JP2005281053A - Forming apparatus for mold press, method of manufacturing optical device, and optical device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the eccentric precision of an optical device by securing coaxiality of upper and lower dies before pressing up to a press limit position, to control pressing load while securing the coaxiality of the upper and the lower dies and to secure the eccentric precision of each optical device even when a plurality of optical devices are simultaneously pressed. <P>SOLUTION: In a forming apparatus for mold press which is provided with the upper die 6 and the lower die 10 at least one of which is vertically movable and a drum mold 5 for guiding the movement of the upper die 6 or the lower die 10, a spring 7 for bringing a step part 5b formed on the inner periphery of the drum mold 5 into press contact with an annular band part 10b of the lower die 10, from above is provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a molding apparatus for molding press that press-molds an optical element such as a glass lens, a method for producing an optical element using the same, and an optical element obtained thereby.

  A method of manufacturing an optical element by press-molding a molding material softened by heating, for example, a glass material, between an upper mold and a lower mold that are precisely processed based on the shape of the optical element to be obtained. Are known.

  By the way, optical elements, such as lenses, are frequently used in imaging devices, optical pickups, and the like, and the required accuracy such as decentering accuracy has become extremely high as the number of pixels and recording density have increased. The decentering accuracy of the optical element is an accuracy that requires that the center axis of the first surface and the center axis of the second surface of the optical element coincide with each other. Parallel decentering (molding decenter), tilt decentering (molding tilt), aspheric decentering (See FIG. 9).

  As a press molding apparatus considering the eccentricity accuracy of the optical element, there is one disclosed in Patent Document 1. In this press molding apparatus, a molding object is placed between the molding surfaces formed on the upper mold and the lower mold, and the upper mold is pressed from above via a push plate, thereby guiding the cylinder (cylinder mold). The upper mold is slid downward in the interior of the mold, and the object to be molded is pressed. When the pressure is continued until the lower surface of the push plate contacts the upper surface of the guide mold or until the upper and lower guide molds contact, the relative position of the upper and lower molds is determined via the guide mold and the inclination is suppressed. Is done. Thereby, in the press-molded lens, the tilt and decenter between the axes of each surface are reduced, and high eccentricity accuracy is obtained.

Patent Document 2 discloses a press molding apparatus that takes into account the production efficiency of optical elements. This press molding apparatus is configured such that a plurality of molding dies are arranged on a mother die and a plurality of glass materials to be molded are press-molded simultaneously. According to such a press molding apparatus, the production efficiency of optical elements can be increased, and a large amount of optical elements can be continuously produced.
Japanese Patent Laid-Open No. 62-227730 JP 11-29333 A

  However, in the press molding apparatus disclosed in Patent Document 1, the relative position of the upper and lower molds is determined only when the pressing plate comes into contact with the upper surface of the guide mold, or when the upper and lower guide molds come into contact. Since the inclination is suppressed, the inclination is not sufficiently suppressed during the deformation of the molding material. Further, after the abutment, there is a problem that the press load applied to the molding material can no longer be controlled and only a simple press-off press can be performed.

For example, in medium and large-diameter lenses, concave meniscuses, biconcave lenses, etc., it is easy to generate asses and habits, and it is difficult to achieve surface accuracy. Thus, temperature control is extremely advantageous in achieving desired surface accuracy.
However, in the press molding apparatus of Patent Document 1, if load control during pressing is to be performed according to a desired schedule, it must be performed before the contact, and thus the tilt due to the contact cannot be suppressed. As a result, the eccentricity accuracy deteriorates. That is, during the press, the inclination of the guide mold with respect to the lower mold and the inclination of the upper mold with respect to the guide mold are allowed, so that a large tilt eccentricity may occur.

Moreover, in the press molding apparatus described in Patent Document 2, a sleeve (body mold) is provided on the outer peripheral surface portion of the lower mold arranged on the mother die, and the upper and lower mold shafts are fitted by fitting the sleeve with the upper mold during pressing. Prevents deviation.
However, this device has the advantage of being able to press-mold many pieces at the same time. However, if the master mold with the mold is thermally deformed or the press shaft is tilted, some of the molds will be There is a possibility that a sleeve cannot be brought into contact with the mold. In this case, since the alignment of the upper and lower molds is insufficient, not only the eccentric accuracy of the molded lens is deteriorated, but also a large variation in the eccentric accuracy occurs.

The present invention has been considered in view of the above circumstances, and it is possible to improve the eccentricity accuracy of the optical element by securing the coaxiality of the upper and lower molds before pressing to the push-off position, and the coaxiality of the upper and lower molds. The purpose of the present invention is to provide a molding apparatus for a mold press and a method for manufacturing an optical element capable of controlling the press load while ensuring the accuracy, and further ensuring the eccentricity accuracy of each optical element even in a plurality of simultaneous presses. To do.
It is another object of the present invention to provide an optical element with high eccentricity manufactured by the method for manufacturing an optical element.

