JP2010243862A - Retardation film, polarizing plate and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a retardation film which has positive A plate characteristics and is usable as a polarizer protective film as well, and to perform further thinning and cost reduction of a polarizing plate and a display device by using the retardation film. <P>SOLUTION: The retardation film includes the mixed resin of polypropylene polymerized using a metallocene catalyst and rosin metal salt, and has the positive A plate characteristics. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical member used in a display device, and more particularly to a retardation film having a positive A plate characteristic and also usable as a polarizer protective film. The present invention also relates to a polarizing plate and a display device using the retardation film.

  In recent years, display devices such as liquid crystal display devices and organic electroluminescence (EL) display devices have been widely used in televisions, computers, mobile phones, and the like. There is also a strong demand for lower costs.

  As an example of the display device, a configuration example of a liquid crystal display device is shown in FIG. In FIG. 3, the liquid crystal cell 6 is provided, and the phase difference plate 5 and the polarizing plate 4 are disposed on one side of the liquid crystal cell 6. The polarizing plate 4 has a polarizer 3 at the center, and a polarizer protective film 1 b is formed on both sides of the polarizer 3 with an adhesive layer 2 interposed therebetween.

  The polarizing plate is an optical member having a function of transmitting one of orthogonal polarization components and shielding the other. A polarizing plate in which a polarizer protective film is formed on one side or both sides of a polarizer is generally used. Among these, the polarizer has a function of transmitting only light having a specific vibration direction, and a uniaxially stretched polyvinyl alcohol (PVA) film dyed with iodine or a dichroic dye is widely used. ing.

  Moreover, the polarizer protective film bears functions such as supporting the polarizer and imparting practical strength to the entire polarizing plate and physically protecting the surface of the polarizer. Therefore, the polarizer protective film is required to have practical strength, good transparency, and low optical nonuniformity such as a moire pattern. A typical example of the polarizer protective film is a triacetyl cellulose (TAC) film which is a cellulose film.

  However, the TAC film has insufficient moisture resistance, and there is a problem in that the dimensions of the film change due to water absorption, or the performance of the polarizer deteriorates due to transmitted water. For this reason, it has been proposed to use polypropylene having excellent moisture resistance as a polarizer protective film (Patent Documents 1 and 2). Patent Document 1 discloses that an optical film using polypropylene polymerized using a metallocene catalyst is suitable for protecting a polarizer by having features such as small haze and excellent transparency. Yes.

The retardation film is an optical member having birefringence that causes a phase difference between orthogonally polarized components, and is used for so-called optical compensation for compensating the phase difference.
A phase difference film having a positive A plate characteristic is a surface where the light whose refractive index does not change no matter which direction the light is incident is normal light, and the light whose refractive index changes according to the light incident direction is abnormal light. A retardation film having an optical axis inside and an extraordinary refractive index larger than that of ordinary light. A retardation film having a positive A plate characteristic is, for example, intended to maintain the orthogonality when two polarizing plates are arranged orthogonally (crossed Nicols) in an oblique vision in a vertical alignment (VA) mode type liquid crystal display device. Therefore, it is disposed between the polarizer and the liquid crystal cell and used as a so-called viewing angle widening film. In addition, in the organic EL display device, a shielding effect that prevents the mirror surface of the transparent electrode from being visually recognized from the outside can be obtained by arranging a retardation film having appropriate positive A plate characteristics between the polarizer and the transparent electrode. .

  In a TAC film widely used as a polarizer protective film, it is difficult to impart positive A plate characteristics to triacetyl cellulose itself. Therefore, when a TAC film is used as the polarizer protective film, a phase difference film having a positive A plate characteristic is separately employed to compensate for the phase difference of the polarizer, or a positive A plate is provided on the surface of the TAC film. It is necessary to specially form a retardation layer having characteristics.

On the other hand, in Patent Document 2, a polypropylene resin raw film obtained by film formation is stretched to develop a retardation, and the retardation film is adhered to a polarizer to protect the polarizing plate. A composite polarizing plate having a structure in which a film also functions as a retardation film is disclosed.
However, when the retardation is expressed by the stretching treatment, the obtained retardation value depends on the thickness of the film. Therefore, of course, the thickness of the film cannot be made thinner than the thickness necessary for obtaining a desired retardation value, which may hinder the thinning of the polarizing plate and the display device. In addition, variations in the phase difference are likely to occur due to fluctuations in the control of the stretching process. Furthermore, since internal heat shrinkage stress accumulates in the film due to stretching, there arises a problem that the dimensional change tends to be large under a high temperature environment or a high humidity environment.

