TW201433594A - Method for manufacturing stretched film - Google Patents

Abstract

Provided is a method for manufacturing stretched film, particularly stretched film for optical uses, that has excellent transparency, few scratches, and is suitable for a variety of processing uses. This method for manufacturing stretched films, which comprises a process for longitudinal stretching of the film (called the longitudinal stretching process below) using two stretching rolls that are disposed at a distance from each other, an upstream side stretching roll (called the first stretching roll below) and a downstream side stretching roll (called the second stretching roll below), is characterized in that there are two or more nip rolls near the first stretching roll and two or more nip rolls near the second stretching roll.

Description

Method for manufacturing stretched film

This invention relates to an extended film, and more particularly to a method of making an extended film suitable for optical use.

From the viewpoint of excellent transparency, dimensional stability, and chemical resistance, a biaxially oriented thermoplastic resin film such as polyester is widely used as various optical films used in a state of transmitting and reflecting light. In particular, it is used in a base film for a liquid crystal display (LCD), a base film for hard coating, a base film for an antireflection (AR) film, a base film for light diffusion, and a transparent conductive film for a touch panel. In applications such as the use, since a strong strength and dimensional stability are required, a relatively thick film is used.

In the optical film described above, when excellent transparency, 稜鏡 lens processing, hard coating processing, and AR processing are required, the coating layer for processing or the like is excellent in adhesion, and even optical defects are desirably extremely small.

A method for improving the handleability (slipiness, take-up property, adhesion resistance, etc.) or scratch resistance of a film is disclosed in Patent Document 1.

Further, in order to obtain a film having more excellent transparency, the content of particles in the base film can be reduced or the particles can be produced. However, in this case, the scratch resistance is lowered and the scratch resistance is lowered. It is easy to produce damage to the surface which is the cause of optical defects. Therefore, as a technique for suppressing the occurrence of such damage, Patent Document 2 discloses a polyester having a length of 20 mm or more and a maximum depth of 0.5 μm or more and having a damage of 10 pieces/m ² or less by having a surfactant on the surface of the film. A film for optics. However, it is difficult to suppress the occurrence of a smaller damage, and it is impossible to satisfy the level required for the recent optical film.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Laid-Open Patent Publication No. 62-214518

[Patent Document 2] Japanese Patent Laid-Open Publication No. Hei 9-183201

In the method disclosed in Patent Document 1, since the transparency formed on the particles is reduced when the film is extended, the transparency of the film is lowered, and thus it is not suitable for a method of producing an optical film which is highly transparent or uniform in optical transparency.

Further, in the method disclosed in Patent Document 2, it is difficult to suppress generation of a smaller damage, and it is impossible to satisfy the level required for the recent optical film.

Therefore, the present invention provides a method for producing an extended film suitable for optical use which is excellent in transparency and has little damage and is suitable for various processing applications.

Carefully explore the results of the aforementioned problems and find that at separation distance In the case where two rolls are disposed, and the roll of the thermoplastic resin is longitudinally stretched, the roll which is close to the two rolls is set as follows, thereby suppressing the occurrence of damage of the film, and the present invention has been completed. That is, the present invention is as follows.

1) A method for producing a stretched film comprising the step of longitudinally stretching a film using a stretching roll (hereinafter referred to as a first stretching roll) on the upstream side and a stretching roll (hereinafter referred to as a second stretching roll) on the downstream side The method for producing a stretched film is characterized in that the number of rolls close to the first stretching roll is two or more.

(2) The method for producing an extended film according to the above, wherein the roll adjacent to the first stretching roll is two pieces; and in the two rolls close to the first stretching roll, the upstream side roll is used as the zeroth roll The roll on the downstream side is the first roll, and the portion sandwiched between the first extension roll and the zero roll is used as the 0th grip portion and the portion sandwiched between the first extension roll and the first roll as the first grip. The position of the 0th grip portion is the end portion on the upstream side of the contact region between the film and the first stretching roller, and the position of the first grip portion is the downstream side of the contact region between the film and the first stretching roller. Ends.

