JP2009073154A - Optical film and method for producing optical film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure the height of an embossed part after a film is taken up in the form of a roll in accordance with an increase in the speed of optical film production, to surely correspond to speed and length rises in the production of the optical film, to improve the quality of the film, and to provide the optical film which can respond to requirements for thinning, widening, and quality-improving a protective film for a polarizing plate etc., in recent years and a method for producing the optical film. <P>SOLUTION: In a solution casting film forming method or the method for producing the optical film in the form of a roll by the solution casting film forming method, when the temperature of knurling is T (°C), the glass transition temperature of a base film is Tg (°C), and the length of time while the base film is in contact with an embossing ring is s (sec), the knurling is carried out in a condition to meet a formula: 0.75≤(T-Tg)×s≤1.00 to produce the rolled optical film. <P>COPYRIGHT: (C)2009,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 method thereof.

  Optical film for liquid crystal display devices is increasing in production year by year due to the increase in size and spread of liquid crystal display devices, and in response to this, improvements in film production speed and expansion of film width are being studied. .

  Along with the improvement in productivity of such an optical film, the film forming process tends to increase in speed, and accordingly, the winding length of the film in the winding process tends to become longer. In general, before taking up the optical film with a winder, the end is slit into the product width and cut off, and knurled (embossed) to prevent sticking and scratching during film roll winding. Although it is applied to both ends in the width direction of the film, the role of embossing in the form of a take-up roll is becoming more and more important due to the recent increase in speed and length in the production of optical films.

  In the manufacturing process of the optical film, in order to ensure the roll-shaped winding shape, it is necessary to secure the embossed portion height (effective nar = embossed portion height after the film is wound into a roll shape) to some extent. However, as the speed increases, the height of the embossed part is less likely to be present. .

  As countermeasures, for example, the embossing temperature can be increased or the pressing pressure can be increased. However, if the embossing temperature is too high, thread-like foreign matter with resin dissolved around the embossed part of the film. If a large number of bearded foreign matters are generated or the pressing pressure in embossing is too high, there is a problem that holes are formed in the embossed portion of the film, which is not preferable.

Here, the following patent documents are related to knurling (embossing) in the method of manufacturing an optical film.
In the production of the photographic support described in JP-A-8-272040, the embossing treatment temperature of the biaxially stretched polyester is Tm-100 ° C + 50 ° C. Here, Tm is the melting point of the biaxially stretched polyester. In this patent document 1, the emboss residual rate after heat processing of biaxially stretched polyester is prescribed | regulated. In the production of an easily embossable film described in JP-A-9-24588, embossing is facilitated by stacking a polyester film and lowering the melting point of the polyester on the embossing side. JP, 2002-187148, A In the manufacturing method of the cellulose-ester film of patent documents 3, a film is good by making small the difference (variation) of the height of the conveyance direction (longitudinal direction) of the embossed part by knurling processing. However, it is only described that the knurling (embossing) temperature is preferably 150 ° C. or higher.

  However, in the above conventional method, the height of the embossed part due to the knurling process is difficult to come out with the speeding up of the production of the optical film, so that the height of the embossed part after winding the film into a roll is secured. There is a problem in that it cannot sufficiently cope with the increase in speed and length in the production of optical films.

  The object of the present invention is to solve the above-mentioned problems of the prior art, and as the production speed of the optical film increases, the height of the embossed part after the film is wound into a roll can be secured. It is possible to reliably cope with speeding up and lengthening in the production of the optical film, and there is little occurrence of thread-like foreign matter (hair-like foreign matter) in which resin is dissolved around the embossed part of the obtained optical film, and embossing It is possible to improve the quality of the film without causing perforation in the embossed part.As a result, it can sufficiently meet the recent demands for thinning, widening, and improving the quality of protective films for polarizing plates. It is in providing the optical film which can be manufactured, and its manufacturing method.

  In order to achieve the above object, the invention of claim 1 is characterized in that the widthwise end of the optical film obtained by the solution casting film forming method or the melt casting film forming method is slit to match the product width. After forming the base film, a knurling process is performed on the widthwise direction of the base film to form an embossed portion, and the roll-shaped optical film is produced by winding the film. Knurling under conditions that satisfy the following relational expression, where T (° C) is the processing temperature, Tg (° C) is the glass transition temperature of the base film, and s (seconds) is the time the base film is in contact with the embossing ring. And a roll-shaped optical film is manufactured.

0.75 ≦ (T−Tg) × s ≦ 1.00
Invention of Claim 2 is a manufacturing method of the optical film of Claim 1, Comprising: In the case of a knurling process, 10-20 degreeC cold wind is applied to the film discharge side of an embossing stamping roll, It is characterized by the above-mentioned.

  Invention of Claim 3 is an optical film manufactured by the manufacturing method of the optical film of Claim 1 or 2, Comprising: The effective nar defined by the following formula of a roll-shaped optical film is 2.5-7. 0.0 μm.

Effective knurl = (embossed part roll cross-sectional area−core cross-sectional area) / winding length−average film thickness The invention of claim 4 is an optical film produced by the method for producing an optical film of claim 1 or 2. In addition, the number of beard-like foreign substances adhering around the embossed portion of the roll-shaped optical film is 0 to 50 / cm ² .

The number of bearded foreign substances is preferably 0 to 20 / cm ² , more preferably 0 to 10 / cm ² .

  Invention of Claim 5 is an optical film manufactured by the manufacturing method of the optical film of Claim 1 or 2, Comprising: The winding length of a roll-shaped film is 3900 m or more and 9100 m or less, It is characterized by the above-mentioned. .

  The invention of claim 1 slits the widthwise end of the optical film obtained by the solution casting film forming method or the melt casting film forming method, and after forming a base film according to the product width, A method of manufacturing a roll-shaped optical film by forming an embossed part by applying a knurling process to a base film in the width direction of the base film, and winding the wound film at a processing temperature of T (° C.) and a base. When the glass transition temperature of the film is Tg (° C.) and the time that the base film is in contact with the embossing ring is s (seconds), knurling is performed under the conditions satisfying the following relational expression, and a roll-shaped optical film is formed. To manufacture.

0.75 ≦ (T−Tg) × s ≦ 1.00
According to the first aspect of the present invention, with the increase in the production speed of the optical film, the height of the embossed part after the film is wound up can be sufficiently secured, and the production speed of the optical film is increased. The length of the optical film can be surely accommodated, and there is little occurrence of thread-like foreign matter (bottle-like foreign matter) in which the resin is dissolved around the embossed portion of the resulting optical film. High quality can be achieved without causing perforation, and as a result, it is possible to sufficiently meet the recent demands for thinning, widening, and high quality of protective films for polarizing plates.

  Invention of Claim 2 is a manufacturing method of the optical film of Claim 1, Comprising: 10-20 degreeC cold wind is applied to the film discharge side of an embossing stamping roll in the case of a knurling process, Claim 2 According to the invention, since the resin portion melted by heat is cooled and solidified by cooling the film and the ring portion immediately after the embossing, the occurrence of thread-like foreign matter (beard-like foreign matter) can be suppressed, and the embossing height is sufficiently high. There is an effect that can be obtained.

  Invention of Claim 3 is an optical film manufactured by the manufacturing method of the optical film of Claim 1 or 2, Comprising: The effective nar defined by the following formula of a roll-shaped optical film is 2.5-7. According to the invention of claim 3, the height of the embossed portion after winding the film into a roll can be sufficiently secured, and the speed is increased and the length is increased in the production of the optical film. There is an effect that it is possible to cope with the problem.

Effective knurl = (embossed part roll cross-sectional area−core cross-sectional area) / winding length−average film thickness The invention of claim 4 is an optical film produced by the method for producing an optical film of claim 1 or 2. The number of the beard-like foreign matters adhering to the periphery of the embossed portion of the roll-shaped optical film is 0 to 50 / cm ^2. According to the invention of claim 4, the periphery of the embossed portion of the optical film In addition, there is little generation of thread-like foreign matter (stubble foreign matter) in which the resin is dissolved, and an effect is achieved that high quality can be achieved.

  Invention of Claim 5 is an optical film manufactured by the manufacturing method of the optical film of Claim 1 or 2, Comprising: The winding length of a roll-shaped film is 3900 m or more and 9100 m or less, Claims According to the invention of No. 5, there is an effect that it is possible to sufficiently cope with the increase in speed and length in the production of the optical film.

(* Please describe each claim if it has its own effect.)

  Hereinafter, the best mode for carrying out the present invention will be described in detail, but the present invention is not limited thereto.

  The method for producing an optical film according to the present invention includes slitting an end in the width direction of an optical film obtained by a solution casting film forming method or a melt casting film forming method, and forming a base film in accordance with the product width. After that, a knurling process is performed on the widthwise direction of the base film to form an embossed portion, and the roll-shaped optical film is produced by winding, and the knurling process temperature is set to T (° C. ), When the glass transition temperature of the base film is Tg (° C.) and the time during which the base film is in contact with the embossing ring is s (seconds), knurling is performed under the conditions satisfying the following relational expression, An optical film is manufactured.

0.75 ≦ (T−Tg) × s ≦ 1.00
The time s (second) during which the base film is in contact with the embossing ring can be changed by changing the film conveyance speed and the nip width, in other words, the pressing pressure. The nip width and the pressing pressure can be changed by adjusting the hardness of the rubber on the surface of the back roll made of a rubber roll, or by changing the diameter of the embossing ring and the back roll.

  In the above, if the value of (T−Tg) × s is less than 0.75, the embossed height cannot be obtained sufficiently, and the effective knurl in the wound state is lowered, so that the film sticking failure Or convex local deformation occurs, and the flatness as an optical film is not satisfied.

Also, if the value of (T-Tg) × s exceeds 1.00, the embossed height is too high and the effective knurl in the wound state becomes high as a result, so that the center of the winding looks like the horse's back It is not preferable because the flat shape as an optical film cannot be maintained. Further, when the temperature at the time of knurling which is the value of T is increased, the value of (T−Tg) × s is also increased. In this case, the temperature of T is increased until the value of (T−Tg) × s exceeds 1.00. If it is increased, a whisker-like failure occurs, which is not preferable.

