TWI576234B - Evaluation method of endless belt, and solution casting method and apparatus - Google Patents

Description

Evaluation method of annular belt, solution film forming method and equipment

The invention relates to an evaluation method of an endless belt, a solution film forming method and a device.

With the large screen of liquid crystal displays (LCDs), the optical film used for LCDs is also required to have a large area. After the optical film is formed into a shape, it is cut into a prescribed size according to the size of the LCD. Therefore, in order to manufacture a larger-area optical film, it is necessary to manufacture an elongated optical film having a larger width than the conventional one.

As a representative manufacturing method of the elongated optical film, there is a solution film forming method. In the solution film forming method, a dope is prepared by dissolving a polymer in a solvent. The dope is cast on the moving casting support, and a casting film is formed on the casting support by the dope. Further, the casting film is evaporated to dry the casting film to have a degree of self-supporting property, and then peeled off from the casting support. The peeled wet film is biaxially stretched in a tenter as needed, and further dried to obtain a product film.

As the casting support, a metal endless belt wound around a plurality of metal rolls is used. The maximum width of a film that can be produced by a solution film forming method is limited by the width of the endless belt. Therefore, in order to manufacture a wider film, a wider endless belt is required. However, the width of the endless belt has been at most about 2 m. This is related to the material of the endless belt, that is, the manufacturing equipment of the metal strip, and new manufacturing equipment is required in order to manufacture a metal strip having a wider width than before. Therefore, it is now difficult to widen the metal strip itself.

In the Korean Patent Publication No. 2009-0110082, the central member which is the center portion in the width direction and the pair of side members which are the respective side portions are welded in the longitudinal direction. To get a wider belt than ever before.

The ring-shaped belt is finished by mirroring the protrusion of the welding line (longitudinal welding line) extending in the longitudinal direction by polishing, and the endless belt itself is finished into a mirror surface as described in Korean Patent Laid-Open Publication No. 2009-0110082. . Therefore, if the endless belt can obtain a constant smoothness by precision inspection or precision polishing, it is a good product. However, it has been found that even when a film is formed by using an annular belt having such a certain degree of smoothness, thickness unevenness is slightly generated in a portion of the film corresponding to the portion of the longitudinal welding line. When such a film is wound up in a roll form, the minute thickness unevenness is generated only in the longitudinal weld line, so that it is concentrated at a constant position of the roll, and a black line can be observed.

The black line extends circumferentially around the film and can be seen on both sides of the film roll. The so-called black line failure of the black line can be seen as the thickness unevenness of the film itself is small and not problematic, but the film roll can be observed, and thus improvement is required. In addition, depending on the degree of the black line, not only the commercial value of the appearance but also the application of the coating liquid to form a coating film on the film may cause uneven coating unevenness. Further, in the future, regarding an LCD or the like requiring high resolution, this thickness unevenness may also become a problem.

Therefore, in addition to the evaluation criteria of the endless belt in which the surface is finished into a mirror surface by precision grinding and the smoothness is in a constant range in the precision inspection, a new evaluation criterion that does not cause a black line failure is required.

SUMMARY OF THE INVENTION An object of the present invention is to provide an evaluation method, a solution film forming method and an apparatus for an endless belt which does not cause a black line failure on a obtained film roll.

As a result of intensive research, the inventors focused on the following contents, and determined the evaluation criteria of the new endless belt, that is, the smoothness of the annular belt alone is not sufficient, and the contact pressure distribution of the endless belt and the drum It is more important, and the contact pressure distribution is related to the temperature distribution of the endless belt, and the temperature distribution becomes uneven in the portion where the contact pressure is higher than the other portions.

The evaluation method of the endless belt of the present invention includes an insertion step, a contact pressure distribution measurement step, and a first evaluation step, and it is evaluated whether or not the metal endless belt is suitable as a casting belt. The endless belt is hung between a pair of metal rollers and rotates. In the inserting step, the pressure sensitive film is inserted between the drum and the endless belt. The color development density of the pressure-sensitive film varies depending on the pressure. In the contact pressure distribution measuring step, the contact pressure distribution of the endless belt with respect to the drum is measured from the color development density of the pressure sensitive film. In the first evaluation step, when the contact pressure distribution is in a constant range, it is evaluated as a ring shape. The belt is suitable as a casting belt.

The thickness of the pressure-sensitive film is preferably in the range of 50 μm or more and 400 μm or less.

It is preferable that the endless belt has a weld line along the longitudinal direction.

It is preferable to evaluate the peak value in the contact pressure distribution and to indicate that the value of the peak is within a constant range.

The evaluation method of the endless belt of the present invention includes a sticking step, a temperature distribution measuring step, and a second evaluation step, and it is evaluated whether or not the metal endless belt is suitable as a casting belt. The endless belt is hung between a pair of metal rollers and rotates. In the attaching step, the temperature sensitive liquid crystal film is attached to the surface of the endless belt. The color of the temperature sensitive liquid crystal film changes depending on the temperature. In the temperature distribution measurement step, a temperature difference is applied between the pair of rollers to measure the temperature distribution before the temperature distribution in the width direction of the endless belt becomes constant. The temperature distribution is determined by the color change of the temperature sensitive liquid crystal film on the drum passing through one of the sides. In the second evaluation step, when the measured temperature distribution is within a constant range, it is evaluated that the endless belt is suitable as a casting belt.

It is preferable to evaluate the peak value in the temperature distribution and to indicate that the value of the peak is within a constant range.

The evaluation method of the endless belt of the present invention includes a sticking step, a temperature distribution measuring step, a heat transfer coefficient distribution detecting step, and a third evaluation step, and it is evaluated whether or not the metal endless belt is suitable as a casting belt. The endless belt is hung between a pair of metal rollers and rotates. In the attaching step, the temperature sensitive liquid crystal film is attached to the surface of the endless belt. The color of the temperature sensitive liquid crystal film changes depending on the temperature. In the temperature distribution measuring step, a temperature difference is applied between the pair of rollers to measure the temperature distribution in the width direction of the endless belt for each elapsed time after contact with the roller. The temperature distribution is determined by the color change of the temperature sensitive liquid crystal film on the drum passing through one of the sides. In the heat transfer coefficient distribution detecting step, the heat transfer coefficient distribution in the width direction of the endless belt is obtained from the temperature distribution. In the third evaluation step, when the heat transfer coefficient distribution is in a constant range, it is evaluated that the endless belt is suitable as the casting belt.

It is preferable to evaluate the peak value in the heat transfer coefficient distribution to indicate that the value of the peak value is within a constant range.

It is preferable that the endless belt has a weld line along the longitudinal direction.

