CN113820776A - Laminate, image display device, and method for manufacturing same - Google Patents

Laminate, image display device, and method for manufacturing same Download PDF

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Publication number
CN113820776A
CN113820776A CN202110665978.XA CN202110665978A CN113820776A CN 113820776 A CN113820776 A CN 113820776A CN 202110665978 A CN202110665978 A CN 202110665978A CN 113820776 A CN113820776 A CN 113820776A
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layer
adhesive layer
laminate
adhesive
film
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Chinese (zh)
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李昇祐
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Sumitomo Chemical Co Ltd
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Sumitomo Chemical Co Ltd
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    • GPHYSICS
    • G06COMPUTING; CALCULATING OR COUNTING
    • G06FELECTRIC DIGITAL DATA PROCESSING
    • G06F3/00Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
    • G06F3/01Input arrangements or combined input and output arrangements for interaction between user and computer
    • G06F3/03Arrangements for converting the position or the displacement of a member into a coded form
    • G06F3/041Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
    • G06F3/0412Digitisers structurally integrated in a display
    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00Optical elements other than lenses
    • G02B5/30Polarising elements
    • G02B5/3025Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state
    • G02B5/3033Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state in the form of a thin sheet or foil, e.g. Polaroid
    • G02B5/3041Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state in the form of a thin sheet or foil, e.g. Polaroid comprising multiple thin layers, e.g. multilayer stacks
    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09JADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J133/00Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Adhesives based on derivatives of such polymers
    • C09J133/04Homopolymers or copolymers of esters
    • C09J133/06Homopolymers or copolymers of esters of esters containing only carbon, hydrogen and oxygen, the oxygen atom being present only as part of the carboxyl radical
    • C09J133/062Copolymers with monomers not covered by C09J133/06
    • C09J133/068Copolymers with monomers not covered by C09J133/06 containing glycidyl groups
    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00Optical elements other than lenses
    • G02B5/30Polarising elements
    • G02B5/3025Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state
    • G02B5/3033Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state in the form of a thin sheet or foil, e.g. Polaroid
    • G02B5/3041Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state in the form of a thin sheet or foil, e.g. Polaroid comprising multiple thin layers, e.g. multilayer stacks
    • G02B5/305Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state in the form of a thin sheet or foil, e.g. Polaroid comprising multiple thin layers, e.g. multilayer stacks including organic materials, e.g. polymeric layers
    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09FDISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
    • G09F9/00Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements
    • G09F9/30Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements in which the desired character or characters are formed by combining individual elements
    • G09F9/301Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements in which the desired character or characters are formed by combining individual elements flexible foldable or roll-able electronic displays, e.g. thin LCD, OLED
    • GPHYSICS
    • G06COMPUTING; CALCULATING OR COUNTING
    • G06FELECTRIC DIGITAL DATA PROCESSING
    • G06F2203/00Indexing scheme relating to G06F3/00 - G06F3/048
    • G06F2203/041Indexing scheme relating to G06F3/041 - G06F3/045
    • G06F2203/04103Manufacturing, i.e. details related to manufacturing processes specially suited for touch sensitive devices

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Optics & Photonics (AREA)
  • Human Computer Interaction (AREA)
  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Polarising Elements (AREA)
  • Liquid Crystal (AREA)
  • Laminated Bodies (AREA)
  • Adhesive Tapes (AREA)
  • Adhesives Or Adhesive Processes (AREA)
  • Devices For Indicating Variable Information By Combining Individual Elements (AREA)

Abstract

The invention relates to a laminate, an image display device and a manufacturing method. The present invention provides a laminate comprising a1 st optical member, a1 st adhesive layer, a 2 nd optical member, a 2 nd adhesive layer, and a 3 rd optical member in this order, wherein the 1 st adhesive layer and the 2 nd adhesive layer each have a viscosity value of 0.8gf or more at a temperature of 25 ℃, and satisfy formula (1): the tack value at 25 ℃ for the 2 nd adhesive layer is greater than the tack value (1) at 25 ℃ for the 1 st adhesive layer.

Description

Laminate, image display device, and method for manufacturing same
Technical Field
The present invention relates to a laminate, and further relates to an image display device including the laminate and a method for manufacturing the laminate.
Background
Patent document 1 describes an optical member including a window film, a 2 nd adhesive film, a touch functional portion, and a1 st adhesive film in this order, and proposes that the distribution of storage elastic modulus corresponding to the temperature of the 1 st adhesive film and the 2 nd adhesive film is within a specific range.
Patent document 2 describes an adhesive composition for a flexible display, and proposes that the ratio of the final stress after deformation to the initial stress at the start of deformation be within a specific range, regarding the storage elastic modulus of the adhesive composition after curing.
Documents of the prior art
Patent document
Patent document 1: korean laid-open patent No. 10-2016-
Patent document 2: korean laid-open patent No. 10-2019-0069334
Disclosure of Invention
An optical laminate for use in an image display device is generally manufactured by laminating a plurality of optical members with an adhesive layer. In order to allow the adhesive layer to exhibit its original performance in the next step, a step of curing (aging) the adhesive layer after coating may be necessary. In recent years, lead time (lead time) from the time of manufacturing an optical laminate to the time of use in the next step has become shorter. Therefore, a sufficient time is not allocated to the aging, and bubbles may be generated in the adhesive layer between the adhesive layer and the optical member during the bending.
The invention aims to provide a laminated body, which is a laminated body sequentially provided with a1 st optical component, a1 st adhesive layer, a 2 nd optical component, a 2 nd adhesive layer and a 3 rd optical component, and when the 3 rd optical component is arranged at the inner side and is bent, the adhesiveness between the adhesive layer and the optical component is maintained and the generation of bubbles in the adhesive layer between the adhesive layer and the optical component is inhibited even under the condition that sufficient time is not distributed for aging.
The invention provides a laminate, an image display device and a method for manufacturing the laminate.
[1] A laminate comprising a1 st optical member, a1 st adhesive layer, a 2 nd optical member, a 2 nd adhesive layer and a 3 rd optical member in this order,
the 1 st adhesive layer and the 2 nd adhesive layer both have a tack value at 25 ℃ of 0.8gf or more and satisfy formula (1):
the tack value at 25 ℃ for the 2 nd adhesive layer is greater than the tack value (1) at 25 ℃ for the 1 st adhesive layer.
[2] The laminate according to [1], wherein both the 1 st adhesive layer and the 2 nd adhesive layer have a tack value at a temperature of 25 ℃ of 10.0gf or less.
[3] The laminate according to any one of [1] and [2], wherein the shear modulus of elasticity at 25 ℃ of the 1 st adhesive layer and the 2 nd adhesive layer is 0.5MPa or less.
[4] The laminate according to any one of [1] to [3], wherein the 1 st optical member is a front panel.
[5] The laminate according to any one of [1] to [4], wherein the 2 nd optical member is a polarizing plate.
[6] The laminate according to any one of [1] to [5], wherein the 3 rd optical member is a touch sensor panel.
