JP6792735B1 - Optical laminate and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical laminate in which generation of bubbles is suppressed when bent, and a display device including the optical laminate. SOLUTION: 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 are provided in this order, and a first pressure-sensitive adhesive layer and a second pressure-sensitive adhesive are provided. When the slopes from the origin to the maximum stress value on the layer stress [Pa] -strain [%] curve are GL1'and GL2', respectively, the following equations (1) and (2): 20≤GL1'≤150 ( 1) An optical laminate 100 satisfying 20 ≦ GL2 ′ ≦ 150 (2). [Selection diagram] Fig. 1

Description

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

Japanese Unexamined Patent Publication No. 2018-027995 (Patent Document 1) describes a flexible image display device provided with an adhesive layer having excellent stress relaxation characteristics.

JP-A-2018-027995

The optical laminate in which a plurality of layers are laminated via the pressure-sensitive adhesive layer has a problem that bubbles are likely to be generated in the pressure-sensitive adhesive layer or between the pressure-sensitive adhesive layer and the layer in contact with the pressure-sensitive adhesive layer when bent. ..

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

The present invention provides an optical laminate and a display device illustrated below.
[1] A front plate, a first pressure-sensitive adhesive layer, a polarizing plate, a second pressure-sensitive adhesive layer, and a back plate are provided in this order.
The stress of the first adhesive layer and said second adhesive layer [Pa] - when the inclination from the origin to the maximum stress value respectively G _{L1 'and} G _L2' in strain [%] curve, the following equation (1 ) And formula (2):
20 ≤ _GL 1'≤ 150 (1)
_{20 ≦ G L2 '≦ 150 (} 2)
An optical laminate that meets the requirements.
[2] Further, the following equation (3):
_GL1 '< _GL2 ' (3)
The optical laminate according to [1], which satisfies the above conditions.
[3] When the stress relaxation rate of the first pressure-sensitive adhesive layer is σ1, the following equation (4):
0.20 ≤ σ 1 ≤ 0.70 (4)
The optical laminate according to [1] or [2], which satisfies the above conditions.
[4] When the stress relaxation rate of the second pressure-sensitive adhesive layer is σ2, the following equation (5):
σ1 <σ2 (5)
The optical laminate according to [3], which satisfies the above conditions.
[5] When the creep rate of the first pressure-sensitive adhesive layer is ε1 [%], the following formula (6):
1.5 ≤ ε 1 ≤ 20 (6)
The optical laminate according to any one of [1] to [4], which satisfies the above conditions.
[6] When the creep rate of the second pressure-sensitive adhesive layer is ε2 [%], the following formula (7):
ε1> ε2 (7)
The optical laminate according to [5], which satisfies the above conditions.
[7] When the deformation restoration rate of the first pressure-sensitive adhesive layer is R1 [%], the following formula (8):
2.5 ≤ R1 ≤ 20 (8)
The optical laminate according to any one of [1] to [6], which satisfies the above conditions.
[8] When the deformation restoration rate of the second pressure-sensitive adhesive layer is R2 [%], the following formula (9):
R1 <R2 (9)
The optical laminate according to [7], which satisfies the above conditions.
[9] The optical laminate according to any one of [1] to [8], wherein the glass transition temperature of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer is −70 ° C. or higher and −40 ° C. or lower, respectively. ..
[10] A display device including the optical laminate according to any one of [1] to [9].
[11] The display device according to [10], which can be bent with the front plate side inside.

According to the present invention, there is provided an optical laminate in which the generation of bubbles is suppressed when bent, and a display device including the optical laminate.

It is the schematic sectional drawing which shows an example of the optical laminated body which concerns on this invention. It is a schematic diagram explaining the method of measuring a parameter by a dynamic mechanical analyzer. It is the schematic explaining the static bending durability test.

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 scales are appropriately adjusted and shown in order to make each component easier to understand, and the scale of each component shown in the drawings does not necessarily match the scale of the actual component.

<Optical laminate>
FIG. 1 is a schematic cross-sectional view of an optical laminate according to an embodiment of the present invention. The optical laminate 100 shown in FIG. 1 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. 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 3000 μm or less, preferably 50 μm or more and 2000 μm or less. It is preferably 70 μm or more and 1000 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 rectangle. 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.

[Slope G _L from the origin to the maximum stress value ']
Stress of the first adhesive layer 102 and the second adhesive layer 104 [Pa] - strain (%) when the inclination from the origin to the maximum stress value was G _{L1 'and} G _L2', respectively, in the curve, the optical laminate 100 Is the following equation (1) and equation (2):
20 ≤ _GL 1'≤ 150 (1)
_{20 ≦ G L2 '≦ 150 (} 2)
The following formulas (1a) and (2a) are preferably satisfied.
25 ≤ _GL 1'≤ 95 (1a)
25 ≤ _GL 2'≤ 95 (2a)
Meet.

