KR101791282B1 - Polarizing plate and method for manufacturing the same - Google Patents

Abstract

A polarizing plate having a polarizer layer and having a durability and capable of providing a good display of contrast ratio in a liquid crystal display, comprising: a first step of leaving the polarizing plate in an atmosphere at 85 캜 for 750 hours; A2 and a3 of the Hunter Lab color system immediately before the initiation of the first step, immediately after the end of the first step and immediately after the end of the second step are set to a1, a2 and a3, respectively, A polarizing plate satisfying the relationship of DELTA Y / DELTA X ≥ 0.7 when DELTA X and the difference between a2 and a3 are DELTA Y, when the evaluation test for obtaining these values with respect to the polarizer layer is performed, And a liquid crystal display device using the polarizing plate.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a polarizing plate,

The present invention relates to a polarizing plate and a manufacturing method thereof.

BACKGROUND ART [0002] A liquid crystal display device is used for various display devices, taking advantage of features such as low power consumption, low voltage operation, light weight and thinness. The liquid crystal display device is composed of many materials such as a liquid crystal cell, a polarizing plate, a phase difference film, a condensing sheet, a diffusion film, a light guide plate, and a light reflection sheet. Therefore, improvements have been actively made aiming at improvement in productivity, lightness, and brightness by reducing the number of constituent films or decreasing the thickness of a film or a sheet.

On the other hand, a liquid crystal display device is required to have a product that can withstand severe endurance conditions depending on its application. For example, a liquid crystal display device for a car navigation system may have a high temperature or humidity inside a vehicle on which it is installed, and the temperature and humidity conditions are harsh as compared with a monitor for a general television or a personal computer. For such applications, polarizers are also required to exhibit high durability.

The polarizing plate usually has a structure in which a transparent protective film is laminated on both sides or one side of a polarizing film made of a polyvinyl alcohol resin in which a dichroic dye is adsorbed and oriented. For example, JP 2004-341503-A discloses a polarizing plate having good color and excellent durability, in which a polyvinyl alcohol film is subjected to iodine dyeing and then uniaxially stretched in an aqueous solution of boric acid to provide a transparent protective film on the surface of the polarizer A polarizing plate is disclosed.

However, the above conventional polarizing plate using a polyvinyl alcohol film as a polarizer has insufficient durability, and when such a polarizing plate is used for a liquid crystal display device, the contrast of the liquid crystal display device may remarkably decrease depending on the environment.

Therefore, it is an object of the present invention to provide a polarizing plate having durability and capable of providing a good contrast ratio display in a liquid crystal display, and a method of manufacturing the polarizing plate.

As a result of intensive studies, the present inventors have found that such conventional polarizing plates are easily changed when they are exposed in a high-temperature environment, leading to a decrease in contrast in liquid crystal displays.

That is, the present invention includes the following.

[1] A polarizing plate having a polarizer layer, wherein the polarizing plate has a first step of leaving the polarizing plate in an atmosphere at 85 캜 for 750 hours and a second step of allowing the polarizing plate to stand for 48 hours in an atmosphere at room temperature immediately after the first step, When the evaluation test for obtaining these values for the polarizer layer is performed with the orthogonal a values of the Hunter Lab color system immediately before the start, immediately after the end of the first step and immediately after the end of the second step, respectively, as a1, a2 and a3, and the difference between a2 and a1 is DELTA X, and the difference between a2 and a3 is DELTA Y, the following relationship is satisfied: DELTA X and DELTA Y satisfy the relationship of the following formula (1).

? Y /? X? 0.7 (1)

[2] The polarizer according to [1], wherein the polarizer layer is preferably made of a polyvinyl alcohol resin having a degree of saponification of 98 mol% or more.

[3] The polarizer according to [1] or [2], wherein the polarizer layer has a thickness of 10 m or less.

[4] A method for producing a polarizing plate according to any one of [1] to [3], wherein a resin layer made of a polyvinyl alcohol resin having a degree of saponification of 98 mol% or more is formed on one side of a base film to obtain a laminated film A resin layer forming step, a stretching step of obtaining a stretched film by uniaxially stretching the laminated film at a stretching magnification of more than 5 times, a dyeing step of obtaining a dyeing film by dying the resin layer of the stretched film with a dichroic dye, A crosslinking step of immersing the resin layer in a solution containing a crosslinking agent to obtain a crosslinked film and a drying step of drying the crosslinked film and wherein the stretching is not performed in the crosslinking step and the drying step.

[5] The polarizing plate according to [4], wherein the formation of the resin layer in the resin layer forming step is carried out by applying a polyvinyl alcohol resin solution on one side of the base film and evaporating the solvent from the coating liquid to dry it. ≪ / RTI >

[6] The resin layer is formed in the resin layer forming step in such a manner that a primer layer is formed on one side of the base film, a polyvinyl alcohol resin solution is applied on the primer layer, and a solvent Followed by evaporation and drying. The polarizing plate according to < 4 >

[7] A production method of a polarizing plate according to any one of [1] to [3], wherein a resin layer made of a polyvinyl alcohol resin having a degree of saponification of 98 mol% or more is formed on one side of a base film to obtain a laminated film A resin layer forming step, a stretching step of obtaining a stretched film by uniaxially stretching the laminated film at a stretching magnification of more than 5 times, a step of dying the resin layer of the stretched film with a dichroic dye to form a polarizer layer, A crosslinking step of immersing the polarizer layer of the dye film in a solution containing a crosslinking agent to obtain a crosslinked film; a drying step of drying the crosslinked film to obtain a polarizing laminated film; A bonding step of bonding a protective film to a surface on the side opposite to the film side to obtain a multilayer film and a peeling step of peeling the base film from the multilayer film, Method for producing a polarizing plate that is subjected to stretching in the manufacturing process.

[8] The polarizing plate according to [7], wherein the formation of the resin layer in the resin layer forming step is carried out by applying a polyvinyl alcohol resin solution onto one side of the base film and evaporating the solvent from the coating liquid to dry it. ≪ / RTI >

[9] The resin layer is formed in the resin layer forming step, wherein a primer layer is formed on one side of the base film, a polyvinyl alcohol resin solution is applied on the primer layer, and a solvent Followed by evaporation and drying. [7] The method for producing a polarizing plate according to [7].

[10] The production method of a polarizing plate according to any one of [7] to [9], wherein the bonding of the polarizer layer and the protective film in the bonding step is carried out via a pressure-sensitive adhesive layer or an adhesive layer.

[11] A polarizing plate according to any one of [1] to [3], which is produced by the production method according to any one of [4] to [10].

[12] A liquid crystal display device having the polarizing plate according to any one of [1] to [3].

[13] A liquid crystal display device having a polarizing plate according to [11].

According to the present invention, it is possible to provide a polarizing plate capable of providing a display of a good contrast ratio in a liquid crystal display device. Further, according to the present invention, it is possible to provide a polarizing plate that is excellent in durability and can provide a display of a good contrast ratio even in a liquid crystal display device used under harsh environments.

Fig. 1 is a flowchart showing a first embodiment of a method for producing a polarizing plate according to the present invention.
Fig. 2 is a flowchart showing a second embodiment of a method for producing a polarizing plate according to the present invention.

Hereinafter, the present invention will be described in more detail with reference to the drawings.

