JP4435009B2 - Optical element manufacturing method and molding die - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a molding die for obtaining a molded article which is free from the eccentric internal stress by molding in such a manner that a spherical thermoplastic material is positioned at the approximately center of a sphere die. <P>SOLUTION: The molding die comprises a main die body 1 which holds the sphere die 5 formed as a spherical shape movably in the pressing direction, an opposed die 8 disposed opposingly to this main die body 1, a sleeve die 9 which guides the main die body 1 and the opposed die 8, and a pushing member 6 which projects the sphere die 5 in a through-bore 2 formed in the main die body 1 toward the opposed die 8 side from an opening 2a of the through-bore 2 by a predetermined distance. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

The present invention relates to an optical element manufacturing method and a molding die, and more particularly to an optical element manufacturing method and a molding die for molding a thermoplastic material such as plastic and glass.

  For example, in a molding die that molds an optical element from a thermoplastic material such as plastic or glass, when molding an optical element having a hemispherical portion (for example, a concave surface, but not including a complete hemisphere) as a transfer surface, The mold is composed of the hemispherical part and a flat part continuing from the hemispherical part. However, since it is difficult to produce this part only by molding means, conventionally, the connecting part between the hemispherical part and the flat part has been finished by grinding (secondary processing) using a grinder after molding. . However, it is difficult to manufacture a molding die in a short period of time because skilled techniques are required for grinding a portion having such a complicated curved surface shape and a great number of man-hours are required.

On the other hand, in Patent Document 1, a sphere as a mold material is fitted to the mold body so that the spherical center is substantially located on the center axis of the mold body and a part of the spherical surface is a molding surface. It is disclosed that a molding die is obtained by fixing a sphere by means such as fastening with screws. According to this, a molding die having a convex molding surface with a particularly small curvature can be obtained at low cost.
Japanese Utility Model Publication No. 63-94929 (first page, FIG. 1)

  However, as in the technique disclosed in Patent Document 1, when a spherical part is pressed against a thermoplastic material using a spherical mold, especially when a spherical material is used as the thermoplastic material, It has been difficult to stably place the spherical thermoplastic material on the center of a spherical molding die. This is because it is difficult to place a ball on the ball. For this reason, for example, it has been difficult to mold a spherical thermoplastic material so as to spread evenly with respect to the optical axis of the optical element as a molded product.

  As a result, during molding, uneven flow of the material occurs during deformation of the thermoplastic material with respect to the circumferential direction of the molded product, resulting in biased internal stress, and an optical element with sufficient surface accuracy can be obtained. It was difficult.

The present invention has been made in order to solve such a problem. The object of the present invention is to position the thermoplastic material at the approximate center of the spherical shape and then mold the thermoplastic material that has been heat-softened. An object of the present invention is to provide a method for manufacturing an optical element and a mold for molding which can obtain a molded product which is deformed so as to be spread evenly with respect to a spherical mold while preventing flow unevenness to eliminate the bias of internal stress.

In order to achieve the above object, the invention according to claim 1 is a method of manufacturing an optical element in which a thermoplastic material is molded by heating and pressing.
A step of accommodating a spherical mold that is processed into a spherical shape and a part of the spherical surface is a molding surface, and is movably accommodated in a hole in a mold main body that extends in a pressurizing direction;
A positioning step of placing and positioning the spherical thermoplastic material equal to or greater than or equal to the diameter of the hole at the opening of the hole;
After the positioning step, an abutting step of abutting the opposed mold disposed facing the mold main body against the thermoplastic material;
After the contact step during heat molding, by the pushing member supporting the spherical type from the back side of the molding surface in said bore, so that the forming surface is out butt toward the opposed side from the opening Moving process to move to ,
After the moving step, the pre-Symbol-to-oriented type is moved relatively to the mold body, a step of compression molding the thermoplastic material,
It is characterized by having .

