JP3297450B2 - Polarizing film for liquid crystal display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizing film for a liquid crystal display, and more particularly to a polarizing film for a liquid crystal display having a protective layer made of a thermoplastic saturated norbornene resin sheet laminated thereon.

[0002]

2. Description of the Related Art A liquid crystal display generally comprises a liquid crystal cell, a polarizer, a reflector or a backlight. The liquid crystal cell is composed of two liquid crystal substrates, spacers, liquid crystal material, etc., provided with transparent electrodes on the inward surface of a transparent substrate made of glass or plastic, and the liquid crystal material is sealed between the two liquid crystal substrates. Has become. Polarizers are arranged on both sides of a liquid crystal cell in the case of a normal TN type liquid crystal.

As a polarizer, a thin film type polarizer (polarizing film) is used, and in order to ensure durability and mechanical strength,
Protective layers made of various films are laminated on both sides by an adhesive. This laminate is called a polarizing film or a polarizing plate.

A polarizing film is attached to a liquid crystal substrate via a transparent acrylic adhesive or the like in order to prevent reflection loss of light at an interface with a liquid crystal cell. Therefore, an ordinary polarizing film is provided with an adhesive layer on one side of the protective layer, and a release film (separator) is formed on the adhesive layer from the viewpoint of protecting the adhesive layer and workability. Is provided. When bonding the polarizing film to the liquid crystal substrate, the release film is peeled off.

The polarizing film has a function of dividing incident light into two polarization components orthogonal to each other, passing only one of them, and absorbing or dispersing the other components. For example, TN
In the case of type liquid crystal, if the absorption axes of two polarizing films are combined in an orthogonal position or a parallel position, and a liquid crystal cell with twisted orientation is interposed between them, light transmission and non-transmission can be switched depending on the presence or absence of an applied voltage. The pattern is displayed by the density ratio of the transmitted light at the orthogonal position and the transmitted light at the parallel position. Therefore, a polarizing film having a higher polarization degree and transmittance has better performance.

In recent liquid crystal displays, in most cases, a transparent polymer film is molecularly arranged in a certain direction.
A polarizing film in which a dichroic substance is adsorbed in a gap between micelles is used. Representative examples of such polarizing film, polyvinyl alcohol (hereinafter abbreviated as PV A) · iodine, P
VA · dye, PV A-based polarizing films such as PVA · polyvinylene-based, or a polyene-based polarizing film.

However, many of these general-purpose polarizing films are:
As described above, the protective layer is provided because the mechanical strength in the transmission axis direction is weak, and furthermore, the film is easily contracted by heat or moisture or the polarizing function is easily deteriorated. The protective layer has no birefringence, high transmittance, good heat resistance and moisture absorption resistance, high mechanical strength, low shrinkage due to changes in temperature and humidity, and a smooth surface. , High resolution, good adhesion to the pressure-sensitive adhesive, and excellent appearance. Conventionally, a solution cast film of cellulose triacetate (hereinafter abbreviated as TAC) having low birefringence and good appearance is mainly used as the protective layer.

However, for example, the PV constituting the polarizing substrate
A film having a water vapor transmission rate of 25 μm
1000 ° C., 90% RH, 1000 to 1200 g / m ²
While it is about 24 hours, the TAC film of the protective layer has a water vapor permeability of about 700 g / m ² · 24 hours under the same conditions, and has insufficient moisture resistance. Therefore, a polarizing film having a TAC film as a protective layer has poor durability at high temperature and high humidity.
Under an environment of 0% RH, it deteriorates in 100 hours or less, and the polarization performance is rapidly lowered.

[0009] The TAC film also has insufficient gas barrier properties, and dichroic substances such as iodine and dyes are liable to be deteriorated by permeated oxygen. Further, since a TAC film contains a plasticizer for forming a film, the TAC film has insufficient heat resistance. Further, the TAC film has a tensile strength of 6
It is only about 11 kg / mm ² and the physical strength is insufficient. Therefore, a TAC film is usually 80 μm thick because a thin film having a thickness of 40 μm or less has low strength and durability.
Thickness is used.

