JP2008009413A - Protection film for polarizer plate lamination, and protection film laminating polarizer plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a protection film having no bright point defect even when flaws or the like adhere on a surface, and to provide a protection film laminating polarizer plate laminated with the protection film. <P>SOLUTION: A polyester film 9 is laminated on the one-side face of a polycarbonate film 8 having optical isotropy. A releasing protection film 6 composed by applying a releasing agent 12 on the polyester film surface of a three-layer film with no extension and non-alignment laminated with a low photo-elastic resin film 10 having photo-elastic coefficient of 50×10<SP>-12</SP>m<SP>2</SP>/N or less in an absolute value on the other face. The releasing protection film 6 is laminated on the one-side face of a polarizer plate 3 so that the releasing agent application face comes into contact with the polarizer plate 3. A surface protection film 5 is laminated on the other one-side face of the polarizer plate 3 to produce a protection film laminating polarizer plate. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a protective film for polarizing plate lamination laminated on a polarizing plate used in a liquid crystal display device, and a protective film laminated polarizing plate obtained by laminating the protective film.

  In general, a polarizing plate used in a liquid crystal display device is formed by laminating a polarizer protective film 2 on both sides of a polarizer 1 as shown in FIG. Then, a pressure-sensitive adhesive layer 4 for bonding is provided on one side of the polarizing plate 3, and the other side of the polarizing plate 3 is used to prevent wrinkling and dust adhesion during handling in the manufacturing process of the liquid layer display device. The surface protective film 5 is laminated. Further, a release protective film 6 is also laminated on the surface of the pressure-sensitive adhesive layer 4 to prevent wrinkling during handling and adhesion of dust. The polarizing plate is shipped in the form of a protective film laminated polarizing plate 7 in which protective films are laminated on the front and back in this way.

  In recent years, liquid crystal display devices have a larger screen and higher brightness, and the extremely small luminescent spots present in the liquid crystal display devices become defects. These bright spots are caused by defects such as very small foreign matter and wrinkles mixed in the polarizer and the polarizer protective film, and the polarizing plate containing these defects needs to be surely removed before shipment. The defect inspection of the polarizing plate is generally performed by visual inspection using a crossed Nicols method. That is, when the two polarizing plates are overlapped and darkened so that their respective alignment axes are orthogonal to each other, the defective portion becomes visible as a bright spot, and the defective portion can be detected.

  In the defect inspection of this polarizing plate, the surface protective film and the release protective film laminated on both sides of the polarizing plate are originally unnecessary, and these films may be removed and inspected. Since it is unavoidable that the polarizing plate is rubbed in handling, the defect inspection is performed in a state where the surface protective film or the release protective film is laminated.

  As a surface protective film or a release protective film, a biaxially stretched polyester film that has been excellent in transparency and hard and does not easily wrinkle has been used in many cases. The orientation does not become constant due to bowing, the contrast of the darkening does not become constant when it is overlapped at the time of inspection using the crossed Nicols method, and the interference color due to the phase difference of the film appears, so that foreign matter can be visually recognized. There was a drawback that made it difficult.

  In order to eliminate the disadvantages of using such an oriented film, Patent Document 1 discloses surface protection for a three-layer unstretched, non-oriented film in which a polyester film is laminated on both sides of a polycarbonate having optical isotropy. Proposed to use as a film and to constitute a release protection film formed by applying a release agent on one surface of this surface protection film, and to laminate these surface protection film and release protection film on a polarizing plate. . However, since the non-oriented polyester film is soft on the release protection film surface, it is easy to be scratched during handling, and stress is generated in the extremely small part of the sticking. As a result, the crossed Nicols method is used. In the defect inspection, the collar portion is visually recognized as a bright spot, and has a drawback that it cannot be distinguished from the defect caused by the polarizing plate itself.

Prior art documents relating to the present invention include the following.
JP 2004-077783 A

  The present invention facilitates inspection of bright spot defects caused by a polarizing plate when a defect is inspected using a crossed Nicol method in a state where a protective film is laminated on the polarizing plate. It aims at providing the protective film for polarizing plate lamination which does not become a defect, and the protective film laminated polarizing plate formed by laminating the protective film on a polarizing plate.