  In the method for producing an optical film according to the present invention, it is preferable to apply cold air of 10 to 20 ° C. to the film discharge side of the embossing stamp roll during knurling. Here, during the knurling process, 10-20 ° C cold air is applied to the film discharge side of the embossing stamping roll because the resin part melted by heat is cooled and solidified by cooling the film and the ring part immediately after the embossing process. For this reason, the generation of thread-like foreign matters (beard-like foreign matters) can be suppressed, and a sufficiently high embossing height can be obtained.

  The optical film manufactured by the method for manufacturing an optical film of the present invention preferably has an effective nar defined by the following formula of the roll-shaped optical film of 2.5 to 7.0 μm. Here, the effective knurl is a so-called rolling value.

Effective nar = (embossed part roll cross-sectional area−core cross-sectional area) / winding length−average film thickness In the above, if the effective nar is less than 2.5 μm, a sticking failure between films may occur or a convex Since local deformation occurs and flatness as an optical film is not satisfied, it is not preferable. On the other hand, if the effective nar exceeds 7.0 μm, the center of the winding is recessed in a shape like the back of a horse and the flatness as an optical film cannot be maintained, which is not preferable.

In the optical film produced by the method for producing an optical film of the present invention, the number of whisker-like foreign substances adhering around the embossed portion of the roll-shaped optical film is preferably 0 to 50 / cm ² , more preferably from 0 to 20 pieces / cm ^2, more preferably from 0 to 10 / cm ^2.

In the above, the number of beard-like foreign matters adhering to the periphery of the embossed portion of the optical film is preferably as small as possible. When the number of beard-like foreign matters exceeds 50 / cm ² , the cleaning apparatus for processing as a polarizing plate If it cannot be completely removed and enters a liquid crystal display device as a foreign substance between the polarizer and the film, it becomes an image defect. The same applies to the case where application processing such as antireflection treatment or antiglare treatment is applied to the surface.

  In the optical film produced by the method for producing an optical film of the present invention, the roll length of the roll film is preferably 3900 m or more and 9100 m or less.

  Here, if the winding length of the roll film is less than 3900 m, it is not preferable because the time for switching the rolled-up roll becomes insufficient when the production speed is increased. Moreover, since the frequency of the film switching operation increases during the polarizing plate processing, the productivity is lowered. On the other hand, when the roll length of the roll film exceeds 9100 m, the load of the core increases due to the weight of the film, and even if the emboss is increased, the effective knurl cannot be maintained and sticking occurs.

  Hereinafter, the present invention will be described in detail.

  The method for producing an optical film of the present invention relates to knurling of an optical film produced by a solution casting film forming method or a melt casting film forming method. First, an optical film produced by a solution casting film forming method is used. A manufacturing method will be described.

  In the method for producing an optical film by the solution casting film forming method, various resins can be used as the film material, and among them, cellulose ester is preferable.

  A cellulose ester 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 groups is preferably 2.0 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 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.

  The cellulose used as a raw material for the cellulose ester used in the present invention is not particularly limited, and examples thereof include cotton linter, wood pulp, and kenaf. Moreover, the cellulose ester obtained from them can be mixed and used in arbitrary ratios, respectively.

  In the present invention, the number average molecular weight of the cellulose ester is preferably in the range of 60000 to 300000, since the mechanical strength of the resulting film is strong. Furthermore, 70000-200000 are preferable. The cellulose ester used in the present invention preferably has an Mw / Mn ratio of 1.4 to 3.0, more preferably 1.4 to 2.3.

  Since the average molecular weight and molecular weight distribution of the cellulose ester can be measured using high performance liquid chromatography, the number average molecular weight (Mn) and the weight average molecular weight (Mw) can be calculated using this, and the ratio can be calculated.

  The measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by weight
Detector: RI Model 504 (GL Science Co., Ltd.)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0 ml / min Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) Mw = 1,000,000-500 calibration curves with 13 samples were used. The 13 samples are preferably used at approximately equal intervals.

  The total acyl group substitution degree of the cellulose ester is 2.3 to 2.9, and 2.6 to 2.9 is preferably used. The total acyl group substitution degree can be measured according to ASTM-D817-96.

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

  In the method for producing an optical film according to the present invention, it is preferable to use a dope composition containing a cellulose ester and an additive for reducing the thickness direction retardation (Rt).

  In the present invention, reducing the thickness direction retardation (Rt) of the optical film is important in terms of expanding the viewing angle of the liquid crystal display device operating in the IPS mode. In the present invention, such a retardation reducing additive is used. The following may be mentioned as:

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

  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 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, polyesters having a weight average molecular weight of 500 to 10,000 have good compatibility with cellulose esters, and neither evaporation nor volatilization occurs during 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. Polyester having a high distribution on the low molecular weight side has a very good compatibility with the cellulose ester, and after forming the film, a moisture permeability is small, and a cellulose ester film rich in 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. It is particularly preferable to contain 5 to 15% by weight.

  In the present invention, the retardation reducing additive further includes the following.

  The dope used for the production of the optical film of the present invention mainly contains a cellulose ester, a polymer as a retardation reducing additive (a polymer obtained by polymerizing an ethylenically unsaturated monomer, an acrylic polymer), and an organic solvent. To do.

  In the present invention, in order to synthesize a polymer as a retardation-reducing additive, it is difficult to control the molecular weight by ordinary polymerization, and it is desirable to use a method that can align the molecular weight as much as possible without increasing the molecular weight. 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 a useful retardation reducing additive are listed below, but are not limited thereto.

  As an ethylenically unsaturated monomer unit constituting a polymer as a retardation reducing additive obtained by polymerizing an ethylenically unsaturated monomer, first, as a vinyl ester, for example, vinyl acetate, vinyl propionate, vinyl butyrate, valeric acid Vinyl, vinyl pivalate, vinyl caproate, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl cyclohexanecarboxylate, vinyl octylate, vinyl methacrylate, vinyl crotrate, vinyl sorbate , Vinyl benzoate, vinyl cinnamate and the like.

  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 highly compatible with cellulose ester, excellent in productivity without evaporation and volatilization, and retainability as a protective film for polarizing plates The moisture permeability is small, and the dimensional stability is excellent.

  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 method for producing an optical film of the present invention, the dope composition preferably contains a cellulose ester and an acrylic polymer having a weight average molecular weight of 500 or more and 3000 or less as a retardation reducing additive.

  Moreover, in the manufacturing method of the optical film of this invention, it is preferable that dope composition contains a cellulose ester and the acrylic polymer of the weight average molecular weight 5000 or more and 30000 or less as a retardation reduction additive.

  In the present invention, if the weight average molecular weight of the polymer as the retardation reducing additive is 500 or more and 3000 or less, or if the polymer has a weight average molecular weight of 5000 or more and 30000 or less, the compatibility with the cellulose ester is good, and There is no evaporation or volatilization in the film. Moreover, the transparency of the optical film after film formation is excellent, and the water vapor transmission rate is also extremely low, which shows excellent performance as a protective film for polarizing plates.

  In the present invention, a polymer having a hydroxyl group in the side chain can also be preferably used as the retardation reducing additive. 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.

  The polymer as described above containing 2 to 20% by weight of the monomer unit having the above hydroxyl group, of course, is excellent in compatibility with cellulose ester, retention, dimensional stability, and low moisture permeability. It is particularly excellent in adhesion 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 the side chain has an effect of significantly improving the compatibility and transparency of the polymer with respect to the cellulose ester.

  In addition to the above, useful retardation reducing additives in the present invention include, for example, ester compounds of diglycerin polyhydric alcohols and fatty acids described in JP-A-2000-63560, and JP-A-2001-247717. Hexose sugar alcohol ester or ether compound, Japanese Patent Application Laid-Open No. 2004-315613, tri-aliphatic alcohol ester compound of phosphoric acid, compound represented by general formula (1) described in Japanese Patent Application Laid-Open No. 2005-41911, Examples thereof include a phosphate ester compound described in JP-A No. 2004-315605, a styrene oligomer described in JP-A-2005-105139, and a polymer of a styrene monomer described in JP-A-2005-105140.

  The content of the retardation reducing additive described above is preferably 5 to 25% by weight based on the cellulose ester resin. If the content of the retardation-reducing additive is less than 5% by weight, the retardation reduction effect of the film is not exhibited, which is not preferable. On the other hand, if the content of the retardation reducing additive exceeds 25% by weight, so-called bleed out occurs and the stability in the film decreases, which is not preferable.

  In the method for producing an optical film according to the present invention, an organic solvent having good solubility with respect to the cellulose derivative is referred to as a good solvent, and has a main effect on dissolution. Organic) solvent or main (organic) solvent.

  Examples of good solvents include ketones such as acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, ethers such as tetrahydrofuran (THF), 1,4-dioxane, 1,3-dioxolane, 1,2-dimethoxyethane, formic acid Esters such as methyl, ethyl formate, methyl acetate, ethyl acetate, amyl acetate, γ-butyrolactone, methyl cellosolve, dimethylimidazolinone, dimethylformamide, dimethylacetamide, acetonitrile, dimethyl sulfoxide, sulfolane, nitroethane, methylene chloride And 1,3-dioxolane, THF, methyl ethyl ketone, acetone, methyl acetate and methylene chloride are preferable.

  In addition to the organic solvent, the dope preferably contains 1 to 40% by weight of an alcohol having 1 to 4 carbon atoms. After casting the dope on the metal support, the solvent starts to evaporate and the alcohol ratio increases, so the web (name of the dope film after casting the cellulose derivative dope on the metal support) Is used as a gelling solvent that makes the web strong and makes it easy to peel off from the metal support, or when these ratios are small, cellulose derivatives of non-chlorine organic solvents There is also a role to promote the dissolution of.

  Examples of the alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, tert-butanol, and propylene glycol monomethyl ether. Of these, ethanol is preferred because it has excellent dope stability, has a relatively low boiling point, good drying properties, and no toxicity. These organic solvents alone are not soluble in cellulose derivatives and are called poor solvents.

  The most preferable solvent for dissolving a cellulose derivative, which is a preferable polymer compound satisfying such conditions, at a high concentration is a mixed solvent having a ratio of methylene chloride: ethyl alcohol of 95: 5 to 80:20. Alternatively, a mixed solvent of methyl acetate: ethyl alcohol 60:40 to 95: 5 is also preferably used.

  The film according to the present invention includes a plasticizer that imparts processability, flexibility, and moisture resistance to the film, fine particles that impart slipperiness to the film (matting agent), an ultraviolet absorber that imparts an ultraviolet absorbing function, and deterioration of the film. You may contain the antioxidant etc. which prevent.