[7] An image display device comprising the laminate according to any one of [1] to [6 ].
[8] A method for producing a laminate according to [1], which comprises: a step of bonding the optical member to the adhesive layer having a viscosity value of 0.8gf or more at a temperature of 25 ℃.
According to the present invention, there is provided a laminate comprising a1 st optical member, a1 st adhesive layer, a 2 nd optical member, a 2 nd adhesive layer, and a 3 rd optical member in this order, wherein when the 3 rd optical member is bent while being set inside, adhesion between the adhesive layer and the optical member is maintained and generation of air bubbles in the adhesive layer between the adhesive layer and the optical member is suppressed even when sufficient time is not allotted to aging.
Drawings
Fig. 1 is a schematic cross-sectional view schematically showing an example of a laminate of the present invention.
Fig. 2 is a schematic cross-sectional view schematically showing a method for producing a laminate according to the present invention.
FIG. 3 is a schematic diagram illustrating a method for measuring a viscosity value at a temperature of 25 ℃.
Fig. 4 is a schematic diagram illustrating a method for evaluating static bending durability.
Description of the symbols
100. 200, 210, 220, 230, 240, 401 laminate, 110 st optical film, 120 st adhesive layer, 130 nd optical member, 2 nd adhesive layer, 140 nd adhesive layer, 150 rd optical member, 3 rd optical member, 30 front panel laminate, 31, 33, 51, 53 release film, 32 front panel, 40, 60 adhesive sheet, 41, 61 light spacer, 42 st adhesive layer, 43, 63 heavy spacer, 50 circular polarizer laminate, 52 circular polarizer, 62 nd adhesive layer, 70 touch sensor layer with PET film, 71 PET film with adhesive, 72 touch sensor layer, 300 cylinder, 301 adhesive layer, 400 test panel, 402 iron rod laminate
Detailed Description
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 drawings below, the scale of each component shown in the drawings is appropriately adjusted to facilitate understanding of each component, and the scale of each component does not necessarily match the scale of the actual component.
< laminate >
Fig. 1 is a schematic cross-sectional view of a laminate. The laminate 100 includes a1 st optical member 110, a1 st adhesive layer 120, a 2 nd optical member 130, a 2 nd adhesive layer 140, and a 3 rd optical member 150 in this order. The 1 st optical member 110 side of the laminate 100 is preferably a visually visible side.
The visually observable side refers to a side where the image display device is observed when the laminate 100 is used in the image display device. In this specification, the 1 st optical member, the 2 nd optical member, and the 3 rd optical member may be collectively referred to as an optical member. In the present specification, the 1 st adhesive layer and the 2 nd adhesive layer may be collectively referred to as an adhesive layer.
The laminate 100 may be bent with the 3 rd optical member 150 side being inside. The bendable means that the laminated body can be bent without generating air bubbles between the adhesive layer and the optical member and within the adhesive layer. The bending includes a bent form in which a curved surface is formed at a bent portion. The bending form is not particularly limited, and the bending radius of the inner surface of the bend may be 15mm or less, 10mm or less, or 5mm or less, for example. The bending radius is, for example, in the range of 0.5mm to 5.0 mm.
The term "bent" includes a form in which the angle of the bent inner surface is greater than 0 degrees and less than 180 degrees, and includes a form in which the radius of curvature of the inner surface is approximately 0 or a form in which the angle of bending of the inner surface is 0 degree, unless otherwise specified. When the bent portion is curved, an angle formed by straight lines sandwiching the bent portion is defined as an angle of the inner surface.
The laminate of the present invention can be bent and is therefore suitable for flexible displays.
[ static bending durability ]
In the case where the laminate 100 was subjected to a static bending durability test in which the 3 rd optical member 150 side was set inside and a bent state with a bending radius of 2.5mm was maintained, bubbles tended to be less likely to be generated between the adhesive layer and the optical member and within the adhesive layer at the bent portion. In the case of performing the static bending durability test, the time until bubbles are initially generated in the adhesive layer and between the bent portion and the optical member in the adhesive layer is preferably more than 48 hours, more preferably more than 72 hours, for the laminate 100. The static bending durability test can be performed by the method described in the examples described later.
The laminate 100 may have a square shape in a plan view, for example, preferably has a square shape having long sides and short sides, and more preferably has a rectangular shape. Each layer constituting the laminate 100 may be subjected to R-processing at the corner, slitting processing at the end, and punching processing.
The laminate 100 can be used for, for example, an image display device or the like. The image display device is not particularly limited, and examples thereof include an organic electroluminescence (organic EL) display device, an inorganic electroluminescence (inorganic EL) display device, a liquid crystal display device, and an electroluminescence display device. The laminate 100 can be bent and is therefore suitable for flexible displays.
[ tack value at 25 ℃ C. of the adhesive layer ]
The 1 st adhesive layer and the 2 nd adhesive layer both have a tack value of 0.8gf or more at a temperature of 25 ℃. The tack value is considered to be related to the initial adhesion force after the adhesive layer and the optical member are bonded. Therefore, it is presumed that: when the viscosity value is within the above range, a laminate having excellent static bending durability can be obtained even when sufficient time cannot be allocated for aging. When either or both of the tack values at 25 ℃ of the 1 st adhesive layer and the 2 nd adhesive layer are less than 0.8gf, interfacial peeling tends to occur easily after bending due to insufficient adhesive force. The tack value at a temperature of 25 ℃ of the adhesive layer was measured by the method described in the examples described later.
From the viewpoint of excellent static bending durability, the 1 st adhesive layer and the 2 nd adhesive layer each have a viscosity value at 25 ℃ of preferably 1.0gf or more, more preferably 1.1gf or more, further preferably 1.2gf or more, particularly preferably 1.3gf or more, more particularly preferably 1.4gf or more, further particularly preferably 1.5gf or more, and particularly preferably 2.0gf or more. The tack value at 25 ℃ of each of the 1 st adhesive layer and the 2 nd adhesive layer may be, for example, 10.0gf or less, preferably 9.0gf or less, more preferably 8.0gf or less, further preferably 7.0gf or less, particularly preferably 6.0gf or less, more particularly preferably 5.0gf or less, and further particularly preferably 3.8gf or less. When the viscosity value at 25 ℃ of the 1 st adhesive layer and the 2 nd adhesive layer exceeds 10.0gf, the cohesive force inside the adhesive layers tends to be easily lowered.
The laminate 100 satisfies the following formula (1).
The tack value at 25 ℃ of the 2 nd adhesive layer > the tack value at 25 ℃ of the 1 st adhesive layer (1)
The following are found: when the laminate is bent with the 3 rd optical member side being on the inside, the 2 nd adhesive layer tends to have a higher tack value at a temperature of 25 ℃ than the 1 st adhesive layer at a temperature of 25 ℃, and to have more excellent static bending durability. When the laminate is bent with the 3 rd optical member side being on the inside, the 2 nd adhesive layer is disposed at a position closer to the 3 rd optical member than the 1 st adhesive layer, and therefore the bending radius is smaller, and the applied stress tends to be larger. Therefore, it is inferred that the adhesive layer having a larger viscosity value is disposed as the 2 nd adhesive layer, and the adhesion state is easily maintained.