When the pressure-sensitive adhesive layer is subjected to a tensile test, a stress-strain curve can be drawn with strain on the horizontal axis and stress on the vertical axis. In general, as the strain increases, the stress generated in the pressure-sensitive adhesive layer also increases, and the stress becomes maximum immediately before the cohesive failure occurs in the pressure-sensitive adhesive layer. Stress of the pressure-sensitive adhesive layer - strain and inclination G _{L 'from} the origin to the maximum stress value in the curve, represented by (maximum stress value [Pa]) / (amount strain when the stress is maximum (%)) .. G L _'are pressure-sensitive adhesive layer reflects up stress change at the time of plastic deformation as well as stress change upon elastic deformation, the adhesive layer may be an indicator of durability until cohesive failure. When G L _'is large, stress generated against distortion of the pressure-sensitive adhesive layer is large, the pressure-sensitive adhesive layer has excellent cohesive force. When G L _'is small, stress generated against distortion of the pressure-sensitive adhesive layer is small, the pressure-sensitive adhesive layer is easily deformed. G L _'can be determined according to the method described in the column of Examples described later.

The optical laminate 100 satisfying the formulas (1) and (2) is in the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer and the pressure-sensitive adhesive layer even if the bent state is maintained (hereinafter, referred to as “static bending”). The generation of air bubbles between the layer in contact with the layer is suppressed. Here, the fact that the generation of bubbles is suppressed when statically bent means that no bubbles are generated within 24 hours even if the optical laminate is subjected to the static bending durability test described later. At this time, the occurrence of floating or peeling between the pressure-sensitive adhesive layer and the layer in contact with the pressure-sensitive adhesive layer is also suppressed. The generation of bubbles can be determined by observation under an optical microscope.

In the present specification, the bending includes a form of bending in which a curved surface is formed in the bent portion, and the radius of curvature of the bent inner surface is not particularly limited. Bending also includes refraction with an inner surface refraction angle greater than 0 degrees and less than 180 degrees, and folding with an inner surface curvature radius close to zero or an inner surface refraction angle of 0 degrees.

G L _', the type and amount of monomers constituting the base polymer in the pressure-sensitive adhesive composition for use in the pressure-sensitive adhesive layer; polymerization initiator, the type of crosslinking agent and other additives and amount; the active energy ray, By adjusting heat and other factors that change the degree of cross-linking, a desired numerical range can be obtained. For example the base polymer contained in the adhesive composition, when containing a large number of 10 or more long chain alkyl (meth) acrylic monomer carbon, G L _'tends to decrease. For example, when the pressure-sensitive adhesive composition containing a large amount of polymerizable compound, in G L _'tends to be increased.

The optical laminate 100 preferably has the following formula (3):
_GL1 '< _GL2 ' (3)
Meet. The optical laminate 100 satisfying the formula (3) is bent in order to further relax the stress generated on the inner diameter side of the optical laminate 100 by the adhesive layer on the inner diameter side when the front plate 101 is statically bent inside. This is easy, and the generation of air bubbles in the pressure-sensitive adhesive layer and between the pressure-sensitive adhesive layer and the layer in contact with the pressure-sensitive adhesive layer is suppressed, so that the bending durability of the optical laminate 100 can be improved.

[Stress relaxation rate σ]
When the stress relaxation rate of the first pressure-sensitive adhesive layer 102 is σ1, the optical laminate 100 preferably has the following formula (4):
0.20 ≤ σ 1 ≤ 0.70 (4)
The following formula (4a):
0.20 ≤ σ 1 ≤ 0.55 (4a)
Meet.

When the stress relaxation rate of the second pressure-sensitive adhesive layer 104 is σ2, the optical laminate 100 preferably has the following formula (4'):
0.20 ≤ σ 2 ≤ 0.70 (4')
The following formula (4'a):
0.20 ≤ σ 2 ≤ 0.55 (4'a)
Meet.

The stress relaxation rate of the pressure-sensitive adhesive layer is expressed as the ratio of the stress after a lapse of a predetermined time to the stress generated immediately after the pressure-sensitive adhesive layer is subjected to a tensile test. When the stress relaxation rate is small, the stress generated in the adhesive layer is easily relaxed. When the stress relaxation rate of the pressure-sensitive adhesive layer is within the above range, the optical laminate 100 is unlikely to generate bubbles in the pressure-sensitive adhesive layer even if it is statically bent. Further, since the adhesive layer and the layer in contact with the adhesive layer have excellent adhesion, the generation of air bubbles between the adhesive layers is suppressed. The stress relaxation rate can be determined according to the method described in the column of Examples described later.

