JP4985506B2 - Optical film, polarizing plate and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical film which has high transmissivity to a visible light beam, superior optical characteristics of small induced birefringence, superior moisture permeability, and superior ultraviolet absorbing performance, and is free of problems of coloration and bleeding, to provide a polarizing plate using the optical film, and to provide an image display device using the polarizing plate. <P>SOLUTION: The optical film for protection film is made of a polypropylene-based resin mixture consisting principally of a polypropylene-based resin synthesized with a metallocene catalyst and containing blended benzotriazol-based phenol, contains 0.3 to 5.5 mass% of benzotriazol-based phenol for the polypropylene-based resin mixture, and satisfies X&gt;20, Y&lt;15, and X+Y&lt;70, where X represents a maximum value (%) of light beam transmissivity at a wavelength of &ge;250 to &lt;280 nm and Y represents a maximum value (%) of light beam transmissivity at a wavelength of &ge;280 nm to &le;370 nm. The polarizing plate has the optical film formed on at least one surface of a polarizer. The image display device uses the polarizing plate. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention is excellent in optical properties such as high visible light transmittance and low birefringence, has good mechanical strength, heat resistance and moisture permeability and excellent ultraviolet absorption performance, and has problems such as coloring and bleeding. The present invention relates to an optical film for a protective film of a polarizer in which no occurrence of light occurs, a polarizing plate using the film as a protective film on one or both sides of the polarizer, and an image display device using the polarizing plate.

  The polarizing plate is a material having a function of transmitting only light having a specific vibration direction and shielding other light, and is widely used as one of components constituting a liquid crystal display device, for example. As such a polarizing plate, what has the structure on which the polarizer and the protective film were laminated | stacked is generally used. The polarizer has a function of transmitting only light having a specific vibration direction. For example, a film of polyvinyl alcohol (hereinafter sometimes referred to as “PVA”) is stretched, and iodine or a dichroic dye is used. The film dye | stained by etc. is generally used. Recently, a coating-type polarizer is also used.

The protective film has a function of holding a polarizer and imparting practical strength to the entire polarizing plate. For example, a triacetyl cellulose (hereinafter referred to as “TAC”) film of a cellulose-based film or the like. Is commonly used. Cellulose film has excellent properties as a polarizer protective film because it has excellent optical uniformity such as good transparency and low birefringence, practical heat resistance and excellent mechanical strength. ing.
In addition, since it has high moisture permeability, when it is bonded to a polarizer such as PVA, it is generally used as a polarizer protective film because it has good workability such as excellent moisture permeability of PVA and adhesive (for example, Patent Document 1).
However, since the cellulose-based film (for example, TAC film) has high water absorption, there have been problems such as deterioration in performance of the polarizer and dimensional stability due to water absorption.

In order to solve this problem, attempts have been made to improve dimensional stability by using a film material having a lower water absorption rate than the conventional TAC film as a polarizer protective film. Films and polyethylene terephthalate films have a large photoelastic constant, and a change in phase difference is caused by the action of external stress, resulting in a deterioration in performance as a polarizing plate.
Therefore, a uniaxially stretched high-density polyethylene or polypropylene film with low moisture permeability has been proposed as a polarizer protective film (see, for example, Patent Document 2).
However, the uniaxially stretched polyethylene or polypropylene has a problem in that a phase difference occurs and the function as a polarizing plate is lowered.

JP-A-7-120617 Japanese Patent Publication No. 6-12362

In view of the above problems, the present inventors have developed a polypropylene resin synthesized with a metallocene catalyst as a resin used for an optical film (for example, Japanese Patent Application No. 2007-261295). Polypropylene resin synthesized with a metallocene catalyst has excellent optical properties such as low haze, excellent transparency, high visible light transmittance, low birefringence, etc., and good mechanical strength, heat resistance and moisture permeability. However, the ultraviolet absorption performance is not sufficient, and there is a problem of further improvement.
By the way, in order to prevent deterioration due to ultraviolet rays, an organic member such as a polarizer is generally protected by a protective film containing an ultraviolet protective filter or containing an ultraviolet absorber. As an ultraviolet absorber used for the protective film, for example, in the case of a TAC film, a wide variety of compounds such as an oxybenzophenone compound, a benzotriazole compound, a salicylic acid ester compound, a benzophenone compound, a cyanoacrylate compound, and a nickel complex compound Are generally listed.
However, when these ultraviolet absorbers are applied to an optical film mainly composed of a polypropylene resin, (i) the stability at the time of film forming processing due to the bleeding out of the ultraviolet absorber that oozes out on the film surface. (Iii) The amount of UV absorber used increases to ensure UV absorption ability due to the disappearance of the UV absorber due to transpiration during molding, etc. (iii) UV absorption performance with respect to the added amount There is a problem such as being too low, and any ultraviolet absorber is not applicable without limitation, and the applicable ultraviolet absorber is different depending on the type of polypropylene resin. Thus, it is desired to study an ultraviolet absorber that can be used in an optical film mainly composed of a polypropylene resin synthesized by the metallocene catalyst used in the present invention.
That is, the problem of the present invention is that it has excellent optical properties such as high visible light transmittance and low birefringence, good mechanical strength, heat resistance and moisture permeability, and excellent ultraviolet absorption performance, and coloring and Provided are an optical film for a protective film of a polarizer that does not cause problems such as bleeding, a polarizing plate using the film as a protective film on one or both sides of the polarizer, and an image display device using the polarizing plate. It is.

As a result of intensive research in order to solve the above problems, the present inventors have developed an optical film comprising a polypropylene resin synthesized by a metallocene catalyst as a main component and blended with a predetermined benzotriazole phenol. It has been found that it is suitable for use as a protective film for a polarizer and can solve the above problems.
That is, the present invention
[1] A polypropylene resin mixture composed mainly of a polypropylene resin synthesized by a metallocene catalyst and blended with a benzotriazole phenol, and the content of the benzotriazole phenol is the polypropylene resin mixture The maximum value of the light transmittance in the range from 250 nm to less than 280 nm is X (%), and the maximum value of the light transmittance at a wavelength of 280 nm to 370 nm is Y. (%), The protective film optical film satisfying the conditions of X> 20, Y <15, and X + Y <70,
[2] A polarizing plate formed by forming the optical film according to [1] on at least one side of a polarizer, and [3] An image display device using the polarizing plate according to [2],
Is to provide.

The optical film of the present invention has excellent optical properties such as high visible light transmittance and low birefringence, excellent moisture permeability, excellent ultraviolet absorption performance, and problems such as coloring and bleeding. There is no. In addition, it has excellent durability such as heat resistance and moist heat resistance, can improve the polarization degree of the polarizing plate without affecting the optical function of the polarizing plate, and is flexible and rich in elasticity. . Furthermore, since the optical film of the present invention has resistance to external impact and deformation, a polarizing plate with significantly improved strength and reliability as a liquid crystal display element can be obtained by bonding to a polarizer. It is done.
In addition, the optical film of the present invention has a protective function equivalent to or higher than that of a conventionally used TAC film. In particular, the TAC film is hydrophilic and hardly moisture proof, whereas the optical film of the present invention is hydrophobic, so that the durability of the polarizing plate can be greatly improved.

[UV absorption performance of optical film]
In general, light energy is classified into UV-A (380 to 315 nm), UV-B (315 to 280 nm), and UV-C (280 to 100 nm) in the order of longer wavelengths of ultraviolet light. As the wavelength becomes shorter, the damage to the optical film becomes stronger. However, since the ozone layer, oxygen in the atmosphere, etc. absorb sunlight having a short wavelength, the amount of ultraviolet rays of 280 nm or less reaching the ground is small. Most of the deterioration of the polypropylene resin is caused by irradiation with light having a wavelength of 280 to 400 nm. Among them, the main absorption wavelengths of the polypropylene resin are 310 nm (UV-B region), 330 nm (UV-A region), and 370 nm. (UV-A region) is known. Therefore, in order to prevent deterioration of the polypropylene resin due to ultraviolet rays, it is necessary to absorb the light in the UV-A region and the light in the UV-B region by the added ultraviolet absorber.

