KR101991974B1 - Adhesive composition - Google Patents

Abstract

The present invention relates to a pressure-sensitive adhesive composition, and more particularly to a pressure-sensitive adhesive composition comprising an acrylic copolymer having a weight average molecular weight (Mw) of 500,000 or more and a solvent, wherein the acrylic copolymer has a carboxyl group- And the viscosity of the pressure-sensitive adhesive composition is lower than the viscosity of the pressure-sensitive adhesive composition by using a small amount of solvent as compared with the prior art, To a pressure-sensitive adhesive composition capable of improving coating properties without defects, shortening a curing time, and maintaining light-shielding properties equal to or higher than those of the prior art.

Description

[0001] ADHESIVE COMPOSITION [0002]

The present invention relates to a pressure-sensitive adhesive composition which has improved coating properties, does not cause coating unevenness, and is easy to secure durability.

2. Description of the Related Art Generally, a liquid crystal display device (LCD) is provided with a liquid crystal cell containing a liquid crystal and a polarizer, and a suitable adhesive layer is used to bond the liquid crystal cell. As the pressure-sensitive adhesive, an acrylic pressure-sensitive adhesive based on an acrylic copolymer having excellent tackiness and transparency is often used.

In recent years, as the liquid crystal panel has become larger, the polarizing plate becomes larger, and the residual stress of the protective film and the pressure-sensitive adhesive layer becomes larger. As a result, birefringence becomes large, and light leakage becomes very severe.

As a method for minimizing the light leakage occurring under such residual stress, a material showing birefringence of a positive value under residual stress is added (blended) to the final pressure-sensitive adhesive layer [Korean Patent Laid-Open Publication No. 2003-0069461] A method of copolymerizing monomers to minimize the total birefringence has been proposed (Japanese Laid-Open Patent Publication No. 2002-332468). In addition, a method of controlling birefringence by introducing an acrylic monomer containing an aromatic group has been proposed (Korean Patent No. 948,778).

These methods improve the light leakage phenomenon, but improve the viscosity of a solution containing an acrylic copolymer generated upon copolymerization of a phenyl group-containing monomer, and thus, coating unevenness is likely to occur during coating. In order to improve the gouging irregularity, a large amount of solvent is further added in order to lower the viscosity of the cohesion degree conjugate. In such a coating, there is a large economic loss due to the energy for removing a large amount of solvent and a waste solvent There are disadvantages. Further, when the concentration of the solvent and the viscosity of the pressure-sensitive adhesive are decreased by reducing the use of the solvent, unevenness of the coating may occur and the yield of the product may be lowered and the productivity may be lowered.

As an effort to reduce the amount of the solvent used as described above, a technique of setting the content of the solvent to 80% by weight or less is disclosed.

Korean Patent Publication No. 2012-0073166 discloses an acrylic copolymer having a weight average molecular weight of 250,000 to 85,000 based on the solid content and a viscosity of 1000 to 4000 cP at 23 ° C when the solid content is 30% by weight, a crosslinking agent and a basic crosslinking accelerator ≪ / RTI >

Korean Patent Laid-Open Publication No. 2013-0129226 discloses a composition comprising 30 to 98.9% by weight of an alkyl (meth) acrylate, 1 to 50% by weight of a polymerizable aromatic ring-containing monomer, 0.1 to 20% by weight of a hydroxyl- (Meth) acryl-based polymer having a weight average molecular weight of 300,000 to 1,200,000 and a solvent, wherein the pressure-sensitive adhesive composition for an optical film has a solid content of 20% by weight or more and a solvent content of 80% Lt; / RTI >

The technique disclosed in the above-mentioned Korean Patent Application No. 2001-0073166 and Korean Patent Publication No. 2013-0129226 has an advantage that the amount of solvent used is small and the energy required for removing the solvent can be reduced and the economic loss due to the waste solvent can be reduced. However, the above technique has a problem in that the viscosity is also increased due to an increase in the concentration of the acrylic copolymer, resulting in poor coating performance, resulting in poor coating smoothness (coating unevenness) and the like, resulting in poor productivity. In particular, benzyl acrylate is used as a polymerizable aromatic ring-containing monomer in the above-mentioned technique. In this case, a solution containing a copolymer rather than a monomer containing an ethyleneoxy group such as phenoxyethyl acrylate and phenoxy diethylene glycol acrylate There is a problem in that although the viscosity increase is small, the viscosity is still increased and the coating property is lowered. Further, as mentioned in the above description, when the molecular weight of the acrylic copolymer is reduced in order to reduce the amount of solvent used, there is a problem that the cohesive force of the pressure-sensitive adhesive is lowered and the durability is liable to be defective.

