CN113260509B

CN113260509B - Laminate, optical film, image display device, and method for manufacturing same

Info

Publication number: CN113260509B
Application number: CN202080008026.4A
Authority: CN
Inventors: 长田润枝; 外山雄祐; 仲野武史
Original assignee: Nitto Denko Corp
Current assignee: Nitto Denko Corp
Priority date: 2019-01-28
Filing date: 2020-01-16
Publication date: 2023-11-03
Anticipated expiration: 2040-01-16
Also published as: KR20210121108A; JP2020118918A; JP7370709B2; CN113260509A; WO2020158397A1; TW202031493A

Abstract

The invention provides a polarizer with an adhesive layer having a novel structure. The laminate of the present invention comprises: a polarizing plate including 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: base polymer, photo-curing agent, and molecular absorbance of 15[ L mol ] at 380nm wavelength ^‑1 cm ^‑1 ]The photopolymerization initiator above.

Description

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

Technical Field

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

Background

In a Liquid Crystal Display (LCD) or the like, polarizing plates are attached to both sides or one side of a liquid crystal cell in terms of its image forming system. As the polarizing plate, a polarizing film having a protective film such as a cellulose triacetate film bonded to both surfaces of a polarizer, which is usually obtained by absorbing a dichroic material such as iodine or a dichroic dye to a polyvinyl alcohol film and stretching and orienting the film, is generally used. When the polarizer is attached to the panel, an adhesive is generally used, and a polarizer with an adhesive layer, which is provided with an adhesive layer in advance on one side of the polarizer, is generally used.

As a necessary characteristic required for an adhesive for a polarizing plate, long-term adhesion (peeling durability) in the case of attaching a polarizing plate with an adhesive layer to a panel is required. For example, it is required that the adhesive does not peel off or lift up even in a high temperature/high humidity environment.

On the other hand, when the polarizing plate is bonded to the panel using an adhesive, bonding defects such as mixing of bubbles and offset of bonding positions may occur. When the lamination failure occurs, the polarizing plate is peeled off from the panel and the panel is reused. Therefore, the pressure-sensitive adhesive is required to have re-peelability (re-workability) such that the polarizing plate can be easily peeled from the panel after a predetermined time has elapsed from the attachment thereof without leaving a paste. With the recent trend of thinning and upsizing of panels, there is an increasing demand for recycling of panels, and the reusability is an important item. However, durability and re-operability are in a trade-off relationship, and therefore, are characteristics that are difficult to be compatible, and studies have been made to achieve compatibility. For example, patent document 1 discloses a polarizing plate with an adhesive layer designed to have low adhesion immediately after bonding to an adherend and to have an increased adhesion after heating.

Prior art literature

Patent literature

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

Disclosure of Invention

There is still a need for a polarizing plate with an adhesive layer having a novel structure, which has properties such as adhesion and reworkability.

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 photo-curing 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:

polarizing plate comprising ultraviolet absorber, and method for producing the same

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

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

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

the polarizer has a transmittance of 20% or less at 380 nm.

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

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

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

the adhesive force of the adhesive layer after curing is larger than the adhesive force before curing.

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

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

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

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

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

the adhesive composition further contains a sensitizer.

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

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

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

the ultraviolet absorber contains at least one selected from the group consisting of benzophenone compounds, oxanilides, cyanoacrylate compounds, benzotriazole compounds, and triazine compounds.

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

the adhesive composition comprises 1 to 50 parts by weight of the photo-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], wherein,

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], wherein,

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

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

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

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

[16] An image display device comprising the laminate of 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 photo-curing agent.

[18] The method of manufacturing an image display device described in [16] or [17], comprising:

the laminate is disposed on a panel with the adhesive layer interposed therebetween, and the adhesive layer is cured by irradiation with active energy rays in a wavelength range of 380nm to 450 nm.

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

the irradiation amount of active energy rays to the adhesive layer in a wavelength range of 380nm to 450nm is 1000mJ/cm ² The above.

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

(1) A laminate useful as a polarizing plate with an adhesive layer is provided. The laminate of the present invention can be preferably used for image display devices such as optical films and liquid crystal display devices (LCDs).

(2) The laminate of the present invention can be bonded to an adherend such as a panel, and then the adhesive layer is cured by light, thereby increasing the adhesive strength. According to a preferred embodiment of the present invention, the re-workability immediately after bonding can be provided, and the adhesion force after photocuring can be increased to provide excellent long-term adhesion (peeling durability).

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

Drawings

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

Symbol description

1. Polarizer

2. 2' transparent protective film

3. Polarizing plate

4. Adhesive layer

5. Diaphragm

6. Laminate body

10. Polarizing film with adhesive layer

Detailed Description

Hereinafter, embodiments of the present application will be described in detail. The present application is not limited to the following embodiments, and may be implemented with any modification within the scope of the present application. In the description of the drawings, the same elements are denoted by the same reference numerals, and duplicate descriptions are omitted. The dimensional ratios of the drawings are sometimes exaggerated for convenience of explanation, and are different from actual ratios.

All documents and publications described in this specification are incorporated herein by reference in their entirety, regardless of the purpose of the document or publication. The present specification includes the disclosure of the claims, the specification, and the drawings of japanese patent application No. 2019-01976 (application filed on 1 month 28 of 2019), which is the basis of priority of the present application.

One embodiment of the present application relates to a laminate, which has: a polarizing plate including 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: base polymer, photo-curing agent, and molecular absorbance of 15[ L mol ] at 380nm wavelength ^-1 cm ^-1 ]The photopolymerization initiator 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 10 with an adhesive layer 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 laminated on one principal surface of the polarizer 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 sides of the polarizer 1, and the transparent protective films 2 and 2' contain an ultraviolet absorber. The transparent protective film may be provided on only one surface of the polarizer. In addition, the ultraviolet absorber may be contained 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 an adhesive layer, a primer layer (primer layer), or other interlayer. In addition, the ultraviolet absorber may be contained in other layers (e.g., an adhesive layer, an undercoating layer, etc.) constituting the polarizing plate.

The adhesive layer 4 contains a base polymer, a photo-curing agent, and has a molar absorptivity of 15[ L mol ] at a wavelength of 380nm ^-1 cm ^-1 ]The above photo-curable adhesive agent of the photopolymerization initiator is photo-cured by irradiation of active energy rays, and has an increased adhesion (peel strength) to an adherend.

