JP2010064386A - Method for manufacturing uneven-thickness resin sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing an uneven-thickness resin sheet which can improve productivity by further curtailing annealing treatment. <P>SOLUTION: The method includes an extrusion process 100 for extruding a molten resin from a die 12 in the shape of a sheet, a sheet molding process 114 in which the extruded molten resin sheet 14a is held between a mold roller 16 and a nip roller 18, a working shape on the surface of the mold roller 16 is transferred, and a resin sheet 14 is molded, a peeling process 115 for peeling the resin sheet 14 from a peeling roller 20, a conveyance process for conveying the resin sheet 14 while it is heated by a heating system 22, a cutting process 124 for cutting the resin sheet 14 at a temperature of (Tg-40)°C or more and Tg or less of the highest temperature of the surface in the width direction of the resin sheet, and an annealing treatment process 126 for annealing the resin sheet 14 continuously at a temperature of (Tg-40)°C or more and Tg or less. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an uneven thickness resin sheet, and more particularly to a method for manufacturing an uneven thickness resin sheet suitable for use in a light guide plate and various optical elements disposed on the back surface of various display devices.

  In general, in resin sheet extrusion molding, a molten resin sheet extruded from a T-die is cooled by a cooling roll, and then cooled and solidified by air cooling in a conveyance section while being taken up by a transaction roll, and is then cut by a cutting machine. Cut in the direction and formed into a sheet.

  The resin sheet molded in this way tends to have residual strain due to temperature changes such as heating for melting and cooling for solidifying during molding. For this reason, there is a problem that the shape is not stable due to a change with time, and the physical properties are not sufficiently exhibited.

  Therefore, so-called annealing treatment is applied for the purpose of relieving residual distortion and deformation of the thermoplastic resin molded article, or for the purpose of increasing the strength by promoting crystallization of the crystalline thermoplastic resin molded article. Yes. The higher the temperature, the greater the effect of annealing treatment, but the higher the temperature, the more the resin will melt and a molded product with the desired shape cannot be obtained. In the case of a thermoplastic resin, the glass transition temperature of the resin In the case of a crystalline resin that is 20 to 40 ° C. lower than Tg, it is generally annealed at a temperature that is 10 to 20 ° C. higher than the highest temperature actually used.

  When the residual strain is relaxed or crystallization progresses, a local volume change occurs, and the shape and dimensions of the molded product change slightly. Therefore, the annealing process is mainly used for products whose shape and dimensional accuracy are not strict. In addition, it has been performed with a molded product having an almost isotropic shape. A sheet-like molded product or the like is prone to deformation such as warping and undulation because the volume change behavior in the thickness direction and the length / width direction is different. In addition, when the size of the sheet is large, it is difficult to uniformly heat the surface during the temperature increase, and therefore deformation is likely to occur even with a non-uniform temperature increase rate. In the case of a shape having a thickness distribution instead of a flat plate, the rate of temperature increase locally varies depending on the thickness, and thus deformation is more likely to occur.

  As a countermeasure, for example, Patent Document 1 below discloses a method of preventing deformation due to annealing by setting and fixing a fixing plate on the side and upper and lower surfaces in a state where flat plates are laminated. However, in this method, when the object is a flat plate, deformation due to annealing can be suppressed, but it cannot be applied to a sheet having a thickness distribution. In addition, since lamination takes time to transfer heat to the inside, the annealing time becomes long, and it takes time to set the annealing, so that productivity is remarkably lowered.

In order to shorten the annealing time, for example, Patent Documents 2 and 3 below disclose a method of continuously annealing using far infrared rays as a heating means.
JP 2005-47126 A Japanese Patent Publication No.7-112715 JP-A-11-172026

  In the methods and apparatuses described in Patent Documents 2 and 3, the heating time of the molded product is remarkably shortened as compared with the conventional hot air heating method, and the annealing treatment time can be shortened. However, when it is necessary to perform a large amount of annealing treatment, it is necessary to further shorten the annealing treatment time.

  This invention is made | formed in view of such a situation, and it aims at providing the manufacturing method of the uneven thickness resin sheet which can shorten an annealing process conventionally and can improve productivity.

