JP2023141058A - Film stretching apparatus and film manufacturing method - Google Patents

Abstract

To provide a film stretching apparatus that can suppress width direction shrinkage of a film.SOLUTION: The film stretching apparatus (100) includes a pair of guide rollers (R1, R2) and a heating unit (H), and in which at least one of the pair of guide rollers has a first portion (R1a, R2a) having a first surface roughness, and a second portion (R1b, R2b) having a second surface roughness greater than the first surface roughness arranged on both sides of the first portion in the width direction.SELECTED DRAWING: Figure 1

Description

The present invention relates to a film stretching device and a method for producing a film.

Patent Document 1 discloses a technique in which the surface roughness of the roll surface is varied depending on the position in the width direction of the roll in a manufacturing method of diagonally stretching a film. Further, Patent Documents 2 and 3 specify the surface roughness of the roll that comes into contact with the original fabric in order to obtain a good product in a film manufacturing method. Patent Document 4 defines the contact distance of the original fabric with respect to the roll in a film manufacturing method.

Japanese Patent Application Publication No. 2013-202979 Japanese Patent Application Publication No. 7-1575 Japanese Patent Application Publication No. 2004-20636 JP2008-307888A

A technique is also known in which a thermoplastic film is used as a raw material, and the film is heated and stretched in the transport direction. In such a technique, since the film is stretched in the length direction, the film may shrink in the width direction, which may cause problems.

One aspect of the present invention aims to reduce shrinkage of a film in the width direction in a film stretching device that stretches the film in the transport direction.

In order to solve the above problems, a film stretching device according to one aspect of the present invention is arranged so as to be spaced apart in the transport direction of a film that is transported while being applied with tension in the transport direction, and in the width direction of the film. a pair of guide rollers extending in the direction of the guide roller, and a heating unit that heats the surface of the film between the pair of guide rollers by thermal radiation, and at least one of the pair of guide rollers has a first surface roughness. The surface roughness includes a first portion, and a second portion having a second surface roughness larger than the first surface roughness, which is disposed on both sides of the first portion in the width direction.

Furthermore, the second portions may be located at both ends of the region in contact with the film.

Further, on each of both sides of the first portion in the width direction, a contact length in the width direction between the second portion and the film may be 15 mm or more and 65 mm or less.

Further, the length of the second portion in the width direction may be 80 mm or more on each of both sides of the first portion in the width direction.

Further, a contact length in the conveyance direction between the second portion and the film may be 110 mm or more on each of both sides of the first portion in the width direction.

Further, a contact area between the second portion and the film may be 1,760 mm ² or more and 15,300 mm ² or less on each of the widthwise opposite sides of the first portion.

Further, the second surface roughness may have a maximum height of 1.6S or more.

Further, the first surface roughness may have a maximum height of 0.4S or less.

Further, each of the pair of guide rollers may have a refrigerant space therein for passing the refrigerant.

Further, when stretching the film, the guide roller on the downstream side in the transport direction may rotate at a rotation speed that is 0.1% or more and 170% or less faster than the guide roller on the upstream side.

Further, the heating section may be a far-infrared heater.

Further, a plurality of the heating units are provided in the conveyance direction, and the temperature of the radiation surface of the heating unit on the downstream side with respect to the conveyance direction is the same as the temperature of the radiation surface of the heating unit on the upstream side with respect to the conveyance direction. The temperature may be (i) higher than or equal to 10°C and lower than 20°C, or (ii) lower than the temperature of the radiation surface by 10°C or higher and lower than 20°C.

Moreover, a plurality of the heating parts may be provided in the width direction of the film.

Further, in a plan view from a direction perpendicular to the surface of the film between the pair of guide rollers, the downstream end of the radiation surface of the heating section in the conveyance direction is located at the downstream end of the guide roller in the conveyance direction. The first position may be located downstream of the first position, which is 20 mm away from the rotation axis in the upstream direction in the transport direction.

Further, the second portion may be provided over the entire circumference of the guide roller.

