JP2010082986A - Film stretching device and film stretching method - Google Patents

Abstract

When a TAC film is stretched by heating, yellowing of both side edges thereof is prevented.
First and second rails 61 and 62 for guiding the travel of a first chain 63 and a second chain 64 are provided in a tenter unit 50 of an off-line stretching device 17. A plurality of clips 65 are provided on both chains 63 and 64. First and second clip covers 67 and 68 are provided around the first and second rails 61 and 62 so as to cover the clip 65 along the rails 61 and 62. The cooling gas C is purged with gas in the clip covers 67 and 68. Since it is possible to prevent the heated air H from entering the both clip covers 67 and 68, the temperature of the side edges 3a can be lowered in the range of 10 ° C. or more and 40 ° C. or less than the temperature of the central portion 3b. Thereby, yellowing of the both side edges 3a of the TAC film 3 is prevented.
[Selection] Figure 4

Description

  The present invention relates to a film stretching equipment and a stretching method in which a film is heated and stretched in the width direction, and then a film ear is cut and reused as a polymer material for recycling.

  In recent years, due to the rapid development and spread of liquid crystal displays and the like, the demand for cellulose acylate films, particularly triacetyl cellulose films (hereinafter referred to as TAC films) used as protective films for polarizing films used in these liquid crystal displays has increased. is doing. With this increase in demand, improvement in the productivity of TAC films is desired. The TAC film is supported by casting a dope containing TAC and a solvent on a continuously running support, and providing the cast film formed on the support with self-supporting properties by drying or cooling. It is manufactured through a peeling process for peeling from the body, and a drying process and a winding process for drying and winding the peeled cast film (soft film). In such a solution casting method (process), a film having no foreign matters and excellent optical characteristics such as permeability and optical isotropy can be obtained as compared with a film forming method by melt extrusion.

  In Patent Documents 1 and 2, as a method for adjusting the optical properties of the TAC film, particularly retardation, in order to orient the polymer molecules in a predetermined direction, a stretching device is used to clip both side edges of the TAC film. Describes a method of stretching a TAC film in the film width direction while gripping the film. In Patent Document 1, the soft film generated in the above-described stripping process is stretched in the film width direction by a stretching device while drying (heating). In Patent Document 2, the TAC film formed by the solution casting method is stretched in the film width direction while being heated again by an offline stretching apparatus.

Since both side edges (ear portions) of the TAC film stretched by the stretching apparatus in this manner are gripped (chucked) with a clip or the like, the optical characteristics are disturbed, so the product is not a product. For this reason, the ear | edge part of a TAC film is cut | disconnected from a product part with an ear-cutting apparatus.
JP 2002-187960 A JP 2002-31245 A

  By the way, the ear | edge part cut | disconnected from the product part by the solution casting process is reused as a raw material of dope. However, the film manufactured using this reusable product may turn yellow, which has been a problem. As a result of intensive studies, the present inventor has found that this yellowing phenomenon occurs when an ear portion heated by an off-line stretching apparatus and separated by an ear-cutting apparatus is used as a dope raw material. In addition, although the width direction center part (product part) of the heat-stretched film is also yellowed, there is no problem as a primary product, and it is a secondary processed product when a yellowed ear part is formed as a dope raw material. Yellowing is noticeable and has become a problem.

  The present invention has been made on the basis of the above findings, and an object of the present invention is to provide a film stretching equipment and a stretching method capable of preventing yellowing of both side edges (ear portions) when a film is heated and stretched. And

  In order to achieve the above object, the film stretching apparatus of the present invention is a tenter body having a plurality of clips that move in the running direction of the film while gripping both side edges of the film and stretch the film in the width direction, A blower that blows heated air on the film held by the clip, a tenter chamber in which the tenter body and the blower are arranged, and is arranged so as to cover the movement path of the plurality of clips that hold the film in the tenter chamber. A tenter device having a clip cover for keeping the temperature of both side edges of the film held by the clip lower in the range of 10 ° C. or more and 40 ° C. or less than the central portion in the width direction of the film, and the film exiting the tenter chamber An ear recovery device that cuts the ear of the film in the film running direction and recovers it as a polymer material for recycling. To.

  The tenter device preferably has a film ear cooling unit that introduces a cooling gas into the clip cover and purges the gas.

  The film is cast on a support running on a dope comprising cellulose acylate and a solvent to form a cast film, and after the cast film has a self-supporting property, the film is peeled off as a soft film. The cellulose acylate film is dried, and the temperature at the central portion in the width direction of the film by the blower is preferably 175 ° C. or higher and 210 ° C. or lower.

  A cast film is formed by casting a dope containing a polymer and a solvent to form a cast film, and after the cast film has a self-supporting property, it is peeled off as a soft film from the support and dried. A step of manufacturing, a stretching step of heating the film while holding both side edges of the manufactured polymer film with a plurality of clips, and stretching in the width direction, and a plurality of clips holding the film in the tenter chamber A film ear cooling unit step that covers a moving path with a clip cover and keeps the temperature of both side edges of the film held by the clip lower in the range of 10 ° C. or more and 40 ° C. or less than the central portion in the width direction of the film; It is preferable to have an ear recovery step of cutting the ear of the film in the film running direction and recovering it as a polymer raw material for recycling.

  In the film ear cooling unit step, it is preferable to perform a gas purge by introducing a cooling gas into the clip cover.

