JP3428744B2 - Optical element manufacturing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical element, and more particularly to a method for manufacturing an optical element for press-molding a highly accurate glass material such as an aspherical lens.

[0002]

2. Description of the Related Art In recent years, glass materials have not been subjected to a polishing process,
It is housed in a molding die with a specified surface accuracy and pressed.
By shaping it, the glass lens used for optical equipment, etc.
A method of manufacturing a lens has been proposed. This method is for example
It is described in Japanese Examined Patent Publication No. 61-32263, and
According to the report, the glass material and the molding die both have a glass viscosity of 10
⁸ -10¹²Press molding at a temperature equivalent to dPa · s
is doing.

However, under such a high temperature, fusion may occur depending on the combination of the glass type and the mold material, or defective fog of the molded product may occur due to deterioration of the surface roughness of the mold.

Many methods have been proposed to solve these problems.

For example, Japanese Patent Publication No. 3-53260 and Japanese Patent Laid-Open No. 62-297225 propose a method of preventing fusion by coating a surface of a glass material with a material having releasability.

Japanese Unexamined Patent Publication (Kokai) No. 64-83529 proposes a method for manufacturing a molding die in which a hard carbon film is formed on SiC to improve the releasability from glass.

In Japanese Patent Publication No. 4-21606, a glass material in which volatile components from high temperature glass such as B ₂ O ₃ and PbO are reduced in the surface layer portion is used. There has been proposed a method of preventing the deterioration of the thickness of the molded product and improving the durability of the molded product due to poor fog.

Further, Japanese Patent Application Laid-Open No. 3-177320 proposes a method of heat-treating a glass material in a vacuum to prevent fusion.

[0009]

However, these methods have the following problems.

Regarding the method of coating the surface of the glass material with a film having a mold releasing property, see Japanese Patent Publication No. 3-53260.
In the publication, it is uneconomical because the coating film needs to be removed after molding, and in the case of the film of JP-A-62-297225, if the film is thick, the surface layer is hard and cracks occur during press deformation, and if it is thin, fusion does not occur. Even if it can be prevented, it becomes difficult to prevent deterioration of the mold. Further, in these methods, it is necessary to select a coating material corresponding to the thermophysical properties of various glasses.

In molding with a mold in which a base material is coated with a hard carbon film, the surface roughness of the glass containing a large amount of volatile components from the glass at high temperatures is severely deteriorated, and the durability of the mold against fog is short.

Further, even if the glass whose volatile component from the glass is reduced in the glass surface layer portion by heat treatment in a vacuum or the like is used, deterioration of the surface roughness can be prevented, but fusion cannot be prevented.

Accordingly, it is an object of the present invention to provide a method for producing an optical element, in which fogging failure of a molded product due to fusion of glass and mold at high temperature and reduction of surface roughness of the mold is improved.

[0014]

That is, according to the present invention, a glass material containing an alkali component in a softened state is pressed with a molding die to provide an optical functional surface corresponding to the molding surface of the die. A method for producing an optical element to be formed on a glass material, the method comprising producing the optical element by adjusting the amount of an alkali component of a surface layer of the glass material up to a depth of 50 nm to 1 to 20 mol% and then pressing the glass. when creating the glass in the material in the molten state, by cooling with a viscosity at 10 ² dPa · s and comprising a temperature of 10 ° C. / sec or more cooling rate of the glass, of the surface layer Al
Decrease the amount of potassium component to reduce the amount of alkali component to 1-2.
It is a method for manufacturing an optical element, which is characterized in that the content is 0 mol%.

[0015]

[0016]

[0017]

In the present invention, by adopting the above-mentioned constitution, the mold releasability is improved and fusion is prevented, and the deterioration of the mold due to the alkaline component is minimized.

Table 1 shows the results of an examination of the formability of glass with various amounts of alkali components and several types of mold materials. FIG. 1 shows the target lens shape.

The glass includes SiO ₂ , B ₂ O ₃ and B.
With aO as a basic component, Li ₂ O as an alkaline component,
A mixture of one or more of Na ₂ O and K ₂ O was used. As the mold material, amorphous carbon prepared by an ion mixing method as a carbon-based material, platinum (Pt), titanium nitride (TiN), and tungsten carbide (WC) were used. Here, the results of amorphous carbon as a carbon-based material are shown, but almost the same results were obtained for other graphite, diamond, and hydrogenated amorphous carbon. In addition, silicon carbide (Si
C), silicon nitride (SiN), etc. gave similar results to TiN.

First, as shown in Table 1, with respect to the glass containing no alkali component (No. 1), fusion occurred at 1 shot in any type, and the alkali component was 5 mo.
Regarding the glass containing 1% or more, except for the TiN type, no fusion occurs, so it is understood that an alkali component is necessary to prevent fusion.

