WO2000007793A1 - Method of manufacturing sheet-shaped plastic product with surface projections - Google Patents

Abstract

A method of manufacturing a diffusion plate used for a screen plate of a projection television, wherein a diffusion plate having substantially over one side surface thereof a multiplicity of projections in the form of quadrangular pyramid is manufactured by injection molding of a plastic material. The method using a first molding die having a first die surface for molding, a preforming die capable of forming a mold cavity of a first volume while being put together with the first molding die, and a second molding die capable of forming a mold cavity of a second volume smaller than the first volume while being put together with the first molding die; and comprising the steps of injecting a molten plastic material into the mold cavity of the first volume between the first molding die and the preforming die from an injection port while the first molding die and the preforming die are put together, after completion of injection and before curing of the plastic material, separating the first molding die from the preforming die and putting it together with the second molding die to effect a second process, and compressing the plastic material, which has been injected in the first process, in the mold cavity of the second volume to mold the plastic material between the first die surface and a second die surface.

Description

 TECHNICAL FIELD The present invention relates to a method for manufacturing a thin plastic article made of a plastic material. In particular, the present invention is suitable for, but not limited to, a method for producing a Fresnel lens diffuser suitable for use in a screen plate for a projection television. 2. Related Art Conventionally, a production television has a configuration shown in FIG. That is, the image projected from the image projection tube 1 is reflected by the mirror 2 and forms an image on the screen plate 3. The screen plate 3 includes a Fresnel lens 4, a diffusion plate 5, and a protection plate 6, as shown in FIG. As shown in FIGS. 2 (b) and 2 (c), the diffusion plate 5 has a configuration in which a large number of mountain-shaped ridges 7 extending in the vertical direction are formed in parallel on both sides. The protection plate 6 is formed of a transparent plastic plate.

The chevron ridges 7 of the diffusion plate 5 have a lens effect in addition to the diffusion effect, and have an effect of expanding the projected image in the horizontal direction. The protection plate 6 protects the diffusion surface of the diffusion plate 5 from scratches and dust.However, since the protection plate 6 is a transparent plate having a smooth surface, the surrounding lighting equipment is projected to make it difficult to view the image. I do. Therefore, the surface exposed on the front side of the protective plate 6 is preferably a matte surface having fine irregularities. In addition, without providing the protection plate 6 separately, the surface opposite to the diffusion surface of the diffusion plate 5 may be configured as the matte surface, and the matte surface may be exposed to the front side. By the way, it is preferable that the Fresnel lens 4, the diffusion plate 5, and the protection plate 6, which are the components of the screen plate 3 of this kind, are formed by molding a plastic material from the viewpoint of cost and weight. It is not easy to form a sheet-like article having a fine uneven pattern on the surface by molding a plastic material.

 SUMMARY OF THE INVENTION An object of the present invention is to provide a method of manufacturing a Fresnel lens diffusion plate used for a screen plate for a projection television, and other thin plate-shaped plastic material articles having irregularities on the surface. I do.

In order to solve the above-mentioned object, the present invention provides a method of manufacturing a thin plate-like article formed with a protruding force so as to be distributed over at least substantially the entire surface on one side by molding a plastic material. The method according to the first aspect of the present invention comprises: a first mold having a first mold surface for molding; and a first mold having a first mold surface. The first molding die having a capacity of 1 can be formed, and can be fitted to a pre-molding die having an injection port of a plastic material into the molding cavity and the first molding die. A mold cavity having a second volume smaller than the first volume can be formed in accordance with the condition, and a second mold having a second mold surface facing the mold cavity is prepared. . In the molding, the first molding die and the preliminary molding die are combined, and the first volume molding cavity formed between the first molding die and the preliminary molding die is melted from the injection port. Performs the first step of injecting the plastic material of the second mold after the injection of the first step is completed and before the plastic material is cured. The plastic material injected in the first step is compressed in the molding cavity of the second volume, and the first molding surface and the second molding surface are formed. This is achieved by molding a plastic material between them. In a method according to another aspect of the present invention, a first mold having a first mold surface for molding and a first mold that can be fitted to the first mold are formed. And a second molding die having a second molding surface facing the molding cavity. Then, in a state where the second molding die is separated from the first molding die, the plastic material in a fluid state is supplied to a plurality of portions of the first molding surface of the first molding die to supply the plastic material. The plastic material is diffused to the first mold surface by fluidity. Next, the molding cavity is formed by matching the second molding die with the first molding die, and the plastic material previously filled in the molding cavity is cured while being compressed.