(1) The protective film for laminating a polarizing plate of the present invention is characterized by laminating a polyester film on one side of a polycarbonate film and laminating a low photoelastic resin film on the other side of the polycarbonate film.
(2) The protective film of the present invention is characterized in that, in the above (1), the glass transition temperature of the polycarbonate is 100 ° C. or higher.
(3) The protective film of the present invention is the protective film according to (1) or (2), wherein the polyester film is an ethylene terephthalate / ethylene isophthalate copolymer, a butylene terephthalate / butylene isophthalate copolymer, a polyethylene terephthalate, or a polybutylene. It is any film of terephthalate.
(4) The protective film of the present invention is any one of the above (1) to (3), wherein the low photoelastic resin film has a photoelastic coefficient of an absolute value of 50 × 10 ⁻¹² m ² / N or less. It is characterized by becoming.
(5) The protective film of the present invention is any one of the above (1) to (3), wherein the low photoelastic resin film has a photoelastic coefficient having an absolute value of 10 × 10 ⁻¹² m ² / N or less. It is characterized by becoming.
(6) The protective film of the present invention is characterized in that, in any one of the above (1) to (5), the low photoelastic resin film is an acrylic resin film.
(7) The protective film of the present invention is characterized in that, in any one of the above (1) to (6), the protective film is a non-oriented film.
(8) The protective film laminated polarizing plate of the present invention is characterized in that the protective film according to any one of (1) to (7) is laminated on a polarizing plate.

  The protective film for laminating a polarizing plate of the present invention is a non-stretched non-oriented 3 film obtained by laminating a polyester film on one side of a polycarbonate film having optical isotropy and laminating the low photoelastic resin film on the other side. Since it is composed of a layer film, it is laminated on one side of the polarizing plate so that the surface coated with the release agent on this protective film is in contact with the polarizing plate, and a surface protective film is laminated on the other side of the polarizing plate, When performing the defect inspection using the crossed Nicols method by stacking two laminates so that the respective release protection film surfaces are inside and the alignment axes are orthogonal to each other and placed on the inspection table, Even if the photoelastic resin film is wrinkled by handling or the like, it does not appear as a bright spot, and only the defect of the polarizing plate is visually recognized as a bright spot.

Embodiments of the present invention will be described below.
When the protective film of the embodiment is used as a release protective film, a polyester film 9 is laminated on one side of a polycarbonate film 8 serving as a base as shown in FIG. 2, and a low photoelastic resin is provided on the other side of the polycarbonate film 8. The film 10 is laminated. Such a release protection film 6 is formed, for example, as an unstretched, non-oriented three-layer film 11 using an extrusion method, and then the release agent 12 is diluted with an organic solvent on the surface of the polyester film 9. It is configured by applying using a coating means such as a roll coating method and drying and solidifying.

  The release protective film 6 is required to be colorless and transparent and have a low phase difference from the viewpoint of improving the defect inspection property of the polarizing plate. On the other hand, as described above, since the solvent-based release agent is coated, solvent resistance is required, and since it passes through the drying step, heat resistance is required.

The polycarbonate used as the base film of the release protection film is excellent in heat resistance and has high mechanical strength, but the glass transition temperature is preferably 100 ° C. or higher, more preferably 150 ° C. or higher. . If the glass transition temperature is less than 100 ° C., the film may be stretched due to heat and tension in the drying process at the time of coating the release agent, and the retardation may be increased.
Polycarbonate is a carbonate resin derived from bicyclic dihydric phenols and phosgene, and has a high glass transition temperature and heat resistance.
Examples of the polycarbonate of this embodiment include bis (4 monooxyphenyl) methane, 1,1-bis (4-oxyphenyl) ethane, 1,1-bis (4-oxyphenyl) butane, 1,1-bis (4 -Oxyphenyl) isobutane, 1,1-bis (4-oxyphenyl) cyclohexane, 2,2-bis (4-oxyphenyl) propane, any bisphenol such as 2,2-bis (4-oxyphenyl) butane It is preferable to use one obtained by blending one or more of polycarbonates having a glass transition temperature of 123 to 171 ° C.