The pressure-sensitive adhesive layer-attached polarizing plate 10 is used by attaching the pressure-sensitive adhesive layer 4 to an adherend.

A separator 5 is temporarily attached to the surface of the adhesive layer 4 of the adhesive layer-attached polarizing film 10 shown in fig. 1. As the separator 5, for example, a separator having a release layer formed by providing a release layer with a release treatment agent on one surface of a sheet-like substrate (liner substrate) so that the one surface becomes a release surface can be preferably used. Before the lamination to the adherend, the separator 5 is peeled off from the surface of the adhesive layer 4, and the exposed surface of the adhesive layer 4 is laminated to the surface of the adherend, whereby the laminate 6 is temporarily adhered to the adherend. The thickness of the separator 5 is usually about 3 to 200. Mu.m, preferably about 10 to 100. Mu.m.

Or may be the following way: the polarizing film 10 with the pressure-sensitive adhesive layer is wound around the pressure-sensitive adhesive layer-attached polarizing film 3 using the polarizing plate 3 having the surface of the polarizing plate 3 not opposed to the pressure-sensitive adhesive layer 4 as a release surface instead of omitting the separator 5, and the pressure-sensitive adhesive layer-attached surface of the pressure-sensitive adhesive layer 4 is brought into contact with the surface of the polarizing plate 3 not opposed to the pressure-sensitive adhesive layer 4 to protect the surface (roll form). Before the lamination to the adherend, the surface of the adhesive layer 4 is exposed, and the exposed surface of the adhesive layer 4 is laminated to the surface of the adherend, thereby temporarily adhering the laminate 6 to the adherend.

The separator 5 is peeled off 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 the exposed surface of the pressure-sensitive adhesive layer 4 is bonded to the surface of an adherend (for example, a panel), whereby the laminate 6 is laminated on the surface of the adherend. Before the pressure-sensitive adhesive layer 4 is cured by light, 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 adhered together via the adhesive layer 4.

In the present specification, "adhesion" refers to a state in which two layers after lamination are firmly bonded, and peeling cannot be performed or is difficult to be performed at the interface between the two layers. The term "temporary adhesion" means a state in which the adhesion between two layers after lamination is small and the adhesion can be easily peeled off at the interface between the two layers.

Hereinafter, members constituting the polarizing plate 10 with an adhesive layer according to the above embodiment will be described.

< polarizer >

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

(polarizer)

The polarizer is not particularly limited, and various polarizers can be used. Examples of the polarizer include a film obtained by unidirectionally stretching a hydrophilic polymer film such as a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, an ethylene-vinyl acetate copolymer partially saponified film, a dehydrated product of polyvinyl alcohol, and a polyene oriented film such as a desalted product of polyvinyl chloride, by adsorbing a dichroic substance such as iodine or a dichroic dye to the polyvinyl alcohol film. Among these, a polarizer formed of a polyvinyl alcohol film and a dichroic substance such as iodine is preferable.

The thickness of these polarizers is not particularly limited, and is usually 2 to 25. Mu.m.

A polarizer produced by dyeing a polyvinyl alcohol film with iodine and stretching the film in one direction can be produced, for example, by immersing the polyvinyl alcohol film in an aqueous solution of iodine, dyeing the film, and stretching the film to 3 to 7 times the original length. If necessary, the aqueous solution 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, if necessary, the polyvinyl alcohol film may be immersed in water before dyeing and washed with water. By washing the polyvinyl alcohol film with water, dirt and an anti-blocking agent on the surface of the polyvinyl alcohol film can be removed, and the polyvinyl alcohol film can be swelled, thereby preventing uneven dyeing and the like. Stretching may be performed after dyeing with iodine, stretching may be performed while dyeing, or dyeing may be performed with iodine after stretching. Stretching may be performed in an aqueous solution of boric acid, potassium iodide, or the like, or in a water bath.

(transparent protective film)

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

As the transparent protective film, a retardation film can be used. The retardation film may have a retardation of 40nm or more in the front side and/or a retardation of 80nm or more in the thickness direction. The front phase difference is usually controlled in the range of 40 to 200nm, and the thickness direction phase difference is usually controlled in the range of 80 to 300 nm. When a retardation film is used as the transparent protective film, the retardation film also functions as a polarizer protective film, and thus can be thinned. The retardation film may be a birefringent film obtained by subjecting a thermoplastic resin film to a unidirectional stretching treatment or a bidirectional stretching treatment. The stretching temperature, stretching ratio, and the like can be appropriately set according to the phase difference value, the material of the film, and the thickness.

The thickness of the transparent protective film can be appropriately determined, but is preferably 3 to 200. Mu.m, from the viewpoints of workability such as strength and workability, and laminability. The thicker the thickness, the more the light transmission amount decreases, and the reaction of the polymerization initiator tends to be delayed. The thinner the thickness, the more components such as a polarizer and the like tend to deteriorate the panel. From the above viewpoints, it is preferably 5 to 100. Mu.m, more preferably 5 to 80. Mu.m. The transparent protective film may be used in a plurality or a plurality of layers.

The surface of the transparent protective film which is not bonded with the polarizer may be provided with a functional layer such as a hard coat layer, an antireflection layer, an anti-adhesion layer, a diffusion layer, an antiglare layer, etc. The functional layers such as the hard coat layer, the antireflection layer, the anti-adhesion layer, the diffusion layer, and the antiglare layer may be provided as a layer different from the transparent protective film itself.

An adhesive layer may be provided on the surface of the functional layer such as the hard coat layer, the antireflection layer, the adhesion preventing layer, the diffusion layer, the antiglare layer, etc.

The transparent protective film and the polarizer may be laminated with an adhesive layer, a primer layer (primer layer), or 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 adhesives, solvent adhesives, hot melt adhesives, and active energy ray curing adhesives. An easy-to-adhere 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, a polarizer) of the image display device due to incident ultraviolet light. Among them, since the polarizer is easily affected by ultraviolet light, the ultraviolet light absorber is preferably contained in the transparent protective film adjacent to the polarizer.

The ultraviolet absorber is not particularly limited, and various ultraviolet absorbers can be used. Specifically, benzophenone compounds, oxanilides, cyanoacrylates, benzotriazoles, and triazines are exemplified. The ultraviolet absorber may be used alone in an amount of 1 or in an amount of 2 or more. Among them, benzotriazole-based compounds and triazine-based compounds are preferable, and particularly, triazine-based compounds are more preferable. The triazine compound can provide a sufficient ultraviolet absorption effect with a small amount of the compound, and can prevent bleeding and the like during film formation.