To achieve the above object, a molding press molding apparatus according to the present invention comprises an upper mold and a lower mold, at least one of which is movable in the vertical direction and formed with opposing molding surfaces, and the upper mold and / or Or a barrel mold that regulates the position of the lower mold and guides the movement of the upper mold and / or the lower mold, and the molding material supplied to the molding surface of the lower mold is the upper mold and the lower mold In a molding press molding apparatus that performs press molding by an approaching operation of a mold, the body mold includes a pressure contact means that presses the body mold against at least a part of the upper mold or the lower mold from above and below.
According to this configuration, the upper and lower molds are pressed against the upper mold or the lower mold in the vertical direction so that the mutual positions of the upper and lower molds are determined through the trunk mold before pressing to the push-off position. Tilt can be suppressed. Accordingly, it is possible to secure the upper and lower mold coaxiality even during deformation of the molding material, and to improve the eccentric accuracy of the obtained optical element.

In the molding press molding apparatus according to the present invention, the body mold is configured to be pressed from above and below with respect to the outer edge portion of the molding surface of the upper mold or the lower mold.
With this configuration, the position control of the body mold and the upper and lower molds by press contact is performed at a position closest to the molding surface, so that compared to the case where the position control is performed away from the molding surface, The influence of shape accuracy and thermal expansion can be reduced, and the coaxiality of the upper and lower molds can be further enhanced.
Further, since the outer edge portion of the molding surface can be precisely processed simultaneously with the molding surface, it is possible to avoid the eccentricity of the upper and lower molds due to insufficient accuracy of the pressure contact surface.

In the molding press molding apparatus according to the present invention, the upper die and the lower die are brought close to each other while the body die is in pressure contact with at least a part of the upper die or the lower die. The operation is performed.
If comprised in this way, it will become possible to perform the position control of the up-and-down type | mold by press-contacting of a trunk | drum at the time of the press start of a shaping | molding raw material, or immediately after the start. Thereby, it is possible to always ensure the coaxiality of the upper and lower molds in the deformation process of the molding material, and to further improve the eccentric accuracy of the obtained optical element.
In addition, since the press load can be controlled while maintaining the coaxiality of the upper and lower molds, the coaxiality of the upper and lower molds can be achieved even in the molding of optical elements where sufficient surface accuracy cannot be obtained with only a simple press-off press. It is possible to ensure the eccentric accuracy of the obtained optical element.

In the molding press molding apparatus according to the present invention, the step formed on the inner peripheral portion of the body mold is configured to be pressed from above with the outer edge portion of the molding surface of the lower mold.
If comprised in this way, the press-contact surface by the side of a trunk | drum will be located inside a trunk | drum, and the stain | pollution | contamination and defect | deletion of a press-contact surface can be prevented effectively. As a result, it is possible to suppress the eccentricity of the upper and lower molds caused by dirt or defects on the pressure contact surface, and to avoid the deterioration of the eccentric accuracy over time.

Further, the molding apparatus for a mold press according to the present invention allows the upper mold and the lower mold to freely move downward while allowing the upper mold and the lower mold to approach each other to a predetermined distance. The upper mold follows the contraction of the molded body between them.
With this configuration, even if the molded body shrinks after pressing, the upper mold can be followed while the molded surface is kept in close contact with the molded body. An optical element having high surface accuracy can be obtained.

Further, the molding apparatus for a mold press according to the present invention is formed on the inner periphery of the barrel mold when the barrel mold moves with respect to the upper mold in accordance with the separation operation of the upper mold and the lower mold. The forced mold release portion is configured to forcibly release the molded body attached to the molding surface of the upper mold.
If comprised in this way, the sticking phenomenon of the molded object with respect to an upper mold | type can be prevented, and the production efficiency of an optical element can be improved. Moreover, since the movement of the barrel mold with respect to the upper mold is reliably performed by the pressure contact means, it is possible to perform a forced release with higher reliability than when the barrel mold is moved by its own weight.

In the molding press molding apparatus according to the present invention, the upper mold or the lower mold is pressed by point contact when the upper mold and the lower mold approach each other.
If comprised in this way, the inclination of the upper mold | type or a lower mold | type with respect to a press member is accept | permitted, and the effect of position control by a trunk | drum can be heightened. As a result, even when the pressing member is inclined, an optical element having a high eccentricity can be obtained while ensuring the vertical coaxiality.

In the molding press molding apparatus of the present invention, a plurality of press molding sections including the upper mold, the lower mold, the body mold, and the press contact means are connected to the mother mold.
If comprised in this way, a several simultaneous press will be attained and the production efficiency of an optical element can be improved. In addition, since each press molding part is provided with a press contact means, even if the mother die is thermally deformed, it is possible to ensure the coaxiality of the upper and lower molds in each press molding part. As a result, even when a plurality of simultaneous presses are performed, high decentering accuracy can be achieved in each optical element.

Moreover, the manufacturing method of the optical element in the present invention is a method of manufacturing an optical element by press-molding a molding material softened by heating, using any of the molding press molding apparatuses described above.
According to such a method, an optical element with high decentration accuracy can be obtained while ensuring the coaxiality of the upper and lower molds before pressing to the push-off position.

Moreover, the manufacturing method of the optical element in the present invention is a method of changing the press load applied to the molding material stepwise in the press molding step.
According to such a method, an optical element with higher accuracy can be obtained by changing the press load stepwise while securing the coaxiality of the upper and lower molds.

