TW201436997A - Stretched film production method and film stretching apparatus - Google Patents

Abstract

An object of the present invention is to provide a stretched film production method and a film stretching apparatus for stretching a film in a transporting direction thereof without generating scratches and corrugated wrinkles on the film. A film is stretched in a transporting direction thereof by utilizing circumferential velocity difference between a low-speed roller pair and a high-speed roller pair. The film after being stretched is cooled by cooling rollers. A slitter is disposed between a high-speed roller and the cooling roller. The film is cut into a central portion and side edge portions in a width direction thereof by the slitter. Since the side edge portions each having a large thickness are cut off, irregularities are not formed on the film on the cooling rollers. Thereby, it is possible to prevent generation of scratches and wrinkles caused by irregularities on the film.

Description

Method for producing stretched film and film stretching device

The present invention relates to a method for producing a stretched film which stretches a film in a conveying direction by a difference in circumferential speed of a pair of rolls, and a film stretching apparatus.

In general, a method for producing a thermoplastic resin film can be roughly classified into a solution film forming method and a melt film forming method. In the solution film forming method, a dope in which a thermoplastic resin is dissolved in a solvent is cast from a mold onto a support such as a cooling roll and a drying belt, and then peeled off to form a thermoplastic resin film. Further, in the melt film forming method, after the thermoplastic resin is melted by an extruder, it is extruded from a die onto a support such as a cooling roll, and then peeled off to form a thermoplastic resin film.

The thermoplastic resin film, such as a cellulose oxime film, which is formed by these methods, usually exhibits an in-plane retardation (Re) and a retardation in the thickness direction by stretching in the longitudinal direction (transport direction) and the transverse direction (width direction). (Rth). Thereby, the viewing angle can be expanded when used as a retardation film of a liquid crystal display device.

In the case of stretching the thermoplastic resin film in the longitudinal direction, for example, the thermoplastic resin film is preheated by a plurality of preheating rolls as described in Japanese Patent Laid-Open Publication No. 2007-54683, and Japanese Patent Publication No. 2011-207168. Thereafter, the drawing process is performed in the longitudinal direction by the circumferential speed difference of the pair of stretching rolls. In this stretching process, the thermoplastic resin film is heated by a preheating roll, a stretching roll, or the like to perform longitudinal stretching. Also, after the longitudinal stretching, cooling is performed by a cooling roll and sent to the next process. In this way, since each of the rolls is heated or cooled in contact with the thermoplastic resin film, wrinkles are generated in the width direction of the thermoplastic resin film, or scratches are caused by the wrinkles.

For example, in Japanese Patent Laid-Open Publication No. 2007-54683, a plurality of preheating is caused in order to prevent scratches or wrinkles on the surface of the film due to contact of the film with a plurality of preheating rolls. The peripheral speed of the roll and the upstream side stretching roll changes according to the temperature before and after the film contacts the rolls, and gradually increases as it goes downstream, thereby imparting appropriate tension between the preheating rolls to suppress the occurrence of scratches and wrinkles. . Further, in Japanese Laid-Open Patent Publication No. 2011-207168, after the longitudinal stretching is performed, scratching is suppressed by rapidly cooling the film.

However, recently, liquid crystal display devices have been required to be lightweight, thin, and high in quality, and the thermoplastic resin film to be used is required to have an ultra-thin and high quality of, for example, about 25 μm to 100 μm. When the thinned thermoplastic resin film is stretched in the longitudinal direction, the method of preheating based on a preheating roll and the rapid cooling method of a thermoplastic resin film are disclosed in Japanese Patent Laid-Open Publication No. Hei. No. 2007-54683, and Japanese Patent Publication No. 2011-207168. There are limitations in that scratches or wrinkles are formed on the surface of the film to require improvement.

An object of the present invention is to provide a method for producing a stretched film which can cope with a reduction in thickness of a thermoplastic resin film and which does not cause scratches and wrinkles in a thermoplastic resin film, and a film stretching apparatus.

An in-depth study of the causes of scratches and wrinkles accompanying thinning results in the following findings. First, after longitudinal stretching, both side edge portions of the thermoplastic resin film are thickened by inward bending of the width contraction. The wall thickness portion is applied with a force when it is bent inward, and the residual stress becomes larger than other portions. If the film having the wall thickness portion at both ends, that is, the thermoplastic resin film enters the cooling roll, the amount of shrinkage in the film conveying direction during the cooling relaxation process is different from the center portion due to the influence of the residual stress and the thickness of the film in the cooling direction. By cooling, the film lengths of the both side edge portions in the conveying direction become shorter than the central portion in the width direction. Therefore, the flatness of the entire width of the thermoplastic resin film in the middle of cooling is deteriorated and unevenness is generated. When such a thermoplastic resin film is transferred by contact between a cooling roll and a transfer roll, the thermoplastic resin film is partially scratched strongly, and scratches and wrinkles are generated on the thermoplastic resin film.

