TW202208960A - Laminated body, image display device, and manufacturing method retain adhesion between adhesive agent layers and optical components even if there is no enough time for aging - Google Patents

Abstract

A laminated body which sequentially comprises: a first optical component, a first adhesive agent layer, a second optical component, a second adhesive agent layer, and a third optical component, where the viscosities of the first adhesive agent layer and the second adhesive agent at temperature of 25 DEG C are 0.8 gf or above, and the laminated body satisfies the formula (1). The viscosity of the second adhesive agent layer at 25 DEG C is higher than the viscosity of the first adhesive agent layer at 25 DEG C, the shear elasticity coefficient of the first adhesive agent and the second adhesive agent at 25 DEG C is 0.5 MPa or less.

Description

Laminated body, image display device, and manufacturing method

The present invention relates to a laminate, and further relates to an image display device including the laminate, and a method for producing the laminate.

Patent Document 1 describes an optical member including a window film, a second adhesive film, a touch function portion, and a first adhesive film in this order, and proposes to adjust the temperature of the first adhesive film and the second adhesive film The distribution of storage elastic coefficients is within a specific range.

Patent Document 2 describes an adhesive composition for a display capable of bending, and proposes to set the ratio of the final stress after deformation to the initial stress at the beginning of deformation regarding the storage elastic modulus after hardening of the adhesive composition. within a specific range. [Prior Art Literature] [Patent Literature]

[Patent Document 1] Korean Laid-Open Patent Publication No. 10-2016-0053788 [Patent Document 2] Korean Laid-Open Patent Publication No. 10-2019-0069334

[The problem to be solved by the invention]

The optical laminated body used for an image display apparatus is usually manufactured by bonding a plurality of optical members with an adhesive layer. In order for the adhesive layer to exhibit its original performance in the next step, a step (aging) of curing the adhesive layer after coating may be required. In recent years, after an optical laminate is produced, the lead time until it is used in the next step has been shortened. Therefore, sufficient time is not given for aging, and air bubbles may be generated between the adhesive layer and the optical member or in the adhesive layer during bending.

An object of the present invention is to provide a layered product comprising, in this order, a first optical member, a first adhesive layer, a second optical member, a second adhesive layer, and a third optical member, wherein the third optical member is on the inner side. During bending, the adhesiveness between the adhesive layer and the optical member is maintained, and the generation of air bubbles between the adhesive layer and the optical member or in the adhesive layer is suppressed even if there is not enough time for aging. . [Means of Solving Problems]

The present invention provides the following laminates, image display devices, and methods for producing the laminates. [1] A layered product including, in this order, a first optical member, a first adhesive layer, a second optical member, a second adhesive layer, and a third optical member, wherein, The viscosity values of the first adhesive layer and the second adhesive layer at a temperature of 25°C are both 0.8 gf or more, and The laminated body satisfies the formula (1): The viscosity value at the temperature of the second adhesive layer at 25°C > the viscosity value at the temperature of the first adhesive layer at 25°C (1). [2] The laminate according to [1], wherein the viscosity values of the first adhesive layer and the second adhesive layer at a temperature of 25° C. are both 10.0 gf or less. [3] The laminate according to any one of [1] or [2], wherein the shear elastic coefficients of the first adhesive layer and the second adhesive layer at a temperature of 25° C. are both 0.5 below MPa. [4] The laminate according to any one of [1] to [3], wherein the first optical member is a front panel. [5] The laminate according to any one of [1] to [4], wherein the second optical member is a polarizing plate. [6] The laminate according to any one of [1] to [5], wherein the third optical member is a touch sensor panel. [7] An image display device including the laminate according to any one of [1] to [6]. [8] A method for producing a layered body, which is the method for producing a layered body according to [1], comprising: A step of bonding an optical member using an adhesive layer having a viscosity value of 0.8 gf or more at a temperature of 25°C. [Effect of invention]

According to the present invention, there is provided a layered product including a first optical member, a first adhesive layer, a second optical member, a second adhesive layer, and a third optical member in this order, which is bent with the third optical member as an inner side. Even if sufficient time is not given for aging, the adhesiveness between the adhesive layer and the optical member is maintained, and the generation of air bubbles between the adhesive layer and the optical member or in the adhesive layer is suppressed.

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

<Laminated body> A schematic cross-sectional view of the layered body is shown in FIG. 1 . The laminated body 100 includes, in this order, a first optical member 110 , a first adhesive layer 120 , a second optical member 130 , a second adhesive layer 140 , and a third optical member 150 . The layered body 100 is preferably such that the side of the first optical member 110 is the visible side. The viewable side refers to the viewable side of the image display device when the laminated body 100 is used for the image display device. In this specification, a 1st optical member, a 2nd optical member, and a 3rd optical member may be collectively called an optical member. In addition, in this specification, a 1st adhesive bond layer and a 2nd adhesive bond layer may be collectively called an adhesive bond layer.

The laminated body 100 can be bent so that the third optical member 150 side is inside. Being able to bend means that the laminated body can be bent without generating air bubbles between the adhesive layer and the optical member and in the adhesive layer. Bending includes a form of bending in which a curved surface is formed at the curved portion. In the bending form, the bending radius of the inner surface to be bent is not particularly limited. For example, 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. In addition, unless otherwise specified, "bending" includes the form of bending in which the angle of the inner surface of the bend is greater than 0 degrees and less than 180 degrees, and the bending radius of the inner surface is approximately zero, or the bending angle of the inner surface is included. A form with an angle of 0 degrees. When the bent portion is a curved line, the angle formed by the straight line sandwiching the bent portion is defined as the angle of the inner surface. Since the laminated body of this invention can bend, it is suitable for a flexible display.

[Static bending durability] When the static bending durability test was performed on the laminated body 100 with the third optical member 150 side as the inner side and a bending state with a bending radius of 2.5 mm maintained, at the bending portion, between the adhesive layer and the optical member, and There is a tendency that air bubbles are not easily generated in the adhesive layer. When the static bending durability test of the laminated body 100 is carried out, the time until air bubbles are first generated between the adhesive layer and the optical member and in the adhesive layer at the bending portion is preferably more than 48 hours, more preferably more than 48 hours. 72 hours. A static bending durability test can be performed by the method demonstrated in the Example mentioned later.

The layered body 100 may have a square shape, for example, in a plan view, preferably a square shape having long sides and short sides, and more preferably a rectangle. Each layer constituting the layered body 100 may be R-processed at the corners, notched at the ends, or punched.

The layered body 100 can be used in, for example, an image display device or the like. The image display device is not particularly limited, and examples thereof include organic electroluminescence (electroluminescence) display devices, inorganic electroluminescence (inorganic EL) display devices, liquid crystal display devices, and electroluminescence display devices. Since the laminated body 100 can be bent, it is suitable for a flexible display.

