JP3869507B2 - Method for forming optical glass element - Google Patents

Description

[0001]
【Technical field】
The present invention relates to an optical glass element molded by a glass mold method, and more particularly to a method for molding an optical glass element having a peripheral plane portion around a central curved surface portion.
[0002]
[Prior art and its problems]
As an optical element (lens), a type is known in which a peripheral plane portion perpendicular to an optical axis that facilitates lens holding is formed around a central curved surface portion that acts as a lens. Conventionally, this type of optical element is made of a plastic having excellent moldability and has not been formed by a glass mold method in which a glass element is heated and softened. When an optical element having a central curved surface portion and a peripheral flat surface portion is formed by a conventional glass mold method, the curved surface portion and the boundary portion between the curved surface portion and the flat surface portion do not have a shape along the mold.
[0003]
However, compared to optical glass, plastic lenses have drawbacks such as poor heat resistance and low service temperature, water resistance and corrosion resistance, but weak against organic solvents, and optical performance changes due to changes in ambient temperature and humidity. is there. For example, when compared at the glass transition point, it can be seen that the plastic lens is lower in heat resistance than the optical glass by 300 ° C. or higher.
[0004]
OBJECT OF THE INVENTION
An object of the present invention is to obtain a molding method capable of molding an optical element having a peripheral plane portion around a central curved surface portion by a glass molding method using optical glass.
[0006]
SUMMARY OF THE INVENTION
According to the first aspect of the molding method of the present invention, a method of molding an optical glass element having, on at least one surface, a central curved surface portion formed of a convex surface and a peripheral flat surface portion positioned around the central curved surface portion. The mold includes a curved surface part mold corresponding to the central curved surface part including a convex surface, and a flat part mold corresponding to the peripheral flat part, which is movable relative to the curved surface part mold. And a step of setting a glass preform in the mold and heating and softening; applying a molding pressure to the flat surface mold and moving a part of the glass preform into the curved surface mold; and A step of applying molding pressure to both the flat surface portion forming die and the curved surface portion forming die to transfer the shapes of the curved surface portion forming die and the flat surface portion forming die to the glass preform.
[0007]
According to the second aspect, the molding method of the present invention is a method of molding an optical glass element having a central curved surface portion and a peripheral flat surface portion located around the central curved surface portion on at least one surface, The mold includes a curved surface part mold corresponding to the central curved surface part and a flat part mold corresponding to the peripheral plane part which can move relative to the curved surface part mold. Setting and heating and softening; applying pressure to the curved surface mold to move a part of the glass preform into the flat mold; and the flat mold and curved mold And a step of transferring the shape of the curved surface portion molding die and the flat surface portion molding die to the glass preform by applying molding pressure to both. This second aspect can be applied whether the central curved surface portion is concave or convex.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an example of a mold used in the molding method according to the present invention. In this example, for simplicity, one surface of the glass optical element to be molded is a flat surface, a central convex curved surface portion (spherical surface portion) at the center of the other surface, and orthogonal to the optical axis around the central convex spherical surface. The case where it has a peripheral plane part is assumed. The lower side of FIG. 1 is a flat die 11, and the upper side is a curved surface portion forming die 12 for forming a central curved surface portion, and a flat surface portion forming die positioned so as to be relatively slidable around the curved surface portion forming die 12. 13 is located in the mold 10 which is a feature of the present invention. That is, the flat part mold 13 is provided with a slide hole 14 at the center thereof, and the curved part mold 12 is slidably fitted into the slide hole 14.
[0009]
Each of the flat mold 11, the curved surface mold 12, and the flat mold 13 is formed of heat resistance, oxidation resistance, and glass on the molding surfaces of the base materials 11a, 12a, and 13a in the same manner as a normal glass mold. Formed thin films 11b, 12b, and 13b having a thickness of about 0.5 μm for improving the releasability are attached. That is, the molding surfaces of the planar mold 11 and the planar portion molding die 13 are planar molding surfaces formed by the molded thin films 11b and 13b and orthogonal to the optical axis, and the molding surface of the curved surface molding die 12 is the molding surface. It is a curved surface (concave surface) molding surface formed by the thin film 12b.
[0010]
The base material is made of, for example, cemented carbide tungsten carbide, silicon carbide, cermet, zirconia, alumina, etc., and after processing the molding surface of this base material into a desired shape with an ultra-precision lathe, using a diamond abrasive or the like Polishing into a desired shape having a surface roughness R _max = 0.02 μm or less, and a formed thin film is adhered thereon. As the formed thin film, various ceramics, a hard carbon thin film, a DLC thin film, a noble metal thin film such as gold or platinum, a combination thereof, or the like is used.
[0011]
The curved surface mold 12 and the flat surface mold 13 which can slide relative to each other in the optical axis direction of the glass optical element to be molded have their curved surfaces formed when the upper reference planes 12c and 13c are positioned on one plane. A series of molding surfaces is formed by the surface 12b and the flat molding surface 13b. The curved surface portion forming die 12 and the flat surface portion forming die 13 can individually exert pressing pressure by the center press cylinder 21 and the peripheral press cylinder 22 shown in FIG. 21 a is formed larger than the diameter of the curved surface portion molding die 12, and only the curved surface portion molding die 12 cannot be pushed into the flat surface portion molding die 13. That is, the descending position of the curved surface portion forming mold 12 with respect to the flat surface portion forming die 13 is regulated by a height at which the reference plane 12c matches the reference plane 13c.