The method for producing a stretched film of the present invention comprises a longitudinal stretching step (A step) and a cooling step (Step B), and a film made of a thermoplastic resin is stretched in a conveying direction to produce a stretched film. In the step A, the film is stretched in the conveying direction by the upstream side low speed roller and the downstream side high speed roller, and the downstream side high speed roller is separately disposed downstream in the conveying direction of the upstream side low speed roller, and is higher than the upstream side low speed roller. The peripheral speed is rotated. The upstream low speed roller contacts the film to heat the film. In the step B, the cooling roll is brought into contact with the film which has passed through the step A. The film is cooled. In the step C, the edge portions on both sides in the width direction of the film are removed between the step A and the step B.

In the step C, when the width from the film thickness change starting point of the film thickness at the edge portions in the width direction to the both side edges of the film is WFS, the film thickness changes from the start point toward both side edges within WFS×0.2. It is preferable to cut the central portion and both side edge portions in the width direction of the film to remove both side edges in the width direction.

In the step A, the film length between the upstream side low speed roll and the downstream side high speed roll divided by the film width before stretching is preferably 0.01 or more and 0.5 or less.

In the step A, when the glass transition temperature of the film is Tg, the film is heated to a stretching temperature Te of (Tg - 20) ° C or more and (Tg + 20) ° C or less by the upstream low-speed roll. The film is cooled to a range of (Tg - 100) ° C or more and (Tg - 5) ° C or less by a downstream side high speed roll.

The method for producing a stretched film further preferably has a preheating step (step D). Step D Preheat the film to a temperature above (Te-40) °C and below (Tg-5) °C before the A step.

In the step D, it is preferred to supply the heating air to the inside of the preheating chamber to preheat the film.

In the step D, it is preferable to change the conveying direction of the film and to transport the film to a plurality of conveying direction changing units for lengthening the path of the film.

The film stretching apparatus of the present invention comprises a longitudinal stretching portion, a cooling portion, and a side edge portion removing portion, and stretches a strip-shaped film made of a thermoplastic resin in the conveying direction to produce a stretched film. The longitudinal stretching portion stretches the film in the conveying direction by the circumferential speed difference between the upstream side low speed roller and the downstream side high speed roller. The upstream low speed roller contacts the film to heat the film. The downstream side high speed rolls are disposed separately downstream of the upstream side low speed rolls in the conveying direction. The cooling section cools the film by a cooling roll. The chill roll is in contact with the film from the longitudinal stretch. The side edge portion removing portion cuts and removes both side edge portions in the width direction of the film from the center portion. The side edge portion removing portion is disposed between the downstream side high speed roller and the cooling roller.

When the width from the start of the film thickness change from the film thickness of the side edge portion in the width direction to the width of both side edges of the film is WFS, the side edge portion removal portion is changed from the film thickness change point to both side edges of the film. Cut the center and both sides of the width direction of the film within WFS × 0.2 It is preferable that the edge portion is removed from both side edges in the width direction.

It is preferable that the film length between the upstream side low speed roll and the downstream side high speed roll is divided by the film width before stretching, and the longitudinal stretching aspect ratio is preferably 0.01 or more and 0.5 or less.

When the glass transition temperature of the film is Tg, the longitudinal stretching portion heats the film to a stretching temperature Te in a range of (Tg - 20) ° C or more and (Tg + 20) ° C or less by an upstream low-speed roll. The film is cooled to a range of (Tg - 100) ° C or more and (Tg - 5) ° C or less by a downstream side high speed roll.

The film stretching apparatus preferably has a preheating portion on the upstream side in the film conveying direction with respect to the longitudinal stretching portion. The preheating section preheats the film to (Te-40) °C or more and (Tg-5) °C or less.

The preheating portion has a preheating chamber and a blowing nozzle that supplies heated air to the preheating chamber, and preheating the film by heating air from the blowing nozzle is preferred.

The preheating section has a plurality of conveying direction changing means for changing the conveying direction of the film, and the film is preferably mounted on the conveying direction changing means.

According to the present invention, since both side edge portions of the thermoplastic resin film which are thickened by the influence of the inward bending caused by the longitudinal stretching are removed, it is possible to suppress the transfer of the thermoplastic resin film during the cooling of the thermoplastic resin film. The unevenness of the film caused by partial shrinkage in the direction. Thereby, scratches and wrinkles of the thermoplastic resin film are not generated, and the thickness of the thermoplastic resin film can be reduced.

