JP2024003889A - Method for manufacturing film using tenter apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a film that can simultaneously reduce oil scattering on the film and overstretching of the film due to insufficient heat at a gripping part by rectifying an airflow near a clip with a clip cover.

SOLUTION: In a method for manufacturing a film using a tenter device having gripping means for gripping both ends of the film and heating means for blowing hot air onto the film, the gripping means includes a clip chain having a clip cover capable of rectifying airflow near a clip.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a method for producing a film that can simultaneously reduce oil scattering onto the film and overstretching of the film due to insufficient heat at the gripping portion in a tenter device for transversely stretching the film.

Plastic films such as biaxially oriented polyester films have excellent heat resistance and productivity, and are therefore widely used in optical applications, release films, dry film resists, printer ribbons, and the like. In recent years, with the growth of the IT field, there has been an increase in the demand for anti-reflection films for displays, diffusion plates for LCD backlights, base materials for touch panels, and processing paper and release materials for optical components such as optical displays, liquid crystal retardation plates, and polarizing plates. Its use in optical applications such as molded films is increasing. The qualities required of the film for such uses include, for example, a reduction in foreign substances such as oil and oligomers adhering to the film surface, a reduction in internal foreign substance defects, and a reduction in film surface scratches.

A tenter device is generally used when producing a biaxially stretched film. This tenter device usually has gripping means for gripping both ends of the film, heating means for blowing hot air onto the film, and oil supply means for supplying oil to the gripping means. Further, the gripping means includes a clip chain for gripping the film, a clip cover, a rail on which the clip runs, and power for driving the clip. In such a tenter device, there are problems such as oil supplied from the oil supply means scattering from the gripping means onto the running film, resulting in oil defects, and overstretching of the film at the portion gripped by the gripping means. It's here.

As a method for solving such problems, Patent Document 1 discloses a method of attaching gripping path cover means to part or all of the gripping means to protect the clip chain from hot air. Patent Document 2 discloses a film manufacturing method that prevents film breakage during the stretching process by setting the air pressure inside the grip path cover, which prevents oil scattering, to be lower than the part through which the film passes.

Japanese Patent Application Publication No. 2015-30185 Japanese Patent Application Publication No. 2000-254966

In the method described in Patent Document 1, part or all of the gripping path along which the clip chain travels has a gripping path cover that protects the clip chain from hot air and an exhaust means, so that oil mist can escape outside the gripping path cover. As a result, it has become possible to produce a film with fewer oil defects. However, since the clip chain is not exposed to hot air, the temperature of the film gripping portion does not rise, causing the problem that the inside of the gripping portion is overstretched and the film breaks.

In addition, in the method described in Patent Document 2, by setting the air pressure inside the grip path cover that prevents oil from scattering onto the film to be lower than that of the film traveling part, the temperature of the film end near the clip is stabilized, and the temperature is stabilized during stretching. It is now possible to reduce film breakage. However, since the air pressure inside the cover is adjusted by supplying and exhausting air for cooling the clip chain within the cover, there is a problem in that it is difficult to adjust the air pressure each time to prevent overstretching.

The present invention solves the above problems and provides a method for producing a film that can simultaneously reduce oil adhesion to the film in a tenter device and overstretching of the film due to insufficient heat at the gripping portion.

As a result of intensive studies, the present inventors have found that the above-mentioned problems can be solved, and have arrived at the present invention.
That is, the present invention is as follows.
(1) A method for producing a film using a tenter device having gripping means for gripping both ends of the film and heating means for blowing hot air onto the film, the gripping means being capable of rectifying airflow near the clips. A method for producing a film, comprising: a clip chain having a clip cover.
(2) The method for producing a film according to (1), wherein at least a portion of the clip cover has a corrugated plate shape.
(3) The method for producing a film according to (1), wherein the clip cover has a plurality of plate-like bodies forming an angle of 50° or more and 90° or less with the film surface.
(4) The method for producing a film according to any one of (1) to (3), wherein the distance between the tip of the clip cover and the film is 20 mm or more and 40 mm or less.

