JP2003034781A - Pressure sensitive adhesive for optical member and optical member provided with the adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acrylic pressure sensitive adhesive for an optical member that relaxes stress caused by a dimensional change in a member such as a film for use in an optical device, especially the film having a large applied area and controls light leakage and irregular color, and to provide an optical member by the use of the pressure sensitive adhesive. SOLUTION: This pressure sensitive adhesive for the optical member comprises a polymer, in which (meth)acrylate is a main component, a crosslinking agent and optionally a silane coupling agent. A gel fraction of the pressure sensitive adhesive is 30-60%, Mw of a sol component of the adhesive determined by GPC is 10<5> -5×10<5> , molecular weight distribution is 40 or more, and a polymer component of molecular weight of 5×10<4> or less is 30-80% in the sol component. Furthermore, the optical member has a pressure sensitive adhesive layer composed of the pressure sensitive adhesive on one surface or both surfaces of a substrate such as a polarizing film, a phase difference film and an elliptically polarizing film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure-sensitive adhesive for an optical member, an optical member using the pressure-sensitive adhesive, and in particular, an optical member for forming a polarizing film with a pressure-sensitive adhesive layer attached to a liquid crystal cell of a liquid crystal display device. It relates to members.

[0002]

2. Description of the Related Art In a liquid crystal cell of a liquid crystal display device, a polarizing film or the like having a three-layer structure in which a triacetate protective film is sandwiched between both sides of a polyvinyl alcohol-based polarizer is generally used as an adhesive layer. Pasted through.

Liquid crystal display devices have been used as display devices for calculators, watches, televisions and various measuring instruments, and have been used under various conditions. Under such circumstances, for example, Japanese Patent Laid-Open No. 3-12471
The publication discloses that a polarizing plate having a pressure-sensitive adhesive layer having excellent durability can be obtained by increasing the degree of crosslinking of an acrylic polymer and setting the weight average molecular weight of an uncrosslinked polymer to 100,000 or more. Has been done.

However, increasing the molecular weight of the pressure-sensitive adhesive or increasing the degree of cross-linking so that the pressure-sensitive adhesive layer can withstand use under harsh conditions is to suppress the dimensional change of the polarizing film with the pressure-sensitive adhesive. However, the stress caused by the dimensional change of the polarizing film caused by heat or wet heat cannot be sufficiently absorbed and relaxed. As a result, the distribution of residual stress acting on the polarizing film becomes non-uniform, and stress concentration particularly occurs in the outer peripheral portion, which causes a problem that light leakage and color unevenness are likely to occur in the liquid crystal display device. Then, liquid crystal display devices have been expanded to fields of use such as those for in-vehicle use and outdoor measuring instruments, and have come to be used under severe conditions in which dimensional changes occur in substrates such as polarizing plates.

Under these circumstances, for example, Japanese Patent Laid-Open No. 2000-109771 uses a pressure-sensitive adhesive composition containing a high-molecular weight polymer and a low-molecular weight polymer to absorb and relax stress caused by dimensional change of a substrate. Therefore, it is disclosed that optical defects can be prevented under the heat and humidity condition. This has made it possible to obtain polarizing plates with pressure-sensitive adhesive layers that have durability under more severe conditions. In fields such as personal computer displays, in-vehicle TVs, in-vehicle navigation system displays, and wall-mounted TVs. Is expected to be a wider liquid crystal display device. To this end, there is a demand for a pressure-sensitive adhesive that can sufficiently absorb and relax stress even if the amount of dimensional change of the base material increases.

[0006]

DISCLOSURE OF THE INVENTION The present invention relieves stress due to dimensional change of a member such as a polarizing film, a retardation film and an elliptical polarizing film having a particularly large attachment area,
It is an object to provide an acrylic pressure-sensitive adhesive for an optical member that suppresses light leakage and color unevenness, and to provide an acrylic pressure-sensitive adhesive sheet for an optical member that uses the pressure-sensitive adhesive.

[0007]

The pressure-sensitive adhesive for optical members of the present invention is a pressure-sensitive adhesive composed of a polymer containing (meth) acrylic acid ester as a main component and a cross-linking agent, and the gel fraction of the pressure-sensitive adhesive is 30% or more and 60% or less, and the weight average molecular weight by GPC of the sol component in the adhesive is 100,000 or more 50
And the molecular weight distribution is 40 or more, and the molecular weight is 50,000 or less.
It is 0% by weight or less.

