JPH02172831A - Molding method for optical glass parts - Google Patents

Abstract

PURPOSE:To cool the outer periphery of a molding base material at the slow temp. gradient and to obtain a precise molded article in a short time by controlling a mold release member at the prescribed temp. and also pressing and molding the base material while bringing the mold release member into contact with a carrier member with the outer periphery of the base material held thereon or approaching the carrier member. CONSTITUTION:A carrier member 5 wherein glass base material is placed on a placing hole 6 is held to a through-hole 10 of a carrier base 7 and carried in a heating oven to heat and soften the glass base material. Thereafter this glass base material is carried between the upper and lower molds 1, 2 and these molds are heated and also a mold release member 8 is heated with a heater 15 fitted with a thermocouple. A driver connected to the upper and lower molds 1, 2 starts to be actuated and simultaneously a driver connected to the mold release member 8 starts to be actuated. The inner peripheral face 13a of the mold release member 8 is fitted to the upper outer peripheral face 12 of the carrier member 5. While the top surface 9a of a stopping projection 9 is brought into the rear surface 13b of the mold release member 8, the glass base material is pressed, molded and transcribed into the shapes of both molding faces 1a, 2a. The vicinity of the outer peripheral part of the glass base material is prevented from being cooled from the upper and lower dies 1, 2 and the atmosphere and bagged via the carrier member 5.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for molding optical glass parts, in which the optical glass parts are softened by heating and then press-molded using a molding die.

(Prior art) Conventionally, after a molding material for optical glass parts is heated and softened, it is press-molded using a pair of molding molds having a desired molding surface.
A method for obtaining optical glass parts such as lenses is known.
For example, it is disclosed in Japanese Patent Laid-Open No. 63-74926. On the other hand, an apparatus used in the above molding method is disclosed in, for example, Japanese Patent Laid-Open No. 62-288119.

The molding method disclosed in Japanese Patent Application Laid-open No. 63-74926 discloses that a mold release member for releasing an optical glass component press-molded by a mold from the mold is heated to a temperature of 200° above the mold temperature of the mold.
The optical glass component is press-molded using a molding die while controlling the temperature to a predetermined temperature between low temperature and mold temperature, and bringing the mold release member into contact with the molding material.

The molding apparatus disclosed in Japanese Patent Application Laid-open No. 62-288119 has a C type so that a molding material can be placed on a body wall carrier provided with heating means and/or cooling means between a pair of molding molds and conveyed.
e is configured.

[Problem to be solved by the invention]

In the molding method disclosed in JP-A No. 63-74926,
Since the mold release member directly contacts the molding material, the generation of a temperature gradient near the contact portion due to heat conduction is unavoidable, and there is a limit to the uniformity of temperature distribution within the molded lens. In particular, when trying to improve productivity by shortening the press molding time, the temperature must be rapidly controlled by bringing the molding material into contact with the mold release member during the press molding time, and the temperature distribution within the molded lens must be controlled. There was a problem that it became difficult to achieve uniformity and the transferability deteriorated.

On the other hand, the molding apparatus disclosed in JP-A No. 62-288119 has the problem that the shell wall carrier becomes expensive due to the material cost and processing cost of the heating means, for example, the heater section, resulting in an expensive molded product. Ta. In particular, when mass-producing molded products, a large number of body wall carriers are required, and the above problem is significant.

The present invention has been made in view of the above-mentioned problems of the prior art.The present invention has been made in view of the above-mentioned problems of the prior art. It is an object of the present invention to provide a method for molding optical glass parts that can uniformize the temperature inside the material, have precise transferability, and can mold inexpensive optical glass parts in a short time.

[Means to solve the problem]

In order to solve the above object, the present invention press-forms a molding material for an optical glass component heated to a predetermined temperature using a molding die whose temperature is lower than the temperature of the molding material, and releases the press-molded product using a mold release member. In the method of molding an optical glass component, controlling the temperature of the mold release member to a predetermined temperature,
Press molding is performed while the mold release member is brought into contact with or close to the conveying member that holds the outer periphery of the molding material.

In such a molding method, heat is transferred from the hot molding material to the molding die, which is colder than the molding material. During this heat transfer, the molding material undergoes viscous flow, and the temperature inside the molding material gradually changes uniformly, while the shape of the molding surface of the molding die is transferred. However, such heat transfer is dominated by the molded material, which has extremely low thermal conductivity, so generally, the isometric temperature change of the molded material is affected by the thickness between the pressed surfaces of the molded material and the difference in thickness between the center and the outer periphery. The time required will be determined.

[For production]

In the method for molding optical glass parts of the present invention, when the conveying member holding the outer periphery of the molding material comes into contact with or approaches the mold release member whose temperature is controlled at a predetermined temperature during press molding, the inside of the molding material is heated. Since temperature uniformity is promoted, the temperature gradient of the molding material is alleviated by heat conduction via the conveying member, and the molding material is cooled with more precise temperature changes. Therefore, even if the shape has a difference in thickness between the center and the outer periphery, for example, a biconvex shape or a concave shape, the isothermal change in the temperature of the molded material is promoted and the isothermal change is alleviated. As a result, an optical glass component with good transfer is formed.