Since the TAC film has a large photoelastic coefficient, the birefringence tends to increase when an external force is applied or when there is a residual stress during molding. Therefore, a TAC film can be produced only by a solution casting method having low birefringence and good appearance, and having a small residual stress.

The polarizing film is laminated on a liquid crystal substrate, a phase plate or the like via an adhesive layer. However, there is a problem in the adhesion between the TAC film and the adhesive.
Air bubbles called tunnels are easily generated between the AC film and the adhesive layer. Further, when a pressure-sensitive adhesive layer containing acrylic acid is laminated on the TAC film, there is a problem that the TAC film is decomposed by acrylic acid.

[0012]

SUMMARY OF THE INVENTION An object of the present invention is to provide excellent water resistance, moisture resistance, physical strength, heat resistance, transparency, low birefringence, etc., adhesion to an adhesive, and durability against an adhesive. An object of the present invention is to provide a polarizing film for a liquid crystal display having excellent properties.

The inventors of the present invention have conducted intensive studies to overcome the problems of the prior art, and as a result, a polarizing film in which a thermoplastic saturated norbornene-based resin sheet is laminated on at least one surface of a polarizing film as a protective layer, has a liquid crystal structure. The inventors have found that they have excellent properties as a polarizing film for a display, and have completed the present invention based on the findings.

[0014]

According to the present invention, at least one surface of the polarizing film has a number average molecular weight of from 25,000 to 25,000.
There is provided a polarizing film for a liquid crystal display, wherein 100,000 thermoplastic saturated norbornene resin sheets are laminated as a protective layer. Hereinafter, the present invention will be described in detail.

(Polarizing Film) The polarizing film used in the present invention is not particularly limited as long as it has a function as a polarizer. For example, a PVA / iodine-based polarizing film, a dye-based polarizing film in which a dichroic dye is adsorbed and oriented on a PVA-based film, or a dehydration reaction is induced from a PVA-based film, or a dehydrochlorination reaction of a polyvinyl chloride film is performed. Examples include a polyene-based polarizing film having a polyene formed thereon, and a polarizing film having a dichroic dye on the surface and / or inside of a PVA-based film made of a modified PVA containing a cationic group in the molecule.

The method for manufacturing the polarizing film is not particularly limited. For example, a method of adsorbing iodine ions after stretching a PVA-based film, a method of stretching a PVA-based film after dyeing with a dichroic dye, a method of stretching a PVA-based film after stretching, and a method of dyeing a dichroic dye, Known methods such as a method of stretching a PVA-based film after printing, and a method of stretching a PVA-based film and then printing a dichroic dye may be used. More specifically, iodine is dissolved in a potassium iodide solution to form higher-order iodine ions, and these ions are adsorbed on a PVA film and stretched. A method of manufacturing a polarizing film by immersing at 40 ° C., or similarly treating a PVA film with boric acid and stretching it about 3 to 7 times in a uniaxial direction, and adding a bath temperature of 0.05 to 5% to a dichroic dye aqueous solution. Dipped at 30-40 ° C to adsorb the dye, 80
There is a method of drying at 膜 100 ° C. and heat setting to produce a polarizing film.

(Thermoplastic Saturated Norbornene Resin) In the present invention, a sheet made of a thermoplastic saturated norbornene resin is laminated as a protective layer on one or both surfaces of the polarizing film.

The thermoplastic saturated norbornene resin used in the present invention includes, for example, (1) a ring-opening (co) polymer of a norbornene monomer, if necessary, a polymer modification such as addition of maleic acid or cyclopentadiene. , A hydrogenated resin, (2) a resin obtained by addition-type polymerization of a norbornene-based monomer, and (3) a resin obtained by addition-type copolymerization of a norbornene-based monomer with an olefin-based monomer such as ethylene or α-olefin. Can be mentioned. The polymerization method and the hydrogenation method can be performed by a conventional method.

