JP2001272535A - Protective film for polarizing plate and polarizing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a protective film for a polarizing plate with sufficient adhesive strength and excellent durability without any lowering of polarization degree or any discoloration resulting from heating operation in the case of adhering a polarizer to the protective film and a polarizing plate using the same. SOLUTION: The protective film 3 for the polarizing plate to be used is composed of a thermoplastic saturated norbornene resin film 31 on which a resin layer 32 containing polyvinyl alcohol and polyethyleneimine is laminated. The resin layer 32 side of the protective film 3 for the polarizing plate is coated with a PVA(polyvinyl alcohol) type adhesive 2. The polarizing plate is manufactured by laminating the protective films 3 for the polarizing plate on both sides of the polarizer 1 via the PVA type adhesive 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polarizing plate protective film and a polarizing plate using the same.

[0002]

2. Description of the Related Art In recent years, liquid crystal displays (LCDs) are often used for vehicles and portable information devices, and there is a strong demand for the reliability of LCDs in high-temperature or high-temperature and high-humidity environments. 2. Description of the Related Art Conventionally, a polarizing plate used for an LCD is used by being attached to one or both sides of a liquid crystal cell in which a liquid crystal is sealed between two electrode substrates forming a transparent electrode. Generally, a polarizer prepared by adsorbing a dichroic dye and having triacetyl cellulose (hereinafter referred to as TAC) adhered to both surfaces as a polarizing plate protective film is used. Since TAC has poor adhesion to a polarizer, alkali-treated TAC (hereinafter referred to as saponified TAC) is used.

[0003] However, saponified TAC has a high water absorption and causes a decrease in the degree of polarization and an increase in transmittance due to fading in a high-temperature and high-humidity environment. However, since the stress causes a large phase difference in the saponified TAC of the protective film,
Problems such as a decrease in the degree of polarization have become apparent.

In order to solve the above and the above problems,
Various resin films have been proposed as polarizing plate protective films. However, it has been difficult for these resin films to adopt the same bonding method as conventional saponified TAC. The reason was that almost all of these resin films were hydrophobic and had poor adhesion to the conventionally used PVA-based adhesive.

On the other hand, Japanese Patent Application Laid-Open No. Hei 5-212828 proposes a method in which a norbornene resin is used as a protective film for a polarizing plate, and adhesion with a polarizer is performed by heating and pressing using an acrylic adhesive. ing. However, in this method, a decrease in the degree of polarization and fading were unavoidable due to the heating operation at the time of bonding, and not only the adhesion was insufficient but also the durability was low. Further, there is a problem that the conventional manufacturing process cannot be used as it is.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and a heating operation for bonding a polarizer and a protective film does not cause a decrease in the degree of polarization and a fading. An object of the present invention is to provide a polarizing plate protective film having excellent adhesion and excellent durability, and a polarizing plate using the same.

[0007]

The polarizing plate protective film of the present invention is characterized in that a resin layer containing polyvinyl alcohol and polyethyleneimine is laminated on a norbornene resin film.

[0008] The polarizing plate of the present invention is characterized in that the polarizing plate protective film according to claim 1 is laminated on at least one side of a polarizer.

Hereinafter, the configuration of the present invention will be described in detail.

The norbornene resin used in the present invention is:
It has a norbornene skeleton in its repeating unit. For example, JP-A-3-14882 and JP-A-3-14882
Known resins disclosed in, for example, JP-A-122137 are exemplified. In the present invention, these conventionally known norbornene-based resins can be suitably used, for example,
Hydrogenated ring-opening polymer of norbornene-based monomer, addition polymer of norbornene-based monomer, addition polymer of norbornene-based monomer and olefin-based monomer such as ethylene and α-olefin; norbornene-based monomer and cyclopentene, cyclooctene; Examples include addition polymers with cyclic olefin monomers such as 5,6-dihydrodicyclopentadiene, and modified products of these polymers.

