JP6185016B2 - Film manufacturing method and film stretching apparatus - Google Patents

Description

  The present invention relates to a film manufacturing method and a film stretching apparatus.

  The strip-shaped thermoplastic resin film is formed into a thin film having a desired thickness by stretching in the transport direction (longitudinal direction) or the width direction (transverse direction). Further, in-plane retardation (Re) and retardation in the thickness direction (Rth) can be expressed by stretching. Due to such characteristics, the thermoplastic resin film is used for optical applications such as a retardation film of a liquid crystal display device.

  When a thin film is produced by stretching in the transverse direction (hereinafter referred to as transverse stretching), both sides of the film are separated from the film product part by a slitter in order to cut off the grip marks by the clips during stretching (for example, Patent Document 1 (see FIG. 7).

  In addition, after lateral stretching, for example, as disclosed in Patent Document 2, wrinkles generated by slack after lateral stretching may cause problems such as breakage of the film during winding. For this reason, in the film manufacturing method described in Patent Document 2, wrinkles that occur in the transport direction and slack in the width direction are eliminated by using an expander roll, a multi-tension roll, or the like.

JP 2013-63569 A JP 2010-162740 A

  By the way, recent liquid crystal display devices are required to be lightweight, thin, and high quality, and a film to be used is required to be thin and high quality of about 40 μm or less, for example. When such a thin film is produced by existing stretching equipment, unevenness in the shape of corrugated deformation that is long in the conveying direction may occur on the side of the film. Such waveform deformation becomes more prominent and becomes a problem after subsequent film drying, film winding, or the like. Further, when the film is cut by a slitter and both side portions are separated from the main body portion, for example, from the above-described film product portion, a cutting failure may occur due to the influence of waveform deformation.

  When an expander roll or a multi-tension roll is used as in Patent Document 2 (paragraph 0015), even if the tension is partially changed in the width direction of the film, the waveform deformation cannot be completely removed. There is a problem. In addition, since the expander roll and multi-tension roll described above apply tension in the width direction, scratches caused by sliding the film in the width direction on the expander roll or multi-tension roll, and rolls with different diameters wound around the width direction There is a concern about scratches due to the difference in peripheral speed.

  The present invention solves such problems, and reduces the influence of waveform deformation in the cutting process in which both sides are continuously cut after the thin film is stretched horizontally, so that cutting defects do not occur. An object is to provide a film manufacturing method and a film stretching apparatus.

In order to achieve the above object, the film production method of the present invention produces a film having a thickness of 40 μm or less by stretching in the width direction while conveying a long thermoplastic resin film. The film manufacturing method includes a stretching process, a cooling process, a cutting process, and a pass roller conveying process. In the stretching step, both sides of the thermoplastic resin film are gripped by the gripping portion and stretched in the width direction. The cooling step cools the thermoplastic resin film in a state where the width stretched in the stretching step is kept constant. In the cutting step, both side portions gripped by the grip portion of the thermoplastic resin film are separated by a cutting blade. In the pass roller transport process, two or more pass rollers that are adjacent to each other in the transport direction so as to be arranged on different surfaces of the thermoplastic resin film, and in which the grip on both sides is released in the cooling process. A resin film is wound around and the conveyance path of the thermoplastic film is folded back at an acute angle in each of the two or more pass rollers and conveyed to a cutting blade.

The film stretching apparatus of the present invention produces a film having a thickness of 40 μm or less by stretching in the width direction while conveying a long thermoplastic resin film. The film stretching apparatus includes a tenter, a cutting blade, and two or more pass rollers. The tenter has a stretching area and a cooling area. In the stretching area, both sides of the thermoplastic resin film are gripped by the gripping portion and stretched in the width direction. In the cooling area, the thermoplastic resin film is cooled in a state where the width stretched in the stretching area is kept constant. The cutting blade cuts off both sides held by the holding part of the thermoplastic resin film. Two or more pass rollers are adjacent to each other in the conveying direction so as to be arranged on different surfaces of the thermoplastic resin film from the grip opening position on both sides in the cooling area to the cutting blade. The thermoplastic resin film conveyance path is folded back at an acute angle .

The thermoplastic resin film cooled in the cooling step is preferably introduced into the pass roller conveyance step without heating. It is preferable that the thermoplastic resin film cooled in the cooling area is wound around the pass roller. The pass roller preferably extends over the entire width direction of the thermoplastic resin film. It is preferable that the grip opening position for releasing the grip on both sides is provided on the downstream side in the transport direction in the cooling process. In the stretching step, the width of the thermoplastic resin film is preferably expanded to 1.07 times or more. Moreover, it is preferable that the conveyance path length of the thermoplastic resin film from the holding open position of the thermoplastic resin film by a holding part to a cutting blade is 1.0 m or more. The gripping portion is preferably a clip that holds both side portions of the thermoplastic resin film. The thermoplastic resin film is preferably a cellulose acylate film.

  According to the present invention, the influence of the waveform deformation of the thermoplastic resin film after transverse stretching is suppressed, so that no cutting failure occurs.

It is a side view which shows the outline | summary of an example of solution casting apparatus. It is a top view which shows the outline | summary of a film extending apparatus. It is a side view which shows the outline | summary of the chamber and duct of a tenter.

  The resin in the film produced according to the present invention is a transparent thermoplastic resin (polymer). In the present embodiment, cellulose acylate is used as the thermoplastic resin.