Except for TiN type, when the amount of alkali component is 20 mol% or less, the fog durability is greatly increased compared to 25 mol%, and in the case of amorphous carbon type, Li ₂ O is used.
If it is 1 mol% (No. 5), the fog durability is 2200 s.
Extends to hot.

As described above, in the case of a glass having an alkali content of 1 to 20 mol% as a glass component, the fog durability of the mold is greatly extended. Especially, by using amorphous carbon or platinum for the mold, fusion prevention and a great improvement of the mold durability are achieved. Can be achieved. However, the glass used as the optical glass needs to have various optical constants, and therefore has various glass compositions. Therefore, the amount of alkali components in the surface layer of the glass material up to a depth of 50 nm is 1 to 20 mol%, preferably 1 to 5
By using mol% and preferably a carbon material or platinum as a mold material, fusion prevention and mold durability can be improved.

Here, attention was paid to the amount of alkali components in the surface layer up to a depth of 50 nm, because the composition ratio of the treatment layer largely changes from the diffusion rate of the alkali components in the glass at high temperature, and if it is less than this, diffusion occurs. This is because the glass base material is affected by the alkali component, and when it exceeds this, the glass base material and the surface layer have different viscosities, and thus cracks are generated in the glass surface layer during pressing. In addition, since the diffusion rate of the alkali component influences, the molding temperature is 10 ⁸ to
In the temperature range of 10 ¹³ dPa · s and when the molding time is on the order of minutes, the amount of alkali up to 50 nm of the glass surface layer has an influence, and when the molding temperature or time changes extremely, this thickness naturally changes.

[0025]

[Table 1]

[0026]

EXAMPLES The present invention will be described below based on examples. Reference Example 1 The lens used here has a refractive index n _d = 1.8071.
1, glass A with dispersion ν _d = 22.8 and n _d = 1.5
8313 and glass B having ν _d = 59.4, both of which are shown in FIG.
The shape shown in FIG. The compositions of these two types of glass are shown in Table 2.

[0027]

[Table 2]

These glasses were ground and polished into a shape similar to that shown in FIG. 1 and then heat-treated in vacuum to obtain amorphous carbon and P.
It was molded with a t and TiN mold. The amount of alkali component on the glass surface was changed by changing the heat treatment temperature in vacuum (holding time was 4 hours). The composition ratio and the processed thickness were measured by a secondary ion mass spectrometer (SIMS).

Both the A and B glasses were pressed at a viscosity of 10
Temperature corresponding to ^9.8 dPa · s (Glass A is 608 ° C,
Glass B is performed at 614 ° C., and at a cooling rate of 60 ° C./min, the viscosity is 10 ¹⁵ dPa · s (450 ° C.).
The molded lens was taken out after cooling to below (° C.). Here, the time during which the glass had a viscosity of 10 ¹³ dPa · s or less was 5 minutes or less.

Table 3 shows the surface composition of each glass and the molding results.

[0031]

[Table 3]

Glass A has an alkali content of 30 mol%
Because of the above content, the amount of alkali component up to 50 nm on the surface layer (average value up to 50 nm on the surface layer, the same applies below) in the one treated at 550 ° C. for 4 hours was 10 mol%, and the cloudiness durability of the amorphous carbon type was extended to 800 shot. However, the one treated at 600 ° C. had an excessively large treatment thickness and had cracks on the glass surface during pressing.

On the other hand, since the amount of the alkali component in the glass B is originally 8 mol%, even if it is not treated, it is an amorphous carbon type and has a fog durability of 800 shot.
By treating at 50 ° C. for 4 hours, the amount of alkali components in the surface layer up to 50 nm becomes 2 mol%, and the haze durability is 1500.
It extended to shot. However, the amount of alkali component becomes 0.1 mol% by treating at 610 ° C. for 4 hours,
Fusion occurred.

In the case of the TiN type, fusion occurred under any condition.

As described above, the amount of the alkali component up to the surface layer of 50 nm is 1 to 20 mol%, preferably 1 to 5 mol%.
In addition, by using the amorphous carbon type or the platinum type, it was possible to prevent fusion and extend the fog durability of the type.

Example 1 In this example, a glass material was made directly from molten glass, not by grinding and polishing, into a shape similar to a molded article. Here, the amount of alkali component on the glass surface was changed by changing the cooling rate from 10 ² dPa · s depending on the viscosity of the glass. Other than this, the shape of the lens, the type of glass, and the mold material are the same as in Reference Example 1.

Molding was carried out under the same conditions as in Reference Example 1.

Table 4 shows the surface composition of each glass and the molding results.

[0039]

[Table 4]

In the case of the glass A, when the cooling rate from the viscosity of 10 ² dPa · s is 2 ° C./sec, the haze durability is 8 shot even with the amorphous carbon type, but when it is 10 ° C./sec or more, the amount of the alkali component in the surface layer of the glass is 20 mol. % Or less, with the exception of the TiN type, the fog durability was greatly extended.

