TW202128916A - Optical laminate and display device - Google Patents

Abstract

The purpose of the present invention is to provide an optical laminate that is prevented from generating air bubbles when being bent, and a display device including the optical laminate. The present invention provides an optical laminate that is equipped with a front plate, a first adhesive layer, a polarizing plate, a second adhesive layer, and a back plate in this order, and, when gradients from an origin point to a maximum stress value in stress [Pa] - strain [%] curves of the first adhesive layer and the second adhesive layer are respectively denoted by GL1' and GL2', satisfies expression (1), expression (2), and expression (3): 20 ≤ GL1' ≤ 150 (1), 20 ≤ GL2' ≤ 150 (2), GL1' ≥ GL2' (3).

Description

Optical laminate and display device

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

Japanese Patent Laid-Open No. 2018-027995 (Patent Document 1) describes a flexible image display device including an adhesive layer with excellent stress relaxation properties. [Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2018-027995

[The problem to be solved by the invention] The optical laminate formed by laminating multiple layers of adhesives has the following problem when bent: bubbles are likely to be generated in the adhesive layer or between the adhesive layer and the layer in contact with the adhesive layer.

An object of the present invention is to provide an optical laminate that suppresses the generation of bubbles when bent, and a display device including the optical laminate. [Means to solve the problem]

The present invention provides the optical laminate and display device shown below. [1] An optical laminate comprising a front surface plate, a first adhesive layer, a polarizing plate, a second adhesive layer, and a back plate in this order, wherein the first adhesive layer and the second adhesive layer When the slope of the stress [Pa]-strain [%] curve from the origin to the maximum stress value is set to G _L1 'and G _L2 ' respectively, the following equations (1), (2) and (3) are satisfied : 20≦G _L1 '≦150 (1) 20≦G _L2 '≦150 (2) G _L1 '≧G _L2 '(3). [2] The optical laminate according to [1], wherein when the stress relaxation rate of the second adhesive layer is σ2, the following formula (4) is satisfied: 0.20≦σ2≦0.70 (4). [3] The optical laminate according to [2], wherein when the stress relaxation rate of the first adhesive layer is σ1, the following formula (5) is satisfied: σ1≧σ2 (5). [4] The optical laminate according to any one of [1] to [3], wherein when the creep rate of the second adhesive layer is ε2[%], the following formula (6 ): 1.5≦ε2≦20 (6). [5] The optical laminate according to [4], wherein when the creep rate of the first adhesive layer is ε1[%], the following formula (7) is satisfied: ε1≦ε2 (7) . [6] The optical laminate according to any one of [1] to [5], wherein when the deformation recovery rate of the second adhesive layer is R2 [%], the following formula (8 ): 2.5≦R2≦20 (8). [7] The optical laminate according to [6], wherein when the deformation recovery rate of the first adhesive layer is R1[%], the following formula (9) is satisfied: R1≧R2 (9) . [8] The optical laminate according to any one of [1] to [7], wherein the glass transition temperatures of the first adhesive layer and the second adhesive layer are respectively -70°C or higher and- Below 40°C. [9] A display device including the optical laminate according to any one of [1] to [8]. [10] The display device according to [9], which can be bent with the front panel side as the outer side. [Effects of the invention]

According to the present invention, there are provided an optical laminate that suppresses the generation of bubbles when bent, and a display device including the optical laminate.

Hereinafter, embodiments of the optical laminate of 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 following drawings, the scales are appropriately adjusted to make the constituent elements easy to understand, and the scales of the respective constituent elements shown in the drawings may not necessarily match the scales of the actual constituent elements.

＜Optical laminated body＞ 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 sequentially includes a front surface plate 101, a first adhesive layer 102, a polarizing plate 103, a second adhesive layer 104 and a back plate 105. Hereinafter, the first adhesive layer 102 and the second adhesive layer 104 may be collectively referred to as an adhesive layer.

The thickness of the optical layered body 100 varies depending on the functions required for the optical layered body and the use of the optical layered body, and is therefore not particularly limited. For example, it is 30 μm or more and 3000 μm or less, preferably 50 μm or more and 2000 μm. Hereinafter, it is more preferably 70 μm or more and 1000 μm or less.

The planar shape of the optical laminate 100 may be, for example, a square shape, preferably a square shape having long sides and short sides, and more preferably a rectangular shape. When the shape of the laminate 100 in the plane direction is a rectangle, the length of the long side may be, for example, 10 mm or more and 1400 mm or less, and 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. For each layer constituting the optical layered body 100, R processing may be performed on the corner portion, or the end portion may be cut or punched.

The optical laminate 100 can be used for, for example, a display device. The display device is not particularly limited, and examples thereof include organic electroluminescence (EL) display devices, inorganic electroluminescence (inorganic EL) display devices, liquid crystal display devices, electroluminescence display devices, and the like. The optical laminate 100 is suitable for a display device that can be bent, and in particular, can be bent with a front surface plate on the outside.

[The slope from the origin to the maximum stress value G _L '] The slopes from the origin to the maximum stress value in the stress [Pa]-strain [%] curves of the first adhesive layer 102 and the second adhesive layer 104 are respectively When set to G _L1 'and G _L2 ', the optical laminate 100 satisfies the following equations (1) and (2): 20≦G _L1 '≦150 (1) 20≦G _L2 '≦150 (2). It is preferable to satisfy the following equations (1a) and (2a): 25≦G _L1 '≦95 (1a) 25≦G _L2 '≦95 (2a).

When the adhesive layer is subjected to a tensile test, a stress-strain curve with strain as the horizontal axis and stress as the vertical axis can be drawn. Generally, as the strain increases, the stress generated in the adhesive layer also becomes larger, and the stress becomes the maximum before the cohesive failure of the adhesive layer occurs. _{The slope G L} 'from the origin to the maximum stress value in the stress-strain curve of the adhesive layer is expressed by (maximum stress value [Pa])/(strain amount when the stress becomes maximum [%]). G _L' not only reflects the stress change when the adhesive layer is elastically deformed, but also reflects the stress change during plastic deformation, and can be used as an indicator of the durability of the adhesive layer before cohesive failure. When G _L'is large, the stress generated by the strain of the adhesive layer is large, and the cohesive force of the adhesive layer is excellent. When G _L'is small, the stress generated by the strain of the adhesive layer is small, and the adhesive layer is easily deformed. G _L 'can be obtained according to the method described in the column of Examples described later.

Even if the optical laminate 100 that satisfies the formulas (1) and (2) maintains a curved state (hereinafter referred to as "static bending"), in the adhesive layer, and between the adhesive layer and the layer in contact with the adhesive layer The generation of air bubbles in between is suppressed. Here, the suppression of the generation of bubbles during static bending means that even if the optical laminate is subjected to the static bending durability test described later, no bubbles are generated within 24 hours. At this time, the occurrence of floating or peeling between the adhesive layer and the layer in contact with the adhesive layer is also suppressed. The generation of bubbles can be judged by observation under an optical microscope.