Among cellulose acylates, the present invention is particularly effective when TAC (cellulose triacetate) is used in which the substitution degree of the acyl group to the hydroxyl group of cellulose satisfies the following formulas (1) to (3). In the formulas (1) to (3), A and B represent the substitution degree of the acyl group with respect to the hydrogen atom in the hydroxyl group of cellulose, A is the substitution degree of the acetyl group, and B is the acyl having 3 to 22 carbon atoms. The degree of substitution of the group. The total acyl group substitution degree Z of cellulose acylate is a value determined by A + B.
(1) 2.7 ≦ A + B ≦ 3.0
(2) 0 ≦ A ≦ 3.0
(3) 0 ≦ B ≦ 2.9

The present invention is also particularly effective when using DAC (cellulose diacetate) in which the substitution degree of the acyl group to the hydroxyl group of cellulose satisfies the following formula (4) instead of or in addition to TAC. .
(4) 2.0 ≦ A + B <2.7

From the viewpoint of retardation wavelength dispersion, while satisfying the formula (4), the substitution degree A of the acetyl group of DAC and the total substitution degree B of the acyl group having 3 to 22 carbon atoms are represented by the following formula (5). And (6) is preferably satisfied.
(5) 1.0 <A <2.7
(6) 0 ≦ B <1.5

  Glucose units having a β-1,4 bond constituting cellulose have free hydroxyl groups (hydroxyl groups) at the 2nd, 3rd and 6th positions. Cellulose acylate is a polymer obtained by esterifying some or all of these hydroxyl groups with an acyl group having 2 or more carbon atoms. The degree of acyl substitution means the ratio at which the hydroxyl group of cellulose is esterified at each of the 2-position, 3-position and 6-position (the substitution degree is 1 in the case of 100% esterification).

  The solution casting apparatus 10 in FIG. 1 is for producing a long cellulose acylate film (hereinafter simply referred to as “film”) 12 from a dope 11. The dope 11 is obtained by dissolving a polymer in a solvent. The solution casting apparatus 10 includes a casting device 14, a film stretching device 17 including a tenter 15 and a slitter (cutting device) 16, a drying chamber 18, a cooling chamber 19, and a winding device 20 from the upstream side. Prepare in order.

  The casting apparatus 14 is for forming the film 12 containing the solvent from the dope 11. The casting apparatus 14 includes a belt 30, a casting die 31, a backup roller 33, and a peeling roller 35 in a chamber 36 that partitions the external space. The casting die 31 flows out the dope 11 toward the belt 30. The belt 30 is an endless casting support formed in an annular shape, and is stretched around a pair of backup rollers 33.

  At least one of the pair of backup rollers 33 has a drive unit (not shown), and the drive unit rotates about the shaft 33a. By this rotation, the belt 30 stretched around the peripheral surface is conveyed in the longitudinal direction. As the dope 11 flows out from the casting die 31 toward the peripheral surface of the belt 30 being conveyed, the dope 11 is cast on the peripheral surface of the belt 30 to become a casting film 32. A bead made of the dope 11 is formed from the casting die 31 to the belt 30. A chamber (not shown) that decompresses the upstream area of the bead by sucking air is provided upstream of the bead in the rotation direction of the backup roller 33.

  The temperature of the peripheral surface of each backup roller 33 is controlled by a temperature controller 33b. Inside the backup roller 33, a flow path through which the heat transfer medium flows is formed. The temperature controller 33 b adjusts the temperature of the heat transfer medium and circulates the heat transfer medium between the backup roller 33. By adjusting the peripheral surface temperature of the backup roller 33, the temperature of the casting film 32 is controlled via the belt 30. For example, in the case of so-called cooling casting in which the casting film 32 is cooled and solidified (gelled), the temperature controller 33 b cools the heat transfer medium and sends the cooled heat transfer medium to the backup roller 33. For example, by continuously performing this feeding, the heat transfer medium goes around the flow path inside the backup roller 33 and returns to the temperature controller 33b. In the case of so-called dry casting in which the casting film 32 is dried and solidified, the temperature controller 33b heats the backup roller 33, for example.

  The casting support is not limited to the belt 30. For example, instead of the belt 30, a drum (not shown) that rotates in the circumferential direction may be used as the casting support. In the case of dry casting, the belt 30 is often used, and in the case of cooling casting, a drum is often used. When the drum is used as a casting support, the temperature of the peripheral surface of the drum is adjusted by passing a heat transfer medium through the drum, and the temperature of the casting film 32 is controlled through this drum.

  The stripping roller 35 is for maintaining a stripping position at which the casting film 32 is stripped from the belt 30, and is arranged so that the axial direction is parallel to the axial direction of the backup roller 33. The film 12 is pulled in the transport direction Z1, and the peeling film 35 supports the film 12 on the peripheral surface, whereby the casting film 32 is peeled off from the belt 30 at a predetermined position. By this continuous peeling, the film 12 is formed to be long.

  Inside the casting apparatus 14, a condenser (condenser) is provided that condenses the solvent evaporated from each of the dope 11, the casting film 32, and the film 12. The solvent liquefied by the condenser is guided to a recovery device arranged outside the chamber 36 and recovered by the recovery device. In addition, illustration of a condenser and a collection | recovery apparatus is abbreviate | omitted.

  The film 12 is guided by the roller 40 from the casting device 14 to the tenter 15 of the film stretching device 17. The tenter 15 is a so-called clip tenter that holds each side portion 12b (see FIG. 2) of the film 12 by holding (gripping) the plurality of clips (gripping portions) 50, and the clip 50 travels on a predetermined track. The film 12 is conveyed by the travel of the clip 50.

