KR101662259B1 - Polarization plate and methdo of fabricating the same - Google Patents

Abstract

A polarizing plate and a manufacturing method thereof are disclosed. A method of manufacturing a polarizing plate includes coating a compensation layer forming material having a negative C characteristic on a base substrate to form a compensation layer; Forming a polarizing layer on the compensation layer; Forming a protective film on the polarizing layer; And separating the base substrate from the compensation layer. Since the compensation layer is formed by the coating, it can have a thin thickness, and the polarizing layer has a thin thickness as well as an improved optical property by the compensation layer.

-C, polarization, liquid crystal, phase difference, compensation, TN

Description

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

The embodiment relates to a polarizing plate and a method of manufacturing the polarizing plate.

Conventionally, cellulose triacetyl cellulose (TAC) films have been used as protective films for polarizers for liquid crystal displays.

The TAC film has a high transmittance, can be easily bonded to a polyvinyl alcohol film of a polarizer, has a small birefringence anisotropy, and does not impart an unnecessary retardation component to the polarizer, and thus has been preferably used as a polarizer protective film.

On the contrary, although the TAC film has negative birefringence anisotropy to some extent, a sufficient retardation can not be expressed even if it is stretched because anisotropy is too small.

Conventional polarizing plates include a thick TAC film in order to realize a sufficient retardation, thereby increasing the thickness of the polarizing plate and the liquid crystal display.

It is an object of the present invention to provide a polarizing plate having a thin thickness and improved optical properties and a method of manufacturing the polarizing plate.

상기 화학식에서,
R1은 수소, 알킬기 및 아릴기로 형성된 그룹으로부터 선택된다.
실시예에 따른 편광판은 편광층; 상기 편광층 상에 배치되는 보호필름; 상기 편광층 아래에 배치되며, 폴리 이미드계 수지를 포함하고 네거티브 C특성을 가지며, -50㎚ 내지 -100㎚의 두께 방향의 위상차값을 가지고, 0.1㎛ 내지 10㎛의 두께를 가지는 보상층; 및 상기 보상층 아래에 배치되는 점착층을 포함하며, 상기 폴리 이미드계 수지는 하기 화학식으로 표시되는 물질 중 적어도 하나를 포함한다.

상기 화학식에서,
R1은 수소, 알킬기 및 아릴기로 형성된 그룹으로부터 선택된다.A method of manufacturing a polarizing plate according to an embodiment includes coating a compensating layer forming material including a polyimide resin on a base substrate and having a negative C characteristic; Forming a compensating layer having a retardation value in a thickness direction of -50 nm to -100 nm by irradiating light to the compensating layer forming material; Forming a polarizing layer on the compensation layer; Forming a protective film on the polarizing layer; And separating the base substrate from the compensation layer, wherein the polyimide-based resin comprises at least one of the following materials.

In the above formulas,
R1 is selected from the group consisting of hydrogen, an alkyl group and an aryl group.
The polarizing plate according to an embodiment includes a polarizing layer; A protective film disposed on the polarizing layer; A compensating layer which is disposed under the polarizing layer and contains a polyimide resin and has a negative C characteristic and has a retardation value in the thickness direction of -50 nm to -100 nm and a thickness of 0.1 to 10 m; And an adhesive layer disposed under the compensation layer, wherein the polyimide resin comprises at least one of the following materials.

In the above formulas,
R1 is selected from the group consisting of hydrogen, an alkyl group and an aryl group.

The method of manufacturing a polarizing plate according to an embodiment forms a compensation layer having a negative C characteristic by coating. Accordingly, the polarizing plate according to the embodiment includes a compensation layer having a thin thickness.

Therefore, the polarizing plate according to the embodiment has a small thickness and can compensate the retardation by the liquid crystal panel.

Therefore, the polarizing plate according to the embodiment is slim and has improved optical characteristics.

In the description of the embodiments, in the case where each layer, panel, film or plate is described as being formed "on" or "under" of each layer, panel, film or plate, The terms " on "and" under " all include being formed "directly" or "indirectly" In addition, the upper or lower reference of each component is described with reference to the drawings. The size of each component in the drawings may be exaggerated for the sake of explanation and does not mean the size actually applied.

Figs. 1 to 5 are cross-sectional views illustrating a method of manufacturing a polarizing plate according to an embodiment.