In this specification, bending includes a bending form in which a curved surface is formed in a bent portion, and the radius of curvature of the bent inner surface is not particularly limited. In addition, bending also includes bends where the bending angle of the inner surface is greater than 0 degrees and less than 180 degrees, and the bends where the radius of curvature of the inner surface is approximately zero or the bending angle of the inner surface is 0 degrees.

Regarding G _L ', it can be adjusted by adjusting the type and blending amount of the monomers of the raw polymer contained in the adhesive composition used in the adhesive layer; the types and blending of the polymerization initiator, crosslinking agent, and other additives The amount; active energy rays, heat, and other factors that change the degree of crosslinking, etc., are in the desired numerical range. For example, when the base polymer contained in the adhesive composition contains a large amount of a long-chain alkyl (meth)acrylic monomer having a carbon number of 10 or more, G _L' tends to decrease. For example, when the adhesive composition contains a large amount of polymerizable compounds, G _L' tends to increase.

The optical laminate 100 satisfies the following formula (3): G _L1 '≧G _L2 '(3). Preferably, the following formula (3') is satisfied: G _L1 '>G _L2 '(3'). When the optical laminate 100 is statically bent on the outside of the front surface plate 101, the adhesive layer on the inner diameter side further relaxes the stress generated on the inner diameter side of the optical laminate 100, so it is easy to bend. The generation of bubbles between the adhesive layer and the layer in contact with the adhesive layer is suppressed, and the bending durability of the optical layered body 100 can be improved.

[Stress relaxation rate σ] When the stress relaxation rate of the second adhesive layer 104 is set to σ2, the optical laminate 100 preferably satisfies the following formula (4): 0.20≦σ2≦0.70 (4) It is more preferable to satisfy the following formula (4a): 0.20≦σ2≦0.55 (4a)

When the stress relaxation rate of the first adhesive layer 102 is set to σ1, the optical laminate 100 preferably satisfies the following formula (4'): 0.20≦σ1≦0.70 (4') It is more preferable to satisfy the following formula (4'a): 0.20≦σ1≦0.55 (4'a).

The stress relaxation rate of the adhesive layer is expressed by the ratio of the stress after a predetermined period of time to the stress generated immediately after stretching when the 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 adhesive layer is in the above-mentioned range, even if the optical layered body 100 is statically bent, it is difficult to generate bubbles in the adhesive layer. In addition, the adhesion between the adhesive layer and the layer in contact with the adhesive layer is also excellent, so the generation of bubbles between the adhesive layers is also suppressed. The stress relaxation rate can be obtained by the method described in the column of Examples described later.

The optical laminate 100 preferably satisfies the following formula (5): σ1≧σ2 (5). It is more preferable to satisfy the following formula (5') σ1>σ2 (5'). When the optical laminate 100 is statically bent on the outside of the front surface plate 101, the second adhesive layer 104 further relaxes the stress generated on the inner diameter side of the optical laminate, so it is easy to bend. The generation of bubbles between the layers in contact with the adhesive layer is easily suppressed.

[Creep rate ε] When the creep rate of the second adhesive layer 104 is set to ε2[%], the optical laminate 100 preferably satisfies the following formula (6): 1.5≦ε2≦20 (6) It is more preferable to satisfy the following formula (6a): 3.0≦ε2≦10 (6a)

When the creep rate of the first adhesive layer 102 is set to ε1[%], the optical laminate 100 preferably satisfies the following formula (6'): 1.5≦ε1≦20 (6') It is more preferable to satisfy the following formula (6'a): 3.0≦ε1≦10 (6'a).

The creep rate of the adhesive layer is the maximum deformation rate when the adhesive layer is stretched for a fixed time under a fixed force. When the creep rate is large, the adhesive layer is easily deformed. When the creep rate of the adhesive layer is in the above-mentioned range, even if the optical layered body 100 is bent statically, it is difficult to generate bubbles in the adhesive layer. In addition, the adhesion between the adhesive layer and the layer in contact with the adhesive layer is also excellent, and therefore the generation of bubbles between layers is also suppressed. The creep rate can be obtained by the method described in the column of Examples described later.

The optical laminate 100 preferably satisfies the following formula (7): ε1≦ε2 (7) It is more preferable to satisfy the following formula (7') ε1<ε2 (7'). When the optical laminate 100 is statically bent on the outside of the front surface plate 101, the second adhesive layer 104 further relaxes the stress generated on the inner diameter side of the optical laminate, so it is easy to bend. The generation of bubbles between the layer and the layer in contact with the adhesive layer is easily suppressed.

[Deformation recovery rate R] When the deformation recovery rate of the second adhesive layer 104 is set to R2[%], the optical laminate 100 preferably satisfies the following formula (8): 2.5≦R2≦20 (8) It is more preferable to satisfy the following formula (8a): 3.0≦R2≦10 (8a).

When the deformation recovery rate of the first adhesive layer 102 is set to R1 [%], the optical laminate 100 preferably satisfies the following formula (8'): 2.5≦R1≦20 (8') It is more preferable to satisfy the following formula (8'a) 3.0≦R1≦10 (8'a).

The deformation recovery rate of the adhesive layer indicates the ratio of shrinkage of the adhesive layer after a predetermined time has elapsed since the load was removed in the tensile test of the adhesive layer. When the deformation recovery rate is large, the shrinkage after stretching of the adhesive layer is excellent. When the deformation recovery rate of the adhesive layer is within the above-mentioned range, even if the optical layered body 100 undergoes static bending, it is difficult to generate bubbles in the adhesive layer. In addition, the adhesion between the adhesive layer and the layer in contact with the adhesive layer is also excellent, and therefore the generation of interlayer bubbles is also suppressed. The deformation recovery rate can be obtained by the method described in the column of Examples described later.

The optical laminate 100 preferably satisfies the following formula (9): R1≧R2 (9) It is more preferable to satisfy the following formula (9') R1>R2 (9'). When the optical laminate 100 is statically bent on the outer side of the front surface plate 101, the first adhesive layer 102 further relaxes the stress generated on the outer diameter side of the optical laminate 100, and therefore is easy to bend. The generation of bubbles between the agent layer and the layer in contact with the adhesive agent layer is easily suppressed.

The stress relaxation rate, creep rate, and deformation recovery rate of the adhesive layer can be adjusted by adjusting the type and amount of monomers of the raw polymer contained in the adhesive composition used in the adhesive layer; polymerization initiator, The type and amount of crosslinking agent and other additives; active energy rays, heat, and other factors that change the degree of crosslinking, etc., are in the desired numerical range.

[Glass transition temperature] In the optical laminate 100, it is preferable that the glass transition temperatures of the first adhesive layer and the second adhesive layer are respectively -70°C or more and -40°C or less. When the glass transition temperature of the adhesive layer is -40°C or lower, the flexibility of the adhesive layer is good, so the optical laminate 100 can be easily bent. When the glass transition temperature of the adhesive layer is lower than -70°C, the cohesive force of the adhesive layer decreases, and the adhesive force under durable conditions may decrease. The glass transition temperature of the adhesive layer can be measured in accordance with the method described in the column of Examples described later.

