JP2012215856A - Polarizing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizing plate which has a propylene-based resin film improved in rigidity and hardly causes deformation under severe conditions such as high temperature conditions while maintaining transparency.SOLUTION: There is provided a polarizing plate in which transparent resin films are laminated on each of both surfaces of a polarizing film made of a polyvinyl alcohol-based resin via an adhesive. One of the transparent resin films is a polarizing plate which is a propylene-based resin film containing a nucleating agent in the range of 50 to 6000 ppm. It is advantageous that one of the transparent resin films laminated on both surfaces of the polarizing film is composed of the propylene-based resin film and the other is composed of a norbornene resin film.

Description

  The present invention relates to a polarizing plate in which a propylene resin film is laminated as a protective film on at least one surface of a polarizing film made of a polyvinyl alcohol resin.

  Applications of liquid crystal display devices are rapidly expanding as thin display devices such as liquid crystal televisions, liquid crystal monitors, and personal computers. In particular, the market for liquid crystal televisions is remarkably expanding, and the demand for cost reduction is very high. Liquid crystal display devices such as liquid crystal televisions are stacked and used in a predetermined configuration using the polarizing plate as a constituent member.

  A polarizing plate is usually a protective film, for example, a cellulose acetate-based protective film represented by triacetyl cellulose, with an adhesive layer on one or both sides of a polarizing film made of a polyvinyl alcohol-based resin to which a dichroic dye is adsorbed and oriented. It is the structure which laminated | stacked. This is bonded to the liquid crystal cell with an adhesive via another optical film as necessary, to obtain a component part of the liquid crystal display device.

  However, when a hydrophilic protective film is used, the moisture content of the polarizing film made of a polyvinyl alcohol-based resin is affected under high-temperature and high-humidity conditions, and the performance as a polarizing plate may change somewhat. For this reason, instead of a protective film made of a hydrophilic resin, a polarizing plate having a structure in which a hydrophobic protective film made of, for example, a propylene resin is used and the influence of the environment can be suppressed as much as possible has been studied (for example, specially No. 2009-258588 (Patent Document 1) and the like).

  On the other hand, there are cases where the usage environment is in a high temperature state, such as in-vehicle use, among liquid crystal display devices, and the polarizing plate which is a constituent member may be in a high temperature state due to the heat from the backlight even in televisions, monitors, etc. In order to exhibit stable performance in a severe condition, a polarizing plate having a higher performance than the polarizing plate using a protective film made of a propylene-based resin disclosed in Patent Document 1 has been desired.

  The polarizing plate described in Patent Document 1 is a polarizing plate in which a film made of a hydrophobic material is disposed on both sides of the polarizing film, so that the polarizing film is less affected by the use environment. When the polarizing film made of polyvinyl alcohol resin is greatly shrunk due to use at a high temperature because the glass transition temperature of the propylene resin is low and flexible, the performance of suppressing the shrinkage may be slightly insufficient. As a polarizing plate, there was a problem that it might be accompanied by deformation.

JP 2009-258588 A

  The present inventors thought that the reason why the polarizing plate deforms in a harsh environment such as a high temperature condition is that the propylene-based resin film as the protective film is too flexible. In order to improve the rigidity of the propylene-based resin film at a high temperature, the propylene-based resin film may be formed by a method in which many crystal components are formed. However, if the propylene-based resin film is produced under more slow cooling conditions, the crystallinity can be increased, but the transparency is impaired, which is not preferable.

  The present invention has been made in order to solve the above-mentioned problems, and the object of the present invention is to provide a propylene-based resin film with improved rigidity while maintaining transparency, and severe conditions such as high temperature conditions. It is to provide a polarizing plate that is hardly deformed in the environment.

  The present invention is a polarizing plate in which a transparent resin film is bonded to both surfaces of a polarizing film made of a polyvinyl alcohol resin via an adhesive, and at least one of the transparent resin films contains a nucleating agent of 50. It is a propylene-type resin film contained in the range of -6000 ppm.

  In the polarizing plate of the present invention, it is preferable that one of the transparent resin films is a propylene-based resin film containing a nucleating agent in a range of 50 to 6000 ppm, and the other transparent resin film is a norbornene-based resin film. .

  In the polarizing plate of the present invention, from the viewpoint of lowering the haze value of the polypropylene resin film, the content of the nucleating agent in the polypropylene resin film is preferably in the range of 250 to 6000 ppm. On the other hand, from the viewpoint of increasing the total light transmittance in a state where reflection and diffusion on the surface of the polypropylene resin film are eliminated, and suppressing the decrease in the transmittance when the polarizing plate is used, the nucleating agent in the polypropylene resin film The content is preferably in the range of 50 to 250 ppm.

  From one viewpoint, the nucleating agent is preferably calcium cyclohexane-1,2-dicarboxylate represented by the following structural formula.

  On the other hand, from another viewpoint, the nucleating agent is N, N ′, N ″ -tris (2-methylcyclohexyl) -propane-1,2,3-tricarboxamide represented by the following structural formula. Is also preferable.

  According to the present invention, it is possible to obtain a polarizing plate that includes a propylene-based resin film with improved rigidity while maintaining transparency and is less likely to be deformed in a severe environment such as a high temperature condition.

Polarized light when the horizontal axis represents the total haze (%) of a film obtained by forming a propylene-based resin with or without a nucleating agent and pasted it on a polarizing film to form a polarizing plate It is a graph when the amount of decrease in the single transmittance (%) of the plate is plotted on the vertical axis, and the relationship between the two is plotted. The total light transmittance (%) at the time of measuring the internal haze of the target film in FIG. 1 is plotted on the horizontal axis, and the amount of decrease in the single transmittance (%) of the polarizing plate when the polarizing film is applied to the polarizing film. Is a graph in which the relationship between the two is plotted.

(Polarizing film)
Specifically, the polarizing film used in the polarizing plate of the present invention is obtained by adsorbing and orienting a dichroic dye on a uniaxially stretched polyvinyl alcohol resin film. The polyvinyl alcohol-based resin can be obtained by saponifying a polyvinyl acetate-based resin. As the polyvinyl acetate resin, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate, copolymers of vinyl acetate and other monomers copolymerizable therewith, such as ethylene-vinyl acetate copolymer, etc. Is mentioned. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

  The saponification degree of the polyvinyl alcohol resin is usually 85 to 100 mol%, preferably 98 mol% or more. These polyvinyl alcohol resins may be modified. For example, polyvinyl formal, polyvinyl acetal, polyvinyl butyral and the like modified with aldehydes may be used. Moreover, the polymerization degree of polyvinyl alcohol-type resin is in the range of 1000-10000 normally, Preferably it exists in the range of 1500-5000.

  A film obtained by forming such a polyvinyl alcohol resin is used as a raw film of a polarizing film. The method for forming the polyvinyl alcohol-based resin is not particularly limited, and can be formed by a conventionally known appropriate method. Although the film thickness of the raw film which consists of polyvinyl alcohol-type resin is not specifically limited, For example, it is about 10-150 micrometers.

  A polarizing film usually includes a process of dyeing a polyvinyl alcohol resin film with a dichroic dye and adsorbing the dichroic dye (dyeing process), and a polyvinyl alcohol resin film on which the dichroic dye is adsorbed. It is manufactured through a step of treating with an acid aqueous solution (boric acid treatment step) and a step of washing with water after the treatment with the boric acid aqueous solution (water washing treatment step).

  Further, in the production of the polarizing film, the polyvinyl alcohol-based resin film is usually uniaxially stretched, but this uniaxial stretching may be performed before the dyeing treatment step or during the dyeing treatment step, It may be performed after the dyeing process. When uniaxial stretching is performed after the dyeing treatment step, this uniaxial stretching may be performed before the boric acid treatment step or during the boric acid treatment step. Of course, it is also possible to perform uniaxial stretching in these plural stages. Uniaxial stretching may be performed uniaxially between rolls having different peripheral speeds, or may be performed uniaxially 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 3 to 8 times.

