Film stretching device

Abstract

To provide a film stretching device that can suppress unevenness in the thickness of a stretched film.SOLUTION: A film stretching device 1 according to one aspect of the present invention includes a pair of tension rolls 11, 12 across which a film F is stretched, a heater 40 that heats the film F between the pair of tension rolls 11, 12, and supporting members 51, 52 which support the tension rolls 11, 12 below the film F.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a film stretching apparatus. [Background technology]

[0002] A stretching device is used to heat and stretch a web of film in the transport direction while transporting it. During this type of stretching, the film may shrink in the width direction, resulting in thickness and phase variations. Patent Document 1 proposes a technology for suppressing shrinkage of the film in the width direction by optimizing the heater arrangement. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-139946 Summary of the Invention [Problem to be solved by the invention]

[0004] The required specifications for films are becoming increasingly higher, and technology that can further suppress unevenness in film thickness and phase due to stretching is desired. Therefore, an object of the present invention is to provide a film stretching device that can suppress unevenness (variation) in the thickness of a stretched film. [Means for solving the problem]

[0005] (1) A film stretching device according to one embodiment of the present invention includes a pair of tension rolls over which a film is tensioned, a heater for heating the film between the pair of tension rolls, and a support for supporting the tension rolls below the film.

[0006] (2) In the film stretching device of (1), the support may be in continuous contact with the tension roll over the entire length of the region in contact with the film.

[0007] (3) In the film stretching device of (2), the support may be a pair of rotatable support rolls that respectively support the pair of tension rolls.

[0008] (4) In the film stretching device of (2), the support may be a single support roll that supports both of the pair of tension rolls.

[0009] (5) In the film stretching apparatus of (3) and (4), at least the outer circumferential surface of the support roll may be made of a metal material.

[0010] (6) In the film stretching device according to any one of (1) to (5), the distance between the centers of the pair of tension rolls may be 20 mm or more and 80 mm or less.

[0011] (7) In the film stretching apparatus according to any one of (1) to (6), the heaters may be opposed to each other continuously across the entire width of the film. [Effects of the Invention]

[0012] According to the present invention, unevenness in the thickness of the stretched film can be suppressed. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic diagram showing a film stretching device according to a first embodiment of the present invention. [Figure 2] FIG. 4 is a schematic view showing a film stretching device according to a second embodiment of the present invention. [Figure 3] FIG. 4 is a schematic view showing a film stretching device according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present invention will be described with reference to the drawings. For convenience, hatching and component reference numerals may be omitted. In such cases, other drawings should be referenced. The dimensions of various components in the drawings have been adjusted for clarity. In addition, in embodiments described later, components similar to those in previously described embodiments may be designated by the same reference numerals, and redundant explanations may be omitted.

[0015] First Embodiment 1 is a schematic diagram showing a film stretching apparatus 1 according to a first embodiment of the present invention. The film stretching apparatus 1 includes a first tension roll 11, a second tension roll 12, a first drive roll 21, a second drive roll 22, a first nip roll 31, a second nip roll 32, a heater 40, a first support 51, and a second support 52.

[0016] The first tension roll 11 and the second tension roll 12 are arranged in a pair so as to rotate freely in parallel, and a web-like film F is stretched between them. The film F is stretched in the longitudinal direction between the pair of tension rolls 11, 12. The tension rolls 11, 12 use frictional force to prevent the film F from shrinking in the width direction during stretching. To ensure the generation of such frictional force and to ensure a sufficient contact area between the tension rolls 11, 12 and the film F, the diameter of the tension rolls 11, 12 is preferably 20 mm or more. To use tension rolls 11, 12 with such diameters, the center-to-center distance between the tension rolls 11, 12 is preferably 20 mm or more.

[0017] Furthermore, since the effect of preventing shrinkage of the film F in the width direction increases as the distance to the tension rolls 11 and 12 decreases, the tension rolls 11 and 12 are arranged at a relatively short interval to apply a force that suppresses shrinkage in the width direction to the entire region where the film F is stretched. The specific center-to-center distance between the tension rolls 11 and 12 is preferably 80 mm or less, more preferably 60 mm or less, and even more preferably 50 mm or less.

[0018] The wrap angle of film F at tension rolls 11 and 12 is preferably 30° or more, more preferably 45° or more, to obtain a large frictional force. The wrap angle of film F at tension rolls 11 and 12 can be set to 90° or less to avoid interference with supports 51 and 52, etc.

[0019] The first drive roll 21 and the second drive roll 22 are each driven to rotate and transport the film F. In other words, the peripheral speeds of the first drive roll 21 and the second drive roll 22 determine the transport speed of the film F. The peripheral speed of the second drive roll 22 is greater than the peripheral speed of the first drive roll 21. The film F is stretched between the tension rolls 11 and 12 due to the difference in transport speed between the first drive roll 21 and the second drive roll 22.

[0020] The first nip roll 31 and the second nip roll 32 press the film F against the first drive roll 21 and the second drive roll 22, ensuring the transport of the film F by the first drive roll 21 and the second drive roll 22.

[0021] The heater 40 heats the film F between the pair of tension rolls 11, 12. By being heated by the heater 40, the film F stretches in the conveyance direction between the pair of tension rolls 11, 12 so as to absorb the speed difference between the pair of drive rolls 21, 22. To heat the film F evenly in the width direction, the heaters 40 are preferably disposed so as to face each other continuously across the entire width of the film F. For this reason, it is preferable to use a rod-shaped or ribbon-shaped infrared heater that is longer than the width of the film F as the heater 40.