  In the optical film of the present invention, the maximum value of the light transmittance in the UV-C region in the range of wavelengths from 250 nm to less than 280 nm is X (%), and the light in the UV-A region and the UV-B region has a wavelength of 280 nm to 370 nm. When the maximum transmittance value is Y (%), the conditions of X> 20, Y <15, and X + Y <70 are satisfied. That is, the optical film of the present invention has a performance of absorbing most of the light in the UV-A region and the UV-B region as described above, and further transmits a predetermined amount of light in the UV-C region. . In the present invention, transmitting a predetermined amount of light in the UV-C region suppresses deterioration of the polypropylene resin due to ultraviolet rays, and at the same time, is very effective for reducing bleeding of the ultraviolet absorber after the production of the optical film. I found out.

The light transmittance of the optical film of the present invention will be described with reference to FIG. FIG. 5 is a graph showing the total light transmittance of the optical film obtained in Example 1. The total light transmittance of the optical film obtained in Example 1 has one peak in the wavelength range of 250 nm or more and less than 280 nm in the UV-C region, and the maximum point of the peak is 31.2%. In the range from 280 nm to 370 nm in the UV-A region and the UV-B region, although a minute peak that seems to be due to some noise is seen, it is close to 0% and absorbs most of the light in the region. Have. Here, in a wavelength range of 250 nm or more and less than 280 nm, it has a peak and a maximum point as shown in FIG. 5, the maximum point may be the maximum value X in the region, and the maximum point is, for example, a wavelength less than 250 nm It exists in the range, and the light transmittance at a wavelength of 250 nm may be the maximum value. Further, it may have two or more peaks in the wavelength range of 250 nm or more and less than 280 nm.
In addition, in the wavelength range of 280 nm to 370 nm, the light transmittance is preferably 0%. However, if the maximum value Y within the range satisfies Y <15 and X + Y <70, there is a peak. You may do it.
In the present invention, the light transmittance described above is adjusted by a specific ultraviolet absorber and the amount of use thereof. The ultraviolet absorber and the amount of use thereof will be described later.

[Polypropylene resin synthesized by metallocene catalyst]
Next, the material which comprises the optical film of this invention is demonstrated from a polypropylene resin. The polypropylene resin used in the present invention is synthesized by a metallocene catalyst described later, and is preferably a copolymer of propylene and α-olefin. As the α-olefin, ethylene, 1-olefin having 4 to 18 carbon atoms is used. Specifically, ethylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-heptene, 4- Examples thereof include methyl-pentene-1, 4-methyl-hexene-1, 4,4-dimethylpentene-1. The proportion of propylene units in the copolymer is preferably 80 mol% or more, and the comonomer is 20 mol% or less. As the comonomer, the above α-olefin is not limited to one type, and two or more types can be used, and the copolymer can be a multi-component copolymer such as a terpolymer.

  The metallocene catalyst used in the present invention may be a single-site catalyst having a uniform active site or a multi-site catalyst having a non-uniform active site, and is preferably a multi-site catalyst. As the metallocene catalyst of this multi-site catalyst, generally, a group 4-6 transition metal compound such as Zr, Ti, Hf, etc., particularly a group 4 transition metal compound, a cyclopentadienyl group or a cyclopentadienyl derivative is used. And organic transition metal compounds having a group.

  As the group of the cyclopentadienyl derivative, an alkyl substituent such as pentamethylcyclopentadienyl, or a group in which two or more substituents are combined to form a saturated or unsaturated cyclic substituent may be used. Typically, an indenyl group, a fluorenyl group, an azulenyl group, or a partial hydrogenated product thereof can be given. Moreover, what combined several cyclopentadienyl group with the alkylene group, the silylene group, the germylene group etc. can be mentioned suitably.

  The co-catalyst is selected from the group consisting of an ionic compound capable of reacting with an aluminum oxy compound, a metallocene compound to convert a metallocene compound component into a cation, or a Lewis acid, a solid acid, or an ion-exchange layered silicate. At least one compound selected can be used. Moreover, an organoaluminum compound can be added with these compounds as needed.

  The above-mentioned layered silicate refers to a silicate compound having a crystal structure in which structured surfaces are stacked in parallel with each other with a weak binding force by ionic bonds or the like. In the present invention, the layered silicate is preferably ion-exchangeable. Here, ion exchange means that the interlayer cation of the layered silicate can be exchanged. Most layered silicates are naturally produced mainly as the main component of clay minerals, but these layered silicates are not limited to natural ones but may be artificially synthesized products.

Specific examples of the layered silicate are not particularly limited as long as they are publicly known layered silicates, for example, kaolins such as dickite, nacrite, kaolinite, anoxite, metahalloysite, halloysite; chrysotile, lizardite, Serpentine group such as antigolite; Smectite group such as montmorillonite, sauconite, beidellite, nontronite, saponite, teniolite, hectorite, stevensite; vermiculite group such as vermiculite; mica, illite, sericite, sea green stone, etc. Attapulgite; sepiolite; palygorskite; bentonite; pyrophyllite; talc; chlorite group. These may form a mixed layer.
Among these, montmorillonite, sauconite, beidellite, nontronite, saponite, hectorite, stevensite, bentonite, teniolite, and other smectites, vermiculites, and mica are preferred.

  These layered silicates can be chemically treated. Here, as the chemical treatment, any of a surface treatment for removing impurities adhering to the surface and a treatment that affects the crystal structure and chemical composition of the layered silicate can be used. Specific examples include (i) acid treatment, (b) alkali treatment, (c) salt treatment, and (d) organic matter treatment. These treatments remove surface impurities, exchange cations between layers, and elute cations such as Al, Fe, Mg in the crystal structure, resulting in ionic complexes, molecular complexes, organic derivatives, etc. The surface area, interlayer distance, solid acidity, etc. can be changed. These processes may be performed independently or two or more processes may be combined.

  As a method (polymerization method) for synthesizing a polypropylene resin using the metallocene catalyst, a slurry method using an inert solvent, a gas phase method without using a solvent, a solution method, or a polymerization in the presence of these catalysts. Examples thereof include a bulk polymerization method using a monomer as a solvent. In addition, a polypropylene resin synthesized with a metallocene catalyst as a multi-site catalyst is easily available as a commercial product, and examples of the commercial product include “Wintech (trade name)” manufactured by Nippon Polypro Co., Ltd. .

[Bending elastic modulus]
The polypropylene resin in the present invention preferably has a flexural modulus of 700 MPa or more, and more preferably 900 MPa or more. When the flexural modulus is in the above range, sufficient strength as an optical film can be obtained, and post-processing can be easily performed.
The polypropylene resin preferably has a melting point (Tm) of 130 ° C. or higher. If the melting point (Tm) is 130 ° C. or higher, the unstretched film is preferable because the flexural modulus is increased, the strength of the optical film is increased, and post-processing is not affected.
Furthermore, the polypropylene resin preferably has a tensile strength of 20 MPa or more. When it is 20 MPa or more, when the optical film is bonded to the polarizer via the adhesive layer by the roll-to-roll method, the orientation is not applied, and the optical film has a retardation exceeding the original optical design. Since it does not generate | occur | produce, the performance of a polarizing plate can be maintained.

