JP2010214940A - Method for producing crystalline resin sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a crystalline resin sheet in which concave warpage is eliminated, and which is excellent in flatness by a simple method. <P>SOLUTION: The method for producing the crystalline resin sheet comprises: the step for extruding crystalline resin in a sheet form from a die 1; the step for forming an extruded sheet by passing the extruded sheet-form crystalline resin through rolling rolls; and the step for conveying the extruded sheet in such a manner that the width direction of the surface of the extruded sheet is kept horizontal. The step for conveying the extruded sheet is carried out by bringing the extruded sheet into contact with at least four conveyance rolls 6 arranged in the conveyance direction of the extruded sheet, and includes a total of two or more steps of at least one step of: the step for bringing the upper surface of the extruded sheet into contact with the conveyance rolls in the conveyance direction and then bringing the lower surface of the extruded sheet into contact with the conveyance rolls in the conveyance direction; and the step for bringing the lower surface of the extruded sheet into contact with the conveyance rolls in the conveyance direction and then bringing the upper surface of the extruded sheet into contact with the conveyance rolls in the conveyance direction. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a crystalline resin plate.

  In recent years, high flatness has been required for a light diffusing plate used in a backlight device constituting a direct liquid crystal display. Conventionally, polymethylmethacrylate (PMMA) resin, methylmethacrylate-styrene copolymer (MS) resin, polystyrene (PS) resin, polycarbonate (PC) resin, etc. have been used as the light diffusion plate. It was a crystalline resin. On the other hand, light diffusing plates made of crystalline resins such as propylene resin are lightweight, have high mechanical strength and are not easily broken, and have the characteristics that they are not easily deformed by the effects of moisture absorption or heat from the light source. Known (for example, Patent Document 1).

  However, when a crystalline resin such as a propylene resin is molded by an extrusion molding method, heat generation due to crystallization is accompanied at the stage of cooling from the molten state and molding, so that it is difficult to control sheet warpage. In particular, as light diffusion plates used in backlight devices for liquid crystal displays, high flatness is required, so light diffusion plates made of crystalline resin such as propylene resin are manufactured while controlling warpage by extrusion molding. It was technically difficult to do.

  As a method for preventing such warpage, conventionally, a method of passing on the transport roll in a flat state after passing the rolling roll at the time of extrusion molding (for example, see FIG. 5) has been adopted. Only concave warpage occurred in a cross section parallel to the direction), and no convex warpage in the MD direction occurred. Therefore, it has been difficult to suppress or control warpage. Since such a concave warp in the MD direction affects the warp of the obtained sheet, various methods for suppressing or eliminating the occurrence of the warp of the sheet including the concave warp in the MD direction have been studied.

  For example, in Patent Document 2, as shown in FIG. 6, the resin sheet 2 that passes through the pressing rolls 3, 4, 5 is heated by the heaters 8, 9, and then conveyed by a conventional method. A method for reducing such distortion is disclosed. Further, in Patent Document 3, as shown in FIG. 7, a warping roll 10 is provided to adjust the warpage amount, and the resin sheet 2 when passing through the warping roll 10 is heated or cooled, A method for controlling the temperature difference between the upper and lower surfaces of the resin sheet 2 during conveyance is disclosed. Patent Document 4 discloses a method of arranging a specific warping roll 20 to suppress the occurrence of warping or adjust the warping, as shown in FIG.

JP 2008-083660 A JP 2002-120248 A JP 2002-120249 A Japanese Patent Laying-Open No. 2005-088310

  However, in the conventional method, the apparatus configuration for suppressing the warp is complicated, and the suppression or adjustment of the warp in the transport direction of the extruded sheet is insufficient, and the concave warp in the transport direction remains. was there. It is an object of the present invention to provide a method for producing a crystalline resin plate having excellent flatness by eliminating a warp of a sheet including such a concave warp and a simple method.

  That is, the present invention includes a step of extruding a crystalline resin from a die into a sheet, a step of passing the extruded sheet-like crystalline resin through a rolling roll to form an extruded sheet, and a width of the sheet surface of the extruded sheet. A method of manufacturing a crystalline resin plate including a step of conveying an extruded sheet so that the direction is horizontal, and the step of conveying includes at least four conveying rolls arranged along the conveying direction of the extruded sheet. A step of bringing the upper surface of the extruded sheet into contact with the transport roll along the transport direction and then bringing the lower surface of the extruded sheet into contact with the transport roll along the transport direction. Crystallinity including at least one of the step of bringing the surface into contact with the transport roll along the transport direction and then bringing the upper surface of the extruded sheet into contact with the transport roll along the transport direction. The method of manufacturing a fat plate.

  The transporting step is performed by contacting at least four transporting rolls arranged along the transporting direction of the extruded sheet, and this contact is performed on either the upper surface or the lower surface of the extruded sheet. It is preferable to alternately contact these along the transport direction.

The transporting step is performed when the crystallization temperature of the crystalline resin is T _c (° C.) and the first transporting roll is brought into contact with the first transporting roll along the transporting direction among four consecutively disposed transporting rolls. _Assuming that the temperature of the sheet surface on the side not in contact with the transport roll is T _warp (° C.), it is preferable that T _warp satisfy the following formula (1).
T _c −30 ≦ T _warp ≦ T _c +20 (1)
The production method of the present invention is suitable when the crystalline resin is a propylene resin.

  According to the present invention, it is possible to suppress or control the concave warp in the conveyance direction by a simple method, and to reduce the warp of the entire sheet, compared to a sheet (resin plate) obtained by a conventional method, Generation | occurrence | production of the wave | undulation of a sheet | seat can be suppressed and the resin board excellent in flatness can be provided. Further, according to the method of the present invention, since the sheet is cooled at a shorter conveying distance than the conventional method, the sheet can be produced even in a small space where the conveying distance is more limited.

It is a schematic sectional drawing of the apparatus used for the manufacturing method of the crystalline resin board of this invention. It is a schematic sectional drawing which shows the pitch of an adjacent conveyance roll. It is a figure which shows the positional relationship of the orthogonal | vertical direction of an adjacent conveyance roll. 1 is a schematic cross-sectional view of an apparatus used in a method for producing a crystalline resin plate in Example 1. FIG. It is a schematic sectional drawing of the apparatus used for the manufacturing method of the conventional crystalline resin board. It is a schematic sectional drawing of the apparatus used for the manufacturing method of the conventional crystalline resin board provided with the heater. It is a schematic sectional drawing of the apparatus used for the manufacturing method of the conventional crystalline resin board provided with the curvature roll. It is a schematic sectional drawing of the apparatus used for the manufacturing method of the conventional crystalline resin board provided with the three warp rolls. It is a schematic sectional drawing of the apparatus used for the manufacturing method of the crystalline resin board in Example 4. FIG. (A) It is a schematic sectional drawing which shows the 1st aspect of the positional relationship of a conveyance roll and the extrusion sheet conveyed, (b) The 2nd aspect of the positional relationship of a conveyance roll and the extrusion sheet conveyed is shown. It is a schematic sectional drawing, (c) It is a schematic sectional drawing which shows the 3rd aspect of the positional relationship of a conveyance roll and the extrusion sheet conveyed, (d) The positional relationship of a conveyance roll and the extrusion sheet conveyed It is a schematic sectional drawing which shows a 4th aspect. 6 is a schematic cross-sectional view of an apparatus used in a method for producing a crystalline resin plate in Comparative Example 2. FIG. It is a schematic diagram which shows the cross-sectional shape of the replica of the groove | channel of a V-shaped dent given to a transfer type | mold. It is a schematic diagram of the cross-sectional shape of the replica of the semicircular recessed groove | channel given to a transfer type | mold. It is a schematic diagram of a cylindrical lens. It is a schematic diagram of an example of the cross-sectional shape of the replica of the recessed groove | channel which is a V-shaped groove | channel-curved surface composite shape given to a transfer type | mold. It is a schematic diagram of an example of a partial cross-sectional shape of a recessed groove that is a V-shaped groove-curved surface combined shape. It is a schematic diagram of another example of the cross-sectional shape of the replica of the recessed groove given to a transfer mold.