As shown in FIG. 1, the release protective film 6 is adhesively laminated to the polarizing plate 3 through the adhesive layer 4, but in order to easily peel and remove after performing the defect inspection, as shown in FIG. 2. A release agent 12 is applied to one side of the release protection film 6. The mold release agent 12 is diluted with an organic solvent and applied using a coating means such as a roll coating method and dried and solidified. However, the non-oriented polycarbonate film has poor solvent resistance, and shrinks when the organic solvent adheres. The polyester film 9 is laminated on one side of the polycarbonate film 8 on the side to which the release agent 12 is applied.
As the polyester film 9, terephthalic acid, isophthalic acid, orthophthalic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, diphenylcarboxylic acid , Diphenoxyethanedicarboxylic acid, diphenylsulfonecarboxylic acid, anthracenedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, hexahydroterphthalic acid, hexahydroisophthalate Acid, malonic acid, dimethylmalonic acid, succinic acid, 3,3-diethylsuccinic acid, glutaric acid, 2,2-dimethylglutaric acid, adipic acid, 2-methyladipic acid, trimethyladipic acid, pimelic acid, azelaic acid, Dima Carboxylic acids such as acid, sebacic acid, suberic acid, dodecyl carboxylic acid, ethylene glycol, propylene glycol, hexamethylene glycol, 1,4-cyclohexanedimethanol, decamethylene glycol, 1,3-propanediol, 1,4- A homopolymer obtained by polycondensation of diols such as butanediol, 1,5-pentanediol, 1,6-hexanediol, 2.2-bis (4′-hydroxyphenyl) propane, respectively, or dicarboxylic acid 1 A copolymer obtained by polycondensation of two or more species and two or more diols, a copolymer obtained by polycondensation of two or more dicarboxylic acids and one or more diols, and two types of these homopolymers and copolymers Polyester made from any of the blended resin blends It can be used Irumu 9.

  The polyester film 9 preferably has a high crystallization rate so that it does not shrink even if an organic solvent for diluting the release agent 12 is attached. On the other hand, the polyester film 9 is dried and solidified after the release agent 12 is applied. When a film is loaded with a light tension necessary for conveyance and passed through a heating oven, the film is stretched in the conveyance direction by the applied tension to be uniaxially oriented, and heat-fixed when passing through the heating oven to be oriented crystals. Therefore, a contradictory characteristic that a low crystallization speed is preferable so that the retardation of the film does not become nonuniform is required. Examples of the polyester film satisfying these contradicting properties include ethylene terephthalate / ethylene isophthalate copolymer, butylene terephthalate / butylene isophthalate copolymer, polyethylene terephthalate, and polybutylene terephthalate.

The mold release protective film 6 is likely to be wrinkled by rubbing on the surface by handling at the time of polarizing plate inspection. In the case of a large wrinkle that can be recognized with the naked eye, this flaw due to abrasion is detected as a defect by itself, but even if a small wrinkle that cannot be recognized with the naked eye is attached, When stress is applied, the phase difference is locally increased and detected as a bright spot. Therefore, in the release protection film of this embodiment, the low photoelastic resin film 10 in which the phase difference is hardly increased even when stress is applied to the resin is laminated on the polycarbonate film 8 serving as a base material.
Examples of the low photoelastic resin film include a film made of a resin having an absolute value of 50 × 10 ⁻¹² m ² / N or less, more preferably 10 × 10 ⁻¹² m ² / N or less. . When a film made of a resin having an absolute value of the photoelastic coefficient exceeding 50 × 10 ⁻¹² m ² / N is used, if the resin surface is wrinkled, stress is applied to the resin in the wrinkled portion, and the resin is localized. Since the phase difference becomes high and is detected as a bright spot in the defect inspection using the crossed Nicols method, it is not preferable.

