JP5654192B2 - Adhesive composition and optical member - Google Patents

Description

  The present invention relates to a pressure-sensitive adhesive composition and an optical member.

  In so-called flat display panels such as a liquid crystal display panel and a plasma display panel, various optical films such as a polarizing plate, a retardation plate, and an antireflection film are generally laminated via an adhesive layer.

For example, an acrylic resin is used for an adhesive layer used for a polarizing plate in order to ensure excellent adhesiveness and optical transparency. The acrylic resin is a resin having an acrylic ester or a methacrylic ester as a main component and having excellent transparency. However, in order to provide reworkability when used as an adhesive layer, 1-hydroxybutyl acrylate or the like is used. A monomer containing a secondary hydroxyl group may be contained. In addition, rework property means the property which is hard to peel off to a to-be-adhered body, and can be easily peeled off if it tries to peel off. Therefore, conventionally, development of an adhesive layer made of an acrylic resin containing a hydroxyl group-containing monomer has been promoted.
International Publication WO2004 / 099334 Pamphlet

Incidentally, the adhesive layer may be required to have heat resistance and heat and moisture resistance as well as reworkability. In order to improve the heat resistance and wet heat resistance of the adhesive layer, it is effective to crosslink the acrylic resin constituting the adhesive layer. On the other hand, if the crosslinking proceeds, the hydroxyl group concentration in the pressure-sensitive adhesive layer is lowered and the reworkability may be lowered. Therefore, in order to impart reworkability, heat resistance, and moist heat resistance simultaneously to the adhesive layer, it is necessary to precisely control the degree of crosslinking and the gel fraction that depends on the degree of crosslinking.
In order to crosslink an acrylic resin containing a monomer containing a hydroxyl group, an isocyanate-based crosslinking agent is suitably used. However, since the isocyanate-based crosslinking agent easily reacts with residual moisture in the pressure-sensitive adhesive composition, the isocyanate-based crosslinking agent involved in the crosslinking reaction is relatively small, and it is difficult to precisely control the degree of crosslinking. There was a problem. For this reason, it is necessary to use another kind of crosslinking agent instead of the isocyanate-based crosslinking agent sensitive to moisture. However, when another cross-linking agent is used, it is necessary to add another monomer having a corresponding functional group, and therefore, it is necessary to relatively reduce the blending ratio of the primary hydroxyl group-containing monomer. However, if the blending ratio of the primary hydroxyl group-containing monomer is relatively small, it is natural that sufficient reworkability cannot be ensured. Thus, it has been difficult for conventional pressure-sensitive adhesive compositions to simultaneously improve the reworkability, heat resistance, and moist heat resistance.

  This invention is made | formed in view of the said situation, Comprising: It aims at providing the acrylic adhesive composition which is excellent in rework property, heat resistance, and heat-and-moisture resistance, and an optical member provided with the same.

In order to achieve the above object, the present invention employs the following configuration.
The pressure-sensitive adhesive composition of the present invention comprises an acrylic ester and / or a methacrylic ester, a primary hydroxyl group-containing monomer having a primary hydroxyl group in the molecule, and a secondary hydroxyl group-containing monomer having a secondary hydroxyl group in the molecule. And / or a tertiary hydroxyl group-containing monomer having a tertiary hydroxyl group, and a copolymer polymer obtained by crosslinking at least with a crosslinking agent.
In the pressure-sensitive adhesive composition of the present invention, the mass ratio of the primary hydroxyl group-containing monomer to the secondary hydroxyl group-containing monomer and / or tertiary hydroxyl group-containing monomer [(secondary hydroxyl group-containing monomer and / or tertiary hydroxyl group-containing) Monomer) / (Primary hydroxyl group-containing monomer)] is preferably 2 or more.
Furthermore, in the pressure-sensitive adhesive composition of the present invention, the copolymer polymer contains an acrylic ester and / or a methacrylic ester having any functional group of a carboxyl group, an epoxy group, and an amine group. Preferably it is.

  Next, the optical member of the present invention is characterized in that the pressure-sensitive adhesive composition described above is applied to one or both surfaces of an optical sheet.

