laid-Open Nos. 2001-4837, 2001-21720, and 2000-206331 disclose retardation films having at least two retardation layers made of a liquid crystal compound.

A retardation layer having the optical properties represented by the above formulas (6) and (7) can be obtained by a known method. That is, a retardation layer obtained by a method other than the method for obtaining a retardation layer having the optical properties represented by the above formulas (1) and (2) generally has the optical properties represented by the formulas (6) and (7).

(First Retardation Layer)
The first retardation layer 31 preferably has optical characteristics represented by formula (4) (in this specification, a retardation layer satisfying the optical characteristics represented by formula (4) is also referred to as a "lambda / 4 layer"), and more preferably has optical characteristics represented by formula (4-1). The in-plane retardation value Re (550) can be adjusted by the same method as the adjustment method of the in-plane retardation value of the retardation layer.
100nm<Re(550)<160nm (4)
130nm<Re(550)<150nm (4-1)

Furthermore, the first retardation layer preferably has optical properties represented by formulas (1) and (2) (in this specification, the optical properties represented by formulas (1) and (2) are also referred to as "reverse dispersion".) Such optical properties can be obtained by the same method as the retardation layer.
Re(450)/Re(550)≦1.00 (1)
1.00≦Re(650)/Re(550) (2)

The first retardation layer preferably has a layer A having optical properties represented by formulas (4), (6), and (7), and a layer B having optical properties represented by formulas (5), (6), and (7). Such optical properties can be obtained by the same method as the retardation layer.
100nm<Re(550)<160nm (4)
200nm<Re(550)<320nm (5)
Re(450)/Re(550)≧1.00 (6)
1.00≧Re(650)/Re(550) (7)
Layer A is preferably a layer having the optical property represented by formula (4-1), and Layer B is preferably a layer having the optical property represented by formula (5-1).
130nm<Re(550)<150nm (4-1)
265nm<Re(550)<285nm (5-1)

In addition, when the retardation plate has a third retardation layer, the first retardation layer preferably has the optical characteristics represented by the formulas (6) and (7). Such optical characteristics can be obtained in the same manner as the above-mentioned retardation layer.
Re(450)/Re(550)≧1.00 (6)
1.00≧Re(650)/Re(550) (7)

The first retardation layer is a coating layer formed by polymerizing one or more polymerizable liquid crystals. When the first retardation layer is composed of one retardation layer and has the optical properties represented by formulas (1) and (2), it is preferable that such a retardation layer is a coating layer formed by polymerizing a polymerizable liquid crystal (A). When the second retardation layer has the optical properties represented by formulas (6) and (7), it is preferable that such a retardation layer is a coating layer formed by polymerizing a polymerizable liquid crystal (B).

Layer A is preferably a coating layer formed by polymerizing a polymerizable liquid crystal (B). Layer B is preferably a coating layer formed by polymerizing a polymerizable liquid crystal (C).

The first retardation layer is a layer formed by polymerizing a polymerizable liquid crystal, and its thickness is usually 20 μm or less, preferably 5 μm or less, and more preferably 0.5 μm or more and 3 μm or less. The thickness of the first retardation layer can be determined by measurement using an interference thickness gauge, a laser microscope, or a stylus thickness gauge.

(Second Retardation Layer)
The second retardation layer 32 preferably has the optical characteristic represented by formula (3) (positive C plate).
nx ≈ ny < nz (3)

The in-plane retardation value Re(550) of the second retardation layer is usually in the range of 0 to 10 nm, and preferably in the range of 0 to 5 nm. The thickness direction retardation value Rth is usually in the range of -10 to -300 nm, and preferably in the range of -20 to -200 nm. The in-plane retardation value Re(550) and the thickness direction retardation value Rth can be adjusted in the same manner as the above retardation layer.

The second retardation layer is a coating layer formed by polymerizing one or more polymerizable liquid crystals. More preferably, it is a coating layer formed by polymerizing a polymerizable liquid crystal (B).

The second retardation layer is a layer formed by polymerizing a polymerizable liquid crystal, and its thickness is usually 10 μm or less, preferably 5 μm or less, and more preferably 0.3 μm or more and 3 μm or less. The thickness of the second retardation layer can be determined in the same manner as the first retardation layer. In addition, it is preferable that the thicknesses of the first retardation layer and the second retardation layer are each 5 μm or less.

(Third Retardation Layer)
The third retardation layer preferably has an optical characteristic represented by formula (5), and more preferably has an optical characteristic represented by formula (5-1). The in-plane retardation value Re(550) can be adjusted by the same method as the adjustment method of the in-plane retardation value of the retardation layer.
200nm<Re(550)<320nm (5)
265nm<Re(550)<285nm (5-1)

The third retardation layer preferably has optical properties represented by the formulas (6) and (7). Such optical properties can be obtained by the same method as for the above retardation layer.
Re(450)/Re(550)≧1.00 (6)
1.00≧Re(650)/Re(550) (7)

The third retardation layer is preferably a coating layer formed by polymerizing one or more polymerizable liquid crystals. More preferably, it is a coating layer formed by polymerizing polymerizable liquid crystal (B) or (C).

The third retardation layer may be a stretched film, and in the case of a stretched film, its thickness is usually 300 μm or less, preferably 5 μm or more and 100 μm or less, and more preferably 10 μm or more and 50 μm or less. In the case of a layer formed by polymerizing a polymerizable liquid crystal, its thickness is usually 10 μm or less, preferably 5 μm or less, and more preferably 0.5 μm or more and 5 μm or less. The thickness of the third retardation layer can be determined in the same manner as the first retardation layer.

(Substrate)
The retardation plate 30 may have a substrate. The substrate is usually a transparent substrate. The transparent substrate means a substrate having transparency capable of transmitting light, particularly visible light, and transparency means a property in which the transmittance for light rays having a wavelength of 380 to 780 nm is 80% or more. A specific transparent substrate is a light-transmitting resin substrate. Resins constituting the light-transmitting resin substrate include polyolefins such as polyethylene and polypropylene; cyclic olefin resins such as norbornene-based polymers; polyvinyl alcohol; polyethylene terephthalate; polymethacrylic acid esters; polyacrylic acid esters; cellulose esters such as triacetyl cellulose, diacetyl cellulose, and cellulose acetate propionate; polyethylene naphthalate; polycarbonate; polysulfone; polyether sulfone; polyether ketone; polyphenylene sulfide, and polyphenylene oxide. From the viewpoints of availability and transparency, polyethylene terephthalate, polymethacrylic acid esters, cellulose esters, cyclic olefin resins, and polycarbonates are preferred.

The surface of the substrate on which the alignment film, the first retardation layer, the second retardation layer, and the third retardation layer are formed may be subjected to a surface treatment before the alignment film or the retardation layer is formed. Examples of the surface treatment method include a method of treating the substrate surface with corona or plasma under vacuum or atmospheric pressure, a method of laser treating the substrate surface, a method of ozone treating the substrate surface, a method of saponifying the substrate surface or a method of flame treating the substrate surface, a primer treatment method in which a coupling agent is applied to the substrate surface, and a graft polymerization method in which a reactive monomer or a reactive polymer is attached to the substrate surface and then reacted by irradiating it with radiation, plasma, or ultraviolet light. Among these, a method of corona or plasma treating the substrate surface under vacuum or atmospheric pressure is preferred.

Methods for treating the surface of a substrate with corona or plasma include a method in which the substrate is placed between opposing electrodes under pressure close to atmospheric pressure and corona or plasma is generated to treat the substrate surface, a method in which gas is passed between opposing electrodes, the gas is converted into plasma between the electrodes, and the plasma gas is sprayed onto the substrate, and a method in which glow discharge plasma is generated under low pressure conditions to treat the substrate surface.

Among these, a method in which a substrate is placed between opposing electrodes under pressure close to atmospheric pressure, and corona or plasma is generated to perform surface treatment of the substrate, or a method in which a gas is caused to flow between opposing electrodes, the gas is converted into plasma between the electrodes, and the plasma gas is sprayed onto the substrate, is preferred. Such surface treatment using corona or plasma is usually performed using a commercially available surface treatment device.

The substrate is preferably one with a small phase difference. Examples of substrates with a small phase difference include cellulose ester films with no phase difference, such as Zerotac (registered trademark) (Konica Minolta Opto, Inc.) and Z-tac (Fuji Film Corporation). Unstretched cyclic olefin resin substrates are also preferred.

In addition, the surface of the substrate on which the alignment film, the first retardation layer, the second retardation layer, and the third retardation layer are not formed may be subjected to a hard coat treatment, an antistatic treatment, etc. In addition, additives such as ultraviolet absorbers may be included to the extent that they do not affect the performance.

The thickness of the substrate is usually 5 to 300 μm, preferably 10 to 200 μm, because if it is too thin, the strength decreases and workability tends to be poor.

(Polymerizable liquid crystal composition)
A layer (retardation layer) formed by polymerizing a polymerizable liquid crystal is usually formed by applying a composition containing one or more polymerizable liquid crystals (hereinafter, sometimes referred to as a polymerizable liquid crystal composition) onto a substrate, an alignment film, a protective layer, or a retardation layer, and polymerizing the polymerizable liquid crystal in the resulting coating film.

The polymerizable liquid crystal composition usually contains a solvent, and the solvent is preferably a solvent capable of dissolving the polymerizable liquid crystal and is inactive in the polymerization reaction of the polymerizable liquid crystal.
Specific examples of the solvent include alcohol solvents such as methanol, ethanol, ethylene glycol, isopropyl alcohol, propylene glycol, methyl cellosolve, butyl cellosolve, propylene glycol monomethyl ether, and phenol; ester solvents such as ethyl acetate and butyl acetate; ketone solvents such as acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, cycloheptanone, methyl amyl ketone, methyl isobutyl ketone, and N-methyl-2-pyrrolidinone; non-chlorinated aliphatic hydrocarbon solvents such as pentane, hexane, and heptane; non-chlorinated aromatic hydrocarbon solvents such as toluene and xylene; nitrile solvents such as acetonitrile; ether solvents such as propylene glycol monomethyl ether, tetrahydrofuran, and dimethoxyethane; and chlorinated hydrocarbon solvents such as chloroform and chlorobenzene. These other solvents may be used alone or in combination.

The content of the solvent in the polymerizable liquid crystal composition is usually preferably 10 parts by mass to 10,000 parts by mass, and more preferably 50 parts by mass to 5,000 parts by mass, per 100 parts by mass of the solid content. The solid content means the total of the components excluding the solvent from the polymerizable liquid crystal composition.

The polymerizable liquid crystal composition is usually applied by known methods such as spin coating, extrusion, gravure coating, die coating, slit coating, bar coating, applicator, or other application methods, or flexographic or other printing methods. After application, a dry film is usually formed by removing the solvent under conditions in which the polymerizable liquid crystal contained in the resulting coating film does not polymerize. Drying methods include natural drying, forced air drying, heat drying, and reduced pressure drying.

(Alignment film)
In this specification, the alignment film has an alignment regulating force for aligning the polymerizable liquid crystal in a desired direction.
The alignment film is preferably one that has solvent resistance that does not dissolve the polymerizable liquid crystal composition when applied, and also has heat resistance in a heat treatment for removing the solvent and orienting the polymerizable liquid crystal. Examples of such an alignment film include an alignment film containing an alignment polymer, a photoalignment film, and a groove alignment film that forms a concave-convex pattern or a plurality of grooves on the surface to achieve alignment.

Examples of oriented polymers include polyamides and gelatins having amide bonds in the molecule, polyimides having imide bonds in the molecule, and their hydrolyzates such as polyamic acid, polyvinyl alcohol, alkyl-modified polyvinyl alcohol, polyacrylamide, polyoxazole, polyethyleneimine, polystyrene, polyvinylpyrrolidone, polyacrylic acid, and polyacrylic acid esters. Of these, polyvinyl alcohol is preferred. Two or more oriented polymers may be used in combination.

Orientation films containing an orienting polymer are usually obtained by applying a composition in which an orienting polymer is dissolved in a solvent (hereinafter, sometimes referred to as an orienting polymer composition) to a substrate and then removing the solvent, or by applying an orienting polymer composition to a substrate, removing the solvent, and then rubbing (rubbing method).

Examples of the solvent include alcohol solvents such as water, methanol, ethanol, ethylene glycol, isopropyl alcohol, propylene glycol, methyl cellosolve, butyl cellosolve, and propylene glycol monomethyl ether; ester solvents such as ethyl acetate, butyl acetate, ethylene glycol methyl ether acetate, γ-butyrolactone, propylene glycol methyl ether acetate, and ethyl lactate; ketone solvents such as acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, methyl amyl ketone, and methyl isobutyl ketone; aliphatic hydrocarbon solvents such as pentane, hexane, and heptane; aromatic hydrocarbon solvents such as toluene and xylene; nitrile solvents such as acetonitrile; ether solvents such as tetrahydrofuran and dimethoxyethane; and chlorinated hydrocarbon solvents such as chloroform and chlorobenzene. These solvents may be used alone or in combination of two or more.

The concentration of the oriented polymer in the oriented polymer composition may be within a range in which the oriented polymer material can be completely dissolved in the solvent, but is preferably 0.1 to 20% in terms of solids content relative to the solution, and more preferably 0.1 to 10%.

As the oriented polymer composition, commercially available alignment film materials may be used as they are. Examples of commercially available alignment film materials include Sunever (registered trademark, manufactured by Nissan Chemical Industries, Ltd.) and Optomer (registered trademark, manufactured by JSR Corporation).

