JPWO2012127893A1 - Manufacturing method of optical film - Google Patents

Abstract

Provided is a method for producing an optical film in which the width of the optical film can be easily changed. An optical film manufacturing apparatus is prepared and an optical film is manufactured. The dope is cast on the casting surface of the casting membrane support to form a casting membrane on the casting surface. The cast film is dried and solidified on the cast surface, and self-supporting property is imparted to the cast film. The cast film imparted with self-supporting property is peeled off from the cast surface to obtain a web. The web is transported by a transport roll group. The transport roll group includes a transport roll in which a slip-suppressing structure that can adjust the position in the roll thrust direction is provided on the peripheral surface at a distance in the roll thrust direction. When the width of the web of the optical film manufactured last time is different from the width of the web of the optical film manufactured this time, the position of the structure in the roll thrust direction is adjusted according to the width of the web of the optical film manufactured this time.

Description

  The present invention relates to a method for producing an optical film by a solution casting method.

  In the production of an optical film by a solution casting film forming method, a dope is cast on a casting surface of a casting film support such as an endless belt or a drum to form a casting film. The formed casting film is dried and solidified on the casting surface, and is given self-supporting property. The casting film provided with self-supporting property is peeled from the casting surface to form a web. The web is transported by a transport roll group. The web is conveyed via a tenter, a drying zone, etc., and is wound up in a roll by a winder.

  When the web is transported by the transport roll group, when the transport speed is increased, the accompanying air accompanying the web enters between the web and the peripheral surface of the transport roll, and the web slips with respect to the peripheral surface. Web slip is undesirable because it causes scratches and the like.

  In order to solve this problem, Patent Documents 1 and 2 propose to provide a structure for suppressing slip on the peripheral surface.

  In Patent Literature 1, a groove is formed on the peripheral surface, and the roll diameter of the peripheral portion in the roll thrust direction (referred to as “non-step portion 54” in Patent Literature 1) is the central portion in the roll thrust direction (Patent Literature). 1 is referred to as “stepped portion 53”).

  In Patent Document 2, a groove is formed in the peripheral portion of the peripheral surface in the roll thrust direction (referred to as “ear contact region 60e” in Patent Document 2), and the roll diameter of the peripheral portion is the center in the roll thrust direction. Part (referred to as “product part contact region 60c” in Patent Document 2) is made thicker than the roll diameter.

  In Patent Documents 1 and 2, entrained air is released by the grooves, and web slip is suppressed. Moreover, in patent document 1 and 2, the tensile force of the width direction is given to a web by a peripheral part, and the slippage of a web is suppressed.

JP 2002-179310 A JP 2009-227447 A

  Both Patent Documents 1 and 2 are effective in suppressing web slip and slip when the width of the optical film is constant. However, in both Patent Documents 1 and 2, when the width of the optical film is changed, slipping and slipping of the web may not be suppressed, and it is not easy to change the width of the optical film.

  The present invention has been made to solve this problem, and an object of the present invention is to provide an optical film manufacturing method in which the width of the optical film can be easily changed.

  The present invention is directed to a method for producing an optical film by a solution casting film forming method.

  In the first aspect of the present invention, an optical film manufacturing apparatus is prepared, and an optical film is manufactured using the prepared optical film manufacturing apparatus. In the production of the optical film, the dope is cast on the casting surface of the casting membrane support to form a casting membrane on the casting surface. The formed casting film is dried and solidified on the casting surface, and self-supporting property is imparted to the casting film. The cast film imparted with self-supporting property is peeled off from the cast surface to obtain a web. The obtained web is transported by a transport roll group. The transport roll group includes a transport roll in which a slip-suppressing structure that can adjust the position in the roll thrust direction is provided on the peripheral surface at a distance in the roll thrust direction. When preparing the optical film manufacturing apparatus, if the web width of the optical film manufactured last time is different from the web width of the optical film manufactured this time, the roll of the structure is adjusted to the width of the web of the optical film manufactured this time. The position in the thrust direction is adjusted.

