JP2021144118A - Optical laminate and display device - Google Patents

Abstract

To provide an optical laminate which suppresses generation of air bubbles in adhesive layers when bent, and a display device comprising the same.SOLUTION: An optical laminate provided herein comprises a front plate, a first adhesive layer, a polarizing plate, a second adhesive layer, and a back plate arranged in the described order, and the first and second adhesive layers satisfy the following expressions (1), (2): 70≤GL1'≤250 ...(1), 70≤GL2'≤250 ...(2), where GL1' and GL2' respectively represent slopes from the origins to maximum stress values on respective stress [Pa] -strain [%] curves at 60°C and 90%RH.SELECTED DRAWING: Figure 1

Description

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

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

Japanese Unexamined Patent Publication No. 2018-027995

An optical laminate in which a plurality of layers are laminated via a pressure-sensitive adhesive layer has a problem that bubbles are likely to be generated in the pressure-sensitive adhesive layer when bent, and bubbles are likely to be generated particularly in a high-temperature and high-humidity environment.

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

The present invention provides an optical laminate and a display device illustrated below.
[1] A front plate, a first pressure-sensitive adhesive layer, a polarizing plate, a second pressure-sensitive adhesive layer, and a back plate are provided in this order.
Said first adhesive layer and the second pressure-sensitive adhesive layer, the temperature 60 ° C., stress at humidity 90% RH [Pa] - Strain [%] inclination from the origin on the curve to a maximum stress value each G _{L1 'and} when the G _L2 ', satisfy the following formula (1) and (2), the optical stack.
70 ≤ _GL 1'≤ 250 (1)
_{70 ≦ G L2 '≦ 250 (} 2)
[2] The optical laminate according to [1], which satisfies the following formulas (1') and (2').
90 ≤ _GL 1'≤ 150 (1')
90 ≤ _GL 2'≤ 150 (2')
[3] The optical laminate according to [1] or [2], wherein the back plate 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 plate side inside.

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

It is the schematic sectional drawing which shows an example of the optical laminated body which concerns on this invention. It is a schematic diagram explaining the method of measuring a stress-strain value by a tensile test. It is the schematic explaining the bending test.

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

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

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

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

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

Stress - inclination of up to maximum stress value from the origin in the strain curve G _L ']
Temperature 60 ° C. of the first adhesive layer 102 and the second adhesive layer 104, stress at humidity 90% RH [Pa] - Strain slope of each _{G L1} from the origin on the curve (%) to the maximum stress value 'and G _{When L2'is set} , the optical laminate 100 satisfies the following formulas (1) and (2).
70 ≤ _GL 1'≤ 250 (1)
_{70 ≦ G L2 '≦ 250 (} 2)

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

The optical laminate 100 satisfying the formulas (1) and (2) is less likely to generate bubbles in the pressure-sensitive adhesive layer even when bent. In particular, even if it is bent in a high temperature and high humidity environment, it is possible to suppress the generation of air bubbles in the pressure-sensitive adhesive layer. The optical laminate 100 satisfying the formulas (1) and (2) is 20,000 times so that the bending radius is 2.5 mm at a temperature of 60 ° C. and a humidity of 90% RH, for example, according to the description in the column of Examples described later. The durability of the pressure-sensitive adhesive layer can be improved to the extent that bubbles are not generated even if the adhesive layer is repeatedly bent. The generation of bubbles in the pressure-sensitive adhesive layer can be determined by observation under an optical microscope.

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

The optical laminate 100 preferably satisfies the following formulas (1') and (2').
90 ≤ _GL 1'≤ 150 (1')
90 ≤ _GL 2'≤ 150 (2')
The optical laminate 100 satisfying the formulas (1') and (2') can further suppress the generation of air bubbles in the pressure-sensitive adhesive layer even when bent in a high-temperature and high-humidity environment.

Further, when the front plate is bent inward, the optical laminate 100 preferably satisfies the following formula (3) or (3').
_{G L1 '≦ G L2' (} 3)
_GL1 '< _GL2 '(3')
When the front plate is bent outward, the optical laminate 100 preferably satisfies the following formula (4) or (4').
_GL1 '≧ _GL2 '(4)
_GL1 '> _GL2 '(4')
When the optical laminate 100 is bent, a large stress is generated by the adhesive layer on the inner diameter side. Thus, G L _'is smaller, the pressure-sensitive adhesive layer having excellent stress relaxation resistance, by arranging such that the inside when bent, more generation of air bubbles in the adhesive layer of the optical stack 100 It can be suppressed.

