JP5242471B2 - Mold for bending molding of thermoplastic resin sheet, bending molding method, and folding molded body - Google Patents

Description

  The present invention relates to a bending mold for bending a thermoplastic resin sheet, a method for bending a thermoplastic resin sheet, and a bent molded body of a thermoplastic resin sheet formed using the same. .

  In recent years, a liquid crystal display device has been widely used as a display device such as a computer because it is power-saving, thin, and lightweight.

  The backlight device used in the liquid crystal display device includes a direct type backlight device in which a plurality of light sources are arranged on the back surface of the display unit of the liquid crystal display device, and a side edge type backlight device in which light sources are arranged on the side of the display unit. Are known. Side-edge type backlight devices are used in liquid crystal display devices such as notebook personal computers that are required to be thin.

An example of a liquid crystal display device provided with a conventional side edge type backlight device is shown in FIG. FIG. 18 is an exploded perspective view showing a conventional liquid crystal display device.
The liquid crystal display device 200 includes a liquid crystal panel 201 and a backlight device 202 for irradiating the liquid crystal panel 201. The backlight device 202 includes a light guide plate 204 made of transparent acrylic resin or the like having a surface with irregularities, two linear light sources 205 disposed along both side surfaces of the light guide plate, and a linear light source 205. Reflected by the reflector 206 that reflects the emitted light toward the side surface of the light guide plate 204, a diffusion sheet 207a for diffusing the light emitted from the light guide plate 204 to reduce luminance unevenness, and diffused by the diffusion sheet 207a A lens sheet 208 that collects the light, a diffusion sheet 207b that diffuses the light collected by the lens sheet 208 again, and a reflection plate 209 that reflects the light emitted from the light guide plate 204 to the front surface. . The light guide plate 204, the diffusion sheets 207 a and 207 b, the lens sheet 208, the light source 205, the reflector 206, and the reflection plate 209 are incorporated in the resin frame 210 and are disposed on the back surface of the liquid crystal panel 201 as the backlight device 202.

  In the liquid crystal display device 200 having the above configuration, the light guided from the linear light source 205 into the light guide plate 204 is diffused and scattered by the light guide plate 204 and is uniformly emitted from the entire surface of the light guide plate. The planar light emitted from the light guide plate 204 is further diffused by transmitting through the diffusion sheet 207a, the lens sheet 208, and the diffusion sheet 207b, and illuminates the liquid crystal panel 201.

  The reflector 206 is made of a metal plate such as stainless steel or aluminum having the same length as that of the linear light source 205, and is formed into a substantially U-shaped cross section that opens on one surface as shown in the figure. The light source 205 is housed inside, and the opening surface is disposed to face the side surface of the light guide plate 204. In order to reflect the light from the linear light source and efficiently enter the light guide plate on the inner surface of the conventional reflector (see Patent Document 1), metal oxide, metal A white paint made of nitride or metal carbide is applied (see Patent Document 2).

JP 2006-32273 A (paragraph 0034) JP 2007-66611 A (paragraph 0028)

  However, the reflector using the conventional metal plate has a problem that the reflectivity is not sufficient, and there is a limit in increasing the brightness of the liquid crystal display device. In addition, it is costly because it is a composite product with metal.

  In order to solve the above-mentioned problem, instead of the metal plate, a thermoplastic resin sheet having fine bubbles or pores in the interior with high light reflectance, a laminated sheet in which a reflective film is bonded to the thermoplastic resin sheet, or It is conceivable to use a sheet or the like obtained by vapor-depositing metal particles on a thermoplastic resin sheet, and heat-mold the sheet into a substantially U-shaped cross section using a mold.

  However, when these reflectors made mainly of thermoplastic resin are heat-molded using a mold, bending back (springback phenomenon) that does not occur in reflectors made of metal plates occurs. There is a problem of poor stability. In general, the molded reflector is sent to a backlight manufacturer, where it is assembled as a backlight panel. In this case, the temperature inside the vehicle during transportation may reach a maximum of 70 ° C. When placed in such a high temperature environment, the reflector opens during transportation or warehouse storage, making assembly difficult or, in some cases, making assembly impossible. In order to suppress this, it is conceivable to suppress the shape change in a high-temperature environment by bending it to 90 degrees or more at the time of molding, but in bending molding using a mold, it is bent to 90 degrees or more. Since this is difficult, after the process of once bending to 90 degrees using a mold, it is necessary to perform the process of bending again to 90 degrees or more by other means, and the number of processes is required. Productivity deteriorates due to the increase and capital investment.

  Then, the objective of this invention used the metal mold | die which can manufacture the bending molded object of the thermoplastic resin sheet excellent in shape stability easily and without requiring large capital investment, and this metal mold | die. An object of the present invention is to provide a method for producing a bent molded body of a thermoplastic resin sheet, and a bent molded body of a thermoplastic resin sheet molded using these.

In order to achieve the above-described object, a mold according to the present invention includes a female mold and a male mold, and is a mold for bending a thermoplastic resin sheet, the male mold. is the portion corresponding to the bent portion of the thermoplastic resin sheet, have a convex portion for crushing the bent portion of the thermoplastic resin sheet in the thickness direction, the female mold, a bottom surface, An inner surface substantially perpendicular to the bottom surface, and the male mold has a projecting surface facing the bottom surface of the female mold and a side surface facing the inner surface of the female mold. And at least one of the projecting surface and the side surface of the male mold is a pressing surface for crushing the resin sheet in the thickness direction toward the inner peripheral surface of the female mold, the female mold further has a female-side inclined surface formed between the inner surface and the bottom surface, wherein the male mold is the female side The female mold, further comprising a male inclined surface formed between the side surface and the projecting surface so as to face the inclined surface, wherein the convex portion of the male mold is on the male inclined surface. provided in the inner surface and the female portion corresponding to the boundary between the inclined surface and the female-side inclined surface portions corresponding to the boundary between the bottom surface of the female mold of the features that you have.

  Furthermore, in the mold, the thickness of the thermoplastic resin sheet is t (mm), the clearance between the inner surface of the female mold and the side surface of the male mold is a (mm), and the female When the clearance between the side inclined surface and the male inclined surface is b (mm), and the clearance between the bottom surface of the female mold and the protruding surface of the male mold is c (mm), It is preferable to satisfy the relationship of t ≧ b> a ≧ c.