The cross-linking agent is preferably any one of an isocyanate-based cross-linking agent, an epoxy-based cross-linking agent and an aziridine-based cross-linking agent, and the pressure-sensitive adhesive further contains a silane coupling agent. Is preferred.

Further, the optical member of the present invention is one in which a pressure-sensitive adhesive layer made of the above-mentioned pressure-sensitive adhesive for an optical member is formed on one side or both sides of a support. The film is preferably either a film or an elliptically polarizing film, and a film having a dimensional change rate of 1% or more after 100 hours at 100 ° C. is preferable.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The pressure-sensitive adhesive for optical members of the present invention is
A pressure-sensitive adhesive comprising a polymer having a (meth) acrylic acid ester as a main component and a cross-linking agent, wherein the pressure-sensitive adhesive has a gel fraction of 30% or more and 60% or less, and the sol content in the pressure-sensitive adhesive is measured by GPC. The weight average molecular weight is 100,000 or more and 500,000 or less, the molecular weight distribution is 40 or more, and the molecular weight is 5
The amount of the polymer component is not more than 30% by weight and not more than 80% by weight in the sol content.

The polymer containing a (meth) acrylic acid ester as a main component used in the present invention is obtained by polymerizing a monomer mixture containing a (meth) acrylic acid ester as a main component by a conventionally known polymerization method. It is a polymer. This monomer mixture contains a (meth) acrylic acid ester as a main component and a functional group-containing monomer having a functional group capable of undergoing a crosslinking reaction with a crosslinking agent as an essential component. Moreover, you may mix | blend other vinyl type monomers.

Examples of the (meth) acrylic acid ester used as the main component include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate and iso-butyl (meth) acrylate. Acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, iso-octyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, Mention may be made of methoxyethyl (meth) acrylate, ethoxymethyl (meth) acrylate and phenoxyethyl (meth) acrylate. These can be used alone or in combination.

Examples of the copolymerizable functional group-containing monomer include carboxyl groups such as (meth) acrylic acid, β-carboxyethyl acrylate, itaconic acid, crotonic acid, maleic acid, fumaric acid and maleic anhydride. Group-containing monomer, 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, chloro-2-hydroxypropyl acrylate,
Hydroxyl group-containing monomers such as diethylene glycol mono (meth) acrylate and allyl alcohol,
Epoxy group-containing monomers such as glycidyl (meth) acrylate, aminomethyl (meth) acrylate, monomers containing amino groups such as dimethylaminoethyl (meth) acrylate, acrylamide, methylol (meth) acrylamide, methoxyethyl (meth) acrylamide, etc. Examples thereof include amide group-containing monomers, alkoxy group-containing monomers such as methacryloxypropylmethoxysilane, and acetoacetyl group-containing monomers such as acetoacetoxyethyl (meth) acrylate. These can be used alone or in combination.

Examples of other monomers include aromatic vinyl monomers such as styrene, methylstyrene and vinyltoluene, vinyl acetate, vinyl chloride, (meth) acrylonitrile and the like. These can be used alone or in combination.

These monomers are functional group-containing monomers of 0.1 to 100 parts by weight of (meth) acrylic acid ester.
1 to 25 parts by weight is preferable, and 0.5 to 15 parts by weight is more preferable. Other monomers may be blended in an amount of about 0 to 25 parts by weight.

Examples of the crosslinking agent used in the present invention include an isocyanate crosslinking agent, an epoxy crosslinking agent, an aziridine crosslinking agent, a metal chelate crosslinking agent and an amine crosslinking agent. Particularly, an isocyanate cross-linking agent, an epoxy cross-linking agent or an aziridine cross-linking agent is preferable. These crosslinking agents may be used alone or in combination of two or more kinds.

Examples of the isocyanate cross-linking agent include tolylene diisocyanate, chlorphenylene diisocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, etc. Isocyanate monomers and isocyanate compounds and isocyanurate compounds obtained by adding these isocyanate monomers with trimethylolpropane, burette type compounds, and further known polyether polyols and polyester polyols, acrylic polyols, polybutadiene polyols, polyisoprene polyols and the like Such as urethane prepolymer type isocyanate Can.

