KR20220118743A - Adhesive composition for polarizing plate, polarizing plate and display device comprising the same - Google Patents

Abstract

The present invention contains a polyvinyl alcohol-based resin, a crosslinking agent, and a water-soluble salt of a polyvalent metal ion, and has a pH of 1 to 4, so that it has excellent durability and heat-and-moisture resistance properties even under humidified heat conditions, and has improved water resistance. It also relates to an adhesive composition for a polarizing plate capable of exhibiting excellent adhesion and adhesion to various polymer films, improving warpage properties, and improving transparency by suppressing an interference fringe phenomenon, a polarizing plate and a display device using the same.

Description

Adhesive composition for polarizing plate, polarizing plate and display device using the same

The present invention relates to an adhesive composition for a polarizing plate, a polarizing plate and a display device using the same.

The polarizing plate is an optically functional film applied to a display device such as a liquid crystal display (LCD) or an organic light emitting diode display (OLED).

In general, a polarizing plate consists of a polarizer and a protective film bonded to one or both surfaces of the polarizer. Specifically, an iodine-based film in which iodine is adsorbed to polyvinyl alcohol or a dye-based film in which dichroic dye is adsorbed and oriented to polyvinyl alcohol is used as a polarizer, and an aqueous solution of polyvinyl alcohol-based resin is applied to at least one surface of the film. Although a polarizing plate having a structure in which a protective film such as triacetyl cellulose (TAC) is bonded through an adhesive layer formed using (polyvinyl alcohol-based adhesive) is used, when only an aqueous solution of polyvinyl alcohol-based resin is used, the spreadability of the aqueous solution is poor. And, there is a problem that the adhesion and adhesion are relatively insufficient, and the water resistance and durability are inferior.

In addition, when the adhesive strength between the polarizer and the protective film is poor, deformation may occur during handling or use during processing, and red discoloration may occur when exposed to high temperature or high humidity conditions for a long time. Therefore, the adhesive composition included in the polarizing plate plays an important role in the durability of the polarizing plate. It should have excellent properties such as durability, moisture and heat resistance and water resistance, it should be possible to prevent deterioration of optical properties, and high adhesion and adhesion to various protective films. An adhesive composition having a

Korean Patent Registration No. 10-0864361, etc. discloses an adhesive for a polarizing plate comprising a polyvinyl alcohol-based resin, a polyvinyl alcohol-based resin containing an acetacetyl group, and an amine-based metal compound crosslinking agent, but acetoacetyl group-modified polyvinyl alcohol When the amine-based metal compound crosslinking agent is included in the resin, the amount of the crosslinking agent is excessively large, and the optical properties (transmittance and polarization degree) of the polarizing plate are deteriorated due to the high content of the amine.

Republic of Korea Patent Registration No. 10-0864361 (2008.10.17. Announcement)

An object of the present invention is to provide an adhesive composition for a polarizing plate having excellent durability and heat-and-moisture resistance properties and improved water resistance even under humidified heat conditions, a polarizing plate and a display device using the same.

In addition, the present invention provides an adhesive composition for a polarizing plate capable of exhibiting excellent adhesion and adhesion to various polymer films, improving the bending properties, and improving transparency by suppressing the interference fringe phenomenon, a polarizing plate and a display device using the same purpose of the invention.

In order to achieve the above object, the present invention provides an adhesive for a polarizing plate comprising (A) a polyvinyl alcohol-based resin, (B) a crosslinking agent, and (C) a water-soluble salt of a polyvalent metal ion, and having a pH of 1 to 4 A composition, a polarizing plate using the same, and a display device are provided.

The adhesive composition for a polarizing plate according to the present invention, a polarizing plate and a display device using the same have excellent durability and heat-and-moisture resistance properties even under humidified heat conditions, and can provide an effect of improved water resistance.

In addition, the adhesive composition for a polarizing plate according to the present invention, a polarizing plate and a display device using the same, exhibit excellent adhesion and adhesion to various polymer films, improve bending properties, and suppress the interference fringe phenomenon to improve transparency. can provide

The present invention relates to an adhesive composition for a polarizing plate, a polarizing plate and a display device using the same.

In the present specification, when a part "includes" a certain component, this means that other components may be further included, rather than excluding other components, unless otherwise stated.

<Adhesive composition for polarizing plate>

The adhesive composition for a polarizing plate according to the present invention comprises (A) a polyvinyl alcohol-based resin, (B) a crosslinking agent, and (C) a water-soluble salt of a polyvalent metal ion, and has a pH of 1 to 4.

Preferably, the adhesive composition for a polarizing plate may be an adhesive composition for a two-component polarizing plate.

When the adhesive composition is prepared in a two-part type, it is preferable because the pot life of the prepared adhesive composition is improved to prevent the adhesive composition from becoming a gel.

In the adhesive composition for a polarizing plate according to an embodiment of the present invention, the adhesive composition for a two-component polarizing plate may include a first liquid and a second liquid, and is a mixture of the first liquid and the second liquid. can be used

The first liquid and the second liquid are arbitrarily divided in order to clarify the difference in composition included in the adhesive composition, and are not intended to be limited to a specific disclosure form, and all changes and equivalents included in the spirit and scope of the present invention It should be understood to include water or substitutes.

Of the adhesive composition for a polarizing plate, the first solution may include (A) a polyvinyl alcohol-based resin and (B) a crosslinking agent.

Of the adhesive composition for a polarizing plate, the second solution may include (A) a polyvinyl alcohol-based resin and (C) a water-soluble salt of a polyvalent metal ion.

The adhesive composition for a polarizing plate may be mixed with the first liquid and the second liquid in a weight ratio of 0:8:1.2 to 1.2:0.8, preferably in a weight ratio of 1:1. When mixing is performed in a range out of the above weight ratio, the mixed addition amount of glyoxal or metal salt increases, causing rapid gelation or deterioration of adhesive performance such as adhesion or water resistance.

The adhesive composition for a polarizing plate of the present invention is a one-component composition comprising (A) a polyvinyl alcohol-based resin, (B) a crosslinking agent, and (C) a water-soluble salt of a polyvalent metal ion, and the first and second solutions described above Includes all of the two-component composition comprising a.