Examples of the benzophenone compound include: 2, 4-dihydroxybenzophenone, 2-hydroxy-4-n-octoxybenzophenone, 2 '-dihydroxy-4, 4' -dimethoxybenzophenone, 2-hydroxy-4-n-octoxybenzophenone, bis (5-benzoyl-4-hydroxy-2-methoxyphenyl) methane, 1, 4-bis (4-benzoyl-3-hydroxyphenone) 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 compound include: octyl 2-cyano-3, 3-diphenylacrylate, and the like.

Examples of the benzotriazole compounds 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- (octoxycarbonylethyl) -2-hydroxyphenyl) benzotriazole, 2' -methylenebis [4- (1, 3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol ], 2- (3, 5-di-tert-butyl-2-hydroxyphenyl) -5-chlorobenzotriazole, 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-butyl-2-yl) -2- (2H-benzotriazol-2-yl) phenol, 2- (2H-benzotriazol-2-yl) p-cresol, 2- (2H-benzotriazol-2-yl) -4- (1, 3-tetramethylbutyl) phenol, 2- (2H-benzotriazol-2-yl) -4-methyl-6- (3, 4,5, 6-tetrahydrophthalimidomethyl) phenol, methyl 3- (3- (2H-benzotriazol-2-yl) -5-tert-butyl-4-hydroxyphenyl) propionate/polyethylene glycol 300 reaction product, 2- (2H-benzotriazol-2-yl) -6- (straight 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, 3-tetramethyl ] phenol, and the like.

The triazine compound is not particularly limited, and various triazine compounds can be used. For example, a triazine compound described in WO2005/109052 and Japanese patent application laid-open No. 2009-52021 can be suitably used. Examples 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-butoxyphenyl) -1,3, 5-triazine, 2, 4-diphenyl-6- (2-hydroxy-4-dodecyloxyphenyl) -1,3, 5-triazine, 2, 4-diphenyl-6- (2-hydroxy-4-butoxyphenyl) -1,3, 5-triazine, 2, 4-diphenyl-6- (2-hydroxy-4-ethoxyphenyl) -1, 4-ethoxyphenyl-2-hydroxy-4-3-ethoxyphenyl-triazine Ultraviolet light absorbers of 2, 4-bis (2, 4-dimethylphenyl) -6- [ 2-hydroxy-4- (3-alkoxy-2-hydroxypropoxy) -5-alpha-cumylphenyl ] -s-triazine skeleton (long chain alkoxy groups such as alkoxy; octyloxy, nonyloxy, decyloxy, etc.), ultraviolet light absorbers having a long chain alkoxy group such as 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-tris (2-hydroxy-4-benzyloxyphenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-4- (1- (2-ethoxyhexyloxy) -1-oxypropane-2-yloxy) phenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-3-methylphenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-4-dodecyloxyphenyl) -1,3, 5-triazine, 2, 6-tris (2-hydroxy-4-benzyloxy-4-methylphenyl) -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-oxypropane-2-yloxy) phenyl) -1,3, 5-triazine, 2, 4-bis (2, 4-dimethylphenyl) -6- [ 2-hydroxy-4- (3-alkoxy-2-hydroxy-propoxy) -2-propoxy ] -s-triazine (α -alkoxy-phenyl) - α -triazine; long-chain alkoxy groups such as octoxy, nonoxy, decyloxy, etc.).

Examples of the commercial products of the triazine compounds include Tinuvin 1577, tinuvin 460 and Tinuvin 477 (manufactured by BASF JAPAN). Examples of the commercially available benzotriazole compounds include Adecastat 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 content of the transparent protective film is preferably 0.01 to 10 wt%, more preferably 0.01 to 7 wt%, and even more preferably 0.05 to 5 wt%, based on the weight of the transparent protective film (100 wt%).

(light transmittance)

The transmittance of the polarizer at a wavelength of 380nm is preferably 20% or less. By having such UV absorbing ability, the polarizer can be prevented from deteriorating even when the adhesive layer is photo-cured by irradiation of active energy rays from the polarizer side. The lower limit of the light transmittance at a wavelength of 380nm is not particularly limited, and is preferably 1% or more in order to promote the photo-curing reaction with the polymerization initiator, and to sufficiently exert the function of the adhesive due to the increase of the adhesive force after photo-curing. The 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 pressure-sensitive adhesive layer of the present invention can be cured by irradiation of active energy rays from the polarizer side having such UV absorbing ability by including a photopolymerization initiator described later.

(thickness)

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

< adhesive layer >)

The adhesive layer is a layer formed from an adhesive composition containing a base polymer, a photo-curing agent, a photopolymerization initiator, and a sensitizer used as needed. The adhesive layer is a photocurable adhesive. The adhesive layer can be cured by irradiation of active energy rays to improve adhesion to an adherend. The adhesive layer may be a cured layer containing a base polymer, a photo-curing agent, a photo-polymerization initiator, and an adhesive composition to be sensitized according to the need for use. 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 polarizer before photo-curing, and thus, it is easy to perform a re-operation. The pressure-sensitive adhesive layer is cured by light to increase the adhesion to an adherend, and is excellent in long-term adhesion (peel durability).

In contrast to the case where the thermosetting adhesive is cured with time in a tubular state, the photocurable adhesive is hardly cured in a normal storage environment, but is cured by irradiation with active energy rays. The laminate of the present invention has advantages in that the curing timing of the adhesive layer can be arbitrarily set, the preparation time for the process can be flexibly dealt with, and the like.

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

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

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

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

When the laminate is used in an optical device such as a display, the total light transmittance of the 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, still more preferably 0.7% or less, particularly preferably 0.5% or less.

The composition of the pressure-sensitive adhesive layer is not particularly limited as long as the pressure-sensitive adhesive layer is cured by light to improve the adhesion to the adherend.

(base Polymer)

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

The crosslinked structure is preferably incorporated into the base polymer from the viewpoint of hardening the adhesive layer before photocuring and easily peeling from the adherend at the time of reworking.

