JP2009220443A - Manufacturing method of uneven-thickness resin sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of uneven-thickness resin sheet capable of manufacturing an uneven-thickness resin sheet of preferable quality by preventing sheet defection of the uneven-thickness resin sheet having a deviation in film thickness with respect to the width direction. <P>SOLUTION: The manufacturing method of uneven-thickness resin sheet capable of manufacturing an uneven-thickness resin sheet having a deviation in film thickness with respect to the width direction comprises: a process of ejecting resin into a sheet shape from a lip port 42 of a die 16; and a process of molding the uneven-thickness resin sheet by nipping a sheet-like resin ejected from the die 16 at a nipping part 46 between the forming roller 20 and the nipping roller 18. With respect to the width direction, a film thickness difference between the thickest film part having the largest film thickness of the uneven-thickness resin sheet and the thinnest film part having the smallest film thickness thereof is 0.5 mm to 5 mm and the angle which a straight line B connecting the lip port 42 and the nipping part 46 forms with respect to the vertical direction A is 7° to 10°. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method of manufacturing an uneven thickness resin sheet having a biased film thickness. For example, a polarizing plate used for an optical element such as a light guide plate of a backlight of a liquid crystal display device or a light guide plate of a decoration / display / illumination display. The present invention relates to a method for producing a meat resin sheet.

  A light guide plate that guides light from a light source and emits a surface light is used in a backlight of a liquid crystal display device and a display device for decoration, display, and illumination. For example, a liquid crystal display device has a light guide plate from the back side of a liquid crystal panel. A backlight for irradiating light through a light guide plate is provided.

  Among such light guide plates, a light guide plate used for a large apparatus such as a large-screen liquid crystal television is generally manufactured by an extrusion molding method against the background of current equipment and technology. In this extrusion molding method, a resin sheet having a uniform film thickness is usually formed by cooling and solidifying a molten resin sheet extruded from a die (T-die or the like) with a cooling roller.

  In such an extrusion method using a molten resin, it is difficult to uniformly spread a molten resin sheet having fluidity, for example, a so-called neck-in phenomenon in which both the ears of the molten resin sheet are thick while the center is thin. For this reason, the thickness unevenness may occur in the resin sheet. From the viewpoint of suppressing such thickness unevenness, the distance between the landing point where the molten resin sheet first contacts the cooling roller and the lip opening of the die is made as small as possible, and the molten resin sheet is tangent to the cooling roller with respect to the cooling roller. It is preferable to touch the direction.

  On the other hand, the so-called air gap formed between the die and the cooling roller becomes larger as the cooling roller becomes larger, and the molten resin discharged from the die tends to be disturbed. Further, when the molten resin sheet is pulled down from the die in the vertical direction, the neck-in in the resin sheet tends to increase. Moreover, if the angle formed by the extrusion direction from the die of the molten resin sheet and the vertical direction is increased, the air gap can be reduced, but if this pulling angle is increased too much, the molten resin is likely to entrain air, Large thickness unevenness may occur.

  Against this backdrop, Patent Document 1 teaches an apparatus for forming a sheet by extruding a thermoplastic resin from a lip opening of a T die onto a chill roller. In this apparatus, a roller member is provided at a portion that contacts both ears of the molten resin sheet, and the drawing angle of the molten resin sheet is adjusted to a predetermined angle, thereby preventing surface defects caused by a neck-in phenomenon or the like. In addition to being peeled off, uneven thickness of the sheet is prevented.

  Also in Patent Document 2, a molten resin sheet having a uniform film thickness in which variations in film thickness are prevented is adjusted by adjusting the pulling angle of the molten resin extruded from the die to a predetermined angle. A method is taught.

Patent Document 3 teaches a resin sheet manufacturing apparatus in which a die discharge port is disposed on the mold roller side with respect to a common tangent line between the mold roller and the nip roller.
JP-A-8-309830 JP 2007-276273 A JP 2007-216505 A

  The techniques described in Patent Document 1 and Patent Document 2 described above can be applied to an apparatus for forming a resin sheet having a uniform film thickness throughout, but the uneven thickness resin having a bias in the film thickness. This is not necessarily a suitable technique for an apparatus for forming a sheet.

  When forming an uneven resin sheet having a large thickness distribution in the width direction, the molten resin sheet is pressed (pressed) against a molten resin sheet with a predetermined mold roller corresponding to the uneven shape of the sheet. On the other hand, the shape of the mold roller is transferred to give a desired uneven shape. At this time, a resin pool called a bank is formed above the sandwiched portion (nip portion) of the molten resin sheet by the high-temperature molten resin supplied from the die, and the desired quality is maintained by keeping this bank in a stable state. It becomes possible to mold the resin sheet.