(Example) Hereinafter, an example of the present invention will be described in detail using the drawings.

(First Embodiment) FIGS. 1 and 2 are diagrams showing a molding apparatus used in a first embodiment of the method for molding optical glass parts according to the present invention. A molding die is composed of a cylindrical upper mold 1 and a lower mold 2. On each opposing surface of the upper mold 1 and the lower mold 2, molding surfaces 1a and 2a having a high surface shape and high surface roughness and facing a desired molded lens 3 are formed.

The upper mold 1 and the lower mold 2 are connected to a drive device (not shown) and can be moved toward and away from each other. In this example,
As an optical glass material, glass transition point 'rg: 53
5°C8 Softening point S p: 639°C1 Yielding point A t
: Using 5KII at 595℃, diameter 16mm, R
A43.6. Rm37.7 (aspherical surface) and wall thickness t
The case where a biconvex lens of =3 mm is molded is shown.

In FIG. 2, 4 indicates a glass material made of the above-mentioned optical glass material, which has been preformed by grinding and polishing. Glass material 4 is molded using both upper and lower molds 1.2 during press molding.
RA43. It is formed to have an approximate radius of Rs36.5, and the glass material 4 is brought into contact (pressed) from the center of the molding surfaces 1a and 2a, so that molding can be performed while preventing the inclusion of air bubbles.

5 is a conveying member that holds and conveys the glass material 4. The conveying member 5 is formed into a ring shape, and a mounting hole 6 for placing the glass material 4 is formed in the center thereof. Placement hole 6
A receiving portion 6a consisting of a stepped portion is formed inside. Furthermore, a locking protrusion 9 that engages with the conveyor table 7 or the mold release member 8 is provided approximately at the center of the outer circumferential surface of the conveyor member 5 . This conveying member 5 is made of a material whose coefficient of linear expansion is smaller than that of the glass material 4;
For example, it is made of cemented carbide (α-6,5XlO-'),
After the glass material 4 is press-molded, during the cooling process, the molded lens 3 and the conveying member 5 are separated due to the difference in shrinkage.

The conveyance table 7 holds the conveyance member 5 and conveys it together with the glass material 4 placed on the conveyance member 5 to a heating furnace (not shown) and between the upper and lower molds 1 and 2 to form a press-molded molded lens. 3 is conveyed to a slow cooling furnace (not shown) together with a conveying member 5. A through hole 1O having the outer diameter of the lower die 2 of the press molding die is provided in the center of the R feed table 7. The conveying member 5 is placed in the through hole 10 at the upper opening edge 1 of the through hole 10.
1 and the locking protrusion 9 of the conveyance member 5 are locked and held.

The mold release member 8 is formed in a ring shape from a heat-resistant material such as heat-resistant stainless steel, and has a through hole 13 in the center thereof having an inner circumferential surface 13a that can freely fit with the rising circumferential surface 12 of the conveying member 5.
is formed. This mold release member 8 is disposed coaxially with the upper mold 1 through the through hole 13, and is movable in the axial direction of the upper mold 1 by a drive device (not shown). When pressing the glass material 4, the mold release member 8 is lowered so that the rising circumferential surface 12 of the vI feeding member 5 and the inner circumferential surface 1 of the through hole 13 are pressed.
3a are fitted or approached, and the mold release member 8
The lower surface 13b of the transport member 5 and the upper surface 9a of the locking protrusion 9 of the conveying member 5 are brought into contact with or approached. Furthermore, a heater 15 and a thermocouple (not shown) are provided inside the mold release member 8, so that the mold release member 8 can be controlled at a predetermined temperature.

Next, a method of molding the molded lens 3 using the molding apparatus described above will be explained.

First, the conveying member 5 with the glass material 4 placed in the mounting hole 6 is held in the through hole 10 of the conveying table 7, and is carried into a heating furnace, where the glass material 4 is heated and softened at 680°C. . Thereafter, as shown in FIG. 2, the glass material 4 is carried between the upper and lower molds 1.2. Here, both the upper and lower molds 1.2 are heated to a mold temperature of 550°C, and
Both upper and lower types 1. The ambient temperature around 2 is maintained at around 300°C, and the mold release member 8 is heated to 5 by a heater 15 with a thermocouple.
It is heated to 60°C.

In connection with the delivery of the glass material 4, both upper and lower molds 1 and 2
At the same time that the drive device connected to the mold release member 8 starts operating, the drive device connected to the mold release member 8 also starts operating.

Then, as shown in FIG. 1, the inner peripheral surface 13 of the mold release member 8
a fits into the rising circumferential surface 12 of the conveying member 5, and the mold release member 8
The glass material 4 is press-molded for 15 seconds while the lower surface 13b and the upper surface 9a of the locking protrusion 9 are in contact with each other, and the re-molded surfaces 1a and 2a are pressed.
At the same time, the glass material 4 is cooled by the upper and lower molds 1.2 and the atmosphere, and is kept warm by heat conduction with a gentle temperature gradient through the conveying member 5. .

