WO2021176853A1

WO2021176853A1 - Optical stack and flexible image display device

Info

Publication number: WO2021176853A1
Application number: PCT/JP2021/000973
Authority: WO
Inventors: 智煕柳; 東輝金; 恩瑛金
Original assignee: 住友化学株式会社
Priority date: 2020-03-06
Filing date: 2021-01-14
Publication date: 2021-09-10
Also published as: TW202140260A; KR20220146424A; CN115210614A

Abstract

The objective of the present invention is to provide an optical stack capable of constituting a flexible image display device, with which deformation after bending is cannot be seen easily and curling can be suppressed. The optical stack 1 comprises a front face plate 2, a first adhesive layer 3, a circular polarizing plate 4, a second adhesive layer 5, and a back face plate 6 in this order. The absolute value of the difference in gradient (kPa) value from the origin to the maximum stress value in the strain (%)-stress (kPa) curve obtained in an environment where the temperature and relative humidity of the first adhesive layer 3 and second adhesive layer 5 are 60°C and 90%, respectively, is 0.8 or less.

Description

Optical laminate, flexible image display device

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

In recent years, the development of a foldable flexible image display device has been promoted. In order to maintain the flatness of the display surface even when the image display device is repeatedly folded and unfolded, not only the image display element can withstand deformation, but also the polarizing layer laminated on the image display element. Films such as plates also need to withstand deformation. Conventionally, an image display device that suppresses the occurrence of wrinkles at a bent portion of a fold has been proposed (see, for example, Patent Document 1).

JP-A-2019-91030

The optical laminate constituting the flexible image display device tends to remain deformed at the bent portion, and in this case, the reflected image is distorted and the visibility of the image deteriorates. In addition, bending may cause new curl in the optical laminate. This curl is a phenomenon in which the end edge of the optical laminate orthogonal to the bending axis warps or warps, and it is required to reduce this. Therefore, an object of the present invention is to provide an optical laminate that can form a flexible image display device, in which deformation is less likely to be visually recognized after bending and curl generation can be suppressed. .. Another object of the present invention is to provide a flexible image display device including such an optical laminate.

The present invention includes a front plate, a first pressure-sensitive adhesive layer, a circularly polarizing plate, a second pressure-sensitive adhesive layer, and a back plate in this order, and is obtained in an environment of a temperature of 60 ° C. and a relative humidity of 90%. The absolute value of the difference between the values of the slope (kPa) from the origin to the maximum stress value in the strain (%) -stress (kPa) curve of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer is 0.8 or less. Provide an optical laminate.

In this optical laminate, the value of the inclination (kPa) of the first pressure-sensitive adhesive layer is 0.15 to 0.9, and the value of the inclination (kPa) of the second pressure-sensitive adhesive layer is 0. It is preferably 1 to 0.9.

This optical laminate may include a glass plate-like body having a front plate having a thickness of 5 to 50 μm.

The present invention also provides a flexible image display device including the above-mentioned optical laminate and a back plate including an image display element.

According to the present invention, it is possible to provide an optical laminate that can form a flexible image display device, that is less likely to be deformed after bending and that can suppress the occurrence of curl. Further, it is possible to provide a flexible image display device including such an optical laminate.

It is a figure which shows the optical laminated body which concerns on one Embodiment of this invention. (A) is a plan view, and (B) is an IB-IB cross-sectional view of (A). Both (A) and (B) are diagrams for explaining a tensile test using a dynamic mechanical analyzer. Both (A) and (B) are diagrams for explaining a bending test of an optical laminate. It is sectional drawing which shows how to obtain a step and width. Both (A) and (B) are schematic views explaining the static bending durability test.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In each figure, the same parts or corresponding parts are designated by the same reference numerals, and duplicate description will be omitted.

The optical laminate of the present embodiment constitutes a flexible image display device as one of the embodiments, for example, an organic electroluminescence (organic EL) display device, an inorganic electroluminescence (inorganic EL) display device, a liquid crystal display device, and an electroluminescent display. Equipment, etc. This flexible image display device may have a touch panel function by being provided with a touch sensor.

<Optical laminate>
As shown in FIG. 1, the optical laminate 1 of the present embodiment is intended to be folded in two in a flat shape as seen in a flexible image display device. As shown in FIGS. 1A and 1B, the optical laminate 1 of the present embodiment has a rectangular shape in a plan view, and has a front plate 2, a first adhesive layer 3, and a circularly polarizing plate. 4, the second pressure-sensitive adhesive layer 5, and the back plate 6 are laminated in this order, and have flexibility as a whole.

The size of the rectangle of the optical laminate 1 can be, for example, one side length of 10 mm or more and 600 mm or less, and when it has a short side and a long side, for example, the length of the short side is 10 mm or more and 300 mm or less. Yes, the length of the long side is 50 mm or more and 600 mm or less. The thickness of the optical laminate 1 is, for example, 100 μm or more and 500 μm or less.

The optical laminate 1 can be bent at any position. Here, "bending" means that a planar object is bent. The bending radius of the bent portion may be 15 mm or less, 10 mm or less, or 5 mm or less. The bending radius is, for example, in the range of 0.5 mm to 5.0 mm. As shown in FIG. 1, when the bending shaft 8 is set in the central portion of the optical laminated body 1, the bending shaft 8 is bent by bending the optical laminated body 1 so that the side having the front plate 2 is the inner side surface. The sides having the front plates of both wings centered on the above can be opposed (faced) so as to be substantially parallel to each other. In this facing state, the sides having the front plates may or may not be in contact with each other. Further, "bending" includes a form of refraction in which the angle of the inner surface is larger than 0 degrees and less than 180 degrees unless otherwise specified, and the bending radius of the inner surface is close to zero, or the refraction angle of the inner surface is 0 degrees. Morphology is included.

(Bending test)
It is preferable that the optical laminate 1 is less likely to have a step in the vicinity of the bending shaft 8 when the bent state is returned to the flat state. Specifically, the temperature is 60 in a state of being bent so as to face each other with the bending shaft 8 as the center and the sides having the front plate 2 facing each other at a surface-to-surface distance (opposing distance) = 3.0 mm (bending radius = 1.5 mm). Let stand for 6 hours under the conditions of ° C. and relative humidity (RH) of 90%. At this time, in order to easily maintain the bent state, it is preferable to sandwich a jig having a thickness of 3.0 mm between the sides having the front plate 2. Then, the optical laminate 1 is returned to the state before bending. Then, it is placed on a flat surface so that the side having the front plate 2 faces upward.