  Depending on the clearance between the rollers that sandwich the molten resin sheet, the inflow amount of the molten resin between these rollers is determined. It changes according to the shape change. Therefore, when the supply amount of the molten resin to the pinching portion between the rollers is constant in the sheet width direction, an imbalance occurs between the portion where the clearance between the rollers is small and the portion where the clearance between the rollers is large. For example, a sufficiently large bank may not be formed at a location where the clearance between rollers is large, or the bank may become too large at a location where the clearance between rollers is small. Therefore, by distributing the die temperature or providing a so-called choke bar on the die, the distribution of the amount of molten resin discharged from the die gives a sufficiently large bank over the entire width. Attempts have been made.

  In addition, the shape of the mold roller in the sheet width direction has periodicity, and molding of a resin sheet that periodically includes a thin film portion and a film thickness portion in the sheet width direction may be required in accordance with product characteristics. When molding a resin sheet having a short shape cycle in an apparatus for molding a resin sheet having such a shape periodicity, the leveling of the molten resin itself can be performed without having a distribution in the amount of the molten resin discharged from the die. The bank tends to stabilize naturally by the action. For example, Patent Document 3 discloses a method of extruding an uneven thickness resin sheet having a thinnest film portion having a pitch of 30 mm. When the shape period is short as described above, the bank is relatively stable, The degree of freedom in the positional relationship between rolls is large. However, when molding a resin sheet with a relatively long shape cycle, it is difficult to keep the bank in a stable state only by the leveling action of the molten resin itself, and the distribution of the amount of molten resin discharged from the die gives the bank Must be in a stable state.

  When forming an uneven thickness resin sheet in this way, it is necessary to have an appropriate distribution in the amount of molten resin discharged from the die, but in order to have a distribution in the amount of molten resin supplied, a uniform film is required. Different molding conditions are required than when molding a thick resin sheet. For example, when molding an uneven thickness resin sheet, a molten resin sheet extruded from a die is likely to be affected by disturbance in the air gap portion and very easily disturbed. In addition, when the lip port of the die is arranged immediately above the clamping part, the molten resin sheet pushed out from the lip port has a direct influence on the bank, and the molded resin sheet to be molded Is prone to streaking. In addition, when the lip port of the die is arranged so as to be shifted from directly above the clamping part, even if the molten resin sheet is discharged from the die at a desirable pulling angle for the molten resin sheet having a uniform film thickness, Air may be caught between the molten resin sheet and the roller.

  The present invention has been made in view of such circumstances, and prevents unevenness of the uneven thickness resin sheet having an uneven thickness in the width direction, and produces an uneven thickness resin sheet of good quality. It aims at providing the manufacturing method of a resin sheet.

  One aspect of the present invention is a method for manufacturing an uneven thickness resin sheet having a deviation in film thickness in the width direction, a discharge step of discharging resin from a lip port of a die into a sheet shape, and a sheet discharged from the die A step of forming an uneven thickness resin sheet by pressing the resin in a shape between the mold roller and the nip roller, and with respect to the width direction, the thickness of the uneven thickness resin sheet The difference in film thickness between the largest film thickness portion with the largest thickness and the thinnest film thickness portion with the smallest film thickness is 0.5 mm or more and 5 mm or less, and the straight line connecting the lip mouth and the pressing portion is the vertical direction The present invention relates to a method for manufacturing an uneven thickness resin sheet, characterized in that the angle formed with respect to is 7 ° or more and 10 ° or less.

  According to this aspect, the resin discharged from the die can be stably supplied between the mold roller and the nip roller, and the bank formed between the mold roller and the nip roller can be prevented from being disturbed and good. An uneven thickness resin sheet having a flat surface shape can be produced. In particular, when molding an uneven thickness resin sheet having a film thickness difference of 0.5 mm or more and 5 mm or less during drying, it is very important to stably supply the resin between the mold roller and the nip roller. Although difficult, by arranging the die, mold roller, and nip roller so as to satisfy the above angle range, the resin can be stably supplied to the clamping part, and a high-quality resin sheet is molded. I found out that

  In particular, the angle formed by the straight line connecting the lip mouth and the clamping portion with respect to the vertical direction is 7.5 ° or more and 9 ° or less, so that the mold roller and the nip roller can be more stably connected. It has been found that the resin can be fed in between.

  The “clamping portion” here refers to a portion between the mold roller and the nip roller that is closest to each other, and is a portion that applies pressure for molding to the resin.

  The uneven thickness resin sheet may include a plurality of the thinnest film parts in the width direction, and the plurality of thinnest film parts may have a pitch of 200 mm or more.

