WO2013111559A1

WO2013111559A1 - Optical film manufacturing method

Info

Publication number: WO2013111559A1
Application number: PCT/JP2013/000263
Authority: WO
Inventors: 啓介溝口
Original assignee: コニカミノルタ株式会社
Priority date: 2012-01-23
Filing date: 2013-01-21
Publication date: 2013-08-01
Also published as: JP5907178B2; JPWO2013111559A1

Abstract

The present invention relates to a method for manufacturing optical films having a film thickness of 10 - 50 µm. The method is characterized in that a pair of slitting devices (11, 12), which are respectively located above the two edges in the width direction of a conveyed film (F), is provided in the film conveyance line prior to the film winding process, and the first slitting device (11) and the second slitting device (12) are offset from each other with an interval (D) of 1 - 20 m in the longitudinal direction of the film.

Description

Manufacturing method of optical film

The present invention can also be used for various functional films such as a protective film for a polarizing plate used for a liquid crystal display (LCD), a retardation film, a viewing angle widening film, an antireflection film used for a plasma display, and the like. The present invention relates to a method for producing an optical film.

With the recent thinning of liquid crystal display panels, it is also required to reduce the thickness of the optical film that is a member thereof. In connection with this, development of the stable conveyance technique of a thin film has been advanced.

In recent years, with the diversification of the size of liquid crystal televisions using liquid crystal display panels, optical films having various widths have been demanded. In general, in the production of an optical film, a pair of slitting devices are provided in a film transport line before the winding process of the transport film, and are provided with a pair of slitting devices positioned at both ends in the width direction of the transport film. By cutting and removing both end portions of the transport film, an optical film having a predetermined width is manufactured.

In recent years, liquid crystal display panels have also been used for mobile phone smartphones and personal computer tablet terminals (slate PCs), and optical films corresponding to various widths are required as thin films.

In particular, unlike conventional LCD TVs, tablet terminals (slate PCs) are often viewed with their screens closer to the eyes, and the liquid crystal display panel has noticeable light unevenness that has not been noticeable until now. Therefore, a high-quality optical film is required.

Investigating the cause of this light unevenness, it was found that there was a small wrinkle in the film during slitting of the transport film, and that this wrinkle caused a minute scratch on the film. And even if the film does not break, once wrinkles occur, the wrinkles remain weakly even after the width change, causing scratches due to conveyance, and the occurrence of light unevenness that was not noticeable until now I found out that it was the cause.

On the other hand, with the diversification of the size of liquid crystal display panels, it is required to produce optical films as members from narrow films to wide films in one factory, along with stable transport technology for thin film films. Development of a technique for stably changing the width when cutting a thin film has also been demanded.

In particular, in changing the width at the time of cutting a thin film, it is important to stabilize the slitter device for adjusting the end width of the film.

In the production of optical films, when changing the product width online, the slitter moves inward or outward. When switching from a wide film to a narrow film, the slitter moves inward, and as a result, stress is generated in the inner direction, wrinkles are generated in the center of the transport film, and the film is folded back when wrinkles become strong. Has a problem of breaking.

Patent Document 1 below discloses a cellulose ester film and a manufacturing apparatus thereof, and describes that both ends in the width direction of a transport film (transport web) are simultaneously cut by a pair of slitting devices facing each other. ing. Further, in Patent Document 2 below, cutting is performed by cutting a wide web such as a film, paper, metal foil or the like while the flexible web is running into a plurality of narrow webs. An automatic cutting ear processing apparatus for automatically processing an ear generated in a machine is disclosed. Regarding the change of the slit width of the web, a plurality of slitting blades arranged in a line in the width direction of the web are used. A method of moving in a direction orthogonal to the transport direction is disclosed.

However, in the methods described in Patent Documents 1 and 2, when changing the width of a thin film (web) or changing the width of a film having low breaking strength, the film breaks due to the inward stress generated by the movement of the slitter. There was still a problem that the danger to do was still left.

JP 2007-276185 A JP-A-8-257990

The object of the present invention is to solve the above-mentioned problems of the prior art, to investigate the cause of light unevenness in optical films in recent years, and to provide a method for producing a high-quality optical film without light unevenness, And to provide a method for producing a high-quality optical film with little risk of film breakage even when changing the width of a thin film (web) or changing the width of a film with low breaking strength and without causing light unevenness. is there.

One aspect of the present invention is a method of manufacturing an optical film having a film thickness of 10 to 50 μm, and a pair of slitting positioned on both ends of the transport film in the width direction on the film transport line before the film winding process. The first slitting device provided at one end and the second slitting device provided at the other end are arranged in a staggered manner with an interval of 1 to 20 m in the film longitudinal direction. It is characterized by having.

According to the above configuration, the first slitting device and the second slitting device are arranged in a staggered manner with a predetermined interval in the film longitudinal direction, so that the film at the time of slitting at both ends in the width direction of the transport film Since the stress applied to each side can escape to the opposite side of each slitting device, there is no generation of small wrinkles, thereby eliminating the occurrence of scratches and scratches. There exists an effect that a film can be manufactured.

FIG. 1 is a schematic flow sheet showing an embodiment of a solution casting film forming apparatus for carrying out the method for producing an optical film of the present invention. FIG. 2 is an enlarged perspective view of a main part of a slitting device portion in the apparatus of FIG.

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

In this specification, the front means the downstream direction of the film transport direction.

FIG. 1 is a schematic flow sheet showing an embodiment of a solution casting film forming apparatus for carrying out the optical film manufacturing method of the present embodiment. FIG. 2 is an enlarged perspective view of a main part of a slitting device portion in the apparatus of FIG. In the drawing, each reference numeral is 1: a rotational drive endless belt support made of stainless steel, 2: a casting die, 3: a peeling roll, 4: a first drying zone, 5: a tenter, and 6: a second drying. Zone: 10: Web, 11: First slitting device, 12: Second slitting device, 13: First take-up roll, 14: Second take-up roll, 17: Winder, F: Cellulose triacetate film ( Optical film).

The optical film manufacturing method by the solution casting film forming method includes a dope preparation step (dissolution step), a dope casting step, a web peeling step, a web first drying step, a web stretching step, a web second drying step, and a film width. It comprises a cutting process at both ends in the direction and a film winding process.

Referring to FIG. 1, a resin such as cellulose ester is dissolved in a mixed solvent of a good solvent and a poor solvent in a dissolution pot (not shown), and an additive such as a plasticizer or an ultraviolet absorber is added to the resin solution ( (Dope) is prepared (dope preparation step). Next, the dope is fed from the casting die (2) to the casting position on the support (1) made of, for example, a rotationally driven stainless steel endless belt, which sends the dope to the casting die (2) and transfers it infinitely. The web (10) formed by casting is brought into contact with the endless belt support (1) (dope casting step).

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

Next, the peeled web (10) is introduced into the first drying zone (4). In the first drying zone (4), the web (10) is meandered by a plurality of conveying rolls (7) arranged in a staggered manner when viewed from the side, and the web (10) is dried by warm air during that time ( Web first drying step). The web after drying is introduced into a tenter (5) in a stretching process, stretched to a predetermined width, and dried (web stretching process). The stretched film (web) (10) is further introduced into the second drying zone (6), and a plurality of transport rolls (8) arranged in a staggered manner as viewed from the side in the second drying zone (6). The web (10) is meandered by this, and the web (10) is dried with warm air during that time (web second drying step).

After drying by the second drying zone (6), for example, the both ends in the width direction of the transport film (F) are, for example, 10 by a pair of slitting devices (11) and (12) positioned at both ends in the film width direction. A base film is formed so as to have a product width by slitting with a width of ˜50 mm and cutting and cutting (cutting process at both ends in the film width direction). Thereafter, the end of the base film in the width direction is knurled by a pair of upper and lower embossing rolls (15) and (16) to form an embossed part, and a roll-shaped optical film (F) is wound on a winder (17 ) (Film winding process).

