WO1993002381A1

WO1993002381A1 - Polarizing film for liquid crystal display

Info

Publication number: WO1993002381A1
Application number: PCT/JP1992/000927
Authority: WO
Inventors: Nobukazu Takahashi; Tsutomu Hani; Tadao Natsuume; Rinjiro Ichikawa; Kenji Hashimoto
Original assignee: Nippon Zeon Co., Ltd.; Fujimori Kogyo Co., Ltd.
Priority date: 1991-07-22
Filing date: 1992-07-21
Publication date: 1993-02-04
Also published as: JP3297450B2; JPH0651117A

Abstract

A polarizing film for liquid crystal display, in which a thermoplastic saturated norbornane series resin sheet is laminated as a protective layer on at least one surface of said film. A polarizing film of this invention is excellent in waterproofness, moisture-proofness, physical strength, thermal resistance and transparency, and low in double refraction as well as strong in adhesion and durability to adhesives.

Description

Description Polarizing film for liquid crystal displays Technical field

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 formed of a thermoplastic saturated norbornene-based resin sheet. Background art

A liquid crystal display is generally composed of a liquid crystal cell, a polarizer, a reflector or a backlight. The liquid crystal cell is composed of two liquid crystal substrates, a spacer, a liquid crystal material, etc., provided with transparent electrodes on the inward surface of a transparent glass or plastic substrate, and the liquid crystal material is sealed between the two liquid crystal substrates. It is a structure that was given. Polarizers are arranged on both sides of a liquid crystal cell in the case of a normal TN type liquid crystal.

As the polarizer, a thin-film type polarizer (polarizing film) is used, and a protective layer made of various films is laminated on both sides with an adhesive to secure durability and mechanical strength. This laminate is called a polarizing film or a polarizing plate.

The polarizing film is attached to the liquid crystal substrate via a transparent acrylic adhesive or the like in order to prevent light reflection loss at the interface with the liquid crystal cell. Therefore, in ordinary polarizing films, an adhesive layer is provided on one side of the protective layer, and a release film (separator) is formed on the adhesive layer from the viewpoint of protection of 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 splits the incident light into two orthogonal polarization components,

-Has the function of absorbing or dispersing other components. For example, in the case of TN type liquid crystal, the absorption axes of two polarizing films are orthogonal When a liquid crystal cell with twisted alignment is interposed between them, the transmission or non-transmission of light is switched according to the presence or absence of an applied voltage, and the pattern is determined by the density ratio of the transmitted light between the orthogonal position and the parallel position. Is displayed. Therefore, the higher the polarization degree and the higher the transmittance, the better the performance.

In most recent liquid crystal displays, a polarizing film is used in which a transparent polymer film is arranged in a certain direction and a dichroic substance is adsorbed in the gaps of micelles. Typical examples of such a polarizing film include polyvinyl alcohol (hereinafter abbreviated as PVC), iodine-based, dye-based, PVA-, polyvinylene-based, and other PVC-based polarizing films, and polyene-based polarizing films.

However, many of these general-purpose polarizing films have low mechanical strength in the direction of the transmission axis, and also tend to shrink due to heat or moisture or deteriorate the polarizing function. . 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 with the adhesive, and excellent appearance are required. Conventionally, as the protective layer, a solution cast film of cellulose triacetate (hereinafter abbreviated as TAC) having good low birefringence and good appearance has been mainly used.

However, for example, the water vapor transmission rate of the PVC film constituting the polarizing substrate is 25 at a thickness of 25 im. C, in an environment of 90% RH, 100 000 ~: L 200 g / m ² · 24 hr, whereas the TAC film of the protective layer is 700 000 under the same conditions. It has a water vapor permeability of about g / m ² · 24 hr, and has insufficient moisture resistance. Therefore, a polarizing film using a TAC film as a protective layer has poor durability at high temperature and high humidity.For example, it deteriorates in 100 hours or less in an environment of 80% and 90% RH, and the polarizing performance is deteriorated. It drops sharply. TAC films also have insufficient gas barrier properties, and dichroic substances such as iodine and dyes are liable to be degraded by oxygen that has permeated. Further, since a TAC film contains a plasticizer for forming a film, the TAC film has insufficient heat resistance. Furthermore, the TAC film has a tensile strength of only about 6 to 11 kg / mm ^{2 and} lacks physical strength. Therefore, a TAC film having a thickness of 80 / m is generally used because its strength and durability are low at a thin film of 40 / m or less.