The glass transition temperature of the adhesive layer can be adjusted by adjusting the types and blending amounts of monomers constituting the raw polymer contained in the adhesive composition; the types and blending amounts of polymerization initiators, crosslinking agents, and other additives; activity; Energy rays, heat, and other factors that change the degree of crosslinking, etc., are in the desired numerical range. In order to set the glass transition temperature of the adhesive layer to -40°C or lower, the raw polymer contained in the adhesive composition is preferably formulated as a homopolymer. The glass transition temperature is -40°C or lower, preferably -45 It is an acrylic monomer having a temperature below °C, more preferably below -50 °C. 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), acrylic acid 2-ethylhexyl ester (T _g : -70°C), isononyl acrylate (T _g : -58°C), isodecyl acrylate (T _g : -60°C), isodecyl methacrylate (T _g ：-41℃), n-lauryl methacrylate (T _g ：-65℃), tridecyl acrylate (T _g ：-55℃), tridecyl methacrylate (T _g ：-40 °C), preferably n-butyl acrylate and 2-ethylhexyl acrylate. These monomers can be used alone or in combination of two or more.

The raw material polymer contained in the adhesive composition preferably contains 80% by mass or more, more preferably 85% by mass or more, and even more preferably 95% by mass or more as a homopolymer with a glass transition temperature of -40°C or less. body. In addition, the raw material polymer contained in the adhesive composition preferably contains 99.9% by mass or less, more preferably 99.5% by mass or less, and still more preferably 99% by mass or less, as homopolymers with a glass transition temperature of -40°C or less. . When the content of the monomer whose glass transition temperature as a homopolymer is -40°C or less is in such a range, the glass transition temperature of the adhesive layer easily falls within the above-mentioned range.

In order to easily set the glass transition temperature of the adhesive layer within the above range, the raw polymer contained in the adhesive composition preferably contains as little as possible monomers whose glass transition temperature exceeds 0°C as homopolymers. Such a monomer is preferably contained as an upper limit of 15% by mass or less, more preferably 10% by mass or less, and still more preferably 5% by mass or less.

[Front Panel] As long as the front surface plate 101 is a plate-shaped body that can transmit light, the material and thickness are not limited. The front surface plate may include only one layer, or may include two or more layers. As the front surface plate 101, a resin-made plate-shaped body (for example, a resin plate, a resin sheet, a resin film, etc.), and a glass-made plate-shaped body (for example, a glass plate, a glass film, etc.) are mentioned. The front surface plate may be a laminate of a plate-shaped body made of resin and a plate-shaped body made of glass. The front surface plate 101 may constitute the outermost surface of the display device.

The thickness of the front surface 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 layered body 100 can be measured in accordance with the thickness measurement method described in the below-mentioned examples.

When the front surface plate 101 is a plate-shaped body made of resin, the plate-shaped body made of resin is not limited as long as it can transmit light. Examples of the resin constituting the resin-made plate-shaped body include: triacetyl cellulose, acetyl cellulose butyrate, ethylene-vinyl acetate copolymer, propylene cellulose, butyl cellulose, and acrylic acid. Cellulose, polyester, polystyrene, polyamide, polyetherimide, poly(meth)acrylic acid, polyimide, polyether turpentine, polysulfide, polyethylene, polypropylene, polymethylpentene Alkene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl acetal, polyether ketone, polyether ether ketone, polyether stubble, polymethyl methacrylate, polyethylene terephthalate, Polymers such as polybutylene terephthalate, polyethylene naphthalate, polycarbonate, and polyimide. The polymer can be used alone or in combination of two or more kinds. From the viewpoint of improving strength and transparency, the resin-made plate-shaped body is preferably a resin film formed of a polymer such as polyimide, polyimide, and polyimide.

From the viewpoint of increasing the hardness, the front surface plate 101 may be a resin film including a hard coat layer. The hard coat layer can be formed on one side of the resin film or on both sides. By providing a hard coat, the hardness and scratch resistance can be improved. The hard coat layer is, for example, a cured layer of ultraviolet curable resin. Examples of ultraviolet curable resins include acrylic resins, silicone resins, polyester resins, urethane resins, amide resins, and epoxy resins. In order to increase the hardness, the hard coat layer may contain additives. The additives are not particularly limited, and examples include inorganic fine particles, organic fine particles, or mixtures of these. When the resin film has hard coat layers on both sides, the composition and thickness of each hard coat layer may be the same or different from each other.

When the front surface plate 101 is a glass plate, it is preferable to use tempered glass for a display as a 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 a glass plate, the front surface 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 surface plate 101 may not only have a function of protecting the front surface (screen) of the display device (function as a window film), but also have a function as a touch sensor , Blu-ray cutoff function, viewing angle adjustment function, etc.

[The first adhesive layer] The first adhesive layer 102 is interposed between the front surface plate 101 and the polarizing plate 103 to bond them together. The first adhesive layer 102 may be one layer, or may include two or more layers, but it is preferably one layer.

The first adhesive layer 102 may contain (meth)acrylic resins, rubber resins, urethane resins, ester resins, silicone resins, polyvinyl ether resins as main components (raw polymer ) Adhesive composition. The adhesive composition constituting the first adhesive layer 102 is preferably an adhesive composition using a (meth)acrylic resin excellent in transparency, weather resistance, heat resistance, etc., as a base polymer. The adhesive composition may be an active energy ray hardening type or a heat hardening type.

As the (meth)acrylic resin used in the adhesive composition, butyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, (methyl) ) Polymers or copolymers in which one type or two or more types of (meth)acrylates such as 2-ethylhexyl acrylate are used as monomers. In the base polymer, it is preferable to copolymerize a polar monomer. Examples of polar monomers include (meth)acrylic acid compounds, 2-hydroxypropyl (meth)acrylate compounds, hydroxyethyl (meth)acrylate compounds, (meth)acrylamide compounds, and (meth)acrylic acid compounds. A monomer having a carboxyl group, a hydroxyl group, an amino group, an amino group, an epoxy group, etc., such as an N,N-dimethylaminoethyl compound and a glycidyl (meth)acrylate compound. As a monomer constituting the (meth)acrylic resin, a photoreactive compound having a benzyl group can also be used, and the compound described as Chemical Formula 1 in Korean Laid-open Patent 10-2019-0005427 can be exemplified. Such a photoreactive compound is activated by additional photocuring and induces additional cross-linking, and thus can improve durability.

The adhesive composition may only contain the base polymer, but usually contains a crosslinking agent. Examples of the crosslinking agent include: metal ions having a valence of 2 or higher and forming a metal salt of a carboxylic acid with a carboxyl group; a polyamine compound that forms an amide bond with a carboxyl group; and an ester bond with a carboxyl group. The polyepoxy compound or polyol; the polyisocyanate compound that forms an amide bond with the carboxyl group. The crosslinking agent is preferably a polyisocyanate compound.