According to the present invention, by rectifying the airflow near the clip with the clip cover, it is possible to simultaneously reduce oil scattering on the running film and overstretching of the film due to insufficient heat in the gripping part. A manufacturing method can be provided.

FIG. 2 is a schematic cross-sectional view showing a first example of a gripping means in a tenter device that can be used in the film manufacturing method of the present invention. FIG. 2 is a schematic plan view showing a first example of a gripping means in a tenter device that can be used in the film manufacturing method of the present invention. FIG. 3 is a schematic cross-sectional view showing a second example of a gripping means in a tenter device that can be used in the film manufacturing method of the present invention. 1 is a schematic plan view of a tenter device that can be used in the film manufacturing method of the present invention.

Hereinafter, the method for manufacturing the film of the present invention will be specifically explained with reference to the drawings. The film manufacturing method of the present invention is a film manufacturing method using a tenter device having gripping means for gripping both ends of the film and heating means for blowing hot air onto the film, wherein the gripping means The invention is characterized by comprising a clip chain having a clip cover capable of rectifying the current.

The tenter device used in the film manufacturing method of the present invention includes gripping means for gripping both ends of the film, and the gripping means includes a clip chain having a clip cover capable of rectifying airflow near the clip. Note that "both ends of the film" here refers to both ends of the film in the width direction, and the width direction refers to the direction in which the film runs during the manufacturing process (sometimes referred to as the machine direction or longitudinal direction). Refers to orthogonal directions within a plane. The configuration of such a gripping means is not particularly limited as long as it can grip both ends in the width direction. A preferred example is one having a plurality of plate-like bodies forming an angle of 50° or more and 90° or less.

An example in which at least a portion of the clip cover has a corrugated plate shape will be described with reference to FIGS. 1 and 2. The gripping means shown in FIGS. 1 and 2 consists of a clip 1 that grips the film 4 and a clip cover 2 that covers it, and a part of the clip cover 2 has a corrugated plate shape (the corrugated plate shape is indicated by numeral 3). 2 is a schematic top view of the gripping means of FIG. 1; In the embodiments shown in FIGS. 1 and 2, the corrugated sheet-shaped portion 3 of the clip cover 2 has a flow direction parallel to the direction inclined by 90°-θ° from the thickness direction of the film 4 toward the width direction, and 4 is installed so that the flow direction is parallel to the width direction of the corrugated plate. Here, the thickness direction of the film refers to a direction perpendicular to the film surface, and the flow direction of the corrugated sheet refers to a direction parallel to the direction of the waves (grooves) of the corrugated sheet-shaped portion. Further, the angle θ shown in FIG. 1 is the angle formed between the film 4 and the corrugated plate-shaped portion 3. With this configuration, the hot air blown from the top of the tenter flows into the film gripping part of the clip 1 along the flow direction of the corrugated plate, so the temperature near the clip 1 increases and the film near the gripping part increases. Overstretching is reduced.

Next, an embodiment in which the clip cover includes a plurality of plate-like bodies whose angles with the film surface are 50° or more and 90° or less will be described with reference to FIG. 3. The gripping means shown in FIG. 3 is composed of a clip 1 and a clip cover 2 that covers it, and a portion of the clip cover 2 is a plurality of plate-shaped bodies (the plurality of plate-shaped bodies are denoted by reference numerals). 5. In the embodiment of FIG. 3, there are two plate-like bodies, but it is also possible to have three or more plates.) Even if the plural plate-like bodies are formed by providing another plate on a part of the clip cover 2 that covers the area other than the film 4 as shown in FIG. It may be formed by providing a member made of a plurality of plates separately from the covering portion.

The angle θ' between the plurality of plate-like bodies 5 and the film 4 is 50° or more and 90° or less. Although it is preferable that the plurality of plate-shaped bodies 5 be provided so that the plates are parallel to each other, they may be attached at different angles. In addition, if a plurality of plate-like bodies are attached at different angles with the film, the angle θ' with the film 4 for at least one of the plurality of plate-like bodies is 50° or more and 90° or less. If so, it can be considered as ``having a plurality of plate-like bodies whose angles with the film surface are 50 degrees or more and 90 degrees or less.''

