JP2011225691A - Optical film and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical film having high transparency and excellent heat resistance even when the film is retained at a specified temperature for a long time or kept in a high temperature state for a long period of time.SOLUTION: The optical film contains from two to five kinds of polymers, wherein the polymer having the highest content in the above two or more polymers contains a monomer having a plurality of ethylenically unsaturated groups as a copolymerization component.

Description

  The present invention relates to a polymer mixture capable of maintaining high compatibility even during high-temperature storage and high-speed film formation, and an optical film produced from the mixture, and relates to a polymer comprising a monomer having a plurality of ethylenically unsaturated groups and a cellulose ester. Relates to polymer blends.

  Optical films used for liquid crystal displays and the like are required to have high transparency, high heat resistance, and the like, and cellulose triacetate, polycarbonate, cyclic olefin polymers, and the like are widely used to satisfy these.

  On the other hand, there is a limit to satisfying all the characteristics of each single resin, and the use of additives is usually performed, but since it suffers from bleedout caused by additives, it is a solution by blending different polymers There are also attempts.

  For example, as seen in Patent Document 1, an invention is disclosed in which an acrylic film having a specific molecular weight and a cellulose ester having a specific substitution degree are compatible with each other to obtain an optical film having certain characteristics.

  First of all, the compatibility or compatibility between polymers is the key to polymer blends. The optical film generally requires high transparency, and a compatible state in which one polymer is finely dispersed in the other is hardly allowed.

  That is, a compatible state in which different polymer chains are entangled at the molecular level is desired. However, combinations of polymers that form such a compatible state are limited, and a great deal of effort is required to find such combinations.

  In addition, seemingly compatible polymer blends also have a high haze because it is difficult to maintain a stable compatibility when they are retained for a long time in a molten state at a specific temperature or are maintained for a long time at a high temperature. Tend.

  As shown in Patent Document 2, a technique is disclosed in which dissimilar polymers that are basically incompatible are dispersed at the nano-level by high shear processing and apparently compatible. Then, they gradually move to the phase equilibrium state and the same discussion as above.

  Patent Document 3 discloses a cellulose ester composition using an acrylic resin having an amide bond in the side chain as a plasticizer in order to ensure compatibility. However, it is necessary to change the chemical composition of the resin, and an optical film. As a result, various performance requirements may be lost.

International Publication No. 2009/047924 JP-A-2005-313608 Japanese Patent No. 4138984

  An object of the present invention is to provide an optical film having excellent heat resistance and high transparency even if it stays at a specific temperature for a long time or is kept at a high temperature for a long time.

  The object of the present invention has been achieved by the following.

  An optical film containing 1.2 or more and 5 or less types of polymers, wherein the polymer having the highest content in the 2 or more and 5 or less types of polymers is a copolymerization component of a monomer having a plurality of ethylenically unsaturated groups An optical film characterized by

  2. 2. The optical film as described in 1 above, wherein one of the polymers other than the polymer having the highest content among the two or more and five or less polymers is a cellulose ester.

  3. A mixture comprising 2 or more and 5 or less polymers as a constituent component, wherein the polymer having the highest content in the two or more polymers comprises a monomer having a plurality of ethylenically unsaturated groups as a copolymerization component A method for producing an optical film, comprising melt-casting a mixture which is an object.

  4). 4. The method for producing an optical film as described in 3 above, further comprising a stretching step after the melt casting, wherein the stretching ratio is 4 times or more and 15 times or less in total in the longitudinal direction and the transverse direction.

  According to the present invention, it is possible to provide an optical film having excellent heat resistance and high transparency even if it stays at a specific temperature for a long time or is kept at a high temperature for a long time.

The optical film of the present invention is an optical film containing two or more kinds of polymers, and the polymer having the highest content in the two or more kinds of polymers includes a monomer having a plurality of ethylenically unsaturated groups as a copolymerization component. It is characterized by being.
<Two or more types of polymers>
Two or more types of polymers mean a mixture of a plurality of polymers having different monomer compositions, and two or more types, preferably a mixture of five or less types of polymers.

  Among two or more types of polymers, the polymer having the highest content in the optical film (hereinafter also referred to as polymer A) is characterized in that a monomer having a plurality of ethylenically unsaturated groups is used as a component for copolymerization.

  Examples of the ethylenically unsaturated group include acryloyl group, methacryloyl group, vinyl group and allyl group. The number of ethylenically unsaturated groups is preferably 2 or more and 10 or less.

  The polymer A is not particularly limited as long as it is a polymer composed of a normal radically polymerizable monomer such as a (meth) acrylic monomer, a vinyl ester monomer, or a styrene monomer, but the (meth) acrylic monomer is 50 mol%. The above is preferable.

  As the (meth) acrylic monomer, a lower aliphatic (meth) acrylic acid ester such as methyl acrylate, methyl methacrylate, or butyl acrylate can be preferably used.

  In addition, vinyl acetate, N-substituted acrylamide, styrene, and the like can be used as a copolymerization component.

  Examples of the monomer having a plurality of ethylenically unsaturated groups of the present invention include divinylbenzene, ethylene glycol diacrylate, polyethylene glycol diacrylate, trimethylpropane triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, and the like.

  The monomer having a plurality of ethylenically unsaturated groups of the present invention (hereinafter also referred to as a crosslinkable monomer) is preferably copolymerized in an amount of 1 to 10,000 ppm (mass) in the polymer, and more preferably 1 to 500 ppm. .

  Furthermore, the polymer A of the present invention preferably has a narrow molecular weight distribution of the basic polymer. Here, “basic” refers to a polymer in an uncrosslinked state.

  In a polymer mixture with slightly low compatibility, in a high-temperature melt state, a disordered compatible state can be maintained due to the kinetic energy of the polymer chain, but as the temperature decreases, the movement of the polymer chain is suppressed and a stable phase equilibrium state Will head to. Conversely, when the temperature is lowered to some extent, the movement toward the phase equilibrium is suppressed, and the state is fixed in the non-equilibrium state. That is, when kept in a molten temperature range for a long time, phase separation is likely to occur and haze is likely to increase.

