KR20110061722A - A polarizing plate and preparing method for the same - Google Patents

Abstract

PURPOSE: A polarization plate and a manufacturing method thereof are provided to maintain balance of adhesion speed between a polarizer and a protection film with different water vapor permeability. CONSTITUTION: A polarization plate includes a protection film whose water vapor permeability at 40°C and 90%RH is below 300g/^2· day. The polarization plate includes a polarizer. The polarization plate includes a protection film whose water vapor permeability at 40°C and 90%RH is 300g/m^2· day. The number contact angle of sides contacting the polarizer at the protection film whose water vapor permeability at 40°C and 90%RH is above 300g/m^2· day is 22 ~ 38°.

Description

Polarizing plate and manufacturing method thereof {A POLARIZING PLATE AND PREPARING METHOD FOR THE SAME}

The present invention relates to a polarizing plate capable of suppressing curl generation of a polarizing plate by effectively bonding protective films having different moisture permeability to a polarizer and a method of manufacturing the same.

The polarizing plate is widely used as a supply element of polarization and a detection element of polarization in a liquid crystal display device.

In general, a polarizing plate is a cellulose acetate type represented by a transparent protective film such as triacetylcellulose (TAC) through an adhesive on both sides of a polarizer made of polyvinylalcohol (PVA) -based resin in which a dichroic dye is adsorbed. The protective film has a laminated structure.

Recently, in order to express unusual optical properties, there has been an increasing number of polarizing plates on which protective films having different physical properties and the like are disposed on both surfaces of the polarizer. However, if a different kind of protective film is disposed on both sides of the polarizer, both sides of the polarizer are asymmetrical, so there is a problem of curling in the polarizer. In particular, when the protective film having different moisture permeability is disposed on both sides of the polarizer, worse curl occurs.

Since the polarizing plate is required to be handled with the improvement of the function of LCD, the improvement of luminance, and the enlargement of size, it is preferable to suppress curl. In addition, the curled polarizing plate has a problem that bubbles are mixed when adhering to the liquid crystal cell.

In order to suppress the occurrence of curling, Korean Laid-Open Patent Publication No. 2007-96826 (published Oct. 2, 2007) is a cycloolefin resin film laminated on one side of the polarizer with an adhesive, and then a cellulose acetate film is laminated on the other side. The polarizing plate manufacturing method in which the moisture content before a cellulose acetate type film is laminated | stacked is adjusted to 0.5% or more is disclosed. This polarizing plate can suppress curl, but the moisture content of the polarizer and the cycloolefin resin film laminated state should be 0.5%, so the moisture content of the film must be maintained at a certain level or more, and the process is complicated. In addition, there is a problem that takes a long time to manufacture a polarizing plate.

Therefore, the development of a polarizing plate capable of suppressing curl by improving the adhesion speed between the protective film and the polarizer having different moisture permeability is required.

It is an object of the present invention to provide a polarizing plate and a method for producing the same in which the adhesion speed between the polarizer and the protective film having different moisture permeability is balanced.

Another object of the present invention is to provide a polarizing plate capable of suppressing curl generation and a method of manufacturing the same.

1. A protective film having a water vapor transmission rate at 40 ° C. and 90% RH of not more than 300 g / m 2 · day; Polarizer; And a protective film having a moisture permeability of more than 300 g / m 2 · day at 40 ° C. and 90% RH, and a surface that is bonded with the polarizer in a protective film having a moisture permeability of more than 300 g / m 2 · day at 40 ° C. and 90% RH. Polarizing plate having a water contact angle of 22 to 38 °.

2. In the above 1, the surface energy of the protective film having a water vapor transmission rate of more than 300g / ㎡ · day at 40 ℃ and 90% RH is 60 to 85 dyne / cm polarizing plate.

3. In the above 1, the protective film having a water vapor transmission rate of less than 300g / ㎡ · day at 40 ℃ and 90% RH is a group consisting of acrylic resin, polyester resin, polyimide resin, norbornene resin and polyolefin resin Polarizing plate is selected from.

4. In the above 1, the protective film having a water vapor transmission rate of more than 300g / ㎡ · day at 40 ℃ and 90% RH is made of a triacetyl cellulose-based resin.

