CN113260509A - Laminate, optical film, image display device, and method for manufacturing same - Google Patents

Abstract

The invention provides a polarizing plate with an adhesive layer having a novel structure. The laminate of the present invention comprises: a polarizing plate comprising an ultraviolet absorber, and an adhesive layer located on at least one side of the polarizing plate, wherein the adhesive layer is formed from an adhesive composition comprising: a base polymer, a light curing agent, and a molar absorption coefficient at a wavelength of 380nm of 15[ L mol [ ]^‑1cm^‑1]The photopolymerization initiator described above.

Description

Laminate, optical film, image display device, and method for manufacturing same

Technical Field

The present invention relates to a laminate comprising a polarizing plate and an adhesive layer, an optical film and an image display device comprising the laminate, and a method for manufacturing the image display device.

Background

In a liquid crystal display device (LCD) or the like, polarizing plates are attached to both sides or one side of a liquid crystal cell in view of an image forming method. As the polarizing plate, a polarizing film in which protective films such as triacetyl cellulose film are bonded to both surfaces of a polarizer is generally used, and the polarizer is generally formed by adsorbing a dichroic material such as iodine or dichroic dye on a polyvinyl alcohol film and stretching and orienting the film. When the polarizing plate is attached to the panel, an adhesive is generally used, and an adhesive layer-attached polarizing plate in which an adhesive layer is provided in advance on one side of the polarizing plate is generally used.

As essential characteristics required for an adhesive used for a polarizing plate, long-term adhesion (peeling durability) when a polarizing plate with an adhesive layer is bonded to a panel is required. For example, it is required that the adhesive does not suffer from problems such as peeling and lifting even in a high-temperature/high-humidity environment.

On the other hand, when the polarizing plate is bonded to the panel using an adhesive, a bonding failure such as mixing of air bubbles or displacement of a bonding position may occur. When the lamination failure occurs, the polarizing plate is peeled off from the panel and the panel is reused. Therefore, the adhesive is required to have removability (removability) to allow the polarizing plate to be easily peeled from the panel after a certain period of time has elapsed from the attachment without leaving the paste. With the recent trend toward thinner and larger panels, the desire for reuse of panels has increased, and reworkability is an important item. However, durability and reworkability are in a trade-off relationship, and therefore, they are properties that are difficult to achieve at the same time, and studies have been made to achieve at the same time. For example, patent document 1 discloses a polarizing plate with an adhesive layer designed to have low adhesiveness immediately after being bonded to an adherend and to have increased adhesive strength after heating.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2018-060172

Disclosure of Invention

A polarizing plate with an adhesive layer having a novel structure and having properties such as adhesiveness and reworkability is still required.

The present inventors have found that the above problems can be solved by a laminate obtained by laminating an adhesive layer formed from an adhesive composition containing a base polymer, a photocurable agent and a specific photopolymerization initiator on a polarizing plate, and have completed the present invention.

The present invention includes the following embodiments.

[1] A laminate, comprising:

a polarizing plate comprising an ultraviolet absorber, and

an adhesive layer on at least one side of the polarizing plate,

the pressure-sensitive adhesive layer is a layer formed from a pressure-sensitive adhesive composition containing: a base polymer, a light curing agent, and a molar absorption coefficient at a wavelength of 380nm of 15[ L mol [ ]^-1cm^-1]The photopolymerization initiator described above.

[2] The laminate according to [1], wherein,

the light transmittance of the polarizing plate at 380nm is 20% or less.

[3] The laminate according to [1] or [2], wherein,

the adhesive layer can be cured by irradiation with an active energy ray having a wavelength range of 380nm to 450 nm.

[4] The laminate according to any one of [1] to [3],

the adhesive layer has a bonding strength after curing greater than a bonding strength before curing.

[5] The laminate according to any one of [1] to [4],

the adhesive force of the adhesive layer before curing to alkali-free glass is 7N/25mm or less, and the adhesive force is measured by 90-degree peeling at a speed of 300 mm/min.

[6] The laminate according to any one of [1] to [5],

the adhesive layer has an adhesion to alkali-free glass of 5N/25mm or more after curing, and the adhesion is measured by 90-degree peeling at a speed of 300 mm/min.

[7] The laminate according to any one of [1] to [6],

the adhesive composition further contains a sensitizer.

[8] The laminate according to any one of [1] to [7],

the photopolymerization initiator contains at least one selected from oxime compounds, metallocene compounds, acylphosphine compounds and aminoacetophenone compounds.

[9] The laminate according to any one of [1] to [8],

the ultraviolet absorber includes at least one selected from benzophenone compounds, oxalic anilide compounds, cyanoacrylate compounds, benzotriazole compounds, and triazine compounds.

[10] The laminate according to any one of [1] to [9],

the adhesive composition contains 1 to 50 parts by weight of the light curing agent and 0.01 to 3 parts by weight of the photopolymerization initiator, based on 100 parts by weight of the base polymer.

[11] The laminate according to any one of [1] to [10],

the base polymer contains an acrylic polymer.

[12] The laminate according to [11], wherein,

the acrylic polymer contains a hydroxyl group-containing monomer and a nitrogen-containing monomer as monomer components.

[13] The laminate according to any one of [1] to [12],

the above-mentioned light curing agent contains a polyfunctional (meth) acrylate.

[14] The laminate according to any one of [1] to [13],

the polarizing plate includes: a polarizer and a transparent protective film on at least one surface of the polarizer, wherein the transparent protective film contains the ultraviolet absorber.

[15] An optical film comprising the laminate according to any one of [1] to [14 ].

[16] An image display device comprising the laminate according to any one of [1] to [14 ].

[17] The apparatus according to [16], wherein,

the adhesive layer contains a cured product of the base polymer and the light curing agent.

[18] The method for manufacturing an image display device according to [16] or [17], comprising:

the pressure-sensitive adhesive layer is cured by irradiating the pressure-sensitive adhesive layer with an active energy ray having a wavelength range of 380nm to 450 nm.

[19] The method according to [18], wherein,

the irradiation amount of the active energy ray in the wavelength range of 380nm to 450nm of the adhesive layer is 1000mJ/cm²The above.

The present invention has one or more of the following effects.

(1) Provided is a laminate which can be used as a polarizing plate having an adhesive layer. The laminate of the present invention can be preferably used for an image display device such as an optical film and a liquid crystal display device (LCD).

(2) After the laminate of the present invention is bonded to an adherend such as a panel, the adhesive layer is photocured, whereby the adhesive strength can be increased. According to a preferred embodiment of the present invention, it is possible to provide reworkability immediately after bonding, increase adhesion after photocuring, and provide excellent long-term adhesion (peeling durability).

(3) The pressure-sensitive adhesive layer constituting the laminate of the present invention is of a photocurable type, and the curing timing after the lamination to an adherend can be arbitrarily set, so that the preparation time of the process can be flexibly coped with.

Drawings

Fig. 1 is a schematic cross-sectional view of a laminate according to an embodiment of the present invention.

Description of the symbols

1 polarizer

2. 2' transparent protective film

3 polarizing plate

4 adhesive layer

5 diaphragm

6 laminated body

10 polarizing film with adhesive layer

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail. The present invention is not limited to the following embodiments, and can be implemented by being arbitrarily modified within the scope not departing from the gist of the present invention. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. For convenience of explanation, the dimensional ratios of the drawings are sometimes exaggerated and are different from the actual ratios.

All documents and publications mentioned in the present specification are incorporated herein by reference in their entirety for all purposes. The present specification includes the disclosure of the claims, the description, and the drawings of japanese patent application No. 2019-011976 (application published on day 28/1/2019), which is the basis of claiming priority of the present application.

One embodiment of the present invention relates to a laminate including: a polarizing plate comprising an ultraviolet absorber, and an adhesive layer located on at least one side of the polarizing plate, wherein the adhesive layer is formed from an adhesive composition comprising: a base polymer, a light curing agent, and a molar absorption coefficient at a wavelength of 380nm of 15[ L mol [ ]^-1cm^-1]The photopolymerization initiator described above.

Fig. 1 is a schematic cross-sectional view showing one embodiment of a polarizing film with an adhesive layer using a laminate.

The polarizing film with an adhesive layer 10 is configured to include a laminate 6 including an adhesive layer 4 on one main surface of a polarizing plate 3. The adhesive layer 4 is fixedly laminated on one main surface of the polarizing plate 3. In fig. 1, the polarizing plate 3 is configured as a polarizing film including a polarizer 1 and transparent protective films 2 and 2 'formed on both surfaces of the polarizer 1, and the transparent protective films 2 and 2' contain an ultraviolet absorber. The transparent protective film may be provided only on one surface of the polarizer. In addition, the ultraviolet absorber may be included in only one of the transparent protective films. Although not shown in fig. 1, the polarizer 1 and the transparent protective films 2 and 2' may be laminated with a spacer layer such as an adhesive layer, and an undercoat layer (undercoat layer) interposed therebetween. In addition, the ultraviolet absorber may be included in other layers (e.g., an adhesive layer, an undercoat layer, and the like) constituting the polarizing plate.

The adhesive layer 4 contains a base polymer, a light curing agent and a molar absorption coefficient of 15[ L mol ] at a wavelength of 380nm^-1cm^-1]The photocurable adhesive containing the above photopolymerization initiator is photocurable by irradiation with active energy rays, and the adhesive strength (peel strength) between the adhesive and an adherend is increased.

The polarizing plate 10 with an adhesive layer is used by attaching the adhesive layer 4 to an adherend.

A separator 5 is temporarily attached to the surface of the pressure-sensitive adhesive layer 4 of the pressure-sensitive adhesive layer-attached polarizing film 10 shown in fig. 1. As the separator 5, for example, a separator configured such that a release layer formed by a release treatment agent is provided on one surface of a sheet-like base material (backing material) and the one surface is a release surface can be preferably used. Before the laminate is attached to an adherend, the separator 5 is peeled off from the surface of the pressure-sensitive adhesive layer 4 and the exposed surface of the pressure-sensitive adhesive layer 4 is attached to the surface of the adherend, whereby the laminate 6 is temporarily attached to the adherend. The thickness of the separator 5 is usually 3 to 200 μm, preferably about 10 to 100 μm.