Accordingly, it is an object of the present invention to solve the above-mentioned problems of the prior art, and it is an object of the present invention to reduce the amount of solvent used to increase the solid content while keeping the viscosity low, thereby improving the coating property, Sensitive adhesive composition capable of suppressing the deterioration of durability due to the lowering of the pressure-sensitive adhesive layer.

In order to accomplish the above object, the present invention provides an inkjet ink comprising an acrylic copolymer and a solvent having a weight average molecular weight (Mw in terms of polystyrene) of 500,000 or more, prepared by copolymerizing a monomer containing 5 to 10% by weight of a monomer having a carboxyl group In addition,

A solids content of 25 wt% or more and a viscosity of 1000 cP or less.

Preferably, the acrylic copolymer may have a weight average molecular weight (Mw in terms of polystyrene) of 500,000 to 100.

Preferably, the pressure-sensitive adhesive composition has a solids content of 25 to 30% by weight and a viscosity of 500 to 1000 cP.

The monomer for producing the acrylic copolymer may contain benzyl methacrylate and 4-hydroxybutyl acrylate.

The monomer for producing the acrylic copolymer may contain a (meth) acrylate monomer having an alkyl group having 1 to 12 carbon atoms, benzyl methacrylate, and 4-hydroxybutyl acrylate.

The monomer for producing the acrylic copolymer is preferably a copolymer of 70 to 85% by weight of a (meth) acrylate monomer having an alkyl group having 1 to 12 carbon atoms, 5 to 20% by weight of benzyl methacrylate, 0.1 to 5 By weight and 5 to 10% by weight of a monomer having a carboxyl group.

The acrylic copolymer may further contain a crosslinkable monomer having at least one functional group selected from the group consisting of an amide group and a tertiary amine group.

The pressure-sensitive adhesive composition may further contain a crosslinking agent.

The pressure-sensitive adhesive composition of the present invention can reduce the amount of solvent used, and thus has a low viscosity despite high concentration of solids, so that it has excellent coating properties. Especially, it does not cause defects such as coating wrinkles and can maintain excellent productivity. Can be suppressed, and the amount of the solvent contained in the composition and the amount of the generated waste (CO ₂ ) generated when the solvent is removed can be remarkably reduced.

In addition, the pressure-sensitive adhesive composition of the present invention has an advantage that the curing time is shortened and good light-emitting property can be maintained.

The present invention relates to a pressure-sensitive adhesive composition capable of suppressing a decrease in durability due to a decrease in molecular weight without causing defects such as coated swells by improving the coating property while maintaining a low viscosity even when the content of the solvent is decreased to increase the solid content .

Hereinafter, the present invention will be described in detail.

The pressure-sensitive adhesive composition of the present invention contains an acrylic copolymer having a weight average molecular weight (in terms of polystyrene, Mw) of 500,000 or more, a solid content of 25% by weight or more, and a viscosity of 1000 cP or less.

In the present invention, the solid content and viscosity refer to the physical properties of a pressure-sensitive adhesive composition diluted with a solvent. The solvent is generally used in the art and is not particularly limited as long as it can dissolve the pressure-sensitive adhesive composition. Specifically, ethyl acetate, methyl ethyl ketone, acetone, toluene and the like can be used.

Usually, the pressure-sensitive adhesive composition is diluted with a solvent to suppress the occurrence of defects during coating. The diluted pressure-sensitive adhesive composition has a solids content of about 14% by weight and a viscosity of about 1000 cP, but the pressure-sensitive adhesive composition of the present invention has a solid content of 25% by weight or more, preferably 25 to 30% by weight, To 1000 cP.