  When molding an uneven thickness resin sheet having a long width as described above, it is particularly difficult to stably supply the resin between the mold roller and the nip roller. By disposing the die, the mold roller, and the nip roller in the above angle range, the resin can be stably supplied to the pinching portion.

  In addition, each said aspect of this invention is when manufacturing the resin sheet in which a film | membrane thin part and a film thickness part are continuously arranged regarding the width direction, ie, the resin sheet which has periodicity regarding the cross-sectional shape of the width direction. Is also effective. For example, with respect to the width direction of the resin sheet, a thin film portion is provided at both end portions and the central portion, and when a resin sheet in which a film thickness portion is provided between the thin film portions is molded, By disposing the mold roller and the nip roller, the resin can be stably supplied to the pinching portion.

  Therefore, the uneven thickness resin sheet may include a plurality of the maximum film thickness portions in the width direction, and the plurality of maximum film thickness portions may have a pitch of 200 mm or more.

  According to the present invention, in a manufacturing process of an uneven thickness resin sheet in which it is difficult to stably supply a resin between a mold roller and a nip roller, the resin discharged from the die is placed between the mold roller and the nip roller. It can be supplied in a very stable state. Thereby, disorder of the bank formed between a type | mold roller and a nip roller can be prevented effectively, and the uneven thickness resin sheet which has a favorable planar shape can be manufactured.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, a case where the uneven thickness resin sheet has a bowl shape (see FIGS. 2 and 3) will be described as an example.

  FIG. 1 is a diagram illustrating an example of an uneven thickness resin sheet manufacturing apparatus for manufacturing an uneven thickness resin sheet. In the uneven thickness resin sheet manufacturing apparatus 10 shown in FIG. 1, the raw material preparation apparatus 11, the extruder 12, the die 16, the molding cooling roller unit 17, the heat treatment zone 24, the cooling zone 26, the surface inspection machine 28, the laminating machine 30, and the cutting The machine 32 and the stacker 34 are sequentially provided from the upstream side to the downstream side.

  The raw material preparation device 11 prepares a raw material by measuring and mixing the raw material of the uneven thickness resin sheet S manufactured by the uneven thickness resin sheet manufacturing device 10, and the raw material is supplied to the extruder 12 through the raw material supply pipe 13. Send to. For example, in this raw material preparation device 11, the raw material resin and additive sent from the raw material tank and additive tank to the mixer are automatically weighed by an automatic meter, and a predetermined ratio of raw material resin and additive are mixed in the mixer. . 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 with a granulator, and the base to which the diffusing particles are not added is prepared. A master batch method in which the pellet and the mixer are mixed at a predetermined ratio can be suitably employed. In addition, also when adding additives other than a diffusion particle, it can mix similarly.

  As the raw material resin, 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, or the like can be used as a raw material resin.

  The extruder 12 melts the raw material sent from the raw material preparation device 11 while kneading to make a molten resin. The extruder 12 may be either a single-screw extruder or a multi-screw extruder, and preferably has a vent function for evacuating the inside of the extruder 12. The molten resin produced by the extruder 12 is sent to the die 16 via the molten resin supply pipe 14 by a metering pump such as a screw pump or a gear pump.

  In the die 16, the molten resin sent from the extruder 12 is extruded into a sheet shape toward the molding cooling roller unit 17 (hereinafter, the sheet-shaped resin is referred to as “resin sheet S”). In the present embodiment, since an uneven thickness resin sheet having a non-uniform film thickness in the sheet width direction is formed, the amount of molten resin extruded and discharged from the die 16 has a predetermined distribution in the sheet width direction. As means for giving a distribution to the amount of molten resin discharged from the die 16, for example, a method using a choke bar or other known methods can be used.

  The molding cooling roller unit 17 includes a nip roller 18, a mold roller 20, and a peeling roller 22. The molding cooling roller unit 17 imparts a bowl-shaped uneven thickness shape to the molten resin supplied from the die 16, and cools and solidifies the molten resin. I do. That is, the sheet-like molten resin extruded from the die 16 is cooled while being nipped by the nip roller 18 and the mold roller 20, and is given a bowl-shaped uneven thickness shape. The cooled and solidified resin sheet S is peeled off from the mold roller 20 by the peeling roller 22 and sent to the heat treatment zone 24 at the subsequent stage.

  In addition, the specific arrangement configuration of the die 16 and the molding cooling roller unit 17 (the nip roller 18, the mold roller 20, and the peeling roller 22) according to the present embodiment will be described later (FIGS. 4 and 5A). b)).

