KR20090049382A - Adhesive composition for polarizing plate - Google Patents

Abstract

The present invention includes a modified polyvinyl alcohol compound and a crosslinking agent, and may further include an additive as necessary. The modified polyvinyl alcohol compound may be 1 wt% to 10 wt% in 100 wt% of the adhesive composition for polarizing plates. It is related with the adhesive composition for polarizing plates characterized by the above-mentioned. The pH of the adhesive composition for polarizing plates is 5 or less, and is adjusted with one or more acids selected from nitric acid, hydrochloric acid, sulfuric acid, and acetic acid. Moreover, the viscosity of the adhesive composition for polarizing plates is characterized by being 1 mPa * s-100 mPa * s. The crosslinking agent uses any one or more of an epoxy crosslinking agent, an isocyanate crosslinking agent, an imine crosslinking agent, a polyvalent metal compound or a multifunctional metal chelate. The additive preferably contains 0.01 to 5.0% by weight relative to 100% by weight of the adhesive composition as the silane coupling agent.

Modified polyvinyl alcohol compounds, zirconyl nitrate, polyethylene imine

Description

Adhesive composition for polarizing plates {ADHESIVE COMPOSITION FOR POLARIZING PLATE}

Adhesive composition for polarizing plates for adhesives used for polarizing plates of thin film transistor liquid crystal displays (TFT-LCDs), such as mobiles, notebooks, computer monitors, and TVs.

The present invention relates to an improved adhesive composition for polarizing plates for improving the water resistance of the polarizing plate. Conventional polarizers have a polyvinyl alcohol (TAC) film on one or both surfaces as a protective role of a polarizer in which a polyvinyl alcohol (PVA) molecular chain containing an iodine compound or a dichroic dye is oriented in a certain direction. (PVA) It is a structure bonded with an aqueous solution. However, the polarizing plate of the general structure lacks water resistance, and when left in a high temperature and high humidity environment for a long time, the polarization performance is reduced by sublimation and shrinkage of the polarizer, and triacetyl cellulose having a protective function of the polyvinyl alcohol (PVA) adhesive, which is vulnerable to moisture, has a protective function. (TAC) has the disadvantage of easy peeling with the film.

In order to solve the above problems, Korean Patent Application (Application No. 10-2005-0052945) proposes to use melamine formaldehyde-based curing agent as a polyvinyl alcohol-based crosslinking agent, and Japanese Patent Laid-Open No. 2000-321430 discloses a polarizing film. It is described that the norbornene resin protective film laminated with a water-soluble polyurethane-based adhesive, but the use of such adhesives and hardeners are reduced in environmental friendliness and workability, it is not excellent in adhesion and water resistance.

The present invention relates to the development of an adhesive composition for a highly water-resistant polarizing plate for adhering a polarizer given a polarization performance and a triacetyl cellulose (TAC) film protecting the same on one or both sides.

The present invention provides an improved adhesive for polarizing plates. The objects and advantages of the present invention can be achieved as an adhesive composition comprising an adhesive polymer, a crosslinking agent. In addition, additives may be further included as necessary.

In the present invention, the adhesive composition for a polarizing plate may have a viscosity such that the adhesive is fluid for cohesion. When the cohesive force of the adhesive composition for the polarizing plate is low, pressing marks remain due to foreign matter between the polarizing plates, or pressed marks are generated on the adhesive layer due to the weight of the polarizing plate itself, which acts as a fatal defect when driving the liquid crystal display. In addition, when the polarizing plate is cut to a certain size, the lack of a property that the adhesive located on one side of the polarizing plate is neatly cut. If this lacking characteristic does not reach the desired level, the glass is contaminated in the process of attaching the polarizing plate to the glass substrate of the liquid crystal display. In addition, when the adhesive composition is vulnerable to moisture, the adhesive composition is easily peeled off with a triacetyl cellulose (TAC) film having a protective function. In the present invention, in order to satisfy the cohesive force, the adhesive composition may have a viscosity of 1 to 100 mPa · s, preferably 13 to 27 mPa · s, more preferably 17 to 23 mPa · s.

You may mix | blend another additive, catalyst, such as an acid as needed. Moreover, when apply | coating the said adhesive composition, you may mix | blend another additive, a catalyst, such as an acid, with the said adhesive composition, for example.