5. In the above 3, the protective film having a water vapor transmission rate of less than 300g / ㎡ · day at 40 ℃ and 90% RH is a polarizing plate made of norbornene-based resin.

6. One side of the polarizer has a protective film having a moisture permeability of 300 g / m 2 · day or less at 40 ° C. and 90% RH, and the other side has a protective film having a moisture permeability of more than 300 g / m 2 · day at 40 ° C. and 90% RH. In manufacturing a polarizing plate by bonding the polarizing plate, the water contact angle of the surface bonded to the polarizer in the protective film having a water vapor transmission rate at 40 ℃ and 90% RH more than 300g / ㎡ · day of the polarizing plate comprising 22 to 38 ° Manufacturing method.

The polarizing plate of the present invention and the method of manufacturing the polarizing plate by reducing the difference between the adhesion rate of the protective film and the polarizer with low moisture permeability as the adhesion time is reduced by adjusting the saponification degree of the surface bonded to the polarizer in the protective film with high moisture permeability. It is possible to suppress the occurrence of curl.

The polarizing plate of the present invention and its manufacturing method is excellent in the adhesive force of the polarizer and the protective film by performing a saponification process so that the water contact angle of the surface bonded to the polarizer in the high moisture permeability protective film is 22 to 38 °.

The polarizing plate of the present invention and a method of manufacturing the same can solve the problem of mixing bubbles in the liquid crystal cell by suppressing curl generation, thereby greatly improving the processability.

The polarizing plate of the present invention and its manufacturing method are advantageous for producing a thinner and larger polarizing plate by suppressing curl generation.

In the present invention, a protective film having a moisture permeability of 300 g / m 2 · day or less at 40 ° C. and 90% RH is bonded to one side of the polarizer, and a moisture permeability of 300 g / m 2 · 40 ° C. and 90% RH is bonded to the other side of the polarizer. Protective film with high moisture permeability by making the water contact angle of the surface bonded to the polarizer 22 to 38 ° in the protective film having a moisture permeability of 300 g / m 2 · over 40 ° C. and 90% RH when the protective film is laminated for more than one day. And a polarization rate between the polarizer and the polarizer is lowered, so that the difference in the adhesion rate of the protective film with low moisture permeability is reduced, and a polarizing plate capable of suppressing curl generation of the polarizing plate and a method of manufacturing the same.

Hereinafter, the present invention will be described in more detail.

The polarizer is a dichroic dye adsorbed on the stretched polyvinyl alcohol-based film. The polyvinyl alcohol-based resin constituting the polarizer can be produced by saponifying a polyvinyl acetate-based resin. As an example of polyvinyl acetate type resin, the copolymer etc. with vinyl acetate and the other monomer copolymerizable with this besides the polyvinyl acetate which is a homopolymer of vinyl acetate are mentioned. Specific examples of the other monomer copolymerizable with vinyl acetate include unsaturated carboxylic acids, unsaturated sulfonic acids, olefins, vinyl ethers, acrylamides having an ammonium group, and the like. In addition, the polyvinyl alcohol-based resin may be modified, for example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used. The degree of saponification of the polyvinyl alcohol-based resin may be 85 to 100 mol%, preferably 98 mol% or more. In addition, the degree of polymerization of the polyvinyl alcohol-based resin is usually 1,000 to 10,000, preferably 1,500 to 5,000.

The manufacturing method of the present invention relates to bonding protective films having different moisture permeability to two polarizers having different components. In particular, the high permeability of the protective film is a saponification (sake) process.

The protective film may have a moisture permeability different according to the type of resin, and a film having excellent transparency, mechanical strength, thermal stability, moisture shielding, and isotropy may be used.