  The process that tends to be in such a state in melt film formation is a cast part in high-speed film formation. In high-speed film formation, there is almost no air cooling of the molten resin extruded from the die, so the high-temperature resin is grounded on the cast roll, but the roll rotation speed is fast, that is, sufficient cooling time can be taken. Therefore, a relatively high temperature state passes as compared with the conventional cooling.

  Even when kept at a high temperature for a long period of time, phase separation is likely to occur and the haze is likely to increase as in the above case.

  In the present invention, it is presumed that the compatibility state can be maintained by taking the degree of freedom of the polymer chain by suppressing the movement toward the phase equilibrium by having a loose cross-linked structure.

  A known method can be selected as a method for controlling the molecular weight distribution. A method in which the crosslinkable monomer is reacted in an extremely low concentration and the overall polymerization reaction rate is slow, or a method in which the crosslinkable monomer is added during the polymerization reaction can be selected. In particular, the living radical polymerization described in Japanese Patent Nos. 3845109 and 4107996 is preferably used.

  In the polymerization reaction, there may be some components that are three-dimensionally cross-linked, and it is difficult to accurately measure the molecular weight distribution. Therefore, the polymerization reaction is performed in a composition in which no crosslinkable monomer is added, and the number average molecular weight Mn Polymerization conditions were employed such that the molecular weight distribution Mw / Mn was 1.1 to 2.5.

The polymer A of the present invention is characterized by the highest content of the polymers constituting the optical film, and preferably occupies 50 to 100% by mass of the optical film.
<A polymer other than the polymer A having the highest content among two or more types of polymers (hereinafter referred to as other polymers)>
Other polymers used in the present invention include polyolefin resins such as polyethylene, polypropylene, polystyrene, and polymethylpentene, polyamide resins such as nylon 6 and nylon 66, polyethylene terephthalate, polybutylene terephthalate, polypropylene terephthalate, polybutylene succinate, and polyethylene. Polyester resins such as succinate polyethylene-2,6-naphthalate, polyglycolic acid, polylactic acid, poly (glycolic acid-lactic acid), polycarbonate resin, polyarylate resin, polyacetal resin, polyvinyl acetate and its saponified product, polyvinyl formal , Polyvinyl acetals such as polyvinyl acetal and polyvinyl butyral, and resins such as cellulose esters.

  In terms of vinyl monomer units, butadiene, vinyl chloride, vinyl acetate, maleic acid, acrylic acid, acrylic ester, vinylidene chloride, acrylonitrile, methacrylic acid, methacrylic ester, styrene, butadiene, ethylene, vinyl butyral, vinyl acetal, A vinyl polymer containing vinylpyrrolidone and vinyl ether as a copolymerization component, or a vinyl copolymer can also be mentioned.

  Examples of vinyl copolymers include butadiene-acrylonitrile copolymers, vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinylidene chloride copolymers, vinyl chloride-acrylonitrile copolymers, acrylate ester-acrylonitrile copolymers. , Acrylic ester-vinylidene chloride copolymer, acrylic ester-styrene copolymer, methacrylic ester-acrylonitrile copolymer, methacrylic ester-vinylidene chloride copolymer, methacrylic ester-styrene copolymer, vinylidene chloride -An acrylonitrile copolymer, a butadiene-acrylonitrile copolymer, a styrene-butadiene copolymer, a chlorovinyl ether-acrylic ester copolymer, a vinyl acetate-vinylpyrrolidone copolymer, and the like.

As the other polymer of the present invention, it is preferable to combine a polymer having high heat resistance and toughness, and preferred examples include cellulose esters.
<Cellulose ester>
The cellulose ester of the present invention has a total substitution degree of acyl groups of 2.0 to 3.0 and a substitution degree of acyl groups of 3 to 7 carbon atoms of 0.5 to 3.0, particularly from the viewpoint of transparency. Preferably there is. That is, the cellulose ester of the present invention is a cellulose ester resin substituted with an acyl group having 3 to 7 carbon atoms. Specifically, propionyl, butyryl and the like are preferably used, and a propionyl group is particularly preferably used.

  The degree of acyl substitution of the cellulose ester of the present invention is no problem if the degree of substitution is 2.0 to 3.0 and the degree of substitution of the acyl group having 3 to 7 carbon atoms is 0.5 to 3.0. However, it is preferable that the total degree of substitution of acyl groups other than those having 3 to 7 carbon atoms, that is, acetyl groups or acyl groups having 8 or more carbon atoms is 1.3 or less.

  Further, the device conversion degree of the acyl group of cellulose ester is more preferably in the range of 2.5 to 3.0.

  In the present invention, the acyl group may be an aliphatic acyl group or an aromatic acyl group. In the case of an aliphatic acyl group, it may be linear or branched and may further have a substituent. The number of carbon atoms of the acyl group in the present invention includes an acyl group substituent.

  The cellulose ester of the present invention is preferably at least one selected from cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate benzoate, cellulose propionate, and cellulose butyrate. Those having 4 acyl groups as substituents are preferred.

  Among these, particularly preferred cellulose esters are cellulose acetate propionate and cellulose propionate.

  The portion not substituted with an acyl group usually exists as a hydroxyl group (hydroxyl group). These can be synthesized by known methods.

  In addition, the substitution degree of an acetyl group and the substitution degree of other acyl groups are obtained by a method prescribed in ASTM-D817-96.

  The weight average molecular weight (Mw) of the cellulose ester of the present invention is 75000 or more, particularly from the viewpoint of improving compatibility with the polymer A and brittleness, and requires a range of 75,000 to 300,000. Preferably, it is in the range of 100,000 to 240,000, and those of 160000 to 240,000 are particularly preferable. In the present invention, two or more kinds of cellulose resins can be mixed and used.

  It is preferable that the other polymer of this invention accounts for 0 to 49 mass% of the polymer which comprises an optical film.

  The average molecular weight can be measured by the following method.

(Average molecular weight measurement method)
The average molecular weights Mn and Mw were measured using gel permeation chromatography. The measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (GL Science Co., Ltd.)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0 ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corp.) Mw = 2,300,000-500 calibration curves with 13 samples were used. Thirteen samples are used at approximately equal intervals.
<Other additives>
The optical film of the present invention can appropriately contain additives in addition to two or more kinds of polymers.

