JP2011158704A - Optical film for protecting polarizer, polarizing plate, and image display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical film which has superior low birefringence and mass production aptitude, and to provide a polarizing plate and an image display apparatus of high performance which uses the optical film. <P>SOLUTION: The optical film for protecting a polarizer is constituted of a polymer alloy, consisting of (A) a polypropylene based copolymer, (B) a polystyrene based polymer and (C) graft-modified polypropylene. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical film for protecting a polarizer, a polarizing plate, and an image display device.

  An optical film is a film for industrial materials that requires transparency. For example, a window film such as a scattering prevention film or an ultraviolet ray prevention film, a polarizer protective film, an optical compensation film, an antireflection film, or the like. Films for industrial use such as film for surface protection and surface protection film used for steel plates and design building materials to prevent scratches and dirt. Among these optical films, with the development of liquid crystal displays including liquid crystal cells, organic electroluminescence display devices, or touch panel displays, optical films used in these image display devices have attracted attention.

  The polarizing plate is an optical member having a function of transmitting only light having a specific vibration direction and shielding other light, and is widely used in the image display apparatus as described above. As such a polarizing plate, what has the structure by which the optical film for polarizer protection was provided in the single side | surface or both surfaces of the 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 (hereinafter referred to as “PVA”) film dyed with iodine or a dichroic dye is used. Recently, a coating type film is also used, but there is a problem that it is generally thin and weak in strength.

  The polarizer protective optical film provided on the polarizer bears functions such as supporting the polarizer, providing practical strength to the entire polarizing plate, and physically protecting the surface of the polarizer. In addition to excellent optical uniformity such as low in-plane retardation, that is, low birefringence, it has practical physical strength and good transparency, etc. More severe performance is required among films that require low birefringence. As such an optical film for protecting a polarizer, a triacetyl cellulose film which is a cellulose film is generally used in many cases. However, the cellulosic film has insufficient moisture resistance, and there are problems such that the dimensions of the film change due to water absorption, and the performance of the polarizer deteriorates due to the transmitted water.

  Until now, a film using polypropylene polymerized using a metallocene catalyst has been proposed as an optical film for protecting a polarizer having good optical properties (see Patent Document 1). However, it is desirable that the optical film for protecting the polarizer originally has no optical influence, and it is expected to realize further low birefringence.

  As a method for controlling the in-plane retardation of an optical film, in a retardation film formed by stretching and orienting a film composed of a mixture of two or more components, the mixture exhibits positive birefringence such as polyethylene or polypropylene. There has been proposed a method in which a resin and a resin exhibiting negative birefringence such as polymethyl methacrylate and polystyrene are mixed (see Patent Document 2). However, (i) due to poor compatibility between the resin showing positive birefringence and the resin showing negative birefringence, it is separated during thermoforming, and the low birefringence and transparency are significantly impaired. In some cases, (ii) the in-plane retardation of the film is increased due to the stretching treatment, so that the technique disclosed in Patent Document 2 is changed to the technique of the optical film for a polarizer protective film. It cannot be used immediately. That is, birefringence control for achieving low birefringence is not established in a low in-plane retardation region where the in-plane retardation is about 20 nm or less, for example.

  Incidentally, in recent years, along with the demand for cost reduction of liquid crystal displays, there has been a further demand for thinner and lighter optical members to be used. That is, it is necessary to reduce the thickness of an optical film for protecting a polarizer used in a liquid crystal display device. On the other hand, in order to put it into practical use as an optical film for protecting a polarizer, in addition to the requirements for optical properties such as transparency and low birefringence and basic properties such as moisture resistance, the optical film must be suitable for mass production. Is required.

  For example, in order to stably produce an optical film for protecting a polarizer in a wide width or at a high speed, a resin used for the optical film for protecting a polarizer needs to have sufficient strength. In addition, an optical film for protecting a polarizer used for a polarizing plate of a thin flexible image display device needs to have sufficient rigidity so that it can be molded with a thin film thickness and can withstand bending. Alternatively, for an in-vehicle use image display apparatus that is also used in a cold region, the optical film for protecting a polarizer is required to have durability against cold (cold shock resistance). Naturally, by having sufficient strength and rigidity as described above, mass production suitability or durability that enables stable mass production without causing wrinkles or breakage has the basic characteristics as described above. It must be satisfied while holding. Furthermore, it is required to provide the optical film for protecting the polarizer with characteristics according to the use of the image display device and the polarizing plate.

Japanese Patent Laid-Open No. 2008-146023 JP-A-4-194902

  The present invention has been made under such circumstances, and an object of the present invention is to provide an optical film having excellent low birefringence and suitability for mass production. Another object of the present invention is to provide a high-performance polarizing plate and an image display device using the same.

As a result of intensive studies to achieve the above object, the present inventors have obtained a polymer obtained by mixing a polypropylene-based copolymer with a polystyrene-based polymer and graft-modified polypropylene as a compatibilizing agent. It has been found that the problem can be solved by using an alloy. The present invention has been completed based on such findings.
That is, the gist of the present invention is as follows.

