JP2008246865A - Manufacturing method and apparatus for uneven thickness resin sheet - Google Patents

Abstract

Provided is a resin sheet manufacturing method capable of obtaining a desired cross-sectional shape without warping or distortion when a resin sheet having a large thickness distribution in the width direction at the time of molding is manufactured.
An extrusion process 112 for extruding a molten resin from a die 12 into a sheet form, and a molding cooling process for cooling and solidifying the extruded resin sheet 14 by niping it with a mold roller 16 and a nip roller 18 while performing uneven thickness molding. 114 and a slow cooling step 116 for gradually cooling the resin sheet peeled off from the mold roller 16, and in at least one of the molding cooling step 114 and the slow cooling step 116, the temperature distribution in the width direction of the resin sheet 14. It has a temperature control process which controls the temperature of the resin sheet 14 by the heating means or the cooling means 22 so that it may become uniform, It is a manufacturing method and apparatus of the uneven thickness resin sheet characterized by the above-mentioned.
[Selection] Figure 4

Description

  The present invention relates to a method and an apparatus for manufacturing a resin sheet, and in particular, manufactures a flat sheet without warping in an uneven thickness resin sheet having a different thickness in the width direction, such as a light guide plate constituting a backlight of a liquid crystal display device. The present invention relates to a manufacturing method and an apparatus.

  As resin sheets used for various optical elements, Fresnel lenses, lenticular lenses, and the like are used in various fields. A regular uneven shape is formed on the surface of such a resin sheet, and this uneven shape exhibits optical performance as a Fresnel lens or a lenticular lens. As a method for producing such a resin sheet, various proposals have been made so far (see Patent Documents 1 to 7). In these proposals, the roller molding method is adopted from the viewpoint of improving productivity.

  For example, Patent Document 1 attempts to improve transferability by devising the cooling means until the resin sheet is peeled from the roller. Patent Document 2 discloses a method of manufacturing a Fresnel lens by winding a die around a roller. In Patent Document 3, a heat buffer member is arranged inside the forming roller to improve productivity and transferability. Patent Document 4 uses a corona discharge treatment to improve transferability and reduce defects.

  Further, Patent Documents 5 to 7 heat or cool both end portions and the central portion of the resin sheet after being extruded from a die in order to reduce the distortion of the resin sheet and realize a highly accurate plate thickness. An attempt is made to produce a resin sheet with excellent plate thickness accuracy.

A typical roller forming system of these prior arts has a configuration shown in FIG. This apparatus configuration includes a sheet die 102 for shaping a resin sheet 101 melted by an extruder (not shown) into a sheet shape, a stamper roller 103 having a concavo-convex shape formed on the surface, and a stamper roller 103. And a peeling mirror roller 105 disposed opposite to the mirror roller 104 and opposed to the stamper roller 103. Then, the sheet-like resin sheet 101 extruded from the die 102 is pressed between the stamper roller 103 and the mirror roller 104, and the uneven shape on the surface of the stamper roller 103 is transferred to the resin sheet 101, and the resin sheet 101 is peeled off by the mirror roller for peeling. It is peeled off from the stamper roller 103 by being wound around 105.
JP-A-8-31025 JP-A-7-314567 JP 2003-53834 A JP-A-8-287530 JP 2002-120248 A JP 2002-67124 A JP-A-2005-349600

  However, all of the methods described in the above-mentioned patent documents relate to a method for producing a resin sheet having a uniform thickness in the width direction, such as a resin sheet of a light guide plate constituting a backlight of a liquid crystal display device. Even if a conventional method is applied to manufacture an uneven thickness resin sheet having a large thickness distribution in the width direction during molding (even if it is uneven), it is difficult to manufacture the uneven thickness resin sheet due to warping and distortion.

  For example, when roller molding is performed after extruding PMMA (polymethyl methacrylate resin), a thickness distribution is given in the width direction, and the difference in thickness between the thickest part and the thinnest part is set to 0.5 mm or more. In this case, irregularities (shrunk due to shrinkage during curing of the resin, elastic recovery amount distribution) occur on the front or back surface, the surface shape transfer rate decreases overall, and molding does not work well, or the sharp edge shape is transferred There were various problems that could not be done. In particular, when there is a large thickness difference (uneven thickness) in the width direction, the temperature of the resin film immediately after being extruded from the die into a sheet can be controlled uniformly in the width direction. However, when cooling is gradually performed from the roll surface or the outside air contact surface, the temperature drop in the thick part is slower than the temperature drop in the thin part, and a temperature distribution is generated in the width direction. As a matter of course, due to the difference in shrinkage, it is inevitable that the sheet is warped or distorted as a result. For this reason, an attempt to reduce warpage and distortion by cooling slowly or pulling as a whole can be considered, but it has been extremely difficult to obtain a highly accurate uneven shape.