Alternatively, the following may be used: a mode (roll form) in which the polarizing plate 3 having a surface of the polarizing plate 3 not facing the pressure-sensitive adhesive layer 4 as a release surface is used instead of the separator 5, and the polarizing film 10 having the pressure-sensitive adhesive layer is wound so that the pressure-sensitive adhesive surface of the pressure-sensitive adhesive layer 4 not facing the polarizing plate 3 and the surface of the polarizing plate 3 not facing the pressure-sensitive adhesive layer 4 are in contact with each other for protection. Before the laminate is attached to an adherend, the surface of the adhesive layer 4 is exposed, and the exposed surface of the adhesive layer 4 is attached to the surface of the adherend, whereby the laminate 6 is temporarily attached to the adherend.

The laminate 6 is laminated on the surface of an adherend (for example, a panel) by peeling and removing the separator 5 from the surface of the pressure-sensitive adhesive layer 4 of the pressure-sensitive adhesive layer-attached polarizing film 10 shown in fig. 1 and bonding the exposed surface of the pressure-sensitive adhesive layer 4 to the surface of the adherend. Before the pressure-sensitive adhesive layer 4 is photo-cured, the polarizing plate 3 is temporarily attached to the adherend via the pressure-sensitive adhesive layer 4. By the photo-curing of the adhesive layer 4, the adherend and the polarizing plate 3 are fixed together via the adhesive layer 4.

In the present specification, "adhesion" means a state in which two layers stacked are firmly adhered to each other and peeling is not possible or difficult at the interface between the two layers. The term "temporary adhesion" means a state in which the adhesion between the two layers after lamination is small and the two layers can be easily peeled off from each other at the interface.

Hereinafter, the members constituting the pressure-sensitive adhesive layer-attached polarizing plate 10 of the above embodiment will be described.

< polarizing plate >

The polarizing plate contains an ultraviolet absorber. The constitution of the polarizing plate is not particularly limited, and the polarizing plate preferably has: a polarizer and a transparent protective film disposed on at least one surface of the polarizer.

(polarizing mirror)

The polarizer is not particularly limited, and various polarizers can be used. Examples of the polarizer include films obtained by uniaxially stretching hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and ethylene-vinyl acetate copolymer partially saponified films, and polyene oriented films such as polyvinyl alcohol dehydrated products and polyvinyl chloride desalted products, and the like. Among these, a polarizer made of a dichroic material such as a polyvinyl alcohol film and iodine is preferable.

The thickness of these polarizers is not particularly limited, but is usually 2 to 25 μm.

The polarizer obtained by uniaxially stretching a polyvinyl alcohol film dyed with iodine can be produced, for example, by dyeing a polyvinyl alcohol film by immersing the film in an aqueous iodine solution and stretching the film to 3 to 7 times the original length. If necessary, the substrate may be immersed in an aqueous solution of potassium iodide or the like optionally containing boric acid, zinc sulfate, zinc chloride or the like. Further, the polyvinyl alcohol film may be immersed in water and washed with water before dyeing, if necessary. By washing the polyvinyl alcohol film with water, dirt and an anti-blocking agent on the surface of the polyvinyl alcohol film can be washed off, and the polyvinyl alcohol film can be swollen to prevent unevenness such as uneven dyeing. The stretching may be performed after the dyeing with iodine, or may be performed while dyeing, or may be performed after the stretching with iodine. Stretching may be carried out in an aqueous solution or water bath of boric acid, potassium iodide, or the like.

(transparent protective film)

The transparent protective film is not particularly limited, and various transparent protective films can be used. As a material constituting the transparent protective film, a material excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, and the like is preferable. Examples thereof include: polyester polymers such as polyethylene terephthalate and polyethylene naphthalate; cellulose polymers such as cellulose diacetate and cellulose triacetate; acrylic polymers such as polymethyl methacrylate; styrene polymers such AS polystyrene and acrylonitrile-styrene copolymer (AS resin); a polycarbonate-series polymer; polyolefin polymers such as polyethylene, polypropylene, cyclic olefin polymers, polyolefins having a norbornene structure, and ethylene-propylene copolymers; vinyl chloride-based polymers; amide polymers such as nylon and aromatic polyamide; an imide polymer; sulfone polymers; polyether sulfone polymers; polyether ether ketone polymers; polyphenylene sulfide-based polymers; a vinyl alcohol polymer; a vinylidene chloride-based polymer; vinyl butyral polymers; an aromatic ester polymer; polyoxymethylene polymers; epoxy polymers, or blends of the above polymers, and the like. These protective films are generally bonded to the polarizer via an adhesive layer. The transparent protective film can be formed by applying a thermosetting resin such as a (meth) acrylic resin, a urethane resin, an acrylic urethane resin, an epoxy resin, or a silicone resin, or an ultraviolet-curable resin to a polarizer and curing the applied resin.

As the transparent protective film, a retardation film can be used. Examples of the retardation film include a retardation film having a front retardation of 40nm or more and/or a thickness direction retardation of 80nm or more. The front phase difference is usually controlled within a range of 40 to 200nm, and the thickness direction phase difference is usually controlled within a range of 80 to 300 nm. When the retardation film is used as the transparent protective film, the retardation film also functions as a polarizer protective film, and therefore, the thickness can be reduced. Examples of the retardation film include a birefringent film obtained by subjecting a thermoplastic resin film to a uniaxial stretching treatment or a biaxial stretching treatment. The temperature and stretch ratio of the stretching can be appropriately set depending on the retardation value, the material and thickness of the film.

The thickness of the transparent protective film can be determined as appropriate, but is preferably 3 to 200 μm in view of strength, workability such as workability, and thin layer property. The thicker the thickness, the more the amount of light transmitted decreases, and the reaction of the polymerization initiator tends to be delayed. As the thickness is reduced, members such as polarizers and panels tend to be deteriorated. From the above viewpoint, the thickness is preferably 5 to 100 μm, and more preferably 5 to 80 μm. The transparent protective film may be used in a plurality of layers.

The transparent protective film may have a functional layer such as a hard coat layer, an antireflection layer, an adhesion prevention layer, a diffusion layer, and an antiglare layer on the surface thereof not bonded to the polarizer. The functional layers such as the hard coat layer, the antireflection layer, the adhesion prevention layer, the diffusion layer, and the antiglare layer may be provided as a transparent protective film itself, or may be provided separately from the transparent protective film.

A pressure-sensitive adhesive layer may be provided on the surface of the functional layer such as the hard coat layer, the antireflection layer, the adhesion prevention layer, the diffusion layer, and the antiglare layer.

The transparent protective film and the polarizer may be laminated together with an adhesive layer, an undercoat layer (undercoat layer), and the like interposed therebetween. The adhesive layer is not particularly limited as long as it is optically transparent, and may be composed of various types of adhesives such as aqueous, solvent-based, hot-melt, and active energy ray-curable adhesives. An easy-adhesion layer may be provided between the transparent protective film and the adhesive layer.

(ultraviolet absorber)

The ultraviolet absorber is included in the polarizing plate for the main purpose of suppressing deterioration of a constituent member (for example, polarizer) of the image display device due to incident ultraviolet light. Among them, since the polarizer is susceptible to the influence of ultraviolet light, it is preferable that the ultraviolet absorber is contained in the transparent protective film adjacent to the polarizer.

The ultraviolet absorber is not particularly limited, and various ultraviolet absorbers can be used. Specific examples thereof include benzophenone compounds, oxalic anilide compounds, cyanoacrylate compounds, benzotriazole compounds, and triazine compounds. The ultraviolet absorber may be used alone in 1 kind, or 2 or more kinds may be selected. Among them, benzotriazole compounds and triazine compounds are preferable, and particularly, triazine compounds are more preferable. The triazine compound can obtain a sufficient ultraviolet absorption effect with a small amount of addition, and can prevent bleeding during film formation.

Examples of the benzophenone compound include: 2, 4-dihydroxybenzophenone, 2-hydroxy-4-n-octyloxybenzophenone, 2 '-dihydroxy-4, 4' -dimethoxybenzophenone, 2-hydroxy-4-n-octyloxybenzophenone, bis (5-benzoyl-4-hydroxy-2-methoxyphenyl) methane, 1, 4-bis (4-benzoyl-3-hydroxybenzophenone) butane and the like.

Examples of the oxanilide compound include: n- (2-ethylphenyl) -N '- (2-ethoxyphenyl) oxamide, N- (2-dodecylphenyl) -N' - (2-ethoxyphenyl) oxamide, and the like.

Examples of the cyanoacrylate-based compound include: octyl 2-cyano-3, 3-diphenylacrylate, and the like.