The viscosity value at a temperature of 25 ℃ of the adhesive layer tends to be higher as the adhesive layer is softer. The tack value at a temperature of 25 ℃ of the adhesive layer can be adjusted by selecting the kind and the addition amount of the monomer constituting the base polymer, the additive (e.g., acrylic acid monomer) added to the adhesive. The tack value at 25 ℃ of the temperature of the adhesive layer can also be adjusted by adding a tackifier (tack inhibitor).
[ optical Member ]
The optical member may be a component used in a general image display device. When the laminate 100 is used in an image display device, the 1 st optical member 110 may be bonded to the image display device so as to be on the visually visible side, and preferably the 1 st optical member 110 is bonded to the image display device so as to be the outermost layer constituting the visually visible side of the image display device.
Examples of the optical member include a front panel, a polarizing plate, a touch sensor panel, and an image display device. The 1 st optical member 110 may be a front panel. The 2 nd optical member 130 may be a polarizing plate. The 3 rd 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 limited as long as the front panel is a plate-like body that can transmit light, and the front panel may have a single-layer structure or a multilayer structure, and examples thereof include a plate-like body made of glass (e.g., a glass plate, a glass film, etc.), a plate-like body made of resin (e.g., a resin plate, a resin sheet, a resin film, etc.), and a laminate of a plate-like body made of resin and a plate-like body made of glass. The front panel may be the layer constituting the outermost surface of the visually visible side of the image display device.
As the glass plate, strengthened glass for display is preferably used. The thickness of the glass plate is, for example, 10 to 1000. mu.m, preferably 20 to 500. mu.m. By using the glass plate, an optical member having excellent mechanical strength and surface hardness can be constituted.
The resin film is not limited as long as it can transmit light. Examples of the film include films formed of polymers such as cellulose triacetate, cellulose acetate butyrate, ethylene-vinyl acetate copolymer, cellulose propionate, cellulose butyrate, cellulose acetate propionate, polyester, polystyrene, polyamide, polyetherimide, poly (meth) acrylic acid, polyimide, polyethersulfone, polysulfone, polyethylene, polypropylene, polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl acetal, polyether ketone, polyether ether ketone, poly (meth) acrylic acid, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, and polyamideimide. These polymers may be used alone or in combination of 2 or more. When the laminate is used for a flexible display, a resin film formed of a polymer such as polyimide, polyamide, or polyamideimide, which has excellent flexibility, high strength, and high transparency, is suitably used. In the present specification, "(meth) acrylic acid" means either acrylic acid or methacrylic acid. The same applies to "(meth)" such as (meth) acrylate.
In the case where the front panel is a resin film, the resin film may be a film in which a hard coat layer is provided on at least one surface of the base film to further increase the hardness. The hard coat layer may be formed on one surface of the substrate film or on both surfaces. In the case where the image display device described later is a touch panel type image display device, since the surface of the front panel serves as a touch surface, a resin film having a hard coat layer can be preferably used. By providing the hard coat layer, a resin film having improved hardness and scratch resistance can be produced. The hard coat layer is a cured layer of, for example, an ultraviolet curable resin. Examples of the ultraviolet curable resin include (meth) acrylic resins, silicone resins, polyester resins, polyurethane resins, amide resins, and epoxy resins. To increase hardness, the hard coating may contain additives. The additive is not limited, and may be inorganic fine particles, organic fine particles, or a mixture thereof. The thickness of the resin film is, for example, 10 to 500. mu.m, preferably 20 to 100. mu.m.
The front panel may have a function of protecting the front surface of the image display device, a function as a touch sensor, a blue light prevention function, a viewing angle adjustment function, and the like.
[ polarizing plate ]
The polarizer 130 may be a linear polarizer or a circular polarizer. The linear polarizer may be laminated with a protective layer on one side of the polarizer. The linearly polarizing plate has a property of transmitting linearly polarized light having a vibration plane perpendicular to an absorption axis when unpolarized light is incident. The linearly polarizing plate may include a polyvinyl alcohol (hereinafter, also simply referred to as "PVA") resin film as a polarizer, or may be a cured film obtained by aligning a composition containing a dichroic dye and a polymerizable compound and polymerizing a polymerizable liquid crystal compound. A polarizer obtained by coating and curing a composition containing a dichroic dye and a polymerizable compound is preferable because the bending direction is not limited as compared with a polarizer containing a PVA-based resin film obtained by a stretching step.
The linearly polarizing plate may include only the polarizer and the protective layer, or may include 1 or more of the substrate, the thermoplastic resin film, the outer coating layer, and the alignment film in addition to the polarizer and the protective layer. The thickness of the linearly polarizing plate is, for example, 2 to 100. mu.m, preferably 5 to 60 μm.
[ polarizer ]
Examples of the polarizer include polarizers obtained by subjecting a hydrophilic polymer film such as a polyvinyl alcohol (hereinafter, also referred to simply as "PVA") film, a partially acetalized PVA film, or an ethylene-vinyl acetate copolymer partially saponified film to a dyeing treatment or a stretching treatment with a dichroic substance such as iodine or a dichroic dye. From the viewpoint of excellent optical properties, it is preferable to use a polarizer obtained by dyeing a PVA-based resin film with iodine and uniaxially stretching the PVA-based resin film.
The polyvinyl alcohol resin can be produced by saponifying a polyvinyl acetate resin. The polyvinyl acetate resin may be a copolymer of vinyl acetate and another monomer copolymerizable with vinyl acetate, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate. Examples of the other monomer copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.
The saponification degree of the polyvinyl alcohol resin is usually about 85 to 100 mol%, and preferably 98 mol% or more. The polyvinyl alcohol resin may be modified, and for example, polyvinyl formal, polyvinyl acetal modified with aldehydes, or the like may be used. The polyvinyl alcohol resin has an average polymerization degree of usually about 1000 to 10000, preferably about 1500 to 5000. The average degree of polymerization of the polyvinyl alcohol resin can be determined in accordance with JIS K6726 (1994). If the average degree of polymerization is less than 1000, it is difficult to obtain preferable polarizing performance, and if it exceeds 10000, film processability may be poor.
Examples of a method for producing a polarizer including another PVA-based resin film include a production method including the steps of: first, a base film is prepared, a solution of a resin such as a polyvinyl alcohol resin is applied to the base film, and the base film is dried by removing the solvent to form a resin layer thereon. The primer layer may be formed in advance on the resin layer-forming surface of the base film. As the base film, a resin film such as PET or a film using a thermoplastic resin which can be used as a protective layer described later can be used. Examples of the material of the primer layer include a resin obtained by crosslinking a hydrophilic resin used for a polarizer.