  According to the first aspect of the present invention, the extrusion process of extruding the molten resin from the die into a sheet shape, the extruded molten resin sheet is sandwiched between the mold roller and the nip roller, and the processed shape of the surface of the mold roller is determined by the molten resin sheet A sheet forming step of forming a resin sheet by transferring to a sheet and cooling and solidifying, a peeling step of peeling the resin sheet from a peeling roller, and a conveyance of pulling and conveying the resin sheet by a heating device while heating the resin sheet And when the glass transition temperature of the resin is defined as Tg, the maximum temperature of the surface in the width direction of the resin sheet is (Tg−40) ° C. to Tg ° C. The step of cutting to length and the resin sheet cut by the cutting means are continuously annealed at a temperature of (Tg-40) ° C. or higher and Tg ° C. or lower. To provide a method of manufacturing uneven thickness resin sheet and having a annealing step of performing, the.

  According to claim 1, the cutting step is performed in a state where the maximum surface temperature in the width direction of the resin sheet has a temperature of (Tg−40) ° C. or higher and Tg ° C. or lower. Since it is performed at a temperature of (Tg-40) ° C. or higher and Tg or lower, there is no need to cool the resin sheet from the cutting step to the annealing step, so the annealing time can be reduced and the productivity is improved. be able to.

  A second aspect of the present invention according to the first aspect is characterized in that the annealing step is performed by supporting the resin sheet with a planar support member.

  According to the second aspect, in the annealing process, the resin sheet is supported by the planar support member and annealed, so that the resin sheet in a soft state at a high temperature is flattened by its own weight, and the resin sheet is deformed. Correction can be performed easily.

  A third aspect is characterized in that, in the first or second aspect, the difference in thickness between the thickest part and the thinnest part of the thickness distribution in the width direction of the resin sheet is 0.5 mm or more and 5 mm or less.

  According to the third aspect, by setting the difference between the thickest portion and the thinnest portion of the thickness distribution within the above range, the temperature of the resin sheet can be easily adjusted in the transporting step and the annealing treatment step. The shape change such as can be suppressed.

  According to the manufacturing method of the uneven thickness resin sheet of the present invention, since the temperature is maintained continuously in the annealing process from the cutting process, it is not necessary to cool the resin sheet. It can be shortened and productivity can be improved.

  Hereinafter, preferred embodiments of a method for producing an uneven thickness resin sheet according to the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is an overall process diagram of a method for producing a resin sheet according to the present invention, and FIG. 2 is a conceptual diagram showing an apparatus configuration in each process.

  As shown in FIG. 1, the manufacturing method of the uneven thickness resin sheet of the present invention mainly includes a raw material process 100 for measuring and mixing raw materials, an extrusion process 112 for continuously extruding molten resin into a sheet shape (band shape), and Then, the extruded molten resin sheet 14a is cooled and solidified to form a resin sheet 14; a peeling process 115 for peeling the resin sheet 14; and a cutting process 124 for removing the peeled resin sheet 14 as the next process. A transporting process 116 for transporting the resin sheet 14, a cutting process 124 for cutting the resin sheet 14 into a predetermined size (length / width), and an annealing process process 126 for gradually cooling the resin sheet 14 and removing residual distortion. Is done.

  Hereinafter, the main structure of the resin sheet manufacturing apparatus to which the present invention is applied will be described with reference to FIG.

  As shown in FIG. 2, in the raw material process 100, the raw resin and additive sent from the raw material silo 128 (or raw material tank) and additive silo 130 (or additive tank) to the automatic weighing machine 132 are automatically measured and mixed. In the vessel 134, the raw material resin and the additive are mixed at a predetermined ratio.

  As the resin material of the raw material resin applied to the present invention, a thermoplastic resin can be used, for example, polymethyl methacrylate resin (PMMA), polycarbonate resin (PC), polystyrene resin (PS), MS resin, AS resin. , Polypropylene resin (PP), polyethylene resin (PE), polyethylene terephthalate resin (PET), polyvinyl chloride resin (PVC), thermoplastic elastomer, or a copolymer thereof, cycloolefin polymer, and the like.