Referring to FIG. 1, a resin composition layer 211 is formed on a base substrate 10. The resin composition layer 211 is formed by spraying a resin composition on the base substrate 10.

Alternatively, the resin composition may be coated on the base substrate 10 by spin coating or the like.

The base substrate 10 is a plastic substrate. Examples of materials used for the base substrate 10 include polymethyl methacrylate (PMMA) or polyethylene terephthalate (PET).

The resin composition contains one or more monomers and a photo-curing initiator.

The monomer is contained in the resin composition in a proportion of about 20 wt% to 90 wt%, and examples of the monomer include imide.

The photo-curing initiator is a substance which is decomposed into radicals by irradiation of light such as ultraviolet rays to initiate a crosslinking and curing reaction of the photo-curable resin composition. The photocuring initiator is appropriately selected and used in consideration of the curing reaction rate, the yellowing property and the adhesion to the substrate of the resin composition. If necessary, two or more kinds of photo-curing initiators may be mixed and used.

Examples of the photocuring initiator include? -Hydroxyketone, phenylglyoxylate, benzyldimethyl ketal,? -Aminoketone, monoacylphosphine, acyl phosphine, bis acyl phosphine, 1,2-dimethoxy-2-phenylacetophenone, and mixtures thereof.

Referring to FIG. 2, the resin composition layer 211 is irradiated with ultraviolet rays, and the resin composition layer 211 is cured to form a compensation layer 210 on the base substrate 10.

The compensation layer 210 has a negative C characteristic. That is, the compensation layer 210 functions as a negative C plate.

The thickness of the compensating layer 210 is in the range of about 0.1 탆 to about 10 탆 and the compensating layer 210 in the thickness direction has a retardation value of about -10 nm to about -100 nm.

Alternatively, the retardation value in the thickness direction of the compensating layer 210 is about -50 nm to about -100 nm.

Here, the negative C characteristic is expressed by the following equation.

nx? ny> nz

Here, nx is the refractive index in the X-axis direction indicating the maximum refractive index in the plane of the compensation layer 210, and ny is the refractive index in the Y-axis direction perpendicular to the X-axis in the plane. and nz is the refractive index in the thickness direction of the compensating layer 210.

The retardation value Rth in the thickness direction of the compensation layer 210 is expressed by the following equation.

Rth = {(nx + ny) / 2 - nz} xd

Where d is the thickness of the compensation layer 210.

1 and 2, the compensation layer 210 may be formed by directly coating the compensation layer 210 with a material having a negative C characteristic.

At this time, the material having the negative C characteristic is dissolved in a solvent or the like to form a solution. Thereafter, the solution is coated on the base substrate 10 by spin coating, spray coating, or the like, and the solvent is evaporated to form the compensation layer 210 on the base substrate 10.

Examples of the solvent include cyclic saturated hydrocarbons such as cyclohexane, cycloheptane and cyclooctane, aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene and cumene, and aromatic hydrocarbons such as chlorobutane, bromohexane, methylene chloride, dichloroethane, Halogenated alkanes such as benzene, chloroform and ethyl chloride, halogenated aryls, saturated carboxylic acid esters such as ethyl acetate, n-butyl acetate and methyl propionate, and ethers such as dibutyl ether and tetrahydrofuran. They can be used alone or in combination. Further, alkanes such as pentane, hexane, octane, nonane, decane and the like may be further added to the above-mentioned solvent.

Examples of the material having the negative C characteristic include a polyimide-based resin and a discotic liquid crystal, and specifically may have the following chemical formula.

Wherein R1 is selected from the group consisting of hydrogen, an alkyl group and an aryl group, and R2 is selected from the group consisting of hydrogen, an alkyl group and an aryl group.

Referring to FIG. 3, after the compensating layer 210 is formed, a polarizing layer 220 is formed on the compensation layer 210. The polarizing layer 220 is laminated on the compensating layer 210 in the form of a film.

The polarizing layer 220 polarizes the passing light. That is, the polarizing layer 220 can filter the passing light so as to pass only the light polarized to a specific optical axis.

Examples of materials used for the polarizing layer 220 include polyvinyl alchol (PVA) and the like. The polarizing layer 220 is formed to a thickness of about 20 μm to 30 μm.

Referring to FIG. 4, a protective film 230 is formed on the polarizing layer 220. The protective film 230 is laminated on the polarizing layer 220 in a film form.