  Hereinafter, the present invention will be described in more detail. In the following description of the embodiments, the description is made with reference to the drawings. In the drawings of the present application, the same reference numerals denote the same or corresponding parts.

<Method for producing crystalline resin plate>
The method for producing a crystalline resin plate of the present invention comprises a step of extruding a crystalline resin from a die into a sheet, a step of passing the extruded sheet-like crystalline resin through a rolling roll to form an extruded sheet, And conveying the extruded sheet so that the width direction of the sheet surface of the sheet is horizontal.

  In the present invention, a crystalline resin (hereinafter sometimes referred to simply as a resin) is a polymer compound having a property of becoming a crystal in a solid state, as defined in a chemical dictionary (Tokyo Kagaku Dojin) and the like. A resin (polymer) showing a crystalline diffraction peak in an X-ray diffraction spectrum. When a resin plate excellent in flatness is produced by extrusion molding in a crystalline resin, the occurrence of warpage of the entire sheet including concave warpage in the transport direction becomes a problem as described above. The present invention is effective for suppressing or eliminating warpage when such a crystalline resin is extruded to form a resin plate.

  The crystalline resin may be composed of a single unit or may be composed of a copolymer containing two or more units. For example, a propylene polymer or propylene copolymer containing 75% by mass or more of propylene units in the crystalline resin can be exemplified. Specifically, the propylene unit content is 75 to 100% by mass and the ethylene unit is 0. It is preferably composed of a propylene polymer or a propylene copolymer containing ˜15% by mass and 1 to 25% by mass of 1-butene unit. More preferably, it is a case where the propylene unit is constituted by a propylene polymer containing 95% by mass or more, 0 to 5% by mass of ethylene units and 0 to 5% by mass of 1-butene units, and more preferably propylene units. This is a case where it is composed of 99% by mass or more, a propylene polymer containing 0 to 1% by mass of ethylene units and 0 to 1% by mass of 1-butene units. The propylene unit content may be 100% by mass. In addition, although the manufacturing method of this invention is especially useful for crystalline resin, also when using a thermoplastic resin or a thermosetting resin, it is possible to suppress the curvature of the whole sheet | seat.

  In addition, additives such as a nucleating agent, a light diffusing agent, an ultraviolet absorber, a heat stabilizer, a processing stabilizer, and an antistatic agent may be added to the resin. The blending amounts of these additives may be adjusted and used within the range where the effects of the present invention are exhibited, and are not particularly limited. In addition, amorphous resins other than crystalline resins may be mixed to such an extent that the effects of the present invention are not impaired. In particular, when the resin constituting the extruded sheet is a propylene-based resin, mixing the acrylic resin causes the refractive indexes of these resins to be approximately equal, so that the mechanical properties such as rigidity are maintained without impairing the transparency of the resulting resin plate. This is useful as a method for improving the characteristics.

  The light diffusing agent may be an inorganic light diffusing agent or an organic light diffusing agent. Examples of the inorganic light diffusing agent include particles of inorganic compounds such as calcium carbonate, barium sulfate, titanium oxide, aluminum hydroxide, silica, inorganic glass, talc, mica, white carbon, magnesium oxide, and zinc oxide. . The inorganic light diffusing agent may be surface-treated with a surface treatment agent such as a fatty acid. Examples of the organic light diffusing agent include organic compound particles such as styrene polymer particles, acrylic polymer particles, and siloxane polymer particles.

  When a light diffusing agent is added, the absolute value of the difference between the refractive index of the added light diffusing agent and the refractive index of the resin is usually 0.02 or more in terms of the effect of light diffusion, and the resulting crystallinity In terms of light transmittance of the resin plate, it is usually 0.25 or less. Thus, when a light diffusing agent is added to resin, the obtained crystalline resin plate can be used as a light diffusing plate. The addition amount of the light diffusing agent is not particularly limited, and may be adjusted as appropriate.

  When a nucleating agent is contained in the crystalline resin, the production efficiency of the sheet can be improved by promoting crystallization. As the nucleating agent, known ones such as organophosphate nucleating agents can be used. For example, the content may be 0.03 to 1.0 part by mass with respect to 100 parts by mass of the crystalline resin. However, it is not limited to this range.

  The step of extruding the crystalline resin into a sheet is performed using a die. As such a die, a metal T die used in a conventionally known extrusion molding can be used. The resin is continuously extruded from the die in a heated and melted state, and an extruder can be used for this extrusion in the same manner as in a normal extrusion molding method. The extruder may be a single screw extruder or a twin screw extruder. The crystalline resin is heated in an extruder, sent to a die in a molten state, and extruded. The resin extruded from the die is continuously extruded in the form of a sheet. The shape of the sheet is not particularly limited, and the thickness and width are adjusted depending on the use of the obtained resin plate. Further, the extruded sheet may have a single layer structure or a laminated structure of two or more layers. What is necessary is just to change these structures suitably according to the use of the resin board obtained as mentioned above. For example, when used as a light diffusion plate, the total thickness is usually 0.1 mm to 3.0 mm, preferably 0.5 mm to 3.0 mm, and more preferably 0.8 mm to 3.0 mm.

  The crystalline resin extruded into the sheet is then subjected to a step of forming an extruded sheet through a rolling roll. FIG. 1 shows a schematic cross-sectional view of an apparatus used in the method for producing a crystalline resin plate of the present invention. The crystalline resin sheet extruded from the die 1 is sandwiched between a first pressing roll and a second pressing roll, which are rolling rolls, and formed into a pressing sheet 2 having a desired thickness. The 1st press roll and the 2nd press roll which are rolling rolls should just be a well-known roll used for manufacture of such a resin board, and the diameter is not specifically limited, either. Further, the first, second and third pressing rolls may be mirror rolls or so-called transfer rolls having a lens shape, an embossed shape, a prism shape or the like. Although the surface temperature of these press rolls is not particularly limited, it is usually preferably set to 50 ° C to 150 ° C. When a pressed sheet is formed by rolling under such temperature conditions, the effect of improving the flatness of the resulting crystalline resin plate is further improved by combining with the subsequent steps of the method for producing the crystalline resin plate of the present invention. Can be made.