≪ Configuration of Polarizer &

The polarizing plate according to the present invention has a polarizer layer and satisfies the relationship of the following formula (1) in the following evaluation test. The evaluation test has a first step of leaving the polarizing plate in an atmosphere of 85 캜 for 750 hours and a second step of leaving the polarizing plate for 48 hours in an atmosphere of room temperature immediately after the first step and immediately before the start of the first step, And the orthogonal a values of the Hunter Lab color system immediately after the end of the second step are a1, a2 and a3, respectively, to obtain these values for the polarizer layer. When the relation of the expression (1) is satisfied, it means that the difference between a2 and a1 is DELTA X, and the difference between a2 and a3 is DELTA Y, DELTA X and DELTA Y satisfy the relation of the following expression (1).

? Y /? X? 0.7 (1)

The closer the value of DELTA Y / DELTA X is to 1, the closer to the original state by the second step, even if the polarizer layer is changed by the first step. It was found that, even if the value was 0.7 or more as in the formula (1), even if it was exposed under a severe environment (first step), there was no problem in clarity of display. Therefore, the polarizing plate of the present invention satisfies the relationship of the formula (1), and therefore the display is excellent in durability and can provide a clear display even if it is exposed in a severe environment. It is more preferable that the value of? Y /? X is 0.8 or more.

[Polarizer layer]

The polarizer layer preferably has a thickness of 10 mu m or less, and preferably, the dichroic dye is adsorbed and oriented on the uniaxially stretched polyvinyl alcohol-based resin layer. As the polyvinyl alcohol-based resin, a saponified polyvinyl acetate-based resin can be used. Examples of the polyvinyl acetate-based resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers with other monomers copolymerizable with vinyl acetate. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

The saponification degree of the polyvinyl alcohol resin is preferably 98 mol% or more. If the saponification degree of the polyvinyl alcohol resin is less than 98 mol%, sufficient optical performance may not be obtained.

The term "saponification degree" as used herein refers to the ratio of the acetic acid group contained in the polyvinyl acetate resin as the raw material of the polyvinyl alcohol resin to the hydroxyl group by the saponification process as a unit ratio (mol%) and is a numerical value defined by the following formula . It can be obtained by the method prescribed in JIS K 6726 (1994).

Saponification degree (mol%) = (number of hydroxyl groups) / (number of hydroxyl groups + number of acetic acid groups) x 100

The higher the degree of saponification, the higher the proportion of hydroxyl groups. That is, the ratio of the acetic acid group which inhibits crystallization is low. The polyvinyl alcohol resin preferably used in the present invention is not particularly limited and may be a modified polyvinyl alcohol in which a part thereof is modified. For example, the polyvinyl alcohol resin may be modified by several percent of an unsaturated carboxylic acid such as olefin such as ethylene or propylene, acrylic acid, methacrylic acid or crotonic acid, an alkyl ester of unsaturated carboxylic acid, . The average degree of polymerization of the polyvinyl alcohol resin is not particularly limited, but is preferably 100 to 10,000, more preferably 1,500 to 10,000.

PVA124H (saponification degree: 99.9 mol% or more), PVA124 (saponification degree: 98.0 to 99.0 mol%) and PVA117H (saponification degree: 99.3 mol%) manufactured by Kuraray Co., Ltd. are used as the polyvinyl alcohol- Mol% or more), PVA117 (saponification degree: 98.0 to 99.0 mol%); NH-18 (saponification degree: 98.0 to 99.0 mol%) and N-300 (saponification degree: 98.0 to 99.0 mol%) manufactured by Nippon Seika Kagakogyo Co., Ltd.; JF-17 (saponification degree: 98.0 to 99.0 mol%), JF-17L (saponification degree: 98.0 to 99.0 mol%) and JF-20 (saponification degree: 98.0 to 99.0 mol%) manufactured by Nihon Sakubi- ), Which can be preferably used in the present invention.

The resulting film of the polyvinyl alcohol resin constitutes a polarizer layer in the polarizing plate of the present invention. The method of forming the polyvinyl alcohol resin is not particularly limited and a film can be formed by a known method. From the standpoint of obtaining a polarizer layer having a desired thickness, a solution of a polyvinyl alcohol resin is coated on the base film It is preferable to apply it to form a film. The polarizer layer is uniaxially stretched at a stretching magnification of preferably more than 5 times.

The polarizer layer preferably has a dichroic dye adsorbed and oriented on the polyvinyl alcohol resin as described above. The thickness of the polarizer layer is preferably 10 占 퐉 or less. By making the thickness of the polarizer layer 10 μm or less, a thin polarizer can be formed.

[Acquisition method of orthogonal a value]

A method of obtaining the orthogonal a value in the above evaluation test will be described. Here, the orthogonal a value is defined by the Hunter colorimetric system. Concretely, an ultraviolet visible spectrophotometer (V7100, manufactured by Nippon Bunko Co., Ltd., VAP-7070 manufactured by Nippon Bunko Co., Ltd.) having an integrating sphere, a 2-degree field of view; C light source). The MD transmittance and the TD transmittance are determined in the wavelength range of 380 nm to 780 nm and the orthogonal transmittance is calculated at a wavelength interval of 5 nm based on the following formula (2). The orthogonal three-pole values (Xc, Yc, Zc) of the sample were measured according to JIS Z 8772 5.4 using the orthogonal transmittances at the obtained wavelengths, and these values were used as a color difference formula in Lab space (Equation (3)), thereby calculating the orthogonal a value.

In the above, "MD transmittance" is the transmittance when the direction of the polarization of light emerging from the Grit Thompson prism is parallel to the transmission axis of the sample of the polarizing plate, and is expressed by "MD" in equation (2). The term " TD transmittance " is the transmittance when the polarizing plate sample is orthogonal to the direction of the polarized light emitted from the Glanthampton prism, and is expressed by " TD "

Orthogonal transmittance (%) = (MD + TD) / 100 (2)

A quadrature value = 17.5 (1.02Xc-Yc) / Yc 1/2 Expression (3)

≪ Polarizing plate production method >

[First Embodiment]

Fig. 1 is a flowchart showing a first embodiment of a method for producing a polarizing plate according to the present invention. According to the method, a polarizing plate manufacturing method includes: a resin layer forming step (S10) of forming a resin layer made of a polyvinyl alcohol resin on one surface of a base film to form a laminated film; A step (S30) of obtaining a dye film by forming a polarizer layer by dying the resin layer with a dichroic dye, a step (S30) of forming the polarizer layer A crosslinking step (S40) of immersing the layer in a solution containing a crosslinking agent to obtain a crosslinked film, and a drying step (S50) of drying the crosslinked film in this order.

The polarizing plate obtained by this manufacturing method becomes a polarizing plate having a polarizing layer on the stretched base film. This can be used as a polarizing plate as a base film as a protective film or as an intermediate product for transferring a polarizing layer to a protective film as described later.

In the present embodiment, the stretching film is not stretched in the crosslinking step (S40), and the stretching of the crosslinking film is not performed in the drying step (S50). If stretching is carried out in the cross-linking step (S40) or the drying step (S50), there is a case where neck-in is developed in the stretched film or the cross-linked film, which is not preferable.

[Second Embodiment]

Fig. 2 is a flowchart showing a second embodiment of the method for producing a polarizing plate according to the present invention. According to the method, a polarizing plate manufacturing method includes: a resin layer forming step (S10) of forming a resin layer made of a polyvinyl alcohol resin on one surface of a base film to form a laminated film; A step (S30) of obtaining a dye film by forming a polarizer layer by dying the resin layer with a dichroic dye, a step (S30) of forming the polarizer layer (S40) of immersing the layer in a solution containing a crosslinking agent to obtain a crosslinked film (S40), and a drying step (S50) of drying the crosslinked film to obtain a polarizing laminated film. Thereafter, the polarizing laminated film (S60) of joining a protective film to the surface of the polarizer layer opposite to the base film to obtain a multilayer film, a peeling step (S70) of peeling the base film from the multilayer film, In this order.