As described above, since the pressure-sensitive adhesive composition according to the present invention exhibits high concentration and low viscosity characteristics, the amount of solvent used can be reduced, and in particular, coating defects such as coating wipes do not occur during coating.

The weight average molecular weight (in terms of polystyrene, Mw) of the acrylic copolymer of the present invention is measured by Gel Permeation Chromatography (GPC), and may be 500,000 or more, preferably 500,000 to 1,000,000 . If the weight-average molecular weight is less than 500,000, the coating properties may be improved, but defects may occur in terms of durability.

The acrylic copolymer may be prepared by copolymerizing a monomer containing 5 to 10% by weight of a monomer having a carboxyl group. Preferably, the monomers for preparing the acrylic copolymer may contain benzyl methacrylate and 4-hydroxybutyl acrylate. More preferably, the monomer for producing the acrylic copolymer may contain a (meth) acrylate monomer having an alkyl group having from 1 to 12 carbon atoms, benzyl methacrylate and 4-hydroxybutyl acrylate.

More specifically, the monomers for preparing the acrylic copolymer include 70 to 85% by weight of a (meth) acrylate monomer having an alkyl group having 1 to 12 carbon atoms, 5 to 20% by weight of benzyl methacrylate, 4-hydroxybutyl acrylate 0.1 to 5% by weight, and 5 to 10% by weight of a monomer having a carboxyl group.

Here, (meth) acrylate means acrylate and methacrylate, and the content of each component is based on the solid content.

The (meth) acrylate monomer having an alkyl group having 1 to 12 carbon atoms constitutes the main skeleton of the acrylic copolymer, and includes n-butyl (meth) acrylate, 2-butyl (meth) acrylate, (Meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, pentyl (meth) acrylate, Acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate and lauryl (meth) acrylate. Of these, n-butyl acrylate, 2-ethylhexyl acrylate or a mixture thereof is preferable. These may be used alone or in combination of two or more.

The (meth) acrylate monomer having an alkyl group having 1 to 12 carbon atoms is preferably contained in an amount of 70 to 85% by weight in the monomer for producing an acrylic copolymer.

Although benzyl methacrylate and 4-hydroxybutyl acrylate are known as components used in a pressure sensitive adhesive composition, the present invention is applicable to a pressure sensitive adhesive composition having a high concentration and a low viscosity, I have used it.

The benzyl methacrylate does not have an ethylene glycol group forming a branching bridge and contains a methacryl group to suppress branch bridging. The 4-hydroxybutyl acrylate has a diacrylate form contained in a general crosslinkable monomer , The formation of branch bridges between the copolymers during copolymerization is suppressed, and it is expected that the pressure-sensitive adhesive composition having high concentration and low viscosity, which is the effect of the present invention, can be produced.

In addition, the benzylmethacrylate serves to minimize birefringence to minimize light leakage, and 4-hydroxybutylacrylate serves as a crosslinking monomer (such as shortening of curing time).

The benzyl methacrylate may be contained in the monomer for producing the acrylic copolymer in an amount of 5 to 20% by weight, preferably 8 to 12% by weight. If the content is less than 5% by weight or exceeds 20% by weight, the light leakage preventing performance may be deteriorated.

The 4-hydroxybutylacrylate may be contained in the monomer for producing the acrylic copolymer in an amount of 0.1 to 5% by weight, preferably 0.5 to 2% by weight. If the content is less than 0.1% by weight, the number of functional groups participating in the crosslinking will be small and the cohesive force will be insufficient. In this case, defective bubbles may easily occur. If the content exceeds 5% by weight, have.

According to the present invention, a monomer having a carboxyl group is included as a monomer for producing an acrylic copolymer. When the monomer having a carboxyl group is used for copolymerization of an acrylic copolymer, strong hydrogen bonds are formed in the copolymer, thereby causing molecular weight aggregation in the polymer, and at the same time, increase in viscosity due to entanglement of the polymers is suppressed, And low viscosity. In particular, if the molecular weight is lowered in order to attain the low viscosity property, the durability may be deteriorated due to the decrease of the cohesive strength. The carboxyl group-containing monomer improves the cohesion of the adhesive by strong hydrogen bonding of the carboxyl group, Thereby facilitating the securing.

