WO2007072799A1

WO2007072799A1 - Adhesive composition for optical use and optical functional film

Info

Publication number: WO2007072799A1
Application number: PCT/JP2006/325230
Authority: WO
Inventors: Takeshi Nagakura; Ryusuke Shimaguchi; Ayano Kondo
Original assignee: Saiden Chemical Industry Co., Ltd.
Priority date: 2005-12-20
Filing date: 2006-12-19
Publication date: 2007-06-28
Also published as: JPWO2007072799A1; JP4918499B2

Abstract

Disclosed is an adhesive composition for optical use which enables to form an adhesive layer for closely bonding a glass substrate and an optical functional film in a liquid crystal cell as a component of a liquid crystal display. Such an adhesive layer has adequate adhesive power and exhibits good adhesion to the optical functional film. In addition, since the adhesive layer is able to absorb the stress caused by expansion or contraction of the optical functional film which have been hardly coped with by the conventional ones, this adhesive layer enables to suppress color unevenness or white spot in the liquid crystal display. Also disclosed is an optical functional film characterized by having an adhesive layer, which is made of such an adhesive composition for optical use, on the surface.

Description

Specification

Optical pressure-sensitive adhesive composition and optical functional film

Technical field

The present invention relates to an optical pressure-sensitive adhesive composition used for adhering an optical functional film such as a polarizing plate or a retardation plate to an optical component such as a liquid crystal cell of a liquid crystal display device, and the composition The present invention relates to an optical functional film having a pressure-sensitive adhesive layer.

Background art

A liquid crystal cell constituting a liquid crystal display device is a pressure-sensitive adhesive formed by sandwiching a liquid crystal component oriented in a predetermined direction between two glass substrates and forming an optical pressure-sensitive adhesive composition outside these glass substrates. An optical functional film such as a polarizing plate or a laminate of a polarizing plate and a phase difference plate is attached via a layer. In recent years, liquid crystal display devices have been widely used due to the reduction in weight and thickness of displays for vehicles, outdoor instruments, displays such as personal computers, and televisions, and the demand for these devices is increasing. As a result, the usage environment of liquid crystal display devices has become extremely harsh, both indoors and outdoors.

[0003] A polarizing plate used in a liquid crystal display device has a three-layer structure in which both sides of a polyvinyl alcohol polarizer are sandwiched between triacetyl cellulose protective films. Poor stability. In addition, since an optical functional film such as a polarizing plate is formed by stretching, it tends to expand and contract over time. For this reason, in a liquid crystal display device, the residual stress acting on the optical functional film is unevenly distributed unless the pressure-sensitive adhesive layer can absorb and relieve internal stress caused by the expansion and contraction of the optical functional film. In particular, stress is concentrated on the peripheral edge. As a result, the peripheral edge of the liquid crystal display device becomes brighter or darker than the center, which causes color unevenness and white blurring in the liquid crystal display device.

[0004] Further, as another factor causing the color unevenness and white spotting phenomenon in the liquid crystal display device, a difference in refractive index between the glass substrate, the optical functional film and the pressure-sensitive adhesive layer can be considered.

[0005] Many means have been studied to solve the above problems. For example, in Patent Document 1, the outline is as follows: “A high molecular weight (meth) acrylic copolymer having a weight average molecular weight of 1 million or more. Adhesive for polarizing plate comprising 100% by mass of polymer, 20 to 200% by mass of low molecular weight (meth) acrylic copolymer having a weight average molecular weight of 30,000 or less, and 0.005 to 5% by mass of polyfunctional compound An invention of “agent composition” is disclosed. The invention describes that a pressure-sensitive adhesive layer that can follow the dimensional change of the polarizing plate is formed, and color unevenness / whitening phenomenon hardly occurs in the liquid crystal element. However, as a result of investigations by the present inventors, the amount of the polyfunctional compound disclosed by the present invention is wide, and in order to make it difficult for color unevenness and white spot phenomenon to occur, a polyfunctional compound is required. Since it is very difficult to adjust the amount of addition, it is difficult to produce an optical functional film having a stable pressure-sensitive adhesive layer.

[0006] Further, in Patent Document 2, a non-birefringent optical resin material to which a low-molecular substance exhibiting orientation birefringence that tends to cancel the orientation birefringence of the pressure-sensitive adhesive layer is added, and the resin material. An adhesive comprising a material is disclosed. However, this Patent Document 2 describes that the adhesive is used for an optical functional film to prevent uneven color and white spots in a liquid crystal display device and to improve its optical characteristics. Then! /

[0007] Patent Document 1: Japanese Patent No. 3533589

Patent Document 2: Japanese Patent No. 3696649

Disclosure of the invention

Problems to be solved by the invention

An object of the present invention is a pressure-sensitive adhesive used for a liquid crystal cell constituting a liquid crystal display device, which absorbs internal stress caused by expansion and contraction of an optical functional film, and causes color unevenness of the liquid crystal display device. It is an object to provide an optical pressure-sensitive adhesive composition for forming a pressure-sensitive adhesive layer capable of preventing the occurrence of a phenomenon.

Means for solving the problem

[0009] In order to solve the above-mentioned problems, the present inventors have conducted intensive research, and as a result, have a compound having at least two benzene rings in the molecule and a molecular weight of 150 to 1,000 (hereinafter referred to as the following). A pressure-sensitive adhesive layer formed from an optical pressure-sensitive adhesive composition containing a “rod-like compound” (sometimes) is provided between a glass substrate constituting a liquid crystal cell of a liquid crystal display device and an optical functional film. When used in the adhesive layer, the pressure-sensitive adhesive layer can follow the expansion and contraction of the optical functional film, and the refractive index of the pressure-sensitive adhesive layer itself increases, so that the color unique to the liquid crystal display device can be obtained. As a result, the present inventors have found that the uneven white spot phenomenon does not occur.