In order to solve the above-mentioned problems, a method for manufacturing a film according to another aspect of the present invention provides a method for producing a film, in which a film is placed spaced apart in the transport direction of the film, which is transported under tension in the transport direction; heating the surface of the film between the pair of guide rollers by thermal radiation while guiding the film by a pair of guide rollers extending in the width direction, at least one of the pair of guide rollers a first portion having a surface roughness of 1, and a second portion disposed on both sides of the first portion in the width direction and having a second surface roughness larger than the first surface roughness.

According to one aspect of the present invention, shrinkage of the film in the width direction can be suppressed.

1 is a perspective view showing an example of a schematic configuration of a film stretching device according to an embodiment of the present invention. 1 is a plan view showing an example of a schematic configuration of a film stretching apparatus according to an embodiment of the present invention. 1 is a side view showing an example of a schematic configuration of a film stretching device according to an embodiment of the present invention. 3 is a diagram showing the internal structure of a guide roller R. FIG. It is a perspective view showing an example of a schematic structure of a film stretching device concerning a modification of the present invention.

[Embodiment 1]
(Overview of film stretching device 100)
FIG. 1 is a perspective view showing an example of a schematic configuration of a film stretching apparatus 100 according to an embodiment of the present invention.

The film stretching device 100 includes a first guide roller R1 and a second guide roller R2 (together referred to as a pair of guide rollers R), and a heating section H. The film F is conveyed in the direction from the first guide roller R1 to the second guide roller R2. The film stretching apparatus 100 further includes drive rollers (not shown) upstream of the first guide roller R1 and downstream of the second guide roller R2. This is a device that stretches the film F in the transport direction by using the difference in circumferential speed between the drive rollers spaced apart. Film F is, for example, a thermoplastic film. The width of the film F is, for example, about 300 mm.

(Pair of guide rollers R)
The first guide roller R1 and the second guide roller R2 are a pair of guide rollers that are arranged apart from each other in the transport direction of the film F, which is transported under tension in the transport direction, and each extend in the width direction of the film F. It is R. The tension applied to film F is approximately 188 N/m.

The first guide roller R1 is the upstream guide roller of the pair of guide rollers R. The second guide roller R2 is the downstream guide roller of the pair of guide rollers R. The first guide roller R1 and the second guide roller R2 may be driven at different rotation speeds, or may be rotated in accordance with the conveyance of the film F.

The pair of guide rollers R are provided with a plurality of sections having different surface roughness in the width direction of the film F. The details will be described later.

(Heating section H)
The heating unit H is a far-infrared heater that heats the surface of the film F between the pair of guide rollers R by thermal radiation. The heating part H is preferably provided at a distance of 40 mm from the film surface (surface) on the heating part H side.

The film F between the pair of guide rollers R is heated by heat radiation from the heating section H, and the surface temperature of the film F is heated to a temperature higher than the glass transition temperature (for example, about 255 to 275° C.). Thereby, the film F can be stretched in the transport direction by the tension of the pair of guide rollers R.

The heating section H is composed of a plurality of far-infrared heaters in the transport direction. The far-infrared heater on the upstream side in the conveyance direction is referred to as a first heating section H1, and the far-infrared heater on the downstream side is referred to as a second heating section H2. The temperatures of the radiation surfaces of the first heating section H1 and the second heating section H2 may be different, and the temperature of the radiation surface of the second heating section H2 is 10° C. or more higher than the temperature of the radiation surface of the first heating section H1. Temperatures higher than 20°C are preferred. By this measure, stretching unevenness can be suppressed.

In addition, the heating section H is not limited to a two-stage structure, and may have a three-stage or more structure. By performing heating in multiple stages, it is possible to compensate for the lack of heat when the conveyance speed is increased.

Depending on the film F, stretching unevenness may occur if a sudden temperature drop is applied. In such a case, the temperature of the downstream heating section H is set lower than the temperature of the upstream heating section H (for example, the temperature of the radiation surface of the second heating section H2 is set lower than the temperature of the radiation surface of the first heating section H1). By lowering the temperature by 10° C. or more and 20° C. or less lower than the above temperature), a sudden temperature drop can be suppressed and stretching unevenness can be suppressed.

That is, by providing the heating section H in multiple stages, effects such as high-speed conveyance and suppression of stretching unevenness can be obtained.