1. An optical film for protecting a polarizer, comprising a polymer alloy comprising (A) a polypropylene copolymer, (B) a polystyrene polymer, and (C) a graft-modified polypropylene.
2. A polarizing plate, wherein the polarizer protective optical film described in 1 is provided on at least one surface of the polarizer.
3. 3. An image display device using the polarizing plate described in 2 above.
4). The manufacturing method of the optical film which has the process of following (1)-(3).
Step (1) (A) Step of polymerizing polypropylene copolymer Step (2) (A) Polypropylene copolymer, (B) Polystyrene polymer and (C) Graft-modified polypropylene are mixed and melted by heating. Step of obtaining a polymer alloy (3) Step of molding the polymer alloy

  According to the present invention, an optical film having excellent low birefringence and mass production suitability can be obtained. In addition, a high-performance polarizing plate and an image display device to which characteristics according to applications are provided can be obtained.

It is a figure which shows the structural example of the optical film of this invention. 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 of the liquid crystal display containing the liquid crystal cell of this invention.

[Optical film for protecting polarizers]
The optical film for protecting a polarizer of the present invention is composed of a polymer alloy comprising (A) a polypropylene copolymer, (B) a polystyrene polymer, and (C) a graft-modified polypropylene. There is a configuration as shown in FIG. 1 as a typical embodiment.
Below, the optical film of this invention and its manufacturing method are demonstrated in detail.

<< (A) Polypropylene copolymer >>
(A) A polypropylene-type copolymer is a copolymer of propylene and 1 type, or 2 or more types of comonomer. Preferred examples of the polypropylene-based copolymer include a copolymer of propylene and at least one comonomer selected from ethylene and an α-olefin having 4 to 20 carbon atoms. In this case, a random copolymer is preferable from the viewpoint of optical properties, not a block copolymer.

Among the α-olefins having 4 to 20 carbon atoms, α-olefins having 4 to 12 carbon atoms are preferable, and α-olefins having 4 to 8 carbon atoms are more preferable. Examples of the α-olefin having 4 to 8 carbon atoms include α-olefins having 4 carbon atoms such as 1-butene and 2-methyl-1-propene; 1-pentene, 2-methyl-1-butene and 3-methyl-1 An α-olefin having 5 carbon atoms such as butene; 1-hexene, 2-ethyl-1-butene, 2,3-dimethyl-1-butene, 2-methyl-1-pentene, 3-methyl-1-pentene, C6-alpha-olefins such as 4-methyl-1-pentene and 3,3-dimethyl-1-butene; 1-heptene, 2-methyl-1-hexene, 2,3-dimethyl-1-pentene, 2 7-carbon α-olefins such as ethyl-1-pentene and 2-methyl-3-ethyl-1-butene; 1-octene, 5-methyl-1-heptene, 2-ethyl-1-hexene, 3, 3-dimethyl-1-hexene, 2- Α-olefins having 8 carbon atoms such as methyl-3-ethyl-1-pentene, 2,3,4-trimethyl-1-pentene, 2-propyl-1-pentene, 2,3-diethyl-1-butene, etc. Preferably mentioned.
Among these, in consideration of copolymerizability with propylene, 1-butene, 1-pentene, 1-hexene and 1-octene are more preferable, and 1-butene and 1-hexene are more preferable.

Specific examples of the polypropylene copolymer preferably include a propylene-ethylene random copolymer, a propylene-α-olefin random copolymer, a propylene-ethylene-α-olefin random copolymer, and the like. Can do.
As the random copolymer of propylene-α-olefin, for example, a random copolymer of propylene-1-butene, a random copolymer of propylene-1-hexene, a random copolymer of propylene-1-octene, and the like are preferable. Can be mentioned. Examples of the random copolymer of propylene-ethylene-α-olefin include, for example, a random copolymer of propylene-ethylene-1-butene, a random copolymer of propylene-ethylene-1-hexene, and propylene-ethylene-1-octene. Preferred are random copolymers of
Among these, a random copolymer of propylene-ethylene, a random copolymer of propylene-1-butene, a random copolymer of propylene-1-hexene, a random copolymer of propylene-ethylene-1-butene, propylene- A random copolymer of ethylene-1-hexene is preferred.

The content of the structural unit derived from the comonomer in the polypropylene copolymer is preferably more than 0 to 40% by mass, more preferably more than 0 to 20% by mass, and still more preferably more than 0, from the viewpoint of the balance between transparency and heat resistance. -10 mass%. In addition, when it is a copolymer of 2 or more types of comonomers and propylene, it is preferable that the total content of the structural unit derived from all the comonomer contained in this copolymer is the said range.
In addition, the content of the structural unit derived from a comonomer in a copolymer can be calculated | required by the measurement of an infrared (IR) absorption spectrum.

  The stereoregularity of the polypropylene-based copolymer is not particularly limited, and may be any of isotactic, syndiotactic, or atactic. From the viewpoint of heat resistance, it is preferably syndiotactic or isotactic stereoregularity.