That is, the present invention is an optical pressure-sensitive adhesive composition containing at least a compound having at least two benzene rings in the molecule and having a molecular weight of 150 to 1,000, an adhesive resin and a crosslinking agent. And the content of the compound is 0.1 to 15 parts by mass per 100 parts by mass of the adhesive resin, and the viscosity coefficient at 90 ° C. of the adhesive layer formed from the composition cover is Provided is the above optical pressure-sensitive adhesive composition, which is 0.5 X 10 ⁷ to 10 X 10 ⁷ Pa's.

[0011] In the above optical pressure-sensitive adhesive composition, the rod-like compound is at least one selected from a group force that also includes transstilbene, fluorene, diphenylsulfide, benzyl benzoate, benzoin, and diphenylacetylene. The cohesive resin is a copolymerizable monomer unit containing (meth) acrylic acid alkyl ester monomer unit (a) having 1 to 18 carbon atoms and a carboxyl group and Z or a hydroxyl group. (b) and a copolymer (A) having a weight average molecular weight of 1,000,000 to 2,000,000; the content of the crosslinking agent is 0.01 per 100 parts by weight of the adhesive resin. The copolymer (A) force further contains a copolymerizable monomer unit (c) containing an aromatic group occupying 20 to 60% by mass of the total amount of the copolymer. I prefer to do that.

[0012] Further, in the above optical pressure-sensitive adhesive composition, a silanic compound (C) containing a mercaptoalkyl group and an alkoxy group in the molecule is added to 0.01 parts by weight of 100 parts by weight of the above-mentioned adhesive resin. Further containing ~ 2 parts by mass; and (meth) acrylic acid having a low molecular weight (co) polymer (D) having a C 1-18 alkyl ester strength, the copolymer (A) 100 parts by mass The (co) polymer (D) has a weight average molecular weight of 1,000 to 50,000 and a dispersity (MWZMN) of 1.0 to 2. 5 and preferably compatible with the copolymer (A).

[0013] Further, the present invention provides an optical functional film characterized by having an adhesive layer formed on the surface thereof from the optical pressure-sensitive adhesive composition of the present invention.

The invention's effect

The pressure-sensitive adhesive layer formed from the optical pressure-sensitive adhesive composition of the present invention constitutes a liquid crystal display device with the pressure-sensitive adhesive layer having an appropriate adhesive force and good adhesion to the optical functional film. When used in a liquid crystal cell, it absorbs the stress caused by the expansion and contraction of the optical functional film, and can prevent the occurrence of uneven color and white spots in the liquid crystal display device.

BEST MODE FOR CARRYING OUT THE INVENTION

Next, the present invention will be described in more detail with reference to the best mode for carrying out the invention. The optical pressure-sensitive adhesive composition of the present invention is characterized by containing the rod-shaped compound. When the pressure-sensitive adhesive layer formed from the optical pressure-sensitive adhesive composition of the present invention by containing the rod-like compound is used as a pressure-sensitive adhesive layer of a liquid crystal cell constituting a liquid crystal display device, a glass substrate, Since the difference in refractive index between the optical functional film and the pressure-sensitive adhesive layer becomes as small as possible, even if the optical functional film undergoes a dimensional change, color unevenness in the liquid crystal display device may occur. Can be prevented.

[0016] The rod-shaped compound used in the present invention has a molecular weight of 150 to 1,000, preferably 150 to 500. The “benzene ring” of the rod-like compound includes a benzene ring forming a condensed ring. That is, naphthalene has two benzene rings and anthracene has three benzene rings. A rod-like compound having a molecular weight of less than 150 is used in the optical pressure-sensitive adhesive composition of the present invention, and when the pressure-sensitive adhesive layer formed from the composition is used in a liquid crystal cell, it becomes an optical functional film. Even if the dimensions change, it is not preferable because the refractive index of the pressure-sensitive adhesive layer does not increase. On the other hand, a rod-like compound having a molecular weight of more than 1,000 has almost the same compatibility as that of the tacky resin, but when used in the optical pressure-sensitive adhesive composition of the present invention, the rod-like compound tends to have an aggregated structure. This is undesirable because the uniformity of the refractive index of the pressure-sensitive adhesive layer formed from the above deteriorates and causes unevenness of color in the liquid crystal display device.

[0017] The optical pressure-sensitive adhesive composition of the present invention contains 0.1 to 15 parts by mass of the rod-like compound per 100 parts by mass of the adhesive resin. When the content of the rod-shaped compound is less than 0.1 part by mass, the refractive index of the pressure-sensitive adhesive layer formed from the optical pressure-sensitive adhesive composition of the present invention is low. When used in a liquid crystal display device, the color This can cause unevenness of white spots. On the other hand, when the amount of the rod-like compound is more than 15 parts by mass, the rod-like compound is not completely dissolved in the optical pressure-sensitive adhesive composition and precipitates, causing a bleed phenomenon. Absent. Furthermore, in the optical pressure-sensitive adhesive composition of the present invention, the viscosity coefficient at 90 ° C. of the pressure-sensitive adhesive layer formed from the composition is 0.5 × 10 ⁷ to 10 × 10 ⁷ Pa ′s. 1 × 10 ^{7 to} 5 × 10 ⁷ Pa ′s. Within this viscosity coefficient range, the pressure-sensitive adhesive layer formed from the optical pressure-sensitive adhesive composition of the present invention has a liquid crystal cell force that hardly causes foaming or peeling when used in a liquid crystal cell. Color irregularities and white spots are unlikely to occur in the liquid crystal display device.