G L _', the type and amount of monomers constituting the base polymer in the pressure-sensitive adhesive composition for use in the pressure-sensitive adhesive layer, the kind and amount of the polymerizable compound, the active energy ray type and dose and minority By doing so, the desired numerical range can be obtained. For example the base polymer contained in the adhesive composition, when containing many structural units derived from the number 10 or more long chain alkyl (meth) acrylic monomer carbon, G L _'tends to decrease. As pressure-sensitive adhesive composition is polymerizable compound having 10 or more long chain alkyl carbon (meth) acrylic monomer, when containing much dilution monomers, G L _'tends to decrease. For example, tetrahydrofurfuryl acrylate can be used as a diluting monomer. For example, as pressure-sensitive adhesive composition is a polymerizable compound, when containing a large amount of compounds having a cyclic structure such as cyclohexyl group, in G L _'tends to be increased.

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

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

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

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

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

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

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

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

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

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

The active energy ray-polymerizable compound is, for example, a (meth) acrylate monomer having at least one (meth) acryloyloxy group in the molecule; obtained by reacting two or more kinds of functional group-containing compounds, and at least two in the molecule. Examples thereof include (meth) acrylic compounds such as (meth) acryloyloxy group-containing compounds such as (meth) acrylate oligomers having individual (meth) acryloyloxy groups. The pressure-sensitive adhesive composition may contain 0.1 part by mass or more or 1 part by mass or more of the active energy ray-polymerizable compound with respect to 100 parts by mass of the base polymer, and may contain 10 parts by mass or less or 5 parts by mass or less. can.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

The thickness of the thermoplastic resin film is usually 100 μm or less, preferably 80 μm or less, more preferably 60 μm or less, still more preferably 40 μm or less, still more preferably 30 μm or less, from the viewpoint of enhancing flexibility. It is usually 5 μm or more, preferably 10 μm or more.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

_{<Slope GL} '> from the origin to the maximum stress value in the stress-strain curve
The slope from the origin to the maximum stress value was measured by performing a tensile test using a dynamic mechanical analyzer (DMA, Q-800, manufactured by TA Instruments). First, as shown in FIG. 2, a test piece was prepared in which the ends of two polycarbonate (PC) bars 501 were joined to each other via an adhesive layer 502. FIG. 2 is a cross-sectional view of the test piece. The shape of the pressure-sensitive adhesive layer 502 was width × length × thickness 6 mm × 10 mm × 25 μm, and the shape of the PC bar 501 was width × length × thickness 6 mm × 20 mm × 1 mm. The adhesive area between the pressure-sensitive adhesive layer 502 and the PC bar 501 was 6 mm × 10 mm in width × length. The test piece was left at a temperature of 60 ° C. and a humidity of 90% RH for 1 day. A jig was attached to a region having a length of 5 mm at both ends of the PC bar 501 of the test piece, and one jig (a region having a length of 5 mm at the upper end in the test piece of FIG. 2) was fixed. The other jig (the region having a length of 5 mm at the lower end in the test piece of FIG. 2) was pulled at a speed of 100 μm / min in an environment of a temperature of 25 ° C. to create a stress [Pa] -strain [%] curve. .. The resulting stress - in strain curve, the stress from the origin was calculated slope G _{L 'to} maximum.

[Preparation of adhesive sheet containing adhesive layer]
2-Ethylhexyl acrylate (2-EHA), butyl acrylate (BA), 2-ethyl acrylate in a 1 L reaction vessel equipped with a cooling tube, a nitrogen introduction tube, a thermometer and a stirrer in the amounts shown in Table 1. A monomer mixed solution of propylheptyl (2-PHA), acrylic acid (AA), behenyl acrylate (C22A), and octyldecyl acrylate (ODA) was added. Nitrogen gas was recirculated for 1 hour to remove oxygen in the container, and the internal temperature was maintained at 60 ° C. After uniformly mixing the monomer mixture solution, the photopolymerization initiator benzyldimethylketal (I-651) and 1-hydroxycyclohexylphenylketone (I-184) were added in the blending amounts shown in Table 1. UV lamps (10 mW) were irradiated with stirring to produce (meth) acrylic polymers A1 to A4.

The obtained (meth) acrylic polymers A1 to A4, tetrahydrofurfuryl acrylate (THFA), isodecyl acrylate (IDA) or isobornyl acrylate (IBOA), and 1-hydroxycyclohexylphenyl ketone (I-184). , Are mixed in the blending amounts shown in Table 2 to produce pressure-sensitive adhesive compositions B1 to B8.

The pressure-sensitive adhesive compositions B1 to B8 were applied on a release film A (polyethylene terephthalate film, thickness 38 μm) coated with a silicon release agent so as to have a thickness of 25 μm. A release film B (polyethylene terephthalate film, thickness 38 μm) was bonded onto the release film B and irradiated with UV to prepare an adhesive sheet composed of the release film A / adhesive layer / release film B. The conditions for UV irradiation were an integrated light intensity of 400 mJ / cm ² and an illuminance of 1.8 mW / cm ² (UVV standard). Subjected to tensile testing a pressure-sensitive adhesive layer, the stress - up to the maximum stress value from the origin in the strain curve of slope G _{L 'shown} in Table 2.

