JP2010064387A - Method for manufacturing uneven-thickness resin sheet - Google Patents

Abstract

An object of the present invention is to provide a method for producing an uneven thickness resin sheet with reduced warpage.
An extrusion process 100 for extruding a molten resin into a sheet form, and the extruded molten resin sheet 14a is sandwiched between a mold roller 16 and a nip roller 18, and a processed shape on the surface of the mold roller 16 is transferred to the molten resin sheet 14a and cooled. A sheet forming step 112 that solidifies, and a conveying step 115 that picks up and conveys the resin sheet 14 with the take-off roller 24. In the conveying step 115, before the surface temperature of the thickest portion of the resin sheet 14 becomes Tg or less. The surface of the thinnest part of the thickness distribution in the width direction of the resin sheet 14 is higher than the surface temperature of the thickest part by heating with the heating device 22c from the side of the resin sheet 14 that is in contact with the peeling roller 20. It is the manufacturing method of the uneven thickness resin sheet characterized by annealing gradually so that the surface temperature distribution of the width direction may be within 30 degreeC until the resin sheet 14 is cut | disconnected.
[Selection] Figure 2

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 conveying section while being taken up by a take-up roll, and formed into a sheet shape. The In such resin sheet extrusion molding, warpage of the molded sheet becomes a problem, and several proposals have been made as countermeasures against warpage.

  For example, in Patent Documents 1 and 2 below, the peripheral speed of the take-up roll is set to the peripheral speed of the polishing roll by heating both ends of the resin sheet at or near the polishing roll or cooling the center of the resin sheet. A method of improving the undulation (edge wave) of the end portion of the resin sheet is disclosed by making the tension equal to the tension state.

  Patent Documents 3 and 4 also reduce internal distortion and warpage due to temperature differences by heating the sheet from the top and bottom of the sheet with a heater in the conveyance unit after the polishing roll to make the temperature of the sheet upper and lower surfaces uniform. A method is disclosed.

Patent Document 5 discloses a method in which the temperature of the cooling roll is adjusted and the extruded sheet is heated to increase the temperature, and then slowly cooled to relieve internal stress.
Japanese Utility Model Publication No. 4-111417 Japanese Patent Laid-Open No. 9-1636 Japanese Patent Laid-Open No. 7-9538 JP 2002-120249 A JP-A-6-344417

  However, the apparatuses and methods described in Patent Documents 1 to 5 are all countermeasures against warping of a flat resin sheet. In the case of extrusion molding of an uneven thickness resin sheet with a large thickness distribution in the width direction, the temperature distribution in the width direction becomes very large, so temperature control is difficult, and during conveyance due to the temperature difference between the thin and thick parts There was a problem that the sheet was twisted. Further, unless the temperature is properly controlled, a desired cross-sectional shape cannot be obtained due to deformation of the sheet. Furthermore, the twisting of the sheet being conveyed is suppressed by increasing the tension of the sheet being conveyed by increasing the peripheral speed of the take-up roll to be higher than the peripheral speed of the cooling roll. Since cooling and solidification are performed in a state where tension is applied, residual strain remains, and there is a problem that warpage occurs when the formed sheet is exposed to a high temperature environment.

  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 reduced generation | occurrence | production of curvature.

  In order to achieve the above object, claim 1 of the present invention is an extrusion process for extruding molten resin from a die into a sheet shape, and sandwiching the extruded molten resin sheet between a mold roller and a nip roller, and the processed shape of the surface of the mold roller Sheet forming step of forming a resin sheet by transferring the resin sheet to the molten resin sheet and cooling and solidifying, a peeling step of peeling off the resin sheet from a peeling roller, and a transporting step of picking up and transporting the resin sheet with a take-off roller And a cutting step of cutting the resin sheet into a predetermined length by a cutting means. In the peeling step, when the glass transition temperature of the resin is Tg, the resin sheet immediately after peeling from the peeling roller The surface temperature of the resin sheet on the side not in contact with the peeling roller is Tg or more and (Tg + 80) ° C. or less. Before the surface temperature of the portion reaches Tg or less, the surface of the thinnest portion of the thickness distribution in the width direction of the resin sheet is heated to the minimum by heating from the side of the resin sheet that is in contact with the peeling roller. The method for producing an uneven thickness resin sheet, characterized by being gradually cooled so that the surface temperature distribution in the width direction of the resin sheet is within 30 ° C. until the surface temperature of the resin sheet is cut by the cutting step. The purpose is to provide.