  ADVANTAGE OF THE INVENTION According to this invention, the acrylic adhesive composition excellent in rework property, heat resistance, and heat-and-moisture resistance, and an optical member provided with the same can be provided.

Hereinafter, embodiments of the present invention will be described.
"Adhesive composition"
The pressure-sensitive adhesive composition of the present embodiment comprises an acrylic ester and / or a methacrylic ester (component A), a primary hydroxyl group-containing monomer having a primary hydroxyl group in the molecule (component B), and a secondary in the molecule. A copolymer which is at least copolymerized with a secondary hydroxyl group-containing monomer having a hydroxyl group and / or a tertiary hydroxyl group-containing monomer having a tertiary hydroxyl group (component C) and crosslinked with a crosslinking agent. It will be.

A component becomes a main component of the adhesive composition of this embodiment, and provides transparency and adhesiveness to an adhesive composition.
Moreover, B component is a monomer containing a primary hydroxyl group, and the primary hydroxyl group contained in this monomer easily undergoes a crosslinking reaction with a crosslinking agent. Therefore, by adding the component B, the degree of crosslinking of the pressure-sensitive adhesive composition can be increased, and heat resistance and heat-and-moisture resistance can be improved.
On the other hand, the component C is a monomer having a hydroxyl group as in the case of the component B, but the hydroxyl group of the component C is a secondary or tertiary hydroxyl group and hardly reacts with the crosslinking agent. Therefore, by adding the C component, the hydroxyl group derived from the C component remains in the pressure-sensitive adhesive composition, thereby ensuring reworkability. Thus, according to the pressure-sensitive adhesive composition of the present embodiment, heat resistance, moist heat resistance and reworkability can be improved at the same time.
Moreover, when a hydroxyl group remains in an adhesive composition, stress relaxation property will become high. Thereby, when the adhesive composition of this embodiment is applied, for example to the adhesion layer of a polarizing plate, the light leakage of a polarizing plate can be prevented.

The copolymer polymer constituting the pressure-sensitive adhesive composition of the present embodiment includes an acrylic ester and / or a methacrylic ester (D component) having any functional group of carboxyl group, epoxy group, and amine group. ) May be contained. By adding D component, the crosslinking degree of an adhesive composition can be raised more, and heat resistance and heat-and-moisture resistance can further be improved.
Hereinafter, A component-D component, a crosslinking agent, and another additive component are demonstrated.

(A component)
The acrylic acid ester and / or methacrylic acid ester as the component A is preferably one having no functional group to be a crosslinking point, and the esterified substituent has an acrylate and / or methacrylate having about 1 to 14 carbon atoms. {Hereinafter referred to as (meth) acrylate. } Is preferable because of excellent transparency and excellent adhesive properties.
The blending ratio of the component A in the copolymer polymer is preferably in the range of 80% by mass to 98.9% by mass, and more preferably in the range of 88% by mass to 97.5% by mass.

  Specific examples of the acrylic acid ester and / or methacrylic acid ester as component A include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth) acrylate, isobutyl (meta ) Acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) ) Acrylate, isodecyl (meth) acrylate, n-dodecyl (meth) acrylate, n-tridecyl (meth) acrylate, n-tetradecyl (meth) acrylate, methoxyethyl (meth) acrylate, ethoxyethyl (meth) a Relate, butoxyethyl (meth) acrylate, cyclohexyl (meth) acrylate, t-cyclohexyl (meth) acrylate, phenoxyethyl (meth) acrylate, nonylphenoxypolyethylene glycol (meth) acrylate, benzyl (meth) acrylate, isobornyl (meth) acrylate And tetrahydrofurfuryl (meth) acrylate. In particular, the component A of the pressure-sensitive adhesive composition for an optical member preferably contains n-butyl acrylate as a main component from the viewpoint that high adhesiveness can be exhibited.

(B component)
The primary hydroxyl group-containing monomer as component B has a primary hydroxyl group in the molecule that serves as a crosslinking point when a crosslinking reaction occurs with the crosslinking agent. Specific examples of the primary hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, and 8-hydroxy. Octyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, (4-hydroxymethylcyclohexyl) methyl acrylate, N-methylol (meth) acrylamide, N-2-hydroxyethyl (meth) ) Acrylamide, vinyl alcohol, allyl alcohol, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, diethylene glycol monovinyl ether and the like. In particular, a (meth) acrylate compound is preferred as the primary hydroxyl group-containing monomer.

