JP5228345B2 - Polarizing plate, elliptically polarizing plate, and liquid crystal display device - Google Patents

Description

  The present invention relates to a polarizing plate in which a protective film having a noise inside is laminated on at least one side of a polarizer. The present invention also relates to a light scattering elliptical polarizing plate and a liquid crystal display device using the polarizing plate.

  Liquid crystal display devices are used in various display devices by taking advantage of low power consumption, low voltage operation, light weight and thinness. The liquid crystal display device is composed of many materials such as a liquid crystal cell, a polarizing plate, a retardation film, a condensing sheet, a diffusion film, a light guide plate, and a light reflecting sheet. Therefore, improvements aimed at productivity, weight reduction, brightness improvement, and the like have been actively performed by reducing the number of constituent films or reducing the thickness of the film or sheet.

  Depending on the application, a product that can withstand severe durability conditions is required. For example, a liquid crystal display device for a car navigation system may have a high temperature and humidity in a vehicle in which the liquid crystal display device is placed, and the temperature and humidity conditions are severe compared to a monitor for a normal television or personal computer. For such applications, polarizing plates that are highly durable are also required.

  The polarizing plate usually has a structure in which transparent protective films are laminated on both sides or one side of a polarizer made of a polyvinyl alcohol resin to which a dichroic dye is adsorbed and oriented. The polarizer is manufactured by a method in which a polyvinyl alcohol-based resin film is subjected to longitudinal uniaxial stretching and dyeing with a dichroic dye, followed by boric acid treatment to cause a crosslinking reaction, followed by washing with water and drying. As the dichroic dye, iodine or a dichroic organic dye is used. A protective film is laminated on both or one side of the polarizer thus obtained to form a polarizing plate, which is incorporated into a liquid crystal display device. As the protective film, a cellulose acetate-based resin film typified by triacetylrose is often used, and the thickness thereof is usually about 30 to 120 μm. In addition, an adhesive composed of an aqueous solution of a polyvinyl alcohol-based resin is often used for laminating the protective film.

  A polarizing plate in which a protective film made of triacetyl cellulose is laminated on both sides or one side of a polarizer to which a dichroic dye is adsorbed and oriented via an adhesive made of an aqueous solution of a polyvinyl alcohol resin is long under wet heat conditions. When used for a long time, there are problems that the polarization performance is deteriorated and the protective film and the polarizer are easily peeled off.

  Therefore, there is an attempt to configure at least one protective film with a resin other than cellulose acetate. For example, in Japanese Patent Laid-Open No. 8-43812 (Patent Document 1), in a polarizing plate in which a protective film is laminated on both sides of a polarizer, at least one of the protective films is a thermoplastic norbornene-based having a retardation film function. It is described that it is made of resin. Japanese Patent Laid-Open No. 2002-174729 (Patent Document 2) includes an amorphous polyolefin resin on one surface of a polarizer composed of a polyvinyl alcohol resin film adsorbed and oriented with iodine or a dichroic organic dye. A protective film is laminated, and on the other surface, a polarizing plate is described in which a protective film made of a resin different from an amorphous polyolefin resin such as a cellulose acetate resin is laminated. Further, JP-A-2004-334168 (Patent Document 3) discloses a protection comprising a cycloolefin resin via a polyvinyl alcohol polarizer and an adhesive containing a urethane adhesive and a polyvinyl alcohol resin. Laminating films is described.

  However, amorphous polyolefin-based resins (cycloolefin-based resins) such as norbornene-based resins are recently put into practical use and are generally expensive. Amorphous polyolefin resins are easily eroded by organic solvents such as acetone, toluene, and ethyl acetate. These organic solvents are used for the preparation of the pressure-sensitive adhesive and may remain therein.

  In the liquid crystal display device, a light diffusing sheet or a light diffusing adhesive may be used for the purpose of eliminating moire fringes due to interference derived from the module. For example, Japanese Patent Laid-Open No. 9-230345 (Patent Document 4) discloses a diffusion surface composed of one or two or more superposed bodies of plastic films, and at least one of the films is formed of fine irregularities on one or both sides. In addition, there is disclosed a diffusion plate that has a phase difference substantially zero in the plate surface and exhibits a phase difference in an inclination direction with respect to the plate surface. Japanese Patent Application Laid-Open No. 2000-75132 (Patent Document 5) discloses a scattering elliptical polarizing plate having a polarizing plate, a retardation plate, and a scattering layer having a haze of 20 to 80%. It is described that the layer can be composed of a pressure-sensitive adhesive containing fine particles having different refractive indexes.

  However, with the configuration using the light diffusion sheet, it is difficult to cope with the trend of thinning required in recent small and medium-sized applications. In the configuration using a light diffusion adhesive, the original adhesive strength of the adhesive is reduced by dispersing fine particles, and peeling progresses between the layers of the bonded product in a durability test, particularly a heat shock test. It is difficult to follow the high durability required for recent small and medium-sized applications.

JP-A-8-43812 JP 2002-174729 A JP 2004-334168 A JP-A-9-230345 JP 2000-75132 A

  The present inventors paid attention to the fact that propylene-based resins known as inexpensive industrial materials are generally crystalline, and used to cool a molten film extruded from a T-die when manufacturing the film. It has been found that by controlling the temperature of the roll to be controlled, the noise inside the propylene-based resin film can be controlled uniformly and freely within the surface. Moreover, in the polarizing plate in which the protective film is laminated on both surfaces of the polarizer composed of the polyvinyl alcohol resin film in which the dichroic dye is adsorbed and oriented, when the propylene resin film is used as at least one protective film, It has been found that moire fringes and Newton rings due to module-derived interference can be effectively eliminated, and that a remarkable thinning can be achieved.

  Furthermore, in the polarizing plate using this propylene-based resin film, since it is not necessary to use a diffusion adhesive in which fine particles are dispersed in the adhesive, the original adhesive strength of the adhesive can be obtained by using a transparent adhesive. In the durability test, particularly the heat shock test, it was found that the delamination of the bonded product due to insufficient adhesive force did not occur. Furthermore, since the propylene-based resin film has low moisture permeability, it has also been found that the hue change is reduced even under wet heat conditions compared to a polarizing plate in which a conventional cellulose acetate-based resin film is laminated on both sides of a polarizer. It was. Thus, by using a propylene-based resin film having a predetermined internal haze as a protective film for at least one of the polarizers, it is possible to simultaneously achieve thinning and high durability. The present invention has been completed based on such findings.

  Accordingly, one of the objects of the present invention is to provide a polarizing plate in which a protective film is laminated on both sides of a polarizer on which a dichroic dye is adsorbed and oriented. By comprising a resin film having a haze inside, it is possible to effectively eliminate moire fringes and Newton rings due to module-derived interference, and to provide a polarizing plate that satisfies thinning and high durability at low cost. . Another object of the present invention is to apply this polarizing plate to an elliptical polarizing plate and further to a liquid crystal display device.

That is, according to the present invention, a protective film is laminated on both sides of a polarizer composed of a polyvinyl alcohol-based resin film on which a dichroic dye is adsorbed and oriented, and the polarizing plate is used by being attached to a liquid crystal cell. At least one of the protective film is made of propylene-based resin, have a size to the interior of 5-50% based on the crystal, the case of bonding the rear side of the liquid crystal cell, a propylene-based resin having an internal haze protective film made is arranged to be on the opposite side of the liquid crystal cell, the case of bonding the front side of the liquid crystal cell, the polarizing plate protective film made of a propylene resin is Ru is arranged so that the liquid crystal cell side having an internal haze Provided.

This polarizing plate may take a form in which a protective film made of a propylene resin having the above internal haze is laminated on one side of a polarizer and a protective film made of a resin other than the propylene resin is laminated on the other side. it can. In this case, the resin other than the propylene resin is advantageously composed of a cellulose acetate resin such as triacetyl cellulose. These polarizing plates can be made into a polarizing plate with an adhesive by forming an adhesive layer on the outside of the protective film bonded to the liquid crystal cell .