Examples of the norbornene-based monomer include norbornene and alkyl- and / or alkylidene-substituted products thereof, for example, 5-methyl-2-norbornene, 5-dimethyl-2-norbornene, 5-ethyl-2-norbornene, -Butyl-2-norbornene,
Polar group substituents such as halogens such as 5-ethylidene-2-norbornene; dicyclopentadiene, 2,3-
Dihydrodicyclopentadiene and the like; dimethanooctahydronaphthalene, its alkyl and / or alkylidene-substituted product, and polar group-substituted product such as halogen, for example,
6-methyl-1,4: 5,8-dimethano-1,4,4
a, 5,6,7,8,8a-octahydronaphthalene,
6-ethyl-1,4: 5,8-dimethano-1,4,4
a, 5,6,7,8,8a-octahydronaphthalene,
6-ethylidene-1,4: 5,8-dimethano-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, 5,6,7,8,8a-octa Hydronaphthalene and the like; adducts of cyclopentadiene with tetrahydroindene and the like; cyclopentadiene trimers and tetramers, for example, 4,9: 5,8-dimethano-3a, 4,4
a, 5,8,8a, 9,9a-octahydro-1H-benzoindene, 4,11: 5,10: 6,9-trimethano-3a, 4,4a, 5,5a, 6,9,9a, 10 ,
10a, 11, 11a-dodecahydro-1H-cyclopentaanthracene;

In the present invention, other ring-opening polymerizable cycloolefins can be used in combination within a range not to impair the object of the present invention. Specific examples of such a cycloolefin include compounds having one reactive double bond such as cyclopentene, cyclooctene, and 5,6-dihydrodicyclopentadiene.

The thermoplastic saturated norbornene resin used in the present invention has a number average molecular weight of usually 25,000 to 100,000, preferably 3 as measured by gel permeation chromatography (GPC) using a toluene solvent.
000-80,000, more preferably 350,000
It is in the range of 0 to 70,000. If the number average molecular weight is too small, the physical strength will be poor, and if it is too large, the operability during molding will be poor.

When the thermoplastic saturated norbornene-based resin is obtained by hydrogenating a ring-opened polymer of a norbornene-based monomer, the hydrogenation ratio is usually 90% from the viewpoint of heat deterioration resistance and light deterioration resistance. Above, preferably 95%
Above, more preferably, 99% or more.

The thermoplastic saturated norbornene resin has transparency, heat resistance, moisture resistance, physical strength, adhesiveness with an adhesive,
Excellent durability against adhesives. A sheet having a thickness of 25 μm and having a moisture absorption of usually 0.05% or less, preferably 0.01% or less, and a water vapor permeability of 20 g / m ² · 24 hr or less in an environment of 25 ° C. and 90% RH is easily obtained. Obtainable. The photoelastic coefficient is 3 to 9 × 1.
Since it is as small as 0 to ¹⁵ cm ² / dyne, even if an external force is applied or a residual stress is applied, the influence on the retardation is small, which is suitable for producing an optically uniform film.

The thermoplastic saturated norbornene-based resin used in the present invention may optionally contain various additives such as phenol-based or phosphorus-based antioxidants, antistatic agents, and ultraviolet absorbers. In particular, liquid crystals are usually deteriorated by ultraviolet rays. Therefore, when no protective means such as laminating an ultraviolet protective filter is taken, it is preferable to add an ultraviolet absorber. As the ultraviolet absorber, a benzophenone-based ultraviolet absorber, a benzotriazole-based ultraviolet absorber, an acrylonitrile-based ultraviolet absorber, and the like can be used. Among them, a benzophenone-based ultraviolet absorber is preferable, and the amount of addition is usually 10%. ~ 100,000p
pm, preferably 100 to 10,000 ppm.
When a sheet is prepared by a solution casting method, it is preferable to add a leveling agent to reduce the surface roughness. As the leveling agent, for example, a fluorine-based nonionic surfactant, a special acrylic resin-based leveling agent, a coating-based leveling agent such as a silicone-based leveling agent, and among them, those having good compatibility with a solvent are preferable, The addition amount is usually 5 to 50,000 ppm, preferably 10 to 20,000 ppm.