  As shown in FIG. 2, the tenter 15 includes a chamber 43 that surrounds the transport path of the film 12 and partitions the transport path and its periphery from the external space. In the following description, simply “conveyance path” means the conveyance path of the film 12. The chamber 43 is divided into a preheating area 45, an extending area 46, and a cooling area 47 in order from the upstream side in the transport direction Z1, and dry air whose temperature is controlled for each area is sent.

  The tenter 15 includes a clip 50, rails 51 and 52, chains 53 and 54, a duct (see FIG. 3) 55 as an air outflow portion, and an air supply portion 56. The clip 50 grips the side portion 12 b of the film 12. The rails 51 and 52 guide the traveling of the clip 50 and are installed on both sides of the conveyance path. The air supply unit 56 sends dry air of a predetermined condition into the duct 55. The duct 55 allows dry air to flow out and dries the film 12.

  The plurality of clips 50 are attached to the chains 53 and 54 at a predetermined interval. The chains 53 and 54 are attached to the rail 51 and the rail 52, respectively, and are movable along the rails 51 and 52. The chains 53 and 54 mesh with a turn wheel 57 disposed on the upstream side of the preheating area 45 and a sprocket 58 disposed on the downstream end of the cooling area 47. As the sprocket 58 rotates, the chains 53 and 54 run continuously. As the chains 53 and 54 run, the clip 50 moves along the rails 51 and 52.

  On the upstream side of the preheating area 45, a grip start member 64 that causes the clip 50 to start gripping the side portion 12 b of the film 12 is provided. Further, on the downstream side of the cooling area 47, a grip release member 65 that causes the clip 50 to release the grip of the side portion 12 b of the film 12 is provided. Thereby, the film 12 is gripped by the clip 50 at the grip start position PA on the upstream side of the preheating area 45, and is transported in the longitudinal direction as the clip 50 moves along the rails 51 and 52. The stretching area 46 and the cooling area 47 are sequentially passed. While passing through the preheating-cooling areas 45-47, the film 12 is subjected to predetermined processing in the preheating-cooling areas 45-47, and the grip by the clip 50 is released at the grip opening position PB on the downstream side of the cooling area 47. The

  The rail 51 and the rail 52 are separated from each other by a predetermined rail width. The rail width can be adjusted by a rail moving mechanism (not shown), and the draw ratio can be changed by changing the rail width. The rail width is constant at the width W1 in the preheating area 45. Thereby, in the preheating area 45, the film 12 is conveyed, maintaining a fixed width | variety in the state in which the width | variety was controlled.

  The extending area 46 is for performing an extending process (extending step), and the rail width gradually becomes wider in the transport direction Z1, that is, toward the downstream. Thus, in the stretching area 46, the film 12 is stretched (laterally stretched) in the width direction Z2 while being conveyed, and the width is expanded. Specifically, when the width of the film 12 introduced into the stretching area 46 is W1, and the width of the film 12 exiting the stretching area 46 is W2, by adjusting the rail width in the stretching area 46, W2 / For example, the draw ratio determined by W1 is 1.01 to 5.0.

  The cooling area 47 is for performing a cooling process (cooling process), and the rail width is constant. Thereby, in the cooling area 47, the film 12 is conveyed in a state where the width is kept constant at W2. The above-mentioned “constant” regarding the rail width in the preheating area 45 and the cooling area 47 does not need to be exact, and can be said to be substantially constant (for example, a change within 2%) in the width W1 and the width W2 from upstream to downstream. A mode in which the rail width is slightly changed to an extent may be used.

  As shown in FIG. 3, the duct 55 is provided above the conveyance path so that the distance between the film 12 and the conveyance path is substantially constant. A blowout port 61 on a slit extending in the width direction Z2 of the film 12 is formed below the duct 55, and a plurality of the blowout ports 61 are provided along the transport direction Z1. A duct having the same configuration as the duct 55 is also provided below the transport path of the film 12 so that the distance from the transport path is substantially constant, but the illustration is omitted. In a duct (not shown) below the conveyance path, each outlet is formed at the top. The transport direction Z1 and the width direction Z2 are orthogonal to each other.

  The inside of the duct 55 is divided into a first supply chamber 55a to a third supply chamber 55c by a plurality of partition plates 62, for example. In the present embodiment, as shown in FIG. 3, a plurality of outlets 61 are provided for the first supply chamber 55a to the third supply chamber 55c. Specifically, the first supply chamber 55a has two outlets 61, and the second supply chamber 55b and the third supply chamber 55c have three outlets 61, respectively. The number of outlets 61 in each of the third to third supply chambers 55c is not limited to this. Although not shown, an exhaust port, an exhaust groove, or the like may be provided between the outlets 61.

  The air supply unit 56 supplies dry air to the first supply chamber 55 a to the third supply chamber 55 c of the duct 55. The air supply unit 56 includes a temperature controller (not shown) that independently controls the temperature of each dry air supplied to the first supply chamber 55a to the third supply chamber 55c. By this temperature controller, the dry air adjusted to a predetermined temperature is supplied to the preheating area 45, the extending area 46, and the cooling area 47 via the first supply chamber 55a to the third supply chamber 55c, respectively. The temperature in the first supply chamber 55a to the third supply chamber 55c may be constant, or the temperature region may be further subdivided in the film transport direction Z1.