Examples of the monomer having a carboxyl group include monovalent acids such as (meth) acrylic acid and crotonic acid; Dicarboxylic acids such as maleic acid, itaconic acid, and fumaric acid, and monoalkyl esters thereof; 3- (meth) acryloylpropionic acid; A succinic anhydride ring-opening addition adduct of 2-hydroxyalkyl (meth) acrylate in which the alkyl group has 2 to 4 carbon atoms, anhydrous succinic ring opening adduct of a hydroxyalkylene glycol (meth) acrylate having 2 to 4 carbon atoms in the alkylene group , Compounds obtained by ring-opening addition of succinic anhydride to caprolactone adducts of 2-hydroxyalkyl (meth) acrylates whose alkyl groups have 2-3 carbon atoms, and among these, (meth) acrylic acid is preferable.

The monomer having a carboxyl group may be contained in the monomer for producing the acrylic copolymer in an amount of 5 to 10% by weight, preferably 5 to 8% by weight. When the content is less than 5% by weight, it is difficult to achieve low viscosity and high durability characteristics. On the contrary, when the content is more than 10% by weight, not only the hydrogen bonding in the acrylic copolymer but also the hydrogen bonding between the acrylic copolymer increases, A problem may arise.

If necessary, a crosslinkable monomer having at least one functional group selected from the group consisting of an amide group and a tertiary amine group in addition to the crosslinkable monomer of 4-hydroxybutylacrylate is added to the monomer for producing the acrylic copolymer ≪ / RTI > At this time, the crosslinkable monomer serves to reinforce the cohesive strength or adhesive strength of the pressure-sensitive adhesive composition by chemical bonding, thereby imparting durability and cutability.

Examples of the monomer having an amide group include (meth) acrylamide, N-isopropylacrylamide, N-tertiary butyl acrylamide, 3-hydroxypropyl (meth) acrylamide, 4-hydroxybutyl (Meth) acrylamide, 8-hydroxyoctyl (meth) acrylamide, and 2-hydroxyethylhexyl (meth) acrylamide. Of these, .

Examples of the monomer having a tertiary amine group include N, N-dimethylaminoethyl (meth) acrylate, N, N- (diethylamino) ethyl (meth) (Meth) acrylate, and the like.

The crosslinkable monomer having at least one functional group selected from the group consisting of the amide group and the tertiary amine group may contain less than 10% by weight, preferably 1 to 8% by weight, in the monomer for producing the acrylic copolymer. If the content is more than 10% by weight, the adhesive strength may be excessively increased, and the recrystallization may be deteriorated or the storage stability of the coating solution at room temperature may be deteriorated.

In addition, the present invention may further include not more than 10% by weight of other crosslinkable monomers other than the above-mentioned monomers in a range that does not lower the adhesive force, for example, in a monomer for producing an acrylic copolymer.

The method for producing the copolymer is not particularly limited and can be produced by methods such as bulk polymerization, solution polymerization, emulsion polymerization or suspension polymerization, which are commonly used in the art, and solution polymerization is preferable. In addition, a solvent, a polymerization initiator, a chain transfer agent for molecular weight control and the like which are usually used in polymerization can be used.

The acrylic pressure sensitive adhesive composition of the present invention may further contain a crosslinking agent.

The crosslinking agent can improve the adhesion and durability, and can maintain the reliability at a high temperature and the shape of the pressure-sensitive adhesive.

The cross-linking agent may be an isocyanate-based, epoxy-based, melamine-based, peroxide-based, metal chelating-based, oxazoline-based, or the like. Preferred is a double isocyanate-based or epoxy-based.

Examples of the isocyanate-based isocyanate include isocyanate-based compounds such as tolylene diisocyanate, xylene diisocyanate, 2,4-diphenylmethane diisocyanate, 4,4-diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, tetramethyl xylene diisocyanate, Diisocyanate compounds such as isocyanate; An adduct obtained by reacting 3 moles of a diisocyanate compound with 1 mole of a polyhydric alcohol compound such as trimethylolpropane, an isocyanurate compound in which 3 moles of a diisocyanate compound is self-condensed, a diisocyanate obtained from 2 moles of 3 moles of a diisocyanate compound And multifunctional isocyanate compounds containing three functional groups such as burette, triphenylmethane triisocyanate and methylene bistriisocyanate in which the remaining one mole of diisocyanate is condensed in urea.