[0022] The first support 51 and the second support 52 are arranged in one-to-one correspondence with the first tension roll 11 and the second tension roll 12, support the first tension roll 11 and the second tension roll 12 below the film F, and prevent the first tension roll 11 and the second tension roll 12 from sagging. It is preferable that the first support 51 and the second support 52 be in continuous contact with the tension rolls 11 and 12 over the entire length of the area where they contact the film F, so as to reliably prevent the tension rolls 11 and 12 from sagging and to prevent temperature unevenness from occurring in the tension rolls 11 and 12.

[0023] In this embodiment, the first support 51 and the second support 52 are rotatable support rolls. By supporting the tension rolls 11 and 12 with the rotatable support rolls 51 and 52, the rotation of the tension rolls 11 and 12 is not hindered, and the stretching rate of the film F can be stabilized. At least the outer circumferential surfaces of the support rolls 51 and 52 are preferably formed from a metal material to suppress temperature unevenness due to heat conduction. Furthermore, if the entire support rolls 51 and 52 are formed from a metal material, the rigidity of the support rolls 51 and 52 can be increased, further suppressing deflection of the tension rolls 11 and 12.

[0024] As described above, the film stretching device 1 prevents deflection of the pair of tension rolls 11, 12 by using the supports 51, 52, so that the tension rolls 11, 12 having small diameters can be arranged with a short center-to-center distance, thereby suppressing the shrinkage in the width direction of the film F during stretching by the frictional force of the tension rolls 11, 12.

[0025] Second Embodiment 2 is a schematic diagram showing a film stretching apparatus 1A according to a second embodiment of the present invention. The film stretching apparatus 1A includes a first tension roll 11, a second tension roll 12, a first drive roll 21, a second drive roll 22, a first nip roll 31, a second nip roll 32, a heater 40, and a common support 53.

[0026] In this embodiment, the common support 53 is a single support roll that supports both of the pair of tension rolls 11 and 12. By supporting the two tension rolls 11 and 12, which have a relatively small diameter, with the single support roll 53, which has a relatively large diameter and high rigidity, it is possible to reduce the distance between the tension rolls 11 and 12 while obtaining a sufficient deflection prevention effect.

[0027] Third Embodiment 3 is a schematic diagram showing a film stretching apparatus 1B according to a second embodiment of the present invention. The film stretching apparatus 1B includes a first tension roll 11, a second tension roll 12, a first drive roll 21, a second drive roll 22, a first nip roll 31, a second nip roll 32, a heater 40, a first support 54, and a second support 55.

[0028] In this embodiment, the first support 54 and the second support 55 are in sliding contact with the tension rolls 11, 12. For this reason, at least the sliding contact surfaces of the first support 54 and the second support 55 with the tension rolls 11, 12 are formed from a material with a low coefficient of friction, such as fluororesin. Because the supports 54, 55 that are in sliding contact with the tension rolls 11, 12 have a high degree of freedom in terms of shape, it is easy to increase the wrap angle of the film F with respect to the tension rolls 11, 12 while reducing the center-to-center distance of the tension rolls 11, 12.

[0029] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and various modifications and variations are possible. For example, a rotatable guide roll that guides the film so as to increase the wrap angle at the tension roll may be disposed between the drive roll and the tension roll. Furthermore, the support may be one that supports the tension roll locally, or may be a multi-stage support roll. [Example]

[0030] The present invention will be specifically described below based on examples, but the present invention is not limited to the following examples.

[0031] A test was conducted in which a 110 μm thick polyimide film was stretched at a stretching ratio of 1.8 times while changing the distance between a pair of tension rolls. The thickness of the stretched film was measured, and the difference between the maximum and minimum values ​​was recorded as thickness unevenness. In addition, the uniformity of transmitted light through the stretched film was visually confirmed using crossed Nicols, and the presence or absence of retardation unevenness was determined. The test results are summarized in Table 1 below.

[0032] [Table 1]

[0033] As described above, it was confirmed that thickness unevenness can be suppressed by reducing the center distance between the tension rolls. [Explanation of symbols]

[0034] 1, 1A, 1B Film stretching device 11 First tension roll 12 Second tension roll 21 First driving roll 22 Second driving roll 31 First nip roll 32 No. 2 nip roll 40 Heater 51 First support (support roll) 52 Second support (support roll) 53 Common support (support roll) 54 First support 55 Second support F film

Claims

1. A pair of tension rolls on which the film is stretched; a heater that heats the film between the pair of tension rolls; a support that supports the tension roll below the film; A film stretching apparatus comprising:

2. The film stretching apparatus according to claim 1 , wherein the support is in continuous contact with the tension roll over the entire length of the region in contact with the film.

3. 3. The film stretching apparatus according to claim 2, wherein the support is a pair of rotatable support rolls that respectively support the pair of tension rolls.

4. The film stretching apparatus according to claim 2 , wherein the support is a single support roll that supports both of the pair of tension rolls.

5. The film stretching apparatus according to claim 3 or 4, wherein at least an outer peripheral surface of the support roll is formed from a metal material.

6. 5. The film stretching apparatus according to claim 1, wherein the center-to-center distance between the pair of tension rolls is 20 mm or more and 80 mm or less.

7. The film stretching apparatus according to claim 1 , wherein the heaters are continuously opposed to each other across the entire width of the film.

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