JP7302999B2 - Optical layered body and image display device using the optical layered body - Google Patents

Description

The present invention relates to an optical layered body and an image display device using the optical layered body.

Image display devices (for example, liquid crystal display devices, organic EL display devices, and quantum dot display devices) often have a polarizing plate disposed on at least one side of the display cell due to the image forming method thereof. there is It is widely known that a polarizing plate disposed on the viewing side of an image display device is provided with a reflection prevention layer on the viewing side in order to prevent external light from reflecting on the display screen. In particular, in a polarizing plate used for a display screen of a notebook computer or the like, a reflection-preventing layer may be useful for preventing reflection of a keyboard or the like. By the way, if such a notebook computer is folded in the presence of foreign matter, a local load may be applied due to the foreign matter. Depending on the structure of the polarizing plate, such a local load may damage the polarizing plate, resulting in light leakage or bright spots (so-called white dots) in the image display device.

JP-A-2002-297041 JP-A-2005-024753

The present invention has been made to solve the above problems, and its main purpose is to prevent cracks from occurring even when a load of a predetermined value or more is applied locally, resulting in light leakage and brightness. An object of the present invention is to provide an optical layered body capable of realizing an image display device in which spots are suppressed and in which warping in a high-temperature environment is suppressed.

The optical laminate of the present invention comprises a polarizing plate having a polarizer and a protective layer provided on one side of the polarizer; a layer, a first base material on which the anti-reflection layer is directly formed, a second base material bonded to the first base material via a second pressure-sensitive adhesive layer, and the second base material. a hard coat layer directly formed on a substrate of the polarizing plate, a first retardation layer and a second retardation layer provided in order from the polarizing plate side on the opposite side of the polarizing plate from the reflection prevention layer; and the total thickness from the protective layer to the outermost layer on the hard coat layer side is 100 μm to 250 μm , and the first retardation layer and the second retardation layer are adhesive layers The thickness of the adhesive layer is 5 μm or less, and the storage elastic modulus of the adhesive layer is 1.0×10 6 ^Pa or more. The optical layered body does not cause light leakage after a piercing test with a load of 3 kg .
In one embodiment, the thicknesses of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer are each 10 μm to 30 μm.
In one embodiment, the indentation elastic moduli of the protective layer and the second base material are each 3.0 GPa or more.
In one embodiment, the thickness of the polarizer is 10 μm or less.
In one embodiment, the anti-glare layer is a fixed alignment layer of a liquid crystal compound.
In one embodiment, the refractive index characteristics of the first retardation layer exhibit a relationship of nx>ny>nz, and the refractive index characteristics of the second retardation layer exhibit a relationship of nz>nx>ny indicates
In one embodiment , the optical laminate has a total thickness of 176 μm to 250 μm from the protective layer to the outermost layer on the hard coat layer side.
Another optical layered body of the present invention comprises a polarizing plate having a polarizer and a protective layer provided on one side of the polarizer, and a second adhesive layer bonded to the protective layer via a second pressure-sensitive adhesive layer. 2 substrate, a hard coat layer formed directly on the second substrate, a first retardation layer provided in order from the polarizing plate side on the opposite side of the polarizing plate to the hard coat layer, and and a second retardation layer, the total thickness from the protective layer to the outermost layer on the hard coat layer side is 100 μm to 250 μm , and the first retardation layer and the second retardation layer The retardation layer is attached via an adhesive layer, the thickness of the adhesive layer is 5 μm or less, and the storage elastic modulus of the adhesive layer is 1.0×10 6 Pa or ^more . . The optical layered body does not cause light leakage after a piercing test with a load of 3 kg . In one embodiment, the refractive index characteristics of the first retardation layer exhibit a relationship of nx>ny>nz, and the refractive index characteristics of the second retardation layer exhibit a relationship of nz>nx>ny indicates
According to another aspect of the present invention, an image display device is provided. This image display device includes the above-described optical layered body on the viewing side, and the above-described hard coat layer of the optical layered body is arranged on the viewing side.

According to the present invention, by setting the total thickness of the constituent elements on one side (typically, the viewing side) of the polarizer in the optical layered body to a predetermined range, a load of a predetermined value or more is applied locally. As a result, an image display device in which light leakage and bright spots are suppressed can be realized, and an optical laminate in which warping in a high-temperature environment is suppressed can be obtained. .

1 is a schematic cross-sectional view of an optical stack according to one embodiment of the invention; FIG. 4 is a schematic cross-sectional view of an optical stack according to another embodiment of the invention; FIG.

Embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.

A. 1. Overall Configuration of Optical Layered Body FIG. 1 is a schematic cross-sectional view of an optical layered body according to one embodiment of the present invention. The illustrated optical laminate 100 includes a polarizing plate 10 having a polarizer 11 and a protective layer 12, an anti-glare layer 40, a first substrate 50, a second substrate 20, and a hard coat layer 30. and are provided in this order. The anti-glare layer 40 is directly formed on the first base material 50 and attached to the protective layer 12 via the first adhesive layer 61 . The second base material 20 is attached to the first base material 50 via the second adhesive layer 62 . A hard coat layer 30 is directly formed on the second base material 20 . As used herein, "directly" means that an adhesive layer (typically, an adhesive layer or a pressure-sensitive adhesive layer) is not interposed. If necessary, the second base material 20 may have an antireflection layer and/or an adhesion layer (both not shown) on the surface on the hard coat layer 30 side. This configuration is also included in the form in which "the hard coat layer is directly formed on the substrate." An antireflection layer may be provided outside the hard coat layer 30 . If necessary, an antifouling layer (not shown) may be provided on the surface of the outermost layer on the hard coat layer side (substantially, the hard coat layer, or the antireflection layer if present). good.