When the adhesive composition for a polarizing plate of the present invention is a two-component composition including the first liquid and the second liquid, each composition of the first liquid and the second liquid is also included in the scope of the present invention. As an example, the present invention provides an adhesive composition for a polarizing plate, comprising (A) a polyvinyl alcohol-based resin and (C) a water-soluble salt of a polyvalent metal ion, (A) a polyvinyl alcohol-based resin and (B) ) to be mixed with the first solution containing a crosslinking agent so that the pH of the adhesive composition is 1 to 4, the second solution includes an adhesive composition for a polarizing plate.

In addition, the present invention is an adhesive composition for a polarizing plate comprising (A) a polyvinyl alcohol-based resin and (B) a crosslinking agent, (A) polyvinyl alcohol-based resin and (C) water solubility of polyvalent metal ions It includes an adhesive composition for a polarizing plate of the first solution, which is for preparing a pH of the adhesive composition to be 1 to 4 by mixing with the second solution containing the salt.

Hereinafter, the configuration included in the adhesive composition for a polarizing plate according to the present invention will be described in detail.

(A) polyvinyl alcohol-based resin

The polyvinyl alcohol-based resin according to the present invention may serve to impart adhesiveness, and may provide an effect of improving adhesion between the protective film and the polarizer.

As the polyvinyl alcohol-based resin, not only a polyvinyl alcohol resin, but also a modified polyvinyl alcohol-based resin can be used.

As the modified polyvinyl alcohol-based resin, for example, at least one selected from an acetoacetyl group-modified polyvinyl alcohol-based resin, a cation-modified polyvinyl alcohol-based resin, and an anionic-modified polyvinyl alcohol-based resin is used alone or mixed In the case of using such a modified polyvinyl alcohol-based resin, it is preferable in terms of improving the water resistance of the adhesive composition.

Moreover, it is more preferable to use acetoacetyl group-modified polyvinyl alcohol-type resin among the said polyvinyl alcohol-type resin.

The acetoacetyl group-modified polyvinyl alcohol-based resin contains a functional group that is highly reactive compared to other modified polyvinyl alcohol-based resins such as carboxyl group-modified, methylol group-modified, and amino group-modified. It can exhibit high durability.

The acetoacetyl group-modified polyvinyl alcohol-based resin may be obtained by reacting a polyvinyl alcohol-based resin and diketene by a known method. Specifically, a method of adding diketene after dispersing a polyvinyl alcohol-based resin in a solvent such as acetic acid, dissolving the polyvinyl alcohol-based resin in a solvent such as dimethylformamide or dioxane, and then diketene The method of adding or the method of making diketene gas or liquid diketene directly contact with polyvinyl alcohol, etc. are mentioned.

Examples of the polyvinyl alcohol-based resin include polyvinyl alcohol and derivatives thereof obtained by saponifying polyvinyl acetate; a saponified product of a copolymer of vinyl acetate and a monomer having copolymerizability; and modified polyvinyl alcohol obtained by acetalization, urethanation, etherification, grafting, or phosphate esterification of polyvinyl alcohol. Examples of the monomer include unsaturated carboxylic acids and esters thereof such as (anhydride) maleic acid, fumaric acid, crotonic acid, itaconic acid, and (meth)acrylic acid; α-olefins such as ethylene and propylene, (meth)allylsulfonic acid (soda), sodium sulfonate (monoalkyl maleate), sodium disulfonate alkyl maleate, N-methylolacrylamide, acrylamide alkylsulfonic acid alkali salt, N- and vinylpyrrolidone or N-vinylpyrrolidone derivatives, and the polyvinyl alcohol-based resin may be used alone or in combination of two or more.

Specifically, the acetoacetyl group-modified polyvinyl alcohol-based resin (A) includes Gohsefimer Z-100, Z-200, Z-200H, Z-210, Z-220 and Z-320 (Japan Synthetic Chemicals). However, the present invention is not limited thereto.

When the acetoacetyl group-modified polyvinyl alcohol-based resin is included, the degree of acetoacetyl group modification may be 0.1 mol% or more, preferably 0.1 to 40 mol%, more preferably 1 to 20 mol%, most preferably It may be 2 to 7 mol%. When the degree of modification of the acetoacetyl group is less than 0.1 mol%, the water resistance of the adhesive layer is insufficient and thus unsuitable. When the degree of modification of the acetoacetyl group exceeds 40 mol%, the effect of improving water resistance may be insignificant.

In addition, the degree of polymerization of the polyvinyl alcohol-based resin may be 100 to 3,000, preferably 100 to 1,500. When the polymerization degree of the polyvinyl alcohol system satisfies the above ranges, it has excellent durability and heat resistance, is advantageous in terms of improving the adhesion between the polarizing plate and the protective film, and the viscosity is not excessively high, so that the adhesive is uniform between the polarizer and the protective film. It is preferable to provide a thickness.

In addition, the saponification degree (saponification degree) of the polyvinyl alcohol-based resin may be 80 mol% or more, preferably 85 mol% or more. When the degree of saponification of the polyvinyl alcohol-based resin is less than the above range, sufficient water solubility is difficult to be expressed, and thus a problem of lowering adhesion may occur.

The polyvinyl alcohol-based resin (A) contained in the first solution according to the present invention may be included in an amount of 20 to 80 parts by weight, preferably 25 to 70 parts by weight, based on 100 parts by weight of the first solution.

In addition, the polyvinyl alcohol-based resin (A) included in the second solution may be included in an amount of 15 to 70 parts by weight, preferably 20 to 65 parts by weight, based on 100 parts by weight of the second solution.

When the content of the polyvinyl alcohol-based resin (A) contained in each of the first and second solutions satisfies the above range, there is an advantage that the adhesive strength can be further improved, and when it is included below each content range There is a fear that the adhesive strength is somewhat lowered, and when included in excess of each content range, the effect of improving the adhesive strength compared to the increased content is insignificant, which may be undesirable from an economic point of view.

(B) crosslinking agent

The adhesive composition for a polarizing plate according to the present invention includes (B) a crosslinking agent. Specifically, the (B) crosslinking agent may be included in the first solution of the adhesive composition for a polarizing plate according to the present invention.