The polarizing plate obtained by this manufacturing method becomes a polarizing plate having a polarizing layer on a protective film. This polarizing plate can be used, for example, by bonding to another optical film or a liquid crystal cell through a pressure sensitive adhesive.

In the present embodiment, the stretching film is not stretched in the crosslinking step (S40), and the stretching of the crosslinking film is not performed in the drying step (S50). If stretching is carried out in the cross-linking step (S40) or the drying step (S50), there is a case where neck-in is developed in the stretched film or the cross-linked film, which is not preferable.

Hereinafter, each step of S10 to S70 in Fig. 1 and Fig. 2 will be described in detail. The steps S10 to S50 in the second embodiment are the same as the corresponding steps in the first embodiment.

(Resin layer forming step (S10))

Here, a resin layer made of polyvinyl alcohol resin is formed on one surface of the base film.

As the material suitable for the base film, for example, a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, stretchability and the like is used. Specific examples of such thermoplastic resins include cellulose ester resins such as cellulose triacetate, polyester resins, polyether sulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, (Meth) acrylic resins, cyclic polyolefin resins (norbornene resins), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. As the material of the base film, it is preferable that at least one selected from the group consisting of a cellulose ester resin, a polyolefin resin, a cyclic polyolefin resin and a (meth) acrylic resin is included.

The cellulose ester resin is an ester of cellulose and a fatty acid. Specific examples of such a cellulose ester-based resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate.

Of these, cellulose triacetate is particularly preferable. Many products of cellulose triacetate are commercially available and are advantageous in terms of availability and cost. Examples of commercially available products of cellulose triacetate include Fuji Tack (registered trademark) TD80 (manufactured by Fuji Film), Fuji Tack (registered trademark) TD80UF (manufactured by Fuji Film), Fuji Tack (registered trademark) TD80UZ Ltd.), KC4UY (manufactured by Konica Minolta Opt.), And the like can be given as examples of the curable resin composition of the present invention.

Examples of the polyolefin-based resin include polyethylene and polypropylene. When a base film made of polypropylene is used, it is preferable that the base film can be stably stretched at a high magnification. As the cyclic polyolefin-based resin, a norbornene-based resin is preferably used.

The cyclic polyolefin-based resin is a generic name of a resin that is polymerized using a cyclic olefin as a polymerization unit, and examples thereof include resins described in JPH01-240517-A, JPH03-14882-A, JPH03-122137-A . Specific examples thereof include ring-opened (co) polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers of cyclic olefins and? -Olefins such as ethylene and propylene (typically, random copolymers) and unsaturated carboxylic acids Graft polymers modified with derivatives thereof, and hydrides thereof. Specific examples of the cyclic olefin include norbornene monomers.

Various products are commercially available as the cyclic polyolefin-based resin. Specific examples thereof include: Topas (registered trademark) (manufactured by Ticona), ATON (registered trademark) (manufactured by JSR Corporation), ZEONOR (registered trademark) (manufactured by Nippon Zeon Corporation), Zeonex ZEONEX (registered trademark) (manufactured by Nippon Zeon Co., Ltd.) and APEL (registered trademark) (manufactured by Mitsui Chemicals, Inc.).

As the (meth) acrylic resin, any suitable (meth) acrylic resin may be employed. Examples thereof include poly (meth) acrylate esters such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic acid copolymers, methyl methacrylate- (meth) acrylic acid ester copolymers, methyl methacrylate- (Meth) acrylic acid copolymer, a (meth) acrylic acid methyl-styrene copolymer (MS resin and the like), a polymer having an alicyclic hydrocarbon group (for example, a methacrylic acid methyl-methacrylic acid cyclohexyl copolymer, Methyl (meth) acrylate norbornyl copolymer, and the like).

Preferable examples include poly (meth) acrylate C _{1 -6} alkyl such as methyl poly (meth) acrylate. As the (meth) acrylic resin, a methyl methacrylate resin having a main component (50 to 100 wt%, preferably 70 to 100 wt%) of methyl methacrylate is used.

In addition to the thermoplastic resin, any appropriate additives may be added to the base film. Examples of such an additive include an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a releasing agent, a coloring inhibitor, a flame retardant, a nucleating agent, an antistatic agent, a pigment and a colorant. The content of the thermoplastic resin exemplified above in the base film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, still more preferably 60 to 98% by weight, particularly preferably 70 to 97% by weight %to be. When the content of the thermoplastic resin in the base film is less than 50% by weight, high transparency and the like inherently possessed by the thermoplastic resin may not be sufficiently developed.

The thickness of the base film can be appropriately determined, but is generally 1 to 500 占 퐉, more preferably 1 to 300 占 퐉, further preferably 5 to 200 占 퐉, from the viewpoint of workability such as strength and handling properties. The thickness of the base film is most preferably from 5 to 150 mu m.

The base film may be subjected to a corona treatment, a plasma treatment, a flame treatment, or the like, on at least the surface of the side on which the polarizer layer is formed, in order to improve the adhesion with the polarizer layer. In order to improve the adhesion, a thin layer such as a primer layer may be formed on the surface of the base film on which the polarizer layer is formed.

In the first and second embodiments, the base film preferably has a melting point of 110 ° C or higher so that it can be stretched in a temperature range suitable for stretching the polyvinyl alcohol resin. Preferably, those having a melting point of 130 ° C or higher are used. If the melting point of the base film is less than 110 캜, the base film tends to be melted in the stretching step (S20) described later, so that the stretching temperature can not be sufficiently increased and stretching exceeding 5 times becomes difficult. The melting point of the base film is a value measured at a heating rate of 10 占 폚 / min based on ISO3146.

The material of the polyvinyl alcohol resin suitable for forming the resin layer is as described in the description of the constitution of the polarizing plate. The thickness of the resin layer to be formed is preferably more than 3 占 퐉 and 30 占 퐉 or less, more preferably 5 to 20 占 퐉. If the thickness is less than 3 탆, the resulting film becomes too thin after stretching to significantly deteriorate the dyeability. If it exceeds 30 탆, the thickness of the finally obtained polarizer layer may exceed 10 탆.

The resin layer is preferably formed by coating a polyvinyl alcohol resin solution obtained by dissolving a polyvinyl alcohol resin powder in a good solvent on one surface of a base film and drying the solvent by evaporation. By forming the resin layer in this way, it becomes possible to form the resin layer thin. Examples of the method for coating a polyvinyl alcohol resin solution on a base film include a roll coating method such as wire bar coating method, reverse coating and gravure coating, a die coating method, a comma coating method, a lip coating method, a spin coating method, Method, a fountain coating method, a dipping method, a spraying method, and the like can be suitably selected and employed by a known method. The drying temperature is, for example, 50 to 200 占 폚, preferably 60 to 150 占 폚. The drying time is, for example, 2 to 20 minutes.

The resin layers in the first and second embodiments may be formed by adhering an original film made of a polyvinyl alcohol resin on one surface of a base film.

Further, in order to improve the adhesion between the base film and the polyvinyl alcohol resin, a primer layer may be formed between the base film and the resin layer. The primer layer is preferably formed from a composition containing a crosslinking agent or the like in a polyvinyl alcohol-based resin from the viewpoint of adhesion.