As shown in FIG. 2, the manufacturing method of the optical film according to the present embodiment is a manufacturing method of an optical film having a film thickness of 10 to 50 μm, and is provided on the film transport line before the film winding process. Are provided with a pair of slitting devices (11) and (12) positioned on the upper side of the film at both ends in the width direction of the first slitting device (11) and the second slitting device (12), respectively. The film is arranged in a staggered manner with an interval (D) of 1 to 20 m in the longitudinal direction of the film.

In addition, the film edge cutting part (20) of the width direction both ends of the conveyance film (F) slit by the pair of slitting apparatuses (11) and (12) is a pair of take-up rolls (13) and (14). Are taken down and removed, respectively, and reused as a raw material for producing optical films.

According to the optical film manufacturing method of the present embodiment, the first slitting device (11) and the second slitting device (12) are arranged in a staggered manner with a predetermined interval (D) in the film longitudinal direction. By doing so, the stress applied to the film (F) when slitting at both ends in the width direction of the transport film (F) can escape to the opposite sides of the slitting devices (11) and (12). Since the generation of small wrinkles is eliminated, thereby eliminating the occurrence of scratches and scratches, it is possible to produce a high-quality optical film (F) with no occurrence of light unevenness.

And in the manufacturing method of the optical film by this embodiment, both slitting apparatus (11) (12) arrange | positioned mutually staggered is enabled to each move in a film width direction, and both slitting apparatus (11) The slit widths at both ends in the width direction of the transport film (F) are changed by the movement of (12). In addition, as a manufacturing apparatus used for the manufacturing method of this embodiment, if the said slitting apparatus is arrange | positioned, another structure will not be specifically limited.

According to this embodiment, the first slitting device (11) and the second slitting device (12) are alternately arranged at predetermined intervals in the film longitudinal direction as described above. Since the stress applied to the film (F) at the time of slitting at both ends in the width direction of (F) can escape to the opposite sides of the slitting devices (11) and (12), the film (F) is scratched. It will not break due to the occurrence of. This tendency was found to be a particularly remarkable phenomenon in the thin film, and the film (F) was broken even when the width of the thin film (web) was changed or the width of the film (F) having low breaking strength was changed. Therefore, it is possible to produce a high-quality optical film (F) that is free from the occurrence of light unevenness.

In the manufacturing method of the optical film according to the present embodiment, the amount of change in the slit width at both ends in the width direction of the transport film (F) due to the movement of both slitting devices (11) and (12) arranged alternately. In other words, it is preferable that the width change amount of the film edge cut portion (20) to be slit is 30 to 300 mm on one side of both ends in the width direction of the transport film (F).

Thus, the amount of change in the slit width at both ends in the width direction of the transport film (F), in other words, the amount of change in the width of the film edge cut portion (20) to be slit is the width of the transport film (F). If it is in the range of 30 to 300 mm on one side of both ends in the direction, the stress applied to the film at the time of slitting will be on the opposite sides of the slitting devices (11) and (12) arranged alternately in the longitudinal direction of the film. Since it is possible to escape, there is no generation of small wrinkles, and thus no generation of rubbing scratches. Therefore, there is an advantage that a high-quality optical film free from light unevenness can be produced.

In the manufacturing method of the optical film according to the present embodiment, the slit width changing speed at both ends in the width direction of the transport film (F) due to the movement of both slitting devices (11) and (12) is the slitting device (11) ( 12) is preferably 10 to 100 mm / min on one side.

Thus, if the slit width changing speed at both ends in the width direction of the transport film (F) is in the range of 10 to 100 mm / min on one side of the slitting devices (11) and (12), the transport film (F) Since the stress applied to the film at the time of slitting at both ends in the width direction can escape to the opposite sides of the slitting devices (11) and (12) arranged alternately in the longitudinal direction of the film. Since the generation of wrinkles is eliminated and the generation of rubbing scratches is eliminated, there is an advantage that a high-quality optical film free from light unevenness can be produced.

In the method for producing an optical film according to the present embodiment, the width of the transport film (F) is preferably 1500 to 2500 mm. Thereby, there exists an advantage that it can respond also to the request | requirement of widening of an optical film (F).

In the method for producing an optical film according to the present embodiment, the traveling speed of the transport film (F) is preferably 80 to 200 m / min. Thereby, there exists an advantage that it can respond also to high-speed film-forming speed of an optical film (F).

The method for producing an optical film according to the present embodiment is performed by, for example, a solution casting film forming method, which will be described in more detail below.

In the optical film manufacturing method according to the present embodiment, various resins can be used as the film material.

Examples of the resin preferably used in the method of this embodiment include cellulose ester resins having an acyl group substitution degree of 1.8 to 2.8, such as cellulose acetate, cellulose acetate propionate, and cellulose acetate butyrate. Cellulose ether resins having a degree of alkyl group substitution of 2.0 to 2.8, such as cellulose methyl ether, cellulose ethyl ether, and cellulose propyl ether, cycloolefin resins, norbornene resins, polycarbonate resins, and polymers of alkylene dicarboxylic acids and diamines Polyamide resins, alkylene dicarboxylic acid and diol polymer, alkylene diol and dicarboxylic acid polymer, cyclohexane dicarboxylic acid and diol polymer, cyclohexane diol and dicarboxylic acid Polymers, polyester resins such as polymers of aromatic dicarboxylic acids and diols, vinyl acetate resins such as polyvinyl acetate and vinyl acetate copolymers, polyvinyl acetal resins such as polyvinyl acetal and polyvinyl butyral, epoxy resins, ketones Examples thereof include polyurethane resins such as resins, linear polymers of alkylene diisocyanates and alkylene diols, and preferably contain at least one selected from these.

Of these, cellulose ester resins such as cellulose acetate, cellulose acetate propionate, and cellulose acetate butyrate, cycloolefin resins, norbornene resins, and polycarbonate resins are particularly preferable. Further, two or more types of compatible polymers may be blended and dope dissolution described later may be performed, but this embodiment is not limited to these.

Other resins preferably used in the present embodiment include homopolymers or copolymers having an ethylenically unsaturated monomer unit. More preferably, poly (methyl acrylate), poly (ethyl acrylate), poly (propyl acrylate), poly (cyclohexyl acrylate), copolymers of alkyl acrylate, poly (methyl methacrylate), poly (ethyl methacrylate), poly (cyclohexyl methacrylate), alkyl methacrylate (s). Examples include homopolymers or copolymers of acrylic acid or methacrylic acid esters such as ester copolymers. Furthermore, since acrylic acid or methacrylic acid esters are excellent in transparency and compatibility, homopolymers or copolymers having acrylic acid ester or methacrylic acid ester units, particularly homopolymers having acrylic acid or methyl methacrylate units. Polymers or copolymers are preferred. Specifically, polymethyl methacrylate is preferable. Preferred are alicyclic alkyl esters of acrylic acid or methacrylic acid such as polyacrylic acid or polymethacrylic acid cyclohexane, which have advantages such as high heat resistance, low hygroscopicity, and low birefringence. .

Hereinafter, the present embodiment will be described by taking cellulose ester as an example.

In this embodiment, a cellulose ester solution containing a cellulose ester and an organic solvent is referred to as a dope, and this is used to form a cellulose ester film by solution casting.

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

As an example of cellulose triacetate, the substitution degree of acetyl group is preferably 2.0 or more and 3.0 or less. By making the degree of substitution within this range, good moldability can be obtained, and desired in-plane retardation (Ro) and thickness direction retardation (Rt) can be obtained. If the substitution degree of the acetyl group is lower than this range, the heat resistance as a retardation film, particularly the dimensional stability under wet heat may be inferior, and if the substitution degree is too large, the necessary retardation characteristics will not be exhibited. There is a case.

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

In this embodiment, the number average molecular weight of the cellulose ester is preferably in the range of 60,000 to 300,000, since the mechanical strength of the resulting film is strong. Furthermore, 70,000 to 200,000 are preferable.