<Method for Producing Polypropylene Copolymer>
Examples of the method for producing a polypropylene-based copolymer include a method in which propylene is copolymerized with at least one monomer selected from ethylene and an α-olefin having 4 to 20 carbon atoms using a known polymerization catalyst. .

  Here, examples of the known polymerization catalyst used for the production of the polypropylene copolymer component include Ziegler-Natta catalysts, metallocene catalysts, etc. Among them, metallocene catalysts are preferable. Polypropylene copolymers polymerized using a metallocene catalyst generally have the characteristics of uniform molecular weight and crystallinity, and low molecular weight and low crystallinity components. Therefore, polypropylene polymerized using a metallocene catalyst is used. This is because the obtained optical film has low birefringence with high transparency and low birefringence.

(Metallocene catalyst)
As the metallocene catalyst, a known catalyst can be appropriately used. Generally, a group 4-6 transition metal compound such as Zr, Ti, or Hf, particularly 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.

(Cocatalyst)
In the production of the polypropylene-based copolymer, a promoter can be used together with the metallocene catalyst. The cocatalyst was selected from the group consisting of an aluminum oxy compound, an ionic compound capable of reacting with the metallocene compound to convert the 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.

(Polypropylene polymerization method using metallocene catalyst)
As a polymerization method used for producing a propylene-based copolymer, solvent polymerization using an inert solvent typified by a hydrocarbon compound such as hexane, heptane, octane, decane, cyclohexane, methylcyclohexane, benzene, toluene, xylene, A bulk polymerization method using a liquid monomer as a solvent, a gas phase polymerization method performed in a gas monomer, and the like can be mentioned, and a bulk polymerization method or a gas phase polymerization method is preferable. These polymerization methods may be a batch method or a continuous method.

  Thus, the obtained polypropylene-type copolymer may be used individually by 1 type, and may mix and use multiple types of polypropylene-type copolymers. At this time, polypropylene copolymers having different kinds of comonomer, proportion of propylene-derived (comonomer-derived) structural unit, number average molecular weight, tacticity, and the like may be mixed. The polypropylene copolymer may be mixed with a propylene homopolymer as long as the optical properties of the copolymer are not impaired.

<Physical properties of polypropylene copolymer>
The (A) polypropylene copolymer preferably has a melt flow rate (hereinafter sometimes referred to as MFR) of 0.5 to 50 g / 10 minutes, more preferably 7 g / 10 minutes or more. Here, MFR is a value measured according to JIS K7210, and the measurement conditions are 230 ° C. and load 21.18N. If the MFR of the polypropylene-based copolymer is within the above range, it is preferable because distortion can be suppressed when forming an unstretched film, and an optical film having low birefringence can be obtained. Moreover, sufficient intensity | strength as an optical film is obtained and a post-process can be performed easily. Furthermore, since the MFR can be easily stabilized in the production lot, stable molding can be performed, and the amount of additives such as the MFR adjusting agent can be suppressed, so that the physical properties are not adversely affected. In addition, adjustment of MFR of a polypropylene-type copolymer can be performed by common MFR regulators, such as an organic peroxide, for example.

  The (A) polypropylene copolymer preferably has a flexural modulus of 700 MPa or more, 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. Here, in this invention, a bending elastic modulus shall be measured based on JISK7171.

  (A) It is preferable that melting | fusing point (Tm) of a polypropylene-type copolymer is 120-170 degreeC. If the melting point (Tm) is within the above range, the heat resistance of the optical film is improved, and it can be used for applications requiring heat resistance such as a polarizing plate. Here, the melting point is evaluated at a temperature at which the peak of the highest intensity appears in the melting curve measured by a differential scanning calorimeter (DSC), and 10 mg of a polypropylene copolymer press film is placed at 230 ° C. in a nitrogen atmosphere. After the heat treatment at 5 ° C., the temperature is lowered to 30 ° C. at a temperature decrease rate of 10 ° C./min, kept at 30 ° C. for 5 minutes, and further heated from 30 ° C. to 230 ° C. at a temperature increase rate of 10 ° C./min. This is the calculated value.

<< (B) Polystyrene polymer >>
(B) Polystyrene such as polystyrene, polymethyl styrene, polydimethyl styrene, poly t-butyl styrene; polyhalogen such as polychlorostyrene, polybromostyrene, polyfluorostyrene, polyfluorostyrene A polyhalogen-substituted alkylstyrene such as polychloromethylstyrene; a polyalkoxystyrene such as polymethoxystyrene and polyethoxystyrene; a polycarboxyalkylstyrene such as polycarboxymethylstyrene; a polyalkylether styrene such as polyvinylbenzylpropyl ether; Preferable examples include polyalkylsilylstyrene such as polytrimethylsilylstyrene; poly (vinylbenzyldimethoxyphosphide) and the like.
Among these, the (B) polystyrene-based polymer is preferably at least one selected from polyalkylstyrenes such as polystyrene, polymethylstyrene, polydimethylstyrene, and poly-t-butylstyrene, and polystyrene is particularly preferable.

