JPH0912318A - Method of press forming optical glass element - Google Patents

Abstract

PURPOSE: To provide a method for press forming optical glass elements by dropping fused glass of a prescribed temp. from the leading-port of a crucible, depositing the fused glass onto a receiving die of a specific shape to form glass gob having a trimmed shape, transferring this gob to forming dies and press forming the gob. CONSTITUTION: This method for press forming the optical glass elements comprises dropping the fused glass of the prescribed temp. from the leading-port of the crucible, depositing the fused glass onto the receiving die to form the prescribed amt. of the glass god, transferring the glass gob to the forming dies from the receiving die in the state of a formable temp. state and forming the final formed goods having optical function surfaces at the top and the bottom by press forming. The glass receiving surface of the receiving die is formed to a projecting shape and a recess approximated to the optical function surface of the recessed shape of the final formed goods is formed on one surface of the glass gob deposited on the receiving die.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is
The present invention relates to a press molding method of an optical glass element for obtaining a highly accurate optical glass element such as a lens and a prism.

[0002]

2. Description of the Related Art In recent years, an optical element of this kind has been manufactured in order to achieve both simplification of purification and weight reduction at the same time, and
In order to reduce the number of elements of the optical device by making the optically functional surface aspherical, there is a tendency to manufacture it by press molding. The method of manufacturing an optical element having an aspherical surface by this press molding is excellent in productivity because polishing in the conventional optical lens manufacturing process is omitted.

This press molding method uses a molding die that has been finished to a desired surface quality and surface precision in advance and has a molding surface of, for example, an aspherical surface, and a lump of optical glass (hereinafter, referred to as
A glass gob) is heated and pressed in a molding die to mold the glass gob, or a method of heating and pressing the above-described glass gob to be heated and pressed (for example, see Japanese Patent Publication No. 54-38126). ).

In the case of optical glass elements such as aspherical lenses and prisms, very high surface accuracy is required. Therefore, the shape and weight of the glass gob used for press molding, especially,
It is important to control the surface condition, and a considerable running cost is required to satisfy the various conditions required for this purpose. As a result, the glass gob becomes expensive, which increases the price of the final molded optical glass element.

That is, since it is necessary to make the surface of the glass gob free from defects (for example, a surface having a surface roughness of 0.1 micron or less, preferably 0.01 micron or less) It was necessary to perform heat processing or etching treatment, and the glass gob became expensive. Therefore, in recent years, molten glass was dropped from the outlet of the crucible, received by a receiving mold, and a predetermined amount of glass gob deposited on the molten glass was used as it was as a glass material for forming an optical element. ing.

[0006]

The glass gob formed here can be used as a precision glass gob without surface scratches by devising the process, but the shape can only be made with convex shapes on both sides. Therefore, as the final molded product,
In the case of molding an optical element having at least one concave optical function surface, that is, a so-called concave lens, the amount of deformation of the glass gob increases during press molding. In this case, the surface of the molding die and the glass are rubbed against each other at a portion where the amount of deformation is large, and the durability of the die is reduced. In particular, when the pressing pressure is applied, the total pressure is applied only to the central part of the molding die at the initial stage, so that the central part of the mold is largely damaged.

Another drawback is that since the glass gob has a biconvex shape, it is difficult to stably hold the glass gob on the molding die (lower die) when molding a biconcave lens. Requires a suitable retainer. Therefore, the device is inevitably complicated.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and when the molten glass is received by the receiving mold, it is convenient to place the molten glass on the molding die in advance, and moreover, the glass gob in the press molding. It is an object of the present invention to provide a method of molding an optical element in which the shape of the glass gob is adjusted so that the deformation of the glass is substantially uniform and the durability of the mold is not impaired.

[0009]

Therefore, in the present invention,
Molten glass heated to a prescribed temperature is dripped from the outlet of the crucible and deposited on the receiving mold to form a prescribed amount of glass gob, and at the same time, it is molded from the receiving mold in a moldable temperature state. In a press molding method of an optical glass element, in which a glass gob is transferred to a mold and a final molded product having upper and lower optical functional surfaces is formed by press molding, the glass receiving surface of the receiving mold is formed into a convex shape and deposited on the receiving mold. It is characterized in that a recess similar to the concave optical function surface of the final molded product is formed on one surface of the glass gob.

