JPH05178625A - Method for forming glass lens - Google Patents

Abstract

PURPOSE:To reduce the surface roughness of the lens by heating and softening a glass material previously worked into a shape resembling that of the lens under conditions where the material is not flexed or deformed by gravity. CONSTITUTION:A glass material 2 previously worked into a shape resembling that of the desired lens is heated in a preheating furnace 1 at a temp. higher than the transition point and lower than the yield point, and the material 2 is made capable of being press-formed and incapable of being deformed by gravity. The preheated glass material 2 is conveyed between halogen lamps 11 by a conveyor arm 12. The material 2 is irradiated with IR from the lamp 11, and only both sides 2a and 2b are heated above the softening point. Consequently, the sides 2a and 2b are reduced in roughness, the inside of the material 2 is kept above the transition point and below the yield point, and the material is not deformed by gravity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass lens molding method for molding a glass lens by pressing a glass material which has been softened by heating with a pair of molding dies.

[0002]

2. Description of the Related Art When a glass material is softened by heating and a glass lens is pressed by a molding die, if the shape of the softened glass material is indefinite and the pressing amount (deformation amount of the glass material) is large, molding becomes difficult, If the surface roughness of the glass material is bad or if the volume of the glass material varies greatly, the molded glass lens will not satisfy sufficient optical performance. For this reason, the glass material is processed in advance into a shape similar to the desired lens shape with the Garb Generator, and the surface of the glass material is polished to finish Rmax of 0.1 μm or less and the glass material is adjusted to a predetermined size (volume). It was necessary to reduce the size. By the way, in the above-mentioned polishing process, there are cases where defects such as stains and stains due to polishing residue or polishing remain on the surface of the glass material, and it takes a long time to finish the surface roughness to a predetermined roughness. I needed it.

In order to solve such a problem, a method of manufacturing a preform has been proposed in Japanese Patent Laid-Open No. 61-251526. In this manufacturing method, a pedestal is placed through a support in a sealable preheating furnace made of a heat insulating material, and the inside of the preheating furnace is evenly supported while the edge of the sized glass material is supported by the pedestal. By heating, the entire glass material is heated to a glass viscosity of at least 10 ⁵ poise, and the surface roughness of the glass material is reduced.

[0004]

However, JP-A-61-161
In the method described in Japanese Patent No. 251526, the inside of the preheating furnace is heated to a temperature equal to or higher than the softening point of the glass material, and the glass material is heated in this high temperature atmosphere. The glass material is also heated to a high temperature, causing the glass material to bend and deform due to its own weight. Therefore, there is a problem that the amount of deformation of the glass material at the time of press molding becomes large and it becomes difficult to mold a glass lens having a shape satisfying desired optical performance.

The present invention has been made in view of the above-mentioned problems of the prior art. When the glass material is heated to reduce the surface roughness, deformation due to its own weight can be prevented and press molding can be performed into a desired lens shape. An object is to provide a method for molding a glass lens.

In order to achieve the above object, the present invention reduces the surface roughness by heating and softening a glass material having a large surface roughness preliminarily processed into a shape close to a desired lens shape.
Then, in the glass lens molding method of pressing with a molding die, a step of heating the pre-processed glass material having a large surface roughness to a temperature of not less than the glass transition point and not more than the sag point, and the surface layer portion of the heated glass material is infrared. The glass lens is molded by a step of heating to a softening point or higher by light to reduce the surface roughness to Rmax of 0.1 μm or less and a step of press-molding a glass material having a reduced surface roughness.

[0007]

In the above process, the entire pre-processed glass material is uniformly heated to a temperature not lower than the glass transition point and not higher than the yield point so that the glass material can be press-formed and is not deformed by its own weight. Then, by using infrared rays as a heating source, it becomes possible to focus infrared light on the surface portion of the glass material and heat only the surface portion. Thereby, while maintaining the inside of the glass material at a temperature not lower than the glass transition point and not higher than the deformation point, only the surface portion of the glass material can be selectively heated above the softening point to reduce the surface roughness. For this reason, press molding can be performed without substantially deforming the shape of the glass material formed in advance.