Examples of the crosslinking agent include alkylenediamines having an alkylene group and two amino groups, such as ethylenediamine, triethylenediamine, and hexamethylenediamine; Tolylene diisocyanate, hydrogenated tolylene diisocyanate, trimethylolpropane tolylene diisocyanate adduct, triphenylmethane triisocyanate, methylenebis (4-phenylmethane triisocyanate, isophorone diisocyanate and their ketoxime block products or phenol block products) isocyanates such as ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin di or triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, di Epoxy such as glycidylaniline and diglycidylamine; Monoaldehyde such as formaldehyde, acetaldehyde, propionaldehyde and butylaldehyde; Glyoxal, malondialdehyde, succindialdehyde, glutaldialdehyde, maledialdehyde dialdehydes such as , phthaldialdehyde; amino-formaldehyde resins such as methylol urea, methylol melamine, alkylated methylol urea, alkylated methylolated melamine, acetguanamine, benzoguanamine and formaldehyde condensate and a glyoxal-based crosslinking agent may be preferably used.

When a glyoxal-based crosslinking agent is included as the crosslinking agent, the aldehyde group in the glyoxal-based crosslinking agent undergoes a condensation reaction with the hydroxyl group included in the (A) polyvinyl alcohol-based resin, polarizer, or protective film to improve the degree of crosslinking of the adhesive composition Thus, it is possible to improve the adhesion, adhesion, and water resistance between the polarizer and the protective film bonded with the adhesive composition.

The content of the (B) crosslinking agent may be 5 to 30 parts by weight, preferably 6 to 20 parts by weight, based on 100 parts by weight of the (A) polyvinyl alcohol-based resin solid content included in the first solution. When the content of the crosslinking agent is less than the above range, the water resistance of the adhesive layer made of the adhesive composition including the crosslinking agent may be deteriorated, and if it exceeds the above range, the stability of the crude solution may be deteriorated. Although the adhesive composition for a polarizing plate of the present invention contains a small amount of the crosslinking agent (B), there is an advantage in that the adhesive strength or adhesion is more excellent.

(C) water-soluble salts of polyvalent metal ions

The adhesive composition for a polarizing plate according to the present invention includes (C) a water-soluble salt of a polyvalent metal ion. Specifically, (C) the water-soluble salt of the polyvalent metal ion may be included in the second solution of the adhesive composition for a polarizing plate according to the present invention.

The adhesive composition for a polarizing plate of the present invention contains one or more (C) water-soluble salts of polyvalent metal ions, thereby enhancing the effect of the (B) crosslinking agent to improve the degree of crosslinking of the adhesive composition comprising the same, and using the same It is possible to provide an effect of improving the degree of crosslinking between the adhered polarizer and a protective film such as PC (polycarbonate), PET (polyethylene tetraphthalate), or PI (polyimide) film.

That is, in the present invention, by including one or more (C) water-soluble salts of polyvalent metal ions under specific conditions, it is possible to provide an effect of improving the adhesion and durability of the polarizer to the protective film, particularly PC, PET, and PI films.

In addition, in the present invention, when a water-soluble salt of a metal ion that satisfies the following conditions is included, better adhesion can be exhibited. Specifically, the water-soluble salt of the polyvalent metal ion may be a water-soluble salt of a metal ion having a pH of 1 to 4 or less and an oxidation number of +1 to +4 after the composition of the adhesive composition.

The water-soluble salt of the polyvalent metal ion is specifically selected from the group consisting of zirconium oxynitrate, zirconium acetate, iron nitrate, zirconium ammonium, zinc chloride, cobalt chloride, magnesium chloride, magnesium acetate, aluminum nitrate, zinc nitrate and zinc sulfate. It may be a hydrate (hydrate) of a polyvalent metal ion compound.

The water-soluble salt of the polyvalent metal ion may be included in an amount of 1.35 to 15 parts by weight based on 100 parts by weight of the solid content of the polyvinyl alcohol-based resin (A) included in the second solution. When the content of the water-soluble salt of the polyvalent metal ion is less than the above range, there may be a problem that the water resistance of the adhesive layer made of the adhesive composition including the metal ion additive is insufficient, and if it exceeds the above range, the stability of the crude solution is lowered Problems can arise.

The pH of the adhesive composition for a polarizing plate according to the present invention is preferably 1 to 4, and more preferably 1 to 3. The pH of the adhesive composition for a polarizing plate may be affected by the type of the water-soluble salt of the polyvalent metal ion.

In the case of the conventional adhesive composition for a polarizing plate, the pH was adjusted by adding an acid such as hydrochloric acid, acetic acid, or nitric acid. However, when the pH is adjusted using an acid, the surface of the polarizer is damaged and discolored by the highly reactive adhesive component. This is not recommended as it may cause problems.

When the pH of the adhesive composition for a polarizing plate according to the present invention satisfies the above range, it is preferable because it has the advantage of sufficiently securing adhesion to PET, PC, and PI substrates using water-based adhesives, including films such as conventional TAC. do. However, when the pH is out of the above range, adhesion may be insufficient, and accordingly, there may be problems such as light leakage of the polarizing plate and lifting during transportation due to peeling of the substrate due to deterioration of water resistance or adhesion.

The viscosity at 25° C. of the adhesive composition for a polarizing plate according to the present invention is preferably within the range of 3 to 25 mPa·sec. When the viscosity of the adhesive composition is less than 3 mPa·sec, the water resistance of the adhesive layer made of the adhesive composition cannot be sufficiently expressed, and when the viscosity exceeds 25 mPa·sec, optical properties of a polarizing plate including the adhesive layer There is a problem of this deterioration.

In addition, the adhesive composition for a polarizing plate of the present invention may further contain additives such as a plasticizer, a silane coupling agent, an antistatic agent, fine particles, and a leveling agent to the extent that the effects of the present invention are not impaired.

The form of the adhesive composition is not particularly limited, but in order to form a uniform adhesive layer on the surface of a polarizer or a protective film as an adherend, it is preferably a liquid type. As such a liquid adhesive, a solution type or dispersion type of various solvents can be used. Considering the coatability of the substrate, the solution type is preferable, and considering the stability, a solution type or dispersion type using water as a solvent is suitable. .