Examples of the benzotriazole compound include: 2- (3, 5-di-tert-amyl-2-hydroxyphenyl) benzotriazole, 2- (3-dodecyl-5-methyl-2-hydroxyphenyl) benzotriazole, 2- (3, 5-bis (2-methyloctan-2-yl) -2-hydroxyphenyl) benzotriazole, 2- (3-tert-butyl-5- (octyloxycarbonylethyl) -2-hydroxyphenyl) benzotriazole, 2' -methylenebis [4- (1,1,3, 3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol ], 2- (3, 5-di-tert-butyl-2-hydroxyphenyl) -5-chlorobenzotriazole, 2-bis (t-butyl-2-hydroxyphenyl) benzotriazole, 2-bis (t-butyl-2-hydroxy-phenyl) benzotriazole, 2-bis (t-butyl-2-hydroxy-2-yl) phenol, 2-bis (t-butyl-2-hydroxy-phenyl) benzotriazole, 2-bis (t-butyl-2-hydroxy-methyl-2-hydroxy-phenyl) benzotriazole, 2-methyl-hydroxy-phenyl) benzotriazole, 2-bis (t-butyl-2-hydroxy-phenyl) benzotriazole, 2-bis (t-methyl-2-ethyl) benzotriazole, 2-bis (t-butyl-2-methyl-phenyl) benzotriazole, 2-methyl-phenyl) benzotriazole, 2-bis(s), 2- (2H-benzotriazol-2-yl) p-cresol, 2- (2H-benzotriazol-2-yl) -4, 6-bis (1-methyl-1-phenylethyl) phenol, 2-benzotriazol-2-yl-4, 6-di-tert-butylphenol, 2- [ 5-chloro (2H) -benzotriazol-2-yl ] -4-methyl-6-tert-butylphenol, 2- (2H-benzotriazol-2-yl) -4, 6-di-tert-butylphenol, 2- (2H-benzotriazol-2-yl) -4- (1,1,3, 3-tetramethylbutyl) phenol, 2- (2H-benzotriazol-2-yl) -4-methyl- 6- (3,4,5, 6-tetrahydrophthalimidomethyl) phenol, the reaction product of methyl 3- (3- (2H-benzotriazol-2-yl) -5-tert-butyl-4-hydroxyphenyl) propionate/polyethylene glycol 300, 2- (2H-benzotriazol-2-yl) -6- (linear and side chain dodecyl) -4-methylphenol, 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [ 2-hydroxy-3, 5-bis (. alpha.,. alpha. -dimethylbenzyl) phenyl ] -2H-benzotriazole, 3- (2H-benzotriazol-2-yl) -5- (1, 1-dimethylethyl) -4-hydroxy-C7-9 side chain and straight chain alkyl esters, 2-methylenebis [6- (2H-benzotriazol-2-yl) -4- (1,1,3, 3-tetramethylbutyl) phenol ], and the like.

The triazine compound is not particularly limited, and various triazine compounds can be used. For example, triazine compounds described in WO2005/109052 and Japanese patent application laid-open No. 2009-52021 can be suitably used. Examples thereof include: having 2, 4-diphenyl-6- (2-hydroxy-4-methoxyphenyl) -1,3, 5-triazine, 2, 4-diphenyl-6- (2-hydroxy-4-ethoxyphenyl) -1,3, 5-triazine, 2, 4-diphenyl (2-hydroxy-4-propoxyphenyl) -1,3, 5-triazine, 2, 4-diphenyl (2-hydroxy-4-butoxyphenyl) -1,3, 5-triazine, 2, 4-diphenyl-6- (2-hydroxy-4-hexyloxyphenyl) -1,3, 5-triazine, 2, 4-diphenyl-6- (2-hydroxy-4-octyloxyphenyl) -1,3, 5-triazine, 2, 4-diphenyl-6- (2-hydroxy-4-dodecyloxyphenyl) -1,3, 5-triazine, 2, 4-diphenyl-6- (2-hydroxy-4-benzyloxyphenyl) -1,3, 5-triazine, 2, 4-diphenyl-6- (2-hydroxy-4-butoxyethoxy) -1,3, 5-triazine, 2, 4-bis [ 2-hydroxy-4-butoxyphenyl ] -6- (2, 4-dibutoxyphenyl) -1,3, 5-triazine, 2, 4-bis (2, 4-dimethylphenyl) -6- [ 2-hydroxy-4- (3-alkoxy-2-hydroxypropoxy) -5-alpha-cumylphenyl ] -s-triazine skeleton (alkoxy; isoxy, nonoxy, decyloxy and the like) ultraviolet absorbers, 2,4, 6-tris (2-hydroxy-4-hexyloxyphenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-4-octyloxyphenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-4-dodecyloxyphenyl) -1,3, 5-triazine, 2,4, 6-triazine, 2,4, 6-tris (2-hydroxy-4-benzyloxyphenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-4- (1- (2-ethoxyhexyloxy) -1-oxopropan-2-yloxy) phenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-3-methyl-4-hexyloxyphenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-3-methyl-4-octyloxyphenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-3-methyl-4-dodecyloxyphenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-3-methyl-4-benzyloxyphenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-3-methyl-4-butoxyethoxyphenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-3-methyl-4-propoxyethoxyphenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-3-methyl-4-methoxycarbonylpropoxyphenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-3-methyl-4-ethoxycarbonylethoxyphenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-3-methyl-4- (1- (2-ethoxyhexyloxy) -1-oxopropan-2-yloxy) phenyl) -1,3, 5-triazine, 2, 4-bis (2, 4-dimethylphenyl) -6- [ 2-hydroxy-4- (3-alkoxy-2-hydroxypropoxy) -5- α -cumylphenyl ] -s-triazine skeleton (alkoxy; isoalkoxy, nonyloxy, decyloxy and the like) ultraviolet absorbers.

Commercially available triazine compounds include Tinuvin 1577, Tinuvin 460 and Tinuvin 477 (manufactured by BASF JAPAN). Commercially available benzotriazole compounds include Adecastab LA-31 (manufactured by ADEKA) and Tinuvin 326 (manufactured by BASF JAPAN).

The content of the ultraviolet absorber in the case where the ultraviolet absorber is contained in the transparent protective film is not particularly limited. For example, the amount of the protective film is preferably 0.01 to 10 wt%, more preferably 0.01 to 7 wt%, and still more preferably 0.05 to 5 wt% based on the weight (100 wt%) of the transparent protective film.

(light transmittance)

The light transmittance of the polarizing plate at a wavelength of 380nm is preferably 20% or less. The polarizing plate has such UV absorption ability, and thus can suppress deterioration of the polarizer even when the pressure-sensitive adhesive layer is photo-cured by irradiation with active energy rays from the polarizing plate side. The lower limit of the light transmittance at a wavelength of 380nm is not particularly limited, and for example, in order to promote the photocuring reaction by the polymerization initiator and sufficiently exhibit the function of the pressure-sensitive adhesive due to the increase in the adhesive force after photocuring, it is preferably 1% or more. The light transmittance at a wavelength of 380nm is more preferably 1 to 20%, still more preferably 1 to 15%, particularly preferably 1.5 to 12%. The light transmittance at a wavelength of 380nm can be measured using a spectrophotometer.

The adhesive layer of the present invention contains a photopolymerization initiator described later, and can be cured by irradiating active energy rays from the polarizer side having such UV absorption ability.

(thickness)

The thickness of the polarizing plate is not particularly limited, but is usually 10 to 200. mu.m.

< adhesive layer >

The pressure-sensitive adhesive layer is a layer formed from a pressure-sensitive adhesive composition containing a base polymer, a photocurable agent, a photopolymerization initiator, and a sensitizer used as needed. The adhesive layer is a photocurable adhesive. The adhesive layer can be subjected to a photocuring reaction by irradiation with active energy rays, thereby improving the adhesion to an adherend. The adhesive layer may be a cured layer of an adhesive composition containing a base polymer, a photo-curing agent, a photo-polymerization initiator, and a sensitizer to be used as needed. For example, the adhesive layer includes a cured product of a base polymer and a photo-curing agent. Preferably, the adhesive layer can be cured by irradiation with active energy rays in a wavelength range of 380nm or more and 450nm or less.

The adhesive layer has a small adhesion to the polarizing plate before photocuring, and therefore, can be easily reworked. The pressure-sensitive adhesive layer increases the adhesion to an adherend by photocuring, and is excellent in long-term adhesion (peeling durability).

While thermosetting adhesives may be cured over time in a storage state, photocurable adhesives are hardly cured in a normal storage environment and are cured by irradiation with active energy rays. The laminate of the present invention has advantages such as the possibility of arbitrarily setting the curing timing of the pressure-sensitive adhesive layer and the flexibility of coping with the preparation time of the process.

From the viewpoint of reworkability and adhesiveness, the adhesive force of the pressure-sensitive adhesive layer after curing is preferably greater than the adhesive force before curing. The method for measuring the adhesive strength of the pressure-sensitive adhesive layer before or after curing is not particularly limited. For example, the adhesion of the pressure-sensitive adhesive layer before and after curing can be measured as the adhesion to the alkali-free glass before and after curing (pre-curing adhesion T1 to the alkali-free glass and post-curing adhesion T2 to the alkali-free glass) based on 90 degree peel at a speed of 300 mm/min. Specifically, T1 and T2 were determined as follows: the adhesion when the adhesive layers before and after curing formed on the alkali-free glass were peeled from the alkali-free glass at a peeling angle of 90 degrees (i.e., in the vertical direction) and a drawing speed of 300 mm/min was measured based on the 90 ° peeling test of JIS Z0237: 2009. In one embodiment, from the viewpoint of reworkability and adhesiveness, the ratio of the adhesion after curing to the adhesion before curing (for example, the adhesion after curing to the alkali-free glass/the adhesion before curing to the alkali-free glass (T2/T1)) of the pressure-sensitive adhesive layer is preferably 1 or more, more preferably 1.5 or more, and still more preferably 2 or more.

From the viewpoint of facilitating the rework and preventing paste residue after peeling, the adhesion force to the alkali-free glass before curing of the pressure-sensitive adhesive layer (adhesion force to alkali-free glass before curing, T1) measured based on 90 degree peeling at a speed of 300 mm/min is preferably 7N/25mm or less, more preferably 6N/25mm or less, further preferably 5N/25mm or less, still further preferably less than 5N/25mm, and particularly preferably 3N/25mm or less. The adhesion force (T1) to the alkali-free glass before curing is preferably 0.1N/25mm or more, more preferably 0.5N/25mm or more, and still more preferably 0.7N/25mm or more, from the viewpoint of preventing peeling during storage and handling.

From the viewpoint of excellent long-term adhesion (peel strength, peel durability) and excellent adhesion reliability to an adherend, the adhesion force of the pressure-sensitive adhesive layer to the alkali-free glass after curing (adhesion force to alkali-free glass after curing, T2) is preferably 5N/25mm or more, more preferably 6N/25mm or more, and further preferably 8N/25mm or more, and the adhesion force is measured based on 90-degree peeling at a speed of 300 mm/min. The higher the post-curing adhesion (T2) of the alkali-free glass, the higher the adhesion, the upper limit of which is not particularly limited, and is usually 20N/25mm or less.