As the epoxy type cross-linking agent, ethylene glycol glycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,3-bis (N,
N-diglycidylaminomethyl) cyclohexane, N, N, N ',
N'-tetraglycidyl-m-xylylenediamine, N, N, N ', N'-
Tetraglycidylaminophenylmethane, triglycidyl isocyanurate, mN, N-diglycidylaminophenylglycidyl ether, N, N-diglycidyltoluidine, N,
Examples thereof include N-diglycidyl aniline. Examples of the aziridine-based cross-linking agent include diphenylmethane-4,
4'-bis (1-aziridinecarboxamide), trimethylolpropane tri-β-aziridinyl propionate, tetramethylolmethane tri-β-aziridinyl propionate, toluene-2,4-bis (1 -Aziridine carboxamide), triethylene melamine, bisisophthaloyl-1- (2
-Methylaziridine), Tris-1- (2-methylaziridine)
Examples thereof include phosphine and trimethylolpropane tri-β- (2-methylaziridine) propionate.

The amount of the cross-linking agent to be added is 100% of the polymer containing the (meth) acrylic acid ester as a main component.
It is 0.001 to 5 parts by weight with respect to parts by weight. When the amount of the crosslinking agent is less than 0.001 part by weight, the gel fraction tends to be less than 30%, the cohesive force of the obtained pressure-sensitive adhesive is low, and foaming is likely to occur in a high temperature atmosphere. On the other hand, if the amount of the crosslinking agent exceeds 5 parts by weight, the gel fraction tends to exceed 60%, and the resulting pressure-sensitive adhesive becomes inferior in stress relaxation property.

The pressure-sensitive adhesive for optical members of the present invention is crosslinked with the above-mentioned polymer containing (meth) acrylic acid ester as a main component and the above-mentioned crosslinking agent, and the gel fraction thereof is 30 to
60%. The gel fraction was about 0.1 g of adhesive, which was sampled in a sample bottle, and 30 cc of ethyl acetate was added to the gel.
After shaking for 4 hours, the contents of the sample bottle were filtered off with a 200-mesh stainless steel wire net, the residue on the wire net was dried at 100 ° C. for 2 hours, and the dry weight was measured, according to the following formula [I]. I asked.

[Equation 1] When this gel fraction is less than 30%, the cohesive force of the pressure-sensitive adhesive is low and foaming easily occurs in a high temperature atmosphere, and when it exceeds 60%, the stress relaxation property remarkably deteriorates.

In the pressure-sensitive adhesive for optical members of the present invention, the weight average molecular weight (Mw) of the uncrosslinked polymer by gel permeation chromatography (GPC method) is 100,000 to 50.
10,000, and preferably 100,000 to 300,000. This Mw
When the value is less than 100,000 or more than 500,000, the stress relaxation property is lowered, and foaming easily occurs in a high temperature atmosphere due to insufficient cohesive strength of the pressure-sensitive adhesive.

The pressure-sensitive adhesive for optical members of the present invention is GP
The molecular weight distribution (weight average molecular weight / number average molecular weight = Mw / Mn) of the uncrosslinked polymer by the C method is 40 or more, preferably 40 to 100. When the molecular weight distribution is less than 40, the stress relaxation property decreases.

Further, the adhesive for optical members of the present invention is G
The uncrosslinked polymer component by the PC method has a polymer content of not more than 50,000 and 30 to 80% by weight, preferably 40 to
It is 70% by weight. Polymer content of 50,000 or less is 30
When it is less than 80% by weight, the stress relaxation property is lowered, and when it exceeds 80% by weight, foaming easily occurs in a high temperature atmosphere due to insufficient cohesive force of the pressure-sensitive adhesive.

A silane coupling agent is preferably blended in the pressure-sensitive adhesive for optical members of the present invention. As the silane coupling agent, a polymerizable unsaturated group-containing silicon compound such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacryloxypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyl Silicon compounds having an epoxy structure such as methyldimethoxysilane and 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) 3-aminopropyltrimethoxysilane , N- (2-aminoethyl) 3-aminopropylmethyldimethoxysilane and other amino group-containing silicon compounds, and 3-chloropropyltrimethoxysilane.

