JP2021140146A - Optical laminate and display device - Google Patents

Abstract

To provide an optical laminate which is less susceptible to air bubble generation when bent, and a display device comprising the same.SOLUTION: An optical laminate 100 provided herein comprises a front plate 101, first adhesive layer 102, polarizing plate 103, second adhesive layer 104, and back plate 105 arranged in the described order, and satisfies the following relational expressions (1), (2): ΔR1={(R1A)-(R1B)}/200≤0.2 ...(1), ΔR2={(R2A)-(R2B)}/200≤0.2 ...(2), where R1A[%] and R1B[%] respectively represent shear recovery rates of a first reference adhesive layer of 200-μm thickness formed using a first adhesive composition measured at 25°C before and after a repeated strain load test, and R2A[%] and R2B[%] respectively represent shear recovery rates of a second reference adhesive layer of 200-μm thickness formed using a second adhesive composition measured at 25°C before and after a repeated strain load test.SELECTED DRAWING: Figure 1

Description

The present invention relates to an optical laminate and further to a display device including the optical laminate.

According to Patent Document 1, when a laminate having a plurality of pressure-sensitive adhesive layers is bent, the storage elastic modulus of the outermost pressure-sensitive adhesive layer on the convex side is substantially the same as the storage elastic modulus of the other pressure-sensitive adhesive layers. Or a small laminate is described.

Patent Document 2 discloses a deformable pressure-sensitive adhesive composition for a display, which maintains adhesive properties at room temperature and high temperature and does not float or break even at an ultra-low temperature of −20 ° C.

Japanese Unexamined Patent Publication No. 2018-28873 Korean Publication No. 10-2019-0069334 Gazette

When a display device including an optical laminate having a plurality of pressure-sensitive adhesive layers is bent, bubbles may be generated in the pressure-sensitive adhesive layer in the optical laminate.

An object of the present invention is to provide an optical laminate in which the generation of bubbles is suppressed even when bent, and a display device containing the same.

The present invention provides an optical laminate and a display device illustrated below.
[1] A front plate, a first pressure-sensitive adhesive layer formed by using the first pressure-sensitive adhesive composition, a polarizing plate, a second pressure-sensitive adhesive layer formed by using the second pressure-sensitive adhesive composition, and a spine. A face plate and, in this order,
In the first reference pressure-sensitive adhesive layer having a thickness of 200 μm formed by using the first pressure-sensitive adhesive composition, the shear recovery rates at temperatures of 25 ° C. before and after the strain repeated loading test were set to R1A [%] and R1B [%, respectively. ], And in the second reference pressure-sensitive adhesive layer having a thickness of 200 μm formed by using the second pressure-sensitive adhesive composition, the shear recovery rates at temperatures of 25 ° C. before and after the strain repeated loading test were set to R2A [%] and R2A [%], respectively. An optical laminate that satisfies the following relational expressions (1) and (2) when R2B [%] is used.
ΔR1 = {(R1A)-(R1B)} / 200≤0.2 (1)
ΔR2 = {(R2A)-(R2B)} /200≤0.2 (2)
[2] The optical laminate according to [1], which further satisfies the following relational expression (3).
R1A ≤ R2A (3)
[3] The optical laminate according to [1] or [2], which further satisfies the following relational expression (4).
ΔR1 ≤ ΔR2 (4)
[4] The optical laminate according to any one of [1] to [3], wherein R1A [%] is 20% or more.
[5] The optical laminate according to any one of [1] to [4], wherein the back plate is a touch sensor panel.
[6] A display device including the optical laminate according to any one of [1] to [5].
[7] The display device according to [6], which can be bent with the front plate side inside.

According to the present invention, it is possible to provide an optical laminate and a display device in which the generation of bubbles is suppressed even when bent.

It is the schematic sectional drawing which shows an example of the optical laminated body which concerns on this invention. It is sectional drawing which shows typically the manufacturing method of the optical laminated body which concerns on this invention.

Hereinafter, embodiments of the optical laminate according to the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments. In all the drawings below, the scale is appropriately adjusted to make it easier to understand each component, and the scale of each component shown in the drawings does not necessarily match the scale of the actual component.

<Optical laminate>
FIG. 1 shows a schematic cross-sectional view of an optical laminate according to an aspect of the present invention. The optical laminate 100 includes a front plate 101, a first pressure-sensitive adhesive layer 102, a polarizing plate 103, a second pressure-sensitive adhesive layer 104, and a back plate 105 in this order. The first pressure-sensitive adhesive layer 102 is formed from the first pressure-sensitive adhesive composition, and the second pressure-sensitive adhesive layer 104 is formed from the second pressure-sensitive adhesive composition. Hereinafter, the first pressure-sensitive adhesive layer 102 and the second pressure-sensitive adhesive layer 104 may be collectively referred to as a pressure-sensitive adhesive layer.

The thickness of the optical laminate 100 is not particularly limited because it varies depending on the function required for the optical laminate, the application of the optical laminate, etc., but is, for example, 30 μm or more and 1500 μm or less, preferably 40 μm or more and 1000 μm or less, and more. It is preferably 50 μm or more and 500 μm or less.

The plan view shape of the optical laminate 100 may be, for example, a rectangular shape, preferably a rectangular shape having a long side and a short side, and more preferably a rectangular shape. When the shape of the optical laminate 100 in the plane direction is rectangular, the length of the long side may be, for example, 10 mm or more and 1400 mm or less, preferably 50 mm or more and 600 mm or less. The length of the short side is, for example, 5 mm or more and 800 mm or less, preferably 30 mm or more and 500 mm or less, and more preferably 50 mm or more and 300 mm or less. Each layer constituting the optical laminate 100 may have corners R-processed, end portions notched, or perforated.

The optical laminate 100 can be used, for example, in a display device or the like. The display device is not particularly limited, and examples thereof include an organic electroluminescence (organic EL) display device, an inorganic electroluminescence (inorganic EL) display device, a liquid crystal display device, and an electroluminescent display device. The optical laminate 100 is suitable for a display device capable of bending.

[Shear restoration rate and reduction rate of shear restoration rate by strain repeated load test]
In the first reference pressure-sensitive adhesive layer having a thickness of 200 μm formed by using the first pressure-sensitive adhesive composition, the shear recovery rates at temperatures of 25 ° C. before and after the strain repeated loading test were set to R1A [%] and R1B [%], respectively. In the second reference pressure-sensitive adhesive layer having a thickness of 200 μm formed by using the second pressure-sensitive adhesive composition, the shear recovery rates before and after the strain repeated loading test at a temperature of 25 ° C. were set to R2A [%] and R2B [, respectively. %], The optical laminate 100 satisfies the following relational expressions (1) and (2).
ΔR1 = {(R1A)-(R1B)} / 200≤0.2 (1)
ΔR2 = {(R2A)-(R2B)} /200≤0.2 (2)

An optical laminate in which a front plate, a first pressure-sensitive adhesive layer, a polarizing plate, a second pressure-sensitive adhesive layer, and a back plate are laminated in this order tends to generate air bubbles in the pressure-sensitive adhesive layer when bent, and particularly adheres to the inner diameter side. It was clarified that bubbles are likely to be generated in the agent layer. The optical laminate 100 satisfying the above formulas (1) and (2) suppresses the generation of bubbles even when bent, and in particular, even when the optical laminate 100 is bent and the state is maintained for a certain period of time, the bubbles are generated. Occurrence is suppressed. In the present specification, the generation of air bubbles is suppressed, for example, when the optical laminate 100 is bent along a mandrel, which is a cylindrical jig having a diameter of 10 mm or less, and left for 24 hours. Also means that no bubbles are generated in the pressure-sensitive adhesive layer and between the pressure-sensitive adhesive layer and the layer in contact with the pressure-sensitive adhesive layer. Hereinafter, such performance is also referred to as excellent bending durability. The generation of bubbles can be determined by observation under an optical microscope.

