JP2008246866A - Method and apparatus for manufacturing particle-containing resin sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a very smooth resin sheet containing fine particles by an extrusion molding method. <P>SOLUTION: The method has an extrusion process 12 of extruding a molten raw resin consisting of a mixture of a resin with fine particles into a sheet from a die, the molding/cooling process 14 of nipping the extruded resin sheet A with a die roller 46 and a nip roller 48 and molding into a predetermined shape while cooling to solidify and the gradually cooling process 16 of cooling the molded resin sheet A gradually in order to manufacture a resin sheet containing fine particles within the sheet. Between the molding/cooling process 14 and the gradually cooling process 16, there is provided the smoothing process 15 of sandwiching the resin sheet A peeled from the die roller 46 with a pair of mirror rollers 15C and 15D in order to smooth the surface of the resin sheet A. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method and an apparatus for producing a particle-containing resin sheet, and in particular, a particle-containing material used as a light guide plate for a backlight of a liquid crystal display device and various large display applications such as a display for decoration, display and illumination. The present invention relates to a resin sheet manufacturing method and apparatus.

  A light guide plate that guides light from a light source to emit light is used in a backlight of a liquid crystal display device, a display device for decoration and illumination, and the like. For example, a liquid crystal display device is provided with a backlight that illuminates the liquid crystal panel by irradiating light from the back side of the liquid crystal panel (LCD) through a light guide plate (for example, Non-Patent Document 1).

  A relatively small-screen liquid crystal panel such as a laptop computer uses a wedge-shaped light guide plate having a thick wall at one end and a thin wall at the other end as shown in FIG. As shown in FIG. 14B, the liquid crystal panel having a screen uses a bowl-shaped light guide plate having a thick central portion and thin both ends.

  And the light-guide plate used for a liquid crystal panel with a comparatively small screen is manufactured by the injection molding method which injection-molds molten resin. However, for example, a light guide plate of a liquid crystal panel of 20 inches or more is not manufactured by an injection molding method because of molding equipment and molding technology, but is manufactured by an extrusion molding method in which a molten resin is extruded.

  In order to manufacture the light guide plate by the extrusion molding method, it is usually manufactured by cooling and solidifying a resin sheet extruded from a die while forming it with a mold roller, and then gradually cooling it.

  Incidentally, recently, a light guide plate having fine particles (diffusion particles) having a function of diffusing light inside a resin sheet has been developed. However, when a resin sheet containing fine particles is produced by a conventional extrusion molding method, there is a problem that “undulation” -shaped irregularities are formed on the resin sheet surface. Thereby, the planar shape of the resin sheet is deteriorated, and when such a resin sheet is used as a light guide plate, the optical characteristics are deteriorated.

As a general technique for improving the surface shape of the resin sheet, there are Patent Documents 2 and 3, for example. Patent Document 2 discloses a method in which a thermoplastic resin is extruded from an extruder, sandwiched between mirror-like first narrow pressure roller, second narrow pressure roller, and third narrow pressure roller, and gradually cooled in a heating furnace with a temperature gradient. It is. Patent Document 3 is a method of adjusting the hardness or uneven shape of the first narrow pressure roller and adjusting the gap distance between the first narrow pressure roller and the second narrow pressure roller.
Development of acrylic materials and molding technology for LCD backlights, Kenji Manabe et al., Sumitomo Chemical Co., Ltd., Research and Development Paper 2002-II JP-A-11-320656 JP 2004-155101 A

  However, the methods of Patent Documents 2 and 3 are improvements in the surface state of a resin that does not contain fine particles, and results that may be applied to the present invention cannot be obtained. That is, when the method of Patent Document 2 is applied to the production of a particle-containing resin sheet, there is a difference in shrinkage between the fine particles and the resin in the process of slow cooling in the heating furnace. Unevenness is generated on the surface, which cannot be solved. On the other hand, when the method of Patent Document 3 is applied to the production of the particle-containing resin sheet, unevenness occurs on the resin sheet surface on the first narrow pressure roller side that does not come into contact with the roller during cooling, which cannot be solved.

  Moreover, when using a particle | grain containing resin sheet as a light-guide plate, it is requested | required that the centerline average roughness Ra of both surfaces of the manufactured resin sheet is 0.03 micrometer or less, and cannot be achieved by the conventional method. In particular, when the resin sheet is manufactured by extrusion molding such as the wedge shape or the ridge shape, the unevenness of the “waviness” shape generated on the surface of the resin sheet. It is difficult to eliminate.

  The present invention has been made in view of such circumstances, and even when a resin sheet containing fine particles therein is produced by an extrusion molding method, a resin sheet having a very smooth resin sheet surface is produced. An object of the present invention is to provide a method and an apparatus for producing a particle-containing resin sheet.

  In order to achieve the above object, the present invention provides an extrusion process in which a raw material resin, which is a mixture of fine particles and resin, is melted and extruded into a sheet form from a die, and the extruded resin sheet is molded with a mold roller and a nip roller. A resin sheet containing a fine particle inside the sheet, and a molding cooling process in which the resin sheet is cooled and solidified while being molded into a predetermined shape by niping and a molded resin sheet is manufactured. In the method for producing a particle-containing resin sheet, smoothing is performed by smoothing the resin sheet surface by sandwiching both surfaces of the resin sheet peeled off from the mold roller between the molding cooling step and the slow cooling step with a pair of mirror rollers. There is provided a method for producing a particle-containing resin sheet, characterized in that a forming step is provided.

