JP4958385B2 - Solution casting method - Google Patents

Description

  The present invention relates to a solution casting method, and more particularly to a solution casting method for producing a film used for a photographic film support, a polarizing plate protective film and the like.

  Cellulose acylate film, particularly cellulose acetate film has low birefringence, transparency, moderate moisture permeability, high mechanical strength, and low humidity and temperature dependency in terms of dimensional stability. Widely used as a support for optical materials such as polarizing plate protective films. Such a cellulose acylate film is generally produced by a solution casting method. In this solution casting method, a dope is cast on a support using a casting die, and the dope is peeled off from the support, and then wound through a drying step. Furthermore, when producing a cellulose acylate film by this solution casting method, after peeling off the film from the support, in order to improve the flatness, mechanical strength, optical properties, etc. of the film, film width regulation and film stretching It is common to provide a device called a tenter for carrying out the drying and to dry the film while transporting it.

  In such a solution casting method, various devices for producing a high-quality film having high flatness have been made. In Patent Document 1, a flatness is prevented by preventing sagging due to the weight of the film. A method for preventing deterioration is described. In Patent Document 1, a rotating roller that rotates so as to spread in the range of an angle of 2 ° to 60 ° outward in the width direction is arranged on both side edges in front of the entrance of the tenter. Tension is applied to the outside of the hand to prevent sagging due to its own weight.

  In Patent Documents 2 and 3, curling occurring at both ends of the film is prevented, and curling is prevented from proceeding in the entire width direction of the film. Moreover, in patent document 4, when it peels from a support body and is sent to a tenter, it introduce | transduces into the tenter with an angle from the horizontal. This prevents flatness deterioration.

  On the other hand, when the speed of the production line is increased in order to improve the productivity by the solution casting method, the residual solvent of the film increases, so that the elastic modulus of the film decreases and the weight increases. As a result, sagging due to the film's own weight may occur near the inlet of the tenter, and the film biting by the tenter clip may become unstable. If the film biting position by the tenter clip is shifted or bitten, the film will be poorly conveyed and the production line will be stopped, resulting in a significant reduction in productivity.

  The demand for cellulose acylate films tends to increase further, and improvement in productivity is also desired in the production of films by the solution casting method. For this reason, there is an increasing need to further increase the speed of the production line, and it is required to reliably bite in the vicinity of the tenter inlet. It is also desired to widen the film, which further increases the slack of the film, making it more difficult to bite at the tenter inlet.

JP-A-11-90944 Japanese Patent Laid-Open No. 11-90942 JP 2003-33933 A JP-A-11-90945

  However, in Patent Document 1, although the film is pulled outward in the width direction to prevent sagging, no particular consideration is given to improving the biting property at the tenter inlet. In addition, the solution casting methods described in Patent Documents 2 and 3 are effective in preventing curling occurring at both ends of the film, but there is no detailed description of biting at the tenter inlet. Furthermore, in Patent Document 4, since the tenter or film transport path that has been positioned horizontally is inclined from the horizontal, the cost of the equipment becomes very high if this is carried out.

  The problem to be solved is to ensure that the film is bitten in the tenter inlet when the film is introduced into the tenter after peeling from the support.

The present invention provides a solution casting method in which a polymer is dissolved in a solvent to prepare a dope, which is cast on an endless support and continuously peeled, and then introduced into a tenter to produce a film. After the conveying means for peeling the support and conveying the film to the tenter, and immediately before the holding start position where the tenter starts to hold the film, the feeding direction is 2 ° with respect to the film running direction by the tenter . It is characterized in that only both ends of the film are supported from below by support means having an inclination angle of less than . In addition, the position where both ends of the film are supported from below immediately before the holding start position is between the same height as the position where the both ends of the film are held by the tenter and 30 mm higher. Features.

In the invention, it is preferable that the support means for supporting both ends of the film from below immediately before the holding start position is a transport roller . The film is a cellulose acylate film having a thickness of 20 μm to 200 μm. Furthermore, the width of the film manufactured by being introduced into the tenter is 1400 mm or more.