As shown in FIG. 1, the protective film having high moisture permeability is bonded to one surface of the polarizer, and the protective film having low moisture permeability is bonded to the other surface. The protective film having a low moisture permeability includes, for example, a protective film having a moisture permeability of 300 g / m 2 · day or less, preferably 5 to 300 g / m 2 · day at 40 ° C. and 90% RH. Specific examples thereof include polyethylene terephthalate, polyethylene or Polyester-based resins such as phthalate, polybutylene terephthalate and polyethylene terephthalate-isophthalate copolymer; A resin prepared by the condensation reaction of an aromatic diamine with an aromatic diamine such as pyromellitic dianhydride with diaminodiphenyl ether and an aromatic carboxylic anhydride, an imide ring closure reaction, and an aromatic diamine obtained with maleic anhydride and diaminodiphenylmethane. Polyimide resins such as polyimide; A resin obtained by introducing a (co) polymer of a ring-open norbornene monomer into a polar group such as maleic acid, cyclopentadiene, and the like after modification, and a resin obtained by addition polymerization of norbornene monomer, norbornene monomer and ethylene, resins obtained by addition polymerization of olefin monomers such as α-olefins, resins obtained by addition polymerization of norbornene monomers and cyclic olefin monomers such as cyclopentene, cyclooctene or 5,6-dihydrodicyclopentadiene, and the like. Norbornene-based resins; And films selected from the group consisting of polyolefin-based resins such as polyethylene, polypropylene, ethylene-propylene copolymers, homopolymers or copolymers of α-olefins such as poly-4-methylpentene-1 having 1 to 6 carbon atoms. .

In addition, the protective film having a high moisture permeability includes, for example, a protective film having a moisture permeability of more than 300 g / m 2 · day at 40 ° C. and 90% RH. For example, an acetyl cellulose resin such as diacetyl cellulose, triacetyl cellulose, etc. corresponds thereto. Can be. Preferably, the acetyl cellulose resin has a water vapor transmission rate of 500 to 1000 g / m 2 · day at 40 ° C. and 90% RH.

A protective film having a water vapor transmission rate of more than 300 g / m 2 · day at 40 ° C. and 90% RH used in the present invention, such as an acetyl cellulose-based protective film, has a water contact angle of 22 to 38 ° or a surface energy of 60 to 85 dynes / cm The surface is preferably saponified so that The water contact angle and surface energy may vary depending on the resin type of the protective film.

The saponification treatment of acetylcellulose protective film is a process of heating the protective film, applying an aqueous alkali solution to the protective film, maintaining the protective film at 40 ° C. and 90% RH, a washing process for washing the aqueous alkaline solution and a drying process It may be carried out including. At this time, before the process of applying the aqueous alkali solution to the protective film, to remove the dust or to even the wettability of the film surface can be subjected to antistatic treatment, dust removal treatment or wet treatment, antistatic treatment is disclosed in Japanese Patent Application Laid-Open No. 62-131500 The damping treatment can be carried out according to the method described in Japanese Patent Laid-Open No. 2-43157.

The process of heating the acetyl cellulose protective film is to dry the protective film uniformly and to prevent staining, so that hot air and hot air collide, contact heat by heating roll, induction heating by microwave, or radiant heat heating by infrared heater, etc. It is heated to 28 to 32 ℃ using. In particular, the contact heat transfer by the heating roll may be a small installation area because the heat transfer efficiency is high, it can be preferably used because the temperature rise of the protective film at the start of the transfer is fast. The contact heat transfer by a heating roll can use a double jacket roll or an electromagnetic induction roll.

In the process of applying an aqueous alkali solution to the protective film and saponification treatment, the aqueous alkali solution is a solution containing an alkali agent. As an alkaline agent, Inorganic alkali agents, such as sodium hydroxide, potassium hydroxide, lithium hydroxide, ammonium hydroxide; Monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monoisopropylamine, diisopropylamine, triisopropylamine, n-butylamine, monoethanolamine, diethanolamine, Organic alkali agents such as triethanolamine, monoisopropanolamine and diisopropanolamine; Or halogenated salts thereof, and these may be used alone or in combination of two or more thereof. Among these, sodium hydroxide and potassium hydroxide are preferable at the point which can adjust pH over a wide range according to content control. The concentration of the alkali agent is preferably at least pH 10, preferably at least pH 12. If the concentration of the alkaline agent is less than pH 10, the saponification rate may be lowered and surface nonuniformity may be caused.

In addition, the aqueous alkali solution may further contain water in order to improve the solubility of the alkali agent. The content (W) of water in the solvent may be contained in the range of 0 to 50% by weight, preferably 0 to 30% by weight. Water makes the protective film excellent in wettability and hardly swells the protective film so as not to roughen the surface of the protective film.

