JP6969141B2 - Phase difference film, polarizing plate compensation film, and external light reflection prevention film - Google Patents

Description

The present invention relates to a retardation film, a polarizing plate compensating film provided with the retardation film, and an external light reflection antireflection film.

As an optical film applied to an image display device or the like, there is a retardation film that imparts a desired retardation to incident light by a retardation layer. For example, in an organic electroluminescence (organic EL) display device, a λ / 4 retardation film is used as a circular polarizing plate in combination with a linear polarizing plate, and functions as an external light reflection antireflection film. Further, in a liquid crystal display device such as an IPS mode, a retardation film in which a positive A plate having a positive A characteristic and a positive C plate having a positive C characteristic are combined in order to enhance the contrast with respect to a field of view from an oblique direction. Is used as a part of the polarizing plate compensating film (for example, Patent Document 1).

Here, the characteristics of positive A are Nx for the refractive index in the X-axis direction along the layer surface, Ny for the refractive index in the Y-axis direction orthogonal to the X-axis in the direction along the layer surface, and Ny for the refractive index in the layer thickness direction. When Nz is set, the relationship is Nx> Ny≈Nz, and the optical axis is in the Nx direction.
The characteristic of negative A has a relationship of Nz≈Nx> Ny and a characteristic that the optical axis is in the Ny direction.
The characteristic of positive C has a relationship of Nz> Nx≈Ny and a characteristic that the optical axis is in the Nz direction.
The negative C characteristic has a relationship of Nx≈Ny> Nz and has a characteristic that the optical axis is in the Nz direction.

Japanese Unexamined Patent Publication No. 2016-53709

However, when the conventionally proposed A plate and C plate are combined, the color of the film often changes depending on the viewing angle, and improvement has been desired.

In view of the above problems, it is an object of the present invention to provide a retardation film in which a positive A plate and a positive C plate are laminated, and which can suppress a color change depending on a viewing angle. Further, the present invention provides a polarizing plate compensating film provided with the retardation film and an external light reflection antireflection film.

As a result of diligent studies on the above problems, the inventor has found that in a retardation film in which a positive A plate and a positive C plate are laminated, the positive A plate has a positive wavelength dispersion characteristic, so that the color of the color depends on the viewing angle. The present invention was completed with the knowledge that the change can be suppressed.
Here, the positive wavelength dispersion characteristic is a wavelength dispersion characteristic in which the phase difference in transmitted light is larger toward the shorter wavelength side, and more specifically, in the positive A plate, frontal retardation (Re ₄₅₀ ) at a wavelength of 450 nm and 550 nm. The relationship with the front retardation (Re _{550 ) at the wavelength of is Re 450} > Re ₅₅₀ and Re ₄₅₀ / Re ₅₅₀ > 1.0. In the positive C plate, the relationship between the _{thickness-direction retardation (Rth 450} ) at a wavelength of 450 nm and the thickness-direction retardation (Rth _{550 ) at a wavelength of 550 nm is Rth 450} > Rth ₅₅₀ and Rth ₄₅₀ / Rth ₅₅₀ > 1. It is a wavelength dispersion characteristic.
On the other hand, the inverse wavelength dispersion characteristic is a wavelength dispersion characteristic in which the phase difference in transmitted light is smaller toward the shorter wavelength side, and more specifically, in the positive A plate, frontal retardation (Re ₄₅₀ ) at a wavelength of 450 nm. The relationship with the front retardation (Re _{550 ) at a wavelength of 550} nm is the wavelength dispersion characteristic of _{Re 450} <Re ₅₅₀ and Re ₄₅₀ / Re 550 <1.0. In the positive C plate, the relationship between the _{thickness-direction retardation (Rth 450} ) at a wavelength of 450 nm and the thickness-direction retardation (Rth _{550 ) at a wavelength of 550 nm is Rth 450} <Rth ₅₅₀ , and Rth ₄₅₀ / Rth ₅₅₀ <1.0. It is a wavelength dispersion characteristic.
Hereinafter, the present invention will be described.