TAC film has a large photoelastic coefficient, so that birefringence tends to increase when external force is applied or when there is residual stress during molding. As a result, TAC films could only be produced by the solution casting method, which provides films with low birefringence and good appearance and low residual stress.

The polarizing film is laminated on a liquid crystal substrate, phase plate, etc. via an adhesive layer, but there is a problem in the adhesion between the TAC film and the adhesive. A bubble of air called a tunnel is likely to be generated. Further, when an adhesive layer containing acrylic acid is laminated on the TAC film, there is also a problem that the TAC film is decomposed by acrylic acid. Disclosure of the invention

An object of the present invention is to provide a polarizing film for a liquid crystal display having excellent water resistance, moisture resistance, physical strength, heat resistance, transparency, low birefringence, etc., excellent adhesiveness with an adhesive, and excellent durability against the adhesive. Is to provide. The present inventors have conducted intensive studies to overcome the problems of the prior art, and as a result, a polarizing film obtained by laminating a thermoplastic saturated norbornene-based resin sheet on at least one side of the polarizing film as a protective layer, The inventors have found that they have excellent properties as a polarizing film for liquid crystal displays, and have completed the present invention based on the findings.

Thus, the present invention is characterized in that a thermoplastically saturated norbornene-based resin sheet is laminated as a protective layer on at least one side of the polarizing film. A polarizing film for a liquid crystal display is provided. BEST MODE FOR CARRYING OUT THE INVENTION

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, an iodine-based polarizing film, a dye-based polarizing film in which a dichroic dye is adsorbed and oriented on a PVA-based film, a dehydration reaction is induced from a PVA-based film, and polyene is formed by a dehydrochlorination reaction of a polyvinyl chloride film. Examples thereof include a formed polyene-based polarizing film, a polarizing film having a dichroic dye on the surface and Z or inside of a PVA-based film made of a modified PVA containing a cationic group in a molecule.

The method for manufacturing the polarizing film is not particularly limited. For example, a method of stretching a PVA-based film and then adsorbing iodine ions, a method of stretching a PVA-based film after dyeing with a dichroic dye, a method of stretching a PVA-based film and dyeing it with a dichroic dye, a method of dichroic dye And a known method such as a method of printing a polymer on a PVA-based film and then stretching, and a method of stretching a PVA-based film and printing a dichroic dye. More specifically, iodine is dissolved in a potassium iodide solution to form higher-order iodine ions, and this ion is adsorbed on a PVA film and stretched, and then is added to a 1 to 4% aqueous boric acid solution. method for producing a polarizing film was immersed in a bath temperature 3 0 to 4 0 ^e C, there have is stretched degrees about 3-7 times in the uniaxial direction by likewise borated PVA film, 0.0 5 A method of manufacturing a polarizing film by immersing the dye in a 5% aqueous solution of dichroic dye at a bath temperature of 30 to 40 ° C. to adsorb the dye, drying at 80 to 100 °, and heat-setting to form a polarizing film. is there.

Thermoplastic saturated norportene resin

In the present invention, a sheet made of a thermoplastic saturated norbornene-based resin is laminated as a protective layer on one or both surfaces of the polarizing film. The thermoplastic saturated norbornene-based resin used in the present invention is known in JP-A-31-48882, JP-A-3-122213, JP-A-4-6387, and the like. A resin obtained by subjecting a ring-opened polymer of a norbornene-based monomer, a hydrogenated product thereof, or a ring-opened polymer of a norbornene-based monomer to polymer modification such as maleic acid addition or cyclopentadiene addition; Examples thereof include a hydrogenated product thereof, an addition polymer of a norbornene monomer, and an addition polymer of a norbornene monomer and olefin.

