JP2009258588A - Polarizing plate, laminated optical member using the same, and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarizing plate which is free from degradation of optical characteristics, in particular, transmittance even when exposed to a high-temperature environment and is durable for use even in a high-temperature environment; and to provide a laminated optical member and a liquid crystal display device using the polarizing plate. <P>SOLUTION: Disclosed is a polarizing plate wherein protective films are arranged on both sides of a polarizing film which is composed of a polyvinyl alcohol resin film onto which a dichroic dye is adsorbed and oriented. At least one of the protective films is composed of a propylene resin film, and the propylene resin film has a xylene-soluble content at 20°C of not more than 1 wt.%. A laminated optical member using the polarizing plate and the liquid crystal display device are also disclosed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a polarizing plate in which protective films are laminated on both sides of a polarizing film, and a laminated optical member 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 optical members such as a liquid crystal cell, a polarizing plate, a retardation film, a light collecting sheet, a diffusion film, a light guide plate, and a light reflecting sheet. Therefore, it is possible to improve the production efficiency and lightness of the liquid crystal display device, and to reduce the weight and thickness by improving the number of films or sheets constituting the optical member and reducing the film thickness. Numerous studies are actively conducted.

  Liquid crystal display devices are required to have strict durability performance depending on their applications. For example, a liquid crystal display device for a car navigation system may have a higher temperature and humidity in the vehicle in which the liquid crystal display device is placed, and therefore has higher moisture and heat resistance than a liquid crystal display device for a normal television or personal computer. Required. High humidity and heat resistance is also required for polarizing plates applied to liquid crystal display devices used for such applications.

  Conventionally, a polarizing plate has a structure in which a transparent protective film is laminated on both sides or one side of a polarizing film made of a polyvinyl alcohol resin on which a dichroic dye is adsorbed and oriented. As the protective film, a cellulose acetate 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. However, a polarizing plate in which a protective film made of triacetyl cellulose is laminated on both sides or one side of a polarizing film on which a dichroic dye is adsorbed and oriented via an adhesive made of an aqueous solution of a polyvinyl alcohol-based resin, 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 polarizing film 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, Patent Document 1 describes that, in a polarizing plate in which protective films are laminated on both surfaces of a polarizing film, at least one of the protective films is composed of a thermoplastic norbornene resin having a retardation film function. Yes. In Patent Document 2, a protective film made of an amorphous polyolefin-based resin is laminated on one surface of a polarizing film made of a polyvinyl alcohol-based resin film on which iodine or a dichroic organic dye is adsorbed and oriented. On the surface, there is described a polarizing plate in which a protective film made of a resin different from an amorphous polyolefin resin such as a cellulose acetate resin is laminated. Furthermore, Patent Document 3 describes that a protective film made of a cycloolefin resin is laminated on a polyvinyl alcohol polarizing film via an adhesive containing a urethane adhesive and a polyvinyl alcohol resin. Yes.

  However, amorphous polyolefin-based resins (cycloolefin-based resins) such as norbornene-based resins are recently put into practical use and are generally expensive. Moreover, although it is often performed to form a pressure-sensitive adhesive layer on the protective film, the pressure-sensitive adhesive layer may contain an organic solvent such as acetone, toluene, and ethyl acetate used for the preparation thereof. The protective film may be eroded by the residual organic solvent.

Here, in Patent Document 4, a protective film is laminated on both sides of a polarizer made of a polyvinyl alcohol resin on which a dichroic dye is adsorbed and oriented, and at least one of the protective films is a polarized light made of a propylene resin. A plate is disclosed.
JP-A-8-43812 JP 2002-174729 A JP 2004-334168 A JP 2007-334295 A

  The polarizing plate described in Patent Document 4 has resistance to organic solvents such as acetone, toluene, and ethyl acetate, and is particularly excellent in dimensional stability under wet heat conditions and adhesion between the polarizer and the protective film. . However, the transmittance of the polarizing plate may be reduced under a severe high temperature environment. Such a decrease in transmittance reduces the luminance of the liquid crystal display device.

  The present invention has been made in order to solve the above-mentioned problems, and its purpose is to prevent deterioration of optical characteristics, particularly transmittance, even when exposed to a high temperature environment, and to prevent the problem from occurring in a high temperature environment. It is to provide a polarizing plate that can sufficiently withstand use in the field. Another object of the present invention is to provide a laminated optical member and a liquid crystal display device using a polarizing plate excellent in durability under such a high temperature environment.

  The present inventors diligently studied to solve the above-mentioned problems, and presumed that the cause of the decrease in transmittance was a bleed material generated from a protective film made of a propylene-based resin. As a result of further studies, the present inventors have found a polarizing plate having a protective film made of a propylene-based resin whose transmittance does not decrease even under a severe high temperature environment.

  That is, according to the present invention, there is provided a polarizing plate in which a protective film is laminated on both surfaces of a polarizing film made of a polyvinyl alcohol resin film in which a dichroic dye is adsorbed and oriented, and at least one of the protective films is propylene There is provided a polarizing plate comprising a resin film, wherein the propylene resin film has a xylene-soluble content at 20 ° C. of 1% by weight or less.

  The propylene-based resin constituting the propylene-based resin film preferably has syndiotactic or isotactic stereoregularity, and is preferably a propylene homopolymer.

  The propylene-based resin film preferably contains a nucleating agent.

  In the polarizing plate of the present invention, both protective films laminated on both sides of the polarizing film may be composed of the propylene-based resin film, or one protective film is composed of the propylene-based resin film. The other protective film may be a protective film made of a resin film other than the propylene resin. In the latter case, the protective film made of a resin film other than the propylene-based resin can be a retardation film such as a wave plate or a viewing angle compensation film.

  Moreover, in the polarizing plate of this invention, it is preferable that at least one protective film is laminated | stacked on a polarizing film through a solventless type epoxy adhesive. The solventless epoxy adhesive is preferably one that cures by cationic polymerization by heating or irradiation with active energy rays.

  Moreover, this invention provides the laminated optical member which consists of a laminated body of the polarizing plate of this invention, and the optical layer which shows another optical function.

  Furthermore, the present invention provides a liquid crystal display device in which the polarizing plate or laminated optical member of the present invention is bonded to a liquid crystal cell via an adhesive layer.

