JP2012021148A - Pressure-sensitive adhesive, pressure-sensitive adhesive for optical member, optical member with pressure-sensitive adhesive layer and image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure-sensitive adhesive, especially a pressure-sensitive adhesive for an optical member, that is excellent in handling properties (tack) and optical properties (haze) of a pressure-sensitive adhesive layer and is excellent in durability performance and optical properties (light leakage resistance) even when laminating an optical member such as a polarizing plate or the like with a glass substrate or the like.SOLUTION: The pressure-sensitive adhesive is produced by curing [I] a pressure-sensitive adhesive composition including (A) an acrylic resin and (B) an aromatic compound containing one ethylenically unsaturated group with an active energy ray and/or heat and is characterized in that a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive has a refractive index of 1.475 to 1.575.

Description

  The present invention relates to a pressure-sensitive adhesive (pressure-sensitive adhesive), a pressure-sensitive adhesive for optical members, an optical member with a pressure-sensitive adhesive layer obtained using the same, and an image display device. Specifically, an optical film (polarizing film, retardation film, optical compensation film, brightness enhancement film, etc.) suitably used for liquid crystal display devices, organic EL display devices, image display devices such as PDP, etc. A pressure-sensitive adhesive for an optical member used for bonding an optical laminate in which a polarizing film is coated with a protective film such as a cellulose triacetate film and a glass substrate of a liquid crystal cell, and a pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive for the optical member The present invention relates to an optical member with an adhesive layer, particularly a polarizing plate with an adhesive layer.

  Conventionally, a polarizing plate coated with a cellulose film, for example, a cellulose triacetate film, on both sides of a polarizing film such as a polyvinyl alcohol film provided with a polarizing property, sandwiched a liquid crystal component aligned between two glass plates. Lamination is performed on the surface of the liquid crystal cell to form a liquid crystal display panel. This lamination to the liquid crystal cell surface is achieved by pressing and pressing the pressure-sensitive adhesive layer provided on the polarizing plate surface against the liquid crystal cell surface. Usually done.

  Such a polarizing plate has a three-layer structure in which both surfaces of a polyvinyl alcohol-based polarizer are sandwiched between triacetyl cellulose-based protective films, but dimensional stability is poor due to the characteristics of these materials. Moreover, since the polyvinyl alcohol-type polarizer is shape | molded by extending | stretching, the dimensional change with time is easy to occur. If the internal stress generated by such a dimensional change cannot be absorbed and relaxed, the distribution of residual stress acting on the polarizing plate becomes non-uniform, and stress is concentrated particularly on the peripheral portion of the polarizing plate. As a result, color unevenness / light leakage phenomenon occurs in the liquid crystal display device such that the peripheral edge of the liquid crystal display device is brighter or darker than the center.

  Therefore, for various optical applications, especially adhesives for attaching polarizing plates, research is being conducted to find adhesives that not only have excellent durability such as foaming and peeling, but also have excellent optical properties such as less light leakage. Has been done.

  For example, Patent Document 1 describes an adhesive having excellent optical properties by using an acrylic resin copolymerized with an aromatic monomer, and Patent Document 2 describes an aromatic resin containing an aromatic ring-containing low molecular weight. A pressure-sensitive adhesive having excellent optical properties by blending a compound is described, and Patent Document 3 discloses that an ethylenically unsaturated monomer (UV curable monomer) used in combination with an acrylic resin is subjected to crosslinking polymerization by irradiation with active energy rays. In addition, an adhesive having a good balance between durability and optical properties is described.

JP 2005-53976 A WO2007 / 072799 JP 2009-132909 A

  However, although the technique disclosed in Patent Document 1 shows a certain optical characteristic, a large amount of aromatic monomer is copolymerized in order to clear the recent demand for higher optical characteristics using this technique. It is necessary to let

However, when polymerization is carried out using a large amount of aromatic monomer, the viscosity in the reaction solution increases, so that a high molecular weight generally used in an adhesive for optical applications (for example, a weight average molecular weight of 1 million or more). It is difficult to produce an acrylic resin, and in general, it is difficult to remove the diacrylate body of impurities generated during the production of aromatic monomers by distillation or the like. In many cases, it was difficult to produce a high molecular weight acrylic resin under the influence of such impurities.
In addition, when low molecular weight aromatic monomers such as benzyl acrylate and phenoxyethyl acrylate, which are relatively easy to polymerize, are used for polymerization, residual monomers may remain after the formation of the adhesive layer. The odor was also a problem.

  Even with the technique disclosed in the above-mentioned Patent Document 2, although it has been obtained that the color unevenness and light leakage are hardly generated, the low molecular weight compound having two or more benzene rings used in Patent Document 2, Due to high crystallinity and low hydrophobic groups, compatibility with acrylic resins is poor. Furthermore, it is a low molecular weight component and its cohesive strength is low, so the cohesive strength as an acrylic adhesive does not increase and the durability of liquid crystal display devices There was a problem that the sex became worse.

  In the technique disclosed in Patent Document 3 described above, although it is surely excellent in durability and optical properties in a well-balanced manner, an ethylenically unsaturated monomer having two or more ethylenically unsaturated groups is mainly used as a UV curable monomer. The cross-linking density and elastic modulus of the pressure-sensitive adhesive layer after UV irradiation are very high compared to general pressure-sensitive adhesives, and the tackiness of the pressure-sensitive adhesive drops and the tackiness when the pressure-sensitive adhesive is bonded to the adherend is reduced. There was a problem of being bad.

  Therefore, in the present invention, under such a background, the pressure-sensitive adhesive layer is an adhesive having excellent handleability (tack) and optical characteristics (haze), and an optical member such as a polarizing plate is bonded to a glass substrate or the like. The purpose of the present invention is to provide an adhesive having excellent durability and optical properties (light leakage resistance), particularly an adhesive for optical members.

  However, as a result of intensive studies in view of such circumstances, the present inventors have determined that a monofunctional monomer having an aromatic ring is used as the curable ethylenically unsaturated monomer in the active energy ray and / or thermosetting adhesive. Compared to conventional adhesives with a refractive index of about 1.46, the adhesive layer that is used and has a higher refractive index than the conventional adhesive has a handleability (tack) and optical properties (haze) In addition, the present invention has been found to be excellent in balance between durability and light leakage resistance, and the present invention has been completed.

That is, the gist of the present invention is that the pressure-sensitive adhesive composition [I] containing an acrylic resin (A) and an aromatic compound (B) containing one ethylenically unsaturated group is an active energy ray and / or The pressure-sensitive adhesive is a pressure-sensitive adhesive that is cured by heat, and has a refractive index of 1.475 to 1.575.
Furthermore, an optical member pressure-sensitive adhesive using the above-mentioned pressure-sensitive adhesive, a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive for the optical member and an optical member with a pressure-sensitive adhesive layer including a laminated structure of the optical member, and an image display comprising the optical member It relates to the device.

The pressure-sensitive adhesive of the present invention is excellent in light leakage resistance, but the reason why light leakage does not occur is estimated as follows.
In general, the cause of light leakage is that stress is concentrated on the triacetyl cellulose (TAC) protective film of the polarizing plate due to shrinkage when the polarizing plate is exposed to heat-resistant conditions, and birefringence (positive photoelastic coefficient). Or the acrylic polymer of the pressure-sensitive adhesive is oriented by following the contraction of the polarizing plate, and birefringence (generally having a negative photoelastic coefficient) is presumed to occur. The

Birefringence derived from a TAC-based protective film having a positive photoelastic coefficient cannot be eliminated only with a conventional acrylic polymer having a negative photoelastic coefficient. That is, when the polarizing plate contracts and tensile stress is generated (the direction in which the stress is generated is defined as the x-axis direction), the refractive index of the TAC-based protective film increased in the x-axis direction is expressed in the x-axis direction of the acrylic polymer. The effect of reducing the refractive index cannot be offset. In order to eliminate this birefringence, it is necessary to reinforce the negative photoelastic coefficient of the pressure-sensitive adhesive layer made of an acrylic polymer.
Therefore, in the present invention, attention was focused on offsetting the positive photoelastic coefficient of the TAC protective film by blending an appropriate amount of a component having a negative photoelastic coefficient into the acrylic resin (A). Specifically, as a component having a negative photoelastic coefficient, by using a certain amount of the polymer of the aromatic monomer (B), the pressure-sensitive adhesive layer has a constant refractive index, thereby being excellent in light leakage resistance. A polarizing plate with an adhesive layer could be obtained. The pressure-sensitive adhesive layer obtained according to the present invention exhibits birefringence opposite to that of the TAC-based protective film depending on the degree of generated stress. It is also effective in eliminating birefringence that has occurred in part.

  The pressure-sensitive adhesive of the present invention can be suitably used particularly as an optical member application, and the pressure-sensitive adhesive layer after curing by active energy rays and / or heat is excellent in handleability (tack) and optical properties (haze). Even under high-temperature and high-humidity environments, it has excellent adhesion between optical laminates, especially optical members such as polarizing plates, and glass substrates, and foaming or peeling occurs between the pressure-sensitive adhesive layer and the glass substrate. Therefore, a liquid crystal display device in which uneven color and light leakage do not occur can be obtained.

The present invention will be described in detail below, but these show examples of desirable embodiments.
In the present invention, (meth) acryl means acryl or methacryl, (meth) acryloyl means acryloyl or methacryloyl, and (meth) acrylate means acrylate or methacrylate.

First, the pressure-sensitive adhesive composition [I] of the present invention will be described.
The pressure-sensitive adhesive composition [I] of the present invention comprises an acrylic resin (A) and an aromatic compound (B) containing one ethylenically unsaturated group.

