Film manufacturing method

Abstract

To provide a film manufacturing method that prevents poor clip gripping and film tearing by controlling an amount of clip gripping.SOLUTION: There is provided a method for manufacturing a film, comprising: a step (step A) of moving a film in a running direction while holding both ends of the film in a width direction with a plurality of clips, and stretching and / or heat-treating the film in the width direction; and after the above step, a step (step B) of measuring coordinates of an end portion in the width direction of the film during running when the clips are released and coordinates of the clip gripping mark by a detector, wherein an amount of film gripping, which is a difference between the coordinate of the end portion of the film in the width direction and the coordinate of the clip gripping mark, is controlled to 5 to 30 mm.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a film that controls the film gripping amount by clips.

Background Art

[0002] Plastic films such as biaxially stretched polyester films are widely used in optical applications, release films, dry film resist applications, printer ribbon applications, etc. because they are excellent in heat resistance and productivity. In recent years, with the growth of the IT field, the use in optical applications has increased, such as anti-reflection films for displays, diffusion plates for backlights of liquid crystals, substrates such as touch panels, process papers for optical members such as optical displays and liquid crystal retardation plates, polarizing plates, and release films.

[0003] When manufacturing a biaxially stretched film, generally a tenter device is used. This tenter device has clip chains at both ends in the traveling direction of the film, and the clips of the clip chain travel while gripping the film to stretch, heat-fix, etc. the film. As clips in the tenter device, for example, those having the configuration shown in FIG. 1 are well known. FIG. 1 is a schematic view when observing an example of a clip of the tenter device from the traveling direction. As shown in FIG. 1, the clip 1 is attached to a clip base 3 that is slidably arranged relative to the rail 2. And this clip 1 has a base 4 and a standing portion 5 that rises from there, and a clip lever 6 is rotatably attached to the standing portion 5 with a support shaft 7 as a starting point. The clip lever 6 is rotated to the position indicated by the dotted line by a spring (not shown), and can grip the end portion in the width direction of the uniaxially stretched film 9 between the tip of its lower part (the part below the support shaft 7) and a plate 8 installed on the base 4.

[0004] In order to obtain a uniformly processed film, this clip must securely grip the film with the correct width, spacing, uniformity in the height direction, tension, etc. However, after a long period of operation, some of the numerous clips may develop looseness, play, mechanical wear, etc., resulting in poor film gripping.

[0005] Also, when the film snakes or its width fluctuates during conveyance, if the width at the tenter entrance is constant, it becomes impossible to correctly grip the edge of the film. Therefore, edge sensors are installed at both ends in front of the tenter to constantly monitor the edges of the film, and when the edge position of the film changes, the width of the tenter entrance is controlled to be adjusted. However, if the film width suddenly changes significantly, there may be cases where the clip cannot keep up and the film cannot be gripped. These poor clip grip conditions make the conveyance of the film unstable and are factors that cause unevenness in processing such as stretching unevenness, wrinkles, and film breakage.

[0006] As a countermeasure against such poor clip grip, a detector for detecting the state of the clip grip mark is provided at the exit of the tenter device, and the quality of the film grip state is determined by comparing the signal from there with a preset pass / fail criterion to discover the clips causing poor grip and perform preventive maintenance (Patent Document 1), a method of detecting and determining an abnormality in the running position from the inclination and shift amount of the clip trajectory (Patent Document 2), etc. are known.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] However, the methods described in Patent Document 1 and Patent Document 2 are for detecting defective clips from the clip gripping marks at the film ends or for determining abnormalities in the clip running positions, and cannot detect film width fluctuations or meandering, nor manage the film gripping amount.

[0009] An object of the present invention is to provide a method for manufacturing a film that can detect film width fluctuations and meandering, which are causes of poor clip gripping, from the coordinates of the end of the film that has passed through a tenter device and the clip gripping marks, and can measure and manage the film gripping amount, which is the difference between those coordinates, to prevent poor clip gripping and film breakage in the tenter device.