9‧‧‧Pre-process equipment

10, 45‧‧‧ Film stretching equipment

11, 44, 70, 83, 86‧ ‧ preheating department

12‧‧‧ longitudinal stretching

13‧‧‧The Ministry of Cooling

14‧‧‧ late process equipment

15‧‧‧film

15a‧‧‧Central Department

15b‧‧‧Edge

16, 16a, 17, 18‧‧‧ preheating rolls

16b, 21b, 22b‧‧‧ clamping rolls

21‧‧‧Low speed roller set

21a‧‧‧low speed roller

22‧‧‧High speed roller set

22a‧‧‧High speed roller

25, 26‧‧‧ chill roll

27, 28‧‧‧Transfer roller

31‧‧‧ slitting machine

31a, 31b‧‧‧ Roller blades

32‧‧‧Rotary cutter

33‧‧‧Reuse Department

46‧‧‧Tensile adjustment department

47a, 47b‧‧‧ free roll

48‧‧‧ Tension roller

49‧‧‧displacement mechanism

50, 68, 79, 84, 89‧‧‧ preheating room

55, 80‧‧‧ free roll

61‧‧‧Air supply nozzle

62‧‧‧Exhaust nozzle

63‧‧‧ catheter

64, 87‧‧‧Air blower

65‧‧‧temperature regulator

66‧‧‧heating wind

68a, 68b, 68c‧‧‧ preheating area

69‧‧‧Baffle

82a, 82b, 82c‧‧ ‧ temperature control mechanism

85‧‧‧ steering rod

88‧‧‧temperature regulator

Ft‧‧‧ film thickness

CL1‧‧‧ tangent

Ls‧‧‧ film length

OS1‧‧‧ offset

P1‧‧‧ film thickness change starting point

W1, W2, WFS‧‧‧ width

Fig. 1 is a schematic side view showing an example of a film stretching apparatus of the present invention.

Fig. 2 is a graph showing an example of a film thickness distribution in the film width direction after longitudinal stretching and cooling.

Figure 3 is a schematic plan view showing the clip.

Fig. 4 is a schematic side view showing an example of a film stretching apparatus having another embodiment of a preheating unit based on air blowing.

Fig. 5 is a schematic side view showing an example of a preheating unit of another embodiment having a plurality of preheating zones.

Fig. 6 is a schematic side view showing an example of a preheating unit of another embodiment in which the temperature of the free roller is controlled.

Fig. 7 is a schematic side view showing a preheating portion of another embodiment using a steering roller.

As shown in FIG. 1, the film stretching apparatus 10 of the present invention includes a preheating portion 11, a longitudinal stretching portion 12, and a cooling portion 13. The film stretching apparatus 10 is connected to the pre-process apparatus 9 at the inlet side and the post-process apparatus 14 to the outlet side. As the pre-processing apparatus 9, there are a film forming apparatus (not shown), a film feeding apparatus, and the like. A well-known solution film forming apparatus, a melt film forming apparatus, etc. are used as a film forming apparatus. Unlike the case where the film 15 is directly fed from the film forming apparatus, the film feeding device feeds the film 15 from the film roll 15 which is wound into a roll shape after film formation, and supplies the film 15. As the post-process apparatus 14, there are a clip tenter and a film take-up apparatus for transverse stretching after longitudinal stretching. The clip tenter was omitted when the transverse stretching was continuously performed in the longitudinal direction, and the film 15 was taken up in a roll shape by a film winding device.

The film 15 to be stretched may be a thermoplastic resin film. For example, it is preferably used for a cellulose halide and a norbornene resin in an optical film such as a retardation film, and a film 15 such as acrylic or polycarbonate.

The preheating unit 11 includes a preheating roller group 16, a first preheating roller 17, and a second preheating roller 18. The preheating roller group 16 has an inlet preheating roller 16a and a nip roller 16b and holds the film 15 for conveyance. The film 15 is wound around the inlet preheating roll 16a, the first preheating roll 17, and the second preheating roll 18 in an alternately wound manner. Thereby, the contact area between the film 15 and the inlet preheating roll 16a, the first preheating roll 17, and the second preheating roll 18 is increased, and effective preheating is performed.

The preheating temperature needs to be set to a temperature lower than the stretchable temperature (tensile temperature) Te. Therefore, when the glass transition temperature of the film 15 is set to Tg, the film 15 is preheated to a certain temperature within a range of (Te - 40) ° C or more and (Tg - 5) ° C or less, and the longitudinal direction portion 12 is drawn. The film 15 is conveyed. Specifically, the inlet preheating roller 16a, the first preheating roller 17, and the second preheating roller 18 preheat the film 15 to a range of (Te - 40) ° C or more and (Tg - 5) ° C or less. It is particularly preferable to preheat the film 15 to (Tg - 60) ° C or more and (Tg - 35) ° C or less by the inlet preheating roll 16a, and preheat the film 15 by the first preheating roll 17 to (Tg-50) In the range of ° C or more and (Tg - 25) ° C or less, the film 15 is preheated by the second preheating roll 18 to a range of (Tg - 40) ° C or more and (Tg - 5) ° C or less. At the time of preheating, the temperature of the film 15 is preferably increased from the inlet preheating roll 16a, the first preheating roll 17, and the second preheating roll 18, that is, toward the downstream. That is, the preheating temperature on the first preheating roller 17 is higher than the preheating temperature on the inlet preheating roller 16a. The degree of high preheating temperature on the second preheating roll 18 is particularly high as compared with the preheating temperature on the first preheating roll 17.