It is preferable that temperature (T) of aqueous alkali solution is 30-70 degreeC, More preferably, it is 30-60 degreeC.

The coating amount of the aqueous alkali solution applied to the protective film is preferably a small coating amount in consideration of the extraction amount of the hydrophobic substance by the organic solvent, more preferably 8 to 12 g / ㎡.

Coating processes of aqueous alkali solution include die coaters, such as an extrusion coater and a slide coater; Roll coaters such as a forward roll coater, a reverse roll coater, and a gravure coater; A rod coater, a blade coater, or the like wound with a thin metal wire may be used, but a rod coater, a gravure coat, a blade coater, a die coater, which can stably operate a small coating amount, is used. The die coater immerses or contacts the protective film in an aqueous alkali solution. At this time, the immersion time (t) may be 1 to 300 seconds, preferably 2 to 60 seconds. If the immersion time is less than 1 second, it is difficult to obtain the desired saponification effect, and if it exceeds 300 seconds, there is a problem that the surface of the protective film is damaged.

The aqueous alkali solution is preferably applied to the lower surface of the protective film, for example, the surface bonded to the polarizer in order to easily wash off the aqueous alkaline solution in a later process.

In order to increase the adhesion to the polarizer and to control the surface properties of the protective film, it is preferable that the saponification process is performed under an atmosphere of reduced oxygen gas. The oxygen concentration in the atmosphere is in the range of less than 18% by weight, preferably 0 to 15% by weight, more preferably 0 to 10% by weight.

The gas component in the atmosphere other than oxygen is preferably an inert gas. As the inert gas, nitrogen, helium, argon and the like can be used, with nitrogen being particularly preferred.

The coating amount of the aqueous alkali solution, the immersion time, the concentration and temperature of the alkali agent can be set according to the material and composition of the protective film, the target water contact angle and the surface energy, etc. within the range in which the protective film is not damaged.

The saponification process is preferably carried out such that the contact angle of the protective film surface with water is a specific range of values. For example, when the protective film is an acetyl cellulose protective film, the water contact angle of the surface is 22 to 38 °, and preferably 28 to 32 °. The water contact angle is inversely proportional to the degree of saponification. If the water contact degree is too high and the water contact angle is less than 22 °, curling may occur due to the fast bonding speed when bonding with the polarizer. If the water contact angle is too low and the water contact angle is more than 38 °, the adhesive The adhesiveness may be lowered due to the lowering of the spreadability.

In addition, the saponification process is preferably carried out so that the protective film has a specific range of surface energy, for example, the surface energy is preferably 60 to 85 dynes / cm, preferably 65 to 80 dynes / cm. If the surface energy is less than 60 dynes / ㎝, the coating of the adhesive is non-uniform may cause a non-uniform adhesion problem, and if the surface energy is greater than 85 dynes / ㎝ may cause a problem of curl deterioration due to an increase in the adhesion speed when bonding with the polarizer. have.

The saponified protective film is maintained at 40 ° C. and 90% RH for the purpose of preventing moisture content change and dimensional change due to the change in temperature and humidity after applying an aqueous alkali solution to the protective film.

Next, the washing | cleaning process which wash | cleans an aqueous alkali solution from a protective film using pure water (water) is performed. In order to improve the detergency, 0 to 50% by weight of alcohol having 1 to 5 carbon atoms may be mixed and used in pure water.

The washing is not particularly limited to a general method, and can be generally performed by immersing in a water tank or spraying a protective film. The washing time t is 40 to 200 seconds, and the temperature of the pure water is preferably 10 to 60 ° C, preferably 15 to 40 ° C.

The protective film may be washed and then dried. As a drying method, well-known methods, such as natural drying, air drying, heating drying (hot air drying), can be used, and heat drying (hot air drying) is generally used preferably. It is preferable that the temperature of heat drying is 40-200 degreeC, More preferably, it is 50-150 degreeC, Most preferably, it is 60-120 degreeC. In addition, the heat drying time is preferably 1 to 200 seconds, more preferably 20 to 120 seconds. When the heat drying temperature and time exceeds the above range, the heat shrinkage phenomenon of the protective film is increased, which causes the cross section of the polarizing plate to be broken, causing display defects.