  According to the present invention, by using a propylene-based resin film having a xylene-soluble content at 20 ° C. of 1% by weight or less as a protective film, a decrease in transmittance under a high temperature environment is greatly suppressed, A polarizing plate that can sufficiently withstand use in a high-temperature environment is provided. The polarizing plate of the present invention can be made into a laminated optical member by, for example, laminating an optical layer thereon. The polarizing plate and the laminated optical member of the present invention can be suitably applied to a liquid crystal display device, and such a liquid crystal display device can exhibit excellent durability in a high temperature environment.

  Hereinafter, the present invention will be described in detail. The polarizing plate of the present invention has a protective film laminated on both sides of a polarizing film, and at least one of the protective films has a xylene-soluble component at 20 ° C. (hereinafter also simply referred to as a xylene-soluble component). It is comprised with the propylene-type resin film which is 1 weight% or less.

<Polarizing film>
The polarizing film is obtained by adsorbing and orienting a dichroic dye on a polyvinyl alcohol-based resin film so that predetermined polarizing characteristics can be obtained. As the dichroic dye, iodine or a dichroic organic dye is used. Specifically, as a polarizing film, specifically, an iodine polarizing film in which iodine is adsorbed and oriented on a polyvinyl alcohol resin film, a dye polarizing film in which a dichroic organic dye is adsorbed and oriented on a polyvinyl alcohol resin film, and the like. Can be mentioned.

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

  The polarizing film is usually a humidity adjusting step for adjusting the moisture of the polyvinyl alcohol-based resin film, a step of uniaxially stretching the polyvinyl alcohol-based resin film, a dichroic pigment by dyeing the polyvinyl alcohol-based resin film with a dichroic pigment, Are produced through a step of adsorbing and orienting, a step of treating a polyvinyl alcohol-based resin film adsorbed and oriented with a dichroic dye with an aqueous boric acid solution, and a washing step of washing off the aqueous boric acid solution. Uniaxial stretching can be performed before dyeing, during dyeing, or during boric acid treatment after dyeing. Moreover, uniaxial stretching may be performed in these several steps. 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 finally obtained polarizing film can be, for example, about 5 to 50 μm.

<Protective film>
In the present invention, a protective film made of a propylene-based resin film is used as at least one of the protective films laminated on both surfaces of the polarizing film, and the propylene-based resin film has a xylene-soluble content of 1 wt. % Or less, more preferably 0.8% by weight or less, and still more preferably 0.5% by weight or less. When the xylene-soluble content of the propylene-based resin film exceeds 1% by weight, when the polarizing plate is exposed to a high temperature environment, the surface of the propylene-based resin film is whitened, and the transmittance of the polarizing plate is significantly reduced. . The whitening of the surface of the propylene-based resin film in such a high temperature environment is presumed to be caused by a bleed out due to a low molecular weight component or a component inferior in stereoregularity present in the resin film. A typical example of such a low molecular weight component is not particularly limited, and examples thereof include an atactic low molecular weight oligomer.

In the present invention, the xylene-soluble content (% by weight) of the propylene-based resin film is measured as follows. That is, first, 5 g of a propylene-based resin film is added to 500 ml of boiling xylene and completely dissolved, and then the temperature is lowered to 20 ° C. and held at 20 ° C. for 4 hours. Next, the xylene solution is filtered to separate the precipitate and the filtrate, the solvent is removed from the filtrate, and the dried xylene-dissolved component is obtained by drying at 70 ° C. under reduced pressure. The xylene-soluble content is obtained from the following formula.
Xylene soluble content [% by weight] = (weight of dried xylene soluble component [g]) / (5 [g]) × 100

  The propylene-based resin constituting the propylene-based resin film is preferably a propylene-based resin having a xylene-soluble content of preferably 1% by weight or less, more preferably 0.8% by weight or less, and further preferably 0.5% by weight or less. Resin is used. The method for measuring the xylene-soluble content of the propylene resin is the same as that for the propylene resin film. The propylene-based resin may be a propylene resin made of a propylene homopolymer, or may be a copolymer of propylene and another monomer copolymerizable therewith. These may be used in combination.

  Examples of other monomers copolymerizable with propylene include ethylene and α-olefin. As the α-olefin, an α-olefin having 4 or more carbon atoms is preferably used, and more preferably an α-olefin having 4 to 10 carbon atoms. Specific examples of the α-olefin having 4 to 10 carbon atoms include linear monoolefins such as 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene and 1-decene; Branched monoolefins such as 3-methyl-1-butene, 3-methyl-1-pentene, 4-methyl-1-pentene; vinylcyclohexane and the like. The copolymer of propylene and other monomers copolymerizable therewith may be a random copolymer or a block copolymer.

  In the case of using the above copolymer as the propylene resin, since a propylene resin having a xylene-soluble content of 1% by weight or less is relatively easily obtained, the copolymerization ratio of other monomers copolymerized with propylene Is preferably 8% by weight or less, and more preferably 4% by weight or less. In addition, the content rate of the structural unit derived from the said other monomer in a copolymer is infrared (IR) according to the method described on page 616 of "Polymer Analysis Handbook" (1995, published by Kinokuniya). ) It can be obtained by performing a spectrum measurement.

  Among the above, propylene-based resins constituting the propylene-based resin film include propylene homopolymer, propylene-ethylene random copolymer, propylene-1-butene random copolymer, and propylene-ethylene-1-butene. Random copolymers are preferably used. These homopolymers and copolymers are relatively easy to obtain a polymer with reduced xylene solubles by selecting an appropriate polymerization catalyst. In particular, by using a propylene homopolymer, a polymer having a reduced xylene-soluble content tends to be obtained more easily.

  The stereoregularity of the propylene resin constituting the propylene resin film is preferably substantially isotactic or syndiotactic. A propylene-based resin film made of a propylene-based resin having substantially isotactic or syndiotactic stereoregularity has relatively good handleability and excellent mechanical strength in a high-temperature environment. In addition, the propylene-based resin having such stereoregularity has a relatively small generation of atactic low molecular weight components that cause whitening of the polarizing plate in the polymerization stage, and the transmittance decreases under a high temperature environment. A suppressed polarizing plate is easily obtained.

In the present invention, the propylene-based resin may be a polymer or copolymer polymerized using a known polymerization catalyst, and examples of the polymerization catalyst 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.