The solution film forming method of the present invention has a preparation step, an insertion step, and a contact pressure The distribution measuring step, the first evaluation step, the cast film forming step, and the peeling step of casting the dope into the casting tape to produce a film. In the preparation step, a metal endless belt is prepared which is wound between a pair of metal drums and rotated. In the inserting step, the pressure sensitive film is inserted between the drum and the endless belt. The color development density of the pressure-sensitive film varies depending on the pressure. In the contact pressure distribution measuring step, the contact pressure distribution of the endless belt with respect to the drum is measured from the color development density of the pressure sensitive film. In the first evaluation step, when the contact pressure distribution is in a constant range, it is evaluated that the endless belt is suitable as the casting belt. In the cast film forming step, a ring-shaped tape which is evaluated as a suitable tape is used as a casting tape, and a dope is cast from the casting die onto the endless belt, thereby forming a cast film. The dope contains the polymer and solvent. In the stripping step, the solvent is evaporated from the cast film to be stripped as a wet film.

The thickness of the pressure-sensitive film is preferably in the range of 50 μm or more and 400 μm or less.

It is preferable that the endless belt has a weld line along the longitudinal direction.

It is preferable to evaluate the peak value in the contact pressure distribution and to indicate that the value of the peak is within a constant range.

The solution film forming method of the present invention includes a preparation step, a sticking step, a temperature distribution measuring step, a second evaluation step, a cast film forming step, and a peeling step, and the dope is cast on the casting tape to produce a film. In the preparation step, a metal endless belt is prepared which is wound between a pair of metal drums and rotated. In the attaching step, the temperature sensitive liquid crystal film is attached to the surface of the endless belt. The color of the temperature sensitive liquid crystal film changes depending on the temperature. In the temperature distribution measurement step, a temperature difference is applied between the pair of rollers to measure the temperature distribution before the temperature distribution in the width direction of the endless belt becomes constant. The temperature distribution is determined by the color change of the temperature sensitive liquid crystal film on the drum passing through one of the sides. In the second evaluation step, when the measured temperature distribution is within a constant range, it is evaluated that the endless belt is suitable as a casting belt. In the cast film forming step, a ring-shaped tape which is evaluated as a suitable tape is used as a casting tape, and a dope is cast from the casting die onto the endless belt, thereby forming a cast film. The dope contains the polymer and solvent. In the stripping step, the solvent is evaporated from the cast film to be stripped as a wet film.

The solution film forming method of the present invention includes a preparation step, a sticking step, a temperature distribution measuring step, a heat transfer coefficient distribution detecting step, a third evaluating step, a cast film forming step, and a peeling step of casting the dope into the casting belt To make a film. In the preparation step, a metal endless belt is prepared which is wound between a pair of metal drums and rotated. In the post step, will The temperature sensitive liquid crystal film is attached to the surface of the endless belt. The color of the temperature sensitive liquid crystal film changes depending on the temperature. In the temperature distribution measuring step, a temperature difference is applied between the pair of rollers to measure the temperature distribution in the width direction of the endless belt for each elapsed time after contact with the roller. The temperature distribution is determined by the color change of the temperature sensitive liquid crystal film on the drum passing through one of the sides. In the heat transfer coefficient distribution detecting step, the heat transfer coefficient distribution in the width direction of the endless belt is obtained from the temperature distribution. In the third evaluation step, when the heat transfer coefficient distribution is in a constant range, it is evaluated that the endless belt is suitable as the casting belt. In the cast film forming step, a ring-shaped tape which is evaluated as a suitable tape is used as a casting tape, and a dope is cast from the casting die onto the endless belt, thereby forming a cast film. The dope contains the polymer and solvent. In the stripping step, the solvent is evaporated from the cast film to be stripped as a wet film.

The solution film forming apparatus of the present invention comprises a pair of metal drums, a metal endless belt, a casting die, a film dryer, and a peeling roll. The endless belt is hung between a pair of rollers and rotates. The endless belt is suitably evaluated by the insertion step, the contact pressure distribution measurement step, and the first evaluation step. In the inserting step, the pressure sensitive film is inserted between the drum and the endless belt. The color development density of the pressure-sensitive film varies depending on the pressure. In the contact pressure distribution measuring step, the contact pressure distribution of the endless belt with respect to the drum is measured from the color development density of the pressure sensitive film. In the first evaluation step, when the contact pressure distribution is in a constant range, it is evaluated that the endless belt is suitable. The casting die flows out of the dope toward the endless belt which is evaluated as suitable. The dope contains the polymer and solvent. The film dryer evaporates the solvent from the casting film by blowing heated air to the casting film, and the casting film is composed of a dope flowing out to the endless belt. The peeling roller peels off the cast film from the endless belt.

The solution film forming apparatus of the present invention comprises a pair of metal drums, a metal endless belt, a casting die, a film dryer, and a peeling roll. The endless belt is hung between a pair of rollers and rotates. The endless belt is preferably evaluated by a sticking step, a temperature distribution measuring step, and a first evaluation step. In the attaching step, the temperature sensitive liquid crystal film is attached to the surface of the endless belt. The color of the temperature sensitive liquid crystal film changes depending on the temperature. In the temperature distribution measurement step, a temperature difference is applied between the pair of rollers to measure the temperature distribution before the temperature distribution in the width direction of the endless belt becomes constant. The temperature distribution is determined by the color change of the temperature sensitive liquid crystal film on the drum passing through one of the sides. In the second evaluation step, when the measured temperature distribution is within a constant range, it is evaluated that the endless belt is suitable. The casting die flows out of the dope toward the endless belt which is evaluated as suitable. The dope contains the polymer and solvent. The film dryer evaporates the solvent from the casting film by blowing heated air to the casting film, and the casting film is composed of a dope flowing out to the endless belt. The peeling roller peels off the cast film from the endless belt.

The solution film forming apparatus of the present invention comprises a pair of metal drums, a metal endless belt, a casting die, a film dryer, and a peeling roll. The endless belt is hung between a pair of rollers and rotates. The endless belt is preferably evaluated by a sticking step, a temperature distribution measuring step, a heat transfer coefficient distribution detecting step, and a third evaluation step. In the attaching step, the temperature sensitive liquid crystal film is attached to the surface of the endless belt. The color of the temperature sensitive liquid crystal film changes depending on the temperature. In the temperature distribution measuring step, a temperature difference is applied between the pair of rollers to measure the temperature distribution in the width direction of the endless belt for each elapsed time after contact with the roller. The temperature distribution is determined by the color change of the temperature sensitive liquid crystal film on the drum passing through one of the sides. In the heat transfer coefficient distribution detecting step, the heat transfer coefficient distribution in the width direction of the endless belt is obtained from the temperature distribution. In the third evaluation step, when the measured heat transfer coefficient distribution is within a constant range, it is evaluated that the endless belt is suitable. The casting die flows out of the dope toward the endless belt which is evaluated as suitable. The dope contains the polymer and solvent. The film dryer evaporates the solvent from the casting film by blowing heated air to the casting film, and the casting film is composed of a dope flowing out to the endless belt. The peeling roller peels off the cast film from the endless belt.