  The content of the (B) polystyrene-based polymer in the polymer alloy is preferably in the range of 0.1 to 40 parts by mass, more preferably in the range of 0.5 to 35 parts by mass with respect to 100 parts by mass of the polymer alloy. More preferably, it is the range of 1-10 mass parts. (B) If the content of the polystyrene-based polymer is 0.1 parts by mass or more, an excellent low birefringence expression effect can be obtained, and if it is 40 parts by mass or less, the tensile strength of the film decreases. As a result, excellent products can be obtained.

<< (C) Graft-modified polypropylene >>
(C) Graft-modified polypropylene is a polypropylene polymer obtained by graft copolymerizing various branch polymers using polypropylene as a backbone polymer. Since the backbone polymer has a polypropylene component, compatibility with the (A) polypropylene copolymer can be obtained. Moreover, the resin modification | reformation according to the processability of the optical film for polarizer protection and a use application can be performed by carrying out graft copolymerization of the branch polymer. Therefore, in the present invention, (C) graft-modified polypropylene is used as one of the essential components of the polymer alloy constituting the optical film for protecting a polarizer of the present invention.

  As the polypropylene as the trunk polymer, a propylene homopolymer, or one or more block copolymers of propylene and an α-olefin, a random copolymer, a copolymer rubber, or the like can be used. 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- Preferable examples 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. In the polymerization reaction for synthesizing the trunk polymer, a Ziegler catalyst or a metallocene catalyst may be used.

  As the polypropylene as the trunk polymer, a propylene homopolymer or a random copolymer of propylene and ethylene is preferable. This is because (A) the compatibility with the polypropylene copolymer is good.

  Various branch polymers can be appropriately selected and used according to the required characteristics as long as they can be graft copolymerized with polypropylene as a trunk polymer. For example, acrylic compounds, vinyl compounds, olefins, dienes, or styrene or derivatives thereof are preferably mentioned. In consideration of the combination of (A) polypropylene copolymer and (B) polystyrene polymer, vinyl compound It is preferable that

Preferred examples of the vinyl compound include aromatic vinyl and vinyl cyanide, and these can be used alone or in combination.
Preferred examples of the aromatic vinyl include styrene, methyl styrene, dimethyl styrene, vinyl naphthalene, and chlorostyrene. Examples of vinyl cyanide include acrylonitrile and methacrylonitrile. As the vinyl compound, other vinyl compounds other than those described above, for example, esters of diene, (meth) acrylic acid and alcohol, maleimide compounds, and the like are also preferable.

  As the vinyl compound used in the branched polymer of the present invention, a homopolymer of aromatic vinyl, a homopolymer of vinyl cyanide, a copolymer of aromatic vinyl and diene such as butadiene / styrene copolymer, Copolymers of aromatic vinyl such as acrylonitrile / styrene copolymer and vinyl cyanide, and copolymers of aromatic vinyl such as acrylonitrile / butadiene / styrene copolymer, vinyl cyanide and diene are preferably used. . Of these, a copolymer of aromatic vinyl such as acrylonitrile / styrene copolymer and vinyl cyanide is preferable.

  (C) 20-60 mass% is preferable and, as for content of the branch polymer (graft component) in graft-modified polypropylene, 20-50 mass parts is more preferable. If the content of the graft component is within the above range, good compatibility between the (A) polypropylene copolymer and the (B) polystyrene polymer can be obtained, so that generation of wrinkles and breakage can be suppressed.

  The content of the (C) graft-modified polypropylene in the polymer alloy is preferably in the range of 0.5 to 10 parts by mass, more preferably in the range of 0.5 to 5 parts by mass, with respect to 100 parts by mass of the polymer alloy. More preferably, it is the range of 1-5 mass parts. When the content of (C) the graft-modified polypropylene is 0.5 parts by mass or more, a sufficient compatibilizing effect is obtained, the kneadability of the film becomes good, and breakage hardly occurs. On the other hand, if the content is 10 parts by mass or less, performance and strength can be improved efficiently, which is advantageous in terms of cost.

  In the present invention, by adopting (C) graft-modified polypropylene as a compatibilizing agent, (A) a polypropylene copolymer and (B) without stretching, that is, without increasing the in-plane retardation. It was possible to make the polystyrene polymer compatible. And the polymer alloy which comprises the optical film of this invention maintains the outstanding optical characteristic and moisture-proof property which (A) polypropylene-type copolymer has, and isolation | separation and a defect do not generate | occur | produce at the time of a thermoforming process.

《Arbitrary component》
In the present invention, various additives and additive resins can be added as optional components of the mixed resin constituting the optical film as desired.