In the present specification, "bending" includes a form of bending in which a curved surface is formed in a bent portion, and the bending radius of the bent inner surface is not particularly limited. Further, "bending" includes a form of refraction in which the refraction angle of the inner surface is greater than 0 degrees and less than 180 degrees, and the bending radius of the inner surface is close to zero, or the refraction angle of the inner surface is 0 degrees. Morphology is included.

ΔR1 and ΔR2 are obtained by dividing the amount of decrease in the shear recovery rate before and after performing the strain repeated load test by the thickness (200 μm) of the first reference pressure-sensitive adhesive layer or the second reference pressure-sensitive adhesive layer. As a result, the amount of reduction in the shear recovery rate by the strain repeated load test per 1 μm of the thickness of the pressure-sensitive adhesive layer formed by using the first pressure-sensitive adhesive composition or the second pressure-sensitive adhesive composition can be obtained. When ΔR1 and ΔR2 are small, it means that the shear recovery rate of the pressure-sensitive adhesive layer is unlikely to decrease even if a strain repeated load test (accelerated test) is performed. That is, when ΔR1 and ΔR2 are small, it is considered that the cohesive force of the pressure-sensitive adhesive is unlikely to decrease even if repeated bending is performed, and the performance of the pressure-sensitive adhesive is likely to be maintained.

The optical laminate 100 preferably satisfies the following relational expressions (1') and (2').
ΔR1 = {(R1A)-(R1B)} / 200≤0.1 (1')
ΔR2 = {(R2A)-(R2B)} / 200≤0.1 (2')
When the optical laminate 100 satisfies the formulas (1') and (2'), the bending durability can be further improved. ΔR1 and ΔR2 can be, for example, 0.001 or more, and may be 0.003 or more.

The optical laminate 100 preferably further satisfies the following relational expression (4).
ΔR1 ≤ ΔR2 (4)
The optical laminate 100 more preferably satisfies the following relational expression (4').
ΔR1 <ΔR2 (4')
When the optical laminate 100 is bent with the front plate 101 inside, a stress larger than that of the second pressure-sensitive adhesive layer 104 is generated in the pressure-sensitive adhesive layer on the inner diameter side, that is, the first pressure-sensitive adhesive layer 102. By arranging the pressure-sensitive adhesive layer on the inner diameter side where the stress is larger, the amount of change in the shear recovery rate before and after executing the strain repeated load test is small, the bending durability of the optical laminate 100 can be further improved.

The optical laminate 100 preferably satisfies the following relational expression (3).
R1A ≤ R2A (3)
The optical laminate 100 more preferably satisfies the following relational expression (3').
R1A <R2A (3')
When the shear recovery rate of the pressure-sensitive adhesive layer is large, the pressure-sensitive adhesive layer tends to return to its original shape when the strain is removed, and when the shear recovery rate of the pressure-sensitive adhesive layer is small, the pressure-sensitive adhesive layer is removed. Is hard to return to its original shape. The shear recovery rate of the pressure-sensitive adhesive layer on the outer diameter side is preferably higher than the shear recovery rate of the pressure-sensitive adhesive layer on the inner diameter side in order to facilitate strain relaxation. The optical laminate 100 satisfying the formula (3) is likely to suppress the generation of air bubbles even when the front plate 101 is bent inside. The shear recovery rate of the pressure-sensitive adhesive layer can be determined according to the method described in the column of Examples described later.

From the viewpoint of improving the surface hardness of the optical laminate 100, the shear recovery rates R1A and R2A before the strain repeated load test are preferably 20% or more, more preferably 30% or more, and more preferably 40%. That is all. The shear recovery rates R1B and R2B after the strain repeated load test are preferably 15% or more, more preferably 30% or more. The upper limits of the shear recovery rates R1A and R2A before the strain repeated load test are not particularly limited, but are, for example, 100% or less, 65% or less, less than 60%, or 55%. It may be as follows. The upper limit values of the shear recovery rates R1B and R2B after the strain repeated load test are not particularly limited as long as the equations (1) and (2) are satisfied, but are, for example, 50% or less, and may be 40% or less.

The shear recovery rates R1A and R2A before the strain repetition test and the shear recovery rates R1B and R2B after the strain repetition test are the types and amounts of the monomers constituting the base polymer contained in the pressure-sensitive adhesive composition, and the types of the polymerization initiators. The desired numerical range can be obtained by adjusting the blending amount, the type of active energy ray, the irradiation amount, and the like.

[Front plate]
The material and thickness of the front plate 101 are not limited as long as it is a plate-like body capable of transmitting light. The front plate 101 may be composed of only one layer, or may be composed of two or more layers. The front plate 101 includes a resin plate (for example, a resin plate, a resin sheet, a resin film, etc.), a glass plate (for example, a glass plate, a glass film, etc.), a resin plate, and a glass. A laminated body with a plate-like body of the above can be mentioned. The front plate 101 can form the outermost surface of the display device.

The thickness of the front plate 101 may be, for example, 10 μm or more and 300 μm or less, preferably 20 μm or more and 200 μm or less, and more preferably 30 μm or more and 100 μm or less. In the present invention, the thickness of each layer constituting the optical laminate 100 can be measured according to the thickness measuring method described in Examples described later.

Examples of the resin constituting the resin plate-like body include triacetyl cellulose, acetyl cellulose butyrate, ethylene-vinyl acetate copolymer, propionyl cellulose, butyryl cellulose, acetyl propionyl cellulose, polyester, polystyrene, polyamide, and polyether. Iimide, poly (meth) acrylic, polyimide, polyethersulfone, polysulfone, polyethylene, polypropylene, polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl acetal, polyether ketone, polyether ether ketone, polyethersulfone , Polymethylmethacrylate, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyamideimide and other polymers. These polymers can be used alone or in admixture of two or more. From the viewpoint of improving strength and transparency, the resin plate-like body is preferably a resin film formed of a polymer such as polyimide, polyamide, or polyamideimide.

From the viewpoint of hardness, the front plate 101 may be a resin film provided with a hard coat layer. The hard coat layer may be formed on one surface of the resin film or may be formed on both sides. By providing the hard coat layer, hardness and scratch resistance can be improved. The hard coat layer is, for example, a cured layer of an ultraviolet curable resin. Examples of the ultraviolet curable resin include acrylic resin, silicone resin, polyester resin, urethane resin, amide resin, epoxy resin and the like. The hard coat layer may contain additives to improve strength. The additive is not particularly limited, and examples thereof include inorganic fine particles, organic fine particles, or a mixture thereof. When the hard coat layers are provided on both sides of the resin film, the composition and thickness of each hard coat layer may be the same or different from each other.

When the front plate 101 is a glass plate, tempered glass for a display is preferably used as the glass plate. The thickness of the glass plate may be, for example, 10 μm or more and 1000 μm or less, or 10 μm or more and 100 μm or less. By using the glass plate, the front plate 101 having excellent mechanical strength and surface hardness can be constructed.

When the optical laminate 100 is used in a display device, the front plate 101 not only has a function of protecting the front surface (screen) of the display device (function as a window film), but also functions as a touch sensor and blue light cut. It may have a function, a viewing angle adjusting function, and the like.