Methods for applying the oriented polymer composition to a substrate include known methods such as spin coating, extrusion, gravure coating, die coating, slit coating, bar coating, and applicator coating, and printing methods such as flexography. When the optical film is manufactured by a roll-to-roll continuous manufacturing method described below, the application method typically employs a printing method such as gravure coating, die coating, or flexography.

Methods for removing the solvent contained in the oriented polymer composition include natural drying, ventilation drying, heat drying, and reduced pressure drying.

If necessary, rubbing can be performed to impart alignment control force to the alignment film (rubbing method).

One method for imparting an orientation control force using the rubbing method is to bring a film of an oriented polymer formed on the surface of a substrate by applying an oriented polymer composition to the substrate and annealing the composition into contact with a rotating rubbing roll wrapped with a rubbing cloth.

If necessary, photo-alignment can be performed to impart an alignment control force to the alignment film (photo-alignment method).

Photo-alignment films are usually obtained by applying a composition containing a polymer or monomer having a photoreactive group and a solvent (hereinafter sometimes referred to as a "photo-alignment film forming composition") to a substrate and irradiating it with light (preferably polarized UV). Photo-alignment films are more preferable in that the direction of the alignment control force can be freely controlled by selecting the polarization direction of the irradiated light.

The photoreactive group refers to a group that generates liquid crystal alignment ability when irradiated with light. Specific examples include groups involved in photoreactions that are the origin of liquid crystal alignment ability, such as molecular alignment induction caused by light irradiation, or isomerization reactions, dimerization reactions, photocrosslinking reactions, or photodecomposition reactions. Among these, groups involved in dimerization reactions or photocrosslinking reactions are preferred in terms of excellent alignment ability. As the photoreactive group, a group having an unsaturated bond, particularly a double bond, is preferred, and a group having at least one selected from the group consisting of a carbon-carbon double bond (C=C bond), a carbon-nitrogen double bond (C=N bond), a nitrogen-nitrogen double bond (N=N bond), and a carbon-oxygen double bond (C=O bond) is particularly preferred.

Examples of photoreactive groups having a C=C bond include vinyl groups, polyene groups, stilbene groups, stilbazolyl groups, stilbazolium groups, chalcone groups, and cinnamoyl groups. Examples of photoreactive groups having a C=N bond include groups having structures such as aromatic Schiff bases and aromatic hydrazones. Examples of photoreactive groups having an N=N bond include azobenzene groups, azonaphthalene groups, aromatic heterocyclic azo groups, bisazo groups, formazan groups, and groups having an azoxybenzene structure. Examples of photoreactive groups having a C=O bond include benzophenone groups, coumarin groups, anthraquinone groups, and maleimide groups. These groups may have substituents such as alkyl groups, alkoxy groups, aryl groups, allyloxy groups, cyano groups, alkoxycarbonyl groups, hydroxyl groups, sulfonic acid groups, and halogenated alkyl groups.

Among these, photoreactive groups involved in photodimerization reactions are preferred, and cinnamoyl and chalcone groups are preferred because they require a relatively small amount of polarized light irradiation for photoalignment and are easy to obtain photoalignment films with excellent thermal and temporal stability. As polymers having photoreactive groups, those having cinnamoyl groups such that the terminals of the polymer side chains form cinnamic acid structures are particularly preferred.

A photo-alignment-inducing layer can be formed on a substrate by applying the photo-alignment film-forming composition onto the substrate. The solvent contained in the composition can be the same as the solvent contained in the above-mentioned alignment polymer composition, and can be appropriately selected depending on the solubility of the polymer or monomer having a photoreactive group.

The content of the polymer or monomer having a photoreactive group in the composition for forming a photo-alignment film can be adjusted as appropriate depending on the type of polymer or monomer and the desired thickness of the photo-alignment film, but is preferably at least 0.2% by mass, and more preferably in the range of 0.3 to 10% by mass. The composition for forming a photo-alignment film may contain a polymer material such as polyvinyl alcohol or polyimide, or a photosensitizer, as long as the properties of the photo-alignment film are not significantly impaired.

The method for applying the composition for forming a photo-alignment film to a substrate can be the same as the method for applying the alignable polymer composition to a substrate. The method for removing the solvent from the applied composition for forming a photo-alignment film can be the same as the method for removing the solvent from the alignable polymer composition.

To irradiate polarized light, polarized UV may be irradiated directly onto the composition for forming a photo-aligned film coated on the substrate from which the solvent has been removed, or polarized light may be irradiated from the substrate side and then transmitted through the substrate. In addition, it is particularly preferable that the polarized light is substantially parallel light. The wavelength of the polarized light to be irradiated is preferably in a wavelength range in which the photoreactive group of the polymer or monomer having a photoreactive group can absorb light energy. Specifically, UV (ultraviolet light) in the wavelength range of 250 to 400 nm is particularly preferable. Examples of light sources used for the polarized light irradiation include xenon lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, ultraviolet lasers such as KrF and ArF, and high-pressure mercury lamps, ultra-high-pressure mercury lamps, and metal halide lamps are more preferable. These lamps are preferable because they have a high emission intensity of ultraviolet light with a wavelength of 313 nm. Polarized UV can be irradiated by passing the light from the light source through an appropriate polarizer. Such polarizers can be polarizing filters, polarizing prisms such as Glan-Thompson and Glan-Taylor, or wire grid type polarizers.

If masking is performed when rubbing or polarized light irradiation is performed, multiple regions (patterns) with different liquid crystal alignment directions can be formed.

A groove alignment film is a film that aligns liquid crystals by using a concave-convex pattern or multiple grooves on the film surface. H. V. Kennell et al. reported that when liquid crystal molecules are placed on a substrate with multiple equally spaced linear grooves (grooves), the liquid crystal molecules align along the grooves (Physical Review A24(5), p. 2713, 1981).

Specific examples of obtaining a groove alignment film include a method in which a photosensitive polyimide surface is exposed through an exposure mask having slits in a periodic pattern, followed by development and rinsing to remove unnecessary polyimide film and form a concave-convex pattern; a method in which a UV-cured resin layer is formed on a plate-shaped master having grooves on its surface, and the resin layer is transferred to a base film and then cured; a method in which a base film on which a UV-cured resin layer has been formed is transported, and a roll-shaped master having multiple grooves is pressed against the surface of the UV-cured resin layer to form concave-convex patterns and then cured; and the methods described in JP-A-6-34976 and JP-A-2011-242743 can be used.

Among the above methods, the method of pressing a roll-shaped master having multiple grooves against the surface of a UV-cured resin layer to form projections and recesses and then curing is preferred. Stainless steel (SUS) can be used as the roll-shaped master from the viewpoint of durability.

As the UV curable resin, a polymer of a monofunctional acrylate, a polymer of a polyfunctional acrylate, or a polymer of a mixture thereof can be used.
The monofunctional acrylate is a compound having one group (hereinafter sometimes referred to as a (meth)acryloyloxy group) selected from the group consisting of an acryloyloxy group (CH2=CH-COO-) and a methacryloyloxy group (CH2=C(CH3)-COO-) in the molecule.

Examples of monofunctional acrylates having one (meth)acryloyloxy group include alkyl (meth)acrylates having 4 to 16 carbon atoms, β-carboxyalkyl (meth)acrylates having 2 to 14 carbon atoms, alkylated phenyl (meth)acrylates having 2 to 14 carbon atoms, methoxypolyethylene glycol (meth)acrylates, phenoxypolyethylene glycol (meth)acrylates, and isobornyl (meth)acrylates.

A polyfunctional acrylate is typically a compound that has 2 to 6 (meth)acryloyloxy groups in the molecule.

Examples of bifunctional acrylates having two (meth)acryloyloxy groups include 1,3-butanediol di(meth)acrylate; 1,3-butanediol (meth)acrylate; 1,6-hexanediol di(meth)acrylate; ethylene glycol di(meth)acrylate; diethylene glycol di(meth)acrylate; neopentyl glycol di(meth)acrylate; triethylene glycol di(meth)acrylate; tetraethylene glycol di(meth)acrylate; polyethylene glycol diacrylate; bis(acryloyloxyethyl)ether of bisphenol A; ethoxylated bisphenol A di(meth)acrylate; propoxylated neopentyl glycol di(meth)acrylate; ethoxylated neopentyl glycol di(meth)acrylate, and 3-methylpentanediol di(meth)acrylate.

Examples of polyfunctional acrylates having 3 to 6 (meth)acryloyloxy groups include trimethylolpropane tri(meth)acrylate; pentaerythritol tri(meth)acrylate; tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate; ethoxylated trimethylolpropane tri(meth)acrylate; propoxylated trimethylolpropane tri(meth)acrylate; pentaerythritol tetra(meth)acrylate; dipentaerythritol penta(meth)acrylate; dipentaerythritol hexa(meth)acrylate. Tripentaerythritol tetra(meth)acrylate; Tripentaerythritol penta(meth)acrylate; Tripentaerythritol hexa(meth)acrylate; Tripentaerythritol hepta(meth)acrylate; Tripentaerythritol octa(meth)acrylate; Reaction product of pentaerythritol tri(meth)acrylate and acid anhydride; Reaction product of dipentaerythritol penta(meth)acrylate and acid anhydride; Reaction product of tripentaerythritol hepta(meth)acrylate and acid anhydride; Caprolactone-modified trimethylol propionate Caprolactone modified pentaerythritol tri(meth)acrylate; Caprolactone modified tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate; Caprolactone modified pentaerythritol tetra(meth)acrylate; Caprolactone modified dipentaerythritol penta(meth)acrylate; Caprolactone modified dipentaerythritol hexa(meth)acrylate; Caprolactone modified tripentaerythritol tetra(meth)acrylate; Caprolactone modified tripentaerythritol penta(meth)acrylate Examples of the polyfunctional acrylate include caprolactone-modified tripentaerythritol hexa(meth)acrylate, caprolactone-modified tripentaerythritol hepta(meth)acrylate, caprolactone-modified tripentaerythritol octa(meth)acrylate, a reaction product of caprolactone-modified pentaerythritol tri(meth)acrylate and an acid anhydride, a reaction product of caprolactone-modified dipentaerythritol penta(meth)acrylate and an acid anhydride, and a reaction product of caprolactone-modified tripentaerythritol hepta(meth)acrylate and an acid anhydride. In the specific examples of the polyfunctional acrylate shown here, (meth)acrylate means acrylate or methacrylate. In addition, caprolactone-modified means that a ring-opened product or a ring-opened polymer of caprolactone is introduced between the alcohol-derived moiety and the (meth)acryloyloxy group of the (meth)acrylate compound.

Commercially available products can also be used for such multifunctional acrylates. Such commercially available products include A-DOD-N, A-HD-N, A-NOD-N, APG-100, APG-200, APG-400, A-GLY-9E, A-GLY-20E, A-TMM-3, A-TMPT, AD-TMP, ATM-35E, A-TMMT, A-9550, A-DPH, HD-N, NOD-N, NPG, TMPT (manufactured by Shin-Nakamura Chemical Co., Ltd.), "ARONIX M-220", "M-325", "M-240", "M-270", "M-309", "M-310", "M-321", "M-350", "M-360", "M-370", "M-380", "M-390", "M-400", "M-410", "M-421", "M-430", "M-440", "M-450", "M-460", "M-470", "M-480", "M-490", "M-500", "M-510", "M-521", "M-530", "M-540", "M-550", "M-560", "M-570", "M-580", "M-590", "M-600", "M-610", "M-620", "M-630", "M-640", "M-650", "M-650", "M-660", "M-670", "M-680", "M-690", "M-700", "M-700", "M-700", "M-800", "M-810", "M-820", "M-900", "M- Examples include "M-305", "M-306", "M-450", "M-451", "M-408", "M-400", "M-402", "M-403", "M-404", "M-405", "M-406" (manufactured by Toa Gosei Co., Ltd.), "EBECRYL11", "145", "150", "40", "140", "180", DPGDA, HDDA, TPGDA, HPNDA, PETIA, PETRA, TMPTA, TMPEOTA, DPHA, and EBECRYL series (manufactured by Daicel-Cytec Co., Ltd.).

The unevenness of the groove alignment film is preferably such that the width of the convex portions is 0.05 to 5 μm, the width of the concave portions is 0.1 to 5 μm, and the depth of the unevenness is 2 μm or less, preferably 0.01 to 1 μm or less. Within this range, liquid crystal alignment with little alignment disturbance can be obtained.

The thickness of the alignment film is usually in the range of 10 nm to 10,000 nm, preferably in the range of 10 nm to 1000 nm, more preferably 500 nm or less, and even more preferably in the range of 10 nm to 500 nm.

The liquid crystal alignment of polymerizable liquid crystals is controlled by the alignment film and the properties of the polymerizable liquid crystals. For example, if the alignment film is made of a material that exerts a horizontal alignment restraining force as an alignment restraining force, the polymerizable liquid crystals can form horizontal alignment or hybrid alignment, and if the alignment film is made of a material that exerts a vertical alignment restraining force, the polymerizable liquid crystals can form vertical alignment or tilted alignment. If the alignment film is made of an alignment polymer, the alignment restraining force can be adjusted arbitrarily by the surface state or rubbing conditions, and if it is made of a photoalignment polymer, it can be adjusted arbitrarily by the polarized light irradiation conditions, etc. In addition, the liquid crystal alignment can also be controlled by selecting the physical properties of the polymerizable liquid crystal, such as the surface tension and liquid crystallinity.

