JP2009226847A - Floating type longitudinally orienting device and forming method of thermoplastic resin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a floating type longitudinally orienting device capable of forming a thermoplastic resin film having the excellent accuracy of a thickness. <P>SOLUTION: The floating type longitudinally orienting device is equipped with a pair of orienting rollers for orienting a thermoplastic resin sheet and a heating furnace positioned between the orienting rollers, and the heating furnace is equipped with a plurality of air nozzles for heating the thermoplastic resin sheet in which at least a part of the air nozzle is oppositely positioned. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a floating type longitudinal stretching apparatus and a method for producing a thermoplastic resin film having excellent thickness accuracy in the width direction.

  Thermoplastic resins represented by polyethersulfone, epoxy, polycarbonate, cyclic polyolefin, polyester, and the like are widely used in the optical field including liquid crystals as disclosed in Non-Patent Document 1, for example. For the production of these resins, a melt film forming method, a solution casting method, a solution casting method and the like are used. For example, when an acrylic thermoplastic resin film is produced by a melt film-forming method, in order to increase its toughness, for example, as disclosed in Patent Document 1, it is possible to increase the molecular weight or add elastomer particles. Although it has been proposed, the viscosity becomes extremely high, and the viscosity becomes too high when discharged from the die, making flattening and smoothing in the casting process extremely difficult. In addition, it has been clarified that molecular anisotropy generated when a heat-melted resin is formed into a film causes optical anisotropy such as phase difference of the film and fluctuation of the optical principal axis of the refractive index ellipsoid. . In terms of productivity and cost, the melt film-forming method is the best, but in optical applications such as liquid crystal, optical anisotropy and flatness are problems.

  When film formation is performed by melt film formation, neck temperature is reduced when the molten resin is extruded from the die, temperature unevenness of the atmosphere until reaching the cooling roll, and shrinkage of the film edge and center when solidified by the cooling roll Due to the deviation of the molecular orientation due to the difference in behavior and the like, there is a distribution in the film width direction in the retardation of the finished film, the direction of the optical principal axis, and the thickness unevenness. The central part in the film width direction is relatively stable, but the deviation is significant at both ends.

  When a film having a distribution in the width direction is applied with tension near the glass transition temperature to control the molecular orientation and reduce the phase difference as in Patent Document 2, a uniform tension is applied in the film width direction. Even if the treatment is performed, the distribution in the width direction formed at the time of film formation is not completely eliminated. Accordingly, as a method for improving the retardation in the film width direction, for example, as shown in Patent Document 3, a thermoplastic resin film is subjected to heat treatment by applying tension in the traveling direction of the floating heating furnace at an alternate position ( As shown in FIG. 1, there has been proposed an apparatus for improving the phase difference in the width direction by having a structure capable of giving a temperature difference in the film width direction inside the heating furnace.

However, in the floating type stretching in which air nozzles are arranged alternately, wrinkles in the vertical direction occur during film conveyance, heat reception from the heating source and the upper and lower nozzles becomes non-uniform, resulting in uneven stretching, and higher flatness is required. Thus, there is a problem that uneven thickness becomes obvious.
"Transparent resin for optics", Technical Information Association, Inc. (Issue: Kazuhiro Takahisa), December 17, 2001, p59 JP 2006-283013 A JP-A-8-15692 JP 2004-299216 A

  In view of such circumstances, the object of the present invention is a floating capable of producing a thermoplastic resin film having excellent thickness accuracy by maintaining optical isotropy in the width direction and equalizing the amount of heat received by the film. It is providing the manufacturing method of a type | formula longitudinal stretch apparatus and a thermoplastic resin film.

  To achieve this object, the present invention has the following configuration.

  (1) A floating type longitudinal stretching apparatus including a pair of stretching rolls for stretching a thermoplastic resin sheet and a heating furnace disposed between the stretching rolls, wherein the heating furnace is a thermoplastic resin sheet. A floating type longitudinal stretching apparatus comprising a plurality of air nozzles for heating and being arranged so that at least a part of these air nozzles are opposed to each other.

