JP2007062063A - Optical film and its manufacturing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical film having excellent quality free from a coating flaw by cleaning the index of the cross-sectional quality of the edge part of a target optical film in the meaning of the magnification of the visual angle of a liquid crystal display device (LCD) operated in an IPS mode capable of obtaining display easy to look having a high contrast ratio over a wide range and ensuring the good cross-section of the edge part of the optical film to keep quality such as the reduction of the released pieces of the film section, the prevention of the destruction of the film, the improvement of the dimensional stability of the film, etc. <P>SOLUTION: The optical film contains an additive which reduces retardation (Rt) in its thickness direction and finally has Rt=-10 to 10 nm and Ro=0 to 5 nm. At least one film end part slitting device is installed in a solution casting film-forming apparatus during from the release of a web to the taking-up of the film in a solution casting film forming apparatus and at least the surface roughness (Ra) of the cross section of the film slitted by a final slitter is set to 0.05 to 1.2 μm. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention can be used for various functional films such as a protective film for a polarizing plate used for a liquid crystal display (LCD), a retardation film, a viewing angle widening film, and an antireflection film used for a plasma display. The present invention relates to a film and a manufacturing apparatus thereof.

  In particular, the present invention can clarify the index of the cross-sectional quality of the target optical film end, reduce the cross section of the film cross section, and prevent the film from breaking by ensuring a good cross section of the optical film end. The present invention relates to an optical film having excellent quality that can maintain quality such as improvement in film dimensional stability and consequently has no coating defects on the film, and a manufacturing apparatus thereof.

  In recent years, liquid crystal display devices (LCDs) have been developed to be thinner and lighter, larger screens, and higher definition. Along with this, the demand for thinner, wider and higher quality protective films for polarizing plates has become stronger, and the required level of optical film quality has become stricter as the image quality of liquid crystal display devices increases. .

  In general, cellulose ester films are widely used as protective films for polarizing plates. However, with the recent increase in screen size, a film original having a wide film width and a long winding length is desired.

  By the way, in the solution casting film-forming apparatus for optical films, when a device for slitting the film edge between the time after peeling and the winding is installed, conventionally, the cross-sectional state of the edge-cut edge of the film in film formation When it deteriorated, the peeling | exfoliation thing (chip) generate | occur | produced and it was a problem.

  In addition, if the cross-sectional state of the edge cut end portion of the film is poor, the film is likely to break during film formation. There was a problem that the moisture absorption state of the part was different, and due to this, the dimensional behavior of the film end part was different, and the dimensional stability deteriorated.

Conventionally, there are the following patent documents related to the slitter device at the film edge in such film formation.
Japanese Patent Application Laid-Open No. 2001-315089 has a chamfered portion that can cut a film with high quality, reduce adhesion of film cutting waste to a rotating blade, and maintain cutting ability for a long time. A slitter device having a slitter blade is disclosed. Japanese Patent Laid-Open No. 7-11055 discloses that, in the process of producing a film by a solution casting film forming method, the film ears are continuously provided along the film conveying method in the course of winding from the casting. A film cutting method provided with a step of cutting and removing is disclosed. And in the cutting method of the film of this patent document 2, the residual volatile matter of the film at the time of cutting was prescribed | regulated. In Patent Document 3, as in Patent Document 2, in the process of producing a film by a solution casting film forming method, a film ear is placed in the middle of casting and winding. A film cutting method provided with a step of continuously cutting and removing along the transport method is disclosed. And in the film cutting method of this patent document 3, the temperature of the film cutting part was prescribed | regulated below the glass transition temperature (Tg) of a polymer. Japanese Patent Laid-Open No. 2003-291091 Patent Document 4 discloses a method for blowing ear dust separated from a web (film) being fed to an ear waste collecting section, in which the ear dust is cut in the feed direction. In addition, a method for feeding ear dust is disclosed, which is formed into a strip shape and winds the strip-like ear dust. Japanese Patent Application Laid-Open No. 2004-50307 discloses a cutting edge portion of a disk-shaped cutting blade in order to reduce generation of chips during film cutting, extend the life of the cutting blade, and lengthen the replacement cycle of the cutting blade. Is inserted into a groove formed on a cutting base for film support in a non-contact state with respect to the cutting base, and a method for cutting the film is disclosed. JP, 2004-66505, A In patent documents 6, in a film manufacturing device, it is provided with an ear-cutting device which cuts an ear part of a film, and the cut ear part is air-fed, and it is under wind blowing used for air-fing An apparatus for producing a film in which an evaporating solvent is adsorbed and removed by an adsorption recovery apparatus is disclosed.

  However, in the conventional apparatus or method described in the above-mentioned patent document, there is no description that clearly defines the roughness of the film edge, and no clear index or countermeasure for solving the conventional problem has been made. .

  By the way, in the optical film, reducing the thickness direction retardation (Rt) of the film is important in terms of increasing the viewing angle of the liquid crystal display device operating in the IPS mode. For an optical film material containing an additive that reduces Rt), when a device for slitting the film end between installation and winding is installed, the cross-sectional state of the edge cut end of the film in film formation is The problem of deterioration and generation of exfoliation (cutting chips) has not been studied.

  The object of the present invention is to solve the above-mentioned problems of the prior art and contain an additive for reducing the thickness direction retardation (Rt), and finally the thickness direction retardation (Rt) =-10 to 10 nm, in-plane direction retardation. For the optical film with (Ro) = 0 to 5 nm, it is possible to clarify the index of the cross-sectional quality of the target optical film end, and by securing a good optical film end cross-section, To provide an optical film having excellent quality that can maintain quality such as reduction, prevention of film breakage, and improvement of film dimensional stability, and as a result, an apparatus for producing the same. It is in.

  It is another object of the present invention to provide an image display device, particularly a liquid crystal display device operating in the IPS mode, which can realize an easy-to-see display having a high contrast ratio over a wide range using the optical film of the present invention.

  As a result of intensive studies in view of the above points, the present inventors have found that an optical film material containing an additive that reduces the thickness direction retardation (Rt) in an optical film solution casting apparatus, after peeling By clarifying the quality index of the target film slit end cross section by visualizing and measuring the slit end of the film when installing a device that slits the film end from start to finish The present inventors have found that the above conventional problems can be solved, and have completed the present invention.

  In order to achieve the above-mentioned object, the invention of claim 1 uses a dope composition containing a cellulose ester resin and an additive for reducing the thickness direction retardation (Rt) to form a film by a solution casting film forming apparatus. When forming an optical film having a thickness of 35 to 85 μm, it is cast on a metal rotating drum or a metal rotating endless belt (hereinafter referred to as a support), peeled, dried, and stretched, and the stretched film is wound up. , An optical film manufacturing apparatus, in which at least one apparatus for slitting the film end between peeling and winding is installed at at least one end of the left and right ends of the film. The surface roughness (arithmetic mean roughness: Ra) of the cross section of the film slit by the slitting device is 0.05 to 1.2 μm.

  According to a second aspect of the present invention, in the optical film manufacturing apparatus according to the first aspect, the number of slit devices installed at one end of the film is 1 to 3 per one end of the film.

  According to a third aspect of the present invention, in the optical film manufacturing apparatus according to the first or second aspect, the product width of the final optical film is 1300 mm or more and 1700 mm or less.

  Invention of Claim 4 is a manufacturing apparatus of the optical film as described in any one of Claims 1-3. WHEREIN: A film slit apparatus is from a disk-shaped rotation upper blade and a roll-shaped rotation lower blade. It is characterized by being composed.

  Invention of Claim 5 is an optical film manufacturing apparatus as described in any one of Claims 1-4. WHEREIN: The disk-shaped rotation upper blade of a slit apparatus is 30-300 mm in diameter, and the thickness of a cutting location. In addition to having a diameter of 0.3 to 3 mm, the material of the rotating upper blade is any one of super steel, super steel fine particles, SKD (alloy tool steel), or SKH (high speed tool steel). The blade has a roll diameter of 75 to 200 mm, and the roll material of the rotating lower blade is any one of super steel, super steel fine particles, SKD, and SKH.

  Invention of Claim 6 is an optical film manufacturing apparatus as described in any one of Claims 1-3. WHEREIN: A film slit apparatus is comprised only by the disk shaped rotary upper blade, It is characterized by the above-mentioned. Yes.

  The invention of claim 7 is the optical film manufacturing apparatus according to claim 6, wherein the disk-shaped rotary upper blade of the slit device has a diameter of 30 to 300 mm and a thickness of the cut portion of 0.3 to 3 mm. The material of the rotating upper blade is any one of super steel, super steel fine particles, SKD, or SKH.

  The invention of claim 8 is the optical film manufacturing apparatus according to any one of claims 1 to 7, wherein the dope composition is a cellulose ester resin and an acrylic resin having a weight average molecular weight of 500 or more and 3000 or less. It is characterized by containing a polymer.

  The invention of claim 9 is the optical film manufacturing apparatus according to any one of claims 1 to 8, wherein the dope composition is a cellulose ester resin and an acrylic resin having a weight average molecular weight of 5,000 to 30,000. It is characterized by containing a polymer.

  The invention of the optical film of claim 10 is characterized in that it is manufactured by the optical film manufacturing apparatus according to any one of claims 1-9.