Norbornene-based monomers are also known in the above-mentioned publications such as Japanese Patent Application Laid-Open No. 2-227424 and Japanese Patent Application Laid-Open No. 2-276842, and examples thereof include norbornene dicyclopentadiene and dimethanooctane. Hydronaphthalene, their alkyl, alkylidene, or aromatic substitution derivatives, and their substituted or unsubstituted halogens, hydroxyl groups, ester groups, alkoxy groups, cyano groups, amide groups, and imide groups And a substituent of a polar group such as a silyl group.

More specifically, norbornene, 5-methyl-2-norbornene, 5-dimethyl-2-norbornene, 5-ethyl-2-norbornene, 5-butyl-2-norbornene, 5-ethylidene-2-norbornene, etc. Polar group substituents: dicyclopentadiene, 2,3-dihydroxycyclopentadiene, etc .; dimethanooctahydrodonaphthalene, its alkyl and Z or alkylidene substituents, and polar group substituents such as halogens, for example, 6-methyl- 1,4: 5,8—Dimethano 1,4,4a, 5,6,7,8,8a—Aged Kuta hydronaphthalene, 6—Ethyru 1,4: 5,8—Dimethano 1,4,4a, 5,6,7,8,8a—octahydronaphthalene, 6—ethylidene-1,4: 5,8—dimethanone 1,4,4a, 5,6 , 7,8,8a—Kuta Hydronaphta 1, 4-: 5,8-dimethano-1,4: 4a, 5,6,7,7,8,8a—Kuta hydronaphthalene, 6—Cyanore 1,4: 5 , 8—Dimethanone 1, 4, 4 a, 5, 6, 7, 8, 8 a—Oktahidronaphthalene, 6-pyridyl 1,: 5, 8—Dimetano 1, 4, 4 a, 5, 6, 7, 8, 8 a —Oktahi dolonaphthalene , 6-Methoxycarbone 1,4: 5,8-Dimethano 1,4,4a, 5,6,7,8,8a-year-old Kutahidronaphthalene, etc .; cyclopentadiene and tetrahydrodroindene Adducts with cyclopentadiene, such as 4,9: 5,8-dimethanol 3a, 4,4a, 5,8,8a, 9,9a-octahi Draw 1 H—Venzoindene, 4, 11: 5, 10: 6,9-trimethano 3a, 4, 4a, 5, 5a, 6, 9, 9a, 10, 10 a, 11 1, 11 a-dodecahydro draw 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 cycloolefins include, for example, compounds having one reactive double bond such as cyclopentene, cyclooctene, and 5,6-dihydroxycyclopentadiene. The thermoplastic saturated norbornene resin used in the present invention generally has a number average molecular weight of 25,000 to 100: 000, as measured by gel permeation chromatography (GPC) using a toluene solvent. It is preferably in the range of 30,000 to 800,000, more preferably in the range of 3,500 to 700,000. 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 rate is usually 90% or more from the viewpoint of heat deterioration resistance and light deterioration resistance. It is preferably at least 95%, more preferably at least 99%.

Thermoplastic saturated norbornene resins have excellent transparency, heat resistance, moisture resistance, physical strength, adhesion to adhesives, and durability to adhesives. A sheet with a thickness of 25 μm, the moisture absorption is usually 0.05% or less. Or properly is 0.0 1% or less, it can be water vapor permeability 2 5 ⁰ C \ 9 environment under RH 0% at ^{2 0 g / m 2 · 2} 4 hr following are obtained easily. Further, the photoelastic coefficient, for ^{^{3~ 9 X 1 0- 13 cm 2}} Z dyne and small, or an external force is applied, rather small impact on Retadeshiyo down even when residual stress, optically uniform film It is suitable for the production of The thermoplastic saturated norbornene-based resin used in the present invention may optionally contain various additives such as an antioxidant such as a fuanol-based or phosphorus-based antioxidant, an antistatic agent, and an ultraviolet absorber. In particular, liquid crystals are usually degraded by ultraviolet rays, so it is preferable to add an ultraviolet absorber if no other protective means such as laminating an ultraviolet protective filter is taken. As the ultraviolet absorber, a benzophenone-based ultraviolet absorber, a benzotriazole-based ultraviolet absorber, an attarylnitrile-based ultraviolet absorber, and the like can be used, and among them, a benzofuyunone-based ultraviolet absorber is preferable. The amount is usually 100 to 100,000 ppm, preferably 100 to 100, OOO ppm. When a sheet is prepared by a solution casting method, a leveling agent is preferably added to reduce the surface roughness. As the reppelling agent, for example, a replating agent for paints such as a fluorine-based nonionic surfactant, a special acrylic resin-based reppelling agent, and a silicone-based reppelling agent can be used. It is preferable to use those having good compatibility with the above, and the amount of addition is usually 5 to 50,000 ppm, preferably 10 to 20, ppm ppm.

