JP2001047456A - Device and method for manufacturing fresnel lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a precise Fresnel lens and easily release the Fresnel lens from a mold. SOLUTION: A Fresnel lens manufacturing device is provided with a mold 10 with a through-hole formed running through from the surface to the back, a core 31 with its surface constituting a part of the surface of the mold 10 by being inserted into the through-hole, a driving device 30 moving the core 31 in the through-hole and an air feeder for feeding the air into a space 40 formed by moving the core 31 by the driving device 30 and encircled with a resin plate 50 press molded by being pressed by the mold 10 with the through- hole wherein the core 31 is inserted, the inner face of the through-hole and the surface of the core 31 to release the resin plate 50 from the mold 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for manufacturing a Fresnel lens, and more particularly to a technique for facilitating demolding in a manufacturing process of a Fresnel lens.

[0002]

2. Description of the Related Art In recent years, Fresnel lenses, which are thin lenses formed in a stepwise manner so as to have the optical properties of a thick lens, have been used in various fields. As one method of manufacturing such a Fresnel lens, a press molding method is known. This press molding method is a heating step of heating a thermoplastic resin sheet sandwiched between a mold and a mirror plate,
Pressing step of press-molding the heated resin sheet, cooling step of cooling the pressed resin sheet, demolding step of removing the cooled resin sheet from the mold, and cutting the removed resin sheet to a desired size Cutting process.

[0003] In the demolding step in such a conventional press molding method, generally, a method is used in which a resin sheet is peeled off little by little from the outer periphery of a mold by hand. However, it is difficult to remove the resin sheet from the mold in the case of a hot-pressed product having a plate shape like a Fresnel lens and precisely transferring the fine shape of the mold.

[0004] A "method of manufacturing a sheet-like lens" which solves such a problem is disclosed in, for example, Japanese Patent Application Laid-Open No. 9-57778 (Japanese Patent No. 2691148). In this method of manufacturing a sheet-shaped lens, one or a plurality of circular or slit-shaped openings are provided in a part of the mold, and a gas, for example, compressed air is injected from the opening to make close contact with the mold. Release the molded product. This makes it easy to release the final product sheet-like lens from the mold,
Production efficiency is improved.

[0005]

However, according to the method disclosed in Japanese Patent Application Laid-Open No. 9-57778, an opening is provided in a part of a mold, so that the Fresnel lens transferred from the mold has a disadvantage. The position corresponding to the opening becomes irregular, and the function as a lens is impaired. When the heating temperature in the heating step is increased and the pressing force in the pressing step is increased in order to accurately transfer the fine shape of the mold, the resin as the lens material enters the opening and the Fresnel It may be rather difficult to release the lens.

The present invention has been made to solve such a problem, and an object of the present invention is to manufacture a precise Fresnel lens and easily release the Fresnel lens from a mold. It is an object of the present invention to provide a Fresnel lens manufacturing apparatus and a manufacturing method therefor.

[0007]

According to a first aspect of the present invention, there is provided an apparatus for manufacturing a Fresnel lens, comprising: a mold provided with a through hole extending from a front surface to a rear surface;
A core whose surface forms a part of the surface of the mold by being inserted into the through hole, a driving device that moves the core in the through hole, and the core that is moved by the driving device A space formed by a resin plate pressed and pressed by a mold in which the core is inserted into the through hole, an inner surface of the through hole, and a surface of the core. And an air supply device for sending air into the mold to release the resin plate from the mold.

In the Fresnel lens manufacturing apparatus, the through hole may be provided at a position corresponding to any ridge line of a plurality of concentric peaks formed in the mold. Further, the through hole may be provided in a plurality of arc shapes at a position of any ridge line among a plurality of concentric slopes formed in the mold.

According to this Fresnel lens manufacturing apparatus, the pressed resin plate is removed from the mold by sending air into a space formed by moving a part of the surface of the mold, thereby producing the manufactured lens. The Fresnel lens is not damaged, and the demolding process itself is simplified.