The invention according to claim 2 is a mold for molding by heating and pressurizing a thermoplastic material,
A spherical shape that is processed into a spherical shape and a part of the spherical surface becomes a molding surface;
A mold body in which a hole for accommodating the spherical mold movably in the vertical direction is formed;
An opposing mold disposed opposite to the mold body;
A guide mold for slidably guiding the mold body and the opposed mold in the vertical direction;
A pushing member that supports the spherical mold from the back side of the molding surface in the hole and is pushed up to project the spherical mold by a predetermined amount from the opening of the hole toward the opposing mold;
A first spring disposed between the mold body and the pushing member and repelling the mold body and the pushing member in a vertical direction;
A second spring disposed between the opposing type and the guiding type, repelling the opposing type and the guiding type in a vertical direction, and having a spring constant larger than that of the first spring;
A stopper that is disposed between the mold body and the pushing member, and controls a push-up amount of the pushing member;
It is characterized by having .

The invention according to claim 3 is a molding die for molding by heating and pressurizing a thermoplastic material,
A spherical shape that is processed into a spherical shape and a part of the spherical surface becomes a molding surface;
A mold body in which a hole for accommodating the spherical mold movably in the vertical direction is formed;
An opposing mold disposed opposite to the mold body;
A first guide mold that slidably guides the mold body and the opposed mold in the vertical direction;
A second guide mold that slidably guides the mold main body, the opposed mold, and the first guide mold, and is provided outside the first guide mold and has a long hole;
A pushing member that supports the spherical mold from the back side of the molding surface in the hole and is pushed up to project the spherical mold by a predetermined amount from the opening of the hole toward the opposing mold;
A first pin which can be inserted into the opposing mold through the first guiding mold and the second guiding mold from the side of the opposing mold, and which is movable in the pressurizing direction in the elongated hole; ,
A second pin capable of supporting the mold body through the second guide mold;
It is characterized by having.

The invention according to claim 4 is the molding die according to claim 2 or 3,
The opening is formed so as to be narrower than a diameter of the spherical shape.

  According to the present invention, since the spherical thermoplastic material before heating can be positioned at the approximate center of the mold, the thermoplastic material can be deformed so as to spread substantially uniformly over the spherical mold while preventing flow unevenness of the thermoplastic material. Therefore, it is possible to obtain a molded product that eliminates the uneven internal stress.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
FIGS. 1A to 1C are diagrams showing a molding die according to the present embodiment and a molding process using the molding die. In FIG. 1A, a molding die 10 molds an optical element by heating and pressurizing a thermoplastic material 7 made of plastic, glass or the like in a spherical shape. The molding die 10 has a hollow cylindrical shape in which a spherical die 5 that is processed into a spherical shape and a part of the spherical surface becomes a molding surface, and a through hole 2 that accommodates the spherical die 5 so as to be movable in a pressurizing direction. The mold main body 1, a counter mold 8 disposed to face the mold main body 1, and a sleeve mold (guide mold) 9 that slidably guides the mold main body 1 and the counter mold 8.

  The mold body 1 and the through hole 2 are formed so that their center lines substantially coincide with each other, and the spherical mold 5 is supported in the through hole 2 from below (the back side of the molding surface of the spherical mold 5). The pushing member 6 is arranged. The pushing member 6 serves to press the spherical mold 5 accommodated in the through-hole 2 from the lower side of the drawing toward the upper facing mold 8 side and to project a predetermined amount from the opening 2a of the through-hole 2. .

  In the present embodiment, a spherical thermoplastic material 7 having a diameter substantially equal to or larger than the diameter of the opening 2 a is placed in the opening 2 a of the through hole 2. At this time, since the spherical mold 5 is supported in a state of being immersed inside the opening 2a, the spherical thermoplastic material 7 is placed on the periphery of the opening 2a, and the degree of freedom is naturally constrained. Positioned. In this state, the mold body 1 and the opposed mold 8 are inserted into the sleeve mold 9. Further, the opposed mold 8 is lightly brought into contact with the upper surface of the spherical thermoplastic material 7 so that the spherical thermoplastic material 7 is not detached from the opening 2 a of the through hole 2.

