TW202134048A - Optical laminate and display device capable of suppressing bubble generation in an adhesive agent layer during bending - Google Patents

Abstract

This invention provides an optical laminate capable of suppressing bubble generation in an adhesive agent layer during bending and a display device comprising the optical laminate. This invention provides an optical laminate, comprising a front surface panel, a first adhesive agent layer, a polarizing plate, a second adhesive agent layer, and a back plate in this order. When the slope from the origin to the maximum stress value in the stress [Pa]-strain [%] curve of the first adhesive agent layer and the second adhesive agent at a temperature of 60 degree Celsius and a humidity of 90%RH are respectively set as G.sub.L1' and G.sub.L2', the following equation (1) and equation (2): 70 ≤G.sub.L1' ≤250 (1) and 70 ≤G.sub.L2' ≤250 (2) can be satisfied.

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, especially in a high-temperature and high-humidity environment.

The object of the present invention is to provide an optical laminate in which the generation of bubbles in an adhesive layer is suppressed when it is bent, and a display device including the optical laminate. [Means to solve the problem]

The present invention provides the optical laminate and display device exemplified 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 in the temperature 60℃ and humidity 90%RH is set to G _L1 'and G _L2 ', the following formula (1) is satisfied And formula (2): 70≦G _L1 '≦250 (1) 70≦G _L2 '≦250 (2). [2] The optical laminate as described in [1], which satisfies the following equations (1') and (2'): 90≦G _L1 '≦150 (1') 90≦G _L2 '≦150 (2 '). [3] The optical laminate according to [1] or [2], wherein the back panel is a touch sensor panel. [4] A display device including the optical laminate according to any one of [1] to [3]. [5] The display device according to [4], which can be bent with the front panel side as the inner side. [Effects of the invention]

According to the present invention, there is provided an optical laminate in which the generation of bubbles in an adhesive layer is suppressed when it is 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 laminate 100 varies depending on the functions required for the optical laminate and the use of the optical laminate, and is therefore not particularly limited. For example, it is 30 μm or more and 1500 μm or less, preferably 40 μm or more and 1000 μm Hereinafter, it is more preferably 50 μm or more and 500 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.

[The slope of the stress-strain curve from the origin to the maximum stress value G _L '] When the temperature of the first adhesive layer 102 and the second adhesive layer 104 is 60°C and the humidity is 90%RH, the stress [Pa]- When the slope of the strain [%] curve from the origin to the maximum stress value is set to G _L1 'and G _L2 ', respectively, the optical laminate 100 satisfies the following equations (1) and (2): 70≦G _L1 '≦ 250 (1) 70≦G _L2 '≦250 (2).

When the adhesive layer is subjected to a tensile test, a stress-strain curve with stress as the vertical axis and strain as the horizontal 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)/(strain amount when the stress becomes the 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, which 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, and it is considered that it is not easily broken. G _L 'can be obtained according to the method described in the column of Examples described later.

The optical laminate 100 that satisfies the formulas (1) and (2) is unlikely to generate bubbles in the adhesive layer even if it is bent. In particular, even if it is bent in a high-temperature and high-humidity environment, the generation of bubbles in the adhesive layer can be suppressed. The optical laminate 100 that satisfies the formulas (1) and (2) can improve the durability of the adhesive layer to a bending radius of 60°C and 90%RH at a temperature of 60°C and a humidity of 90%RH according to the description in the Examples section described later. The 2.5 mm method repeatedly bends more than 20,000 times without generating air bubbles. The generation of bubbles in the adhesive layer 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.

The optical laminate 100 preferably satisfies the following formula (1′) and formula (2′). 90≦G _L1 '≦150 (1') 90≦G _L2 '≦150 (2'). The optical laminate 100 that satisfies the formula (1′) and the formula (2′) can further suppress the generation of bubbles in the adhesive layer even if it is bent in a high-temperature and high-humidity environment.

In addition, when the front surface plate is bent inside, the optical laminate 100 preferably satisfies the following formula (3) or formula (3′). G _L1 '≦G _L2 '(3) G _L1 '<G _L2 '(3') When the front surface plate is bent on the outside, the optical laminate 100 preferably satisfies the following formula (4) or formula (4) '). G _L1 '≧G _L2 '(4) G _L1 '>G _L2 '(4') When the optical laminate 100 is bent, a large stress is generated by becoming an adhesive layer on the inner diameter side. Therefore, by arranging _{an adhesive layer with a smaller G L} ′ and excellent stress relaxation properties to be inside when bent, the generation of bubbles in the adhesive layer of the optical laminate 100 can be further suppressed.