As the norbornene-based monomer, for example, norbornene, 5-methyl-2-norbornene,
5-ethyl-2-norbornene, 5-butyl-2-norbornene, 5-ethylidene-2-norbornene, 5-methoxycarbonyl-2-norbornene, 5,5-dimethyl-2-norbornene, 5-cyano-2-norbornene , 5-methyl-5-methoxycarbonyl-2-norbornene, 5-phenyl-2-norbornene, 5-phenyl-5-methyl-2-norbornene, ethylene-tetracyclododecene copolymer, 6-methyl-1, 4: 5,8
-Dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-ethyl-1,4: 5,8-
Dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-ethyl-1,4: 5,8-ethylidene-1,4,4a, 5,6,7,8, 8a-octahydronaphthalene, 6-chloro-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-cyano-1,4: 5 8-Dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-pyridyl-1,4: 5,8-dimetano-1,4,4a, 5,6,7, 8,8a-octahydronaphthalene, 6-methoxycarbonyl-1,4:
5,8-Dimethano-1,4,4a, 5,6,7,8,8
a-octahydronaphthalene, 1,4-dimethano-1,
4,4a, 4b, 5,8,8a, 9a-octahydrofluorene, 5,8-methano-1,2,3,4,4a,
5,8,8a-octahydro-2,3-cyclopentadienonaphthalene, 4,9: 5,8-dimethano-3a,
4,4a, 5,8,8a, 9,9a-octahydro-1
H-benzoindene, 4,11: 5,10: 6,9-trimethano-3a, 4,4a, 5,5a, 6,9,9a,
10,10a, 11,11a-dodecahydro-1H-cyclopentaanthracene and the like.

The norbornene-based monomer may be polymerized by a known method. If necessary, the norbornene-based monomer may be copolymerized with another copolymerizable monomer, or a hydrogenated norbornene-based polymer may be obtained by hydrogenation. . In addition, the polymer or polymer hydrogenated product, by a known method, α-, β- unsaturated carboxylic acid and its derivative, styrene hydrocarbon, olefinic unsaturated bond, and, having a hydrolyzable group It may be modified using an organosilicon compound, an unsaturated epoxy monomer or the like.

In the above polymerization, Ir, O,
s, Ru trichloride hydrate, MoC _Fifteen, WC₁₆, Re
Cl_Five, (C_TwoH_Five)_ThreeAl, (C_TwoH_Five)_ThreeAl / T
iCl _Four, (Π-C_FourH₇)_FourMo / TiCl_Four, (Π
-C_FourH₇)_FourW / TiCl_Four, (Π-C_ThreeH_Five)_ThreeC
r / WCl₆And the like.

Examples of the norbornene-based resin include “ZEONOR” and “ZE” manufactured by Zeon Corporation.
ONEX "; a product name" ARTON "manufactured by JSR Corporation; a product name" OPTOREZ "manufactured by Hitachi Chemical Co., Ltd .; a product name" APEL "manufactured by Mitsui Petrochemical Co., Ltd. are marketed as commercial products.

The lower the number average molecular weight of the norbornene resin, the lower the moisture resistance and the higher the moisture permeability as the molecular weight decreases, and the lower the film formability as the molecular weight increases. Therefore, gel permeation chromatography (GPC) using a toluene solvent is necessary. The measured number average molecular weight is preferably 25,000 to 100,000, and more preferably 30,000 to 80,000.

As the method for producing the norbornene-based resin film, any known method may be employed. For example, the film can be formed by a solution casting method, a melt molding method or the like.

In order to form a film by the solution casting method, first, a high boiling solvent such as toluene, xylene, ethylbenzene, chlorobenzene, triethylbenzene, diethylbenzene, isopropylbenzene or the like, or a mixture of these high boiling solvents with cyclohexane, benzene, Tetrahydrofuran,
The above-mentioned norbornene-based resin is mixed with a low-boiling solvent such as hexane or octane, preferably in a concentration of 5 to 60 wt.
% To obtain a resin solution.