3) The method for producing an extended film according to the above 1) or 2), wherein the number of rolls close to the second stretching roll is two or more.

(4) The method for producing an extended film according to any one of (1) to (3), wherein the roll adjacent to the second stretching roll is two; and in the two rolls close to the second stretching roll, upstream The side roll is used as the third roll as the second roll and the downstream side roll, and the portion sandwiched between the second stretching roll and the second roll is used as the second grip portion and is sandwiched between the second stretching roll and the third roll. When the third portion is used as the third grip portion, the position of the second grip portion is a film and a second extension. An end portion on the upstream side of the contact region of the roller, and the position of the third grip portion is an end portion on the downstream side of the contact region between the film and the second stretching roller.

(5) The method for producing an extended film according to any one of the preceding claims, wherein the 0th roll has a cleaning mechanism (hereinafter referred to as a first cleaning mechanism), and the first cleaning mechanism can clean the first stretching roller. The first conveyance roller on the upstream side.

(6) The method for producing an extended film according to any one of the preceding claims, wherein the third roll has a cleaning mechanism (hereinafter referred to as a second cleaning mechanism), and the second cleaning mechanism can clean the second stretching roller. The second conveyance roller on the downstream side.

According to the method for producing an stretched film of the present invention, it is possible to provide a film which can suppress the occurrence of damage and reduce the disadvantages of the cause of the damage, particularly optical disadvantages.

1‧‧‧0th roll

2‧‧‧1st roll

3‧‧‧2nd roll

4‧‧‧3rd roll

5‧‧‧1st extension roller

6‧‧‧2nd extension roller

7‧‧‧film

8‧‧‧1st contact area

9‧‧‧2nd contact area

10‧‧‧1st cleaning mechanism

11‧‧‧2nd cleaning mechanism

12‧‧‧1st conveying roller

13‧‧‧2nd carrying roller

Fig. 1 is a schematic view showing a manufacturing method of the present invention.

[Formation of the Invention]

The invention will now be described.

The film of the present invention is not particularly limited, but refers to a thermoplastic resin film.

The thermoplastic resin film is not particularly limited, and, as a representative example, polyethylene terephthalate, polyethylene 2,6-naphthalenedicarboxylate, nylon-6, polyphenylene sulfide can be suitably used. Wait.

In order to produce a film as described above, a raw material such as polyethylene terephthalate or the like is used to prepare a pellet containing particles or substantially A pellet containing no particles or the like. In a film suitable for optical use, in order to ensure transparency, a pellet containing no particles is preferred. These were appropriately dried, and then supplied to a known melt extruder and filtered using a polymer filter.

Slitting from a slit-like slit into a sheet and on a casting roll The film was cooled and solidified to produce an unstretched (unaligned) film. The stretched film can be obtained by sequentially biaxially stretching the unaligned polyester film in the longitudinal direction and the width direction of the film.

The present invention is to include an extension roller using the upstream side (below A method of producing a stretched film in which a stretching roll (hereinafter referred to as a second stretching roll) on the downstream side and a stretching roll on the downstream side (hereinafter referred to as a second stretching roll) are subjected to a longitudinal stretching process (hereinafter referred to as a longitudinal stretching step). That is, in the present invention, it is important to use two stretching rolls to perform the longitudinal stretching treatment.

Specifically, using a stretching roller, it is carried while carrying Heat and heat until the temperature is set. In order to suppress the occurrence of damage, the surface roughness Ra of the stretching rolls is preferably 0.1 μm or less. In the production method of the present invention, the heating temperature immediately before the first stretching roll is preferably 68 to 83 ° C, more preferably 70 to 80 ° C, and particularly preferably 72 to 75 ° C. When the heating temperature immediately before the first stretching roller is lower than 68 ° C, the film is easily broken; when it is higher than 83 ° C, the film adheres to the roller, and surface defects become easy to occur.

The use of the stretch film of the present invention is described below using Figure 1. The longitudinal extension step in the manufacturing method will be described. In addition, the one shown in the first figure is not limited to one embodiment, and the present invention is not limited to the figure.