The type of the base polymer is not particularly limited, and an acrylic polymer, a silicone polymer, a urethane polymer, a rubber polymer, or the like may be appropriately selected. The base polymer may be used alone in 1 kind, or may be used in the selection of 2 or more kinds. In particular, from the viewpoints of excellent optical transparency and adhesion and easy control of various properties such as friction force, the adhesive composition preferably contains an acrylic polymer as a base polymer, and 50% by weight or more (more preferably 60% by weight or more, still more preferably 70% by weight or more) of the 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, relative to 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 the alkyl (meth) acrylate, there may be mentioned: 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, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, nonadecyl (meth) acrylate, aryl (meth) acrylate, and the like.

The acrylic polymer preferably 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 them, the copolymerization component of the base polymer preferably contains a hydroxyl group-containing monomer. The hydroxyl groups and carboxyl groups of the base polymer become reaction points with a crosslinking agent described later. By introducing a crosslinked structure into the base polymer, the cohesive force is improved, the adhesiveness of the adhesive layer is improved, and the fluidity of the adhesive is reduced, so that the paste residue on the adherend tends to be reduced during the re-operation.

Examples of the hydroxyl group-containing monomer include: 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, relative to the total amount (100% by weight) of the constituent monomer components. It is particularly preferable that the content of the hydroxyl group-containing (meth) acrylate is within the above range.

Preferably, the acrylic polymer contains N-vinylpyrrolidone, methyl vinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyridine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinylpyrazineNitrogen-containing monomers such as oxazoles, vinylmorpholines, N-acryloylmorpholines, N-vinylcarboxamides, N-vinylcaprolactams, and the like are used as constituent monomer components. The acrylic polymer containing the nitrogen-containing monomer component exhibits moderate water absorption in a hot and humid environment and can suppress local water absorption of the adhesive, and thus helps to prevent local whitening, local swelling, peeling, and the like of the 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, relative to the total amount (100% by weight) of the constituent monomer components. The acrylic polymer particularly preferably contains N-vinylpyrrolidone as a nitrogen-containing monomer within the above-mentioned 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% by weight, more preferably 10 to 40% by weight, and still more preferably 15 to 35% by weight, relative to the total amount (100% by weight) of the constituent monomer components.

The acrylic polymer may contain a monomer component (other monomer component) other than the 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 sulfo group-containing monomer, a phosphoric acid group-containing monomer, an 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, still more preferably 0 to 20% by weight, relative to the total amount (100% by weight) of the constituent monomer components.

In one embodiment of the present invention, the acrylic polymer contains, as the monomer components, 40 to 99% by weight (preferably 50 to 97% by weight, more preferably 55 to 95% by weight) of the alkyl (meth) acrylate monomer, 1 to 30% by weight (preferably 3 to 25% by weight, more preferably 5 to 20% by weight) 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% by weight (preferably 3 to 25% by weight, more preferably 5 to 20% by weight) of the nitrogen-containing monomer, relative to the total amount (100% by weight) of the constituent monomer components.

The adhesion of the adhesive layer before curing is easily affected by the constituent components and molecular weight of the base polymer. From the viewpoint of both moderate adhesion and re-workability, the weight average molecular weight of the acrylic polymer is preferably 10 to 500 tens of thousands, more preferably 30 to 300 tens of thousands, still more preferably 50 to 200 tens of thousands. In the case of introducing a crosslinked structure into a base polymer, the molecular weight of the base polymer means the molecular weight before the crosslinked structure. The weight average molecular weight of the acrylic polymer can be determined using 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 harden. 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 ℃), dicyclopentanyl acrylate (Tg: 120 ℃), isobornyl methacrylate (Tg: 173 ℃), isobornyl acrylate (Tg: 97 ℃), methyl methacrylate (Tg: 105 ℃), 1-adamantyl methacrylate (Tg: 250 ℃), 1-adamantyl acrylate (Tg: 153 ℃); amido-containing vinyl monomers such as acryloylmorpholine (Tg: 145 ℃), dimethylacrylamide (Tg: 119 ℃), diethylacrylamide (Tg: 81 ℃), dimethylaminopropyl acrylamide (Tg: 134 ℃), isopropylacrylamide (Tg: 134 ℃) and hydroxyethylacrylamide (Tg: 98 ℃); n-vinylpyrrolidone (Tg: 54 ℃ C.), and the like.

The content of the monomer having a Tg of 40 ℃ or higher in the homopolymer is preferably 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 an adhesive layer having moderate hardness and excellent in 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 content of the monomer having a Tg of 100 ℃ or higher in the homopolymer is preferably 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, relative to the total amount of the constituent monomer components. It is particularly preferable that the content of methyl methacrylate is in the above range.

The acrylic polymer as the 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 viewpoints of balance of properties such as adhesion and holding power of the adhesive, cost and the like. As the 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% by weight. As the polymerization initiator, various known polymerization initiators such as azo-based and peroxide-based can be used. Chain transfer agents may also be used for adjusting 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 adhesive, it is preferable to introduce a crosslinked structure into the base polymer. For example, a crosslinking agent is added to the solution of the base polymer after polymerization, and the base polymer is heated as necessary, whereby a crosslinked structure can be introduced into the base polymer. Examples of the crosslinking agent include isocyanate-based crosslinking agents, epoxy-based crosslinking agents,An oxazoline-based crosslinking agent, an aziridine-based crosslinking agent, a carbodiimide-based crosslinking agent, a metal chelate-based crosslinking agent, and the like. These crosslinking agents react with functional groups such as hydroxyl groups introduced into the base polymer to form a crosslinked structure.

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-toluene diisocyanate, 4' -diphenylmethane diisocyanate, and xylylene diisocyanate; trimethylol propane/toluene diisocyanate trimer adduct (e.g., "Coronate L" from Tosoh), trimethylol propane/hexamethylene diisocyanate trimer adduct (e.g., "Coronate HL" from Tosoh), trimethylol propane adduct of xylylene diisocyanate (e.g., "Takenate D110N" from Mitsui chemical), isocyanurate of hexamethylene diisocyanate (e.g., "Coronate HX" from Tosoh), and the like.

The crosslinking agent may be used alone or in combination of 1 kind or 2 or more kinds.

The amount of the crosslinking agent 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, still more preferably 0.5 to 5 parts by weight, and still 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 is larger than that of a usual acrylic transparent adhesive, the reworkability tends to be improved.