  The blending ratio of component B in the copolymer polymer is preferably in the range of 0.1% by mass to 5% by mass, and more preferably in the range of 0.5% by mass to 2% by mass. If the component B is less than 0.1% by mass, the number of hydroxyl groups serving as cross-linking points is insufficient, and the degree of cross-linking of the copolymer polymer is lowered, thereby reducing the heat resistance of the pressure-sensitive adhesive composition. Moreover, when B component exceeds 5 mass%, since a bridge | crosslinking degree increases and the softness | flexibility of a copolymer polymer falls and rework property and adhesiveness fall, it is unpreferable.

(C component)
The secondary hydroxyl group-containing monomer and / or tertiary hydroxyl group-containing monomer as component C is one having a secondary hydroxyl group or a tertiary hydroxyl group that hardly undergoes a crosslinking reaction with a crosslinking agent in the molecule. Either the secondary hydroxyl group-containing monomer or the tertiary hydroxyl group-containing monomer may be added, or both may be added simultaneously.
Secondary hydroxyl group-containing monomers include 2-hydroxypropane (meth) acrylate, 2-hydroxybutane (meth) acrylate, 3-hydroxybutane (meth) acrylate, 2-hydroxy-1-ethylpropane (meth) acrylate, 2-hydroxy Hexane (meth) acrylate, 2-hydroxycyclohexane (meth) acrylate, 2-hydroxypentane (meth) acrylate, 3-hydroxy-2-ethylhexane (meth) acrylate, 3-chloro-2-hydroxypropyl (meth) acrylate, An aliphatic epoxy acrylate can be illustrated.
Examples of the tertiary hydroxyl group-containing monomer include 3-hydroxy-1,3-diethylbutane (meth) acrylate.

  The blending ratio of component C in the copolymer polymer is preferably in the range of 1% by mass to 15% by mass, and more preferably in the range of 2% by mass to 10% by mass. When the component C is less than 1% by mass, the number of hydroxyl groups remaining in the copolymer polymer is insufficient, and the reworkability of the pressure-sensitive adhesive composition is lowered, which is not preferable. On the other hand, when the C component exceeds 15% by mass, a part of the hydroxyl group contained in the C component becomes a crosslinking point, the degree of crosslinking increases, the flexibility of the copolymer polymer decreases, and reworkability and adhesiveness are reduced. Since it falls, it is not preferable.

  Further, the mass ratio of the primary hydroxyl group-containing monomer as component B to the secondary hydroxyl group-containing monomer and / or tertiary hydroxyl group-containing monomer as component C [(secondary hydroxyl group-containing monomer and / or tertiary hydroxyl group-containing monomer) / (Primary hydroxyl group-containing monomer)] is preferably 2 or more. A mass ratio of less than 2 is not preferable because the number of hydroxyl groups (secondary and / or tertiary hydroxyl groups) remaining in the copolymer polymer is relatively lowered and reworkability is lowered.

(D component)
Acrylic acid ester and / or methacrylic acid ester (hereinafter referred to as (meth) acrylic acid ester) having any functional group of carboxyl group, epoxy group, and amine group as D component. } Is an optional component and is added when the degree of crosslinking of the copolymer polymer is further improved.

Specific examples of the (meth) acrylic acid ester containing a carboxyl group include acrylic acid (H ₂ C═CHCOOH) and β-carboxyethyl acrylate (H ₂ C═CHCOOCH ₂ CH ₂ COOH). Further, an epoxy group-containing (meth) e.g. Specific examples of acrylic acid ester, glycidyl methacrylate _{(H 2 C = CCH 3 COOCH} 2 - (C 2 H 3 O)) can be exemplified. Furthermore, specific examples of the (meth) acrylic acid ester containing an amine group include, for example, N-dimethylaminoethyl acrylate (H ₂ C═CHCOOC ₂ H ₄ —N (CH ₃ ) ₂ ) or N-diethylaminoethyl acrylate ( H ₂ C═CHCOOC ₂ H ₄ —N (C ₂ H ₅ ) ₂ ).