[0019] The viscosity coefficient of the pressure-sensitive adhesive layer can be determined by a method according to the holding power measurement method of JIS Z-0237. In this measurement method, an optical functional film having an adhesive layer is attached to a glass plate, a test sample is prepared, a load is applied to the test sample, and the test sample is kept in an atmosphere of 90 ° C for a certain period of time. The amount of misalignment is measured, and the viscosity coefficient (Pa's) of the adhesive layer can be calculated from the amount of misalignment according to [Equation 1] below.

1]

Viscosity coefficient (Pa's) = Deviation stress Z Deviation speed

In addition,

Misalignment stress (N / m ² ) = Load (N) / Bonded area (m ² )

And

Deviation speed (lZs) = deviation amount (m) Z test time (seconds) Z adhesive layer thickness (m).

[0020] Specific examples of the rod-like compound used in the optical pressure-sensitive adhesive composition of the present invention preferably having good compatibility with the adhesive resin include biphenyl, diphenylsulfone, and 4 Phenolphenol, benzoin, diphenylsulfide, diphenol ether, 4-hydroxybiphenyl 4'-strength rubonic acid, 4, 4'-biphenol, 4, 4'-dihydroxydiphenylmethane, 4-α-tamylphenol Diphenylacetylene, azobenzene, dibenzofuran, diphenylmethane, benzyl benzoate, diphenyl phthalate, Ν— (4 —methoxybenzylidene) —4—acetoxyline, 4 — [((methoxybenzylidene) amino] azobenzene, 4 , 4'-sulfo-didiphenol, 4-phenoxyphenol, 4'-methoxybenzylideneaminostilbene, bisphenol Le Alpha, Benjiridenfue - Ruamin, New, New, one dibenzylidene hydrazine, trans-stilbene, [rho di § - monkey benzyl Dane, Terephthalbis (p-phenetidine), carbazole, 1,4-diphenyl-2-1,3-butadiene, 1,4-diphenyl-1,3,5-hexagen, fluorene and dibenzothiophene group forces are selected At least one can be used, but is not limited to these. Among these compounds, it is more preferable to use at least one selected from the group consisting of transstilbene, fluorene, diphenylsulfide, benzyl benzoate, benzoin, and diphenylacetylene.

For example, the rod-like compound is represented by the following structural formula.

[0022]

[0023] The adhesive resin used in the optical pressure-sensitive adhesive composition of the present invention comprises (meth) acrylic acid alkyl ester monomer unit (a) having 1 to 18 carbon atoms, a carboxyl group and Z or a hydroxyl group. A copolymerizable monomer unit (b) having a weight average molecular weight (MW)

) Is preferably 1 to 2 million copolymers (A)! /.

[0024] The weight average molecular weight in the present invention is a polystyrene equivalent molecular weight measured by gel permeation chromatography. Specifically, the coating film obtained by drying the (co) polymer at room temperature is dissolved in tetrahydrofuran, and a high performance liquid chromatograph (manufactured by Shimadzu Corporation) is dissolved.

, LC 10ADvp, column; KF-G + KF-806 X 2), and the retention time was measured, and the weight average molecular weight (MW) was calculated in terms of polystyrene.

In the present invention, “(meth) acrylic acid” means both “acrylic acid” and “methacrylic acid”.

[0026] Specific examples of the monomer unit (a) constituting the copolymer (A) include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl ( (Meth) Atylate, Isobutyl (Meth) Atylate, 2-Ethylhexyl (Meth) Atylate, Octyl (Meth) Atylate, Iso-Otatil (Meth) Atylate, Isanol (Meth) Atarylate, Lauryl ( (Meta) attalate can be mentioned, and at least one of them can be used.

[0027] The proportion of the monomer unit (a) in the copolymer (A) is such that the copolymer (A) is a force only for the monomer unit (a) and the monomer unit (b). If Nio Te, copolymer (a) is taken as 100 mass ^_0/0, the 90-99. a 8 mass ^_0/0. Preferably Ru 93 to 99.5 mass ^_0/0 der. When the proportion of the monomer unit (a) is less than 90% by mass, the adhesiveness of the pressure-sensitive adhesive layer formed from the optical pressure-sensitive adhesive composition of the present invention to the optical functional film decreases. On the other hand, when the proportion of the monomer unit (a) exceeds 99.8% by mass, the proportion of the monomer unit (b) below becomes relatively low and depends on the crosslinking agent of the copolymer (A). This is not preferable because the degree of crosslinking decreases and the viscosity of the optical pressure-sensitive adhesive composition of the present invention decreases.

[0028] Among the monomer units (b), a copolymerizable monomer unit containing a carboxyl group

Examples of (bl) include (meth) acrylic acid, itaconic acid, maleic acid, maleic anhydride, fumaric acid, fumaric anhydride, and carboxyethyl acrylate. Preferred is (meth) acrylic acid or carboxyethyl acrylate. On the other hand, as the copolymerizable monomer unit (b2) containing a hydroxyl group, 2-hydroxyethyl (meth) acrylate, 4-hydroxy Examples thereof include polyethylene-modified (meth) acrylate, polyethylene glycol (meth) acrylate and polypropylene glycol (meth) acrylate. As the monomer unit of the copolymer (A), the monomer unit (bl) and the monomer unit (b2) may be used alone or in combination.

