JPH0477321A - Glass blank for producing optical element - Google Patents

Abstract

PURPOSE:To prevent the melt sticking of a glass blank to die members and to also prevent the clouding and coloring of a molded body by adhering a specified coat to the surface of the glass substrate of the glass blank when the blank is used as stock for molding at the time of producing an optical element by press molding. CONSTITUTION:When a glass blank is used as stock for molding at the time of producing an optical element by press molding, a hydrocarbon coat 4 such as a CH4 coat is adhered to the surface of the glass substrate 2 of the glass blank forming at least optical functional faces.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a glass blank used as a molding material in press molding of optical elements such as lenses, and in particular to a glass blank used as a molding material in press molding of optical elements such as lenses. The present invention relates to a glass blank for obtaining good optical elements by reducing cracking and preventing cracking during the cooling process.

[Prior art and problems to be solved by the invention] Conventionally,
In order to obtain a good molded product in glass reheat pressing, it has been a major issue to prevent fusion between the molding material glass and the molding die member. For this reason, various techniques for improving mold members have been proposed in the past, and in recent years, improvements in molding materials have begun to be proposed in order to further prevent the above-mentioned fusion. Proposals for improving such molding materials include, for example, Japanese Patent Publication No. 2-1778, Japanese Patent Publication No. 2-1779, Japanese Patent Publication No. 2-1780, and Japanese Patent Publication No. 61-29890. It is disclosed that a glass coating having a glass transition temperature higher than that of the glass substrate, a silicon oxide coating, or a carbon coating is applied to the surface of the glass substrate. Further, Japanese Patent Application Laid-Open No. 1-264937 discloses disposing a thin layer of an organic material on the surface of a glass substrate.

Although the above-mentioned improvements have the effect of preventing fusion with the mold member, the method disclosed in the above-mentioned publication has the following problems.

(b) When a glass coating with a glass transition temperature higher than that of the glass substrate is applied to the surface of the glass substrate, the coating glass layer cracks due to the press pressure and oozes into the substrate glass, causing partial damage to the surface. Clouding may occur, partial fusion may occur with the mold member, or the frictional force between the glass blank and the mold member may increase during the cooling process (as a result, cracks may occur in the glass).

(b) When a silicon oxide coating is applied to the surface of the glass substrate, the same problem as in (a) above occurs; in particular, silicon oxide is easy to crack during the cooling process because it blends well with mold members; Silicon oxide has a thermal expansion coefficient significantly lower than that of ordinary optical glass constituting the glass substrate, so the coating tends to crack when heated.

(c) When a carbon coating is applied to the surface of a glass substrate to be thicker than necessary, since carbon is a reducing agent, it also reacts with oxygen in the glass to reduce the glass components and color the glass brown. In particular, when a lead-containing glass is used as the glass substrate, PbO in the glass is reduced, resulting in significant coloring and a decrease in transmittance.

(d) When a thin organic layer is placed on the surface of a glass substrate, the thin organic layer decomposes during heating and may generate corrosive gas (e.g. chlorine gas or fluorine gas), causing There is a problem in that it tends to contaminate the molding equipment and impair the durability of the equipment including the mold member. Furthermore, since the above-mentioned decomposition occurs locally and randomly, the surface precision may deteriorate.

In view of the above-mentioned problems of the prior art, the present invention has been developed to prevent fusion of glass blanks and mold members, as well as to prevent molded products from becoming fused, discolored, cracked, and with a decrease in surface precision. The purpose is to prevent

[Means for Solving the Problems] According to the present invention, the above object is achieved by providing a glass blank used as a molding material when manufacturing an optical element by press molding, which comprises at least an optical fiber of a glass substrate. Provided is a glass blank for manufacturing optical elements, characterized in that a hydrocarbon coating is applied to the surface on which a functional surface is formed.