Polymerization of the polymerizable liquid crystal can be carried out by a known method of polymerizing a compound having a polymerizable functional group. Specific examples include thermal polymerization and photopolymerization, with photopolymerization being preferred from the viewpoint of ease of polymerization. When polymerizing the polymerizable liquid crystal by photopolymerization, it is preferable to apply a polymerizable liquid crystal composition containing a photopolymerization initiator, dry the resulting dried coating, and then photopolymerize the polymerizable liquid crystal in the dry coating while maintaining the liquid crystal state.

Photopolymerization is usually performed by irradiating the dry film with light. The light to be irradiated is appropriately selected depending on the type of photopolymerization initiator contained in the dry film, the type of polymerizable liquid crystal (particularly the type of photopolymerizable group possessed by the polymerizable liquid crystal) and the amount thereof. Specifically, light selected from the group consisting of visible light, ultraviolet light and laser light, and active electron beams are included. Among them, ultraviolet light is preferred because it is easy to control the progress of the polymerization reaction and because photopolymerization devices widely used in this field can be used. It is preferable to select the type of polymerizable liquid crystal and photopolymerization initiator so that photopolymerization can be performed by ultraviolet light. In addition, the polymerization temperature can be controlled by irradiating light while cooling the dry film with an appropriate cooling means during polymerization. By adopting such a cooling means, if polymerization of the polymerizable liquid crystal is performed at a lower temperature, a retardation layer can be formed appropriately even if a substrate with relatively low heat resistance is used. During photopolymerization, a patterned retardation layer can also be obtained by performing masking or development.

The polymerizable liquid crystal composition may contain a reactive additive. The reactive additive preferably has a carbon-carbon unsaturated bond and an active hydrogen reactive group in its molecule. The "active hydrogen reactive group" here means a group that is reactive to groups having active hydrogen, such as a carboxyl group (-COOH), a hydroxyl group (-OH), or an amino group (-NH2), and representative examples thereof include a glycidyl group, an oxazoline group, a carbodiimide group, an aziridine group, an imide group, an isocyanate group, a thioisocyanate group, and a maleic anhydride group. The number of carbon-carbon unsaturated bonds and active hydrogen reactive groups contained in the reactive additive is usually 1 to 20 each, and preferably 1 to 10 each.

In the reactive additive, it is preferable that there are at least two active hydrogen reactive groups, and in this case, the multiple active hydrogen reactive groups may be the same or different.

The carbon-carbon unsaturated bond of the reactive additive may be a carbon-carbon double bond or a carbon-carbon triple bond, or a combination thereof, but is preferably a carbon-carbon double bond. In particular, the reactive additive preferably contains a carbon-carbon unsaturated bond as a vinyl group and/or a (meth)acrylic group. Furthermore, the active hydrogen reactive group is preferably at least one selected from the group consisting of an epoxy group, a glycidyl group, and an isocyanate group, and a reactive additive having an acrylic group and an isocyanate group is particularly preferred.

Specific examples of reactive additives include compounds having a (meth)acrylic group and an epoxy group, such as methacryloxyglycidyl ether and acryloxyglycidyl ether; compounds having a (meth)acrylic group and an oxetane group, such as oxetane acrylate and oxetane methacrylate; compounds having a (meth)acrylic group and a lactone group, such as lactone acrylate and lactone methacrylate; compounds having a vinyl group and an oxazoline group, such as vinyl oxazoline and isopropenyl oxazoline; oligomers of compounds having a (meth)acrylic group and an isocyanate group, such as isocyanatomethyl acrylate, isocyanatomethyl methacrylate, 2-isocyanatoethyl acrylate, and 20-isocyanatoethyl methacrylate. Also included are compounds having a vinyl group or vinylene group and an acid anhydride, such as methacrylic anhydride, acrylic anhydride, maleic anhydride, and vinyl maleic anhydride. Among these, methacryloxyglycidyl ether, acryloxyglycidyl ether, isocyanatomethyl acrylate, isocyanatomethyl methacrylate, vinyloxazoline, 2-isocyanatoethyl acrylate, 2-isocyanatoethyl methacrylate, and oligomers thereof are preferred, and isocyanatomethyl acrylate, 2-isocyanatoethyl acrylate, and oligomers thereof are particularly preferred.

［式（Ｙ）中、
ｎは１～１０までの整数を表わし、Ｒ１’は、炭素数２～２０の２価の脂肪族又は脂環式炭化水素基、或いは炭素数５～２０の２価の芳香族炭化水素基を表わす。各繰り返し単位にある２つのＲ２’は、一方が－ＮＨ－であり、他方が＞Ｎ－Ｃ（＝Ｏ）－Ｒ３’で示される基である。Ｒ３’は、水酸基又は炭素－炭素不飽和結合を有する基を表す。
式（Ｙ）中のＲ３’のうち、少なくとも１つのＲ３’は炭素－炭素不飽和結合を有する
基である。］ Specifically, a compound represented by the following formula (Y) is preferred.

[In formula (Y),
n represents an integer of 1 to 10, and R1' represents a divalent aliphatic or alicyclic hydrocarbon group having 2 to 20 carbon atoms, or a divalent aromatic hydrocarbon group having 5 to 20 carbon atoms. Of the two R2' in each repeating unit, one is -NH- and the other is a group represented by >N-C(=O)-R3'. R3' represents a hydroxyl group or a group having a carbon-carbon unsaturated bond.
At least one of R3' in formula (Y) is a group having a carbon-carbon unsaturated bond.

Among the reactive additives represented by the formula (Y), the compound represented by the following formula (YY) (hereinafter, sometimes referred to as compound (YY)) is particularly preferred (n has the same meaning as above).

化合物（ＹＹ）には、市販品をそのまま又は必要に応じて精製して用いることができる。市販品としては、例えば、Ｌａｒｏｍｅｒ（登録商標）ＬＲ－９０００（ＢＡＳＦ社製）が挙げられる。

Compound (YY) may be a commercially available product, either as is or after purification as necessary. Examples of commercially available products include Laromer (registered trademark) LR-9000 (manufactured by BASF).

When the polymerizable liquid crystal composition contains a reactive additive, the content is usually 0.1 to 30 parts by mass, and preferably 0.1 to 5 parts by mass, per 100 parts by mass of the polymerizable liquid crystal.

The polymerizable liquid crystal composition preferably contains one or more leveling agents. The leveling agent has the function of adjusting the fluidity of the polymerizable liquid crystal composition and making the coating film obtained by coating the polymerizable liquid crystal composition flatter, and specifically includes a surfactant. The leveling agent is preferably at least one selected from the group consisting of leveling agents mainly composed of a polyacrylate compound and leveling agents mainly composed of a fluorine atom-containing compound.

Leveling agents whose main component is a polyacrylate compound include "BYK-350", "BYK-352", "BYK-353", "BYK-354", "BYK-355", "BYK-358N", "BYK-361N", "BYK-380", "BYK-381" and "BYK-392" [BYK Chemie].

Leveling agents that contain fluorine atoms as the main component include "Megafac (registered trademark) R-08", "R-30", "R-90", "F-410", "F-411", "F-443", "F-445", "F-470", "F-471", "F-477", "F-479", "F-482" and "F-483" [DIC Corporation]; "Surflon (registered trademark) S-381", "S-3 82", S-383, S-393, SC-101, SC-105, KH-40 and SA-100 [AGC Seimi Chemical Co., Ltd.]; E1830, E5844 [Daikin Fine Chemicals Research Institute Ltd.]; F-top EF301, F-top EF303, F-top EF351 and F-top EF352 [Mitsubishi Materials Electronic Chemicals Co., Ltd.].

When the polymerizable liquid crystal composition contains a leveling agent, the content is preferably 0.01 parts by mass or more and 5 parts by mass or less, more preferably 0.05 parts by mass or more and 5 parts by mass or less, and even more preferably 0.05 parts by mass or more and 3 parts by mass or less, relative to 100 parts by mass of the polymerizable liquid crystal. When the content of the leveling agent is within the above range, it is easy to align the polymerizable liquid crystal horizontally, and the obtained polarizing layer tends to be smoother. When the content of the leveling agent relative to the polymerizable liquid crystal is within the above range, the obtained retardation layer tends to be less prone to unevenness.

The polymerizable liquid crystal composition preferably contains one or more polymerization initiators. The polymerization initiator is a compound capable of initiating the polymerization reaction of the polymerizable liquid crystal, and a photopolymerization initiator is preferred because it can initiate the polymerization reaction under lower temperature conditions. Specifically, photopolymerization initiators capable of generating active radicals or acids under the action of light are exemplified, and among these, photopolymerization initiators that generate radicals under the action of light are preferred.

Polymerization initiators include benzoin compounds, benzophenone compounds, alkylphenone compounds, acylphosphine oxide compounds, triazine compounds, iodonium salts, and sulfonium salts.

Benzoin compounds include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether and benzoin isobutyl ether.

Benzophenone compounds include benzophenone, o-benzoylmethylbenzoate, 4-phenylbenzophenone, 4-benzoyl-4'-methyldiphenyl sulfide, 3,3',4,4'-tetra(tert-butylperoxycarbonyl)benzophenone, and 2,4,6-trimethylbenzophenone.

Examples of alkylphenone compounds include diethoxyacetophenone, 2-methyl-2-morpholino-1-(4-methylthiophenyl)propan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butan-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1,2-diphenyl-2,2-dimethoxyethane-1-one, 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]propan-1-one, 1-hydroxycyclohexyl phenyl ketone, and oligomers of 2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propan-1-one.

Examples of acylphosphine oxide compounds include 2,4,6-trimethylbenzoyldiphenylphosphine oxide and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

Triazine compounds include 2,4-bis(trichloromethyl)-6-(4-methoxyphenyl)-1,3,5-triazine, 2,4-bis(trichloromethyl)-6-(4-methoxynaphthyl)-1,3,5-triazine, 2,4-bis(trichloromethyl)-6-(4-methoxystyryl)-1,3,5-triazine, and 2,4-bis(trichloromethyl)-6-[2-(5-methylfuran-2-yl)ethenyl] -1,3,5-triazine, 2,4-bis(trichloromethyl)-6-[2-(furan-2-yl)ethenyl]-1,3,5-triazine, 2,4-bis(trichloromethyl)-6-[2-(4-diethylamino-2-methylphenyl)ethenyl]-1,3,5-triazine, and 2,4-bis(trichloromethyl)-6-[2-(3,4-dimethoxyphenyl)ethenyl]-1,3,5-triazine.

Commercially available polymerization initiators can be used. Commercially available polymerization initiators include "Irgacure (registered trademark) 907", "Irgacure (registered trademark) 184", "Irgacure (registered trademark) 651", "Irgacure (registered trademark) 819", "Irgacure (registered trademark) 250", "Irgacure (registered trademark) 369" (Ciba Japan Co., Ltd.); "Seikuol (registered trademark) BZ", "Seikuol (registered trademark) Z", "Seikuol (registered trademark) 100", "Seikuol (registered trademark) 200", "Seikuol (registered trademark) 1 ... Examples include "BEE (trademark)" (Seiko Chemical Co., Ltd.); "Kayacure (registered trademark) BP100" (Nippon Kayaku Co., Ltd.); "Kayacure (registered trademark) UVI-6992" (Dow Corporation); "ADEKA Optomer SP-152", "ADEKA Optomer SP-170" (ADEKA Corporation); "TAZ-A", "TAZ-PP" (Nippon SiberHegner Co., Ltd.); and "TAZ-104" (Sanwa Chemical Co., Ltd.).

When the polymerizable liquid crystal composition contains a polymerization initiator, the content can be adjusted appropriately depending on the type and amount of polymerizable liquid crystal contained in the composition, but is preferably 0.1 to 30 parts by mass, more preferably 0.5 to 10 parts by mass, and even more preferably 0.5 to 8 parts by mass, per 100 parts by mass of polymerizable liquid crystal. If the content of the polymerization initiator is within this range, polymerization can be performed without disturbing the alignment of the polymerizable liquid crystal.

When the polymerizable liquid crystal composition contains a photopolymerization initiator, the composition may further contain a photosensitizer. Examples of photosensitizers include xanthone compounds such as xanthone and thioxanthone (e.g., 2,4-diethylthioxanthone, 2-isopropylthioxanthone, etc.); anthracene compounds such as anthracene and alkoxy group-containing anthracene (e.g., dibutoxyanthracene, etc.); phenothiazine and rubrene.

When the polymerizable liquid crystal composition contains a photopolymerization initiator and a photosensitizer, the polymerization reaction of the polymerizable liquid crystal contained in the composition can be further promoted. The amount of the photosensitizer used can be adjusted appropriately depending on the type and amount of the photopolymerization initiator and the polymerizable liquid crystal, but is preferably 0.1 to 30 parts by mass, more preferably 0.5 to 10 parts by mass, and even more preferably 0.5 to 8 parts by mass, relative to 100 parts by mass of the polymerizable liquid crystal.

In order to make the polymerization reaction of the polymerizable liquid crystal proceed more stably, the polymerizable liquid crystal composition may contain an appropriate amount of a polymerization inhibitor, which makes it easier to control the degree of progress of the polymerization reaction of the polymerizable liquid crystal.

Polymerization inhibitors include radical scavengers such as hydroquinone, alkoxy group-containing hydroquinone, alkoxy group-containing catechol (e.g., butylcatechol), pyrogallol, and 2,2,6,6-tetramethyl-1-piperidinyloxy radical; thiophenols; β-naphthylamines, and β-naphthols.