  The film 12 is heated in advance before entering the stretching area 46 by supplying dry air from the first air supply chamber 55a. By the heating in the preheating area 45, stretching in the stretching area 46 is started quickly, and more uniform tension is applied to the film 12 in the width direction Z2 when stretching in the stretching area 46.

  In the stretching step of the tenter 15, it is preferable to stretch the film 12 in the width direction Z <b> 2 while keeping the temperature of the film 12 at, for example, 140 ° C. or lower. The draw ratio can be arbitrarily set within a range of 1.01 times to 5.0 times. In this embodiment, the draw ratio is 1.07 times or more and 5.0 times or less, preferably 1.07 times or more and 2.00 times or less.

  The film 12 is dried while passing through the tenter 15. In the tenter 15, it is preferable that the residual solvent amount of the film 12 is set within a range of, for example, 3% by mass or more and 20% by mass or less by promoting the drying of the film 12. In the present specification, the residual solvent amount means that the mass of the film 12 to be measured for which the residual solvent amount is to be obtained is X, and the mass after completely drying the film 12 is Y ({(XY)). / Y} × 100 is a so-called dry weight reference value. Note that “completely dry” does not require the amount of the solvent to be strictly 0 (zero). For example, the mass after drying the film 12 to be measured at 140 ° C. for 3 hours may be Y.

  The slitter 16 disposed downstream of the tenter 15 includes a first pass roller 71 to a fourth pass roller 74 and a cutting blade 75, and performs cutting (cutting process). The first pass roller 71 to the fourth pass roller 74 are spaced apart from the upstream side to the downstream side in the transport direction Z1, and the film 12 is transported by the first pass roller 71 to the fourth pass roller 74 (pass roller transport). Process). The first pass roller 71 to the third pass roller 73 are arranged upstream of the cutting blade 75, and the fourth pass roller 74 is arranged downstream of the cutting blade 75.

  The film 12 is wound around at least two of the first pass roller 71 to the third pass roller 73 disposed upstream of the cutting blade 75, and the total winding angle is 90 ° or more. The total winding angle is the sum of the winding angles (wrap angles) of each of the plurality of pass rollers disposed upstream of the cutting blade 75. In this example, each of the first pass roller 71 to the third pass roller 73 It is the sum total of the winding angle (wrap angle) at. That is, when the winding angle of the first pass roller 71 is θ71, the winding angle of the second pass roller 72 is θ72, and the winding angle of the third pass roller 73 is θ73, the total winding angle is a calculation formula of θ71 + θ72 + θ73. Desired. The winding angle is a fan-shaped central angle formed by a winding region of the peripheral surface around which the film 12 is wound and the center of a circular section when the pass roller is viewed from the side as shown in FIG. is there.

  In the present embodiment, the first pass roller 71 supports the film 12 that has exited the tenter 15 from below. Thus, the 1st pass roller 71 is provided in order to maintain a conveyance path horizontally, and the direction of the conveyance path of the upstream and downstream of the 1st pass roller 71 is the same. That is, the winding angle θ71 of the film 12 in the first pass roller 71 is 0 °. However, the direction of the transport path may be changed by the first pass roller 71. In this case, the film 12 is wound around the first pass roller 71, and the direction of the transport path upstream and downstream of the first pass roller 71 is changed. Shall be different from each other. That is, when the direction of the transport path is changed in this way, the winding angle θ71 of the film 12 with respect to the first pass roller 71 is set to be larger than 0 °. Even when the first pass roller 71 is provided so as to keep the transport path horizontal, the contact with the first pass roller 71 is not a line contact but a surface contact due to the weight of the film 12. Thus, the film 12 may be wound around the first pass roller 71. In this way, when the film 12 is supported from below in order to keep the transport path horizontal, the winding angle of the film 12 with respect to the pass roller is Considered 0 °.

  The film 12 is wound around the second pass roller 72 and the third pass roller 73, and the winding angle θ72 and the winding angle θ73 are each set to be larger than 0 °. Since the winding angle θ71 is 0 ° as described above, in this example, the second pass roller 72 and the third pass roller 73 have a winding angle of the film 12 so that the total winding angle is 90 ° or more. The sum is 90 ° or more, whereby the shape of the conveyance path (path) when the film 12 is viewed from the side is folded back into a Z-shape. That is, in this embodiment, the total winding angle is the sum of the winding angles of the film 12 that is wound around the second pass roller 72 and the third pass roller 73. When the film 12 is also wound around the first pass roller 71, θ71 is also an object for calculating the total winding angle. Note that the Z-shape includes a substantially Z shape having an obtuse angle (90 ° or more and less than 180 °) in addition to the original Z shape having an acute angle (less than 90 °).

  In the present embodiment, the pass rollers disposed upstream of the cutting blade 75 are the first pass roller 71 to the third pass roller 73, but the number is not limited thereto. When the number is 2, the film 12 is wound around both of the two pass rollers, and the total winding angle is set to 90 ° or more. When the number is 4 or more, the film 12 is wound around at least two pass rollers so that the total winding angle is 90 ° or more. Thus, the number of pass rollers that are subject to the total winding angle is three. It may be the above.

  As described above, the second pass roller 72 is disposed on the side of the film 12 peeled off from the belt 30 and the third pass roller 73 is peeled off so that the shape of the transport path (pass) is folded back into a Z-shape. It is arranged on the anti-peeling surface side opposite to the surface. As described above, the pass rollers around which the film 12 is wound are more preferably arranged in a staggered manner with respect to the conveyance path.