  The blending ratio of component D in the copolymer polymer is preferably in the range of 0% by mass to 5% by mass, and more preferably in the range of 0% by mass to 2% by mass. If the component D exceeds 5% by mass, the degree of crosslinking increases, the flexibility of the copolymer polymer decreases, and the reworkability and tackiness decrease, which is not preferable.

  The weight average molecular weight of the copolymer polymer is preferably in the range of 800,000 to 2,000,000. When the weight average molecular weight is in the range of 1,000,000 to 1,500,000, sufficient adhesive force can be obtained as an adhesive composition constituting the adhesive layer of the optical member. In addition, a weight average molecular weight is calculated | required in polystyrene conversion by gel permeation chromatography.

(Crosslinking agent)
In the pressure-sensitive adhesive composition of this embodiment, the copolymer polymer is preferably cross-linked by a cross-linking agent. As the crosslinking agent, it is preferable to use one or more of an isocyanate compound or a metal chelate compound.
Moreover, when D component is added to a copolymer polymer, in addition to an isocyanate compound or a metal chelate compound, you may add another kind of crosslinking agent. That is, in the case where the D component is a (meth) acrylic acid ester having a hydroxyl group, it is preferable to use only a crosslinking agent made of an isocyanate compound or a metal chelate compound. In the case where the D component is a (meth) acrylic acid ester having a carboxyl group, a crosslinking agent composed of an epoxy compound may be further added. Furthermore, when D component is a (meth) acrylic acid ester having an epoxy group, a crosslinking agent comprising a carboxyl group-containing compound or an amine group-containing compound may be further added. Furthermore, when the component D is a (meth) acrylic acid ester having an amine group, a crosslinking agent made of an epoxy compound may be further added.

  The blending ratio of the crosslinking agent is preferably in the range of 0.05 to 5 parts by mass, more preferably in the range of 0.07 to 3 parts by mass with respect to 100 parts by mass of the copolymer polymer. If the blending ratio of the cross-linking agent is less than 0.05 parts by mass, the heat resistance of the pressure-sensitive adhesive composition is lowered, which is not preferable. This is not preferable because the reworkability and the adhesiveness are lowered.

Among the cross-linking agents, the isocyanate compound includes lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate, alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate and isophorone diisocyanate, and 2,4-tolylene diisocyanate. Aromatic diisocyanates such as 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate, trimethylolpropane / tolylene diisocyanate trimer adduct (trade name Coronate L), trimethylolpropane / hexamethylene diisocyanate trimer adduct (Trade name Coronate HL), isocyanurate of hexamethylene diisocyanate (trade name Coronate HX) Tan Industrial Co., Ltd.] and the like isocyanate adducts such as. Further, as the isocyanate compound, tolylene diisocyanate, hydrogenated tolylene diisocyanate, tolylene diisocyanate adduct of trimethylolpropane, xylylene diisocyanate adduct of trimethylolpropane, triphenylmethane triisocyanate, methylene bis (4-phenylmethane) triisocyanate, Isophorone diisocyanate and ketoxime block or phenol block thereof can also be used.
Examples of the metal chelate compound include acetylacetone and acetoacetate coordination compounds of polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium.

  Epoxy compounds include bisphenol A / epichlorohydrin type epoxy resin, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin di or triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, Diglycidylaniline, diglycidylamine, N, N, N, N′-tetraglycidyl-m-xylenediamine (trade name TETRAD-X), 1,3-bis (N, N′-diglycidylaminomethyl) cyclohexane ( Trade name TETRAD-C) [all manufactured by Mitsubishi Gas Chemical Co., Ltd.].

As the carboxyl group-containing compound, terminal carboxyl group type saturated polyester resin (manufactured by Unitika Ltd., “ER-8000 series”), acid pendant type polyester adhesive resin (Toyo Ink Manufacture Co., Ltd. “Dyna Leo VA-9020”) 1,8-octanedicarboxylic acid, methyl 1,4-hexanedicarboxylate, 2,6-naphthalenedicarboxylic acid, and the like.
Examples of the amine group-containing compound include hexamethylenediamine, triethyldiamine, polyethyleneimine, hexamethylenetetramine, diethylenetriamine, triethyltetramine, isophoronediamine, amino resin, and melamine resin.