[0029] The copolymer (A) preferably has a weight average molecular weight of 1 million to 2 million.

When the copolymer (A) having a weight average molecular weight of less than 1 million is used in the optical pressure-sensitive adhesive composition of the present invention, the pressure-sensitive adhesive layer formed from the composition lacks cohesive force, and the pressure-sensitive adhesive layer Foaming occurs and the optical functional film is easily peeled off. On the other hand, when the copolymer (A) having a weight average molecular weight exceeding 2 million is used in the optical pressure-sensitive adhesive composition of the present invention, the viscosity of the composition becomes too high and workability is lowered. In addition, the pressure-sensitive adhesive layer formed from the composition cannot sufficiently absorb and relieve stress caused by the expansion and contraction of the optical functional film.

[0030] The proportion of the monomer unit (b) in the copolymer (A) is such that the copolymer (A) is a force only for the monomer unit (a) and the monomer unit (b). In this case, when the copolymer (A) is 100% by mass, it is preferably 0.210% by mass. More preferably, it is 0.5 7 mass%. When the proportion of the monomer unit (b) is less than 0.2% by mass, the degree of cross-linking of the copolymer (A) by the cross-linking agent decreases, and the viscosity becomes low when the pressure-sensitive adhesive layer is formed. It is not preferable. On the other hand, when the proportion of the monomer unit (b) exceeds 10% by mass, the crosslinking density of the copolymer (A) by the crosslinking agent becomes too high, and the formed pressure-sensitive adhesive layer becomes an optical functional film. This is not preferable because the ability to absorb and relax the stress caused by expansion and contraction is reduced.

[0031] The copolymer (A) can be produced by bulk polymerization or solution polymerization. Solution polymerization is preferred. As the solvent used for the solution polymerization, an organic solvent usually used for a solution polymerization reaction, such as ethyl acetate, toluene, n-xane, acetone, methyl ethyl ketone, can be used. The polymerization initiator used for the polymerization may be a peroxide such as benzoyl peroxide or lauryl peroxide, an azobis compound such as azobisisobutyryl-tolyl, azobisvalero-tolyl, or a polymer azo polymerization initiator alone. Can be used together. [0032] The crosslinking agent used in the optical pressure-sensitive adhesive composition of the present invention is necessary for increasing the cohesive strength of the adhesive resin, and reacts with the carboxyl group and Z or hydroxyl group of the monomer unit (b). It is preferable that it is a compound to be. The amount used is preferably 0.01 to 1 part by mass per 100 parts by mass of the adhesive resin, and is preferably 0.05 to 0.5 part by mass. When the amount used is less than 0.01 parts by mass, the cohesive force of the pressure-sensitive adhesive layer formed from the optical pressure-sensitive adhesive composition containing the crosslinking agent is low, which may cause foaming or peeling of the pressure-sensitive adhesive layer. It is not preferable because it becomes. On the other hand, when the amount used exceeds 1 part by mass, it becomes difficult for the pressure-sensitive adhesive layer to sufficiently absorb and relax the stress caused by the expansion and contraction of the optical functional film.

[0033] The crosslinking agent that can be used in the optical pressure-sensitive adhesive composition of the present invention includes a glycidyl compound having at least two glycidyl groups in one molecule, and an isocyanate compound having two or more isocyanate groups in one molecule. Compounds, aziridin compounds having at least two aziridinyl groups in one molecule, oxazoline compounds having an oxazoline group in one molecule, metal chelate compounds and butylated melamine compounds it can. Preferably, a glycidyl compound having at least two glycidyl groups in one molecule, an isocyanate compound having two or more isocyanate groups in one molecule, and an aziridin compound having at least two aziridinyl groups in one molecule. It is a compound.

[0034] Examples of the glycidyl compound include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycerin diglycidyl ether, neopentyl glycol diglycidyl ether, 1 , 6-hexanediol diglycidyl ether, N, N, Ν ', Ν, monotetraglycidyl, 1-m-xylenediamine, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, trimethylolpropane poly And polyfunctional glycidyl compounds such as glycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether and sorbitol polyglycidyl ether, of which At least one of these can be used.

[0035] Examples of the isocyanate compound include tolylene diisocyanate, xylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and prepolymers modified therefrom. Use at least one of can do.

[0036] Examples of the above-mentioned aziridine compounds include 1,1,-(methylenedi-p-phenylene-bis) 3,3 aziridylurea, 1,1,-(hexamethylene) bis3,3 aziridylurea, ethi Renbis mono (2-aziridyl-lpropionate), Tris (1-aziridyl-l) phosphine oxide, 2, 4, 6 Triaziridyl-l, 3, 5 triazine and trimethylolpronone tris-l (2-aziridyl-lpropionate) ) And at least one of these can be used.