  Examples of the solid catalyst component (1) include catalyst systems described in JP-A-61-218606, JP-A-61-287904, JP-A-7-216017, and the like. Preferred examples of the organoaluminum compound in the catalyst system of (2) above include triethylaluminum, triisobutylaluminum, a mixture of triethylaluminum and diethylaluminum chloride, tetraethyldialumoxane, and the like. Preferable examples include cyclohexylethyldimethoxysilane, tert-butylpropyldimethoxysilane, tert-butylethyldimethoxysilane, dicyclopentyldimethoxysilane and the like.

  Examples of the metallocene catalyst (3) include catalyst systems described in Japanese Patent No. 2587251, Japanese Patent No. 2627669, Japanese Patent No. 2668732, and the like.

  Among these, metallocene catalysts are preferably used because a polymer or copolymer having a reduced xylene-soluble content is easily obtained.

  Propylene resins include, for example, solution polymerization using an inert solvent typified by hydrocarbon compounds such as hexane, heptane, octane, decane, cyclohexane, methylcyclohexane, benzene, toluene, and xylene, and liquid monomers as solvents. It can be produced by a bulk polymerization method to be used 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 method for reducing the xylene-soluble content of the propylene-based resin to 1% by weight or less is not particularly limited. For example, in the polymerization stage, the degree of polymerization of the propylene-based resin is increased, and the ratio of relatively low molecular weight components is increased. Methods known to those skilled in the art, such as a method of lowering, a method of washing a propylene-based resin obtained by polymerization with a solvent and extracting and removing solvent-soluble components such as low molecular weight components, and a combination of these methods be able to. In addition, for example, a propylene-based polymer obtained by appropriately selecting a polymerization catalyst and controlling the stereoregularity of the propylene-based resin to isotactic or syndiotactic and / or polymerizing propylene alone. When the xylene-soluble content of the resin is 1% by weight or less, the treatment for reducing the xylene-soluble content of the propylene-based resin obtained by polymerization is not always necessary.

  The propylene-based 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 in a range of 0.1 to 200 g / 10 minutes in accordance with JIS K 7210. It is preferably within a range of 0.5 to 50 g / 10 minutes, and more preferably within a range of 0.5 to 15 g / 10 minutes. By using a propylene resin having an MFR within this range, a uniform propylene resin 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. Examples of antioxidants include phenolic antioxidants, phosphorus antioxidants, sulfur antioxidants, hindered amine light stabilizers, and the like, and for example, phenolic antioxidant mechanisms in one molecule. It is also possible to use a composite antioxidant having a unit having both a phosphorus-based antioxidant mechanism and a phosphorus-based antioxidant mechanism. 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. 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.

  The nucleating agent used in the present invention may be either an inorganic nucleating agent or an organic nucleating agent. Examples of the inorganic nucleating agent include talc, clay, calcium carbonate and the like. Examples of the organic nucleating agent include metal salts such as aromatic carboxylic acid metal salts and aromatic phosphoric acid metal salts, high-density polyethylene, poly-3-methylbutene-1, polycyclopentene, and polyvinylcyclohexane. It is done. Among these, organic nucleating agents are preferable, and the above metal salts and high density polyethylene are more preferable. Moreover, 0.01 to 3 weight% is preferable and, as for the addition amount of the nucleating agent with respect to propylene-type resin, if it is 0.05 to 1.5 weight%, it is more preferable. A plurality of these additives may be used in combination.

  The protective film made of the propylene-based resin film used for the polarizing plate of the present invention can be obtained by forming the propylene-based resin. The protective film made of such a propylene-based resin film is preferably excellent in transparency. Specifically, the total haze value measured according to JIS K 7105 is 10% or less, preferably 7% or less.

  The thickness of the protective film made of a propylene-based resin film is preferably about 5 to 200 μm. More preferably, it is 10 μm or more, and more preferably 150 μm or less.

  The film forming method of the propylene-based resin is not particularly limited, but is an extrusion molding method from a molten resin, a solvent casting method in which a resin dissolved in an organic solvent is cast on a flat plate, and the solvent is removed to form a film. According to these film forming methods, a propylene-based resin film having substantially no in-plane retardation can be obtained.

  A method for producing a propylene-based resin film by extrusion molding will be described in detail. In this method, the propylene-based resin is melted and kneaded by rotation of a screw in an extruder and extruded from a T die into a sheet. The temperature of the molten sheet to be extruded is about 180 to 300 ° C. If the temperature of the molten sheet at this time is lower than 180 ° C., the spreadability is not sufficient, the thickness of the obtained film becomes non-uniform, and there is a possibility that the film has a phase difference unevenness. Further, when the temperature exceeds 300 ° C., the resin is easily deteriorated or decomposed, and bubbles may be generated in the sheet or carbides may be contained.

The extruder may be a single screw extruder or a twin screw extruder. For example, when a single screw extruder is used, 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 V ₁ in the resin supply section, and the screw groove in the resin metering section. The compression ratio, which is the ratio (V ₁ / V ₂ ) to the space volume V ₂ , is about 1.5 to 4 and is a full flight type, a barrier type, or a screw having a Maddock type kneading part. Can be used. From the viewpoint of suppressing deterioration and decomposition of the propylene-based resin and uniformly melting and kneading, the barrier type L / D is 28 to 36 and the compression ratio V ₁ / V ₂ is 2.5 to 3.5. It is preferable to use a screw. In order to suppress deterioration and decomposition of the propylene resin as much as possible, the inside of the extruder is preferably a nitrogen atmosphere or a vacuum. Furthermore, in order to remove the volatile gas generated when the propylene-based resin is deteriorated or decomposed, it is also preferable to provide an orifice of about 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 leading end of the extruder by installing an orifice means increasing the back pressure at the leading end, 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 sharp edge shape with a lip tip 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 (A) or (B), and more preferably satisfies the condition (C) or (D).

(A) When the lip width of the T die is less than 1500 mm: the thickness direction length of the T die> 180 mm,
(B) When the lip width of the T die is 1500 mm or more: length in the thickness direction of the T die> 220 mm,
(C) When the lip width of the T die is less than 1500 mm: the length of the T die in the height direction> 250 mm,
(D) When the lip width of the T die is 1500 mm or more: Length in the height direction of the T die> 280 mm.