Means for Solving the Problems

[0010] To solve such problems, the present invention comprises the following configuration. (1) A method for manufacturing a film having a step (Step A) of moving in the running direction of the film while gripping both ends in the width direction of the film with a plurality of clips and stretching and / or heat-treating the film in the width direction, and after the step, having a step (Step B) of measuring, by a detector, the coordinates of the end in the running film width direction where the clip is released and the coordinates of the clip gripping marks, and controlling the film gripping amount, which is the difference between the coordinates of the end in the film width direction and the coordinates of the clip gripping marks, to 5 to 30 mm. (2) The method for manufacturing a film according to claim 1, having a step (Step C) of measuring, by a detector, the area of the clip gripping marks after Step A, and controlling the ratio of the area of the clip gripping marks to the clip gripping portion area to 80% or more and 100% or less. (3) The method for manufacturing a film according to (1) or (2), wherein the measurement is performed by taking an image of at least 50 mm from the end in the film width direction and performing image processing. (4) The method for manufacturing a film according to (3), wherein the image is taken when the film is on a roll. (5) The manufacturing method of the film according to any one of (1) to (4), wherein the film conveyance speed in the step B or the step C is 70 to 250 m / min. (6) The manufacturing method of the film according to any one of (1) to (4), wherein the thickness of the film in the step B or the step C is 1 μm or more and 100 μm or less.

Effect of the Invention

[0011] According to the present invention, it is possible to detect film width fluctuations and meandering, which are causes of poor clip gripping, from the coordinates of the edge of the film that has passed through the tenter device and the clip gripping marks, and by measuring and managing the film gripping amount, which is the difference between those coordinates, it is possible to provide a manufacturing method of a film that prevents poor clip gripping and film breakage in the tenter device.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiment for Carrying Out the Invention

[0013] Hereinafter, the manufacturing method of the film of the present invention will be specifically described. The manufacturing method of the film of the present invention is a film manufacturing method having a step (step A) of moving in the traveling direction of the film while gripping both ends in the width direction of the film with a plurality of clips, and stretching and / or heat-treating the film in the width direction. After the step A, it has a step B of measuring, by a detector, the coordinates of the end portion in the width direction of the film running with the clip released and the coordinates of the clip gripping mark, and controlling the film gripping amount, which is the difference between the coordinates of the film end portion and the coordinates of the clip gripping mark, to 5 to 30 mm.

[0014] The manufacturing method of the film of the present invention is not particularly limited in other steps as long as it has the step A and a step B of measuring, by a detector, the coordinates of the end portion in the width direction of the film running with the clip released after the step A and the coordinates of the clip gripping mark. It preferably has a longitudinal stretching step of stretching the sheet in the longitudinal direction, and the film obtained in the longitudinal stretching step has the step A by a tenter device. Here, the sheet refers to a sheet formed by cooling and solidifying a molten thermoplastic resin into a sheet shape. The longitudinal direction refers to the direction in which the sheet or film travels in the film manufacturing process, and the width direction refers to the direction orthogonal to the longitudinal direction within the sheet surface or film surface.

[0015] The uniaxially stretched film obtained in the longitudinal stretching step is gripped at the film end portions by the left and right clips at the tenter inlet and travels in the longitudinal direction along the clip rail. The film traveling with the clips is stretched at a predetermined magnification within the tenter device, and at the tenter outlet, the left and right clips release the gripping of the film end portions and send the film to the next step. As shown in FIG. 2, which is a schematic view of the film end portion exiting the tenter, a clip gripping mark 11a remains on the uniaxially stretched film 9 exiting the tenter. The distance from the film end portion 10 to the clip gripping mark 11a is called the film gripping amount 12.

[0016] Generally, the film gripping amount is generally constant, but due to clip defects, sudden serpentine movement and width variation of the film, etc., the film gripping amount may change or gripping failure may occur. If the film gripping amount is too small, the clip may not be able to grip the film and clip detachment may occur. Also, generally, the film thickness including the step of stretching in the film width direction is the thickest at the outermost ends and gradually becomes thinner toward the center. The present invention can be suitably applied to a film whose film thickness is the thickest at the outermost ends and gradually becomes thinner toward the center. If the film gripping amount is too large, since the thin portion of the film is gripped by the clip and the actual stretching magnification also becomes high, stress may be applied and film breakage may occur. From the viewpoints of reducing the gripping failure of the clip and film forming stability, it is important to detect the coordinates of the film end portion and the clip gripping trace and control the film gripping amount to be 5 mm or more and 30 mm or less. The film gripping amount is preferably 5 mm or more and 25 mm or less, more preferably 5 mm or more and 20 mm or less, and still more preferably 7 mm or more and 13 mm or less.