When the polymerizable liquid crystal composition contains a polymerization inhibitor, the content can be adjusted as appropriate depending on the type and amount of polymerizable liquid crystal, the amount of photosensitizer used, etc., but is preferably 0.1 to 30 parts by mass, more preferably 0.5 to 10 parts by mass, and even more preferably 0.5 to 8 parts by mass, per 100 parts by mass of polymerizable liquid crystal. If the content of the polymerization inhibitor is within this range, polymerization can be performed without disturbing the alignment of the polymerizable liquid crystal.

[Method of manufacturing phase difference plate]
When manufacturing a retardation plate, the first retardation layer, the second retardation layer, and the third retardation layer may be formed in any order. Also, the order in which the layer A and the layer B in the first retardation layer are formed may be any order.

A layer A may be formed on a substrate with or without an alignment film, a layer B may be formed on the layer A with or without an alignment film, and a second retardation layer may be formed on the layer B with or without an alignment film.
On the substrate, a layer B may be formed with or without an alignment film, a layer A may be formed with or without an alignment film on the layer B, and a second retardation layer may be formed with or without an alignment film on the layer A.
A second retardation layer may be formed on a substrate with or without an alignment film, a layer A may be formed on the second retardation layer with or without an alignment film, and a layer B may be formed on the layer A with or without an alignment film.
A second retardation layer may be formed on a substrate with or without an alignment film, a layer B may be formed on the second retardation layer with or without an alignment film, and a layer A may be formed on the layer B with or without an alignment film.
A layer A may be formed on one surface of the substrate with or without an alignment film, a layer B may be formed on the layer A with or without an alignment film, and a second retardation layer may be formed on the other surface of the substrate with or without an alignment film.
A layer B may be formed on one surface of the substrate with or without an alignment film, a layer A may be formed on the layer B with or without an alignment film, and a second retardation layer may be formed on the other surface of the substrate with or without an alignment film.

When layer B is formed on layer A with or without an alignment film, or when layer A is formed on layer B with or without an alignment film, a protective layer may be provided between layer A and layer B. Also, when layer A is formed on the second retardation layer with or without an alignment film, when layer A is formed on the second retardation layer with or without an alignment film, when the second retardation layer is formed on layer A with or without an alignment film, or when the second retardation layer is formed on layer B with or without an alignment film, a protective layer may be provided between the second retardation layer and layer A or layer B.

A first retardation layer may be formed on a substrate with or without an alignment film, a second retardation layer may be formed on the first retardation layer with or without an alignment film, and a third retardation layer may be formed on the second retardation layer with or without an alignment film.
A third retardation layer may be formed on the substrate with or without an alignment film, a second retardation layer may be formed on the third retardation layer with or without an alignment film, and a first retardation layer may be formed on the second retardation layer with or without an alignment film. A first retardation layer may be formed on one side of the substrate with or without an alignment film, a second retardation layer may be formed on the first retardation layer with or without an alignment film, and a third retardation layer may be formed on the other side of the substrate with or without an alignment film.
A second retardation layer may be formed on one surface of the substrate with or without an alignment film, a first retardation layer may be formed on the second retardation layer with or without an alignment film, and a third retardation layer may be formed on the other surface of the substrate with or without an alignment film.
A third retardation layer may be formed on one surface of the substrate with or without an alignment film, a second retardation layer may be formed on the third retardation layer with or without an alignment film, and a first retardation layer may be formed on the other surface of the substrate with or without an alignment film.
A second retardation layer may be formed on one surface of the substrate with or without an alignment film, a third retardation layer may be formed on the second retardation layer with or without an alignment film, and a first retardation layer may be formed on the other surface of the substrate with or without an alignment film.

A first retardation layer may be formed on a substrate with or without an alignment film, and a second retardation layer may be formed on the first retardation layer with or without an alignment film.
A second retardation layer may be formed on one surface of the substrate with or without an alignment film, and a first retardation layer may be formed on the second retardation layer with or without an alignment film.
The second retardation layer may be formed on one surface of the substrate with or without an alignment film, and the first retardation layer may be formed on the other surface of the substrate with or without an alignment film.

When the second phase difference layer is formed on the first phase difference layer with or without an alignment film, or when the first phase difference layer is formed on the second phase difference layer with or without an alignment film, a protective layer may be provided between the first phase difference layer and the second phase difference layer. Also, when the third phase difference layer is formed on the second phase difference layer with or without an alignment film, or when the second phase difference layer is formed on the third phase difference layer with or without an alignment film, a protective layer may be provided between the second phase difference layer and the third phase difference layer.

(Protective Layer)
The protective layer is preferably formed from a protective layer-forming composition that contains a water-soluble polymer, such as an acrylic oligomer or polymer made of a multifunctional acrylate (methacrylate), urethane acrylate, polyester acrylate, or epoxy acrylate, polyvinyl alcohol, an ethylene-vinyl alcohol copolymer, polyvinylpyrrolidone, starches, methyl cellulose, carboxymethyl cellulose, or sodium alginate, and a solvent.

The solvent contained in the composition for forming the protective layer may be the same as the solvent described above. Among them, at least one solvent selected from the group consisting of water, alcohol solvents, and ether solvents is preferred in that it does not dissolve the layer that forms the protective layer. Examples of the alcohol solvent include methanol, ethanol, butanol, ethylene glycol, isopropyl alcohol, propylene glycol, ethylene glycol methyl ether, ethylene glycol butyl ether, and propylene glycol monomethyl ether. Examples of the ether solvent include ethylene glycol monomethyl ether acetate and propylene glycol monomethyl ether acetate. Among them, ethanol, isopropyl alcohol, propylene glycol monomethyl ether, and propylene glycol monomethyl ether acetate are preferred.

The thickness of the protective layer is usually 20 μm or less. The thickness of the protective layer is preferably 0.5 μm or more and 10 μm or less, and more preferably 1 μm or more and 5 μm or less. The thickness of the protective layer can usually be determined by measurement using an interference film thickness meter, a laser microscope, or a stylus film thickness meter.

Next, a method for continuously manufacturing a retardation plate will be described. A suitable method for continuously manufacturing the present optical film is a roll-to-roll method. Here, a method for manufacturing a retardation layer formed by polymerizing a polymerizable liquid crystal will be described. However, instead of the retardation layer formed by polymerizing a polymerizable liquid crystal, a retardation layer made of a stretched film may be used. In this case, "applying a polymerizable liquid crystal composition" in the following manufacturing process may be read as "laminating a stretched film".
In addition, a manufacturing method for a representative configuration will be exemplified below, but other configurations may be carried out in accordance with the manufacturing method below.

(1) preparing a roll in which a substrate is wound around a core;
(2) continuously delivering the substrate from the roll;
(3) continuously forming an alignment film on the substrate;
(4) applying a polymerizable liquid crystal composition onto the alignment film to continuously form a first retardation layer;
(5) A step of continuously forming a protective layer on the first retardation layer obtained in (4);
(6) A step of continuously forming an alignment film on the protective layer obtained in (5);
(7) A step of applying a polymerizable liquid crystal composition onto the alignment film obtained in (6) above to continuously form a second retardation layer;
(8) A method of sequentially winding the optical film obtained continuously on a second core to obtain a second roll. Note that steps (3), (5) and (6) may be omitted as necessary, and in this case, "on the alignment film" in step (4) is replaced with "on the substrate", "the protective layer obtained in (5)" in step (6) is replaced with "the first retardation layer", and "the alignment film obtained in (6)" in step (7) is replaced with "the first retardation layer" or "the protective layer obtained in (5)". In addition, in order to suppress wrinkles and curls during transport, a protective film may be attached during film transport in each step.

Also,
(1a) preparing a roll having a substrate wound around a core;
(2a) continuously delivering the substrate from the roll;
(3a) continuously forming an alignment film on the substrate;
(4a) applying a polymerizable liquid crystal composition onto the alignment film to continuously form a second retardation layer;
(5a) a step of continuously forming a protective layer on the second retardation layer obtained in (4a);
(6a) a step of continuously forming an alignment film on the protective layer obtained in (5a);
(7a) a step of applying a polymerizable liquid crystal composition onto the alignment film obtained in (6a) to continuously form a first retardation layer;
(8a) A method of sequentially winding the optical film obtained continuously on a second core to obtain a second roll is also included. Note that steps (3a), (5a) and (6a) may be omitted as necessary, and in this case, "on the alignment film" in step (4a) is replaced with "on the substrate", "the protective layer obtained in (5a)" in step (6a) is replaced with "the second retardation layer", and "the alignment film obtained in (6a)" in step (7a) is replaced with "the second retardation layer" or "the protective layer obtained in (5a)". In addition, in order to suppress wrinkles and curls during transport, a protective film may be attached during film transport in each step.

Also,
(1b) preparing a roll having a substrate wound around a core;
(2b) continuously delivering the substrate from the roll;
(3b) continuously forming an alignment film on the substrate;
(4b) applying a polymerizable liquid crystal composition onto the alignment film to continuously form a first retardation layer;
(5b) A step of continuously forming an alignment film on the substrate surface opposite to the first retardation layer obtained in (4b);
(6b) a step of applying a polymerizable liquid crystal composition onto the alignment film obtained in (5b) to continuously form a second retardation layer;
(7b) A method of sequentially winding the optical film obtained continuously on a second core to obtain a second roll can also be mentioned. Note that steps (3b) and (5b) may be omitted as necessary, and in this case, "on the alignment film" in step (4b) is replaced with "on the substrate", and "on the alignment film obtained in (5b)" in step (6b) is replaced with "the substrate surface opposite to the first retardation layer obtained in (4b)". In addition, in order to suppress wrinkles and curls during transport, a protective film may be attached during film transport in each step.

Also,
(1c) preparing a roll having a transparent substrate wound around a core;
(2c) continuously delivering the transparent substrate from the roll;
(3c) continuously forming an alignment film on the transparent substrate;
(4c) applying a polymerizable liquid crystal composition onto the alignment film to continuously form a second retardation layer;
(5c) A step of continuously forming an alignment layer on the substrate surface opposite to the second retardation layer obtained in (4c);
(6c) applying a polymerizable liquid crystal composition onto the alignment film obtained in (5c) to continuously form a first retardation layer;
(7c) A method of sequentially winding the optical film obtained continuously on a second core to obtain a second roll can also be mentioned. Note that steps (3c) and (5c) may be omitted as necessary, and in this case, "on the alignment film" in step (4c) is replaced with "on the substrate", and "on the alignment film obtained in (5c)" in step (6c) is replaced with "the substrate surface opposite to the second retardation layer obtained in (4c)". In addition, in order to suppress wrinkles and curls during transport, a protective film may be attached during film transport in each step.

Also,
(1d) preparing a roll having a substrate wound around a core;
(2d) continuously delivering the substrate from the roll;
(3d) continuously forming an alignment film on the substrate;
(4d) applying a polymerizable liquid crystal composition onto the alignment film to continuously form a layer A;
(5d) a step of continuously forming a protective layer on the layer A obtained in (4d);
(6d) a step of continuously forming an alignment film on the protective layer obtained in (5d);
(7d) a step of applying a polymerizable liquid crystal composition onto the alignment film obtained in (6d) to continuously form a layer B;
(8d) a step of continuously forming a protective layer on the layer B obtained in (7d);
(9d) a step of continuously forming an alignment film on the protective layer obtained in (8d);
(10d) applying a polymerizable liquid crystal composition onto the alignment film obtained in (9d) to continuously form a second retardation layer;
(11d) A method of sequentially winding the optical film obtained continuously on a second core to obtain a second roll. Note that steps (3d), (5d), (6d), (8d), and (9d) may be omitted as necessary, and in this case, "on the alignment film" in step (4d) is replaced with "on the substrate", "the protective layer obtained in (5d)" in step (6d) is replaced with "the layer A", "the alignment film obtained in (6d)" in step (7d) is replaced with "the layer A" or "the protective layer obtained in (5d)", "the protective layer obtained in (8d)" in step (9d) is replaced with "the layer B", and "the alignment film obtained in (9d)" in step (10d) is replaced with "the layer B" or "the protective layer obtained in (9d)". In addition, in order to suppress wrinkles and curls during transport, a protective film may be attached when the film is transported in each step.

Also,
(1e) preparing a roll having a substrate wound around a core;
(2e) continuously delivering the substrate from the roll;
(3e) continuously forming an alignment film on the substrate;
(4e) applying a polymerizable liquid crystal composition onto the alignment film to continuously form a first retardation layer;
(5e) a step of continuously forming a protective layer on the first retardation layer obtained in (4e);
(6e) a step of continuously forming an alignment film on the protective layer obtained in (5e);
(7e) A step of applying a polymerizable liquid crystal composition onto the alignment film obtained in (6e) to continuously form a second retardation layer;
(8e) A step of continuously forming an alignment film on the substrate surface opposite to the first retardation layer obtained in (4e);
(9e) a step of applying a polymerizable liquid crystal composition onto the alignment film obtained in (8e) to continuously form a third retardation layer;
(10e) A method in which the step of winding the continuously obtained optical film around a second core to obtain a second roll is also included.
Steps (3e), (5e) and (8e) may be omitted as necessary. In this case, "on the alignment film" in step (4e) is replaced with "on the substrate", "the protective layer obtained in (5e)" in step (6e) is replaced with "the first retardation layer obtained in (4e)", and "on the alignment film obtained in (8e)" in step (9e) is replaced with "the substrate surface opposite to the first retardation layer obtained in (4e)". In addition, in order to suppress wrinkles and curls during transport, a protective film may be attached during film transport in each step. In addition, in order to suppress wrinkles and curls during transport, a protective film may be attached during film transport in each step.

