JP7348719B2 - Composite retardation plate, optical laminate, and image display device - Google Patents

Description

The present invention relates to a composite retardation plate, an optical laminate including the composite retardation plate, and an image display device including the optical laminate.

Conventionally, in image display devices, a method has been adopted in which an optical laminate having antireflection properties is disposed on the viewing side of an image display panel to suppress a decrease in visibility due to reflection of external light.

As an optical laminate having antireflection performance, an optical laminate composed of a polarizing plate and a retardation layer is known. In an optical laminate having antireflection performance, external light directed toward an image display panel is converted into linearly polarized light by a polarizing plate, and then converted into circularly polarized light by a subsequent retardation layer. External light, which is circularly polarized light, is reflected on the surface of the image display panel, but upon this reflection, the direction of rotation of the plane of polarization is reversed, and after being converted into linearly polarized light by the retardation layer, it is blocked by the subsequent polarizing plate. Ru. As a result, radiation to the outside is significantly suppressed.

As a retardation plate that is a component of an optical laminate having antireflection performance, a composite retardation plate formed by bonding a plurality of retardation layers with an adhesive layer is known. For example, Patent Documents 1 and 2 describe a composite retardation plate formed by bonding a 1/2 wavelength layer and a 1/4 wavelength layer with an adhesive layer.

Japanese Patent Application Publication No. 2015-21975 JP2015-21976A

The composite retardation plate, alone or as an optical laminate including the same, can be transported, rolled up, etc. by contacting a roll-shaped member or on the surface of an image display panel having a bent part. When the composite retardation plate is bent due to the arrangement, wrinkles may occur at the bent portion, which may lead to quality defects. In particular, when the composite retardation plate is formed of a thin film, this phenomenon may occur significantly.

The present invention provides a method for bending a composite retardation plate by contacting a roll-shaped member or by being placed on the surface of an image display device panel having a bending portion during a process of conveyance, winding, etc. It is an object of the present invention to provide a composite retardation plate in which the occurrence of wrinkles at bent portions is suppressed even when the retardation plate is bent, an optical laminate including the composite retardation plate, and an image display device including the optical laminate.

The present invention provides a composite retardation plate, an optical laminate, and an image display device shown below.
[1] Includes a first retardation layer, a second retardation layer, and a first adhesive layer that adheres the first retardation layer and the second retardation layer,
The first adhesive layer is a composite retardation plate having a piercing slope in the thickness direction of 400 g/mm to 800 g/mm.

[2] Includes a first retardation layer, a second retardation layer, and a first adhesive layer that adheres the first retardation layer and the second retardation layer,
The first adhesive layer is a composite retardation plate having a storage modulus of 600 MPa or more at a temperature of 30°C.

[3] Includes a first retardation layer, a second retardation layer, and a first adhesive layer that adheres the first retardation layer and the second retardation layer,
The first adhesive layer is a composite retardation plate having a glass transition temperature of 60°C to 200°C.

[4] The composite retardation plate according to any one of [1] to [3], wherein the first adhesive layer is a cured product layer of an active energy ray-curable adhesive.

[5] The composite retardation plate according to any one of [1] to [4], wherein the first adhesive layer has a thickness of 0.5 μm to 5 μm.

[6] The composite retardation plate according to any one of [1] to [5], wherein the first retardation layer is a 1/2 wavelength layer and the second retardation layer is a 1/4 wavelength layer. .

[7] The first retardation layer is a 1/2 wavelength layer or a 1/4 wavelength layer, and the second retardation layer is an optical compensation layer, according to any one of [1] to [5]. composite retardation plate.

[8] The composite retardation plate according to any one of [1] to [7], wherein at least one of the first retardation layer and the second retardation layer includes a retardation expression layer that is a liquid crystal layer.

[9] The composite retardation plate according to any one of [1] to [8], which has a thickness of 2 μm to 50 μm.

[10] Comprising a polarizing plate and the composite retardation plate according to any one of [1] to [9] laminated on the polarizing plate,
The composite retardation plate is an optical laminate in which the first retardation layer is stacked in a direction facing the polarizing plate.

[11] The optical laminate according to [10], which is a circularly polarizing plate.
[12] The optical laminate according to [10] or [11], further comprising a second adhesive layer that adheres the polarizing plate and the composite retardation plate.

[13] The optical laminate according to [12], wherein the second adhesive layer is a cured layer of an active energy ray-curable adhesive.

[14] An image display device comprising an image display panel and the optical laminate according to any one of [10] to [13] arranged on the viewing side of the image display panel.

[15] The image display device according to [14], wherein the optical laminate is arranged in such a direction that the polarizing plate is located on the viewing side.

[16] The image display device according to [15], which is an organic electroluminescence display device.

According to the composite retardation plate of the present invention, by contacting a roll-shaped member during the process of conveying, winding, etc., or by being placed on the surface of an image display device panel having a bent portion, Even when the composite retardation plate is bent, the generation of wrinkles at the bent portion can be suppressed.

1 is a schematic cross-sectional view schematically showing an example of a composite retardation plate of the present invention. FIG. 2 is a schematic cross-sectional view schematically showing an example of a retardation layer including a liquid crystal layer as a retardation layer. (A) to (C) are schematic cross-sectional views schematically showing an example of each manufacturing step in the method for manufacturing a composite retardation plate of the present invention.

Hereinafter, the composite retardation plate and optical laminate of the present invention will be explained with reference to the drawings.
[Composite retardation plate]
FIG. 1 is a schematic cross-sectional view schematically showing an example of the composite retardation plate of the present invention. As shown in FIG. 1, the composite retardation plate 5 includes a first retardation layer 1, a second retardation layer 2, and a first adhesive bonding the first retardation layer 1 and the second retardation layer 2 together. layer 4. The first adhesive layer 4 satisfies at least one of the following conditions a, b, and c, and preferably satisfies two of the following conditions a, b, and c, and the following condition a. , b, and c are more preferable.
a) The piercing inclination in the thickness direction is 400 g/mm to 800 g/mm,
b) The storage modulus at a temperature of 30°C is 600 MPa or more,
c) Glass transition temperature is 60°C to 200°C.

When the first adhesive layer 4 satisfies the above condition a, even when the composite retardation plate 5 is bent, wrinkles will not occur in the first retardation layer 1 and/or the second retardation layer 2 at the bent portions. can be suppressed. When the first adhesive layer 4 satisfies the above condition a, it is preferable that the first adhesive layer 4 also satisfies the following condition a'.
a') The piercing slope in the thickness direction is 500 g/mm to 800 g/mm.

The piercing inclination of the first adhesive layer 4 represents the strength when the adhesive layer is torn when the piercing jig is perpendicularly piercing the adhesive layer. The puncture inclination can be calculated from the puncture strength, and the puncture strength can be measured using, for example, a small tabletop tester [trade name "EZ Test" manufactured by Shimadzu Corporation].

The puncture strength of the first adhesive layer 4 was determined by forming an adhesive layer test piece on a release paper under the same conditions as for the formation of the first adhesive layer 4 (type of adhesive, thickness, curing conditions). The sample is peeled off from the release paper and measured using the following method.

The puncture strength is measured by sandwiching an adhesive layer between two sample stands each having a circular hole with a diameter of 15 mm or less through which a puncture jig can pass. It is preferable that the stabbing jig is a cylindrical rod and includes a stabbing needle whose tip contacting the adhesive layer is spherical or hemispherical. The diameter of the spherical or hemispherical portion at the tip is preferably 0.5 mmφ or more and 5 mmφ or less. Further, it is preferable that the radius of curvature is larger than 0R and smaller than 0.7R. The stabbing speed of the stabbing jig is preferably 0.05 cm/sec or more and 0.5 cm/sec or less.

To measure the puncture strength, the adhesive layer test piece is fixed to a jig and punctured, and the strength is measured when it is torn at one point. The obtained puncture strength A (kg), the puncture depth B (mm) until tearing, and the following formula:
E=A/B
The piercing slope E (kg/mm) in the thickness direction is calculated using The puncture inclination of the adhesive layer is the average value of the puncture inclinations E of five or more adhesive layers produced under the same conditions.

If the first adhesive layer 4 satisfies the above condition b, wrinkles will not occur in the first retardation layer 1 and/or the second retardation layer 2 at the bent portions even when the composite retardation plate is bent. Can be suppressed. When the first adhesive layer 4 satisfies the above condition b, the storage modulus at a temperature of 30°C is preferably 600 MPa to 4000 MPa, more preferably 700 MPa to 3500 MPa, and even more preferably 1000 MPa to 3000 MPa. Preferably, it is 1500 MPa to 3000 MPa, most preferably.

The storage elastic modulus of the first adhesive layer 4 at a temperature of 30°C is the measured value if the storage elastic modulus of the first adhesive layer 4 of the composite retardation plate 5 at a temperature of 30°C can be directly measured by the following method. If direct measurement is not possible, form an adhesive layer test piece on a release paper under the same conditions as for forming the first adhesive layer 4 (type of adhesive, thickness, curing conditions), and remove the adhesive layer test piece from the release paper. This value can be regarded as the same as the storage modulus measured by the method below for the peeled product.

The storage modulus of the first adhesive layer 4 or the adhesive layer test piece can be measured using a commercially available dynamic viscoelasticity measuring device, such as a dynamic viscoelasticity measuring device (manufactured by IT Keizai Control Co., Ltd., product name: DVA-200).

When the first adhesive layer 4 satisfies the above condition c, even when the composite retardation plate 5 is bent, wrinkles are not generated in the first retardation layer 1 and/or the second retardation layer 2 at the bent portions. Can be suppressed. When the first adhesive layer 4 satisfies the above condition c, it is preferable that the first adhesive layer 4 also satisfies the following condition c'.
c') Glass transition temperature is 100 to 200°C.

The glass transition temperature of the first adhesive layer 4 is a value measured by the following method. The glass transition temperature of the first adhesive layer 4 can be measured using a differential scanning calorimeter (DSC). Note that an adhesive layer test piece was formed on a release paper under the same conditions as for the formation of the first adhesive layer 4 (type of adhesive, thickness, curing conditions), and the adhesive layer test piece was peeled from the release paper. The glass transition temperature measured by the above method can also be considered to be the same as the glass transition temperature of the first adhesive layer 4.

For example, the composite retardation plate 5 may be coated by contacting with a roll-shaped member such as a transport roll or a winding roll during the process of transporting, winding up, etc. the composite retardation plate 5 or an optical laminate including the same. Alternatively, the composite retardation plate may be held in a bent state by being placed on the surface of an image display panel having a bent portion. According to the composite retardation plate 5 of the present invention, it is possible to suppress the generation of wrinkles in the first retardation layer 1 and/or the second retardation layer 2 even in a bent state.

The thickness of the composite retardation plate 5 is preferably from 1 μm to 100 μm, more preferably from 1 μm to 50 μm, and even more preferably from 2 μm to 50 μm, from the viewpoint of thinning.
<First retardation layer and second retardation layer>
The first retardation layer 1 and the second retardation layer 2 are not particularly limited as long as they include at least one retardation expressing layer that gives a predetermined retardation to light, and for example, a 1/2 wavelength layer. , a 1/4 wavelength layer, a positive C plate, or the like, or a retardation layer with reverse wavelength dispersion. In particular, in the case of a reverse dispersion retardation layer, transmission of light is suppressed at any wavelength, so it is effective as an optical laminate having antireflection performance. As long as the first retardation layer 1 and the second retardation layer 2 include at least one retardation layer, they may be composed of only a retardation layer, or may be composed of a retardation layer and a retardation layer. It may also include other layers. Examples of other layers include a base material layer, an alignment film layer, and a protective layer. Note that other layers do not affect the value of phase difference.