The protective film may contain appropriate one or more additives. Specific examples of the additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, colorants, flame retardants, nucleating agents, antistatic agents, pigments, colorants, and the like.

Conventionally, one side is provided with a high moisture-permeable protective film, the other side is provided with a low-moisture-permeable protective film, the polarizer is first bonded with a high moisture-permeable protective film during the drying process, the low moisture-permeability that was dried at the same speed Since the protective film is not bonded, shrinkage stress is generated in the direction of the film with high moisture permeability, resulting in a large curl.

In order to improve this, the present invention adjusts the degree of saponification of the surface of the protective film having high moisture permeability bonded to the polarizer. The protective film having high moisture permeability has a fast adhesion speed (drying speed) with the polarizer, thereby controlling the degree of saponification of the protective film having high moisture permeability, thereby slowing the adhesion speed with the polarizer. Therefore, the moisture permeability is low and the adhesion rate of the protective film and the polarizer is slow to reduce the shrinkage stress is suppressed to suppress the occurrence of curl. In this case, the saponification-protected film, such as an acetyl cellulose-based protective film, since the acetyl group on the surface is substituted with a hydroxy group when the saponification process is performed on the surface, when the degree of saponification decreases, the substitution rate of the hydroxy group is also reduced and the adhesion speed is slowed. Therefore, by saponifying the protective film having a high moisture permeability to control the degree of saponification so that the water contact angle is 22 to 38 ° or surface energy of 60 to 85 dyne / ㎝ can slow the adhesion rate of the protective film and polarizer with high moisture permeability.

The adhesive for bonding the polarizer and the protective film is applied to either side of the polarizer and the protective film or both. The coating operation is not particularly limited, and various methods such as a roll method, a spray (spray) method, and a dipping method can be used. The adhesive may further add a crosslinking agent to the polyvinyl alcohol-based resin.

Polyvinyl alcohol-based resin, which is one of the components of the adhesive, is a vinyl-based polymer resin and is excellent in adhesion with a polyvinyl alcohol-based polarizer. In order to improve the durability of the polarizing plate, a polyvinyl alcohol resin containing acetoacetyl group is preferable, and a carboxyl group-modified polyvinyl alcohol resin containing a highly reactive functional group is preferable in order to improve the adhesiveness and moisture-heat resistance of the adhesive composition.

The degree of polymerization and the degree of saponification of the polyvinyl alcohol-based resin are not particularly limited. It is preferable that the average degree of polymerization is 100 to 3,000 and the average degree of saponification is 85 to 100 mol% in consideration of adhesion.

The crosslinking agent may be a conventional crosslinking agent to improve the water resistance and durability of the adhesive. Specific examples of the crosslinking agent include aldehyde compounds such as formaldehyde, glyoxal, and glutaraldehyde as organic crosslinking agents; Amino group-containing compounds such as urea resin, guanamine resin, aniline aldehyde resin, melamine resin, and methylolmelamine resin; Glycidyl group-containing compounds such as water-soluble epoxy resins and polyaminopolyamide-epichlorohydrin; Amine compounds such as ethylenediamine, hexamethylenediamino, methaxylenediamine, 1,3-bisaminocyclohexane, polyoxyalkylenediamine and polyamine; Hydrazide compounds such as adipic acid hydrazide, carbohydrazide, and polyacrylic acid hydrazide; Isocyanate compounds, such as polyisocyanate and block isocyanate; Hydrazine compounds; Boron compounds such as boric acid and borax as acid anhydrides and inorganic crosslinking agents; Zirconium compounds, such as chlorohydroxyoxo zirconium, zirconyl nitrate, and zircosol; Titanium compounds such as tetraalkoxy titanate and water-soluble titanium compounds; Aluminum compounds such as aluminum sulfate, aluminum chloride and aluminum nitrate; Phosphoric acid compounds such as phosphite ester and bisphenol A-modified polyphosphoric acid; And a silicon compound having a reactive functional group such as an alkoxy group or glycidyl group.