Further, the method for manufacturing a Fresnel lens according to the second aspect of the present invention is characterized in that, for the same purpose as described above, a through-hole provided from the front surface to the back surface of the mold is provided with the front surface of the metal. A first step of inserting a core formed so as to constitute a part of the surface of the mold, and a second step of press-molding by pressing a resin plate against the mold having the core inserted into the through hole. And a space formed by moving the core inserted into the through hole, which is surrounded by a resin plate press-molded on the mold, an inner surface of the through hole, and a surface of the core. A third step of blowing air into the closed space to release the resin plate from the mold.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a configuration of a main part of a Fresnel lens manufacturing apparatus according to an embodiment of the present invention. As shown in FIG. 1A, the Fresnel lens manufacturing apparatus includes a mold 10 fixed to a fixing plate 20, the mold 10 and the fixing plate 2.
The cylinder 21 is formed so as to penetrate through the cylinder 21, a core 31 that moves in the cylinder 21 in the direction of the arrow in the figure, and a driving device 30 that moves the core 31.

The mold 10 is formed by cutting the surface of a Fresnel lens (the surface having irregularities; the same applies hereinafter) to the reverse shape. This mold 10 is 255 mm x 255 m
m, and the surface thereof has a saw-shaped peak of 0.
It is formed concentrically at a pitch of 5 mm.
In (A), the number of mountains is limited and exaggerated for ease of understanding. Here, the saw-like shape means that when the mold 10 is cut along a line passing through the center of a concentric circle, one of the cut surfaces is perpendicular to the back surface of the Fresnel lens (a surface having no irregularities; the same applies hereinafter). And the other has a shape having a slope. The height of the peak is about 0.3 mm at the outermost periphery, and gradually decreases toward the center of the concentric circle.

A through hole as shown in FIG. 1B is provided in the center of the mold 10, and a cylinder 21 is formed in cooperation with the through hole provided in the fixing plate 20. I have. The size (diameter) of the through-hole is shown in FIG.
0 is the same as the diameter of the ridgeline of the innermost mountain (the diameter is 1 mm). However, the size of the through hole is not limited to this, and may be the same as the diameter of the ridgeline of the plurality of peaks from the innermost circumference of the mold 10.

A cavity 11 is provided inside the mold 10, and a temperature control pipe 12 is provided in the cavity 11. The temperature control pipe 12 is a mold 10
The temperature of the mold 10 is adjusted by passing air from an air supply device (not shown). That is, the temperature of the mold 10 is adjusted via the cavity 11 by passing heated air in the heating step and cooled air in the cooling step through the temperature control pipe 12. According to this configuration, the reaction rates of heating and cooling can be improved. Also, cavity 1
A pipe 13 having an opening in a cylinder 21 is laid inside 1. The other end of the tube 13 (not shown in FIG. 1A) is connected to an air supply device (not shown). In the demolding process, the air from the air supply device is sent into the cylinder 21 through the pipe 13.

In the cylinder 21, a core 3 fixed to a shaft movable in the direction of the arrow by a driving device 30 is provided.
1 is provided. Surface of core 31 (upper surface in the figure)
Is used as a part of the surface of the mold 10 with the core 31 moved to the uppermost part. Therefore, on the surface of the core 31, a mountain that would have been formed if the through hole was not provided in the mold 10 is formed.

The mold 10 may be provided with a plurality of arc-shaped through holes as shown in FIG. The positions where these arc-shaped through holes are provided may be the positions of the ridge lines of the innermost circumference of the mold 10 or the positions of the ridge lines of a plurality of the mountain from the innermost circumference of the mold 10. in this case,
As shown in FIG. 2A, the core 31 is formed in a shape to be inserted into an arc-shaped through hole.

Next, a process of manufacturing a Fresnel lens by a hot press method using the Fresnel lens manufacturing apparatus configured as described above will be described.

First, when the driving device 30 is driven, the core 31 is moved to the uppermost position. Thereby, the surface of the core 31 becomes a part of the surface of the mold 10 and a complete mold is formed. Next, a resin plate 50 is placed on the mold 10 and the core 31, and a mirror plate (not shown) for smoothing the back surface of the Fresnel lens is further placed thereon.

Here, the resin plate 50 is a lens member that becomes a Fresnel lens when molded. As the resin plate 50, for example, an acrylic resin, a polycarbonate resin, a polystyrene resin, a vinyl chloride resin, or the like can be used.

The manufacturing process of the Fresnel lens according to this embodiment includes a heating process, a pressing process, a cooling process, a demolding process, and a cutting process. Hereinafter, description will be made step by step for each process.

(1) Heating step: In this heating step, the resin plate 50 sandwiched between the mold 10 and the mirror plate is heated. Thereby, the resin plate 50 is softened.

