Film stretching apparatus and film manufacturing method

Abstract

To provide a film drawing device which has a compact structure and has reduced formation of a poor appearance such as a wrinkle in a film.SOLUTION: A film drawing device (100) includes: a pair of guide rollers (1, 2) which are arranged apart from each other in a transportation direction of a film (F) to be transported in a transportation direction while being applied with a tensile force and extending respectively in a width direction of the film (F); a heating part (3) for heating the film (F) between the pair of guide rollers (1, 2) by heat radiation; and a pair of nip rollers (4) positioned over the guide roller (2) on the downstream side in the transportation direction and sandwiching both end parts of the film (F) respectively between the guide roller (2) and themselves.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a film stretching device and a method for manufacturing a film.

Background Art

[0002] In the production of films such as thermoplastic resin films, a technique is known in which the film itself is heated and tension is applied in the film conveyance direction to stretch the film. Due to thermal expansion of the film or the like, wrinkles may occur in the film. As a technique for reducing the occurrence of wrinkles, Patent Document 1 discloses generating tension in the width direction of the film by a cross guide. Patent Document 2 discloses arranging a cross guide that sandwiches the end portions in the width direction of the film from the front and back to impart distortion to the film. Patent Document 3 discloses having a nip roller that grips the end of the film and applying a tensile force in the width direction to the film. Patent Document 4 discloses providing a pair of disks each composed of a rotatable disk at positions on both sides in the width direction of the traveling film so as to apply an expanding force to the film. Patent Document 5 discloses arranging a cross guide in the vicinity of both end portions in the width direction of the conveyed film.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a film stretching apparatus that uses thermoplastic film as the raw material and heats and stretches the film in the transport direction, there is a need for a compact configuration that reduces the occurrence of appearance defects such as wrinkles in the film.

[0005] One aspect of the present invention aims to provide a film stretching apparatus that stretches a film in the direction of film transport, enabling film stretching with a compact configuration while reducing the occurrence of wrinkles and other appearance defects in the film. [Means for solving the problem]

[0006] To solve the above problems, one embodiment of the present invention includes the following configuration. [1] A film stretching device comprising: a pair of guide rollers positioned spaced apart in the transport direction of a film that is transported under tension in the transport direction and each extending in the width direction of the film; a heating unit that heats the film between the pair of guide rollers by thermal radiation; and a pair of nip rollers located on the downstream guide roller in the transport direction, which sandwich each end of the film between itself and the guide rollers. [2] The film stretching apparatus according to [1], wherein the pair of nip rollers are arranged to contact 1.0% to 15% of the total width of the film. [3] The film stretching apparatus according to [1] or [2], wherein the nip roller is arranged such that its axis of rotation is greater than 0° and 60° or less with respect to the axis of rotation of the downstream guide roller. [4] The film stretching apparatus according to [1] or [2], wherein the nip roller is a rubber roller in which the roller core is coated with one or more rubbers selected from the group consisting of nitrile rubber, chloroprene rubber, ethylene propylene rubber, silicone rubber, butyl rubber, styrene rubber, urethane rubber, Hypalon rubber, and fluororubber. [5] The film stretching apparatus according to [1] or [2], wherein the surface roughness of the downstream guide roller has a maximum height of 1.6S or less, and the diameter of the guide roller is 10 mm or more. [6] The film stretching apparatus according to [1] or [2], wherein uniaxial stretching is performed by the speed ratio of the pair of guide rollers. [7] The film stretching apparatus according to [1] or [2], wherein the heating section has an infrared heater. A method for manufacturing a film using the film stretching apparatus described in [8], [1], or [2]. [9] The method for manufacturing the film according to [8], wherein the glass transition temperature of the film is 80°C to 250°C.