  According to claim 1 of the present invention, the resin sheet between the molding cooling step and the slow cooling step in the extrusion molding method has a plastic state near the surface and an elastic state inside the resin sheet. Since the resin sheet is sandwiched between the pair of mirror rollers, a resin sheet excellent in surface smoothness can be produced even with a particle-containing resin sheet containing fine particles therein. That is, by containing fine particles inside, even if “undulation” -shaped irregularities occur in the molding and cooling step, the irregularities can be effectively corrected in the subsequent smoothing process.

  A second aspect of the present invention is the first aspect, wherein in the smoothing step, the center average roughness Ra of the mirror surface is 0.2 μm or less, and the surface temperature of the resin sheet before the smoothing treatment is the glass transition temperature of the resin. The resin sheet is characterized by satisfying the following three conditions: Tg-20 ° C. or more and Tg + 40 ° C. or less, and the surface temperature of the resin sheet during the smoothing treatment is Tg−20 ° C. or more and Tg or less.

  The second aspect of the invention prescribes a preferable roller surface roughness of the mirror surface roller and a preferable resin sheet surface temperature between the smoothing process and before the smoothing process (smoothing process), and the smoothing process is performed under such conditions. This is more effective in correcting unevenness on the resin surface.

  A third aspect of the present invention is the method according to the first or second aspect, wherein in the smoothing step, the resin sheet before the smoothing treatment is heated so that the surface temperature of the resin sheet before the smoothing treatment is Tg or more and Tg + 40 or less. It is characterized by doing.

  According to a third aspect of the present invention, the resin sheet is heated before the smoothing treatment, so that it is Tg or more and Tg + 40 or less, which is a more preferable range before the smoothing treatment.

  A fourth aspect of the present invention is characterized in that in any one of the first to third aspects, the fine particles are diffusion particles having a function of diffusing light.

  This is because it is particularly effective to apply the present invention when the fine particles are diffusing particles having a function of diffusing light.

  A fifth aspect according to any one of the first to fourth aspects is characterized in that the fine particles are 15 μm or less and are contained in the particle-containing resin sheet at a concentration of 0.005 to 0.5 mass%. To do.

  Claim 5 defines the preferable numerical values of the particle diameter of the fine particles contained in the produced particle-containing resin sheet and the concentration of the fine particles.

  A sixth aspect of the present invention is characterized in that, in any one of the first to fifth aspects, in the molding cooling step, a resin sheet having an uneven thickness is molded by a mold roller and a nip roller.

  This is because in the case where the resin sheet is an uneven thickness resin sheet such as a wedge shape or a ridge shape, it is difficult to correct the “undulation” shape unevenness generated on the resin sheet surface, and the present invention is more effective.

  In a sixth aspect of the present invention, in the sixth aspect, in the case of the uneven thickness resin sheet, one of the pair of mirror rollers used in the smoothing step is the same shape as the uneven thickness. It is a roller.

  According to the seventh aspect, since one of the pair of mirror surface rollers is an uneven shape roller having the same shape as the uneven thickness shape, the uneven thickness resin sheet is sandwiched between the pair of mirror surface rollers and smoothed. However, the uneven thickness shape is not damaged.

  In an eighth aspect of the present invention, in any one of the first to seventh aspects, the particle-containing resin sheet is a light guide plate used for a backlight of a liquid crystal display device.

  This is because, when the present invention is applied to the manufacture of a light guide plate, a light guide plate having good surface smoothness and excellent optical characteristics can be manufactured.

  According to a ninth aspect of the present invention, in order to achieve the above object, an extrusion means for melting a raw material resin, which is a mixture of fine particles and a resin, and extruding the extruded resin sheet into a sheet shape, a molded roller and a nip roller A resin sheet containing fine particles inside the sheet is manufactured, comprising: a molding cooling means that cools and solidifies while being molded into a predetermined shape by niping and a slow cooling means that gradually cools the molded resin sheet. In the apparatus for producing a particle-containing resin sheet, a sheet heating unit that heats the resin sheet peeled from the mold roller and a pair of mirror rollers that sandwich the heated resin sheet between the molding cooling unit and the slow cooling unit And an apparatus for producing a particle-containing resin sheet.

  According to a ninth aspect of the present invention, the present invention is configured as an apparatus, and a sheet heating unit that heats a resin sheet peeled from a mold roller and a heated resin sheet between a molding cooling unit and the slow cooling unit. Since a pair of mirror-surface rollers to be sandwiched is provided, a resin sheet having a very smooth resin sheet surface can be produced even when a resin sheet containing fine particles therein is produced by extrusion molding. .

  A tenth aspect of the present invention provides the first thermometer for measuring the surface temperature of the resin sheet heated by the heating unit before the smoothing process, and the second thermometer for measuring the surface temperature of the resin sheet after the smoothing process. Thermometer, roller heating means for heating the roller surfaces of the pair of mirror rollers, a third thermometer for measuring the roller surface temperature of the mirror rollers, and the measurement results of the first to third thermometers And a control means for controlling the sheet heating means and the roller heating means.

  In the tenth aspect, the first and second thermometers measure the temperature before and after the smoothing of the resin sheet surface, and the third thermometer measures the roller surface temperature of the mirror roller. And since it was set as the structure which can control surface temperature and roller surface temperature by a control means based on the measured value of these thermometers, optimal temperature conditions can be set in smoothing. For example, the control means is such that the surface temperature of the resin sheet before smoothing is not less than the glass transition temperature Tg-20 ° C. of the resin and not more than Tg + 40 ° C., and the surface temperature of the resin sheet during the smoothing is Tg-20. It controls so that it may become more than ℃ and Tg or less.

  According to the method and apparatus for producing a particle-containing resin sheet of the present invention, even when a resin sheet containing fine particles therein is produced by an extrusion molding method, a resin sheet having an extremely smooth resin sheet surface is produced. can do.