Then, in the cross-sectional shape of the optical laminate 1 near the bending axis 8, the average value of the minimum height position and the maximum height position (step 1, step 2) of both wings around the bending axis is obtained, and the difference thereof. Let be "step". In addition, the horizontal distance between the highest height positions on both wings is defined as the "width".
At this time, the "step" is preferably 560 μm or less, more preferably 520 μm or less, and further preferably 460 μm or less. The "width" is preferably 15 mm or more, more preferably 18 mm or more, and even more preferably 20 mm or more. The "step / width" (μm / mm) ratio is preferably 30 or less, more preferably 25 or less, and even more preferably 23 or less. The height position and width were measured by using a three-dimensional measuring device (model name: PREMIUM-600C) manufactured by Ammon Tech to measure the outermost step 1, step 2, and width. N = 5 is measured and the average value is calculated.

<First adhesive layer, second adhesive layer>
For each of the first pressure-sensitive adhesive layer 3 and the second pressure-sensitive adhesive layer 5, a strain (%) -stress (kPa) curve is obtained in an environment of a temperature of 60 ° C. and a relative humidity of 90%, and the maximum is further increased from the origin. When the value of the slope (kPa) up to the stress value is obtained, the absolute value of the difference is 0.8 or less. This absolute value is preferably 0.6 or less, and more preferably 0.3 or less.
This absolute value may be greater than 0.0 or greater than or equal to 0.05. By taking these values, the optical laminate 1 does not remain deformed after bending, and the occurrence of curl can be suppressed.

When the pressure-sensitive adhesive layer is subjected to a tensile test, a strain-stress curve can be drawn with strain on the horizontal axis and stress on the vertical 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. In the strain-stress curve of the pressure-sensitive adhesive layer obtained in an environment with a temperature of 60 ° C. and a relative humidity of 90%, the slope G from the origin to the maximum stress value is (maximum stress value) / (strain when the stress is maximum). It is represented by. G reflects not only the stress change when the pressure-sensitive adhesive layer is elastically deformed but also the stress change when the pressure-sensitive adhesive layer is plastically deformed, and can be an index of durability until the pressure-sensitive adhesive layer is cohesively broken. When G is large, the stress generated with respect to the strain of the pressure-sensitive adhesive layer is large, and the pressure-sensitive adhesive layer has excellent cohesive force. When G is small, the stress generated with respect to the strain of the pressure-sensitive adhesive layer is small, and the pressure-sensitive adhesive layer is easily deformed. G can be determined according to the method described in the column of Examples described later.

The value of the inclination (kPa) of the first pressure-sensitive adhesive layer 3 is preferably 0.15 to 0.9, more preferably 0.2 to 0.6, and 0.2 to 0.5. Is more preferable. The value of the inclination (kPa) of the second pressure-sensitive adhesive layer 5 is preferably 0.1 to 0.9, more preferably 0.1 to 0.6, and 0.2 to 0. It is more preferably .5.

G is the type and amount of the monomer constituting the base polymer contained in the pressure-sensitive adhesive composition used for the pressure-sensitive adhesive layer; the type and amount of the polymerization initiator, the cross-linking agent and other additives; the active energy ray, heat and the like. By adjusting the factors that change the degree of cross-linking of the above, the desired numerical range can be obtained. For example, when the base polymer contained in the pressure-sensitive adhesive composition contains a large amount of structural units derived from a monomer having a reactive functional group, G tends to be large. Examples of the reactive functional group include a hydroxyl group, a carboxyl group, an amino group, an amide group, an epoxy group and the like.

The first pressure-sensitive adhesive layer 3 and the second pressure-sensitive adhesive layer 5 may both be composed of one layer or two or more layers, but are preferably composed of one layer. Is. The second pressure-sensitive adhesive layer 5 may be the same as or different from the first pressure-sensitive adhesive layer 3 in the composition, compounding components, thickness, etc. of the pressure-sensitive adhesive composition described below.

The first pressure-sensitive adhesive layer 3 and the second pressure-sensitive adhesive layer 5 are mainly composed of (meth) acrylic resin, rubber resin, urethane resin, ester resin, silicone resin, and polyvinyl ether resin (base polymer). ) Can be composed of the pressure-sensitive adhesive composition. The pressure-sensitive adhesive composition constituting the first pressure-sensitive adhesive layer 3 and the second pressure-sensitive adhesive layer 5 is a pressure-sensitive adhesive composition using a (meth) acrylic resin as a base polymer, which is excellent in transparency, weather resistance, heat resistance, and the like. The thing is suitable. The pressure-sensitive adhesive composition may be an active energy ray-curable type or a thermosetting type.

Examples of the (meth) acrylic resin used in the pressure-sensitive adhesive composition include (meth) butyl (meth) acrylate, ethyl (meth) acrylate, isooctyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. A polymer or copolymer containing one or more acrylates 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) acrylate compound, (meth) 2-hydroxypropyl acrylate compound, (meth) hydroxyethyl acrylate compound, (meth) acrylamide compound, and N, N-dimethylaminoethyl (meth) acrylate compound. , A monomer having a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, etc., such as a glycidyl (meth) acrylate compound. As the monomer constituting the (meth) acrylic resin, a photoreactive compound having a benzoyl group can also be used, and the compound described as Chemical Formula 1 in Korean Patent Publication No. 10-2019-0005427 is exemplified. Such photoreactive compounds are activated by additional photocuring to induce additional cross-linking, so that durability can be improved.

The pressure-sensitive adhesive composition may contain only the above-mentioned base polymer, but usually further contains a cross-linking agent. The cross-linking agent is a metal ion having a divalent value or higher and forming a carboxylic acid metal salt with a carboxyl group, a polyamine compound forming an amide bond with the carboxyl group, and a carboxyl group. Examples thereof include a polyepoxy compound that forms an ester bond with, a polyol, and a polyisocyanate compound that forms an amide bond with a carboxyl group. The cross-linking agent is preferably a polyisocyanate compound.