  The second aspect of the present invention adds further matters to the first aspect of the present invention. In the second aspect of the present invention, the structure is a cylindrical body that is placed on the peripheral surface of the transport roll and is movable in the roll thrust direction. When the structure is a cylinder, the position of the structure in the roll thrust direction is adjusted by moving the cylinder to the position where the peripheral part of the web of the optical film manufactured this time runs over the cylinder. The

  The third aspect of the present invention adds further matters to the first aspect of the present invention. In the third aspect of the present invention, the structure is a film body that is formed on the peripheral surface by applying and curing a precursor made of a fluid to the peripheral surface of the transport roll and can be removed from the peripheral surface with a solvent. . When the structure is a film body, the film body is removed with a solvent, and the film body is formed at a position where the peripheral portion in the width direction of the web of the optical film manufactured in this time rides, so that the roll thrust direction of the structure The position of is adjusted.

  The fourth aspect of the present invention adds further matters to the first aspect of the present invention. In the fourth aspect of the present invention, the structure is a tape or a sheet that is attached to the peripheral surface of the transport roll and can be peeled off from the peripheral surface. When the structure is a tape or sheet, the tape or sheet is peeled off, and the tape or sheet is attached to the position where the peripheral part of the optical film web manufactured in this time runs up in the width direction. The position of is adjusted.

  The fifth aspect of the present invention adds further matters to any one of the second to fourth aspects of the present invention. In the fifth aspect of the present invention, the height from the peripheral surface of the structure is constant at 10 μm or more.

  The sixth aspect of the present invention adds further matters to the first aspect of the present invention. In the sixth aspect of the present invention, the structure is a nip roll that can move in the roll thrust direction. When the structure is a nip roll, the position of the structure in the roll thrust direction is adjusted by moving the nip roll to a position where the peripheral portion in the width direction of the web of the optical film manufactured this time is nipped.

  The seventh aspect of the present invention adds further matters to any one of the first to sixth aspects of the present invention. In the seventh aspect of the present invention, the interval in the roll thrust direction of the structure is 80% or more and 99% or less of the width of the web.

  The eighth aspect of the present invention adds further matters to any one of the first to seventh aspects of the present invention. In the eighth aspect of the present invention, the film thickness of the optical film is 20 μm or more and 80 μm or less. According to the ninth aspect of the present invention, in any one of the first to eighth aspects, the conveyance speed is 80 m / min or more and 300 m / min or less.

  According to the invention of the first aspect of the present invention, it is possible to cope with a change in the width of the optical film by adjusting the position of the structure for slip suppression in the roll thrust direction, and the change in the width of the optical film is facilitated.

  According to the fifth aspect of the present invention, a tensile force in the width direction is applied to the web, and the web is less likely to slip, and the uniformity of the physical properties of the optical film is improved. Further, the level difference in the portion of the web that easily curls is reduced, and the web is less likely to wrinkle, thereby improving the uniformity of the physical properties of the optical film.

  According to the seventh aspect of the present invention, there is no step in the range where the web is easily curled, and it is difficult for wrinkles to occur on the web, thereby improving the uniformity of the physical properties of the optical film. Further, the range of the web W to which the tensile force in the width direction is applied is widened, so that the web is less likely to be distorted, and the uniformity of the physical properties of the optical film is improved. Furthermore, the range in which the unevenness is difficult to be transferred becomes narrow, and the uniformity of the physical properties of the optical film tends to be lowered.

  These and other objects, features, aspects and advantages of the invention will become more apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.

It is a schematic diagram of an optical film manufacturing apparatus. It is a perspective view of the conveyance roll and web by which the cylindrical body for slip suppression was attached to the surrounding surface. It is a schematic diagram which shows the procedure of the preparation for the change of the width | variety of an optical film. It is a schematic diagram which shows the procedure of the preparation for the change of the width | variety of an optical film. It is a perspective view of the conveyance roll in which the film body for slip suppression was formed in the surrounding surface. It is a schematic diagram which shows the procedure of the change of the width | variety of an optical film. It is a schematic diagram which shows the procedure of the change of the width | variety of an optical film. It is a schematic diagram which shows the procedure of the change of the width | variety of an optical film. It is a perspective view of the conveyance roll by which the tape for slip suppression was affixed on the surrounding surface. It is a schematic diagram which shows the procedure of the change of the width | variety of an optical film. It is a schematic diagram which shows the procedure of the change of the width | variety of an optical film. It is a schematic diagram which shows the procedure of the change of the width | variety of an optical film. It is a perspective view of the conveyance roll which the nip roll for slip suppression contacts a peripheral surface. It is a schematic diagram which shows the procedure of the change of the width | variety of an optical film. It is a schematic diagram which shows the procedure of the change of the width | variety of an optical film. It is a schematic diagram of the conveyance roll provided with the structure for slip suppression.