[0017] By adopting such an aspect, it is possible to detect the serpentine movement, width variation of the film, and change in the film gripping amount in real time, and it is possible to immediately take measures to prevent the serpentine movement, width variation, and film gripping amount variation. The means for controlling the film gripping amount to be 5 mm or more and 30 mm or less is not particularly limited as long as the effects of the present invention are not impaired. For example, the method of changing the width of the tenter inlet according to the width variation or serpentine movement, or changing the conditions of the casting drum to prevent the width variation, etc. can be mentioned.

[0018] The area of the portion that contacts and grips the clip's film (clip gripping portion area) is a value specific to the clip and is determined by the equipment specifications (the area where the clip is expected to contact the film). Usually, the area of the film gripping mark 11a is approximately equal to the clip gripping portion area. However, due to chipping, inclination, etc. of the clip gripping portion, the area of the film gripping mark may become smaller than the clip gripping portion area as shown in 11b. In defective clips with a small clip gripping mark area, the film may not be gripped, resulting in clip detachment and film breakage. Also, since it is film breakage caused by defective clips, there is a high possibility that clip detachment and film breakage will occur again even if the film is passed through the tenter again. From the perspective of early detection of defective clips, it is preferable to control the ratio (X / Y) of the area (X) of the clip gripping mark to the clip gripping portion area (Y) to be 80% or more and 100% or less. The ratio (X / Y) of the area (X) of the clip gripping mark to the clip gripping portion area (Y) is preferably 85% or more and 100% or less, and more preferably 90% or more and 100% or less.

[0019] The method for manufacturing the film of the present invention includes, after the step A, a step B of measuring, by a detector, the coordinates of the end portion in the film width direction during running with the clip released and the coordinates of the clip gripping mark, and a step C of measuring, by a detector, the area of the clip gripping mark. The step B and the step C may be in any order as long as they are after the step A, and the same detector may be used. The means for measuring the coordinates of the film end portion and the clip gripping mark or the area of the clip gripping mark is not particularly limited as long as the effects of the present invention are not impaired. For example, a camera can be used. The camera is not particularly limited as long as it can receive the light after the illumination light has passed through the end portion in the width direction, and the imaging may be monochrome or color. The imaging range is preferably set to capture at least 50 mm from the film end portion in order to surely capture the film end portion and the clip gripping mark. It is more preferable to capture at least 70 mm from the film end portion, and even more preferable to capture at least 100 mm from the film end portion. The coordinates of the film end portion and the clip gripping mark or the area of the clip gripping mark are measured from the captured image. As the method, a method of visually identifying and measuring the film end portion and the clip gripping mark from the obtained image, a known image processing method (automatic measurement by software), etc. can be used. Further, a known image processing AI technology (deep learning) etc. may be used.

[0020] The step B of measuring the coordinates of the film end portion and the clip gripping mark and the step C of measuring the area of the clip gripping mark are not particularly limited as long as they are steps after the step A (downstream of the tenter), but if the film end portion is flat and there is no positional variation in the film thickness direction, more accurate detection can be achieved. Therefore, detection on the roll after the film has been sufficiently cooled is preferred. Also, it is preferable to continuously measure the coordinates or the clip gripping mark area, which means measuring in real time or at regular intervals under the condition that the production line is operating.

[0021] In the method for manufacturing the film of the present invention, the coordinates of the film end and the clip gripping mark, or the film conveyance speed at the measurement location of the clip gripping mark area is preferably 70 to 250 m / min, and the film thickness at the measurement location is preferably 1 μm or more and 100 μm or less, more preferably 100 to 200 m / min, and the film thickness at the measurement location is preferably 10 μm or more and 40 μm or less.

