Sakamaki, Satoshi c/o Fuji Film Corporation (210 Nakanum, Minami-ashigara-shi Kanagawa, 250-0193, JP)
Maki, Takeshi c/o Fuji Film Corporation (210 Nakanum, Minami-ashigara-shi Kanagawa, 250-0193, JP)
Sakamaki, Satoshi c/o Fuji Film Corporation (210 Nakanum, Minami-ashigara-shi Kanagawa, 250-0193, JP)
| 1. | A casting film forming apparatus including a dope casting device for casting a dope from a casting die onto a running support to form a casting film and an air feeding device for feeding an air to all range in a width of said casting film just after the formation, said air feeding device comprising: an outlet for feeding out said air, said outlet opening to a running direction of said support; and a first rectifier member for partitioning said outlet into plural areas in a widthwise direction of said support , such that said air may be fed out in parallel to said running direction of said support . |
| 2. | A casting film forming apparatus according to claim 1, wherein the feeding of said air is started when a content of a remaining solvent in said casting film is at least a predetermined value . |
| 3. | A casting film forming apparatus according to claim 2 , wherein said predetermined value is 300 wt.%. |
| 4. | A casting film forming apparatus according to claim 1 , wherein said air feeding device has a plurality of said first rectifier members, and a distance Cl between said first rectifier members is in the range of 30 mm to 80 mm. |
| 5. | A casting film forming apparatus according to claim 1, said air feeding device further comprising: a boxlike main body whose one face has said outlet; and an air shielding member provided with each side surface of said main body, for reducing an entrained air generated by feeding said air. |
| 6. | A casting film forming apparatus according to claim 5 , wherein said air shielding members are air shielding plates disposed perpendicularly to said support and protruding from a bottom of said main body to said support. |
| 7. | A casting film forming apparatus according to claim 6 , wherein a distance C2 from a lower end of each of said air shielding plates to said casting film is in the range of 1 mm to 30 mm. |
| 8. | A casting film forming apparatus according to claim 7 , wherein a distance C3 from said bottom of said main body to said casting film is more than 1 mm and at most 300 mm, and larger than said distance C2. |
| 9. | A casting film forming apparatus according to claim 1 , wherein at least one second rectifier member is attached to a bottom of said main body such that said air may flow in said running direction of said support and in parallel to said support . |
| 10. | A casting film forming apparatus according to claim 9, wherein said second rectifier member is a rectifier plate, and a plurality of said rectifier plates are arranged in widthwise direction with an interval in the range of 50 mm to 400 mm. |
| 11. | A casting film forming apparatus according to claim 1, wherein a width of said outlet is the same as that of said casting film. |
| 12. | A solution casting apparatus comprising: a dope casting device for casting a dope from a casting die onto a running support so as to form a casting film; an air feeding device having an outlet for feeding out an air to all range in a width of said casting film just after the formation, said outlet opening to a running direction of said support ; a first rectifier member for partitioning said outlet into plural areas in a widthwise direction of said support, such that said air may be fed out in parallel to said running direction of said support; a peeling roller for peeling said casting film as a film from said support; and a drying device for drying said film. |
| 13. | A solution casting method comprising steps of: casting a dope onto a running support so as to form a casting film; feeding out an air through an outlet of an air feeding device to said casting film just after the formation, said outlet being partitioned in a widthwise direction of said casting film by a rectifier fin such that said air may be fed out in said running direction of said support and in parallel to said support; peeling said casting film as a film from said support; and drying said film. |
| 14. | A solution casting method according to claim 13, wherein the feeding of said air is started when a content of a remaining solvent in said casting film is at least a predetermined value. |
| 15. | A solution casting method according to claim 4, wherein said predetermined value is 300 wt.%. |
| 16. | A solution casting method according to claim 13, wherein a plurality of said rectifier fins is provided, and a distance Cl between said rectifier fins is set so as to reduce turbulence of a blowing direction from said outlet. |
| 17. | A solution casting method according to claim 16, wherein said distance Cl is in the range of 30 mm to 80 mm. |
| 18. | A solution casting method according to claim 13, wherein said outlet is provided in one face of a boxlike main body of said air feeding device and opens to said running direction of said support , and each side face of said main body is provided with an air shielding member for reducing an entrained air generated by feeding said air, and wherein a distance C2 from said air shielding member and said casting film is set so as to reduce said entrained air. |
| 19. | A solution casting method according to claim 18, wherein said distance C2 is at least 1 mm and at most 30 mm. |
| 20. | solution casting method according to claim 19, wherein a distance C3 from said bottom of said main body to said casting film is more than 1 mm and at most 300 mm, and larger than said distance C2. |
APPARATUS AND METHOD FOR PRODUCING FILM FROM DOPE
Technical Field
The present invention relates to a dope casting device, a film production equipment and a solution casting method.
Background Art
A polymer film is used in an optical field. Especially, a cellulose aclate film is widely used as an optical film for producing a reasonable and thin liquid crystal device since the celluloce acylate film has merits to be used as a protective film for a polarizing filter.
Such cellulose acylate film is mainly produced by a solution casting method in which a polymer solution (namely dope) containing polymer (such as cellulose acylate and the like) and solvent is onto a running support to form a casting film. Then the casting film is peeled as a wet film which is dried to a filim.
When it is designated to produce the film by the solution casting method, it is contrived to make the casting speed higher so as to increase the productivity. In this case, for example, an initial drying is made to the casting film just after the casing onto the support with use of a drying device. Thus the evaporation of the solvent from the casting film effectively proceeds .
When an air duct is used as the drying device, a drying air is fed out from an outlet of the air duct in a running direction of the support, so as to be parallel to the support. However, the drying air from the outlet and the involving of
the air near the film surface of the casting film to the drying air cause a wind (entrained air) to make a turbulence of aerial current near the casting film. The turbulence of aerial current causes diagonally extending unevenness (diagonal unevenness) and unevenness of film thickness (thickness unevenness). A generic term of both inclination variation and thickness unevenness is asperity. When the unevenness occurs, the planarity of the film becomes lower. Therefore, a development of a method for drying the casting film by reducing the occurrence of the unevenness has been required.
As developments thereof, an air duct is disposed such that an outlet is directed in a casting direction (or a running direction of the support) with inclination in the range of 45° to 80° to the support . The drying is made by feeding a wind from the outlet (see, Japanese Patent Laid-Open Publication No. 64-55214). Otherwise, an air duct in which an inlet and an outlet are disposed at predetermined positions is used to feed the drying air with adjustment of the wind speed from the outlet (see, Japanese Patent Laid-Open Publication No. 2001-113545). Further, an air duct provided with a slit-like opening is disposed in the most upstream side (see, Japanese Patent Laid-Open Publication No.2003-103544). Furthermore, after the casting of the dope, an air shielding plate is disposed at a predetermined position so as to extend to a casting direction. Thus the intrusion of the wind close to the film surface of the casting film is prevented (see, Japanese Patent Laid-Open Publication No. 2004-314527).
Any methods above has predetermined effects for reducing asperity, such that the produced film may be excellent in planarity. However, in recent years, the electric devices are made miniaturized and thinner rapidly. Accordingly, the requirement of the miniaturization and the thinning of the
optical film is large. Therefore, the optical film must be more excellent in planarity. However, in the above methods, it is difficult that the produced film has the enough planarity with the satisfaction with the requirement of recent years . An object of the present invention is to provide a casting film forming apparatus for casting a dope on a support to form a casting film in which the generation of unevenness is reduced, such that a polymer film excellent in planarity may be obtained.
Another object of the present invention is to provide A solution casting apparatus for casting a dope on a support to form a casting film in which the generation of unevenness is reduced, such that a polymer film excellent in planarity may be obtained.
Still another object of the present invention is to provide a solution casting method for casting a dope on a support to form a casting film in which the generation of unevenness is reduced, such that a polymer film excellent in planarity may be obtained.
Disclosure of Invention
In order to achieve the object and the other object, a casting film forming apparatus includes a dope casting device for casting a dope from a casting die onto a running support to form a casting film and an air feeding device for feeding an air to all range in a width of the casting film just after the formation. The air feeding device includes an outlet and a first rectifier member. The outlet opens to a running direction of the support , and the air is fed out from the outlet . The plural rectifier member partitions the outlet into plural areas in a widthwise direction of the support, such that the air may be fed out in parallel to the running direction of the support .
Preferably, the feeding of the air is started when a content of a remaining solvent in the casting film is at least a predetermined value. Especially preferably, the predetermined value is 300 wt.%. Preferably, the air feeding device has a plurality of the first rectifier members, and a distance Cl between the first rectifier members is in the range of 30 mm to 80 mm.
Preferably, the air feeding device further includes a box-like main body whose one face has the outlet, and an air shielding member provided with each side surface of the main body. The air shielding member reduces a retaining an entrained air generated by feeding the air. Particularly preferably, the air shielding members are air shielding plates disposed perpendicularly to the support and protruding from a bottom of the main body to the support. Especially preferably, a distance C2 from a lower end of each air shielding plates to the casting film is in the range of 1 mm to 30 mm. Furthermore, a distance C3 from the bottom of the main body to the casting film is more than 1 mm and at most 300 mm, and larger than the distance C2. Preferably, at least one second rectifier member is attached to a bottom of the main body such that the air may flow in parallel to the running direction of the support. Particularly preferably, the second rectifier member is a rectifier plate, and a plurality of rectifier plates is arranged in widthwise direction with an interval in the range of 50 mm to 400 mm.
Preferably, a width of the outlet is the same as that of the casting film.