In another embodiment (not shown), an optical laminate comprises a polarizing plate, a second substrate and a hard coat layer in this order. The hard coat layer is formed directly on the second base material. In this embodiment, the second base material is attached to the protective layer via the second pressure-sensitive adhesive layer. That is, in the embodiment of the present invention, the anti-glare layer (and the substrate on which the anti-glare layer is formed) and the first substrate to which the anti-glare layer is adhered may be omitted.

In the embodiment of the present invention, the total thickness ( hereinafter sometimes simply referred to as total thickness) is 100 μm to 250 μm . If the total thickness is within such a range, cracks do not occur even when a load of a predetermined value or more is applied locally, and as a result, an image display device in which light leakage and bright spots are suppressed is realized. In addition, it is possible to obtain an optical layered body in which warping in a high-temperature environment is suppressed. The total thickness is preferably 120 μm to 250 μm , more preferably 150 μm to 250 μm , even more preferably 180 μm to 250 μm , particularly preferably 200 μm to 250 μm . If the total thickness is too small, the effect of suppressing cracks may be insufficient. If the total thickness is too large, the holding stress when shrinking or expanding under the influence of environmental temperature and/or humidity becomes large, and warping of the optical laminate in a high temperature and/or high humidity environment becomes a problem. There is In addition, since the thickness of any of the optionally provided layers (for example, the adhesion layer, the antireflection layer, or the antifouling layer) is very small, the presence or absence of these layers does not substantially affect the total thickness. It does not substantially affect the effects of the present invention.

Each of the first adhesive layer 61 and the second adhesive layer 62 preferably has a thickness of 10 μm to 30 μm, more preferably 12 μm to 25 μm. If the thicknesses of the first and second pressure-sensitive adhesive layers are within such ranges, the desired total thickness can be easily achieved. If the thickness of at least one of the first and second pressure-sensitive adhesive layers is too small, the resulting optical layered body may have insufficient durability. If the thicknesses of the first and second pressure-sensitive adhesive layers are too large, the adjacent substrates may easily deform when stress is applied, resulting in an insufficient crack control effect.

The indentation elastic moduli of the protective layer 12 and the second base material 52 are each preferably 3.0 GPa or more, more preferably 3.5 GPa to 5.0 GPa. If the indentation elastic moduli of the protective layer and the second base material are in such ranges, respectively, the effect of suppressing cracks can be more pronounced.

The optical laminate may be provided with a retardation layer as shown in FIG. In the optical laminate 101 of the illustrated example, a first retardation layer 71 and a second retardation layer 72 are provided in order from the polarizer 11 side on the opposite side of the polarizer 11 from the protective layer 12 . The first retardation layer 71 typically has refractive index characteristics of nx>ny>nz. The second retardation layer 72 typically has refractive index characteristics of nz>nx>ny. The first retardation layer 71 may also serve as a protective layer on the side opposite to the viewing side of the polarizer. In the optical layered body 101 , the first retardation layer 71 and the second retardation layer 72 are bonded together with an adhesive layer 80 interposed therebetween. By using an adhesive for laminating the retardation layer, the effect of suppressing cracks can be more remarkable. If an adhesive is used for laminating the retardation layer, the effect of suppressing cracks may be insufficient.

In the illustrated example, the protective layer 12 is provided only on one side of the polarizer 11, but another protective layer may be provided on the side opposite to the protective layer 12 depending on the purpose. Furthermore, any appropriate functional layer may be provided depending on the purpose. Representative examples of the functional layer include a conductive layer and a retardation layer other than the above. The type, number, combination, arrangement position, and characteristics of the functional layers can be appropriately set according to the purpose. If a conductive layer is provided, the conductive layer is typically provided on the opposite side of the polarizer 11 from the protective layer 12 . By providing the conductive layer at such a position, the optical layered body can be suitably used for an inner touch panel type input display device.

The optical layered body according to the embodiment of the present invention preferably does not cause light leakage after a piercing test with a load of 3 kg. The piercing test can be performed, for example, by attaching a predetermined needle to a compression tester and piercing the optical layered body with the needle with a load of 3 kg. "No light leakage" means that the optical layered body after the penetration test and the standard polarizing plate are arranged so that the polarizer of the optical layered body and the polarizer of the polarizing plate are in a crossed Nicols state, and visually observed. A state in which no light leakage is observed when observed.

The constituent elements of the optical layered body will be described below.

B. Polarizing plate B-1. Polarizer The polarizer 11 is typically composed of a resin film containing a dichroic substance. Any appropriate resin film that can be used as a polarizer can be adopted as the resin film. The resin film is typically a polyvinyl alcohol-based resin (hereinafter referred to as "PVA-based resin") film. The resin film may be a single-layer resin film or a laminate of two or more layers.

A specific example of a polarizer composed of a single-layer resin film is a PVA-based resin film that has been dyed with iodine and stretched (typically, uniaxially stretched). The dyeing with iodine is performed by, for example, immersing the PVA-based film in an aqueous iodine solution. The draw ratio of the uniaxial drawing is preferably 3 to 7 times. Stretching may be performed after the dyeing treatment, or may be performed while dyeing. Moreover, you may dye after extending|stretching. If necessary, the PVA-based resin film is subjected to swelling treatment, cross-linking treatment, washing treatment, drying treatment, and the like. For example, by immersing the PVA-based resin film in water and washing it with water before dyeing, it is possible not only to wash away stains and anti-blocking agents on the surface of the PVA-based film, but also to swell the PVA-based resin film to prevent uneven dyeing. etc. can be prevented.