  The polymer is cellulose acylate, and it is preferable that the temperature at the center in the width direction of the film is 175 ° C. or higher and 210 ° C. or lower.

  The film stretching equipment and the stretching method of the present invention provide a clip cover for moving a clip that grips a film when the film is heated and stretched in the film width direction while transporting by gripping both side edges with a plurality of clips. Since the temperature of both side edge portions of the film is kept lower in the range of 10 ° C. or more and 40 ° C. or less than the temperature in the width direction center portion, yellowing of both side edge portions can be prevented. Thereby, both sides of the film can be recycled, and the recycling ratio can be further increased. In addition, since the temperature difference between the side edge portions and the center portion in the width direction is increased, unevenness in the optical characteristics of the film due to temperature unevenness is prevented.

  As shown in FIG. 1, a solution casting apparatus 10 for forming a TAC film 3 includes a stock tank 11, a casting chamber 12, a pin tenter 13, a drying chamber 14, a cooling chamber 15, and a winding chamber 16. And an off-line stretching device (tenter device) 17.

  The stock tank 11 includes a stirring blade 11a and a jacket 11b. The stock tank 11 stores a dope 20 in which a polymer as a raw material of the TAC film 3 is dissolved in a solvent. The dope 20 in the stock tank 11 is adjusted by the jacket 11b so that the temperature becomes substantially constant. Further, the rotation of the stirring blade 11a keeps the dope 20 in a uniform quality while suppressing the aggregation of polymers and the like. The dope 20 in the stock tank 11 is fed to the casting die 22 of the casting chamber 12 through a pipe 21 by a pump (not shown).

  In the casting chamber 12, a casting die 22, a casting drum 23 as a support, a peeling roller 24, temperature control devices 25 and 26, and a decompression chamber 27 are installed. The casting drum 23 is rotated in the Z1 direction about the shaft 23a by a driving device (not shown). The temperature in the casting chamber 12 and the casting drum 23 is set to a temperature at which the casting film 28 is easily cooled and solidified (gelled) by the temperature control devices 25 and 26.

  The casting die 22 discharges the dope 20 (casting bead) toward the peripheral surface of the rotating casting drum 23. The casting bead is cast on the peripheral surface of the casting drum 23 to form a casting film 28. Then, while the casting drum 23 rotates about 3/4, self-supporting property due to gelation is expressed in the casting film 28, and the casting film 28 is peeled off from the casting drum 23 by the peeling roller 24, A soft film (wet film) 30 is obtained.

  The decompression chamber 27 is disposed in the vicinity of the casting die 22 and decompresses the back side of the casting bead to a desired pressure. As a result, the influence of the accompanying air generated by the rotation of the casting drum 23 is reduced, a stable casting bead is formed between the casting die 22 and the casting drum 23, and the casting film with little film thickness unevenness is formed. 28 can be formed.

  The material of the casting die 22 is formed of a material having high corrosion resistance against a mixed solution of an electrolyte aqueous solution, dichloromethane, methanol, and the like, and a low coefficient of thermal expansion. The finishing accuracy of the liquid contact surface of the casting die 22 is preferably 1 μm or less in terms of surface roughness, and the straightness is preferably 1 μm / m or less in any direction.

  The peripheral surface of the casting drum 23 is chrome-plated and has sufficient corrosion resistance and strength. Further, the temperature control device 26 circulates a heat transfer medium inside the casting drum 23 in order to keep the temperature of the peripheral surface of the casting drum 23 at a desired temperature. The heat transfer medium is maintained at a desired temperature, and the temperature of the peripheral surface of the casting drum 23 is maintained at a desired temperature by passing through the heat transfer medium flow path in the casting drum 23.

  The width of the casting drum 23 is not particularly limited, but it is preferable to use a casting drum having a width in the range of 1.1 to 2.0 times the casting width of the dope. The material of the casting drum 23 is preferably made of stainless steel, and more preferably made of SUS316 so as to have sufficient corrosion resistance and strength. The chrome plating treatment applied to the peripheral surface of the casting drum 23 is preferably so-called hard chrome plating with a Vickers hardness of Hv 700 or more and a film thickness of 2 μm or more.

  The casting chamber 12 is provided with a condenser (condenser) 32 for condensing the evaporated solvent and a recovery device 33 for recovering the condensed and liquefied solvent. The solvent recovered by the recovery device 33 is reused as a dope preparation solvent after being regenerated by the regeneration device.

  A crossover 35 and a pin tenter 13 are installed in this order downstream of the casting chamber 12. In the transfer section 35, the transport roller 35 a transports the soft film 30 to the pin tenter 13.

  The pin tenter 13 has a number of pin plates that penetrate and hold both side edges of the buffy coat 30. The pin plate travels on a predetermined track. Dry air is sent to the soft film 30 traveling by the pin plate, and the soft film 30 is dried to become the TAC film 3. The pin tenter 13 dries the TAC film 3 until the residual volatile content becomes 10 wt% or less.

  An ear recovery device 37 is provided downstream of the pin tenter 13 in the film conveyance direction. The ear collection device 37 cuts both side edges of the TAC film 3. The both side edges thus cut are sent to the crusher 38 by air blowing and cut into small pieces, and then reused as a raw material for the dope 20 and the like.