  The heat treatment zone 24 is a zone for subjecting the resin sheet S having an uneven thickness structure to a smoothing treatment or other heat treatment, and a plurality of non-contact heating means (not shown) such as a far infrared heater are arranged. In the case of the smoothing treatment, the resin sheet S is smoothed by being sandwiched between a pair of mirror rollers in a state where the surface temperature is adjusted within a predetermined temperature range based on the glass transition temperature. The non-contact type heating means used at this time can be installed in a mode according to the required heat treatment. For example, a far-infrared heater is disposed in the immediate vicinity of the peeling roller 22 or the resin sheet S is thin. It is also possible to arrange non-contact heating means so as to suppress the temperature difference generated in the entire resin sheet S by intensively heating the location. Further, the temperature of the resin sheet S moving through the heat treatment zone 24 is measured by a temperature sensor (not shown) such as a radiation thermometer, and the temperature in the heat treatment zone 24 is adjusted based on the measured temperature. In addition, if the surface temperature of the resin sheet S is excessively raised, problems such as warping may occur during conveyance. Therefore, the heating conditions including the heating temperature and the heating time are based on the line speed and the heater position. Adjust as appropriate.

  The cooling zone 26 is a zone that performs a slow cooling (annealing) process on the resin sheet S sent from the heat treatment zone 24, and prevents a rapid temperature change of the resin sheet S. When the resin sheet S is rapidly cooled, the surface shape is likely to deteriorate or warp due to a difference in shrinkage between the vicinity of the surface and inside, a temperature difference, or the like. In particular, in the case of an uneven thickness resin sheet having a distribution in film thickness, warpage is likely to occur due to rapid cooling or the like. Therefore, as an example of the slow cooling method in the cooling zone 26, the thin film portion is focused on the non-contact heating means so that a temperature difference does not occur between the thin film portion and the thin film portion of the resin sheet S in the first half. There is a method in which the entire resin sheet S is gradually naturally cooled by heating the resin sheet S, and forced cooling is performed to about room temperature by applying cold air to the resin sheet S in the latter half.

  In the heat treatment zone 24 and the cooling zone 26 described above, the resin sheet S is transported so as to prevent deformation such as warpage accompanying heat treatment and cooling and to maintain a desired uneven thickness shape. Specifically, a conveying means for feeding the resin sheet S to the subsequent stage while supporting the resin sheet S so as to maintain the uneven shape is used, and the resin sheet S from the conveying means is within a range that does not hinder the conveyance of the resin sheet S. External force is applied to the resin sheet S so that the uneven shape of the resin sheet S is maintained. Such a conveying means can have an arbitrary configuration. For example, a roller pair having an outer shape corresponding to the uneven shape of the resin sheet S or a combination of a plurality of rollers holds the uneven shape of the resin sheet S. An apparatus or the like can be used as the conveying means. By using such a conveying means, even if an internal stress (internal force) that causes a warp in the heat treatment zone 24 and the cooling zone 26 is generated in the resin sheet S, a pressure (external force) is applied to the resin sheet S from the conveying means. ) Is added, and the resin sheet S is held in an uneven shape with no inherent warpage. The internal stress is gradually relaxed with the progress of slow cooling.

  The surface inspection machine 28 evaluates the surface shape and warpage of the resin sheet S sent from the cooling zone 26. The evaluation by the surface inspection machine 28 is performed by an arbitrary method using sensors, and the evaluation result is based on the discharge control of the molten resin sheet S from the die 16 provided in the preceding stage, the heat treatment zone 24 and the cooling zone 26. Is fed back to heat treatment and cooling control.

  The laminating machine 30 attaches a protective film such as polyethylene to the front and back surfaces of the resin sheet S. For example, the protective film is drawn out so as to sandwich the resin sheet S from a pair of reels, and the protective film is pressure-bonded to the front and back surfaces of the resin sheet S by a roller or the like, whereby the resin sheet S can be laminated with the protective film. .

  The cutting machine 32 cuts out both ends (ear portions) of the resin sheet S in the width direction and cuts the resin sheet S into a predetermined length. The cutting machine 32 can have an arbitrary configuration. For example, a guillotine type cutting machine 32 including a receiving blade and a pressing blade, a cutting machine 32 using a laser cutter or an electron beam, and the like can be used.

  The uneven thickness resin sheets S cut into a predetermined shape by the cutting machine 32 are sequentially stacked on the stacker 34. The uneven thickness resin sheet S stored in the stacker 34 is sent to another processing step or shipped as a product.