{First embodiment}
(Optical film manufacturing equipment)
The schematic diagram of FIG. 1 shows an optical film manufacturing apparatus used for manufacturing an optical film by a solution casting film forming method.

  The optical film manufacturing apparatus 100 shown in FIG. 1 includes a first drum 102, a second drum 104, an endless belt 106, a peeling roll 108, a transport roll group 110, a first drying zone 112, a tenter 114, and a second drying. A zone 116, a winder 118, a casting die 120, and a dope (thermoplastic resin solution) supply mechanism 122 are provided. The casting die 120 is close to the endless belt outer surface 130 of the endless belt 106 and faces the endless belt outer surface 130. Instead of the endless belt outer surface 130, the dope may be cast on the drum peripheral surface of the drum. The endless belt 106 and the drum are examples of a casting membrane support, and the endless belt outer surface 130 and the drum peripheral surface are examples of a casting surface. The number, position, size, and the like of the transport rolls constituting the transport roll group 110 are changed as necessary.

(Manufacture of optical film)
When the optical film OF is manufactured using the optical film manufacturing apparatus 100, the first drum 102 and the second drum 104 rotate after the optical film manufacturing apparatus 100 is prepared, and the first drum 102 and the second drum 104 are rotated. The endless belt 106 applied to the second drum 104 circulates and the outer surface 130 of the endless belt travels in the vicinity of the casting die 120. At the same time, the dope is supplied from the dope supply mechanism 122 to the casting die 120, the dope is cast from the casting die 120 to the endless belt outer surface 130, and a casting film CF is formed on the endless belt outer surface 130. The dope is sent from the dope tank 150 to the casting die 120 by the liquid feed pump 152.

  The formed casting film CF is dried and solidified on the outer surface 130 of the endless belt, and self-supporting property is imparted to the casting film CF. The cast film CF provided with the self-supporting property is peeled from the outer surface 130 of the endless belt, and the web W is obtained. The obtained web W is transported by the transport roll group 110. The web W is conveyed to the winder 118 via the first drying zone 112, the tenter 114 and the second drying zone 116. The web W is dried in the first drying zone 112, stretched by the tenter 114, further dried in the second drying zone 116, and wound up in a roll shape by the winder 118.

(Material of endless belt)
The material of the endless belt 106 is not particularly limited as long as it is a metal or an alloy. When the material of the endless belt 106 is an alloy, the alloy is preferably stainless steel such as SUS304 or SUS314. A plating process such as hard chrome plating or amorphous chrome plating may be performed on the outer surface 130 of the endless belt.

(Casting die)
The casting die 120 is not particularly limited, but is preferably a pressure die such as a coat hanger die or a T die. This is because it becomes easy to make the thickness of the casting film CF uniform. The film thickness of the casting film CF may be adjusted by a doctor blade, a reverse roll coater or the like.

(Dope)
The dope is a viscous fluid in which a thermoplastic resin and necessary additives are dissolved or dispersed in a solvent.

(Conveying roll and cylindrical body)
FIG. 2 is a schematic view (perspective view) of a transport roll and a web in which a cylindrical body, which is an example of a structure for suppressing slip, is attached to a peripheral surface.

  As shown in FIG. 2, slip suppression cylindrical bodies 202 and 204 are attached to all or a part of the transport rolls 206 constituting the transport roll group 110. The cylindrical bodies 202 and 204 are separated from each other in the roll thrust direction (roll axis direction) and are placed on the circumferential surface 208. The cylindrical bodies 202 and 204 can move in the roll thrust direction.