  The acrylic resin (A) used in the present invention comprises a (meth) acrylic acid alkyl ester monomer (a1) as a main component and, if necessary, a functional group-containing monomer (a2) as a copolymerization component. Furthermore, another copolymerizable monomer (a3) can be used as a copolymerization component. The acrylic resin (A) in the present invention uses the functional group-containing monomer (a2) as a copolymerization component, which becomes a cross-linking point of the acrylic resin (A), and the base resin or adherend. It is preferable at the point which raises adhesiveness further.

  As such a (meth) acrylic acid alkyl ester monomer (a1), the alkyl group usually has 1 to 20, particularly 1 to 12, more preferably 1 to 8, particularly 4 to 8 carbon atoms. Specifically, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, iso-butyl (meth) acrylate, tert-butyl (meth) acrylate, n-propyl (meth) acrylate , N-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isodecyl (meth) acrylate, lauryl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl (Meth) acrylate, isobornyl (meth) ac Rate, and the like. These can be used alone or in combination of two or more.

  Among such (meth) acrylic acid alkyl ester monomers (a1), n-butyl (meth) acrylate and 2-ethylhexyl (meth) are preferable in terms of copolymerizability, adhesive properties, ease of handling, and availability of raw materials. An acrylate is preferably used, and more preferably n-butyl (meth) acrylate is used in terms of excellent durability.

  Examples of the functional group-containing monomer (a2) include a hydroxyl group-containing monomer, an amino group-containing monomer, an acetoacetyl group-containing monomer, an isocyanate group-containing monomer, a carboxyl group-containing monomer, and a glycidyl group-containing monomer. A hydroxyl group-containing monomer and a carboxyl group-containing monomer are preferably used in terms of efficient crosslinking reaction.

  Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 5-hydroxypentyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meta ) Acrylic acid hydroxyalkyl esters such as acrylate, caprolactone-modified 2-hydroxyethyl (meth) acrylate and other caprolactone-modified monomers, diethylene glycol (meth) acrylate, polyethylene glycol (meth) acrylate and other oxyalkylene-modified monomers, and other 2-acrylic Primary hydroxyl group-containing monomers such as leuoxyethyl 2-hydroxyethylphthalic acid and N-methylol (meth) acrylamide; 2-hydroxypropyl (meth) acrylate Secondary hydroxyl group-containing monomers such as 2-hydroxybutyl (meth) acrylate and 3-chloro-2-hydroxypropyl (meth) acrylate; tertiary hydroxyl group-containing monomers such as 2,2-dimethyl 2-hydroxyethyl (meth) acrylate Can be mentioned.

  Among the above hydroxyl group-containing monomers, a primary hydroxyl group-containing monomer is preferable from the viewpoint of excellent reactivity with a crosslinking agent, and a monomer having a hydroxyl group at the molecular chain end is considered preferable because it exhibits excellent antistatic performance. Furthermore, it is particularly preferable to use 2-hydroxyethyl acrylate because it has few impurities such as di (meth) acrylate and is easy to produce.

  In addition, as a hydroxyl-containing monomer used by this invention, it is also preferable to use a thing with the content rate of di (meth) acrylate which is an impurity 0.5% or less, and also 0.2% or less, especially 0 It is preferable to use one having a content of 1% or less, specifically 2-hydroxyethyl acrylate or 2-hydroxypropyl acrylate.

  Examples of the carboxyl group-containing monomer include (meth) acrylic acid, acrylic acid dimer, crotonic acid, maleic acid, maleic anhydride, fumaric acid, citraconic acid, glutaconic acid, itaconic acid, acrylamide N-glycolic acid, and cinnamic acid. Among them, (meth) acrylic acid is preferably used.

  Examples of the amino group-containing monomer include t-butylaminoethyl (meth) acrylate, ethylaminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, and the like.

  Examples of the acetoacetyl group-containing monomer include 2- (acetoacetoxy) ethyl (meth) acrylate and allyl acetoacetate.

  Examples of the isocyanate group-containing monomer include 2-acryloyloxyethyl isocyanate, 2-methacryloyloxyethyl isocyanate, and alkylene oxide adducts thereof.

Examples of the glycidyl group-containing monomer include glycidyl (meth) acrylate and allyl glycidyl (meth) acrylate.
These functional group-containing monomers (a2) may be used alone or in combination of two or more.

  Among these, it is preferable to use a carboxyl group-containing monomer in terms of improving adhesion, and in this case, the content ratio of the carboxyl group-containing monomer is preferably 0.1 to 30% by weight, particularly preferably 1 to 20%. % By weight, more preferably 2 to 10% by weight.

  Other copolymerizable monomers (a3) include, for example, acrylonitrile, methacrylonitrile, vinyl acetate, vinyl propionate, vinyl stearate, vinyl chloride, vinylidene chloride, alkyl vinyl ether, vinyl toluene, vinyl pyridine, vinyl pyrrolidone, and itacone. Examples thereof include monomers such as acid dialkyl esters, fumaric acid dialkyl esters, allyl alcohol, acrylic chloride, methyl vinyl ketone, N-acrylamidomethyltrimethylammonium chloride, allyltrimethylammonium chloride, and dimethylallylvinylketone.

  Further, as other copolymerizable monomer (a3), phenyl (meth) acrylate, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, ethoxylated o-phenylphenyl ( Aromatic ring-containing monomers such as (meth) acrylate, phenyldiethylene glycol (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, and styrene may be used.

  As a content ratio of the monomer component in the copolymer component, the (meth) acrylic acid alkyl ester monomer (a1) is preferably 30 to 100% by weight, particularly preferably 60 to 99% by weight, and further preferably 80 to 80%. The functional group-containing monomer (a2) is preferably 0 to 30% by weight, particularly preferably 0.1 to 20% by weight, and further preferably 1 to 10% by weight. (A3) is preferably 0 to 30% by weight, particularly preferably 1 to 20% by weight, and more preferably 2 to 10% by weight.

When the amount of the (meth) acrylic acid alkyl ester monomer (a1) is too small, for example, when used as an adhesive, the adhesive strength tends to be lowered.
If the amount of the functional group-containing monomer (a2) is too small, the cohesive force decreases in the same manner, so that the durability performance tends to decrease. If the amount is too large, the viscosity increases or the stability of the resin tends to decrease.
When there are too many other copolymerizable monomers (a3), the effects of the present invention tend to be difficult to obtain.

  For the purpose of increasing the molecular weight, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate A compound having two or more ethylenically unsaturated groups such as divinylbenzene can also be used in combination.

  The acrylic resin (A) is produced by polymerizing the monomer components (a1) to (a3) described above. In this polymerization, conventional methods such as solution radical polymerization, suspension polymerization, bulk polymerization, and emulsion polymerization are used. It can be performed by a known method. For example, a polymerization monomer such as a (meth) acrylic acid alkyl ester monomer (a1), a functional group-containing monomer (a2), another copolymerizable monomer (a3), or a polymerization initiator is mixed or dropped in an organic solvent. Polymerization is conducted for 2 to 20 hours at reflux or at 50 to 90 ° C.

  Examples of the organic solvent used for the polymerization include aromatic hydrocarbons such as toluene and xylene, esters such as methyl acetate, ethyl acetate and butyl acetate, aliphatic alcohols such as n-propyl alcohol and isopropyl alcohol, acetone, Examples include ketones such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone.

  As the polymerization initiator used for such radical copolymerization, azo-based polymerization initiators such as azobisisobutyronitrile and azobisdimethylvaleronitrile, which are usual radical polymerization initiators, benzoyl peroxide, lauroyl peroxide, Specific examples thereof include peroxide polymerization initiators such as -t-butyl peroxide and cumene hydroperoxide.

  The weight average molecular weight of the acrylic resin (A) is usually 100,000 to 3,000,000, preferably 300,000 to 2,500,000, particularly preferably 600,000 to 2,000,000, particularly preferably 1,000,000 to 1,800,000. When the weight average molecular weight is too small, the durability performance tends to be lowered. When the weight average molecular weight is too large, a large amount of a diluent solvent is required, which tends to be undesirable in terms of coating property and cost.

  The degree of dispersion (weight average molecular weight / number average molecular weight) of the acrylic resin (A) is preferably 20 or less, particularly preferably 10 or less, more preferably 7 or less, and particularly preferably 4 or less. preferable. When the degree of dispersion is too high, the durability performance of the pressure-sensitive adhesive layer is lowered, and foaming or the like tends to occur. The lower limit of the degree of dispersion is usually 2 from the viewpoint of production limit.

  Furthermore, the glass transition temperature of the acrylic resin (A) is preferably −80 to −20 ° C., particularly preferably −75 to −30 ° C., more preferably −60 to −40 ° C., and the glass transition temperature is too high. When the adhesive strength is too low, the heat resistance tends to decrease.