The active energy ray curable adhesive composition has the property of being irradiated with active energy rays such as ultraviolet rays or electron rays to be hardened, so that it has adhesiveness before the active energy rays are irradiated and can adhere to adherends such as films. , And hardened by the irradiation of active energy rays, the properties of adhesion can be adjusted. The active energy ray curable adhesive composition is preferably an ultraviolet curable adhesive composition. The active energy ray curable adhesive composition contains an active energy ray polymerizable compound in addition to the raw material polymer and the crosslinking agent. If necessary, it also contains a photopolymerization initiator, a photosensitizer, and the like.

Examples of the active energy ray polymerizable compound include: a (meth)acrylate monomer having at least one (meth)acryloyloxy group in the molecule; (Meth)acrylic compounds such as (meth)acryloxy group-containing compounds such as (meth)acrylic acid ester oligomers having at least two (meth)acryloxy groups. With respect to 100 parts by mass of the solid content of the adhesive composition, the adhesive composition may contain 0.1 parts by mass or more and may contain 10 parts by mass or less, 5 parts by mass or less, or 2 parts by mass or less of the active energy ray polymerizable compound.

As a photopolymerization initiator, benzophenone, benzyl dimethyl ketal, 1-hydroxycyclohexyl phenyl ketone, etc. are mentioned, for example. The photopolymerization initiator may contain one kind or two or more kinds. When the adhesive composition contains a photopolymerization initiator, the total content thereof may be 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 adhesive composition, for example.

The adhesive composition may contain fine particles, beads (resin beads, glass beads, etc.), glass fibers, resins other than raw polymers, tackifiers, fillers (metal powder or other inorganic powders, etc.) for imparting light scattering properties. , Antioxidants, ultraviolet absorbers, dyes, pigments, colorants, defoamers, anti-corrosion agents, photopolymerization initiators and other additives.

The first adhesive layer 102 can be formed by coating the organic solvent dilution of the adhesive composition on a substrate and drying it. The first adhesive layer 102 can also be formed using an adhesive sheet formed of an adhesive composition. When an active energy ray curable adhesive composition is used, by irradiating the formed adhesive layer with active energy rays, an adhesive layer having a desired degree of curing can be formed.

The thickness of the first adhesive layer 102 is not particularly limited. For example, it is preferably 1 μm or more and 100 μm or less, more preferably 3 μm or more and 50 μm or less, and may also be 20 μm or more.

From the viewpoint of improving the cohesive force of the first adhesive layer 102, when the first adhesive layer 102 is used as a reference adhesive layer with a thickness of 150 μm, the shear elastic coefficient at a temperature of 25° C. is preferably 0.01 Mpa or more. It is more preferably 0.02 Mpa or more, preferably 0.50 Mpa or less, more preferably 0.10 Mpa or less, and may also be 0.08 MPa or less. When the shear elastic coefficient of the first adhesive layer 102 is within this range, even if the optical layered body 100 is bent, it is not easy to cause aggregation failure, and air bubbles are not likely to be generated. The coefficient of shear elasticity can be adjusted by changing the type and content of monomers constituting the base polymer contained in the adhesive composition, additives, degree of crosslinking, 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 polarizer includes a linear polarizer and a retardation layer. The circularly polarizing plate can absorb external light reflected by the image display device, and therefore, can provide the optical laminate 100 with a function as an anti-reflection film.

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

(Straight Polarizing Plate) The linear polarizing plate selectively transmits linearly polarized light in one direction from natural light and other non-polarized light. The linear polarizing plate may include a stretched film or a stretched layer that adsorbs a dichroic dye, a liquid crystal layer, etc., as a polarizer layer. The liquid crystal layer includes a cured product of a polymerizable liquid crystal compound and a dichroic dye. The polymerizable liquid crystal compound is dispersed and aligned in the cured product. The dichroic dye refers to a dye having a property that the absorbance in the long axis direction of the molecule is different from the absorbance in the short axis direction of the molecule. A linear polarizing plate in which a liquid crystal layer is used as a polarizer layer has no limitation in the bending direction as compared with a stretched film or stretched layer to which a dichroic dye is adsorbed, and therefore is preferable.

(As a polarizer layer of a stretched film or stretched layer for adsorbing dichroic pigments) The polarizer layer as a stretched film that adsorbs dichroic dyes can usually be manufactured through the following steps: a step of uniaxially stretching a polyvinyl alcohol-based resin film; The step of dyeing the resin film to adsorb the dichroic pigment; the step of treating the polyvinyl alcohol resin film having the dichroic pigment adsorbed with the boric acid aqueous solution; and the step of washing with water after the treatment with the boric acid aqueous solution.

The thickness of the polarizer layer is generally 30 μm or less, preferably 18 μm or less, and more preferably 15 μm or less. Reducing the thickness of the polarizer layer is beneficial to thinning the polarizer 103. The thickness of the polarizer layer is usually 1 μm or more, for example, it may be 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, copolymers of vinyl acetate and other monomers that can be copolymerized therewith can also be used. Examples of other monomers that can be copolymerized with vinyl acetate include unsaturated carboxylic acid compounds, olefin compounds, vinyl ether compounds, unsaturated sulfonic acid compounds, and (meth)acrylic acid compounds having an ammonium group. Amine compounds.

The degree of saponification of the polyvinyl alcohol-based resin is generally 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 and polyvinyl acetal modified with aldehydes may also be used. The degree of polymerization of the polyvinyl alcohol-based resin is usually 1,000 or more and 10,000 or less, preferably 1,500 or more and 5,000 or less.

The polarizer layer as the stretched layer to which the dichroic dye is adsorbed can usually be manufactured through the following steps: a step of applying a coating solution containing the polyvinyl alcohol-based resin on a base film; and laminating the resulting laminate The step of uniaxial stretching of the film; the step of dyeing the polyvinyl alcohol-based resin layer of the uniaxially stretched laminate film with a dichroic dye to adsorb the dichroic dye to prepare a polarizer; using boric acid The step of treating the film with the dichroic dye adsorbed by the aqueous solution; and the step of washing with water after the treatment with the aqueous solution of boric acid. The base film used to form the polarizer layer can be used as a protective layer for the polarizer layer. If necessary, the base film can be peeled and removed 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 polarizer layer that is a stretched film or stretched layer to which a dichroic dye is adsorbed can be directly used as a linear polarizing plate, or it can be used as a linear polarizing plate by forming a protective layer on one or both sides thereof. 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.

Examples of the thermoplastic resin film include: cyclic polyolefin resin film; cellulose acetate resin film containing resins such as triacetyl cellulose and diacetyl cellulose; containing polyethylene terephthalate and polyethylene naphthalate Polyester resin films of resins such as ethylene glycol and polybutylene terephthalate; polycarbonate resin films; (meth)acrylic resin films; polypropylene resin films and other films known in the art. The polarizer layer and the protective layer can be laminated via the 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, further preferably 30 μm or less, and usually It is 5 μm or more, preferably 10 μm or more.