Further, in the method of manufacturing an optical element according to the present invention, the press molding step includes at least an initial press and a secondary press, and the thickness is larger by a predetermined amount than the final thickness of the optical element to be obtained by the initial press. And then performing the secondary press.
According to such a method, an optical element with higher accuracy can be obtained by performing the initial press and the secondary press while ensuring the vertical coaxiality.

In the optical element manufacturing method of the present invention, the press molding step includes at least an initial press and a secondary press, and cooling is started at the start of the initial press or during the initial press.
According to such a method, it is possible to obtain a more accurate optical element by controlling the temperature of the molded body while ensuring the coaxiality of the upper and lower molds.

The optical element of the present invention is press-molded using any one of the above-described optical element manufacturing methods.
In this way, it is possible to provide an optical element with extremely high decentering accuracy, for example, parallel decentering within 10 μm and tilt decentering within 4 minutes.

As described above, according to the present invention, the upper die and the lower die are pressed against the upper die or the lower die from the upper and lower directions so that the upper die and the lower die can be positioned relative to each other before being pressed to the push-off position. Confirmed and its inclination is suppressed. Accordingly, it is possible to secure the upper and lower mold coaxiality even during deformation of the molding material, and to improve the eccentric accuracy of the obtained optical element.
In addition, since the press load can be controlled with the upper and lower molds coaxially secured, even in the molding of optical elements where sufficient surface accuracy cannot be obtained with a press-cut press alone, the vertical mold coaxiality is ensured. The eccentric accuracy of the optical element can be increased.
In addition, even when pressing multiple molding materials at the same time, it is possible to ensure the coaxiality of the upper and lower molds at each press molding part, avoiding a decrease in molding accuracy due to thermal deformation of the mother mold, etc. Can be improved.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In the following, the present invention will be described along with an embodiment in which the present invention is applied to a glass optical element manufacturing apparatus, but the present invention is not limited to this embodiment. The present invention can also be applied to manufacturing parts other than glass and resin optical elements.

[Mold press molding equipment]
First, a molding apparatus for a mold press according to a first embodiment of the present invention will be described with reference to FIGS. 1 and 2.
FIG. 1 is a longitudinal sectional view showing a press forming part of a molding apparatus for a mold press according to a first embodiment of the present invention.

As shown in this figure, the press molding part A of the molding apparatus for mold press includes an upper unit 1 and a lower unit 2 at least one of which can move in the vertical direction.
The upper unit 1 includes an upper plate 3, an upper mother die 4, a barrel die 5, an upper die 6 and a spring (pressure contact means) 7, and the lower unit 2 includes a lower plate 8, a lower mother die 9 and a lower die 10. Configured.

The upper plate 3 integrally supports the upper mother die 4 on the lower surface thereof, and the body die 5, the upper die 6, and the spring 7 are incorporated in the upper mother die 4.
The body mold 5 has a cylindrical shape and is supported by the upper mother mold 4 so as to be movable up and down. A flange portion 5 a that protrudes outward is formed on the outer peripheral surface of the trunk mold 5, and the flange mold 5 is prevented from coming off by engaging the flange section 5 a with the inner circumferential convex portion 4 a of the upper mother mold 4. The body mold 5 has a step portion 5b on the inner peripheral surface, and a pressure contact surface 5c facing downward is formed by the step portion 5b.

The upper mold 6 has a cylindrical shape, and the movement in the vertical direction is guided by the inner peripheral surface of the trunk mold 5 (above the step portion 5b). A flange portion 6 a that protrudes outward is formed at the upper end portion of the upper die 6, and a molding surface 6 b is formed at the lower end surface of the upper die 6. The molding surface 6b is a portion for transferring the shape of the optical element to the molding material, and is precisely processed based on the shape of the optical element to be obtained.
The spring 7 is, for example, a compression coil spring, and is interposed between the flange portion 5 a of the body mold 5 and the flange portion 6 a of the upper mold 6. Thereby, the trunk mold 5 is urged downward.

The lower plate 8 integrally supports the lower mother die 9 on its upper surface, and the lower die 10 is incorporated in the lower mother die 9.
The lower die 10 has a columnar shape having a diameter larger than that of the upper die 6 and is supported by the lower mother die 9 and is vertically moved by the inner peripheral surface of the barrel die 5 (below the step portion 5b) during press molding. The relative movement of the direction is guided. A molding surface 10 a for transferring the shape of the optical element to the molding material is formed on the upper end surface of the lower mold 10. The molding surface 10a is precisely processed based on the shape of the optical element to be obtained, like the molding surface 6b of the upper mold 6. An annular zone 10b facing upward is formed on the outer edge of the molding surface 10a. This ring zone portion 10b is a portion to which the pressure contact surface 5c of the body mold 5 is pressed, and is precision processed together with the molding surface 6b.