The film 15 which has been preheated to a certain temperature through the preheating portion 11 is sent to the longitudinal stretching portion 12. The longitudinal stretching portion 12 includes a low speed roller group 21 and a high speed roller group 22. The low speed roller group 21 has a low speed roller 21a and a nip roller 21b. The high speed roller group 22 has a high speed roller 22a and a nip roller 22b. In the low speed roller 21a and the high speed roller 22a, a temperature control medium such as water, oil, water vapor, or the like is supplied from the temperature control medium circulation portion. By the cyclic supply of the temperature control medium, the low speed roller 21a and the high speed roller 22a are set to a desired surface temperature. For example, the surface temperature of the low-speed roll 21a is in the range of (Tg-20) ° C or more and (Tg + 20) ° C or less as the stretching temperature Te, and the surface temperature of the high-speed roll 22a is (Tg - 100) ° C. Above and below (Tg-5) °C or less. By setting this temperature range, it is possible to uniformly stretch the thin film 15 having a thickness of 25 μm or more and 100 μm or less.

The film 15 longitudinally stretched in the longitudinal stretching portion 12 is wound around the first cooling roll 25 and the second cooling roll 26 to be conveyed and cooled. The temperature control medium is supplied from the temperature control medium circulation portion to the first cooling roller 25 and the second cooling roller 26, respectively, and the first cooling roller 25 and the second cooling roller 26 are set to a desired surface temperature. For example, the surface temperature of the first cooling roll 25 is (Tg - 40) ° C or lower, and the surface temperature of the second cooling roll 26 is (Tg - 50) ° C or less. The film 15 after cooling is sent to the post-processing apparatus 14 by the transfer rolls 27, 28.

A motor (not shown) is connected to the inlet preheating roller 16a, the first preheating roller 17, the second preheating roller 18, the low speed roller 21a, the high speed roller 22a, the first cooling roller 25, and the second cooling roller 26. The components are capable of rotating at the desired rotational speed. In the longitudinal stretching portion 12, the film 15 is elongated in the conveying direction by the difference in circumferential speed between the low speed roller 21a and the high speed roller 22a, and is longitudinally stretched. The "low speed," and "high speed" of the low speed roller 21a and the high speed roller 22a mean that the speed is relatively low and relatively high, respectively. That is, the peripheral speed of the high speed roller 22a is higher than the peripheral speed of the low speed roller 21a. The circumferential speed difference between the low speed roller 21a and the high speed roller 22a is appropriately changed depending on the stretching ratio in the longitudinal direction (may be referred to as a longitudinal stretching magnification), and is set, for example, in a range of 2 m/min or more and 100 m/min or less. It is better.

In the longitudinal stretching, the longitudinal stretching ratio is preferably in the range of more than 1.0 and 1.5 or less. When the longitudinal stretching ratio is in the range of more than 1.0 and 1.5 or less, the occurrence of thickness unevenness can be appropriately suppressed, and the uneven distribution of delay which appears can be suppressed.

Further, the length Ls of the film 15 between the upstream low-speed stretching roll 21a and the downstream side high-speed roll 22a is divided by the width W1 of the film F before stretching, and the longitudinal stretching aspect ratio (Ls/W1) is 0.01 or more. A range of 0.5 or less is preferred. The smaller the longitudinal stretching aspect ratio is, the smaller the inward bending is, and the proportion of the uniform film thickness portion (hereinafter referred to as the uniform film thickness portion) of the central portion 15a (see FIG. 2) in the film width direction is changed. Big. Thereby, the width of the side edge portions 15b of the film cut by the slitter 31 described later can be made small, and the central portion 15a serving as a product can be increased by a corresponding amount, and product loss can be suppressed.

When the film 15 is preheated to (Te - 40) ° C or higher by the preheating portion 11, the temperature rise amount when the film 15 is heated by the low speed roller 21a of the longitudinal stretching portion 12 does not become excessively large, and the low speed roller can be suppressed. Corrugated plate-like pleats are produced on 21a. Further, by preheating the film 15 to (Tg - 5) ° C or less by the preheating portion 11, the film 15 can be uniformly stretched in the longitudinal stretching portion 12 without being stretched in the preheating portion 11.

A slitter 31 is disposed between the longitudinal stretching portion 12 and the cooling portion 13. The slitter 31 has a pair of roller blades 31a, 31b and cuts the film 15 in the conveying direction. Thereby, the film 15 is cut into the center portion 15a and both side edge portions (see FIG. 2) 15b in the width direction.

As shown in FIG. 2, the film 15 is cut by a tangent line CL1 which is shifted from the side edge edge side of the film 15 to the offset amount OS1 from the film thickness change start point P1 which will be described later.

Fig. 2 shows the film thickness distribution of the film 15 in the width direction when the film 15 is cut without longitudinal cutting and cooling by the slitter 31. The central portion 15a is a uniform film thickness portion. The film thickness Ft of the both side edge portions 15b of the film 15 is gradually thickened as it goes toward both side edges by being bent inward.