  In the present embodiment, the case where the spherical thermoplastic material 7 is placed in the opening 2a of the through hole 2 has been described. However, for example, the opposed mold 8 and the spherical mold 5 are disposed upside down. The same effect can be obtained by positioning the spherical thermoplastic material 7 on the opposing mold 8 with the mold body 1 and inserting the spherical mold 5. On the other hand, it is also conceivable to place and form a flat material on the opposed mold 8. However, in this case, a planar material is placed on the plane of the opposing mold 8 and is placed in the middle, and it is difficult to obtain good transferability because air is confined between the two.

  Next, as shown in FIG. 1B, the molding die 10 including the thermoplastic material 7 and the like is heated with a heater (not shown) to raise the temperature of the thermoplastic material 7 to a deformable temperature. Further, the pushing member 6 is pushed up to the opening 2a side of the through hole 2, and the spherical mold 5 is projected from the opening 2a by a predetermined amount. From this state, the opposing mold 8 is pushed into the pressing direction on the mold body 1 side with a predetermined pressure (arrow direction), and the thermoplastic material 7 is pressure-molded.

  Thus, as shown in FIG. 1C, the substantially disc-shaped molded product 15 is molded, and a spherical concave surface 15 a is formed at the approximate center on the side facing the spherical mold 5. In this case, if there is a slight gap g between the opening 2a of the through hole 2 and the spherical mold 5, the molten portion of the thermoplastic material 7 enters the gap g, and the flash 15b is formed around the concave surface 15a. Since it may occur, it is preferable to make the gap g as small as possible.

  Further, in this embodiment, in order to make the coefficient of linear expansion of the component member due to temperature constant, all the cemented carbide is used as the material of the mold body 1, the spherical mold 5, the pushing member 6, the opposing mold 8 and the sleeve mold 9. (WC) was used. Further, in the present embodiment, the case where the molding die 10 has one through hole 2 has been described. However, the present invention is not limited to this, and the molding die 10 has, for example, a plurality of through holes 2 and a spherical die 5 inserted therein. Can be installed adjacent to each other. By doing so, a lens array having a plurality of molding surfaces in one lens can be obtained.

  As shown in FIG. 1C, the thermoplastic material 7 is subjected to secondary processing by grinding, polishing or the like when the flash 15b is generated around the concave surface 15a after being molded. The beam 15b is deleted to become a product. In addition to removing burrs, etc., for example, the thermoplastic material 7 is formed into a shape substantially similar to a product by molding, and finally a highly accurate product is obtained by secondary processing such as grinding or polishing. Also good.

  According to the present embodiment, since the spherical thermoplastic material 7 can be placed on the center line of the spherical mold 5 in advance before molding, the spherical thermoplastic material 7 is placed between the spherical mold 5 and the opposed mold 8. When sandwiched and molded, the molten resin can be spread substantially uniformly with respect to the central axis, and the uneven thickness can be improved to obtain a good molded product. In addition, an inexpensive spherical thermoplastic material 7 having a low processing cost can be used as a molding material, and there is an advantage that it is easy to ensure accuracy. Furthermore, since the spherical mold 5 can be manufactured at low cost and with high accuracy, the molding mold 10 can be easily regenerated and corrected by using replacement parts (consumable parts).

[Second Embodiment]
2A to 2C are views showing a molding die and a molding process thereof according to the second embodiment. In addition, the same code | symbol is attached | subjected to the same or equivalent member as embodiment mentioned above, and the description is abbreviate | omitted.

  In this embodiment, the spherical mold 5 is biased by the spring pressure of the main body spring 11, and the counter mold 8 is biased against the spring pressure of the counter spring 12. In this case, the spring constant of the counter spring 12 is set larger than the spring constant of the main body spring 11.

  2 (a) and 2 (b), when the opposing mold 8 is pressed downward, the main body spring 11 contracts ahead of the opposing spring 12, and the opposing mold 8 and the pushing member 6 approach each other. As a result, the pushing member 6 moves relative to the mold body 1 and the spherical mold 5 is pushed into the spherical thermoplastic material 7 that has been heat-softened. Further, when the opposing mold 8 is pressed downward, the opposing spring 12 is also contracted, the opposing mold 8 moves to the pushing member 6 side, and the spherical thermoplastic material 7 is pressure-molded. Then, as shown in FIG. 2C, a desired molded product 15 having a medium thickness is obtained.