[Viscosity value at a temperature of the adhesive layer at 25°C] The viscosity values of the first adhesive layer and the second adhesive layer at a temperature of 25° C. are both 0.8 gf or more. The viscosity value is considered to be related to the initial adhesion force after bonding the adhesive layer and the optical member. Therefore, if the viscosity value is included in the above-mentioned range, it is presumed that even if sufficient time is not given for aging, a laminated body excellent in static bending durability can be obtained. When either or both of the viscosity values at 25°C of the first adhesive layer and the second adhesive layer are less than 0.8 gf, there is a tendency that interface peeling tends to occur after bending due to insufficient adhesion. The viscosity value in the temperature 25 degreeC of an adhesive bond layer was measured by the method demonstrated in the Example mentioned later.

From the viewpoint of being excellent in static bending durability, the viscosity values of the first adhesive layer and the second adhesive layer at a temperature of 25°C are both preferably 1.0 gf or more, more preferably 1.1 gf or more, and still more preferably 1.2. gf or more, particularly preferably 1.3 gf or more, still more preferably 1.4 gf or more, still more preferably 1.5 gf or more, particularly preferably 2.0 gf or more. The viscosity values of the first adhesive layer and the second adhesive layer at a temperature of 25°C can be, for example, 10.0 gf or less, preferably 9.0 gf or less, more preferably 8.0 gf or less, and more preferably 7.0 gf or less. It is preferably 6.0 gf or less, more preferably 5.0 gf or less, and still more preferably 3.8 gf or less. When the viscosity value at 25° C. of the first adhesive layer and the second adhesive layer exceeds 10.0 gf, the cohesive force inside the adhesive layer tends to decrease easily.

The layered body 100 satisfies the following formula (1). The viscosity value at the temperature of the second adhesive layer at 25°C > the viscosity value at the temperature of the first adhesive layer at 25°C (1) It was found that when the laminated body was bent with the third optical member side as the inner side, the viscosity value of the second adhesive layer at a temperature of 25°C was larger than the viscosity value of the first adhesive layer at a temperature of 25°C. There is a tendency to easily obtain better static bending durability. When the laminated body is bent with the third optical member side as the inner side, since the second adhesive layer is arranged at a position closer to the third optical member than the first adhesive layer, the bending radius becomes smaller, and therefore there is applied stress. Tendency to grow larger. Therefore, it is presumed that the adhesion state can be easily maintained by arranging the adhesive layer with a larger viscosity value as the second adhesive layer.

The viscosity value at the temperature of the adhesive layer at 25°C tends to be higher as the adhesive layer is softer. The viscosity value of the adhesive layer at a temperature of 25°C can be adjusted by selecting the type and amount of the monomer constituting the base polymer, or the additive (eg, acrylic monomer) added to the adhesive. The viscosity value at a temperature of 25°C of the adhesive layer can also be adjusted by adding an adhesion imparting agent (tackifier).

[Optical components] The optical member may be a constituent element used in a general image display device. When the laminated body 100 is used for an image display device, it can be attached to the image display device so that the first optical member 110 becomes the visible side, and it is preferable that the first optical member 110 constitutes the image display device. The outermost layer on the visual side is attached to the image display device.

As an optical member, a front panel, a polarizing plate, a touch sensor panel, an image display element, etc. are mentioned, for example. The first optical member 110 may be a front panel. The second optical member 130 may be a polarizing plate. The third optical member 150 may be a touch sensor panel or an image display element, and is preferably a touch sensor panel.

[front panel] The material and thickness of the front panel are not particularly limited as long as it is a plate-shaped body that can transmit light, and may be a single-layer structure or a multi-layer structure, and a glass-made plate-shaped body (eg, glass plate, glass film, etc.) can be exemplified. , a resin-made plate-shaped body (eg, a resin plate, a resin sheet, a resin film, etc.), a laminate of a resin-made plate-shaped body and a glass-made plate-shaped body. The front panel may be the outermost layer constituting the viewable side of the image display device.

As the glass plate, tempered glass for display is preferably used. The thickness of the glass plate is, for example, 10 μm or more and 1000 μm or less, or preferably 20 μm or more and 500 μm or less. By using the glass plate, an optical member having excellent mechanical strength and surface hardness can be formed.

The resin film is not limited as long as it can transmit light. For example, a film containing the following polymers can be mentioned: triacetyl cellulose, acetyl cellulose butyrate, ethylene-vinyl acetate copolymer, acyl cellulose, butyl cellulose, acetyl propyl cellulose, poly Ester, polystyrene, polyamide, polyetherimide, poly(meth)acrylic acid, polyimide, polyether, polystyrene, polyethylene, polypropylene, polymethylpentene, polyvinyl chloride , polyvinylidene chloride, polyvinyl alcohol, polyvinyl acetal, polyether ketone, polyether ether ketone, polymethyl (meth)acrylate, polyethylene terephthalate, polybutylene terephthalate ester, polyethylene naphthalate, polycarbonate, polyamide imide, etc. The polymers may be used alone or in combination of two or more. When the laminate is used for a flexible display, it is preferable to use a resin film formed of a polymer such as polyimide, polyimide, and polyimide, which can be configured to have excellent flexibility, And has high strength and high transparency. In addition, in this specification, "(meth)acrylic acid" means that either acrylic acid or methacrylic acid may be used. "(meth)", such as (meth)acrylate, also has the same meaning.

When the front panel is a resin film, the resin film may have a hard coat layer provided on at least one surface of the base film to further increase the hardness. The hard coat layer may be formed on one side of the base film, or may be formed on both sides. When the image display device described later is an image display device of a touch panel type, since the surface of the front panel becomes the touch surface, it is preferable to use a resin film having a hard coat layer. By providing the hard coat layer, a resin film with improved hardness and scratch resistance can be produced. The hard coat layer is, for example, a hardened layer of an ultraviolet curable resin. As an ultraviolet curable resin, (meth)acrylic resin, a silicone resin, a polyester resin, a urethane resin, an amide resin, an epoxy resin etc. are mentioned, for example. In order to increase hardness, the hard coat layer may contain additives. The additive is not limited, and examples thereof include inorganic fine particles, organic fine particles, or a mixture thereof. The thickness of the resin film is, for example, 10 μm or more and 500 μm or less, or preferably 20 μm or more and 100 μm or less.

The front panel not only has a function of protecting the front surface of the image display device, but also has a function as a touch sensor, a blue light blocking function, a viewing angle adjustment function, and the like.

[polarizing plate] The polarizer 130 can be a linear polarizer or a circular polarizer. The linear polarizer can be formed by layering a protective layer on one area of the polarizer. The linear polarizer has a property of transmitting linearly polarized light having a vibration plane orthogonal to the absorption axis when unpolarized light is incident. The linear polarizing plate may include a polyvinyl alcohol (hereinafter, sometimes abbreviated as "PVA (poly vinyl alcohol)")-based resin film as a polarizer, and may also be used for aligning a composition including a dichroic dye and a polymerizable compound. A cured film obtained by polymerizing a polymerizable liquid crystal compound. Compared with a polarizer of a PVA-based resin film including a stretching step, a polarizer obtained by coating a composition containing a dichroic dye and a polymerizable compound and curing it has no restrictions on the bending direction, which is preferable.