One aspect of the present invention comprises a positive A-type characteristics, when the front retardation at the wavelength of 450nm was front retardation at a wavelength of _Re A450, 550 nm and _{Re A550,} .DELTA.N _A obtained by Re A450 _{/ Re A550} is It is a retardation film having a positive A plate larger than 1.0 and a positive C plate having a positive C type characteristic.

In the above retardation film, when the thickness direction retardation at a wavelength of 450nm of the positive C plate in the thickness direction retardation and _{Rth C550} at a wavelength of _Rth C450, 550 _nm, and a value obtained by Rth C450 _{/ Rth C550} and .DELTA.N _C,
| ΔN _A -ΔN _C | ≦ 0.2
Can be configured to be.

Another aspect of the invention has a positive A plate with positive A-type characteristics and a positive C plate with positive C-type characteristics, and the front retardation of the positive A plate at a wavelength of 450 nm is Re _A450. when the front retardation at a wavelength of 550nm was _{Re A550,} .DELTA.N _a obtained by Re A450 _{/ Re A550,} along with a 0.94 to 1.10, a thickness direction retardation at a wavelength of 450nm of the positive C plate the thickness direction retardation and _{Rth C550} at a wavelength of Rth _C450, 550nm, ΔN _C obtained by Rth C450 _{/ Rth C550} is 0.82 to 1.00, a phase difference film.

In the retardation film, at least one of the positive A plate and the positive C plate can be made to contain a polymerizable rod-shaped liquid crystal material.

In the above retardation film, positive A plate and the thickness direction retardation at a wavelength of 450nm in a stacked state between the positive C plate Rth _p, the thickness direction retardation at a wavelength of 550nm in a stacked state between the positive A plate and the positive C plate When Rth _q , the thickness direction retardation at a wavelength of 650 nm in the laminated state of the positive A plate and the positive C plate is Rth _r , the maximum value and the minimum value among _{Rth p} , Rth _q , and Rth _r The difference can be 25 or less.
_{Further, the front retardation Re A550} of the positive A plate at a wavelength of 550 nm at this time may be 110 nm or more and 160 nm or less.

Further, it is possible to provide a polarizing plate compensating film comprising two polarizing plates and the retardation film arranged between the two polarizing plates.

Further, it is possible to provide an external light reflection antireflection film including the above-mentioned retardation film arranged on the light emitting side of the organic EL display panel and a polarizing element for linearly polarized light laminated on the retardation film.

According to the present invention, even in a retardation film in which a positive A plate and a positive C plate are laminated, it is possible to suppress a change in color depending on a viewing angle. It is also possible to apply this to a polarizing plate compensating film or an external light reflection antireflection film.

It is a figure which shows an example of the layer structure of the retardation film 10. It is a figure explaining the layer structure of the liquid crystal display device 20 to which the retardation film 10 is applied. It is a figure explaining the layer structure of the organic EL display device 30 to which the retardation film 10 is applied. It is a figure explaining the evaluation method in an Example. It is a figure explaining the evaluation of the hue in an Example.

Hereinafter, the present invention will be described in detail with specific examples. However, the present invention is not limited to the following embodiments, and various modifications can be made without changing the gist of the present invention.

FIG. 1 is a diagram illustrating a layer structure of a retardation film 10 according to one form. In this embodiment, for example, by arranging the retardation film 10 together with various other optical films on a liquid crystal display panel and an organic EL display panel for an image display device, various optical characteristics can be improved. Examples of the optical characteristics include external light reflection, improvement of viewing angle characteristics, optical compensation for reducing light leakage in the oblique direction, and the like.
As can be seen from FIG. 1, the retardation film 10 of this embodiment includes a base material 11, an alignment film 12, a positive C plate 13, and a positive A plate 14.

Examples of the base material 11 include a glass base material, a metal foil, a resin base material, and the like. Among them, the base material preferably has transparency, and can be appropriately selected from conventionally known transparent base materials. Examples of the transparent base material include acetyl cellulose-based resins such as triacetyl cellulose, polyethylene terephthalates, polyethylene naphthalates, polybutylene terephthalates, polyester resins such as polylactic acid, polypropylene, polyethylene, polymethylpentene and the like, in addition to glass base materials. Formed using resins such as olefin resin, acrylic resin, polyurethane resin, polyether sulfone, polycarbonate, polysulfone, polyether, polyether ketone, acronitrile, methacrylonitrile, cycloolefin polymer, cycloolefin copolymer, etc. A transparent resin base material can be mentioned.