Further, in the present invention, the molten glass heated to a predetermined temperature is dripped from the outlet of the crucible and deposited on the receiving mold to form a predetermined amount of glass gob, and at the same time, a temperature condition in which molding is possible. As it is, by transferring the glass gob from the receiving mold to the molding die, by press molding, in the press molding method of the optical glass element to form the final molded product having the upper and lower optical functional surface, the glass receiving surface of the receiving mold As a convex or concave shape, on one surface of the glass gob deposited in the receiving mold, a recess or ridge similar to the concave or convex optical function surface of the final molded product is formed, and the above glass gob is transferred to the molding mold. Prior to this, a depression is formed on the upper surface of the glass gob, which is similar to the concave optical function surface of the final molded product.

[0011]

Therefore, according to the first aspect of the present invention, when an optical element having at least one side having a concave optical function surface is formed by press molding, the shape of the glass gob is adjusted in advance in the receiving mold. Therefore, not only can it be stably held when placed on the molding die, but also the amount of deformation of the glass gob during press molding can be small. As a result, the pressing time is shortened, which shortens the tact time, which in turn leads to cost reduction.

Further, according to the second aspect of the present invention, since the shape of the glass gob is closer to the final lens shape,
Since the friction between the mold and the glass during press molding is minimized, the durability of the mold is greatly improved. Further, since the time required for the deformation becomes shorter, the cost can be further reduced. In particular, the effect is remarkable when molding a lens whose both surfaces are concave.

Further, as described in the claims, the recess formed by the invention has a radius of curvature larger than the radius of curvature of the optically functional surface of the final molded product, so that the mold and the glass are molded during molding. It is possible to prevent the gas in the molding atmosphere from being trapped during the time period and causing the accumulation of air (depression defects) in the molded product.

[0014]

EXAMPLES The molding method of the optical element of the present invention will be described in detail below with reference to FIGS. In the figure,
Reference numeral 1 is a platinum crucible, 2 is molten glass, and 3 is, for example, 430 cc of molten glass dropped from the outlet of the crucible 1. Reference numeral 4 is a nozzle at the outlet, and 5 is a receiving type having a concave receiving surface. The receiving surface of the receiving die 5 is a spherical surface having a radius of curvature R = 30 mm and a diameter = φ16 mm.

As another example, a receiving die 5'having a convex receiving surface is shown, and this receiving die 5'is a spherical surface having a radius of curvature R = 20 mm and a diameter = φ16 mm. Is. Further, in order to press-mold the final molded product, the pressing mold 6 is lowered with respect to the glass gob before being transferred to a molding mold (described later), and the molding surface of the pressing mold 6 has a radius of curvature R = It is a spherical surface having a diameter of 20 mm and a diameter of 16 mm. Reference numerals 7, 7 ', 7 "are examples of the shape of the glass gob transferred to the molding die.

In the present invention, however, as one of the methods, as shown in FIG. 1, the molten glass 3 heated to a predetermined temperature is dropped from the outlet (nozzle 4) of the crucible 1 and received. The glass gob is deposited on the mold 5'to form a predetermined amount of glass gob, and the glass gob 7'is transferred from the receiving mold 5'to the mold for molding while maintaining a moldable temperature state. In this case, the glass receiving surface of the receiving die 5'is formed as a convex shape on one surface of the glass gob deposited on the receiving die 5 ', as shown in FIG. 2 (A). , Forming a recess similar to the concave optical function surface of the final molded product.

In the present invention, as another method,
Molten glass 3 heated to a predetermined temperature is dropped from the outlet of the crucible 1 and deposited on the receiving mold 5 (or 5 '),
A predetermined amount of glass gob is formed, and the glass gob 7 (or 7 ″) is transferred from the receiving die 5 (or 5 ′) to the forming die while maintaining a moldable temperature state, and by press molding, the optical function is performed vertically. A final molded article having a surface is formed, and the glass receiving surface of the receiving die 5 (or 5 ′) is formed into a convex shape or a concave shape as shown in FIG. On one side of the deposited glass gob,
A dent or a ridge similar to the concave or convex optical function surface of the final molded product is formed, and before the glass gob is transferred to the molding die, as shown in FIG. A recess is formed on the upper surface, which is similar to the concave optical function surface of the final molded product.