 In a method according to still another aspect of the present invention, in a state where the second mold is separated from the first mold, the plastic material in a flowable state is placed on the first mold surface of the first mold. By displacing the plastic material on the first molding surface by moving the nozzle and the first molding die relatively laterally while supplying the plastic material in a linear manner through the elongated nozzle, the second molding is performed. The mold is matched with the first mold to form a molding cavity, and the plastic material previously filled in the molding cavity is cured while being compressed.

In a method according to a further preferred embodiment of the present invention, there is provided a plastic material supply station, a first molding station provided adjacent to a side of the plastic material supply station, and a plastic material supply station located at a position different from the first molding station. A second molding station provided adjacent to the supply station; and a second molding station provided in association with each of the first molding station and the second molding station, for establishing a connection between the associated molding station and the plastic material supply station. A movable first mold having a first mold surface, and a first molding station and a second molding station are provided at each of the first molding station and the second molding station. Molding cavities can be formed in accordance with the molding dies, and molding facing molding cavities A second mold having a second mold surface and an elongated nozzle provided at a plastic material supply station are used. Then, first, the first molding die associated with the first molding station is moved to the plastic material supply station, and the plastic material in a fluid state is placed on the first molding surface of the first molding die. The plastic material is diffused on the first molding surface by relatively laterally moving the nozzle and the first molding die without force to supply linearly through the elongated nozzle of the supply station and the nozzle, Next, the first molding die associated with the first molding station is moved to the first molding station, and the second molding die provided at the first molding station is moved to the first molding stage. A molding cavity is formed in accordance with the mold, and a plastic material previously filled in the molding cavity is cured while being compressed. In this method, during this time, the first molding die associated with the second molding station is moved to the plastic material supply station, and the first molding die associated with the second molding station is subjected to the same procedure. Spread the plastic material on the first molding surface of. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view showing a schematic configuration of a conventional general projection television.

 FIGS. 2A and 2B show a screen plate of a conventional production television. FIG. 2A is a cross-sectional view showing the whole, FIG. 2A is a plan view of a part thereof, and FIG. 3A and 3B show an example of a diffusion plate used for the screen plate of the present invention. FIG. 3A is a partially enlarged plan view, and FIG. 3B is a perspective view.

4A and 4B show another embodiment of the diffusion plate used for the screen plate of the present invention. FIG. 4A is a partially enlarged plan view, and FIG. 4B is a perspective view. FIG. 5 is a sectional view of an embodiment of the screen plate of the present invention.

 FIGS. 6A and 6B show a process of manufacturing a diffusion plate used for the screen plate of the present invention, wherein FIG. 6A shows a first process and) shows a second process.

 FIGS. 7A and 7B show another embodiment of the method of the present invention, wherein FIG. 7A is a plan view of an apparatus used for the method, and FIG.

 FIG. 8 is a plan view showing an example of an apparatus used in a method of a modified example of the embodiment shown in FIG. 7. FIG. 9 shows still another embodiment of the present invention. Is a plan view of the device used in (1), and () is a side view in partial section.

 FIG. 10 is a side view of a molding apparatus showing still another embodiment of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIGS. 3 (a) and 3 (b) show an example of a diffusion plate manufactured by the method of the present invention. In the drawing, the diffusion plate 5 has square pyramid-shaped projections 5a arranged vertically and horizontally. Is formed. Further, as shown in FIGS. 4 (a) and 4 (b), the quadrangular pyramid-shaped projections 5b can be arranged diagonally. It is preferable that the surface of the diffusion plate 5 opposite to the surface having the protrusions 5a and 5b be an opaque surface.

 FIG. 5 shows an example of a screen plate using a diffusion plate manufactured by the method of the present invention. The diffusion plate 5 is arranged with the surface having the projections 5 a facing the lens surface of the Fresnel lens 4. It is fixed to the Fresnel lens 4 by bonding or the like. The same applies to the diffusion plate 5 having the projection 5b. The arrow indicates the visual direction.

FIG. 6 shows a method according to the first embodiment of the present invention for manufacturing the diffusion plate 5 used for the above-mentioned screen plate by molding a plastic material. Used for manufacturing The mold to be formed is an upper mold having a concave portion 6a for pre-molding, that is, a pre-molding die 6, a lower mold 7 having a concave portion 7a for molding having a molding surface, and a molding having a molding surface. For the upper die 8 having the concave portion 8a and the force. A gate 6b for injecting a molten plastic material is formed in the center of the preforming die 6, and a cylinder 9 for injecting a plastic material is arranged in the gate 6b. The concave portion 6a of the upper die 6 for pre-molding and the convex portion 7a of the lower die 7 are configured so that a surplus region 10 is formed outside the molding region of the diffusion plate. The upper mold 6 for preforming and the lower mold 7 form a first volume of the cavity 11 for preforming in a state in which they are put together.