The base material 11 preferably has a transmittance of 80% or more in the visible light region, and more preferably 90% or more. Here, the transmittance of the base material can be measured by JIS K7361-1 (a test method for the total light transmittance of a plastic-transparent material).

The thickness of the base material 11 is not particularly limited as long as it is within the range in which the required supportability can be imparted, depending on the use of the retardation film and the like, but it is usually within the range of about 10 μm or more and 200 μm or less. Among them, the thickness of the base material is preferably in the range of 25 μm or more and 125 μm or less, and more preferably in the range of 30 μm or more and 100 μm or less. If the thickness is thicker than the above range, for example, when a long retardation film is formed and then cut to obtain a single-wafer retardation film, processing chips increase or the cutting blade is worn. This is because it may become faster.

In this embodiment, the alignment film 12 is a layer for arranging the liquid crystal components contained in the positive C plate 13 in a certain direction, and is a vertical alignment film. However, as the alignment film, a necessary one can be appropriately applied depending on the properties of the liquid crystal component of the positive C plate. For example, when the liquid crystal component of the positive C plate itself has vertical alignment, the alignment film does not necessarily have a vertical alignment restricting force.
In this embodiment, the vertical alignment film is an alignment film having a vertical alignment restricting force, and is applied to various vertical alignment films used for producing known C-plate retardation films, VA liquid crystal display devices, and the like. A vertical alignment film can be applied, for example, a polyimide alignment film, an alignment film made of an LB film, or the like can be applied. Specifically, examples of the constituent material of the alignment film include silane coupling-based vertical such as lecithin, silane-based surfactant, titanate-based surfactant, pyridinium salt-based polymer surfactant, and n-octadecyltriethoxysilane. Compositions for alignment membranes, soluble polyimides having long-chain alkyl groups and alicyclic structures on the side chains, polyamic acids having long-chain alkyl groups and alicyclic structures on the side chains, and other compositions for polyimide-based vertical alignment films. Can be applied.

The method for forming the alignment film 12 is not particularly limited, but for example, the alignment film can be formed by applying a composition for forming an alignment film on the base material 11 and imparting an alignment restricting force. As a means for imparting an orientation regulating force to the alignment film, conventionally known means can be used.

The thickness of the alignment film 12 may be appropriately set as long as the liquid crystal components in the positive C plate 13 can be arranged in a certain direction. The thickness of the alignment film is usually in the range of 1 nm or more and 10 μm or less, and preferably in the range of 60 nm or more and 5 μm or less.

The positive C plate 13 is a layer having the characteristics of positive C and having an optical function. The positive C plate 13 may be composed of a polymerizable liquid crystal composition containing a liquid crystal compound which is a liquid crystal material used for producing retardation layers of various optical films. That is, in this positive C plate 13, the liquid crystal compound is vertically (homeotropic) oriented.

Here, the positive C plate 13 may have the characteristics of the positive C type, and the forward or reverse of the wavelength dispersion characteristics does not matter.

The thickness of the positive C plate 13 is not particularly limited, but is preferably 0.3 μm or more and 3.0 μm or less.

The polymerizable liquid crystal composition in this embodiment is preferably liquid crystal and contains a liquid crystal compound (rod-like compound) having a polymerizable functional group in the molecule.
Therefore, the liquid crystal compound may be any conventionally known liquid crystal compound and is not particularly limited. For example, if it is a positive C plate having a positive wavelength dispersion characteristic, the one described in JP-A-2016-53709 can be exemplified, and if it is a positive C plate having a reverse wavelength dispersion characteristic, it is described in JP-A-2010-522892. Things can be exemplified.
Examples of the liquid crystal compound include materials showing a liquid crystal phase such as a nematic phase and a smectic phase, but the nematic phase is shown from the viewpoint that it is easier to arrange them regularly as compared with liquid crystal compounds showing other liquid crystal phases. It is more preferable to use a liquid crystal compound. As the liquid crystal compound exhibiting the nematic phase, it is preferable to use a material having spacers at both ends of the mesogen. A liquid crystal compound having spacers at both ends of the mesogen is excellent in flexibility.