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

The active energy ray-polymerizable compound is, for example, a (meth) acrylate monomer having at least one (meth) acryloyloxy group in the molecule; obtained by reacting two or more kinds of functional group-containing compounds, and at least 2 in the molecule. Examples thereof include (meth) acrylic compounds such as (meth) acryloyloxy group-containing compounds such as (meth) acrylate oligomers having individual (meth) acryloyloxy groups. The pressure-sensitive adhesive composition can contain 0.1 part by mass or more of the active energy ray-polymerizable compound with respect to 100 parts by mass of the solid content of the pressure-sensitive adhesive composition, and is 10 parts by mass or less, 5 parts by mass or less, or 2 parts by mass. Can include less than one copy.

Examples of the photopolymerization initiator include benzophenone, benzyl dimethyl ketal, 1-hydroxycyclohexylphenyl 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 powders and other inorganic powders). Etc.), antioxidants, UV absorbers, dyes, pigments, colorants, antifoaming agents, corrosion inhibitors, photopolymerization initiators and other additives can be included.

The first pressure-sensitive adhesive layer 3 and the second pressure-sensitive adhesive layer 5 can be formed by applying an organic solvent-diluted solution of the pressure-sensitive adhesive composition on a substrate and drying it. The first pressure-sensitive adhesive layer 3 and the second pressure-sensitive adhesive layer 5 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 3 and the second pressure-sensitive adhesive layer 5 is not particularly limited, but is preferably, for example, 1 μm or more and 100 μm or less, more preferably 3 μm or more and 50 μm or less, and 20 μm or more. There may be.

From the viewpoint of improving the cohesive force of the first pressure-sensitive adhesive layer 3 and the second pressure-sensitive adhesive layer 5, the first pressure-sensitive adhesive layer 3 and the second pressure-sensitive adhesive layer 5 were designated as a reference pressure-sensitive adhesive layer having a thickness of 150 μm. Occasionally, the shear modulus at a temperature of 25 ° C. is preferably 0.01 MPa or more, more preferably 0.02 MPa or more, preferably 0.50 MPa or less, and even more preferably 0.10 MPa or less. , 0.08 MPa or less. The storage elastic modulus can be measured using a viscoelasticity measuring device (MCR-301, Antonio Par). A plurality of pressure-sensitive adhesive layers are laminated so as to have a thickness of 150 μm, bonded to a glass plate, and then adhered to a measurement chip in a temperature range of -20 ° C to 100 ° C. The measurement can be performed under the condition of a heating rate of 5 ° C./min. When the shear modulus of the first pressure-sensitive adhesive layer 3 and the second pressure-sensitive adhesive layer 5 is within this range, the optical laminate 1 is unlikely to undergo cohesive failure even when bent, and is unlikely to generate air bubbles. The shear modulus can be adjusted by changing the type and content of the monomers constituting the base polymer contained in the pressure-sensitive adhesive composition, the additives, the degree of cross-linking, and the like.

The basic configuration of the optical laminate 1 of this embodiment is as described above. Conventionally, the optical laminate constituting the flexible image display device tends to remain deformed at the bent portion. In this case, the reflected image is distorted and the visibility of the image is deteriorated, and the optical laminate is newly curled by the bending. However, according to the optical laminate 1 of the present embodiment, no deformation remains after bending, and the occurrence of curl can be suppressed.

<Other configurations>
Hereinafter, more detailed configurations and materials of each member constituting the optical laminate 1 will be described.

(Front plate)
The material and thickness of the front plate 2 are not limited as long as it is a plate-like body capable of transmitting light, and the front plate 2 may be composed of only one layer or may be composed of two or more layers. Examples are resin plate-like bodies (for example, resin plates, resin sheets, resin films, etc.), glass plate-like bodies (for example, glass plates, glass films, etc.), resin plate-like bodies and glass products. A laminated body with a plate-shaped body can be mentioned. The front plate can be a layer constituting the outermost surface of the display device, and may have a function as a window film.

The thickness of the front plate 2 may be, for example, 10 μm or more and 1,000 μm or less, preferably 20 μm or more and 500 μm or less, more preferably 30 μm or more and 300 μm or less, and 30 μm or more and 100 μm or less. This thickness can be measured by a thin film thickness measuring device (model: digital gauge stand (DZ-501, manufactured by Sony Corporation)) in the same manner as the thickness of a polarizer, a protective film, etc., which will be described later.

When the front plate 2 is a resin plate-like body, the resin plate-like body is not limited as long as it can transmit light. Examples of the resin include triacetyl cellulose, acetyl cellulose butyrate, ethylene-vinyl acetate copolymer, propionyl cellulose, butyryl cellulose, acetyl propionyl cellulose, polyester, polystyrene, polyamide, polyetherimide, poly (meth) acrylic, and polyimide. , Polyether sulfone, Polysulfone, Polyethylene, Polypropylene, Polymethylpentene, Polyvinyl chloride, Polyvinylidene chloride, Polyvinyl alcohol, Polyvinylacetate, Polyetherketone, Polyetheretherketone, Polyethersulfone, Polymethylmethacrylate, Polyethylene terephthalate, Examples thereof include films formed of polymers such as polybutylene terephthalate, polyethylene naphthalate, polycarbonate, and polyamideimide. These polymers can be used alone or in combination of two or more. From the viewpoint of improving strength and transparency, a resin film formed of a polymer such as polyimide, polyamide, or polyamideimide is preferable. The thickness of the resin plate-like body may be, for example, 10 μm or more and 1,000 μm or less, preferably 20 μm or more and 500 μm or less, more preferably 30 μm or more and 300 μm or less, and may be 100 μm or less.

The front plate 2 may be a film having a hard coat layer provided on at least one surface of the base film to further improve the hardness. As the base film, a film made of the above resin can be used. The hard coat layer may be formed on one surface of the base film or may be formed on both surfaces. By providing the hard coat layer, a resin film having improved hardness and scratch resistance can be obtained. 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. Additives are not limited, and examples thereof include inorganic fine particles, organic fine particles, and mixtures thereof.