  The resin sheet produced by extrusion molding is gradually cooled in the conveying process after being peeled off from the peeling roller. However, in the uneven thickness resin sheet, since the thickness of the resin sheet is distributed, the resin sheet is thick. Compared with, the temperature of the thin part tends to decrease. Therefore, a temperature difference occurs in the width direction of the resin sheet, and the warp occurs in the resin sheet due to this temperature difference.

  According to claim 1, the temperature of the resin sheet peeled from the peeling roller is set to a temperature equal to or higher than Tg, and further, the temperature of the thinnest portion is set by a heating device before the temperature of the thickest portion of the resin film becomes Tg or lower. It is higher than the temperature of the thickest part. Therefore, in the cooling by air cooling, the thinnest part and the thickest part, the thinnest part has a faster cooling because the cooling is faster, but in the present invention, the thinnest part by the heating device in the transport process Therefore, the temperature difference can be prevented from spreading even in the subsequent air cooling.

  Furthermore, since the temperature difference in the width direction of the resin sheet until it is cut in the cutting step is maintained within 30 ° C., warping due to the temperature difference can be prevented.

  A second aspect of the present invention is characterized in that, in the first aspect, a ratio (Va / Vb) between a peripheral speed Va of the outermost diameter of the take-up roller and a peripheral speed Vb of the mold roller is 0.98 or more and 1.02 or less. To do.

  According to the present invention, since the occurrence of warpage is suppressed by controlling the temperature, the occurrence of warpage can be suppressed without applying tension to the resin sheet. By setting the peripheral speed ratio between the take-up roller and the mold roller in the above range, the resin sheet can be manufactured without residual distortion remaining in the resin sheet.

  A third aspect is characterized in that, in the first or second aspect, the heating device is a far infrared heater.

  According to the third aspect, since the far infrared heater is used for the heating device, the resin sheet can be efficiently heated.

  A fourth aspect of the present invention is the method according to any one of the first to third aspects, further comprising an annealing process step of performing an annealing process at a temperature of (Tg-40) ° C. or higher and (Tg-10) ° C. or lower after the cutting step. .

  According to claim 4, by performing the annealing treatment at the above temperature, it is possible to further remove residual strain in a short time, and to suppress the occurrence of warpage over time and the occurrence of warpage during secondary processing. Can do.

  A fifth aspect of the present invention is characterized in that in any one of the first to fourth aspects, the annealing treatment step is performed by supporting the resin sheet with a planar support member.

  According to claim 5, at the time of 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 sixth aspect of the present invention is characterized in that, in any one of the first to fifth aspects, the difference in thickness between the thickest portion and the thinnest portion of the thickness distribution in the width direction of the resin sheet is 0.5 mm to 5 mm.

  According to the sixth aspect, since the temperature adjustment of the resin sheet can be easily performed by setting the difference between the thickest portion and the thinnest portion of the thickness distribution in the above range, the occurrence of warpage of the resin sheet is prevented. be able to.

  A seventh aspect is characterized in that, in any one of the first to sixth aspects, the thickness distribution in the width direction of the resin sheet has a periodicity with a pitch of 200 mm or more.

  According to claim 7, when the thickness distribution in the width direction of the resin sheet has periodicity, the occurrence of warpage can be suppressed by controlling the temperature of the seam of the periodic shape, thereby producing the resin sheet. It can be carried out.

  According to the method for producing a resin sheet of the present invention, the thinnest resin sheet having a thickness distribution in the resin sheet is heated by heating and cooling the thinnest part of the resin sheet which is easily cooled after being peeled off from the peeling roller. Also in manufacture, since the temperature difference can be reduced between the thinnest part and the thickest part of the resin sheet, it is possible to manufacture a resin sheet in which the occurrence of warpage is suppressed.

  Hereinafter, preferred embodiments of a method for producing a 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 resin sheet manufacturing method 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 (band), and extrusion. Sheet forming step 114 for cooling and solidifying the molten resin sheet 14a while forming, a peeling step 115 for peeling the resin sheet 14, and a transporting step for transporting the peeled resin sheet 14 to the cutting step 124 which is the next step 116, a cutting process 124 for cutting the resin sheet 14 into a predetermined size (length / width), and an annealing process 126 for gradually cooling the resin sheet 14 to remove residual strain.

