Film manufacturing method

Abstract

To provide a method of manufacturing a film that suppresses the film from being flawed (made defective) by a carrier roll.SOLUTION: A method of manufacturing a film comprises a drawing process of heating and drawing a film F1 by the use of a drawing furnace 10, a carrying process of carrying the film F1 sent out of the drawing furnace 10 with a plurality of rolls, and a sticking process of sticking protective films F2, F3 on the carried film F1. A surface of the foremost-stage roll 21 closest to the drawing furnace 10 among the plurality of rolls in the carrying process satisfies all of conditions (1) to (3). Here, (1) the hardness is 1,000 to 2,200 HV. (2) The electric resistivity is 106 to 1012 Ω cm. (3) The thermal conductivity is 0.15 to 0.25 W / (m k).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing a film. [Background technology]

[0002] Resin films that are used as optical films for liquid crystal displays, etc. Patent Document 1 discloses a method for producing an optical film as a method for producing such a resin film.

[0003] The method for producing an optical film described in Patent Document 1 is as follows: a mixing and preparing step of mixing a resin and a solvent to prepare a dope to be cast onto a support; a casting step of casting the prepared dope onto a support, and drying and solidifying or cooling and solidifying the dope to form a web as a cast film; a peeling step of peeling the web from the support; a drying step for drying the web; A stretching step of stretching the web (for example, a tenter method in which both side edges of the web are fixed with clips or the like and stretched), a cutting step of cutting both ends of the formed optical film in the width direction by a slitter while conveying the formed optical film; a winding step of winding the optical film by a winding device to obtain an original roll (film roll) of the optical film; Includes: [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2019 / 239625 Summary of the Invention [Problem to be solved by the invention]

[0005] In such film manufacturing methods, rolls are used to support the film while it is being transported within or between processes, and the transport rolls can sometimes cause minute scratches (defects) on the film.

[0006] Such fine scratches on the film disappear or are reduced by the heating and stretching in the stretching process, so it is desirable to prevent the film from being scratched by the transport rolls after the stretching process.

[0007] An object of the present invention is to provide a method for producing a film that suppresses the occurrence of scratches (defects) on the film caused by transport rolls. [Means for solving the problem]

[0008] The method for producing a film according to the present invention comprises a stretching step of heating and stretching a film in a stretching furnace, a transport step of transporting the film output from the stretching furnace using a plurality of rolls, and a laminating step of laminating a protective film to the transported film. The surface of the foremost roll, which is the closest to the stretching furnace among the plurality of rolls in the transporting step, satisfies all of the following conditions (1) to (3): (1) The hardness is 1000HV or more and 2200HV or less. (2) Electrical resistivity is 10 6 Ω cm or more 10 12 Ω·cm or less. (3) The thermal conductivity is 0.15 W / (m·k) or more and 0.25 W / (m·k) or less. [Effects of the Invention]

[0009] According to the present invention, it is possible to prevent scratches (defects) on the film caused by the transport rolls. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic side view illustrating a stretching step, a transporting step, and a laminating step in the production of a film according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic perspective view of a first transport roll in the transport step shown in FIG. [Figure 3] 3 is a partially enlarged cross-sectional view of the surface of the first transport roll shown in FIG. 2. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] An example of an embodiment of the present invention will be described below with reference to the accompanying drawings. The same or equivalent parts in each drawing are designated by the same reference numerals. For convenience, hatching and reference numerals may be omitted. In such cases, reference should be made to other drawings.

[0012] The method for producing the film according to this embodiment is the same as described above, for example, a mixing and preparing step of mixing a resin and a solvent to prepare a dope to be cast onto a support; a casting step of casting the prepared dope onto a support and drying or cooling it to solidify it to form a film as a cast membrane; a peeling step of peeling the film from the support; A drying process to dry the film; a stretching step of stretching the film; a conveying process for conveying the film; a lamination step of laminating a protective film onto the film; a cutting step of cutting both ends of the film in the width direction by a slitter while conveying the film; A winding process in which the film is wound up to obtain the original film roll; Includes:

[0013] Examples of films to which this manufacturing method can be applied include optical films.