[Benzotriazole phenol]
The polypropylene resin mixture used in the optical film of the present invention contains a benzotriazole phenol in order to achieve the desired light transmittance of the optical film due to its ultraviolet absorption performance. As represented by the following general formula (1), the benzotriazole phenol is a compound in which at least one phenol group which may be substituted is bonded to the nitrogen atom of the benzotriazole group.

In formula (1), R ¹ is a monovalent hydrocarbon group having 1 to 10 carbon atoms, may be substituted, and may be linear or branched. K is an integer of 0-4. As the monovalent hydrocarbon group, an alkyl group is preferable, and among them, a methyl group and a tert-alkyl group are preferable because the benzotriazole phenol does not bleed after the production of the optical film. A plurality of R ¹ may be the same or different.

  The benzotriazole phenol used in the present invention preferably has a molecular weight of 250 or more, more preferably in the range of 250 to 400. If the molecular weight of the benzotriazole phenol is within the above range, the benzotriazole phenol will not bleed after the production of the optical film.

  More specific examples of such benzotriazole phenols include 2- (5-chloro-2H-benzotriazol-2-yl) -4-methyl-6-tert-butylphenol and 2- (2H-benzotriazole). -2-yl) -4- (1,1,3,3-tetramethylbutyl) -phenol, 2- (2H-benzotriazol-2-yl) -4,6-di-tert-pentylphenol, and the like. It is done. Among them, 2- (2H-benzotriazol-2-yl) -4- (1,1,3,3-tetramethylbutyl) is less from the viewpoint of the stability of ultraviolet absorption performance with less bleed after optical film production. -Phenol and 2- (2H-benzotriazol-2-yl) -4,6-di-tert-pentylphenol are particularly preferred. A benzotriazole type phenol may be used independently, or may mix and use two or more types by arbitrary ratios.

  The content of the benzotriazole-based phenol is required to be 0.3 to 5.5% by mass, and preferably 0.5 to 1.5% by mass with respect to the polypropylene resin mixture. If it is in the above-mentioned range, the optical film of the present invention can be provided with good ultraviolet absorption performance, and good transparency of the film can be secured, and problems such as coloring and bleeding do not occur.

[Ultraviolet absorbing metal oxide]
The polypropylene resin mixture may contain an ultraviolet absorbing metal oxide in addition to the benzotriazole phenol described above. Preferred examples of the ultraviolet absorbing metal oxide include zinc oxide, titanium oxide, cerium oxide, and iron oxide, and zinc oxide and titanium oxide are particularly preferable. These ultraviolet absorbers are used alone or in admixture of two or more at an arbitrary ratio.
The average particle diameter of the primary particles of the ultraviolet absorbing metal oxide is preferably 5 to 90 nm, more preferably 5 to 70 nm, and more preferably 5 to 50 nm from the viewpoint of ensuring the ultraviolet absorption performance while improving the visible light transmittance. Further preferred. The average particle size of the ultraviolet absorbing metal oxide is preferably as small as possible from the above viewpoint, but the lower limit is 5 nm in view of the production cost. Here, the average particle size is taken using a transmission electron microscope (TEM) after a dispersion obtained by sufficiently diluting and dispersing carbon black with a solvent such as chloroform is spread on a mesh with a collodion film and dried. Computer image analysis of the obtained TEM photograph, the diameter of a circle having an area equal to the area of each extracted aggregate (equal area circle diameter) as the particle diameter, and the arithmetic average diameter obtained from the obtained particle size distribution ( Number average value).
The content of the UV-absorbing metal oxide is usually 0.08 to 5.5% by mass with respect to the polypropylene resin mixture in order to obtain good transparency while ensuring good UV absorption performance of the optical film. Degree.

  These ultraviolet-absorbing metal oxides can be usually used in the form of powder. When the UV-absorbing metal oxide is a powder, the UV-absorbing metal oxide is inferior in dispersibility, so a masterbatch of polypropylene resin and UV-absorbing metal oxide is prepared in advance and then kneaded into the polypropylene resin. It will be necessary. The content of the ultraviolet absorbing metal oxide at the time of preparing the master batch is preferably 50% by mass or less, and more preferably 20% by mass or less, with respect to the mixture of the polypropylene resin and the ultraviolet absorbing metal oxide. When the content of the ultraviolet absorbing metal oxide is within the above range, the dispersibility of the ultraviolet absorbing metal oxide in the master batch is good.

[Sorbitol-based additive]
In the present invention, the polypropylene resin mixture may further contain a sorbitol-based additive in order to improve the tensile strength and improve the transparency. The sorbitol-based additive is preferably a dibenzylidene sorbitol-based additive that has a slight influence on the phase difference.
Dibenzylidene sorbitol-based additives include 1,3-2,4-dibenzylidene sorbitol, di-substituted dibenzylidene sorbitol such as 1,3-2,4-diparamethyldibenzylidene sorbitol, and di-substituted benzylidene sorbitol Preferred is a combination of glycerin and diglycerin monofatty acid ester.
The dibenzylidene sorbitol-based additive is known to contribute to the improvement of transparency and strength of polypropylene resin as a clearing nucleating agent. In the present invention, it is used as an optical film for a protective film of a polarizer. Has also found that the influence on the phase difference is very small.

  Among the above-mentioned dibenzylidene sorbitol-based additives, a diglycerin monofatty acid ester-added dibenzylidene sorbitol-based nucleating agent with less bleeding is desirable. As the diglycerin monofatty acid ester, diglycerin monolaurate, diglycerin monomyristic acid ester, diglycerin monostearic acid ester and the like are preferable, and these are used alone or in combination.

The content of the dibenzylidene sorbitol-based additive is preferably in the range of 0.03 to 0.5% by mass and more preferably 0.05 to 0.25% by mass with respect to the polypropylene resin mixture. When it is 0.03 parts by mass or more, it is possible to improve transparency and sufficiently improve strength. On the other hand, if it is 0.5 parts by mass or less, it is advantageous in terms of cost since it is possible to efficiently improve transparency and strength.
Moreover, when using the di-substituted benzylidene sorbitol to which the diglycerin monofatty acid ester is added, the content of the di-substituted benzylidene sorbitol may be 0.03 to 0.3% by mass with respect to the polypropylene resin composition. Preferably, the content of the diglycerin monofatty acid ester to be mixed is preferably 0.01 to 0.2% by mass with respect to the polypropylene resin composition.

  The dibenzylidene sorbitol-based additive and benzotriazole-based phenol are preferably used alone or mixed and granulated for the purpose of improving the dispersibility in the polypropylene resin mixture. These granulations can be performed by methods such as melt extrusion granulation, dry extrusion granulation, and compression granulation.

[Various olefin resins and additives]
Moreover, according to the desired physical property of the film obtained, various olefin resins and additives can be mix | blended with the optical film in this invention in the range which does not impair required transparency.
Examples of the olefin resin include homopolypropylene and random polypropylene synthesized with a Ziegler catalyst, and these may be blended in a small amount within a range not exceeding 10% by mass with respect to the optical film.
Examples of the additive include a weather resistance improver, an abrasion resistance improver, a polymerization inhibitor, a crosslinking agent, an infrared absorber, an antistatic agent, an adhesion improver, a leveling agent, a thixotropic agent, and a coupling agent. , Surfactants, polymer electrolytes, conductive complexes, antiblocking agents, lubricants, plasticizers, antifoaming agents, fillers, solvents, and the like.

