JPH04367530A - Glass optical element producing device - Google Patents

Abstract

PURPOSE:To dispense with the exchange of a frequently used mold having a boron nitride film on the forming face and the modification of the forming face. CONSTITUTION:Upper mold 1 and lower mold 2 in which forming faces 1a and 2a are opposed are arranged in a vessel 3, which is constituted so as to be hermetically sealable. An antenna for high-frequency wave 6 is arranged around the upper mold 1 and lower mold 2. When boron nitride film of the forming faces 1a and 2a is released by forming of glass optical element and shape and surface roughness of the mold become worse, nitrogen gas and boron chloride gas are introduced into the vessel 3 and plasma is generated from the antenna for high-frequency wave 6 in closed state and boron nitride film is deposited on the forming face and used for forming in the next stage as such.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a manufacturing apparatus for molding a glass optical element into a desired shape by pressing a heated and softened glass material.

0002

[Prior Art] Glass optical elements have traditionally been manufactured by pressing a heat-softened glass material in a mold, but the molding surface of the mold used for such manufacturing is , mold releasability that prevents softened glass materials from fusing is required. This mold releasability is especially required in the case of molding without preforming since the viscosity of the glass material is low. In order to provide such mold releasability, a mold containing boron nitride (BN) as a main component has conventionally been used, as described in Japanese Patent Publication No. 61-317. This is because BN has a hexagonal crystal structure and is loosely bonded in the C-axis direction, so that BN has the property of being peeled off very thinly during molding of a molded glass optical element.

0003

[Problem to be solved by the invention] However, when releasing the mold, BN
Even when peeling is extremely thin, the shape of the molding surface of the mold changes in roughness, and the accuracy of the molding surface deteriorates over time. For this reason, glass optical elements that require highly accurate shapes and roughness have a short usable life cycle, with the problem that they can withstand only about 100 uses at most. Therefore, in the past, the mold had to be removed from the manufacturing equipment every time the life cycle progressed, and the molding surface had to be processed and corrected, or the mold had to be replaced with a new mold, which required troublesome work.

[0004] The present invention has been made in consideration of the above circumstances, and even with a high-precision molded surface mainly composed of BN, it can be used for a long period of time without the need for processing corrections or replacement of molds. An object of the present invention is to provide a glass optical element manufacturing apparatus that can perform the following steps.

[0005]

Means and Effects for Solving the Problems The glass optical element manufacturing apparatus of the present invention comprises: a mold having a molding surface for molding a heated glass material; a sealable container housing the mold; The method is characterized by comprising a film forming means for forming a boron nitride film on the molding surface of the mold while the container is in a sealed state.

FIG. 1 shows the basic configuration of the present invention, in which a molding surface 1
A mold consisting of an upper mold 1 and a lower mold 2 facing each other, a container 3 that stores the upper mold 1 and the lower mold 2, and the upper mold 1,
A high frequency antenna 6 is provided as a film forming means for forming boron nitride on the molding surfaces 1a and 2a of the lower mold 2. Here, the container 3 has an exhaust port 4 and a gas inlet 5 for introducing a reaction gas containing nitrogen gas (N gas) and boron gas (B gas). Mouth 5
By closing, the inside becomes airtight. On the other hand, the high-frequency antenna 6 generates plasma in the container 3 by supplying high-frequency power, and decomposes the B gas and the N gas to atomize or ionize them. The atomized or ionized B and N become a BN thin film and are deposited on the molding surfaces 1a and 2a of the upper mold 1 and the lower mold 2. In this case, plasma is generated by opening a part of the container 3 and passing through the opening into the container 3.
It can also be configured to supply microwaves inside.

FIG. 2 shows another configuration of the film forming means, in which the upper mold 1
, a lower mold 2 is inserted into a cylindrical sleeve body 7, and a high frequency antenna 6 is provided on the outside of this sleeve body 7. The sleeve body 7 is formed of a sintered body mainly composed of BN, and the upper mold 1 or the lower mold 2 is inserted into the sleeve body 7.
slides. Further, a gas introduction hole 8 is formed in the side surface of the sleeve body 7 located between the molding surface 1a of the upper mold 1 and the molding surface 2a of the lower mold 2. Plasma can be generated within the sleeve body 7 by supplying high frequency power to the high frequency antenna 6 while inert gas or N2 gas is introduced into the sleeve body 7 through the gas introduction hole 8. Then, since the BN of the sleeve body 7 is sputtered by the positive ions in the generated plasma, the molding surface 1
A BN film can be deposited on a and 2a. Note that the upper mold 1 and lower mold 2 in FIGS. 1 and 2 may be made of a heat-resistant, high-strength base material such as cemented carbide or carbon silicon.