  The transfer roll is a roll having a transfer mold on the surface. The transfer mold is pressed against the surface of the continuous resin sheet, and the surface shape is transferred to the continuous resin sheet as a reverse mold. The transfer mold is composed of, for example, a plurality of recesses or protrusions provided on the surface of the transfer roll, and the pitch interval between the recesses or protrusions is usually 10 μm or more, preferably 30 μm or more, because the transfer mold can be easily produced. Preferably it is 50 micrometers or more. The upper limit is not particularly limited, but is usually 500 μm or less, preferably 250 μm or less.

  Further, the groove depth of the concave portion or the top height of the convex portion is 30 μm to 1500 μm from the viewpoint of manufacturing the transfer mold, but is not limited to this range.

  The ratio of the groove depth to the pitch interval of the recesses of the transfer mold (groove depth / pitch interval) or the ratio of the top height to the pitch interval of the protrusions (top height / pitch interval) is the resin's crystallization temperature peak. When a crystalline polymer resin having a width of 9 ° C. or less is used, suitable transfer can be performed even if the ratio is 1 or more, and further 1.2 or more. The ratio of groove depth (groove depth / pitch interval) to the pitch interval of recesses of this transfer mold or the ratio of top height to the pitch interval of protrusions (top height / pitch interval) is usually 5 or less, preferably 3 or less. The ratio may be less than 1.

FIG. 12 is an example of a transfer mold surface, and is a cross-sectional surface view of a transfer mold having a V-shaped (triangle) cross-sectional shape. In FIG. 12, the top of the cross-sectional shape and the entire cross-sectional shape of the concave portion or the convex portion are V-shaped (triangles). As shown in FIG. 12, the transfer mold is provided with a plurality of concave portions or convex portions, and the pitch interval (P ′) between the concave portions or convex portions is the distance between the groove portions of adjacent concave portions (P in FIG. 12). ₁ ′) or the distance between the tops of adjacent convex parts (P ₂ ′ in FIG. 12), and the groove depth (H ′) of the concave part means the vertical distance from the transfer roll surface to the deepest part of the concave part. The top height of the convex portion refers to the vertical distance from the bottom surface of the convex portion to the surface of the transfer roll, and is the same as the groove depth (H ′) of the concave portion in FIG.

  When the top of the cross-sectional shape is V-shaped (triangle), the apex angle Θ ′ of the triangle can be 10 ° to 100 °. The apex angle Θ ′ may be in the range of 10 ° to 90 °. When a crystalline polymer resin having a crystallization temperature peak width of 9 ° C. or less is used as the resin, a fine transfer mold having a triangular apex angle Θ ′ of 10 ° to 60 ° is used. However, the transfer can be performed with high accuracy, and the surface shape of the obtained sheet is almost the same as that of the transfer mold.

  The shape of the transfer mold is not limited to the one having a V-shaped cross section as shown in FIG. 12. For example, a substantially semicircular recess (substantially semicircular recess) having a substantially semicircular shape as shown in FIG. ), Or a concave groove having a V-shaped (triangular) apex angle Θ ′ and a curved side 12 ′ formed by a straight line 11 ′ having a V-shaped groove-curved surface as shown in FIG. Can be illustrated. In the transfer mold surface 1 ′ of FIG. 13, the pitch interval (P ′) is the distance between the groove portions of the adjacent recesses as in FIG. 12, and the groove depth (H ′) of the recesses is from the transfer roll surface to the recesses. The vertical distance to the deepest part. Further, a substantially semicircular convex portion obtained by inverting a groove of a substantially semicircular concave portion is also included in the shape of the transfer mold. When the transfer mold is a substantially semicircular convex portion, the pitch interval refers to the distance between the top portions of adjacent convex portions, and the top height of the convex portion refers to the vertical distance from the bottom surface of the convex portion to the transfer roll surface. The substantially semicircular shape is not limited to a shape having a semicircular cross section as shown in FIG. 13. For example, like a cylindrical lens 8 ′ shown in FIG. The shape may be any arc shape of the cross section when cut by a plane not including the axis, or the cross section is a semi-elliptical arc shape, or a flat curve that is a part of the semi-elliptical arc shape It may be a shape such as a shape. The “substantially semicircular concave portion” or “substantially semicircular convex portion” includes such a concave portion or convex portion having a substantially semicircular cross section.

  In FIG. 15, the pitch interval (P ′) is the distance between the groove portions of the adjacent concave portions or the distance between the top portions of the adjacent convex portions, as in FIG. 12, and the groove depth (H ′) of the concave portions is the transfer. The vertical distance from the roll surface to the deepest part of the recess. The top height of the convex portion is a vertical distance from the bottom surface of the convex portion to the surface of the transfer roll, and is the same distance as the groove depth (H ′) of the concave portion. For example, as shown in FIG. 16, the V-shaped groove-curved surface combined shape has a slope formed by a V-shaped (triangular) apex angle Θ ′ and a curved side 12 ′ formed by a straight line 11 ′. If it is, it may have any shape of a cross section when cut by a plane not including the axis of the cylindrical body including the curved surface. The curved surface here may be a part of an arc shape, a part of an elliptical arc shape, or a shape formed of a curve other than an elliptical arc shape. The “V-groove-curved composite concave portion” includes such a concave portion having a substantially V-groove-curved composite cross section. Further, the shape of the concave portion or the convex portion does not include a straight portion as shown in FIG. 15, but also includes a groove having a shape formed by intersecting curves 13 'as shown in FIG.

  In addition, the concave portions or the convex portions in the transfer mold may be provided continuously as shown in FIG. 12, or may be provided in parallel with an arbitrary interval d ′ as shown in FIGS. The interval between the concave portions or the interval between the convex portions is selected depending on the use of the obtained sheet. In the present invention, the pitch interval (P ′) and the groove depth (H ′) or the top height in the transfer mold are not necessarily constant in the entire transfer mold, but between the partially adjacent concave portions or convex portions. The case of different shapes is also included. In addition, the present invention includes a case where the V-shaped concave portion is inverted and the substantially semicircular convex portion is inverted. The interval d ′ may be arbitrarily set depending on the use of the obtained sheet. However, when a crystalline polymer resin having a crystallization temperature peak width of 9 ° C. or less is used as the resin, the interval d ′ is 10 μm. In the following, or even a fine transfer mold in which the interval d ′ is not provided, a method for producing a surface shape transfer resin sheet with good transfer rate and production efficiency can be obtained.

  As a method for producing the transfer mold, a known method can be adopted. For example, a plating treatment such as chromium plating, copper plating, nickel plating, or nickel-phosphorous plating is performed on the surface of the transfer roll made of stainless steel, steel, or the like. Examples of methods for processing the shape by performing removal processing using a diamond tool, a metal grindstone, etc., laser processing, or chemical etching on the plated surface after applying the method are limited to these methods. Is not to be done.

