JPH0632623A - Production of optical element - Google Patents

Abstract

PURPOSE:To improve permeability of an optical element by heating and softening an optical glass raw material into which carbon is injected in a non-oxidizing atmosphere and then subjecting the softened glass raw material to press forming and annealing the formed article in an atmosphere having higher oxygen concentration than that of the air. CONSTITUTION:A glass raw material 1 is held on a plate 3 having same material as the glass raw material and an ion injecting device 4 is installed. Then a carbon source such as methane gas is introduced from a gas inlet 5 and the pressure of the gas is controlled to a prescribed pressure and N2 gas is introduced from a gas inlet 6 in the upper part and the gas is ionized in an ion generating part 10 consisting of a filament 7, coil 8 and electrode 9 and N ion is injected through a mass part 13 consisting of a magnet 11 and slit 12 and an accelerating part 16 consisting of an accelerating pipe 14 and XY scanning electrodes 15 into the glass raw material. A carbon ion dissociated and excited by colliding with N ion is injected into the glass raw material and the glass raw material 1 in which a modifying layer is formed is heated and softened in a non-oxidizing atmosphere and then subjected to press forming between a pair of molds. The formed article released from the mold is annealed in an atmosphere having an oxygen concentration higher than that in the air to provide the objective optical element having >=90% permeability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element manufacturing method for molding a glass optical element by hot pressing.

[0002]

2. Description of the Related Art Generally, an optical glass material is softened by heating,
It is widely practiced to press-mold into a desired shape with a molding die and obtain an optical element without the need for subsequent grinding and polishing. In the case of this heating press molding method,
It is important to satisfy the surface shape and surface characteristics (surface roughness, appearance, etc.) required for the image forming optical lens. Therefore, the molding die has high heat resistance and oxidation resistance and high accuracy. However, it is necessary to use a molding die material which has poor wettability with a glass material and has good mold release property. However, there is a limit to completely preventing fusion between the mold and the glass material only by improving the mold material, and it is only possible to mold with a limited kind of glass material. Therefore, conventionally, attempts have been made to prevent fusion by focusing on the glass material side.
For example, a proposal as disclosed in JP-A-63-222023 has been made. This is the molding surface of the glass material adjusted to a predetermined shape and capacity by grinding and polishing,
Forming a continuous carbon coating with a thickness of about 1 to 100 nm,
By covering the surface of the glass material with a coating, fusion of the glass material and the molding die is prevented.

[0003]

However, the molding surface of the glass material flows and deforms when it is press-molded by the molding die, but the continuous carbon film formed on the molding surface has no fluidity. Since the film does not deform, the film always cracks when the film tries to follow the molding surface of the molding die. Therefore, when pressed by the molding die, a portion where the die and the glass material are in direct contact with each other and a portion where the carbon film is interposed occur. From this,
There is a problem that the mold and the glass material are fused to each other in the portion in direct contact. Further, between the portion in direct contact and the portion via the carbon coating, a step difference corresponding to the film thickness of the carbon coating is generated on the surface of the glass molded product, which causes poor appearance during molding and deterioration of optical characteristics. . Furthermore, when the glass material is released from the mold, the carbon film may peel off (adhere) to the molding surface of the mold. When continuously molding, this carbon film peeled off makes the glass molded product. It may cause poor appearance.

Further, it is necessary to consider the surface defect of the glass material as one of the causes of the fusion between the mold and the glass material. The glass material before forming a carbon film that has been ground and polished has minute surface defects called latent scratches such as mechanically weak scratches hidden in the surface layer. Furthermore, in many cases, a chemically unstable reaction layer formed by the action of water or alkali, called so-called scorch, is present on the surface of the glass material during grinding and polishing. Due to these surface defects, the surface state of the glass material becomes unstable, and cracks occur from latent scratches on the surface layer during press molding after the carbon coating is formed (latent scratches progress to cracks), resulting in carbon coating or glass. There are problems that the cracked portion of the surface of the material is fused to the surface of the mold, and that the optical characteristics of the optical glass element from which the carbon coating is removed after molding are deteriorated (for example, the transmittance is lowered).

In order to solve such problems, at least carbon is injected into the molding surface of the optical glass material to form an optical glass material containing carbon in a non-equilibrium state on the molding surface, and then this material is formed. Is softened by heating, press-molded between a pair of molds, taken out from the molds, and then the molded product may be annealed.

In this case, the mold releasability is enhanced by injecting carbon, but the injected carbon is oxidized in the step of heating and softening the glass material and leaves as CO gas. . Therefore, it is necessary to inject a large amount of carbon in order to maintain sufficient releasability even after heat-softening, which requires a long time for the injecting step, which leads to an increase in cost.