Moreover, according to this invention, the elliptical polarizing plate by which the phase difference plate is bonded to said polarizing plate is also provided. The retardation plate in this case can be composed of, for example, a quarter wavelength plate alone, or a half wavelength plate and a quarter wavelength plate are laminated in this order from the polarizing plate side. It can also be configured. Also in these elliptically polarizing plates, an adhesive layer can be formed on the outside of the polarizing plate bonded to the liquid crystal cell or on the outside of the retardation plate to obtain an elliptically polarizing plate with an adhesive.

  Furthermore, according to this invention, the liquid crystal display device by which said polarizing plate with an adhesive or an elliptically polarizing plate with an adhesive is bonded to the liquid crystal cell by the adhesive layer side is also provided.

  The polarizing plate of the present invention is a protective film made of an acetylcellulose-based resin on both sides of a polarizer by constituting a protective film disposed on at least one surface of the polarizer with a propylene-based resin having a predetermined internal noise. Compared with a polarizing plate in which is laminated, moire fringes and Newton rings derived from modules can be effectively erased. Moreover, since it is not necessary to laminate | stack a light-diffusion sheet separately, thickness reduction as the whole optical film bonded together to a liquid crystal cell can be achieved. Furthermore, even in durability tests such as a heat shock test and a moist heat resistance test, delamination and hue change of the bonded product do not occur, and the durability performance is excellent.

  The elliptically polarizing plate of the present invention is obtained by bonding a retardation plate to the above polarizing plate, which can effectively eliminate the moire fringes and Newton rings derived from the module, and the entire optical film bonded to the liquid crystal cell. As a result, the thickness can be reduced, and the durability is excellent. The liquid crystal display device of the present invention is a combination of the above polarizing plate or elliptically polarizing plate with a liquid crystal cell, and also exhibits the same effect.

  Hereinafter, the present invention will be described in detail. The polarizing plate of the present invention is obtained by laminating protective films on both sides of a polarizer, and at least one of the protective films is composed of a propylene-based resin having a predetermined interior.

[Polarizer]
The polarizer is obtained by adsorbing and orienting a dichroic dye on a polyvinyl alcohol-based resin film to develop predetermined polarization characteristics. As the dichroic dye, iodine or a dichroic organic dye is used. Therefore, specific examples of the polarizer include an iodine polarizing film in which iodine is adsorbed and oriented on a polyvinyl alcohol resin film, and a dye polarizing film in which a dichroic organic dye is adsorbed and oriented on a polyvinyl alcohol resin film. Can do.

  The polyvinyl alcohol resin can be obtained by saponifying a polyvinyl acetate resin. Examples of the polyvinyl acetate resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerized with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. The polyvinyl alcohol-based resin may be modified, and for example, polyvinyl formal, polyvinyl acetal, polyvinyl butyral and the like modified with aldehydes may be used.

  The polarizing plate is usually a humidity adjusting step for adjusting the moisture of the polyvinyl alcohol-based resin film, a step for uniaxially stretching the polyvinyl alcohol-based resin film, and the dichroic pigment by dyeing the polyvinyl alcohol-based resin film with a dichroic pigment. The process of adsorbing, the process of treating the polyvinyl alcohol resin film with the dichroic dye adsorbed and oriented with the boric acid aqueous solution, the washing process of washing off the boric acid aqueous solution, and the dichroic dye being adsorbed and oriented by these steps It is manufactured through a process of pasting a protective film on the uniaxially stretched polyvinyl alcohol resin film. Uniaxial stretching may be performed before dyeing, may be performed during dyeing, or may be performed during boric acid treatment after dyeing. Moreover, it may be uniaxially stretched in these multiple stages. For uniaxial stretching, rolls having different peripheral speeds may be uniaxially stretched or uniaxially stretched using a hot roll. Moreover, the dry-type extending | stretching which extends | stretches in air | atmosphere may be sufficient, and the wet extending | stretching which extends | stretches in the state swollen with the solvent may be sufficient. The draw ratio is usually about 4 to 8 times. The thickness of the polyvinyl alcohol polarizer is, for example, about 5 to 50 μm.

[Propylene resin]
In the present invention, a protective film is laminated on both surfaces of such a polyvinyl alcohol-based polarizer, and at least one of the protective films is made of a propylene-based resin having a predetermined interior. A propylene resin is a polymer composed mainly of propylene units, and generally exhibits crystallinity. In addition to a propylene homopolymer, propylene is a copolymer of unsaturated hydrocarbons such as other olefins. It may be a polymer. From the viewpoint of improving processability, it is preferable to use a random copolymer of propylene as a main component and any unsaturated hydrocarbon. Among these, a copolymer with ethylene is preferable.

  The propylene-based resin can be produced by a method of homopolymerizing propylene using a known polymerization catalyst or a method of copolymerizing propylene and another copolymerizable comonomer. Examples of known polymerization catalysts include the following.

(1) Ti—Mg-based catalyst comprising a solid catalyst component containing magnesium, titanium and halogen as essential components,
(2) a catalyst system in which a solid catalyst component containing magnesium, titanium and halogen as essential components is combined with an organoaluminum compound and, if necessary, a third component such as an electron donating compound,
(3) Metallocene catalysts.

  Among these catalyst systems, in the production of the propylene-based resin used in the present invention, the combination of an organic aluminum compound and an electron donating compound with a solid catalyst component containing magnesium, titanium and halogen as essential components is the most common. Can be used. More specifically, the organoaluminum compound is preferably triethylaluminum, triisobutylaluminum, a mixture of triethylaluminum and diethylaluminum chloride, tetraethyldialumoxane, etc., and the electron donating compound is preferably cyclohexylethyldimethoxysilane. Tert-butylpropyldimethoxysilane, tert-butylethyldimethoxysilane, dicyclopentyldimethoxysilane and the like.

  On the other hand, examples of the solid catalyst component containing magnesium, titanium and halogen as essential components include the catalysts described in JP-A-61-218606, JP-A-61-287904, JP-A-7-216017, and the like. Examples of the metallocene catalyst include the catalyst systems described in Japanese Patent No. 2587251, Japanese Patent No. 2627669, Japanese Patent No. 2668732 and the like.

  The propylene resin is, for example, a solution polymerization method using an inert solvent typified by a hydrocarbon compound such as hexane, heptane, octane, decane, cyclohexane, methylcyclohexane, benzene, toluene, xylene, or a liquid monomer as a solvent. It can be produced by a bulk polymerization method or a gas phase polymerization method in which a gaseous monomer is polymerized as it is. Polymerization by these methods may be carried out batchwise or continuously.

  The stereoregularity of the propylene-based resin may be any of isotactic, syndiotactic, and atactic. In the present invention, a syndiotactic or isotactic propylene resin is preferably used from the viewpoint of heat resistance.

  The propylene-based resin used in the present invention can be composed of a homopolymer of propylene, and a small amount of a comonomer mainly composed of propylene and composed of unsaturated hydrocarbons copolymerizable therewith, for example, a ratio of 10% by weight or less. Copolymerized with

  The comonomer copolymerized with propylene can be, for example, ethylene or an α-olefin having 4 to 20 carbon atoms. Specific examples of the α-olefin in this case include the following.

1-butene, 2-methyl-1-propene (above C ₄ );
1-pentene, 2-methyl-1-butene, 3-methyl-1-butene (above C ₅ );
1-hexene, 2-ethyl-1-butene, 2,3-dimethyl-1-butene, 2-methyl-1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 3,3- Dimethyl-1-butene (above C ₆ );
1-heptene, 2-methyl-1-hexene, 2,3-dimethyl-1-pentene, 2-ethyl-1-pentene, 2-methyl-3-ethyl-1-butene (above C ₇ );
1-octene, 5-methyl-1-heptene, 2-ethyl-1-hexene, 3,3-dimethyl-1-hexene, 2-methyl-3-ethyl-1-pentene, 2,3,4-trimethyl- 1-pentene, 2-propyl-1-pentene, 2,3-diethyl-1-butene (above C ₈ );
1-nonene (C ₉ ); 1-decene (C ₁₀ ); 1-undecene (C ₁₁ );
1-dodecene (C ₁₂ ); 1-tridecene (C ₁₃ ); 1-tetradecene (C ₁₄ );
1-pentadecene (C ₁₅ ); 1-hexadecene (C ₁₆ ); 1-heptadecene (C ₁₇ );
1-octadecene (C ₁₈ ); 1-nonadecene (C ₁₉ ) and the like.

