KR101340543B1 - Adhesive composition for polarizing plate - Google Patents

Abstract

The present invention relates to an adhesive composition for a polarizing plate which includes a compound having a hydroxamic acid functional group and a reaction initiator having an aromatic sulfonyl group in an adhesive composition to provide high adhesion, high durability and high reliability.

Description

Adhesive composition for polarizing plate

The present invention relates to an adhesive composition for polarizing plates. More specifically, the present invention relates to an adhesive composition for polarizing plates which includes a compound having a hydroxamic acid functional group and a reaction initiator having an aromatic sulfonyl group in an adhesive composition to provide high adhesion, high durability and high reliability.

The adhesive for a polarizing plate has the adhesive agent containing hydrophilic and water-soluble polyvinyl alcohol as a binder in order to have the adhesive force to the polyvinyl alcohol film which is a base film of a polarizer, and the cellulose film which is a protective film. However, the adhesive force in such an adhesive is provided by the hydrogen bond of the hydroxyl group contained in the polyvinyl alcohol, there is a problem that the adhesive strength is poor. In addition, since the hydrophilic adhesive has a high water absorption, there is a problem in that the adhesive strength is deteriorated in the long term, and the film to which the adhesive is applied is discolored and shrunk, thereby deteriorating durability.

In order to improve the adhesiveness and durability of the adhesive for polarizing plates, an adhesive including a water-dispersible NCO has been developed. Adhesives containing water-dispersible NCO provide high adhesive strength by providing urethane bonds with hydroxyl groups on the protective film and polarizer. However, in an adhesive containing water-dispersible NCO, NCO is likely to be hydrolyzed into amines by reacting with water, which may result in poor adhesion and durability. In addition, there is a problem in that it can be hydrolyzed by reaction with moisture in the air, so that the problem of storage and the desired reaction as the adhesive cannot be sufficiently caused.

It is an object of the present invention to provide an adhesive composition that provides high adhesion, high durability and high reliability.

It is another object of the present invention to provide an adhesive composition that provides high adhesion, high durability and high reliability compared to PVA-based adhesives including water dispersible NCO.

Still another object of the present invention is to provide a polarizing plate including the adhesive composition.

The adhesive composition of the present invention includes an aqueous binder having at least one hydroxyl group; a compound having a hydroxamic acid functional group; And a reaction initiator having an aromatic sulfonyl group.

In one embodiment, the compound may have two or more hydroxamic acid functional groups.

In one embodiment, the compound may include a compound having Formula 1 below.

       ≪ Formula 1 >

(Where n is an integer of 0-20.)

In one embodiment, the adhesive composition may include 5-40 parts by weight of the compound and 1-40 parts by weight of the reaction initiator based on 100 parts by weight of the aqueous binder solids.

The adhesive of the present invention is formed by a compound having a hydroxamic acid functional group and a reaction initiator having an aromatic sulfonyl group, and may include aromatic sulfonic acid ions.

Polarizing plate of the present invention is a polarizer; And a protective film adhered to one or both surfaces of the polarizer through the adhesive composition.

The adhesive composition of the present invention can provide high adhesion, high durability and high reliability. In addition, the adhesive composition of the present invention can provide high adhesion, high durability and high reliability compared to PVA-based adhesives including water dispersible NCO.

Adhesive composition of the present invention

(A) an aqueous binder having at least one hydroxyl group;

(B) a compound having a hydroxamic acid functional group; And

(C) A reaction initiator having an aromatic sulfonyl group may be included.

(A) aqueous binder

Aqueous binders include binders having water-soluble or hydrophilic groups. For example, the aqueous binder may be a binder including one or more hydroxy groups. Preferably, the aqueous binder is a polyvinyl alcohol resin, an unsaturated carboxylic acid having 5 to 20 carbon atoms having at least one hydroxy group or a derivative thereof, an olefin having at least one hydroxyl group, a vinyl ether having at least one hydroxyl group ether) or a modified polyvinyl alcohol resin containing a copolymer of an unsaturated sulfonate of 5 to 20 carbon atoms having at least one hydroxy group and vinyl acetate, and the like. More preferably, the aqueous binder may be a polyvinyl alcohol-based resin.