The solvent of the cellulose ester is not particularly limited as long as it is a solvent that can dissolve the cellulose ester, but even a solvent that cannot be dissolved alone can be used if it can be dissolved by mixing with other solvents. Can do. In general, a mixed solvent consisting of a good solvent, methylene chloride and a poor solvent of cellulose ester, is used, and the mixed solvent preferably contains 4 to 30% by weight of the poor solvent.

Other good solvents that can be used include, for example, methylene chloride, methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2- Trifluoroethanol, 2,2,3,3-tetrafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro-2-methyl-2- Examples include propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, nitroethane, and the like, such as methylene chloride. Preferred organic solvents (so-called organic solvents such as dioxolane derivatives, methyl acetate, ethyl acetate, acetone) Given as the good solvent). The use of methyl acetate is particularly preferred because the resulting film has less curl.

Examples of the poor solvent for cellulose ester include alcohols having 1 to 8 carbon atoms such as methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, tert-butanol, methyl ethyl ketone, methyl isobutyl ketone, and acetic acid. Examples thereof include ethyl, propyl acetate, monochlorobenzene, benzene, cyclohexane, tetrahydrofuran, methyl cellosolve, and ethylene glycol monomethyl ether. These poor solvents can be used alone or in combination of two or more.

In this embodiment, various additives can be added to the cellulose ester.

In this embodiment, 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. Examples of the citrate ester include acetyl triethyl citrate and acetyl citrate. Mention may be made of tributyl. In addition, butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, triacetin, and the like are also included. Alkylphthalylalkyl glycolates are also preferably used for this purpose. The alkyl in the alkylphthalylalkyl glycolate is an alkyl group having 1 to 8 carbon atoms. Examples of alkyl phthalyl alkyl glycolates include methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, octyl phthalyl octyl glycolate, methyl phthalyl ethyl glycolate, Ethyl phthalyl methyl glycolate, ethyl phthalyl propyl glycolate, propyl phthalyl ethyl glycolate, methyl phthalyl propyl glycolate, methyl phthalyl butyl glycolate, ethyl phthalyl butyl glycolate, butyl phthalyl methyl glycolate, butyl Phthalyl ethyl glycolate, propyl phthalyl butyl glycolate, butyl phthalyl propyl glycolate, methyl phthalyl octyl glycolate, ethyl phthalyl octyl Collate, octyl phthalyl methyl glycolate, octyl phthalyl ethyl glycolate and the like can be mentioned, such as methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, Octyl phthalyl octyl glycolate is preferable, and ethyl phthalyl ethyl glycolate is particularly preferably used. A plasticizer having a large molecular weight is preferable because it can suppress volatilization during extrusion. Examples of these include aliphatic polyesters composed of glycol and dibasic acids such as polyethylene adipate, polybutylene adipate, polyethylene succinate and polybutylene succinate, and fats composed of oxycarboxylic acids such as polylactic acid and polyglycolic acid. Aliphatic polyesters composed of lactones such as aromatic polyesters, polycaprolactone, polypropiolactone and polyvalerolactone, and vinyl polymers such as polyvinylpyrrolidone. These plasticizers can be used alone or in combination.

The content of the plasticizer described above is preferably 1 to 30% by weight based on the cellulose ester. By containing the plasticizer in this range, the dimensional stability of the cellulose ester film under wet heat can be improved.

In this embodiment, examples of the ultraviolet absorber that can be used include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like. However, 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 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 ultraviolet absorbers useful in this embodiment include 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-tert-butyl) Phenyl) 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- '-Tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2H-benzotriazol-2-yl) -6- (straight and side chain dodecyl) -4-methylphenol, octyl- 3- [3-tert-butyl-4-hydroxy-5- (chloro-2H-benzotriazol-2-yl) phenyl] propionate and 2-ethylhexyl-3- [3-tert-butyl-4-hydroxy-5 A mixture of (5-chloro-2H-benzotriazol-2-yl) phenyl] propionate can be mentioned, but is not limited thereto. 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 are 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, based on the cellulose ester. 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.

In the present embodiment, the plasticizer and the ultraviolet absorber described above may also have a role as an additive for reducing the thickness direction retardation (Rt).

If the substitution degree of the acetyl group of the cellulose ester is low, the heat resistance may decrease. 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 5-di-t-butyl-4-hydroxyphenyl) propionate, N, N′-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide), 1,3,5- Trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-t-butyl-4-hydroxybenzyl) -isocyanurate, etc. Is 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-tert-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 Phosphorus processing stabilizers such as -butylphenyl phosphate may be used in combination.

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

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

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

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

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

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

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

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

The above fine particles are used by adding 0.04 to 1.0% by weight to the cellulose ester. When the amount of fine particles added is 0.04% by weight or less, the film surface roughness becomes too smooth and blocking occurs due to an increase in the friction coefficient. If the amount of fine particles added exceeds 0.5% by weight, the coefficient of friction on the film surface will be too low, causing winding misalignment during winding, and the transparency of the film will be low and haze will be high. The above range is indispensable because it has no value as a film for an apparatus.

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

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

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

The method for producing an optical film according to the present embodiment includes a dope preparation step (dissolution step), a casting step, a drying step, a film width cutting step, and a winding step.

In the method for producing an optical film according to the present embodiment, taking the case where the optical film is a cellulose ester film as an example, the dissolution of the cellulose ester is first performed by stirring and dissolving in a dissolution vessel, heating and dissolving, ultrasonic A method such as a dissolution method is usually used, and a method in which the solution is heated at a temperature not lower than the boiling point of the solvent at normal pressure and in a range where the solvent does not boil and dissolved while stirring is a lump called gel or mamaco In order to prevent generation | occurence | production of an undissolved substance, it is more preferable. Further, a cooling dissolution method described in JP-A-9-95538, or a dissolution method under high pressure described in JP-A-11-21379 may also be used.

A method in which the cellulose ester is mixed with a poor solvent and wetted or swollen, and then mixed with a good solvent and dissolved is also preferably used. At this time, an apparatus for mixing or dissolving cellulose ester with a poor solvent and an apparatus for mixing and dissolving with a good solvent may be separately provided.

The type of the pressure vessel used for dissolving the cellulose ester is not particularly limited as long as it can withstand a predetermined pressure and can be heated and stirred under pressure. In addition, instruments such as a pressure gauge and a thermometer are appropriately disposed in the pressurized container. The pressurization may be performed by a method of injecting an inert gas such as nitrogen gas or by increasing the vapor pressure of the solvent by heating. Heating is preferably performed from the outside. For example, a jacket type is preferable because temperature control is easy.

The heating temperature after adding the solvent is higher than the boiling point of the solvent to be used. In the case of two or more mixed solvents, the heating temperature is higher than the boiling point of the lower boiling solvent and the solvent does not boil. Is preferred. If the heating temperature is too high, the required pressure increases and productivity decreases. A preferable heating temperature range is 20 to 120 ° C., more preferably 30 to 100 ° C., and still more preferably 40 to 80 ° C. The pressure is adjusted so that the solvent does not boil at the set temperature.

In addition to cellulose ester and solvent, additives such as necessary plasticizers and UV absorbers can be mixed with the solvent in advance, dissolved or dispersed, and then added to the solvent before dissolving the cellulose ester. It may be put into the dope.

After dissolving the cellulose ester, it is taken out from the container while cooling, or it is taken out from the container with a pump or the like and cooled with a heat exchanger or the like, and the resulting polymer dope is used for film formation. May be cooled to room temperature.

The particle size d of the cellulose ester as a raw material is such that particles having a size of 0.1 mm ≦ d ≦ 20 mm are constituted at a ratio of 60% by weight or more, so that good solubility can be obtained without generating an aggregate of cellulose ester. Desirable to get.

The mixture of the raw material cellulose ester and the solvent is dissolved in a dissolving kettle having a stirrer, and at this time, the peripheral speed of the stirring blade is preferably at least 0.5 m / second or more and stirred and dissolved for 30 minutes or more.