In this embodiment, the upper unit 1 (upper plate 3) is attached to a fixed main shaft (not shown), and the lower unit 2 (lower plate 8) can be moved up and down by a servo motor (not shown). It is attached to a main shaft (not shown).
A high frequency induction heating coil (not shown) for induction heating of the mother dies 4 and 9 is arranged around the mother dies 4 and 9. The upper die 6 and the lower die 10 are induction heated mothers. Heated by heat conduction from the molds 4 and 9. In this way, temperature lowering and temperature rising of the upper mold 6 and the lower mold 10 can be controlled. Iron, nickel, cobalt, tungsten, and alloys thereof can be used as a matrix material that is induction-heated by the high-frequency induction coil.

The upper mold 6 and the lower mold 10 are made of a dense material having heat resistance and sufficient hardness, such as ceramics such as SiC and Si ₃ N ₄ , cemented carbide (WC), BN, TiN, and stainless steel. A mirror-finished surface is used that is precisely processed based on the surface shape of the element.
Moreover, it is preferable to form a film having releasability on the molding surfaces 6b and 10a. As the release film, a film mainly containing a noble metal (for example, a white metal noble metal) or a film mainly containing carbon can be used.
The sliding surfaces of the body mold 5 and the upper and lower molds 6 and 10 may be subjected to a process for increasing slipping in order to reduce sliding friction.
The material of the spring 7 is preferably one that has heat resistance and can give a sufficient urging force. For example, silicon nitride or zirconium oxide is used.

  Moreover, the press molding part A of the present embodiment has a structure in which the upper unit 1 and the lower unit 2 are completely separated from each other and the opposing molding surfaces 6b and 10a appear. According to this, since a desired space can be opened in the separation part, a molding material carry-in device (especially in the case of levitation conveyance), a molding material position correction means, a molded article take-out means, etc. are inserted from the separation part. And can be dismissed.

Next, the operation of the molding press molding apparatus according to the first embodiment of the present invention will be described with reference to FIG.
FIG. 2 is a longitudinal cross-sectional view of a press-molding portion showing the operation of the molding press molding apparatus according to the first embodiment of the present invention.

  As shown in these drawings, when the optical element is press-molded in the press molding section A of the molding press molding apparatus, a molding material is set on the molding surface 10a of the lower mold 10, and the upper unit 1 or the lower unit 2 is used. The upper die 6 and the lower die 10 are moved closer to each other by driving up and down. This approaching operation may be performed up to the push-off position where the lower surface of the upper mother die 4 and the upper surface of the lower mother die 9 are in contact (FIG. 2B), or may be up to the front of the push-off position (FIG. 2A )). When the proximity operation is performed up to the push-off position, the approach of the upper and lower molds 6 and 10 is mechanically restricted at the push-off position, so that the thickness of the molded body can be controlled with good reproducibility. Further, when the proximity operation is performed up to the position before the push-off position, the thickness of the molded body can be controlled by detecting the gap between the upper mother die 4 and the lower mother die 9.

  As shown in FIG. 2, when the upper die 6 and the lower die 10 are moved closer to each other, in the process, the step portion 5b of the trunk die 5 comes into contact with the ring zone portion 10b of the lower die 10 from above, and the spring 7 is urged and brought into a pressure contact state. When the step portion 5b of the trunk mold 5 is in pressure contact with the annular zone 10b of the lower mold 10, the position of the trunk mold 5 is fixed with respect to the lower mold 10, and the inclination of the trunk mold 5 with respect to the lower mold 10 is restricted. . Then, by guiding the upper die 6 with the barrel die 5 whose position is regulated with respect to the lower die 10, axial misalignment between the upper die 6 and the lower die 10 is prevented. Thereby, it is possible to ensure the coaxiality of the upper and lower molds 6 and 10 even during deformation of the molding material, and to improve the eccentric accuracy of the obtained optical element.

That is, when the body mold 5 is in pressure contact with the lower mold 10, the inclination of the lower mold 10 and the body mold 5 is substantially eliminated. Therefore, the axial displacement between the lower mold 10 and the body mold 5 is a horizontal displacement. Only (parallel eccentricity) can occur, but this can be suppressed by reducing the clearance between the lower mold 10 and the trunk mold 5. This clearance can be set to 1 to 10 μm, and in the case of an optical element with high accuracy, it can be set to 1 to 5 μm.
In addition, in order to prevent the inclination between the lower mold 10 and the body mold 5, there is a method of increasing the length of the sliding surface, but according to the present invention, it is good even if the length of the sliding surface is short. Therefore, there is an advantage that problems such as poor sliding hardly occur.

Further, the position control of the upper and lower molds 6 and 10 by the pressure contact of the body mold 5 can be performed at the start of pressing of the molding material or immediately after the start. Thereby, the coaxiality of the upper and lower molds 6 and 10 is always ensured in the deformation process of the molding material.
In addition, the press load can be controlled in a state where the coaxiality of the upper and lower molds 6 and 10 is ensured by the pressure contact of the body mold 5. Therefore, even in the molding of an optical element in which sufficient surface accuracy cannot be obtained only by a press-off press, the press load is controlled while the coaxiality of the upper and lower molds 6 and 10 is secured, and the molding accuracy of the optical element can be increased. it can.