FIG. 1 is a sectional view showing a main part of a molding apparatus used in each embodiment of the glass lens molding method of the present invention. In the figure, reference numeral 1 denotes a cylindrical preheating furnace in which a heater 3 for heating the glass material 2 to a predetermined temperature is provided. A molding chamber 4 for press-molding the glass material 2 that has been softened by heating is connected to one end of the preheating furnace 1. In the molding chamber 4, an upper mold 5 and a lower mold 6 each having a molding surface in which a desired lens surface shape is reversed are arranged opposite to each other so as to be vertically movable on the same axis, and the upper mold 5 and Heaters 7 and 8 for heating the lower mold 6 to desired mold temperatures are provided so as to be surrounded by heat insulating materials 9 and 10, respectively. The drive devices for the upper mold 5 and the lower mold 6 and the mold temperature measuring means are not shown.

In the preheating furnace 1 near the molding chamber 4 side,
A pair of halogen lamps 11 each having a reflector are provided.
The two glass surfaces 2a and 2b of the glass material 2 held in step 2 are arranged so as to face each other in order to heat them to a predetermined temperature. The transfer arm 12 is a ring-shaped transfer member 1 for the glass material 2.
It is mounted on the No. 3 and is conveyed in the preheating furnace 1, between the halogen lamps 11 and between the upper mold 5 and the lower mold 6, and a supporting portion of the above-mentioned conveying member 13 is formed at the tip thereof. By means of a transporting device, the reciprocating motion is performed between the receiving position of the glass material 2 outside the preheating furnace 1 and the passing position of the glass lens outside the molding chamber.

[0010]

Example 1 In this example, BAL41 was used as the glass material.
(Ohara, transition point 535 ℃, yield point 559 ℃, softening point 6
The glass lens was press-molded using (39 ° C.). Then, the above-mentioned glass material is approximated to a desired lens shape (aspherical shape) with a curve generator by a radius of curvature R = 20 m.
Both sides of the glass material were ground and preliminarily processed into a glass material 2 having a thickness of 4 mm and an outer diameter of 18 mm. At this time, the surface roughness of the ground surface of the glass material 2 was Rmax 5 μm.

The glass material 2 is placed on the carrying member 13 and is carried by the carrying arm 12 while being carried into the preheating furnace.
After the glass material 2 is uniformly heated to 550 ° C. in the preheating furnace 1, the pair of halogen lamps 1 is moved by the transfer arm 12.
1 (100 V, 2 KW was used). And
With the pair of halogen lamps 11 separated from the glass material 2 by 30 mm, both glass surfaces 2 of the glass material 2
From a halogen lamp 11 to a and 2b, the wavelength is about 1μ.
Irradiate infrared rays of around m with a condensing diameter of 20 mm for about 10 seconds,
The surfaces of both glass surfaces 2a and 2b were heated to 950 ° C.
By this heating, the surface roughness of the glass material 2 is 0.1 μm.
The radius of curvature decreases to m on the upper glass surface 2a.
= 19.95 mm, the lower glass surface 2b has R = 20.1
changed to mm. After that, with the heaters 7 and 8, the glass material 2
The glass material 2 is conveyed by the conveying arm 12 between the upper mold 5 and the lower mold 6 which are respectively heated to 520 ° C., which is 15 ° C. lower than the transition temperature of 1, and the upper 5 and the lower mold 6 press-mold a glass lens of a desired shape. did.

According to this embodiment, the halogen lamp 11 keeps the inside of the glass material 2 at a temperature below the yield point and heats only the surface layer of the glass material 2 above the softening point to reduce the surface roughness. can do. As a result, the shape deformation of the glass material 2 due to its own weight becomes extremely small, and a glass lens sufficiently satisfying the desired optical performance can be press-molded.

[0013]

Example 2 In this example, PBL6 was used as the glass material.
(Ohara, transition point 398 ° C, yield point 501 ° C, softening point 6
The glass lens was press-molded using (37 ° C.). Then, similar to the first embodiment, the glass material is curved with a radius of curvature R = 40 approximate to a desired lens shape by a curve generator.
Grinding both sides to mm, thickness 3mm, outer diameter 10mm
It was pre-processed to the glass material 2 of. At this time, glass material 2
The surface roughness of the ground surface was Rmax 3.5 μm.