The thickness of the adhesive layer is, for example, about 1 to 300 μm. The larger the thickness of the pressure-sensitive adhesive layer is, the more the adhesiveness to the adherend is improved, but the reworkability tends to be deteriorated. Therefore, the thickness of the adhesive layer is preferably 5 to 100 μm, more preferably 8 to 50 μm, still more preferably 10 to 40 μm, and particularly preferably 13 to 30 μm.

When the laminate is used for an optical device such as a display, the total light transmittance of the pressure-sensitive adhesive layer is preferably 80% or more, more preferably 85% or more, and still more preferably 90% or more. The haze of the pressure-sensitive adhesive layer is preferably 2% or less, more preferably 1% or less, further preferably 0.7% or less, and particularly preferably 0.5% or less.

The pressure-sensitive adhesive layer is not particularly limited in composition as long as the adhesive strength to an adherend is improved by photocuring.

(base Polymer)

The base polymer is a main constituent of the adhesive composition, and is a main factor determining the adhesive strength of the adhesive.

In view of hardening the pressure-sensitive adhesive layer before photocuring and facilitating the peeling from the adherend during the rework, it is preferable to introduce a crosslinked structure into the base polymer.

The type of the base polymer is not particularly limited, and an acrylic polymer, a silicone polymer, a urethane polymer, a rubber polymer, and the like can be appropriately selected. The base polymer may be used alone in 1 kind, or may be selected from 2 or more kinds. In particular, from the viewpoint of excellent optical transparency and adhesiveness and easy control of various characteristics such as friction force, the pressure-sensitive adhesive composition preferably contains an acrylic polymer as a base polymer, and 50% by weight or more (more preferably 60% by weight or more, and even more preferably 70% by weight or more) of the pressure-sensitive adhesive composition is preferably an acrylic polymer.

As the acrylic polymer, an acrylic polymer containing an alkyl (meth) acrylate as a main monomer component can be preferably used. In the present specification, "(meth) acrylic acid" means acrylic acid and/or methacrylic acid. The content of the alkyl (meth) acrylate is preferably 40% by weight or more, more preferably 50% by weight or more, and still more preferably 55% by weight or more, based on the total amount (100% by weight) of the monomer components constituting the acrylic polymer.

As the alkyl (meth) acrylate, an alkyl (meth) acrylate having an alkyl group with 1 to 20 carbon atoms can be preferably used. The alkyl group of the alkyl (meth) acrylate may be linear or branched. As examples of alkyl (meth) acrylates, mention may be made of: methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, neopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, isotridecyl (meth) acrylate, tetradecyl (meth) acrylate, isotetradecyl (meth) acrylate, tert-butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, decyl (meth) acrylate, hexyl (meth) acrylate, hexyl (meth) acrylate, butyl acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, butyl acrylate, hexyl (meth) acrylate, butyl acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, isostearyl (meth) acrylate, nonadecyl (meth) acrylate, aryl (meth) acrylate, and the like.

Preferably, the acrylic polymer contains a monomer component having a crosslinkable functional group as a copolymerization component. Examples of the monomer having a crosslinkable functional group include a hydroxyl group-containing monomer and a carboxyl group-containing monomer. Among these, the copolymerization component of the base polymer preferably contains a hydroxyl group-containing monomer. The hydroxyl group and the carboxyl group of the base polymer become reaction sites with a crosslinking agent described later. By introducing a crosslinked structure into the base polymer, cohesive force is improved, adhesiveness of the adhesive layer is improved, and fluidity of the adhesive is lowered, so that paste residue on an adherend tends to be reduced at the time of rework.

As the hydroxyl group-containing monomer, there may be mentioned: 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, 4- (hydroxymethyl) cyclohexylmethyl (meth) acrylate, and the like.

Examples of the carboxyl group-containing monomer include (meth) acrylic acid, 2-carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid.

The total amount of the hydroxyl group-containing monomer and the carboxyl group-containing monomer in the acrylic polymer is preferably 1 to 30% by weight, more preferably 3 to 25% by weight, and still more preferably 5 to 20% by weight, based on the total amount (100% by weight) of the constituent monomer components. The content of the hydroxyl group-containing (meth) acrylate is particularly preferably in the above range.

Preferably, the acrylic polymer contains N-vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyl

And nitrogen-containing monomers such as azole, vinyl morpholine, N-acryloyl morpholine, N-vinyl carboxamides, and N-vinyl caprolactam as constituent monomer components. The acrylic polymer containing a nitrogen-containing monomer component exhibits appropriate water absorption in a hot and humid environment, and can suppress partial water absorption of the pressure-sensitive adhesive, and therefore contributes to prevention of partial whitening, partial swelling, peeling, and the like of the pressure-sensitive adhesive layer.

The content of the nitrogen-containing monomer in the acrylic polymer is preferably 1 to 30% by weight, more preferably 3 to 25% by weight, and still more preferably 5 to 20% by weight, based on the total amount (100% by weight) of the constituent monomer components. The acrylic polymer particularly preferably contains N-vinylpyrrolidone as the nitrogen-containing monomer within the above range.

The acrylic polymer preferably contains a hydroxyl group-containing monomer and a nitrogen-containing monomer as monomer components. When the acrylic polymer contains both a hydroxyl group-containing monomer and a nitrogen-containing monomer as monomer components, the cohesive force and transparency of the adhesive tend to be improved. The total amount of the hydroxyl group-containing monomer and the nitrogen-containing monomer in the acrylic polymer is preferably 5 to 50 wt%, more preferably 10 to 40 wt%, and still more preferably 15 to 35 wt% based on the total amount (100 wt%) of the constituent monomer components.

The acrylic polymer may contain a monomer component (other monomer component) other than those described above. The acrylic polymer may contain, for example, a cyano group-containing monomer, a vinyl ester monomer, an aromatic vinyl monomer, an epoxy group-containing monomer, a vinyl ether monomer, a sulfonic group-containing monomer, a phosphoric group-containing monomer, an acid anhydride group-containing monomer, or the like as a monomer component. The content of these other monomer components is preferably 0 to 40% by weight, more preferably 0 to 30% by weight, and still more preferably 0 to 20% by weight, based on the total amount (100% by weight) of the constituent monomer components.

In one embodiment of the present invention, the acrylic polymer contains, as monomer components, 40 to 99 wt% (preferably 50 to 97 wt%, more preferably 55 to 95 wt%) of the alkyl (meth) acrylate monomer, 1 to 30 wt% (preferably 3 to 25 wt%, more preferably 5 to 20 wt%) of the monomer having a crosslinkable functional group (preferably the hydroxyl group-containing monomer and/or the carboxyl group-containing monomer, more preferably the hydroxyl group-containing monomer), and 1 to 30 wt% (preferably 3 to 25 wt%, more preferably 5 to 20 wt%) of the nitrogen-containing monomer, based on the total amount (100 wt%) of the constituent monomer components.

The adhesion of the pressure-sensitive adhesive layer before curing is easily affected by the constituent components and molecular weight of the base polymer. From the viewpoint of satisfying both appropriate adhesiveness and reworkability, the weight average molecular weight of the acrylic polymer is preferably 10 to 500 ten thousand, more preferably 30 to 300 ten thousand, and even more preferably 50 to 200 ten thousand. When a crosslinked structure is introduced into the base polymer, the molecular weight of the base polymer is the molecular weight before the crosslinked structure is introduced. The weight average molecular weight of the acrylic polymer can be measured by Gel Permeation Chromatography (GPC).

The higher the content of the high Tg monomer component in the constituent components of the base polymer, the more the adhesive tends to become hard. The high Tg monomer is a monomer having a high glass transition temperature (Tg) of a homopolymer. Examples of the monomer having a homopolymer Tg of 40 ℃ or higher include: (meth) acrylic monomers such as dicyclopentanyl methacrylate (Tg: 175 ℃ C.), dicyclopentanyl acrylate (Tg: 120 ℃ C.), isobornyl methacrylate (Tg: 173 ℃ C.), isobornyl acrylate (Tg: 97 ℃ C.), methyl methacrylate (Tg: 105 ℃ C.), 1-adamantyl methacrylate (Tg: 250 ℃ C.), and 1-adamantyl acrylate (Tg: 153 ℃ C.); amide group-containing vinyl monomers such as acryloyl morpholine (Tg: 145 ℃ C.), dimethylacrylamide (Tg: 119 ℃ C.), diethylacrylamide (Tg: 81 ℃ C.), dimethylaminopropylacrylamide (Tg: 134 ℃ C.), isopropylacrylamide (Tg: 134 ℃ C.), and hydroxyethylacrylamide (Tg: 98 ℃ C.); n-vinylpyrrolidone (Tg: 54 ℃ C.), etc.

The acrylic polymer preferably contains a monomer having a homopolymer Tg of 40 ℃ or higher in an amount of 5 to 50% by weight, more preferably 10 to 40% by weight, based on the total amount of the constituent monomer components. In order to form a pressure-sensitive adhesive layer having an appropriate hardness and excellent reworkability, the monomer component of the base polymer preferably contains a monomer component having a homopolymer Tg of 80 ℃ or higher, and more preferably contains a monomer component having a homopolymer Tg of 100 ℃ or higher. The acrylic polymer preferably contains the monomer having a homopolymer Tg of 100 ℃ or higher in an amount of 0.1 wt% or more, more preferably 0.5 wt% or more, still more preferably 1 wt% or more, and particularly preferably 3 wt% or more, based on the total amount of the constituent monomer components. The content of methyl methacrylate is particularly preferably in the above range.

The acrylic polymer as a base polymer can be obtained by polymerizing the above monomer components by various known methods such as solution polymerization, emulsion polymerization, and bulk polymerization. The solution polymerization method is preferable from the viewpoint of balance of properties such as adhesion and holding power of the adhesive, cost, and the like. As a solvent for the solution polymerization, ethyl acetate, toluene, or the like can be used. The concentration of the solution is usually about 20 to 80 wt%. As the polymerization initiator, various known polymerization initiators such as azo type and peroxide type can be used. Chain transfer agents may also be used to adjust the molecular weight. The reaction temperature is usually about 50 to 80 ℃ and the reaction time is usually about 1 to 8 hours.