(Drawing step S20)

Here, the laminated film composed of the base film and the resin layer is uniaxially stretched so as to have a stretching magnification of preferably more than 5 times the original length of the laminated film to obtain a stretched film. More preferably, it is uniaxially stretched so as to have a stretching magnification of 5 times to 17 times or less. More preferably not less than 5 times but not more than 8 times. If the stretching magnification is 5 times or less, the resin layer made of polyvinyl alcohol resin is not sufficiently oriented, and as a result, the degree of polarization of the polarizer layer does not become sufficiently high. On the other hand, if the stretching magnification exceeds 17 times, the laminated film tends to be broken at the time of stretching, and the thickness of the stretched film becomes thinner than necessary, which may lower the workability and handling property in subsequent steps. The stretching process in the stretching process (S20) is not limited to the single-stage stretching but may be performed in multiple stages. In the case of multi-stage drawing, the drawing process is performed so that the sum of the front ends of the drawing process is preferably 5 times or more.

In the stretching step (S20) in the first and second embodiments, it is preferable to perform the longitudinal stretching treatment in the longitudinal direction of the laminated film. Examples of the longitudinal stretching method include an inter-roll stretching method, a compression stretching method, and a stretching method using a tenter. The stretching treatment is not limited to the longitudinal stretching treatment, but may be an oblique stretching treatment or the like. It is also preferable to be free-end uniaxial stretching.

Any of the wet drawing method and the dry drawing method can be adopted as the drawing treatment, but the dry drawing method is preferable because the temperature at the time of drawing the laminated film can be selected in a wide range.

In the first and second embodiments, it is preferable to conduct the stretching treatment at a temperature ranging from -30 ° C to + 5 ° C of the melting point of the base film. More preferably, the stretching treatment is performed at a temperature ranging from -25 ° C to the melting point of the base film. When the stretching temperature is lower than -30 캜 of the melting point of the base film, high-magnification stretching exceeding 5 times becomes difficult. If the stretching temperature exceeds +5 캜 of the melting point of the base film, stretching becomes difficult due to melting of the base film, which is not preferable. The stretching temperature is within the above range, more preferably 120 deg. When the stretching temperature is 120 DEG C or more, even if the stretching ratio is higher than 5 times, the stretching process is not accompanied with difficulty. The temperature adjustment of the stretching treatment is usually carried out by adjusting the temperature of the heating furnace.

(Dyeing process (S30))

Here, the resin layer of the stretched film is dyed with a dichroic dye to form a polarizer layer to obtain a dye film. Examples of the dichroic dye include iodine and organic dyes. Examples of organic dyes include red dyes such as Red BR, Red LR, Red R, Pink LB, Rubin BL, Bordeaux GS, Sky Blue LG, Lemon Yellow, Blue BR, Blue 2R, Navy RY, Green LG, Violet LB, B, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Kongogred, Brilliant Violet BK, Supra Blue G, Supra Blue GL, Supra Orange GL, Direct Sky Blue, Direct First Orange S, First Black and the like can be used. These dichroic substances may be used alone or in combination of two or more.

The dyeing step is carried out, for example, by immersing the entire stretched film in a solution (dyeing solution) containing the dichroic dye. As the dyeing solution, a solution obtained by dissolving the dichroic dye in a solvent can be used. As a solvent for the dyeing solution, water is generally used, but an organic solvent having compatibility with water may be further added. The concentration of the dichroic dye is preferably 0.01 to 10% by weight, more preferably 0.02 to 7% by weight, and particularly preferably 0.025 to 5% by weight.

When iodine is used as the dichroic dye, it is preferable to further add iodide because the dyeing efficiency can be further improved. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide and the like. The addition ratio of these iodides is preferably 0.01 to 10% by weight in the dyeing solution. Among iodides, it is preferable to add potassium iodide. When potassium iodide is added, the ratio of iodine to potassium iodide is preferably in the range of 1: 5 to 1: 100, more preferably in the range of 1: 6 to 1:80, more preferably 1: 7 to 1: 70.

The immersing time of the stretched film in the dyeing solution is not particularly limited, but it is preferably in the range of 15 seconds to 15 minutes, and more preferably in the range of 1 to 3 minutes. The temperature of the dyeing solution is preferably in the range of 10 to 60 占 폚, and more preferably in the range of 20 to 40 占 폚.

(Crosslinking step (S40))

The dyed film obtained by the dyeing step (S30) is subjected to a crosslinking treatment. The crosslinking treatment can be carried out, for example, by immersing the dyeing film in a solution (crosslinking solution) containing a crosslinking agent. As the crosslinking agent, conventionally known materials can be used. Examples thereof include boron compounds such as boric acid and borax, and glyoxal and glutaraldehyde. These may be used alone or in combination of two or more.

As the crosslinking solution, a solution in which a crosslinking agent is dissolved in a solvent can be used. As the solvent, for example, water may be used, but an organic solvent having compatibility with water may be further contained. The concentration of the crosslinking agent in the crosslinking solution is not limited to this, but is preferably in the range of 1 to 10 wt%, more preferably 2 to 6 wt%.

Iodide may be added to the crosslinking solution. By adding iodide, the polarization characteristics in the plane of the polarizer layer can be made more uniform. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide and titanium iodide. The content of iodide is 0.05 to 15% by weight, more preferably 0.5 to 8% by weight.

The immersion time of the dye film to the crosslinking solution is preferably 15 seconds to 20 minutes, more preferably 30 seconds to 15 minutes. The temperature of the cross-linking solution is preferably in the range of 10 캜 to 90 캜, and more preferably in the range of 70 캜 to 85 캜.

In the crosslinking step, it is preferable that the film (crosslinked film) after the crosslinking treatment is subjected to a washing treatment. As the cleaning treatment, a water cleaning treatment can be performed. The water washing treatment can be usually carried out by immersing the drawn film in purified water such as ion-exchanged water or distilled water. The water washing temperature is usually in the range of 3 to 50 캜, preferably 4 to 20 캜. The immersion time is usually from 2 to 300 seconds, preferably from 3 seconds to 240 seconds.

The cleaning treatment may be a combination of a cleaning treatment with a iodide solution and a water cleaning treatment, or a solution in which a liquid alcohol such as methanol, ethanol, isopropyl alcohol, butanol, or propanol is blended.

(Drying step (S50))

After the crosslinking step, the drying step is carried out. As the drying step, any appropriate method (for example, natural drying, air blow drying, heat drying) may be employed. For example, in the case of heat drying, the drying temperature is usually 20 to 95 占 폚, and the drying time is usually about 1 to 15 minutes. By the above steps, a polarizing laminated film having a polarizer layer on a base film can be obtained. The polarizer layer has a polarizing function after the resin layer has undergone the above-described series of steps. The above-mentioned polarizing laminated film can be used as it is as a polarizing plate as described above. Hereinafter, S60 and S70 in the second embodiment will be described in detail.

(Bonding step (S60))

Here, a protective film is bonded to the surface of the polarizing layer of the polarizing laminated film opposite to the base film to obtain a multilayer film. As a method for bonding the protective film, there are a method of bonding the polarizer layer and the protective film with a pressure sensitive adhesive, and a method of bonding the polarizer layer surface and the protective film with an adhesive.