In the present invention, a solution casting apparatus includes a dope casting device for casting a dope from a casting die onto a running support so as to form a casting film, and an air feeding device having an outlet for feeding out an air
to all range in a width of the casting film just after the formation so as to dry the casting film. The outlet opens to a running direction of the support . A solution casting apparatus further includes plural first rectifier members for partitioning the outlet into plural areas in a widthwise direction of the support, such that the air may be fed out in parallel to the running direction of the support . In the solution casting instrument, a peeling roller peels the casting film as a film from the support, and a drying device dries the film.
In a solution casting method of the present invention, after a dope is cast onto a running so as to form a casting film, an air is fed out through an outlet of an air feeding device to the casting film just after the formation. The outlet is partitioned in a widthwise direction of the casting film by a rectifier fin such that the air may be fed out in a running direction of the support and in parallel to the support . Then the casting film is peeled as a film from the support and the film is dried. Preferably, the feeding of the air is started when a content of a remaining solvent in the casting film is at least a predetermined value. Especially preferably, the predetermined value is 300 wt.%.
Preferably, a plurality of said rectifier fins is provided, and a distance Cl between the rectifier fins is set so as to reduce turbulence of a blowing direction from the outlet . Especially preferably, the distance Cl is in the range of 30 mm to 80 mm.
In a solution casting method, the outlet is provided in a face of a box-like main body of the air feeding device and opens to the running direction of the support. Each side face of the main body is provided with an air shielding member for
reducing an entrained air generated by feeding the air. A distance C2 from the air shielding member and the casting film is set so as to reduce the entrained air. Particularly preferably, the distance C2 is at least lmm and at most 30 mm. Especially preferably, a distance C3 from the bottom of the main body to the casting film is more than 1 mm and at most 300 mm, and larger than the distance C2.
According to the present invention, in the air feeding device, the air is fed out through the outlet of the air duct in parallel to the running direction of the support, and the plural first rectifier members partition into plural areas in widthwise direction of the support. Therefore, the feeding direction of the air is controlled to be in parallel to the running direction of the support . Thus the generation of the unevenness on the surface of the casting film is reduced. Further, since the air feeding device is provided with air shielding plates , the entrained air generated by feeding the air may be reduced. Further, the feeding of the air is started from the air feeding device to all range in a width of the casting film just after the formation of the casting film with rectification of the air, the generation of the unevenness on the surface of the casting film is reduced. Thus in the present invention, the produced film is excellent in planarity.
Brief Description of Drawings
Figure 1 is a schematic diagram of a dope production line in the present invention;
Figure 2 is a schematic diagram of a film production line of the present invention; Figure 3 is an exploded partial view of a first embodiment of an air duct, illustrating a positional relation thereof ,to a belt in a casting chamber of the film production line in Figure
2;
Figure 4 is a front view of the air duct of Figure 3;
Figure 5 is a perspective view of a second embodiment of an air duct; Figure 6 is a perspective view of a third embodiment of an air duct .
Best Mode for Carrying Out the Invention
As polymer in this embodiment, cellulose acylate is used and especially preferably triacetyl cellulose . As for cellulose acylate, it is preferable that the degree of substitution of acyl groups for hydrogen atoms on hydroxyl groups of cellulose preferably satisfies all of following formulae (I)-(III).
(I) 2.5≤A+B≤3.0 (II) 0≤A≤3.0 (III) 0≤B≤2.9
In these formulae (I)-(III), A is the degree of substitution of the acetyl groups for the hydrogen atoms on the hydroxyl groups of cellulose, and B is the degree of substitution of the acyl groups for the hydrogen atoms while each acyl group has carbon atoms whose number is from 3 to 22.
Note that at least 90 wt.% of TAC is particles having diameters from 0.1 mm to 4 mm. However, the polymer to be used in the present invention is not restricted in cellulose acylate, but may be polymers already known.
A glucose unit constructing cellulose with β-1,4 bond has the free hydroxyl groups on 2 nd , 3 rd and 6 th positions. Cellulose acylate is polymer in which, by esterification, the hydrogen atoms on the part or all of the hydroxyl groups are substituted by the acyl groups having at least two carbon atoms . The degree of acylation is the degree of the esterification of the hydroxyl groups on the 2 nd , 3 rd , 6 th positions. In each hydroxyl group.
if the esterification is made at 100%, the degree of acylation is 1. Therefore if the esterification of all of the hydroxyl groups on 2 nd , 3 rd and 6 th positions are made, the degree of acylation is 3. Herein, if the acyl group is substituted for the hydrogen atom on the 2 nd position in a glucose unit, the degree of the acylation is described as DS2 (the degree of substitution by acylation on the 2 nd position) , and if the acyl group is substituted for the hydrogen atom on the 3 rd position in the glucose unit, the degree of the acylation is described as DS3 (the degree of substitution by acylation on the 3 rd position) . Further, if the acyl group is substituted for the hydrogen atom on the 6 th position in the glucose unit , the degree of the acylation is described as DS6 (the degree of substitution by acylation on the 6 th position) . The total of the degree of acylation, DS2+DS3+DS6, is preferably 2.00 to 3.00, particylarly 2.22 to 2.90, and especially 2.40 to 2.88. Further, DS6/(DS2+DS3+DS6) is preferably at least 0.28, particularly at least 0.30, and especially 0.31 to 0.34. In the present invention, the number and sort of the acyl groups in cellulose acylate may be only one or at least two. If there are at least two sorts of acyl groups, one of them is preferable the acetyl group. If the hydrogen atoms on the 2 nd , 3 rd and 6 th hydroxyl groups are substituted by the acetyl groups , the total degree of substitution is described as DSA, and if the hydrogen atoms on the 2 nd , 3 rd and 6 th hydroxyl groups are substituted by the acyl groups other than acetyl groups, the total degree of substitution is described as DSB. In this case, the value of DSA+DSB is preferably 2.22 to 2.90, especially 2.40 to 2.88. Further, DSB is preferably at least 0.30, and especially at least 0.7. According to DSB, the percentage of the substitution on the 6 th position to that on the 2 nd , 3 rd and
6 th positions is at least 20%. However, the percentage is preferably at least 25%, particularly at least 30%, and especially at least 33%. Further, DSA+DSB of the 6 th position of the cellulose acylate is preferably at least 0.75, particularly at least 0.80, and especially at least 0.85. When these sorts of cellulose acylate are used, a solution (or dope) having excellent solubility can be produced. Especially if non-chrorine type organic solvent is used as solvent, the non-chrorine type organic solvent is excellent in solubility and used for preparing the dope which has low viscosity and filterability.
Cellulose acylate is may be produced from cotton linter or cotton pulp, and preferably cellulose acylate is produced from cotton linter. In cellulose acylate, the acyl group having at least 2 carbon atoms may be aliphatic group or aryl group, and is not restricted especially. Such cellulose acylate is, for example, alkylcarbonyl ester and alkenylcarbonyl ester of cellulose. Further, there are aromatic carbonyl ester, aromatic alkyl carbonyl ester, or the like, and these compounds may have other substituents. As preferable examples of the compounds, there are propionyl group, butanoyl group, pentanoly group, hexanoyl group, oσtanoyl group, decanoyl group, dodecanoyl group, tridecanoyl group, tetradecanyol group, hexadecanoyl group, octadecanoyl group, iso-butanoyl group, t-butanoyl group, σyclohexanecarbonyl group, oleoyl group, benzoyl group, naphthylcarbonyl group , σinamoyl group and the like . Among them, the particularly preferable groups are propionyl group, butanoyl group, dodecanoyl group, octadecanoyl group, t-butanoyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, cinamoyl group and the like, and the especially preferable groups are propionyl group and butanoyl
group .
Further, as solvents for preparing the dope, there are aromatic hydrocarbons (for example, benzene, toluene and the like), hydrocarbon halides (for example, dichloromethane , chlorobenzene and the like), alcohols (for example, methanol, ethanol, n-propanol, n-butanol, diethyleneglycol and the like) , ketones (for example, acetone, methylethyl ketone and the like) , esters (for example, methyl acetate, ethyl acetate, propyl acetate and the like), ethers (for example, tetrahydrofuran, methylcellosolve and the like) and the like.
The solvents are preferably hydrocarbon halides having 1 to 7 carbon atoms, and especially dichloromethane. Then in view of the solubility of cellulose acylate, the peelability of a casting film from a support, a mechanical strength of a film, optical properties of the film and the like, it is preferable that one or several sorts of alcohols having 1 to 5 carbon atoms is mixed with dichloromethane . Thereat the content of the alcohols to the entire solvent is preferably in the range of 2 mass% to 25 mass%, and particularly in the range of 5 mass% to 20 mass%. Concretely, there are methanol, ethanol, n-propanol, iso-propanol, n-butanol and the like. The preferable examples for the alcohols are methanol, ethanol, n-butanol, or a mixture thereof.
By the way, recently in order to reduce the effect to the environment to the minimum, the solvent composition when dichloromethane is not used is progressively considered. In order to achieve this object, ethers having 4 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, esters having 3 to 12 carbon atoms, alcohols having 3 to 22 carbon atoms are preferable, and a mixture thereof can be used. As mixture, there are for example mixtures of methyl acetate, acetone, ethanol and n-butanol. These ethers, ketones and esters may have the ring structure.
Further, the compounds having at least two of functional groups (namely, -O- , -CO- and -COO-) in ethers, ketones and esters can be used for the solvent.
The detail explanation of cellulose aσylate is made from [0140] to [0195] in Japanese Patent Laid-Open Publication No. 2005-104148. The description of this publication is also applied to the present invention. Further, the additives (such as the solvent, plasticizer, deterioration inhibitor, UV absorbing agent, optically anisotropic controller, retardation controller, dyne, matting agent, release agent, releasing accelerator and the like) are described in detail from [0196] to [0516] of Japanese Patent Laid-Open Publication No. 2005-104148.