A hard coat layer can 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 a hard coat layer, a thermoplastic resin film with improved hardness and scratch resistance can be produced. The hard coat layer can be formed in the same manner as the hard coat layer formed on the above-mentioned resin film.

(Polarizer layer as 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 that participates in the polymerization reaction, and is preferably a photopolymerizable reactive group. The photopolymerizable reactive group refers to a group that can participate in a polymerization reaction by a living radical or acid generated from a photopolymerization initiator. Examples of the photopolymerizable functional group include vinyl, vinyloxy, 1-chlorovinyl, isopropenyl, 4-vinylphenyl, acryloxy, methacryloxy, and oxa Cyclopropanyl, oxetanyl, etc. Among them, propyleneoxy, methacryloxy, vinyloxy, oxetanyl, and oxetanyl are preferred, and propyleneoxy is more preferred. The type of the polymerizable liquid crystal compound is not particularly limited, and rod-shaped liquid crystal compounds, discotic liquid crystal compounds, and mixtures thereof can be used. The liquid crystal properties of the polymerizable liquid crystal compound may be thermotropic liquid crystal or lyotropic liquid crystal, and as a phase order structure, it may be nematic liquid crystal or smectic liquid crystal.

The dichroic dye used in the polarizer layer as the liquid crystal layer preferably has a maximum absorption wavelength (λMAX) in the range of 300 nm to 700 nm. Examples of such dichroic dyes include acridine dyes, oxazine dyes, cyanine dyes, naphthalene dyes, azo dyes, and anthraquinone dyes. Among them, azo dyes are preferred. Examples of azo dyes include monoazo dyes, bisazo dyes, trisazo dyes, tetrasazo dyes, and stilbene azo dyes, and bisazo dyes and trisazo dyes are preferred. The dichroic dye may be singly or in combination of two or more, preferably three or more in combination. In particular, it is more preferable to combine three or more azo compounds. A part of the dichroic dye may have a reactive group, and may also have liquid crystallinity.

For the polarizer layer as the liquid crystal layer, for example, a composition for forming a polarizer layer containing a polymerizable liquid crystal compound and a dichroic dye can be applied to an alignment film formed on a base film to polymerize the polymerizable liquid crystal compound. Make it harden to form. The polarizer layer can also be formed by applying the composition for forming a polarizer layer on a base film to form a coating film, and stretching the coating film together with the base film. The base film used to form the polarizer layer can also 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 above-mentioned thermoplastic resin film.

As a composition for forming a polarizer layer containing a polymerizable liquid crystal compound and a dichroic dye, and a method for manufacturing a polarizer layer using the composition, Japanese Patent Laid-Open No. 2013-37353 and Japanese Patent Laid-Open Those described in 2013-33249, Japanese Patent Laid-Open No. 2017-83843, etc. In addition to the polymerizable liquid crystal compound and the dichroic dye, the composition for forming a polarizer layer may further contain additives such as a solvent, a polymerization initiator, a crosslinking agent, a leveling agent, an antioxidant, a plasticizer, and a sensitizer. These components may be used individually by only 1 type, and may be used in combination of 2 or more types.

The polymerization initiator that may be contained in the composition for forming a polarizing layer is a compound that can initiate a polymerization reaction of a polymerizable liquid crystal compound. In terms of initiating a polymerization reaction under a lower temperature condition, a photopolymerizable initiator is preferred . Specifically, a photopolymerization initiator that can generate active radicals or an acid by the action of light is mentioned, and among them, a photopolymerization initiator that generates a radical by the action of light is preferred. The content of the polymerization initiator relative to 100 parts by mass of the total amount of the polymerizable liquid crystal compound is preferably 1 part by mass or more and 10 parts by mass or less, more preferably 3 parts by mass or more and 8 parts by mass or less. When it is within this range, the reaction of the polymerizable group proceeds sufficiently, and it is easy to stabilize the alignment state of the liquid crystal compound.

The thickness of the polarizer layer as the 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 as the liquid crystal layer can be used as a linear polarizer without peeling and removing the base film, or the base film may be peeled and removed from the polarizer layer and used as a linear polarizer. The polarizer layer as a liquid crystal layer can also be used as a linear polarizer by forming a protective layer on one or both surfaces. As the protective layer, the above-mentioned thermoplastic resin film can be used.

Regarding the polarizer layer as the liquid crystal layer, in order to protect the polarizer layer and the like, an overcoat layer may be provided on one or both sides of the polarizer layer. The overcoat layer can be formed, for example, by coating a material (composition) for forming the overcoat layer on the polarizer layer. Examples of materials constituting the overcoat layer include photocurable resins and water-soluble polymers. As the material constituting the overcoat layer, (meth)acrylic resin, polyvinyl alcohol resin, etc. can be used.

The polarizing plate 103 is arranged such that the linear polarizing plate is located on the side of the first adhesive layer 102 with respect to the retardation layer. The outermost layer that constitutes the polarizing plate 103 and is in contact with the first adhesive layer 102 is preferably a base film, a protective layer, or an outer coating contained in the linear polarizing plate.

(Retardation layer) The retardation layer may be one layer, or two or more layers. The retardation layer may have an overcoat to protect its surface, 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 any one of a λ/2 layer or a positive C layer. When the retardation layer includes a λ/2 layer, a λ/2 layer and a λ/4 layer are laminated in this order from the side of the linear polarizer. When the retardation layer includes a positive C layer, a λ/4 layer and a positive C layer may be laminated in order from the linear polarizing plate side, or a positive C layer and a λ/4 layer may be laminated in order from the linear polarizing plate side. 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 include the resin film exemplified as the material of the protective layer, or may include a layer formed by curing a polymerizable liquid crystal compound. 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 can 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 a layer formed by curing the polymerizable liquid crystal compound, the retardation layer may be assembled in the optical laminate in the form of an alignment film and/or a base film. The retardation layer can be bonded to the linear polarizing plate via the bonding layer.

[Second Adhesive Layer] The second adhesive layer 104 is interposed between the polarizing plate 103 and the back plate 105 and adheres these. The second adhesive layer 104 may be one layer, or may include two or more layers, preferably one layer.

Regarding the composition and compounding components of the adhesive composition constituting the second adhesive layer 104, the type of the adhesive composition (whether it is an active energy ray hardening type or a thermosetting type, etc.), the additives that can be formulated in the adhesive composition, The manufacturing method of the second adhesive layer, the thickness of the second adhesive layer, etc. are the same as those shown in the description of the first adhesive layer 102. The second adhesive layer 104 may be the same as or different from the first adhesive layer 102 in terms of the composition, blending components, thickness, etc. of the adhesive composition.