Preferred among the α-olefins are α-olefins having 4 to 12 carbon atoms, specifically 1-butene, 2-methyl-1-propene; 1-pentene, 2-methyl-1- Butene, 3-methyl-1-butene; 1-hexene, 2-ethyl-1-butene, 2,3-dimethyl-1-butene, 2-methyl-1-pentene, 3-methyl-1-pentene, 4- Methyl-1-pentene, 3,3-dimethyl-1-butene; 1-heptene, 2-methyl-1-hexene, 2,3-dimethyl-1-pentene, 2-ethyl-1-pentene, 2-methyl- 3-ethyl-1-butene; 1-octene, 5-methyl-1-heptene, 2-ethyl-1-hexene, 3,3-dimethyl-1-hexene, 2-methyl-3-ethyl-1-pentene,
2,3,4-trimethyl-1-pentene, 2-propyl-1-pentene, 2,3-diethyl-1-butene; 1-nonene; 1-decene; 1-undecene; 1-dodecene and the like. it can. From the viewpoint of copolymerizability, 1-butene, 1-pentene, 1-hexene and 1-octene are preferable, and 1-butene and 1-hexene are more preferable.

  The copolymer may be a random copolymer or a block copolymer. Preferred copolymers include propylene / ethylene copolymers and propylene / 1-butene copolymers. In the propylene / ethylene copolymer and the propylene / 1-butene copolymer, the ethylene unit content and the 1-butene unit content are, for example, 616 of “Polymer Analysis Handbook” (published by Kinokuniya, 1995). Infrared (IR) spectrum measurement can be performed by the method described on the page.

  From the viewpoint of increasing the workability of the polarizing plate as a protective film, it is preferable to use propylene as a main component and a random copolymer with any unsaturated hydrocarbon. Among these, a copolymer with ethylene is preferable. When making it into a copolymer, it is advantageous that unsaturated hydrocarbons other than propylene have a copolymerization ratio of about 1 to 10% by weight, and a more preferable copolymerization ratio is 3 to 7% by weight. By setting the unit of unsaturated hydrocarbons other than propylene to 1% by weight or more, the effect of improving workability tends to appear. However, if the ratio exceeds 10% by weight, the melting point of the resin tends to decrease and the heat resistance tends to deteriorate, so the copolymerization ratio of other unsaturated hydrocarbons is preferably limited to about 10% by weight. . In addition, when setting it as the copolymer of 2 or more types of comonomers and propylene, it is preferable that the total content of the unit derived from all the comonomer contained in the copolymer is the said range.

  As the propylene-based resin in the present invention, if the above-described propylene-derived unit is a random copolymer or propylene homopolymer of 90% by weight or more and less than 100% by weight, the molecular weight or the constituent ratio of the constituent unit derived from propylene Two or more kinds of polymers having different tacticities may be blended.

  In accordance with JIS K 7210, the propylene resin used in the present invention has a melt flow rate (MFR) measured at a temperature of 230 ° C. and a load of 21.18 N of 0.1 to 200 g / 10 minutes, especially 0.5. It is preferably in the range of ˜50 g / 10 minutes. By using a propylene resin having an MFR in this range, a uniform film can be obtained without imposing a large load on the extruder.

  The propylene-based resin may be blended with known additives as long as the effects of the present invention are not impaired. Examples of the additive include an antioxidant, an ultraviolet absorber, an antistatic agent, a lubricant, a nucleating agent, an antifogging agent, and an antiblocking agent. Antioxidants include, for example, phenolic antioxidants, phosphorus antioxidants, sulfur antioxidants, hindered amine light stabilizers, etc., and, for example, a phenolic antioxidant mechanism in one molecule A composite antioxidant having a unit having a phosphorus-based antioxidant mechanism can also be used. Examples of the UV absorber include UV absorbers such as 2-hydroxybenzophenone and hydroxyphenylbenzotriazole, and benzoate UV blockers. The antistatic agent may be polymer type, oligomer type or monomer type. Examples of the lubricant include higher fatty acid amides such as erucic acid amide and oleic acid amide, higher fatty acids such as stearic acid, and salts thereof. Examples of the nucleating agent include sorbitol nucleating agents, organophosphate nucleating agents, and polymer nucleating agents such as polyvinylcycloalkane. As the anti-blocking agent, fine particles having a spherical shape or a shape close thereto can be used regardless of inorganic type or organic type. A plurality of these additives may be used in combination.

[Propylene resin film]
As the protective film disposed on at least one surface of the polarizer, in the present invention, as described above, a propylene-based resin film having an internal haze of 5 to 50% is employed. The internal haze is a numerical value represented by (diffuse light transmittance / total light transmittance) × 100 (%), and can be measured according to JIS K 7105. A method for developing such an internal haze is not particularly limited, but a molten film of a propylene-based resin extruded from a T-die of an extruder is pressed in a circumferential direction of a metal cooling roll and the metal cooling roll. Thus, it is possible to advantageously employ a method of cooling and solidifying by pressing with a touch roll including an elastic body that rotates. By controlling the cooling rate at this time, specifically the temperature of the cooling roll, a propylene-based resin film having an arbitrary internal haze can be obtained.

  The propylene-based resin is melt-kneaded by rotation of a screw in an extruder and extruded from a T-die as a molten film. The temperature of the molten film is, for example, about 180 to 300 ° C, and preferably 240 to 280 ° C. If the temperature of the molten film at this time is lower than 180 ° C., the spreadability is not sufficient, and the final film thickness may be nonuniform. Further, when the temperature exceeds 300 ° C., the resin is likely to be deteriorated or decomposed, and there is a possibility that bubbles or carbides are generated in the film or gel is generated.

  The extruder may be a single screw extruder or a twin screw extruder. For example, in the case of a single screw extruder, L / D, which is the ratio of the screw length L to the diameter D, is about 24 to 36, the screw groove space volume in the resin supply unit, and the screw groove space volume in the resin metering unit The compression ratio, which is the ratio (the former / the latter), is about 1.5 to 4, and a screw such as a full flight type, a barrier type, and a type having a Maddock type kneading portion can be used. From the viewpoint of suppressing deterioration and decomposition of the propylene-based resin and uniformly melting and kneading, it is necessary to use a barrier type screw having an L / D of 28 to 36 and a compression ratio of 2.5 to 3.5. preferable. Moreover, in order to suppress deterioration and decomposition | disassembly of propylene-type resin as much as possible, it is preferable to make the inside of an extruder into nitrogen atmosphere or a vacuum. Furthermore, in order to remove the volatile gas generated by the deterioration or decomposition of the propylene-based resin, it is also preferable to provide an orifice of 1 mmφ to 5 mmφ at the tip of the extruder to increase the resin pressure at the tip of the extruder. Increasing the resin pressure at the tip of the extruder at the orifice means increasing the back pressure at the tip, thereby improving the stability of extrusion. The diameter of the orifice to be used is more preferably 2 mmφ or more and 4 mmφ or less.

  The T die used for extrusion preferably has no fine steps or scratches on the surface of the resin flow path, and its lip portion is plated or coated with a material having a low coefficient of friction with the molten propylene resin, Further, a lip tip having a sharp edge shape polished to 0.3 mmφ or less is preferable. Examples of the material having a small friction coefficient include tungsten carbide type and fluorine type special plating. By using such a T-die, it is possible to suppress the generation of eyes and simultaneously suppress the die line, so that a resin film having excellent appearance uniformity can be obtained. In the T-die, the manifold has a coat hanger shape and preferably satisfies the following condition (1) or (2), and more preferably satisfies the condition (3) or (4).

When the lip width of the T die is less than 1500 mm: length in the thickness direction of the T die> 180 mm (1)
When the lip width of the T die is 1500 mm or more: length of the T die in the thickness direction> 220 mm (2)
When the lip width of the T die is less than 1500 mm: Length in the height direction of the T die> 250 mm (3)
When the lip width of the T die is 1500 mm or more: Length in the height direction of the T die> 280 mm (4)

  By using a T die that satisfies such conditions, the flow of the molten propylene-based resin inside the T die can be adjusted, and the lip portion can be extruded while suppressing thickness unevenness, so that the thickness is increased. A film with excellent accuracy and more uniform internal haze can be obtained.