In addition, said weight average molecular weight is a weight average molecular weight by standard polystyrene molecular weight conversion, and it is a column in high performance liquid chromatography (The Japan Waters company "Waters 2695 (main body)" and "Waters 2414 (detector)"). : Shodex GPC KF-806L (exclusion limit molecular weight: 2 × 10 ⁷ , separation range: 100 to 2 × 10 ⁷ , theoretical plate number: 10,000 plates / piece, filler material: styrene-divinylbenzene copolymer, filler The particle diameter is measured by using three series of 10 μm), and the same method can be used for the number average molecular weight. The degree of dispersion is determined from the weight average molecular weight and the number average molecular weight. The glass transition temperature is calculated from the following Fox equation.
Tg: Glass transition temperature of copolymer (K)
Tga: Glass transition temperature of monomer A homopolymer (K) Wa: Weight fraction of monomer A Tgb: Glass transition temperature of homopolymer of monomer B (K) Wb: Weight fraction of monomer B Tgn: Homogeneous of monomer N Glass transition temperature of polymer (K) Wn: weight fraction of monomer N (Wa + Wb +... + Wn = 1)

  The aromatic compound (B) containing one ethylenically unsaturated group used in the present invention (hereinafter sometimes abbreviated as “monofunctional aromatic compound (B)”) includes an aromatic ring in the molecule. And a compound having one ethylenically unsaturated group. Examples of the functional group containing such an ethylenically unsaturated group include a (meth) acryloyl group, a crotonoyl group, a vinyl group, and an allyl group.

  The monofunctional aromatic compound (B) is a compound containing a (meth) acryloyl group among the above functional groups in its structure, that is, a mono (meth) acrylate compound, an active energy ray and / or Or it is preferable at the point which reaction tends to advance when it hardens | cures with a heat | fever.

  The number of aromatic rings contained in the monofunctional aromatic compound (B) may be one, or a plurality may be contained. A compound containing one aromatic ring is preferable in terms of balancing the physical properties of the adhesive, and it is a compound containing two aromatic rings in terms of efficiently controlling the refractive index and birefringence of the adhesive layer. Although it is preferred, it is particularly preferred that it contains one aromatic ring.

  Specific examples of the monofunctional aromatic compound (B) include ether-based monofunctional aromatic compounds (b1), ester-based monofunctional aromatic compounds (b2), and other monofunctional aromatic compounds. (B3) and the like. Examples of the ether-based monofunctional aromatic compound (b1) include dihydroxybenzene derivatives such as phenol derivatives, catechol, resorcinol and hydroquinone, and ester-based monofunctional aromatic compounds. Examples of the compound (b2) include benzoic acid derivatives and phthalic acid derivatives. Other monofunctional aromatic compounds (b3) include an aromatic ring and an acryloyl group without using an ether bond or an ester bond. The compound which the ethylenically unsaturated group couple | bonded is mentioned.

The phenol derivative is preferably a derivative (b1-1) having a structure in which the hydrogen atom of the hydroxyl group of phenol is replaced with a structural site containing a (meth) acryloyl group. As the dihydroxybenzene derivative, the resorcinol has 2 A derivative (b1-2) in which one or both hydrogen atoms of one hydroxyl group are replaced with a structural site containing a (meth) acryloyl group is preferable.
As the structural moiety containing such a (meth) acryloyl group, those represented by the following general formula (1) also containing an oxyalkylene structure are preferable.

(In the formula, R is a hydrogen atom or a methyl group, X is an alkylene group, and n is an integer of 1 or more.)

X in the above general formula (1) is an alkylene group, among which an alkylene group having 1 to 10 carbon atoms is preferable, and in particular, an alkylene group having 1 to 4 carbon atoms such as an ethylene group, a propylene group, or a tetramethylene group. Groups are preferred, especially ethylene groups.
When n is a polyoxyalkylene chain moiety having 2 or more, a homopolymer of the same oxyalkylene chain may be used, or different oxyalkylene chains may be copolymerized randomly or in a block form.
The alkylene group may have a substituent. Examples of the substituent include a halogen atom, a hydroxyl group, an alkoxy group, an amino group, a sulfanyl group, an aryl group, and a heteroaryl group. Of these, a hydroxyl group is preferred.

  N in the general formula (1) is an integer of 1 or more, preferably 1 to 10, particularly preferably 1 to 2, and further preferably 2. If the value of n is too large, the heat and humidity resistance of the acrylic resin tends to decrease, and in order to control the refractive index and birefringence, shorter alkylene groups and oxyalkylene structures are preferable, so n is small. It is preferable.

Specific examples of the above (b1-1) include, for example, phenoxyethyl (meth) acrylate, phenyldiethylene glycol (meth) acrylate, phenyl polyethylene glycol (meth) acrylate, phenoxypropyl (meth) acrylate, and phenyldipropylene glycol (meth). Alkyl glycol-modified (meth) acrylates of alkylphenols such as acrylate, phenyl polypropylene glycol (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, nonylphenylethylene oxide modified (meth) acrylate, ethoxylated phenylphenyl (meta ) Acrylate and the like, and as a commercial product, phenyl polyethylene glycol acrylate (manufactured by Osaka Organic Chemical Co., Ltd., trade name “Visco” No. 193)), 2-hydroxy-3-phenoxypropyl acrylate (trade name “Biscoat # 220” manufactured by Osaka Organic Chemical Co., Ltd.), phenyldiethylene glycol acrylate (trade name “light acrylate P2HA” manufactured by Kyoeisha), ethoxylated o -Phenylphenyl acrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., trade name “NK Ester A-LEN-10”) and the like.

The benzoic acid derivative is preferably a derivative (b2-1) having a structure in which the hydrogen atom of the carboxyl group of benzoic acid is replaced with a structural site containing a (meth) acryloyl group. It is preferably a derivative (b2-2) having a structure in which one or both hydrogen atoms of the two carboxyl groups of the acid are replaced with a structural site containing a (meth) acryloyl group.
As the structural moiety containing such a (meth) acryloyl group, those represented by the general formula (1) described above are preferable.

  As a specific example of the derivative (b2-1), an esterified product in which one hydroxyl group of neopentyl glycol is esterified with acrylic acid and the other hydroxyl group is esterified with benzoic acid (manufactured by Kyoeisha Chemical Co., Ltd., trade name “ BA-104 ") and the like.

  Specific examples of the derivative (b2-2) include 2-acryloyloxyethyl-2-hydroxypropyl phthalate (trade name “Biscoat # 2311HP” manufactured by Osaka Organic Chemical Co., Ltd.), 2-acryloyloxyethyl hydrogen as commercially available products. Phthalate (trade name “Biscoat # 2000” manufactured by Osaka Organic Chemical Co., Ltd.), 2-acryloyloxypropyl hydrogen phthalate (trade name “Biscoat # 2100” manufactured by Osaka Organic Chemical Co., Ltd.), 2-methacryloyloxyethylphthalic acid (new) Nakamura Chemical Co., Ltd., trade name “CB-1”) and the like.

  Note that the monofunctional aromatic compound (B) does not contain a functional group that easily reacts with the acrylic resin (A) or the crosslinking agent (E) described later, in the crosslinked network of the acrylic resin (A). Incorporated, the degree of freedom of the cured product of the monofunctional aromatic compound (B) and the later-described ethylenically unsaturated compound (C) is lost, which is preferable in that there is little possibility that the light leakage resistance improving effect is reduced. .

  Specific examples of such functional groups include at least one selected from an isocyanate group, a hydroxyl group, and a carboxyl group.

  The molecular weight of the monofunctional aromatic compound (B) is usually 200 to 10,000, preferably 210 to 1,000, particularly preferably 220 to 500. If the molecular weight is too large, the aromatic ring concentration tends to decrease, making it difficult to adjust the refractive index and adjusting birefringence. If the molecular weight is too small, the pressure-sensitive adhesive tends to volatilize and the effect of the invention is difficult to obtain. Tend to be.

  The monofunctional aromatic compound (B) preferably has a flash point of 120 ° C. or higher, particularly preferably 145 to 500 ° C., more preferably 150 to 400 ° C., particularly preferably 160 to 300 ° C. is there. If the flash point is too high, the birefringence adjusting ability tends to decrease due to an increase in molecular weight. If the flash point is too small, volatility increases, and the adhesive is likely to volatilize when dried, making it difficult to obtain the effects of the invention. Tend.

  Examples of the monofunctional aromatic compound (B) satisfying such a flash point include phenyl diethylene glycol acrylate (flash point: 165 ° C.), ethoxylated orthophenylphenol acrylate (flash point: 170-199 ° C.), and the like. [<Reference value>, phenoxyethyl acrylate (flash point: 139 to 141 ° C.), benzyl acrylate (flash point: 107 ° C.)]

  Further, as the monofunctional aromatic compound (B), when 1 g of the monofunctional aromatic compound (B) and 10 g of ethyl acetate are mixed and then dried under the condition of 105 ° C. × 5 min, the monofunctional aromatic compound (B) is used. What has the ratio of the remainder (weight) of a compound (B) being 95% or more is preferable.

  Examples of the monofunctional aromatic compound (B) that satisfies the residual ratio in the volatility test include phenyldiethylene glycol acrylate (residual ratio: 100%), ethoxylated orthophenylphenol acrylate (residual ratio: 100%). ). [<Reference value>, phenoxyethyl acrylate (residual ratio: 89.5%), benzyl acrylate (residual ratio: 67.8%), styrene (residual ratio: 0.5%)]

  The content of the monofunctional aromatic compound (B) is preferably 5 to 300 parts by weight, more preferably 8 to 100 parts by weight, particularly preferably 100 parts by weight of the acrylic resin (A). 12 to 60 parts by weight, particularly preferably 15 to 45 parts by weight. When the content of the monofunctional aromatic compound (B) is too large, both durability and light leakage resistance tend to decrease. When the content is too small, the refractive index becomes too low, and light leakage resistance tends to decrease. There is.

  In the present invention, the pressure-sensitive adhesive composition [I] containing the acrylic resin (A) and the monofunctional aromatic compound (B) as essential components contains active energy rays and / or heat (active energy ray irradiation and It is a pressure-sensitive adhesive that is cured by heating), and provides a pressure-sensitive adhesive having a refractive index of 1.475 to 1.575.