[First adhesive layer]
The first pressure-sensitive adhesive layer 102 is interposed between the front plate 101 and the polarizing plate 103, and these are bonded together. The first pressure-sensitive adhesive layer 102 may be composed of one layer or two or more layers, but is preferably composed of one layer.

The first pressure-sensitive adhesive layer 102 is composed of a pressure-sensitive adhesive composition containing (meth) acrylic resin, rubber-based resin, urethane-based resin, ester-based resin, silicone-based resin, and polyvinyl ether-based resin as main components (base polymer). can do. As the pressure-sensitive adhesive composition constituting the first pressure-sensitive adhesive layer 102, a pressure-sensitive adhesive composition using a (meth) acrylic resin having excellent transparency, weather resistance, heat resistance and the like as a base polymer is suitable. The pressure-sensitive adhesive composition may be an active energy ray-curable type or a thermosetting type.

Examples of the (meth) acrylic resin used in the pressure-sensitive adhesive composition include (meth) butyl (meth) acrylate, ethyl (meth) acrylate, isooctyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. A polymer or copolymer containing one or more acrylic acid esters as a monomer is preferably used. It is preferable that the base polymer is copolymerized with a polar monomer. Examples of the polar monomer include (meth) acrylic acid compound, (meth) acrylic acid 2-hydroxypropyl compound, (meth) acrylic acid hydroxyethyl compound, (meth) acrylamide compound, and N, N-dimethylaminoethyl (meth) acrylate compound. , A monomer having a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, etc., such as a glycidyl (meth) acrylate compound.

The active energy ray-curable pressure-sensitive adhesive composition has a property of being cured by being irradiated with active energy rays such as ultraviolet rays and electron beams, and has adhesiveness even before irradiation with active energy rays, such as a film. It has the property that it can be brought into close contact with the adherend of the above, and can be cured by irradiation with active energy rays to adjust the adhesion. The active energy ray-curable pressure-sensitive adhesive composition is preferably an ultraviolet-curable type. The active energy ray-curable pressure-sensitive adhesive composition further contains an active energy ray-polymerizable compound in addition to the base polymer and the cross-linking agent. If necessary, a photopolymerization initiator, a photosensitizer, or the like may be contained.

The active energy ray-polymerizable compound is, for example, a (meth) acrylate monomer having at least one (meth) acryloyloxy group in the molecule; obtained by reacting two or more kinds of functional group-containing compounds, and at least two in the molecule. Examples thereof include (meth) acrylic compounds such as (meth) acryloyloxy group-containing compounds such as (meth) acrylate oligomers having individual (meth) acryloyloxy groups. When a (meth) acrylic compound having a cyclohexyl group or a (meth) acrylic compound having an ethoxy group is used as the active energy ray-polymerizable compound, the cohesive force in the pressure-sensitive adhesive layer is improved, and the formula (1) and It becomes easier to satisfy the equation (2). Examples of the (meth) acrylic compound having a cyclohexyl group include Miramer M1130 and Miramer M1150 manufactured by Miwon Specialty Chemical. Examples of the (meth) acrylic compound having an ethoxy group include Miramer M140, Miramer M142, and Miramer M144 manufactured by Miwon Specialty Chemical. The pressure-sensitive adhesive composition may contain an active energy ray-polymerizable compound in an amount of 0.1 part by mass or more or 5 parts by mass or more with respect to 100 parts by mass of the solid content of the pressure-sensitive adhesive composition, and is 30 parts by mass or less and 10 parts by mass or less. It can include 5 parts by mass or less or 2 parts by mass or less.

Examples of the photopolymerization initiator include benzophenone, benzyl dimethyl ketal, 1-hydroxycyclohexyl ketone and the like. The photopolymerization initiator may contain one kind or two or more kinds. When the pressure-sensitive adhesive composition contains a photopolymerization initiator, the total content thereof may be, for example, 0.01 part by mass or more and 3.0 parts by mass or less with respect to 100 parts by mass of the solid content of the pressure-sensitive adhesive composition.

The pressure-sensitive adhesive composition includes fine particles for imparting light scattering properties, beads (resin beads, glass beads, etc.), glass fibers, resins other than the base polymer, pressure-sensitive adhesives, fillers (metal powders and other inorganic powders). Etc.), antioxidants, UV absorbers, dyes, pigments, colorants, antifoaming agents, corrosion inhibitors, photopolymerization initiators and other additives can be included.

The first pressure-sensitive adhesive layer 102 can be formed by applying an organic solvent-diluted solution of the pressure-sensitive adhesive composition onto a substrate and drying it. The first pressure-sensitive adhesive layer 102 can also be formed by using a pressure-sensitive adhesive sheet formed by using the pressure-sensitive adhesive composition. When the active energy ray-curable pressure-sensitive adhesive composition is used, the formed pressure-sensitive adhesive layer can be irradiated with active energy rays to obtain a pressure-sensitive adhesive layer having a desired degree of curing.

The thickness of the first pressure-sensitive adhesive layer 102 is not particularly limited, but is preferably 1 μm or more and 100 μm or less, more preferably 3 μm or more and 50 μm or less, and may be 20 μm or more.

[Polarizer]
The polarizing plate 103 can be, for example, a linear polarizing plate, a circular polarizing plate, an elliptical polarizing plate, or the like. The circular polarizing plate includes a linear polarizing plate and a retardation layer. Since the circularly polarizing plate can absorb the external light reflected in the image display device, it is possible to impart the function as an antireflection film to the optical laminate 100.

The thickness of the polarizing plate 103 is usually 5 μm or more, may be 20 μm or more, 25 μm or more, or 30 μm or more. The thickness of the polarizing plate 103 is preferably 80 μm or less, and more preferably 60 μm or less.

(Linear polarizing plate)
The linear polarizing plate has a function of selectively transmitting linearly polarized light in a certain direction from unpolarized light rays such as natural light. The linear polarizing plate includes a stretched film or stretched layer on which a dichroic dye is adsorbed, a cured product of a polymerizable liquid crystal compound, and a dichroic dye, and the dichroic dye is dispersed in the cured product of the polymerizable liquid crystal compound. , An oriented liquid crystal layer or the like can be provided as a polarizer layer. When the dye is dispersed and oriented in an anisotropic medium, it may appear colored in one direction and almost colorless in the direction perpendicular to it. A pigment exhibiting such a phenomenon is called a dichroic pigment. A linear polarizing plate using a liquid crystal layer as a polarizer layer is preferable because there is no limitation in the bending direction as compared with a stretched film or a stretched layer on which a dichroic dye is adsorbed.

(1) Stretched film or stretched layer having a dichroic dye adsorbed The polarizer layer, which is a stretched film having a dichroic dye adsorbed, is usually a step of uniaxially stretching a polyvinyl alcohol-based resin film. , A step of adsorbing a dichroic dye by dyeing the polyvinyl alcohol-based resin film with a dichroic dye such as iodine, and treating the polyvinyl alcohol-based resin film on which the dichroic dye is adsorbed with an aqueous boric acid solution. It can be produced through a step and a step of washing with water after treatment with an aqueous boric acid solution.

The thickness of the polarizer layer is usually 30 μm or less, preferably 18 μm or less, and more preferably 15 μm or less. Reducing the thickness of the polarizer layer is advantageous for thinning the polarizing plate 103. The thickness of the polarizer layer is usually 1 μm or more, and may be, for example, 5 μm or more.