(Formation of Sheet) The protective layer used in the present invention is a sheet of a thermoplastic saturated norbornene resin.
The sheet of the thermoplastic saturated norbornene resin as the protective layer is preferably produced by a solution casting method. However, unlike the case of TAC, the sheet is produced by a melt molding method because the resin has a small photoelastic coefficient. Even so, a sheet having sufficiently small birefringence can be obtained.

1. Solution casting method In order to cast a thermoplastic saturated norbornene resin in a solution, the resin is dissolved in a solvent. The solvent used preferably has a boiling point of 100 ° C. or higher, more preferably 120 ° C. or higher. Particularly, a solvent capable of uniformly dissolving the thermoplastic saturated norbornene-based resin even at a solid content concentration of 10% by weight or more at 25 ° C. is preferable.

Examples of such a solvent include toluene, xylene, ethylbenzene, chlorobenzene, trimethylbenzene, diethylbenzene, isopropylbenzene, chlorobenzene and the like, among which xylene, ethylbenzene and chlorobenzene are preferred.

As long as the thermoplastic saturated norbornene-based resin is dissolved, these solvents may contain a cyclic ether such as cyclohexane, chloroform, benzene, tetrahydrofuran or dioxane, or n-hexane or n-hexane.
-A straight chain hydrocarbon such as octane may be contained.

As a material that satisfies these conditions favorably, there is a material containing 50% or more of an aromatic solvent having a boiling point of 100 ° C. or more such as xylene or ethylbenzene.

The resin concentration in the solution used for casting is usually 5
６０60% by weight, preferably 10-50% by weight, more preferably 20-45% by weight. If the concentration of the resin is too low, it is difficult to adjust the thickness of the sheet because the viscosity is low, and if the concentration is too high, the film-forming properties are poor due to the high viscosity, and a film with good appearance cannot be obtained.

The method for casting the resin solution is not particularly limited, and a general solution casting method can be used. Specifically, the resin solution is applied to a bar coater, a T-die, a T-die with a bar, a doctor knife, a Meir bar, a roll coat,
Using a die coat or the like, a method of casting on a flat plate or roll such as a heat-resistant material such as polyethylene terephthalate, a steel belt, or a metal foil can be used.

The sheet prepared by the solution casting method is dried to a residual solvent concentration of 2% by weight or less. If the concentration of the residual solvent is too high, the heat resistance is poor, and when used in a high-temperature environment, the residual solvent evaporates, adversely affecting the surroundings and causing deformation.

The sheet is preferably dried in two stages. First, as drying in the first stage, a sheet on a flat plate or a roll is heated at 30 to 100 ° C., preferably 4 to 100 ° C.
It is dried in a temperature range of 0 to 80 ° C. until the residual solvent concentration becomes 10% by weight or less, preferably 5% by weight or less. In this case, if the drying temperature is too high, the sheet foams upon evaporation of the solvent.

Next, the sheet is peeled off from the flat plate or roll, and as a second stage of drying, the temperature is raised to a temperature range from room temperature to 60 ° C. or higher, preferably from 70 ° C. to the glass transition temperature (Tg) of the resin. Solvent concentration of 2% by weight or less,
Preferably not more than 1% by weight, more preferably 0.5% by weight
Dry to the following.

If the drying temperature is too low, drying does not proceed, and if the temperature is too high, foaming occurs. The first stage of drying is performed, and after the drying is completed, the sheet is peeled off from a flat plate or a roll.
Even if the stage drying is performed or after the first stage drying,
The sheet may be cooled once, and the sheet may be peeled off from the flat plate or the roll, and the second-stage drying may be performed.

2. Melt molding method When a sheet is produced by a melt molding method, there are a melt extrusion method such as a method using a T-die and an inflation method, a calender method, a hot press method, an injection molding method, and the like. Above all, a melt extrusion method using a T-die which has a small thickness unevenness, is easy to be processed into a thickness of about 10 to 500 μm, and can reduce the absolute value of the retardation and the variation thereof is preferred.