The pH of the adhesive composition may be 5 or less. When the pH of the adhesive composition is adjusted to 5 or less, an adhesive for polarizing plates having excellent storage stability may be provided. In addition, when the adhesive composition for a polarizing plate according to the present invention is used in a polarizing plate used in various display devices, the adhesion and water resistance between the elements become good, and peeling does not occur even in a high humidity environment, and stains may not occur.

It is preferable that the said adhesive composition adjusts its pH to 5 or less using a pH adjuster. More preferably, it can be adjusted in the range of 2-3. It is possible to maintain the desired viscosity of the adhesive for the polarizing plate mentioned above in the above range and may be gelated when the pH is less than the above range.

The pH adjusting agent may be at least one acid selected from nitric acid, hydrochloric acid, sulfuric acid, and acetic acid.

 The adhesive composition may have a glass transition temperature in the range of 40-100 ° C., or 60-90 ° C. The glass transition temperature of the adhesive composition used herein is obtained from the dried adhesive composition.

Hereinafter, the adhesive polymer, the crosslinking agent, and the additive, which are components of the adhesive composition for polarizing plates, will be described in detail.

(1) adhesive polymer

The adhesive polymer used in the present invention is suitable as the adhesive polymer not only to impart cohesion, adhesion, and weakness but also to be excellent in transparency, moisture resistance and heat resistance.

Adhesive polymers for satisfying the cohesion and lacking properties of the adhesive composition for polarizing plates mentioned above include modified polyvinyl alcohol compounds, polyurethane compounds, polyester compounds, polyacryl compounds, polyepoxy compounds, polycyanoacrylate compounds, and the like. It is preferable to use an adhesive consisting of. Herein, the polyvinyl alcohol-based compound, the modified polyvinyl alcohol-based compound, the polyurethane-based compound, the polyester compound, the polyacryl-based compound, the polyepoxy compound, the polycyanoacrylate-based compound, and the like are respectively polyvinyl alcohol-based adhesives and modified polyvinyl. Alcohol, polyurethane adhesive, polyester adhesive, polyacrylic adhesive, polyepoxy adhesive, and polycyanoacrylate adhesive are main components.

In the present invention, the modified polyvinyl alcohol-based compound is mainly used in consideration of aspects such as polarizer and bonding properties, post-bonding physical properties and water resistance, and the remaining compounds are preferably used alone or in combination. In addition, the modified polyvinyl alcohol-based adhesive is a modified polyvinyl alcohol-based adhesive composed of monomers of the modified polyvinyl alcohol-based compound alone, a modified polyvinyl alcohol-based adhesive composed of two or more monomers of the modified polyvinyl alcohol-based compound, and modified polyvinyl alcohol-based It is possible to use a modified polyvinyl alcohol-based adhesive using a modified polyvinyl alcohol-based compound made of a monomer containing a functional group in the adhesive alone or in combination.

In the present invention, the modified polyvinyl alcohol compound refers to a vinyl alcohol polymer containing a predetermined amount of acetacetyl group. Vinyl alcohol polymers containing a predetermined amount of acetacetyl group are dissolved in water and have a tough and transparent property. In addition, the adhesive using the same is stable and excellent adhesion and at the same time very strong water resistance.

The polymerization degree and saponification degree of the modified polyvinyl alcohol compound used in the present invention are not particularly limited as long as they contain an acetacetyl group, but the polymerization degree is 1000 to 2500, and the saponification degree is preferably 85 mol% to 99.9 mol%. Considering the flexible mixing with the containing material according to the freedom of molecular movement, the degree of polymerization is 1500 to 2000, and the degree of saponification is more preferably 95 mol% to 99.9 mol%. It is preferable that the said modified polyvinyl alcohol-type compound contains the said acetacetyl group in 10-50 mol%. Within the above range, the reaction with the water-soluble crosslinking agent may be smooth, and sufficient attention may be paid to the water resistance of the desired adhesive.

It is preferable that the modified polyvinyl alcohol-type compound is 1 to 10 weight% in 100 weight% of the said adhesive compositions. In consideration of economy, viscosity and water resistance, the content of the polyvinyl alcohol-based resin is more preferably 1% by weight to 5% by weight.