According to the present invention, in consideration of the main cause of the black line failure which cannot be found in the conventional precision inspection, the evaluation of the endless belt for solution film formation can be appropriately performed, and no black line failure occurs in the film roll.

10‧‧‧Ring belt

10a‧‧‧ surface

10b‧‧‧Roller contact surface

11‧‧‧Central components

12‧‧‧ side members

13‧‧‧ longitudinal welding line

15, 16‧‧‧ Roller

20, 27‧‧‧ pressure sensitive film

20a, 27a‧‧‧A film

20c, 27c‧‧‧C film

21‧‧‧ Temperature sensitive liquid crystal film

24‧‧‧ camera

25, 26‧‧‧ thermostat

30‧‧‧solution film making equipment

31‧‧‧casting device

32, 34‧‧‧ tenter

33‧‧‧Drying device

35‧‧‧ slitting machine

36‧‧‧Winding device

41, 42‧‧‧ Roller

44‧‧‧casting mode

45‧‧‧Tube (membrane dryer)

46‧‧‧Decompression chamber

47‧‧‧ Stripping roller

50‧‧‧Liquor

51‧‧‧cast film

52‧‧‧film

53, 58‧‧‧ clip

54‧‧‧Liquid beads

56‧‧‧ Roll

59‧‧‧ catheter

60‧‧‧ film roll

A‧‧‧ arrow

Fig. 1 is a perspective view showing a method of measuring a contact pressure distribution by winding an endless belt of a large width based on longitudinal welding between rolls.

Fig. 2 is a flow chart showing the evaluation method of the endless belt of the present invention.

Fig. 3 is a graph for explaining the specificity and determination of the peak from the contact pressure distribution.

Fig. 4 is a graph showing an example of a contact pressure distribution obtained by a pressure sensitive film.

Fig. 5 is a graph showing an example of the contact pressure distribution of the other portion.

Fig. 6 is a graph showing an example of a heat transfer coefficient distribution in the width direction of the endless belt obtained by using a temperature sensitive liquid crystal film.

Fig. 7 is a graph showing an example of the heat transfer coefficient distribution.

Fig. 8 is a perspective view showing a method of measuring a temperature distribution in the width direction of an endless belt using a temperature sensitive liquid crystal film.

Figure 9 is a view showing the width direction of the endless belt which is evaluated as qualified by the evaluation method of the present invention. A graph of an example of contact pressure distribution.

Fig. 10 is a graph showing an example of a heat transfer coefficient distribution in the width direction of an endless belt which has been evaluated by the evaluation method of the present invention.

Fig. 11 is a side view showing another evaluation apparatus for obtaining a contact pressure distribution in the entire circumferential width direction of the endless belt using a roll-shaped pressure-sensitive film.

Fig. 12 is a flow chart showing a method of evaluating the endless belt of the present invention using a temperature sensitive liquid crystal film.

Fig. 13 is a side view showing an outline of a solution film forming apparatus using an endless belt evaluated by the evaluation method of the present invention.

(annular belt)

As shown in Fig. 1, the endless belt 10 is joined to the side member 12 by longitudinal welding (welding in the longitudinal direction), and is widened in the width direction. In the endless belt 10, the inner surface of the entire circumference including the longitudinal welding line 13 is finished into a mirror surface by precision grinding or the like. In the mirror finishing, the surface roughness is set to 0.05 μm or less, and the endless belt 10 is finished to be polished while the smoothness can be confirmed. Further, the longitudinal welding line 13 is not actually recognizable, but in FIGS. 1 and 8, it is indicated by a chain double-dashed line for the sake of explanation.

(Evaluation method of annular belt)

As shown in the flowchart of FIG. 2, after the endless belt 10 was qualified by mirror finishing, it was evaluated whether it is suitable as a casting support for a solution film formation. As shown in Fig. 1, in the evaluation test, the endless belt 10 was hung between the pair of rolls 15, 16 and the contact pressure distribution was measured. Therefore, the pressure sensitive film (pressure measuring film) 20 is placed on the tape entry side of the first roller 15, and the endless belt 10 is rotated at a constant traveling speed. The pressure sensitive film 20 is held by the first roller 15 and the endless belt 10 by the travel of the endless belt 10. Thereafter, the grip is released at the tape outlet of the first roller 15, and the pressure sensitive film 20 is discharged. The discharged pressure-sensitive film 20 is recovered, and a contact pressure distribution is obtained from the pressure-sensitive film 20. Since the surfaces of the rolls 15 and 16 have been finished to be smooth, and the use of any of the rolls 15 and 16 shows substantially the same contact pressure distribution, the contact pressure between the first roll 15 and the endless belt 10 is measured in the present embodiment. Of course, the contact pressure with the second roller 16 can also be measured. In the present embodiment, the first roller 15 is a drive roller, and the second roller 16 is a driven roller.

As the pressure-sensitive film 20, a two-piece type, ultra-low pressure (LLLW) of Prescale (trade name) manufactured by Fujifilm Co., Ltd. was used. This pressure-sensitive film 20 is composed of two sheets of the A film 20a and the C film 20c. The thickness of the A film 20a is 80 to 100 μm (the thickness varies depending on the variety) and is contained in a black plastic bag. In the case of the A film 20a, a coloring agent layer is applied onto a support made of a polyethylene terephthalate (PET) film. The color former layer contains microcapsules in which a color former is placed. The thickness of the C film 20c is also 80 to 100 μm (the thickness varies depending on the variety) and is contained in a blue plastic bag. In the case of the C film 20c, a developer layer is coated on a support made of a PET film. The developer layer contains a color developer that reacts with the color former to form a red color. At the time of use, the two films 20a and 20c are superimposed so that the matte smooth surfaces (coating layers) are bonded to each other, and then sandwiched between the measurement portions and pressurized. The film Cc is colored red by the pressurization. Moreover, the higher the pressure, the higher the concentration. The pressure distribution can be visually inspected based on the chromogenic concentration of the portion where the concentration changes. Further, it is also possible to perform analysis using a dedicated contact pressure distribution analysis device, thereby replacing the visual inspection.