The film thickness change start point P1 is a point at which the film thickness Ft changes from the center to the side edge in the film thickness distribution in the film width direction. The film thickness change starting point P1 may be used as the cutting position. However, in this case, the width of both side edge portions 15b of the film which is cut by the slitting machine 31 is increased, so that the central portion 15a of the product can be reduced by a corresponding amount, and the product loss is increased. In order to prevent such occurrences, the tangential line CL1 is shifted from the film thickness change starting point P1 to the side edge side by only the offset amount OS1 until the position where the scratch is not generated in the next cooling process.

The offset amount OS1 is obtained, for example, by the following method. When the width from the film thickness change start point P1 to the both side edges of the film is WFS, the offset amount is the value of the width WFS multiplied by a coefficient of 0.2 (WFS × 0.2).

The side edge portions 15b cut by the slitter 31 from the center portion 15a are sent to the rotary cutter 32 as shown in Figs. 1 and 3 to be cut into slices. The slice is sent to the recycling unit 33 and reused as a raw material of the film 15 or the like. The reuse unit 33 blows the slice by a blower (not shown), creates a micro slice through a crusher, a separator, or the like, and stores the micro slice in the silo.

The film 15 which is longitudinally stretched in the longitudinally stretched portion 12 is taken up into a film web by, for example, a film winder of the post-process apparatus 14.

In the present embodiment, the both side edge portions 15b of the film which are thickened by the influence of the inward bending caused by the longitudinal stretching are removed, so that the film 15 can be suppressed from being partially shrunk in the conveying direction during the cooling of the film 15. And the bumps are generated. Thereby, scratches and wrinkles of the film 15 are not generated during the cooling by the first cooling roll 25 and the second cooling roll 26.

Further, before the cooling, the both side edge portions 15b are cut from the center portion 15a by the slitter 31, so that the first cooling roller 25 and the second cooling roller 26 can be removed without causing scratches and wrinkles. Cool down. However, as shown in FIG. 2, the tangent line CL1 is shifted from the film thickness change start point P1 to the side edge by only the offset amount OS1, and then the both side edge portions 15b are cut from the center portion 15a by the slitter 31, thereby enabling The wider central portion 15a is retained as much as possible, and product loss can be suppressed.

Next, as shown in FIG. 1, instead of using the preheating of the inlet preheating roller 16a, the first preheating roller 17, and the second preheating roller 18, as shown in FIG. 4, the preheating portion having the preheating by the air supply is provided. A film stretching apparatus 45 of another embodiment of 44 will be described. As shown in Fig. 1, when the inlet preheating roller 16a, the first preheating roller 17, and the second preheating roller 18 are used, and the film 15 is preheated by direct contact, the film 15 may be changed. The film 15 is thermally expanded on the inlet preheating roll 16a, the first preheating roll 17, and the second preheating roll 18 to have a corrugated plate shape. This corrugated plate expansion may cause wrinkles and scratches on the film 15. Instead of performing heat conduction to the film 15 by direct contact and heating by blowing air, it is possible to suppress the film 15 from being expanded in a corrugated shape on the inlet preheating roll 16a, the first preheating roll 17, and the second preheating roll. In particular, the film having a thickness of 25 μm or more and 100 μm or less before the stretched film 15 can suppress wrinkles and scratches caused by preheating.

A tension adjusting portion 46 is provided between the preliminary processing device 9 and the film stretching device 45. The tension adjusting portion 46 causes the tension roller 48 between the free rollers 47a, 47b to be displaced by the displacement mechanism 49. The lift is performed to maintain the tension of the film 15 in the preheating portion 44 constant. The film tension in the preheating portion 44 is in the range of 20 N/m or more and 200 N/m or less. When the tension is 20 N/m or more, the rotation failure of the free roller 55 does not occur, and the film 15 can be prevented from being scratched. In addition, when the tension is 200 N/m or less, longitudinal stretching is not performed in the preheating portion 11, and appropriate longitudinal stretching is performed in the longitudinally stretched portion 12. Further, the film tension (unit: N/m) is a tension per unit width (unit: N).

The preheating unit 11 includes a preheating chamber 50. A plurality of free rollers (transport direction changing units) 55 are disposed apart from each other in the vertical direction in the preheating chamber 50. The film 15 is alternately wound between the free rollers 55, whereby the film 15 is transported in the vertical direction between the rolls 55, and the film path (passage) in the preheating chamber 50 is set to be long.

The length of the film passage of the preheating chamber 50 also depends on the preheating temperature and the conveying speed of the film 15, however, it is preferably in the range of, for example, 5 m or more and 50 m or less. The free roller 55 has, for example, a diameter of 80 mm, and the contact area between the film 15 and the free roller 55 is small due to the winding of the film 15. The diameter of the free roller 55 is preferably in the range of 40 mm or more and 150 mm or less. When the diameter is 40 mm or more, no deflection occurs in the free roller 55, and unevenness in rotation and generation of flaws due to deflection can be suppressed. In addition, when the diameter is 150 mm or less, the contact time with the free roller 55 is within an appropriate range, and the occurrence of wrinkles can be suppressed. In addition, it is possible to suppress the occurrence of scratches of the film 15 due to the rotation failure of the free roller 55. It is preferable that the outer peripheral surface of the free roller 55 is plated with hard chrome. By performing hard chrome plating, the adhesion to the film 15 is improved, and the film 15 is less likely to slip.