From the viewpoint of improving the cohesive force of the second adhesive layer 104, when the second adhesive layer 104 is set as a reference adhesive layer with a thickness of 150 μm, the shear elastic coefficient at a temperature of 25° C. is preferably 0.01 Mpa or more , More preferably 0.02 Mpa or more, preferably 0.50 Mpa or less, more preferably 0.10 Mpa or less, and may also be 0.08 MPa or less. When the shear elastic coefficient of the second adhesive layer 104 is within the above range, even if the optical layered body 100 is bent, it is not easy to cause aggregation failure, and it is not easy to generate bubbles. The coefficient of shear elasticity can be adjusted by changing the type and content of monomers constituting the base polymer contained in the adhesive composition, additives, degree of crosslinking, and the like.

[Laminated layer] The optical laminate 100 may include a bonding layer for bonding two layers. The bonding layer is a layer including an adhesive or bonding agent. As the adhesive as the material of the bonding layer, the same adhesive composition as the adhesive composition constituting the first adhesive layer 102 can be used. The bonding layer may also use other adhesives, such as (meth)acrylic adhesives, styrene-based adhesives, silicone-based adhesives, rubber-based adhesives, which are different from the adhesive that constitutes the first adhesive layer 102. Urethane-based adhesives, polyester-based adhesives, epoxy-based copolymer adhesives, etc.

The adhesive used as the material of the bonding layer can be formed by combining, for example, one or two or more of water-based adhesives, active energy ray curable adhesives, and the like. Examples of water-based adhesives include polyvinyl alcohol-based resin aqueous solutions, water-based two-component urethane-based emulsion adhesives, and the like. Active energy ray curable adhesives are adhesives that are cured by irradiating active energy rays such as ultraviolet rays. Examples include adhesives containing polymerizable compounds and photopolymerizable initiators, adhesives containing photoreactive resins, and Adhesives for adhesive resins and photoreactive crosslinking agents. Examples of the polymerizable compound include photopolymerizable monomers such as photocurable epoxy monomers, photocurable acrylic monomers, and photocurable urethane monomers, and monomers derived from these monomers. Oligomers and so on. Examples of the photopolymerization initiator include compounds containing a substance that generates active species such as neutral radicals, anionic radicals, and cationic radicals by irradiating active energy rays such as ultraviolet rays.

The thickness of the bonding 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 still more preferably 2.5 μm or more and 5 μm or less.

The two opposing surfaces bonded via the bonding layer may be subjected to corona treatment, plasma treatment, flame treatment, etc. in advance, and may have an undercoat layer or the like.

[Back Panel] As the back plate 105, a plate-shaped body capable of transmitting light, a structural member 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-shaped body used for the back panel 105 may include only one layer, or may include two or more layers, and the plate-shaped body exemplified in the front panel 101 may be used.

As a structural member used in the normal display device used for the back panel 105, a touch sensor panel, an organic electroluminescent display element, etc. are mentioned, for example. Examples of the stacking order of the constituent components in the display device include: window film/circular polarizer/touch sensor panel/organic EL display element, window film/touch sensor panel/circular polarizer/organic EL Display components, etc.

(Touch sensor panel) The touch sensor panel is not limited as long as it has a sensor (that is, a touch sensor) capable of detecting a touched position. The detection method of the touch sensor is not limited, and examples can include touch sensor panels such as resistive film method, electrostatic capacitance coupling method, optical sensor method, ultrasonic method, electromagnetic induction coupling method, surface acoustic wave method, etc. . In terms of low cost, it is preferable to use a touch sensor panel of a resistive film method or an electrostatic capacitance coupling method.

As an example of a resistive film type touch sensor, a pair of substrates arranged facing each other, an insulating spacer sandwiched between the pair of substrates, and a front surface on the inner side of each substrate can be cited as The transparent conductive film provided on the resistive film and the components of the touch position detection circuit. In an image display device provided with a resistive film type touch sensor, when the surface of the front panel is touched, the opposing resistive films are short-circuited, and current flows through the resistive film. The touch position detection circuit detects the voltage change at this time, thereby detecting the touched position.

As an example of the touch sensor of the capacitive coupling method, a member including a substrate, a transparent electrode for position detection provided on the entire surface of the substrate, and a touch position detection circuit can be cited. In the image display device provided with the touch sensor of the electrostatic capacitance coupling method, if the surface of the front surface plate is touched, the transparent electrode is grounded via the electrostatic capacitance of the human body at the touched point. The touch position detection circuit detects the grounding of the transparent electrode, thereby detecting the touched position.

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 may also be 5 μm or more and 20 μm. the following.

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

[Method of manufacturing optical laminate] The optical layered body 100 can be manufactured by a method including a step of bonding the layers constituting the optical layered body 100 to each other through an adhesive layer. When the layers are bonded to each other via the adhesive layer or the bonding layer, in order to adjust the adhesive force, it is preferable to perform surface activation treatment such as corona treatment on one or both sides of the bonding surface. The conditions of the corona treatment can be appropriately set, and the conditions may be different on one side and the other side of the bonding surface.

＜Display device＞ The display device of the present invention includes the optical laminate 100 described above. The display device is not particularly limited, and examples thereof include image display devices such as organic EL display devices, inorganic EL display devices, liquid crystal display devices, and electroluminescence display devices. Touch sensors can be further laminated in the optical laminate, and the display device can also have a touch panel function. The display device including the optical laminate of the present invention exhibits excellent durability in static bending, and can be used as a flexible display capable of bending, winding, or the like.

In the display device, the optical laminate 100 has the front surface plate 101 facing the outside (the side opposite to the display element side, that is, the visible side), and is arranged on the visible side of the display element included in the display device. The display device can bend the front panel 101 side outward.

The display device of the present invention can be used as mobile devices such as smart phones, input panels, televisions, digital photo frames, electronic billboards, measuring devices or meters, office equipment, medical equipment, computer equipment, and the like. [Example]

Hereinafter, examples are given to illustrate the present invention in more detail, but the present invention is not limited to these examples.

[Adhesive layer] In order to reflux the nitrogen gas and easily adjust the temperature, a 1-L reactor equipped with a cooling device was charged with 2-ethylhexyl acrylate (2-EHA) and n-butyl acrylate ( n-BA (butyl acrylate), N-(2-hydroxyethyl) acrylamide (HEAA), Isodecyl acrylate (IDA), Behenyl Acrylate (BHA), compound I's a monomer mixture. After refluxing nitrogen for 1 hour in order to remove oxygen, the solution was maintained at 60°C. After the above-mentioned monomer mixture was uniformly mixed, the photopolymerization initiator benzyl dimethyl ketal (I-651) and 1-hydroxycyclohexyl phenyl ketone (I-184) were added in the formulation amounts shown in Table 1. An ultraviolet (Ultraviolet, UV) lamp (10 mW) was irradiated while stirring to produce acrylic polymer A1 to acrylic polymer A6.