In addition, the pressure-sensitive adhesive for optical members of the present invention contains an ultraviolet absorber, an antioxidant, an antiseptic, a fungicide, as long as the transparency, the visibility and the effect of the present invention are not impaired. You may mix | blend a tackifying resin, a plasticizer, a defoaming agent, a wettability adjusting agent, etc.

The optical member of the present invention has a pressure-sensitive adhesive layer formed of the pressure-sensitive adhesive for optical members on one side or both sides of a support. As the support, a polarizing film, a retardation film, an elliptically polarizing film, an antireflection film,
Examples of the brightness improving film include a polarizing film, a retardation film and an elliptically polarizing film, and the stress relaxation property of the pressure-sensitive adhesive for an optical member can be more exhibited.

The polarizing film, the retardation film, or the elliptically polarizing film has a dimensional change rate of more than 2% when left to stand at a high heat of 100 ° C. for 500 hours. In the case where a conventionally known adhesive is formed on one side of these supports and further adhered to a glass substrate, the dimensional change rate after 100 hours at 500 ° C. is less than 1%, and thus the dimensional change is suppressed. In addition, the thermal stress cannot be relaxed sufficiently and stress concentrates on the periphery of the sticking surface, causing light leakage.

A polarizing film suitable for the optical member of the present invention,
The optical member in which the pressure-sensitive adhesive layer made of the pressure-sensitive adhesive for an optical member is formed on the retardation film or the elliptically polarizing film has a thickness of 100 in order that the pressure-sensitive adhesive layer sufficiently relaxes thermal stress when attached to a glass substrate or the like. The dimensional change rate after 500 ° C. for 500 hours is 1% or more, and light leakage does not occur.

[0029]

EXAMPLES The present invention will be described more specifically by showing examples, but the present invention is not limited thereto.

<Production Example 1> Acrylic polymer solution A
Preparation of n-butyl acrylate (n-BA) 75 parts by weight, methyl acrylate (MA) 20 parts by weight, 2-hydroxy acrylate (2-HEA) 5 parts by weight, ethyl acetate 100 parts by weight and azobisisobutyronitrile ( AIBN) (0.2 parts by weight) was placed in a reaction vessel, the air in the reaction vessel was replaced with nitrogen gas, the temperature of the reaction vessel was raised to 60 ° C. in a nitrogen atmosphere with stirring, and the reaction was carried out for 4 hours. It was 4 hours later,
100 parts by weight of toluene, α-methylstyrene dimer 5
1 part by weight and 2 parts by weight of AIBN were added, the temperature was raised to 90 ° C., and the reaction was continued for 4 hours. After the reaction, the mixture was diluted with ethyl acetate to obtain an acrylic polymer solution A having a solid content of 20%.

<Production Example 2> Acrylic polymer solution B
Preparation of 2-ethylhexyl acrylate (2-EHA) 98 parts by weight, acrylic acid (AA) 2 parts by weight, ethyl acetate 90 parts by weight and benzoyl peroxide 0.2 parts by weight were placed in a reaction container, and the air in the reaction container was added. Was replaced with nitrogen gas, the temperature of this reaction vessel was raised to 67 ° C. in a nitrogen atmosphere with stirring, and the reaction was carried out for 4 hours. After 4 hours, 100 parts by weight of toluene, 5 parts by weight of n-dodecyl mercaptan and AIBN2
Parts by weight were added, the temperature was raised to 95 ° C., and the reaction was further continued for 4 hours. After the reaction, the mixture was diluted with ethyl acetate to obtain an acrylic polymer solution B having a solid content of 20%.

<Production Example 3> Acrylic polymer solution C
Preparation of n-BA 95 parts by weight, AA 5 parts by weight, ethyl acetate 100 parts by weight and AIBN 0.2 parts by weight were placed in a reaction vessel, and the air in the reaction vessel was replaced with nitrogen gas, and then in a nitrogen atmosphere with stirring. , Raise the temperature of the reaction vessel to 60 ° C.,
Reacted for hours. After the reaction, the mixture was diluted with ethyl acetate to obtain an acrylic polymer solution C having a solid content of 20%.

<Production Example 4> Acrylic polymer solution D
Preparation of n-BA 88 parts by weight, methoxyethyl acrylate (ME
A) 10 parts by weight, 2 parts by weight of acrylic amide, 100 parts by weight of toluene, 5 parts by weight of α-methylstyrene dimer and 3 parts by weight of AIBN were placed in a reaction vessel, and the air in the reaction vessel was replaced with nitrogen gas, followed by stirring. Under a nitrogen atmosphere, the temperature of this reaction vessel was raised to 100 ° C. and the reaction was performed for 6 hours. After the reaction, the mixture was diluted with toluene to obtain an acrylic polymer solution D having a solid content of 40%.