Further, the liquid crystal compound is preferably a polymerizable liquid crystal compound having a polymerizable functional group in the molecule as described above. By having a polymerizable functional group, it becomes possible to polymerize and fix the liquid crystal compound, so that the arrangement stability is excellent and the phase difference property with time is less likely to change. Further, it is more preferable that the polymerizable liquid crystal compound has a polymerizable functional group capable of three-dimensional cross-linking in the molecule. Having a polymerizable functional group capable of three-dimensional cross-linking can further enhance the sequence stability. In addition, "three-dimensional cross-linking" means that liquid crystal molecules are polymerized three-dimensionally with each other to form a network structure.

Examples of the polymerizable functional group include those that polymerize by the action of ultraviolet rays, ionizing radiation such as an electron beam, or heat. Examples of these polymerizable functional groups include radically polymerizable functional groups. Representative examples of the radically polymerizable functional group include a functional group having at least one addition-polymerizable ethylenically unsaturated double bond, and specific examples thereof include a vinyl group having or not having a substituent and an acrylate group. (A generic term including an acryloyl group, a methacryloyl group, an acryloyloxy group, and a methacryloyloxy group) and the like.

Further, the liquid crystal compound is particularly preferably one having a polymerizable functional group at the terminal. By using such a liquid crystal compound, for example, they can be polymerized three-dimensionally to each other to form a network structure, so that they are stable and have excellent optical characteristics. A retardation film can be formed.

The content of the liquid crystal compound in the polymerizable liquid crystal composition is not particularly limited, but is contained in a proportion of 5 parts by mass or more and 40 parts by mass or less when the entire polymerizable liquid crystal composition is 100 parts by mass. It is preferable that it is contained in a proportion of 10 parts by mass or more and 30 parts by mass or less. If the amount of the liquid crystal compound is less than 5 parts by mass, the light incident on the positive C plate 13 may not be properly polarized because the content is too small. On the other hand, if it exceeds 40 parts by mass, the viscosity of the polymerizable liquid crystal composition becomes too high, and the workability of forming the layer deteriorates.

The liquid crystal compound may be used alone or in combination of two or more.

The liquid crystal compound described above is usually dissolved in a solvent. As the solvent, it is necessary that the above-mentioned liquid crystal compound can be uniformly dispersed, but a known solvent can be used. Such solvents include hydrocarbons such as toluene and xylene, ketones such as acetone, methyl ethyl ketone, cyclohexanone and methyl isobutyl ketone, ethers such as tetrahydro, 1-methoxy-2-propanol and 1-methoxypropyl-2-. Examples thereof include glycol ethers such as acetate, and esters such as methyl acetate, ethyl acetate and butyl acetate.

The content of the solvent in the polymerizable liquid crystal composition is preferably 66 parts by mass or more and 1900 parts by mass or less with respect to 100 parts by mass of the liquid crystal compound. If the amount of the solvent is less than 66 parts by mass, the liquid crystal compound may not be uniformly dissolved. On the other hand, if it exceeds 1900 parts by mass, a part of the solvent may remain and the reliability may be lowered, and uniform coating may not be possible. From this point of view, it is more preferably 900 parts by mass or less.

The polymerizable liquid crystal composition may contain other additives as needed. The other compounds are not particularly limited as long as they do not impair the arrangement order of the liquid crystal compounds described above, and examples thereof include plasticizers, surfactants, and silane coupling agents.

The positive A plate 14 has the characteristics of positive A and preferably has positive wavelength dispersion characteristics and carries out an optical function. The positive A plate 14 is a liquid crystal material used for producing retardation layers of various optical films, and is preferably composed of a polymerizable liquid crystal composition containing a liquid crystal compound having a positive wavelength dispersion characteristic. That is, the liquid crystal compound has a homogeneous orientation.

Positive A plate 14 specifically comprises a positive A-type properties, when the front retardation at a wavelength of 450nm front retardation at a wavelength of _Re A450, 550 nm was _{Re C550,} obtained by _Re A450 _/ Re _A550 ΔN _A should be greater than 1.0.