[Dope Production Method] It is to be noted in a dope production line 10 that the production method of the dope used in the present invention is not restricted in the embodiment shown in FIG.l. The dope production line 10 is constructed of a solvent tank 11, an additive tank 14, a hopper 13, a mixing tank 12, a filtration device 17 and a stock tank 41. Several sorts of the devices constructing the dope production line 10 are connected through plural pipes .
In the dope production line 10, a dope 27 is produced in the following order. When a valve 18 is opened, the solvent is sent from the solvent tank 11 to the mixing tank 12. Amount of the solvent is controlled by adjusting the valve 18. Then the cellulose acylate in the hopper 13 is sent to the mixing tank 12. Thereafter, the valve 18 is opened such that the additive is sent from the additive tank 14 to the mixing tank 12. The method of feeding the additive to the dissolution tank is not restricted in the above description. If the additive is in the liquid state in the room temperature, it may be fed in
the liquid state to the mixing tank 12 without preparing for the additive solution. Otherwise, if the additive is in the solid state in the room temperature, it may be fed in the solid state to the mixing tank 12 with use of a hopper. If plural sorts of additive compounds are used, the additive containing the plural additive compounds may be accumulated in the additive tank 14 altogether. Otherwise plural additive tanks may be used so as to contain the respective additive compounds, which are sent through independent pipes to the mixing tank 12. In the above explanation, the solvent, the cellulose acylate, and the additive are sequentially sent to the mixing tank 12. However, the sending order is not restricted in it. For example, after the predetermined amount of cellulose acylate is sent to the mixing tank 12, the feeding of the predetermined amount of the solvent and the additive may be performed to obtain a cellulose acylate solution. Otherwise, it is not necessary to feed the additive to the mixing tank 12 previously, and the additive may be added to a mixture of TAC and solvent in following processes. The mixing tank 12 is provided with a jacket 20 covering over an outer surface of the mixing tank 12, a first stirrer 22 to be rotated by a motor 21, and a second stirrer 24 to be rotated by a motor 23. The first stirrer 22 preferably has an anchor blade, and the second stirrer 24 is preferably an eccentric stirrer of a dissolver type. The jacket is provided with a temperature controller for controlling the temperature of a heat transfer medium flowing in the jacket. Thus the inner temperature in the mixing tank 12 is controlled. The preferable inner temperature is in the range of -1O 0 C to 55 0 C . At least one of the first and second stirrers 22, 24 is adequately chosen for performing the rotation. Thus a swelling liquid 25 in which TAG is swollen in the solvent is obtained.
In a downstream from the mixing tank 12, the dope production line 10 further includes a pump 26, a heating device 15, a temperature controlling device 16, a filtration device 17, and the stock tank 41. The pump 26 is driven such that the swelling liquid 25 in the mixing tank 12 may be sent to the heating device 15 which is preferably a pipe with a jacket. Further, the heating device 15 preferably pressurizes the swelling liquid 25. While the swelling liquid 25 is continuously in only the heating condition or both of the heating and pressurizing condition, the dissolution of TAC proceeds such that the swelling liquid 25 may be a polymer solution. Note that the polymer solution may be a solution in which the polymer is entirely dissolved and a swelling liquid in which the polymer is swollen. Further, the temperature of the swelling liquid 25 is preferably in the range of 50 0 C to 12O 0 C . Instead of the heat-dissolution with use of the heating device 15, the swelling liquid 25 may be cooled in the range of -100 0 C to -30 0 C so as to perform the dissolution, which is already known as the cool-dissolution method. In this embodiment, one of the heat-dissolution and cool-dissolution methods can be chosen in accordance with the properties of the materials, so as to control the solubility. Thus the dissolution of TAC to the solvent can be made enough. The polymer solution is fed to the temperature controlling device 16 , so as to control the temperature nearly to the room temperature.
Then the polymer solution is fed to the filtration device 17, such that impurities may be removed from the polymer solution. The filter material of the filtration device 17 preferably has an averaged nominal diameter of at most 100 μm. The flow rate of the filtration in the filtration device 17 is preferably at least 50 liter/hr. The polymer solution after the filtration is fed through a valve 28 to the stock tank 41.
The polymer solution can be used as dope 27 for a film production, which will be explained. However, in the method in which the dissolution of TAC is performed after the preparation of the swelling liquid, if it is designated that a polymer solution of high concentration is produced, the time for production of such dope becomes longer. Consequently, the production cost becomes higher. Therefore, it is preferable that a polymer solution of the lower concentration than the predetermined value is prepared at first and then the concentrating of the polymer solution is made. In this embodiment , the polymer solution after the filtration is sent to a flushing device 30 through the valve 28. In the flushing device 30, the solvent of the polymer solution is partially evaporated. The solvent vapor generated in the evaporation is condensed by a condenser (not shown) to a liquid state, and recovered by a recovery device 32. The recovered solvent is recycled by a recycling device 33 and reused. According to this method, the decrease of cost can be designated, since the production efficiency becomes higher and the solvent is reused. The polymer solution after the concentrating as the above description is extracted from the flushing device 30 through a pump 34. Further, in order to remove bubbles generated in the polymer solution, it is preferable to perform the bubble removing treatment . As a method for removing the bubble , there are many methods which are already known, for example, an ultrasonic irradiation method and the like. Then the polymer solution is fed to a filtration device 31, in which the undissolved materials are removed. Note that the temperature of the polymer solution in the filtration device 31 is preferably in the range of 0 0 C to 200 0 C . The polymer solution after the filtration, is stored in the stock tank 41, which is provided with a stirrer 61 rotated by a motor 60. The stirrer
61 is rotated so as to continuously stir the dope 27.
Thus a dope produced the produced dope preferably has the TAC concentration in the range of 5 mass% to 40 mass%, particularly 15 mass% to 30 mass%, and especially 17 mass% to 25 mass%. Further, the concentration of the additive (mainly plasticizer) is preferably in the range of 1 mass% to 20 mass%, if the solid content in the dope 27 is 100 mass%.
Note that the method of producing the polymer solution is disclosed in detail in [0517] to [0616] in Japanese Patent Laid-Open Publication No.2005-104148, for example, the dissolution method and the adding methods of the materials , the raw materials and the additives in the solution casting method for forming the TAC film, the filtering method, the bubble removing method, and the like. [Solution Casting Method]
An embodiment of the solution casting method will be described in reference with FIG.2, now. However, the present invention is not restricted in the embodiment . As shown in FIG.2 , the film production line 40 includes the stock tank 41, a filtration device 42, a casting die 43, back-up rollers 44, 45, a belt supported by the back-up rollers 44, 45, and a tenter device 47. Further, there are an edge slitting device 50, a drying chamber 51, a cooling chamber 52 and a winding chamber 53. Furthermore, the stock tank 41 connects the dope production line 10 to the film production line 40, while being connected to the casting die 43 through the pump 62 and the filtration device 42.
The materials of the casting die 43 are preferably precipitation hardening stainless steel. The preferable material has coefficient of thermal expansion of at most 2 x 10 "5 ( °C '1 J . Further, the material to be used has an anti-corrosion property, which is almost the same as SUS316,
in the examination of forcible corrosion in the electrolyte solution. Preferably, the materials to be used for the casting die 43 has such resistance of corrosion that the pitting doesn't occur on the gas-liquid interface even if the material is dipped in a mixture of diσhloromethane, methanol and water for three months. The casting die 43 is preferably manufactured by performing the polishing after a month from the material casting. Thus the surface condition of the dope flowing in the casting die 43 is kept uniform. The finish precision of a contact face of the casting die to the dope 27 is at most 1 μm in surface roughness and at most 1 μm/m in straightness . The clearance of a slit of the casting die 43 is automatically adjustable in the range of 0.5 mm to 3.5 mm. According to an edge of the contact portion of a lip end of the casting die 43 to the dope, R (R is chamfered radius) is at most 50 μm in all of a width. Further, the shearing rate in the casting die 43 is controlled in the range of 1 to 5000 per second.
A width of the casting die 43 is not restricted especially. However, the width is preferably at least 1.1 times and at most 2.0 times as large as a film width. Furthermore, the casting die 43 is preferably a coat hanger type die. Further, in order to adjust a film thickness, the casting die 43 is preferably provided with an automatic thickness adjusting device. For example, thickness adjusting bolts (heat bolts) are disposed at a predetermined interval in a widthwise direction of the casting die 43. According to the heat bolts, it is preferable that the profile is set on the basis of a predetermined program, depending on feed rate of pumps (preferably, high accuracy gear pumps), while the film production is performed. Further, the film production line 40 may be provided with a thickness meter (not shown) , such as infrared ray thickness meter and the like. In this case, the feed back control of the adjustment value of
the heat bolts may be made by the adjusting program on the base of the profile of the thickness meter. The thickness difference between any two points in the widthwise direction except the side edge portions in the casting film is controlled preferably to at most 1 μm. The difference between the maximum and the minimum of the thickness in the widthwise direction is at most 3 μm, and especially at most 2 μm. Further, the accuracy to the designated object value of the thickness is preferably in ±1.5 μm. Preferably, a hardened layer is preferably formed on a top of a lip end of the casting die 43. A method of forming the hardened layer is not restricted. But it is, for example, ceramics hard coating, hard chrome plating, neutralization processing, and the like. If ceramics is used as the hardened layer, it is preferable that the used ceramics is grindable but not friable, with a lower porosity, high resistance of corrosion, and poor adhesiveness to the casting die 43. Concretely, there are tungsten carbide (WC), Al 2 O 3 , TiN, Cr 2 O 3 , and the like. Especially preferable ceramics is tungsten carbide. Tungsten carbide coating can be made by a spraying method.