[Table 1] Acrylic polymer Acrylic monomer (mass%) Photopolymerization initiator (mass%) 2-EHA n-BA HEAA IDA BHA Compound I 1-651 1-184 A1 80.6 14.8 0.3 0.2 3.0 1 0.05 0.05 A2 83.4 10.5 0.5 1.0 2.5 2 0.05 0.05 A3 78.4 15.5 0.5 0.5 3.0 2 0.05 0.05 A4 77.3 15.5 0.5 0.8 2.8 3 0.05 0.05 A5 68.0 15.5 0.2 15 1.2 - 0.05 0.05 A6 99.3 - 0.1 - - 0.5 0.05 0.05

[化1]

The acrylic polymers A1 to A6, isodecyl acrylate (IDA), N-(2-hydroxyethyl)acrylamide (HEAA), and benzophenone (benzophenone, BPO) is mixed to produce adhesive compositions B1 to B9.

[Table 2] Adhesive composition Acrylic polymer additive Photopolymerization initiator type Allocation amount (mass%) type Allocation amount (mass%) type Allocation amount (mass%) type Allocation amount (mass%) B1 A1 96.5 IDA 3 HEAA - BPO 0.5 B2 A2 97.5 IDA 2 HEAA - BPO 0.5 B3 A3 93.5 IDA 1 HEAA 5 BPO 0.5 B4 A4 89.5 IDA 1 HEAA 8 BPO 1.5 B5 A5 93.5 IDA 1 HEAA 5 BPO 0.5 B6 A6 96.5 IDA 3 HEAA - BPO 0.5 B7 A6 97.5 IDA 2 HEAA - BPO 0.5 B8 A6 98.5 IDA 1 HEAA - BPO 0.5 B9 A5 84.5 IDA 5 HEAA 9 BPO 1.5

The adhesive composition B1 to the adhesive composition B9 were coated on the release film A (polyethylene terephthalate film, thickness 38 μm) coated with a silicon release agent in a thickness of 25 μm. The release film B (polyethylene terephthalate film, thickness 38 μm) was joined thereon, and UV irradiation was performed to produce an adhesive sheet including release film A/adhesive layer/release film B. The conditions of UV irradiation are 400 mJ/cm ² of accumulated light and 1.8 mW/cm ^{2 of} illuminance (UVV standard).

The source of the compound used is shown below. 2-EHA: Tokyo Chemical Industry Co., Ltd., Japan n-BA: Tokyo Chemical Industry Co., Ltd., Japan HEAA: Tokyo Chemical Industry Co., Ltd., Japan IDA: Miwon specialty chemical, South Korea BHA: Tokyo Chemical Industry Co., Ltd., Japan I-651: BASF, Germany I-184: BASF, Germany BPO: Tokyo Chemical Industry Co., Ltd., Japan

[Front Panel] As the front surface plate 101, a film in which a hard coat layer was formed on one surface of a resin film was prepared. The resin film is a polyimide resin film with a thickness of 40 μm. The hard coat layer is a layer having a thickness of 10 μm and a composition containing a dendrimer compound having a polyfunctional acrylic group at the terminal.

[Circular Polarizing Plate] A circular polarizing plate is prepared as the polarizing plate 103. Prepare a film with Triacetyl Cellulose (TAC) film (KC2UA, manufactured by Konica Minolta Co., Ltd., thickness 25 μm), alignment film, linear polarizer layer, and outer coating in sequence Linear polarizing plate. The linear polarizer layer is formed using a composition containing a polymerizable liquid crystal compound and a dichroic dye, and has a thickness of 2 μm. The outer coating is a polyvinyl alcohol resin layer with a thickness of 1.0 μm.

On the outer coating side of the linear polarizing plate, a phase difference laminate was laminated via an adhesive to obtain a circular polarizing plate. The retardation laminate has a λ/4 retardation layer, an adhesive layer, and a positive C layer in this order from the linear polarizer side. The λ/4 retardation layer is a hardened layer of a polymerizable liquid crystal compound and has a thickness of 3 μm. The thickness of the adhesive layer is 5 μm. The positive C layer is a hardened layer of a polymerizable liquid crystal compound and has a thickness of 3 μm.

[Back Panel] 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 is prepared. The touch sensor pattern layer includes an ITO layer as a transparent conductive layer and a hardened layer of an acrylic resin composition as a separation layer, and has a thickness of 7 μm. The adhesive layer is arranged on the side of the separation layer of the touch sensor pattern layer and has a thickness of 3 μm. The base layer uses a cyclic olefin resin (Cycloolefin Polymer, COP) film (ZF-14, manufactured by Zeon Co., Ltd., thickness 23 μm).

[Production of optical laminate] As shown in Table 3, an adhesive sheet containing the adhesive composition shown in Table 2 was used as the first adhesive layer 102, and the side of the front surface plate 101 that did not have a hard coat layer was connected to The polarizing plate 103 is attached to the TAC film side. In addition, as shown in Table 3, an adhesive sheet containing the adhesive composition shown in Table 2 was used as the second adhesive layer 104, and the phase difference layer side of the circular polarizer and the touch sensor of the touch sensor The measuring device pattern layer side was bonded together, and the optical laminated body 100 (Example 1, Example 2, and Comparative Example 1-Comparative Example 3) of the layer structure shown in FIG. 1 was produced. The bonding surfaces of the front surface plate, circular polarizer, touch sensor and adhesive layer were treated with double-sided corona before bonding. For the corona treatment, TEC-4AX (manufactured by USHIO Electric Co., Ltd.) was used. The slope G _L ', the stress relaxation rate σ, the creep rate ε, the deformation recovery rate R, the glass transition temperature T _g , the shear elastic coefficient, and the optical The static bending durability of the laminate 100. The results are shown in Table 3.

[table 3] Example 1 Example 2 Comparative example 1 Comparative example 2 Comparative example 3 1st adhesive layer Adhesive composition B4 B6 B1 B2 B9 The slope from the origin to the maximum stress value G _L1 ' 121 twenty three 26 54 170 Stress relaxation rate σ1 0.55 0.15 0.21 0.3 0.85 Creep rateε1〔%〕 3.3 31 9.3 6.3 0.4 Deformation recovery rate R1〔%〕 16.5 1.4 4.0 3.7 twenty four Glass transition temperature T _g 〔℃〕 -30 -63 -58 -55 -15 Shear elastic coefficient (MPa) 0.095 0.021 0.041 0.051 0.201 2nd adhesive layer Adhesive composition B5 B7 B2 B3 B8 The slope from the origin to the maximum stress value G _L2 ' 105 20 54 91 15 Stress relaxation rate σ2 0.51 0.11 0.3 0.54 0.09 Creep rateε2〔%〕 4.1 35 6.3 4.9 46 Deformation recovery rate R2〔%〕 13.4 1.1 3.7 4.4 0.9 Glass transition temperature T _g 〔℃〕 -33 -70 -55 -52 -73 Shear elastic coefficient (MPa) 0.104 0.018 0.051 0.053 0.016 Static bending durability A B C C C

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

<The slope from the origin to the maximum stress value G _L '> The slope from the origin to the maximum stress value was measured using a dynamic mechanical analysis device (DMA, Q-800, manufactured by TA Instruments). First, as shown in FIG. 2, a test piece in which the ends of two polycarbonate (PC) rods 501 are joined to each other via an adhesive layer is prepared. The shape of the adhesive layer 502 is width×length×thickness 6 mm×10 mm×25 μm, and the shape of the PC rod 501 is width×length×thickness 6 mm×20 mm×1 mm. The bonding area between the adhesive layer 502 and the PC rod 501 is 6 mm×10 mm in width×length. Fixtures were installed in the 5 mm area at both ends of the PC rod 501 of the test piece, and one of the fixtures was fixed. Another jig was stretched at a speed of 100 μm/min. at a temperature of 25°C to create a stress [Pa]-strain [%] curve. Calculate the slope from the origin to the maximum stress in the obtained stress-strain curve.