Next, a concrete example of the molding method of the present invention will be described. First, in the crucible 1, the temperature is 12
The glass 2 is heated and melted so that the temperature becomes 50 ° C., and the glass is dropped from the nozzle 4 at a nozzle temperature of 900 ° C. This is received by a carbon-made receiving mold 5 or 5'heated to 500 ° C., but is separated when a predetermined amount of glass is received to obtain a glass gob. Then, the press mold 6 is used to perform press molding at a pressure of 5 kg / cm ² for 5 seconds to obtain a precision glass gob 7 or 7 ″ having a desired shape as shown in FIG.

The glass gob 7 has a radius of curvature R = 25 mm on the upper surface thereof and R = 26 mm on the lower surface thereof, and the glass gob 7 ″ has a radius of curvature R = upper surface thereof.
25 mm, and R = 28 mm on the lower surface. Further, the glass gob 7'only received by the receiving die 5'without press molding by the pressing die 6 has a radius of curvature R of its upper surface.
= 35 mm, and the lower surface R was 28 mm.
Table 1 shows the analysis results (wt%) of the optical glass used here.
Shown in

Then, the glass gob is picked up from the receiving die 5 (5 ') using an adsorption finger or the like and transferred, and as shown in FIG. 5 or 6, the press forming die heated to 570.degree. Using the mold 8 or 8 ′ and the lower mold 9), press molding was performed under the conditions of the pressing pressure: 80 kg / cm ² and the pressing time: 20 seconds.

Then, the molded lens 10 which is the final molded product.
(10 ′) is cooled as it is, and the mold is opened at 480 ° C. and taken out from the upper and lower molds by an appropriate automatic hand. Then, as shown in FIG. 7, at least one surface has a desired optical function surface having a concave shape.

5 or 6, the press-molding die uses a cemented carbide as a base material, and the upper die 8 or 8'has a convex or concave forming surface 11 with a radius of curvature R = 20 mm. Or 11 ', and the lower mold 9 has a radius of curvature R
= 20 mm, the convex molding surface 12 is formed. The molding surface 11 or 11 ', 12 is mirror-finished. Titanium nitride (TiN) coating is applied to the surface of the mold to protect the mirror surface of the mold, and then carbon is further coated to enhance releasability from glass. I am doing it. The upper mold 8 or 8'and the lower mold 9 are contained in the chamber, and the chamber is filled with an inert atmosphere. Further, in the figure, reference numeral 13 is a barrel mold, 14 is a press cylinder, 15 is a heater for heating the mold, and 16 is an entrance / exit of a glass gob.

Table 2 shows the results of the continuous press-molding test of the optical glass in Table 1 by the press-molding process using such a molding die. Here, as a comparative example, a conventional precision glass gob, that is, a glass gob formed only in the step (B) of FIG. 2 was used to perform continuous molding in the same manner as described above in the present invention. This glass gob is
Radius of curvature of the upper surface = 40 mm, R of the lower surface = 20 m
m.

[0024]

[Table 1]

[0025]

[Table 2] As shown in Table 2, in the molding using the glass gob of the present invention, 500 shots were continuously possible, whereas in the conventional glass gob, 200 shots were continuously produced.
At about hot, film peeling occurs in the central part of the mold, and the peripheral part of the mold is deteriorated, resulting in clouding failure. This is because the conventional gob has a large amount of deformation at the center, and the molding surface of the mold and the glass rub during the deformation,
Since the pressure is concentrated on the center of the mold, the corresponding part is greatly damaged. Incidentally, in the glass gob of the present invention, the amount of deformation is uniform and the mold does not deteriorate.

Further, in the conventional glass gob, when the continuous molding is attempted, the stability of the gob when the gob is placed on the molding surface of the lower mold is poor, and the gob often drops from the mold and the molding must be interrupted. I had to do it. The method for press-molding an optical glass element of the present invention is characterized in that an optical glass gob having a depression is formed before the press-molding to mold the optical glass element. The material of the mold, the type of optical glass, the manufacturing method, the shape of the depression, and other press molding conditions are not limited to those in this embodiment.

The glass gob according to the present invention is macroscopically such that the central part of the gob has a shape similar to that of a concave lens, and is larger than the radius of curvature of the lens obtained by molding, and Is the radius of curvature of the value.

Generally, the surface of the glass gob is microscopically
Although there are irregularities in units of several μm, these irregularities are not called the depressions of the present invention. In addition, a gob having a depression refers to a case where there is a depression on at least one of the two surfaces of the gob.