  (2) The heating furnace is partitioned into a plurality of rooms, and in a room having an air nozzle that blows out air having the highest temperature, at least a part of the air nozzle is disposed so as to face each other (1) Floating type longitudinal stretching apparatus described in 1.

  (3) The floating type longitudinal stretching apparatus according to the above (1) or (2), wherein the air nozzle is a slit nozzle, and the distance between a pair of opposed air nozzles is 10 to 150 mm.

  (4) The amorphous thermoplastic resin sheet having an average thickness of 10 to 120 μm is stretched between a pair of stretching rolls using the floating type longitudinal stretching apparatus according to any one of (1) to (3) above. A method for producing a thermoplastic resin film.

  According to the present invention, as described below, it is possible to provide a method for producing a thermoplastic resin film having excellent thickness accuracy and a floating type longitudinal stretching apparatus that can be suitably used to obtain such a film. It becomes.

  The floating type longitudinal stretching apparatus of the present invention will be described with reference to FIG.

  In FIG. 2, the floating longitudinal stretching apparatus 1 includes a heating furnace 12 having chambers 5 to 7 partitioned by partitions 13 and 14 between a pair of stretching rolls (stretching roll 2 and stretching roll 2 ′). In each room in the heating furnace, air nozzles (air nozzle 9, air nozzle 10, air nozzle 11) are arranged above and below the conveyance path of the thermoplastic resin sheet. The air nozzle 9 and the air nozzle 11 arranged in the room 5 and the room 7 are respectively arranged at alternate positions (there is no air nozzle facing each air nozzle), and the air nozzle 10 arranged in the room 6 is located at the facing position ( There is an air nozzle facing each air nozzle). Also, dancer rolls (dancer roll 3, dancer roll 3 ') and drive rolls (drive roll 4, drive roll 4') are arranged at the entrance and exit of the heating furnace, respectively.

  In the said apparatus, a thermoplastic resin sheet moves along the thermoplastic resin sheet conveyance path | route 8, and is extended | stretched while it is heated with a heating furnace between extending | stretching rolls. This stretching is performed by utilizing a tension difference or a circumferential speed difference between rolls (stretching rolls, etc.) respectively disposed at the entrance and exit of the heating furnace. For this reason, it is preferable to perform the tension cut between the rolls by a dancer roll, a nip roll (not shown), a suction roll (not shown) having a porous hole that can be sucked on the roll surface, and the like.

  The inlet speed of the thermoplastic resin sheet is preferably 1 to 50 m / min, and the peripheral speed of the outlet side roll is preferably increased to 400% of the peripheral speed of the inlet side roll.

  As for the heating furnace, an example in which the heating furnace is partitioned into three chambers (rooms 5 to 7) is shown in FIG. 2, but it is preferable that the heating furnace is partitioned into at least two chambers. More preferably, there are three rooms.

  Further, it is important that at least a part of the plurality of air nozzles provided in the heating furnace are arranged at positions facing each other. As the stretching tension is higher, wrinkles are generated in the traveling direction. However, at the alternate positions, the amount of heat received by the film is uneven in the width direction depending on how the film blows up and down at the air nozzle portion. By disposing the air nozzles at the opposed positions instead of the alternate positions, the amount of heat received from the upper and lower air nozzles becomes uniform compared to the alternate positions, and uniform stretching in the width direction is possible. Of course, all the air nozzles may be at the opposing positions.

  In a room having an air nozzle having the highest temperature of air blown out by the air nozzle, it is preferable that at least a part of the air nozzles are arranged at positions facing each other. This is because the film is stretched in the highest temperature atmosphere and uneven stretching occurs in the film width direction. This is because it becomes possible to stretch the film. Of course, all the air nozzles in the above-described room may be at the opposing positions.

  It is preferable that the space | interval between the air nozzles distribute | arranged to the opposing position is 10-150 mm, More preferably, it is 20-50 mm. The interval is preferably small in order to give a uniform amount of heat to the thermoplastic resin sheet, but if it is too small, it may come into contact with the air nozzle. When the distance is in the above range, it is possible to suppress contact between the thermoplastic resin sheet and the air nozzle, and to prevent generation or tearing.