The glass material 2 is placed on the transfer member 13 and transferred to the preheating furnace 1 by the transfer arm 12 to uniformly heat the glass material 2 to 490 ° C., and then the transfer arm 12 sets the pair of halogen lamps 11. (Use 100V, 500W)
It was transported in between. Then, with the pair of halogen lamps 11 separated from the glass material 2 by 20 mm, the halogen lamps 1 are formed on both glass surfaces 2a and 2b of the glass material 2.
Infrared rays with a wavelength of around 1 μm from 1 to 1 with a condensing diameter of 10 mm
Irradiation was performed for 4 seconds, and the surfaces of both glass surfaces 2a and 2b were heated to 950 ° C. By this heating, glass material 2
The surface roughness was reduced to 0.07 μm, and the radius of curvature was changed to R = 39.5 mm for the upper glass surface 2a and R = 40.8 mm for the lower glass surface 2b. After that, the heaters 7 and 8 lower the transition temperature of the glass material 2 by 15 ° C. 38
The glass material 2 was conveyed by the conveying arm 12 between the upper mold 5 and the lower mold 6 which were respectively heated to 3 ° C., and a glass lens having a desired shape was press-molded by the upper mold 5 and the lower mold 6. Also in this embodiment, as in the case of the above-described first embodiment, it is possible to press-mold a glass lens sufficiently satisfying the desired optical performance.

[0015]

Example 3 In this example, LAL7 was used as the glass material.
(Ohara, transition point 617 ℃, yield point 658 ℃, softening point 6
The glass lens was press-molded using (94 ° C.). Then, similar to the first embodiment, the above-mentioned glass material is used in a curve generator to approximate a desired lens shape to a radius of curvature R = 20.
Grinding both sides to mm, thickness 4 mm, outer diameter 18 mm
It was pre-processed to the glass material 2 of. At this time, glass material 2
The surface roughness of the ground surface was Rmax 4.8 μm.

The glass material 2 is placed on the transfer member 13 and transferred to the preheating furnace 1 by the transfer arm 12 to uniformly heat the glass material 2 to 645 ° C., and then the transfer arm 12 sets the pair of halogen lamps 11. It was transported between (using 100 V and 2 KW). Then, with the pair of halogen lamps 11 separated from the glass material 2 by 20 mm, the halogen lamps 11 are formed on both glass surfaces 2a and 2b of the glass material 2.
Infrared with a wavelength of around 4 μm is about 20 with a condensing diameter of 18 mm
The surfaces of both glass surfaces 2a and 2b were heated to 1000 ° C. by irradiating each for 2 seconds. By this heating, glass material 2
The surface roughness was reduced to 0.05 μm, and the radius of curvature was changed to R = 19.5 mm on the upper glass surface 2a and R = 20.2 mm on the lower glass surface 2b. After that, the heaters 7 and 8 lower the transition temperature of the glass material 2 by 25 ° C. 59
The glass material 2 was conveyed by the conveying arm 12 between the upper mold 5 and the lower mold 6 heated to 2 ° C., and the upper mold 5 and the lower mold 6 press-molded a glass lens having a desired shape. Also in this embodiment, as in the case of the above-described first embodiment, it is possible to press-mold a glass lens sufficiently satisfying the desired optical performance.

[0017]

As described above, according to the present invention, the glass material is first heated to a temperature not lower than the glass transition point and not higher than the yield point so that the glass material can be press-molded and is not deformed by its own weight. While maintaining the temperature, only the surface layer of the glass material is heated above the softening point by infrared light to reduce the surface roughness. Therefore, even if the glass material is heated above the softening point to obtain the surface roughness required for press molding, the glass material hardly undergoes flexural deformation due to its own weight, and the shape of the preprocessed glass material Since it can be press-molded, it is possible to mold a glass lens having a good moldability and a shape sufficiently satisfying the desired optical performance.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a main part of a molding apparatus used in each example of a glass lens molding method of the present invention.

[Explanation of symbols] 1 preheating furnace 2 glass material 3 heater 4 molding chamber 5 upper mold 6 lower mold 7,8 heater 9,10 heat insulating material 11 halogen lamp 12 transfer arm 13 transfer member

Claims (1)

[Claims] 1. A method of molding a glass lens, wherein a glass material having a large surface roughness preliminarily processed into a shape close to a desired lens shape is softened by heating to reduce the surface roughness, and then pressed by a molding die. A step of heating a pre-processed glass material having a large surface roughness to a temperature of not less than the glass transition point and not more than the yield point, and heating the surface layer part of the heated glass material to a softening point or more by infrared light to obtain a surface roughness Rmax.
A method of molding a glass lens, which comprises a step of making the surface roughness 0.1 μm or less and a step of press-molding a glass material having a reduced surface roughness.