Next, the obtained resin solution is applied to a bar coater,
Using a doctor knife, a Meyer bar, a roll, a T-die, or the like, a norbornene-based resin film is obtained by casting on a heat-resistant film such as polyethylene terephthalate, a steel belt, a metal foil, or the like, and drying by heating.

In order to form a film by a melt molding method, a melt extrusion method such as a T-die method or an inflation method, a calendar method, a hot press method, an injection molding method, or the like is used.

In order to improve the heat resistance, ultraviolet resistance, smoothness, etc. of the film within a range that does not impair the effects of the present invention, the norbornene-based resin film contains an antioxidant such as a phenol-based or phosphorus-based antioxidant; Phenol-based thermal degradation inhibitors; amines and other antistatic agents; aliphatic alcohol esters, polyhydric alcohol partial esters and partial ethers and other lubricants; benzophenone-based ultraviolet absorbers;
An ultraviolet absorber such as a benzotriazole-based ultraviolet absorber and an acrylonitrile-based ultraviolet absorber; a leveling agent such as a fluorine-based nonionic surfactant, a special acrylic resin-based leveling agent, and a silicone-based leveling agent may be added.

The thickness of the norbornene resin film is usually preferably from 5 to 200 μm, more preferably from 1 to 200 μm.
0 to 100 μm. When the thickness of the film is less than 5 μm, not only does the strength decrease, but also the durability of the polarizing plate undergoes a durability test. On the contrary, 100
If it exceeds μm, not only the transparency is lowered, but also the moisture permeability becomes small, and the drying of water, which is the solvent of the PVA-based adhesive, becomes slow.

The above-mentioned norbornene-based resin film is preferably subjected to a surface treatment before laminating a resin layer described later. Examples of the surface treatment include a corona discharge treatment and an ultraviolet irradiation treatment, and preferably have a wetting index of 45 dyn.
/ Cm or more, more preferably 50 dyn / cm or more. The wetting index means a critical surface tension according to Zisman, and is measured with a standard wetting reagent based on JIS K8768.

The protective film for a polarizing plate of the present invention functions as a protective film for a polarizer. At least one surface of a norbornene-based resin film has polyvinyl alcohol (hereinafter, referred to as PVA) and polyethyleneimine (hereinafter, referred to as PEI). Are laminated.

As the above polarizer, a PVA film or sheet having the function of a polarizer is usually used.
PVA / iodine-based polarizer uniaxially stretched in a boric acid bath after adsorbing iodine on a PVA film; PVA / dye-based polarizing film uniaxially stretched after diffusing and adsorbing a highly dichroic direct dye onto the PVA film A PVA / polyvinylene-based polarizing film having a polyvinylene structure formed by adsorbing iodine on a PVA film and stretching.

The PVA film or sheet having the function of a polarizer is obtained by stretching a PVA-based film or sheet. PVA is usually produced by saponifying polyvinyl acetate obtained by polymerizing vinyl acetate. In the present invention, the present invention is not necessarily limited to these, and vinyl acetate may contain a small amount of unsaturated carboxylic acid (including salts, esters, amides, nitriles, etc.), olefins, vinyl ethers, unsaturated sulfonates and the like. It may be one obtained by copolymerizing a copolymerizable component.

The resin layer is formed from PVA and PEI. The average degree of polymerization and the degree of saponification of the PVA are not particularly limited, but are preferably 200 to 4,000 and the degree of saponification is 90 mol% or more.

The above-mentioned PEI includes primary amino groups obtained by cationic polymerization of ethyleneimine, and secondary and tertiary amino groups.
A polyamine having a branched structure with a graded amino group is used. Examples of commercially available PEI include “Epomin” (trade name) manufactured by Nippon Shokubai Kagaku Co., Ltd.