  The temperature and speed of the air blown from the air nozzle are preferably set for each chamber, and may be controlled for each air nozzle.

  The temperature of the air is preferably the highest temperature in the second and subsequent rooms counted from the upstream side in the sheet traveling direction, and the temperature at that time is Tg when the glass transition temperature of the thermoplastic resin used is Tg. It is preferable to set it as Tg-10 degreeC-Tg + 20 degreeC.

  The air wind speed is preferably controlled in the range of 1 to 30 m / s, and is preferably set to 10 to 20 m / s in order to prevent insufficient heat due to insufficient air volume and sheet flutter due to excessive air volume.

  The air nozzle described above is preferably a unidirectional or bi-directional slit nozzle.

  In order to prevent sheet meandering, an EPC (edge position controller) may be installed at the entrance / exit of the longitudinal stretching device, and a CPC (center position controller) may be installed at the exit in consideration of the width shrinkage of the film width. preferable.

  The stretching ratio may be appropriately controlled depending on the required film properties and thickness. For example, by stretching a thermoplastic resin sheet having a thickness of 80 μm vertically by 1.4 times or more, thickness unevenness in an arbitrary direction before stretching. Can be made 1.5 μm or less.

  In the present invention, the thermoplastic resin sheet stretched by the floating longitudinal stretching apparatus preferably has a thickness in the range of 10 to 120 μm. The sheet thickness should be adjusted as appropriate depending on the film properties, handling properties, target final thickness, etc., but if the sheet thickness is less than 10 μm, the yield tends to deteriorate when the sheet is stretched longitudinally. In some cases, when the thickness exceeds 120 μm, the transparency is lowered or the thickness of the member becomes too large. Further, the thickness unevenness of the thermoplastic resin sheet in an arbitrary direction is desirably 2.5% or less, for example, 2.0 μm or less if the sheet thickness is 80 μm. This is because, depending on the shape / location of thickness unevenness, wrinkles are likely to occur by locally stretching a portion having a small thickness when longitudinal stretching is performed.

  Note that it is preferable to trim both ends of the sheet edge before stretching. This is because both end portions of the sheet are thick and the phase difference increases when the sheet is stretched as it is. The present invention is particularly effective for an amorphous thermoplastic resin. However, since an amorphous thermoplastic resin is very brittle, blades such as leather blades, rotary blades, shear blades and the like that are usually used are used. When trimming is performed, the sheet is likely to break during cutting, and breakage may occur, or when a fine sheet burr is tensioned in the sheet traveling direction by longitudinal stretching, the burr may break from the starting point. For this reason, it is desirable to employ a heating / melting method using a laser or the like for trimming. However, it is preferable to adjust the laser output so that the rise of the end due to heat or melting is within 30%, and preferably within 20%.

  As a film forming method in which the floating type longitudinal stretching apparatus of the present invention is suitably employed, a melt film forming method is preferable from the viewpoint of cost and productivity. The melt film forming method can be classified into a straight die method, a cross head die method, a flat die method, and a special die method depending on the shape of the die used. In the present invention, the flat die method is preferable. Resin melted by a melt extrusion apparatus or the like is measured by a gear pump and then continuously sent to a die. The die has only to be designed so that the molten resin does not stay therein, and any type of commonly used manifold die, coat hanger die, and fish tail die may be used in the flat die method. The molten resin extruded from the die into a sheet can be cooled and solidified on a cooling medium such as a drum to obtain a film. In melt film formation by the flat die method, a predetermined film thickness can be obtained by adjusting the extrusion temperature, the take-up speed during take-up, and the lip gap of the die.