(crosslinking agent)

From the viewpoint of imparting a moderate cohesive force to the binder, it is preferable to introduce a crosslinked structure into the base polymer. For example, a crosslinking structure can be introduced into the base polymer by adding a crosslinking agent to a solution after polymerization of the base polymer and heating the solution as necessary. As the crosslinking agent, isocyanate is exemplifiedCrosslinking agent, epoxy crosslinking agent,

Oxazoline crosslinking agents, aziridine crosslinking agents, carbodiimide crosslinking agents, metal chelate crosslinking agents, and the like. These crosslinking agents form a crosslinked structure by reacting with a functional group such as a hydroxyl group introduced into the base polymer.

As the crosslinking agent, a polyisocyanate having 2 or more isocyanate groups in 1 molecule is preferable. Examples of the polyisocyanate-based crosslinking agent include: lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate; alicyclic isocyanates such as cyclopentene diisocyanate, cyclohexene diisocyanate, isophorone diisocyanate, and the like; aromatic isocyanates such as 2, 4-tolylene diisocyanate, 4' -diphenylmethane diisocyanate, and xylylene diisocyanate; examples of the isocyanate adduct include trimethylolpropane/tolylene diisocyanate trimer adduct (e.g., "Coronate L" manufactured by Tosoh), trimethylolpropane/hexamethylene diisocyanate trimer adduct (e.g., "Coronate HL" manufactured by Tosoh), xylylene diisocyanate trimethylolpropane adduct (e.g., "Takenate D110N" manufactured by Mitsui chemical Co., Ltd.), and hexamethylene diisocyanate adduct (e.g., "Coronate HX" manufactured by Tosoh Co., Ltd.).

The crosslinking agent can be used alone in 1 kind, or more than 2 kinds are selected.

The amount of the crosslinking agent to be used may be appropriately adjusted depending on the composition, molecular weight, etc. of the base polymer. The amount of the crosslinking agent to be used is preferably about 0.1 to 10 parts by weight, more preferably 0.3 to 7 parts by weight, much more preferably 0.5 to 5 parts by weight, and much more preferably 1 to 4 parts by weight, based on 100 parts by weight of the base polymer before crosslinking. When the amount of the crosslinking agent to be used is larger than that of a conventional acrylic transparent adhesive for optical use, the reworkability tends to be improved.

To promote the formation of a crosslinked structure, a crosslinking catalyst may be used. As the crosslinking catalyst, there may be mentioned: metal crosslinking catalysts (particularly tin crosslinking catalysts) such as tetra-n-butyl titanate, tetra-isopropyl titanate, iron acetylacetonate, butyltin oxide, and dioctyltin dilaurate. The crosslinking catalyst is generally used in an amount of 0.05 parts by weight or less relative to 100 parts by weight of the base polymer.

By introducing a crosslinked structure into the base polymer, the gel fraction rises. The higher the gel fraction is, the harder the binder is, and when the laminate is peeled from an adherend by a rework or the like, the more the adhesive tends to be inhibited from remaining as a paste on the adherend. The gel fraction of the pressure-sensitive adhesive layer before photocuring is preferably 30% or more, more preferably 50% or more, further preferably 60% or more, and particularly preferably 65% or more. The gel fraction of the adhesive layer before photocuring may be 70% or more or 75% or more.

Since the adhesive layer contains an unreacted photo-curing agent, the gel fraction of the adhesive layer before photo-curing is usually 90% or less. If the gel fraction of the adhesive layer before photocuring is too large, the anchoring force to the adherend may be reduced, and the initial adhesion may be insufficient. Therefore, the gel fraction of the pressure-sensitive adhesive layer before photocuring is preferably 85% or less, and more preferably 80% or less.

The gel fraction can be determined as an insoluble component with respect to a solvent such as ethyl acetate, and specifically, can be determined as a weight fraction (unit: weight%) of an insoluble component after the pressure-sensitive adhesive layer is immersed in ethyl acetate at 23 ℃ for 7 days with respect to the sample before immersion. In general, the gel fraction of a polymer is equivalent to the degree of crosslinking, the more crosslinked portions of the polymer, the greater the gel fraction. In addition, the larger the amount of the light curing agent, the smaller the gel fraction.

(light curing agent)

The pressure-sensitive adhesive layer containing a light curing agent increases the frictional force by light curing after being bonded to an adherend, and improves the adhesion to the adherend.

As the photocuring agent, a photocurable monomer or a photocurable oligomer is used. As the light curing agent, a compound having 2 or more ethylenically unsaturated bonds in 1 molecule is preferable. In addition, the light curing agent is preferably a compound showing compatibility with the base polymer. The light curing agent is preferably liquid at ordinary temperature from the viewpoint of exhibiting moderate compatibility with the base polymer. The light curing agent is compatible with the base polymer and is uniformly dispersed in the composition, whereby a contact area with an adherend can be secured and an adhesive layer having high transparency can be formed.

By controlling the compatibility of the base polymer with the light curing agent, there is a case where a small amount of the light curing agent bleeds out to the surface of the adhesive Layer, thereby forming an adhesion barrier Layer (Weak Boundary Layer; WBL; fragile Layer) at the adhesion interface with the adherend. If the WBL is formed, the characteristics of the surface (bonding interface) change while maintaining the characteristics of the adhesive layer main body (bulk). That is, if the WBL is formed, the adhesive layer is kept at hardness, and the friction force and the frequency dependence of the friction force become small, so that the adhesive layer is easily peeled off at the time of rework, and the paste residue on the adherend can be reduced. After photocuring, the photocuring agent reacts, whereby WBL disappears or the thickness of WBL becomes thin, and thus the adhesive strength is improved. This makes it possible to realize excellent reworkability before photocuring and excellent adhesion (peeling durability) after photocuring.

The compatibility of the base polymer with the photocuring agent is mainly affected by the structure of the compound. The compatibility with the structure of the compound can be evaluated by, for example, hansen solubility parameters, and the smaller the difference between the solubility parameters of the base polymer and the photocurable agent is, the higher the compatibility tends to be.

From the viewpoint of high compatibility with the acrylic polymer as the base polymer, it is preferable to use a polyfunctional (meth) acrylate as the light curing agent. As the polyfunctional (meth) acrylate, there may be mentioned: polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, polytetramethylene glycol di (meth) acrylate, bisphenol A ethylene oxide-modified di (meth) acrylate, bisphenol A propylene oxide-modified di (meth) acrylate, alkanediol di (meth) acrylate, tricyclodecane dimethanol di (meth) acrylate, ethoxylated isocyanuric acid tri (meth) acrylate, pentaerythritol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, ethoxylated pentaerythritol tetra (meth) acrylate, dipentaerythritol poly (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and mixtures thereof, Neopentyl glycol di (meth) acrylate, glycerol di (meth) acrylate, urethane (meth) acrylate, epoxy (meth) acrylate, butadiene (meth) acrylate, isoprene (meth) acrylate, and the like.

The photo-curing agent may be used alone in 1 kind, or 2 or more kinds may be selected.

The compatibility of the base polymer with the photocuring agent is also governed by the molecular weight of the compound. As the molecular weight of the photocurable compound is smaller, the compatibility with the base polymer tends to be higher. The molecular weight of the light curing agent is preferably 1,500 or less, more preferably 1,000 or less, from the viewpoint of compatibility with the base polymer.

The type and content of the light curing agent mainly affect the bonding force after light curing. The smaller the functional group equivalent (i.e., the larger the number of functional groups per molecular weight) and the larger the content of the photo-curing agent, the greater the adhesive strength after photo-curing tends to be.

From the viewpoint of improving the adhesion after photocuring, the functional group equivalent (g/eq) of the photocuring agent is preferably 500 or less, more preferably 450 or less. On the other hand, when the photocrosslinking density is excessively increased, the viscosity of the adhesive may be decreased, and the adhesive strength may be decreased. Therefore, the functional group equivalent of the photocurable agent is preferably 100 or more, more preferably 130 or more, further preferably 150 or more, and particularly preferably 180 or more.

In the combination of the acrylic polymer as the base polymer and the polyfunctional acrylate as the light curing agent, when the functional group equivalent of the light curing agent is small, the interaction between the base polymer and the light curing agent is strong, and the initial adhesion tends to increase. In the application of the present invention, the initial adhesion is excessively increased, which may result in a reduction in reworkability. From the viewpoint of maintaining the adhesion between the pressure-sensitive adhesive layer and the adherend before photocuring in an appropriate range, the functional group equivalent of the photocuring agent is also preferably within the above range.

The content of the light curing agent in the adhesive composition is preferably 1 to 50 parts by weight, more preferably 5 to 40 parts by weight, and still more preferably 10 to 35 parts by weight, based on 100 parts by weight of the base polymer. In order to allow the light curing agent to be contained in the adhesive layer in an uncured state, it is preferable to add the light curing agent to a polymer solution after polymerization of the base polymer.

When the content of the light curing agent is increased, the light curing agent easily bleeds out on the surface. The light curing agent oozed out on the surface forms a WBL, contributing to a reduction in the friction of the adhesive layer. Accordingly, the adhesive strength with the adherend can be appropriately reduced, and the reworkability tends to be improved. On the other hand, if the light curing agent bleeds out in a large amount, the transparency may be lowered and the adhesive strength may be lowered. From the above viewpoint, it is preferable to control the amount of the light curing agent to the above range.

(photopolymerization initiator)

The photopolymerization initiator generates active species by irradiation with active energy rays, and accelerates the curing reaction of the photocurable agent. The photopolymerization initiator is only required to have a molar absorption coefficient of 15[ L mol ] at a wavelength of 380nm^-1cm^-1]The above is not particularly limited. The molar absorption coefficient of the photopolymerization initiator at a wavelength of 380nm can be measured using an absorptiometer. The photopolymerization initiator preferably has a molar absorptivity of 20[ L mol ] at a wavelength of 380nm^-1cm^-1]More preferably 25[ L mol [ ]^{- 1}cm^-1]The above. The upper limit of the molar absorptivity of the photopolymerization initiator at a wavelength of 380nm is not particularly limited, and is, for example, 1000[ L mol [ ]^-1cm^-1]The following.