The linear polarizer may only include a polarizer and a protective layer, or may include any one or more of a substrate, a thermoplastic resin film, an overcoat layer and an alignment film in addition to the polarizer and the protective layer. The thickness of the linear polarizing plate is, for example, 2 μm or more and 100 μm or less, and preferably 5 μm or more and 60 μm or less.

[Polarizer] Examples of polarizers include hydrophilic polymers such as polyvinyl alcohol (hereinafter, also simply referred to as "PVA") films, partially formalized PVA films, and ethylene-vinyl acetate copolymer-based partially saponified films. The film is obtained by performing a dyeing process with a dichroic substance such as iodine or a dichroic dye, and a stretching process. From the viewpoint of being excellent in optical properties, a polarizer obtained by uniaxially stretching a PVA-based resin film dyed with iodine is preferably used.

The polyvinyl alcohol-based resin can be produced by saponifying the polyvinyl acetate-based resin. The polyvinyl acetate-based resin may be a copolymer of vinyl acetate and other monomers copolymerizable with vinyl acetate other than polyvinyl acetate which is a homopolymer of vinyl acetate. Examples of other monomers that can be copolymerized with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, acrylamides having an ammonium group, and the like.

The degree of saponification of the polyvinyl alcohol-based resin is usually about 85 mol % to 100 mol %, preferably 98 mol % or more. The polyvinyl alcohol-based resin may be modified, and for example, aldehyde-modified polyvinyl formal, polyvinyl acetal, or the like may be used. The average degree of polymerization of the polyvinyl alcohol-based resin is usually about 1,000 to 10,000, preferably about 1,500 to 5,000. The average degree of polymerization of the polyvinyl alcohol-based resin can be determined according to Japanese Industrial Standard (JIS) K 6726 (1994). When the average degree of polymerization is less than 1,000, it is difficult to obtain favorable polarization performance, and when it exceeds 10,000, the film processability may be poor.

As another method for producing a polarizer containing a PVA-based resin film, a method including the steps of first preparing a base film, applying a solution of a resin such as a polyvinyl alcohol-based resin on the base film, and drying to remove the solvent can be exemplified. etc. to form a resin layer on the base film. In addition, an undercoat layer may be formed in advance on the surface of the base film on which the resin layer is to be formed. As the base film, a resin film such as PET, or a film using a thermoplastic resin that can be used for a protective layer described later can be used. As a material of an undercoat layer, the resin etc. which bridge|crosslinked the hydrophilic resin used for a polarizer are mentioned.

Next, the amount of solvent such as moisture in the resin layer is adjusted as necessary, the base film and the resin layer are uniaxially stretched, and then the resin layer is dyed with a dichroic dye such as iodine, and the dichroic dye is adsorbed and aligned on the resin. layer. Next, if necessary, the resin layer in which the dichroic dye is adsorbed and aligned is treated with a boric acid aqueous solution, and a washing step of washing off the boric acid aqueous solution is performed. Thereby, the resin layer in which the dichroic dye is adsorbed and aligned, that is, a polarizer is produced. A known method can be adopted for each step.

The uniaxial stretching of the base film and the resin layer may be carried out before dyeing, during dyeing, or in boric acid treatment after dyeing, or may be uniaxially stretched in each of the plurality of stages. The base film and the resin layer can be uniaxially stretched in the MD direction (film conveying direction). In addition, the base film and the resin layer can be uniaxially stretched in the TD direction (direction perpendicular to the film conveying direction), and in this case, a so-called tenter method can be used. In addition, the stretching of the base film and the resin layer may be either dry stretching or wet stretching, wherein the dry stretching is performed in the atmosphere, and the wet stretching is performed in which the resin layer is swelled with a solvent. stretch in the state. In order to express the performance of the polarizer, the draw ratio is 4 times or more, preferably 5 times or more, and particularly preferably 5.5 times or more. There is no particular upper limit to the draw ratio, but from the viewpoint of suppressing breakage and the like, it is preferably 8 times or less.

The thickness of the polarizer including the PVA-based resin film 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.

As the manufacturing method of the polarizer of the cured film formed by aligning the composition containing a dichroic dye and a polymerizable compound, and polymerizing a polymerizable liquid crystal compound, it is possible to include coating on a base film via an alignment film containing A method for forming a polarizer with a composition for forming a polarizer of a polymerizable liquid crystal compound and a dichroic dye; The composition for forming a polarizer of a dye is a method of forming a polarizer by polymerizing and curing a polymerizable liquid crystal compound in a state of maintaining a liquid crystal state. The polarizer thus obtained is in a state of being laminated on the protective layer of the base film, and can also be used as a linear polarizing plate with a base film. As the base film, a thermoplastic resin film such as a polyethylene terephthalate film or the like can be used.

As the dichroic dye, a dye having a property that the absorbance in the long-axis direction of the molecule is different from the absorbance in the short-axis direction of the molecule can be used. pigment. Examples of such dichroic dyes include acridine dyes, oxazine dyes, cyanine dyes, naphthalene dyes, azo dyes, and anthraquinone dyes, among which azo dyes are preferred. The azo dyes include monoazo dyes, disazo dyes, trisazo dyes, tetrazo dyes, stilbene azo dyes, and the like, and more preferred are disazo dyes and trisazo dyes.

The polarizer-forming composition may contain a solvent, a polymerization initiator such as a photopolymerization initiator, a photosensitizer, a polymerization inhibitor, and the like. Regarding the polymerizable liquid crystal compound, dichroic dye, solvent, polymerization initiator, photosensitizer, polymerization inhibitor, etc. contained in the composition for forming a polarizer, known ones can be used, for example, Japanese Patent Laid-Open Those exemplified in Gazette No. 2017-102479 and Japanese Patent Laid-Open No. 2017-83843. Regarding the method of forming a polarizer using the composition for forming a polarizer, the method exemplified in the above-mentioned publication can also be employed.

The thickness of the polarizer obtained by coating 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, more preferably 1 μm or more and 5 μm or less. μm or less.

An overcoat layer (hereinafter also referred to as an OC (overcoat) layer) may be provided on the surface of the linear polarizer on the polarizer side. As a material which comprises an OC layer, a photocurable resin, a water-soluble polymer, etc. are mentioned, for example. As photocurable resin, (meth)acrylic resin, urethane resin, (meth)acrylate urethane resin, epoxy resin, silicone resin etc. are mentioned, for example. Examples of water-soluble polymers include poly(meth)acrylamide-based polymers; polyvinyl alcohol, ethylene-vinyl alcohol copolymers, ethylene-vinyl acetate copolymers, (meth)acrylic acid or its anhydride- Vinyl alcohol-based polymers such as vinyl alcohol copolymers; carboxyvinyl-based polymers; polyvinylpyrrolidone; starches; sodium alginate; polyethylene oxide-based polymers, etc. The thickness of the OC layer is preferably 20 μm or less, more preferably 15 μm or less, still more preferably 10 μm or less, may be 5 μm or less, and may be 0.05 μm or more, or 0.5 μm or more.