  The present invention has been made in view of such circumstances, and when producing an uneven thickness resin sheet having a large thickness distribution in the width direction during molding, obtaining a desired cross-sectional shape without warping or distortion. In particular, it is an object of the present invention to provide a method for producing 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.

  According to a first aspect of the present invention, in order to achieve the above object, an extrusion step of extruding a molten resin from a die into a sheet shape, and cooling while forming an uneven thickness by niping the extruded resin sheet with a mold roller and a nip roller A method of producing an uneven thickness resin sheet having a biased sheet thickness in the resin sheet width direction, comprising: a molding cooling step for solidifying and a slow cooling step for gradually cooling the resin sheet peeled from the mold roller. In addition, at least one of the molding cooling step and the slow cooling step has a temperature control step of controlling the temperature of the resin sheet by a heating means or a cooling means so that the temperature distribution in the width direction of the resin sheet is uniform. The manufacturing method of the uneven thickness resin sheet characterized by this is provided.

  According to the first aspect, in the method of manufacturing the uneven thickness resin sheet, the manufacturing is performed so that the temperature distribution in the width direction of the resin sheet is uniform. Therefore, since the temperature distribution in the width direction is eliminated, it is possible to obtain a desired sheet shape that suppresses deformation such as distortion and warpage. In addition, the present invention relates to a method for manufacturing an uneven thickness resin sheet. When the resin sheet is cooled and molded, the portion with a thick resin film is slow to cool and the thin portion is fast to cool. Therefore, in the temperature control step, more precise temperature control is possible by arranging the cooling means in the thick resin film portion and the heating means in the thin resin film portion. In addition, when only the heating means is used, the cooling rate of the thin part is fast, so the temperature control of the thin part can be controlled by increasing the temperature setting of the heating means and the thin part by decreasing the temperature setting. Become.

  According to a second aspect of the present invention, in order to achieve the above object, an extrusion step of extruding a molten resin from a die into a sheet shape, and cooling while performing uneven thickness molding by niping the extruded resin sheet with a mold roller and a nip roller A method of producing an uneven thickness resin sheet having a biased sheet thickness in the resin sheet width direction, comprising: a molding cooling step for solidifying and a slow cooling step for gradually cooling the resin sheet peeled from the mold roller. The temperature control step of controlling the temperature of the resin sheet by heating means or cooling means while maintaining a predetermined temperature distribution in the width direction of the resin sheet in at least one of the molding cooling step and the slow cooling step The manufacturing method of the uneven thickness resin sheet characterized by having is provided.

  In order for the final product to be molded without distortion or warpage, depending on the uneven thickness of the final product, it may not always be a condition that the temperature distribution in the width direction of the resin sheet be uniform. For example, when the temperature distribution of the resin sheet when peeled from the roller has a specific distribution, the resin sheet may be molded without distortion or warping. In this case, it is necessary to control the specific temperature distribution.

  According to claim 2 of the present invention, in the method for manufacturing the uneven thickness resin sheet, the manufacturing is performed so that the temperature distribution in the width direction of the resin sheet becomes a predetermined temperature distribution. Even if the temperature distribution in the width direction of the resin sheet is made uniform, distortion and warping may be formed depending on the shape. According to the second aspect, since it is possible to form with a temperature distribution in which distortion and warpage are not formed, it is possible to deal with sheets having various shapes.

  A third aspect of the present invention is characterized in that, in the first or second aspect, the temperature control step detects a temperature distribution in the width direction of the resin sheet with a sensor and performs temperature control in the width direction based on the value.

  According to the third aspect, the temperature distribution of the resin sheet is detected by the sensor, and the temperature is controlled so that the temperature distribution in the width direction of the resin film becomes a predetermined temperature distribution. Therefore, more accurate temperature control is possible. Further, the temperature control at this time is preferably automatic control.

  A fourth aspect of the present invention according to the third aspect is characterized in that in the temperature control step, a plurality of the sensors and the heating means or the cooling means are installed in the width direction of the resin sheet.

  According to the fourth aspect, since a plurality of sensors and heating means or cooling means are provided in the width direction of the resin sheet, more precise temperature control is possible.

  A fifth aspect of the present invention according to the fourth aspect is characterized in that the position of the sensor and the heating means or the cooling means can be changed in the width direction in accordance with the cross-sectional shape of the final product.

  According to the fifth aspect, since the positions of the sensor and the heating means or the cooling means can be changed, it is possible to deal with end products having various cross-sectional shapes.