Specific examples of the polarizer obtained using a laminate include a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a resin substrate and the resin A polarizer obtained by using a laminate with a PVA-based resin layer formed by coating on a substrate can be mentioned. A polarizer obtained by using a laminate of a resin base material and a PVA-based resin layer formed by coating on the resin base material is obtained, for example, by applying a PVA-based resin solution to the resin base material and drying the resin base material. forming a PVA-based resin layer thereon to obtain a laminate of a resin substrate and a PVA-based resin layer; stretching and dyeing the laminate to use the PVA-based resin layer as a polarizer; obtain. In this embodiment, stretching typically includes immersing the laminate in an aqueous boric acid solution and stretching. Furthermore, stretching may further include stretching the laminate in air at a high temperature (eg, 95° C. or higher) before stretching in an aqueous boric acid solution, if necessary. The obtained resin substrate/polarizer laminate may be used as it is (that is, the resin substrate may be used as a protective layer for the polarizer), or the resin substrate may be peeled off from the resin substrate/polarizer laminate. Then, any appropriate protective layer may be laminated on the release surface according to the purpose. Details of a method for manufacturing such a polarizer are described, for example, in Japanese Patent Application Laid-Open No. 2012-73580. The publication is incorporated herein by reference in its entirety.

The thickness of the polarizer is preferably 10 μm or less, more preferably 8 μm or less, still more preferably 7 μm or less. On the other hand, the thickness of the polarizer is preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 3 μm or more. If the thickness of the polarizer is within such a range, it is possible to satisfactorily suppress curling during heating, and obtain excellent durability in appearance during heating. Furthermore, if the thickness of the polarizer is within such a range, even if the total thickness is set within a predetermined range, the thickness of the optical layered body (and, as a result, the image display device) can be reduced.

The polarizer preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The single transmittance of the polarizer is preferably 43.0% to 46.0%, more preferably 44.5% to 46.0%. The degree of polarization of the polarizer is preferably 97.0% or higher, more preferably 99.0% or higher, still more preferably 99.9% or higher.

B-2. Protective Layer Any appropriate resin film is used as the protective layer 12 . Materials for forming the resin film include, for example, (meth)acrylic resins, cellulose resins such as diacetyl cellulose and triacetyl cellulose, olefin resins such as polypropylene, ester resins such as polyethylene terephthalate resins, polyamide resins, Examples include polycarbonate resins and copolymer resins thereof. In addition, "(meth)acrylic resin" refers to acrylic resin and/or methacrylic resin.

In one embodiment, a (meth)acrylic resin having a glutarimide structure is used as the (meth)acrylic resin. (Meth)acrylic resins having a glutarimide structure (hereinafter also referred to as glutarimide resins) are disclosed, for example, in JP-A-2006-309033, JP-A-2006-317560, JP-A-2006-328329, and JP-A-2006-328329. 2006-328334, JP 2006-337491, JP 2006-337492, JP 2006-337493, JP 2006-337569, JP 2007-009182, JP 2009- No. 161744 and Japanese Patent Application Laid-Open No. 2010-284840. These descriptions are incorporated herein by reference.

The thickness of the protective layer is typically 10 μm to 100 μm, preferably 20 μm to 40 μm. If the thickness of the protective layer is within such a range, the desired total thickness can be easily achieved. A protective layer is typically laminated on a polarizer via an adhesive layer (specifically, an adhesive layer, an adhesive layer). The adhesive layer is typically formed of a PVA-based adhesive or an activated energy ray-curable adhesive. The adhesive layer is typically formed with an acrylic adhesive.

As described above, the indentation modulus of the protective layer is preferably 3.0 GPa or more, more preferably 3.5 GPa to 5.0 GPa. As described above, when the indentation elastic modulus of the protective layer is within this range, the effect of suppressing cracks can be more pronounced due to the synergistic effect with the effect of the indentation elastic modulus of the second base material. The indentation modulus can be measured according to JIS Z 2255.

C. Anti-Reflection Layer The anti-reflection layer is provided to prevent reflection of the user's face of the image display device, the keyboard of the image display device, external light (for example, fluorescent lamp), and the like. The glare-preventing layer is typically an alignment and solidification layer of a liquid crystal compound. As used herein, the term "fixed alignment layer" refers to a layer in which a liquid crystal compound is aligned in a predetermined direction and the alignment state is fixed. In addition, the "alignment fixed layer" is a concept including an alignment cured layer obtained by curing a liquid crystal monomer. The anti-glare layer is typically formed by coating a composition containing a liquid crystal compound on the surface of an alignment film (not shown) formed on the first substrate, and solidifying and/or curing the coating layer. It is formed by The liquid crystal compound may be a rod-like liquid crystal compound, a discotic (disk-like) liquid crystal compound, or a combination thereof.

The thickness of the anti-glare layer is preferably 1 μm to 5 μm, more preferably 1 μm to 3 μm.

Details of constituent materials, optical properties, formation methods, etc. of the anti-glare layer are described in, for example, Japanese Patent Application Laid-Open No. 2018-155998. The description of the publication is incorporated herein by reference.

D. First and Second Substrates The first substrate 50 is used to form the anti-glare layer 40 . A second substrate 20 is used to form a hard coat layer 30 (or an antireflection layer if necessary).

As described above, the indentation modulus of the second base material is preferably 3.0 GPa or more, more preferably 3.5 GPa to 5.0 GPa. As described above, if the indentation elastic modulus of the second base material is within such a range, the effect of suppressing cracks can be more pronounced due to the synergistic effect with the effect of the indentation elastic modulus of the protective layer. Note that the indentation modulus of elasticity of the first substrate may also be the same as that of the second substrate.