The conditions of the melt molding method are the same as general conditions used for an optical material having a similar glass transition temperature (Tg). For example, in a melt extrusion method using a T-die, it is preferable to select a condition that allows the resin sheet to be gradually cooled by setting the temperature of the take-up roll to a relatively high temperature of about 100 to 150 ° C. at a resin temperature of about 240 to 300 ° C.
In addition, in order to reduce surface defects such as die lines, the die needs to have a structure in which the stagnation portion is as small as possible. It is preferable to use a structure in which the inside of the die and the lip have as little scratches as possible.

(Sheet) The thickness of the sheet is usually from 5 to 50.
0 μm, preferably 10 to 150 μm, more preferably 20 to 100 μm. If the thickness of the sheet is too thin, the strength will decrease. Conversely, if the sheet is too thick, the transparency is poor, the birefringence is high, the appearance is reduced, and drying is difficult when the sheet is prepared by a solution casting method. However, in the case of a TAC film, in order to have sufficient moisture resistance and strength, a thickness of 80 μm or more is usually required, whereas a thermoplastic norbornene-based resin sheet has a thickness of 80 μm if it has a thickness of about 30 μm. TA
It can have moisture resistance, heat resistance, and strength equal to or higher than that of the C film, can function sufficiently as a protective layer even when it is thin, and has good visual dependency.

The thickness unevenness of the sheet is within ± 5%, preferably ± 3%, more preferably ± 2% of the average thickness over the entire surface. If the thickness unevenness of the sheet is large, it causes image distortion and uneven retardation, which is not preferable as a protective layer of a polarizing film for a liquid crystal display.

The light transmittance of this sheet is 80% or more, preferably 85% or more, more preferably 90% or more.

The heat resistance of this sheet is determined by the type of the thermoplastic saturated norbornene resin, the type of the solvent used, and the residual solvent concentration when the sheet is prepared by the solution casting method.
The higher the residual solvent concentration, the lower the heat resistance. The thermoplastic saturated norbornene resin forming the sheet has a glass transition temperature (Tg) of usually 90 ° C. or higher, preferably 110 ° C.
Above, it is particularly preferable that the temperature be 120 ° C. or higher.

(Polarizing Film for Liquid Crystal Display) The polarizing film for liquid crystal display of the present invention is obtained by laminating a thermoplastic saturated norbornene resin sheet as a protective layer on at least one surface of a polarizing film. When only one side has a protective layer, in order to protect the polarizing film from the humidity around the liquid crystal display, in the production of the liquid crystal display,
It is necessary that the protective layer be outside the polarizing film.
However, protective layers can be laminated on both sides to maintain the quality of the polarizing film before manufacturing the liquid crystal display, prevent the polarizing film from absorbing moisture during the manufacturing process, prevent the degree of polarization from decreasing due to heating, and protect from scratches. preferable. Note that a protective layer made of a conventionally known material may be provided on one surface.

In order to laminate the thermoplastic saturated norbornene resin sheet on the polarizing film, usually, an adhesive or an adhesive is used.
The bonding is performed by a bonding method suitable for the adhesive or the adhesive.

As the pressure-sensitive adhesive, a pressure-sensitive adhesive excellent in transparency, small in birefringence and the like, and capable of sufficiently exerting a pressure-sensitive adhesive force even when used as a thin layer is preferable. Examples of such an adhesive include natural rubber, synthetic rubber / elastomer, vinyl chloride / vinyl acetate copolymer, polyvinyl alkyl ether,
Examples include polyacrylate, modified polyolefin-based resin-based pressure-sensitive adhesives, and curable pressure-sensitive adhesives obtained by adding a curing agent such as isocyanate to these pressure-sensitive adhesives. Particularly, the pressure-sensitive adhesives used for bonding polyolefin foams and polyester films are used. Mold adhesives are preferred.

