JP5347406B2 - Manufacturing method of optical film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an optical film which does not cause disturbance of cut surfaces in cutting edges of the film even when the laser intensity somewhat varies and requires no time for adjustment of the height of the crest in accordance with film thickness and the depth of the trough of embossed portions. <P>SOLUTION: The method of manufacturing the optical film includes the process of irradiating an optical film containing a compound absorbing a laser beam with the laser beam to process the optical film. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

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 a functional film, various functional films used in an organic EL display, and the like, a manufacturing method thereof, and a polarizing plate.

  In recent years, image display devices such as notebook personal computers and TVs have been developed to be thinner and lighter, larger screens, and higher definition. Along with this, optical films used in image display devices are also increasingly demanded for thinning, widening and high quality.

  The manufacturing method of such an optical film is usually a roll-like process in which a resin film cast on a support is peeled off by a solution casting method or a melt casting method, and then subjected to a stretching process or a drying process. It is wound around and manufactured as a film original.

  In such a manufacturing method, when the film width direction end is clipped and processed such as stretching in the width direction, after the clip remains on the both ends of the film, or the end is cracked. As a result, a part that does not become a product occurs. Even when the transverse stretching is not performed, there may be a difference in film thickness between the film both ends and the center. Therefore, it is necessary to slit an unnecessary portion of the film end before winding the film into a roll.

  As a method of slitting unnecessary portions of the film edge, there are a mechanical cutting method that uses a rotary blade or the like and a laser cutting method that uses laser light to cut, but the laser cutting method is better. It is said that the cutting residue is excellent because it is less likely to be generated and the cutting residue is less likely to adhere to the film surface and cause a foreign matter failure. For example, Patent Document 1 proposes a laser processing method in which a good cut surface can be obtained by processing a laser beam into a rectangular shape.

  Further, when the film is wound in a roll shape, the film surfaces rub against each other and the film surface is damaged. For this reason, embossing is generally performed in which irregularities are formed on the surface of both ends of the film before the film is wound into a roll shape so that the film surface is hardly rubbed during winding.

As a method of forming irregularities on the surfaces of both ends of the film, generally, an embossed portion having irregularities is formed on the surfaces of both ends in the width direction of the film by pressing an embossing roll having irregularities on the film. It is. For example, in Patent Document 2, by providing a plurality of embossed portions with different pitches on both sides in the film width direction, a gap is formed between the surfaces of the films when wound in a roll shape. A method of forming and preventing the rubbing, adhesion and wrinkling of surfaces has been proposed.
JP 2008-73742 A JP 7-108603 A

  However, in the method described in Patent Document 1, it is difficult to control to an appropriate laser intensity, and only a slight deviation from the appropriate laser intensity disturbs the cut surface and causes uneven film thickness at the cut portion. This caused the problem of uneven film conveyance and distortion of the film at the time of winding, resulting in a problem that a flat film could not be obtained.

  Moreover, in the method of the said patent document 2, if the film thickness specification of the film to manufacture changes, unless the uneven | corrugated shape of an embossing roll also changes, the appropriate uneven | corrugated height cannot be formed in a film edge part. Therefore, every time a film having a different film thickness specification is manufactured, it takes time to replace the embossing roll, and there is a problem that productivity is deteriorated.

  The object of the present invention is to solve the above-mentioned problems of the prior art, and in the cutting process of the film end, even if the laser intensity varies somewhat, the cut surface is not disturbed, and the surface of the film end is embossed However, according to the film thickness of the film, it does not take time to adjust the height of the unevenness of the embossed part, it is excellent in film productivity, and also suppresses the occurrence of scratches on the film surface. It is providing the manufacturing method of a film, the optical film manufactured using this manufacturing method, and the polarizing plate using this optical film.

  In order to solve the above problems, the present invention has the following features.

1.

An optical film containing a compound that absorbs the wavelength of the laser light is irradiated with the laser light, it has a step of processing the optical film,
The wavelength of the laser light is in the far infrared region, and the compound is a compound that absorbs light in the wavelength region of 4 to 25 μm,
The compounds, by irradiating the laser beam, before the step of processing the optical film manufacturing method of an optical film wherein a laser beam is characterized that you have been applied to the portion to be irradiated.

2.
2. The method for producing an optical film as described in 1 above, wherein the step is a step of cutting the optical film.

3.
2. The method for producing an optical film as described in 1 above, wherein the step is a step of forming irregularities on the surface of the optical film.

  According to the present invention, since the film contains a compound that absorbs the wavelength of the laser beam, excessive laser intensity is not required, and even if the laser intensity varies somewhat, the cut surface is not disturbed, and the film Even in the embossing to the surface of the end, it eliminates the need for excessive laser intensity, and according to the film thickness of the film, it does not require time to adjust the height of the unevenness of the embossed part, and it excels in productivity, It is possible to provide an optical film manufacturing method, an optical film manufactured using the manufacturing method, and a polarizing plate using the optical film, in which generation of scratches on the film surface is suppressed.