Each of the first and second substrates may be composed of any appropriate resin film capable of satisfying the desired indentation elastic modulus. Materials for forming the resin film include, for example, polyester resins such as polyethylene terephthalate (PET), cellulose resins such as triacetyl cellulose (TAC), and acrylic resins.

The thicknesses of the first and second substrates can be appropriately set according to the purpose. The thickness of the first and second substrates is typically 20 μm to 200 μm, preferably 25 μm to 100 μm. If the thicknesses of the first and second substrates are within this range, the desired total thickness can be easily achieved.

E. First and Second Adhesive Layers The first and second adhesive layers 61 and 62 are collectively described as adhesive layers. As described above, the thickness of the adhesive layer is preferably 10 μm to 30 μm, more preferably 12 μm to 25 μm. As described above, if the thickness of the pressure-sensitive adhesive layer is within such a range, the desired total thickness can be easily achieved.

The adhesive layer can be composed of any appropriate adhesive. Typical examples of adhesives constituting the adhesive layer include acrylic adhesives, urethane adhesives, and rubber adhesives. An acrylic pressure-sensitive adhesive is preferred. This is because it has excellent transparency and it is easy to adjust the mechanical properties (for example, storage modulus) by changing the compounding ratio of the monomer units. An acrylic pressure-sensitive adhesive (acrylic pressure-sensitive adhesive composition) typically contains a (meth)acrylic polymer as a main component. The (meth)acrylic polymer can be contained in the PSA composition in a proportion of, for example, 50% by weight or more, preferably 70% by weight or more, more preferably 90% by weight or more, based on the solid content of the PSA composition. A (meth)acrylic polymer contains alkyl (meth)acrylate as a main component as a monomer unit. (Meth)acrylate refers to acrylate and/or methacrylate. Alkyl groups of alkyl (meth)acrylates include, for example, linear or branched alkyl groups having 1 to 18 carbon atoms. The average number of carbon atoms in the alkyl group is preferably 3-9. Monomers constituting the (meth)acrylic polymer include carboxyl group-containing monomers, hydroxyl group-containing monomers, amide group-containing monomers, aromatic ring-containing (meth)acrylates, etc., in addition to alkyl (meth)acrylates. The acrylic pressure-sensitive adhesive composition can preferably contain a silane coupling agent and/or a cross-linking agent. Silane coupling agents include, for example, epoxy group-containing silane coupling agents. Examples of cross-linking agents include isocyanate-based cross-linking agents and peroxide-based cross-linking agents. Details of the acrylic pressure-sensitive adhesive composition are described, for example, in JP-A-2016-190996, and the description of the publication is incorporated herein by reference.

The storage modulus of the adhesive layer at 25° C. is preferably 0.05 MPa to 0.25 MPa, more preferably 0.10 MPa to 0.22 MPa, and more preferably 0.13 MPa to 0.20 MPa.

F. Hard Coat Layer The hard coat layer 30 preferably has sufficient surface hardness, excellent mechanical strength, and excellent optical transparency. The hard coat layer can be formed from any suitable resin as long as it has such desired properties. Specific examples of resins include thermosetting resins, thermoplastic resins, ultraviolet curing resins, electron beam curing resins, and two-liquid mixed resins. A UV curable resin is preferred. This is because the hard coat layer can be formed with simple operation and high efficiency.

Specific examples of UV curable resins include polyester, acrylic, urethane, amide, silicone and epoxy UV curable resins. UV-curable resins include UV-curable monomers, oligomers, and polymers. Preferred UV-curable resins include resin compositions containing acrylic monomer or oligomer components having preferably 2 or more, more preferably 3 to 6, UV-polymerizable functional groups. Typically, the UV curable resin contains a photopolymerization initiator.

A hard coat layer may be formed by any appropriate method. For example, the hard coat layer can be formed by coating a hard coat layer-forming resin composition on the second base material, drying it, and curing the dried coating film by irradiating it with ultraviolet rays.

The thickness of the hard coat layer is, for example, 0.5 μm to 20 μm, preferably 1 μm to 15 μm. If the thickness of the hard coat layer is within such a range, the desired total thickness can be easily achieved.

G. First Retardation Layer The first retardation layer 71 may be composed of a retardation film having any suitable optical properties and/or mechanical properties depending on the purpose.

The in-plane retardation Re(550) of the first retardation layer is preferably 80 nm to 150 nm, more preferably 90 nm to 140 nm, still more preferably 100 nm to 130 nm. As used herein, "Re(λ)" is an in-plane retardation measured with light having a wavelength of λ nm at 23°C. For example, "Re(550)" is the in-plane retardation measured with light having a wavelength of 550 nm at 23°C. Re(λ) is obtained by the formula: Re(λ)=(nx−ny)×d, where d (nm) is the thickness of the layer (film). Here, “nx” is the refractive index in the direction in which the in-plane refractive index is maximized (that is, the slow axis direction), and “ny” is the in-plane direction orthogonal to the slow axis (that is, the fast axial direction).

The thickness of the first retardation layer is preferably 10 μm to 60 μm, more preferably 30 μm to 50 μm.

The first retardation layer preferably exhibits a refractive index characteristic of nx>ny>nz. The Nz coefficient of the first retardation layer is preferably 1.1-3.0, more preferably 1.3-2.7. The Nz coefficient is obtained by Nz=Rth(λ)/Re(λ). Rth(λ) is the retardation in the thickness direction. For example, Rth(550) is the retardation in the thickness direction measured at 23° C. with light having a wavelength of 550 nm. Rth(550) is obtained by Rth=(nx−nz)×d. "nz" is the refractive index in the thickness direction.