[0008] The thickness of the BN film formed by the film forming means is 1 μm to 0.0 μm in the case of high-precision glass optical element molding.
A thickness of about 1 μm is good. If the thickness of the BN film exceeds this range, the inherent strength of the BN film becomes dominant and the required strength for the mold cannot be obtained, while in the following cases, the frequency of BN film deposition increases. It is. Therefore, it is preferable to form the BN film in one molding process, and to perform it every predetermined number of moldings, with reference to how much the surface roughness of the molding surfaces 1a and 2a of the mold deteriorates. For example, there is a deterioration in accuracy of about 10 Å in one molding process, and if the required surface roughness is 0.1 μm or less, it is necessary to form a film every 100 times. This film formation fills in the concave portions, making it possible to reproduce a flat molding surface. In addition, the container 3 having such a configuration
is installed between a heating section that heats and softens the glass material and a cooling section that cools and anneals the formed glass optical element (both not shown).

In the above structure, the glass material softened in the heating section is supplied onto a mold on which a BN film has been previously formed on the molding surface. After molding the glass optical element by pressing for a predetermined time, it is released from the mold, transported to a cooling section, and taken out after being cooled for a predetermined time. After repeating this cycle a predetermined number of times (for example, 100 times), a gas containing boron and nitrogen is introduced into the container 3 at a predetermined pressure after exhausting the gas used during molding. Plasma is generated by supplying high frequency power or microwave power, and a BN film is deposited on the molding surface of the mold. After a predetermined period of time, power supply and gas introduction are stopped.
The reaction gas is exhausted and the gas used in normal molding is resupplied. Then, the molding cycle is repeated again. After repeating the molding a predetermined number of times as described above, the cycle of forming a BN film on the molding surface of the mold is repeated with the mold as it is.

0010

[Embodiment 1] FIG. 3 shows embodiment 1 of the present invention, in which the heating section 1
0, the molding section 11, and the cooling section 12 are arranged in succession in this order. The heating unit 10 has a heater 13 made of silicon carbide or the like disposed therein, and has a normal upper limit temperature of about 1300°C. The glass material is placed on a sialon body mold and heated in this heating section 1.
After being heated, the material is transferred to the molding section 11 by a carry-in arm. Reference numeral 14 denotes an entrance shutter that is provided at the boundary between the heating section 10 and the molding section 11 and is openable and closable.

The molding section 11 has an upper mold 15 in a sealable container.
, and the lower molds 16 are arranged to face each other. The upper mold 15 and the lower mold 16 are made of cemented carbide as a base material, and their molding surfaces 15a,
A BN film with a thickness of 0.1 μm is formed on the layer 16a. The upper mold 15 and the lower mold 16 each have a ring-shaped heater 29,
28, which is heated to a temperature that matches the type of glass material. In the illustrated example, the upper mold 15 is fixed, while the lower mold 16 is connected to a pressure mechanism 20 and moves up and down, and its upward movement presses the glass material. Further, a coil-shaped high frequency antenna 21 is provided around the upper mold 15 and lower mold 16 with a distance of 10 mm from each mold 15 and 16. This antenna 21 is connected to a matching box 17 and a high frequency power source 18 provided outside the molded part 11. 19 is a hydraulic exhaust pump for exhausting the gas in the molding section 11; 22 is an exhaust shutter that communicates and blocks the molding section 11 and the cooling section 12; 30 is the molding section 1;
This is a vacuum gauge that detects the pressure inside 1. Furthermore, the molding part 1
A gas introduction pipe 24 is inserted into 1, and this gas introduction pipe 24 is connected to an N2 gas cylinder 26 and a BCl gas cylinder 27 via a switching valve 25.

A heater 23 made of silicon carbide or the like is provided inside the cooling section 12, and the temperature is maintained at about 200.degree. The glass optical element molded in the molding section 11 is introduced into the cooling section 12 by a carry-out arm, and is taken out from the cooling section 12 after being cooled for a predetermined period of time.

Next, the operation of the first embodiment will be explained. SF11 optical glass was used as the glass material and mirror-finished into a spherical shape with a radius of 10 mm. The upper mold 15 and the lower mold 16 both have a diameter of 22 mm and a length of 50 mm, and the molding surface 15a of the upper mold 15 is mirror-finished to have a concave radius of 30 mm, and the molding surface 16a of the lower mold 16 has a radius of 100 mm. First, the glass material was heated for 1 minute in the heating section 10 in an atmosphere of about 700.degree. C., and then transferred onto the lower die 16 of the forming section 11. The upper mold 15 and the lower mold 16 were heated to 550° C., and molding was carried out for 10 seconds under a pressure of a total load of 100 kgf. At this time, the inside of the molding section 11 is filled with N2 gas at 1 atmosphere. The molded glass is transferred to the cooling section 12, held for 1 mm, and then taken out. After repeating the above cycle 100 times, a film forming process was performed. First, BCl gas is supplied into the molding section 11 at 10 cc/min using the switching valve 25, and after about 1 minute, the gas ratio in the molding section 11 is brought into equilibrium. In this state, 500W of high frequency power is applied to the antenna 21.
Generate plasma from. After forming a film for 17 minutes, the switching valve 25 is turned to the N2 gas cylinder 26 side to stop the supply of BCl gas and the power supply. Under these conditions, the film thickness is 0.
．． A BN film with a thickness of 0.05 μm could be formed. and,
After this film formation, the molding cycle was performed again.