  A groove 212 is formed on the outer peripheral surface 210 of the cylindrical body 202, and a groove 216 is formed on the outer peripheral surface 214 of the cylindrical body 204. The entrained air is released by the grooves 212 and 216, the frictional force between the web W and the outer peripheral surfaces 210 and 214 is suppressed from being reduced by the entrained air, and the slip of the web W is suppressed. Instead of forming the grooves 212 and 216, or in addition to forming the grooves 212 and 216, the outer peripheral surfaces 210 and 214 may be formed into a mat surface, and the surface roughness of the outer peripheral surfaces 210 and 214. May be made rougher than the outer peripheral surface 208. The “matt surface” refers to a surface that has a rough surface, the matting agent is dispersed and exposed, and has irregularities. It is allowed that the grooves 212 and 216 are omitted and the outer peripheral surfaces 210 and 214 are not matted. Even if the grooves 212 and 216 are omitted and the outer peripheral surfaces 210 and 214 are not formed as mat surfaces, the accompanying air is released by the step between the peripheral surface 208 and the outer peripheral surfaces 210 and 214, and the slippage of the web W is suppressed to some extent. Because it is done.

(Cylinder spacing)
The distance D1 between the cylindrical body 202 and the cylindrical body 204 in the roll thrust direction is narrower than the width D2 of the web W. Accordingly, the peripheral portion WS in the width direction of the web W rides on the cylindrical bodies 202 and 204, and the frictional force between the peripheral portion WS and the outer peripheral surfaces 210 and 214 suppresses the slip of the web W. The central portion WC in the width direction of the web W does not ride on the cylindrical bodies 202 and 204 but comes into contact with the peripheral surface 208 of the mirror surface. Thereby, the unevenness is hardly transferred to the central portion WC, and the uniformity of the physical properties of the optical film OF is improved.

  The distance D1 is desirably 80 to 99% of the width D2. If the distance D1 is larger than this upper limit value, the step between the outer peripheral surfaces 210 and 214 and the peripheral surface 208 is located at the extreme peripheral portion (near the end portion) where the web W is easily curled, and wrinkles are likely to occur on the web W. This is because the uniformity of the physical properties of the optical film OF tends to decrease. If the distance D1 is narrower than the lower limit value, the range of the web W to which the tensile force in the width direction is applied becomes narrow, and the web W is likely to be creased, and the uniformity of the physical properties of the optical film OF is likely to be lowered. is there. Moreover, it is because the range in which unevenness | corrugation is difficult to transfer becomes narrow, and the uniformity of the physical property of the optical film OF tends to fall.

  The cylindrical bodies 202 and 204 are particularly effective when transporting a web W having a wide width D2, for example, a web W having a width D2 of 2 m or more.

(Cylinder height)
The height H of the cylindrical bodies 202 and 204 from the peripheral surface 208, that is, the thickness of the cylindrical bodies 202 and 204 is selected so that the cylindrical bodies 202 and 204 have a strength that can withstand their own weight, but is 10 μm or more. It is desirable. This is because the tensile force in the width direction is sufficiently applied to the web W, the web W is less likely to be distorted, and the physical properties of the optical film OF are improved.

  The height H is preferably constant. This is because the level difference in contact with the extremely peripheral portion of the web W that is easily curled is reduced, the wrinkles are less likely to occur in the web W, and the uniformity of the physical properties of the optical film OF is improved.

(Type of transport roll)
The transport roll 206 includes a drive roll driven by a drive source and a free rotating roll not driven by the drive source. The cylindrical bodies 202 and 204 are generally attached to a free rotating roll, but the cylindrical bodies 202 and 204 may be attached to a drive roll instead of or in addition to the free rotating roll.

(Preparation for changing the width of the optical film)
FIGS. 3 and 4 are schematic diagrams illustrating a preparation procedure for changing the width of the optical film performed when preparing the optical film manufacturing apparatus.

  As shown in FIGS. 3 and 4, when the width WA of the web W of the optical film OF manufactured last time and the width WB of the web of the optical film OF manufactured this time are different, the peripheral portion WS of the web W of the width WA is The cylinders 202 and 204 are moved in the roll thrust direction from the position shown in FIG. 3 that rides on the cylinders 202 and 204 to the position shown in FIG. 4 where the peripheral portion WS of the web W having the width WB rides on the cylinders 202 and 204. The positions of the cylindrical bodies 202 and 204 in the roll thrust direction are adjusted according to the width WB of the web W of the optical film OF manufactured this time. Thereby, even if the width of the optical film OF is changed, the state in which the peripheral portion WS rides on the cylindrical bodies 202 and 204 is maintained. That is, it is possible to cope with the change in the width of the optical film OF by adjusting the positions of the cylindrical bodies 202 and 204 in the roll thrust direction, and the width of the optical film OF can be easily changed.