The average degree of polymerization of the polyvinyl alcohol-based resin may be 500 or more, preferably 1000 to 5000. Within this range, the adhesive modulus can be properly maintained to expect cohesive failure resistance. The saponification degree of the polyvinyl alcohol-based resin may be 85 mol% or more. Within this range, it is possible to expect the activity of interfacial bonding by improving the cohesive energy by increasing the degree of crystallinity of the adhesive and by increasing the hydroxyl group. Preferably, it may be 98 mol% or more.

(B) compound

를 가질 수 있다. 상기 화합물에 포함된 히드록삼산 작용기는 하기에서 서술된 반응 개시제와의 반응(예: Lossen Rearrangement)에 의해 이소시아네이트 기로 변환된다. 변환된 이소시아네이트 기는 접착제 조성물, 기재 필름 또는 보호 필름에 포함된 히드록시기와 우레탄 결합 또는 우레아 결합을 형성할 수 있다. 이는 접착제-접착제 간 및 접착제-필름 간에 공유 결합을 제공함으로써 접착력과 내구성을 높이게 한다."Compound" means an intermediate step material for crosslinking an aqueous binder or forming a crosslinking agent for crosslinking an aqueous binder and a base film or a protective film. Compounds have two or more hydroxamic acid functional groups

Lt; / RTI > Hydroxamic acid functional groups included in the compound are converted to isocyanate groups by reaction with a reaction initiator described below (eg, Lossen Rearrangement). The converted isocyanate groups can form urethane bonds or urea bonds with the hydroxyl groups included in the adhesive composition, the base film or the protective film. This enhances adhesion and durability by providing covalent bonds between the adhesive-adhesive and the adhesive-film.

The compound is stable at 25 ° C. and is not hydrolyzed by moisture. Therefore, it can be maintained for a long time in the mixed state with the aqueous binder and the reaction initiator.

Preferably, the compound may include a compound having a structure of Formula 1 below.

[Formula 1]

(Where n is an integer of 0 to 20).

Preferably n may be 0-10.

Specific examples of the compound may be oxalyl dihydroxysamic acid (compound wherein n is 0 in Formula 1), but is not limited thereto. The compounds may be purchased commercially or prepared through chemical reactions commonly known to those skilled in the art. For example, the hydroxamic acid group included in the compound may be prepared by an Angeli-Rimini reaction including the reaction of aldehyde and sulfonamide, as shown in Scheme 1 below.

[Reaction Scheme 1]

In an embodiment, an example of a compound, oxalyl dihydroxysamic acid, can be prepared by using aldehyde glyoxal and using N-hydroxybenzenesulfonamide as the sulfonamide.

The compound may be included in an amount of 5-40 parts by weight, preferably 5-30 parts by weight based on 100 parts by weight of the aqueous binder solids. Within this range, an optimum crosslinking reactivity between interfaces between polyvinyl alcohol adhesives can be expected.

The compound and the following reaction initiator may be included in a weight ratio of 1: 0.5 to 1: 2. Within this range, it is possible to effectively proceed the Angeli-Rimini reaction of the crosslinked intermediate having hydroxamic acid.

(C) reaction Initiator

'Reaction initiator' refers to a substance which forms a crosslinking agent, in particular an isocyanate-based crosslinking agent by reacting with a compound. The reaction initiator may have an aromatic sulfonyl group. Preferably, the reaction initiator may be aromatic sulfonyl chloride having 6 to 10 carbon atoms. More preferably toluene sulfonyl chloride can be used.

The reaction initiator reacts with the compound to form isocyanate-based crosslinkers and aromatic sulfonic acid ions. The isocyanate-based crosslinking agent can provide a covalent bond between the aqueous binder containing a hydroxy functional group, a protective film or the base film constituting the polarizer.

The reaction initiator may be included in an amount of 1-40 parts by weight, preferably 5-30 parts by weight based on 100 parts by weight of the aqueous binder solids. Within this range, an optimum crosslinking reactivity between interfaces between polyvinyl alcohol adhesives can be expected.

