JP2000266932A - Polarizing plate protection film and polarizing plate using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily adhere to a polarizer by processing at least one face of a thermoplastic saturated norbornene resin film by ultraviolet irradiation, and specifying the wetting index of the surface. SOLUTION: At least one face of a thermoplastic saturated norbornene resin film is processed by ultraviolet irradiation, and the wetting index of the surface is set over 40 dyne/cm. For thermoplastic saturated norbornene resin in this case, well-known thermoplastic saturated norbornene resin is suitably used, for example, hydrogenated substance of ring-opening polymer of norbornene monomer, additive type polymer of norbornene monomer and olefinic monomer, and the modified substance of these polymers or the like are cited. For the manufacturing method of this polarizing plate protecting film, a well-known optional method can be adopted, for example a solution spreading method is desirable.

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 A polarizing plate used in a liquid crystal display or the like is generally formed by laminating protective films on both surfaces of a polarizer. A stretched polyvinyl alcohol film on which iodine or a dichroic dye is adsorbed is used as a polarizer, and a triacetyl cellulose film is used as a protective film.

However, the triacetylcellulose film has insufficient heat resistance and moisture resistance, and when used under high temperature or high humidity, the polarizer and the triacetylcellulose film may peel off or the triacetylcellulose may be hydrolyzed. There are drawbacks that the transparency is reduced and the performance of the polarizing plate is reduced, and the degree of polarization of the polarizer is reduced. Therefore,
Even when used in a liquid crystal display, there is a disadvantage that image quality is reduced in a short period of time.

As a countermeasure, it has been proposed to use a thermoplastic saturated norbornene-based resin as a protective film (for example, JP-A-8-5836). However, thermoplastic saturated norbornene resins have poor adhesion and are difficult to adhere to a polarizer.
No. 28, lamination of a polarizer and a thermoplastic saturated norbornene-based resin sheet via an acrylic pressure-sensitive adhesive layer,
A method of bonding by heating and pressing for 5 minutes has been proposed.

[0005] However, in the above-mentioned bonding method, it is necessary to heat and press the entire film uniformly for a certain period of time, the equipment becomes expensive and the production efficiency is poor. Fading and polarization function decrease,
Further, there is a disadvantage that if the heating temperature or pressure at the time of heating and pressurization varies, the adhesion becomes uneven and the polarization performance deteriorates.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a polarizing plate protective film which can be easily bonded to a polarizer, and a polarizing plate using the polarizing plate protective film. is there.

[0007]

According to a first aspect of the present invention, there is provided a polarizing plate protective film, wherein at least one surface of a thermoplastic saturated norbornene resin film is subjected to an ultraviolet irradiation treatment, and the surface has a wetting index of 40 dynes / cm or more. There is a feature.

[0008] A polarizing plate according to a second aspect is characterized in that the polarizing plate protective film according to the first aspect is adhered to at least one surface of a polarizer.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail.

As the above-mentioned thermoplastic saturated norbornene-based resin, conventionally known thermoplastic saturated norbornene-based resins are suitably used. For example, hydrogenated products of ring-opened polymers of norbornene-based monomers and addition-type polymerization of norbornene-based monomers And an addition type polymer of a norbornene-based monomer and an olefin-based monomer, and a modified product of these polymers.

As the norbornene-based monomer, for example, 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-phenyl-5 -Methyl-2-norbornene, ethylene-tetracyclododecene copolymer, 6-methyl-1,4: 5,8-dimethanol 1,
4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-ethyl-1,4: 5,8-dimethanol 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-dimethanol 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-dimethanol 1,
4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-methoxycarbonyl-1,4: 5,8-dimethanol 1,4,4a, 5,6,7,8,8a-octahydronaphthalene , 1,4-dimethanoux 1,4,4a, 4
b, 5,8,8a, 9a-octahydrofluorene,
5,8-Methanolau 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-1H-benzoindene, 4,11: 5,10: 6,9-trimethano 3
a, 4,4a, 5,5a, 6,9,9a, 10,10
a, 11,11a dedecahydro-1H-cyclopentaanthracene;

When the number average molecular weight of the thermoplastic saturated norbornene resin decreases, the moisture resistance decreases, and when the number average molecular weight increases, the film formability decreases. Therefore, the number average molecular weight is measured by gel permeation chromatography using a toluene solvent. It is preferably 25,000 to 100,000, and more preferably 30,000 to 80,000.