G _L' 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, the type and amount of polymerizable compound, the type and amount of active energy rays, and the amount of irradiation Etc., while in the desired numerical range. For example, when the base polymer contained in the adhesive composition contains a large amount of structural units derived from a long-chain alkyl (meth)acrylic monomer having a carbon number of 10 or more, G _L' tends to be smaller. When the adhesive composition contains a large amount of a long-chain alkyl (meth)acrylic monomer having a carbon number of 10 or more, a diluting monomer, etc., as a polymerizable compound, G _L' tends to decrease. For example, tetrahydrofurfuryl acrylate can be used as the diluting monomer. For example, when the adhesive composition contains a large amount of a compound having a cyclohexyl-like cyclic structure as a polymerizable compound, G _L' tends to increase.

[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 101 may include only one layer, or may include two or more layers. As the front surface plate 101, a plate-shaped body made of resin (for example, a resin plate, a resin sheet, a resin film, etc.), a plate-shaped body made of glass (for example, a glass plate, a glass film, etc.), a plate-shaped body made of resin, and A laminate of plate-like bodies 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.

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 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 10 μm or more and 1000 μm or less, or may be 10 μm or more and 100 μm or less, for example. 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 the function of protecting the front surface (screen) of the display device (function as a window film), but also have the 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 include one layer or two or more layers, but preferably includes 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.

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.

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 base polymer, the adhesive composition may contain 0.1 part by mass or more or 1 part by mass or more, and may contain 10 parts by mass or less or 5 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, UV absorbers, dyes, pigments, colorants, defoamers, anticorrosives, crosslinking agents 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.

[Polarizer] The polarizing plate 103 may be, for example, a linear polarizing plate, a circular polarizing plate, an elliptical polarizing plate, or the like. Hereinafter, sometimes the circular polarizing plate and the elliptical polarizing plate are collectively referred to as a circular polarizing plate for short. The circular polarizer includes a linear polarizer and a retardation layer. The circular polarizing plate can absorb external light reflected in 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 has a function of selectively transmitting linearly polarized light in one direction from non-polarized light such as natural light. The linear polarizing plate may include a stretched film or a stretched layer to which a dichroic dye is adsorbed, a liquid crystal layer, etc., as a polarizer layer, the liquid crystal layer including a cured product of a polymerizable liquid crystal compound and a dichroic dye and a dichroic dye Disperse and align in the cured polymerizable liquid crystal compound. When the pigment is dispersed and aligned in a medium having a different square shape, there are cases where it looks colored from a certain direction, and it looks almost colorless from a direction perpendicular to it. Pigments that show this phenomenon are called dichroic pigments. 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.

(1) Polarizer layer as a stretched film or stretched layer to which dichroic pigments are adsorbed The polarizer layer, which is a stretched film with a dichroic pigment, can usually be manufactured through the following steps: a step of uniaxially stretching a polyvinyl alcohol-based resin film; The step of dyeing the alcohol-based resin film to adsorb the dichroic pigment; the step of treating the polyvinyl alcohol-based resin film with the dichroic pigment adsorbed by 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 polarizer layer and the protective layer can be laminated via the bonding layer described later. 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.

From the viewpoint of improving flexibility, the thickness of the thermoplastic resin film is generally 100 μm or less, preferably 80 μm or less, more preferably 60 μm or less, still more preferably 40 μm or less, and still more preferably 30 μm or less. It is usually 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 by the same method as the hard coat layer formed on the above-mentioned resin film.

(2) 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, acid, etc. 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 the liquid crystal layer may have an alignment film, or may not have an alignment film. 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.

(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 surface of the linear polarizing plate on the side opposite to the visible side via the bonding layer described later.

[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.

[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 plate 105 may include only one layer, or may include two or more layers. As the back panel 105, a plate-shaped body exemplified in the front panel 101 can be used.