Sheet molding

The protective layer used in the present invention is a sheet of a thermoplastic saturated norbornene-based resin. The sheet of the thermoplastic saturated norbornene resin as the protective layer is preferably prepared by a solution casting method.However, since the resin has a small photoelastic coefficient, unlike the case of the TAC, the sheet is formed by a melt molding method. Even if a sheet is manufactured, a sheet with sufficiently low 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 at least 10 ° C., more preferably 120. More than C is more preferable. In particular, a solvent capable of uniformly dissolving the thermoplastic saturated norbornene-based resin is preferable even when the solid content concentration is 10% by weight or more in 25.

Examples of such a solvent include toluene, xylene, ethylbenzene, benzene benzene, trimethylbenzene, ethynolbenzen, isopropylbenzene, benzene benzene and the like. Among them, xylene, ethylbenzene, chlorobenzene and the like are exemplified. Mouth benzene is preferred.

In addition, as long as the thermoplastic saturated norbornene resin is dissolved, these solvents may contain cyclic ethers such as cyclohexane, chloroform, benzene, tetrahydrofuran dioxane, or n-hexane or n-butyl ether. A linear hydrocarbon such as butane may be contained.

Those satisfying these conditions favorably include those containing 50% or more of an aromatic solvent such as xylene or ethylbenzene having a boiling point of 100 ° C. or more.

The resin concentration in the solution used for casting is usually 5 to 60% by weight, preferably 10 to 50% by weight, more preferably 20 to 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 property is poor because the viscosity is high, 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. Concretely, the resin solution is coated with a bar coater, T die, T die with bar, doctor knife, Meyer's bar, roll coat, die coat, etc., using a heat-resistant material such as polyethylene terephthalate, steel. A method of casting on a flat plate such as a belt or a metal foil or a roll can be used.

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

It is usually preferable to dry the sheets in two stages. First, as the first stage of drying, the residual solvent concentration is preferably 10% by weight or less in a temperature range of 30 to 100 ° C., preferably 40 to 80 ° C. Is dried to less than 5% by weight. In this case, if the drying temperature is too high, the sheet foams as the solvent evaporates.

Next, the sheet is peeled off from the flat plate or roll, and as a second stage of drying, the temperature is raised from room temperature to 60 or more, preferably 70 to a temperature range from the glass transition temperature (T g) of the resin, Dry until the residual solvent concentration is less than 2% by weight, preferably less than 1% by weight, more preferably less than 0.5% by weight.

If the drying temperature is too low, drying will not proceed, and if the temperature is too high, foaming will occur. After the first stage of drying, the sheet is peeled off from the flat plate or roll after drying is completed, and the second stage of drying is performed, or after the first stage of drying, the sheet is cooled and the sheet is flat or rolled. And a second drying step.

2. Melt molding method

In the case of producing a sheet by a melt molding method, there are a melt extrusion method such as a method using a T-die and an extrusion method, a calendar method, a hot press method, and an injection molding method. Among them, a melt extrusion method using a T-die, which has a small thickness unevenness, is easily processed to a thickness of about 10 to 500 m, and can reduce the absolute value of the retardation and its variation, is possible. I like it.

The conditions of the melt molding method are the same as the general conditions used for optical materials having the same glass transition temperature (T g). For example, in the melt extrusion method using a T-die, the resin sheet is set at a resin temperature of about 240 to 300, and the temperature of the take-up roll is set at a relatively high temperature of about 100 to 150 ° C. It is preferable to select conditions that allow for slow cooling. Also die In order to reduce surface defects such as lines, the die must have a structure that minimizes the stagnation area, and it is necessary to use a die or a lip that has as few scratches as possible. preferable.