[0012]
In the present mold having the above-described configuration, a body-shaped spacer 16 is set on the outer periphery of the planar mold 11 as shown in FIG. The flat part molding die 13 of the mold 10 is slidably fitted into the barrel spacer 16 with the center position properly positioned, and the flat part molding die 13 is closest to the flat mold 11. The position is regulated by the contact between the flange 15 formed on the flat part forming die 13 and the trunk spacer 16.
[0013]
Next, a molding method using the above mold will be described. As shown in FIG. 3, the mold mold 10, the planar mold 11, and the body mold spacer 16 are set in a heating device having a quartz tube 23 and a heater 24, and between the planar mold 11 and the mold mold 10, A pre-weighed glass preform 30 is set. The glass preform 30 is formed in a size straddling the curved surface portion forming die 12 and the flat surface portion forming die 13 of the mold 10. In a state where nitrogen gas (inert gas) is introduced into the quartz tube 23, the glass preform 30 is softened by heating with the heater 24. The heating temperature at this time is about 10 ° C. higher than the temperature at which the glass preform 30 can be softened and pressed (temperature in a normal glass molding method; Tg (glass transition point) +50 to 70 ° C.). Should be softer than the conventional glass mold method. Specifically, it is good to set to about Tg + 60-80 degreeC.
[0014]
In the softened state of the glass preform 30, first, the mold 10 is placed in the glass preform 30 with the molding surface 13 b of the flat surface molding die 13 and the molding surface 12 b of the curved surface molding die 12 being a series of molding surfaces. Then, a molding pressure is applied to the flat part molding die 13 by the peripheral press cylinder 22. Then, the softened glass preform 30 moves into the curved surface 12b of the curved surface mold 12. Preferably, after the molding by the peripheral press cylinder 22 is performed until the glass preform 30 comes into full contact with the curved molding surface 12b, the molding pressure is also exerted on the curved surface mold 12 by the center press cylinder 21. Then, this time, the glass preform 30 moves from the curved surface portion molding die 12 side to the flat surface portion molding die 13 side, and the pressing plane 21a of the center press cylinder 21 is changed from the reference flat surface 12c of the curved surface portion molding die 12. It will be in the state contact | abutted simultaneously with the reference plane 13c of the plane part shaping | molding die 13, and shaping | molding by the curved surface part shaping | molding die 12 and shaping | molding by the plane part shaping | molding die 13 will arise simultaneously. Finally, as shown in FIG. 4, the flange 15 of the flat portion molding die 13 comes into contact with the body spacer 16 and the molding is completed. When the molded glass optical element is taken out after cooling after molding, a glass optical element having a correct shape without any abnormality such as sink marks is obtained at the boundary between the curved molded surface 12b and the flat molded surface 13b.
[0015]
In the above example, the glass preform 30 is first set across the curved surface portion forming die 12 and the flat surface portion forming die 13. However, initially, the glass preform 30 may be set so as to contact only the curved surface portion forming die 12. it can. 5 and 6 show the molding mode. In this molding mode, the flat part mold 13 is first lowered to a certain reference position by the peripheral press cylinder 22 and then the molding pressure is applied to the curved part mold 12 by the central press cylinder 21 to The glass preform 30 sandwiched between the glass preforms 30 is moved along the curved surface 12b, and a part of the glass preform 30 protrudes toward the flat portion forming die 13 side. Thereafter, when a molding pressure is applied to the flat portion molding die 13 by the peripheral press cylinder 22, molding can be performed in the same manner as in the molding method of FIGS.
[0016]
In the above embodiment, the planar molding surface 13b of the planar part molding die 13 is orthogonal to the optical axis, but the present invention can also be applied to a plane that is not strictly orthogonal. Further, the curved surface forming surface 12b of the curved surface portion forming die 12 is concave (the formed glass element is convex), but conversely, the present invention can also be applied to a case where the curved surface is a convex surface (the formed glass element is concave).
[0017]
7 and 8 show this molding mode. The curved surface 12b ′ of the curved surface mold 12 is a convex surface (the forming element is a concave surface), and other configurations are the same as in the previous embodiment. In this embodiment, the glass preform 30 is first processed with the curved surface part mold 12 at the center (FIG. 7), and then processed with the flat part mold 13 at the peripheral part (FIG. 8). In this embodiment, as shown in FIGS. 1 to 4, when the glass preform 30 is first processed by the flat portion mold 13, the space between the curved surface portion mold 12 and the preform 30 is closed. This is not preferable because there is no gas escape area.
[0018]
In the above, one surface of the molded glass element is a flat surface, but the present invention can also be applied to a case where both surfaces have a central curved surface portion and a peripheral flat surface portion.
[0019]
【The invention's effect】
According to the present invention, an optical glass element having a central curved surface portion and a peripheral flat surface portion can be formed into a correct set shape.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing an example of a mold of an optical glass element used in a molding method according to the present invention.
2 is a longitudinal sectional view showing a state in which the mold die and the barrel spacer of FIG. 1 are set. FIG.
3 is a longitudinal sectional view showing a molding state using the mold of FIG. 2. FIG.
FIG. 4 is a longitudinal sectional view showing the same different molding state.
FIG. 5 is a longitudinal sectional view at the initial stage of molding showing a molding state different from the molding mode of FIGS. 1 to 4;
FIG. 6 is a longitudinal sectional view at the end of the molding.
FIG. 7 is a longitudinal sectional view at the initial stage of molding showing a molding mode when the curved surface portion molding die is a convex surface.
FIG. 8 is a longitudinal sectional view at the end of the molding.