<Polarizer>

The polarizing plate of the present invention may be one in which a protective film is laminated together with an adhesive layer made of the adhesive composition for a polarizing plate of the present invention on at least one surface of a polarizer (polarizing film).

polarizer

The polarizer (or polarizing film) according to the present invention is an optical film that serves to change incident natural light into a desired single polarization state (linear polarization state). It may be a polarizer commonly used in the art manufactured according to a process including steps such as.

As the polarizer, the type is not particularly limited as long as it is a dichroic material, that is, a film that can be dyed with iodine. a film, a polyethylene terephthalate film, an ethylene-vinyl acetate copolymer film, an ethylene-vinyl alcohol copolymer film, a cellulose film, these partially saponified films, etc. are mentioned. Among them, a polyvinyl alcohol-based film is preferable in that it is excellent in the effect of enhancing the uniformity of the degree of polarization in the plane and also has excellent dyeing affinity to iodine.

The polyvinyl alcohol-based film or resin used as the polarizer is independent of the (A) polyvinyl alcohol-based resin included in the adhesive composition for a polarizing plate according to the present invention.

The polyvinyl alcohol-based resin constituting the polarizer can be produced by saponifying polyvinyl acetate-based resin. The degree of saponification of the polyvinyl alcohol-based resin may be 85 to 100 mol%, preferably 90 mol% or more, and more preferably 98 to 100 mol%.

Examples of the polyvinyl acetate-based resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, or a copolymer of vinyl acetate and other copolymerizable monomers. Specific examples of the other monomer copolymerizable with vinyl acetate include unsaturated carboxylic acids, unsaturated sulfonic acids, olefins, unsaturated amines, vinyl ethers, and acrylamides having an ammonium group.

In addition, the polyvinyl alcohol-based resin may be modified, for example, polyvinyl formal, polyvinyl acetal or polyvinyl butyral modified with aldehydes may be used.

The degree of polymerization of the polyvinyl alcohol-based resin is 1,000 to 10,000, preferably 1,500 to 5,000.

The polyvinyl alcohol-based resin may be formed into a film and used as a polarizer. A method for forming a film of the polyvinyl alcohol-based resin is not particularly limited, and various methods known in the art may be used. For example, the process of uniaxially stretching a polyvinyl alcohol-type resin film; dyeing the stretched film with a dichroic dye to adsorb the dye; a process of treating the dye-adsorbed film with an aqueous solution of boric acid; And it can be manufactured through a process of washing with water.

Uniaxial stretching may be performed before dyeing with a dye, may be performed simultaneously with dyeing, and may be performed after dyeing. When performing uniaxial stretching after dyeing|staining, uniaxial stretching may be performed before a boric-acid process, may be performed during a boric-acid process, and may be performed after a boric-acid process. Moreover, uniaxial stretching can be performed in several steps. As a uniaxial stretching method, a raw film can be uniaxially stretched between different rolls, or can be uniaxially stretched using a hot roll. Moreover, it can carry out by dry-type extending|stretching which extends|stretching in air|atmosphere, and can carry out by wet extending|stretching which extends|stretches in the state made it swollen with a solvent. In the uniaxial stretching process, the draw ratio is usually 3 to 8 times.

In order to dye a polyvinyl alcohol-type film with a dichroic dye, it can carry out according to a well-known method, For example, the polyvinyl alcohol-type film can be immersed in the aqueous solution containing a dichroic dye, and can be dyed. Specifically, as the dichroic dye, iodine or dichroic dye can be used. Further, the polyvinyl alcohol-based resin film is preferably immersed in water before the dyeing treatment.

When iodine is used as a dichroic dye, it can be carried out by immersing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide and dyeing the film. The content of iodine in the aqueous solution may be 0.01 to 1 part by weight per 100 parts by weight of water, and the content of potassium iodide may be usually included in an amount of 0.5 to 20 parts by weight per 100 parts by weight of water. The temperature of the aqueous solution used for dyeing is 20 to 40 ℃, the immersion time for the aqueous solution may be 20 to 1800 seconds.

In the case of using a dichroic dye as the dichroic dye, it may be carried out by immersing a polyvinyl alcohol-based resin film in an aqueous solution containing a water-soluble dichroic dye and dyeing the film. The content of the dichroic dye in the aqueous solution may be included in an amount of 1×10 ^-4 to 10 parts by weight, preferably 1×10 ^-3 to 1 parts by weight, per 100 parts by weight of water. The aqueous solution may further contain an inorganic salt such as sodium sulfate as a dyeing aid. The temperature of the aqueous dye solution used for dyeing is 20 to 80 °C, and the immersion time for the aqueous solution may be 10 to 1,800 seconds.

The boric acid treatment after dyeing with a dichroic dye is performed by immersing the dyed polyvinyl alcohol-type resin film in a boric-acid containing aqueous solution. The amount of boric acid in the boric acid-containing aqueous solution may be included in an amount of 2 to 15 parts by weight, preferably 5 to 12 parts by weight, per 100 parts by weight of water.

When using an iodine as a dichroic dye, it is preferable that the said boric-acid containing aqueous solution contains potassium iodide. The potassium iodide may be included in an amount of 0.1 to 15 parts by weight, preferably 5 to 12 parts by weight, per 100 parts by weight of water, and the immersion time in the boric acid-containing aqueous solution is 60 to 1,200 seconds, preferably 150 to 600 seconds, More preferably, it may be 200 to 400 seconds. The temperature of the boric acid-containing aqueous solution may be 50 °C or higher, preferably 50 to 85 °C, more preferably 60 to 80 °C.

The polyvinyl alcohol-based resin film after the boric acid treatment may be washed with water. The said water washing process is performed by immersing the polyvinyl alcohol-type resin film by which the boric acid process was carried out, for example in water. The preferable water temperature in a water washing process is 5-40 degreeC, and immersion time is 1 to 120 second.