Examples of the retardation layer include a layer formed using a liquid crystal compound (hereinafter referred to as "liquid crystal layer") or a stretched film. From the viewpoint of reducing the thickness of the composite retardation plate, at least one of the retardation layers included in the first retardation layer and the second retardation layer is preferably a liquid crystal layer, and both are liquid crystal layers. It is even more preferable. It is generally easier to make a retardation layer that is a liquid crystal layer thinner than a retardation layer that is a stretched film.
The thickness of each of the first retardation layer 1 and the second retardation layer 2 is preferably 0.5 μm to 10 μm, more preferably 0.5 μm to 5 μm. In addition, when the first retardation layer 1 and the second retardation layer each include other layers (base material layer, alignment film layer, protective layer, etc.) other than the retardation expressing layer, the total thickness is 0.5 μm or more. The thickness is preferably 300 μm, more preferably 0.5 μm to 150 μm.

As the thickness of the first retardation layer 1 and the second retardation layer 2 is thinner, when the composite retardation plate is bent, the first retardation layer 1 and the second retardation layer Although wrinkles are likely to occur in the layer 2, according to the composite retardation plate of the present invention, even if the first retardation layer 1 and the second retardation layer 2 are as thin as 5 μm or less as described above, wrinkles will not occur. The occurrence of can be suppressed.

Examples of the combination of the first retardation layer 1 and the second retardation layer 2 in the composite retardation plate of the present invention include:
i) combination of 1/2 wavelength layer and 1/4 wavelength layer,
ii) combination of a 1/2 wavelength layer and an optical compensation layer,
iii) a combination of a quarter wavelength layer and an optical compensation layer,
iv) combination of a reverse wavelength dispersion 1/4 wavelength layer and an optical compensation layer,
etc.

The 1/2 wavelength layer gives a phase difference of π (=λ/2) to the electric field vibration direction (polarization plane) of the incident light, and has the function of changing the direction of linearly polarized light (polarization direction). . Furthermore, when circularly polarized light is incident, the direction of rotation of the circularly polarized light can be reversed.

The 1/2 wavelength layer is a layer in which Re(λ), which is an in-plane retardation value at a specific wavelength λnm, satisfies Re(λ)=λ/2. Although Re(λ)=λ/2 may be achieved at any wavelength in the visible light range, it is preferably achieved at a wavelength of 550 nm. It is preferable that Re (550), which is an in-plane retardation value at a wavelength of 550 nm, satisfies 210 nm≦Re (550)≦300 nm. Further, it is more preferable to satisfy 220 nm≦Re(550)≦290 nm.

Rth (550), which is the retardation value in the thickness direction of the 1/2 wavelength layer measured at a wavelength of 550 nm, is preferably -150 to 150 nm, more preferably -100 to 100 nm.

The 1/4 wavelength layer gives a phase difference of π/2 (=λ/4) to the electric field vibration direction (polarization plane) of the incident light, and converts linearly polarized light of a certain wavelength into circularly polarized light (or circularly polarized light). It has the function of converting polarized light into linearly polarized light.

The 1/4 wavelength layer is a layer in which the in-plane retardation value Re (λ) at a specific wavelength λ nm satisfies Re (λ) = λ/4, and is achieved at any wavelength in the visible light range. However, it is preferable to achieve the wavelength of 550 nm. It is preferable that Re (550), which is an in-plane retardation value at a wavelength of 550 nm, satisfies 100 nm≦Re (550)≦160 nm. Further, it is more preferable to satisfy 110 nm≦Re(550)≦150 nm.

Rth (550), which is the retardation value in the thickness direction of the λ/4 wavelength layer measured at a wavelength of 550 nm, is preferably -120 to 120 nm, more preferably -80 to 80 nm.

Examples of the optical compensation layer include a positive A plate and a positive C plate. A positive A plate satisfies Nx>Ny, where the refractive index in the slow axis direction in the plane is Nx, the refractive index in the fast axis direction in the plane is Ny, and the refractive index in the thickness direction is Nz. It satisfies the relationship. The positive A plate preferably satisfies the relationship Nx>Ny≧Nz. The positive A plate can also function as a quarter wavelength layer. A positive C plate satisfies the relationship Nz>Nx≧Ny.

Reverse wavelength dispersion is an optical property in which the liquid crystal alignment in-plane retardation value at a short wavelength is smaller than the liquid crystal alignment in-plane retardation value at a long wavelength, and is preferably expressed by the following formula (a):
Re(450)≦Re(550)≦Re(650) (a)
It is to satisfy the following. Note that Re(λ) represents an in-plane retardation value for light with a wavelength of λ nm.

The optical properties of the retardation layer can be adjusted by the orientation state of the liquid crystal compound constituting the retardation layer or the stretching method of the stretched film constituting the retardation layer. By appropriately adjusting the optical properties of the retardation layer, the composite retardation plate 5 and the polarizing plate can be laminated to obtain an optical laminate having antireflection performance. The optical laminate referred to in this specification is formed by laminating a polarizing plate and a composite retardation plate 5, and the composite retardation plate 5 is oriented such that the first retardation layer 1 is located on the polarizing plate side. It is assumed that they are laminated. Even when the same composite retardation plate 5 is used, if the stacking direction of the composite retardation plate 5 is reversed, the optical properties of the optical laminate usually differ.

(Retardation layer formed from liquid crystal layer)
A case where the retardation layer is a liquid crystal layer will be described. FIG. 2 is a schematic cross-sectional view schematically showing an example of a retardation layer including a retardation expression layer, which is a liquid crystal layer, and other layers. As shown in FIG. 2, the retardation layer 30 includes a base material layer 31, an alignment layer 32, and a retardation layer 33, which is a liquid crystal layer, laminated in this order. The retardation layer is not limited to the retardation layer 30 shown in FIG. 2 as long as it includes the retardation expression layer 33 of the liquid crystal layer, and the base material layer 31 is peeled off from the retardation layer 30 to form an alignment layer. 32 and the retardation layer 33, or a structure in which the base layer 31 and the alignment layer 32 are peeled off from the retardation layer 30 and only the retardation layer 33 of the liquid crystal layer is formed. good.
From the viewpoint of thinning the layer, the retardation layer preferably has a structure in which the base layer 31 is peeled off, and more preferably a structure in which only the retardation layer 33 of the liquid crystal layer is formed. The base layer 31 functions as a support layer that supports the alignment layer 32 formed on the base layer 31 and the retardation layer 33 of the liquid crystal layer. The base layer 31 is preferably a film made of a resin material.

As the resin material, for example, a resin material having excellent transparency, mechanical strength, thermal stability, stretchability, etc. is used. Specifically, polyolefin resins such as polyethylene and polypropylene; cyclic polyolefin resins such as norbornene polymers; polyester resins such as polyethylene terephthalate and polyethylene naphthalate; (meth)acrylic acid, poly(meth)methyl acrylate, etc. (meth)acrylic acid resins; cellulose ester resins such as triacetyl cellulose, diacetyl cellulose and cellulose acetate propionate; vinyl alcohol resins such as polyvinyl alcohol and polyvinyl acetate; polycarbonate resins; polystyrene resins; Arylate resins; polysulfone resins; polyethersulfone resins; polyamide resins; polyimide resins; polyetherketone resins; polyphenylene sulfide resins; polyphenylene oxide resins, and mixtures and copolymers thereof. I can do it. Among these resins, it is preferable to use any one of a cyclic polyolefin resin, a polyester resin, a cellulose ester resin, and a (meth)acrylic acid resin, or a mixture thereof. In addition, the above-mentioned "(meth)acrylic acid" means "at least one kind of acrylic acid and methacrylic acid."

The base material layer 31 may be a single layer made of one or more of the above resins, or may have a multilayer structure of two or more layers. When having a multilayer structure, the resins forming each layer may be the same or different.

Arbitrary additives may be added to the resin material forming the resin film. Examples of additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, color inhibitors, flame retardants, nucleating agents, antistatic agents, pigments, and colorants.

The thickness of the base material layer 31 is not particularly limited, but generally from the viewpoint of workability such as strength and handleability, it is preferably 5 to 200 μm, more preferably 10 to 200 μm, and 10 to 150 μm. It is even more preferable that there be.

In order to improve the adhesion between the base layer 31 and the alignment layer 32, at least the surface of the base layer 31 on the side where the alignment layer 32 is formed may be subjected to corona treatment, plasma treatment, flame treatment, etc. A primer layer or the like may also be formed. Note that when the base material layer 31 or the base material layer 31 and the alignment layer 32 are peeled off to form a retardation layer, the peeling can be facilitated by adjusting the adhesion force at the peeling interface.

The alignment layer 32 has an alignment regulating force that causes the liquid crystal compound contained in the retardation layer 33 of the liquid crystal layer formed on the alignment layer 32 to align the liquid crystal in a desired direction. Examples of the alignment layer 32 include an alignment polymer layer formed of an alignment polymer, a photoalignment polymer layer formed of a photoalignment polymer, and a groove alignment layer having an uneven pattern or a plurality of grooves on the layer surface. be able to. The thickness of the alignment layer 32 is usually 0.01 to 10 μm, preferably 0.01 to 5 μm.

The oriented polymer layer can be formed by applying a composition in which an oriented polymer is dissolved in a solvent to the base material layer 31, removing the solvent, and performing a rubbing treatment if necessary. In this case, in an oriented polymer layer formed of an oriented polymer, the alignment regulating force can be arbitrarily adjusted by adjusting the surface condition of the oriented polymer and rubbing conditions.

The photo-alignable polymer layer can be formed by applying a composition containing a polymer having a photo-reactive group or a monomer and a solvent to the base layer 31, and irradiating it with polarized light. In this case, the alignment regulating force in the photo-alignable polymer layer can be arbitrarily adjusted by adjusting the polarized light irradiation conditions for the photo-alignable polymer.

The groove alignment layer can be formed, for example, by exposing and developing the surface of a photosensitive polyimide film through an exposure mask having pattern-shaped slits to form a concavo-convex pattern, or by applying activation to a plate-shaped master having grooves on the surface. A method of forming an uncured layer of an energy ray curable resin, transferring this layer to the base material layer 31 and curing it, forming an uncured layer of an active energy ray curable resin on the base material layer 31, The layer can be formed by a method of forming irregularities by pressing a roll-shaped master having irregularities on the layer and curing the layer.

The retardation developing layer 33, which is a liquid crystal layer, is not particularly limited as long as it gives a predetermined retardation to light. Examples include those that function as a retardation expression layer, a retardation expression layer for an optical compensation layer such as a positive C plate, and a retardation expression layer for a reverse wavelength dispersion 1/4 wavelength layer.

The retardation expression layer 33, which is a liquid crystal layer, can be formed using a known liquid crystal compound.
The type of liquid crystal compound is not particularly limited, and rod-like liquid crystal compounds, discotic liquid crystal compounds, and mixtures thereof can be used. Further, the liquid crystal compound may be a polymeric liquid crystal compound, a polymerizable liquid crystal compound, or a mixture thereof. Examples of liquid crystal compounds include, for example, Japanese Patent Publication No. 11-513019, Japanese Patent Application Publication No. 2005-289980, Japanese Patent Application Publication No. 2007-108732, Japanese Patent Application Publication No. 2010-244038, Japanese Patent Application Publication No. 2010-31223, and Japanese Patent Application Publication No. 2010-31223. Liquid crystal compounds described in JP 2010-270108, JP 2011-6360, JP 2011-207765, JP 2016-81035, International Publication No. 2017/043438, and Japanese Patent Publication No. 2011-207765 can be mentioned.