Here, a light stabilizer can be used as the weather resistance improving agent.
As the light stabilizer, a hindered amine light stabilizer (HALS) is preferable. The hindered amine light stabilizer (HALS) functions as a radical scavenger. As such a hindered amine light stabilizer (HALS), N, N ′, N ″, N ″ ″-tetrakis- (4,6-bis- (butyl- (N-methyl-2,2,6) , 6-Tetramethylpiperidin-4-yl) amino) -triazin-2-yl) -4,7-diazadecane-1,10-diamine, dibutylamine 1,3,5-triazine N, N'-bis (2,2,6,6-tetramethyl-4-piperidyl-1,6-hexamethylenediamine and N- (2,2,6,6-tetramethyl-4-piperidyl) butylamine polycondensate, poly [{6- (1,1,3,3-tetramethylbutyl) amino-1,3,5-triazine-2,4-diyl} {(2,2,6,6-tetramethyl-4-piperidyl) Imino} hexamethylene {(2,2,6,6- Tramethyl-4-piperidyl) imino}], dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol, bis (2,2,6,6-decanoic acid) Reaction product of tetramethyl-1 (octyloxy) -4-piperidinyl) ester, 1,1-dimethylethyl hydroperoxide and octane, bis (1,2,2,6,6-pentamethyl-4-piperidyl) [ [3,5-bis (1,1-dimethylethyl) -4-hydroxyphenyl] methyl] butyl malonate, bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and methyl 1, A mixture of 2,2,6,6-pentamethyl-4-piperidyl sebacate, bis (2,2,6,6-pentamethyl-4-piperidyl) sebacate, 2- 3,5-di-tert-butyl-4-hydroxybenzyl) -2'-n-butylmalonate bis (1,2,2,6,6-pentamethyl-4-piperidyl), bis (1,2,2 , 6,6-pentamethyl-4-piperidyl) sebacate, tetrakis (2,2,6,6-tetramethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate.
Further, as the light stabilizer, a reactive agent having a polymerizable group such as a (meth) acryloyl group in the molecule can be used.

  Examples of the wear resistance improver include spherical particles such as α-alumina, silica, kaolinite, iron oxide, diamond, and silicon carbide. Examples of the particle shape include a sphere, an ellipsoid, a polyhedron, a scale shape, and the like. Organic materials include synthetic resin beads such as cross-linked acrylic resin and polycarbonate resin. The particle size is usually about 30 to 200% of the film thickness of the optical film. Among these, spherical α-alumina is particularly preferable because it has high hardness and a large effect on improving wear resistance, and it is relatively easy to obtain spherical particles.

  Examples of the polymerization inhibitor include hydroquinone, p-benzoquinone, hydroquinone monomethyl ether, pyrogallol, and t-butylcatechol. Examples of the crosslinking agent include a polyisocyanate compound, an epoxy compound, a metal chelate compound, an aziridine compound, and an oxazoline compound. Used.

As the filler, for example, barium sulfate, talc, clay, calcium carbonate, aluminum hydroxide and the like are used.
As the infrared absorber, for example, a dithiol metal complex, a phthalocyanine compound, a diimmonium compound, or the like is used.

  Various additives are added to the optical film for various functions, for example, high hardness and scratch resistance, so-called hard coating function, anti-fogging coating function, anti-fouling coating function, anti-glare coating function, anti-reflection A coating function, an ultraviolet shielding coating function, an infrared shielding coating function, and the like can also be imparted.

[Method for producing optical film]
Hereinafter, the manufacturing method of the optical film of this invention is demonstrated. The optical film of the present invention is an extrusion coating molding method, a casting method, a T-die extrusion molding method, an inflation method, an injection molding method, and a polypropylene resin mixture containing the above-described polypropylene resin, benzotriazole phenol, and other various components. It can manufacture by various shaping | molding methods, such as. Furthermore, a polarizing plate using the optical film can be produced directly on the polarizer by the various molding methods described above (see FIG. 1), and the optical film 4 is produced in advance by the various molding methods described above. In addition, after that, it may be produced by bonding to a polarizer via an adhesive layer. In the present invention, since it is desired that the optical film produced on the polarizer is not oriented, unstretched T-die extrusion that does not stretch is desirable.
Moreover, you may perform shaping | molding by the above-mentioned various shaping | molding methods under a heating. The heating temperature condition is preferably 160 to 250 ° C, and more preferably 180 to 220 ° C.

A method for producing an optical film directly on a polarizer will be further described with reference to FIG. In FIG. 1, an adhesive layer 5 is applied on the polarizer 3 in advance, and a polypropylene molten resin 1 is formed by an extrusion method (FIG. 1, left diagram). The formed polypropylene resin is solidified to form the protective film 4.
Alternatively, the protective film 4 may be formed in advance by the T-die method, and the adhesive layer 2 may be applied in advance and bonded to the polarizer 3.

  The thickness of the optical film is preferably in the range of 10 to 200 μm, more preferably 30 to 150 μm. When the thickness is 10 μm or more, the strength as a protective film of the polarizer is sufficiently ensured, and when it is 200 μm or less, sufficient flexibility is obtained, and since it is lightweight, handling is easy. It is also advantageous in terms of cost.

[Polarizer]
The polarizing plate according to the present invention is obtained by pasting the optical film of the present invention on one side or both sides of a polarizer, and in consideration of cost, one obtained by pasting the optical film on one side of the polarizer is preferable. Here, the optical film is bonded to a polarizer and functions as a protective film. When the polarizing plate is applied in a liquid crystal display device without being protected by an optical film, the polarizer and the liquid crystal may be deteriorated by external light and ultraviolet light from the backlight. In order to prevent such deterioration, when the polarizing plate of the present invention is used by being bonded to a liquid crystal cell in a liquid crystal display device, the polarizing plate on the external light side in the liquid crystal display device is used as the upper polarizing plate and the back polarizing plate. When the polarizing plate on the light side is a lower polarizing plate, on one side of the upper polarizing plate and on the side opposite to the liquid crystal cell, and on one side of the lower polarizing plate on the side opposite to the liquid crystal cell, It is preferable to have an embodiment in which the optical film of the present invention is bonded.

As the polarizer used in the polarizing plate of the present invention, any polarizer may be used as long as it has a function of transmitting only light having a specific vibration direction. For example, a polyvinyl alcohol film is stretched, and iodine or two-color Polyvinyl alcohol polarizers dyed with reactive dyes; polyene polarizers such as dehydrated polyvinyl alcohol and dehydrochlorinated polyvinyl chloride; reflective polarizers using cholesteric liquid crystals; thin film crystal film polarizers Among them, a polyvinyl alcohol polarizer is preferably used.
Examples of the polyvinyl alcohol polarizer include hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, ethylene / vinyl acetate copolymer partially saponified films, iodine and dichroic dyes, etc. A dichroic substance is adsorbed and uniaxially stretched. Among these, a polarizer composed of a polyvinyl alcohol film and a dichroic substance such as iodine is preferably used. The thickness of these polarizers is not particularly limited, and is generally about 1 to 100 μm.

A PVA resin suitably used as a resin constituting the polarizer can be obtained by saponifying a polyvinyl acetate resin. Examples of the polyvinyl acetate resin include, in addition to polyvinyl acetate, which is a homopolymer of vinyl acetate, copolymerization of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerized with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids.
The degree of saponification of the PVA-based resin is usually 85 to 100 mol%, preferably 98 to 100 mol%. This PVA-based resin may be further modified, and for example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used. The degree of polymerization of the PVA resin is usually in the range of 1,000 to 10,000, preferably 1,500 to 10,000.

  The polarizing plate is, for example, a step of uniaxially stretching a PVA resin film as described above, a step of dyeing a PVA resin film with a dichroic dye, and adsorbing the dichroic dye, and a dichroic dye adsorbing A process of treating the prepared PVA resin film with an aqueous boric acid solution, a process of washing with water after the treatment with an aqueous boric acid solution, and a uniaxially stretched PVA resin film on which dichroic dyes are adsorbed and oriented by applying these steps Manufactured through a process of laminating films.