Further, in order to prevent the partial dry-solidifying of the dope 27 flowing on slit ends of the casting die 43, it is preferable to provide a solvent supplying device (not shown) at the slit ends, on which a gas-liquid interfaces are formed between both edges of the slit and between both bead edges and the outer gas. Preferably, these gas-liquid interfaces are supplied with the solvent which can dissolve the dope, (for example a mixture solvent of dichloromethane 86.5 pts.mass, acetone 13 pts.mass, n-butanol 0.5 pts.mass). The supply rate to each slit end is preferably in the range of 0.1 mL/min to 1.0 mL/min, in order to prevent the foreign materials from mixing into the casting film. Note that the pump for supplying
the solvent has a pulse rate (or ripple factor) at most 5%.
A belt 46 is positioned below the casting die 43, and lapped on back-up rollers 44, 45. When the back-up rollers 44,
45 are rotated by the driving device (not shown) , and thus the belt 46 runs endlessly in accordance with the rotation of the back-up rollers 44, 45. Then the casting speed is preferably in the range of 10 m/min to 200 m/min. Further, the temperatures of the back-up rollers 44, 45 are controlled by a heat transfer medium circulator 63 for cycling a heat transfer medium. It is preferable that the surface temperature of the belt 46 is adjusted in the range of -20 0 C to 40 0 C by heat transmission from the back-up rollers 44, 45. In this embodiment, paths (not shown) of the heat transfer mediums are formed in the back-up rollers 44, 45, and the heat transfer mediums whose temperatures are controlled by the heat transfer medium circulator 63 pass through the paths . Thus the temperature of the back-up rollers 44, 45 are kept to the predetermined values.
The width, the length and the material of the belt 46 are not restricted especially. However, it is preferably 1.1 to 2.0 times as large as the casting width. Preferably, the length is from 20m to 200m, and the thickness is from 0.5 mm to 2.5 mm. The surface is preferably polished so as to have a surface roughness at most 0.05 μm. The belt 46 is preferably made of stainless steel, and especially of SUS 316 so as to have enough resistance of corrosion and strength. The thickness unevenness of the entire belt 46 is preferably at most 0.5%.
Note that it is possible to use one of the back-up rollers 44, 45 as support. In this case, the back-up roller used as support is preferably rotated at high accuracy such that a rotation flutter may be at most 0.2 mm. Therefore the surface roughness is preferably at most 0.01 μm. Further, the chrome plating is preferably performed to the drum such that the drum
may have enough hardness and endurance. As described above, it is preferable in the support that the surface defect must be reduced to be minimal. Concretely there are no pin hole of at least 30 μm, at most one pin hole in the range of 10 μm to 30 μm, and at most two pin holes of less than 10 μm per 1 m 2 .
A temperature controlling device 65 is provided for controlling the inner temperature of a casting chamber 64 to the predetermined value, and a condenser 66 is provided for condensing organic solvent evaporated in the casting chamber 64. Further a recovering device 67 for recovering the condensed organic solvent outside the casting chamber 64. Further, the cast dope forms a bead between the casting die 43 and the belt 46. In order control the pressure in a rear side of the bead, it is preferable to dispose a decompression chamber 68, as in this embodiment .
An air duct 70 is disposed around and near the belt 46, so as to dry a casting film 69 formed on the belt 46. Note that the detail explanation of the air duct 70 will be made later. Further, in the drying chamber 51, the casting film 69 is peeled as a film 82 in a situation of containing the solvent from the belt 46 with support of a peeling roller 75.
In an interval section 80, there is an air blower 81. Then the film 82 is stretched and dried in the tenter device and fed out as a film 82. Thereafter, the edge slitting device 50 slit off both side edge portions of the film 82 into tips, and the tips of both side edge portions are crushed by a crusher connected to the edge slitting device 50.
In the drying device 51, the film 82 is transported with lapping on rollers 91. The solvent vapor evaporated from the film 82 by the drying device 51 is adsorbed by an adsorbing device 92.
The film 82 is transported into a cooling chamber 52, and
cooled therein to around the room temperature. A humidity control chamber (not shown) may be provided for conditioning the humidity between the drying device 51 and the cooling chamber 52. Thereafter, a compulsory neutralization device (or a neutralization bar) 85 eliminates the charged electrostatic potential of the film 82 to the predetermined value (for example, in the range of -3kV to +3kV) . The position of the neutralization process is not restricted in this embodiment. For example, the position may be a predetermined position in the drying section or in the downstream side from a knurling roller 94, and otherwise, the neutralization may be made at plural positions. In the winding chamber 56, the film 82 is wound by a winding shaft 95. At this moment, a tension is applied at the predetermined value to a press roller 96. As shown in FIG.3, just after forming the casting film 69, namely near and downstream from the casting die 43, the air duct 70 is positioned for feeding a drying air so as to evaporate the solvent from the casting film 69. The air duct 70 is connected to an air feed controller (not shown) for independently controlling the air feed conditions (such as feed rate, temperature, humidity and the like) of the drying air, and an air feed section (not shown) for feeding to the air duct 70 the drying air whose conditions has been controlled. A box-like duct main body 71 of the air duct 70 has a plurality of outlets 71a extending in a widthwise direction of the casting film 69 and a plurality of rectifier fins 100 as first rectifier member for partitioning each outlet 71a into plural areas in the widthwise direction of the belt 46. Thus the drying air is fed out from each outlet 71a so as to be in parallel to the belt 46 with rectifying the flow of the drying air more. Therefore, the occurrence of unevenness on the casting film is prevented. Furthermore, the duct main body 71 has air shielding plates 101
as air shielding members for reducing the entrained air during the air feeding.
As shown in FIG.4, the duct main body 71 has two side members 71b in both sides so as to be positioned above both side edge portion of the casting film 69 and perpendicular to the belt 46. Further, on inner surfaces of lower member 71c and upper member 7Id, plural grooves 7Oe are formed in a running direction of the belt 46 , and both ends of the rectifier fins 100 are fitted into the grooves 7Oe respectively. The rectifier fins 100 are disposed perpendicularly to the belt 46.
The distance Cl (mm) between the rectifier fins 100 can be adjusted by selecting the grooves 7Oe into which the rectifier fins 100 are to be fitted, in order to reduce the turbulence of the drying air. The distance Cl is preferably in the range of 30 mm to 80 mm, particularly 35 mm to 75 mm, and especially 40 mm to 70 mm. Thus the drying air can be fed out with the rectification. However, if the distance Cl is more than 80 mm, the areas between the rectifier fins 100 in the outlet 71a are not many, and therefore the effects of the rectification of the drying air becomes lower. Further, if the distance Cl is less than 30 mm, the effects are almost the same as when the distance is 30mm. further, in this case, many rectifier fins 100 are necessary, which causes the higher cost and the longer labor hour. To outer surfaces of both side members 71b are attached the air-shielding plates 101 as air shielding members. The distance C2 (mm) from the air shielding plate 101 to the casting film 69 on the belt 46 is preferably in the range of 1 mm to 30 mm, particularly 3 mm to 27 mm, and especially 5 mm to 25 mm. Thus the entrained air generated by feeding the drying air from the outlet 71a is reduced, and therefore, the casting film 69 can be dried without occurrence of unevenness. However, if
the distance C2 is less than 1 mm, the duct main body 71 is closed to the casting film 69 too much, and therefore the drying air fed out from the outlet 71a applies a strong pressure onto the casting film 69, which causes a lot of unevenness. If the distance C2 is more than 30 mm, the duct main body 71 is too far from the casting film 69, and therefore the occurrence of the entrained air cannot be reduced, which causes unevenness on the casting film 69. The air shielding plate 101 is shifted up- and downwardly by a shifting device (not shown) , such that the position of the air shielding plate may be adjusted. Note that a distance from the lower end of the air shielding plate 101 to the belt 46 as support is a distance CA, and the thickness of ten casting film 69 is a thickness CB. In this case, the distance C2 is described as CA-CB. The distance C3 (mm) from the duct main body 71 to the casting film 69 is preferably more than 1 mm and at most 300 mm, particularly in the range of 2 mm to 250 mm, and especially 5 mm to 200 mm. Thus the drying air can be fed without retaining in a lower side of the air duct 70 and the effects of the rectifier fin 100 and the air shielding plate 101 become sufficient. Therefore the drying air fed out from the outlet 71a can be parallel to the casting film 69. However, if the distance C3 (mm) is larger than 300 mm, the duct main body 71 is too far from the casting film, and therefore it is necessary to make the feed rate of the drying wind larger. It is not preferable. If the distance C3 (mm) is at most 1 mm, the distance C2 cannot satisfy the above conditions. Further, in this case, the drying air fed out from the outlet 71a is applied too strongly to the casting film 69, which causes unevenness on the casting film 69.
Preferably, a lower end of each air shielding plate 101 protrudes towards the casing film 69 from a bottom (or the lower
member 71c) of the duct main body 71. The protrusion length Ll of the air shielding plate 101 is preferably in the range of 10 mm to 35 mm, particularly 8 mm to 33 mm, and especially 6 mm to 30 mm. Thus the effects of the air shielding plate 101 for preventing the entrained air caused by the feed of the drying air from the outlet 71a become sufficient. However, if the protrusion length Ll is larger than 35 mm, the drying air retains in an area surrounded by the lower member 71c and the air shielding plates 101, which causes the turbulence of flow of the drying air. If the protrusion length Ll is less than 10 mm, the protrusion length Ll of the air shielding plates 101 is too small, and therefore the air shielding effect of the air shield plate 101 cannot be sufficient.
The width of the drying air fed out through the outlet 71a is so wide as the casting film 69. Therefore, the duct main body 71 is preferably designed such that the width Wl (m) of the duct main body 71 may be the same as the width W2 (m) of the casting film 69. Note that the values of Wl, W2 are not restricted especially and may be selected adequately, so far as the drying air can be applied to all area in width of the casting film 69.