Next, if necessary, the amount of solvent such as water in the resin layer is adjusted, and then the base film and the resin layer are uniaxially stretched, and then the resin layer is dyed with a dichroic dye such as iodine to adsorb and orient the dichroic dye in the resin layer. Next, a washing step of treating the resin layer in which the dichroic dye is adsorbed and aligned with the aqueous boric acid solution and washing off the aqueous boric acid solution is performed as necessary. In this way, a polarizer, which is a resin layer in which the dichroic dye is adsorbed and aligned, is produced. The respective steps may be performed by known methods.
The uniaxial stretching of the substrate film and the resin layer may be performed before dyeing, during boric acid treatment after dyeing, or in several stages of the uniaxial stretching. The substrate film and the resin layer may be uniaxially stretched in the MD direction (film carrying direction), and in this case, the uniaxial stretching may be performed between rolls having different peripheral speeds, or the uniaxial stretching may be performed using a hot roll. The substrate film and the resin layer may be uniaxially stretched in the TD direction (direction perpendicular to the film conveyance direction), and in this case, a so-called tenter method may be used. The stretching of the base film and the resin layer may be dry stretching in which the stretching is performed in the atmosphere, or wet stretching in which the stretching is performed in a state in which the resin layer is swollen with a solvent. In order to exhibit the performance of the polarizer, the stretching magnification is 4 times or more, preferably 5 times or more, and particularly preferably 5.5 times or more. There is no particular upper limit of the stretch ratio, but from the viewpoint of suppressing breakage and the like, it is preferably 8 times or less.
The thickness of the polarizer comprising the PVA-based resin film is, for example, 2 to 40 μm.
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.
Examples of the method for producing a polarizer, which is a cured film obtained by aligning a composition containing a dichroic dye and a polymerizable compound and polymerizing the polymerizable liquid crystal compound, include a method for forming a polarizer by coating a composition for forming a polarizer containing a polymerizable liquid crystal compound and a dichroic dye on a base film through an alignment film, and a method for forming a polarizer by coating a composition for forming a polarizer containing a polymerizable liquid crystal compound and a dichroic dye on a protective layer, which is formed on a base film, through an alignment film, and polymerizing and curing the polymerizable liquid crystal compound while 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 be used as a linear polarizing plate with a base film. As the substrate film, a thermoplastic resin film, for example, a polyethylene terephthalate film, or the like can be used.
As the dichroic dye, a dye having the following properties can be used: the absorbance of the molecule in the major axis direction is different from the absorbance in the minor axis direction, and a dye having a maximum absorption wavelength (. lamda.max) in the range of 300 to 700nm, for example, is preferable. As such a dichroismExamples of the sex pigments include acridine pigment,
Figure BDA0003116827330000091
Oxazine pigments, cyanine pigments, naphthalene pigments, azo pigments, anthraquinone pigments, and the like, and among them, azo pigments are preferable. Examples of the azo dye include monoazo dyes, disazo dyes, trisazo dyes, tetraazo dyes, and stilbene azo dyes, and disazo dyes and trisazo dyes are more preferable.
The composition for forming a polarizer may contain a solvent, a polymerization initiator such as a photopolymerization initiator, a photosensitizer, a polymerization inhibitor, and the like. Known materials such as a polymerizable liquid crystal compound, a dichroic dye, a solvent, a polymerization initiator, a photosensitizer, and a polymerization inhibitor contained in the composition for forming a polarizer can be used, and for example, materials exemplified in japanese patent application laid-open nos. 2017-102479 and 2017-83843 can be used. The method for forming a polarizer using the composition for forming a polarizer can also employ the method exemplified in the above publication.
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 to 8 μm, and more preferably 1 to 5 μm.
An overcoat layer (hereinafter, also referred to as OC layer) may be provided on the polarizer-side surface of the linear polarizer. Examples of the material constituting the OC layer include a photocurable resin and a water-soluble polymer. Examples of the photocurable resin include a (meth) acrylic resin, a polyurethane resin, a (meth) acrylic urethane resin, an epoxy resin, and a silicone resin. Examples of the water-soluble polymer include poly (meth) acrylamide polymers; vinyl alcohol polymers such as polyvinyl alcohol and ethylene-vinyl alcohol copolymers, ethylene-vinyl acetate copolymers, (meth) acrylic acid or anhydride thereof-vinyl alcohol copolymers; a carboxyvinyl polymer; polyvinylpyrrolidone; starches; sodium alginate; polyethylene oxide polymers, and the like. 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, and may be 5 μm or less, and further may be 0.05 μm or more, and may be 0.5 μm or more.
The polarizer produced by the above method can be used as a linear polarizer by peeling off the substrate film or together with the substrate film. According to the above method, the substrate film can be peeled, and therefore the polarizer can be further thinned.
[ protective layer ]
The protective layer has a function of protecting the surface of the polarizer. In the laminate 100, the linearly polarizing plate may be generally disposed so that the protective layer is closer to the 1 st 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-shielding property, isotropy, stretchability, and the like can be used. Specific examples of such thermoplastic resins include cellulose resins such as cellulose triacetate; polyester resins such as polyethylene terephthalate and polyethylene naphthalate; polyether sulfone resin; polysulfone resin; a polycarbonate resin; polyamide resins such as nylon and aromatic polyamide; a polyimide resin; polyolefin resins such as polyethylene, polypropylene and ethylene-propylene copolymers; a cyclic polyolefin resin having a ring system and a norbornene structure (also referred to as norbornene-based resin); (meth) acrylic resins; a polyarylate resin; a polystyrene resin; polyvinyl alcohol resins and mixtures thereof. When protective layers are laminated on both surfaces of the polarizer, the two protective layers may be the same type or different types. The thickness of the thermoplastic resin film may be, for example, 3 to 50 μm, preferably 5 to 30 μm.
The protective layer may be an organic layer or an inorganic layer, for example. The organic layer or the inorganic layer may be a layer formed by coating. The organic layer can be formed using a composition for forming a protective layer, such as a (meth) acrylic resin composition, an epoxy resin composition, a polyimide resin composition, or the like. The protective layer-forming composition may be an active energy ray-curable composition or a thermosetting composition. The inorganic 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 also be referred to as a hard coat layer.
When the protective layer is an organic layer, the protective layer can be produced by applying an active energy ray-curable composition for forming a protective layer to a base film and curing the composition by irradiation with active energy. The substrate film is as described above. The substrate film is usually peeled off and removed. Examples of the method for applying the composition for forming a protective layer include spin coating. When the protective layer is an inorganic 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 to 10 μm, preferably 0.5 to 5 μm.
[ phase difference plate ]
The polarizing plate can function as a circularly polarizing plate by including a linearly polarizing plate and a retardation plate. The circularly polarizing plate having the linearly polarizing plate and the retardation plate arranged so that the absorption axis of the linearly polarizing plate and the slow axis of the retardation plate form a predetermined angle can exhibit an antireflection function.