  Uniaxial stretching may be performed before dyeing with a dichroic dye, may be performed simultaneously with dyeing with a dichroic dye, or may be performed after dyeing with a dichroic dye. When uniaxial stretching is performed after dyeing with a dichroic dye, this uniaxial stretching may be performed before boric acid treatment or during boric acid treatment. Moreover, it is also possible to perform uniaxial stretching 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.

In order to dye the PVA resin film with the dichroic dye, for example, the PVA resin film may be immersed in an aqueous solution containing the dichroic dye. Specifically, iodine or a dichroic dye is used as the dichroic dye.
When iodine is used as the dichroic dye, a method of immersing and dyeing a PVA resin film in an aqueous solution containing iodine and potassium iodide is usually employed. The content of iodine in this aqueous solution is usually about 0.01 to 0.5 parts by mass per 100 parts by mass of water, and the content of potassium iodide is usually about 0.5 to 10 parts by mass per 100 parts by mass of water. It is. The temperature of this aqueous solution is usually about 20 to 40 ° C., and the immersion time in this aqueous solution is usually about 30 to 300 seconds.

On the other hand, when a dichroic dye is used as the dichroic dye, a method of immersing and dyeing a PVA resin film in an aqueous solution containing a water-soluble dichroic dye is usually employed. The content of the dichroic dye in this aqueous solution is usually about 1 × 10 ⁻³ to 1 × 10 ⁻² parts by mass per 100 parts by mass of water. This aqueous solution may contain an inorganic salt such as sodium sulfate. The temperature of this aqueous solution is usually about 20 to 80 ° C., and the immersion time in this aqueous solution is usually about 30 to 300 seconds.
The boric acid treatment after dyeing with a dichroic dye is performed by immersing the dyed PVA resin film in an aqueous boric acid solution. The boric acid content in the boric acid aqueous solution is usually about 2 to 15 parts by mass, preferably about 5 to 12 parts by mass per 100 parts by mass of water.
When iodine is used as the dichroic dye, the aqueous boric acid solution preferably contains potassium iodide. The content of potassium iodide in the boric acid aqueous solution is usually about 2 to 20 parts by mass, preferably 5 to 15 parts by mass per 100 parts by mass of water. The immersion time in the boric acid aqueous solution is usually about 100 to 1,200 seconds, preferably about 150 to 600 seconds, and more preferably about 200 to 400 seconds. The temperature of the boric acid aqueous solution is usually 50 ° C. or higher, preferably 50 to 85 ° C.

The PVA resin film after boric acid treatment is usually washed with water. The water washing treatment is performed, for example, by immersing a boric acid-treated PVA resin film in water. After washing with water, a drying process is performed to obtain a polarizer. The temperature of water in the water washing treatment is usually about 5 to 40 ° C., and the immersion time is usually about 2 to 120 seconds. The drying process performed thereafter is usually performed using a hot air dryer or a far infrared heater. The drying temperature is usually 40 to 100 ° C. The processing time in the drying process is usually about 120 to 600 seconds.
In this way, a polarizer comprising a PVA resin film in which iodine or dichroic dye is adsorbed and oriented is obtained.

[Adhesive layer]
As a method of pasting an optical film and a polarizer, as mentioned above, it is performed through an adhesive layer.
As an adhesive for forming the adhesive layer, a PVA adhesive, an epoxy adhesive, an acrylic adhesive, a polyolefin grafted with an unsaturated carboxylic acid or an anhydride thereof, or a polyolefin system blended with the grafted polyolefin Examples include adhesives. In addition, it is possible to use an adhesive having transparency, for example, an adhesive such as polyvinyl ether or rubber. Among these, a PVA adhesive is preferable.

The PVA-based adhesive contains a PVA-based resin and a cross-linking agent. Examples of the PVA-based resin include PVA obtained by saponifying polyvinyl acetate and its derivatives, and a single copolymer having a copolymerizable property with vinyl acetate. Examples thereof include a saponified product of a copolymer with a monomer, a modified PVA obtained by acetalizing, urethanizing, etherifying, grafting or phosphoric esterifying PVA. These PVA resins can be used singly or in combination of two or more. Monomers copolymerizable with vinyl acetate include (anhydrous) maleic acid, fumaric acid, crotonic acid, itaconic acid, (meth) acrylic acid and other unsaturated carboxylic acids and esters thereof, ethylene and propylene, etc. α-olefin, (meth) allylsulfonic acid (soda), sulfonic acid soda (monoalkylmalate), disulfonic acid soda alkylmalate, N-methylolacrylamide, acrylamide alkylsulfonic acid alkali salt, N-vinylpyrrolidone, N- Examples include vinyl pyrrolidone derivatives.
The degree of polymerization of the PVA resin is not particularly limited, but since the adhesiveness and the like are improved, the average degree of polymerization is about 100 to 3000, preferably 500 to 3000, and the average saponification degree is about 85 to 100 mol%, preferably It is preferable to use about 90-100 mol%.

  Examples of the epoxy adhesive include a hydrogenated epoxy resin, an alicyclic epoxy resin, and an aliphatic epoxy resin. The epoxy resin may further contain a compound that promotes cationic polymerization, such as okitacenes and polyols.

  Acrylic adhesives include acrylic esters such as butyl acrylate, ethyl acrylate, methyl acrylate and 2-ethylhexyl acrylate, and α-mono such as acrylic acid, maleic acid, itaconic acid, methacrylic acid and crotonic acid. Those mainly composed of copolymers with olefin carboxylic acids (including those added with vinyl monomers such as acrylonitrile, vinyl acetate and styrene) are particularly preferred because they do not interfere with the polarization characteristics of the polarizer. .

  Further, a polyolefin grafted with an unsaturated carboxylic acid or an anhydride thereof or a polyolefin blended with the grafted polyolefin can also be used as an adhesive. Examples of polyolefins used for grafting include low density polyethylene, high density polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, ethylene-propylene copolymer, and ethylene-1-butene copolymer. , Propylene-1-butene copolymer, and mixtures thereof. Examples of the unsaturated carboxylic acid or anhydride thereof used for polyolefin grafting include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, citraconic acid, citraconic anhydride, itaconic acid, and itaconic anhydride. The modified polyolefin thus obtained may be used as it is, but can also be used by blending with polyolefin.

  The adhesive layer is formed by applying an adhesive on either or both sides of the optical film and the polarizer. The thickness of the adhesive layer is preferably 0.01 to 10 μm, more preferably 0.03 to 5 μm.

  Moreover, when bonding the said optical film with a polarizer, an easily bonding process can be performed for the adhesive improvement to the surface which contact | connects the polarizer of an optical film. Examples of the easy adhesion treatment include surface treatment such as corona treatment, plasma treatment, low-pressure UV treatment, and saponification treatment, and a method of forming an anchor layer, and these can be used in combination. Among these, a corona treatment, a method of forming an anchor layer, and a method of using these in combination are preferable.

  Next, an adhesive layer is formed on the surface subjected to the easy adhesion treatment as described above, and the optical film of the present invention and the polarizer are bonded through the adhesive layer. This bonding can be performed by a roll laminator or the like. The heating drying temperature and drying time are appropriately determined according to the type of adhesive.

  The polarizing plate of the present invention, which is bonded to at least one surface of the polarizer as the protective film of the polarizer of the present invention, is laminated with the optical film of the present invention on the other surface of the polarizer, if necessary. It is also possible to laminate films made of other resins. Examples of other resin films include fumaric acid diester resin, triacetyl cellulose film, polyethersulfone film, polyarylate film, polyethylene terephthalate film, polynaphthalene terephthalate film, polycarbonate film, cyclic polyolefin film, and maleimide resin. Examples thereof include a film and a fluorine resin film. The film made of the other resin may be a retardation film having a specific retardation.