  The dyeing of the polyvinyl alcohol-based resin film with the dichroic dye in the dyeing treatment step is performed, for example, by immersing the polyvinyl alcohol-based resin film in an aqueous solution containing the dichroic dye. As the dichroic dye, for example, iodine, a dichroic dye or the like is used. Examples of dichroic dyes include C.I. I. Dichroic direct dyes composed of disazo compounds such as DIRECT RED 39 and dichroic direct dyes composed of compounds such as trisazo and tetrakisazo are included. In addition, it is preferable that the polyvinyl alcohol-type resin film performs the immersion process to water before a dyeing process.

  When iodine is used as the dichroic dye, a method of dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide is usually employed. The content of iodine in this aqueous solution is usually 0.01 to 1 part by weight per 100 parts by weight of water, and the content of potassium iodide is usually 0.5 to 20 parts by weight per 100 parts by weight of water. When iodine is used as the dichroic dye, the temperature of the aqueous solution used for dyeing is usually 20 to 40 ° C., and the immersion time (dyeing time) in this aqueous solution is usually 20 to 1800 seconds.

On the other hand, when a dichroic dye is used as the dichroic dye, a method of immersing and dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing an aqueous dichroic dye is usually employed. The content of the dichroic dye in this aqueous solution, usually, 1 × 10 ^-4 to 10 parts by weight per 100 parts by weight of water, preferably 1 × 10 ^-3 to 1 parts by weight, particularly preferably 1 × 10 ^{- 3} to 1 × 10 ⁻² parts by weight. This aqueous solution may contain an inorganic salt such as sodium sulfate as a dyeing assistant. When a dichroic dye is used as the dichroic dye, the temperature of the dye aqueous solution used for dyeing is usually 20 to 80 ° C., and the immersion time (dyeing time) in this aqueous solution is usually 10 to 1800 seconds. is there.

  The boric acid treatment step is performed by immersing a polyvinyl alcohol-based resin film dyed with a dichroic dye in a boric acid-containing aqueous solution. The amount of boric acid in the boric acid-containing aqueous solution is usually 2 to 15 parts by weight, preferably 5 to 12 parts by weight per 100 parts by weight of water. When iodine is used as the dichroic dye in the dyeing process described above, the boric acid-containing aqueous solution used in this boric acid treatment process preferably contains potassium iodide. In this case, the amount of potassium iodide in the boric acid-containing aqueous solution is usually 0.1 to 15 parts by weight, preferably 5 to 12 parts by weight per 100 parts by weight of water. The immersion time in the boric acid-containing aqueous solution is usually 60 to 1200 seconds, preferably 150 to 600 seconds, and more preferably 200 to 400 seconds. The temperature of the boric acid-containing aqueous solution is usually 50 ° C. or higher, preferably 50 to 85 ° C., more preferably 60 to 80 ° C.

  In the subsequent washing process, the polyvinyl alcohol-based resin film after the boric acid treatment described above is washed with water, for example, by immersing it in water. The water temperature in the water washing treatment is usually 5 to 40 ° C., and the immersion time is usually 1 to 120 seconds. After the water washing treatment, a drying treatment is usually performed to obtain a polarizing film. The drying process is preferably performed using, for example, a hot air dryer or a far infrared heater. The temperature of the drying treatment is usually 30 to 100 ° C, preferably 50 to 80 ° C. The time for the drying treatment is usually 60 to 600 seconds, preferably 120 to 600 seconds.

  In this way, the polyvinyl alcohol resin film is uniaxially stretched, dyed with a dichroic dye, treated with boric acid and washed with water to obtain a polarizing film. The thickness of this polarizing film is usually in the range of 5 to 40 μm. The polarizing plate of the present invention is produced by laminating a transparent resin film on both sides of such a polarizing film via an adhesive, and at least one of the transparent resin films to be laminated on both sides is manufactured. It is comprised with the polarizing plate protective film which consists of a propylene-type resin film containing 50-6000 ppm of a nucleating agent.

(Protective film)
In the present invention, a propylene-based resin film containing 50 to 6000 ppm of a nucleating agent is bonded to at least one surface of the polarizing film as a protective film. When the content of the nucleating agent is within the above range, the propylene-based resin film is improved in rigidity while maintaining transparency. This makes it a good polarizing plate with little deformation even under various usage environments.

  The propylene-based resin may be a propylene homopolymer or 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. The α-olefin has 4 or more carbon atoms, preferably an α-olefin having 4 to 12 carbon atoms. Specific examples of the α-olefin having 4 to 12 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 and 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.

  When the propylene-based resin is composed of the copolymer, specific examples of the copolymer include propylene-ethylene random copolymer, propylene-1-butene random copolymer, and propylene-ethylene-1-butene random copolymer. Examples thereof include binary to ternary copolymers of propylene and one or more monomers selected from the group consisting of ethylene and an α-olefin having 4 to 12 carbon atoms. .

  When the propylene resin is made of the copolymer, the structural unit derived from propylene can be selected according to characteristics such as heat resistance. When high heat resistance is required, it is preferable to contain a large amount of structural units derived from propylene, specifically 96% by weight or more. 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.

  In addition, the stereoregularity of the propylene homopolymer and the propylene copolymer may be any of isotactic, syndiotactic, and atactic, but from the viewpoint of excellent balance of rigidity and transparency after being formed into a film. A propylene polymer having high isotacticity is preferred.

  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.

(A) a Ti—Mg-based catalyst comprising a solid catalyst component containing magnesium, titanium and halogen as essential components;
(B) 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,
(C) Metallocene catalyst.

  Examples of the solid catalyst component (A) 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 (B) 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 (C) include catalyst systems described in Japanese Patent No. 2587251, Japanese Patent No. 2627669, Japanese Patent No. 2668732, and the like.

  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 propylene-based resin film used in the present invention is formed into a film by extruding the propylene-based resin by a melt extrusion method. In this case, the propylene-based resin has a temperature of 230 ° C. and a load according to JIS K7210. The melt flow rate (MFR) measured at 21.18N is preferably in the range of 1-30 g / 10 minutes, more preferably in the range of 1-20 g / 10 minutes, and 1.5-15 g More preferably, it is within the range of / 10 minutes. By using a propylene-based resin having an MFR within this range, a film having a uniform thickness can be easily produced while reducing the load on the extruder in film forming by melt extrusion.

  In the present invention, a film is formed from a resin composition in which a nucleating agent is blended in the proportion of 50 to 6000 ppm with the propylene-based resin described above, and this is at least a transparent resin film bonded to both surfaces of the polarizing film. Use as one. Here, ppm is based on weight. The nucleating agent is a compound that becomes a nucleus of crystallization when the propylene-based resin composition is solidified from a molten state and crystallized. Such a polarizing plate bonded with a propylene-based resin film in which a nucleating agent is blended at a predetermined ratio has improved rigidity particularly at high temperatures while maintaining transparency. When the blending ratio of the nucleating agent is less than 50 ppm, the effect of improving the rigidity becomes insufficient, and when the blending ratio exceeds 6000 ppm, problems may occur when forming a film.

  When film forming is performed by melt extrusion method, the problem at the time of film formation is that the molten film of propylene-based resin extruded from the T-die is cooled and solidified by contact with a cooling roll and wound into a film. At this time, for example, the following will be taken. That is, for one thing, if the amount of the nucleating agent is too large, the crystallization speed becomes too fast, so that the crystallization of the molten film starts before contacting the cooling roll, and it becomes impossible to adhere to the cooling roll uniformly. The film tends to be a film having a rough surface. The other is that the melted film extruded from the T-die is placed in contact with the cooling roll by static electricity or air before the center in the width direction in order to ensure molding stability. If the amount of the nucleating agent is too large, crystallization will occur from the moment the molten film contacts the both ends of the cooling roll, even if crystallization does not occur in the molten film before contacting the cooling roll. As a result, only both end portions of the film first undergo volume contraction and stress is applied to the central portion. As a result, only the central portion is poorly adhered to the cooling roll, and the appearance of the film is easily damaged. From these viewpoints, the addition amount of the nucleating agent is 50 to 6000 ppm as described above.