  The solution film-forming method of the present invention has an advantage that the film can be reliably bitten, such as a wide one or a low elastic modulus, in which the tenter is liable to fail to bite.

  FIG. 1 shows a typical example of the solution casting process embodying the present invention. The dope 10 is cast from a casting die 11 onto a band 12 as an endless support, and the solvent gradually evaporates in the drying chamber 13 of the band 12 to form a film and have self-supporting properties. Here, the film 14 is peeled off from the band 12, conveyed while being brought into contact with the plurality of rolls 15 to 18, and introduced into the tenter drying chamber 19. In the roll conveying step before the introduction of the tenter drying chamber 19, temperature control is performed. In the tenter drying chamber 19, a tenter process is performed in which the film 14 is dried while being restricted in width by the tenter 20 and being stretched. In the tenter 20, the tenter clips 21 a and 21 b (see FIG. 2) travel while gripping both end portions of the film 14 and transport the film 14. A pin clip may be used in place of the tenter clip 21. Then, it sends to the roll drying chambers 23 and 24 via the guide roll 22, and it is made to dry, conveying a film with many rolls 25 in this drying chamber 23 and 24, and a residual solvent is reduced. Next, the take-up device 26 takes up the take-up shaft 27.

  2 and 3 are a plan view and a perspective view showing a configuration in the vicinity of the introduction port that is introduced into the tenter 20 from the roll conveyance process using the rolls 15 to 18. The tenter 20 is supported by the right rail 31, the left rail 32, the endless chains 33, 34 guided by the rails 31, 32, and the endless chains 33, 34 and travels along the rails 31, 32. The clip 21a, 21b and a chain drive unit (not shown) are configured.

  The film 14 is introduced into the tenter 20 from the introduction port 35. In the introduction port 35, the tenter clips 21 a and 21 b are guided by the tip end corners 31 a and 32 a of the rails 31 and 32 and wrap around from the outside to the inside. The tenter clips 21 a and 21 b go inward, and the holding of the film 14 by the tenter clips 21 a and 21 b is started and introduced into the tenter 20 from the holding start position A (illustrated by a one-dot chain line) positioned at both ends of the film 14. And the width | variety is controlled and the film 14 is extended | stretched by conveying while both ends are hold | gripped by the tenter clips 21a and 21b.

  Immediately before the holding start position A, support rollers 36 and 37 as support means are provided at positions below both end edges 14a and 14b of the film 14. The support rollers 36 and 37 are provided at positions symmetrical with respect to each other with the center line 14c of the film 14 traveling by the tenter 20 as the axis of symmetry. In the present embodiment, “immediately before the holding start position A” is from the end of the roll conveying process to before introduction into the tenter 20, that is, from the position downstream of the last roll 18 in the roll conveying process from the holding start position A. Within the range up to the upstream position. Further, as a more preferable position, when the width of the film 14 at the time of introduction to the tenter 20 is W, the position is upstream of the holding start position A and the distance from the holding start position A is W / 2 or less. The position is preferably W / 3 or less. In the figure, two support rollers 36 and 37 are provided for each of both end edges 14a and 14b of the film 14. However, the present invention is not limited to this, and the support rollers 36 and 37 can be arranged between the roll conveying step and the holding start position A. If the number is large, a larger number of support rollers 36 and 37 may be arranged.

  The rotation direction B of the support rollers 36 and 37 is provided so as to be positioned substantially parallel to the traveling direction C of the film 14 by the tenter 20. That is, it is preferable that the inclination α (see FIG. 4) of the rotation direction B with respect to the traveling direction C is less than 2 °, and the inclination α is as close to 0 ° as possible. The support rollers 36 and 37 are rotatably supported by central shafts 38 and 39 protruding from one end surfaces 36a and 37a located outside the both end edges 14a and 14b of the film 14, respectively. The center shafts 38 and 39 are provided so as not to protrude from the other end faces 36 b and 37 b of 37. This prevents the central shafts 38 and 39 from coming into contact with the film 14 and prevents the film 14 from being damaged.