The drying air from the outlet 71a starts being applied to the casting film 69 when the content of the remaining solvent in the casting film 69 is at least 300 wt.%. While the content of the remaining solvent in the casting film 69 is too large, the drying hardly proceeds. In this situation, when the drying air is applied in the manner of the present invention, the generation of the unevenness is prevented. If the content of the remaining solvent in the casting film 69 is less than 300 wt.%, the drying has proceeded in part of the casting film 69. Therefore, the unevenness sometimes occurs. In this situation, if the drying is made, the unevenness remains on the produced
film. Note that the content of the remaining solvent is that on dry basis and. measured with use of the samples of the casting film 69 and the produced film 82 which is completely dried. If the sample weight of the casting film 69 was x and the sample weight after the drying was y, the solvent content on the dry basis (%) was calculated in the formula, { (x-y)/y}xlOO. Note that in the content of the remaining solvent on dry basis, the weight of the solid obtained by completely drying the dope corresponds to 100%. The material of the retainer fins 100 and the air shielding plate 101 are not restricted especially. For example, it may be plastic plate or a metal plate of stainless and the like. In this embodiment, the air duct 70 with the outlet 71a whose inside is partitioned by the rectifier fins 100 is used. However, the air duct having plural areas as outlets can be also applied to the present invention. For example, plural boxes each of which there is an outlet can be integrated to the air duct to be used in the present invention.
In this embodiment, one air duct 70 is used just in downstream from the casting die 43. However, the position and a number of the air duct are not restricted especially in area in which the content of remaining solvent in the casting film 69 is at least 300 wt.%. For example, the plural air duct may be arranged along the belt 46. In this case, the evaporation of the casting film 69 proceeds and the asperity is reduced in the drying the casting film 69. Further, the air duct 70 in this embodiment is called single plate type, since having one flat air shielding plate 101.
In followings, an embodiment of a method for producing a film 82 in the film production line 40 will be explained. Note that the present invention is not restricted in it. •
The dope 27 is always made uniform by rotating the stirrer
61. Also in the stirring, the additive (for example, plastiσizer and the UV-absorbing agent and the like) can be mixed. The pump 62 is driven to feed the dope 27 to the filtration device 42, and then filtration is made. Thereafter the dope 27 is cast from the casting die 43 onto the belt 46 to form the casting film 69. The drive of the back-up rollers 44, 45 is controlled such that the tension generating in the belt 46 may be in the range of 10 4 N/m to 10 5 N/m. Further, the relative speed between the belt and the back-up rollers 44, 45 adjusted to at most 0.01 m/min.
The control was made such that the variation of the speed of the belt 46 was at most 0.5% to the predetermined value. The position of the belt in the widthwise direction was controlled with detection of the position of the side end, such that meandering in one circle of the moving belt 46 was reduced in 1.5 mm. Further, below the casting die 43, the variation of the position in the vertical direction between the lip end of the casting die and the belt 46 was in 200 μm. The belt 46 is preferably incorporated in the casting chamber 64 which has air pressure controller (not shown) . Further, the temperature in the casting chamber 64 is controlled in the range of -10 0 C to 57 °C . Note that the solvent vapor is recovered by the recoverying device 67, and used as a solvent for preparing the dope after the refinement. The dope 27 is cast from the casting die 43 onto the belt 46, so as to form the casting film 69. At the casting, the temperature of the dope 27 is preferably controlled in the range of -10 0 C to 57 0 C . Further, in order to stabilize the formation of a bead of the cast dopes, the decompression chamber 68 controlls the pressure in the back side of the bead. It is preferable to provide.the decompression chamber 68 with a jacket (not shown) for controlling the inner temperature. The
temperature of the decompression chamber 68 is not restricted especially. However, the temperature is preferably at least the boiling point of the used organic solvent. Further, aspirators (not shown) may be provided with the decompression chamber 68 so as to be near both side edges of a dope outlet of the casting die 43. Thus the aspiration in both side edges of the bead is made to stabilize the shape of the bead. In this case, the force velocity of the aspiration is preferably in the range of one to one hundred Litter/min. the drying air is applied from the air duct to the casting film 69 conveyed in accordance with running the belt 46, such that the evaporation of the solvent may proceed.
When the cast dope has self-supporting property, the casting film 69 is continuously peeled as the film 82 with support of the peeling roller 75. The solvent content at the peeling is preferably in the range of 20 mass% to 250 mass% to the solid content. Then the film 82 is transported in the interval section 80 in which many rollers are provided, and thus transported into the tenter device 47. In the interval section 80, while the film 82 is transported with the support of the pass rollers, a drying air is fed from the air blower to dry the film 82, such that the drying may proceed. Preferably, the temperature of the drying air is in the range of 20 0 C to 250 0 C . Note in the interval section 80 that the rotating speed of the pass roller may be set to be higher in the downstream side, so as to draw the film 82.
During the transportation in the tenter device 47, the film 82 is held by clipping both side edge portions, and at the same time the drying is made to evaporate the solvent. The tenter device 47 is preferably partitioned into several temperature areas of different temperatures, such that the drying is made
under different drying conditions of the respective temperature areas. At the same time, the stretching of the film 82 in the widthwise direction may be made. In this case, in the interval section or/and the tenter device 47, the stretching in the widthwise direction and the drawing in the lengthwise direction are made such that the width and the length may be in the range of 0.5% to 300% larger than the original size.
The film 82 is dried until the content of the remaining solvent become the predetermined value, and fed out from the tenter device 47 toward an edge slitting device 50 for slitting off both side edge portions. The slit side edge portions are sent to a crusher 90 by a cutter blower (not shown) , and crushed to tips by the crusher 90. The tips are reused for preparing the dope, which is effective in view of the decrease of the production cost. Note that the slitting process of both side edge portions may be omitted. However, it is preferable to perform the slitting between the casting process and the winding process.
The film 82 whose side edge portions are slit off is sent to a drying device 51 and dried furthermore . In the drying device 51, the film 82 is transported with lapping on the rollers 91. The inner temperature of the drying device 51 is not restricted especially. However, it is preferable in the range of 5O 0 C to 16O 0 C . The solvent vapor evaporated from the film 82 by the drying device 51 is adsorbed by the adsorbing device 92. The air from which the solvent components are removed is reused for the drying air in the drying device 51. Note that the drying device 51 preferably has plural partitions for variation of the drying temperature. Further, a pre-drying device (not shown) is provided between the edge slitting device 50 and the drying device 51, so as to perform the pre-drying of the film 82. Thus it is prevented that the temperature of the film 82 increases
rapidly, and therefore the change of the shape of the film 82 is reduced.
The film 82 is transported into a cooling chamber 52, and cooled therein to around the room temperature. A humidity control chamber (not shown) may be provided for conditioning the humidity between the drying device 51 and the cooling chamber 52. Preferably, in the humidity control chamber, an air whose temperature and humidity are controlled is applied to the film 82. Thus the curling of the film 82 and the winding defect in the winding process can be reduced.
Thereafter, a compulsory neutralization device (or a neutralization bar) 93 eliminates the charged electrostatic potential of the film 82 to the predetermined value (for example, in the range of -3kV to +3kV) . The position of the neutralization process is not restricted in this embodiment. For example, the position may be a predetermined position in the drying section or in the downstream side from the knurling roller 94, and otherwise, the neutralization may be made at plural positions. After the neutralization, the embossing of both side portions of the film 82 is made by the embossing rollers to provide the knurling. The emboss height from the bottom to the top of the embossment is in the range of 1 μm to 200 μm.
In the last process, the film 82 is wound by the winding shaft 95 in the winding chamber 56. At this moment, a tension is applied at the predetermined value to a press roller 96. Preferably, the tension is gradually changed from the start to the end of the winding. In the present invention, the length of the film 82 is preferably at least 100m. The width of the film is preferably at least 600 mm, and particularly in the range of 1400 mm to 1800mm. Further, even if the width is more than 1800 mm, the present invention is effective. When it is designated to produce the film which is 15 μm to 100 μm in
thickness, the present invention is also applied.
In this embodiment, a number of the air shielding plate 101 is one. However, a number is not restricted especially, when the conditions of C1-C3 described above are satisfied. Further, the shape of the air shielding plate has variations. In FIG.5, for example, each air shielding plate 112 has an L-shaped form. The L-shaped air shielding plate 112 may be formed by integrating two plates, or may be one plate. If the two air shielding plates 112 are attached to the respective side members 71b of the air duct 70, protrusions 112a of the air shielding plates 112 positioned in parallel to the belt 46, so as to increase the pressure loss of the air blow. Therefore, the entrained air occurring in accordance with feeding the drying air from the outlet 71a is reduced. Note that the air duct 70 in this embodiment is called L-shaped plate type, since having the L-shaped air shielding plate 112. Further, in this figure that the same numbers are applied to the same members as FIG.4, and the explanations thereof are omitted in followings .
The length L2 (mm) of each protrusion 112a protruding in parallel to the belt 46 is preferably in the range of 2 mm to 20 mm, particularly in the range of 5 mm to 19 mm, and especially in the range of 10 mm to 18 mm. However, if the length L2 is larger than 20 mm, the pressure loss becomes too large, which causes the turbulence of flow of the drying air from the outlet 71a. If the length L2 is smaller than 2. mm, the length L2 of the protrusion 112a is too short to increase the pressure loss. Therefore, the entrained air cannot be reduced. Note that there is a shifting device for shifting the air shielding plates up- and downwardly on the both side members 71b. As shown in FIG.6, even when rectifier plates 122 are provided on the lower surface of the lower member 71c forming the outlet 71a, the rectifying effect is enough. Note that the
air duct 70 in this embodiment is called bottom disposition type because of the position of the rectifier plates 122. Further, the illustration of the grooves 7Oe and the rectifier fins 100 in the outlet 71a is omitted. In the air duct 70, the air shielding plate 101 of single plate type is attached to each side member 71b, and the rectifier plates 122 are attached as second rectifier members to the lower member 71c. Thus the rectification of the air blow flowing between the lower member 71c and the belt 46 can be made. The rectifier plates 122 may be obtained from the rectifier fins 100.