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

  The method for producing an optical film according to the present invention comprises a step of irradiating an optical film containing a compound that absorbs the wavelength of laser light with laser light to process the optical film.

  By using this method for producing an optical film of the present invention, for example, a laser processing step (a step of processing an optical film by irradiating a laser beam, hereinafter sometimes referred to simply as laser processing) is performed in the width direction of the film. In the process of cutting the edge, the film contains a compound that absorbs the wavelength of the laser beam, so the absorption efficiency of the laser beam is improved, excessive laser intensity is not required, the cut part melts, and the cut part has poor appearance The damage to the film is small, and the shape of the cut portion is not disturbed even if the laser intensity varies slightly. In addition, the process of forming irregularities at both ends in the width direction of the film is the process of processing by laser irradiation instead of the process of processing with the conventional embossing roller with irregularities, and the predetermined irregularities are formed satisfactorily. We were able to. In addition, even if the film thickness specification changes, it is not necessary to replace the embossing roller that corresponds to the film thickness as in the past, excessive laser intensity is unnecessary, and damage to the film such as damage to uneven parts is small, Further, by adjusting the intensity of the laser beam, appropriate embossing can be easily performed, so that the film productivity is excellent. In addition, it is preferable that the laser beam irradiation position is variable and the embossed portion is formed at a predetermined position according to the film width. Thus, 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. During processing, there is no failure such as micro wrinkles or scratches on the film surface caused by contacting the embossing roll for pressing with the back roll, and the surface quality of the film can be dramatically improved. is there.

  In addition, the laser processing step according to the present invention is not limited to cutting and embossing as described above, but may be any laser processing performed in the film manufacturing process, for example, to improve transportability. Laser processing such as processing for roughening the surface of the film end portion, processing for forming grooves and irregularities, and the like may be used.

Moreover, in this invention, when the laser beam in a laser processing process is light of a far-infrared area | region, the compound contained in a film is a compound which absorbs the light of a wavelength range of 4-25 micrometers. For example, when the laser beam is a CO ₂ laser, the wavelength of the laser beam is 9.3 to 10.6 μm, and therefore a compound that absorbs a wavelength in this range is preferable.

  In the present invention, when the laser beam in the laser processing step is UV light in the ultraviolet region, the compound contained in the film or applied to the film surface has a wavelength region of 0.2 to 0.4 μm. It is a compound that absorbs light. For example, UV lasers include KrF excimer laser (wavelength 0.248 μm), YAG-FHG laser (wavelength 0.266 μm), YAG-THG laser (wavelength 0.355 μm), etc. Absorbing compounds are preferred.

  Moreover, in this invention, it is preferable to make the part which irradiates the laser beam of the surface of a film contain the compound which absorbs the wavelength of a laser beam before a laser processing process.

  Examples of the method of inclusion include coating and spraying, but other methods may be used, and the means for inclusion is not particularly limited.

  The amount of the compound used can be reduced by, for example, applying the compound to the laser-irradiated part, and the physical properties (color change, transparency, etc.) of the optical film other than the laser-irradiated part depend on the compound. There is no impact. The method for applying the compound to the surface of the film is not particularly limited, and any layer including a compound having a required film thickness may be formed, and an ink jet method, a roller coating method, or the like can be used.

By the way, the laser light means “Light Amplification by Stimulated Emission of Radiation” and is classified into the CO ₂ laser light and the UV laser light according to the oscillation wavelength.

  Next, the optical film of the present invention will be described in detail.

  In the optical film according to the present invention, the film substrate (polymer compound) is preferably a resin selected from the group consisting of cellulose ester resins, norbornene resins, cycloolefin resins, and olefin resins. .

  Here, as a cellulose ester which is the main raw material of a cellulose ester film, cellulose triacetate, cellulose diacetate, cellulose acetate butyrate, cellulose acetate propionate, etc. are mentioned. In the case of cellulose triacetate, cellulose triacetate having a polymerization degree of 250 to 400 and a bound acetic acid amount of 54 to 62.5% is preferable, and a cellulose triacetate having a bound acetic acid amount of 58 to 62.5% has a strong base strength. More preferred. As the cellulose triacetate, either cellulose triacetate synthesized from cotton linter or cellulose triacetate synthesized from wood pulp can be used alone or in combination.

  In the case of the solution casting film forming method, it is better to use a lot of cellulose triacetate synthesized from a cotton linter that is easy to peel off from a support made of a driven rotating stainless steel endless belt (or a driven rotating stainless steel drum). High productivity efficiency is preferable. Since the ratio of cellulose triacetate synthesized from cotton linter is 60% by mass or more and the effect of releasability becomes remarkable, 60% by mass or more is preferable, more preferably 85% by mass or more, and furthermore, use alone. Is most preferred.