  The plasticizer used in the present invention is not particularly limited. However, a cellulose derivative or a reactive metal compound capable of hydrolytic polycondensation can be used so as not to cause haze, bleed out or volatilize from the film. It preferably has a functional group capable of interacting with the condensate by hydrogen bonding or the like.

  Examples of such functional groups include hydroxyl groups, ether groups, carbonyl groups, ester groups, carboxylic acid residues, amino groups, imino groups, amide groups, imide groups, cyano groups, nitro groups, sulfonyl groups, sulfonic acid residues, Examples thereof include a phosphonyl group and a phosphonic acid residue, and a carbonyl group, an ester group and a phosphonyl group are preferred.

  Examples of such plasticizers include phosphate ester plasticizers, phthalate ester plasticizers, trimellitic acid ester plasticizers, pyromellitic acid plasticizers, polyhydric alcohol ester plasticizers, glycolate plasticizers. Agents, citric acid ester plasticizers, fatty acid ester plasticizers, carboxylic acid ester plasticizers, polyester plasticizers, etc. can be preferably used, but polyhydric alcohol ester plasticizers, glycolate plasticizers are particularly preferred. And non-phosphate ester plasticizers such as polycarboxylic acid ester plasticizers.

  The polyhydric alcohol ester is composed of an ester of a dihydric or higher aliphatic polyhydric alcohol and a monocarboxylic acid, and preferably has an aromatic ring or a cycloalkyl ring in the molecule.

  The polyhydric alcohol used in the present invention is represented by the following general formula (1).

Formula _{(1) R 1 - (OH} ) n
(However, R ₁ represents an n-valent organic group, and n represents a positive integer of 2 or more.)
Examples of preferred polyhydric alcohols include the following, but the present invention is not limited to these.

  Examples of preferred polyhydric alcohols include adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1, 2-butanediol, 1,3-butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, gallium Examples include lactitol, mannitol, 3-methylpentane-1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, and xylitol. In particular, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylolpropane, and xylitol are preferable.

  There is no restriction | limiting in particular as monocarboxylic acid used for the polyhydric alcohol ester of this invention, Well-known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid, etc. can be used. Use of an alicyclic monocarboxylic acid or aromatic monocarboxylic acid is preferred in terms of improving moisture permeability and retention.

  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 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 1-10. When acetic acid is contained, the compatibility with the cellulose derivative is increased, and it is also preferable to use a mixture of acetic acid and another monocarboxylic acid.

  Examples of preferred aliphatic monocarboxylic acids include 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, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, mellicic acid, laccellic acid, etc., undecylen Examples thereof include unsaturated fatty acids such as acid, oleic acid, sorbic acid, linoleic acid, linolenic acid, and arachidonic acid.

  Examples of preferred alicyclic monocarboxylic acids include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid, or derivatives thereof.

  Examples of preferred aromatic monocarboxylic acids include those in which an alkyl group is introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, and two or more benzene rings such as biphenylcarboxylic acid, naphthalenecarboxylic acid, and tetralincarboxylic acid. Examples thereof include aromatic monocarboxylic acids and derivatives thereof, and benzoic acid is particularly preferable.

  The molecular weight of the polyhydric alcohol ester is not particularly limited, but is preferably 300 to 1500, and more preferably 350 to 750. A higher molecular weight is preferred because it is less likely to volatilize, and a smaller one is preferred in terms of moisture permeability and compatibility with cellulose derivatives.

  The carboxylic acid used for the polyhydric alcohol ester may be one kind or a mixture of two or more kinds. Moreover, all the OH groups in the polyhydric alcohol may be esterified, or a part of the OH groups may be left as they are.

  The glycolate plasticizer is not particularly limited, but a glycolate plasticizer having an aromatic ring or a cycloalkyl ring in the molecule can be preferably used. As preferred glycolate plasticizers, for example, butyl phthalyl butyl glycolate, ethyl phthalyl ethyl glycolate, methyl phthalyl ethyl glycolate and the like can be used.

  For phosphate ester plasticizers, triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, etc. For phthalate ester plasticizers, diethyl phthalate, dimethoxy Ethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, dicyclohexyl phthalate, and the like can be used, but in the present invention, it is preferable that a phosphate ester plasticizer is not substantially contained.

  Here, “substantially does not contain” means that the content of the phosphoric ester plasticizer is less than 1% by weight, preferably 0.1% by weight, and particularly preferably not added.

  These plasticizers can be used alone or in combination of two or more.

  The amount of the plasticizer used is preferably 1 to 20% by weight. 6 to 16% by weight is further preferable, and 8 to 13% by weight is particularly preferable. If the amount of the plasticizer used is less than 1% by weight relative to the cellulose derivative, the effect of reducing the moisture permeability of the film is small, so this is not preferred. If it exceeds 20% by weight, the plasticizer bleeds out from the film, and the film Since the physical properties of the material deteriorate, it is not preferable.

  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.

  Here, if the average particle size 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 also a Manton Gorin type high-pressure dispersing device such as Izumi Food Machinery. A homogenizer etc. are mentioned.

  In the present invention, the fine particles are dispersed in a solvent containing 25 to 100% by weight of a lower alcohol, and then mixed with a dope in which a cellulose ester (cellulose derivative) is dissolved in a solvent, and the mixed solution is placed on a metal support. A cellulose ester film is obtained which is cast and dried to form a film.

  Here, the content ratio of the lower alcohol is preferably 50 to 100% by weight, more preferably 75 to 100% by weight.

  Examples of lower alcohols preferably include methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol and the like.

  Although it does not specifically limit as solvents other than a lower alcohol, It is preferable to use the solvent used at the time of film formation of a cellulose ester.

  The fine particles are dispersed in the solvent at a concentration of 1 to 30% by weight. Dispersing at a concentration higher than this is not preferable because the viscosity increases rapidly. The concentration of the fine particles in the dispersion is preferably 5 to 25% by weight, more preferably 10 to 20% by weight.

  The ultraviolet absorbing function of the film is preferably imparted to various optical films such as a polarizing plate protective film, a retardation film, and an optical compensation film from the viewpoint of preventing deterioration of the liquid crystal. For such an ultraviolet absorbing function, a material that absorbs ultraviolet rays may be included in the cellulose derivative, and a layer having an ultraviolet absorbing function may be provided on a film made of the cellulose derivative.

  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. In addition, 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 the ultraviolet absorber, those having excellent absorption ability of ultraviolet rays having a wavelength of 370 nm or less from the viewpoint of preventing deterioration of a polarizer or liquid crystal and those having little absorption of visible light having a wavelength of 400 nm or more from the viewpoint of liquid crystal display properties. preferable.

  Specific examples of useful UV absorbers 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'-tert-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 A mixture of-(5-chloro-2H-benzotriazol-2-yl) phenyl] propionate can be mentioned, but is not limited thereto.

  Further, as commercially available products of ultraviolet absorbers, TINUVIN 109, TINUVIN 171 and TINUVIN 326 (all manufactured by Ciba Specialty Chemicals) can be preferably used.

  Specific examples of the benzophenone-based compound that is an ultraviolet absorber that can be used in the present invention include 2,4-dihydroxybenzophenone, 2,2′-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-5- Examples thereof include, but are not limited to, sulfobenzophenone and bis (2-methoxy-4-hydroxy-5-benzoylphenylmethane).

  In this invention, the compounding quantity of these ultraviolet absorbers has the preferable range of 0.01 to 10 weight% with respect to a cellulose ester (cellulose derivative), and also 0.1 to 5 weight% is preferable. If the amount of the ultraviolet absorber used is too small, the ultraviolet absorbing effect may be insufficient. If the amount of the ultraviolet absorber is too large, the transparency of the film may be deteriorated. The ultraviolet absorber is preferably one having high heat stability.

  Further, as the ultraviolet absorber that can be used in the optical film of the present invention, the polymer ultraviolet absorber (or ultraviolet absorbing polymer) described in JP-A-6-148430 and JP-A-2002-47357 is preferably used. be able to. In particular, it is represented by the general formula (1) described in JP-A-6-148430, the general formula (2), or the general formulas (3), (6), and (7) described in JP-A-2002-47357. A polymer ultraviolet absorber is preferably used.

  In general, the antioxidant is also referred to as a deterioration inhibitor, but is preferably contained in a cellulose ester film as an optical film. That is, when a liquid crystal image display device or the like is placed in a high humidity and high temperature state, the cellulose ester film as an optical film may be deteriorated. The antioxidant has a role of delaying or preventing the film from being decomposed by, for example, halogen in the residual solvent in the film or phosphoric acid of the phosphoric acid plasticizer, so that it is preferably contained in the film. .

  As such an antioxidant, a hindered phenol compound is preferably used. For example, 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], 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-tert-butyl-4-hydroxyphenyl) propionate], octa Sil-3- (3,5-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-hydroxy Benzyl) -isocyanurate and the like. 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.

  The amount of these compounds added is preferably 1 ppm to 1.0% by weight, more preferably 10 to 1000 ppm by weight with respect to the cellulose derivative.

  Hereafter, the manufacturing method of the optical film by this invention is described in detail. The film can be produced by a solution casting method.

  FIG. 1 is a flow sheet showing a specific example of an apparatus for carrying out the method for producing an optical film of the present invention by a solution casting film forming method. Note that the implementation of the present invention is not limited to the process of FIG.

  In the method for producing an optical film by the solution casting film forming method of the present invention, a thermoplastic resin solution (dope) is cast on a metal support (1) to form a casting film (web). After evaporating the part, the step of peeling the web (10) from the metal support (1), the step of stretching the peeled web (10) in the width direction by the tenter (4), and the stretched film And a winding process for winding.

  First, in a melting pot (not shown), a thermoplastic resin, for example, a cellulose ester resin is dissolved in a mixed solvent of a good solvent and a poor solvent, and an additive such as the above plasticizer or ultraviolet absorber is added to the resin. A solution (dope) is prepared.

  Next, the dope adjusted in the melting pot is fed to the casting die (2) by a conduit through, for example, a pressurized metering gear pump, and is made of a metal made of a rotationally driven stainless steel endless belt as shown in FIG. The dope is cast from the casting die (2) to the casting position on the support (1).

  Although not shown in the drawings, for example, a dope fed to the casting die (2) through, for example, a pressurized metering gear pump is rotated by a stainless steel having a surface mirror-treated by hard chrome plating from the casting die (2). It may be cast on a cooling drum.