In order to promote the formation of the 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 increases. The higher the gel fraction, the harder the adhesive, and the more the adhesive tends to be capable of suppressing the residue of the paste on the adherend when the laminate is peeled off from the adherend by a reworking or the like. The gel fraction of the adhesive layer before photo-curing is preferably 30% or more, more preferably 50% or more, still more preferably 60% or more, particularly preferably 65% or more. The gel fraction of the adhesive layer before photo-curing 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 photo-curing is too large, the anchoring force to the adherend may be reduced, and the initial adhesion may become insufficient. Therefore, the gel fraction of the adhesive layer before photo-curing is preferably 85% or less, more preferably 80% or less.

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

(photo-curing agent)

The adhesive layer containing the photo-curing agent is photo-cured after bonding to the adherend, thereby increasing friction force and improving adhesion to the adherend.

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

By controlling the compatibility of the base polymer and the photo-curing agent, a small amount of the photo-curing agent may ooze out to the surface of the adhesive layer, thereby forming an adhesion barrier layer (Weak Boundary Layer; WBL; frangible layer) at the adhesion interface with the adherend. If WBL is formed, the characteristics of the surface (bonding interface) change while maintaining the characteristics of the adhesive layer body (bulk). That is, if WBL is formed, the friction force and the frequency dependence of the friction force become small in a state where the hardness of the adhesive layer is maintained, and therefore, peeling at the time of re-handling becomes easy, and the paste residue on the adherend can be reduced. After the photo-curing, the photo-curing agent reacts, whereby WBL disappears or WBL becomes thin, and thus the adhesion is improved. Thus, excellent reworkability before photocuring and excellent adhesion (peeling durability) after photocuring can be achieved.

The compatibility of the base polymer with the photo-curing 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 solubility parameters of the base polymer and the photo-curing agent, 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 photo-curing agent. Examples of the polyfunctional (meth) acrylate include: 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, di (trimethylolpropane) tetra (meth) acrylate, ethoxylated pentaerythritol tetra (meth) acrylate, dipentaerythritol poly (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 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 an amount of 1 or 2 or more.

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

The kind and content of the photo-curing agent mainly affect the adhesion after photo-curing. The smaller the equivalent of the functional group (i.e., the larger the number of functional groups per unit molecular weight), the larger the content of the photo-curing agent, and the more the adhesive force after photo-curing tends to be increased.

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, if the photocrosslinking density excessively increases, the tackiness of the adhesive may be reduced, or the adhesion may be reduced. Therefore, the equivalent weight of the functional group of the photo-curing agent is preferably 100 or more, more preferably 130 or more, still more preferably 150 or more, particularly preferably 180 or more.

In the combination of the acrylic polymer as the base polymer and the multifunctional acrylate as the photo-curing agent, when the functional group equivalent of the photo-curing agent is small, the interaction between the base polymer and the photo-curing agent is strong, and initial adhesion tends to be increased. In the application of the present invention, there is a case where the initial adhesion is excessively increased, which may cause a reduction in the reworkability. From the viewpoint of keeping the adhesion between the pressure-sensitive adhesive layer before photo-curing and the adherend in an appropriate range, it is also preferable that the functional group equivalent of the photo-curing agent is in the above range.

The content of the photo-curing agent in the adhesive composition is preferably 1 to 50 parts by weight, more preferably 5 to 40 parts by weight, still more preferably 10 to 35 parts by weight, relative to 100 parts by weight of the base polymer. In order to include the photo-curing agent in the adhesive layer in an uncured state, it is preferable to add the photo-curing agent to the polymer solution of the base polymer after polymerization.

When the content of the photo-curing agent increases, the photo-curing agent easily oozes out on the surface. The photo-curing agent oozing out on the surface forms WBL, contributing to the reduction of friction force of the adhesive layer. Accordingly, the adhesion to the adherend can be reduced appropriately, and the reworkability tends to be improved. On the other hand, if the photo-curing agent oozes out in a large amount, there are cases where the transparency is lowered and the adhesion is lowered. From the above viewpoint, the amount of the photo-curing agent is preferably controlled to the above range.

(photopolymerization initiator)

The photopolymerization initiator generates an active species by irradiation with active energy rays, and accelerates the curing reaction of the photocuring agent. The photopolymerization initiator has a molar absorptivity of 15[ L mol ] at a wavelength of 380nm ^-1 cm ^-1 ]As described above, there is no particular limitation. The molar absorptivity of the photopolymerization initiator at a wavelength of 380nm can be measured using an absorbance meter. The photopolymerization initiator preferably has a molar absorptivity of 20[ L mol ] at a wavelength of 380nm ^-1 cm ^-1 ]Above, 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 ] ^-1 cm ^-1 ]The following is given.

In order to suppress deterioration of a polarizer or the like due to incidence of ultraviolet light, the polarizing plate of the present invention includes an ultraviolet absorber. When the laminate of the polarizer and the adhesive layer to which such ultraviolet absorptivity is applied is irradiated with active energy rays, light having a wavelength shorter than 380nm is absorbed by the ultraviolet absorber to inhibit the light from reaching the adhesive layer, and therefore, it is generally difficult to perform a curing reaction. However, in the present invention, by using a photopolymerization initiator having a specific molar absorption coefficient, the curing reaction of the photo-curing 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, the acylphosphine compound and the oxime compound are preferable in view of wide absorption characteristics (particularly, a large absorption coefficient of 380nm or more).

As the oxime compound, for example, can be used: the compounds described in Japanese patent application laid-open No. 2001-233846, japanese patent application laid-open No. 2000-80068, japanese patent application laid-open No. 2006-342166, J.C.S. Perkin II (1979) pp.1653-1660, J.C.S. Perkin II (1979) pp.156-162, journal of Photopolymer Science and Technology (1995) pp.202-232, japanese patent application laid-open No. 2000-66385, japanese patent application laid-open No. 2000-80068, japanese patent application laid-open No. 2004-534797, japanese patent application laid-open No. 2006-342166, WO2015/36910, and Japanese patent application laid-open No. 0154-0156 of WO2017/146152, 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 us patent application No. 7626957 in which a hetero substituent is introduced at a benzophenone position, a compound described in japanese patent application laid-open No. 2010-15025 and us patent application No. 2009-292039 in which a nitro group is introduced at a pigment position, a ketoxime compound described in international publication No. WO2009-131189, a compound described in us patent application No. 7556910 in which a triazine skeleton and an oxime skeleton are contained in the same molecule, a compound described in japanese patent application No. 2009-221114 in which a high absorption at 405nm and a good sensitivity to a g-ray light source are also usable.