Further, the total thickness of the pressure-sensitive adhesive film 20 (thickness when the two films 20a and 20c are overlapped) is preferably in the range of 50 μm or more and 400 μm or less. The total thickness of the pressure-sensitive adhesive film 20 is preferably in the range of 50 μm or more and 400 μm or less, more preferably in the range of 120 μm or more and 300 μm or less, and particularly preferably in the range of 150 μm or more and 250 μm or less. If the integrated thickness of the pressure sensitive film 20 exceeds 400 μm, the smoothness of the surface of the endless belt 10 or the rollers 15, 16 is adversely affected when the pressure sensitive film 20 is added between the endless belt 10 and the rolls 15, 16. . Further, if the total thickness of the pressure-sensitive film 20 is less than 50 μm, the operation of the pressure-sensitive film 20 becomes difficult, and it is not preferable. As the pressure-sensitive film 20, in addition to the two-piece type, one sheet may be used and the concentration may vary depending on the contact pressure.

A dedicated contact pressure distribution analyzer, for example, a pressure image analysis system Data Shot FPD-100/100S manufactured by Fujifilm Co., Ltd., and a pressure image analysis system FPD-8010E or FPD manufactured by Fujifilm Co., Ltd. -9270. In the contact pressure distribution device, for example, the contact pressure distribution in the width direction of the endless belt 10 is converted into a color density distribution of one line amount read by the scanner.

Next, as shown in FIG. 3, each extreme value (indicated by a black rectangle mark) is obtained from the contact pressure distribution, and the extreme value in which the maximum value is defined is defined as a peak. The method of specific peak is performed visually or automatically according to a well-known numerical algorithm such as the Savitzky-Golay method. Instead of visual inspection. The numerical algorithm is described in detail in "Microcomputer/Computer Application Technology in Waveform Data Processing Measurement System for Scientific Measurement" (edited by Nan Maofu, 1986, CQ Publishing).

Next, regarding the specific peak value, the values (ΔP/Po) and (ΔP.W)/(Po.Wh) indicating the sharpness of the peak based on the following formula (1) are used, by whether or not these values are constant. Within the range, the pass (OK) or the unqualified (NG) is judged as the evaluation of the tape. Wh is obtained from the value of the intermediate value of the contact pressure between the extreme values (indicated by a white rectangular mark).

When the value (ΔP/Po) and (ΔP.W)/(Po.Wh) indicating the sharpness of the peak satisfy the following formula (2), it is suitable as an endless belt for a casting device, and it is judged as qualified. . When the following formula (2) is not satisfied, it is determined that the contact pressure distribution is poor, and the contact pressure distribution improvement process is performed.

Further, the threshold value of the above formula (2) can be appropriately changed depending on the characteristics of the endless belt 10 and the like.

In the contact pressure distribution improvement process, the peak contact pressure is suppressed by performing the improvement treatment (for example, polishing) on the drum contact surface 10b of the endless belt 10, and the contact pressure in the width direction of the endless belt 10 is made uniform. Further, the surface 10a on the opposite side of the roller contact surface 10b is also polished as needed.

4 and 5 show an example of the contact pressure distribution, and it is understood that the peak of the contact pressure is present on the longitudinal weld line 13 of the endless belt 10, respectively. In addition, the horizontal axis in FIG. 4, FIG. 5, FIG. 6, FIG. 7, FIG. 9, and FIG. 10 is the distance (unit is mm) from a welding line, and it is shown by the + (plus) from the welding line to one side. The distance in time, with - (minus sign) indicates the distance to the other side.

Next, the contact pressure distribution, the heat transfer coefficient between the endless belt and the drum The relationship between the cloth and the temperature distribution of the endless belt will be described. The temperature-sensitive liquid crystal film (see FIG. 8) was attached to a region including the portion of the endless belt 10 of the data of FIGS. 4 and 5, and the temperature distribution in the width direction of the endless belt 10 was measured. The heat transfer coefficient α between the endless belt 10 and the drum 16 is obtained from the temperature distribution. Therefore, it is understood that the distribution of the obtained heat transfer coefficient α and the contact pressure distribution are substantially the same.

As shown in FIG. 8, in the temperature distribution measurement, the endless belt 10 is rotationally driven by the first roller 15. Further, the second roller 16 is a driven roller that is freely rotatable, and the temperature distribution in the width direction of the endless belt 10 on the second roller 16 is measured by the camera 24. The first roller 15 was set to 30 ° C by the temperature controller 25, and the second roller 16 was set to 40 ° C by the temperature controller 26. And the surface temperature distribution of the endless belt 10 is measured by the camera 24.

The temperature measurement distribution was carried out using a temperature sensitive liquid crystal film (heat distribution measurement film) 21. The temperature-sensitive liquid crystal film 21 is obtained by applying a liquid crystal microcapsule whose color changes due to temperature to a support. The temperature-sensitive liquid crystal film 21 is a color-changing liquid that changes from red to green to blue, for example, using Japanese capsular products. Further, unlike the pressure-sensitive film 20, the temperature-sensitive liquid crystal film 21 is not held between the endless belt 10 and the drum 16, and therefore the thickness is not particularly limited. However, from the viewpoint of the operation, the thickness of the temperature-sensitive liquid crystal film 21 is preferably in the range of 50 μm or more and 400 μm or less. Further, a more preferable range is also the same as that of the pressure-sensitive film 20. The temperature-sensitive liquid crystal film 21 was discolored from red to green at 32 °C. The color change is captured by the camera by animation, and the heat transfer coefficient α between the endless belt 10 and the drum is obtained by the following formula (3) based on the animation photographed data.

Further, in the above formula (3), T is the temperature (° C.) of the endless belt 10, and T _O is the temperature (30 ° C) of the endless belt 10 when the second drum 16 is started to come into contact, and T _D is the second drum. The temperature of 16 (40 ° C), t is the elapsed time (sec) from the start of contact with the second roller 16, C is the specific heat (constant) of the endless belt 10, and θ is the thickness (constant) of the endless belt 10, ρ It is the density (constant) of the endless belt 10, and α is the heat transfer coefficient between the endless belt 10 and the second drum 16. The contact time t until the temperature-sensitive liquid crystal film 21 becomes green (T=32° C.) is read from the moving image data. And, the heat transfer coefficient α is calculated by the formula (3).

Fig. 6 and the seventh graph show the distribution of the heat transfer coefficient α in the width direction of the endless belt 10 obtained as described above.

The distribution of the heat transfer coefficient α as shown in FIGS. 6 and 7 thus obtained corresponds to the contact pressure distribution shown in FIGS. 4 and 5, and the contact pressure is higher than the longitudinal welding line 13 of the other portions. , a change in the heat transfer coefficient α occurs. The peak of the distribution of the heat transfer coefficient α is substantially the same as the peak of the contact pressure distribution, and it is understood that there is a constant relationship between the two. Therefore, it is understood that the unevenness of the contact pressure distribution causes unevenness in the temperature distribution in the width direction of the endless belt, and as a result, thickness unevenness occurs in the cast film.