  Furthermore, an angle formed by the inner surface of the female mold and the female inclined surface is α (degree), and an angle formed by the bottom surface of the female mold and the female inclined surface is β (degree). Then, the convex portion of the male mold provided at a portion corresponding to the boundary between the inner surface of the female mold and the female inclined surface on the male inclined surface has an apex angle of γ ( The convex portion of the male mold provided at a portion corresponding to a boundary between the bottom surface of the female mold and the female inclined surface on the male inclined surface. It is preferable that the apex angle is δ (degrees) in cross-sectional triangle and satisfy the relationship of α> γ and β> δ.

  Furthermore, it is preferable that the convex portion of the male mold has a triangular cross section with an apex angle of approximately 90 degrees or less.

  The method for bending a thermoplastic resin sheet according to the present invention includes a pressing step of pressing the thermoplastic resin sheet using any of the above-described molds.

  In the bending method of the thermoplastic resin sheet, after the pressing step, a heating step of heating the die to 70 ° C. or more and 200 ° C. or less, and cooling for cooling the die to 40 ° C. or less after the heating step. It is preferable to have a process.

  Moreover, in the bending method of the thermoplastic resin sheet, the cooling step includes a water-cooling step of water-cooling the mold to a glass transition temperature (Tg) of the thermoplastic resin sheet, and the thermoplasticity after the water-cooling step. It is preferable to have an air-cooling step of cooling to 40 ° C. or lower by spraying air on the resin sheet.

  In the bending method of the thermoplastic resin sheet, the heating step may be performed by vibrating the mold with ultrasonic waves.

  Furthermore, in the bending method of the thermoplastic resin sheet, in the pressing step, the thermoplastic resin sheet is preferably pressed with a pressure of 294 MPa or more.

  Furthermore, in the bending method of the thermoplastic resin sheet, it is preferable to have a fold line forming step of providing a fold line at a bent portion of the thermoplastic resin sheet before the pressing step.

A bent molded body of a thermoplastic resin sheet according to the present invention is a folded molded body obtained by bending a thermoplastic resin sheet using any of the above-described molds, and a bottom portion and the bottom portion. The resin sheet has an upright side wall part and a connection part that connects the bottom part and the side wall part, and the side wall part is based on a bent part between the side wall part and the connection part. The bottom portion has a thin portion of the thermoplastic resin sheet with a bent portion between the bottom portion and the connection portion as a base point, and the side wall portion has the thin portion. It is characterized in that it is bent 90 degrees or more on the bottom side with respect to the bottom.

  In the bent molded body of the thermoplastic resin sheet, when the thickness of the side wall portion is A (mm), the thickness of the connecting portion is B (mm), and the thickness of the bottom portion is C (mm), B> It is preferable to satisfy the relationship of A ≧ C.

  In the mold and the method for producing a bent body of a thermoplastic resin sheet according to the present invention, the bent portion of the thermoplastic wire resin sheet is crushed in the thickness direction of the sheet by a convex portion provided on the mold, and folded. Forces in the direction of pulling each other are generated on the two surfaces of the thermoplastic resin sheets connected via the bent portion. As a result, the thermoplastic resin sheet can be bent and molded at 90 degrees or more in one mold, so that the spring of the thermoplastic resin sheet 20 does not require an increase in the number of processes and significant capital investment. Generation of a back phenomenon can be suppressed, and a molded body of a thermoplastic resin sheet excellent in shape stability can be manufactured.

It is a side view which shows the metal mold | die concerning embodiment of this invention. It is a figure for demonstrating the manufacturing method of the reflector concerning embodiment of this invention. It is a perspective view which shows the reflector shape | molded using the metal mold | die of this invention. It is a side view which shows the reflector shape | molded using the metal mold | die of this invention. It is a side view which shows the metal mold | die 40 concerning the modification of the 1st Embodiment of this invention. It is a side view which shows the metal mold | die 50 concerning the 2nd Embodiment of this invention. It is a side view which shows the reflector shape | molded using the metal mold | die concerning the 2nd Embodiment of this invention. It is a side view which shows the metal mold | die concerning other embodiment concerning this invention. It is a side view which shows the modification of a metal mold | die. It is a side view which shows the other modification of a metal mold | die. It is a perspective view which shows a chassis integrated reflector. It is a schematic perspective view for demonstrating the bending shaping | molding of the thermoplastic resin sheet by a forming roll. It is sectional drawing in each forming roll which passes along the roll rotating shaft perpendicular | vertical with respect to the conveyance direction of a thermoplastic resin sheet. It is a figure for demonstrating the state by which the thermoplastic resin sheet was shape | molded. It is a side view which shows the metal mold | die of a comparative example. It is a figure for demonstrating the evaluation method of the shape stability of a reflector. It is a side view which shows the metal mold | die of Example 7. FIG. It is a disassembled perspective view which shows the conventional liquid crystal display device.

Embodiments of the present invention will be described below in detail with reference to the drawings.
(First embodiment)
FIG. 1 is a side view showing a mold 10 according to the first embodiment of the present invention. The mold 10 of the present embodiment is a mold for molding a reflector having a substantially J-shaped cross section (see FIGS. 3 and 4) using a thermoplastic resin sheet as a main material. The mold 10 has a female mold 11 and a male mold 12 as shown in the figure.

  The female die 11 has a bottom surface 13, an inner side surface 14 substantially perpendicular to the bottom surface 13, and a female side inclined surface 15 formed between the bottom surface 13 and the inner side surface 14.

  The male mold 12 projects from the side surface 17 facing the protruding surface 16 facing the bottom surface 13 of the female mold 11, the side surface 17 facing the inner surface 14 of the female mold 11, and the female inclined surface 15. And a male inclined surface 18 formed between the surface 16 and the surface 16. And on this male side inclined surface 18, the convex part for crushing the bending part of a thermoplastic resin sheet in the thickness direction in the part corresponding to the bending part of the thermoplastic resin sheet which is bending object. 19 is provided.

  The convex portion 19 is a portion on the male inclined surface 18 corresponding to the boundary between the inner surface 14 of the female mold 11 and the female inclined surface 15, and the female inclined surface 15 and the bottom surface 13 of the female mold. It is provided in the part corresponding to the boundary. The convex portion 19 is a linear projection having a triangular shape with apex angles γ and δ of approximately 90 degrees, and when the thermoplastic resin sheet is bent, the bent portion of the thermoplastic resin sheet is pushed in the thickness direction. It can be crushed. The angles of the apex angles γ and δ of the convex portion 19 are not particularly limited, but preferably have an angle of about 90 degrees in order to exhibit the crushing function more effectively.