Claims (2)

A method of forming an optical glass element having a central curved surface portion formed of a convex surface and a peripheral flat surface portion located around the central curved surface portion on at least one surface,
The mold includes a curved surface part molding die made of a concave surface corresponding to the central curved surface part made of a convex surface, and a flat surface part molding die corresponding to the peripheral plane part, which can be moved relative to the curved surface part molding die,
A step of setting a glass preform in a mold and heating and softening; a step of applying a molding pressure to the flat part mold to move a part of the glass preform into the curved part mold; and a flat part mold Applying a molding pressure to both the curved surface mold and the curved surface mold to transfer the shapes of the curved mold and the flat mold to the glass preform;
A method for forming an optical glass element, comprising: A method of forming an optical glass element having a central curved surface portion and a peripheral flat surface portion around the central curved surface portion on at least one surface,
The mold includes a curved surface part mold corresponding to the central curved surface part, and a flat surface part mold corresponding to the peripheral flat part, which can move relative to the curved surface part mold,
Setting a glass preform in a mold and heating and softening; applying a molding pressure to the curved surface mold and moving a part of the glass preform into the flat mold; and a flat mold Applying a molding pressure to both the curved surface mold and the curved surface mold to transfer the shapes of the curved mold and the flat mold to the glass preform;
A method for forming an optical glass element, comprising:

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