JP4114136B2 - Film manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a film manufacturing method, and more particularly to a method for manufacturing a cellulose ester film.
[0002]
[Prior art]
Cellulose ester films, particularly cellulose acetate films, are widely used for electronic display applications, photographic support applications, and other optical applications. Such a cellulose ester film is generally produced by a solution casting method.
[0003]
The film production apparatus by the solution casting method mainly comprises a dope preparation step for preparing a concentrated solution of cellulose ester (hereinafter referred to as a dope), and the prepared dope is cast on an endless support such as a band or a drum. It comprises a casting / peeling process for peeling from a support, a drying process for drying the peeled film, and a winding process for winding the dried film.
[0004]
By the way, the cellulose ester film is required to perform each process in a clean environment in order to reduce defects such as foreign substances with the recent high performance and high functionality. For example, it has been proposed that the process average atmosphere of the process from casting to peeling is set to be 10 or more and 10,000 or less (see Patent Document 1).
[0005]
From such a background, the conventional film manufacturing apparatus is installed in a clean clean room, and the periphery is partitioned for each process, and the interior of the partitioned room is maintained in a cleaner state. . That is, the interior of the clean room is provided with a casting / peeling chamber for performing the casting / peeling process, a drying chamber for performing the drying process, and a winding chamber for performing the winding process, and each room is higher than the clean room. Clean air is supplied. Each chamber is connected along the film production line, and only a small portion through which the film passes is opened. The winding chamber is provided with a door that can be opened and closed. By opening the door, the winding core after winding the film can be taken out and a new winding core can be attached.
[0006]
By performing each process inside the clean chamber configured as described above, it is possible to manufacture a high-quality product free from dust adhesion.
[0007]
[Patent Document 1]
JP 2000-246747 A (page 8)
[0008]
[Problems to be solved by the invention]
However, in the conventional film manufacturing apparatus, when the conditions for supplying and exhausting clean air in each chamber are changed, a defect whose cause is unknown may occur in the film product. For this reason, even if it is desired to change the supply / exhaust conditions of each chamber, particularly the supply / exhaust conditions of the drying chamber, there is a drawback that it cannot be easily changed.
[0009]
Therefore, the inventor of the present invention conducted various tests on the supply and exhaust conditions in order to investigate the cause of the defect. As a result, it was possible to ascertain that the main cause was the internal pressure of the winding chamber that changed due to the supply and exhaust of clean air. Specifically, when the internal pressure of the winding chamber changes and becomes larger than the internal pressure of the drying chamber, the air in the winding chamber flows into the drying chamber from a small opening between the winding chamber and the drying chamber, It became clear that the temperature of the drying chamber decreased. As a result, the dry state of the film deteriorated, and dew condensation occurred inside the drying chamber, and the dew condensation adhered to the film and was the main cause of defects.
[0010]
If it judges based on such knowledge, it is preferable to make the internal pressure of a winding chamber small. However, when the internal pressure of the winding chamber is small, when the door of the winding chamber is opened and closed, dust enters the winding chamber from the outside and the dust adheres to the film. And the problem of a surface defect and the bright spot defect in a polarizing plate arises, and the quality of a film falls generate | occur | produces.
[0011]
The present invention has been made in view of such circumstances, and it is possible to prevent the occurrence of condensation in the drying process, as well as to prevent surface failure due to dust adhesion and bright spot defects on the polarizing plate. It aims at providing the film manufacturing method which can be performed.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 is a casting / peeling process in which a solution of a polymer material is cast on a support and peeled off as a film from the support, and the peeled film is dried. In the film manufacturing method for producing a cellulose ester film by continuously performing a drying step and a winding step for winding the dried film, the periphery of the winding step is separated from the other steps and wound. A take-up chamber is formed, a circulation line is connected to the upper and lower surfaces of the take-up chamber, and a fan provided in the circulation line is driven to circulate the air in the take-up chamber from the upper surface of the take-up chamber. with blown, and dedusted circulating air by a filter provided in the circulation line, by the rectifying means provided on an upper portion of the winding-up chamber to form a downflow in said winding-up chamber, pressure in the winding chamber It is characterized by controlling the pressure difference -5 to +15 less Pa relative to the pressure of the take-up chamber.
[0013]
As described above, the inventor of the present invention has obtained the knowledge that the main cause of defects in the film is the internal pressure of the winding chamber through tests. The present invention has been made based on such knowledge, and by newly defining the pressure difference between the internal pressure and the external pressure of the winding chamber, the occurrence of defects is prevented and the quality of the film is improved. It is.