  The preferred embodiments of the production method and apparatus of the production method of the particle-containing resin sheet of the present invention are described in detail below with reference to the accompanying drawings. In the present embodiment, an example in which diffusion particles are contained in a ridge-shaped uneven thickness resin sheet as the particle-containing resin sheet to be manufactured will be described.

  FIG. 1 is an example of an overall process diagram for producing the particle-containing resin sheet of the present invention, and FIG. 2 is a conceptual diagram of a particle-containing resin sheet production apparatus provided with various devices for carrying out each process.

  As shown in FIG. 1, the particle-containing resin sheet production method of the present invention mainly includes a raw material process 10 for measuring and mixing raw materials, and an extrusion process 12 for continuously extruding molten resin into a sheet shape (band shape). A molding cooling step 14 for cooling and solidifying the extruded resin sheet A while performing uneven thickness molding, a smoothing step 15 for smoothing the front and back surfaces of the cooled and solidified resin sheet A, and a smoothed resin sheet A A slow cooling step 16 for gradually cooling, a warp measuring step 18 for measuring pass / fail of the slowly cooled resin sheet A with respect to a predetermined criterion, and a molding cooling step 14 and a slow cooling step 16 when the warp exceeds a predetermined criterion. And a control step 20 for controlling the cooling rate and slow cooling rate in the resin sheet width direction to be uniform, and laminating a film for surface protection on the front and back surfaces of the resin sheet A Constituted by the laminating step 22, the cut and cutting step 24 of cutting Court the resin sheet A to a predetermined size (length and width), and the load process 26 for loading the cut resin sheet A Court that.

  As shown in FIG. 2, in the raw material process 10, the raw material resin and the diffusion particles sent from the raw material silo 28 (or raw material tank) and the diffusion particle silo 30 (or diffusion particle tank) to the automatic weighing machine 32 are automatically measured, In the mixer 34, the raw material resin and the diffusing particles are mixed at a predetermined ratio.

  As the raw material resin used in 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.

The diffusing particles used in the present invention preferably have a particle diameter of 15 μm or less, more preferably 3 μm or more and 12 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.

  When adding diffusion particles to the raw material resin, a master pellet in which the diffusion particles are added to the raw material resin at a concentration higher than a predetermined concentration is manufactured by a granulator (see FIG. 12), and the diffusion particles are added. A master batch system in which a predetermined ratio of base pellets are mixed in the mixer 34 can be suitably employed. The same applies when additives other than the diffusion particles are added.

  The raw material resin appropriately weighed and mixed in the raw material process 10 is sent to the extrusion process 12.

  In the extrusion process 12, the raw material resin mixed in the mixer 34 is charged into the extruder 38 through the hopper 36 and melted while being kneaded by the extruder 38. The extruder 38 may be either a single-screw extruder or a multi-screw extruder, and preferably includes a vent function that evacuates the inside of the extruder 38. The raw material resin melted by the extruder 38 is sent to a die 44 (for example, a T die) through a supply pipe 42 by a metering pump 40 such as a screw pump or a gear pump. The resin sheet A extruded from the die 44 into a sheet is then sent to the molding cooling step 14.

  In the molding cooling step 14, the resin sheet A extruded from the die 44 is nipped between the mold roller 46 and the nip roller 48, cooled and solidified while being formed by uneven thickness molding, and the solidified resin sheet A is peeled off by the peeling roller 50. To do. These rollers 46, 48 and 50 will be referred to as forming cooling rollers.

  As shown in the enlarged views of FIG. 3A and FIG. 4, the mold roller 46 is formed in a concave shape with a narrow central portion and thick at both ends, and the nip roller 48 is formed in a flat shape. That is, a reverse shape for forming the uneven thickness resin sheet is formed on the roller surface of the mold roller 46. As a result, the high-temperature resin sheet A pushed out from the die 44 is narrowed (nip) at a predetermined nip pressure by the mold roller 46 and the nip roller 48 to be formed into a bowl shape.

  As the material of the mold roller 46, various steel members, stainless steel, copper, zinc, brass, these metal materials having a metal core 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 46 is rotationally driven in a direction indicated by an arrow in FIG. 4 at a predetermined peripheral speed by driving means (not shown).

  Further, as shown in FIG. 5, the mold roller 46 is provided with means for imparting a cooling temperature distribution in the resin sheet width direction so as to substantially match the uneven thickness shape. As shown in FIG. 6A, such a cooling control means 52 preferably employs a configuration in which the temperature-controlled cooling liquid is circulated through the same diameter flow path 53 formed from one end side to the other end side of the roller. it can. The supply and discharge of the cooling liquid can be realized by a configuration in which a rotary joint is provided at the end of the roller. Thereby, both end portions of the mold roller 46 have a large roller thickness, and the cold heat of the mold roller 46 is not easily transmitted to the thin end portions of the resin sheet A. On the contrary, the central portion of the mold roller 46 has a small roller thickness, and the cold heat of the mold roller 46 is easily transmitted to the thick central portion of the resin sheet A. Thereby, the cooling rate in the resin sheet width direction can be made uniform. The roller thickness distribution formed on the mold roller 46 can be formed by the heat insulating material 55, for example. The thermal conductivity of the heat insulating material 55 is preferably 1 W / mK or less at room temperature, and for example, a polyimide resin or glass can be suitably used.

  As shown in FIGS. 3 and 4, the nip roller 48 is a roller that is disposed so as to face the mold roller 46 and clamps the resin sheet A with the mold roller 46. The material of the nip roller 48 includes various steel members, stainless steel, copper, zinc, brass, those metal materials made of a metal core, and a rubber lining on the surface, and these metal materials are HCr plated, Cu plated, Ni plated, etc. These materials, ceramics, and various composite materials can be used.