When the front plate 2 is a glass plate-like body, the plate-like body may be ultra-thin glass (Ultra-Thin Glass: UTG). The thickness of the ultrathin glass is preferably 5 to 50 μm. A commercially available glass plate can be thinned by etching, and the thickness of the glass plate can be adjusted according to the degree to obtain ultra-thin glass.

(Circular polarizing plate)
The circularly polarizing plate 4 of the present embodiment may be a circularly polarizing plate (λ / 4 plate) or an elliptical polarizing plate. That is, the "circularly polarized light" in the present embodiment is a concept including a circularly polarizing plate and an elliptical polarizing plate. The circularly polarizing plate 4 is formed by laminating a linearly polarizing plate having a polarizing element and a retardation film.

-Linear polarizing plate The linear polarizing plate includes a polarizing element and a protective film laminated on one side or both sides thereof. Examples of the linear polarizing plate include a stretched film on which a dichroic dye is adsorbed, a film containing a film obtained by applying and curing a composition containing a dichroic dye and a polymerizable compound as a polarizer, and the like. Specifically, as the dichroic dye, iodine or a dichroic organic dye is used. For dichroic organic dyes, C.I. I. Included are dichroic direct dyes made of disuazo compounds such as DIRECT RED 39 and dichroic direct dyes made of compounds such as trisazo and tetrakisazo.
The polarizer obtained by applying and curing a composition containing a dichroic dye and a polymerizable compound is a composition containing a dichroic dye having a liquid crystal display or a composition containing a dichroic dye and a polymerizable liquid crystal. Examples thereof include a polarizer containing a cured product of a polymerizable liquid crystal compound such as a layer obtained by applying and curing the above. A polarizer obtained by applying and curing a composition containing a dichroic dye and a polymerizable compound 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 polarizer that is a stretched layer The polarizer, which is a stretched film on which a dichroic dye is adsorbed, is usually a step of uniaxially stretching a polyvinyl alcohol-based resin film, and dichroic polyvinyl alcohol-based resin film. A step of adsorbing the dichroic dye by dyeing with a dye, a step of treating a polyvinyl alcohol-based resin film on which the dichroic dye is adsorbed with an aqueous boric acid solution, and a step of washing with water after the treatment with the aqueous boric acid solution. Can be manufactured after. The thickness of the polarizer is, for example, 2 μm or more and 40 μm or less. The thickness of the polarizer may be 5 μm or more, 20 μm or less, 15 μm or less, and further 10 μm or less.

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 acids, olefins, vinyl ethers, unsaturated sulfonic acids, and ammonium groups (mesides and the like).

The degree of saponification of the polyvinyl alcohol-based resin is usually about 85 mol% or more and 100 mol% or less, preferably 98 mol% or more. The polyvinyl alcohol-based resin may be modified, and for example, polyvinyl formal or polyvinyl acetal modified with aldehydes can 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, which is a stretched layer on which a bicolor dye is adsorbed, is usually a step of applying a coating liquid containing the polyvinyl alcohol-based resin on a base film, a step of uniaxially stretching the obtained laminated film, and a uniaxial stretching. By dyeing the polyvinyl alcohol-based resin layer of the laminated film with a dichroic dye, the dichroic dye is adsorbed to form a polarizer, and the film on which the dichroic dye is adsorbed is coated with a boric acid aqueous solution. It can be produced through a step of treating and a step of washing with water after treatment with an aqueous boric acid solution. The polarizing element, which is a stretched layer on which the dichroic dye is adsorbed, may peel off and remove the base film from the polarizing element, if necessary. 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, which is a stretched layer, may be incorporated into the laminate in the form in which a thermoplastic resin film is bonded to one side or both sides thereof. This thermoplastic resin film can function as a protective film for a polarizer or a retardation film. The thermoplastic resin film is, for example, a polyolefin resin such as a chain polyolefin resin (polypropylene resin, etc.), a cyclic polyolefin resin (norbornen resin, etc.); a cellulose resin such as triacetyl cellulose; polyethylene terephthalate, polyethylene na. A film made of a polyester resin such as phthalate or polybutylene terephthalate; a polycarbonate resin; a (meth) acrylic resin; or a mixture thereof can be used.

The thermoplastic resin film may or may not have a phase difference. From the viewpoint of thinning, the thickness of the thermoplastic resin film is usually 300 μm or less, preferably 200 μm or less, more preferably 100 μm or less, still more preferably 80 μm or less, still more preferably 60 μm or less. Is. The thickness of the thermoplastic resin film is usually 5 μm or more, preferably 10 μm or more. The thermoplastic resin film can be attached to the polarizer using, for example, an adhesive layer.

(2) Polarizer obtained by applying and curing a composition containing a dichroic dye and a polymerizable compound As a polarizing element obtained by applying and curing a composition containing a dichroic dye and a polymerizable compound, liquid crystallinity is used. A cured product of a polymerizable liquid crystal compound such as a layer obtained by applying a composition containing a polymerizable dichroic dye having a dichroic dye or a composition containing a dichroic dye and a polymerizable liquid crystal to a base film and curing the mixture. Included polarizers are included.

For the polarizer obtained by applying and curing the composition containing the dichroic dye and the polymerizable compound, the base film may be peeled off from the polarizer if necessary. The material and thickness of the base film may be the same as the material and thickness of the thermoplastic resin film described above. The polarizer may include an alignment film. The alignment film may be peeled off.

The polarizer obtained by applying and curing the composition containing the dichroic dye and the polymerizable compound may be incorporated into the optical laminate in the form of a thermoplastic resin film bonded to one side or both sides thereof. As the thermoplastic resin film, the same one as the thermoplastic resin film that can be used for the stretched film or the polarizer that is the stretched layer can be used. The thermoplastic resin film can be attached to the polarizer using, for example, an adhesive layer.

An overcoat (OC) layer may be formed as a protective layer on one side or both sides of a polarizer obtained by applying and curing a composition containing a dichroic dye and a polymerizable compound. Examples thereof include photocurable resins and water-soluble polymers. Examples of the photocurable resin include (meth) acrylic resin, urethane resin, (meth) acrylic urethane resin, epoxy resin, silicone resin and the like. Examples of the water-soluble polymer include poly (meth) acrylamide-based polymers; polyvinyl alcohol, ethylene-vinyl alcohol copolymer, ethylene-vinyl acetate copolymer, (meth) acrylic acid or its anhydride-vinyl alcohol co-weight. Examples thereof include vinyl alcohol-based polymers such as coalescence; carboxyvinyl-based polymers; polyvinylpyrrolidone; starches; sodium alginate; polyethylene oxide-based polymers. The thickness of the OC layer is preferably 20 μm or less, more preferably 15 μm or less, further preferably 10 μm or less, 5 μm or less, and 0.05 μm or more. , 0.5 μm or more.