JP 2008-146023 A JP 2007-316603 A

  The present invention has been made under the circumstances described above. An object of the present invention is to find a technique for imparting positive A plate characteristics to polypropylene polymerized by using a metallocene catalyst by means other than stretching, so that it has positive A plate characteristics and can be used as a polarizer protective film. The object is to provide a possible retardation film. Further, by using the retardation film, it is possible to further reduce the thickness and cost of the polarizing plate and the display device.

The first invention is a retardation film made of a mixed resin of polypropylene and rosin metal salt polymerized using a metallocene catalyst and having positive A plate characteristics.
A second invention is the retardation film according to the first invention, wherein the rosin metal salt is 0.03 to 1 part by mass with respect to 100 parts by mass of polypropylene.
A third invention is a retardation film which is not subjected to stretching treatment in the first invention or the second invention.
A fourth invention is a polarizing plate in which the retardation film according to any one of the first to third inventions is formed on at least one side of a polarizer.
A fifth invention is a display device having the polarizing plate according to the fourth invention.
A sixth invention is a display device in which a polarizing film and the retardation film according to any one of the first invention to the third invention are arranged on at least one side of the polarizing plate.

  According to the present invention, a retardation film having positive A plate characteristics and usable as a polarizer protective film can be obtained. The present inventors have found that an in-plane retardation that provides positive A plate characteristics can be developed by mixing a rosin metal salt with polypropylene polymerized using a metallocene catalyst. At this time, since the value of the in-plane retardation to be expressed depends on the mixing ratio of the rosin metal salt, it can be adjusted to a desired in-plane retardation value by increasing or decreasing the mixing ratio of the rosin metal salt. it can.

  Furthermore, by using the retardation film, a thin and low-cost polarizing plate and display device can be obtained.

It is a figure which shows the structural example of the polarizing plate of this invention. It is a figure which shows the structural example (example in which the phase difference film which has a positive A plate characteristic serves as a polarizer protective film) of the liquid crystal display device of this invention. It is a figure which shows the structural example (example which has a polarizer protective film and retardation film which has a positive A plate characteristic) of the liquid crystal display device of this invention.

Hereinafter, embodiments of the present invention will be described in detail.
[Phase difference film]
The retardation film of the present invention is made of a mixed resin of polypropylene and rosin metal salt polymerized using a metallocene catalyst, and has a positive A plate characteristic.
The retardation film of the present invention is prepared by mixing polypropylene polymerized using a metallocene catalyst and a rosin metal salt, melting them by heating, and then molding them by various molding methods such as an unstretched T-die extrusion molding method. Manufactured.
Below, a retardation film and its manufacturing method are demonstrated in detail.

(Polypropylene polymerized using metallocene catalyst)
Polypropylene polymerized using a metallocene catalyst is a propylene polymer synthesized by a polymerization reaction using a metallocene catalyst described later. Polypropylene polymerized using a metallocene catalyst generally has a uniform molecular weight and crystallinity compared to polypropylene polymerized using a Ziegler-Natta catalyst, which has low molecular weight and low crystallinity. Have Therefore, a retardation film using polypropylene polymerized using a metallocene catalyst is higher in transparency than a retardation film using polypropylene polymerized using a Ziegler-Natta catalyst. Therefore, in the present invention, polypropylene polymerized using a metallocene catalyst is used as one of the essential components of the mixed resin constituting the retardation film of the present invention.

  The polypropylene polymerized using the metallocene catalyst is preferably a random 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- And 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 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.

  As the metallocene catalyst, a known catalyst can be appropriately used. Generally, a group 4-6 transition metal compound such as Zr, Ti, Hf, etc., in particular, a group 4 transition metal compound and an organic transition metal compound having a cyclopentadienyl group or a cyclopentadienyl derivative group is used. be able to.

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

  The 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 bonding 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 known layered silicates, for example, kaolins such as dickite, nacrite, kaolinite, anorxite, 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 the like are preferable smectite group, vermiculite group and mica group.

  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. Specifically, acid treatment, alkali treatment, salt treatment, organic matter treatment and the like can be mentioned. These treatments have actions such as removing impurities on the surface, exchanging cations between layers, and eluting cations such as Al, Fe, and Mg in the crystal structure. As a result, ion complexes, molecules Complexes, organic derivatives and the like can be formed, and 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 polypropylene 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 include bulk polymerization using a monomer as a solvent.

  The polypropylene polymerized using the metallocene catalyst preferably has a melting point (Tm) of 130 ° C. or higher.