  The degree of crosslinking of the copolymer polymer in the pressure-sensitive adhesive composition is preferably in the range of 40 to 85% in terms of gel fraction, and more preferably about 70%. If the gel fraction is within this range, the adhesive strength of the adhesive composition can be increased. The gel fraction is determined from the initial mass and the mass after immersion drying when the pressure-sensitive adhesive composition is immersed in ethyl acetate at 25 ° C. for 1 day: “gel fraction = mass after immersion drying / initial mass × 100 ".

(Other additive components)
Further, the pressure-sensitive adhesive composition of the present embodiment includes various conventionally known antistatic agents, tackifiers, surface lubricants, leveling agents, antioxidants, corrosion inhibitors, light stabilizers, ultraviolet absorbers, and polymerization inhibition. Additives according to the use of various conventionally known additives such as additives, silane coupling agents, inorganic or organic fillers, powders such as metal powders and pigments, particles, and foils. I can do it. In particular, as the antistatic agent, an ionic compound or an ionic liquid compatible with the copolymer polymer can be used.
In the pressure-sensitive adhesive composition of this embodiment, secondary hydroxyl groups and / or tertiary hydroxyl groups remain, and these hydroxyl groups have lone electron pairs. The lone electron pair expresses polarity in the pressure-sensitive adhesive composition of the present embodiment. Therefore, for example, when an ionic compound or an ionic liquid is added, the surface resistance is remarkably reduced, and conductivity can be expressed.

"Production method of pressure-sensitive adhesive composition"
Examples of the method for producing the pressure-sensitive adhesive composition of the present embodiment include, for example, components A to C which are raw materials for the copolymer polymer and various monomers of component D as necessary, ethyl acetate, toluene, acetone, hexanes, A copolymer polymer is prepared by mixing in an organic solvent having a boiling point of about 120 ° C. or less, such as ketones and alcohols, and adding a polymerization initiator to cause a monomer to undergo a polymerization reaction. The obtained copolymer polymer is obtained in a state dissolved in an organic solvent or in a state swollen in an organic solvent.
Next, a crosslinking agent and other additives are added to the organic solvent containing the copolymer polymer, and then the copolymer polymer is crosslinked by aging. In this way, a pressure-sensitive adhesive composition is obtained.
The obtained pressure-sensitive adhesive composition becomes, for example, a pressure-sensitive adhesive layer by drying after coating on a substrate. The crosslinking by aging may be performed after the pressure-sensitive adhesive composition is applied on the substrate.

"Optical members"
The optical member of the present embodiment is formed by forming the pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition as described above on one side or both sides of the optical sheet so that the thickness is usually 3 to 200 μm, preferably about 10 to 100 μm. is there. The pressure-sensitive adhesive layer can be formed by a method in which the pressure-sensitive adhesive composition is directly applied to the optical sheet, a method in which a pressure-sensitive adhesive layer is once formed on another substrate (for example, a release liner), or the like.

  As a method for coating and forming the adhesive layer, known methods used for the production of adhesive tapes are used, and specific examples include roll coating, gravure coating, reverse coating, roll brushing, spray coating, air knife coating, and die coating. It is done.

  As the optical sheet, those used in the production of various display devices and the like are used, and the type thereof is not particularly limited, but includes, for example, a polarizing plate, a retardation plate, a brightness enhancement plate, or an antiglare sheet. The optical sheet is a laminate of two or more optical materials such as a laminate of a polarizing plate and a retardation plate, a laminate of retardation plates, a laminate of a polarizing plate and a brightness enhancement plate or an antiglare sheet. May be. As the polarizing plate, for example, a polyvinyl alcohol polarizing plate film as a base material and a protective layer provided thereon can be used.