The first retardation layer may preferably be arranged such that its slow axis is substantially parallel to the absorption axis of the polarizer. As used herein, the expressions “substantially parallel” and “substantially parallel” include cases where the angle formed by two directions is 0°±7°, preferably 0°±5°, more preferably is 0°±3°. The expressions "substantially orthogonal" and "substantially orthogonal" include the case where the angle formed by the two directions is 90°±7°, preferably 90°±5°, more preferably 90°± 3°. Further, references herein to simply "orthogonal" or "parallel" are intended to include substantially orthogonal or substantially parallel states. Also, references herein to angles include both clockwise and counterclockwise relative to a reference direction.

The absolute value of the photoelastic coefficient of the first retardation layer is preferably 2×10 ⁻¹¹ m ² /N or less, more preferably 2.0×10 ⁻¹³ m ^{2 /} N to 1.5×10 ⁻¹¹ m ² /N, more preferably 1.0×10 ⁻¹² m ² /N to 1.2× ^{10 −11} m ² /N of resin. If the absolute value of the photoelastic coefficient is within such a range, the phase difference is less likely to change when shrinkage stress occurs during heating. Therefore, by forming the first retardation layer using a resin having such an absolute value of photoelastic coefficient, heat unevenness can be satisfactorily prevented when the optical layered body is applied to an image display device.

The first retardation layer may exhibit a reverse wavelength dispersion characteristic in which the retardation value increases according to the wavelength of the measurement light, or has a positive wavelength dispersion characteristic in which the retardation value decreases according to the wavelength of the measurement light. It may also show a flat wavelength dispersion characteristic in which the phase difference value hardly changes even with the wavelength of the measurement light. It preferably exhibits a flat wavelength dispersion characteristic. Specifically, Re(450)/Re(550) of the first retardation layer is preferably 0.99 to 1.03, and Re(650)/Re(550) is preferably 0.98 to 1.02. By arranging a λ / 2 plate (first retardation layer) and a λ / 4 plate (second retardation layer) having flat wavelength dispersion characteristics at a predetermined axis angle, ideal reverse wavelength dispersion It is possible to obtain characteristics close to the characteristics, and as a result, very excellent antireflection characteristics can be realized.

The first retardation layer may be composed of any appropriate resin film that can satisfy the properties as described above. Representative examples of such resins include cyclic olefin-based resins, polycarbonate-based resins, cellulose-based resins, polyester-based resins, polyvinyl alcohol-based resins, polyamide-based resins, polyimide-based resins, polyether-based resins, polystyrene-based resins, and acrylic resins. system resin. Among them, cyclic olefin resins can be preferably used. The first retardation layer is obtained, for example, by stretching a film formed from the above resin. Details of the cyclic olefin resin and the stretching method of the resin film (method of forming the retardation film) are described in, for example, JP-A-2015-210459 and JP-A-2016-105166. The description of this publication is incorporated herein by reference.

H. Second Retardation Layer The second retardation layer 72 may be composed of a retardation film having any appropriate optical properties and/or mechanical properties depending on the purpose.

The in-plane retardation Re(550) of the second retardation layer is preferably 10 nm to 60 nm, more preferably 20 nm to 50 nm, still more preferably 30 nm to 40 nm.

The thickness of the second retardation layer is preferably 10 μm to 50 μm, most preferably 20 μm to 40 μm.

The second retardation layer preferably exhibits a refractive index characteristic of nz>nx>ny. The Nz coefficient of the second retardation layer is preferably -10 to -0.1, more preferably -5 to -1.

The second retardation layer can preferably be arranged such that its slow axis is substantially orthogonal to the absorption axis of the polarizer.

The second retardation layer may be composed of any appropriate resin film that can satisfy the properties as described above. Such resins can typically be polymers with negative intrinsic birefringence. A polymer having negative intrinsic birefringence refers to a polymer whose refractive index in the orientation direction is relatively small when the polymer is oriented by stretching or the like. Examples of polymers having negative intrinsic birefringence include those in which chemical bonds or functional groups with large polarization anisotropy such as aromatic groups or carbonyl groups are introduced into the side chains of the polymer. Specific examples include modified polyolefin-based resins (eg, modified polyethylene-based resins), acrylic resins, styrene-based resins, maleimide-based resins, fumarate-based resins, and the like. The second retardation layer can be obtained, for example, by appropriately stretching a film formed from the above resin.

I. Adhesive Layer The adhesive layer 80 is used for laminating the first retardation layer 71 and the second retardation layer 72 as described above. By using an adhesive for laminating the retardation layer, the effect of suppressing cracks can be more remarkable. Representative examples of adhesives include water-based adhesives, solvent-based adhesives, emulsion-based adhesives, non-solvent-based adhesives, active energy ray-curable adhesives (e.g., ultraviolet-curable adhesives, electron beam-curable adhesives, ) and thermosetting adhesives. Active energy ray-curable adhesives are preferred. This is because it has the advantage that chemical stability (for example, solvent resistance and chemical resistance) can be easily obtained.

The active energy ray-curable adhesive can be selected from radical-curing, cationic-curing, and anion-curing adhesives as needed. For example, a radical-curing and cationic-curing hybrid can be used in combination as appropriate. is also possible. As the active energy ray-curable adhesive, desired properties (for example, storage elastic modulus after curing) can be obtained by adjusting the type, combination, and blending ratio of double bond-containing monomers and/or oligomers, cross-linking agents, etc. ) can be obtained. Specific examples of active energy ray-curable adhesives include (meth)acrylate adhesives. (Meth)acrylate means acrylate and/or methacrylate. The curable component in the (meth)acrylate adhesive includes, for example, a compound having a (meth)acryloyl group and a compound having a vinyl group. A compound having an epoxy group or an oxetanyl group can also be used as a cationic polymerization-curable adhesive. The compound having an epoxy group is not particularly limited as long as it has at least two epoxy groups in the molecule, and various commonly known curable epoxy compounds can be used.