Protective film

The protective film may be a simple protective film having no optical function, or may be a protective film having an optical function such as a retardation film or a brightness enhancement film. Examples of the material of the protective film include, but are not limited to, a cyclic polyolefin resin film, acetic acid cellulose resin film made of a resin such as triacetylcellulose and diacetylcellulose, polyethylene terephthalate, polyethylene naphthalate, A polyester resin film made of a resin such as terephthalate, a polycarbonate resin film, an acrylic resin film, a polypropylene resin film, and the like.

As the cyclic polyolefin-based resin, suitable commercially available products such as TOPAS (registered trademark) (manufactured by Ticona), ATON (registered trademark) (manufactured by JSR Corporation), ZEONOR (registered trademark) ZEONEX (manufactured by Nippon Zeon Co., Ltd.) and APEL (registered trademark) manufactured by Mitsui Chemicals, Inc. can be preferably used. When a film of such an annular polyolefin-based resin is formed into a film, known methods such as a solvent casting method and a melt extrusion method are suitably used. In addition, pre-formed films such as Essen (registered trademark) (manufactured by Sekisui Chemical Co., Ltd.), SCA40 (manufactured by Sekisui Chemical Co., Ltd.) and Zeonoa (registered trademark) A commercial product of a film made of a cyclic polyolefin resin may be used.

The cyclic polyolefin-based resin film may be uniaxially stretched or biaxially stretched. By stretching, an arbitrary retardation value can be imparted to the cyclic polyolefin-based resin film. The stretching is usually carried out while releasing the film roll, and is stretched in the heating direction in the heating direction, the direction perpendicular to the traveling direction of the roll, or both directions. The temperature of the heating furnace is usually in the range from the vicinity of the glass transition temperature of the cyclic polyolefin-based resin to the glass transition temperature + 100 ° C. The magnification of the stretching is usually 1.1 to 6 times, preferably 1.1 to 3.5 times in one direction.

Since the surface activity of the cyclic polyolefin-based resin film is generally inferior, the surface to be bonded to the polarizing film is preferably subjected to surface treatment such as plasma treatment, corona treatment, ultraviolet ray irradiation treatment, frame (flame) treatment and saponification treatment Do. Among them, a plasma treatment and a corona treatment which can be performed relatively easily are preferable.

As the cellulose acetate based resin film, suitable commercially available products such as Fuji Tack (registered trademark) TD80 (manufactured by Fuji Film), Fuji Tack (registered trademark) TD80UF (manufactured by Fuji Film) KC4UY (manufactured by KONICA MINOLTA OPT Co., Ltd.), KC8UX2M (manufactured by Konica Minolta Optical Co., Ltd.), and KC4UY (manufactured by Konica Minolta Optical Co., Ltd.) Can be preferably used.

A liquid crystal layer or the like may be formed on the surface of the cellulose acetate-based resin film in order to improve the viewing angle characteristics. Further, in order to impart a phase difference, a cellulose acetate-based resin film may be stretched. The cellulose acetate-based resin film is usually subjected to saponification treatment in order to improve the adhesion with the polarizing film. As the saponification treatment, a method of immersing in an aqueous alkaline solution such as sodium hydroxide or potassium hydroxide can be employed.

On the surface of the protective film as described above, an optical layer such as a hard coat layer, an antiglare layer, and an antireflection layer may be formed. The method of forming these optical layers on the surface of the protective film is not particularly limited and a known method can be used.

The thickness of the protective film is preferably as thin as possible from the viewpoint of thinning, more preferably 88 占 퐉 or less, and more preferably 48 占 퐉 or less. On the contrary, when the thickness is excessively thin, the strength is lowered and the workability is deteriorated. Therefore, it is preferably 5 탆 or more.

The pressure-

The pressure sensitive adhesive to be used for bonding the protective film and the polarizer layer is usually a composition obtained by using an acrylic resin, a styrene resin, a silicone resin or the like as a base polymer and adding thereto a crosslinking agent such as an isocyanate compound, an epoxy compound, or an aziridine compound . It is also possible to use a pressure-sensitive adhesive layer containing fine particles and exhibiting light scattering properties.

The thickness of the pressure-sensitive adhesive layer is preferably from 1 to 40 占 퐉, but it is preferably thinly coated, more preferably from 3 to 25 占 퐉, within a range not deteriorating workability and durability characteristics. When the thickness is 3 to 25 占 퐉, the film has good processability and a preferable thickness for suppressing the dimensional change of the polarizing film. If the pressure-sensitive adhesive layer is less than 1 占 퐉, the pressure-sensitive adhesive property is deteriorated, and if it exceeds 40 占 퐉, the pressure-sensitive adhesive is likely to be discharged.

In the method of bonding the protective film to the polarizer layer by the pressure-sensitive adhesive, the pressure-sensitive adhesive layer may be formed on the protective film surface and then bonded to the polarizer layer. Alternatively, a protective film may be adhered to the surface of the polarizer layer good.

The method of forming the pressure-sensitive adhesive layer is not particularly limited. The pressure-sensitive adhesive layer is formed by applying a solution containing each component including the base polymer to the protective film surface or the polarizer layer surface, Alternatively, the pressure-sensitive adhesive layer may be formed on the separator and then transferred to the protective film surface or the polarizer layer surface to be laminated. When the pressure-sensitive adhesive layer is formed on the surface of the protective film or polarizer layer, adhesion treatment, for example, corona treatment, or the like may be applied to one or both of the protective film or the polarizer layer surface or the pressure-sensitive adhesive layer.

Adhesive layer

The adhesive used for bonding the protective film and the polarizer layer includes, for example, an aqueous adhesive using a polyvinyl alcohol resin aqueous solution, a water-based liquid type urethane emulsion adhesive, or the like. When a cellulose acetate film treated with a saponification treatment such as saponification treatment is used as the protective film, a polyvinyl alcohol resin aqueous solution is preferably used as an aqueous adhesive for bonding with the polarizer layer. The polyvinyl alcohol resin used as the adhesive includes a vinyl alcohol homopolymer obtained by saponifying a polyvinyl acetate which is a homopolymer of vinyl acetate, a vinyl alcohol homopolymer obtained by saponifying a copolymer of vinyl acetate and another monomer capable of copolymerization with the vinyl alcohol, Based copolymers, and further modified polyvinyl alcohol polymers obtained by partially modifying hydroxyl groups thereof. As the water-based adhesive, polyaldehyde, a water-soluble epoxy compound, a melamine compound, a zirconia compound, a zinc compound or the like may be added as an additive. When such an aqueous adhesive is used, the adhesive layer obtained therefrom usually has a size of 1 mu m or less, and even if a cross section is observed with an ordinary optical microscope, the adhesive layer is practically not observed.

The method of bonding the polarizer layer and the protective film using an aqueous adhesive is not particularly limited. For example, the adhesive may be uniformly applied to the surface of the polarizer layer and / or the protective film, Or the like, and the like. Normally, the adhesive is applied at a temperature of 15 to 40 캜 after its preparation, and the bonding temperature is usually in the range of 15 to 30 캜.

When an aqueous adhesive is used, the polarizer layer and the protective film are bonded together and then dried to remove water contained in the aqueous adhesive. The temperature of the drying furnace is preferably 30 ° C to 90 ° C. If it is less than 30 占 폚, the adhesion surface of the polarizer layer and the protective film tends to be easily peeled off. If it is 90 DEG C or higher, there is a fear that the optical performance is deteriorated by heat. The drying time can be 10 to 1000 seconds, and is preferably 60 to 750 seconds, and more preferably 150 to 600 seconds from the viewpoint of productivity.