  Propylene-based resin nucleating agents include inorganic compounds and organic compounds. Talc is a typical inorganic nucleating agent. Propylene-based resin nucleating agents may be classified into a dispersion type and a dissolution type. The dispersion type nucleating agent is dispersed in the resin without being dissolved even in the molten propylene resin, and becomes a starting point of crystal growth in the cooling process. Talc, which is an inorganic compound, is classified as a dispersion type nucleating agent. On the other hand, the melt-type nucleating agent dissolves in the molten propylene resin, and the nucleating agent itself forms a three-dimensional network by hydrogen bonding in the molten propylene resin during the cooling process. From this point, the crystal is grown. Therefore, the melt-type nucleating agent is composed exclusively of organic compounds. The melt type nucleating agent will be described later. As described above, the dispersion-type nucleating agent is dispersed in the molten propylene-based resin and becomes the starting point of crystal growth in the cooling process. Therefore, the amount of addition is within the range of 50 to 6000 ppm. What is necessary is just to select suitably according to the characteristic of these. However, depending on the addition amount, the nucleating agent itself may cause a deterioration in transmittance, so the preferable addition amount is 50 to 2000 ppm. On the other hand, when a melt-type nucleating agent is used, it is sufficient to add an amount capable of forming a network, and therefore the preferable addition amount is 50 to 1500 ppm.

  Examples of the dispersion type organic nucleating agent include a monocarboxylic acid metal salt compound, a dicarboxylic acid metal salt compound, a phosphate ester metal salt compound, and a rosin ester metal salt compound. Examples of the monocarboxylic acid metal salt nucleating agent include sodium benzoate. As a dicarboxylic acid metal salt-based nucleating agent, bicyclo [2.2.1] heptane-2,3-dicarboxylate having the structure of the following formula (1) and cyclohexane having the structure of the following formula (2) An example is calcium 1,2-dicarboxylate. Examples of the phosphoric acid ester metal salt nucleating agent include [phosphoric acid {2,2′-methylenebis (4,6-di-tert-butylphenyl)}] sodium having the structure of the following formula (3): Examples of the rosin ester metal salt nucleating agent include magnesium dehydroabietic acid having a structure of the following formula (4).

  Examples of the melt-type nucleating agent include sorbitol compounds and trisamide compounds. As the sorbitol nucleating agent, 1-O, 3-O having the structure of the following formula (5); 2-O, 4-O-bis (4-methylbenzylidene) -D-sorbitol, the following formula (6) 1-O, 3-O having the structure: 2-O, 4-O-bis (4-ethylbenzylidene) -D-sorbitol, 1-O, 3-O having the structure of the following formula (7); 2 -O, 4-O-bis (3,4-dimethylbenzylidene) -D-sorbitol, and 1-O, 3-O having the structure of the following formula (8); 2-O, 4-O-bis (4 -Propylbenzylidene) -1-propyl-D-sorbitol is exemplified.

  As the trisamide nucleating agent, N, N ′, N ″ -tricyclohexyl-1,3,5-benzenetricarboxamide having the structure of the following formula (9), and the structure of the following formula (10) are used. N, N ′, N ″ -tris (2-methylcyclohexyl) -propane-1,2,3-tricarboxamide is exemplified.

  The nucleating agents exemplified above can be obtained from manufacturers such as ADEKA Corporation of Japan, Shin Nippon Rika Co., Ltd., and MILIKEN CHEMICAL Corporation of the United States. Among these nucleating agents, from the viewpoint of excellent transparency and rigidity improvement effect, a dispersed organic nucleating agent composed of a phosphate ester metal salt compound or a carboxylic acid metal salt compound or a sorbitol compound. Alternatively, a melt type nucleating agent composed of a trisamide compound is preferable. Specifically, calcium cyclohexane-1,2-dicarboxylate having the structure of the above formula (2), 1-O, 3-O having the structure of the above formula (8); 2-O, 4-O-bis (4-Propylbenzylidene) -1-propyl-D-sorbitol and N, N ′, N ″ -tris (2-methylcyclohexyl) -propane-1,2,3- having the structure of the above formula (10) Tricarboxamide is a preferred example. Among these, calcium cyclohexane-1,2-dicarboxylate having the structure of the above formula (2) and N, N ′, N ″ -tris (2-methylcyclohexyl) -propane- having the structure of the above formula (10) 1,2,3-Tricarboxamide is a preferred nucleating agent because it has a high effect of increasing rigidity while maintaining the transparency of the propylene-based resin film with a small addition amount.

  The following facts were found as a result of experiments conducted by blending propylene-based resins with nucleating agents at various ratios. First, from the viewpoint of lowering the total haze of the propylene-based resin film, the amount of nucleating agent was set to 250 ppm or more from the viewpoint of reducing the total haze of the resin film. It is preferable to make it small. Here, the haze is defined by (diffuse transmittance / total light transmittance) × 100 (%) as defined in JIS K7136: 2000 “Plastics—How to Obtain Haze of Transparent Material”.

  On the other hand, even if the total haze of the propylene-based resin film is lowered, the transmittance (single transmittance) of the polarizing plate may be easily lowered when the polarizing plate is applied to the polarizing film. FIG. 1 shows the total haze (unit:%) of a film obtained by forming a propylene-based resin with or without a nucleating agent, including data of Examples and Comparative Examples described later. Is the amount of decrease in the single transmittance (unit:%) of the polarizing plate when iodine is adsorbed and oriented on polyvinyl alcohol, and this is applied to a polarizing film that gives a certain single transmittance. Is a graph in which the vertical axis is plotted. Here, the amount of decrease in single transmittance (%) when used as a polarizing plate is obtained by subtracting the single transmittance when a polarizing plate is used by attaching a propylene-based resin film from the single transmittance of the polarizing film itself. Value. In the examples and comparative examples described later, a polarizing plate is prepared by laminating a propylene-based resin film on one surface of a polarizing film and a cycloolefin-based resin film on the other surface, and obtaining the single transmittance. Yes. FIG. 1 shows that the total haze of the propylene-based resin film and the amount of decrease in the single transmittance (%) of the polarizing plate hardly correlate.

  Next, the transparency of the propylene-based resin film was examined from another viewpoint. The total haze described above is a value obtained as the sum of internal haze caused by foreign matter or crystal grain boundaries existing inside the film and external haze caused by irregularities on the film surface (also called surface haze). It is. The internal haze itself is obtained by measuring the total light transmittance and the diffuse transmittance by entering light in a state where the resin film is immersed in a liquid having substantially the same refractive index as that of the resin film. Therefore, the total light transmittance (unit:%) when measuring the internal haze was considered as a new index. The total light transmittance when measuring the internal haze corresponds to the total light transmittance in a state in which reflection and diffusion on the film surface are virtually eliminated.

  2 shows the total light transmittance (unit:%) when measuring the internal haze of the target film in FIG. 1 on the horizontal axis, and shows the amount of decrease in the single transmittance (unit:%) of the same polarizing plate as in FIG. For the vertical axis, it is a plotted graph. In this case, it can be seen that the amount of decrease in the single transmittance (%) of the polarizing plate on the vertical axis and the total light transmittance (%) at the time of internal haze measurement on the horizontal axis are generally correlated. FIG. 2 also shows a linear approximation expression “y = −0.4417x + 44.455” calculated by the spreadsheet software Excel, where the horizontal axis is x and the vertical axis is y.