<Plasticizer>
Examples of the plasticizer include phthalate ester, fatty acid ester, trimellitic ester, phosphate ester, polyester, and epoxy. Of these, polyester and phthalate plasticizers are preferably used. Polyester plasticizers are superior in non-migration and extraction resistance compared to phthalate ester plasticizers such as dioctyl phthalate, but are slightly inferior in plasticizing effect and compatibility.

  The polyester plasticizer is a reaction product of a monovalent or tetravalent carboxylic acid and a monovalent or hexavalent alcohol, and is mainly obtained by reacting a divalent carboxylic acid with a glycol. . Representative divalent carboxylic acids include glutaric acid, itaconic acid, adipic acid, phthalic acid, azelaic acid, sebacic acid and the like.

  In particular, when adipic acid, phthalic acid or the like is used, those having excellent plasticizing properties can be obtained. Examples of the glycol include glycols such as ethylene, propylene, 1,3-butylene, 1,4-butylene, 1,6-hexamethylene, neopentylene, diethylene, triethylene, and dipropylene. These divalent carboxylic acids and glycols may be used alone or in combination.

  The ester plasticizer may be any of ester, oligoester (including sucrose octabenzoate, Monopet SB Daiichi Kogyo Seiyaku Co., Ltd., etc.) and polyester, and the molecular weight is preferably in the range of 100 to 10,000. Preferably, the range of 600 to 3000 has a large plasticizing effect.

<Antioxidant>
In this invention, what is generally known can be used as an antioxidant. In particular, lactone, sulfur, phenol, double bond, hindered amine, and phosphorus compounds can be preferably used.

  For example, the thing containing what is marketed by the brand name "IrgafosXP40" and "IrgafosXP60" from Ciba Japan KK is preferable.

  The phenolic compound preferably has a 2,6-dialkylphenol structure. For example, Ciba Japan Co., Ltd., “Irganox 1076”, “Irganox 1010”, and ADEKA “ADEKA STAB AO-50” are trade names. And those commercially available.

  Examples of the phosphorous compounds are Sumitomo Chemical Co., Ltd., “Sumilizer GP”, ADEKA Co., Ltd., “ADK STAB PEP-24G”, “ADK STAB PEP-36” and “ADK STAB 3010”, Ciba Japan Co., Ltd. “IRGAFOS P-EPQ”, commercially available from Sakai Chemical Industry Co., Ltd. under the trade name “GSY-P101” is preferable.

  As the hindered amine compound, for example, those commercially available from Ciba Japan Co., Ltd. under the trade names “Tinuvin 144” and “Tinvin 770”, and from ADEKA Co., Ltd. as “ADK STAB LA-52” are preferable.

  The sulfur compound is preferably commercially available from Sumitomo Chemical Co., Ltd. under the trade names “Sumilizer TPL-R” and “Sumilizer TP-D”.

  The above-mentioned double bond type compounds are preferably those commercially available from Sumitomo Chemical Co., Ltd. under the trade names “Sumilizer GM” and “Sumilizer GS”.

  Furthermore, it is possible to contain a compound having an epoxy group as described in US Pat. No. 4,137,201 as an acid scavenger.

  The amount of these antioxidants and the like to be appropriately added is determined in accordance with the process at the time of recycling, but generally 0.05 to 20% by mass, preferably with respect to the resin as the main raw material of the film Is added in the range of 0.1 to 1% by mass.

  These antioxidants can obtain a synergistic effect by using several different types of compounds in combination rather than using only one kind. For example, the combined use of lactone, phosphorus, phenol and double bond compounds is preferred.

<Colorant>
In the present invention, it is preferable to use a colorant. The colorant means a dye or a pigment. In the present invention, the colorant means an effect of making the color tone of a liquid crystal screen blue, adjusting the yellow index, and reducing haze.

  Various dyes and pigments can be used as the colorant, but anthraquinone dyes, azo dyes, phthalocyanine pigments and the like are effective.

<Ultraviolet absorber>
Although the ultraviolet absorber used in the present invention is not particularly limited, for example, oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, triazine compounds, nickel complex compounds, inorganic powders Examples include the body. It is good also as a polymer type ultraviolet absorber.

<Matting agent>
In the present invention, it is preferable to add a matting agent in order to impart film slipperiness.

  As the matting agent used in the present invention, any inorganic compound or organic compound may be used as long as it has heat resistance at the time of melting without impairing the transparency of the obtained film. For example, talc, mica, zeolite, diatomaceous earth, Calcined siliceous clay, kaolin, sericite, bentonite, smectite, clay, silica, quartz powder, glass beads, glass powder, glass flakes, milled fiber, wollastonite, boron nitride, boron carbide, titanium boride, magnesium carbonate, Heavy calcium carbonate, light calcium carbonate, calcium silicate, aluminum silicate, magnesium silicate, magnesium aluminosilicate, alumina, silica, zinc oxide, titanium dioxide, iron oxide, magnesium oxide, zirconium oxide, aluminum hydroxide, calcium hydroxide, water Magnesium oxide Beam, calcium sulfate, barium sulfate, silicon carbide, aluminum carbide, titanium carbide, aluminum nitride, silicon nitride, titanium nitride, and white carbon. These matting agents can be used alone or in combination of two or more.

  By using particles having different particle sizes and shapes (for example, acicular and spherical), both transparency and slipperiness can be made highly compatible.

  Among these, silicon dioxide is particularly preferably used since it has a refractive index close to that of cellulose ester and is excellent in transparency (haze).

  Specific examples of silicon dioxide include Aerosil 200V, Aerosil R972V, Aerosil R972, R974, R812, 200, 300, R202, OX50, TT600, NAX50 (manufactured by Nippon Aerosil Co., Ltd.), Sea Hoster KEP-10, Sea Hoster KEP- 30, Seahoster KEP-50 (manufactured by Nippon Shokubai Co., Ltd.), Silo Hovic 100 (manufactured by Fuji Silysia), nip seal E220A (manufactured by Nippon Silica Industry), Admafine SO (manufactured by Admatechs), etc. Goods etc. can be preferably used.