  In the embodiment described above, the apex angles γ (degrees) and δ (degrees) of the convex portion 19 are set to approximately 90 degrees, but the angle formed between the inner side surface 14 of the female mold 11 and the female side inclined surface 15 is α ( Degree), and the angle formed by the female inclined surface 15 and the bottom surface 13 of the female mold is β (degrees), the inner surface 14 of the female mold 11 on the male inclined surface 18 and the female inclined surface 15 The portion corresponding to the apex angle γ (degree) of the convex portion 19 provided at the portion corresponding to the boundary of the female side, and the boundary between the female side inclined surface 15 on the male side inclined surface 18 and the bottom surface 13 of the female mold It is preferable that the apex angle δ (degree) of the convex portion 19 provided in is set so as to satisfy the relationship of α> γ and β> δ, and the apex angles γ and δ are 90 degrees or less. Is more preferable.

  In the above-described embodiment, the convex portion 19 is a linear protrusion having a triangular cross section, but the boundary portions 19a and 19b between the convex portion 19 and the male inclined surface 18 have a smooth curve (R shape). ) May be a linear protrusion.

Next, the thermoplastic resin sheet which is the molding target of the present invention will be described.
In the present invention, the thermoplastic resin sheet is composed of a thermoplastic resin sheet alone, a laminated sheet in which a reflective film is bonded to a thermoplastic resin sheet, a sheet in which metal particles are vapor-deposited on a thermoplastic resin sheet, and the like. Is included. Examples of the thermoplastic resin sheet include a general plastic sheet obtained by processing a thermoplastic resin into a sheet shape, and a thermoplastic foam resin sheet having fine bubbles or pores having an average cell diameter of 50 nm to 50 μm inside. be able to. As such a thermoplastic foam resin sheet, for example, an extruded sheet of polyethylene terephthalate is impregnated with carbon dioxide under high pressure and then heated and foamed. The foamed plastic sheet has an internal cell diameter of 50 μm or less. There is a light reflection sheet (for example, MCPET (registered trademark) manufactured by Furukawa Electric Co., Ltd.). Another example of the thermoplastic resin sheet is a thermoplastic resin sheet containing a filler, in which a large number of voids are formed with the filler as a core.

Next, a method for manufacturing a reflector using the mold 10 of FIG. 1 will be described with reference to FIG.
First, as shown to Fig.2 (a), the bending line 21 is provided in the target bending part of the thermoplastic resin sheet 20 (folding line formation process). The fold line 21 may be formed by, for example, pressing the thermoplastic resin sheet 20 to provide a linear recess (pressed ruled line). Moreover, you may shape | mold by making a ruled line-like cut | interruption or perforation into the surface (surface which covers a linear light source, and reflects light) or the skin part of a back surface of the thermoplastic resin sheet 20 using a sharp blade. . Further, the fold line 21 may be formed by a perforation penetrating from the front surface to the back surface. The bend line forming step can be omitted, but through this step, when the thermoplastic resin sheet 20 is inserted into the mold 10 later, the molding can be performed without shifting the molding position of each surface. it can.

  Next, as shown in FIG. 2B, the thermoplastic resin sheet 20 is set in the mold 10 (sheet setting step).

Next, as shown in FIG. 2C, the thermoplastic resin sheet 20 is sandwiched and pressed between the female mold 11 and the male mold 12 (pressing step). The pressure during pressing is preferably a high pressure, and is preferably 294 MPa (3.0 t / cm ² ) or more. Further, the pressurization time may be longer than the time required for the female mold 11 and the male mold 12 to reach the following predetermined temperature, and it is preferable to increase the pressurization time. .

  Next, as shown in FIG.2 (d), the female metal mold | die 11 and the male metal mold | die 12 are heated at 70 degreeC or more and 200 degrees C or less with a heater etc. (mold heating process). If the temperature of the mold is lower than 70 ° C, the shape cannot be maintained after bending (spring back phenomenon) in a high temperature environment (70 ° C) after molding. However, since the ultraviolet ray inhibitor is discolored when heated at a high temperature, for example, when the thermoplastic resin sheet 20 is provided with a coating layer of the ultraviolet ray inhibitor, the temperature is preferably set to 150 ° C. or lower.

  You may implement the heating process of the metal mold | die 10 before a press process. That is, the thermoplastic resin sheet 20 may be pressed after the mold 10 is heated in advance. Moreover, you may heat the thermoplastic resin sheet 20 previously.

Next, as shown in FIG. 2 (e), the female mold 11 and the male mold 12 are cooled to 40 ° C. or lower with cooling water (cooling step), and the thermoplastic resin sheet 20 is taken out from the mold 10.
In the cooling step, the female die 11 and the male die 12 are cooled to the glass transition temperature (Tg) with cooling water (water cooling step), and then air is sprayed onto the molded thermoplastic resin sheet 20. Thus, the thermoplastic resin sheet 20 may be cooled to 40 ° C. or lower (air cooling step), and the thermoplastic resin sheet 20 may be taken out from the mold 10.

  In this embodiment, the mold 10 is heated with a heater or the like and then cooled with cooling water. However, the present invention is not limited to this. For example, an ultrasonic wave using the male mold 12 as a vibrator is used. It is good to make it vibrate. As a result, when the thermoplastic resin sheet 20 is pressed between the female mold 11 and pressed, vibration concentrates on the convex portion 19 to which the most pressure is applied, so that the portion corresponding to the bent portion of the thermoplastic resin sheet 20 is concentrated. Is heated and stretched. As a result, the moldability can be improved efficiently.

  3 and 4, the bottom portion 31, the side wall portions 32 and 33 erected with respect to the bottom portion 31, and the connection portion that connects the bottom portion 31 and the side wall portions 32 and 33, respectively, as shown in FIGS. 3 and 4. A reflector 30 having a substantially J-shaped cross section having 34 and 35 can be obtained.

  In the reflector 30 thus obtained, the side of the fold line 21 is crushed by the convex portion 19 of the male mold 12 so that the side walls 32 and 33 are formed as shown in FIGS. The thickness of the bent portion 21a and 21d between the connecting portions 34 and 35 is reduced, and the bottom portion 31 includes two bent portions 21b and 21b between the connecting portions 34 and 35, respectively. The wall thickness is thin with 21c as a base point. Thereby, two surfaces (ie, the inner side surface 32a of the side wall portion 32, the inner side surface 34a of the connection portion 34, and the inner side surface 34a of the connection portion 34) connected to each other via the bent portions 21a, 21b, 21c and 21d. The stress was exerted on the upper surface 31a of the bottom portion 31, the upper surface 31a of the bottom portion 31 and the inner side surface 35a of the connecting portion 35, the inner side surface 35a of the connecting portion 35 and the inner side surface 33a of the side wall portion 33). As shown in FIGS. 3 and 4, the reflector 30 has a shape in which the side walls 32 and 33 are bent by 90 degrees or more with respect to the bottom 31 with respect to the bottom 31, and the thermoplastic resin sheet 20 is bent back (spring back phenomenon). Is suppressed.