(2) Pressurizing step: When this heating is completed,
By operating a press mechanism (not shown), the mold 1
The resin plate 50 sandwiched between the zero and the mirror plate is pressed. Thereby, the softened resin plate 50 penetrates into the details of the mold 10 and the shape of the mold 10 is reproduced well.

(3) Cooling step: In this cooling step, the resin plate 50 sandwiched between the mold 10 and the mirror plate is cooled to 70 to 80 ° C. Thereby, the resin plate 50 is solidified,
A Fresnel lens whose front surface is formed into a reverse mold of the mold 10 and whose back surface is formed into a mirror surface is manufactured.

(4) Demolding step: In this demolding step, the Fresnel lens formed by cooling to 70 to 80 ° C. in the cooling step is peeled from the mold 10. Specifically, by driving the drive mechanism 30, the core 31 is lowered downward in the figure to a position where the opening of the tube 13 faces the inside of the cylinder 21. Thereby, the resin plate 50, the cylinder 2
A space 40 is formed which is surrounded by the inner side surface of the core 1 and the upper surface of the core 31.

In this state, air supplied from an air supply device (not shown) is supplied to the pipe 1 laid in the cavity 11.
The gas is ejected into the space 40 through the space 3 to increase the pressure in the space 40. Thereby, the resin plate 50 is peeled off from the mold 10, and the mold is removed.

(5) Cutting step: The Fresnel lens removed from the Fresnel lens manufacturing apparatus is cut into a desired size, and a Fresnel lens as a final product is manufactured.

According to the embodiment described above, the core 3
Since the resin plate is released from the mold by sending air into the space 40 formed by moving 1 downward, without damaging the manufactured Fresnel lens,
In addition, the demolding process itself is simplified.

In the above embodiment, the resin plate 5
0, the supply of air to the space 40 surrounded by the inner side surface of the cylinder 21 and the upper surface of the core 31 is performed by using the tube 13 laid in the cavity 11.
3, the space 4 passes through the fixing plate 20 and the core 31.
It is also possible to form a hole reaching 0 and supply air from this hole.

Further, in the above-described embodiment, the manufacturing apparatus and the manufacturing method of the Fresnel lens have been described. However, the manufacturing apparatus and the manufacturing method of the present invention can be used for manufacturing various lenses other than the Fresnel lens.

[0031]

As described in detail above, according to the present invention,
An apparatus and a method for manufacturing a Fresnel lens that can manufacture a precise Fresnel lens and that can easily release the Fresnel lens from a mold can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a Fresnel lens manufacturing apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing another configuration of the Fresnel lens manufacturing apparatus according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Mold 11 Cavity 12 Temperature control piping 13 Pipe 20 Fixing plate 21 Cylinder 30 Drive 31 Core 40 Space 50 Resin plate

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Masahiko Nakayama 1-10-1 Shinsayama, Sayama-shi, Saitama Honda Engineering Co., Ltd. F-term (reference) 4F202 AG05 AH75 CA09 CB01 CK53 CK73 CM08 4F213 AG05 AH75 WA05 WA67 WC01 WK05

Claims (4)

[Claims] 1. A mold provided with a through hole extending from a front surface to a back surface, a core whose surface forms a part of the surface of the mold by being inserted into the through hole, A driving device for moving in the through-hole, and a space formed by moving the core by the driving device, wherein the space is formed by pressing a mold in which the core is inserted into the through-hole and press-formed. Producing a Fresnel lens, comprising: a resin plate, an air supply device for sending air into a space surrounded by an inner side surface of the through hole and a surface of the core, and removing the resin plate from the mold. apparatus. 2. The Fresnel lens manufacturing apparatus according to claim 1, wherein the through hole is provided at a position corresponding to any ridge line of a plurality of concentric peaks formed in the mold. 3. The Fresnel lens according to claim 1, wherein the through-hole is provided in a plurality of arcs at any one of ridges of a plurality of concentric slopes formed in the mold. apparatus. 4. A first step of inserting a core, the surface of which is formed into a part of the front surface of the mold, into a through hole provided from the front surface to the back surface of the mold; A second step of press-molding by pressing a resin plate against the mold in which the core is inserted into the through hole, and a space formed by moving the core inserted into the through hole. A third step of blowing air into a space surrounded by the resin plate press-molded on the mold, the inner side surface of the through hole, and the surface of the core, thereby removing the resin plate from the mold. And a step of manufacturing a Fresnel lens.