The polarizer produced by the method can peel off the base film, or can be used as a linear polarizer together with the base film. According to this method, since the base film can be peeled off, further thinning of the polarizer can be achieved.

[The protective layer] The protective layer has a function of protecting the surface of the polarizer. In the laminated body 100 , the linear polarizer may be generally arranged such that the protective layer is closer to the first optical member 110 side than the polarizer.

As the protective layer, for example, a thermoplastic resin film excellent in transparency, mechanical strength, thermal stability, moisture barrier properties, square shape, and stretchability can be used. Specific examples of such thermoplastic resins include: cellulose resins such as triacetyl cellulose; polyester resins such as polyethylene terephthalate and polyethylene naphthalate; polyether resins; polyether resins Resins; polycarbonate resins; polyamide resins such as nylon or aromatic polyamide; polyimide resins; polyolefin resins such as polyethylene, polypropylene, ethylene-propylene copolymer, etc.; with ring system and norbornene structure cyclic polyolefin resins (also known as norbornene-based resins); (meth)acrylic resins; polyarylate resins; polystyrene resins; polyvinyl alcohol resins, and mixtures of these. In the case where the two surface layers of the polarizer have protective layers, the two protective layers may be of the same type or of different types. The thickness of the thermoplastic resin film may be, for example, 3 μm or more and 50 μm or less, and preferably 5 μm or more and 30 μm or less.

The protective layer may be, for example, an organic layer or an inorganic layer. The organic layer or the inorganic layer may be a layer formed by a coating. The organic substance layer can be formed using a composition for forming a protective layer, for example, a (meth)acrylic resin composition, an epoxy resin composition, a polyimide resin composition, or the like. The composition for forming a protective layer may be an active energy ray hardening type or a thermosetting type. The inorganic material layer may be formed of, for example, silicon oxide or the like. In the case where the protective layer is an organic layer, the protective layer may be a layer called a hard coat layer.

When the protective layer is an organic layer, the protective layer can be produced by, for example, applying an active-energy-ray-curing-type protective layer-forming composition on a base film, and irradiating active energy to harden it. The description of the base film is applied to the base film. The base film is usually peeled off. As a method of apply|coating the composition for protective layer formation, a spin coating method etc. are mentioned, for example. When the protective layer is an inorganic material layer, the protective layer can be formed by, for example, a sputtering method, a vapor deposition method, or the like. When the protective layer is an organic layer or an inorganic layer, the thickness of the protective layer may be, for example, 0.1 μm or more and 10 μm or less, preferably 0.5 μm or more and 5 μm or less.

[Phase plate] The polarizing plate can function as a circular polarizing plate by including a linear polarizing plate and a retardation plate. A circular polarizer in which the linear polarizer and the retardation plate are arranged so that the absorption axis of the linear polarizer and the retardation axis of the retardation plate form a predetermined angle can exhibit an antireflection function. The retardation plate may include one or more than two retardation layers. When the retardation plate includes two retardation layers, it may be referred to as a first retardation layer and a second retardation layer in order from the polarizer side. The retardation layer may be one layer or two or more layers. The retardation layer may have an overcoat layer protecting the surface thereof, a base film supporting the retardation layer, and the like. Examples of the retardation layer include a retardation layer (λ/4 layer) imparting a λ/4 retardation, a retardation layer (λ/2 layer) imparting a λ/2 retardation, a positive C layer, and the like. The retardation plate preferably includes a λ/4 layer, and more preferably includes at least one of a λ/4 layer, a λ/2 layer, or a positive C layer. When the retardation plate includes the λ/2 layer, the λ/2 layer and the λ/4 layer are laminated in this order from the linearly polarizing plate side. When the retardation plate includes a positive C layer, the λ/4 layer and the positive C layer may be sequentially laminated from the linear polarizer side, or the positive C layer and the λ/4 layer may be sequentially laminated from the linear polarizer side. The thickness of the retardation plate 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 contain the resin film exemplified as the material of the thermoplastic resin film, or may contain a layer in which a polymerizable liquid crystal compound is cured. The retardation layer may further include an alignment film and a base film, and the λ/4 layer, the λ/2 layer, and the positive C layer may be joined by an interlayer bonding layer described later.

When the retardation layer includes a layer obtained by curing a polymerizable liquid crystal compound, it can be formed by applying a composition containing a polymerizable liquid crystal compound to a base film and curing it. An alignment film may also be formed between the base film and the coating layer. As the polymerizable liquid crystal compound, the polymerizable liquid crystal compound in the description of the polarizer can be used. The material and thickness of the base film may be the same as those of the thermoplastic resin film. When the retardation layer includes a layer obtained by curing a polymerizable liquid crystal compound, it may be incorporated into a laminate in the form of an alignment film and a base film.

A polarizing plate in which the linear polarizing plate and the retardation plate are arranged so that the absorption axis of the linear polarizing plate and the retardation axis of the retardation layer form a predetermined angle have an antireflection function, that is, can function as a circular polarizing plate. When the retardation plate includes the λ/4 layer, the angle formed by the absorption axis of the linear polarizer and the retardation axis of the λ/4 layer may be 45°±10°. The retardation layer may have positive wavelength dispersion or reverse wavelength dispersion. The λ/4 layer preferably has reverse wavelength dispersion. The linear polarizer and the retardation plate can be joined by the bonding layer described later.

[Interlayer bonding layer] The interlayer bonding layer is disposed between the retardation layers, for example, between the first retardation layer and the second retardation layer, and has the function of bonding the first retardation layer and the second retardation layer. The interlayer adhesive layer may include an adhesive or adhesive. The interlayer bonding layer is preferably an adhesive layer.

The thickness of the interlayer bonding layer is not particularly limited, but when an adhesive layer is used as the interlayer bonding layer, it is preferably 1 μm or more, may be 5 μm or more, usually 50 μm or less, and may be 25 μm or less . When the adhesive layer is used as the interlayer bonding layer, the thickness of the interlayer bonding layer is preferably 0.1 μm or more, may be 0.5 μm or more, preferably 10 μm or less, and may be 5 μm or less.

The adhesive used for the interlayer bonding layer can use the above-mentioned adhesive composition, or other adhesives, such as (meth)acrylic adhesives, styrene-based adhesives, Silicone adhesives, rubber adhesives, urethane adhesives, polyester adhesives, epoxy copolymer adhesives, etc.

As the adhesive used for the interlayer bonding layer, for example, one or two or more of water-based adhesives, active energy ray-curable adhesives, and the like can be formed in combination. As an aqueous adhesive, a polyvinyl alcohol-type resin aqueous solution, an aqueous two-component urethane emulsion adhesive, etc. are mentioned, for example. Active energy ray-curable adhesives are adhesives that are cured by irradiating active energy rays such as ultraviolet rays, and examples thereof include adhesives containing a polymerizable compound and a photopolymerizable initiator, adhesives containing a photoreactive resin, Adhesives containing binder resins and photoreactive crosslinking agents, etc. Examples of the polymerizable compound include photopolymerizable monomers such as photocurable epoxy-based monomers, photocurable acrylic monomers, and photocurable urethane-based monomers, and monomers derived from these monomers. oligomers, etc. Examples of the photopolymerization initiator include compounds containing substances that generate active species such as neutral radicals, anionic radicals, and cationic radicals by irradiation with active energy rays such as ultraviolet rays.