In the method of the present embodiment, the cellulose ester dope dissolved in the dissolution vessel is sent to a filter by a pump and filtered in the filter. This filtration can be performed by a normal method, but the method of filtering while heating under pressure at a temperature not lower than the boiling point of the solvent at normal pressure and in a range where the solvent does not boil is the differential pressure before and after the filter medium (hereinafter referred to as the pressure difference). The increase in the pressure may be small, which is preferable.

In the method of this embodiment, the cellulose ester dope is filtered to remove foreign substances, particularly foreign substances that are mistakenly recognized as images in the liquid crystal image display device. It may be said that the quality of the protective film for polarizing plates is determined by this filtration.

Filter media used for filtration preferably have a low absolute filtration accuracy. However, if the absolute filtration accuracy is too low, the filter media is likely to be clogged, and the filter media must be frequently replaced, resulting in increased productivity. There is a problem of lowering.

For this reason, in the method of this embodiment, the filter medium used for the cellulose ester dope preferably has an absolute filtration accuracy of 0.020 mm or less. As the filter paper, for example, No. of Azumi Filter Paper Co., Ltd., a commercially available product. 244, 277, etc. can be mentioned and used preferably.

There are no particular restrictions on the material of the filter medium, and normal filter media can be used. However, plastic fiber filter media such as polypropylene and Teflon (registered trademark), and metal filter media such as stainless steel fibers are used to remove fibers. It is preferable because there is no

The preferred temperature range for the dope filtration is 45 to 120 ° C., more preferably 45 to 70 ° C., and even more preferably 45 to 55 ° C.

The filtration pressure is preferably 3500 kPa or less, more preferably 3000 kPa or less, and even more preferably 2500 kPa or less. The filtration pressure can be controlled by appropriately selecting the filtration flow rate and the filtration area. The dope thus obtained is stored in a stock tank, defoamed and then used for casting.

Thus, in the case where a dope is prepared by previously mixing a domain forming material, a cellulose ester, and a solvent in a melting pot, it is usually unnecessary to add the domain forming material in-line. However, if necessary, all or part of the domain forming material can be mixed in-line.

For example, an amorphous particle dispersion mixed or dispersed in a suitable solvent in a dissolution vessel is sent to a filter by a pump and filtered in the filter. The obtained dope is stored in the second stock tank and defoamed.

Cellulose ester solution (or may be referred to as dope stock solution) transferred from the first stock tank through the conduit by the pump, and domain-forming material solution transferred from the second stock tank by the pump (the amorphous particle dispersion). Is merged with a merge pipe.

A filter is arranged immediately before the junction tube, and for example, lump and large foreign matter generated from the path due to exchange of filter media etc. can be removed from the amorphous particle dispersion or dope stock solution being fed. . Here, a metal filter having solvent resistance is preferably used.

The filter medium is preferably a metal, particularly stainless steel, from the viewpoint of durability. From the viewpoint of clogging, a porosity of 60 to 80% is preferable. Most preferably, the filtration is performed with a metal filter medium having an absolute filtration accuracy of 30 to 60 μm and a porosity of 60 to 80%, so that coarse foreign substances can be reliably removed over a long period of time. preferable. Examples of metal filter media having an absolute filtration accuracy of 30 to 60 μm and a porosity of 60 to 80% include NF-10, NF-12, and NF-13 of Finepore NF series manufactured by Nippon Seisen Co., Ltd. be able to.

The two liquids that have joined together as described above migrate in a layered manner in the conduit and are difficult to mix as they are. Therefore, after the two liquids are merged, they are transferred to the next step while being sufficiently mixed by a mixer such as an in-line mixer.

As the in-line mixer that can be used in this embodiment, for example, a static mixer SWJ (Toray static type in-pipe mixer, Hi-Mixer, manufactured by Toray Engineering) is preferable.

Referring to FIG. 1, in the method for producing a cellulose ester film of the present embodiment, first, a resin such as cellulose ester is dissolved in a mixed solvent of a good solvent and a poor solvent in a dissolving pot (not shown) and plasticized. A resin solution (dope) is prepared by adding additives such as an agent and an ultraviolet absorber.

Next, the dope adjusted to have a dope viscosity of 1 to 200 poise in a melting pot is fed to the casting die (2) through a conduit, for example, through a pressurized metering gear pump (not shown), and transferred indefinitely. A dope is cast from a casting die (2) at a casting position on a support (1) made of a rotationally driven stainless steel endless belt, and a web (10) formed thereby is passed through an endless belt support ( 1) Touch the top. The endless belt support (1) is held by a pair of front and rear drums and a plurality of intermediate rolls (not shown), and is attached to one or both of the drums at both ends of the endless belt support (1). The endless belt support (1) is provided with a driving device for applying tension (not shown), whereby the endless belt support (1) is used in a tensioned state.

The dope casting by the casting die (2) includes a doctor blade method in which the film thickness of the cast web (10) is adjusted with a blade, or a reverse roll coater method in which the film is adjusted with a reverse rotating roll. However, it is preferable to use a pressure die that can adjust the slit shape of the die part and easily make the film thickness uniform. Examples of the pressure die include a coat hanger die and a T die, and any of them is preferably used.

In addition, as the casting die (2), a pressure die that can adjust the slit shape of the die part and easily make the film thickness uniform is preferable.

When the web (10) is formed on the rotary drive endless belt support (1), the pressure is reduced from the upstream side of the casting so that the web (10) is formed in close contact with the support (1). A decompression chamber (not shown) opened downward is provided.

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

The casting die (2) is cast so as to have a substantially uniform film thickness on the support (1). Generally, when the residual solvent amount in the web is 200% or more by weight of the solid content, the web When the temperature is below the boiling point of the solvent and the residual solvent amount is in the range of 100 to 200% by weight of the solid content, the boiling point of the solvent is + 10 ° C. or less, and the residual solvent amount is 100% or less to the peeling until the solvent boiling point is + 20 ° C. It is preferable to dry the web (10) with drying air so as to be in the range.

When the web (10) dried on the endless belt support (1) moves approximately 3/4 rounds by the rotation of the support (1), it is peeled off by the peeling roll (3).

Since the web (10) is dried and solidified on the support (1) until the web (10) has a peelable film strength, generally the residual solvent amount in the web (10) is 150% by weight. It is preferably dried to the following, more preferably 80 to 120% by weight.

In general, 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. The web temperature at the time of peeling is more preferably 5 to 30 ° C. for easy condensation.

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

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

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

Next, the web (10) after peeling from the endless belt support (1) is introduced into the first drying zone (4). In the first drying zone (4), the web (10) is meandered by a plurality of conveying rolls arranged in a staggered manner as viewed from the side, while the web (10) is at the bottom of the first drying zone (4). It is blown from the front portion and dried by the warm air discharged from the rear portion of the ceiling of the first drying zone (4).

In the method for producing a cellulose ester film by the solution casting film forming method, the residual solvent amount of the web (10) when the web (10) is peeled from the belt support (1) is 80 to 170% by weight, and the tenter (5 It is preferable that the amount of residual solvent of the web (10) when entering is set to 2 to 20% by weight and the drying temperature of the first drying zone (4) between them is 60 to 110 ° C.

In the stretching step using the tenter (5), for example, the stretching ratio when producing a cellulose ester film is 1.01 to 3 times, preferably 1.5 to 3 times with respect to the film forming direction or the width direction. Is double. When stretching in the biaxial direction, the side to be stretched at a high magnification is 1.01 to 3 times, preferably 1.5 to 3 times, and the stretching ratio in the other direction is 0.8 to 1.5. The film can be stretched by a factor of preferably 0.9 to 1.2.

The width maintenance or lateral stretching in the film forming step is preferably performed by a tenter (5), and may be a pin tenter or a clip tenter.

In addition, in the extending | stretching process by a tenter (5), a web (10 abbreviate | omits illustration) is blown in from the front part of the bottom of a tenter (5), and is discharged | emitted from the rear part of the ceiling of a tenter (5). ) Is dried with stretching.