  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 protective film made of a propylene-based resin film having excellent accuracy and more uniform retardation can be obtained.

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

  The desired propylene-based resin film consists of a molten sheet extruded from a T-die, a metal cooling roll (also called a chill roll or a casting roll), and an elastic body that rotates by pressing in the circumferential direction of the metal cooling roll. It can obtain by pinching between touch rolls to include and solidifying by cooling. In this case, the touch roll may be one in which an elastic body such as rubber is directly on the surface, or may be one in which the surface of the elastic body 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, cooling is usually performed by directly sandwiching a molten sheet of propylene-based resin between the metal cooling roll and the touch roll. . On the other hand, when using a touch roll whose surface is an elastic body, a biaxially stretched film of a thermoplastic resin can be interposed between the molten sheet of propylene-based resin and the touch roll, and can be sandwiched.

  When the molten sheet of propylene-based resin is cooled and solidified by being sandwiched between the cooling roll and the touch roll as described above, the surface temperature of the cooling roll and the touch roll is lowered, and the molten sheet is rapidly cooled. preferable. For example, the surface temperature of both rolls is preferably adjusted to a range of 0 ° C. or higher and 30 ° C. or lower. When these surface temperatures exceed 30 ° C., it takes time to cool and solidify the molten sheet, so that the crystal component in the propylene resin grows, and the resulting film may be inferior in transparency. . On the other hand, when the surface temperature of the roll is lower than 0 ° C., the surface of the metal cooling roll is dewed and water droplets are attached, which tends to deteriorate the appearance of the raw film.

  Since the surface state of the metal cooling roll to be used is transferred to the surface of the propylene-based resin film, there is a possibility that the thickness accuracy of the resulting propylene-based resin film may be lowered if the surface has irregularities. . 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 as a standard sequence of the maximum height. .

  As for the metal roll and the touch roll forming the nip part, the surface hardness of the elastic body is 65 to 80 as a value measured by a spring type hardness test (A type) defined in JIS K 6301. It is preferable that there is, more preferably 70-80. By using a rubber roll having such a surface hardness, it becomes easy to maintain a uniform linear pressure applied to the molten sheet, and a bank of the molten sheet (resin pool) is provided between the metal cooling roll and the touch roll. ) Can be easily formed into a film.

  The pressure (linear pressure) when sandwiching the molten sheet 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 sandwiching a biaxially stretched film of a thermoplastic resin together with a molten sheet of propylene resin between a metal cooling roll and a touch roll, the thermoplastic resin constituting the biaxially stretched film is composed of a propylene resin and Any resin that does not strongly heat-seal can be used. 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 case, the thickness of the biaxially stretched film is usually about 5 to 50 μm, preferably 10 to 30 μm.

  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 sheet extruded from the T-die is stretched from the lip to the roll, and orientation tends 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.

  Moreover, 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 sheet. When the diameter of the metal cooling roll to be used is increased, the distance at which the molten sheet is in contact with the cooling roll becomes longer, so that production at a higher speed is 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 sheet 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 turns into a roll-like propylene resin film. At this time, in order to protect the surface until the roll-shaped propylene-based resin film is used, the surface protection film made of another thermoplastic resin is bonded to one side or both sides of the roll-shaped propylene resin film. Also good. When a molten sheet of propylene 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. As described above, a protective film made of a propylene-based resin film can be produced.

<Polarizing plate>
In the polarizing plate of the present invention, the protective film composed of the propylene-based resin film may be laminated on both surfaces of the polarizing film, or a protective film composed of the propylene-based resin film is laminated on one surface of the polarizing film, You may make it laminate | stack the protective film which consists of resin films other than a propylene-type resin on the other surface. Examples of the resin film other than the propylene resin include a film made of a cellulose acetate resin such as triacetyl cellulose and diacetyl cellulose, a polyester resin film, a (meth) acrylic resin film, and a polycarbonate resin film. . The thickness of these protective films is usually about 20 to 200 μm, preferably 20 to 120 μm.

  When a protective film made of a propylene-based resin film is laminated on one surface of the polarizing film and a protective film made of a resin film other than the propylene-based resin is laminated on the other surface, the protective film is laminated on the other surface. The protective film made of a resin film other than the propylene-based resin may be a wave plate such as a quarter wave plate or a half wave plate, or a retardation film such as a viewing angle compensation film. In this way, since one protective film also serves as a retardation film, the number of laminated films can be reduced. Therefore, it is possible to reduce the weight and thickness of a liquid crystal display device to which the protective film is applied. It becomes. As a retardation film such as a wave plate or a viewing angle compensation film, a conventionally known film can be used.

  In addition, when integrating with a polarizing film and retardation film, the angle which the absorption axis of a polarizing film and the slow axis of a retardation film make is suitably selected according to the use. For example, in the case of a wave plate, the angle formed between the absorption axis of the polarizing film and the slow axis of the wave plate is 5 to 85 °, and in the case of a viewing angle compensation film, the absorption axis and the field of view of the polarizing film. The angle formed with the slow axis of the angle compensation film is substantially 0 ° or 90 °.

  Next, the bonding method of a polarizing film and a protective film is demonstrated. In the present invention, an adhesive is preferably used for bonding the polarizing film and the protective film. As the adhesive, an adhesive having an epoxy resin, urethane resin, cyanoacrylate resin, acrylamide resin, or the like as an adhesive component can be used. One of the adhesives preferably used in the present invention is a solventless adhesive. Solventless adhesives do not contain a significant amount of solvent, and are curable compounds (monomers or oligomers) that are reactively cured by heating or irradiation with active energy rays (for example, ultraviolet rays, visible light, electron beams, X-rays, etc.) ), And an adhesive layer is formed by curing of the curable compound, and typically includes a curable compound that is reactively cured by heating or irradiation of active energy rays, and a polymerization initiator. Among the solventless adhesives, those that are cured by cationic polymerization are preferable from the viewpoint of reactivity. In particular, solventless epoxy adhesives having an epoxy compound as a curable compound are polarizing films and propylene-based adhesives. Since it is excellent in the adhesiveness with a resin film, and the adhesiveness with a protective film which consists of resin films other than a polarizing film and propylene-type resin, it is more preferable.

