JP5056218B2 - Optical film and method for producing the same - Google Patents

Description

  The present invention relates to an optical film and a production method thereof, in particular, a protective film for a polarizing plate used for a liquid crystal display (LCD) and the like, a retardation film, a viewing angle widening film, an antireflection film used for a plasma display, and the like. The present invention relates to an optical film that can be used for functional films and various functional films used in organic EL displays and the like, and a method for producing the same.

  In recent years, notebook computers have been developed to be thinner and lighter, larger screens, and higher definition. Along with this, there is an increasing demand for thinner, wider and higher quality protective films for liquid crystal polarizing plates. In general, cellulose ester films are widely used as protective films for polarizing plates. The cellulose ester film is usually wound around a core to become a film original, which is stored and transported.

  With the recent enlargement of the screen, there is a demand for a film film having a wide film width and a long winding length. When the film width is wide and the winding length is long, the storage stability of the film becomes a problem. For example, a cracking failure in which the films stick to each other and the film is deformed, or a convex failure in which a foreign object is deformed in a convex shape as if a foreign object is sandwiched between the films is likely to occur.

Conventionally, embossed portions having irregularities are formed on the surfaces of the left and right end portions of the transport film by knurling. Patent documents relating to this include, for example, the following.
Japanese Patent Application Laid-Open No. 2002-301751 describes that an embossing roll having a large number of protrusions is pressed on an end in the width direction of the film to perform an embossing process to form an uneven embossed pattern. Has been.

  In the conventional embossing method by knurling to the optical film, the pressing roll with irregularities is heated, and the left and right ends of the transport film are sandwiched between the metal and rubber back rolls. By pressurizing the film, irregularities were formed on the surfaces of the left and right ends of the film, and this was effective in preventing the film from sticking and preventing winding deviation.

  However, in the knurling process using the pressure roll by the conventional heating / pressurizing mechanism described in the above-mentioned patent document, especially when the original film is widened to a width of 1.4 m or more, the knurling process is performed on both sides. There is a problem that the effect of the embossed portion provided by is reduced and the storage stability of the original fabric is likely to deteriorate.

  Also, when changing the height of the unevenness according to the film thickness, it takes time to adjust the pressing roll indentation pressure, especially when the back roll surface layer is made of rubber, As the surface layer was worn out, it took time for the adjustment, which was not preferable for production. In addition, when the back roll is made of metal and the surface layer portion of the back roll is metal, conversely, it becomes sensitive to the indentation pressure by the pressure roll, and there is a risk of causing a scratching failure on the film surface. However, the adjustment takes time, which is not preferable for production.

  By the way, conventionally, a technique for producing an anti-glare film by imparting an anti-glare property to the film by making a dent on the entire film surface using laser light, particularly YAG laser light, is already known.

  However, it has not been known so far to use a laser beam for the knurling of the film end intended to improve the rollability of the optical film.

  The object of the present invention is to solve the above-mentioned problems of the prior art, and in the case of changing the height of the unevenness of the embossed part according to the film thickness of the film, without taking time for adjustment, To provide an optical film that is excellent in productivity and that can dramatically improve the surface properties of the film by eliminating the occurrence of minor wrinkles and scratches on the film surface, and a method for manufacturing the same. It is to do.

As a result of intensive research in view of the above points, the inventor of the present invention uses laser light, particularly CO ₂ laser light, for the knurling of the film end, and the output of the laser light can be varied according to the film thickness of the film. By doing so, it becomes possible to easily adjust the height of the unevenness of the embossed part at the end of the film, and the fineness of the film surface caused by bringing the pressing roll into contact with the back roll during the knurling process so far The present inventors have found that the surface properties of the film can be remarkably improved without any troubles such as wrinkles and scratches, and the present invention has been completed.

In order to achieve the above-mentioned object, the invention of the method for producing an optical film according to claim 1 is characterized in that the film surface of at least the left and right end portions of the left and right end portions and the central portion of the transport film is uneven by irradiating laser light. In the method for producing an optical film for forming an embossed portion, the blending ratio of the plasticizer on the film surface on the laser light irradiation side: A and the blending ratio of the plasticizer on the film surface on the laser light non-irradiation side: B It is characterized by a relationship of A> B.

  Invention of Claim 2 is a manufacturing method of the optical film of Claim 1, Comprising: The embossed part which adjusts the irradiation output of a laser beam according to the film thickness of a film, and has unevenness | corrugation of 3-20 micrometers in height It is characterized by forming.

  Invention of Claim 3 is a manufacturing method of the optical film of Claim 1 or 2, Comprising: The irradiation position of a laser beam is made variable, An embossing part is formed in a predetermined location according to a film width, It is characterized by the above-mentioned. Yes.

A fourth aspect of the present invention, a method for producing an optical film according to any one of claims 1 to 3, the laser beam is characterized by a CO ₂ laser beam.

Invention of Claim 5 is a manufacturing method of the optical film as described in any one of Claims 1-4 , Comprising: The film obtained by the solution casting film forming method or the melt casting film forming method is used. It is characterized by use.

Invention of Claim 6 is a manufacturing method of the optical film as described in any one of Claims 1-5 , Comprising: The resin material of a film is a cellulose ester resin or a norbornene resin, It is characterized by the above-mentioned. It is said.

The invention of the optical film of claim 7 is characterized by being produced by the method for producing an optical film according to any one of claims 1 to 6 .