  A sixth aspect of the present invention includes the sensor and the heating means or the cooling means according to any one of the first to fifth aspects, comprising: a peeling roller for peeling the resin sheet from the mold roller; and a slow cooling zone for performing the cooling step. Is installed at two or more locations selected from the mold roller portion, the peeling roller portion, and the slow cooling zone.

  According to the sixth aspect, since the sensor and the heating means or the cooling means are installed in at least two or more steps of each manufacturing process, the temperature can be controlled in a plurality of steps, and high-precision temperature control, that is, shape control. Is possible.

  A seventh aspect of the present invention provides the resin sheet according to any one of the first to sixth aspects, wherein the thickness difference between the thickest portion and the thinnest portion in the width direction is 0.5 mm. It is characterized by the above.

  An eighth aspect is characterized in that in the first to seventh aspects, the thickness of the thinnest portion of the resin sheet is 5 mm or less.

  Claims 7 and 8 define the thickness of the resin sheet produced by the production method of the present invention. According to the manufacturing method of the present invention, since the temperature of the resin sheet can be controlled, even in a resin sheet having a large difference between the thickest part and the thinnest part, or even in a thick resin sheet, distortion and A resin sheet in which molding such as warpage is suppressed can be formed. As described above, the effect of the present invention can be exhibited in the molding of a resin sheet having a cross-sectional shape that has been difficult to mold.

  A ninth aspect of the present invention is characterized in that, in the first to eighth aspects, the temperature control step heats or cools both surfaces of the resin sheet.

  According to the ninth aspect, since heating or cooling is performed from both sides of the resin sheet, even when the film thickness of the resin sheet is thick, uniform temperature control in the depth direction of the resin sheet is possible.

  A tenth aspect according to the first to ninth aspects is characterized in that the resin sheet includes diffusion particles.

  According to the tenth aspect, since the diffusing particles are included in the resin sheet, the light propagating through the resin film is diffused. Therefore, the uniformity of the light source light emitted from the resin film can be improved.

  According to claim 11 of the present invention, in order to achieve the above object, an extrusion means for extruding molten resin from a die into a sheet shape, and cooling while forming the uneven thickness by niping the extruded resin sheet with a mold roller and a nip roller An apparatus for producing an uneven thickness resin sheet having a biased sheet thickness in the width direction of the resin sheet, and a cooling means for gradually cooling the resin sheet peeled off from the mold roller. In addition, at least one of the molding cooling unit and the slow cooling unit includes a temperature control unit that controls the temperature using a heating unit or a cooling unit so that the temperature distribution in the width direction of the resin sheet is uniform. An apparatus for manufacturing an uneven thickness resin sheet is provided.

  According to a twelfth aspect of the present invention, in order to achieve the above object, an extruding means for extruding the molten resin from the die into a sheet shape, and cooling the extruding resin sheet by niping it with a mold roller and a nip roller and forming the uneven thickness An apparatus for producing an uneven thickness resin sheet having a biased sheet thickness in the width direction of the resin sheet, and a cooling means for gradually cooling the resin sheet peeled off from the mold roller. In addition, at least one of the molding cooling unit and the slow cooling unit includes a temperature control unit that controls the temperature using a heating unit or a cooling unit so that the temperature distribution in the width direction of the resin sheet maintains a predetermined temperature distribution. An apparatus for manufacturing an uneven thickness resin sheet is provided.

  Claims 11 and 12 constitute the present invention as an apparatus.

  According to the present invention, when a resin sheet having a large thickness distribution in the width direction is produced, the temperature distribution in the width direction of the resin sheet is made uniform or a predetermined temperature distribution, such as distortion and warping. No desired cross-sectional shape can be obtained. And these resin sheets can be used suitably for a light-guide plate and various optical elements. In addition, since the temperature can be detected using a sensor and feedback control can be performed, fluctuations or variations in the extrusion or atmosphere can be corrected and manufacturing can be performed under a constant temperature condition. Therefore, the uneven thickness resin sheet can be manufactured under stable temperature conditions.

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

  FIG. 1 is an overall process diagram of a method for manufacturing an uneven thickness resin sheet according to the present invention, and FIG. 2 shows 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 and an extrusion process 112 for continuously extruding molten resin into a sheet (band). A molding cooling step 114 in which the extruded resin sheet 14 is cooled and solidified while being unevenly formed, a slow cooling step 116 in which the solidified resin sheet 14 is gradually cooled, and a predetermined standard for warping of the slowly cooled resin sheet 14 A warpage inspection step 118 for measuring pass / fail for the resin, a control step 120 for controlling the temperature distribution in the resin sheet width direction by feeding back to the molding cooling step 114 and the slow cooling step 116 when the warpage exceeds a predetermined standard, and a resin A laminating process 122 for laminating a film for protecting the surface on the front and back surfaces of the sheet 14, and the resin sheet 14 is cut into a predetermined size (length / width). That consists of a cut and cutting step 124, the loading step 126 of stacked cut resin sheet 14 Court.