[0014]
According to the first aspect of the present invention, the pressure inside the winding process is controlled to a pressure difference of −5 Pa or more with respect to the outdoor pressure. The amount of dust entering the inside from the inside is small. Therefore, it can prevent that dust adheres to a film and the quality of a film falls.
[0015]
According to the first aspect of the present invention, the pressure in the winding process chamber is controlled to a pressure difference of +15 Pa or less with respect to the outdoor pressure. The flow rate of air flowing into the process chamber is reduced. Therefore, it can prevent that the temperature of the chamber of a drying process falls, and can prevent that dew condensation occurs.
[0016]
According to the first aspect of the present invention, since air is supplied from the upper part of the chamber in the winding process and exhausted from the lower part, a downflow is formed inside the chamber. Therefore, it is possible to prevent dust from floating inside the chamber.
[0017]
The present invention, high performance of, and suitable for the production of cellulose ester film high functionality are required.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of a film manufacturing method according to the present invention will be described below with reference to the accompanying drawings.
[0019]
FIG. 1 is a diagram schematically showing the configuration of a film manufacturing apparatus 10 in which the present invention is employed.
[0020]
As shown in the figure, the film manufacturing apparatus 10 mainly comprises a casting / peeling process section 12, a tenter drying process section 14, a roll drying process section 16, and a winding process section 18.
[0021]
The casting / peeling process section 12 is provided with a pair of support rollers 20, 20, a casting band 22, and a casting die 24. The casting band 22 is formed endlessly with a stainless steel plate or the like, and is wound around the pair of support rollers 20 and 20. At least one of the pair of support rollers 20 is connected to a driving device (not shown). By rotating the support roller 20, the casting band 22 circulates between the pair of support rollers 20 and 20.
[0022]
The casting die 24 is provided above the casting band 22, and a cellulose ester dope is supplied to the casting die 24. The dope is prepared by, for example, dissolving cellulose ester in a solvent together with a plasticizer, a UV absorber, a slip agent, and other additives, and is cast from the casting die 24 onto the casting band 22 at a constant thickness. The cast dope is conveyed together with the casting band 22, and the organic solvent evaporates from the surface opposite to the casting band 22 during the conveyance. When the dope has a self-supporting property, it is peeled off from the casting band 22 as a film 26.
[0023]
The peeled film 26 is introduced into the tenter drying process unit 14 after contacting the peeling roll 28. In this tenter drying process section 14, the film 26 is transported and dried in a state where the end in the width direction is held by a clip, a pin, or the like and tension is applied. In addition to the peeling roll 28, a roll may be installed to stabilize the film 26 in the previous stage of the tenter drying process unit 14.
[0024]
The film 26 dried in the tenter drying process unit 14 is sent to the roll drying process unit 16. The temperature of the roll drying process unit 16 is controlled in the range of 50 to 150 ° C., and the film 26 sent to the roll drying process unit 16 is wound around a plurality of rolls 30, 30. The The dried film 26 is sent to the winding process unit 18 and wound up by the winder 32.
[0025]
In the above-described embodiment, the casting band 22 is used as a support for the dope, but a casting drum may be used. That is, the dope may be cast on the surface of the drum while rotating the drum whose surface is smoothed by chrome plating or the like.
[0026]
By the way, the film manufacturing apparatus 10 is installed in a clean clean room 34. The configuration of the clean room 34 is not particularly limited. For example, an FFU (fan filter unit) is installed on the ceiling surface, the floor surface is grating, and communicates with an underfloor space (not shown). Thereby, a downflow is formed by the clean air blown out from the FFU, and the inside of the clean room 34 is maintained in a clean state.
[0027]
Inside the clean room 34, the process units 12, 14, 16, and 18 described above are partitioned around each other, thereby forming chambers 42, 44, 46, and 48. Here, the chamber 42 in which the casting / peeling process unit 12 is installed is referred to as a casting / peeling chamber 42, and similarly, the tenter drying process unit 14, the roll drying process unit 16, and the winding process unit 18 are installed. The chambers are referred to as a tenter drying chamber 44, a roll drying chamber 46, and a winding chamber 48, respectively.