  A large number of rollers 14 a are provided in the drying chamber 14, and the TAC film 3 is wound around and conveyed. The temperature in the drying chamber 14 is adjusted to be substantially constant in the range of 50 ° C. or higher and 150 ° C. or lower. By passing through the drying chamber 14, the solvent remaining in the TAC film 3 is volatilized. An adsorption recovery device 40 is attached to the drying chamber 14. The volatile solvent is adsorbed and recovered by the adsorption recovery device 40. The air from which the solvent component has been removed is blown again as dry air into the drying chamber 14.

  A cooling chamber 15 is provided on the outlet side of the drying chamber 14, and the TAC film 3 is cooled to room temperature in the cooling chamber 15. A forced static elimination device (static elimination bar) 41 is provided downstream of the cooling chamber 15 to neutralize the TAC film 3. Further, a knurling application roller 42 is provided on the downstream side of the forced static elimination device 41, and knurling is applied to both side edges of the TAC film 3.

  In the winding chamber 16, a winding machine 44 having a press roller 43 is installed, and the TAC film 3 is wound around the winding core in a roll shape, and a film roll 45 is obtained by the winding machine 44. The film roll 45 is set in the off-line stretching device 17.

  As shown in FIG. 2, the off-line stretching apparatus 17 heat-stretches the TAC film 3 formed by the above-mentioned solution casting method in the film width direction. The offline stretching apparatus 17 is roughly composed of a supply chamber 49, a tenter unit 50, a heat relaxation chamber 51, a cooling chamber 52, and a winding chamber 53.

  The previously manufactured film roll 45 is set in the supply chamber 49, and the TAC film 3 is drawn from the film roll 45 by the supply roller 49 a and supplied to the tenter unit 50. A dancer roller (reservoir), a film bonding apparatus, or the like may be provided between the supply chamber 49 and the tenter unit 50.

  The tenter unit 50 corresponds to the tenter body of the present invention. The tenter unit 50 heats the TAC film 3 and grips and conveys both side edges 3a (see FIG. 3) with a plurality of clips in the film width direction. Stretch. In addition, the arrow A in a figure shows a film conveyance direction.

  The TAC film 3 heated and stretched by the tenter unit 50 is sent out to the ear collecting device 56. The side edges 3a of the TAC film 3 are cut off by the ear collecting device 56, and the cut slit-like side edges 3a (ears) are sent to the crusher 57 by an air blower (not shown), where they are fed to the chip. Disconnected. This chip is reused for dope preparation.

  The heat relaxation chamber 51 is provided with a large number of rollers 51 a, and the TAC film 3 is conveyed through the heat relaxation chamber 51 by the rollers 51 a to be heat relaxed, and then sent to the cooling chamber 52. In the heat relaxation chamber 51, wind at a desired temperature is blown from a blower (not shown). The temperature of the wind at this time is preferably 20 ° C to 250 ° C.

  After the thermal relaxation, the TAC film 3 is cooled to 30 ° C. or less in the cooling chamber 52 and then sent to the winding chamber 53. Inside the winding chamber 53, a winding core 53a and a press roller 53b are provided. The TAC film 3 sent to the winding chamber 53 is wound around the winding roller 53a while being pressed by the press roller 53b.

  As shown in FIG. 3, the tenter unit 50 is disposed in the tenter chamber 60. The tenter 50 is roughly divided into first and second rails 61 and 62, first and second chains (endless chains) 63 and 64, a clip 65, a blower 66 (see FIG. 4), a first The first and second clip covers 67 and 68, and a casing (not shown) that covers these parts. In addition, the arrow B in a figure shows a film width direction.

  The first and second rails 61 and 62 guide the travel of the first chain 63 and the second chain 64, respectively. The distance between the rails 61 and 62 is adjusted so as to gradually increase from the film inlet IN side toward the film outlet OUT side. In addition, since the draw ratio in this embodiment is set to 103%, there is not much difference in the rail interval between the film entrance IN side and the film exit OUT side in FIG. 3, but the draw ratio is set high. In this case, the rail interval on the film exit OUT side becomes larger than the state shown in FIG.

  A plurality of clips 65 are attached to the first and second chains 63 and 64 at regular intervals. Each clip 65 moves along both rails 61 and 62 while gripping both side edges 3a of the TAC film 3, whereby the TAC film 3 is transported in the film transport direction A and stretched in the film width direction B. Is done.

  The first and second chains 63 and 64 are respectively stretched between the driving sprocket 70a and the driven sprocket 70b and between the driving sprocket 71a and the driven sprocket 71b. Between these sprockets 70 a, 70 b, 71 a, 71 b, the first chain 63 is guided by the first rail 61, and the second chain 64 is guided by the second rail 62. The driving sprockets 70a and 71a are provided on the film outlet OUT side of both rails 61 and 62, and are driven to rotate by driving mechanisms (not shown).

  An opening member 73 for opening the clip 65 is disposed in the vicinity of each sprocket 70a, 70b, 71a, 71b at the film inlet IN and the film outlet OUT. Reference sign PA indicates a grip start position by the clip 65, and reference sign PB indicates a grip release position.

  In FIG. 4, which shows a cross section taken along line IV-IV in FIG. 3, the clip 65 includes a substantially U-shaped frame 75, a flapper 76, and a rail attachment portion 77. The flapper 76 is rotatably attached to the frame 75 by an attachment shaft 75a. The flapper 76 is displaced between a film gripping position where the flapper 76 is in a vertical state (see FIG. 6) and an open position where the engaging head 76a is in contact with the opening member 73 and rotated obliquely. The flapper 76 is normally urged to be in the film gripping position by its own weight.