In the present embodiment, in order to extend the film (7), the first extension The roller (5) and the second stretching roller (6) are disposed apart from each other.

In the present invention, the number of rolls close to the first stretching roll is two The upper system is important. In the present invention, the number of rolls close to the first stretching roll is not particularly limited, but is preferably 2 to 3, and particularly preferably 2. In other words, according to Fig. 1, the number of rolls close to the first stretching roll is two, and in the two rolls close to the first stretching roll, the upstream side roll is used as the zeroth roll and the downstream side. When the roll is used as the first roll, the 0th roll (1) and the first roll (2) are placed in the vicinity of the first stretching roll in order to grip the film in the first stretching roll. When only the first roll is used, that is, when there is only one roll close to the first stretching roll, the stretching tension cannot be sufficiently cut, and the film is placed on the first conveying roller (12) on the upstream side of the first stretching roll. Sliding, and there is a problem that damage becomes easy to occur.

In the present invention, it is preferable that the first stretching roller and the first roller are clamped When the portion of the 0 roll is the 0th grip portion and the portion sandwiched between the first extension roll and the first roll is the first grip portion, the position of the 0th grip portion is the contact area between the film and the first extension roller. The end portion on the upstream side, the position of the first grip portion is the end portion on the downstream side of the contact region between the film and the first stretching roller. That is, according to Fig. 1, the position of the 0th gripping portion of the 0th roll is gripped on the first stretching roller, and the upstream end portion of the contact region (8) between the film and the first stretching roller is preferably. . More preferably, the position at which the first grip portion of the first roll is gripped on the first stretching roll is preferably the end portion on the downstream side in the contact region between the film and the first stretching roll. By performing the above, the film does not slide on the first stretching roller, and the occurrence of damage can be suppressed.

In the present invention, the number of rolls close to the second stretching roll is two It is better. In the present invention, the number of rolls close to the second stretching roll is preferably 2 or more, more preferably 2 to 3, and particularly preferably 2. That is, according to the In the first roll, the number of rolls close to the second stretching roll is two, and in the two rolls close to the second stretching roll, when the upstream roll is the second roll and the downstream roll is the third roll In order to hold the film in the second stretching roll, it is preferable to arrange the second roll (3) and the third roll (4) in the vicinity of the second stretching roll. When there is only the second roll, that is, when there is only one roll close to the second stretching roll, the stretching tension cannot be sufficiently cut, and the film is placed on the second conveying roller (13) on the downstream side of the second stretching roll. Sliding and there is a problem with the damage.

In the present invention, it is preferable that the second stretching roller is to be clamped When the portion of the second roll is the second grip portion and the portion sandwiched between the second stretching roll and the third roll is the third grip portion, the position of the second grip portion is the contact between the film and the second stretching roller. The end portion on the upstream side of the region, the position of the third grip portion is the end portion on the downstream side of the contact region between the film and the second stretching roller. That is, according to Fig. 1, the position of the third gripping portion of the third roll is gripped on the second stretching roller, and the end portion on the downstream side in the contact region (9) between the film and the second stretching roller is preferably . More preferably, the position at which the second grip portion of the second roll is gripped on the second stretching roll is preferably the end portion on the upstream side in the contact region between the film and the second stretching roll. By performing the above, the film does not slide on the second stretching roller, and the occurrence of damage can be suppressed.

In the present invention, there is a A cleaning mechanism for the conveyance roller is preferred. In the present invention, the 0th roll has a cleaning mechanism (hereinafter referred to as a first cleaning mechanism), and the first cleaning mechanism can preferably clean the first conveyance roller located on the upstream side of the first extension roller. That is, according to Fig. 1, the 0th roll has the first cleaning mechanism (10), and it is preferable to clean the first conveyance roller located on the upstream side of the first extension roller. Long time When the film is produced, the stretching roller becomes dirty and causes damage. Therefore, the mechanism for cleaning can be minimized by providing a mechanism that can be cleaned without cutting the film.

Furthermore, the so-called cleaning mechanism refers to a pair of rollers. The fixed load presses the cloth for cleaning and the like and can move in the width direction. By using the cleaning mechanism as described above, it is possible to safely clean without cutting the film.