 The upper mold 8 and the lower mold 7 for molding can be moved together from the position shown in FIG. 6 (b) in the direction of each other. The cavities form 1 1 a. A molding surface is formed in the molding recess 8a of the molding upper die 8.

 During manufacturing, as shown in Fig. 6 (a), the preforming cavity 11 is held between the preforming upper die 6 and the lower die 7 so that the dies 6 and 7 are held so as to be formed. Then, a molten or softened plastic material is injected from the plastic injection cylinder 9 held in the gate 6b. As a material, methyl methacrylate, polycarbonate, polystyrene and the like can be used.

When a predetermined amount of the molten or softened plastic material is injected into the molding cavity 10, the injection is stopped, the lower mold 7 is separated from the preforming upper mold 6, and the injected plastic material is recessed 7a. While holding the inside, move it to below the upper mold for molding to obtain the state shown in Fig. 6 (b). Next, the lower mold 7 is moved upward, and the molding cavity 11 a is formed between the lower mold 7 and the upper mold 8. By this operation, the plastic material injected into the molding cavity 11a having a smaller volume than the preliminary molding cavity 11 shown in Fig. 6 (a) is compressed, and the concave portions 7a and 8a are molded. Molded by surface. During this process, the excess plastic material in the molding cavity 11 Extruded into the surplus area 10. According to this method, both the pyramidal projections 5a and 5b of the diffusion plate and the matte surface on the opposite side can be simultaneously molded.

 FIGS. 7A and 7B show another embodiment of the present invention. In this embodiment, the lower mold 7 has the same structure as in the previous embodiment. Although not shown in the figure, the upper die has the same structure as the upper die 8 in the previous embodiment. In this embodiment, a nozzle device 12 is provided to supply the plastic material to the lower mold 7. The nozzle device 12 includes a nozzle block 13, which has an X-shaped injection manifold 14 extending along two intersecting diagonals 13 a, 13 b. Is provided. An injection nozzle 15 is arranged at each end of the X-shaped injection manifold 14. The injection nozzle 15 has a well-known structure that is opened and closed by the shut-off pin 16. When the shut-off pin 16 is retracted and the nozzle port is opened, the plastic material from the injection manifold 14 is discharged from the nozzle 15. Is done. An injection passage 18 from a plastic material injection cylinder 17 is connected to the X-shaped intersection of the injection manifold 14.

 When manufacturing a thin plate made of plastic material, first, the lower die 7 is positioned below the nozzle device 12 with the lower die 7 separated from the upper die (not shown) by force, and the injection cylinder 17 is operated to supply the molten plastic material in a fluidized state from the injection nozzle 15 to the molding recess 7 a of the lower die 7. The plastic material supplied onto the molding recess 7a of the lower mold 7 diffuses into the molding surface of the molding recess 7a of the lower mold 7 due to its fluidity. Therefore, the nozzle 15 is closed with the shut-off pin 16 in the closed position, the nozzle device 2 is separated from the lower die 7, and the lower die 7 is moved below the upper die, and in the same manner as in the previous embodiment, Molding is performed between the lower mold 7 and the upper mold.

FIG. 8 shows a modification of the embodiment of FIG. In this embodiment, the X-shaped injection manifold 14 provided in the nozzle block 13 of the nozzle device 12 has, in addition to the four nozzles 15, an X-shaped central part, that is, two Diagonal intersection The nozzle 15a is further arranged in the vicinity of. Other configurations are the same as those in the embodiment of FIG.

 FIGS. 9A and 9B show still another embodiment of the present invention. In this embodiment, a nozzle device 21 is used instead of the nozzle device 12 in the embodiment of FIG. The lower mold 7 and the upper mold (not shown) for molding have the same structure as those in the above-described embodiments. The nozzle device 21 is provided with a nozzle 22 having an elongated slit-like discharge port 22 a, and an extrusion cylinder or an extrusion screw 23 of a plastic material is connected to the nozzle 22. The nozzle device 21 and the lower mold 7 can move relatively. In the present embodiment, the lower die 7 has a structure in which the lower die 7 can be moved in the lateral direction with respect to the nozzle device 21 as shown by a broken line in FIG. 9B.

