Film stretching apparatus and film manufacturing method

Abstract

To provide a film stretching device that reduces a facility cost while suppressing film oxidation phenomena.SOLUTION: A film stretching device (100) comprises: a pair of guide rollers (R1 and R2); a heater (4); and an inert box (5) that is filled with inert gas, and covers at least the heater and a heating area heated by the heater in the film between the pair of guide rollers.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] Patent Documents 1 to 6 disclose a film stretching device that stretches a film in the conveying direction of the film by applying tension in the conveying direction of the film and heating the film by a heating unit such as a hot air oven or an infrared heater.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Summary of the Invention

Problems to be Solved by the Invention

[0004] When heating a film with a hot air oven, it takes a long time to heat the film to a temperature at which it can be stretched. Therefore, there is a problem that the hot air oven needs to be very long along the conveying direction of the film, resulting in an increase in equipment costs. In addition, there is also a problem that the time the film is exposed to a high-temperature environment becomes long, and the oxidation phenomenon of the film progresses.

[0005] Furthermore, when heating the film with an infrared heater, the film can be heated to a stretchable temperature in a short time. Therefore, compared to heating the film with a hot air oven, it is possible to suppress the oxidation phenomenon of the film. However, our investigations have shown that even in such a film stretching apparatus, there is room to further suppress the oxidation phenomenon of the film.

[0006] One aspect of the present invention aims to reduce equipment costs while suppressing the oxidation phenomenon of the film. [Means for solving the problem]

[0007] To solve the above problems, a film stretching apparatus according to one aspect of the present invention comprises: a pair of guide rollers arranged spaced apart in the conveying direction of a film that is conveyed under tension in the conveying direction and each extending in the width direction of the film; a first heating unit that heats the surface of the film between the pair of guide rollers by thermal radiation; and an inert box filled with inert gas that covers at least the first heating unit and the heating region in the film between the pair of guide rollers that is heated by the first heating unit.

[0008] Furthermore, the pair of guide rollers may each contact the back surface of the film, such that the upstream first guide roller of the pair guides the film being conveyed from the opposite side of the first heating unit with respect to a first virtual plane extending the main surface of the film between the pair of guide rollers, and the downstream second guide roller of the pair guides the conveyed film on the opposite side of the first heating unit with respect to the first virtual plane.

[0009] Furthermore, the film stretching apparatus further comprises a third guide roller positioned upstream of the first guide roller and extending in the width direction of the film, a fourth guide roller positioned downstream of the second guide roller and extending in the width direction of the film, a second heating unit that heats the surface of the film between the third guide roller and the first guide roller by thermal radiation, and a third heating unit that heats the surface of the film between the second guide roller and the fourth guide roller by thermal radiation, wherein the third guide roller guides the film being conveyed from the opposite side of the second guide roller to a second virtual plane extending the main surface of the film between the first guide roller and the third guide roller, and the fourth guide roller may contact the surface of the film so as to guide the conveyed film on the opposite side of the second guide roller to a third virtual plane extending the main surface of the film between the second guide roller and the fourth guide roller.

[0010] Furthermore, the inert box may further cover the second heating section, the third heating section, the heating region in the film between the third guide roller and the first guide roller that is heated by the second heating section, and the heating region in the film between the second guide roller and the fourth guide roller that is heated by the third heating section.

[0011] Furthermore, the angle at which the film is gripped by the second guide roller, the downstream of the pair of guide rollers, may be 90°±10°.

[0012] Furthermore, the distance between the film between the pair of guide rollers and the radiating surface of the first heating unit is 20 to 100 mm, and in a plan view from a direction perpendicular to the main surface of the film between the pair of guide rollers, the downstream end of the radiating surface of the first heating unit may be located downstream from the first position, which is 20 mm upstream from the rotation axis of the second guide roller, the downstream of the pair of guide rollers.

[0013] Further, the film may be stretched by the tension applied in the conveying direction in the heating region.