  When the cellulose ester film is produced as the optical film of the present invention by the solution casting film forming method, examples of the cellulose ester solvent include lower alcohols such as methanol, ethanol, n-propyl alcohol, iso-propyl alcohol, and n-butanol. , Cyclohexanedioxanes, lower aliphatic hydrocarbon chlorides such as methylene chloride, and the like.

  As a solvent ratio, for example, methylene chloride is preferably 70 to 95% by mass, and other solvents are preferably 30 to 5% by mass. The concentration of the cellulose ester is preferably 10 to 50% by mass. The heating temperature with the addition of the solvent is preferably a temperature not lower than the boiling point of the solvent used and in a range where the solvent does not boil, for example, preferably 60 ° C. or higher and 80 to 110 ° C. The pressure is determined so that the solvent does not boil at the set temperature.

  After dissolution, it is taken out from the container while cooling, or extracted from the container with a pump or the like and cooled with a heat exchanger or the like, and used for film formation.

  In the optical film according to the present invention, the norbornene-based resin that is the main raw material of the norbornene-based resin film is a known resin, and is described in, for example, Japanese Patent Laid-Open Nos. 3-14882 and 3-122137. Yes.

  Examples of the monomer constituting the thermoplastic saturated norbornene resin film include, for example, norbornene, 5-methyl-2-norbornene, 5-ethyl-2-norbornene, 5-butyl-2-norbornene, 5-ethylidene-2-norbornene, 5-methoxycarbonyl-2-norbornene, 5,5-dimethyl-2-norbornene, 5-cyano-2-norbornene, 5-methyl-5-methoxycarbonyl-2-norbornene, 5-phenyl-2-norbornene, 5- Examples include phenyl-5-methyl-2-norbornene.

  The thermoplastic saturated norbornene resin is, for example, (A) a ring-opening polymer or ring-opening copolymer of a norbornene monomer, which is subjected to modification such as maleic acid addition or cyclopentadiene addition, and then hydrogenated. (B) a resin obtained by addition polymerization of a norbornene monomer, (C) a resin obtained by addition polymerization of a norbornene monomer and an olefin monomer such as ethylene or α-olefin, (D) a norbornene monomer and cyclopentene, cyclohexane Examples include resins obtained by addition polymerization with cyclic olefin monomers such as octene and 5,6-dihydrodicyclopentadiene, and modified products of these resins. These polymerizations can be carried out by conventional methods.

  The optical film of the present invention contains a compound that absorbs light in the wavelength region of 4 to 25 μm when the optical film of the present invention has a laser processing step of irradiating laser light in the far infrared region to the film to be conveyed. Has been. Although it does not specifically limit as a compound which absorbs the light of a wavelength range of 4-25 micrometers, For example, the periodic table 1A group, the inorganic metal oxide which has a metal which belongs to 2A group, periodic table 1A group, 2A Inorganic metal composite oxides having at least two metals belonging to Group 3A, Group 3A, inorganic metal composite oxides having at least three metals, hydroxide compounds, sulfate compounds, phosphate compounds, hydrous compounds having at least one metal A talcite compound and a metal complex salt compound having at least two metals are preferable. For example, magnesium oxide, calcium oxide, lithium hydroxide, magnesium hydroxide, calcium hydroxide described in JP-A-2004-344074 , Aluminum hydroxide, magnesium carbonate, calcium sulfate, magnesium sulfate, aluminum sulfate, phosphorus Lithium, calcium aluminate, magnesium aluminate, mica, zeolite, hydrotalcite compound, lithium / aluminum composite hydroxide, aluminum / lithium / magnesium composite carbonate compound, metal composite hydroxide salt containing multiple anions Etc. Further, compounds described as far-infrared absorbers in JP-A Nos. 2001-172608 and 2008-31375 can also be used.

  These compounds are preferably contained in the optical film at 0.001% by mass or more and 10% by mass or less, more preferably 0.05% by mass or more and 5% by mass or less, and more preferably 0.01% by mass or more. It is particularly preferable that the content is 1% by mass or less. When the content is 0.001% by mass or less, the effect of the present invention is not observed, and when the content is 10% by mass or more, the transparency of the film is impaired.

  Further, these compounds are dispersed in an organic solvent, in particular, dispersed in an organic solvent used for dissolving a resin constituting an optical film, and contained by adding it to a resin solution constituting an optical film. it can. By forming this as described above, these compounds can be contained in the film.

  In addition, in the optical film of the present invention, in the optical film manufacturing process, when the film to be conveyed has a laser processing step of irradiating laser light in the ultraviolet region, light in a wavelength region of 0.2 to 0.4 μm is emitted. Contains absorbing compounds. A compound that absorbs light in the wavelength region of 0.2 to 0.4 μm that can be used in the present invention, a so-called ultraviolet absorber (this expression may be used hereinafter) may be a single compound or a mixture. As the mixture, those composed of structural isomers can be preferably used.