  From the viewpoint of suppressing the extrusion fluctuation of the propylene-based resin, it is preferable to attach a gear pump via an adapter between the extruder and the T die. In addition, it is preferable to attach a leaf disk filter to remove foreign substances in the propylene-based resin.

  The molten film extruded from the T-die is between a metal cooling roll (also referred to as a chill roll or a casting roll) and a touch roll including an elastic body that rotates by pressing in the circumferential direction of the metal cooling roll. The film which has a desired inside can be obtained by making it pinch and cooling and solidifying. The touch roll may be one in which an elastic body such as rubber is used as it is, or may be one in which the surface of the elastic roll is covered with an outer cylinder made of a metal sleeve. When using a touch roll in which the surface of the elastic roll is covered with an outer cylinder made of a metal sleeve, the molten film of propylene-based resin is directly sandwiched between the metal cooling roll and the touch roll for cooling. On the other hand, in the case of using a touch roll whose surface is an elastic body, a biaxially stretched film of a thermoplastic resin can be interposed between the melted film of the propylene resin and the touch roll to sandwich the pressure.

  In order to cool and solidify the molten film of propylene-based resin between the cooling roll and the touch roll as described above, the cooling roll preferably has its surface temperature adjusted to 25 ° C. or more and 120 ° C. or less, The surface temperature of the touch roll is preferably adjusted to 25 ° C. or higher. When the surface temperature of each of these rolls is less than 25 ° C., the molten sheet is quickly cooled and solidified, so that the crystal component in the propylene-based resin does not grow sufficiently, the resulting film becomes transparent, and the internal haze Becomes difficult to express. The surface temperature of the cooling roll and the touch roll is preferably 30 ° C. or higher. On the other hand, when the surface temperature of the metallic cooling roll exceeds 120 ° C., it becomes close to the crystalline melting point of the propylene-based resin, so that it tends to be difficult to handle as a film.

  Since the surface state of the metal cooling roll to be used is transferred to the surface of the propylene-based resin film, if the surface is uneven, the thickness accuracy of the resulting propylene-based resin film is reduced, and the internal The uniformity of haze may be impaired. Therefore, it is preferable that the surface of the metal cooling roll is in a mirror surface state as much as possible. Specifically, the roughness of the surface of the metal cooling roll is preferably 0.3 S or less, more preferably 0.1 S to 0.2 S, expressed in the standard sequence of the maximum height. .

  The touch roll forming the nip portion with the metal cooling roll has a surface hardness of 65 to 80 as a value measured by a spring type hardness test (A type) defined in JIS K 6301. Is more preferable, and 70 to 80 is more preferable. By using a rubber roll having such a surface hardness, it is easy to maintain a uniform linear pressure applied to the molten film, and a molten sheet bank (resin pool) is interposed between the metal cooling roll and the touch roll. ) Can be easily formed into a film.

  The pressure (linear pressure) when sandwiching the molten film is determined by the pressure for pressing the touch roll against the metal cooling roll. The linear pressure is preferably 50 N / cm or more and 300 N / cm or less, and more preferably 100 N / cm or more and 250 N / cm or less. By setting the linear pressure within the above range, it becomes easy to produce a propylene-based resin film while maintaining a constant linear pressure without forming a bank.

  When a biaxially stretched film of a thermoplastic resin is sandwiched between a metal cooling roll and a touch roll together with a molten film of a propylene resin, the thermoplastic resin constituting the biaxially stretched film is strong with the propylene resin. Any resin may be used as long as it is not heat-sealed, and specific examples include polyester, polyamide, polyvinyl chloride, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, and polyacrylonitrile. Among these, polyesters that have little dimensional change due to humidity, heat, and the like are most preferable.

  In this method, the distance (air gap) from the lip of the T die to the pressure between the metal cooling roll and the touch roll is preferably 200 mm or less, and more preferably 160 mm or less. The molten film extruded from the T-die is stretched between the lip and the roll, and orientation is likely to occur. By shortening the air gap as described above, a film having a smaller orientation can be obtained. The lower limit value of the air gap is determined by the diameter of the metal cooling roll to be used, the diameter of the touch roll, and the tip shape of the lip to be used, and is usually 50 mm or more.

  The processing speed when producing a propylene-based resin film by this method is determined by the time required for cooling and solidifying the molten film. When the diameter of the metal cooling roll to be used is increased, the distance at which the molten film is in contact with the cooling roll becomes longer, so that production at a higher speed becomes possible. Specifically, when a 600 mmφ metal cooling roll is used, the processing speed is about 5 to 20 m / min at the maximum.

  The molten film sandwiched between the metal cooling roll and the touch roll is cooled and solidified by contact with the roll. And after slitting an edge part as needed, it is wound up by a winder and becomes a propylene-based resin film having internal haze. Under the present circumstances, in order to protect the surface until a propylene-type resin film is used, you may wind up in the state which bonded the surface protection film which consists of another thermoplastic resin to the single side | surface or both surfaces. When a molten film of propylene-based resin is sandwiched between a metal cooling roll and a touch roll together with a biaxially stretched film made of a thermoplastic resin, the biaxially stretched film is used as one surface protective film. You can also.

  The propylene-based resin film used in the present invention preferably has a thickness of usually 5 μm to 200 μm, more preferably 10 μm to 150 μm. If the thickness is too large, the polarizing plate using it as a protective film will also become thick, and when the film is produced by the above method, the cooling efficiency by the roll is not sufficient, and the resulting film has a uniform inside May not be shown. On the other hand, when the thickness of the propylene-based resin film is too small, it is difficult to handle the laminated film on the polarizer, and the function of the polarizer as a protective film may not be sufficiently exhibited.

  In the present invention, when the polarizing plate is applied to a liquid crystal display device, the elements of the visual characteristics such as brightness, whiteness, resolution, and viewing angle are arranged side by side, and their overall balance is harmonized to achieve good visual recognition. From the viewpoint of obtaining properties, the propylene-based resin film laminated on at least one surface of the polarizer is composed of a film having a noise value of 5 to 50%. This internal haze value is preferably 10 to 40%. In the region where the internal haze is larger than 50%, the incident light can be sufficiently diffused and interference fringes such as Newton's rings can be eliminated. However, the display is blurred, the resolution is lowered, and a pair of transmitted light and reflected light is paired. It becomes difficult to control the crossed Nicols relationship through the polarizing plate, or the front contrast is lowered. On the other hand, if the internal haze value is less than 5%, incident light cannot be sufficiently diffused, resulting in poor brightness and whiteness, or interference fringes cannot be completely eliminated. Further, the in-plane variation of the haze value is preferably within ± 10% from the center value.

  The protective film made of a propylene-based resin having an internal haze used here has substantially no in-plane retardation, and the in-plane retardation is usually 10 nm or less, preferably 5 nm or less. For example, as described above, a propylene-based resin film having substantially no in-plane retardation is obtained by a method of cooling and solidifying by sandwiching between a metal cooling roll and a touch roll including an elastic body after melt extrusion. Can be obtained.

[Polarizer]
It is good also as a polarizing plate by laminating | stacking the protective film which consists of propylene-type resin on both surfaces of a polyvinyl alcohol-type polarizer. In this case, both sides may be composed of a protective film made of a propylene-based resin having internal haze, or a protective film made of a propylene-based resin having internal haze is laminated on one side and the other side is substantially internal. A protective film made of a transparent propylene-based resin having no haze may be laminated.

  On the other hand, it is also effective to laminate a protective film made of a propylene-based resin having an inside to one side and to laminate a protective film made of a resin other than propylene-based on the other side. Examples of resins other than propylene-based resins include cellulose acetate-based resins such as triacetyl cellulose and diacetyl cellulose, polyester-based resins, acrylic resins, and polycarbonate-based resins. Considering the ease of adhesion with the polarizer and the ease of forming the surface treatment layer, a cellulose acetate resin film, particularly a triacetyl cellulose film is preferably used. When using a cellulose acetate resin film as one protective film, it is desirable to saponify the surface with an alkaline aqueous solution prior to bonding with a polarizer. The thickness of the protective film made of a resin other than propylene is usually about 10 to 200 μm, preferably 10 to 120 μm, and more preferably 10 to 85 μm. You may have various surface treatment layers, such as an antireflection layer and a glare-proof layer, in the surface of the protective film on the side different from the surface bonded to a liquid crystal cell.