  Examples of these resins having a low photoelastic coefficient include films made of cyclic olefin resins such as norbornene, tetracyclododecene and derivatives thereof, acrylic resin films, and copolymerized polycarbonate resin films. As an acrylic resin, the homopolymer which consists of methacrylic acid ester, such as methyl methacrylate, ethyl methacrylate, and butyl methacrylate, and the copolymer of these methacrylic acid ester and the monomer which has a copolymerizability are mentioned. Examples of the copolymerizable monomer include methyl methacrylate, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, stearyl methacrylate, and methacrylic acid. Methacrylates such as benzyl, glycidyl methacrylate, 2-hydroxydiethyl methacrylate, 2-hydroxypropyl methacrylate, and methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, Such as 2-ethylhexyl acrylate, lauryl acrylate, stearyl acrylate, benzyl acrylate, glycidyl acrylate, 2-hydroxydiethyl acrylate, 2-hydroxypropyl acrylate, etc. Acrylic acid esters, and acrylic acid, and unsaturated acids such as methacrylic acid. Further, these homopolymers and copolymer polymers can be blended at an arbitrary ratio and used. Furthermore, these homopolymers and copolymers alone or blends are blended with acrylic rubber such as polyalkyl acrylate ester-styrene copolymer or modified acrylic elastomer for the purpose of improving impact resistance. It is also possible. These low photoelastic resins are harder than polycarbonate and polyester, and are not easily wrinkled by scratches.

  The thickness of the three-layer film 11 in which the polyester film 9 is laminated on one side of the polycarbonate film 8 serving as the base material and the low photoelastic resin film 10 is laminated on the other side of the polycarbonate film 8 is the polyester film ( 1 to 50 μm) / polycarbonate film (5 to 58 μm) / low photoelastic resin film (1 to 50 μm), and the total thickness of the three-layer film 11 is preferably 25 to 60 μm. When the thickness of the polyester film 9 is less than 1 μm, the solvent resistance becomes poor when the release agent 12 diluted with an organic solvent is applied. On the other hand, if it exceeds 50 μm, the heat resistance for retaining the shape during heating for drying and solidification after applying the release agent 12 becomes poor. When the thickness of the polycarbonate film 8 is less than 5 μm, the heat resistance at the time of the above heating is poor, and when it exceeds 58 μm, the effect of improving the heat resistance is saturated and it is not economical. When the thickness of the low photoelastic resin film 10 is less than 1 μm, when the deep wrinkles are attached, the wrinkles reach the polycarbonate layer, and the phase difference increases due to the stress load caused by the polycarbonate. On the other hand, if it exceeds 50 μm, the heat resistance for retaining the shape during the above heating becomes poor.

  Said 3 layer film 11 can be manufactured using well-known film manufacturing methods, such as a coextrusion method, for example. In addition, the three-layer film 11 is manufactured in a long strip shape, and the release agent 12 is applied while being wound around the coiler or unwound from the coiler, and either the polyester film 9 or the low photoelastic resin film 10 is applied. If one or both of them contains 0.05 to 3% by weight of a lubricant such as silica powder having a particle size of 0.1 to 3.0 μm, the winding operation and the rewinding operation can be performed smoothly. . If it does not contain a lubricant, it is particularly difficult to wind it around a coiler. If the particle size and content of the lubricant are within the above ranges, the detection of optical defects of the polarizing plate 3 will not be adversely affected.

Preferable examples of the release agent 12 applied to the surface of the polyester film 9 of the three-layer film 11 include silicon release agents, higher fatty acids, higher fatty acid amides, higher fatty acid esters, metal soaps, fluorocarbons, and the like. In an oven heated to 100 to 140 ° C. after applying a solution obtained by dissolving or diluting any of the above in an organic solvent such as toluene, ethyl acetate, methyl ethyl ketone, or the like, or applying an emulsion using a coating method such as a roll coating method. To dry and solidify.
Thus, when the release protective film 6 having the release agent 12 is adhesively laminated to the polarizing plate 3 through the adhesive layer 4, it is easily peeled off after being subjected to a defect inspection and then attached to the liquid crystal display device. Can do.