  And in order to suppress the amount of decrease in the single transmittance when a propylene-based resin film is applied to a polarizing film as a polarizing plate, the total light transmittance at the time of measuring the internal haze of the propylene-based resin film, that is, the film surface It has been found that it is effective to bring the total light transmittance close to 100% in a state where the reflection and diffusion of the light is virtually eliminated. Specifically, the total light transmittance is preferably 98% or more, more preferably 99% or more, and particularly preferably 99.5% or more. For this purpose, it has also been found that it is effective to limit the blending amount of the nucleating agent to a low range of 50 to 250 ppm.

  By blending the nucleating agent, crystallization when the propylene-based resin is solidified is promoted, and the diffusion transmittance is reduced. Therefore, although the total haze itself is reduced, the internal haze caused by the grain boundary is developed to some extent. Therefore, the total light transmittance tends to be somewhat lost when measuring the internal haze, that is, in a state where the reflection and diffusion of the surface are virtually eliminated. Therefore, it is also preferable that the crystal grains themselves do not become too small.

  In order to add a nucleating agent to a propylene resin and produce a film as a propylene resin composition, for example, the following method can be employed.

(1) A pellet made of a resin composition containing 1 to 10 parts by weight of a nucleating agent with respect to 100 parts by weight of a propylene-based resin (sometimes referred to as “nucleating agent master batch pellet”) is manufactured in advance. , A method of melt-mixing this and propylene-based resin pellets to form a film so that the nucleating agent is in a predetermined amount,
(2) Propylene-based resin composition pellets in which a predetermined amount of a nucleating agent is blended with a propylene-based resin, and the pellet is melt-kneaded to form a film,
(3) A method in which a propylene-based resin is melt-kneaded with a predetermined amount of a nucleating agent and formed into a film.

  Among these, from the viewpoint of uniformity and production cost of the resulting propylene-based resin film, a nucleating agent master batch pellet is manufactured in advance as in (1), and this is not mixed with a nucleating agent. A method of melt-kneading with propylene-based resin pellets is most preferable.

  Preparation of a nucleating agent master batch pellet in the method (1) and preparation of a propylene-based resin composition pellet containing a predetermined amount of the nucleating agent in the method (2) are performed by uniaxial or biaxial extrusion. A twin screw extruder is preferably used from the viewpoint of increasing the shear rate and more uniformly dispersing the nucleating agent in the propylene resin. In the extrusion, it is preferable to set the temperature of the propylene-based resin in the die portion of the extruder to be in a range of 180 to 260 ° C. If the temperature exceeds 260 ° C., the resin may be deteriorated. Moreover, when the temperature exceeds 210 degreeC, it is desirable to add antioxidants, such as a phenol type and a phosphorus type, from a viewpoint of suppressing deterioration of resin. The combined use of a phenolic antioxidant and a phosphorus antioxidant may further improve the effect of suppressing the deterioration of the resin, and thus is more preferable. When the antioxidant is blended, the amount is sufficient up to about 2 parts by weight with respect to 100 parts by weight of the propylene resin.

  Nucleating agent master batch pellets are known to be added to propylene resins, for example, additives such as UV absorbers, lubricants, antistatic agents, antiblocking agents, antifogging agents, It can also mix | blend in the range which does not inhibit an effect, and can also be set as a mixing masterbatch. In addition, these additives can be used alone in the form of a masterbatch with a propylene resin and added to the base propylene resin.

  The propylene-based resin film containing a predetermined amount of the nucleating agent used in the present invention is preferably produced by a melt extrusion method. The melt extrusion method is excellent in productivity and excellent in cost. In this melt extrusion method, a powder-form or pellet-form propylene-based resin material is supplied to an extruder heated to about 180 to 300 ° C., melted and kneaded by an extruder screw, and formed into a sheet form from a slit of a T die. After melt extrusion, the film is produced by bringing it into contact with a cooling roll by various means and cooling.

  When producing propylene-based resin films by the melt extrusion method, or when producing master batch pellets of additives including the nucleating agent described above by melt-kneading with an extruder, a single-screw or twin-screw extruder It is also preferable to seal the vicinity of the hopper and / or die outlet with nitrogen from the viewpoint of protecting the propylene-based resin from oxidative degradation. In addition, before supplying the material to be melt-extruded or melt-kneaded to the extruder, it is stored in an inert gas environment in which nitrogen having an oxygen concentration of 1% by volume or less is a typical example, and oxygen contained in the material. Replacing the molecule with an inert gas such as a nitrogen molecule is often effective for suppressing deterioration of the resin.

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 melt-kneading, it is preferable to use a screw having an L / D of 28 to 36 and a compression ratio V ₁ / V _{2 of 2} to 3. In order to suppress deterioration and decomposition of the propylene-based resin, it is preferable to purge oxygen in the extruder by purging with nitrogen or the like. Furthermore, it is also preferable to provide an orifice having a diameter of 1 to 5 mm 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 by installing an orifice means increasing the back pressure at the tip, which may improve the uniformity of melt kneading and improve the stability of extrusion. is there. The diameter of the orifice to be used is more preferably 2 to 4 mmφ.

  As the T die used for extrusion, a flow channel having a coat hanger shape is used, and the flow rate and pressure of the molten propylene resin are designed to be as uniform and balanced as possible in the width direction of the T die slit portion. It is preferable. Also, it is preferable that the surface of the flow path of the resin does not have a minute step or scratch, and the lip portion may be hard chrome plating, but the fluorine-based or silicone-based impregnated fluorine-based material or silicone-based material It is preferable that the plating surface has a small coefficient of friction with the molten propylene-based resin, such as material-containing plating, or is sprayed with a hard material such as tungsten carbide. Further, the lip portion is preferably polished and has a surface with a surface roughness as flat as 0.1 S or less as much as possible, and has a surface with few irregularities. Particularly, the lip portion has a sharp edge shape with a lip tip polished to 0.3 mmφ or less. preferable. By using a T-die having a lip as described above, it is possible to suppress the generation of eyes and simultaneously suppress the die line, so that it is easy to obtain a resin film having excellent appearance uniformity.

  In addition, from the viewpoint of suppressing the extrusion fluctuation of the propylene-based resin, it is preferable to attach a gear pump between the extruder and the T die via an adapter to stabilize the pressure and supply the resin to the T die. The pressure at this time is preferably within 0.1 MPa as a fluctuation value. In order to achieve this fluctuation value, the gear pump is preferably a direct acting type, and it is most preferable to use a gear pump of the type that eliminates the phase for feeding resin with three gears instead of two.

  Furthermore, it is preferable to attach a leaf disk filter to remove foreign substances in the propylene resin. The number of leaf disk filters and the filtration area per sheet can be arbitrarily selected depending on the viscosity and extrusion amount (flow rate) of the molten propylene resin and the heat resistance of the resin. Regarding the filtration accuracy, in the case of the propylene-based resin film used as a protective film in the present invention, the amount of foreign matter in the film can be reduced by using a filter having a foreign matter collection rate of 98% or more and a foreign matter size of 10 μm or less. Since the quality as a film can be improved, it is preferable. For the same reason, the filtration accuracy is more preferably 5 μm or less, and most preferably 3 μm or less. Further, the leaf disk filter is preferably installed in the order of the extruder, the gear pump, the leaf disk filter, and the T die from the viewpoint that stable foreign matter removal is possible.

  The molten film-like propylene-based resin extruded from the T-die is subsequently brought into contact with a metal cooling roll (also referred to as a chill roll or a casting roll) and is cooled by being in close contact with the cooling roll. At this time, the adhesion method to the cooling roll may affect the transparency. The adhesion to the cooling roll is, for example, a) a method in which static electricity is imparted to the molten sheet-like propylene resin and the surface state is adhered to the cooling roll having a mirror surface, and b) a molten sheet-like propylene resin. A method in which a cooling roll having a mirror surface and a metal roll (also referred to as a touch roll) or a metal belt having a mirror surface having a mirror surface is sandwiched between the cooling roll and closely contacting the cooling roll to cool the sheet, and c) a molten sheet When the propylene-based resin is brought into contact with the cooling roll, it can be carried out by a known method such as a method in which the propylene-based resin is cooled by being brought into close contact with the cooling roll by the air blown from the air chamber.