The adhesive strength of the adhesive layer (adhesive composition) formed on the optical sheet is preferably about 1 (N / 25 mm) to 15 (N / 25 mm), and about 5 (N / 25 mm) to 10 (N / 25 mm). Is more preferable. When the adhesive strength is in the range of 1 to 15 (N / 25 mm), the adhesive strength of the adhesive layer of the optical member is sufficient. In addition, adhesive strength is calculated | required by measuring according to the adhesive tape and the adhesive sheet test method of JISZ0237. Specifically, the optical member provided with the pressure-sensitive adhesive layer is allowed to stand for 7 days in an atmosphere of 23 ° C. and 50% RH, then cut to a width of 25 mm, and bonded to a glass plate, for example, and 50 ° C. × 5 kg / cm ^2. × 20 minutes autoclave treatment, then, using a tensile tester, measure the adhesive strength according to JIS Z0237 at 23 ° C, 50% RH atmosphere at 90 ° peel angle and 0.3m / min peel rate. And the adhesive strength may be evaluated.

As described above, according to the pressure-sensitive adhesive composition of this embodiment, the heat resistance, heat and humidity resistance and reworkability can be improved at the same time. Further, according to the pressure-sensitive adhesive composition of the present embodiment, an antistatic function can be imparted by adding an ionic compound or an ionic liquid that is compatible with the copolymer polymer.
Moreover, according to the optical member of this embodiment, since the adhesive layer which consists of said adhesive composition is provided, the rework property, heat resistance, and heat-and-moisture resistance of an optical member can be improved.

(Pressure-sensitive adhesive composition and optical member of Example 1)
94.5 parts by mass of butyl acrylate (A component), 0.5 part by mass of 4-hydroxyl butyl acrylate as a primary hydroxyl group-containing monomer (B component), and 2-hydroxyl as a secondary hydroxyl group-containing monomer (C component) 5 parts by mass of propyl acrylate and 140 parts by mass of ethyl acetate as a solvent were charged into a flask equipped with a reflux condenser and a stirrer and heated to 65 ° C. while performing nitrogen substitution. Next, 0.075 parts by mass of AIBN was added as a polymerization initiator, and a polymerization reaction was performed over 6 hours while maintaining 65 ° C. After completion of the polymerization reaction, 260 parts by mass of ethyl acetate was further added to adjust the viscosity, and the mixture was cooled to room temperature.
Next, 0.25 mass of trimethylolpropane / tolylene diisocyanate trimer adduct (isocyanate-type cross-linking agent, manufactured by Nippon Polyurethane Industry Co., Ltd., trade name Coronate L) as a cross-linking agent is added to the cooled solution. Furthermore, 0.1 parts by mass of 3-glycidoxypropylmethyldiethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name Shin-Etsu Silicone KBM-403) as a silane coupling agent is added and mixed thoroughly. Thus, a pressure-sensitive adhesive composition solution was obtained.
The obtained pressure-sensitive adhesive composition solution was applied to a peeled PET film (trade name: MRF38, manufactured by Mitsubishi Chemical Polyester Film Co., Ltd.) so that the thickness after drying was 25 μm, and aged for 7 hours at room temperature for crosslinking reaction. The pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition was formed. And Example 1 provided with the adhesion layer which consists of an adhesive composition of the composition shown in Table 1 by bonding together an adhesion layer and exfoliation PET film to a polarizing plate (Corporation Mine Imaging Co., Ltd. make, brand name MLPH). The optical member was manufactured.