  The optical film manufacturing apparatus according to the present invention is an optical film having a film thickness of 35 to 85 μm by a solution casting film forming apparatus using a dope composition containing a cellulose ester resin and an additive for reducing the thickness direction retardation (Rt). An apparatus for producing an optical film, in which a film is cast, cast on a metal rotating drum or a metal rotating endless belt (hereinafter referred to as a support), peeled, dried and stretched, and wound up the stretched film. In this case, one or more devices for slitting the film end between peeling and winding are installed at at least one end of the left and right ends of the film, and at least the final slitting device is used for slitting. The surface roughness (arithmetic mean roughness: Ra) of the cross section of the film is 0.05 to 1.2 μm, and according to the optical film manufacturing apparatus of the present invention. In particular, when manufacturing an optical film using a dope composition containing a cellulose ester-based resin and an additive for reducing thickness direction retardation (Rt), an index of the cross-sectional quality at the end of the optical film as a target is shown. As a result, by securing a good optical film end section, quality can be maintained such as reduction of film cross-section release, prevention of film breakage, improvement of film dimensional stability, etc. In addition, there is an effect that an optical film having excellent quality with no film coating defect can be produced.

  The optical film according to the present invention is manufactured by the above-described optical film manufacturing apparatus of the present invention, and particularly uses a dope composition containing a cellulose ester resin and an additive for reducing the thickness direction retardation (Rt). Therefore, quality maintenance such as improvement of dimensional stability of the film can be achieved, and as a result, there is no user application defect, that is, repellency failure or foreign matter failure that occurs when the user applies a coating film to the film It has excellent quality.

  By using the protective film for a polarizing plate comprising the optical film of the present invention, it is possible to provide a polarizing plate excellent in durability, dimensional stability, and optical isotropy as well as thinning.

  Furthermore, a liquid crystal display device using this polarizing plate can maintain stable display performance over a long period of time.

  In addition, the present invention can provide an image display device that can realize an easy-to-view display having a high contrast ratio over a wide range, particularly a liquid crystal display device that operates in the IPS mode, using the optical film of the present invention. .

  Next, embodiments of the present invention will be described, but the present invention is not limited thereto.

  The optical film manufacturing apparatus according to the present invention is an optical film having a film thickness of 35 to 85 μm by a solution casting film forming apparatus using a dope composition containing a cellulose ester resin and an additive for reducing the thickness direction retardation (Rt). An apparatus for producing an optical film, in which a film is cast, cast on a metal rotating drum or a metal rotating endless belt (hereinafter referred to as a support), peeled, dried and stretched, and wound up the stretched film. In this case, one or more devices for slitting the film end between peeling and winding are installed at at least one end of the left and right ends of the film, and at least the final slitting device is used for slitting. The surface roughness (arithmetic mean roughness: Ra) of the cross section of the film is 0.05 to 1.2 μm.

  According to the apparatus for producing an optical film of the present invention, various resins can be used as a film material, and among these, a cellulose ester resin is preferable.

  The cellulose ester resin is a cellulose ester in which a hydroxyl group derived from cellulose is substituted with an acyl group or the like. Examples thereof include cellulose acylates such as cellulose acetate, cellulose triacetate, cellulose acetate propionate, cellulose acetate butyrate, and cellulose acetate propionate butyrate, and cellulose acetate having an aliphatic polyester graft side chain. Among these, cellulose acetate, cellulose acetate propionate, and cellulose acetate having an aliphatic polyester graft side chain are preferable. Other substituents may be included as long as the effects of the present invention are not impaired.

  As an example of cellulose triacetate, the substitution degree of acetyl group is preferably 1.4 or more and 3.0 or less. By setting the degree of substitution within this range, good moldability can be obtained, and desired in-plane direction retardation (Ro) and thickness direction retardation (Rt) can be obtained. If the substitution degree of the acetyl group is lower than this range, the heat resistance as a retardation film, particularly the dimensional stability under wet heat may be inferior, and if the substitution degree is too large, the necessary retardation characteristics will not be exhibited. There is a case.

  Although there is no limitation in particular as a raw material of the cellulose ester-type resin used for this invention, Cotton linter, wood pulp, kenaf, etc. can be mentioned. Moreover, the cellulose ester-type resin obtained from them can be mixed and used in arbitrary ratios, respectively.

  In the present invention, the cellulose ester-based resin is an organic acid such as acetic acid or an organic solvent such as methylene chloride when the acylating agent of the cellulose raw material is an acid anhydride (acetic anhydride, propionic anhydride, butyric anhydride). And using a protic catalyst such as sulfuric acid.

When the acylating agent is acid chloride (CH ₃ COCl, C ₂ H ₅ COCl, C ₃ H ₇ COCl), the reaction is carried out using a basic compound such as an amine as a catalyst. Specifically, it can be synthesized by the method described in JP-A-10-45804.

  The measuring method of the substitution degree of an acyl group can be measured according to ASTM-D817-96.

  Examples of the cellulose acetate having an aliphatic polyester graft side chain include cellulose acetate having an aliphatic polyester graft side chain containing lactic acid as a main repeating unit. The degree of acetyl substitution of cellulose acetate having an aliphatic polyester graft side chain mainly composed of lactic acid is preferably 2.5 to 3.0 per glucose unit. A thermoplastic cellulose acetate having an aliphatic polyester graft side chain having an acetyl substitution degree within this range exhibits a significant plasticizing effect, and the brittleness of the resulting polymer is not a problem. When the degree of acetyl substitution is less than 2.5, hydrogen bonding is caused by residual hydroxyl groups in cellulose acetate, so that even if an aliphatic polyester is grafted on the side chain, the plasticizing effect is small and the moldability may be poor. The degree of acetyl substitution is preferably 2.7 to 3.0, and most preferably 2.7 to 2.9. Polylactic acid containing lactic acid as a main repeating unit has a feature that thermal stability is particularly high among aliphatic polyesters.

  In the present invention, the molecular weight of the aliphatic polyester graft side chain is preferably 1000 to 10,000. By setting the molecular weight in the range of 1000 to 10,000, good moldability can be obtained. The molecular weight is more preferably 2000 to 9000, and most preferably 3000 to 8000.

  In the present invention, in order to obtain cellulose acetate having an aliphatic polyester graft side chain, it can be synthesized by a known method such as a method of performing ring-opening graft polymerization onto cellulose acetate using lactide as a monomer. When performing the ring-opening graft reaction, a known ring-opening polymerization catalyst can be used. Examples thereof include metals such as tin, zinc, titanium, bismuth, zirconium, germanium, antimony, sodium, potassium, and aluminum, and derivatives thereof. Particularly, the derivatives are preferably metal organic compounds, carbonates, oxides, and halides. Specific examples include tin octoate, tin chloride, zinc chloride, alkoxy titanium, germanium oxide, zirconium oxide, antimony trioxide, and alkyl aluminum.

  In the present invention, the number average molecular weight of the cellulose ester resin is preferably in the range of 60,000 to 300,000, since the mechanical strength of the obtained film is strong. Furthermore, 70000-200000 are preferable.

  In the present invention, various additives can be added to the cellulose ester-based resin.

  The apparatus for producing an optical film according to the present invention uses a dope composition containing a cellulose ester resin and an additive for reducing the thickness direction retardation (Rt), and the additive for reducing the thickness direction retardation (Rt). Is added in an amount of 10 to 20% by weight based on the solid content in the dope.

  In the present invention, reducing the thickness direction retardation (Rt) of the optical film is important in terms of increasing the viewing angle of the liquid crystal display device operating in the IPS mode. In the present invention, such thickness direction retardation (Rt) Examples of the additive for reducing Rt) include the following.

  In general, the retardation of the cellulose ester resin film appears as the sum of the retardation derived from the cellulose ester resin and the retardation derived from the additive. Therefore, the additive for reducing the retardation of the cellulose ester resin is an agent that disturbs the orientation of the cellulose ester resin and is difficult to orient itself and / or has a small polarizability anisotropy. It is a compound that effectively reduces (Rt). Therefore, an aliphatic compound is preferable to an aromatic compound as an additive for disturbing the orientation of the cellulose ester resin.

  Here, as a specific retardation reducing agent, for example, a polyester represented by the following general formula (1) or (2) may be mentioned.

Formula (1) B _1- (GA-) mG-B ₁
Formula _{(2) B 2 - (G} -A-) nG-B 2
In the above formula, B ₁ represents a monocarboxylic acid component, B ₂ represents a monoalcohol component, G represents a divalent alcohol component, A represents a dibasic acid component, and these are synthesized. . B ₁ , B ₂ , G, and A are all characterized by not containing an aromatic ring. m and n represent the number of repetitions.

Monocarboxylic acid component represented by B _1, not particularly limited, and may be known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid.

  Examples of preferred monocarboxylic acids include the following, but the present invention is not limited thereto.

  As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. The number of carbon atoms is more preferably 1-20, and particularly preferably 1-12. When acetic acid is contained, the compatibility with the cellulose ester resin is increased, and it is also preferable to use a mixture of acetic acid and another monocarboxylic acid.

  Preferred monocarboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, lauric acid, tridecylic acid , Saturated fatty acids such as myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, melicic acid, and laccelic acid, undecinic acid, Examples thereof include unsaturated fatty acids such as oleic acid, sorbic acid, linoleic acid, linolenic acid and arachidonic acid.

The monoalcohol component represented by B ₂ is not particularly limited ,, and may be a known alcohol. For example, an aliphatic saturated alcohol or aliphatic unsaturated alcohol having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. The number of carbon atoms is more preferably 1-20, and particularly preferably 1-12.

  Examples of the divalent alcohol component represented by G include the following, but the present invention is not limited thereto. For example, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 1,5-pentanediol, 1,6- Hexanediol, 1,5-pentylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol and the like can be mentioned. Among these, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1 1,2-butylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 1,6-hexanediol, diethylene glycol, and triethylene glycol are preferable, and 1,3-propylene glycol, 1,4-butylene Call, 1,6-hexanediol, diethylene glycol is preferably used.