In the present invention, the third roll has a cleaning mechanism (hereinafter referred to as It is preferable that the second cleaning mechanism can clean the second conveyance roller located on the downstream side of the second extension roller. That is, according to Fig. 1, the third roll has a second cleaning mechanism, and it is preferable to clean the second conveyance roller located on the downstream side of the second extension roller. When the film is produced for a long period of time, the stretching roller becomes dirty and causes damage. Therefore, the mechanism for cleaning can be minimized by providing a mechanism that can be cleaned without cutting the film.

In the present invention, between the first stretching roller and the second stretching roller A mechanism for heating the film in a non-contact manner is preferred. As the mechanism as described above, for example, an infrared heater or the like can be given.

The film temperature at the time of extension of the longitudinal stretching step is, for example, 70 ~130 ° C, preferably 75 to 120 ° C, more preferably 80 to 110 ° C. When the film temperature at the time of extending the longitudinal stretching step is lower than 70 ° C, the film is easily broken. When the film temperature at the time of stretching is higher than 130 ° C, it is difficult to align the polymer, and it is likely to be broken when extending in the width direction. The film temperature at the time of extending the longitudinal stretching step means the film temperature in the region between the first stretching roll and the second stretching roll.

Moreover, the stretching ratio of the longitudinal stretching step is, for example, 2.5 to 5.0. Times, preferably 2.7 to 3.5 times. When the longitudinal stretching ratio is less than 2.5 times, it is difficult On the other hand, when the stretching ratio of the longitudinal stretching step becomes more than 5.0 times, the alignment of the polymer is strong, and the film is easily broken when it extends in the width direction.

After the longitudinal stretching step, it may also be on both sides of the stretched film or The one-sided coating is easy to adhere to the layer and leads to the lateral extension step. The method of coating is not particularly limited, and for example, a reverse coating method, a gravure coating method, a bar coating method, a bar coating method, a wire bar coating method, a die coating method, a spray coating method, or the like can be used.

Although depending on the thickness of the film, the speed, the presence or absence of coating, etc. However, the uniaxially stretched film (the stretched film of the present invention) obtained by the above method may be extended to 2.5 in the width direction, for example, at 80 to 160 ° C, preferably 85 to 130 ° C, more preferably 90 to 120 ° C. ~6.0 times, preferably 3.0 to 5.5 times, more preferably 3.5 to 5.0 times. Exceeding this temperature and the range of magnification may cause problems such as uneven stretching or film breakage. In particular, when the stretching temperature of the lateral stretching step is lower than 80 ° C, the film may be easily broken and it may be difficult to manufacture. On the other hand, when the elongation temperature of the lateral stretching step is higher than 160 ° C, sufficient strength cannot be obtained as a release application.

After extension, it can be 200~240°C, preferably 205. ~235 ° C, more preferably 210 ~ 230 ° C, for heat fixation, and then, within 25% of relaxation. In particular, when the temperature at the time of heat setting is less than 200 ° C, the crystallinity may not progress, and thus the structure of the polyester is unstable.

The manufacturing method of the present invention may also be carried out after the longitudinal stretching step There is a lateral stretching step, and even after the lateral stretching step, the step of cutting and removing the edge portion having a thick thickness at the same time as the cutting step and the embossing portion is preferable.

The stretched film obtained by the present invention, as described above, is transparent It is excellent in clarity, has few damages, and is suitable for various processing applications. Therefore, it can be used for various optical films, particularly for base films for enamel sheets, base films for hard coating, and anti-reflection (AR) films. A base film, a base film for light diffusion, a transparent conductive film, and the like.

[Examples]

Hereinafter, the present invention will be described in detail by way of examples. The evaluation method of the effect is as follows.

(1) Visual inspection

A sheet-like sample (product width × 1 to 2 m) was taken from the surface of the film roll having a certain winding length, and the number of damages having a maximum long diameter of 500 μm or more was visually observed in a dark room in a slanting state. For the number of damages per 1 m ² , the scores were as follows.