After washing with water, a polarizer can be obtained through a drying process. The said drying process can use a hot-air dryer or a far-infrared heater. The temperature of the drying treatment is 30 to 100°C, preferably 50 to 80°C, and the time for the drying treatment is 60 to 600 seconds, preferably 120 to 600 seconds.

The thickness of the polarizer according to the present invention may be 5 to 40 μm, preferably 10 to 35 μm. When the thickness of the polarizer is less than 5 μm, there is a problem in that fairness and mass productivity are insufficient during the polarizer stretching process, and when it exceeds 40 μm, there is a problem that the thinning of the polarizing plate cannot be achieved.

protective film

The protective film according to the present invention is not particularly limited as long as it is a resin film excellent in transparency, mechanical strength, thermal stability, moisture shielding property, isotropy, and the like.

Specifically, as the protective film, a polyester-based resin film such as polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate, which is a polymer obtained by condensation polymerization of a dibasic acid and a dihydric alcohol;

Cellulose resin films, such as a diacetyl cellulose and a triacetyl cellulose;

Polycarbonate-type resin film which is a polymer which has a carbonate bond in a principal chain, and is obtained by condensation polymerization of bisphenol A and phosgene;

Acrylic resin films, such as polymethyl (meth)acrylate and polyethyl (meth)acrylate which are a homopolymer of methyl methacrylate, or a copolymer of methyl methacrylate and acrylic acid ester like methyl acrylate;

styrene-based resin films such as polystyrene and acrylonitrile-styrene copolymer;

polyolefin-based resin films such as cycloolefin, cycloolefin copolymer, polynorbornene, polypropylene, polyethylene, and ethylenepropylene copolymer;

vinyl chloride-based film; polyamide-based resin films such as nylon and aromatic polyamide;

other imide-based resin films; sulfone-based resin film; polyether sulfone-based resin film; polyether ketone-based resin film; sulfide polyphenylene-based resin film; vinyl alcohol-based resin film; vinylidene chloride-based resin film; vinyl butyral-based resin film; allylate-based resin film; polyoxymethylene-based resin film; urethane-based resin film; epoxy resin film; Or a silicone-based resin film, etc. may be used,

Preferably, a polycarbonate (PC)-based film, a polyethylene terephthalate-based (PET) film, or a polyimide-based (PI) film is preferable.

The bonding method of the polarizer and the protective film using the adhesive composition is not particularly limited, for example, the polarizer and/or the protective film by a casting method, a Mayer bar coating method, a gravure coating method, a die coating method, a dip coating method, a spraying method, etc. A method of applying an adhesive composition to the adhesive surface of The said casting method is a method of apply|coating an adhesive composition to the surface, while moving the polarizer or protective film which is a to-be-coated object in a mostly vertical direction, a mostly horizontal direction, or the diagonal direction between both.

After applying the adhesive composition, the polarizer and the protective film are sandwiched and bonded by a nip roll.

In addition, in order to improve the adhesiveness, the surface of the polarizer and/or the protective film may be appropriately subjected to surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, frame treatment, and saponification treatment. As said saponification process, the method of immersing in the aqueous solution of alkalis, such as sodium hydroxide and potassium hydroxide, is mentioned.

After laminating a polarizer and a protective film, a drying process is performed. The drying treatment is performed, for example, by spraying hot air, the temperature of the drying treatment may be 50 to 100° C., and the drying time may be 30 to 1,000 seconds, but is not limited thereto.

<Display device>

Another aspect of the present invention is a display device provided with the above-described polarizing plate.

The display device of the present invention includes the polarizing plate, and specific examples thereof include, but are not limited to, a liquid crystal display, an OLED, a flexible display, and the like.

Hereinafter, examples will be given to describe the present invention in detail. However, the embodiments according to the present invention may be modified in various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the present invention to those of ordinary skill in the art.

production example

Preparation Example 1: Preparation of polarizer

A 75 μm-thick polyvinyl alcohol film having an average degree of polymerization of 2,400 and a saponification degree of 99.9 mol% or more is uniaxially stretched at 5 times elongation in a dry method, and then dipped in water (distilled water) at 60° C. for 1 minute while maintaining the stretched state. After immersion, the iodine:potassium iodide:distilled water weight ratio was 0.05:5:100 immersed in an aqueous solution at 28 ℃ for 60 seconds. Thereafter, the potassium iodide: boric acid: distilled water weight ratio of 8.5: 8.5: 100 immersed in an aqueous solution at 72 ° C. for 300 seconds, washed with distilled water at 26 ° C. for 20 seconds and dried at 65 ° C. An adsorption-oriented polarizer was prepared.

Preparation Example 2: Preparation of a protective film

A polyethylene terephthalate (PET) film (LGC) having a thickness of 80 μm was used after saponification.

Preparation Example 3-1: Preparation of Example 1 Adhesive Composition

(1) Preparation of the first liquid composition

Dissolve acetoacetyl group-modified polyvinyl alcohol-based resin (Cosenol Z200, Nippon Synthetic Chemical Co., Ltd., saponification degree: 99.2 mol%, 4% aqueous solution viscosity: 12.5 mPa sec) in water (distilled water) to a concentration of 3.0% of an aqueous solution was prepared. A first solution was prepared by adding and mixing a 40% aqueous solution of a glyoxal crosslinking agent to the aqueous solution of the acetoacetyl group-modified polyvinyl alcohol-based resin. At this time, the acetoacetyl-modified polyvinyl alcohol-based resin and the glyoxal crosslinking agent were mixed so that the solid content weight ratio was 100:18.4.

(2) Preparation of the second liquid composition

Dissolve acetoacetyl group-modified polyvinyl alcohol-based resin (Cosenol Z200, Nippon Synthetic Chemical Co., Ltd., saponification degree: 99.2 mol%, 4% aqueous solution viscosity: 12.5 mPa sec) in water (distilled water) to a concentration of 3.0% of an aqueous solution was prepared. A second solution was prepared by adding and mixing zirconium oxynitrate hydrate (ZrO(NO ₃ ) ₂ ·H ₂ O) as a water-soluble salt of a polyvalent metal ion to the aqueous solution of the acetoacetyl group-modified polyvinyl alcohol-based resin. At this time, the acetoacetyl-modified polyvinyl alcohol-based resin and the water-soluble salt of the polyvalent metal ion were mixed so that the solid content weight ratio was 100:5.84, and 2 wt% of ethanol (99%) was added as an additive to the total weight of the second liquid composition. added.