[Touch sensor panel] As a touch sensor panel, as long as it is a sensor capable of detecting the touched position, the detection method is not limited, and examples include resistive film method, electrostatic capacitance coupling method, optical sensor method, ultrasonic wave touch sensor panel of the method, electromagnetic induction coupling method, surface acoustic wave method, etc. From the viewpoint of low cost, it is preferable to use the touch sensor panel of the resistive film method and the electrostatic capacitive coupling method. The touch sensor panel may be arranged on the side opposite to the visible side of the laminate.

An example of a resistive film type touch sensor panel includes a pair of substrates arranged to face each other, an insulating spacer sandwiched between the pair of substrates, and a resistive film provided on the inner front surface of each substrate The transparent conductive film, and the touch position detection circuit. In an image display device provided with a resistive film type touch sensor panel, when the surface of the front panel is touched, the opposing resistive films are short-circuited, and current flows in the resistive film. The touch position detection circuit detects the voltage change at this time, so as to detect the touched position.

An example of a capacitive coupling-type touch sensor panel includes a substrate, a position detection transparent electrode provided on the entire surface of the substrate, and a touch position detection circuit. In an image display device provided with a capacitively coupled touch sensor panel, when the surface of the front panel is touched, at the touched point, the transparent electrode is grounded via the electrostatic capacitance of the human body. The touch position detection circuit detects the grounding of the transparent electrode, thereby detecting the touched position.

[image display element] The image display element includes, for example, a liquid crystal cell, an organic electroluminescence (organic EL) display element, an inorganic electroluminescence (inorganic EL) display element, a plasma display element, and an electric field emission type display element.

[Adhesive layer] The adhesive layer is a layer that is interposed between optical members to bond these. In this specification, "adhesive" refers to a substance that is a high-viscosity liquid or a gel-like solid in the state after curing reaction, and can be adhered only by applying a small pressure for a short time at room temperature. For example, it is also called a pressure-sensitive type. Then agent. On the other hand, the "adhesive" in this specification refers to an adhesive other than an adhesive (pressure-sensitive adhesive), and refers to an elastic modulus at a temperature of 25°C after curing, which is solid in a state after curing reaction The range of the adhesive is 100 MPa or more. The adhesive layer may include one layer, or may include two or more layers, and preferably includes one layer.

The shear elastic modulus [MPa] of the adhesive layer at a temperature of 25°C may be, for example, 0.5 MPa or less, preferably 0.4 MPa or less, more preferably 0.3 MPa or less, still more preferably 0.2 MPa or less, and particularly preferably 0.1 MPa or less . The shear elastic modulus [MPa] of the adhesive layer at a temperature of 25°C is usually 0.001 MPa or more, for example, 0.005 MPa or more or 0.01 MPa or more. The shear elastic modulus [MPa] at the temperature of the adhesive layer at 25°C was measured according to the method described in the section of Examples described later.

From the viewpoint of securing the adhesiveness, the thickness of the adhesive layer is preferably 4 μm or more, more preferably 5 μm or more, and still more preferably 10 μm or more. From the viewpoint of improving flexibility, the thickness of the adhesive layer is preferably 100 μm or less, more preferably 50 μm or less. The thickness of the adhesive layer was set as the maximum thickness of the adhesive layer.

The adhesive layer may contain an adhesive mainly composed of resins such as (meth)acrylic resins, rubber-based resins, urethane-based resins, ester-based resins, silicone-based resins, and polyvinyl ether-based resins. composition. Among them, an adhesive composition using a (meth)acrylic resin excellent in transparency, weather resistance, heat resistance, etc. as a raw material polymer is preferable. The adhesive composition may be of an active energy ray hardening type or a thermosetting type.

As the (meth)acrylic resin (base polymer) used in the adhesive composition, for example, butyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate can be preferably used. A polymer or copolymer of one or more of (meth)acrylates such as octyl ester and 2-ethylhexyl (meth)acrylate as monomers. In the base polymer, it is preferable to copolymerize a polar monomer. Examples of polar monomers include (meth)acrylic acid, 2-hydroxypropyl (meth)acrylate, hydroxyethyl (meth)acrylate, (meth)acrylamide, and N,N (meth)acrylate. - Monomers having a carboxyl group, a hydroxyl group, an amide group, an amine group, an epoxy group, and the like, such as dimethylaminoethyl ester and glycidyl (meth)acrylate.

The adhesive composition may contain only the base polymer, but may further contain a crosslinking agent. Examples of the crosslinking agent include: a metal ion having a valence of two or more, and a metal carboxylate salt is formed with a carboxyl group; a polyamine compound, and an amide bond is formed with a carboxyl group; a polyepoxy compound or A polyhydric alcohol that forms an ester bond with a carboxyl group; a polyisocyanate compound that forms an amide bond with a carboxyl group. Among them, polyisocyanate compounds are preferred.

The adhesive composition may contain an adhesive imparting agent. Examples of tackifiers include hydrocarbon-based tackifiers, terpene-based tackifiers, rosin-based tackifiers, phenol-based tackifiers, epoxy-based tackifiers, polyamide-based tackifiers, elastic System adhesion imparting agent, ketone-based adhesion imparting agent, etc.

Examples of hydrocarbon-based tackifiers include aliphatic hydrocarbon resins, aromatic hydrocarbon resins (eg, xylene resin, etc.), aliphatic cyclic hydrocarbon resins, aliphatic-aromatic petroleum resins (eg, styrene resins). -olefin-based copolymers, etc.), aliphatic-alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone-based resins, coumarone-indene-based resins, and the like.

Examples of terpene-based adhesion imparting agents include terpene-based resins such as α-pinene polymers and β-pinene polymers; modified terpene-based resins (eg, phenol modification, aromatic modification, hydrogenation modified terpene-based resins (such as terpene-phenol-based resins, styrene-modified terpene-based resins, hydrogenated terpene-based resins, etc.); and the like.

Examples of rosin-based adhesion imparting agents include unmodified rosin (raw rosin) such as gum rosin and wood rosin; modified rosin obtained by modifying unmodified rosin by hydrogenation, disproportionation, polymerization, or the like Rosins (eg, hydrogenated rosins, disproportionated rosins, polymerized rosins, other chemically modified rosins, etc.); various other rosin derivatives; and the like.

As a phenolic adhesion-imparting agent, a resol-type or novolak-type alkylphenol etc. are mentioned, for example.

The active energy ray-curable adhesive composition refers to an adhesive composition that has a property of being cured by irradiation with active energy rays such as ultraviolet rays or electron rays, and thus has adhesiveness even before the active energy rays are irradiated. In addition, it can be adhered to adherends such as films, and is cured by irradiation of active energy rays, and the properties of the adhesion force can be adjusted. The active energy ray-curable adhesive composition is preferably an ultraviolet-curable type. The active energy ray curable adhesive composition further contains a raw material polymer and an active energy ray polymerizable compound. Moreover, a photopolymerization initiator, a photosensitizer, etc. are also contained as needed.

