KR20100039681A - Manufacturing method of optical film - Google Patents

Abstract

PURPOSE: An optical film manufacturing method is provided to form a knurling unit without overlapping a part where a thickness deviation of films generates by oscillating the optical film before a knurling process. CONSTITUTION: An optical film manufacturing method comprises the following: producing a sheet by flowing a dope solution on a supporting body; manufacturing a film by supporting both ends of the sheet separated from the supporting body before drying the film; removing the solution by drying the film; oscillating the film to the perpendicular direction to the film progress direction; perpendicular the film to make a pattern on both ends of the film; trimming the edge of the film; and rolling the film.

Description

Manufacturing method of optical film

The present invention relates to a method for manufacturing an optical film, and more particularly, to a method for manufacturing an optical film that can prevent surface damage from being caused by the thickness variation of the entire film width.

In general, a cellulose acetate film (also called a TAC film) forms a film by a solvent casting method. Specifically, after preparing a dope solution, it is flexible to a casting drum or a casting band, and the peeled film is supported at both ends by a tenter. After the transfer, it is dried and the film is wound into the final step.

Although the thickness of the film is uniformly produced during the manufacturing process, there is a slight variation in the product specification. In general, even in a stable manufacturing process, there is a thickness variation in the specification and the variation of the deviation is small. In other words, the relatively thick parts continue to be thick, on the contrary, the relatively thin parts continue to be made thin so that the thick parts of the film touch each other when the film is rolled up, so that vertical stripes appear on the film. Even if loosened, the marks remain, which causes serious problems for use as optical films.

In the case of cellulose acetate film (aka TAC film), a pattern is formed at both ends of the film by a knurling process before the winding process to prevent such streaks or thickened by attaching a protective film at both ends of the film to protect it. The parts to which the films are attached are laminated, and the center product part is wound up in the shape which floats in the air.

Japanese Laid-Open Patent Publication No. 2003-147092 describes a method of oscillating the core of a roll from side to side so that the thickness of the knurling portion is 2 to 12 µm thicker than the film portion, and the height of the knurling does not have to be accurate. That is, although the film is moved left and right by the winding roll in the winding step of the film, this is for leveling the height difference of the knurling portion, and not for reducing the effect of the thickness difference on the whole film.

The knurling process puts a pattern on both ends of the film to make it thicker than the other part, so that only the both ends (the knurling part) contact with each other when the film is wound, and the product part is wound in the shape of floating in the air.

However, as in the Japanese Laid-Open Patent Publication No. 2003-147092, when oscillating the winder itself after the knurling process, the portion having the knurling pattern is disturbed and the knurling effect disappears, thereby reducing the effect of the knurling portion.

Japanese Laid-Open Patent Publication No. 1997-040235 is provided with a meandering detector for detecting the meandering state of a molded article, and a device for trimming the edges of a film while the hoisting drum is moved left and right in response to a meandering detector signal. . As such, when oscillation is performed using a winder, a large equipment, generally called a biaxial winder, which is used commercially, must be moved, and at the same time, the device is equipped with knurling, edge trimming, and edge winding or processing facilities. It gets complicated and the parts that need to move get bigger. Moreover, since the knurling facility and the winder form a facility, there is a disadvantage in that foreign matters that may be generated when the knurling pattern is taken are incorporated in the take-up roll.

Japanese Laid-Open Patent Publication 1995-144814 discloses a film winding method in which both ends of a film sent out from a film forming step are cut by an ear cutter, and then wound in a roll shape by a winding machine. This invention oscillates the ear cutter and the winder, and is characterized in that the oscillation position at the film end can be changed. In addition, Japanese Patent Application Laid-Open No. 1996-175708 discloses that an uneven portion is formed in a portion of both inner ends of the film rather than both ends of the film, the height of the convex portion is higher than the average height of the film, and both ears are cut by the cutter, and the ear cutter and A method is disclosed in which a winding machine is simultaneously oscillated to position cut lines in the uneven portion forming zone and the amount of the uneven portion forming zone is changed to wind the film according to the winding machine.

All of the above-described patents are configured to oscillate the winding roll itself when winding the winding roll, and a method of maximizing the knurling effect while reducing foreign matter mixing by the knurling and reducing the thickness variation of the film is still not developed.

The present invention is to provide a method for reducing the influence of the thickness difference in the full width of the film, to provide a manufacturing method for stabilizing the difference in the thickness of the full width by performing an oscillation step of applying a reciprocating transfer to the film before the kneading process. .

Specifically, the present invention is not a method of oscillating the winder (winding roll) itself from side to side, but by oscillating the film itself before the nerling step, it is possible to prevent overlapping of portions where the thickness variation of the film is generated, and then the thickness variation. It is to provide a method of manufacturing an optical film that can be maximized by the lamination of the knuckle portion because the knurling portion is continuously laminated by winding through the knurling process on the running film so as not to generate a reciprocating transfer.