  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. Since an uneven thickness resin sheet has a thickness distribution in the width direction of the film, when it is cooled by air cooling, the temperature of the thin part of the resin film tends to decrease, and the temperature of the thick part is difficult to decrease. There is a temperature difference in the direction. Therefore, if the resin film is cut while a temperature difference is generated, the resin film is warped. Therefore, in the present invention, the temperature of the resin sheet is adjusted using a heating device in the sheet forming step.

  The transporting process 116 is a process of transporting the resin sheet 14 peeled from the peeling roller 20 to the cutting process 124. Since an uneven thickness resin sheet has a thickness distribution in the width direction of the film, when it is cooled by air cooling, the temperature of the thin part of the resin film tends to decrease, and the temperature of the thick part is difficult to decrease. There is a temperature difference in the direction. Therefore, if the resin film is cut while a temperature difference is generated, the resin film is warped. Therefore, in the present invention, the temperature of the resin sheet is adjusted using a heating device in the transporting process from the peeling process to the cutting process.

  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 sheet resin sheet 14 is conveyed to the next processing by a conveyor belt 196 driven by a roller 194 and is not displaced during traveling by the drum-shaped member 192 from the width direction of the resin sheet 14. Is held down.

  Next, among the above steps, details of the sheet forming step 114 to the conveying step 116 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 preferably such that the thickness difference between the thickest part and the thinnest part of the resin sheet is 0.5 mm or more and 5 mm or less, more preferably 0. More preferably, it is 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 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.

  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 the mold roller 16), a configuration employing a crown shape (middle and high shape), and rigidity of the central portion in the axial direction of the roller It is possible to adopt a configuration of a roller having a strength distribution that increases the size of the roller, a configuration combining these, and the like.

  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. The temperature distribution can be made uniform by heating the thin part of the resin sheet having a temperature lower than that of the thick part with the heating device. As shown in FIG. 3, the heating device 22 is installed in the vicinity of the mold roll, in the vicinity of the peeling roll, 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.

  The heating temperature by the heating device is equal to or higher than Tg ° C. when the surface temperature of the resin sheet 14 that is not in contact with the peeling roller immediately after the resin sheet 14 is peeled from the peeling roller 20 is Tg as the glass transition temperature of the resin. It is preferable to set it as Tg + 80) degrees C or less. When the temperature is Tg ° C. or lower, the resin sheet starts to be cooled and solidified, so that the resin sheet is warped. Conversely, when the temperature is set to (Tg + 80) ° C. or higher, the resin sheet 14 is deformed by heat, which is not preferable. The preferable range of the temperature of the resin sheet after the peeling step is Tg ° C. or higher and (Tg + 60) ° C. or lower, more preferably Tg ° C. or higher and (Tg + 40) ° C. or lower.

  After the resin sheet 14 is peeled off from the peeling roller 20, the heating is performed by the heating device 22 c from the lower surface side (the surface side without the mold) of the resin sheet 14 before the surface temperature of the resin sheet becomes Tg or less. 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 may be deformed by subsequent thermal contraction, and a resin sheet having a desired shape may not be obtained. Therefore, when 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 14.

  The heating is performed on the thin part of the resin sheet. Specifically, when the thickness of the resin sheet thickest part in the product width is Dmax and the thickness of the thinnest part is Dmin, the thickness t of the sheet is t = It is preferable to heat a portion satisfying Dmin + (Dmax−Dmin) / 3. If the cross-sectional shape of the resin sheet 14 is the shape as shown in FIG. 4A, at least the thin portions at both ends within the above range are heated, and if the cross-sectional shape is as shown in FIG. However, it is preferable to heat the thin portion at the center, but the range to be heated varies depending on the sheet shape and molding conditions, so that it is preferable to optimize appropriately.

  Heating is performed until the surface temperature of the thinnest part on the heating surface side becomes higher, and the temperature difference between the surface temperature of the thinnest part on the heating surface side and the surface temperature of the thickest part is 30. It is preferable that the temperature be within 20 ° C., preferably within 20 ° C., more preferably within 10 ° C. By setting it as the said temperature range, since a temperature difference can be made small between the thickest part and the thinnest part of the resin sheet 14, generation | occurrence | production of curvature can be suppressed. In addition, by heating until the surface temperature of the thinnest part becomes higher than the surface temperature of the thickest part, the thinnest part of the resin sheet is more easily cooled by the subsequent air cooling. By making the surface temperature of the thinnest part higher than the surface temperature of the thickest part, the temperature control of the resin film can be easily performed.