As the above-mentioned thermoplastic saturated norbornene resin, trade names "ZEONOR", "Z
"EONEX", product name "ART" from JSR Corporation
ON ", marketed by Mitsui Petrochemical Company under the trade name" APEL ".

The polarizing plate protective film according to claim 1 is made of the above-mentioned thermoplastic saturated norbornene-based resin, and its production method may be any known method.
Examples include a solution casting method and a melt molding method, and the solution casting method is preferable.

In order to form a film by the solution casting method, first, for example, a high boiling solvent such as toluene, xylene, ethylbenzene, chlorobenzene, triethylbenzene, diethylbenzene, isopropylbenzene, or a solvent having such a high boiling point and cyclohexane, benzene, tetrahydrofuran, The above-mentioned thermoplastic saturated norbornene-based resin is preferably dissolved in a mixed solvent of a low boiling point solvent such as hexane and octane in an amount of 5 to 60% by weight to obtain a resin solution.

Next, the obtained resin solution is coated with a bar coater.
It is cast on a heat-resistant film such as polyethylene terephthalate, a steel belt, a metal foil or the like using a doctor knife, a Meyer bar, a roll, a T-die or the like, and dried by heating.

In order to improve the heat resistance, ultraviolet resistance, smoothness and the like of the polarizing plate protective film, a phenol-based or phosphorus-based antioxidant, a phenol-based heat deterioration inhibitor, an amine, etc. An antistatic agent such as a system, a lubricant such as an ester of an aliphatic alcohol and a partial ester of a polyhydric alcohol, and an ultraviolet absorber such as a benzophenone or a benzotriazole may be added.

The thickness of the polarizing plate protective film is preferably from 5 to 500 μm, more preferably from 10 to 150 μm, because the strength decreases as the thickness decreases, and the transparency decreases and the birefringence increases as the thickness increases. And more preferably 15 to 100 μm.

When the wetting index of the polarizing plate protective film is small, it becomes difficult to adhere to the polarizer with an adhesive.
It is required to be 0 dynes / cm or more, preferably 45 dynes / cm or more. In addition, the wetting index means a critical surface tension according to Zisman, and is measured with a standard wetting reagent based on JIS K6768.

As a method for setting the wetting index of the polarizing plate protective film to 40 dynes / cm or more, an ultraviolet irradiation treatment method is employed. The ultraviolet irradiation treatment is preferably performed by irradiating ultraviolet rays with a lamp having a peak at a short wavelength of 300 nm or less. Examples of the lamp include a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a chemical lamp, and a black light. Lamps, microwave-excited mercury lamps, metal halide lamps and the like can be mentioned, and low-pressure mercury lamps are preferably used.

The conditions for the ultraviolet irradiation treatment may be such that the surface wetting index of the protective film is 40 dynes / cm or more, and is generally preferably 0.1 to 100 mW / cm ² , more preferably 0.5 to 100 mW / cm ^2. It is 50 mW / cm ² .

In the polarizing plate according to the second aspect, the polarizing plate protective film according to the first aspect is bonded to at least one surface of the polarizer such that the surface having a wetting index of 40 dynes / cm or more is in contact with the polarizer. However, in order to improve the heat resistance, moisture resistance and the like of the polarizing plate, it is preferable that a polarizing plate protective film is adhered to both surfaces of the polarizer.

The adhesion between the polarizer and the polarizing plate protective film is as follows:
The surface wetting index of the polarizing plate protective film is 40 dynes / c
m or more, and can be easily bonded with a conventionally known (viscosity) adhesive. Preferred (sticky) adhesives include, for example, polyurethane-based, polyester-based, polyacryl-based adhesives, and acrylic-, silicone-, and rubber-based adhesives. It is needless to say that the thermocompression bonding may be performed under the condition that the polarizing function of the polarizer does not deteriorate. In this case, the bonding can be performed under gentle thermocompression bonding conditions.

[0024]

EXAMPLES The present invention will be described below in more detail with reference to examples, but the present invention is not limited to the examples.

Examples 1 to 3 Thermoplastic saturated norbornene resin (ZEON Corporation, ZE
ONOR1600R) to a single screw extruder,
Extruded at 290 ° C. to obtain a 60 μm thick thermoplastic saturated norbornene resin film.