  A cutting blade 75 is disposed between the third pass roller 73 and the fourth pass roller 74. As the cutting blade 75, a leather blade or a Gobel blade is used, and the side portions 12b of the film 12 are continuously cut in the transport direction Z1. Thereby, the film 12 which cuts each side part 12b from the center part 12a which becomes the product part of the film 12 is cut (cutting process), and the holding trace by the clip 50 in the tenter 15 is removed.

  The length (hereinafter referred to as the conveyance path length) L1 of the transport path of the film 12 from the grip open position PB of the tenter 15 to the cutting blade 75 is 1.0 m or more. The transport path length L1 is a length when the first pass roller 71 to the third pass roller 73 are in between. Note that the conveyance path length L1 shown in FIG. 2 looks like the distance between the grip opening position PB and the cutting blade 75 in a plan view, but this distance is not the length of the conveyance path folded in a Z-shape. That is, it is the length along the conveyance direction Z1 in FIG.

  A fourth pass roller 74 is disposed on the downstream side of the cutting blade 75. The fourth pass roller 74 rotates and supports each separated side portion 12 b and sends each side portion 12 b to the side air feeding device 78. As is well known, the side air blowing device 78 cuts each side portion 12b continuously fed into fine chips and sends them to a collecting device (not shown) by suction air. It is to be noted that a fifth pass roller (not shown) is provided downstream of the cutting blade 75 and upstream of the fourth pass roller 74 or downstream of the fourth pass roller 74 to transport the film 12 from which each side portion 12b has been cut. For example, the road may be changed upward.

  The drying chamber 18 is provided with a plurality of rollers 80 that support the film 12 on the peripheral surface. Among the plurality of rollers 80, there is a driving roller that rotates in the circumferential direction, and the film 12 is conveyed by the rotation of the driving roller. The drying chamber 18 is supplied with heated dry air. The film 12 is further dried by passing through the drying chamber 18.

  Room-temperature dry air is supplied to the cooling chamber 19. Room temperature is a temperature within the range of 15 ° C. or higher and 30 ° C. or lower. The temperature of the film 12 is lowered by passing through the cooling chamber 19. The film 12 whose temperature has been lowered is guided from the cooling chamber 19 to the winding device 20 and wound around the core 82.

  Next, the operation of the above configuration will be described. The film 12 that has exited the tenter 15 and has been released from the gripping of the clip 50 contracts due to residual stress due to stretching or temperature drop. At this time, although tension is applied to the film 12 due to the transport tension, the tension is applied in the transport direction Z1, but since the tension is removed in the width direction Z2 due to the gripping and releasing of the clip 50, the film 12 extends in the transport direction Z1. Waveform deformation occurs. When both side portions 12b of the film 12 are separated from the central portion 12a by the cutting blade 75 in a state where the waveform deformation has occurred, a cutting defect occurs due to the waveform deformation. When a cutting failure occurs, the side line 12b is clogged in the next side air blowing device 78, so the production line may be stopped. In this case, various operations for starting up again in the casting process or the like are necessary, and time and raw materials are wasted.

  In the above configuration, the film 12 that has exited the tenter 15 passes through the first pass roller 71 to the third pass roller 73 and is sent to the cutting blade 75, and both side portions 12b of the film 12 are separated from the central portion 12a. In the present embodiment, the film 12 is passed through the three first pass rollers 71 to the third pass roller 73, and the film 12 is wound around the second pass roller 72 and the third pass roller 73, and the total winding angle is 90. Since the angle is not less than °, the waveform deformation is relaxed while passing through the second pass roller 72 and the third pass roller 73, and the influence of the waveform deformation is reduced when the both side portions 12b are separated by the cutting blade 75. The both side portions 12b can be cut off smoothly.

  The second pass roller 72 and the third pass roller 73 around which the film 12 is wound are arranged in a staggered manner with respect to the conveyance path, and thereby the wave-like deformation is further relaxed, so that the side portions 12b can be separated more smoothly.

  In this embodiment, a clip tenter is used as the tenter 15, but a pin tenter may be used instead of the clip tenter. Also in this case, the holding marks by the pins are removed by separating each side 12b using the slitter 16. The pin tenter has a pin plate for penetrating and holding a plurality of pins on the side portion 12b of the film 12, and the film 12 is conveyed by the pin plate traveling on a predetermined track. When the pin tenter is used as the tenter 15, it is preferable that the residual amount of the solvent in the film 12 be within a range of, for example, 20% by mass or less by proceeding with the drying of the film 12 as in the case of using the clip tenter.

  A second tenter (not shown) may be provided on the downstream side of the slitter 16 as necessary. The second tenter is used when the optical characteristics are changed by a specific stretching pattern. Even in the second tenter, the slitter 16 is provided in the same manner as the first tenter 15, so that it can be cut while suppressing the influence of the waveform deformation of the film 12.

  When TAC is used as the polymer, the film 12 preferably has a single layer structure made of TAC. On the other hand, when DAC is used as the polymer, the film 12 preferably has a multilayer structure. A preferable multilayer structure is a structure in which a layer made of TAC is provided on one surface of a layer made of DAC. A more preferable multilayer structure is a structure in which a layer made of TAC is provided on one surface and the other surface of a layer made of DAC, respectively. Such an optical film having a multilayer structure having a DAC layer is preferably produced by a solution casting method, and is preferably produced by simultaneous co-casting or sequential casting. The casting die 31 in the case of simultaneous co-casting is a known multi-manifold die. Instead of a multi-manifold die, a feed block and a single manifold die may be used in combination. The feed block joins a plurality of types of supplied dopes inside, and sends the joined flow to a single manifold die.