  In order to cast the dope by the casting die (2), there is a doctor blade method in which the film thickness of the cast dope film (web) is adjusted with a blade, or a reverse roll coater method in which the film is adjusted with a reverse rotating roll. However, a pressure die that can adjust the slit shape of the die portion and can easily make the film thickness uniform is preferable. Examples of the pressure die include a coat hanger die and a T die, and any of them is preferably used.

  In addition, as a casting die (2), the pressure die which can adjust the slit shape of a nozzle | cap | die part and is easy to make a film thickness uniform is preferable.

  Here, it is preferable that the solid content concentration of the cellulose ester solution (dope) is 20 to 30% by weight.

  Here, if the solid content concentration of the cellulose ester solution (dope) is less than 20% by weight, sufficient drying cannot be performed on the metal support (1), and a part of the dope film is removed from the metal support (at the time of peeling). 1) Since it remains on top and leads to drum contamination, it is not preferable. If the solid content concentration exceeds 30%, the dope viscosity increases, filter clogging becomes faster in the dope adjustment process, or the pressure increases during casting on the metal support (1), and cannot be extruded. It is not preferable.

  In the illustrated film forming apparatus provided with a rotationally driven endless belt as the metal support (1), the belt metal support (1) is disposed between a pair of drums and the endless belt metal support (1 ), A plurality of rolls (not shown) that respectively support the upper transition portion and the lower transition portion from the back side.

  One or both of the drums at both ends of the rotary drive endless belt metal support (1) is provided with a drive device for applying tension to the belt metal support (1), thereby supporting the belt metal support. The body (1) is used in a tensioned state.

  The width of the metal support is 1800 to 2200 mm, the casting width of the cellulose ester solution is 1600 to 2150 mm, and the width of the film after winding is 1490 to 3000 mm. Thereby, the wide cellulose-ester film for liquid crystal display devices can be manufactured by a metal support body system.

  Here, when the width of the metal support (1), the casting width of the cellulose ester solution, and the width of the film after winding are less than the above lower limit values, respectively, it is possible to cope with the recent enlargement of liquid crystal display devices. If the width of the metal support (1), the casting width of the cellulose ester solution, and the width of the film after winding exceed the upper limit values, the residual solvent amount of the film after peeling In a state where there is a large amount of film, the film hangs down at the entrance of a tenter in the stretching process described later, unevenness in width is generated, and dispersion of retardation is increased, which is not preferable. In addition, the sagging film may hit the guide of the tenter, and the film may break and stop production.

  Moreover, in the manufacturing method of the optical film of this invention, it is preferable that the peripheral speed of a metal support body (1) is 80-200 m / min.

  That is, since the amount of solvent to be dried is small in a thin film, the production speed of the film can be increased by making the peripheral speed of the metal support (1) faster than the conventional drum peripheral speed. Productivity can be increased.

  When an endless belt is used as the metal support (1), the belt temperature during film formation is a general temperature range of 0 ° C. to a temperature lower than the boiling point of the solvent, and the mixed solvent is lower than the boiling point of the lowest boiling solvent. The temperature is more preferably in the range of 5 ° C to the boiling point of the solvent-5 ° C. At this time, it is necessary to control the ambient atmospheric humidity above the dew point.

  The dope cast on the surface of the metal support (1) as described above increases the gel film strength (film strength) due to cooling gelation, and further promotes drying until stripping. This also increases the strength (film strength) of the gel film.

  Further, in order to increase the film forming speed, two or more pressure casting dies (2) may be provided on the casting metal support (1), and the dope amount may be divided to form a multilayer film.

  In the system using an endless belt as the metal support (1), the film strength on which the web (10) can be peeled from the metal support (1) by the peeling roll (3) on the metal support (1). In order to dry and solidify until it becomes, it is preferable to dry to 150 weight% or less of the residual solvent amount in a web (10), and 80 to 120 weight% is more preferable. Moreover, as for web temperature when peeling a web (10) from metal support bodies (1), 0-30 degreeC is preferable. Further, immediately after the web (10) is peeled off from the metal support (1), the temperature rapidly decreases once due to the solvent evaporation from the metal support (1) adhesion surface side, and water vapor or solvent vapor in the atmosphere. For example, the web temperature at the time of peeling is more preferably 5 to 30 ° C. because volatile components are easily condensed.

  Here, the residual solvent amount can be expressed by the following equation.

Residual solvent amount (% by weight) = {(M−N) / N} × 100
In the formula, M represents the weight of the film at an arbitrary time point, and N represents the weight after drying a film having a weight of M at 110 ° C. for 3 hours.

  The dope film (web) formed by the dope cast on the endless belt metal support (1) is heated on the metal support (1), and the release roll ( The solvent is evaporated until the web is peelable by 3).

  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 surface of the metal support (1) by a liquid, a method of transferring heat from the front and back by radiant heat, and the like.

  In the system using an endless belt for the metal support (1), the peeling tension when the metal support (1) and the web (10) are peeled by the peeling roll (3) is usually 100 N / m to 200 N / In the optical film produced by the present invention, which is made thinner than in the past, the amount of residual solvent of the web (10) is large at the time of peeling, and it is easy to stretch in the conveying direction. The film is easy to shrink in the hand direction, and when drying and shrinkage overlap, the end curls and folds, so that wrinkles are likely to occur. Therefore, it is preferable to peel at a minimum tension that can be peeled off to 170 N / m, more preferably , Peeling at a minimum tension of 140 N / m.

  After drying and solidifying until the web (10) has a peelable film strength on the metal support (1), the web (10) is peeled off by the peeling roll (3).

  Next, the peeled web (10) is introduced into a tenter (4) in the stretching process. In the method of the present invention, as the tenter (4) in the stretching step, a pin tenter and a clip tenter can be used. Among them, as a film for a liquid crystal display device, a web (or film) (10) A clip tenter is preferred in which both side edges are fixed with a clip and stretched, and is preferred in order to improve the flatness and dimensional stability of the film.

  The residual solvent amount of the web (film) (10) immediately before entering the tenter (4) in the stretching step is preferably 10 to 50% by weight.

  In the stretching process, warm air is blown from the warm air blowing means at the front portion of the bottom of the tenter (4), that is, the warm air blowing slit port, and exhaust air is blown from the discharge port at the rear portion of the ceiling of the tenter (4). By being discharged, the web (10) is stretched and dried.

  In the present invention, the stretch ratio of the web (10) in the tenter (4) is preferably 3 to 80%, more preferably 6 to 60%.

  If the stretch ratio in the width direction of the web (10) in the tenter (4) is less than 3%, it is impossible to obtain a wide film even with the widest belt and casting width apparatus. Is not preferable. Moreover, since the film will tear depending on extending | stretching temperature when the extending | stretching rate of the width direction of the web (10) in a tenter (4) exceeds 80%, it is unpreferable.

  In addition, the hot air blowing means in the stretching step in the present invention specifically refers to a hot air blowing slit port of the tenter (4) in the stretching step, but a shape that efficiently heats the film by blowing hot air. If it is, it will not be specifically limited. The temperature of the warm air is preferably 165 to 190 ° C, and more preferably 170 to 185 ° C.

  Next, the stretched film (web) (10) is introduced into the roll conveyance drying device (5) and dried while being conveyed by the conveyance roll (7) composed of a non-driven free roll in the drying device (5). .

  In this drying device (5), the web (10) is meandered by the conveying rolls (7) arranged in a staggered manner as viewed from the side of 50 to 1000, and the web (10) is dried in the meantime. is there. Moreover, although the film conveyance tension | tensile_strength in drying apparatus (5) is influenced by the physical property of dope, the amount of residual solvents at the time of peeling and a film conveyance process, the temperature in drying apparatus (5), etc., it is 30-250 N / m. Is preferable, and 60 to 150 N / m is more preferable. 80 to 120 N / m is most preferable.

  The means for drying the web (or film) (10) is not particularly limited, and is generally performed by hot air, infrared rays, a heating roll, microwaves, or the like. It is preferable to dry with hot air from the viewpoint of simplicity. For example, it is dried by the drying air blown from the warm air inlet at the front portion of the bottom of the drying device (5), and the rear portion of the ceiling of the drying device (5). It is dried by exhausting the exhaust air from the outlet. The temperature of the drying air is preferably 40 to 160 ° C, and more preferably 50 to 160 ° C in order to improve the flatness and dimensional stability.

  The process from casting to final post-drying may be performed in an air atmosphere or an inert gas atmosphere such as nitrogen gas. In this case, it goes without saying that the dry atmosphere is carried out in consideration of the explosion limit concentration of the solvent.

  After drying by the roll conveyance drying device (5), both ends of the film were slit into a product width by a pair of upper and lower slitters (11) and (12), cut and cut, and a base film was formed according to the product width. Then, a roll-shaped optical film is manufactured by giving an embossed part by giving a knurling process to the width direction Shiro of this base film, and winding up.

  In the optical film manufacturing method according to the present invention, the knurling processing temperature is T (° C.), the glass transition temperature of the base film is Tg (° C.), and the time that the base film is in contact with the embossing ring is s (seconds). Then, knurling is performed under the conditions satisfying the following relational expression to produce a roll-shaped optical film.

0.75 ≦ (T−Tg) × s ≦ 1.00
The time s (seconds) for which the base film (10) is in contact with the embossing ring (13) can be changed by changing the transport speed of the film (10) and the nip width, in other words, the pressing pressure. Is possible. In order to change the nip width and the pressing pressure, the rubber hardness on the surface of the back roll (14) made of a rubber roll is adjusted, or the diameters of the embossing ring (13) and the embossing back roll (14) are changed. be able to.

  In the above, if the value of (T−Tg) × s is less than 0.75, the embossed height cannot be obtained sufficiently, and the effective knurl in the wound state is lowered, so that the film sticking failure Or convex local deformation occurs, and the flatness as an optical film is not satisfied.

  Also, if the value of (T−Tg) × s exceeds 1.00, the embossed height is too high, and as a result, the effective knurl in the wound state also becomes high, so that the center of the winding is on the back of the horse It is not preferable because it is recessed in such a shape and flatness as an optical film cannot be maintained. Further, when the temperature at the time of knurling which is the value of T is increased, the value of (T−Tg) × s is also increased. In this case, the temperature of T is increased until the value of (T−Tg) × s exceeds 1.00. If it is increased, a whisker-like failure occurs, which is not preferable.