[0014] In order to solve the above problems, a method for manufacturing a film according to an aspect of the present invention includes a step of applying tension to a film that is conveyed while tension is applied in the conveying direction, and arranging the film spaced apart in the conveying direction, and applying tension to the film by a pair of guide rollers that respectively extend in the width direction of the film; and a step of heating the film by a first heating unit that heats the surface of the film between the pair of guide rollers by thermal radiation. In the step of heating the film, the film is heated inside an inert box filled with an inert gas that at least covers the first heating unit and a heating region of the film between the pair of guide rollers that is heated by the first heating unit.

[0015] Further, the glass transition temperature of the film may be 200 to 350°C.

Advantages of the Invention

[0016] According to an aspect of the present invention, it is possible to reduce equipment costs while suppressing the oxidation phenomenon of the film.

Brief Description of the Drawings

[0017] [Figure 1] It is a schematic diagram showing an example of the schematic configuration of a film stretching device according to an embodiment of the present invention. [Figure 2] It is a perspective view showing an example of the schematic configuration of the above film stretching device. [Figure 3] It is a schematic diagram showing the positional relationship between the heater and the guide roller in the above film stretching device. [Figure 4] It is a schematic diagram showing still another example of the schematic configuration of a film stretching device according to an embodiment of the present invention.

Modes for Carrying Out the Invention

[0018] 〔Embodiment 1〕 (Schematic Configuration of Film Stretching Apparatus) FIG. 1 is a schematic diagram showing an example of the schematic configuration of a film stretching apparatus 100 according to an embodiment of the present invention. FIG. 2 is a perspective view showing an example of the schematic configuration of the film stretching apparatus 100. FIG. 1 is a view seen from a direction perpendicular to a plane parallel to the length direction of the film F and perpendicular to the width direction of the film F. In FIGS. 1 and 2, the conveyance direction is the length direction of the film F.

[0019] As shown in FIGS. 1 and 2, the film stretching apparatus 100 includes a first guide roller R1, a second guide roller R2, and a heater 4 (first heating unit). In FIG. 2, the illustration of the heater 4 is omitted. The film stretching apparatus 100 further includes drive rollers (not shown) on the upstream side of the first guide roller R1 and the downstream side of the second guide roller R2, respectively. The film stretching apparatus 100 is a device that stretches the film F in the conveyance direction by the peripheral speed difference of such spaced-apart drive rollers.

[0020] The film F is, for example, a thermoplastic film. In the present embodiment, the film F may have a relatively high glass transition temperature (for example, 200 to 350°C). The film F is, for example, a PI (polyimide) film.

[0021] The first guide roller R1 and the second guide roller R2 are arranged at a distance (for example, by about 300 mm) in the conveyance direction of the film F that is conveyed while being tensioned in the conveyance direction, and are a pair of guide rollers R1 and R2 that extend in the width direction of the film F, respectively. The tension applied to the film F is, for example, 100 to 400 N / m.

[0022] The first guide roller R1 is the upstream guide roller among the pair of guide rollers. The second guide roller R2 is the downstream guide roller among the pair of guide rollers.

[0023] The heater 4 heats the surface of the film F between a pair of guide rollers R1 and R2 (hereinafter referred to as the inter-roller film F12) by thermal radiation. The heater 4 heats the surface temperature of the film F to a temperature higher than the glass transition temperature (for example, about 255 to 275°C). This makes the film F stretchable in the transport direction by tension. Hereinafter, the region of the transported film F in which the surface temperature is heated to a temperature higher than the glass transition temperature by thermal radiation from the heater 4 (making it stretchable) will be referred to as the heated region H1. In a plan view from a direction perpendicular to the main surface of the inter-roller film F12 (hereinafter referred to as "the above plan view"), the end of the heated region H1 in the transport direction substantially coincides with the end of the radiating surface 4S of the heater 4 in the transport direction.

[0024] The heater 4 may comprise at least one far-infrared heater. The radiating surface of each far-infrared heater is substantially rectangular in shape. The heater 4 may comprise multiple far-infrared heaters arranged in parallel along the width direction of the film F. For example, five far-infrared heaters, each with dimensions of approximately 120 mm x 120 mm, may be installed with an installation interval of approximately 5 mm in the width direction to uniformly heat the surface of the film F along the width direction. With such a configuration, the radiating area of ​​the heater 4 can be made wider than the width of the film F, and the surface temperature of the film F heated by the heater 4 can be kept uniform across the width direction of the film F. Note that the configuration of the heater 4 is not limited to the above configuration. For example, the number of far-infrared heaters provided in the width direction may be selected according to the length of the width of the film F. In addition, the heater 4 may comprise multiple far-infrared heaters arranged in parallel along the transport direction of the film F. Hereinafter, the surface to which the radiating surfaces of one or more of the above-mentioned far-infrared heaters are connected will be referred to as the radiating surface 4S of the heater 4.