Invention of the method for manufacturing the optical film of claim 1 is based, at least in the left and right end portions of the film surface of the left and right end portions and the center portion of the conveying film, by irradiation of a laser beam, an optical film to form the embossed portion having an uneven In the manufacturing method, the blending ratio of the plasticizer on the film surface on the laser beam irradiation side: A and the blending ratio of the plasticizer on the film surface on the laser beam non-irradiation side: B have a relationship of A> B. According to the first aspect of the present invention, even when the height of the unevenness of the embossed portion is changed in accordance with the film thickness, the film does not require time for height adjustment. In addition, the surface property of the film can be remarkably improved since there is no occurrence of a fine wrinkle or scratch on the film surface . In addition, regarding contamination due to divergence of the irradiated part, which has been a concern in the past by laser light irradiation, by setting the plasticizer concentration of the laser light irradiated part higher than the plasticizer concentration of the laser light non-irradiated part, There is an effect that contamination can be suppressed .

  Invention of Claim 2 is a manufacturing method of the optical film of Claim 1, Comprising: The embossed part which adjusts the irradiation output of a laser beam according to the film thickness of a film, and has unevenness | corrugation of 3-20 micrometers in height According to the invention of claim 2, in the knurling of the film end, the output of the laser beam is made variable according to the film thickness, thereby embossing the film end. It is possible to easily adjust the height of the unevenness of the part, and there are no defects such as minute wrinkles or scratches on the film surface caused by the pressure roll contacting the back roll during the conventional knurling process. As a result, the surface property of the film can be dramatically improved.

  Invention of Claim 3 is a manufacturing method of the optical film of Claim 1 or 2, Comprising: The irradiation position of a laser beam is made variable, An embossing part is formed in a predetermined location according to a film width, It is characterized by the above-mentioned. Therefore, according to the invention of claim 3, in the knurling of the film end, by changing the irradiation position of the laser beam, it is possible to emboss at either the width direction end or the center of the film. It is possible to easily form irregularities on the part, and there are no defects such as minute wrinkles or scratches on the film surface caused by contacting the pressure roll to the back roll during the conventional knurling process. The effect is that the surface properties of the film can be dramatically improved.

A fourth aspect of the present invention, a method for producing an optical film according to any one of claims 1 to 3, in which laser beam, characterized in that it is a CO ₂ laser beam, wherein According to the invention of claim 4, the knurling of the film end, in particular using a CO ₂ laser beam of high output, by a variable according to the output of the laser light to the film thickness of the film, embossing the film edge It is possible to easily adjust the height of the unevenness of the part, and there are no defects such as minute wrinkles or scratches on the film surface caused by the pressure roll contacting the back roll during the conventional knurling process. As a result, the surface property of the film can be dramatically improved.

  In the method for producing an optical film of the present invention, a film obtained by a solution casting film forming method or a melt casting film forming method can be used, and as a resin material of the film, a cellulose ester resin or norbornene is used. It is preferable that it is a resin.

Invention of the optical film according to claim 7, which has been produced by the manufacturing method of an optical film according to any one of claims 1 to 6, according to the invention of an optical film according to claim 7, the film the embossed portion having an uneven height corresponding to the thickness, is provided in the film end, yet with small wrinkles scratches failure or the like of the film surface is nil, the surface property of the film is dramatically There is an effect of improving.

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

Method of manufacturing an optical film according to the present invention, at least in the left and right end portions of the film surface of the left and right end portions and the center portion of the conveying film, by irradiation of a laser beam, a manufacturing method of an optical film to form embossed portions having irregularities In the above, the blending ratio A of the plasticizer on the film surface on the laser beam irradiation side and the blending ratio B of the plasticizer on the film surface not irradiated with the laser beam are in a relationship of A> B.

According to the method of the present invention, even when changing the height of the unevenness of the embossed part according to the film thickness, the film productivity is excellent without requiring time for height adjustment. . In addition, the occurrence of failures such as minute wrinkles and scratches on the film surface is eliminated, and the surface properties of the film can be dramatically improved. In addition, regarding contamination due to divergence of the irradiated part, which has been a concern in the past by laser light irradiation, by setting the plasticizer concentration of the laser light irradiated part higher than the plasticizer concentration of the laser light non-irradiated part, Contamination can be suppressed.
In this invention, it is preferable to adjust the irradiation output of a laser beam according to the film thickness of a film, and to form the embossed part which has an unevenness | corrugation of 3-20 micrometers in height.

  Here, if the height of the unevenness of the embossed portion is less than 3 μm, it is not preferable because the films can be easily attached and the embossing effect cannot be exhibited. Moreover, when the height of the unevenness of the embossed portion exceeds 20 μm, the apparent difference in diameter between the end portion with the embossed portion and the unembossed central portion becomes large in the original film, and the horse's back failure, deformation failure, etc. This is not preferable because it induces a failure.

  Moreover, in the manufacturing method of the optical film of this invention, it is preferable to make an irradiation position of a laser beam variable and to form an embossed part in a predetermined location according to a film width. In this way, by making the irradiation position of the laser light variable, it becomes possible to easily form the unevenness of the embossed part at either the end or the center in the width direction of the film. At the time of processing, there is no failure such as minute wrinkles or scratches on the film surface caused by bringing the pressure roll into contact with the back roll, and the surface properties of the film can be dramatically improved.

  Furthermore, in the present invention, the blending ratio of the plasticizer on the film surface on the laser beam irradiation side: A and the blending ratio of the plasticizer on the film surface on the laser beam non-irradiation side: B have a relationship of A> B. Is preferred.