  In particular, as shown in FIG. 3B, the relationship between the mold roller 46 and the nip roller 48 is such that a tapered taper 46A is formed at both ends of the mold roller 46, and the resin sheet A is narrowly pressed with the nip roller 48. When it does, it is preferable that the taper corresponding | compatible part of the resin sheet A is cut. This is because both end portions (ear portions) of the resin sheet A extruded from the die 44 tend to be thicker than desired, and the thick film portion promotes the formation of warpage in the subsequent steps. Because. In this case, since the mold roller 46 and the taper top portion 46B come into contact with the nip roller 48 and are easily worn, it is preferable that the contact portion is subjected to a carbide treatment with a carbide material such as tungsten carbide or quenched. . Similarly, for the mold roller 46 and the peeling roller 50, it is preferable that the abutting portion is subjected to cemented carbide treatment with a cemented carbide material such as tungsten carbide or quenched.

  The surface of the nip roller 48 is preferably processed into a mirror surface, and the center line average roughness Ra is preferably 0.5 μm or less, more preferably 0.2 μm or less. By setting it as such a smooth surface, the back surface of the resin sheet A after shaping | molding can be made into a favorable state. Further, the nip roller 48 is rotationally driven in the direction of the arrow in FIG. 4 by a driving means (not shown) at a predetermined peripheral speed. In addition, although the structure which does not provide a drive means in the nip roller 48 is also possible, it is preferable to provide a drive means from the point which can make the back surface of the resin sheet A a favorable state.

  The nip roller 48 is provided with a pressing means (not shown) so that the resin sheet A between the nip roller 46 and the mold roller 46 can be pressed 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 48 and the mold roller 46, and various known means such as a motor driving means, an air cylinder, and a hydraulic cylinder are employed. it can.

  The nip roller 48 may be configured to be less likely to bend due to the reaction force of the clamping pressure. As such a configuration, a configuration in which a backup roller (not shown) is provided on the back side of the nip roller 48 (opposite side of the mold roller 46), a configuration in which a crown shape (middle and high shape) is adopted, 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.

  Further, similarly to the mold roller 46, the nip roller 48 is preferably provided with a cooling control means 52 for applying a cooling temperature distribution (see FIG. 5) in the resin sheet width direction so as to substantially match the uneven shape. . As the cooling control means 52 provided in the nip roller 48, for example, those shown in FIGS. 6B to 6E can be suitably employed. FIG. 6B shows a case where the cooling liquid is caused to flow through a crown-shaped channel 53 formed inside the nip roller 48. Thereby, both end portions of the nip roller 48 have a large roller thickness, and the cold heat of the nip roller 48 is not easily transmitted to the thin end portions of the resin sheet A. On the contrary, the central portion of the nip roller 48 has a small roller thickness, and the cold heat of the nip roller 48 is easily transmitted to the thick central portion of the resin sheet A. Thereby, since temperature distribution is formed in the resin sheet width direction, the cooling rate in the resin sheet width direction can be made uniform. As the roller structure, various roller structures such as a spiral roller, a drilled roller, and a jacket roller can be adopted.

  The cooling control means 52 in FIG. 6C is a case where the heating liquid is allowed to flow through the concave channel 53. Also in this case, since the temperature distribution is formed in the resin sheet width direction, the cooling rate in the resin sheet width direction can be made uniform. The heating fluid in this case is naturally a temperature lower than the temperature of the resin sheet A.

  The cooling control means 52 in FIG. 6D is a case where a sheath heater is embedded in place of the heating liquid in FIG. 6C. FIG. 6E shows an induction heating type induction heater (IH heater) as a roller. A plurality of them are provided in the width direction so that the heating temperature in the roller width direction can be controlled. In addition, various heating methods such as a band heater, a silicon rubber heater, and a steam heater can be employed.

  As shown in FIGS. 3 and 4, the peeling roller 50 is disposed opposite to the mold roller 46 and is a roller for peeling the resin sheet A from the mold roller 46 by winding the resin sheet A. It is arranged 180 degrees downstream of 46. The surface of the peeling roller 50 is preferably processed into a mirror surface. By setting it as such a surface, the back surface of the resin sheet A after 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. As the material of the peeling roller 50, various steel members, stainless steel, copper, zinc, brass, these metal materials having a metal core 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 50 is rotationally driven in a direction indicated by an arrow in FIG. 4 at a predetermined peripheral speed by a driving unit (not shown). In addition, although the structure which does not provide a drive means in the peeling roller 50 is also possible, it is preferable to provide a drive means from the point which can make the back surface of the resin sheet A a favorable state.

  Further, like the mold roller 46 and the nip roller 48, the peeling roller 50 is also provided with a cooling control means 52 for providing a cooling temperature distribution (see FIG. 5) in the resin sheet width direction so as to substantially match the uneven shape. Preferably it is.

  The mold roller 46, the nip roller 48, and the peeling roller 50 are preferably provided with a plurality of surface temperature measuring means (not shown) so that the temperature of the roller surface can be monitored in the roller width direction. As such surface temperature measuring means, various known measuring means such as an infrared thermometer and a radiation thermometer can be employed.

  According to the molding cooling step 14 configured in this way, the cooling rate in the width direction of the unevenly shaped resin sheet can be made uniform, so that it is effective that the resin sheet A is warped in the molding cooling step 14. Can be suppressed.

  The resin sheet A that has undergone the molding cooling step 14 is then sent to the smoothing step 15.