Sheet

The thickness of the sheet is usually 5 to 500πι, preferably 10 to: 150μπι ^, and more preferably 20 to 100 # m. 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, a thickness of 80 m or more is usually required to provide sufficient moisture resistance and strength, whereas a thermoplastic norbornene-based resin sheet has a thickness of about 30 im. If it is thick, it can have moisture resistance, heat resistance, and strength equal to or higher than that of a TAC film with a thickness of 80 zm, and even if it is thin, it functions sufficiently as a protective layer and has good visual dependency. You.

The thickness unevenness of the sheet is within ± 5%, preferably ± 3%, more preferably ± 2% of the average thickness over the entire surface. If the sheet has a large uneven thickness, it may cause distortion of the image and dispersion of the retardation, and is not preferred 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, and more preferably 90% or more.

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

Polarizing film for liquid crystal display The liquid crystal display / polarizing film of the present invention is obtained by laminating a thermoplastic saturated norbornene resin sheet as a protective layer on at least one surface of the polarizing film. When a protective layer is provided on only one side, the polarizing film is protected from the humidity around the liquid crystal display. Therefore, in manufacturing a liquid crystal display, it is necessary to make the protective layer outside the optical film. However, protective layers are laminated on both sides to maintain the quality of the polarizing film before manufacturing the LCD, 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. It is preferable. A protective layer made of a conventionally known material may be provided on one side.

Lamination of a thermoplastic saturated norbornene-based resin sheet on a polarizing film is usually performed using an adhesive or an adhesive and by an adhesion method suitable for the adhesive or the adhesive.

As the pressure-sensitive adhesive, it is preferable to use a pressure-sensitive adhesive which has excellent transparency, small birefringence, etc., and which can sufficiently exhibit pressure-sensitive adhesive force even when used as a thin layer. Examples of such adhesives include natural rubber, synthetic rubber, elastomer, vinyl chloride / vinyl acetate copolymer, polyvinyl alkyl ether, polyacrylate, modified polyolefin resin adhesive, and the like. These include curable pressure-sensitive adhesives to which a curing agent such as an isocyanate is added. Among them, a curable pressure-sensitive adhesive is preferable among pressure-sensitive adhesives used for bonding a polyolefin foam or a polyester film.

Further, as the adhesive, an adhesive used for bonding polyethylene, polypropylene, or the like can be used for laminating a thermoplastic saturated norbornene-based resin sheet on a polarizing film. For example, an adhesive for dry laminating, which mixes a polyurethane resin solution and a polyisocyanate resin solution, a styrene-butadiene rubber-based adhesive, an epoxy-based two-liquid curing adhesive, for example, a two-liquid epoxy resin and polythiol And two-part epoxy resin and polyamide, especially solvent-based adhesives and epoxy two-part curing type. Adhesives are preferred, and transparent ones are preferred. 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.

Furthermore, in the case of a polarizing film mainly for a liquid crystal display, in order to improve the workability of laminating a liquid crystal substrate or a transparent electrode layer laminated on the liquid crystal substrate, when a protective layer is provided on both surfaces, the protective film is usually provided on one surface. However, when a protective layer is provided on one side, it is preferable to laminate an adhesive layer on the side having no protective layer.

As the pressure-sensitive adhesive, the pressure-sensitive adhesive described above 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 preferable. When an adhesive layer is provided, usually a release film such as release paper or a release film is further laminated on the surface of the liquid crystal display so that the polarizing film does not adhere to surroundings before manufacturing the liquid crystal display. It is preferable to keep it.

The appropriate thickness of the pressure-sensitive adhesive layer is usually 5 to 40 m.

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

Hereinafter, the present invention will be described more specifically with reference to Reference Examples, Examples, and Comparative Examples. However, the present invention is not limited to only these Examples. In the following examples, parts and percentages are by 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 the GPC method using toluene as a solvent.

(2) The hydrogenation rate was measured by ¹ H-NMR. (3) The glass transition temperature (T g) was measured by the DSC method.