The optical laminate 100 preferably has the following formula (5):
σ1 <σ2 (5)
Meet. The optical laminate 100 satisfying the formula (5) is easy to bend because the stress generated on the inner diameter side of the optical laminate 102 is further relaxed when the first adhesive layer 102 is statically bent with the front plate 101 inside. Therefore, the generation of air bubbles in the pressure-sensitive adhesive layer and between the pressure-sensitive adhesive layer and the layer in contact with the pressure-sensitive adhesive layer is easily suppressed.

[Creep rate ε]
When the creep rate of the first pressure-sensitive adhesive layer 102 is ε1 [%], the optical laminate 100 preferably has the following formula (6):
1.5 ≤ ε 1 ≤ 20 (6)
The following formula (6a):
3.0 ≤ ε 1 ≤ 10 (6a)
Meet.

When the creep rate of the second pressure-sensitive adhesive layer 104 is ε2 [%], the optical laminate 100 preferably has the following formula (6'):
1.5 ≤ ε 2 ≤ 20 (6')
The following formula (6'a):
3.0 ≤ ε 2 ≤ 10 (6'a)
Meet.

The creep rate of the pressure-sensitive adhesive layer is the maximum deformation rate when the pressure-sensitive adhesive layer is pulled with a constant force for a certain period of time. When the creep rate is high, the adhesive layer is easily deformed. When the creep rate of the pressure-sensitive adhesive layer is within the above range, the optical laminate 100 is unlikely to generate bubbles in the pressure-sensitive adhesive layer even if it is statically bent. Further, since the adhesive layer and the layer in contact with the adhesive layer have excellent adhesion, the generation of air bubbles between the layers is suppressed. The creep rate can be determined according to the method described in the column of Examples described later.

The optical laminate 100 preferably has the following formula (7):
ε1> ε2 (7)
Meet. The optical laminate 100 satisfying the formula (7) is easy to bend because the stress generated on the inner diameter side of the optical laminate 102 is further relaxed when the first adhesive layer 102 is statically bent with the front plate 101 inside. Therefore, the generation of air bubbles in the pressure-sensitive adhesive layer and between the pressure-sensitive adhesive layer and the layer in contact with the pressure-sensitive adhesive layer is easily suppressed.

[Deformation restoration rate R]
When the deformation restoration rate of the first pressure-sensitive adhesive layer 102 is R1 [%], the optical laminate 100 preferably has the following formula (8):
2.5 ≤ R1 ≤ 20 (8)
The following formula (8a):
3.0 ≤ R1 ≤ 10 (8a)
Meet.

When the deformation restoration rate of the second pressure-sensitive adhesive layer 104 is R2 [%], the optical laminate 100 preferably has the following formula (8'):
2.5 ≤ R2 ≤ 20 (8')
The following equation (8'a):
3.0 ≤ R2 ≤ 10 (8'a)
Meet.

The deformation restoration rate of the pressure-sensitive adhesive layer indicates the rate at which the pressure-sensitive adhesive layer shrinks after a lapse of a predetermined time from unloading in the tensile test of the pressure-sensitive adhesive layer. When the deformation restoration rate is large, the pressure-sensitive adhesive layer has excellent shrinkage after stretching. When the deformation restoration rate of the pressure-sensitive adhesive layer is within the above range, the optical laminate 100 is unlikely to generate bubbles in the pressure-sensitive adhesive layer even if it is statically bent. Further, since the adhesive layer and the layer in contact with the adhesive layer have excellent adhesion, the generation of air bubbles between the layers is suppressed. The deformation restoration rate can be obtained according to the method described in the column of Examples described later.

The optical laminate 100 preferably has the following formula (9):
R1 <R2 (9)
Meet. The optical laminate 100 satisfying the formula (9) is bent in order to further relax the stress generated on the outer diameter side of the optical laminate 100 when the second adhesive layer 104 is statically bent with the front plate 101 inside. Is easy, and the generation of air bubbles in the pressure-sensitive adhesive layer and between the pressure-sensitive adhesive layer and the layer in contact with the pressure-sensitive adhesive layer is easily suppressed.