The retardation plate may include 1 or 2 or more retardation layers. When the retardation plate includes 2 retardation layers, the retardation plate may be referred to as a1 st retardation layer and a 2 nd retardation layer in this order from the polarizer side. The retardation layer may be 1 layer or 2 or more layers. The retardation layer may have an overcoat layer for protecting the surface thereof, a substrate film for supporting the retardation layer, and the like. Examples of the retardation layer include a retardation layer (λ/4 layer) giving a retardation of λ/4, a retardation layer (λ/2 layer) giving a retardation of λ/2, and a positive C layer. The phase difference plate preferably includes a λ/4 layer, and more preferably includes at least one of a λ/4 layer and a λ/2 layer or a positive C layer. When the retardation plate includes a λ/2 layer, the λ/2 layer and the λ/4 layer are stacked in this order from the linear polarizer side. When the retardation plate includes the positive C layer, the λ/4 layer and the positive C layer may be stacked in this order from the linear polarizer side, or the positive C layer and the λ/4 layer may be stacked in this order from the linear polarizer side. The thickness of the retardation plate is, for example, 0.1 to 10 μm, preferably 0.5 to 8 μm, and more preferably 1 to 6 μm.
The retardation layer may be formed of the resin film exemplified as the material of the thermoplastic resin film described above, or may be formed of a layer obtained by curing a polymerizable liquid crystal compound. 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 bonded by an interlayer lamination layer described later.
When the retardation layer is formed of a layer obtained by curing a polymerizable liquid crystal compound, the retardation layer can be formed by applying a composition containing a polymerizable liquid crystal compound to a substrate film and curing the composition. An alignment film may also be formed between the substrate film and the coating layer. The polymerizable liquid crystal compound used in the above description of the polarizer can be a polymerizable liquid crystal compound. The material and thickness of the base film may be the same as those of the thermoplastic resin film described above. The retardation layer may be incorporated in a laminate in the form of a film having an alignment film and a base film when the retardation layer is formed by curing a polymerizable liquid crystal compound.
The 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 slow axis of the retardation layer form a predetermined angle has an antireflection function, that is, functions as a circular polarizing plate. In case the phase difference plate comprises a layer of lambda/4, the angle of the absorption axis of the linear polarizer to the slow axis of the layer of lambda/4 may be 45 deg. + -10 deg.. The retardation layer may have a positive wavelength dispersion property or a negative wavelength dispersion property. The lambda/4 layer preferably has reverse wavelength dispersion.
The linearly polarizing plate and the retardation plate may be bonded to each other through a bonding layer described later.
[ interlayer lamination layer ]
The interlayer lamination layer is disposed between the retardation layers, for example, the 1 st retardation layer and the 2 nd retardation layer, and has a function of laminating the 1 st retardation layer and the 2 nd retardation layer. The interlayer adhesive layer may be made of an adhesive or a bonding agent. The interlayer adhesive layer is preferably an adhesive layer.
The thickness of the interlayer adhesive layer is not particularly limited, but when an adhesive layer is used as the interlayer adhesive layer, it is preferably 1 μm or more, and may be 5 μm or more, and usually 50 μm or less, and may be 25 μm or less. When an adhesive layer is used as the interlayer adhesive layer, the thickness of the interlayer adhesive layer is preferably 0.1 μm or more, and 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 adhesive layer may be the above-mentioned adhesive composition, or other adhesives such as (meth) acrylic adhesives, styrene adhesives, silicone adhesives, rubber adhesives, urethane adhesives, polyester adhesives, and epoxy copolymer adhesives, which are different from the material of the adhesive layer, may be used.
The adhesive used for the interlayer adhesive layer may be formed by combining 1 or 2 or more kinds of water-based adhesives, active energy ray-curable adhesives, and the like. Examples of the aqueous adhesive include a polyvinyl alcohol resin aqueous solution and an aqueous two-pack polyurethane latex adhesive. The active energy ray-curable adhesive is an adhesive that is cured by irradiation with an active energy ray such as ultraviolet ray, and examples thereof include an adhesive containing a polymerizable compound and a photopolymerization initiator, an adhesive containing a photoreactive resin, and an adhesive containing a binder resin and a photoreactive crosslinking agent. Examples of the polymerizable compound include photopolymerizable monomers such as a photocurable epoxy monomer, a photocurable acrylic monomer, and a photocurable urethane monomer, and oligomers derived from these monomers. Examples of the photopolymerization initiator include compounds containing an active species that generates a neutral radical, an anionic radical, a cationic radical, and the like by irradiation with an active energy ray such as ultraviolet ray.
[ touch sensor Panel ]
The touch sensor panel is not limited to the detection method as long as it is a sensor capable of detecting a touched position, and examples thereof include touch sensor panels of a resistive film method, a capacitive coupling method, an optical sensor method, an ultrasonic wave method, an electromagnetic induction coupling method, a surface acoustic wave method, and the like. From the viewpoint of low cost, a touch sensor panel of a resistive film type or a capacitive coupling type is suitably used. The touch sensor panel may be disposed on a side opposite to a visually visible side of the laminate.
An example of a resistive touch sensor panel includes a pair of substrates arranged to face each other, an insulating spacer sandwiched between the pair of substrates, a transparent conductive film serving as a resistive film provided on the inner front surface of each substrate, and a touch position detection circuit. In an image display device provided with a resistive touch sensor panel, if a surface of a front panel is touched, the opposing resistive films are short-circuited, and a current flows through the resistive films. The touch position detection circuit detects a change in voltage at that time, and detects a 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 capacitive coupling type touch sensor panel, if the front surface of the front panel is touched, the transparent electrode is grounded at the touched point via the capacitance of a human body. The touch position detection circuit detects the grounding of the transparent electrode and detects the touched position.
[ image display element ]
Examples of the image display element include a liquid crystal cell, an organic electroluminescence (organic EL) display element, an inorganic electroluminescence (inorganic EL) display element, a plasma display element, and a field emission type display element.
[ adhesive layer ]
The adhesive layer is a layer that is interposed between the optical members to attach them. In the present specification, the term "adhesive" refers to a preparation which is in a state of a high-viscosity liquid or gel-like solid after a curing reaction and can be adhered by applying a small amount of pressure at normal temperature in a short time, and is also referred to as a pressure-sensitive adhesive, for example. On the other hand, in the present specification, the "adhesive" refers to an adhesive other than an adhesive (pressure-sensitive adhesive), and refers to an adhesive which is solid after a curing reaction and has an elastic modulus at a temperature of 25 ℃ after curing of 100MPa or more. The adhesive layer may be composed of 1 layer or 2 or more layers, but is preferably composed of 1 layer.
The shear elastic modulus [ MPa ] at 25 ℃ of the adhesive layer may be, for example, 0.5MPa or less, preferably 0.4MPa or less, more preferably 0.3MPa or less, still more preferably 0.2MPa or less, and particularly preferably 0.1MPa or less. The shear modulus [ MPa ] of the adhesive layer at 25 ℃ is usually 0.001MPa or more, for example, 0.005MPa or more or 0.01MPa or more. The shear modulus [ MPa ] of the adhesive layer at a temperature of 25 ℃ was measured by the method described in the following examples.