[0029]

As described above, according to the present invention, the molten glass heated to a predetermined temperature is dropped from the outlet of the crucible and deposited on the receiving mold to form a predetermined amount of glass gob. While maintaining the moldable temperature state, the glass gob is transferred from the receiving mold to the molding mold, and by press molding,
In the press molding method of an optical glass element for forming a final molded product having upper and lower optical functional surfaces, the glass receiving surface of the receiving mold is formed into a convex shape, and a concave surface of the final molded product is formed on one surface of the glass gob deposited on the receiving mold. It is characterized by forming a recess similar to the optical function surface of the shape.

Further, in the present invention, the molten glass heated to a predetermined temperature is dripped from the outlet of the crucible and deposited on the receiving mold to form a predetermined amount of glass gob, and at a temperature condition at which the glass can be molded. As it is, by transferring the glass gob from the receiving mold to the molding die, by press molding, in the press molding method of the optical glass element to form the final molded product having the upper and lower optical functional surface, the glass receiving surface of the receiving mold As a convex or concave shape, on one surface of the glass gob deposited in the receiving mold, a recess or ridge similar to the concave or convex optical function surface of the final molded product is formed, and the above glass gob is transferred to the molding mold. Prior to this, a depression is formed on the upper surface of the glass gob, which is similar to the concave optical function surface of the final molded product.

Therefore, when at least one optical element having a concave optical functional surface is formed by press molding,
Since the shape of the glass gob is adjusted in advance in the receiving mold, not only can it be held stably when it is placed on the molding die, but the amount of deformation of the glass gob at the time of press molding is almost equal. Excellent effects such as not impairing durability can be obtained.

[Brief description of the drawings]

FIG. 1 is a side view showing a state of a melting crucible in a press molding method of the present invention.

FIG. 2 is a side view showing a state in which a receiving mold receives molten glass.

FIG. 3 is a side view showing a state in which a precision glass gob is molded using a pressing die.

FIG. 4 is a side view showing the shape of a molded precision glass gob.

FIG. 5 is a vertical sectional side view of a press-molding die showing a state in which the above-mentioned precision glass gob is loaded.

FIG. 6 is likewise a vertical sectional side view of a press-molding die.

FIG. 7 is a vertical cross-sectional side view of an optical element as a final molded product.

FIG. 8 is a vertical sectional side view of a press mold for explaining a conventional example.

[Explanation of symbols]

1 Crucible 2 Molten glass 3 Dropping glass 4 Nozzle 5 Receiving die with concave molding surface 5'⊥ Receiving die with convex molding surface 6 Pushing die 7, 7 ', 7 " Mass (glass gob) 8 Press mold (upper mold) 8'Press mold (upper mold) 9 Press mold (lower mold) 10 Molded lens 10 'Molded lens 11 Molded surface of 11' mold Molding surface 12 Molding surface of mold 13 Body mold 14 Press cylinder 15 Heater 16 Auto hand entrance / exit

Claims (3)

[Claims] 1. A molten glass heated to a predetermined temperature,
Dropping from the outlet of the crucible, deposited on the receiving mold, to form a predetermined amount of glass gob, while maintaining a moldable temperature state, transfer the glass gob from the receiving mold to the molding die,
In a press molding method of an optical glass element for forming a final molded product having upper and lower optical functional surfaces by press molding, a glass receiving surface of the receiving mold is formed into a convex shape, and one surface of the glass gob deposited on the receiving mold is finished. A method for press-molding an optical glass element, which comprises forming a recess close to a concave optical function surface of a molded product. 2. A molten glass heated to a predetermined temperature,
Dropping from the outlet of the crucible, deposited on the receiving mold, to form a predetermined amount of glass gob, while maintaining a moldable temperature state, transfer the glass gob from the receiving mold to the molding die,
In a press molding method of an optical glass element for forming a final molded product having upper and lower optical functional surfaces by press molding, the glass receiving surface of the receiving mold is convex or concave, and one surface of the glass gob deposited on the receiving mold. In addition, while forming a recess or ridge close to the concave or convex optical function surface of the final molded product, before transferring the glass gob to the molding die, by the pressing mold, on the upper surface of the glass gob, the final molded product A method for press-molding an optical glass element, which comprises forming a recess similar to the concave optical function surface of the above. 3. The method of press molding an optical glass element according to claim 1, wherein the recess is formed with a radius of curvature larger than a radius of curvature of the optical function surface of the final molded product.