[10] The method for manufacturing the film according to [8], wherein the film is a transparent polyimide having a total light transmittance of 80% or more at a thickness of 50 μm. [Effects of the Invention]

[0007] According to one aspect of the present invention, a compact configuration can be used to reduce the occurrence of appearance defects such as wrinkles in the film. [Brief explanation of the drawing]

[0008] [Figure 1] This is a perspective view showing an example of the schematic configuration of a film stretching apparatus according to an embodiment of the present invention. [Figure 2] This is a perspective view showing the internal structure of a second guide roller according to an embodiment of the present invention. [Figure 3] This is a perspective view showing the arrangement of the nip roller with respect to the rotation axis of the second guide roller according to an embodiment of the present invention. [Modes for carrying out the invention]

[0009] [Technical concept of the embodiment of the present invention] Conventional film stretching equipment used an oven to heat the film itself. As a result, it took a long time from preheating to full heating, and to improve production efficiency, a very long oven was used along the direction of film transport. This increased the fixed costs of production equipment, which was a problem. In some cases, the long heating time caused a deterioration in the properties of the film. Therefore, the applicant decided to adopt a film stretching device using an infrared heater, particularly a far-infrared heater, which can heat the film in a short time. While this type of film stretching device can achieve stretching in a small space, it was found that it could induce wrinkles and other appearance defects in the film during processing. Therefore, it was necessary to take measures to address this while maintaining a compact configuration.

[0010] The inventors of the present invention have discovered that by providing nip rollers that nip both ends of the film on the roller downstream of the film heating area of ​​the film stretching device, it is possible to widen the film in a compact configuration and reduce the occurrence of wrinkles and other defects in the film, thereby completing the present invention.

[0011] The following will provide a detailed explanation based on the drawings.

[0012] [Embodiment] (Overview of the film stretching device 100) Figure 1 is a perspective view showing an example of the schematic configuration of a film stretching apparatus 100 according to one embodiment of the present invention. In Figure 1, the X-axis direction is the left-right direction, the Y-axis direction is the front-back direction, and the Z-axis direction is the up-down direction. The Y-axis direction is also the width direction of the film F being transported.

[0013] The film stretching device 100 includes a first guide roller 1, a second guide roller 2, a heater (heating unit) 3, and a nip roller 4. The film F is conveyed from the first guide roller 1 to the second guide roller 2 in the left - right direction (X - axis direction). The film stretching device 100 further includes drive rollers (not shown) for applying a driving force for conveyance to the film F upstream of the first guide roller 1 and downstream of the second guide roller 2, respectively. As the film F is conveyed, the first guide roller 1 and the second guide roller 2 that are in frictional contact with the film F also rotate respectively. The film stretching device 100 is preferably a device that uniaxially stretches the film F in the conveyance direction by the peripheral speed difference (speed ratio) of the separated drive rollers, that is, the speed ratio of the first guide roller 1 and the second guide roller 2. In other words, it is preferable that stretching is performed by the tension applied to the film F and the heating by the heater 3. In this case, by monitoring the tension and feeding back the speed of the drive roller, uneven thickness in the conveyance direction can be reduced and the accuracy of the stretching ratio can be improved.

[0014] (Film) The film F is, for example, a thermoplastic film. When the film F is a thermoplastic film, the glass transition temperature (Tg) is preferably 80°C or higher and 250°C or lower. The glass transition temperature means the temperature of the inflection point when measuring the dynamic viscoelasticity of the film F and plotting the correlation between the storage elastic modulus of the film F and the measurement temperature. The measurement of the dynamic viscoelasticity of the film F is performed, for example, using a DMS - 200 manufactured by Seiko Instruments Inc., under the conditions of a measurement jig interval of 20 mm and a frequency of 5 Hz. When the glass transition temperature is 80°C or higher and 250°C or lower, it has been confirmed that the film F is well widened by the nip roller 4. The width of the film F is, for example, about 300 mm.

