JPH0477322A - Glass blank for optical element manufacturing - Google Patents

Abstract

PURPOSE:To prevent the reaction of a glass blank with die members and the melt sticking of the blank to the members and to also prevent the clouding and coloring of a molded body by adhering plural specified coats 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 reaction preventing coat 3 such as a vapor-deposited glass coat and a hydrocarbon coat 4 such as a CH4 coat are successively 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 [Industrial Application Field] 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 that prevents reaction with mold members during pressing and has a material that adheres tightly. The present invention relates to a glass blank for obtaining good optical elements by reducing force and frictional force 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 coating of glass 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, causing cracks 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.

Therefore, in view of the above-mentioned problems of the prior art, the present invention aims to prevent the reaction between the glass blank and the mold member to prevent the molded product from forming, and also to prevent the fusion between the molded product and the mold member. The purpose is to prevent cracking and discoloration.

[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 an optical element, characterized in that a reaction prevention coating and a hydrocarbon coating are applied in this order to the surface on which a functional surface is formed.

Here, in order to prevent the glass blank from reacting with the mold member at the molding temperature and causing the glass blank to become cloudy, the reaction prevention coating is preferably made of a substance having a higher melting point than the glass blank, such as Alx 03. .5iOa
, MgFz or vapor deposition glass. In addition, the thickness of the reaction prevention coating has a lower limit of the thickness at which the glass component does not diffuse through the reaction prevention coating layer and reaches the surface of the mold member at the molding temperature, and an upper limit of the thickness at which no cracks occur during molding.
For example, 100 to 500 people.

In addition, the above-mentioned hydrocarbon coating is achieved by forming an extremely small amount of reactive gas layer at the interface between the mold member and the glass blank.
This reduces the adhesion between the mold member and the glass blank to prevent fusion and cracking. For this purpose, the thickness of the hydrocarbon coating layer is, for example, from 10 to 50 mm. If the thickness of the hydrocarbon coating layer is too thin, a sufficient effect of reducing adhesion cannot be obtained, and if the thickness of the hydrocarbon coating layer is too thick, the molded article will be significantly colored and the transmittance will be lowered. Therefore, if the thickness is made too thick, it becomes necessary to remove the hydrocarbon film remaining on the surface of the glass blank after molding and the reaction product between the hydrocarbon film and the glass in a post-process, such as an annealing process. .

Compared to a carbon coating layer, a hydrocarbon coating layer contains a large amount of CH2 at the same thickness, so it does not significantly reduce the transmittance of the glass blank, and it also prevents fusion and cracking. The prevention effect is an extremely thin layer (10 to 50 people thick)
But it's enough.

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 an embodiment of a glass blank according to the present invention. This example 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 reaction prevention coating 3 and a hydrocarbon coating 4 are applied in this order to the surfaces (upper and lower surfaces) of the glass substrate 2 on which the optically functional surfaces are formed.

As the reaction prevention coating 3, for example, At.

Os, 5ins, MgFa or vapor deposition glass can be used. The thickness of the anti-reaction coating 3 is, for example, 100 to 500 mm. The anti-reaction coating 3 can be formed using thin film deposition techniques such as vacuum evaporation.

The thickness of the hydrocarbon coating is, for example, 10-50, preferably 15-35. If the thickness of the hydrocarbon coating is too thin, the effect will not be sufficient, and if it is too thick, the transmittance of the molded article will be significantly reduced and an annealing step will be required. The hydrocarbon coating 4 can be formed using simple 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, 10/6 to 1010.5, particularly 10/15 to 10/10/1.
1 is preferred.

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).

In the vacuum chamber 2, an evaporation source 18 and a shutter 20 are arranged at the bottom, and a dome-shaped holder 22 for holding the glass substrate, a heater 24 for heating the glass substrate, and a coating thickness measuring device are arranged at the top. A crystal film thickness monitor 26 is arranged for this purpose. 28 is a high frequency application antenna. Note that 30 is a glass substrate held by the holder 22.

When applying the anti-reaction coating 3 and the hydrocarbon coating 4 to the surface of the glass substrate 30 (2) in this order, exhaust the air from the exhaust port 14 to reduce the pressure inside the vacuum chamber 12, and then remove the evaporation source 18 from the evaporation source 18. The anti-reaction coating forming material is evaporated, and then hydrocarbon gas is introduced from the gas inlet 16, for example, 5×10-”
A high frequency of 100 to 500 W, for example, 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, wear something like the above! An example in which the glass blank of the above example was manufactured using the following will be described.

A glass substrate 30 made of flint-based optical glass (SF8) polished into a predetermined shape was cleaned and set in the holder 22. Heating to 300°C with heater 24, vacuum chamber 12
After evacuating through the exhaust port 14 until the degree of vacuum inside became 1X10"" Torr or less, Ar gas was introduced from the gas introduction 016 until the vacuum level reached 5X10-'Torr. Then, 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 30 was performed. After that, the introduction of Ar gas was stopped, and l
The vacuum level was returned to Xl0-'Torr, and the glass for deposition was evaporated from the evaporation source 18 to form a reaction prevention coating (glass layer for deposition) 3 of about 300 ml. Next, evaporation from the evaporation source 18 was stopped, and CH and gas were introduced from the gas inlet 16 until the temperature reached lXl0-''Torr. Then, a high frequency of 400 W was applied to the high frequency application antenna 28 to generate high frequency discharge. 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;
54, 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 * N4+SiC,
Sialon, Cermet, Alz Os.

Six N4, TiN, TaN, BN is applied to the surface of the base material made of Zr0z, Cry Ox, etc. as necessary.

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 5ixN4, and the surfaces of these mold members for forming optical functional surfaces have a surface accuracy of 3 newtons or less and a center line average surface roughness of 0.
．． It was set within 0.02 μm.

Place the glass blank in the mold, and place the 1XIO- in the vacuum chamber.
``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/am” 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.

Moreover, no fusion occurred with the mold member, and no cracking of the molded product occurred. Furthermore, the surface precision of both surfaces of the lens was good.

[Effect of the Invention J As explained above, according to the present invention, by applying a reaction prevention coating and a hydrocarbon coating in this order to a small portion of a glass substrate (both surfaces on which an optically functional surface is formed), a glass blank can be formed. In addition to preventing reaction with mold members and preventing fusion, it is possible to prevent cloudiness, coloring, cracking, and deterioration of surface precision in the molded product.

30 Ni glass substrate.

Claims (4)

[Claims] (1) A glass blank used as a molding material when manufacturing optical elements by press molding, in which a reaction prevention coating and a hydrocarbon coating are applied in this order to at least the surface on which the optical functional surface of the glass substrate is formed. A glass blank for manufacturing optical elements, which is characterized by: (2) The reaction prevention coating is Al_2O_3, SiO_2
, MgF_2 or vapor deposition glass, according to claim 1 . (3) The glass blank for manufacturing optical elements according to claim 1, wherein the reaction prevention coating has a thickness of 100 to 500 Å. (4) the thickness of the hydrocarbon coating is 10 to 50 Å;
The glass blank for manufacturing an optical element according to claim 1.