Class A: 50/m ² or less

B grade: more than 50 / m ² , 75 / m ² or less

C grade: more than 75 / m ² , 100 / m ² or less

D grade: more than 100 / m ² , 120 / m ² or less

E grade: more than 120 / m ² (failed)

Among the above-mentioned criteria, a film having a D grade or higher is practically free from problems and is a usable level, but a C grade or higher is preferable.

(Manufacturing example)

The pellet of polyethylene terephthalate was dried at 160 ° C for 8 hours, and then supplied to an extruder, melted at 275 ° C, and filtered. Thereafter, a slit die maintained at 285 ° C was wound on a cooling roll by a casting method using static electricity, wound around a casting drum having a surface temperature of 25 ° C, and cooled and solidified to obtain an unstretched film.

In order to extend in the longitudinal direction, the surface roughness Ra is A 0.1 μm roll was used to raise the temperature of the unstretched film up to 74 °C. Then, the film temperature at the time of extension of the longitudinal stretching step was maintained at 74 °C. In the vertical stretching step, the additional speed is extended by 3.0 times between the first stretching roll and the second stretching roll. There is a first roll in the vicinity of the first stretching roll (only one roll in the vicinity of the first stretching roll), and the position of the first grip portion of the first roll holding film is the area where the first stretching roll and the film are in contact with each other. a downstream end portion; a second roll in the vicinity of the second stretching roll (only one roll in the vicinity of the second stretching roll), and a position of the second grip portion of the second roll holding film is located in the second extending roll The most upstream end of the region where the film is in contact. Further, the vertical stretching step is performed while the temperature of the film is raised by the infrared heater between the first stretching roller and the second stretching roller. This method is referred to as a basic longitudinal extension method.

(Example 1)

In addition to the above-described basic longitudinal stretching method, the 0th roll in the vicinity of the first stretching roll and the 0th gripping portion of the 0th roll gripping film may be located upstream from the contact area of the first extending roll and the film. An extension device formed at a position on the downstream side of the 30° side of the most end portion of the side; the other is carried out in the same manner as in the production example, and extends in the longitudinal direction.

Thereafter, the stretched film is introduced into a tenter at a temperature After extending at 3.6 times in the width direction at 100 ° C, heat treatment was performed at a width of 225 ° C. Next, a 6% relaxation treatment was further applied to the width direction to obtain a biaxially oriented polyester film having a thickness of 188 μm.

The damage level of the obtained stretched film is shown in Table 1. . Moreover, the number of damages after one day of production is also shown in Table 1.

(Example 2)

In the longitudinal stretching step of the first embodiment, the position of the 0th gripping portion was changed to the end portion on the upstream side of the contact region between the first stretching roller and the film, and the same procedure as in Example 1 was carried out to obtain a double. Axial extension film.

The number of damages of the obtained film is shown in Table 1. also, The number of damages after one day of production is also shown in Table 1.

(Example 3)

In the longitudinal stretching step of the second embodiment, the third roll is provided in the vicinity of the second stretching roll, and the position of the third holding portion of the third roll holding film is downstream from the contact area of the second extending roll and the film. A biaxially stretched film was obtained in the same manner as in Example 2 except that the position of the side end portion on the upstream side of 30° was obtained.

The number of damages of the obtained film is shown in Table 1. also, The number of damages after one day of production is also shown in Table 1.

(Example 4)

In the longitudinal stretching step of the third embodiment, the position of the third gripping portion was changed to the position of the downstream end portion of the contact region between the second stretching roller and the film, and the same procedure as in Example 3 was carried out. Biaxially stretched film.

The number of damages of the obtained film is shown in Table 1. also, The number of damages after one day of production is also shown in Table 1.

(Example 5)

In the longitudinal stretching step of Example 4, a biaxially stretched film was obtained in the same manner as in Example 4 except that the 0th roll had the first cleaning mechanism.

The number of damages of the obtained film is shown in Table 1. also, The number of damages after one day of production and the number of damages of the film obtained by using the first cleaning mechanism and cleaning the first conveyance roller after one day of production are shown in Table 1.