  In the case of the present embodiment, the push-up amount of the pushing member 6, that is, the protruding amount of the spherical die 5 from the opening 2a is determined by the height of the stopper 13 arranged between the die body 1 and the pushing member 6. Can be controlled. Further, as shown in FIG. 3, the protrusion amount T at this time can be controlled by setting the hole diameter D of the throttle portion 2b of the opening 2a to a predetermined value. For example, the hole diameter D of the narrowed portion 2b of the opening 2a of the through hole 2 is set to a value that matches the protrusion amount T that the spherical mold 5 protrudes from the opening 2a.

Next, based on FIG. 3, the hole diameter D is calculated from the protrusion amount T.
If the curvature of the spherical mold 5 is R,
^{T = R-√ (R 2} - (D 2/4)) , and the
Solving this,
D = 2 × √ (2RT−T ² )
It can be derived from the relational expression

  According to the present embodiment, since the spherical thermoplastic material 7 can be placed on the substantially center line of the spherical mold 5 in advance before molding, the heat-softened spherical thermoplastic material 7 is even with respect to the center line. Thus, a molded product having the required surface accuracy can be obtained. Further, since the opening 2a is formed in the narrowed portion 2b smaller than the diameter of the spherical mold 5, the flash 15b formed on the outer peripheral portion of the concave surface 15a made of a spherical surface can be suppressed as the molded product 15. Furthermore, if the softened spherical thermoplastic material 7 enters the through hole 2, the operation in the through hole 2 will be hindered. In the present embodiment, however, the strength of the two springs 11 and 12 is reduced. By associating these, the pressing order of the spherical mold 5 is restricted, and consideration is given to prevent the softened spherical material 7 from entering the through hole 2 of the mold body 1.

[Third Embodiment]
FIGS. 4A to 4E are views showing a molding die and its molding process according to the third embodiment. In this embodiment, as shown in FIGS. 4A and 4B, the spherical mold 5 is supported on the receiving surface of the pushing member 6 via the plastic metal 17 (or elastic body), and the receiving surface This prevents the spherical mold 5 from being scratched. Examples of the plastic metal 17 include Au, Pt, Cu, and Al. In addition to the above, in order to prevent the spherical mold 5 from being scratched, for example, the receiving surface of the pushing member 6 may have a curved surface shape that fits the spherical mold 5 exactly.

  Next, as shown in FIG. 4 (c), a spherical thermoplastic material 7 having a diameter substantially equal to or larger than the diameter of the opening 2a is placed in the opening 2a of the through hole 2 in the opening 2a. It is placed and positioned on the periphery of the diaphragm 2b. Further, the opposed mold 8 is lightly brought into contact with the upper surface of the spherical thermoplastic material 7.

  Next, as shown in FIG. 4D, the molding die 10 including the thermoplastic material 7 and the like is heated with a heater (not shown) to raise the temperature of the thermoplastic material 7 to a deformable temperature. Further, the pushing member 6 is pushed up to the opening 2a side of the through hole 2, and the spherical mold 5 is projected from the throttle part 2b by a predetermined amount. From this state, the opposed mold 8 is pushed in the pressurizing direction at a predetermined pressure (in the direction of the arrow), and the thermoplastic material 7 is press-molded to obtain a molded product 15 as shown in FIG.

  According to the present embodiment, since a part of the spherical mold 5 can be supported by the entire receiving surface of the pushing member 6, it is possible to prevent the occurrence of scratches on the spherical surface of the spherical mold 5 that is not used during molding. Can do. Thereby, for example, after molding, the molding surface of the spherical mold 5 can be changed over to make a new mold.

[Fourth Embodiment]
FIGS. 5A to 5D are views showing a molding die and its molding process according to the fourth embodiment. In this embodiment, the molding operation sequence of the second embodiment is performed by sequentially removing the pins 18 and 21.