<Production Example 5> Acrylic polymer solution E
Preparation of n-BA 88 parts by weight, MEA 10 parts by weight, acrylic amide 2 parts by weight, toluene 100 parts by weight, α-methylstyrene dimer 0.5 parts by weight and AIBN 1 part by weight are put in a reaction container, and air in the reaction container is removed. After purging with nitrogen gas, the reaction vessel is stirred at 100 ° C. in a nitrogen atmosphere.
The temperature was raised to ° C and the reaction was performed for 6 hours. After the reaction, the mixture was diluted with toluene to obtain an acrylic polymer solution E having a solid content of 40%.

<Production Example 6> Preparation of acrylic polymer F 50 parts by weight of n-BA, 50 parts by weight of MEA and 3 parts by weight of n-dodecyl mercaptan as a molecular weight modifier were placed in a reaction vessel, and the air in the reaction vessel was replaced with nitrogen gas. After replacing with
Heated to 60 ° C. under nitrogen atmosphere with stirring. Then,
As a polymerization initiator, 0.005 parts by weight of 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile) was added under stirring and uniformly mixed. After charging the polymerization initiator, the temperature of the reaction system increased, and when the polymerization reaction was continued without cooling,
The temperature of the reaction system reached 110 ° C., and then gradually began to drop. The temperature in the system was forcibly cooled to 60 ° C. with a water bath. After forced cooling, 2,2'-azobis (4-methoxy-
0.004 parts by weight of (2,4-dimethylvaleronitrile) was added with stirring to uniformly mix them. After the second charge of initiator,
The temperature of the reaction system rose, but when the polymerization reaction was continued without cooling, the temperature of the reaction system reached 105 ° C. Then, the temperature of the reaction system was forcibly cooled to 75 ° C. with a water bath.

Further, 0.01 part of dimethyl 2,2'-azobis (2-methylpropionate) was added. When the temperature of the reaction system rose, but the polymerization reaction was continued without cooling,
The temperature of the reaction system reached 120 ° C. The temperature of the reaction system was cooled to 110 ° C. with a water bath. Continuing, polymerization initiator 1,
1'-azobis (cyclohexane-1-carbonitrile) 0.1
After adding 5 parts by weight of the mixture under stirring and performing a polymerization reaction for 2 hours,
The reaction system was cooled to room temperature with a water bath, and the solid content was 99% by weight.
Polymer F was obtained.

<Production Example 7> Acrylic polymer solution G
(Syrup) 98 parts by weight of 2-EHA and 2 parts by weight of AA are put into a reaction container,
After replacing the air in the reaction vessel with nitrogen gas, the mixture was heated to 50 ° C. in a nitrogen atmosphere with stirring. Then, as a polymerization initiator, 0.025 parts by weight of 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile) was added under stirring and uniformly mixed. After the addition of the polymerization initiator, the temperature of the reaction system rose, and when the polymerization reaction was continued without cooling, the temperature of the reaction system reached 119 ° C., and then gradually began to drop.
19.6 parts by weight of 2-EHA and 0.4 parts by weight of AA were added, and the temperature of the reaction system was cooled to 110 ° C. Further, it was cooled to room temperature with a water bath to obtain a polymer solution G having a solid content of 29% by weight.

<Production of Optical Member Adhesive Sheet> As a support, the dimensional change rate after 100 hours at 100 ° C. was 2.
A polarizing film of 0% was used to form a pressure-sensitive adhesive layer having a thickness of 25 μm on a polyester film obtained by subjecting the pressure-sensitive adhesive composition containing the above acrylic polymer solution to release treatment, and transferred to a support at a temperature of 23 ° C. 7 at a humidity of 65%
It was aged for a day to prepare an optical member.

<Measurement of gel fraction> About the gel fraction, about 0.1 g of a pressure-sensitive adhesive aged on a support at a temperature of 23 ° C. and a humidity of 65% for 7 days was sampled in a sample bottle and extracted with ethyl acetate. 30 cc was added and the mixture was shaken for 24 hours, the contents of the sample bottle were filtered off with a 200-mesh stainless steel wire net, the residue on the wire net was dried at 100 ° C. for 2 hours, and the dry weight was measured. It was determined by the formula [I].