  When the clip 65 passes the grip start position PA (see FIG. 3), the release member 73 and the engagement head 76a are not in contact with each other, and the flapper 76 is displaced to the film grip position. As a result, the side edges 3 a of the TAC film 3 are gripped by the lower surface 76 b of the flapper 76 and the frame 75. When the clip 65 reaches the grip release position PB (see FIG. 3), the flapper 76 is displaced to the open position by the contact between the release member 73 and the engagement head 76a, and the grip of the side edges 3a is released. The

  The rail attachment portion 77 includes an attachment frame 79 and guide rollers 80, 81, and 82. The first chain 63 or the second chain 64 is attached to the attachment frame 79. The guide rollers 80 to 82 rotate in contact with the support surfaces of the driving sprockets 70 a and 71 a and the support surfaces of the first and second rails 61 and 62. Accordingly, the frame 75 and the flapper 76 are guided along the rails 61 and 62 without dropping from the driving sprockets 70a and 71a and the rails 61 and 62.

  The air blowing unit 66 blows the heating air H onto the TAC film 3, that is, heats the TAC film 3, and includes air blowing ducts 85 a and 85 b and a heating air supply device 86. The air ducts 85a and 86b are respectively arranged above and below the conveyance path of the TAC film 3, and a plurality of the air ducts 85a and 86b are arranged at a predetermined pitch in the film conveyance direction A. Each of the air ducts 85a and 85b has a shape extending long in the film width direction B, and a plurality of air outlets (not shown) are provided on the surface side facing the TAC film 3.

  The hot air supply device 86 supplies hot air to the air ducts 85a and 85b. As a result, hot air is blown to the TAC film 3 from the outlets of the air ducts 85a and 85b. The hot air supply device 86 is a temperature / supply of hot air to be supplied to each air duct 85a so that the temperature of the central portion (hereinafter referred to as the central portion) 3b of the TAC film 3 is in the range of 175 ° C. to 210 ° C. Adjust the amount. Here, the center part 3b means the part pinched | interposed into the both-sides edge part 3a. The tenter unit 50 is also provided with an exhaust duct (not shown).

  Thus, in the tenter unit 50, the TAC film 3 (central portion 3b) is heated at a high temperature during heating and stretching. This is because in the case of off-line stretching, since the solvent is not contained in the polymer film (TAC film), the polymer molecules are easily moved only by thermal energy. Further, the additive contained in the polymer film evaporates even in this off-line stretching, but among the vaporizing additives, the high boiling point additive has a high boiling point, so that the temperature in the tenter unit 50 is the boiling point. This is because there is a possibility that the polymer film in the tenter unit 50 is condensed and crystallized due to a slight temperature drop.

  Therefore, in the present embodiment, first and second clip covers 67 and 68 (see FIG. 6) are provided around the first and second rails 61 and 62 so as to cover the clip 65 along both the rails 61 and 62. ing. Both clip covers 67 and 68 are formed of, for example, a heat insulating material, and the entire region between the grip start position PA and the grip release position PB [that is, the movement path of the clip 65 in a state of gripping both side edges 3a. It is provided over almost the entire area (hereinafter simply referred to as the moving path of the clip 65).

  In addition, slit-like film passages 67a and 68a are formed in both clip covers 67 and 68 over the entire region in the film transport direction A so as not to hinder the transport of the TAC film 3. The width of each film passage 67a, 68a is preferably as narrow as possible in order to prevent hot air from entering the covers 67, 68.

  Thus, by covering the both side edges 3a of the TAC film 3 held by the clip 65 with the first and second clip covers 67, 68, the hot air from the air ducts 85a, 85b hits the both edges 3a. Therefore, the temperature of the side edge portions 3a can be made lower than the temperature of the central portion 3b. And in this embodiment, the temperature of the both-sides edge part 3a is made low in the range of 10 to 40 degreeC rather than the temperature of the center part 3b. This is because when the temperature difference between the two is less than 10 ° C., particularly when the temperature of the central portion 3b is set high (for example, 190 ° C. to 210 ° C.), yellowing occurs on both side edges 3a. . Conversely, if the temperature difference between the two exceeds 40 ° C., temperature unevenness occurs in the central portion 3b, and unevenness occurs in the optical characteristics of the TAC film 3 (product).

  Therefore, in this embodiment, in order to make the temperature of both side edge portions 3a lower than the temperature of the central portion 3b within the above range, the material and thickness of both clip covers 67, 68 and the width of the film passages 67a, 68a are large. Is determined as appropriate. Further, in this embodiment, a cooling gas C such as nitrogen gas (see FIGS. 5 and 6) is introduced (gas purge) into both the clip covers 67 and 68.

  As shown in FIG. 5, the tenter unit 50 corresponds to the film ear cooling unit of the present invention, and the first cooling unit 88 and the second cooling unit that introduce the cooling gas C into the clip covers 67 and 68, respectively. 89 is provided. Both cooling units 88 and 89 are connected to a plurality of locations in both clip covers 67 and 68 via a gas pipe 90 branched into a plurality. Since both cooling units 88 and 89 have basically the same structure except that the supply destination for supplying the cooling gas C is different, in the following description, cooling into the first clip cover 67 by the first cooling unit 88 will be described. An explanation will be given by taking introduction of gas C as an example.