The epoxy system may be an ethylene glycol diglycidyl ether, a diethylene glycol diglycidyl ether, a polyethylene glycol diglycidyl ether, a propylene glycol diglycidyl ether, a tripropylene glycol diglycidyl ether, a polypropylene glycol di Hexanediol diglycidyl ether, polytetramethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, diethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, Glycerol polyglycidyl ether, polyglycerol polyglycidyl ether, resorcinol diglycidyl ether, 2,2-dibromoneopentyl glycol diglycidyl ether, trimethylol propane triglycidyl ether, pentaerythritol poly Glycidyl ether, sorbitol polyglycidyl ether, adipic acid diglycidyl ester, phthalic acid diglycidyl ester, tris (glycidyl) isocyanurate N, N, N ', N'-tetraglycidyl-m-hexyldicyclohexyl) isocyanurate, 1,3-bis (N, N-glycidylaminomethyl) cyclohexane, Xylylenediamine, and the like.

Examples of the melamine type include hexamethylol melamine, hexamethoxymethyl melamine, and hexabutoxymethyl melamine.

Such a crosslinking agent may be contained in an amount of 0.1 to 15 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the acrylic copolymer. If the content is less than 0.1 part by weight, the cohesive strength may be decreased due to insufficient crosslinking, which may deteriorate the durability of the adhesive durability and the cutability. If the content is more than 15 parts by weight, the residual stress due to the excessive crosslinking reaction may be deteriorated.

In addition to the above components, the pressure-sensitive adhesive composition may further contain a silane coupling agent, a tackifier resin, an antioxidant, a leveling agent, a surface-treating agent, a surface- Lubricants, dyes, pigments, antifoaming agents, fillers, light stabilizers, antistatic agents, and the like.

The double silane coupling agent serves to improve the adhesion between the pressure-sensitive adhesive and the substrate. Therefore, it is preferable that the double silane coupling agent contains an alkoxysilane containing an amino group, an epoxy group, an acetoacetyl group, a polyalkylene glycol group, an acryl group, Can be used.

The amount of such an additive can be appropriately controlled within a range that does not impair the effect of the present invention. For example, the silane coupling agent is added in an amount of 0.1 to 2 parts by weight, preferably 0.1 to 2 parts by weight, per 100 parts by weight of the acrylic copolymer, May be contained in an amount of 0.1 to 0.5 parts by weight. If the content is less than 0.1 parts by weight, the adhesion may be deteriorated. If the content is more than 2 parts by weight, peeling may occur under heat-resistant conditions.

The pressure-sensitive adhesive composition of the present invention can be used particularly as a pressure-sensitive adhesive for a polarizing plate or a pressure-sensitive adhesive for a surface protective film for bonding with a liquid crystal cell. It can be used not only as a protective film, a reflective sheet, a structural adhesive sheet, a photographic adhesive sheet, a lane marking adhesive sheet, an optical adhesive product, an electronic component adhesive, but also a general commercial adhesive sheet product.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the present invention. Such variations and modifications are intended to be within the scope of the appended claims.

Manufacturing example  : Acrylic copolymer preparation

Manufacturing example  One

8 parts by weight of n-butyl acrylate (BA), 8 parts by weight of benzyl methacrylate (BzMA), 5 parts by weight of acrylic acid (AA), and 4 parts by weight of benzyl methacrylate (BzMA) were placed in a 1 L reactor equipped with a cooling device And 1 part by weight of hydroxybutyl acrylate (4-HBA), and then 100 parts by weight of ethyl acetate (EA) was added as a solvent. After that, nitrogen gas was poured in for 1 hour to remove oxygen, and the temperature was maintained at 80 ° C. After uniformly stirring the monomer mixture, 0.07 part by weight of azobisisobutyronitrile (AIBN) as a reaction initiator was added and reacted for 8 hours to prepare an acrylic copolymer (A-1) having a weight average molecular weight of about 800,000.