  As described above, by setting the plasticizer concentration in the laser light irradiated portion higher than the plasticizer concentration in the laser light non-irradiated portion, contamination due to divergence of the laser light irradiated portion can be suppressed. In addition, it was found that there was no problem in production by installing a scattering material discharge near the laser beam irradiation.

By the way, the laser light means “Light Amplification by Stimulated Emission of Radiation”, and there are several types depending on the oscillation wavelength. The laser light used in the present invention has a high output. Of these, CO ₂ laser light is preferred. The wavelength of the CO ₂ laser light is 9.3 to 10.6 micrometers, and has a wavelength about 10 times that of the YAG laser light (wavelength 1.064 micrometers). The CO ₂ laser beam is obtained by exciting gas (CO ₂ ) as a medium, and the laser beam YAG laser beam is obtained by exciting a YAG (yttrium, aluminum, garnet) crystal. It is.

  In the method for producing an optical film according to the present invention, a film obtained by a solution casting method or a melt casting method can be used.

  Hereinafter, these will be described in detail.

  Various resins can be used for the optical film of the present invention, and among them, cellulose ester resins and norbornene resins are preferable.

  The cellulose ester resin is a cellulose ester in which a hydroxyl group derived from cellulose is substituted with an acyl group or the like. Examples thereof include cellulose acylates such as cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate, and cellulose acetate propionate butyrate, and cellulose acetate having an aliphatic polyester graft side chain. Among these, 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 acetate propionate, it is preferable that the substitution degree of the acyl group is 2.0 or more and 3.0 or less, and the substitution degree of the acetyl group is 1.4 or more and 2.4 or less. Further, the substitution degree of the acyl group is preferably 2.5 or more and 2.8 or less, and the substitution degree of the acetyl group is preferably 1.5 or more and 2.0 or less. By setting the degree of substitution within this range, good moldability by the melt casting film forming method can be obtained, and desired in-plane direction retardation (Ro) and thickness direction retardation (Rt) can be easily obtained. It is. 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.

  When a propionyl group is introduced as a substituent, the plasticity of the cellulose ester is improved and the moldability is improved.

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

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

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

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

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

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

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

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

  As the norbornene-based resin used in the present invention, for example, (1) a ring-opening (co) polymer of a norbornene-based monomer is subjected to polymer modification such as maleic acid addition or cyclopentadiene addition, if necessary, and then hydrogenated. Examples thereof include resins added, (2) resins obtained by addition polymerization of norbornene monomers, and (3) resins obtained by addition polymerization with norbornene monomers and olefin monomers such as ethylene and α-olefin. The polymerization method and the hydrogenation method can be performed by conventional methods.

  In the present invention, various additives can be blended in the resin material.

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

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

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

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

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

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

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

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

  In the present invention, in order to impart the slipperiness of the film, the surface is roughened by surface processing to impart the slipperiness, so that it is not necessary to add fine particles as conventionally used. However, in the case where the same film production line as the conventional manufacturing method is shared, there is a possibility that fine particles which have been conventionally added are mixed as contamination. Even in that case, since the addition process of the fine particles is not substantially used, the content of the fine particles in the film may be contained at 0.02% by weight or less with respect to the resin. There is no effect.

  In the present invention, the fine particles refer to particles having an average particle size of less than 5 μm present in the film or on the surface thereof, and are mainly inorganic fine particles. The content and presence state of these can be confirmed by an electron microscope, or can be confirmed by elemental analysis with an inductively coupled plasma emission spectrometer after dissolving the film with alkali or the like.

  The optical film of the present invention is produced by first forming a cellulose ester-based resin or a norbornene resin into a sheet, and stretching and orienting the sheet.

  In the present invention, the sheet is formed by a solution casting film forming method or a melt casting film forming method. Any of them can be formed by a known method.

  FIG. 1 is a schematic cross-sectional view 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 figure, for example, a cellulose ester film production apparatus is based on a solution casting film forming method, and a dope casting die (dope casting) for casting a dope, which is a raw material solution of a cellulose ester film, on a support 1. Means) 2, and the web 10 formed on the support 1 by the dope casting die 2 is peeled from the support 1 by the peeling roll (peeling means) 3 for peeling from the support 1 and the peeling roll 3. A drying unit that dries the web 10 while being conveyed, and a winder (winding unit) 15 that winds the dried film F are provided.

  In FIG. 1, first, a cellulose ester resin is dissolved in a mixed solvent of a good solvent and a poor solvent, and the above plasticizer and ultraviolet absorber are added thereto to prepare a resin solution (dope). The dope is fed to the casting die (2) through, for example, a pressurized metering gear pump, and the dope is cast from the casting die (2) onto the stainless steel endless belt support (1) at the casting position. The belt temperature during film formation can be cast at a temperature in the general temperature range of 0 ° C. to less than the boiling point of the solvent, and 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 atmosphere temperature to be higher than the dew point.

  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.

  When casting the dope onto the support (1), the temperature is controlled below the boiling point of the solvent used for dissolving the raw resin, and below the boiling point of the solvent having the lowest boiling point in the mixed solvent. The temperature can be cast at a temperature in the general temperature range of 0 ° C. to less than the boiling point of the solvent, but is more preferably cast on a support (1) at 5 to 30 ° C.

  In the illustrated film forming apparatus comprising a rotationally driven endless belt as the support (1), the belt support (1) is disposed between a pair of drums and the upper transition portion of the endless belt support (1). And a plurality of rolls each supporting the lower transition portion from the back side. In addition, one or both of the drums wound at both ends of the rotationally driven endless belt support (1) are provided with a drive device that applies tension to the belt support (1), whereby the belt support (1). Is used under tension and tension.