In the preheating unit 44, for example, an air supply nozzle 61 is disposed on the upper side, and an exhaust nozzle 62 is disposed on the lower side. A blower 64 and a temperature regulator 65 are connected to the air supply nozzle 61 and the exhaust nozzle 62 via a duct 63. The temperature regulator 65 heats, for example, air as a heating medium to a desired temperature. The blower 64 transmits the air whose temperature is adjusted by the temperature regulator 65 to the air supply nozzle 61 via the duct 63. The heated air is sent from the air supply nozzle 61, and the film 15 in the preheating portion 44 is preheated to a constant temperature by the heated air 66. The heated air 66 enters the inside of the preheating chamber 50 from the side of the film 15, and preheats the entire upper surface and the lower surface of the film 15.

It is necessary to set the preheating temperature based on the heated air 66 to a temperature lower than the stretchable temperature (tensile temperature) Te. Then, when the glass transition temperature of the film 15 is Tg, the heating air 66 is supplied into the preheating portion 44 to preheat the film 15 to a range of (Te - 40) ° C or more and (Tg - 5) ° C or less. Inside. Further, the blowing speed of the heated air from the air supply nozzle 61 is 2 m/sec or more. It is preferably in the range of 15 m/sec or less. When the blowing speed is 2 m/sec or more, the temperature of the preheating chamber 50 can be kept uniform, and stretching unevenness does not occur. Further, when the blowing speed is 15 m/sec or less, scratching due to the swing of the film 15 does not occur. In addition, the preheating unit 44 is configured by the preheating chambers 50 that are preheated by the air blowing, and has the same configuration as that of the above-described embodiment, and the same components are denoted by the same reference numerals.

In the present embodiment, since the heating air 66 is sent to the preheating chamber 50 and heated by the heating air 66, the film 15 does not become corrugated by the thermal conduction thermal expansion of the direct contact from the preheating roller. It can suppress wrinkles and scratches.

Further, if one preheating chamber 50 is preheated at the same temperature, the temperature of the free roller 55 may also be a temperature close to the room temperature of the preheating chamber 50. Therefore, the film 15 that has entered the preheating chamber 50 is in contact with the inlet side free roller 55 whose temperature rises to the outlet temperature of the preheating chamber 50. Therefore, the film 15 thermally expands and may become corrugated plate-like wrinkles in which the unevenness is repeated in the film width direction. To prevent this from occurring, the diameter of the free roller 55 is minimized so as to suppress the heating caused by the heat conduction of the free roller 55, and the heat conduction of the film 15 by the free roller 55 is suppressed by reducing the wrap angle. Therefore, in the case where the film transport speed is 40 m/min, the diameter of the free roller 55 is set to be in the range of 40 mm or more and 150 mm or less, so that even if the free roller 55 heated by the heated wind 66 contacts the film 15, Will cause deformation due to thermal expansion. Actually, the free roller 55 becomes a temperature lower than the temperature in the preheating chamber 50 by being in contact with the film 15 (temperature lower than the temperature of the preheating chamber 50) continuously fed, and thus sometimes does not come into contact with the film. The free roller 55 is thermally deformed.

In the above embodiment, the film 15 is heated by one preheating chamber 50. However, as shown in Fig. 5, the preheating portion 70 having the preheating regions 68a to 68c may be used, and the preheating regions 68a to 68c are The preheating chamber 68 is divided into a plurality of regions by the partition 69 in the film transport direction. Incidentally, the same components as those of the above-described embodiment are denoted by the same reference numerals. In this case, the air supply nozzle 61, the exhaust nozzle 62, the duct 63, the blower 64, and the temperature regulator 65 are provided in the respective preheating areas 68a to 68c, and the temperatures in the respective preheating areas 68a to 68c are set to be The film is gradually raised in the direction of transport. The temperature difference between the adjacent preheating zones 68a to 68c is, for example, in the range of 20 ° C or more and 50 ° C or less. If the temperature difference is less than 20 ° C, a plurality of preheating zones are required when it reaches a desired temperature, for example, 180 ° C. As the number of divisions increases, the power of the device also decreases accordingly. Moreover, if the temperature difference exceeds 50 ° C, due to the adjacent preheating areas 68a to 68c The air exchange causes temperature unevenness, and uneven temperature is generated in the film 15 to cause uneven stretching.

The number of divisions of each of the preheating zones 68a to 68c is increased or decreased according to the preheating temperature. For example, if a preheating chamber 68 is preheated at the same temperature, the film 15 entering the preheating chamber 68 is brought into contact with the inlet side free roller 55 whose temperature rises to the outlet temperature of the preheating chamber 68, so that the film 15 is thermally expanded. There may be corrugated plate-like wrinkles in which the unevenness is repeated in the width direction of the film. In order to prevent this, the preheating temperature of each of the preheating zones 68a to 68c is set to be small, that is, even if the free roller 55 heated by the heating wind 66 contacts the film 15, it does not thermally expand and deform. The extent of it. Further, preheating is performed stepwise by a plurality of preheating zones 68a to 68c until the temperature in which longitudinal stretching is possible.