  As shown in FIG. 6, the gas pipe 90 is connected to the upper surface and the lower surface of the first clip cover 67. Thereby, the cooling gas C is sprayed toward the clip 65 from above and below the clip 65, respectively.

  On the outer surface of the first clip cover 67, a first temperature sensor 95a for detecting the temperature in the vicinity of the central portion 3b of the TAC film 3 being conveyed is provided. A second temperature sensor 95b that detects the temperature in the vicinity of the side edge 3a is provided on the inner surface of the first clip cover 67. Each temperature sensor 95a, 95b outputs the temperature detection result to the first cooling unit 88 via a signal line (not shown).

  The 1st cooling unit 88 is comprised from the cooling gas supply part 97, the blower 98, and CPU99, for example. The cooling gas supply unit 97 includes a gas tank 97a for storing the cooling gas C (for example, liquid nitrogen may be used when the cooling gas C is nitrogen) and a temperature adjusting unit 97b for adjusting the temperature of the cooling gas C. ing. The cooling gas supply unit 97 supplies the cooling gas adjusted to a predetermined temperature by the temperature adjustment unit 97 b to the blower 98. The blower 98 introduces (gas purges) the cooling gas C from the cooling gas supply unit 97 into the first clip cover 67 via the gas pipe 90.

  The CPU 99 controls the operation of the cooling gas supply unit 97 and the blower 98. CPU99 calculates | requires the temperature difference of both, after calculating | requiring the temperature of the center part 3b and the both-sides edge part 3a of the TAC film 3, respectively based on the temperature detection result input from the 1st and 2nd temperature sensors 95a and 95b.

  In addition, although a "deviation" occurs between the temperature detection results of the temperature sensors 95a and 95b and the actual temperatures of the central portion 3b and the side edge portion 3a, the magnitude of each deviation should be obtained through experiments or the like. Can do. Accordingly, the CPU 99 corrects the temperature detection results of the temperature sensors 95a and 95b based on the correction values obtained from the experimental results and the like so that the temperatures of the central portion 3b and the side edge portion 3a are accurately determined. To detect. When a plurality of temperature sensors 95a and 95b are provided, the average value of the temperature detection results is determined as the temperature of the central portion 3b and the side edge portion 3a.

  When the CPU 99 determines that the temperature difference between the central portion 3b and the side edge portions 3a is less than 10 ° C., for example, the CPU 99 controls the cooling gas supply portion 97 and the blower 98 to enter the first clip cover 67. The purge amount of the cooling gas C to be supplied is increased and the temperature is lowered. Conversely, if the CPU 99 determines that the temperature difference between the two exceeds 40 ° C., the CPU 99 controls the cooling gas supply unit 97 and the blower 98 to supply the cooling gas C supplied into the first clip cover 67. Reduce or reduce the purge amount or increase its temperature. Thereby, the temperature of the side edge part 3a by the side of the 1st rail 61 of the TAC film 3 can be kept low in the range of 10 degreeC or more and 40 degrees C or less rather than the temperature of the center part 3b.

  Similarly to the first cooling unit 88, the second cooling unit 89 also adjusts the purge amount and temperature of the cooling gas C supplied into the second clip cover 68, so that the second rail 62 of the TAC film 3 is adjusted. The temperature of the side edge portion 3a on the side can be kept lower than the temperature of the central portion 3b in the range of 10 ° C to 40 ° C.

  As described above, in the present invention, the moving path of the clip 65 that holds the side edges 3a of the TAC film 3 is covered with the clip covers 67 and 68, and the cooling gas C is further purged with gas into the clip covers 67 and 68. Thus, the temperature in the cover can be lowered while preventing the heated air H from entering the both clip covers 67 and 68. As a result, when the TAC film 3 having a residual volatile content of 10% or less is heated and stretched at 175 ° C. or more and 210 ° C. or less, the temperature of the side edges 3a is lower by 10 ° C. or more and 40 ° C. or less than the temperature of the central portion 3b. can do. This prevents yellowing of the side edges 3a due to heating and prevents unevenness in the optical characteristics of the TAC film 3 due to temperature unevenness.

  In the above embodiment, the cooling gas C is supplied into the clip covers 67 and 68 by the both cooling units 88 and 89, but the present invention is not limited to this. For example, the air inside the clip covers 67 and 68 may be sucked and the sucked air may be cooled and returned to the clip covers 67 and 68. Further, the cooling gas C and the cooling air may be supplied into the clip covers 67 and 68 by one cooling unit.

  The clip covers 67 and 68 are not particularly limited to the shapes shown in FIGS. 3 to 6 as long as they cover the moving path of the clip 65.

  In the above embodiment, the heat stretching process is performed by the off-line stretching apparatus 17, but the present invention is not limited to this, and between the pin tenter 13 and the drying chamber 14 of the solution casting apparatus 10 or the drying chamber 14. A heating and stretching process similar to the process performed by the offline stretching apparatus 17 may be performed between the cooling chamber 15 and the cooling chamber 15. Further, the drying process performed by the pin tenter 13 (the drying process performed until the residual volatile content becomes 10% or less) may be performed at an arbitrary point between the pin tenter 13 and the tenter unit 50.