  Then, the dope adjusted to have a dope viscosity of 1 to 200 poise is cast from the casting die (2) onto the support (1) so as to have a substantially uniform film thickness. When the residual solvent amount in the solid content weight is 200% or more, the casting membrane temperature is lower than the solvent boiling point, and in the range where the residual solvent amount is 100 to 200% solid weight, the solvent boiling point is + 10 ° C. or lower. In addition, the cast film (web) is dried with drying air so that the residual solvent amount is 100% or less to peeling until the solvent boiling point is + 20 ° C. or less.

  A dope is cast from a casting die (2) onto a stainless steel endless belt support (1) having a mirror-finished surface to obtain a dope film (web) (10), the web (10) being an endless belt. When the substrate (1) has moved approximately 3/4 rounds by the rotation of the support (1), it is peeled off by the peeling roll (3).

  On the support (1), in order to dry and solidify the web (10) until the film strength is peelable from the support (1), the residual solvent amount in the web (10) is dried to 150% by weight or less. Is preferable, and 80 to 120% by weight is more preferable.

  The temperature of the web (10) when peeling the web (10) from the support (1) is preferably 0 to 30 ° C. Further, immediately after the web (10) is peeled off from the support (1), the temperature is once lowered rapidly by the solvent catalyst from the contact surface side of the support (1), and volatile components such as water vapor and solvent vapor in the atmosphere are removed. Since it is easy to condense, the web temperature during peeling is more preferably 5 to 30 ° C.

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

Residual solvent amount (% by weight) = {(M−N) / N} × 100
Here, M is the weight of the web at any point in time, and N is the weight when a weight M is dried at 110 ° C. for 3 hours.

  Peeling is usually performed at a peeling tension of 20 to 25 kg / m when peeling the support (1) and the web (10), but peeling is preferably performed at a minimum tension of 17 kg / m. More preferably, peeling is performed with a minimum tension of -14 kg / m.

  The web (10) is then introduced into the tenter dryer (4). Therefore, the side edges of the web (10) are gripped with a clip and stretched, and the web (10) is dried. In the tenter drying device (4), the web (10) is blown from the front portion of the bottom of the tenter drying device (4) and dried by warm air discharged from the rear portion of the ceiling of the tenter drying device (4). Is done.

  In the tenter drying apparatus (4), drying is performed using warm air, but the means for drying the film is not particularly limited, and is performed by hot air as described above, or also by infrared rays, heating rolls, microwaves, or the like. It is preferable to carry out with hot air in terms of simplicity. The drying temperature is preferably in the range of 40 to 150 ° C. and gradually increased to 3 to 5 stages, and more preferably in the range of 80 to 140 ° C. in order to improve dimensional stability.

  Next, the stretched cellulose ester film (web) (10) is introduced into a roll transport drying device (5). In the roll transport drying device (5), the web (10) is meandered by 50 to 1000 transport rolls (7), while the web (10) is, for example, in front of the bottom of the roll transport drying device (5). It is blown from the near part and dried by the warm air discharged from the rear part of the ceiling of the roll transport drying device (5).

  The both ends of the width direction of the film dried by the roll conveyance drying device (5) are slit to a product width by the slitter (12) and cut off. Here, it is preferable that the width | variety of the both ends of the width direction of the web 10 to be cut | disconnect is 50-100 mm.

  Next, by the method of the present invention, an embossed portion having irregularities on the film surfaces of at least the left and right ends of the left and right ends and the central portion of the transport film (F) after slitting by means of a laser beam irradiation device (13). Form. In addition, (14) is a conveyance roll.

As shown in FIG. 2, according to the method of the present invention, for example, laser light output: 7 is applied to the film surfaces of the left and right end portions of the transport film (F) after slitting by a CO ₂ laser light irradiation device (13a) (13b). The embossed portion (E) having unevenness with a wavelength height of 3 to 20 μm is formed by irradiating CO ₂ laser light of 9.3 to 10.6 μm at 0.5 to 30 W.

  According to the method of the present invention, since the embossed part (E) having irregularities is formed by laser light irradiation, the height of the irregularities of the embossed part (E) according to the film thickness of the film (F). Even in the case of changing the thickness, it takes no time to adjust the height, and the productivity of the film (F) is excellent. In addition, the occurrence of failures such as minute wrinkles and scratches on the surface of the film (F) is eliminated, and the surface properties of the film (F) can be dramatically improved.

  In this invention, it is preferable to adjust the irradiation output of a laser beam according to the film thickness of a film (F), and to form the embossed part (E) which has an unevenness | corrugation with a height of 3-20 micrometers.

  Moreover, in the manufacturing method of the optical film of this invention, it is preferable to make an irradiation position of a laser beam variable and to form an embossed part (E) in a predetermined location according to a film (F) width. In this way, by making the irradiation position of the laser light variable, it is possible to easily form the unevenness of the embossed portion (E) at either the widthwise end portion or the central portion of the film (F). Thus, there is no failure such as minute wrinkles or scratches on the surface of the film (F), and the surface properties of the film (F) can be remarkably improved.

  Furthermore, in the present invention, the blending ratio of the plasticizer on the surface of the film (F) on the laser beam irradiation side: A and the blending ratio of the plasticizer on the surface of the film (F) on the laser beam non-irradiation side: B are: It is preferable that the relationship is> B.