The thickness of the polarizer obtained by applying and curing the composition containing the dichroic dye and the polymerizable compound 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. Is.

A circularly polarizing plate can be obtained by laminating a retardation film described later (for example, a retardation film containing a λ / 4 plate as a retardation layer) on a linearly polarizing plate. At this time, the angle formed by the absorption axis of the polarizer and the slow axis of the λ / 4 plate can be 45 ° ± 10 °.

-The retardation film The retardation film may include one layer or two or more retardation layers. The retardation layer can be a positive A plate such as a λ / 4 plate or a λ / 2 plate, and a positive C plate. The λ / 4 plate may have an inverse wavelength dispersibility. When the retardation layer includes a λ / 2 plate, the λ / 2 plate and the λ / 4 plate are laminated in order from the linearly polarizing layer side. When the retardation layer contains a positive C plate, the λ / 4 plate and the positive C plate may be laminated in order from the linear polarizing layer side, or the positive C plate and the λ / 4 plate may be laminated in order from the linear polarizing plate side. May be good.

The retardation layer may be formed from the resin material exemplified as the material of the protective film described above, 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 or a base film, and may have a bonding layer for bonding the λ / 4 plate and the λ / 2 plate. The bonding layer is a pressure-sensitive adhesive layer or an adhesive layer, and can be formed by using the above-mentioned pressure-sensitive adhesive composition or a known adhesive composition.

The thickness of the entire retardation film is not particularly limited, but can be, for example, 1 μm or more and 50 μm or less.

(Back plate)
As the back plate 6, a plate-like body capable of transmitting light, a component used in a normal display device, or the like can be used. Examples of the components used in the ordinary display device used for the back plate 6 include a separator, a touch sensor panel, an organic EL display element, and the like. The stacking order of the components in the display device is, for example, front plate / circular polarizing plate / separator, front plate / circular polarizing plate / organic EL display element, front plate / circular polarizing plate / touch sensor panel / organic EL display element, front. Examples thereof include a face plate / touch sensor panel / circular polarizing plate / organic EL display element. The back plate 6 is preferably a touch sensor panel.

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

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

An example of a capacitance coupling type touch sensor is 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, and more preferably 5 μm or more and 50 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. The thickness of the touch sensor pattern may be, for example, 1 μm or more and 20 μm or less.

The image display element may be accompanied by a touch sensor panel. As the touch sensor panel, as long as it is a sensor that can detect the touched position, the detection method is not limited, and the resistance film method, the capacitance coupling method, the optical sensor method, the ultrasonic method, and the electromagnetic induction coupling method are used. A touch sensor panel of a method, a surface acoustic wave method, or the like is exemplified. Since the cost is low, a touch sensor panel of a resistance film type or a capacitance coupling type is preferably used.

(Other adhesive layer)
In the optical laminate 1 of the present embodiment, in addition to the first pressure-sensitive adhesive layer 3 and the second pressure-sensitive adhesive layer 5, the pressure-sensitive adhesive layer used for bonding the linear polarizing plate and the retardation film, and the phase difference Other pressure-sensitive adhesive layers are used, such as the pressure-sensitive adhesive layer as the bonding layer in the film. The pressure-sensitive adhesive composition for forming these pressure-sensitive adhesive layers is not particularly limited, and for example, (meth) acrylic polymer, urethane-based polymer, polyester-based polymer, silicone-based polymer, polyvinyl ether-based polymer, and rubber-based polymer. Anything may be used as long as it contains a polymer such as a polymer as a main component. Here, the "main component" refers to a component containing 50% by mass or more of the total solid content of the pressure-sensitive adhesive composition. The pressure-sensitive adhesive composition may be an active energy ray-curable type or a thermosetting type.

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. It is an adhesive composition having a property of being able to adhere to an adherend such as, etc., and being cured by irradiation with active energy rays to adjust the adhesive force. 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. Further, if necessary, a photopolymerization initiator, a photosensitizer, or the like may be contained.

The pressure-sensitive adhesive layer can be formed by applying an organic solvent diluent of the above-mentioned pressure-sensitive adhesive composition on a substrate and drying it.

The thickness of the pressure-sensitive adhesive layer is, for example, preferably 3 μm or more and 100 μm or less, more preferably 5 μm or more and 50 μm or less, and may be 20 μm or less.

Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. For example, in the above embodiment, the plan view shape of the optical laminate is a rectangle having vertices of 90 °, but the vertices may be rounded and the sides may have dents. Further, the shape is not limited to a rectangle, and may be a circle or other shape.

Hereinafter, the contents of the present invention will be described more specifically with reference to Examples and Comparative Examples. The present invention is not limited to the following examples.

<Manufacturing of adhesive layer>
2-Ethylhexyl acrylate (2-EHA) and n-butyl acrylate (n-BA) shown in Table 1 were placed in a 1 L reactor equipped with a cooling device so that the nitrogen gas returned and the temperature could be easily controlled. , 2-propylheptyl acrylate (2-PHA), acrylic acid (AA), behenyl acrylate (C22A), octyldecyl acrylate (ODA), a monomer mixture was added. After refluxing the nitrogen gas for 1 hour to remove oxygen, the solution was maintained at 60 ° C. After uniformly mixing the above-mentioned monomer mixture, the photopolymerization initiator benzyldimethylketal (I-651) and 1-hydroxycyclohexylphenylketone (I-184) were added in the blending amounts shown in Table 1. An acrylic polymer (polymer A, polymer B, polymer C, polymer D) was produced by irradiating with a UV lamp (10 mW) with stirring.