As described above, the contact pressure distribution based on the color development density of the pressure-sensitive film 20 and the distribution of the heat transfer coefficient α based on the discoloration of the temperature-sensitive liquid crystal film 21 are also changed on the longitudinal welding line 13. For example, by precise measurement, even if the surface is finished into a mirror surface, the contact pressure distribution on the longitudinal weld line 13 becomes a peak. Further, it is understood that the temperature distribution of the endless belt 10 also changes in the width direction in the portion where the contact pressure peaks. Therefore, it is considered that only this portion is dried, for example, compared with the other portions, and as a result, a slight film thickness difference is generated on the cast film.

In the present invention, based on the above findings, when the endless belt 10 is used as the casting tape of the casting device 31 (see FIG. 13) of the solution film forming apparatus 30, the above-described evaluation test is performed to determine the contact pressure distribution. Further, no peak or peak was observed in the contact pressure distribution, but it was evaluated as a good product in a constant range. Therefore, the following tape can be evaluated as unacceptable in advance, that is, a good product which is mirror-finished in appearance, but the film thickness is broken due to uneven temperature distribution in the peak portion due to unevenness in contact pressure distribution. In this way, it is possible to select only the endless belt that is most suitable for the solution film forming apparatus.

As described above, the endless belt 10 which does not cause a black line failure can be provided in the solution film forming apparatus 30. Therefore, the black line failure does not occur after the installation as in the related art, and the countermeasure against the failure is not required, and the installation work of the new endless belt can be performed reliably and without waste.

The ninth graph shows an example of the contact pressure distribution after the improvement treatment is performed such that the contact pressure distribution becomes substantially constant. Further, the tenth graph shows an example of the distribution in the width direction of the heat transfer coefficient α of the endless belt 10 after the improvement treatment. The distribution in the width direction of the heat transfer coefficient α is obtained by measuring the temperature distribution in the width direction of the endless belt 10 by the temperature sensitive liquid crystal film 21. By adopting such an evaluation method, temperature distribution unevenness caused by the longitudinal welding line 13 which is hardly found only by surface inspection is eliminated, and minute thickness unevenness failure is eliminated. In this way, When the film is taken up in the form of a roll, the black line failure caused by the longitudinal weld line 13 disappears.

Further, in the above embodiment, the case where the endless belt 10 having the longitudinal welding line 13 is used in the solution film forming apparatus 30 has been described. In addition to this, the present invention can be applied to a general endless belt having no longitudinal weld line 13, so that even if the endless belt is used for solution film formation, thickness unevenness does not occur. Further, when the solution film forming apparatus is regularly repaired, the present invention can also be applied to measure the contact pressure distribution or temperature distribution of the endless belt, and the evaluation of the endless belt can be carried out based on the measurement.

In the above embodiment, the contact pressure distribution in the width direction is measured for a portion of the endless belt 10 by the pressure sensitive film 20, and the peak value of the contact pressure is obtained in the contact pressure distribution of the portion, and the value of the peak value exceeds a constant value. At the time of the value, it is determined that the endless belt 10 needs to be improved. However, not only this part of the contact pressure distribution but also the plurality of circumferential directions of the endless belt 10 or the contact pressure distribution measured over the entire circumference can be evaluated based on the measurement. For example, when the strip-shaped pressure-sensitive film 20 is used, a plurality of pressure-sensitive films 20 are placed in the endless belt 10 in such a manner as to be arranged at a constant pitch in the longitudinal direction of the endless belt 10, and the endless belt 10 and the drum 16 are measured. Contact pressure between.

Further, the embodiment is not limited to the use of the strip-shaped pressure-sensitive adhesive film 20 extending in the width direction of the endless belt 10 as shown in FIG. For example, it may be set as shown in FIG. 11 instead of the aspect. In the aspect shown in Fig. 11, the pressure sensitive film 27 composed of the two-piece A film 27a and the C film 27c is previously in a roll form, and the pressure sensitive film 27 is continuously supplied to the drum 16 and the endless belt 10. between. The pressure-sensitive adhesive film 27 is placed in a roll form on the drum outlet side, respectively, or wound up on the take-up shaft 28. At this time, the contact pressure distribution can be obtained once over the entire length of the endless belt 10.

In the above embodiment, the contact pressure distribution of the drum 16 and the endless belt 10 in the belt width direction is obtained by using the pressure sensitive film 20, and whether or not the endless belt 10 is suitable as the casting belt is evaluated based on the distribution, but is not limited to the aspect. . For example, in the flowchart of FIG. 12, the temperature distribution in the width direction of the endless belt 10 is obtained by the temperature sensitive liquid crystal film 21, thereby replacing the pressure sensitive film 20. The heat transfer coefficient distribution in the width direction of the endless belt 10 can be obtained from the temperature distribution, and when the peak value of the heat transfer coefficient is within a constant range, it can be judged that it is suitable as a casting tape.

At this time, in Fig. 8, the temperature of the circumferential surface of the drums 15, 16 is set to a different temperature in each of the rolls 15, 16 by the temperature controllers 25, 26 provided in the respective rolls 15, 16. The temperature change of the endless belt 10 through the rollers 15 and 16 is read by the color change of the temperature-sensitive liquid crystal film 21, and the heat transfer coefficient distribution is obtained from the read color change. Specific peaks in the heat transfer coefficient distribution, Whether or not it is suitable as a casting tape is evaluated by whether or not the value of the peak is within a constant range. The determination of whether the value of the specific or peak value of the peak is within a constant range is performed by the same process as the peak in the contact pressure distribution.

Further, whether or not the endless belt 10 is suitable as a casting belt can be evaluated depending on whether or not the temperature distribution is within a constant range depending on the temperature distribution of the temperature sensitive liquid crystal film 21. At this time, when the endless belt 10 comes into contact with the second roller 16 and changes in temperature, for example, the contact time becomes long, and the temperature distribution in the width direction of the endless belt 10 becomes constant, that is, the temperature in the width direction becomes uniform. The temperature distribution of the stage. Whether or not the endless belt is suitable as the casting tape is determined whether or not the width direction becomes substantially uniform in the measurement of the temperature distribution after the treatment is improved by the temperature distribution in which the temperature unevenness in the width direction is generated. Further, when it became uniform, it was evaluated as suitable (passed), and when temperature unevenness still occurred, it was evaluated as unsuitable (failed).