  The uneven thickness resin sheet S manufactured by such an uneven thickness resin sheet manufacturing apparatus 10 has, for example, a cross-sectional shape shown in FIG. That is, in the uneven thickness resin sheet S, the film thickness part 52 having the largest film thickness is provided in the center part, and the film thin parts 54 having the smallest film thickness are provided in both end parts. Moreover, as shown in FIG. 3, it is also possible to manufacture a resin sheet S having a cross-sectional shape in which a plurality (two) of the resin sheets S shown in FIG. 2 are arranged in the sheet width direction. The resin sheet S shown in FIG. 3 has a cross-sectional structure in which the film thickness part 52 and the film thin part 54 are periodically arranged, and the film thin part 54 and the film thickness part 52 appear alternately in the sheet width direction. It has become.

  In addition, when manufacturing the uneven thickness resin sheet illustrated in FIG. 2 and FIG. 3, as the sheet width of the resin sheet S increases, the bank (see reference numeral 44 in FIG. 4) tends to be disturbed. It becomes difficult to prevent surface defects. Further, the larger the pitch P1 of the thin film portion 54 and the pitch P2 of the film thickness portion 52 are, the more easily the bank is disturbed, and it becomes difficult to prevent the surface defect of the resin sheet S. Further, as the film thickness difference in the sheet width direction of the resin sheet S, that is, the film thickness difference between the film thickness portion 52 and the film thin portion 54 increases, the bank is more likely to be disturbed, and it is difficult to prevent surface defects of the resin sheet S. Become. However, by adjusting the arrangement of the die 16 and the molding cooling roller portion 17 as described later, the sheet width is 200 mm or more and 750 mm or less (especially 450 mm or more and 750 mm or less), the pitch P1 of the thin film portion 54 and the film thickness portion 52 Molded resin sheet S with a pitch P2 of 200 mm or more and a difference in film thickness between the film thickness part 52 and the film thin part 54 of 0.5 mm or more and 5 mm or less (especially 0.5 mm or more and 3 mm or less) in a good state. can do.

  The pitch P1 of the thin film portion (most thin film portion) 54 and the pitch P2 of the film thickness portion (maximum film thickness portion) 52 may be 1000 mm or less, and the resin sheet S having such a pitch may be used. It can be used for a wide range of applications such as displays.

  Next, a specific arrangement configuration of the die 16 and the molding cooling roller unit 17 (the nip roller 18, the mold roller 20, and the peeling roller 22) will be described.

  4 is a view of the die 16 and the molding cooling roller portion 17 as viewed from the side, and FIG. 5A is a view of the molding cooling roller portion 17 as viewed from below. Moreover, the modification of the shaping | molding cooling roller part 17 is shown in FIG.5 (b).

  While the nip roller 18 and the peeling roller 22 have a cylindrical shape with a uniform thickness, the mold roller 20 has a so-called concave shape with a narrow central portion and thick both ends. The concave shape of the mold roller 20 corresponds to the inverted shape of the uneven shape of the bowl shape of the resin sheet S, and the mold roller 20 and the nip roller 18 press the high temperature resin sheet S to form a bowl shape. Is done.

  As shown in FIG. 5B, the mold roller 20 can also have a shape having tapered tapered recesses 20A at both ends. In this case, when the resin sheet S is clamped between the nip roller 18 and the mold roller 20, a portion of the resin sheet S corresponding to the tapered recess 20A can be easily cut. This is because the both end portions (ear portions) of the resin sheet S tend to be thicker than a desired film thickness, and the film thickness portion takes into consideration the possibility of promoting the warpage of the resin sheet S in the subsequent steps. is there. Further, since the portion 18A of the nip roller 18 that contacts the thin film forming portion 20B of the mold roller 20 is easily worn, the abutting portion 18A of the nip roller 18 is made of super hard material such as tungsten carbide. It is preferable to perform a hard treatment or quenching. Similarly, for the mold roller 20 and the peeling roller 22, it is preferable to perform a cemented carbide treatment or quenching on a contact portion such as the thin film forming portion 20 </ b> B.

  A film thickness forming portion 20 </ b> C corresponding to the film thickness portion 52 of the resin sheet S is provided in the central portion of the mold roller 20 shown in FIGS. 5A and 5B having such a configuration.

  As shown in FIG. 4, the die 16 is disposed slightly above the mold roller 20 above the nip roller 18 and the mold roller 20. Further, the nip roller 18, the mold roller 20, and the peeling roller 22 are rotationally driven in a direction indicated by an arrow shown in FIG. 4 at a predetermined peripheral speed by a driving device (not shown). In addition, although the structure which does not provide a drive means with respect to the nip roller 18 and the peeling roller 22 is also possible, from a viewpoint which shape | molds the planar shape (especially back surface) of the resin sheet S favorably, the nip roller 18 and A configuration in which the peeling roller 22 is also rotationally driven is preferable. In such a configuration, the molten resin discharged from the lip port 42 of the die 16 forms a bank 44 between the nip roller 18 and the mold roller 20, and also the nip roller 18 and the mold roller 20 in the clamping unit 46. It is pinched by. The molten resin sheet S imparted with the uneven thickness shape by the nip roller 18 and the mold roller 20 is sent out while being wound around the mold roller 20, and is peeled off from the mold roller 20 by the peeling roller 22.