  The above embodiment is a case where the film 12 is stretched in the width direction Z2 in the solution casting process, but the present invention is not limited to this aspect. For example, also in the case of so-called off-line stretching in which a once produced thermoplastic resin film is stretched in the width direction Z2, both side portions 12b of the film 12 may be separated from the central portion 12a using the slitter 16.

  The film 12 is used as an optical film. Specifically, the film 12 can be particularly preferably used as a retardation film that is used for a polarizing plate and optically compensates for light from a light source. Especially, it is particularly effective as a retardation film for VA and a retardation film for IPS.

  First, cellulose acylate (TAC) having an acyl group substitution degree of 2.81 was prepared. When making, sulfuric acid was used as a catalyst. The addition amount of this catalyst with respect to 100 mass parts of cellulose acylate is 7.8 mass parts. Carboxylic acid as a raw material for the acyl substituent was added and an acylation reaction was performed at 40 ° C. The type of acyl group and the degree of substitution were adjusted by adjusting the type and amount of carboxylic acid. Moreover, it age | cure | ripened at 40 degreeC after acylation. Further, the low molecular weight component of the cellulose acylate was removed by washing with acetone.

  A dope 11 having the following formulation was prepared.

(Dope)
Cellulose acylate 100 parts by mass Additive A: A-3 in Table 1 11.3 parts by mass Compound D: Compound shown in Chemical formula 4 parts by mass Dichloromethane 406 parts by mass Methanol 61 parts by mass

  The dope 11 was mixed and stirred with a matting agent dispersion. The matting agent (AEROSIL R972, manufactured by Nippon Aerosil Co., Ltd., secondary average particle size of 1.0 μm or less) as fine particles was 0.13 parts by mass with respect to 100 parts by mass of cellulose acylate.

  The additive A is a polyester, and this polyester is obtained by the combination and ratio of dicarboxylic acid and diol described in Table 1. In Table 1, “TPA” in the “aromatic dicarboxylic acid” column represents terephthalic acid, and “SA” in the “aliphatic dicarboxylic acid” column represents succinic acid. The “dicarboxylic acid ratio” column in Table 1 indicates aromatic dicarboxylic acid / aliphatic dicarboxylic acid, and the “diol ratio” column indicates diol 1 / diol 2.

  Experiments 1 to 19 were carried out in which a film 12 was produced from the dope 11 using the solution casting apparatus 10 to obtain a film 12 with a thickness of 20, 40, 60 μm. The film 12 having a thickness of 20, 40, 60 μm is obtained by adjusting the thickness of the casting film 32 by the casting apparatus 14 and changing the stretching ratio (W2 / W1) in the tenter 15. Further, the draw ratio (W2 / W1) of the film stretching device 17, the transport path length L1 from the grip opening position PB to the cutting blade 75, and the pass roller on which the film 12 is wound on the transport path between the tenter 15 and the cutting blade 75. N and the total winding angle θ of the wound pass rollers were set as shown in Table 2. Then, the stability of cutting (hereinafter referred to as cutting stability) for cutting off both side portions 12b in the film stretching device 17 was evaluated. The thickness of the film in each experiment is shown in the “film thickness” column in Table 2. The number N of pass rollers around which the film 12 is wound in the transport path between the tenter 15 and the cutting blade 75 is “wound pass roller wound”. This is shown in the “Number N” column.

  In Experiments 1 to 19, the winding angle of the film 12 around the first pass roller 71 was set to 0 °. In Experiments 1 to 8, in FIG. 1, the second pass roller 72 and the third pass roller 73 are omitted, the shape of the film transport path is made linear, and the cutting blade 75 is placed between the first pass roller 71 and the fourth pass roller 74. The reference example which has is shown. In Experiment 1, the cutting stability was evaluated when the thickness was 60 μm, the draw ratio was 1.00, and the conveyance path length L1 was 0.6 m. In Experiment 2, the same conditions as in Experiment 1 were used except that the film thickness in Experiment 1 was 40 μm. In Experiment 3, the conditions were the same as in Experiment 1 except that the film thickness in Experiment 1 was 20 μm. In Experiments 4 to 6, the conditions were the same as those in Experiments 1 to 3, except that the draw ratio in Experiments 1 to 3 was 1.07. In Experiment 7, the conditions were the same as in Experiment 5 except that the draw ratio in Experiment 5 was set to 1.12. In Experiment 8, the conditions were the same as in Experiment 6 except that the draw ratio in Experiment 6 was 1.12. Experiment 9 and Experiment 10 show a reference example in which the second pass roller 72 is arranged between the first pass roller 71 and the fourth pass roller 74 in FIG. In Experiment 9, the conditions were the same as in Experiment 6 except that the winding angle around the second pass roller 72 was 30 °. In Experiment 10, the conditions were the same as in Experiment 9 except that the winding angle around the second pass roller 72 in Experiment 9 was 90 °.