The polarizing plate of the present invention is preferably a laminate having at least one hard coat layer in order to improve surface properties and scratch resistance. Examples of the hard coat layer include a hard coat layer made of, for example, a silicone resin, an acrylic resin, an acrylic silicone resin, an ultraviolet curable resin, a urethane hard coat agent, etc. Among them, transparency, scratch resistance, From the viewpoint of chemical resistance, a hard coat layer made of an ultraviolet curable resin is preferable. One or more of these hard coat layers can be used.
Examples of the ultraviolet curable resin include one or more ultraviolet curable resins selected from ultraviolet curable acrylic urethane, ultraviolet curable epoxy acrylate, ultraviolet curable (poly) ester acrylate, ultraviolet curable oxetane, and the like.
As for the thickness of a hard-coat layer, 0.1-100 micrometers is preferable, Especially preferably, it is 1-50 micrometers, More preferably, it is 2-20 micrometers. Further, a primer treatment can be performed between the hard coat layers.

  Moreover, the polarizing plate of this invention can perform well-known anti-glare processes, such as antireflection and a low reflection process, as needed.

[Image display device]
The polarizing plate formed by forming the optical film of the present invention on at least one side is used by being bonded to a liquid crystal cell, for example. In FIG. 2, the structural example of the liquid crystal cell which has the optical film and polarizing plate of this invention is shown. In FIG. 2, 6 indicates a liquid crystal cell. Examples of the liquid crystal cell 6 include an active matrix drive type typified by a thin film transistor type and a simple matrix drive type typified by a twist nematic type and a super twist nematic type. In the configuration example of the liquid crystal cell in FIG. 2, a retardation plate 8 is laminated on the liquid crystal cell 6 via an adhesive layer (not shown; the same applies hereinafter), and an adhesive layer ( The polarizing plate 7 of the present invention is laminated through a not-shown). Here, the optical element 2 is formed by laminating the retardation plate 8 and the polarizing plate 7, and the polarizing plate 7 has the polarizer 3 at the center, and the adhesive layer 5 is provided on the surfaces on both sides thereof. The protective film 4 made of the optical film of the present invention is laminated. When laminating the polarizing plate 7 and the retardation plate 8 and the retardation plate 8 and the liquid crystal cell 6 of the present invention, an adhesive layer may be provided on the polarizing plate 7, the retardation plate 8 and the liquid crystal cell 6 in advance.

The pressure-sensitive adhesive for laminating the polarizing plate and the liquid crystal cell of the present invention is not particularly limited. For example, an acrylic polymer, silicone polymer, polyester, polyurethane, polyamide, polyether, fluorine-based or rubber-based polymer is a base polymer. Can be appropriately selected and used. Among these, acrylic pressure-sensitive adhesives are preferable because they are excellent in optical transparency, exhibit appropriate wettability, cohesiveness, and adhesive pressure-sensitive adhesive properties, and are excellent in weather resistance and heat resistance.
The pressure-sensitive adhesive is required to be excellent in optical transparency, suitable wettability, cohesiveness, adhesive properties such as adhesion, weather resistance, heat resistance and the like. Furthermore, the moisture absorption rate is low in terms of prevention of foaming and peeling phenomena due to moisture absorption, deterioration of optical characteristics due to thermal expansion differences, prevention of warping of liquid crystal cells, and the formation of high-quality and durable image display devices. Therefore, a pressure-sensitive adhesive layer having excellent heat resistance is required.

  Examples of the pressure-sensitive adhesive include natural and synthetic resins, in particular, tackifier resins, fillers and pigments made of glass fibers, glass beads, metal powders, other inorganic powders, colorants, antioxidants, and the like. Etc. may be contained. Moreover, the adhesive layer which contains microparticles | fine-particles and shows light diffusibility may be sufficient.

The application of the pressure-sensitive adhesive to the polarizing plate of the present invention is not particularly limited, and can be performed by an appropriate method. For example, a pressure-sensitive adhesive solution of about 10 to 40% by mass in which a base polymer or a composition thereof is dissolved or dispersed in a solvent composed of an appropriate solvent alone or a mixture such as toluene and ethyl acetate is prepared, and the resulting solution is allowed to flow. A method of coating directly on the polarizing plate of the present invention by an appropriate development method such as a rolling method or a coating method, or forming a pressure-sensitive adhesive layer on a releasable base film according to this method and applying it to the present invention. The method of transferring to a polarizing plate is mentioned.
As the coating method, various methods such as gravure coating, bar coating, roll coating, reverse roll coating, and comma coating are possible, but gravure coating is the most common.

The pressure-sensitive adhesive layer can also be provided on one or both sides of the polarizing plate of the present invention as a superimposed layer of different compositions or types. Moreover, when providing in both surfaces, the adhesive does not need to be the same composition in the front and back of the polarizing plate of this invention, and it is not necessary to be the same thickness. It can also be set as the adhesive layer of a different composition and different thickness.
The thickness of the pressure-sensitive adhesive layer can be appropriately determined according to the purpose of use and adhesive force, and is generally 1 μm to 500 μm, preferably 5 μm to 200 μm, particularly preferably 10 μm to 100 μm.

  The exposed surface of the pressure-sensitive adhesive layer is preferably covered with a releasable film for the purpose of preventing contamination until it is put to practical use. Thereby, it can prevent contacting an adhesive layer in the usual handling state. As a releasable film, for example, a suitable thin leaf body such as a plastic film, rubber sheet, paper, cloth, non-woven fabric, net, foamed sheet, metal foil, and laminate thereof, silicone type or long chain alkyl type as necessary Conventionally known materials such as those coated with an appropriate release agent such as fluorine-based or molybdenum sulfide can be used.

  In the present invention, each layer such as the polarizer, protective film layer, and pressure-sensitive adhesive layer includes, for example, a salicylic acid ester compound, a benzophenol compound, a benzotriazole compound, a cyanoacrylate compound, and a nickel complex compound. Ultraviolet absorbing ability may be imparted by a method of treating with an ultraviolet absorber.

  The polarizing plate of the present invention can be preferably used for forming various devices such as an image display device. Here, examples of the image display device include a liquid crystal display including a liquid crystal cell, an organic EL display device, a touch panel, and the like, and the type of the image display device is not limited as long as a polarizing plate is used. In the case of a liquid crystal display, an image display device is generally formed by appropriately assembling components such as a liquid crystal cell, an optical film, and an illumination system as necessary, and incorporating a drive circuit. In the invention, the configuration of the image display device is not particularly limited except that the polarizing plate is used. For example, an appropriate image display device such as an image display device in which a polarizing plate is disposed on one side or both sides of a liquid crystal cell, or a backlight or a reflection plate as an illumination system is exemplified. As the liquid crystal cell, any type such as a TN type, an STN type, or a π type can be used. In configuring the image display device, for example, a single layer of appropriate components such as a diffusion plate, an antiglare layer, an antireflection film, a protective plate, a prism array, a lens array sheet, a light diffusion plate, and a backlight are provided at appropriate positions. Alternatively, two or more layers can be arranged.

[Application to organic EL display devices]
The polarizing plate of the present invention can be suitably used for an organic EL display device.
Generally, in an organic EL display device, a transparent electrode, an organic light emitting layer, and a metal electrode are sequentially laminated on a transparent substrate to form a light emitter (organic electroluminescent light emitter). Here, the organic light emitting layer is a laminate of various organic thin films, for example, a laminate of a hole injection layer made of a triphenylamine derivative and a light emitting layer made of a fluorescent organic solid such as anthracene, Or, there are known configurations having various combinations such as a laminate of such a light-emitting layer and an electron injection layer made of a perylene derivative, or a laminate of these hole injection layer, light-emitting layer, and electron injection layer. Yes.