Further, a cyclic oxime compound described in JP-A2007-231000 or JP-A2007-322744 may be suitably used. Among the cyclic oximes, the cyclic oximes having condensed rings on carbazole pigments described in japanese unexamined patent application publication No. 2010-32985 and japanese unexamined patent application publication No. 2010-185072 are particularly preferred from the viewpoint of having high light absorption and high sensitivity.

Further, there may be mentioned: a compound having an unsaturated bond at a specific site of an oxime compound (for example, a compound described in JP 2009-242469A), an oxime compound having a fluorine atom (for example, a compound described in JP 2010-261028A, a compound 24, 36-40 described in paragraph 0345 of JP 2014-500852A, a compound (C-3) described in paragraph 0101 of JP 2013-164471A, and the like).

Among them, oxime esters are preferable as oxime compounds.

The oxime compounds may be used as commercially available products. As a commercial product, for example, there can be used: IRGACURE OXE-01 (manufactured by BASF), IRGACURE OXE-02 (manufactured by BASF), TR-PBG-304 (manufactured by Changzhou powerful electronic materials Co., ltd.), DFI-091 (manufactured by Daito Chemix Co., ltd.), and the like.

Examples of the metallocene compound include: JP-A59-152396, JP-A61-151197, JP-A63-41484, JP-A2-249, JP-A2-291, JP-A2-4705, and JP-A1-304553, and JP-A1-152109.

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

Examples of the acylphosphine compound include 2,4, 6-trimethylbenzoyl diphenyl phosphine oxide and the like. In addition, an acylphosphine oxide initiator described in Japanese patent publication No. 4225898 may be used.

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

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

Among them, preferred aminoacetophenone compounds include 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one.

As the aminoacetophenone compound, commercially available ones can be used. For example, commercially available Omnirad-907, omnirad-369, or Omnirad-379 (trade name: all manufactured by IGM JAPAN) may be used.

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, relative to 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 the change with time of the adhesive force of the adhesive layer when the laminate is stored for a long period of time and when the laminate is stored in a state after being adhered to an adherend and before being cured by light. The content of the photopolymerization initiator in the 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 the photopolymerization initiator in combination with the sensitizer, the reaction rate 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 adhesion 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]

(wherein R is ¹ R is R ² Respectively and independently represent-H, -CH ₃ 、-CH ₂ CH ₃ 、-CH(CH ₃ ) ₂ Or Cl, R ¹ R is R ² Optionally the same or different

Among them, R is particularly preferable ¹ R is R ² is-CH ₂ CH ₃ Diethyl thioxanthone of (a).

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)

In addition to the above-exemplified components, 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, an antistatic agent, and the like, within a range that does not impair the characteristics of the present invention.

< use of laminate >

The laminate of the above embodiment may be used in the form of an optical film formed by laminating the laminate with other optical layers on a polarizing plate in practical 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 which is used in the formation of a liquid crystal display device such as a reflection plate, a semi-transmission plate, a phase difference plate (including a 1/2 wave plate, a 1/4 wave plate, etc.), a viewing angle compensation film, etc. of 1 layer or 2 layers or more may be used. In particular, in the laminated body of the above embodiment, a reflective polarizer or a semi-transmissive polarizer in which a reflective plate or a semi-transmissive reflective plate is further laminated on a polarizing plate, an elliptical polarizer or a circular polarizer in which a phase difference plate is further laminated on a polarizing plate, a wide viewing angle polarizer in which a viewing angle compensation film is further laminated on a polarizing plate, or a polarizing plate in which a brightness enhancement 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 optical layers in the manufacturing process of a liquid crystal display device or the like, but when the optical film is formed by lamination in advance, there is an advantage that stability of quality, assembly work or the like is excellent and the manufacturing process of the liquid crystal display device or the like can be improved. The optical layers may be laminated with the same adhesive as the adhesive layers constituting the laminate, or by other conventional bonding methods. For example, an acrylic polymer, a silicone polymer, a polyester, a polyurethane, a polyamide, a polyether, a fluorine polymer, a rubber polymer, or the like can be suitably selected and used as the binder for the base polymer.

The laminate or the optical film according to 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-described embodiments can be provided. Examples of the image display device include: liquid crystal display devices, organic EL display devices, and the like.

< manufacturing 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-like form on a releasable surface (release surface) by a transfer method in which the pressure-sensitive adhesive layer is transferred to the polarizing plate, or may be formed by a combination of these methods. The release surface may be a surface of a release liner, a back surface of a substrate after release treatment, or the like. The separator may be directly formed of a substrate having a release surface for forming the adhesive layer.

For example, an adhesive composition containing a base polymer, a photo-curing agent, a photopolymerization initiator, and optionally a sensitizer, other additives, and a solvent is applied to a polarizing plate or a substrate by roll coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, knife coating, air knife coating, shower coating, die lip coating, die coating, or the like, and the solvent is dried and removed as necessary, 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 even more preferably 70 to 170 ℃. The drying time is preferably 5 seconds to 20 minutes, more preferably 5 seconds to 15 minutes, still more preferably 10 seconds to 10 minutes.

In the case where the adhesive composition contains a crosslinking agent, crosslinking is preferably performed by heating or aging at the same time as or after drying of the solvent. The heating temperature and heating time are appropriately set according to the type of the crosslinking agent used, and crosslinking is usually performed by heating at 20 to 160℃for about 1 minute to 7 days. The heat used for drying the solvent off can be used simultaneously as the heat for crosslinking.

After the cross-linking structure is introduced into the polymer by the cross-linking agent, the photo-curing agent remains unreacted. Thus, a photocurable adhesive layer containing a base polymer and a photocurable agent is formed.

In the case of forming an adhesive layer on a polarizing plate, a separator is preferably provided on the adhesive layer for the purpose of protecting the adhesive layer or 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 the adherend, the pressure-sensitive adhesive layer is irradiated with active energy rays, whereby the pressure-sensitive adhesive layer is photo-cured. The pressure-sensitive adhesive layer in the laminate of the present invention is photocurable, and the timing of curing can be arbitrarily set. The processing such as the re-operation and the processing can be performed at any time from the time when the laminate is attached to the adherend to the time when the adhesive is photo-cured, and thus the preparation time for the device manufacturing process can be flexibly handled.