  As shown in FIG. 7, in the smoothing step 15, the surface temperature of the resin sheet A peeled from the mold roller 46 by the peeling roller 50 is in the range of the glass transition temperature Tg-20 ° C. or higher and Tg + 40 ° C. or lower by the sheet heating means 15A. To be heated. The surface temperature of the resin sheet A is measured by the first thermometer 15B and input to the control means (DCS in FIGS. 12 and 13). And the surface of the resin sheet A is smooth | blunted by pinching the heated resin sheet A with a pair of mirror surface rollers 15C and 15D. The center line average roughness Ra of the mirror surfaces of the mirror rollers 15C and 15D is preferably 0.5 μm or less, and more preferably 0.1 μm or less. As the mirror rollers 15C and 15D, a metal roller, a resin roller, a rubber roller, a metal thin film roller, or the like can be used.

  Of the pair of mirror rollers 15C and 15D, the mirror roller 15D disposed on the convex side of the resin sheet A preferably has the same shape as the mold roller 46 used in the molding and cooling step 14. Thereby, when sandwiching the uneven thickness resin sheet A by the pair of mirror rollers 15C and 15D, the uneven shape of the resin sheet A can be smoothed without being damaged. The sandwiching pressure is preferably in the range of 10 kgf / cm to 50 kgf / cm.

  In particular, the mirror roller 15D disposed on the convex side of the resin sheet A preferably forms a taper at both ends of the mirror roller 15D, as with the mold roller 46 described with reference to FIG. And the smoothing process is performed by inserting | pinching the part except the ear | edge part of the resin sheet A.

  The surface temperature of the resin sheet A during the smoothing treatment is preferably maintained in the range of Tg-20 ° C. or higher and Tg or lower. Whether or not this temperature is maintained is monitored by measuring the surface temperature of the resin sheet A with a second thermometer 15E provided after the mirror rollers 15C and 15D, and the monitored data is input to the control means. Is done. The pair of mirror rollers 15C and 15D is provided with a roller heating means 15F for heating the roller surface and a third thermometer 15G for measuring the roller surface temperature. Data measured by the third thermometer 15G is input to the aforementioned control means. And a control means is based on the measured value measured with the 1st-3rd thermometer 15B, 13E, 15G so that the resin sheet surface temperature before smoothing processing and during smoothing processing may satisfy the said temperature range. The sheet heating unit 15A and the roller heating unit 15F are controlled.

  Thereby, even if it is a case where the resin sheet A which made the inside contain the diffusion particle is manufactured by an extrusion molding method, the resin sheet surface with a very smooth resin sheet surface can be manufactured.

  As the sheet heating means 15A and the roller heating means 15F, a structure in which temperature-controlled air (warm air) is jetted toward the resin sheet A from a plurality of nozzles, a nichrome wire heater, an infrared heater, a dielectric heating means, etc. Various known means such as a configuration for heating the sheet A can be employed. As the first to third thermometers, various known measuring means such as an infrared thermometer and a radiation thermometer can be employed.

  The resin sheet A smoothed in the smoothing step 15 is then sent to the slow cooling step 16.

  The slow cooling step (or annealing step) 16 is provided in order to prevent a rapid temperature change of the resin sheet A downstream of the peeling roller 50, as shown in FIG. When a sudden temperature change occurs in the resin sheet A, for example, the inside of the resin sheet A is in a plastic state while the vicinity of the surface of the resin sheet A is in a plastic state. The surface shape of A deteriorates. Further, a temperature difference is generated between the front and back surfaces of the resin sheet A, and the resin sheet A is likely to warp. 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.

  In the slow cooling step 16, a tunnel-like slow cooling zone 54 (or annealing zone) having an inlet and an outlet is provided. In the first half of the slow cooling zone 54, the resin sheet A is gradually heated while being heated by the heating means 55. In the second half of the slow cooling zone 54, forced cooling is performed by applying cold air to the resin sheet A.

  As the heating means 55 provided in the first half of the slow cooling zone 54, a structure in which air (hot air) whose temperature is controlled from a plurality of nozzles is jetted toward the resin sheet A, a nichrome wire heater, an infrared heater, a dielectric heating means, etc. Thus, various known means such as a structure for heating the resin sheet A can be employed.

  The first half of the slow cooling zone 54 is provided with shape holding means 56 for holding the bowl shape of the resin sheet A when the resin sheet A is slowly cooled and conveyed. As the shape holding means 56, for example, those shown in FIGS. 8 to 10 can be suitably used.

  The shape holding means 56 in FIG. 8 has a concave roller 58 disposed on the convex surface of the bowl-shaped resin sheet A, and a roller 60 having a flat roller surface disposed on the opposite surface. It is designed to be sandwiched by pressure.

  9 has a plurality of short rollers 62 with a flat and short roller surface on the convex surface of the bowl-shaped resin sheet A. The shape holding means 56 is divided in the resin sheet width direction (FIG. 7 shows two short lengths). A long long roller 64 having a flat roller surface is disposed on the opposite surface, and the resin sheet A is sandwiched with a predetermined pressure. Both ends of the rotating shaft of the short roller 62 are rotatably supported by a bearing 66, and an air cylinder 68 is provided on the bearing 66. And the pressure pinched | interposed by the stroke which expands the piston of the air cylinder 68 is adjusted. Reference numeral 70 denotes a bearing of the long roller 64, and the bearing 70 of the long roller 64 and the air cylinder 68 of the short roller 62 are supported by a slow cooling apparatus main body (not shown).