  In FIG. 5A, a predetermined molding load (arrow direction) is always applied to the opposed mold 8 toward the mold body 1 side. Further, a pin 18 is fitted into the opposing mold 8 so as to penetrate the inner and outer sleeve molds 9 and 19 from the side, and a long hole 20 is formed in the outer sleeve mold 19. Thereby, the pin 18 can freely move in the long hole 20 in the pressing direction of the opposed mold 8. Further, the main pin 21 that supports the mold body 1 at the lower side is disposed through the outer sleeve mold 19. In this state, even if the above-described molding load (in the direction of the arrow) is applied to the opposing mold 8, the mold body 1, the pushing member 6 and the like do not move.

  Next, as shown in FIG. 5B, the molding die 10 is heated with a heater (not shown) to soften the spherical thermoplastic material 7. In this state, first, the lower main pin 21 is first pulled out sideways (in the direction of the arrow), whereby the pushing member 6 supporting the spherical mold 5 is relatively pushed into the mold body 1. Then, the spherical mold 5 protrudes toward the thermoplastic material 7 by a predetermined amount from the narrowed portion 2b of the opening 2a.

  Next, as shown in FIG. 5C, when the upper pin 18 is pulled sideways from the opposed mold 8 with the main pin 21 removed, the opposed mold 8 is thermoplastic due to the molding load (arrow direction). It moves to the raw material 7 side and pressurizes the thermoplastic material 7. Thereby, the thermoplastic material 7 is pressure-deformed until it reaches a desired volume. Note that the movement of the facing mold 8 at this time is regulated by the facing mold 8 coming into contact with the upper end surface 9 a of the inner sleeve mold 9. In this way, as shown in FIG. 5D, the molded product 15 is obtained after the molding die 10 is cooled.

  According to this embodiment, since the springs 11 and 12 are not used as in the second embodiment (FIG. 2), the sliding between the mold body 1 and the sleeve mold 9 is unstable, or the thermoplasticity. Regardless of variations in the softened state of the material 7, the height position (push-in amount) of each member can be fixedly set. Thereby, the molded product 15 with stable accuracy can be obtained.

[Fifth Embodiment]
FIGS. 6A to 6C are diagrams showing a molding die and a molding process thereof according to the fifth embodiment. In this embodiment, as shown in FIG. 6A, heating plates 23 and 24 are arranged opposite to each other in the molding apparatus 30, and the molding die 10 is sandwiched between the heating plates 23 and 24. It is fixed and heated. In this molding apparatus 30, during pressure molding, the pressure shafts 25, 26 protrude forward and backward from hole portions 27, 28 formed in the central portions of the opposed heating plates 23, 24, thereby forming the molding. The mold 10 is sandwiched and pressed for molding.

  That is, as shown in FIG. 6B, the mold body 1 and the sleeve mold 9 are fixedly sandwiched between the opposed heating plates 23 and 24, and the molding mold 10 is heated to form a spherical thermoplastic material 7. Softens. Then, the pushing member 6 is pushed upward by the pressing shaft 26 from the lower heating plate 24 side, and the spherical mold 5 is projected from the throttle portion 2b of the opening 2a to a predetermined position. Next, the opposed mold 8 is pushed into the thermoplastic material 7 side by the pressure shaft 25, and the thermoplastic material 7 is pressure-molded until it reaches a predetermined volume. Then, as shown in FIG. 6C, after the molding die 10 is cooled, the molded product 15 is taken out.

  According to the present embodiment, when the springs 11 and 12 are used as in the second embodiment, a slight instability remains in the operation sequence due to instability such as sliding resistance, and the third When the fixing pins 18 and 21 are used as in the embodiment, it is difficult to automate the operation. However, according to the present embodiment, the molding die 10 is firmly fixed by the opposed heating plates 23 and 24. In addition, the molding operation can be performed in order one by one on the upper and lower sides, so that the automation of the operation is excellent.