For example, when using a polymerizable liquid crystal compound, a composition containing the polymerizable liquid crystal compound is applied onto the alignment layer 32 to form a coating film, and this coating film is cured to form the retardation developing layer 33. can be formed. The thickness of the retardation layer 33 is preferably 0.5 μm to 10 μm, more preferably 0.5 μm to 5 μm.

In addition to the liquid crystal compound, the composition containing the polymerizable liquid crystal compound may contain a polymerization initiator, a polymerizable monomer, a surfactant, a solvent, an adhesion improver, a plasticizer, an alignment agent, and the like. Examples of the method for applying the composition containing the polymerizable liquid crystal compound include known methods such as die coating. As a method for curing a composition containing a polymerizable liquid crystal compound, known methods such as irradiation with active energy rays (for example, ultraviolet rays) can be mentioned.

(Retardation layer comprising a stretched film as a retardation expression layer)
A case where the retardation developing layer is a stretched film will be explained. Stretched films are usually obtained by stretching a base material. As a method for stretching the base material, for example, a roll (rolled body) in which the base material is wound onto a roll is prepared, and the base material is continuously unwound from the rolled body. Transport the substrate to a heating furnace. The temperature setting of the heating furnace is in the range of around the glass transition temperature of the substrate (°C) to [glass transition temperature +100] (°C), preferably around the glass transition temperature (°C) to [glass transition temperature +50] (°C). The range shall be . In the heating furnace, when stretching the base material in the direction of travel or in a direction perpendicular to the direction of travel, uniaxial or biaxial hot stretching is performed by adjusting the conveyance direction and tension and tilting it at an arbitrary angle. conduct. The stretching ratio is usually 1.1 to 6 times, preferably 1.1 to 3.5 times.

Further, the method for stretching in the diagonal direction is not particularly limited as long as the orientation axis can be continuously tilted at a desired angle, and any known stretching method can be employed. Examples of such stretching methods include the methods described in JP-A-50-83482 and JP-A-2-113920. When imparting retardation properties to a film by stretching, the thickness after stretching is determined by the thickness before stretching and the stretching ratio.

The substrate is usually a transparent substrate. Transparent substrate refers to a substrate that has transparency that allows light, particularly visible light, to pass through, and transparency refers to the property that the transmittance for light rays with a wavelength of 380 to 780 nm is 80% or more. say. A specific example of the transparent base material is a translucent resin base material. Examples of resins constituting the translucent resin base material include polyolefins such as polyethylene and polypropylene; cyclic olefin resins such as norbornene polymers; polyvinyl alcohol; polyethylene terephthalate; polymethacrylate ester; polyacrylate ester; triacetyl cellulose; Cellulose esters such as diacetyl cellulose and cellulose acetate propionate; polyethylene naphthalate; polycarbonate; polysulfone; polyether sulfone; polyether ketone; polyphenylene sulfide and polyphenylene oxide. From the viewpoint of availability and transparency, polyethylene terephthalate, polymethacrylate, cellulose ester, cyclic olefin resin, or polycarbonate are preferred.

Cellulose ester is obtained by esterifying some or all of the hydroxyl groups contained in cellulose, and can be easily obtained from the market. Furthermore, cellulose ester base materials are also easily available on the market. Commercially available cellulose ester base materials include, for example, "Fujitac (registered trademark) film" (Fuji Film Co., Ltd.); "KC8UX2M", "KC8UY", and "KC4UY" (Konica Minolta Opto Co., Ltd.). .

Polymethacrylic esters and polyacrylic esters (hereinafter, polymethacrylic esters and polyacrylic esters may be collectively referred to as (meth)acrylic resins) are easily available on the market.

Examples of the (meth)acrylic resin include a homopolymer of an alkyl methacrylate or an alkyl acrylate, a copolymer of an alkyl methacrylate and an alkyl acrylate, and the like. Specific examples of methacrylic acid alkyl esters include methyl methacrylate, ethyl methacrylate, and propyl methacrylate, and specific examples of acrylic acid alkyl esters include methyl acrylate, ethyl acrylate, propyl acrylate, and the like. As the (meth)acrylic resin, commercially available general-purpose (meth)acrylic resins can be used. As the (meth)acrylic resin, what is called an impact-resistant (meth)acrylic resin may be used.

In order to further improve the mechanical strength, it is also preferable that the (meth)acrylic resin contains rubber particles. The rubber particles are preferably acrylic. Here, the acrylic rubber particles have rubber elasticity obtained by polymerizing an acrylic monomer mainly composed of an acrylic acid alkyl ester such as butyl acrylate or 2-ethylhexyl acrylate in the presence of a polyfunctional monomer. It is a particle. The acrylic rubber particles may be formed of a single layer of particles having such rubber elasticity, or may be a multilayer structure having at least one rubber elastic layer. Acrylic rubber particles with a multilayer structure include those in which a particle having rubber elasticity as described above is the core and the surrounding area is covered with a hard alkyl methacrylate ester polymer; A core with a rubber-elastic acrylic polymer surrounding it, or a hard core with a rubber-elastic acrylic polymer and a hard alkyl methacrylate ester surrounding it. Examples include those covered with a polymer. The average diameter of the rubber particles formed in the elastic layer is usually in the range of about 50 to 400 nm.

The content of rubber particles in the (meth)acrylic resin is usually about 5 to 50 parts by mass per 100 parts by mass of the (meth)acrylic resin. (Meth)acrylic resin and acrylic rubber particles are commercially available in a mixed state, so commercially available products can be used. Examples of commercially available (meth)acrylic resins containing acrylic rubber particles include "HT55X" and "Technolloy S001" sold by Sumitomo Chemical Co., Ltd. “Technoloy S001” is sold in film form.

Cyclic olefin resins are easily available on the market. Commercially available cyclic olefin resins include “Topas” (registered trademark) [Ticona (Germany)], “Arton” (registered trademark) [JSR Corporation], and “ZEONOR” (registered trademark) [Japan Zeon Co., Ltd.], “ZEONEX” (registered trademark) [Nippon Zeon Co., Ltd.], and “APEL” (registered trademark) [Mitsui Chemicals Co., Ltd.]. Such a cyclic olefin resin can be formed into a film by a known method such as a solvent casting method or a melt extrusion method to form a base material. Moreover, a commercially available cyclic olefin resin base material can also be used. Commercially available cyclic olefin resin base materials include “Escina” (registered trademark) [Sekisui Chemical Co., Ltd.], “SCA40” (registered trademark) [Sekisui Chemical Co., Ltd.], and “Zeonor Film” (registered trademark). ) [Optes Co., Ltd.] and "Arton Film" (registered trademark) [JSR Co., Ltd.].

When the cyclic olefin resin is a copolymer of a cyclic olefin and a chain olefin or an aromatic compound having a vinyl group, the content ratio of structural units derived from the cyclic olefin is based on the total structural units of the copolymer. On the other hand, the amount is usually 50 mol% or less, preferably in the range of 15 to 50 mol%. Examples of chain olefins include ethylene and propylene, and examples of aromatic compounds having a vinyl group include styrene, α-methylstyrene, and alkyl-substituted styrene. When the cyclic olefin resin is a terpolymer of a cyclic olefin, a chain olefin, and an aromatic compound having a vinyl group, the content ratio of structural units derived from the chain olefin is The content of structural units derived from aromatic compounds having vinyl groups is usually 5 to 80 mol% based on the total structural units of the copolymer. It is. Such a terpolymer has the advantage that a relatively small amount of expensive cyclic olefin can be used in its production.

<First adhesive layer>
The first adhesive layer 4 is not particularly limited as long as it satisfies at least one of the conditions a, b, and c described above, and includes, for example, a water-based adhesive, an active energy ray-curable adhesive, and any of these Can be formed from a combination. Among these, since the first adhesive layer 4 is a cured layer of an active energy ray-curable adhesive, it becomes easier to obtain the first adhesive layer 4 that satisfies at least one of the above-mentioned conditions a, b, and c. preferable. The thickness of the first adhesive layer 4 is preferably 0.1 μm to 50 μm, more preferably 0.1 μm to 10 μm, and even more preferably 0.5 μm to 5 μm.

The active energy ray-curable adhesive is one that is cured by irradiation with active energy rays, and is capable of forming the first adhesive layer 4 that satisfies at least one of the conditions a, b, and c described above. There are no limitations. For example, a cationically polymerizable active energy ray-curable adhesive containing an epoxy compound and a cationic polymerization initiator, a radically polymerizable active energy ray-curable adhesive containing an acrylic curing component and a radical polymerization initiator, and an epoxy compound. An active energy ray-curable adhesive containing both a cationic polymerizable curing component such as and a radically polymerizable curing component such as an acrylic compound, and a cationic polymerization initiator and a radical polymerization initiator blended therein; and an electron beam curable adhesive that is cured by irradiating an active energy ray curable adhesive that does not contain an initiator with an electron beam. Preferably, it is a radically polymerizable active energy ray-curable adhesive containing an acrylic curing component and a radical polymerization initiator. Further, a cationically polymerizable active energy ray-curable adhesive containing an epoxy compound and a cationic polymerization initiator, which can be used substantially without solvent, is preferred.

Select a cationically polymerizable epoxy compound that is itself liquid at room temperature, has appropriate fluidity even in the absence of a solvent, and provides appropriate cured adhesive strength, and uses a suitable cation. The active energy ray-curable adhesive containing a polymerization initiator can omit the drying equipment normally required in the process of bonding the first retardation layer and the second retardation layer in the manufacturing equipment for composite retardation plates. I can do it. Furthermore, by irradiating with an appropriate dose of active energy, the curing speed can be accelerated and the production speed can be improved.

Epoxy compounds used in such adhesives include, for example, glycidyl ethers of aromatic compounds or chain compounds having hydroxyl groups, glycidyl aminations of compounds having amino groups, and chain compounds having C-C double bonds. epoxides, glycidyloxy or epoxyethyl groups are bonded directly to saturated carbocycles or via alkylene, or alicyclic epoxy compounds in which epoxy groups are bonded directly to saturated carbocycles. can. These epoxy compounds may be used alone or in combination of different types. Among them, alicyclic epoxy compounds are preferably used because they have excellent cationic polymerizability.

A glycidyl etherified product of an aromatic compound or a chain compound having a hydroxyl group can be produced, for example, by a method of addition-condensing epichlorohydrin to the hydroxyl group of the aromatic compound or chain compound under basic conditions. Such glycidyl etherified aromatic compounds or chain compounds having a hydroxyl group include diglycidyl ethers of bisphenols, polyaromatic epoxy resins, diglycidyl ethers of alkylene glycols or polyalkylene glycols, etc. .

Examples of diglycidyl ethers of bisphenols include glycidyl etherified bisphenol A and oligomers thereof, glycidyl etherified bisphenol F and oligomers thereof, 3,3',5,5'-tetramethyl-4,4'- Examples include glycidyl etherified biphenols and oligomers thereof.

Examples of polyaromatic epoxy resins include glycidyl ethers of phenol novolac resins, glycidyl ethers of cresol novolak resins, glycidyl ethers of phenol aralkyl resins, glycidyl ethers of naphthol aralkyl resins, and glycidyl ethers of phenol dicyclopentadiene resins. Examples include chemical substances. Furthermore, glycidyl etherified products of trisphenols and their oligomers also belong to polyaromatic ring type epoxy resins.