Further, if the entire sheet is crushed in the thickness direction, not only the bent portion of the thermoplastic resin sheet 20, the molding becomes easy, and the shape stability after molding is good.
As shown in FIG. 4, the thickness of the side wall portions 32 and 33 of the reflector 30 is A, the thickness of the connection portions 34 and 35 is B, the thickness of the bottom portion 31 is C, and the thickness of the thermoplastic resin sheet 20 is t
t ≧ B> A ≧ C (Formula 1)
It is preferable to satisfy the relationship. For example, when t = 0.4 to 1 mm, C is 28% to 72% of t, more preferably 38% to 56%, and A is 28% to 93%, more preferably 82% to 90% of t. % And B is preferably substantially the same as t.

  When the bottom 31 is crushed, that is, when the condition of t> C is satisfied, the stress toward the bottom 31 is promoted in the two connection surfaces 34 and 35 connected to the bottom 31, so that the shape stability Can be further enhanced.

  The connecting portions 34 and 35 may be crushed (that is, t> B), but if the amount of crushing at this portion is large, the amount of crushing at the bent portions 21a, 21b, 21c and 21d is reduced. The stress of the mutually attracting direction which generate | occur | produces on the two surfaces mutually connected via the bending parts 21a, 21b, 21c, and 21d falls. Therefore, the condition of t = B is more preferable.

  Even if the side walls 32 and 33 are not crushed, they do not affect the return of bending than the bottom 31. However, if the amount of crushing of the side parts 32 and 33 is small, the folded parts 21a, 21b, 21c and 21d are crushed. Since the amount also decreases, the stress in the direction of attracting each other generated on the two surfaces connected to each other via the bent portions 21a, 21b, 21c and 21d is reduced. Therefore, the condition of t> A is preferable.

  Specifically, for example, when t = 0.7 mm, C = 0.2 to 0.5 mm, particularly 0.27 to 0.39 mm is preferable. When it is thicker than 0.5 mm, bending back tends to occur particularly in a high temperature environment. On the other hand, if it is crushed to be thinner than 0.2 mm, the original function as a reflector of the linear light source, that is, the reflection characteristic is deteriorated. Further, A = 0.2 to 0.65 mm, particularly 0.58 to 0.63 mm is preferable.

In order to realize the relationship between the thicknesses of the respective parts represented by the above formula (1), the clearances of the female mold 11 and the male mold 12 are preferably set as follows.
That is, as shown in FIG. 1, the clearance between the inner side surface 14 of the female die 11 and the side surface 17 of the male die 12 is a (mm), and the clearance between the female side inclined surface 15 and the male side inclined surface 18 is set. And the clearance between the bottom surface 13 of the female mold 11 and the protruding surface 16 of the male mold 12 is c (mm),
t ≧ b> a ≧ c (Formula 2)
It is preferable to set so as to satisfy this relationship. Thus, by setting the clearances a and c to be smaller than the thickness t of the thermoplastic resin sheet 20, the side surface 17 and the projecting surface 16 of the male mold 12 cause the thermoplastic resin sheet 20 to become the female mold. 11 functions as a pressing surface that is crushed toward the inner peripheral surface.

  c is preferably 28% to 43% of t, a is 28% to 86% of t, more preferably 72% to 86%, and b is preferably substantially the same as t. Specifically, for example, when t = 0.7 mm, c = 0.2 to 0.3 mm is preferable, a = 0.2 to 0.6 mm, particularly 0.5 to 0.6 mm is preferable, and b = 0.7 mm is preferable.

  As described above, according to the present embodiment, the thermoplastic resin sheet 20 can be bent and molded at 90 degrees or more by a single mold forming, which increases the number of processes and a large capital investment. It is not necessary to suppress the occurrence of the spring back phenomenon of the thermoplastic resin sheet 20 and to produce a molded body of the thermoplastic resin sheet 20 having excellent shape stability.

  In this embodiment, the case where the reflector 30 having a substantially J-shaped cross section is described as an example. However, it is of course possible to form a reflector having a substantially U-shaped cross section having the same length on both side walls. It is.

  Moreover, in this embodiment, although the case where the reflector 30 of the backlight unit used for a liquid crystal display device was shape | molded using the thermoplastic resin sheet 20 was demonstrated to the example, the application object of this invention is limited to this. Not. The present invention can be applied to any bent molded body using a thermoplastic resin sheet having a springback force, and contributes to the reduction of the number of steps for shape retention and the improvement of productivity. can do.

(Modification of the first embodiment)
FIG. 5 is a side view showing a mold 40 according to a modification of the first embodiment of the present invention. The mold 40 according to the present embodiment is a mold for molding a reflector having a substantially J-shaped cross section (see FIGS. 3 and 4) using a thermoplastic resin sheet as a main material. In the description of the mold 40, differences from the mold 10 according to the first embodiment of FIG. 1 will be described in detail.

  As shown in FIG. 5, the female die 41 includes a bottom surface 43, an inner side surface 44 substantially perpendicular to the bottom surface 43, and a female side inclined surface 45 formed between the bottom surface 43 and the inner side surface 44. Have.

  The male mold 42 protrudes from the side face 47 opposite to the protruding face 46 facing the bottom face 43 of the female mold 41, the side face 47 opposite to the inner side face 44 of the female mold 41, and the female inclined face 45. And a male inclined surface 48 formed between the surface 46 and the surface 46. And between this male side inclined surface 48 and the side surface 47, and between this male side inclined surface 48 and the protrusion surface 46, it corresponds to the bending part of the thermoplastic resin sheet which is bending object. The portion is provided with a convex portion 49 for crushing the bent portion of the thermoplastic resin sheet in the thickness direction.

  Moreover, the convex part 49 between the male side inclined surface 48 and the side surface 47 and the convex part 49 between the male side inclined surface 48 and the protruding surface 46 are respectively connected to the inner side surface 44 of the female mold 41. It is provided in a portion corresponding to the boundary between the female side inclined surface 45 and a portion corresponding to the boundary between the female side inclined surface 45 and the bottom surface 43 of the female mold. The convex portion 49 is a linear protrusion having a triangular cross section, and the bent portion of the thermoplastic resin sheet can be crushed in the thickness direction when the thermoplastic resin sheet is bent. In addition, although the angle of the apex angle of the convex part 49 is not specifically limited, In order to exhibit a crushing function more effectively, it is preferable that it is an acute angle.

