KR100702732B1 - Adhesive composition, adhesive optical member and liquid crystal display device using the same - Google Patents

Abstract

An object of the present invention is to provide a pressure-sensitive adhesive composition having excellent adhesion to the adherend and adhesion durability even under high temperature and high humidity conditions, and having a responsiveness to stretching of the adherend, and the present invention provides an acrylic pressure-sensitive adhesive and the acrylic pressure-sensitive adhesive 100 The said subject is solved by setting it as the adhesive composition containing 0.005-20 weight part urethane elastomer per weight part.

Description

Adhesive composition, adhesive optical functional member and liquid crystal display device using the same {ADHESIVE COMPOSITION, ADHESIVE OPTICAL MEMBER AND LIQUID CRYSTAL DISPLAY DEVICE USING THE SAME}

The present invention relates to an adhesive composition, an adhesive optical functional member and a liquid crystal display device using the same. More specifically, the present invention provides a pressure-sensitive adhesive composition having excellent adhesion to the adherend and adhesion durability even under high temperature and high humidity conditions, and having a responsiveness to stretching of the adherend, the adhesive optical provided with the pressure-sensitive adhesive composition layer on a polarizing plate or the like. It relates to a liquid crystal display device formed by disposing an optical functional member such as a polarizing plate on both sides of the liquid crystal cell through the functional member and the pressure-sensitive adhesive composition layer.

Conventionally, in articles to which adherends adhere to each other via an adhesive layer, there is a problem that the adherend may peel off at an end because the adhesive durability of the adhesive is insufficient under high temperature and high humidity conditions.

In order to solve this problem, means such as increasing the molecular weight of the resin component constituting the pressure-sensitive adhesive or increasing the degree of crosslinking have been known. However, in such an adhesive, although adhesive durability is improved, when used for a large elastic adherend, the adhesive cannot respond to the expansion and contraction of the adherend, causing various problems.

On the other hand, the liquid crystal display device generally includes two transparent electrode substrates on which an alignment layer is formed, with the alignment layer inward so as to have a predetermined gap through the spacer, and the liquid crystal cell is formed by sealing the periphery thereof. At the same time, the liquid crystal material is sandwiched between the electrode substrates, and an optical function member such as a polarizing plate is disposed on the outer surface of the two electrode substrates via an adhesive layer.

Although the optical functional member used for such a liquid crystal display element is easy to expand and contract under high temperature, high humidity conditions, an adhesive layer cannot fully cope with the expansion and contraction of this optical functional member, and various problems are easy to arise. For example, when the optical functional member is a polarizing plate, the internal stress generated in the polarizing plate causes distortion in the absorption axis around the polarizing plate, so that the light transmittance is changed and so-called "white emission" easily occurs. Lose.

In order to solve such a problem, conventionally, the method which adds a plasticizer and a liquid paraffin to an adhesive, softens to an appropriate grade, and gives stress relaxation property (for example, Japanese Patent Application Laid-Open No. 5 (1993) No. 45517). And Japanese Patent Application Laid-Open No. 9 (1997) No. 137143).

However, in these plasticizers and adhesives containing liquid paraffin, a plasticizer or liquid paraffin that is bleeded out when the plasticizer or liquid paraffin bleeds out or is peeled off when the polarizing plate is peeled off. Problems such as contamination may occur.

The present invention has excellent adhesion to the adherend and adhesion durability even under high temperature and high humidity conditions in such a situation, and has an adhesive composition having a responsiveness to stretch of the adherend, and an adhesive optical function provided with the adhesive composition layer on a polarizing plate. An object of the present invention is to provide a liquid crystal display device formed by disposing an optical function member such as a polarizing plate on both sides of a liquid crystal cell through the member and the pressure-sensitive adhesive composition layer.

As a result of intensive studies to achieve the above object, the present inventors have found that the object can be achieved by making the pressure-sensitive adhesive composition in which a specific ratio of urethane elastomer is added to the acrylic pressure-sensitive adhesive. The present invention has been completed based on these findings. That is, the present invention

(1) an adhesive composition comprising an acrylic pressure sensitive adhesive and 0.005 to 20 parts by weight of a urethane elastomer per 100 parts by weight of the acrylic pressure sensitive adhesive,

(2) the pressure-sensitive adhesive composition of (1), wherein the polyurethane elastomer has a 100% modulus of 1 to 6 MPa;