(3) Preparation of adhesive composition

An adhesive composition for a polarizing plate was prepared by mixing the prepared first liquid composition and the second liquid composition at room temperature and stirring for about 1 hour. At this time, the mixing weight ratio of the first solution and the second solution was 1:1 to 1:1.1.

Preparation Example 3-2: Examples 2 to 10 and Comparative Examples 1 to 20 Preparation of adhesive compositions

In the same manner as in Example 1, adhesive compositions for polarizing plates according to Examples 2 to 10 and Comparative Examples 1 to 20 were prepared according to the water solubility of polyvalent metal ions shown in Table 1 below.

(unit:
parts by weight) first amount second amount pH note polyvinyl
Alcohol-based resin (Z200) crosslinking agent
(glyoxal) polyvinyl
Alcohol-based resin (Z200) polyvalent metal ions
water soluble salt Example 1 100 18.4 100 5.83 ZrO(NO ₃ ) ₂ H ₂ O 2-3 Example 2 100 18.4 100 5.83 ZrO(NO ₃ ) ₂ One Example 3 100 18.4 100 5.83 ZrO(C ₂ H ₃ O ₂ ) ₂ 3 Example 4 100 18.4 100 5.83 Fe(NO ₃ ) ₃ 9H ₂ O 3 Example 5 100 20 100 5.83 ZrO(NO ₃ ) ₂ H ₂ O 2-3 Example 6 100 18.4 100 5.83 ZrO(NO ₃ ) ₂ H ₂ O 2-3 Mixing ratio 1.1:1.0 Example 7 100 18.4 100 5.83 ZrO(NO ₃ ) ₂ H ₂ O 2-3 Mixing ratio 1.0:1.1 Example 8 100 18.4 100 5.83 ZrO(NO ₃ ) ₂ H ₂ O 2-3 Mixing ratio 1.0:1.2 Example 9 100 25 100 5.83 ZrO(NO ₃ ) ₂ H ₂ O 2-3 Example 10 100 18.4 100 7.00 ZrO(NO ₃ ) ₂ H ₂ O 2-3 Comparative Example 1 100 18.4 100 5.83 FeCl ₃ 2-3 Comparative Example 2 100 18.4 100 5.83 ZnCl ₂ 6-7 Comparative Example 3 100 18.4 100 5.83 Al(NO ₃ ) ₃ 9H ₂ O 5 Comparative Example 4 100 18.4 100 5.83 HCl One Comparative Example 5 100 18.4 100 5.83 H ₂ SO ₄ One Comparative Example 6 100 18.4 100 5.83 HNO ₃ One Comparative Example 7 100 18.4 100 5.83 Cu(NO ₃ ) ₂ ·3H ₂ O 6-7 Comparative Example 8 100 18.4 100 5.83 Zn(NO ₃ ) ₂ 6H ₂ O 6-7 Comparative Example 9 100 18.4 100 5.83 Mn(NO ₃ ) ₂ 6H ₂ O 6-7 Comparative Example 10 100 18.4 100 5.83 CoCl ₂ 6H ₂ O 6-7 Comparative Example 11 100 18.4 100 5.83 NiCl2·6H ₂ O 6-7 Comparative Example 12 100 18.4 100 5.83 K4[Fe(CN) ₆ ]·3H ₂ O 6-7 Comparative Example 13 100 18.4 100 5.83 NaCl 7 Comparative Example 14 100 18.4 100 5.83 HCOOK 7 Comparative Example 15 100 18.4 100 5.83 FeCl ₂ 4H ₂ O 6 Comparative Example 16 100 18.4 100 5.83 AlCl ₃ 6H ₂ O 6 Comparative Example 17 100 18.4 100 5.83 H ₃ BO ₃ 6 Comparative Example 18 100 18.4 100 5.83 KOH 14 Comparative Example 19 100 18.4 100 5.83 ZrO(NO ₃ ) ₂ H ₂ O 2 sulfuric acid 0.1 Comparative Example 20 100 18.4 100 5.83 ZrO(NO ₃ ) ₂ H ₂ O 1-2 sulfuric acid 0.5

Preparation Example 4: Preparation of a polarizing plate

After applying the adhesive composition for a polarizing plate of Examples and Comparative Examples to both sides of the polarizer prepared in Preparation Example 1, the protective film of Preparation Example 2 was bonded using a nip roll. The bonded polarizing plate was dried in a hot air dryer at 80° C. for 5 minutes to prepare a polarizing plate.

<Experimental example>

Experimental Example 1: Adhesion evaluation (cutter evaluation and bending evaluation)

Adhesion was evaluated for the Examples and Comparative Examples. After the prepared polarizing plate was left at room temperature for 1 hour, the cutter blade was placed between each film of the polarizing plate (between the polarizer and the protective film), and the degree of entry of the blade when the blade was pushed forward was evaluated by the following criteria and the results are shown in Table 2 below.

<Evaluation criteria>

(double-circle): The blade of a cutter does not enter between any films.

○: When the blade is pushed forward, it stops when the blade enters 1 to 2 mm between at least one of the films.

Δ: When the blade is pushed forward, it stops when the blade enters 3 to 5 mm between at least one of the films.

Х: When the blade is pushed forward, the blade smoothly enters between at least one of the films.

In the bending evaluation, after leaving the manufactured polarizing plate under the same conditions, after cutting about 50% of the thickness of the protective film using a cutter knife, when the film is strongly bent, bubbles and changes occurring between the cut protective films are evaluated. and the results are shown in Table 2 below.

<Evaluation criteria>

(double-circle): There is no bubble in the bent cross section, and there is no float.

(circle): One bubble of less than 0.5 micrometer generate|occur|produced in the bent cross section.

(triangle|delta): Two bubbles of less than 0.5 micrometer generate|occur|produce in the bent cross section.

Х: A large number of bubbles (3 or more) are generated in the bent section.