In addition, in FIG. 8, the temperature sensitive liquid crystal film 21 is attached only to a part of the longitudinal direction of the endless belt 10, but the temperature sensitive liquid crystal film may be attached over the entire length of the endless belt 10. At this time, the temperature distribution in the width direction is measured over the entire length of the endless belt 10, and the heat transfer coefficient distribution in the width direction of the entire length is obtained from the temperature distribution. Further, the temperature sensitive liquid crystal film 21 is attached to one of the longitudinal welding wires 13 in the traveling direction instead of the entire width of the endless belt. In this case, the temperature distribution in the vicinity of the longitudinal welding line 13 can also be measured. Also, the pressure-sensitive adhesive films 20, 27 may be attached only in a direction in which the longitudinal welding line 13 is included, instead of being disposed over substantially the entire width of the endless belt.

The central member 11 and the side member 12 constituting the endless belt 10 are formed of the same material, for example, stainless steel is preferable, and it is preferable to form the same raw material and forming process. Stainless steel such as SUS316 is preferred. As the center member 11, a belt which is used as a conventional casting support can be used. The width of the center member 11 is wider than that of the side member 12. In the present embodiment, the width of the center member 11 is constant within a range of 1500 mm or more and 2100 mm or less, and the width of the side member 12 is constant within a range of 50 mm or more and 500 mm or less. Further, the width of the endless belt 10 is preferably in the range of 2000 mm or more and 3000 mm or less, but may be in other ranges.

(solution film making equipment)

As shown in FIG. 13, the solution film forming apparatus 30 connects, for example, a casting device 31, a first tenter 32, a roll drying device 33, a second tenter 34, a slitter 35, and a winding device in series from the upstream side. 36 constitutes. The type of the polymer is not particularly limited, and it can be used in a solution. A well-known polymer in which a film is formed in a film. In the following embodiments, a case where a cellulose telluride is used as a polymer will be described as an example.

The casting device 31 includes an endless belt 10 wound around the first drum 41 and the second drum 42, a casting die 44, a duct (film dryer) 45, a decompression chamber 46, and a stripping roller 47. The endless belt 10 is an annular metal casting support formed in a ring shape and is wound around the circumferential surfaces of the first drum 41 and the second drum 42. The endless belt 10 was evaluated by the above evaluation method as that there was no unevenness in the contact pressure distribution. The first roller 41 is rotationally driven by a motor (not shown), whereby the endless belt 10 travels in the first direction indicated by the arrow A.

The casting die 44 is placed above the first drum 41. The casting die 44 continuously flows out of the dope 50 against the traveling endless belt 10. Thereby, the casting film 51 is formed on the endless belt 10. The dope 50 is produced, for example, by dissolving a cellulose halide in a solvent, and is produced in a dope production line (not shown) and supplied to the casting die 44.

A decompression chamber 46 is provided upstream of the traveling direction of the endless belt 10 with respect to the liquid bead 54 from the casting die 44. The decompression chamber 46 sucks the atmosphere of the upstream side region of the liquid droplet 54 to decompress the region, thereby reducing the vibration of the liquid droplet 54.

In order to increase the manufacturing speed, the casting film 51 facing the peeling roller 47 is heated by the second roller 42 and the endless belt 10. Further, at the casting position, the endless belt 10 is cooled by the first drum 41 so as not to excessively raise the temperature of the endless belt 10. Therefore, each of the rollers 41 and 42 has a temperature adjustment device (not shown).

A plurality of ducts 45 are arranged along the traveling path of the endless belt 10. Each of the ducts 45 is connected to a warm air controller (not shown) having a blower, and blows dry air from the outflow port. The temperature controller independently controls the temperature, humidity, and flow of the dry air. The temperature of the casting film 51 is adjusted by the temperature control of the temperature and flow rate of the drying wind and the temperature control by the temperature adjusting means of the drums 41 and 42 themselves, and the casting film 51 is dried. Further, the casting film 51 is hardened to be self-supporting until it can be conveyed in the first tenter 32. Further, a membrane dryer may be constructed instead of the duct 45 or by other heaters or the like on the basis of the duct.

A peeling roller 47 is provided on the upstream side in the traveling direction of the casting die 44 of the first drum 41. When the cast film 51 which has been dried in a state containing a solvent is peeled off from the endless belt 10, the peeling roll 47 supports the cast film 51. The stripped cast film 51, that is, the film 52, is guided to the first tenter 32.

In the first tenter 32, the film 52 is conveyed by the clip 53 while the film 52 is conveyed, and the tension in the film width direction is imparted to enlarge the width of the film 52. In the first tenter 32, a preheating zone, an extension zone, and a relaxation zone are formed in this order from the upstream side. In addition, the mitigation area is set as needed.

The first tenter 32 has a pair of guide rails and a chain (none of which are shown). The guide rails are disposed at both sides of the conveying path of the film 52 at predetermined intervals. The rail spacing is constant in the preheating zone and gradually widens in the extension zone as it goes downstream. It is constant in the relaxation zone or gradually narrows toward the downstream. Clips 53 are attached to the chain at constant intervals.

The preheating zone, the extension zone, and the mitigation zone are formed into space by sending dry air from the duct 45, so there is no clear boundary between these zones. Dry air adjusted to a predetermined temperature or humidity is sent from the slit of the duct 45 toward the film 52.

In the roll drying device 33, the film 52 is wound around a plurality of rolls 56 for transport. The temperature or humidity of the internal atmosphere of the roll drying device 33 is adjusted by a thermostat (not shown), and the solvent evaporates from the film 52 during the transfer of the film 52.

The second tenter 34 has the same configuration as that of the first tenter 32, and has a clip 58 and a duct 59. In the second tenter 34, the film 52 is held and extended by the clip 58. By this extension, the film 52 having the desired optical characteristics is obtained. The obtained film 52 can be used, for example, as a retardation film for liquid crystal displays. Further, the second tenter 34 may not be used depending on the optical characteristics of the film 52.

The slitter 35 cuts out the side portions of the holding marks of the respective clips 53, 58 based on the first tenter 32 or the second tenter 34. The side-cut film 52 is taken up in a roll shape by the winding device 36. The film roll 60 obtained by the present invention can be especially used for a retardation film or a polarizing plate protective film.

Further, the width of the endless belt 10 is preferably in the range of, for example, 1.1 times or more and 2.0 times or less of the casting width of the dope 50. The length of the endless belt 10 is preferably in the range of, for example, 20 m or more and 200 m or less. The thickness of the endless belt 10 is preferably in the range of, for example, 0.5 mm or more and 2.5 mm or less. It is preferable that the thickness unevenness of the endless belt 10 is 0.5% or less with respect to the entire thickness. Further, the surface roughness of the surface 10a on which the casting film 51 is formed is preferably 0.05 μm or less.