Here, by setting the thickness of the hydrocarbon coating to, for example, 10 to 50, a trace amount of reactive gas layer is formed at the interface between the mold member and the glass blank, and the adhesion between the mold member and the glass blank is increased. It is possible to prevent fusion and cracking. Compared to the carbon coating layer, the hydrocarbon coating layer has
Because the film contains a large amount of CHa at the same film thickness,
The ultra-thin layer (10~
(50 people thick) is sufficient.

Further, as a method for forming the hydrocarbon coating layer, a method that has good coverage for the glass blank, such as high frequency discharge treatment of hydrocarbon gas, ion gun treatment, or direct current discharge treatment, can be used; It has the advantage of being a low-cost treatment method.

[Example] Hereinafter, specific examples of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing one embodiment of a glass blank according to the present invention. This embodiment shows an example in which the optical element is a biconvex lens.

In FIG. 1, numeral 2 denotes a glass substrate which is a material for press molding. As the glass substrate, an optical glass having a refractive index value and dispersion value necessary to obtain a lens with desired optical characteristics is used. The glass substrate 2 is finished to have a shape and dimensions that approximate the shape of the intended lens.

A hydrocarbon coating 4 is applied to the surfaces (upper and lower surfaces) of the glass substrate 2 on which the optically functional surfaces are formed. The thickness of the hydrocarbon coating is, for example, 10 to 50, preferably 15 to 3
There are 5 people. If the thickness of the hydrocarbon coating is too thin, the effect will not be sufficient, and if it is too thick, there is a high possibility that the film will peel off.

The hydrocarbon coating 4 can be formed using thin film deposition techniques such as plasma treatment or ion gun treatment. The carbon:hydrogen atomic ratio in the hydrocarbon coating 4 is, for example, 10
76 to 1010.5, particularly preferably 1015 to 10/1.

FIG. 2 is a schematic diagram showing the general configuration of a thin film deposition apparatus used for manufacturing the glass blank of the above embodiment. below,
An example of blank manufacturing will be explained with reference to this figure.

In FIG. 2, 12 is a vacuum chamber, and 14 is an exhaust port formed in the vacuum chamber. The exhaust port is connected to a vacuum exhaust source (not shown). 16 is a gas introduction port for introducing gas into the vacuum chamber 12. The gas inlet is connected to a gas source (not shown).

Inside the vacuum chamber 12, a dome-shaped holder 22 for holding the glass substrate, a heater 24 for heating the glass substrate, and a crystal film thickness monitor 26 for measuring the coating thickness are arranged at the top. 28 is a high frequency application antenna. Note that 30 is a glass substrate held by the holder 22.

When applying the hydrocarbon coating 4 to the surface of the glass substrate 30 (2), exhaust is exhausted from the exhaust port 14 to reduce the pressure inside the vacuum chamber 12, and then a hydrocarbon gas, for example 5XlO- ”～5x10-'T o r r
A high frequency wave of, for example, 100 to 500 W is applied to the high frequency application antenna 28 to form hydrocarbon plasma.

Examples of the hydrocarbon gas introduced into the vacuum chamber 12 include methane, ethane, propane, ethylene, propylene,
Examples include acetylene.

Since the carbon:hydrogen atomic ratio in the hydrocarbon coating 4 changes depending on the deposition conditions, the conditions are set so as to obtain the desired atomic ratio.

Next, an example in which the glass blank of the above embodiment was manufactured using the above-described apparatus will be described.

A glass substrate 3o made of flint optical glass (SF8) polished into a predetermined shape was cleaned and set in the holder 22. Heat to 300"C with heater 24 and vacuum chamber 1.
After evacuating through the exhaust port 14 until the degree of vacuum inside the chamber became 1X10-'Torr or less, Ar gas was introduced from the gas inlet 16 until the vacuum level reached 5X10-'Torr. and,
A high frequency of 300 W was applied to the high frequency application antenna 28 to generate high frequency discharge, and plasma cleaning of the glass substrate 3o was performed. After that, the introduction of Ar gas was stopped,
Return the vacuum to lXl0-'Torr and open the gas inlet port 1.
6 color CH, Kasuworu X 10-”T.