Experimental Example 2: Water resistance evaluation

Water resistance was evaluated for the Examples and Comparative Examples. For each polarizing plate left to stand for 24 hours under an environment of 23 °C and 55% relative humidity, a hot water resistance test was performed as follows to evaluate water resistance.

First, with the absorption axis (stretching direction) of the polarizing plate as the long side, the polarizing plate was cut into a size of 5 cm Х 2 cm to prepare a sample, and the dimension in the long side direction was accurately measured. At this time, the sample exhibits a unique color uniformly over the entire surface due to the iodine adsorbed to the polarizer. First, one short side of the sample was gripped by a gripper, and 80% of the longitudinal direction was immersed in a water bath at 60°C and held for 4 hours. Thereafter, the polarizing plate was taken out of the water bath and moisture was wiped off.

The polarizer of the polarizing plate is contracted by the hot water immersion as described above. The shrinkage length and degree of shrinkage were evaluated by measuring the distance of the contracted polarizer from the end (end of the protective film) at the center of the short side of the polarizing plate.

Further, when the polarizer is contracted by immersion in warm water, iodine is eluted from the periphery of the polarizer in contact with the warm water, and a region in which the color is lost is generated in the periphery of the polarizing plate. The distance from the tip of the contracted polarizer in the center of the short side of the polarizing plate to the region where the characteristic color of the polarizing plate remains was measured to evaluate the length of iodine loss and the degree of discoloration.

The sum of the shrinkage length and the iodine release length was taken as the total erosion length. The total erosion length is the distance from the distal end of the polarizing plate (end of the protective film) to the region where the characteristic color of the polarizing plate remains. It can be judged that the adhesion (water resistance) in the presence of water is high, so that the shrinkage length, iodine release length, and total erosion length are small. The total erosion length was measured using a microscope and the values are shown in Table 2 below.

Experimental Example 3: Moiré evaluation (interference fringe prevention properties)

One side of the polarizing plate prepared in Preparation Example was bonded to a black acrylic plate using a transparent adhesive, and the level of occurrence of interference fringes on the acrylic substrate surface under a 3-wavelength lamp was evaluated as follows.

<Evaluation criteria>

○: Interference fringes are not recognized

△: weakly recognized interference fringes

×: the interference fringes are clearly recognized

Experimental Example 4: Adhesion evaluation

A sample was prepared by cutting the polarizing plate prepared in Preparation Example to have a width of 2.5 mm and a length of 20 cm or more based on the stretching direction of the polarizer. The sample was cut using a precision sample cutter (TOKO, TMC-600). The PET side of the polarizing plate was fixed to the glass with double-sided tape, and the force measured while peeling the PET substrate and the PVA+PET (back) substrate at 180° was evaluated. UTM equipment (Shimadzu, CA-210) was used as a measuring device.

Experimental Example 5: Evaluation of heat-and-moisture durability

The spectral transmittance τ (λ) of the polarizing plate prepared in Preparation Example was measured using a spectrophotometer (Nippon Spectroscopy, V7100). An orthogonal spectral transmittance spectrum was obtained from the measured spectral transmittance τ(λ), and transmittance and polarization degree were calculated from the spectral transmittance spectrum. Thereafter, the polarizing plate was stored for 48 hours under moist heat-resistant conditions (85° C., 85%), and then the transmittance and polarization degree of the sample were measured with a V7100 instrument to check the amount of change in transmittance and polarization degree. When the amount of change in transmittance exceeds 2%, the color change of the polarizing plate may occur and thus the performance of the color filter may decrease, and if the change in polarization degree exceeds 3%, problems such as light leakage may occur.

Experimental Example 6: Warpage evaluation

A polarizing plate/Glass/polarizing plate sample was prepared by cutting and attaching the polarizing plate prepared in the above preparation example with the long side in the stretching direction on the upper surface of the 6-inch glass and the short side in the stretching direction on the lower surface of each glass at a distance of 10 mm from each corner of the glass. . The polarizing plate / glass / polarizing plate sample was left for 72 hours at 25 ° C., 70% condition, then stored at room temperature for 1 hour, and then the warpage of the sample was measured using a three-dimensional measuring instrument. The lifting length of each corner was measured, and it was shown in Table 2 below as a warpage value. The excitation length is preferably 0.3 mm or less, and if it is 0.3 mm or more, light leakage may occur in the image display device due to distortion of the polarizing plate.

Experimental Example 7: Evaluation of poor white point

By observing the polarizing plate made in the above preparation example through a searchlight, a phenomenon in which a white circular defect occurs between the protective film and the polarizer in the polarizing plate is confirmed.

<Evaluation criteria>

○: No white circular defect

X: One or more white circular defects occurred

Experimental Example 8: Mixed Stability Evaluation

When mixing and using the adhesive composition made according to the Preparation Examples and Comparative Examples, check the time at which the gel is generated after mixing.