  For example, a dibenzylidene sorbitol-based additive can be suitably used because it can improve the tensile strength and transparency while minimizing the influence on the phase difference. As dibenzylidene sorbitol-based additives, di-substituted dibenzylidene sorbitol, diglycerin mono-fatty acid ester-added dibenzylidene sorbitol-based nucleating agent containing di-substituted benzylidene sorbitol and diglycerin mono-fatty acid ester can be suitably used. .

  It is preferable that content of the said additive is the range of 0.03-0.5 mass part with respect to 100 mass parts of mixed resin. When it is 0.03 parts by mass or more, it is possible to improve transparency and sufficiently improve strength. On the other hand, when the amount is 0.5 parts by mass or less, the effect of improving transparency and strength can be effectively obtained, which is advantageous in terms of cost.

  In addition, depending on the desired physical properties of the resulting film, various olefin resins other than (A) polypropylene-based copolymer and (C) graft-modified polypropylene are blended as additive resins as long as the low birefringence and transparency are not impaired. You can also

  Furthermore, depending on the desired physical properties, it is within a range that does not affect the low birefringence and transparency, for example, a weather resistance improving agent such as an ultraviolet absorber or a light stabilizer; Abrasion improvers; polymerization inhibitors such as hydroquinone; cross-linking agents such as polyisocyanate compounds, epoxy compounds and metal chelate compounds; infrared absorbers such as dithiol metal complexes and phthalocyanine compounds; barium sulfate, talc, clay, calcium carbonate In addition, an antistatic agent, an adhesion improver, a leveling agent, a thixotropic agent, a coupling agent, a plasticizer, an antifoaming agent, a solvent, and the like can be added.

<Physical properties of optical film for protecting polarizer>
The thickness of the optical film for protecting a polarizer of the present invention is preferably in the range of 10 to 200 μm, more preferably 30 to 150 μm. When the thickness of the optical film is 10 μm or more, the protective strength of the optical film is sufficiently secured, and when it is 200 μm or less, sufficient flexibility is obtained, and since it is lightweight, handling during work becomes easy. In addition, it is advantageous in terms of cost.

  The in-plane retardation of the optical film for protecting a polarizer is an in-plane retardation measured at an incident angle of 0 degree using a light having a wavelength of R589.5 nm using a phase difference measuring machine, and may be 20 nm or less. Preferably, it is 10 nm or less, more preferably 5 nm or less, particularly preferably 4 nm or less. Thus, the optical film for protecting a polarizer of the present invention has a small in-plane retardation, that is, excellent low birefringence, and thus is suitable as an optical film for protecting a polarizer.

  The bending elastic modulus of the polarizer protecting optical film is preferably 700 MPa or more. When the flexural modulus is within the above range, sufficient strength when handled in a film state can be obtained, and post-processing can be easily performed. When used as a protective sheet for a polarizing plate, sufficient scratch resistance is obtained. This is because Furthermore, the flexural modulus of the optical film is more preferably 900 MPa or more. This is because if the pressure is 900 MPa or more, the in-plane retardation can be stabilized when manufactured by T-die extrusion. Here, the bending elastic modulus is measured in accordance with JIS K7171 like the above-described polypropylene.

  There is no restriction | limiting in particular as an adjustment method of the bending elastic modulus of the optical film for polarizer protection, It can adjust with the following methods. For example, a method of selecting by the original properties (crystallinity, average molecular weight, etc.) of polypropylene, a method of adding a filler selected from inorganic or organic fillers to a resin, a method of adding a crosslinking agent, etc. Examples thereof include a method of mixing two or more different types of resins, a method of selecting a plasticizer composition of a curable resin, or a method of appropriately combining a plurality of these methods.

  The tensile strength of the optical film for protecting a polarizer is preferably 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 phase difference exceeding the original optical design. Therefore, the performance of the polarizing plate can be maintained. Here, in this invention, tensile strength shall be measured based on ASTMD638 (Type4 conditions).

  The optical film for protecting a polarizer can be subjected to an easy adhesion treatment for improving adhesiveness on the surface in contact with the polarizer. 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.

In the case of forming an adhesive layer in order to improve the adhesion between the polarizer protecting optical film of the present invention and the polarizer, an adhesive is applied to either or both sides of the optical film or the polarizer. By doing.
After bonding the optical film and the polarizer through the surface subjected to the easy adhesion treatment or the surface on which the adhesive layer is formed, a drying step is performed to form an adhesive layer composed of a coating dry layer. This can also be bonded after forming the adhesive layer. Bonding of the polarizer and the optical film can be performed by a roll laminator or the like. The heating and drying temperature and drying time are appropriately determined according to the type of adhesive.
The thickness of the adhesive layer is preferably 0.01 to 10 [mu] m, more preferably 0.03 to 5 [mu] m, since it is not preferable from the viewpoint of adhesiveness of the optical film if the thickness after drying becomes too thick.

  Moreover, on the surface of the optical film for protecting the polarizer, a functional layer is laminated, and various functions, for example, a high hardness and scratch resistance, a so-called hard coat function, anti-fogging coat function, anti-fouling coating function, An antiglare coating function, an antireflection coating function, an ultraviolet shielding coating function, an infrared shielding coating function, and the like can also be imparted.