In addition, the body mold 5 is pressed against the outer edge portion (ring zone portion 10b) of the molding surface 10a in the lower mold 10, so that the position restriction is performed based on the closest position of the molding surface 10a. Therefore, compared with the case where position control is performed away from the molding surface 10a, the influence of the shape accuracy and thermal expansion of each mold member is reduced, and the coaxiality of the upper and lower molds 6 and 10 is enhanced. Moreover, since the ring zone part 10b can be precisely processed simultaneously with the molding surface 10a, the eccentricity of the upper and lower molds 6 and 10 due to insufficient accuracy of the pressure contact surface can be avoided.
Further, since the pressure contact surface 5c on the body mold 5 side is located inside the body mold 5, it is possible to effectively prevent the pressure contact surface 5c from being stained or damaged. As a result, the eccentricity of the upper and lower molds 6 and 10 due to the dirt or chipping of the pressure contact surface 5c can be suppressed, and the deterioration of the eccentric accuracy over time can be avoided.

  Next, another embodiment of a molding apparatus for a mold press will be sequentially described with reference to FIGS. However, about the structure common to 1st embodiment, the same code | symbol is attached | subjected and description of 1st embodiment is used.

FIG. 3 is a longitudinal sectional view showing a press forming part of a molding apparatus for a mold press according to the second embodiment of the present invention.
As shown in this figure, the press molding part B of the molding press molding apparatus according to the second embodiment is such that the urging force of the spring 7 does not act on the upper mold 6, and this point is the same as the first embodiment. It is different. Specifically, the upper end side of the spring 7 is supported not by the flange portion 6 a of the upper mold 6 but by the lower surface of the upper plate 3.
In the present embodiment, an annular stopper member 11 is interposed between the spring 7 and the upper plate 3. The stopper member 11 functions as a stopper for preventing the lateral displacement of the spring 7 and restricting the lowering range of the upper die 6 relative to the upper mother die 4.

  According to the second embodiment configured as described above, the upper mold 6 is allowed to freely move downward, so that the upper mold 6 follows the thermal contraction of the molded body by its own weight in the cooling process after pressing. Through the cooling process, it is possible to maintain the close contact between the upper and lower molding surfaces 6b and 10a and the molded body. This is very advantageous in obtaining surface accuracy. In particular, when the optical element to be obtained is a meniscus lens (particularly a concave meniscus lens) or a biconcave lens, it is easy to generate asses and peculiarities on the molding surface of the molded product due to the behavior of thermal contraction during cooling. Can be effectively prevented.

FIG. 4 is a longitudinal sectional view showing a press forming portion of the molding press molding apparatus according to the third embodiment of the present invention, and FIG. 5 shows the operation of the molding press molding apparatus according to the third embodiment of the present invention. It is a longitudinal cross-sectional view of a press molding part.
As shown in this figure, the press molding part C of the molding apparatus for mold presses according to the third embodiment has a forced mold release part 5d on the inner periphery of the body mold 5, and the molded product is formed by this forced mold release part 5d. Is different from the above embodiment in that the mold is forcibly released from the upper mold 6.

  That is, after the press molding, the molded body in the mold is cooled and released at an appropriate temperature (for example, near the transition point). At this time, the molded body may stick to the upper mold 6. This is particularly noticeable when the upper surface of the molded body is concave. If the mold release temperature is made sufficiently low, the adhesion of the glass is lowered, so that the phenomenon of sticking to the upper mold 6 hardly occurs. However, the molding cycle time becomes unnecessarily long and the molding efficiency is poor. That is, it is advantageous to perform the mold release as soon as possible, that is, in a state where the temperature is relatively high as long as the surface accuracy is not adversely affected. At this time, if the molded body is not on the lower mold 10 and is attached to the molding surface 6b of the upper mold 6, the molded body can be removed even if the molded body take-out means (for example, suction conveyance means using a suction pad) is inserted. Unable to take out, causing troubles such as process stoppage. Therefore, it is important that the molded body is surely on the molding surface 10a of the lower mold 10 at the time of mold release.

As shown in FIG. 4, the forced mold release portion 5 d of the present embodiment is formed as a second step portion above the step portion 5 b on the inner periphery of the body mold 5.
As shown in FIG. 5, after supplying the molding material (FIG. 5 (a)) and press molding (FIG. 5 (b)), when releasing the molded body (FIG. 5 (c)), the upper unit 1 and When the lower unit 2 is separated, the body mold 5 moves downward with respect to the upper mold 6 by the biasing force of the spring 7 or the like. At this time, the forced mold release portion 5 d comes into contact with the outer peripheral portion of the molded body formed to have a diameter larger than that of the upper mold 6, and the molded body is forcibly released from the upper mold 6.

In this embodiment, when the upper unit 1 and the lower unit 2 are separated from each other, the upper mold 6 is lowered together with the trunk mold 5, but even after the lowering of the upper mold 6 is restricted by the stopper member 11, Since the mold 5 is allowed to descend until it comes into contact with the inner peripheral convex part 4a of the upper mother mold 4, the body mold 5 descends with respect to the upper mold 6, and the molded body adhered to the upper mold 6 is surely released. Can be made.
Further, the forced release part 5d is not limited to the step part, and may be tapered or convex. In other words, any material can be used as long as it projects inward from the outer diameter of the molded body and can contact the outer periphery of the molded body.