The sources of the compounds used are as follows.
2-EHA: Tokyo Chemical Industry Co., Ltd., Japan n-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

For 100 parts by mass of each of the obtained acrylic polymers, 1.5 parts by mass of isodecyl acrylate (IDA) and 0.05 parts by mass of 1-hydroxycyclohexylphenyl ketone (I-184) were mixed and adhered. An agent composition was prepared. Each pressure-sensitive adhesive composition was applied on a release film A (polyethylene terephthalate film, thickness 38 μm) that had been subjected to silicone release treatment so as to have a thickness of 25 μm. Another release film B (polyethylene terephthalate film, thickness 38 μm) was bonded onto the release film B and irradiated with UV to prepare a pressure-sensitive adhesive sheet composed of the release film A / adhesive layer / release film B. The UV irradiation conditions were an integrated light intensity of 400 mJ / cm ² and an illuminance of 1.8 mW / cm ² (UVV standard). Table 2 shows the correspondence between each acrylic polymer and each pressure-sensitive adhesive layer. In addition, Table 2 also shows "G" obtained by the following method.

<Slope G from the origin to the maximum stress value>
The value of the slope (kPa) from the origin to the maximum stress value on the strain (%) -stress (kPa) curve measured in an environment with a temperature of 60 ° C. and a relative humidity of 90% using the pressure-sensitive adhesive layers A to D (“G). ") Was asked. For this, a tensile test was performed using a dynamic mechanical analyzer (DMA, Q-800, manufactured by TA Instruments). First, as shown in FIG. 2, a test piece in which the ends of two polycarbonate (PC) bars 101 and 101 were joined to each other via an adhesive layer was prepared. The shape of the pressure-sensitive adhesive layer 102 was width × length × thickness 6 mm × 10 mm × 25 μm, and the shape of the PC bars 101 and 101 was width × length × thickness 6 mm × 20 mm × 1 mm.
The adhesive area between the pressure-sensitive adhesive layer 102 and the PC bars 101 and 101 was 6 mm × 10 mm in width × length. A jig was attached to a region A having a length of 5 mm at both ends of the PC bar 501 of the test piece as a jig fixing portion, and one of the jigs was fixed. The other jig is attached to the region A, which is the fixing part of the other jig, and is pulled at a speed of 100 μm / min in an environment of a temperature of 60 ° C. and a relative humidity of 90%, and strain (%) -stress (MPa). ) Created a curve. In the obtained strain-stress curve, the slope (“G”) from the origin to the maximum stress was calculated.

A pressure-sensitive adhesive layer E was manufactured separately from the pressure-sensitive adhesive layers A to D. Using the same equipment as the equipment for producing polymers A to D, 68 parts by mass of butyl acrylate (BA), 30 parts by mass of methyl methacrylate (MMA), and 1 mass of 2-ethylhexyl acrylate (2-EHA). Acrylic polymer (polymer E) was produced by polymerizing 1 part by mass of acrylic acid (AA). To 100 parts by mass of this polymer E, 3 parts by mass of Coronate L (manufactured by Tosoh Corporation) as a cross-linking agent and 0.5 parts by mass of KBM-403 (manufactured by Shin-Etsu Chemical Co., Ltd.) as a silane coupling agent are mixed and adhered. The agent composition was prepared. This pressure-sensitive adhesive composition was applied to a release-treated film using an applicator so that the thickness after drying was 5 μm. The coating layer was dried at 100 ° C. for 1 minute to produce an adhesive layer E. Then, another release film that had been released was attached onto the pressure-sensitive adhesive layer. Then, it was cured for 7 days under the conditions of a temperature of 23 ° C. and a relative humidity of 50% to prepare a pressure-sensitive adhesive sheet provided with the pressure-sensitive adhesive layer E.

<Example 1>
[Linear polarizing plate]
A triacetyl cellulose (TAC) film (thickness 25 μm) was prepared as a base material.
A composition for forming an alignment film was applied onto the alignment film by a bar coating method. The coating was dried at 80 ° C. for 1 minute. Next, using the above UV irradiation device and wire grid, the coating film was irradiated with polarized UV to impart orientation performance to the coating film. The exposure amount was 100 mJ / cm ² (based on 365 nm). As the wire grid, UIS-27132 ## (manufactured by Ushio, Inc.) was used.
In this way, the alignment film was formed. The thickness of the alignment film was 100 nm. A composition for forming a polarizer containing a polymerizable liquid crystal compound and a dichroic dye was applied onto the formed alignment film by a bar coating method. The coating film was heat-dried at 100 ° C. for 2 minutes and then cooled to room temperature. A polarizer was formed by irradiating the coating film with ultraviolet rays at an integrated light amount of 1200 mJ / cm ^{2 (365 nm standard) using the above UV irradiation device.} The thickness of the obtained polarizer was 3 μm. A composition containing polyvinyl alcohol and water is applied onto the polarizer so that the thickness after drying is 0.5 μm, and dried at a temperature of 80 ° C. for 3 minutes to form a protective layer (protective film). bottom. In this way, a linear polarizing plate having a structure of a base material / an alignment film / a polarizer / a protective layer was produced.

[Front plate]
The following two types were prepared and used.
-Plate-shaped body made of polyamide-imide resin (Examples 1 to 5, Comparative Examples 1 and 2)
(Polyamide-imide film)
In a nitrogen gas atmosphere, 14.67 g (45.8 mmol) of 2,2'-bis (trifluoromethyl) benzidine (TFMB) and a water content of 200 ppm were prepared in a 1 L separable flask equipped with a stirring blade. -233.3 g of dimethylacetamide (DMAc) was added, and TFMB was dissolved in DMAc with stirring at room temperature. Next, 4.283 g (13.8 mmol) of 4,4'-oxydiphthalic dianhydride (OPDA) was added to the flask, and the mixture was stirred at room temperature for 16.5 hours. Then, 1.359 g (4.61 mmol) of 4,4'-oxybis (benzoyl chloride) (OBBC) and 5.609 g (27.6 mmol) of terephthaloyl chloride (TPC) were added to the flask, and the mixture was stirred at room temperature for 1 hour. .. Next, 4.937 g (48.35 mmol) of acetic anhydride and 1.501 g (16.12 mmol) of 4-picoline were added to the flask, and the mixture was stirred at room temperature for 30 minutes, heated to 70 ° C. using an oil bath, and further. The mixture was stirred for 3 hours to obtain a reaction solution. After cooling the obtained reaction solution to room temperature, 360 g of methanol and 170 g of ion-exchanged water were added to obtain a precipitate of polyamide-imide. It was immersed in methanol for 12 hours, collected by filtration and washed with methanol. Next, the precipitate was dried under reduced pressure at 100 ° C. to obtain a polyamide-imide (PAI) resin having a thickness of 40 μm.