  Moreover, in the manufacturing method of the optical film by this invention, it is preferable to apply 10-20 degreeC cold air to the film discharge side of an embossing stamping roll in the case of a knurling process. Here, during the knurling process, 10-20 ° C cold air is applied to the film discharge side of the embossing stamping roll because the resin part melted by heat is cooled and solidified by cooling the film and the ring part immediately after the embossing process. For this reason, the generation of thread-like foreign matters (beard-like foreign matters) can be suppressed, and a sufficiently high embossing height can be obtained.

  The optical film manufactured by the method for manufacturing an optical film of the present invention preferably has an effective nar defined by the following formula of the roll-shaped optical film of 2.5 to 7.0 μm.

  Effective nar = (embossed part roll cross-sectional area−core cross-sectional area) / winding length−average film thickness In the above, if the effective nar is less than 2.5 μm, a sticking failure between films may occur or a convex Since local deformation occurs and flatness as an optical film is not satisfied, it is not preferable. On the other hand, if the effective nar exceeds 7.0 μm, the center of the winding is recessed in a shape like the back of a horse and the flatness as an optical film cannot be maintained, which is not preferable.

In the optical film produced by the method for producing an optical film of the present invention, the number of whisker-like foreign substances adhering around the embossed portion of the roll-shaped optical film is preferably 0 to 50 / cm ² , more preferably from 0 to 20 pieces / cm ^2, more preferably from 0 to 10 / cm ^2.

In the above, the number of beard-like foreign matters adhering to the periphery of the embossed portion of the optical film is preferably as small as possible. When the number of beard-like foreign matters exceeds 50 / cm ² , the cleaning apparatus for processing as a polarizing plate If it cannot be completely removed and enters a liquid crystal display device as a foreign substance between the polarizer and the film, it becomes an image defect. The same applies to the case where application processing such as antireflection treatment or antiglare treatment is applied to the surface.

  Here, the height h (μm) of the embossed portion is set in a range of 0.05 to 0.3 times the film thickness H, and the width W is set in a range of 0.005 to 0.02 times the film width L. To do. You may form an embossing part in both surfaces of a film. In this case, the height h1 + h2 (μm) of the embossed portion is set in the range of 0.05 to 0.3 times the film thickness H, and the width W is set in the range of 0.005 to 0.02 times the film width L. . For example, when the film thickness is 40 μm, the height h1 + h2 (μm) of the embossed portion is set to 2 to 12 μm.

The embossed part width is set to 5 to 30 mm.

  The lower limit of the height of the embossed part is from the height necessary to prevent partial adhesion unevenness between the films. On the other hand, the upper limit is too high for the embossed part to be too high. This is because it deforms into a polygonal shape and induces a failure.

  Regarding the width of the embossed part, the embossed part will eventually become a loss part, but it is desirable to reduce it. However, for example, it is a minimum for suppressing slippage of a film at a high speed of 50 m / min or more with a thin film within 50 μm. Required embossed part width.

  However, it is also linked to the height of the embossed portion described above, and it is necessary to set the height of the embossed portion × the width of the embossed portion that clears all the convex shape, pyramid shape, horse back, polygonal shape, and winding failure.

  The roll length of the roll film in the optical film produced by the method of the present invention is preferably 3900 m or more and 9100 m or less.

  Here, if the winding length of the roll film is less than 3900 m, it is not preferable because the time for switching the rolled-up roll becomes insufficient when the production speed is increased. Moreover, since the frequency of the film switching operation increases during the polarizing plate processing, the productivity is lowered.

  On the other hand, when the roll length of the roll film exceeds 9100 m, the load of the core increases due to the weight of the film, and even if the emboss is increased, the effective knurl cannot be maintained and sticking occurs.

  In addition, a film with good dimensional stability can be obtained by setting the residual solvent amount of the film taken up by the take-up device (15) to 0.5% by weight or less, preferably 0.1% by weight or less.

  Below, the manufacturing method of the optical film by the melt casting film forming method of this invention is demonstrated.

  FIG. 2 is a flow sheet schematically showing an apparatus for carrying out the method for producing an optical film by the melt casting film forming method of the present invention.

  Referring to the figure, for example, cellulose ester pellets, a plasticizer, and an antioxidant are introduced into a hopper (21), and raw materials are conveyed from the hopper (21) to the Henschel mixer (22) at a predetermined supply rate. , Mixed.

  In the method for producing an optical film by the melt casting film forming method of the present invention, the thermoplastic resin used is not particularly limited as long as it can be formed by the melt casting film forming method. For example, cellulose ester, polycarbonate, alicyclic structure-containing polymer, polyvinyl alcohol, polyamide, polyimide, polyester and the like can be mentioned. Among them, cellulose esters and alicyclic structure-containing polymers are preferable because of their small photoelastic coefficient, and alicyclic structure-containing polymers are particularly preferable because of their low water absorption.

  In the present invention, the optical film includes an ester plasticizer having a structure in which an organic acid and a trihydric or higher alcohol are condensed as an additive, an ester plasticizer comprising a polyhydric alcohol and a monovalent carboxylic acid, At least one plasticizer selected from ester plasticizers composed of monovalent carboxylic acids and monohydric alcohols, phenolic antioxidants, hindered amine light stabilizers, phosphorus stabilizers, and sulfur stabilizers. It is preferable to contain a stabilizer, and in addition, a peroxide decomposing agent, a radical scavenger, a metal deactivator, an ultraviolet absorber, a matting agent, a dye, a pigment, and other plasticizers and hinders. Antioxidants other than dephenol antioxidants can be included.

  When the film composition is heated and melted, the decomposition reaction becomes remarkable, and this decomposition reaction may be accompanied by deterioration of the strength of the constituent material due to coloring or molecular weight reduction. Moreover, generation | occurrence | production of an unfavorable volatile component may be accompanied by the decomposition reaction of a film composition.

  When the film composition is heated and melted, the presence of the above-mentioned additives is excellent in terms of suppressing the deterioration of the strength based on the deterioration and decomposition of the material, or maintaining the inherent strength of the material. In the presence of the aforementioned additives.

  It is preferable to dry the resin pellets and the powder material as raw materials in advance. It is desirable to dry the moisture to 1000 ppm or less, preferably 200 ppm or less, using a vacuum or reduced pressure dryer or a dehumidifying hot air dryer.

  When the raw material is introduced from the supply hopper (21) shown in FIG. 2 into the extruder (23) through the mixer (22), it is prevented from oxidative decomposition or the like under vacuum, reduced pressure, or inert gas atmosphere. It is preferable. When additives such as a plasticizer are not mixed in advance, they may be kneaded in the middle of the extruder (23). In order to add uniformly, it is preferable to use a mixing device (22) such as a Henschel mixer.

  In the present invention, pellets and powder made of thermoplastic resin are melt-kneaded with an extruder (not shown) to produce pellets, and the pellets are melt-kneaded with another extruder (23). The film is cast from a casting die (24) onto a cooling roll (metal support) (25), and the pellets and powder are melt-kneaded by an extruder (23), and the film is left as it is. Both methods of casting from a casting die (24) onto a cooling roll (metal support) (25) to form a film can be used for film formation.

  The particle size of the powder is preferably a sieve mesh opening of 250 μm or less (JIS Z 8801-1). If the particle size of the powder is too large, sufficient mixing and dispersion cannot be obtained even by kneading in the extruder (23), and in some cases, the powder may adhere to the barrel inner wall of the extruder (23). The heat-degraded product of the resin accumulates in the part, and it occasionally flows out, and the trouble of the foreign matter due to the heat-degraded product is likely to occur in the film. Further, when the particle size is too small, it may cause a problem in handling. The pellets preferably have a diameter and a particle size of 1 to 5 mm in length.

  In a system in which a plurality of materials having different melting points are mixed, a temporary semi-melt is once produced at a temperature at which only a material having a low melting point is melted, and the semi-melt is put into an extruder (23). It is also possible to form a film. When using resins and additives that are susceptible to thermal decomposition, in order to reduce the number of times the resin is melted, a method of directly forming a film without producing pellets, A method of forming a film from is preferred.

  In the present invention, the extruder (23) used for film formation may be a single screw extruder or a twin screw extruder. When forming a film directly without producing pellets from the material, it is preferable to use a twin-screw extruder because an appropriate degree of kneading is required. However, even with a single-screw extruder, the screw shape is a Maddock type or Unimelt type. By changing to a kneading type screw such as dull mage, moderate kneading can be obtained and film formation becomes possible. In both the single screw extruder and the twin screw extruder, it is desirable to provide a vent port and remove the gas from the vent port using a vacuum pump or the like. In the case of producing a pellet or braided semi-melt, it may be a single screw extruder or a twin screw extruder.

  In the cooling step in the extruder (23) and after extrusion, it is preferable to reduce the oxygen concentration by replacing with an inert gas such as nitrogen gas or reducing the pressure.

  The melting temperature of the resin in the extruder (23) varies depending on the viscosity of the resin, the discharge amount, the thickness of the sheet to be produced, etc., but in general, the Tg relative to the glass transition temperature (Tg) of the molding material. As mentioned above, it is preferable that it is the range of Tg + 100 degrees C or less. More preferably, the melting temperature is Tg + 10 ° C. or higher and Tg + 90 ° C. or lower. The melt viscosity at the time of extrusion is 10 to 100,000 poise, preferably 100 to 10,000 poise. The residence time of the resin in the extruder (23) is preferably short, and is within 5 minutes, more preferably within 3 minutes, and most preferably within 2 minutes. The residence time depends on the type of the extruder (23) and the extrusion conditions, but can be shortened by adjusting the material supply amount, L / D, screw rotation speed, screw groove depth, etc. Is possible.

  The screw shape, rotation speed, and the like of the extruder (23) are appropriately selected depending on the viscosity of the resin, the discharge amount, and the like. In the present invention, the shear rate in the extruder (23) is preferably 1 / second to 10000 / second, more preferably 5 / second to 1000 / second, and most preferably 10 / second to 100 / second. In order to prevent biting of the gear pump and to reduce the main filter load, it is preferable to provide a prefilter on the outlet side of the extruder (23).

  For example, a 50/80/100 mesh screen or a metal fiber sintered filter is preferably provided as necessary. It is preferable to use a type that can be changed online.