Examples of the diglycidyl ether of alkylene glycol or polyalkylene glycol include glycidyl ether of ethylene glycol, glycidyl ether of diethylene glycol, glycidyl ether of 1,4-butanediol, and glycidyl ether of 1,6-hexanediol. Can be mentioned.

A glycidylaminated compound of a compound having an amino group can be produced, for example, by a method of addition-condensing epichlorohydrin to the amino group of the compound under basic conditions. A compound having an amino group may also have a hydroxyl group. Such glycidylaminated compounds having an amino group include glycidylaminated products of 1,3-phenylenediamine and oligomers thereof, glycidylaminated products of 1,4-phenylenediamine and oligomers thereof, and 3-aminophenol. These include glycidylaminated and glycidyl etherified products of 4-aminophenol and oligomers thereof, glycidylaminated and glycidyl etherified products of 4-aminophenol, and oligomeric products thereof.

An epoxidized product of a chain compound having a C--C double bond can be produced by a method of epoxidizing the C--C double bond of the chain compound using a peroxide under basic conditions. Chain compounds having a C—C double bond include butadiene, polybutadiene, isoprene, pentadiene, hexadiene, and the like. Terpenes having double bonds can also be used as raw materials for epoxidation, and examples of acyclic monoterpenes include linalool. The peroxide used in epoxidation can be, for example, hydrogen peroxide, peracetic acid, tert-butyl hydroperoxide, and the like.

Alicyclic epoxy compounds in which a glycidyloxy group or an epoxyethyl group is bonded to a saturated carbon ring directly or via an alkylene are the aromatic rings of aromatic compounds having a hydroxyl group, representative examples of which are the bisphenols listed above. Examples include a glycidyl etherified product of a hydrogenated polyhydroxy compound obtained by hydrogenation, a glycidyl etherified product of a cycloalkane compound having a hydroxyl group, and an epoxidized product of a cycloalkane compound having a vinyl group.

The epoxy compounds described above can be easily obtained commercially, and for example, the "jER" series sold by Mitsubishi Chemical Corporation and the "Epiclon" series sold by DIC Corporation are available under the respective trade names. ”, “Epotote (registered trademark)” sold by Toto Kasei Co., Ltd., “ADEKA RIN (registered trademark)” sold by ADEKA Co., Ltd., and “Denacol (registered trademark)” sold by Nagase ChemteX Co., Ltd. )", "Dowepoxy" sold by Dow Chemical Company, and "Tepic (registered trademark)" sold by Nissan Chemical Industries, Ltd.

On the other hand, an alicyclic epoxy compound in which an epoxy group is directly bonded to a saturated carbon ring, for example, has a C-C double bond in a non-aromatic cyclic compound that has a C-C double bond in the ring. It can be produced by epoxidation using peroxide under certain conditions. Examples of non-aromatic cyclic compounds having a C--C double bond in the ring include compounds having a cyclopentene ring, compounds having a cyclohexene ring, and compounds having at least two carbon atoms further bonded to the cyclopentene ring or cyclohexene ring. Examples include polycyclic compounds forming additional rings. A non-aromatic cyclic compound having a C--C double bond within the ring may have another C--C double bond outside the ring. Examples of non-aromatic cyclic compounds having a C--C double bond in the ring include cyclohexene, 4-vinylcyclohexene, monocyclic monoterpenes limonene and α-pinene.

Alicyclic epoxy compounds in which an epoxy group is directly bonded to a saturated carbocyclic ring are those in which the alicyclic structure having an epoxy group directly bonded to a ring as described above is inserted into the molecule via an appropriate linking group. A compound may be formed of at least two. The linking group here includes, for example, an ester bond, an ether bond, an alkylene bond, and the like.

Specific examples of alicyclic epoxy compounds in which an epoxy group is directly bonded to a saturated carbon ring include the following.

3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexane carboxylate,
1,2-epoxy-4-vinylcyclohexane,
1,2-epoxy-4-epoxyethylcyclohexane,
1,2-epoxy-1-methyl-4-(1-methylepoxyethyl)cyclohexane, 3,4-epoxycyclohexylmethyl (meth)acrylate,
an adduct of 2,2-bis(hydroxymethyl)-1-butanol and 4-epoxyethyl-1,2-epoxycyclohexane,
Ethylene bis(3,4-epoxycyclohexanecarboxylate),
Oxydiethylene bis(3,4-epoxycyclohexanecarboxylate),
1,4-cyclohexanedimethyl bis(3,4-epoxycyclohexanecarboxylate),
3-(3,4-epoxycyclohexylmethoxycarbonyl)propyl 3,4-epoxycyclohexane carboxylate, etc.

The above-described alicyclic epoxy compounds in which an epoxy group is directly bonded to a saturated carbocyclic ring are also easily available commercially; for example, they are sold under the respective trade names by Daicel Corporation. Examples include the "Celoxide" series, "Cyclomer" and the "Cyracure UVR" series sold by Dow Chemical Company.

The curable adhesive containing an epoxy compound may further contain an active energy ray curable compound other than the epoxy compound. Examples of active energy ray-curable compounds other than epoxy compounds include oxetane compounds and acrylic compounds. Among these, it is preferable to use an oxetane compound in combination, since the curing rate may be accelerated in cationic polymerization.

Oxetane compounds are compounds having a 4-membered ring ether in the molecule, and include, for example, the following compounds.

1,4-bis[(3-ethyloxetan-3-yl)methoxymethyl]benzene,
3-ethyl-3-(2-ethylhexyloxymethyl)oxetane,
bis(3-ethyl-3-oxetanylmethyl)ether,
3-ethyl-3-(phenoxymethyl)oxetane,
3-ethyl-3-(cyclohexyloxymethyl)oxetane,
phenol novolac oxetane,
xylylene bisoxetane,
1,3-bis[(3-ethyloxetan-3-yl)methoxy]benzene, etc.

Oxetane compounds are also easily available as commercial products, for example, the "Aron Oxetane (registered trademark)" series sold by Toagosei Co., Ltd. and the "Aron Oxetane (registered trademark)" series sold by Ube Industries, Ltd. under the respective trade names. Examples include the "ETERNACOLL (registered trademark)" series.

It is preferable to use a curable compound including an epoxy compound or an oxetane compound that has not been diluted with an organic solvent or the like so that the adhesive containing these compounds is solvent-free. In addition, small amounts of other components constituting the adhesive, including the cationic polymerization initiator and sensitizer described later, are more important than those dissolved in an organic solvent after the organic solvent has been removed and dried. It is preferable to use powder or liquid of the compound alone.

The active energy ray-curable adhesive of the present invention preferably contains an alicyclic epoxy compound. The content of the alicyclic epoxy compound is preferably 30% by mass or more, more preferably 40% by mass or more, and may be 85% by mass or less, based on the total amount of the curable compound. The active energy ray-curable adhesive of the present invention may further contain an oxetane compound. When an oxetane compound is included, the ratio between the content of the oxetane compound and the content of the alicyclic epoxy compound (oxetane content/alicyclic epoxy compound) is preferably 1 or less.

A cationic polymerization initiator is a compound that generates cationic species when irradiated with active energy rays, such as ultraviolet rays. For example, aromatic diazonium salts; onium salts such as aromatic iodonium salts and aromatic sulfonium salts; iron-arene complexes. Examples include. Each of these cationic polymerization initiators may be used alone, or a plurality of different types may be used in combination.

Examples of aromatic diazonium salts include the following.
Benzenediazonium hexafluoroantimonate,
benzenediazonium hexafluorophosphate,
Benzenediazonium hexafluoroborate, etc.

Examples of aromatic iodonium salts include the following.
diphenyliodonium tetrakis(pentafluorophenyl)borate,
diphenyliodonium hexafluorophosphate,
diphenyliodonium hexafluoroantimonate,
Bis(4-nonylphenyl)iodonium hexafluorophosphate, etc.

Examples of aromatic sulfonium salts include the following.
triphenylsulfonium hexafluorophosphate,
triphenylsulfonium hexafluoroantimonate,
triphenylsulfonium tetrakis(pentafluorophenyl)borate,
diphenyl(4-phenylthiophenyl)sulfonium hexafluoroantimonate,
4,4'-bis(diphenylsulfonio)diphenylsulfide bishexafluorophosphate,
4,4'-bis[di(β-hydroxyethoxyphenyl)sulfonio]diphenyl sulfide bishexafluoroantimonate,
4,4'-bis[di(β-hydroxyethoxyphenyl)sulfonio]diphenyl sulfide bishexafluorophosphate,
7-[di(p-tolyl)sulfonio]-2-isopropylthioxanthone hexafluoroantimonate,
7-[di(p-tolyl)sulfonio]-2-isopropylthioxanthone tetrakis(pentafluorophenyl)borate,
4-phenylcarbonyl-4'-diphenylsulfoniodiphenylsulfide hexafluorophosphate,
4-(p-tert-butylphenylcarbonyl)-4'-diphenylsulfoniodiphenylsulfide hexafluoroantimonate,
4-(p-tert-butylphenylcarbonyl)-4'-di(p-tolyl)sulfonio-diphenyl sulfide tetrakis(pentafluorophenyl)borate, etc.

Examples of iron-arene complexes include the following.
Xylene-cyclopentadienyl iron(II) hexafluoroantimonate,
Cumene-cyclopentadienyl iron(II) hexafluorophosphate, xylene-cyclopentadienyl iron(II) tris(trifluoromethylsulfonyl)methanide, etc.

Among cationic polymerization initiators, aromatic sulfonium salts have ultraviolet absorption properties even in the wavelength region of 300 nm or more, so they have excellent curability and can provide adhesive layers with good mechanical strength and adhesive strength. Therefore, it is preferably used.

Cationic polymerization initiators can also be easily obtained as commercially available products, such as the "Kayarad (registered trademark)" series sold by Nippon Kayaku Co., Ltd. and the Dow Chemical Company under the respective trade names. "Cyracure UVI" series sold by Sun-Apro Co., Ltd., photoacid generator "CPI" series sold by Sun-Apro Co., Ltd., photoacid generators "TAZ", "BBI" and "DTS" sold by Midori Kagaku Co., Ltd. , the "ADEKA Optomer" series sold by ADEKA Co., Ltd., and "RHODORSIL (registered trademark)" sold by Rhodia.

In the active energy ray curable adhesive, the cationic polymerization initiator is usually blended in a proportion of 0.5 to 20 parts by mass, preferably 1 to 15 parts by mass, based on 100 parts by mass of the total amount of the active energy ray curable adhesive. Part by mass. If the amount is too small, curing may be insufficient and the mechanical strength and adhesive strength of the adhesive layer may be reduced. Furthermore, if the amount is too large, the amount of ionic substances in the adhesive layer increases, which increases the hygroscopicity of the adhesive layer, which may reduce the durability of the resulting polarizing plate.

When using an active energy ray curable adhesive as an electron beam curable type, it is not particularly necessary to include a photopolymerization initiator in the composition, but when using an ultraviolet ray curable type adhesive, a photo radical generator is used. It is preferable. Examples of the photo-radical generator include hydrogen abstraction-type photo-radical generators and cleavage-type photo-radical generators.