The stress relaxation rate, creep rate, and deformation restoration rate of the pressure-sensitive adhesive layer are the types and blending amounts of the monomers constituting the base polymer contained in the pressure-sensitive adhesive composition used for the pressure-sensitive adhesive layer; addition of a polymerization initiator, a cross-linking agent, and the like. The desired numerical range can be obtained by adjusting the type and blending amount of the agent; active energy rays, heat and other factors that change the degree of cross-linking.

[Glass-transition temperature]
In the optical laminate 100, the glass transition temperature of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer is preferably −70 ° C. or higher and −40 ° C. or lower, respectively. When the glass transition temperature of the pressure-sensitive adhesive layer is −40 ° C. or lower, the flexibility of the pressure-sensitive adhesive layer is good, so that the optical laminate 100 can be easily bent. When the glass transition temperature of the pressure-sensitive adhesive layer is lower than −70 ° C., the cohesive force of the pressure-sensitive adhesive layer becomes low, and the adhesive strength under durable conditions may decrease. The glass transition temperature of the pressure-sensitive adhesive layer can be measured according to the method described in the column of Examples described later.

The glass transition temperature of the pressure-sensitive adhesive layer is determined by the type and blending amount of the monomers constituting the base polymer contained in the pressure-sensitive adhesive composition; the type and blending amount of the polymerization initiator, the cross-linking agent and other additives; the active energy ray, heat and the like. By adjusting the factors that change the degree of cross-linking of the above, the desired numerical range can be obtained. In order to keep the glass transition temperature of the pressure-sensitive adhesive layer at −40 ° C. or lower, the base polymer contained in the pressure-sensitive adhesive composition has a glass transition temperature of −40 ° C. or lower, preferably −45 ° C. or lower, more preferably as a homopolymer. Is preferably blended with an acrylic acid monomer of −50 ° C. or lower. Examples of such monomers include n-butyl acrylate (T _g : -55 ° C), n-octyl acrylate (T _g : -65 ° C), isooctyl acrylate (T _g : -58 ° C), and acrylic acid. 2-Ethylhexyl (T _g : -70 ° C), Isononyl acrylate (T _g : -58 ° C), Isodecyl acrylate (T _g : -60 ° C), Isodecyl methacrylate (T _g : -41 ° C), Methacrylic acid n-lauryl (T _g : -65 ° C), tridecyl acrylate (T _g : -55 ° C), tridecyl methacrylate (T _g : -40 ° C), and n-butyl acrylate and 2-ethylhexyl acrylate. Is preferable. These monomers may be used alone or in combination of two or more.

The base polymer contained in the pressure-sensitive adhesive composition preferably contains a monomer having a glass transition temperature of −40 ° C. or lower as a homopolymer in an amount of preferably 80% by mass or more, more preferably 85% by mass or more, still more preferably 95% by mass or more. To do. Further, as the base polymer contained in the pressure-sensitive adhesive composition, a monomer having a glass transition temperature of −40 ° C. or lower as a homopolymer is preferably 99.9% by mass or less, more preferably 99.5% by mass or less, still more preferably. Contains 99% by mass or less. When the content of the monomer having a glass transition temperature of −40 ° C. or lower as a homopolymer is in such a range, the glass transition temperature of the pressure-sensitive adhesive layer tends to fall within the above range.

In order to facilitate setting the glass transition temperature of the pressure-sensitive adhesive layer in the above range, the base polymer contained in the pressure-sensitive adhesive composition preferably contains as little monomer as a homopolymer having a glass transition temperature exceeding 0 ° C. , Such a monomer is preferably contained in an upper limit of 15% by mass or less, more preferably 10% by mass or less, and further preferably 5% by mass or less.

[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 may be composed of only one layer, or may be composed of two or more layers. Examples of the front plate 101 include a resin plate-like body (for example, a resin plate, a resin sheet, a resin film, etc.) and a glass plate-like body (for example, a glass plate, a glass film, etc.). The front plate may be a laminate of a resin plate-like body and a glass plate-like body. 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.

When the front plate 101 is a resin plate-like body, the resin plate-like body is not limited as long as it can transmit light. 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, polyetherketone, polyetheretherketone, polyethersulfone , Polymethylmethacrylate, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyamideimide and other polymers. These polymers can be used alone or in combination 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 improving 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 in order to improve the hardness. 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 the hard coat layers may be the same as each other 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 20 μm or more and 500 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 one layer or may be composed of two or more layers, but is preferably 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. As the monomer constituting the (meth) acrylic resin, a photoreactive compound having a benzoyl group can also be used, and the compound described as Chemical Formula 1 in Korean Patent Publication No. 10-2019-0005427 is exemplified. Such photoreactive compounds are activated by additional photocuring to induce additional cross-linking, so that durability can be improved.