  The refractive index is required to be 1.475 to 1.575, preferably 1.478 to 1.550, particularly preferably 1.480 to 1.520, and particularly preferably. 1.480 to 1.500. If the refractive index is too low, birefringence compensation of the entire optical laminate tends to be insufficient, and if it is too high, the refractive index difference from the optical film becomes large, and interface reflection tends to occur.

  This refractive index is a value measured at 23 ° C. with NaD line using an “Abbe refractometer 1T” manufactured by Atago Co., Ltd.

  In the present invention, in order to achieve such physical properties, the type of acrylic resin (A) and monofunctional aromatic compound (B) is selected, or two or more ethylenically unsaturated groups described later are further contained. The refractive index can be achieved by using an ethylenically unsaturated compound (C), a polymerization initiator (D), and a crosslinking agent (E) in combination, or by selecting curing conditions.

When curing with the active energy ray and / or heat, the pressure-sensitive adhesive composition [I] further contains an ethylenically unsaturated compound (C) (hereinafter referred to as “multiple”) containing at least two ethylenically unsaturated groups. It may be abbreviated as “functional unsaturated compound (C)” in that the cohesive force of the entire pressure-sensitive adhesive layer can be adjusted, and it is preferable to contain a polymerization initiator (D). This is preferable in that the reaction during irradiation and / or heating can be stabilized.
In such curing, the monofunctional aromatic compound (B) and the polyfunctional unsaturated compound (C) are polymerized (polymerized) by active energy rays and / or heat and cured.

  In the present invention, as a method of curing the pressure-sensitive adhesive composition [I], in addition to the component (A) and the component (B) (the component (C) or the component (D) as required) Further, there may be mentioned a method in which a crosslinking agent (E) is contained, and the pressure-sensitive adhesive composition [I] is cured with active energy rays and / or heat and cured with a crosslinking agent. In addition, when using a crosslinking agent (E), it is preferable that acrylic resin (A) has a functional group, and hardening (crosslinking) is performed by this functional group and a crosslinking agent reacting.

  In the present invention, the above-described curing by active energy rays and / or heat (irradiation of active energy rays and / or heating) is preferable in that it can be cured by irradiation of active energy rays such as ultraviolet rays for a very short time. However, it is also preferable to use curing (crosslinking) with a cross-linking agent in combination, and the cross-linking density of the pressure-sensitive adhesive is increased, the cohesive force is increased, and a further superior durability can be obtained.

  Further, when the acrylic resin (A) is an unsaturated group-containing acrylic resin, the monofunctional aromatic compound (B) (and the polyfunctional unsaturated compound (C )) Not only polymerizing but also curing accompanying polymerization of unsaturated group-containing acrylic resin (A) and monofunctional aromatic compound (B) (and polyfunctional unsaturated compound (C)) Will occur.

  As the polyfunctional unsaturated compound (C), for example, an ethylenically unsaturated monomer containing two or more ethylenically unsaturated groups in one molecule, for example, a bifunctional monomer, a trifunctional or higher monomer, Urethane (meth) acrylate compounds, epoxy (meth) acrylate compounds, and polyester (meth) acrylate compounds can be used. Among these, it is preferable to use an ethylenically unsaturated monomer and a urethane (meth) acrylate-based compound from the viewpoint of excellent curing rate and ultimate physical properties.

  The bifunctional monomer may be any monomer containing two ethylenically unsaturated groups. For example, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene Glycol di (meth) acrylate, propylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, butylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, ethylene Oxide modified bisphenol A type di (meth) acrylate, propylene oxide modified bisphenol A type di (meth) acrylate, 1,6-hexanediol di (meth) acrylate 1,6-hexanediol ethylene oxide modified di (meth) acrylate, glycerin di (meth) acrylate, pentaerythritol di (meth) acrylate, ethylene glycol diglycidyl ether di (meth) acrylate, diethylene glycol diglycidyl ether di ( (Meth) acrylate, diglycidyl phthalate di (meth) acrylate, hydroxypivalic acid-modified neopentyl glycol di (meth) acrylate, isocyanuric acid ethylene oxide-modified diacrylate, 2- (meth) acryloyloxyethyl acid phosphate diester It is done.

  The tri- or higher functional monomer may be any monomer containing three or more ethylenically unsaturated groups. For example, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) ) Acrylate, dipentaerythritol tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, tri (meth) acryloyloxyethoxytrimethylolpropane, Glycerin polyglycidyl ether poly (meth) acrylate, isocyanuric acid ethylene oxide modified tri (meth) acrylate, ethylene oxide modified dipentaerythritol (Meth) acrylate, ethylene oxide modified dipentaerythritol hexa (meth) acrylate, ethylene oxide modified pentaerythritol tri (meth) acrylate, ethylene oxide modified pentaerythritol tetra (meth) acrylate, succinic acid modified pentaerythritol tri (meth) acrylate Etc.

  The urethane (meth) acrylate compound is a (meth) acrylate compound having a urethane bond in the molecule, a (meth) acrylic compound containing a hydroxyl group and a polyvalent isocyanate compound (if necessary, a polyol What is necessary is just to use what is obtained by making it react by a well-known general method, and what is necessary is just to use the thing of 300-4000 normally as the weight average molecular weight.

  The content of the polyfunctional unsaturated compound (C) is desirably 0.01 to 30 parts by weight, preferably 0.5 to 10 parts by weight, with respect to 100 parts by weight of the acrylic resin (A). More preferably, it is 1 to 5 parts by weight. When the content of the polyfunctional unsaturated compound (C) is too large, both durability and light leakage resistance tend to decrease, and when it is too small, the light leakage resistance tends to be insufficient.

  In the present invention, the monofunctional aromatic compound (B) and the above-described monofunctional aromatic compound (B) can be appropriately adjusted to have a proper crosslinking density, to properly adjust the tack feeling, and to balance durability. The content ratio (mol%) of the monofunctional aromatic compound (B) with respect to the total amount of the polyfunctional unsaturated compound (C) is preferably greater than 50 mol%, particularly preferably greater than 50 mol% and less than 100 mol%, More preferably, it is 55-99 mol%, Most preferably, it is 60-98 mol%.

  When the content ratio of the monofunctional aromatic compound (B) with respect to the total amount of the monofunctional aromatic compound (B) and the polyfunctional unsaturated compound (C) is too small, the amount relative to the monofunctional aromatic compound (B) Since the content of the polyfunctional unsaturated compound (C) is increased, the crosslinking density tends to be too high and the tackiness tends to be lacking. In addition, when the content ratio of the monofunctional aromatic compound (B) with respect to the total amount of the monofunctional aromatic compound (B) and the polyfunctional unsaturated compound (C) is too large, the monofunctional aromatic compound (B ), The content of the polyfunctional unsaturated compound (C) decreases, so that the crosslinking density does not increase so much and the durability tends to be poor.

  As the polymerization initiator (D), for example, various polymerization initiators such as a photopolymerization initiator (d1) and a thermal polymerization initiator (d2) can be used. It is preferable to use d1) in that it can be cured by irradiation with active energy rays such as ultraviolet rays for a very short time.

  Moreover, when using the said photoinitiator (d1), adhesive composition [I] is hardened by active energy ray irradiation, and when using a thermal polymerization initiator (d2), adhesive composition [ I] is cured, but it is also preferable to use both together if necessary.

  Examples of the photopolymerization initiator (d1) include diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyldimethyl ketal, 4- (2-hydroxyethoxy) phenyl- (2 -Hydroxy-2-propyl) ketone, 1-hydroxycyclohexyl phenylketone, 2-methyl-2-morpholino (4-thiomethylphenyl) propan-1-one, 2-benzyl-2-dimethylamino-1- (4- Acetophenones such as morpholinophenyl) butanone and 2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl] propanone oligomer; benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl Ben such as ether Ins; benzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone, 4-benzoyl-4'-methyl-diphenyl sulfide, 3,3 ', 4,4'-tetra (t-butylperoxycarbonyl) benzophenone, 2,4,6-trimethylbenzophenone, 4-benzoyl-N, N-dimethyl-N- [2- (1-oxo-2-propenyloxy) ethyl] benzenemethananium bromide, (4-benzoylbenzyl) trimethylammonium Benzophenones such as chloride; 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone, 1-chloro-4-propoxythioxanthone, 2- (3-dimethylamino-2-hydroxy -3 Thioxanthones such as 4-dimethyl-9H-thioxanthone-9-one mesochloride; 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethyl- And acyl phosphine oxides such as pentylphosphine oxide and bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide; In addition, as for these photoinitiators (d1), only 1 type may be used independently and 2 or more types may be used together.

  These auxiliary agents include triethanolamine, triisopropanolamine, 4,4′-dimethylaminobenzophenone (Michler ketone), 4,4′-diethylaminobenzophenone, 2-dimethylaminoethylbenzoic acid, 4-dimethylaminobenzoic acid. Ethyl, 4-dimethylaminobenzoic acid (n-butoxy) ethyl, isoamyl 4-dimethylaminobenzoate, 2-ethylhexyl 4-dimethylaminobenzoate, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone Etc. can be used in combination.

  Among these, benzyl dimethyl ketal, 1-hydroxycyclohexyl phenyl ketone, benzoyl isopropyl ether, 4- (2-hydroxyethoxy) -phenyl (2-hydroxy-2-propyl) ketone, 2-hydroxy-2-methyl-1- It is preferable to use phenylpropan-1-one.