The thickness of the adhesive layer is typically 0.01 μm to 7 μm, preferably 0.01 μm to 5 μm. According to the embodiment of the present invention, on one side (typically, the viewing side) of the polarizer of the optical layered body, it is preferable that the total thickness is equal to or greater than a predetermined value as described above, but on the opposite side It is preferable to employ an adhesive layer having such a small thickness instead of a pressure-sensitive adhesive layer that can ensure a sufficient thickness. This result is the opposite of what is expected from the technical common sense in the industry, and is an unexpectedly excellent effect.

The storage elastic modulus of the adhesive layer is preferably 1.0×10 ⁶ Pa or more, more preferably 1.0×10 ⁷ Pa or more in the region of 70° C. or lower. The upper limit of the storage elastic modulus of the adhesive layer is, for example, 1.0×10 ¹⁰ Pa. If the storage elastic modulus of the adhesive layer is in such a range, the unexpected excellent effect as described above can be achieved.

J. Image Display Device The optical layered body according to the embodiment of the present invention can be applied to an image display device. Accordingly, embodiments of the present invention also include such image display devices. An image display device typically includes the above-described optical layered body on the viewing side. The optical layered body is typically arranged with the hard coat layer on the viewing side. Typical examples of image display devices include liquid crystal display devices, organic electroluminescence (EL) display devices, and quantum dot display devices. In the optical layered body according to the embodiment of the present invention, cracking is suppressed even when a load of a predetermined value or more is applied locally. As a result, the image display device according to the embodiment of the present invention including such an optical layered body has suppressed light leakage and bright spots. That is, according to the embodiment of the present invention, the so-called white dot phenomenon can be prevented. Therefore, if the image display device is a notebook computer, the effect of the present invention can be remarkable. Furthermore, according to the embodiments of the present invention, it is possible to realize an image display device in which warpage is suppressed.

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not limited to these Examples. In addition, the measuring method of each characteristic is as follows.

(1) Puncture test The optical laminates obtained in Examples and Comparative Examples were placed in a compression tester equipped with a needle (manufactured by Kato Tech Co., Ltd., product name “NDG5”, needle penetration force measurement specifications), and tested at room temperature. It was pierced with a load of 3 kg under an environment of (23°C ± 3°C). After the piercing test, the optical layered body and the standard polarizing plate were arranged so that the polarizer of the optical layered body and the polarizer of the polarizing plate were in a crossed Nicols state. evaluated with
◎: Light leakage is not observed ○: Light leakage is slightly observed, but no practical problem (2) Durability The optical laminates obtained in Examples and Comparative Examples were bonded to glass plates to prepare test samples. After placing this test sample in an environmental tester (two conditions of 85° C. and 65° C./90% RH) for a predetermined period of time, it was placed on top of the backlight with another polarizing plate in a crossed Nicols state. The appearance was observed with an optical microscope and evaluated according to the following criteria. As for the appearance, the degree of light leakage at the corners and bubbling and peeling at the edges were observed.
◎: No poor appearance is observed ○: Slight appearance failure is observed but there is no practical problem △: Appearance failure is observed to the extent that it can affect practical use (3) Warp The focal lengths at the four corners of the optical laminates obtained in Examples and Comparative Examples were measured using a plane biaxial measuring device (manufactured by Mitutoyo Corporation, product name: Quick Vision Apex). Then, the laminate was placed under reliability test conditions (85° C.) for 24 hours, and the focal lengths of the four corners of the optical laminate were similarly measured. The difference in focal length before and after the placement of the reliability test at each corner was calculated, and the average value of the four corners was taken as the amount of warpage of each polarizing plate set. Based on the amount of warpage obtained, the warpage was evaluated according to the following criteria.
◎: 0 mm or more and 0.5 mm or less ○: More than 0.5 mm and 1.0 mm or less △: More than 1.0 mm and 2.0 mm or less ×: More than 2.0 mm