Figure 2 is a schematic cross-sectional view showing a specific example of a retardation plate 30. Figure 2(a) is a retardation plate 30 in which a first retardation layer 31 and a second retardation layer 32 are laminated. Figure 2(b) is a retardation plate 30 in which a substrate 33, a first retardation layer 31, and a second retardation layer 32 are laminated in this order. Figure 2(c) is a retardation plate 30 in which a substrate 33, a second retardation layer 32, and a first retardation layer 31 are laminated in this order. Figure 2(d) is a retardation plate 30 in which a first retardation layer 31, a substrate 33, and a second retardation layer are laminated in this order.

By removing the substrate 33 from the retardation film 30, a retardation film 30 without a substrate (Figure 2(a)) can be obtained.

The retardation film 30 can also be manufactured by bonding a substrate 33 having a first retardation layer 31 and a substrate 33' having a second retardation layer 32 together. Specific examples are shown in Fig. 2(e), Fig. 2(f) and Fig. 2(g). A bonding layer (hereinafter, the bonding layer used for bonding between layers in the retardation film 30 is also referred to as the "third bonding layer") can be used for bonding.

Figure 3 is a schematic cross-sectional view showing a specific example of a retardation plate 30 in which the first retardation layer is composed of layers A and B, or in which a third retardation layer is included. Figure 3(a) is a retardation plate 30 in which a layer A34, a layer B35, and a second retardation layer 32 are laminated in this order. Figure 3(b) is a retardation plate 30 in which a layer B35, a layer A34, and a second retardation layer 32 are laminated in this order. Figure 3(c) is a retardation plate 30 in which a substrate 33, a layer A34, a layer B35, and a second retardation layer 32 are laminated in this order. Figure 3(d) is a retardation plate 30 in which a substrate 33, a first retardation layer 31, a second retardation layer 32, and a third retardation layer 38 are laminated in this order. Figure 3(e) is a retardation plate 30 in which a substrate 33, a layer B35, a layer A34, and a second retardation layer 32 are laminated in this order. FIG. 3(f) shows a retardation plate 30 in which a substrate 33, a third retardation layer 38, a second retardation layer 32, and a first retardation layer 31 are laminated in this order. FIG. 3(g) shows a retardation plate 30 in which a substrate 33, a second retardation layer 32, a layer B35, and a layer A34 are laminated in this order. FIG. 3(h) shows a retardation plate 30 in which a substrate 33, a second retardation layer 32, a layer A34, and a layer B35 are laminated in this order. A retardation plate 30 without a substrate 33 (FIGS. 3(a) and (b)) can also be obtained by peeling off the substrate 33 from a retardation plate 30 having the substrate 33.

In the case of a configuration including the first phase difference layer 31, the layer A34, and the layer B35, or in the case of having the third phase difference layer 33, each layer may be laminated on both sides of the substrate 33. As a specific example, for example, FIG. 3(i) is a phase difference plate 30 in which the second phase difference layer 32, the substrate 33, the layer A34, and the layer B35 are laminated in this order. FIG. 3(j) is a phase difference plate 30 in which the second phase difference layer 32, the substrate 33, the layer B35, and the layer A34 are laminated in this order. FIG. 3(k) is a phase difference plate 30 in which the first phase difference layer 31, the substrate 33, the third phase difference layer 38, and the second phase difference layer 32 are laminated in this order. FIG. 3(l) is a phase difference plate 30 in which the first phase difference layer 31, the substrate 33, the second phase difference layer 32, and the third phase difference layer 38 are laminated in this order. FIG. 3(m) shows a retardation plate 30 in which a third retardation layer 38, a substrate 33, a first retardation layer 31, and a second retardation layer 32 are laminated in this order. FIG. 3(n) shows a retardation plate 30 in which a third retardation layer 38, a substrate 33, a second retardation layer 32, and a first retardation layer 31 are laminated in this order. The second retardation layer 32, layer A 34, and layer B 35 may be formed by direct coating on each layer, or each layer may be laminated by lamination after production, or each layer may be laminated by sequential transfer.

The retardation plate 30 may have another layer interposed between the first retardation layer 31 and the second retardation layer 32, or may have no other layer interposed between the first retardation layer 31 and the second retardation layer 32. Examples of the other layer interposed include the base material 33, the above-mentioned protective layer, the above-mentioned alignment film, and the third bonding layer. In the retardation plate 30, when the first retardation layer 31 and the second retardation layer 32 have only an alignment film as the other layer interposed between them, or when the retardation plate 30 has no other layer interposed between them, the piercing elastic modulus is likely to be 35 g/mm or more. In this specification, the layer interposed between the first retardation layer 31 and the second retardation layer 32 means a layer interposed between the outermost surface of the first retardation layer 31 on the second retardation layer 32 side and the outermost surface of the second retardation layer 32 on the first retardation layer 31 side. Therefore, when the first phase difference layer 31 is composed of a layer A and a layer B, the layer interposed between the layer A and the layer B is not considered to be a layer interposed between the first phase difference layer 31 and the second phase difference layer 32.

[Second lamination layer, third lamination layer]
The second bonding layer is a bonding layer used to bond layers together within the linear polarizer 10, and the third bonding layer is a bonding layer used to bond layers together within the retarder 30. Hereinafter, the term "bonding layer" includes both the second bonding layer and the third bonding layer.

The attachment layer is a pressure-sensitive adhesive layer formed using a pressure-sensitive adhesive composition, or an adhesive layer formed using an adhesive composition. The second attachment layer and the third attachment layer are preferably adhesive layers from the viewpoint of suppressing thermal shrinkage behavior when heat is applied.

When the pasting layer is an adhesive layer, the adhesive composition used to form the adhesive layer is not particularly limited as long as it can satisfy the moisture permeability. The adhesive composition may contain, for example, a polymer such as a rubber-based polymer, a (meth)acrylic-based polymer, a urethane-based polymer, a polyester-based polymer, a silicone-based polymer, a polyvinyl ether-based polymer, a polyvinyl alcohol-based polymer, a polyolefin-based polymer, a vinyl alkyl ether-based polymer, a polyvinyl pyrrolidone-based polymer, a poly(meth)acrylamide-based polymer, or a cellulose-based polymer as a main component. In this specification, the main component refers to a component that contains 50% by mass or more of the total solid content of the adhesive composition. The adhesive composition may be an active energy ray curable type or a heat curable type. The adhesive composition is preferably a rubber-based polymer. The above-mentioned "(meth)acrylic" means "at least one of acrylic and methacrylic". The same applies to the notation "(meth)acrylate".

Examples of rubber-based polymers include natural rubber; synthetic rubbers such as polyisobutylene rubber (PIB), isoprene rubber (IR), isobutylene-isoprene rubber (IIR), normal butylene-isobutylene copolymer rubber, butadiene rubber (BR), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), styrene-butadiene rubber (SBR), styrene-isoprene rubber (SIR), styrene-isoprene-styrene block copolymer rubber (SIBS), styrene-ethylene-butylene-styrene block copolymer rubber (SEBS), styrene-ethylene-propylene-styrene block copolymer rubber (SEPS), styrene-butadiene-styrene block copolymer rubber (SBS), and styrene-ethylene-propylene block copolymer rubber (SEP). Preferred rubber-based polymers are polyisobutylene rubber (PIB), isobutylene-isoprene rubber (IIR), and normal butylene-isobutylene copolymer rubber, with polyisobutylene rubber (PIB) being more preferred.

As the (meth)acrylic polymer, a polymer or copolymer having one or more monomers of (meth)acrylic acid esters such as butyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate is preferably used. It is preferable to copolymerize a polar monomer into the base polymer. Examples of polar monomers include monomers having a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, etc., such as (meth)acrylic acid, 2-hydroxypropyl (meth)acrylate, hydroxyethyl (meth)acrylate, (meth)acrylamide, N,N-dimethylaminoethyl (meth)acrylate, and glycidyl (meth)acrylate.

An active energy ray curable adhesive composition is an adhesive composition that has the property of being cured when exposed to active energy rays such as ultraviolet rays or electron beams, that has adhesiveness even before exposure to active energy rays and can be adhered to an adherend such as a film, and that has the property of being cured by exposure to active energy rays and capable of adjusting the adhesive strength. The active energy ray curable adhesive composition is preferably an ultraviolet ray curable type. The active energy ray curable adhesive composition further contains an active energy ray polymerizable compound in addition to a base polymer and a crosslinking agent. If necessary, it may further contain a photopolymerization initiator, a photosensitizer, etc.

In addition to the polymer, the adhesive composition may contain additives such as a solvent, a tackifier, a softener, a filler (metal powder or other inorganic powder, etc.), an antioxidant, an ultraviolet absorber, a dye, a pigment, a colorant, an antifoaming agent, a corrosion inhibitor, and a photopolymerization initiator. When an active energy ray curable adhesive composition is used, the formed adhesive layer can be irradiated with active energy rays to form a cured product having the desired degree of cure.

The adhesive layer can be formed by applying a diluted solution of the adhesive composition in an organic solvent onto a substrate and drying it.

When the lamination layer is an adhesive layer, the adhesive composition used to form the adhesive layer is not particularly limited as long as it can satisfy the above moisture permeability requirements. Examples of adhesive compositions include water-based adhesives, active energy ray curing adhesives, natural rubber adhesives, α-olefin adhesives, urethane resin adhesives, ethylene-vinyl acetate resin emulsion adhesives, ethylene-vinyl acetate resin hot melt adhesives, epoxy resin adhesives, vinyl chloride resin solvent-based adhesives, chloroprene rubber adhesives, cyanoacrylate adhesives, silicone adhesives, styrene-butadiene rubber solvent-based adhesives, nitrile rubber adhesives, nitrocellulose adhesives, reactive hot melt adhesives, phenolic resin adhesives, modified silicone adhesives, polyester hot melt adhesives, polyamide resin hot melt adhesives, polyimide adhesives, polyurethane resin hot melt adhesives, polyolefin resin hot melt adhesives, polyvinyl acetate resin solvent-based adhesives, polystyrene resin solvent-based adhesives, polyvinyl alcohol adhesives, polyvinylpyrrolidone resin adhesives, polyvinyl butyral adhesives, polybenzimidazole adhesives, polymethacrylate resin solvent-based adhesives, melamine resin adhesives, urea resin adhesives, and resorcinol adhesives. Such adhesives can be used alone or in combination of two or more types.

Examples of water-based adhesives include aqueous polyvinyl alcohol resin solutions and water-based two-liquid urethane emulsion adhesives. Examples of active energy ray curing adhesives are adhesives that are cured by irradiation with active energy rays such as ultraviolet rays, and include those containing a polymerizable compound and a photopolymerization initiator, those containing a photoreactive resin, and those containing a binder resin and a photoreactive crosslinking agent. Examples of the polymerizable compounds include photopolymerizable monomers such as photocurable epoxy monomers, photocurable (meth)acrylic monomers, and photocurable urethane monomers, as well as oligomers derived from these monomers. Examples of the photopolymerization initiators include those containing a substance that generates active species such as neutral radicals, anion radicals, and cation radicals when irradiated with active energy rays such as ultraviolet rays.

The thickness of the lamination layer is not particularly limited, but when the lamination layer is a pressure-sensitive adhesive layer, it is preferably 5 μm or more, may be 15 μm or more, may be 20 μm or more, may be 25 μm or more, and is usually 200 μm or less, may be 100 μm or less, or may be 50 μm or less. When the lamination layer is an adhesive layer, the thickness of the lamination layer is preferably 0.01 μm or more, may be 0.05 μm or more, may be 0.5 μm or more, and is preferably 5 μm or less, may be 3 μm or less, or may be 2 μm or less.

[Method of manufacturing polarizing plate]
The polarizing plate of this embodiment can be obtained by bonding the above-mentioned retardation plate and the above-mentioned linear polarizing plate together using a first bonding layer. When the first retardation layer of the retardation plate is composed of only one layer and has only one slow axis, it is preferable to set the transmission axis of the linear polarizing plate to be substantially 45° with respect to the slow axis (optical axis) of the first retardation layer of the retardation plate. Substantially 45° is usually in the range of 45±5°. In such an angle arrangement, the polarizing plate can function as a circular polarizing plate.

Methods for attaching a retardation plate without a substrate to a linear polarizing plate include a method of attaching a retardation plate from which the substrate has been removed (peeled off) to a linear polarizing plate using a first attachment layer, and a method of attaching a retardation plate to a linear polarizing plate using a first attachment layer and then removing (peeling off) the substrate. In this embodiment, a form in which the substrate is removed after the retardation plate is attached to the linear polarizing plate is preferable. According to the present invention, even in such a form, damage to the retardation layer of the retardation plate can be suppressed when removing the substrate.

The first attachment layer may be formed directly by applying a pressure-sensitive adhesive to the retardation layer side of the retardation plate, or may be formed directly by applying a pressure-sensitive adhesive to the linear polarizer side, or the first attachment layer formed in advance on another substrate may be interposed between the linear polarizer and the retardation plate. If there is an alignment film between the substrate and the retardation layer, the alignment film may be removed together with the substrate.

A substrate having functional groups on its surface that form chemical bonds with a retardation layer or an alignment film, etc., tends to form chemical bonds with the retardation layer or alignment film, etc., and become difficult to remove. Therefore, when removing the substrate by peeling, a substrate with few functional groups on the surface is preferable, and a substrate that has not been subjected to a surface treatment that forms functional groups on the surface is also preferable.