[0015] As the material of the film F, for example, acrylic resins such as polymethyl methacrylate and polyacrylate, polyolefins such as polyethylene, polypropylene, and halogenated polyethylene, polyamides such as nylon 6, nylon 66, nylon 610, nylon 12, and nylon 11, polyesters such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate, aromatic polyethers such as polyethersulfone (PES), polyphenylene oxide (PPO), polyetheretherketone (PEEK), and polyphenylene sulfide (PPS), polyimide, etc. may be mentioned. Among them, polyimide is preferable. Among polyimides, a transparent polyimide with a total light transmittance of 80% or more at a thickness of 50 μm is preferable. The total light transmittance is measured in accordance with JIS standard K7361-1:1997.

[0016] (First guide roller and second guide roller) The first guide roller 1 and the second guide roller 2 are arranged apart in the conveyance direction so as to guide the film F conveyed in a state where tension is applied in the conveyance direction, and are a pair of guide rollers extending in the width direction (Y-axis direction) of the film F. That is, the rotation axis K of the second guide roller 2 and the rotation axis of the first guide roller 1 are parallel in the Y-axis direction. The film F is conveyed in the positive direction of the X-axis by the first guide roller 1 and the second guide roller 2. The tension applied to the film F is, for example, 188 N / m.

[0017] The first guide roller 1 is the guide roller on the upstream side in the conveyance direction. The second guide roller 2 is the guide roller on the downstream side in the conveyance direction. The first guide roller 1 and the second guide roller 2 may each rotate at different rotational speeds as described above, or may rotate in accordance with the conveyance of the film F.

[0018] The surface roughness of the roller surface portion 21 of the second guide roller 2, described later, is preferably 1.6S or less at its maximum height. The maximum height of the surface roughness is measured in accordance with JIS standard B 0601:1994. If the maximum height of the surface roughness of the second guide roller 2 exceeds 1.6S, the gripping force on the film F increases, preventing the nip roller 4 from pulling the film F outward, and thus preventing the film F from being widened properly.

[0019] The diameter of the second guide roller 2 is preferably 10 mm or more. The diameter of the second guide roller 2 may be 30 mm or more, 40 mm or more, or 100 mm or more. When the second guide roller 2 is used as a cooling roller as described later, the diameter is preferably 100 mm or more, and more preferably 150 mm or more. The total length of the second guide roller 2 can be selected according to the diameter, for example, 300 mm, 500 mm, or 1500 mm.

[0020] (Internal structure of the guide roller) Figure 2 is a perspective view showing the internal structure of the second guide roller 2. Since the second guide roller 2 is close to the heater 3, it may be exposed to the heat radiation from the heater 3. As a result, there is a risk that the surface temperature of the second guide roller 2 will be unevenly distributed, and the film F may not be stretched uniformly. Therefore, in order to make the surface temperature of the contact surface of the second guide roller 2 with the film F uniform, the second guide roller 2 may have the following internal structure as a cooling roller.

[0021] The second guide roller 2 comprises a roller surface portion 21 and a roller shaft portion 22. An axially extending refrigerant space 23 is formed inside the second guide roller 2. An inlet pipe 25 and an outlet pipe 26 for refrigerant (or heat transfer medium) are connected to both ends of the roller shaft portion 22 of the second guide roller 2, respectively. A partition member 24 is provided in the refrigerant space 23, which defines a helical path along the rotation axis K. As a result, the refrigerant (or heat transfer medium) flowing in from the inlet pipe 25 rotates around the axis of the refrigerant space 23 (as shown by the arrow in Figure 2), passes through the partition member 24, and is discharged from the outlet pipe 26. By passing the refrigerant through the refrigerant space 23, the surface temperature of the second guide roller 2 can be kept uniform. Therefore, even if the second guide roller 2 is exposed to heat radiation from the heater 3, the jacket structure described above keeps the surface temperature of the contact surface between the second guide roller 2 and the film F uniform, allowing the film F to be stretched uniformly.

[0022] Examples of refrigerants (or heat transfer fluids) include, but are not limited to, cooling water or oil. The refrigerant only needs to be able to control the surface temperature of the second guide roller 2 to a temperature lower than its glass transition temperature. Also, although Figure 2 shows a structure in which the refrigerant flows in a single pass, it is not limited to this. Furthermore, the second guide roller 2 may not have the cooling structure described above.