(2) crosslinking agent

In the present invention, a multifunctional compound can be used as the crosslinking agent. The multifunctional compound is, for example, an organic cross-linking agent, a polyvalent metal compound or a multifunctional metal chelate. Epoxy type crosslinking agents, cross-linking agents of isocyanate type and imine type cross-linking agents are included in the examples of organic crosslinking agents. Further examples of the polyvalent metal compound include zirconyl nitrate and zirconium carbonate animonium. The multifunctional metal chelate is a compound formed by bonding a polyvalent metal atom and an organic compound through covalent or coordinating bonds. Examples of polyvalent metal atoms include Al, Cr, Zr, Co, Cu, Fe, Ni, V, Zn, In, Ca, Mg, Mn, Y, Ce, Sr, Ba, Mo, La, SN, and Ti. have. As an example of the atom of the organic compound which forms a covalent bond or coordination bond, an oxygen atom can be mentioned. Examples of such organic compounds include alkyl esters, alcohol compounds, carboxylic acid compounds, ether compounds and ketone compounds. In the present invention, it is preferable to use zirconium nitrate, which is a multivalent metal compound, or polyethylene imine, which is an imine type, alone or in combination as a crosslinking agent.

In the present invention, the crosslinking agent is preferably 0.01% to 50% by weight in 100% by weight of the adhesive composition. More preferably, it is 0.1 to 30 weight%. If the water-soluble crosslinking agent is less than 0.01% by weight, it is difficult to expect the effect of increasing the durability due to the addition of the water-soluble crosslinking agent, and if the water-soluble crosslinking agent is 50% by weight or more, the crosslinking density is significantly increased to increase viscosity, making it difficult to easily process the adhesive composition. do. Moreover, when there is too much compounding quantity of a crosslinking agent, reaction of a crosslinking agent will advance easily in a short time, and there exists a tendency for an adhesive agent to gelatinize. As a result, the usable time (pot life) as an adhesive may be shortened.

(3) additive

In the present invention, the adhesive composition comprises glass fiber, glass beads, metal powders and other inorganic powders, pigments, coloring agents, bulking agents, antioxidants, ultraviolet absorbers as needed. Fillers, plasticizers, tackifiers and silane coupling agents made of ultraviolet absorbents can be used. In addition, various additives may be used as appropriate within the scope of the present invention. In addition, the adhesive composition may include fine particles, and may be formed of an adhesive layer exhibiting light diffusing properties. In the present invention, the addition of the silane coupling agent is suitable for adjusting the adhesive strength.

 Examples of silane coupling agents that can be used for this purpose include, but are not limited to, vinyltriethoxysilane, vinyltri (beta-methoxyethoxy) silane, gamma-methacryl Γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, gamma-glycidoxypropyltrimethoxysilane, gamma- glycidoxypropyltriethoxy Silane (γ-glycidoxypropyltriethoxysilane), beta- (3,4-ethoxycyclohexyl) ethyltrimethoxysilane (β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane), gamma-chloropropylmethoxysilane (γ- chloropropylmethoxysilane, vinyltrichlorosilane, gamma-mercaptoprophiltrimethoxysilane, gamma-aminopropyltriethoxysilane, and Small-beta (aminoethyl) -γ- aminopropyl trimethoxy silane (N-β (aminoethyl) -γ-aminopropyltrimethoxysilane). These silanes may be used alone or in combination of two or more thereof. In the present invention, the addition of the silane coupling agent in an amount of 0.01% to 5.0% by weight, preferably 0.03% to 2.0% by weight in terms of 100% by weight of the adhesive composition may take into account the processability and adhesive strength of the adhesive for polarizing plates. When appropriate.

As described above, by using a modified polyvinyl alcohol and a crosslinking agent in the adhesive composition for polarizing plates according to the present invention, an adhesive for polarizing plates having excellent adhesiveness and water resistance in a high temperature and high humidity environment can be made.

In the case of manufacturing polarizing plate using this, even if left for a long time in high temperature and high humidity environment, iodine does not sublimate and shrink polarizer, no polarization performance is deteriorated, and polyvinyl alcohol (PVA) adhesive, which is vulnerable to moisture, provides a protective function. It does not peel off even with a triacetylcellulose (TAC) film.

In Figure 1 it can be confirmed the excellent effect on the water resistance test of the polarizing plate using the adhesive for polarizing plate of the present invention.

Polarizer shrinkage, iodine discoloration, and TAC separation were measured using the polarizing plates prepared from the examples. In the comparative example, the experiment was performed using general polyvinyl alcohol instead of modified polyvinyl alcohol.