  The surface of the transfer roll may be subjected to plating treatment such as chromium plating, copper plating, nickel plating, nickel-phosphorous plating, etc. at a level that does not impair the accuracy of the surface shape after the transfer mold is formed.

  After the step of forming the extruded sheet, the extruded sheet undergoes a step of transporting the sheet surface in a horizontal direction. Here, the extruded sheet may be conveyed to the first pressing roll and the second pressing roll in the horizontal direction and then conveyed by the conveying roll as it is. For example, as shown in FIG. It may include a step of being pressed by the third pressing roll 5 provided on the upper side, and then transported by the transporting roll 6. The addition of such steps may be adjusted by the crystallization temperature of the crystalline resin used as described later. In FIG. 1, the obtained pressing sheet 2 is conveyed by being moved upward from the die 1 by the first pressing roll 3 and the second pressing roll 4, but the second pressing roll 3 is below the first pressing roll 3. A form in which a third pressing roll is provided below the roll and the pressing sheet 2 is moved below the die 1 and then conveyed is also included in the manufacturing method of the present invention (see FIG. 9). In addition, the horizontal direction is sufficient if the width direction of the sheet surface is substantially parallel to the horizontal direction. For example, even if the width direction of the sheet surface is inclined within a range of ± 30 ° from the horizontal direction, The effect of the invention is achieved. Such a direction may be set within a range in which, for example, separation of the sheet from the conveyance roll due to inclination does not occur from the viewpoint of efficient conveyance of the sheet.

  In the present invention, the transporting step is performed by contacting at least four transport rolls arranged along the transport direction of the extruded sheet, and the upper surface of the extruded sheet is brought into contact with the transport roll along the transport direction. After the process, the lower surface of the extruded sheet is brought into contact with the transport roll along the transport direction (hereinafter may be referred to as A process), and the lower surface of the extruded sheet is brought into contact with the transport roll along the transport direction. Thereafter, at least one step of bringing the upper surface of the extruded sheet into contact with the transport roll along the transport direction (hereinafter sometimes referred to as B step) is included in total. The step A and the step B may be included in a total of 2 or more, preferably 3 or more, and more preferably 4 or more. With the above configuration, since the sheet is cooled with a shorter conveying distance than in the conventional method, the sheet can be produced even in a small space where the conveying distance is more limited. Further, it is possible to suppress or control the concave warpage in the conveying direction and reduce the warpage of the entire sheet, and it is possible to manufacture a crystalline resin plate having excellent flatness as compared with the conventional method.

  In each of the A process and the B process, there is one transport roll that contacts the lower surface of the extruded sheet and one transport roll that contacts the upper surface of the extruded sheet. Even when one or more rolls are provided, the effect of the present invention is exhibited as long as two or more of the A process and the B process are included and are in contact with at least four transport rolls.

  That is, the process of performing at least one of the process A and the process B in combination of two or more is included, for example, continuously within 20 transport rolls continuous in the transport direction or via another transport roll. Preferably, it is included within 10 continuous transport rolls, and more preferably included within 6 continuous transport rolls. By including two or more of the A process and the B process in the range of the number of the transport rolls, the concave warp in the transport direction can be more efficiently suppressed or controlled.

  FIG. 10A to FIG. 10D are schematic cross-sectional views showing the positional relationship between a transport roll satisfying such a configuration and a transported extruded sheet. FIG. 10A to FIG. 10D show an embodiment in which at least one of the A process and the B process is included in six transport rolls in total. 10 (a) and 10 (b), after the lower surface of the extruded sheet comes into contact with one transport roll, the upper surface of the extruded sheet is brought into contact with the lower surface of the extruded sheet into one transport roll. A step (B step) of contacting the upper surface of the extruded sheet with one conveying roll, and then a step of bringing the lower surface of the extruded sheet into contact with one conveying roll (A). Step), and then the step of bringing the upper surface of the extruded sheet into contact with one further conveying roll (FIG. 10A), or the step of bringing the lower surface of the extruded sheet into contact with one further conveying roll (see FIG. 10). b)). In FIG.10 (c), after making the lower surface of an extrusion sheet contact one conveyance roll, the process (B process) which makes the upper surface of an extrusion sheet contact one conveyance roll is repeated twice, And a step (A step) of bringing the lower surface of the extruded sheet into contact with one transport roll after the upper surface is brought into contact with one transport roll. Here, in the repetition of the B process, the part where the lower surface of the extruded sheet in the second half of the B process contacts is regarded as the first half of the A process, and the part where the upper surface of the extruded sheet in the first half of the second B process contacts the second half of the A process. In FIG. 10C, the process A and the process B are included four times in total, but each process is considered along the transport direction for convenience. In addition, the transport rolls are not considered redundantly between the processes. That is, in FIG.10 (c), A process is 1 time and B process is 2 times, and 3 processes are included in total. In FIG.10 (d), after making the lower surface of an extrusion sheet contact one conveyance roll, the process (B process) which makes the upper surface of an extrusion sheet contact one conveyance roll, and one conveyance roll A step of bringing the upper surface of the extruded sheet into contact with each other, a step of bringing the upper surface of the extruded sheet into contact with one conveying roll and then bringing the lower surface of the extruded sheet into contact with one conveying roll (step A), Furthermore, the process of making the lower surface of an extrusion sheet contact one conveyance roll is included.

In another preferred embodiment of the present invention, the transporting step is performed by contacting at least four transport rolls. These four rolls are arrange | positioned along the conveyance direction of an extrusion sheet | seat, and are arrange | positioned continuously. Assuming that the Nth transport roll from the transport direction is R _n , a process of transporting by means of an apparatus including _four of R _{1 to} R ₄ as transport rolls in FIG. 1 can be performed. The transport rolls may be brought into contact with the extruded sheet so as to satisfy the conditions described later. For example, when the four rolls R _{2 to} R _{5 in} FIG. The effect is produced.

  The upper limit of the number of the transport rolls is not particularly limited as long as it is at least four, but for example, the upper limit can be ten, and is generally up to about 300 in terms of the configuration on the apparatus. is there. However, even if the number of transport rolls exceeds this, the effect of the present invention is exhibited as long as the extruded sheet that contacts at least four of the transport rolls satisfies the conditions described later. Moreover, although the surface temperature of a conveyance roll does not need to be adjusted, the direction which can be adjusted to arbitrary temperature is preferable from the point of the ease of adjustment of curvature. Such adjustment of the surface temperature of the conveying roll may be performed by a temperature adjusting device provided in the conveying roll or a temperature adjusting device such as a heater provided above and below the conveying roll. In the case of heating the extruded sheet by adjusting the temperature in the transport roll, it is preferable because the heat resistance of the obtained crystalline resin plate is further improved.