[0025] Additionally, a reflector (not shown) may be provided on the opposite side of the heater 4 from the film F. The reflector reflects the heat or heat rays radiated from the heater 4 towards the film F.

[0026] The first guide roller R1 guides the film F being transported from the opposite side of the heater 4 relative to the first virtual plane S1, which is an extension of the film F12 between the rollers. The first guide roller R1 contacts the back surface of the film F. The second guide roller R2 guides the transported film F toward the opposite side of the heater 4 relative to the first virtual plane S1. The second guide roller R2 contacts the back surface of the film F. That is, as shown in Figures 1 and 2, the pair of guide rollers R1 and R2 define the transport path of the film F in a convex shape so that the surface of the film F faces toward the heater 4.

[0027] With the above configuration, the film stretching device 100 can stretch the film F in the transport direction by tension from the guide rollers R1 and R2 and heating from the heater 4. Furthermore, by bringing the heated film F into contact with the surfaces of the guide rollers R1 and R2, the film F can be cooled to below its glass transition temperature, while the shrinkage in the width direction due to the cooling of the film F can be suppressed by the gripping force of the guide rollers R1 and R2.

[0028] Furthermore, the surface of the film F is heated by thermal radiation from the heater 4. This allows the film F to be heated to a stretchable temperature in a shorter time compared to heating the film F by blowing hot air onto its surface. In particular, even films F with relatively high glass transition temperatures (e.g., 200-350°C) can be heated to a stretchable temperature in a short time. Therefore, oxidation of the film F can be suppressed.

[0029] Furthermore, the degree of oxidation of film F contributes to the YI value (yellowness) of film F. The more the oxidation of film F progresses, the higher the YI value of film F. When film F is heated by heat radiation from heater 4, the YI value of film F can be reduced compared to when film F is heated by blowing hot air onto its surface. In other words, a transparent film F can be obtained.

[0030] As shown in Figures 1 and 2, the film stretching apparatus 100 further includes an inert box 5 filled with an inert gas. The inert gas is, for example, nitrogen gas or helium gas. The inert box 5 is a box-shaped member that covers at least the heater 4 and the heating region H1 in the film F12 between the rollers that is heated by the heater 4. In this case, the length L0 of the inert box 5 in the conveying direction is 100 to 650 mm. The film F is stretched by the tension applied in the conveying direction in the heating region H1.

[0031] The film F, guided by the first guide roller R1, enters the inert box 5 through a hole 51 provided on one side of the inert box 5. Next, the film F is heated by the heater 4 inside the inert box 5. Then, the film F exits the inert box 5 through a hole 52 provided on the other side of the inert box 5.

[0032] Furthermore, the inert box 5 is equipped with an intake port (not shown) through which inert gas is supplied and an exhaust port (not shown) through which inert gas is discharged. By supplying inert gas as needed from the intake port, the inside of the inert box 5 can be kept constantly filled with inert gas.

[0033] With the above configuration, the film F can be heated in an inert gas atmosphere. This further suppresses the oxidation phenomenon of the film F. Also, since the film F can be heated to a stretchable temperature in a short time, the heating region H1 of the film F can be made more compact (compared to the case where the film is heated by blowing hot air onto the film surface). Therefore, as described above, the inert box 5, which is installed to cover the heating region H1 of the film F (to suppress the oxidation phenomenon), can be made more compact. Consequently, equipment costs and inert gas consumption can be reduced. In addition, by covering the heater 4 with the inert box 5, the surface of the film F is heated efficiently, and at the same time, the oxidation phenomenon of the film F during high-temperature processing can be suppressed by filling the inside of the inert box 5 with inert gas.

[0034] The configuration of the inert box 5 is not limited to this. For example, the inert box 5 may further cover the guide rollers R1 and R2 shown in Figure 1. This allows the inert box 5 to cover the heating region H1 even when the end of the heating region H1 in the transport direction is near the rotation axis of the guide rollers R1 and R2 in the above plan view.