(Example 6)

In the longitudinal stretching step of Example 5, a biaxially stretched film was obtained in the same manner as in Example 5 except that the third roll had the second cleaning mechanism.

The number of damages of the obtained film is shown in Table 1. also, The number of damages after one day of production and the number of damages of the film obtained by using the first and second cleaning mechanisms after one day of production and cleaning the first and second conveyance rolls are shown in Table 1.

(Comparative Example 1)

Table 1 shows the damage level of the biaxially stretched film obtained by the basic longitudinal stretching method and the number of damages after one day of production.

In Comparative Example 1, the number of rolls close to the first stretching roll is one. However, the portion where the roll and the first stretching roller are sandwiched is the end portion on the downstream side of the contact region between the film and the first stretching roller. Therefore, in the table, the portion sandwiched between the roller and the first stretching roller is used as the first portion. 1 gripping department handles the record.

Example 1, 2, and Comparative Example 1, which are close to the second stretching roller The number of the rolls is one, but the portion where the roll and the second stretching roll are sandwiched is the end portion on the upstream side of the contact area between the film and the second stretching roll. Therefore, in the table, the roll and the second stretching roll are used. The portion to be clamped is described as the second grip portion.

[Industrial availability]

The stretched film obtained by the production method of the present invention has excellent transparency and less damage, and is suitable for various processing applications. Therefore, it can be suitably used for various optical films, particularly for base films for hard sheets and for hard coating. A film for a film, an antireflection (AR) film, a base film for light diffusion, a transparent conductive film, or the like.

1‧‧‧0th roll

2‧‧‧1st roll

3‧‧‧2nd roll

4‧‧‧3rd roll

5‧‧‧1st extension roller

6‧‧‧2nd extension roller

7‧‧‧film

8‧‧‧1st contact area

9‧‧‧2nd contact area

10‧‧‧1st cleaning mechanism

11‧‧‧2nd cleaning mechanism

12‧‧‧1st conveying roller

13‧‧‧2nd carrying roller

Claims (6)

A method for producing a stretched film, which comprises an extension of a step of longitudinally stretching a film using a stretching roll on the upstream side (hereinafter referred to as a first stretching roll) and a stretching roll on the downstream side (hereinafter referred to as a second stretching roll) The method for producing a film is characterized in that the number of rolls close to the first stretching roll is two or more. The method for producing an extended film according to claim 1, wherein the roll adjacent to the first stretching roll is two; and in the two rolls close to the first stretching roll, the upstream side roll is used as the zeroth roll The roll on the downstream side is the first roll, and the portion sandwiched between the first extension roll and the zero roll is used as the 0th grip portion and the portion sandwiched between the first extension roll and the first roll as the first grip. In the first portion, the position of the 0th grip portion is the upstream end portion of the contact region between the film and the first stretching roller, and the position of the first grip portion is the downstream end of the contact region between the film and the first stretching roller. unit. The method for producing an extended film according to claim 1 or 2, wherein the number of rolls close to the second stretching roll is two or more. The method for producing an extended film according to any one of claims 1 to 3, wherein the roll adjacent to the second stretching roll is two; and, in the two rolls close to the second stretching roll, the upstream side is The second roll and the downstream roll are used as the third roll, and the portion sandwiched between the second stretching roll and the second roll is used as the second gripping portion and is sandwiched between the second stretching roller and the third roller. When the portion is the third grip portion, the position of the second grip portion is the end portion on the upstream side of the contact region between the film and the second stretching roller, and the position of the third grip portion is the contact between the film and the second stretching roller. The end of the downstream side of the area. The method for producing an extended film according to any one of claims 1 to 4, wherein the 0th roll has a cleaning mechanism (hereinafter referred to as a first cleaning mechanism), and the first cleaning mechanism can clean the upstream side of the first stretching roller. The first conveyance roller. The method for producing an extended film according to any one of claims 1 to 5, wherein the third roll has a cleaning mechanism (hereinafter referred to as a second cleaning mechanism), and the second cleaning mechanism can clean the downstream side of the second stretching roller. The second conveyance roller.