The thickness of the positive A plate 14 is not particularly limited, but is preferably 0.3 μm or more and 3.0 μm or less.

The polymerizable liquid crystal composition constituting the positive A plate 14 preferably contains a liquid crystal compound (rod-like compound) that exhibits liquid crystallinity and has a polymerizable functional group in the molecule. The liquid crystal compound is not particularly limited, and represents all the liquid crystal compounds contained in the composition forming the positive A plate, and even if it is composed of one liquid crystal compound, it is a mixture of two or more kinds of liquid crystal compounds. There may be.

As the liquid crystal compound, any conventionally known liquid crystal compound may be used as long as it is a liquid crystal compound exhibiting positive wavelength dispersion characteristics, and is not particularly limited. Examples thereof include the following equations (1) to (17).

Examples of the polymerizable functional group include those that polymerize by the action of ultraviolet rays, ionizing radiation such as an electron beam, or heat. Examples of these polymerizable functional groups include radically polymerizable functional groups. Representative examples of the radically polymerizable functional group include a functional group having at least one addition-polymerizable ethylenically unsaturated double bond, and specific examples thereof include a vinyl group having or not having a substituent and an acrylate group. (A generic term including an acryloyl group, a methacryloyl group, an acryloyloxy group, and a methacryloyloxy group) and the like.

The content of the liquid crystal compound in the polymerizable liquid crystal composition is not particularly limited, but is contained in a proportion of 5 parts by mass or more and 40 parts by mass or less when the entire polymerizable liquid crystal composition is 100 parts by mass. It is preferable that it is contained in a proportion of 10 parts by mass or more and 30 parts by mass or less. If the amount of the liquid crystal compound is less than 5 parts by mass, the light incident on the positive A plate 14 may not be properly polarized because the content is too small. On the other hand, if it exceeds 40 parts by mass, the viscosity of the polymerizable liquid crystal composition becomes too high, and the workability of forming the layer deteriorates.

The liquid crystal compound described above is usually dissolved in a solvent. As the solvent, it is necessary that the above-mentioned liquid crystal compound can be uniformly dispersed, but a known solvent can be used. Such solvents include hydrocarbons such as toluene and xylene, ketones such as acetone, methyl ethyl ketone, cyclohexanone and methyl isobutyl ketone, ethers such as tetrahydro, 1-methoxy-2-propanol and 1-methoxypropyl-2-. Examples thereof include glycol ethers such as acetate, and esters such as methyl acetate, ethyl acetate and butyl acetate.

The content of the solvent in the polymerizable liquid crystal composition is preferably 66 parts by mass or more and 1900 parts by mass or less with respect to 100 parts by mass of the liquid crystal compound. If the amount of the solvent is less than 66 parts by mass, the liquid crystal compound may not be uniformly dissolved. On the other hand, if it exceeds 1900 parts by mass, a part of the solvent may remain and the reliability may be lowered, and uniform coating may not be possible. From this point of view, it is more preferably 900 parts by mass or less.

The polymerizable liquid crystal composition may contain other additives as needed. The other compounds are not particularly limited as long as they do not impair the arrangement order of the liquid crystal compounds described above, and examples thereof include plasticizers, surfactants, and silane coupling agents.

The retardation film 10 having the above configuration has the following features. That is, the positive A plate, when the front retardation at the wavelength of 450nm was front retardation at a wavelength of _Re A450, 550 nm and _{Re A550,} .DELTA.N _A obtained by Re A450 _{/ Re A550} greater than 1.0 normal wavelength dispersibility It is equipped with.

Preferably, when the thickness direction retardation was _{Rth C550} a thickness direction retardation at a wavelength of 450nm of the positive C plate at the wavelength of the _Rth C450, 550 _nm, in .DELTA.N _C obtained by Rth C450 _{/ Rth C550,}
| Has a ≦ 0.2 the relationship | ΔN _A -ΔN _C.