  As described above, by setting the plasticizer concentration in the laser light irradiated portion higher than the plasticizer concentration in the laser light non-irradiated portion, contamination due to divergence of the laser light irradiated portion can be suppressed. In addition, it was found that there was no problem in production by installing a scattering material discharge near the laser beam irradiation.

The laser beam used in the present invention is preferably a high output CO ₂ laser beam. The wavelength of the CO ₂ laser light can be selected between 9.3 and 10.6 micrometers.

  By the method of this invention, the embossed part (E) which has an unevenness | corrugation was formed in the film (F) surface of the left and right both ends and center part of a conveyance film (F) by the laser beam irradiation at least. After that, the film (F) is wound up by a winder (15).

  The winder (15) related to the production of the optical film of the present invention may be a commonly used one such as a constant tension method, a constant torque method, a taper tension method, a program tension control method with a constant internal stress, and the like. It can be wound up by a winding method.

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

  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.

  To adjust the film thickness, the dope concentration, the pumping amount, the slit gap of the die of the casting die (2), the extrusion pressure of the die, the casting support ( It is better to control the speed of 1).

  As described above, in the method for producing an optical film according to the present invention, a resin film produced by a melt casting method can be used.

  Here, as the melt casting film forming method, although not shown, there are a melt extrusion method such as a method using a T die and an inflation method, a calendar method, a hot press method, an injection molding method and the like. Among them, a melt extrusion method using a T die that has a small thickness unevenness, can be easily processed to a thickness of about 50 to 500 μm, and can reduce the absolute value of retardation and its variation is preferable.

  The conditions of the melt casting film forming method can be molded in the same manner as the conditions used for other thermoplastic resins. For example, the dried cellulose ester resin and norbornene resin were melted at an extrusion temperature of about 200 to 300 ° C. using a uniaxial or biaxial extruder and filtered with a leaf disk type filter to remove foreign matters. Then, it casts into a sheet form from T-die and solidifies on a cooling drum.

  When introducing from the supply hopper to the extruder, it is preferable to prevent oxidative decomposition or the like under reduced pressure or in an inert gas atmosphere. The temperature of the cooling drum is preferably equal to or lower than the glass transition temperature (Tg) of the cellulose ester resin. In order to bring the resin into close contact with the cooling drum, it is preferable to use a method in which the resin is brought into contact by applying electrostatic force, a method in which the resin is brought into contact with wind pressure, a method in which the full width or the end is attached in a nip, a method in which the resin is brought into contact with reduced pressure. Further, in order to reduce surface defects such as die lines, it is preferable that the piping from the extruder to the die has a structure in which the staying portion is minimized. It is preferable to use a die that has as few scratches as possible inside the lip. Since the volatile component may be deposited from the resin around the die and cause a die line, it is preferable to suck the atmosphere containing the volatile component. Moreover, since it may precipitate also in apparatuses, such as an electrostatic application, it is preferable to apply alternating current or to prevent precipitation with another heating means.

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

  There is no restriction | limiting in particular in the thickness of a sheet | seat, What is necessary is just to set so that it may become desired thickness after extending | stretching, and 50-500 micrometers is preferable. Of course, the smaller the thickness unevenness, the better. The entire surface is within ± 5%, preferably within ± 3%, and more preferably within ± 1%.

  Unlike the cellulose ester resin sheet molded by the solution casting film forming method, the cellulose ester resin sheet molded by such a melt casting film forming method has a feature that the thickness direction retardation (Rt) is small. Yes, it is easy to express in-plane retardation (Ro) by stretching such a cellulose ester-based resin sheet, and it is not necessary to increase the stretch ratio. Therefore, the cellulose ester-based resin film is excellent in transparency without white turbidity. Is obtained.

  Next, the obtained sheet is stretched in a uniaxial direction. The molecules are oriented by stretching. The stretching method is not particularly limited, but a known pin tenter or clip type tenter can be preferably used. The stretching direction can be the length direction, the width direction, or an arbitrary direction (oblique direction). However, in the present invention, the stretching direction is set to the width direction, which is preferable because lamination with a polarizing film can be performed in a roll form. By stretching in the width direction, the slow axis of the cellulose ester resin film becomes the width direction. On the other hand, the transmission axis of the polarizing film is also usually in the width direction. A good viewing angle can be obtained by incorporating in a liquid crystal display device a polarizing plate laminated so that the transmission axis of the polarizing film and the slow axis of the cellulose ester resin film are parallel to each other.

  As the stretching conditions, the temperature and magnification can be selected so that desired retardation characteristics can be obtained. Usually, the draw ratio is 1.1 to 2.0 times, preferably 1.2 to 1.5 times, and the drawing temperature is usually Tg to Tg + 50 ° C., preferably Tg to Tg + 40 ° C. of the resin constituting the sheet. In the temperature range. If the draw ratio is too small, the desired retardation may not be obtained, and if it is too large, it may break. If the stretching temperature is too low, it will break, and if it is too high, the desired retardation may not be obtained.

  When correcting the retardation of the optical film produced by the above method to a desired value, the film may be stretched or shrunk in the length direction or the width direction. In order to shrink in the length direction, for example, there is a method in which width stretching is temporarily clipped out and relaxed in the length direction, or the film is shrunk by gradually narrowing the interval between adjacent clips of the transverse stretching machine. is there. The latter method can be performed by using a general simultaneous biaxial stretching machine and by using a pantograph method or a linear drive method to drive the clip portion in a smooth and gradually narrowing interval between adjacent clips in the longitudinal direction. it can. In addition, since the film is deform | transforming and cannot use as a product normally, the holding | grip part of the clip of both ends of a film is cut out and reused as a raw material.