The protective film 230 protects the polarizing layer 220 and examples of the protective film 230 include cellulose triacetate (TAC).

The thickness of the protective film 230 is about 40 占 퐉 to about 80 占 퐉.

Thereafter, the compensation layer 210 is separated from the base substrate 10. That is, the compensating layer 210, the polarizing layer 220, and the protective film 230 are detached from the base substrate 10 while being attached to each other.

Referring to FIG. 5, an adhesive layer 240 is formed under the compensation layer 210. The adhesive layer 240 has adhesiveness and is bonded to the compensation layer 210. Further, the adhesive layer 240 is adhered to a liquid crystal panel or the like.

The thickness of the adhesive layer 240 is about 20 탆 to about 30 탆.

Thus, a polarizing plate including the protective film 230, the polarizing layer 220, the compensation layer 210, and the adhesive layer 240 is formed.

Since the compensation layer 210 is formed without being laminated in a film form, it can be freely adjusted in thickness. That is, the compensation layer 210 may be formed to have a very thin thickness.

The compensation layer 210 has a negative C characteristic and is easy to control the refractive index and can have a high retardation even when formed with a very low thickness.

As described above, the compensation layer 210 may have a thickness of about 0.1 μm to about 10 μm, and may have a retardation value in a thickness direction of about -50 nm to about -100 nm.

For example, the polarizing plate according to an embodiment may have a thickness of about 80 占 퐉 to about 1210 占 퐉. In contrast, when a conventional polarizing plate in which a TAC film is used instead of the compensating layer 210 is formed to a thickness of about 130 μm to 210 μm, it may have optical characteristics similar to those of the polarizing plate according to the present embodiment.

Therefore, the polarizing plate manufacturing method according to the embodiment provides a polarizing plate having a thin thickness and improved optical characteristics such as realizing a wide viewing angle.

That is, the polarizing plate according to the embodiment has a thickness that is thinner than that of a conventional polarizing plate in which a TAC film is used in place of the compensation layer 210, and has further improved optical characteristics.

6 is a cross-sectional view illustrating a liquid crystal display device including a polarizing plate according to an embodiment. In the present embodiment, the liquid crystal panel 100 will be further described with reference to the above-described embodiments.

Referring to FIG. 6, the liquid crystal display includes a liquid crystal panel 100, a first polarizer 200, and a second polarizer 300.

The liquid crystal panel 100 changes the path of light passing by pixel unit. The liquid crystal panel 100 includes a TFT substrate, a color filter substrate, and a liquid crystal layer.

The TFT substrate includes a plurality of gate lines, a plurality of data lines, a plurality of thin film transistors, and a plurality of pixel electrodes.

The gate wirings are arranged side by side. The gate wirings cross the data wirings. By the gate lines and the data lines, a plurality of pixels are defined.

The thin film transistors are arranged in an area where the gate lines and the data lines intersect. The thin film transistor selectively connects the data line and the pixel electrode by a gate signal applied from the gate line.

The pixel electrodes are arranged in the pixels one by one. The pixel electrodes receive a data signal through the data lines and the thin film transistors.

The color filter substrate is opposed to the TFT substrate. The color filter substrate includes color filters corresponding to the pixels and a common electrode facing the pixel electrode.

The liquid crystal layer is interposed between the TFT substrate and the color filter substrate. The liquid crystal layer may include a TN (twisted nematic) type liquid crystal. The liquid crystal contained in the liquid crystal layer may be oriented in a direction perpendicular to the TFT substrate and the color filter substrate. That is, the liquid crystal panel 100 may be a VA type liquid crystal panel 100.

The liquid crystal contained in the liquid crystal layer is aligned by an electric field formed by a data signal applied to the pixel electrode and a common signal applied to the common electrode.

Accordingly, the liquid crystal layer adjusts the path of the light passing through the pixel unit. More specifically, the liquid crystal layer adjusts the direction of an optical axis of light passing through the liquid crystal layer in pixel units.

The first polarizing plate 200 is disposed on the liquid crystal panel 100. More specifically, the first polarizing plate 200 is bonded to the upper surface of the liquid crystal panel 100.

The first polarizing plate 200 includes a first polarizing layer 220, a first compensation layer 210, a first adhesive layer 240, and a first protective film 230.

The first polarizing layer 220 polarizes light passing through the optical axis in the first direction. The polarizing layer 220 may filter the passing light so as to pass only the polarized light to the optical axis in the first direction.