Examples of the hydrogen abstraction type photoradical generator include 1-methylnaphthalene, 2-methylnaphthalene, 1-fluoronaphthalene, 1-chloronaphthalene, 2-chloronaphthalene, 1-bromonaphthalene, 2-bromonaphthalene, and 1-iodonaphthalene. , 2-iodonaphthalene, 1-naphthol, 2-naphthol, 1-methoxynaphthalene, 2-methoxynaphthalene, naphthalene derivatives such as 1,4-dicyanonaphthalene, anthracene, 1,2-benzanthracene, 9,10-dichloroanthracene , 9,10-dibromoanthracene, 9,10-diphenylanthracene, 9-cyanoanthracene, 9,10-dicyanoanthracene, 2,6,9,10-tetracyanoanthracene and other anthracene derivatives, pyrene derivatives, carbazole, 9- Methylcarbazole, 9-phenylcarbazole, 9-prop-2-ynyl-9H-carbazole, 9-propyl-9H-carbazole, 9-vinylcarbazole, 9H-carbazol-9-ethanol, 9-methyl-3-nitro-9H -Carbazole, 9-methyl-3,6-dinitro-9H-carbazole, 9-octanoylcarbazole, 9-carbazolemethanol, 9-carbazolepropionic acid, 9-carbazolepropionitrile, 9-ethyl-3,6-dinitro -9H-carbazole, 9-ethyl-3-nitrocarbazole, 9-ethylcarbazole, 9-isopropylcarbazole, 9-(ethoxycarbonylmethyl)carbazole, 9-(morpholinomethyl)carbazole, 9-acetylcarbazole, 9-allylcarbazole , 9-benzyl-9H-carbazole, 9-carbazoleacetic acid, 9-(2-nitrophenyl)carbazole, 9-(4-methoxyphenyl)carbazole, 9-(1-ethoxy-2-methyl-propyl)-9H- Carbazoles such as carbazole, 3-nitrocarbazole, 4-hydroxycarbazole, 3,6-dinitro-9H-carbazole, 3,6-diphenyl-9H-carbazole, 2-hydroxycarbazole, 3,6-diacetyl-9-ethylcarbazole Derivatives, benzophenone, 4-phenylbenzophenone, 4,4'-bis(dimethoxy)benzophenone, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone, 2-benzoylbenzoic acid methyl ester , 2-methylbenzophenone, 3-methylbenzophenone, 4-methylbenzophenone, 3,3'-dimethyl-4-methoxybenzophenone, benzophenone derivatives such as 2,4,6-trimethylbenzophenone, aromatic carbonyl compounds, [4-( 4-Methylphenylthio)phenyl]-phenylmethanone, xanthone, thioxanthone, 2-chlorothioxanthone, 4-chlorothioxanthone, 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone , thioxanthone derivatives such as 1-chloro-4-propoxythioxanthone, and coumarin derivatives.

A cleavage-type photoradical generator is a type of photoradical generator that generates radicals by cleavage of the compound when irradiated with active energy rays. Examples include, but are not limited to, ketones, oxime ketones, acylphosphine oxides, S-phenyl thiobenzoates, titanocenes, and high molecular weight derivatives thereof. Commercially available cleavable photoradical generators include 1-(4-dodecylbenzoyl)-1-hydroxy-1-methylethane, 1-(4-isopropylbenzoyl)-1-hydroxy-1-methylethane, and 1-benzoyl. -1-hydroxy-1-methylethane, 1-[4-(2-hydroxyethoxy)-benzoyl]-1-hydroxy-1-methylethane, 1-[4-(acryloyloxyethoxy)-benzoyl]-1-hydroxy- 1-Methylethane, diphenylketone, phenyl-1-hydroxy-cyclohexylketone, benzyldimethylketal, bis(cyclopentadienyl)-bis(2,6-difluoro-3-pyryl-phenyl)titanium, (η6-isopropylbenzene) -(η5-cyclopentadienyl)-iron(II) hexafluorophosphate, trimethylbenzoyldiphenylphosphine oxide, bis(2,6-dimethoxy-benzoyl)-(2,4,4-trimethyl-pentyl)-phosphine oxide, Bis(2,4,6-trimethylbenzoyl)-2,4-dipentoxyphenylphosphine oxide or bis(2,4,6-trimethylbenzoyl)phenyl-phosphine oxide, (4-morpholinobenzoyl)-1-benzyl- Examples include, but are not limited to, 1-dimethylaminopropane, 4-(methylthiobenzoyl)-1-methyl-1-morpholinoethane, and the like.

Among the active energy curable adhesives used in the present invention, the photo radical generators included in the electron beam curable type, that is, hydrogen abstraction type or cleavage type photo radical generators, can be used alone. In addition, a combination of a plurality of photo-radical generators may be used, but in terms of stability and curability of the photo-radical generator alone, a combination of one or more cleavage-type photo-radical generators is more preferable. Among the cleavage type photoradical generators, acylphosphine oxides are preferable, and more specifically, trimethylbenzoyldiphenylphosphine oxide (trade name "DAROCURE TPO"; Ciba Japan Co., Ltd.), bis(2,6-dimethoxy- benzoyl)-(2,4,4-trimethyl-pentyl)-phosphine oxide (trade name "CGI 403"; Ciba Japan Co., Ltd.), or bis(2,4,6-trimethylbenzoyl)-2,4- Dipentoxyphenylphosphine oxide (trade name "Irgacure 819"; manufactured by Ciba Japan Co., Ltd.) is preferred.

The active energy ray-curable adhesive may contain a sensitizer, if necessary. By using a sensitizer, the reactivity is improved and the mechanical strength and adhesive strength of the adhesive layer can be further improved. As the sensitizer, those mentioned above can be used as appropriate.

When a sensitizer is blended, the blending amount is preferably in the range of 0.1 to 20 parts by mass based on 100 parts by mass of the total amount of the active energy ray-curable adhesive.

Various additives can be added to the active energy ray-curable adhesive within a range that does not impair its effectiveness. Examples of additives that can be blended include ion trapping agents, antioxidants, chain transfer agents, tackifiers, thermoplastic resins, fillers, fluidity regulators, plasticizers, antifoaming agents, and the like.

These components constituting the active energy ray-curable adhesive are usually used in a state dissolved in a solvent. When the active energy ray curable adhesive contains a solvent, the adhesive layer can be obtained by applying the active energy ray curable adhesive to the coated surface and drying it. Components that do not dissolve in the solvent may be in a dispersed state in the system.

The active energy ray-curable adhesive is applied to the adhesive surface of the first retardation layer 1 with the second retardation layer 2, the adhesive surface of the second retardation layer 2 with the first retardation layer 1, or both. be done. The adhesive surface of the first retardation layer 1 with the second retardation layer 2 and the adhesive surface of the second retardation layer 2 with the first retardation layer 1 are subjected to corona treatment, plasma treatment, flame treatment, etc. in advance. Alternatively, a primer layer or the like may be formed.
The thickness of the primer layer is usually about 0.001 to 5 μm, preferably 0.01 μm or more, more preferably 4 μm or less, and more preferably 3 μm or less. If the primer layer is too thick, the appearance of the composite retardation plate 5 tends to be poor.

The viscosity of the active energy ray-curable adhesive may be any viscosity that can be applied by various methods, but the viscosity at a temperature of 25°C is preferably in the range of 10 to 1,000 mPa·sec. , more preferably in the range of 20 to 500 mPa·sec. If the viscosity is too low, it tends to be difficult to form a layer with a desired thickness. On the other hand, if the viscosity is too high, it becomes difficult to flow and it tends to be difficult to obtain an even and homogeneous coating film. Further, when the viscosity is low to some extent, it tends to be easier to make the adhesive layer thinner. The viscosity here is a value measured at 10 rpm after controlling the temperature of the adhesive to 25° C. using an E-type viscometer.

The above-mentioned active energy ray curable adhesive can be used in an electron beam curable or ultraviolet ray curable form. In this specification, an active energy ray is defined as an energy ray that can generate active species by decomposing a compound that generates active species. Examples of such active energy rays include visible light, ultraviolet rays, infrared rays, X-rays, α-rays, β-rays, γ-rays, and electron beams.

In the electron beam curable adhesive, any suitable electron beam irradiation conditions can be employed as long as the active energy ray curable adhesive can be cured. For example, in electron beam irradiation, the acceleration voltage is preferably 5 kV to 300 kV, more preferably 10 kV to 250 kV. If the accelerating voltage is less than 5 kV, the electron beam may not reach the adhesive, resulting in insufficient curing. If the accelerating voltage exceeds 300 kV, the penetrating force through the sample is too strong and the electron beam bounces off, causing damage to the transparent protective film and the like. There is a risk of damaging the polarizer. The irradiation dose is 5 to 100 kGy, more preferably 10 to 75 kGy. If the irradiation dose is less than 5 kGy, the adhesive will be insufficiently cured, and if it exceeds 100 kGy, the retardation layer will be damaged, resulting in a decrease in mechanical strength and yellowing, making it impossible to obtain desired optical properties.

Electron beam irradiation is usually performed in an inert gas, but if necessary, it may be performed in the atmosphere or with a small amount of oxygen introduced. By appropriately introducing oxygen, oxygen inhibition is created on the surface of the retardation layer that is first hit by the electron beam, which prevents damage to the retardation layer and allows only the adhesive to be efficiently irradiated with the electron beam. be able to.

In the ultraviolet curable type, the light irradiation intensity of the active energy ray curable adhesive is determined depending on the composition of the adhesive and is not particularly limited, but is preferably 10 to 1,000 mW/cm ² . If the light irradiation intensity to the resin composition is less than 10 mW/cm ² , the reaction time will be too long, and if it exceeds 1,000 mW/cm ² , the reaction time will be too long due to the heat radiated from the light source and the heat generated during polymerization of the composition. , yellowing of the constituent materials of the adhesive may occur. The irradiation intensity is preferably an intensity in a wavelength range effective for activating the photocationic polymerization initiator, more preferably an intensity in a wavelength range of 400 nm or less, and even more preferably an intensity in a wavelength range of 280 to 320 nm. is the strength at . The light is irradiated once or multiple times at such a light irradiation intensity, and the cumulative amount of light is preferably set to 10 mJ/cm ² or more, more preferably 100 to 1,000 mJ/cm ² . If the cumulative amount of light to the adhesive is less than 10 mJ/cm ² , the generation of active species derived from the polymerization initiator will not be sufficient, resulting in insufficient curing of the adhesive. On the other hand, if the cumulative amount of light exceeds 1,000 mJ/cm ² , the irradiation time becomes extremely long, which is disadvantageous for improving productivity. At this time, the required integrated light amount in which wavelength range (UVA (320 to 390 nm), UVB (280 to 320 nm), etc.) differs depending on the type of retardation layer film used, the combination of adhesive types, etc.

The light source used to polymerize and harden the adhesive by irradiation with active energy rays in the present invention is not particularly limited, but includes, for example, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a xenon lamp, a halogen lamp, a carbon Examples include arc lamps, tungsten lamps, gallium lamps, excimer lasers, LED light sources that emit light in the wavelength range of 380 to 440 nm, chemical lamps, black light lamps, microwave-excited mercury lamps, and metal halide lamps. From the viewpoint of energy stability and device simplicity, it is preferable that the ultraviolet light source has an emission distribution at a wavelength of 400 nm or less.

[Optical laminate]
The optical laminate of the present invention is formed by laminating a polarizing plate and the above-described composite retardation plate. The optical laminate may include a second adhesive layer that adheres the polarizing plate and the composite retardation plate. By adjusting the layer structure of the composite retardation plate laminated on the polarizing plate, an optical laminate having antireflection performance can be obtained. The optical laminate having antireflection performance is, for example, a circularly polarizing plate. In an image display device, by providing an optical laminate having antireflection properties on the viewing side of an image display panel, it is possible to suppress a decrease in visibility due to reflection of external light.