If the angle formed between the film surface and the plurality of plate-shaped bodies is less than 50°, the amount of heat inside the tenter will be insufficient because excessive hot air will be taken in from the upper part of the plurality of plate-shaped bodies. As a result, overstretching occurs only in the vicinity of the gripped portion that has a sufficient amount of heat, and the film may break. On the other hand, when the angle between the film surface and the plurality of plate-like bodies exceeds 90°, the hot air flowing along the plurality of plate-like bodies becomes difficult to flow inside the clip cover. As a result, the temperature of the film gripping portion does not rise, and overstretching occurs inside the gripping portion, which may cause the film to break. From the above viewpoint, in the film manufacturing method of the present invention, it is more preferable to have a plurality of plate-shaped bodies whose angle with the film surface is 60° or more and 80° or less.

The tenter device used in the film manufacturing method of the present invention has heating means for blowing hot air onto the film. By having such a means, it is possible to adjust the temperature of the film to a temperature suitable for stretching, and to heat set the film after stretching at a high temperature.

Hereinafter, the tenter device used in the film manufacturing method of the present invention will be explained with reference to the drawings. FIG. 4 is a schematic plan view of a tenter device that can be used in the film manufacturing method of the present invention. In FIG. 4, the film 4 is held at both ends in the width direction by a plurality of clips 1 (individual clips are not shown, but the entire clip chain is shown) at the entrance of the tenter device 6, and is held at the preheating zone 7 of the tenter device 6. sent to. The film 4 is heated in a preheating zone 7 by being blown with hot air at a predetermined temperature, and then heated in a stretching zone 8 by hot air at a temperature suitable for stretching and then stretched. Thereafter, the film 4 is heat-set in a heat-setting zone 9 by being blown with hot air at a temperature suitable for heat-setting. The heat-set film 4 is further cooled to a predetermined temperature in a cooling zone (not shown), discharged from the tenter device 6, and released from the grip by the clips 1.

A plurality of clips 1 are connected to a clip chain and are covered by a clip cover 2 in a section from the entrance to the exit of the tenter device 6. Focusing on one clip 1, the clip 1 grips the film at the entrance of the tenter device 6, passes through the plurality of bends of the gripping path inside the tenter device 6, releases the film 4 at the exit, and passes through the outside of the tenter device 6. Return to the entrance via the return route. This movement is repeated by driving the clip chain.

Further, it is desirable to provide a cover means to prevent outside air from hitting the clip 1 also in the return path (the section from when the clip 1 releases the film 4 until it returns to the entrance). Since the cover means for the return path does not require a space for holding the film 4, it is preferable that the return path cover means be a closed system and insulated, and have a means for supplying cold air for cooling and an exhaust means.

The gripping path within the tenter device 6 also has a clip cover 2 to prevent oil from scattering from the clip 1. It is desirable that the clip cover 2 has a structure that rectifies the airflow in the vicinity of the gripping portion of the film 4, as shown in FIGS. 1 to 3, for example. Although it is not possible to create a closed system because the film is gripped, it is preferable that the distance between the tip of the clip cover and the film (d (Figs. 1, 2), d' (Fig. 3)) is 20 mm or more and 40 mm or less. . If the distance d, d' between the tip of the clip cover and the film is less than 20 mm, the film may come into contact with the clip cover, causing scratches on the film. If the distance d, d' between the tip of the clip cover and the film is 40 mm or more, oil may scatter from the clip chain and oil-derived defects may occur on the film.

When a film is manufactured using a tenter device equipped with a clip that does not have a clip cover, the oil supplied to the bearings of the clip chain is blown away by the centrifugal force of the bearings and adheres to the film, resulting in oil-related defects. There is. In addition, when a film is manufactured using a tenter device that has a conventional oil scattering prevention cover, although the adhesion of oil supplied to the bearings can be reduced, the inside of the film gripping part may be overstretched and whitened, causing the film to break. There is. In the film manufacturing method of the present invention, it is possible to reduce both adhesion of oil supplied to the bearing and film breakage due to whitening of the inside of the film gripping portion.