(4) The retardation was measured with a Belek compensator with a wavelength of 55 Onm.

(5) The thickness of the sheet and film was measured using a dial-type thickness gauge.

(6) The light transmittance was measured with a spectrophotometer while continuously changing the wavelength in the wavelength range of 400 to 700 nm, and the minimum transmittance was defined as the light transmittance.

(7) The residual solvent concentration in the sheet was measured by gas chromatography at a temperature of 200 ° C.

Reference example 1

6-Methyl-1,4,5,8-dimethanone 1,4,4a, 5,6,7,8,8a-titahidronaphthalene (hereinafter abbreviated as MTD) and triethyl as a polymerization catalyst 10 parts of a 15% cyclohexane solution of aluminum, 5 parts of triethylamine, and 10 parts of a 20% cyclohexane solution of titanium tetrachloride were added, and ring-opening polymerization was performed in cyclohexane. The obtained ring-opened polymer was hydrogenated with a Nigel catalyst to obtain a polymer solution. This polymer solution was coagulated in isopropyl alcohol and dried to obtain a powdery resin. This resin had a number average molecular weight of 40,000, a hydrogenation ratio of 99.8% or more, and a Tg of 142 ° C. Example 1

Dissolve 15 g of the resin obtained in Reference Example 1 in 85 g of xylene, add 500 ppm of a leveling agent (Fluorard FC-430, Sumitomo 3LEM) and an ultraviolet stabilizer (Viosorb 80, Kyodo Pharmaceutical) After adding 300 ppm, a resin solution composition was obtained. This resin solution composition was spread on a glass plate whose surface was polished, and an appropriate amount was cast by a bar coater to a width of about 30 mm and a length of 500 mm. This was the first stage of drying, in which the glass plate was dried by raising the temperature from 20 to 50 ° C over 20 minutes in an air-circulating oven. Then, as the second stage of drying, The resin film was peeled off from the glass plate, dried for 30 minutes in an open at 90 ° C., cooled to room temperature, and a sheet of 10 mm in circumference was cut off to obtain a sheet. The residual solvent concentration of this sheet was 1.2% by weight.

The surface of the sheet was observed visually and with an optical microscope, but no foaming, streaks, or scratches were observed. T g is 13.8, average thickness is 80 / m, thickness unevenness is at most ± 4 / im or less, light transmittance is 91.0%, and absolute retardation value is 3 nm over the entire surface It was below. Water vapor permeability of this sheet is converted to a thickness of 2 5 ^e C, 9 in an environment of RH 0% 3. 0 g / m 2 · 2 4 hr (2 5 m to about 1 ² g 2 · 24 hr).

A styrene-butadiene rubber-based adhesive (S cotch 3M adhesive by application plastic, Sumitomo Sleam Co., Ltd.) is used on both sides of a PVA polarizing film (thickness of about 100 / ίπι) stretched by adsorbing iodine. An 80 m thick thermoplastic norbornene-based resin sheet was laminated as a protective layer.

Furthermore, it was laminated on a glass substrate with a thickness of 1.2 mm via an adhesive (Diabond DA735, manufactured by Nogawa Chemical) with a thickness of about 8 m on one side.

The heat cycle test was repeated 200 times for 1 hour at a humidity of 90%, a temperature of 80, 1 hour, and a temperature of 20 hours, but no abnormality was found.

Comparative Example 1

An 80 µm thick TAC sheet (water vapor transmission) was applied to both sides of the same polarizing film used in Example 1 using a dry laminating adhesive (AD-329 AZB, manufactured by Nogawa Chemical). The rate was 210 g / ^z · 24 hr) in a 25 ° C., 90% RH environment as a protective layer.

Furthermore, it was laminated on a glass substrate with a thickness of 1.2 mm via an adhesive (Diabond DA735) with a thickness of about 8 m on one side.