[0014] In the mixing and preparation process, at least the resin and the solvent are mixed to prepare a uniform dope. The resin used in the mixing and preparation process can be any resin that is soluble in the solvent. Examples include cycloolefin resin (COP), polycarbonate, polyarylate, cellulose ester resin, polyimide resin, and acrylic resin.

[0015] In the stirring preparation step, any solvent capable of dissolving the resin can be used. Specific examples include chlorine-containing solvents such as dichloromethane, aromatic solvents such as toluene and xylene, ketone solvents such as methyl ethyl ketone and acetone, and ester solvents such as ethyl acetate and methyl acetate. Furthermore, a poor solvent that does not dissolve the resin by itself can be added as long as it does not impair the homogeneity of the resin solution.

[0016] In the stirring and preparation step, a solvent-soluble additive can be added as a third component, such as an ultraviolet absorber or an infrared absorber.

[0017] In the casting process, the dope prepared in the stirring and preparation process is sent to a support and cast onto it. The thickness of the dope cast onto the support is adjusted by a known method to adjust the thickness of the coating film. The resulting coating film is heated on the support to remove the solvent to an extent that the film can be peeled off. To evaporate the solvent, there are a method of blowing air from the film side, a method of transferring heat from the backside of the support using a liquid, a method of transferring heat from the front and back using radiant heat, etc., and these may be used alone or in combination as appropriate.

[0018] The support can be made of a material that is resistant to the dope, such as a polyethylene terephthalate film, and is used under tension.

[0019] In the above casting step, the film is dried and solidified or cooled and solidified on the support until it has a film strength that allows it to be peeled off, and then in the peeling step, the film is peeled off from the support while retaining its self-supporting properties.

[0020] The amount of solvent remaining in the film on the support at the time of peeling is preferably in the range of 5 to 20% by weight, depending on the strength of the drying conditions, the length of the support, etc. If it is more than this, it will put a strain on the drying in the subsequent drying step, which will cause productivity issues. On the other hand, if it is less than this, problems such as spontaneous peeling of the film from the support during the casting step may occur.

[0021] The amount of residual solvent is defined by the following formula. Residual solvent amount (wt%) = (weight of film before heat treatment - weight of film after heat treatment) / (weight of film before heat treatment) × 100 Here, the heat treatment when measuring the amount of residual solvent means a heat treatment at 150°C for 1 hour.

[0022] The stretching step, the transporting step, and the laminating step will be described in detail below.

[0023] FIG. 1 is a schematic side view showing the stretching step, the transporting step, and the laminating step in the film manufacturing method according to this embodiment.

[0024] (Stretching process) The film F1 is heated and stretched in one or two directions in a stretching furnace (tenter furnace) 10. The stretching method is not particularly limited, but examples thereof include a tenter method in which both side edges of the film are fixed with clips or the like and stretched.

[0025] The temperature of the stretching furnace 10 may be determined depending on the type of film F1. The temperature of the stretching furnace 10 is set so that the glass transition temperature of the film F1 is lower than the maximum temperature of the stretching furnace 10 within a range that does not cause thermal decomposition of the film F1, for example, so that the difference between the glass transition temperature of the film F1 and the maximum temperature of the stretching furnace 10 is 5°C or more and 50°C or less. For example, when the film F1 is a polycarbonate film (glass transition temperature 154°C), the temperature of the drawing furnace 10 is set to 159°C to 189°C (maximum temperature 189°C).

[0026] (Transportation process) A plurality of rolls transports the film F1 output from the stretching furnace 10. In the example of Fig. 1, the plurality of rolls includes a first transport roll 21, a second transport roll 22, a third transport roll 23, a tension detection roll 25, and adhesive rolls 27 and 28.