Next, by the method of the present invention, the embossed portion having irregularities on the film surface of at least the left and right end portions of the left and right end portions and the central portion of the stretched transport film by the above-described CO ₂ laser light irradiation device (13). (E) is formed.

  According to the method of the present invention, since the embossed part (E) having unevenness is formed by laser light irradiation, the height of the unevenness of the embossed part (E) is changed according to the film thickness of the film. Even in such a case, the film productivity is excellent without requiring time for height adjustment. In addition, the occurrence of failures such as minute wrinkles and scratches on the film surface is eliminated, and the surface properties of the film can be dramatically improved.

  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 can be adjusted by controlling the extrusion flow rate, the slit gap of the die base, the speed of the cooling drum, etc. so as to obtain a desired thickness. Further, as a means for making the film thickness uniform, it is preferable to use a film thickness detection means to feed back and adjust the programmed feedback information to each of the above devices.

  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. In particular, in the protective film for polarizing plate which has strict requirements for moisture permeability and dimensional stability, the optical film of the present invention is preferably used.

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

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

  The polarizing plate thus obtained can be used for various display devices. In particular, a liquid crystal display device using a VA mode liquid crystal molecule in which liquid crystal molecules are substantially vertically aligned when no voltage is applied, or a TN mode liquid crystal cell in which liquid crystal molecules are substantially horizontal and twisted when no voltage is applied. Is preferred.

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

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

  Thus, the obtained polarizing plate is provided in the one or both surfaces of a liquid crystal cell, and the liquid crystal display device of this invention is obtained using this.

  By using the protective film for a polarizing plate comprising the optical film of the present invention, it is possible to provide a polarizing plate excellent in durability, dimensional stability, and optical isotropy as well as thinning. Furthermore, the liquid crystal display device using the polarizing plate or retardation film of the present invention can maintain stable display performance over a long period of time.

  The optical film of the present invention can also be used as a base material for an antireflection film or an optical compensation film.

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

Examples 1 to 3 and Examples 5 to 6 are given as reference examples.
Example 1
In producing the cellulose chromatography scan acetate propionate film of the target dry film thickness 40μm by solution casting film forming method, and the first dope was prepared.

(Dope composition)
Cellulose acetate propionate 100 parts by weight (acetyl group substitution degree 1.9, propionyl group substitution degree 0.8,
Mn = 70000, Mw = 220,000, Mw / Mn = 3.14)
Triphenyl phosphate 8 parts by weight Ethylphthalyl ethyl glycolate 2 parts by weight Tinuvin 109 (manufactured by Ciba Specialty Chemicals) 0.5 part by weight Tinuvin 171 (manufactured by Ciba Specialty Chemicals) 0.5 part by weight Methylene chloride 300 parts by weight Parts ethanol 60 parts by weight silicon dioxide fine particles 2 parts by weight (trade name: AEROSIL-R972V, primary particle size: 16 nm)
The above materials were put into a sealed dope melting pot, heated, and completely dissolved while stirring. Of the above materials, the ultraviolet absorber and the silicon dioxide fine particles were charged into the additive solution dissolution vessel in order to prepare the ultraviolet absorber additive solution.

  Thereafter, the dope in the melting pot is guided to the main filter by the operation of the liquid feed pump, and the dope is subjected to primary filtration. In the main filter, the dope solution was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd.

  The dope after the primary filtration is temporarily stored in a dope stock kettle. Next, the dope after primary filtration was guided from the dope stock kettle to the filter set with the sintered metal filter by operating the liquid feed pump, and the dope was subjected to secondary filtration in the filter 6.

  On the other hand, the ultraviolet absorbent additive liquid prepared by the additive liquid dissolving pot is guided to a filter by the operation of the liquid feed pump, and the ultraviolet absorbent additive liquid is filtered in advance by the filter 9. Then, the dope after the secondary filtration is introduced into the static mixer, and the pre-filtered ultraviolet absorbent additive solution is introduced before the static mixer, and the ultraviolet absorbent additive solution is added in-line to the dope.

  The dope after the addition of the ultraviolet absorber addition liquid is introduced into a casting die of a belt casting apparatus, and a cellulose acetate propionate film is produced by a solution casting film forming method.

  That is, the cellulose acetate propionate dope prepared as described above was uniformly cast on a stainless steel band support at a temperature of 30 ° C. With the stainless steel band support, the solvent was evaporated until the amount of residual solvent reached 100% by weight, and the release band was peeled off from the stainless steel band support with a peeling tension of 162 N / m. The peeled cellulose acetate propionate web was evaporated at 35 ° C., slit to 1650 mm width, and then dried at a drying temperature of 135 ° C. while stretching 1.1 times in the width direction with a tenter. .

  Then, drying was terminated while conveying the drying zone of 110 degreeC and 120 degreeC with many rolls, and it slit to 1430 mm width.

A marked, the film surface of the left and right end portions of the conveying film after slits (F), CO ₂ laser beam irradiation device (MLZ9510, Keyence Corporation Inc.), the laser light output: 30 W Setting a 100% In Example 1, an embossed portion (E) having unevenness with a wavelength height of 5 μm is formed by irradiating a 10.2 μm CO ₂ laser beam with a laser light output of 25%, and an initial tension of 220 N / m, A cellulose acetate propionate film was obtained by winding it around a 6 inch inner diameter core with a final tension of 110 N / m.