  In Experiments 11 to 19, as shown in FIG. 1, the first pass roller 71 to the fourth pass roller 74 were arranged, and the film 12 was wound around the second pass roller 72 and the third pass roller 73. The sum of the winding angles around the second pass roller 72 and the third pass roller 73 was set to 60 °, 90 °, and 180 ° as the total winding angle θ. In Experiment 11, the same conditions as in Experiment 6 were used except that the second pass roller 72 and the third pass roller 73 were added to Experiment 6 to form a Z-shaped film conveyance path, and the total winding angle θ was 60 °. In Experiment 12, the conditions were the same as in Experiment 11 except that the total winding angle in Experiment 11 was 90 °. In Experiment 13, the conditions were the same as in Experiment 11 except that the total winding angle in Experiment 11 was 180 °. In Experiment 14, the same conditions as in Experiment 12 were used except that the conveyance path length L1 in Experiment 12 was set to 0.8 m. In Experiment 15, the same conditions as in Experiment 12 were used except that the conveyance path length L1 in Experiment 12 was set to 1.0 m. In Experiment 16, the conditions were the same as in Experiment 15 except that the total winding angle θ in Experiment 15 was set to 180 °. In Experiment 17, the conditions were the same as in Experiment 12 except that the film thickness of Experiment 12 was 40 μm. In Experiment 18, the conditions were the same as in Experiment 17 except that the draw ratio in Experiment 17 was set to 1.12. In Experiment 19, the conditions were the same as in Experiment 18 except that the conveyance path length L1 in Experiment 18 was set to 1.0 m.

  In Experiments 20 to 22, the conveyance path length L1 of Experiment 8 is changed to 0.6 m, 0.8 m, and 1.0 m, and the first pass roller 71 to the fourth pass roller 74 are arranged, and the second pass roller 72 and the third pass roller are arranged. The film 12 was wound around 73. The conditions were the same as in Experiment 8 except that the sum of the winding angles around the second pass roller 72 and the third pass roller 73 was set to 90 ° as the total winding angle θ.

  In Experiments 23 to 26, the conditions were the same as in Experiments 8 and 20 to 22, except that the film material of Experiments 8 and 20 to 22 was changed from TAC to COP (cyclic olefin polymer). The COP film was obtained by forming ZEONOR (registered trademark) 1020R according to the method described in Production Example 1 in WO2006 / 019086, and the film thickness was 20 μm.

  In Experiments 27-30, the conditions were the same as in Experiments 8, 20-22, except that the film material of Experiments 8, 20-22 was changed from TAC to PET (polyethylene terephthalate). The PET film was formed as follows, and the film thickness was 20 μm. First, PET having an intrinsic viscosity of 0.64 polycondensed using a Ti compound as a catalyst was dried to a moisture content of 50 ppm or less and melted in an extruder having a heater temperature of 280 ° C. or higher and 300 ° C. or lower. Next, the molten PET was extruded from a die part onto a chill roll electrostatically applied to obtain a PET film made of a band-shaped amorphous base.

  The cutting stability was evaluated based on the presence or absence of breakage, the stability of the cutting line, and the roughness of the cut end face. Evaluation A was given when the film 12 was not broken, the cutting line was straight in the transport direction Z1 and stable, and there was no roughness on the cut end face. In addition, the film 12 was not broken and the cutting line was straight in the transport direction Z1 and was stable. However, when the cutting end face was rough, the evaluation was B. Although the film 12 does not break, the evaluation C was assigned when the cutting line meanders in the transport direction Z1 and is unstable. The meandering in the transport direction Z1 means that the cutting line is shifted in the width direction of the film 12. The cutting line was not straight in the transport direction Z1 and was unstable, and evaluation D was made when the film 12 was broken after several hours. Furthermore, the cutting line is not straight in the transport direction Z1, is unstable, and the film 12 is broken in a few minutes. The stability of the cutting line was evaluated by visually observing the side edge of the central portion 12a from which both side portions 12b were cut off. As for the roughness of the cut end surface, when the side end surface of the central portion 12a from which both side portions 12b are cut off is touched, or the surface end surface of the central portion 12a is rubbed with a black cloth, It was evaluated that there was roughness when. When the stability of the cutting line was evaluated as unstable, the roughness of the cut end face was not evaluated. When the evaluation is located between the two evaluations, for example, it is described as A to B.

  The group of Experiment 1 to Experiment 10 corresponds to a reference example, and it can be seen that the cutting stability decreases as the film 12 becomes thinner. Moreover, it turns out that cutting stability falls as a draw ratio becomes high. It can be seen that the cutting stability is improved by increasing the number N of wound pass rollers. However, it can be seen that when the film thickness is 40 μm or 20 μm and the draw ratio is 1.07, the cutting stability is lowered.

  In the groups of Experiment 1 to Experiment 6, it can be seen that the cutting stability gradually decreases as the film thickness decreases to 60 μm, 40 μm, and 20 μm. It can also be seen that the cutting stability gradually decreases as the draw ratio increases from 1.02 to 1.07.

  In the groups of Experiments 2, 5, 7, 3, 6, and 8, even when the thickness is the same, it can be seen that the cutting stability gradually decreases as the draw ratio increases to 1.02, 1.07, and 1.10. .

  In the groups of Experiments 6 and 9-13, when the total winding angle θ was increased to 30 °, 60 °, 90 °, and 180 ° with the film thickness being 20 μm and the draw ratio being 1.07, It can be seen that the cutting stability gradually improves as the total winding angle θ increases and as the number N of the wound pass rollers increases.

  In the groups of Experiments 14 to 16, the transport path length L1 is increased when the transport path length L1 is increased to 0.8 m and 1.0 m in a state where the film thickness is 20 μm and the draw ratio is 1.07. It can be seen that the cutting stability gradually improves. In the group of Experiment 17 to Experiment 19, when the film thickness was changed to 40 μm, the draw ratio was changed to 1.07 and 1.10, and the conveyance path length L1 was 0.6 m and 1.0 m, the conveyance path It can be seen that the cutting stability gradually improves as the length L1 increases.