FIG. 6 is a longitudinal sectional view showing a press forming part of a molding apparatus for a mold press according to the fourth embodiment of the present invention.
As shown in this figure, the press molding part D of the molding press molding apparatus according to the fourth embodiment is configured such that the upper mold 6 is pressed by point contact when the upper mold 6 and the lower mold 10 are moved closer to each other. This is different from the above embodiment. In the present embodiment, a plate member 12 having a spherical convex surface is provided on the upper surface of the upper die 6 so that the lower surface of the upper plate 3 that presses the upper die 6 and the upper surface of the upper die 6 are in point contact. However, a similar convex portion may be processed on the upper surface of the upper mold 6. Further, a ball or the like may be arranged at the center of the upper surface of the upper mold 6 so as to make point contact with the upper plate 3.

  If comprised in this way, even if the upper plate 3 inclines to some extent, the effect that the inclination of the upper mold | type 6 is not deteriorated is acquired. That is, in press molding of a molding material, when a pressing force is applied between the upper and lower molds 6 and 10 and the upper and lower molds 6 and 10 are brought close to each other, this pressing force is given by a driving means (not shown) such as a servo motor. It is done. However, when the drive shaft does not exactly coincide with the axes of the upper and lower molds 6 and 10, this becomes a cause of deterioration of the eccentricity accuracy. In this embodiment, even if the drive shaft of the drive means is deviated from the axes of the upper and lower molds 6 and 10, the upper and lower molds 6 that allow the upper mold 6 to be inclined with respect to the upper plate 3 and are secured by the trunk mold 5, 10 coaxiality is not affected. Thereby, molding of an optical element having extremely high eccentricity accuracy (for example, an objective lens for an optical pickup) is suitably performed. In addition, it is possible to prevent an excessive load from acting on the upper die 6 due to the deviation of the drive shaft, so that the die can be prevented from being damaged.

FIG. 7 is a longitudinal sectional view showing a press forming part of a molding apparatus for a mold press according to a fifth embodiment of the present invention.
As shown in this figure, the molding apparatus for mold presses according to the fifth embodiment includes a plurality of press molding sections including a body mold 5, an upper mold 6, a spring 7, a lower mold 10, etc., connected to the mother mold. This is different from the above embodiment. Specifically, four press forming parts C similar to those in the third embodiment are arranged in the mother die so that four press forming can be performed simultaneously.

  In the case where a plurality of press-formed parts C are continuously provided in this way, the upper and lower mother dies 4 and 9 and the upper and lower plates 3 and 8 are repeatedly formed by the thermal expansion of each member at a high temperature and the temperature increase and decrease in the mass production process. Thermal deformation such as warping may occur. Conventionally, in such a situation, it has been difficult to control all the decentering accuracy of the optical element formed by the four press forming portions. However, according to the present embodiment, in each press forming section, the body mold 5 is pressed against the lower mold 10 and the position control of the independent upper and lower molds 6 and 10 is performed. Eccentricity accuracy can be ensured and yield reduction can be avoided.

[Method for Manufacturing Optical Element]
Next, a method for manufacturing an optical element according to an embodiment of the present invention will be described with reference to FIG.
In the present invention, a glass preform heated and softened to a viscosity suitable for molding is press-molded between the upper and lower molds 6 and 10 under an appropriate load, and the upper and lower molds 6 and 6 are formed on a molding material (for example, a glass preform). Ten molding surfaces 6b and 10a are transferred.

  First, a molding material is supplied between the upper and lower molds 6 and 10. The molding material may be at room temperature but is preferably preheated. The upper and lower molds 6 and 10 are preheated, the lower mold 10 is lowered, the upper and lower molds 6 and 10 are separated, and a molding material preheated in another heating furnace is supplied by a supply means (not shown). Fig.5 (a) is a figure which shows the state which supplied the preheated shaping | molding raw material to the preheated type | mold.

  Immediately after this, when the lower mold 10 is raised by the servo motor, the inner periphery of the lower end of the body mold 5 is fitted to the side surface of the lower mold 10. Subsequently, the step part 5 b on the inner periphery of the body mold 5 comes into contact with the annular part 10 b of the lower mold 10, and the body mold 5 is pressed against the lower mold 10 by the urging force of the spring 7. Thereby, the inclination of the trunk mold 5 and the lower mold 10 is regulated. Thereafter, the body mold 5 is raised, a load is applied to the molding material, and pressing is started. The load may be increased or decreased while being added. That is, in the initial press, after applying the first load, a smaller second load may be applied, or after adding the first load, applying a second load smaller than that, You may perform, and you may perform the press which adds the 3rd load smaller than a 1st load and larger than a 2nd load after that. In addition, the thickness may be increased by a predetermined amount from the final thickness of the optical element to be obtained by the initial pressing, and then the secondary pressing may be performed.