Results obtained by evaluating the number of whisker-like faults, the number of perforated faults, and the height distribution (%) of irregularities when 50 rolls of 3000 m cellulose acetate propionate film were produced continuously Is shown in Table 1 below. Table 1 shows the film thickness (μm) of the obtained film, the CO ₂ laser light output used (%), the set height of the unevenness (μm), and the presence or absence of scattering of the plasticizer at the time of laser irradiation. Showed.

  Here, the number of beard-like failures in the film is evaluated by evaluating whether or not the film is partially melted by heating by laser irradiation and fuzzing (whisker-like failure) occurs. Expressed by the number of rolls of the film.

  Further, the evaluation of the number of holes in the film was evaluated by evaluating the presence or absence of holes perforated instantaneously in the film when heated by laser irradiation, and expressed by the number of windings of the film in which the holes were broken.

  Furthermore, the height distribution (%) of the unevenness of the embossed part of the film was evaluated as follows.

  That is, in one roll of film (one piece), the film thickness of the embossed part and the film thickness of the unembossed part are measured at intervals of 10 cm between 1 m in the longitudinal (conveyance) direction, and the height of the embossing (= Embossed part film thickness-Unembossed part film thickness) 10 points, 20 points on both left and right ends were measured, and a total of 50 3000 m rolls of the cellulose acetate propionate film were produced continuously. The average value of the height was evaluated according to the following formula when the standard deviation was calculated.

(Standard deviation of unevenness / average height of unevenness) x 100 (%)
Here, it is preferable that the unevenness distribution (%) of the embossed portion of the film is narrow and monodispersed, since there is less concern about failures such as sticking, horse back, deformation, and the like.

  The evaluation of the unevenness distribution (%) of the embossed portion of the film is preferably 30% or less, more preferably 20% or less, and most preferably 10% or less.

Examples 2-4
In the same manner as in Example 1, but making a cellulose acetate propionate film, as in Example 1, the thickness of the film ([mu] m), CO ₂ laser beam output to be used (%) Cellulose acetate propionate films were produced by changing the set height of unevenness (μm) in various ways.

At this time, the CO ₂ laser light irradiation device (MLZ9510, manufactured by Keyence Corporation) makes the output of the laser light variable according to the film thickness of the film, so that the embossed portion (E) at the end of the film is It is possible to easily adjust the height of the unevenness, easily adjust the output of the CO ₂ laser light, irradiate the laser light, and provide an embossed portion (E) having unevenness having a desired height. Could be formed.

In particular, in Example 4, before the irradiation with CO ₂ laser light, the laser irradiation surface of the film was overcoated with a plasticizer equivalent to 20% of the film content by an inkjet method.

Comparative Examples 1 and 2
For comparison, it is carried out in the same manner as in Example 1, but on the film surfaces at the left and right ends of the transport film (F) after slitting, by a conventional so-called hot press method (275 ° C., variable pressure method), An embossed part having irregularities was formed.

  In Comparative Examples 1 and 2, the number of whisker-like failures, the number of perforated failures, and the height distribution (%) of the irregularities of the cellulose acetate propionate film when continuously producing 50 rolls of 3000 m was obtained. The results obtained are shown in Table 1 below. In addition, Table 1 shows the film thickness (μm) of the obtained film and the set height (μm) of the unevenness.

  In addition, as for the film thickness (μm) and the set height (μm) of the unevenness, Comparative Example 1 corresponds to Example 1, and Comparative Example 2 corresponds to Example 3.

Example 5
A norbornene resin film was prepared in substantially the same manner as in Example 2 except that a norbornene resin was used in place of cellulose acetate propionate as the transparent resin.

(Preparation of fine particle dispersion)
Ethanol 27 parts by weight Fine particles I / Silicon dioxide fine particles 3 parts by weight
(Product name: AEROSIL-R972V, primary particle size: 16 nm)
The above materials were mixed in a predetermined container, stirred for 30 minutes at 500 rpm, dispersed in a Manton Gorin type high pressure disperser at a pressure of 250 kgf / cm ² , and then the dispersion was dissolved in methylene chloride 27. The fine particle dispersion was prepared by diluting with parts by weight.

(Preparation of norbornene resin solution)
Norbornene resin (Arton G, manufactured by JSR) 80 parts by weight Triphenyl phosphate 8 parts by weight Ethylphthalyl ethyl glycolate 2 parts by weight Methylene chloride 250 parts by weight Ethanol 10 parts by weight The above materials are charged in a melting kettle and heated to 70 ° C. While stirring, the norbornene resin was completely dissolved to obtain a norbornene resin solution. The time required for dissolution was 4 hours. Then, the norbornene-based resin solution is discharged from the flow pipe connected to the bottom of the dissolving kettle and transferred by the operation of the liquid feed pump. In the filter, filter paper having an absolute filtration accuracy of 0.005 mm is used, and the filtration flow rate is 300 l. Filtration was performed at a filtration pressure of 1.0 × 10 ⁶ Pa at / m ² · hr.

(Preparation of additive solution)
Norbornene resin solution 75 parts by weight Tinuvin 109 (manufactured by Ciba Specialty Chemicals Co., Ltd.) 0.5 part by weight Tinuvin 171 (manufactured by Ciba Specialty Chemicals Co., Ltd.) 0.5 part by weight The fine particle dispersion 60 parts by weight Methylene chloride 290 parts by weight In the dissolution vessel, while stirring the methylene chloride, a part of the norbornene resin solution after filtration was added, and then added in the order of the ultraviolet absorber and the fine particle dispersion. After the addition, the mixture was heated to 40 ° C. and dissolved for 30 minutes to prepare the additive solution. Subsequently, this additive solution was discharged from the flow pipe connected to the bottom of the dissolution vessel, transferred by the operation of the liquid feed pump, and filtered with a filter having a nominal filtration accuracy of 20 μm.