Further, more preferably, in a state where the positive A plate and the positive C plate are laminated, the thickness direction retardation at a wavelength of 450 nm is Rth _p , the thickness direction retardation at a wavelength of 550 nm is Rth _q , and the thickness direction retardation at a wavelength of 650 nm is performed. When Rth _r is defined and the difference between the maximum value and the minimum value among these Rth _p , Rth _q , and Rth _{r is Rth s} , Rth _s is 25 or less. _{Further, it is more preferable that the front retardation Re A550} of the positive A plate at a wavelength of 550 nm at this time is 110 nm or more and 160 nm or less.

As a result, it is possible to exhibit external light reflection and optical compensation functions as basic functions of the retardation film, and it is possible to suppress a change in color due to a viewing angle.

Further, in addition to the above, .DELTA.N _A ≒ 1.0, and it may be 0.82 ≦ ΔN _C ≦ 1.00. This also makes it possible to exhibit external light reflection and optical compensation functions as basic functions of the retardation film, and also to suppress color changes depending on the viewing angle. Here, .DELTA.N _A ≒ 1.0 is specifically a 0.94 ≦ ΔN _A ≦ 1.10. More preferably 0.95 ≦ ΔN _A ≦ 1.05. On the other hand, .DELTA.N _C is more preferably 0.85 ≦ ΔN _C ≦ 0.94. At this time, when using a positive A plate having a reverse wavelength dispersion characteristic, a known liquid crystal material can be applied.

Next, a method for manufacturing the retardation film 10 will be described. For example, the retardation film 10 includes a base material supply step, an alignment film forming step, a positive C plate forming step, and a positive A plate forming step.

In the base material supply step, the base material 11 is provided by a roll.

Then, in the alignment film forming step, the alignment film 12 is formed on one surface of the base material 11. Specifically, it is as follows.
The base material 11 is pulled out from the supply reel, and the composition constituting the alignment film is laminated on the base material 11. The method for laminating the composition on the substrate 11 is not particularly limited, and for example, a die coating method, a gravure coating method, a reverse coating method, a knife coating method, a dip coating method, a spray coating method, and an air knife coating method. A method, a spin coat method, a roll coat method, a print method, a dipping pulling method, a curtain coat method, a casting method, a bar coat method, an extrusion coat method, an E-type coating method and the like can be used.
Then, the laminated composition is dried to form an alignment film 12.

In the positive C plate forming step, the composition constituting the positive C plate is laminated on the alignment film 12 in the same manner as in the alignment film forming step, and the composition is cured by irradiating with ultraviolet rays to cure the positive C. Obtain plate 13. Low-pressure mercury lamps (sterilization lamps, fluorescent chemical lamps, black lights), high-pressure discharge lamps (high-pressure mercury lamps, metal halide lamps), short arc discharge lamps (ultra-high pressure mercury lamps, xenon lamps, mercury xenon) are used as light sources for ultraviolet irradiation. A lamp) or the like can be used. Among them, metal halide lamps, xenon lamps, high-pressure mercury lamps and the like can be preferably used. The wavelength of ultraviolet rays is appropriately set according to the material or the like constituting the composition. Specifically, the wavelength is 210 nm or more and 380 nm or less, preferably 230 nm or more and 380 nm or less, and more preferably 250 nm or more and 380 nm or less. It is preferable to use the irradiation light of. As the irradiation amount of the ultraviolet (integrated light quantity) is not particularly limited, for example, it is preferably in the range of 100 mJ / cm ² or more 1500 mJ / cm ² or less, 100 mJ / cm ² or more 800 mJ / cm ² or less of It is more preferable that it is within the range.

In the step of forming the positive A plate, for example, the composition constituting the positive A plate is laminated on the positive C plate 13 and cured. This can be done in the same manner as the formation of the positive C plate 13. In this case, it is preferable to provide an alignment film on the positive A plate.
However, the present invention is not limited to this, and a positive A plate can be prepared separately and transferred to the positive C plate for laminating.

Next, the optical functional laminate to which the above-mentioned retardation film 10 is applied will be described. In this optical functional laminate, it can be arranged by including the retardation film 10 in one of the configurations of various optical functional laminates arranged on the image display panel.