[0035] Here, in the film stretching apparatus 100, the film F is stretched in a compact heating region H1 due to the heat radiation of the heater 4. Therefore, the stretched film F may cool rapidly and deform. The following describes a configuration to suppress such deformation of the film F after heating. That is, with the following configuration, deformation of the stretched film F can be suppressed even when the film F is stretched in a compact heating region H1.

[0036] (Film angle of contact) In the film stretching device 100, the gripping angle of the film F by the second guide roller R2 may be in the range of 90° ± 10°. In the example shown in Figure 1, the gripping angle of the film F by the second guide roller R2 is 90°. This allows the contact area between the second guide roller R2 and the film F to be appropriately widened, enabling the film F to be conveyed while being properly gripped. Here, the gripping angle refers to the angle of the film from one roller to the next.

[0037] If the angle at which the second guide roller R2 grips the film F is less than 80°, the contact area between the second guide roller R2 and the film F increases, resulting in a higher gripping force on the film F by the second guide roller R2. This makes the film F more susceptible to scratches. Conversely, if the angle at which the second guide roller R2 grips the film F is greater than 100°, the contact area between the second guide roller R2 and the film F decreases, resulting in a lower gripping force on the film F by the second guide roller R2. This causes the film F to move in the width direction relative to the second guide roller R2 during transport, making it more prone to wrinkles on both ends of the film F in the width direction.

[0038] On the other hand, when the gripping angle of the film F by the second guide roller R2 is within the range of 90°±10°, the contact area between the second guide roller R2 and the film F is made appropriately wide, allowing the film F to be transported while being properly gripped. Therefore, in the film stretching device 100, by setting the gripping angle of the film F by the second guide roller R2 to 90°±10°, a film F with reduced wrinkle and scratch occurrence can be obtained. Note that the gripping angle of the film F by the first guide roller R1 should also be within the range of 90°±10°.

[0039] (Positional relationship between the heater and the guide roller) Figure 3 is a schematic diagram showing the positional relationship between the heater 4 and the guide rollers R1 and R2 in the film stretching apparatus 100. Referring to Figure 3, the positional relationship between the heater 4 and the guide rollers R1 and R2 will be explained in detail below.

[0040] The distance L1 (irradiation distance L1) between the roller film F12 and the radiating surface 4S of the heater 4 is 20 to 100 mm. By making the distance L1 between the roller film F12 and the radiating surface 4S of the heater 4 smaller, the surface of the film F can be heated efficiently. The irradiation distance L1 of the heater 4 is set according to the output of the heater 4. For example, if the output of the heater 4 is 140V, it is preferable to set the irradiation distance L1 of the heater 4 to about 40 mm.

[0041] Furthermore, as shown in Figure 3, in the plan view, the downstream end of the radiating surface 4S of the heater 4 is located downstream (to the right in Figure 3) of the first position A1. Here, the first position A1 is located at a distance L2 (20 mm) upstream (to the left in Figure 3) from the rotation axis of the second guide roller R2 in the plan view. This shortens the region in which the film F is not heated by the heater 4 up to the point where the gripping force of the second guide roller R2 begins to act on the film F. Therefore, the width shrinkage of the film F can be suppressed. As shown in Figure 3, the downstream end of the heater 4 is located upstream of the rotation axis of the second guide roller R2 in the plan view. However, the downstream end of the heater 4 may also be located downstream of the rotation axis of the second guide roller R2 in the plan view.

[0042] Furthermore, as shown in Figure 3, in the plan view, the downstream end of the radiating surface 4S of the heater 4 may be located between the first position A1 and the second position A2. Here, the second position A2 is located at a distance L3 (20 mm) downstream from the rotation axis of the second guide roller R2 in the plan view. This brings the downstream end of the heating region H1 of the heater 4 as close as possible to the position where the gripping force of the second guide roller R2 begins to act on the film F, thereby efficiently heating the surface of the film F while suppressing the width shrinkage of the film F.