The shape and the materials of the rectifier plates 122 are not restricted especially. However, the height Hl (mm) of the rectifier plates 122 is preferably in the range of 10 mm to 20 mm, particularly 11 mm to 19 mm, and especially 12 mm to 18mm. If the height Hl is too large, especially larger than 20 mm, the rectifier plates inhibit the flow of the air near the surface of the casting film 69. If the height Hl is less than 10 mm, the height Hl of the rectifier plates 122 is too small, and therefore the rectifying effect is too small.
There is a shifting device (not shown) for shifting the rectifier plates 122 for- and backwards to adjust the positions of the rectifier plates 122. In this case, the length L3 (mm) from the outlet 71a to the front end of each rectifier plate 122 is preferably in the range of 10 mm to 100 mm, preferably 15 mm to 95 mm, and especially 20 mm to 90 mm. Thus the rectifying effect of the rectifier plates 122 becomes excellent. Note that the length from the outlet 71a to the back end of the rectifier plate 122 is not restricted, when the above conditions of the length L3 are satisfied.
On the lower member 71c of the air duct 70, the rectifier plates 122 are disposed with interval C4 which is preferably
in the range of 50 mm to 400 mm, particularly 55 mm to 395 mm, and especially 60 mm to 390 mm. Thus the rectifying effect near the lower member 71c can be made larger. If the interval C4 is larger than 400 mm, a number of the rectifier plates 122 provided with the lower member 71c is too small, and therefore the rectifying effect is not enough. If the interval C4 is smaller than 50 mm, the rectifying effect is the same as when the interval C4 is 50 mm. Further, in this case, a number of the rectifier plates 122 is larger, which increases the cost. A number of the rectifier plates 122 is not restricted especially, and decided depending on the length of the outlet 71a or the lower member
71c, when the above conditions of the interval C4 are satisfied.
In the solution casting method of the present invention, there are casting methods for casting plural dopes , for example , a co-casting method and a sequential casting method. In the co-casting method, a feed block may be attached to the casting die as in this embodiment, or a multi-manifold type casting die (not shown) may be used. In the production of the film having multi-layer structure, the plural dopes are cast onto a support to form a casting film having a first layer (uppermost layer) and a second layer (lowermost layer) . Then in the produced film, at least one of the thickness of the first layer and that of the lowermost layer opposite thereto is preferably in the range of 0.5% to 30% of the total film thickness. Furthermore, when it is designated to perform the co-casting, a dope of higher viscosity is sandwiched by lower-viscosity dopes. Concretely, it is preferable that the dopes for forming the surface layers have lower viscosity than the dope for forming a layer sandwiched by the surface layers. Further, when the co-casting is designated, it is preferable in the bead between a die slit (or die lip) and the. support that the composition of alcohol is higher in the two outer dopes than the inner dope.
Japanese Patent Laid-Open Publication No. 2005-104148 describes from [0617] to [0889] in detail about the structures of the casting die, the decompression chamber, the support and the like, and further about the co-casting, the peeling, the stretching, the drying conditions in each process, the handling method, the curling, the winding method after the correction of planarity, the solvent recovering method, the film recovering method. The descriptions thereof can be applied to the present invention.
[Properties & Measuring Method]
(Degree of Curl & Thickness)
Japanese Patent Laid-Open Publication No. 2005-104148 describes from [0112] to [0139] about the properties of the wound cellulose acylate film and the measuring method thereof .
The properties and the measuring methods can be applied to the present invention.
[Surface Treatment] The cellulose acylate film is preferably used in several ways after the surface treatment of at least one surface. The preferable surface treatments are vacuum glow discharge, plasma discharge under the atmospheric pressure, UV-light irradiation, corona discharge , flame treatment , acid treatment and alkali treatment. Further it is preferable to make one of these sorts of the surface treatments.
[Functional Layer]
(Antistatic, Curing, Antireflection. Easily Adhesive & Antiglare Layers)
The cellulose . acylate film may be provided with an undercoating layer on at least one of the surfaces, and used
in the several ways.
It is preferable to use the cellulose acylate film as a base film to which at least one of functional layers may be provided. The preferable functional layers are an antistatic layer, a cured resin layer, an antireflection layer, an easily adhesive layer, an antiglare layer and an optical compensation layer.
Conditions and Methods for forming the functional layer are described in detail from [0890] to [1087] of Japanese Patent Laid-Open Publication No. 2005-104148, which can be applied to the present invention . Thus , the produced film can have several functions and properties .
These functional layers preferably contain at least one sort of surfactants in the range of 0.1 mg/m 2 to 1000 mg/m 2 . Further, the functional layers preferably contain at least one sort of plasticizers in the range of 0.1 mg/m 2 to 1000 mg/m 2 .
The functional layers preferably contain at least one sort of matting agents in the range of 0.1 mg/m 2 to 1000 mg/m 2 . The functional layers preferably contain at least one sort of antistatic agents in the range of 1 mg/m 2 to 1000 mg/m 2 .
(Variety of Use)
The produced cellulose acylate film can be effectively used as a protection film for a polarizing filter. In the polarizing filter, the cellulose acylate film is adhered to a polarizer. Usually, two polarizing filters are adhered to a liquid crystal layer such that the liquid crystal display may be produced. Note that the arrangement of the liquid crystal layer and the polarizing filters are not restricted in it, and several arrangements already known are possible. Japanese Patent Laid-Open Publication No. 2005-104148 discloses the liquid crystal displays of TN type, STN type, VA type, OCB type.
reflective type, and other types in detail. The description may be applied to the present invention. Further, in this publication No.2004-264464 describes a cellulose acylate film provided with an optical anisotropic layer and that having antireflection and antiglare functions. Further, the produced film can be used as an optical compensation film since being double axial cellulose acylate film provided with adequate optical properties. Further, the optical compensation film can be used as a protective film for a polarizing filter. The detail description thereof is made from [1088] to [1265] in the publication No. 2005-104148.
In the method of forming the polymer film of the present invention, the formed cellulose acylate film is excellent in optical properties . The TAC film can be used as the protective film for the polarizing filter, a base film of the photosensitive material, and the like. Further, in order to improve the view angular dependence of the liquid crystal display (used for the television and the like) , the produced film can be also used for the optical compensation film. Especially, the produced film is effectively used when it doubles as protective film for the polarizing filter. Therefore, the film is not only used in the TN-mode as prior mode, but also IPS-mode, OCB-mode, VA-mode and the like. Further, the polarizing filter may be constructed so as to have the protective film as construction element .
In followings, Experiment of the present invention will be explained. However, the present invention is not restricted in it . The explanation will be made in detail according to Example 1. The experimental conditions and results of Examples 2-3 and Comparisons 1-3 will be shown in Table 1.
In followings ,. the explanation of Examples the present invention will be made. The composition of the dope (or polymer
solution) used for the film production will be shown.
tExample 1 ] (Composition) Cellulose Triacetate 100 pts.mass
(Powder: degree of substitution, 2.84; viscosity-average degree of polymerization, 306; water content, 0.2 mass%; viscosity of 6 mass% dichloromethane solution , 315 mPa-s ; averaged particle diameter, 1.5 mm; standard deviation of particle, 0.5 mm)
Dichloromethane (first solvent compound) 320 pts.mass Methanol (second solvent compound) 83 pts.mass
1-butanol (third solvent compound) 3 pts.mass
Plasticizer A ( triphenylphosphate) 7.6 pts.mass Plasticizer B (diphenylphosphate) 3.8 pts.mass
UV-agent A 0.7 pts.mass
(2(2' -hydroxy-3 ' , 5 ' -di-tert-butylphenyl) -5- benzotriazol)
UV-agent B 0.3 pts.mass (2(2' -hydroxy-3' ,5' -di-tert-amylphenyl) -5- chlorobenzotriazol)
Mixture of citric acid esters 0.006 pts.mass
(Mixture of citric acid, citric acid monoethyl ester, citric acid dimethyl ester, citric acid triethyl ester) Particles 0.05 pts.mass
(particle diameter, 15nm; Mohs Hardness, about 7)
[Cellulosetriacetate ]
According to cellulose triacetate used in this experiment , the remaining content of acetic acid was at most 0.1 mass%, the Ca content was 58 ppm, the Mg content was 42 ppm, the Fe content was 0.5 ppm, the free acetic acid was 40 ppm, and the sulfuric
ion content was 15 ppm. The degree of acetylation at 6 th position was 0.91, and the percentage of acetyl groups at 6 th position to the total acetyl groups was 32.5 %. The acetone extract was 8 mass%, and a ratio of weight-average molecular weight to number-average molecular weight was 2.5. Further, yellow index was 1.7, haze was 0.08, and transparency was 93.5%. Tg (measured by DSC) was 160 °C , and calorific value in crystallization was 6.4J/g. This cellulose triacetate is synthesized from cellulose as material obtained from cotton, and called cotton TAC in the following explanation.