[0028]
The chambers 42 to 48 are connected along the production line of the film 26. That is, the casting / peeling chamber 42, the tenter drying chamber 44, the roll drying chamber 46, and the winding chamber 48 are arranged in this order. Adjacent chambers are communicated with each other by opening only a portion through which the film 26 passes. For example, the winding chamber 48 communicates with the adjacent roll drying chamber 46 through an opening. The opening is formed with a width slightly larger than the width of the film 26 and a size of several centimeters in the thickness direction of the film 26.
[0029]
The air supply side of the circulation line 36 is connected to the upper surface of the winding chamber 48, and the exhaust side of the circulation line 36 is connected to the lower surface. The circulation line 36 is provided with a filter member 38 and a fan 40, and the air in the winding chamber 48 circulates through the circulation line 36 by driving the fan 40. At that time, the circulating air is removed by passing through the filter member 38 and blown out from the upper surface into the winding chamber 48. Thereby, a downflow of clean air is formed inside the winding chamber 48, and dust is prevented from floating. The cleanliness inside the winding chamber 48 is maintained at a higher degree of cleanliness than the space outside the winding chamber 48 and inside the clean room 34 (hereinafter referred to as the outside of the winding chamber 48). Note that a rectifying means such as a punching plate is attached to the upper portion of the winding chamber 48 so that a uniform downflow is formed. The fan 40 is installed outside the clean room 34 so that dust generated in the fan 40 does not affect the cleanliness of the clean room 34.
[0030]
The internal pressure of the winding chamber 48 is adjusted by changing the rotational speed of the fan 40. At this time, the internal pressure of the winding chamber 48 is set to be a differential pressure of −5 to +15 Pa, preferably 0 to +5 Pa, with respect to the pressure outside the winding chamber 48.
[0031]
The winding chamber 48 is provided with a door (not shown) so that the core 50 after winding the film 26 can be replaced with a new core 50 by opening the door. It has become.
[0032]
In the chambers 42 to 46 other than the winding chamber 48, as with the winding chamber 48, clean air is downflowed. However, in the roll drying chamber 46, the air supply position and the exhaust position are arbitrarily set according to the selected drying method. The tenter drying chamber 44 and the roll drying chamber 46 are supplied with high-temperature air whose temperature has been adjusted, and the interiors of the chambers 44 and 46 are controlled within a predetermined temperature range. For example, the inside of the roll drying chamber 46 is controlled to 50 to 150 ° C. A filter member 38 and a fan 40 may be provided for each circulation line 36 of each chamber 42 to 48, or a common filter member 38 and fan 40 may be used. Further, the dust removing means and the air blowing means may be used also as the air conditioner of the clean room 34.
[0033]
Next, the operation of the film manufacturing apparatus 10 configured as described above will be described.
[0034]
While the film manufacturing apparatus 10 is installed in the clean clean room 34, each process part 12-18 is installed in the clean chambers 42-48. Accordingly, the film 26 is manufactured in an environment with very little dust.
[0035]
However, when the manufactured film 26 is conveyed, it is necessary to open the door of the winding chamber 48. Since the outside of the winding chamber 48 (the inside of the clean room 34) is a work area, the cleanliness is slightly lower than the inside of the winding chamber 48. For this reason, when the internal pressure of the winding chamber 48 is too small with respect to the external pressure, dust enters from the outside, the cleanliness of the winding chamber 48 is lowered, and the quality of the film 26 may be lowered. Therefore, when the internal pressure of the winding chamber 48 that does not deteriorate the quality of the film 26 is obtained by a test, it is -5 Pa (that is, a value lower by 5 Pa than the external pressure) or more, preferably 0 Pa (that is, the external pressure If it is equal to or greater than the same value, the quality of the film 26 was not affected.
[0036]
On the other hand, if the internal pressure of the winding chamber 48 is too high, there arises a problem that the flow rate of air flowing from the winding chamber 48 to the roll drying chamber 46 through the opening increases. Since the inside of the roll drying chamber 46 is maintained at a high temperature of 50 to 150 ° C., when the flow rate of the outflow air from the winding chamber 48 increases, the temperature of the winding chamber 48 rapidly decreases and condensation occurs. There is a risk. The internal pressure of the winding chamber 48 that does not cause dew condensation was obtained by a test, and it was +15 Pa (that is, a value higher by 15 Pa than the external pressure) or less, preferably +5 Pa or less with respect to the external pressure.