On the other hand, since the amount of the alkaline component in Glass B is originally 8 mol%, the cooling rate is 2 ° C./s.
Even in ec, it is an amorphous carbon type and has a cloud resistance of 800 sh
However, at 30 ° C./sec, the amount of alkali components up to the surface layer of 50 nm is 4 mol%, and the haze durability is 1100.
It extended to shot.

Therefore, the viscosity of the glass is 10 ² dPa · s.
It can be seen that at the above temperatures, the amount of alkali components volatilized from the glass surface is large, and by increasing the cooling rate from that temperature, the state in which the amount of alkali components on the glass surface is small can be frozen.

In the case of the TiN type, fusion occurred under any condition.

Thus, the viscosity of the glass is 10 ² dPa ·
The cooling rate from s is 10 ° C./sec or more, and a glass material having an approximate shape to the molded lens is directly produced from the molten glass, so that the amount of the alkali component up to the surface layer 50 nm is 1 to 20 mol%, preferably 1 to 5 mol%. In addition, by using the amorphous carbon type or the platinum type, it was possible to prevent fusion and extend the fog durability of the type.

Reference Example 2 In this Reference Example, a glass material which had been ground and polished into a shape similar to that shown in FIG. 1 and then immersed in a 3N nitric acid solution at 26 ° C. was used. Here, the amount of alkali component on the glass surface was changed by changing the treatment time. Other than this, the shape of the lens, the type of glass, and the mold material are the same as in Reference Example 1.

Molding was carried out under the same conditions as in Reference Example 1.

Table 5 shows the surface composition of each glass and the molding results.

[0048]

[Table 5]

When the glass A was soaked for 100 seconds, the amount of alkali component was 6 mol%, and the cloudiness durability of the amorphous carbon type was extended to 900 shot. But 1
When it was immersed for 50 seconds, it became 0 mol%, and fusion occurred regardless of which mold was used.

On the other hand, when the glass B is soaked for 100 seconds, the amount of alkali becomes 2 mol% and the fog durability is 15
However, the treated layer was thick and the amount of alkali was 0 mol% at 150 seconds or more, so that fusion or cracking occurred in the surface layer portion.

In the case of the TiN type, fusion occurred under any condition.

Thus, by immersing the glass material in the acidic solution, the amount of the alkaline component up to the surface layer of 50 nm is adjusted to 1 to 20 mol%, preferably 1 to 5 mol%,
By using the amorphous carbon type or the platinum type, it was possible to prevent fusion and extend the fog durability of the type.

Although 3N nitric acid was used in this reference example, it is also possible to use other acidic solutions such as sulfuric acid and hydrochloric acid.

[0054]

As described above, according to the present invention,
When creating a glass material from molten glass,
Lath viscosity : cooling rate from 10 ² dPa · s to 10 ° C
/ Sec or more, the amount of alkali on the glass surface
It is possible to control various types of glass.
As a result, it is possible to prevent fusion and improve the fog durability of the mold.

In the present invention, a carbon material (amorphous carbon, graphite, diamond, hydrogenated amorphous carbon) or platinum is used as the mold material.
If so , the mold releasability and the durability against clouding of the mold can be further improved.

[0056]

[0057]

[0058]

[0059]

[Brief description of drawings]

FIG. 1 is a diagram showing dimensions of a convex lens targeted in an example.

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Nao Miyazaki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Kiyoshi Yamamoto 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (56) References JP-A-6-279034 (JP, A) JP-A-4-321525 (JP, A) JP-A-1-239030 (JP, A) JP-B-61-32263 (JP, B1) (58) Fields investigated (Int.Cl. ⁷ , DB name) C03B 11/00

Claims (3)

(57) [Claims] 1. A softened state, containing an alkaline component
A method of manufacturing an optical element, comprising forming a glass material having an optical functional surface corresponding to the molding surface of the mold by pressing the glass material with a molding die, the depth of the glass material being 50 nm.
In the method for producing an optical element by adjusting the amount of the alkaline component in the surface layer to 1 to 20 mol% and then pressing, when the glass material is made from glass in a molten state, the viscosity of the glass is 10 ² dPa · By cooling at a cooling rate of 10 [deg.] C./sec or more from the temperature of s , the amount of the alkaline component of the surface layer is reduced, and the amount of the alkaline component is 1 to 20 mol%. A method for manufacturing an optical element, comprising: 2. The method for producing an optical element according to claim 1, wherein the molding surface of the molding die is made of amorphous carbon, graphite, diamond or hydrogenated amorphous carbon. 3. The method of manufacturing an optical element according to claim 1, wherein the molding surface of the molding die is made of platinum.