<Evaluation criteria>

○: No gelation

△: occurrence of gelation within 6 to 12 hours

Х: gelation occurred within 6 hours

composition adhesion
(Cutter/Bend) water resistance
(um) moiré adhesion
(N) moisture heat resistance
(85℃, 85%, 48 hours) warp
(mm) one hundred points
error mix
stability transmittance Polarization degree Example 1 ◎/◎ 350 ○ 2.10 0.5 0.4 0.15 ○ ○ Example 2 ◎/O 450 ○ 2.00 1.0 0.5 0.20 ○ ○ Example 3 ◎/O 350 ○ 1.50 0.5 0.7 0.16 ○ ○ Example 4 ◎/O 350 ○ 1.60 0.6 0.6 0.16 ○ ○ Example 5 ◎/◎ 350 ○ 2.20 0.6 0.4 0.16 ○ ○ Example 6 ◎/O 350 ○ 2.30 0.5 0.5 0.15 ○ ○ Example 7 ◎/O 350 ○ 2.30 0.5 0.6 0.15 ○ ○ Example 8 O/△ 350 ○ 2.10 0.5 0.4 0.15 ○ △ Example 9 O/△ 400 ○ 1.70 0.6 0.7 0.15 ○ △ Example 10 O/△ 350 ○ 1.90 0.5 0.4 0.15 ○ △ Comparative Example 1 O/O 1000 △ 0.60 1.5 4.0 0.40 ○ ○ Comparative Example 2 O/X record X 0.80 2.2 4.2 0.80 ○ ○ Comparative Example 3 O/X 1600~1800 X 0.40 3.5 7.2 0.40 ○ ○ Comparative Example 4 X/△ 1000 X 0.50 3.8 5.0 0.40 X ○ Comparative Example 5 X/△ 650 △ 0.60 4.0 4.8 0.80 X ○ Comparative Example 6 O/O 1100 X 0.50 3.2 7.0 0.80 X ○ Comparative Example 7 O/X record X 0.60 5.7 8.1 0.90 ○ ○ Comparative Example 8 O/△ record X 0.60 6.1 9.1 0.90 ○ ○ Comparative Example 9 O/△ record X 0.80 5.7 4.5 0.90 ○ ○ Comparative Example 10 O/△ record X 0.40 5.8 7.8 0.90 △ ○ Comparative Example 11 O/△ record X 0.50 5.8 9.8 0.90 △ ○ Comparative Example 12 O/X 3000~record X 0.60 3.1 4.1 0.80 ○ ○ Comparative Example 13 X/X record X 0.70 4.9 5.7 0.90 ○ ○ Comparative Example 14 X/X record X 0.25 4.8 4.9 0.90 ○ ○ Comparative Example 15 O/△ 2300 X 0.50 3.0 4.2 0.50 ○ ○ Comparative Example 16 O/X record X 0.30 4.9 5.9 0.80 ○ ○ Comparative Example 17 X/X record X 0.20 7.0 8.1 0.80 X O Comparative Example 18 O/O record X 0.20 9.0 10.2 0.70 X X Comparative Example 19 O/O 600 △ 0.80 2.1 3.4 0.16 X X Comparative Example 20 O/O 600 △ 0.90 2.3 3.5 0.16 X X

Referring to Table 2, in the case of the adhesive composition of the present invention containing a water-soluble salt of a polyvalent metal ion, and the pH of the adhesive composition satisfies 1 to 4, adhesion, adhesion, water resistance, moisture and heat resistance, moire evaluation and warpage evaluation It can be seen that all of them are excellent.

On the other hand, if the polyvalent metal ion water-soluble salt is not included or included, when the pH is out of 1 to 4, the adhesion and adhesion are poor, water resistance, durability, and heat-and-moisture properties are also poor, and the moiré evaluation results showed poor results.

Claims (15)

An adhesive composition for a polarizing plate comprising (A) a polyvinyl alcohol-based resin, (B) a crosslinking agent, and (C) a water-soluble salt of a polyvalent metal ion,
The adhesive composition for a polarizing plate, characterized in that the pH of the adhesive composition is 1 to 4.
According to claim 1,
The (A) polyvinyl alcohol-based resin is an acetacetyl group-modified polyvinyl alcohol-based resin, an adhesive composition for a polarizing plate.
3. The method of claim 2,
The acetacetyl group-modified polyvinyl alcohol-based resin is an adhesive composition for a polarizing plate, characterized in that the degree of modification of the acetoacetyl group is 0.1 to 40 mol%.
According to claim 1,
The (B) crosslinking agent is an adhesive composition for a polarizing plate, characterized in that the glyoxal-based crosslinking agent.
The method of claim 1,
(C) the water-soluble salt of the polyvalent metal ion, the crosslinking agent consists of zirconium oxynitrate, zirconium acetate, iron nitrate, zirconium ammonium, zinc chloride, cobalt chloride, magnesium chloride, magnesium acetate, aluminum nitrate, zinc nitrate and zinc sulfate. An adhesive composition for a polarizing plate, characterized in that it is a hydrate of one or more polyvalent metal ion compounds selected from the group.
According to claim 1,
The adhesive composition is an adhesive composition for a polarizing plate comprising a first liquid and a second liquid,
The first solution includes (A) a polyvinyl alcohol-based resin and (B) a crosslinking agent,
The second liquid, (A) a polyvinyl alcohol-based resin and (C) an adhesive composition for a polarizing plate, characterized in that it contains a water-soluble salt of a polyvalent metal ion.
7. The method of claim 6,
The polyvinyl alcohol-based resin included in the first solution is an adhesive composition for a polarizing plate, characterized in that it is included in an amount of 20 to 80 parts by weight based on 100 parts by weight of the total first solution.
7. The method of claim 6,
The polyvinyl alcohol-based resin contained in the second liquid is an adhesive composition for a polarizing plate, characterized in that it is included in an amount of 15 to 70 parts by weight based on 100 parts by weight of the total of the second liquid.
7. The method of claim 6,
The adhesive composition for a polarizing plate, characterized in that the crosslinking agent included in the first solution is included in an amount of 5 to 30 parts by weight based on 100 parts by weight of the solid content of the polyvinyl alcohol-based resin included in the first solution.
7. The method of claim 6,
The water-soluble salt of the polyvalent metal ion contained in the second liquid is an adhesive composition for a polarizing plate, characterized in that it is included in an amount of 1.35 to 15 parts by weight based on 100 parts by weight of the solid content of the polyvinyl alcohol-based resin contained in the second liquid.
7. The method of claim 6,
The first liquid and the second liquid are mixed in a weight ratio of 0:8:1.2 to 1.2:0.8, the adhesive composition for a polarizing plate.
(A) a polyvinyl alcohol-based resin and (C) an adhesive composition for a polarizing plate comprising a water-soluble salt of a polyvalent metal ion,
(A) a polyvinyl alcohol-based resin and (B) to be mixed with the first solution comprising a crosslinking agent to prepare the adhesive composition to have a pH of 1 to 4, the adhesive composition for a polarizing plate.
A polarizing plate comprising a polarizer and a protective film adhered to at least one surface of the polarizer using the adhesive composition for a polarizing plate according to any one of claims 1 to 12.
14. The method of claim 13,
The protective film is a polarizing plate, characterized in that at least one selected from the group consisting of a polycarbonate (PC)-based film, a polyethylene terephthalate-based (PET) film, or a polyimide-based (PI) film.
A display device comprising the polarizing plate of claim 13 .