  The shape holding means 56 in FIG. 10 has the same basic structure as that in FIG. 9, and the length of the short rollers 62 arranged in the resin sheet width direction is shorter than that in FIG. 8 (with the four short rollers 62). The configuration is configured so that the resin sheet A can be pinched precisely following the shape of the ridge. In addition, the shape holding means 56 is not limited to the structure of FIGS. 8-10, and the point is that the resin sheet A is not warped without inhibiting the conveyance of the resin sheet A that is slowly cooled. Any material can be used as long as it can be held in a bowl shape. For example, the shape holding means can be formed by densely arranging pressing means provided with wheels in which the short rollers 62 are further shortened in the width direction of the resin sheet A.

  Of the rollers constituting the shape holding means 56, at least the roller disposed on the convex surface of the resin sheet A is preferably an elastic roller. Examples of the material of the elastic roller include silicon rubber (SR), styrene butadiene rubber (SBR), chloroprene rubber (CR), chlorosulfonated polyethylene (CSM), acrylonitrile butadiene rubber (NBR), urethane rubber (U), and ethylene propylene. Examples include rubber (EPT), chlorinated polyethylene rubber (CPE), fluoro rubber (FPM), hydrogenated nitrile rubber (HNBR), butyl rubber (IIR), and hyperon rubber (CMS). Absent.

  Further, the shape holding means 56 in FIGS. 8 to 10 is provided with a slow cooling temperature distribution (see the temperature distribution curve in FIG. 5) in the resin sheet width direction so as to substantially match the uneven shape of the mold roller. It is preferable that a slow cooling control means 57 is provided. For the concave roller 58 and the roller 60 constituting the shape holding means 56 of FIG. 8, the slow cooling control means 57 having the same structure as described in FIG. 6 can be adopted. When the short rollers 62 shown in FIGS. 9 and 10 are used, it is necessary to form the above-described slow cooling temperature distribution by the plurality of short rollers 62 arranged in the resin sheet width direction. As a result, the resin sheet A conveyed through the first half of the slow cooling zone 54 is gradually cooled by the shape holding means 56 in the form of a bowl without warping, and at the same time in the resin sheet width direction by the slow cooling control means 57. Since the slow cooling rate is made uniform in the slow cooling step 16, it can be gradually cooled so as not to warp. Further, even if the resin sheet A is warped in the molding cooling step 14 before the slow cooling step 16, the internal stress can be relaxed while correcting the warp. In this case, the surface temperature of the resin sheet A in contact with the first shape holding means 56 provided at the inlet of the slow cooling zone 54 is the glass transition temperature Tg-20 ° C. to Tg + 10 ° C. of the resin, and the first half of the slow cooling zone 54 The surface temperature of the resin sheet A at the exit, that is, when the shape holding means 56 is not held is preferably Tg−20 ° C. or less, more preferably Tg−50 ° C. or less.

  The interval between the shape holding means 56 disposed in the slow cooling zone 54 is preferably 1000 mm or less, and more preferably 500 mm or less, in the transport direction of the resin sheet A. The pressure with which the resin sheet A is sandwiched by the shape holding means 56 is preferably 5 kgf / cm or more and 200 kgf / cm or less, more preferably 10 kgf / cm or more and 50 kgf / cm or less in terms of linear pressure.

  In addition, a plurality of air nozzle devices 74 that blast and convey the resin sheet A by blowing cold air are provided on the upper and lower sides of the slow cooling zone 54 with the resin sheet A interposed therebetween. As the air nozzle device 74, a well-known device used when a web-like conveyance object is floated and conveyed can be used. Thereby, the resin sheet A is cooled to about normal temperature in a non-contact state where it does not contact the roller.

  Next, the resin sheet A cooled in the slow cooling step 16 is taken up by the nip type feed roller 76 and sent to the warpage measurement step 18.

  In the warpage measurement step 18, the warpage measuring device 78 measures the pass / fail of the warpage of the resin sheet A with respect to a predetermined standard. Here, the warp will be described using an example of a bowl-shaped resin sheet A. As shown in FIG. 11, the back surface (flat surface side) of the resin sheet A cut out to a length of 1060 mm and a width of 620 mm is the upper surface of the flat measurement substrate 80. The maximum distance H between the resin sheet A and the measurement substrate 80 is referred to as a warp amount. Since the predetermined reference (standard value) of the amount of warpage is set according to the use of the resin sheet A and the standard on the user side, the warpage measuring device 78 measures pass / fail with respect to the predetermined reference. As the warpage measuring device 78, for example, the surface (outer periphery) of the resin sheet A is scanned with an electrostatic sensor or the like, the distance (shape) between the resin sheet A and the electrostatic sensor is measured, and the measurement prepared in advance. A method for obtaining the warpage amount from the relationship between the value and the warpage amount can be employed. When the warpage amount measured by the warpage measuring device 78 exceeds a predetermined reference, it is fed back to the molding cooling step 14 and the slow cooling step 16 so that the cooling rate and the slow cooling rate in the resin sheet width direction become uniform. To control. That is, the cooling control means 52 in the molding cooling step 14 described above and the slow cooling control means 57 in the slow cooling step 16 form a temperature distribution having the same uneven thickness as the mold roller in the resin sheet width direction. Uniform cooling rate and slow cooling rate in the sheet width direction.

  In this case, the uneven-shaped resin sheet A may or may not be warped depending on the type of uneven shape, the degree of uneven distribution, etc., and therefore, feedback is performed only when the warpage exceeds a predetermined standard. That's fine. If the cooling rate and the slow cooling rate in the resin sheet width direction are uniformly controlled in spite of no warping, there are cases where it is not good.

  A laminating process 22, a cutting / cutting process 24, and a stacking process 26 including a stocker 79 are sequentially provided downstream of the warp measuring process 18. Among these, the lamination process 22 is a process which affixes a protective film (films, such as polyethylene) on the front and back of the resin sheet A, and the protective film 84 rewinded from a pair of reels 82 as shown in FIG. The resin sheet A is merged so as to be sandwiched, and is laminated by passing through the nip roller 86.