The adhesive composition may contain fine particles for imparting light scattering properties, beads (resin beads, glass beads, etc.), glass fibers, resins other than base polymers, fillers (metal powder, other inorganic powders, etc.), antioxidants, Additives such as UV absorbers, dyes, pigments, colorants, defoamers, anti-corrosion agents, photopolymerization initiators, etc.

The adhesive layer can be formed by coating the adhesive composition on a substrate. When an active-energy-ray-curable adhesive composition is used, a cured product having a desired degree of hardening can be obtained by irradiating the formed first adhesive layer with active energy rays.

[other layers] The layered body 100 may include, as another layer, a bonding layer for bonding a linear polarizer and a retardation plate.

[lamination layer] The laminated body 100 may further include a bonding layer for bonding the linear polarizer and the retardation plate. The adhesive layer may be formed of an adhesive or an adhesive. Adhesives and adhesives can be used as exemplified in the above-mentioned interlayer adhesive layer.

[Manufacturing method of laminated body] The manufacturing method of a laminated body may include the process of bonding an optical member using the adhesive bond layer whose viscosity value in temperature 25 degreeC is 0.8 gf or more. Regarding the viscosity value of the adhesive layer, the shear elastic modulus and thickness at a temperature of 25° C., and the adhesive composition, the description in the above-mentioned adhesive layer applies.

In order to improve the adhesiveness, it is preferable to perform surface activation treatment such as corona treatment or plasma treatment on one or both surfaces of the bonding surface.

The adhesive layer can be prepared as an adhesive sheet. The adhesive sheet can be formed by preliminarily forming a layer containing an adhesive in a sheet shape on a release film (hereinafter, also referred to as a separator) that has undergone mold release treatment, and then laminating another layer on the adhesive layer. It is produced by a method of peeling off the film, etc. Each layer can be attached by a method of attaching the adhesive sheet from which one of the release films has been peeled off to one of the layers, then peeling off the other release film, and attaching the other layer.

The manufacturing method of a laminated body can include the following steps (a)-(d), for example. The manufacturing method of a laminated body is demonstrated with reference to FIG.2(a) - FIG.2(d). (a) Prepare the front panel laminate 30 including the release film 31 , the front panel 32 and the release film 33 , the adhesive sheet 40 including the light release film 41 , the first adhesive layer 42 , and the heavy release film 43 , and apply the laminate to the front panel laminate. One side of 30 peeled off the release film 33, and the side of the adhesive sheet 40 with the light release film 41 peeled off are subjected to corona treatment and lamination, so as to obtain the peeling film 31, the front panel 32, and the first adhesive in sequence. Step of the layered body 200 of the layer 42 and the re-isolation film 43 [ FIG. 2( a )].

(b) Prepare the circular polarizer laminate 50 including the release film 51 , the circular polarizer 52 , and the release film 53 , and peel off the release film from the surface of the laminate 200 from which the heavy separation film 43 is peeled off and from the circular polarizer laminate 50 The surface of 51 is subjected to corona treatment and then lamination is carried out to obtain a layered body 210 including the release film 31, the front panel 32, the first adhesive layer 42, the circular polarizer 52 and the release film 53 in sequence [Fig. 2 (b). )].

(c) Prepare the adhesive sheet 60 including the light release film 61 , the second adhesive layer 62 , and the heavy release film 63 , and peel off the light release film 61 from the adhesive sheet 60 on the surface where the release film 53 is peeled off from the laminate 210 . After corona treatment is performed on the surface of the film, the laminated body 220 including the release film 31, the front panel 32, the first adhesive layer 42, the circular polarizer 52, the second adhesive layer 62 and the re-isolation film 63 is obtained in sequence. steps [Figure 2(c)].

(d) Prepare the touch sensor layer 70 with the PET film, peel off the PET film 71 with the adhesive from the touch sensor layer 70 with the PET film, and peel off the heavy isolation film from the laminated body 220 The surface of 63 is subjected to corona treatment, and the surface is attached to the touch sensor layer 72 to obtain a release film 31, a front panel 32, a first adhesive layer 42, a circular polarizer 52, and a second adhesive layer in sequence. 62. After the laminate 230 of the touch sensor layer 72, peel off the release film 31 from the laminate 230 to obtain the front panel 32, the first adhesive layer 42, the circular polarizer 52, and the second adhesive layer 62 in sequence and the step of the layered body 240 of the touch sensor layer 72 [FIG. 2(d)].

<Image display device> The image display device of the present invention includes the laminate. The image display device is not particularly limited, and examples thereof include image display devices such as an organic EL display device, an inorganic EL display device, a liquid crystal display device, and an electroluminescence display device. The image display device may have a touch panel function. The laminate is suitable for an image display device having flexibility such as bending and bending. In the image display device, when the laminated body has a front panel, the laminated body is disposed on the viewable side of the image display device with the front panel facing the outside (the side opposite to the image display element side, that is, the viewable side). .

The image display device of the present invention can be used as mobile devices such as smart phones and input boards, televisions, digital photo frames, electronic billboards, measuring instruments or instruments, office equipment, medical equipment, computer equipment, and the like. Since the image display device of the present invention has excellent flexibility, it is suitable for flexible displays and the like. [Example]

Hereinafter, the present invention will be described in more detail by way of examples. Unless otherwise specified, "%" and "part" in an example are mass % and mass part.

[Determination of thickness] The measurement was performed using a contact-type film thickness measuring apparatus (“MS-5C” manufactured by Nikon Corporation). However, the polarizer, the retardation layer, and the alignment film were measured using a laser microscope (LEXT, manufactured by Olympus Co., Ltd.).

[Measurement of viscosity value at a temperature of 25° C.] The measurement of the viscosity value at a temperature of 25° C. of the adhesive layer was performed using a Texture Analyzer (STABLE MICRO SYSTEMS). The procedure for measuring the viscosity value at a temperature of 25° C. will be described with reference to (A) to (C) in FIG. 3 . First, in the joining step [(A) in FIG. 3 ], the release film was peeled off from the same adhesive sheet used in the Examples and Comparative Examples, and the release film was left to stand, and the diameter was adjusted at room temperature (25° C.). The 5 mm stainless steel cylinder 300 was brought close to the surface of the exposed adhesive layer 301, and after being pressed, it was maintained for 1 second with a bonding force based on a load of 100 g (contact area: 19.6 mm ² ). After joining, in the peeling step [FIG. 3(B)], when the stainless steel cylinder 300 is lifted at a speed of 60 mm/min, the peeling force measured is maximized [FIG. 3(C)] The measured value was taken as the viscosity value. In addition, the viscosity value in the temperature of 25 degreeC of an adhesive bond layer was measured 24 hours after an adhesive bond layer was produced.