[0022] The resin constituting the film in the method for manufacturing the film of the present invention is not particularly limited as long as the effects of the present invention are not impaired. For example, polyester resins such as polyethylene terephthalate, polyethylene isophthalate, and polybutylene terephthalate, polyolefin resins such as polyethylene and polypropylene, polyamide resins such as nylon 6, nylon 66, nylon 12, aromatic nylon, and aramid, other polyimide resins, polysulfone resins, polyvinyl resins, polyester ether resins, polycarbonate resins, polyphenylene sulfide resins, polylactic acid resins, cellulose resins, acrylic resins, etc. can be used alone or in combination. Among them, it is preferable to use polyethylene terephthalate, polypropylene, aramid, and polyimide resins. In addition, various resins may contain a copolymer component in the molecular chain as long as the effects of the present invention and the performance as a film are not impaired, and may also contain additives such as antistatic agents, weathering agents, inorganic or organic particles, lubricants such as waxes, and pigments.

[0023] Hereinafter, the method for manufacturing the film of the present invention will be specifically described by taking a polyethylene terephthalate (PET) film as an example, but the present invention is not limited to the following embodiments.

[0024] After drying PET under reduced pressure at 100°C to 170°C for 8 hours, it is supplied to a known extrusion machine for melt lamination and heated to melt at 240°C to 310°C. Then, the extrusion amount is made uniform by a gear pump or the like, and the melted PET is extruded, and foreign matters, gelated substances, etc. are removed through a high-precision filter with a collection efficiency of 95% or more for particles of 5 μm or more. At this time, usually, when the film is a single-layer structure, one extrusion machine is used, and when it is a laminated structure, a plurality of extrusion machines can be used. When using a plurality of extrusion machines, the thermoplastic resin that has passed through the filter is fed into a laminating device. As the laminating device, a multi-manifold die, a feed block, a static mixer, etc. can be used, and these can be arbitrarily combined.

[0025] Subsequently, the obtained molten PET is extruded in a sheet form onto a cooling body such as a casting drum maintained at 280°C to 300°C and cooled and solidified to obtain an unstretched film. As a specific method for obtaining an unstretched film from the sheet-like melt, a method of using an electrode such as a wire-shaped, tape-shaped, needle-shaped or knife-shaped electrode to adhere the sheet-like melt to a cooling body such as a casting drum by electrostatic force and rapidly cooling and solidifying it is preferable.

[0026] Next, this unstretched film is heated to 60°C to 160°C with a roll heated to 60°C to 150°C and a radiation heater and stretched in the longitudinal direction to obtain a uniaxially stretched film. The stretching ratio in the longitudinal direction is preferably 3 to 5 times, more preferably 3.5 to 3.8 times. This longitudinal stretching can be performed in one step using one or a plurality of stretching rolls with the same peripheral speed, or can be performed in multiple steps using a plurality of stretching rolls with different peripheral speeds.

[0027] Also, after the longitudinal stretching step and before proceeding to the transverse stretching step described later, it is also possible to provide a step of applying a coating material for forming a functional layer such as an easy-adhesion layer on both sides or one side of the obtained uniaxially stretched film. The method of applying the coating material is not particularly limited, and for example, a reverse coating method, a gravure coating method, a rod coating method, a bar coating method, a wire bar coating method, a die coating method, a spray coating method, etc. can be used.

[0028] Subsequently, the obtained uniaxially stretched film is conveyed to a tenter device and stretched in the width direction (Step A). In the transverse stretching step, clips that grip both end portions in the width direction of the uniaxially stretched film at 90°C to 130°C are run along a rail, so that while the uniaxially stretched film is running in the longitudinal direction, the uniaxially stretched film is stretched in the transverse direction by widening the interval in the width direction of the clips. The magnification of the transverse stretching can be appropriately adjusted within a range that does not impair the effects of the present invention, but is preferably 3 to 5 times, and more preferably 4.0 to 4.3 times.

[0029] The film obtained by stretching in the width direction may then be subjected to a heat treatment (heating and / or cooling) as necessary to stabilize the structure of PET by crystallization. The means for performing these treatments is not particularly limited as long as the effects of the present invention are not impaired, but it is preferable to perform them within the tenter device from the viewpoint of simplicity. After performing the heat treatment at 90°C to 240°C, a relaxation treatment is performed, and it is cooled in the conveying step to obtain a biaxially stretched film.