  In the above-described configuration, the inventor of the present invention, as a result of experiments to be described later, shows an angle formed by a straight line B connecting the lip port 42 of the die 16 and the pinching portion 46 with the vertical direction (vertical line) A (push-out angle: withdrawal). By setting the angle) θ to 7 ° to 10 °, more preferably 7.5 ° to 9 °, the bank 44 can be in a stable state, and the uneven thickness resin sheet S has a good surface shape. Obtained the knowledge that can be molded. The range of the extrusion angle θ is, in particular, the pitch P1 of the thin film portion 54 and the pitch P2 of the film thickness portion 52 shown in FIGS. 2 and 3 when molding an uneven thickness resin sheet having a deviation in film thickness with respect to the sheet width direction. Has a pitch of 200 mm or more, and the thickness difference between the film thickness part 52 and the film thin part 54 is 0.5 mm or more and 5 mm or less (especially 0.5 mm or more and 3 mm or less). Is very effective. This is because the bank 44 is very easily disturbed because the mold roller 20 has a concave shape, but by setting the extrusion angle θ in the above range, the nip roller 18 and the mold roller 20 are separated from the die 16. This is because the molten resin can be stably supplied in the meantime, and the disturbance of the bank 44 can be effectively prevented.

  In addition, as materials of the nip roller 18, the mold roller 20, and the peeling roller 22, various steel members, stainless steel, copper, zinc, brass, a material in which these metal materials are cored, and a rubber lining on the surface, these Metal materials plated with HCr plating, Cu plating, Ni plating, etc., ceramics, and various composite materials can be used.

  In addition, the reverse shape of the surface of the mold roller 20 can be formed by a known processing method. For example, grinding, ultrasonic processing, electrical discharge processing, cutting with an NC lathe, finishing buffing, etc. It is possible to form a combination as appropriate. 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 centerline average roughness Ra.

  Further, the nip roller 18, the mold roller 20, and the peeling roller 22 are provided with temperature adjusting means (not shown) for providing the resin sheet S with a cooling temperature distribution corresponding to the ridge shape of the uneven thickness resin sheet S. Is provided. As the temperature adjusting means, for example, a configuration in which the temperature-controlled cooling liquid is allowed to flow from one end side to the other end side inside the mold roller 20 can be employed.

  The nip roller 18 is provided with a pressing means (not shown) so that the resin sheet S between the nip roller 18 and the mold roller 20 can be pressed with a predetermined pressure. 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 20, and various known means such as a motor driving means, an air cylinder, and a hydraulic cylinder can be employed. . Further, 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 (on the side opposite to the mold roller 20), a configuration employing a middle-high crown shape, and rigidity of the central portion in the axial direction of the roller. A configuration of a roller having a strength distribution that increases, or a configuration combining them can be adopted.

  The surfaces of the nip roller 18 and the peeling roller 22 are preferably processed into a mirror surface. By setting it as such a surface, the back surface of the resin sheet S after shaping | molding can be finished in a favorable state. The surface roughness of the nip roller 18 and the peeling roller 22 is preferably 0.5 μm or less, more preferably 0.2 μm or less in terms of the center line average roughness Ra.

  The nip roller 18, the mold roller 20, and the peeling roller 22 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.

  The present invention is not limited to the above-described embodiments and modifications thereof, and various modifications such as design changes can be added based on the knowledge of those skilled in the art. The described embodiments can also be included in the scope of the present invention.

  Based on the above-described embodiment, the present inventor manufactured an uneven thickness resin sheet under the conditions described in the following examples and comparative examples, and visually evaluated the warpage and surface shape of the uneven thickness resin sheet (FIG. 6). reference).