[Measurement of shear elastic coefficient at a temperature of 25°C] The shear elastic modulus at a temperature of 25° C. of the adhesive layer was measured using a viscoelasticity measuring apparatus (MCR-301, Anton Paar). The same adhesive sheets as those used in the examples and comparative examples were set to 20 mm in width and 20 mm in length, the release film was peeled off, and a plurality of sheets were laminated so as to have a thickness of 150 μm and were bonded to a glass plate. In the state where the wafers were bonded, the measurement was performed in a temperature range of -20°C to 100°C under the conditions of a frequency of 1.0 Hz, a deformation amount of 1%, and a temperature increase rate of 5°C/min, and the shear elastic coefficient at a temperature of 25°C was confirmed. In addition, the shear elastic modulus in the temperature 25 degreeC of an adhesive bond layer was measured 24 hours after the adhesive bond layer was produced.

[Evaluation of static bending durability] FIG. 4(A) and FIG. 4(B) show the method of the static bending durability test (mandrel bending test). First, the layered body was cut into test pieces of 1 cm×10 cm. The layered body 401 was placed on the test plate 400 so that the front panel side was down, and an iron rod 402 having a diameter of 5 mm was placed thereon [ FIG. 4(A) ]. The test piece is folded and fixed together with the test plate 400 by hand so that the front panel becomes the outer side [ FIG. 4(B) ]. Maintain this state, and measure the maximum time during which no air bubbles are generated between the circularly polarizing plate and the adhesive layer, or in the adhesive layer. A: No bubbles were generated within 72 hours. B: Over 48 hours, and bubbles were generated within 72 hours. C: Over 24 hours, and bubbles were generated within 48 hours. D: Bubbles were generated within 24 hours.

[Manufacture of Adhesive Sheet C1 to Adhesive Sheet C8] In order to make it easier to adjust the temperature by refluxing nitrogen gas, a 1 L reactor equipped with a cooling device was charged with 2-ethylhexyl acrylate (2-ethylhexyl acrylate (2-ethylhexyl acrylate) shown in Table 1. hexyl acrylate (2-EHA), n-butyl acrylate (n-BA), β-carboxy ethyl acrylate (β-CEA), acrylic acid (AA), A monomer mixture of glycidyl methacrylate (GMA) and 2-Hydroxyethyl Methacrylate (2-HEMA). After refluxing nitrogen for 1 hour to remove oxygen, the solution was maintained at 60°C. After the monomer mixture was uniformly mixed, the photopolymerization initiators benzyl dimethyl ketal (I-651) and 1-hydroxycyclohexyl phenyl ketone (I-184) were added according to the preparation amounts shown in Table 1. ). A UV lamp (10 mW) was irradiated while stirring to manufacture (meth)acrylic resin A1 to (meth)acrylic resin A8. The obtained (meth)acrylic resin A1 to (meth)acrylic resin A8, compound T1 to compound T3, and 1-hydroxycyclohexyl phenyl ketone (I-184) were mixed in the amounts shown in Table 1 to produce an adhesive Agent composition B1 to adhesive composition B8. Apply the adhesive composition B1 to the adhesive composition B8 on the release film A (polyethylene terephthalate film, thickness 38 μm) coated with a silicon release agent in a thickness of 25 μm, A release film B (polyethylene terephthalate film, 38 μm thick) was bonded thereon, and UV irradiation was performed to prepare adhesive sheets C1 to C8 including release film A/adhesive layer/release film B. The viscosity value and shear elastic modulus at a temperature of 25°C were measured 24 hours after the production of the adhesive sheets C1 to C8. The conditions of UV irradiation were a cumulative light amount of 400 mJ/cm ² and an illuminance of 1.8 mW/cm ² (UVV standard).

[Table 1] adhesive composition Composition of (meth)acrylic resin (parts by mass) photopolymerization initiator additive photopolymerization initiator type 2-EHA BA β-CEA AA GMA 2-HEMA I-651 I-184 type Preparation amount (mass parts) type Preparation amount (mass parts) B1 A1 94 1 1 - 3.5 0.5 0.05 0.05 T1 5 I-184 0.05 B2 A2 91 5 1 0.1 2.1 0.8 0.05 0.05 T2 5 I-184 0.05 B3 A3 93 3 0.5 0.6 2.1 0.8 0.02 0 02 T3 8 I-184 0.05 B4 A4 77 15 2.5 2.5 0.8 2.2 0.05 0.05 T3 4 I-184 0.05 B5 A5 79 17 0.5 1.9 1.5 0.1 0.05 0.05 T2 8 I-184 0.05 B6 A6 91 1 3.5 - 3.5 1.0 0.10 0.10 T2 3 I-184 0.05 B7 A7 97 1.5 0.5 - 0.5 0.5 0.15 0.10 T1 5 I-184 0.05 B8 A8 91 1 3.5 - 3.5 1.0 0.05 0.05 T1 3 I-184 0.05 Parts by mass: parts by mass when the (meth)acrylic resin is 100 parts by mass

The abbreviations in Table 1 have the following meanings. 2-EHA: 2-Ethylhexyl acrylate (Tokyo Chemical Industry Co., Ltd.) BA: Butyl acrylate (Tokyo Chemical Industry Co., Ltd.) β-CEA: β-carboxyethyl acrylate (Sigma-Aldrich, USA) AA: Acrylic (Tokyo Chemical Industry Co., Ltd.) GMA: Glycidyl methacrylate (Sigma-Aldrich, USA) 2-HEMA: 2-Hydroxyethyl methacrylate (Tokyo Chemical Industry Co., Ltd.) I-651: Benzyl dimethyl ketal (BASF) I-184: 1-Hydroxycyclohexyl phenyl ketone (BASF) T1: 3,3,5-trimethylcyclohexyl acrylate (Miramer M1130, Miwon specialty chemical, Korea) T2: Lauryl acrylate (Miramer M120, Miwon specialty chemical, Korea) T3: Phenol (EO) acrylate (Miramer M140, Miwon specialty chemical, Korea)

<Example 1> (Preparation of front panel) After applying the following composition for hard coat layers on one surface of a transparent base film (polyamide imide film, thickness 40 μm) produced according to Example 4 of JP-A No. 2018-119141, The solvent was dried and UV-cured to produce a front panel (thickness 50 μm) in which a hard coat layer having a thickness of 10 μm was formed on one side of the base film. [Composition for forming a hard coat layer] Use a mixer to prepare 30 parts by mass of multifunctional acrylate (Specialty Chemical, MIWON, "MIRAMER M340") and 50 parts by mass of nano-silica sol dispersed in propylene glycol monomethyl ether ( Particle size 12 nm, solid content 40%), 17 parts by mass of ethyl acetate, 2.7 parts by mass of a photopolymerization initiator (BASF, I184), 0.3 parts by mass of a fluorine-based additive (Shin-Etsu Chemical Co., Ltd., KY1203), which is manufactured by filtering with a polypropylene (Polypropylene, PP) filter.