The pressure-sensitive adhesive composition may contain only the above-mentioned base polymer, but usually further contains a cross-linking agent. The cross-linking agent is a metal ion having a divalent value or higher and forming a carboxylic acid metal salt with a carboxyl group, a polyamine compound forming an amide bond with the carboxyl group, and a carboxyl group. Examples thereof include polyepoxy compounds or polyols that form an ester bond with, and polyisocyanate compounds that form an amide bond with a carboxyl group. The cross-linking agent is preferably a polyisocyanate 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 2 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. The pressure-sensitive adhesive composition can contain 0.1 part by mass or more of the active energy ray-polymerizable compound with respect to 100 parts by mass of the solid content of the pressure-sensitive adhesive composition, and is 10 parts by mass or less, 5 parts by mass or less, or 2 parts by mass. Can include less than one copy.

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 imparting agents, and 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 above-mentioned 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.

From the viewpoint of improving the cohesive force of the first pressure-sensitive adhesive layer 102, when the first pressure-sensitive adhesive layer 102 is used as a reference pressure-sensitive adhesive layer having a thickness of 150 μm, the shear modulus at a temperature of 25 ° C. is preferably 0.01 MPa. It is more preferably 0.02 MPa or more, preferably 0.50 MPa or less, more preferably 0.10 MPa or less, and may be 0.08 MPa or less. When the shear modulus of the first pressure-sensitive adhesive layer 102 is within this range, the optical laminate 100 is less likely to undergo cohesive failure even when bent, and is less likely to generate bubbles. The shear modulus can be adjusted by changing the type and content of the monomers constituting the base polymer contained in the pressure-sensitive adhesive composition, the additives, the degree of cross-linking, and the like.

[Polarizer]
The polarizing plate 103 may 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 unidirectional linearly polarized light composed of unpolarized light rays such as natural light. The linear polarizing plate contains 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. The dichroic dye refers to a dye having a property in which the absorbance in the major axis direction and the absorbance in the minor axis direction of the molecule are different. 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.

(Stretched film or stretched layer with a dichroic dye adsorbed on it)
The polarizer layer, which is a stretched film on which a bicolor dye is adsorbed, is usually obtained by uniaxially stretching the polyvinyl alcohol-based resin film and dyeing the polyvinyl alcohol-based resin film with a bicolor dye such as iodine. It can be produced through a step of adsorbing a bicolor dye, a step of treating a polyvinyl alcohol-based resin film on which the bicolor dye is adsorbed with an aqueous boric acid solution, and a step of washing with water after the treatment with the 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 polyvinyl alcohol-based resin on a base film, a step of uniaxially stretching the obtained laminated film, and uniaxial. A step of dyeing the polyvinyl alcohol-based resin layer of the stretched laminated film with a dichroic dye to adsorb the dichroic dye to form a polarizer layer, and boric acid on the film on which the dichroic dye is adsorbed. 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 for forming 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 on which the dichroic dye is adsorbed or the polarizer layer which is a stretched layer 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 film; (meth) acrylic-based resin film; polypropylene-based resin film 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 surface 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.

(Polarizer layer, which is a liquid crystal layer)
The polymerizable liquid crystal compound used for forming the liquid crystal layer is a compound having a polymerizable reactive group and exhibiting liquid crystallinity. 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 a maximum absorption 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, and an anthraquinone dye, and among them, the azo dye is preferable. Examples of the azo dye include a monoazo dye, a bisazo dye, a trisazo dye, a tetrakisazo dye, a stilbene azo dye, and the like, and a bisazo dye and a trisazo dye 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 base film to form a coating film, and stretching the coating film together with the substrate film. The base film used for forming 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 polarizing element layer using this composition are JP-A-2013-373353 and JP-A-2013-3324. , 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 polarizing element 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 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.

The polarizing plate 103 is arranged so that the linear polarizing plate is on the side of the first pressure-sensitive adhesive layer 102 with respect to the retardation layer. The outermost layer constituting the polarizing plate 103 and in contact with the first pressure-sensitive adhesive layer 102 is preferably a base film, a protective layer or an overcoat layer contained in the linear polarizing plate.

(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 alignment film 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 film and a base film. The retardation layer can be bonded to the linear polarizing plate via the bonding layer.

[Second adhesive layer]
The second pressure-sensitive adhesive layer 104 is interposed between the polarizing plate 103 and the back plate 105 to bond them 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.