[Equation 2]

<Measurement of molecular weight and molecular weight distribution of sol content> An adhesive aged on a support for 7 days at a temperature of 23 ° C. and a humidity of 65% was subjected to gel permeation chromatography under the following measurement conditions. , Weight average molecular weight of uncrosslinked polymer, molecular weight distribution and molecular weight 5
A weight percentage of less than ten thousand was determined. Device name: Tosoh Corporation, HLC-8120 Column: Tosoh Corporation, G7000HXL 7.8mm ID x 30cm 1 GMHXL 7.8mm ID x 30cm 2 G2000HXL 7.0mm ID x 30cm 1 sample concentration: 1.5mg Dilute with tetrahydrofuran so that the concentration becomes / ml Mobile phase solvent: Tetrohydrofuran Flow rate: 1.0 ml / min Column temperature: 40 ° C

[0041]

Example 1 1.0 part by weight of an isocyanate cross-linking agent (trade name: Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.) was added to 100 parts by weight of the solid content of the polymer solution A, and the mixture was well stirred to give an adhesive composition. Got It is applied to a peeled polyester film and dried to form a pressure-sensitive adhesive layer having a thickness of 25 μm, which is then transferred to one side of a polarizing film at a temperature of 23
An optical member was obtained by aging for 7 days under conditions of ° C and humidity of 65%.

[0042]

[Example 2] An epoxy cross-linking agent (trade name: Tetrad X, Mitsubishi Gas Chemical Co., Ltd.) was added to 100 parts by weight of the solid content of the polymer solution B.
(Manufactured by K.K.) and 0.2 part by weight of a silane coupling agent (trade name: KBE403, manufactured by Shin-Etsu Chemical Co., Ltd.) were added and well stirred to obtain an adhesive composition. Apply it to a polyester film that has been subjected to release treatment, dry it,
After providing a pressure-sensitive adhesive layer having a thickness of 25 μm, the pressure-sensitive adhesive layer was transferred onto one side of the polarizing film and aged for 7 days under the conditions of a temperature of 23 ° C. and a humidity of 65% to obtain an optical member.

[0043]

Example 3 67 parts by weight of the solid content of the polymer solution C and 33 parts by weight of the solid content of the polymer solution D were mixed, and this was mixed with an aziridine-based crosslinking agent (trade name: TAZM, manufactured by Mutual Yakuko Co., Ltd.).
0.05 parts by weight and silane coupling agent (trade name: K
BM9007 (manufactured by Shin-Etsu Chemical Co., Ltd.) (0.2 parts by weight) was added and well stirred to obtain an adhesive composition. Apply it to a polyester film that has been subjected to release treatment, dry it, and
After providing the pressure-sensitive adhesive layer of m, it was transferred to one surface of the polarizing film and aged for 7 days under the conditions of temperature 23 ° C. and humidity 65% to obtain an optical member.

[0044]

Example 4 50 parts by weight of the solid content of the polymer solution C and 50 parts by weight of the solid content of the polymer F were mixed, 0.02 parts by weight of the epoxy cross-linking agent (Tetrad X) was added thereto, and the mixture was stirred well. An adhesive composition was obtained. It is applied to a peeled polyester film and dried to form a pressure-sensitive adhesive layer of 25 μm, which is then transferred to one side of a polarizing film and aged for 7 days at a temperature of 23 ° C. and a humidity of 65% to give an optical member. Got

[0045]

Example 5 100 parts by weight of polymer solution G, a photopolymerization initiator (trade name: Darocur 1173, Ciba Geigy Co., Ltd.)
0.3 part by weight, epoxy type cross-linking agent (Tetrad X)
A photopolymerizable acrylic pressure-sensitive adhesive composition was prepared by thoroughly mixing 0.05 parts by weight.

This adhesive composition was applied onto a polyester film which had been subjected to a release treatment. This was irradiated with light from a high pressure mercury lamp under a nitrogen gas atmosphere at 10 W / m ² for 360 seconds (generation of high molecular weight polymer) and then at 3000 W / m ² for 45 seconds (generation of low molecular weight polymer). Polymerization was carried out. This was transferred to one side of a polarizing film and aged for 7 days under the conditions of a temperature of 23 ° C. and a humidity of 65% to obtain an optical member.