  In the above-described embodiment, the casting drum 23 is used as the support. However, the present invention is not limited to this, and a casting band that spans the roller and runs endlessly by the rotation of the roller may be used. Good.

  In the said embodiment, although the cast film was formed from one kind of dope, this invention is not limited to this. In the solution casting method described above, two or more kinds of dopes can be simultaneously laminated or sequentially laminated when casting the dopes. Furthermore, you may combine both casting. When performing simultaneous lamination and co-casting, a casting die to which a feed block is attached may be used, or a multi-manifold casting die may be used. It is preferable that at least one of the thickness of the layer on the air surface side and the thickness of the layer on the support side is 0.5% to 30% of the thickness of the entire film of the film composed of multiple layers by co-casting. Furthermore, when performing simultaneous lamination co-casting, it is preferable that the high-viscosity dope is wrapped with the low-viscosity dope when the dope is cast from the die slit to the support. Moreover, when performing simultaneous lamination | stacking co-casting, it is preferable that the dope which contact | connects an external field has a larger alcohol composition ratio than an internal dope among the casting beads formed from a die slit to a support body.

  In the said embodiment, although the cellulose acylate film (TAC film 3) was mentioned as an example and demonstrated as a polymer film, this invention is applied with respect to the polymer film manufactured by the solution casting method other than a cellulose acylate film. Can be applied.

(Cellulose acylate)
As the cellulose acylate, triacetyl cellulose (TAC) is particularly preferable. Of the cellulose acylates, those in which the hydroxyl group of cellulose is esterified with carboxylic acid, that is, the substitution degree of the acyl group satisfies all of the following formulas (I) to (III) are more preferable. In the following formulas (I) to (III), A and B represent the substitution degree of the acyl group, the substitution degree A is the substitution degree of the acetyl group, and the substitution degree B is the acyl group having 3 to 22 carbon atoms. Is the degree of substitution. In addition, it is preferable that 90 weight% or more of TAC is a particle | grain of 0.1 mm-4 mm.
(I) 2.5 ≦ A + B ≦ 3.0
(II) 0 ≦ A ≦ 3.0
(III) 0 ≦ B ≦ 2.9
The polymer used in the present invention is not limited to cellulose acylate.

  Glucose units having β-1,4 bonds constituting cellulose have free 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 of the hydroxyl group of cellulose esterified at each of the 2-position, 3-position and 6-position (100% esterification has a substitution degree of 1).

  The total acylation substitution degree, that is, DS2 + DS3 + DS6 is preferably 2.00 to 3.00, more preferably 2.22 to 2.90, and particularly preferably 2.40 to 2.88. Further, DS6 / (DS2 + DS3 + DS6) is preferably 0.28 or more, more preferably 0.30 or more, and particularly preferably 0.31 to 0.34. Here, DS2 is the degree of substitution of the hydroxyl group at the 2-position of the glucose unit with an acyl group (hereinafter also referred to as “degree of acyl substitution at the 2-position”), and DS3 is the degree of substitution of the hydroxyl group at the 3-position with an acyl group (hereinafter, referred to as “acyl group”). DS6 is the substitution degree of the hydroxyl group at the 6-position with an acyl group (hereinafter also referred to as “acyl substitution degree at the 6-position”).

  Only one type of acyl group may be used in the cellulose acylate of the present invention, or two or more types of acyl groups may be used. When two or more kinds of acyl groups are used, it is preferable that one of them is an acetyl group. When the sum of the substitution degrees by the hydroxyl groups at the 2nd, 3rd and 6th positions is DSA, and the sum of the substitution degree by an acyl group other than the acetyl group at the 2nd, 3rd and 6th hydroxyl groups is DSB, the value of DSA + DSB is More preferably, it is 2.22 to 2.90, and particularly preferably 2.40 to 2.88. The DSB is 0.30 or more, particularly preferably 0.7 or more. Further, 20% or more of DSB is a substituent at the 6-position hydroxyl group, more preferably 25% or more is a substituent at the 6-position hydroxyl group, more preferably 30% or more, and particularly 33% or more is a 6-position hydroxyl group. It is preferable that it is a substituent. Furthermore, the cellulose acylate having a substitution degree of 6-position of cellulose acylate of 0.75 or more, further 0.80 or more, and particularly 0.85 or more can be mentioned. With these cellulose acylates, a solution having a preferable solubility (dope) can be produced. In particular, in a non-chlorine organic solvent, a good solution can be produced. Furthermore, it is possible to produce a solution having a low viscosity and good filterability. Cellulose, which is a raw material for cellulose acylate, may be obtained from either linter or pulp.

  The acyl group having 2 or more carbon atoms of the cellulose acylate of the present invention may be an aliphatic group or an aryl group and is not particularly limited. These are, for example, cellulose alkylcarbonyl esters, alkenylcarbonyl esters, aromatic carbonyl esters, aromatic alkylcarbonyl esters, and the like, each of which may further have a substituted group. Preferred examples of these include propionyl, butanoyl, pentanoyl, hexanoyl, octanoyl, decanoyl, dodecanoyl, tridecanoyl, tetradecanoyl, hexadecanoyl, octadecanoyl, iso-butanoyl, t-butanoyl, cyclohexanecarbonyl, oleoyl, benzoyl , Naphthylcarbonyl, cinnamoyl group and the like. Among these, propionyl, butanoyl, dodecanoyl, octadecanoyl, t-butanoyl, oleoyl, benzoyl, naphthylcarbonyl, cinnamoyl and the like are more preferable, and propionyl and butanoyl are particularly preferable.