[Example 1]
1. Preparation of polarizing plate (polarizer laminate) As a resin substrate, a long, amorphous isophthalic acid-copolymerized polyethylene terephthalate (IPA-copolymerized PET) film with a Tg of 75°C and a water absorption of 0.75% (thickness: 100 μm) was used. One side of the substrate was subjected to corona treatment, and the corona-treated side was coated with polyvinyl alcohol (degree of polymerization: 4,200, degree of saponification: 99.2 mol%) and acetoacetyl-modified PVA (degree of polymerization: 1,200, degree of acetoacetyl modification: 4.6). %, degree of saponification 99.0 mol% or more, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOSEFIMER Z200") at a ratio of 9:1. A PVA-based resin layer was formed to produce a laminate.
The resulting laminate was uniaxially stretched 2.0 times at the free end in the machine direction (longitudinal direction) between rolls with different peripheral speeds in an oven at 120° C. (in-air auxiliary stretching).
Next, the laminate was immersed in an insolubilizing bath (an aqueous boric acid solution obtained by blending 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 30° C. for 30 seconds (insolubilizing treatment).
Then, it was immersed in a dyeing bath at a liquid temperature of 30° C. while adjusting the iodine concentration and the immersion time so that the polarizing plate had a predetermined transmittance. In this example, 0.2 parts by weight of iodine was added to 100 parts by weight of water, and 1.5 parts by weight of potassium iodide was added to the resulting iodine aqueous solution for 60 seconds (dyeing treatment). .
Next, it was immersed for 30 seconds in a cross-linking bath at a liquid temperature of 30°C (an aqueous solution of boric acid obtained by blending 3 parts by weight of potassium iodide and 3 parts by weight of boric acid with respect to 100 parts by weight of water). (crosslinking treatment).
After that, the laminate is immersed in an aqueous solution of boric acid having a liquid temperature of 70° C. (an aqueous solution obtained by blending 4 parts by weight of boric acid and 5 parts by weight of potassium iodide with respect to 100 parts by weight of water). Meanwhile, the film was uniaxially stretched in the machine direction (longitudinal direction) between rolls with different circumferential speeds so that the total draw ratio was 5.5 (underwater stretching).
After that, the laminate was immersed in a cleaning bath having a liquid temperature of 30° C. (aqueous solution obtained by blending 4 parts by weight of potassium iodide with 100 parts by weight of water) (cleaning treatment).
Subsequently, on the surface of the PVA-based resin layer (polarizer) of the laminate, a cyclic olefin-based film (refractive index characteristics: nx>ny>nz, in-plane retardation: 116 nm) as a first retardation layer, and a second As the second retardation layer, modified polyethylene films (refractive index characteristics: nz>nx>ny, in-plane retardation: 35 nm) were sequentially laminated. An ultraviolet curable adhesive (thickness 1 μm) was used for bonding. The slow axis of the first retardation layer is 0° with respect to the absorption axis of the polarizer, and the slow axis of the second retardation layer is 90° with respect to the absorption axis of the polarizer. and pasted together. After that, the resin substrate was peeled off from the PVA-based resin layer. Subsequently, a PVA-based resin aqueous solution (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOSEFIMER (registered trademark) Z-200", resin concentration: 3% by weight) was applied, and an acrylic resin film (thickness: 40 μm, indentation modulus: 4.4 GPa) constituting the protective layer was laminated, and heated in an oven maintained at 60° C. for 5 minutes. Thus, a polarizer laminate (polarizing plate having a configuration of protective layer/polarizer/first retardation layer/adhesive layer/second retardation layer) was obtained. The polarizer had a thickness of 5 μm and a single transmittance of 42.3%.

2. Preparation of Optical Laminate A method described in <Example 1> of JP-A-2014-214177 is applied to one side of a TAC film (product name: TG40UL, thickness: 40 μm) manufactured by Fuji Film Co., Ltd. as a first base material. An alignment film and an aligned and fixed layer of a liquid crystal compound (total thickness of anti-reflection layer and alignment film: 2 μm) were formed according to No. 2, to produce a reflection-preventing laminate. The anti-glare layer had an in-plane retardation Re(550) of 270 nm, and was formed so that its slow axis formed an angle of 45° with respect to the absorption axis of the polarizer. On the other hand, a hard coat layer and an antireflection layer were sequentially formed on one side of a TAC film (product name: TD80UL, thickness: 80 μm) manufactured by Fuji Film Co., Ltd. as a second substrate by a conventional method to prepare a hard coat laminate. bottom. The total thickness of the hard coat layer and the antireflection layer was 4 μm. The anti-reflection layer of the anti-reflection laminate was attached to the protective layer (thickness: 40 µm) of the polarizing plate obtained above via an acrylic pressure-sensitive adhesive (thickness: 23 µm) as the first pressure-sensitive adhesive layer. Matched. Next, the second base material of the hard coat laminate was attached to the opposite side of the first base material from the anti-reflection layer via an acrylic adhesive (thickness: 23 μm) as a second adhesive layer. Matched. Thus, antireflection layer/hard coat layer/second substrate/second adhesive layer/first substrate/anti-glare layer/first adhesive layer/protective layer/polarizer/ An optical laminate having a structure of first retardation layer/adhesive layer/second retardation layer was obtained. In the optical laminate, the total thickness from the protective layer to the outermost layer (antireflection layer) on the hard coat side was 212 μm. The obtained optical layered body was subjected to the above evaluation. Table 1 shows the results.

[Example 2]
Same as Example 1 except that a 20 μm thick acrylic resin film (indentation modulus: 4.4 GPa) was used as the protective layer, and that the thickness of the first and second pressure-sensitive adhesive layers were each 12 μm. Then, an optical laminate was produced. In the optical laminate, the total thickness from the protective layer to the outermost layer (antireflection layer) on the hard coat side was 170 μm. The obtained optical layered body was subjected to the same evaluation as in Example 1. Table 1 shows the results.

[Example 3]
Antireflection layer/hard coat layer/second substrate/second adhesive in the same manner as in Example 1 except that the anti-glare layer, the first substrate and the first adhesive layer are not included. An optical laminate having a structure of layer/protective layer/polarizer/first retardation layer/adhesive layer/second retardation layer was obtained. In the optical laminate, the total thickness from the protective layer to the outermost layer (antireflection layer) on the hard coat side was 147 μm. The obtained optical layered body was subjected to the same evaluation as in Example 1. Table 1 shows the results.

[Example 4]
An optical laminate was produced in the same manner as in Example 3, except that the thickness of the second substrate was 40 μm. In the optical laminate, the total thickness from the protective layer to the outermost layer (antireflection layer) on the hard coat side was 107 μm. The obtained optical layered body was subjected to the same evaluation as in Example 1. Table 1 shows the results.

[Example 5]
An optical layered body was produced in the same manner as in Example 1, except that the thickness of each of the first and second pressure-sensitive adhesive layers was 5 μm. In the optical laminate, the total thickness from the protective layer to the outermost layer (antireflection layer) on the hard coat side was 176 μm. The obtained optical layered body was subjected to the same evaluation as in Example 1. Table 1 shows the results.