To release the molded lens 3 obtained in this way,
If the adhesion to the lower mold 2 is strong, when the lower mold 2 descends,
By locking the conveying member 5 with the conveying table 7, the molded lens 3 is held by the conveying member 5 and released from the mold. on the other hand,
When the degree of adhesion to the upper mold 1 is strong, the molded lens 3 is lowered together with the conveying member 5 by the lowering movement of the mold release member 8,
The mold is released from the upper mold 1. After the mold is released, the conveying member 5 is held in the through hole 10 of the conveying table 7, and the molded lens 3 is
By moving the conveyor table 7, it is carried into an annealing furnace (not shown) and annealed.

FIG. 3 is an interference pattern showing an interference image of the spherical part of the glass lens obtained by the above example using a Fizeau interferometer. It turns out that it is a good lens.

In contrast, FIG. 4 shows an interference pattern of the spherical portion of a glass lens obtained by the conventional molding method in which a low-temperature mold release member is brought into direct contact with the glass material during press molding. As can be seen from FIG. 4, according to the conventional method, sink marks occur in the biconvex glass lens 18 having a large diameter as in this embodiment.

(Second Example) FIGS. 5 and 6 show a second example of the method for molding an optical glass component according to the present invention.

This example shows a case where a biconcave lens having a thin center wall thickness is press-molded. Note that the molding apparatus used in this embodiment has a molding surface 31a with a high surface shape and surface roughness corresponding to the desired molded lens 30.

Upper mold 31. having 32a. The parts other than the lower mold 32 are the same as those in the first embodiment, so the same parts are designated by the same numbers and the explanation thereof will be omitted.

That is, in this example, 5KII is used as the glass material as in the first example, the diameter is 14++ua, and RA45.
．． 3. R139,4 (aspherical surface) and wall thickness t = 3.5
The glass material 33 is preformed by grinding and polishing, and is molded with R, 44, It is processed to approximately R of 5, R, 38, 7.

The molding method of this embodiment is the same as that of the first embodiment, except that the temperature of the mold release member 8 is controlled to 480° C. by the heater 15 with a thermocouple, so the explanation thereof will be omitted.

According to this example, the glass material 33 is of both upper and lower types 31.32.
The shape of the forming surfaces 31a and 32a of the glass material 33 is transferred to the shapes of the molded surfaces 31a and 32a, and cooling is slower than that of the thick central portion of the glass material 33. It is possible to cool the glass material 33 and promote a uniform temperature change of the glass material 33.

FIG. 7 is an interference pattern showing the interference image of the spherical part of the glass lens obtained in the above example by a Fizeau interferometer. It turns out that it is a good lens.

In contrast, FIG. 8 shows an interference pattern of the spherical portion of the glass lens obtained by the conventional molding method in which a low-temperature member is brought into direct contact with the glass material during press molding. As can be seen from FIG. 8, according to the conventional method, sink marks occur in the biconcave glass lens 36 having a large diameter as in this embodiment.

[Effects of the Invention] As described above, according to the method for molding optical glass parts of the present invention, the temperature of the mold release member is controlled to a predetermined value, and the mold release member is brought into contact with the conveying member holding the outer periphery of the molding material. Alternatively, since the molding material is press-molded without being brought close to each other, the vicinity of the outer periphery of the molding material is cooled with a gentle temperature gradient via the conveying member, and a molded product with precise transferability can be obtained in a short time and at low cost.

[Brief explanation of the drawing]

1 and 2 show a molding apparatus in a first embodiment of the molding method of the present invention, in which FIG. 1 is a longitudinal cross-sectional view during press molding, FIG. 2 is a vertical cross-sectional view before press molding, Figures 3 and 4
The figure shows an interference pattern showing the interference image of each glass lens molded by the example shown in Figure 1 and the conventional example, respectively. Figures 5 and 6 show a molding apparatus in a second embodiment of the molding method of the present invention. FIG. 5 is a longitudinal cross-sectional view before press forming, FIG. 6 is a longitudinal cross-sectional view during press forming, and FIGS. 7 and 8 are according to the embodiment and conventional example shown in FIG. 5, respectively. It is an interference pattern showing an interference image in each molded glass lens. 1.31... Upper mold 2.32... Lower mold 3.30... Molded lens 4.33... Glass material 5... Conveying member 8... Mold release member 15... Heater Patent Applicant: Olympus Optical Industry Co., Ltd. 1... Upper mold 2... Lower mold 3 - Molded lens 5... Conveying member 8... Mold release member 15... Heater 252 =

Claims (1)

[Claims] (1) In a method for molding optical glass parts, the molding material for optical glass parts heated to a predetermined temperature is press-molded using a molding die that is lower than the temperature of the molding material, and the press-molded product is released from the mold by a mold release member. A method for molding an optical glass component, comprising controlling the temperature of the mold release member to a predetermined temperature, and press-molding the mold release member while contacting or approaching a conveying member holding the outer periphery of the molding material.