  The thermoplastic resin is not particularly limited, but is desirably a cellulose ester such as cellulose triacetate or cellulose acetate propionate.

  The solvent is not particularly limited, but is preferably a mixture of a good solvent and a poor solvent. When the thermoplastic resin is a cellulose ester, the good solvent includes methylene chloride and the poor solvent includes methanol and ethanol.

  Additives include plasticizers, ultraviolet absorbers, fine particles, and the like. Examples of the plasticizer include phosphate ester type. Examples of the ultraviolet absorber include a benzotriazole type. Examples of the fine particles include Aerosil. A retardation adjusting agent and other additives may be further added to the dope.

{Second Embodiment}
(Film body)
The second embodiment relates to a film body that is an example of a structure for slip suppression employed instead of the cylindrical body for slip suppression of the first embodiment.

  FIG. 5 is a schematic view (perspective view) of a transport roll in which a film body for slip suppression is formed on the peripheral surface.

  As shown in FIG. 5, the film bodies 302 and 304 are formed on the circumferential surface 208 apart in the roll thrust direction, and make one round in the roll circumferential direction. The film bodies 302 and 304 can be removed from the peripheral surface 208 with a solvent. The film bodies 302 and 304 are formed by applying a precursor made of a fluid to the peripheral surface 208 and curing it.

  The film bodies 302 and 304 are, for example, mat layers in which a mat agent is dispersed in a matrix. The matrix is not limited as long as it can hold the matting agent and can be added to the peripheral surface 208. For example, the matrix is a resin such as a cured product of a mixture of polyester and an isocyanate curing agent. The matting agent is, for example, a powder such as silicon resin particles. When the matrix is a cured product of a mixture of polyester and isocyanate curing agent, the film bodies 302 and 304 are removed from the peripheral surface 208 with acetone or the like. The precursor is, for example, a viscous fluid in which a resin and a matting agent are dissolved or dispersed in a solvent. The film body outer surface 310 of the film body 302 and the film body outer surface 314 of the film body 304 form a mat surface that is exposed by dispersing the matting agent and has irregularities.

(Distance and height of membrane bodies)
The distance D1 in the roll thrust direction between the film body 302 and the film body 304 is preferably narrower than the width D2 of the web W, and the distance D1 is preferably 80 to 99% of the width D2. The height H of the film bodies 302 and 304 from the peripheral surface 208, that is, the film thicknesses of the film bodies 302 and 304 are desirably 10 μm or more and constant. The reason is the same as in the case of the cylindrical bodies 202 and 204.

(Preparation for changing the width of the optical film)
FIGS. 6 to 8 are schematic diagrams illustrating a preparation procedure for changing the width of the optical film performed when preparing the optical film manufacturing apparatus.

  As shown in FIGS. 6 and 8, when the width WA of the web W of the optical film OF manufactured last time is different from the width WB of the web of the optical film OF manufactured this time, the peripheral portion WS of the web W of the width WA is The old film bodies 302 and 304 formed at the position shown in FIG. 6 are removed with a solvent (FIG. 7), and the new film bodies 302 and 304 are located at the position shown in FIG. 8 where the peripheral part WS of the web W having the width WB rides. The positions of the film bodies 302 and 304 in the roll thrust direction are adjusted according to the width WB of the web W of the optical film OF manufactured this time. Thereby, even if the width of the optical film OF is changed, the state where the peripheral portion WS rides on the film bodies 302 and 304 is maintained. That is, it is possible to cope with a change in the width of the optical film OF by adjusting the positions of the film bodies 302 and 304 in the roll thrust direction, and the width of the optical film OF can be easily changed.

{Third embodiment}
3rd Embodiment is related with the tape which is an example of the structure for slip suppression employ | adopted instead of the cylindrical body for slip suppression of 1st Embodiment.

  FIG. 9 is a schematic view (perspective view) of a transport roll in which a tape for slip suppression is attached to the peripheral surface.