  The ultraviolet absorber that can be used in the present invention can take any structure as long as it is a compound that absorbs light in the wavelength region of 0.2 to 0.4 μm, but from the viewpoint of light fastness of the ultraviolet absorber itself, A 2- (2′-hydroxyphenyl) benzotriazole-based compound represented by the formula (1) is preferable.

In the above formula, R ₁ , R ₂ and R ₃ each represent a hydrogen atom, a halogen atom, an alkyl group, an aryl group, an alkoxy group, an aryloxy group, an alkenyl group, a nitro group or a hydroxyl group.

  Examples of the halogen atom include a fluorine atom, a chlorine atom and a bromine atom, and a chlorine atom is particularly preferable.

  As an alkyl group and an alkoxy group, those having 1 to 30 carbon atoms are preferable, and as an alkenyl group, those having 2 to 30 carbon atoms are preferable, and these groups may be linear or branched. These alkyl group, alkoxy group and alkenyl group may further have a substituent. Specific examples of the alkyl group, alkoxy group and alkenyl group include, for example, methyl group, ethyl group, isopropyl group, t-butyl group, sec-butyl group, n-butyl group, n-amyl group, sec-amyl group, t -Amyl group, octyl group, nonyl group, dodecyl group, eicosyl group, α, α-dimethylbenzyl group, octyloxycarbonylethyl group, methoxy group, ethoxy group, octyloxy group, allyl group and the like. As the aryloxy group and aryl group, for example, a phenyl group and a phenyloxy group are particularly preferable and may have a substituent. Specific examples include a phenyl group, 4-t-butylphenyl group, 2,4-di-t-amylphenyl group, and the like.

Of the groups represented by R ₁ and R ₂ , a hydrogen atom, an alkyl group, an alkoxy group, and an aryl group are preferable, and a hydrogen atom, an alkyl group, and an alkoxy group are particularly preferable.

Of the groups represented by R ₃ , a hydrogen atom, a halogen atom, an alkyl group, and an alkoxy group are particularly preferable, and a hydrogen atom, an alkyl group, and an alkoxy group are more preferable.

Of the groups represented by R ₁ , R ₂ and R ₃ , at least one is preferably an alkyl group, and more preferably at least two are alkyl groups in order to be liquid at room temperature.

The alkyl group may take any form, but at least one is preferably a tertiary alkyl group or a secondary alkyl group. In particular, at least one of the alkyl groups represented by R ₁ and R ₂ is preferably a tertiary alkyl group or a secondary alkyl group.

  Below, the typical example of the liquid ultraviolet absorber preferably used for this invention is shown.

  The amount of the ultraviolet absorber preferably used in the present invention is 0.1 to 5% by mass, preferably 0.3 to 5% by weight, based on the absorption effect of ultraviolet rays and transparency, when contained in a film. It is 3 mass%, More preferably, it is 0.5-2 mass%.

  Moreover, when not applying to a film and apply | coating to the location irradiated with a laser beam, a compound can be disperse | distributed to a solution and it can apply | coat with a spray coating device, a spraying device, a roller coating device, etc.

  Various additives can be blended in the optical film of the present invention.

  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, those particularly excellent in compatibility are preferable, and for example, phosphate esters and carboxylic acid esters are preferable. 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 alkyl phthalyl alkyl glycolates include methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, octyl phthalyl octyl glycolate, methyl phthalyl ethyl glycolate, Ethyl phthalyl methyl glycolate, ethyl phthalyl propyl glycolate, propyl phthalyl ethyl glycolate, methyl phthalyl propyl glycolate, methyl phthalyl butyl glycolate, ethyl phthalyl butyl glycolate, butyl phthalyl methyl glycolate, butyl Phthalyl ethyl glycolate, propyl phthalyl butyl glycolate, butyl phthalyl propyl glycolate, methyl phthalyl octyl glycolate, ethyl phthalyl octyl Collate, octyl phthalyl methyl glycolate, octyl phthalyl ethyl glycolate and the like can be mentioned, such as methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, Octyl phthalyl octyl glycolate is preferable, and ethyl phthalyl ethyl glycolate is particularly preferably used. A plasticizer having a large molecular weight is preferable because it can suppress volatilization during extrusion. Examples of these include aliphatic polyesters composed of glycol and dibasic acids such as polyethylene adipate, polybutylene adipate, polyethylene succinate and polybutylene succinate, and fats composed of oxycarboxylic acids such as polylactic acid and polyglycolic acid. Aliphatic polyesters composed of lactones such as aromatic polyesters, polycaprolactone, polypropiolactone and polyvalerolactone, and vinyl polymers such as polyvinylpyrrolidone. These plasticizers can be used alone or in combination.