(3) the pressure-sensitive adhesive composition of the above (1) or (2), wherein the acrylic pressure-sensitive adhesive is a weight average molecular weight of 500,000 to 2 million (meth) acrylic acid ester homopolymer or copolymer;

(4) the pressure-sensitive adhesive composition of the above (1) or (2), wherein the acrylic pressure-sensitive adhesive consists of a weight-average molecular weight 500,000 to 2 million (meth) acrylic acid ester copolymer having a crosslinking point and a crosslinking agent,

(5) an adhesive optical functional member, characterized in that a layer made of the pressure-sensitive adhesive composition of any one of (1) to (4) is provided on one or both surfaces of the optical functional member,

(6) the adhesive optical functional member of (5), wherein the optical functional member is a polarizing plate, and

(7) It is to provide a liquid crystal display device formed by disposing an optical function member on both sides of a liquid crystal cell through a layer made of the pressure-sensitive adhesive composition of any one of (1) to (4).

As an acrylic adhesive in the adhesive composition of this invention, a (meth) acrylic acid ester homopolymer or copolymer is used preferably.

The weight average molecular weight of these (meth) acrylic acid ester homopolymers or copolymers is preferably 500,000 or more in order to obtain necessary adhesion or adhesion durability, and 2 million or less in order to obtain responsiveness to the stretching of the required adherend. That is, the weight average molecular weight of the (meth) acrylic acid ester homopolymer or copolymer is preferably in the range of 500,000 to 2 million, and particularly preferably in the range of 800,000 to 1.8 million.

In addition, the said weight average molecular weight is the value measured by the gel permeation chromatography (GPC) method using polyethylene as a reference material.

As a monomer used for the said (meth) acrylic acid ester homopolymer or a monomer used as a main component of a (meth) acrylic acid ester copolymer, the (meth) acrylic-acid alkylester whose C1-C20 alkyl group of the alcohol component which forms ester is Preferably, for example, methyl (meth) acrylate, ethyl (meth) acrylate, (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, pentyl (meth) acrylate, (meth) Hexyl acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, myristyl (meth) acrylate, (meth) acrylic acid Palmityl, (meth) acrylic acid stearyl, etc. are mentioned. These monomers may be used independently or may be used in combination of 2 or more type.

On the other hand, as a comonomer used for a (meth) acrylic acid ester copolymer, (meth) acrylic acid 2-hydroxyethyl, (meth) acrylic acid 2-hydroxypropyl, (meth) acrylic acid 3-hydroxypropyl, (Meth) acrylic-acid hydroxy alkyl esters, such as 2-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate; Acrylamides such as acrylamide, methacrylamide, N-methyl acrylamide, N-methyl methacrylamide, N-methylol acrylamide, and N-methylol methacrylamide; (Meth) acrylic acid monoalkyl aminoalkyl esters, such as (meth) acrylic acid monomethyl aminoethyl, (meth) acrylic acid monoethyl aminoethyl, (meth) acrylic acid monomethyl aminopropyl, and (meth) acrylic acid monoethyl aminopropyl; (Meth) acrylic acid dialkyl aminoalkyl esters; Ethylenically unsaturated carbon acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, citraconic acid, maleic anhydride and acid anhydrides thereof; Vinyl esters such as vinyl acetate and vinyl propionate; Olefins such as ethylene, propylene and isobutylene; Halogenated olefins such as vinyl chloride and vinylidene chloride; Styrene monomers such as styrene and α-methylstyrene; Diene monomers such as butadiene, isoprene and chloroprene; Nitrile monomers such as acrylonitrile and methacrylonitrile; N, N- dialkyl substituted acrylamide, such as N, N- dimethyl acrylamide and N, N- dimethyl methacrylamide, etc. are mentioned. These comonomers may be used independently or may be used in combination of 2 or more type.

In the (meth) acrylic acid ester copolymer, the content of the unit derived from the comonomer is usually selected from 0.1 to 20% by weight, preferably from 0.5 to 10% by weight.

In the pressure-sensitive adhesive composition of the present invention, by using a (meth) acrylic acid ester copolymer having a comonomer having a crosslinkable functional group as a copolymerization component and by including a crosslinking agent, the cohesive force can be increased to improve adhesion to the adherend and adhesion durability. .

As a comonomer which has a crosslinkable functional group in this case, (meth) acrylic-acid hydroxyalkyl ester, acrylamide, (meth) acrylic-acid monoalkyl aminoalkyl ester, ethylenically unsaturated carboxylic acid, or its acid anhydride in the said comonomer is preferable. .