Either the upper surface or the lower surface of the extruded sheet is in contact with each transport roll. In the present invention, the at least four transport rolls have an upper surface and a lower surface along the transport direction. It is preferable to make it the aspect which contacts alternately. Such contact will be specifically described with reference to FIG. When the extruded sheet 2 comes into contact with the four conveying rolls 6 of the conveying rolls R _{1 to} R ₄ shown in FIG. 1, the lower surface of the extruded sheet 2 comes into contact with the _first conveying roll R ₁ along the conveying direction. Once transported Te for the first second transport roll R ₂ contacts the upper surface of the extruded sheet 2. Next, the lower surface of the extruded sheet 2 comes into contact with the third transport roll R _3, and the upper surface of the extruded sheet 2 comes into contact with the fourth transport roll R ₄ . Further, when the upper surface of the extruded sheet 2 comes into contact with the _first transport roll R ₁ , the lower surface of the extruded sheet 2 comes into contact with the second transport roll R _2, and the third transport roll R _{2 3} is in contact with the upper surface of the extruded sheet 2, and the lower surface of the extruded sheet 2 is in contact with the fourth transport roll R ₄ . In this way, even when the extruded sheet is conveyed so that the upper surface and the lower surface of the extruded sheet are alternately contacted along the conveying direction with respect to at least four conveying rolls, It becomes possible to suppress or eliminate the concave warp and the warp of the entire sheet. As a result, the planarity of the obtained crystalline resin plate can be improved.

  As a method of making the contact between the extruded sheet and the transport roll in the case of including the A process and the B process as described above, and alternately contacting the upper surface and the lower surface of the extruded sheet with the transport roll, for example, for each transport roll This can be achieved by providing a known guide roll. Further, in at least four transport rolls, each surface of the extruded sheet is brought into contact with each other so that at least one of the step A and the step B is included in two or more, preferably each surface of the extruded sheet. As long as these are alternately brought into contact, for example, the contact surface of the fifth conveyance roll of the five conveyance rolls and the extruded sheet is not particularly limited, and the same applies even when more conveyance rolls are provided.

As the transport roll, a known transport roll can be used. The schematic sectional drawing which shows the pitch of the conveyance roll adjacent to FIG. 2 is shown. The diameter D of each conveyance roll can be made into a desired magnitude | size, for example, what is necessary is just to set to the diameter D of 20 mm-800 mm. When indicating the center distance between the N-th transport roll R _n and the N + 1 th transport roll R _{n + 1} adjacent to each other in pitch P, the pitch P is preferably set to 30Mm～2000mm, and 100mm~800mm More preferably. By setting it as such a pitch P, cooling of an extrusion sheet | seat and suppression of a concave curvature are performed more favorably. Pitch P of the transfer roll adjacent is not limited to certain ones, a transfer roll R _{n + 1} pitch P and the N + 1 th of the N-th transport roll R _n and the N + 1 th transport roll R _{n + 1} The pitch P with the (N + 2) th transport roll R _{n + 2} may be different. Further, the ratio P / D between the pitch P and the diameter D of the transport rolls is preferably 0.6 to 10, more preferably 1 to 6.

Although FIG. 1 illustrates a case where the transport rolls are provided at the same height in the vertical direction, the vertical heights of adjacent transport rolls are not necessarily the same. FIG. 3 shows a vertical positional relationship between adjacent conveyance rolls. When at least four transport rolls are set to R _m , R _{m + 1} , R _{m + 2} and R _{m + 3 in} order along the transport direction, and the height position of the extruded sheet in the direction perpendicular to the extruded sheet is d _A For example, as shown in the track (A) of FIG. 3, the transport rolls R _m , R _{m + 1} , R _{m + 2} and R _{m +} are used so that the extruded sheet is transported in a track maintaining the height of d _{A. The} case where ₃ is arranged is included. Further, for example, as shown in the track (B) in FIG. 3, the transport rolls R _m and R _{m + 2} are arranged at a position where they contact the lower surface of the extruded sheet at a height of d _A , and the transport roll R _{m + A} mode in which the center of ₁ and R _{m + 3} is arranged higher than R _m so as to be the height of d _A is also included. Moreover, as shown in the track (C) of FIG. 3, a mode in which all the transport rolls R _{m to} R _{m + 3} are arranged at the same position in the vertical direction is also included. As shown in the track (D) of FIG. 3, the transport rolls R _m and R _{m + 2} are arranged at a position where they contact the lower surface of the extruded sheet at a height of d _A , and the transport rolls R _{m + 1} and R _m The center of _{m + 3} may be lower than d _A , that is, lower than R _m . The tracks (A) to (D) are exemplary, and the position in the vertical direction is not limited to that shown in the figure, and the tracks (A) to (D) are combined to form, for example, a transport roll R _m. The effect of the present invention can be obtained even when the positions ₊₁ are arranged as in the track (B) and the transport rolls R _{m + 3} are arranged as in the track (D) and their vertical positions are different from each other. Is done. Among these, when the at least four transport rolls are arranged so as to have the trajectories shown in the trajectories (B) to (D) in FIG. 3, the moving distance of the pressing sheet between the transport rolls is, for example, It becomes longer than the case shown in the orbit (A), the pressure sheet is cooled, and the crystalline resin plate can be manufactured in a short time.

The transporting step is performed when the crystallization temperature of the crystalline resin is T _c (° C.) and the first transporting roll is brought into contact with the first transporting roll along the transporting direction among four consecutively disposed transporting rolls. _Assuming that the temperature of the sheet surface on the side not in contact with the transport roll is T _warp (° C.), it is preferable that T _warp satisfy the following formula (1).
T _c −30 ≦ T _warp ≦ T _c +20 (1)
When the temperature T _warp (° C.) of the sheet surface satisfies the formula (1), the warpage amount of the entire extruded sheet can be reduced. The temperature T _warp (° C.) of the sheet surface is preferably T _C −20 (° C.) or higher, and more preferably T _C +10 (° C.) or lower. In such a case, the warpage amount of the entire extruded sheet can be further reduced.

  In the manufacturing method of this invention, you may provide the roll which is technically unrelated to this invention other than the said press roll and a conveyance roll. Such a roll is in contact with the extruded sheet. For example, a guide roll for conveying the extruded sheet so as to follow the first pressing roll and the second pressing roll, or the conveying roll, and the pressing sheet for the second pressing. The touch roll for making it closely_contact | adhere to a roll and a 3rd press roll can be mentioned. Such guide rolls and touch rolls are used for the above purpose, and conventionally known rolls can be applied.

  The crystalline resin plate produced by the method for producing a crystalline resin plate of the present invention has improved flatness compared to a resin plate produced by a conventional method, and is therefore suitable for a backlight device. Used for

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

Example 1
[Manufacture of intermediate layer material master batch 1]
54.0 parts by mass of a propylene-ethylene copolymer (propylene unit content 99% by mass or more, ethylene unit content less than 1% by mass, trade name “FSX20L8”, manufactured by Sumitomo Chemical Co., Ltd.) as a light diffusing agent 40.0 parts by mass of styrene polymer particles (average particle size 0.8 μm, trade name “XX307K”, manufactured by Sekisui Plastics Co., Ltd.) and processing stabilizer (trade name “IRGAFOS168”, manufactured by Ciba Geigy) 2 0.0 parts by mass and 4.0 parts by mass of an antistatic agent (trade name “Electro Stripper TS-2B”, manufactured by Kao Corporation) were dry blended, and then 180 ° C. to 250 ° C. with a 65 mm twin screw extruder. Pelletization was performed to obtain a pellet-shaped intermediate layer material master batch 1.