  The epoxy compound, which is a curable compound contained in the solventless epoxy adhesive, is not particularly limited, but is preferably one that is cured by cationic polymerization, and particularly from the viewpoint of weather resistance, refractive index, and the like. It is more preferable to use an epoxy compound that does not contain an aromatic ring. Examples of such epoxy compounds that do not contain an aromatic ring in the molecule include hydrides of aromatic epoxy compounds, alicyclic epoxy compounds, and aliphatic epoxy compounds. In addition, the epoxy compound that is a curable compound usually has two or more epoxy groups in the molecule.

  First, the hydride of an aromatic epoxy compound will be described. The hydride of an aromatic epoxy compound can be obtained by selectively hydrogenating an aromatic epoxy compound to an aromatic ring under pressure in the presence of a catalyst. Examples of the aromatic epoxy compound include bisphenol type epoxy resins such as bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, and bisphenol S diglycidyl ether; phenol novolac epoxy resin, cresol novolac epoxy resin, hydroxybenzaldehyde Examples include novolak-type epoxy resins such as phenol novolac epoxy resins; glycidyl ethers of tetrahydroxyphenylmethane, glycidyl ethers of tetrahydroxybenzophenone, and polyfunctional epoxy resins such as epoxidized polyvinylphenol. Especially, it is preferable to use the glycidyl ether of hydrogenated bisphenol A as a hydride of an aromatic epoxy compound.

  Next, the alicyclic epoxy compound will be described. An alicyclic epoxy compound means an epoxy compound having one or more epoxy groups bonded to an alicyclic ring, and “having one or more epoxy groups bonded to an alicyclic ring” is represented by the following formula: Means having the structure shown. In formula, m is an integer of 2-5.

Therefore, the alicyclic epoxy compound is a compound having at least one structure represented by the above formula and having a total of two or more epoxy groups in the molecule. More specifically, a compound in which a group in which one or more hydrogen atoms in (CH ₂ ) _m in the above formula are removed is bonded to another chemical structure can be an alicyclic epoxy compound. One or more hydrogen atoms in (CH ₂ ) _m may be appropriately substituted with a linear alkyl group such as a methyl group or an ethyl group. Among such alicyclic epoxy compounds, an epoxy compound having an epoxycyclopentane ring (m = 3 in the above formula) or an epoxycyclohexane ring (m = 4 in the above formula) has high adhesion strength. It is more preferably used because an excellent adhesive can be obtained. Although the structure of the alicyclic epoxy compound preferably used in the present invention is specifically illustrated below, it is not limited to these compounds.

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 (this compound is 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.

  Examples of the aliphatic epoxy compound include polyglycidyl ethers of aliphatic polyhydric alcohols or alkylene oxide adducts thereof. More specifically, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, glycerin triglycidyl ether, trimethylolpropane triglycidyl ether, polyethylene glycol diglycidyl ether, propylene Polyethers of polyether polyols obtained by adding one or more alkylene oxides (ethylene oxide or propylene oxide) to aliphatic polyhydric alcohols such as glycol diglycidyl ether, ethylene glycol, propylene glycol and glycerin Examples thereof include glycidyl ether.

  In this invention, an epoxy compound may be used individually by 1 type, or may use 2 or more types together.

  The epoxy equivalent of the epoxy compound contained in the solventless epoxy adhesive is usually in the range of 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, when the epoxy equivalent exceeds 3,000 g / equivalent, the compatibility with other components contained in the epoxy adhesive may be lowered.

  The solventless epoxy adhesive preferably contains a cationic polymerization initiator in order to cationically polymerize the epoxy compound. 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. In the present invention, any type of cationic polymerization initiator may be used. However, it is preferable from the viewpoint of workability that the potential is imparted. In the following, a cationic polymerization initiator that generates a cationic species or a Lewis acid upon irradiation with active energy rays such as visible light, ultraviolet rays, X-rays, and electron beams to initiate a polymerization reaction of an epoxy group is a photocationic polymerization initiator. Also called.

  The use of a cationic photopolymerization initiator allows the adhesive component to be cured at room temperature, reducing the need to take into account the heat resistance of the polarizing film or distortion due to expansion. Can be formed. In addition, when a cationic photopolymerization initiator is used, it acts catalytically by light, so that it is excellent in storage stability and workability even when mixed with an epoxy adhesive.

  Although it does not specifically limit as a photocationic polymerization initiator, For example, aromatic diazonium salt, aromatic iodonium salt, onium salts, such as an aromatic sulfonium salt, an iron- allene complex etc. can be mentioned. These cationic photopolymerization initiators may be used alone or in combination of two or more. 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” and “Kayarad PCI-620” (Nippon Kayaku Co., Ltd. )), “UVI-6990” (manufactured by Union Carbide), “Adekaoptomer SP-150”, “Adekaoptomer SP-170” (manufactured by ADEKA, Inc.), “CI-5102”, “ "CIT-1370", "CIT-1682", "CIP-1866S", "CIP-2048S", "CIP-2064S" (Nippon Soda Co., Ltd.), "DPI-101", "DPI-102" , “DPI-103”, “DPI-105”, “MPI-103”, “MPI-105”, “BBI-101”, “BBI-102”, “B I-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.

  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.

  The solventless epoxy adhesive may further contain a photosensitizer as necessary together with the photocationic polymerization initiator. 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 with respect to 100 weight part of epoxy compounds.

  In addition, as a thermal cationic polymerization initiator that generates a cationic species or a Lewis acid by heating and initiates a polymerization reaction of an epoxy group, for example, benzylsulfonium salt, thiophenium salt, thiolanium salt, benzylammonium salt, pyridinium salt, hydrazinium Examples thereof include salts, carboxylic acid esters, sulfonic acid esters, and amine imides. These thermal cationic polymerization initiators can also be easily obtained as commercial products. For example, “ADEKA OPTON CP77”, “ADEKA OPTON CP66” (manufactured by ADEKA Corporation), “CI-” 2639 "," CI-2624 "(manufactured by Nippon Soda Co., Ltd.)," Sun-Aid SI-60L "," Sun-Aid SI-80L "," Sun-Aid SI-100L "(manufactured by Sanshin Chemical Industry Co., Ltd.) ) And the like. These thermal cationic polymerization initiators may be used alone or in admixture of two or more. Moreover, it is also preferable to use photocationic polymerization initiator heat and a cationic polymerization initiator together.