  The cutting / cutting step 24 is a step of cutting both ends (ear portions) in the width direction of the resin sheet A and cutting the resin sheet A 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 90A or electron beam cutting can be preferably used, but the cutting machine 90 is not limited to this.

  According to the apparatus for producing a particle-containing resin sheet of the present invention configured as described above, the resin sheet A is pressed by pressing the sheet-shaped resin sheet A extruded from the die 44 between the mold roller 46 and the nip roller 48. After forming into a bowl shape and cooling and solidifying, it is peeled off from the mold roller 46 by the peeling roller 50. The resin sheet A peeled off from the mold roller 46 is smoothed by a pair of mirror rollers 15C and 15D, and is gradually cooled by passing through the slow cooling zone 54 while horizontally transporting the smoothed resin sheet A, and distortion is removed. In this state, the product is cut into a predetermined length at the downstream product take-up portion and accommodated as a product of the resin sheet A. In this case, the extrusion speed of the resin sheet A extruded from the die 44 can be 0.1 to 50 m / min, preferably 0.3 to 30 m / min. Therefore, the peripheral speed of the mold roller 46 is also substantially matched with this. It should be noted that the speed unevenness of each of the mold roller 46, the nip roller 48, and the peeling roller 50 is preferably controlled to be within 1% of the set value. Moreover, it is preferable that the resin sheet A in the location of the peeling roller 50 is the temperature below the softening point Ta of resin. At this time, when a polymethyl methacrylate resin is employed for the resin sheet A, the set temperature of the peeling roller 50 can be 50 to 110 ° C.

  In the production of the particle-containing resin sheet, in the smoothing step 15, the resin sheet A is smoothed by sandwiching the resin sheet A between the pair of mirror rollers 15C and 15D, so that the particle-containing resin containing fine particles therein. Even if it is a sheet | seat, the resin sheet excellent in the smoothness of the surface can be manufactured.

  Further, in the molding cooling step 14 and the slow cooling step 16, when the resin sheet A has a warp exceeding a predetermined reference, the cooling temperature distribution and the resin sheet width direction so as to substantially match the uneven shape of the mold roller 46. Since the slow cooling temperature distribution is provided, the warp of the resin sheet A can be effectively suppressed. Further, in the slow cooling step 16, in addition to the above-described slow cooling temperature distribution, the shape holding means 56 gradually cools the resin sheet A while maintaining the shape of the ridge, thereby further suppressing the warpage of the resin sheet A. it can.

  In this case, the peripheral speed of the rollers used in the molding and cooling process 14 and later is also effective in suppressing warpage of the uneven thickness resin sheet by performing draw control in which the peripheral speed increases as the roller is located on the downstream side of the process. . Furthermore, in the molding cooling process, appropriately controlling the gap between the mold roller 46 and the nip roller 48 is also effective in suppressing the warpage of the uneven thickness resin sheet A.

  12 and 13 show a control system of a manufacturing apparatus for uneven thickness resin sheets. 12 and 13 includes, in addition to the above-described warp measuring device 78, a thickness measuring device that measures the thickness of the resin sheet A, a transmittance measuring device that measures the light transmittance of the resin sheet A, and a resin. The apparatus includes various measuring instruments such as a roughness measuring instrument for measuring the surface roughness of the sheet A and a retardation measuring instrument for measuring the retardation of the resin sheet A.

  As shown in FIG. 12, various types of measurement data measured by the measurement apparatus are input to a DCS (Distributed Control System) including a PLC (Programmable Logic Controller). In addition, operation data is input to the DCS from each device. The DCS stores measurement data and operation data, and performs calculations for appropriately controlling each device based on the measurement data and operation data. And the control signal obtained by the calculation is output to each device such as an automatic weighing machine, a mixer, a hopper, an extruder, a die, a forming cooling roller, a mirror roller, a slow cooling machine, and a sorting device. Here, the sorting device is a device for removing defective products of the resin sheet from the production line to the waste removal box, and it is out of standard products for evaluation items such as warpage, thickness, transmittance, surface roughness, and retardation. The resin sheet is removed as a defective product.

  As specific control of each device by DCS, as shown in FIG. 13, in the raw material process, from the extruder to the die by controlling the mixing amount of the automatic metering machine, the metering pump such as a screw pump or a gear pump. Control the extrusion amount of the molten resin. In the raw material process, the flow rate of the resin sheet in the die width direction is controlled. In the molding cooling step, control of each rotation driving unit of the molding cooling roller (mold roller, nip roller, peeling roller), control of the gap driving unit for adjusting the gap between the rollers, and control of each temperature control unit are performed. In the smoothing step, the pressure driving unit that adjusts the sandwiching pressure between the pair of mirror rollers is controlled. In the first half of the slow cooling process, the temperature control unit and the pressure control unit of the shape holding means are controlled. It also controls a feed roller (take-off roller) drive unit, a laminator drive unit, a cutting machine drive unit, a cutter drive unit, an end surface finish drive unit, and the like.

  In the embodiment of the present invention, the example of manufacturing the flange-shaped uneven thickness resin sheet has been described. However, the present invention is not limited to this, and the wedge-shaped uneven thickness resin sheet or the like is used in the resin width direction. It can be applied to an uneven thickness resin sheet having a wall thickness distribution. In the case of this wedge-shaped uneven thickness resin sheet, the wedge-shaped uneven thickness resin sheet can be manufactured by manufacturing and cutting in half.