(A) (b) is a figure which shows the shaping | molding die of 1st Embodiment, and its shaping | molding process, (c) is a figure which shows the molded article. (A) (b) is a figure which shows the shaping | molding die of 2nd Embodiment, and its shaping | molding process, (c) is a figure which shows the molded article. It is a figure which shows the relationship between the dimension of the opening part of a through-hole, and the amount of protrusions of a spherical type. (A)-(d) is a figure which shows the shaping | molding die of 3rd Embodiment, and its shaping | molding process, (e) is a figure which shows the molded article. (A)-(c) is a figure which shows the shaping | molding die and its shaping | molding process of 4th Embodiment, (d) is a figure which shows the molded article. (A) (b) is a figure which shows the shaping | molding die and its shaping | molding process of 5th Embodiment, (c) is a figure which shows the molded article.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Type | mold main body 2 Through-hole 2a Opening part 2b Restriction part 5 Spherical type | mold 6 Pushing member 7 Spherical thermoplastic material 8 Opposite type | mold 9 Sleeve type | mold 10 Mold | molding die | dye 11 Main body spring 12 Face-to-face spring 15 19 Outer sleeve type 20 Long hole 21 Pin 30 Molding device

Claims (4)

In the method of manufacturing an optical element that is molded by heating and pressurizing a thermoplastic material,
A step of accommodating a spherical mold that is processed into a spherical shape and a part of the spherical surface is a molding surface, and is movably accommodated in a hole in a mold main body that extends in a pressurizing direction;
A positioning step of placing and positioning the spherical thermoplastic material equal to or greater than or equal to the diameter of the hole at the opening of the hole;
After the positioning step, an abutting step of abutting the opposed mold disposed facing the mold main body against the thermoplastic material;
After the contact step, during thermoforming, by the pushing member supporting the spherical type from the back side of the molding surface in said bore, so that the forming surface is out butt toward the opposed side from the opening Moving process to move to ,
After the moving step, the pre-Symbol-to-oriented type is moved relatively to the mold body, a step of compression molding the thermoplastic material,
A method for producing an optical element, comprising : In a mold for molding by heating and pressing a thermoplastic material,
A spherical shape that is processed into a spherical shape and a part of the spherical surface becomes a molding surface;
A mold body in which a hole for accommodating the spherical mold movably in the vertical direction is formed;
An opposing mold disposed opposite to the mold body;
A guide mold for slidably guiding the mold body and the opposed mold in the vertical direction ;
A pushing member that supports the spherical mold from the back side of the molding surface in the hole and is pushed up to project the spherical mold by a predetermined amount from the opening of the hole toward the opposing mold;
A first spring disposed between the mold body and the pushing member and repelling the mold body and the pushing member in a vertical direction;
A second spring disposed between the opposing type and the guiding type, repelling the opposing type and the guiding type in a vertical direction, and having a spring constant larger than that of the first spring;
A stopper that is disposed between the mold body and the pushing member, and controls a push-up amount of the pushing member;
A mold for molding, comprising: In a mold for molding by heating and pressing a thermoplastic material,
A spherical shape that is processed into a spherical shape and a part of the spherical surface becomes a molding surface;
A mold body in which a hole for accommodating the spherical mold movably in the vertical direction is formed;
An opposing mold disposed opposite to the mold body;
A first guide mold that slidably guides the mold body and the opposed mold in the vertical direction ;
A second guide mold that slidably guides the mold main body, the opposed mold, and the first guide mold, and is provided outside the first guide mold and has a long hole;
A pushing member that supports the spherical mold from the back side of the molding surface in the hole and is pushed up to project the spherical mold by a predetermined amount from the opening of the hole toward the opposing mold;
A first pin which can be inserted into the opposing mold through the first guiding mold and the second guiding mold from the side of the opposing mold, and which is movable in the pressurizing direction in the elongated hole; ,
A second pin capable of supporting the mold body through the second guide mold;
A mold for molding, comprising: In the molding die according to claim 2 or 3,
A mold for molding, wherein the opening is formed to be narrower than the diameter of the spherical mold.

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