[Example 6]
In the same manner as in Example 1, a laminate having a structure of resin substrate/PVA-based resin layer (polarizer) was produced. A PVA-based resin aqueous solution (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name “GOSEFIMER (registered trademark) Z-200”, resin concentration: 3% by weight) is applied to the surface of the PVA-based resin layer (polarizer) of the laminate. Then, an acrylic resin film (thickness: 25 μm) constituting another protective layer was adhered, and this was heated in an oven maintained at 60° C. for 5 minutes. After that, the resin substrate was peeled off from the PVA-based resin layer. Subsequently, a PVA-based resin aqueous solution (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOSEFIMER (registered trademark) Z-200", resin concentration: 3% by weight) was applied, and an acrylic resin film (thickness: 40 μm, indentation modulus: 4.4 GPa) constituting the protective layer was adhered, and this was heated in an oven maintained at 60° C. for 5 minutes. Thus, a polarizer laminate (polarizing plate having a structure of protective layer/polarizer/another protective layer) was obtained. An optical laminate was produced in the same manner as in Example 1 except that this polarizer laminate was used. In the optical laminate, the total thickness from the protective layer to the outermost layer (antireflection layer) on the hard coat side was 212 μm. The obtained optical layered body was subjected to the same evaluation as in Example 1. Table 1 shows the results.

[Comparative Example 1]
An optical laminate was prepared in the same manner as in Example 3, except that a 20 μm thick acrylic resin film (indentation modulus: 4.4 GPa) was used as the protective layer and the thickness of the second substrate was 40 μm. was made. In the optical laminate, the total thickness from the protective layer to the outermost layer (antireflection layer) on the hard coat side was 87 μm. The obtained optical layered body was subjected to the same evaluation as in Example 1. Table 1 shows the results.

[Comparative Example 2]
An optical layered body was produced in the same manner as in Example 1, except that the thickness of each of the first and second pressure-sensitive adhesive layers was 50 μm. In the optical laminate, the total thickness from the protective layer to the outermost layer (antireflection layer) on the hard coat side was 266 μm. The obtained optical layered body was subjected to the same evaluation as in Example 1. Table 1 shows the results.

[Reference example 1]
An optical layered body was produced in the same manner as in Example 1, except that the first retardation layer and the second retardation layer were bonded together with an acrylic pressure-sensitive adhesive (thickness: 23 μm). In the optical laminate, the total thickness from the protective layer to the outermost layer (antireflection layer) on the hard coat side was 212 μm. The obtained optical layered body was subjected to the same evaluation as in Example 1. Table 1 shows the results.

As is clear from Table 1, the optical layered bodies of the examples of the present invention are excellent in balance between the puncture test and warpage. That is, the optical layered bodies of the examples of the present invention are suppressed from cracking even when a load of a predetermined value or more is applied locally, and it can be seen that the so-called white dot phenomenon can be prevented. Moreover, as is clear from Comparative Example 2, by setting the total thickness from the protective layer to the outermost layer on the hard coat side to a predetermined value or less, it is possible to suppress the warping of the optical layered body in a high-temperature environment. Furthermore, as is clear from a comparison of Examples 1 to 4 and Example 5, the durability can be remarkably improved by setting the thickness of the first and second pressure-sensitive adhesive layers to a predetermined value or more. In addition, as is clear from Reference Example 1, when two retardation layers are provided on the opposite side of the polarizer to the viewing side, an adhesive is preferable for bonding these retardation layers.

The optical laminate of the present invention is suitably used for image display devices such as liquid crystal display devices, organic EL display devices, and quantum dot display devices.

REFERENCE SIGNS LIST 10 polarizing plate 11 polarizer 12 protective layer 20 second substrate 30 hard coat layer 40 anti-glare layer 50 first substrate 61 first adhesive layer 62 second adhesive layer 71 first retardation Layer 72 Second retardation layer 80 Adhesive layer 100 Optical laminate

Claims (6)

A polarizing plate having a polarizer and a protective layer provided on one side of the polarizer, an anti-reflection layer bonded to the protective layer via a first adhesive layer, and the anti-reflection layer is formed directly on the first base material, the second base material is bonded to the first base material via the second pressure-sensitive adhesive layer, and the second base material is formed directly on the a hard coat layer, and a first retardation layer and a second retardation layer provided in order from the polarizing plate side on the opposite side of the polarizing plate from the anti-reflection layer,
The total thickness from the protective layer to the outermost layer on the hard coat layer side is 176 μm to 250 μm,
The thickness of the first pressure-sensitive adhesive layer and the thickness of the second pressure-sensitive adhesive layer are each 10 μm to 30 μm,
The first retardation layer and the second retardation layer are bonded via an adhesive layer, the thickness of the adhesive layer is 5 μm or less, and the temperature of the adhesive layer reaches 70 ° C. Storage modulus in the following region is 1.0 × 10 ⁶ Pa or more,
No light leakage occurs after a piercing test with a load of 3 kg.
Optical laminate. 2. The optical layered body according to claim 1 , wherein the indentation elastic moduli of the protective layer and the second base material are each 3.0 GPa or more. 3. The optical laminate according to claim 1 , wherein the polarizer has a thickness of 10 [mu]m or less. 4. The optical layered body according to claim 1, wherein the glare-preventing layer is a fixed alignment layer of a liquid crystal compound. from claim 1, wherein the refractive index characteristics of the first retardation layer exhibit a relationship of nx>ny>nz, and the refractive index characteristics of the second retardation layer exhibit a relationship of nz>nx>ny 5. The optical laminate according to any one of 4 . An image display device comprising the optical layered body according to any one of claims 1 to 5 on the viewing side, wherein the hard coat layer of the optical layered body is arranged on the viewing side.

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