[0037]
In the film manufacturing apparatus 10 of the present embodiment, the internal pressure of the winding chamber 48 is controlled within a differential pressure range of −5 to +15 Pa with respect to the external pressure, so that dust enters from the outside of the winding chamber 48. Therefore, it is possible to prevent the quality of the film 26 from being deteriorated and to prevent the air from entering the roll drying chamber 46 from the winding chamber 48 and the temperature from being lowered. Furthermore, by controlling the internal pressure of the winding chamber 48 within a differential pressure range of −5 to +15 Pa with respect to the external pressure, it is possible to suppress the evaporation solvent existing inside the winding chamber 48 from diffusing to the surroundings. It is possible to improve the safety of workers working in the clean room 34.
[0038]
In addition, since the film manufacturing apparatus 10 of the present embodiment supplies air from the ceiling surface of the winding chamber 48 and exhausts air from the bottom surface, a clean air downflow is formed inside the winding chamber 48. Is done. Thereby, scattering of dust can be suppressed. Thereby, the high quality film 26 can be manufactured.
[0039]
By the way, when a polymer solution containing a volatile component having a boiling point higher than that of the solvent is used as the dope, when the flow rate flowing from the winding chamber 48 to the roll drying chamber 46 increases and the temperature of the roll drying chamber 46 decreases, the film 26 volatile components tend to harden. For this reason, for example, a plasticizer etc. become easy to harden, and the problem that the quality of a film product falls will generate | occur | produce. However, as in the present embodiment, this can be prevented by setting the internal pressure of the winding chamber 48 to 15 Pa or less, preferably 5 Pa or less with respect to the external pressure. Examples of plasticizers that can be used in cellulose acetate include phosphate esters such as triphenyl phosphate, biphenyl diphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, trioctyl phosphate, and tributyl phosphate, diethyl Phthalates such as phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, triacetin, tributyrin, butyl phthalyl butyl glycolate, ethyl phthalyl ethyl glycolate, methyl phthalyl ethyl Examples include glycolate esters such as glycolate. These plasticizers can be used alone or in combination as necessary. Further, the ratio of the plasticizer in the finished film is preferably 1 to 20 wt%, and more preferably 5 to 15 wt% from the viewpoint of dimensional stability, workability, and optical characteristics, particularly for liquid crystal display members such as polarizing plates. ~ 12% is most preferred.
[0040]
In addition, although embodiment mentioned above partitioned off the circumference | surroundings of each process part 12-18, and formed the chambers 42-48, the shape and magnitude | size of the chambers 42-48 are not specifically limited.
[0041]
Moreover, the structure of the film manufacturing apparatus 10 is not limited to embodiment mentioned above, For example, you may provide the adjustment process part of dope in the inside of the clean room 34. FIG.
[0042]
【The invention's effect】
As described above, according to the film manufacturing method of the present invention, since the internal pressure of the chamber in the winding process is a differential pressure of −5 to +15 with respect to the external pressure, dust entering the inside from the outside of the winding process The amount can be reduced, and condensation can be prevented from occurring in the adjacent drying process chamber. Thereby, it can prevent that dust adheres to a film and quality falls.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a film manufacturing apparatus according to the present invention.
DESCRIPTION OF SYMBOLS 10 ... Film manufacturing apparatus, 12 ... Casting and peeling process part, 14 ... Tenter drying process part, 16 ... Roll drying process part, 18 ... Winding process part, 20 ... Support roller, 22 ... Casting band, 24 ... Flow Rolling die, 26 ... film, 28 ... peeling roll, 30 ... roll, 32 ... winder, 34 ... clean room, 36 ... circulation line, 38 ... filter member, 40 ... fan, 42 ... casting / peeling chamber, 44 ... Tenter drying room, 46 ... roll drying room, 48 ... winding room

Claims (1)

A casting / peeling process in which a solution of a polymer material is cast on a support and peeled off as a film from the support; a drying process for drying the peeled film; and a winding process for winding the dried film; In the film production method for producing a cellulose ester film by continuously performing
A winding chamber is formed by partitioning the periphery of the winding process from the other processes,
A circulation line is connected to the upper and lower surfaces of the winding chamber, and a fan provided in the circulation line is driven to circulate the air in the winding chamber and blow out from the upper surface of the winding chamber. Circulating air is removed by the filter provided in the
By the rectifying means provided in the upper part of the winding chamber, a down flow is formed in the winding chamber,
The film manufacturing method characterized by controlling the pressure in the winding chamber to a pressure difference of −5 to +15 Pa with respect to the pressure outside the winding chamber.

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