After drying, it may be cured at room temperature or slightly higher temperature, for example, at a temperature of about 20 to 45 캜 for about 12 to 600 hours. The temperature at the time of curing is generally set lower than the temperature employed at the time of drying.

Further, a photo-curing adhesive may be used as an adhesive when bonding the polarizer layer and the protective film. The photo-curable adhesive includes, for example, a mixture of a photo-curable epoxy resin and a photo cationic polymerization initiator.

As a method of bonding the polarizer layer and the protective film with the photo-curable adhesive, conventionally known methods can be used. For example, a flexible method, a Meyer bar coat method, a gravure coat method, a comma coater method, a doctor blade method, A method in which an adhesive is applied to the bonding surface of the polarizer layer and / or the protective film by a coating method, a dip coating method, a spraying method, or the like, and both are overlapped. The flexible method is a method for applying an enlarged coating by causing an adhesive to flow down on the surface while moving the polarizer layer or protective film to be coated in a substantially vertical direction, a substantially horizontal direction, or an inclined direction between them.

An adhesive is applied to the surface of the polarizer layer or the protective film, and then the polarizer layer and the protective film are bonded to each other with a nip roll or the like interposed therebetween through the adhesive application surface. A method of dropping an adhesive between the polarizer layer and the protective film in a state in which the polarizer layer and the protective film are overlapped with each other, and then pressing the laminate with a roll or the like to uniformly press and spread. In this case, metal, rubber, or the like can be used as the material of the roll. Further, a method of dropping an adhesive between the polarizer layer and the protective film, passing the film between the rolls and the roll, and pressing and pressing the film are spread out. In this case, these rolls may be made of the same material or different materials. The thickness of the adhesive layer after bonding using the nip roll or the like before drying or curing is preferably 5 m or less and 0.01 m or more.

The bonding surface of the polarizer layer and / or the protective film may be appropriately subjected to surface treatment such as plasma treatment, corona treatment, ultraviolet ray irradiation treatment, frame (flame) treatment and saponification treatment, in order to improve the adhesiveness. As the saponification treatment, there may be mentioned a method of immersing in an aqueous solution of an alkali such as sodium hydroxide or potassium hydroxide.

When a photo-curable resin is used as the adhesive, the photo-curable adhesive is cured by bonding the polarizer layer and the protective film and then irradiating with an active energy ray. A light source of an active energy ray is not particularly limited, but an active energy ray having a light emission distribution at a wavelength of 400 nm or less is preferable. Specifically, a low energy mercury lamp, medium pressure mercury lamp, high pressure mercury lamp, ultra high pressure mercury lamp, A wave excitation mercury lamp, a metal halide lamp and the like are preferably used.

The light irradiation intensity for the photo-curing adhesive is appropriately determined according to the composition of the photo-curable adhesive and is not particularly limited, but it is preferable that the irradiation intensity in the wavelength region effective for activating the polymerization initiator is 0.1 to 6000 mW / cm 2. When the irradiation intensity is not less than 0.1 mW / cm 2, the reaction time is not excessively long. When the irradiation intensity is not more than 6000 mW / cm 2, the heat radiated from the light source and the heat generated during curing of the photo-curing adhesive deteriorate the yellowing of the epoxy resin, . The light irradiation time for the photo-curable adhesive is not particularly limited as long as it is applied in accordance with the photo-curing adhesive to be cured, but it is preferable that the accumulated light quantity represented by the product of the irradiation intensity and the irradiation time is set to 10 to 10,000 mJ / Do. When the total amount of light for the photo-curable adhesive is 10 mJ / cm 2 or more, a sufficient amount of active species derived from the polymerization initiator can be generated sufficiently to allow the curing reaction to proceed more surely. When the amount is less than 10000 mJ / cm 2, So that good productivity can be maintained. The thickness of the adhesive layer after irradiation with active energy rays is usually about 0.001 to 5 mu m, preferably 0.01 mu m or more and 2 mu m or less, more preferably 0.01 mu m or more and 1 mu m or less.

When the photo-curing adhesive is cured by irradiation of an active energy ray, it is preferable to perform curing under such a condition that various functions of the polarizing plate are not deteriorated, such as the degree of polarization, transmittance and hue of the polarizing layer, and transparency of the protective film.

(Peeling step S70)

In the polarizing plate manufacturing method of the second embodiment, as shown in Fig. 2, the peeling step (S70) of the base film is performed after the bonding step (S60) of bonding the protective film to the polarizer layer. In the peeling step (S70) of the base film, the base film is peeled from the multi-layer film. The method of peeling the base film is not particularly limited, and can be peeled off in the same manner as in the peeling film peeling process performed in a polarizing plate provided with a usual pressure sensitive adhesive. After the step of bonding the protective film (S60), the protective film may be peeled off as it is, or may be peeled once by setting the peeling step separately after winding it into a roll shape.

(Different process)

The polarizing plate of the present invention, which is manufactured as described above, may further have a step of laminating other optical layers for practical use, and may be a polarizing plate in which such optical layers are laminated. Further, the protective film may have the function of such an optical layer. Examples of other optical layers include a reflective polarizing film that transmits polarized light of a certain type and reflects polarized light exhibiting properties opposite to the polarized light, a film having an antireflection function having a concavo-convex shape on the surface, A reflective film having a reflective function on its surface, a transflective film having a reflective function and a transmissive function, and a viewing angle compensating film.

Examples of commercially available products that correspond to a reflective polarizing film that transmits polarized light of a certain kind and reflect polarized light exhibiting properties opposite to that of the polarized light include DBEF (available from 3M Company, available from Sumitomo 3M Ltd.) APF (available from 3M, available from Sumitomo 3M Ltd.). Examples of the viewing angle compensation film include an optical compensation film coated with a liquid crystalline compound on the surface of the substrate and an oriented retardation film made of a polycarbonate based resin and a retardation film made of a cyclic polyolefin based resin. As a commercially available product corresponding to the optical compensation film on which the liquid crystal compound is coated on the surface of the base material, there are WV film (manufactured by Fuji Film), NH film (manufactured by Shin-Nippon Sekiyu Co., Ltd.) (Manufactured by Shin-Nippon Sekiyu Co., Ltd.). Examples of commercially available products corresponding to the retardation film made of the cyclic polyolefin resin include Aton (registered trademark) film (manufactured by JSR Corporation), Eschina (registered trademark) (manufactured by Sekisui Chemical Co., Ltd.) (Registered trademark) film (manufactured by Optesis Co., Ltd.).

According to the manufacturing method of the first and second embodiments, it is possible to provide a polarizing plate having excellent durability by suppressing necking in the manufacturing process. The neckline means that the molten resin contracts inward in the width direction, and both ends of the polarizer become thicker than the central portion.

<Liquid Crystal Display Device>

The liquid crystal display device using the polarizing plate manufactured by the first or second embodiment can be constituted. The production of the liquid crystal display device can be carried out according to a conventionally known method.

That is, the liquid crystal display device is generally formed by appropriately assembling the liquid crystal cell, the polarizing plate, and other components such as a lighting system if necessary, and further assembling the driving circuit. However, in the present invention, Except point, there is no particular limitation, and it is same as conventional. As the liquid crystal cell, any type of TN type or STN type can be used, for example.