The ratio of PVA to PEI in the resin layer is such that PEI is 50 to 95% by weight and PEI is 50 to 5% by weight.
% By weight is preferred. When the proportion of PVA is less than 50% by weight, blocking tends to occur when the resin layer is formed into a roll after being formed, and when it exceeds 95% by weight, the adhesion to the norbornene-based resin film is reduced.

The resin layer may contain a PEI crosslinking agent and other additives. As the crosslinking agent, PE
It is not particularly limited as long as it has a functional group capable of forming a crosslinked structure by reacting with the amino group of I. Examples of the functional group capable of forming a crosslinked structure include aldehyde, ketone, alkyl halide, isocyanate, Examples include thioisocyanate, double bond, epoxy, acid, acid anhydride, acyl halides, esters, and the like, and compounds having these in the molecule are used.

Examples of the other additives include coupling agents such as a silane coupling agent and a titanium coupling agent; terpene resins, phenol resins, and terpene resins.
Tackifiers such as phenolic resins, rosin resins, and xylene resins; stabilizers such as ultraviolet absorbers, antioxidants, heat stabilizers, and hydrolysis stabilizers; and PEI yellowing inhibitors.

The method for forming the resin layer is as follows.
An appropriate concentration (for example, 0.0
After preparing an aqueous solution (coating solution) in which PVA and PEI are mixed in a predetermined amount so as to be 1 to 50% by weight, the coating solution is prepared by a known method (for example, a gravure coater, a microgravure coater, or the like). A method of applying, drying with hot air or the like, and bonding is used.

To prepare the above coating liquid, an alcohol other than water may be used as a solvent, or a mixed solvent of water and an alcohol may be used. Examples of the alcohol include methanol, ethanol, and isopropanol.

The thickness of the resin layer after drying is from 0.01 to
20 μm is preferable, and more preferably 0.05 to 10 μm
m. When the thickness is less than 0.01 μm, a sufficient adhesive strength cannot be obtained, and when the thickness exceeds 20 μm, fading of the polarizing plate easily occurs in a moisture resistance test.

A polarizing plate is manufactured by laminating the norbornene-based resin film as a polarizing plate protective film on at least one surface of a polarizer.

When a polarizing plate is manufactured using the above polarizing plate protective film, it can be bonded to both surfaces of the above polarizer by wet lamination using a PVA-based adhesive as in the case of the polarizing plate protective film using saponified TAC. The conventional manufacturing process can be used as it is. Wet lamination considers thickness after drying, smoothness of coating, etc.
For example, a PVA-based adhesive is diluted with water to an appropriate concentration (for example, 0.01 to 50% by weight) to prepare a coating solution, and then applied by a known method (for example, a gravure coater, a microgravure coater, or the like). Or by dripping, laminating an excess coating liquid with a pair of rolls while ironing, drying with hot air or the like, and bonding.

As the PVA-based adhesive, an aqueous solution of a PVA-based polymer such as PVA, copolymer-modified PVA, or graft-modified PVA having various degrees of polymerization and saponification is used, and a crosslinking agent may be blended. . However, an unmodified aqueous PVA solution is usually sufficient.

The polarizing plate protective film of the present invention only needs to be laminated on at least one surface of the polarizer, and a resin film having high transparency can be laminated on the other surface. Of course, a norbornene-based resin film may be laminated on both surfaces of the polarizer. At least one surface on which the film must be laminated is the surface on the liquid crystal cell side, because a change in retardation under high temperature and high humidity cannot be suppressed unless the protective film is used.

The method of laminating the polarizing plate protective film on the polarizer is performed by a conventionally known method, but it is preferable to bond the polarizer by wet lamination using a PVA-based adhesive. This is a method in which a PVA adhesive aqueous solution is applied or lowered on a polarizing plate protective film, and an excess aqueous solution is laminated with a pair of rolls while ironing, and dried by hot air or the like to be bonded.