(Composition for forming a hard coat layer)
30 parts by mass of polyfunctional acrylate (Miramer M340, manufactured by Miwon Specialty Chemical), 50 parts by mass of propylene glycol monomethyl ether dispersion (12 nm, solid content 40%) of nanosilica sol, 17 parts by mass of ethyl acetate, and a photopolymerization initiator. 2.7 parts by mass of (Irgacure-184, manufactured by Ciba Corporation) and 0.3 parts by mass of a fluorine-based additive (KY1203, manufactured by Shin-Etsu Chemical Industry Co., Ltd.) were mixed to obtain a composition for forming a hard coat layer. ..

(Making the front plate)
The composition for forming a hard coat layer is applied to one surface of a polyamide-imide film, the obtained coating film is dried at a temperature of 80 ° C. for 5 minutes, and a UV irradiation device (SPOT CURE SP-7, Ushio, Inc.) A hard coat layer was formed by irradiating with UV light having an exposure amount of 500 mJ / cm ^{2 (365 nm standard).} The coating was applied so that the thickness after curing was 10.0 μm. As described above, a front plate having a hard coat layer / polyamide-imide film structure was obtained.

-Glass plate-like body (Examples 6 and 7)
A glass plate (manufactured by Corning, 400 μm in thickness) was prepared. By etching, the glass was thinned to a thickness of 50 μm. The glass was chemically strengthened, and the glass was chamfered by ultrasonic polishing and cutting polishing using an end mill. In this way, a glass plate (front plate) having a thickness of 50 μm was produced.

[Optical laminate]
As the first embodiment, the surface opposite to the surface on which the hard coat layer of the front plate is laminated and one of the release films of the pressure-sensitive adhesive sheet provided with the pressure-sensitive adhesive layer B produced above are peeled off and exposed. After corona treatment was applied to the surface of the agent layer B, both were bonded together. Next, the surface of the pressure-sensitive adhesive layer B exposed by peeling off the other release film of the pressure-sensitive adhesive sheet and the surface of the linearly polarizing plate on the base material (TAC film) side are subjected to corona treatment, and then both are subjected to corona treatment. I pasted them together. After that, corona treatment is applied to the surface of the linear polarizing plate on the protective layer side and the surface of the pressure-sensitive adhesive layer E which is exposed by peeling off one release film of the pressure-sensitive adhesive sheet provided above. After that, both were pasted together. Next, the other release film was peeled off from the pressure-sensitive adhesive layer E to expose the pressure-sensitive adhesive layer E. In this way, a laminate having the composition of front plate / pressure-sensitive adhesive layer B / base material / alignment film / polarizer / protective layer / pressure-sensitive adhesive layer E was obtained.

A retardation film was prepared in which a λ / 4 plate composed of a layer in which a polymerizable liquid crystal compound was cured and a positive C layer composed of a layer in which a polymerizable liquid crystal compound was cured were laminated via an adhesive layer E. This retardation film was laminated on the laminated body via the adhesive layer E so that the λ / 4 plate side was the protective layer side of the laminated body to prepare a circularly polarizing plate. The slow axis of the λ / 4 plate was 45 ° with respect to the absorption axis of the polarizer.

After that, one release film was peeled off from another pressure-sensitive adhesive sheet provided with the pressure-sensitive adhesive layer B to expose the surface of the pressure-sensitive adhesive layer B. After corona treatment was applied to the surface of the positive C layer and the surface of the pressure-sensitive adhesive layer B, both were bonded together. Next, the other release film was peeled off from the pressure-sensitive adhesive layer B, and a substitute for the organic EL panel (35 μm polyimide (PI) film / pressure-sensitive adhesive layer A / 50 μm PI film) was laminated. In this way, the front plate / pressure-sensitive adhesive layer B / base material / alignment film / polarizer / protective layer / pressure-sensitive adhesive layer E / (λ / 4 layer) / pressure-sensitive adhesive layer E / positive C layer / pressure-sensitive adhesive layer B / An optical laminate of Example 1 having a configuration (substitute for an organic EL panel) was obtained.

While changing the adhesive to be used, the following optical laminates of Examples 2 to 7 and Comparative Examples 1 and 2 were produced in the same manner as in Example 1 above. In the following notation, "PAI" means the "front plate having the structure of the hard coat layer / polyamide-imide film" produced above, and "glass" means the "glass plate having a thickness of 50 μm" produced above. doing.

<Example 2>
Front plate (PAI) / Adhesive layer B / Base material / Alignment film / Polarizer / Protective layer / Adhesive layer E / (λ / 4 layer) / Adhesive layer E / Positive C layer / Adhesive layer A / Organic Substitute for EL panel <Example 3>
Front plate (PAI) / Adhesive layer C / Base material / Alignment film / Polarizer / Protective layer / Adhesive layer E / (λ / 4 layer) / Adhesive layer E / Positive C layer / Adhesive layer A / Organic Substitute for EL panel <Example 4>
Front plate (PAI) / Adhesive layer A / Base material / Alignment film / Polarizer / Protective layer / Adhesive layer E / (λ / 4 layer) / Adhesive layer E / Positive C layer / Adhesive layer A / Organic Substitute for EL panel <Example 5>
Front plate (PAI) / Adhesive layer A / Base material / Alignment film / Polarizer / Protective layer / Adhesive layer E / (λ / 4 layer) / Adhesive layer E / Positive C layer / Adhesive layer B / Organic Substitute for EL panel <Example 6>
Front plate (glass) / Adhesive layer B / Base material / Alignment film / Polarizer / Protective layer / Adhesive layer E / (λ / 4 layer) / Adhesive layer E / Positive C layer / Adhesive layer A / Organic Substitute for EL panel <Example 7>
Front plate (glass) / Adhesive layer A / Base material / Alignment film / Polarizer / Protective layer / Adhesive layer E / (λ / 4 layer) / Adhesive layer E / Positive C layer / Adhesive layer A / Organic EL panel substitute <Comparative example 1>
Front plate (PAI) / Adhesive layer D / Base material / Alignment film / Polarizer / Protective layer / Adhesive layer E / (λ / 4 layer) / Adhesive layer E / Positive C layer / Adhesive layer A / Organic EL panel substitute <Comparative example 2>
Front plate (PAI) / Adhesive layer A / Base material / Alignment film / Polarizer / Protective layer / Adhesive layer E / (λ / 4 layer) / Adhesive layer E / Positive C layer / Adhesive layer D / Organic EL panel substitute

Each of the following tests was performed using the optical laminates of Examples 1 to 7 and Comparative Examples 1 and 2.