(Pressure-sensitive adhesive compositions and optical members of Examples 2 to 6)
Butyl acrylate (component A), primary hydroxyl group-containing monomer (component B) as 4-hydroxyl butyl acrylate, secondary hydroxyl group-containing monomer (component C) as 2-hydroxylpropyl acrylate, acrylic acid ester having a functional group such as hydroxyl group, and / Or 100 parts by weight of acrylic acid ester (D component) appropriately mixed with 140 parts by weight of ethyl acetate as a solvent, charged in a flask equipped with a reflux and a stirrer, and nitrogen replacement Heated to 65 ° C. Next, 0.075 parts by mass of AIBN was added as a polymerization initiator, and a polymerization reaction was performed over 6 hours while maintaining 65 ° C. After completion of the polymerization reaction, 260 parts by mass of ethyl acetate was further added to adjust the viscosity, and the mixture was cooled to room temperature.
Next, trimethylolpropane / tolylene diisocyanate trimer adduct (isocyanate-type crosslinking agent, manufactured by Nippon Polyurethane Industry Co., Ltd., trade name Coronate L) is added as a crosslinking agent to the cooled solution. Further, 3-glycidoxypropylmethyldiethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name Shin-Etsu Silicone KBM-403) was added as a silane coupling agent. 1-hexyl-3-methylimidazolium hexafluorophosphate (manufactured by Tokyo Chemical Industry Co., Ltd.) was added and mixed well to obtain a pressure-sensitive adhesive composition solution.
The obtained pressure-sensitive adhesive composition solution was applied to a peeled PET film (trade name: MRF38, manufactured by Mitsubishi Chemical Polyester Film Co., Ltd.) so that the thickness after drying was 25 μm, and aged for 7 hours at room temperature for crosslinking reaction. The pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition was formed. And Example 2 provided with the adhesion layer which consists of an adhesive composition of the composition shown in Table 1 by bonding together an adhesion layer and exfoliation PET film to a polarizing plate (Corporation Mine Imaging Co., Ltd. make, brand name MLPH). ˜6 optical members were produced.

(Pressure-sensitive adhesive compositions and optical members of Comparative Examples 1 to 3)
As a solvent, 100 parts by mass of 4-hydroxybutyl acrylate as a primary hydroxyl group-containing monomer (B component) and 2-hydroxyl propyl acrylate as a secondary hydroxyl group-containing monomer (C component) are mixed as appropriate. While adding 140 parts by mass of ethyl acetate, as a cross-linking agent, trimethylolpropane / tolylene diisocyanate trimer adduct (isocyanate-type cross-linking agent, manufactured by Nippon Polyurethane Industry Co., Ltd., trade name Coronate L) and silane Except that 3-glycidoxypropylmethyldiethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name Shin-Etsu Silicone KBM-403) was appropriately added as a coupling agent, the same as in Examples 2-6 above, Comparative example 1 provided with the adhesion layer which consists of an adhesive composition of the composition shown in Table 1 The third optical member was produced.

  The obtained optical member was measured for heat resistance, heat and humidity resistance, light leakage, reworkability, and surface resistance. The results are also shown in Table 1. The procedure of each performance test is as follows.

<Test method for performance test>
"Heat-resistant"
The optical member was cut into a size of 120 mm (polarizing plate MD direction) × 60 mm, bonded to a glass plate, and autoclaved at 50 ° C. × 5 kg / cm ² × 20 minutes. Thereafter, the appearance after leaving for 120 hours in an 80 ° C. atmosphere was observed, and the presence or absence of foaming, floating or peeling was evaluated. When there was no foaming or the like, it was considered good.
"Heat and heat resistance"
After the autoclave treatment, the appearance after standing was observed and the presence or absence of foaming, floating, or peeling was evaluated in the same manner as the above heat resistance test except that it was left for 120 hours in an atmosphere of 60 ° C. and 90% RH. . When there was no foaming or the like, it was considered good.

"Light leakage"
The optical member is cut into a size of 120 mm (polarizing plate MD direction) × 60 mm and 120 mm (polarizing plate TD direction) × 60 mm, and bonded to overlap both surfaces of the glass plate, and 50 ° C., 5 kg / cm ² × The autoclave process was performed for 20 minutes. Thereafter, the appearance after leaving for 120 hours in an 80 ° C. atmosphere was observed. A case where no light leakage was observed was judged as good, and a case where light leakage was observed was judged as defective.

"Reworkability (adhesive strength and peeled state)"
The optical member was cut to a width of 25 mm, bonded to a glass plate, and autoclaved at 50 ° C. × 5 kg / cm ² × 20 minutes. Then, using a tensile tester, in accordance with JIS Z0237 (adhesive tape / adhesive sheet test method) in an atmosphere of 23 ° C. and 50% RH under conditions of a peeling angle of 90 degrees and a peeling speed of 0.3 m / min. Force measurements were taken.
Moreover, at the time of the said adhesive force measurement, the peeling state was observed and the presence or absence of transfer of the adhesion layer with respect to a glass substrate was evaluated.

"Surface resistance"
The surface resistance value of the adhesive layer of the optical member was measured using a microelectrometer (manufactured by Kawaguchi Electric Co., Ltd.) in an atmosphere of 20 ° C. and 50% RH.