Example 1
PMMA (80NH manufactured by Asahi Kasei Co., Ltd., glass transition temperature 110 ° C.) was used as a raw material resin, and the molten resin was extruded into a sheet form at 100 kg / hr from a die (T die) 16 set at a temperature of 255 ° C. The resin sheet S was processed in the nip roller 18, the mold roller 20, the peeling roller 22, the heat treatment zone 24, and the cooling zone 26, so that the resin sheet S was formed to have a bowl-shaped cross section illustrated in FIG. 2. Then, both ends of the resin sheet S were cut by the cutting machine 32. The resin sheet S thus produced had a cross-sectional width of 594 mm, a film thickness of the thin film portion 54 of 2 mm, and a film thickness of the film thickness portion 52 of 3.8 mm in a dry state. . The surface temperatures of the nip roller 18, the mold roller 20, and the peeling roller 22 were 70 ° C, 90 ° C, and 95 ° C, respectively. The roller diameters of the nip roller 18 and the peeling roller 22 were Φ350 mm, the roller diameter of the thin film forming portion 20B of the mold roller 20 was Φ350 mm, and the roller diameter of the film forming portion 20C was Φ345.6 mm. The rotation speed of each roll was 0.75 m / min for the nip roller 18, 0.75 m / min for the mold roller 20, and 0.77 m / min for the peeling roller 22. The clearance between the nip roller and the mold roller was 3.9 mm at the maximum portion at the center of the roller, and the clearance between the mold roller and the peeling roller was 4.0 mm at the maximum portion at the center of the roller. The die lip width was 660 mm, the lip opening was 4 mm, and the flow rate distribution in the width direction was adjusted with a choke bar so as to be approximately proportional to the clearance amount between the nip roller 18 and the mold roller 20.

  Then, an angle (push-out angle: pull-down angle) θ formed by a straight line B connecting the center of the lip port 42 of the die 16 and the center of the clamping part 46 formed by the nip roller 18 and the mold roller 20 is 9. Set to 0 °. The vertical distance between the lip port 42 and the pinching portion 46 was 133 mm. When the resin sheet S thus obtained was visually evaluated, a resin sheet S having a relatively good surface shape was obtained, and the bank 44 formed between the nip roller 18 and the mold roller 20 was also stable. I kept the state.

(Example 2)
Under the same conditions as in Example 1, the extrusion angle θ was set to 7.7 ° without changing the vertical distance between the lip port 42 and the pinching portion 46, and the cross-sectional shape shown in FIG. The resin sheet S having was molded. In this case, the bank 44 was stable and the resin sheet S having a very good surface shape could be formed.

(Example 3)
In this example, the resin sheet S having the cross-sectional shape shown in FIG. 3 in which the film thickness part 52 and the film thin part 54 are periodically arranged in the sheet width direction was molded. A roller having a shape corresponding to the cross-sectional shape of the resin sheet S shown in FIG. 3 is used as the molding cooling roller unit 17 (the nip roller 18, the mold roller 20, and the peeling roller 22). The molten resin was extruded. Other conditions were the same as in Example 1, and the resin sheet S was molded. The total width of the cross-sectional shape in the sheet width direction of the molded resin sheet S is 560 mm, the pitch P2 of the film thickness part 52 and the pitch P1 (cycle of the cross-sectional shape) of the film thin part 54 are 280 mm, and the film thin part 54 The film thickness was 2 mm, and the film thickness of the film thickness portion 52 was 3.5 mm.

  When the state of the resin sheet S thus obtained was visually evaluated, a resin sheet S having a good surface shape was obtained in the same manner as in Example 1, and the nip roller 18 and the mold roller 20 The bank 44 formed between them kept a stable state.

Example 4
The extrusion rate from the die is 133 kg / hr, the rotation speeds of the nip roller 18, the mold roller 20, and the peeling roller 22 are 1.00, 1.00, and 1.02 m / min, respectively, and the nip roller 18, the mold roller 20, 2 and the surface temperature of the peeling roller 22 are set to 70 ° C., 75 ° C., 90 ° C., respectively, and the other conditions are the same as those in the first embodiment, and the extrusion angle θ is set to 9.0 °. A resin sheet S having a cross-sectional shape was molded. In this case, the bank 44 was stable and the resin sheet S having a very good surface shape could be formed.

(Example 5)
Under the same conditions as in Example 4, the extrusion angle θ was set to 7.7 ° without changing the vertical distance between the lip port 42 and the pinching portion 46, and the cross-sectional shape shown in FIG. The resin sheet S having was molded. In this case, the bank 44 was stable and the resin sheet S having a good surface shape could be formed.

(Example 6)
Under the same conditions as in Example 4, the extrusion angle θ was set to 7.4 ° without changing the vertical distance between the lip port 42 and the pinching portion 46, and the cross-sectional shape shown in FIG. The resin sheet S having was molded. In this case, the bank 44 was relatively stable, and the resin sheet S having a relatively good surface shape could be formed.

(Comparative Example 1)
Under the same conditions as in Example 1, the extrusion angle θ was set to 7.3 ° without changing the vertical distance between the lip port 42 and the pinching portion 46, and the cross-sectional shape shown in FIG. The resin sheet S having was molded. In this case, the molten resin extruded from the die 16 is disturbed in the air gap portion, and the stable bank 44 cannot be formed. The surface shape of the resin sheet S was relatively good.