[0047]

Comparative Example 1 0.2 part by weight of an isocyanate cross-linking agent (Coronate L) was added to 100 parts by weight of the solid content of the polymer solution A, and well stirred to obtain a pressure-sensitive adhesive composition. It is applied to a polyester film that has been subjected to a release treatment and dried, then 25
After providing a pressure-sensitive adhesive layer having a thickness of μm, the pressure-sensitive adhesive layer was transferred onto one surface of the polarizing film and aged for 7 days under the conditions of a temperature of 23 ° C. and a humidity of 65% to obtain an optical member.

[0048]

[Comparative Example 2] To 100 parts by weight of the solid content of the polymer solution B, 0.1 parts by weight of an epoxy cross-linking agent (Tetrad X) and 0.2 parts by weight of a silane coupling agent (KBE403) were added, and the mixture was sufficiently stirred to give an adhesive property. An agent composition was obtained. Apply it to a polyester film that has been subjected to release treatment, dry it, and
After providing the pressure-sensitive adhesive layer of m, it was transferred to one surface of the polarizing film and aged for 7 days under the conditions of temperature 23 ° C. and humidity 65% to obtain an optical member.

[0049]

Comparative Example 3 An adhesive composition was obtained by adding 0.03 part by weight of an epoxy-based crosslinking agent (Tetrad X) to 100 parts by weight of the solid content of the polymer solution C and stirring well. It is applied to a peeled polyester film and dried to 25 μm
After the pressure-sensitive adhesive layer was prepared, it was transferred onto one side of the polarizing film and aged for 7 days under the conditions of a temperature of 23 ° C. and a humidity of 65% to obtain an optical member.

[0050]

Comparative Example 4 An adhesive composition was obtained by adding 0.01 parts by weight of an epoxy crosslinking agent (Tetrad X) to 100 parts by weight of the solid content of the polymer solution C and stirring them well. It is applied to a peeled polyester film and dried to 25 μm
After the pressure-sensitive adhesive layer was prepared, it was transferred onto one side of the polarizing film and aged for 7 days under the conditions of a temperature of 23 ° C. and a humidity of 65% to obtain an optical member.

[0051]

Comparative Example 5 80 parts by weight of the solid content of the polymer solution C and 20 parts by weight of the solid content of the polymer solution D were mixed, and 0.06 parts by weight of the aziridine cross-linking agent (TAZM) and the silane coupling agent (KBM9007) were mixed therein. 0.2 parts by weight was added and well stirred to obtain an adhesive composition. It is applied to a peeled polyester film and dried to 25 μm
After the pressure-sensitive adhesive layer was prepared, it was transferred onto one side of the polarizing film and aged for 7 days under the conditions of a temperature of 23 ° C. and a humidity of 65% to obtain an optical member.

[0052]

COMPARATIVE EXAMPLE 6 67 parts by weight of the solid content of the polymer solution C and 33 parts by weight of the solid content of the polymer solution E were mixed, and 0.05 parts by weight of an aziridine-based cross-linking agent (TAZM) and a silane coupling agent (KBM9007) were mixed therein. 0.2 parts by weight was added and well stirred to obtain an adhesive composition. It is applied to a peeled polyester film and dried to 25 μm
After the pressure-sensitive adhesive layer was prepared, it was transferred onto one side of the polarizing film and aged for 7 days under the conditions of a temperature of 23 ° C. and a humidity of 65% to obtain an optical member.

[0053]

[Table 1]

<Durability Test of Optical Member> Examples 1 to 1 above
The 15-inch size optical members obtained in Example 5 and Comparative Examples 1 to 6 were attached to both surfaces of a 0.5 mm-thick non-alkali glass plate using a laminator roll so as to form a crossed Nicol. Then, place in an autoclave at 50 ° C and 5 atm for 20
Hold for minutes to bond. The sample thus obtained is 1
The sample was left under conditions of 00 ° C. and 80 ° C. and 90% RH for 500 hours, and light leakage caused by peeling of the optical member, foaming at the adhesive interface, and residual stress due to dimensional change was visually observed. The results are shown in Table 2. "O" in the table means that there is no problem in practical use, and "x" indicates that there is a problem in practical use.