Next, the obtained film was erected 10 mm away from the tube wall of a low-pressure mercury lamp (SUV110GS-36, 110W, manufactured by Sen Engineering Co., Ltd.), and set for 30 seconds (Example 1) and 90 seconds (Example 2). ) For 120 seconds (Example 3) to obtain a protective film. The UV irradiation intensity was 6 mW at 254 nm.
/ Cm ² .

A polyvinyl alcohol film having a thickness of 75 μm and having a saponification degree of 99% is stretched 5 times uniaxially in a longitudinal direction, and 0.5% by weight of iodine and potassium iodide 5.
It was immersed in an aqueous solution containing 0% by weight to adsorb the dichroic dye. Then, boric acid 10% by weight and potassium iodide 1
Crosslinking treatment was performed for 5 minutes with an aqueous solution at 50 ° C. containing 0.0% by weight to obtain a polarizer.

100 parts by weight of a polyester polyol solution (manufactured by Toyo Morton, TM-593) and 18 parts of an isocyanate-based curing agent solution (manufactured by Toyo Morton, CAT-56) 18
By weight, ethyl acetate was added to obtain an adhesive having a solid content of 30% by weight. The obtained adhesive was applied on both surfaces of the polarizer and dried at 80 ° C. for 1 minute to obtain a polarizer having a 3 μm-thick adhesive layer laminated thereon.

A protective film is laminated on both surfaces of the polarizer so that the surfaces irradiated with ultraviolet rays come into contact with each other, and is heated to 80 ° C.
g by one reciprocation of the roll, and then 40 ° C.
For 2 days to obtain a polarizing plate.

Comparative Example 1 A polarizing plate was obtained in the same manner as in Example 1 except that no ultraviolet treatment was performed.

COMPARATIVE EXAMPLE 2 A polarizing plate was heated in the same manner as in Example 1 except that the polarizing plate protective film and the polarizer were heated at 90 ° C. for 2 minutes, laminated, and reciprocated with a 5 kg roll once. Obtained.

The physical properties of the obtained polarizing plate protective film and polarizing plate were measured as follows, and the results are shown in Table 1. (1) Wetting index Measured using a standard wetting reagent according to JIS K 6768.

(2) Degree of polarization According to JIS K 7105
The total light transmittance was measured, and the degree of polarization was determined by the following equation.
I did. Degree of polarization (%) = ｛(Y₀-Y₉₀) / (Y₀+ Y₉₀)｝^1/2
× 100 where Y₀Is when the parallel axes of the two polarizing plates are aligned in parallel.
Total light transmittance, Y_{9 0}Is the parallel axis of the two polarizing plates
This is the total light transmittance when crossed.

(3) Heat resistance test and moisture resistance test After the test, the peeled state and the foamed state of the polarizer and the protective film were visually observed and evaluated as follows. ○ Neither peeling nor foaming △ No peeling but bubbles were generated × Peeling occurred In the heat resistance test, the polarizing plate was kept in a dryer at 80 ° C. for 700 hours. In the moisture resistance test, the polarizing plate was kept in a dryer at 60 ° C. and 90% RH for 700 hours.

[0035]

[Table 1]

[0036]

The polarizing plate protective film according to claim 1 is
It is made of a thermoplastic saturated norbornene resin, at least one surface of which has been subjected to an ultraviolet irradiation treatment, and has a surface wetting index of 40 dynes / cm or more, so that it has excellent heat resistance and moisture resistance, and has an adhesive property with a polarizer. Is better.

Since the polarizing plate according to the second aspect has the polarizer protective film according to the first aspect adhered to at least one surface of the polarizer, it can be easily applied with an arbitrary (sticky) adhesive without heating and pressing for a long time. In addition, it is possible to continuously adhere with high productivity. Therefore, the polarizer of the polarizing plate does not fade and the polarizing function is not deteriorated, and the polarizing function is not deteriorated at the time of bonding, and can be suitably used in a liquid crystal display or the like.

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Claims (2)

[Claims] 1. A polarizing plate protective film, wherein at least one surface of a thermoplastic saturated norbornene resin film is subjected to an ultraviolet irradiation treatment, and the surface has a wetting index of 40 dynes / cm or more. 2. A polarizing plate, wherein the polarizing plate protective film according to claim 1 is adhered to at least one surface of a polarizer.