From the viewpoint of securing 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 the bendability, the thickness of the adhesive layer is preferably 100 μm or less, and more preferably 50 μm or less. The thickness of the adhesive layer is the maximum thickness of the adhesive layer.
The adhesive layer may be composed of an adhesive composition containing a resin as a main component, such as a (meth) acrylic resin, a rubber-based resin, a polyurethane-based resin, an ester-based resin, a silicone-based resin, or a polyvinyl ether-based resin. Among these, an adhesive composition containing a (meth) acrylic resin as a base polymer, which is excellent in transparency, weather resistance, heat resistance, and the like, is preferable. The adhesive composition may be an active energy ray-curable adhesive composition or a thermosetting adhesive composition.
As the (meth) acrylic resin (base polymer) used in the adhesive composition, for example, a polymer or copolymer in which 1 or 2 or more kinds of (meth) acrylic esters such as butyl (meth) acrylate, ethyl (meth) acrylate, isooctyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate are used as monomers can be preferably used. In the base polymer, it is preferable to copolymerize a polar monomer. Examples of the polar monomer include monomers having a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, and the like, such as (meth) acrylic acid, 2-hydroxypropyl (meth) acrylate, hydroxyethyl (meth) acrylate, amide (meth) acrylate, N-dimethylaminoethyl (meth) acrylate, and glycidyl (meth) acrylate.
The adhesive composition may contain only the above-mentioned base polymer, but may also contain a crosslinking agent. Examples of the crosslinking agent include: a metal ion having a valence of 2 or more with a carboxyl group; polyamine compounds forming amide bonds with carboxyl groups; polyepoxy compounds, polyhydric alcohols, which form ester bonds with carboxyl groups; a polyisocyanate compound forming an amide bond with a carboxyl group. Among them, polyisocyanate compounds are preferable.
The adhesive composition may contain a tackifier. Examples of the tackifier include hydrocarbon-based tackifiers, terpene-based tackifiers, rosin-based tackifiers, phenol-based tackifiers, epoxy-based tackifiers, polyamide-based tackifiers, elastomer-based tackifiers, and ketone-based tackifiers.
Examples of the hydrocarbon-based tackifier include aliphatic hydrocarbon resins, aromatic hydrocarbon resins (e.g., xylene resins), aliphatic cyclic hydrocarbon resins, aliphatic/aromatic petroleum resins (e.g., styrene/olefin copolymers), aliphatic/alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone resins, and coumarone/indene resins.
Examples of the terpene-based tackifier include terpene-based resins such as α -pinene polymer and β -pinene polymer; modified terpene resins (e.g., terpene-phenol resins, styrene-modified terpene resins, hydrogenated terpene resins, etc.) obtained by modifying terpene resins (e.g., phenol modification, aromatic modification, hydrogenation modification, etc.); and the like.
Examples of the rosin-based tackifier include unmodified rosins (raw rosins) such as gum rosin and wood rosin; modified rosins obtained by modifying unmodified rosins by hydrogenation, disproportionation, polymerization, or the like (for example, hydrogenated rosins, disproportionated rosins, polymerized rosins, other chemically modified rosins, or the like); other various rosin derivatives; and the like.
Examples of the phenolic thickener include a resol-type or linear alkylphenol.
The active energy ray-curable adhesive composition has a property of being cured by irradiation with active energy rays such as ultraviolet rays and electron beams, and means an adhesive composition having the following properties: the adhesive has adhesiveness even before irradiation with an active energy ray and can be adhered to an adherend such as a film, and the adhesive force can be adjusted by curing the adhesive by irradiation with an active energy ray. The active energy ray-curable adhesive composition is preferably an ultraviolet-curable adhesive composition. The active energy ray-curable adhesive composition further contains a base polymer and an active energy ray-polymerizable compound. Further, a photopolymerization initiator, a photosensitizer and the like may be contained as necessary.
The adhesive composition may contain additives such as fine particles, beads (resin beads, glass beads, and the like), glass fibers, resins other than the base polymer, fillers (metal powder, other inorganic powder, and the like), antioxidants, ultraviolet absorbers, dyes, pigments, colorants, antifoaming agents, anticorrosion agents, and photopolymerization initiators for imparting light scattering properties.
The adhesive layer may be formed by applying the above adhesive composition to a substrate. When an active energy ray-curable adhesive composition is used, a cured product having a desired degree of curing can be obtained by irradiating the 1 st adhesive composition layer formed with an active energy ray.
[ other layers ]
The laminate 100 may include a lamination layer for laminating the linear polarizer and the retardation plate as another layer.
[ adhesive layer ]
The laminate 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 a bonding agent. The adhesive and the pressure-sensitive adhesive can be those exemplified above for the interlayer lamination layer.
[ method for producing laminate ]
The method for producing the laminate may include a step of bonding the optical member to an adhesive layer having a viscosity value of 0.8gf or more at a temperature of 25 ℃. The tack value of the adhesive layer, the shear modulus of elasticity and thickness at a temperature of 25 ℃ and the adhesive composition are as described for the adhesive layer above.
In order to improve the adhesion, it is preferable to subject one or both surfaces of the bonded surface to a surface activation treatment such as corona treatment or plasma treatment.
The adhesive layer may be prepared as an adhesive sheet. The adhesive sheet can be produced by the following method or the like: for example, a release film (hereinafter also referred to as a separator) subjected to a release treatment is formed into a sheet-like layer with an adhesive layer, and another release film is further bonded to the adhesive layer. Each layer can be attached by attaching an adhesive sheet from which one release film is peeled to one layer, and then attaching another layer by peeling another release film.
The method for producing the laminate may include, for example, the following steps (a) to (d). A method for manufacturing the laminate will be described with reference to fig. 2.
(a) A step of preparing a front panel laminate 30 composed of a release film 31, a front panel 32 and a release film 33, and an adhesive sheet 40 composed of a light separator 41, a1 st adhesive layer 42 and a heavy separator 43, and subjecting the surface of the front panel laminate 30 from which the release film 33 has been peeled and the surface of the adhesive sheet 40 from which the light separator 41 has been peeled to corona treatment to bond them together to obtain a laminate 200 having the release film 31, the front panel 32, the 1 st adhesive layer 42 and the heavy separator 43 in this order [ fig. 2(a) ].
(b) A step of preparing a circularly polarizing plate laminate 50 composed of a release film 51, a circularly polarizing plate 52 and a release film 53, subjecting the surface from which the heavy separator 43 is peeled from the laminate 200 and the surface from which the release film 51 is peeled from the circularly polarizing plate laminate 50 to corona treatment, and then bonding them together to obtain a laminate 210 having the release film 31, the front panel 32, the 1 st adhesive layer 42, the circularly polarizing plate 52 and the release film 53 in this order [ fig. 2(b) ].