  The dibasic acid (dicarboxylic acid) component represented by A is preferably an aliphatic dibasic acid or an alicyclic dibasic acid. Examples of the aliphatic dibasic acid include malonic acid, succinic acid, glutaric acid, and adipic acid. , Pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid and the like, in particular, aliphatic carboxylic acid having 4 to 12 carbon atoms, at least one selected from these To do. That is, two or more dibasic acids may be used in combination.

  The number of repetitions m and n in the above general formula (1) or (2) is preferably 1 or more and 170 or less.

  The weight average molecular weight of the polyester is preferably 20000 or less, and more preferably 10,000 or less. In particular, a polyester having a weight average molecular weight of 500 to 10,000 has good compatibility with a cellulose ester resin, and neither evaporation nor volatilization occurs in film formation.

  Polycondensation of polyester is carried out by a conventional method. For example, a direct reaction of the dibasic acid and glycol, a hot melt condensation method by the polyesterification reaction or transesterification reaction of the dibasic acid or alkyl esters thereof, for example, a methyl ester of dibasic acid and glycols, or Although it can be easily synthesized by any method of dehydrohalogenation reaction between acid chloride of these acids and glycol, it is preferable that polyester having a weight average molecular weight not so large is by direct reaction. A polyester having a high distribution on the low molecular weight side has a very good compatibility with the cellulose ester resin, and after forming the film, a moisture permeability is small, and a cellulose ester resin film having high transparency can be obtained.

  The method for adjusting the molecular weight is not particularly limited, and a conventional method can be used. For example, although depending on the polymerization conditions, the amount of these monovalent compounds can be controlled by a method of blocking the molecular ends with a monovalent acid or monovalent alcohol. In this case, a monovalent acid is preferable from the viewpoint of polymer stability. For example, acetic acid, propionic acid, butyric acid, etc. can be mentioned, but during the polycondensation reaction, it is not distilled out of the system, but is stopped and such monovalent acid is removed from the reaction system. The one that is easy to accumulate is selected. These may be used in combination. In the case of direct reaction, the weight average molecular weight can also be adjusted by measuring the timing of stopping the reaction by the amount of water distilled off during the reaction. In addition, it can be adjusted by biasing the number of moles of glycol or dibasic acid to be charged, or can be adjusted by controlling the reaction temperature.

  The polyester represented by the general formula (1) or (2) is preferably contained in an amount of 1 to 40% by weight based on the cellulose ester resin. It is particularly preferable to contain 5 to 15% by weight.

  In the present invention, examples of the additive for reducing the thickness direction retardation (Rt) include the following.

  The dope used in the production of the optical film of the present invention is mainly composed of a cellulose ester resin, a polymer as an additive for reducing retardation (Rt) (a polymer obtained by polymerizing an ethylenically unsaturated monomer, an acrylic polymer). ), And an organic solvent.

  In the present invention, if the weight-average molecular weight of the polymer as an additive for reducing the thickness direction retardation (Rt) is 500 to 10,000, the compatibility with the cellulose ester resin is good, and during film formation Neither evaporation nor volatilization occurs. In particular, if the acrylic polymer is preferably 500 to 5,000, in addition to the above, the cellulose ester resin film after film formation is excellent in transparency and moisture permeability is extremely low. As an excellent performance.

  As described above, in the present invention, the polymer as an additive for reducing the thickness direction retardation (Rt) has a weight average molecular weight of 500 or more and less than 10,000, and is therefore considered to be between the oligomer and the low molecular weight polymer. It is. In order to synthesize a polymer as an additive for reducing such a thickness direction retardation (Rt), it is difficult to control the molecular weight in a normal polymerization, and a method capable of aligning the molecular weight as much as possible by a method that does not increase the molecular weight is used. It is desirable. Such polymerization methods include a method using a peroxide polymerization initiator such as cumene peroxide and t-butyl hydroperoxide, a method using a polymerization initiator in a larger amount than normal polymerization, and a mercapto compound in addition to the polymerization initiator. And a method using a chain transfer agent such as carbon tetrachloride, a method using a polymerization terminator such as benzoquinone and dinitrobenzene in addition to the polymerization initiator, and JP-A No. 2000-128911 or JP-A No. 2000-344823. Examples include a compound having a single thiol group and a secondary hydroxyl group as described in the publication, or a bulk polymerization method using a polymerization catalyst in which the compound and an organometallic compound are used in combination. In particular, the method described in the publication is preferred.

  In the present invention, monomers as monomer units constituting a polymer as an additive for reducing useful thickness direction retardation (Rt) are listed below, but are not limited thereto.

  As the ethylenically unsaturated monomer unit constituting the polymer as an additive for reducing the thickness direction retardation (Rt) obtained by polymerizing an ethylenically unsaturated monomer, first, as a vinyl ester, for example, vinyl acetate, propionic acid, etc. Vinyl, vinyl butyrate, vinyl valerate, vinyl pivalate, vinyl caproate, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl cyclohexanecarboxylate, vinyl octylate, vinyl methacrylate, Examples include vinyl crotonate, vinyl sorbate, vinyl benzoate, and vinyl cinnamate.

  Next, as acrylate ester, for example, methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), butyl acrylate (n-, i-, s-, t-), pentyl acrylate ( n-, i-, s-), hexyl acrylate (n-, i-), heptyl acrylate (n-, i-), octyl acrylate (n-, i-), nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), cyclohexyl acrylate, acrylic acid (2-ethylhexyl), benzyl acrylate, phenethyl acrylate, acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl) ), Acrylic acid (2-hydroxypropyl), acrylic acid (3-hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2- Dorokishibuchiru) acrylate-p-hydroxymethylphenyl,-p-acrylic acid (2-hydroxyethyl) phenyl and the like; as methacrylic acid ester, the acrylic acid ester include those changed to methacrylic acid esters.

  Furthermore, examples of the unsaturated acid include acrylic acid, methacrylic acid, maleic anhydride, crotonic acid, itaconic acid, and the like.

  The polymer composed of the above monomers may be a copolymer or a homopolymer, and is preferably a vinyl ester homopolymer, a vinyl ester copolymer, or a copolymer of vinyl ester and acrylic acid or methacrylic acid ester.

  In the present invention, an acrylic polymer (simply referred to as an acrylic polymer) refers to a homopolymer or copolymer of acrylic acid or alkyl methacrylate having no monomer unit having an aromatic ring or a cyclohexyl group.

  Examples of the acrylate monomer having no aromatic ring and cyclohexyl group include, for example, methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), butyl acrylate (n-, i-, s-, t-), pentyl acrylate (n-, i-, s-), hexyl acrylate (n-, i-), heptyl acrylate (n-, i-), octyl acrylate (n-, i-) , Nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), acrylic acid (2-ethylhexyl), acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3-hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), acrylic acid 2-methoxy-ethyl), acrylic acid (2-ethoxyethyl), or the acrylic acid ester may include those obtained by changing the methacrylic acid ester.

  The acrylic polymer is a homopolymer or copolymer of the above-mentioned monomers, but it is preferable that the acrylic acid methyl ester monomer unit has 30% by weight or more, and the methacrylic acid methyl ester monomer unit has 40% by weight or more. It is preferable. In particular, a homopolymer of methyl acrylate or methyl methacrylate is preferred.

  Polymers obtained by polymerizing the above ethylenically unsaturated monomers and acrylic polymers are both excellent in compatibility with cellulose ester resins, excellent in productivity without evaporation and volatilization, and as protective films for polarizing plates. Good holdability, low moisture permeability, and excellent dimensional stability.

  In the present invention, an acrylic acid or methacrylic acid ester monomer having a hydroxyl group is not a homopolymer but a constituent unit of a copolymer. In this case, the acrylic acid or methacrylic acid ester monomer unit having a hydroxyl group is preferably contained in the acrylic polymer in an amount of 2 to 20% by weight.

  In the present invention, a polymer having a hydroxyl group in the side chain can also be preferably used as an additive for reducing the thickness direction retardation (Rt). The monomer unit having a hydroxyl group is the same as the monomer described above, but acrylic acid or methacrylic acid ester is preferable. For example, acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3 -Hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), acrylic acid-p-hydroxymethylphenyl, acrylic acid-p- (2-hydroxyethyl) phenyl, or these acrylic acids. The thing replaced by methacrylic acid can be mentioned, Preferably, it is 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate. The acrylic acid ester or methacrylic acid ester monomer unit having a hydroxyl group in the polymer is preferably contained in the polymer in an amount of 2 to 20% by weight, more preferably 2 to 10% by weight.

  A polymer containing 2 to 20% by weight of the above-mentioned monomer unit having a hydroxyl group is, of course, excellent in compatibility with cellulose ester resin, retention property, dimensional stability, and low moisture permeability. In particular, it has excellent adhesiveness with a polarizer as a protective film for a polarizing plate, and has an effect of improving the durability of the polarizing plate.

  In the present invention, it is preferable that at least one terminal of the main chain of the polymer has a hydroxyl group. The method of having a hydroxyl group at the end of the main chain is not particularly limited as long as it has a hydroxyl group at the end of the main chain, but radical polymerization having a hydroxyl group such as azobis (2-hydroxyethylbutyrate). A method of using an initiator, a method of using a chain transfer agent having a hydroxyl group such as 2-mercaptoethanol, a method of using a polymerization terminator having a hydroxyl group, a method of having a hydroxyl group at the terminal by living ion polymerization, Using a polymerization catalyst in which a compound having one thiol group and a secondary hydroxyl group as disclosed in JP-A No. 2000-128911 or JP-A No. 2000-344823, or a combination of the compound and an organometallic compound is used. It can be obtained by a polymerization method or the like, and the method described in the publication is particularly preferable. The polymer produced by the method related to the description in this publication is commercially available as Act Flow Series manufactured by Soken Chemical Co., Ltd., and can be preferably used.