  Furthermore, the range in which the support rollers 36 and 37 support both end portions of the film 14 is the distance from the end edges 14a and 14b of the film 14 to the inner end surfaces 36b and 37b of the support rollers 36 and 37. 2), and the support range H is preferably 1.0 to 20.0% of the film width W, and more preferably 2.0 to 10.0%.

The support rollers 36 and 37 arranged in this way support both ends of the film 14 from below. It should be noted that the position Z ₁ at which both ends of the film 14 are supported by the support rollers 36 and 37 is −5 mm from the position Z ₂ at which both ends of the film 14 are held by the tenter 20 as shown in FIG. It is preferably at a position that is higher by ~ 30 mm, and more preferably at a position that is higher by 0 mm to +10 mm. As a result, the film 14 is stably introduced into the tenter 20. FIG. 5 shows a Y ₁ -Y ₁ vertical cross-sectional shape parallel to the center line 14c.

The operation of the above configuration will be described below. The dope 10 is cast from the casting die 11 to the band 12, and the film 14 having self-supporting properties is peeled off from the band 12 and sent to the tenter drying chamber 19 by rolls 15 to 18. Until it is separated from the last roll 18 and introduced into the tenter 20, both ends of the film 14 are supported from below by the support rollers 36 and 37 as described above. , Stably introduced into the tenter 20. FIG. 6 shows an X ₁ -X ₁ vertical cross-sectional shape cut along the holding start position A. The film 14 introduced into the tenter 20 is securely bitten by the tenter clips 21a and 21b, and is stretched and regulated in the width direction.

  If the both ends of the film 14 are not supported by the support rollers 36 and 37 as in the above configuration, the state shown in FIG. 7 is obtained. FIG. 7 shows a vertical sectional shape cut along the holding start position in the conventional solution casting process. Since the film 14 introduced into the tenter 20 without supporting both ends is slackened due to its own weight, the both ends are separated from the tenter clips 21a and 21b. As a result, in the conventional solution casting process, the biting is lost or the biting position shifts. However, this is not the case in the solution casting process in which the present invention is implemented.

  In the present embodiment, the cellulose acylate film having a thickness of 20 μm to 200 μm is particularly effective when producing a film having a width W of 1400 mm or more. That is, in such a wide film, the sagging due to its own weight is particularly large, but by supporting both ends of the film 14 as described above, the tenter clips 21a and 21b can be stably bitten and the quality is high. A film can be produced.

  In the above-described embodiment, both ends of the film 14 are supported by the support roller and stably introduced into the tenter 20, but the present invention is not limited to this, and the endless belt or gas spraying is performed. You may support by.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely using an Example, the content of this invention is not limited to these. Since the preparation of the raw material dope is the same in both the examples and the comparative examples, this will be explained first, and the production results of the film by the solution casting method will be explained respectively.

(Preparation of raw material dope)
Cellulose triacetate (substitution degree 2.8) 89.3% by weight, triphenyl phosphate 7.1% by weight, biphenyl diphenyl phosphate 100% by weight solid content 100 parts by weight, dichloromethane 8% by weight, methanol A dope was prepared by appropriately adding a mixed solvent of 13 wt% and stirring and dissolving. The solid content concentration of the prepared dope was 19.0%. Further, the dope thus prepared was filtered, the silica matting agent dispersion and the ultraviolet absorber solution were mixed with an in-line mixer, and the solution was sent to the film forming process.

  About Examples 1-3 which manufactured the film in the solution casting process which implemented this invention, and Comparative Example 1 which manufactured the film in the solution casting process for the comparison with this invention, the stability of a production line was evaluated, The results are shown in Table 1.