(Rosin metal salt)
A rosin metal salt is a reaction product of a rosin and a metal compound. The rosin metal salt is used as one of the essential components of the mixed resin constituting the retardation film of the present invention in order to impart an in-plane retardation that provides positive A plate characteristics. The rosin metal salt can be generally added to polypropylene polymerized using a Ziegler-Natta catalyst as a crystal nucleating agent. However, since the polypropylene polymerized using the metallocene catalyst has sufficiently high transparency, the need to use a rosin metal salt as a crystal nucleating agent is extremely low. In the present invention, a rosin metal salt is mixed with polypropylene polymerized using a metallocene catalyst for the purpose of developing an in-plane retardation that provides positive A plate characteristics.

As rosins, natural rosins such as gum rosin, tall oil rosin and wood rosin; various modifications such as disproportionated rosin, hydrogenated rosin, dehydrogenated rosin, polymerized rosin, α, β-ethylenically unsaturated carboxylic acid modified rosin Examples of rosin; purified natural rosin, modified rosin and the like. Here, the rosin is a singular resin acid selected from pimaric acid, sandaracopimalic acid, parastrinic acid, isopimaric acid, abietic acid, dehydroabietic acid, neoabietic acid, dihydropimaric acid, dihydroabietic acid, tetrahydroabietic acid, and the like. Or more than one. Examples of the unsaturated carboxylic acid used in the preparation of the above-mentioned α, β-ethylenically unsaturated carboxylic acid-modified rosin include maleic acid, maleic anhydride, fumaric acid, itaconic acid, itaconic anhydride, citraconic acid, acrylic Examples include acid and methacrylic acid.
Among the rosins, at least one rosin selected from the group consisting of natural rosin, modified rosin, purified natural rosin, and purified modified rosin is preferable.

  Examples of the metal compound that reacts with rosins to form a metal salt include compounds having a metal element such as sodium, potassium, and magnesium and salting with the rosins. Specific examples include chlorides, nitrates, acetates, sulfates, carbonates, oxides and hydroxides of the above metal elements.

The rosin metal salt is preferably at least one rosin metal salt selected from the group consisting of a sodium salt of the rosin, a potassium salt of the rosin, and a magnesium salt of the rosin.
The rosin metal salt is preferably at least one rosin metal salt selected from the group consisting of a metal salt of hydrogenated rosin, a metal salt of disproportionated rosin, and a metal salt of dehydrogenated rosin. Further, at least one rosin metal salt selected from the group consisting of a metal salt of dehydroabietic acid, a metal salt of dihydroabietic acid and a metal salt of dihydropimaric acid is more preferable.

The rosin metal salt is preferably used in the form of fine particles. This is because the dispersibility of the rosin metal salt in polypropylene is improved by making the rosin metal salt fine, so that the rosin metal salt can be uniformly dispersed in the polypropylene.
A conventionally known method can be employed as a method for making rosin metal salt into fine particles. For example, (i) a method of pulverizing a solid material of a rosin metal salt in a wet or dry manner, (ro) a solution state without distilling off the organic solvent after the reaction between the rosin and the metal compound is completed. And water and, if necessary, a surfactant and / or a water-soluble polymer, followed by emulsification and dispersion, and then water and the organic solvent are distilled off. At this time, in the method (b), after removing water and the organic solvent, a washing operation or the like may be performed to remove the surfactant or the water-soluble polymer from the rosin metal salt. As the surfactant and / or water-soluble polymer that can be used in the method (b), conventionally known ones are used. Specifically, nonionic surfactants and anionic surfactants are used. , Polyvinyl alcohol, poly (meth) acrylic acid alkali metal salt, (meth) acrylic acid-acrylamide copolymer, water-soluble cellulose, starch and the like.

The blending ratio of the rosin metal salt to the polypropylene can be appropriately selected according to the desired in-plane retardation value. Increasing the blending ratio increases the in-plane retardation value obtained.
At this time, the blending ratio of the rosin metal salt is preferably 0.03 to 1 part by mass with respect to 100 parts by mass of polypropylene. This is because the retardation can be adjusted to a range generally required for a retardation film having a positive A plate characteristic.
Furthermore, the blending ratio of the rosin metal salt is more preferably 0.5 parts by mass or less. This is because when the mixing ratio exceeds 0.5 parts by mass, poor dispersion of the rosin metal salt is likely to occur, and variation in retardation may occur.

(Other ingredients)
In the present invention, various additives and additive resins can be added as optional components of the mixed resin constituting the retardation film as desired.
For example, depending on the desired physical properties of the obtained film, various olefin resins other than polypropylene polymerized using a metallocene catalyst may be added as an additive resin within a range that does not impair birefringence and transparency necessary for a retardation film. In addition, weather resistance improver, abrasion resistance improver, polymerization inhibitor, crosslinking agent, infrared absorber, antistatic agent, adhesion improver, leveling agent, thixotropic agent, coupling agent, plasticizer Antifoaming agents, fillers, solvents and the like can be added.