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

  In the case of using a solvent-free epoxy adhesive, the polarizing film and the protective film can be bonded by applying the adhesive to the adhesive surface of the protective film and / or the polarizing film and bonding them together. it can. There is no particular limitation on the method of applying the solvent-free epoxy adhesive to the polarizing film and / or protective film. For example, various coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater. A scheme is available. 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 is not particularly limited as long as it can dissolve the epoxy adhesive well without deteriorating the optical performance of the polarizing film. For example, hydrocarbons typified by toluene, typified by ethyl acetate, and the like. Organic solvents such as esters can be used.

  After bonding a protective film to the polarizing film through an adhesive layer made of an uncured epoxy adhesive, the adhesive layer is cured and protected by irradiating active energy rays or heating. The film is fixed on the polarizing film. 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 such as ultraviolet rays are appropriately selected so as to sufficiently activate the cationic polymerization initiator and not adversely affect the cured adhesive layer, polarizing film, and protective film. In addition, when cured by heating, it can be heated by a generally known method, and the temperature and time at that time can sufficiently activate the cationic polymerization initiator, and the cured adhesive layer or It is appropriately selected so as not to adversely affect the polarizing film and the protective film.

  The thickness of the adhesive layer made of the epoxy adhesive after curing obtained as described above is usually 50 μm or less, preferably 20 μm or less, more preferably 10 μm or less, and usually 1 μm or more.

  The solventless epoxy adhesive is bonded to a protective film made of a propylene-based resin film and a polarizing film, or bonded to a protective film made of a resin film other than a propylene-based resin and a polarizing film, or these It can use preferably for both bonding.

  Another preferable adhesive that can be used in the present invention includes a water-based adhesive, that is, an adhesive component dissolved in water, or a dispersion in water. When a water-based adhesive is used, the thickness of the adhesive layer can be further reduced. Examples of the water-based adhesive include an adhesive component containing, for example, a water-soluble crosslinkable epoxy resin or a water-soluble urethane resin.

  As a water-soluble crosslinkable epoxy resin, for example, a polyalkylene polyamine such as diethylenetriamine or triethylenetetramine and a polyamide polyamine obtained by a reaction of a dicarboxylic acid such as adipic acid are reacted with epichlorohydrin. Mention may be made of the polyamide epoxy resin obtained. Examples of such commercially available polyamide epoxy resins include “Smiles Resin 650” and “Smiles Resin 675” (both trade names) sold by Sumika Chemtex Co., Ltd.

  When a water-soluble crosslinkable 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. Of these, a saponified product of a copolymer of vinyl acetate and an 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 alcohol include, for example, “Kuraray Poval KL-506”, “Kuraray Poval KL-318”, “Kuraray Poval 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. "AF-17", "AT-17", "AP-17" etc. which are sold from the corporation | Co., Ltd. are mentioned.

  The adhesive containing a water-soluble crosslinkable epoxy resin can be prepared as an adhesive solution by dissolving the above epoxy resin and other water-soluble resin such as a polyvinyl alcohol resin added as necessary in water. In this case, it is preferable that the water-soluble crosslinkable epoxy resin has a concentration in the range of about 0.2 to 2 parts by weight with respect to 100 parts by weight of water. Moreover, when mix | blending polyvinyl alcohol-type resin, it is preferable that the quantity shall be about 1-10 weight part with respect to 100 weight part of water, Furthermore, it is 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-type 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 preferable to further blend 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 dissolved or dispersed in water are preferred. When the isocyanate crosslinking agent is blended, the blending amount is 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.

  In the case of using the above water-based adhesive, the polarizing film and the protective film can be adhered by applying the adhesive to the adhesive surface of the protective film and / or the polarizing film and bonding them together. More specifically, a water-based adhesive is uniformly applied to the polarizing film and / or protective film by, for example, a coating method such as a doctor blade, a wire bar, a die coater, a comma coater, or a gravure coater. The other film is stacked and bonded with a roll or the like and dried. Drying can be performed at a temperature of about 60 to 100 ° C., for example. In order to further improve the adhesiveness, it is preferable to cure for about 1 to 10 days after drying at a temperature slightly higher than room temperature, for example, a temperature of about 30 to 50 ° C.

  The water-based adhesive is bonded to a protective film made of a propylene-based resin film and a polarizing film, or a protective film made of a resin film other than a propylene-based resin and polarized light, like the solventless epoxy adhesive. It can be preferably used for pasting with a film or for pasting both of them. When a protective film made of a propylene resin film is laminated on both surfaces of the polarizing film, a protective film made of a propylene resin film is laminated on one surface of the polarizing film, and a resin film other than the propylene resin is laminated on the other surface In the case of laminating a protective film (including a retardation film such as a wave plate or a viewing angle compensation film, the same applies hereinafter), the same adhesion as that of the film laminated on both surfaces of the polarizing film An agent may be used or a different adhesive may be used, but it is preferable to use the same adhesive in order to simplify the manufacturing process and reduce the number of constituent members of the polarizing plate.

  In the production of the polarizing plate, a corona discharge treatment is applied to the surface of the protective film made of a propylene-based resin or the protective film made of a resin film other than the propylene-based resin, which is bonded to the polarizing film. It is preferable. By performing the corona discharge treatment, the adhesive force between these films and the polarizing film 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 the corona discharge treatment varies depending on the type of electrode, electrode interval, voltage, humidity, type of resin film used, etc., 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 polarizing film is bonded to the treated surface via the adhesive as described above.

  As described above, a protective film made of a propylene-based resin film is laminated on one side of a polarizing film made of a polyvinyl alcohol-based resin on which a dichroic dye is adsorbed and oriented, and a protective film made of the same or different resin is laminated on the other side. A polarizing plate on which films are laminated is obtained.

  The polarizing plate thus obtained can be formed as a polarizing plate with an adhesive layer by forming an adhesive layer on one protective film. Such an adhesive layer can be suitably used, for example, for bonding with a liquid crystal cell when the polarizing plate is applied to a liquid crystal display device. When a protective film made of a propylene-based resin film is laminated on one surface of a polarizing film and a protective film made of a resin film other than a propylene-based resin is laminated on the other surface, the adhesive layer is on any protective film It may be formed. In the case where a protective film made of a propylene-based resin film is laminated on one surface of the polarizing film and a protective film that is a retardation film such as a wavelength plate or a viewing angle compensation film is laminated on the other surface, an adhesive The layer may be formed on a protective film that is the retardation film.