The polarizing plate of the present invention contains an ultraviolet absorber in order to suppress deterioration of a polarizer and the like due to incidence of ultraviolet light. When the laminate of the polarizing plate and the pressure-sensitive adhesive layer to which such ultraviolet absorption ability is imparted is irradiated with active energy rays, light having a wavelength shorter than 380nm is absorbed by the ultraviolet absorber and prevented from reaching the pressure-sensitive adhesive layer, and therefore, the curing reaction is generally difficult to proceed. However, in the present invention, by using a photopolymerization initiator having a specific molar absorption coefficient, the curing reaction of the photocuring agent can be promoted even when an ultraviolet absorber is contained in the polarizing plate. This increases the adhesion between the pressure-sensitive adhesive layer after photocuring and the adherend, and improves long-term adhesion (peel durability).

As the photopolymerization initiator, an initiator having absorption in a long wavelength region is preferable, and examples thereof include: oxime compounds, metallocene compounds, acylphosphine compounds, and aminoacetophenone compounds. Among them, acylphosphine compounds and oxime compounds are preferable in view of wide absorption characteristics (particularly, a large absorption coefficient of 380nm or more).

As the oxime compound, for example: the compounds described in Japanese patent laid-open No. 2001-233842, the compounds described in Japanese patent laid-open No. 2000-80068, the compounds described in Japanese patent laid-open No. 2006-342166, the compounds described in J.C.S.Perkin II (1979) pp.1653-1660, J.C.S.Perkin II (1979) pp.156-162, the compounds described in Journal of Photopharmaceuticals Science and Technology (1995) pp.202-232, the compounds described in Japanese patent laid-open Nos. 2000-66385, 2000-80068, JP patent laid-open No. 2004-534797, JP patent laid-open No. 2006-342166, WO 2015/201510, WO2017/146152, paragraphs 0154-0156, and the like.

Further, a compound described in Japanese patent application laid-open No. 2009-519904 in which an oxime is linked to the N-position of a carbazole ring, a compound described in U.S. Pat. No. 7626957 in which a hetero substituent is introduced into a benzophenone moiety, a compound described in Japanese patent application laid-open No. 2010-15025 and U.S. Pat. No. 2009-292039 in which a nitro group is introduced into a dye moiety, a ketoxime compound described in International publication No. WO2009-131189, a compound described in U.S. Pat. No. 7556910 in which a triazine skeleton and an oxime skeleton are contained in the same molecule, a compound described in Japanese patent application laid-open No. 2009-221114 in which absorption is extremely large at 405nm and which has good sensitivity to a g-ray light source, and the like can be used.

In addition, the cyclic oxime compounds described in Japanese patent application laid-open Nos. 2007-231000 and 2007-322744 may be used as appropriate. Among the cyclic oximes, the cyclic oximes fused to the carbazole dye described in jp 2010-32985 a and jp 2010-185072 a are particularly preferable from the viewpoint of having high light absorption and high sensitivity.

Further, there may be mentioned: examples of the oxime compound include compounds having an unsaturated bond at a specific site of the oxime compound (e.g., compounds described in Japanese patent laid-open No. 2009-242469), and oxime compounds having a fluorine atom (e.g., compounds described in Japanese patent laid-open No. 2010-262028, compounds 24, 36-40 described in section 0345 of Japanese patent laid-open No. 2014-500852, and compounds (C-3) described in section 0101 of Japanese patent laid-open No. 2013-164471).

Among these, oxime esters are preferred oxime compounds.

The oxime compound may be a commercially available compound. As commercially available products, for example: IRGACURE OXE-01 (manufactured by BASF), IRGACURE OXE-02 (manufactured by BASF), TR-PBG-304 (manufactured by Changzhou powerful New electronic Material Co., Ltd.), DFI-091 (manufactured by Daito Chemix Co., Ltd.), and the like.

Examples of the metallocene-based compound include: the cyclopentadienyl titanium compound described in Japanese patent application laid-open Nos. 59-152396, 61-151197, 63-41484, 2-249, 2-291, 2-4705 and 0159 of WO2017/146152 and the iron-arene complex described in Japanese patent application laid-open Nos. 1-304453 and 1-152109.

As the metallocene-based compound, commercially available products can be used. For example, bis (methylcyclopentadienyl) -Ti-bis (2, 6-difluorophenyl) may be mentioned IRGACURE-727 (manufactured by BASF), and bis (cyclopentadienyl) -bis (2, 6-difluoro-3- (pyrrol-1-yl) phenyl) titanium may be mentioned IRGACURE-784 (manufactured by BASF).

Examples of the acylphosphine compound include 2,4, 6-trimethylbenzoyldiphenylphosphine oxide and the like. Further, an acylphosphine oxide initiator described in Japanese patent No. 4225898 may be used.

As the acylphosphine compound, commercially available products can be used. For example, Omnirad-819 and Omnirad-TPO (trade name: manufactured by IGM JAPAN) are commercially available.

As the aminoacetophenone compound, for example: a compound described in Japanese patent laid-open No. 10-291969. Further, as the aminoacetophenone compound, the compound described in Japanese patent laid-open No. 2009-191179, which has a maximum absorption wavelength matched to a long-wave region such as 365nm or 405nm, can be used.

Among these, a preferable aminoacetophenone compound includes 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one.

As the aminoacetophenone compound, commercially available products can be used. For example, Omnirad-907, Omnirad-369 and Omnirad-379 (trade name: manufactured by IGM JAPAN) are commercially available.

The photopolymerization initiator may be used alone or in combination of two or more.

The content of the photopolymerization initiator in the adhesive composition is preferably 0.01 to 3 parts by weight, more preferably 0.02 to 1 part by weight, and still more preferably 0.04 to 0.5 part by weight, based on 100 parts by weight of the base polymer. The content of the photopolymerization initiator in the adhesive composition is preferably 3 parts by weight or less, more preferably 1 part by weight or less, and even more preferably 0.5 part by weight or less, from the viewpoint of suppressing a change with time in the adhesive strength of the adhesive layer when the laminate is stored for a long period of time, and when the laminate is stored in a state of being attached to an adherend and before photocuring. The content of the photopolymerization initiator in the pressure-sensitive adhesive composition is preferably 0.01 parts by weight or more, more preferably 0.02 parts by weight or more, from the viewpoint of sufficiently performing photocuring by ultraviolet irradiation or the like and improving adhesion reliability.

(sensitizer)

The adhesive composition may contain a sensitizer. By using a photopolymerization initiator in combination with a sensitizer, the reaction speed of the photocuring reaction can be retarded. Therefore, even when the laminate is stored under irradiation of visible light such as a fluorescent lamp after bonding, the initial adhesive force can be kept low, and a laminate excellent in reworkability can be obtained.

The sensitizer is not particularly limited, and examples thereof include compounds represented by the following general formula (e 1).

[ chemical formula 1]

(in the formula, R¹And R²Independently represent-H, -CH₃、-CH₂CH₃、-CH(CH₃)₂Or Cl, R¹And R²Optionally the same or different)

Among them, R is particularly preferable¹And R²is-CH₂CH₃Diethyl thioxanthone (ll).

The sensitizer may be used alone or in combination of two or more.

The content of the sensitizer in the adhesive composition is preferably 0.001 to 10 parts by weight, more preferably 0.01 to 5 parts by weight, relative to 100 parts by weight of the base polymer.

(other additives)

The adhesive composition may contain additives such as a silane coupling agent, a tackifier, a plasticizer, a softener, an anti-deterioration agent, a filler, a colorant, an ultraviolet absorber, an antioxidant, a surfactant, and an antistatic agent in addition to the components exemplified above, within a range not to impair the characteristics of the present invention.

< use of laminate >

The laminate of the above embodiment can be used as an optical film in which a polarizing plate is laminated with another optical layer in actual use. That is, according to an embodiment of the present invention, an optical film including the laminate of the above embodiment can be provided.

The optical layer is not particularly limited, and for example, an optical layer used in the formation of a liquid crystal display device or the like such as a 1-layer or 2-layer or more reflective plate, semi-transmissive plate, retardation plate (including a wave plate such as 1/2 or 1/4), viewing angle compensation film or the like may be used. In particular, in the laminate of the above embodiment, a reflection-type polarizing plate or a semi-transmission-type polarizing plate in which a reflection plate or a semi-transmission reflection plate is further laminated on a polarizing plate, an elliptic polarizing plate or a circular polarizing plate in which a phase difference plate is further laminated on a polarizing plate, a wide-viewing-angle polarizing plate in which a viewing angle compensation film is further laminated on a polarizing plate, or a polarizing plate in which a luminance improvement film is further laminated on a polarizing plate is preferable.

The optical film in which the optical layers are laminated on the polarizing plate in the laminate may be formed by sequentially laminating the respective layers in the manufacturing process of the liquid crystal display device, but when the optical film is laminated in advance, there are advantages in that the optical film is excellent in stability of quality, assembling work, and the like, and the manufacturing process of the liquid crystal display device and the like can be improved. The optical layer may be laminated using the same adhesive as the adhesive layer constituting the laminate, or may be laminated using another conventional bonding method. For example, a polymer such as an acrylic polymer, a silicone polymer, a polyester, a polyurethane, a polyamide, a polyether, a fluorine polymer, or a rubber polymer can be suitably selected and used as a binder of the base polymer.

The laminate or the optical film of the above embodiment can be preferably used for various image display devices such as a liquid crystal display device. That is, according to an embodiment of the present invention, an image display device including the laminate of the above embodiment can be provided. Examples of the image display device include: liquid crystal display devices, organic EL display devices, and the like.