Examples of the active energy ray include ultraviolet rays, visible rays, infrared rays, X-rays, α rays, β rays, and γ rays. The active energy ray is preferably in the wavelength range of 380nm to 450nm in view of the fact that the curing of the adhesive layer in the stored state can be suppressed and the curing of the adhesive layer can be easily performed. By using active energy rays having a wavelength longer than ultraviolet rays (wavelength less than 380 nm), even in the case of using a polarizing plate including an ultraviolet absorber, a photo-curing reaction by a polymerization initiator can be promoted, and the function of an adhesive agent due to an increase in adhesive force after photo-curing can be fully exhibited.

As the light source of active energy rays in the wavelength range of 380nm to 450nm, gallium-enclosed metal halide lamps and LED light sources that emit light in the wavelength range of 380 to 440nm are 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 irradiation time of the active energy ray can be appropriately set according to the composition, thickness, and the like of the adhesive layer. From the viewpoint of peel strength (adhesion), the irradiation amount of active energy rays in the wavelength range of 380nm to 450nm is preferably 1,000mJ/cm ² The above, more preferably 2,000mJ/cm ² The above, further preferably 3,000mJ/cm ² The 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 or the like ² Hereinafter, 30,000J/cm is more preferable ² Hereinafter, 10,000J/cm is more preferable ² The following is given. The irradiation amount of the active energy ray is, for example, 1,000 to 50,000mJ/cm ² Or 1,000 to 30,000mJ/cm ² Or 2,000 to 30,000mJ/cm ² Is not limited in terms of the range of (a).

The adherend to be laminated is not particularly limited, and various electronic devices, optical devices, and constituent members thereof, etc. requiring a polarizing plate may be mentioned. 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. After the laminate is bonded to the entire surface of the adherend, the laminate at an unnecessary position may be cut and peeled off. In the case of the laminate before the photo-curing, the laminate is temporarily adhered to the surface of the adherend, and therefore the laminate can be easily peeled off 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 laminate is disposed on a panel with the adhesive layer interposed therebetween, and the adhesive layer is cured by irradiation with active energy rays in a wavelength range of 380nm to 450 nm.

The irradiation direction of the active energy ray is not particularly limited, and in general, it is preferable to irradiate from the polarizer side because the panel is less likely to transmit light than the wiring or the like. In the present invention, since the polarizing plate contains an ultraviolet absorber, deterioration of the polarizer in the case of irradiation of active energy rays can be suppressed. In addition, by using a photopolymerization initiator having a specific molar absorption coefficient, even when active energy rays are irradiated through a polarizer to which ultraviolet absorption capability 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 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 weight basis. The room temperature conditions not specifically defined below were all 23℃and 65% RH.

The physical properties were measured by the following methods.

< weight average molecular weight >

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

Sample concentration: 0.2 wt% (tetrahydrofuran solution)

Sample injection amount: 10 μl of

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)

Transmittance of < 380nm >)

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

[ polymerization of acrylic Polymer ]

< Polymer A1 >)

Into a reaction vessel equipped with a thermometer, a stirrer, a reflux condenser and a nitrogen inlet tube, 63 parts by weight of 2-ethylhexyl acrylate (2 EHA), 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 part by weight of azobisisobutyronitrile as a polymerization initiator and 233 parts by weight of ethyl acetate as a solvent were charged, and nitrogen was purged while stirring for about 1 hour. 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 compositions 1 to 8 >

The adhesive compositions having the compositions shown in table 1 below were prepared by adding a photo-curing agent, a crosslinking agent, and a photopolymerization initiator and a sensitizer, if necessary, to the acrylic polymer solution and mixing them uniformly. The amount added in table 1 is an amount (parts by weight of solid content) added to 100 parts by weight of the acrylic polymer. Details of the photopolymerization initiator, the photocuring agent, the crosslinking agent, and the sensitizer used are as follows.

(crosslinking agent)

B1: takenate D110N (75% ethyl acetate solution of trimethylolpropane adduct of xylylene diisocyanate; sanjing chemical Co., ltd.)

(photopolymerization initiator)

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

C2: omnirad907 (aminoacetophenone type compound; 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one; manufactured by IGM JAPAN)

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

(photo-curing agent)

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

(sensitizer)

E1: KAYACURE DETX-S (diethyl thioxanthone; manufactured by Japanese chemical Co., ltd.)

TABLE 11

[ production of polarizing film ]

< polarizing film 1 >)

A polyvinyl alcohol (PVA) film (average polymerization degree: 2400, saponification degree: 99.9 mol%) having a thickness of 80 μm was stretched to 3 times 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 sheet was immersed in an aqueous solution containing 4% boric acid and 10% potassium iodide at 60℃for 0.5 minutes, and stretched to a total stretching ratio of 6 times. Then, the resultant was immersed in an aqueous solution containing 1.5% potassium iodide at 30℃for 10 seconds to clean the film, and then dried at 50℃for 4 minutes to obtain a polarizer having a thickness of 25. Mu.m.

The polarizing film 1 was produced by applying an aqueous PVA-based resin solution to both surfaces of the polarizer, bonding an acrylic resin film having a thickness of 30 μm to one surface, and bonding a cellulose Triacetate (TAC) -based film (containing an ultraviolet absorber) having a thickness of 40 μm to the other surface. 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 (layered bodies 1 to 8)

The adhesive composition shown in Table 2 was applied to the release treated surface of the separator (polyethylene terephthalate film having a thickness of 25 μm after the silicone release treatment) using a spray roll so that the thickness after drying became 25. Mu.m. After drying at 130℃for 1 minute to remove the solvent, the coated surface of the adhesive was bonded to an acrylic resin film of the polarizing film. Then, the crosslinked structure was introduced into the acrylic polymer as the base polymer by aging treatment at 25℃for 4 days. Thus, a laminate in which an adhesive layer was laminated on a polarizing film and a separator was temporarily stuck thereon was obtained.

Reference example 1 (laminate 9)

The adhesive composition shown in Table 2 was applied to a polyethylene terephthalate (PET) film (produced by Toray, "Lumiror S10") having a thickness of 75 μm, which was not subjected to surface treatment, using a spray roll so that the thickness after drying became 25. Mu.m. After drying at 130℃for 1 minute to remove the solvent, the release treated surface of the separator (a polyethylene terephthalate film having a thickness of 25 μm after the silicone release treatment on the surface) was bonded to the coated surface of the adhesive. Then, aging treatment was performed in an atmosphere at 25 ℃ for 4 days, and crosslinking was performed, whereby a laminate was obtained in which an adhesive layer was fixedly laminated on a PET film and a separator was temporarily adhered thereon.