As a component used for a normal display device, a touch sensor panel, an organic EL display element, etc. are mentioned, for example. The back panel 105 is preferably a touch sensor panel. Examples of the stacking order of the components in the display device include: front panel/circular polarizer/touch sensor panel/organic EL display element, front panel/touch sensor panel/circular polarizer/ Organic EL display elements, 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 100 of the present invention has excellent bending durability, 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 as the inside or the outside.

Examples of image display elements included in the image display device include organic EL display elements, inorganic EL display elements, liquid crystal display elements, plasma display elements, and field emission display elements.

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.

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

<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 of the stress-strain curve from the origin to the maximum stress value G _L '> The tensile test was carried out using a dynamic mechanical analysis device (DMA, Q-800, TA Instruments), and the measurement from the origin to the The slope of the maximum stress value. 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 502 is prepared. Fig. 2 is a cross-sectional view of a test piece. 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. The test piece was left at a temperature of 60° C. and a humidity of 90% RH for 1 day. Fixtures were installed on the 5 mm length area of the PC rod 501 of the test piece, and one of the jigs was fixed (in the test piece of FIG. 2, the upper end portion had a length of 5 mm area). Another jig (in the test piece of Fig. 2 is the area with a length of 5 mm at the lower end) was stretched at a speed of 100 μm/min under a temperature of 25°C to create a stress [Pa]-strain [%] curve. _{Calculate the slope G L} 'from the origin to the maximum stress in the obtained stress-strain curve.

[Production of Adhesive Sheet Containing Adhesive Layer] Put 2-ethylhexyl acrylate (2-EHA) and butyl acrylate into a 1 L reaction vessel including a cooling tube, a nitrogen introduction tube, a thermometer, and a stirrer according to the mixing amount shown in Table 1. (Butyl acrylate, BA), 2-propylheptyl acrylate (2-PHA), acrylic acid (AA), behenyl acrylate (C22A), octyl decyl acrylate (octyl decyl) acrylate, ODA) monomer mixed solution. Nitrogen gas was refluxed for 1 hour to remove oxygen in the container, and the internal temperature was maintained at 60°C. After the monomer mixture solution was uniformly mixed, the photopolymerization initiator benzyl dimethyl ketal (I-651) and 1-hydroxycyclohexyl phenyl ketone (I-184) were added in the amounts shown in Table 1. A UV lamp (10 mW) was irradiated while stirring to produce (meth)acrylic polymers A1 to A4.

[Table 1] (Meth) acrylic polymer Acrylic monomer (parts by mass) Photopolymerization initiator (parts by mass) 2-EHA BA 2-PHA AA C22A ODA 1-651 1-184 A1 92 3.5 2 - 0.5 2 0.05 0.05 A2 85 4 4 - 5 2 0.05 0.05 A3 95 - 2 - 1 2 0.05 0.05 A4 80 5 0.5 13 1 0.5 0.05 0.05

The obtained (meth)acrylic polymers A1 to A4, Tetra hydro furfuryl acrylate (THFA), isodecyl acrylate (Isodecyl acrylate, IDA), or isobornyl acrylate (IBOA) ), and 1-hydroxycyclohexyl phenyl ketone (I-184) were mixed in the compounding amounts shown in Table 2 to produce adhesive compositions B1 to B8.

[Table 2] Adhesive composition (Meth) acrylic polymer additive Photopolymerization initiator The slope from the origin to the maximum stress value G _L '(Pa) type Allocation amount (parts by mass) type Allocation amount (parts by mass) type Allocation amount (parts by mass) B1 A1 100 THFA 2 I-184 0.05 124 B2 A1 100 THFA 3.5 I-184 0.05 80 B3 A2 100 IDA 2 I-184 0.05 95 B4 A2 100 IOBA 4 I-184 0.05 180 B5 A3 100 IDA 2 I-184 0.05 75 B6 A2 100 IOBA 5.5 I-184 0.08 233 B7 A3 100 THFA 30 I-184 0.05 50 B8 A4 100 THFA 1 I-184 0.05 270

The adhesive composition B1 to the adhesive composition B8 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). Table 2 shows _{the slope G L} ′ from the origin to the maximum stress value in the stress-strain curve obtained by applying the adhesive layer to the tensile test.