Further, as shown in FIG. 6, the preheating portion 68 may be substituted for the preheating chamber 68 divided into a plurality of regions. The preheating unit 83 supplies the temperature control medium to each of the rollers 80 by the temperature adjustment mechanisms 82a to 82c in one preheating chamber 79, thereby tempering the surface temperature of the free roller 80 in groups. In this case, the surface temperature of the free roller 80 is sequentially raised in order from the inlet side. The surface temperature of each of the free rollers 80 is set such that the temperature of the corrugated plate wrinkles is not generated by the film 15 due to contact and thermal expansion. Further, in addition to the temperature adjustment by the group, the temperature adjustment may be performed for each of the free rollers 80. Further, the free roller 55 in the preheating chamber 68 divided as shown in Fig. 5 can be tempered in the same manner. The temperature difference between the adjacent downstream side group and the upstream side group free roller 80 is 50 ° C or lower, and the most upstream group free roller 80 is in the range of (Te - 40) ° C or more and (Tg - 5) ° C or less.

In the above embodiment, the film path lengths in the preheating chambers 50, 68, and 79 are set to be long by the free rollers 55, 80. However, as shown in FIG. 7, the steering rod (transport direction changing unit) 85 may be used instead of the preheating portion 86 of the free rollers 55, 80. In this case, the blower 87 and the temperature regulator 88 are connected to the steering lever 85 to supply the suspension rod 85 with the suspended air. The suspended air may be set to be the same temperature as or lower than the preheating temperature of the preheating chamber 84. In addition, in FIGS. 6 and 7, although the preheating chambers 79 and 89 are provided with the blower 64 and the temperature regulator 65 as shown in FIG. 4, illustration is abbreviate|omitted. Further, similarly to the embodiment of Fig. 5, the preheating chambers 79, 89 may be divided into a plurality of regions to form a preheating region, and the blower 64 and the temperature adjustment may be provided in the preheating regions of the preheating chambers 79, 89. The heater 65 sets a preheating temperature for each of the preheating zones so that the preheating temperature gradually rises from the inlet side toward the outlet side. Further, similarly to the free roller 80 of the embodiment of Fig. 6, the temperature of the suspended air from each of the steering levers 85 is changed for each of the steering levers 85 or for each group, and the temperature gradually rises from the inlet of the preheating chamber 89 toward the outlet. high.

[Examples]

As the film 15, a cellulose halide film was used and preheated, longitudinally stretched, and cooled. The longitudinal stretching portion 12 is longitudinally stretched in one step by the upstream side low speed roller group 21 and the downstream side high speed roller group 22. A film feeder is used as the pre-processing apparatus 9, and the film 15 is taken out from the film roll, and then sent to the preheating section 11, and the film winding machine is used as the post-process apparatus 14, and the film 15 is wound up as a film roll. The experiment was carried out under the following conditions: the preheating temperature was set to 130 ° C, the stretching temperature was set to 150 ° C, the longitudinal stretching ratio was set to 1.5 times, the stretching length was set to 300 mm, and the cooling temperature was set to 100 ° C. The speed was set to 2 m/min, the film width before stretching was set to 600 mm, the film thickness before stretching was set to 100 μm, and the film width after stretching was set to 580 mm, and the uniform film thickness at the center portion after stretching (see FIG. 2) The width W2 is set to 480 mm, and the offset amount OS1 from the film thickness change start point P1 to the side edge direction is set to 15 mm, 10 mm (= WFS × 0.2), 0 mm, -10 mm, and not for the wall thickness portion width WFS of 50 mm. The side edge portions 15b are cut. In addition, the film thickness change start point P1 is a point where the uniform film thickness at the center portion after stretching exceeds the film thickness unevenness of the film (raw material film) before stretching. The film thickness of the film before stretching was not the difference between the film thickness maximum value (Ftmax) and the film thickness minimum value (Ftmin), and the value (Ftmax - Ftmin) was 1.5 μm.

When the offset amount OS1 was set to 10 mm, 0 mm, or -10 mm, no scratches and wrinkles were generated. Further, when the both side edge portions 15b and the offset amount OS1 were not cut at 15 mm, no scratches and wrinkles were generated. Further, when the width of the scratch observed by the microscope was 0.05 mm or more and the depth was 0.02 mm or more, it was evaluated as "produced (poor)". If wrinkles are recognized by visual inspection, they are evaluated as "produced".