It was introduced until it reached rr. Then, a high frequency of 200 W was applied to the high frequency application antenna 28 to generate a high frequency discharge, thereby forming a hydrocarbon coating 4 having a thickness of about 30λ. The atomic ratio of carbon to hydrogen in the hydrocarbon coating 4 was approximately 10/2 as measured by infrared spectroscopy.

FIG. 3 is a sectional view showing an example of an apparatus in which press molding is performed using the glass blank obtained as described above.

In FIG. 3, 32 is the vacuum chamber body, and 34 is its lid. Reference numerals 36, 38, and 40 are an upper mold member, a lower mold member, and a body mold member for press-molding lenses, respectively. 42 is a mold holder, and 44 is an upper mold member presser.

46 is a heater, 48 is a push-up rod for pushing up the lower mold member, and 50 is a cylinder for operating the push-up rod. 52 is a vacuum pump;
4.56, 58.60 are valves, 62 is a pipe for introducing non-oxidizing gas such as nitrogen gas, 64 is a leak pipe, and 66 is a valve. 68 is a temperature sensor, and 70 is a water-cooled vibrator. 72 is a vacuum chamber support member.

The upper mold member 36, the lower mold member 38, and the body mold member 40 are made of, for example, cemented carbide, S l Na H3iC,
Sialon, Cermet, AttoriOs+Zr0t, C
If necessary, Sis is added to the surface of the base material made of rz Ox, etc.
N4, TiN, TaN, BN.

A material coated with AIN, SiC, TaC, WC, platinum alloy, etc. can be used.

Next, an example in which the glass blank of the above embodiment was press-molded using the above-described apparatus will be described.

The upper mold member 36 and the lower mold member 38 are made of SiSN4, and the surfaces of these mold members for forming the optically functional surface have a surface accuracy of 3 newtons or less and a center line average surface roughness of 0.02 μm or less. did.

A glass blank is placed in the mold, and the inside of the vacuum chamber is
``The vacuum chamber was evacuated until the pressure became below Torr, and then nitrogen gas was introduced into the vacuum chamber.

After heating to 530° C., the cylinder 50 was activated to press at a pressure of 100 kg/cm” for 5 minutes. Thereafter, the temperature was gradually cooled to 200° C. or lower.

Then, air was introduced into the vacuum chamber, the mold was opened, and the molded product was taken out.

100 lenses were molded in the manner described above.

When the functional surface of the obtained lens was observed with a scanning electron microscope at a magnification of 3750 times, no surface defects were observed, and both surfaces were free from coloration and cloudiness.

Furthermore, no cracking occurred in the molded product. Furthermore, the surface precision of both surfaces of the lens was good.

[Effects of the Invention] As explained above, according to the present invention, by applying a hydrocarbon coating to at least the surface on which the optically functional surface of the glass substrate is formed, fusion between the glass blank and the mold member can be prevented. In addition, it is possible to prevent clouding, discoloration, cracking, and deterioration of surface precision in the molded product.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing an embodiment of a glass blank according to the present invention. FIG. 2 is a schematic diagram showing the general configuration of a thin film deposition apparatus used for manufacturing the glass blank of the above embodiment. FIG. 3 is a sectional view showing an example of an apparatus in which press molding is performed. Figure 1 Figure 2 2 Glass substrate, 4: Hydrocarbon coating, 12: Vacuum chamber, 16: Gas inlet, 24: Heater,
28: High frequency antenna, 30 glass substrate.

Claims (2)

[Claims] (1) A glass blank used as a molding material when manufacturing optical elements by press molding, characterized in that a hydrocarbon coating is applied to at least the surface on which the optically functional surface of the glass substrate is formed. Glass blank for manufacturing optical elements. (2) the thickness of the hydrocarbon coating is 10 to 50 Å;
The glass blank for manufacturing an optical element according to claim 1.