On the other hand, as a crosslinking agent, a polyisocyanate compound, an epoxy compound, a metal chelate compound, a metal alkoxide, a metal salt, an amine compound, a hydrazine compound, an aldehyde compound, etc. are mentioned.

Examples of the polyisocyanate compound include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate and xylylene diisocyanate, aliphatic polyisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate and the like. Alicyclic polyisocyanate; Examples of the epoxy compound include sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, glycerol polyglycidyl ether, and trimethylolpropane polyglycidyl ether. , Resorcinol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, hydrogenated bisphenol A diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene Glycol diglycidyl ether and the like.

Examples of the urethane elastomer in the pressure-sensitive adhesive composition of the present invention include urethane elastomers, modified urethane elastomers, and the like. As a modified urethane elastomer, Michael addition type urethane urea resin containing the structure which introduce | transduced various functional groups by Michael addition of unsaturated compound to a polyamino compound as a component is preferable.

Urethane elastomer is comprised from the soft segment which has a polymer polyol as a main component, and the hard segment which consists of polyisocyanate, such as diisocyanate, and a chain extender. Examples of the urethane elastomer include thermoplastic urethane elastomers obtained by polymerizing polyisocyanates such as polymer polyol and diisocyanates such as tolylene diisocyanate (TDI) and 4,4'-diphenylmethane diisocyanate (MDI) in an organic solvent. The dilute one-component thing or the two-component thing which adds and hardens further, before apply | coating a polyisocyanate to another system is mentioned. In addition, a moisture hardening type hot melt urethane elastomer in which isocyanate is reacted with moisture in the air may be used.

The urethane elastomer preferably has a 100% modulus of 1 MPa or more from the viewpoint of proper adhesion to the adherend, damage to the adherend when peeling, and contamination, and from the viewpoint of appropriate adhesion to the adherend and adhesion to the adherend. It is preferred that the 100% modulus is 6 MPa or less.

In the pressure-sensitive adhesive composition of the present invention, the amount of urethane elastomer to be blended is required to be in the range of 0.005 to 20 parts by weight per 100 parts by weight of the acrylic pressure-sensitive adhesive, and if it is less than 0.005 parts by weight, the correspondence to the stretching of the required adherend is not obtained. If it exceeds, the adhesive will whiten from the problem of compatibility of an adhesive composition.

The range of the preferred compounding amount of the urethane elastomer can not be determined collectively because the type of the acrylic adhesive, that is, the (meth) acrylic acid ester polymer depends on the homopolymer or the copolymer, the type of the functional group, the presence or absence of a crosslinking agent, Preferably it is the range of 0.01-15 weight part per 100 weight part of acrylic adhesive.

In the pressure-sensitive adhesive composition of the present invention, various known additives such as tackifiers, plasticizers, antioxidants, ultraviolet absorbers, heat stabilizers, fillers, silane coupling agents, etc. may be appropriately used as required, within the scope of not impairing the object of the present invention. It can be contained.

Next, the adhesive optical functional member of the present invention is provided with a layer (hereinafter, referred to as an "adhesive layer") made of the pressure-sensitive adhesive composition of the present invention on both or one side of the optical functional member.

An adhesive layer may be formed by apply | coating an adhesive composition to the both surfaces or one side of an optical function member, and is formed by apply | coating an adhesive composition to the peeling process surface of the peeling process which peeled, and bonding to both surfaces or one side of an optical function member. can do.

The pressure-sensitive adhesive composition (hereinafter, abbreviated as "adhesive liquid") may be any of an organic solvent system, an emulsion system, and a solventless system.

As an organic solvent used for an organic solvent adhesive liquid, toluene, xylene, methanol, ethanol, isobutanol, n-butanol, acetone, methyl ethyl ketone, ethyl acetate, tetrahydrofuran, etc. are mentioned, for example. These may be used individually by 1 type, or may be used in combination of 2 or more type.

It is preferable to prepare an adhesive liquid so that solid content concentration may be in the range of 10-50 weight% using these organic solvents for ease of application | coating.

Application of the pressure-sensitive adhesive may be carried out according to a conventionally known coating method such as a bar coating method, a roll coating method, a knife coating method, a roll knife coating method, a die coating method, a gravure coating method, an air doctor coating method or a doctor blade coating method. Can be.

The thickness of the pressure-sensitive adhesive layer is usually preferably in the range of 5 to 150 µm, particularly preferably in the range of 10 to 100 µm.