  The details of cellulose acylate are described in paragraphs [0140] to [0195] of JP-A-2005-104148. The same applies to additives such as solvents and plasticizers, deterioration inhibitors, UV absorbers (UV agents), optical anisotropy control agents, retardation control agents, dyes, matting agents, release agents, release accelerators, etc. JP-A-2005-104148 describes in detail in paragraphs [0196] to [0516]. In addition, some substances used as additives contained in the film to be heat-stretched have a high boiling point. Examples of such additives include triphenyl phosphate (TTP) and biphenyl diphenyl phosphate (BDP). Also, a film production method by a solution casting method using cellulose acylate is also described in detail in paragraphs [0517] to [0913] of JP-A-2005-104148. These descriptions can also be applied to the present invention.

(Cyclic olefin)
The cyclic olefin is preferably polymerized from a norbornene compound. This polymerization can be carried out by either ring-opening polymerization or addition polymerization. Examples of the addition polymerization include those described in Japanese Patent No. 3517471, Japanese Patent No. 3559360, Japanese Patent No. 3867178, Japanese Patent No. 3817721, Japanese Patent No. 3907908, Japanese Patent No. 3945598, Japanese Patent Publication No. 2005-527696, Japanese Patent Laid-Open No. 2006-2006. No. 28993 and International Publication No. 2006/004376 pamphlet. Particularly preferred is the one described in Japanese Patent No. 3517471.

  As the ring-opening polymerization, WO 98/14499 pamphlet, Japanese Patent No. 30605532, Japanese Patent No. 3320478, Japanese Patent No. 3273046, Japanese Patent No. 3404027, Japanese Patent No. 3428176, Japanese Patent No. 3687231, Japanese Patent No. 3873934, Patent No. 3912159 is mentioned. Among them, those described in WO98 / 14499 pamphlet and Japanese Patent No. 30605532 are preferable. Of these cyclic olefins, those of addition polymerization are more preferred.

(Lactone ring-containing polymer)
This refers to those having a lactone ring structure represented by the following (General Formula 1).

In (General Formula 1), R ¹ , R ² , and R ³ each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms. The organic residue may contain an oxygen atom.

  The content ratio of the lactone ring structure of (General Formula 1) is preferably 5 to 90% by weight, more preferably 10 to 70% by weight, and still more preferably 10 to 50% by weight.

  In addition to the lactone ring structure represented by (General Formula 1), at least selected from (meth) acrylic acid esters, hydroxyl group-containing monomers, unsaturated carboxylic acids, and monomers represented by the following (General Formula 2). A polymer structural unit (repeating structural unit) constructed by polymerizing one kind is preferred.

In General Formula 2, R ⁴ represents a hydrogen atom or a methyl group, X is a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group, an —OAc group, a —CN group, a —CO—R ⁵ group, or an -C-O-R ⁶ group, Ac group represents an acetyl group, R ⁵ and R ⁶ represents a hydrogen atom or an organic residue having 1 to 20 carbon atoms.

  For example, those described in International Publication No. 2006/025445, JP 2007-70607 A, JP 2007-63541 A, JP 2006-171464 A, and JP 2005-162835 A can be used. .

(Polymer used in melt film forming method)
The polymer that can be used in the melt film-forming method is not particularly limited as long as it is a thermoplastic resin. For example, cellulose acylate, lactone ring-containing polymer, cyclic olefin, polycarbonate and the like can be mentioned. Of these, cellulose acylate and cyclic olefin are preferred, cellulose acylate containing an acetate group and propionate group, and cyclic olefin obtained by addition polymerization, more preferably cyclic olefin obtained by addition polymerization. It is.

  Hereinafter, examples and comparative examples performed on the present invention will be specifically described.

  In Example 1, the TAC film 3 formed by the solution casting apparatus 10 shown in FIG. 1 was stretched by heating using the offline stretching apparatus 17 shown in FIG. As shown in Table 1 below, the TAC film 3 was dried with the pin tenter 13 of the solution casting apparatus 10 until the residual volatile content was 9 wt%.

  In the offline stretching apparatus 17, the TAC film 3 was stretched by heating in a tenter unit 50 (see FIGS. 2 to 6) having both clip covers 67 and 68. At this time, the film surface temperature of the central portion 3b of the TAC film 3 was adjusted to 190 ° C., and the temperature of the side edge portions 3a was adjusted to 170 ° C., which was 20 ° C. lower than the central portion 3b. Next, both side edge portions 3a of the TAC film 3 were cut by the ear portion collecting device 56, and the both side edge portions 3a (ear portions) were crushed by the crusher 57 into chips. And what melt | dissolved this chip | tip in the solvent again was used as the raw material of dope 20.

  The TAC film 3 was manufactured using the solution casting apparatus 10 and the offline stretching apparatus 17 using the dope 20 made of such a recycled material. If the TAC film 3 does not turn yellow even when 30% or more of the recycled material is used, “◯” indicates that the use of the recycled material is less than 30%. Even if the usage was less than 30%, when the TAC film 3 turned yellow, it was evaluated as “x”. Note that whether or not the TAC film 3 was yellowed was determined visually with reference to the color of the TAC film 3 manufactured with the dope 20 that does not use recycled raw materials.