A liquid crystal display device can be constituted by disposing a polarizing plate on one or both sides of the liquid crystal cell and appropriately using a backlight or a reflection plate for the illumination system. In such a liquid crystal display device, at least one of the polarizing plates disposed on one or both sides of the liquid crystal cell is a polarizing plate according to the present invention. When polarizing plates are provided on both sides, they may be the same or different. Further, the liquid crystal display device can be constituted by combining appropriate elements such as a diffusion plate, an anti-reflection film, a protective plate, a prism array, a lens array sheet and the like in addition to the above.

Example

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1

Thereby preparing a polarizing plate according to the present invention.

(Substrate film)

As the base film, an unoriented homo-propylene (PP) film having a thickness of 100 mu m was used.

(Formation of primer layer)

A polyvinyl alcohol aqueous solution having a concentration of 3% by weight was prepared by dissolving a polyvinyl alcohol powder (trade name: Koshe Pimer Z-200, manufactured by Nihon Seika Kagakukogyo Co., Ltd.) in hot water at 95 캜. 5 parts by weight of a crosslinking agent (Sumirez (registered trademark) resin 650, manufactured by Sumitomo Mogaka Co., Ltd.) was added to the polyvinyl alcohol aqueous solution to 6 parts by weight of the polyvinyl alcohol powder. The obtained mixed aqueous solution was coated on the surface of the corona-treated base film and dried at 80 DEG C for 10 minutes to form a primer layer having a thickness of 0.2 mu m.

(Resin layer forming step)

Polyvinyl alcohol powder (manufactured by Kuraray Co., Ltd., average degree of polymerization: 2400, degree of saponification: 98 to 99 mol%) was dissolved in hot water at 95 캜 to prepare a polyvinyl alcohol aqueous solution having a concentration of 8% by weight. The resulting aqueous solution was coated on the primer layer and dried at 80 ° C for 20 minutes to form a three-layer laminated film comprising a base film, a primer layer and a resin layer. At this time, the thickness of the resin layer was 6.1 탆.

(Drawing step, dyeing step, crosslinking step, drying step)

The laminated film was stretched 5.8 times in the longitudinal direction by free-end uniaxial stretching in the longitudinal direction at a preheating temperature of 140 占 폚 and a stretching temperature of 150 占 폚 to 160 占 폚 using a tenter apparatus to obtain a stretched film. Thereafter, the stretched film was immersed in a hot bath at 60 DEG C for 60 seconds in the stretching axis direction and immersed in a mixed aqueous solution of iodine and potassium iodide at 30 DEG C for 420 seconds, and then the excess iodine solution was washed with pure water at 10 DEG C. [ And then immersed in a mixed aqueous solution of boric acid and potassium iodide at 76 DEG C for 600 seconds. At this time, stretching of the stretched film was not performed, and necking was not seen in the width direction. Thereafter, the film was washed with pure water at 10 캜 for 4 seconds and finally dried at 80 캜 for 300 seconds without being stretched to obtain a polarizing laminated film composed of three layers of a polarizer layer, a primer layer and a base film. Neck India was not seen by drying.

(Bonding step, peeling step)

A polyvinyl alcohol-based adhesive was applied to the surface of the polarizing element layer of the polarizing element layer opposite to the surface on the base film side of the polarizing laminated film, and then a protective film (manufactured by Konica Corp., film thickness 40 탆, TAC) Lt; 0 &gt; C for 300 seconds to obtain a multilayer film composed of a protective film, a polarizer layer, a primer layer, and a base film.

The base film was peeled from the obtained multilayer film to obtain a polarizing plate. The base film was easily peeled off to obtain a polarizing plate of Example 1 having three layers of a protective film, a polarizer layer and a primer layer. The thickness of the polarizer layer was 6.1 mu m.

(Evaluation test)

The polarizing plate of Example 1 was subjected to the evaluation test described above to obtain orthogonal a values (a1, a2, a3) as described above. Then, the difference between a2 and a1 is denoted by DELTA X, and the difference between a2 and a3 is denoted by DELTA Y, and the value of DELTA Y / DELTA X is calculated. Table 1 shows the calculation results.

(Mounting test)

A layer of an acrylic pressure-sensitive adhesive having a thickness of 25 占 퐉 was formed on the surface of the primer layer with respect to the polarizing plate of Example 1 after the evaluation test. After peeling off the original polarizing plate disposed above and below the liquid crystal panel of the mobile phone (IPS mode, trade name: W53CA, manufactured by CASIO), the adhesive layer side of the polarizing plate of Example 1 in which the adhesive layer was formed was peeled off from the liquid crystal panel Junction. The optical axis was the same as that of the original polarizer. After standing at room temperature for 48 hours, an image was displayed, and the display state was evaluated by visually determining the general indoor environment and the image clarity in the dark room. The display state was clear and good display was obtained. Table 1 shows the results.

Example 2

Except that a polyvinyl alcohol powder (manufactured by Kuraray Co., Ltd., average degree of polymerization: 1700, degree of saponification: 99.3 mol% or more, trade name: Kurarupo foot 117H) was used as the polyvinyl alcohol used for the resin layer A stretched film was obtained. The thickness of the resin layer in the stretched film was 6.5 mu m.

The protective film, the polarizer layer, and the primer layer were formed in the same manner as in Example 1, except that the time for immersion in the dyeing solution was set to 1320 seconds and that the drying in the drying step was conducted at 90 DEG C for 60 seconds. To obtain a polarizing plate of Example 2. The thickness of the polarizer layer was 6.5 탆.

(Evaluation test)

The polarizing plate of Example 2 was subjected to the evaluation test described above in the same manner as in Example 1 to obtain orthogonal a values (a1, a2, a3) as described above. Then, the difference between a2 and a1 is denoted by DELTA X, and the difference between a2 and a3 is denoted by DELTA Y, and the value of DELTA Y / DELTA X is calculated. Table 1 shows the calculation results.

(Mounting test)

The polarizing plate of Example 2 after the evaluation test was subjected to a mounting test in the same manner as in Example 1. As a result, the display state was clear and good display was obtained. Table 1 shows the results.

Example 3

As the polyvinyl alcohol used for the resin layer, a polyvinyl alcohol (manufactured by Kuraray Co., Ltd., average polymerization degree: 2400, degree of saponification: 99.9 mol% or more, trade name: Kurarupo Corporation VF-PS # 7500) , A stretched film was obtained in the same manner as in Example 1. The thickness of the resin layer in the stretched film was 6.5 占 퐉.

A protective film, a polarizer layer, and a primer layer were formed in the same manner as in Example 1, except that the time for immersion in the dyeing solution was changed to 2400 seconds in the dyeing step and that the drying in the drying step was performed at 70 ° C for 300 seconds. To obtain a polarizing plate of Example 3. The thickness of the polarizer layer was 6.5 탆.

(Evaluation test)

The polarizing plate of Example 3 was subjected to the evaluation test described above in the same manner as in Example 1 to obtain orthogonal a values (a1, a2 and a3) as described above. Then, the difference between a2 and a1 is denoted by DELTA X, and the difference between a2 and a3 is denoted by DELTA Y, and the value of DELTA Y / DELTA X is calculated. Table 1 shows the calculation results.

(Mounting test)

The polarizing plate of Example 3 after the evaluation test was subjected to a mounting test in the same manner as in Example 1. As a result, the display state was clear and good display was obtained. Table 1 shows the results.