The source of the compound used is shown below. 2-EHA: Tokyo Chemical Industry Co., Ltd., Japan BA: Tokyo Chemical Industry Co., Ltd., Japan 2-PHA: BASF, Germany AA: Tokyo Chemical Industry Co., Ltd., Japan C22A: Tokyo Chemical Industry Co., Ltd., Japan ODA: Miwon Specialty Chemical, South Korea I-651: BASF, Germany I-184: BASF, Germany THFA: Tokyo Chemical Industry Co., Ltd., Japan IDA: Tokyo Chemical Industry Co., Ltd., Japan IOBA: 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.

[Polarizer] A circular polarizing plate is prepared as the polarizing plate 103. Prepare a straight line with Triacetyl Cellulose (TAC) film (KC2UA, manufactured by Konica Minolta Co., Ltd., thickness 25 μm), alignment film, polarizer layer, and outer coating in sequence Polarizing plate. The 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 panel 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. fit. 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 was connected to the touch sensor panel of the touch sensor panel. The sensor pattern layer side is attached. The optical laminate 100 (Example 1 to Example 6 and Comparative Example 1 to Comparative Example 2) having the layer structure shown in FIG. 1 was obtained. The bonding surfaces of the front panel, circular polarizer, touch sensor panel, 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 following bending test was performed on the produced optical layered body 100. The results are shown in Table 3.

＜Bending test＞ For the optical laminate, an evaluation test to confirm the flexibility was performed using a bending evaluation device (manufactured by Science Town, STS-VRT-500). 3(a) and 3(b) are diagrams schematically showing the method of this evaluation test. As shown in Figure 3(a) and Figure 3(b), set the two mounting tables 601 and 602 that can be moved separately with a gap C of 5 mm (bending radius of 2.5 mm) or a gap C of 3 mm (bending radius of 1.5 mm) ) Is arranged so that the center in the width direction is located at the center of the gap C, and the optical laminate is fixedly arranged so that the front surface plate is located on the upper side (Figure 3(a)). Then, the two mounting tables 601 and 602 are rotated upward by 90 degrees with the position P1 and the position P2 as the center of the rotation axis, and bending force is applied to the region of the laminate corresponding to the gap C of the mounting table (Figure 3(b)) . After that, the two mounting tables 601 and 602 are returned to their original positions (Fig. 3(a) ). After completing the above series of operations, count the number of additional bending forces as one. After repeating this at a temperature of 60° C. and a humidity of 90% RH, it was confirmed whether or not bubbles were generated in the adhesive layer in the region corresponding to the gap C between the mounting table 601 and the mounting table 602 of the optical layered body 100. The moving speed of the mounting table 601 and the mounting table 602 and the additional step of the bending force were set to the same conditions in the evaluation test of any optical laminate. A: Even if the number of additional bending forces reaches 50,000, no bubbles are generated. B: Air bubbles were generated when the number of additional bending force was 20,000 or more and less than 50,000. C: When the number of times the bending force is applied is 10,000 or more and less than 20,000, bubbles are generated. D: Air bubbles were generated when the number of additional bending forces was less than 10,000.

[table 3] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative example 1 Comparative example 2 First adhesive layer B1 B2 B3 B4 B5 B6 B7 B8 Second adhesive layer B1 B2 B3 B4 B5 B6 B1 B7 Flexibility (60/90, 2.5R) A A A A A A C D Flexibility (60/90, 1.5R) A B A B B B D D

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 601, 602: Mounting table P1, P2: position C: gap

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 method of measuring a stress-strain value by a tensile test. Figures 3(a) and 3(b) are schematic diagrams for explaining the bending test.

100: Optical laminate

101: front panel

102: The first adhesive layer

103: Polarizing plate

104: second adhesive layer

105: back panel

Claims (5)

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 temperature of the first adhesive layer and the second adhesive layer When the slope from the origin to the maximum stress value in the stress [Pa]-strain [%] curve at 60°C and humidity 90%RH is set to G _L1 'and G _L2 ', the following equations (1) and equations are satisfied (2): 70≦G _L1 '≦250 (1) 70≦G _L2 '≦250 (2). The optical laminate according to claim 1, which satisfies the following equations (1') and (2'): 90≦G _L1 '≦150 (1') 90≦G _L2 '≦150 (2'). The optical laminate according to claim 1 or 2, wherein the back panel is a touch sensor panel. A display device includes the optical laminate according to any one of claim 1 to claim 3. The display device according to claim 4, which can be bent with the front surface plate side as the inner side.

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