  Examples of the thermal polymerization initiator (d2) include methyl ethyl ketone peroxide, cyclohexanone peroxide, methylcyclohexanone peroxide, methyl acetoacetate peroxide, acetyl acetate peroxide, 1,1-bis (t-hexyl peroxide). ) -3,3,5-trimethylcyclohexane, 1,1-bis (t-hexylperoxy) -cyclohexane, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, 1, 1-bis (t-butylperoxy) -2-methylcyclohexane, 1,1-bis (t-butylperoxy) -cyclohexane, 1,1-bis (t-butylperoxy) cyclododecane, 1,1- Bis (t-butylperoxy) butane, 2,2-bis (4 -Di-t-butylperoxycyclohexyl) propane, p-menthane hydroperoxide, diisopropylbenzene hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, cumene hydroperoxide, t-hexyl hydroper Oxide, t-butyl hydroperoxide, α, α′-bis (t-butylperoxy) diisopropylbenzene, dicumyl peroxide, 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane, t-Butyl cumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-bis (t-butylperoxy) hexyne-3, isobutyryl peroxide, 3,5,5-trimethylhexa Noyl peroxide, octanoyl per Oxide, lauroyl peroxide, stearoyl peroxide, succinic acid peroxide, m-toluoyl benzoyl peroxide, benzoyl peroxide, di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, bis (4-t-butyl) (Cyclohexyl) peroxydicarbonate, di-2-ethoxyethyl peroxydicarbonate, di-2-ethoxyhexyl peroxydicarbonate, di-3-methoxybutyl peroxydicarbonate, di-s-butyl peroxydicarbonate, Di (3-methyl-3-methoxybutyl) peroxydicarbonate, α, α'-bis (neodecanoylperoxy) diisopropylbenzene, cumylperoxyneodecanoate, 1,1,3,3-te Lamethylbutyl peroxyneodecanoate, 1-cyclohexyl-1-methylethylperoxyneodecanoate, t-hexylperoxyneodecanoate, t-butylperoxyneodecanoate, t-hexylperoxy Pivalate, t-butylperoxypivalate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, 2,5-dimethyl-2,5-bis (2-ethylhexanoylper) Oxy) hexanoate, 1-cyclohexyl-1-methylethylperoxy-2-ethylhexanoate, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t- Hexyl peroxyisopropyl monocarbonate, t-butyl peroxyisobutyrate t-butyl peroxymalate, t-butyl peroxy-3,5,5-trimethylhexanoate, t-butyl peroxylaurate, t-butyl peroxyisopropyl monocarbonate, t-butyl peroxy-2 -Ethylhexyl monocarbonate, t-butyl peroxyacetate, t-butyl peroxy-m-toluylbenzoate, t-butyl peroxybenzoate, bis (t-butylperoxy) isophthalate, 2,5-dimethyl-2,5 -Bis (m-toluylperoxy) hexane, t-hexylperoxybenzoate, 2,5-dimethyl-2,5-bis (benzoylperoxy) hexane, t-butylperoxyallyl monocarbonate, t-butyltrimethylsilylper Oxide, 3,3 ', 4,4'-tetra Organic peroxide initiators such as (t-butylperoxycarbonyl) benzophenone and 2,3-dimethyl-2,3-diphenylbutane; 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile, 1- [(1-cyano-1-methylethyl) azo] formamide, 1,1′-azobis (cyclohexane-1-carbonitrile), 2,2′-azobis (2-methylbutyronitrile), 2,2′- Azobisisobutyronitrile, 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (2-methylpropionamidine) dihydrochloride, 2,2'-azobis (2-methyl- N-phenylpropionamidine) dihydrochloride, 2,2'-azobis [N- (4-chlorophenyl) -2-methylpropionamidine] Hydride chloride, 2,2'-azobis [N- (4-hydrophenyl) -2-methylpropionamidine] dihydrochloride, 2,2'-azobis [2-methyl-N- (phenylmethyl) propionamidine] dihydrochloride 2,2'-azobis [2-methyl-N- (2-propenyl) propionamidine] dihydrochloride, 2,2'-azobis [N- (2-hydroxyethyl) -2-methylpropionamidine] dihydrochloride, 2,2'-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride, 2,2'-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride, 2,2'-azobis [2- (4,5,6,7-tetrahydro-1H-1,3-diazepin-2-yl) Lopan] dihydrochloride, 2,2'-azobis [2- (3,4,5,6-tetrahydropyrimidin-2-yl) propane] dihydrochloride, 2,2'-azobis [2- (5-hydroxy-3 , 4,5,6-tetrahydropyrimidin-2-yl) propane] dihydrochloride, 2,2'-azobis [2- [1- (2-hydroxyethyl) -2-imidazolin-2-yl] propane] dihydrochloride 2,2'-azobis [2- (2-imidazolin-2-yl) propane], 2,2'-azobis [2-methyl-N- [1,1-bis (hydroxymethyl) -2-hydroxyethyl] ] Propionamide], 2,2'-azobis [2-methyl-N- [1,1-bis (hydroxymethyl) ethyl] propionamide], 2,2'-azobis [2-me Til-N- (2-hydroxyethyl) propionamide], 2,2'-azobis (2-methylpropionamide), 2,2'-azobis (2,4,4-trimethylpentane), 2,2'- Azobis (2-methylpropane), dimethyl-2,2-azobis (2-methylpropionate), 4,4'-azobis (4-cyanopentanoic acid), 2,2'-azobis [2- (hydroxymethyl ) Propionitrile] and the like; and the like. In addition, only 1 type may be used independently for these thermal polymerization initiators, and 2 or more types may be used together.

  About content of the said polymerization initiator (D), 0.01-10 weight part with respect to 100 weight part of said acrylic resin (A), Especially 0.1-7 weight part, Furthermore, 0.3 It is preferably ~ 3 parts by weight. If the content of the polymerization initiator (D) is too small, the curability tends to be poor and the physical properties tend to become unstable, and if it is too much, no further effect can be obtained. Moreover, it is preferable that it is 0.01-100 weight part with respect to a total of 100 weight part of a monofunctional aromatic compound (B) and a polyfunctional unsaturated compound (C), More preferably, it is 0.1-100 weight part. 20 parts by weight, particularly preferably 1 to 12 parts by weight.

  In the active energy ray irradiation, far ultraviolet rays, ultraviolet rays, near ultraviolet rays, infrared rays and other electromagnetic waves, X rays, γ rays and other electromagnetic waves, as well as electron beams, proton rays, neutron rays, etc. can be used. Curing by ultraviolet irradiation is advantageous from the standpoint of availability of the device and price. In addition, when performing electron beam irradiation, it can harden | cure without using the said photoinitiator (d1).

As a light source for the ultraviolet irradiation, a high pressure mercury lamp, an electrodeless lamp, an ultrahigh pressure mercury lamp, a carbon arc lamp, a xenon lamp, a metal halide lamp, a chemical lamp, a black light, or the like is used. In the case of the high-pressure mercury lamp, for example, it is performed under conditions of 5 to 3000 mJ / cm ² , preferably 10 to 1000 mJ / cm ² . Moreover, in the case of the said electrodeless lamp, it is performed on the conditions of 2-1500 mJ / cm < ² >, for example, Preferably 5-500 mJ / cm < ² >. The irradiation time varies depending on the type of the light source, the distance between the light source and the coating surface, the coating thickness, and other conditions, but it may be usually from several seconds to several tens of seconds, and in some cases, a fraction of a second. On the other hand, in the case of the electron beam irradiation, for example, an electron beam having an energy in the range of 50 to 1000 Kev is used, and the irradiation amount is preferably 2 to 50 Mrad.

  Moreover, when using a thermal-polymerization initiator (d2) as said polymerization initiator (D), a polymerization reaction is started and advanced by heating. The treatment temperature and treatment time at the time of curing by heating vary depending on the type of the thermal polymerization initiator (d2) to be used, and are usually calculated from the half-life of the initiator, but the treatment temperature is usually The temperature is preferably 70 ° C to 170 ° C, and the treatment time is usually preferably 0.2 to 20 minutes, and particularly preferably 0.5 to 10 minutes.

  Examples of the crosslinking agent (E) include isocyanate crosslinking agents, epoxy crosslinking agents, aziridine crosslinking agents, melamine crosslinking agents, aldehyde crosslinking agents, amine crosslinking agents, and metal chelate crosslinking agents. Among these, an isocyanate-based crosslinking agent is preferably used from the viewpoint of improving the adhesion to the substrate and the reactivity with the base polymer.

  Examples of the isocyanate crosslinking agent include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, hydrogenated tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, and hexamethylene. Diisocyanate, diphenylmethane-4,4-diisocyanate, isophorone diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, tetramethylxylylene diisocyanate, 1,5-naphthalene diisocyanate, triphenylmethane triisocyanate, and polyisocyanate compounds thereof And adducts of a polyol compound such as trimethylolpropane, and burettes and isocyanurates of these polyisocyanate compounds.

  Examples of the epoxy crosslinking agent include bisphenol A / epichlorohydrin type epoxy resin, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, and 1,6-hexanediol diglycidyl ether. , Trimethylolpropane triglycidyl ether, sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl erythritol, diglycerol polyglycidyl ether and the like.

  Examples of the aziridine-based crosslinking agent include tetramethylolmethane-tri-β-aziridinylpropionate, trimethylolpropane-tri-β-aziridinylpropionate, N, N′-diphenylmethane-4,4. '-Bis (1-aziridinecarboxamide), N, N'-hexamethylene-1,6-bis (1-aziridinecarboxamide) and the like can be mentioned.