[0030] The obtained biaxially stretched film exits the tenter and is conveyed to the next step. At this time, in order to detect the meandering and width fluctuation of the film in real time, it is preferable to continuously measure the coordinates of the film end portion and the clip gripping mark of the conveyed film. Also, in order to prevent film breakage and clip detachment, it is also preferable to control the film gripping amount to 5 mm or more and 30 mm or less. Furthermore, in order to detect and maintain defective clips in real time, it is also preferable to continuously measure the area of the clip gripping mark and control the ratio (X / Y) of the area (X) of the clip gripping mark to the clip gripping portion area (Y) to 80% or more and 100% or less.

[0031] The measurement of the coordinates of the film end portion and the clip gripping mark of the biaxially stretched film, or the area of the clip gripping mark, is preferably performed by taking an image of the end portion in the film width direction and performing image processing. In order to surely capture the film end portion and the clip gripping mark, it is preferable to take an image up to at least 50 mm from the film end portion.

[0032] Also, if the measurement location is a process after the film end is flat, there is no positional variation in the film thickness direction, and the film is sufficiently cooled, more accurate detection can be achieved. Therefore, detection on the roll after cooling the film temperature at the center in the film width direction to 10 to 50°C is preferred.

[0033] After the transverse stretching process, the biaxially stretched film obtained by cooling in the conveying process is once wound as an intermediate roll under the conditions of a winding speed of 75 m / min to 250 m / min and a winding tension of 40 N / m to 790 N / m using a wide-width winder. Thereafter, it is cut into the required width and length by a slitter to become the final product.

Example

[0034] Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not construed as being limited thereto. The measurement methods and the like for each item in the examples and comparative examples are as follows. (Implementation conditions and evaluation methods) (1) Film formation stability 〇: Film breakage in the tenter did not occur for 48 hours or more from the start of production. △: Film breakage in the tenter did not occur for 24 hours or more from the start of production, but occurred before reaching 48 hours. ×: Film breakage in the tenter occurred before reaching 24 hours from the start of production. (2) Measurement of film gripping amount When the difference between the film gripping amount measured according to the present invention and the film gripping amount measured visually is 0 mm or more and 2 mm or less, it was defined that the film gripping amount was correctly measured. 〇: The ratio of the film gripping amount that could be correctly measured was 70% or more. △: The ratio of the film gripping amount that could be correctly measured was 50% or more and less than 70%. ×: The ratio of the film gripping amount that could be correctly measured was less than 50%. (3) Clip gripping trace area [%] For all clips, measure the area of the clip gripping mark [m 2 , and define the ratio (X / Y) of the clip gripping mark area (X), which is the minimum value among them, to the clip gripping part area (Y) as the clip gripping mark area [%]. (4) Presence or absence of defective clips 〇: There was no defective clip where the ratio (X / Y) of the area of the clip gripping mark (X) to the clip gripping part area (Y) was less than 80%. ×: There was one or more defective clips where the ratio (X / Y) of the area of the clip gripping mark (X) to the clip gripping part area (Y) was less than 80%.

[0035] (Example 1) After drying polyethylene terephthalate (PET) under reduced pressure at 160 °C for 8 hours, it was supplied to a known extrusion machine for melt lamination and melt-extruded at 275 °C, and filtered through a high-precision filter with a collection efficiency of 95% and a particle size of 5 μm or more. Subsequently, the obtained molten PET was extruded in a sheet form from a slit die maintained at 285 °C, and cooled and solidified on a casting roll with a surface temperature of 25 °C using the electrostatic application casting method to obtain an unstretched film. This unstretched film was longitudinally stretched 4.2 times at a temperature of 110 °C using a stretching roll with a surface roughness Ra of 0.2 μm to obtain a uniaxially stretched film. Subsequently, a clip chain in which 1000 clips with a width of 100 mm and the same shape were connected at intervals of 25 mm was introduced into a tenter device provided on both outer sides of the uniaxially stretched film, and while gripping both widthwise ends with clips at a position where the film gripping amount was 10 mm, it was stretched 4.5 times in the width direction under hot air at 115 °C, heat-treated at 215 °C, and then subjected to a relaxation treatment, and cooled to room temperature in a conveying process with a conveying speed of 180 m / min to obtain a biaxially stretched film with a thickness of 25 μm.