  The method of a) is a method sometimes referred to as an electrostatic pinning method, and only the both end portions (sometimes referred to as ear portions) of a film-like product of a molten propylene resin extruded from a T die, or A core-like, thread-like or belt-like power source is installed on the front side in the width direction of the film-like material, a high voltage is applied to the molten propylene resin using a high-frequency power source, static electricity is charged, and the cooling roll is used. It is the method of making it contact and cooling and solidifying. In this method, film flapping is unlikely to occur from the lip portion of the T die to the portion where the molten propylene resin comes into contact with the cooling roll (referred to as an air gap), and the length of the air gap is unstable. Since the thickness can be shortened, it is easy to ensure the uniformity of the film.

  Since the cooling roll used in the method a) has a tendency that the surface of the cooling roll is transferred to the film surface, the surface of the roll is preferably 0.5S or less in surface roughness. The surface material may be a conductive material such as hard chrome plating or tungsten carbide spraying, but is preferably a spraying surface such as chromium oxide that does not conduct electricity.

  The method of b) is a method called touch roll molding, in which a molten propylene-based resin film-like material extruded from a T-die is sandwiched between a cooling roll and an elastically deformable metal roll or metal belt. In this method, the film is brought into close contact with a cooling roll, and the film is cooled and solidified to obtain a film having excellent transparency. An elastically deformable metal roll has a roll surface with a thickness of 5 mm or less, and a resin pool (sometimes referred to as a bank) when a molten propylene-based resin is sandwiched between cooling rolls. A metal roll that is clamped without making, and a metal belt is a metal endless belt having a thickness of 1 mm or less, supported by a rubber roll or a metal roll, moved, and a film of molten propylene resin between the cooling roll The object is clamped. This method is preferable from the viewpoint of easily increasing the molding speed when using a crystalline resin whose transparency is impaired depending on cooling conditions.

  The cooling roll used in any of the methods b) and the elastically deformable metal roll or metal belt sandwiching the molten sheet-like propylene resin between them are transferred directly to the film surface. Therefore, it is preferable that each surface has a surface roughness of 0.3 S or less. In addition, since the film is made of a molten propylene-based resin in some cases, it may be too close to the cooling roll or the elastically deformable metal roll or metal belt surface, resulting in poor roll separation. There is also. From the viewpoint of preventing this, as a sealing treatment for filling microcracks on the surface of hard chrome plating, silicone-based materials or fluorine-based materials are used, or a sprayed surface such as chromium oxide or tungsten carbide or its sealing is used. A treated surface is also preferred.

  The method of c) is a method called “air chamber method”. When the film-like product of the molten propylene resin extruded from the T-die is brought into contact with the cooling roll, it is melted from the opposite side of the cooling roll. Air is blown onto the film-like material of the propylene-based resin by an air chamber, thereby causing the film-like material of the molten propylene-based resin to adhere to the cooling roll. As the air chamber, a commercially available appropriate one can be used without particular limitation. For example, the air to be blown is sucked through a high performance air filter (HEPA filter: High Efficiency Particulate Air Filter) with a blower or the like. It is preferable that the air chamber is in a pressurized state of 50 to 500 Pa. If the pressure in the air chamber is within this range, the air pressure applied to the film will be moderate. Therefore, the distance between the lip of the T die and the molten sheet-shaped resin contacting the cooling roll (air gap) will fluctuate. This makes it possible to form a stable film, and naturally the stability such as the thickness accuracy of the film is improved. For this reason, it is more preferable that the pressure in the air chamber be 100 to 400 Pa. Although the surface state of the cooling roll in the method c) tends to be transferred to the propylene-based resin film, it is not as much as in the method a) or b), and is a mirror-state cooling roll. Is used, there is no escape from the air entrained between the film of the molten propylene-based resin and the cooling roll, and uniform molding becomes difficult. Therefore, in the case of the method c), a cooling roll having a surface roughness of about 0.6 to 4S is used. From the viewpoint of improving the uniformity of the film surface, about 0.8 to 2S is preferable.

  The surface temperature of the cooling roll in the methods a) to c) is preferably adjusted in the range of 30 to 120 ° C., for example. The molten sheet-like propylene-based resin extruded from the above-mentioned T-die generally has a thickness of about 0.5 to 2.0 mm, and is in contact with the cooling roll (air gap). It is gradually extended and thinned, and after contacting the cooling roll, it is extended to a predetermined thickness while being rapidly cooled. The propylene-based resin used in the present invention has a nucleating agent added thereto, whereby the molten sheet-like propylene-based resin has a high crystallization speed, so the surface temperature of the cooling roll is not optimal, For example, when the temperature is too low, crystallization occurs radically at the time of contact with the cooling roll, so that it is considered that the expansion of the molten sheet-like propylene resin is insufficient. Further, when the temperature is too high, the propylene-based resin is not cooled and solidified, so that it may not be separated from the cooling roll and may be undesirably wound or may be deformed when leaving. Since it varies depending on the type and addition amount of the nucleating agent to be added, the processing speed, the size of the cooling roll, etc., it cannot be generally stated. It is preferable to select between -100 ° C.

  The processing speed when producing a propylene-based resin film is about 10 to 100 m / min. When the processing speed is high, the transparency tends to deteriorate from the viewpoint of uneven cooling. When the total haze value measured according to JIS K7136 is adopted as the transparency index, the total haze value is preferably 10% or less, and more preferably 6% or less. On the other hand, as an index of transparency, the total light transmittance at the time of internal haze measurement measured according to JIS K7136 described above, that is, the total light transmittance in a state in which reflection and diffusion on the film surface are virtually eliminated. When employed, the total light transmittance is preferably 98% or more, more preferably 99% or more, and particularly preferably 99.5% or more. For the propylene-based resin film defined in the present invention, it is preferable to employ the total light transmittance in a state in which reflection and diffusion on the latter film surface are virtually eliminated. If this total light transmittance is small, there is a possibility that the luminance will be lowered when incorporated in a liquid crystal television or the like.

  The propylene-based resin film in the polarizing plate of the present invention preferably has a thickness of about 5 to 200 μm. More preferably, it is 10 μm or more and 150 μm or less.

  The propylene-based resin film used in the present invention can be subjected to a surface treatment such as a corona treatment or a plasma treatment as long as the effects of the present invention are not impaired. Further, an antireflection layer, a hard coat layer, or the like may be provided on the surface by a technique such as coating.

(Norbornene resin film)
As for the polarizing plate of this invention, the transparent resin film is also bonded by the surface on the opposite side to which the propylene-type resin film of the polarizing film mentioned above was bonded. As a transparent resin film bonded to the surface opposite to the one where such a propylene-based resin film is bonded, an in-plane retardation and a thickness-direction retardation are within a specific range, respectively. A retardation film made of is preferable. The norbornene resin film here is a film made of a thermoplastic resin having a monomer unit made of a cyclic olefin (cycloolefin) such as norbornene or a polycyclic norbornene monomer. The norbornene-based resin film can be a hydrogenated product of the ring-opening polymer of the cycloolefin or a ring-opening copolymer using two or more kinds of cycloolefin, and has a cycloolefin and a cyclic olefin or a vinyl group. An addition copolymer with an aromatic compound or the like may be used. In addition, a polar group may be introduced.