The adhesive composition includes 1 to 100 parts by weight of the crosslinking agent based on 100 parts by weight of the polyvinyl alcohol-based resin (based on the solid content). When the content of the crosslinking agent is less than 1 part by weight based on 100 parts by weight of the polyvinyl alcohol-based resin, the heat and moisture resistance may be weak, and when the content of the crosslinking agent is greater than 100 parts by weight, the adhesive strength may be lowered.

It is preferable to apply | coat the adhesive bond layer so that the thickness of the adhesive bond layer formed after drying in consideration of solid content may be 10-5,000 nm, Preferably it is 30-600 nm. When the thickness is less than 10 nm, the adhesion may be poor, and when the thickness is greater than 5,000 nm, uniform application of the adhesive may be difficult or thickness irregularity may occur, resulting in poor appearance. In addition, when the polarizer and the protective film is bonded, the tension may be applied to the protective film, but the tension is preferably as low as possible because the deformation is applied to the protective film.

After applying the adhesive, the polarizer and the protective film are bonded by a roll laminator or the like. After bonding the polarizer and the protective film, a drying process is performed to form an adhesive layer comprising a coating dry layer.

The polarizing plate to which the polarizer and the protective film are bonded is subjected to a drying process. An example of the drying process is hot air drying in which the drying temperature is 40 to 100 ° C., preferably 60 to 100 ° C. using hot air. The drying time is 20 to 1200 seconds, but it is preferable that the drying time is as short as possible in order to improve productivity. After hot air drying, curing at room temperature or higher than room temperature, for example, 20 to 50 ° C. for 12 to 600 hours is preferable.

In the polarizing plate of the present invention, a surface coating layer such as a hard coating layer, an antireflection layer, an antifouling layer, a diffusion layer, and an antiglare layer may be further laminated on the other side of the protective film not bonded with the polarizer. In addition, the optical functional film may be further laminated by the pressure-sensitive adhesive layer.

The hard coating layer is performed to prevent damage to the surface of the polarizing plate, for example, a cured coating film having excellent hardness, sliding properties, etc. formed by a system for adding a suitable ultraviolet curable resin such as a silicone resin to the surface of the protective film. have. In addition, the antireflection layer is performed for the purpose of preventing external light from being reflected from the surface of the polarizing plate. The antireflective layer can be achieved by forming an antireflective film according to the prior art. In addition, the anti-stick layer is performed for the purpose of preventing the protective film from being in close contact with the adjacent layer. The anti-glare layer is performed to prevent the visual perception of light transmitted through the polarizer from being inhibited by external light reflected from the surface of the polarizing plate, for example, a roughening system or a transparent particle mixing system using sand blasting, embossing, or the like. Etc., the micro-corrugated structure can be imparted to the surface of the protective film. Transparent particles have an average particle size of 0.5 to 20㎛, specific examples include particles made of silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide and the like. In addition, the transparent particles may use inorganic fine particles having conductivity or organic fine particles made of a crosslinked or uncrosslinked granular polymer or the like. The transparent particles are 2 to 70 parts by weight, preferably 5 to 50 parts by weight with respect to 100 parts by weight of the resin. The anti-glare layer containing the transparent fine particles may be provided as the protective film itself or as a coating layer applied to the surface of the protective film. The anti-glare layer can also function as a diffusion layer (viewing angle compensation function, etc.) that expands the viewing angle by diffusing light transmitted through the polarizing plate.

The polarizing plate manufactured by the manufacturing method of the present invention can be used in a liquid crystal display device. The liquid crystal display device may be manufactured by peeling a release film of a pressure-sensitive adhesive polarizing plate and then attaching an adhesive layer to a liquid crystal panel.

Hereinafter, the present invention will be described in more detail with reference to Examples. It is obvious that the examples are not intended to limit the scope of the present invention but only to show an example belonging to the present invention. It is natural that modifications and variations of the embodiments fall within the scope of the present invention without departing from the basic technical spirit of the present invention.