Here, as the weather resistance improving agent, an ultraviolet absorber or a light stabilizer can be used.
The ultraviolet absorber may be either inorganic or organic, and as the inorganic ultraviolet absorber, titanium dioxide, cerium oxide, zinc oxide or the like having an average particle diameter of about 5 to 120 nm can be preferably used. Moreover, as an organic type ultraviolet absorber, benzotriazole type, for example, 2- (2-hydroxy-5-methylphenyl) benzotriazole, 2- (2-hydroxy-3,5-di-tert-) is specifically mentioned. Amylphenyl) benzotriazole, 3- [3- (benzotriazol-2-yl) -5-tert-butyl-4-hydroxyphenyl] propionic acid ester of polyethylene glycol, and the like.
On the other hand, examples of the light stabilizer include hindered amines, specifically 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 and the like.
Further, as the ultraviolet absorber or light stabilizer, a reactive ultraviolet absorber or light stabilizer having a polymerizable group such as a (meth) acryloyl group in the molecule can be used.

  Examples of the wear resistance improver include, for inorganic substances, 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. Although there is no particular limitation, a spherical shape is preferable. 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 thickness of the retardation 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.

(Retardation film)
The retardation film of the present invention has positive A plate characteristics. The positive A plate characteristic means that the light whose refractive index does not change no matter which direction the light is incident is ordinary light, and the light whose refractive index changes depending on the light incident direction is abnormal light, the optical axis is in-plane. It has an optical characteristic that the extraordinary refractive index is larger than the ordinary refractive index. That is, when the in-plane main refractive index is nx (slow axis direction), ny (fast axis direction), and the refractive index in the thickness direction is nz, the refractive index distribution is a positive value satisfying nx> ny = nz. A uniaxial optical element. Ideally, a positive uniaxial optical element whose refractive index distribution satisfies nx> ny = nz has an optical axis in one direction in the plane. Note that ny = nz includes not only the case where ny and nz are completely the same, but also the case where ny and nz are substantially the same. Here, the case where ny and nz are substantially the same includes, for example, a case where the absolute value of the difference between the in-plane retardation value and the thickness direction retardation value is 10 nm or less.

When used in a VA mode / IPS mode type liquid crystal display device, organic EL display device, etc., the retardation range generally required for a retardation film having a positive A plate characteristic is a wavelength of R589.5 nm. And 20 to 600 nm under the condition of an incident angle of 0 degree. The thickness is preferably 20 nm to 300 nm, and the function of the optical element in each display device is exhibited synergistically by setting the above phase difference range at the wavelength R589.5 nm. In particular, in the VA mode type liquid crystal display device, the contrast ratio in the oblique direction can be increased and the color shift amount in the oblique direction can be reduced.
The in-plane retardation can be set to a desired value by increasing or decreasing the mixing ratio of the rosin metal salt. In addition to the mixing of rosin metal salts, the in-plane retardation value can be adjusted by performing a stretching treatment as necessary.

  The thickness of the retardation 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 of the retardation film can be ensured. When the thickness is 200 μm or less, sufficient flexibility can be obtained, and since it is lightweight, handling is easy and cost is advantageous.

The retardation film preferably has a flexural modulus of 700 MPa or more. This is because sufficient rigidity is obtained when handled in a film state, and post-processing can be easily performed. Furthermore, the flexural modulus of the retardation film is more preferably 900 MPa or more. This is because the in-plane retardation can be stabilized when manufactured by T-die extrusion molding.
The bending elastic modulus of the retardation film is selected, for example, by a method inherent to polypropylene (crystallinity, average molecular weight, etc.), a method of adding a filler selected from inorganic or organic fillers to the resin, and a crosslinking agent. And the like, a method of mixing two or more resins having different elastic moduli, a method of selecting a plasticizer composition of a curable resin, or a combination of a plurality of these methods as desired. Can be adjusted within the range.

  The retardation film preferably has a tensile strength of 20 MPa or more. When the pressure is 20 MPa or more, when the retardation film is bonded to the polarizer by the roll-to-roll method via the adhesive layer, the orientation is not applied and the variation in retardation is unlikely to occur. The performance of the polarizing plate provided with characteristics can be improved.

  The retardation film can be subjected to an easy adhesion treatment on the surface in contact with the polarizer in order to improve adhesion. 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.