It is preferable to provide the second drying zone (6) after the stretching step by the tenter (5). In the second drying zone (6), the web (10) is meandered by a plurality of transport rolls (8) arranged in a staggered manner as viewed from the side, and the web (10) is dried during that time. The film transport tension in the second drying zone (6) is affected by the properties of the dope, the amount of residual solvent at the time of peeling and in the film transport process, the temperature in the second drying zone (6), etc. Is preferably 250 N / m, and more preferably 60 to 150 N / m. 80 to 120 N / m is most preferable.

The means for drying the web (or film) (10) is not particularly limited, and is generally performed by hot air, infrared rays, a heating roll, a microwave, or the like. It is preferable to dry with hot air from the viewpoint of simplicity, for example, hot air blown from the front portion of the bottom of the second drying zone (6) and discharged from the rear portion of the ceiling of the second drying zone (6). Dried by. The drying temperature is preferably 40 to 160 ° C., more preferably 50 to 160 ° C. in order to improve the flatness and dimensional stability.

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

The web conveyance tension during drying is 30 to 300 N / width m, and more preferably 40 to 270 N / width m.

In the method for producing a cellulose ester film according to the present embodiment, after the second drying zone (6) and before the film winding step, on both ends in the width direction of the transport film (F), A pair of slitting devices (11) and (12) are provided respectively on the upper side of the transport film (F), and the first slitting device (11) and the second slitting device (12) are arranged in the longitudinal direction of the film. It is characterized by being arranged in a staggered manner with an interval (D) of 1 to 20 m in the direction.

In addition, the film edge cutting part (20) of the width direction both ends of the conveyance film (F) slit by the pair of slitting apparatuses (11) and (12) is a pair of take-up rolls (13) and (14). Are taken down and removed by each of them and reused as a raw material for producing a cellulose ester film.

According to the method for producing a cellulose ester film of the present embodiment, the first slitting device (11) and the second slitting device (12) are alternately arranged with a predetermined interval (D) in the film longitudinal direction. As a result, the stress applied to the film (F) at the time of slitting at both ends in the width direction of the transport film (F) can escape to the opposite sides of the slitting devices (11) and (12). Therefore, since generation | occurrence | production of a small wrinkle is eliminated and the generation | occurrence | production of an abrasion is also eliminated, the high quality cellulose-ester film (F) without generation | occurrence | production of an optical nonuniformity can be manufactured.

Here, the distance (D) between the first slitting device (11) and the second slitting device (12) in the longitudinal direction of the film is preferably 1 to 20 m. It will occur.

That is, with the diversification of the size of liquid crystal televisions in recent years, cellulose ester films having various widths are also required. Furthermore, liquid crystal display panels are also used in mobile phone smartphones and tablet terminals (slate PCs) of personal computers, and cellulose ester films corresponding to various widths are required as thin members.

In particular, unlike conventional LCD TVs, tablet terminals (slate PCs) are often viewed with their screens closer to the eyes, and the liquid crystal display panel has noticeable light unevenness that has not been noticeable until now. Therefore, a high-quality cellulose ester film is required.

The present inventor investigated the cause of the occurrence of the light unevenness. As a result, when the conveying film (F) was slit, the film (F) had small wrinkles. Due to the wrinkles, the film (F) was minute. I found out that there were scratches. Even if the film (F) does not break, if wrinkles occur even once, the wrinkles remain weakly even after the width change, causing scratches due to conveyance, and light unevenness that has not been noticeable until now. It was found that this was the cause of

On the other hand, as in the present invention, a pair of slitting devices positioned on the upper side of the transport film (F) at both ends in the width direction of the transport film (F) on the film transport line before the film winding process. (11) and (12) are provided, and the first slitting device (11) and the second slitting device (12) are spaced from each other with a distance (D) of 1 to 20 m in the film longitudinal direction. Arranged in a staggered manner, the slit positions at both ends in the width direction of the transport film (F) are staggered with an interval (D) of 1 to 20 m in the film longitudinal direction, not at positions facing the width direction. If it is arranged at a position shifted in the shape, the stress applied at the time of slitting at both ends in the width direction of the transport film (F) can escape to the opposite side, so that small wrinkles are generated. No longer found that rubbing scratches is not generated, in which the present invention has been completed.

In the method for producing a cellulose ester film according to the present embodiment, both slitting devices (11) and (12) arranged in a staggered manner are movable in the width direction of the film. The slit widths at both ends in the width direction of the transport film (F) are changed by the movement of the devices (11) and (12).

According to this embodiment, the first slitting device (11) and the second slitting device (12) are alternately arranged at predetermined intervals in the film longitudinal direction as described above. Since the stress applied to the film (F) at the time of slitting at both ends in the width direction of (F) can escape to the opposite sides of the slitting devices (11) and (12), the film (F) is scratched. It will not break due to the occurrence of. This tendency was found to be a particularly remarkable phenomenon in the thin film, and the film (F) was broken even when the width of the thin film (web) was changed or the width of the film (F) having low breaking strength was changed. Therefore, it is possible to produce a high-quality cellulose ester film (F) that is free from light unevenness.

That is, in recent years, it has been demanded to produce from a narrow film to a wide film in one factory, and stable width change of a thin film having a film thickness of, for example, 10 to 50 μm can be performed together with a stable conveyance technique of the thin film. There is also a need for the development of technologies to be performed. In particular, in changing the width of the thin film, it is important to stabilize a pair of left and right slitting devices located at both ends in the width direction of the transport film for adjusting the end width of the film (F).

In the cellulose ester film manufacturing method, when the product width is changed online, so-called slitting devices located at both ends in the width direction of the transport film (F) move inward or outward. For example, when switching from a wide film to a narrow film by changing the width of the film, the slitting device moves inward, and accordingly, stress in the inner direction is generated in the transport film (F), and the transport film ( There was a problem that wrinkles were generated at the center of F) and the film (F) was broken when the wrinkles were strong.

The present inventor, for such a conventional problem, on the film transport line before the film winding process, on both ends in the width direction of the transport film (F), respectively, on the upper side as in this embodiment. A pair of positioned slitting devices (11) and (12) are arranged in a staggered manner with an interval (D) of 1 to 20 m in the longitudinal direction of the film, and both ends in the width direction of the transport film (F) If the slit positions are not opposed to each other in the width direction, but are arranged in staggered positions with an interval (D) of 1 to 20 m in the film longitudinal direction, both ends of the transport film (F) in the width direction It has been found that the stress applied to the film (F) at the time of slitting of the portion can escape to the opposite side, so that it will not break, and the present invention has been completed. Such a tendency has been found to be a particularly prominent phenomenon in a thin film having a thickness of 10 to 50 μm, for example.

In the method for producing a cellulose ester film according to the present embodiment, the slit width at both ends in the width direction of the transport film (F) is changed by the movement of both slitting devices (11) and (12) arranged alternately. In other words, the width change amount of the film edge cut portion (20) to be slit is preferably 30 to 300 mm on one side of both ends in the width direction of the transport film (F). Thus, the amount of change in the slit width at both ends in the width direction of the transport film (F), in other words, the amount of change in the width of the film edge cut portion (20) to be slit is the width of the transport film (F). If it is in the range of 30 to 300 mm on one side of both ends in the direction, the stress applied to the film at the time of slitting will be on the opposite sides of the slitting devices (11) and (12) arranged alternately in the longitudinal direction of the film. Since it is possible to escape, there is no generation of small wrinkles, and thus no generation of rubbing scratches. Therefore, there is an advantage that a high-quality optical film free from light unevenness can be produced.

Moreover, in the manufacturing method of the cellulose-ester film by this embodiment, the slit width change speed of the width direction both ends of the conveyance film (F) by the movement of both slitting apparatus (11) (12) is slitting apparatus ( 11) It is preferably 10 to 100 mm / min on one side of (12). Thus, if the slit width changing speed at both ends in the width direction of the transport film (F) is in the range of 10 to 100 mm / min on one side of the slitting device (11) (12), the film is applied at the time of slitting. Since the stress can escape to the opposite sides of the slitting devices (11) and (12) arranged in a staggered manner in the longitudinal direction of the film, the generation of small wrinkles is eliminated, thereby generating scratches. Therefore, there is an advantage that it is possible to manufacture a high-quality optical film free from light unevenness.