[Example]

Preparation Example 1 Preparation of Polarizer

After uniaxially stretching a polyvinyl alcohol (PVA) film having a degree of polymerization of 2,400 and having a saponification degree of 99.9 mol% or more by about 5 times dry, immersed in distilled water at 60 ° C. for 1 minute while maintaining a tension state. It was immersed for 60 seconds in the aqueous solution of 28 degreeC whose weight ratio of iodine / potassium iodide / distilled water is 0.05 / 5/100. After immersion for 300 seconds in a 72 ℃ aqueous solution having a weight ratio of potassium iodide / boric acid / distilled water for 8.5 / 8.5 / 100, washed for 20 seconds with distilled water at 26 ℃ and dried at 65 ℃ to adsorb the iodine to the PVA-based film An oriented polarizer was prepared.

Preparation Example 2 Adhesive Composition

An adhesive composition was prepared by adding 5 parts by weight of acetoacetylene-modified polyvinyl alcohol resin (Z200, Nippon Synthetic Chemical Co., Ltd.) and 0.5 parts by weight of glyoxal crosslinking agent to 100 parts by weight of distilled water.

Preparation Example 3 Pretreatment of Protective Film 1 (Norbornene Film)

(1) Production of norbornene-based films

One side of the norbornene-based film (manufactured by Japan Zeon, trade name "ZEONOR", 40 µm) was subjected to corona treatment with a discharge amount of 200 w · min / m 2, and the water vapor transmission rate was 250 g / m 2 · day.

Preparation Example 4 Pretreatment of Protective Film 2 (Triacetyl Cellulose Film)

(1) Preparation of triacetyl cellulose film

The triacetyl cellulose film (Konica Tack KC80UVSHF, manufactured by Konica Co., Ltd.) was heated to 30 ° C. and then immersed in a potassium hydroxide solution of 4.5 normal concentration maintained at 40 ° C. for 28 seconds. After that, the protective film is maintained at 40 ° C. and 90% RH, and washed with flowing pure water for 60 seconds to remove the potassium hydroxide solution. The washed triacetyl cellulose film was dried in an oven at 100 ° C. for 60 seconds to prepare a triacetyl cellulose film in which alkali saponification was completed. The triacetyl cellulose film of which alkali saponification was completed has a water vapor transmission rate of 900 g / m 2 · day and a thickness of 80 μm.

(2) Preparation of triacetyl cellulose film

The preparation was carried out in the same manner as in Preparation Example 4-1, except that the solution was immersed in a potassium hydroxide solution for 24 seconds.

(3) Preparation of triacetyl cellulose film

The preparation was carried out in the same manner as in Preparation Example 4-1, except that the solution was immersed in a potassium hydroxide solution for 19 seconds.

(4) Preparation of triacetyl cellulose film

The preparation was carried out in the same manner as in Preparation Example 4-1, except for immersion in the potassium hydroxide solution for 11 seconds.

(5) Preparation of triacetyl cellulose film

The preparation was carried out in the same manner as in Preparation Example 4-1, except that the solution was immersed in a potassium hydroxide solution for 43 seconds.

Example 1

After spraying the adhesive of Preparation Example 2 to a thickness of 500 nm between the protective film 1 of Preparation Example 3 and the protective film 2 of Preparation Example 4 located on both sides of the PVA-based polarizer prepared in Preparation Example 1, respectively. Then, it bonded using the nip roll. The bonded polarizing plate was placed in a hot air oven and dried at 60 ° C. for 5 minutes to prepare a polarizing plate.

Example 2

A polarizing plate was manufactured in the same manner as in Example 1 except that the protective film of Preparation Example 4-2 was used instead of the protective film of Preparation Example 4-1.

Example 3

A polarizing plate was manufactured in the same manner as in Example 1 except that the protective film of Preparation Example 4-3 was used instead of the protective film of Preparation Example 4-1.

Comparative Example 1

A polarizing plate was manufactured in the same manner as in Example 1 except that the protective film of Preparation Example 4-4 was used instead of the protective film of Preparation Example 4-1.

Comparative Example 2

A polarizing plate was manufactured in the same manner as in Example 1 except that the protective film of Preparation Example 4-5 was used instead of the protective film of Preparation Example 4-1.

Test Example

1. Measurement of water contact angle of triacetylcellulose film

The water contact angle was measured using a water contact angle measuring instrument (manufactured by Kyowa Interface Science Co., Ltd., model name CA-A type).