Manufacturing example  2 to 6 and comparison Manufacturing example  1 to 9

The acrylic copolymer was prepared in the same manner as in Preparation Example 1, except that the monomer composition shown in Table 1 was used.

The following Production Example 4 was carried out in the same manner as in Preparation Example 1 except that 130 parts by weight of ethyl acetate (EA) was used. In Comparative Preparation Example 7, 200 parts by weight of ethyl acetate (EA) Was carried out in the same manner as in Production Example 1.

division
(Parts by weight) BA An acrylate having an aromatic group Crosslinkable acrylate having a hydroxy group The monomer having a carboxyl group Other crosslinking monomers Weight average molecular weight BzMA BzA PEA 4-HBA HEA HEMA AA AM DMAEA Production Example 1 84 10 - - One - - 5 - - 80 million Production Example 2 77 15 - - 3 - - 5 - - 78 million Production Example 3 70 20 - - 5 - - 5 - - 85 million Production Example 4 84 10 - - One - - 5 - - 55 million Production Example 5 81 10 - - One - - 8 - - 82 million Production Example 6 79 10 - - One - - 10 - - 88 million Comparative Preparation Example 1 84 10 - - One - - - 5 - 82 million Comparative Production Example 2 84 10 - - One - - - - 5 80 million Comparative Production Example 3 84 - 10 - One - - 5 - - 82 million Comparative Production Example 4 84 - - 10 One - - 5 - - 83 million Comparative Preparation Example 5 84 10 - - - - - One - 5 83 million Comparative Preparation Example 6 84 10 - - - - - - One 5 81 million Comparative Preparation Example 7 84 10 - One 5 45 million Comparative Preparation Example 8 85 10 - - One - - 4 - - 79 million Comparative Preparation Example 9 78 10 - - One - - 11 - - 95 million BzMA: Benzyl methacrylate
BzA: benzyl acrylate
PEA: Phenoxyethyl acrylate
4-HBA: 4-hydroxybutyl acrylate
4-HBMA: 4-hydroxybutyl methacrylate
HEA: hydroxyethyl acrylate
HEMA: Hydroxy methacrylate
AA: Acrylic acid
AM: Acrylamide
DMAEA: Dimethylaminoethyl acrylate

Example  1-12 and Comparative Example  1-9

And the mixture was mixed with the composition shown in Table 2, followed by dilution with methyl ethyl ketone to prepare a pressure-sensitive adhesive composition. The pressure-sensitive adhesive composition prepared above was applied on a releasing film coated with silicone release agent to a thickness of 25 탆 and dried at 100 캜 for 1 minute to form an adhesive layer.

The pressure-sensitive adhesive layer prepared above was laminated on an iodine-based polarizing plate having a thickness of 185 탆 by pressure-sensitive adhesive processing to produce a polarizer with a pressure-sensitive adhesive.

division
(Parts by weight) Acrylic
Copolymer Cross-linking agent Silane
Coupling agent
Daejeon
Inhibitor Solids
density
(weight%) Viscosity
(cP) Manufacturing example compare
Manufacturing example A-1 A-2 A-3 A-4 Example 1 1 (100) - 0.5 - - - 0.5 3 28 780 Example 2 2 (100) - 0.5 - - - 0.5 3 28 820 Example 3 3 (100) - 0.5 - - - 0.5 3 28 880 Example 4 4 (100) - 0.5 - - - 0.5 3 28 490 Example 5 5 (100) - 0.5 - - - 0.5 3 28 750 Example 6 6 (100) - 0.5 - - - 0.5 3 28 950 Example 7 1 (100) - - 0.5 - - 0.5 3 28 780 Example 8 1 (100) - - - 0.5 - 0.5 3 28 780 Example 9 1 (100) - - - - 0.5 0.5 3 28 780 Example 10 1 (100) - 0.5 - - - 0.5 3 25 450 Example 11 1 (100) - 0.5 - - - 0.5 3 30 980 Example 12 4 (100) - 0.5 - - - 0.5 3 35 930 Comparative Example 1 1 (100) 0.5 - - - 0.5 3 28 950 Comparative Example 2 2 (100) 0.5 - - - 0.5 3 28 810 Comparative Example 3 - 3 (100) 0.5 - - - 0.5 3 28 1350 Comparative Example 4 - 4 (100) 0.5 - - - 0.5 3 28 3500 Comparative Example 5 - 5 (100) 0.5 - - - 0.5 3 28 1280 Comparative Example 6 - 6 (100) 0.5 - - - 0.5 3 28 1190 Comparative Example 7 - 7 (100) 0.5 - - - 0.5 3 28 380 Comparative Example 8 - 8 (100) 0.5 - - - 0.5 3 28 805 Comparative Example 9 - 9 (100) 0.5 - - - 0.5 3 28 1150 A-1: Coronate-L (TDI-TMP Adduct, Japan Urethane Industry)
A-2: Coronate-HXR (HDI trimer, Japan Urethane Industry)
A-3: D110N (HDI-TMP adduct, Mitsui Chemicals)
A-4: D140N (IPDI-TMP adduct, Mitsui Chemicals)
Silane coupling agent: KBM-403 product (3-glycidoxypropyltrimethoxysilane, Shin-Etsu)
Antistatic agent: HQ-115 product (trifluoromethylsulfonylimide lithium salt, 3M)