 As shown in FIG. 9 (a), the nozzle 22 is arranged such that the slit-shaped discharge port 22a extends in the width direction of the molding concave portion 7a of the lower molding die 7. A gear pump 24 is arranged at the upper part of the nozzle 22 so as to communicate with the plastic material passage in the nozzle 22. When operating, push the cylinder or push screw 2

3 is operated to supply the molten plastic material to the nozzle 22. The plastic material is supplied from a discharge port 22 a of the nozzle 22 onto the molding recess 7 a of the lower die 7. In the meantime, the lower mold 7 is relatively moved with respect to the nozzle device 21 as shown by a broken line in FIG. 9 (b). Since the plastic material is supplied linearly and is in a flowing state, it spreads in the width direction of the molding concave portion 7a of the lower die 7. When the lower mold 7 moves relative to the nozzle device 21, the plastic material is supplied so as to spread over almost the entire length of the lower mold concave portion 7 a in the length direction. Therefore, the operation of the extrusion cylinder or the extrusion screw 23 is stopped, and the gear pump 24 is operated to suck back the molten plastic material remaining in the nozzle 22. This can prevent the plastic material from dripping from the discharge port 22 a of the nozzle 22. Thereafter, the lower mold 7 is moved to a position below the upper mold (not shown), and the same as in the previous embodiment is performed. Perform molding.

 FIG. 10 shows an application of the embodiment of FIG. The device used in the method of this example comprises a nozzle device 21 similar to that shown in FIG. A first molding station A is provided adjacent to one side of the plastic material supply station S, and a second molding station B is provided adjacent to the opposite side. Each of the first and second molding stations A and B is provided with an upper die 8 movably up and down. In addition, each of the first and second molding stations A and B has a lower die that can move between the first and second molding stations A and S. On the side of the first molding station A with respect to the nozzle device 21 of the plastic material supply station S, a leveling roller 25 a that rotates in the direction of arrow a is used. On the sides, the leveling rollers rotating in the direction of the arrow b are arranged with a strength of 25 b.

 In the method of the present invention using the apparatus shown in FIG. 10, first, the lower mold 7 associated with the first molding station A is moved downward to the nozzle device 21 of the plastic material supply station S, The molten plastic material is supplied linearly to the molding surface 7a of the lower mold 7 by the same procedure as described with reference to FIG. During this time, the lower mold 7 is moved in the direction of the first molding station A as shown by an arrow c in FIG. 10, and the plastic material is supplied to almost the entire molding surface 7 a of the lower mold 7. . The molten plastic material supplied onto the molding surface 7a of the lower mold 7 is leveled by the leveling roller 25b rotating in the direction of arrow a. When the supply of the plastic material is completed, the extruding cylinder or the extruding screw 23 is stopped, and the molten plastic material in the nozzle 22 is sucked back by the gear pump 24. Next, the lower mold 7 is returned to the first molding station A,

The upper die 8 of A is lowered to a position where the lower die 7 can be fitted, and a plastic material is molded in a molding cavity formed between the lower die 7 and the molding surface 7a. During this time Then, the lower mold 7 of the second molding stage B is moved to the plastic material supply station S, and the plastic material in a molten state is supplied to the molding surface 7a of the lower mold 7 by the same action. You. This method is effective in increasing the efficiency of production. According to the method of the present invention, a plastic material article having a thin plate-like shape and having a fine concavo-convex pattern on the surface can be easily produced. When a diffusion plate as shown in FIG. 3 is used, there is no need to provide a protection plate outside the screen plate, and the structure is simplified. Further, by making the surface of the diffusion plate opposite to the surface having the projections a matte surface, it is possible to solve the problem that the image is difficult to see due to the reflection of ambient light. The method of the present invention has an effect that a Fresnel lens or a diffusion plate in which unevenness is formed on a wide flat surface can be molded without any trouble.

 As described above, the present invention has been described with reference to the specific embodiments with reference to the drawings. However, the present invention is not limited to the specific forms shown in the drawings, but may be variously embraced within the spirit of the present invention described in the claims. Can be changed and modified. Accordingly, the invention is not limited to the specific structures shown, but is only limited by the scope of the appended claims.