[Manufacture of intermediate layer material master batch 2]
84.0 parts by mass of a propylene-ethylene copolymer (propylene unit content of 99% by mass or more, ethylene unit content of less than 1% by mass, trade name “FSX20L8”, manufactured by Sumitomo Chemical Co., Ltd.) and a processing stabilizer ( Product name “IRGAFOS168” (Ciba Geigy) 4.0 parts by mass, nucleating agent (organophosphate, product name “NA11”, ADEKA) 4.0 parts by mass, and antistatic agent (trade name) After dry blending 8.0 parts by weight of “Electro Stripper TS-2B” (manufactured by Kao Corporation), the mixture is pelletized by a 65 mm twin screw extruder at 180 ° C. to 250 ° C. to obtain a pellet intermediate layer material master batch 2 was obtained.

[Manufacture of surface material master batch]
86.0 parts by mass of a propylene-ethylene copolymer (propylene unit content of 99% by mass or more, ethylene unit content of less than 1% by mass, trade name “FSX20L8”, manufactured by Sumitomo Chemical Co., Ltd.) and an ultraviolet absorber ( 5.0 parts by mass of benzotriazole, trade name “LA31”, manufactured by ADEKA), 5.0 parts by mass of light stabilizer (hindered amine, trade name “Tin855FF”, manufactured by Ciba Japan), and nucleating agent After dry blending 2.0 parts by weight (trade name “NA11”, manufactured by ADEKA) and 2.0 parts by weight of processing stabilizer (trade name “IRGAFOS168”, manufactured by Ciba Geigy), 180 ° C. to 260 ° C. Pelletization was performed with a 65 mm twin screw extruder to obtain a pellet-shaped surface material masterbatch.

[Production of crystalline resin plate]
In the present Example 1, the apparatus provided with the roll structure shown in FIG. 4 was used. The die 1 is provided with a main extruder and a sub-extruder (not shown), and a resin or the like is introduced into each of these extruders at a compounding ratio described later, and laminated via a multi-manifold die. Co-extrusion in the state.

  In the main extruder, 79.0 parts by mass of propylene-ethylene copolymer (propylene unit content of 99 mass% or more, ethylene unit content of less than 1 mass%, trade name “FSX20L8”, manufactured by Sumitomo Chemical Co., Ltd.) And 16.0 parts by mass of the intermediate layer material masterbatch 1 and 5.0 parts by mass of the intermediate layer material masterbatch 2 are fed and melted at 200 ° C. to 250 ° C. It was. Melt kneading in the main extruder was performed at 50.6 rpm under the condition of 759 kg / h.

  In the sub-extruder, 90.0 parts by mass of propylene-ethylene copolymer (propylene unit content 99% by mass or more, ethylene unit content less than 1% by mass, trade name “FSX20L8”, manufactured by Sumitomo Chemical Co., Ltd.) Then, a blend obtained by dry blending 10.0 parts by mass of the surface material masterbatch was supplied and melted at 190 ° C to 250 ° C. Melting and kneading in the sub-extruder was performed at 41.5 rpm and 40.0 kg / h.

  These melted blends are coextruded through a multi-manifold die at a die temperature of 250 ° C. to 260 ° C., and using the roll configuration shown in FIG. 4, a surface layer of 0.05 mm, an intermediate layer (light diffusion layer) ) A crystalline resin plate (A) having a three-layer structure of 1.1 mm and a surface layer of 0.05 mm, a total thickness of 1.2 mm, and an average width of 1400 mm was obtained. The crystallization temperature of the obtained resin plate was 125.1 ° C.

[Transport roll]
Ten transport rolls having a diameter D of 75 mm were used. The relative positions of the adjacent conveying rolls are the height in the vertical direction of the extruded sheet at the contact point between the _first conveying roll (R _{1 in} FIG. 4) and the extruded sheet when counted along the sheet conveying direction, and the roll. So that the difference between the height in the vertical direction of the extruded sheet at the contact point between the second conveyed roll (R _{2 in} FIG. 4) and the extruded sheet when counted along the sheet conveying direction adjacent to the sheet is 75 mm. Arranged (see trajectory (C) in FIG. 3). That is, the height of the first-th transporting roll R ₁ and the second vertical extruded sheet and the transport roll R ₂ is substantially the same.

Further, as for the interval between adjacent transport rolls, the transport rolls R _{1 to} R ₅ in FIG. 4 have a pitch P of 250 mm shown in FIG. 2 and the pitch P of the transport rolls R _{5 to} R ₁₀ is 300 mm. The transport rolls R _{1 to} R ₁₀ each had a surface temperature set to 90 ° C.

[Transport method]
Up to the transport roll R ₁₀ , the sheet surface of the extruded sheet is sequentially passed from the transport roll R ₁ so as to contact the transport roll, and after the transport roll R ₁₁ , the sheet is passed above the transport roll (FIG. 4). ). Note the diameter of the subsequent conveyor rolls R ₁₁ rolls and 75 mm, the pitch as 300 mm, the vertical position of the rolls were the same as R _10. The temperature of the transfer roll R ₁₁ subsequent roll surface was not adjusted.

[Extruded sheet surface temperature: T _warp ]
The surface temperature of the extruded sheet when passing through the _first conveying roll R ₁ counted along the conveying direction, and the surface temperature T _warp of the extruded sheet on the side not in contact with the conveying roll was 116.0 ° C. It was.

<Evaluation: Warpage measurement 1>
Three test plates each having a size of 400 mm × 400 mm were cut out at different points in the width direction of the crystalline resin plate (A) obtained in Example 1. The warpage was measured for each of these test plates. The warpage measurement is placed on a natural stone standing board (600 mm x 600 mm) made by Mitutoyo Corporation, and the amount (distance) floating from the standing board at each of the midpoints and the vertexes of the four sides of the test plate is a total of 8 points. It was measured. For each test plate, the amount of floating from the 16-plate total board on both sides was measured, and the maximum value among them was defined as the warpage amount (1). The measurement was performed at room temperature. The results for each test plate are shown in Tables 1 and 2.

<Evaluation: Warpage measurement 2>
Three test plates having a size of 400 mm × 400 mm were cut out at different points in the width direction of the obtained crystalline resin plate (A). Each of these test plates was subjected to visual warpage measurement. The warpage evaluation result by visual judgment is shown in Table 1 as “◯” when there is no waviness on the sheet and as “x” when there is waviness on the sheet.

(Example 2)
Using the intermediate layer material master batch 1, the intermediate layer material master batch 2, and the surface layer material master batch prepared in Example 1, a crystalline resin plate was manufactured by the following method.