  The raw materials mixed by the Henschel mixer (22) are conveyed to an extruder (23) and heated and melted at, for example, 250 ° C., and the melt is extruded from a casting die (24) according to the present invention. The melt extruded from the casting die (24) is cooled and surface-corrected by a stainless steel cooling roll (metal support) (25). In this case, it is preferable that the web (film) (20) and the cooling roll (25) are in close contact with each other, and a touch roll (26) is used as a method for bringing the web (film) (20) into close contact with the cooling roll (25). Press.

  If the thickness of the resin immediately after adhering to the cooling roll (25) is h, t / h is 10 or less when the film thickness is 70 μm or more and less than 100 μm, and t / h is 50 μm or more and 70 μm or less. If it is 15 or less, and less than 50 μm, t / h is preferably 20 or less. By setting t / h to the above value, the elongation of the ribbon can be suppressed and the retardation in the flow direction can be kept small. By making R at the lip tip preferably 100 μm or less, more preferably 50 μm or less, the flatness of the film can be kept good.

  Thickness adjustment mechanisms include a heater type that adjusts the temperature by dividing in the width direction, a manual bolt type that adjusts the lip opening mechanically, or a lip opening adjustment that uses expansion and contraction of the bolts with a heater. It is preferable to use a heat bolt system or the like.

  The die material is sprayed or plated with nickel, hard chromium, chromium carbide, chromium nitride, titanium carbide, titanium carbonitride, titanium nitride, carbide, ceramic (tungsten carbide, aluminum oxide, chromium oxide), etc. Buffing, lapping using a # 1000 or higher grinding wheel, plane cutting using a # 1000 or higher diamond grinding wheel (the cutting direction is perpendicular to the resin flow direction), electrolytic polishing, electrolytic composite polishing, etc. Stuff.

  A preferable material of the die slip portion is the same as that of the die. In order to prevent shark skin, it is important to reduce friction between the lip and the resin, and Dual Spiral Systems Inc. It is preferable to use K05MFC manufactured by the company. Further, the surface roughness of the lip portion is preferably 0.5 S or less, and more preferably 0.2 S or less.

  In the present invention, the material extruded from the casting die (24) is cooled and surface-corrected by the cooling roll (25). When the cooling roll (25) first contacted by the material extruded from the casting die (24) is the cooling roll (25), the time until the material contacts the cooling roll (25) from the casting die (24). Is preferably shorter than 10 seconds, preferably within 5 seconds, and most preferably within 2 seconds. The distance from the casting die (24) to the cooling roll (25) is preferably 10 mm or more and 100 mm or less.

  The temperature of the resin immediately before adhering to the cooling roll (25) is preferably Tg or higher, more preferably Tg + 50 ° C. or higher. By keeping the temperature of the resin high, retardation in the flow direction generated by the elongation of the ribbon can be reduced. It is preferable to keep the temperature of the resin in the air gap immediately before the resin comes into close contact with the cooling roll (25) from the outlet of the casting die (24). As the heat-retaining method, induction heating using a microwave, radiant heat heating using an infrared heater or the like can be preferably used. As the infrared heater, an electric, gas, oil or steam far infrared ceramic heater can be used.

  In the present invention, when the polymer flows out from the casting die (24), a suction device is provided in the vicinity of the casting die (24) in order to prevent contamination of the casting die (24) and the cooling roll (25) with sublimates. It is preferable to attach. The suction device needs to be treated such as heating with a heater so that the device itself does not become a place where the sublimate is attached. Further, if the suction pressure is too large, the film quality such as unevenness is affected. If the suction pressure is too small, the sublimate cannot be sucked effectively.

  In the present invention, the film and the cooling roll (25) are preferably in close contact. As a method for bringing the film and the cooling roll (25) into close contact, pressing using a touch roll (26), an electrostatic contact method, an air knife, a decompression chamber, or the like can be used.

  The number of cooling rolls (25) may be one or more, but it is preferable that two or more cooling rolls (25) are brought into contact with the cooling roll (25) in order to improve smoothness with respect to both sides of the film. The cooling roll (25) can be provided with cleaning equipment such as a cleaning roll. The temperature unevenness of the cooling roll (25) is preferably 0.5 ° C. or less. The speed unevenness is preferably 0.5% or less. The surface of the cooling roll (25) can use hard chrome plating, but is not limited thereto. The surface roughness is preferably 0.1 s or less.

  On the other hand, as the material of the touch roll (26), a metal or a material obtained by winding a resin, rubber or the like around a metal roll can be used. Further, a crown roll having a diameter changed as it goes from the width central portion to the side can also be used.

  In addition, the temperature immediately before contacting the touch roll (26) is preferably not less than the glass transition temperature (Tg) of the resin, and more preferably not less than Tg + 50 ° C.

  The temperature of the cooling roll (25) is preferably adjusted by flowing a heat medium such as water or oil through the cooling roll (25).

  Next, the cooled and solidified film is stretched in the width direction. The molecules are oriented by stretching. As a stretching method, a known tenter (27) or the like can be preferably used.

  The stretching is preferably performed under a controlled uniform temperature distribution. The temperature is preferably within ± 2 ° C, more preferably within ± 1 ° C, and particularly preferably within ± 0.5 ° C.

  For the purpose of reducing the dimensional change rate of the thermoplastic resin film produced by the above method, the film may be stretched or shrunk in the longitudinal direction or the width direction. In order to shrink in the longitudinal direction, for example, there is a method in which the film is contracted by temporarily stretching out the width stretching and relaxing in the longitudinal direction, or by gradually narrowing the interval between adjacent clips of the transverse stretching machine. The latter method can be performed by using a general simultaneous biaxial stretching machine and 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. You may combine with extending | stretching of arbitrary directions (diagonal direction) as needed. The dimensional change rate of the optical film can be reduced by shrinking 0.5% to 10% in both the longitudinal direction and the width direction.

  The film thickness variation of the optical film is preferably in the range of ± 3%, and more preferably ± 1%. For the purpose of reducing the film thickness variation, a method of stretching in the biaxial directions orthogonal to each other is effective, and the stretching ratios in the biaxial directions orthogonal to each other are finally 1.0-2. It is preferable that the range is 1.01 to 2.5 times in the width direction, 0 times, 1.01 to 1.5 times in the casting direction, and 1.05 to 2.0 times in the width direction. Is preferable.

  The method for stretching the film is not particularly limited. For example, a method in which a difference in peripheral speed is provided between a plurality of rolls and the film is stretched in the longitudinal direction using the difference in peripheral speed between the rolls, both ends of the web (10) are clipped. There are a method of fixing with a pin and extending the interval between clips and pins in the moving direction and extending in the vertical direction, a method of extending in the horizontal direction and extending in the horizontal direction, or a method of extending both in the vertical and horizontal directions and extending in both the vertical and horizontal directions. Can be mentioned. Of course, these methods may be used in combination.

  In the case of the so-called tenter method, driving the clip portion by the linear drive method is preferable because smooth stretching can be performed and the risk of breakage and the like can be reduced.

  These width maintenance or lateral stretching in the film forming step is preferably performed by a tenter, and may be a pin tenter or a clip tenter.

The web (film) (20) is guided to a stretching machine (not shown) and stretched in the longitudinal direction in the stretching machine. Subsequently, the web (film) (20) is stretched in the width direction using a tenter (27). Later, it is relaxed.

  After stretching by the tenter (27), both ends of the film are slit into a product width by a pair of upper and lower slitters (28) and (29), and then embossed to prevent sticking and scratching during winding. A knurling process (embossing process) is applied to both ends of the film (20) in the width direction by the ring (30) and the back roll (31). Thereafter, the film is wound up by a winder (32) to obtain a roll-shaped optical film.

  In the optical film manufacturing method according to the present invention, the knurling processing temperature is T (° C.), the glass transition temperature of the base film is Tg (° C.), and the time that the base film is in contact with the embossing ring is s (seconds). Then, knurling is performed under the conditions satisfying the following relational expression to produce a roll-shaped optical film.

0.75 ≦ (T−Tg) × s ≦ 1.00
The time s (seconds) for which the base film (20) is in contact with the embossing ring (30) can be changed by changing the conveyance speed of the film (20) and the nip width, in other words, the pressing pressure. Is possible. To change the nip width and pressing pressure, adjust the rubber hardness on the surface of the back roll (31) made of a rubber roll, or change the diameter of the embossing ring (30) and back roll (31). Can do.

  Moreover, in the manufacturing method of the optical film by this invention, it is preferable to apply 10-20 degreeC cold air to the film discharge side of an embossing stamping roll (30) in the case of a knurling process. Thus, during the knurling process, the film and the ring part were melted by heat by cooling the film and the ring part immediately after the embossing process by applying cold air of 10 to 20 ° C. to the film discharge side of the embossing stamp roll (30). Since the resin portion is cooled and solidified, there is an advantage that the occurrence of thread-like foreign matters (whisker-like foreign matters) can be suppressed and a sufficiently high embossed height can be obtained.

  The optical film manufactured by the method for manufacturing an optical film of the present invention preferably has an effective nar defined by the following formula of the roll-shaped optical film of 2.5 to 7.0 μm.

Effective nar = (embossed portion roll cross-sectional area−core cross-sectional area) / winding length−average film thickness The optical film produced by the method for producing an optical film of the present invention adheres to the periphery of the embossed portion of the roll-shaped optical film. and that the number of whisker-like foreign matter, preferably from 0 to 50 pieces / cm ^2, more preferably 0 to 20 pieces / cm ^2, more preferably from 0 to 10 / cm ^2.

  In the optical film produced by the method for producing an optical film of the present invention, the roll length of the roll film is preferably 3900 m or more and 9100 m or less.

  In the method of the present invention, it is preferable that a static eliminator is installed before winding and immediately after the winding unit to neutralize the film.

  The static eliminator can be configured in such a way that a reverse potential is applied by a static eliminator or a forced charging device at the time of winding so that the charging potential when the original winding is re-drawn is ± 2 KV or less. It can also be set as the structure which static-eliminates with the static elimination device converted into positive / negative alternately at 1-150Hz.

  Moreover, it can replace with said static elimination device and can utilize the ionizer and static elimination bar which generate | occur | produce ion wind. Here, the ionizer static elimination is performed by blowing an ion wind toward the film wound up from the embossing device through the transport roll. The ion wind is generated by a static eliminator. Any known static eliminator can be used without limitation.

  The static elimination at the time of film formation winding is to induce coating unevenness when the charged potential is ± 2KV or more when the original film is redrawn and the functional film is applied. Especially when pursuing thin film and high speed Since film peeling electrification at the time of re-feeding becomes high, static elimination during film formation is essential.