Moreover, it is preferable that each clearance of the female metal mold | die 41 and the male metal mold | die 42 is set as follows. That is, as shown in FIG. 5, the clearance between the inner surface 44 of the female mold 41 and the side surface 47 of the male mold 42 is a (mm), and the clearance between the female inclined surface 45 and the male inclined surface 48 is set. When the clearance between the bottom surface 43 of the female mold 41 and the protruding surface 46 of the male mold 42 is c (mm),
a≈b≈c≈t (Formula 3)
Is set to satisfy the relationship.

  2, the bottom 31, the side walls 32 and 33 erected with respect to the bottom 31, and the bottom 31 and the side walls 32 and 33, as shown in FIGS. A reflector 30 having a substantially J-shaped cross section having connection portions 34 and 35 to be connected to each other can be obtained. However, the thickness is A≈B≈C.

(Second Embodiment)
FIG. 6 is a side view showing a mold 50 according to the second embodiment of the present invention. The mold 50 of the present embodiment is a mold for molding a reflector having a substantially J-shaped cross section (see FIG. 7) using a thermoplastic resin sheet as a main material. The mold 50 has a female mold 51 and a male mold 52 as shown in the figure. In the description of the mold 50, differences from the mold 10 according to the first embodiment of FIG. 1 will be described in detail.

  The female mold 51 has two inner side surfaces 54 that are substantially parallel to each other, and a bottom surface 53 that has a smooth curve (R shape) in cross section with respect to the inner side surface 54.

  The male die 52 has a side surface 57 that faces the inner side surface 54 of the female die 51 and a protruding surface 56 that faces the bottom surface 53 of the female die 51. When the protruding surface 56 is opposed to the bottom surface 53, the protruding surface 56 has a curve (R shape) with a smooth cross section in which the distance between the protruding surface 56 and the bottom surface 53 is substantially the same on the protruding surface 56. The protruding surface 56 is provided with three protrusions for crushing the bent portion of the thermoplastic resin sheet in the thickness direction on the portion corresponding to the bent portion of the thermoplastic resin sheet to be bent. A portion 59 is provided.

The convex portion 59 corresponds to a portion corresponding to the boundary between the inner side surface 54 of the female die 51 and the bottom surface 53 of the female die 51 on the protruding surface 56 and a central portion of the bottom surface 53 of the female die 51. It is provided in the part. The convex portion 59 is a linear protrusion having a triangular shape with an apex angle of approximately 90 degrees, and when the thermoplastic resin sheet is bent, the bent portion of the thermoplastic resin sheet may be crushed in the thickness direction. It is possible. Although the angle of the apex angle of the convex part 59 is not specifically limited, In order to exhibit a crushing function more effectively, it is preferable to have an angle of about 90 degrees.
Further, as shown in FIG. 6, the clearance between the inner surface 54 of the female die 41 and the side surface 57 of the male die 52 is d (mm), and the bottom surface 53 of the female die 51 and the protrusion of the male die 52 are provided. The clearance between the surface 56 is defined as e (mm).

  2, the curved portion 64 and the curved portion 65 curved inward as shown in FIG. 7, and the side wall portions 62 and 63 erected with respect to the curved portion 64 and the curved portion 65, Thus, the reflector 60 having a substantially J-shaped cross section can be obtained.

  In the reflector 60 obtained in this way, the fold line portion is crushed by the convex portion 59 of the male mold 52, so that the gap between the side wall portion 62 and the curved portion 64 is as shown in FIG. The thickness in the vicinity of the bent portion 25a, the thickness in the vicinity of the bent portion 25b between the bent portion 64 and the bent portion 65, and the bent portion 25c between the bent portion 65 and the side wall portion 63. The thickness of the vicinity is thin with the bent portions 25a, 25b, and 25c as base points.

  As shown in FIG. 7, the outer surface 62 b of the side wall 62 and the outer surface 64 b of the curved portion 64 are connected by a curved line (R shape) having a smooth cross section, and the outer surface 65 b of the curved portion 65 and the side wall 63. The outer side surfaces 63b are connected by a curved line (R shape) having a smooth cross section. Further, the outer surface 64b of the bending portion 64 and the outer surface 65b of the bending portion 65 are also connected, and the outer surface 64b of the connected bending portion 64 and the outer surface 65b of the bending portion 65 are all over the entire surface including the connecting portion. The cross section has a smooth curve (R shape).

  Thus, two surfaces connected to each other through the bent portions 25a, 25b, and 25c (that is, the inner side surface 62a of the side wall portion 62 and the inner side surface 64a of the bending portion 64, the inner side surface 64a of the bending portion 64, and the bending portion). As shown in FIG. 7, the obtained reflector 60 has a side wall portion 62 because stress in a direction attracting each other acts on the inner side surface 65 a of 65, the inner side surface 65 a of the curved portion 65, and the inner side surface 63 a of the side wall portion 63. And 63 have a shape closer to the plane P passing through the bent portion 25b than the lower portions connected to the curved portions 64 and 65 of the side wall portions 62 and 63, and are thermoplastic. Bending back (spring back phenomenon) of the resin sheet is suppressed.

(Third embodiment)
FIG. 8 is a side view showing a mold 70 according to the third embodiment of the present invention. The mold 70 of the present embodiment is a mold for forming a molded body having a substantially L-shaped cross section using a thermoplastic resin sheet as a main material. The mold 70 has a female mold 71 and a male mold 72 as shown in the figure.

  The female mold 71 is a L-shaped mold having a bottom surface 73 and an inner surface 74 that is substantially perpendicular to the bottom surface 73. The male mold 72 has a lower surface 76 that faces the bottom surface 73 of the female mold 71 and a side surface 77 that faces the inner side surface 74 of the female mold 1. The corner of the male mold 72 has a protrusion for crushing the bent portion of the thermoplastic resin sheet in the thickness direction at a portion corresponding to the bent portion of the thermoplastic resin sheet to be bent. A portion 75 is provided.