From the viewpoint of improving the cohesive force of the second pressure-sensitive adhesive layer 104, when the second pressure-sensitive adhesive layer 104 is used as a reference pressure-sensitive adhesive layer having a thickness of 150 μm, the shear modulus at a temperature of 25 ° C. is preferably 0.01 MPa. It is more preferably 0.02 MPa or more, preferably 0.50 MPa or less, more preferably 0.10 MPa or less, and may be 0.08 MPa or less. When the shear modulus of the second pressure-sensitive adhesive layer 104 is within this range, the optical laminate 100 is less likely to undergo cohesive failure even when bent, and is less likely to generate bubbles. The shear modulus can be adjusted by changing the type and content of the monomers constituting the base polymer contained in the pressure-sensitive adhesive composition, the additives, the degree of cross-linking, and the like.

[Lated layer]
The optical laminate 100 can include a laminating layer for joining the two layers. The bonding layer is a layer composed of an 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 is cured by irradiating it with active energy rays such as ultraviolet rays. 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 photocurable epoxy-based monomers, photocurable acrylic-based monomers, and photocurable urethane-based monomers, and oligomers derived from these monomers. Examples of the photopolymerization initiator include compounds containing substances that generate active species such as neutral radicals, anionic 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, may be composed of two or more layers, and an example of the plate-like body described in the front plate 101 shall be used. Can be done.

Examples of the components used in the ordinary display device used for the back plate 105 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 window film / circular polarizing plate / touch sensor panel / organic EL display element, window film / touch sensor panel / circular polarizing plate / organic EL display element, and the like.

(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 above description of the thermoplastic resin film. Further, the touch sensor panel may be transferred from the base film to the adherend via the 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 bonding layers 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 of the present invention can be used as a flexible display that exhibits excellent durability against static bending 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.

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.

[Adhesive layer]
2-Ethylhexyl acrylate (2-EHA) and n-butyl acrylate (n-BA) shown in Table 1 were placed in a 1 L reactor equipped with a cooling device so that the nitrogen gas could return and the temperature could be easily controlled. , N- (2-Hydroxyethyl) acrylamide (HEAA), isodecyl acrylate (IDA), behenyl acrylate (BHA), and a monomer mixture consisting of compound I. The solution was maintained at 60 ° C. after refluxing nitrogen gas for 1 hour to remove oxygen. After uniformly mixing the above-mentioned monomer mixture, the photopolymerization initiator benzyldimethylketal (I-651) and 1-hydroxycyclohexylphenylketone (I-184) were added in the blending amounts shown in Table 1. Acrylic polymers A1 to A6 were produced by irradiating with a UV lamp (10 mW) with stirring.

The obtained acrylic polymers A1 to A6, isodecyl acrylate (IDA), N- (2-hydroxyethyl) acrylamide (HEAA), and benzophenone (BPO) were mixed in the amounts shown in Table 2 to form an adhesive composition. Objects B1 to B9 were manufactured.

The pressure-sensitive adhesive compositions B1 to B9 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 UV irradiation was performed 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 used are as follows.
2-EHA: Tokyo Kasei Kogyo Co., Ltd., Japan n-BA: Tokyo Kasei Kogyo Co., Ltd., Japan HEAA: Tokyo Kasei Kogyo Co., Ltd., Japan IDA: Miwon specialty chemical, Korea BHA: Tokyo Kasei Kogyo Co., Ltd., Japan I-651 : BASF, Germany I-184: BASF, Germany BPO: Tokyo Chemical Industry Co., Ltd., Japan

[Front plate]
As the front plate 101, a film having a hard coat layer formed on one surface of the resin film was prepared. The resin film was a polyimide resin 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.

[Circular polarizing plate]
A circular polarizing plate was prepared as the polarizing plate 103. A linear polarizing plate having a triacetyl cellulose (TAC) film (KC2UA, manufactured by Konica Minolta Co., Ltd., thickness 25 μm), an alignment film, a linear polarizing element layer, and an overcoat layer in this order was prepared. The linear polarizer layer was formed using a composition containing a polymerizable liquid crystal compound and a dichroic dye, and had a thickness of 2 μm. The overcoat layer was a polyvinyl alcohol resin layer and had a thickness of 1.0 μm.

A retardation laminate was laminated on the overcoat layer side of the linear polarizing plate via an adhesive layer to obtain a circular polarizing plate. The retardation laminate had a λ / 4 retardation layer, an adhesive layer, and a positive C layer in this order from the linear polarizing plate side. The λ / 4 retardation layer was a cured layer of a polymerizable liquid crystal compound and had a thickness of 3 μm. The thickness of the pressure-sensitive adhesive layer was 5 μm. The positive C layer was a cured layer of the polymerizable liquid crystal compound and had a thickness of 3 μm.