As the adhesive, if it is an adhesive used for bonding polyethylene, polypropylene or the like,
It can be used for laminating a thermoplastic saturated norbornene resin sheet on a polarizing film. For example, a dry laminating adhesive for mixing a polyurethane resin solution and a polyisocyanate resin solution, a styrene-butadiene rubber-based adhesive, an epoxy-based two-part curable adhesive, for example, an epoxy resin and polythiol two-part adhesive, epoxy A two-component resin and a polyamide can be used. Particularly, a solvent-based adhesive and an epoxy-based two-component curable adhesive are preferable, and a transparent adhesive is preferable. Depending on the adhesive,
Some adhesives can improve the adhesive strength by using an appropriate adhesive primer. When such an adhesive is used, it is preferable to use an adhesive primer.

Further, in the case of a polarizing film mainly for a liquid crystal display, usually, in order to improve the workability of lamination on a liquid crystal substrate or a transparent electrode layer laminated on the liquid crystal substrate,
In the case where the protective layer is provided on both sides, it is preferable to laminate the pressure-sensitive adhesive layer on one side of the protective layer, and in the case where the protective layer is provided on one side, on the side having no protective layer.

As the pressure-sensitive adhesive, the above-mentioned pressure-sensitive adhesives can be used. However, when the pressure-sensitive adhesive layer is not laminated on a liquid crystal substrate or the like immediately after lamination, a curable pressure-sensitive adhesive is not preferred.
Also, when providing an adhesive layer, so that the polarizing film does not stick to surroundings before the production of the liquid crystal display,
Usually, it is preferable to further laminate a release film such as release paper or a release film on the surface. An appropriate thickness of the pressure-sensitive adhesive layer is usually 5 to 40 μm.

Usually, as described above, a polarizing film is manufactured and then laminated on a liquid crystal substrate or the like. For example, after a polarizing film is laminated on a liquid crystal substrate or the like via an adhesive layer, A polarizing film integrated with a liquid crystal substrate or the like can also be manufactured by a method of laminating a protective layer with an adhesive or the like.

[0049]

EXAMPLES The present invention will be described in more detail with reference to Reference Examples, Examples and Comparative Examples, but the present invention is not limited to only these Examples. In the following examples, parts and% are based on weight unless otherwise specified.

In the following examples, the methods for measuring physical properties are as follows. (1) The number average molecular weight was measured by a GPC method using toluene as a solvent. (2) The hydrogenation rate was measured by ¹ H-NMR. (3) The glass transition temperature (Tg) was measured by the DSC method. (4) The retardation is Belek wavelength 550 nm.
It was measured by a compensator. (5) The thickness of the sheet and the film was measured by a dial thickness gauge. (6) The light transmittance is determined by a spectrophotometer at a wavelength of 400 to
Measurement was performed by continuously changing the wavelength in the range of 700 nm, and the minimum transmittance was defined as the light transmittance. (7) The residual solvent concentration of the sheet was measured by gas chromatography at a temperature of 200 ° C.

Reference Example 1 6-methyl-1,4,5,8
-Dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene (hereinafter abbreviated as MTD) was used as a polymerization catalyst in 10 parts of a 15% solution of triethylaluminum in cyclohexane, 5 parts of triethylamine, and Add 10 parts of a 20% solution of titanium chloride in cyclohexane,
Ring-opening polymerization was performed in cyclohexane, and the obtained ring-opened polymer was hydrogenated with a nickel catalyst to obtain a polymer solution. This polymer solution is coagulated in isopropyl alcohol,
After drying, a powdery resin was obtained. This resin had a number average molecular weight of 40,000, a hydrogenation rate of 99.8% or more, and a Tg of 142 ° C.