The transport film (F) slit at both ends in the width direction by the pair of slitting devices (11) and (12) is then wound up by the winder (15). Here, for example, the winder (15) relating to the production of the cellulose ester film (F) may be a commonly used one, and is a constant tension method, a constant torque method, a taper tension method, a program of constant internal stress. It can be wound by a winding method such as a tension control method.

In the method for producing a cellulose ester film according to the present embodiment, the width of the transport film (F) is preferably 1500 to 2500 mm. Thereby, there exists an advantage that it can respond also to the request | requirement of the widening of a cellulose-ester film (F).

In the method for producing a cellulose ester film according to the present embodiment, the traveling speed of the transport film (F) is preferably 80 to 200 m / min. Thereby, there exists an advantage that it can respond also to the increase in the film forming speed of a cellulose-ester film (F).

Although the film thickness of the cellulose ester film (F) varies depending on the purpose of use, the film thickness range used in the present embodiment as a finished film is preferably in the range of 10 to 50 μm. The average film thickness of the film (F) is controlled by controlling the extrusion flow rate, the gap of the casting die (2), the speed of the endless belt support (1), etc. so that the desired thickness is obtained. Can be adjusted.

The cellulose ester film (F) produced by the method of this embodiment preferably has an in-plane retardation value (Ro) of 60 nm or less.

Here, the retardation value of the film was measured by three-dimensional refractive index at a wavelength of 590 nm using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments Co., Ltd.), and the obtained refractive indexes Nx, Ny, It can be calculated from Nz.

In-plane retardation (Ro) = (Nx−Ny) × d
Thickness direction retardation (Rt) = [(Nx + Ny) / 2−Nz] × d
In the formula, Nx, Ny, and Nz represent the refractive indexes in the principal axes x, y, and z directions of the refractive index ellipsoid, respectively, Nx, Ny represent the refractive index in the film in-plane direction, and Nz represents the film thickness direction. Refractive index. Nx ≧ Ny, and d represents the thickness (μm) of the film.

The method for producing an optical film according to the present embodiment is performed by the solution casting film forming method as described above, but can also be performed by the melt casting film forming method.

Here, as the melt casting film forming method, a method using a T-die that can reduce film thickness unevenness and retardation unevenness is preferable. In the melt casting film forming method using an extrusion method using a T die, the polymer is melted at a temperature at which the polymer can be melted, and a film-like (sheet-like) molten resin is extruded from the T die onto a cooling drum (support). Subsequently, the film-like (sheet-like) molten resin is cooled and solidified by a cooling drum, the resin film is peeled off from the cooling drum, and further stretched as necessary to form a film, which is wound up. And when performing the manufacturing method of the optical film by this embodiment by such a melt casting film forming method, it is located in the film conveyance line before a film winding process, and the both ends of the width direction of a conveyance film. A pair of slitting devices is provided, and the first slitting device provided at one end and the second slitting device provided at the other end are spaced from each other by 1 to 20 m in the film longitudinal direction. It is characterized by being arranged in a staggered manner.

The cellulose ester film produced by the method of this embodiment is preferably used for a liquid crystal display member, specifically, a protective film for a polarizing plate. In particular, in a protective film for a polarizing plate that has strict requirements on moisture permeability and dimensional stability, the cellulose ester film produced by the method of this embodiment is preferably used.

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

The polarizing plate may be prepared by laminating a cellulose ester film produced by the method of this embodiment as a retardation film, and the cellulose ester film produced by the method of this embodiment may be produced by retardation. A film and a protective film may be combined to be directly bonded to a polarizing film. 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, a long polarizing film is obtained by laminating a long polarizing film that has been stretched in the longitudinal direction and treated with a dichroic dye and a long retardation film manufactured by the method of this embodiment. Can do. 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.

Incidentally, the polarizing plate can be produced by a general method. For example, there is a method in which a cellulose ester film is subjected to alkali saponification treatment, and a polyvinyl alcohol film is immersed and stretched in an iodine solution, and bonded to both surfaces 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.

For cellulose ester film, hard coat layer, antiglare layer, antireflection layer, antifouling layer, antistatic layer, conductive layer, optically anisotropic layer, liquid crystal layer, alignment layer, adhesive layer, adhesive layer, subbing layer, etc. Various functional layers 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.

The polarizing plate thus obtained is provided on one side or both sides of the liquid crystal cell, and a liquid crystal display device is obtained using this.

By using a protective film for a polarizing plate made of a cellulose ester film produced by the method of the present embodiment, it is possible to provide a polarizing plate excellent in durability, dimensional stability, and optical isotropy as well as in a thin film. it can. Furthermore, a liquid crystal display device using this polarizing plate or retardation film can maintain stable display performance over a long period of time.

The cellulose ester film produced by the method of this embodiment can also be used as a base material for an antireflection film or an optical compensation film.

This specification discloses various modes of technology as described above, and the main technologies are summarized below.

According to the above configuration, the left slitting device and the right slitting device are arranged in a staggered manner with a predetermined interval therebetween in the film longitudinal direction, so that the slits at both ends in the width direction of the transport film can be obtained. Since the stress applied to the film can escape to the opposite side of each slitting device, there is no generation of small wrinkles, thereby eliminating the occurrence of scratches and scratches. There exists an effect that an optical film can be manufactured.

Further, in the above manufacturing method, both the left and right slitting devices arranged in a staggered manner can be moved in the width direction of the film, respectively, and both ends of the transport film in the width direction can be moved by moving the left and right slitting devices. It is preferable that the slit width of the part is changed. As a result, the left slitting device and the right slitting device are arranged in a staggered manner with a predetermined interval between them in the longitudinal direction of the film. Since the stress can escape to the opposite side of each slitting device, the film will not break due to scratches, and this tendency was found to be a particularly prominent phenomenon in thin film. Even when changing the width of a thin film or changing the width of a film having a low breaking strength, there is almost no risk of the film breaking, and it is possible to produce a high-quality optical film free from light unevenness.

Further, in the above manufacturing method, the amount of change in the slit width at both ends in the width direction of the transport film due to the movement of the left and right slitting devices arranged alternately is changed on one side of both ends in the width direction of the transport film. 30 to 300 mm is more preferable. By having such a configuration, if the width change amount of the slit width at both ends in the width direction of the transport film to be slit is in the range of 30 to 300 mm on one side of both ends in the width direction of the transport film, The stress applied to the film at the time of slitting can escape to the opposite sides of the slitting devices arranged in a staggered manner in the longitudinal direction of the film, thereby eliminating the occurrence of small wrinkles and thereby eliminating the occurrence of scratches. Therefore, there is an effect that it is possible to manufacture a high-quality optical film without occurrence of light unevenness.

In the above manufacturing method, it is more preferable that the changing speed of the slit width at both ends in the width direction of the transport film due to the movement of both the left and right slitting devices is 10 to 100 mm / min on one side of the slitting device. Accordingly, if the slit width speed at both ends in the width direction of the transport film is in the range of 10 to 100 mm / min on one side of the slitting apparatus, the stress applied to the film when slitting at both ends in the width direction of the transport film is reduced. Since it is possible to escape to the opposite sides of the slitting devices arranged in a staggered manner in the longitudinal direction of the film, there is no generation of small wrinkles, thereby eliminating the occurrence of scratches and scratches, resulting in generation of light unevenness There is an effect that it is possible to produce a high-quality optical film without any defects.

Furthermore, in the above manufacturing method, it is desirable that the width of the transport film is 1500 to 2500 mm. With such a configuration, there is an effect that it is possible to meet the demand for widening the optical film.

Further, in the above manufacturing method, if the traveling speed of the transport film is 80 to 200 m / min, it is possible to cope with an increase in the film forming speed of the optical film.