  In the present invention, the polymer having a hydroxyl group at the terminal and / or the polymer having a hydroxyl group in a side chain has an effect of significantly improving the compatibility and transparency of the polymer with respect to the cellulose ester resin.

  In the present invention, useful additives for reducing the thickness direction retardation (Rt) include, in addition to the above, for example, an ester compound of diglycerin polyhydric alcohol and fatty acid described in JP-A No. 2000-63560, An ester or ether compound of a hexose sugar alcohol described in JP-A-2001-247717, a trialiphatic alcohol phosphate compound described in JP-A-2004-315613, and a general formula (1) described in JP-A-2005-41911 A phosphoric acid ester compound described in JP-A No. 2004-315605, a styrene oligomer described in JP-A No. 2005-105139, and a polymer of a styrene monomer described in JP-A No. 2005-105140. .

  In the present invention, an additive for reducing the thickness direction retardation (Rt) can also be found by the following method.

  A dope formulation in which a cellulose ester resin is dissolved in methylene chloride is formed on a glass plate and dried at 120 ° C./15 min to prepare a cellulose ester resin film having a thickness of 80 μm. The retardation in the thickness direction of the cellulose ester-based resin film is measured, and this is defined as Rt1.

  Next, 10% by weight of the above polymer additive is added to the cellulose ester resin and dissolved in methylene chloride to prepare a dope formulation. A cellulose ester resin film having a film thickness of 80 μm is prepared in the same manner as described above for this dope formulation. The retardation in the thickness direction of the cellulose ester-based resin film is measured, and this is defined as Rt2.

And the relationship of retardation in the thickness direction of the above two cellulose ester resin films is Rt2 <Rt1
If so, it can be said that the polymer additive added to the cellulose ester-based resin is an additive for reducing the thickness direction retardation (Rt).

  In the present invention, it is preferable to add a so-called plasticizer in order to improve dimensional stability under wet heat. It has not been known so far that a plasticizer has an effect of improving dimensional stability under wet heat. As the plasticizer, conventionally known plasticizers for cellulose ester resins can be preferably used. In particular, those having excellent compatibility are preferred, and for example, phosphate esters and carboxylic acid esters are preferred. Examples of phosphate esters include triphenyl phosphate, tricresyl phosphate, phenyl diphenyl phosphate, and the like. Examples of carboxylic acid esters include phthalic acid esters and citric acid esters. Examples of phthalic acid esters include dimethyl phthalate, diethyl phthalate, dioctyl phthalate, and diethyl hexyl phthalate. Citric acid esters include acetyltriethyl citrate and acetyl citrate. Mention may be made of tributyl. In addition, butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, triacetin, and the like are also included. Alkylphthalylalkyl glycolates are also preferably used for this purpose. The alkyl in the alkylphthalylalkyl glycolate is an alkyl group having 1 to 8 carbon atoms. Examples of alkyl phthalyl alkyl glycolates include methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, octyl phthalyl octyl glycolate, methyl phthalyl ethyl glycolate, Ethyl phthalyl methyl glycolate, ethyl phthalyl propyl glycolate, propyl phthalyl ethyl glycolate, methyl phthalyl propyl glycolate, methyl phthalyl butyl glycolate, ethyl phthalyl butyl glycolate, butyl phthalyl methyl glycolate, butyl Phthalyl ethyl glycolate, propyl phthalyl butyl glycolate, butyl phthalyl propyl glycolate, methyl phthalyl octyl glycolate, ethyl phthalyl octyl Collate, octyl phthalyl methyl glycolate, octyl phthalyl ethyl glycolate and the like can be mentioned, such as methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, Octyl phthalyl octyl glycolate is preferable, and ethyl phthalyl ethyl glycolate is particularly preferably used. A plasticizer having a large molecular weight is preferable because it can suppress volatilization during extrusion. Examples of these include aliphatic polyesters composed of glycol and dibasic acids such as polyethylene adipate, polybutylene adipate, polyethylene succinate and polybutylene succinate, and fats composed of oxycarboxylic acids such as polylactic acid and polyglycolic acid. Aliphatic polyesters composed of lactones such as aromatic polyesters, polycaprolactone, polypropiolactone and polyvalerolactone, and vinyl polymers such as polyvinylpyrrolidone. These plasticizers can be used alone or in combination.

  It is preferable to contain 1-30 weight% of content of the plasticizer mentioned above with respect to cellulose-ester-type resin. By containing the plasticizer in this range, the dimensional stability of the cellulose ester resin film under wet heat can be improved.

  Examples of ultraviolet absorbers that can be used in the present invention include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like. A benzotriazole-based compound with little coloring is preferable. Further, ultraviolet absorbers described in JP-A-10-182621 and JP-A-8-337574, and polymer ultraviolet absorbers described in JP-A-6-148430 are also preferably used. As an ultraviolet absorber, from the viewpoint of preventing the deterioration of polarizers and liquid crystals, it is excellent in the ability to absorb ultraviolet rays having a wavelength of 370 nm or less, and from the viewpoint of liquid crystal display properties, the absorption of visible light having a wavelength of 400 nm or more is small. Is preferred.

  Specific examples of UV absorbers useful in the present invention include 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) ) Benzotriazole, 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl)- 5-chlorobenzotriazole, 2- (2′-hydroxy-3 ′-(3 ″, 4 ″, 5 ″, 6 ″ -tetrahydrophthalimidomethyl) -5′-methylphenyl) benzotriazole, 2,2-methylenebis ( 4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol), 2- (2'-hydroxy-3'- ert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2H-benzotriazol-2-yl) -6- (linear and side chain dodecyl) -4-methylphenol, octyl-3- [3-tert-butyl-4-hydroxy-5- (chloro-2H-benzotriazol-2-yl) phenyl] propionate and 2-ethylhexyl-3- [3-tert-butyl-4-hydroxy-5- (5 -Chloro-2H-benzotriazol-2-yl) phenyl] propionate and the like can be mentioned, but not limited thereto. As commercially available products, TINUVIN 109, TINUVIN 171 and TINUVIN 326 (all manufactured by Ciba Specialty Chemicals) can be preferably used.

  Specific examples of benzophenone compounds include 2,4-dihydroxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, bis (2-methoxy-4-hydroxy- 5-benzoylphenylmethane) and the like, but is not limited thereto.

  The blending amount of these ultraviolet absorbers is preferably in the range of 0.01 to 10% by weight, more preferably 0.1 to 5% by weight with respect to the cellulose ester resin. If the amount used is too small, the UV absorption effect may be insufficient, and if it is too large, the transparency of the film may be deteriorated. The ultraviolet absorber is preferably one having high heat stability.

  When the substitution degree of the acetyl group of the cellulose ester resin is low, the heat resistance may be lowered. In this case, it is effective to add an antioxidant.

  As the antioxidant, a hindered phenol compound is preferably used, and 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl- 4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3,5 -Di-t-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino) -1,3,5 -Triazine, 2,2-thio-diethylenebis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3 -Di-t-butyl-4-hydroxyphenyl) propionate, N, N'-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide), 1,3,5-trimethyl -2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-t-butyl-4-hydroxybenzyl) -isocyanurate, etc. Can be mentioned. In particular, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] is preferred. Further, for example, hydrazine-based metal deactivators such as N, N′-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine and tris (2,4-di-t A phosphorus-based processing stabilizer such as -butylphenyl) phosphite may be used in combination.

  In order to impart slipperiness to the cellulose derivative in the present invention, it is preferable to add fine particles such as a matting agent. Examples of the fine particles include fine particles of an inorganic compound or fine particles of an organic compound.

  Examples of the fine particles of the inorganic compound include fine particles of silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, tin oxide and the like. Of these, fine particles of a compound containing a silicon atom are preferred, and fine silicon dioxide particles are particularly preferred. Examples of the silicon dioxide fine particles include Aerosil 200, 200V, 300, R972, R972V, R974, R202, R812, R805, OX50, and TT600 manufactured by Aerosil Co., Ltd.

  Examples of the organic compound fine particles include fine particles such as acrylic resin, silicone resin, fluorine compound resin, and urethane resin.

  The primary particle size of the fine particles is not particularly limited, but the average particle size in the film is preferably about 0.05 to 5.0 μm. More preferably, it is 0.1-1.0 micrometer.

  When the cellulose ester film is observed with an electron microscope or an optical microscope, the average particle diameter of the fine particles indicates an average value of the lengths in the major axis direction of the particles at the observation position of the film. As long as the particles are observed in the film, they may be primary particles or secondary particles in which the primary particles are aggregated, but most of the particles that are usually observed are secondary particles.

As an example of the measurement method, 10 vertical cross-sectional photographs are taken at random for each film, and the number of particles in 100 μm ² whose major axis length is in the range of 0.05 to 5 μm for each cross-sectional photograph. Count. The average value of the major axis lengths of the particles counted at this time is obtained, and a value obtained by averaging the average values of 10 locations is defined as the average particle size.

  In the case of fine particles, the primary particle size, the particle size after being dispersed in a solvent, and the particle size added to the film often change, and it is important that the fine particles are finally combined with the cellulose ester in the film. It is to control the particle size formed by aggregation.

  When the average particle diameter of the fine particles exceeds 5 μm, haze deterioration or the like may be observed, or it may cause a failure in a wound state as a foreign matter. Moreover, when the average particle diameter of fine particles is less than 0.05 μm, it becomes difficult to impart slipperiness to the film.