[0027] The first transport roll 21, the second transport roll 22, and the third transport roll 23 are rolls that transport the film F1. The tension detection roll 25 is a roll that detects the tension of the film F1 between the second transport roll 22 and the third transport roll 23. This allows the tension of the film F1 to be adjusted. The adhesive roll 27 is a roll that adsorbs and removes foreign matter adhering to one side of the film F1, and the adhesive roll 28 is a roll that adsorbs and removes foreign matter adhering to the other side of the film F1.

[0028] The film produced by this production method can be slit to any desired width. In particular, when tenter stretching is performed, the film edges may have marks from the tenter clips, and these marks can be slit to ensure stable transport.

[0029] (Lamination process) Protective films F2 and F3 are laminated onto the transported film F1 by a pair of laminating rolls 31 and 32. For example, the protective film F2 is laminated onto one surface of the film F1, and the protective film F3 is laminated onto the other surface of the film F1.

[0030] (Details of the transport process) Here, the transport rolls can cause minute scratches (defects) in the film. Furthermore, when a relatively long film is transported (manufactured), the condition of the film and roll changes over time during the transport process, which tends to increase the number of minute scratches (defects) occurring from the inside to the outside of the film roll.

[0031] Such fine scratches on the film disappear or are reduced by the heating and stretching in the stretching process, so it is desirable to prevent the film from being scratched by the transport rolls after the stretching process.

[0032] In this regard, in this embodiment, the surface of the first transport roll 21, which is the frontmost roll closest to the drawing furnace among the multiple rolls in the transport process, satisfies all of the following conditions (1) to (3). (1) The hardness (Vickers hardness) is 1000 HV or more and 2200 HV or less, for example, 1600 HV. (JIS Z 2244, ISO 6507-1) (2) Electrical resistivity is 10 6 Ω cm or more 10 12 Ω·cm or less. (JIS C 2525, IEC 60468) (3) The thermal conductivity is 0.15 W / (m·k) or more and 0.25 W / (m·k) or less, for example, 0.2 W / (m·K). (JIS A 1412, ISO 8302)

[0033] Fig. 2 is a schematic perspective view of the first transport roll 21 in the transport step shown in Fig. 1, and Fig. 3 is an enlarged cross-sectional view of a portion of the surface of the first transport roll 21 shown in Fig. 2. As shown in Fig. 2, the first transport roll 21 may be composed of a columnar or cylindrical body 21b and a coating film 21a on the surface of the body 21b. The body 21b may be made of metal such as iron, aluminum, etc. The roll diameter of the body 21b may be about 118 mm. The coating film 21a may be made of a material that satisfies the above conditions (1) to (3), such as a diamond-like carbon (DLC) film. The thickness of the coating film 21a may be approximately 3 μm. The coating film 21a may be made of multiple overlapping films made of the same or different materials.

[0034] 3, the surface of the first transport roll 21 has an uneven structure. For example, it is preferable that the surface of the first transport roll 21 satisfies the following conditions (4) to (6). (4) The 10-point average roughness Rzjis is 0.3 <Rzjis<1.0である。 (5) The arithmetic mean roughness Ra is 0 <Ra≦1.0である。 (6) Maximum height Rz is 0.3 <Rz<1.0である。 (JIS B 0601-2001, ISO 4287-1997)

[0035] As described above, according to the film manufacturing method of this embodiment, among the multiple rolls in the conveying process from the stretching step to the laminating step, the surface of the first conveying roll 21, which is the frontmost roll closest to the stretching furnace 10, satisfies the above conditions (1) to (3). This makes it possible to prevent scratches (defects) on the film F1 caused by the first conveying roll 21.

[0036] Specifically, according to the film manufacturing method of this embodiment, the surface of the first transport roll 21 has a low electrical resistivity, so the first transport roll 21 is less likely to become charged, and foreign matter is less likely to adhere to the surface of the first transport roll 21. This makes it possible to prevent scratches (defects) on the film F1 caused by the first transport roll 21. Furthermore, even with a relatively long film F1, it is possible to prevent an increase in the number of scratches (defects) occurring from the inside to the outside of the film F1.