[0037] The copolymer (A) may further contain a copolymerizable monomer unit (c) having an aromatic group. Specific examples of the monomer unit (c) include 2-phenoxychetyl (meth) acrylate, benzyl (meth) acrylate, styrene, and α-methyl styrene, and at least one of them. Can be used. Preferred monomer units (c) are 2-phenoxychetyl (meth) acrylate and benzyl (meth) acrylate. The proportion of the monomer unit (c) is 20 to 60% by mass, preferably 30 to 50% by mass, when the total amount of the copolymer (Α) is 100% by mass. When the proportion is less than 20% by mass or exceeds 60% by mass, an adhesive layer formed from the optical adhesive composition containing the copolymer (Α) may be used in a liquid crystal cell. The liquid crystal display device is not preferable because the color unevenness and white spotting phenomenon cannot be suppressed. When the copolymer (Α) is composed of the monomer unit (a), the monomer unit (b) and the monomer unit (c), the total amount of the copolymer (A) is 100% by mass. The proportion of the monomer unit (a) is 39.8 to 79.8% by mass, preferably 43 to 69.5% by mass. The proportion of the monomer unit (b) is 0.2 to 10% by mass, preferably 0.5 to 7% by mass.

[0038] The optical pressure-sensitive adhesive composition of the present invention may further contain a silane compound (C) containing a mercaptoalkyl group and an alkoxy group in the molecule! By containing the silane compound (C), the pressure-sensitive adhesive layer formed from the composition further improves the adhesion with the glass substrate surface that is the adherend in the liquid crystal cell.

[0039] When the silane compound (C) is used in the optical pressure-sensitive adhesive composition of the present invention, the amount is preferably 0.01 to 2 parts by mass per 100 parts by mass of the copolymer (A). When the amount used exceeds 2 parts by mass, the pressure-sensitive adhesive layer formed from the optical pressure-sensitive adhesive composition tends to peel off. It is not preferable.

[0040] Specific examples of the silane compound (C) include γ mercaptopropyltrimethoxysilane, γ mercaptopropyltriethoxysilane, γ mercaptobutyltrimethoxysilane, and oligomer, and at least of these. One species can be used.

[0041] The optical pressure-sensitive adhesive composition of the present invention is an alkyl ester of (meth) acrylic acid having 1 to 18 carbon atoms in a proportion of 1 to 50 parts by mass per 100 parts by mass of the copolymer (Α). Low molecular weight (co) polymers (D) can also be used. The (co) polymer (D) has a weight average molecular weight of 1,000 to 50,000 and a dispersity (MWZMN) of 1.0 to 2.5, and the copolymer (A) and Preferable to be compatible. The (meth) acrylic acid alkyl ester monomer unit constituting the (co) polymer (D) is the same as the monomer unit (a) in the copolymer (A). In the present invention, the term “(co) polymer” means to include both a homopolymer and a copolymer. When the (co) polymer (D) is a copolymer, the proportion of the monomer unit (a) in the copolymer (D) is as follows when the copolymer (D) is 100% by mass. 98-99.9% by mass is preferable. In addition, monomer units other than (meth) acrylic acid alkyl esters, except for monomer units (b) containing functional groups, copolymerizable monomer units containing aromatic groups (c )ヽ.

[0042] When the weight average molecular weight of the (co) polymer (D) is smaller than 1,000, the viscosity of the pressure-sensitive adhesive layer formed from the optical pressure-sensitive adhesive composition is lowered, and used in a liquid crystal cell. In this case, it is not preferable because it causes bleeding of the pressure-sensitive adhesive layer and a decrease in adhesiveness and color unevenness / whitening phenomenon of the liquid crystal display device. On the other hand, when the weight average molecular weight exceeds 50,000, the (co) polymer (D) in the optical pressure-sensitive adhesive composition is interposed between the crosslinked structures formed by the copolymer (A). It becomes difficult to enter, and the elasticity and flexibility of the pressure-sensitive adhesive layer formed from the composition are reduced. For this reason, even if the pressure-sensitive adhesive layer is used in a liquid crystal display device, the effect of preventing uneven whitening can not be expected. Further, when the (co) polymer (D) having a dispersity exceeding 2.5 is used in the optical pressure-sensitive adhesive composition of the present invention, the cohesive force of the pressure-sensitive adhesive layer formed from the composition is reduced. This is not preferable because it causes foaming and peeling of the pressure-sensitive adhesive layer.

[0043] In the optical pressure-sensitive adhesive composition of the present invention, when the (co) polymer (D) is used, Copolymer (A) 1 to 50 parts by mass per 100 parts by mass is preferred, preferably 5 to 40 parts by mass, and more preferably 10 to 30 parts by mass. By using the (co) polymer (D) in the optical pressure-sensitive adhesive composition of the present invention, the pressure-sensitive adhesive layer formed from the composition can expand and contract the optical functional film in the liquid crystal cell. Absorbs the stress caused by it and increases the effect of preventing foaming and peeling of the adhesive layer. This is because the (co) polymer (D) does not contain a functional group having a small weight average molecular weight, and thus does not contribute to the formation of a crosslinked structure by the crosslinking agent, and is a pressure-sensitive adhesive layer formed from the composition. This is thought to be due to the high degree of flexibility given to the company.

[0044] However, when the amount used exceeds 50 parts by mass, the cohesive force of the pressure-sensitive adhesive layer is reduced, which causes foaming or peeling of the adhesive layer.

[0045] The (co) polymer (D) can be produced by the same method as the copolymer (A) described above.

[0046] Further, in the production of the optical pressure-sensitive adhesive composition of the present invention, various additives may be blended as necessary for the purpose of adjusting the adhesiveness of the copolymer (A). . Specific examples of such additives include terpene series, terpene monophenol series, coumarone indene series, styrene series, rosin series, xylene series, phenol series and petroleum series tackifiers and acid-proofing agents. Examples thereof include a stopper, an ultraviolet absorber, a filler, and a pigment.