The meanings of the abbreviations in Table 1 are as follows.
BA: butyl acrylate, 4HBA: 4-hydroxyl butyl acrylate, 2HPA: 2-hydroxylpropyl acrylate, AA: acrylic acid, antistatic agent: 1-hexyl-3-methylimidazolium hexafluorophosphate (Tokyo Chemical Industry Co., Ltd.) Made)

  As shown in Table 1, the optical members of Examples 1 to 6 were superior in heat resistance, moist heat resistance, light leakage, and reworkability as compared with Comparative Examples 1 to 3. In the optical member of Example 6, the surface resistance of the adhesive layer was relatively low, and it was possible to impart antistatic performance. In Comparative Examples 1 and 2, since the C component was not added, the heat resistance, heat and humidity resistance, and light leakage were deteriorated. In Comparative Example 3, gelation of the solution occurred during polymerization of the pressure-sensitive adhesive composition, and various tests could not be performed.

Claims (4)

Acrylic acid esters and / or methacrylic acid ester, and primary hydroxyl group-containing monomer having a primary hydroxyl group in the molecule, and secondary hydroxyl group-containing monomer over having secondary hydroxyl group in the molecule is at least copolymerized, and A pressure-sensitive adhesive composition comprising a copolymer polymer crosslinked by a crosslinking agent,
The mixing ratio of the acrylic acid ester and / or methacrylic acid ester in the copolymer polymer is 88 mass% to 97.5 mass%, and the mixing ratio of the primary hydroxyl group-containing monomer having a primary hydroxyl group in the molecule. is 0.5 wt% to 2 wt%, the mixing ratio of secondary hydroxyl group-containing monomer over having secondary hydroxyl group in the molecule are two% to 10% by mass,
The acrylic ester and / or methacrylic ester is an acrylate and / or methacrylate having 1 to 14 carbon atoms of the esterified substituent,
The primary hydroxyl group-containing monomer includes 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) ) Acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, (4-hydroxymethylcyclohexyl) methyl acrylate,
The secondary hydroxyl group-containing monomer includes 2-hydroxypropane (meth) acrylate, 2-hydroxybutane (meth) acrylate, 3-hydroxybutane (meth) acrylate, 2-hydroxy-1-ethylpropane (meth) acrylate, 2-hydroxy Hexane (meth) acrylate, 2-hydroxycyclohexane (meth) acrylate, 2-hydroxypentane (meth) acrylate, 3-hydroxy-2-ethylhexane (meth) acrylate, 3-chloro-2-hydroxypropyl (meth) acrylate Yes,
The crosslinking agent includes butylene diisocyanate, hexamethylene diisocyanate, cyclopentylene diisocyanate, cyclohexylene diisocyanate, isophorone diisocyanate, 4,4′-diphenylmethane diisocyanate, xylylene diisocyanate, trimethylolpropane / tolylene diisocyanate trimer adduct, Methylolpropane / hexamethylene diisocyanate trimer adduct, isocyanurate of hexamethylene diisocyanate, tolylene diisocyanate, hydrogenated tolylene diisocyanate, tolylene diisocyanate adduct of trimethylol propane, xylylene diisocyanate adduct of trimethylol propane, triphenyl Methane triisocyanate, methylenebis (4-phenylmethane) It is a polyisocyanate,
The compounding ratio of the crosslinking agent is 0.05 to 5 parts by mass with respect to 100 polymer parts of the copolymer . And a primary hydroxyl group-containing monomer, claim mass ratio of secondary hydroxyl-containing monomer chromatography [(2 hydroxyl group-containing monomer chromatography) / (primary hydroxyl group-containing monomer), characterized in that it is 2 or more 2. The pressure-sensitive adhesive composition according to 1.   The acrylic copolymer and / or methacrylic ester having a functional group of any one of a carboxyl group, an epoxy group, and an amine group is contained in the copolymer polymer. 2. The pressure-sensitive adhesive composition according to 2.   An optical member, wherein the pressure-sensitive adhesive composition according to any one of claims 1 to 3 is applied to one surface or both surfaces of an optical sheet.