  Further, when an adhesive layer is formed in order to improve the adhesion between the retardation film and the polarizer, it can be performed by applying an adhesive on either or both sides of the retardation film or the polarizer. . The thickness of the adhesive layer is preferably 0.01 to 10 μm, more preferably 0.03 to 5 μm, since it is not preferable in terms of the adhesiveness of the retardation film if the thickness after drying becomes too thick.

  After the retardation film and the polarizer are bonded together through the surface subjected to the easy adhesion treatment or the surface on which the adhesive layer is formed, the bonding is performed by performing a drying process. This can also be bonded after forming the adhesive layer. The polarizer and the retardation film can be bonded together using a roll laminator or the like. The drying temperature and drying time are appropriately determined according to the type of adhesive.

  In addition, a functional layer is laminated on the surface of the retardation film, and various functions, for example, high hardness and scratch resistance, so-called hard coat function, anti-fogging coat function, anti-fouling coating function, anti-glare coating A function, an antireflection coating function, an ultraviolet shielding coating function, an infrared shielding coating function, and the like can also be imparted.

(Method for producing retardation film)
Retardation film is made by mixing polypropylene polymerized using a metallocene catalyst, rosin metal salt, and various additives and additive resins as required, heat-melting, extrusion coating molding method, casting It can be manufactured by being molded into a film shape by various molding methods such as a method, a T-die extrusion molding method, an inflation method, and an injection molding method.

The stretching treatment in the present invention refers to a process of aligning the obtained film in a certain direction after being formed into a film shape by the above forming method. By the stretching treatment, a retardation having positive A plate characteristics can be imparted to the film.
In the present invention, when performing the stretching treatment, in addition to the expression of in-plane retardation by addition of rosin metal salt, the expression of in-plane retardation is obtained by stretching treatment. Can be reduced.
In the present invention, when no stretching treatment is performed, in-plane retardation variation and internal heat shrinkage stress due to stretching do not occur, and it becomes easy to stably produce a high-quality retardation film. Further, the cost can be reduced by reducing the number of steps, and the cost of the retardation film can be reduced.

[Polarizer]
In the polarizing plate of the present invention, the retardation film of the present invention is formed as a polarizer protective film on at least one side of the polarizer. As a method of forming a polarizing plate, a retardation film may be prepared first, and then bonded to a polarizer via an adhesive layer, or a retardation film may be directly formed on a polarizer. May be. The polarizing plate of the present invention is a high value-added polarizing plate provided with positive A plate characteristics. In addition, the retardation film of the present invention can be made thinner than a thickness necessary for obtaining a desired retardation value only by stretching, so that a thin and low-cost polarizing plate can be obtained. .
In FIG. 1, the structural example of the polarizing plate of this invention is shown. In FIG. 1, reference numeral 3 denotes a polarizer, and the retardation film of the present invention is formed as a polarizer protective film 1 a on one side of the polarizer via an adhesive layer 2 to constitute a polarizing plate 4 as a whole.

As the polarizer used in the polarizing plate, any polarizer may be used as long as it has a function of transmitting only light having a specific vibration direction. For example, a PVA film or the like is stretched, and iodine or a dichroic dye is used. Dyed PVA polarizers; polyene polarizers such as dehydrated PVA and polyvinyl chloride dehydrochlorination; reflective polarizers using cholesteric liquid crystals; thin film crystal film polarizers, etc. Of these, a PVA polarizer is preferably used.
Examples of PVA polarizers include hydrophilic polymers such as PVA films, partially formalized polyvinyl alcohol films, and ethylene / vinyl acetate copolymer partially saponified films, and two colors such as iodine and dichroic dyes. And uniaxially stretched by adsorbing the active substance. Among these, a polarizer composed of a PVA 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. 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 process of uniaxially stretching a PVA film as described above, a process of dyeing a PVA resin film with a dichroic dye, and adsorbing the dichroic dye, and a dichroic dye being adsorbed. A step of treating a PVA film with an aqueous boric acid solution, a step of washing with water after treatment with an aqueous boric acid solution, and a retardation film on a uniaxially stretched PVA film on which dichroic dyes are adsorbed and oriented by applying these steps. It is manufactured through a pasting process.

  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 film with the dichroic dye, for example, the PVA 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 dyeing a PVA 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 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 the dichroic dye is performed by immersing the dyed PVA 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 film after the boric acid treatment is usually washed with water. The water washing treatment is performed, for example, by immersing a boric acid-treated PVA 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.
Thus, a polarizer composed of a PVA film on which iodine or dichroic dye is adsorbed and oriented is obtained.