  In Example 1, it was confirmed that the TAC film 3 did not turn yellow even when 30% or more of the recycled material was used.

[Example 2]
Example 1 except that the film surface temperature of the central portion 3b of the TAC film 3 was adjusted to 175 ° C. and the temperature of the side edge portions 3a was adjusted to 165 ° C., which was 10 ° C. lower than the central portion 3b, during the heat stretching treatment. The same conditions were used. It was confirmed that the TAC film 3 was not yellowed even when 30% or more of recycled materials were used.

[Example 3]
Example 1 except that the film surface temperature of the central portion 3b of the TAC film 3 was adjusted to 210 ° C. and the temperature of the side edge portions 3a was adjusted to 170 ° C., which was 40 ° C. lower than the central portion 3b, during the heat stretching treatment. The same conditions were used. It was confirmed that the TAC film 3 was not yellowed even when 30% or more of recycled materials were used.

[Comparative Example 1]
The same conditions as in Example 1 were applied except that heat stretching was performed in the tenter part from which both clip covers 67 and 68 had been removed, and the temperature of the central part 3b and both side edge parts 3a of the TAC film 3 were both adjusted to 190 ° C. did. The TAC film 3 turned yellow even when the use of recycled materials was less than 30%.

[Comparative Example 2]
The conditions were the same as in Comparative Example 1 except that the temperatures of the central portion 3b and both side edge portions 3a of the TAC film 3 were both adjusted to 175 ° C. The TAC film 3 turned yellow when the recycled material was used at 30% or more.

[Comparative Example 3]
The conditions were the same as those in Comparative Example 1 except that the temperatures of the central portion 3b and both side edge portions 3a of the TAC film 3 were both adjusted to 210 ° C. The TAC film 3 turned yellow even when the use of recycled materials was less than 30%.

[Comparative Example 4]
The conditions were the same as in Example 1 except that the film surface temperature of the central portion 3b of the TAC film 3 was adjusted to 210 ° C, and the temperature of the side edge portions 3a was adjusted to 165 ° C, which was 45 ° C lower than the central portion 3b. Although the yellowing of the TAC film 3 did not occur even when 30% or more of the recycled materials were used, the temperature difference between the central portion 3b and the side edge portions 3a was too large, so that the product portion (central portion 3b) A temperature distribution occurred, and the optical characteristics were uneven.

It is the schematic of solution casting apparatus. It is the schematic of an online extending | stretching apparatus. It is the schematic which looked at the tenter part from the upper part. It is sectional drawing which follows the IV-IV line in FIG. It is explanatory drawing for demonstrating a 1st and 2nd cooling unit. It is sectional drawing of the connection location of a 1st clip cover, gas piping, and suction piping.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 TAC film 3a Both-sides edge part 3b Center part 10 Solution film forming equipment 13 Pin tenter 17 Off-line extending | stretching apparatus 50 Tenter part 65 Clip 66 Blower part 67 1st clip cover 68 2nd clip cover 88 1st cooling unit 89 2nd cooling unit

Claims (6)

A tenter body having a plurality of clips that move in the running direction of the film while gripping both side edges of the film and extend the film in the width direction;
A blower that blows heated air against the film held by the clip;
A tenter chamber in which the tenter body and the blower are disposed;
It is arranged so as to cover the movement path of the plurality of clips holding the film in the tenter chamber, and the temperature of both side edges of the film held by the clips is 10 ° C. or more than the center in the width direction of the film. A tenter device having a clip cover that is kept low in the range of ℃ or less;
A film stretching apparatus comprising: an ear recovery device that cuts an ear portion of the film exiting the tenter chamber in a film running direction and recovers it as a polymer material for recycling.   2. The film stretching apparatus according to claim 1, wherein the tenter device includes a film ear cooling unit that introduces a cooling gas into the clip cover and purges the gas.   The film is cast on a support running on a dope comprising cellulose acylate and a solvent to form a cast film, and after the cast film has a self-supporting property, the film is peeled off as a soft film. The film stretching equipment according to claim 1 or 2, wherein the film is a dried cellulose acylate film, and the temperature of the central portion in the width direction of the film by the blower is 175 ° C or higher and 210 ° C or lower. A cast film is formed by casting a dope containing a polymer and a solvent to form a cast film, and after the cast film has a self-supporting property, it is peeled off as a soft film from the support and dried. Manufacturing process;
A stretching step of heating the film while gripping both side edges of the produced polymer film with a plurality of clips, and stretching in the width direction;
The movement path of the plurality of clips holding the film in the tenter chamber is covered with a clip cover, and the temperature of both side edges of the film held by the clip is 10 ° C. or more and 40 ° C. than the center in the width direction of the film. Film ear cooling section process to keep low in the following range,
A film stretching method comprising: an ear recovery step of cutting an ear portion of the film in a film running direction and recovering it as a polymer material for recycling.   5. The film stretching method according to claim 4, wherein in the film ear cooling unit step, a gas is purged by introducing a cooling gas into the clip cover.   6. The film stretching method according to claim 4, wherein the polymer is cellulose acylate, and the temperature of the central portion in the width direction of the film is 175 ° C. or higher and 210 ° C. or lower.

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