<< Optical film manufacturing method >>
The optical film of the present invention is preferably a step (1) of polymerizing the above-described (A) polypropylene copolymer, (A) a polypropylene copolymer, (B) a polystyrene polymer, and (C) a graft modification. It can be produced by a production method comprising a step (2) of obtaining a polymer alloy by mixing with polypropylene and heating and melting, and a step (3) of molding the polymer alloy.

  In step (2), more specifically, (A) the polypropylene copolymer obtained in step (1), the above-mentioned (B) polystyrene polymer and (C) graft-modified polypropylene, Accordingly, the above-described various optional components are mixed, heated and melted, that is, kneaded to obtain a polymer alloy.

  The obtained polymer alloy becomes the optical film for protecting a polarizer of the present invention through the molding process of the step (3). The molding process is not particularly limited as long as it is a method that does not require stretching, but a T-die extrusion molding method or an inflation molding method is preferable. This is because the optical film for protecting a polarizer produced on the polarizer is desirably not subjected to stretching treatment because it is not oriented and low birefringence is desired.

[Polarizer]
In the polarizing plate of the present invention, the optical film for protecting a polarizer of the present invention is provided on at least one surface of the polarizer. As a method of providing the optical film, the polarizer protecting optical film may be directly formed on the polarizer, or the polarizer protecting optical film is prepared in advance, and then the adhesive layer is formed. It may be attached to a polarizer via the polarizer.
FIG. 2 shows an example of the polarizing plate of the present invention. In FIG. 2, reference numeral 2 denotes a polarizer, and an optical film 1 for protecting a polarizer is formed on one surface of the polarizer via an adhesive layer 3, thereby constituting a polarizing plate 4 as a whole.
As described above, the polarizing plate of the present invention is a high-performance polarizing plate to which characteristics according to the application are imparted by the optical film for protecting a polarizer of the present invention.

《Polarizer》
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-based film 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, 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.

<< Polarizing plate manufacturing method >>
The polarizing plate includes, for example, a step (I) of uniaxially stretching a PVA film as described above, a step (II) of dyeing a PVA resin film with a dichroic dye, and adsorbing the dichroic dye. Process (III) for treating PVA film adsorbed with chromic dye with boric acid aqueous solution, process for washing with water after boric acid aqueous solution treatment (IV), and dichroic dye adsorbed and oriented by these steps It is manufactured through a step (V) of attaching an optical film for protecting a polarizer to the uniaxially stretched PVA-based film.

(Process (I))
Uniaxial stretching can be performed before, simultaneously with, or after dyeing with a dichroic dye. When uniaxial stretching is performed after dyeing with a dichroic dye, this uniaxial stretching can be performed before boric acid treatment or during boric acid treatment. Moreover, it is also possible to perform uniaxial stretching in these several steps. In order to uniaxially stretch, you may extend | stretch uniaxially between rolls from which peripheral speeds differ, or using a heat roll. Stretching can be performed by dry stretching in which stretching is performed in the air or wet stretching in which stretching is performed in a state swollen by a solvent. The draw ratio is usually about 4 to 8 times.

(Process (II))
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. Moreover, when using a dichroic dye as a dichroic pigment | dye, the method of immersing and dye | staining a PVA-type film in the aqueous solution containing a water-soluble dichroic dye is normally employ | adopted.

(Step (III))
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.

(Process (IV))
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.

(Process (V))
As a method of laminating the polarizer and the optical film, it can be performed through an adhesive layer. Examples of the adhesive that forms the adhesive layer include a PVA adhesive, an epoxy adhesive, an acrylic adhesive, and a polyolefin adhesive. 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 crosslinking agent. Examples of the PVA-based resin include PVA obtained by saponifying polyvinyl acetate and its derivatives, and a non-polymerizable copolymer with vinyl acetate. Saponification products of copolymers with monomers such as saturated carboxylic acids and esters thereof and α-olefins, modified PVA obtained by subjecting PVA to acetalization, urethanization, etherification, grafting or phosphoric esterification, etc. It is done. These PVA resins can be used singly or in combination of two or more.
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%.

  In the present invention, the polarizer and the adhesive layer are treated with, for example, an ultraviolet absorber such as a salicylic acid ester compound, a benzophenol compound, a benzotriazole compound, a cyanoacrylate compound, or a nickel complex compound. The ultraviolet absorbing ability may be imparted.

  The adhesive layer is formed by applying an adhesive on either or both sides of the polarizer protecting optical 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 addition, when the polarizer protecting optical film is bonded to the polarizer, the surface of the polarizer protecting optical film in contact with the polarizer is subjected to corona treatment, plasma treatment, low pressure UV treatment, saponification treatment, etc. in order to improve adhesion. Easy adhesion treatment such as surface treatment or a method of forming an anchor layer can be performed. Of 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 optical film for protecting the polarizer are bonded through the adhesive layer.
Bonding of the polarizer and the optical film for protecting the polarizer 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.