[Back plate]
As the back plate 105, a touch sensor in which a touch sensor pattern layer, an adhesive layer, and a base material layer are laminated in this order was prepared. The touch sensor pattern layer included an ITO layer as a transparent conductive layer and a cured layer of an acrylic resin composition as a separation layer, and had a thickness of 7 μm. The adhesive layer was provided on the separation layer side of the touch sensor pattern layer and had a thickness of 3 μm. A cyclic olefin resin (COP) film (ZF-14, manufactured by Nippon Zeon Corporation, thickness 23 μm) was used as the base material layer.

[Preparation of optical laminate]
As shown in Table 3, the pressure-sensitive adhesive sheet composed of the pressure-sensitive adhesive composition shown in Table 2 is used as the first pressure-sensitive adhesive layer 102, and the side of the front plate 101 having no hard coat layer and the side of the polarizing plate 103 on the TAC film. Was pasted together. Further, the pressure-sensitive adhesive sheet composed of the pressure-sensitive adhesive composition shown in Table 2 is used as the second pressure-sensitive adhesive layer 104 as shown in Table 3, and the retardation layer side of the circular polarizing plate and the touch sensor pattern layer side of the touch sensor are used. They were bonded together to prepare an optical laminate 100 (Examples 1 to 4 and Comparative Examples 1 and 2) having a layered structure shown in FIG. The front plate, the circular polarizing plate, the touch sensor, and the adhesive layer were subjected to double-sided corona treatment before bonding. TEC-4AX (manufactured by Ushio, Inc.) was used for the corona treatment. About the pressure-sensitive adhesive layer Inclination from the origin to the maximum stress _GL ', stress relaxation rate σ, creep rate ε, deformation restoration rate R, glass transition temperature T _g , shear modulus, and static bending durability of the optical laminate 100 Was measured according to the following method. The results are shown in Table 3.

<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).

<Slope from the origin to the maximum stress value _GL '>
The slope from the origin to the maximum stress value was measured using a dynamic mechanical analyzer (DMA, Q-800, manufactured by TA Instruments). First, as shown in FIG. 2, a test piece in which the ends of two polycarbonate (PC) bars 501 were bonded to each other via an adhesive layer was prepared. The shape of the pressure-sensitive adhesive layer 502 was width × length × thickness 6 mm × 10 mm × 25 μm, and the shape of the PC bar 501 was width × length × thickness 6 mm × 20 mm × 1 mm. The adhesive area between the pressure-sensitive adhesive layer 502 and the PC bar 501 was 6 mm × 10 mm in width × length. A jig was attached to a region having a length of 5 mm at both ends of the PC bar 501 of the test piece, and one jig was fixed. The other jig was placed at a temperature of 25 ° C. at 100 μm / min. A stress [Pa] -strain [%] curve was created by pulling at the speed of. In the obtained stress-strain curve, the slope from the origin to the maximum stress was calculated.

<Stress relaxation rate σ>
The stress relaxation rate of the pressure-sensitive adhesive layer was measured using a dynamic mechanical analyzer (DMA, Q-800, manufactured by TA Instruments). The test piece is the same as the test piece used for measuring the slope from the origin to the maximum stress value. A jig was attached to a region having a length of 5 mm at both ends of the PC bar 501 of the test piece, and one jig was fixed. The stress was measured by continuing to pull the other jig for 300 seconds in an environment at a temperature of 25 ° C. to maintain a strain of 25%.
Stress relaxation rate = stress after 300 seconds [MPa] / stress after 7.0 seconds [MPa]

<Creep rate ε>
A dynamic mechanical analyzer (DMA, Q-800, manufactured by TA Instruments) was used to measure the creep rate (Creep) of the pressure-sensitive adhesive layer. The test piece is the same as the test piece used for measuring the slope from the origin to the maximum stress value. A jig was attached to a region having a length of 5 mm at both ends of the PC bar 501 of the test piece, and one jig was fixed. The other jig was continuously pulled so that the stress became 1 MPa, and the strain [%] value after 1200 seconds was measured.
Creep rate [%] = strain [%] after 1200 seconds

<Deformation restoration rate R>
The deformation recovery rate (Recovery) of the pressure-sensitive adhesive layer was measured using a dynamic mechanical analyzer (DMA, Q-800, manufactured by TA Instruments). The test piece is the same as the test piece used for measuring the slope from the origin to the maximum stress value. A jig was attached to a region having a length of 5 mm at both ends of the PC bar 501 of the test piece, and one jig was fixed. The other jig was pulled to maintain a 25% strain for 300 seconds. The load was unloaded after 300 seconds had passed, and the strain was measured when 5 seconds had passed (305 seconds had passed).
Deformation restoration rate [%] = strain after 300 seconds (= 25%) -strain after 305 seconds [%]

<Glass transition temperature T _g >
After the pressure-sensitive adhesive was dried at 100 ° C. for 1 hour, the glass transition temperature (T _g ) was measured using a differential scanning calorimeter (DSC, Q-1000, manufactured by TA Instruments).