  The fine particles are used by adding 0.04 to 0.5% by weight to the cellulose ester. Preferably, 0.05 to 0.3% by weight, more preferably 0.05 to 0.25% by weight is added. When the amount of fine particles added is 0.04% by weight or less, the film surface roughness becomes too smooth and blocking occurs due to an increase in the friction coefficient. If the amount of fine particles added exceeds 0.5% by weight, the coefficient of friction on the film surface will be too low, causing winding misalignment during winding, and the transparency of the film will be low and haze will be high. The above range is essential because it has no value as a film.

  For the dispersion of the fine particles, it is preferable to treat the composition in which the fine particles and the solvent are mixed with a high-pressure dispersion apparatus. The high-pressure dispersion apparatus used in the present invention is an apparatus that creates special conditions such as high shear and high pressure by passing a composition in which fine particles and a solvent are mixed at high speed through a narrow tube.

It is preferable that the maximum pressure condition inside the apparatus is 980 N / cm ² or more in a thin tube having a tube diameter of 1 to 2000 μm, for example, by processing with a high-pressure dispersion apparatus. More preferably, the maximum pressure condition inside the apparatus is 1960 N / cm ² or more. Further, at that time, those having a maximum reaching speed of 100 m / sec or more and those having a heat transfer speed of 100 kcal / hr or more are preferable.

  Examples of the high-pressure dispersing device as described above include an ultra-high pressure homogenizer (trade name: Microfluidizer) manufactured by Microfluidics Corporation or a nanomizer manufactured by Nanomizer, and other manton gorin type high-pressure dispersing devices such as those manufactured by Izumi Food Machinery. A homogenizer etc. are mentioned.

  In the present invention, when an optical film is formed by a solution casting film forming apparatus, it can be formed by a known method.

  When correcting the retardation of the optical film produced by the above method to a desired value, the film may be stretched or shrunk in the length direction or the width direction. In order to shrink in the length direction, for example, there is a method in which width stretching is temporarily clipped out and relaxed in the length direction, or the film is shrunk by gradually narrowing the interval between adjacent clips of the transverse stretching machine. is there. The latter method can be performed by using a general simultaneous biaxial stretching machine and by using a pantograph method or a linear drive method to drive the clip portion in a smooth and gradually narrowing interval between adjacent clips in the longitudinal direction. it can. In addition, since the film is deform | transforming 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.

  In the winding process of the obtained optical film, a generally used winding method may be used, such as a constant torque method, a constant tension method, a taper tension method, a program tension control method with a constant internal stress, and the like. You can use them properly.

  In the optical film manufacturing apparatus of the present invention, it is preferable that the production speed of the optical film is 30 to 100 m / min.

  In the present invention, when the optical film having a film thickness of 35 to 85 μm is formed by the above solution casting film forming apparatus, the film is cast on a metal rotating drum or a metal rotating endless belt (support), and after peeling. In a device for drying or cooling and stretching and winding a stretched film, one device for slitting the film end between peeling and winding is provided at one end of at least one of the left and right ends of the film. The surface roughness (arithmetic mean roughness: Ra) of the cross section of the film installed as described above and slit at least by the final slitting device is defined to be 0.05 to 1.2 μm.

  Here, the surface roughness of the film cross-section may be measured, for example, using a surface roughness measuring device (NewView 5010) manufactured by ZYGO, under the apparatus conditions of an objective lens 50 times and an image zoom 1.3 times. In this case, the measurement conditions are set as appropriate with the Measurement Ctrl key, and the measured data is subjected to data processing with the Analyze Control key set as appropriate.

  In the optical film manufacturing apparatus of the present invention, it is preferable that the number of slit devices installed at one end of the film is 1 to 3 per one end of the film.

  The product width of the final optical film is preferably 1400 mm or more and 1700 mm or less.

  In the optical film manufacturing apparatus of the present invention, it is preferable that the film slitting device is composed of a disk-shaped rotating upper blade and a roll-shaped rotating lower blade.

  Here, the disk-shaped rotating upper blade of the slit device has a diameter of 30 to 300 mm and a thickness of the cut portion of 0.3 to 3 mm, and the rotating upper blade is made of super steel, super steel fine particles, SKD ( Alloy tool steel) or SKH (high speed tool steel). Moreover, it is preferable to make the toe-in angle of the upper blade 30 to 90 degrees.

  The roll-shaped rotating lower blade has a roll diameter of 75 to 200 mm, and the roll material of the rotating lower blade is super steel, super steel fine particles, SKD, or SKH.

  In the optical film manufacturing apparatus of the present invention, the film slitting device may be constituted only by a disk-shaped rotating upper blade. In this case, the disk-shaped rotating upper blade of the slit device has a diameter of 30 to 300 mm and a thickness of the cut portion of 0.3 to 3 mm, and the material of the rotating upper blade is super steel, super steel fine particles, SKD, Or SKH.

  In the present invention, it is preferable that the temperature around the slitter is 20 to 50 ° C. and the humidity is 50 to 70% RH.

  Further, in the present invention, it is preferable to provide a suction device in which the periphery of the upper blade is boxed and sucked in a range of wind speed of 0.8 to 10 m / sec. In this case, the suction position of the end film is the downstream side in the base transport direction from the slitting point.

  In the present invention, it is preferable to provide a mechanism for conveying the slit end film (film piece) to the next cutting step. For example, a mechanism for niping and / or sucking the slit end film is provided. Is preferred.

  Furthermore, it is preferable to provide a mechanism for niping and / or winding the slit end film.

  Here, it is preferable that the draw ratio, that is, the value obtained by dividing the nip and / or winding film speed by the slit edge film speed is 0.8 to 1.5.

  Further, it is preferable to set the suction pressure to −100 to −1000 Pa. The nip pressure is preferably 0.1 to 17 MPa.

  In the optical film manufacturing apparatus of the present invention, the slit end film has a width of 20 to 150 mm and a thickness of 30 to 150 μm.

  In the present invention, there is also a method of slitting after the transport film is covered with a masking base.

  The masking base material is not particularly limited as long as it can protect the film, and examples thereof include a polyethylene terephthalate (PET) film, a polyethylene (PE) film, and a polypropylene (PP) film.

  Moreover, it is preferable that the charged amount of the slit end film is in the range of 0 to ± 10 kV. For this reason, it is preferable to provide a static eliminator around the upper blade. As the static eliminator, for example, any one of a static eliminator, a static eliminator blower, and a static eliminator is used.

  The slit end film (film fragment) is preferably treated with an edge cleaner.

  Moreover, it is preferable to process the edge part of the product film after a slit with a web cleaner, and to remove chips.

  In the present invention, the film thickness of the optical film varies depending on the purpose of use, but as a finished film, the film thickness range used in the present invention is preferably in the range of 30 to 120 μm, particularly 35 to 35 μm for the recent thin tendency. A range of 85 μm is preferred. The film thickness can be adjusted by controlling the extrusion flow rate, the slit gap of the die base, the speed of the cooling drum, etc. so as to obtain a desired thickness. Further, as a means for making the film thickness uniform, it is preferable to use a film thickness detection means to feed back and adjust the programmed feedback information to each of the above devices.

  In forming an optical film with a casting film forming apparatus, the present invention casts the film on a metal rotating drum (support), peels, cools and stretches, and peels off the stretched film. At least one device for slitting the film end between the back and the end of the film is installed on at least one end of the left and right ends of the film, and at least the surface of the film cross section slit by the final slitting device The roughness (arithmetic average roughness: Ra) is defined as 0.05 to 1.2 μm. According to the optical film manufacturing apparatus of the present invention, the index of the cross-sectional quality at the end of the optical film is set as a target. By ensuring a good optical film end cross section, it is possible to achieve quality maintenance such as reduction of film cross-section delamination, prevention of film breakage, and improvement of film dimensional stability. Manner, it is possible to manufacture an optical film having excellent quality is not coated film defects.

  In addition, according to the present invention, in order to maintain the quality of the optical film, the correspondence between the slitter equipment and the slitter conditions is clarified, and the above conventional problems can be solved.

  In manufacturing the optical film according to the present invention, in the solution casting film forming apparatus, a dope preparation step, a casting step, a drying step, a surface processing step, and a winding step are sequentially performed.

  Although illustration is omitted, first, as a film material resin, for example, a cellulose ester-based resin and a solvent are introduced into a dope dissolving kettle and mixed and dissolved to prepare a cellulose ester-based resin solution (dope). Thereafter, the dope is guided to a primary filter and subjected to primary filtration. The dope after the primary filtration is temporarily stored in a dope stock kettle. Next, the dope is introduced into a secondary filter and subjected to secondary filtration.

  On the other hand, after an additive solution such as an ultraviolet absorber prepared in the additive solution dissolution vessel is filtered in advance, the additive solution such as an ultraviolet absorber is added in-line to the dope. The dope after addition is introduced into a casting die, and a cellulose ester film is produced by a solution casting film forming apparatus.

  In the casting process of the solution casting film forming apparatus, the dope obtained as described above is fed to a pressure die through a pressurized metering gear pump, and an endless metal belt that moves infinitely at the casting position or This is a step of casting a dope from a pressure die onto a casting support of a rotating metal drum. The surface of the casting support is a mirror surface.

  Other casting methods include a doctor blade method in which the film thickness of the cast dope film is adjusted with a blade, or a reverse roll coater method in which the film is adjusted with a reverse rotating roll. A pressure die that can be prepared and facilitates uniform film thickness is preferred. Examples of the pressure die include a coat hanger die and a T die, and any of them is preferably used.