As an optical function member used for the adhesive optical function member of this invention, a polarizing plate, an antireflection plate, a phase difference plate, a viewing angle expansion film, etc. are mentioned, for example, A polarizing plate is especially suitable among these.

As said polarizing plate, the thing which covered the both surfaces of the polarizing film formed by extending | stretching orienting a transparent polymer film to the uniaxial direction and making adsorption orientation of iodine and / or a dichroic dye etc. into an orientation molecule | interval gap is used with a protective film. Most of the transparent polymer film is a polyvinyl alcohol film, and a triacetyl cellulose film is widely used as a protective film.                     

As this polarizing plate, an iodine type polarizing film, a dye type polarizing film, a color polarizing film, a polyvinylene polarizing film, an infrared polarizing film, an ultraviolet polarizing film, etc. were used as a polarizing film, for example, There is no restriction | limiting in particular in this invention, Even thing can use.

In addition, the polarizing plate is used for liquid crystal display devices (digital clocks, electronic calculators, measuring instrument displays, wall-mounted TVs, optical defect detectors, etc.), reflection light removal (sunglasses, photographic films, etc.), light quantity adjustment (photo filters, Density variable filters, etc.), applications as optical locks (for automobile headlights, anti-glare, etc.), polarization interference devices (distortion checkers, stage lighting, advertising displays, etc.) The polarizing plate of a use can also be used. Among these uses, the polarizing plate for liquid crystal display elements is preferably used.

In the liquid crystal display device of the present invention, the optical function member is disposed on both sides of the liquid crystal cell through the pressure-sensitive adhesive composition layer of the present invention.

As an optical function member, the optical function member used for the said adhesive optical function member is mentioned, Among these, a polarizing plate is especially suitable.

What arrange | positioned the some optical function member on the surface of a liquid crystal cell can be bonded together through the adhesive composition layer of this invention in all the optical function members. Of course, it is not necessary to bond through the adhesive composition layer of this invention in all the optical function members, It is preferable to perform at least bonding of a polarizing plate through the adhesive composition layer of this invention.                     

For example, in the case of providing a retardation plate between the liquid crystal cell and the polarizing plate to compensate for birefringence, at least bonding of the retardation plate and the polarizing plate is preferably performed through the pressure-sensitive adhesive composition layer of the present invention. You may use for joining of a phase difference plate.

Next, although an Example demonstrates this invention still in detail, this invention is not limited at all by these examples.

Example 1

100 parts by weight of an acrylic ester copolymer having a weight average molecular weight of 1.7 million consisting of 99% by weight of butyl acrylate units and 1% by weight of 4-hydroxybutyl acrylate, a weight average molecular weight of 100,000, and a 100% modulus of 2 MPa urethane elastomer , Trade name: HP-H) 0.2 parts by weight of a crosslinking agent (manufactured by Souken Chemical Co., Ltd., product name: TD-75) consisting of 10 parts by weight of a polyisocyanate compound, and a pressure-sensitive adhesive solution having a solid content of 30% by weight It was made.

This pressure-sensitive adhesive solution was coated on a peeled surface of a polyethylene terephthalate peeled sheet (manufactured by Lintec, trade name: SP-PET 3811) having a silicone-based peeling treatment on one surface with a knife coater, dried at 90 ° C for 1 minute, and 25 µm thick. An adhesive layer was formed.

Then, the polarizing plate [three-layer laminated body of a triacetyl cellulose film / polyvinyl alcohol film / triacetyl cellulose film (having a viewing angle enlargement function, thickness 200 micrometers)] was laminated on the said adhesive layer, and the polarizing plate with an adhesive layer was obtained.

Example 2

It carried out similarly to Example 1 except having changed the urethane elastomer compounding quantity from 10 weight part to 1 weight part (solid content content of an adhesive solution is 30 weight%) in an adhesive solution, and obtained the polarizing plate with an adhesive layer.

Example 3

Except having changed the urethane elastomer compounding quantity from 10 weight part to 0.05 weight part in the adhesive solution (solid content content of an adhesive solution is 30 weight%), it carried out similarly to Example 1 and obtained the polarizing plate with an adhesive layer.

Comparative Example 1

Except having changed the urethane elastomer compounding quantity from 10 weight part to 50 weight part in the adhesive solution (solid content content of an adhesive solution is 30 weight%), it carried out similarly to Example 1 and obtained the polarizing plate with an adhesive layer.