  The shape of the particles can be used without particular limitation, such as indefinite shape, needle shape, flat shape, spherical shape, etc. However, the use of spherical particles is particularly preferable because the transparency of the resulting film can be improved.

  When the particle size is close to the wavelength of visible light, light is scattered and the transparency is deteriorated. Therefore, the particle size is preferably smaller than the wavelength of visible light, and more preferably ½ or less of the wavelength of visible light. . If the size of the particles is too small, the slipperiness may not be improved, so the range of 80 nm to 180 nm is particularly preferable.

  The particle size means the size of the aggregate when the particle is an aggregate of primary particles. Moreover, when a particle is not spherical, it means the diameter of a circle corresponding to the projected area.

<Viscosity reducing agent>
In the present invention, a hydrogen bonding solvent can be added for the purpose of reducing the melt viscosity. The hydrogen bonding solvent is J.I. N. As described in Israel Ativili, “Intermolecular Forces and Surface Forces” (Takeshi Kondo, Hiroyuki Oshima, Maglow Hill Publishing, 1991) and electrically negative atoms (oxygen, nitrogen, fluorine, chlorine) An organic solvent capable of producing a hydrogen atom-mediated “bond” between a hydrogen atom covalently bonded to an electronegative atom, ie, a bond having a large bond moment and containing hydrogen, such as O—H (Oxygen hydrogen bond), N—H (nitrogen hydrogen bond), and organic solvent that can arrange adjacent molecules by including F—H (fluorine hydrogen bond).

  These have the ability to form stronger hydrogen bonds with cellulose than intermolecular hydrogen bonds of cellulose resin. In the melt casting method performed in the present invention, the glass transition temperature of the cellulose resin used alone is higher than that. The melting temperature of the cellulose resin composition can be lowered by the addition of a hydrogen bonding solvent, or the melt viscosity of the cellulose resin composition containing a hydrogen bonding solvent can be lowered at the same melting temperature as the cellulose resin. .

<Acrylic particles>
The optical film of the present invention can contain a multilayer structure acrylic granular composite, and examples of commercially available products include “Metablene” manufactured by Mitsubishi Rayon Co., “Kaneace” manufactured by Kaneka Chemical Co., Ltd., Kureha “Paraloid” manufactured by Chemical Industries, “Acryloid” manufactured by Rohm and Haas, “Staffyroid” manufactured by Gantz Kasei Kogyo Co., Ltd., “Parapet SA” manufactured by Kuraray Co., Ltd., and the like are used alone or in combination of two or more. Can do.
<Method for producing optical film>
The optical film of the present invention can employ either a solution casting film forming method or a melt casting film forming method, but a more preferable melt casting method will be described.
(Step of pelletizing a composition containing cellulose ester)
It is preferable that a plurality of raw materials used for melt extrusion are usually kneaded and pelletized in advance. Pelletization may be performed by a known method. For example, the polymer of the present invention and other additives are fed to an extruder with a feeder, kneaded using a single or twin screw extruder, and extruded from a die into a strand. Can be done by water cooling or air cooling and cutting.

  It is important to dry the raw material before extruding to prevent decomposition of the raw material. In particular, since the cellulose ester easily absorbs moisture, it is preferable to dry it at 70 to 140 ° C. for 3 hours or more with a dehumidifying hot air dryer or a vacuum dryer to keep the moisture content at 200 ppm or less, and further 100 ppm or less.

  The additives may be mixed before being supplied to the extruder, or may be supplied by individual feeders. A small amount of an additive such as an antioxidant is preferably mixed in advance in order to mix uniformly. Mixing of the antioxidants may be performed by mixing solids, and if necessary, the antioxidant may be dissolved in a solvent, impregnated in a polymer and mixed, or sprayed and mixed. Good.

A vacuum nauter mixer or the like is preferable because drying and mixing can be performed simultaneously. Further, if the contact with air, such as the exit from the feeder unit or die, it is preferable that the atmosphere such as dehumidified air and dehumidified N ₂ gas.

  In addition, it is preferable to keep the supply hopper and the like to the extruder warm because moisture absorption can be prevented.

  A matting agent, an ultraviolet absorber and the like may be applied to the obtained pellets or added in an extruder during film formation.

  The extruder is preferably processed at a temperature as low as possible so as to suppress the shearing force and prevent the resin from deteriorating (molecular weight reduction, coloring, gel formation, etc.). For example, in the case of a twin screw extruder, it is preferable to rotate in the same direction using a deep groove type screw. From the uniformity of kneading, the meshing type is preferable.

  Kneader discs can improve kneadability, but care must be taken for shearing heat generation, and the mixability is sufficient even without using a kneader disc. The suction from the vent hole may be performed as necessary. Since the volatile component is hardly generated at a low temperature, the vent hole may be omitted.

  The color of the pellet is preferably such that the b * value, which is an index of yellowness, is in the range of -5 to 10, more preferably in the range of -1 to 8, and in the range of -1 to 5. More preferred. The b * value can be measured at a viewing angle of 10 ° using a spectrocolorimeter CM-3700d (manufactured by Konica Minolta Sensing Co., Ltd.) using D65 (color temperature 6504K) as a light source.

A film is formed using the pellets obtained as described above. Of course, the raw material powder can be directly fed to the extruder by a feeder without being pelletized to form a film as it is.
(Process of heating and melting the pelletized cellulose ester composition to a temperature showing fluidity to produce a melt)
Dehydrated hot air or polymer dried under vacuum or reduced pressure using a single or twin screw type extruder with a melting temperature of about 200-300 ° C and filtered through a leaf disk type filter to remove foreign matter A melt is produced.

(Process of casting and cooling the melt to form a film)
The produced melt is cast from a T die and solidified on a cooling roll to form a film.

  When introducing from the supply hopper to the extruder, it is preferable to prevent oxidative decomposition or the like under vacuum, reduced pressure, or inert gas atmosphere.

  The extrusion flow rate is preferably performed stably by introducing a gear pump or the like. Further, a stainless fiber sintered filter is preferably used as a filter used for removing foreign substances.