  In the method for producing an optical film according to the present invention, the winding method of the film may be a commonly used winder in any of the solution casting film forming method and the melt casting film forming method, a constant torque method, There are methods for controlling the tension, such as a constant tension method, a taper tension method, and a program tension control method with a constant internal stress.

  The film may be bonded to the winding core (winding core) by either a double-sided adhesive tape or a single-sided adhesive tape.

  In the optical film according to the present invention, the width of the film after winding is preferably 1490 to 3000 mm.

  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 30 to 200 μm, and the recent thin tendency is preferably 40 to 120 μm, particularly 40 to A range of 100 μm is preferred. The film thickness after drying refers to a film in which the amount of residual solvent in the film is 0.5% by weight or less.

  Here, when the film thickness of the optical film after winding is too thin, the intensity | strength required as a protective film for polarizing plates may not be acquired, for example. If the film thickness is too thick, the advantage of thinning the film over the conventional optical film is lost.

  In the case of the solution casting film forming method, referring to FIG. 1, for adjusting the film thickness, the dope concentration, the pumping amount of the pump, the slit of the die of the casting die (2) are adjusted so as to obtain a desired thickness. It is preferable to control the gap, the extrusion pressure of the casting die (2), the conveyance speed of the metal support (1), and the like.

  In the case of the melt casting film forming method, referring to FIG. 2, the adjustment of the film thickness is performed by adjusting the viscosity of the resin melt, the slit gap of the die of the casting die (24), the flow so as to obtain a desired thickness. It is preferable to control the extrusion pressure of the rolling die (24), the rotational speed of the cooling roll (metal support) (25), and the like.

  As a means for making the film thickness uniform, in any method, it is preferable that the film thickness detection means is used to feed back the programmed feedback information to each of the above-mentioned devices.

  In the present invention, the optical film desirably has a transmittance of 90% or more, more preferably 92% or more, and still more preferably 93% or more.

  Moreover, the optical film manufactured by the method of the present invention has a haze of 0.3 to 2.0 when three sheets are stacked. According to the optical film of the present invention, the haze of the film is very high. It is low and has optical characteristics excellent in transparency and flatness.

  Here, the haze of the optical film may be measured using, for example, a haze meter (1001DP type, manufactured by Nippon Denshoku Industries Co., Ltd.) according to the method defined in JIS K6714.

  The optical film produced by the method of the present invention is preferably used for a liquid crystal display member, specifically a protective film for a polarizing plate.

  By using the protective film for polarizing plates which consists of the optical film of this invention, the polarizing plate excellent in durability, dimensional stability, and optical isotropy is provided with thickness reduction.

  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
A cellulose triacetate film was produced as follows by the method for producing an optical film by the solution casting method of the present invention.

(Dope composition 1)
100 parts by weight of cellulose triacetate (Mn = 148000, Mw = 310000, Mw / Mn = 2.1)
Triphenyl phosphate 8 parts by weight Ethylphthalyl ethyl glycolate 2 parts by weight Methylene chloride 440 parts by weight Ethanol 40 parts by weight Tinuvin 109 (manufactured by Ciba Specialty Chemicals) 0.5 part by weight Tinuvin 171 (Ciba Specialty Chemicals) 0.5 parts by weight Aerosil 972V (manufactured by Nippon Aerosil Co., Ltd.) 0.2 parts by weight The material of the above dope composition 1 was put into a sealed container, heated, stirred and completely dissolved and filtered. . The filtration was performed through a sintered metal filter (capture particle size = 10 microns) after filtration by a filter press. Subsequently, the dope was uniformly cast to a width of 1800 mm on a stainless steel band support (1) having a width of 2000 mm at a temperature of 35 ° C. using the belt casting apparatus shown in FIG.

  On the stainless steel band support (1), the solvent was evaporated until the residual solvent amount reached 100% by weight, and the web (film) (10) was peeled from the stainless steel band support (1). Next, both ends of the web (10) in the width direction (TD direction) were held by the tenter (4), and stretched in the width direction of the web (10) at a stretching ratio of 10%. In addition, the residual solvent amount of the web (film) (10) immediately before entering the tenter (4) in the stretching process was 30% by weight.

  In the stretching step, warm air is blown at a temperature of 180 ° C. from the warm air blowing means at the front part of the bottom of the tenter (4), that is, the warm air blowing slit port, and the outlet of the rear part of the ceiling of the tenter (4). The web (10) was stretched and dried by the exhaust air being discharged from.

  Next, the stretched film (web) (10) is introduced into a roll transport dryer (5), and this film is mirror transported with a surface roughness (Rmax) of 0.8 μm in the roll transport dryer (5). It dried, conveying with the conveyance roll (7) comprised by the 500 non-driving free roll which consists of a roll (surface length 2200mm, diameter 110mm). The film conveyance tension in the drying device (5) was 80 N / m. In the drying device (5), drying was performed by a drying air having a temperature of 150 ° C. blown from a hot air inlet at a front portion of the bottom of the drying device.

  After drying with the drying device (5), both ends of the film were slit into a product width by a pair of upper and lower slitters (11) and (12) and cut and cut.

  Subsequently, the left and right ends of the slit film (10) were knurled by an embossing ring (13) and a back roll (14) to give an embossed portion (not shown) having a width of 10 mm to the film end.

  Here, when the processing temperature of the knurling process is T (° C.), the glass transition temperature of the cellulose triacetate base film is Tg (° C.), and the time that the base film is in contact with the embossing ring is s (seconds), The knurling process was performed on the conditions which satisfy | fill a relational expression, and the roll-shaped cellulose triacetate film was manufactured.

0.75 ≦ (T−Tg) × s ≦ 1.00
In Example 1, the glass transition temperature (Tg) of the cellulose triacetate base film is 125 ° C., the treatment temperature (T) of the knurling process is 250 ° C., and the rotational peripheral speed of the embossing ring (13) is The time (s) during which the base film (10) was in contact with the embossing ring (13) was set to 0.006 seconds at 50 m / min.

  Therefore, the relational expression was (T−Tg) × s = 0.75.

  In the knurling process, cold air having a temperature of 20 ° C. was applied to the embossing ring, that is, the film discharge side of the embossing stamp roll (13).

  Thereafter, a cellulose triacetate film (F) having a final product width of 1490 mm and an embossed portion and a film thickness of 80 μm was wound up by a winding device (15). The wound length of the rolled cellulose triacetate film (F) was 3900 m.

  When the effective nal defined by the following formula was calculated, the roll-shaped cellulose triacetate film produced in Example 1 was 2.7 μm. Here, the effective nal is a so-called roll-up value of the rolled cellulose triacetate film.

Effective knurl = (embossed roll cross-sectional area−core cross-sectional area) / winding length−average film thickness (number of whiskers)
About the roll-shaped cellulose triacetate film manufactured in this Example 1, the embossed part was observed with the 30 time optical microscope. Then, the number of whisker-like foreign matters having a length of 200 μm or more attached around the embossed part of the film was counted and converted into the number per 1 cm ² . The number of shaped foreign substances was 0 / cm ² .

The embossing processing temperature (° C.), the embossing rotation speed (m / min), the time s (seconds) when the base film is in contact with the embossing ring, and the relational expression (T−Tg) × s. Values, embossed part cooling air temperature (° C.), winding length (m), film thickness (μm) are shown in Table 1 below, effective nal value (μm) for the obtained cellulose triacetate film, number of bearded foreign matters The results of (pieces / cm ² ) are shown in Table 1 below.

Examples 2-12
A cellulose triacetate film is produced in the same manner as in Example 1 above, but the embossing processing temperature (° C.), embossing rotation speed (m / min), and base film are embossed as in Example 1 above. The time s (seconds) in contact with the film, the value of the relational expression (T-Tg) × s, the embossed part cooling air temperature (° C.), the winding length (m), and the film thickness (μm) were variously varied. A triacetate film was produced. In Example 11, cold air was not applied to the embossing, that is, the film discharge side of the embossing stamping roll (13) during the knurling process.

And about the obtained cellulose triacetate film, while calculating the effective nal (micrometer), the number of bearded foreign materials (pieces / cm < ² >) was measured, and the obtained result was combined with following Table 1, and was shown.

Comparative Examples 1-3
For comparison, a cellulose triacetate film is produced in the same manner as in Example 1, except that in Comparative Examples 1 to 3, the relational expression (T−Tg) × The value of s was outside the scope of the present invention. In Comparative Examples 1 and 2, cold air was not applied to the film discharge side of the embossing ring, that is, the embossing stamp roll (13), during the knurling process.

  In order to evaluate the winding performance of the roll-shaped cellulose triacetate films obtained in Examples 1 to 12 and Comparative Examples 1 to 3, the following tests were performed.

(Evaluation of winding quality)
As a method for evaluating the winding quality, the roll-like wound films of the cellulose triacetate films obtained in Examples 1 to 12 and Comparative Examples 1 to 3 were observed and evaluated for the appearance, and the protrusions observed on the outer periphery of the winding were shown. The following four grades were performed according to the number of convex portions. The obtained results are shown in Table 1 below.

A: 0 to 5 O: 6 to 10 Δ: 11 to 20 ×: 21 or more (evaluation of winding deformation and occurrence of film sticking failure)
The rolls of the cellulose triacetate films obtained in Examples 1 to 12 and Comparative Examples 1 to 3 were stored at a temperature of 40 ° C. and a humidity of 80% RH for 2 weeks, and then the appearance was confirmed. The presence or absence of the occurrence was confirmed, and the winding deformation was evaluated.

  Next, the roll-shaped wound films obtained in Examples 1 to 12 and Comparative Examples 1 to 3 were respectively fed out and inspected whether the films were adhered to each other. Then, the following four grades were applied according to the state of film sticking.

◎: Not attached at all ○: Slightly attached, but easily peeled △: Sticked but easily peeled ×: Many sticking and difficult to peel off The results are shown in Table 1.

  As is clear from the results in Table 1 above, according to the cellulose ester films produced in Examples 1 to 12 of the present invention, the evaluation of winding quality, the evaluation of winding deformation, and the evaluation of occurrence of sticking failure of the film are anyway. There is little generation of thread-like foreign matter (bottle-like foreign matter) in which the resin is dissolved around the embossed portion of the obtained optical film, and the embossed film does not cause holes in the embossed portion. It was possible to achieve higher quality. Thus, according to the cellulose-ester film produced in Examples 1-12 of this invention, with the speeding-up of manufacture of an optical film, ensuring the embossing part height after winding a film in roll shape. Thus, it was possible to reliably cope with the increase in speed and length in the production of optical films.