In organic EL display devices, holes and electrons are injected into the organic light-emitting layer by applying a voltage to the transparent electrode and the metal electrode, and the energy generated by recombination of these holes and electrons excites the phosphor material. Then, light is emitted on the principle that the excited fluorescent material emits light when returning to the ground state. The mechanism of recombination in the middle is the same as that of a general diode, and as can be predicted from this, the current and the emission intensity show strong nonlinearity with rectification with respect to the applied voltage.
In an organic EL display device, in order to extract light emitted from the organic light emitting layer, at least one of the electrodes must be transparent, and a transparent electrode usually formed of a transparent conductor such as indium tin oxide (ITO) is used as an anode. It is used as. On the other hand, in order to facilitate electron injection and increase luminous efficiency, it is important to use a material having a small work function for the cathode, and usually metal electrodes such as Mg—Ag and Al—Li are used.

  In the organic EL display device having such a configuration, the organic light emitting layer is formed of a very thin film having a thickness of about 10 nm. For this reason, the organic light emitting layer transmits light almost completely like the transparent electrode. As a result, light that is incident from the surface of the transparent substrate at the time of non-light emission, passes through the transparent electrode and the organic light emitting layer, and is reflected by the metal electrode is again emitted to the surface side of the transparent substrate. The display surface of the organic EL display device looks like a mirror surface.

  In an organic EL display device comprising an organic electroluminescent light emitting device comprising a transparent electrode on the surface side of an organic light emitting layer that emits light upon application of a voltage and a metal electrode on the back side of the organic light emitting layer, the surface of the transparent electrode The polarizing plate of the present invention can be provided on the side, and a birefringent layer (retardation plate) can be provided between the transparent electrode and the polarizing plate.

Since the polarizing plate of the present invention has a function of polarizing light incident from the outside and reflected by the metal electrode, there is an effect that the mirror surface of the metal electrode is not visually recognized from the outside by the polarization action. In particular, if the birefringent layer is composed of a λ / 4 plate and the angle between the polarizing direction of the polarizing plate and the birefringent layer is adjusted to π / 4, the mirror surface of the metal electrode can be completely shielded. .
That is, only the linearly polarized light component of the external light incident on the organic EL display device is transmitted by the polarizing plate. This linearly polarized light generally becomes elliptically polarized light by the birefringent layer, but becomes circularly polarized light when the birefringent layer is a λ / 4 plate and the angle formed by the polarization direction with the polarizing plate is π / 4. This circularly polarized light is transmitted through the transparent substrate, the transparent electrode, and the organic thin film, is reflected by the metal electrode, is again transmitted through the organic thin film, the transparent electrode, and the transparent substrate, and becomes linearly polarized light again at the birefringent layer. And since this linearly polarized light is orthogonal to the polarization direction of a polarizing plate, it cannot permeate | transmit a polarizing plate. As a result, the mirror surface of the metal electrode can be completely shielded.

[Applied to touch panel]
The optical film of this invention can be used conveniently also for the polarizing plate of a touchscreen. In general, a touch panel is a device in which an operator operates a device or a system by touching a transparent surface provided at the top of a display screen with a pen or a finger. In recent years, touching directly on the screen has become more and more popular in recent years because it is more direct and intuitive than pressing the cursor with a direction key to determine the position. . In recent years, the growth of mobile terminals such as mobile phones and PDAs (Personal Digital Assistants) has been remarkable, and visibility under sunlight and thin and light weight are strongly required. Became. There are various types of touch panels, and they are properly used depending on their advantages and disadvantages. The touch panel includes a resistive film type, an optical type, a capacitive coupling type (also called an analog capacitive coupling type), an infrared type, an ultrasonic type, and an electromagnetic induction type. Here, an example of a resistive film type touch panel will be described.

  Resistive touch panels include a glass / glass type and a glass / film type. In the glass / glass type, a glass substrate with a transparent conductive layer and a glass substrate with a transparent conductive layer are held via a space, and this is mounted on the display surface. The glass / film type is a type of touch panel in which an upper glass substrate with a transparent conductive layer is replaced with an optical film because a lighter / thinner one is desired in an in-vehicle or portable touch panel.

A glass / glass type touch panel is shown in FIG. 3, and a glass / film type touch panel is shown in FIG. A glass / glass type touch panel and a glass / film type touch panel will be described below with reference to FIGS.
If a linearly polarizing plate or a circularly polarizing plate made by combining a polarizing plate with a λ / 4 plate is used on the outermost surface of the touch panel, sufficient strength can be obtained as a touch panel, and visibility can be improved due to the antireflection effect. Will improve. The polarizing plates of the touch panel are 9 in FIG. 3 and 17 in FIG. The optical film of this invention can be used conveniently for the polarizing plate of these touch panels.
A polarizing plate and a λ / 4 plate comprising the optical film of the present invention and a polarizer are laminated so that the angle between the slow axis in the plane of the λ / 4 plate and the polarizing axis of the polarizing plate is substantially 45 °. A circularly polarizing plate is then obtained. Substantially 45 ° means 40 ° to 50 °. The angle between the slow axis in the plane of the λ / 4 plate and the polarization axis of the polarizing film is preferably 41 to 49 °, more preferably 42 to 48 °, and 43 to 47 °. Is more preferable, and it is most preferable that it is 44-46 degrees.

The optical film of the present invention can be used for any of the upper, lower and lower outer layers (lightweight reduction film provided with ITO) of the polarizing plate. There are two types of anti-reflection for touch panels: linearly polarized light type and circularly polarized light type (linearly polarized light has a higher reflectance than circularly polarized light). Can also be used.
The circularly polarizing plate or linearly polarizing plate using the optical film of the present invention can be used for both transmissive and reflective touch panels.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by this example.
(Evaluation methods)
1. Flexural modulus Measured according to JIS K7171.
2. Evaluation of in-plane retardation The in-plane retardation was measured using a phase difference measuring device (“KOBRA-WR (model number)” manufactured by Oji Scientific Instruments) at a wavelength of 589.3 nm and an incident angle of 0 degree.
3. Transparency Measured according to JIS K7105.
4). Evaluation of ultraviolet absorption performance The light transmittance at wavelengths of 260 nm (UV-C region) and 310 nm (UV-B region) was measured using an ultraviolet visible absorption spectrometer ("UV-2400 (model number)" manufactured by Shimadzu Corporation). And measured as X (%) and Y (%), respectively.
Evaluation of X (%) ○: 20 or more ×: Less than 20 Evaluation of Y (%) ○: Less than 10 ×: 10 or more Evaluation of X + Y ○: Less than 70 ×: 70 or more 5. Evaluation of Visible Light Transmittance Light transmittance at wavelengths of 550 nm and 750 nm was measured using an ultraviolet visible absorption spectrometer (“UV-2400 (model number)” manufactured by Shimadzu Corporation).
○: Transmittance is 80% or more and 100% or less X: Transmittance is less than 80% Evaluation of bleeding (bleeding out) of ultraviolet absorber The optical film appearance (presence / absence of bleeding of ultraviolet absorbing agent) is visually evaluated according to the following evaluation criteria after 1,000 hours have elapsed under the following two conditions after film production. evaluated.
(conditions)
Condition 1) Dry at 80 ° C. Condition 2) 60 ° C., 90% 8 (relative humidity)
(Evaluation criteria)
○: There is no bleeding.
Δ: Bleeding (bleeding) occurs and whitening is partially observed, but there is no practical problem.
X: Bleed (exudation) occurs and whitening is observed as a whole.