  As a method of laminating the polarizer and the retardation film, it can be performed through an adhesive layer. As an adhesive for forming an 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, an adhesive having transparency, for example, an adhesive such as polyvinyl ether or rubber can be used. 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 alone 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-based 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. Polyolefins used for grafting include, for example, low-density polyethylene, high-density polyethylene, Ziegler-based catalyst or metallocene catalyst polymerized polypropylene, poly-1-butene, poly-4-methyl-1-pentene, ethylene-propylene Copolymers, ethylene-1-butene copolymers, propylene-1-butene copolymers, 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, itaconic anhydride, and the like. The modified polyolefin thus obtained may be used as it is, but can also be used by blending with polyolefin.

  The polarizer and the adhesive layer have an ultraviolet absorbing ability by a method of treating with an ultraviolet absorber such as a salicylic acid ester compound, a benzophenol compound, a benzotriazole compound, a cyanoacrylate compound, or a nickel complex compound. May be given.

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

  In adhering the retardation film to the polarizer, an easy adhesion treatment can be performed on the surface of the retardation film in contact with the polarizer to improve adhesion. 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 polarizer and the retardation film are bonded to each other through the adhesive layer.
Bonding of the polarizer and the retardation film can be performed with a roll laminator or the like. The heating drying temperature and drying time are appropriately determined according to the type of adhesive.

  In the polarizing plate in which the retardation film of the present invention is formed on one surface of the polarizer, the retardation film of the present invention can be formed on the other surface of the polarizer as necessary. A film made of a resin can also be formed. 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 other resin film may be a retardation film having a specific retardation.

The polarizing plate 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. Alternatively, primer treatment can be performed between the coated layers.

  Further, the polarizing plate can be subjected to a known anti-glare treatment such as anti-reflection or low-reflection treatment as necessary.

[Display device]
The retardation film and polarizing plate of the present invention can be preferably used for various display devices. Since the retardation film of the present invention has positive A plate characteristics and can be used as a polarizer protective film, it can be formed as a polarizer protective film of a polarizing plate having an optical compensation function. This contributes to the simplification of the configuration of the display device using and the productivity.
In addition, the retardation film of the present invention can be used in a display device in combination with a polarizing plate not imparted with positive A plate characteristics without being used as a polarizer protective film.

There is no limitation on the type of display device as long as it uses a polarizing plate and requires positive A plate characteristics. Examples of the image display device include a liquid crystal display including a liquid crystal cell, an organic EL display device, and a touch panel. 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 above polarizing plate is used and the positive A plate characteristic is required. 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. When configuring an image display device, for example, 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 placed at appropriate positions. A layer or two or more layers can be arranged.
An example of a liquid crystal display device including a liquid crystal cell and an example of an organic EL display device will be described below.

(Liquid crystal display device including liquid crystal cell)
The polarizing plate of the present invention is used by being laminated, for example, on a liquid crystal cell. As an example of the display device of the present invention, FIGS. 2 and 3 show configuration examples of a liquid crystal display device including a liquid crystal cell. FIG. 2 shows an example in which the retardation film having positive A plate characteristics of the present invention is used also as a polarizer protective film of a polarizing plate. On the other hand, FIG. 3 shows that the retardation film having positive A plate characteristics of the present invention is not used as a polarizer protective film, and both the retardation film and the polarizer protective film are used as constituent members of a liquid crystal display device. It is an example used.

  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. The polarizing plate 4 is laminated on the liquid crystal cell 6 via an adhesive layer (not shown). The polarizing plate 4 has a polarizer 2 at the center, and a positive A made of the retardation film of the present invention through an adhesive layer 3 on the surface side where the liquid crystal cell of the polarizer 2 and the polarizing plate are disposed. A polarizer protective film 1 a having plate characteristics is laminated, and a polarizer protective film 1 b not having positive A plate characteristics is laminated on the other surface side of the polarizer 2. When laminating the polarizing plate 4 and the liquid crystal cell 6, an adhesive layer may be provided on the polarizing plate 4 and / or the liquid crystal cell 6 in advance. When an optical compensation function other than the positive A plate characteristic is required, an optical film having a necessary optical compensation function can be appropriately employed as a constituent member of the display device.