[Production of crystalline resin plate]
In Example 2, an apparatus having the roll configuration shown in FIG. 4 was used. The die 1 is provided with a main extruder and a sub-extruder (not shown), and a resin or the like is introduced into each of these extruders at a compounding ratio described later, and laminated via a multi-manifold die. Co-extrusion in the state.

  In the main extruder, 83.0 parts by mass of a propylene-ethylene copolymer (propylene unit content of 99 mass% or more, ethylene unit content of less than 1 mass%, trade name “FSX20L8”, manufactured by Sumitomo Chemical Co., Ltd.) 12.0 parts by mass of the intermediate layer material masterbatch 1 and 5.0 parts by mass of the intermediate layer material masterbatch 2 are supplied and melted at 200 ° C. to 250 ° C. It was. Melt kneading in the main extruder was performed at 43.6 rpm and 654 kg / h.

  In the sub-extruder, 90.0 parts by mass of propylene-ethylene copolymer (propylene unit content 99% by mass or more, ethylene unit content less than 1% by mass, trade name “FSX20L8”, manufactured by Sumitomo Chemical Co., Ltd.) Then, a blend obtained by dry blending 10.0 parts by mass of the surface material masterbatch was supplied and melted at 190 ° C to 250 ° C. The melt-kneading in the sub-extruder was performed at 48.4 rpm and 46.7 kg / h.

  These melted blends are coextruded through a multi-manifold die at a die temperature of 250 ° C. to 260 ° C., and using the roll configuration shown in FIG. 4, a surface layer of 0.05 mm, an intermediate layer (light diffusion layer) ) A crystalline resin plate (B) having a three-layer structure of 1.4 mm and a surface layer of 0.05 mm, a total thickness of 1.5 mm, and an average width of 1400 mm was obtained. The crystallization temperature of the obtained resin plate was 125.9 ° C. About the obtained crystalline resin board (B), the curvature evaluation similar to a crystalline resin board (A) was performed. The results are shown in Tables 1 and 2.

  The conveyance roll, the arrangement method thereof, and the extrusion sheet conveyance method were performed in the same manner as in Example 1.

[Extruded sheet surface temperature: T _warp ]
The surface temperature of the extruded sheet when passing through the _first conveying roll R ₁ counted along the conveying direction, and the surface temperature T _warp of the extruded sheet on the side not in contact with the conveying roll was 119.9 ° C. It was.

Example 3
Using the intermediate layer material master batch 1, the intermediate layer material master batch 2, and the surface layer material master batch prepared in Example 1, a crystalline resin plate was manufactured by the following method.

[Production of crystalline resin plate]
In Example 3, an apparatus having the roll configuration shown in FIG. 4 was used. The die 1 is provided with a main extruder and a sub-extruder (not shown), and a resin or the like is introduced into each of these extruders at a compounding ratio described later, and laminated via a multi-manifold die. Co-extrusion in the state.

  The main extruder has 95.0 parts by mass of a propylene-ethylene copolymer (propylene unit content of 99 mass% or more, ethylene unit content of less than 1 mass%, trade name “FSX20L8”, manufactured by Sumitomo Chemical Co., Ltd.) Then, a blend obtained by dry blending 5.0 parts by mass of the intermediate layer material master batch 2 was supplied and melted at 200 ° C to 250 ° C. Melt kneading in the main extruder was performed at 36.7 rpm and 550 kg / h.

  In the sub-extruder, 90.0 parts by mass of propylene-ethylene copolymer (propylene unit content 99% by mass or more, ethylene unit content less than 1% by mass, trade name “FSX20L8”, manufactured by Sumitomo Chemical Co., Ltd.) Then, a blend obtained by dry blending 10.0 parts by mass of the surface material masterbatch was supplied and melted at 190 ° C to 250 ° C. The melt-kneading in the sub-extruder was performed at 51.8 rpm under the condition of 50.0 kg / h.

  These melted blends are coextruded through a multi-manifold die at a die temperature of 250 ° C. to 260 ° C., and using the roll configuration shown in FIG. 4, a surface layer of 0.05 mm, an intermediate layer (light diffusion layer) ) A crystalline resin plate (C) having a three-layer structure of 1.9 mm and a surface layer of 0.05 mm, a total thickness of 2.0 mm, and an average width of 1400 mm was obtained. The crystallization temperature of the obtained resin plate was 125.3 ° C. The obtained crystalline resin plate (C) was subjected to the same warp evaluation as the crystalline resin plate (A). The results are shown in Tables 1 and 2.

  The conveyance roll, the arrangement method thereof, and the extrusion sheet conveyance method were performed in the same manner as in Example 1.

[Extruded sheet surface temperature: T _warp ]
The surface temperature of the extruded sheet when passing through the _first conveying roll R ₁ counted along the conveying direction, and the surface temperature T _warp of the extruded sheet on the side not in contact with the conveying roll was 120.9 ° C. It was.

(Comparative Example 1)
A crystalline resin plate was produced by the same method as in Example 2 except that the conveying method was changed to the following conditions. The obtained crystalline resin plate was subjected to warpage evaluation in the same manner as in Example 1. The results are shown in Table 2.

[Conveying method]
The sheet was passed over all the transport rolls (FIG. 5). The size and pitch of the transport rolls were the same as in Example 2.

[Extruded sheet surface temperature: T _warp ]
The surface temperature of the extruded sheet when passing through the _first conveying roll R ₁ counted along the conveying direction, and the surface temperature T _warp of the extruded sheet on the side not in contact with the conveying roll was 121.0 ° C. It was.

In Table 1, the symbols a to k of the sheet temperature indicate the places where the temperature of the pressing sheet was measured, and these are schematically shown in FIG. For each of the symbols a to k, three different sheet temperatures were measured in the width direction, and the three sheet temperatures are listed in Table 1. In the measurement of the symbol f, “on f” indicates the surface of the pressure sheet 2 on the side not in contact with the conveyance roll when the conveyance roll R ₁ and the pressure sheet are in contact. In other symbols ek, the upper surface and the lower surface of the press sheet immediately before the press sheet 2 comes into contact with each transport roll are indicated by “upper” and “lower”, respectively. The line speed (m / min) indicates the extrusion speed from the die, and the take-off ratio indicates the ratio of the take-up ratio of the press sheet between the third press roll 5, the transport roll 6 and the take-off roll (not shown). In the examples and comparative examples, the third pressing roll 5 / the transporting roll 6 / the take-up roll = 1.025 / 0.998 / 0.960.

  “First”, “second”, and “third” in the roll temperature column of Table 1 indicate a first pressing roll, a second pressing roll, and a third pressing roll, respectively. As for the amount of warpage, all show the maximum value, “−” in front of the numerical value indicates that the warpage is recessed from the horizontal direction of the sheet conveyance, and “+” indicates that the warpage is from the horizontal direction of the sheet conveyance. Is also convex.