As a more specific example, a case where it is applied to a liquid crystal display device provided with a retardation film 10 will be described. FIG. 2 is a diagram showing a layer structure of a liquid crystal display device 20 including a retardation film 10. In the liquid crystal display device 20, the optical functional laminate 26 is arranged on the exit surface side of the liquid crystal display panel 23. This is an example in which a polarizing element 27 for linearly polarized light and a retardation film 10 are included and used for polarizing plate compensation.

The liquid crystal display device 20 is an IPS liquid crystal display device (IPS-LCD), and a liquid crystal display panel 23 is arranged on the side of the observer of the backlight 22.

The liquid crystal display panel 23 is provided with a liquid crystal cell 25 made of IPS liquid crystal, and a linear polarizing plate 24 is provided on the backlight 22 side of the liquid crystal cell 25, for example, with a pressure-sensitive adhesive layer (not shown). The linear polarizing plate 24 is configured by sandwiching a polarizing element that functions as a linear polarizing plate between two substrates made of a transparent film.

In the liquid crystal display panel 23, the optical functional laminate 26 is arranged on the exit surface of the liquid crystal cell 25. The optical functional laminate 26 includes a retardation film 10 constituting a polarizing plate compensating film for polarizing plate compensation, a polarizing element 27, and a base material (protective film) 28 as a surface material. A transparent film such as TAC is applied to the base material 28, and a polarizing element 27 as a linear polarizing plate is provided therein.

As described above, the retardation film 10 constituting the optical functional laminate 26 functions as a polarizing plate compensating film from an oblique field of view in a wide band.

As another specific example, a case where it is applied to an organic EL display device provided with a retardation film 10 will be described. FIG. 3 is a diagram showing a layer structure of an organic EL display device 30 including a retardation film 10. In the organic EL display device 30, the optical functional laminate 36 is an external light reflection antireflection film arranged on the emission surface side of the organic EL display panel 33. The optical functional laminate 36 includes a polarizing element 37 for linearly polarized light and a retardation film 10, and has an external light reflection function as a so-called circular polarizing plate.

The organic EL display device 30 is a device that provides the observer with the image light that is self-luminous by the organic EL display panel 33, and the optical functional laminate 36 is arranged on the emission surface of the organic EL display panel 33. The optical functional laminate 36 functions as a circular polarizing plate for preventing external light reflection, and includes a retardation film 10, a polarizing element 37 as a linear polarizing plate, and a base material (protective film) 38 as a surface material. At this time, the positive A plate 14 of the retardation film 10 functions as a λ / 4 retardation layer, and the positive C plate 13 is laminated on the positive A plate 14.

In this way, the retardation film 10 constituting the optical functional laminate 36 functions as an external light reflection antireflection film.

The simulation in the embodiment, by modeling the laminate following the liquid crystal display panel 23 shown in FIG. 2, by changing the .DELTA.N _C of .DELTA.N _A and the positive C plate of the positive A plate retardation film 10 contained herein , The hue change at a viewing angle of 60 ° was evaluated.

The simulation was performed using LCD-MASTER (Shintech Co., Ltd.). From the observer side, the layer structure of the model consists of an upper polarizing plate with the absorption axis at 90 degrees to the reference, a positive C plate, a positive A plate with the optical axis parallel to the absorption axis of the upper polarizing plate, and an absorption axis. The lower polarizing plate was set to 0 degrees with respect to the reference, and the condition was set to irradiate light from the lower polarizing plate side.