Further, since the annealing treatment is usually carried out in the atmosphere, oxygen contained in the glass is combined with carbon to form CO gas, which is released from the molded article and reduces the transmittance of the glass. It may happen. Conventionally, annealing is continued even after the carbon in the glass becomes CO gas and is almost completely desorbed, and oxygen around the annealing furnace is introduced into the molded product to prevent a decrease in the transmittance of the glass. ing. However, if such an annealing process is performed, it takes a lot of time for the annealing process in order to prevent a decrease in the transmittance of the glass, which leads to an increase in cost.

The present invention has been made in view of the above problems, and there is no fusion between the mold and the glass material during press molding,
Manufacture of optical elements that can produce excellent optical elements at low cost without causing deterioration of optical characteristics or appearance defects in the optical elements that are molded products, and without causing surface defects of the glass material before press molding to the optical elements. The purpose is to provide a method.

[0009]

In order to solve the above-mentioned problems, the invention according to claim 1 provides an optical glass material in which at least carbon is injected into the molding surface of the material, after heating and softening the optical glass material,
In the method of manufacturing an optical element, in which a molded product is press-molded between a pair of molds and taken out of the molds, the molded product is annealed.

In the invention according to claim 2, the optical glass material in which at least carbon is injected into the molding surface of the material is softened by heating, press-molded between a pair of molds, taken out from the molds, and then molded. In the method for manufacturing an optical element in which an article is annealed, the oxygen concentration in the atmosphere to be annealed is higher than that in the atmosphere.

[0011]

According to the method of the first aspect, the injected carbon is not separated during the step of heating and softening the material. Therefore, it is only necessary to inject carbon in the minimum amount necessary for mold release, and it is possible to significantly reduce the time required for the injection process. The non-oxidizing atmosphere can be easily created by flowing an inert gas such as Ar or a non-oxidizing gas such as N ₂ gas into the heating furnace. Further, it is desirable that the oxygen concentration be as low as possible, and the lower the oxygen concentration, the more the effect of reducing the carbon desorption amount is recognized. Particularly, when the oxygen concentration is 1% or less, a remarkable effect is obtained.

On the other hand, according to the method of the second aspect, in the step of annealing the molded product, the rate of oxidation of the injected carbon can be increased, and the time of the annealing step can be shortened. Further, since sufficient oxygen is supplied to the glass surface, oxygen in the glass is not deficient and the transmittance of the molded product does not decrease.

[0013]

Example The shape of the glass material 1 used in this example after grinding and polishing is biconvex, and one surface is R1.
6.9 mm, the other surface is R97.3 mm, the outer diameter is φ1
1.8mm, medium meat 1.8mm, edge meat 0.56mm
Is. The glass type is SF type, the components are Si, O, Pb, etc., and the transition point is 460 ° C and the softening point is 590 ° C. Further, the surface roughness of the surface is finished to Rmax 0.02 μm.

A modified layer was formed on the surface of the glass material 1 by using a commercially available ion implantation apparatus whose schematic diagram is shown in FIG.

Specifically, as shown in FIG. 1, the glass material 1 was held on a plate 3 made of the same glass material and set in the ion implantation apparatus 4 described above. Then, CH ₄ gas is introduced from the gas introduction port 5 at the bottom of the device, and the pressure is 3 × 1.
It was adjusted to be 0 ^-5 Torr. Then, N ₂ gas is introduced from the gas introduction port 6 in the upper part of the device, and ionized by the ion generation unit 10 including the filament 7, the coil 8, the extraction electrode 9, etc., and the magnet 11 and the slit 1
A mass spectrometric section 13 and an acceleration tube 14, which are composed of
After passing through the accelerating unit 16 including the XY scanning electrodes 15 and the like,
N ion acceleration voltage 40 keV, implantation amount 1 × 10 ¹⁵ io
It was injected at n / cm ² . At that time, C colliding with N ions
The H ₄ gas was dissociated and excited, and carbon among them was injected into the glass material 1 together with N ions.

Subsequently, in the apparatus shown in FIGS. 2 and 3, the glass material 1 having the modified layer formed thereon is softened by heating and press-molded between a pair of molds, and after taking out from the molds, a molded product is obtained. Annealed.