  As shown in FIG. 9, the tapes 402 and 404 are affixed to the circumferential surface 208 apart in the roll thrust direction and make about one round in the roll circumferential direction. The tapes 402 and 404 can be peeled off from the peripheral surface 208. A sheet made of silicon or the like may be attached to the peripheral surface 208 instead of the tapes 402 and 404.

  The materials of the tapes 402 and 404 are selected so that the frictional force generated between the tape outer surfaces 410 and 414 and the web W is larger than the frictional force generated between the peripheral surface 208 and the web W, respectively. The material of the tapes 402 and 404 is, for example, kraft paper. The tape outer surfaces 410 and 414 may be matte surfaces.

(Width and height of the tape)
The distance D1 in the roll thrust direction between the tape 402 and the tape 404 is preferably narrower than the width D2 of the web W, and the distance D1 is preferably 80 to 99% of the width D2. The height H of the tapes 402 and 404 from the peripheral surface 208, that is, the film thickness of the tapes 402 and 404 is preferably 10 μm or more and constant. The reason is the same as in the case of the cylindrical bodies 202 and 204.

(Preparation for changing the width of the optical film)
FIGS. 10 to 12 are schematic diagrams illustrating a preparation procedure for changing the width of the optical film performed when preparing the optical film manufacturing apparatus.

  As shown in FIGS. 10 and 12, when the width WA of the web W of the optical film OF manufactured last time is different from the width WB of the web of the optical film OF manufactured this time, the peripheral portion WS of the web W having the width WA is shown. The old tapes 402 and 404 attached at the position shown in FIG. 10 are peeled off (FIG. 11), and the new tapes 402 and 404 are attached at the positions shown in FIG. 12 where the peripheral part WS of the web W having the width WB rides. The position of the tapes 402 and 404 in the roll thrust direction is adjusted in accordance with the width WB of the web W of the optical film OF manufactured this time. Applying a new tape includes reusing an old tape. Thereby, even if the width of the optical film OF is changed, the state where the peripheral portion WS rides on the tapes 402 and 404 is maintained. That is, the adjustment of the position of the tapes 402 and 404 in the roll thrust direction can cope with the change of the width of the optical film OF, and the change of the width of the optical film OF becomes easy.

{Fourth embodiment}
The fourth embodiment relates to a nip roll that is an example of a slip-suppressing structure that is employed instead of the slip-suppressing cylindrical body of the first embodiment.

  FIG. 13 is a schematic view (perspective view) of a transport roll in which a slip suppression nip roll contacts the circumferential surface.

  As shown in FIG. 13, the nip rolls 502 and 504 are brought into contact with the peripheral surface 208 apart in the roll thrust direction. The nip rolls 502 and 504 can move in the roll thrust direction.

(Nip roll spacing)
The distance D1 in the roll thrust direction between the nip roll 502 and the nip roll 504 is preferably narrower than the width D2 of the web W, and the distance D1 is preferably 80 to 99% of the width D2. The reason is the same as in the case of the cylindrical bodies 202 and 204.

(Preparation for changing the width of the optical film)
FIG. 14 and FIG. 15 are diagrams illustrating a preparation procedure for changing the width of the optical film performed when preparing the optical film manufacturing apparatus.

  As shown in FIGS. 14 and 15, when the width WA of the web W of the optical film OF manufactured last time is different from the width WB of the web W of the optical film OF manufactured this time, the peripheral portion WS of the web W of the width WA. The nip rolls 502 and 504 are moved from the position shown in FIG. 14 to the position shown in FIG. 15 to nip the peripheral portion WS of the web W having the width WB, and the positions in the roll thrust direction of the nip rolls 502 and 504 are the optically manufactured in this time. It is adjusted according to the width WB of the web W of the film OF. Thereby, even if the width of the optical film OF is changed, the state in which the peripheral portion WS is nipped between the nip rolls 502 and 504 is maintained. That is, the adjustment of the position of the nip rolls 502 and 504 in the roll thrust direction can cope with the change of the width of the optical film OF, and the change of the width of the optical film OF becomes easy.