The adhesive composition of the present invention may further include one or more selected from the group consisting of a solvent and a crosslinking agent, in addition to the (A) aqueous binder, the (B) compound, and the (c) reaction initiator.

The solvent is a solvent which can be mixed with an aqueous binder, a compound or a reaction initiator, and may include an alcohol solvent, but is not limited thereto. The alcohol solvent may include a lower alcohol having 1-3 carbon atoms.

The crosslinking agent is a crosslinking agent capable of crosslinking the aqueous binder, and may include one or more selected from a methylol group-containing compound or a glycidyl group-containing compound, but is not limited thereto.

The present invention also provides an adhesive comprising a compound having an isocyanate functional group and an aromatic sulfonic acid ion.

The compound having an isocyanate functional group may be formed by the reaction of a compound having a hydroxamic acid functional group and a reaction initiator having an aromatic sulfonyl group.

Aromatic sulfonic acid ions are derived from an aromatic sulfonic acid formed from the reaction of a reaction initiator or a compound having an unreacted aromatic sulfonyl group with a reaction initiator. Preferably the aromatic sulfonic acid ions may comprise toluene sulfonate ions.

Aromatic sulfonic acid ions can be detected by automated combustion ion chromatography (Combustion IC) or NMR, but are not limited to these.

The detail about the compound which has the said hydroxamic acid functional group, and the reaction initiator which has an aromatic sulfonyl group is as above-mentioned.

In addition, the present invention is a polarizer; And it provides a polarizing plate comprising a protective film adhered to one or both sides of the polarizer through the adhesive composition.

Although the base film which comprises a polarizer can use a conventionally well-known thing, the base film containing resin which has a hydroxy functional group can be used. For example, polyvinyl alcohol-based, unsaturated carboxylic acids having 5 to 20 carbon atoms having at least one hydroxy group or derivatives thereof, olefins having at least one hydroxyl group, vinyl ethers having at least one hydroxyl group, or One or more selected from the group consisting of modified polyvinyl alcohol resins including copolymers of unsaturated sulfonates of 5 to 20 carbon atoms having at least one hydroxy group with vinyl acetate and the like can be used.

Although a protective film can use a conventionally well-known thing, the film containing resin which has a hydroxy functional group can be used. For example, the protective film may be a film including at least one member selected from the group consisting of a cellulose polymer, a vinyl alcohol polymer and a polyoxymethylene polymer. Preferably, the protective film may be a polymer including a cellulosic polymer. The cellulose polymer may include at least one selected from the group consisting of cellulose esters, diacetyl cellulose, triacetyl cellulose (TAC), cellulose propionate, cellulose acetate propionate, cellulose diacetate and cellulose acetate butyrate. Can be.

At least one of the base film and the protective film constituting the polarizer may be surface treated by at least one method of saponification treatment, plasma treatment, corona treatment, ultraviolet treatment, and flame (flame) treatment before being bonded by the adhesive composition.

A polarizing plate can be manufactured by apply | coating an adhesive composition on a polarizer or a protective film, laminating | stacking a polarizer or a protective film, and drying. For example, it may be dried at 50-80 ° C. for 1-30 minutes.

Hereinafter, the configuration and operation of the present invention through the preferred embodiment of the present invention will be described in more detail. It is to be understood, however, that the same is by way of illustration and example only and is not to be construed in a limiting sense.

Details that are not described herein will be omitted since the description can be inferred by those skilled in the art.

Example

Manufacturing example : Preparation of Compound

After dissolving 3 g of methoxide sodium (97% purity, powder, Fluka) in 1 L of glyoxal (40% aqueous solution, Samjeon Chemical), 500 g of N-hydroxybenzenesulfonamide (powder, Fluka) was added. By stirring at room temperature for 24 hours, oxalyl dihydroxysamic acid was prepared.

Example  One

30g of polyvinyl alcohol (JC-25, saponification degree of more than 99%, JVP) was slowly added thereto while stirring 970ml of room temperature in a 1L reactor. The temperature of the reactor was raised to 90 ° C. and then dissolved for 2 hours and cooled slowly. 1.5 g of the prepared compound and 1.5 g of 4-toluenesulfonyl chloride (TsCl, powder, Fluka) were added thereto. The 4-toluenesulfonyl chloride powder was dissolved by stirring at 25 ° C. for 30 minutes to prepare an adhesive composition.