(1) Example 1

A polarizing plate formed of an adhesive composition containing a modified polyvinyl alcohol resin, zirconyl nitrate, and polyethylene imine was immersed in 55 ° C. water for 2 hours to evaluate water resistance. The polarizing plate was manufactured under the following conditions.

(a) Preparation of Polarizer 10

The polyvinyl alcohol film having a thickness of 75 μm was moved by using a guide roll, and immersed and dyed in a dye solution of iodine and potassium iodine, and then stretched about 3 to 5 times. The film was introduced into a bath of boric acid and potassium iodide, crosslinked, and dried at 80 ° C. for 5 to 8 minutes to obtain a polarizer.

(b) Preparation of Adhesive Composition

An adhesive composition was prepared by adding 3.3% by weight of modified polyvinyl alcohol (average degree of polymerization,% reduction), 3% by weight of zirconyl nitrate and polyethylene imine in 100% by weight of the adhesive composition.

(c) Preparation of Polarizing Plate 40

Using the adhesive prepared above, a saponified TAC film having a thickness of 80 μm as the polarizer protective layer 20 while applying the adhesive layer 30 to both surfaces of the polarizer 10 at a thickness of 50 μm and maintaining 35 ° C. After adhering, laminating and drying, a polarizing plate 40 was prepared.

(2) Example 2

 The polarizing plate formed from the adhesive composition prepared by adding 3% by weight of zirconyl nitrate in 100% by weight of the adhesive composition was immersed in 55 ° C water for 2 hours to evaluate the water resistance. Other conditions are the same as in Example 1.

(3) Example 3

The polarizing plate formed from the adhesive composition prepared by adding 3% by weight of polyethylene imine in 100% by weight of the adhesive composition was immersed in 55 ° C water for 2 hours to evaluate water resistance. Other than that was the same condition as Example 1.

(4) Example 4

The polarizing plate formed of 7.5 parts by weight of zirconyl nitrate and polyethylene imine and 3.0 parts by weight of the adhesive composition in 100% by weight of the adhesive composition was immersed in 55 ° C. water for 2 hours to evaluate water resistance.

(5) Comparative Example

The polyvinyl alcohol (PVA) resin was dissolved in 3.0 wt%, and used as an adhesive to prepare a polarizing plate, and immersed in 55 ° C water for 2 hours to evaluate water resistance. Other than that was the same conditions as the Example.

Adhesive composition Polarizer shrinkage (mm) Iodine bleaching (mm) TAC isolation Comparative Example 3.3 weight% of PVA resin in 100 weight% of adhesive compositions 2.15 4.20 detach Example 1 3.3 weight% of modified polyvinyl alcohol compounds, ₃ weight% of ZrO (NO3) ₂ + 3 weight% of polyetherinimines in 100 weight% of adhesive compositions 0.02 0.05 none Example 2 3.3 weight% of modified polyvinyl alcohol compounds, ₃ weight% of ZrO (NO3) _{2 in} 100 weight% of adhesive compositions 0.06 0.12 none Example 3 3.3 weight% of modified polyvinyl alcohol compounds, 3 weight% of polyethyleneimines in 100 weight% of adhesive compositions 0.12 0.26 none Example 4 The adhesive composition of 3.3% by weight of modified polyvinyl alcohol compound in 100% by weight, ZrO (NO _{3) 2} 7.5 parts by weight of polyethyleneimine + 3% by weight 0.00 0.02 none

In the comparative example of Table 1, the polarizer shrinkage, iodine decolorization, and TAC separation were described numerically when a general PVA resin was used. In addition, in the case of using a general PVA resin in Figure 1, the polarizer shrinkage degree (A) and iodine decolorization phenomenon (B) is severe as shown in the water resistance experiment is separated from the TAC, the performance of the polarizing plate can be significantly reduced in high humidity environment I can guess.

However, when zirconium nitrate or polyethylene imine was used as the modified polyvinyl alcohol resin and the crosslinking agent in Examples 1 to 4, it was confirmed that the polarizer shrinkage phenomenon and iodine decolorization were not significantly separated from the TAC as a result of the water resistance test.

In particular, the experimental results according to Example 4 are shown in FIG. The polarizer shrinkage does not occur at all, the discoloration of iodine is negligible and the separation with TAC does not occur, so when manufacturing a polarizing plate by the adhesive composition for a polarizing plate according to the present invention changes in performance even in a high humidity environment It was possible to produce an excellent polarizing plate.