  When using a copolymer of a cycloolefin and a chain olefin or an aromatic compound having a vinyl group, examples of the chain olefin include ethylene and propylene, and examples of the aromatic compound having a vinyl group include styrene, Examples include α-methylstyrene and nuclear alkyl-substituted styrene. In such a copolymer, the monomer unit composed of cycloolefin may be 50 mol% or less (preferably 15 to 50 mol%). In particular, when a terpolymer of a cycloolefin, a chain olefin, and an aromatic compound having a vinyl group is used, the amount of the monomer unit composed of the cycloolefin can be made relatively small as described above. In such a terpolymer, the monomer unit composed of a chain olefin is usually 5 to 80 mol%, and the monomer unit composed of an aromatic compound having a vinyl group is usually 5 to 80 mol%.

  Cycloolefin-based resins are commercially available as appropriate, such as TOPAS (Topas Advanced Polymers GmbH), Arton (manufactured by JSR), ZEONOR (manufactured by ZEON Corporation), ZEONEX (ZEON Japan) (Made by Mitsui Chemical Co., Ltd.) etc. can be used conveniently. When such a cycloolefin-based resin is formed into a film, a known method such as a solvent casting method or a melt extrusion method is appropriately used. Further, for example, escina (manufactured by Sekisui Chemical Co., Ltd.), SCA40 (manufactured by Sekisui Chemical Co., Ltd.), zeonoa film (manufactured by Nippon Zeon Co., Ltd.), arton film (manufactured by JSR Co., Ltd.) and the like are formed in advance. You may use the commercial item of the film made from the made cycloolefin resin as a transparent protective film.

If the norbornene-based resin film is stretched in at least one direction and provided with a phase difference, it can contribute to optical compensation and / or widening of the viewing angle of the liquid crystal panel. From this point of view, this norbornene-based resin film has an in-plane retardation value R _{0 in} the range of 40 to 100 nm, further 40 to 80 nm, and a thickness direction retardation value R _th of 80 to 250 nm, more preferably 100 to 100 nm. It is preferably in the range of 250 nm. Plane retardation value R ₀ and the thickness direction retardation R _th of birefringent film, the direction perpendicular to plane slow axis direction of the refractive index of the film n _x, the slow axis in the plane (Susumu The refractive index in the direction of the phase axis) is defined as n _y , the refractive index in the thickness direction as n _z , and the thickness of the film as d.

_{R 0 = (n x -n y} ) × d
R _th = [(n _x + _ny ) / 2−n _z ] × d
When the in-plane retardation value R ₀ is less than 40 nm or exceeds 100 nm, the viewing angle compensation ability of the panel tends to be lowered. In addition, when the thickness direction retardation value _Rth is less than 80 nm or more than 250 nm, the viewing angle compensation ability of the panel is also lowered. The in-plane retardation value R ₀ and the thickness direction retardation value R _th described above can be measured using, for example, KOBRA 21ADH (manufactured by Oji Scientific Instruments).

  In order to obtain the norbornene-based resin film having the refractive index characteristics as described above, the stretching ratio and stretching speed are adjusted appropriately, and various temperatures such as preheating temperature, stretching temperature, heat set temperature, and cooling temperature during stretching are used. And the change pattern thereof may be appropriately selected. Such a refractive index characteristic can be obtained by stretching under relatively loose conditions. For example, the stretching ratio is preferably in the range of 1.05 to 1.6, and more preferably 1.1 to 1. More preferably, it is 5 times. In the case of biaxial stretching, the stretching ratio in the maximum stretching direction may be in the above range.

  The norbornene-based resin film subjected to stretching used in the present invention is not particularly limited with respect to the thickness, but is preferably in the range of 20 to 80 μm, and more preferably in the range of 40 to 80 μm. This is because when the thickness of the norbornene-based resin film is less than 20 μm, it is difficult to handle the film and it is difficult to express a predetermined retardation value. On the other hand, the thickness of the norbornene-based resin film is 80 μm. When exceeding, it will become inferior to workability, there exists a possibility that transparency may fall or the weight of the obtained polarizing plate may become large.

(adhesive)
In the polarizing plate of the present invention, a polypropylene resin film and, for example, the above-described norbornene-based resin film are bonded to both surfaces of the above-described polarizing film via an adhesive. In the polarizing plate of the present invention, the same type of adhesive may be used for the resin film bonded to both surfaces of the polarizing film, or different types of adhesive may 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. Moreover, as a preferable adhesive from the viewpoint of adhesive strength, a photo-curable adhesive that is cured by light itself can be used.

  As a photocurable adhesive agent, mixtures, such as a photocurable epoxy resin and a photocationic polymerization initiator, are mentioned, for example. A combination of this adhesive and a propylene-based resin film to which a specific ultraviolet absorber is added is most preferable in terms of adhesive strength. This photocurable adhesive is cured by irradiation with active energy rays. The light source of the active energy ray is not particularly limited, but an active energy ray having a light emission distribution at a wavelength of 400 nm or less is preferable. Specifically, the low-pressure mercury lamp, the medium-pressure mercury lamp, the high-pressure mercury lamp, the ultrahigh-pressure mercury lamp, the chemical lamp, and the black light lamp A microwave excitation mercury lamp, a metal halide lamp and the like are preferable.

  As a method of laminating the above-mentioned transparent resin film on the polarizing film, generally known methods may be used, for example, Mayer bar coating method, gravure coating method, comma coater method, doctor blade method, die coating method, dip coating. The method of apply | coating an adhesive agent to the adhesive surface of a polarizing film and / or the film bonded there by the method, the spraying method, etc., and superimposing both is mentioned. Among the above coating methods, the gravure coating method or the die coating method is preferable from the viewpoint of the thickness accuracy of the coating film, the coating thickness, the size of equipment, and the like, and the gravure coating method is more preferable from the same viewpoint. The gravure coating method is a coating method that uses a selected gravure roll in consideration of the coating amount, and a chamber is installed at a position surrounding the gravure roll that rotates in the opposite direction to the flow direction of the film to be coated. It is the method of apply | coating by the system which supplies a liquid in the inside. After applying the adhesive, the polarizing film and the film bonded thereto are sandwiched by nip rolls and bonded together.

  The surface of the polarizing film and / or transparent resin film to which the adhesive is applied is appropriately subjected to surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment, saponification treatment, etc. in order to increase adhesion. May be. Examples of the saponification treatment include a method of immersing in an aqueous alkali solution such as sodium hydroxide or potassium hydroxide.

  After laminating a transparent resin film on both surfaces of the polarizing film via an adhesive layer, when a water-based adhesive is used, it is heated and dried. The heat treatment is performed by blowing hot air, for example, and the temperature is usually in the range of 40 to 100 ° C, preferably in the range of 60 to 100 ° C. The drying time is usually 20 to 1200 seconds. In this case, the thickness of the adhesive layer can be 0.1 μm or less.

  On the other hand, when a photocurable adhesive is used, the adhesive is cured by irradiation with active energy rays, and the polarizing film and the transparent resin films on both sides are adhered. In this case, the thickness of the adhesive layer is usually 0.5 to 5 μm, preferably 1 to 4 μm, and more preferably 1.5 to 4 μm. When the thickness of the adhesive layer is less than 0.5 μm, the adhesion may be insufficient, and when the thickness of the adhesive layer exceeds 5 μm, the appearance of the polarizing plate may be poor.

(Adhesive)
The polarizing plate of this invention may have the adhesive layer laminated | stacked on at least any one of the transparent resin film. This pressure-sensitive 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 propylene-based resin film containing a nucleating agent in the range of 50 to 6000 ppm is bonded to one surface of the polarizing film and a norbornene-based resin film is bonded to the other surface, the adhesive layer is usually It is provided on a norbornene-based resin film. A conventionally well-known appropriate adhesive can be used for an adhesive layer without a restriction | limiting in particular, For example, an acrylic adhesive, a urethane type adhesive, a silicone type adhesive etc. are mentioned. Among these, an acrylic pressure-sensitive adhesive is preferably used from the viewpoints of transparency, adhesive strength, reliability, reworkability, and the like. The pressure-sensitive adhesive layer can be provided by a method in which a solution containing a pressure-sensitive adhesive is applied to a norbornene-based resin film with a die coater or a gravure coater and dried, and a plastic film that has been subjected to a release treatment (called a separate film) ) The pressure-sensitive adhesive layer formed thereon can also be provided by a method of transferring to a norbornene-based resin film. In general, the thickness of the pressure-sensitive adhesive layer is preferably in the range of 2 to 40 μm.