2. Curling amount of polarizer

Place the concave side of the curled sample on a reference plane, such as a plane on the table, facing upwards, and adjust the humidity for 48 hours at 25 ° C., 65% RH. The sample was cut | disconnected so that the rectangular sample of 305 mm of long sides and 254 mm of short sides may be made into the angle of 45 degrees with respect to the film forming direction of each side of a polarizing film.

The angles of both ends of the diagonal line forming the angle close to the film-forming direction of the polarizing film among the two diagonal lines of the humidity-controlled sample were measured by the curled height from the reference plane and averaged to measure the curl amount of the polarizing plate.

The practically acceptable curl amount of a polarizing plate is 20 mm or less, Preferably it is 15 mm or less, More preferably, it is 10 mm or less.

3. Adhesive

Peeling degree and damage degree were observed by peeling between the polarizer and the protective film 1 of the polarizing plate, the polarizer and the protective film 2 by hand, respectively, and evaluated by the following reference | standard. At this time, the polarizer and the protective film do not peel off each other, the better the adhesive strength.

(Circle): It is broken without peeling.

(Triangle | delta): The area which peels is large and a part is damaged.

X: Mostly peeled off.

division Water contact angle (°) Curling volume (mm) Adhesive evaluation Example 1 25 14.5 ○ Curl relief Example 2 31 13.0 ○ Curl relief Example 3 35 11.0 ○ Curl relief Comparative Example 1 46 14.0 × Curl relief Comparative Example 2 19 49.0 ○ Deteriorate curl

As shown in the above table, the polarizing plates of Examples 1 to 3 in which the saponification degree controlled moisture permeability according to the present invention and the polarizer bonded to the polarizer with an adhesive were suppressed compared to the polarizing plate of Comparative Example 2. Moreover, when the water contact angle increased like the polarizing plate of the comparative example 1 compared with the range of this invention, it was confirmed that curling is suppressed but adhesiveness falls.

Since the polarizing plate of the present invention reduces the difference in the adhesion speed between the polarizer and the protective films 1 and 2, it is expected that the production yield will be improved and the processability will be remarkably increased when the polarizing plate is used in the manufacturing process of the polarizing plate and the liquid crystal display device. .

As described above, the present invention can be applied to the manufacturing process of various image display devices such as liquid crystal display devices in which a polarizing plate without curling is required.

1 is a vertical cross-sectional view of a polarizing plate according to the present invention.

Claims (6)

A protective film having a water vapor transmission rate at 40 ° C. and 90% RH of 300 g / m 2 · day or less; Polarizer; And a protective film having a moisture permeability of more than 300 g / m 2 · day at 40 ° C. and 90% RH, and a surface that is bonded with the polarizer in a protective film having a moisture permeability of more than 300 g / m 2 · day at 40 ° C. and 90% RH. Polarizing plate having a water contact angle of 22 to 38 °. The polarizing plate according to claim 1, wherein the surface energy of the protective film having a moisture permeability of more than 300 g / m 2 · day at 40 ° C. and 90% RH is 60 to 85 dynes / cm. The protective film according to claim 1, wherein the protective film having a moisture permeability of 300 g / m 2 · day or less at 40 ° C. and 90% RH is selected from the group consisting of acrylic resin, polyester resin, polyimide resin, norbornene resin, and polyolefin resin. The polarizing plate will be. The polarizing plate according to claim 1, wherein the protective film having a moisture permeability of more than 300 g / m 2 · day at 40 ° C. and 90% RH is made of a triacetyl cellulose resin. The polarizing plate according to claim 3, wherein the protective film having a moisture permeability of 300 g / m 2 · day or less at 40 ° C. and 90% RH is made of a norbornene-based resin. On one side of the polarizer, a protective film having a moisture permeability of 300 g / m 2 · day or less at 40 ° C. and 90% RH is bonded. To prepare a polarizing plate, the method of manufacturing a polarizing plate comprising the water contact angle of the surface bonded to the polarizer in the protective film having a water vapor transmission rate at 40 ℃ and 90% RH is more than 300g / ㎡ · day 22 to 38 ° .

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