  As the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer, 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. In the pressure-sensitive adhesive, a polar monomer is usually copolymerized in these base polymers. Examples of the polar monomer include (meth) acrylic acid, 2-hydroxyethyl (meth) acrylate, (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. The pressure-sensitive adhesive usually contains one or more crosslinking agents in addition to the base polymer. Examples of the crosslinking agent include divalent or polyvalent metal salts that form a carboxylic acid metal salt with a carboxyl group, and polyisocyanate compounds that form an amide bond with a carboxyl group.

  The thickness of the pressure-sensitive adhesive layer can be about 5 to 50 μm. When the pressure-sensitive adhesive layer is applied to the polarizing plate, a surface treatment such as corona treatment may be applied to the surface of the protective film of the polarizing plate. Moreover, when forming an adhesive layer, it is normal to cover the surface with a peeling film.

<Laminated optical member>
When the polarizing plate of the present invention is applied to a liquid crystal display device, an optical layer showing an optical function other than the polarizing function can be provided on one protective film side to form a laminated optical member. Examples of the optical layer laminated on the polarizing plate for the purpose of forming a laminated optical member include a retardation film, a light collecting sheet, a brightness enhancement film, and a surface treatment layer such as an antireflection layer and an antiglare layer. Can do.

  As said retardation film, when one protective film bonded by a polarizing film is a retardation film (for example, 1/2 wavelength plate), it can be set, for example as a 1/4 wavelength plate, In this case, The retardation film is bonded onto a protective film that is a retardation film. Moreover, when the protective film bonded to the polarizing film is not a retardation film, the retardation film used for forming the laminated optical member may be a half-wave plate or a quarter-wave plate, Further, it may be a broadband quarter wavelength plate combining these. In this case, the retardation film may be laminated on any protective film. Therefore, the retardation film used for forming the laminated optical member may be a laminate of two or more films for the purpose of controlling optical properties such as broadening the bandwidth.

  Examples of the resin constituting the retardation film include polycarbonate resins, polyvinyl alcohol resins, polystyrene resins, (meth) acrylate resins, polyolefin resins such as polypropylene, polyarylate resins, polyimide resins, and polyamides. Based resins and the like. A retardation film can be obtained by stretching a film made of such a resin by an appropriate method such as uniaxial or biaxial. The retardation film may be a birefringent film in which the refractive index in the thickness direction of the film is controlled by applying a shrinkage force and / or stretching force under adhesion with the heat-shrinkable film.

  An adhesive layer may be formed on the retardation film for bonding with a liquid crystal cell or the like. As the pressure-sensitive adhesive layer, the same layer as described above can be used.

  The condensing sheet is used for the purpose of optical path control and can be formed as a prism array sheet, a lens array sheet, or a dot-attached sheet.

  The brightness enhancement film is used for the purpose of improving the brightness in a liquid crystal display device or the like. For example, a plurality of thin film films having different refractive index anisotropies are laminated to anisotropy in reflectance. Examples thereof include a reflection type polarization separation sheet designed so as to produce a cholesteric liquid crystal polymer alignment film, and a circular polarization separation sheet in which the alignment liquid crystal layer is supported on a film substrate.

  Further, the laminated optical member of the present invention may be one in which a surface treatment layer such as an antireflection layer or an antiglare layer is formed on one surface of the polarizing plate. Such a surface treatment layer is usually formed on a protective film on the side opposite to the side to be bonded to the liquid crystal cell in the polarizing plate.

<Liquid crystal display device>
The polarizing plate of the present invention or the laminated optical member in which an optical layer is laminated thereon can be suitably applied to a liquid crystal display device. The liquid crystal display device of the present invention includes the polarizing plate or laminated optical member of the present invention and a liquid crystal cell, and preferably these are bonded via an adhesive layer. As described above, the pressure-sensitive adhesive layer is usually a pressure-sensitive adhesive layer laminated on one protective film of a polarizing plate or a pressure-sensitive adhesive layer formed on a laminated optical member. In the case where the laminated optical member is bonded to the liquid crystal cell via the pressure-sensitive adhesive layer, the laminated optical member may be bonded to the liquid crystal cell on any protective film side. For example, one protective film has a retardation. In the case of a film or when a retardation film is laminated on one protective film, it is usually bonded to a liquid crystal cell on the retardation film side.

  As the liquid crystal cell constituting the liquid crystal display device, various types known in this field such as TN (Twisted Nematic), STN (Super Twisted Nematic), VA (Vertical Alignment), IPS (In-Plane Switching), OCB, etc. The mode can be mentioned.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited by these examples. Various physical properties in Examples and Comparative Examples were measured by the following methods.

(A) Measurement of xylene-soluble content of propylene-based resin film at 20 ° C. After 5 g of propylene-based resin film was added to 500 ml of boiling xylene and completely dissolved, the temperature was lowered to 20 ° C. and held at 20 ° C. for 4 hours. . Subsequently, the xylene solution was filtered to separate the precipitate and the filtrate, the solvent was removed from the filtrate, and further dried at 70 ° C. under reduced pressure to obtain a dried xylene-soluble component, and the weight was measured. . The xylene solubles were determined from the following formula.
Xylene soluble content [% by weight] = (weight of dried xylene soluble component [g]) / (5 [g]) × 100

(B) Ethylene content (% by weight) in propylene resin
The ethylene content was determined by IR spectrum measurement and according to the method relating to (i) random copolymer described on page 616 of “Polymer Analysis Handbook” (1995, published by Kinokuniya Shoten).

(C) Change in transmittance of polarizing plate The decrease in the transmittance of the polarizing plate in a high temperature environment was evaluated by measuring the change in haze before and after the heat resistance test shown below. The haze of the polarizing plate was measured according to JIS K 7105. It shows that the fall of the transmittance | permeability is so large that the change of the haze before and behind a heat resistance test is large.