The polymer solution was prepared with use of the dissolution tank having first and second stirrers that was made of stainless and 4000L in volume. Into the dissolution tank, plural solvent compounds were mixed such that a mixture solvent was obtained. Note that the water content in each solvent compound is at most 0.5 mass%. The stirring was made with use of the first stirrer having the anchor blade and the second stirrer which was eccentric stirrer of dissolver type . At first , the first stirrer performed the stirring at one m/sec as circumferential velocity, and the second stirrer performed the stirring at shear rate at first 5 m/sec. Thus the dispersion was made for 30 minutes during the stirring. The dissolving started at 25 0 C , and the temperature of the dispersion became 48 0 C at last. While the stirring of the mixture solvent was made, the cellulose triacetate flakes were added from the hopper 14 to the mixture solvent gradually, such that the total mass of the mixture solution and the cellulose triacetate flakes might be 2000kg. After the dispersion, the high speed stirring (of the second stirrer) was stopped, and the stirring was performed by the first stirrer at 0.5 m/sec as circumferential velocity for 100 minutes. Thus cellulose triacetate flakes was swollen such that the swelling liquid was obtained. Until the
end of the swelling, the inner pressure of the dissolution tank was increased to 0.12 MPa with use of nitrogen gas . At this moment , the hydrogen concentration in the dissolution tank was less than 2 vol.%, which does not cause the explosion. Further, water content in the polymer solution was 0.3 mass%.
The swelling liquid was fed to the heating device which is the tube with the jacket, and heated to 5O 0 C , and thereafter heated under the application of pressure at 2MPa to 90 0 C . Thus the dissolving was made completely. The heating time was 15 minutes . The temperature of the swelling liquid is decreased to 36 0 C by the temperature controlling device, and then filtrated through the filtration device having filtration material whose nominal diameter was 8 μm. At this moment, the upstream side filtration pressure was 1.5 MPa, and the downstream side filtration pressure was 1.2 MPa. Since the filter, the housing and the pipes were made of hastelloy alloy and used at high temperature, they were made from materials excellent in corrosion resistance.
The polymer solution was fed into the flushing device whose pressure was kept to the atmospheric pressure at 80 9 C , such that the flush evaporation of the polymer solution was made. The solvent vapor was condensed by the condenser to the liquid state, and recovered by the recovering device. After the flushing, the content of solid compounds in the polymer solution was 21.8 mass%. Note that the recovered solvent was recycled by the recycling device and reused. The anchor blade is provided at a center shaft of a flush tank of the flushing device, and the polymer solution was stirred by the anchor blade at 0.5 m/sec as circumferential velocity. The temperature of the polymer solution in the flush tank was 25 0 C , the retaining period of the polymer solution.in the flush tank was 50 minutes. Part of the polymer solution was sampled, and the measurement of the
shearing viscosity was made at 25°C . The shearing viscosity- was 450Pα-s at 10 (1/s) of sheafing rate.
Then the defoaming was further made by irradiating very weak ultrasonic waves . Thereafter, the polymer solution was fed to the filtration device by the pump under the application of pressure at 1.5 MPa. In the filtration device, the polymer solution was fed at first through a sintered fiber metal filter whose nominal diameter was 10 μm, and then through the same filter of 10 μm nominal diameter. At the forward and latter filters, the primary pressures were respectively 1.5 MPa and 1.2 MPa, and the secondary pressures were respectively 1.0 MPa and 0.8 MPa. The temperature of the polymer solution after the filtration was controlled to 36 0 C , and stored as the dope 27 in the stainless stock tank 41 whose volume was 2000L. The anchor blade is provided to a center shaft of the stock tank 41, and the dope 27 was always stirred by the anchor blade at 0.3 m/sec as circumferential velocity. Note that when the concentrating of the polymer solution is made, corrosions of parts or portions contacting to the polymer solution in the devices didn't occur at all. Further, the mixture solvent for preparing the additive liquid contained dichloromethane of 86.5 pts.wt., acetone 13 pts.wt., and n-butanol 0.5 pts.wt.
The film is formed in the film production line 40 shown in FIG.l. The pump 62 for increasing the primary pressures was high accuracy gear pumps and driven to feed the dope 27 while the feed back control was made by an inverter motor. Thus the primary pressure of high accuracy gear pump was controlled to 0.8 MPa. As for the pump 62, volumetric efficiency was 99.2%, and the variation rate of the discharging was at most 0.5%. Further, the discharging pressure was 1.5MPa.
The width of the casting die 43 was 1.8 m, The flow rate of the dope 27 near a die lip of the casting die 43 is controlled
such that the dried film may be 80 μm in thickness. The casting width of the dope 27 from the die lip was 1700 mm. The casting speed was 20 m/min. Further, in order to control the temperature of the dope 27 to 36 °C , the temperature of the heat transfer medium at an entrance of the jacket was 36°C .
The casting die 43 was the coat hunger type, in which heat bolts for adjusting the film thickness were disposed at the pitch of 20 mm. Thus the film thickness (or the thickness of the dopes) is automatically controlled by the heat bolt. A profile of the heat volt can be set corresponding to the flow rate of the high accuracy gear pump, on the basis of the preset program. Thus the feed back control can be made by the control program on the basis of the profile of an infrared ray thickness meter (not shown) disposed in the film production line 40. The control was made such that, with exception of both side edge portions (20 mm each in the widthwise direction of the produced film) , the difference of the film thickness between two positions which were 50 mm far from each other might be at most 1 μm, and the largest difference between the minimal values of the film thickness in the widthwise direction might be at most 3 μm/m. Further, the average film thickness might was controlled in ±1.5%.
The primary side of the casting die 43 is provided with the decompression chamber 68. The decompression rate of the decompression chamber 68 was controlled in accordance with the casting speed, such that the pressure difference might occur in the range of one Pa to 5000Pa between the upstream and downstream sides of the bead of the cast dope above the casting die. At this time, the pressure difference between both side of a bead of the cast dope was determined such that the length of the bead might be from 20 mm to 50 mm. Further, an instrument was provided such that the temperature of the decompression
chamber 68 might be set to be higher than the condensation temperature of the gas around the casting section. Further, there were labyrinth packings (not shown) in the upstream and downstream sides of the beads. Further, an opening was provided in both edges. Further, an edge suctioning device (not shown) for reducing the disturbance of the bead was provided.
The material of the casting die 43 was the precipitation hardening stainless steel, whose coefficient of thermal expansion was at most 2 x 10 "5 ( °C ~x ) . In the compulsory corrosion experiment in an electrolyte solution, the corrosion resistance was almost the same as that of SUS316. Further, the material to be used for the casting die 43 had enough corrosion resistance, such that the pitting (or pitting corrosion) might not occur on the gas-liquid interface even if this material were dipped in a mixture liquid of dichloromethane, methanol and water for three months . The finish accuracy of the contact surface of each casting die to the dope 27 was at most 1 μm in surface roughness, and the slit clearance was adjusted to 1.5 mm in straightness . According to an edge of the contact portion of a lip end of the casting die 43, R is at most 50 μm in all of a width. Further, the shearing rate in the casting die 43 controlled in the range of one to 5000 per second. Further, the WC coating was made on the lip end from the casting die 43 by a melt extrusion method, so as to provide the hardened layer. In order to prevent the dry and solidification on part of the slit end of the casting die 43, the mixture solvent A dissolvable of the solidified dope was supplied to each edge portion of the gas-liquid interface of the slit at 0.5 ml/min. Thus the mixture solvent is supplied to each bead edge. The pulse rate of a pump for supplying the mixture solvent was at most 5%. Note that the mixturesolvent A is obtained by mixing dichloromethane (86.5 pts.mass), acetone (13 pst.mass) and
1-butanol (0.5 pts .mass) . Further, the decompression chamber 68 was provided for decreasing the pressure in the rear side by 150 Pa. In order to control the temperature of the decompression chamber 68, a jacket (not shown) was provided, and a heat transfer medium whose temperature was controlled at 35 0 C was supplied into the jacket. The edge suction rate could be controlled in the range of 1 L/min to 100 L/min, and was adequately controlled in this experiment so as to be in the range of 30 L/min to 40 L/min. The belt 46 was an endless stainless belt which was 2.1m in width and 70m in length. The thickness of the belt 46 was 1.5 mm, and the surface of the belt 46 was polished, such that the surface roughness might be at most 0.05 μm. The material was SUS316, which had enough corrosion resistance and strength. The thickness unevenness of the entire belt 46 was at most 0.5% of the predetermined value. The belt 46 was moved by rotating the back-up rollers 44, 45. At this moment, the tension of the belt 46 was controlled to 1.5xlO 5 N/m 2 . Further, the relative speed to each roller to the belt 46 changed. However, in this experiment , the control was made such that the difference of the relative speed between the back-up rollers 44, 45 was at most 0.01 m/min. Further the control was made such that the variation of the speed of the belt 46 was at most 0.5% to the predetermined value. The position of the belt in the widthwise direction was controlled with detection of the position of the side end, such that meandering in one circle of the moving belt 46 was reduced in 1.5 mm. Further, below the casting die 43, the variation of the position in the vertical direction between the lip end of the casting die 43 and the belt 46 was in 200 μm.
In this experiment, the back-up rollers 44, 45 were supplied therein with a heat transfer medium, such that the
temperature of the belt 46 might be controlled. The back-up roller 45 disposed in a side of the casting die 43 was supplied with the heat transfer medium (water) at 5°C , and the back-up roller 44 was supplied with the heat transfer medium (water) at 40 0 C . The surface temperature of the middle portion of the belt 46 at a position just before the casting was 15 0 C , and the temperature difference between both sides of the belt was at most 6 0 C . Note that a number of pinhole (diameter, at least 30 μm) was zero, a number of pinhole (diameter, 10 μm to 30 μm) was at most one in square meter, and a number of pinhole (diameter, less than 10 μm) was at most two in square meter. Further, the temperature of the casting chamber 64 was kept to 35 0 C . At first, the drying air was fed out in parallel to the casting film 69 so as to make the drying. The overall heat transfer coefficient from the drying air to the casting film 69 was 24 kcal/(m 2 -Ar-°C ) .