The sources of the compounds used are as follows.
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 , 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 plate]
As the front plate 101, a film having a hard coat layer formed on one surface of the resin film was prepared. The resin film was a polyimide resin film having a thickness of 40 μm. The hard coat layer was a layer having a thickness of 10 μm and formed from a composition containing a dendrimer compound having a polyfunctional acrylic group at the end.

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

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

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

[Preparation of optical laminate]
As shown in Table 3, the pressure-sensitive adhesive sheet composed of the pressure-sensitive adhesive composition shown in Table 2 is used as the first pressure-sensitive adhesive layer 102, and the side of the front plate 101 that does not have the hard coat layer and the side of the polarizing plate 103 that does not have the hard coat layer and the TAC film side of the polarizing plate 103. Was pasted together. Further, the pressure-sensitive adhesive sheet composed of the pressure-sensitive adhesive composition shown in Table 2 is used as the second pressure-sensitive adhesive layer 104 as shown in Table 3, and the retardation layer side of the circularly polarizing plate and the touch sensor pattern layer side of the touch sensor panel are used. Was pasted together. Optical laminates 100 (Examples 1 to 6 and Comparative Examples 1 to 2) having the layer structure shown in FIG. 1 were obtained. The front plate, circularly polarizing plate, touch sensor panel, and adhesive layer were subjected to double-sided corona treatment before bonding. TEC-4AX (manufactured by Ushio, Inc.) was used for the corona treatment.

The following bending test was performed on the produced optical laminate 100. The results are shown in Table 3.

<Bending test>
An evaluation test for confirming the flexibility of the optical laminate was carried out using a bending evaluation facility (STS-VRT-500 manufactured by Science Town). FIG. 3 is a diagram schematically showing the method of this evaluation test. As shown in FIG. 3, two individually movable mounting tables 601, 602 are arranged so that the gap C is 5 mm (bending radius 2.5 mm) or the gap C is 3 mm (bending radius 1.5 mm). The optical laminate was fixedly arranged so that the center in the width direction was located at the center of the gap C and the front plate was located on the upper side (FIG. 3A). Then, the two mounting tables 601, 602 were rotated upward by 90 degrees with the position P1 and the position P2 as the center of the rotation axis, and a bending force was applied to the region of the laminated body corresponding to the gap C of the mounting tables (FIG. 3 (b)). After that, the two mounting tables 601, 602 were returned to their original positions (FIG. 3 (a)). After completing the above series of operations, the number of times the bending force was applied was counted as one. After repeating this at a temperature of 60 ° C. and a humidity of 90% RH, it was confirmed whether or not air bubbles were generated in the pressure-sensitive adhesive layer in the region corresponding to the gap C of the mounting tables 601, 602 of the optical laminate 100. The moving speed of the mounting tables 601, 602 and the pace of application of the bending force were set to the same conditions in the evaluation test for all the optical laminates.
A: No bubbles were generated even when the number of times the bending force was applied reached 50,000.
B: Bubbles were generated when the number of times the bending force was applied was 20,000 or more and less than 50,000.
C: Bubbles were generated when the number of times the bending force was applied was 10,000 or more and less than 20,000.
D: Bubbles were generated when the number of times the bending force was applied was less than 10,000.

100 optical laminate, 101 front plate, 102 first adhesive layer, 103 polarizing plate, 104 second adhesive layer, 105 back plate, 501 polycarbonate bar, 502 adhesive layer, 601,602 mounting table.

Claims (5)

A front plate, a first pressure-sensitive adhesive layer, a polarizing plate, a second pressure-sensitive adhesive layer, and a back plate are provided in this order.
Said first adhesive layer and the second pressure-sensitive adhesive layer, the temperature 60 ° C., stress at humidity 90% RH [Pa] - Strain [%] inclination from the origin on the curve to a maximum stress value each G _{L1 'and} when the G _L2 ', satisfy the following formula (1) and (2), the optical stack.
70 ≤ _GL 1'≤ 250 (1)
_{70 ≦ G L2 '≦ 250 (} 2) The optical laminate according to claim 1, which satisfies the following formulas (1') and (2').
90 ≤ _GL 1'≤ 150 (1')
90 ≤ _GL 2'≤ 150 (2') The optical laminate according to claim 1 or 2, wherein the back plate is a touch sensor panel. A display device including the optical laminate according to any one of claims 1 to 3. The display device according to claim 4, wherein the display device can be bent with the front plate side inside.

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