(Preparation of circular polarizing plate) A polyvinyl alcohol (PVA) film having an average degree of polymerization of about 2,400, a degree of saponification of 99.9 mol% or more, and a thickness of 20 μm was prepared. The PVA film was immersed in pure water at 30°C, and then immersed in an aqueous solution having a mass ratio of iodine/potassium iodide/water of 0.02/2/100 at 30°C to perform iodine dyeing (iodine dyeing step). The PVA film subjected to the iodine dyeing step was immersed in an aqueous solution with a mass ratio of potassium iodide/boric acid/water of 12/5/100 at 56.5°C for boric acid treatment (boric acid treatment step). The PVA film subjected to the boric acid treatment step was washed with pure water at 8° C., and then dried at 65° C. to obtain a polarizer with iodine adsorption and alignment to polyvinyl alcohol. The stretching of the PVA film is performed in the iodine dyeing step and the boric acid treatment step. The total draw ratio of the PVA film was 5.3 times. The thickness of the obtained polarizer was 7 μm.

The obtained polarizer and 13 μm thick cycloolefin polymer (Cyclo Olefin Polymer, COP) film (ZF-14, Japan Zeon (ZEON) Co., Ltd. make, the in-plane retardation value at a wavelength of 550 nm) 1 nm) were bonded with a nip roll via a water-based adhesive. While maintaining the tension of the obtained laminate at 430 N/m, drying was performed at 60° C. for 2 minutes to obtain a linear polarizing plate having a COP film on one side. In addition, the water-based adhesive was prepared by adding 3 parts by mass of carboxyl group-modified polyvinyl alcohol ("Kuraray Poval KL318", manufactured by Kuraray Co., Ltd.) and 1.5 parts by mass of water-soluble to 100 parts by mass of water. Polyamide epoxy resin ("SUMIREZ RESIN 650" (aqueous solution with a solid content concentration of 30%), manufactured by Tagoka Chemical Industry Co., Ltd.) was prepared.

The polarizer side of the linear polarizing plate and the retardation layer were bonded together via an acrylic adhesive layer with a thickness of 5 μm. The thickness of the retardation layer is 5 μm, and the layer structure is a λ/2 layer (thickness 2 μm) containing a liquid crystal compound cured layer / UV curing adhesive layer (thickness 2 μm) / containing a liquid crystal compound cured and formed layer of λ/4 layer (thickness 1 μm). In this way, a circular polarizing plate (thickness 30 μm, layer structure: COP film/polarizer/retardation layer) was produced.

(Preparation of the touch sensor laminate) An acrylic resin was applied to a glass plate to form a separation layer. Next, a light-transmitting electrode layer was formed on the separation layer, thereby fabricating a touch sensor layer (thickness 7 μm) including the light-transmitting electrode layer and the separation layer. Then, the release film A is laminated on the side opposite to the separation layer side of the translucent electrode layer. The release film B was laminated on the surface from which the glass plate was removed, and a touch sensor laminate having a layer structure of release film A/touch sensor layer/release film B was produced.

(production of laminated body) The adhesive sheet described in Table 2 was used for the adhesive layer, and the members were bonded together to produce a laminate. The laminated body sequentially includes a front panel (thickness 50 μm), a first adhesive layer (thickness 25 μm), a circular polarizer (thickness 30 μm), a second adhesive layer (thickness 25 μm), a touch sensor layer (thickness 7 μm), its total thickness is 137 μm. When bonding each member, corona treatment is performed on the bonding surface. After the produced laminate was left to stand for 24 hours in an environment with a temperature of 23° C. and a relative humidity of 55%, the static bending durability of the laminate was evaluated. The results are shown in Table 2.

<Example 2 and Comparative Examples 1 to 5> A laminate was produced in the same procedure as in Example 1, except that the adhesive sheets described in Table 2 were used for the first adhesive layer and the second adhesive layer. The static bending durability was evaluated for the laminated body. The time from the preparation of the adhesive layer to the evaluation of the static bending durability was the same as that of Example 1. The results are shown in Table 2.

[Table 2] Example Comparative example 1 2 1 2 3 4 5 first adhesive layer Viscosity value at 25°C (gf) 2.7 2.7 4.2 4.1 1.6 5.4 0.3 Shear elastic modulus (MPa) at 25°C 0.05 0.05 0.05 0.06 0.09 0.03 0.65 adhesive sheet C5 C5 C2 C3 C4 C7 C6 second adhesive layer Viscosity value at 25°C (gf) 3.4 4.2 3.4 3.4 1.6 0.3 0.7 Shear elastic modulus (MPa) at 25°C 0.06 0.05 0.06 0.06 0.09 0.65 0.59 adhesive sheet C1 C2 C1 C1 C4 C6 C8 Static Bending Durability A B C C C D D

30: Front panel laminate 31, 33, 51, 53: release film 32: Front panel 40, 60: Adhesive tablets 41, 61: Light isolation film 42: The first adhesive layer 43, 63: Heavy isolation film 50: Circular polarizing plate laminate 52: Circular polarizer 62: Second Adhesive Layer 70: Touch sensor layer with PET film 71: PET film with adhesive 72: Touch sensor layer 100, 200, 210, 220, 230, 240, 401: Laminate 110: First Optical Film/First Optical Member 120: The first adhesive layer 130: Second Optical Member/Polarizing Plate 140: Second Adhesive Layer 150: Third Optical Member 300: Cylinder 301: Adhesive layer 400: Test Board 402: Iron rod

FIG. 1 is a schematic cross-sectional view schematically showing an example of the laminate of the present invention. FIGS. 2( a ) to 2 ( d ) are schematic cross-sectional views schematically showing a method for producing a laminate of the present invention. (A)-(C) in FIG. 3 is a schematic diagram explaining the measuring method of the viscosity value in temperature 25 degreeC. FIG. 4(A) and FIG. 4(B) are schematic diagrams for explaining the evaluation method of static bending durability.

Claims (8)

A laminated body, comprising in sequence: a first optical member, a first adhesive layer, a second optical member, a second adhesive layer, and a third optical member, wherein, The viscosity values of the first adhesive layer and the second adhesive layer at a temperature of 25°C are both 0.8 gf or more, and The laminated body satisfies the formula (1): The viscosity value at the temperature of the second adhesive layer at 25°C > the viscosity value at the temperature of the first adhesive layer at 25°C (1). The laminate according to claim 1, wherein the viscosity values of the first adhesive layer and the second adhesive layer at a temperature of 25°C are both 10.0 gf or less. The layered product according to claim 1 or claim 2, wherein the shear elastic coefficients of the first adhesive layer and the second adhesive layer at a temperature of 25°C are both 0.5 MPa or less. The laminate according to any one of Claims 1 to 3, wherein the first optical member is a front panel. The laminate according to any one of Claims 1 to 4, wherein the second optical member is a polarizing plate. The laminate according to any one of claim 1 to claim 5, wherein the third optical member is a touch sensor panel. An image display device including the laminate according to any one of claim 1 to claim 6. A method for manufacturing a layered body is the method for manufacturing a layered body as claimed in claim 1, comprising: A step of bonding an optical member using an adhesive layer having a viscosity value of 0.8 gf or more at a temperature of 25°C.

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