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

  When the substitution degree of the acetyl group of the cellulose ester 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, fine particles may be added in order to impart film slipperiness. The fine particles used in the present invention may be either inorganic fine particles or organic fine particles as long as they have heat resistance during melting.

  In the present invention, organic fine particles are preferably used in order to reduce the difference in refractive index from the resin. As the organic fine particles, for example, polymers such as silicone resin, fluorine resin, and acrylic resin are preferable, and among them, silicone resin and acrylic resin are preferably used.

  Among the above-described silicone resins, those having a three-dimensional network structure are particularly preferable. For example, Tospearl 103, 105, 108, 120, 145, 3120 and 240 (manufactured by Toshiba Silicone Co., Ltd.) Commercial products having a trade name such as can be used. Cross-linked PMMA particles are also preferably used. For example, commercial products having trade names such as MX-150, 300, 500, 1000, 1500H (manufactured by Soken Chemical Co., Ltd.) can be used.

  Further, in the present invention, it is preferable to use fine particles having a refractive index difference of 0.04 or less from the resin because a film having a high transparency and a low transparency can be obtained. Examples of such fine particles include an E-poster MA having a refractive index of 1.49, an E-poster GP having a refractive index of 1.52 (manufactured by Nippon Shokubai Co., Ltd.), and a techpolymer made by Sekisui Plastics Co., Ltd. with an adjustable refractive index. This can be achieved by combining the MSX series and the like with a resin.

  On the other hand, as inorganic fine particles, silicon-containing compounds, silicon dioxide, aluminum oxide, zirconium oxide, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate and Calcium phosphate and the like are preferable, and inorganic fine particles containing silicon and zirconium oxide are more preferable. Among these, silicon dioxide is particularly preferably used because the turbidity of the cellulose ester laminated film can be reduced. As specific examples of silicon dioxide, commercially available products having trade names such as Aerosil 200V, Aerosil R972V, Aerosil R972, R974, R812, 200, 300, R202, OX50, TT600 (above Nippon Aerosil Co., Ltd.) can be preferably used. .

  As the fine particles of zirconium oxide according to the present invention, for example, those commercially available under trade names such as Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.) can be used.

  In the present invention, the film-to-slip property can be imparted by setting the particle diameter of the fine particles in the film to an equivalent circle diameter of 0.05 to 5.0 μm. When the fine particles used in the present invention are monodisperse particles, the average particle size of the fine particles in the powder becomes the average particle size in the film, so the above range can be selected by selecting the average particle size of the added fine particles. Can be achieved. When the particle size is less than 0.05 μm, the projection height from the film is low, and the films stick to each other and cause deformation. If it exceeds 5.0 μm, even if the refractive index difference between the resin and the fine particles is small, the haze increase cannot be suppressed and the transparency of the film is impaired, which is not preferable as a liquid crystal member.

  The content of the fine particles in the film is preferably 0.05 to 0.5% by mass in order to provide the slipperiness between the films. When the content is less than 0.05% by mass, the number of protrusions from the film is small, and the films stick to each other and cause deformation. If it exceeds 0.5% by mass, an increase in haze cannot be suppressed even if the difference in refractive index between the resin and the fine particles is small, and the transparency of the film is impaired.

  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 manufacturing apparatus is based on a solution casting film forming method, and a casting die 2 for casting a dope, which is a raw material solution of a cellulose ester film, on a support 1, and a casting The web 10 formed on the support 1 by the die 2 is peeled off from the support 1 and the web 10 peeled off from the support 1 by the peeling roll 3 is dried while being conveyed. And a winder (winding means) 15 for winding the web 10 after drying (also referred to as film F).

  In FIG. 1, first, a cellulose ester-based resin is dissolved in a mixed solvent of a good solvent and a poor solvent, and a compound that absorbs light in the above wavelength range of 4 to 25 μm or a wavelength of 0.2 to 0.4 μm. A resin solution (dope) is prepared by adding additives such as a compound that absorbs light in the region and a plasticizer. 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 support 1 of the stainless steel endless belt 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.

  The casting of the dope by the casting die 2 includes 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. In addition, 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 of the support 1 is controlled to be lower than the boiling point of the solvent used for dissolving the raw resin, and lower than the boiling point of the solvent having the lowest boiling point in the mixed solvent. The casting can be carried out at a temperature ranging from 0 ° C. to less than the boiling point of the solvent, but it is more preferred that the casting is carried out on the support 1 at 5 to 30 ° C.

  In the illustrated film forming apparatus having a rotationally driven endless belt as the support 1, the belt support 1 is disposed between a pair of drums and an intermediate portion thereof, and an upper transition portion and a lower transition portion of the endless belt support 1 are respectively provided. Consists of a plurality of rolls supported from the back side. In addition, one or both of the drums at both ends of the rotary drive endless belt support 1 are provided with a drive device that applies tension to the belt support 1, whereby the belt support 1 is applied with tension. Used in a stretched state.