Also, since an alignment film having functional groups that form chemical bonds with a substrate tends to have a strong adhesive force between the substrate and the alignment film, when the substrate is to be removed by peeling, an alignment film having fewer functional groups that form chemical bonds with the substrate is preferred. Also, it is preferable that the alignment film does not contain a reagent that crosslinks the substrate and the alignment film, and further, it is preferable that the solution of the alignment polymer composition and the photoalignment film forming composition does not contain a component such as a solvent that dissolves the substrate.

Also, an alignment film having a functional group that forms a chemical bond with the retardation layer tends to have a strong adhesive force between the retardation layer and the alignment film. Therefore, when removing the alignment film together with the substrate, an alignment film having a small number of functional groups that form a chemical bond with the retardation layer is preferable. Also, it is preferable that the retardation layer and the alignment film do not contain a reagent that crosslinks the retardation layer and the alignment film.

In addition, a retardation layer having a functional group that forms a chemical bond with the alignment film tends to have a strong adhesive force between the alignment film and the retardation layer. Therefore, when removing the substrate or removing the alignment film together with the substrate, a retardation layer having a small number of functional groups that form a chemical bond with the substrate or alignment film is preferred. In addition, the polymerizable liquid crystal composition preferably does not contain a reagent that crosslinks the substrate or alignment film with the retardation layer.

For example, a polarizing plate having the configuration shown in FIG. 1 in which the linear polarizing plate 10, the first adhesive layer 21, the first phase difference layer 31, and the second phase difference layer 32 are laminated in this order of the retardation plate 30 can be manufactured by attaching a first adhesive layer 21 to the surface of the first phase difference layer 31 of the retardation plate 30 in which the substrate, the second phase difference layer 32, and the first phase difference layer 31 are laminated in this order, and then removing the substrate of the retardation plate 30. Also, a polarizing plate having the linear polarizing plate, the second phase difference layer, and the first phase difference layer laminated in this order can be manufactured by attaching a first adhesive layer to the surface of the second phase difference layer of the retardation plate in which the substrate, the first phase difference layer, and the second phase difference layer are laminated in this order, and then removing the substrate of the retardation plate. From the viewpoint of thinning, it is preferable to peel off the substrate.

When the first retardation layer includes the layer A and the layer B, or when the first retardation layer includes the third retardation layer, there is a restriction on the lamination direction of each layer.
Specifically, when layer A having a phase difference of λ/4 and layer B having a phase difference of λ/2 are laminated, layer B is first formed so that the slow axis of layer B is at 75° with respect to the absorption axis of the linear polarizer, and then layer A is formed so that the slow axis of layer A is at 15°.
In addition, when the first retardation layer has a phase difference of λ/4 and the third retardation layer has a phase difference of λ/2, the third retardation layer is first formed so that the slow axis of the third retardation layer is 75° with respect to the absorption axis of the linear polarizer, and then the first retardation layer is formed so that the slow axis of the first retardation layer is 15°. There is no limitation on the position of the second retardation layer, but it is necessary that the linear polarizer, layer B and layer A are laminated in this order, or the linear polarizer, the third retardation layer and the first retardation layer are laminated in this order. By laminating in this way, the obtained polarizer can function as a wideband circular polarizer. Here, there is no limitation on the axial angle forming Layer A and Layer B. For example, as described in JP-A-2004-126538, it is known that the function of a broadband λ/4 plate can be exhibited even if the slow axis angles of Layer A and Layer B are 30° and −30°, or 45° and −45° with respect to the absorption axis of the polarizing plate. Therefore, it is possible to laminate the layers in a desired manner.

[Image display device]
Fig. 4 is a schematic cross-sectional view showing an example of an image display device according to the present embodiment. As shown in Fig. 4, the image display device 2 has, from the front side, the polarizing plate 1 shown in Fig. 1 and an image display panel 40, in this order. In the image display device 2, the polarizing plate 1 is disposed in an orientation such that the linear polarizing plate 10 side is closer to the front than the retardation plate 30.

When the polarizing plate 1 is a circular polarizing plate, in the image display device 2, the incident light from the outside is divided into light reflected by the polarizing plate 1 and light transmitted through the polarizing plate 1. The polarizing plate 1 may have an anti-reflection layer on the front surface, and by providing an anti-reflection layer, the light reflected on the surface of the polarizing plate 1 (hereinafter also referred to as "externally reflected light") can be reduced. The light transmitted through the polarizing plate 1 is reflected by the image display panel 40 and becomes reflected light (hereinafter also referred to as "internal reflected light") and is absorbed by the polarizing plate 1. Although it is desirable that all of the internally reflected light is absorbed by the polarizing plate 1, a portion of the internally reflected light is emitted from the front surface (hereinafter such light is also referred to as "emitted internally reflected light").

The polarizing plate 1 may be configured as a polarizing plate with an adhesive layer by having an adhesive layer on the rear surface that can be used to attach the polarizing plate 1 to the image display panel 40.

<Other Layers That the Image Display Device May Have>
The image display device 2 may have layers other than the layers described above. Examples of other layers that the image display device 2 may have are given below.

(Touch sensor panel)
The touch sensor panel is a device (sensor) that detects (senses) a finger or the like that touches the screen of an image display device, and is used as an input means that detects the position of the finger on the screen and inputs the finger to the image display device. The touch sensor panel may be disposed between the polarizing plate 1 and the image display panel 40, or may be disposed on the front side of the polarizing plate 1. As the touch sensor panel, the detection method is not limited as long as it is a sensor that can detect the touched position, and examples of touch sensor panels include resistive film type, electrostatic capacitance coupling type, optical sensor type, ultrasonic type, electromagnetic induction coupling type, surface acoustic wave type, infrared type, etc. Resistive film type and electrostatic capacitance coupling type touch sensor panels are preferably used because of their low cost.

One example of a resistive touch sensor panel is composed of a pair of substrates arranged opposite each other, an insulating spacer sandwiched between the pair of substrates, a transparent conductive film provided as a resistive film on the inner front surface of each substrate, and a touch position detection circuit. In an image display device equipped with a resistive touch sensor panel, when the surface of the front panel is touched, the opposing resistive film shorts out and a current flows through the resistive film. The touch position detection circuit detects the change in voltage at this time, and the touched position is detected.

An example of a capacitive touch sensor panel is composed of a substrate, a transparent electrode for position detection provided on the entire surface of the substrate, and a touch position detection circuit. In an image display device equipped with a capacitive touch sensor panel, when the surface of the front panel is touched, the transparent electrode is grounded via the electrostatic capacitance of the human body at the touched point. The touch position detection circuit detects the grounding of the transparent electrode and detects the touched position. A capacitive touch sensor panel is divided into an active area and an inactive area located on the outer periphery of the active area. The active area is an area corresponding to the area (display section) where the screen is displayed on the display panel and is an area where the user's touch is detected, and the inactive area is an area corresponding to the area (non-display section) where the screen is not displayed on the display device.

The thickness of the touch sensor panel may be, for example, 5 μm or more and 2,000 μm or less, or 5 μm or more and 100 μm or less.

<Flexible image display device>
The image display device may be a flexible image display device. The flexible image display device is a foldable image display device. The flexible image display device includes an optical fingerprint authentication system incorporated therein, a foldable image display element, and the polarizing plate of the present invention. The foldable image display element is, for example, an organic EL display panel. The polarizing plate of the present invention is disposed on the viewing side of the organic EL display panel, and is configured to be foldable. The polarizing plate for the flexible image display device may further include a front panel and a touch sensor panel.
It is preferable that the front plate, the polarizing plate of the present invention, and the touch sensor panel are laminated in this order from the viewing side, or that the front plate, the touch sensor panel, and the polarizing plate of the present invention are laminated in this order from the viewing side. If a polarizer is present on the viewing side of the touch sensor panel, the pattern of the touch sensor panel becomes difficult to see, and as a result, the visibility of the displayed image is improved. Therefore, it is more preferable to have a configuration in which the polarizing plate of the present invention is provided on the viewing side of the touch sensor panel, that is, the front plate, the polarizing plate of the present invention, and the touch sensor panel are provided in this order. Each member can be laminated using an adhesive, a pressure-sensitive adhesive, or the like. In addition, a light-shielding pattern formed on at least one surface of any of the layers of the front plate, the polarizing plate, and the touch sensor panel can be provided.

In a flexible image display device including, from the viewing side, a front plate, the polarizing plate of the present invention, and a foldable image display panel, the front plate and the polarizing plate of the present invention constitute a front plate-attached polarizing plate including a polarizing plate and a front plate. In this front plate-attached polarizing plate, the front plate is usually disposed on the viewing side of the polarizing plate, and is laminated with the polarizing plate, for example, by a pressure-sensitive adhesive or adhesive.
In a flexible image display device comprising, from the viewing side, a touch sensor panel, the polarizing plate of the present invention, and a foldable image display panel, the touch sensor panel and the polarizing plate of the present invention constitute a polarizing plate with a touch sensor panel comprising a polarizing plate and a touch sensor panel. In a flexible image display device comprising, from the viewing side, the polarizing plate of the present invention, a touch sensor panel, and a foldable image display element, the touch sensor panel and the polarizing plate of the present invention constitute a polarizing plate with a touch sensor panel comprising a polarizing plate and a touch sensor panel. In this polarizing plate with a touch sensor panel, the touch sensor panel may be disposed on the rear side (opposite the viewing side) of the polarizing plate, or may be disposed on the viewing side of the polarizing plate. The touch sensor panel and the polarizing plate are laminated together, for example, with an adhesive or a bonding agent.

The polarizing plate of the present invention can also be used as a polarizing plate with a front plate by laminating a front plate on the viewing side. A polarizing plate with a front plate comprises the polarizing plate of the present invention and a front plate disposed on the viewing side.

(Front panel)
Examples of the front plate include glass and resin film having a hard coat layer on at least one surface. As the glass, for example, highly transparent glass or reinforced glass can be used. In particular, when a thin transparent surface material is used, chemically reinforced glass is preferable. The thickness of the glass can be, for example, 100 μm to 5 mm.

A front panel comprising a hard coat layer on at least one side of a resin film can have flexible properties, rather than being rigid like existing glass. The thickness of the hard coat layer is not particularly limited, and may be, for example, 5 μm to 100 μm.

The resin film may be a film formed of a polymer such as norbornene, a cycloolefin derivative having a monomer unit containing a cycloolefin such as a polycyclic norbornene monomer, cellulose (diacetyl cellulose, triacetyl cellulose, acetyl cellulose butyrate, isobutyl ester cellulose, propionyl cellulose, butyryl cellulose, acetylpropionyl cellulose), ethylene-vinyl acetate copolymer, polycycloolefin, polyester, polystyrene, polyamide, polyetherimide, polyacrylic, polyimide, polyamideimide, polyethersulfone, polysulfone, polyethylene, polypropylene, polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl acetal, polyether ketone, polyether ether ketone, polyethersulfone, polymethyl methacrylate, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyurethane, or epoxy. Each of these polymers can be used alone or in a mixture of two or more.
The resin film may be an unstretched film or a stretched film, such as a uniaxially stretched film or a biaxially stretched film. As the resin film, polyamideimide film, polyimide film, uniaxially stretched polyester film, and biaxially stretched polyester film are preferred because of their excellent transparency and heat resistance, cycloolefin derivative film and polymethyl methacrylate film are preferred because of their excellent transparency and heat resistance and their ability to accommodate large-sized films, and triacetyl cellulose and isobutyl ester cellulose films are preferred because of their relative ease of availability as transparent and optically non-anisotropic resin films. The thickness of the resin film is usually 5 to 200 μm, and preferably 20 to 100 μm.

(Light blocking pattern)
The light-shielding pattern is a member also called a bezel, and can be formed on the display element side of the front panel. By providing the light-shielding pattern, it is possible to hide each wiring constituting the display device so that it is not visible to the user. The color and material of the light-shielding pattern are not particularly limited, and the light-shielding pattern can be formed of a resin material having various colors such as black, white, gold, etc. In one embodiment, the thickness of the light-shielding pattern may be 2 μm to 50 μm, preferably 4 μm to 30 μm, and more preferably 6 μm to 15 μm. In addition, a shape can be given to the light-shielding pattern in order to suppress the inclusion of air bubbles and the visibility of the boundary due to a step between the light-shielding pattern and the display part.

The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. The blending amounts expressed as "%" and "parts" in the examples and comparative examples are % by mass and parts by mass unless otherwise specified.

[Evaluation of circularly polarizing plate (durability against substrate peeling)]
An adhesive layer was laminated on the protective film on the outermost surface of the linear polarizing plate of the circular polarizing plate. This was cut to prepare a test piece with a width of 25 mm and a length of about 150 mm. The adhesive layer of the test piece was attached to a glass plate. A peeling tape (width 25 mm x length about 180 mm) was attached to the surface (one side with a width of 25 mm) of the substrate (substrate used to form the second retardation layer) on the outermost surface of the retardation body of the circular polarizing plate. One end of the peeling tape was grasped, and the substrate layer was peeled off using a tensile tester. The peeling speed was both 300 mm/min and 15,000 mm/min. The peeling angle was 180°. When damage occurred to the retardation layer close to the substrate during peeling, it was judged as zipping occurrence (evaluation C), when this phenomenon was not observed, there was no zipping (evaluation A), and when this phenomenon was observed slightly, there was slight zipping (evaluation B).