  As shown in FIG. 2, in the raw material process 100, the raw material resin and additive sent from the raw material silo 128 (or raw material tank) and the additive silo 130 (or additive tank) to the automatic weighing machine 132 are automatically measured, In the mixer 134, the raw material resin and the additive are mixed at a predetermined ratio. When adding diffusing particles as an additive to the raw material resin, a master pellet in which the diffusing particles are added to the raw material resin at a concentration higher than a predetermined concentration is manufactured using a granulator (not shown). A master batch method in which the base pellets not added are mixed at a predetermined ratio by the mixer 134 can be suitably employed. The same applies when additives other than the diffusion 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 and 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 resin sheet 14 extruded from the die 12 into a sheet shape is then sent to the molding cooling step 114.

  In the molding cooling step 114, the resin sheet 14 extruded from the die 12 is nipped between the mold roller 16 and the nip roller 18 and cooled and solidified while being formed with uneven thickness molding, and the solidified resin sheet 14 is peeled off by the peeling roller 20. To do.

  The resin sheet 14 that has undergone the molding cooling step 114 is then sent to the slow cooling step 116.

  The slow cooling step (or annealing step) 116 is provided in order to prevent a rapid temperature change of the resin sheet 14 downstream of the peeling roller 20. 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. 14 surface shape deteriorates. Further, a temperature difference is generated between the front and back surfaces of the resin sheet 14, and the resin sheet 14 is easily warped. In particular, warping is likely to occur when there is a thickness distribution in the resin sheet width direction, such as an uneven thickness resin sheet.

  The resin sheet 14 cooled in the slow cooling step 116 is taken up by a nip type feed roller 76 and sent to a warp inspection step 118.

  In the warp inspection step 118, the warp measuring device 78 measures the pass / fail of the warp of the resin sheet 14 with respect to a predetermined standard. Here, the warp will be described using an example of the bowl-shaped resin sheet 14. As shown in FIG. 3, the back surface (flat surface side) of the resin sheet 14 cut out to a length of 600 mm and a width of 1100 mm is the upper surface of the flat measurement base 80. The maximum distance H between the resin sheet 14 and the measurement base surface 80 is referred to as a warp amount. Since the predetermined reference (standard value) of the warpage amount is set according to the use of the resin sheet 14 and the user side standard, the warpage measuring device 78 measures the pass / fail with respect to the predetermined reference. As the warpage measuring device 78, for example, the surface (outer periphery) of the uneven thickness resin sheet after the slow cooling zone 36 is scanned with an electrostatic sensor or the like, and the distance (shape) between the uneven thickness resin sheet and the electrostatic sensor is measured. Thus, a method of converting the warpage amount can be suitably used.

  When the amount of warpage measured by the warpage measuring device 78 exceeds a predetermined reference, the temperature distribution in the resin sheet width direction is controlled by feeding back to the molding cooling step 114 and the slow cooling step 116. The temperature control will be described later.

  Downstream of the warp inspection step 118, a laminating step 122, a cutting / cutting step 124, and a stacking step 126 including a stocker 79 are sequentially provided. Among them, the laminating step 122 is a step of attaching a protective film (a film such as polyethylene) to the front and back surfaces of the resin sheet 14 so that the protective film 84 rewound from the pair of reels 82 sandwiches the resin sheet 14. They are merged and laminated by passing through a nip roller 86.

  The cutting / cutting step 124 is a step of cutting both end portions (ear portions) in the width direction of the resin sheet 14 and cutting the resin sheet 14 to a predetermined length. As the cutting machine 88, as shown in FIG. 2, a guillotine type cutting machine comprising a receiving blade 88A and a pressing blade 88B can be suitably used, but is not limited thereto. Further, as the cutting machine 90, as shown in FIG. 2, a laser cutter or an electron beam cutting can be preferably used, but the cutting machine 90 is not limited to this.

  Next, among the above steps, the details of the molding cooling step 114 and the slow cooling step 116 that characterize the present invention and the temperature control performed in the molding cooling step 114 and the slow cooling step 116 will be described with reference to FIGS. Explain in detail.

[Molding cooling step to slow cooling step]
The uneven thickness 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. The nip roller 18 disposed oppositely, the peeling roller 20 disposed opposite to the mold roller 16, heating means or cooling means 22, 24, 26, 28, 29, and a slow cooling zone 36 are configured. And the heating means or cooling means 22, 24, 26, 28, 29 are controlled by the temperature detected by the sensors 30, 32, 33, 34, 35, and the temperature distribution in the width direction of the resin sheet 14 is uniform, or A predetermined temperature distribution can be obtained.