  In order to increase the film forming speed, two or more pressure dies may be provided on the casting support, and the dope amount may be divided and stacked. Or the inside of die | dye can be divided | segmented by a slit, and several dope liquids from which a composition differs can be cast simultaneously (it is also called co-casting), and the cellulose-ester film of a laminated structure can also be obtained.

  Thus, the obtained dope is cast on a support such as a belt or a drum to form a film. The present invention is particularly effective in a solution casting film forming apparatus using a belt. This is because it is easy to finely adjust the drying conditions on the support as described later.

  In the solvent evaporation step, the web (in the present invention, the dope is cast on the casting support and the formed dope film is called a web) is heated on the casting support to evaporate the solvent. It is. In order to evaporate the solvent, there are a method of blowing air from the web side and / or a method of transferring heat from the back side of the support by a liquid, a method of transferring heat from the front and back by radiant heat, and the like. Drying efficiency is preferred. A method of combining them is also preferable. The web on the support after casting is preferably dried on the support in an atmosphere at a temperature of 20 to 100 ° C. In order to maintain the atmosphere at a temperature of 20 to 100 ° C., it is preferable to apply hot air at this temperature to the upper surface of the web or to heat by means such as infrared rays.

  In particular, in the present invention, it is desirable to peel the web from the support within 30 to 90 seconds after casting. Here, if it peels in less than 30 seconds, not only the surface quality of a film will fall but it is unpreferable also in terms of moisture permeability. If the drying time is longer than 90 seconds, it is not preferable because surface quality is deteriorated due to deterioration of peelability and strong curling occurs in the film.

  In the peeling step, the web in which the solvent has evaporated on the support is peeled off from the support at the peeling position. The peeled web is sent to the next process. If the residual solvent amount of the web at the time of peeling (the following formula) is too large, it will be difficult to peel, or conversely, if it is peeled off after sufficiently drying on the support, part of the web will be peeled off .

The temperature at the peeling position on the support is preferably 10 to 40 ° C, more preferably 11 to 30 ° C. The amount of residual solvent of the web at the peeling position is preferably 60 to 125% by weight.

  In the present invention, the residual solvent amount of the web is defined by the following formula.

Residual solvent amount = (weight before heat treatment of web−weight after heat treatment of web) / (weight after heat treatment of web) × 100%
Note that the heat treatment for measuring the residual solvent amount means that the heat treatment is performed at a temperature of 115 ° C. for one hour.

  In order to adjust the residual solvent amount at the time of peeling as described above, the surface temperature of the casting support after casting is controlled, and the casting of the organic solvent from the web can be performed efficiently. It is preferable to set the temperature at the peeling position on the support for the above-mentioned temperature range. In order to control the temperature of the support, it is preferable to use a heat transfer method with good heat transfer efficiency. For example, a back surface heat transfer method using a liquid is preferable.

  The heat transfer method using radiant heat or hot air is difficult to control the temperature of the support, and is not the preferred method. However, in the belt (support) machine, the temperature control at the place where the belt to be transferred has come down is moderate. The belt temperature can be adjusted with a gentle breeze.

  The temperature of the support can be partially changed by dividing the heating means, and can be set to different temperatures such as a casting position, a drying part, and a peeling position of the casting support.

  As a method for increasing the film forming speed (because the film is peeled off while the residual solvent amount is as large as possible, the film forming speed can be increased), there is a gel casting method (gel casting) in which even a large amount of residual solvent can be peeled off.

  For example, a poor solvent for the cellulose ester-based resin is added to the dope, and after the dope is cast, the gel is formed, and the temperature of the support is lowered to form a gel. There is also a method of adding a metal salt in the dope. By gelling on the support and strengthening the film, it is possible to accelerate the peeling and increase the film forming speed.

  After the optical film according to the present invention is formed, when the residual solvent amount is 40 wt% or more, the film starts to be stretched in the MD direction, and when the residual solvent amount is less than 40 wt%, the TD direction It is preferable to stretch the film. When the residual solvent amount is 40% by weight or more, the film is stretched in the MD direction, and when the residual solvent amount is less than 40% by weight, it is stretched in the TD direction. If stretched in both the MD and TD directions in the state, even if stretched in the MD direction and the orientation of the cellulose ester resin is increased, the orientation is disturbed by stretching in the TD direction and the elastic modulus is improved. This is because the effect of is reduced. In the present invention, the cellulose ester resin film can maintain the improvement in elastic modulus without disturbing the orientation of the cellulose ester resin. When the amount of residual solvent is 60 to 120% by weight, it is more preferable to start stretching the film in the MD direction, and most preferably 90 to 110% by weight. When the residual solvent amount is less than 1 to 30% by weight, it is more preferable to stretch in the TD direction, and most preferably 5 to 20% by weight.

  In order to stretch in the MD direction, the peeling tension is preferably 80 N / m or more, particularly preferably 80 to 200 N / m. Since the web after peeling is also in a high residual solvent state, stretching in the MD direction can be performed by maintaining the same tension as the peeling tension. As the web dries and the residual solvent amount decreases, the draw ratio in the MD direction decreases.

  In this invention, it is preferable that the roll span of the extending | stretching zone which extends | stretches a cellulose-ester-type resin film to MD direction is 1.0 m or less. In the present invention, when a cellulose ester resin film having a molecular weight distribution as described above is stretched in the MD direction in a state of a high residual solvent amount, slippage in the MD direction is likely to occur, and the roll span is 1.0 m or less. And slipping can be prevented. Moreover, 10-40 degreeC is preferable for the film temperature when extending | stretching to MD direction, It is because the planarity of a film becomes good by setting it as this range.

In the present invention, the draw ratio in the MD direction was calculated from the rotation speed of the belt support and the tenter operation speed.

  In order to stretch in the TD direction, for example, the entire drying process or a part of the process as shown in Japanese Patent Application Laid-Open No. 62-46625 is performed while the width ends of the web are held with clips or pins in the width direction. A drying method (referred to as a tenter method), among them, a tenter method using a clip and a pin tenter method using a pin are preferably used.

  The drying temperature when performing the tenter is preferably 110 to 160 ° C. The lower the drying temperature, the less the transpiration of the UV absorber, the plasticizer, etc., the better the process contamination, and the higher the drying temperature, the better the flatness and elastic modulus of the film. When the cellulose ester-based resin film is stretched, foreign matters are likely to protrude on the surface, and foreign matter failures occur more than usual. Therefore, the present invention is particularly effective in a cellulose ester resin film having a stretching process.

  In the present invention, the retardation value of the film is measured by three-dimensional refractive index measurement at a wavelength of 590 nm using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments), and the obtained refractive indexes Nx and Ny. , Nz.

  The in-plane retardation value Ro is preferably 20 to 200 nm, and the retardation value Rt in the thickness direction is preferably in the range of 70 to 400 nm.

Ro = (Nx−Ny) × d
Rt = ((Nx + Ny) / 2−Nz) × d
(In the formula, Nx, Ny, and Nz represent the refractive indexes in the principal axes x, y, and z, respectively, of the refractive index ellipsoid, and Nx, Ny represent the refractive index in the film in-plane direction, and Nz represents the thickness direction of the film. In addition, Nx ≧ Ny, and d represents the thickness (nm) of the film.
In the present invention, the cellulose ester-based resin film has an angle θ (radian) formed between the slow axis direction and the film forming direction and a retardation value Ro in the in-plane direction, and particularly a protective film for a polarizing plate, etc. It is preferably used as an optical film.

P ≦ 1-sin ² (2θ) sin ² (πRo / λ)
Here, P is 0.9999 or less.

  θ is the angle (° radians) formed between the slow axis direction in the film plane and the film forming direction (straight direction of the film), and λ is the three-dimensional refractive index measurement for obtaining the above Nx, Ny, Nz, and θ. The wavelength of light is 590 nm, and π is the circumference.

  In the drying process, the web is dried while holding the width using a drying device that alternately conveys the web through rolls arranged in a staggered pattern and / or a tenter device that conveys while holding both ends of the web with clips or pins. It is a process to do. Maintaining the conveyance tension in the drying step as low as possible is preferable because the retardation value Ro can be maintained low, and is preferably 190 N / m or less. Further, it is preferably 170 N / m or less, more preferably 140 N / m or less, and particularly preferably 60 to 130 N / m. In particular, it is effective to maintain the above-mentioned conveyance tension range until the residual solvent amount in the film is at least 5% by weight or less.

  As a drying means, hot air is generally blown on both sides of the web, but there is also a means of heating by applying microwaves instead of wind. Too rapid drying tends to impair the flatness of the finished film. Drying at a high temperature is preferably carried out from about 8% by weight or less of residual solvent. Throughout the whole, the drying temperature is approximately 100 to 150 ° C.

  In the drying process after peeling from the casting support surface, the web tends to shrink in the width direction by evaporation of the solvent. The sharper the drying at higher temperatures, the greater the shrinkage.

  Drying while suppressing this shrinkage as much as possible is preferable for improving the flatness of the finished film.

  From this viewpoint, for example, a method of drying all or part of the drying process as shown in JP-A-62-46625 while holding the width at both ends of the web with clips or pins in the width direction ( Among them, a tenter method using a clip and a pin tenter method using a pin are preferably used.

  At this time, the stretching ratio in the width direction is preferably 1 to 12% when used for the purpose of expanding the viewing angle of the liquid crystal display device operating in the IPS mode of the present invention. The retardation value Ro can be controlled by the draw ratio.

  When the tenter is used, the residual solvent amount of the web is preferably 40 to 100% by weight at the start of the tenter, and drying is performed while the tenter is applied until the residual solvent amount of the web becomes 10% by weight or less. Preferably, it is 5% by weight or less.