(Liquid crystal display device)
The polarizing plate of the present invention can be suitably applied to a liquid crystal display device. In the liquid crystal display device, the polarizing plate of the present invention is preferably disposed on the back side of the liquid crystal panel via an adhesive layer. Under the present circumstances, the polarizing plate of this invention is arrange | positioned so that the propylene-type resin film may become the side far from a liquid crystal cell, ie, may oppose a backlight. Since such a liquid crystal display device uses the polarizing plate of the present invention, it has excellent durability and stability in display performance. In the liquid crystal display device, regarding the portions other than the above-described features, an appropriate configuration in a conventionally known liquid crystal display device can be adopted, and the constituent members (light diffusing plate, backlight) that the liquid crystal display device normally includes other than the liquid crystal panel Etc.) can be provided as appropriate. The “rear side” of the liquid crystal panel means the backlight side when the liquid crystal panel is mounted on the liquid crystal display device, while the “front side” of the liquid crystal panel mounts the liquid crystal panel on the liquid crystal display device. It means the viewer side.

  The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In the examples, “%” and “ppm” representing the content or amount used are based on weight unless otherwise specified. In addition, measurement of haze and measurement of total light transmittance in a state where reflection and diffusion on the surface are eliminated, measurement of retardation value, measurement of tensile elastic modulus, measurement of single transmittance, and durability evaluation of polarizing plate are as follows: Each was carried out by the following method.

[Measurement of total haze and measurement of total light transmittance with no surface reflection and diffusion]
The total haze of the film was measured using a haze meter HM150 manufactured by Murakami Color Research Laboratory Co., Ltd., which conforms to JIS K7136: 2000 “Plastics—How to Obtain Haze of Transparent Materials”. Moreover, the total light transmittance was measured using the same haze meter in the state which immersed the film in the quartz cell filled with dimethyl phthalate. The state in which the film is immersed in a quartz cell filled with dimethyl phthalate corresponds to a state in which the internal haze of the film is measured, that is, the reflection and diffusion of the film surface are virtually eliminated.

[Measurement of phase difference value]
The in-plane retardation value R ₀ and the thickness direction retardation value R _th of the film were measured using KOBRA-WR manufactured by Oji Scientific Instruments.

[Measurement of tensile modulus]
Tensile modulus at temperatures of 23 ° C. and 80 ° C. was measured using Autograph AG-1 manufactured by Shimadzu Corporation.

[Measurement of single transmittance]
The single transmittance of the polarizing film and the polarizing plate was measured using a spectrophotometer V-7100 manufactured by JASCO Corporation.

[Durability evaluation of polarizing plate]
The polarizing plate is cut into 200 mm × 300 mm (short side is the absorption axis of the polarizing plate), bonded to soda glass via an adhesive, put into an oven at 80 ° C. and kept for 100 hours, and then glass and polarized light. Whether or not peeling occurred between the plates was observed and evaluated according to the following criteria.

○: There is no peeling of the polarizing plate from the glass surface or even if it is smaller than 1 mm.
X: The peeling of the polarizing plate from the glass surface is 1 mm or more.

<Example 1>
A propylene / ethylene copolymer having an ethylene content of 0.4% and an MFR of 9 g / 10 min was added to a trisamide nucleating agent N, N ′, N ″ -tris (2-methylcyclohexyl) -propane-1. , 2,3-tricarboxamide [having a structure of the above formula (10), obtained from Shin Nippon Rika Co., Ltd.] was melt-kneaded in a 50 mmφ extruder heated to 275 ° C. Next, it was extruded in a molten state from a T-die having a width of 600 mm, and cooled with a cooling roll whose temperature was adjusted to 50 ° C. to produce a film having a thickness of 75 μm. Measure the total haze, total light transmittance without surface reflection and diffusion, retardation values (R ₀ and R _th ), and tensile modulus at 23 ° C. and 80 ° C. of the resulting propylene-based resin film. The results are summarized in Table 1. Incidentally, the total light transmittance in a state where reflection and diffusion on the surface are eliminated is shown in Table 1 simply by the item name “total light transmittance”. Moreover, there was no problem in the processing characteristics when forming the film in this example.

Next, after corona treatment is performed on one side of the propylene-based resin film produced above, a photocurable adhesive containing a photocurable epoxy resin and a photocationic polymerization initiator is applied to the corona-treated surface at a thickness of 4 μm. Worked. On the other hand, after corona treatment is performed on one side of a norbornene-based resin film that is biaxially stretched and has a thickness of 50 μm, an in-plane retardation value R ₀ of 55 nm, and a thickness direction retardation value R _th of 124 nm, the corona treatment The same photo-curable adhesive as above was applied to the surface with a thickness of 4 μm. Next, an adhesive layer of the propylene resin film is bonded to one surface of a polarizing film in which iodine is adsorbed and oriented to polyvinyl alcohol, and an adhesive layer of the norbornene resin film is bonded to the other surface. And pressed with a pair of nip rolls of 100 mmφ. Thereafter, ultraviolet rays were irradiated from the norbornene-based resin film side to cure both adhesive layers to produce a polarizing plate. When the durability of the polarizing plate thus obtained was evaluated by the method shown above, no peeling was observed between the glass surface and the polarizing plate. The polarizing film used here had a single-piece transmittance of 42.3% by itself, but the single-piece transmittance when the above resin films were bonded to both sides to form a polarizing plate was 41.9%. Thus, the amount of decrease (difference) in single transmittance (%) when the polarizing plate was obtained was 0.4 points. The value obtained by subtracting the single transmittance (unit:%) when the polarizing film itself is used from the single transmittance of the polarizing film itself is the amount of decrease in the single transmittance (%) when the polarizing film is used. In Table 1, it is indicated by the item name “amount of decrease in transmittance (%)”.

<Example 2>
A propylene-based resin film was produced in the same manner as in Example 1 except that the blending amount of the nucleating agent was changed to 1000 ppm. The physical properties of the resulting propylene-based resin film are summarized in Table 1. Moreover, there was no problem in processing characteristics when the film in this example was formed. A polarizing plate was produced in the same manner as in Example 1 except that the propylene-based resin film obtained here was used, and the durability was evaluated. As a result, no peeling was observed between the glass surface and the polarizing plate. Table 1 shows the amount of decrease in single transmittance (%) when the polarizing plate is used.

<Example 3>
The nucleating agent was changed to a carboxylic acid metal salt-based nucleating agent calcium cyclohexane-1,2-dicarboxylate (obtained from MILKEN CHEMICAL, USA, having the structure of the above formula (2)), and the amount was changed. A propylene-based resin film was produced in the same manner as in Example 1 except that the concentration was 1000 ppm. The physical properties of the resulting propylene-based resin film are summarized in Table 1. The adhesion with the cooling roll was good in the visible range, but when passing through the cooling roll, some unevenness was observed on the surface of the central portion in the width direction (adhesion was not good in the unknown range) ). A polarizing plate was produced in the same manner as in Example 1 except that the propylene-based resin film obtained here was used, and the durability was evaluated. As a result, no peeling was observed between the glass surface and the polarizing plate. Table 1 shows the amount of decrease in single transmittance (%) when the polarizing plate is used.