When molding was performed a total of 5,000 times in the above steps, the molded glass optical element maintained high precision. Further, no burn-in occurred at all. In addition, in Example 1, high frequency was used to generate plasma, but
The antenna may be removed and microwaves may be introduced through a dedicated hole. Further, the base materials of the molds 15 and 16 may be high-strength ceramics such as silicon carbide, or high-melting point metals such as molybdenum (Mo). Furthermore, the type of glass material to be molded is not limited to this example.

[0015]

[Example 2] FIG. 4 shows Example 2 of the present invention, and Example 1
Elements that are the same as ``are'' corresponded to by the same reference numerals. Further, in this second embodiment, only the molding section 11 is illustrated, and the heating section and cooling section are omitted. In this second embodiment, an upper mold 15 and a lower mold 16 provided in a container 31 are inserted into a sleeve body 32. The sleeve body 32 is formed into a cylindrical shape from a BN sintered body, and the high frequency antenna 21 is provided in a coil shape on the outside thereof. Note that the sleeve body 32 is formed with an introduction hole 33 for introducing a glass material and an extraction hole 34 for taking out a molded glass optical element. These introduction holes 33 and extraction holes 34 are also used to introduce gas into the sleeve body 32 during BN film formation.

In the above structure, a silicon carbide sintered body is used as the base material of the upper mold 15 and the lower mold 16, and the molding surface 15
A BN film with a thickness of 0.5 μm is formed on a and 16a. Also, both the upper mold 15 and the lower mold 16 have a diameter of 12 mm and a length of 30 m.
The molding surface 15a of the upper mold 15 has a radius of 20 mm, and the molding surface 16a of the lower mold 16 has a concave surface mirror-finished with a radius of 60 mm. The sleeve body 32 has an inner diameter of 12 mm and an outer diameter of 22 m.
m, and the length is 100 mm, and the antenna 21 is spaced apart from the sleeve body 32 by 10 mm. BK7 optical glass was used as the glass material, and a disk shape with an outer diameter of 10 mm and a thickness of 5 mm was cut from this glass block. First, the glass material is heated at about 900° C. for 1 minute in a heating section, and then transferred onto the lower mold 16. Then, the molds 15 and 16 heated to 600°C are heated to 12 cm with a total load of 30 kgf.
Shape for seconds. At this time, the inside of the container 31 of the molding section 11 is 5×
It is filled with N2 gas at 10-2 Torr. The molded glass is transferred to a cooling section, held for one minute, and then taken out. After repeating the above cycle 100 times, a film forming process is performed.

During the film forming process, the pressure inside the container remains the same;
Plasma is generated by applying 700 W of high frequency power. After forming a film for 20 minutes, power is turned off. This results in 0
．． A 3 mm thick BN film could be formed on the molding surface. After this film formation, the molding cycle was performed again. Molding was performed a total of 5,000 times through the steps described above. Of course, the mold was not removed or replaced during this time. Moreover, the molded glass optical element maintained high precision. Further, no seizure occurred at all. In addition,
In this example as well, the mold base material is not limited as long as it has excellent heat resistance and high-humidity strength as in Example 1. The glass material is not limited to this example either. moreover,
Non-reactive gas such as an inert gas may be used instead of N2 gas.

[0018]

[Effects of the Invention] Since the present invention is equipped with a film forming mechanism that forms a BN film on the molding surface of the mold, the mold with the BN molding surface can be used for a long period of time without removing or replacing the mold. can do. Therefore, a glass element having a highly accurate shape can be supplied at low cost.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the basic configuration of the present invention.

FIG. 2 is a sectional view showing another basic configuration of the present invention.

FIG. 3 is a sectional view of Example 1 of the present invention.

FIG. 4 is a sectional view of Example 2 of the present invention.

[Explanation of symbols]

1 Upper mold 2 Lower mold 3 Container 6 High frequency antenna

Claims (1)

[Claims] 1. A mold having a molding surface for molding a heated glass material, a sealable container housing the mold, and a boron nitride film on the molding surface of the mold when the container is sealed. 1. A glass optical element manufacturing apparatus comprising: a film forming means for forming a glass optical element.