[0037] Furthermore, according to the film manufacturing method of this embodiment, the surface of the first transport roll 21 has a low thermal conductivity, so when the first transport roll 21 comes into contact with the film F1 that has been heated and stretched in the stretching furnace 10, shrinkage of the film F1 can be reduced, and the occurrence of wrinkles in the film F1 due to shrinkage can be suppressed. This makes it possible to suppress scratches (defects) in the film F1 due to wrinkles. Furthermore, even with a relatively long film F1, it is possible to suppress an increase in the number of scratches (defects) occurring from the inside to the outside of the roll.

[0038] Furthermore, according to the film manufacturing method of this embodiment, the surface of the first transport roll 21 has an uneven structure. For example, the ten-point average roughness Rzjis, arithmetic mean roughness Ra, and maximum height Rz of the surface of the first transport roll 21 satisfy the above conditions (4) to (6). As a result, as shown in FIG. 3, foreign matter X adhering to the surface of the first transport roll 21 is positioned in the valleys of the uneven structure, reducing contact with the film F1. This makes it possible to suppress the occurrence of scratches (defects) on the film F1.

[0039] Generally, the first transport roll 21, which is the front-most roll closest to the drawing furnace 10, tends to have more foreign matter attached to it than the other rolls, so the surface of the first transport roll 21 is polished to remove the foreign matter every time a film roll is produced. As a result, the maximum height Rz of the surface of the first transport roll 21 decreases over time.

[0040] In this regard, according to the film manufacturing method of the present embodiment, the surface of the first transport roll 21 is relatively hard and therefore resistant to wear, which makes it possible to suppress a decrease over time in the maximum height Rz of the surface of the first transport roll 21 due to polishing cleaning.

[0041] As described above, foreign matter is unlikely to adhere to the surface of the first transport roll 21. For example, only wiping with alcohol may be performed. In this way, by not performing polishing cleaning or by reducing the number of times polishing cleaning is performed, it is possible to further suppress the decrease over time in the maximum height Rz of the surface of the first transport roll 21.

[0042] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and various changes and modifications are possible. [Explanation of symbols]

[0043] 10. Tenter furnace 21 First transport roll (frontmost roll) 21a Coating film (surface) 21b Body 22 Second transport roll 23 Third transport roll 25 Tension detection roll 27,28 Adhesive roll 31, 32 Laminating roll F1 Film F2, F3 protective film

Claims

1. a stretching step of heating and stretching the film in a stretching furnace; a conveying step of conveying the film output from the stretching furnace by a plurality of rolls; a lamination step of laminating a protective film onto the transported film; Equipped with The surface of the frontmost roll, which is the closest to the drawing furnace among the plurality of rolls in the conveying step, satisfies all of the following conditions (1) to (3): Film manufacturing method. (1) Hardness is 1000 HV or more and 2200 HV or less, (2) Electrical resistivity is 10 ６ Ω・cm or more 10 １２ Ω cm or less, (3) The thermal conductivity is 0.15 W / (m·k) or more and 0.25 W / (m·k) or less.

2. The method for producing a film according to claim 1 , wherein the surface of the front-stage roll is made of a diamond-like carbon (DLC) film.

3. The method for producing a film according to claim 1 or 2, wherein the surface of the front-stage roll satisfies all of the following conditions (4) to (6): (4) The 10-point average roughness Rzjis is 0.3<Rzjis<1.0, (5) The arithmetic mean roughness Ra is 0<Ra≦1.0; (6) The maximum height Rz is 0.3<Rz<1.

0.

4. the glass transition temperature of the film is lower than the maximum temperature of the stretching oven; The difference between the glass transition temperature of the film and the maximum temperature of the stretching furnace is 5 degrees or more and 50 degrees or less. The method for producing the film according to any one of claims 1 to 3.

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