  In FIG. 3, a liquid crystal cell 6 is provided. As the liquid crystal cell, those exemplified above can be used. On this liquid crystal cell 6, a retardation film 5 made of a retardation film having a positive A plate property of the present invention is laminated via an adhesive layer (not shown), and an adhesive layer ( The polarizing plate 4 is laminated via a not-shown). The polarizing plate 4 has a polarizer 3 in the center, and a polarizer protective film 1b having no positive A plate characteristics is laminated on both surfaces of the polarizing plate 4 with an adhesive layer 2 interposed therebetween. When laminating the polarizing plate 4 and the retardation plate 5, and the retardation plate 5 and the liquid crystal cell 6, an adhesive layer may be provided on the polarizing plate 4, the retardation plate 5 and the liquid crystal cell 6 in advance. In addition, as a polarizer protective film which does not have a positive A plate characteristic, the TAC film, the polypropylene film polymerized using the metallocene catalyst with which the rosin metal salt is not mixed, etc. can be used. Further, when an optical compensation function other than the positive A plate characteristic is required, an optical film having the necessary optical compensation function can be appropriately employed as a constituent member of the display device.

  The pressure-sensitive adhesive for laminating the polarizing plate and the liquid crystal cell is not particularly limited. For example, an acrylic polymer, silicone polymer, polyester, polyurethane, polyamide, polyether, fluorine-based or rubber-based polymer is used as 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, moderate wettability, cohesiveness, adhesive properties such as adhesion, weather resistance, heat resistance and the like. Furthermore, the moisture absorption rate is low in terms of preventing foaming and peeling due to moisture absorption, reducing optical characteristics due to thermal expansion differences, preventing warping of liquid crystal cells, and forming high-quality and durable display devices. 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 pressure-sensitive adhesive layer may be provided with UV absorbing ability by, for example, treatment with a UV absorber such as a salicylic acid ester compound, a benzophenol compound, a benzotriazole compound, a cyanoacrylate compound, or a nickel complex compound. Good.

The application of the pressure-sensitive adhesive to the polarizing plate 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 or ethyl acetate is prepared, and the resulting solution is allowed to flow. A method of coating directly on the polarizing plate by an appropriate development method such as a rolling method or a coating method, or forming an adhesive layer on a releasable base film according to this method and transferring it to the polarizing plate. The method etc. are mentioned.
As the coating method, various methods such as gravure coating, bar coating, roll coating, reverse roll coating, comma coating and the like are possible, but gravure coating is the most common.

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

(Organic EL display device)
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 the like and a light emitting layer made of a fluorescent organic solid such as anthracene, Or, a structure having various combinations such as a laminate of an electron injection layer composed of such a light emitting layer and a perylene derivative, a laminate of these hole injection layer, light emitting layer, and electron injection layer is known. 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 the 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 usually a transparent electrode formed of a transparent conductor such as indium tin oxide (ITO) is used. Used as the anode. 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, A polarizing plate is provided on the side, and a retardation plate is provided between the transparent electrode and the polarizing plate.

Since the polarizing plate 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 by the polarization function. If the retardation plate is a λ / 4 plate and the angle formed by the polarization 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 phase difference plate, but becomes circularly polarized light when the phase difference plate is a λ / 4 plate and the angle formed by the polarization direction with respect to 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 by the phase difference plate. 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.

  The retardation film of the present invention can be used as the retardation plate for the purpose of shielding the mirror surface of the metal electrode.

Next, the present invention will be described in more detail with reference to examples. In addition, this invention is not limited at all by this example.
[Phase difference film]
(Evaluation methods)
In-plane retardation: In-plane position of retardation film using retardation measuring machine (manufactured by Oji Scientific Instruments Co., Ltd., KOBRA (registered trademark) -WR) under conditions of wavelength R589.5 nm and incident angle 0 degree. The phase difference was measured.
Tensile strength: The tensile strength of the retardation film was measured in accordance with ASTM D638 (Type 4 condition).

Example 1
Polypropylene polymerized using a metallocene catalyst (manufactured by Nippon Polypro Co., Ltd., Wintech (registered trademark), melting point 142 ° C., flexural modulus 900 MPa, described as “mPP-A” in Table 1), rosin metal salts (Arakawa Chemical Industries, Ltd., Pine Crystal (registered trademark), KM-1500) was mixed with 100 parts by mass of polypropylene so as to be 0.3 parts by mass of a rosin metal salt, and heated and melted. A retardation film was obtained by T-die single layer extrusion molding with a film thickness of 100 μm under conditions of a processing temperature of 200 ° C. and a take-up roll temperature of 50 ° C. In addition, the extending | stretching process after a shaping | molding process was not performed.

(Example 2)
Polypropylene polymerized using a metallocene catalyst (manufactured by Nippon Polypro Co., Ltd., Wintech (registered trademark), melting point 135 ° C., flexural modulus 1200 MPa, described as “mPP-B” in Table 1) is used in the polypropylene of Example 1. A retardation film was obtained in the same manner as in Example 1 except that it was used instead of.