  A stainless steel fiber sintered filter is an integrated stainless steel fiber body that is intricately entangled and then compressed and sintered at the contact point. The density is changed according to the thickness of the fiber and the amount of compression, and the filtration accuracy is improved. Can be adjusted.

  It is preferable to use a multilayer body in which the filtration accuracy is repeated coarsely and densely a plurality of times. Further, it is preferable to adopt a configuration in which the filtration accuracy is sequentially increased or a method in which coarse and dense filtration accuracy is repeated, so that the filtration life of the filter can be extended and the accuracy of supplementing foreign matters and gels can be improved.

  If flaws or foreign matter adhere to the die, streaky defects may occur. Such defects are also referred to as die lines, but in order to reduce surface defects such as die lines, it is preferable to have a structure in which the resin retention portion is minimized in the piping from the extruder to the die. . It is preferable to use a die that has as few scratches as possible inside the lip.

  The inner surface that contacts the molten resin such as an extruder or a die is preferably subjected to surface treatment that makes it difficult for the molten resin to adhere to the surface by reducing the surface roughness or using a material having a low surface energy. Specifically, a hard chrome plated or ceramic sprayed material is polished so that the surface roughness is 0.2 S or less.

  Additives such as plasticizers may be mixed with the resin in advance, or may be kneaded in the middle of the extruder, but it is preferable to use a mixing device such as a static mixer in order to add uniformly. .

  The film temperature on the touch roll side when the film-like material is nipped by the cooling roll and the elastic touch roll is preferably Tg or more and Tg + 110 ° C. or less of the film. A well-known roll can be used for the roll which has the elastic body surface used for such a purpose.

When peeling the film-like material from the cooling roll, it is preferable to prevent the deformation of the film-like material by controlling the tension.
(Stretching process)
The stretching step is preferably performed in the order of MD (also referred to as a conveyance direction or film forming direction) stretching and TD (also referred to as a direction perpendicular to the MD direction or width direction) stretching.

<MD stretching process>
Here, the roll stretching in the MD stretching step will be described in detail. Roll stretching is a method in which a film is MD-stretched by a difference in peripheral speed between a low-speed roll group and a high-speed roll group.

  Typical methods for roll stretching include a heater heating method and an oven heating method.

  The heater heating method is a method in which a film preheated in a low-speed roll group is instantaneously heated to a stretching temperature by a heater installed between the low-speed roll group and the high-speed roll group, and stretched with a relatively short stretching span. In the oven heating method, an oven is installed between the low-speed roll group and the high-speed roll group, and preheating, stretching, and cooling steps are included in the oven, and stretching is performed with a relatively long stretching span.

  For the production of a wide optical film, the heater heating method is preferred because the amount of width shrinkage can be kept relatively small and the retardation can be easily adjusted. Here, the heater heating method will be described in detail, but the present invention is not limited to this.

  The film is preheated by a low-speed roll group, heated rapidly to the stretching temperature by a heater provided between the low-speed roll group and the high-speed roll group, MD stretched, cooled by the high-speed roll group, and conveyed to the next process. . The number of the preheating rolls in the low-speed roll group is preferably small from the viewpoint of scratches, but the number may be selected according to the preheating temperature of the film, and is 1 or more, 20 or less, preferably 2 or more, 15 Use the following roles:

  The upper limit temperature of the preheating roll group is, in principle, not to cause MD stretching between the preheating rolls and to prevent adhesion failure, etc., and is not higher than the glass transition temperature (Tg) of the film, preferably (Tg-5) ° C. or lower. It is. The temperature increase rate by the preheating roll group is set so that the film temperature difference between the entrance side and the exit side of each roll is 80 ° C. or less, preferably 50 ° C. or less, considering that wrinkles do not occur due to thermal expansion. Is preferred.

  The number of cooling rolls in the high-speed roll group may be selected according to the temperature to be cooled, and 1 or more and 15 or less, preferably 2 or more and 10 or less rolls are used. The upper limit temperature of the cooling roll group is not higher than the rapid cooling, and is not higher than the glass transition temperature (Tg) of the film, preferably not higher than (Tg-5) ° C. The temperature drop rate by the cooling roll group is preferably such that wrinkles do not occur due to heat shrinkage, and the film temperature difference between the entry side and the exit side of each roll is 100 ° C. or less, and 70 ° C. or less. More preferred.

  The roll diameters of the preheating roll group and the cooling roll group are 100 mmφ or more and 400 mmφ or less, preferably 150 mmφ or more and 300 mmφ or less from the viewpoint of roll strength and contact area (heat transfer / slip). In particular, the stretching roll (the roll positioned immediately upstream and downstream of the heater) is preferably 250 mmφ or less in order to shorten the substantial stretching span S.

  By the way, in order to prevent the film from slipping and being damaged or being MD-stretched between rolls, a draw is applied according to thermal expansion or thermal contraction. Roll draw is 5% or less, preferably 1% or less, between adjacent rolls.

  Here, the roll draw is a ratio of the peripheral speed V1 of the low-speed roll and the peripheral speed V2 of the high-speed roll, and is (V2-V1) / V1. In order to control the draw of the rolls, each of the rolls in the preheating roll group and the cooling roll group is preferably a drive roll, but if it is a part, an auxiliary drive roll and a free roll are used. Also good.

  A planetary roller, a roll gear, etc. are used suitably for a reduction gear. A direct drive system can also be used, and these may be selected as appropriate according to the system.

  The roll surface roughness in the preheating roll group and the cooling roll group may be changed according to the roll material and roughness.

  For example, a mirror surface roll having a surface roughness of 0.5 S or less, preferably 0.2 S or less is used to prevent rolls or slippage coming into contact with the film at high temperatures, and surface roughness is used to prevent tension cut or sticking. It is preferable to use a roll having a rough surface with a degree of 1.0 S or more.

  Roll surface materials in the preheating roll group and the cooling roll group are, for example, hard chrome (H-Cr), aluminum oxide, titanium oxide, chromium oxide, etc., and rubbers such as ceramics, silicon, fluorine, chlorobrene, etc., which are surface-treated from these composites. Resin such as Teflon (registered trademark) is used.