(Outline)
Cellulose triacetate films (hereinafter referred to as “TAC films”) having the film thicknesses shown in Tables 1 to 8 while transporting the web W at the transport speeds shown in Tables 1 to 8 using the optical film manufacturing apparatus 100 shown in FIG. .) Was manufactured. Tables 1 to 8 also show the type and height of the structure for slip suppression. “None” in the column of “Type of structure” means that the structure for slip suppression was not used, and “groove” indicates that the structure for slip suppression is not used and This means that a groove has been formed in a portion where the peripheral portion WS contacts. The interval in the roll thrust direction of the structures for suppressing slip in Tables 1 to 5 was 95 to 98% of the web width of the optical film. The reason why the ratio is wide is that the ratio varies slightly because the width of the web changes from peeling to winding. In the case of Table 7, it was 75 to 95%.

  The components of the dope and the contents of each component are shown below.

Cellulose acetate propionate (total acetyl group substitution degree and propionyl group substitution degree is 2.45) (Mn = 60000, Mw = 18000, Mw / Mn = 3.00): 100 parts by weight Triphenyl phosphate: 8% by weight Part Ethylphthalyl ethyl glycate (EPEG): 4 parts by weight Tinuvin (registered trademark) 109 (manufactured by Ciba Specialty Chemicals): 0.5 part by weight Tinuvin (registered trademark) 171 (Ciba Specialty Chemicals, Inc.) Manufactured): 0.5 part by weight Methylene chloride: 418 parts by weight Methanol: 23 parts by weight Aerosil (AEROSIL R972V manufactured by Nippon Aerosil Co., Ltd.): 0.1 part by weight.

  The drying temperatures in the first drying zone 112 and the second drying zone 116 were 90 ° C. and 125 ° C., respectively. Stretching in the tenter 114 was performed under the condition that the casting film CF was stretched 1.3 times in the width direction in an atmosphere at 120 ° C. when the residual solvent amount was 10%.

  The material of the endless belt 106 was SUS316, and the outer surface 130 of the endless belt was a super mirror surface. A coat hanger die was used as the casting die 120.

In-plane retardation variation ΔR ₀ and crossed Nicols unevenness of the manufactured TAC film were evaluated.

In evaluating the in-plane retardation variation ΔR ₀ , the manufactured TAC film was left in an environment of a temperature of 23 ° C. and a humidity of 55% RH for 24 hours.

Subsequently, the retardation of the TAC film at 590 nm was measured with an automatic birefringence meter (KOBRA-21ADH manufactured by Oji Scientific Instruments). Further, the in-plane retardation R ₀ is calculated from the average refractive index and the film thickness d of the constituent material of the TAC film measured with an Abbe refractometer, and the in-plane retardation in the central region 20 mm away from both ends in the width direction of the TAC film. The variation ΔR ₀ was identified. Tables 1 to 7 show the ratio ΔR ₀ (WB) / ΔR of the variation ΔR ₀ (WB) of the in-plane retardation of the TAC film having the width WB to the variation ΔR ₀ (WA) of the in-plane retardation of the TAC film having the width WA. ₀ (WA). The width WB was made wider than the width WA (WA <WB), and the difference WB−WA between the width WA and the width WB was 200 mm or more. Since the variation ΔR0 in the in-plane retardation increases as the width increases, the ratio ΔR ₀ (WB) / ΔR ₀ (WA) takes a value of 1 or more. When the type of the structure was a groove, the position of the groove was determined so as to overlap the TAC film having the width WA.

  In evaluating the crossed Nicol unevenness, the polarizing plate on which the manufactured TAC film was attached was inspected under a condition slightly shifted from the crossed Nicol, and the presence or absence of the crossed Nicol unevenness was judged visually by the evaluator. The evaluation criteria are shown below.

A: All evaluators did not find any irregularities.
B: Some evaluators found irregularities,
C: All the evaluators found unevenness.