＜Stress relaxation rate σ＞ The stress relaxation rate (Stress Relaxation) of the 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 to measure the slope from the origin to the maximum stress value. Fixtures were installed in the 5 mm area at both ends of the PC rod 501 of the test piece, and one of the fixtures was fixed. The other jig was stretched continuously for 300 seconds in an environment with a temperature of 25°C while maintaining a strain of 25%, and the stress was measured. Stress relaxation rate = stress after 300 seconds (MPa) / stress after 7.0 seconds (MPa)

＜Creep rate ε＞ The creep rate (Creep) of the adhesive layer was measured using a dynamic mechanical analysis device (DMA, Q-800, manufactured by TA Instruments (TA Instruments)). The test piece is the same as the test piece used to measure the slope from the origin to the maximum stress value. Fixtures were installed in the 5 mm area at both ends of the PC rod 501 of the test piece, and one of the fixtures was fixed. Continue to stretch another clamp so that the stress reaches 1 MPa, and measure the strain [%] value after 1200 seconds. Creep rate (%) = strain after 1200 seconds (%)

＜Deformation recovery rate R＞ The deformation recovery rate (Recovery) of the adhesive layer was measured using a dynamic mechanical analysis device (DMA, Q-800, manufactured by TA Instruments). The test piece is the same as the test piece used to measure the slope from the origin to the maximum stress value. Fixtures were installed in the 5 mm area at both ends of the PC rod 501 of the test piece, and one of the fixtures was fixed. Stretch the other clamp and maintain the 25% strain for 300 seconds. The load is removed after 300 seconds, and the strain is measured after another 5 seconds (305 seconds have passed). Deformation recovery rate (%) = strain after 300 seconds (=25%)-strain after 305 seconds (%)

<Glass transition temperature T _g > After drying the adhesive 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 elasticity coefficient＞ The coefficient of shear elasticity was measured using a viscoelasticity measuring device (MCR-301, Anton Paar). Set the adhesive sheet to a width of 20 mm × a length of 20 mm, peel off the release film, and laminate multiple sheets with a thickness of 150 μm. After bonding the laminated adhesive layer to the glass plate, in the state of bonding with the measurement wafer, at a temperature range of -20°C to 100°C, at a frequency of 1.0 Hz, a deformation amount of 1%, and a heating rate of 5°C Measure under the condition of /min, and confirm the shear elastic modulus value at 25°C.

＜Static bending durability test＞ Figure 3 shows the method of static bending durability test (mandrel bending test). First, the optical laminate 100 is cut into a test piece of 1 cm×10 cm. On the test plate 504, the front surface plate 101 of the optical laminate 100 was placed downward, and an iron rod 503 having a diameter of 5 mm was placed thereon ((A) in FIG. 3). It is folded and fixed by hand so that it is wound on the iron rod 503 and the front surface board 101 may become an outer side (FIG. 3(B)).

Based on the period during which no air bubbles are generated between the polarizing plate 103 and the first adhesive layer 102 and the second adhesive layer 104, or in the first adhesive layer 102 and the second adhesive layer 104, the static bending durability is evaluated as follows. The generation of bubbles is judged by observation under an optical microscope. A: No bubbles were generated at the time point when 48 hours passed. B: Bubbles are generated in more than 24 hours and 48 hours. C: Air bubbles were generated within 24 hours.

100: Optical laminate 101: front panel 102: The first adhesive layer 103: Polarizing plate 104: second adhesive layer 105: back panel 501: Polycarbonate rod/PC rod 502: Adhesive layer 503: Iron Rod 504: Test Board

Fig. 1 is a schematic cross-sectional view showing an example of the optical laminate of the present invention. Fig. 2 is a schematic diagram illustrating a parameter measurement method by a dynamic mechanical analyzer. Fig. 3 is a schematic diagram illustrating a static bending durability test.

100: Optical laminate

101: front panel

102: The first adhesive layer

103: Polarizing plate

104: second adhesive layer

105: back panel

Claims (10)

An optical laminate, including a front surface plate, a first adhesive layer, a polarizing plate, a second adhesive layer, and a back plate in sequence, wherein the stress of the first adhesive layer and the second adhesive layer -When the slope from the origin to the maximum stress value in the strain curve is set to G _L1 'and G _L2 ', respectively, the following equations (1), (2) and (3) are satisfied, and the unit of stress is Pa, The unit of strain is %, 20≦G _L1 '≦150 (1) 20≦G _L2 '≦150 (2) G _L1 '≧G _L2 '(3). The optical laminate according to claim 1, wherein when the stress relaxation rate of the second adhesive layer is σ2, the following formula (4) is satisfied: 0.20≦σ2≦0.70 (4). The optical laminate according to claim 2, wherein when the stress relaxation rate of the first adhesive layer is σ1, the following formula (5) is satisfied: σ1≧σ2 (5). The optical laminate according to any one of claims 1 to 3, wherein when the creep rate of the second adhesive layer is set to ε2, the following formula (6) is satisfied, wherein the creep The unit of rate of change is %, 1.5≦ε2≦20 (6). The optical laminate according to claim 4, wherein when the creep rate of the first adhesive layer is set to ε1, the following formula (7) is satisfied, wherein the unit of the creep rate is %, ε1≦ε2 (7). The optical laminate according to any one of claims 1 to 5, wherein when the deformation recovery rate of the second adhesive layer is R2, the following formula (8) is satisfied, wherein the deformation The unit of recovery rate is %, 2.5≦R2≦20 (8). The optical laminate according to claim 6, wherein when the deformation recovery rate of the first adhesive layer is R1, the following formula (9) is satisfied, wherein the unit of the deformation recovery rate is %, R1≧R2 (9). The optical laminate according to any one of claims 1 to 7, wherein the glass transition temperatures of the first adhesive layer and the second adhesive layer are respectively -70°C or higher and -40°C or lower . A display device includes the optical laminate according to any one of claim 1 to claim 8. The display device according to claim 9, which can be bent with the front surface plate side as the outer side.

Images