[0023] (Rotation speed of the guide roller) The length of rotation around the outer circumference of the second guide roller 2 is longer than the length of rotation around the outer circumference of the first guide roller 1 by the amount by which the film F is stretched. In other words, the rotational speed of the second guide roller 2 is faster than the rotational speed of the first guide roller 1. For example, the rotational speed of the second guide roller 2 may be 0.1% to 200% faster than the rotational speed of the first guide roller 1.

[0024] (heater) The heater 3 heats the film F by thermal radiation so that the surface temperature of the film F between the first guide roller 1 and the second guide roller 2 is in the range from near the glass transition temperature to near the softening temperature of the film F. The heater 3 is, for example, a far-infrared heater. It is preferable to install the heater 3 at a distance of approximately 40 mm from the film surface on the heater 3 side.

[0025] The heat radiation from the heater 3 heats the film F between the first guide roller 1 and the second guide roller 2, raising the surface temperature of the film F to a temperature higher than the glass transition temperature (for example, about 255-275°C). The film F softens in the softening zone A shown in Figure 1, and becomes stretchable in the conveying direction due to the tension between the first guide roller 1 and the second guide roller 2.

[0026] Multiple heaters 3 may be arranged in the width direction of the film F. This is because a single far-infrared heater cannot heat the entire width of the film F. Furthermore, uneven stretching can be reduced by creating a gradient in the temperature settings of the far-infrared heaters in the width direction of the film F (for example, setting the temperature lower in the center of the film F). Figure 1 shows a state in which multiple heaters 3 are arranged in the width direction of the film F.

[0027] Figure 1 shows a configuration where the heaters 3 are arranged in a single row in the width direction of the film F. However, the heaters 3 may be arranged in multiple rows in the transport direction. Heating in multiple rows can compensate for insufficient heat when the transport speed is increased. In this case, the temperatures of the radiating surfaces of the heaters 3 in the upstream row and the heaters 3 in the downstream row may be different. In this case, it is preferable that the temperature of the radiating surface of the downstream heater 3 is 10°C to 20°C higher than the temperature of the radiating surface of the upstream heater 3. This can reduce uneven stretching. Depending on the film F, uneven stretching may occur if there is a rapid drop in temperature. In such cases, setting the temperature of the downstream heater 3 lower than the temperature of the upstream heater 3 (for example, setting the temperature of the radiating surface of the downstream heater 3 to 10°C to 20°C lower than the temperature of the radiating surface of the upstream heater 3) can suppress a rapid drop in temperature and reduce uneven stretching.

[0028] (Niplora) The film stretching device 100 includes a pair of nip rollers 4. The pair of nip rollers 4 are positioned on the second guide roller 2 to nip both ends of the film F. That is, the pair of nip rollers 4 sandwich each end of the film between themselves and the second guide roller 2. The nip rollers 4 have a widening function that pulls the film F outward in the width direction. The rotation axis L of the nip rollers 4 is parallel to the horizontal plane. It is preferable that the nip rollers 4 contact the film F in the region B shown in Figure 1 where the second guide roller 2 and the film F are in contact. The nip rollers 4 are not drive rollers that drive themselves, but rotate in accordance with the transport of the film F. That is, as shown in Figure 1, as the second guide roller 2 rotates in rotation direction M around the rotation axis K, the nip rollers 4 rotate in rotation direction N around the rotation axis L.

[0029] It is preferable that the nip roller 4 is positioned to nip 1.0% to 15% of the total width of the film F. This allows the heat-shrunk film F to be expanded and reduces the occurrence of wrinkles. It is more preferable that the nip roller 4 is positioned to nip 5.0% to 15% of the total width of the film F, considering the balance between the function of expanding the film F and the gripping force on the film F.