The present invention for achieving the above object

a) casting the dope solution onto a support to produce a sheet;

b) supporting both ends of the sheet peeled from the support with a tenter, and transporting and drying to prepare a film;

c) drying the film to remove the solvent;

d) reciprocating the left and right or at an angle in a direction perpendicular to the traveling direction of the film;

e) a knurling step of forming a pattern at both ends of the film;

f) a trimming step of removing the edge portion of the film; And

g) winding up step;

It provides a method for producing an optical film comprising a.

Hereinafter, in the present invention, the round-trip transfer means oscillation, and the term may be used interchangeably.

The present invention will be described in more detail with reference to the drawings.

In the present invention, the optical film is a cellulose triacetate film, the thickness is preferably 40 ~ 100 ㎛.

In general, the cellulose acylate film can produce a film having excellent optical properties or physical properties compared to other manufacturing methods through a solution casing method (solvent casing method).

Cellulose acylate films have high transparency and mechanical strength and also have dimensional stability that is not highly dependent on humidity and temperature. Therefore, it is widely used as a support for optical materials requiring such characteristics. Usually cellulose acylate film is prepared by casting a dope made by dissolving a solvent and a polymer together on an endless support.

The solution flexible film forming method as described above first produces a solution (hereinafter referred to as 'dope') in which cellulose acylate is dissolved in a solvent. Various additives are added to the dope according to various purposes of the film to be produced. Next, the dope is cast on a support such as a drum or steel band through a cast die and then dried to obtain a cellulose acylate film.

More specifically, in the present invention, the dope for manufacturing the optical film may be manufactured according to a conventional manufacturing method, and the patents for manufacturing such dope are disclosed in Japanese Patent Laid-Open No. 2006-089691, Japanese Patent Laid-Open No. 2007- 304287 et al.

The dope of the present invention is not limited, but the solid content of 10 to 30% by weight is advantageous for film forming.

In step a), the support may be a drum or a steel band.

Next, the sheet separated from the support in step b) is transferred to a tenter such as a pin tenter or a clip tenter and dried to prepare a film.

Next, the film is dried in step c) to completely remove the solvent used in preparing the dope solution. At this time, it is preferable to dry, conveying a film with the roller of the multistage in a drying part specifically, It is not limited to this.

In the present invention, the step (d) of the reciprocating transfer (oscillation) step may be performed according to a method commonly used in the film field, and specifically, installed in a direction perpendicular to the advancing direction of the film at the top or the bottom of the film. The guide roller 10 can be reciprocated by slowly reciprocating the left and right (see FIG. 1) or by making the traveling direction bent at an angle from the left and the right (see FIG. 2). At this time, by allowing the reciprocating conveyance at a predetermined width or a certain angle, even if a deviation in the film thickness occurs, it can be prevented from continuously picked up in one portion.

Since the cellulose triacetate film has a small tensile elongation of the film itself and a high modulus, a break occurs easily when the deformation is large, it is preferable to reduce the width and the rate of change of the oscillation. Although not limited, preferably, the reciprocating feed width is within 5 cm of left and right, more specifically 1 to 5 cm, and the reciprocating feed rate is 5 cm / min, and more specifically 1 to 5 cm / min. .

In addition, even when the driving direction is shifted by a given angle, it is preferable that the resulting reciprocating conveying width is within 5 cm of the left and right, more specifically 1 to 5 cm.

Next, in step e), the knurling process is performed at the end of the film so that the knurling portion 21 having regular irregularities is formed so as to be wound without forming a line in the film. At this time, as a method of forming regular irregularities, the irregularities are generated by the stamping portion formed on the rollers while being pressed by the pair of rollers 20. The knurling process is to be formed on both ends of the film, it is possible to be formed only on one side and may be formed on both sides. In order to be formed only on one side, one pair of rollers use the stamping roller, and one flat roller. To form a knurling portion on both sides, a roller may be imprinted on both sides of the pair of rollers.

In this case, as shown in FIGS. 1 and 2, the knurling portion 21 is uniformly formed at a predetermined portion irrespective of the conveying direction of the film that is reciprocated from side to side by the reciprocating step. Therefore, unlike removing the thickness variation formed in the film by oscillating and winding after conventional kneading, even if winding as it is formed by constantly forming the knurling portion in the film in the direction of the step difference portion of the film, the thickness variation of the film does not occur, The lamination effect can be maximized.

Next, trimming and removing the edge of the film on which the knurling part is formed, that is, the edge part, cuts the edge from the trimming part 30 to reciprocate the left and right by the oscillation step in the film traveling direction. Cut out regularly. Trimming is then possible by conventional devices.