  Examples of the thermoplastic resin applicable in the present invention include polyolefin resins such as polyethylene, polypropylene and polymethylpentene, polyamide resins such as nylon 6 and nylon 66, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene-2. , 6-naphthalate (PEN), polybutylene naphthalate (PBN), polytrimethylene terephthalate (PPT), polyethylene-p-oxybenzoate, poly-1,4-cyclohexylenedimethylene terephthalate (PCT), polycarbonate, and co As polymerization components, for example, diol components such as diethylene glycol, neopentyl glycol, polyalkylene glycol, adipic acid, sebacic acid, phthalic acid, isophthalic acid, 2,6 Polyester resins such as polyester obtained by copolymerizing such a dicarboxylic acid component such as naphthalene dicarboxylic acid, other, a polyacetal resin, polyphenylene sulfide resin. In addition, for optical use films that require strict control of retardation and thickness unevenness, amorphous resins such as polycarbonate resins, polyolefin resins, cyclic polyolefin resins, and polyacryl resins are particularly preferable. A polymer resin having a structure, for example, a resin containing a cyclic norbornene resin or a cyclopentane structure is preferable, and is particularly preferably used for a so-called acrylic resin. As acrylic resins, polymethacrylic acid resin, polymethyl methacrylate resin and other polymethacrylic acid ester resins and their derivatives, glutaric anhydride, glutaric imide, maleic anhydride, lactone ring, etc. And a copolymer having the following cyclic structure.

  In order to use the thermoplastic resin film obtained by the present invention for optical applications, the haze is preferably 1.0% or less, more preferably 0.6% or less. That is, if the film has a haze exceeding 1.0%, it gives a cloudy impression, is unsatisfactory in appearance, leaks light due to light scattering, and is not used in a liquid crystal display.

  Moreover, it is preferable that the light transmittance of a thermoplastic resin film is 91% or more, More preferably, it is 93% or more. That is, if the light transmittance is less than 91%, light for display cannot be sufficiently transmitted, and it is not used in a liquid crystal display. In order to realize these characteristics, the film can be removed and reduced as much as possible, and the film discharged from the die in the form of a sheet can be smooth and flat. It is preferable not to occur.

  The thermoplastic resin film of the present invention is provided with an antistatic layer or an easy-adhesion layer by coating on the surface depending on the purpose of use, a hard coat layer made of an ultraviolet curable resin, a triangular prism layer, a microlens array, etc. A metal oxide deposition layer, a transparent conductive layer formed by sputtering, or other optically isotropic films, polarizers, optical functional films such as retardation films, glass substrates, etc. are used via an adhesive layer. be able to.

  Hereinafter, the present invention will be described based on examples. However, the present invention is not limited to the following examples. Prior to the description of each example, various physical property measurement methods employed in the example will be described.

(1) Unevenness of thickness of sheet or film A sheet or film is cut out with a width of 50 mm in each of the longitudinal direction and the width direction, and 1.5 m / min at a load of measuring pressure of 0.15 g by “Film Synex” manufactured by Anritsu Corporation. The thickness was continuously measured while running at a speed of 1 mm, and the difference between the maximum value and the minimum value was obtained from the thickness chart in the range of 1 m in length.

(2) Light transmittance of film It measured using colorimetric color difference meter ZE-2000 (made by Nippon Denshoku Industries Co., Ltd.) according to JIS-K7361-1 (1997).

(3) Haze of film It measured using the haze meter (made by Suga Test Instruments) according to JIS-K-6714 (1995).

(4) In-plane retardation and thickness direction retardation of film Oval Measurement Co., Ltd. elliptic polarization measurement device (KOBRA-WPR) and retardation measurement device KOBRA-RE (KOBRA-WR software) Ver. 1.21 was used. Measurement is performed in a single N calculation mode of incident angle dependence measurement, using a low phase difference measurement method, with the slow axis as the tilted central axis and an incident angle of 40 ° (wavelength 590 nm). A phase difference (Δnd) and a thickness direction retardation (Rth) were obtained. The R0 value, which is the phase difference at an incident angle of 0 °, was defined as the in-plane phase difference (Δnd). Further, the measurement was performed on a sample stored for 24 hours in a desiccator, and the average value of N = 5 times was defined as an in-plane retardation (Δnd) and a thickness direction retardation (Rth).