Example 1 15 g of the resin obtained in Reference Example 1 was dissolved in 85 g of xylene, and 500 ppm of a leveling agent (Fluorard FC-430, Sumitomo 3M) was added thereto.
And UV stabilizer (Viosorb 80, Kyodo Pharmaceutical)
By adding 300 ppm, a resin solution composition was obtained. Apply this resin solution composition on a surface-polished glass plate,
This is about 300 mm wide and 500 long by a bar coater.
An appropriate amount was cast in mm. This is the first stage of drying,
20 ° C to 50 ° C in an air-reflux oven together with the glass plate
The temperature was raised to ° C over 20 minutes and dried. Next, as a second stage of drying, the resin film was peeled off from the glass plate,
Dry at 0 ° C for 30 minutes and cool to room temperature.
The sheet was obtained by cutting off the width of 0 mm. The residual solvent concentration of this sheet was 1.2% by weight.

The surface of this sheet was visually observed and observed with an optical microscope, and no foaming, streaks, scratches, etc. were observed. The Tg was 138 ° C., the average thickness was 80 μm, the thickness unevenness was at most ± 4 μm or less, the light transmittance was 91.0%, and the absolute value of the retardation value was 3 nm or less over the entire surface.
The water vapor permeability of this sheet was 3.0 g / m ² · 24 hr (about 12 g / m ² · 24 hr in terms of a thickness of 25 μm) under an environment of 25 ° C. and 90% RH.

A styrene-butadiene rubber-based adhesive (Scotch 3M adhesive for each application plastic, Sumitomo 3M Ltd.) was used on both sides of a PVA polarizing film (thickness: about 100 μm) stretched by adsorbing iodine.
A 0 μm thermoplastic norbornene resin sheet was laminated as a protective layer.

Further, it was laminated on a glass substrate having a thickness of 1.2 mm via an adhesive (Diabond DA 753, manufactured by Nogawa Chemical) having a thickness of about 8 μm on one side.

A heat cycle test of 90% humidity, 80 ° C. for 1 hour and -20 ° C. for 1 hour was repeated 200 times, and no abnormality was found.

Comparative Example 1 An adhesive for dry lamination (AD-329) was applied to both surfaces of the same polarizing film as used in Example 1.
A / B, manufactured by Nogawa Chemical Co., Ltd.)
An AC sheet (water vapor permeability: 210 g / m ² · 24 hr in an environment of 25 ° C. and 90% RH) was laminated as a protective layer.

Further, one side was laminated on a glass substrate having a thickness of 1.2 mm via an adhesive (diabond DA 753) having a thickness of about 8 μm.

When a heat cycle test of 90% humidity, 80 ° C. for 1 hour, and -20 ° C. for 1 hour was repeated 200 times, the degree of polarization was reduced to 50% or less.
A bubble called a tunnel was generated between the pressure-sensitive adhesive layer and the protective layer.

Example 2 15 g of the resin obtained in Reference Example 1 was dissolved in 85 g of xylene, and 500 ppm of a leveling agent (Fluorard FC-430) and an ultraviolet stabilizer (V
iosorb 80) 300 ppm was added to obtain a resin solution composition. This resin solution composition was spread on a glass plate whose surface was polished, and was spread with a bar coater to a width of about 3 mm.
An appropriate amount was cast to a thickness of 00 mm and a length of 500 mm. This was dried as a first stage by heating the glass plate together with the glass plate from 25 ° C. to 60 ° C. over 15 minutes in an air reflux type oven. Next, as a second stage of drying, the resin film was peeled off from the glass plate, dried at 90 ° C. for 10 minutes, cooled to room temperature, and then cut off around 10 mm wide to obtain a sheet. The residual solvent concentration of this sheet is the measurement limit of 0.1.
0% by weight or less.

The surface of this sheet was observed visually and with an optical microscope, and no foaming, streaks, scratches, etc. were observed. Tg was 139 ° C., the average thickness was 30 μm, the thickness unevenness was at most ± 4 μm or less, the light transmittance was 91.2%, and the absolute value of the retardation value was 3 nm or less over the entire surface.
The water vapor permeability of this sheet was 9.5 g / m ² · 24 hr (about 11 g / m ² · 24 hr in terms of a thickness of 25 μm) in an environment of 25 ° C. and 90% RH.