< production of laminate >

The laminate may be formed by laminating an adhesive layer on the surface of the polarizing plate. The pressure-sensitive adhesive layer may be formed directly on the polarizing plate, or may be formed in a sheet form on a releasable surface (releasable surface) by a transfer method in which the pressure-sensitive adhesive layer is transferred to the polarizing plate, or a combination of these methods. As the release surface, a surface of a release liner, a back surface of a base material after a release treatment, or the like can be used. The substrate having a release surface used for forming the adhesive layer may be used as the separator as it is.

For example, an adhesive composition containing a base polymer, a photocurable agent and a photopolymerization initiator, and a sensitizer, other additives and a solvent used as needed is applied to a polarizing plate or a base material by a roll coating method, a roll-and-lick coating method, a gravure coating method, a reverse coating method, a roll brush method, a spray coating method, a dip roll coating method, a bar coating method, a blade coating method, an air knife coating method, a curtain coating method, a lip coating method, a die coating method or the like, and the solvent is dried and removed as needed, thereby forming an adhesive layer. As the drying method, an appropriate method can be suitably employed. The heating and drying temperature is preferably 40 to 200 ℃, more preferably 50 to 180 ℃, and still more preferably 70 to 170 ℃. The drying time is preferably 5 seconds to 20 minutes, more preferably 5 seconds to 15 minutes, and still more preferably 10 seconds to 10 minutes.

When the adhesive composition contains a crosslinking agent, crosslinking is preferably performed by heating or aging simultaneously with or after drying of the solvent. The heating temperature and the heating time are appropriately set depending on the kind of the crosslinking agent used, and the crosslinking is usually carried out by heating at 20 to 160 ℃ for about 1 minute to 7 days. The heating for drying off the solvent may be simultaneously used as the heating for crosslinking.

The photocurable agent also remains unreacted after the crosslinked structure is introduced into the polymer by the crosslinking agent. Thus, a photocurable adhesive layer including a base polymer and a photocuring agent is formed.

In the case where the adhesive layer is formed on the polarizing plate, a separator is preferably provided on the adhesive layer for the purpose of protection of the adhesive layer and the like. The crosslinking may also be performed after the separator is disposed on the adhesive layer.

< photocuring of adhesive layer >

After the laminate is bonded to an adherend, the adhesive layer is irradiated with active energy rays to photocure the adhesive layer. The pressure-sensitive adhesive layer in the laminate of the present invention is photocurable, and the timing of curing can be set arbitrarily. The treatment such as the reworking or the processing can be performed at any time during a period from the time when the laminate is attached to the adherend to the time when the adhesive is photocured, and therefore, the preparation time of the device manufacturing process can be flexibly coped with.

The active energy rays include ultraviolet rays, visible light, infrared rays, X-rays, α -rays, β -rays, and γ -rays. The active energy ray is preferably an active energy ray having a wavelength range of 380nm to 450nm, from the viewpoint that curing of the pressure-sensitive adhesive layer in a storage state can be suppressed and curing of the pressure-sensitive adhesive layer can be easily performed. By using an active energy ray having a wavelength longer than that of ultraviolet rays (wavelength less than 380nm), even when a polarizing plate containing an ultraviolet absorber is used, the photocuring reaction by the polymerization initiator can be promoted, and the function of the adhesive due to the increase in adhesive force after photocuring can be sufficiently exhibited.

As the light source of the active energy ray in the wavelength range of 380nm to 450nm, a gallium-sealed metal halide lamp or an LED light source emitting light in the wavelength range of 380 to 440nm is preferable. Alternatively, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a xenon lamp, a halogen lamp, a carbon arc lamp, a metal halide lamp, a fluorescent lamp, a tungsten lamp, a gallium lamp, an excimer laser, or sunlight may be used as a light source, and light having a wavelength shorter than 380nm may be shielded by a band-pass filter.

The irradiation intensity and the irradiation time of the active energy ray may be appropriately set depending on the composition, the thickness, and the like of the pressure-sensitive adhesive layer. The irradiation dose of the active energy ray in the wavelength range of 380nm to 450nm is preferably 1,000mJ/cm from the viewpoint of peel strength (adhesiveness)²More preferably 2,000mJ/cm²More preferably 3,000mJ/cm²The above. In addition, the irradiation amount of the active energy ray is preferably 50,000J/cm from the viewpoint of deterioration of the polarizing plate and the like²Less than, more preferably 30,000J/cm²The lower, more preferably 10,000J/cm²The following. The irradiation dose of the active energy ray is, for example, 1,000 to 50,000mJ/cm²In the range of 1,000 to 30,000mJ/cm²In the range of 2,000 to 30,000mJ/cm²The range of (1).

The adherend to be laminated with the laminate is not particularly limited, and various electronic devices, optical devices, and their constituent members that require a polarizing plate can be exemplified. The adherend is, for example, a panel (e.g., a liquid crystal panel, an organic EL panel). The laminate may be bonded to the entire surface of the adherend, or may be selectively bonded to only a part thereof. Further, after the laminate is bonded to the entire surface of the adherend, the laminate at an unnecessary position may be cut and peeled off. Before photocuring, the laminate is temporarily adhered to the surface of an adherend, and therefore, the laminate can be easily peeled and removed from the surface of the adherend.

One embodiment of the present invention relates to a method for manufacturing an image display device. The manufacturing method comprises the following steps: the pressure-sensitive adhesive layer is cured by irradiating the pressure-sensitive adhesive layer with an active energy ray having a wavelength range of 380nm to 450 nm.

The irradiation direction of the active energy ray is not particularly limited, and in general, the panel is preferably irradiated from the polarizer side because the panel transmits light less easily than wiring and the like. In the present invention, since the polarizing plate contains the ultraviolet absorber, deterioration of the polarizer in the case of irradiation with active energy rays can be suppressed. Further, by using a photopolymerization initiator having a specific molar absorption coefficient, even when active energy rays are irradiated through a polarizing plate to which ultraviolet absorption ability is imparted, the curing reaction of the photocurable agent can be promoted, and the adhesion between the adhesive layer and the adherend can be improved.

Examples

The present invention will be described in detail below with reference to examples, but the technical scope of the present invention is not limited thereto. Unless otherwise specified, parts and% in each example are based on weight. The following conditions of standing at room temperature, which are not particularly specified, are all 23 ℃ and 65% RH.

The measurement of each physical property was performed by the following method.

< weight average molecular weight >

The weight average molecular weight (in terms of polystyrene) of the base polymer was measured by the following conditions using GPC ("HLC-8220 GPC" manufactured by Tosoh).

Sample concentration: 0.2 wt% (tetrahydrofuran solution)

Sample injection amount: 10 μ l

Eluent: THF (tetrahydrofuran)

Flow rate: 0.6ml/min

Measuring temperature: 40 deg.C

Sample column: TSKguardcolumn SuperHZ-H (1 root) + TSKgel SuperHZM-H (2 roots)

Reference column: TSKgel SuperH-RC (1 root)

A detector: RI (Ri)

Light transmittance < 380nm >

The measurement was performed using a spectrophotometer (UV 2450, manufactured by Shimadzu corporation).

[ polymerization of acrylic Polymer ]

< Polymer A1 >

In a reaction vessel equipped with a thermometer, a stirrer, a reflux condenser and a nitrogen gas inlet tube, 63 parts by weight of 2-ethylhexyl acrylate (2EHA), 15 parts by weight of N-vinylpyrrolidone (NVP), 9 parts by weight of Methyl Methacrylate (MMA), 13 parts by weight of hydroxyethyl acrylate (HEA), 0.2 parts by weight of azobisisobutyronitrile as a polymerization initiator and 233 parts by weight of ethyl acetate as a solvent were charged as monomers, and nitrogen substitution was performed for about 1 hour while flowing nitrogen gas and stirring. Then, the mixture was heated to 60 ℃ and reacted for 7 hours to obtain a solution of an acrylic polymer (polymer A) having a weight average molecular weight (Mw) of 120 ten thousand.

[ preparation of adhesive composition ]

< adhesive composition 1-8 >

A photo-curing agent, a crosslinking agent, and a photopolymerization initiator and a sensitizer, which are used as needed, were added to a solution of an acrylic polymer and uniformly mixed to prepare a pressure-sensitive adhesive composition having a composition shown in table 1 below. The addition amounts in table 1 are the addition amounts (parts by weight of solid content) relative to 100 parts by weight of the acrylic polymer. Details of the photopolymerization initiator, the photocuring agent, the crosslinking agent, and the sensitizer to be used are as follows.

(crosslinking agent)

B1: takenate D110N (75% ethyl acetate solution of trimethylolpropane adduct of xylylenediisocyanate; manufactured by Mitsui chemical Co., Ltd.)

(photopolymerization initiator)

C1: omnirad819 (acylphosphine compound: bis (2,4, 6-trimethylbenzoyl) phenylphosphine oxide; manufactured by IGM JAPAN)

C2: omnirad907 (Aminoacetophenone Compound; 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one; manufactured by IGM JAPAN)

C3: omnirad184 (1-hydroxycyclohexyl phenyl ketone; manufactured by IGM JAPAN)

(light curing agent)

D1: APG700 (Polypropylene glycol #700 (n-12) diacrylate; functional group equivalent 404g/eq)

(sensitizer)

E1: KAYACURE DETX-S (diethylthioxanthone; manufactured by Nippon Kagaku Co., Ltd.)

Watch 11

[ production of polarizing film ]

< polarizing film 1 >

A polyvinyl alcohol (PVA) film having a thickness of 80 μm (average degree of polymerization: 2400, degree of saponification: 99.9 mol%) was stretched 3-fold between rolls having different speed ratios while being dyed in an iodine solution having a concentration of 0.3% at 30 ℃ for 1 minute. Then, the resultant was immersed in an aqueous solution containing 4% boric acid and 10% potassium iodide at 60 ℃ for 0.5 minute, and stretched to 6 times the total stretching ratio. Next, the plate was immersed in an aqueous solution containing potassium iodide at a concentration of 1.5% at 30 ℃ for 10 seconds to wash the plate, and then dried at 50 ℃ for 4 minutes to obtain a polarizer having a thickness of 25 μm.