(Other)
For the polarizing plate in which the polarizer protective optical film of the present invention is formed on one surface of the polarizer, the polarizer protective optical film of the present invention is formed on the other surface of the polarizer, if necessary. It is also possible to form a film made of other resin. Examples of films made of other resins include polyethylene terephthalate films, polycarbonate films, cyclic polyolefin films, maleimide resin films, and fluorine resin films. The film made of the other resin 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 ultraviolet curable resins such as ultraviolet curable acrylic urethane, ultraviolet curable epoxy acrylate, ultraviolet curable (poly) ester acrylate, and ultraviolet curable oxetane, silicone resins, acrylic resins, and urethane resins. Examples thereof include a hard coat layer made of a hard coat agent, and a hard coat layer made of an ultraviolet curable resin is preferable from the viewpoint of transparency, scratch resistance, and chemical resistance. One or more of these hard coat layers can be used.
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.

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

[Image display device]
The polarizing plate of the present invention can be preferably used for various devices for image display.
Examples of the image display device include a liquid crystal display including a liquid crystal cell, an organic electroluminescence (hereinafter referred to as “organic EL”) display device, a touch panel, and the like. There is no. 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. 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.

<Liquid crystal display including liquid crystal cell>
The polarizing plate of the present invention is suitably used by being laminated, for example, on a liquid crystal cell.
As an example of the image display device of the present invention, FIG. 3 shows a configuration example of a liquid crystal display including a liquid crystal cell. In FIG. 3, 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. A phase difference plate (birefringent plate) 5 is laminated on the liquid crystal cell 6 via an adhesive layer (not shown), and a polarizing plate is formed on the liquid crystal cell 6 via an adhesive layer (not shown). The plate 4 is laminated. The polarizing plate 4 has a polarizer 2 at the center, and a polarizer protecting optical film 1 is laminated on both surfaces of the polarizing plate 4 via an adhesive layer 3. 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.

The pressure-sensitive adhesive for laminating the polarizing plate and the liquid crystal cell is not particularly limited. For example, an acrylic pressure-sensitive adhesive is excellent in optical transparency, exhibits appropriate wettability, cohesiveness, and adhesive pressure-sensitive adhesive properties, and is weather resistant. It is preferable because it is excellent in properties 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 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.

  Application of the above-mentioned pressure-sensitive adhesive to the polarizing plate is, for example, 10 to 40% by mass in which a base polymer or a composition thereof is dissolved or dispersed in a solvent composed of a single solvent or a mixture of appropriate solvents such as toluene and ethyl acetate. Prepare a pressure-sensitive adhesive solution to the extent, and apply it directly on the polarizing plate by an appropriate development method such as a coating method such as gravure coating, bar coating, roll coating, or casting method, or according to this method. Examples thereof include a method of forming an adhesive layer on a releasable base film and transferring it to a polarizing plate.

  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 coated with an appropriate thin film such as a plastic film, if necessary, with an appropriate release agent such as a silicone film for the purpose of preventing contamination until it is put to practical use. It is preferable that the released release film is temporarily attached and covered. Thereby, it can prevent contacting an adhesive layer in the usual handling state.

(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).

  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 A polarizing plate may be provided on the side, and a birefringent layer (retardation plate) may be 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. 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. .

(Touch panel)
The polarizing plate of the present invention can also be suitably used for a touch panel.
There are various types of touch panels, such as 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.

  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 optical film for protecting a polarizer of the present invention can be suitably used for the polarizing plate of these touch panels.

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 and circularly polarized types (linearly polarized light has higher reflectivity than circularly polarized light). Can also be used on plates.
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) In-plane retardation: Measured at a wavelength of R589.5 nm and an incident angle of 0 degree using a phase difference measuring device (“KOBRA-21ADH” manufactured by Oji Scientific Instruments).
(2) Occurrence of wrinkles The appearance of the wound roll of the formed film was visually confirmed, and the occurrence of wrinkles was evaluated according to the following criteria.
○: Wrinkles were not observed (or were rarely seen)
Δ: Some wrinkles were observed, but there was no problem in practical use. ×: Wrinkles were observed. (3) Situation of cuts Evaluation based on the criteria.
○: The occurrence of cutting was not seen (or was rarely seen)
Δ: Slight occurrence of cut was observed, but there was no problem in practical use. ×: Generation of cut was observed.

Example 1
(A) Polypropylene copolymer ("Wintech WFW4 (trade name)", manufactured by Nippon Polypro Co., Ltd., a polypropylene copolymer polymerized using a metallocene catalyst, melting point: 135 ° C, flexural modulus: 900 MPa , Hereinafter referred to as “PP1”) 93.5 parts by mass, (B) 5 parts by mass of polystyrene (“Toyo Styrol GP HRM12 (trade name)”, manufactured by Toyo Styrene Co., Ltd.), and (C) Graft-modified polypropylene (“Modiper A3400 (trade name)”, polypropylene-poly (styrene / acrylonitrile) block copolymer (mass ratio of polypropylene to poly (styrene / acrylonitrile) is 70/30, NOF Corporation (Manufactured) was mixed with 1.5 parts by mass and melted by heating to obtain a polymer alloy. -An optical film for protecting a polarizer was obtained by T-die single layer extrusion molding with a film width of 1000 mm and a film thickness of 100 μm under the condition of a take-up roll temperature of 30 ° C.