The first heating section H1 and the second heating section H2 may each include a plurality of far-infrared heaters 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. Further, by setting a gradient in the temperature setting of the far-infrared heater in the width direction of the film F (for example, setting the temperature at the center of the film F to be lower), it is possible to suppress stretching unevenness.

(a reflector)
The film stretching apparatus 100 may further include a reflecting plate (not shown) on the opposite side of the heating section H with the film F interposed therebetween. The reflector plate reflects the heat radiation from the heating section H that has passed through the film F, and serves to heat the film surface (front surface) on the side of the heating section H as well as the film surface (back surface) on the opposite side of the heating section H. It is a board. The reflective plate may be an aluminum flat plate, and is preferably provided at a distance of 20 mm from the back surface of the film.

(Geometric arrangement of film stretching device 100)
FIG. 2 is a plan view showing an example of a schematic configuration of a film stretching apparatus 100 according to an embodiment of the present invention. FIG. 2 is a plan view perpendicular to the surface of the film F.

As shown in FIG. 2, the width of the film F is W1. Further, each of the pair of guide rollers R has a length W2 and a diameter D1. For example, W1 is 300 mm, W2 is 400 mm, and D1 is φ150 mm.

The film F is held in the center of a pair of guide rollers R, and the film F is conveyed by the frictional force caused by the contact between the film F and the guide rollers R.

The first guide roller R1 has a first portion R1a having a first surface roughness and a second portion R1b having a second surface roughness larger than the first surface roughness at the center in the width direction of the film F. Contains. Further, the first guide roller R1 further includes a third portion R1c as a portion that is not the first portion R1a between both ends of the second portion R1b.

Similarly, the second guide roller R2 has a first portion R2a having a first surface roughness, a second portion R2b having a second surface roughness located at both ends of the first portion, and both ends of the second portion R2b. and a third portion R2c located at.

The first portions R1a, R2a and the second portions R1b, R2b are provided over the entire circumference of the guide roller R, respectively. Further, the first portions R1a, R2a and the second portions R1b, R2b may be provided on at least one of the pair of guide rollers R.

The second portions R1b and R2b are located at both ends of the area where the film F comes into contact. Further, the second surface roughness is a maximum height (JIS B 0601 1994) of 1.6S or more. As a result, a large frictional force can be generated between the second portions R1b and R2b with the back surface of the film F, and both ends of the film F can be gripped with sufficient frictional force, and the width direction of the film F can be gripped with sufficient frictional force. can prevent shrinkage.

Further, the first surface roughness is a maximum height of 0.4S or less. This prevents scratches on the back surface of the film F that is in contact with the first portions R1a and R2a, making it possible to obtain good products and improving yield.

The length of the second portions R1b and R2b in the width direction with respect to the film F is W3. For example, W3 is 80 mm. In addition, on each of the widthwise sides of the first portions R1a and R2a, if the widthwise length of the second portions R1b and R2b that contacts the film F is W4, W4 is 15 mm or more and 65 mm or less, especially 40 mm. It is preferable that there be. The reason why the value of W4 has a permissible range is that there may be meandering during transportation.

As a result, the required size of the area where the second portions R1b, R2b and the film F come into contact becomes clear, and the guide rollers R1, R2 can generate sufficient frictional force. Therefore, the guide rollers R1 and R2 can grip the film F stably.

Next, the geometric arrangement of the film F in the transport direction will be explained. The pitch of the pair of guide rollers R is L1. For example, L1 is 260 mm. Further, the irradiation area of the far-infrared heater of the heating section H is a rectangle of 120 mm x 120 mm (length L2 in the conveyance direction).

In plan view from a direction perpendicular to the surface of the film F, the upstream end of the far-infrared heater of the first heating section H1 in the transport direction is within a distance of L3 from the rotation axis of the first guide roller R1. For example, L3 is 20 mm. Similarly, in a plan view from a direction perpendicular to the surface of the film F, the downstream end of the far-infrared heater of the second heating section H2 in the conveyance direction is at a distance of L4 from the rotation axis of the second guide roller R2. It fits in. For example, L4 is 20 mm. This makes it possible to shorten the area where the film F is not heated by the heating section H up to the position where the gripping force of the second guide roller R2 starts acting on the film F. Therefore, shrinkage of the film F in the width direction can be suppressed. Here, the upstream end of the first heating section H1 may be located either upstream or downstream from the rotation axis of the first guide roller R1. Similarly, the downstream end of the second heating section H2 may be located either upstream or downstream from the rotation axis of the second guide roller R2.