<Shear modulus>
The shear modulus was measured using a viscoelasticity measuring device (MCR-301, Antonio Par). The pressure-sensitive adhesive sheet had a width of 20 mm and a length of 20 mm, the release film was peeled off, and a plurality of pressure-sensitive adhesive sheets were laminated so as to have a thickness of 150 μm. After bonding the laminated adhesive layer to the glass plate, the condition is that the frequency is 1.0 Hz, the deformation amount is 1%, and the temperature rise rate is 5 ° C./min in the temperature range of -20 ° C to 100 ° C. The shear modulus value at 25 ° C. was confirmed.

<Static bending durability test>
FIG. 3 shows the method of the static bending durability test (mandrel bending test). First, the optical laminate 100 was cut into 1 cm × 10 cm test pieces. An iron rod 503 having a diameter of 5 mm was placed on the test plate 504 so that the front plate 101 side of the optical laminate 100 was facing up (FIG. 3 (A)). The front plate 101 was manually folded and fixed so as to be wound around the iron rod 503 (FIG. 3 (B)).

Static bending durability based on the period during which no bubbles are generated between the polarizing plate 103 and the first pressure-sensitive adhesive layer 102 and the second pressure-sensitive adhesive layer 104, or in the first pressure-sensitive adhesive layer 102 and the second pressure-sensitive adhesive layer 104. Gender was evaluated as follows. The generation of bubbles was determined by observation under an optical microscope.
A: No bubbles were generated after 72 hours.
B: Bubbles were generated within 72 hours over 48 hours.
C: Bubbles were generated within 24 hours and 48 hours.
D: Bubbles were generated within 24 hours.

100 optical laminate, 101 front plate, 102 first pressure-sensitive adhesive layer, 103 polarizing plate, 104 second pressure-sensitive adhesive layer, 105 back plate, 501 polycarbonate bar, 502 pressure-sensitive adhesive layer, 503 iron rod, 504 test plate.

Claims (11)

A front plate, a first pressure-sensitive adhesive layer, a polarizing plate, a second pressure-sensitive adhesive layer, and a back plate are provided in this order.
The stress of the first adhesive layer and said second adhesive layer [Pa] - when the inclination from the origin to the maximum stress value respectively G _{L1 'and} G _L2' in strain [%] curve, the following equation (1 ) And formula (2):
20 ≤ _GL 1'≤ 150 (1)
_{20 ≦ G L2 '≦ 150 (} 2)
An optical laminate that meets the requirements. Furthermore, the following formula (3):
_GL1 '< _GL2 ' (3)
The optical laminate according to claim 1. When the stress relaxation rate of the first pressure-sensitive adhesive layer is σ1, the following equation (4):
0.20 ≤ σ 1 ≤ 0.70 (4)
The optical laminate according to claim 1 or 2. When the stress relaxation rate of the second pressure-sensitive adhesive layer is σ2, the following equation (5):
σ1 <σ2 (5)
The optical laminate according to claim 3. When the creep rate of the first pressure-sensitive adhesive layer is ε1 [%], the following formula (6):
1.5 ≤ ε 1 ≤ 20 (6)
The optical laminate according to any one of claims 1 to 4, which satisfies the above conditions. When the creep rate of the second pressure-sensitive adhesive layer is ε2 [%], the following formula (7):
ε1> ε2 (7)
The optical laminate according to claim 5. When the deformation restoration rate of the first pressure-sensitive adhesive layer is R1 [%], the following formula (8):
2.5 ≤ R1 ≤ 20 (8)
The optical laminate according to any one of claims 1 to 6, which satisfies the above conditions. When the deformation restoration rate of the second pressure-sensitive adhesive layer is R2 [%], the following formula (9):
R1 <R2 (9)
The optical laminate according to claim 7. The optical laminate according to any one of claims 1 to 8, wherein the glass transition temperature of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer is −70 ° C. or higher and −40 ° C. or lower, respectively. A display device including the optical laminate according to any one of claims 1 to 9. The display device according to claim 10, which is bendable with the front plate side inside.

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