[0030] Figure 3 is an explanatory diagram showing the arrangement of the nip roller 4 with respect to the rotation axis K of the second guide roller 2. Preferably, the nip roller 4 is positioned such that it forms an angle θ greater than 0° and 60° or less with respect to the rotation axis K of the second guide roller 2, as shown in Figure 3. If the angle θ exceeds 60°, the gripping force increases, and there is a risk of the film F bending. An angle θ of 5° or more is more preferable. An angle θ of 40° or less is even more preferable, and 30° or less is even more preferable.

[0031] The nip roller 4 is preferably a rubber roller. A rubber roller is a roller in which an elastic substance such as rubber is coated over a roller core made of a metal material such as carbon steel or stainless steel. Examples of elastic substances include one or more selected from the group consisting of nitrile rubber (NBR), chloroprene rubber (CR), ethylene propylene rubber (EPT), silicone rubber (Q), butyl rubber (IIR), styrene rubber (SBR), urethane rubber (U), Hypalon rubber (CSM), fluororubber, etc. Among these, NBR is preferred from the viewpoint of obtaining good grip force on the film F. Rubber rollers have the characteristics of having a high coefficient of friction, being non-slip, and rapidly returning to their original shape even after deformation. By constructing the nip roller 4 with a rubber roller, even if the nip roller 4 is positioned so that its rotation axis L makes the above-mentioned angle with respect to the rotation axis K of the second guide roller 2, it can contact the film F by surface contact rather than point contact due to deformation. This allows for a wider range of nipping, specifically, 1.0% to 15% of the total width of film F can be nipped, thus widening film F and reducing the occurrence of wrinkles.

[0032] The diameter of the nip roller 4 may be smaller or larger than that of the second guide roller 2. From the viewpoint of achieving a more compact configuration, it is preferable that the diameter of the nip roller 4 be smaller than that of the second guide roller 2. For example, if the diameter of the second guide roller 2 is 150 mm and the total length is 1500 mm, the diameter of the nip roller 4 can be 40 mm and the total length 100 mm.

[0033] Figure 1 shows a case where a pair of nip rollers 4 are provided at both ends of the second guide roller 2, but the design is not limited to this case. Another pair of nip rollers 4 may be provided at both ends further downstream of the second guide roller 2.

[0034] (reflector) The film stretching apparatus 100 may also be equipped with a reflector (not shown) on the opposite side of the heater 3, sandwiching the film F. The reflector is a reflector that reflects the heat radiation from the heater 3 that has passed through the film F, and heats the film surface on the heater 3 side (front surface) as well as the film surface on the opposite side of the heater 3 (back surface). The reflector may be a flat aluminum plate, and it is preferable to install it at a distance of 20 mm from the back surface of the film.

[0035] (Film manufacturing method) When manufacturing a film F using the film stretching apparatus 100 of this embodiment, two drive rollers are driven at a predetermined speed ratio to transport the film F. The film F is heated by a heater 3 between the first guide roller 1 and the second guide roller 2, and the film F is stretched by the tension generated by the speed ratio and the heating. Immediately after heating, the film F is widened by nip rollers 4 that contact it at both ends in the width direction. The speed ratio of the drive rollers is feedback controlled by monitoring the tension.

[0036] (Applications of thermoplastic resin films) The films according to the embodiments of the present invention are not particularly limited, but can be used in various applications where aesthetic design is required, such as automotive interior and exterior parts, mobile phone components, AV equipment components, personal computer equipment components, furniture products, various displays, lenses, window glass, small items, and miscellaneous goods.

[0037] (effect) As described above, the film stretching apparatus 100 according to the embodiment has nip rollers 4 on the downstream second guide roller 2 that nip both ends of the film F, so that the film F can be widened in the width direction (direction of the rotation axis K of the second guide roller 2).Therefore, stretching can be achieved in a space-saving manner using a heater 3 such as a far-infrared heater, while reducing the occurrence of wrinkles and other appearance defects in the film F.Since the nip rollers 4 are located on the second guide roller 2, no installation space is required in the left-right direction of the second guide roller 2 in Figure 1.If a small roller is used as the nip roller 4 relative to the second guide roller 2, no large installation space is required above the second guide roller 2 in Figure 1.Therefore, a compact structure can be achieved, and the occurrence of wrinkles and other defects in the film F can be reduced.