  The convex part 75 is a substantially rectangular parallelepiped, and is provided so that one long side thereof faces the corner part of the female mold 71. When the thermoplastic resin sheet is bent, the bent part of the thermoplastic resin sheet is thick. It can be crushed in the vertical direction. In addition, the shape of the convex part 75 is not limited to the shape shown in FIG. 8, What kind of shape may be sufficient as long as the bending part of a thermoplastic resin sheet can be crushed in the thickness direction. For example, instead of the convex portion 75, linear protrusions 78 and 79 having a triangular cross section with an acute apex angle as shown in FIGS. 9 and 10 can be employed. If the metal mold | die shown in FIG. 9 is used, a thermoplastic resin sheet will become a shape where the bending part, a part of bottom part, and a part of side part were crushed in the thickness direction. In addition, when the mold shown in FIG. 10 is used, the thermoplastic resin sheet has a shape in which a bent part, a bottom part, and a part of the side part are crushed in the thickness direction.

  By using the mold 70 having such a shape and bending the thermoplastic resin sheet in the same manner as in the first embodiment, a molded body having a substantially L-shaped cross section can be obtained. In the obtained molded body, when the bent portion is crushed by the convex portion 75 of the male mold 72, stress in a direction attracting each other acts on two surfaces connected via the bent portion. For this reason, the molded object of the thermoplastic resin sheet by which the one end part was bent at an angle of 90 degree | times or more can be obtained.

  Also in the present embodiment, the thermoplastic resin sheet can be bent and molded at 90 degrees or more by a single molding, so that the thermoplastic resin sheet does not require an increase in the number of processes and significant capital investment. It is possible to produce a molded body of a thermoplastic resin sheet that suppresses the occurrence of the spring back phenomenon and is excellent in shape stability.

  Further, by using the mold 10 of the first embodiment of the present invention and the mold 70 of the third embodiment, for example, a chassis-integrated reflector 80 of a backlight device as shown in FIG. 11 is formed. can do. When such a chassis-integrated reflector 80 is molded, for example, a thermoplastic resin sheet is punched into a developed shape that becomes a target shape when assembled, and a chassis (housing) is formed using a mold 70. ) The two side portions 82 of 81 are bent and finally, the two reflectors 83 are bent using the mold 10. Thereby, the chassis integrated reflector 80 excellent in shape stability can be obtained.

  The reflector described above is molded using a mold, but can also be molded using a forming roll. A method of manufacturing a reflector using a forming roll will be described with reference to FIGS. FIG. 12 is a schematic perspective view for explaining bending molding of a thermoplastic resin sheet by a forming roll, FIG. 12 (a) is a schematic perspective view of the first molding roll, and FIG. FIG. 12C is a schematic perspective view of the second molding roll, FIG. 12C is a schematic perspective view of the third molding roll, and FIG. 12D is a schematic perspective view of the fourth molding roll.

  FIG. 13 is a cross-sectional view of each forming roll passing through a roll rotation axis perpendicular to the conveyance direction of the thermoplastic resin sheet, and FIG. 13A is a cross-sectional view of the first forming roll. (B) is sectional drawing in a 2nd forming roll, FIG.13 (c) is sectional drawing in a 3rd forming roll, FIG.13 (d) is sectional drawing in a 4th forming roll.

  Moreover, FIG. 14 is a figure for demonstrating the state by which the thermoplastic resin sheet was shape | molded, FIG.14 (a) is a figure which shows the state of the thermoplastic resin sheet after the 1st step | molding, FIG. 14B is a diagram showing the state of the thermoplastic resin sheet after the second stage molding, and FIG. 14C is a diagram showing the state of the thermoplastic resin sheet after the third stage molding. FIG. 14 (d) is a diagram showing a state of the thermoplastic resin sheet after the fourth stage molding. Here, a forming roll having four stages of molding will be described as an example. Further, the manufactured reflector will be described by taking the case of the reflector having a substantially J-shaped cross section shown in FIGS. 3 and 4 as an example.

  12 (a), (b), (c) and (d) and FIGS. 13 (a), (b), (c) and (d), the thermoplastic resin sheet 20 is 4 The reflector 30 as shown in FIG. 3 and FIG. 4 is manufactured through the step molding. This is because forming the thermoplastic resin sheet 20 little by little at each stage does not cause excessive deformation or distortion. The first stage molding is performed by the first molding roll 91, the second stage molding is performed by the second molding roll 92, the third stage molding is performed by the third molding roll 93, and the fourth stage molding is performed by the fourth molding roll 94. Is formed by.

  As shown in FIGS. 12A and 13A, the first forming roll 91 includes a first forming lower roll 101 and a first forming upper roll 102, and the first forming lower roll 101 and the first forming upper stage 102. Each of the rolls 102 is a rotating body having the same cross section passing through the roll rotation axes S1 and S2 that rotate about the roll rotation axes S1 and S2.

  The first forming lower roll 101 connects a cylindrical lower stage central part 101a, a cylindrical lower stage end part 101c having a larger radius than the lower stage central part 101a, and the lower stage central part 101a and the lower stage end part 101c. And a lower inclined portion 101b having a trapezoidal cross section. The first forming upper roll 102 includes a cylindrical upper middle portion 102a, a columnar upper stage end portion 102c having a smaller radius than the upper middle portion 102a, and the upper middle portion 102a and the upper stage end portion 102c. And an upper inclined portion 102b having a trapezoidal cross section to be connected.

  In addition, the width of the lower middle portion 101a and the upper middle portion 102a (the length in the roll rotation shafts S1 and S2 directions) is substantially the same, and the width of the lower edge portion 101c and the upper edge portion 102c is substantially the same. The widths of the portion 101b and the upper inclined portion 102b are substantially the same. Further, the trapezoidal slopes of the cross sections of the lower slope portion 101b and the upper slope portion 102b are substantially parallel. Further, the distance (clearance) between the first molding lower roll 101 and the first molding upper roll 102 is substantially the same as the thickness of the thermoplastic resin sheet 20.

  The thermoplastic resin sheet 20 is conveyed while being sandwiched between the first molding lower roll 101 and the first molding upper roll 102, and stands up against the bottom 111 and the bottom 111 as shown in FIG. It is formed into a substantially J-shaped cross section having side walls 112 and 113 provided. The first forming roll 91 is adjusted so that the angle formed by the bottom 111 and the side walls 112 and 113 is about 28 degrees.

  As shown in FIGS. 12B and 12C and FIGS. 13B and 13C, the second forming roll 92 and the third forming roll 93 have the same configuration as the first forming roll 91. ing. As shown in FIG. 12B and FIG. 13B, the second forming roll 92 includes a second forming lower roll 103 and a second forming upper roll 104, and the second forming lower roll 103 and the second forming upper stage. Each of the rolls 104 is a rotating body having the same cross section passing through the roll rotation axes S3 and S4 that rotate about the roll rotation axes S3 and S4.