  Examples of the melamine-based crosslinking agent include hexamethoxymethyl melamine, hexaethoxymethyl melamine, hexapropoxymethyl melamine, hexaptoxymethyl melamine, hexapentyloxymethyl melamine, hexahexyloxymethyl melamine, and melamine resin. .

  Examples of the aldehyde-based crosslinking agent include glyoxal, malondialdehyde, succindialdehyde, maleindialdehyde, glutardialdehyde, formaldehyde, acetaldehyde, benzaldehyde and the like.

  Examples of the amine-based crosslinking agent include hexamethylenediamine, triethyldiamine, polyethyleneimine, hexamethylenetetraamine, diethylenetriamine, triethyltetraamine, isophoronediamine, amino resin, polyamide, and the like.

  Examples of the metal chelate-based crosslinking agent include acetylacetone and acetoacetyl ester coordination compounds of polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, panadium, chromium, and zirconium. Can be mentioned.

  Moreover, these crosslinking agents (E) may be used independently and may use 2 or more types together.

  Usually, the content of the crosslinking agent (E) is preferably 0.01 to 10 parts by weight, more preferably 0.05 to 5 parts by weight with respect to 100 parts by weight of the acrylic resin (A). Particularly preferred is 0.1 to 2 parts by weight. When the amount of the crosslinking agent (E) is too small, there is a tendency that the cohesive force is insufficient and sufficient durability cannot be obtained. When the amount is too large, the flexibility and the adhesive strength are lowered, the durability is lowered, and peeling is caused. Since it tends to occur, the use as an optical member tends to be difficult.

  In the present invention, it is preferable to further contain a silane coupling agent (F) as a constituent component of the pressure-sensitive adhesive composition [I] from the viewpoint of improving the adhesion to the optical member.

  Examples of the silane coupling agent (F) include an epoxy group-containing silane coupling agent, a (meth) acryloyl group-containing silane coupling agent, a mercapto group-containing silane coupling agent, a hydroxyl group-containing silane coupling agent, and a carboxyl group-containing. Examples thereof include a silane coupling agent, an amino group-containing silane coupling agent, an amide group-containing silane coupling agent, and an isocyanate group-containing silane coupling agent. These may be used alone or in combination of two or more.

  Specific examples of the epoxy group-containing silane coupling agent include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, and γ-glycol. Sidoxypropylmethyldimethoxysilane, methyltri (glycidyl) silane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, and the like can be mentioned. γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, and β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane.

  Specific examples of the mercapto group-containing silane coupling agent include, for example, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, γ-mercaptopropyldimethoxymethylsilane, oligomer type mercapto silane coupling agent ( For example, trade name, “X-41-1805” manufactured by Shin-Etsu Chemical Co., Ltd.

  Among these, epoxy group-containing silane coupling agents and mercapto group-containing silane coupling agents are preferably used, particularly preferably epoxy group-containing silane coupling agents, and more preferably oligomer-type mercapto-based silane coupling agents. is there.

  The content of the silane coupling agent (F) is usually 0.001 to 10 parts by weight, preferably 0.01 to 1 part by weight, particularly preferably 100 parts by weight of the acrylic resin (A). Is 0.03 to 0.8 parts by weight. If the content of the silane coupling agent (F) is too small, there is a tendency that the addition effect cannot be obtained. If the content is too large, the compatibility with the acrylic resin (A) is lowered, and adhesive strength and cohesive strength are obtained. There is a tendency to disappear.

The pressure-sensitive adhesive composition [I] further includes an antistatic agent, other acrylic pressure-sensitive adhesives, other pressure-sensitive adhesives, urethane resin, rosin, rosin ester, and hydrogenated rosin as long as the effects of the present invention are not impaired. Tackifiers such as esters, phenol resins, aromatic modified terpene resins, aliphatic petroleum resins, alicyclic petroleum resins, styrene resins, xylene resins, colorants, fillers, anti-aging agents, UV absorbers Conventionally known additives such as functional dyes, and compounds that cause coloration or discoloration by irradiation with ultraviolet rays or radiation can be blended.
In addition to the above additives, a small amount of impurities contained in the raw materials for producing the constituent components of the pressure-sensitive adhesive composition [I] may be contained.

  Examples of the antistatic agent include cationic antistatic agents of quaternary ammonium salts such as imidazolium salts and tetraalkylammonium sulfonates, aliphatic sulfonates, higher alcohol sulfates, and higher alcohol alkylene oxide additions. Anion-type antistatic agents such as sulfuric acid ester salts, higher alcohol phosphate salts, higher alcohol alcohol alkylene oxide adduct phosphate salts, potassium bis (fluorosulfonyl) imide, lithium bis (trifluorosulfonyl) imide and lithium chloride And alkali metal salts such as alkaline earth metal salts, higher alcohol alkylene oxide adducts, and polyalkylene glycol fatty acid esters.

  Thus, in the present invention, a pressure-sensitive adhesive obtained by curing the pressure-sensitive adhesive composition [I] is obtained.

  And the optical member with an adhesive layer can be obtained by carrying out the lamination formation of the adhesive layer which consists of the said adhesive on an optical member (optical laminated body).

  It is preferable that the optical member with the pressure-sensitive adhesive layer is further provided with a release sheet on the surface opposite to the optical member surface of the pressure-sensitive adhesive layer.

  As the method for producing the optical member with the pressure-sensitive adhesive layer, when the pressure-sensitive adhesive composition [I] is cured by at least one of active energy ray irradiation and heating, [1] the pressure-sensitive adhesive composition on the optical member After applying and drying the product [I], a release sheet is bonded, and the treatment is performed by at least one of active energy ray irradiation and heating, [2] the pressure-sensitive adhesive composition [I] on the release sheet After applying and drying, a method of pasting the optical member and performing treatment by at least one of active energy ray irradiation and heating, [3] applying and drying the adhesive composition [I] on the optical member, A method of pasting a release sheet after performing treatment by at least one of irradiation with active energy rays and heating, [4] coating and drying the adhesive composition [I] on the release sheet, and further active energy rays After performing the morphism and at least one by treatment with heating, and a method of bonding an optical member. Among these, the case of performing active energy ray irradiation by the method [2] is preferable from the viewpoint of not damaging the substrate, workability and stable production.

  In addition, when a crosslinking agent is used for the pressure-sensitive adhesive composition [I] (when curing with a crosslinking agent (crosslinking) is also used), an aging treatment is performed after the optical member with the pressure-sensitive adhesive layer is produced using the above method. It is preferable to apply. Such aging treatment is performed to balance the physical properties of the adhesive. As aging conditions, the temperature is usually from room temperature to 70 ° C., and the time is usually from 1 day to 30 days. What is necessary is just to carry out on conditions, such as 1 day-20 days at 23 degreeC, 3-10 days at 23 degreeC, 1 day-7 days at 40 degreeC.

  In applying the pressure-sensitive adhesive composition [I], it is preferable to dilute the pressure-sensitive adhesive composition [I] in a solvent, and the dilution concentration is preferably 5 to 95% by weight, particularly preferably 10%. -80% by weight, more preferably 15-60% by weight, particularly preferably 20-40% by weight. The solvent is not particularly limited as long as it can dissolve the pressure-sensitive adhesive composition [I]. Examples thereof include ester solvents such as methyl acetate, ethyl acetate, methyl acetoacetate, and ethyl acetoacetate, acetone Further, ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone, aromatic solvents such as toluene and xylene, and alcohol solvents such as methanol, ethanol and propyl alcohol can be used. Among these, ethyl acetate and methyl ethyl ketone are preferably used from the viewpoints of solubility, drying property, price, and the like.

  In addition, the application of the pressure-sensitive adhesive composition [I] is performed by a conventional method such as roll coating, die coating, gravure coating, comma coating, or screen printing.

  About the gel fraction of the adhesive layer manufactured by the said method, it is preferable that it is 30 to 90% from the point of durability performance and light leakage prevention performance, and 60 to 85% is especially preferable. If the gel fraction is too low, durability tends to be insufficient due to insufficient cohesive force. Moreover, when the gel fraction is too high, tackiness is insufficient due to an increase in cohesive force, and the tackiness of the pressure-sensitive adhesive on the adherend tends to decrease.

  The pressure-sensitive adhesive layer produced by the above method preferably has a good tack feeling when touched with a finger, because it has good wettability when actually attached to an adherend, and therefore tends to improve workability. .

  In adjusting the gel fraction of the optical member pressure-sensitive adhesive to the above range, for example, adjusting the irradiation amount and irradiation intensity of the active energy ray, adjusting the type and amount of the unsaturated group-containing compound, This is achieved by adjusting the type of polymerization initiator and the combination ratio thereof, adjusting the blending amount of the polymerization initiator, adjusting the type and amount of the crosslinking agent, and the like. Moreover, since the gel fraction changes by each interaction, the irradiation amount and irradiation intensity | strength of said active energy ray, the composition ratio of a polymerization initiator, and addition amount need to balance each.

  The gel fraction is a measure of the degree of crosslinking (curing degree), and is calculated, for example, by the following method. That is, a pressure-sensitive adhesive sheet (not provided with a separator) in which a pressure-sensitive adhesive layer is formed on a polymer sheet (for example, polyethylene terephthalate film or the like) as a base material is wrapped with a 200-mesh SUS wire mesh, and 23 in toluene. The weight percentage of the insoluble pressure-sensitive adhesive component immersed in the wire mesh at 24 ° C. for 24 hours is defined as the gel fraction. However, the weight of the substrate is subtracted.