  And the dope adjusted so that dope viscosity may be set to 1-200 poise is cast so that it may become a substantially uniform film thickness on the support body 1 from the casting die 2, and the amount of residual solvent in a casting film However, when the solid content mass is 200% or more, the casting membrane temperature is below the boiling point of the solvent, and when the residual solvent amount is within the range of 100 to 200% of the solid content mass, the residual solvent amount is below the solvent boiling point + 10 ° C. From 100% or less to peeling, the cast film (web) is dried with drying air so that 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 web (dope film) 10, and the web 10 is approximately 3 by rotation of the endless belt support 1. When it has moved / 4 rounds, it is peeled off by the peeling roll 3.

  Since the web 10 is dried and solidified until the web 10 has a peelable film strength from the support 1, the residual solvent amount in the web 10 is preferably dried to 150% by mass or less, and preferably 80 to 120% by mass. Is more preferable.

  As for the temperature of the web 10 when peeling the web 10 from the support body 1, 0-30 degreeC is preferable. Further, immediately after the web 10 is peeled off from the support 1, the temperature is once lowered rapidly by a solvent catalyst from the support 1 contact surface side, and volatile components such as water vapor and solvent vapor in the atmosphere tend to condense. The web temperature at that time is more preferably 5 to 30 ° C.

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

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

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

  Next, the web 10 is 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 is dried by warm air discharged from the rear portion of the ceiling of the tenter drying device 4.

  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 by infrared rays, a heating roll, microwaves, or the like. It is preferable to carry out with hot air in terms of simplicity. The drying temperature is preferably divided into 3 to 5 stages in the range of 40 to 150 ° C. and gradually increased, and more preferably in the range of 80 to 140 ° C. in order to improve dimensional stability.

  Next, the stretched web 10 is introduced into the roll conveyance 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 blown from, for example, the front portion of the bottom of the roll transport drying device 5, and the roll transport drying device. 5 is dried by the warm air discharged from the rear part of the ceiling.

  Next, according to the method of the present invention, both ends in the width direction of the film dried by the roll conveyance drying device 5 are slit to a product width by the laser beam irradiation device 12 as a cutting step 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, as shown in FIGS. 2 (a) and 2 (b), according to the method of the present invention, the height h as an embossing process is applied to the film surfaces of the left and right ends of the film F after slitting by the laser beam irradiation device 13. The embossed part having the unevenness is formed. Reference numeral 14 denotes a transport roll.

When the film F contains a compound that absorbs light in the wavelength region of 4 to 25 μm according to the method of the present invention, the above-described cutting and embossing are performed on the film surfaces at the left and right ends of the film (F). _2. Processing with a laser beam irradiation device. When cutting, for example, it is possible to cut by irradiating a CO ₂ laser beam of 9.3 to 10.6 μm at a laser beam output of 50 to 800 W. In the case of embossing, for example, an embossed portion E having unevenness with a wavelength height of 3 to 20 μm by irradiating a CO ₂ laser beam of 9.3 to 10.6 μm with a laser light output of 7.5 to 30 W. Can be formed. Laser beam irradiation time, irradiation intensity, spot diameter, and the like can be appropriately adjusted to obtain desired irregularities, and are not limited to the above values.

  According to the method of the present invention, since the embossed portion E having unevenness is formed by laser light irradiation, even when the height of the unevenness of the embossed portion E is changed according to the film thickness of the film F. The film F is excellent in productivity without requiring time for height adjustment. In addition, by forming the embossed portion, there is no occurrence of failure such as minute wrinkles or scratches on the surface of the film F that is likely to occur during winding, 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 the film F, and to form the embossed part E which has unevenness | corrugation of height 3-20 micrometers.

  Moreover, in the manufacturing method of the optical film of this invention, it is preferable to make the irradiation position of a laser beam variable and to form the embossed part E in a predetermined location according to the film F width. As described above, by making the irradiation position of the laser light variable, the position of the film F can be easily adjusted even if it is a film having different specifications.

  In addition, as the laser light used in the present invention, when the film F contains a compound that absorbs light in the wavelength region of 0.2 to 0.4 μm, laser processing can be performed using a UV laser. preferable.

  After the embossed portion E having irregularities is formed on the surfaces of the left and right end portions of the film F by laser light irradiation according to the method of the present invention, the film F is wound by the winder 15.

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

  In adjusting 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, and the speed of the casting support 1 are adjusted so as to obtain a desired thickness. It is good to control etc.

  In the method for producing an optical film according to the present invention, a melt casting film forming 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 compounds that absorb light in the wavelength region of 4 to 25 μm, compounds that absorb light in the wavelength region of 0.2 to 0.4 μm, antioxidants, and plasticizers according to the present invention are mixed with the resin in advance. It may be left or 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 driving the clip portions in the longitudinal direction by, for example, a pantograph method or a linear drive method to smoothly and gradually narrow the clip portion. it can. 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.