9‧‧‧Pre-process equipment

10‧‧‧film stretching equipment

11‧‧‧Preheating Department

12‧‧‧ longitudinal stretching

13‧‧‧The Ministry of Cooling

14‧‧‧ late process equipment

15‧‧‧film

16, 16a‧‧‧Preheating roller

16b, 21b, 22b‧‧‧ clamping rolls

17‧‧‧1st preheating roller

18‧‧‧2nd preheating roller

21‧‧‧Low speed roller set

21a‧‧‧low speed roller

22‧‧‧High speed roller set

22a‧‧‧High speed roller

25‧‧‧1st chill roll

26‧‧‧2nd cooling roller

27, 28‧‧‧Transfer roller

31‧‧‧ slitting machine

31a, 31b‧‧‧ Roller blades

32‧‧‧Rotary cutter

33‧‧‧Reuse Department

Ls‧‧‧ film length

Claims (14)

A method for producing a stretched film, which comprises stretching a film of a thermoplastic resin film in a transport direction to produce a stretched film, wherein the method for producing a stretched film comprises the following steps: (A) The upstream side low speed roll and the downstream side high speed roll stretch the film in the conveying direction, and the downstream side high speed roll is disposed downstream of the upstream side of the upstream side low speed roll in the conveying direction, and is higher than the peripheral speed of the upstream side low speed roll Rotating, the upstream low speed roller contacting the film to heat the film; (B) cooling the film by a cooling roll that is in contact with the film of the A step; and (C), in the foregoing A The edge portions on both sides in the width direction of the film are removed between the step and the aforementioned step B. The method for producing a stretched film according to the first aspect of the invention, wherein, in the step C, a film thickness change start point from a film thickness of both side edges in the width direction to both sides of the film When the width of the edge is WFS, the center portion and both side edge portions in the width direction of the film are cut in the WFS × 0.2 from the start point of the film thickness change toward the both side edges, and the edge portions on both sides in the width direction are removed. The method for producing a stretched film according to the above aspect, wherein in the step A, the film length between the upstream low speed roll and the downstream side high speed roll is divided by the stretched length. The longitudinal stretch aspect ratio of the film width is 0.01 or more and 0.5 or less. The method for producing a stretched film according to the first or second aspect of the invention, wherein, in the step A, when the glass transition temperature of the film is Tg, the upstream low-speed roll is used. The film is heated to a stretching temperature Te in the range of (Tg-20) ° C or more and (Tg + 20) ° C or less, and the film is cooled to (Tg - 100) ° C or more by the downstream side high speed roller. (Tg-5) Within the range of °C or less. The method for producing a stretched film according to claim 4, wherein the method further comprises the step of: (D) preheating the film to (Te-40) ° C or higher before the step A. And (Tg-5) °C or less. The method for producing a stretched film according to claim 5, wherein in the step D, heating air is supplied to the inside of the preheating chamber to preheat the film. The method for producing a stretched film according to claim 5, wherein in the step D, the conveying direction of the film is changed, and the film is stretched over a plurality of conveying directions for lengthening a path of the film. Change the component and transfer it. A film stretching apparatus for producing a stretched film by stretching a film of a thermoplastic resin in a belt direction, wherein the film stretching apparatus includes a longitudinal stretching portion, and a high speed roller on the upstream side and a high speed downstream side The film has a peripheral speed difference, and the film is stretched in the conveying direction, the upstream low speed roller contacts the film to heat the film, and the downstream high speed roller is disposed downstream of the upstream low speed roller in the conveying direction; The film is cooled by a cooling roll, the cooling roll is in contact with the film from the longitudinally stretched portion, and the side edge portion removing portion cuts both side edges of the film in the width direction from the center portion. In the removal, the side edge portion removing portion is disposed between the downstream side high speed roller and the cooling roller. The film stretching apparatus according to claim 8, wherein the width from the start of the film thickness change from the film thickness of the width direction side edge portion to the width of both side edges of the film is WFS, The side edge portion removing portion cuts the center portion and the both side edge portions in the film width direction from the start point of the film thickness change toward both side edges of the film in the WFS × 0.2, thereby removing the both side edge portions in the width direction. The film stretching apparatus according to Item 8 or 9, wherein the film length between the upstream side low speed roll and the downstream side high speed roll is divided by the longitudinal stretch width of the film width before stretching. The size ratio is 0.01 or more and 0.5 or less. The film stretching apparatus according to Item 8 or 9, wherein when the glass transition temperature of the film is Tg, the longitudinal stretching portion is formed by the upstream side low speed roller. Heating to a stretching temperature Te in the range of (Tg - 20) ° C or more and (Tg + 20) ° C or less, and cooling the film to (Tg - 100) ° C or more and (Tg - by the downstream side high speed roller) 5) Within the range of °C or less. The film stretching apparatus according to claim 11, wherein the longitudinal stretching portion has a preheating portion on the upstream side in the film conveying direction, and the preheating portion preheats the film to (Te-40) ) ° C or more and (Tg - 5) ° C or less. The film stretching apparatus according to claim 12, wherein the preheating portion has a preheating chamber and a blowing nozzle that supplies heated air to the preheating chamber, and is heated by the air from the air blowing nozzle. The aforementioned film was preheated. The film stretching apparatus according to claim 12, wherein the preheating unit has a plurality of conveying direction changing units that change a conveying direction of the film, and the film is placed on the conveying direction changing unit.