Next, it is wound on the take-up roller 40, in which case the take-up roller is wound as it is without oscillation so that the knurling parts are stacked and stacked.

The present invention forms a knurling portion so that the thickness deviation of the film does not overlap by reciprocating transfer (oscillation) before the knurling step, so that the thickness deviation of the film occurs even if the winding is performed without oscillation in the winding step. The overlapping can be prevented from affecting the appearance of the film, and since the knurling portion is continuously stacked uniformly, the knurling effect can be maximized.

Hereinafter, the present invention will be described by way of example for the detailed description of the present invention, but the present invention is not limited to the following examples.

Example 1

The dope solution formed by dissolving methylene chloride: metalol in a solvent of 92: 8 weight ratio so that the cellulose triacetate has a solid content of 17 wt% was discharged at a rate of 10 m / min through a casting die and then It was dried with 30% by weight of residual solvent and then peeled off.

The peeled sheet was further dried while being supported by both ends in a tenter provided with hot air at 140 ° C., and finally dried through a dryer provided with hot air at 140 ° C.

The film exiting the dryer was oscillated at a width of 5 cm / min at a left and right 5 cm width, and the film proceeded while oscillating in a predetermined direction as shown in FIG. 1, and then trimming edge portions of both ends to wind the film.

Comparative Example 1

A film was prepared in the same manner as in Example 1, but was wound by kneading and trimming without oscillation.

Comparative Example 2

The dope solution formed by dissolving methylene chloride in a solvent in a weight ratio of 92: 8 so that the cellulose triacetate had a solid content of 17 wt% was discharged at a rate of 10 m / min through a casting die to obtain an endless steel. The belt was dried with 30% by weight of residual solvent and then peeled off.

The peeled sheet was further dried while passing through the tenter provided with hot air at 140 ° C, and finally dried through a dryer provided with hot air at 140 ° C.

After kneading the film out of the dryer in a predetermined direction, the edge portions at both ends were trimmed, and the winding rolls were wound while oscillating at a width of 5 cm / min at a width of 5 cm.

As a result, the knurling portion was not formed uniformly.

Comparative Example 3

A film was prepared in the same manner as in Comparative Example 2, but was wound while oscillating at a 5 cm / min speed at a width of 5 cm left and right by using an integrated winder formed in one device such as a knurling part, trimming part, and winding part.

As a result, it was found that a lot of foreign matter was on the film.

In the above Examples and Comparative Examples, after winding 300m on a 3-inch core, the wound appearance of each of the two rolls was compared, and is shown in Table 1 below.

At this time, the average thickness except the knurling part of the film was 80 micrometers, and the deviation was ± 0.5 micrometer.

TABLE 1

As shown in Table 1 above, when the same average thickness has a deviation but undergoes an oscillation and undergoes a knurling and trimming step, there is no change in the appearance of the film, but the oscillation does not change even though the deviation is small. Stripes were faintly observed while winding up, and thus the stripes were generated to be visible even when unrolling and observing the roll again.

In addition, in the case of oscillation of only the winding part, the knurling part does not overlap, and in this case, the oscillation effect cannot be sufficient because the oscillation width can be reduced to form the knurling part properly.

In addition, in the case of using a winder in which the knurling part, the trimming part and the winding part are integrated, the apparatus is complicated, and foreign matter defects occur more than other cases due to the proximity of the knurling part.

Figure 1 is a schematic diagram for explaining the oscillation, knurling, trimming and winding process of the manufacturing method of the present invention.

Figure 2 is a schematic diagram for explaining the oscillation, nuring, trimming and winding process of the manufacturing method of the present invention.

Claims (5)

a) casting the dope solution onto a support to produce a sheet; b) supporting both ends of the sheet peeled from the support with a tenter, and transporting and drying to prepare a film; c) drying the film to remove the solvent; d) reciprocating the left and right or at an angle in a direction perpendicular to the traveling direction of the film; e) a knurling step of forming a pattern at both ends of the film; f) a trimming step of removing the edge portion of the film; And g) winding up step; Method for producing an optical film comprising a. The method of claim 1, Reciprocating transfer in the step d) is a method of manufacturing an optical film reciprocating at a predetermined width or a predetermined angle using a guide roller installed in a direction perpendicular to the film traveling direction. 3. The method of claim 2, The reciprocating transfer width is within 5cm left and right, the reciprocating transfer rate is 5cm / min manufacturing method of the optical film. The method of claim 3, The film is a cellulose triacetate film, the method of producing an optical film having a thickness of 40 ~ 100㎛. The method of claim 4, wherein The dope solution is a method for producing an optical film having a solid content of 10 to 30% by weight.

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