  Further, these thermoplastic resins may contain light diffusing particles. Examples of the light diffusing particles include inorganic materials such as silicone, silica, calcium carbonate, barium sulfate, aluminum hydroxide, titanium oxide, glass beads, and calcium silicate. Examples thereof include particles and polymethyl methacrylate particles. When adding scattering particles, first, master pellets in which scattering particles are added to a raw material resin at a concentration higher than a predetermined concentration are manufactured by a granulator. Next, by suitably adopting the master batch method, the master pellets to which the scattering particles are added at a higher concentration than the predetermined concentration and the base pellets to which the scattering particles are not added are mixed at a predetermined ratio by the mixer 134. The same applies when additives other than the scattering particles are added.

  The raw resin appropriately weighed and mixed in the raw material process 100 is sent to the extrusion process 112.

  In the extrusion step 112, the raw material resin mixed in the mixer 134 is charged into the extruder 138 through the hopper 136. The raw material resin is melted while being kneaded by the extruder 138. The extruder 138 may be either a single-screw extruder or a multi-screw extruder, and preferably includes a vent function that evacuates the interior of the extruder 138. The raw material resin melted by the extruder 138 is sent to a die 12 (for example, a T die) through a supply pipe 142 by a metering pump 140 such as a screw pump or a gear pump. The molten resin sheet 14 a extruded from the die 12 into a sheet is then sent to the sheet forming step 114.

  In the sheet forming step 114, the molten resin sheet 14 a extruded from the die 12 is sandwiched between the mold roller 16 and the nip roller 18. The molten resin sheet 14a is cooled and solidified while being formed into a shape having a thickness distribution in the width direction. The solidified resin sheet 14 is peeled off by the peeling roller 20 (peeling step). The resin sheet 14 that has undergone the sheet forming step 114 is then sent to a conveying step 116.

  The transporting process 116 is a process of transporting the resin sheet 14 peeled from the peeling roller 20 to the cutting process 124. The conveyance is performed by the resin sheet being pulled by the take-up roll 24. In the present invention, the resin sheet 14 is heated in the conveying process, and the annealing process is performed using the remaining heat. Therefore, in the conveyance process, the temperature of the resin sheet is adjusted using a heating device.

  The resin sheet 14 whose temperature is controlled and conveyed by the conveying step 116 is sent to the cutting step 124. The cutting step 124 is a step of cutting the resin sheet 14 to a predetermined length. Moreover, it can also have the process of excising the width direction both ends (ear part) of the resin sheet 14. FIG. As the cutting means 174, a laser cutter, an electron beam cutting, an ultrasonic cutter, or the like can be used. A guillotine-type cutting means composed of a receiving blade and a pressing blade can also be used.

  Further, when the shape formed on the resin sheet has a plurality of thick portions, the cutting step 124 can also include a step of cutting in the conveyance direction at the joint of the shape.

  Moreover, although the resin sheet 14 is shape | molded by the predetermined | prescribed shape in the sheet | seat shaping | molding process 114, both edge parts of the resin sheet 14 become worse in dimensional accuracy compared with a center part in the shape. Moreover, since residual distortion also becomes large, it is preferable to cut | disconnect. The cut part is preferably cut at 20 to 30 mm at both ends of the resin sheet 14. As shown in FIG. 2, both edges of the resin sheet can be cut before cutting the resin sheet in a direction perpendicular to the conveying direction, or before cutting the sheet into a predetermined shape and performing an annealing treatment. It can also be cut.

  A part of the cut resin sheet 14 is collected in a collection box 176, and the collected resin is discarded or reused.

  The cut resin sheet 14 is conveyed to the annealing process 126 by the conveyor belt 196 driven by the roller 194. The annealing process is provided to prevent a rapid temperature change of the resin sheet 14. When a sudden temperature change occurs in the resin sheet 14, for example, the inside of the resin sheet 14 is in an elastic state while the vicinity of the surface of the resin sheet 14 is in a plastic state. The surface shape of the sheet 14 is deteriorated. Further, there is a problem that a temperature difference occurs between the front and back surfaces of the resin sheet 14 and the resin sheet 14 is warped.

  Next, among the above steps, details of the sheet forming step 114 to the annealing step 126 that characterize the present invention will be described with reference to FIGS.