The laminate obtained in examples 1 to 6, comparative examples 1 to 2 and reference example 1 was evaluated as follows, and the results are shown in table 2.

< evaluation of adhesive force >)

The separator was peeled off from the adhesive surface of the adhesive-equipped polarizing plate cut out 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 obtain a test sample before photocuring.

The adhesive layer was photo-cured by irradiation with active energy rays (light source: LED) from the polarizer side of the test sample before photo-curing, as a test sample after photo-curing.

Using these test samples before and after photocuring, and using a tensile tester (device name: precision universal tester, autograph AG-IS, manufactured by Shimadzu corporation), the 90℃peel adhesion (adhesion T1 to alkali-free glass before photocuring and adhesion T2 to alkali-free glass after photocuring) was measured under the conditions of a peel angle of 90℃and a tensile speed of 300 mm/min according to JIS Z0237:2009. The measurement was performed 3 times, and the average value thereof was found and shown in the columns of "before light curing" and "after light curing" in "adhesion to alkali-free glass" in table 2. The ratio (=t2/T1) of increase in the adhesion (T2) to the alkali-free glass after photocuring to the adhesion (T1) to the alkali-free glass before photocuring was calculated, and is shown in the column of "increase ratio" in table 2.

(re-operability)

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

A:3N/25mm or less

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

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

D: exceeding 7N/25mm

The results are shown in Table 2.

(adhesion)

The adhesion (peeling durability) was determined based on the following criteria and based on the values of the adhesion of the test samples before and after photo-curing.

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 laminate of a polarizing film containing an ultraviolet absorber and an adhesive layer (examples 1 to 6) comprising a base polymer, a photocurable agent and a polymer having a molar absorptivity of 15[ L mol ] ^-1 cm ^-1 ]The adhesive composition of the photopolymerization initiator is formed. It was confirmed that the adhesion after photocuring was 1.4 times or more as high as before photocuring in these laminates, and that the adhesion was increased by photocuring the adhesive layer after bonding to the adherend.

It was confirmed that even when the photopolymerization initiator and the sensitizer were used in combination (examples 2 and 3), the adhesion after photocuring (adhesion improvement) could be 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 force before and after photo-curing due to the difference in the addition amount of the photopolymerization initiator (comparison of example 1 and example 4).

Due to the difference in UV irradiation amount, a difference was observed in the adhesion after photo-curing (comparison of example 1 and example 5).

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

In the laminate using the adhesive composition 8 containing no photo-curing agent (comparative example 2), the increase in the adhesion by photo-curing was hardly confirmed. In comparative example 2, the adhesion before photo-curing was high, and the re-workability was poor. This is presumably because WBL (adhesion barrier 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 in order to examine the influence of the polarizing film on the photo-curing reaction. It was confirmed that in the case of using a PET film instead of the polarizing film 1 containing an ultraviolet absorber (reference example 1), even if the adhesive composition 6 containing a photopolymerization initiator having a molar absorption coefficient of less than 15 was used in the same way as comparative example 1, the adhesion was increased by photocuring. The following implications are thus given: in the photo-curing reaction of the adhesive layer laminated to the polarizing film containing the ultraviolet absorber, the molar absorption coefficient was 15[ L mol ] ^-1 cm ^-1 ]The presence of the above photopolymerization initiator is important.

It is considered that the ultraviolet absorber is used in a polarizing plate comprising the ultraviolet absorber, the polarizing plate having a molar absorptivity of 15[ L mol ] ^- ¹ cm ^-1 ]The adhesive composition of the photopolymerization initiator described above is capable of sufficiently performing a photocuring reaction of the adhesive layer by irradiation with active energy rays (UV), and improving adhesive force (adhesion) after curing.

Industrial applicability

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

Claims

1. A laminate, comprising:

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

the adhesive layer is a layer formed of an adhesive composition comprising: base polymer, photo-curing agent, and molecular absorbance of 15[ L mol ] at 380nm wavelength ^-1 cm ^-1 ]The above photopolymerization initiator is used as a solvent,

the adhesive layer has an adhesive force of 6N/25mm or less with respect to 90 DEG peeling of alkali-free glass at a speed of 300 mm/min before curing.

2. The laminate according to claim 1, wherein,

the polarizer has a transmittance of 20% or less at 380 nm.

3. The laminate according to claim 1 or 2, wherein,

4. The laminate according to claim 1 or 2, wherein,

the adhesive layer has a higher adhesion after curing than before curing.

5. The laminate according to claim 1 or 2, wherein,

the adhesive layer has an adhesive force of 5N/25mm or more with respect to 90 DEG peeling of alkali-free glass at a speed of 300 mm/min after curing.

6. The laminate according to claim 1 or 2, wherein,

the adhesive composition further contains a sensitizer.

7. The laminate according to claim 1 or 2, wherein,

8. The laminate according to claim 1 or 2, wherein,

the ultraviolet absorber comprises at least one selected from benzophenone compounds, oxanilides, cyanoacrylate compounds, benzotriazole compounds and triazine compounds.

9. The laminate according to claim 1 or 2, wherein,

the adhesive composition comprises 1 to 50 parts by weight of the photo-curing agent and 0.01 to 3 parts by weight of the photopolymerization initiator, relative to 100 parts by weight of the base polymer.

10. The laminate according to claim 1 or 2, wherein,

the base polymer contains an acrylic polymer.

11. The laminate according to claim 10, wherein,

12. The laminate according to claim 1 or 2, wherein,

the photo-curing agent comprises a multifunctional (meth) acrylate.

13. The laminate according to claim 1 or 2, wherein,

the polarizing plate has: the light source device comprises a polarizer and a transparent protective film positioned on at least one surface of the polarizer, wherein the transparent protective film comprises the ultraviolet absorber.

14. An optical film comprising the laminate of any one of claims 1 to 13.

15. An image display device comprising the laminate according to any one of claims 1 to 13.

16. The apparatus of claim 15, wherein,

the adhesive layer includes a cured product of the base polymer and the photo-curing agent.

17. A method of manufacturing the image display device according to claim 15 or 16, the method comprising:

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

18. The method of claim 17, wherein,

an irradiation amount of active energy rays in a wavelength range of 380nm to 450nm with respect to the adhesive layer is 1000mJ/cm ² The above.