Comparative Example 2

Except having changed the urethane elastomer compounding quantity from 10 weight part to 0.0005 weight part in the adhesive solution (solid content content of an adhesive solution is 30 weight%), it carried out similarly to Example 1 and obtained the polarizing plate with an adhesive layer.

Comparative Example 3

In the adhesive solution, it carried out similarly to Example 1 except having not mix | blended the urethane elastomer (solid content content of an adhesive solution is 30 weight%), and obtained the polarizing plate with an adhesive layer.

About the polarizing plate with an adhesive layer obtained by Examples 1-3 and Comparative Examples 1-3, durability and brightness difference (DELTA) L ^* were measured in accordance with the following method, and the result is shown in Table 1.

(1) durability

After peeling off the release sheet, a 15-inch (233 mm × 309 mm) polarizing plate with a pressure-sensitive adhesive layer was peeled off, and then attached to a glass plate, and left for 120 hours at 80 ° C. dry or 60 ° C. 90% RH, and then visually observed. The following criteria evaluated.

○: no exfoliation

×: Exfoliation is present

(2) brightness difference ΔL ^*

A 15-inch (233 mm × 309 mm) adhesive layer polarizing plate with cross nicol was peeled off on both sides of the alkali-free glass plate after peeling off the sheet, and the plate was left to stand at 80 ° C and dry environmental conditions for 120 hours. The brightness in the range of 1 cm and the brightness in the center were measured, and the difference between the average value of the brightness of each side and the brightness value in the center of a polarizing plate was calculated | required.

Brightness was measured on condition of 23 degreeC65% RH using the measuring apparatus (MCPD-2000) made from Otsuka Electronics.

It shows that the correspondence of an adhesive layer is bad, so that lightness difference (DELTA) L ^* is large.

Durability (120 hours) Brightness Difference (ΔL ^* ) 80 ℃ dry 60 ° C, 90% RH 80 ℃ dry, 120 hours Example 1 ○ ○ 0.34 Example 2 ○ ○ 0.56 Example 3 ○ ○ 2.89 Comparative Example 1 × × 0.24 Comparative Example 2 ○ ○ 5.83 Comparative Example 3 ○ ○ 6.09

The pressure-sensitive adhesive composition of the present invention has excellent adhesion with the adherend under high temperature and high humidity conditions, excellent adhesion durability, and responsiveness to expansion and contraction of the adherend. It is suitably used for bonding.

The liquid crystal display device of the present invention by disposing the optical functional member on the surface of the liquid crystal cell using the pressure-sensitive adhesive composition has excellent adhesion with the liquid crystal cell even under high temperature and high humidity conditions, excellent adhesion durability, and expansion and contraction of the optical functional member. It is difficult to produce various problems, for example, a so-called "white emission" phenomenon in a polarizing plate because of its responsiveness.

Claims (9)

An adhesive composition comprising an acrylic pressure-sensitive adhesive and a urethane elastomer of 0.005 to 20 parts by weight per 100 parts by weight of the acrylic pressure-sensitive adhesive. The method of claim 1, Pressure-sensitive adhesive composition, characterized in that 100% modulus of the urethane elastomer is 1 ~ 6MPa. The method of claim 1, The pressure-sensitive adhesive composition, wherein the acrylic pressure-sensitive adhesive is a weight average molecular weight of 500,000 to 2 million (meth) acrylic acid ester homopolymer or copolymer. The method of claim 2, The pressure-sensitive adhesive composition, wherein the acrylic pressure-sensitive adhesive is a weight average molecular weight of 500,000 to 2 million (meth) acrylic acid ester homopolymer or copolymer. The method of claim 1, The pressure-sensitive adhesive composition, wherein the acrylic pressure-sensitive adhesive comprises a weight-average molecular weight 500,000 to 2 million (meth) acrylic acid ester copolymer having a crosslinking point and a crosslinking agent. The method of claim 2, The pressure-sensitive adhesive composition, wherein the acrylic pressure-sensitive adhesive comprises a weight-average molecular weight 500,000 to 2 million (meth) acrylic acid ester copolymer having a crosslinking point and a crosslinking agent. The adhesive optical function member which provided the layer which consists of the adhesive composition in any one of Claims 1-6 on one side or both sides of an optical function member. The adhesive optical function member which provided the layer which consists of an adhesive composition in any one of Claims 1-6 on one side or both sides of a polarizing plate. A liquid crystal display device comprising the optical functional member disposed on both sides of a liquid crystal cell through a layer made of the pressure-sensitive adhesive composition according to any one of claims 1 to 6.