[0043] Furthermore, as shown in Figure 3, in the plan view, the upstream end of the radiating surface 4S of the heater 4 may be located further upstream than the third position A3. Here, the third position A3 is located at a distance L4 (20 mm) downstream from the rotation axis of the first guide roller R1 in the plan view. This makes it possible to efficiently heat the film while suppressing film width shrinkage by making the heating region H1 of the heater 4 cover almost the entire film F12 between the rollers.

[0044] Similarly, as shown in Figure 1, in the plan view, the upstream end of the radiating surface 4S of the heater 4 may be located between the third position A3 and the fourth position A4. Here, the fourth position A4 is located at a distance L5 (20 mm) upstream from the rotation axis of the first guide roller R1 in the plan view.

[0045] By aligning both ends of the film F12 between the rollers in the conveying direction with both ends of the radiating surface 4S of the heater 4 as much as possible, the region of the film F that is not heated by the heater 4 is shortened, and the width shrinkage of the film F can be suppressed.

[0046] [Embodiment 2] Other embodiments of the present invention are described below. For the sake of clarity, components having the same function as those described in the above embodiments will be denoted by the same reference numerals, and their descriptions will not be repeated.

[0047] Figure 4 is a schematic diagram showing yet another example of the schematic configuration of a film stretching apparatus 100 according to one embodiment of the present invention. Figure 4 is a view from a direction perpendicular to a plane that is parallel to the length direction of the film F and perpendicular to the width direction of the film F. In Figure 4, the transport direction is the length direction of the film F.

[0048] As shown in Figure 4, the film stretching apparatus 100 further comprises a third guide roller R3, a fourth guide roller R4, a heater 4A (second heating section), and a heater 4B (third heating section). The third guide roller R3 is positioned upstream of the first guide roller R1 and extends in the width direction of the film F. The fourth guide roller R4 is positioned downstream of the second guide roller R2 and extends in the width direction of the film F. Heater 4A heats the surface of the film F between the third guide roller R3 and the first guide roller R1 (hereinafter referred to as the inter-roller film F31) by thermal radiation. Heater 4B heats the surface of the film F between the second guide roller R2 and the fourth guide roller R4 (hereinafter referred to as the inter-roller film F24) by thermal radiation.

[0049] Furthermore, the third guide roller R3 guides the film F being transported from the opposite side of the first guide roller R1 with respect to the second virtual plane S2, which is an extension of the main surface of the inter-roller film F31. The fourth guide roller R4 guides the transported film F from the opposite side of the second guide roller R2 with respect to the third virtual plane S3, which is an extension of the main surface of the inter-roller film F24. The third guide roller R3 and the fourth guide roller R4 are in contact with the surface of the film F. That is, as shown in Figure 4, the four guide rollers R1 to R4 divide the transport path of the film F into three paths (short spans) each sandwiched between a pair of guide rollers. In each of these three paths, the inter-roller film is stretched in the transport direction by the tension of the pair of guide rollers and the heating of the heater.

[0050] This makes it possible to suppress the width shrinkage of the film compared to the case where the transport path of the film F is defined as a single (long-span) path sandwiched between a pair of guide rollers.

[0051] As shown in Figure 4, the film stretching apparatus 100 further includes an inert box 5. The inert box 5 covers heater 4A, heater 4B, and heating regions H2, H3 in addition to heater 4 and heating region H1. Here, heating region H2 is the region of the film F31 between rollers that is heated by heater 4A. Heating region H3 is the region of the film F24 between rollers that is heated by heater 4B. In this case, the length L0 of the inert box 5 in the conveying direction is approximately 1100 mm. With this configuration, heating of the film F under an inert gas atmosphere by three heaters 4, 4A, and 4B can be achieved with a single inert box 5. Note that although Figure 4 shows the third guide roller R3 and the fourth guide roller R4 placed inside the inert box 5, the third guide roller R3 and the fourth guide roller R4 may be placed outside the inert box 5. This makes the inert box 5 more compact. Furthermore, the film stretching apparatus 100 may include three inert boxes 5 that cover the heater 4 and heating area H1, the heater 4A and heating area H2, and the heater 4B and heating area H3, respectively.

[0052] Furthermore, the angle at which the film F is gripped by the third guide roller R3 and the fourth guide roller R4 should be within the range of 90° ± 10°, similar to the angle at which the film F is gripped by the second guide roller R2. This makes it possible to obtain a film F with reduced wrinkle and scratch occurrence.