The width of the film as the product is preferably 600 mm or more, and more preferably 1400 mm or more. More preferably in the range of 2,500 mm or less. Moreover, the present invention is also effective when the width of the film is greater than 2,500 mm. Further, the thickness of the film is preferably in the range of 20 μm or more and 80 μm or less.

(polymer)

In the above embodiment, the polymer which is a raw material of the polymer film is not particularly limited, and examples thereof include cellulose oxime or cyclic polyolefin.

(cellulose cellulose)

The thiol group used for the cellulose halide of the present invention may be used alone or two or more kinds of fluorenyl groups may be used. When two or more kinds of mercapto groups are used, one of them is preferably an ethylidene group. It is preferred that all of the following formulas (I) to (III) are satisfied by the ratio of the hydroxyl group of the carboxylic acid esterified cellulose, that is, the degree of substitution of the thiol group. Further, in the following formulas (I) to (III), A and B represent the degree of substitution of a mercapto group, A is a degree of substitution of an ethylidene group, and B is a degree of substitution of a mercapto group having 3 to 22 carbon atoms. Further, it is preferred that 90% by weight or more of the cellulose triacetate (TAC) is 0.1 mm to 4 mm.

(I) 2.0 A+B 3.0

(II) 1.0 A 3.0

(III)0 B 2.0

The total substitution degree A+B of the fluorenyl group is preferably 2.20 or more and 2.90 or less, and more preferably 2.40 or more and 2.88 or less. Further, the substitution degree B of the fluorenyl group having 3 to 22 carbon atoms is more preferably 0.30 or more, and particularly preferably 0.5 or more.

Further, the details of the cellulose halide are described in paragraph [0195] of [0140] of Japanese Patent Laid-Open Publication No. 2005-104148. These descriptions also apply to the present invention. Further, a solvent, a plasticizer, a deterioration inhibitor, an ultraviolet absorber (UV agent), an optical anisotropy control agent, and a delay are described in detail in paragraph [0516] of [0196] of Japanese Patent Laid-Open Publication No. 2005-104148. Additives such as inhibitors, dyes, matting agents, strippers, and stripping accelerators.

In order to confirm the effect of the evaluation method of the endless belt of the present invention, an experiment was conducted. In Experiment 1, as in the first embodiment, the endless belt 10 is first ground and finished to have a smoothness within a constant range. Thereafter, the pressure sensitive film 20 is inserted between the second roller 16 and the endless belt 10, and the second roller 16 is passed, and the contact pressure distribution between the second roller 16 and the endless belt 10 at this time is obtained. Further, a peak is obtained from the contact pressure distribution, and when the peak value is within a constant range, it is used as a pass for a solution film forming apparatus. At this time, a film 52 which does not cause a black line failure is obtained. With this When the above-described evaluation method is not carried out and the smoothness of the surface is set to a good value in a constant range, the solution is formed into a film, and a black line failure occurs.

Further, in the above test, the effect was judged by the presence or absence of a black line when the film roll was taken up as a film roll, but the sample film may be cut out and evaluated. At this time, the sample film is cut out from the film before being wound up on the winding core in the winding device 36. Further, when 10 pieces of the sample film were stacked and light was transmitted to the overlapped sample film, the shadow appearing on the surface of the sample film was visually observed. When no shadow was observed in the portion of the sample film formed on the longitudinal weld line 13, it was effective, and when a shadow was observed in a portion of the sample film formed on the weld line, it was judged to be ineffective.

10‧‧‧Ring belt

10a‧‧‧ surface

10b‧‧‧Roller contact surface

11‧‧‧Central components

12‧‧‧ side members

13‧‧‧ longitudinal welding line

15, 16‧‧‧ Roller

20‧‧‧ Pressure sensitive film

20a‧‧‧A film

20c‧‧‧C film

Claims (19)

An evaluation method of an endless belt for evaluating whether a metal endless belt is suitable as a casting belt, and the endless belt is hung around a pair of metal drums and is rotated, and is characterized in that the annular belt is evaluated The method includes the steps of: inserting a pressure sensitive film between the roller and the endless belt, wherein a color development density of the pressure sensitive film changes according to a pressure; and the ring shape is determined by a color development concentration of the pressure sensitive film. The contact pressure distribution of the belt with respect to the drum; and the aforementioned contact pressure distribution are in a constant range, and the annular belt is preferably used as the casting belt. The method for evaluating an endless belt according to claim 1, wherein the pressure-sensitive film has a thickness of 50 μm or more and 400 μm or less. The method for evaluating an endless belt according to the first or second aspect of the invention, wherein the endless belt has a weld line in a longitudinal direction. The method for evaluating an endless belt according to the first or second aspect of the invention, wherein the peak value in the contact pressure distribution is determined, and when the value of the peak is within a constant range, it is evaluated as appropriate. The method for evaluating an endless belt according to claim 3, wherein the peak value in the contact pressure distribution is determined, and when the value of the peak is within a constant range, it is evaluated as appropriate. An evaluation method of an endless belt for evaluating whether a metal endless belt is suitable as a casting belt, and the endless belt is hung around a pair of metal drums and is rotated, and is characterized in that the annular belt is evaluated The method includes the steps of: applying a temperature sensitive liquid crystal film to a surface of the endless belt, wherein a color of the temperature sensitive liquid crystal film changes according to temperature; and applying a temperature difference between the pair of rollers to measure the ring shape The temperature distribution in the width direction of the belt becomes a constant temperature distribution, wherein the temperature distribution is determined by a color change of the temperature sensitive liquid crystal film on the drum passing through one of the sides; and the temperature distribution measured as described above is in a constant range The inner time evaluation is that the aforementioned endless belt is suitable as the front Casting tape. The method for evaluating an endless belt according to claim 6, wherein the peak value in the temperature distribution is determined, and when the value of the peak is within a constant range, it is evaluated as appropriate. An evaluation method of an endless belt for evaluating whether a metal endless belt is suitable as a casting belt, and the endless belt is hung around a pair of metal drums and is rotated, and is characterized in that the annular belt is evaluated The method includes the steps of: applying a temperature sensitive liquid crystal film to a surface of the endless belt, wherein a color of the temperature sensitive liquid crystal film changes according to temperature; and applying a temperature difference between the pair of rollers to measure contact with the roller a temperature distribution in the width direction of the endless belt after each elapsed time, wherein the temperature distribution is determined by a color change of the temperature sensitive liquid crystal film on the drum passing through one of the sides; The distribution of the heat transfer coefficient in the width direction of the endless belt; and the distribution of the heat transfer coefficient in a constant range is considered to be suitable as the above-mentioned endless belt. The method for evaluating an endless belt according to the eighth aspect of the invention, wherein the peak value in the heat transfer coefficient distribution is determined, and when the value of the peak value is within a constant range, it is evaluated as appropriate. The method for evaluating an endless belt according to any one of claims 6 to 9, wherein the endless belt has a weld line in a longitudinal direction. A solution film forming method for casting a dope on a casting tape to produce a film, characterized in that the solution film forming method comprises the steps of preparing a metal endless belt which is hung around a pair of metal And rotating between the rollers; inserting a pressure sensitive film between the roller and the endless belt, wherein a color development density of the pressure sensitive film changes according to a pressure; and the color density of the pressure sensitive film is used to determine the color a contact pressure distribution of the endless belt relative to the drum; when the contact pressure distribution is within a constant range, the annular belt is preferably used as the casting belt; Forming a cast film by using the above-mentioned endless belt as a suitable casting tape and casting a dope from the casting die onto the endless belt, wherein the dope contains a polymer and a solvent; The solvent is evaporated from the casting film to be peeled off as a wet film. The solution film forming method according to claim 11, wherein the pressure-sensitive film has a thickness of 50 μm or more and 400 μm or less. The solution film forming method according to the invention of claim 11, wherein the endless belt has a weld line in a longitudinal direction. The solution film forming method according to Item 11 or 12, wherein the peak value in the contact pressure distribution is determined, and when the value of the peak value is within a constant range, it is evaluated as appropriate. A solution film forming method for casting a dope on a casting tape to produce a film, characterized in that the solution film forming method comprises the steps of preparing a metal endless belt which is hung around a pair of metal Rotating between the rollers; applying a temperature-sensitive liquid crystal film to the surface of the endless belt, wherein the color of the temperature-sensitive liquid crystal film changes according to temperature; and applying a temperature difference between the pair of rollers to measure the foregoing The temperature distribution in the width direction of the endless belt becomes a constant temperature distribution, wherein the temperature distribution is determined by a color change of the temperature sensitive liquid crystal film on the drum passing through one of the sides; the measured temperature distribution is constant In the range, it is evaluated that the endless belt is suitable as the casting belt; the endless belt which is evaluated as suitable is used as the casting belt, and a dope is cast from the casting die onto the endless belt, thereby forming a flow. a film, wherein the dope comprises a polymer and a solvent; and the solvent is evaporated from the cast film to be a wet film. A solution film forming method for casting a dope on a casting tape to produce a film, characterized in that the solution film forming method comprises the steps of preparing a metal endless belt which is hung around a pair of metal Rotating between the rollers; applying a temperature-sensitive liquid crystal film to the surface of the endless belt, wherein the color of the temperature-sensitive liquid crystal film changes according to temperature; and applying a temperature difference between the pair of rollers to measure the foregoing a temperature distribution in the width direction of the aforementioned endless belt for each elapsed time after the roller contact, wherein the aforementioned temperature distribution is Measuring the color change of the temperature sensitive liquid crystal film on the drum on one side; determining the heat transfer coefficient distribution in the width direction of the endless belt from the temperature distribution; when the heat transfer coefficient is distributed within a constant range It is evaluated that the endless belt is suitable as the casting belt; the annular belt which is evaluated as suitable is used as the casting belt, and a dope is cast from the casting die onto the endless belt, thereby forming a casting film. The dope contains a polymer and a solvent; and the solvent is evaporated from the cast film to be a wet film. A solution film forming apparatus comprising: a pair of metal drums; a metal endless belt wound between the pair of rollers and rotating, wherein the endless belt is inserted, The contact pressure distribution measuring step and the first evaluation step are preferably evaluated. In the inserting step, the pressure sensitive film is interposed between the roller and the endless belt, wherein the color development density of the temperature sensitive film changes depending on the pressure. In the contact pressure distribution measuring step, the contact pressure distribution of the endless belt with respect to the drum is measured by the color development density of the pressure sensitive film, and the first evaluation step is evaluated when the contact pressure distribution is within a constant range. Suitable for the above-mentioned endless belt; a casting die which is directed to the above-mentioned endless belt outflow dope, wherein the dope contains a polymer and a solvent; and the film dryer blows the heated wind by casting the film The solvent is evaporated from the casting film, and the casting film is composed of the concentrated liquid flowing out onto the endless belt; and a peeling roller that peels off the aforementioned endless belt Cast film. A solution film forming apparatus comprising: a pair of metal drums; and a metal endless belt wound around the pair of rollers and rotating, wherein the endless belt is attached by a laminating step The temperature distribution measuring step and the second evaluation step are preferably evaluated. In the attaching step, a temperature sensitive liquid crystal film is attached to the surface of the endless belt, wherein the color of the temperature sensitive liquid crystal film changes depending on temperature, and the temperature distribution is In the measuring step, a temperature difference is obtained between the pair of rollers to measure a temperature distribution before the temperature distribution in the width direction of the endless belt becomes constant, wherein the temperature distribution is on the aforementioned roller passing through one of the rollers The color change measurement of the temperature sensitive liquid crystal film is measured in the second evaluation step. When the temperature distribution is within a constant range, it is evaluated that the above-mentioned endless belt is suitable; the casting die is oriented toward the above-mentioned endless belt outflow concentrated liquid, wherein the dope contains a polymer and a solvent; The solvent is evaporated from the casting film by blowing heated air to the casting film, and the casting film is composed of the concentrated liquid flowing out onto the endless belt; and a peeling roller that peels off the casting from the endless belt membrane. A solution film forming apparatus comprising: a pair of metal drums; and a metal endless belt wound around the pair of rollers and rotating, wherein the endless belt is attached by a laminating step The temperature distribution measuring step, the heat transfer coefficient distribution detecting step, and the third evaluation step are preferably evaluated. In the attaching step, the temperature sensitive liquid crystal film is attached to the surface of the endless belt, wherein the temperature of the temperature sensitive liquid crystal film depends on the temperature. In the temperature distribution measuring step, a temperature difference is applied to the pair of rollers, and a temperature distribution in the width direction of the endless belt is measured for each elapsed time after contact with the roller. The temperature distribution is determined by the color change of the temperature sensitive liquid crystal film on the drum passing through one of the sides, and in the heat transfer coefficient distribution detecting step, the heat transfer coefficient in the width direction of the endless belt is obtained from the temperature distribution. Distribution, in the third evaluation step, when the measured heat transfer coefficient distribution is within a constant range, it is suitable to evaluate the annular band; a die extending toward the above-mentioned endless belt outflow concentrate, wherein the dope comprises a polymer and a solvent; and a film dryer blows heated air from the casting film to cause the solvent to pass from the cast film Evaporating, the cast film is composed of the dope flowing out onto the endless belt; and a peeling roll that peels off the cast film from the endless belt.