  Moreover, the thickness of the pressure-sensitive adhesive layer in the obtained optical member with the pressure-sensitive adhesive layer is not particularly limited, but is preferably 5 to 300 μm, particularly preferably 10 to 50 μm, and more preferably 12 to 30 μm. If the thickness of the pressure-sensitive adhesive layer is too thin, the adhesive physical properties tend to be difficult to stabilize, and if it is too thick, the thickness of the entire optical member tends to increase too much.

  The optical member with the pressure-sensitive adhesive layer of the present invention has a release sheet directly or after the release sheet is peeled off, and then the surface of the pressure-sensitive adhesive layer is bonded to a glass substrate and used for a liquid crystal display panel, for example. .

  The initial adhesive strength of the pressure-sensitive adhesive layer of the present invention is appropriately determined according to the material of the adherend. For example, when sticking on a glass substrate, it preferably has an adhesive strength of 0.2 N / 25 mm to 20 N / 25 mm, and more preferably 0.5 N / 25 mm to 10 N / 25 mm.

  The initial adhesive strength is calculated as follows. About a polarizing plate with an adhesive layer, it cuts into width 25mm width, peels off a release film, presses the adhesive layer side to a non-alkali glass board (Corning company make, "Corning XG"), A glass plate is bonded. Then, after autoclaving (50 ° C., 0.5 MPa, 20 minutes), 23 ° C. and 50% R.D. H. Then, after leaving for 24 hours, perform a 180 ° C. peel test.

  The optical member in the present invention is not particularly limited, and an optical film suitably used for an image display device such as a liquid crystal display device, an organic EL display device, or a PDP, such as a polarizing plate, a retardation plate, or an elliptical polarizing plate. , Optical compensation films, brightness enhancement films, and those in which these are laminated. Among them, a polarizing plate is particularly effective in the present invention.

  The polarizing plate used in the present invention is usually a laminate of a cellulose triacetate film as a protective film on both sides of a polarizing film. The polarizing film has an average degree of polymerization of 1,500 to 10,000, A uniaxially stretched film dyed with an aqueous solution of iodine-potassium iodide or a dichroic dye using a film made of a polyvinyl alcohol resin having a degree of conversion of 85 to 100 mol% as a raw film (usually 2 to 10 times, preferably Is a stretching ratio of about 3 to 7 times.

  The polyvinyl alcohol resin is usually produced by saponifying polyvinyl acetate obtained by polymerizing vinyl acetate, but a small amount of unsaturated carboxylic acid (including salt, ester, amide, nitrile, etc.), olefins, vinyl ether And a component copolymerizable with vinyl acetate, such as an unsaturated sulfonate. Moreover, what is called polyvinyl acetal resin and polyvinyl alcohol derivatives, such as polybutyral resin and polyvinyl formal resin, which are obtained by reacting polyvinyl alcohol with an aldehyde in the presence of an acid can be mentioned.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist. In the examples, “parts” and “%” mean weight basis.

First, various acrylic resins were prepared as follows. In addition, regarding the measurement of the weight average molecular weight of acrylic resin, dispersion degree, and glass transition temperature, it measured according to the above-mentioned method.
In addition, regarding the measurement of a viscosity, it measured according to the 4.5.3 rotational viscometer method of JISK5400 (1990).

[Preparation of Acrylic Resin (A)] (See Table 1)
[Acrylic resin (A-1)]
In a 4-neck round bottom flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet and a thermometer, 95 parts of butyl acrylate (a1), 5 parts of acrylic acid (a2), 120 parts of ethyl acetate, 45 parts of acetone After starting the reflux with heating, 0.03 part of azobisisobutyronitrile (AIBN) was added as a polymerization initiator, reacted at the reflux temperature of ethyl acetate for 3 hours, diluted with ethyl acetate, and then the acrylic resin (A -1) A solution (weight average molecular weight (Mw) 1,500,000, dispersity (Mw / Mn) 3.4, glass transition temperature -51 ° C., solid content 23%, viscosity 8000 mPa · s (25 ° C.)) was obtained.

[Acrylic resin (A-2)]
In a four-neck round bottom flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet and a thermometer, 96.8 parts of butyl acrylate (a1), 3 parts of acrylic acid (a2), 2-hydroxyethyl acrylate ( a2) 0.2 parts, 100 parts of ethyl acetate and 45 parts of acetone were added, and after heating to reflux, 0.03 part of azobisisobutyronitrile (AIBN) was added as a polymerization initiator, and the mixture was refluxed at ethyl acetate for 3 hours. After the reaction, it was diluted with ethyl acetate, and the acrylic resin (A-2) solution (weight average molecular weight (Mw) 1.8 million, dispersity (Mw / Mn) 3.2, glass transition temperature -53 ° C., solid content 18 %, Viscosity 8,000 mPa · s (25 ° C.)).

[Acrylic resin (A-3)]
In a four-neck round bottom flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet and a thermometer, 61.3 parts of butyl acrylate (a1), 35 parts of benzyl acrylate, 2-hydroxyethyl acrylate (a2) 3 0.5, 0.2 part (a2) of acrylic acid, 150 parts of ethyl acetate and 45 parts of acetone were added, and after heating to reflux, 0.03 part of azobisisobutyronitrile (AIBN) was added as a polymerization initiator, and acetic acid was added. After reacting at ethyl reflux temperature for 3 hours, diluted with ethyl acetate to obtain an acrylic resin (A-3) solution (weight average molecular weight (Mw) 1.5 million, dispersity (Mw / Mn) 3.5, glass transition temperature − 36 ° C., solid content 20%, viscosity 8,000 mPa · s (25 ° C.)).

(Note) BA: Butyl acrylate
HEA: 2-hydroxyethyl acrylate AAc: acrylic acid BzA: benzyl acrylate

[Monofunctional aromatic compound (B)]
The following were prepared as the monofunctional aromatic compound (B-1).
Phenyl diethylene glycol acrylate (manufactured by Kyoeisha, trade name “Light acrylate P2HA”: molecular weight 236.3)

[Polyfunctional unsaturated compound (C)]
The following were prepared as the polyfunctional unsaturated compound (C-1).
・ Trimethylolpropane triacrylate (molecular weight 296.3)

[Polymerization initiator (D)]
The following were prepared as the photopolymerization initiator (D-1).
A mixture of benzophenone and 1-hydroxycyclohexyl phenyl ketone in a mass ratio of 1: 1 (Ciba Specialty Chemicals, “Irgacure 500”)

[Crosslinking agent (E)]
The following were prepared as a crosslinking agent (E-1).
・ 55% ethyl acetate solution of trimethylolpropane tolylene diisocyanate adduct (manufactured by Nippon Polyurethane Co., Ltd., “Coronate L-55E”)

[Silane coupling agent (F)]
The following were prepared as the silane compound (F-1).
・ Mercapto silane coupling agent (oligomer type) (manufactured by Shin-Etsu Chemical Co., Ltd., “X-41-1805”)

[Examples 1-3, Comparative Examples 1-3]
Prepare the pressure-sensitive adhesive composition to be a pressure-sensitive adhesive forming material for optical members by blending the components prepared and prepared as described above in the proportions shown in Table 2 below, and dilute them with ethyl acetate. (Viscosity [500 to 10000 mPa · s (25 ° C.)]) to prepare an adhesive composition solution.

Then, the pressure-sensitive adhesive composition solution obtained above is applied to a polyester release sheet so that the thickness after drying is 25 μm, and dried at 90 ° C. for 3 minutes to form a pressure-sensitive adhesive composition layer. It was.
In Examples 1 to 3 and Comparative Example 1, the obtained pressure-sensitive adhesive composition layer was transferred onto a polyethylene terephthalate (PET) film (thickness 38 μm), and an electrodeless lamp [LH6UV lamp H bulb] manufactured by Fusion. UV irradiation was performed at a peak illuminance of 600 mW / cm ² and an integrated exposure amount of 240 mJ / cm ² (120 mJ / cm ² × 2 passes), 23 ° C. × 50% R.D. H. The film was aged for 10 days under the above conditions to obtain a PET film with an adhesive layer.
In Comparative Examples 2 and 3, the obtained pressure-sensitive adhesive composition layer was transferred onto a polyethylene terephthalate (PET) film (thickness 38 μm), and 23 ° C. × 50% R.D. H. The film was aged for 10 days under the above conditions to obtain a PET film with an adhesive layer.

  Using the PET film with the pressure-sensitive adhesive layer thus obtained, handleability, odor resistance, and gel fraction were measured and evaluated according to the following methods. These results are also shown in Table 2 below.

[Handling]
After the obtained PET film with the pressure-sensitive adhesive layer was cut to 25 × 40 mm, the release sheet was peeled off, and the pressure-sensitive adhesive layer was touched with a finger, and the tackiness was evaluated according to the following criteria.
○: Good tack feeling ×: Not much tack feeling

[Odor resistance]
The obtained PET film with an adhesive layer was 23 ° C. × 50% R.D. H. And then left for 3 hours under temperature and humidity control conditions, the release sheet was peeled off, the smell was sniffed, and evaluated according to the following criteria.
○: Do not feel monomer odor ×: Feel monomer odor

[Gel fraction]
After the obtained PET film with the pressure-sensitive adhesive layer is cut into 40 × 40 mm, the release sheet is peeled off and the pressure-sensitive adhesive layer side is bonded to a 50 × 100 mm SUS mesh sheet (200 mesh), and then the SUS mesh sheet. The sample was wrapped from the center with respect to the longitudinal direction, and the sample was wrapped. Then, the gel fraction was measured by weight change when immersed in a sealed container containing 250 g of toluene.