Specifically, it was carried out as follows. The glass lens molding apparatus 20 of the present embodiment includes a molding chamber 21, a preheating furnace 22 and a slow cooling furnace 23 which are arranged in parallel on both sides of the molding chamber 21, and a preheating furnace 22 and a slow cooling furnace 23 which serve as a gob carrier. 24, the lens carriers 25 are placed at equal intervals, and are intermittently driven by drive gears 26 to convey caterpillars 27a and 27b, the molding chamber 21, the outlet 22a of the preheating furnace 22, and the inlet 2 of the slow cooling furnace 23.
3a, the main heating furnace 28 and the slow cooling start furnace 29, the molding chamber 21, the molding chamber 21, and the main heating furnace 28, respectively.
The shutters 30 and 31, the gob carrier 24 and the lens carrier 25, which are respectively provided between the molding chamber 21 and the transport caterpillars 27a and 27b.
A main part of the gob carrier transfer arm 32 and the lens carrier transfer arm 33 for transferring between them is configured.

Ar gas was flown into the preheating furnace 22 to keep the oxygen concentration in the preheating furnace 22 at 1%. O ₂ gas was flown into the slow cooling furnace 23 to keep the oxygen concentration in the slow cooling furnace 23 at 40%.

The glass material 1 having the modified layer formed thereon is placed on the gob carrier 24, heated in the preheating furnace 22 kept at 420 ° C. for 8 minutes, and then heated to 700 ° C. by the gob carrier carrying arm 32. Transfer it to the main heating furnace 28
Heated for 0 seconds. The shutter 30 is operated to carry in the loading port 2
1a was opened, and the glass material 1 was transferred by the gob carrier transfer arm 32 between the upper mold 36 and the lower mold 37 which were held at 490 ° C. Immediately thereafter, the lower mold 37 is raised to perform press molding, the gob carrier carrying arm 32 is moved backward to return to the original position, and the shutter 30 is closed to reduce the oxygen concentration in the preheating furnace 22. I kept it.

The shutter 3 is synchronized with the completion of press molding.
1 to open the lens carrier transfer arm 33 to the molding chamber 2
Then, the lens carrier 25 was held by moving the lens carrier 1. 43
The lens carrier 25 on which the molded product 39 is placed is conveyed to the slow cooling start furnace 29 kept at 0 ° C. and held for 1 minute, and then 420
It was passed through the slow cooling furnace 23 having a temperature gradient from 0 ° C to 300 ° C for 10 minutes.

The lens manufactured as described above had no fusion with the mold, was excellent in shape accuracy, and had a transmittance of 90% or more, showing sufficient optical performance.

In this embodiment, the preheating furnace 2 is used.
Ar gas, which is a non-oxidizing gas, was introduced into only 2
Ar gas is caused to flow in the pre-heating furnace 22 as well as in the pre-heating furnace 22, so that the pre-heating furnace 22 and the molding chamber 2 can be processed as in the present embodiment.
By keeping the oxygen concentration in 1 at 1%, the effect of the present embodiment can be made more reliable.

[0023]

[Comparative Example] When Ar gas is not flown into the preheating furnace 22, the glass is fused to the mold when the optical element is molded in the same manner as described above. In order to prevent fusion, it is necessary to set the injection amount to 1 × 10 ¹⁶ ion / cm ² or more, which increases the time required for the injection process by 10 times, resulting in high cost. On the other hand, when annealing is performed in the atmosphere without flowing O ₂ gas into the slow cooling furnace 23, when the optical element is molded in the same manner as described above, Pb in the glass is reduced and the glass is colored. The transmittance is as low as 86 to 89% in the visible light region, and sufficient optical characteristics cannot be obtained. In order to set the transmittance to 90% or more, the annealing time needs to be 2 hours or more, which increases the cost.

[0024]

As described above, according to the method of manufacturing an optical element of the present invention, it is possible to shorten the time of the injection step and the annealing step and to reduce the cost.
Further, it is possible to secure a transmittance of 90% or more, and it is possible to obtain an optical element having sufficient optical performance and no appearance defect.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an ion implantation apparatus used in an example of the present invention.

FIG. 2 is a plan view showing a glass lens forming apparatus used in the same example.

3 is a cross-sectional view taken along the line AA in FIG.

[Explanation of symbols]

 1 glass material 4 ion implantation device 20 glass lens molding device

Claims (2)

[Claims] 1. An optical element in which an optical glass material in which at least carbon has been injected into the molding surface of the material is heated and softened, press-molded between a pair of molds, taken out from the molds, and then the molded product is annealed. In the manufacturing method, the heating and softening atmosphere is a non-oxidizing atmosphere. 2. An optical element in which an optical glass material in which at least carbon has been injected into a molding surface of a material is softened by heating, press-molded between a pair of molds, taken out from the molds, and then the molded product is annealed. In the manufacturing method, an oxygen concentration of an annealing atmosphere is higher than that of the atmosphere, and a manufacturing method of an optical element.