  The drying temperature when performing the tenter is preferably 110 to 160 ° C. The lower the drying temperature, the less the transpiration of UV absorbers, plasticizers, etc., the better the process contamination, and the higher the drying temperature, the better the flatness of the film. In addition, by using an ultraviolet absorber that is difficult to evaporate even when the drying temperature is high, the effect is remarkably exhibited under the production conditions where the tenter drying temperature is high and the draw ratio is high.

  In the film drying step, the film peeled from the support is further dried, and the residual solvent amount is preferably 0.5% by weight or less, more preferably 0.1% by weight or less, and still more preferably Is 0 to 0.01% by weight or less.

  In the process from immediately after casting through the solution casting film forming apparatus to drying, the atmosphere in the drying apparatus may be air, but it may be performed in an inert gas atmosphere such as nitrogen gas, carbon dioxide gas, or argon. Good.

  Of course, the danger of the explosion limit of the evaporating solvent in the dry atmosphere must always be taken into account.

  The winding step is a step of winding as a cellulose ester resin film after the residual solvent amount in the web is 2% by weight or less, and the dimensional stability is reduced by making the residual solvent amount 0.4% by weight or less. A good film can be obtained.

  As a winding method, a generally used method may be used. There are a constant torque method, a constant tension method, a taper tension method, a program tension control method with a constant internal stress, and the like.

  Moreover, in the optical film manufacturing apparatus according to the present invention, when an optical film having a film thickness of 35 to 85 μm is formed by a solution casting film forming apparatus, it is preferable to use a cellulose acylate resin as a resin material for the film.

  To adjust the film thickness, it is necessary to control the dope concentration, the pumping amount, the slit gap of the die base, the extrusion pressure of the die, the speed of the casting support, etc., so that the desired thickness is obtained. Good.

  Further, as a means for making the film thickness uniform, it is preferable to use a film thickness detection means to feed back and adjust the programmed feedback information to each of the above devices.

  The film thickness of the cellulose ester-based resin film varies depending on the purpose of use, but the finished film is usually preferably in the range of 35 to 80 μm, and particularly in the range of 40 to 80 μm as the film for a liquid crystal image display device.

In the present invention, the cellulose ester-based resin film preferably has a tensile strength of 90 to 170 N / mm ² in both the MD direction and the TD direction, particularly preferably 120 to 160 N / mm ² .

  The moisture content is preferably 0.1 to 5%, more preferably 0.3 to 4%, and still more preferably 0.5 to 2%.

  In the present invention, the cellulose ester-based resin film desirably has a transmittance of 90% or more, more preferably 92% or more, and further preferably 93% or more. Further, the haze is preferably 0.5% or less, particularly preferably 0.1% or less, and more preferably 0%.

  In the present invention, in the cellulose ester resin film, the curl value preferably has a smaller absolute value, and the deformation direction may be the + direction or the-direction. The absolute value of the curl value is preferably 30 or less, more preferably 20 or less, and particularly preferably 10 or less. The curl value is expressed by a radius of curvature (1 / m).

  In the present invention, the cellulose ester resin film may be produced in the form of any of the solution casting film forming apparatuses described above.

  In the present invention, the slit device at the end of the film provided between the time after peeling and the winding is the same as in the case of the melt casting film forming apparatus.

  In the present invention, when forming an optical film having a film thickness of 35 to 85 μm with the above-described solution casting film forming apparatus, the film is cast on a metal rotating drum or a metal rotating endless belt (support), and after peeling, In a device for drying or cooling and stretching and winding a stretched film, one or more devices for slitting the film end between peeling and winding are provided at at least one end of the left and right ends of the film. The apparatus for producing the optical film of the present invention is to set the surface roughness (arithmetic mean roughness: Ra) of the cross section of the film installed and slit at least by the final slitting device to 0.05 to 1.2 μm. According to the above, it is possible to clarify the index of the cross-sectional quality of the target optical film end, and by securing a good cross-section of the end of the optical film, it is possible to reduce the film cross-section exfoliation, Quality maintenance such as prevention of breakage and improvement of film dimensional stability can be achieved, and as a result, an optical film having excellent quality free from coating defects of the film can be produced.

  According to the present invention, particularly in a material containing an additive for reducing the thickness direction retardation (Rt), by securing a favorable cross section at the end of the optical film, reduction of the film cross-section release, prevention of film breakage, film dimensional stability As a result, it is possible to provide an optical film having excellent quality free from film coating defects.

  Since the optical film according to the present invention is manufactured by the above-described optical film manufacturing apparatus, it can achieve quality maintenance such as improvement of the dimensional stability of the film, and as a result, there is no coating defect of the user. , It has excellent quality without any repelling or foreign matter failure that occurs when the user applies a coating film to the film.

  Since the optical film of the present invention has good moisture permeability, dimensional stability, etc., it is preferably used for a liquid crystal display member, specifically a polarizing plate protective film. In particular, the optical film of the present invention is preferably used in a protective film for a polarizing plate that has strict requirements for moisture permeability and dimensional stability.

  Here, the polarizing film is obtained by longitudinally stretching a conventionally used film, such as a polyvinyl alcohol film, that can be stretched and oriented with a dichroic dye such as iodine. Since the polarizing film itself does not have sufficient strength and durability, a polarizing plate is generally obtained by adhering a cellulose triacetate film having no anisotropy as a protective film to both sides thereof.

  In the above, the polarizing plate may be prepared by laminating the retardation film of the present invention to the polarizing plate, or the retardation film of the present invention also serves as a protective film and directly pasted to the polarizing film. It may be produced. The method of bonding is not particularly limited, but can be performed with an adhesive composed of an aqueous solution of a water-soluble polymer. The water-soluble polymer adhesive is preferably a completely saponified polyvinyl alcohol aqueous solution. Furthermore, as described above, a long polarizing plate can be obtained by laminating a long polarizing film stretched in the longitudinal direction and treated with a dichroic dye and a long retardation film of the present invention. . A polarizing plate is a sticking type in which a peelable sheet is laminated on one or both sides thereof via a pressure sensitive adhesive layer (for example, an acrylic pressure sensitive adhesive layer). Or the like can be easily attached).

  Said polarizing plate can be produced by a general method. For example, there is a method in which an optical film or a cellulose ester film is subjected to alkali saponification treatment, and a polyvinyl alcohol film is immersed and stretched in an iodine solution and bonded to both surfaces of a polarizing film using a completely saponified polyvinyl alcohol aqueous solution. is there. The alkali saponification treatment refers to a treatment in which the cellulose ester film is immersed in a high-temperature strong alkaline solution in order to improve the wetness of the water-based adhesive and improve the adhesion.

  In the present invention, the cellulose ester resin film includes a hard coat layer, an antiglare layer, an antireflection layer, an antifouling layer, an antistatic layer, a conductive layer, an optical anisotropic layer, a liquid crystal layer, an alignment layer, an adhesive layer, and an adhesive layer. Various functional layers such as a layer and an undercoat layer can be provided. These functional layers can be provided by a method such as coating or vapor deposition, sputtering, plasma CVD, or atmospheric pressure plasma treatment.

  Further, the polarizing plate constitutes at least one of the two polarizing plate protective films disposed on both sides of the polarizing film, and the polarizing plate thus obtained is A liquid crystal display device is obtained by using one or both surfaces of the liquid crystal cell.

  By using the protective film for a polarizing plate comprising the optical film of the present invention, it is possible to provide a polarizing plate excellent in durability, dimensional stability, and optical isotropy as well as thinning.

  Furthermore, a liquid crystal display device using this polarizing plate can maintain stable display performance over a long period of time.

  The present invention also provides an image display device capable of realizing an easy-to-view display having a high contrast ratio over a wide range using the optical film of the present invention, particularly a liquid crystal display device operating in the IPS mode.

  In addition, the optical film according to the present invention can also be used as a base material for an antireflection film or an optical compensation film.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

Example 1
In producing a cellulose triacetate film as an optical film of the present invention having a target dry film thickness of 40 μm by a solution casting film forming apparatus, a dope was first prepared.

(Dope composition)
Cellulose triacetate 85 parts by weight (acetyl substitution degree 2.88)
Thickness direction retardation (Rt) reducing agent Methyl acrylate polymer (Mw = 1000) 5 parts by weight Methyl methacrylate-hydroxyethyl acrylate copolymer 10 parts by weight
(Weight ratio 80/20 Mw = 8000)
UV absorber 2- (2′-hydroxy-3 ′, 5′-di-t-butylphenyl) benzotriazole 1.5 parts by weight Solvent Methylene chloride 475 parts by weight Ethanol 50 parts by weight The solution was completely dissolved with stirring and heating. Of the above materials, the ultraviolet absorber was added to the additive solution dissolving kettle in order to prepare the ultraviolet absorber additive solution described later. Thereafter, the dope in the dissolution vessel was guided to a primary filter, and the dope was subjected to primary filtration. In the primary filter, the dope solution was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd.

  The dope after the primary filtration was once stored in a dope stock kettle, and then the dope was introduced from the dope stock kettle into a secondary filter set with a sintered metal filter and subjected to secondary filtration.

  On the other hand, the ultraviolet absorbent additive solution prepared in the additive solution dissolution vessel is guided to a filter and filtered in advance. Then, the dope after the secondary filtration was introduced into the static mixer, and the pre-filtered ultraviolet absorbent additive solution was introduced before the static mixer, and the ultraviolet absorbent additive solution was added in-line to the dope.