Claims

The scope of the claims 1. A method for producing a sheet-like article having a shape molded substantially over at least one side by molding a plastic material,  A first molding die having a first molding surface,  The first mold can be matched with the first mold, and a mold cavity having a first volume can be formed in a state in which the mold cavity is matched with the first mold, and a spare having an injection port of a plastic material to the mold cavity is formed. A molding die,  The molding cavity having a second volume smaller than the first volume can be formed in a state in which the molding cavity is aligned with the first molding die, and faces the molding cavity. A second molding die having a second molding surface;  Prepare  In a state where the preliminary molding die is fitted to the first molding die, the injection port is inserted into a first volume of the molding cavity formed between the first molding die and the preliminary molding die. Performing a first step of injecting a plastic material in a molten state from the second step, and after the injection is completed, before the plastic material is cured, the first mold is separated from the pre-molding mold and the second mold is removed. Performing a second step of matching the molding material with the molding die, compressing the plastic material injected in the first step in a molding cavity having a second volume, and forming the molding first mold surface and the molding Molding of the plastic material between the two mold surfaces,  A method for producing a thin plate-like article by molding a plastic material. 2. A method for producing a thin plate-like article having a shape molded over at least substantially the entire surface on one side by molding a plastic material, A first molding die having a first molding surface, A second molding die having a second molding surface facing the first molding die, forming a molding cavity facing the first molding die, and having a second molding surface facing the molding cavity. When,  Prepare  In a state where the second molding die is separated from the first molding die, a plastic material in a flowable state is supplied to a plurality of portions of the first molding surface of the first molding die. Diffusing the plastic material to the first mold surface by the fluidity of the plastic material,  Next, a molding cavity is formed by matching the second molding die with the first molding die, and the plastic material previously filled in the molding cavity is cured while being compressed.  A method for producing a thin plate-like article by molding a plastic material. 3. The method according to claim 2, wherein the supply of the plastic material is performed at two locations on each of two intersecting diagonals, a total of four locations.  4. The method according to claim 3, wherein the plastic material is supplied also near the intersection of the two diagonal lines.  5. A method for producing a thin plate-like article having a shape molded over at least substantially one side thereof by molding a plastic material,  A first molding die having a first molding surface,  A second molding die having a second molding surface facing the first molding die, forming a molding cavity facing the first molding die, and having a second molding surface facing the molding cavity. When, Prepare In a state where the second molding die is separated from the first molding die, a plastic material having fluidity is linearly passed through an elongated nozzle on the first molding surface of the first molding die. The plastic material is diffused on the first molding surface by relatively laterally moving the nozzle and the first molding die while supplying the plastic material,  Next, a molding cavity is formed by matching the second molding die with the first molding die, and the plastic material previously filled in the molding cavity is cured while being compressed,  A method for producing a thin plate-like article by molding a plastic material. 6. The method according to claim 1, wherein the thin plate-like article is a diffuser plate having quadrangular pyramid-shaped protrusions.  7. The method according to claim 1, wherein the sheet-like article is a Fresnel lens.  8. The method according to claim 2, wherein the thin plate-shaped article is a diffuser plate having quadrangular pyramid-shaped projections.  9. The method according to claim 5, wherein the thin plate-shaped article is a diffuser plate having quadrangular pyramid-shaped projections.  10. The method according to claim 2, wherein the sheet-like article is a Fresnel lens.  11. The method according to claim 5, wherein the sheet-like article is a Fresnel lens.  12. A method for producing a sheet-like article having a shape molded substantially over at least one side thereof by molding a plastic material,  A plastic material supply station, A first component provided adjacent to a side of the plastic material supply station; Mold station,  A second molding station provided at a different position from the first molding station and adjacent to the plastic material supply station;  A first mold having a first mold surface for molding provided in association with each of the first molding station and the second molding station and movable between the associated molding station and the plastic material supply station. Mold and  Provided in each of the first molding station and the second molding station, can be adapted to the first molding die, and can form molding cavities in a state in accordance with the first molding die; A second mold having a second mold surface facing the mold cavity;  Providing an elongate nozzle provided at the plastic material supply station;  The first molding die associated with the first molding stage is moved to the plastic material supply station, and the plastic material in a fluid state is placed on the first molding surface of the first molding die. By relatively laterally moving the nozzle and the first molding die while supplying the plastic material linearly through an elongated nozzle, the plastic material is diffused on the first molding surface,  Next, the first molding die associated with the first molding station is moved to the first molding stage, and the second molding die provided at the first molding station is moved to the first molding station. Forming a molding cavity in accordance with the first molding die moved to, and curing the plastic material pre-filled in the molding cavity while compressing the plastic material; In the meantime, the first molding die associated with the second molding station is moved to the plastic material supply station, and the same procedure is performed to perform the first molding associated with the second molding station. Brass on the first molding surface of the mold Diffuse tic material,  A method for producing a thin plate-like article by molding a plastic material. 13. The method according to claim 12, wherein the plastic material supplied to the first mold surface of the first molding die at the plastic material supply station is combined with the nozzle and the first molding die. A method characterized by flattening during relative lateral movement between and.  14. The method according to claim 13, wherein the plastic material is leveled by a rotating leveling port.