An epoxy-based two-part curable adhesive (Hyper Super 30, Cemedine Co., Ltd.) was used on both surfaces of the same polarizing film used in Example 1, and an adhesive primer (Unistor P, Mitsui) was applied on the adhesive surface. Petrochemical Industry Co., Ltd.) was thinly applied, and a 30 μm thick thermoplastic saturated norbornene resin sheet was laminated as a protective layer.

Further, it was laminated on a glass substrate having a thickness of 1.2 mm via an adhesive (Diabond DA 753) having a thickness of about 8 μm on one side.

A heat cycle test of 90% humidity, a temperature of 80 ° C. for 1 hour, and a temperature of −20 ° C. for 1 hour was repeated 200 times, and no abnormality was found.

[0065]

According to the present invention, a polarizing film having excellent water resistance, moisture resistance, physical strength, heat resistance, transparency, low birefringence, adhesion to an adhesive, and durability to an adhesive. Is provided. When the polarizing film of the present invention is laminated on a liquid crystal substrate or the like via an adhesive layer, since the protective layer and the adhesive layer are well adapted, bubbles are generated between the protective layer and the adhesive layer of the polarizing film. Hateful. The liquid crystal does not function when it has moisture. However, in the liquid crystal display using the polarizing film of the present invention, the liquid crystal is hardly affected by moisture because of its excellent moisture proof property, and the life is extended.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Shinichi Takahashi 1-2-1, Yakko, Kawasaki-ku, Kawasaki-shi, Kanagawa Japan Zeon Corporation R & D Center (72) Inventor Tsutomu Hani Kawasaki-ku, Kawasaki-shi, Kanagawa 1-1-2 Nikko Zeon Co., Ltd. R & D Center (72) Inventor Io Natsuume 1-2-1 Yakko Kawasaki-ku, Kawasaki-ku, Kanagawa Prefecture Nippon Zeon Co., Ltd. R & D Center (72) Invention Person Rinjiro Ichikawa 1-4-16 Nihombashi Bakurocho, Chuo-ku, Tokyo Inside Fujimori Kogyo Co., Ltd. (72) Inventor Kenji Hashimoto 1-46-1 Nihonbashi Bakurocho, Chuo-ku, Tokyo Fujimori Kogyo Co., Ltd. (56) References Special JP-A-2-256003 (JP, A) JP-A-2-133413 (JP, A) JP-A-2-42441 (JP, A) JP-A-61- 272216 (JP, A) JP-A-1-240517 (JP, A) Masayoshi Oshima "New polyolefin resin for optical materials" Chemical Industry, February 1991, pp. 20-26.

Claims (5)

(57) [Claims] 1. A polarizing film for a liquid crystal display in which a thermoplastic saturated norbornene resin sheet having a number average molecular weight of 25,000 to 100,000 is laminated as a protective layer on at least one surface of a polarizing film. 2. The polarizing film for a liquid crystal display according to claim 1, wherein the thermoplastic saturated norbornene-based resin sheet is produced by a solution casting method. 3. The liquid crystal display according to claim 1, wherein an adhesive layer is laminated on one surface of the two protective layers laminated on both surfaces of the polarizing film or on a surface of the polarizing film on which the protective layer is not laminated. Polarizing film. 4. The polarizing film for a liquid crystal display according to claim 3, wherein a release film layer is laminated on the pressure-sensitive adhesive layer. 5. The method according to claim 1 , wherein at least one surface of the polarizing film is a thermoplastic resin.
Add the norbornene resin sheet to (1) vinyl chloride / vinegar
Acid vinyl copolymer adhesive, polyvinyl alkyl ether
Adhesive, polyacrylate adhesive, and modified poly
Adhesion selected from the group consisting of olefin resin adhesives
Agent or (2) polyurethane resin solution and polyisocyanate
Adhesion for dry lamination by mixing anate resin solution
Agent, styrene-butadiene rubber-based adhesive, and epoxy-based
Via an adhesive selected from the group consisting of two-component curing adhesives
2. The polarizing filter for a liquid crystal display according to claim 1, wherein the polarizing filter is laminated.
Lum.