  FIG.5 (b) shows the time of a press having been complete | finished when the molded object became predetermined | prescribed thickness. That is, in this embodiment, the thickness of the molded body is controlled by the contact between the upper and lower mother dies 4 and 9. The predetermined thickness is slightly larger than the thickness of the optical element to be finally obtained. Since the preform capacity is selected in advance, it is pressed to a diameter slightly larger than the outer diameter of the upper mold 6.

  The cooling step may be performed immediately after completion of the press, or may be started at the start of the initial press or during the initial press. In the course of cooling, the molded body heat shrinks, but free movement of the upper mold 6 is allowed. Therefore, the upper mold 6 follows the heat shrinkage of the molded body, and the molding surface 6b of the upper mold 6 is in contact with the molded body. Maintain close contact. Thereby, deterioration of the surface accuracy during cooling is prevented.

When cooled to about Tg (glass transition temperature), the lower mold 10 is lowered to release the mold. The mold release temperature is preferably equivalent to 10 ^12.5 to 10 ^13.5 dPa · s in terms of glass viscosity. The body mold 5 is lowered by the force of the spring 7, and the forced mold release portion 5 d comes into contact with the outer periphery of the molded body, so that the molded body is released from the upper mold 6. FIG. 5C shows the state. Further, the lower mold 10 is lowered so that the upper and lower molds 6 and 10 are completely separated in the same manner as in FIG. 5A, and the molded product is taken out from the lower mold 10 by a take-out jig (not shown). Thereafter, the lower die 10 is raised, induction heating is started, and the next press cycle is started.

If the preform used for the press molding is not preheated, it is placed between the upper and lower molds 6 and 10 and then heated and heated together with the mold (for example, 10 ⁷ to 10 ⁹ dPa · s in terms of glass viscosity). Press to form. However, preferably, a preform preheated outside the mold (for example, to a temperature corresponding to 10 ⁶ to 10 ⁹ dPa · s in terms of glass viscosity) is supplied between heated molds and press-molded. In the latter case, the molding material heated outside the mold is supplied between the molds heated to a lower temperature (for example, to a temperature equivalent to 10 ⁸ to 10 ¹² dPa · s in terms of glass viscosity). It can be press-molded by bringing the mold close and applying a load. This is advantageous for shortening the molding cycle time. The molding atmosphere is preferably non-oxidizing such as nitrogen gas. As a result, oxidation and decomposition of the surface treatment material of the mold can be suppressed.

  Further, when supplying the glass preform between the upper and lower molds 6 and 10 or when taking out the molded product (optical element) after pressing, the supply means and the taking-out means are placed between the spaced apart upper and lower molds 6 and 10. To intervene. At this time, in order to supply the preform onto the lower mold 10 or take out the molded body from the lower mold 10, the molding surface 10a of the lower mold 10 is exposed when the upper and lower molds 6 and 10 are separated from each other. It is preferable that

[Example]
A concave meniscus lens (φ17 mm, t = 1.5 mm, concave paraxial r = 5 mm, convex surface r = 36 mm) having an aspherical surface on one side was molded using a four-piece press molding apparatus shown in FIG. The glass material used was barium borosilicate glass (Tg 515 ° C.) and was a hot-formed flat spherical preform having a capacity of 430 mm ³ . The mold material and the press procedure were the same as the conditions described in the embodiment of the present invention.

  The used mold clearance (upper mold or lower mold and body mold clearance) is about 10 μm for both the upper mold and the lower mold. When calculated from this measured value, the tilt eccentricity when the spring 7 of the present invention is not used ( The molding tilt (maximum) was estimated to be 7 'and the parallel eccentricity (molding decenter) was estimated to be 10 μm.

The lens having a convex surface was the lower mold, and the preform preheating temperature at the time of supply to the lower mold was 610 ° C., and the mold preheating temperature was 580 ° C.
A total of 400 presses were performed, but all the molds were released smoothly and the presses were not interrupted. The result of measuring the aspherical eccentricity of the molded lens is shown in FIG. It can be seen that the aspheric eccentricity is within about 3.5 '. FIG. 9 shows a formula for calculating the aspherical eccentricity when tilt eccentricity (molding tilt) and parallel eccentricity (molding center) occur. This is a calculation formula when tilt eccentricity and parallel eccentricity occur in the same plane, and shows the maximum and minimum values of aspherical eccentricity when eccentricity occurs.

  FIG. 10 shows the calculation result of the aspherical eccentricity in the concave meniscus lens. The parallel eccentricity is determined by the clearance between the body mold and the upper and lower molds, and it can be estimated that 10 μm or more does not occur. From this, in the situation where there is no spring, the aspherical eccentricity may occur at 7.0 'even at the minimum (maximum value 9.4'). On the other hand, in the press using the mold structure of the present invention, the aspherical eccentricity is only 3.5 'at the maximum. From this, referring to FIG. 9, it is considered that the maximum tilt eccentricity when the same type structure is used is 4 ′ (parallel eccentricity is 10 μm), and the tilt eccentricity is suppressed to about half. The minimum inclination eccentricity of the same structure is 2 '(parallel eccentricity is 10 μm). Further, although the clearance is 10 μm under these conditions, it is possible to manufacture a lens with better eccentricity by narrowing the clearance.