  The resin sheet production line 10 includes a die 12 for shaping the raw material resin melted by the extruder 138 into a sheet shape, a mold roller 16 having an uneven thickness formed on the surface, and a mold roller 16 facing the mold roller 16. The nip roller 18 is formed, the peeling roller 20 is disposed opposite to the mold roller 16, and the heating device 22 that controls the temperature of the resin sheet 14.

  The sheet-shaped molten resin sheet 14 a extruded from the die 12 is pressed between the mold roller 16 and a nip roller disposed opposite to the mold roller 16, and the uneven shape inverted mold on the surface of the mold roller 16 is transferred to the resin sheet 14. Then, the resin sheet 14 is gradually cooled by being wound around a peeling roller 20 disposed opposite to the mold roller 16, and is transported in a state where distortion is removed.

  In the production of this resin sheet, the extrusion speed of the resin sheet 14 of the die 12 can be 0.1 to 50 m / min, preferably 0.3 to 30 m / min. Accordingly, the peripheral speed of the mold roller 16 is also substantially matched with this. In addition, it is preferable to control the speed unevenness of each roller within 1% with respect to the set value.

  The pressing pressure of the nip roller 18 against the mold roller 16 should be 0 to 200 kN / m (kgf / cm) in terms of linear pressure (value converted assuming that the surface contact due to elastic deformation of each nip roller is linear contact). Is more preferable, and 0 to 100 kN / m (kgf / cm) is more preferable.

  On the surface of the mold roller 16, for example, a reverse shape for forming the uneven thickness resin sheet shown in FIGS. 4A and 4B is formed. FIG. 4 is a cross-sectional view of the resin sheet 14 after molding. That is, the back surface of the resin sheet 14 is a flat surface, and a linear uneven shape surface parallel to the traveling direction is formed on the surface of the resin sheet 14. Therefore, an endless groove having an inverted shape of the resin sheet 14 after the formation shown in FIGS. 4A and 4B may be formed on the surface of the mold roller 16. The thickness of the uneven thickness resin sheet produced by the method for producing a resin sheet of the present invention is such that the thickness of the thickest part of the resin sheet is Dmax and the thickness of the thinnest part is Dmin. The thickness difference Dmax−Dmin is preferably 0.5 mm or more and 5 mm or less, more preferably 0.5 mm or more and 3 mm or less. Moreover, as shown in FIG.4 (b), when there are two or more thick parts, the pitch L is preferably 200 mm or more, and more preferably 400 mm or more.

  The material of the mold roller 16 includes various steel members, stainless steel, copper, zinc, brass, and a metal lining of these metal materials, and a rubber lining on the surface. These metal materials are HCr plated, Cu plated, Ni plated. Those plated with ceramics, ceramics, and various composite materials can be used.

  The formation of an inverted saddle shape on the surface of the mold roller depends on the material of the roller surface, but generally a combination of cutting with an NC lathe and finishing buffing can be preferably employed. Also, other known processing methods (cutting, ultrasonic processing, electric discharge processing, etc.) can be employed. The surface roughness of the mold roller surface is preferably 0.5 μm or less, and more preferably 0.2 μm or less, in terms of the center line average roughness Ra. The mold roller 16 is rotationally driven at a predetermined peripheral speed by driving means (not shown).

  The nip roller 18 is disposed so as to face the mold roller 16 and is a roller for sandwiching the resin sheet 14 with the mold roller 16. The material of the nip roller 18 is a variety of steel members, stainless steel, copper, zinc, brass, a metal lining of these metal materials, a rubber lining on the surface, HCr plating, Cu plating, Ni plating, etc. on these metal materials These materials, ceramics, and various composite materials can be used.

  The surface of the nip roller 18 is preferably processed into a mirror shape, and the center line average roughness Ra is preferably 0.5 μm or less, and more preferably 0.2 μm or less. By setting it as such a smooth surface, the back surface of the resin sheet 14 after a shaping | molding can be made into a favorable state. The nip roller 18 is rotationally driven at a predetermined peripheral speed by a driving means (not shown). In addition, although the structure which does not provide a drive means in the nip roller 18 is possible, it is preferable to provide a drive means from the point which can make the back surface of the resin sheet 14 a favorable state.