FIG. 3 is a side view showing an example of a schematic configuration of a film stretching apparatus 100 according to an embodiment of the present invention. In the film stretching apparatus 100, the film F is carried in from below to the first guide roller R1, and after being stretched while being heated by the heating section H, the film F is carried out to the bottom side by the second guide roller R2. . The film F in the section carried into the first guide roller R1 and the film F in the section heated by the heating section H are perpendicular to each other, and the film F in the section heated by the heating section H and the film F in the section heated by the heating section H are separated from each other by the second guide roller R2. The film F in the section to be carried out is orthogonal to each other. This is because the film F that has come out of the heat radiating area of the heating section H moves away from the heating section H as quickly as possible, thereby limiting the influence of the heating section H on the film F to only the section heated by the heating section H. This is to do so. Therefore, heating and stretching can be prevented in other sections, and shrinkage in the width direction at unintended locations can be suppressed.

The first guide roller R1 and the second guide roller R2 each hold the film F in a 90 degree section. Therefore, the section L5 which is this contact length is L5=D1*π/4≈118 mm. Here, although the angle of each of the first guide roller R1 and the second guide roller R2 is set to 90 degrees, it is not limited to this and may be any angle. However, in order to ensure sufficient frictional force, it is preferable that the contact length of the first guide roller R1 and the second guide roller R2 with the film F in the transport direction be 110 mm or more.

(Internal structure of guide roller R)
FIG. 4 is a diagram showing the internal structure of the guide roller R. Due to the above-described configuration, the guide roller R may be exposed to heat radiation from the heating section H. Therefore, the surface temperature of the guide roller R may be distributed, and the film F may not be stretched uniformly. Therefore, in order to make the surface temperature of the contact surface of the guide roller R with the film F uniform, the guide roller R may have the following internal structure.

The guide roller R includes a roller surface layer portion 11 and a roller shaft portion 12. A refrigerant space 13 extending in the axial direction is formed inside the guide roller R. An inlet 14 and an outlet 15 for a coolant (or heat medium) are formed at both ends of the guide roller R in the axial direction, respectively. Further, the refrigerant space 13 is provided with a partition member that defines a spiral path along the axial direction. Thereby, the refrigerant (or heat medium) flowing in from the inlet 14 passes through the refrigerant space 13 by turning around the axis (as shown by the arrow in FIG. 4), and flows out to the outlet 15. Therefore, by passing the refrigerant through the refrigerant space 13, the surface temperature of the guide roller R can be kept uniform. Therefore, even if the guide roller R is exposed to heat radiation from the heater 4, the above-mentioned jacket structure can maintain a uniform surface temperature of the contact surface of the guide roller R with the film F. Can be stretched uniformly.

Note that the refrigerant (or heat medium) includes, for example, cooling water, oil, etc., but is not limited thereto. The coolant only needs to be able to control at least the surface temperature of the guide roller R to be lower than the glass transition temperature. Further, although FIG. 4 shows a structure in which the refrigerant flows in one pass, the structure is not limited to this.

(Rotational speed of guide roller R)
The film F is transported by the drive roller, and since the film F and the pair of guide rollers R are in frictional contact, the pair of guide rollers R also rotate. The rotated length of the second guide roller R2 on the outer periphery is longer than the rotated length of the first guide roller R1 on the outer periphery by the length of the stretched film F. In other words, the rotational speed of the second guide roller R2 is faster than the rotational speed of the first guide roller R1. For example, the rotational speed of the second guide roller R2 may be higher than the rotational speed of the first guide roller R1 by 0.1% or more and 170% or less.

(Modification 1)
Note that the pair of guide rollers R does not need to have the third portions R1c and R2c. Specifically, like the third guide roller R3 and the fourth guide roller R4 shown in FIG. 5, the second portions R1b and R2b may be formed up to the ends of the guide rollers. In this case, there is an advantage that the guide roller can be easily processed.