  On the surface of the mold roller 16, for example, an inverted shape for forming an uneven thickness resin sheet shown in FIGS. 5A to 5C is formed. FIG. 5 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 molded resin sheet 14 shown in FIGS. 5A to 5C may be formed on the surface of the mold roller 16. In addition, the detail of the uneven thickness shape of the resin sheet 14 surface is mentioned later.

  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. For example, 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. In addition, other known processing methods (grinding processing, ultrasonic processing, electric discharge processing, etc.) can also 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 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, etc. 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.

  As the slow cooling zone 36, a horizontal tunnel shape as shown in FIG. 4, a temperature adjusting means provided inside the tunnel, and a cooling temperature profile of the resin sheet 14 can be controlled can be adopted. 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 heating means (nichrome wire heater, infrared heater, dielectric heating means, etc.) Various known means such as a structure for heating the front and back surfaces of the sheet 14 can be employed. The temperature adjusting means controls the cooling temperature profile of the entire resin sheet 14, and the temperature controlling means described below is a means for controlling the temperature distribution in the width direction of the resin film and having a different purpose. .

[Temperature control means]
The uneven thickness resin sheet manufacturing apparatus of the present invention mainly includes heating means or cooling means 22, 24, 26, 28, 29 for heating and cooling the resin sheet 14, and the temperature in the width direction of the resin sheet 14. A temperature control means for controlling the distribution is provided. By this temperature control means, the temperature can be controlled so that the temperature distribution in the width direction of the resin sheet 14 is uniform, and the resin sheet 14 having a desired shape can be manufactured. Depending on the shape, it may be preferable to have a specific temperature distribution in the width direction of the resin sheet 14 in order to form a sheet in which distortion and warpage are suppressed. In this case, control is performed so that the temperature distribution is obtained. In the following description, the heating means is used as an example. However, this can be replaced with a cooling means, and the heating means and the cooling means can be used simultaneously.

  Moreover, it is preferable that the temperature control means includes sensors 30, 32, 33, 34, and 35 corresponding to the heating means. In FIG. 4, the sensor 30 for the heating unit 22, the sensor 32 for the heating unit 24, the sensor 33 for the heating unit 26, the sensor 34 for the heating unit 28, and the heating unit 29. Is provided with a sensor 35. The temperature can be controlled by detecting the temperature by this sensor and obtaining an appropriate PID value for feedback control to the heating means or the cooling means. This can be performed by a known method such as a method of giving an impulse and determining from the response.

  The sensor and heating means or cooling means used in the present invention are not particularly limited as long as they do not contact the resin sheet, and conventionally known ones can be used. A non-contact radiation thermometer is preferably used as the sensor, and an infrared heater or a spot cooler is preferably used as the heating means or the cooling means. However, in order to control the temperature in the width direction with high accuracy, it is preferable that the heating / cooling effect is achieved with a spot.

  FIG. 6 is a view of the mold roller 16 portion of the production line 10 for uneven thickness resin sheet as viewed from below, and shows an arrangement example of the heating means 22 and the sensor 30. As shown in FIG. 6, it is preferable to provide a plurality of heating means 22 and sensors 30 in the width direction of the resin sheet 14. Highly accurate control is possible by disposing a plurality of heating means 22 in the width direction. However, if the heating means at a certain position can heat a wide area, the overall control becomes difficult in relation to the adjacent heating means, so the number of heating means, the distance between the heating means, It is preferable to set.

  About a sensor, it is possible to arrange | position and arrange sensors, and it is also possible to install more than a heating means. By increasing the number of sensors, more accurate temperature control is possible. Moreover, if a sensor with quick response is used, the temperature can be detected by scanning the sensor in the width direction of the resin sheet, and the number of sensors can be minimized. In FIG. 6, the number of sensors and heating means is the same, but is not particularly limited, and the number of sensors can be increased or decreased as compared with the heating means.

  In addition, about the number of a heating means and a sensor, although the example arrange | positioned at the type | mold roller 16 using FIG. 6 was demonstrated, it can arrange | position similarly about another location.

  Moreover, it is preferable that the position of the sensor and the heating means can be changed in the width direction. Specifically, it is preferable that the position of the sensor and the heating means can be moved to the thickest part or the thinnest part of the uneven thickness resin sheet. By making it movable, it becomes possible to control the temperature in accordance with the shape of the final product, and the shape can be controlled with higher accuracy.