Test Example

The properties of the pressure-sensitive adhesive composition and the polarizer with a pressure-sensitive adhesive prepared in the above Examples and Comparative Examples were measured by the following methods, and the results are shown in Table 3 below.

One. Coating property

The pressure-sensitive adhesive composition thus prepared was coated on the release film with automatic air, and the coated surface was observed in a reflection mode to observe the coating surface.

<Evaluation Criteria>

○: No coatings were observed

△: The coated cloth was confirmed but weakly recognized.

X: The coated cloth was clearly observed.

2. Curing period

The adhesive sheet thus prepared was cured for 1 to 10 days at 23 DEG C and 65% RH, and the gel fraction was measured in the following manner for each day, and the curing period was measured, in which the gel fraction was no longer increased.

Approximately 0.25 g of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is attached to a wire mesh (100 mm x 100 mm) of a 250 mesh precisely weighed, and the gel is wrapped so as not to leak. After accurately weighing the weight with a precision balance, the wire net is immersed in the ethyl acetate solution for 3 days. The immersed wire mesh is taken out, washed with a small amount of ethyl acetate solution, dried at 120 ° C for 24 hours and then weighed. Using the measured weight, the gel fraction was calculated by the following equation (1). The curing period was determined on the basis of the time when the calculated gel fraction was included in the range of 70 to 80% and there was no change with time.

B is the weight of the wire netting attached to the pressure-sensitive adhesive layer (BA: weight of the pressure-sensitive adhesive, g); C is the weight of the wire netted after immersion (CA: weight of the gelled resin, g )being].

3. Durability (heat resistance, Wet heat )

The prepared polarizer with a pressure-sensitive adhesive was cut into a size of 90 mm × 170 mm, and the release film was peeled off. Then, the optical absorption axis was perpendicularly attached to both sides of the glass substrate (110 mm × 190 mm × 0.7 mm). At this time, the applied pressure was 5 kg / cm &lt; 2 &gt;, and the clean room operation was performed so that bubbles or foreign matter would not occur. The heat resistance characteristics were evaluated by observing the occurrence of bubbles or peeling after being left at a temperature of 80 ° C. for 1000 hours. The moisture resistance characteristics were evaluated by observing the occurrence of bubbles or peeling after being left at a temperature of 60 ° C. and 90% RH for 1000 hours Respectively. At this time, the sample was allowed to stand at room temperature for 24 hours immediately before evaluating the state of the specimen.

<Evaluation Criteria>

Ⓞ: No bubbles or peeling.

○: Bubbles or peeling <5

?: 5 pieces? Bubbles or peeling <10 pieces

X: 10 pieces &lt; bubble &

4. Light resistance  evaluation

In order to investigate the uniformity of light transmittance using the same specimen as above, it was observed whether light leakage occurred in the dark room using a backlight. As a method of testing the light transmission uniformity, a method of observing a coated polarized plate (200 mm x 200 mm) on both sides of a glass substrate (210 mm x 210 mm x 0.7 mm) at 90 degrees was adopted. The uniformity of light transmittance was evaluated according to the following criteria.