<State after bending (flexion test)>
After cutting each optical laminate into a size of 20 mm × 110 mm, as shown in FIG. 3 (A), two

glass plates

201 and 201 having a thickness of 2 mm are attached to the substitute side of the organic EL panel as an adhesive. They were laminated using layers. The two

glass plates

201 and 201 have half the area of the optical laminate, and the pressure-sensitive

adhesive layers

202 and 202 have a thickness of 25 μm and are bonded to each other 40 mm apart from the center line of the optical laminate. When this is placed on a flat table, the

glass plates

201 and 201 come into contact with each other on their side surfaces. 1. Bend the optical laminate along the bending axis in the center so that the optical laminate side is on the inside (Fig. 3 (B)), and use a plate with a thickness of 3.0 mm (3.0 mm thick) between the opposing surfaces. By setting it to 5R (not shown in FIG. 3), "glass / adhesive layer / optical laminate ('U' shape sandwiching a 3.0 mm thick plate) / adhesive layer / glass A sample for measurement was prepared. After leaving it in an oven at a temperature of 60 ° C. and a relative humidity of 90% for 6 hours, the shape of the bent portion, which was a bent portion, was confirmed.

(Step, width)
The bent optical laminate was opened, placed on a flat table with the front plate side facing upward, and the shape of wrinkles was measured using a two-dimensional measuring machine. In the cross-sectional shape as shown in FIG. 4, the average value of the differences between the _{lowest height position (H 1} ) and the highest height position (H ₂₁ , H _{22) on both wings around the bending axis.} Was obtained, and the difference was defined as a "step" ({(H _21- H ₁ ) + (H _22- H ₁ )} / 2). Further, the horizontal distance (D) between the highest height positions on both wings was defined as "width". The results are shown in Table 3.

(Visibility)
With the optical laminate opened as described above, the distortion of the bent portion was observed using the reflection image of the fluorescent lamp, and the smoothness of the surface was visually evaluated. This observation is in a dark room (0.02 lux when the fluorescent lamp is off, 2000 lux when the optical laminate is placed when the fluorescent lamp is on. To measure this illuminance, "YL-102 Digital Light Meter" (manufactured by UNITS) Was used) and indoors (about 300 lux when the fluorescent lamp was turned on). The evaluation criteria are as follows. The evaluation results are shown in Table 3.
A: The reflected elephant distortion of the fluorescent lamp was hardly seen in the dark room and the room.
B: Reflective distortion of the fluorescent lamp in the dark room was observed, but it was hardly observed in the room.
C: Reflective elephant distortion of the fluorescent lamp was noticeably observed in the dark room and the room.

(curl)
The curl in the open state of the optical laminate as described above was visually evaluated. The evaluation criteria are as follows. The evaluation results are shown in Table 3.
A: No curl generation phenomenon was observed at the end side orthogonal to the bending axis in the plane.
C: In the plane, a curl generation phenomenon was observed at the end edge orthogonal to the bending axis.

<Bending durability>
A static bending durability test was performed using an optical laminate. As shown in FIG. 5, a bending device (STS-VRT-500 manufactured by Science Town) provided with two

stages

301 and 301 was prepared, and the optical laminate was placed on the stages 301 and 301 (). FIG. 5 (A). The distance (gap) between the two

stages

301 and 301 was set to 3 mm (1.5R). The

stages

301 and 301 can swing about between the two stages (gap), and the two

stages

301 and 301 initially form the same plane. In an environment of a temperature of 60 ° C. and a relative humidity of 90%, the two

stages

301 and 301 were rotated by 90 degrees to close the two stages 301 and 301 (FIG. 5 (B)), and the two

stages

301 and 301 were held in this posture for 10 days. After 10 days, it was confirmed whether or not bubbles or peeling occurred in the pressure-sensitive adhesive layer. The evaluation criteria are as follows. The evaluation results are shown in Table 3.
A: No bubbles / peeling occurred inside the adhesive.
C: Bubbles / peeling occurred inside the adhesive.

In Table 3, the G value of the pressure-sensitive adhesive layer used for bonding the front plate and the base material is "G ₁ ", and the G value of the pressure-sensitive adhesive layer used for bonding the positive C layer and the substitute for the organic EL panel. Is displayed as "G _2". From these results, it can be _{seen that when the absolute value of the difference between the two G values (G 1} , G ₂ ) is small, both the visibility and the curl of the optical laminate are good.

The present invention can be used as one aspect of an image display device.

1 ... Optical laminate, 2 ... Front plate, 3 ... First pressure-sensitive adhesive layer, 4 ... Circularly polarized light plate, 5 ... Second pressure-sensitive adhesive layer, 6 ... Back plate, 8 ... Bending shaft.

Claims

A front plate, a first pressure-sensitive adhesive layer, a circularly polarizing plate, a second pressure-sensitive adhesive layer, and a back plate are provided in this order.
The slope (kPa) from the origin to the maximum stress value in the strain (%) -stress (kPa) curve of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer determined in an environment of a temperature of 60 ° C. and a relative humidity of 90%. An optical laminate in which the absolute value of the difference between the values of) is 0.8 or less.
The value of the inclination (kPa) of the first pressure-sensitive adhesive layer is 0.15 to 0.9, and the value of the inclination (kPa) of the second pressure-sensitive adhesive layer is 0.1 to 0. 9. The optical laminate according to claim 1.
The optical laminate according to claim 1 or 2, wherein the front plate includes a glass plate having a thickness of 5 to 50 μm.
The optical laminate according to any one of claims 1 to 3 is provided.
The back plate is a flexible image display device including an image display element.