The resin constituting the film in the film manufacturing method of the present invention is not particularly limited as long as it does not impair the effects of the present invention, and examples thereof include polyester resins such as polyethylene terephthalate, polyethylene isophthalate, and polybutylene terephthalate, polyethylene, polypropylene, etc. Polyolefin resins, nylon 6, nylon 66, nylon 12, aromatic nylon, polyamide resins such as aramid, other polyimide resins, polysulfone resins, polyvinyl resins, polyester ether resins, polycarbonate resins, polyphenylene sulfide resins Resins, polylactic acid resins, cellulose resins, acrylic resins, etc. can be used alone or in combination. Among these, it is preferable to use polyethylene terephthalate, polypropylene, aramid, and polyimide resins. The various resins may contain copolymerized components in their molecular chains as long as they do not impair the effects of the present invention or the performance as a film, and may also contain antistatic agents, weathering agents, inorganic or organic particles, and wax. It may also contain lubricants such as, additives such as pigments, etc.

Hereinafter, the method for manufacturing the film of the present invention will be specifically explained using a polyethylene terephthalate (PET) film as an example, but the present invention is not limited to the following embodiments.

After drying the PET under reduced pressure at 100°C to 170°C for 8 hours, it is fed to a known extruder for melt lamination and melt extruded at 240°C to 310°C to achieve high precision with a collection efficiency of 95% or more for particles of 5 μm or more. Filter. Next, the obtained molten PET was extruded into a sheet through a slit die kept at 280°C to 300°C, and cooled and solidified on a casting roll with a surface temperature of 20°C to 30°C using an electrostatic casting method. An unstretched film is obtained. This unstretched film is heated to 60° C. to 160° C. using a roll heated to 60° C. to 150° C. and a radiation heater, and stretched 3 to 5 times in the longitudinal direction to form a uniaxially stretched film. Subsequently, the obtained uniaxially stretched film was transported to a tenter device, stretched 3 to 5 times in the width direction at 90 ° C to 130 ° C, heat treated at 90 ° C to 240 ° C, and then subjected to relaxation treatment. A biaxially stretched film is obtained by cooling during the conveyance process. Thereafter, the biaxially stretched film is wound up at a winding speed of 75 m/min to 250 m/min and a winding tension of 40 N/m to 790 N/m to obtain a film roll.

The tenter device includes a gripping means for gripping both ends of the film and a heating means for blowing hot air onto the film, and the gripping means holds a clip chain having a clip cover capable of rectifying the airflow near the clip. Use what you have.

Examples of clip covers that can rectify the airflow near the clip include those in which at least a portion of the clip cover has a corrugated plate shape, and clip covers in which the angle with the film surface is 50° or more and 90° or less. A material having a plate-like body can be suitably used.

EXAMPLES The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited thereto. In addition, each evaluation shown in an Example was performed by the method and conditions shown below.

(Evaluation method)
(1) Oil scattering The film was unwound for 1000 m from the obtained film roll, and the presence or absence of oil defects was inspected using a reflection inspection machine (“MaxEye. .
○: As a result of inspecting a film length of 1000 m, no oil defects were found in the film.
Δ: As a result of inspecting a film length of 1000 m, 1 to 4 oil defects were found in the film.
×: As a result of inspecting a film length of 1000 m, five or more oil defects were found in the film.

(2) Whitening of film edges A film was unwound 100 m from the obtained film roll, and the whitening state due to overstretching at the edges in the width direction of the film was visually observed and evaluated according to the following criteria.
○: No whitening was observed at the edges of the film in the width direction.
Δ: Whitening with a width of 3 mm or more and 5 mm or less was found at the edge of the film in the width direction.
x: Whitening with a width of 5 mm or more was found at the edge of the film in the width direction.

(3) Film breakage starting from whitening at the edges in the width direction The situation of film breakage starting from the whitening portion was visually confirmed and evaluated according to the following criteria.
○: Whitening itself did not occur. Alternatively, film breakage starting from the whitened portion did not occur for 48 hours or more from the start of production.
×: Film breakage starting from the whitened portion occurred before 48 hours had passed from the start of production.