[0047] The optical functional film of the present invention is characterized by having a pressure-sensitive adhesive layer formed from the optical pressure-sensitive adhesive composition of the present invention on the surface of an optical functional film as a substrate. Examples of the optical functional film as the substrate include a film light guide plate, an antireflection film, a conductive film, a viewing angle widening film, a retardation film, and a polarizing plate. By using the optical functional film of the present invention for the production of a liquid crystal cell, the liquid crystal cell has high-quality optical functionality and does not cause uneven coloration or white blurring in a liquid crystal display device. Can be provided.

[0048] The optical functional film of the present invention is usually used! An optical functional film using the optical pressure-sensitive adhesive composition of the present invention as a base material using a coating apparatus such as a roll coating apparatus. After the coating, it can be obtained by drying and, if necessary, heat-crosslinking or curing with light such as ultraviolet rays to form an adhesive layer. Optical machine of the present invention The thickness of the pressure-sensitive adhesive layer in the performance film is usually preferably about 10 to 50 m.

[0049] Color unevenness of the optical functional film of the present invention 'white spot test is performed by visual inspection and using a haze meter (for example, NDH2000 manufactured by Nippon Denshoku Industries Co., Ltd.). From this point, the total light transmittance (%) was measured, and the difference Δ of the total light transmittance from the maximum total light transmittance and the minimum total light transmittance was calculated as follows: It can be done by calculating from

[Formula 2]

Total light transmittance difference Δ = Maximum total light transmittance—Minimum total light transmittance

[0050] The difference in total light transmittance Δ of the optical functional film of the present invention is preferably 0.1 or less, more preferably 0.05 or less. When an optical functional film having Δ greater than 0.1 is used in a liquid crystal display device, uneven color and white spotting may be a problem.

Example

[0051] Next, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. In the following text, “part” and “%” are based on mass unless otherwise specified.

[0052] [Production Example 1 (Copolymer A-1)]

Nitrogen gas is sealed in a reactor equipped with a stirrer, thermometer, reflux condenser and nitrogen inlet tube, and then 100 parts of ethyl acetate, 98 parts of butyl acrylate, 2 parts of acrylic acid and a polymerization initiator (azobisisobutyor-tolyl) 0. 1 part was charged and a polymerization reaction was carried out at 68 ° C for 8 hours in a nitrogen gas stream while stirring. After completion of the reaction, 300 parts of ethyl acetate is added, and the contents are cooled at room temperature to obtain a solution of copolymer A-1 having a viscosity of 2, OOOmPa-s, a solid content of 20%, and a weight average molecular weight of 1.3 million. It was.

[0053] [Production Example 2 (Copolymer A-2)]

Polymerization was carried out in the same manner as in Production Example 1 except that 98 parts of butyl acrylate in Production Example 1 were replaced with 58 parts of butyl acrylate and 40 parts of phenoxy shell acrylate, and the viscosity was 1,800 mPa's, the solid content was 20%, A solution of copolymer A-2 having a weight average molecular weight of 1,220,000 was obtained.

[0054] [Production Example 3 (Copolymer A-3)] Polymerization was conducted in the same manner as in Production Example 1 except that 2 parts of acrylic acid in Production Example 1 was replaced with 2 parts of hydroxyethyl acrylate, and the viscosity was 1,900 mPa's, the solid content was 20%, and the weight average molecular weight was 1.32 million. A solution of Copolymer A-3 was obtained.

[0055] [Production Example 4 (Copolymer A-4)]

Polymerization was carried out in the same manner as in Production Example 1 except that 98 parts of butyl acrylate in Production Example 1 were replaced with 48 parts of butyl acrylate and 15 parts of phenoxycetyl acrylate and 35 parts of benzyl acrylate. A solution of copolymer A-4 having 2, OOOmPa-s, solid content of 20%, and weight average molecular weight of 1,220,000 was obtained.

[0056] [Production Example 5 (Copolymer D-1)]

After nitrogen gas is sealed in a reactor equipped with a stirrer, thermometer, reflux condenser and nitrogen inlet tube, 20 parts of ethyl acetate, 60 parts of toluene, 5 parts of α-methylstyrene dimer, 60 parts of butyl phthalate, phenol 40 parts of shetyl acrylate and 0.5 parts of a polymerization initiator (azobisisobutyro-tolyl) were charged and reacted for 8 hours at reflux temperature in a nitrogen gas stream while stirring. After completion of the reaction, 20 parts of ethyl acetate is added, the contents are cooled at room temperature, viscosity 20 mPa, s, solid content 50%, weight average molecular weight 10,000, number average molecular weight 5,900, dispersity 1.7. A solution of copolymer D-1 was obtained.

[0057] [Example 1]

For 100 parts of the solid content of the copolymer A-1 obtained in Production Example 1, 0.5 part of transstilbene (rod-like compound) (molecular weight 180) and polyisocyanate (trade name; Coroneichi Toray Nippon Polyurethane Industry Co., Ltd. (0.2 parts) and silane coupling agent (trade name; KBM — 803, y-mercaptopropylmethyltrimethoxysilane, Shin-Etsu Chemical Co., Ltd.) 0.1 Part of the mixture was added and mixed to obtain an optical pressure-sensitive adhesive composition of the present invention.