[Measurement of piercing elastic modulus of retardation plate]
A needle was attached to a handy compression tester "NDG5 piercing tester, needle penetration force measurement specification" manufactured by Kato Tech Co., Ltd. The needle was pierced perpendicularly to the surface from the surface of the second retardation layer side of the retardation body from which the substrate was peeled off from the outermost surface. The stress F (g) just before the sample for the piercing test for the measurement sample broke and the strain S (mm) at that time were calculated, and the piercing elastic modulus (g/mm) was calculated from the formula of stress F (g) / strain S (mm). This operation was performed for each of the five measurement samples, and the average value was taken as the piercing elastic modulus. As the needle, one with a tip diameter of 1 mmφ and 0.5R was used. The needle piercing speed was 0.33 cm/sec. The measurement was performed in a room temperature environment of 23 ° C. and relative humidity 55%.
The above-mentioned method was used to measure the piercing elastic modulus of the retardation plates A, B, and C used in the preparation of the circular polarizing plates of Examples 1 to 6, Comparative Examples 1 and 2, and Reference Example 1 described below. Table 1 shows the measurement results.

[Measurement of tensile modulus of first bonding layer]
The adhesive used as the first bonding layer was coated on one side of a release paper using a coating machine (bar coater, manufactured by Daiichi Rika Co., Ltd.), and a release paper was further laminated on the top surface of the adhesive layer, heat-treated at 90°C for 1 minute, and aged for 7 days under conditions of a temperature of 23°C and a relative humidity of 55%. The laminate was cut into a size of 100 mm in MD length and 50 mm in TD length, and the release papers on both sides were peeled off to obtain an adhesive layer film consisting of only the adhesive layer. The adhesive layer was also cured by a predetermined curing method to obtain a film consisting of only the adhesive layer.

In accordance with JIS K7161:1994 and JIS K7127:1999, the tensile breaking strain was used as the breaking elongation when the test piece did not have a yield point, and the tensile breaking elongation strain was used as the breaking elongation when the test piece had a yield point. The adhesive layer film obtained as described above was clamped at both ends of the MD length direction of the measurement sample with the upper and lower grips of a tensile testing machine (Autograph AG-Xplus test machine manufactured by Shimadzu Corporation) so that the distance between the grips was 5 cm, and the measurement sample was pulled in the MD length direction at a pulling speed of 300 mm/min under an environment of a temperature of 23°C and a relative humidity of 55%, and the tensile modulus of elasticity [Pa] in the MD length direction at a temperature of 23°C and a relative humidity of 55% was calculated.

[Production Example 1: Preparation of a laminate including a first retardation layer]
(i) Preparation of a composition for forming a photo-alignment film 5 parts of a photo-alignment material (weight average molecular weight: 30,000) having the following structure was mixed with 95 parts of cyclopentanone (solvent). The resulting mixture was stirred at 80° C. for 1 hour to obtain a composition for forming a photo-alignment film.

(ii) Preparation of the first retardation layer forming composition The following polymerizable liquid crystal compound A and polymerizable liquid crystal compound B were mixed in a mass ratio of 90: 10. To 100 parts of this mixture, 1.0 part of a leveling agent (F-556; manufactured by DIC Corporation) and 6 parts of a polymerization initiator, 2-dimethylamino-2-benzyl-1-(4-morpholinophenyl)butan-1-one ("Irgacure 369 (Irg369)" manufactured by BASF Japan Ltd.) were added.

Furthermore, N-methyl-2-pyrrolidone (NMP) was added so that the solid content concentration became 13%, and the mixture was stirred at 80°C for 1 hour to obtain a composition for forming the first retardation layer.

Polymerizable liquid crystal compound A was produced by the method described in JP-A-2010-31223. Polymerizable liquid crystal compound B was produced in accordance with the method described in JP-A-2009-173893. The molecular structures of each compound are shown below.

(Polymerizable liquid crystal compound A)

(Polymerizable liquid crystal compound B)

(iii) Preparation of Retardation Layer Substrate A cycloolefin resin film (manufactured by Zeon Corporation, "ZF-14-50") having a thickness of 50 μm was subjected to corona treatment to prepare a retardation layer substrate. The corona treatment was performed using TEC-4AX manufactured by Ushio Inc. The corona treatment was performed once under the conditions of an output of 0.78 kW and a treatment speed of 10 m/min.

(iv) Formation of photo-alignment film The photo-alignment film-forming composition was applied to the retardation layer substrate by a bar coater. The coating film was dried at 80°C for 1 minute, and polarized UV exposure was performed with an integrated light amount of 100 mJ/ ^cm2 using a polarized UV irradiation device (SPOT CURE SP-7; manufactured by Ushio Inc.). The thickness of the obtained horizontal alignment film was measured with a laser microscope (LEXT, manufactured by Olympus Corporation) and found to be 100 nm.

(v) Formation of the first retardation layer Next, in an environment of room temperature 25 ° C. and relative humidity 30%, the composition for forming the first retardation layer was passed through a PTFE membrane filter (manufactured by Advantec Toyo Co., Ltd., product number: T300A025A) having a pore size of 0.2 μm, and applied using a bar coater onto a substrate film with an alignment film kept at 25 ° C. The coating film was dried at 120 ° C. for 1 minute, and then irradiated with ultraviolet light (under a nitrogen atmosphere, wavelength: 365 nm, accumulated light amount at a wavelength of 365 nm: 1000 mJ / cm ² ) using a high-pressure mercury lamp (Uniquer VB-15201BY-A, manufactured by Ushio Electric Co., Ltd.). The thickness of the obtained coating film was measured with a laser microscope (LEXT, manufactured by Olympus Corporation) and was 2 μm.
The retardation values of the obtained first retardation layer were measured to find that Re(450) was 121 nm, Re(550) was 139 nm, and Re(650) was 146 nm.
The relationship between the in-plane retardation values at each wavelength was as follows:
Re(450)/Re(550)=0.87
Re(650)/Re(550)=1.05

[Production Example 2: Preparation of a laminate including a second retardation layer]
(i) Preparation of Oriented Polymer Composition (1) One part of Sunever SE-610 (Nissan Chemical Industries, Ltd.) and 99 parts of 2-butoxyethanol were mixed to obtain an oriented polymer composition (1).

(ii) Preparation of the second retardation layer forming composition 19.2 parts of the polymerizable liquid crystal (BASF, LC242) shown in the figure below, 0.1 parts of a leveling agent (BYK Japan, "BYK-361N"), 0.5 parts of a polymerization initiator (BASF Japan, "Irgacure 907"), 1.1 parts of a reaction additive (BASF Japan, "Laromar LR-9000"), and 79.1 parts of propylene glycol 1-monomethyl ether 2-acetate were mixed. The mixture was stirred at 80 ° C. for 1 hour to obtain a second retardation layer forming composition.

(iii) Preparation of Retardation Layer Substrate A cycloolefin resin film (manufactured by Zeon Corporation, "ZF-14-50") having a thickness of 50 μm was subjected to corona treatment to prepare a retardation layer substrate. The corona treatment was performed using TEC-4AX manufactured by Ushio Inc. The corona treatment was performed once under the conditions of an output of 0.78 kW and a treatment speed of 10 m/min.

(iv) Formation of Oriented Polymer Film The oriented polymer composition (1) was applied to the retardation layer substrate using a bar coater and dried at 90° C. for 1 minute to obtain an oriented film. The thickness of the obtained oriented film was measured with a laser microscope to be 34 nm.

(v) Formation of the second retardation layer Next, the composition for forming the second retardation layer was applied onto the alignment film using a bar coater, dried at 90° C. for 1 minute, and then irradiated with ultraviolet light using a high-pressure mercury lamp (under a nitrogen atmosphere, temperature: 25° C., cumulative light amount at a wavelength of 365 nm: 1000 mJ/cm ² ) to obtain a second retardation layer. The thickness of the obtained second retardation layer was measured with a laser microscope, and the thickness was 450 nm. In addition, the retardation value at a wavelength of 550 nm of the obtained retardation film (2) was measured, and the results were Re(550)=1 nm and Rth(550)=−70 nm. That is, the second retardation layer had optical properties represented by the following formula (3). Note that the retardation value at a wavelength of 550 nm of COP is approximately 0, so there is no effect on the optical properties.
nx ≈ ny < nz (3)

[Production Example 3: Preparation of Retardation Plate A]
The laminate including the first retardation layer obtained in Manufacturing Example 1 and the laminate including the second retardation layer obtained in Manufacturing Example 2 were bonded together with the following active energy ray curable adhesive A so that the retardation layer surface (surface opposite to the surface on the substrate side) of each was the bonding surface. Then, the active energy ray curable adhesive A was cured by irradiating ultraviolet light. In this way, a retardation plate A including two retardation layers, the first retardation layer and the second retardation layer, was produced.

<Active energy ray curable adhesive A>
The following components were blended and mixed, and then degassed to prepare an active energy ray-curable adhesive A.
3',4'-Epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate (product name: CEL2021P, manufactured by Daicel Corporation): 70 parts by mass Neopentyl glycol diglycidyl ether (product name: EX-211, manufactured by Nagase ChemteX Corporation): 20 parts by mass 2-Ethylhexyl glycidyl ether (product name: EX-121, manufactured by Nagase ChemteX Corporation): 10 parts by mass Cationic polymerization initiator (product name: CPI-100_50% solution, manufactured by San-Apro Co., Ltd.): 4.5 parts by mass (actual solid content 2.25 parts by mass)
1,4-diethoxynaphthalene: 2 parts by mass

[Production Example 4: Preparation of Retardation Plate B]
A retardation plate B having a substrate/alignment layer/second retardation layer (positive C plate)/alignment layer/first retardation layer (λ/4 layer) laminated in this order was produced as follows.

(Substrate)
As a substrate, a cycloolefin polymer film (COP) (ZF-14 manufactured by Zeon Corporation) was prepared.

(Corona treatment)
The corona treatment device used was AGF-B10 manufactured by Kasuga Denki Co., Ltd. The corona treatment was carried out once using the corona treatment device under conditions of an output of 0.3 kW and a treatment speed of 3 m/min.

(High pressure mercury lamp)
As the high pressure mercury lamp, a Uniqure VB-15201BY-A manufactured by Ushio Inc. was used.

The surface of the substrate subjected to the corona treatment was coated with the oriented polymer composition (1) prepared in the preparation of the retardation plate A using a bar coater, and dried at 90 ° C. for 1 minute. The thickness of the obtained oriented film was measured with a laser microscope and found to be 34 nm. Subsequently, the second retardation layer forming composition prepared in the preparation of the retardation plate A was coated on the oriented film using a bar coater, and dried at 90 ° C. for 1 minute, and then irradiated with ultraviolet light (under a nitrogen atmosphere, integrated light amount at a wavelength of 365 nm: 1000 mJ / cm ² ) using a high-pressure mercury lamp to form a second retardation layer (positive C plate), thereby obtaining a second retardation film having a second retardation layer. The thickness of the obtained second retardation layer was measured with a laser microscope and found to be 450 nm. In addition, the retardation value at a wavelength of 550 nm of the obtained second retardation film was measured and found to be Re (550) = 1 nm, Rth (550) = -70 nm. That is, the second retardation layer has the following formula (3):
nx ≈ ny < nz (3)
In addition, since the retardation value of the base material at a wavelength of 550 nm is approximately 0, the optical properties are not affected.

Next, the following orientation polymer composition (2) was applied onto the second retardation layer of the second retardation film using a bar coater and dried at 100 ° C. for 1 minute. The thickness of the obtained alignment film was measured with a laser microscope (LEXT, manufactured by Olympus Corporation) and found to be 100 nm. Subsequently, the alignment film was subjected to a rubbing treatment, and the composition for forming the first retardation layer prepared in the preparation of the retardation plate A was applied onto the treated surface using a bar coater and dried at 120 ° C. for 1 minute. The coating film was irradiated with ultraviolet light (under a nitrogen atmosphere, integrated light amount at a wavelength of 365 nm: 1000 mJ / cm ² ) using a high-pressure mercury lamp to form a first retardation layer on the second retardation layer, thereby obtaining a retardation plate B. The thickness of the obtained first retardation layer was measured with a laser microscope (LEXT, manufactured by Olympus Corporation) and found to be 2 μm. The retardation values of the obtained retardation plate B were measured to find that Re(450)=121 nm, Re(550)=139 nm, and Re(650)=146 nm.
The relationship between the in-plane retardation values at each wavelength was as follows:
Re(450)/Re(550)=0.87
Re(650)/Re(550)=1.05
That is, the obtained retardation plate B had the optical properties represented by the above formulas (1), (2) and (4).

(Oriented polymer composition (2))
Commercially available polyvinyl alcohol (polyvinyl alcohol 1000 fully saponified type, manufactured by Wako Pure Chemical Industries, Ltd.) and water were added and heated at 100° C. for 1 hour to obtain an oriented polymer composition (2) with a solid content of 2% by mass (solvent concentration of 98% by mass).

[Production Example 5: Preparation of Retardation Plate C]
In the preparation of the retardation plate A, the laminate including the first retardation layer and the laminate including the second retardation layer were bonded together by using the pressure-sensitive adhesive layer 3 (a sheet-shaped acrylic pressure-sensitive adhesive having a thickness of 5 μm) instead of the active energy ray-curable adhesive A to prepare the retardation plate. The retardation plate C was prepared in the same manner as the retardation plate A.

[Production Example 6: Preparation of polarizer]
A polyvinyl alcohol film having a thickness of 20 μm, a degree of polymerization of 2,400, and a degree of saponification of 99.9% or more was uniaxially stretched to a stretching ratio of 4.5 times in a dry state, and while maintaining the tension, was immersed for 60 seconds in a dye bath at 28° C. containing 0.05 parts by weight of iodine and 5 parts by weight of potassium iodide per 100 parts by weight of water.