(Example 2)
In Example 1, polypropylene obtained by polymerizing PP1 using a Ziegler-Natta catalyst (“Novatech EG3FTB (trade name)”, manufactured by Nippon Polypro Co., Ltd., melting point: 140 ° C., flexural modulus: 1,000 MPa, hereinafter “ An optical film for protecting a polarizer was obtained in the same manner as in Example 1 except that it was expressed as “PP2”.

(Examples 3 to 5)
In Example 1, an optical film for protecting a polarizer was obtained in the same manner as in Example 1 except that (A) to (C) were mixed at the ratio shown in Table 1.

(Comparative Example 1)
In Example 1, an optical film for protecting a polarizer was obtained in the same manner as in Example 1 except that PP1 was 100 parts by mass and (B) and (C) were not mixed.

(Comparative Example 2)
In Example 2, an optical film for protecting a polarizer was obtained in the same manner as in Example 1 except that PP2 was 100 parts by mass and (B) and (C) were not mixed.

(Comparative Example 3)
In Example 1, an optical film for protecting a polarizer was obtained in the same manner as in Example 1 except that PP1 was 90 parts by mass, (B) was 10 parts by mass, and (C) was not mixed.

The evaluation result of the optical film for polarizer protection obtained in Examples 1-5 and Comparative Examples 1-3 was shown in Table 1.
The optical films obtained in Examples 1 and 3 to 5 were compared with the optical film of Comparative Example 1 in which (B) and (C) were not mixed and the optical film of Comparative Example 3 in which (C) was not mixed. The phase difference was changed from 6 to 8 nm to 3 to 5 nm, and it was confirmed to have excellent low birefringence. Comparing Comparative Example 2 and Example 2 using only PP2, the phase difference was changed from 25 nm to 8 nm, confirming the superiority of the present invention in low birefringence.
Further, in Comparative Example 3 in which (C) was not mixed, wrinkles and cuts occurred, and the optical films obtained in Examples 1 to 5 were also excellent in evaluation of wrinkles and cuts, while they could not be used as optical films. It was also confirmed that it had excellent mass production suitability and excellent quality as an optical film.

  Since the optical film for protecting a polarizer of the present invention has excellent low birefringence and suitability for mass production, as an optical sheet for protecting a polarizer that requires low birefringence such as a polarizing plate and a polarizer constituting the polarizing plate. Is preferred. The polarizing plate obtained by combining the optical film of the present invention and a polarizer can be effectively used for image display devices such as a liquid crystal display including a liquid crystal cell, an organic electroluminescence display device, and a touch panel. Moreover, it can be used not only for the use as an optical film for protecting a polarizer but also for other industrial materials. For example, it can be used for an anti-scattering film used for window glass or a protective film for industrial materials.

1: Optical film for protecting a polarizer 2: Polarizer 3: Adhesive layer 4: Polarizing plate 5: Phase difference plate (birefringent plate)
6: Liquid crystal cell

Claims (11)

  An optical film for protecting a polarizer, comprising a polymer alloy comprising (A) a polypropylene copolymer, (B) a polystyrene polymer, and (C) a graft-modified polypropylene.   The optical film for protecting a polarizer according to claim 1, wherein the (A) polypropylene copolymer is a random copolymer.   The optical film for protecting a polarizer according to claim 1 or 2, wherein the (A) polypropylene copolymer is polymerized using a metallocene catalyst.   (B) The optical film for protecting a polarizer according to any one of claims 1 to 3, wherein the polystyrene-based polymer is at least one selected from polystyrene, polymethylstyrene, polydimethylstyrene, and poly-t-butylstyrene.   The optical film for protecting a polarizer according to any one of claims 1 to 4, wherein (C) the graft-modified polypropylene is obtained by graft polymerization of a vinyl compound.   The optical film for protecting a polarizer according to claim 5, wherein the vinyl compound is at least one selected from aromatic vinyl and vinyl cyanide.   In-plane retardation is 20 nm or less, The optical film for polarizer protection in any one of Claims 1-6.   A polarizing plate, wherein the polarizer protective optical film according to claim 1 is provided on at least one surface of the polarizer.   An image display device using the polarizing plate according to claim 8. The manufacturing method of the optical film which has the process of following (1)-(3).
Step (1) (A) Step of polymerizing polypropylene copolymer Step (2) (A) Polypropylene copolymer, (B) Polystyrene polymer and (C) Graft-modified polypropylene are mixed and melted by heating. Step of obtaining a polymer alloy (3) Step of molding the polymer alloy   The process according to claim 10, wherein step (1) is a step using a metallocene catalyst.

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