(Modification 2)
It is preferable that the length W4 in the width direction of the film F where the second portions R1b and R2b are in contact with the film F is 15 mm or more and 65 mm or less, or the contact length in the transport direction is 110 mm or more, but is not limited thereto. For example, the contact area between the second portions R1b, R2b and the film F may be set to 1,760 mm ² or more and 15,300 mm ² or less on each of the first portions R1a, R2a on both sides in the width direction. Due to this. Grip force can be ensured by ensuring a sufficient contact area having the second surface roughness.

[Additional notes]
The present invention is not limited to the embodiments described above, and various modifications can be made within the scope of the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. are also included within the technical scope of the present invention.

100, 101 Film stretching device F Film H Heating section H1 First heating section H2 Second heating section R Guide roller R1 First guide roller R2 Second guide roller R3 Third guide roller R4 Fourth guide roller R1a, R2a First part R1b, R2b second part R1c, R2c third part

Claims (16)

a pair of guide rollers that are spaced apart in the transport direction of a film that is transported with tension applied thereto, and each extending in the width direction of the film;
a heating unit that heats the surface of the film between the pair of guide rollers by heat radiation,
At least one of the pair of guide rollers has a first portion having a first surface roughness, and a second portion having a second surface roughness larger than the first surface roughness disposed on both sides of the first portion in the width direction. A film stretching device comprising: two parts. The film stretching apparatus according to claim 1, wherein the second portions are located at both ends of the area where the film comes into contact. The film stretching device according to claim 1 or 2, wherein a contact length in the width direction between the second portion and the film on each of the width direction sides of the first portion is 15 mm or more and 65 mm or less. The film stretching device according to any one of claims 1 to 3, wherein the length in the width direction of the second portion is 80 mm or more on each of both sides of the first portion in the width direction. The film stretching according to any one of claims 1 to 4, wherein a contact length in the transport direction between the second portion and the film on each of the width direction sides of the first portion is 110 mm or more. Device. The film stretching device according to any one of claims 1 to 5, wherein a contact area between the second portion and the film on each of the width direction sides of the first portion is 1760 mm ² or more and 15300 mm ² or less. . The film stretching apparatus according to any one of claims 1 to 6, wherein the second surface roughness has a maximum height of 1.6S or more. The film stretching apparatus according to any one of claims 1 to 7, wherein the first surface roughness has a maximum height of 0.4S or less. The film stretching apparatus according to any one of claims 1 to 8, wherein each of the pair of guide rollers has a refrigerant space therein for passing a refrigerant. Any one of claims 1 to 9, wherein when the film is stretched, the guide roller on the downstream side in the conveyance direction rotates at a rotation speed that is 0.1% or more and 170% or less faster than the guide roller on the upstream side. The film stretching device according to item 1. The film stretching apparatus according to any one of claims 1 to 10, wherein the heating section is a far-infrared heater. A plurality of the heating units are provided in the transport direction,
The temperature of the radiation surface of the heating section on the downstream side with respect to the conveyance direction is higher than the temperature of the radiation surface of the heating section on the upstream side with respect to the conveyance direction by (i) 10°C or more and 20°C or less or (ii) a lower temperature of 10°C or more and 20°C or less. The film stretching apparatus according to any one of claims 1 to 12, wherein a plurality of the heating units are provided in the width direction of the film. In a plan view from a direction perpendicular to the surface of the film between the pair of guide rollers, the downstream end in the conveyance direction of the radiation surface of the heating section is located at the rotation of the guide roller on the downstream side with respect to the conveyance direction. The film stretching device according to any one of claims 1 to 13, wherein the film stretching device is located downstream from the first position, which is 20 mm away from the axis in the upstream direction in the conveyance direction. The film stretching device according to any one of claims 1 to 14, wherein the second portion is provided around the entire circumference of the guide roller. While guiding the film by a pair of guide rollers that are spaced apart in the transport direction of the film that is transported with tension applied in the transport direction and each extending in the width direction of the film, the pair of guide rollers heating the surface of the film between them by thermal radiation,
At least one of the pair of guide rollers has a first portion having a first surface roughness, and a second portion having a second surface roughness larger than the first surface roughness disposed on both sides of the first portion in the width direction. A method of manufacturing a film, comprising: two parts.

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