An aqueous PVA type resin solution was applied to both surfaces of the polarizer, and an acrylic resin film having a thickness of 30 μm was laminated on one surface, and a cellulose Triacetate (TAC) type film (containing an ultraviolet absorber) having a thickness of 40 μm was laminated on the other surface, thereby producing a polarizing film 1. The transmittance of the obtained polarizing film 1 at 380nm was 2.5%.

[ production of crosslinked/laminated body ]

Examples 1 to 6 and comparative examples 1 to 2 (laminates 1 to 8)

The pressure-sensitive adhesive composition shown in Table 2 was applied to the release-treated surface of a separator (a polyethylene terephthalate film having a thickness of 25 μm after the surface was subjected to silicone release treatment) using a spray roller so that the thickness after drying became 25 μm. After drying at 130 ℃ for 1 minute to remove the solvent, the coated side of the adhesive was attached to the acrylic resin film of the polarizing film. Then, aging treatment was performed at 25 ℃ for 4 days to progress crosslinking, thereby introducing a crosslinked structure into the acrylic polymer as a base polymer. Thus, a laminate was obtained in which the pressure-sensitive adhesive layer was fixedly laminated on the polarizing film and the separator was temporarily attached thereon.

Reference example 1 (laminate 9)

The adhesive composition shown in Table 2 was coated on a polyethylene terephthalate (PET) film ("Lumiror S10" manufactured by Toray) having a thickness of 75 μm without surface treatment using a spray roller so that the thickness after drying became 25 μm. After drying at 130 ℃ for 1 minute to remove the solvent, the release-treated surface of a separator (a polyethylene terephthalate film having a thickness of 25 μm and a silicone release-treated surface) was bonded to the coated surface of the adhesive. Then, aging treatment was performed at 25 ℃ for 4 days to crosslink the film, thereby obtaining a laminate in which an adhesive layer was fixed and laminated on a PET film and a separator was temporarily attached thereon.

The following evaluations were performed on the laminates obtained in examples 1 to 6, comparative examples 1 to 2, and reference example 1, and the results are shown in table 2.

< evaluation of adhesive Strength >

The separator was peeled and removed from the adhesive surface of the adhesive-attached polarizing plate cut to have a width of 25mm × a length of 100mm, and the exposed adhesive surface was bonded to alkali-free glass (EagleXG, manufactured by corning corporation) using a hand press roll to prepare a test sample before photocuring.

The adhesive layer was photocured by irradiating the test sample with active energy rays (light source: LED) from the polarizer side of the test sample before photocuring to obtain a photocured test sample.

The test samples before and after photocuring were used, and the 90 ° peel adhesion (adhesion to alkali-free glass before photocuring T1 and adhesion to alkali-free glass after photocuring T2) was measured at a peel angle of 90 degrees and a tensile rate of 300 mm/min in accordance with JIS Z0237:2009 using a tensile tester (device name: precision Universal testing machine, Autograph AG-IS, Shimadzu corporation). The measurement was performed 3 times, and the average values thereof were obtained and shown in the columns of "before photocuring" and "after photocuring" of "adhesion to alkali-free glass" in table 2, respectively. The increase ratio of the adhesion to alkali-free glass after photocuring (T2) to the adhesion to alkali-free glass before photocuring (T1) (═ T2/T1) was calculated and is shown in the column "increase ratio" in table 2.

(reworkability)

The reworkability was judged from the value of the adhesion force of the test sample before photocuring based on the following criteria.

A: 3N/25mm or less

B: more than 3N/25mm and 6N/25mm or less

C: more than 6N/25mm and 7N/25mm or less

D: more than 7N/25mm

The results are shown in Table 2.

(Adhesivity)

The adhesiveness (peel durability) was determined from the values of the adhesive strength of the test sample before and after photocuring based on the following criteria.

A: 8N/25mm or more

B: 5N/25mm or more and less than 8N/25mm

C: less than 5N/25mm

The results are shown in Table 2.

[ Table 2]

As shown in Table 2, it was confirmed that the laminates (examples 1 to 6) of the polarizing film containing an ultraviolet absorber and the pressure-sensitive adhesive layer comprising a base polymer, a light-curing agent and having a molar absorption coefficient of 15[ L mol ] were excellent in reworkability and adhesion^-1cm^-1]A pressure-sensitive adhesive composition containing the photopolymerization initiator. It was confirmed that in these laminates, the adhesion after photocuring was 1.4 times or more the adhesion before photocuring, and the adhesion could be increased by photocuring the pressure-sensitive adhesive layer after adhesion to an adherend.

It was confirmed that even when a photopolymerization initiator and a sensitizer were used in combination (examples 2 and 3), the adhesion after photocuring could be improved (adhesion was improved) while maintaining low adhesion before photocuring (good reworkability) (examples 2 and 3 were compared with example 6).

A difference was observed in the adhesion before and after photocuring depending on the amount of the photopolymerization initiator added (comparison between example 1 and example 4).

A difference in adhesion after photocuring was observed due to the difference in UV irradiation amount (comparison of example 1 with example 5).

On the other hand, in the laminate (comparative example 1) using the pressure-sensitive adhesive composition 6 containing the photopolymerization initiator having a molar absorption coefficient of less than 15, the increase in adhesive strength by photocuring was insufficient, and the adhesion was insufficient.

In the laminate (comparative example 2) using the pressure-sensitive adhesive composition 8 containing no photo-curing agent, almost no increase in adhesive strength by photo-curing was observed. In comparative example 2, the adhesion before photocuring was high, and the reworkability was poor. This is presumably because the WBL (adhesion preventing layer; fragile layer) was not formed at the interface between the pressure-sensitive adhesive layer and the adherend in the laminate of comparative example 2.

Reference example 1 was conducted to examine the influence of the polarizing film on the photocuring reaction. It was confirmed that when a PET film was used instead of the polarizing film 1 containing an ultraviolet absorber (reference example 1), the adhesive strength was increased by photocuring even when the pressure-sensitive adhesive composition 6 containing a photopolymerization initiator having a molar absorption coefficient of less than 15 was used as in comparative example 1. The following is hereby given: in the photocuring reaction of the adhesive layer laminated on the polarizing film containing an ultraviolet absorber, the molar absorption coefficient is 15[ L mol ]^-1cm^-1]The presence of the above photopolymerization initiator is important.

It is considered that the use of a polarizing plate containing an ultraviolet absorber has a molar absorption coefficient of 15[ L mol ]^{- 1}cm^-1]The pressure-sensitive adhesive composition of the photopolymerization initiator described above is sufficiently subjected to a photocuring reaction of the pressure-sensitive adhesive layer by irradiation with active energy rays (UV), and thus improves the adhesion after curing (improves the adhesion).

Industrial applicability

The laminate of the present invention can be suitably used for a polarizing plate with an adhesive layer, an optical film using the polarizing plate with an adhesive layer, or an image display device.

Claims (19)

1. A laminate, comprising:

a polarizing plate comprising an ultraviolet absorber, and

an adhesive layer on at least one side of the polarizer,

the adhesive layer is a layer formed from an adhesive composition comprising: a base polymer, a light curing agent, and a molar absorption coefficient at a wavelength of 380nm of 15[ L mol [ ]^-1cm^-1]The photopolymerization initiator described above.

2. The laminate according to claim 1, wherein,

the light transmittance of the polarizing plate at 380nm is 20% or less.

3. The laminate according to claim 1 or 2,

the adhesive layer is curable by irradiation with active energy rays in a wavelength range of 380nm to 450 nm.

4. The laminate according to any one of claims 1 to 3,

the adhesive layer has a bonding strength after curing that is greater than a bonding strength before curing.

5. The laminate according to any one of claims 1 to 4,

the adhesive layer has an adhesion force to alkali-free glass before curing, which is 7N/25mm or less based on 90-degree peeling at a speed of 300 mm/min.

6. The laminate according to any one of claims 1 to 5,

the adhesive layer has an adhesion after curing of 5N/25mm or more to alkali-free glass based on 90-degree peel at a speed of 300 mm/min.

7. The laminate according to any one of claims 1 to 6,

the adhesive composition further contains a sensitizer.

8. The laminate according to any one of claims 1 to 7,

the photopolymerization initiator contains at least one selected from oxime compounds, metallocene compounds, acylphosphine compounds, and aminoacetophenone compounds.

9. The laminate according to any one of claims 1 to 8,

the ultraviolet absorber contains at least one selected from benzophenone compounds, oxalic anilide compounds, cyanoacrylate compounds, benzotriazole compounds and triazine compounds.

10. The laminate according to any one of claims 1 to 9,

the adhesive composition contains 1 to 50 parts by weight of the light curing agent and 0.01 to 3 parts by weight of the photopolymerization initiator, based on 100 parts by weight of the base polymer.

11. The laminate according to any one of claims 1 to 10,

the base polymer contains an acrylic polymer.

12. The laminate according to claim 11,

the acrylic polymer contains a hydroxyl group-containing monomer and a nitrogen-containing monomer as monomer components.

13. The laminate according to any one of claims 1 to 12,

the light curing agent comprises a multifunctional (meth) acrylate.

14. The laminate according to any one of claims 1 to 13,

the polarizing plate has: the polarizer comprises a polarizer and a transparent protective film positioned on at least one surface of the polarizer, wherein the transparent protective film contains the ultraviolet absorbent.

15. An optical film comprising the laminate as set forth in any one of claims 1 to 14.

16. An image display device comprising the laminate according to any one of claims 1 to 14.

17. The apparatus of claim 16, wherein,

the adhesive layer includes a cured product of the base polymer and the photocuring agent.

18. A method of manufacturing an image display device according to claim 16 or 17, the method comprising:

a laminate is disposed on a panel with the pressure-sensitive adhesive layer interposed therebetween, and the pressure-sensitive adhesive layer is cured by irradiating the pressure-sensitive adhesive layer with an active energy ray having a wavelength range of 380nm to 450 nm.

19. The method of claim 18, wherein,

the irradiation amount of active energy rays in the wavelength range of 380nm to 450nm of the adhesive layer is 1000mJ/cm²The above.

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