  After the surface temperature of the resin sheet becomes equal to or lower than Tg, the temperature is adjusted so that the surface temperature distribution in the width direction in the product width of the resin sheet is within 30 ° C, preferably within 20 ° C, more preferably within 10 ° C. Heat the thin thin part. In FIG. 3, the heating devices 22 c and 22 d are used from the upper surface side of the resin sheet 14, but the heating device can be positioned from the lower surface side of the resin sheet 14. Moreover, if the surface temperature distribution is also within the above range, a resin sheet that suppresses the occurrence of warping can be produced regardless of whether the temperature of the thickest part or the thinnest part of the resin sheet 14 is high.

  Further, in the conveying step 116, increasing the peripheral speed of the take-up roller 24 has an effect of suppressing tension of the resin sheet 14 being conveyed and suppressing the warpage of the resin sheet 14, but residual distortion occurs. . In the present invention, since the warpage of the resin sheet is prevented by temperature control in the transport process, the peripheral speed of the take-up roller 24 can be increased and the occurrence of warpage can be suppressed without applying tension. Specifically, the ratio Va / Vb of the peripheral speed Va of the outermost diameter of the take-up roller 24 and the peripheral speed Vb of the outermost diameter of the mold roll is preferably 0.98 or more and 1.02 or less, and 0.99 More preferably, it is 1.01 or less.

  The resin sheet 14 is preferably subjected to an annealing process 126 after the cutting process 124. In the annealing treatment, the resin sheet is placed on a flat surface with the resin sheet below the flat side, and heat treatment is performed to correct the deformation and warpage of the resin sheet using its own weight and to remove residual strain. It is a process. Since the flatness of the flat support member 198 that supports the resin sheet is reflected in the flatness of the resin sheet after the annealing treatment, it is preferably 0.5 mm or less in the region where the resin sheet is supported. More preferably, it is 3 mm or less. The support member is not limited to a flat plate, and may have an opening as long as it is planar, such as a lattice plate or a punching metal. As a material of the support member, a material having high heat resistance such as a fluororesin-impregnated fiber can be used in addition to a metal such as stainless steel or iron. The annealing temperature is preferably (Tg−40) ° C. or more and (Tg−10) ° C. or less, and the humidity is preferably dry. After the heat treatment, it is preferably slowly cooled at a rate of 5 ° C./min or less, more preferably slowly cooled at a rate of 2 ° C./min or less. The heating means can be performed by hot air heating or far infrared heating.

  Next, a method for measuring warpage will be described. As shown in FIG. 5, when the back surface (flat surface side) of the resin sheet 14 is placed on the upper surface of the flat measurement base 26, the maximum distance H between the resin sheet 14 and the measurement base 26 is called a warp amount. . The maximum distance H can be measured with a laser displacement meter.

  The features of the present invention will be specifically described below with reference to examples and comparative examples. In the following examples, materials, processing contents, processing procedures, and the like can be appropriately changed without departing from the gist of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

[Example 1]
The resin sheet was manufactured using the apparatus shown in FIG.

  PMMA (manufactured by Asahi Kasei Co., Ltd., 80NH, glass transition temperature 110 ° C.) is extruded from a T die set at a temperature of 255 ° C., formed into a sheet through a nip roll, a mold roll having a shape as shown in FIG. Both ends of the resin sheet were cut to obtain a resin sheet having a width of 594 mm, a thinnest part of 2.0 mm, and a thickest part of 3.8 mm as shown in FIG.

  In the extrusion process, the lip width of the die is 660 mm, the lip opening (lip clearance) is 4 mm, and the flow rate distribution in the width direction is substantially proportional to the clearance amount between the nip roll and the mold roll at each position. Adjusted with chalk bar.

  In the sheet forming process, the surface temperature of the nip roll, the mold roll, and the release roll are 70 ° C., 75 ° C., and 80 ° C., respectively, the roll diameter of the nip roll is φ350 mm, the roll diameter of the release roll is φ500 mm, and the thick roll forming part of the mold roll The roll diameter was 345.6 mm, the roll diameter of the thin-wall forming part was 349.4 mm, and the roll diameter (outermost diameter) of the resin sheet and the non-contact part was 350 mm. The clearance between the nip roll and the mold roll is 3.90 mm at the maximum part in the center of the roll and 1.70 mm at the minimum part at the end of the roll, and the clearance between the mold roll and the peeling roll is 4.00 mm at the maximum part in the center of the roll. The minimum end portion was 1.80 mm. The peripheral speeds (outermost diameters) of the nip roll, mold roll, release roll, and take-up roll were 1.205 m / min, 1.209 m / min, 1.230 m / min, and 1.207 m / min, respectively. The ratio Va / Vb between the outer peripheral diameter Va of the take-up roll and the outer peripheral diameter Vb of the mold roll was 0.998. The nip roll, the mold roll, and the release roll are subjected to hard chrome plating, and the surface material of the take-up roll is EPT rubber.