  The nip roller 18 is provided with a pressing means (not shown) so that the resin sheet 14 between the nip roller 18 and the mold roller 16 can be clamped with a predetermined pressure. Each of the pressurizing means is configured to apply pressure in the normal direction at the contact point between the nip roller 18 and the mold roller 16, and various known means such as a motor driving means, an air cylinder, and a hydraulic cylinder are employed. it can.

  The nip roller 18 may be configured to be less likely to bend due to the reaction force of the clamping pressure. As such a configuration, a back-up roller (not shown) is provided on the back side of the nip roller 18 (opposite side of the mold roller 16), and a roller configuration is provided with a strength distribution that increases the rigidity of the central portion in the axial direction of the roller. , And combinations of these can be employed.

  The peeling roller 20 is disposed opposite to the mold roller 16 and is a roller for peeling the resin sheet 14 from the mold roller 16 by winding the resin sheet 14, and is disposed 180 degrees downstream of the mold roller 16. . The surface of the peeling roller 20 is preferably processed into a mirror surface. By setting it as such a surface, the back surface of the resin sheet 14 after a shaping | molding can be made into a favorable state. The surface roughness of the surface of the peeling roller is preferably 0.5 μm or less, more preferably 0.2 μm or less in terms of the center line average roughness Ra. The material of the peeling roller 20 includes various steel members, stainless steel, copper, zinc, brass, and a metal lining of these metal materials, and a rubber lining on the surface. These metal materials are HCr plated, Cu plated, Ni plated. For example, ceramics and various composite materials can be used. The peeling roller 20 is rotationally driven in the direction of the arrow at a predetermined peripheral speed by a driving means (not shown). In addition, although the structure which does not provide a drive means in the peeling roller 20 is also possible, it is preferable to provide a drive means from the point which can make the back surface of the resin sheet 14 a favorable state.

  In the sheet forming step 114 and the subsequent conveying step 116, it is preferable to provide the heating device 22. As shown in FIG. 3, the heating device 22 is installed in the vicinity of the mold roll, in the vicinity of the peeling roller, and on the lower surface side and the upper surface side of the resin sheet 14 in the conveying step. The heating device 22 is not particularly limited as long as it is a non-contact type such as warm air, a far infrared heater, or a near infrared heater, but a far infrared heater is preferably used from the viewpoint of heating efficiency.

  Heating by the heating device 22 is such that the maximum temperature of the surface in the width direction of the resin sheet 14 can be cut at a temperature of (Tg−40) ° C. or higher when the glass temperature of the resin is Tg in cutting in the cutting step 124. Heat. More preferably, it is (Tg-30) ° C. or higher. Moreover, it is preferable that the upper limit of the temperature at the time of a cutting process is Tg degrees C or less, More preferably, it is (Tg-10) degrees C or less. By performing at the above temperature, the annealing process can be performed using the remaining heat in the next annealing process step 126.

  It is preferable that the heating in the transporting process is first performed by the heating device 22c from the lower surface side (the surface side without the mold) of the resin sheet 14 after being peeled off by the peeling roller 20. This is because if the resin sheet 14 is heated too much from the upper surface side (the surface side where the mold is attached), the resin sheet 14 is deformed by the subsequent heat shrinkage, and a resin sheet having a desired shape may not be obtained. When at least the surface temperature of the resin sheet 14 is equal to or higher than Tg, it is preferable to heat from the lower surface side of the resin sheet.

  The resin sheet 14 is sent to the annealing process 126 after the cutting process 124. In the annealing process, the resin sheet 14 is placed on a flat surface with the flat side of the resin sheet facing down, and heat treatment is performed to correct the deformation and warpage of the resin sheet using its own weight, thereby reducing residual distortion. It is a process of slow cooperation.

  As the annealing process 126, a configuration is adopted in which a horizontal tunnel shape is provided, temperature adjusting means is provided inside the tunnel, and the cooling temperature profile of the resin sheet can be controlled. As the temperature adjusting means, a structure in which air (hot air or cold air) whose temperature is controlled from a plurality of nozzles is jetted toward the resin sheet 14, and a resin sheet by a heating means (nichrome wire heater, infrared heater, dielectric heating means, etc.) Each well-known means, such as the structure which heats each 14 front and back, can be employ | adopted.