(Comparative Example 2)
Under the same conditions as in Example 1, the extrusion angle θ was set to 9.4 ° without changing the vertical distance between the lip port 42 and the pinching portion 46, and the cross-sectional shape shown in FIG. The resin sheet S having was molded. In this case, the molten resin entrained air while reaching the bank 44 from the die 16, and the bank 44 was somewhat disturbed. Although the surface state of the obtained resin sheet S was somewhat affected by the air that was involved, there was no level of disturbance that could not be used in the product.

(Comparative Example 3)
Under the same conditions as in Example 4, the extrusion angle θ was set to 6.8 ° without changing the vertical distance between the lip port 42 and the pinching portion 46, and the cross-sectional shape shown in FIG. The resin sheet S having was molded. In this case, the molten resin extruded from the die 16 is disturbed in the air gap portion, and the stable bank 44 cannot be formed. The surface shape of the resin sheet S was relatively good.

(Comparative Example 4)
Under the same conditions as in Example 4, the extrusion angle θ was set to 10.2 ° without changing the vertical distance between the lip port 42 and the pinching portion 46, and the cross-sectional shape shown in FIG. The resin sheet S having was molded. In this case, the molten resin entrained air while reaching the bank 44 from the die 16, and the bank 44 was somewhat disturbed. Further, the surface shape of the obtained resin sheet S was also affected by the entrained air, and a good surface shape could not be obtained.

  The evaluation results of Examples 1 to 6 and Comparative Examples 1 to 4 are shown in FIG. As is clear from FIG. 6, the extrusion angle θ formed by the straight line B connecting the lip port 42 of the die 16 and the pinching portion 46 with the vertical direction A is set in the range of 7 ° to 10 °. An uneven thickness resin sheet S having a good surface shape was obtained, and in particular, an uneven thickness resin sheet S having a very good surface shape was obtained by setting in a range of 7.5 ° to 9 °. Further, as is clear from the comparison between Example 1 and Example 3, the setting range of the extrusion angle θ described above is a case where the cross-sectional shape in the width direction of the resin sheet S has periodicity, It turns out to be effective.

  In addition, said various dimensions are fundamentally based on the time of drying of the uneven thickness resin sheet.

It is a figure which shows an example of the whole process which manufactures the uneven thickness resin sheet which concerns on one Embodiment of this invention. It is a figure which shows an example of the cross-sectional shape of an uneven thickness resin sheet. It is a figure which shows the other example of the cross-sectional shape of an uneven thickness resin sheet. It is the figure which looked at the die | dye and the shaping | molding cooling roller part from the side. (A) is the figure which looked at an example of the shaping | molding cooling roller part from the downward direction. (B) is the figure which looked at the other example of the shaping | molding cooling roller part from the downward direction. It is a table | surface which shows the planar evaluation of the uneven thickness resin sheet obtained in the Example and the comparative example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Uneven thickness resin sheet manufacturing apparatus, 11 ... Raw material preparation apparatus, 12 ... Extruder, 13 ... Raw material supply pipe, 14 ... Molten resin supply pipe, 16 ... Die, 17 ... Molding cooling roller part, 18 ... Nip roller, 20 ... mold roller, 20A ... tapered concave part, 20B ... tapered convex part, 22 ... peeling roller, 24 ... heat treatment zone, 26 ... cooling zone, 28 ... surface inspection machine, 30 ... laminating machine, 32 ... cutting machine, 34 ... stacker 42 ... Lip port, 44 ... Bank, 46 ... Clamping part, 52 ... Film thickness part, 54 ... Thin film part, S ... Resin sheet

Claims (2)

A method for manufacturing an uneven thickness resin sheet having a bias in film thickness with respect to the width direction,
A discharge step of discharging resin from the lip opening of the die into a sheet,
A molding step of molding an uneven thickness resin sheet by clamping the sheet-like resin discharged from the die at a clamping part between a mold roller and a nip roller,
Regarding the width direction, the difference in film thickness between the thickest film thickness portion of the uneven thickness resin sheet and the thinnest film thickness of the smallest film thickness is 0.5 mm or more and 5 mm or less,
The manufacturing method of the uneven thickness resin sheet characterized by the angle which the straight line which connects the said lip mouth and the said clamping part comprises with respect to a perpendicular direction is 7 degrees or more and 10 degrees or less. The uneven thickness resin sheet includes a plurality of the thinnest film portions in the width direction,
The manufacturing method of the uneven thickness resin sheet according to claim 1, wherein the plurality of thinnest film portions have a pitch of 200 mm or more.

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