As is apparent from the comparison between Tables 1 to 5 and Tables 6 to 8, when the structure for slip suppression is used, variation in in-plane retardation ΔR ₀ (WB) / ΔR ₀ (WA ) And cross Nicol unevenness were obtained, and a TAC film with good uniformity in physical properties was obtained. Further, as shown in Tables 1 to 5, even when high-speed conveyance is performed at a conveyance speed of 80 to 300 m / min, in-plane retardation variation ΔR ₀ (WB) / ΔR ₀ (WA) and crossed Nicols unevenness It was small. However, in the case of Sample 2-7 in which the type of structure for slip suppression is a film body and high-speed conveyance was performed at a conveyance speed of 300 m / min, 10 scratches were formed in the length of 100 mm of the TAC film. Had occurred. Further, even when the film thickness was reduced to 20 to 60 or 80 μm, the in-plane retardation variation ΔR ₀ (WB) / ΔR ₀ (WA) and the crossed Nicols unevenness were small. In addition, when the structure for slip suppression was not used, or when the height of the structure was low, scratches occurred on the surface of the TAC film, and a TAC film that could be used as an optical film was not obtained. And Table 8 does not show the evaluation results of ΔR ₀ (WB) / ΔR ₀ (WA) and crossed Nicols unevenness.

  While the invention has been shown and described in detail, the above description is illustrative in all aspects and not restrictive. Thus, it will be appreciated that numerous modifications and variations can be devised without departing from the scope of the invention.

DESCRIPTION OF SYMBOLS 100 Optical film manufacturing apparatus 110 Conveyance roller group 202,204 Cylindrical body 206 Conveyance roller 208 Peripheral surface 302,304 Film body 402,404 Tape 502,504 Nip roll W Web

Claims (9)

(a) preparing an optical film manufacturing apparatus;
(b) a step of producing an optical film using the optical film production apparatus prepared in the step (a);
With
The step (b)
(b-1) a step of casting a dope on a casting surface of a casting membrane support and forming a casting membrane on the casting surface;
(b-2) a step of drying and solidifying the casting film formed in the step (b-1) on the casting surface to impart self-supporting property to the casting film;
(b-3) a step of separating the casting film provided with self-supporting property in the step (b-2) from the casting surface to obtain a web;
(b-4) The web obtained in the step (b-3) includes a conveyance roll provided with a structure for slip suppression capable of adjusting the position in the roll thrust direction and separated in the roll thrust direction on the peripheral surface. A process of transporting by a transport roll group;
(b-5) a step of winding the web conveyed in the step (b-4);
With
The step (a)
(a-1) When the width of the web of the optical film manufactured last time is different from the width of the web of the optical film manufactured this time, the roll thrust direction of the structure is adjusted in accordance with the width of the web of the optical film manufactured this time. Adjusting the position;
A method for producing an optical film by a solution casting film forming method. The structure is
A cylindrical body that is covered with the peripheral surface and is movable in the roll thrust direction,
The step (a-1)
(a-1-1) a step of moving the cylindrical body to a position where the peripheral part in the width direction of the web of the optical film manufactured this time rides on the cylindrical body;
A method for producing an optical film according to claim 1. The structure is
It is a film body that is formed on the peripheral surface by applying and curing a precursor made of a fluid to the peripheral surface, and can be removed with a solvent from the peripheral surface,
The step (a-1)
(a-1-2) removing the film body with a solvent;
(a-1-3) forming a film body at a position where the peripheral portion in the width direction of the web of the optical film manufactured this time rides;
A method for producing an optical film according to claim 1. The structure is
A tape or sheet that is affixed to the peripheral surface and can be peeled off from the peripheral surface;
The step (a-1)
(a-1-4) a step of peeling the tape or sheet;
(a-1-5) a step of attaching a tape or sheet to the position where the peripheral portion in the width direction of the web of the optical film manufactured this time runs on;
A method for producing an optical film according to claim 1.   The method for producing an optical film according to any one of claims 2 to 4, wherein a height of the structure from the peripheral surface is 10 µm or more and constant. The structure is
It is a nip roll that can move in the roll thrust direction,
The step (a-1)
(a-1-6) a step of moving the nip roll to a position where the peripheral portion in the width direction of the web of the optical film manufactured this time is nipped,
A method for producing an optical film according to claim 1.   The method for producing an optical film according to claim 1, wherein the interval in the roll thrust direction of the structure is 80% or more and 99% or less of the width of the web of the optical film produced this time.   The method for producing an optical film according to claim 1, wherein the film thickness of the optical film is 20 μm or more and 80 μm or less.   The manufacturing method of the optical film of Claim 1 whose conveyance speed of an optical film is 80 m / min or more and 300 m / min or less.

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