  In the group of Experiments 8 and 20-23, when the thickness of the film was 20 μm and the draw ratio was 1.12 times, and the conveyance path length L1 was increased to 0.6 m, 0.8 m, and 1.0 m, It can be seen that the cutting stability gradually improves as the conveying path length L1 increases.

  In the groups of Experiments 23 to 26, the film material of Experiments 8 and 20 to 22 is TAC. However, even when the film material is changed to COP, the conveyance path length L1 is 0.6 m,. It can be seen that, when the length is 8 m and 1.0 m, the cutting stability gradually improves as the conveyance path length L1 increases. Similarly, in the groups of Experiments 27 to 30, it can be seen that, even when the film material is changed to PET, the cutting stability gradually improves as the conveyance path length L1 increases as in the case of the TAC film.

  From the above experimental results, in the cutting in which both sides after stretching of a thin film having a thickness of 40 μm or less are cut with a cutting blade, the film is stretched around two or more pass rollers so that the total winding angle θ is 90 ° or more. As a result of being wound and conveyed to the cutting blade, the influence of the waveform deformation that occurs immediately after stretching is not transmitted to the cutting blade, and the occurrence of cutting defects is suppressed. In particular, when stretching is performed by increasing the stretching ratio to 1.07 times or more, the occurrence of cutting defects in the thin film can be suppressed. In addition, when a thinner film is produced by increasing the draw ratio to 1.07 times or more, the occurrence of cutting defects can be suppressed with respect to the thinner film by setting the conveyance path length L1 to 1.0 m or more. In addition, even when the film material is changed to COP or PET other than TAC, the occurrence of cutting defects is similarly suppressed for thin films.

DESCRIPTION OF SYMBOLS 10 Solution casting equipment 12 Film 12a Center part 12b Side part 15 Tenter 16 Slitter 17 Film stretcher 71-74 1st-4th pass roller 75 Cutting blade

Claims (15)

In the film production method for producing a film having a thickness of 40 μm or less by stretching in the width direction while conveying a long thermoplastic resin film,
A stretching step of gripping both sides of the thermoplastic resin film by a gripping portion and stretching in the width direction;
A cooling step for cooling the thermoplastic resin film in a state where the width stretched in the stretching step is kept constant;
A cutting step of cutting off both side portions gripped by the grip portion of the thermoplastic resin film with a cutting blade;
The thermoplastic resin in which gripping of the both side portions is released in the cooling step to two or more adjacent pass rollers spaced apart in the transport direction so as to be arranged on different surfaces of the thermoplastic resin film the conveying path of the thermoplastic film wound around the film wrapping at an acute angle in each of the two or more pass rollers, the film production method and a path Surora conveying step of conveying to the cutting blade. The film manufacturing method according to claim 1, wherein the thermoplastic resin film cooled in the cooling step is introduced into the pass roller conveyance step without heating. The film manufacturing method according to claim 1, wherein the pass roller extends across the entire width direction of the thermoplastic resin film. The film manufacturing method according to any one of claims 1 to 3, wherein a grip opening position for releasing the grip on both side portions is provided on the downstream side in the transport direction in the cooling step. The film manufacturing method of any one of Claim 1 to 4 which expands the width | variety of the said thermoplastic resin film more than 1.07 time at the said extending process. The film manufacturing method according to any one of claims 1 to 5 , wherein a conveyance path length of the thermoplastic resin film from a grip opening position that opens the grip of the both side portions to the cutting blade is 1.0 m or more. Clip method of the film manufacturing any of the preceding claims 1 6 for clamping the both side portions of the grip portion is the thermoplastic resin film. The method of film production the thermoplastic resin film is a cellulose acylate film in a claims 1 to 7 any one of claims. In a film stretching apparatus for producing a film having a thickness of 40 μm or less by stretching in the width direction while conveying a long thermoplastic resin film,
A stretching area that grips both sides of the thermoplastic resin film by a gripping portion and stretches in the width direction, and a cooling area that cools the thermoplastic resin film in a state where the width stretched in the stretching area is held constant. A tenter having
A cutting blade for cutting off the both side portions gripped by the grip portion of the thermoplastic resin film;
Adjacent to each other in the conveying direction so as to be arranged on different surface sides of the thermoplastic resin film, from the grip open position on the both sides in the cooling area to the cutting blade, the thermoplastic A film stretching apparatus comprising: two or more pass rollers that each turn a resin film conveyance path at an acute angle . The film stretching apparatus according to claim 9, wherein the thermoplastic resin film cooled in the cooling area is wound around the pass roller. The film stretching apparatus according to claim 9 or 10, wherein the pass roller extends across the entire width direction of the thermoplastic resin film. The film stretching apparatus according to claim 9, wherein the grip opening position is provided on the downstream side in the transport direction in the cooling area. The film stretcher according to any one of claims 9 to 12 , wherein the tenter expands the width of the thermoplastic resin film by 1.07 times or more. The film stretching apparatus according to any one of claims 9 to 13 , wherein a length of a conveyance path of the thermoplastic resin film from the grip opening position to the cutting blade is 1.0 m or more. The film stretching apparatus according to any one of claims 9 to 14, wherein the gripping part is a clip that holds the both side parts of the thermoplastic resin film.

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