[0053] Furthermore, the positional relationship between heater 4A and the pair of guide rollers R1 and R3 may be defined in the same way as the positional relationship between heater 4 and the pair of guide rollers R1 and R2 shown in Figure 3. Similarly, the positional relationship between heater 4B and the pair of guide rollers R2 and R4 may be defined in the same way as the positional relationship between heater 4 and the pair of guide rollers R1 and R2 shown in Figure 3. This shortens the region of film F that is not heated by heaters 4, 4A, and 4B, thereby suppressing width shrinkage of film F.

[0054] Furthermore, the temperature of heater 4 may be set 10 to 20°C higher than the temperature of heater 4A. Similarly, the temperature of heater 4 may be set 10 to 20°C higher than the temperature of heater 4B. This allows the film stretching apparatus 100 to perform preheating, stretching, and relaxation processes on the film F in order from upstream. Performing a preheating process on the film F can reduce deformation and curling of the film F due to uneven stretching. In addition, performing a relaxation process on the film F can reduce residual stress on the film F when its temperature drops.

[0055] 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]

[0056] 4. Heater (First heating section) 4A Heater (Second heating section) 4B Heater (Third heating section) 5 Inert Box 100 Film stretching machine A1 1st position H1, H2, H3 heating area R1 First guide roller R2 Second guide roller R3 Third Guide Roller R4 4th guide roller S1 First virtual plane S2 Second virtual plane S3 Third Virtual Plane

Claims

1. A pair of guide rollers are arranged spaced apart in the conveying direction of a film that is conveyed under tension in the conveying direction, and each extends in the width direction of the film, A first heating unit that heats the surface of the film between the pair of guide rollers by thermal radiation, The system comprises an inert box filled with inert gas that covers at least the first heating unit and the heating region in the film between the pair of guide rollers that is heated by the first heating unit, The first guide roller on the upstream side of the pair of guide rollers guides the film being conveyed from the opposite side of the first heating unit with respect to a first virtual plane that extends the main surface of the film between the pair of guide rollers, The second guide roller, the downstream of the pair of guide rollers, guides the conveyed film toward the opposite side of the first heating section relative to the first virtual plane. The pair of guide rollers each contact the back surface of the film, A third guide roller is positioned upstream of the first guide roller and extends in the width direction of the film, A fourth guide roller is positioned downstream of the second guide roller and extends in the width direction of the film, A second heating unit that heats the surface of the film between the third guide roller and the first guide roller by thermal radiation, The device further includes a third heating unit that heats the surface of the film between the second guide roller and the fourth guide roller by thermal radiation, The third guide roller guides the film being conveyed from the opposite side of the second guide roller with respect to a second virtual plane that extends the main surface of the film between the first guide roller and the third guide roller, The fourth guide roller guides the conveyed film on the opposite side from the second guide roller with respect to a third virtual plane extending the main surface of the film between the second guide roller and the fourth guide roller. A film stretching apparatus in which the third guide roller and the fourth guide roller each contact the surface of the film.

2. The film stretching apparatus according to claim 1, wherein the inert box further covers the second heating section, the third heating section, the heating region in the film between the third guide roller and the first guide roller that is heated by the second heating section, and the heating region in the film between the second guide roller and the fourth guide roller that is heated by the third heating section.

3. The film stretching apparatus according to claim 1, wherein the angle at which the film is gripped by the second guide roller is 90° ± 10°.

4. The distance between the film between the pair of guide rollers and the radiating surface of the first heating section is 20 to 100 mm. The film stretching apparatus according to claim 1, wherein, in a plan view from a direction perpendicular to the main surface of the film between the pair of guide rollers, the downstream end of the radiating surface of the first heating unit is located downstream of a first position 20 mm upstream from the rotation axis of the second guide roller.

5. The film stretching apparatus according to claim 1, wherein the film is stretched by tension applied in the transport direction in the heating region.

6. A method for manufacturing a film using the film stretching apparatus described in any one of Claims 1 to 5.

7. The method for manufacturing a film according to claim 6, wherein the glass transition temperature of the film is 200 to 350°C.

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