  As shown in FIG. 3, the resin sheet is produced by installing a far-infrared ceramic heater at a position 50 mm away from the resin sheet surface on the side opposite to the surface in contact with the mold roll and the release roll, A range of 150 mm was heated from both ends of the sheet. At this time, the surface temperature of the far-infrared ceramic heater was 500 ° C., and it was heated for 20 seconds during contact with the mold roll and for 15 seconds during contact with the peeling roll.

  Also in the transport process, a far infrared ceramic heater is installed at a position 120 mm from the peeling roll and 50 mm away from the resin sheet on the lower surface side, the heater surface temperature is set to 500 ° C., and the resin is positioned at 470 mm and 730 mm from the peeling roll. A far-infrared ceramic heater was installed at a position 50 mm away from the sheet on the upper surface side, the surface temperature of the heater was set to 400 ° C., and a range of 150 mm from each end of the sheet was heated for 20 seconds.

  The resin sheet is cut in the width direction with a cutting machine to obtain a sheet of 1050 mm, and then both end portions (both ears) in the width direction of the resin sheet are formed into a resin sheet of a desired size so that the width becomes 594 mm. As shown, when the distance from the measurement base 26 was measured with a laser displacement meter on the flat measurement base 26, the maximum value was 3.3 mm.

  The resin sheet is placed in a hot air heating type thermostatic chamber on a flat stainless steel shelf so that the plane side of the resin sheet faces down, and annealed in a dry state at 90 ° C. for 2 hours to 1 ° C. / It was gradually cooled at a rate of min and returned to room temperature. When the deformation amount of the obtained resin sheet was measured again by the method shown in FIG. 5, the maximum value was 0.5 mm.

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 the sheet | seat shaping | molding process of a resin sheet manufacturing apparatus, a peeling process, and a conveyance process. It is sectional drawing which shows an example of the shape of a resin sheet. It is explanatory drawing explaining the measuring method of the curvature of a resin sheet. It is a side view of the type | mold roller used in the Example.

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, 192 ... drum-shaped member, 194 ... roller, 196 ... conveyor belt

Claims (7)

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 picking up and conveying the resin sheet with a take-off roller;
Cutting the resin sheet to a predetermined length by a cutting means,
In the peeling step, when the glass transition temperature of the resin is Tg, the surface temperature of the resin sheet on the side not in contact with the peeling roller immediately after peeling from the peeling roller is Tg or more (Tg + 80) ° C. or less. Yes,
In the conveying step, before the surface temperature of the thickest part of the resin sheet becomes equal to or lower than Tg, the resin sheet is heated with a heating device from the side in contact with the peeling roller, and the width of the resin sheet is increased. The surface temperature of the thinnest part of the thickness distribution is made higher than the surface temperature of the thickest part, and is gradually cooled so that the surface temperature distribution in the width direction of the resin sheet is within 30 ° C. until it is cut by the cutting step. The manufacturing method of the uneven thickness resin sheet characterized by these.   2. The uneven thickness according to claim 1, wherein a ratio (Va / Vb) between a peripheral speed Va of the outermost diameter of the take-up roller and a peripheral speed Vb of the mold roller is 0.98 or more and 1.02 or less. Manufacturing method of resin sheet.   The method for producing an uneven thickness resin sheet according to claim 1 or 2, wherein the heating device is a far infrared heater.   4. The uneven thickness resin according to claim 1, further comprising an annealing treatment step of performing an annealing treatment at a temperature of (Tg−40) ° C. to (Tg−10) ° C. after the cutting step. 5. Sheet manufacturing method.   5. The method for producing 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 uneven thickness resin sheet according to any one of claims 1 to 5, wherein a difference in thickness between the thickest portion and the thinnest portion of the thickness distribution in the width direction of the resin sheet is 0.5 mm or more and 5 mm or less. Manufacturing method.   The thickness distribution in the width direction of the said resin sheet has the periodicity of the pitch of 200 mm or more, The manufacturing method of the uneven thickness resin sheet in any one of Claim 1 to 6 characterized by the above-mentioned.

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