[Adhesion between polarizer and propylene-based protective film]
For adhesion between a polarizer and a protective film made of a propylene-based resin, for example, an adhesive containing an epoxy-based resin, a urethane-based resin, a cyanoacrylate-based resin, an acrylamide-based resin, or the like can be used. A preferable adhesive from the viewpoint of thinning the adhesive layer includes an aqueous adhesive, that is, an adhesive component dissolved in water or dispersed in water. Another preferred adhesive is a solventless adhesive, specifically, an adhesive layer that is formed by reacting and curing a monomer or oligomer by heating or irradiation with an active energy ray.

  First, the water-based adhesive will be described. Examples of the adhesive component that can be a water-based adhesive include water-soluble crosslinkable epoxy resins and urethane resins.

  Examples of water-soluble crosslinkable epoxy resins are obtained by reacting epichlorohydrin with a polyamide polyamine obtained by reacting a polyalkylene polyamine such as diethylenetriamine or triethylenetetramine with a dicarboxylic acid such as adipic acid. The polyamide epoxy resin which can be mentioned can be mentioned. Examples of such commercially available polyamide epoxy resins include “Smiles Resin 650” and “Smiles Resin 675” sold by Sumika Chemtex Co., Ltd.

  When a water-soluble epoxy resin is used as the adhesive component, it is preferable to mix other water-soluble resins such as a polyvinyl alcohol-based resin in order to further improve coatability and adhesiveness. Polyvinyl alcohol resins are modified such as partially saponified polyvinyl alcohol and fully saponified polyvinyl alcohol, as well as carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, methylol group-modified polyvinyl alcohol, and amino group-modified polyvinyl alcohol. Polyvinyl alcohol resin may be used. Among them, a saponified product of a copolymer of vinyl acetate and unsaturated carboxylic acid or a salt thereof, that is, carboxyl group-modified polyvinyl alcohol is preferably used. Here, the “carboxyl group” is a concept including —COOH and a salt thereof.

  Examples of suitable commercially available carboxyl group-modified polyvinyl alcohols include, for example, “Kuraraypoval KL-506”, “Kuraraypoval KL-318” and “Kuraraypoval KL-118” sold by Kuraray Co., Ltd. “GOHSENAL T-330” and “GOHSENAL T-350” sold by Nippon Synthetic Chemical Industry Co., Ltd. “DR-0415” sold by Denki Kagaku Kogyo Co., Ltd. Examples include “AF-17”, “AT-17”, and “AP-17” sold by Co., Ltd.

  When an adhesive containing a water-soluble epoxy resin is used, the epoxy resin and other water-soluble resins such as a polyvinyl alcohol-based resin added as necessary are dissolved in water to constitute an adhesive solution. In this case, the water-soluble epoxy resin preferably has a concentration in the range of about 0.2 to 2 parts by weight per 100 parts by weight of water. Moreover, when mix | blending polyvinyl alcohol-type resin, the quantity is about 1-10 weight part per 100 weight part of water, Furthermore, it is preferable to set it as about 1-5 weight part.

  On the other hand, when a water-based adhesive containing a urethane resin is used, examples of suitable urethane resins include ionomer-type urethane resins, particularly polyester-based ionomer-type urethane resins. Here, the ionomer type is obtained by introducing a small amount of an ionic component (hydrophilic component) into the urethane resin constituting the skeleton. The polyester ionomer type urethane resin is a urethane resin having a polyester skeleton, into which a small amount of an ionic component (hydrophilic component) is introduced. Such an ionomer-type urethane resin is suitable as a water-based adhesive because it is emulsified directly in water without using an emulsifier to form an emulsion. Examples of commercially available polyester ionomer urethane resins include “Hydran AP-20” and “Hydran APX-101H” sold by Dainippon Ink and Chemicals, Inc., both of which are available in the form of emulsions. it can.

  When an ionomer type urethane resin is used as an adhesive component, it is usually preferable to add an isocyanate-based crosslinking agent. The isocyanate-based crosslinking agent is a compound having at least two isocyanato groups (—NCO) in the molecule. Examples thereof include 2,4-tolylene diisocyanate, phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 1, In addition to polyisocyanate monomers such as 6-hexamethylene diisocyanate and isophorone diisocyanate, adducts in which a plurality of these molecules are added to a polyhydric alcohol such as trimethylolpropane, and three molecules of diisocyanate are each of the isocyanate groups at one end. There are trifunctional isocyanurate forms in which isocyanurate rings are formed at the part, and polyisocyanate modified forms such as burettes formed by hydration and decarboxylation of the three diisocyanate molecules at the respective one-end isocyanato groups. . Examples of commercially available isocyanate-based crosslinking agents that can be suitably used include “Hydran Assist C-1” sold by Dainippon Ink and Chemicals, Inc.

  When an aqueous adhesive containing an ionomer type urethane resin is used, the concentration of the urethane resin is about 10 to 70% by weight, further 20% by weight or more, and 50% by weight or less from the viewpoint of viscosity and adhesiveness. Thus, those dispersed in water are preferred. When the isocyanate crosslinking agent is blended, the blending amount may be appropriately selected so that the isocyanate crosslinking agent is about 5 to 100 parts by weight with respect to 100 parts by weight of the urethane resin.

  A polarizing plate can be obtained by applying the adhesive as described above to a protective film made of a propylene-based resin and / or an adhesive surface of a polarizer and bonding them together. After the lamination, for example, a drying process is performed at a temperature of about 60 to 100 ° C. Furthermore, after that, it is preferable to cure at a temperature slightly higher than room temperature, for example, at a temperature of about 30 to 50 ° C. for about 1 to 10 days, in order to further increase the adhesive strength.

  Next, the solventless adhesive will be described. The solventless adhesive does not contain a significant amount of solvent, and generally comprises a curable compound that is polymerized by heating or irradiation with active energy rays, and a polymerization initiator. From the viewpoint of reactivity, those that are cured by cationic polymerization are preferred, and epoxy adhesives are particularly preferred.

  Therefore, in one preferred embodiment of the polarizing plate of the present invention, a polarizer and a protective film made of a polypropylene resin are laminated via a solventless epoxy adhesive. The adhesive is more preferably cured by cationic polymerization by heating or irradiation with active energy rays. In particular, from the viewpoint of weather resistance and refractive index, an epoxy compound that does not contain an aromatic ring in the molecule is suitably used as the curable compound. An adhesive using an epoxy compound that does not contain an aromatic ring in the molecule is described in, for example, JP-A-2004-245925. Examples of such epoxy compounds that do not contain an aromatic ring include hydrides of aromatic epoxy compounds, alicyclic epoxy compounds, aliphatic epoxy compounds, and the like. The curable epoxy compound used for the adhesive usually has two or more epoxy groups in the molecule.

  The hydride of an aromatic epoxy compound will be described. This can be obtained by selectively hydrogenating an aromatic epoxy compound to an aromatic ring under pressure in the presence of a catalyst. Examples of aromatic epoxy compounds include bisphenol-type epoxy compounds such as diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, diglycidyl ether of bisphenol S; phenol novolac epoxy resin, cresol novolac epoxy resin, hydroxy Examples include novolak-type epoxy resins such as benzaldehyde phenol novolac epoxy resins; glycidyl ethers of tetrahydroxydiphenylmethane, glycidyl ethers of tetrahydroxybenzophenone, and polyfunctional epoxy compounds such as epoxidized polyvinylphenol. Among these hydrides of aromatic epoxy compounds, hydrogenated bisphenol A diglycidyl ether is preferred.

  Next, the alicyclic epoxy compound will be described. This is a compound having at least one epoxy group bonded to the alicyclic ring in the molecule, as shown in the following formula.

In the formula, m represents an integer of 2 to 5.

A compound in which one or more hydrogen atoms in (CH ₂ ) _m in this formula are removed and bonded to another chemical structure can be an alicyclic epoxy compound. Further, the hydrogen forming the alicyclic ring may be appropriately substituted with a linear alkyl group such as a methyl group or an ethyl group. Among them, it is preferable to use a compound having an epoxycyclopentane ring (m = 3 in the above formula) or an epoxycyclohexane ring (m = 4 in the above formula). Specific examples of the alicyclic epoxy compound include the following.