The polyvinyl alcohol-based resin is obtained by saponifying a polyvinyl acetate-based resin. As the polyvinyl acetate-based resin, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate, a copolymer of vinyl acetate and another monomer copolymerizable therewith is used. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acid compounds, olefin compounds, vinyl ether compounds, unsaturated sulfone compounds, and (meth) acrylamide compounds having an ammonium group. ..

The degree of saponification of the polyvinyl alcohol-based resin is usually about 85 mol% or more and 100 mol% or less, preferably 98 mol% or more. The polyvinyl alcohol-based resin may be modified, and polyvinyl formal, polyvinyl acetal, and the like modified with aldehydes can also be used. The degree of polymerization of the polyvinyl alcohol-based resin is usually 1000 or more and 10000 or less, preferably 1500 or more and 5000 or less.

The polarizer layer, which is a stretched layer on which a dichroic dye is adsorbed, is usually a step of applying a coating liquid containing the above-mentioned polyvinyl alcohol-based resin on a base film, a step of uniaxially stretching the obtained laminated film, and uniaxial. A step of dyeing a polyvinyl alcohol-based resin layer of a stretched laminated film with a dichroic dye to adsorb the dichroic dye to form a polarizer layer, and a film on which the dichroic dye is adsorbed is boric acid. It can be produced through a step of treating with an aqueous solution and a step of washing with water after treatment with an aqueous boric acid solution. The base film used to form the polarizer layer may be used as a protective layer for the polarizer layer. If necessary, the base film may be peeled off from the polarizer layer. The material and thickness of the base film may be the same as the material and thickness of the thermoplastic resin film described later.

The stretched film or the polarizing element layer which is the stretched layer on which the dichroic dye is adsorbed may be used as it is as a linear polarizing plate, or a protective layer may be formed on one or both sides thereof and used as a linear polarizing plate. As the protective layer, a thermoplastic resin film described later can be used. The thickness of the obtained linear polarizing plate is preferably 2 μm or more and 40 μm or less.

The thermoplastic resin film is, for example, a cyclopolyolefin resin film; a cellulose acetate resin film made of a resin such as triacetyl cellulose or diacetyl cellulose; a polyester resin film made of a resin such as polyethylene terephthalate, polyethylene naphthalate, or polybutylene terephthalate; Examples of films known in the art such as polycarbonate-based resin films; (meth) acrylic-based resin films; polypropylene-based resin films and the like can be mentioned. The polarizer layer and the protective layer can be laminated via a bonding layer described later.

From the viewpoint of thinning, the thickness of the thermoplastic resin film is usually 100 μm or less, preferably 80 μm or less, more preferably 60 μm or less, still more preferably 40 μm or less, still more preferably 30 μm or less. Yes, it is usually 5 μm or more, preferably 10 μm or more.

A hard coat layer may be formed on the thermoplastic resin film. The hard coat layer may be formed on one side of the thermoplastic resin film, or may be formed on both sides. By providing the hard coat layer, a thermoplastic resin film having improved hardness and scratch resistance can be obtained. The hard coat layer can be formed in the same manner as the hard coat layer formed on the resin film described above.

(2) Polarizer layer which is a liquid crystal layer The polymerizable liquid crystal compound used for forming the liquid crystal layer is a compound which has a polymerizable reactive group and exhibits liquid crystal property. The polymerizable reactive group is a group involved in the polymerization reaction, and is preferably a photopolymerizable reactive group. The photopolymerizable reactive group refers to a group that can participate in the polymerization reaction by an active radical, an acid, or the like generated from the photopolymerization initiator. Examples of the photopolymerizable functional group include a vinyl group, a vinyloxy group, a 1-chlorovinyl group, an isopropenyl group, a 4-vinylphenyl group, an acryloyloxy group, a methacryloyloxy group, an oxylanyl group, an oxetanyl group and the like. Of these, an acryloyloxy group, a methacryloyloxy group, a vinyloxy group, an oxylanyl group and an oxetanyl group are preferable, and an acryloyloxy group is more preferable. The type of the polymerizable liquid crystal compound is not particularly limited, and a rod-shaped liquid crystal compound, a disk-shaped liquid crystal compound, and a mixture thereof can be used. The liquid crystal property of the polymerizable liquid crystal compound may be a thermotropic liquid crystal or a lyotropic liquid crystal, and the phase-ordered structure may be a nematic liquid crystal or a smectic liquid crystal.

The dichroic dye used for the polarizing element layer, which is a liquid crystal layer, preferably has an absorption maximum wavelength (λMAX) in the range of 300 to 700 nm. Examples of such a bicolor dye include an acridine dye, an oxazine dye, a cyanine dye, a naphthalene dye, an azo dye, an anthraquinone dye and the like, and among them, the azo dye is preferable. Examples of the azo dye include monoazo dyes, bisazo dyes, trisazo dyes, tetrakisazo dyes, and stillbenazo dyes, and bisazo dyes and trisazo dyes are preferable. The dichroic dye may be used alone or in combination of two or more, but it is preferable to combine three or more. In particular, it is more preferable to combine three or more kinds of azo compounds. A part of the dichroic dye may have a reactive group or may have a liquid crystallinity.

In the polarizing layer, which is a liquid crystal layer, for example, a composition for forming a polarizing layer containing a polymerizable liquid crystal compound and a dichroic dye is applied onto an alignment film formed on a base film, and the polymerizable liquid crystal compound is polymerized. It can be formed by curing it. A polarizer layer may be formed by applying a composition for forming a polarizer layer on a substrate film to form a coating film, and then stretching the coating film together with the substrate film. The base film used to form the polarizer layer may be used as a protective layer for the polarizer layer. The material and thickness of the base film may be the same as the material and thickness of the thermoplastic resin film described above.

Examples of a composition for forming a polarizer layer containing a polymerizable liquid crystal compound and a dichroic dye, and a method for producing a polarizer layer using this composition are JP-A-2013-373353 and JP-A-2013-33249. , JP-A-2017-83843, etc. can be exemplified. In the composition for forming a polarizer layer, in addition to the polymerizable liquid crystal compound and the dichroic dye, additives such as a solvent, a polymerization initiator, a cross-linking agent, a leveling agent, an antioxidant, a plasticizer, and a sensitizer are further added. It may be included. Only one of these components may be used, or two or more of these components may be used in combination.

The polymerization initiator that may be contained in the composition for forming a polarizer layer is a compound that can initiate a polymerization reaction of a polymerizable liquid crystal compound, and is photopolymerized in that the polymerization reaction can be initiated under lower temperature conditions. Sex initiators are preferred. Specific examples thereof include photopolymerization initiators capable of generating active radicals or acids by the action of light, and among them, photopolymerization initiators that generate radicals by the action of light are preferable. The content of the polymerization initiator is preferably 1 part by mass or more and 10 parts by mass or less, and more preferably 3 parts by mass or more and 8 parts by mass or less, based on 100 parts by mass of the total amount of the polymerizable liquid crystal compound. Within this range, the reaction of the polymerizable group proceeds sufficiently, and the orientation state of the liquid crystal compound is likely to be stabilized.

The thickness of the polarizer layer, which is a liquid crystal layer, is usually 10 μm or less, preferably 0.5 μm or more and 8 μm or less, and more preferably 1 μm or more and 5 μm or less.

The polarizer layer, which is a liquid crystal layer, may be used as a linear polarizing plate without peeling and removing the base film, or may be used as a linear polarizing plate by peeling and removing the base film from the polarizer layer. The polarizing element layer, which is a liquid crystal layer, may or may not have an alignment film. The polarizing element layer, which is a liquid crystal layer, may be used as a linear polarizing plate by forming a protective layer on one side or both sides thereof. As the protective layer, the above-mentioned thermoplastic resin film can be used.