<Example 1>
A propylene homopolymer having a melt flow rate of 8 g / min and having isotactic stereoregularity was formed by an extruder to obtain a protective film made of a propylene-based resin film having a thickness of 80 μm. The xylene-soluble content of this protective film at 20 ° C. was 0.2% by weight. Next, one side of this protective film is subjected to a corona discharge treatment under the condition of an integrated irradiation amount of 1,680 J, and then within 30 seconds, the corona treatment surface and the polarizing film are passed through an epoxy-based ultraviolet curable adhesive. And pasted. Separately, one side of a retardation film made of norbornene-based resin [“ZB-55124” obtained from Optes Co., Ltd.] was subjected to a corona discharge treatment under the condition of an integrated irradiation amount of 1,680 J. The corona-treated surface and the other surface of the polarizing film were bonded through the same epoxy-based ultraviolet curable adhesive. Thereafter, using an ultraviolet irradiation system manufactured by Fusion UV Systems, ultraviolet rays were irradiated from the propylene resin film side under the conditions of an output of 200 mW and an irradiation amount of 200 mJ to cure the adhesive. Thus, a polarizing plate was obtained in which a protective film made of a propylene-based resin film was laminated on one side of the polarizing film, and a retardation film made of a norbornene-based resin was laminated on the other side via an epoxy-based ultraviolet curable adhesive. In addition, as an epoxy type ultraviolet curable adhesive, the product name "Celoxide 2021P" manufactured by Daicel Corporation is included as an adhesive component, and the product name "Adeka Opton CP77" manufactured by ADEKA Corporation as a photocationic polymerization initiator. A solvent-free epoxy adhesive containing was used.

  When the above polarizing plate was subjected to a heat resistance test for 500 hours under drying at 80 ° C., the surface of the protective film made of the propylene-based resin film was as good as before the test. Moreover, when the hazes before and after the heat resistance test were measured, the amount of change was 0.1%, and it was confirmed that almost no decrease in transmittance occurred.

<Example 2>
As a protective film composed of a propylene-based resin film, a propylene-ethylene random copolymer having an melt flow rate of 7 g / min and an isotactic stereoregularity (ethylene content 3.7% by weight, using a metallocene catalyst) A polarizing plate was prepared in the same manner as in Example 1 except that a propylene-based resin film comprising a synthetic resin was used and the resin film having a xylene-soluble content at 20 ° C. of 0.4% by weight was used. .

  When the same heat resistance test was performed on the polarizing plate, the surface of the protective film made of the propylene-based resin film was as good as before the test. Further, when the haze before and after the heat resistance test was measured, the amount of change was 0.14%, and it was confirmed that there was almost no decrease in transmittance.

<Example 3>
As a protective film made of a propylene-based resin film, a high-density polyethylene G1900 manufactured by Keiyo Polyethylene Co., Ltd. is 1 wt% to a propylene homopolymer having a melt flow rate of 8 g / min and isotactic stereoregularity. A polarizing plate was produced in the same manner as in Example 1 except that the added propylene-based resin film having a xylene-soluble content at 20 ° C. of 0.2% by weight was used.

  When the same heat resistance test was performed on the polarizing plate, the surface of the protective film made of the propylene-based resin film was as good as before the test. Moreover, when the hazes before and after the heat resistance test were measured, the amount of change was 0.1%, and it was confirmed that almost no decrease in transmittance occurred.

<Example 4>
As a protective film made of a propylene-based resin film, a propylene homopolymer having a melt flow rate of 8 g / min and an isotactic stereoregularity is added to an organic nucleating agent “ADEKA STAB NA-21 manufactured by ADEKA Corporation. A polarizing plate in the same manner as in Example 1 except that a 0.1% by weight propylene-based resin film having a xylene-soluble content at 20 ° C. of 0.2% by weight was used. Was made.

  When the same heat resistance test was performed on the polarizing plate, the surface of the protective film made of the propylene-based resin film was as good as before the test. Moreover, when the hazes before and after the heat resistance test were measured, the amount of change was 0.1%, and it was confirmed that almost no decrease in transmittance occurred.

<Example 5>
A retardation film made of a norbornene resin [“ZB-55124” obtained from Optes Co., Ltd.] was replaced with a triacetyl cellulose film [“KC8UX2MW” obtained from Konica Co., Ltd.] and polarized in the same manner as in Example 1. A plate was made.

  When the same heat resistance test was performed on the polarizing plate, the surface of the protective film made of the propylene-based resin film was as good as before the test. Moreover, when the hazes before and after the heat resistance test were measured, the amount of change was 0.1%, and it was confirmed that almost no decrease in transmittance occurred.

<Comparative Example 1>
As a protective film comprising a propylene resin film, a propylene resin comprising a propylene-ethylene random copolymer (ethylene content 4.6% by weight) having a melt flow rate of 8 g / min and having isotactic stereoregularity A polarizing plate was produced in the same manner as in Example 1 except that a resin film having a xylene-soluble content at 20 ° C. of 4% by weight was used.

  When the same heat resistance test was performed on the polarizing plate, a white bleed product was generated on the entire surface of the protective film made of the propylene-based resin film. Moreover, when the haze before and behind a heat resistance test was measured, the change amount was 14% and it was confirmed that the transmittance | permeability has fallen.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

Claims (9)

A polarizing plate in which protective films are laminated on both sides of a polarizing film made of a polyvinyl alcohol-based resin film on which a dichroic dye is adsorbed and oriented,
At least one of the protective films is made of a propylene-based resin film,
The propylene-based resin film has a xylene soluble content at 20 ° C. of 1% by weight or less.   The polarizing plate according to claim 1, wherein the propylene-based resin constituting the propylene-based resin film has a syndiotactic or isotactic stereoregularity.   The polarizing plate according to claim 1, wherein the propylene resin constituting the propylene resin film is a homopolymer of propylene.   The polarizing plate according to claim 1, wherein the propylene-based resin film contains a nucleating agent. Of the protective films laminated on the polarizing film, one is a protective film made of the propylene-based resin film,
5. The polarizing plate according to claim 1, wherein the other is a wave plate or a viewing angle compensation film.   The polarizing plate according to claim 1, wherein at least one protective film is laminated on the polarizing film via a solvent-free epoxy adhesive.   The polarizing plate according to claim 6, wherein the solventless epoxy adhesive is cured by cationic polymerization by heating or irradiation with active energy rays.   The laminated optical member which consists of a laminated body of the polarizing plate in any one of Claims 1-7, and the optical layer which shows another optical function.   A liquid crystal display device, wherein the polarizing plate according to claim 1 or the laminated optical member according to claim 8 is bonded to a liquid crystal cell via an adhesive layer.