[0055]

[Table 2]

From the results of Table 1 and Table 2, Examples 1 to
The optical member in which the pressure-sensitive adhesive of No. 5 and the pressure-sensitive adhesive layer made of the pressure-sensitive adhesive were formed on one surface of the polarizing film had a 15-inch size and a considerably large attachment area, but was left to stand in a high temperature atmosphere of 100 ° C. for 500 hours. However, again, 80 ℃, 90
Even when left standing in a high temperature and high humidity atmosphere of% RH for 500 hours, peeling, foaming and light leakage did not occur.

On the other hand, in the pressure-sensitive adhesive and the optical member of Comparative Example 1, since the gel fraction of the pressure-sensitive adhesive was low, the cohesive force of the pressure-sensitive adhesive was insufficient and foaming occurred in a high temperature and high humidity temperature atmosphere. ing. In the pressure-sensitive adhesive and the optical member of Comparative Example 2, since the gel fraction of the pressure-sensitive adhesive is high and the molecular weight distribution of the sol is low, the stress relaxation property of the pressure-sensitive adhesive is lowered and light leakage occurs in a high temperature atmosphere,
Peeling and light leakage occurred in a high-humidity temperature atmosphere. In the pressure-sensitive adhesive and the optical member of Comparative Example 3, the gel fraction of the pressure-sensitive adhesive was high, and the stress relaxation property of the pressure-sensitive adhesive was lowered because the molecular weight distribution of the sol and the polymer having a molecular weight of 50,000 or less in the sol were small. Light leakage occurs in a high temperature and high humidity atmosphere.
In the pressure-sensitive adhesive and the optical member of Comparative Example 4, since the gel fraction of the pressure-sensitive adhesive is high and the polymer having a molecular weight of 50,000 or less in the sol content is small, the stress relaxation property of the pressure-sensitive adhesive is lowered, and high temperature and high humidity Light leakage is occurring in the atmosphere. The pressure-sensitive adhesive and the optical member of Comparative Example 5 have a high gel content and a small amount of a polymer having a molecular weight of 50,000 or less in the sol, so that the stress relaxation property of the pressure-sensitive adhesive is reduced, and the pressure-sensitive adhesive and the optical member are exposed to light under high temperature and high humidity atmosphere. There is a leak.
Since the pressure-sensitive adhesive and the optical member of Comparative Example 6 have a low sol molecular weight distribution and a weight of 50,000 or less in the sol, the cohesive force of the pressure-sensitive adhesive is insufficient and peeling and foaming occur in a high temperature atmosphere. However, peeling occurred in a high humidity temperature atmosphere.

[0058]

As described above, the pressure-sensitive adhesive for an optical member of the present invention and the optical member of the present invention using the pressure-sensitive adhesive for an optical member have a stress relaxation property of the pressure-sensitive adhesive layer under heat or wet heat conditions. Therefore, peeling, foaming and light leakage can be significantly suppressed in a high temperature and high temperature and high humidity atmosphere. In particular, as shown in the examples, the effect is remarkable when the attachment area is large.

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Claims (6)

[Claims] 1. A pressure-sensitive adhesive comprising a polymer having a (meth) acrylic acid ester as a main component and a crosslinking agent, wherein the gel fraction of the pressure-sensitive adhesive is 30% or more and 60% or less. The weight average molecular weight of the sol component by GPC is 100,000 or more and 500,000 or less, the molecular weight distribution is 40 or more, and the molecular weight is 50,000 or less. The polymer component is 30% by weight in the sol component.
The pressure-sensitive adhesive for optical members, which is not less than 80% by weight. 2. The pressure-sensitive adhesive for an optical member according to claim 1, wherein the crosslinking agent is an isocyanate crosslinking agent, an epoxy crosslinking agent, or an aziridine crosslinking agent. 3. The pressure-sensitive adhesive for optical members according to claim 1, wherein the pressure-sensitive adhesive is mixed with a silane coupling agent. 4. An optical member having a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive according to claim 1 formed on one surface or both surfaces of a support. 5. The optical member according to claim 4, wherein the support is a polarizing film, a retardation film or an elliptically polarizing film. 6. The optical member according to claim 5, wherein the dimensional change rate after 500 hours at 100 ° C. is 1% or more.