The layer structure of an optical laminate consisting of a polarizing plate and a composite retardation plate that can suppress a decrease in visibility due to reflection of external light is as follows:
v) Optical device with a layered structure in which a polarizing plate, a 1/2 wavelength layer (first retardation layer), a second adhesive layer, and a 1/4 wavelength layer (second retardation layer) are laminated in this order from the viewing side. laminate,
vi) A polarizing plate, a quarter wavelength layer (first retardation layer), a second adhesive layer, and an optical compensation layer (second retardation layer) such as a positive C plate are laminated in this order from the viewing side. optical laminate with layered structure,
is specifically exemplified.

The thickness of the optical laminate is usually 50 to 500 μm, preferably 50 to 200 μm, and more preferably 50 to 150 μm, from the viewpoint of thinning.

<Polarizing plate>
The polarizing plate may be any film having a polarizing function to obtain linearly polarized light from transmitted light. Examples of the film include a stretched film on which a dye having absorption anisotropy is adsorbed, a film containing a film coated with a dye having absorption anisotropy as a polarizer, and the like. Examples of dyes having absorption anisotropy include dichroic dyes. A film coated with a dye having absorption anisotropy and used as a polarizer may be a stretched film on which a dye having absorption anisotropy is adsorbed, or a composition containing a dichroic dye having liquid crystallinity or a dichroic dye. Examples include a film having a liquid phase layer obtained by applying a composition containing a chromatic dye and a polymerizable liquid crystal.

(Polarizing plate with stretched film as a polarizer)
A polarizing plate including a stretched film as a polarizer on which a dye having absorption anisotropy is adsorbed will be described. Stretched films that have adsorbed dyes with absorption anisotropy, which are polarizers, are usually produced through a process of uniaxially stretching a polyvinyl alcohol resin film or by dyeing the polyvinyl alcohol resin film with a dichroic dye. It is manufactured through the steps of adsorbing a dichroic dye, treating the polyvinyl alcohol resin film with the dichroic dye adsorbed with an aqueous boric acid solution, and washing with water after the treatment with the aqueous boric acid solution. Such a polarizer may be used as it is as a polarizing plate, or a transparent protective film bonded to at least one surface of such a polarizer may be used as a polarizing plate.

Polyvinyl alcohol resin is obtained by saponifying polyvinyl acetate resin. As the polyvinyl acetate resin, in addition to polyvinyl acetate, which is a homopolymer of vinyl acetate, copolymers of vinyl acetate and other monomers copolymerizable therewith are used. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

The saponification degree of the polyvinyl alcohol resin is usually about 85 to 100 mol%, preferably 98 mol% or more. The polyvinyl alcohol resin may be modified, and for example, polyvinyl formal or polyvinyl acetal modified with aldehydes can also be used. The degree of polymerization of the polyvinyl alcohol resin is usually about 1,000 to 10,000, preferably 1,500 to 5,000.

A film formed from such a polyvinyl alcohol resin is used as an original film of a polarizing plate. The method of forming a polyvinyl alcohol resin into a film is not particularly limited, and any known method can be used to form the film. The thickness of the polyvinyl alcohol base film can be, for example, about 10 to 150 μm.

Uniaxial stretching of the polyvinyl alcohol resin film can be performed before, simultaneously with, or after dyeing with a dichroic dye. When uniaxial stretching is performed after dyeing, this uniaxial stretching may be performed before or during the boric acid treatment. Moreover, it is also possible to perform uniaxial stretching in these plural steps. In the uniaxial stretching, it may be uniaxially stretched between rolls having different circumferential speeds, or it may be uniaxially stretched using hot rolls. Further, the uniaxial stretching may be dry stretching in which the film is stretched in the atmosphere, or wet stretching in which the polyvinyl alcohol resin film is stretched in a swollen state using a solvent. The stretching ratio is usually about 3 to 8 times.

Staining of a polyvinyl alcohol resin film with a dichroic dye is carried out, for example, by immersing the polyvinyl alcohol resin film in an aqueous solution containing the dichroic dye. Specifically, iodine or a dichroic organic dye is used as the dichroic dye. Dichroic organic dyes include dichroic direct dyes made of disazo compounds such as C.I. DIRECT RED 39, and dichroic direct dyes made of compounds such as trisazo and tetrakisazo. It is preferable that the polyvinyl alcohol resin film is soaked in water before being dyed.

When using iodine as a dichroic dye, a method is usually employed in which a polyvinyl alcohol resin film is immersed in an aqueous solution containing iodine and potassium iodide for dyeing. The content of iodine in this aqueous solution is usually about 0.01 to 1 part by mass per 100 parts by mass of water. The content of potassium iodide is usually about 0.5 to 20 parts by mass per 100 parts by mass of water. The temperature of the aqueous solution used for dyeing is usually about 20 to 40°C. The immersion time (staining time) in this aqueous solution is usually about 20 to 1,800 seconds.

On the other hand, when using a dichroic organic dye as the dichroic dye, a method of dyeing by immersing a polyvinyl alcohol resin film in an aqueous solution containing a water-soluble dichroic dye is usually employed.
The content of the dichroic organic dye in this aqueous solution is usually about 1 x 10 ^-4 to 10 parts by weight, preferably 1 x 10 ^{-3 to 1 part by weight, and more preferably about 1 x 10 -3} to 1 part by weight, per 100 parts by weight of water. The amount is 1×10 ⁻³ to 1×10 ⁻² parts by mass. This aqueous solution may also contain inorganic salts such as sodium sulfate as dyeing aids. The temperature of the dichroic dye aqueous solution used for dyeing is usually about 20 to 80°C. The immersion time (staining time) in this aqueous solution is usually about 10 to 1,800 seconds.

The boric acid treatment after dyeing with a dichroic dye can usually be carried out by immersing the dyed polyvinyl alcohol resin film in an aqueous boric acid solution. The content of boric acid in this boric acid aqueous solution is usually about 2 to 15 parts by weight, preferably 5 to 12 parts by weight, per 100 parts by weight of water. When iodine is used as the dichroic dye, the boric acid aqueous solution preferably contains potassium iodide, and the content of potassium iodide in this case is usually 0.1 to 100 parts by mass of water. The amount is about 15 parts by mass, preferably 5 to 12 parts by mass. The immersion time in the boric acid aqueous solution is usually about 60 to 1,200 seconds, preferably 150 to 600 seconds, and more preferably 200 to 400 seconds. The temperature of the boric acid treatment is usually 50°C or higher, preferably 50 to 85°C, more preferably 60 to 80°C.

The polyvinyl alcohol resin film treated with boric acid is usually washed with water. The water washing treatment can be performed, for example, by immersing a boric acid-treated polyvinyl alcohol resin film in water. The temperature of water in the washing process is usually about 5 to 40°C.
The immersion time is usually about 1 to 120 seconds.

After washing with water, a drying process is performed to obtain a polarizer. The drying process can be performed using, for example, a hot air dryer or a far-infrared heater. The temperature of the drying treatment is usually about 30 to 100°C, preferably 50 to 80°C. The drying time is usually about 60 to 600 seconds, preferably 120 to 600 seconds. The drying process reduces the moisture content of the polarizer to a practical level. Its moisture content is usually about 5 to 20% by weight, preferably 8 to 15% by weight. When the moisture content is less than 5% by mass, the flexibility of the polarizer is lost and the polarizer may be damaged or broken after drying. Furthermore, if the moisture content exceeds 20% by mass, the thermal stability of the polarizer may deteriorate.

The thickness of the polarizer obtained by subjecting the polyvinyl alcohol resin film to uniaxial stretching, dyeing with a dichroic dye, boric acid treatment, washing with water, and drying is preferably 5 to 40 μm.

The material of the protective film attached to one or both sides of the polarizer is not particularly limited, but examples include cyclic polyolefin resin films, cellulose acetate-based resins such as triacetylcellulose, and diacetylcellulose. Films known in the art, such as resin films, polyester resin films made of resins such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate, polycarbonate resin films, (meth)acrylic resin films, and polypropylene resin films. can be mentioned. From the viewpoint of thinning, the thickness of the protective film is usually 300 μm or less, preferably 200 μm or less, more preferably 50 μm or less, and usually 5 μm or more, preferably 20 μm or more. . Further, the protective film on the viewing side may or may not have a retardation. On the other hand, it is preferable that the protective film laminated on the first retardation layer has a retardation of 10 nm or less.

(Polarizing plate comprising a film having a liquid crystal layer as a polarizer)
A polarizing plate including a film having a liquid crystal layer as a polarizer will be described. A film coated with a dye having absorption anisotropy and used as a polarizer may be coated with a composition containing a dichroic dye having liquid crystal properties, or a composition containing a dichroic dye and a liquid crystal compound. Examples include the resulting film. The film may be used alone as a polarizing plate, or may be used as a polarizing plate with a protective film on one or both sides. Examples of the protective film include the same one as the polarizing plate having the above-mentioned stretched film as a polarizer.

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

Specific examples of the film coated with the dye having absorption anisotropy include the films described in JP-A No. 2012-33249 and the like.

An optical laminate formed by laminating a composite retardation plate and a polarizing plate may be obtained by directly applying the dye having absorption anisotropy to the first retardation layer side of the composite retardation plate. . In this case, the composite retardation plate and the polarizing plate can be laminated without having the second adhesive layer.

<Second adhesive layer>
The second adhesive layer can be composed of, for example, an adhesive, a water-based adhesive, an active energy ray-curable adhesive, or a combination thereof. Among these, the second adhesive layer is a cured product layer of an active energy ray-curable adhesive, so even when the optical laminate including the composite retardation plate of the present invention is bent, wrinkles at the bent portion can be avoided. This is preferable because it can further suppress the occurrence of. In this specification, the term "second adhesive layer" includes not only an adhesive layer made of an adhesive but also an adhesive layer made of an adhesive.

Regarding the active energy ray-curable adhesive forming the second adhesive layer, the explanation for the first adhesive layer above applies. When the first adhesive layer and the second adhesive layer are formed from an active energy ray curable adhesive, the first adhesive layer and the second adhesive layer may be formed from the same active energy ray curable adhesive, They may be formed from different active energy ray-curable adhesives.

[Method for manufacturing composite retardation plate and optical laminate]
The composite retardation plate of the present invention includes a first retardation layer 10 including a first retardation layer 13, a first alignment layer 12, and a first base layer 11 as shown in FIG. Manufactured by laminating a second retardation layer 20 including a second retardation layer 23, a second alignment layer 22, and a first base layer 21 as shown in (B) via a first adhesive layer 40. can. For example, as shown in FIG. 3C, the composite retardation plate of the present invention includes a first base layer 11, a first alignment layer 12, a first retardation layer 13, a first adhesive layer 40, a second This is a laminate in which a retardation expression layer 23, a second alignment layer 22, and a second base layer 21 are laminated in this order. Further, the composite retardation plate of the present invention includes a first retardation layer 13 , a first orientation layer 12 , a first base layer 11 , a first adhesive layer 40 , a second base layer 21 , a second orientation layer 22 , the second phase difference expressing layer 23 may be stacked in this order. In FIGS. 3A to 3C, W represents the width direction of the composite retardation plate or the laminate.

As a method for bonding the first retardation layer 10 and the second retardation layer 20, adhesive is attached to either or both of the bonding surface of the first retardation layer 10 or the bonding surface of the second retardation layer 20. An example of this method is to apply an adhesive, laminate the other bonding surface thereon, and harden the adhesive constituting the first adhesive layer 40. Various coating methods can be used to apply the adhesive constituting the first adhesive layer 40, such as a doctor blade, wire bar, die coater, comma coater, and gravure coater.