  12C and 13C, the third forming roll 93 includes a third forming lower roll 105 and a third forming upper roll 106, and the third forming lower roll 105 and the third forming roll The forming upper roll 106 is a rotating body having the same cross section passing through the roll rotation axes S5 and S6 rotating around the roll rotation axes S5 and S6.

  The thermoplastic resin sheet 20 molded by the first molding roll 91 is conveyed while being sandwiched between the second molding lower roll 103 and the second molding upper roll 104, and the bottom portion as shown in FIG. 111 and side wall portions 112 and 113 erected with respect to the bottom portion 111 are formed into a substantially J-shaped cross section. In addition, the 2nd shaping | molding roll 92 is adjusted so that the angle | corner which the bottom part 111 and the side wall parts 112 and 113 make may be about 52 degree | times.

  Further, the thermoplastic resin sheet 20 molded by the second molding roll 92 is conveyed while being sandwiched between the third molding lower roll 105 and the third molding upper roll 106, as shown in FIG. 14 (c). The cross section is formed in a substantially J-shape having a bottom portion 111 and side wall portions 112 and 113 erected with respect to the bottom portion 111. In addition, the 3rd shaping | molding roll 93 is adjusted so that the angle | corner which the bottom part 111 and the side wall parts 112 and 113 make may be about 72.5 degree | times.

  As shown in FIG. 12D and FIG. 13D, the fourth forming roll 94 includes a fourth forming lower roll 107 and a fourth forming upper roll 108, and the fourth forming lower roll 107 and the fourth forming upper stage. Each of the rolls 108 is a rotating body having the same cross section passing through the roll rotation axes S7 and S8 that rotate about the roll rotation axes S7 and S8.

  The fourth forming lower roll 107 connects a columnar lower stage central portion 107a, a columnar lower stage end 107c having a larger radius than the lower stage central portion 107a, and the lower stage central portion 107a and the lower stage end 107c. And a lower inclined portion 107b having a trapezoidal cross section. Further, in the cross section of the lower central portion 107a, the surface shape composed of the lower central portion 107a, the lower inclined portion 107b, and the lower end portion 107c is the cross sectional shape of the female mold 41 shown in FIG. 5 (or the female metal shown in FIG. The cross-sectional shape of the mold 11 is the same.

  The fourth forming upper roll 108 includes an upper central portion 108a of a rotating body having a circumferential surface having the same cross section as the cross section of the male mold 42 shown in FIG. 5 (or the cross section of the male mold 12 shown in FIG. 1). It has a cylindrical upper stage end portion 108c. Further, the distance (clearance) between the fourth molding lower roll 107 and the fourth molding upper roll 108 is the clearance between the female mold 41 and male mold 42 in FIG. 5 (or the female mold 11 and male mold in FIG. 1). Each clearance of the mold 12 is the same.

  The thermoplastic resin sheet 20 molded by the third molding roll 93 is conveyed while being sandwiched between the fourth molding lower roll 107 and the fourth molding upper roll 108, as shown in FIG. 3 and 4, the reflector 30 including the bottom portion 31, the side wall portions 32 and 33, and the connection portions 34 and 35 is formed. Here, the bottom portion 111 is formed into the bottom portion 31, the side wall portion 112 is formed into the side wall portion 32 and the connection portion 34, and the side wall portion 113 is formed into the side wall portion 33 and the connection portion 35.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

(Examples 1-3)
A polyethylene terephthalate resin sheet having a thickness of 0.7 mm was used as the thermoplastic resin sheet, punched into a predetermined shape, and a creased line was put at the folding position. Next, the thermoplastic resin sheet is pressed using a mold having the shape shown in FIG. 1 and having the clearance shown in Table 1, the mold is heated to the temperature shown in Table 1, and pressing and heating are performed. Molding was performed. Thereafter, the mold was cooled to 40 ° C., and the reflector was taken out.

Example 4
A polyethylene terephthalate resin sheet having a thickness of 0.7 mm was used as the thermoplastic resin sheet, punched into a predetermined shape, and a creased line was put at the folding position. Next, the thermoplastic resin sheet is pressed using a mold having the shape shown in FIG. 5 and having the clearance shown in Table 1, the mold is heated to 120 ° C., and pressing and thermoforming are performed. It was. Thereafter, the mold was cooled to 40 ° C., and the reflector was taken out.

(Example 5)
A polyethylene terephthalate resin sheet having a thickness of 0.7 mm was used as the thermoplastic resin sheet, punched into a predetermined shape, and a creased line was put at the folding position. Next, the thermoplastic resin sheet is pressed using a mold having the shape shown in FIG. 6 and having the clearance shown in Table 1, the mold is heated to 100 ° C., and pressing and thermoforming are performed. It was. Thereafter, the mold was cooled to 40 ° C., and the reflector was taken out.

(Example 6)
A polyethylene terephthalate resin sheet having a thickness of 0.7 mm was used as the thermoplastic resin sheet, punched into a predetermined shape, and a creased line was put at the folding position. Next, the thermoplastic resin sheet is pressed using a mold having the shape shown in FIG. 6 and having the clearance shown in Table 1, the mold is heated to 100 ° C., and pressing and thermoforming are performed. It was. Thereafter, the mold was cooled to 40 ° C., and the reflector was taken out.

(Comparative Examples 1-5)
A polyethylene terephthalate resin sheet having a thickness of 0.7 mm was used as the thermoplastic resin sheet, punched into a predetermined shape, and a fold line was placed at the folding position. Next, the thermoplastic resin sheet is pressed using a mold having the shape shown in FIG. 15 and having the clearance shown in Table 1, the mold is heated to the temperature shown in Table 1, and pressing and thermoforming are performed. Went. Thereafter, the mold was cooled to 40 ° C., and the reflector was taken out.

<Measurement of reflector dimensions>
For the reflectors obtained in Examples 1 to 6 and Comparative Examples 1 to 5, before molding (that is, at the stage of the thermoplastic resin sheet), immediately after taking out from the mold, and after standing for 1 hour in a 70 ° C. environment. Dimensional measurements were taken. The results are shown in Table 1.

<Evaluation of reflector shape stability>
Further, for each reflector, as shown in FIG. 16, before and after leaving at 70 ° C. for 1 hour, as shown in FIG. 16, the angle θ formed between the bottom of the reflector and the side wall (short side), and both side walls on the opening side of the reflector The width W between them was measured. The results are shown in Table 2.