The polarizing element layer, which is a liquid crystal layer, may have an overcoat layer on one side or both sides of the polarizer layer for the purpose of protecting the polarizer layer or the like. The overcoat layer can be formed, for example, by applying a material (composition) for forming the overcoat layer on the polarizer layer. Examples of the material constituting the overcoat layer include a photocurable resin and a water-soluble polymer. As a material constituting the overcoat layer, a (meth) acrylic resin, a polyvinyl alcohol-based resin, or the like can be used.

(Phase difference layer)
The retardation layer may be one layer or two or more layers. The retardation layer may have an overcoat layer that protects the surface thereof, a base film that supports the retardation layer, and the like. The retardation layer includes a λ / 4 layer, and may further include at least one of a λ / 2 layer and a positive C layer. When the retardation layer includes a λ / 2 layer, the λ / 2 layer and the λ / 4 layer are laminated in order from the linear polarizing plate side. When the retardation layer contains a positive C layer, the λ / 4 layer and the positive C layer may be laminated in order from the linear polarizing plate side, or the positive C layer and the λ / 4 layer may be laminated in order from the linear polarizing plate side. May be good. The thickness of the retardation layer is, for example, 0.1 μm or more and 10 μm or less, preferably 0.5 μm or more and 8 μm or less, and more preferably 1 μm or more and 6 μm or less.

The retardation layer may be formed from the resin film exemplified as the material of the protective layer, or may be formed from a layer in which the polymerizable liquid crystal compound is cured. The retardation layer may further include an alignment film. The retardation layer may have a bonding layer for bonding the λ / 4 layer, the λ / 2 layer, and the positive C layer.

When the polymerizable liquid crystal compound is cured to form a retardation layer, the retardation layer can be formed by applying a composition containing the polymerizable liquid crystal compound to a base film and curing it. An orientation layer may be formed between the base film and the coating layer. The material and thickness of the base film may be the same as the material and thickness of the thermoplastic resin film. When the retardation layer is formed from the layer obtained by curing the polymerizable liquid crystal compound, the retardation layer may be incorporated into the optical laminate in the form of having an alignment layer and a base film. The retardation layer can be bonded to the surface of the linear polarizing plate on the side opposite to the visible side via a bonding layer described later.

[Second adhesive layer]
The second pressure-sensitive adhesive layer 104 is interposed between the polarizing plate 103 and the back plate 105, and these are bonded together. The second pressure-sensitive adhesive layer 104 may be one layer or may be composed of two or more layers, but is preferably one layer.

The composition and compounding components of the pressure-sensitive adhesive composition constituting the second pressure-sensitive adhesive layer 104, the type of the pressure-sensitive adhesive composition (whether it is an active energy ray-curable type or a thermosetting type, etc.), and blended in the pressure-sensitive adhesive composition. The additives to be obtained, the method for producing the second pressure-sensitive adhesive layer, the thickness of the second pressure-sensitive adhesive layer, and the like are the same as those shown in the above description of the first pressure-sensitive adhesive layer 102.
The second pressure-sensitive adhesive layer 104 may be the same as or different from the first pressure-sensitive adhesive layer 102 in terms of the composition, composition, thickness, and the like of the pressure-sensitive adhesive composition.

[Lated layer]
The optical laminate 100 can include a laminating layer for joining the two layers. The bonding layer is a layer composed of a pressure-sensitive adhesive or an adhesive. As the pressure-sensitive adhesive used as the material of the bonding layer, the same pressure-sensitive adhesive composition as the pressure-sensitive adhesive composition constituting the first pressure-sensitive adhesive layer 102 can be used. The bonding layer is different from other adhesives, for example, the adhesives constituting the first adhesive layer 102 (meth) acrylic adhesive, styrene adhesive, silicone adhesive, rubber adhesive, urethane adhesive. Adhesives, polyester adhesives, epoxy copolymer adhesives and the like can also be used.

As the adhesive used as the material of the bonding layer, for example, one or a combination of two or more of water-based adhesives, active energy ray-curable adhesives, and the like can be formed. Examples of the water-based adhesive include a polyvinyl alcohol-based resin aqueous solution, a water-based two-component urethane-based emulsion adhesive, and the like. The active energy ray-curable adhesive is an adhesive that cures by irradiating with active energy rays such as ultraviolet rays, and is, for example, an adhesive containing a polymerizable compound and a photopolymerizable initiator, and an adhesive containing a photoreactive resin. , Adhesives containing a binder resin and a photoreactive cross-linking agent, and the like. Examples of the polymerizable compound include photopolymerizable monomers such as a photocurable epoxy monomer, a photocurable acrylic monomer, and a photocurable urethane monomer, and oligomers derived from these monomers. Examples of the photopolymerization initiator include compounds containing substances that generate active species such as neutral radicals, anion radicals, and cationic radicals by irradiating them with active energy rays such as ultraviolet rays.

The thickness of the bonded layer may be, for example, 1 μm or more, preferably 1 μm or more and 25 μm or less, more preferably 2 μm or more and 15 μm or less, and further preferably 2.5 μm or more and 5 μm or less.

The two opposing surfaces that are bonded via the bonding layer may be subjected to corona treatment, plasma treatment, flame treatment, or the like in advance, or may have a primer layer or the like.

[Back plate]
As the back plate 105, a plate-like body capable of transmitting light, a component used in a normal display device, or the like can be used.

The thickness of the back plate 105 may be, for example, 5 μm or more and 2000 μm or less, preferably 10 μm or more and 1000 μm or less, and more preferably 15 μm or more and 500 μm or less.

The plate-like body used for the back plate 105 may be composed of only one layer, or may be composed of two or more layers. As the back plate 105, the plate-like body exemplified in the front plate 101 can be used.

Examples of the components used in a normal display device include a touch sensor panel, an organic EL display element, and the like. Examples of the stacking order of the components in the display device include a front plate / circular polarizing plate / touch sensor panel / organic EL display element, a front plate / touch sensor panel / circular polarizing plate / organic EL display element, and the like. The back plate 105 is preferably a touch sensor panel.

(Touch sensor panel)
The touch sensor panel is not limited as long as it is a panel having a sensor (that is, a touch sensor) capable of detecting the touched position. The detection method of the touch sensor is not limited, and touch sensor panels such as a resistive film method, a capacitance coupling method, an optical sensor method, an ultrasonic method, an electromagnetic induction coupling method, and a surface acoustic wave method are exemplified. Since the cost is low, a touch sensor panel of a resistance film type or a capacitance coupling type is preferably used.

As an example of a resistance film type touch sensor, a pair of substrates arranged opposite to each other, an insulating spacer sandwiched between the pair of substrates, and a transparent conductive film provided as a resistance film on the inner front surface of each substrate. Examples thereof include a member composed of a film and a touch position detection circuit. In an image display device provided with a resistance film type touch sensor, when the surface of the front plate is touched, the opposing resistance films are short-circuited and a current flows through the resistance film. The touch position detection circuit detects the change in voltage at this time, and the touched position is detected.

An example of a capacitance coupling type touch sensor includes a member composed of a substrate, a transparent electrode for position detection provided on the entire surface of the substrate, and a touch position detection circuit. In an image display device provided with a capacitance coupling type touch sensor, when the surface of the front plate is touched, the transparent electrode is grounded via the capacitance of the human body at the touched point. The touch position detection circuit detects the grounding of the transparent electrode, and the touched position is detected.