In the above, this invention was demonstrated in detail with reference to an Example and a comparative example centering on a structure. However, the scope of the present invention is not limited to the above embodiments, but may be embodied in various forms of embodiments within the scope of the appended claims. Without departing from the gist of the invention as claimed in the claims, any person of ordinary skill in the art is deemed to be within the scope of the claims underlying the present invention to the extent possible for various modifications.

1 is a photograph of the water resistance test results of the polarizing plate manufactured by a comparative example of the prior art,

Figure 2 is a photograph of the water resistance test results of the polarizing plate according to Example 4 of the present invention,

3 is a cross-sectional view illustrating a structure of a polarizing plate in which a polarizer protective layer is bonded to both upper and lower sides of a polarizer by the adhesive layer according to the present invention.

<Explanation of symbols for the main parts of the drawings>

A: polarizer shrinkage degree

B: iodine discoloration degree

10: polarizer

20: polarizer protective layer

30: adhesive layer

40: polarizer

Claims (11)

A modified polyvinyl alcohol compound and a crosslinking agent, wherein the modified polyvinyl alcohol compound is 1% by weight to 10% by weight in an adhesive composition for a polarizing plate, characterized in that the polarizing plate adhesive composition. The method of claim 1, PH of the said adhesive composition for polarizing plates is 5 or less, The adhesive composition for polarizing plates characterized by the above-mentioned. The method of claim 2, PH of the adhesive composition for polarizing plate is adjusted to at least one acid selected from nitric acid, hydrochloric acid, sulfuric acid and acetic acid adhesive composition for a polarizing plate. The method of claim 1, The viscosity of the said adhesive composition for polarizing plates is 1 mPa * s-100 mPa * s, The adhesive composition for polarizing plates characterized by the above-mentioned. The method of claim 1, Said crosslinking agent is 0.01 weight%-50 weight% in 100 weight% of adhesive composition, The adhesive composition for polarizing plates characterized by the above-mentioned. The method of claim 1, The crosslinking agent is an adhesive composition for a polarizing plate using any one or more of an epoxy crosslinking agent, an isocyanate crosslinking agent, an imine crosslinking agent, a polyvalent metal compound or a multifunctional metal chelate. The method of claim 6, Adhesive composition for a polarizing plate, characterized in that the imine crosslinking agent is polyethylene imine. The method of claim 6, The polyvalent metal compound is zirconyl nitrate, zirconium carbonate ammonium characterized in that the adhesive composition for a polarizing plate. The method of claim 6, The multifunctional metal chelate is a compound formed by bonding a polyvalent metal atom and an organic compound through a covalent bond or a coordinating bond, and the multivalent metal atom is Al, Cr, Zr, Co, Cu, Fe, Ni, V, Zn, In, Ca, Mg, Mn, Y, Ce, Sr, Ba, Mo, La, SN and Ti, and the organic compounds forming covalent or coordinating bonds are alkyl esters, alcohol compounds, carboxylic acid compounds, ether compounds and ketone compounds Adhesive composition for polarizing plates characterized by the above-mentioned. The method of claim 1, The adhesive composition further comprises an additive, the adhesive composition for a polarizing plate comprising 0.01 to 5.0% by weight of the silane coupling agent as an additive in 100% by weight of the adhesive composition. The method of claim 10, The silane coupling agent is vinyltriethoxysilane, vinyltri (beta-methoxyethoxy) silane, gamma-methacryloxypropyltrimethoxysilane (γ-methacryloxypropyltrimethoxysilane), vinyltriacetoxysilane, gamma-glycidoxypropyltrimethoxysilane, gamma-glycidoxypropyltriethoxysilane (γ-glycidoxypropyltriethoxysilane), Beta- (3,4-ethoxycyclohexyl) ethyltrimethoxysilane (β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane), gamma-chloropropylmethoxysilane, vinyltrichlorosilane (vinyltrichlorosilane), gamma-mercaptoprohiltrimethoxysilane, gamma-aminopropyltriethoxysilane, and nitrogen-beta (aminoethyl) -γ-aminoprop Peel-trimethoxy silane (N-β (aminoethyl) -γ-aminopropyltrimethoxysilane) a polarizing plate alone or an adhesive composition which is characterized by using a mixture of two or more.

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