The first compensation layer 210 is interposed between the first polarizing layer 220 and the liquid crystal panel 100. More specifically, the first compensation layer 210 is in contact with the first polarizing layer 220.

The first compensation layer 210 has a negative C characteristic. That is, the first compensation layer 210 functions as a negative C plate.

The thickness of the first compensation layer 210 is about 0.1 μm to about 10 μm, and the retardation value of the first compensation layer 210 in the thickness direction is about -10 nm to about -200 nm.

Alternatively, the retardation value in the thickness direction of the first compensation layer 210 may be about -50 nm to about -100 nm.

Examples of the material used as the first compensation layer 210 include the polyimide resin or the plate-like liquid crystal described above.

The first adhesive layer 240 is interposed between the liquid crystal panel 100 and the first compensation layer 210. The first adhesive layer 240 is adhered to the upper surface of the liquid crystal panel 100 and bonded to the first compensation layer 210.

The first protective film 230 is disposed on the first polarizing layer 220. The first protective film 230 protects the first polarizing layer 220. Examples of the material used as the first protective film 230 include cellulose triacetate and the like.

The second polarizing plate 300 is disposed below the liquid crystal panel 100. The second polarizing plate 300 is bonded to the lower surface of the liquid crystal panel 100.

The second polarizing plate 300 includes a second polarizing layer 320, a second compensating layer 310, a second adhesive layer 340, and a second protective film 330.

The second polarizing layer 320 is disposed under the liquid crystal panel 100. The second polarizing layer 320 polarizes light passing through the optical axis in a second direction perpendicular to the first direction.

The second compensation layer 310 is interposed between the second polarizing layer 320 and the liquid crystal panel 100. More specifically, the second compensation layer 310 contacts the second polarizing layer 320.

The second compensation layer 310 has a negative C characteristic. That is, the second compensation layer 310 functions as a negative C plate.

The thickness of the second compensation layer 310 is about 0.1 μm to about 10 μm, and the retardation value of the second compensation layer 310 in the thickness direction is about -10 nm to about -200 nm.

Alternatively, the retardation value in the thickness direction of the second compensation layer 310 may be about -50 nm to about -100 nm.

The second adhesive layer 340 is interposed between the second compensation layer 310 and the liquid crystal panel 100. The second adhesive layer 340 adheres to the lower surface of the liquid crystal panel 100 and is bonded to the second compensation layer 310.

The second protective film 330 is disposed under the second polarizing layer 320. The second protective film 330 protects the second polarizing layer 320.

The liquid crystal display device according to the present embodiment displays an image using light emitted from a backlight or the like. More specifically, light emitted from a backlight or the like passes through the second polarizing layer 320 and is polarized to the optical axis in the second direction.

Thereafter, an electric field is applied to the liquid crystal layer, the liquid crystal contained in the liquid crystal layer is aligned, and the direction of the optical axis of the polarized light is changed to the first direction.

In addition, the light whose optical axis is changed passes through the first polarizing layer 220, and the liquid crystal display according to the embodiment displays an image.

At this time, the first compensation layer 210 and the second compensation layer 310 improve the characteristics of light passing therethrough. For example, since the first compensation layer 210 and the second compensation layer 310 have negative C characteristics, it is possible to delay the phase of light passing therethrough, and accordingly, the liquid crystal display device according to the embodiment An improved viewing angle can be obtained.

Particularly, when the liquid crystal panel 100 is a liquid crystal panel of a TN mode and a VA mode, the effect of improving the viewing angle of the first compensation layer 210 and the second compensation layer 310 is further improved.

In addition, since the first compensation layer 210 and the second compensation layer 310 have a very thin thickness, the liquid crystal display according to the present embodiment has a small thickness.

7 is a cross-sectional view illustrating a liquid crystal display device according to another embodiment. In this embodiment, the first protective film and the second protective film will be further described with reference to the above-described embodiments.

Referring to FIG. 7, the first polarizing plate 400 includes a first protective film 430. The first protective film 430 has a thickness of about 30 탆 to about 40 탆. Examples of the material used for the first protective film 430 include a polyacrylic resin and a polyterephthalate resin. Specifically, examples of the material used for the first protective film 430 include polymethyl methacrylate or polyethylene terephthalate.