  The dope after the addition of the ultraviolet absorber addition liquid was introduced into a casting die of a solution casting film forming apparatus, and was cast uniformly on a cooling drum support at 30 ° C. from the casting die. The solvent was evaporated on the cooling drum support until the residual solvent amount reached 100% by weight, and the peeling drum was peeled from the cooling drum support with a peeling tension of 162 N / m. The peeled cellulose triacetate web was evaporated at 35 ° C., slit to 1650 mm width, and then dried at a drying temperature of 135 ° C. while stretching 1.1 times in the width direction with a tenter. Then, drying was completed, conveying a drying zone of 110 degreeC and 120 degreeC with many rolls.

  Between the time after drying and the winding up, two devices for slitting the film edge were installed on the left and right ends of the film (two slit devices per side), and the film edge was slit. Here, the slitting device is composed of a disk-shaped rotating upper blade and a roll-shaped rotating lower blade, and the material of the rotating upper blade is a super steel material, the diameter of the rotating upper blade is 200 mm, and cutting The thickness of the blade at the place was 0.5 mm.

  On the other hand, the material of the roll-shaped rotary lower blade was a super steel material, and the roll diameter of the rotary lower blade was 100 mm.

  And when the surface roughness (arithmetic mean roughness: Ra) of the cross section of the slit film was measured, it was 0.2 micrometer. The slit film cross section was relatively smooth and free from chips. Further, in the production of the cellulose triacetate film, there was no breakage of the film during transportation.

  Here, the surface roughness of the cross section of the film was measured using a surface roughness measuring device (NewView 5010) manufactured by ZYGO under the conditions of an objective lens 50 times and an image zoom 1.3 times. In this case, the measurement conditions were set as appropriate with the Measurement Ctrl key, and the measured data was subjected to data processing with the Analyze Control key set as appropriate.

  Thus, a cellulose triacetate film having a final product width of 1400 mm and a film thickness of 40 μm was obtained and wound up by a winder.

  Moreover, the dimensional change rate of the film edge part-20 mm width location of the slit cellulose triacetate film was measured.

  Here, the dimensional change rate was evaluated by changing the dimension (width) after holding for 120 hours in an environment of a temperature of 90 ° C. and a humidity of 5% RH with respect to the dimension immediately after the production of the cellulose triacetate film (length in the width direction). Evaluation was made by taking the percentage of the length in the hand direction.

  As a result, the dimensional change rate at the end of the cellulose triacetate film to 20 mm wide was −0.15%.

  The production conditions of the cellulose triacetate film in Example 1 and the measurement results obtained are summarized in Table 1 below.

Example 2
In the same manner as in Example 1, a cellulose triacetate film was produced using a solution casting film forming apparatus. Here, the difference from the case of Example 1 is that a cellulose triacetate dope prepared in the same manner as in Example 1 was cast on a stainless steel band support at a temperature of 30 ° C., after stretching. Before winding up, three devices for slitting the film edge are installed on the left and right ends of the film (three slit devices per side), and the film ends are slit, the final product film A cellulose triacetate film having a thickness of 80 μm was produced.

  And when the surface roughness (arithmetic mean roughness: Ra) of the cross section of the slit film was measured like the case of the said Example 1, it was 0.5 micrometer. The slit film cross-section was relatively smooth and free from chips. Further, in the production of the cellulose triacetate film, there was no breakage of the film during transportation.

  Further, the dimensional change rate of the slit cellulose triacetate film at the film edge to 20 mm width was measured in the same manner as in Example 1 above. As a result, the dimensional change rate was -0.20%.

  The production conditions of the cellulose triacetate film in Example 2 and the measurement results obtained are shown in Table 1 below.

Example 3
In the same manner as in Example 1, a cellulose triacetate film was produced using a solution casting film forming apparatus. Here, the difference from Example 1 is that cellulose triacetate dope was cast on a stainless steel band support at a temperature of 30 ° C., and the disk-shaped rotating upper blade material of the slit device was SKD (alloy). Tool steel), the diameter of the rotating upper blade is 180 mm, the thickness of the blade at the cutting site is 0.8 mm, and the diameter of the roll-shaped lower blade whose material is super steel steel material is 120 mm.

  And when the surface roughness (arithmetic mean roughness: Ra) of the cross section of the slit film was measured like the case of the said Example 1, it was 0.3 micrometer. The slit film cross-section was relatively smooth and free from chips. Further, in the production of the cellulose triacetate film, there was no breakage of the cellulose triacetate film during transportation.

  Moreover, it was -0.20% when the dimensional change rate of the film edge part-20 mm width location of the slit cellulose triacetate film was measured similarly to the case of the said Example 1. FIG.

  The production conditions of the cellulose triacetate film in Example 3 and the measurement results obtained are shown in Table 1 below.

Comparative Example For comparison, the same procedure as in Example 2 was carried out, but two devices were installed on both the left and right ends of the film between the drying and winding, respectively. (The number of slit devices per side was two), and the film edge was slit. Here, the slitting device is composed of a disk-shaped rotating upper blade and a roll-shaped rotating lower blade, and the material of the rotating upper blade is SUS316 steel, the diameter of the rotating upper blade is 180 mm, and the cutting location The blade thickness was 0.2 mm.

  On the other hand, the material of the roll-shaped rotating lower blade was SUS316 steel, and the roll diameter of the rotating lower blade was 73 mm.

  And when the surface roughness (arithmetic mean roughness: Ra) of the cross section of the slit film was measured like the case of the said Example 1, it was 1.5 micrometers. Moreover, the cross section of the slit film was relatively rough.

  Thus, a cellulose triacetate film having a final product width of 1200 mm and a film thickness of 80 μm was obtained and wound up by a winder.

  Further, the dimensional change rate of the slit cellulose triacetate film at the film edge to 20 mm width was measured in the same manner as in Example 1 above. As a result, the dimensional change rate was -0.63%.

The production conditions of the cellulose triacetate film in this comparative example and the measurement results obtained are shown in Table 1 below.

  As is clear from the results in Table 1 above, in Examples 1 to 3 according to the present invention, the surface roughness (arithmetic mean roughness: Ra) of the slit film cross section is 0.2 μm, 0.5 μm, and The cross section of the slit film was 0.3 μm, and the cross section of the slit film was relatively smooth, without chips, and in the film formation of the cellulose triacetate film, there was no breakage of the film during transportation. Furthermore, the dimensional change rate of the slit cellulose triacetate film at the end of the film to 20 mm wide was very small, -0.15%, -0.20%, and -0.20%, respectively. .

  Therefore, according to the present invention, in particular, in a material containing an additive for reducing the thickness direction retardation (Rt), by securing a good film end section, it is possible to reduce film cross-section separation, prevent film breakage, and film Quality maintenance such as improvement in dimensional stability could be achieved, and as a result, an optical film having excellent quality free from film coating defects could be obtained.

  On the other hand, in the comparative example, the surface roughness (arithmetic mean roughness: Ra) of the slit film cross section was 1.5 μm, and the slit film cross section was relatively rough. And in the comparative example, in the film formation of the cellulose triacetate film, breakage of the film was observed when 94 minutes passed after the conveyance.

  Moreover, the dimensional change rate of the slit end portion of the cellulose triacetate film to 20 mm wide was −0.63%, which was very large.

Claims (10)

  In forming an optical film having a film thickness of 35 to 85 μm by a solution casting film forming apparatus using a dope composition containing a cellulose ester resin and an additive for reducing the thickness direction retardation (Rt), a metal rotation An apparatus for producing an optical film, which is cast on a drum or a metal rotating endless belt (hereinafter referred to as a support), peeled, dried and stretched, and takes up the stretched film. At least one device for slitting the film edge between the two right and left ends of the film is installed, and at least the surface roughness of the cross section of the film slit by the final slit device (arithmetic) Average roughness: Ra) is 0.05-1.2 micrometers, The manufacturing apparatus of the optical film characterized by the above-mentioned.   The apparatus for producing an optical film according to claim 1, wherein the number of slit devices installed at one end of the film is 1 to 3 per one end of the film.   The product width of the last optical film is 1300 mm or more and 1700 mm or less, The manufacturing apparatus of the optical film of Claim 1 or 2 characterized by the above-mentioned.   The film slitting device is composed of a disk-shaped rotating upper blade and a roll-shaped rotating lower blade, The production of an optical film according to any one of claims 1 to 3, apparatus.   The disk-shaped rotating upper blade of the slit device has a diameter of 30 to 300 mm and a thickness of the cutting portion of 0.3 to 3 mm, and the material of the rotating upper blade is super steel, super steel fine particles, SKD (alloy tool steel) ) Or SKH (high speed tool steel), the roll-shaped rotating lower blade has a roll diameter of 75 to 200 mm, and the roll material of the rotating lower blade is super steel, super steel fine particles, SKD The apparatus for producing an optical film according to claim 1, wherein the apparatus is any one of SKH and SKH.   The apparatus for producing an optical film according to any one of claims 1 to 3, wherein the film slitting device is constituted only by a disk-shaped rotating upper blade.   The disk-shaped rotating upper blade of the slit device has a diameter of 30 to 300 mm and a thickness of the cutting portion of 0.3 to 3 mm, and the material of the rotating upper blade is super steel, super steel fine particles, SKD, or SKH. It is either, The manufacturing apparatus of the optical film of Claim 6 characterized by the above-mentioned.   The optical film according to any one of claims 1 to 7, wherein the dope composition contains a cellulose ester resin and an acrylic polymer having a weight average molecular weight of 500 or more and 3000 or less. Manufacturing equipment.   The dope composition contains a cellulose ester resin and an acrylic polymer having a weight average molecular weight of 5,000 to 30,000, wherein the optical film according to any one of claims 1 to 8 is used. Manufacturing equipment.   An optical film manufactured by the optical film manufacturing apparatus according to claim 1.