Subsequently, according to the method of the present invention, the film surface is processed by using the above-described CO ₂ laser light irradiation device 13 or UV laser light irradiation device as cutting and embossing of the left and right ends of the stretched transport film. After processing, it is wound up by a winding device to form a roll-shaped optical film.

  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.

  The polarizer used for the polarizing plate is a conventionally used film, for example, a film that can be stretched and oriented, such as a polyvinyl alcohol film, which is longitudinally stretched by treatment with a dichroic dye such as iodine. Since the polarizer itself does not have sufficient strength and durability, the optical film of the present invention can be disposed and used on at least one side of the polarizer. Preferably, the polarizing plate is formed by adhering the optical film of the present invention on both sides as a protective film.

  A polarizing plate may be prepared by laminating the optical film of the present invention as a retardation film to the polarizer, 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.

  Further, among the optical films according to the present invention, an optical film containing a compound that absorbs light in a wavelength region of 4 to 25 μm is used for a long time of a polarizer of a polarizing plate using the optical film as a protective film for a polarizing plate. There is also an effect of preventing the deterioration of the performance of the liquid crystal display device using the polarizing plate. This is considered to be due to the large influence of light in the wavelength region of 4 to 25 μm as a deterioration factor of the polarizer. Furthermore, in addition to compounds that absorb light in the wavelength region of 4 to 25 μm, including compounds that absorb light in the wavelength region of 0.2 to 0.4 μm prevents further deterioration in performance during long-term use of the polarizer. It has also been found that the deterioration of the visibility of the liquid crystal display device can be prevented.

  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.

Next, examples of the present invention will be described together with comparative examples.
(Examples 1-5)
(Production of optical film by the solution casting film forming method of FIG. 1)
In producing the cellulose triacetate film of the present invention having a target dry film thickness of 40 μm by the solution casting film forming method, first, a dope was prepared. That is, the following blended composition in which triacetyl cellulose was dissolved in a solvent was put into a sealed container, dissolved with stirring to prepare a dope, and the prepared dope was filtered with a filter paper.
(Dope composition)
100 parts by mass of cellulose triacetate having a degree of acetyl substitution of 2.88 (number average molecular weight of 150,000)
Triphenyl phosphate 10 parts by weight Ethylphthalyl ethyl glycolate 2 parts by weight AEROSIL 200V 0.1 part by weight Methylene chloride 475 parts by weight Ethanol 25 parts by weight absorbs light in the wavelength region of 4 to 25 μm (compound A) , Using hydrotalcite (Kyowa Chemical Industry Co., Ltd., “Alkamizer DHT-4A”), UV-23L as a compound (compound B) that absorbs light in the wavelength region of 0.2 to 0.4 μm, The dope compositions of Examples 1 to 5 were obtained by mixing at the blending ratio shown in FIG.

  Hydrotalcite dispersed in ethanol at 5% by mass was diluted with the same amount of methylene chloride and mixed with the dope. In addition, UV-23L was mixed with a dope by dissolving 1% by mass in a mixed solution of ethanol and methylene chloride (mass ratio 1: 1).

  In a raw material mixer, a cellulose triacetate solution (dope) is prepared, and the dope is cast from a casting die onto a support made of a driven rotating stainless steel endless belt having a mirror-finished surface. That is, a web was obtained, and the web reached the lower surface of the support made of an endless belt.

Next, the web peeled by the peeling roll was stretched by the tenter 4. The stretched web F was dried by the drying device 5 and then cut into a predetermined film width by the slitter 12. Table 2 shows the film thickness of the obtained film. Thereafter, the embossing device 13 processed the film in the vicinity of the end of the film with an embossing height of 6 μm. Table 2 shows laser irradiation apparatuses used in Examples 1 to 6 and Comparative Examples 1 and 2. As a CO ₂ laser light irradiation device, SILAS-ASAM (SPL2305, manufactured by Kasuya Kogyo Co., Ltd., wavelength 10.6 μm) is used for the slitter 12, and MLZ9510 (manufactured by Keyence Corporation, wavelength 10.6 μm) is used for the embossing device 13. Was used. When the standard laser intensity in the slitter 12 was P1 (= 120 W), the end of each example was cut at four levels of laser intensity of 0.5P1, 0.7P1, P1, and 1.5P1. Further, when the standard laser intensity in the embossing device 13 is P2 (= 30 W), the embossing is performed at the end of each embodiment with four levels of laser intensity of 0.5P2, 0.7P2, P2, and 1.5P2. Went.