(c) A step of preparing an adhesive sheet 60 composed of a light separator 61, a 2 nd adhesive layer 62 and a heavy separator 63, subjecting the surface from which the release film 53 is peeled off from the laminate 210 and the surface from which the light separator 61 is peeled off from the adhesive sheet 60 to corona treatment, and then bonding them together to obtain a laminate 220 having the release film 31, the front panel 32, the 1 st adhesive layer 42, the circularly polarizing plate 52, the 2 nd adhesive layer 62 and the heavy separator 63 in this order [ fig. 2(c) ].
(d) A step of preparing a touch sensor layer 70 with a PET film, peeling the PET film 71 with an adhesive from the touch sensor layer 70 with a PET film, subjecting the surface from which the heavy separator 63 is peeled from the laminate 220 to corona treatment, and bonding the surface to the touch sensor layer 72 to obtain a laminate 230 having the release film 31, the front panel 32, the 1 st adhesive layer 42, the circularly polarizing plate 52, the 2 nd adhesive layer 62, and the touch sensor layer 72 in this order, and then peeling the release film 31 from the laminate 230 to obtain a laminate 240 having the front panel 32, the 1 st adhesive layer 42, the circularly polarizing plate 52, the 2 nd adhesive layer 62, and the touch sensor layer 72 in this order [ fig. 2(d) ].
< image display device >
An image display device of the present invention includes the laminate. The image display device is not particularly limited, and examples thereof include an organic EL display device, an inorganic EL display device, a liquid crystal display device, an electroluminescence display device, and the like. The image display device may also have a touch panel function. The laminate is suitable for an image display device having flexibility such as bending or bending. In the image display device, when the laminate has a front panel, the laminate is disposed on the visually-visible side of the image display device with the front panel facing outward (the side opposite to the image display element side, i.e., the visually-visible side).
The image display device of the present invention can be used as a mobile device such as a smart phone or a tablet computer, a television, a digital photo frame, an electronic signboard, a measuring instrument or a measuring instrument, an office machine, a medical machine, a computer machine, or the like. The image display device of the present invention has excellent flexibility, and is therefore suitable for flexible displays and the like.
Examples
The present invention will be described in more detail below with reference to examples. In the examples, "%" and "part(s)" are% by mass and part(s) by mass unless otherwise specified.
[ measurement of thickness ]
The film thickness was measured using a contact type film thickness measuring apparatus ("MS-5C" manufactured by Nikon K.K.). The polarizer, the retardation layer and the alignment film were measured using a laser microscope (LEXT, manufactured by olympus corporation).
[ measurement of viscosity at 25 ℃ C ]
Of adhesive layersThe viscosity value at 25 ℃ was measured using a Texture Analyzer (STABLE MICRO SYSTEMS). The procedure for measuring the viscosity at a temperature of 25 ℃ will be described with reference to FIG. 3. First, in the joining step [ FIG. 3(A) ]]In the above examples, the release film was peeled from the same adhesive sheet as used in the examples and comparative examples, and the sheet was left to stand, and a stainless steel cylindrical body 300 having a diameter of 5mm was brought close to the surface of the exposed adhesive layer 301 at room temperature (25 ℃ C.), and the bonding force was maintained for 1 second (contact area: 19.6 mm) with a load of 100g after pressing2). After the joining, in a peeling step (FIG. 3(B)]When the stainless steel cylinder 300 was lifted at a speed of 60 mm/min, the peel force was measured to be maximum [ FIG. 3(C) ]]The measured value of (A) was taken as a viscosity value. The tack value at a temperature of 25 ℃ of the adhesive layer was measured 24 hours after the adhesive layer was produced.
[ measurement of shear elastic modulus at a temperature of 25 ]
The shear modulus at 25 ℃ of the adhesive layer was measured using a viscoelasticity measuring apparatus (MCR-301, Anton Paar Co.). An adhesive sheet similar to the adhesive sheets used in examples and comparative examples was prepared to have a width of 20mm × a length of 20mm, a release film was peeled off, a plurality of sheets were laminated so as to have a thickness of 150 μm and bonded to a glass plate, and then the shear modulus at a temperature of 25 ℃ was confirmed by measuring the strain in a temperature range from-20 ℃ to 100 ℃ in a state of being bonded to a measurement chip under conditions of a frequency of 1.0Hz, a deformation amount of 1%, and a temperature rise rate of 5 ℃/min. The shear modulus at 25 ℃ of the adhesive layer was measured 24 times after the adhesive layer was formed.
[ evaluation of static bending durability ]
Fig. 4 shows the method of the static bending durability test (mandrel bending test). First, the laminate was cut into test pieces of 1cm × 10 cm. On the test plate 400, a laminate 401 was placed so that the front plate side was downward, and a steel rod 402 having a diameter of 5mm was placed thereon [ FIG. 4(A) ]. The test piece was folded together with the test plate 400 by hand so that the front panel was on the outside and fixed [ fig. 4(B) ]. The state was maintained, and the maximum time during which no air bubbles were generated between the circularly polarizing plate and the adhesive layer or in the adhesive layer was measured.
A: no bubbles were generated within 72 hours.
B: bubbles were generated over 48 hours and within 72 hours.
C: bubbles were generated over 24 hours and within 48 hours.
D: bubbles were generated within 24 hours.
[ production of adhesive sheets C1-C8 ]
A1-liter reactor equipped with a cooling device so as to allow easy temperature adjustment by nitrogen reflux was charged with a monomer mixture shown in Table 1, which was composed of 2-ethylhexyl acrylate (2-EHA), n-butyl acrylate (n-BA), β -carboxyethyl acrylate (B-CEA), Acrylic Acid (AA), Glycidyl Methacrylate (GMA), and 2-hydroxyethyl methacrylate (2-HEMA). To remove oxygen, the solution was maintained at 60 ℃ after 1 hour of nitrogen reflux. The monomer mixture was uniformly mixed, and then the photopolymerization initiators benzildimethylketal (I-651) and 1-hydroxycyclohexylphenone (I-184) were added in the amounts shown in Table 1. (meth) acrylic resins A1 to A8 were produced by irradiating the resins with a UV lamp (10mW) while stirring. The obtained (meth) acrylic resins a1 to A8, additives T1 to T3, and 1-hydroxycyclohexyl phenyl ketone (I-184) were mixed in amounts shown in table 1 to prepare adhesive compositions B1 to B8. Adhesive compositions B1 to B8 were applied to a release film A (polyethylene terephthalate film, thickness 38 μm) coated with a silicon release agent so that the thickness became 25 μm, and a release film B (polyethylene terephthalate film, thickness 38 μm) was bonded thereto and subjected to UV irradiation to prepare adhesive sheets C1 to C8 each composed of release film A/adhesive layer/release film B. The adhesive sheets C1 to C8 were produced, and the viscosity at 25 ℃ and the shear modulus were measured 24 hours later. The condition of UV irradiation was a cumulative light amount of 400mJ/cm2Illuminance of 1.8mW/cm2(UVV reference).