[evaluation]
<Change in viewing angle phase>
As shown in the schematic diagram in FIG. 4, the color at a viewing angle inclined by θ = 60 ° with respect to the normal line n extending from the center of the surface of the laminated body to be evaluated was measured. The upper view of FIG. 4 is a plan view of the laminated body, and the lower view of FIG. 4 is a side view of the laminated body. As can be seen from FIG. 4, since the viewing angle of θ = 60 ° exists so as to draw a circle centered on O, the circle is drawn around O along the arrow K starting from S. The hue at each position was obtained.
As a result, as shown in FIGS. 5 (a) and 5 (b) one by one, a color change occurs when one circle is made, and this is represented by the xy coordinates of the xy color system. .. This makes it possible to evaluate the relationship between the orientation (circumferential position) and the color change at a 60 ° viewing angle.
It is preferable that the change in hue is small, and it is preferable that various colors are not straddled when going around at a viewing angle of 60 °. Therefore, it can be said that the thin shape shown by E2 in FIG. 5 (b) has less change in hue and is preferable to the shape close to a circle as shown in E1 in FIG. 5 (a).
Table 1 shows the results under each condition. In Table 1, the one close to a circle like E1 is referred to as "circular", and the thin shape indicated by E2 is referred to as "linear". Those that are close to a circle are represented in three stages, large, medium, and small, depending on the area. In addition, the linear ones are divided into three stages according to the fineness, and are represented by A, B, and C in the order of fineness. It can be said that a thinner one is preferable because the change in color can be further suppressed.

Table 1 shows the results of changes in the viewing angle hue.

As can be seen from Table 1, .DELTA.N _A becomes linear at greater than 1.0 range, it was possible to reduce the change in hue.
Further, 0.94 ≦ ΔN _A ≦ 1.10 and,, 0.82 ≦ .DELTA.N in _C ≦ 1.00, but there is a case where if the circular is linear, middle is the area even if it is circular Or it is small, and it can be said that the change in hue is relatively small.

<Phase difference during stacking>
With the positive A plate and the positive C plate laminated, the thickness direction retardation Rth _p at a wavelength of 450 nm, the thickness direction retardation Rth _q at a wavelength of 550 nm, and the thickness direction retardation Rth _r at a wavelength of 650 nm were calculated, and these Rth _p. , Rth _q , Rth _r , the difference between the maximum value and the minimum value was calculated, and Rth _s was obtained. The results are shown in Table 2.

Results of this Rth _s, was subjected to comparison with the evaluation result of a change in hue described above, Rth _s has been found to be particularly change in hue is small when it is 25 or less.

10 Phase difference film 11 Base material 12 Alignment film 13 Positive C plate 14 Positive A plate 20 Liquid crystal display device 22 Surface light source device 23 Liquid crystal display panel 24 Linear polarizing plate 25 Liquid crystal cell 26 Optical functional laminate 27 Polarizer 28 Base material 30 Organic EL display device 33 Organic EL display panel 36 Optical functional laminate 37 Polarizer 38 Base material

Claims (5)

It comprises a positive A-type characteristics, when the front retardation at the wavelength of 450nm was front retardation at a wavelength of _Re A450, 550 nm and _{Re A550,} .DELTA.N _A obtained by Re A450 _{/ Re A550} is 1. With a positive A plate that is 10 or more,
Possess a positive C plate with a positive C-type properties and,
Wherein the thickness direction retardation at a wavelength of the positive C plate of 450nm thickness direction retardation and _{Rth C550} at a wavelength of _Rth C450, 550 _nm, when the value obtained by Rth C450 _{/ Rth C550} and .DELTA.N _C, Nc is 1.10 or more Both are
| ΔN _A -ΔN _C | ≦ 0.2
And
The thickness direction retardation at a wavelength of 450 nm in the laminated state of the positive A plate and the positive C plate is Rth _p , and the thickness direction retardation at a wavelength of 550 nm in the laminated state of the positive A plate and the positive C plate is Rth _q . When the thickness direction retardation at a wavelength of 650 nm in the laminated state of the positive A plate and the positive C plate is Rth _r , the maximum value and the minimum value among the _{Rth p} , the Rth _q , and the Rth _r. The difference with is 25 or less,
Phase difference film. The retardation film according to claim 1, wherein at least one of the positive A plate and the positive C plate contains a polymerizable rod-shaped liquid crystal material. The retardation film according to claim 1 or 2 , wherein the front retardation of the positive A plate at a wavelength of 550 nm is 110 nm or more and 160 nm or less. Two polarizing plates and
A polarizing plate compensating film comprising the retardation film according to any one of claims 1 to 3 arranged between the two polarizing plates. The retardation film according to any one of claims 1 to 3 arranged on the light emitting side of the organic EL laminate, and the retardation film.
A polarizing element for linearly polarized light laminated on the retardation film and
External light anti-reflection film.

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