  The positions of the sensor and the heating means are preferably arranged in the mold roller 16, the peeling roller 20, or the slow cooling zone 36, and are preferably installed in two or more places. As the number of positions is increased, more accurate temperature control is possible. However, it is preferable to make an appropriate determination in consideration of the manufacturing cost of the apparatus and the installation space.

  The sensor and the heating means are preferably provided on the front surface side and the back surface side of the resin sheet 14. By heating from the front side and the back side of the resin sheet 14, even in the manufacture of thick resin sheets with a large film thickness, a uniform temperature distribution can be formed in the depth direction of the resin sheet 14. Accurate temperature control is possible, and it can be formed into a desired shape. In FIG. 4, only one side of the resin sheet can be arranged on the mold roller portion, but the slow cooling zone 36 is arranged on both sides of the resin sheet 14. In addition, the peeling roller portion cannot be disposed on the back side of the resin sheet 14, but can be dealt with by heating the peeling roller 20.

  In the present invention, the “surface side of the resin sheet” refers to the surface on which the uneven shape is formed by the mold roller 16, and the “back surface side of the resin sheet” refers to the side pressed by the nip roller 18. I mean.

  The mold roller 16 and the nip roller 18 can also be provided with temperature adjusting means. The roller set temperatures of the mold roller 16 and the nip roller 18 are the material of the resin sheet 14, the temperature when the resin sheet 14 is melted (for example, the slit exit of the die 12), the conveyance speed of the resin sheet 14, the outer diameter of the mold roller 16, An optimum value can be selected depending on the concave / convex pattern shape of the mold roller 16 or the like.

  As the temperature adjusting means of the mold roller 16 and the nip roller 18, a configuration in which the temperature-controlled oil is circulated inside the rollers can be preferably employed. This supply and discharge of oil can be realized by a configuration in which a rotary joint is provided at the end of the roller. As other temperature adjusting means, various known means such as a structure in which a sheath heater is embedded in the roller and a structure in which a dielectric heating means is disposed in the vicinity of the roller can be employed. By providing such a temperature adjusting means, it is possible to suppress the temperature rise and rapid temperature drop of the mold roller 16 and the nip roller 18 due to the high-temperature resin sheet 14.

  Further, the uneven thickness resin sheet production line 10 may be provided with a warpage measuring device for measuring the amount of warpage as described above. For example, the surface (outer periphery) of the uneven thickness resin sheet after the slow cooling zone 36 is scanned with an electrostatic sensor or the like, the distance (shape) between the uneven thickness resin sheet and the electrostatic sensor is measured, and the amount of warpage is converted. . By feeding back this numerical value, it is possible to obtain a more optimal shape.

[Method of manufacturing uneven thickness resin sheet]
Next, a resin sheet manufacturing method using the resin sheet manufacturing line 10 shown in FIG. 4 will be described.

  As the resin sheet 14 applied to the present invention, a thermoplastic resin can be used. For example, polymethyl methacrylate resin (PMMA), polycarbonate resin, polystyrene resin, MS resin, AS resin, polypropylene resin, polyethylene resin, polyethylene Examples include terephthalate resins, polyvinyl chloride resins (PVC), thermoplastic elastomers, copolymers thereof, and cycloolefin polymers.

  Further, it is possible to include diffusing particles in the resin sheet. By adding diffusing particles, it can be suitably used for a light guide plate and various optical elements arranged on the back surface of various display devices. Furthermore, by adding diffusion particles, the warpage of the sheet is likely to occur, but according to the manufacturing method of the present invention, the temperature of the resin sheet can be made uniform, so that the sheet can be manufactured with a stable shape. Is possible.

The diffusion particles preferably have a particle diameter of 10 μm or less, and more preferably 1 μm or less. As the kind of the diffusion particles, metal particles, inorganic particles, organic particles, semiconductor particles, polymer particles, and the like can be used. More specifically, silicon dioxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), oxidation Titanium (IV) (TiO ₂ ), yttrium oxide (Y ₂ O ₃ ), magnesium oxide (MgO), zinc oxide (ZnO), carbon (C), silicon (Si), magnesium (Mg), calcium (Ca), Silver (Ag), platinum (Pt), titanium (Ti), nickel (Ni), ruthenium (Ru), rhodium (Rh), gallium arsenide (GaAs), aluminum gallium arsenide (AlGaAs), zirconia (ZrO ₂ ), carbonized silicon (SiC), silicon nitride _{(Si 3 N} 4), zeolite, nano-diamond, nanocrystal, Sukumetaito, mica, Dendori Chromatography, may be mentioned a star polymer, hyperbranched polymers, microporous methyl phosphonic acid aluminum, and the like.

  Moreover, as a density | concentration of the spreading | diffusion particle contained in the particle | grain containing resin sheet manufactured, it is preferable that it is the range of 0.005-0.5 mass%, and is the range of 0.03-0.08 mass%. It is more preferable.