[0038] 〔summary〕 Embodiments of the present invention may also have the following configurations. [1] A film stretching device comprising: a pair of guide rollers positioned spaced apart in the transport direction of a film that is transported under tension in the transport direction and each extending in the width direction of the film; a heating unit that heats the film between the pair of guide rollers by thermal radiation; and a pair of nip rollers located on the downstream guide roller in the transport direction, which sandwich each end of the film between itself and the guide rollers. [2] The film stretching apparatus according to [1], wherein the pair of nip rollers are arranged to contact 1.0% to 15% of the total width of the film. [3] The film stretching apparatus according to [1] or [2], wherein the nip roller is arranged such that its axis of rotation is greater than 0° and 60° or less with respect to the axis of rotation of the downstream guide roller. [4] The film stretching apparatus according to any one of [1] to [3], wherein the nip roller is a rubber roller in which the roller core is coated with one or more rubbers selected from the group consisting of nitrile rubber, chloroprene rubber, ethylene propylene rubber, silicone rubber, butyl rubber, styrene rubber, urethane rubber, Hypalon rubber, and fluororubber. [5] The film stretching apparatus according to any one of [1] to [4], wherein the surface roughness of the downstream guide roller has a maximum height of 1.6S or less, and the diameter of the guide roller is 10 mm or more. [6] A film stretching apparatus according to any one of [1] to [5], wherein uniaxial stretching is performed by the speed ratio of the pair of guide rollers. [7] The film stretching apparatus according to any one of [1] to [6], wherein the heating section has an infrared heater. A method for manufacturing a film using a film stretching apparatus described in any one of [8], [1], to [7]. [9] The method for manufacturing the film according to [8], wherein the glass transition temperature of the film is 80°C to 250°C.

[10] The method for manufacturing the film according to [8] or [9], wherein the film is a transparent polyimide having a total light transmittance of 80% or more at a thickness of 50 μm.

[0039] [Additional Notes] The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Explanation of symbols]

[0040] 1. First guide roller 2. Second guide roller 21 Roller surface 22 Roller shaft section 23 Refrigerant space 24 Partition members 25 Introductory tube 26 Discharge pipe 3. Heater (heating section) 4 Nipple Roller 100 Film stretching machine F Film

Claims

1. A pair of guide rollers, each extending in the width direction of a polyimide film, are positioned spaced apart in the conveying direction and conveyed under tension in the conveying direction, A heating unit that heats the film between the pair of guide rollers by thermal radiation, A pair of nip rollers are positioned on the downstream guide roller in the aforementioned transport direction, and each of the ends of the film is sandwiched between them and the guide roller, Equipped with, The surface roughness of the downstream guide roller has a maximum height of 1.6S or less. The nip roller is a rubber roller in which a roller core is coated with nitrile rubber, and the rotation axis is arranged such that it forms an angle greater than 5° and less than or equal to 30° with respect to the rotation axis of the downstream guide roller, so as to pull the film outward in the width direction.

2. The film stretching apparatus according to claim 1, wherein the pair of nip rollers are arranged to contact 1.0% to 15% of the total width of the film.

3. The film stretching apparatus according to claim 1 or 2, wherein the diameter of the guide roller is 10 mm or more.

4. The film stretching apparatus according to claim 1 or 2, wherein uniaxial stretching is performed by the speed ratio of the pair of guide rollers.

5. The film stretching apparatus according to claim 1 or 2, wherein the heating section has an infrared heater.

6. A method for manufacturing a film using the film stretching apparatus according to claim 1 or 2.

7. The method for manufacturing a film according to claim 6, wherein the glass transition temperature of the film is 80°C to 250°C.

8. The method for producing the film according to claim 6, wherein the film is a transparent polyimide having a total light transmittance of 80% or more at a thickness of 50 μm.

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