[0058] The obtained optical pressure-sensitive adhesive composition was applied onto a silicon-coated polyethylene terephthalate film (PET film) so that the thickness after drying was 25 μm, and the solvent was removed at 90 ° C. While being dried, a pressure-sensitive adhesive layer was formed by crosslinking reaction. A polarizing film having a thickness of 250 m, which is an optical functional film as a base material, was bonded to the obtained pressure-sensitive adhesive layer to produce an optical functional film of the present invention. The optical functional film of the present invention was cured for 7 days at 23 ° C. and 50% relative humidity (hereinafter abbreviated as “RH”), and then durable. Property, adhesive strength, holding power, viscosity coefficient, and white spots (measured according to the test method described later) were evaluated. All the results were good. The results are shown in Table 2.

[0059] [Examples 2 to 8]

As shown in Table 1, the optical pressure-sensitive adhesive composition of the present invention and the optical functional film of the present invention were the same as in Example 1 except that the types and amounts of the adhesive resin, rod-like compound and crosslinking agent were changed. Were fabricated and evaluated for durability and the like. All the results were good. The results are shown in Table 2.

[0060] [Examples 9 and 10]

In Example 9, 100 parts of the solid content in the solution of the copolymer A-2 obtained in Production Example 2 is 10 parts of the copolymer D-1 obtained in Production Example 5 and 7 parts of transstilbene. , Polyisocyanate (trade name; Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.) 0.2 part and silane coupling agent (trade name; KBM-803, γ-mercaptopropylmethyltrimethoxysilane, Shin-Etsu Chemical Co., Ltd.) 0.1 part) was added, and the optical pressure-sensitive adhesive composition of the present invention and the optical functional film of the present invention were prepared in the same manner as in Example 1, and the durability and the like were evaluated. Example 10 is the same as Example 9 except that the copolymer D-1 of Example 9 is changed to 30 parts, and the optical adhesive composition of the present invention and the optical functional film of the present invention are produced. Sexuality was evaluated. The results were all good. The results are shown in Table 2.

[0061] [Example 11]

Example 11 produced the optical pressure-sensitive adhesive composition of the present invention and the optical functional film of the present invention in the same manner as in Example 2 except that no silane coupling agent was used. evaluated. All the results were good. The results are shown in Table 2.

[0062] [Comparative Example 1]

Comparative Example 1 produced the optical pressure-sensitive adhesive composition of the present invention and the optical functional film of the present invention in the same manner as in Example 1 except that 20 parts of the rod-like composite was added, and evaluated durability and the like. . As a result, the pressure-sensitive adhesive layer foamed in the durability test, and the white spot evaluation was bad. The results are shown in Table 2.

[0063] [Comparative Example 2]

Comparative Example 2 was the same as that of Example 2 except that no crosslinking agent was used. Pressure-sensitive adhesive composition and the optical functional film of the present invention were prepared, and durability and the like were evaluated.

. As a result, the durability and the strength with bad holding power were good. The results are shown in Table 2.

[0064] [Comparative Example 3]

Comparative Example 3 is an example except that no rod-like compound was used and the amount of the crosslinking agent was 1.0 part.

In the same manner as in Example 1, the optical pressure-sensitive adhesive composition of the present invention and the optical functional film of the present invention were prepared, and durability and the like were evaluated. As a result, the force-viscosity coefficient and white spots that had good durability were bad. The results are shown in Table 2.

[0065]

Specify the abbreviations and product names listed in Table 1.

Rod-shaped compound

A: Transstilbene (Molecular weight: 180)

B: Fluorene (Molecular weight: 166)

C: Benzoin (Molecular weight: 212)

D: Diphenylsulfide (Molecular weight: 186)

E: Benzyl benzoate (Molecular weight: 212)

F: Diphenyl-acetylene (Molecular weight: 178)

Cross-linking agent

Coronate L: Polyisocyanate, manufactured by Nippon Polyurethane Industry Co., Ltd.

Takenate D—HON: Polyisocyanate, manufactured by Mitsui Takeda Chemical Co., Ltd.

Takenate D—160N: Polyisocyanate, manufactured by Mitsui Takeda Chemical Co., Ltd.

Tetrad X: Multifunctional glycidyl compound, manufactured by Mitsubishi Gas Chemical Co., Ltd.

Silane coupling agent

KBM-803: y-mercaptopropylmethyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd.

X—41— 1805: Mercapto group-substituted alkoxy oligomer, manufactured by Shin-Etsu Chemical Co., Ltd. X—41—1810: Mercapto group-substituted alkoxy oligomer, manufactured by Shin-Etsu Chemical Co., Ltd. KBM-802: y—Mercaptopropylmethyldimethoxy Silane, manufactured by Shin-Etsu Chemical Co., Ltd.

Table 2

[Test method]

1.Durability

The optical functional films of Examples and Comparative Examples were each cut to 90 mm × 150 mm, the PET film was peeled off, the optical functional film was attached to a glass plate, and this was placed in an autoclave 50. C, and under the conditions of 5 kg / cm ^2, after holding for 18 minutes, 80. 500 at C For test samples left for a long time, or for test samples left for 500 hours in an environment of 60 ° C and 95% RH, foam generated in the adhesive layer and peeling of the optical functional film as the substrate The durability was evaluated according to the following criteria.

[0069] <Evaluation criteria>

[Foam]

○: Foam was not confirmed in the adhesive layer.

Δ: Slight foaming was confirmed in the pressure-sensitive adhesive layer.

X: Foaming was confirmed in the pressure-sensitive adhesive layer.

[Peeling]

◯: The optical functional film as a substrate was strong enough to prevent peeling.