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

Example 1
(Preparation of dope)
100 parts by weight of cellulose triacetate (Mn = 148000, Mw = 310000, Mw / Mn = 2.1)
Triphenyl phosphate 8 parts by weight Ethylphthalyl ethyl glycolate 2 parts by weight Methylene chloride 440 parts by weight Ethanol 40 parts by weight Tinuvin 109 (manufactured by BASF Japan) 0.5 part by weight Tinuvin 171 (manufactured by BASF Japan) 0.5 part by weight Aerosil 972V (manufactured by Nippon Aerosil Co., Ltd.) 0.2 parts by weight The material having the above dope composition was put into a closed container (dissolution kettle) of a solution casting film forming apparatus and completely dissolved while heating and stirring. Thereafter, stirring was stopped and filtration was performed to prepare a dope.

Next, as shown in FIG. 1, the dope adjusted in the melting pot is fed to the casting die (2) by a conduit through a pump, and continuously runs at 100 m / mm with a width of 2400 mm and a surface temperature of 30 ° C. A dope (30 ° C.) is cast from a casting die (2) to a casting position on a support (1) made of a rotationally driven stainless steel endless belt, and the casting die (2) and an endless belt support ( 1) and a web (10) were formed, and a web (10) having a width of 2000 mm was formed on the support (1).

The surface temperature of the stainless steel endless belt support (1) after casting is controlled at 25 ° C., and the drying air at a temperature of 45 ° C. is supplied from a dryer (not shown) above the web (10) at a wind speed of 10 m / sec. The web (10) was dried from a dryer (not shown) on the endless belt support (1) side at a temperature of 40 ° C. at a wind speed of 10 m / sec (solvent evaporation step). The dried web (10) was peeled off by the peeling roll (3) (peeling step). The amount of residual solvent in the web (10) immediately before the peeling step was 80% by weight.

Next, the peeled web (10) was introduced into the first drying zone (4). In the first drying zone (4), the web (10) is meandered by a large number of conveying rolls (7) arranged in a staggered manner as viewed from the side, while the web (10) is heated by hot air at a temperature of 80 ° C. It was dried for 1 minute (first drying step).

When the web (10) after drying is introduced into the tenter (5) and the residual solvent amount is 3 to 10% by weight, the both ends of the web (10) in the width direction (TD direction) are gripped, The web (10) was stretched in the width direction at a stretching ratio of 1.25 times in an atmosphere of 100 ° C. (stretching step).

The stretched web (10) was introduced into the second drying zone (6). In the second drying zone (6), the web (10) is meandered by a large number of conveying rolls arranged in a staggered manner as viewed from the side, and the web (10) is dried by warm air at a temperature of 125 ° C. for 20 minutes. (Second drying step).

As shown in FIG. 2, after drying in the second drying zone (6), a pair of films positioned on the upper side at both ends in the width direction of the transport film (F) on the film transport line before the film winding step Slitting devices (11) and (12) are installed, and the first slitting device (11) and the second slitting device (12) are arranged in a staggered manner with a distance (D) of 1 m in the film longitudinal direction. did. And the width direction both ends of a conveyance film (F) are each slitted by the width | variety of 150 mm with these slitting apparatuses (11) (12), and it cuts and cuts, A base film ( F) was formed (cutting step at both ends in the film width direction). Embossing (knurling) is applied to both ends in the width direction of the film (F) after slitting to give an embossed portion having a width of 10 mm to each end of the film, and then the final product width 2200 mm comprising the embossed portion. The cellulose triacetate film (F) having a film thickness of 50 μm was finally cooled to 20 ° C. and wound up by a winding device (17) (winding step).

Examples 2 and 3
A cellulose triacetate film is produced in the same manner as in Example 1 above. In Example 2, the first slitting device (11) and the second slitting device (12) are 10 m long in the film longitudinal direction. In the third embodiment, the first slitting device (11) and the second slitting device (12) are separated from each other by a distance of 20 m in the film longitudinal direction (D). It was carried out by arranging them in a staggered pattern with a gap.

Comparative Examples 1 and 2
For comparison, a cellulose triacetate film is prepared in the same manner as in Example 1. The difference from Example 1 is that Comparative Example 1 has both ends in the width direction of the transport film (F). In this section, a pair of slitting devices are installed so as to face each other as in the conventional case. Further, in Comparative Example 2, the first slitting device and the second slitting device are separated from each other at both ends in the width direction of the transport film (F) by a distance of 25 m in the film longitudinal direction which is outside the scope of the present invention (D ) And are arranged in a staggered manner.

Examples 4 and 5
A cellulose triacetate film is produced in the same manner as in Example 1 above, but the difference from Example 1 is that in Examples 4 and 5, the film thickness of the film (F) is determined by the extrusion flow rate of the dope. By adjusting the gap of the casting port of the casting die (2) and the speed of the endless belt support (1), they are adjusted to 30 μm and 40 μm, respectively.

Comparative Example 3
For comparison, a cellulose triacetate film is produced in the same manner as in Example 1, except that a difference between the cellulose triacetate film and Example 1 is that a pair of slips are formed at both ends in the width direction of the transport film (F). In the same manner as in the conventional case, the dating device is installed so as to face each other, and the film thickness of the film (F) is adjusted to 30 μm.

In Table 1 below, the film longitudinal direction between the slitting devices at both ends installed in both ends in the width direction of the transport film (F) in Examples 1 to 5 and Comparative Examples 1 to 3 is shown. The interval (D) (m) and the film thickness (μm) of the cellulose triacetate film are described.

Examples 6-8
A cellulose triacetate film is produced in the same manner as in Example 1 described above. In Examples 6 to 8, both slitting devices (11) and (12) arranged in a staggered manner are used in the width direction. The slit width of both ends in the width direction of the transport film (F) is changed by the movement of both slitting devices (11) and (12).

In Example 6, the amount of change in the slit width at both ends in the width direction of the transport film (F) due to the movement of the slitting devices (11) and (12) arranged alternately is changed to the transport film ( F) 50 mm on one side of both ends in the width direction, and the slit width changing speed of the slit width change at both ends in the width direction of the transport film (F) due to the movement of both slitting devices (11) and (12) (11) One side of (12) was 10 mm / min.

In Example 7, the change amount of the slit width at both ends in the width direction of the transport film (F) was set to 30 mm, and in Example 8, the change amount of the width was set to 300 mm. In Examples 7 and 8, the slit width changing speed at both ends in the width direction of the transport film (F) due to the movement of both slitting devices (11) and (12) is the same as in Example 6. It was set to 10 mm / min on one side of the dipping device (11) (12).

Examples 9 and 10
A cellulose triacetate film is produced in the same manner as in Example 6 above, but in Example 9, the transport film (F) by the movement of both slitting devices (11) and (12) arranged in a staggered manner. The slit width changing speed at both ends in the width direction is set to 20 mm / min on one side of the slitting devices (11) and (12). In Example 10, the slitting devices (11) and (12) are moved by moving the slitting devices (11) and (12). The slit width changing speed at both ends in the width direction of the film (F) was set to 100 mm / min on one side of the slitting apparatuses (11) and (12).

Comparative Examples 4 and 5
For comparison, a cellulose triacetate film is prepared in the same manner as in Example 6. The difference from Example 6 is that Comparative Example 4 has both ends in the width direction of the transport film (F). In this section, a pair of slitting devices are installed so as to face each other as in the conventional case. In Comparative Example 5, similarly, a pair of slitting devices are installed so as to face each other, and the slit width changing speeds at both ends in the width direction of the transport film (F) due to the movement of both slitting devices are set. The slitting apparatus is at 100 mm / min on one side.

In Table 2 below, the distance in the longitudinal direction of the film between the slitting devices installed at both ends in the width direction of the transport film (F) in Examples 6 to 10 and Comparative Examples 4 and 5 (D ) (M), film thickness (μm) of cellulose triacetate film, amount of change in slit width (mm) at both widthwise ends of transport film (F), and slit at both widthwise ends of transport film (F) The width changing speed (mm / min) is described.