The thickness of the touch sensor panel may be, for example, 5 μm or more and 2000 μm or less, preferably 5 μm or more and 100 μm or less, more preferably 5 μm or more and 50 μm or less, and 5 μm or more and 20 μm or less.

The touch sensor panel may be a member in which a touch sensor pattern is formed on a base film. The example of the base film may be the same as the example in the description of the thermoplastic resin film described above. Further, the touch sensor panel may be transferred from the base film to the adherend via the pressure-sensitive adhesive layer. That is, the touch sensor panel does not have to have a base film. The thickness of the touch sensor pattern may be, for example, 1 μm or more and 20 μm or less.

[Manufacturing method of optical laminate]
The optical laminate 100 can be manufactured by a method including a step of laminating the layers constituting the optical laminate 100 via an adhesive layer. When the layers are bonded to each other via an adhesive layer or a bonding layer, one or both of the bonding surfaces may be subjected to a surface activation treatment such as corona treatment for the purpose of adjusting the adhesion. preferable. The conditions for corona treatment can be set as appropriate, and the conditions may differ between one surface of the bonded surface and the other surface.

[Display device]
The display device according to the present invention includes the optical laminate 100. The display device is not particularly limited, and examples thereof include an image display device such as an organic EL display device, an inorganic EL display device, a liquid crystal display device, and an electroluminescent display device. A touch sensor may be further laminated on the optical laminate, and the display device may have a touch panel function. The display device including the optical laminate 100 of the present invention can be used as a flexible display that has excellent bending durability and can be bent or wound.

In the display device, the optical laminate 100 is arranged on the visible side of the display element of the display device with the front plate 101 facing outward (the side opposite to the display element side, that is, the visual recognition side). The display device can be bent with the front plate 101 side inside.

Examples of the image display element included in the image display device include an organic EL display element, an inorganic EL display element, a liquid crystal display element, a plasma display element, an electric field radiation type display element, and the like.

The display device according to the present invention can be used as a mobile device such as a smartphone or tablet, a television, a digital photo frame, an electronic signboard, a measuring instrument or an instrument, an office device, a medical device, a computer device, or the like.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

[Measuring method]
The measurement method and calculation method of each physical property value (layer thickness, adhesive layer property, etc.) used in this example are as follows.

<Layer thickness>
The measurement was performed using a contact type film thickness measuring device (“MS-5C” manufactured by Nikon Corporation). The polarizer layer and the alignment film were measured using a laser microscope (“OLS3000” manufactured by Olympus Corporation).

<Shear restoration rate>
The shear recovery rate was measured using a viscoelasticity measuring device (MCR-301, Antonio Par). The pressure-sensitive adhesive sheet was cut into a width of 20 mm and a length of 20 mm, the release film was peeled off, and eight pressure-sensitive adhesive layers having a thickness of 25 μm were laminated to form a reference pressure-sensitive adhesive layer having a thickness of 200 μm, which was bonded to a glass plate. The measurement was performed under the conditions of Normal force 1N and Torque 1200 μNm at a temperature of 25 ° C. in a state of being adhered to the measuring chip, and after measuring the amount of shear deformation in 1200 seconds, the measurement was continued by changing to the condition of Torque 0 μNm 1206. The amount of shear deformation in seconds was measured. Based on these measured values, the shear recovery rate R was calculated from the following formula.
R = {(1200 seconds shear deformation amount-1206 seconds shear deformation amount) / 1200 seconds shear deformation amount} x 100 [%]

<Strain repeated load test>
The strain repeated load test as an accelerated test was performed using a viscoelasticity measuring device (MCR-301, Antonio Par). The pressure-sensitive adhesive sheet was cut into a width of 20 mm and a length of 20 mm, the release film was peeled off, and eight pressure-sensitive adhesive layers having a thickness of 25 μm were laminated to form a reference pressure-sensitive adhesive layer having a thickness of 200 μm, which was bonded to a glass plate. With respect to the reference adhesive layer on the glass plate, under the conditions of a temperature of 25 ° C., a Normal Force Free, and a frequency of 2 Hz in a state of being adhered to the measuring chip in the above apparatus, the strain of 0% and 1000%. The load was applied repeatedly over 1000 seconds.

[Preparation of adhesive sheet containing adhesive layer]
2-Ethylhexyl acrylate (2-EHA), butyl acrylate (BA), β-carboxy acrylate in a 1 L reaction vessel equipped with a cooling tube, a nitrogen introduction tube, a thermometer and a stirrer in the amounts shown in Table 1. A monomer mixed solution of ethyl (B-CEA), acrylic acid (AA), glycidyl methacrylate (GMA), and 2-hydroxyethyl methacrylate (2-HEMA) was added. Nitrogen gas was recirculated for 1 hour to remove oxygen in the container, and the internal temperature was maintained at 60 ° C. After uniformly mixing the above monomer mixture solution, the photopolymerization initiator benzyl dimethyl ketal (I-651) and 1-hydroxycyclohexylphenyl ketone (I-184) were added in the blending amounts shown in Table 1. UV lamps (10 mW) were irradiated with stirring to produce (meth) acrylic polymers A1 to A6.

The obtained (meth) acrylic polymers A1 to A6 and 3,3,5-trimethylcyclohexyl acrylate (Miramer M1130), lauryl acrylate (Miramer M120), 2-phenoxyethyl acrylate (Miramer M140) and 1- Hydroxycyclohexylphenyl ketone (I-184) was mixed in the blending amounts shown in Table 2 to prepare pressure-sensitive adhesive compositions B1 to B8.

The pressure-sensitive adhesive compositions B1 to B8 were applied on a release film A (polyethylene terephthalate film, thickness 38 μm) coated with a silicon release agent so as to have a thickness of 25 μm. A release film B (polyethylene terephthalate film, thickness 38 μm) was bonded onto the release film B and irradiated with UV to prepare an adhesive sheet composed of the release film A / adhesive layer / release film B. The conditions for UV irradiation were an integrated light intensity of 400 mJ / cm ² and an illuminance of 1.8 mW / cm ² (UVV standard).

The sources of the compounds in Tables 1 and 2 are as follows.
2-EHA: Tokyo Kasei Kogyo Co., Ltd., Japan BA: Tokyo Kasei Kogyo Co., Ltd., Japan B-CEA: Sigma Aldrich, USA AA: Tokyo Kasei Kogyo Co., Ltd., Japan GMA: Sigma Aldrich, USA 2-HEMA: Tokyo Kasei Kogyo Japan I-651: BASF, Germany I-184: BASF, Germany Miramer M1130: Miwon Specialty Chemical, Korea Miramer M120: Miwon Specialty Chemical, Korea Miramer M140: Miwan

[Front plate]
As the front plate 101, a film (50 μm) having a hard coat layer formed on one surface of the resin film was prepared. The resin film was a polyimide film having a thickness of 40 μm. The hard coat layer was a layer having a thickness of 10 μm and formed from a composition containing a dendrimer compound having a polyfunctional acrylic group at the end.

[Polarizer layer]
1) As a base film, a triacetyl cellulose (TAC) film (KC2UA, manufactured by Konica Minolta Co., Ltd., thickness 25 μm) was prepared.

2) A solution in which the polymer 1 shown below was dissolved in cyclopentanone at a concentration of 5% by mass was prepared as a composition for forming an alignment film. The polymer 1 is composed of the following structural units and has a photoreactive group.

3) A composition for forming a polarizer layer was prepared.
First, as the polymerizable liquid crystal compound, the polymerizable liquid crystal compound represented by the formula (1-1) [hereinafter, also referred to as compound (1-1)] and the polymerizable liquid crystal compound represented by the formula (1-2) [ Hereinafter, it is also referred to as compound (1-2)].