  The sheet-shaped resin sheet 14 extruded from the die 12 is pressed between the mold roller 16 and the nip roller 18 disposed opposite to the mold roller 16, and the uneven-shaped inverted mold on the surface of the mold roller 16 is transferred to the resin sheet 14. Then, the resin sheet 14 is peeled off from the mold roller 16 by being wound around a peeling roller 20 disposed opposite to the mold roller 16.

  The resin sheet 14 peeled from the mold roller 16 is transported in the horizontal direction, gradually cooled by passing through the slow cooling zone 36, and cut into a predetermined length at the downstream product removing portion in a state where distortion is removed. And accommodate as a resin sheet product.

  In the production of this resin sheet, the extrusion speed of the resin sheet 14 from 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% of the set value.

  The pressing pressure of the nip roller 18 against the mold roller 16 is set to 0 to 200 kN / m (kgf / cm) in terms of linear pressure (a value obtained by converting surface contact due to elastic deformation of each nip roller as linear contact). Is more preferable, and 0 to 100 kN / m (kgf / cm) is more preferable.

  The temperature control of the nip roller 18 and the peeling roller 20 is preferably performed for each individual roller. And it is preferable that the resin sheet 14 in the location of the peeling roller 20 is the temperature below the softening point Ta of resin. At this time, when a polymethyl methacrylate resin is employed for the resin sheet 14, the set temperature of the peeling roller 20 can be set to 50 to 110 ° C.

  Next, the uneven pattern shape on the surface of the resin sheet will be described. Fig.5 (a)-(c) is an example of sectional drawing of the state which cut off the end surface of the uneven thickness resin sheet after shaping | molding on the straight line. The back surface of the resin sheet is flat. In the uneven thickness resin sheet produced by the production method and apparatus of the present invention, the thickness of the thinnest portion is preferably 5 mm or less, and more preferably 2 mm or less. Further, the difference in thickness between the thickest part and the thinnest part of the uneven thickness resin sheet is preferably 1 mm or more, and more preferably 2.5 mm or more. By setting it as such a dimension, it can be used conveniently for the light-guide plate and various optical elements which are distribute | arranged to the back surface of various display apparatuses.

  In the case of the shape as described above, after the resin sheet 14 extruded from the die 12 is wound around the mold roller 16 and molded, it is divided into a thick part and a thin part of the resin film. Therefore, the thick part of the resin film has a large heat capacity, so the cooling is slow, while the thin part is fast to cool. And in order to suppress this temperature distribution, as shown in FIG. 4, from the top of the resin sheet 14 wound around the type | mold roll 16, the heating means 22 is arrange | positioned in the width direction like FIG. At the same time, the sensors 30 are arranged downstream in the same manner as the heating means 22. And the output of the temperature of the heating means 22 is controlled so that the temperature of the width direction of the resin sheet 14 may become uniform.

  Thereby, the width direction temperature of the resin sheet 14 can be uniformly controlled while being in contact with the mold roller 16. Further, heating means 26 for directly heating the peeling roll 20 is arranged so that the heating means 24 can be arranged in a row in the width direction from above the resin sheet wound around the peeling roller, and further the heating can be controlled from the back side. It arrange | positions and the temperature sensors 32 and 33 are arrange | positioned from the both surfaces of the resin sheet downstream, and the output of the heating means 22 and 24 is controlled so that the width direction temperature becomes uniform. In addition, as a method for controlling the temperature distribution to be a specific temperature distribution, in order to obtain the temperature distribution, the output of the heating means is controlled while measuring the strain or the amount of warpage, and the temperature setting is performed. A means to change and narrow down by trial and error can be mentioned.

  Using the uneven thickness resin sheet production line 10 of FIG. 4, a plurality of heating means were arranged in the width direction as shown in FIG. 6 to manufacture the uneven thickness resin sheet. The uneven thickness resin sheet manufactured the resin sheet of the shape of Fig.5 (a). By manufacturing by controlling the temperature in the width direction of the resin sheet uniformly, it was possible to obtain an uneven thickness resin sheet having a highly accurate shape without distortion or warping. Further, when the resin sheet having the shape shown in FIG. 5A was manufactured without controlling the temperature in the width direction, distortion and warpage were significant, and the warpage amount was 10 mm or more.