  As is apparent from the results in Table 2, the amount of warpage of each test plate corresponding to the crystalline resin plate produced by the method of the present invention is the same as that of the test plate corresponding to the crystalline resin plate obtained by the conventional method. In comparison, the warpage was suppressed in all cases. It can also be seen that the absolute value of the warpage amount is also reduced by 5.9 mm at the maximum.

Example 4
[Manufacture of intermediate layer material master batch 3]
85.0 parts by mass of a propylene-ethylene copolymer (propylene unit content 99% by mass or more, ethylene unit content less than 1% by mass, trade name “E111G”, manufactured by Prime Polymer Co., Ltd.), hindered amine light stability 5.0 parts by weight of an agent (trade name “Kimasorb 119FL”, manufactured by Ciba Japan Co., Ltd.), 4.0 parts by weight of a processing stabilizer (trade name “Sumilyzer GP”, manufactured by Sumitomo Chemical Co., Ltd.), After dry blending 6.0 parts by mass of a nucleating agent (trade name “HPN-20E”, manufactured by Milliken Japan Co., Ltd.), the mixture was pelletized with a 65 mm twin screw extruder at 180 ° C. to 260 ° C. Intermediate layer material master batch 3 was obtained.

[Production of crystalline resin plate]
In Example 4, an apparatus having the roll configuration shown in FIG. 9 was used. The die 1 was equipped with an extruder, and a resin or the like was charged at a blending ratio described later and extruded in a single layer state via a feed block die.

  In the main extruder, 95.0 parts by mass of a propylene-ethylene copolymer (propylene unit content of 99% by mass or more, ethylene unit content of less than 1% by mass, trade name “E111G”, manufactured by Prime Polymer Co., Ltd.) A blend obtained by dry blending 5.0 parts by mass of the intermediate layer material master batch 3 was supplied and melted at 200 ° C to 250 ° C. Melt kneading in the main extruder was performed at 12.6 rpm and 281 kg / h.

  The melted blend is extruded through a feed block die at a die temperature of 250 ° C. to 265 ° C., and using the roll configuration shown in FIG. 9, it has a single layer structure with a thickness of 0.6 mm and an average width. A 1100 mm crystalline resin plate (B) was obtained. The crystallization temperature of the obtained resin plate was 125.0 ° C.

[Transport roll]
A total of six transport rolls having a diameter D of 60 mm were used. The relative positions of the adjacent conveying rolls are the height in the vertical direction of the extruded sheet at the contact point between the _first conveying roll (R _{1 in} FIG. 9) and the extruded sheet when counted along the sheet conveying direction, and the roll. The difference between the height of the extruded sheet in the vertical direction between the second conveying roll (R _{2 in} FIG. 9) and the contact point of the extruded sheet when counted along the sheet conveying direction adjacent to the sheet is 60 mm. Arranged (see trajectory (C) in FIG. 3). That is, the vertical heights of the extruded sheets of the first transport roll R ₁ and the second transport roll R ₂ are substantially the same.

Further, as for the distance between adjacent transport rolls, the transport rolls R _{1 to} R ₆ in FIG. 9 have a pitch P shown in FIG. 2 of 300 mm, and the surface temperature of the transport rolls is not adjusted, and the crystalline resin plate is used at room temperature. Was manufactured.

[Conveying method]
Up to the transport roll R ₆ , as shown in FIG. 9, the extruded sheet is above the transport roll R ₁ , below the transport roll R ₂ , above the transport rolls R ₃ and R ₄ , below the transport rolls R ₅ and R ₆ . The sheet was passed so as to be in contact with the side, and after the transport roll R ₇ , the sheet was passed over the transport roll. Note the diameter of the subsequent transport roll R ₇ rolls and 60 mm, pitch was 300 mm, the temperature of the conveying roll R ₇ and subsequent roll surface was not adjusted.

[Extruded sheet surface temperature: T _warp ]
The surface temperature of the extruded sheet when passing through the _first conveying roll R ₁ counted along the conveying direction, and the surface temperature T _warp of the extruded sheet on the side not in contact with the conveying roll was 111.6 ° C. It was.

  The obtained extruded sheet was evaluated in the same manner as in Example 1. The results are shown in Table 3 below.

(Comparative Example 2)
A crystalline resin plate was produced by the same method as in Example 4 except that the conveying method was changed to the following conditions. The obtained crystalline resin plate was subjected to warpage evaluation in the same manner as in Example 1. The results are shown in Table 3.

[Transport method]
The sheet was passed over all the transport rolls (FIG. 11). The size and pitch of the transport roll were the same as in Example 4.

[Extruded sheet surface temperature: T _warp ]
The surface temperature of the extruded sheet when passing through the _first conveying roll R ₁ counted along the conveying direction, and the surface temperature T _warp of the extruded sheet on the side not in contact with the conveying roll was 112.0 ° C. It was.

  As described above, according to the method of the present invention, it is understood that a crystalline resin plate excellent in flatness with remarkably suppressed warpage can be manufactured only by changing the conveying method in the configuration of the conventional apparatus.

  Although the embodiments and examples of the present invention have been described as described above, it is also planned from the beginning to appropriately combine the configurations of the above-described embodiments and examples.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  Since the crystalline resin plate produced by the production method of the present invention is excellent in flatness, it is suitable for a light diffusion plate, that is, a backlight device constituting a direct liquid crystal display device.

  1 die, 2 extruded sheet, 3 first pressing roll, 4 second pressing roll, 5 third pressing roll, 6 transport roll, 7 take-up roll, 8, 9 heater, 10, 20 warping roll.

Claims (4)

A step of extruding the crystalline resin from a die into a sheet, a step of passing the extruded sheet-like crystalline resin through a rolling roll to form an extruded sheet, and the width direction of the sheet surface of the extruded sheet is horizontal. A method for producing a crystalline resin plate comprising a step of conveying an extruded sheet as follows:
The step of conveying is performed in contact with at least four conveying rolls arranged along the conveying direction of the extruded sheet, and
A step of bringing the upper surface of the extruded sheet into contact with the conveying roll along the conveying direction and then bringing the lower surface of the extruded sheet into contact with the conveying roll along the conveying direction; A method for producing a crystalline resin plate, comprising at least one step of bringing the upper surface of the extruded sheet into contact with a transport roll along the transport direction after contacting the transport direction along the transport direction. The step of conveying is performed in contact with at least four conveying rolls arranged along the conveying direction of the extruded sheet, and
The method for producing a crystalline resin plate according to claim 1, wherein either the upper surface or the lower surface of the extruded sheet is alternately brought into contact with the respective transport rolls along the transport direction. In the transporting step, the crystallization temperature of the crystalline resin is T _c (° C.), and among the four transport rolls arranged in succession, the first transport roll along the transport direction. The crystallinity according to claim 1 or 2, wherein the temperature of the sheet surface on the side that does not come into contact with the conveying roll at the time of contact is T _warp (° C), and the T _warp is performed under a condition satisfying the following formula (1). Manufacturing method of resin plate.
T _c −30 ≦ T _warp ≦ T _c +20 (1)   The method for producing a crystalline resin plate according to claim 1, wherein the crystalline resin is a propylene resin.

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