Example  2-7

An adhesive composition was prepared in the same manner as in Example 1, except that the content of the compound and 4-toluenesulfonyl chloride was changed as described in Table 1 below.

Comparative Example  1-2

Instead of the compound and 4-toluenesulfonyl chloride in Example 1, 3g of an aqueous dispersible isocyanate crosslinking agent (aqueous NCO, Bayhydur304, liquid, Bayer) was added and stirred to prepare an adhesive composition.

Comparative Example  3

An adhesive composition was prepared in the same manner as in Example 1, except that the content of the compound and 4-toluenesulfonyl chloride was changed as described in Table 1 below.

PVA (g) Compound (g) Compound for PVA
ratio(%) TsCl (g) TsCl for PVA
ratio(%) Water-based NCO (g) Water NCO Ratios (%) to PVA Example 1 30 1.5 5 1.5 5 - - Example 2 30 3 10 3 10 - - Example 3 30 9 30 9 30 - - Example 4 30 3 10 1.5 5 - - Example 5 30 3 10 6 20 - - Example 6 30 3 10 3 10 - - Example 7 30 3 10 3 10 - - Comparative Example 1 30 - - - - 3 10 Comparative Example 2 30 - - - - 3 10 Comparative Example 3 30 3 10 - - - -

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Experimental Example

Physical properties such as wet adhesion, water resistance, high temperature water resistance and high temperature durability of the polarizing plate including the prepared adhesive composition were measured and the results are shown in Table 2 below.

≪ Production of polarizing plate &

(1) Preparation of light polarizer: As a base film, the polyvinyl alcohol film (thickness 80 micrometers, saponification degree: 99.5, polymerization degree: 2000) was used. The polyvinyl alcohol film was immersed in 0.3% aqueous solution of iodine for dyeing, and then stretched so that the draw ratio was 5.0. The stretched base film was immersed in a 3% concentration of boric acid solution and 2% aqueous potassium iodide solution to perform color correction. The polarizer was prepared by drying at 50 ° C. for 4 minutes.

(2) Preparation of protective film: The triacetate cellulose (thickness 80 micrometers) (TAC) was used for the protective film as a base film. Triacetate cellulose was added to an aqueous solution of sodium hydroxide at a concentration of 0.1N, and immersed at 50 ° C. for 2 minutes and 30 seconds to prepare a protective film.

(3) Preparation of polarizing plate: The polarizing plate was produced with the polarizer, adhesive composition, and protective film which were prepared above. At this time, the adhesive composition was prepared as described in Table 2 below and used immediately (Examples 1-5, Comparative Examples 1 and 3) or after being left at 25 ° C. for 60 minutes or 120 minutes (Example 6 -7, comparative example 2). It laminated | stacked on the surface of a protective film in order of an adhesive composition, a polarizer, an adhesive composition, and a protective film. It dried at 70 degreeC for 5 minutes, and manufactured the polarizing plate.

≪ Method for measuring physical properties &

① Wet Adhesion: The polarizing plate was cut to 20 mm in width and left for 1 hour at 60 ° C. 95% humidity. The adhesive force at the time of peeling a protective film with a tensile velocity of 250 mm / min and a peeling angle of 180 degrees was measured. At this time, when adhesive force was strong enough to break a polarizing plate without peeling a protective film, it described as "breaking".

② Water resistance: The polarizing plate was cut into 20 mm × 50 mm so that the stretching direction was in the longitudinal direction, and then submerged at 60 ° C. for 8 hours. After immersion, shrinkage and discoloration of the polarizers were measured. If not contracted, it is denoted as "X", and if contracted, as "complete contraction". Decolorization was expressed as the length of decolorization (mm) in the polarizing plate, and "completely decoloring" when the polarizing plate was completely decolorized.