The second polarizing plate 500 includes a second protective film 530. The second protective film 530 has a thickness of about 30 탆 to about 40 탆. Examples of the material used as the second protective film 530 include a polyacrylic resin or a polyterephthalate resin.

Since the first compensation layer 410 and the second compensation layer 510 have negative C characteristics, the characteristics of light passing therethrough are sufficiently compensated. Therefore, the first protective film 430 and the second protective film 530 may not include an optical compensation function, but may include a material having a higher strength. In addition, the first protective film 430 and the second protective film 530 may be formed to have a thinner thickness.

Therefore, the liquid crystal display device according to the present embodiment has a thinner thickness and a higher strength.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be understood that various modifications and applications are possible. For example, each component specifically shown in the embodiments can be modified and implemented. It is to be understood that all changes and modifications that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Experimental Example

A compensating layer was formed by coating a polyimide material having a -C characteristic on the PMMA substrate to a thickness of about 10 mu m. Thereafter, a PVA film having a thickness of about 25 탆 was laminated on the compensation layer to form a polarizing layer. Thereafter, a TAC film having a thickness of about 40 탆 was laminated on the polarizing layer. After separating the PMMA substrate from the compensating layer, an adhesive layer having a thickness of about 25 탆 was formed on the compensating layer to form the polarizing plate # 1. The Rth of the compensation layer was about 50 nm.

Comparative Example

A polarizing plate # 2 was formed such that a TAC film having a thickness of about 40 탆 was used in place of the compensating layer, and the remaining layers had the same properties as in the experimental example.

Thereafter, polarizing plate # 1 and polarizing plate # 2 were attached to liquid crystal panels of the same TN mode, respectively, and optical properties were measured for each, to obtain the results shown in Table 1.

Comparative Example Experimental Example Front CR 1981 1982
CR 10: 1 Right and left 43.5 / 43.5 44/44 Up / Down 29/56 29.5 / 57
Maximum luminance white 0.31113 0.311575 black 0.186474 0.182582
Color shift white 0.278568 0.280357 dark 0.53768 0.51517

As shown in Table 1, it can be seen that the liquid crystal display according to the experimental example having a thinner thickness has similar or improved optical characteristics.

Figs. 1 to 5 are cross-sectional views illustrating a method of manufacturing a polarizing plate according to an embodiment.

6 is a cross-sectional view illustrating a liquid crystal display device including a polarizing plate according to an embodiment.

7 is a cross-sectional view illustrating a liquid crystal display device according to another embodiment.

Claims (12)

Coating a compensating layer forming material including a polyimide resin on the base substrate and having a negative C characteristic; Forming a compensating layer having a retardation value in a thickness direction of -50 nm to -100 nm by irradiating light to the compensating layer forming material; Forming a polarizing layer on the compensation layer; Forming a protective film on the polarizing layer; And And spacing the base substrate away from the compensation layer Wherein the step of separating the compensation layer is performed after the step of forming the protective film, Wherein the polyimide-based resin comprises at least one of a material represented by the following formula.

In the above formulas, R1 is selected from the group consisting of hydrogen, an alkyl group and an aryl group. 2. The method of claim 1, wherein forming the compensation layer comprises: Spraying a resin composition onto the base substrate; And And curing the resin composition layer. The method of producing a polarizing plate according to claim 2, wherein the resin composition comprises a monomer and a photo-curing initiator. delete delete The method of claim 1, wherein the compensating layer has a thickness of 0.1 占 퐉 to 10 占 퐉. The method for producing a polarizing plate according to claim 1, wherein the protective film comprises a polyacrylic resin or a polyterephthalate-based resin, and has a thickness of 10 μm to 80 μm. A polarizing layer; A protective film provided on the polarizing layer; And a retardation value in the thickness direction of -50 nm to -100 nm and a thickness of 0.1 to 10 mu m, Compensation layer; And And an adhesive layer provided under the compensation layer, Wherein the polyimide-based resin comprises at least one of the following materials.

In the above formulas, R1 is selected from the group consisting of hydrogen, an alkyl group and an aryl group. delete The method of claim 1, wherein the compensating layer forming material further comprises a material represented by the following formula.

In the above formulas, R2 is selected from the group consisting of hydrogen, an alkyl group, and an aryl group. delete 9. The polarizer of claim 8, wherein the compensation layer further comprises a material represented by the following formula.

In the above formulas, R2 is selected from the group consisting of hydrogen, an alkyl group, and an aryl group.

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