  Moreover, although the surface protective film 5 is laminated | stacked on the opposite side to the side which laminate | stacks the mold release protective film 6 of the polarizing plate 3, it replaces with a mold release agent on the protective film surface of this embodiment, and is an adhesive layer. Can be used as the surface protective film 5.

Hereinafter, the present invention will be described in detail with reference to examples.
(Creation of three-layer resin film)
Using an extrusion method, a long length composed of three resin layers obtained by laminating the polyester layer shown in Table 1 on one side of the polycarbonate layer shown in Table 1 and the low photoelastic resin layer shown in Table 1 on the other side. Strip-shaped unstretched resin films (sample numbers 1 to 6) were prepared. For comparison, an unstretched resin film (Sample No. 7) composed of three resin layers obtained by laminating the polyester layer shown in Table 1 on the front and back of the polycarbonate layer shown in Table 1 was prepared.

(Confirmation of bright spot generation)
Two test pieces each having a size of 100 mm × 100 mm were cut out from a laminate of a release protective film using the resin films of sample numbers 1 to 7 shown in Table 1 on the adhesive surface of the polarizing plate. For the resin films of Sample Nos. 1 to 6, the surface roughness is obtained by etching on the low photoelastic resin film surface of one sample, and for the resin film of Sample No. 7 on the polyester resin surface on one side of one sample. A steel plate (weight: 1 kg) with Ra of 0.5 μm was placed and pulled to form scratches on the surface. Next, the specimens on which the scratches are formed and the other specimens on which the scratches are not formed are overlapped so that the release protective film surface is inward and the orientation axes of the polarizing plates are perpendicular to each other. In addition, the generation state of the bright spot when the specimen was observed from above with the light beam from below using the crossed Nicols method was visually observed and evaluated.
The evaluation results are shown in Table 2. As shown in Table 2, the three-layer resin film formed by laminating the polyester layer on one side of the polycarbonate layer and the low photoelastic resin layer on the other side hardly generates bright spots even if the surface is wrinkled. I understand that.

  Since the protective film for laminating a polarizing plate of the present invention does not cause a local phase difference increase due to wrinkle generation stress even if the protective film is wrinkled due to handling or the like when performing a defect inspection of the polarizing plate, Does not appear as a bright spot, and only the defect of the polarizing plate is visually recognized as a bright spot, and the detection defect accuracy can be greatly improved, and the industrial applicability is extremely high.

It is a schematic sectional drawing which shows an example of a structure of a polarizing plate. It is a schematic sectional drawing which shows one Embodiment of the protective film of this invention.

Explanation of symbols

1: Polarizer 2: Polarizer protective film 3: Polarizing plate 4: Adhesive layer 5: Surface protective film 6: Release protective film 7: Protective film laminated polarizing plate 8: Polycarbonate film 9: Polyester film 10: Low photoelasticity Resin film 11: Three-layer film 12: Release agent

Claims (8)

A protective film for laminating a polarizing plate obtained by laminating a polyester film on one side of a polycarbonate film and laminating a low photoelastic resin film on the other side of the polycarbonate film. The protective film according to claim 1, wherein the polycarbonate has a glass transition temperature of 100 ° C. or higher. The polyester film is an ethylene terephthalate / ethylene isophthalate copolymer, butylene terephthalate / butylene isophthalate copolymer, polyethylene terephthalate, or polybutylene terephthalate film. The protective film as described. The said low photoelastic resin film consists of resin which has a photoelastic coefficient of absolute value 50 * 10 < ^-12 > m < ² > / N or less, The protective film of any one of Claims 1-3 characterized by the above-mentioned. The said low photoelastic resin film consists of resin which has a photoelastic coefficient of an absolute value of 10 * 10 < ^-12 > m < ² > / N or less, The protective film in any one of Claims 1-3 characterized by the above-mentioned. The protective film according to claim 1, wherein the low photoelastic resin film is an acrylic resin film. The protective film according to claim 1, wherein the protective film is a non-oriented film. The protective film laminated polarizing plate formed by laminating | stacking the protective film in any one of Claims 1-7 on a polarizing plate.

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