(Examples 1 to 11)
A polyacrylic resin was used as an amorphous thermoplastic resin. The pellets of the resin were dried under reduced pressure at 80 ° C. for 8 hours, extruded at 260 to 270 ° C. using a single screw extruder with a vent, and the discharge rate was made constant with a gear pump, and then a metal fiber sintered type 7 μm cut filter was used. It was used and filtered, and it discharged to the sheet form through the flat die (setting temperature 260-270 degreeC) of width 1,770mm. The thermoplastic resin sheet is discharged from the lip in the vertical direction and hung so that it contacts the tangential direction of the stainless steel cooling roll (110 ° C), then starts cooling, and then transported by a roll of the same diameter and the same material. Allow to cool. As a result, a sheet with an edge (edge) having a width of 1,680 mm is formed due to the effect of necking, and thereafter, an average of 175 mm each of the ear portions at both ends of the sheet is laser-cut (CO ₂ , wavelength 10.6 μm, output 4. 5W) to obtain a sheet having thickness unevenness of 2.0 μm or less. While further transporting this, longitudinal stretching was carried out using the longitudinal stretching apparatus shown in FIG. 2 utilizing the speed difference of the rolls arranged at the entrances and exits of the heating furnace. Various conditions are shown in Table 1. Various characteristics of the obtained film are shown in Table 2.

(Comparative Example 1)
A device similar to the stretching device shown in FIG. 2 was used except that the positions of all the air nozzles were alternate positions of the conventional type, and other conditions were obtained after longitudinal stretching in the same manner as in Example 3. The film thickness unevenness, light transmittance, haze, and retardation were measured. The results are shown in Table 2.

(Comparative Examples 2 to 10)
The film was stretched longitudinally in the same manner as in Comparative Example 1 except that various conditions were as shown in Table 1, and then the thickness unevenness, light transmittance, haze, and retardation of the obtained film were measured. The results are shown in Table 2.

(Examples 12 to 13)
A stretched film was obtained in the same manner as in Example 3 except that polycarbonate or cyclic polyolefin pellets were used as the amorphous thermoplastic resin. The results are shown in Table 2.

(Comparative Examples 11 and 12)
Except that the positions of all the air nozzles were alternate positions of the conventional type, the same apparatus as the stretching apparatus shown in FIG. 2 was used, and other conditions were the same as in Examples 12 and 13, respectively. Obtained. The results are shown in Table 2.

It is a schematic cross-sectional view of the film heat treatment apparatus described in Patent Document 3. 1 is a schematic cross-sectional view of a floating type longitudinal stretching apparatus according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Floating type longitudinal stretching apparatus 2 Stretching roll 2 'Stretching roll 3 Dancer roll 3' Dancer roll 4 Driving roll 4 'Driving roll 5 Room (room partitioned by a partition in the heating furnace)
6 rooms (rooms separated by partitions in the heating furnace)
7 rooms (rooms separated by partitions in the heating furnace)
8 Thermoplastic sheet transport path 9 Air nozzle (alternate position)
10 Air nozzle (opposite position)
11 Air nozzle (alternate position)
DESCRIPTION OF SYMBOLS 12 Heating furnace 13 Partition 14 Partition 20 Floating type longitudinal stretching apparatus 21 Heating furnace 22 Heating furnace inlet side roll group 23 Heating furnace outlet side roll group 24 Sheet conveyance path 25 Air nozzle 26 Air nozzle 27 Air nozzle

Claims (4)

A floating type longitudinal stretching apparatus comprising a pair of stretching rolls for stretching a thermoplastic resin sheet and a heating furnace disposed between the stretching rolls, the heating furnace for heating the thermoplastic resin sheet And a plurality of air nozzles, and at least a part of these air nozzles are arranged to face each other. The floating furnace according to claim 1, wherein the heating furnace is partitioned into a plurality of rooms, and in a room having an air nozzle that blows out air having the highest temperature, at least a part of the air nozzle is arranged to face each other. Type longitudinal stretching device. The floating type longitudinal stretching apparatus according to claim 1 or 2, wherein the air nozzle is a slit nozzle, and a distance between a pair of opposed air nozzles is 10 to 150 mm. Manufacture of a thermoplastic resin film that stretches an amorphous thermoplastic resin sheet having an average thickness of 10 to 120 µm between a pair of stretching rolls using the floating type longitudinal stretching apparatus according to any one of claims 1 to 3. Method.

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