3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate,
3,4-epoxy-6-methylcyclohexylmethyl 3,4-epoxy-6-methylcyclohexanecarboxylate,
Ethylene bis (3,4-epoxycyclohexanecarboxylate),
Bis (3,4-epoxycyclohexylmethyl) adipate,
Bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate,
Diethylene glycol bis (3,4-epoxycyclohexyl methyl ether),
Ethylene glycol bis (3,4-epoxycyclohexyl methyl ether),
2,3,14,15-diepoxy-7,11,18,21-tetraoxatrispiro- [5.2.2.5.2.2] henicosane (also 3,4-epoxycyclohexanespiro-2 ' , 6′-Dioxanespiro-3 ″, 5 ″ -Dioxanespiro-3 ′ ″, 4 ′ ″-epoxycyclohexane)
4- (3,4-epoxycyclohexyl) -2,6-dioxa-8,9-epoxyspiro [5.5] undecane,
4-vinylcyclohexene dioxide,
Bis-2,3-epoxycyclopentyl ether,
Dicyclopentadiene dioxide etc.

  Next, the aliphatic epoxy compound will be described. The polyglycidyl ether of an aliphatic polyhydric alcohol or an alkylene oxide adduct thereof corresponds to this. Examples include 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, glycerin triglycidyl ether, trimethylolpropane triglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol Polyglycidyl of a polyether polyol obtained by adding one or more alkylene oxides (ethylene oxide or polypropylene oxide) to an aliphatic polyhydric alcohol such as diglycidyl ether, ethylene glycol, polypropylene glycol or glycerin Examples include ether.

  The epoxy compounds illustrated here may be used alone or in combination with a plurality of epoxy compounds.

  The epoxy equivalent of the epoxy compound used for the solventless adhesive is usually 30 to 3,000 g / equivalent, preferably 50 to 1,500 g / equivalent. When the epoxy equivalent is less than 30 g / equivalent, the flexibility of the protective film after curing may be lowered, or the adhesive strength may be reduced. On the other hand, if it exceeds 3,000 g / equivalent, the compatibility with other components may decrease.

  In order to cure the epoxy compound by cationic polymerization, a cationic polymerization initiator is blended. The cationic polymerization initiator generates a cationic species or a Lewis acid by irradiation with active energy rays such as visible light, ultraviolet rays, X-rays, electron beams, or heating, and initiates an epoxy group polymerization reaction. Regardless of the type of cationic polymerization initiator, it is preferable from the viewpoint of workability that latency is imparted.

  Hereinafter, the cationic photopolymerization initiator will be described. When a photocationic polymerization initiator is used, curing at room temperature becomes possible, the need to consider the heat resistance of the polarizer or distortion due to expansion is reduced, and the protective film can be bonded well. Moreover, since a photocationic polymerization initiator acts catalytically by light, it is excellent in storage stability and workability even when mixed with an epoxy compound. Examples of the compound that generates a cationic species or a Lewis acid upon irradiation with active energy rays include aromatic diazonium salts, onium salts such as aromatic iodonium salts and aromatic sulfonium salts, and iron-allene complexes. Among these, aromatic sulfonium salts are particularly preferably used because they have ultraviolet absorption characteristics even in a wavelength region of 300 nm or more, and can provide a cured product having excellent curability and good mechanical strength and adhesive strength. It is done.

These photocationic polymerization initiators can be easily obtained as commercial products. For example, “Kayarad PCI-220”, “Kayarad PCI-620” (manufactured by Nippon Kayaku Co., Ltd.), “UVI” -6990 "(manufactured by Union Carbide)," Adekaoptomer SP-150 "," Adekaoptomer SP-170 "(above, manufactured by ADEKA Corporation)," CI-5102 "," CIT-1370 ",
"CIT-1682", "CIP-1866S", "CIP-2048S", "CIP-2064S" (above, manufactured by Nippon Soda Co., Ltd.), "DPI-101", "DPI-102", "DPI-103 ”,“ DPI-105 ”,“ MPI-103 ”,
“MPI-105”, “BBI-101”, “BBI-102”, “BBI-103”, “BBI-105”, “TPS-101”,
“TPS-102”, “TPS-103”, “TPS-105”, “MDS-103”, “MDS-105”, “DTS-102”,
“DTS-103” (manufactured by Midori Chemical Co., Ltd.), “PI-2074” (manufactured by Rhodia), and the like. In particular, “CI-5102” manufactured by Nippon Soda Co., Ltd. is one of preferred initiators.

  The compounding quantity of a photocationic polymerization initiator is 0.5-20 weight part normally with respect to 100 weight part of epoxy compounds, Preferably it is 1 weight part or more, Preferably, it is 15 weight part or less.

  Furthermore, a photosensitizer can be used in combination as necessary. By using a photosensitizer, the reactivity is improved, and the mechanical strength and adhesive strength of the cured product can be improved. Examples of the photosensitizer include carbonyl compounds, organic sulfur compounds, persulfides, redox compounds, azo and diazo compounds, halogen compounds, and photoreductive dyes. When mix | blending a photosensitizer, the quantity is about 0.1-20 weight part about 100 weight part of photocationic polymerizable epoxy resin compositions.

Next, the thermal cationic polymerization initiator will be described. Examples of the compound that generates a cationic species or a Lewis acid by heating include benzylsulfonium salt, thiophenium salt, thiolanium salt, benzylammonium, pyridinium salt, hydrazinium salt, carboxylic acid ester, sulfonic acid ester, and amine imide. These thermal cationic polymerization initiators can also be easily obtained as commercial products, for example, “Adeka Opton CP77” and “Adeka Opton CP66” (all manufactured by ADEKA Co., Ltd.)
“CI-2639” and “CI-2624” (manufactured by Nippon Soda Co., Ltd.), “Sun-Aid SI-60L”,
"Sun-Aid SI-80L" and "Sun-Aid SI-100L" (manufactured by Sanshin Chemical Industry Co., Ltd.)

  It is also a useful technique to combine the photocationic polymerization and the thermal cationic polymerization described above.

  The epoxy adhesive may further contain a compound that promotes cationic polymerization, such as oxetanes and polyols.

  Even when a solventless type adhesive is used, the adhesive can be applied to a protective film made of a propylene-based resin and / or an adhesive surface of a polarizer, and both can be bonded to form a polarizing plate. There is no particular limitation on the method of applying the solventless adhesive to the protective film or the polarizer, and various coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be used. Moreover, since each coating method has an optimum viscosity range, the viscosity may be adjusted using a small amount of solvent. The solvent used for this purpose only needs to dissolve the epoxy adhesive well without degrading the optical performance of the polarizer. For example, hydrocarbons typified by toluene, esters typified by ethyl acetate, and the like. Organic solvents such as When an epoxy adhesive is used, the thickness of the adhesive layer is usually 50 μm or less, preferably 20 μm or less, more preferably 10 μm or less, and usually 1 μm or more.

  As described above, after pasting a protective film made of a propylene-based resin to a polarizer through an uncured adhesive layer, the epoxy-based adhesive layer is exposed by irradiating active energy rays or heating. Curing and fixing the protective film on the polarizer. In the case of curing by irradiation with active energy rays, ultraviolet rays are preferably used. Specific examples of the ultraviolet light source include a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, a black light lamp, and a metal halide lamp. The irradiation intensity and irradiation amount of active energy rays or ultraviolet rays may be appropriately selected so that the polymerization initiator is sufficiently activated and does not adversely affect the cured adhesive layer, polarizer and protective film. In addition, when curing by heating, it can be heated by a generally known method, and the temperature and time at that time sufficiently activate the polymerization initiator, and the cured adhesive layer or polarizer The protective film may be appropriately selected so as not to adversely affect the protective film.

  In addition, when laminating a protective film made of a propylene-based resin having an inside to one side of a polarizer and laminating a protective film made of a resin other than a propylene-based resin on the other surface, a protective film made of a resin other than a propylene-based resin Adhesives similar to those described above may be used for adhesion, or different adhesives may be used, but between the polarizer and the propylene-based protective film and other than the polarizer and the propylene-based resin. It is preferable to use the same adhesive with the protective film because the number of steps and materials can be reduced.