  The relational expression (T−Tg) × s and the effective nar have a proportional relation that when one of the relational expressions (T−Tg) × s increases, the other effective nar also increases. I understood that.

  On the other hand, in the cellulose ester films of Comparative Examples 1 to 3, the number of bearded foreign matters is very large. In particular, in the cellulose ester films of Comparative Examples 1 and 2, horse-back-like winding deformation occurs. It was. In any of the cellulose ester films of Comparative Examples 1 to 3, the evaluation of film sticking failure occurrence is Δ or ×, and at such an evaluation level of Δ, a coating defect occurs in the coating process on the film surface. Therefore, it cannot be used for coating, and at the evaluation level of x, it breaks when the film is fed out, so that it cannot be used for a polarizing plate.

Example 13
Next, examples of the method for producing an optical film by the melt casting method of the present invention will be described.

[Production of cellulose ester film]
(Thermoplastic resin)
100 parts by weight of cellulose acetate propionate (acetyl substitution degree: 2.0, propionyl substitution degree: 0.7,
Number average molecular weight: 75000)
(Plasticizer)
Trimethylolpropane tribenzoate 10 parts by weight Sumilizer GP 0.5 part by weight (antioxidant)
IRGANOX1010 1 part by weight (Ciba Specialty Chemicals)
Needle-like TiO ₂ (trade name FTL-100, manufactured by Ishihara Sangyo Co., Ltd.) 5 parts by weight First, cellulose acetate propionate was dried in air at 120 ° C. for 1 hour and allowed to cool to room temperature. Next, the dried cellulose acetate propionate was heated using an extruder to produce pellets and allowed to cool.

  Referring to FIG. 2, pellets of cellulose acetate propionate, a plasticizer, an antioxidant and needle-like particles are mixed and introduced into a raw material supply hopper (21), and a Henschel mixer (22) is supplied at a supply rate of 2.0 Kg / hr. ) Introduce raw materials into and mix. The mixed raw materials are led to an extruder (23) and heated and melted at 250 ° C. The melt is then extruded from a casting die (24).

  The melt extruded from the casting die (24) is cooled by a cooling roll (25) and subjected to surface correction. In this case, as a method for bringing the web (film) (20) and the cooling roll (25) into close contact, the web (film) (20) was pressed using the touch roll (26).

  Next, the web (film) (20) is guided to a stretching machine (not shown), and stretched in the longitudinal direction at a temperature of 150 ° C. in the stretching machine, and subsequently 160 ° C. using a tenter (27) in the width direction. After extending | stretching by temperature, the film both ends were slit to the width | variety used as a product with a pair of upper and lower slitters (28) and (29), and it cut and cut.

  Next, the left and right ends of the slit film (20) were knurled by an embossing ring (30) and a back roll (31) to give an embossed portion (not shown) having a width of 10 mm to the film end.

  Here, when the processing temperature of the knurling process is T (° C.), the glass transition temperature of the cellulose acetate propionate base film is Tg (° C.), and the time that the base film is in contact with the embossing ring is s (seconds). Then, knurling was performed under the conditions satisfying the following relational expression to produce a roll-shaped cellulose acetate propionate film.

0.75 ≦ (T−Tg) × s ≦ 1.00
In Example 13, the cellulose acetate propionate base film has a glass transition temperature (Tg) of 150 ° C., a knurling treatment temperature (T) of 250 ° C., and the rotation of the embossing ring (30). The speed (50 m / min) and the time (s) during which the base film (20) was in contact with the embossing ring (30) were 0.0072 seconds.

  Therefore, the relational expression was (T−Tg) × s = 0.76.

  In the knurling process, cold air having a temperature of 20 ° C. was applied to the embossing ring, that is, the film discharge side of the embossing stamp roll (30).

  Thereafter, a cellulose acetate propionate film having an end product width of 1490 mm and a film thickness of 60 μm having an embossed portion was wound up by a winding device (32). The roll length of the rolled cellulose acetate propionate film was 3900 m.

  The roll-like cellulose acetate propionate film produced in Example 13 was 2.8 μm when the effective nal defined by the following formula was calculated. Here, the effective nal is a so-called roll-up value of the rolled cellulose acetate propionate film.

Effective nar = (embossed portion roll cross-sectional area−core cross-sectional area) / winding length−average film thickness About the roll-like cellulose acetate propionate film produced in this Example 13, as in the case of Example 1 above. When the number of beard-like foreign matters was counted, the number of beard-like foreign matters attached around the embossed portion of the cellulose acetate propionate film was 0 / cm ² .

The embossing processing temperature (° C.), the embossing rotation speed (m / min), the time s (seconds) when the base film is in contact with the embossing ring, and the relational expression (T−Tg) × s. The values, embossed part cooling air temperature (° C.), winding length (m), film thickness (μm) are shown in Table 2 below, and the effective nal value (μm) of the obtained cellulose acylate film, whisker-like foreign matter The results of the number (pieces / cm ² ) are shown in Table 2 below.

Examples 14-24
A cellulose triacetate film is prepared in the same manner as in Example 13 above. However, in the case of Example 13, the embossing processing temperature (° C.), the embossing rotation speed (m / min), and the base film is embossed. The time s (seconds) in contact with the film, the value of the relational expression (T-Tg) × s, the embossed part cooling air temperature (° C.), the winding length (m), and the film thickness (μm) were variously varied. An acylate film was produced. In Example 23, cold air was not applied to the embossing, that is, the film discharge side of the embossing stamp roll (30) during the knurling process.

And about the obtained cellulose acylate film, while calculating an effective nar (micrometer), the number of beard-like foreign materials (pieces / cm < ² >) was measured, and the obtained result was shown according to Table 2 below. .

Comparative Examples 4-6
For comparison, a cellulose triacetate film is produced in the same manner as in Example 13, but the difference from Example 13 is that in Comparative Examples 4 to 6, the relational expression (T−Tg) × The value of s was outside the scope of the present invention. In Comparative Examples 4 and 5, cold air was not applied to the film discharge side of the embossing ring, that is, the embossing stamp roll (30), during the knurling process.

In order to evaluate the winding performance of the roll-shaped cellulose acylate films obtained in Examples 13 to 24 and Comparative Examples 4 to 6, as in the case of the above Examples, evaluation of winding quality, evaluation of winding deformation, The film sticking failure occurrence was evaluated and the obtained results are shown in Table 2 below.

  As is clear from the results of Table 2 above, according to the cellulose ester films prepared in Examples 13 to 24 of the present invention, the evaluation of winding quality, the evaluation of winding deformation, and the evaluation of occurrence of sticking failure of the film are anyway. There is little generation of thread-like foreign matter (bottle-like foreign matter) in which the resin is dissolved around the embossed portion of the obtained optical film, and the embossed film does not cause holes in the embossed portion. It was possible to achieve higher quality. Thus, according to the cellulose-ester film produced in Examples 13-24 of this invention, with the speeding-up of manufacture of an optical film, ensuring the embossed part height after winding a film in roll shape. Thus, it was possible to reliably cope with the increase in speed and length in the production of optical films.

  The relational expression (T−Tg) × s and the effective nar have a proportional relation that when one of the relational expressions (T−Tg) × s increases, the other effective nar also increases. I understood that.

  On the other hand, in the cellulose ester films of Comparative Examples 4 to 6, all the number of bearded foreign matters was generated, and in particular, in the cellulose ester films of Comparative Examples 4 and 5, horse-back-like winding deformation occurred. It was. In each of the cellulose ester films of Comparative Examples 4 to 6, the evaluation of occurrence of film sticking failure is Δ or ×, and at such an evaluation level of Δ, a coating defect occurs in coating processing on the film surface. Therefore, it cannot be used for coating, and at the evaluation level of x, it breaks when the film is fed out, so that it cannot be used for a polarizing plate.

It is a flow sheet which shows typically the device which enforces the manufacturing method of the optical film by the solution casting film forming method of the present invention. It is a flow sheet which shows typically the device which enforces the manufacturing method of the optical film by the melt casting film forming method of the present invention.

Explanation of symbols

1: Endless belt support 2: Casting die 3: Peeling roll 4: Tenter 5: Roll transporting and drying device 7: Transporting roll 10: Web 11: Upper slitter roll 12: Lower slitter roll 13: Embossing ring 14: Back roll 15: Winding device F: Cellulose triacetate film (optical film)
20: Web (film)
21: Supply hopper 22: Henschel mixer 23: Extruder 24: Casting die 25: Cooling roll 26: Touch roll 27: Tenter 28: Upper slitter roll 29: Lower slitter roll 30: Embossing ring 31: Back roll 32: Winding Take-off machine

Claims (5)

After slitting the widthwise end of the optical film obtained by the solution casting film forming method or the melt casting film forming method to form a base film according to the product width, the width direction of the base film It is a method of producing a roll-shaped optical film by forming an embossed part by applying a knurling process to Saburo, and winding the temperature of the knurling process to T (° C.) and the glass transition temperature of the base film to Tg. (° C), when the time that the base film is in contact with the embossing ring is s (seconds), knurling is performed under the conditions satisfying the following relational expression to produce a roll-shaped optical film. The manufacturing method of an optical film.
0.75 ≦ (T−Tg) × s ≦ 1.00   The method for producing an optical film according to claim 1, wherein a cold air of 10 to 20 ° C. is applied to the film discharge side of the embossing stamp roll during knurling. It is an optical film manufactured by the manufacturing method of the optical film of Claim 1 or 2, Comprising: The effective nar defined by the following formula of a roll-shaped optical film is 2.5-7.0 micrometers, It is characterized by the above-mentioned. An optical film.
Effective knurl = (embossed roll cross-sectional area−core cross-sectional area) / winding length−average film thickness It is an optical film manufactured by the manufacturing method of the optical film of Claim 1 or 2, Comprising: The number of the beard-like foreign material adhering to the embossing part periphery of a roll-shaped optical film is 0-50 piece / cm. ^{2. An} optical film, wherein   An optical film manufactured by the method for manufacturing an optical film according to claim 1, wherein a roll length of the roll film is 3900 m or more and 9100 m or less.

Images