[0036] As shown in Fig. 4, which is a schematic view of the film end and the installation location of the clip gripping mark detection device as seen from the side of the roll, in the biaxially stretched film exiting the tenter, both ends of the uniaxially stretched film 9 on the conveying roll 13 were photographed with a camera 15 from a point where the distance 14 from the film was 370 mm in a direction perpendicular to the film conveyance direction and parallel to the sheet surface. At this time, the temperature at the center in the width direction of the uniaxially stretched film 9 on the conveying roll 13 was 30°C. As shown in Fig. 5, which is a schematic view of the film end and the installation location of the clip gripping mark detection device as seen from above, the image shooting range 16 was set to shoot a range of ±100 mm in the width direction centered on the position 19, which is half the length of the biaxially stretched film width from the center 18 in the width direction of the tenter 17, so that the image shooting range from the film edge was 100 mm. From the photographed image, the coordinates of the film end and the clip gripping mark and the area of the clip gripping mark were measured by image processing. The camera used was the FS-B4KU7GES-F from Omron Sentech Co., Ltd., and the image processing method used was an application created using the image processing application development software "MERLIC" from MVTec Co., Ltd. Also, the imaging resolution was 50 μm in the width direction and 115 μm in the flow direction, and it was ensured that at least one clip gripping mark was imaged in each image.

[0037] Finally, the biaxially stretched film was wound up to obtain a film roll. Table 1 shows the evaluation results of the film manufacturing method.

[0038] (Examples 2 to 4, Comparative Examples 1 to 3) A biaxially stretched polyester film was obtained in the same manner as in Example 1, except that the film gripping amount, the image shooting range from the film edge, the film conveyance speed, and the film thickness were changed as shown in Table 1. Table 1 shows the evaluation results.

[0039] From the results of Examples 1 to 4 and Comparative Examples 1 to 3, it was confirmed that the film forming stability was high when the film gripping amount was 5 to 30 mm, the image shooting range from the film edge was at least 50 mm, the film conveyance speed was 70 to 250 m / min, the film thickness was 1 μm or more and 100 μm or less, and there were no defective clips.

[0040]

Table 1

Explanation of Symbols

[0041] 1 Clip 2 Rail 3 Clip Stand 4 Base 5 Upright Portion 6 Clip Lever 7 Support Shaft 8 Liner 9 Film 10 Film End 11a Normal Clip Gripping Trace 11b Defective Clip Gripping Trace 12 Film Gripping Amount 13 Conveyor Roll 14 Distance from Film 15 Camera 16 Image Shooting Range 17 Tenter 18 Center in the Width Direction of the Tenter 19 Position at a Length of 1 / 2 of the Biaxially Stretched Film Width from the Center in the Width Direction of the Tenter

Claims

1. A method for manufacturing a film, comprising a step (step A) of moving in the running direction of the film while gripping both ends in the width direction of the film with a plurality of clips, and stretching and / or heat-treating the film in the width direction, wherein after the step, a step (step B) of measuring, by a detector, the coordinates of the end portion in the running film width direction where the clip is released and the coordinates of the clip gripping trace is included, and the film gripping amount, which is the difference between the coordinates of the end portion in the film width direction and the coordinates of the clip gripping trace, is controlled to be 5 to 30 mm.

2. The method for manufacturing a film according to claim 1, further comprising a step (step C) of measuring, by a detector, the area of the clip gripping trace after the step A, and controlling the ratio of the area of the clip gripping trace to the clip gripping portion area to be 80% or more and 100% or less.

3. The method for manufacturing a film according to claim 1 or claim 2, wherein the measurement is performed by image processing by taking an image of at least 50 mm from the end portion in the film width direction.

4. The method for manufacturing a film according to claim 3, wherein the image is taken when the film is on a roll.

5. The method for manufacturing a film according to claim 1 or claim 2, wherein the film conveyance speed in the step B or the step C is 70 to 250 m / min.

6. The method for manufacturing a film according to claim 1 or claim 2, wherein the thickness of the film in the step B or the step C is 1 μm or more and 100 μm or less.

Images