(Function) In the present invention, the photoelastic constant can be reduced by using a norbornene-based resin film as the protective film for the polarizing plate, and even if stress generated due to shrinkage of the PVA polarizer in a durability test is applied. The protective film can suppress a decrease in the degree of polarization without generating a large retardation. Further, the water vapor transmission rate can be made smaller than that of the saponified TAC, and water intrusion can be suppressed in the moisture resistance test of the polarizing plate. By providing a resin layer made of PVA and PEI on this norbornene-based resin film, a conventional bonding method can be used, and a sufficient bonding strength can be obtained with a PVA-based adhesive.

[0040]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited only to these examples.

Preparation of Polarizer An unstretched PVA film having a thickness of 75 μm and a saponification degree of 99% was washed with water at room temperature, and then stretched 5 times uniaxially. While maintaining the tension of the film, 0.5w of iodine
The dichroic dye was adsorbed by immersion in an aqueous solution containing t% and potassium iodide 5 wt%. Furthermore, boric acid 10wt
% And potassium iodide of 10 wt% at 50 ° C. for 5 minutes to obtain a PVA polarizer used in the present invention.

Polarizing plate protective film (1) Preparation of norbornene-based resin film Norbornene-based resin (manufactured by JSR, trade name: ARTO)
N) was dissolved in toluene at a concentration of 35 wt%, cast on a polyethylene terephthalate process film, and dried at 150 ° C. for 3 minutes after peeling off from the process film at 80 ° C. for 5 minutes, 120 ° C. for 5 minutes, A norbornene-based resin film was obtained. In addition, the thickness of the norbornene-based resin film after drying was 50 μm.

(2) Polycarbonate (PC) Film A commercially available PC film having a thickness of 70 μm (manufactured by Teijin Limited, product number: C
-120-70) was used.

(3) Saponified TAC Film A commercially available 80 μm thick TAC film (trade name: Fujitack Clear, manufactured by Fuji Photo Film Co., Ltd.) was saponified.

The above norbornene resin film and PC
One surface of the film was subjected to a corona discharge treatment. After treatment,
In the measurement of the wetting index using the wetting indicator, each film was 70 dyn / cm or more.

Example 1 A 5 wt% aqueous solution of PVA (“Kuraray Poval PVA-117H” manufactured by Kuraray Co., Ltd.) and P
A coating solution was obtained by mixing a 5 wt% aqueous solution of EI (“Epomin P-1000” manufactured by Nippon Shokubai Chemical Co., Ltd.) at a weight ratio of 7: 1. After applying this coating solution to the corona-treated surface of the norbornene-based resin film with a Mayer bar # 8, 100
The resin layer was formed by drying at 3 ° C. for 3 minutes to prepare a polarizing plate protective film. The thickness of the resin layer after drying was 0.6 μm.

Example 2 A 5 wt% aqueous solution of PVA ("Kuraray Poval PVA-117H" manufactured by Kuraray Co., Ltd.)
A 5 wt% aqueous solution of EI ("Epomin P-1000" manufactured by Nippon Shokubai Kagaku Co., Ltd.) and an epoxy compound ("Denacol 313" manufactured by Nagase Kasei Co., Ltd.) as a crosslinking agent were used in a weight ratio of 7:
1: 2.6 to obtain a coating liquid. The coating liquid was applied to the corona-treated surface of the norbornene-based resin film with a Mayer bar # 8, and then dried at 100 ° C. for 3 minutes to form a resin layer, thereby producing a polarizing plate protective film. The thickness of the resin layer after drying was 0.6 μm.

Example 3 A 1 wt% aqueous solution of PVA ("Kuraray Poval PVA-117H" manufactured by Kuraray Co., Ltd.)
A 1 wt% aqueous solution of EI (“Epomin P-1000” manufactured by Nippon Shokubai Chemical Co., Ltd.) was blended at a weight ratio of 7: 1 to obtain a coating liquid. After applying this coating solution to the corona-treated surface of the norbornene-based resin film with a Mayer bar # 8, 100
The resin layer was formed by drying at 3 ° C. for 3 minutes to prepare a polarizing plate protective film. The thickness of the resin layer after drying was 0.2 μm.