Δ: Slight peeling was confirmed on the optical functional film as the substrate.

X: Peeling was confirmed on the optical functional film as the substrate.

[0070] 2. Adhesive strength

For the optical functional films of Examples and Comparative Examples, the 180 ° peeling adhesive strength was measured according to JIS Z-0237. A glass plate was used as the adherend.

[0071] 3. Holding force

The viscosity coefficient of the pressure-sensitive adhesive layer was determined by the following method according to the holding power measurement method of JIS Z-0237. The long side of the optical functional film (polarizing film) of Examples and Comparative Examples having an adhesive layer is cut into a size of 25 mm x 55 mm with a cutting line at 90 ° to the absorption axis of the polarizing film. To do. The cut polarizing film was attached to a glass plate so that the adhesion area was 25 mm × 10 mm, and this was held in an autoclave at 50 ° C. and 5 kgZcm ² for 18 minutes to prepare a test sample. A load (9.8 N) was applied to the lower end of the polarizing film of the test sample, and after maintaining for 1 hour in an atmosphere at 90 ° C, the distance (the amount of deviation) that the polarizing film adhered to the glass plate shifted downward. ) Was measured, and the holding power was expressed by this amount of deviation.

[0072] 4. Viscosity coefficient

3. The viscosity coefficient (Pa's) of the pressure-sensitive adhesive layer was calculated according to the above [Equation 1] from the amount of deviation obtained by measuring the holding force.

In this example, in [Formula 1], Displacement stress (NZm ² ) = load Z adhesion area = 9.8 N / (0. 025m X O. 01m)

Displacement speed (lZs) = Displacement amount Z test time Z Adhesive layer thickness = Displacement amount (m) Z3600 seconds /0.000025m

It is.

[0073] 5. White spot evaluation

(1) Visual inspection

In the “1. Durability Test”, two optical functional films of the same type after being left at 80 ° C. for 500 hours are bonded together in a cross-cord, and this is placed on the backlight of the LCD monitor. The state of white spots was visually observed and evaluated according to the following criteria.

○: No white spots were found on the optical functional film.

Δ: Slight white spots were confirmed on the optical functional film.

X: White spots were confirmed on the optical functional film.

[0074] (2) Total light transmittance evaluation

For the optical functional film that was visually evaluated for white spots, the total light transmittance (%) of 35 points was measured using a haze meter (NDH2000, manufactured by Nippon Denshoku Industries Co., Ltd.). The difference Δ in total light transmittance was calculated from the above [Equation 2] from the maximum total light transmittance and the minimum total light transmittance.

Industrial applicability

[0075] According to the present invention, there is provided an optical pressure-sensitive adhesive composition for forming a pressure-sensitive adhesive layer for closely adhering a glass substrate and an optical functional film to a liquid crystal cell constituting a liquid crystal display device. Is done. The pressure-sensitive adhesive layer has moderate adhesive strength, absorbs stress caused by expansion and contraction of the optical functional film, which has good adhesion to the optical functional film and is difficult to improve with conventional adhesives. As a result, it is possible to suppress the occurrence of color unevenness and white spots in the liquid crystal display device.

Claims

The scope of the claims

[1] An optical pressure-sensitive adhesive composition containing at least two benzene rings in a molecule and a molecular weight of 150 to 1,000, an adhesive composition, an adhesive resin, and a crosslinking agent, The content of the compound is from 0.1 to 15 parts by mass per 100 parts by mass of the adhesive resin, and the viscosity coefficient at 90 ° C of the adhesive layer formed from the composition is 0.5. X 10 ⁷ to 10 X 10 ⁷ Pa 's

[2] A compound having at least two benzene rings in the molecule and having a molecular weight of 150 to 1,000 is transstilbene, fluorene, diphenylsulfide, benzyl benzoate, benzoin, and diphenylacetylene. The optical pressure-sensitive adhesive composition according to claim 1, which is at least one selected from group power.

[3] The adhesive resin is a copolymerizable monomer unit containing (meth) acrylic acid alkyl ester monomer unit (a) having 1 to 18 carbon atoms and a carboxyl group and Z or hydroxyl group ( The optical pressure-sensitive adhesive composition according to claim 1, which is a copolymer (A) containing at least b) and having a weight average molecular weight of 1,000,000 to 2,000,000.

[4] The optical pressure-sensitive adhesive composition according to claim 1, wherein the content of the cross-linking agent is 0.01 to 1 part by mass per 100 parts by mass of the adhesive resin.

[5] The copolymer (A) further comprises a copolymerizable monomer unit (c) containing an aromatic group that occupies 20 to 60% by mass of the total amount of the copolymer. The optical pressure-sensitive adhesive composition as described.

[6] The silanic compound (C) containing a mercaptoalkyl group and an alkoxy group in the molecule, further comprising 0.01 to 2 parts by mass per 100 parts by mass of the adhesive resin. The optical adhesive composition of description.

[7] Further, a low molecular weight (co) polymer (D) having an alkyl ester power of 1 to 18 carbon atoms of (meth) acrylic acid is added in an amount of 1 to 50 parts by mass per 100 parts by mass of the copolymer (A). The (co) polymer (D) has a weight average molecular weight of 1,000 to 50,000 and a dispersity (MWZ MN) of 1.0 to 2.5, and the copolymer 2. The optical pressure-sensitive adhesive composition according to claim 1, which is compatible with (A).

[8] The surface has an adhesive layer formed from the optical adhesive composition according to claim 1. An optical functional film characterized by: