Method for manufacturing phase difference thin films

Abstract

This invention provides a method for manufacturing a phase retardation film, which, during the stretching step, can suppress stress concentration on the first and second clamps holding the film, thereby stably manufacturing a phase retardation film with the desired in-plane phase difference. One embodiment of the method includes a holding step, a stretching step, and a release step. In the holding step, a plurality of first clamps hold the first end of the film with a Δn(550) of 0.002 to 0.009, and a plurality of second clamps hold the second end. The holding area of ​​the film for each of the first and second clamps is 10 cm² to 300 cm². In the stretching step, while changing the distance between the plurality of first clamps, the plurality of first clamps and the plurality of second clamps are moved to stretch the film obliquely at a temperature below 180°. In the release step, the film is released from the clamps.

Description

Technical Field

[0001] Invention Field This invention relates to a method for manufacturing a phase retardation thin film. Prior Technology

[0002] Background of the Invention Circular polarizers are used in image display devices such as liquid crystal displays (LCDs) and organic light-emitting diode (OLEDs) to improve display characteristics or prevent reflections. The polarizing element and retardation film (typically a λ / 4 plate) of a circular polarizer are usually laminated at a 45° angle between the absorption axis of the polarizing element and the slow axis of the retardation film. Traditionally, retardation films are typically fabricated by uniaxial or biaxial stretching in the longitudinal and / or transverse directions. Therefore, the slow axis is usually formed in the transverse (width direction) or longitudinal (length direction) direction of the elongated film substrate. Consequently, to fabricate a circular polarizer, the retardation film needs to be cut at a 45° angle to the width or length direction and laminated piece by piece.

[0003] Therefore, it is desirable to manufacture a phase retardation film having a slow axis extending in a direction inclined relative to the length direction. As a method for manufacturing such a phase retardation film, for example, a method for obliquely extending a sheet / film has been proposed as follows: the left and right ends of a strip-shaped film in the width direction are respectively held by left and right clamps of a variable spacing type with a longitudinal clamp spacing, and one of the left and right clamps is set as the forward side and the other as the slow side, so that the clamp spacing on the forward side is greater than the clamp spacing on the slow side, thereby extending in a direction inclined relative to the length direction (hereinafter also referred to as "oblique extension") (see, for example, Patent Document 1).

[0004] Previous technical documents Patent documents Patent Document 1: Japanese Patent No. 4845619 Summary of the Invention

[0005] Invention Summary [The problem the invention aims to solve] In recent years, with the diversification of applications for retardation films, the range of materials selected for retardation films has also expanded. Therefore, in some cases, it is desirable to construct retardation films from materials with relatively low in-plane birefringence (hereinafter referred to as low birefringence materials). In this case, in order for the retardation film to exhibit sufficient in-plane phase retardation, it is necessary to stretch the film made of low birefringence material at a relatively low temperature (usually below 180°C). However, in the oblique stretching method of the sheet / film described in Patent Document 1, if the film made of a low birefringence material is stretched obliquely at a relatively low temperature, the stress will be concentrated on the clamp holding the film, and there is a concern that the film cannot be stretched stably. The main objective of this invention is to provide a method for manufacturing a phase difference film, which can suppress stress concentration on the first and second clamps holding the film during the stretching step, thereby enabling the stable manufacture of a phase difference film with the desired in-plane phase difference.

[0006] [Methods used to solve problems] [1] A method for manufacturing an extended thin film according to one embodiment of the present invention sequentially includes a holding step, an extending step, and a releasing step. In the holding step, a first end of the elongated thin film in the width direction is held by a plurality of first clamps arranged along the length direction of the film, and a second end of the thin film in the width direction is held by a plurality of second clamps arranged along the length direction. In the extending step, while changing the distance between the plurality of first clamps, the plurality of first clamps and the plurality of second clamps are moved along the length direction, and the thin film is extended in an oblique direction intersecting both the length direction and the width direction. In the releasing step, the first end of the thin film is released from the plurality of first clamps, and the second end of the thin film is released from the plurality of second clamps. The in-plane birefringence Δn(550) of the thin film is 0.002~0.009. The temperature in the extending step is 180°C or below. The holding area of ​​the film in each of the aforementioned plurality of first clamps is substantially the same as the holding area of ​​the film in each of the aforementioned plurality of second clamps. The holding area of ​​the film in each of the aforementioned plurality of first clamps is 10 cm² to 300 cm².

[0007] [Invention Effects] According to an embodiment of the present invention, stress concentration on the first and second clamps holding the film can be suppressed during the stretching step, thereby enabling the stable manufacture of a phase difference film with the desired in-plane phase difference. Simple Explanation of the Diagram

[0008] Figure 1 is a schematic diagram of an example of an extension apparatus for a method of manufacturing a phase difference thin film that can implement one embodiment of the present invention. Figure 2 is a schematic top view illustrating the holding steps implemented by the extension device in Figure 1. Figure 3 is a schematic cross-sectional view illustrating the holding steps implemented by the extension device in Figure 1. Figure 4 is a schematic diagram showing the general distance between the clamps in the extension step performed by the extension device in Figure 1. Figure 5 is a schematic top view illustrating the linkage mechanism of the extension device in Figure 1. Figure 6 is a schematic top view used to illustrate the operation of the linkage mechanism in Figure 5. Figure 7 is a schematic top view of the upstream side spacing control wheel of the extension device in Figure 1. Implementation

[0009] Forms used to implement inventions The following describes embodiments of the present invention, but the present invention is not limited to these embodiments. Furthermore, for ease of observation and understanding, the drawings are schematic or conceptual, and the length, width, shape, size, ratio, direction, number, etc., may sometimes differ from the actual situation, and may not correspond between the drawings.

[0010] (Definitions of terms and symbols) The definitions of terms and symbols used in this specification are as follows. (1) Refractive index (nx, ny, nz) "nx" refers to the refractive index in the direction of maximum refractive index within the plane (i.e., the slow axis direction), "ny" refers to the refractive index in the direction orthogonal to the slow axis within the plane (i.e., the fast axis direction), and "nz" refers to the refractive index in the thickness direction. (2) In-plane birefringence (Δn) "Δn(λ)" refers to the in-plane birefringence measured at 23°C using light with a wavelength of λnm. For example, "Δn(550)" refers to the in-plane birefringence measured at 23°C using light with a wavelength of 550nm. The in-plane birefringence (Δn) is calculated using the formula: Δn = nx - ny. (3) In fact, they are parallel or orthogonal. The expressions "substantially orthogonal" and "approximately orthogonal" include cases where the angle between the two directions is 90°±10°, preferably 90°±7°, and more preferably 90°±5°. The expressions "substantially parallel" and "approximately parallel" include cases where the angle between the two directions is 0°±10°, preferably 0°±7°, and more preferably 0°±5°. Furthermore, when simply referred to as "orthogonal" or "parallel" in this specification, it may include states that are substantially orthogonal or substantially parallel.

[0011] A. An overview of the manufacturing method for phase retardation thin films Figure 1 is a schematic configuration diagram of an example of an extension apparatus for a method of manufacturing a phase difference thin film that can implement one embodiment of the present invention. Figure 2 is a schematic top view illustrating the holding step performed by the extension apparatus of Figure 1. Figure 3 is a schematic cross-sectional view illustrating the holding step performed by the extension apparatus of Figure 1. Figure 4 is a schematic diagram showing the general situation of the clamp spacing in the extension step performed by the extension apparatus of Figure 1. One embodiment of the present invention includes a method for manufacturing a phase difference thin film, which sequentially includes a holding step, a stretching step, and a releasing step. As shown in Figures 2 and 3, in the holding step, the first end 1R of the film 1 is held by a plurality of first clamps 40R, and the second end 1L of the film 1 is held by a plurality of second clamps 40L. The film 1 is elongated. The first end 1R is located at one end of the film 1 in the width direction (the direction orthogonal to the length direction). The second end 1L is located at the other end of the film 1 in the width direction (the direction orthogonal to the length direction), opposite to the first end 1R. The in-plane birefringence Δn(550) of the film 1 is, for example, 0.002~0.009, preferably 0.003~0.007, and more preferably 0.003~0.005. During the holding step, a plurality of first clamps 40R are arranged along the length direction of the film 1, and a plurality of second clamps 40L are arranged along the length direction of the film 1. As shown in Figure 4, in the extension step, while changing the distance between the plurality of first clamps 40R, the plurality of first clamps 40R and the plurality of second clamps 40L are moved along the length direction of the film 1. In one embodiment, the distance between the plurality of first clamps 40R is greater than the distance between the plurality of second clamps 40L. Furthermore, in this specification, "distance" refers to the length of an imaginary line segment connecting the centers of adjacent components (clamps, clamp support members, etc.) among the plurality of components. The temperature in this extension step is 180°C or below. In the release step, the first end 1R of the film 1 is released from the plurality of first clamps 40R, and the second end 1L of the film 1 is released from the plurality of second clamps 40L (see Figure 3). In the above-described holding step, the holding area of ​​the film 1 of each of the plurality of first clamps 40R is substantially the same as the holding area of ​​the film 1 of each of the plurality of second clamps 40L. The holding area of ​​the film 1 of each of the plurality of first clamps 40R is 10 cm² to 300 cm². According to this method, the area of ​​the portion of the film held by one clamp (first clamp or second clamp) (the holding area) is within the above range. Therefore, even if the film with in-plane birefringence Δn(550) of less than 0.009 is obliquely extended at 180°C, excessive stress concentration in the clamp (first clamp or second clamp) can be suppressed. Therefore, the film can be successfully stretched during the stretching step, resulting in the stable fabrication of a phase difference film with the desired in-plane phase difference. In particular, if the in-plane birefringence Δn(550) of the thin film sent into the holding step reaches or exceeds the aforementioned lower limit, the phase difference thin film can stably exhibit sufficient in-plane phase difference.

[0012] In one embodiment, the method for manufacturing a phase difference film further includes a first spacing adjustment step. In the first spacing adjustment step, the distance between the plurality of first clamps 40R and the distance between the plurality of second clamps 40L are substantially the same as before the holding step. Therefore, even if the distance between the plurality of first clamps 40R changes during the extension step, the first clamps 40R and the second clamps 40L can be sufficiently maintained in the desired relative positional relationship. Furthermore, since the distance between the plurality of first clamps 40R and the distance between the plurality of second clamps 40L are adjusted before holding the film 1, the influence of this spacing adjustment on the variability of the distance between the plurality of first clamps 40R during the extension step can be suppressed, and the first clamps 40R and the second clamps 40L can stably hold the film 1 during the holding step. As a result, the distance between the plurality of first clamps 40R can be sufficiently and smoothly changed during the extension step, and a phase difference film with suppressed alignment angle shift can be stably manufactured.

[0013] During the release step, the plurality of first clamps 40R typically move along the length of the film 1 while releasing the first end 1R of the film 1 (see Figure 3). Also, during the release step, the plurality of second clamps 40L typically move along the length of the film 1 while releasing the second end 1L of the film 1 (see Figure 3). In the extension step, if the distance between the plurality of first clamps is greater than the distance between the plurality of second clamps, the second clamp on the slow-moving side may be pulled by the first clamp on the advancing side through the membrane. In this case, there is a concern that in the release step, the distance between the plurality of second clamps may become too narrow, causing blockage and hindering the smooth movement of the plurality of second clamps. In contrast, in one embodiment, the method for manufacturing the phase difference film further includes a second spacing adjustment step. In this second spacing adjustment step, after the release step described above, the distance between the plurality of first clamps 40R and the distance between the plurality of second clamps 40L are adjusted. Therefore, during the release step, blockage of the plurality of second clamps can be suppressed, thereby enabling the plurality of second clamps to move smoothly.

[0014] In one embodiment, the method for manufacturing a phase difference thin film further includes a preheating step and a heat-fixing step. The preheating step is performed between the holding step and the stretching step. In the preheating step, the film 1 is preheated to any suitable temperature. The heat-setting step is performed between the stretching step and the release step. In the heat-setting step, the film 1 is heat-set at any suitable temperature.

[0015] B. Extension device Next, referring to FIG1, the extension apparatus 100 capable of continuously performing the above-described phase difference film manufacturing method will be described. The extension device 100 includes: a first extension unit 101R comprising a plurality of first clamps 40R, and a second extension unit 101L comprising a plurality of second clamps 40L.

[0016] The first extension unit 101R and the second extension unit 101L are arranged at intervals from each other in a first direction orthogonal to the vertical direction (usually the vertical direction). In the extension device 100, between the first extension unit 101R and the second extension unit 101L, there are sequentially arranged a holding region A for implementing the holding step, a preheating region B for implementing the preheating step, an extension region C for implementing the extension step, a heat-fixing region D for implementing the heat-fixing step, and a release region E for implementing the release step. Furthermore, these regions are not mechanically or structurally independent areas. Also, the length ratios of the regions in the extension device of FIG1 sometimes differ from the actual length ratios.

[0017] Furthermore, an area for performing any appropriate treatment can be provided between the extension area C and the heat-fixing area D, as needed. For example, lateral shrinkage treatment can be cited as such a treatment. Also, the aforementioned extension device typically includes a heating device (e.g., various ovens of hot air, near-infrared, and far-infrared types) to create a heating environment from the preheating area B to the heat-fixing area D or the release area E.

[0018] The first extension unit 101R has a configuration in which the spacing between a plurality of first clamps 40R can be changed (variable spacing type). In one embodiment, the first extension unit 101R includes a reference track 10, a spacing setting track 20, a plurality of clamp support members 30, a linkage mechanism 80 (see Figure 5), a plurality of first clamps 40R, a driving means 50, an upstream spacing control wheel 60, and a downstream spacing control wheel 70.

[0019] B-1. Reference Track The reference track 10 typically has a ring shape. The reference track 10 has a first bend 10a, a second bend 10b, a third bend 10c, and a fourth bend 10d. The first bend 10a and the second bend 10b are separated in a second direction orthogonal to the vertical direction and the first direction. The first bend 10a is located in the second direction on the side opposite to the extension region C relative to the holding region A. The second bend 10b is located in the second direction on the side opposite to the extension region C relative to the release region E. The third bend 10c is separated from the second bend 10b in the first direction. The fourth bend 10d is separated from the third bend 10c in the second direction and from the first bend 10a in the first direction. The central angle of each of the first bend 10a, the second bend 10b, the third bend 10c and the fourth bend 10d is usually 90°.

[0020] In the example shown, the portion of the reference track 10 corresponding to the holding region A and the preheating region B extends along the second direction. Furthermore, the portion of the reference track 10 corresponding to the extension region C extends in a direction intersecting the second direction, moving away from the second extension unit 101L as it moves closer to the heat-fixing region D from the preheating region B. Also, the portion of the reference track 10 corresponding to the heat-fixing region D and the release region E extends along the second direction. Furthermore, the configuration of the reference track 10 is not limited to the example shown in the figure above. For example, the portion of the reference track 10 corresponding to the holding region A to the release region E can also extend linearly along the second direction.

[0021] B-2. Spacing Setting Track The spacing setting track 20 is typically positioned at predetermined intervals inside the reference track 10. The spacing setting track 20 is movable relative to the reference track 10. In the example shown, the spacing setting track 20 has an annular shape along the reference track 10.

[0022] B-3. ​​Fixture support components As shown in Figures 5 and 6, in one embodiment, a plurality of clamp support members 30 are disposed above a reference track 10 and a spacing setting track 20. The plurality of clamp support members 30 are generally arranged along the reference track 10 and are guided by the reference track 10 to move in a circular pattern. Each of the plurality of clamp support members 30 generally extends in a direction orthogonal to the reference track 10. A plurality of clamp support members 30 respectively support the first clamp 40R. More specifically, one end of the first support member 30R in the extension direction supports the first clamp 40R.

[0023] In the example shown in the figure, the clamp support member 30 includes a frame 31, a first axis member 33, a second axis member 34, and a slider 32.

[0024] Frame 31 extends in a direction orthogonal to reference track 10. In one embodiment, viewed from the direction of movement of clamp support member 30, frame 31 has a generally rectangular frame shape. Frame 31 has an elongated hole 31a. The elongated hole 31a is formed in the upper beam of frame 31. The elongated hole 31a extends in the same direction as the upper beam of frame 31.

[0025] The first shaft member 33 extends vertically. The first shaft member 33 passes through the clamp support member 30 between the first clamp 40R and the elongated hole 31a. A guide roller is rotatably disposed at the lower end of the first shaft member 33 (not shown). The guide roller is embedded in a groove (not shown) provided by the reference track 10.

[0026] The second shaft member 34 extends vertically. The second shaft member 34 is located on the side opposite to the first clamp 40R relative to the first shaft member 33 and passes through the clamp support member 30. A spacing setting roller is rotatably disposed at the lower end of the second shaft member 34 (not shown). The spacing setting roller is embedded in a groove (not shown) provided in the spacing setting track 20. In the example shown, the upper end of the second shaft member 34 is inserted into the elongated hole 31a.

[0027] The slider 32 is guided by the inner surface of the elongated hole 31a and can slide relative to the frame 31. In the example shown, it is located at the upper end of the second shaft member 34.

[0028] The clamp support member 30 may further include a drive roller 39. The drive roller 39 can engage with the drive means 50. In the example shown, the drive roller 39 is disposed at the upper end of the first shaft member 33.

[0029] B-4. Linkage Mechanism The linkage mechanism 80 is configured to change the distance between a plurality of clamp support members 30 by changing the interval between the reference track 10 and the spacing setting track 20. In one embodiment, the linkage mechanism 80 has a scaling device structure. As shown in Figure 6, the linkage mechanism 80 has a plurality of main linkage components 81 and a plurality of secondary linkage components 82.

[0030] A plurality of main connecting rod members 81 respectively connect a first shaft member 33 of one adjacent clamp support member 30 to a second shaft member 34 of another adjacent clamp support member 30. In the example shown, one end of the main connecting rod member 81 is rotatably connected to the first shaft member 33 relative to the first shaft member 33. The other end of the main connecting rod member 81 is rotatably connected to the second shaft member 34 relative to the second shaft member 34.

[0031] A plurality of secondary link members 82 respectively connect the main link member 81 to a first shaft member 33 that is not connected to the main link member 81. In the example shown, one end of the secondary link member 82 is rotatably connected to the main link member 81 relative to the main link member 81 via a pivot 87. The other end of the secondary link member 82 is rotatably connected to the first shaft member 33 relative to the first shaft member 33.

[0032] As shown in Figure 5, if the gap between the reference track 10 and the spacing setting track 20 increases relatively, the slider 32 moves away from the reference track 10 within the elongated hole 31a. This causes the main connecting rod member 81 and the secondary connecting rod member 82 to tilt, and the adjacent clamp support members 30 move closer together. As a result, the distance between the plurality of first clamps 40R decreases. On the other hand, as shown in Figure 6, if the interval between the reference track 10 and the spacing setting track 20 becomes relatively smaller, the slider 32 moves closer to the reference track 10 within the elongated hole 31a. This causes the main connecting rod member 81 and the secondary connecting rod member 82 to stand upright, and the adjacent clamp support members 30 to move further apart. As a result, the distance between the plurality of first clamps 40R increases.

[0033] B-5. Fixture A plurality of first clamps 40R are supported on corresponding clamp support members 30. The first clamps 40R are located on the side opposite to the reference track 10 and the spacing setting track 20 in a direction orthogonal to the reference track 10.

[0034] As shown in Figure 3, the first clamp 40R is configured to hold the first end 1R of the film 1. In one embodiment, the first clamp 40R is capable of clamping the first end 1R of the film 1 in the thickness direction of the film 1. In the example shown, the first clamp 40R includes a base 401 and a clamping part 402. The base 401 is fixed to one end of the first support member 30R in the extending direction. The clamping part 402 is supported at one end of the first support member 30R in the extending direction so as to be movable relative to the base 401 along the thickness direction of the film 1.

[0035] B-6. Driving methods As shown in Figure 1, the drive means 50 is configured to apply driving force to a plurality of clamp support members 30. The drive means 50 is disposed at any suitable position. In the example shown, the drive means 50 is disposed inside the spacing setting track 20. In the first direction, the drive means 50 is located at a distance from the downstream spacing control wheel 70 on the side opposite to the second extension unit 101L.

[0036] In one embodiment, the drive means 50 is a sprocket 50a. The sprocket 50a is capable of rotating about an axis extending in the vertical direction. The sprocket 50a is configured to receive driving force from the motor 90. In the example shown, if the driving force from the motor 90 is input to the sprocket 50a, the sprocket 50a will rotate and selectively engage with the drive roller 39 of the clamp support member 30. In this way, the driving force is sequentially transmitted to a plurality of clamp support members 30, causing the plurality of clamp support members 30 to move around.

[0037] B-7. Upstream Side Spacing Control Wheel The upstream side spacing control wheel 60 is configured to adjust the distance between a plurality of first clamps 40R. The upstream side spacing control wheel 60 is typically located upstream of the holding region A (i.e., opposite to the extension region C relative to the holding region A) in the circumferential movement direction of the plurality of clamp support members 30. In one embodiment, the upstream side spacing control wheel 60 is located between the holding region A and the fourth bend 10d in the circumferential movement direction of the plurality of clamp support members 30. In the example shown, the upstream side spacing control wheel 60 is arranged along the first bend 10a of the reference track 10.

[0038] As shown in Figure 7, the upstream side spacing control wheel 60 can rotate about an axis extending in the vertical direction. The upstream side spacing control wheel 60 is configured to be driven by a motor, but is not shown in the figure. The outer diameter of the upstream side spacing control wheel 60 is, for example, 10cm~120cm, and preferably 30cm~100cm.

[0039] In the example shown, a plurality of recesses 61 are provided on the circumferential surface of the upstream spacing control wheel 60. Each of the plurality of recesses 61 is generally configured to receive the end portion of the frame 31 opposite to the first clamp 40R. The plurality of recesses 61 are equally spaced from each other in the circumferential direction of the upstream spacing control wheel 60. Viewed from above, each of the plurality of recesses 61 has a generally V-shaped shape that opens radially outward toward the upstream spacing control wheel 60. There is no particular limitation on the number of multiple recesses 61. For example, the number of multiple recesses 61 can be 2 to 10, but preferably 4 to 6. The depth of the plurality of recesses 61 (the radial dimension of the upstream side spacing control wheel 60) is, for example, 5cm to 100cm, preferably 20cm to 80cm.

[0040] B-8. Downstream Side Spacing Control Wheel As shown in Figure 1, the downstream side spacing control wheel 70 is configured to adjust the spacing between a plurality of first clamps 40R. The downstream side spacing control wheel 70 is typically located further downstream of the release region E (i.e., opposite to the extension region C relative to the release region E) in the circumferential movement direction of the plurality of clamp support members 30. In one embodiment, the downstream side spacing control wheel 70 is located between the release region E and the third bend 10c in the circumferential movement direction of the plurality of clamp support members 30. In the example shown, the upstream side spacing control wheel 60 is configured along the second bend 10b of the reference track 10.

[0041] As shown in Figure 7, the downstream side spacing control wheel 70 typically has the same configuration as the upstream side spacing control wheel 60 described above. Therefore, a detailed description of the downstream side spacing control wheel 70 is omitted.

[0042] B-9. Second Extension Unit As shown in Figure 1, the second extension unit 101L has a configuration in which the distance between a plurality of second clamps 40L can be changed (variable spacing type). The second extension unit 101L typically has a configuration that is linearly symmetrical to the first extension unit 101R with respect to the second direction. The second extension unit 101L is described in the same manner as the first extension unit 101R, except that it has a plurality of second clamps 40L replacing a plurality of first clamps 40R. Therefore, a description of the configuration of the second extension unit 101L is omitted.

[0043] C. Details of the manufacturing method of the phase retardation thin film Next, the method for manufacturing a phase difference film by means of the extension device 100 will be explained. In one embodiment, the extension device 100 sequentially performs the first spacing adjustment step, the holding step, the preheating step, the extension step, the heat fixing step, the release step, and the second spacing adjustment step.

[0044] C-1. First Spacing Adjustment Step In the first spacing adjustment step, the distance between the plurality of first clamps 40R and the distance between the plurality of second clamps 40L are substantially the same by means of the upstream side spacing control wheel 60.

[0045] More specifically, firstly, in the first extension unit 101R and the second extension unit 101L, the driving force from the motor 90 is input to the sprocket 50a. Therefore, in the example shown, the plurality of clamp support members 30 of the first extension unit 101R, driven by the sprocket 50a, move clockwise when viewed from above. Consequently, the plurality of first clamps 40R and the plurality of clamp support members 30 similarly move clockwise when viewed from above. Furthermore, the plurality of clamp support members 30 of the second extension unit 101L are driven by a sprocket 50a and move counterclockwise when viewed from above. In this way, the plurality of second clamps 40L and the plurality of clamp support members 30 also move counterclockwise when viewed from above. Furthermore, the moving speeds of the plurality of first clamps 40R in the first extension unit 101R and the plurality of second clamps 40L in the second extension unit 101L can be independently controlled to arbitrary values ​​by adjusting the output of the motor 90 to change the driving force transmitted from the sprocket 50a to the clamp support member 30.

[0046] Furthermore, in the first extension unit 101R and the second extension unit 101L, the driving force from the motor (not shown) is input to the upstream side spacing control wheel 60 and the downstream side spacing control wheel 70, respectively. Therefore, the upstream side spacing control wheel 60 and the downstream side spacing control wheel 70 of the first extension unit 101R rotate clockwise when viewed from above. Furthermore, the upstream side spacing control wheel 60 and the downstream side spacing control wheel 70 of the second extension unit 101L rotate counterclockwise when viewed from above. The rotational speed of the upstream spacing control wheel 60 of the first extension unit 101R is substantially the same as that of the upstream spacing control wheel 60 of the second extension unit 101L. Furthermore, the rotational speed of the downstream spacing control wheel 70 of the first extension unit 101R is substantially the same as that of the downstream spacing control wheel 70 of the second extension unit 101L.

[0047] In the first spacing adjustment step, if the upstream spacing control wheel 60 rotates in each of the first extension unit 101R and the second extension unit 101L, the ends of the frames 31 of the plurality of clamp support members 30 are sequentially inserted into the recesses 61 of the upstream spacing control wheel 60. In this way, the distance between the plurality of first clamps 40R in the first extension unit 101R is substantially the same as the distance between the plurality of second clamps 40L in the second extension unit 101L. In other words, the phase of the plurality of first clamps 40R is consistent with the phase of the plurality of second clamps 40L at a predetermined interval. At this point, as shown in Figure 4, the imaginary line segment connecting the center of the first clamp 40R and the center of the second clamp 40L is substantially orthogonal to the film conveying direction (second direction). The angle between this imaginary line segment and the film conveying direction (second direction) is, for example, 87°~93°, preferably 89°~91°, more preferably 89.5°~90.5°, and even more preferably 90°. In the first spacing adjustment step, the distance between the multiple first clamps 40R after adjustment is, for example, 100mm~200mm, preferably 125mm~175mm, and more preferably 140mm~160mm. When the distance between the plurality of first fixtures 40R is set to 100%, the distance between the plurality of second fixtures 40L after adjustment in the first distance adjustment step is, for example, 97%~103%, preferably 99%~101%, more preferably 99.5%~100.5%, and even more preferably 100%.

[0048] C-2. Holding Steps As shown in Figure 1, in the holding step, a strip-shaped film 1 is typically supplied along the second direction to the holding region A located between the first extension unit 101R and the second extension unit 101L.

[0049] Film 1 is composed of any suitable resin material. Examples of resin materials include: polycarbonate resins, polyvinyl acetal resins, cycloolefin resins, acrylic resins, cellulose ester resins, cellulose resins, polyester resins, polyester carbonate resins, olefin resins, and polyurethane resins; polycarbonate resins are a preferred example. Resin materials can be used alone or in combination.

[0050] As a polycarbonate resin, examples of polycarbonate resins that contain structural units derived from dihydroxy compounds are worth mentioning. Specific examples of dihydroxy compounds include: 9,9-bis(4-hydroxyphenyl) bacon, 9,9-bis(4-hydroxy-3-methylphenyl) bacon, 9,9-bis(4-hydroxy-3-ethylphenyl) bacon, 9,9-bis(4-hydroxy-3-n-propylphenyl) bacon, 9,9-bis(4-hydroxy-3-isopropylphenyl) bacon, 9,9-bis(4-hydroxy-3-n-butylphenyl) bacon, 9,9-bis(4-hydroxy-3-secondary butylphenyl) bacon, 9,9-bis(4-hydroxy-3-tertiary butylphenyl) bacon, 9,9-bis(4-hydroxy-3-cyclohexylphenyl) bacon, 9,9-bis(4-hydroxy-3-phenylphenyl) bacon, 9,9-bis(4-(2-hydroxyethoxy)phenyl) bacon, 9,9-bis(4-( 2-Hydroxyethoxy)-3-methylphenyl) fu, 9,9-bis(4-(2-hydroxyethoxy)-3-isopropylphenyl) fu, 9,9-bis(4-(2-hydroxyethoxy)-3-isobutylphenyl) fu, 9,9-bis(4-(2-hydroxyethoxy)-3-tert-butylphenyl) fu, 9,9-bis(4-(2-hydroxyethoxy)-3-cyclohexylphenyl) fu, 9,9-bis(4-(2-hydroxyethoxy)-3-phenylphenyl) fu, 9,9-bis(4-(2-hydroxyethoxy)-3,5-dimethylphenyl) fu, 9,9-bis(4-(2-hydroxyethoxy)-3-tert-butyl-6-methylphenyl) fu, 9,9-bis(4-(3-hydroxy-2,2-dimethylpropoxy)phenyl) fu. In addition to structural units derived from the aforementioned dihydroxy compounds, polycarbonate resins may also contain structural units derived from dihydroxy compounds such as isosorbide, dehydromannitol, isotretinoin, spirodiol, dialkyl glycol, diethylene glycol (DEG), triethylene glycol (TEG), polyethylene glycol (PEG), cyclohexanediethanol (CHDM), tricyclodecanediethanol (TCDDM), and bisphenols.

[0051] Details of the polycarbonate resins described above are described, for example, in Japanese Patent Application Publication No. 2012-67300 and Japanese Patent No. 3325560. The descriptions in these patent documents are incorporated herein by reference.

[0052] The glass transition temperature of this resin material is preferably between 110°C and 250°C, and more preferably between 120°C and 230°C. If the glass transition temperature is too low, the heat resistance tends to deteriorate, which may cause dimensional changes after film formation. If the glass transition temperature is too high, the forming stability of the film may deteriorate, and the transparency of the film may be compromised. Furthermore, the glass transition temperature is determined according to JIS K 7121 (1987).

[0053] The width of film 1 is, for example, 500cm~2000cm, preferably 650cm~1500cm. The thickness of film 1 is, for example, 30μm~200μm, preferably 60μm~150μm.

[0054] In the example shown, in the holding region A, the reference track 10 of the first extension unit 101R and the reference track 10 of the second extension unit 101L extend along the second direction (the length direction of the film 1) and are substantially parallel. Therefore, in the holding region A, a plurality of first clamps 40R with consistent spacing due to the first spacing adjustment step are arranged along the second direction (the length direction of the film 1), and a plurality of second clamps 40L with consistent spacing due to the first spacing adjustment step are arranged along the second direction (the length direction of the film 1).

[0055] In one embodiment, the two ends of the film 1 in the width direction are held in the holding region A by the first clamp 40R and the second clamp 40L. More specifically, the first clamp 40R holds the first end 1R of the film 1 when it moves to any position, and the second clamp 40L holds the second end 1L of the film 1 when it moves to any position. At this time, the holding time of the first clamp 40R and the holding time of the second clamp 40L should be simultaneous.

[0056] As shown in Figure 3, in one embodiment, the holding area of ​​the film 1 of each of the plurality of first clamps 40R is substantially the same as the holding area of ​​the film 1 of each of the plurality of second clamps 40L. The holding area of ​​the first clamp 40R is specifically the area of ​​the portion of the film 1 clamped between the base 401 and the pressing part 402, and is preferably 50 cm2 to 200 cm2. When the holding area of ​​the first clamp 40R is set to 100%, the holding area of ​​the second clamp 40L is, for example, 97% to 103%, preferably 99% to 101%, more preferably 99.5% to 100.5%, and even more preferably 100%. If the holding areas of the first clamp and the second clamp are within this range, then even if the film has the aforementioned in-plane birefringence Δn(550), stress concentration on the film can be stably suppressed during the stretching step. As a result, the load applied to the stretching device can be suppressed, thereby suppressing, for example, the bending of the reference track.

[0057] C-3. Preheating Steps As shown in Figure 1, the film 1 is conveyed to the preheating zone B along with the movement of the first clamp 40R and the second clamp 40L. In preheating zone B, a preheating step is performed, during which the film 1 is heated (preheated) while being transported by the first clamp 40R and the second clamp 40L. In preheating zone B, the reference track 10 of the first extension unit 101R and the reference track 10 of the second extension unit 101L are substantially parallel. Therefore, in the example shown, in preheating zone B, the film 1 is heated without undergoing either lateral or longitudinal extension. However, to avoid adverse conditions such as film deflection due to preheating and contact with the nozzles inside the oven, the distance (in the width direction) between the first clamp 40R and the second clamp 40L can be slightly increased.

[0058] The preheating temperature T1 in the preheating step is, for example, above the glass transition temperature (Tg) of film 1, preferably above Tg+2°C, and more preferably above Tg+5°C. On the other hand, the preheating temperature T1 is, for example, below Tg+40°C, preferably below Tg+30°C. The preheating temperature T1 can be adjusted appropriately according to the material of film 1. The preheating temperature T1 is, for example, 70°C to 190°C, preferably 80°C to 180°C.

[0059] The heating time to reach the preheating temperature T1 and the holding time at the preheating temperature T1 can be appropriately set according to the constituent materials of the film or manufacturing conditions (e.g., the film conveying speed). These heating times and holding times can be controlled by adjusting the moving speed of the first clamp 40R and the second clamp 40L, the length of the preheating zone, and the temperature of the preheating zone.

[0060] C-4. Extension Steps Subsequently, the film 1 is conveyed to the extension area C along with the movement of the first clamp 40R and the second clamp 40L. In the extension region C, an extension step is performed to extend the thin film 1 obliquely. This process fabricates a phase retardation thin film. During the extension step, while varying (increasing and / or decreasing) the distance between the plurality of first clamps 40R, the plurality of first clamps 40R and the plurality of second clamps 40L are moved at least along the second direction (the length direction of the film 1). In the example shown, the distance between the plurality of first clamps 40R is greater than the distance between the plurality of second clamps 40L. During the extension step, the distance between the plurality of second clamps 40L can vary (increasing and / or decreasing), or the distance between the plurality of second clamps 40L can be kept fixed. In this way, one of the first and second clamps (the first clamp in the example) that simultaneously reaches the extension area arrives at the end of the extension area first. Through this oblique extension, in the film 1, the end of the first clamp side extends at a higher extension ratio than the end of the second (slower) clamp side, resulting in the formation of a slow axis in the desired direction of the film 1 (e.g., a direction at 45° relative to the length direction).

[0061] Details of the oblique extension as described above are described, for example, in Japanese Patent Application Publication No. 2023-46840. The description in that patent document is incorporated herein by reference.

[0062] The extension step may also include lateral extension. In this case, the extension step is, for example, configured as shown in FIG1, performed while increasing the gap (distance in the width direction) between the first clamp 40R and the second clamp 40L.

[0063] When the stretching step includes lateral stretching, the ratio of the width Wfinal of the film after oblique stretching to the lateral (TD) stretching ratio (the initial width Winitial of the film) (Wfinal / Winitial) is, for example, 1.05 to 6.00, preferably 1.10 to 5.00.

[0064] In the extension step, the product of the rate of change of the distance between the first clamps 40R and the rate of change of the clamp spacing of the second clamp 40L is, for example, 0.7 to 1.5, preferably 0.8 to 1.45, and more preferably 0.85 to 1.40. If the product of the rates of change is within this range, a phase difference film with high uniaxiality and in-plane alignment can be manufactured.

[0065] The stretching temperature T2 in the stretching step, relative to the glass transition temperature (Tg) of the thin film, is, for example, Tg-20℃ to Tg+30℃, preferably Tg-10℃ to Tg+20℃, and more preferably Tg. The stretching temperature T2 can be adjusted appropriately according to the material of the thin film 1. The stretching temperature T2 is preferably below 160℃, and more preferably below 150℃. On the other hand, the stretching temperature T2 is, for example, above 130℃, and preferably above 140℃. If the stretching temperature is within this range, the breakage of the film during the stretching step can be stably suppressed. The difference between the preheating temperature T1 and the stretching temperature T2 (T1-T2) is, for example, ±2°C or more, preferably ±5°C or more. In one embodiment, T1>T2, therefore, the film heated to the preheating temperature T1 in the preheating zone can be cooled to the stretching temperature T2.

[0066] C-5. Heat Fixing Step Subsequently, the stretched film 1 (phase difference film) is transported to the heat fixing region D as the first clamp 40R and the second clamp 40L move. In the heat fixing region D, a heat fixing step is performed, and the stretched film 1 (phase difference film) is heat-treated while being transported by the first clamp 40R and the second clamp 40L. In the heat fixing region D, the reference orbit 10 of the first stretching unit 101R and the reference orbit 10 of the second stretching unit 101L are substantially parallel. Therefore, in the illustrated example, in the heat fixing region D, the film 1 is substantially neither stretched horizontally nor vertically. However, the distance between a plurality of the first clamps 40R may be reduced as needed to relieve stress.

[0067] The heat fixing temperature T3 in the heat fixing step varies depending on the film to be stretched. Sometimes T2≥TЗ, and sometimes T2<T3. Generally, when the film is an amorphous material, T2≥T3 is set, and when the film is a crystalline material, crystallization treatment can be performed by setting T2<T3. In the case of T2≥T3, the difference between the temperature T2 and T3 (T2 - T3) is, for example, 0°C to 50°C. The heat fixing time is, for example, 10 seconds to 10 minutes. The heat treatment time can be controlled by adjusting the length of the heat treatment region and / or the transport speed of the film. >

[0068] C-6. Release Step Subsequently, the phase difference film after heat fixing is transported to the release region E as the first clamp 40R and the second clamp 40L move. In the release region E, a release step is performed, and the first end 1R of the phase difference film is released from the first clamp 40R and the second end 1L of the phase difference film is released from the second clamp 40L at an arbitrary position. More specifically, when the first clamp 40R reaches an arbitrary position by moving, the first end 1R of the film 1 is released, and when the second clamp 40L reaches an arbitrary position by moving, the second end 1L of the film 1 is released. In the release region E, the reference orbit 10 of the first stretching unit 101R and the reference orbit 10 of the second stretching unit 101L are substantially parallel. Therefore, in the illustrated example, in the release region E, the phase difference film after heat fixing is cooled to the required temperature without being stretched horizontally or vertically and then released from the first clamp and the second clamp.

[0069] The temperature of the phase difference film when released from the first and second clamps is, for example, below 150°C, preferably 70°C to 140°C, and more preferably 80°C to 130°C.

[0070] The phase retardation film obtained by extending film 1 is thus obtained. Details regarding the phase retardation film will be described below.

[0071] C-7. Second Spacing Adjustment Step In the second spacing adjustment step, the distance between the plurality of first clamps 40R after the first end 1R of the release film 1 and the distance between the plurality of second clamps 40L after the second end 1L of the release film 1 are adjusted by the downstream spacing control wheel 70. More specifically, the distance control wheel 70 of the downstream side of the first extension unit 101R is reached through a plurality of first clamps 40R in the release area E. Also, the distance control wheel 70 of the downstream side of the second extension unit 101L is reached through a plurality of second clamps 40L in the release area E. Therefore, in each of the first extension unit 101R and the second extension unit 101L, the ends of the frames 31 of the plurality of clamp support members 30 are sequentially embedded in the recesses 61 of the downstream spacing control wheel 70. This allows for the appropriate adjustment of the distance between the plurality of first clamps 40R in the first extension unit 101R and the distance between the plurality of second clamps 40L in the second extension unit 101L. In one embodiment, the phases of the plurality of first clamps 40R and the phases of the plurality of second clamps 40L are aligned at a predetermined interval.

[0072] In the second spacing adjustment step, the distance between the multiple first clamps 40R after adjustment is, for example, 40mm~200mm, preferably 60mm~190mm, and more preferably 80mm~180mm. When the distance between the plurality of first fixtures 40R is set to 100%, the distance between the plurality of second fixtures 40L after adjustment in the second distance adjustment step is, for example, 30% to 100%, preferably 40% to 100%, more preferably 50% to 100%, and even more preferably 100%.

[0073] Subsequently, in the second spacing adjustment step, a plurality of first clamps 40R, whose spacing has been adjusted, move around the reference track 10 and are then sent back to the first spacing adjustment step. Also, in the second spacing adjustment step, a plurality of second clamps 40L, whose spacing has been adjusted, move around the reference track 10 and are then sent back to the first spacing adjustment step.

[0074] In such an extension device 100, it is possible to continuously manufacture a long strip-shaped retardation film having a desired in-plane retardation. In one embodiment, the refractive indices of the retardation film exhibit a relationship of nx > ny. The retardation film preferably functions as a λ / 4 plate. When the retardation film functions as a λ / 4 plate, the in-plane retardation Re(550) of the retardation film (λ / 4 plate) is, for example, 100 nm to 180 nm, preferably 135 nm to 155 nm. In another embodiment, the retardation film can function as a λ / 2 plate. When the retardation film functions as a λ / 2 plate, the in-plane retardation Re(550) of the retardation film (λ / 2 plate) is, for example, 230 nm to 310 nm, preferably 250 nm to 290 nm.

[0075] Furthermore, the retardation film preferably exhibits a wavelength dependence of so-called inverse dispersion. Specifically, its in-plane retardation satisfies the relationship of Re(450) < Re(550) < Re(650). Re(450) / Re(550) is, for example, 0.8 or more and less than 1.0, preferably 0.8 to 0.95. Re(550) / Re(650) is, for example, 0.8 or more and less than 1.0, preferably 0.8 to 0.97.

[0076] [Examples] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited by these examples. The measurement methods for each characteristic are as follows. The measurement methods for each characteristic in the examples and comparative examples are as follows.

[0077] (1) In-plane birefringence Δn(550) Using Axoscan (manufactured by Axometrics), the in-plane birefringence of the films fed into the holding step in the examples and comparative examples was automatically measured. The measurement wavelength was 550 nm, and the measurement temperature was 23°C. The results are shown in Table 1.

[0078] (2) Track load A pressure measuring device was set on the reference track after the release step in the examples and comparative examples, and the load on the reference track in the extension step was evaluated based on the following criteria. The results are shown in Table 1. Good: The load applied to the track is 50 kN or less. Poor: The load applied to the track exceeds 50 kN.

[0079] (3) Fracture The fabrication of the phase retardation thin films in the Examples and Comparative Examples were evaluated against the following benchmarks. The results are shown in Table 1. Good: The resin film is extended in the stretching device without breaking. Defect: The resin film breaks from the center or end in the stretching device.

[0080] <<Preparation of the Film>> <Preparation Example 1> A PC (polycarbonate) resin film was prepared in the same manner as in Manufacturing Example 9 of Japanese Patent Application Publication No. 2022-150732. The PC resin film is elongated and has a thickness of 130 μm. The in-plane birefringence Δn of the PC resin film in Preparation Example 1 is 0.004. <Preparation Example 2> A PC-based resin (manufactured by Mitsubishi Chemical Corporation, trade name "D5380R-3") was prepared. A thin film was then prepared using the same method as in Example 9 of Japanese Patent Application Publication No. 2022-150732. The PC-based resin film was elongated and had a thickness of 100 μm. The in-plane birefringence Δn of the PC-based resin film in Example 2 was 0.006. <Preparation Example 3> A COP (cyclo-olefin polymer) based resin film (manufactured by Zeon Corporation, Japan, trade name "ZF16") was prepared. The COP based resin film was elongated and had a thickness of 120 μm. The in-plane birefringence Δn of the COP based resin film in Example 3 was 0.007. <Preparation Example 4> An acrylic resin film (manufactured by Kaneka Corporation, product name "HTX-Z") was prepared. The acrylic resin film was elongated and 100 μm thick. The in-plane birefringence Δn of the acrylic resin film in Example 4 was 0.001.

[0081] [Example 1] The PC-based resin film prepared in Example 1 is placed in the stretching device shown in Figure 1. The stretching device includes a first stretching unit comprising a plurality of first clamps and a second stretching unit comprising a plurality of second clamps. The reference rails of the first stretching unit and the second stretching unit are made of high manganese steel. More specifically, the first end of the PC resin film in the width direction is held by a plurality of first clamps, and the second end of the PC resin film in the width direction is held by a plurality of second clamps (holding step). The area of ​​the PC resin film held by one clamp (first clamp or second clamp) (held area) is shown in Table 1.

[0082] Subsequently, the PC resin film is preheated to 150°C (preheating step). Subsequently, while varying the distance between the plurality of first clamps, the plurality of first clamps and the plurality of second clamps are moved along the length direction, and the PC resin film is stretched in an oblique direction intersecting both the length direction and the width direction (stretching step). The temperature during the stretching step (stretching temperature) is shown in Table 1. The ratio of the width of the PC resin film after oblique extension to the initial width of the PC resin film is 1.84.

[0083] Subsequently, the stretched PC resin film was heat-cured at 140°C (heat curing step). Then, the first end of the PC resin film is released from a plurality of first clamps, and the second end of the PC resin film is released from a plurality of second clamps (release step). The phase retardation film was obtained from the above. The thickness of the phase retardation film is 57 μm. The in-plane phase difference Re(550) of the phase retardation film is shown in Table 1.

[0084] [Example 2] The PC-based resin film of Preparation Example 1 was replaced with the COP-based resin film of Preparation Example 2. The holding area of ​​the clamp was changed to 200 cm², and the stretching temperature was changed to 136°C. Otherwise, the phase retardation film was obtained in the same manner as in Example 1. The thickness of the phase retardation film was 53 μm.

[0085] [Example 3] The PC-based resin film of Preparation Example 1 was changed to the PC-based resin film of Preparation Example 2, and the stretching temperature was changed to 134°C. Otherwise, the phase retardation film was obtained in the same manner as in Example 1. The thickness of the phase retardation film was 45 μm.

[0086] [Comparative Example 1] The clamp holding area was changed to 100 cm2 and the extension temperature was changed to 185°C. Otherwise, it was carried out in the same way as in Example 1, and the PC resin film broke.

[0087] [Comparative Example 2] The clamp holding area was changed to 5 cm2, and otherwise carried out in the same manner as in Example 1. As a result, the PC resin film broke.

[0088] [Comparative Example 3] The PC-based resin film of Preparation Example 1 was replaced with the acrylic-based resin film of Preparation Example 4, and the stretching temperature was changed to 125°C. Otherwise, a phase retardation film was obtained in the same manner as in Example 1. The thickness of the phase retardation film was 44 μm.

[0089] [Table 1]

[0090] [evaluate] As can be clearly seen from Table 1, if the holding area of ​​the fixture is 10cm2~300cm2, even if the film with in-plane birefringence Δn(550) is less than 0.009 is obliquely extended at 180°C, stress concentration in the fixture can be suppressed during the extension step. As a result, the load on the reference track of the extension device can be reduced. Furthermore, it is known that if the stretching temperature is below 180°C, the breakage of the phase retardation film during the stretching step can be stably suppressed. It is further known that if the in-plane birefringence Δn(550) of the film sent into the holding step is above 0.002, sufficient in-plane phase retardation can be exhibited in the phase retardation film. Therefore, it is possible to stably manufacture phase difference films with the desired in-plane phase difference.

[0091] [Industrial Applicability] The method for manufacturing the phase retardation thin film of the present invention can, for example, help in the manufacture of image display devices such as liquid crystal display (LCD) and organic light-emitting diode (OLED).

[0092] 1: film 1L: Second end 1R: First end 10: Reference Orbit 10a: First bend 10b: Second bend 10c: Third bend 10d: 4th bend 20: Spacing Setting Track 30: Fixture support component 31: Framework 31a: Elongated hole 32: Slider 33: First Axis Component 34: Second Axis Component 39: Drive roller 40L: Second clamp 40R: First clamp 50: Driving methods 50a: Sprocket 60: Upstream side spacing control wheel 61: concave part 70: Downstream side spacing control wheel 80: Linkage Mechanism 81: Main connecting rod component 82: Secondary connecting rod components 87: Pivot 90: Motor 100: Extension device 101L: Second Extension Unit 101R: First Extension Unit 401:pedestal 402: Press-fit section A: Fixed Area B: Preheating area C: Extended Area D: Heat-fixed area E: Release area

Claims

1. A method for manufacturing a phase retardation thin film, comprising the following steps in sequence: a holding step, wherein a first end of a strip-shaped thin film in the width direction is held by a plurality of first clamps arranged along the length direction of the thin film, and a second end of the thin film in the width direction is held by a plurality of second clamps arranged along the length direction; an extending step, wherein the plurality of first clamps and the plurality of second clamps are moved along the length direction while the distance between the plurality of first clamps is changed, and the thin film is extended in an oblique direction intersecting both the length direction and the width direction; and a releasing step, wherein the first end of the thin film is released from the plurality of first clamps, and the second end of the thin film is released from the plurality of second clamps; wherein the in-plane birefringence Δn(550) of the thin film is 0.002 to 0.009, and the temperature in the extending step is below 180°C. In the aforementioned holding step, the holding area of ​​the aforementioned film of each of the plurality of first clamps is substantially the same as the holding area of ​​the aforementioned film of each of the plurality of second clamps, and is 10 cm2 to 300 cm2.

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