Compound (1-1) and compound (1-2) are described in Lub et al. Recl. Trav. Chim. It was synthesized by the method described in Pays-Bas, 115, 321-328 (1996).

As the dichroic dye, the azo dye described in Examples of Japanese Patent Application Laid-Open No. 2013-101328 represented by the following formulas (2-1a), (2-1b) and (2-3a) was prepared.

The composition for forming the polarizer layer contains 75 parts by mass of the compound (1-1) and 25 parts by mass of the compound (1-2), and the above formulas (2-1a) and (2-) as a dichroic dye. 2.5 parts by mass of each of the azo dyes shown in 1b) and (2-3a) and 2-dimethylamino-2-benzyl-1- (4-morpholinophenyl) butane-1-one (4-morpholinophenyl) butane-1-one as a polymerization initiator (4). 6 parts by mass of Irgacure 369 (manufactured by BASF Japan) and 1.2 parts by mass of a polyacrylate compound (BYK-361N, manufactured by BYK-Chemie) as a leveling agent were mixed with 400 parts by mass of toluene as a solvent. The resulting mixture was prepared by stirring at 80 ° C. for 1 hour.

4) Composition for forming a protective layer The composition for forming a protective layer contains 100 parts by mass of water and 3 parts by mass of polyvinyl alcohol resin powder (manufactured by Kuraray Co., Ltd., average degree of polymerization 18000, trade name: KL-318). , Polyamide epoxy resin (crosslinking agent, manufactured by Sumika Chemtex Co., Ltd., trade name: SR650 (30)) was prepared by mixing with 1.5 parts by mass.

5) A polarizer layer was prepared by the following procedure.
First, the TAC film side of the base film was subjected to corona treatment once. The conditions for corona treatment were an output of 0.3 kW and a processing speed of 3 m / min. Then, the composition for forming an alignment film was applied onto the TAC film by a bar coating method, and dried by heating in a drying oven at 80 ° C. for 1 minute. The obtained dry film was subjected to polarized UV irradiation treatment to form a first alignment film (AL1). In the polarized UV treatment, the light emitted from the UV irradiation device (SPOT CURE SP-7; manufactured by Ushio, Inc.) is transmitted through a wire grid (UIS-27132 ##, manufactured by Ushio, Inc.) to have a wavelength of 365 nm. The test was performed under the condition that the integrated light amount measured in 1 was 100 mJ / cm ^2. The thickness of the first alignment film was 100 nm.

Subsequently, the composition for forming a polarizer layer was applied onto the first alignment film by a bar coating method, heated and dried in a drying oven at 120 ° C. for 1 minute, and then cooled to room temperature. A polarizer layer was formed by irradiating the dry film with ultraviolet rays at an integrated light intensity of 1200 mJ / cm ^{2 (365 nm standard) using the above UV irradiation device.} The thickness of the obtained polarizer layer was 1.8 μm.

6) The composition for forming a protective layer was applied onto the polarizer layer by a bar coating method so that the thickness after drying was 1.0 μm, and dried at a temperature of 80 ° C. for 3 minutes. In this way, a linear polarizing plate composed of a "base film / polarizer layer / overcoat layer)" was obtained.

[Phase difference layer]
1) As a base film, a polyethylene terephthalate (PET) film having a thickness of 100 μm was prepared.

2) As the alignment film forming composition, the same composition as the above-mentioned alignment film forming composition was used.

3) Each component shown below was mixed, and the obtained mixture was stirred at 80 ° C. for 1 hour to obtain a composition for forming a retardation layer.

Compound (b-1) represented by the following formula: 80 parts by mass

Compound (b-2) represented by the following formula: 20 parts by mass

Polymerization initiator (Irgacure 369, 2-dimethylamino-2-benzyl-1- (4-morpholinophenyl) butane-1-one, manufactured by BASF Japan Ltd.): 6 parts by mass leveling agent (BYK-361N, polyacrylate compound, BYK) -Chemie): 0.1 parts by mass Solvent (cyclopentanone): 400 parts by mass.

4) A retardation layer was prepared by the procedure shown below.
First, the composition for forming an alignment film was applied to a base film by a bar coating method, and dried by heating in a drying oven at 80 ° C. for 1 minute. The obtained dry film was subjected to polarized UV irradiation treatment to form a second alignment film. The polarized UV treatment was carried out under the condition that the integrated light amount measured at a wavelength of 365 nm was 100 mJ / cm ^{2 using the above UV irradiation device.} The polarization direction of the polarized UV was set to 45 ° with respect to the absorption axis of the polarizer layer.

5) Subsequently, the composition for forming a retardation layer was applied onto the second alignment film by the bar coating method, heated and dried in a drying oven at 120 ° C. for 1 minute, and then cooled to room temperature. A retardation layer was formed by irradiating the obtained dry film with ultraviolet rays having an integrated light intensity of 1000 mJ / cm ^{2 (365 nm standard) using the above UV irradiation device.} The thickness of the obtained retardation layer was 2.0 μm. The retardation layer was a λ / 4 plate showing a retardation value of λ / 4 in the in-plane direction. In this way, a retardation layer composed of a "base film / λ / 4 retardation layer" was obtained.

[Attachment sheet]
Acrylic resin was obtained by reacting the following components at 55 ° C. with stirring in a nitrogen atmosphere.
Butyl acrylate: 70 parts by mass Methyl acrylate: 20 parts by mass Acrylic acid: 2.0 parts by mass Radical polymerization initiator (2,2'-azobisisobutyronitrile): 0.2 parts by mass.

Subsequently, the following components were mixed to obtain a composition for a laminated layer.
Acrylic resin: 100 parts by mass Crossing agent (“Coronate L” manufactured by Tosoh Corporation): 1.0 parts by mass Silane coupling agent (“X-12-981” manufactured by Shin-Etsu Chemical Co., Ltd.): 0.5 parts by mass.

The obtained composition for the laminated layer was prepared by adding ethyl acetate so that the total solid content concentration was 10% by mass.

The liquid-prepared composition for the bonding layer is applied onto the release-treated release film A (polyethylene terephthalate film, thickness 38 μm) by using an applicator so that the thickness after drying is 5 μm. Got a layer. This coating layer was dried at 100 ° C. for 1 minute to obtain a film having a bonding layer. Then, a release-treated release film B (polyethylene terephthalate film, thickness 38 μm) was bonded onto the exposed surface of the bonded layer. It was cured for 7 days under the conditions of a temperature of 23 ° C. and a relative humidity of 50% RH to obtain a bonded sheet having a layer structure of release film A / bonding layer / release film B.

[Back plate]
As the back plate 105, a touch sensor panel in which a transparent conductive layer, a separation layer, an adhesive layer, and a base material layer are laminated in this order was prepared. The transparent conductive layer contained an ITO layer, and the separation layer contained a cured layer of an acrylic resin composition, and the total thickness of both was 7 μm. The adhesive layer had a thickness of 2 μm. The base material layer was a cycloolefin (COP) film (ZF-14, manufactured by Nippon Zeon Corporation, thickness 23 μm).

[Preparation of optical laminate]
The optical laminates of Examples 1 to 5 and Comparative Example 1 were produced by the procedure shown in FIGS. 2 (a) to 2 (e). The pressure-sensitive adhesive sheet composed of the pressure-sensitive adhesive composition shown in Table 2 was used as the first pressure-sensitive adhesive layer or the second pressure-sensitive adhesive layer as shown in Table 3.