<Example 4>
A propylene-based resin film was produced in the same manner as in Example 3 except that the blending amount of the nucleating agent was 3000 ppm. The physical properties of the resulting propylene-based resin film are summarized in Table 1. The adhesion with the cooling roll was good in the visible range, but when passing through the cooling roll, some unevenness was observed on the surface of the central portion in the width direction (adhesion was not good in the unknown range) ). A polarizing plate was produced in the same manner as in Example 1 except that the propylene-based resin film obtained here was used, and the durability was evaluated. As a result, no peeling was observed between the glass surface and the polarizing plate. Table 1 shows the amount of decrease in single transmittance (%) when the polarizing plate is used.

<Example 5>
A propylene-based resin film was produced in the same manner as in Example 3 except that the blending amount of the nucleating agent was 5000 ppm. The physical properties of the resulting propylene-based resin film are summarized in Table 1. The adhesion with the cooling roll was good in the visible range, but when passing through the cooling roll, some unevenness was observed on the surface of the central portion in the width direction (adhesion was not good in the unknown range) ). A polarizing plate was produced in the same manner as in Example 1 except that the propylene-based resin film obtained here was used, and the durability was evaluated. As a result, no peeling was observed between the glass surface and the polarizing plate. Table 1 shows the amount of decrease in single transmittance (%) when the polarizing plate is used.

<Example 6>
The nucleating agent is 1-O, 3-O; 2-O, 4-O-bis (4-propylbenzylidene) -1-propyl-D-sorbitol [formula (8), which is a sorbitol nucleating agent. The propylene-based resin film was produced in the same manner as in Example 1 except that the structure was changed to “MILKEN CHEMICAL, USA” and the amount was changed to 3000 ppm. The physical properties of the resulting propylene-based resin film are summarized in Table 1. There was no problem in processing characteristics when the film was formed. A polarizing plate was produced in the same manner as in Example 1 except that the propylene-based resin film obtained here was used, and the durability was evaluated. As a result, no peeling was observed between the glass surface and the polarizing plate. Table 1 shows the amount of decrease in single transmittance (%) when the polarizing plate is used.

<Example 7>
A propylene-based resin film was produced in the same manner as in Example 6 except that the blending amount of the nucleating agent was 5000 ppm. The physical properties of the resulting propylene-based resin film are summarized in Table 1. There was no problem in processing characteristics when the film was formed. A polarizing plate was produced in the same manner as in Example 1 except that the propylene-based resin film obtained here was used, and the durability was evaluated. As a result, no peeling was observed between the glass surface and the polarizing plate. Table 1 shows the amount of decrease in single transmittance (%) when the polarizing plate is used.

<Example 8>
The nucleating agent is a phosphoric acid ester metal salt nucleating agent [phosphoric acid {2,2′-methylenebis (4,6-di-tert-butylphenyl)}] sodium [the structure of the above formula (3) The propylene-based resin film was produced in the same manner as in Example 1 except that the amount was changed to 2000 ppm, and the amount was changed to 2000 ppm. The physical properties of the resulting propylene-based resin film are summarized in Table 1. The adhesion with the cooling roll was good in the visible range, but when passing through the cooling roll, some unevenness was observed on the surface of the central portion in the width direction (adhesion was not good in the unknown range) ). A polarizing plate was produced in the same manner as in Example 1 except that the propylene-based resin film obtained here was used, and the durability was evaluated. As a result, no peeling was observed between the glass surface and the polarizing plate. Table 1 shows the amount of decrease in single transmittance (%) when the polarizing plate is used.

<Comparative Example 1>
A propylene resin film was produced in the same manner as in Example 1 except that no nucleating agent was added to the propylene resin. The physical properties of the resulting propylene-based resin film are summarized in Table 1. There was no problem in processing characteristics when the film was formed. Except using the propylene-type resin film obtained here, the polarizing plate was produced similarly to Example 1 and durability was evaluated, and 1.1 mm peeling occurred between the glass surface and the polarizing plate. . Table 1 shows the amount of decrease in single transmittance (%) when the polarizing plate is used.

<Comparative example 2>
A propylene-based resin film was produced in the same manner as in Comparative Example 1 except that the temperature of the cooling roll for cooling the propylene-based resin extruded from the T-die was changed to 20 ° C. The physical properties of the resulting propylene-based resin film are summarized in Table 1. There was no problem in processing characteristics when the film was formed. Except using the propylene-type resin film obtained here, the polarizing plate was produced similarly to Example 1 and durability was evaluated, and 1.3 mm of peeling occurred between the glass surface and the polarizing plate. . Table 1 shows the amount of decrease in single transmittance (%) when the polarizing plate is used.

The evaluation criteria for “workability” in Table 1 were as follows.
(Processability)
○: Good adhesion between the film and the cooling roll,
Δ: Slightly lacking in adhesion between the film and the cooling roll.

<Example 9>
The same procedure as in Example 1, except that the amount of N, N ′, N ″ -tris (2-methylcyclohexyl) -propane-1,2,3-tricarboxamide, which is a trisamide nucleating agent, was changed to 100 ppm. Then, a propylene-based resin film was produced, and a polarizing plate was produced in the same manner as in Example 1 using the propylene-based resin film. There was no problem in processing characteristics when forming a propylene-based resin film. The physical properties of the propylene-based resin film, the durability test results of the polarizing plate, and the amount of decrease in the single transmittance (%) when the polarizing plate is obtained are summarized in Table 2 in the same manner as in Table 1.

<Example 10>
A propylene-based resin film was prepared in the same manner as in Example 3 except that the compounding amount of the carboxylic acid metal salt-based nucleating agent calcium cyclohexane-1,2-dicarboxylate was changed to 100 ppm. A polarizing plate was produced in the same manner as in Example 3 using the film. There was no problem in processing characteristics when forming a propylene-based resin film. The physical properties of the propylene-based resin film, the durability test results of the polarizing plate, and the amount of decrease in the single transmittance (%) when the polarizing plate is obtained are summarized in Table 2 in the same manner as in Table 1.

  As shown in Table 1, by blending 500 ppm or more of the nucleating agent and forming a film under appropriate conditions, the resulting propylene-based resin film has a small total haze, and the tensile modulus at 80 ° C. is also 200 MPa or more. Therefore, the polarizing plate to which the rigidity is applied is excellent in durability. In this case, the propylene-based resin film has a total light transmittance slightly less than 100% in a state where reflection and diffusion on the surface are eliminated, and the amount of decrease in the single transmittance (%) when it is made a polarizing plate is slightly large. Become.

  On the other hand, as shown in Table 2, if the blending amount of the nucleating agent is 250 ppm or less, the resulting propylene-based resin film has a slightly increased total haze, but the tensile modulus at 80 ° C. is 200 MPa or more. Rigidity is imparted, and the polarizing plate to which it is applied has excellent durability. In this case, the propylene-based resin film has a total light transmittance of approximately 100% in a state where reflection and diffusion on the surface are eliminated, and the amount of decrease in the single transmittance (%) when the polarizing plate is made is further reduced.

Claims (6)

It is a polarizing plate in which a transparent resin film is bonded to both surfaces of a polarizing film made of a polyvinyl alcohol resin via an adhesive,
At least one of the transparent resin films is a polarizing plate that is a propylene-based resin film containing a nucleating agent in a range of 50 to 6000 ppm.   The polarizing plate according to claim 1, wherein one of the transparent resin films is a propylene-based resin film containing a nucleating agent in a range of 50 to 6000 ppm, and the other transparent resin film is a norbornene-based resin film.   The polarizing plate according to claim 1 or 2, wherein the polypropylene resin film contains a nucleating agent in a range of 250 to 6000 ppm.   The polarizing plate according to claim 1 or 2, wherein the polypropylene resin film contains a nucleating agent in a range of 50 to 250 ppm. The polarizing plate according to claim 1, wherein the nucleating agent is calcium cyclohexane-1,2-dicarboxylate represented by the following structural formula.

5. The nucleating agent according to claim 1, wherein the nucleating agent is N, N ′, N ″ -tris (2-methylcyclohexyl) -propane-1,2,3-tricarboxamide represented by the following structural formula. The polarizing plate as described in.

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