Comparative Example 1

A polyvinyl alcohol film having a thickness of 75 탆 and made of polyvinyl alcohol having an average degree of polymerization of about 2400 and a degree of saponification of 99.9 mol% or more was uniaxially stretched by about 5 times in a dry state and maintained in a relaxed state, Immersed in a mixed aqueous solution of iodine and potassium iodide at 28 DEG C for 60 seconds. Thereafter, it was immersed in a mixed aqueous solution of boric acid and potassium iodide at 72 ° C for 300 seconds. At this time, the film showed a neckline in the width direction. Subsequently, the film was washed with pure water at 10 占 폚 for 5 seconds and then dried at 90 占 폚 for 180 seconds (at this time also, a neckline was observed in the transverse direction) to obtain a polarizing film in which iodine was adsorbed and oriented in polyvinyl alcohol.

Separately, 3 parts of Kurarupo foot 117H (Kuraray Co., Ltd.), 3 parts of Gosei Pimer Z-200 (manufactured by Nippon Seika Kagaku Kogyo Co., Ltd.), 3 parts of zinc chloride (Nacalai Tesk Co., Ltd.) and 1.4 parts of glyoxal (available from Nacalai Tesque, Inc.) were dissolved to prepare a polyvinyl alcohol resin adhesive.

On one surface of the polarizing film obtained above, a protective film (manufactured by Konica Corp., thickness: 40 mu m, trade name: TAC) subjected to a saponification treatment was bonded with a nip roll through the adhesive. And then dried at 50 DEG C for 300 seconds to obtain a polarizing plate of Comparative Example 1. [

(Evaluation test)

The polarizing plate of Comparative Example 1 was subjected to the evaluation test described above in the same manner as in Example 1 to obtain orthogonal a values (a1, a2, a3) as described above. Then, the difference between a2 and a1 is denoted by DELTA X, and the difference between a2 and a3 is denoted by DELTA Y, and the value of DELTA Y / DELTA X is calculated. Table 1 shows the calculation results.

(Mounting test)

The polarizing plate of Comparative Example 3 after the evaluation test was subjected to a mounting test in the same manner as in Example 1. As a result, the display state was unclear. Table 1 shows the results.

In the polarizing plates of Examples 1 to 3, the polarizing layer was changed in accordance with the first step of the evaluation test (indicating that the value of? X was not changed, but changed), and the second step (left at room temperature for 48 hours) And it was found that the enemy transition was restrained by returning to the state close to the original state. The polarizing plates of Examples 1 to 3, in which DELTA Y / DELTA X was not less than 0.7, obtained satisfactory results that clear display was obtained in the mounting test. On the other hand, in the liquid crystal display device of Comparative Example 1, it was found that the value of DELTA Y / DELTA X was small and remained even after passing through the second step. Further, clear display could not be obtained in the mounting test. In addition, in the production steps of the polarizing plates of Examples 1 to 3, no neck-in was observed, but in the production process of the polarizing plate of Comparative Example 1, neck-in was found.

From the above results, it is presumed that there is a correlation between the suppression of the side edge in the polarizing plate and the clarity of display when the polarizing plate is used in a liquid crystal display device. Hereinafter, the correlation between the inhibition of neck phosphorus in the production step and the inhibition of the side chains in the polarizing plate will be examined.

In Examples 1 to 3, a resin layer made of a polyvinyl alcohol resin was formed on a base film, uniaxial stretching exceeding 5 times was performed, and then dyeing, crosslinking, and drying were conducted to form a thin polarizer layer , A phenomenon called neck-in was not generated. It can be inferred that the crosslinking structure in the polarizer layer is prevented from being excessively dense due to the absence of the neck phosphor. Thus, even if the polyvinyl alcohol-iodine complex is once destroyed by heat in the first step of the evaluation test, it can be assumed that the polyvinyl alcohol-iodine complex is easily cooled through the second step and then re-complexed. The above conjecture is inconsistent with the above-described result of producing the polarizing plates of Examples 1 to 3, in which it is difficult to observe the red transition even after the first step and the second step.

Claims (13)

A polarizing plate having a polarizer layer,
And a second step of leaving the polarizing plate in an atmosphere at 85 캜 for 750 hours and a second step of leaving the polarizing plate for 48 hours in an atmosphere of room temperature immediately after the first step and immediately after the start of the first step, When the evaluation test for obtaining these values for the polarizer layer is carried out with the orthogonal a values of Hunter Lab color system immediately after the end of the second step as a1, a2 and a3 respectively,
and the difference between a2 and a1 is DELTA X, and the difference between a2 and a3 is DELTA Y, the following relationship is satisfied: DELTA X and DELTA Y satisfy the relationship of the following formula (1).
? Y /? X? 0.7 (1) The polarizing plate according to claim 1, wherein the polarizer layer comprises a polyvinyl alcohol-based resin having a degree of saponification of 98 mol% or more. The polarizing plate according to claim 1 or 2, wherein the polarizer layer has a thickness of 10 탆 or less. A method for producing a polarizing plate according to claim 1,
A resin layer forming step of forming a resin layer made of a polyvinyl alcohol resin having a degree of saponification of 98 mol% or more on one surface of a base film to obtain a laminated film,
A stretching step of uniaxially stretching the laminated film at a stretching magnification of more than 5 times to obtain a stretched film,
A dyeing step of dying the resin layer of the stretched film with a dichroic dye to obtain a dye film,
A crosslinking step of immersing the resin layer of the dye film in a solution containing a crosslinking agent to obtain a crosslinked film,
Drying process for drying the crosslinked film
Lt; / RTI &gt;
Wherein the stretching is not performed in the crosslinking step and the drying step. The method for producing a polarizing plate according to claim 4, wherein the formation of the resin layer in the resin layer forming step is carried out by applying a polyvinyl alcohol resin solution onto one side of the substrate film, drying the solvent from the coating liquid by evaporation, Way. 5. The method according to claim 4, wherein the formation of the resin layer in the resin layer forming step is performed by forming a primer layer on one side of the base film, applying a polyvinyl alcohol resin solution onto the primer layer, And evaporating the solvent therefrom to dry the polarizing plate. A method for producing a polarizing plate according to claim 1,
A resin layer forming step of forming a resin layer made of a polyvinyl alcohol resin having a degree of saponification of 98 mol% or more on one surface of a base film to obtain a laminated film,
A stretching step of uniaxially stretching the laminated film at a stretching magnification of more than 5 times to obtain a stretched film,
A dyeing step of dying the resin layer of the stretched film with a dichroic dye to form a polarizer layer to obtain a dye film,
A crosslinking step of immersing the polarizing layer of the dye film in a solution containing a crosslinking agent to obtain a crosslinked film,
A drying step of drying the crosslinked film to obtain a polarizing laminated film,
A joining step of joining a protective film to a surface of the polarizing layer opposite to the base film of the polarizing laminated film to obtain a multilayered film,
Peeling process for peeling the base film from the multi-layer film
Lt; / RTI &gt;
Wherein the stretching is not performed in the crosslinking step and the drying step. The method for producing a polarizing plate according to claim 7, wherein the formation of the resin layer in the resin layer forming step is carried out by applying a polyvinyl alcohol resin solution onto one side of the base film, drying the solvent from the coating liquid by evaporation, Way. The method for producing a resin layer according to claim 7, wherein a resin layer is formed in a resin layer forming step, after forming a primer layer on one side of the base film, applying a polyvinyl alcohol resin solution onto the primer layer, And evaporating the solvent therefrom to dry the polarizing plate. The method of manufacturing a polarizing plate according to claim 7, wherein bonding of the polarizer layer and the protective film in the bonding step is performed via a pressure-sensitive adhesive layer or an adhesive layer. delete A liquid crystal display device having the polarizing plate according to claim 1 or 2. delete

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