(Preparation of polarizing film)
Next, in order to produce a liquid crystal display device using the cellulose triacetate films according to Examples 1 to 10 and Comparative Examples 1 to 5, a polarizing film was first produced. That is, a polyvinyl alcohol film having a thickness of 120 μm was uniaxially stretched at a temperature of 110 ° C. and a stretch ratio of 5 times. This was immersed in an aqueous solution consisting of 0.075 g of iodine, 5 g of potassium iodide and 100 g of water for 60 seconds, and then immersed in an aqueous solution of 68 ° C. consisting of 6 g of potassium iodide, 7.5 g of boric acid and 100 g of water. This was washed with water and dried to obtain a polarizing film.

(Preparation of polarizing plate)
Next, according to the following Step 1 to Step 5, the cellulose triacetate films (polarizing plate protective films) prepared in Examples 1 to 10 and Comparative Examples 1 to 5 were bonded to both surfaces of the polarizing film to form a polarizing plate. Produced.

Step 1: The polarizing plate protective film obtained by immersing the polarizing plate protective film in a 1 mol / L sodium hydroxide solution at a temperature of 50 ° C. for 60 seconds, then washing with water and drying, and saponifying the side to be bonded to the polarizing film. Got.

Step 2: The polarizing film was immersed in a polyvinyl alcohol adhesive tank having a solid content of 2% by weight for 1 to 2 seconds.

Step 3: Excess adhesive adhered to the polarizing film in Step 2 was gently wiped off, and a polarizing plate protective film saponified in Step 1 was laminated and disposed on both sides of the polarizing film.

Step 4: The polarizing film laminated in Step 3 and the polarizing plate protective film were bonded at a pressure of 20 to 30 N / cm ² and a conveying speed of about 2 m / min.

Process 5: The sample which bonded the polarizing film produced at the process 4 and the polarizing plate protective film was dried for 2 minutes in the 80 degreeC drying machine, and the polarizing plate was produced.

(Production of liquid crystal display device)
Next, two polarizing plates of a commercially available liquid crystal TV (manufactured by Sharp Corporation, Aquos 32AD5) were peeled off, and the prepared polarizing plates were bonded to both surfaces of the glass surface of the liquid crystal cell to prepare a liquid crystal display device. .

At that time, the direction of bonding of the polarizing plate was such that the absorption axis was in the same direction as the polarizing plate bonded in advance.

(Visibility evaluation)
In order to evaluate the visibility performance of each liquid crystal display device manufactured using the cellulose triacetate films according to Examples 1 to 10 and Comparative Examples 1 to 5, the liquid crystal display device was set at a temperature of 23 ° C. and a humidity of 55% RH. In this environment, after turning on the backlight of the liquid crystal TV display device of the liquid crystal display device and leaving it as it is for 30 minutes, the visibility of whether or not the display device has uneven light is evaluated according to the following criteria, The obtained results are shown in Table 1 and Table 2 below.

Visibility evaluation criteria ○: No light unevenness Δ: There are several weak light unevenness, which is a problem.
X: There is regular and strong light unevenness, which causes a problem.

As is clear from the results in Table 1 above, in the cellulose triacetate films produced in Examples 1 to 3 of the present invention, the first slitting device (11) and the second slitting device (12) are in the longitudinal direction of the film. Are arranged in a staggered manner with an interval (D) of 1 to 20 m, so that the stress applied to the film (F) when slitting at both ends in the width direction of the transport film (F) 11) Since it is possible to escape to the opposite side of (12), there is no generation of small wrinkles, and thus no generation of rubbing scratches, so that a high-quality cellulose triacetate film without light unevenness is produced. The visibility of the liquid crystal display device was good.

On the other hand, as in the case of Comparative Example 1, when the pair of slitting devices are installed so as to face each other as in the conventional case, the cellulose ester film (F) is slit when the film is slit. Small wrinkles entered, the wrinkles caused fine scratches on the film (F), resulting in light unevenness, and the visibility of the liquid crystal display device was not good. Further, as in Comparative Example 2, if the predetermined distance (D) in the film longitudinal direction between the slitting devices at both ends is too long outside the scope of the present invention, the width of the transport film (F) Small wrinkles are not generated in the film (F) when slitting at both ends in the direction, but the center of gravity of the transport film (F) and the center of tension applied to the film (F) are transported for a long distance with a shift. Therefore, wrinkles occurred. Due to the wrinkles, the film (F) was slightly scratched to cause light unevenness, and the visibility of the liquid crystal display device was not good. This was the same as the phenomenon that occurs when the slitting device is installed only on one side of the widthwise ends of the transport film (F) in the film transport line before the film winding process.

Further, it was found that when the film thickness of the film (F) was reduced as in Comparative Example 3, wrinkles were more likely to occur. On the other hand, in the cellulose triacetate films produced in Examples 4 and 5 of the present invention, the first slitting device (11) and the second slitting device (12) even when the film (F) is thin. By arranging them in a staggered manner with an interval (D) of 10 m in the longitudinal direction of the film, there is no generation of wrinkles on the film (F) when slitting at both ends in the width direction of the transport film (F), The visibility of the liquid crystal display device was good without causing light unevenness.

Further, as apparent from the results in Table 2 above, in the cellulose triacetate films produced in Examples 6 to 10 of the present invention, the two slitting devices (11) and (12) moved in a staggered manner. The amount of change in the slit width at both ends in the width direction of the transport film (F) and various slit width changing speeds at both ends in the width direction of the transport film (F) due to the movement of both slitting devices (11) and (12) Even if it is changed, the film (F) does not wrinkle when slitting at both ends in the width direction of the transport film (F), light unevenness does not occur, and the visibility of the liquid crystal display device is good. It was.

On the other hand, as in the case of Comparative Examples 4 and 5, a pair of slitting devices are installed so as to face each other as in the conventional case, and the transport film is formed by the movement of both slitting devices facing each other. When the slit width changing speed at both ends in the width direction of (F) is changed variously, small wrinkles enter the film (F) at the time of slitting, and this wrinkle causes minute scratches on the film (F). As a result, unevenness of light occurred and the visibility of the liquid crystal display device was poor.

This application is based on Japanese Patent Application No. 2012-11044 filed on January 23, 2012, the contents of which are included in the present application.

In order to express the present invention, the present invention has been described appropriately and sufficiently through the embodiments with reference to the drawings and the like. However, those skilled in the art can easily change and / or improve the above-described embodiments. It should be recognized that it can be done. Therefore, unless the modifications or improvements implemented by those skilled in the art are at a level that departs from the scope of the claims recited in the claims, the modifications or improvements are not limited to the scope of the claims. To be construed as inclusive.

The present invention has wide industrial applicability in the technical field of optical films and manufacturing methods thereof.

Claims

A method for producing an optical film having a film thickness of 10 to 50 μm, comprising a pair of slitting devices positioned at both ends in the width direction of the transport film in the film transport line before the film winding process, The first slitting device provided at the end portion and the second slitting devices provided at the other end portion are alternately arranged with an interval of 1 to 20 m in the film longitudinal direction. The manufacturing method of an optical film.
Both slitting devices arranged in a staggered manner can be moved in the width direction of the film, respectively, and the slit widths at both ends in the width direction of the transport film are changed by the movement of both slitting devices. The method for producing an optical film according to claim 1, wherein:
The amount of change in the slit width at both ends in the width direction of the transport film due to the movement of both slitting devices arranged alternately is set to 30 to 300 mm on one side of both ends in the width direction of the transport film. The manufacturing method of the optical film of Claim 2 characterized by the above-mentioned.
4. The slit width changing speed at both ends in the width direction of the transport film due to the movement of both slitting devices is 10 to 100 mm / min on one side of the slitting device. Manufacturing method of the optical film.
The method for producing an optical film according to any one of claims 1 to 4, wherein the width of the transport film is 1500 to 2500 mm.
6. The method for producing an optical film according to claim 1, wherein the traveling speed of the transport film is 80 to 200 m / min.