[Haze]
-Manufacture of sample for haze measurement The pressure-sensitive adhesive composition solution was applied to a polyester-based light release release sheet so that the thickness after drying was 25 μm, and dried at 90 ° C. for 3 minutes. Formed.
In Examples 1 to 3 and Comparative Example 1, the obtained pressure-sensitive adhesive composition layer side was bonded with a polyester-based heavy release release sheet, and the peak illuminance was measured with an electrodeless lamp [H bulb of LH6UV lamp] manufactured by Fusion. 600 mW / cm ² , integrated exposure: 240 mJ / cm ² , ultraviolet irradiation (120 mJ / cm ² × 2 passes), then 23 ° C. × 50% R.D. H. A base material-less pressure-sensitive adhesive layer was obtained by aging for 10 days under the above conditions.
In Comparative Examples 2 and 3, the obtained pressure-sensitive adhesive composition layer side was bonded with a polyester-based heavy release release sheet, and then 23 ° C. × 50% R.D. H. A base material-less pressure-sensitive adhesive layer was obtained by aging for 10 days under the above conditions.
The obtained substrate-less pressure-sensitive adhesive layer was cut out to 3 cm × 4 cm, the light release release sheet was peeled off, and the pressure-sensitive adhesive layer side was pressed against an alkali-free glass plate (Corning Corp., Eagle XG), and further The heavy release release sheet was peeled off to obtain a sample for haze measurement.
-Measurement of haze value The diffuse transmittance and the total light transmittance of the sample for haze measurement were measured using HAZE MATER NDH2000 (manufactured by Nippon Denshoku Industries Co., Ltd.). This machine complies with JIS K7361-1.
The values of the obtained diffuse transmittance and total light transmittance were substituted into the following formula to calculate haze.
Haze value (%) = (diffuse transmittance / total light transmittance) × 100

[Refractive index]
Using the above sample for haze measurement, "Abbe refractometer 1T" manufactured by Atago Co., Ltd.
The value at 23 ° C. was measured with the NaD line.

Next, the said adhesive composition solution was apply | coated to the polyester-type release sheet so that the thickness after drying might be set to 25 micrometers, and it dried at 90 degreeC for 3 minute (s), and formed the adhesive composition layer.
In Examples 1 to 3 and Comparative Example 1, the obtained pressure-sensitive adhesive composition layer was transferred onto a polarizing plate (thickness 190 μm), and a peak illuminance of 600 mW was obtained with an electrodeless lamp [H bulb of LH6UV lamp] manufactured by Fusion. / Cm ² , integrated exposure: 240 mJ / cm ² and ultraviolet irradiation (120 mJ / cm ² × 2 passes), 23 ° C. × 50% R.D. H. The film was aged for 10 days under the above conditions to obtain a polarizing plate with an adhesive layer.
In Comparative Examples 2 and 3, the obtained pressure-sensitive adhesive composition layer was transferred onto a polarizing plate (thickness 190 μm), and 23 ° C. × 50% R.D. H. The film was aged for 10 days under the above conditions to obtain a polarizing plate with an adhesive layer.
In addition, “MLP38U” manufactured by Biei Imaging Co., Ltd. was used as the polarizing plate, and the polarizing plate was cut at 45 ° C. with respect to the stretching axis.

  Using the polarizing plate with the pressure-sensitive adhesive layer thus obtained, durability (wet heat resistance test, heat cycle test, heat resistance test) and adhesive strength were measured and evaluated according to the following methods. These results are also shown in Table 3 below.

[durability]
The release sheet of the obtained polarizing plate with the pressure-sensitive adhesive layer was peeled off, and the pressure-sensitive adhesive layer side was pressed against a non-alkali glass plate (Corning Corp., Eagle XG) to bond the polarizing plate and the glass plate. After that, autoclave treatment (50 ° C., 0.5 MPa, 20 minutes) is performed, and then foaming and peeling are evaluated in the following durability tests (1) to (4) (moisture and heat resistance test, heat cycle test, heat resistance test). I did it. Furthermore, in the heat resistance test of (4) below, in addition to the evaluation of foaming and peeling, a sample for light leakage observation was prepared by bonding the same sample on both the front and back surfaces so that the polarizing plate became crossed Nicol. The light leakage phenomenon was also evaluated.
In addition, the used test piece size was punched into 20 cm × 15 cm.

[An endurance test]
(1) Moisture and heat resistance test 60 ° C., 90% R.D. H. Endurance test for 150 hours (2) Heat cycle test Endurance test for 75 cycles with the operation of leaving at -35 ° C for 60 minutes and then at 70 ° C for 60 minutes (3) Heat resistance test (A)
Durability test at 90 ° C for 150 hours (4) Heat resistance test (B)
80 ° C, 150 hours durability test and light leakage

[Evaluation criteria]
(Foam)
○: Foam is hardly seen △ ... Foam is slightly seen × ... Foam is seen a lot (peeling)
○ ・ ・ ・ Peeling of less than 0.5 mm or occurrence of floating marks less than 0.5 mm Δ ・ ・ ・ Peeling of 0.5 mm or more and less than 10 mm, or generation of lift marks of 0.5 mm or more and less than 10 mm × ・ ・ ・10 mm or more peeling or 10 mm or more of lift mark (light leakage)
◎ ・ ・ ・ There is almost no light leakage ○ ・ ・ ・ Slight leakage occurs △ ・ ・ ・ Slight leakage occurs × ・ ・ ・ Large light leakage occurs on 4 sides

[Adhesive force]
About the prepared polarizing plate with an adhesive layer, it cuts to width 25mm width, peels off a release film, presses the adhesive layer side to a non-alkali glass board (Corning company make, "Corning 1737"), and polarized light The plate and the glass plate were bonded together. Thereafter, autoclaving (50 ° C., 0.5 MPa, 20 minutes) was performed, and 23 ° C., 50% R.D. H. A 180 ° C. peel test was performed after leaving the sample for 24 hours. In the peelability, it is desired that the adhesive strength is small, and the target is 10 N / 25 mm or less after one day.

  The pressure-sensitive adhesives of the examples are excellent in balance at a very high level of durability, light leakage resistance, and adhesive strength when a polarizing plate and a glass plate are pasted. The comparative examples 1 to 4 did not satisfy the required performance in the following points, whereas the haze and odor resistance were excellent.

・ Although it has a low refractive index value, it is usually known by a technique for increasing the gel fraction of the pressure-sensitive adhesive layer using only the polyfunctional unsaturated compound (C) without blending the monofunctional aromatic compound (B). In Comparative Example 1 in which the refractive index was somewhat higher than that of the pressure-sensitive adhesive, the physical properties of the pressure-sensitive adhesive layer itself were inferior in handleability, and also inferior in light leakage resistance when the polarizing plate and the glass plate were attached.
・ Comparison with low refractive index value, not containing monofunctional unsaturated compound (B), polyfunctional unsaturated compound (C), polymerization initiator (D), and not cured by irradiation with active energy rays In Example 2, although the physical properties of the pressure-sensitive adhesive layer itself were excellent, the light leakage performance at the time of pasting the polarizing plate and the glass plate was inferior, and foaming occurred in the heat resistance test.
In Comparative Example 3, which uses an acrylic resin copolymerized with an aromatic monomer and has a high refractive index, an unpleasant monomer odor dependent on the aromatic monomer that has not been copolymerized is generated, and also due to the influence of the residual monomer In the heat resistance test, foaming slightly occurred.

  In the pressure-sensitive adhesive of the present invention, the pressure-sensitive adhesive layer after curing by active energy rays and / or heat is excellent in handleability (tack) and optical properties (haze), and even in a high temperature and high humidity environment, A liquid crystal display device that has excellent adhesion between an optical laminate, particularly an optical member such as a polarizing plate, and a glass substrate, does not cause foaming or peeling between the pressure-sensitive adhesive layer and the glass substrate, and does not cause color unevenness or light leakage. Obtainable. Therefore, it is particularly effective as a pressure-sensitive adhesive for optical members, and is very useful as a pressure-sensitive adhesive for obtaining an optical member with a pressure-sensitive adhesive layer and an image display device obtained by using them.

Claims (11)

  An adhesive obtained by curing an adhesive composition [I] containing an acrylic resin (A) and an aromatic compound (B) containing one ethylenically unsaturated group by active energy rays and / or heat And the refractive index of the pressure-sensitive adhesive layer made of the pressure-sensitive adhesive is 1.475 to 1.575.   The pressure-sensitive adhesive according to claim 1, wherein the aromatic compound (B) is a mono (meth) acrylate-based aromatic compound.   The pressure-sensitive adhesive according to claim 1 or 2, wherein the flash point of the aromatic compound (B) is 145 ° C or higher.   The pressure-sensitive adhesive according to any one of claims 1 to 3, wherein the aromatic compound (B) has a molecular weight of 200 to 10,000.   The pressure-sensitive adhesive composition according to any one of claims 1 to 4, wherein the pressure-sensitive adhesive composition [I] contains an ethylenically unsaturated compound (C) containing two or more ethylenically unsaturated compounds.   The pressure-sensitive adhesive composition [I] contains a polymerization initiator (D), and the pressure-sensitive adhesive according to any one of claims 1 to 5.   The pressure-sensitive adhesive composition [I] contains a crosslinking agent (E) and is crosslinked by a crosslinking agent.  A pressure-sensitive adhesive for optical members, comprising the pressure-sensitive adhesive according to claim 1.  The pressure-sensitive adhesive for optical members according to claim 8, wherein the optical member is a polarizing plate.   The optical member with an adhesive layer containing the laminated structure of the adhesive layer containing the adhesive for optical members of Claim 8 or 9, and an optical member.   An image display device using the optical member with an adhesive layer according to claim 10.