③ High temperature water resistance: The polarizing plate was cut into 20 mm × 50 mm so that the stretching direction was in the longitudinal direction, and then immersed at 85 ° C. for 1 hour. After immersion, shrinkage and discoloration of the polarizers were measured. In case of no contraction, it is expressed as "X" and in case of contraction, as contracted length (mm). Decolorization was indicated by the decolorized length (mm) in the polarizing plate.

④ High Temperature Durability: The polarizing plate was cut into 20 mm × 50 mm so that the stretching direction was in the longitudinal direction, and then left for 72 hours at 70 ° C. and 97% humidity, and then the shrinkage and discoloration of the polarizing plate were measured. In case of no contraction, it is expressed as "X" and in case of contraction, as contracted length (mm). Decolorization was indicated by the decolorized length (mm) in the polarizing plate.

Use adhesive composition
Condition Wetting
Adhesion
(gf / 25 mm) Water resistance High temperature water resistance High temperature durability Shrink decolorization
(mm) Shrink
(mm) decolorization
(mm) Shrink
(mm) decolorization
(mm) Example 1 Use immediately after manufacture Destruction X 0.4 X 0.1 X 0.3 Example 2 Use immediately after manufacture Destruction X 0.2 X 0.1 X 0.2 Example 3 Use immediately after manufacture Destruction X 0.8 X 0.4 X 0.6 Example 4 Use immediately after manufacture Destruction X 0.5 X 0.3 X 0.5 Example 5 Use immediately after manufacture Destruction X 0.7 X 0.5 X 0.5 Example 6 Leave at room temperature for 60 minutes Destruction X 0.4 X 0.2 X 0.4 Example 7 120 minutes at room temperature Destruction X 0.6 X 0.3 X 0.4 Comparative Example 1 Use immediately after manufacture Destruction X 1.8 0.8 1.1 0.9 1.8 Comparative Example 2 Leave at room temperature for 60 minutes 40 Complete shrinkage Decolorization 1.3 1.4 2.5 5.3 Comparative Example 3 Use immediately after manufacture 16 Complete shrinkage Decolorization 1.8 2.5 2.4 4.3
As salping in Table 2, the adhesive composition of the present invention can provide high adhesion and high durability between the polarizer and the protective film. The adhesive composition of the present invention can provide high water resistance, high temperature water resistance and high temperature durability as compared to the adhesive composition including the water dispersible isocyanate crosslinking agent (see Examples 1-7 and Comparative Examples 1-2).

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Claims (14)

An aqueous binder having at least one hydroxy group;
Compounds having a hydroxamic acid functional group; And
Adhesive composition containing the reaction initiator which has aromatic sulfonyl group.
The adhesive composition of claim 1, wherein the compound has two or more hydroxamic acid functional groups.
According to claim 2, wherein the compound is an adhesive composition, characterized in that the compound having the formula (1).
[Chemical Formula 1]

(N is an integer of 0-20 in the above.)
The method of claim 1, wherein the aqueous binder is a polyvinyl alcohol (PVA) resin, an unsaturated carboxylic acid having 5 to 20 carbon atoms having one or more hydroxyl groups or derivatives thereof, an olefin having one or more hydroxyl groups, one or more At least one selected from the group consisting of a vinyl ether having a hydroxy group or a modified polyvinyl alcohol resin including a copolymer of an unsaturated sulfonate having 5 to 20 carbon atoms having at least one hydroxy group with vinyl acetate, and the like. Adhesive composition comprising a.
The adhesive composition of claim 1, wherein the reaction initiator is toluene sulfonyl chloride.
The adhesive composition of claim 1, wherein the adhesive composition comprises 5-40 parts by weight of the compound and 1-40 parts by weight of the reaction initiator based on 100 parts by weight of the aqueous binder solids.
The adhesive composition of claim 1, wherein the adhesive composition further comprises at least one member selected from the group consisting of a solvent and a crosslinking agent.
delete delete delete delete delete A polarizer; And
Polarizing plate comprising a protective film bonded to one or both sides of the polarizer through the adhesive composition of claim 1.
The polarizing plate of Claim 13 in which the said polarizer and a protective film contain resin which has a hydroxyl group.