The air duct 70 is provided as an air feeding device in downstream and near the casting position of the dope 27 above the belt 46 (see, FIG.3) . According to the air duct 70, as shown in FIG.4, the rectifier fins 100 made of stainless are provide in the outlet 71a with the distance Cl at 50 mm. Further, the air shielding plates 101 are attached to the both side members 71b, such that the distance C2 may be 5 mm. further, the drying air at 135 °C is fed out from the outlet 71a to dry the casting film 69. Note that the oxygen concentration in the drying atmosphere on the belt 46 was kept to 5 vol% by substituting the air for nitrogen gas. The solvent vapor in the casting chamber 64 was recovered by setting the temperature of exit of the condenser 66 to -1O 0 C . When the solvent content in the casting film 69 became 50 mass% on dry basis, the casting film 69 was peeled as the film 82 from the belt 46 by the peeling roller 75. Further, the
peeling tension was IxIO 2 N/m 2 . In order to reduce the peeling defects, the percentage of the peeling speed (the draw of the peeling roller) to the speed of the belt 46 was controlled from 100.1% to 110%. The surface temperature of the film 82 was 15 0 C . The solvent vapor generated in the evaporation is condensed by the condenser 66 at -10 0 C to a liquid state, and recovered by the recovering device 67. The water content of the recovered solvent was adjusted to at most 0.5%. Further, the air from which the solvent components were removed was heated again and reused for the drying air. The film 82 was transported with the rollers in the interval section 80 toward the tenter device 47. Note that the tension about 3ON was applied to the film 82 in the lengthwise direction of the rollers in the interval section 80.
In the tenter device 47, while both side edge portions of the film 82 are held by clips, the stretch of the film 82 in the widthwise direction was made with the transportation. The transportation is made with chain, and clips for the clipping was cooled to 20 0 C with use of a heat transfer medium. The drying device 51 was partitioned into three zones. The temperature of the drying air in each zone was 9O 0 C , 110 0 C , 120 0 C from the upstream side. The gas concentration in the drying air at -10 0 C was the saturated gas concentration. The condition of each zone was controlled such that the content of the remaining solvent in the film 82 might be 7 mass% at the exit of the tenter device 47. If the percentage of the film width before the tenter device 47 was determined to 100%, the stretching ratio of the film width after the tenter device 47 was 103%. Further, the film 82 was drawn in the lengthwise direction between the peel roller 86 and the tenter device 47. The drawing ratio in percentage was 102%.
According to the stretching ratio in the tenter device 47, the difference of the actual stretching ratio was at most
10% between positions which were at least 10 mm apart from the holding positions of the clips, and at most 5% between positions which were 20 mm apart from the holding portions. In the side edge portions in the tenter device 47, the ratio of the length in which the fixation was made was 90%. The solvent vapor generated in the tenter device 47 was condensed at -10 0 C to a liquid state and recovered. For the condensation, a condenser (not shown) was provided, and a temperature at an exit thereof was -8 °C . The water content in the recovered solvent was regulated to at most 0.5 mass%, and then the recovered solvent was reused. The film 82 was fed out as the film 82 from the tenter device 47.
In 30 seconds from exit of the tenter device 47, both side edge portions were slit off in the edge slitting device 50. In this experiment, each side portion of 50 mm in the widthwise direction of the film 82 was determined as the side edge portion, which were slit off by an NT type slitter of the edge slitting device 50. The slit side edge portions were sent to the crusher 90 by applying air blow from a blower (not shown) , and crushed to tips about 80 mm 2 . The tips were reused as raw material with the TAC frame for the dope production. The oxygen concentration in the drying atmosphere in the tenter device 47 was kept to 5 vol.%. Note that the air was substituted by nitrogen gas in order to keep the oxygen concentration at 5 vol.%. Before the drying at the high temperature in the drying device 51, the pre-heating of the film 82 was made in a pre-heating chamber (not shown in which the air blow at 100 0 C was supplied.
The film 82 was dried at high temperature in the drying device 51 , which was partitioned into four partitions . Air blows whose temperatures were 120 0 C, 130 0 C, 130 0 C and 130 0 C from the upstream side were fed from air blowers (not shown) to the partitions. The transporting tension of each roller 91 to the
film 82 was 100 N/m. The drying was made for ten minutes such that the content of the remaining solvent might be 0.3 mass%. The lapping angle of the roller 4 was 90° and 180° . The rollers 91 were made of aluminum or carbon steel. On the surface, the hard chrome coating was made. The surfaces of the rollers 91 were flat or processed by blast of matting process. The swing of the roller in the rotation was in 50 μm. Further, the bending of the roller 91 at the tension of 100N/m was reduced to at most 0.5 mm. The solvent vapor contained in the drying air is removed with use of the adsorbing device 92 in which an adsorbing agent was used. The adsorbing agent was active carbon, and the desorption was performed with use of dried nitrogen. The recovered solvent was reuse as the solvent for the dope preparation after the water content might be at most 0.3 mass%. The drying air contains not only the solvent vapor but also gasses of the plasticizer, UV-absorbing agent, and materials of high boiling points. Therefore, a cooler for removing by cooling and a preadsorber were used to remove them. Thus the drying air was reused. The ad- and desorption condition was set such that a content of VOC (volatile organic compound) in exhaust gas might be at most 10 ppm. Furthermore, in the entire solvent vapor, the solvent content to be recovered by condensation method was 90 mass%, and almost of the remaining solvent vapor was recovered by the adsorption recovering.
The film 82 was transported to a first moisture controlling chamber (not shown) . In the interval section between the drying device 51 and the first moisture controlling chamber, the drying air at 110 °C was fed. In the first moisture controlling chamber, the air whose temperature was 50 0 C and dewing point was 2O 0 C was fed. Further, the film 82 was fed into a second moisture chamber (not shown) in which the curling
of the film 82 was reduced. An air whose temperature was 90 0 C and humidity was 70% was applied to the film 82 in the second moisture controlling chamber.
After the moisture adjustment, the film 82 was cooled to 30 0 C in the cooling chamber 107, and then the edge slitting was performed. The compulsory neutralization device (or a neutralization bar) 93 was provided, such that in the transportation, the charged electrostatic potential of the film might be in the range of -3kV to +3kV. Further, the film knurling was made on a surface of each side of the film 82 by the knurling roller 94. The width of the knurling was 10 mm, and the knurling pressure was set such that the maximal thickness might be at most 12 μm larger in average than the averaged thickness.
The film 82 was transported to a winding chamber 110 , whose inside temperature and humidity were respectively kept to 28 0 C and 70%. Further, a compulsory neutralization device (not shown) was provided, such that the charged electrostatic potential of the film might be in the range of -1.5 kV to +1.5 kV. The obtained film 82 was 1475 mm in width. The diameter of the winding shaft 95 was 169 mm. The tension pattern was set such that the winding tension was 300 N/m at first, and 200 N/m at last. The film 82 was entirely 3940m in length. The winding cycle was 400m, and the oscillation width was in ± 5 mm. Further, the pressure of the press roller 96 to the winding shaft 95 was set to 50 N/m. The temperature of the film at the winding was 25 0 C , the water content was 1.4 mass%, and the content of the remaining solvent was 0.3 mass% . The film production was continuously made for 8760 hours. Through all processes, according to the drying speed, 20 mass% of the solvent in dry weight standard was evaporated per minute in average. Further, the loose winding and wrinkles didn ' t occur, and the film didn>' t transit in the film roll even in 1OG impact test. Further, the
roll appearance was good.
[Example 2]
The film 82 was produced from the same dope by the same production method as Example 1. However, in the air duct 70, the L-shaped air shielding plates 101 were attached to both side members 71b (see, FIG.5). Note that the sorts and the disposition conditions of the rectifier fins 100 and the distance C2 were the same as Example 1.
[Example 3]
The film 82 was produced from the same dope by the same production method as Example 1. However, in the air duct 70, the air shielding plates 101 of single plate type were attached to both side members 71b, and the rectifier plates 122 were attached to the lower member 71c (see, FIG.6). Note that the sorts and the disposition conditions of the rectifier fins 100 and the distance C2 were the same as Example 1.
[Example 4]
The film 82 was produced from the same dope 27 by the same production method as Example 1. However, the air shielding plates 101 were not provided for the air duct 70, but the rectifier fins 100 were disposed in the outlet 71a. Note that the sorts and the disposition conditions of the rectifier films were the same as Example 1.
[Example 5]
The film 82 was produced from the same dope 27 by the same production method as Example 1. the air duct was the single plate type, the same as example 1. But the distance Cl was 35mπκ
[Comparison 1]
The film was produced from the same dope 27 by the same production method as Example 1. However, in the air duct 70, neither rectifier fin 100 nor air shielding plates 101 was provided.
[Estimation of Film]
In the estimation of the film, the surface of the produced film was observed to know how much the unevenness occurs . The estimation was made with use of an electric micrometer (Anritsu Corporation), such that a thickness was measured at voluntary 10 positions of the film. A relative standard deviation, RSD, (unit; %) was calculated from an average of the measured value and deviation. The value RDS is calculated as follows: RDS = { (deviation) /(average)} x 100. In Table 1, the numbers of the result of the estimation of asperity represent as follows.
1. RDS was less than 5%, and the planarity was extremely excellent
2. RDS was at least 5% and less than 10%, and the planarity was excellent
3. RDS was at least 10% and less than 15%, and little asperity was recognized although the film has no problems for products at all
4. RDS was at least 15% and less than 2θ%, and the asperity was recognized although the film has no problems for products
5. RDS was more than 20%, and the asperity was generated clearly such that the film cannot be used as product.
The production conditions and the estimation results of the produced films in Examples 1-5 and Comparison 1 are shown in Table 1. . .
[Table 1]
R.Fin : rectifier fin
A. S.P : air shielding plate
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