Example 1
Polypropylene resin synthesized with a metallocene catalyst ("Wintech (trade name)" manufactured by Nippon Polypro Co., Ltd., flexural modulus: 900 MPa, melting point 142 ° C., hereinafter referred to as “mPP-A”) as an ultraviolet absorber. Benzotriazole phenol (2- (2H-benzotriazol-2-yl) -4- (1,1,3,3-tetramethylbutyl) phenol, “TINUVIN 329 (trade name)”: Ciba Specialty Chemicals Co., Ltd. To make a polypropylene resin mixture. Here, the content of the benzotriazole phenol was 1.0 mass% with respect to the polypropylene resin mixture. This polypropylene resin mixture was subjected to T-die extrusion molding with a thickness of 100 μm under the conditions of a processing temperature of 200 ° C. and a take-up roll temperature of 50 ° C. to obtain an optical film. The optical film was evaluated by the above evaluation method. The results are shown in Tables 1 and 2. Moreover, the graph of the total light transmittance in wavelength 250-800 nm is shown in FIG.

Example 2
In Example 1, an optical film was obtained in the same manner as in Example 1 except that the content of benzotriazole-based phenol was 0.5% by mass. The results evaluated in the same manner as in Example 1 are shown in Tables 1 and 2.

Example 3
In Example 1, an optical film was obtained in the same manner as in Example 1 except that the content of benzotriazole-based phenol was changed to 5% by mass. The results evaluated in the same manner as in Example 1 are shown in Tables 1 and 2.

Example 4
In Example 1, instead of mPP-A, a polypropylene resin synthesized with a metallocene catalyst (“Wintech (trade name)”; manufactured by Nippon Polypro Co., Ltd., flexural modulus: 700 MPa, melting point 125 ° C., hereinafter “mPP-B An optical film was obtained in the same manner as in Example 1 except that the above was used. The results evaluated in the same manner as in Example 1 are shown in Tables 1 and 2.

Example 5
In Example 1, benzotriazole-based phenol was converted into 2- (2H-benzotriazol-2-yl) -4,6-di-tert-pentylphenyl (“TINUVIN 328 (trade name)”: Ciba Specialty Chemicals Co., Ltd. An optical film was obtained in the same manner as in Example 1 except that the product was manufactured. The results evaluated in the same manner as in Example 1 are shown in Tables 1 and 2.

Comparative Example 1
In Example 1, an optical film was obtained in the same manner as in Example 1 except that the content of the benzotriazole phenol was 0.25% by mass. The results evaluated in the same manner as in Example 1 are shown in Tables 1 and 2.

Comparative Example 2
In Example 1, an optical film was obtained in the same manner as in Example 1 except that the content of the benzotriazole phenol was 6% by mass. The results evaluated in the same manner as in Example 1 are shown in Tables 1 and 2.

Comparative Example 3
In Example 1, an optical film was obtained in the same manner as in Example 1 except that benzotriazole-based phenol was used as a benzophenone-based compound (octabenzone, “CHIMASSORB 81 (trade name)” manufactured by Ciba Specialty Chemicals Co., Ltd.). It was. The results evaluated in the same manner as in Example 1 are shown in Tables 1 and 2.

Comparative Example 4
In Example 1, a benzotriazole-based phenol was converted into a benzophenone-based compound (2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5-[(hexyl) oxy] -phenol, “TINUVIN1577FF ( Product name) ”: An optical film was obtained in the same manner as in Example 1 except that Ciba Specialty Chemicals Co., Ltd.) was used. The results evaluated in the same manner as in Example 1 are shown in Tables 1 and 2.

Comparative Example 5
Other than using 2- (2H-benzotriazol-2-yl) -p-cresol (“TINUVIN P (trade name)” manufactured by Ciba Specialty Chemicals Co., Ltd.) as the benzotriazole-based phenol of Example 1. Obtained an optical film in the same manner as in Example 1. The results evaluated in the same manner as in Example 1 are shown in Tables 1 and 2.

＊１，フィルム端部に応力がかかるために、実施例に記載の製造方法においては 、面内位相差にばらつきがでるが、面内位相差が低く一定のロットでは偏光板 として使用可能である。

* 1 Because stress is applied to the film edge, the in-plane retardation varies in the manufacturing method described in the examples, but the in-plane retardation is low and can be used as a polarizing plate in a certain lot. .

According to the present invention, it has excellent optical characteristics such as high transmittance of visible light and low birefringence, excellent moisture permeability, excellent ultraviolet absorption performance, and problems such as coloring and bleeding may occur. No optical film can be provided. The optical film of the present invention is excellent in various durability such as heat resistance and moist heat resistance, can improve the degree of polarization of the polarizing plate without affecting the optical function of the polarizing plate, and is flexible and flexible. And it is rich in elasticity.
In addition, the optical film of the present invention has resistance to external impacts and deformation, and also has good ultraviolet absorption performance. Therefore, by using this optical film attached to a polarizer, a liquid crystal display element can be obtained. A polarizing plate with significantly improved strength and reliability can be obtained.
Furthermore, the optical film of the present invention is more hydrophobic than the conventionally used TAC film, whereas the optical film of the present invention is hydrophobic, whereas the optical film of the present invention is hydrophobic. The durability of the polarizing plate can be greatly improved. Therefore, the optical film of the present invention can be suitably used as a protective film laminated on at least one surface of the polarizing plate and bonded to the liquid crystal cell surface substrate, and can also be used as a protective film on the other side of the polarizing plate. it can.

It is a schematic diagram which shows the manufacturing process of the polarizing plate of this invention. It is a schematic diagram which shows the structural example of the liquid crystal cell which has the polarizing plate of this invention. It is a schematic diagram which shows the structural example of the resistive film type touchscreen (glass / glass type) which has the polarizing plate of this invention. It is a schematic diagram which shows the structural example of the resistive film type touchscreen (glass / film type) which has the polarizing plate of this invention. 4 is a graph showing the total light transmittance of the optical film obtained in Example 1 at a wavelength of 250 to 800 nm.

Explanation of symbols

1: Molten resin (PP)
2: Optical element 3: Polarizer 4: Protective film (optical film)
5: Adhesive layer 6: Liquid crystal cell 7: Polarizing plate 8: Phase difference plate (birefringent layer)
9: Polarizing plate of touch panel 10: Antireflection film 11: λ / 4 plate 12: Protective film for polarizer [top]
12 ': Polarizer protective film [bottom]
13: Polarizer (PVA)
14: Glass 15: ITO protective film 16: Protective film for polarizer [lower and outer]
17: Polarizing plate for touch panel

Claims (8)

  It is composed of a polypropylene resin mixture composed mainly of a polypropylene resin synthesized with a metallocene catalyst and blended with a benzotriazole phenol, and the content of the benzotriazole phenol relative to the polypropylene resin mixture The maximum value of the light transmittance in the range of 0.3 to 5.5% by mass, the wavelength in the range of 250 nm to less than 280 nm is X (%), and the maximum value of the light transmittance in the wavelength of 280 nm to 370 nm is Y (%). An optical film for a protective film satisfying the conditions of X> 20, Y <15, and X + Y <70.   The optical film according to claim 1, wherein the flexural modulus of the polypropylene resin is 700 MPa or more.   The optical film according to claim 1 or 2, wherein the molecular weight of the benzotriazole-based phenol is 250 to 400.   The benzotriazole phenol is 2- (2H-benzotriazol-2-yl) -4- (1,1,3,3-tetramethylbutyl) phenol or 2- (2H-benzotriazol-2-yl) -4 The optical film according to claim 1, which is 1,6-di-tert-pentylphenol.   The optical film according to claim 1, wherein the optical film is an unstretched film.   A polarizing plate formed by forming the optical film according to claim 1 on at least one surface of a polarizer.   The polarizing plate according to claim 6, wherein the polarizing plate is used by being bonded to a liquid crystal cell, and the optical film is formed opposite to the liquid crystal cell side of the polarizer.   An image display device using the polarizing plate according to claim 6.

Images