  The method of bonding the polyvinyl alcohol polarizer and the protective film is not particularly limited. For example, an adhesive is uniformly applied to the surface of the polyvinyl alcohol polarizing film or the protective film, and the other surface is applied to the coated surface. A method of stacking films and bonding them with a roll or the like can be employed.

  In the production of the polarizing plate, the protective film made of propylene-based resin is preferably subjected to corona discharge treatment on the surface to be bonded to the polarizer. By performing the corona discharge treatment, the adhesive force between the protective film made of propylene resin and the polarizer can be increased. The corona discharge treatment is a treatment for activating the resin film disposed between the electrodes by discharging by applying a high voltage between the electrodes. The effect of corona discharge treatment varies depending on the type of electrode, electrode interval, voltage, humidity, type of resin film used, etc., but for example, the electrode interval is set to 1 to 5 mm and the moving speed is set to about 3 to 20 m / min. It is preferable to do this. After the corona discharge treatment, a polarizer is bonded to the treated surface via an adhesive as described above.

  Thus, a protective film made of a propylene-based resin having a noise to the inside is laminated on one side of a polarizer made of a polyvinyl alcohol-based resin on which a dichroic dye is adsorbed and oriented, and the other side is made of the same or different resin. A polarizing plate on which a protective film is laminated is obtained.

[Polarizing plate with adhesive]
The polarizing plate thus obtained can be made into a polarizing plate with an adhesive by forming an adhesive layer on the outside of one protective film. In a polarizing plate with an adhesive, the surface of the adhesive layer is usually covered with a release film. When a protective film made of a propylene-based resin having internal haze is laminated on both surfaces of the polarizer, an adhesive layer is formed on one of the surfaces, and is bonded to the liquid crystal cell via the adhesive layer. What should I do?

On the other hand, if a polarizing plate is formed by laminating a protective film made of a propylene-based resin having internal haze on one side of the polarizer and laminating a protective film made of a transparent resin having substantially no internal haze on the other side, The pressure-sensitive adhesive layer is formed on the outer side of the protective film that is bonded to the liquid crystal cell . The this polarizing plate rear side of the liquid crystal cell (viewing surface opposite, i.e., the back light side when the transmission) When placed in the you place a protective film having an internal haze on the opposite side of the liquid crystal cell the in, in this case, providing the adhesive layer to the protective film side of a transparent resin. In addition, when disposing the polarizing plates on the front side (viewing side) of the liquid crystal cell, a protective film having an internal haze than you place the liquid crystal cell side, in this case, the propylene-based resin having an internal haze A pressure-sensitive adhesive layer is provided on the protective film side.

  The pressure-sensitive adhesive is also called a pressure-sensitive adhesive, and those using a base polymer such as an acrylic ester, methacrylic ester, butyl rubber, or silicone can be used. Although not particularly limited, based on (meth) acrylate esters such as butyl (meth) acrylate, ethyl (meth) acrylate, isooctyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate And polymers based on copolymers using two or more of these (meth) acrylic esters are preferably used. The pressure-sensitive adhesive usually has a polar monomer copolymerized in these base polymers. Examples of the polar monomer include (meth) acrylic acid, 2-hydroxyethyl (meth) acrylate, and (meth) acrylic acid 2. Examples thereof include monomers having a carboxyl group, a hydroxyl group, an amino group, an epoxy group, and the like, such as -hydroxypropyl, (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylate, and glycidyl (meth) acrylate. Examples of the crosslinking agent include those that generate a divalent or polyvalent metal ion and a carboxylic acid metal salt, and those that form an amide bond with a polyisocyanate compound. These compounds may be used alone or in combination as a crosslinking agent. , Mixed with the base polymer. A typical pressure-sensitive adhesive layer has a thickness of about 2 to 50 μm. When the pressure-sensitive adhesive layer is applied to the polarizing plate, surface treatment such as corona treatment may be applied to the protective film surface of the polarizing plate depending on the situation.

[Elliptically polarizing plate]
When the polarizing plate of the present invention is used as a light scattering elliptical polarizing plate, a retardation plate such as a quarter-wave plate or a half-wave plate is bonded. For example, a stretched film or a liquid crystal film that gives an appropriate phase difference such as ½ wavelength or ¼ wavelength for 550 nm light can be used. In general, for example, a film obtained by stretching a polymer film by a uniaxial or biaxial method is preferably used.

  Although the kind of polymer which comprises a stretched film is not specifically limited, What is excellent in transparency is preferable. Incidentally, as an example, polycarbonate system, polyester system, polysulfone system, polyethersulfone system, polystyrene system, polyolefin system, polyvinyl alcohol system, cellulose acetate system, polyvinyl chloride system, polyacrylic system represented by polymethyl methacrylate, Examples thereof include polymers such as polyarylate, polyamide, polyimide, and amorphous polyolefin.

  When a circular polarization mode is used as in a reflective liquid crystal display device, a quarter wave plate is preferably used as the retardation plate. For example, the quarter-wave plate may provide a quarter-wave phase difference with respect to light having a wavelength of 550 nm. However, the high-contrast monochrome display and the color display with high color purity are achieved. Is preferably one that functions as a quarter-wave plate in a wide wavelength region such as a visible light region.

  A retardation plate that functions as a quarter-wave plate in a wide wavelength range, that is, a broadband quarter-wave plate, is, for example, a stretched film that gives a half-wave retardation to monochromatic light and a quarter-wave plate. It can be obtained as a stretched film giving a phase difference, such as a laminate in which at least two phase difference plates are laminated so that their optical axes intersect. According to this, the wavelength dispersion of the retardation defined by the product (Δn · d) of the birefringence difference (Δn) and the thickness (d) is superimposed or adjusted via the laminated stretched film, and is arbitrarily set. A retardation plate that suppresses chromatic dispersion while controlling the overall phase difference to a predetermined value and gives a phase difference of ¼ wavelength over a wide wavelength region such as the entire visible light region. Can be obtained. As an example, a polarizing plate, a half-wave plate and a quarter-wave plate are laminated in this order, and the slow axis directions of the half-wave plate and the quarter-wave plate are respectively set with respect to the absorption axis of the polarizing plate. Examples thereof are 15 ° and 75 °.

  In particular, in the light scattering elliptical polarizing plate on the liquid crystal cell rear side, it is also a useful technique to use a propylene-based resin film having internal haze for both protective films on both sides of the polarizer. Thus, if the polarizing plate is formed by laminating a protective film made of a propylene-based resin having a noise on both sides of the polarizer, the retardation plate as described above is bonded to either protective film side. It becomes an elliptically polarizing plate. On the other hand, if a polarizing plate is formed by laminating a protective film made of a propylene-based resin having internal haze on one side of the polarizer and laminating a protective film made of a transparent resin having substantially no internal haze on the other side, The retardation plate as described above is bonded to any one of the protective films to form an elliptically polarizing plate. Generally, the retardation plate is often bonded to the protective film made of a transparent resin.

  The same adhesive as described above can also be used for bonding between a polarizing plate and a retardation plate, or bonding between retardation plates such as a half-wave plate and a quarter-wave plate. Furthermore, even when the retardation plate is bonded to the polarizing plate of the present invention to form an elliptical polarizing plate, an adhesive layer is formed on the outer side of the polarizing plate or the outer side of the retardation plate, and the elliptical polarizing plate with the adhesive is used. It can be. For example, when an elliptically polarizing plate with a retardation plate bonded to one side of a polarizing plate in which a protective film made of propylene-based resin is laminated on both sides of the polarizer is disposed on the rear side of the liquid crystal cell, It is advantageous to provide a pressure-sensitive adhesive layer on the phase difference plate side and bond the liquid crystal cell on the pressure-sensitive adhesive layer side. On the other hand, for a polarizing plate in which a protective film made of a propylene-based resin having internal haze is laminated on one side of the polarizer and a protective film made of a transparent resin having substantially no internal haze is laminated on the other side, In the case of an elliptically polarizing plate in which a retardation plate is bonded to the protective film side made of the transparent resin, depending on whether it is arranged on the rear side or the front side of the liquid crystal cell, the outer side of the retardation plate or It is advantageous to provide a pressure-sensitive adhesive layer on the outside of the protective film made of a propylene-based resin having internal haze, and bond the liquid crystal cell on the pressure-sensitive adhesive layer side.

