WO2010029874A1

WO2010029874A1 - Process for producing resin sheet with thickness unevenness

Info

Publication number: WO2010029874A1
Application number: PCT/JP2009/065300
Authority: WO
Inventors: 卓弘林; 芳彦佐野; 勝本　隆一
Original assignee: 富士フイルム株式会社
Priority date: 2008-09-11
Filing date: 2009-09-02
Publication date: 2010-03-18
Also published as: JP2010064386A; JP4995163B2

Abstract

A process for producing a resin sheet with thickness unevenness, characterized by comprising: an extrusion step in which a molten resin is extruded from a die into a sheet form; a sheet forming step in which the molten resin sheet extruded is sandwiched between a die roller and a nipping roller to transfer a surface shape of the die roller to the molten resin sheet, and this sheet is cooled and solidified to form a resin sheet; a stripping step in which the resin sheet is stripped from a release roller; a conveyance step in which the resin sheet is drawn and conveyed with take-off rollers while heating the sheet with a heater; a cutting step in which the resin sheet is cut into a given length with a cutter when the resin sheet has a width-direction maximum surface temperature of (Tg-40) ºC to Tg ºC, provided that Tg is the glass transition temperature of the resin; and an annealing step in which the resin sheet cut with the cutter is successively annealed at a temperature of (Tg-40) ºC to Tg ºC.

Description

Manufacturing method of uneven thickness resin sheet

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

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

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

Therefore, a so-called annealing treatment is performed for the purpose of correcting residual strain relaxation or deformation of the thermoplastic resin molded article or for increasing the strength by promoting crystallization of the crystalline thermoplastic resin molded article. Yes. As the temperature is higher, the annealing treatment has a larger effect in a shorter time. However, if the temperature is too high, the resin melts and a molded body having a desired shape cannot be obtained. Therefore, in the case of a thermoplastic resin, it is generally annealed at a temperature 20 to 40 ° C. lower than the glass transition temperature Tg of the resin, and in the case of a crystalline resin, it is annealed at a temperature 10 to 20 ° C. higher than the highest temperature actually used. .

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

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

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

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

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method for manufacturing an uneven thickness resin sheet that can further shorten the annealing process and improve the productivity.

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

According to the first aspect, the cutting step is performed in a state where the maximum temperature of the surface in the width direction of the resin sheet is (Tg−40) ° C. or more and Tg ° C. or less, and the annealing step of the next step is also performed (Tg Since it is performed at a temperature of −40) ° C. or more and Tg or less, there is no need to cool the resin sheet after the cutting step and before the annealing treatment step. For this reason, annealing treatment time can be reduced and productivity can be improved.

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

According to the second aspect, during the annealing treatment step, the resin sheet is supported by the flat support member and annealed, so that the resin sheet in a soft state at high temperature becomes flat due to its own weight, and the resin sheet is deformed. Can be easily corrected.

According to a third aspect of the present invention, in the first or second aspect, the difference in thickness between the thickest part and the thinnest part of the thickness distribution in the width direction of the resin sheet is 0.5 mm or more and 5 mm or less. Features.

According to the third aspect, by adjusting the difference between the thickest part and the thinnest part of the thickness distribution in the above range, the temperature of the resin sheet can be easily adjusted in the transport process and the annealing process, Shape changes such as warping can be suppressed.

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

FIG. 1 is a process diagram illustrating a flow of a method for producing a resin sheet to which the present invention is applied; FIG. 2 is a conceptual diagram of a resin sheet manufacturing apparatus to which the present invention is applied; FIG. 3 is a structural diagram showing the annealing process from the sheet forming process of the resin sheet manufacturing apparatus; FIG. 4A is a cross-sectional view showing an example of the shape of a resin sheet; FIG. 4B is a cross-sectional view showing another example of the shape of the resin sheet; FIG. 5 is a configuration diagram illustrating another aspect of the resin sheet manufacturing apparatus.

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

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

As shown in FIG. 1, the manufacturing method of the uneven thickness resin sheet of the present invention mainly includes a raw material process 100 for measuring and mixing raw materials and an extrusion process 112 for continuously extruding molten resin into a sheet (band). And a sheet forming step 114 for forming the resin sheet 14 by cooling and solidifying the extruded molten resin sheet 14a, a peeling step 115 for peeling the resin sheet 14, and a cutting step for cutting the peeled resin sheet 14 as the next step. A conveying process 116 for conveying to 124, a cutting process 124 for cutting the resin sheet 14 into a predetermined size (length / width), an annealing process 126 for gradually cooling the resin sheet 14 and removing residual distortion, Consists of.

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

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

A thermoplastic resin can be used as the resin material of the raw material resin applied to the present invention. 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 Examples thereof include a resin (PVC), a thermoplastic elastomer, a copolymer thereof, and a cycloolefin polymer.

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

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

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

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

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

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

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

In addition, the resin sheet 14 is formed into a predetermined shape in the sheet forming step 114, but both edge portions of the resin sheet 14 have a dimensional accuracy worse than that of the central portion in the shape, and a large residual distortion. Therefore, it is preferable to cut. The cut portion is preferably cut at 20 to 30 mm at both ends of the resin sheet 14. As shown in FIG. 2, both edges of the resin sheet can be cut before cutting the resin sheet in a direction perpendicular to the conveying direction, or before cutting the sheet into a predetermined shape and performing an annealing treatment. It can also be cut.

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

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

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

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

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

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

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

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

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

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

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

The surface of the nip roller 18 is preferably processed into a mirror 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 14 after a shaping | molding can be made into a favorable state. The nip roller 18 is rotationally driven at a predetermined peripheral speed by a driving means (not shown). In addition, although the structure which does not provide a drive means in the nip roller 18 is also possible, when the point which can make the back surface of the resin sheet 14 a favorable state is provided, it is preferable to provide a drive means.

The nip roller 18 is provided with a pressing means (not shown) so that the resin sheet 14 between the nip roller 18 and the mold roller 16 can be 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 18 and the mold roller 16, and various known means such as a motor driving means, an air cylinder, and a hydraulic cylinder are employed. it can.

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

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

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

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

It is preferable that the heating in the transporting process is first performed by the heating device 22c from the lower surface side (the surface side not having the mold) of the resin sheet 14 after being peeled off by the peeling roller 20. This is because if the resin sheet 14 is heated too much from the upper surface side (the surface side where the mold is attached), the resin sheet 14 is deformed by the subsequent heat shrinkage, and a resin sheet having a desired shape may not be obtained. When at least the surface temperature of the resin sheet 14 is equal to or higher than Tg, it is preferable to heat from the lower surface side of the resin sheet.

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

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

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

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

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

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

DESCRIPTION OF SYMBOLS 12 ... Die 14 ... Resin sheet 14a ... Molten resin sheet 16 ... Mold roller 18 ... Nip roller 20 ... Peeling roller 22 ... Heating device 24 ... Take-off roller 26 ... Measuring base 100 ... Raw material process 112 ... Extrusion process 114 ... Sheet forming process 115 ... Peeling process 116 ... Conveying process 124 ... Cutting process 128 ... Raw material silo 130 ... Additive silo 132 ... Automatic meter 134 ... Mixer 136 ... Hopper 138 ... Extruder 140 ... Metering pump 142 ... Supply pipe 174 ... Cutting means 176 ... Recovery Box 194 ... Roller 196 ... Conveyor belt

Claims

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