Then, it was immersed for 110 seconds in boric acid aqueous solution 1 at 64°C, which contains 5.5 parts by weight of boric acid and 15 parts by weight of potassium iodide per 100 parts by weight of water. It was then immersed for 30 seconds in boric acid aqueous solution 2 at 67°C, which contains 5.5 parts by weight of boric acid and 15 parts by weight of potassium iodide per 100 parts by weight of water. It was then washed with pure water at 3°C and dried to obtain a polarizer with a thickness of 8 μm.

[Production Example 7: Preparation of linear polarizing plate]
The following protective films were prepared:
Protective film: 13 μm thick norbornene-based resin film (manufactured by Zeon Corporation, product name "ZEONOR")
The above protective film was laminated on one side of the polarizer prepared above using a roll laminator via a water-based adhesive. After lamination, a drying treatment was performed at 80° C. for 3 minutes. A linear polarizing plate in which the protective film was laminated only on one side of the polarizer was obtained. The linear polarizing plate was a laminate of a polarizer, an adhesive layer, and a protective film in this order.

[Production Example 8: Preparation of Pressure-Sensitive Adhesive Layer 1]
A reaction vessel equipped with a cooling tube, a nitrogen inlet tube, a thermometer, and a stirrer was charged with a mixed solution of 81.8 parts of ethyl acetate, 90.0 parts of butyl acrylate, 5.0 parts of methyl acrylate, and 5.0 parts of acrylic acid, and the air in the vessel was replaced with nitrogen gas to make it oxygen-free, while raising the internal temperature to 55°C. Then, a solution of 0.15 parts of azobisisobutyronitrile (polymerization initiator) dissolved in 10 parts of ethyl acetate was added in its entirety. After the addition of the polymerization initiator, the temperature was maintained for 1 hour, and then ethyl acetate was continuously added to the reaction vessel at an addition rate of 17.3 parts/hr while maintaining the internal temperature at 54 to 56°C, and the addition of ethyl acetate was stopped when the concentration of the (meth)acrylic resin reached 35% by mass, and the temperature was maintained until 6 hours had elapsed from the start of the addition of ethyl acetate. Finally, ethyl acetate was added to adjust the concentration of the (meth)acrylic resin to 20% by mass, and acrylic resin solution 1 was prepared. The resulting acrylic resin had a weight average molecular weight Mw of 1.6 million and a molecular weight distribution Mw/Mn of 4.5. Mw and Mn were measured in terms of standard polystyrene using two "TSKgel GMHHR-H(S)" columns manufactured by Tosoh Corporation connected in series as columns in a GPC apparatus, tetrahydrofuran as an eluent, a sample concentration of 2 mg/mL, a sample introduction amount of 100 μL, a temperature of 40° C., and a flow rate of 1 mL/min.

0.15 parts of a crosslinking agent (manufactured by Tosoh Corporation: product name "Coronate L" (a solution of a trimethylolpropane adduct of tolylene diisocyanate in ethyl acetate (solids concentration 75% by mass)) was added on an active ingredient basis to 100 parts of the solids content of the acrylic resin solution 1, and 0.2 parts of a silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd.: product name "KBM-403") were added, and ethyl acetate was further added to bring the solids concentration to 13%, to obtain adhesive composition 1.

Adhesive composition 1 was applied to the release-treated surface of a separate film made of release-treated polyethylene terephthalate film ["PLR-382190" obtained from Lintec Corporation] using an applicator so that the thickness after drying would be 25 μm, and the applied film was dried at 100°C for 1 minute to produce an adhesive layer (adhesive sheet). Next, the surface of the resulting adhesive layer opposite the separator film was bonded to the release-treated surface of a separate film made of release-treated polyethylene terephthalate film ["PET-251130" obtained from Lintec Corporation] to produce adhesive layer 1.

[Production Example 9: Preparation of Pressure-Sensitive Adhesive Layer 2]
A reaction vessel equipped with a cooling tube, a nitrogen inlet tube, a thermometer, and a stirrer was charged with a mixed solution of 100 parts of ethyl acetate, 99.0 parts of butyl acrylate, 0.5 parts of 2-hydroxyethyl acrylate, and 0.5 parts of acrylic acid, and the internal temperature was raised to 55°C while the air in the vessel was replaced with nitrogen gas to make it oxygen-free. Then, the entire amount of a solution in which 0.12 parts of azobisisobutyronitrile (polymerization initiator) was dissolved in 10 parts of ethyl acetate was added. After the addition of the polymerization initiator, the temperature was maintained for 1 hour, and then ethyl acetate was continuously added to the reaction vessel at an addition rate of 17.3 parts/hr while maintaining the internal temperature at 54 to 56°C, and the addition of ethyl acetate was stopped when the concentration of the (meth)acrylic resin reached 35% by mass, and the temperature was maintained for 6 hours from the start of the addition of ethyl acetate. Finally, ethyl acetate was added to adjust the concentration of the (meth)acrylic resin to 20% by mass, and acrylic resin solution 2 was prepared. The resulting acrylic resin had a weight average molecular weight Mw of 1.7 million and a molecular weight distribution Mw/Mn of 3.9. Mw and Mn were measured in terms of standard polystyrene using two "TSKgel GMHHR-H(S)" columns manufactured by Tosoh Corporation connected in series as columns in a GPC apparatus, tetrahydrofuran as an eluent, a sample concentration of 2 mg/mL, a sample introduction amount of 100 μL, a temperature of 40° C., and a flow rate of 1 mL/min.

To 80 parts of the solid content of the acrylic resin solution 2, 20 parts (solid content) of a bifunctional acrylate (obtained from Shin-Nakamura Chemical Co., Ltd.; product number "A-DOG"), 2.5 parts of a crosslinking agent (manufactured by Tosoh Corporation: product name "Coronate L" (ethyl acetate solution of trimethylolpropane adduct of tolylene diisocyanate (solid content concentration 75% by mass)) based on active ingredients, 1.5 parts of a photopolymerization initiator (manufactured by Ciba Specialty Chemicals: product name "Irgacure 500"), and 0.3 parts of a silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd.: product name "KBM-403") were added, and ethyl acetate was further added so that the solid content concentration became 13%, to obtain a pressure-sensitive adhesive composition 2.
A-DOG is a diacrylate of an acetal compound of hydroxypivalaldehyde and trimethylolpropane, and has the following structure:

The adhesive composition 2 was applied to the release-treated surface of a separate film made of a release-treated polyethylene terephthalate film ["PLZ-383030" obtained from Lintec Corporation] using an applicator so that the thickness after drying would be 15 μm, and the applied adhesive layer (adhesive sheet) was prepared by drying at 100° C. for 1 minute. Next, the surface of the obtained adhesive layer opposite the separator film was bonded to the release-treated surface of a separate film made of a release-treated polyethylene terephthalate film ["PLR-381031" obtained from Lintec Corporation]. Subsequently, ultraviolet light was irradiated under the following conditions to prepare adhesive layer 2.
<UV irradiation conditions>
- Fusion UV lamp system (manufactured by Fusion UV Systems) H bulb used - Accumulated light amount in UV wavelength region UVA: 250 mJ/cm ² (measurement device: measured value using UV Power Puck II manufactured by Fusion UV)

[Production Example 10: Preparation of Pressure-Sensitive Adhesive Layer 3]
An adhesive layer 3 was prepared in the same manner as in Production Example 9, except that the adhesive composition 2 was applied so as to have a thickness of 5 μm after drying.

[Example 1]
The laminate (circular polarizing plate) of Example 1 was prepared as follows. The adhesive layer 1 (a sheet-shaped acrylic adhesive having a thickness of 25 μm) was laminated on the polarizer of the linear polarizing plate prepared above. The tensile modulus of the adhesive layer 1 measured by the above method was as shown in Table 1. The substrate used to form the first retardation layer was peeled off from the retardation plate A prepared in Production Example 3. The exposed horizontal alignment film and the adhesive layer (first bonding layer) were bonded together to prepare a laminate (circular polarizing plate) in which the linear polarizing plate, the first bonding layer, and the retardation plate A were laminated in this order. The angle between the absorption axis of the polarizer and the slow axis of the first retardation layer was 45°.

[Example 2]
A laminate (circular polarizing plate) in which a linear polarizing plate, a first bonding layer, and a retardation plate A were laminated in this order was obtained in the same manner as in Example 1, except that the adhesive layer 2 (a sheet-shaped acrylic adhesive having a thickness of 15 μm) was used instead of the adhesive layer 1 used in the preparation of the laminate (circular polarizing plate) of Example 1. The tensile modulus of elasticity of the adhesive layer 2 measured by the above method was as shown in Table 1.

[Example 3]
A laminate (circular polarizing plate) in which a linear polarizing plate, a first bonding layer, and a retardation plate A were laminated in this order was obtained in the same manner as in Example 1, except that adhesive layer 3 (a sheet-shaped acrylic adhesive having a thickness of 5 μm) was used instead of adhesive layer 1 used in the preparation of the laminate (circular polarizing plate) of Example 1. The tensile modulus of elasticity of adhesive layer 3 measured by the above method was as shown in Table 1.

[Example 4]
A laminate (circular polarizing plate) in which a linear polarizing plate, a first bonding layer, and a retardation plate B were laminated in this order was obtained in the same manner as in Example 1, except that the retardation plate B prepared in Manufacturing Example 4 was used instead of the retardation plate A used in the preparation of the laminate (circular polarizing plate) of Example 1, and a pressure-sensitive adhesive layer 1 (first bonding layer) was bonded to the first retardation layer of the retardation plate B.

[Example 5]
A laminate (circular polarizing plate) in which a linear polarizing plate, a first bonding layer, and a retardation plate B were laminated in this order was obtained in the same manner as in Example 2, except that the retardation plate B prepared in Manufacturing Example 4 was used instead of the retardation plate A used in the preparation of the laminate (circular polarizing plate) of Example 2, and a pressure-sensitive adhesive layer 2 (first bonding layer) was bonded to the first retardation layer of the retardation plate B.

[Example 6]
A laminate (circular polarizing plate) in which a linear polarizing plate, a first bonding layer, and a retardation plate B were laminated in this order was obtained in the same manner as in Example 4, except that adhesive layer 3 (a sheet-shaped adhesive having a thickness of 5 μm) was used instead of adhesive layer 1 used in the preparation of the laminate (circular polarizing plate) of Example 4.

[Comparative Example 1]
A laminate (circular polarizing plate) in which a linear polarizing plate, a first attachment layer, and a retardation plate A were laminated in this order was obtained in the same manner as in Example 1, except that an adhesive layer A (thickness after drying: 1.5 μm) formed from the above-mentioned active energy ray curable adhesive A was used instead of the pressure-sensitive adhesive layer 1 used in the preparation of the laminate (circular polarizing plate) of Example 1. The tensile modulus of the adhesive layer A measured by the above-mentioned method was as shown in Table 1.

[Comparative Example 2]
A laminate (circular polarizing plate) in which a linear polarizing plate, a first bonding layer, and a retardation plate B were laminated in this order was obtained in the same manner as in Example 4, except that the adhesive layer A (thickness after drying: 1.5 μm) formed from the above-mentioned active energy ray-curable adhesive A was used instead of the pressure-sensitive adhesive layer 1 used in the preparation of the laminate (circular polarizing plate) in Example 4.

[Reference Example 1]
A laminate (circular polarizing plate) in which a linear polarizing plate, a first bonding layer, and a retardation plate were laminated in this order was obtained in the same manner as in Example 3, except that the retardation plate C prepared in Production Example 5 was used instead of the retardation plate A used in the preparation of the laminate (circular polarizing plate) of Example 3.

[evaluation]
The durability of the circularly polarizing plates of Examples 1 to 6, Comparative Examples 1 and 2, and Reference Example 1 when the base material used for forming the second retardation layer was peeled off was evaluated according to the above-mentioned method. The evaluation results are shown in Table 1.

1 polarizing plate, 2 image display device, 10 linear polarizing plate, 21 first bonding layer, 30 retardation plate, 31 first retardation layer, 32 second retardation layer, 40 image display panel.

Claims (6)

A polarizing plate formed by laminating a linear polarizing plate, a first bonding layer, and a retardation plate in this order,
The retardation plate is
A first retardation layer , an adhesive layer, and a second retardation layer in this order ,
Further, the adhesive layer has a substrate on a surface opposite to the first adhesive layer,
The first retardation layer and the second retardation layer include a cured product of a liquid crystal compound,
The puncture elastic modulus is 70 g/mm or more,
The first bonding layer has a tensile modulus of elasticity of 1.3×10 ⁵ Pa or more and 1.0×10 ⁶ Pa or less at a temperature of 23° C. and a relative humidity of 55%;
After the base material is peeled off, the polarizing plate is attached to an image display panel for use. The polarizing plate according to claim 1, wherein the product of the thickness (m) of the first bonding layer and the tensile modulus (Pa) is 500 or less. The linear polarizing plate has a polarizer,
The polarizing plate according to claim 1 , wherein the polarizer has a thickness of 15 μm or less. the linear polarizing plate has a protective film provided on a surface of the polarizer opposite to the first attachment layer,
The polarizing plate according to claim 3 , wherein the protective film has a thickness of 30 μm or less. The polarizing plate according to claim 1 or 2, wherein the first retardation layer is a λ/4 layer having reverse dispersion. The polarizing plate according to claim 1 or 2, wherein the second retardation layer is a positive C plate.

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