  It is preferable that the arrangement / interval of the rolls in the preheating roll group and the cooling roll group be narrow in order to prevent MD stretching between the rolls and to prevent the film from cooling. Between each roll, the distance from roll peeling to landing on the next roll is 200 mm or less, preferably 100 mm or less.

  As the material of the nip roll, a rubber roll such as silicon rubber, fluorine rubber or chlorobrene rubber which is easily elastically deformed, or a resin roll such as fluororesin is preferably used. The position of the nip roll is preferably pressed at a position where the film is peeled / landed. Further, the pressure of the nip roll is 0.1 to 50 N / mm, preferably 0.5 to 20 N / mm, from the viewpoints that the film can be pressure-bonded and the film is not damaged.

  Further, the nip roll may nip only the end of the film in order to prevent scratches on the film, or the roll may be a drum shape from the viewpoint of suppressing the width shrinkage, or may be arranged at an angle with respect to the width direction of the film.

  Next, as the type of heater, because it is clean, highly efficient, and space-saving, for example, a radiation type heat source such as an infrared heater, a halogen lamp heater, or a ceramic heater is desirable, and it can be selected according to the absorption characteristics of the resin. Good.

  The number of heaters may be calculated from the heater capacity, MD stretching / preheating temperature, conveying speed, film thickness, thermal conductivity, and the like, and usually 1 to 12, preferably 1 to 8, are used. The height of the heater is preferably as close as possible to the film as long as it is not in contact with the film in order to increase efficiency. For example, it is 5 to 100 mm, preferably 10 to 50 mm. The output of the heater may be adjusted as appropriate in consideration of the stretching temperature, the heating rate, and the like.

  The MD stretching speed is 3000 or more and 75000% / min or less, preferably 5000 or more and 50000% / min or less. Here, the MD stretching speed (% / min) is defined as follows.

  That is, when the peripheral speed of the low-speed side stretching roll is V1, the peripheral speed of the high-speed side stretching roll is V2, and the substantial stretching span is S, it is expressed in the following initial stage.

MD stretching speed (% / min) = [(V2-V1) / S] × 100
Moreover, as for the space | interval of MD extending | stretching roll, width contraction is suppressed, so that the area where the film is not hold | maintained at the roll is short. Here, the distance between the centers of the rolls is 400 mm or less, preferably 300 mm or less.

  One or a plurality of cleaning devices for the preheating / stretching / cooling rolls in the MD stretching zone may be provided, may be provided in-line or off-line, and may not be provided depending on circumstances.

  As the cleaning means, a known roll cleaning means such as a method of wiping off the dirt by pressing the nonwoven fabric is preferably used.

<TD stretching process>
After the MD stretching, TD stretching can be performed by tenter stretching {holding both ends of the film with a chuck and stretching the film in the width direction (perpendicular to the conveying direction)}.
<Extension conditions>
The film is preferably stretched under a uniform temperature distribution controlled in the width direction. The temperature is preferably within ± 2 ° C, more preferably within ± 1 ° C, and particularly preferably within ± 0.5 ° C. The stretching temperature is preferably in the range of Tg-20 ° C to Tg + 40 ° C.

  The draw ratio is preferably 4 to 15 times as the total of MD and TD directions. The draw ratio in each direction is preferably 1.1 to 4 times.

  In addition, the meaning of the sum in the case of simply describing the draw ratio is, for example, 1.4 × 1.5 = 2.1 times when stretched 1.4 times in the MD direction and 1.5 times in the TD direction. calculate.

  In general, an optical film composed of two or more kinds of resins tends to be in a fine phase separation state due to large deformation and holding at a high temperature, and the haze after stretching tends to increase. According to the polymer blend of the present invention, an increase in haze can be suppressed even when stretching at a high magnification is performed.

<Post-stretching process (including winding process)>
In the film produced by the above method, after the aggregate such as plasticizer is reduced to such an extent that haze failure does not occur, the film is shrunk in the MD direction or TD direction for the purpose of reducing retardation and reducing the dimensional change rate. It is preferable.

  In order to shrink in the MD direction, for example, there is a method of contracting the film by temporarily clipping out the width stretching and relaxing in the MD direction, or by gradually narrowing the interval between adjacent clips of the transverse stretching machine.

  The latter method can be performed by using a general simultaneous biaxial stretching machine and driving the clip portions in the longitudinal direction by, for example, a pantograph method or a linear drive method to smoothly and gradually narrow the clip portion. it can.

  You may combine with extending | stretching of arbitrary directions (diagonal direction) as needed.

  Prior to winding, the ends may be slit and cut to the width of the product, and knurling (embossing) may be applied to both ends to prevent sticking or scratching during winding. The knurling method can process a metal ring having an uneven pattern on its side surface by heating or pressing.

In addition, since the film has deform | transformed and cannot use as a product normally, the holding | grip part of the clip of both ends of a film is cut out and reused as a raw material.
<Optical film>
The optical film of the present invention is preferably an optical film used as a polarizing plate protective film used in a liquid crystal display device.
<Polarizing plate>
The optical film of the present invention can be used as a polarizing plate protective film of a polarizing plate having a structure in which a polarizer is sandwiched between two polarizing plate protective films.

  The polarizing plate can be produced by a general method. The cellulose ester film of the present invention is preferably subjected to alkali saponification treatment, and the treated film is bonded to at least one surface of a polarizer produced by immersing and stretching in an iodine solution using a completely saponified polyvinyl alcohol aqueous solution. .

  The polarizer of the present invention is a polyvinyl alcohol-based polarizer, which is one in which a polyvinyl alcohol-based film is dyed with iodine or one in which a dichroic dye is dyed.

  For the polarizer, a polyvinyl alcohol aqueous solution is formed into a film and dyed by uniaxial stretching or dyed or uniaxially stretched and then preferably subjected to a durability treatment with a boron compound.

  On the surface of the polarizer, one side of the cellulose ester film of the present invention is bonded to form a polarizing plate. It is preferably bonded with an aqueous adhesive mainly composed of completely saponified polyvinyl alcohol or the like.