As a method for curing the adhesive constituting the first adhesive layer, a curing method may be selected as appropriate depending on the type of adhesive. When the adhesive is an active energy ray-curable adhesive, a method of curing with active energy rays is preferred, as described above. Corona treatment, plasma treatment, etc. may be performed on either or both of the bonding surface of the first retardation layer 10 or the bonding surface of the second retardation layer 20, or a primer layer may be formed. .

The composite retardation plate of the present invention may be a laminate as shown in FIG. 3(C), or a laminate obtained by peeling off at least one of the first base layer 11 and the second base layer 21. It may be. Alternatively, the first base layer 11 and the first alignment layer 12 may be peeled off from the laminate shown in FIG. 3(C), or the second base layer may be removed from the laminate shown in FIG. It may be a laminate in which the material layer 21 and the second alignment layer 22 are separated.

[Applications of optical laminate]
An optical laminate that is a circularly polarizing plate can be used in various image display devices as an optical laminate that is placed on the viewing side of an image display panel and provides antireflection performance. An image display device is a device having an image display panel, and includes a light emitting element or a light emitting device as a light source. Image display devices include liquid crystal display devices, organic electroluminescence (EL) display devices, inorganic electroluminescence (EL) display devices, touch panel display devices, and electron emission display devices (e.g., field emission displays (FEDs), surface field emission displays). (SED)), electronic paper (display devices using electronic ink or electrophoretic elements, plasma display devices, projection type display devices (e.g. grating light valve (GLV) display devices, displays with digital micromirror devices (DMD)) LCD devices) and piezoelectric ceramic displays.Liquid crystal display devices include transmission type liquid crystal display devices, transflective type liquid crystal display devices, reflective type liquid crystal display devices, direct view type liquid crystal display devices, and projection type liquid crystal display devices. These image display devices may be image display devices that display two-dimensional images or stereoscopic image display devices that display three-dimensional images.In particular, optical laminated devices that are circularly polarizing plates The body can be advantageously used in organic electroluminescent (EL) display devices that can include image display panels with bends.

According to the present invention, even if the optical laminate is bent and placed along the surface of an image display panel having a bent portion, it is possible to obtain an optical laminate that does not generate wrinkles.

Hereinafter, the present invention will be explained in more detail with reference to Examples.
[Preparation of photocurable adhesives 1 to 15]
(1) Preparation of cationic curable component The following cationic curable component was prepared.

(A-1) 3',4'-epoxycyclohexylmethyl 3,4-epoxycyclohexane carboxylate (product name: CEL2021P, manufactured by Daicel Corporation),
(A-2) 1,2-epoxy-4-(2-oxiranyl)cyclohexane adduct of 2,2-bis(hydroxymethyl)-1-butanol (trade name: EHPE3150, manufactured by Daicel Corporation),
(B-1) Neopentyl glycol diglycidyl ether (product name: EX-211, manufactured by Nagase ChemteX Corporation),
(B-2) 1,4-butanediol diglycidyl ether (product name: EX-214, manufactured by Nagase ChemteX Corporation),
(B-3) 2-ethylhexyl glycidyl ether (product name: EX-121, manufactured by Nagase ChemteX Corporation)
(C-1) Resorcinol diglycidyl ether (product name: EX-201, manufactured by Nagase ChemteX Corporation)
(C-2) Polyfunctional glycidyl ether (product name: VG3101L, manufactured by Printec Co., Ltd.)
(D-1) 3-ethyl-3{[(3-ethyloxetan-3-yl)methoxy]methyl}oxetane (product name: OXT-221, Toagosei Co., Ltd.)
(D-2) Xylylene bisoxetane (product name: OXT-121, Toagosei Co., Ltd.)
(2) Preparation of radical curable component The following radical curable component was prepared.

(E-1) 4-hydroxybutyl acrylate (product name: 4HBA, manufactured by Nippon Kasei Co., Ltd.)
(E-2) 1,4-cyclohexanedimethanol monoacrylate (trade name: CHDMMA, manufactured by Nippon Kasei Co., Ltd.)
(E-3) Dimethylacrylamide (product name: DMAA, manufactured by Kojin Co., Ltd.)
(E-4) Polyurethane acrylate (product name: Shiko UV-3000B, manufactured by Nippon Gosei Chemical Industry Co., Ltd.)
(3) Preparation of cationic polymerization initiator and radical polymerization initiator The following cationic polymerization initiator and radical polymerization initiator (abbreviated as "initiator" in Table 1) were prepared.

(F-1) Cationic polymerization initiator (product name: CPI-100, manufactured by San-Apro Co., Ltd.)
(F-2) Radical polymerization initiator (product name: IRGACURE1173, manufactured by BASF)
(4) Preparation of sensitizer The following sensitizer was prepared.

(G-1) 1,4-diethoxynaphthalene (abbreviated as “DEN” in Table 1)
(5) Preparation of Adhesives 1 to 15 The above cationic curable component and cationic polymerization initiator, or the radical curable component and radical polymerization initiator were mixed in the proportions shown in Table 1 (unit: parts by mass). Thereafter, the mixture was defoamed to prepare photocurable adhesives 1 to 15. The cationic polymerization initiator (F-1) was blended as a 50% propylene carbonate solution, and Table 1 shows the solid content.

[Preparation of adhesive 1]
(1) Preparation of materials The following acrylic base polymer (G-1), isocyanate crosslinking agent (G-2), and silane coupling agent (G-3) were prepared.

(H-1) Copolymer of butyl acrylate, methyl acrylate, acrylic acid and hydroxyethyl acrylate (H-2) Ethyl acetate solution (solid content concentration 75%) of trimethylolpropane adduct of tolylene diisocyanate ("Coronate L") ” (product name), manufactured by Tosoh Corporation)
(H-3) 3-glycidoxypropyltrimethoxysilane, liquid (“KBM-403” (trade name), manufactured by Shin-Etsu Chemical Co., Ltd.)
(2) Preparation of adhesive 1 100 parts by mass of the above acrylic base polymer (H-1), 0.2 parts by mass of isocyanate crosslinking agent (H-2), and 0 parts by mass of silane coupling agent (H-3). Adhesive 1 was prepared by mixing .2 parts by mass, stirring thoroughly, and diluting with ethyl acetate.

[Test Example 1] (Viscosity measurement)
The viscosity of the adhesives 1 to 15 prepared above was measured at a temperature of 25° C. and 10 rpm using an E-type viscometer “TVE-25” manufactured by Toki Sangyo Co., Ltd. The results are shown in Table 1.

[Test Example 2] (Measurement of piercing inclination)
(1) Preparation of adhesive layer test pieces using Adhesives 1 to 15 The adhesives 1 to 15 prepared above were coated on release paper, and an ultraviolet lamp "H Bulb" manufactured by Fusion UV Systems was attached. The adhesive was cured by irradiating the adhesive with ultraviolet rays using a UV irradiation device with a light irradiation intensity of 400 mW/cm ² and an integrated light amount of 400 mJ/cm ² at a wavelength of 280 to 320 nm. was peeled off from the release paper to prepare an adhesive layer test piece. The thickness of the adhesive layer test piece was 30 μm. The thickness of the adhesive layer test piece was measured using a contact type film thickness meter [trade name "DIGIMICRO MH-15M" manufactured by Nikon Corporation].

(2) Preparation of adhesive layer test piece using adhesive 1 The adhesive 1 prepared above was coated on release paper, heat treated at 90°C for 1 minute, and the resulting adhesive layer was peeled from the release paper. An adhesive layer test piece was prepared. The thickness of the adhesive layer test piece was 5 μm and 25 μm. The thickness of the adhesive layer test piece was measured using a contact type film thickness meter [trade name "DIGIMICRO MH-15M" manufactured by Nikon Corporation].

(3) Measurement of the piercing slope of the adhesive layer test piece and the adhesive layer test piece The piercing slope of the adhesive layer test piece and adhesive layer test piece prepared in (1) and (2) above was measured and calculated by the following method. . First, the puncture strength was measured using a small tabletop tester [trade name "EZ Test" manufactured by Shimadzu Corporation] equipped with a puncture jig with a diameter of 1 mm and a tip radius of curvature of 0.5R. . The puncture inclination E (kg/mm) per unit film thickness was calculated using the obtained puncture strength A (kg), the puncture depth B (mm) until tearing, and the following formula.
E=A/B
The measurement was performed on five or more test pieces, and the average value of the piercing inclination calculated using the above formula was determined. The measurement results are shown in Table 1.

[Test Example 3] (Measurement of storage modulus)
(1) Preparation of adhesive layer film using Adhesives 1 to 15 The adhesives 1 to 15 prepared above were applied to a 50 μm thick cyclic polyolefin resin film [“Zeonor Film” sold by Nippon Zeon Co., Ltd.] ] on one side using a coating machine [Bar coater, manufactured by Daiichi Rika Co., Ltd.], and then coated with a 50 μm thick cyclic polyolefin resin film [sold by Nippon Zeon Co., Ltd.] on the coated surface. ``Zeonor Film''] was laminated. Next, the adhesive was cured by irradiating ultraviolet rays using an ultraviolet lamp "H Bulb" manufactured by Fusion UV Systems, Inc. such that the cumulative amount of light was 1500 mJ/cm ² (UVB). The thickness of the adhesive layer was 30 μm. This laminate was cut into a size of 5 mm x 30 mm, and the cyclic polyolefin resin films on both sides were peeled off to obtain an adhesive layer film consisting only of the adhesive layer.

(2) Preparation of adhesive layer film using adhesive 1 Apply adhesive 1 prepared above to one side of release paper using a coating machine [bar coater, manufactured by Daiichi Rika Co., Ltd.]. A release paper was further laminated on the top surface of the adhesive layer, heat treated at 90° C. for 1 minute, and cured for 7 days at 23° C. and 50% RH. The thickness of the adhesive layer after curing was 25 μm. This laminate was cut into a size of 5 mm x 30 mm, and the release paper on both sides was peeled off to obtain an adhesive layer film consisting only of the adhesive layer.

(3) Measurement of storage modulus of adhesive layer film and adhesive layer film The adhesive layer film prepared in (1) above and the adhesive layer film prepared in Using a dynamic viscoelasticity measuring device "DVA-220" manufactured by Tee Keisaku Control Co., Ltd., the samples were gripped with a gap of 2 cm between the grips, the tension and contraction frequency was 10 Hz, the measurement temperature was 30°C, and the temperature was 30°C. The storage modulus was determined. The measurement results are shown in Table 1.

[Test Example 4] (Measurement of glass transition temperature)
(1) Preparation of measurement samples using Adhesives 1 to 15 Adhesives 1 to 15 prepared above were applied to a 50 μm thick cyclic polyolefin resin film [“Zeonor Film” sold by Nippon Zeon Co., Ltd.] ] on one side using a coating machine [Bar coater, manufactured by Daiichi Rika Co., Ltd.], and then coated with a 50 μm thick cyclic polyolefin resin film [sold by Nippon Zeon Co., Ltd.] on the coated surface. ``Zeonor Film''] was laminated. Next, the adhesive was cured by irradiating ultraviolet rays using an ultraviolet lamp "H Bulb" manufactured by Fusion UV Systems, Inc. such that the cumulative amount of light was 1500 mJ/cm ² (UVB). The thickness of the adhesive layer was 30 μm. Next, the cyclic polyolefin resin film sandwiching the adhesive layer was peeled off, and 5 mg of the adhesive layer was collected, placed in an aluminum press lid-type container, and sealed by pressing to prepare a measurement sample.