Example 3
Polypropylene polymerized using a metallocene catalyst (manufactured by Nippon Polypro Co., Ltd., Wintech (registered trademark), melting point 125 ° C., flexural modulus 700 MPa, described as “mPP-C” in Table 1) is used in the polypropylene of Example 1. A retardation film was obtained in the same manner as in Example 1 except that it was used instead of.

Example 4
A retardation film was obtained in the same manner as in Example 1 except that the rosin metal salt was mixed so that the rosin metal salt was 0.02 part by mass with respect to 100 parts by mass of polypropylene.

(Example 5)
A retardation film was obtained in the same manner as in Example 1 except that the rosin metal salt was mixed so as to be 0.05 part by mass of the rosin metal salt with respect to 100 parts by mass of the polypropylene.

(Example 6)
A retardation film was obtained in the same manner as in Example 1 except that the rosin metal salt was mixed with 100 parts by mass of polypropylene so as to be 1.1 parts by mass of the rosin metal salt.

(Comparative Example 1)
A film was obtained in the same manner as in Example 1 except that the rosin metal salt was not mixed.

Table 1 shows the evaluation results of the retardation films obtained in Examples 1 to 6 and Comparative Example 1.
In Examples 1 to 6, by mixing a rosin metal salt with polypropylene polymerized using a metallocene catalyst, the retardation of the film is improved as compared with Comparative Example 1 in which no rosin metal salt was mixed. And positive A plate characteristics were obtained. Further, when the mixing ratio of the rosin metal salt was increased, the in-plane retardation value was increased.

However, when the mixing ratio of the rosin metal salt is 0.02 parts by mass in Example 4, the in-plane retardation generally used as a retardation film having a positive A-plate characteristic in the in-plane retardation value. The range is smaller than 20 to 600 nm. In Example 6, when the mixing ratio of the rosin metal salt is 1.1 parts by mass, the in-plane retardation may be larger than the above range. Therefore, the mixing ratio of the rosin metal salt to 100 parts by weight of polypropylene is preferably in the range of 0.03 to 1.0 part by mass. In Example 6, when the mixing ratio of the rosin metal salt was 1.1 parts by mass, variation in the in-plane retardation value estimated to be caused by poor dispersion of the rosin metal salt was observed.
Further, in the case where polypropylene having a flexural modulus of 700 MPa was used in Example 3, variation in the in-plane retardation value was observed particularly at the film end.
In the retardation films obtained in Examples 1 to 6 and Comparative Example 1, the tensile strength was in the range of 20 to 35 MPa, and no particular problem was found in workability.

[Polarizer]
(Evaluation methods)
Heat resistance test: The sample was left in an oven controlled at a temperature of 90 ° C. and no humidity for 1000 hours, and then the sample was visually evaluated for deformation and coloring. The criteria for evaluation were as follows: ○: Deformation and coloring were not observed, and X: Deformation and / or coloring were observed.
Humidity and heat resistance test: The sample was left in an oven at a temperature of 90 ° C. and a humidity of 95% HR for 1,000 hours, and then the sample was visually evaluated for deformation and coloring. The criteria for evaluation were as follows: ○: Deformation and yellowing were not observed, and X: Deformation and / or yellowing were observed.

(Example 7)
A PVA obtained by saponifying polyvinyl acetate on the both sides of a polarizer made of a polyvinyl alcohol film in which iodine is adsorbed and oriented with the retardation film (width 150 mm × length 150 mm) obtained in Example 1 A polarizing plate was obtained by using and bonding.
The polarizing plate obtained in Example 7 was subjected to a heat resistance test and a moist heat resistance test. As for the evaluation results of both tests, ○: Deformation and yellowing were not observed.

1a: Polarizer protective film having positive A plate characteristics 1b: Polarizer protective film not having positive A plate characteristics 2: Adhesive layer 3: Polarizer 4: Polarizing plate 5: Phase difference plate having positive A plate characteristics 6 : LCD cell

Claims (6)

  A retardation film comprising a mixed resin of polypropylene and a rosin metal salt polymerized using a metallocene catalyst, and having a positive A plate characteristic.   The retardation film according to claim 1, wherein the rosin metal salt is 0.03 to 1 part by mass with respect to 100 parts by mass of polypropylene.   The retardation film according to claim 1, wherein the retardation film is not stretched.   The retardation film as described in any one of Claims 1-3 is formed in the at least single side | surface side of a polarizer, The polarizing plate characterized by the above-mentioned.   A display device comprising the polarizing plate according to claim 4. A display device comprising: a polarizing plate; and the retardation film according to claim 1 disposed on at least one side of the polarizing plate.

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