The long cellulose ester film produced by the melt casting film-forming method according to the present invention can be bonded to a long polarizer (polarizing film) after being subjected to alkali saponification treatment. A productive effect is obtained with a long length of 1, and the longer the length is 1500 m, 2500 m, and 5000 m, the higher the productive effect of manufacturing a polarizing plate.
<Liquid crystal display device>
The polarizing plate including the optical film of the present invention can exhibit high display quality as compared with a normal polarizing plate.

  The polarizing plate of the present invention includes a multi-domain vertical alignment (MVA) mode, a patterned vertical alignment (PVA) mode, a continuous pinwheel alignment (CPA) mode, an OCB (Optical Compensation InP mode, OCB (Optical Compensation InP) mode, and the like. Can be used.

  The liquid crystal display device is applied as a device for colorization and moving image display, and the display quality is improved by the present invention, and the contrast is improved and the resistance of the polarizing plate is improved. .

  In the case of an optical film, the thickness of the film is preferably 10 to 500 μm. In particular, the lower limit is 20 μm or more, preferably 30 μm or more. The upper limit is 150 μm or less, preferably 120 μm or less.

  A particularly preferred range is 25 to 90 μm. If the film is thick, the polarizing plate after polarizing plate processing becomes too thick, and it is not suitable for the purpose of thin and light in liquid crystal displays used for notebook computers and mobile electronic devices.

  On the other hand, if the film is thin, the moisture permeability of the film increases, and the ability to protect the polarizer from humidity tends to be reduced.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
<Examples of synthesis and polymerization>
Synthesis Example 1 (Synthesis of 2-methyl-2-methylterranyl-propionitrile)
6.38 g (50 mmol) of metal tellurium (manufactured by Aldrich Co., Ltd., trade name: Tellurium (-40 mesh)) was suspended in 50 ml of THF, and 52.9 ml of methyllithium (manufactured by Kanto Chemical Co., Ltd., diethyl ether solution). (1.04M diethyl ether solution, 55 mmol) was slowly added dropwise at room temperature (10 minutes).

The reaction solution was stirred until the metal tellurium disappeared completely (20 minutes). To this reaction solution, 10.4 g (70 mmol) of 2-bromo-2-methyl-propionitrile was added at room temperature and stirred for 2 hours. After completion of the reaction, the solvent was concentrated under reduced pressure, followed by distillation under reduced pressure to obtain 4.10 g (yield 39%) of a red oily substance.
Synthesis Example 2 (Dimethylditelluride)
Metallic tellurium (manufactured by Aldrich, trade name: Tellurium (-40 mesh)) 3.19 g (25 mmol) was suspended in 25 ml of THF, and 25 ml (28.5 mmol) of methyllithium (manufactured by Kanto Chemical Co., Ltd., diethyl ether solution) was 0. Slowly added at 10 ° C. (10 minutes).

  The reaction solution was stirred until the metal tellurium disappeared completely (10 minutes). To this reaction solution, 20 ml of ammonium chloride solution was added at room temperature and stirred for 1 hour. The organic layer was separated and the aqueous layer was extracted 3 times with diethyl ether.

The collected organic layer was dried over sodium sulfate and concentrated under reduced pressure to obtain 2.69 g (9.4 mmol: yield 75%) of a black purple oily substance.
Reference polymerization example 1
In a nitrogen-substituted glove box, 21.1 mg (0.10 mmol) of the compound prepared in Synthesis Example 1 with 0.95 g (9.5 mmol) of methyl methacrylate and 0.043 g (0.5 mmol) of methyl acrylate and AIBN (Otsuka) 16.4 mg (0.10 mmol) manufactured by Kagaku Co., Ltd., trade name: AIBN) and 28.5 mg (0.10 mmol) of the compound prepared in Synthesis Example 2 were stirred at 50 ° C. for 3 hours.

After completion of the reaction, the reaction mixture was dissolved in 5 ml of chloroform, and the solution was then poured into 200 ml of hexane which was being stirred. The precipitated polymer was suction filtered at room temperature and dried to obtain 0.977 g of polymethyl methacrylate. Mn = 32000 and Mw / Mn = 1.18.
Synthesis Example 3 (Ethyl-2-methyl-2-methylterranyl-propionate)
6.38 g (50 mmol) of metal tellurium (same as synthesis example 1) was suspended in 50 ml of THF, and 52.9 ml (1.04 M diethyl ether solution, 55 mmol) of methyllithium (same as synthesis example 1) was added thereto at room temperature. Slowly dropped (10 minutes). The reaction solution was stirred until the metal tellurium disappeared completely (20 minutes).

To this reaction solution, 10.7 g (55 mmol) of ethyl-2-bromo-isobutyrate was added at room temperature and stirred for 2 hours. After completion of the reaction, the solvent was concentrated under reduced pressure, followed by distillation under reduced pressure to obtain 6.53 g (yield 51%) of a yellow oil.
Reference polymerization example 2
In a nitrogen-substituted glove box, 20.02 g (200 mmol) of methyl methacrylate, 26.0 mg (0.10 mmol) of ethyl-2-methyl-2-methylterranyl-propionate prepared in Synthesis Example 3 and AIBN (Otsuka Chemical Co., Ltd.) 16.4 mg (0.10 mmol) manufactured and trade name: AIBN) and 28.5 mg (0.10 mmol) of dimethylditelluride prepared in Synthesis Example 2 were stirred at room temperature to obtain a uniform solution.

  Thereto, 101.6 g (1001 mmol) of methyl methacrylate was added and stirred at room temperature. Then, it stirred at 60 degreeC for 3 hours. After completion of the reaction, the reaction mixture was dissolved in 1000 ml of chloroform, and the solution was then poured into 4000 ml of hexane which was being stirred. The precipitated polymer was suction filtered at room temperature and dried to obtain polymethyl methacrylate. Mn = 148000 and Mw / Mn = 1.22.

  In producing the polymer A having the highest content in the two or more types of polymers of the present invention, a crosslinkable monomer is added at 1.5 hours from the start of polymerization using the methods of the above Reference Polymerization Examples 1 and 2. The method was adopted.