(Preparation of dope for norbornene resin film)
In the above filter, a filter paper having an absolute filtration accuracy of 0.005 mm is used, the filtration is performed at a filtration flow rate of 300 l / m ² · hour, the filtration pressure is 1.0 × 10 ⁶ Pa, and the filtrate is fed by a feeding pipe. The dope for norbornene-based resin film was prepared by adding in-line the above-mentioned additive solution after filtration from the flow tube to the main part (remainder) of the norbornene-based resin solution and mixing with a static mixer. .

(Preparation of norbornene resin film sample)
A dope for the norbornene resin film was prepared using a solution casting film forming apparatus (FIG. 1) in the same manner as in Example 2 to prepare a norbornene resin film having a thickness of 80 μm.

At this time, the CO ₂ laser light irradiation device (MLZ9510, manufactured by Keyence Corporation) makes the output of the laser light variable according to the film thickness of the film, so that the embossed portion (E) at the end of the film is it is possible to adjust the height of the unevenness easily, CO ₂ laser beam output to be used (%), setting the irregularity height ([mu] m), was prepared in the same manner as in example 2 above, the laser Irradiated with light, an embossed part (E) having irregularities having a height of 10 μm could be formed.

Example 6
(Manufacture of cellulose acetate film)
A 80 μm film was produced by a melt film-forming method using cellulose acetate (Eastman Chemical Co., CA-398-3) to obtain a cellulose ester film.

  As heat stabilizers, epoxidized tall oil 0.6% by weight, para-tert-butylphenol 0.4% by weight, neopentylphenyl phosphite 0.07% by weight, strontium naphthoate 0.02% by weight, and silicon dioxide part 0.05% by weight of particles (Aerosil R972V) was added.

At this time, the above-mentioned CO ₂ laser light irradiation device (MLZ9510, manufactured by Keyence Corporation) installed in front of the film winding device makes the output of the laser light variable according to the film thickness of the film. It is possible to easily adjust the height of the unevenness of the embossed portion (E) at the end, and the CO ₂ laser light output (%) to be used and the set height (μm) of the unevenness are the same as those in Example 2 above. In the same manner as in the case, the laser beam was irradiated to form an embossed portion (E) having irregularities having a height of 10 μm.

  The film width was 1430 mm, the winding length was 3000 m, and the film forming speed was 25 m / min.

In Examples 2 to 6, the number of beard-like failures, the number of perforated failures, and the height distribution (%) of unevenness were evaluated when 50 rolls of 3000 m of each film were continuously produced. The results obtained are shown in Table 1 below. In addition, Table 1 shows the film thickness (μm) of the obtained film, the CO ₂ laser light output used (%), the set height of irregularities (μm), and the presence or absence of scattering of the plasticizer during laser irradiation. Showed.

As is clear from the results in Table 1 above, according to Example 4 of the present invention , and Examples 1 to 3 and Examples 5 to 6 given as reference examples, according to the film thickness of the film, Even when changing the height of the unevenness of the embossed part (E), it does not take time to adjust the height, it is excellent in film productivity, and there are fine wrinkles and scratches on the film surface. There was no occurrence of failure (beard-like failure, perforation failure), the surface properties of the film were dramatically improved, and a film with excellent optical properties could be produced.

  On the other hand, in the film of Comparative Example 1, there were many occurrences of failures such as minute wrinkles and scratches on the film surface (skin failure), and there was a problem in use as an optical film such as a protective film for polarizing plates. .

It is a general | schematic flow sheet of the solution casting film forming apparatus which enforces the manufacturing method of the optical film of this invention. The method of the present invention, the CO ₂ laser irradiation apparatus on the film surface of the left and right end portions of the conveying film from the slit is a partially enlarged perspective view showing a state of forming an embossed portion having an uneven.

1: Endless belt support 2: Casting die 3: Peeling roll 4: Tenter dryer 5: Roll transport dryer 6: Transport roll 7: Transport roll 10: Web 12: Slitter 13: CO ₂ laser light irradiation device 14 : Transport roll 15: Winding machine E: Embossed part F: Cellulose ester film

Claims (7)

In the manufacturing method of an optical film in which embossed portions having irregularities are formed by irradiating laser light on the film surface of at least the left and right end portions of the left and right end portions and the central portion of the transport film, the film surface on the laser light irradiation side A method for producing an optical film, wherein the blending ratio of the plasticizer: A and the blending ratio of the plasticizer on the film surface on the laser beam non-irradiated side: B have a relationship of A> B.   2. The method for producing an optical film according to claim 1, wherein the laser beam irradiation output is adjusted in accordance with the film thickness to form an embossed portion having unevenness with a height of 3 to 20 μm.   The method for producing an optical film according to claim 1, wherein the laser beam irradiation position is variable, and an embossed portion is formed at a predetermined location according to the film width. Laser light, wherein the CO ₂ laser beam der Rukoto method for producing an optical film according to any one of claims 1 to 3. Characterized Rukoto using the obtained film by a solution casting film forming method or a melt casting film forming method, manufacturing method of an optical film according to any one of claims 1 to 4. The method for producing an optical film according to any one of claims 1 to 5, wherein the resin material of the film is a cellulose ester resin or a norbornene resin . An optical film produced by the method for producing an optical film according to any one of claims 1 to 6 .

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