Humidity 90%, temperature 80 ^eC , 1 hour, temperature-20 ° C, 1 hour heat When the cycle test was repeated for 200 cycles, the degree of polarization was reduced to 50% or less, and bubbles called tunnels were 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 (Viosorb 80) 3 At 0 ppm, a resin solution composition was obtained. This resin solution composition was spread on a glass plate whose surface was polished, and an appropriate amount thereof was cast to a width of about 300 mm and a length of 500 mm using a bar coater. As a first-stage drying, the entire glass plate was dried by heating from 25 ° C. to 60 over 15 minutes in an air-flow oven. Next, as the second stage of drying, the resin film was peeled off from the glass plate, dried for 10 minutes by opening at 90, cooled to room temperature, and then cut around the width of 10 mm to obtain a sheet. Was. The residual solvent concentration of this sheet was below the measurement limit of 0.1% by weight.

The surface of the sheet was visually observed and observed with an optical microscope, but no bubbles, streaks, or scratches were observed. T g is 1339 ° C, average thickness is 30 m, thickness unevenness is at most ± 4 // m or less, light transmittance is 91.2%, absolute absolute value of letter value is 3 nm or less. This sheet has a water vapor permeability of 9.5 g / m ² · 24 hr (approx. 11 gZm ² · 24 hr in 25 / m thickness at 25 ° C and 90% RH). ) 7Z o

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

Furthermore, it was laminated on a glass substrate having a thickness of 1.2 mm via an adhesive (Diabond DA753) having a thickness of about 8 m on one side. Humidity 90%, temperature 80. The heat cycle test was repeated for 200 hours at C, 1 hour, and at a temperature of 20 ° C for 1 hour, but no abnormality was observed. Industrial applicability

According to the present invention, a polarizing film excellent in water resistance, moisture resistance, physical strength, heat resistance, transparency, low birefringence, adhesion to an adhesive, durability to an adhesive, and the like is provided. When the polarizing film of the present invention is laminated on a liquid crystal substrate or the like via an adhesive layer, bubbles are generated between the protective layer and the adhesive layer of the polarizing film because the protective layer and the adhesive layer are well adapted. Hateful. Further, 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 eroded by moisture due to its excellent moisture resistance, and the life is extended.

Therefore, the polarizing film of the present invention is very useful in the field of a liquid crystal display.

Claims

The scope of the claims

1. A polarizing film for liquid crystal displays, in which a thermoplastic saturated norbornene resin sheet is laminated on at least one side of the polarizing film as a protective layer.

2. The number average molecular weight of the thermoplastic saturated norbornene resin is 25, 0 0 0

2. The polarizing film for a liquid crystal display according to claim 1, wherein the thickness is in a range of 100 to 100,000.

3. The glass transition temperature of thermoplastic saturated norbornene resin is 90. 2. The polarizing film for a liquid crystal display according to claim 1, which is C or higher.

4. The polarizing film for a liquid crystal display according to claim 1, wherein the thickness of the thermoplastic saturated norbornene resin sheet is in the range of 5 to 500 / zm.

5. The polarizing film for a liquid crystal display according to claim 1, wherein the thickness unevenness of the thermoplastic saturated norbornene resin sheet is within 5% of the average thickness of the entire surface.

6. When the water vapor permeability of the thermoplastic saturated norbornene-based resin sheet is 25 zm and the sheet thickness is 25, measured at 90% RH, 20 g Z m ² 2. The polarizing film for a liquid crystal display according to claim 1, which is 24 hours or less.

7. The polarizing film for a liquid crystal display according to claim 1, wherein the light transmittance of the thermoplastic saturated norbornene resin sheet is 80% or more.

8. The polarizing film for a liquid crystal display according to claim 1, wherein the thermoplastic saturated norbornene-based resin sheet is manufactured by a solution casting method.

9. The polarizing film for a liquid crystal display according to claim 8, wherein the residual solvent concentration of the thermoplastic saturated norbornene resin sheet is 2% by weight or less.

10. The polarizing film for a liquid crystal display according to claim 1, wherein a thermoplastic saturated norbornene-based resin sheet is laminated on both surfaces of the polarizing film as a protective layer, and an adhesive layer is further laminated on the surface of one of the protective layers. .

10. The polarizing film for a liquid crystal display according to claim 10, wherein a release film layer is further laminated on the pressure-sensitive adhesive layer.