The monomers used are as follows.
MMA: methyl methacrylate MA: methyl acrylate ACMO: acryloylmorpholine VP: vinylprolidone The crosslinkable monomers used are as shown in B1 to B3 below. In addition, a crosslinkable monomer is represented as what is used additionally by mass ppm when the main monomer composition component is 100 mol%.
B1: Divinylbenzene B2: Polyethylene glycol diacrylate (average molecular weight 400)
B3: Ethylene glycol diacrylate The prepared polymers are shown in Table 1.

  Using the produced polymer, an optical film was produced as follows.

The cellulose ester used is as follows.
C1: CAP482-20 manufactured by Eastman Chemical Co., Ltd. C2: Cellulose acetate propionate with an acetyl group substitution degree of 1.65, propionyl group substitution degree of 1.20, Mw of 130,000 C3: acetyl group substitution degree of 2.10, Mw10 Ten thousand cellulose acetates <Preparation of optical films 1-5>
70 parts by weight of polymer A1, 30 parts by weight of C1 (water content 200 ppm), 0.01 parts by weight of PEP-36 (ADEKA) as a phosphorus compound, Irganox 1010 (Ciba Japan Co., Ltd.), dried at 80 ° C. for 6 hours 0.5 parts by mass), 0.24 parts by mass of Sumilizer GS (manufactured by Sumitomo Chemical Co., Ltd.), 0.1 parts by mass of Aerosil R972V (manufactured by Nippon Aerosil Co., Ltd.) at 80 ° C. and 1 Torr at 3 ° C. Further drying while mixing for a period of time.

  The obtained mixture was melt-mixed at 235 ° C. using a twin-screw extruder and pelletized. The cellulose ester film was produced by the production apparatus shown in FIG.

  Pellets (moisture content of 50 ppm) were melt-extruded from a T-die onto a first cooling roll having a surface temperature of 90 ° C. at a melting temperature of 240 ° C. using a single screw extruder to obtain a cast film having a thickness of 120 μm. . At this time, the film was pressed on the first cooling roll with an elastic touch roll having a 2 mm thick metal surface.

Similarly, optical films 2 to 5 shown in Table 2 were produced. In addition, since it was normal film forming conditions, melt viscosity was not measured.
<Preparation of optical films 6-11>
70 parts by mass of polymer A5, 30 parts by mass of C1 (water content 200 ppm), 0.01 parts by mass of PEP-36 (ADEKA) as a phosphorus compound, Irganox 1010 (Ciba Japan Co., Ltd.), dried at 80 ° C. for 6 hours 0.5 parts by mass), 0.24 parts by mass of Sumilizer GS (manufactured by Sumitomo Chemical Co., Ltd.), 0.1 parts by mass of Aerosil R972V (manufactured by Nippon Aerosil Co., Ltd.) at 80 ° C. and 1 Torr at 3 ° C. Further drying while mixing for a period of time.

  The obtained mixture was melt-mixed at 235 ° C. using a twin-screw extruder and pelletized. The cellulose ester film was produced by the production apparatus shown in FIG.

Pellets (moisture content of 50 ppm) were melt-extruded from a T-die onto a first cooling roll having a surface temperature of 90 ° C. at a melting temperature of 240 ° C. using a single screw extruder to obtain a cast film having a thickness of 120 μm. . At this time, the film was pressed on the first cooling roll with an elastic touch roll having a 2 mm thick metal surface. A part of the unstretched film at this time was collected and used for high-temperature storage evaluation. Further, a cast film having the same film thickness was prepared by triple the extrusion flow rate / casting speed and used for high-speed film formation evaluation.
(MD stretching process)
MD stretching was performed by the difference in peripheral speed between the two rolls under the infrared heater. The stretching temperature is 150 ° C. and the stretching ratio is 2.0 times.
(TD stretching process)
The obtained film is introduced into a tenter having a preheating zone, a stretching zone, a holding zone, and a cooling zone (there is also a neutral zone between each zone to ensure thermal insulation between the zones). The film was stretched 2.0 times at 0 ° C., then cooled to 120 ° C., and kept at 120 ° C. for heat treatment.

  Thereafter, the clip gripping part was cut off to obtain an optical film 6 having a film thickness of 40 μm and a film width of 2300 mm.

  Similarly, optical films 7 to 11 described in Table 2 were produced.

  The melt viscosity (Pa · s) was measured with a cone plate type rotary rheometer under the conditions of a measurement temperature of 240 ° C., a strain amount of 5%, and an angular velocity of 100 rad / sec.

The following evaluation was performed about the produced optical film. The results are shown in Table 3.
<Haze evaluation>
The obtained film was measured using a haze meter (1001DP type, manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JISK-6714 under each condition, and used as an index of transparency. Unless otherwise noted, the measurement conditions are in an atmosphere of 23 ° C. and 55% RH.
(Immediately)
The unstretched ones of the optical films 1 to 5 and the optical films 6 to 11 were measured as they were.
(After storage at high temperature: unstretched)
The unstretched optical films 1 to 5 and optical films 6 to 11 were measured after being stored at 75 ° C. for 2 months.
(High speed film formation)
It measured about what performed high-speed film formation with respect to the optical films 6-11.
(After stretching)
It measured about the film after extending | stretching of the optical films 6-11.

  As is apparent from Table 3, the present invention is excellent in heat resistance and transparency.

Claims (4)

  An optical film containing 2 or more and 5 or less types of polymers, wherein the polymer having the highest content in the 2 or more and 5 or less types of polymers uses a monomer having a plurality of ethylenically unsaturated groups as a copolymerization component. An optical film characterized by the above.   2. The optical film according to claim 1, wherein one of the polymers other than the polymer having the highest content among the two or more and five or less polymers is a cellulose ester.   A mixture comprising two or more and five or less types of polymers as a constituent component, wherein the polymer having the highest content in the two or more types of polymers comprises a monomer having a plurality of ethylenically unsaturated groups as a copolymerization component. A method for producing an optical film, comprising melting and casting a mixture.   The method for producing an optical film according to claim 3, further comprising a stretching step after the melt casting, wherein the stretching ratio is 4 times or more and 15 times or less in total in the longitudinal direction and the transverse direction.