(4) Scratches caused by scratches between the clip cover and the film The film was unwound for 100 m from the obtained film roll, and the occurrence of scratches caused by the film coming into contact with the clip cover was visually confirmed and evaluated using the following criteria. did.
○: No scratches on the film due to contact with the clip cover were observed.
×: Scratches on the film due to contact with the clip cover were found.

(Example 1)
After polyethylene terephthalate (PET) was dried under reduced pressure at 160°C for 8 hours, it was fed to a known extruder for melt lamination, melt extruded at 275°C, and filtered with a high-precision filter of 5 μm or more with a collection efficiency of 95%. . Subsequently, the obtained molten PET was extruded into a sheet form through a slit die kept at 285°C, and was cooled and solidified using an electrostatic casting method in the form of a casting roll with a surface temperature of 25°C to obtain an unstretched film. . This unstretched film was heated to 105° C. using a roll heated to 103° C. and a radiation heater, and stretched 4.3 times in the longitudinal direction to obtain a uniaxially stretched film. Subsequently, the obtained uniaxially stretched film was transported to the tenter device shown in FIG. 4, stretched 4.4 times in the width direction at 110°C, heat treated at 210°C, subjected to relaxation treatment, and transported. It was cooled in the process to obtain a biaxially stretched film. Thereafter, the biaxially stretched film was wound up at a winding speed of 200 m/min and a winding tension of 150 N/m to obtain a film roll. Table 1 shows the obtained film roll and the evaluation results of film breakage starting from whitening. As shown in Figures 1 and 2, the clip cover in the tenter device has a part in the shape of a corrugated plate, and the angle θ between the corrugated plate-shaped part and the film and the distance d between the tip of the clip cover and the film are, respectively. 70° and 20 mm were used.

(Examples 2-7, Comparative Examples 1-2)
A film roll was obtained in the same manner as in Example 1, except that the clip cover conditions were as shown in Table 1. Table 1 shows the obtained film roll and the evaluation results of film breakage starting from whitening. The clip covers of Examples 2, 6, and 7 are of the form shown in Figs. 1 and 2, the clip covers of Examples 3 to 5 are of the form shown in Fig. 3, and the clip cover of Comparative Example 1 is of the form shown in Fig. 3. In this embodiment, a portion formed by a plurality of plate-like bodies was used as a single plate-like body (in both cases, the angles θ and θ' with the film and the distances d and d' with the film are as shown in Table 1. ). Furthermore, in Comparative Example 2, a film was produced using a tenter device without a clip cover.

According to the present invention, it is an object of the present invention to provide a method for producing a film that can simultaneously reduce oil scattering on the film and overstretching of the film due to insufficient heat at the film gripping part in a tenter device for transversely stretching the film. Can be done. The film obtained by the film production method of the present invention has few oil defects and whitening due to overstretching and is easy to process, so it can be suitably used for optical applications, mold release applications, dry film resist applications, printer ribbon applications, etc. can.

1 Clip (gripping means)
2 Clip cover 3 Corrugated plate-shaped portion of the clip cover 4 Film 5 Plural plate-like bodies 6 Tenter device 7 Preheating zone 8 Stretching zone 9 Heat setting zones d, d' Distances between the clip cover and the film θ, θ' Clip cover and Angle with film

Claims (4)

A method for manufacturing a film using a tenter device having gripping means for gripping both ends of the film and heating means for blowing hot air onto the film, the gripping means having a clip cover capable of rectifying airflow near the clip. 1. A method for producing a film, comprising: a clip chain having a clip chain. 2. The method for manufacturing a film according to claim 1, wherein at least a portion of the clip cover has a corrugated plate shape. 2. The method for manufacturing a film according to claim 1, wherein the clip cover has a plurality of plate-shaped bodies forming an angle of 50 degrees or more and 90 degrees or less with the film surface. 4. The method for producing a film according to claim 1, wherein the distance between the tip of the clip cover and the film is 20 mm or more and 40 mm or less.

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