Process drawing explaining the flow of the manufacturing method of the uneven thickness resin sheet of this invention Conceptual diagram of manufacturing apparatus for uneven thickness resin sheet of the present invention Explanatory drawing explaining the structure of a shaping | molding cooling roller Enlarged view of molding cooling roller Explanatory drawing explaining the temperature distribution in the resin sheet width direction in a shaping | molding cooling process and a slow cooling process Explanatory drawing explaining the cooling control means and slow cooling control means which form temperature distribution Explain the equipment configuration of the smoothing process Explanatory drawing explaining an example of a shape holding means Explanatory drawing explaining another aspect of a shape holding means Explanatory drawing explaining another aspect of a shape holding means Explanatory drawing explaining the curvature of a resin sheet Explanatory drawing explaining the control system of the manufacturing apparatus of an uneven thickness resin sheet Explanatory drawing explaining the apparatus driven with the control system of the manufacturing apparatus of an uneven thickness resin sheet Explanatory drawing explaining an example of the shape of an uneven thickness resin sheet

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Raw material process, 12 ... Extrusion process, 14 ... Molding cooling process, 15 ... Smoothing process, 15A ... Sheet heating means, 15B ... 1st thermometer, 15C, 15D ... Mirror surface roller, 15E ... 2nd thermometer , 15F ... roller heating means, 15G ... third thermometer, 16 ... slow cooling step, 18 ... warpage measuring step, 20 ... control step, 22 ... laminating step, 24 ... cutting / cutting step, 26 ... loading step, 28 ... Raw material silo, 30 ... Additive silo, 32 ... Automatic metering machine, 34 ... Mixer, 36 ... Hopper, 38 ... Extruder, 40 ... Metering pump, 42 ... Feed pipe, 44 ... Die, 46 ... Mold roller, 48 Nip roller, 50 peeling roller, 52 cooling control means, 53 flow path, 54 slow cooling zone, 55 heat insulating material, 56 shape retaining means, 58 concave roller, 60 roller, 62 short roller, 64 Long roller, 66 ... bearing, 68 ... air cylinder, 70 ... bearing, 74 ... feed roller, 78 ... warpage measuring device, 79 ... stocker, 80 ... measurement base, 82 ... reel, 84 ... protective film, 86 ... nip roller, 88 ... Cutting machine, 90 ... Cutting machine

Claims (10)

The raw material resin, which is a mixture of fine particles and resin, is melted and extruded into a sheet from a die, and the extruded resin sheet is nipped by a mold roller and a nip roller to be cooled and solidified while being molded into a predetermined shape. In the method for producing a particle-containing resin sheet, comprising a molding cooling step, and a slow cooling step of slowly cooling the molded resin sheet, and producing a resin sheet containing fine particles inside the sheet,
A smoothing step is provided between the molding cooling step and the slow cooling step to smooth the resin sheet surface by sandwiching both surfaces of the resin sheet peeled from the mold roller with a pair of mirror rollers. To produce a particle-containing resin sheet. In the smoothing step,
The center average roughness Ra of the mirror roller surface is 0.2 μm or less,
The surface temperature of the resin sheet before the smoothing treatment is a glass transition temperature Tg-20 ° C. or higher and Tg + 40 ° C. or lower of the resin,
The method for producing a particle-containing resin sheet according to claim 1, wherein the surface temperature of the resin sheet during the smoothing treatment satisfies three conditions of Tg-20 ° C or more and Tg or less.   The said smoothing process heats this resin sheet before performing the said smoothing process so that the surface temperature of the resin sheet before the said smoothing process may be Tg or more and Tg + 40 or less. Of producing a particle-containing resin sheet.   The method for producing a particle-containing resin sheet according to any one of claims 1 to 3, wherein the fine particles are diffusion particles having a function of diffusing light.   The particle-containing resin sheet according to any one of claims 1 to 4, wherein the fine particles are 15 µm or less and are contained in the particle-containing resin sheet at a concentration of 0.005 to 0.5 mass%. Manufacturing method.   6. The method for producing a particle-containing resin sheet according to claim 1, wherein in the molding cooling step, a resin sheet having an uneven thickness is formed by a mold roller for uneven thickness and a nip roller.   In the case of the uneven thickness resin sheet, one of the pair of mirror rollers used in the smoothing step is an uneven shape roller having the same shape as the uneven thickness shape. Item 7. A method for producing a particle-containing resin sheet according to Item 6.   The method for producing a particle-containing resin sheet according to any one of claims 1 to 7, wherein the particle-containing resin sheet is a light guide plate used for a backlight of a liquid crystal display device. The raw material resin, which is a mixture of fine particles and resin, is melted and extruded from a die into a sheet, and the extruded resin sheet is nipped between a mold roller and a nip roller to be cooled into a predetermined shape and solidified by cooling. In a production apparatus for a particle-containing resin sheet comprising a molding cooling means and a slow cooling means for gradually cooling the molded resin sheet, and producing a resin sheet containing fine particles inside the sheet,
Between the molding cooling means and the slow cooling means,
Sheet heating means for heating the resin sheet peeled from the mold roller;
An apparatus for producing a particle-containing resin sheet, comprising: a pair of mirror rollers that sandwich a heated resin sheet. A first thermometer for measuring the surface temperature of the resin sheet heated by the heating means before the smoothing treatment;
A second thermometer for measuring the surface temperature of the resin sheet after smoothing;
Roller heating means for heating the roller surfaces of the pair of mirror surface rollers;
A third thermometer for measuring the roller surface temperature of the mirror roller;
10. The particle-containing resin sheet according to claim 9, further comprising: a control unit that controls the sheet heating unit and the roller heating unit based on measurement results of the first to third thermometers. apparatus.

Images