First, the linear polarizing plate 410 [base film 301 / polarizer layer 302 / overcoat layer 303] including the polarizer layer and the above-mentioned bonding sheet 420 (release film A304 / bonding layer 305 / release film B306) are combined. Prepared (Fig. 2 (a)). The overcoat layer 303 side of the linear polarizing plate 410 including the polarizer layer and the surface from which the release film A304 of the bonding sheet 420 has been peeled off are subjected to corona treatment (output 0.3 KW, speed 3 m / min) and then bonded. The mixture was combined to obtain a laminated body A430. Further, a retardation layer 440 [base film 308 / λ / 4 retardation layer 307] was prepared. (Fig. 2 (b)).

The surface on which the λ / 4 retardation layer 307 side of the retardation layer 440 and the release film B306 of the laminated body A430 were peeled off were subjected to corona treatment (output 0.3 KW, speed 3 m / min), and then bonded. A circularly polarizing plate 450 was obtained. Further, the adhesive sheet prepared above was prepared as the adhesive sheet 460 (release film A309 / adhesive layer 310 / release film B311) (FIG. 2 (c)). The pressure-sensitive adhesive layer 310 of the pressure-sensitive adhesive sheet 460 corresponds to the second pressure-sensitive adhesive layer.

The surface from which the base film 308 of the circularly polarizing plate 450 was peeled off and the surface from which the release film A309 of the adhesive sheet 460 was peeled off were subjected to corona treatment (output 0.3 KW, speed 3 m / min), and then bonded. A laminate B470 was obtained. Further, the pressure-sensitive adhesive sheet prepared above was prepared as the pressure-sensitive adhesive sheet 490 (release film A314 / pressure-sensitive adhesive layer 315 / release film B316). The surface from which the release film A314 was peeled off and the resin film 313 side of the front plate 480 (resin film 313 / hard coat layer 312) were subjected to corona treatment (output 0.3 KW, speed 3 m / min) and then bonded. , A laminated body C500 was obtained (FIG. 2 (d)). The pressure-sensitive adhesive layer 315 of the pressure-sensitive adhesive sheet 490 corresponds to the first pressure-sensitive adhesive layer.

The surface from which the release film B316 of the laminate C500 was peeled off and the base film 301 side of the laminate B470 were subjected to corona treatment (output 0.3 KW, speed 3 m / min) and then bonded to obtain the laminate D510. (Fig. 2 (e)).

Corona on the transparent electrode layer 317 side of the touch sensor panel 520 on which the transparent conductive layer 317, the separation layer 318, the adhesive layer 319, and the base material layer 320 are laminated, and the surface on which the release film B311 of the laminate D510 is peeled off. After being treated (output 0.3 KW, speed 3 m / min), they were bonded to obtain an optical laminate.

The following flexibility test and surface hardness test were performed on the optical laminates of Examples 1 to 5 and Comparative Example 1. The results are shown in Table 3.

<Flexibility evaluation test>
The optical laminates of each example and each comparative example are bent so that the front plate 101 side is inside (bending radius 1.5 mm), that is, the distance between the opposing front plates is 3.0 mm, and the temperature is 60. After leaving it for 24 hours under the conditions of ° C. and humidity of 90% RH, it was taken out and left at room temperature for 30 minutes (durability test).
After the endurance test was completed, the bent state of the optical laminate was eliminated. From the optical laminate after the durability test, a test piece having a length of 100 mm and a width of 10 mm was cut out using a super cutter so that the bent portion was in the center. For this test piece, use a bending resistance tester (cylindrical mandrel method) manufactured by TP Giken Co., Ltd., and place the test piece around a cylindrical mandrel so that the front plate of the test piece is on the inside. A flexibility evaluation test (mandrel test) was conducted in which the test piece was bent along the length direction at a temperature of 25 ° C. As a result, the minimum diameter of the mandrel that does not generate air bubbles in the pressure-sensitive adhesive layer of the test piece was determined, and ranked based on the following criteria. In the flexibility evaluation test, it can be evaluated that the smaller the value of this minimum diameter, the better the bending durability of the pressure-sensitive adhesive layer.
A: Bubbles were generated in the adhesive layer when wound around a mandrel having a diameter (φ) of 10 mm or less.
B: Bubbles were generated in the adhesive layer when wound around a mandrel having a diameter of more than φ10 mm and a diameter of 15 mm or less.
C: Bubbles were generated in the adhesive layer when wound around a mandrel having a diameter of more than φ15 mm and a diameter of 20 mm or less.
D: Bubbles were generated in the adhesive layer when wound around a mandrel exceeding φ20 mm.

<Surface hardness evaluation test>
The optical laminates of each example and each comparative example are bent so that the front plate 101 side is inside (bending radius 1.5 mm), that is, the distance between the opposing front plates is 3.0 mm, and the temperature is 60. After leaving it for 24 hours under the conditions of ° C. and humidity of 90% RH, it was taken out and left at room temperature for 30 minutes (durability test).
A pencil hardness tester (PHT, manufactured by SUKBO SCIENCE) was used to load a load of 100 g on the surface of the bent portion of the optical laminate after the durability test on the front plate 101 side at a temperature of 25 ° C. A concave mark was formed on the surface of the pencil by the state of the pencil (manufactured by Mitsubishi Pencil Co., Ltd., the hardness of the core was 6B). Then, the time until the recess marks disappeared was measured, and the surface hardness of the optical laminate of each Example and each Comparative Example was evaluated by ranking based on the following criteria. In this surface hardness test, it can be evaluated that the shorter the time until the recess marks disappear, the better the surface hardness.
A: The recess marks disappeared in less than 30 minutes.
B: The concave mark disappeared in 30 minutes or more and less than 60 minutes.
C: The concave mark disappeared in 60 minutes or more and less than 90 minutes.
D: The recess marks did not disappear even after 90 minutes had passed.

100 laminate, 101 front plate, 102 first pressure-sensitive adhesive layer, 103 polarizing plate, 104 second pressure-sensitive adhesive layer, 105 back plate.

Claims (7)

A front plate, a first pressure-sensitive adhesive layer formed using the first pressure-sensitive adhesive composition, a polarizing plate, a second pressure-sensitive adhesive layer formed using the second pressure-sensitive adhesive composition, and a back plate. In this order,
In the first reference pressure-sensitive adhesive layer having a thickness of 200 μm formed by using the first pressure-sensitive adhesive composition, the shear recovery rates at temperatures of 25 ° C. before and after the strain repeated loading test were set to R1A [%] and R1B [%, respectively. ], And in the second reference pressure-sensitive adhesive layer having a thickness of 200 μm formed by using the second pressure-sensitive adhesive composition, the shear recovery rates at temperatures of 25 ° C. before and after the strain repeated loading test were set to R2A [%] and R2A [%], respectively. An optical laminate that satisfies the following relational expressions (1) and (2) when R2B [%] is used.
ΔR1 = {(R1A)-(R1B)} / 200≤0.2 (1)
ΔR2 = {(R2A)-(R2B)} /200≤0.2 (2) The optical laminate according to claim 1, further satisfying the following relational expression (3).
R1A ≤ R2A (3) The optical laminate according to claim 1 or 2, further satisfying the following relational expression (4).
ΔR1 ≤ ΔR2 (4) The optical laminate according to any one of claims 1 to 3, wherein R1A [%] is 20% or more. The optical laminate according to any one of claims 1 to 4, wherein the back plate is a touch sensor panel. A display device including the optical laminate according to any one of claims 1 to 5. The display device according to claim 6, which can be bent with the front plate side inside.

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