Figure BDA0003116827330000191
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.)
B-CEA: beta carboxyethyl acrylate (Sigma-Aldrich, USA)
AA: acrylic acid (Tokyo chemical industry Co., Ltd.)
GMA: glycidyl methacrylate (Sigma-Aldrich, USA)
2-HEMA: 2-hydroxyethyl methacrylate (Tokyo Kasei Co., Ltd.)
I-651: benzil dimethyl ketal (BASF)
I-184: 1-Hydroxycyclohexylphenone (BASF)
T1: acrylic acid 3, 3, 5-trimethylcyclohexyl ester (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 a hard coat layer to one surface of a transparent base film (a polyamideimide film, thickness 40 μm) produced according to example 4 of jp 2018-119141 a, a front panel (thickness 50 μm) having a hard coat layer of 10 μm formed on one surface of the base film was produced by drying the solvent and UV curing.
[ composition for Forming hard coat layer ]
The resin composition was prepared by mixing 30 parts by mass of a multifunctional acrylate (MIWON specialty chemical, MIRAMER M340), 50 parts by mass of a nano silica sol (particle size 12nm, solid content 40%) dispersed in propylene glycol monomethyl ether, 17 parts by mass of ethyl acetate, 2.7 parts by mass of a photopolymerization initiator (BASF corporation, I184), and 0.3 part by mass of a fluorine-based additive (KY 1203, kyo chemical industries co., ltd.) with a mixer, and filtering the mixture using a polypropylene (PP) filter.
(preparation of circular polarizing plate)
A polyvinyl alcohol (PVA) film having an average polymerization degree of about 2400, a saponification degree of 99.9 mol% or more and a thickness of 20 μm was prepared. The PVA film was immersed in pure water at 30 ℃ and then immersed in an aqueous solution having a mass ratio of iodine/potassium iodide/water of 0.02/2/100 at 30 ℃ to carry out iodine dyeing (iodine dyeing step). The PVA film subjected to the iodine dyeing step was immersed in an aqueous solution of potassium iodide/boric acid/water at a mass ratio of 12/5/100 at 56.5 ℃ to be subjected to boric acid treatment (boric acid treatment step). The PVA film subjected to the boric acid treatment step was washed with pure water at 8 ℃ and then dried at 65 ℃ to obtain a polarizer in which iodine was adsorbed in polyvinyl alcohol and oriented. The PVA film is stretched 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 resulting polarizer was 7 μm.
The polarizer obtained above was bonded to a cycloolefin polymer (COP) film (ZF-14, manufactured by Nippon Ruiz Co., Ltd., in-plane retardation value of 1nm at a wavelength of 550 nm) having a thickness of 13 μm with a nip roll through a water-based adhesive. The obtained laminate was dried at 60 ℃ for 2 minutes while maintaining the tension of 430N/m, to obtain a linear polarizing plate having a COP film on one side. The water-based adhesive was prepared by adding 3 parts by mass of carboxyl-modified polyvinyl alcohol ("KURARAY POVAL KL 318", KURARAY co., ltd.) and 1.5 parts by mass of water-soluble polyamide epoxy Resin ("Sumirez Resin 650" (aqueous solution having a solid content of 30%), manufactured by takaoka chemical industries co., ltd.) to 100 parts by mass of water.
The polarizer side of the linearly polarizing plate and the retardation layer were bonded via an acrylic adhesive layer having a thickness of 5 μm. The retardation layer had a thickness of 5 μm, and the layer was constituted of a layer λ/2 (thickness 2 μm)/a UV-curable adhesive layer (thickness 2 μm)/a layer λ/4 (thickness 1 μm) containing a layer obtained by curing a liquid crystal compound. Thus, a circularly polarizing plate (thickness: 30 μm, layer structure: COP film/polarizer/retardation layer) was produced.
(preparation of touch sensor laminate)
A separation layer is formed by applying an acrylic resin to a glass plate. Next, a light-transmitting electrode layer was formed on the separation layer, and a touch sensor layer (thickness 7 μm) composed of the light-transmitting electrode layer and the separation layer was produced. Then, a release film a is laminated on the side of the light-transmitting electrode layer opposite to the side of the separation layer. A release film B was laminated on the surface from which the glass plate was removed, and a touch sensor laminate having a layer of release film a/touch sensor layer/release film B was produced.
(preparation of laminate)
The above members were bonded using the adhesive sheet described in table 2 as an adhesive layer to prepare a laminate. The laminate comprises a front panel (thickness 50 μm), a1 st adhesive layer (thickness 25 μm), a circularly polarizing plate (thickness 30 μm), a 2 nd adhesive layer (thickness 25 μm), and a touch sensor layer (thickness 7 μm) in this order, and the total thickness is 137 μm. When the members are bonded, the bonding surfaces are subjected to corona treatment. The laminate thus produced was left to stand in an environment of 23 ℃ and 55% relative humidity for 24 hours, and then the laminate was evaluated for static bending durability. The results are shown in Table 2.
< example 2 and comparative examples 1 to 5 >
A laminate was produced in the same manner as in example 1, except that the adhesive sheets described in table 2 were used for the 1 st adhesive layer and the 2 nd adhesive layer. The laminate was evaluated for static bending durability. 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]
Figure BDA0003116827330000221

Claims (8)

1. A laminate comprising a1 st optical member, a1 st adhesive layer, a 2 nd optical member, a 2 nd adhesive layer and a 3 rd optical member in this order,
the 1 st adhesive layer and the 2 nd adhesive layer each have a tack value at a temperature of 25 ℃ of 0.8gf or more and satisfy formula (1):
the tack value at 25 ℃ for the 2 nd adhesive layer is greater than the tack value (1) at 25 ℃ for the 1 st adhesive layer.
2. The laminate according to claim 1, wherein each of the 1 st adhesive layer and the 2 nd adhesive layer has a tack value at a temperature of 25 ℃ of 10.0gf or less.
3. The laminate according to claim 1 or 2, wherein the shear elastic modulus at a temperature of 25 ℃ of each of the 1 st adhesive layer and the 2 nd adhesive layer is 0.5MPa or less.
4. The laminate according to any one of claims 1 to 3, wherein the 1 st optical member is a front panel.
5. The laminate according to any one of claims 1 to 4, wherein the 2 nd optical member is a polarizing plate.
6. The laminate of any one of claims 1 to 5, wherein the 3 rd optical member is a touch sensor panel.
7. An image display device comprising the laminate according to any one of claims 1 to 6.
8. A method for producing a laminate according to claim 1, comprising: a step of bonding the optical member to the adhesive layer having a viscosity value of 0.8gf or more at a temperature of 25 ℃.
CN202110665978.XA 2020-06-19 2021-06-16 Laminate, image display device, and method for manufacturing same Pending CN113820776A (en)

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