Overall process diagram for manufacturing uneven thickness resin sheet Schematic diagram showing equipment configuration in each process Explanatory drawing explaining the curvature of a resin sheet The block diagram which shows a shaping | molding cooling process and a slow cooling process among the manufacturing apparatuses of an uneven thickness resin sheet Sectional drawing which shows an example of the uneven thickness resin sheet after shaping | molding It is the figure which looked at the type | mold roller part of the production line of an uneven thickness resin sheet from the lower part, and is a figure which shows the example of arrangement | positioning of a heating means and a sensor Configuration diagram showing production line of resin sheet of conventional example

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Production line of uneven thickness resin sheet, 12 ... Die, 14 ... Resin sheet, 16 ... Mold roller, 18 ... Nip roller, 20 ... Peeling roller, 22, 24, 26, 28, 29 ... Heating means or cooling means, 30 32, 33, 34, 35 ... sensor, 36 ... slow cooling zone

Claims (12)

Extrusion process of extruding molten resin from a die into a sheet, molding cooling process in which the extruded resin sheet is cooled and solidified while being nipped between a mold roller and a nip roller, and resin peeled from the mold roller A method of producing an uneven thickness resin sheet having a bias in the sheet thickness in the resin sheet width direction.
At least one of the molding cooling step and the slow cooling step has a temperature control step of controlling the temperature of the resin sheet by a heating means or a cooling means so that the temperature distribution in the width direction of the resin sheet is uniform. The manufacturing method of the uneven thickness resin sheet characterized by these. Extrusion process of extruding molten resin from a die into a sheet, molding cooling process in which the extruded resin sheet is cooled and solidified while being nipped between a mold roller and a nip roller, and resin peeled from the mold roller A method of producing an uneven thickness resin sheet having a bias in the sheet thickness in the resin sheet width direction.
In at least one of the molding cooling step and the slow cooling step, a temperature control step of controlling the temperature of the resin sheet by a heating unit or a cooling unit while maintaining a predetermined temperature distribution in the width direction of the resin sheet. The manufacturing method of the uneven thickness resin sheet characterized by having.   The said temperature control process detects the temperature distribution of the width direction of the said resin sheet with a sensor, and performs the temperature control of the width direction by the value, The uneven thickness resin sheet of Claim 1 or 2 characterized by the above-mentioned. Production method.   The said temperature control process is a manufacturing method of the uneven thickness resin sheet of Claim 3 with which the said sensor and the said heating means or the said cooling means are installed with two or more in the width direction of the said resin sheet.   The method of manufacturing an uneven thickness resin sheet according to claim 4, wherein the position of the sensor and the heating means or the cooling means can be changed in the width direction according to a cross-sectional shape of a final product. A peeling roller for peeling the resin sheet from the mold roller, and a slow cooling zone for performing the cooling step,
The said sensor and the said heating means or the said cooling means are installed in two or more places selected from the said mold | die roller part, the said peeling roller part, and the said slow cooling zone, The one in any one of Claim 1 to 5 characterized by the above-mentioned. The manufacturing method of the uneven thickness resin sheet of description.   The uneven thickness according to any one of claims 1 to 6, wherein the thickness difference between the thickest portion and the thinnest portion in the sheet width direction is 0.5 mm or more. Manufacturing method of resin sheet.   8. The method of manufacturing an uneven thickness resin sheet according to claim 1, wherein the thickness of the thinnest resin sheet is 5 mm or less.   The method for producing an uneven thickness resin sheet according to any one of claims 1 to 8, wherein the temperature control step is performed by heating or cooling from both surfaces of the resin sheet.   The method for producing an uneven thickness resin sheet according to any one of claims 1 to 9, wherein the resin sheet contains diffusing particles. Extruding means for extruding molten resin from a die into a sheet, molding cooling means for cooling and solidifying while extruding the extruded resin sheet by nipping between a mold roller and a nip roller, and resin released from the mold roller An apparatus for producing an uneven thickness resin sheet having a bias in the sheet thickness in the resin sheet width direction, comprising a slow cooling means for gradually cooling the sheet,
At least one of the molding cooling unit and the slow cooling unit includes a temperature control unit that controls the temperature using a heating unit or a cooling unit so that the temperature distribution in the width direction of the resin sheet is uniform. An apparatus for manufacturing an uneven thickness resin sheet. Extruding means for extruding molten resin from a die into a sheet, molding cooling means for cooling and solidifying while extruding the extruded resin sheet by nipping between a mold roller and a nip roller, and resin released from the mold roller An apparatus for producing an uneven thickness resin sheet having a bias in the sheet thickness in the resin sheet width direction, comprising a slow cooling means for gradually cooling the sheet,
At least one of the molding cooling unit and the slow cooling unit includes a temperature control unit that controls the temperature using a heating unit or a cooling unit so that the temperature distribution in the width direction of the resin sheet maintains a predetermined temperature distribution. The manufacturing apparatus of the uneven thickness resin sheet characterized by the above-mentioned.

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