<Evaluation Criteria>

Ⓞ: Unevenness of light transmittance is difficult to judge with naked eyes

○: slight non-uniformity of light transmittance

×: There is a little light non-uniformity phenomenon

division Coating property Curing time durability Light resistance Heat resistance Humidity Durability Example 1 ○ 1 day Ⓞ Ⓞ Ⓞ Example 2 ○ 18 hours Ⓞ Ⓞ ○ Example 3 ○ 12 hours Ⓞ Ⓞ ○ Example 4 ○ 2 days ○ Ⓞ Ⓞ Example 5 ○ 18 hours Ⓞ Ⓞ Ⓞ Example 6 ○ 18 hours Ⓞ ○ ○ Example 7 ○ 3 days ○ Ⓞ Ⓞ Example 8 ○ 3 days Ⓞ Ⓞ Ⓞ Example 9 ○ 3 days ○ Ⓞ Ⓞ Example 10 ○ 1 day Ⓞ Ⓞ Ⓞ Example 11 ○ 1 day Ⓞ Ⓞ Ⓞ Example 12 ○ 2 days ○ ○ Ⓞ Comparative Example 1 ○ 2 days × ○ ○ Comparative Example 2 ○ 1 day × ○ ○ Comparative Example 3 × 1 day Ⓞ Ⓞ Ⓞ Comparative Example 4 × 1 day Ⓞ Ⓞ Ⓞ Comparative Example 5 △ 5 days ○ ○ ○ Comparative Example 6 △ 5 days ○ ○ ○ Comparative Example 7 ○ 1 day × △ ○ Comparative Example 8 ○ 1 day △ ○ Ⓞ Comparative Example 9 × 18 hours Ⓞ ○ ○

As shown in Table 3, the pressure-sensitive adhesive compositions of Examples 1 to 12 according to the present invention using a monomer having a carboxyl group as a monomer had excellent coating properties as compared with Comparative Examples 1 to 9, (Heat resistance and humid heat resistance) and light leakage resistance. In particular, in Comparative Example 1 and Comparative Example 2 in which monomers having a carboxyl group as a monomer were not used, the durability was significantly lower than those of Examples. In addition, in Comparative Examples 8 and 9 in which the content of the monomer having a carboxyl group deviates from the preferred range of the present invention, it is confirmed that the durability is poor or the coating property is inferior to the examples.

Claims (8)

An acrylic copolymer having a weight average molecular weight (in terms of polystyrene, Mw) of 500,000 or more prepared by copolymerizing a monomer containing 5 to 10% by weight of a monomer having a carboxyl group, and a solvent,
A solids content of 25% by weight or more and a viscosity of 1000 cP or less,
Wherein the monomer for producing the acrylic copolymer contains benzyl methacrylate and 4-hydroxybutyl acrylate. The pressure-sensitive adhesive composition according to claim 1, wherein the acrylic copolymer has a weight-average molecular weight (Mw in terms of polystyrene) of 500,000 to 1,000,000. The pressure-sensitive adhesive composition according to claim 1, wherein the pressure-sensitive adhesive composition has a solids content of 25 to 30% by weight and a viscosity of 500 to 1000 cP. delete The pressure-sensitive adhesive composition according to claim 1, wherein the monomer for producing the acrylic copolymer contains a (meth) acrylate monomer having an alkyl group having 1-12 carbon atoms, benzyl methacrylate, and 4-hydroxybutyl acrylate. [7] The method of claim 5, wherein the monomer for producing the acrylic copolymer is 70 to 85% by weight of a (meth) acrylate monomer having an alkyl group having 1-12 carbon atoms, 5 to 20% by weight of benzyl methacrylate, 0.1 to 5% by weight of an acrylate and 5 to 10% by weight of a monomer having a carboxyl group. The pressure-sensitive adhesive composition according to claim 5, wherein the acrylic copolymer further comprises a crosslinkable monomer having at least one functional group selected from the group consisting of an amide group and a tertiary amine group. The pressure-sensitive adhesive composition according to claim 1, wherein the pressure-sensitive adhesive composition further comprises a crosslinking agent.