For comparison, when molding was attempted with an apparatus similar to the above except that no spring was used, the lower mold was not inserted into the barrel mold and the press was interrupted. This is probably because the tilt eccentricity due to the tilt of the barrel mold was too large when inserted into the lower barrel mold.
By using the molding press molding apparatus of the present invention, it was possible to suppress tilting and decentering during optical element molding. Moreover, the release effect of the optical element can be enhanced, and the production cycle time can be shortened. Further, the surface accuracy of the molded optical element was good.

  The present invention can be applied to a molding apparatus for press molding an optical element such as a glass lens, and a method for manufacturing an optical element using the same. In particular, it can be suitably used for molding lenses for imaging devices and optical pickup lenses that require high eccentricity accuracy.

It is a longitudinal cross-sectional view which shows the press molding part of the shaping | molding apparatus for mold presses concerning 1st embodiment of this invention. It is a longitudinal cross-sectional view of the press molding part which shows the effect | action of the shaping | molding apparatus for mold presses concerning 1st embodiment of this invention. It is a longitudinal cross-sectional view which shows the press molding part of the shaping | molding apparatus for mold presses concerning 2nd embodiment of this invention. It is a longitudinal cross-sectional view which shows the press molding part of the shaping | molding apparatus for mold presses concerning 3rd embodiment of this invention. It is a longitudinal cross-sectional view of the press molding part which shows the effect | action of the shaping | molding apparatus for mold presses concerning 3rd embodiment of this invention. It is a longitudinal cross-sectional view which shows the press molding part of the shaping | molding apparatus for mold presses concerning 4th embodiment of this invention. It is a longitudinal cross-sectional view which shows the press molding part of the shaping | molding apparatus for mold presses concerning 5th embodiment of this invention. It is a graph which shows the measurement result of the aspherical surface eccentricity in the Example of this invention. It is a relational expression between eccentricity at the time of molding and aspherical eccentricity. It is a correlation table of eccentricity at the time of molding and aspherical eccentricity.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Upper unit 2 Lower unit 3 Upper plate 4 Upper mother die 4a Inner peripheral convex part 5 Body die 5a Flange part 5b Step part 5c Pressure contact surface 5d Forced mold release part 6 Upper mold 6a Flange part 6b Molding surface 7 Spring 8 Lower plate 9 Lower mother Mold 10 Lower mold 10a Molding surface 10b Ring zone 11 Stopper member 12 Plate members A to D Press molding section

Claims (13)

The upper mold and the lower mold, at least one of which is movable in the vertical direction and having an opposing molding surface formed thereon, and the upper mold and / or the lower mold are regulated in position, and the upper mold and / or the above-mentioned In a molding apparatus for a mold press that includes a barrel mold that guides the movement of the lower mold, and press-molds a molding material supplied to the molding surface of the lower mold by an approach operation of the upper mold and the lower mold,
A molding apparatus for a mold press, comprising press contact means for pressing the body mold against at least a part of the upper mold or the lower mold from above and below.   The molding apparatus for mold presses according to claim 1, wherein the body mold is pressed against an outer edge portion of a molding surface of the upper mold or the lower mold from above and below.   3. The mold according to claim 1, wherein the upper die and the lower die are moved closer to each other while the body die is pressed against at least a part of the upper die or the lower die from above and below. Press molding equipment.   The molding apparatus for mold presses according to any one of claims 1 to 3, wherein a step portion formed on an inner peripheral portion of the body mold is pressed from above with an outer edge portion of a molding surface of the lower mold.   The upper mold and the lower mold are allowed to freely move downward while the upper mold and the lower mold are close to a predetermined distance, and the upper mold is contracted by the molded body between the upper mold and the lower mold. The molding apparatus for mold presses according to any one of claims 1 to 4, wherein   When the upper die and the lower die are moved away from each other, when the barrel die moves relative to the upper die, a forced mold release portion formed on the inner periphery of the barrel die is formed by the upper die. The molding apparatus for mold presses according to any one of claims 1 to 5, wherein the molded body attached to the surface is forcibly released.   The molding apparatus for a mold press according to any one of claims 1 to 6, wherein the upper mold or the lower mold is pressed by point contact when the upper mold and the lower mold approach each other.   The molding apparatus for mold presses according to any one of claims 1 to 7, wherein a plurality of press molding sections including the upper mold, the lower mold, the body mold, and the press contact means are provided continuously with respect to a mother mold.   A method for manufacturing an optical element, wherein the optical element is manufactured by press-molding a molding material softened by heating, using the molding press molding apparatus according to claim 1.   The method for manufacturing an optical element according to claim 9, wherein in the step of press molding, a press load applied to the molding material is changed stepwise.   The press molding step includes at least an initial press and a secondary press, and the initial press sets the thickness to be a predetermined amount larger than the final thickness of the optical element to be obtained, and then the secondary press is performed. A method for producing an optical element according to 9 or 10.   The method for manufacturing an optical element according to claim 9, wherein the press molding step includes at least an initial press and a secondary press, and cooling is started at the start of the initial press or during the initial press.   An optical element, which is press-molded using the method for producing an optical element according to claim 9.

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