Further, as the UV laser irradiation device, an Nd-YAG laser device (model UVTH-4000, manufactured by Takano Co., Ltd., wavelength 0.266 μm) was used for the slitter 12 and the embossing device 13. When the standard laser intensity in the slitter 12 was P1 (= 150 mW), the end portion of each example was cut with four levels of laser intensity of 0.5P1, 0.7P1, P1, and 1.5P1. Further, when the standard laser intensity in the embossing device 13 is P2 (= 30 mW), the embossing is performed at the end of each embodiment with four levels of laser intensity of 0.5P2, 0.7P2, P2, and 1.5P2. Went.
(Example 6)
In Example 6, the compound (hydrotalcite) that absorbs light in the wavelength region of 4 to 25 μm in Example 1 was not mixed during the preparation of the dope, and the dope was cast on the support, and then supported. A liquid in which hydrotalcite was dispersed in ethanol at 5% by mass in a dope film on the body was applied to a slit processing region and an embossing region with a spray device. At this time, the coating amount was 1/10 of the content in the film of Example 2. Others were produced in the same manner as in Example 1.
(Comparative Example 1)
In Comparative Example 1, the compound (hydrotalcite) that absorbs light in the wavelength region of 4 to 25 μm and the compound (UV-23L) that absorbs light in the wavelength region of 0.2 to 0.4 μm in Example 1 are used. It was produced in the same manner as in Example 1 except that it was not added.
(Comparative Example 2)
Comparative Example 1 was prepared in the same manner as in Example 5 except that the compound (UV-23L) that absorbs light in the wavelength region of 0.2 to 0.4 μm in Example 5 was not added.
(Evaluation of cut surface shape by slitter)
The cut surfaces of Examples 1 to 6 and Comparative Examples 1 and 2 cut by the slitter 12 were evaluated as follows, and the evaluation results are shown in Table 2.

  A: Beautiful.

  ○: There is no problem as a product although there is a cutting defect.

  X: Fluffing of the film in the vicinity of the end portion was recognized due to cutting failure, and there was a problem as a product.

  XX: Cutting failure is severe and does not become a product.

From the results shown in Table 2, the use of a CO ₂ laser and an Nd-YAG laser for the laser light irradiation device, and the optical film contains a compound that absorbs the wavelength of the laser light, it is possible to obtain a good cut surface with less laser intensity. You can see that Moreover, in Examples 1-3, even if content of hydrotalcite changes in the range of 0.05-0.8 mass part, a favorable cut surface is obtained, and Examples 2 and 4 are optical films. It can be seen that a good cut surface can be obtained even if the film thickness changes.
(Embossed shape, appearance, surface scratch assessment)
The embossing height after embossing of Examples 1 to 6 and Comparative Examples 1 and 2 was measured, and the appearance and scratches on the surface (if the embossing was not optimal, the film surfaces slipped during winding and scratched on the surface. Is evaluated as follows, and the evaluation results are shown in Table 3.

Appearance ◎: Beautiful.

    ○: There is a slight defect (the part that has not been embossed), but there is no problem on the product.

    ×: Remarkable defects and product problems.

    XX: There is a perforated part and there is a problem on the product.

Surface scratches ◎: clean with no scratches.

    ○: Slight scratches are observed, but there is no product problem.

    X: There is a scratch and there is a problem on the product.

    XX: Scratches are severe and not a product.

From the results in Table 3, using a CO ₂ laser and an Nd-YAG laser as a laser light irradiation device, the optical film contains a compound that absorbs the wavelength of the laser light, so that a predetermined height can be obtained with less laser intensity. It can be seen that an embossing can be performed and an optical film with few scratches can be obtained. In Examples 1 to 3, good embossing was obtained even when the hydrotalcite content was changed in the range of 0.05 to 0.8 parts by mass. From Examples 2 and 4, the optical film It can be seen that embossing with the required height can be obtained by adjusting the laser intensity even if the thickness of the film changes.

It is the schematic which shows one Embodiment of the manufacturing apparatus of the optical film which concerns on this invention. It is the schematic for demonstrating the embossing which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Support body 2 Casting die 3 Peeling roll 4 Tenter dryer 5 Roll conveyance drying apparatus 6 Conveyance roll 7 Conveyance roll 10 Web 12 Laser beam irradiation apparatus 13 for cutting processing Laser beam irradiation apparatus 14 for embossing 14 Conveyance roll 15 rolls Take-off machine E Embossed part F Film

Claims (3)

An optical film containing a compound that absorbs the wavelength of the laser light is irradiated with the laser light, it has a step of processing the optical film,
The wavelength of the laser light is in the far infrared region, and the compound is a compound that absorbs light in the wavelength region of 4 to 25 μm,
The compounds, by irradiating the laser beam, before the step of processing the optical film manufacturing method of an optical film wherein a laser beam is characterized that you have been applied to the portion to be irradiated. The method for producing an optical film according to claim 1, wherein the step is a step of cutting the optical film. The method for producing an optical film according to claim 1, wherein the step is a step of forming irregularities on the surface of the optical film.

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