[Liquid Crystal Display]
The polarizing plate of the present invention can have desired optical characteristics by combining with a light collecting sheet, a diffusion film, a light reflecting sheet, a light guide plate, an antiglare sheet, etc. in addition to the retardation plate described above. it can. As a result, a liquid crystal display device having desired characteristics can be provided. In forming a liquid crystal display device, an adhesive layer is formed on the outer side of one of the protective films as described above to form a polarizing plate with an adhesive, and the adhesive layer side is bonded so as to face the liquid crystal cell. Moreover, if it is an elliptical polarizing plate with a retardation plate bonded to a polarizing plate, an adhesive layer is formed on the outside of the polarizing plate or outside of the retardation plate to form an elliptical polarizing plate with an adhesive, and the adhesive layer It is bonded so that the side faces the liquid crystal cell. The liquid crystal cell constituting the liquid crystal display device has various modes known in this field such as TN (Twisted Nematic), STN (Super Twisted Nematic), VA (Vertical Alignment), IPS (In-Plane Switching), etc. Can be.

  EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated further more concretely, this invention is not limited by these examples. In the examples, “%” and “part” representing the content or amount used are based on weight unless otherwise specified.

[Example 1]
(A) Production of propylene-based resin film having internal haze The propylene-based resin “Sumitomo Nobrene W151” (trade name) sold by Sumitomo Chemical Co., Ltd. is propylene-ethylene random having an ethylene content of about 4.6%. The copolymer had a melting point of 136 ° C., a melt flow rate of 8 g / 10 minutes measured at a temperature of 230 ° C. and a load of 2.16 kg (21.18 N). The resin pellets were put into a 65 mmφ extruder having a cylinder temperature set at 250 ° C., melt-kneaded, and extruded from a 1200 mm wide T-die attached to the extruder at an extrusion rate of 65 kg / h. The extruded molten resin was cooled by being sandwiched between a metal cooling roll having an outer diameter of 400 mmφ and a touch roll covered with an outer cylinder made of a metal sleeve around the elastic body roll. At this time, the surface temperature of the cooling roll and the touch roll was adjusted to 30 ° C., respectively. Thus, a propylene-based resin film having a thickness of 80 μm was obtained. With respect to this film, when the internal haze was measured using a haze meter “HGM-2DP” manufactured by Suga Test Instruments Co., Ltd., it was 8.0%.

(B) Preparation of Adhesive 3 parts of carboxyl group-modified polyvinyl alcohol “Kuraray Poval KL-318” obtained from Kuraray Co., Ltd. is dissolved in 100 parts of water, and further, there is a water-soluble polyamide epoxy resin. 1.5 parts of “Smileze Resin 650” (30% solids aqueous solution) obtained from Kachemtechs Co., Ltd. was added to give an adhesive.

(C) Production of polarizing plate A protective film made of triacetyl cellulose [Konica Minolta Opto Co., Ltd.] via the adhesive prepared in (b) above on one side of a polarizer having iodine adsorbed and oriented on a polyvinyl alcohol film. "KC8UX"] obtained from On the other hand, a corona discharge treatment was performed on one side of the propylene-based resin film having an internal haze of 8.0% produced in (a) so that the integrated irradiation amount was 1,680 J. Within 30 seconds after this corona discharge treatment, the corona discharge treatment surface was applied to the polyvinyl alcohol film surface of the polarizer having the triacetyl cellulose film bonded to one side obtained above, and the adhesive prepared in the above (b). And dried at 80 ° C. for 5 minutes. Further, the film was cured at 40 ° C. for 3 days to obtain a polarizing plate in which a protective film made of triacetyl cellulose was laminated on one side of the polarizer and a protective film made of a propylene-based resin having internal haze was laminated on the other side. .

(D) Evaluation on mounting on TV Disassembled Sony's LCD TV “BRAVIA 32” and peeled off the polarizing plate on the lower side of the liquid crystal cell, and obtained in (c) above instead of the original polarizing plate. The polarizing plate was bonded on the triacetyl cellulose film side via an adhesive. When the TV was assembled again and the backlight was turned on, Newton's ring was not recognized at all.

[Example 2]
In Example 1 (a), the same operation was performed except that the surface temperature of the casting roll and the touch roll for sandwiching the molten resin after extrusion was adjusted to 55 ° C., and a propylene-based resin film having a thickness of 80 μm was obtained. . The internal haze of this film was 15.0%. A polarizing plate was produced in the same manner as in Example 1 (c) except that this propylene resin film was used. When the obtained polarizing plate was evaluated in the same manner as in (d) of Example 1, no Newton ring was observed.

[Example 3]
In Example 1 (a), the same operation was performed except that the surface temperature of the casting roll and the touch roll for sandwiching the molten resin after extrusion was adjusted to 100 ° C., and a propylene-based resin film having a thickness of 80 μm was obtained. . The internal haze of this film was 28.7%. A polarizing plate was produced in the same manner as in Example 1 (c) except that this propylene resin film was used. When the obtained polarizing plate was evaluated in the same manner as in (d) of Example 1, no Newton ring was observed.

[Comparative Example 1]
In Example 1 (a), the same operation was performed except that the surface temperature of the casting roll and the touch roll for sandwiching the molten resin after extrusion was adjusted to 20 ° C., and a propylene-based resin film having a thickness of 80 μm was obtained. . The internal haze of this film was 4.2%. A polarizing plate was produced in the same manner as in Example 1 (c) except that this propylene resin film was used. When the obtained polarizing plate was evaluated in the same manner as in Example 1 (d), Newton rings were observed.

Claims (13)

Protective film on both surfaces of a polarizer dichroic dye comprising a polyvinyl alcohol-based resin film that is adsorbed and oriented is is laminated a polarizing plate that is used by adhering to the liquid crystal cell,
At least one of the protective film is made of a propylene resin, it has a haze to the interior 5-50% of based on the crystal,
When pasted to the rear side of the liquid crystal cell, a protective film made of a propylene-based resin having an internal haze is arranged on the opposite side of the liquid crystal cell,
If bonded to the front side of the liquid crystal cell, a polarizing plate protective film made of a propylene resin having internal haze is characterized Rukoto arranged so that the liquid crystal cell side.   The polarizing plate according to claim 1, wherein the protective film made of a propylene-based resin having a haze is composed of a copolymer mainly composed of propylene units and containing 1 to 10% by weight of ethylene units.   The polarizing plate according to claim 1 or 2, wherein the protective film made of a propylene-based resin having an internal haze has an in-plane retardation of 10 nm or less.   The protective film which consists of a propylene-type resin which has a noise to the inside is laminated | stacked on the single side | surface of a polarizer, and the protective film which consists of a cellulose acetate type resin is laminated | stacked on the other surface. Polarizing plate.   The polarizing plate according to any one of claims 1 to 4, wherein a polarizer and a protective film made of a propylene-based resin having an internal haze are laminated via an aqueous adhesive.   The polarizing plate according to claim 5, wherein the aqueous adhesive contains a crosslinkable epoxy resin.   The polarizing plate according to any one of claims 1 to 4, wherein a polarizer and a protective film made of a propylene-based resin having internal haze are laminated via a solvent-free epoxy adhesive.   The polarizing plate according to claim 7, wherein the solventless epoxy adhesive is cured by cationic polymerization by heating or irradiation with active energy rays. The polarizing plate in any one of Claims 1-8 in which the adhesive layer is formed in the outer side of the protective film bonded together to a liquid crystal cell .   An elliptical polarizing plate, wherein a retardation plate is bonded to the polarizing plate according to claim 1.   11. The elliptically polarizing plate according to claim 10, wherein the retardation plate is a ¼ wavelength plate, or a ½ wavelength plate and a ¼ wavelength plate are laminated in this order from the polarizing plate side. The elliptically polarizing plate according to claim 10 or 11, wherein an adhesive layer is formed on the outer side of the polarizing plate bonded to the liquid crystal cell or on the outer side of the retardation plate.   The polarizing plate of Claim 9 or the elliptically polarizing plate of Claim 12 is bonded by the liquid crystal cell by the adhesive layer side, The liquid crystal display device characterized by the above-mentioned.