(Comparative Example 1) A resin layer was formed on the corona-treated surface of the PC film in the same manner as in Example 1 to prepare a polarizing plate protective film.

Comparative Example 2 The saponified TAC film was used as it was as a polarizing plate protective film.

Fabrication of polarizing plate by wet lamination
As a PVA-based adhesive coating solution, a 5 wt% aqueous solution of commercially available PVA (“Kuraray Poval PVA-117H” manufactured by Kuraray Co., Ltd.) was prepared, and this coating solution was applied to Examples 1-3 and Comparative Examples using a Meyer bar # 8. The polarizing plate protective film was applied on the resin layer of the polarizing plate protective film obtained in 1, and the polarizing plate protective film was wet-laminated on both sides of the polarizer while squeezing excess aqueous solution with a pair of rolls. In Comparative Example 2, the coating liquid was applied directly to the saponified TAC film and then wet-laminated on both surfaces of the polarizer. These were treated at 50 ° C. × 3 minutes,
After drying with hot air in 3 steps of 3 ° C. × 3 minutes,
After curing for days, a polarizing plate sample having the configuration shown in FIG. 1 was produced. In the figure, 1 is a polarizer, 2 is a PVA-based adhesive, 3
Denotes a polarizing plate protective film, 31 denotes a norbornene-based resin film, and 32 denotes a resin layer.

Durability Evaluation A durability test was performed on a test piece obtained by punching the polarizing plate sample obtained above into a square of 50 mm × 50 mm, and the results are shown in Tables 1 and 2. The durability test condition is 90 ° C dr.
For y and 60 ° C. 90% RH, observation was made up to 500 hours each. The change in the degree of polarization and the change in the transmittance before and after the durability test at 500 hr were measured by the following optical measurement method to evaluate the display characteristics. Optical Measurement Method Change in Transmittance Transmittance was measured by measuring the change in transmittance of fading of a polarizing plate sample. The measurement was performed using a spectrophotometer ("TC-18" manufactured by Tokyo Denshoku Industries Co., Ltd.
00 ”) was used to measure the Y value. Change in polarization degree The total light transmittance of the two polarizing plates was measured in accordance with JIS K 7105, and the change in polarization degree was calculated from the following equation. {(Y ₀ −Y ₉₀ ) / (Y ₀ + Y ₉₀ )} ^1/2 × 100 Y ₀ : Total light transmittance of two sheets in which the polarization axes of the polarizing plates are aligned in parallel. Y ₉₀ : total light transmittance of two polarizing plates whose polarizing axes are aligned at right angles.

[0053]

[Table 1]

[0054]

[Table 2]

From the above results, it can be seen that the examples of the present invention have a small change in transmittance and a degree of polarization even after a durability test under high temperature and high humidity conditions for 500 hours, and have excellent durability. Have.

[0056]

The polarizing plate protective film of the present invention has the above-mentioned structure, and has a sufficient adhesive strength without a decrease in the degree of polarization or fading due to a heating operation for bonding the polarizer and the protective film. Therefore, a polarizing plate having excellent durability is provided. Further, since the polarizer and the polarizing plate protective film can be wet-laminated, there is an advantage that the polarizing plate can be manufactured without changing the bonding step between the polarizer and the polarizing plate protective film as in the conventional method.

[Brief description of the drawings]

FIG. 1 is an exploded sectional view showing a configuration of a polarizing plate of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 polarizer 2 PVA-based adhesive 3 protective film for polarizing plate 31 norbornene-based resin film 32 resin layer

Claims (2)

[Claims] 1. A polarizing plate protective film, wherein a resin layer containing polyvinyl alcohol and polyethylene imine is laminated on a norbornene-based resin film. 2. The polarizing plate protective film according to claim 1,
A polarizing plate, which is laminated on at least one side of a polarizer.