[Example 1]
The dope was used to form a film in the solution casting process described in the above embodiment. Support rollers 36 and 37 having a diameter of 30 mm were used. In this solution casting process, the dope 10 was cast on the band 12 from the casting die 11, dried on the band until the dope 10 had self-supporting properties, and peeled off as a film 14. After peeling off from the endless support, the film 14 was conveyed by rolls 15 to 18 and introduced into the tenter 20. The width W of the film 14 when introduced into the tenter 20 was 1600 mm. At this time, the support range H in which the support rollers 36 and 37 support the film 14 is 90 mm, and the inclination α between the support rollers 36 and 37 and both end edges 14a and 14b of the film 14 is 0 °. Furthermore, the positions at which both ends of the film 14 are held by the tenter clips 21a, 21b are set to the same height as the positions supported by the support rollers 36, 37. When the film 14 is manufactured under these conditions, in the above-described tenter process, the film 14 is not bitten by the tenter clips 21a and 21b and the biting position shift may occur even if the film 14 is manufactured for 100 hours or more. The production line was stable. After the tenter process, a drying process and an edge cutting process were further performed, and the film was wound by the winder 26 to produce a film having a width of 1470 mm. The dry thickness of the film was 80 μm.

[Example 2]
The dope was used to form a film in the solution casting process described in the above embodiment. In the second embodiment, both ends of the film 14 are set to be 5 mm higher at positions supported from below by the support rollers 36 and 37 than positions held by the tenter clips 21a and 21b. When the film 14 is manufactured under the same conditions as in Example 1 except for these conditions, even if the film 14 is manufactured for 100 hours or more, the tenter clips 21a and 21b do not bite the film 14 and the biting position. The production line was stable without any deviation.

[Example 3]
Using the dope, a film was produced in a solution casting process. Instead of the support rollers 36 and 37 used in the above embodiment, air nozzles that blow air are used as support means for supporting the film 14, and both ends of the film 14 are supported from below by blowing air from the air nozzles. . Further, at this time, both ends of the film 14 are held at the same height as the positions supported by the tenter clips 21a and 21b from below by blowing air. When the film 14 is manufactured under the same conditions as in Example 1 except for these conditions, the film 14 can be manufactured stably for 20 hours or more, and the biting position by the tenter clips 21a and 21b is not good. Although it became stable, no biting failure occurred.

[Comparative Example 1]
Using the dope, a film was formed by a solution casting process. Unlike the above-described embodiment, just before the holding start position A, the support for both ends of the film 14 was not arranged at all, and the introduction into the tenter was performed. Other than these conditions, when the film 14 was manufactured under the same conditions as in Example 1, 3 hours after the start of manufacture, the tenter clips 21a and 21b were damaged by the film 14, and the production line was stopped.

It is the schematic which shows the solution casting process which implemented the solution casting method of this invention. It is a top view which shows the structure of the tenter inlet vicinity which implemented 1st Embodiment of this invention. It is a perspective view which shows the structure of the tenter inlet vicinity vicinity which implemented 1st Embodiment of this invention. It is a top view which shows arrangement | positioning of a conveyance roller. A main part cross-sectional view showing a state before and after the holding start position of the film 14, a Y ₁ -Y ₁ vertical cross-section of the plan view shown in FIG. It is X ₁ -X ₁ vertical cross-section along the holding start position A of the plan view shown in FIG. It is the vertical cross-sectional shape which shows one of the comparative examples with respect to this invention.

Explanation of symbols

10 dope 14 film 20 tenter 21a, 21b tenter clip 35 inlet 36, 37 transport roll

Claims (5)

In a solution casting method in which a polymer is dissolved in a solvent to prepare a dope, which is cast on an endless support and continuously peeled, and then introduced into a tenter to produce a film.
After the conveying means for peeling the endless support and conveying the film to the tenter, and immediately before the holding start position where the tenter starts holding the film, the feeding direction is relative to the film running direction by the tenter . A solution casting method characterized in that only both ends of a film are supported from below by supporting means having an inclination angle of less than 2 ° . The position where both ends of the film are supported from below just before the holding start position is between the same height as the position where both ends of the film are held by the tenter and 30 mm higher. The solution casting method according to claim 1. 3. The solution casting method according to claim 2, wherein the supporting means for supporting both ends of the film from below immediately before the holding start position is a transport roller .   4. The solution casting method according to claim 1, wherein the film is a cellulose acylate film having a thickness of 20 μm to 200 μm.   5. The solution casting method according to claim 1, wherein the width of the film produced by being introduced into the tenter is 1400 mm or more.

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