  As a support member for supporting the resin sheet 14 in the annealing process, a steel belt 198 as shown in FIG. 3 can be used, and a belt of heat-resistant fluororesin-impregnated fiber or a stainless chain can be used. Since the direction in which the support member has flatness is reflected in the flatness of the resin sheet after the annealing treatment, the flatness of the support member may be 0.5 mm or less in the region where the resin sheet is supported. Preferably, it is 0.3 mm or less.

  The atmospheric temperature (annealing temperature) in the annealing process 126 is preferably (Tg-40) ° C. or higher and (Tg-10) ° C. or lower, more preferably (Tg-30) ° C. or higher and (Tg-10) ° C. or lower. The humidity is preferably in a dry state. The temperature of the resin sheet is heated in the conveying step 116 so as to maintain (Tg−40) ° C. or higher which is the temperature of the resin sheet in the cutting step 124. More preferably, it is (Tg-30) ° C. or higher. Further, the upper limit is preferably Tg ° C or lower, more preferably (Tg-10) ° C or lower. By performing the annealing process 126 with the remaining heat after heating in the transfer process 116, it is not necessary to perform processes such as cooling and heating in the middle, so that the apparatus can be simplified and the annealing process time is also shortened. Therefore, the uneven thickness resin sheet can be manufactured with high productivity.

  After the annealing treatment, it is preferable to slowly cool at a rate of 5 ° C./min or less, and it is preferable to slowly cool at a rate of 2 ° C./min or less.

  2 and 3, after the cutting step 124, the resin sheet 14 is moved in the horizontal direction and the annealing treatment step 126 is performed. As shown in FIG. It is also possible to perform the annealing process by moving up and down one by one. By setting it as the said structure, even when the size of the resin sheet 14 becomes large, an installation can be reduced in size and an enlargement of an installation can be prevented.

It is process drawing explaining the flow of the manufacturing method of the resin sheet to which this invention is applied. It is a conceptual diagram of the manufacturing apparatus of the resin sheet to which this invention is applied. It is a block diagram which shows an annealing process from the sheet | seat formation process of the manufacturing apparatus of a resin sheet. It is sectional drawing which shows an example of the shape of a resin sheet. It is a block diagram which shows another aspect of the manufacturing apparatus of a resin sheet.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 12 ... Die, 14 ... Resin sheet, 14a ... Molten resin sheet, 16 ... Mold roller, 18 ... Nip roller, 20 ... Peeling roller, 22 ... Heating device, 24 ... Take-off roller, 26 ... Measurement base, 100 ... Raw material process, 112 ... extrusion process, 114 ... sheet forming process, 115 ... peeling process, 116 ... conveying process, 124 ... cutting process, 128 ... raw material silo, 130 ... additive silo, 132 ... automatic weighing machine, 134 ... mixer, 136 ... raw material Resin is a hopper, 138 ... extruder, 140 ... metering pump, 142 ... supply pipe, 174 ... cutting means, 176 ... collection box, 194 ... roller, 196 ... conveyor belt,

Claims (3)

An extrusion process of extruding the molten resin from the die into a sheet,
A sheet molding step of molding the resin sheet by sandwiching the extruded molten resin sheet between a mold roller and a nip roller, transferring the processed shape of the surface of the mold roller to the molten resin sheet, and cooling and solidifying;
A peeling step of peeling the resin sheet from the peeling roller;
A conveying step of pulling and conveying the resin sheet with a take-up roller while heating with a heating device;
When the glass transition temperature of the resin is Tg, the maximum temperature of the surface in the width direction of the resin sheet is (Tg−40) ° C. to Tg ° C. A cutting step for cutting;
An annealing process step of continuously annealing the resin sheet cut by the cutting means at a temperature of (Tg-40) ° C. or higher and Tg ° C. or lower. .   The method of manufacturing an uneven thickness resin sheet according to claim 1, wherein the annealing treatment step is performed by supporting the resin sheet with a planar support member.   The thickness difference of the thickness direction in the width direction of the said resin sheet WHEREIN: The difference of the thickness of the thickest part and the thinnest part is 0.5 mm or more and 5 mm or less, The manufacture of the uneven thickness resin sheet of Claim 1 or 2 characterized by the above-mentioned. Method.

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