(2) Preparation of measurement sample using adhesive 1 Apply adhesive 1 prepared above to one side of release paper using a coating machine [bar coater, manufactured by Daiichi Rika Co., Ltd.]. A release paper was further laminated on the top surface of the adhesive layer, heat treated at 90° C. for 1 minute, and cured for 7 days at 23° C. and 50% RH. The thickness of the adhesive layer was 25 μm. Next, the release paper sandwiching the adhesive layer was peeled off, and 5 mg of the adhesive layer was collected, placed in an aluminum presser lid type container, and sealed by pressing to prepare a measurement sample.

(3) Measurement of glass transition temperature (Tg) of adhesive layer sample and adhesive layer sample The adhesive layer sample prepared in (1) and (2) and the container containing the adhesive layer sample (measurement sample) were set, and the temperature was lowered from 20°C to -60°C while purging with nitrogen gas, and the temperature was lowered to -60°C. After reaching the temperature, the temperature was held for 1 minute, and then the temperature was raised from -60°C to 200°C at a rate of 10°C/min, and when it reached 200°C, the temperature was immediately lowered to 20°C. Then, from the DSC curve when the temperature is raised from -60°C to 200°C, the midpoint glass transition temperature specified in JIS K 7121-1987 "Method for measuring the transition temperature of plastics" is determined, and this is determined as the glass transition temperature of the object to be measured. Temperature (Tg). The results are shown in Table 1.

[Example of manufacturing composite retardation plate]
(1-1) Production of the first composite retardation plate (Examples 1 to 14 and Comparative Examples 1 to 4) 1/2 wavelength consisting of three layers: a retardation layer that is a liquid crystal layer, an alignment layer, and a base material layer (first retardation layer), and a quarter wavelength layer (second retardation layer) consisting of three layers: a retardation layer, which is a liquid crystal layer, an alignment layer, and a base material layer. The adhesives shown in Table 2 (Adhesives 1 to 15) were laminated so that the inner side was exposed, and the adhesive layer was irradiated with ultraviolet rays under the same conditions as when forming the adhesive layer test piece in Test Example 2 above to be photocured. The adhesive in the mold was cured to form a cured material layer to obtain a laminate. The thickness of the adhesive layer after curing was as shown in Table 2. After peeling off the first base layer, first alignment layer, second base layer, and second alignment layer from the obtained laminate, the first composite retardation plate (Examples 1 to 14 and Comparative Examples 1 to 4).

(1-2) Production of first composite retardation plate (Comparative Examples 5 and 6) Adhesive 1 was applied on the retardation layer of the same 1/2 wavelength layer as in (1) above, and Test Example 2 An adhesive layer was formed under the same conditions as when forming the adhesive layer test piece in , and the same 1/4 wavelength layer as in (1) above was laminated on it so that the retardation layer was in contact with the adhesive layer. A laminate was obtained.
The thickness of the adhesive layer was set as shown in Table 2. The first composite retardation plate (Comparative Examples 5 and 6) was obtained after peeling off the first base layer, first alignment layer, second base layer, and second alignment layer from the obtained laminate. (2-1) Production of second composite retardation plate (Examples 15 to 28 and Comparative Example 7) Reverse dispersion 1/4 consisting of three layers: a retardation layer which is a liquid crystal layer, an alignment layer and a base material layer A positive C plate (second retardation layer) consisting of a wavelength layer (first retardation layer), a retardation layer (liquid crystal layer), an alignment layer, and a base material layer, with the retardation layer on the inside. The adhesives shown in Table 3 (adhesives 1 to 15) were laminated so that The adhesive was cured to form a cured product layer to obtain a laminate. The thickness of the adhesive layer after curing was as shown in Table 3. A second composite retardation plate (Examples 15 to 28 and Comparative Example 7) was obtained after the first base layer and the second base layer were peeled off from the obtained laminate.

(2-2) Production of second composite retardation plate (Comparative Examples 8 and 9) Adhesive 1 was applied on the same reverse dispersion 1/4 wavelength layer as in (3) above, and adhesive An adhesive layer was formed under the same conditions as when forming the layer test piece, and the same positive C plate as in (3) above was laminated thereon so that the retardation layer was in contact with the adhesive layer to obtain a laminate. Ta. The thickness of the adhesive layer was set as shown in Table 3. A second composite retardation plate (Comparative Examples 8 and 9) was obtained after peeling off the first base layer and the second base layer from the obtained laminate. [Production example of optical laminate]
(1) Manufacture of polarizing plate After immersing a 75 μm thick polyvinyl alcohol film with an average degree of polymerization of about 2,400 and a degree of saponification of 99.9 mol% or more in pure water at 30°C, iodine/potassium iodide/ Iodine dyeing was performed by immersing the sample in an aqueous solution having a water mass ratio of 0.02/2/100 at 30° C. (iodine dyeing step). The polyvinyl alcohol film that had undergone the iodine dyeing process was immersed in an aqueous solution with a mass ratio of potassium iodide/boric acid/water of 12/5/100 at 56.5°C to perform boric acid treatment (boric acid treatment process). ). After washing the polyvinyl alcohol film that had undergone the boric acid treatment process with pure water at 8°C, it was dried at 65°C to obtain a polarizer (thickness 27 μm after stretching) in which iodine was adsorbed and oriented in polyvinyl alcohol. . At this time, stretching was performed in the iodine dyeing step and the boric acid treatment step. The total stretching ratio in this stretching was 5.3 times. A saponified triacetylcellulose film (trade name: KC4UYTAC, manufactured by Konica Minolta, thickness 40 μm) was bonded to both sides of the obtained polarizer using a nip roll via a water-based adhesive. While maintaining the tension of the obtained bond at 430 N/m, it was dried at 60° C. for 2 minutes to obtain a polarizing plate having triacetyl cellulose films as protective films on both sides. The above-mentioned water-based adhesive contains 100 parts of water, 3 parts of carboxyl group-modified polyvinyl alcohol (Kuraray Poval KL318, manufactured by Kuraray), and a water-soluble polyamide epoxy resin (Sumirezu Resin 650, manufactured by Sumika Chemtex, solid content concentration 30%). was prepared by adding 1.5 parts of an aqueous solution of

(2) Production of the first optical laminate (Examples 1 to 14 and Comparative Examples 1 to 4) The polarizing plate produced above and the first composite retardation produced in (1-1) or (1-2) above The first composite retardation plate was bonded to the first optical laminate using an acrylic adhesive (thickness: 25 μm) so that the first retardation layer side of the first composite retardation plate served as the adhesive surface, thereby producing a first optical laminate. At this time, the first retardation layer was laminated so that the slow axis of the first retardation layer was -15° with the counterclockwise direction being positive with respect to the absorption axis direction (0°) of the polarizing plate manufactured above, and The polarizing plates were laminated so that the absorption axis direction of the polarizing plate and the slow axis of the second retardation layer were -75°.

(3) Production of second optical laminate (Examples 15 to 28 and Comparative Examples 7 to 9)
The polarizing plate manufactured above and the second composite retardation plate manufactured in (2-1) or (2-2) above are bonded together so that the first retardation layer side of the second composite retardation plate is the adhesive surface. They were laminated using an acrylic pressure-sensitive adhesive (film thickness: 25 μm) to produce a second optical laminate. At this time, the layers were stacked so that the slow axis of the first retardation layer was at 45° with respect to the absorption axis direction (0°) of the polarizing plate manufactured above.

[Test Example 5] (Evaluation of wrinkle occurrence)
The first optical laminate produced in (2) above and the second optical laminate produced in (3) above were bonded using an acrylic adhesive (film thickness 25 μm) so that the composite retardation plate side was the adhesive surface. The film was bonded to an aluminum plate having a bent portion 2R, and the occurrence of wrinkles at the bent portion was visually observed, and the occurrence of wrinkles was evaluated based on the following criteria. The evaluation results are shown in Tables 2 and 3.
1: No wrinkles were observed at the bent part.
2: It was confirmed that there were slight wrinkles at the bent part (number of wrinkles: 1 to 5),
3: It was confirmed that there were wrinkles at the bent part (number of wrinkles: 5 or more).

1 First retardation layer, 2 Second retardation layer, 4 First adhesive layer, 5 Composite retardation plate, 10 First retardation layer, 11 First base layer, 12 First orientation layer, 13 First place Retardation expression layer, 20 Second retardation layer, 21 Second base layer, 22 Second alignment layer, 23 Second retardation expression layer, 40 First adhesive layer, 50 Laminated body (composite retardation plate), W Width direction.

Claims (15)

including a first retardation layer, a second retardation layer, and a first adhesive layer that adheres the first retardation layer and the second retardation layer,
The first adhesive layer has a piercing slope in the thickness direction of 400 g/mm to 800 g/mm,
The first adhesive layer is a cured product layer of an active energy ray-curable adhesive,
The active energy ray-curable adhesive is a composite retardation plate containing an alicyclic epoxy compound in an amount of 35% by mass or more based on the total amount of the curable compound. including a first retardation layer, a second retardation layer, and a first adhesive layer that adheres the first retardation layer and the second retardation layer,
The first adhesive layer has a storage modulus of 600 MPa or more at a temperature of 30°C, a piercing slope in the thickness direction of 400 g/mm to 800 g/mm, and a cured product layer of an active energy ray-curable adhesive. and
The active energy ray-curable adhesive is a composite retardation plate containing an alicyclic epoxy compound in an amount of 35% by mass or more based on the total amount of the curable compound. including a first retardation layer, a second retardation layer, and a first adhesive layer that adheres the first retardation layer and the second retardation layer,
The first adhesive layer has a glass transition temperature of 60° C. to 200° C., a piercing inclination in the thickness direction of 400 g/mm to 800 g/mm, and is a cured layer of an active energy ray-curable adhesive. ,
The active energy ray-curable adhesive is a composite retardation plate containing an alicyclic epoxy compound in an amount of 35% by mass or more based on the total amount of the curable compound. The composite retardation plate according to any one of claims 1 to 3, wherein the first adhesive layer has a thickness of 0.5 μm to 5 μm. The composite retardation plate according to any one of claims 1 to 4, wherein the first retardation layer is a 1/2 wavelength layer and the second retardation layer is a 1/4 wavelength layer. The composite retardation plate according to any one of claims 1 to 4, wherein the first retardation layer is a 1/2 wavelength layer or a 1/4 wavelength layer, and the second retardation layer is an optical compensation layer. . The composite retardation plate according to any one of claims 1 to 6, wherein at least one of the first retardation layer and the second retardation layer includes a retardation expression layer that is a liquid crystal layer. The composite retardation plate according to any one of claims 1 to 7, having a thickness of 2 μm to 50 μm. comprising a polarizing plate and the composite retardation plate according to any one of claims 1 to 8 laminated on the polarizing plate,
The composite retardation plate is an optical laminate in which the first retardation layer is stacked in a direction facing the polarizing plate. The optical laminate according to claim 9, which is a circularly polarizing plate. The optical laminate according to claim 9 or 10, further comprising a second adhesive layer that adheres the polarizing plate and the composite retardation plate. The optical laminate according to claim 11, wherein the second adhesive layer is a cured layer of an active energy ray-curable adhesive. An image display device comprising an image display panel and the optical laminate according to any one of claims 9 to 12, which is disposed on the viewing side of the image display panel. The image display device according to claim 13, wherein the optical laminate is arranged in such a direction that the polarizing plate is located on the viewing side. The image display device according to claim 14, which is an organic electroluminescent display device.

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