As is apparent from Table 2, in Examples 1 to 6, the value of the angle θ after molding shows a negative value, and it is possible to bend the molding to 90 degrees or more by one molding. confirmed. Further, even after being left at 70 ° C. for 1 hour, the bent state of 90 degrees or more was maintained, and it was within the designed dimensional tolerance, and no bending return was observed. In addition, the bending angle tended to increase further after standing at 70 ° C. for 1 hour.
Dimensional tolerance standard: 6.389 + 0.05 / −0.10 (6.289-6.439)

(Example 7)
In Example 7, the die 10A shown in FIG. 17 in which the female die 11 of the die 10 having the shape shown in FIG. 1 is provided with the air ejection holes 121 and the male die 12 is provided with the air ejection holes 122 is used. The reflector was manufactured using it.
A polyethylene terephthalate resin sheet having a thickness of 0.7 mm was used as the thermoplastic resin sheet, punched into a predetermined shape, and a creased line was put at the folding position. Next, the thermoplastic resin sheet was pressed using the mold 10A having the shape shown in FIG. 17, and the mold 10A was heated to 100 ° C. to perform pressing and thermoforming. Thereafter, the mold 10A was cooled with water to the glass transition temperature (Tg = 80 ° C.) of the polyethylene terephthalate resin sheet. Thereafter, when the reflector is taken out from the mold 10A, air is discharged to the reflector using the air ejection hole 121 of the female mold 11 and the air ejection hole 122 of the male mold 12, and the reflector is cooled to 40 ° C. Then, the reflector was taken out.
As a result of Example 7, the cooling time was 69 seconds for the cooling of the mold alone compared with the case where the mold was cooled to 40 ° C. by water cooling, whereas it was 15 seconds for the air cooling together. It was shortened to about one fifth. Thereby, the manufacturing time of a reflector can be shortened.

DESCRIPTION OF SYMBOLS 10 Mold 11 Female mold 12 Male mold 13 Bottom surface 14 Inner side surface 15 Female side inclined surface 16 Projecting surface 17 Side surface 18 Male side inclined surface 19 Convex part 20 Thermoplastic resin sheet 21 Bending line 30 Reflector

Claims (12)

A mold for bending a thermoplastic resin sheet having a female mold and a male mold,
The male mold is a portion corresponding to the bent portion of the thermoplastic resin sheet, it has a convex portion for crushing the bent portion of the thermoplastic resin sheet in the thickness direction,
The female mold has a bottom surface and an inner surface substantially perpendicular to the bottom surface;
The male mold has a protruding surface facing the bottom surface of the female mold and a side surface facing the inner side surface of the female mold;
At least one of the protruding surface and the side surface of the male mold is a pressing surface for crushing the resin sheet in the thickness direction toward the inner peripheral surface of the female mold,
The female mold further has a female inclined surface formed between the bottom surface and the inner surface;
The male mold further has a male-side inclined surface formed between the side surface and the protruding surface, facing the female-side inclined surface,
The convex portion of the male mold has a portion on the male inclined surface corresponding to a boundary between the inner surface of the female mold and the female inclined surface, and the female inclined surface and the female mold. mold characterized that you have provided for a portion corresponding to a boundary between the bottom surface. The thickness of the thermoplastic resin sheet is t (mm), the clearance between the inner surface of the female mold and the side surface of the male mold is a (mm), the female inclined surface and the male side When the clearance between the inclined surface is b (mm) and the clearance between the bottom surface of the female mold and the protruding surface of the male mold is c (mm), t ≧ b> a ≧ c The mold according to claim 1, wherein the relationship is satisfied . When the angle formed between the inner surface of the female mold and the female inclined surface is α (degrees), and the angle formed between the bottom surface of the female mold and the female inclined surface is β (degrees) ,
The convex portion of the male mold provided at a portion corresponding to the boundary between the inner surface of the female mold and the female inclined surface on the male inclined surface has an apex angle of γ (degrees). Having a triangular cross-section,
The convex portion of the male mold provided at a portion corresponding to the boundary between the bottom surface of the female mold and the female inclined surface on the male inclined surface has a vertical angle of δ (degrees). Has a triangular shape,
The mold according to claim 1 or 2, wherein a relationship of α> γ and β> δ is satisfied . The mold according to any one of claims 1 to 3, wherein the convex part of the male mold has a triangular cross section with an apex angle of approximately 90 degrees or less . A method of bending a thermoplastic resin sheet,
A method of bending a thermoplastic resin sheet, comprising a pressing step of pressing the thermoplastic resin sheet using the mold according to any one of claims 1 to 4. It has a heating process which heats the above-mentioned metallic mold to 70 ° C or more and 200 ° C or less after the above-mentioned pressing process, and a cooling process which cools the above-mentioned metallic mold to below 40 ° C after the above-mentioned heating process. 5. A method for bending a thermoplastic resin sheet according to 5. The cooling step includes a water cooling step of water cooling the mold to a glass transition temperature (Tg) of the thermoplastic resin sheet, and after the water cooling step, air is blown onto the thermoplastic resin sheet to a temperature of 40 ° C. or lower. The method of bending a thermoplastic resin sheet according to claim 6, further comprising an air cooling step of cooling . The method for bending a thermoplastic resin sheet according to claim 6 or 7 , wherein the heating step is performed by vibrating the mold with ultrasonic waves . The method for bending a thermoplastic resin sheet according to any one of claims 5 to 8, wherein, in the pressing step, the thermoplastic resin sheet is pressed with a pressure of 294 MPa or more . The heat according to any one of claims 5 to 9 , further comprising a fold line forming step of providing a fold line in a bent portion of the thermoplastic resin sheet before the pressing step. A method for bending a plastic resin sheet. A bent molded body obtained by bending a thermoplastic resin sheet using the mold according to any one of claims 1 to 4,
A bottom portion, a side wall portion erected with respect to the bottom portion, and a connecting portion that connects the bottom portion and the side wall portion;
The side wall portion has a thin thickness of the resin sheet based on a bent portion between the side wall portion and the connection portion,
The bottom portion has a thin thickness of the thermoplastic resin sheet with a bent portion between the bottom portion and the connection portion as a base point,
The bent molded body of a thermoplastic resin sheet, wherein the side wall portion is bent at 90 degrees or more with respect to the bottom portion. When the thickness of the side wall portion is A (mm), the thickness of the connecting portion is B (mm), and the thickness of the bottom portion is C (mm), the relationship of B> A ≧ C is satisfied. The bent molded body of a thermoplastic resin sheet according to claim 11.

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