JPH06171962A - Die for forming glass and its production - Google Patents

Abstract

PURPOSE:To improve durability by introducing specific reactive gases into a reaction chamber where a die base body is installed, heating this die base body and irradiating the base body with a UV laser beam to effect reaction, thereby forming a release film contg. carbon nitride on the surface thereof. CONSTITUTION:The die base material 1 of the die for forming glass formed with an SiC film as a ground surface film on a forming surface consisting of an SiC sintered body, etc., is set in the reaction chamber 2 and after the pressure in the chamber is reduced down to 0.1 to 200Torr, the base body is heated to 300 to 1000 deg.C by a heater 3. The reactive gases consisting of C-contg. gases, such as C2H2 and CH4 and N-contg. gases, such as NH3 at a ratio of C/N=1/10 to 10/1 are introduced together with a carrier gas into the reaction chamber 2. The reactive gases are brought into reaction by irradiating the die base body 1 via a mirror 8 and a laser beam introducing window 5 from the outside of the reaction chamber 2, by which the release film of 0.1 to 5mum film thickness contg. the carbon nitride expressed by CxNy (x is 1 to 6, y is 1 to 8) is formed and the die for forming glass having excellent durability is obtd. Gaseous H2 is returned to protect the laser beam introducing window and waste gases are treated with waste gas treatment device 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold for manufacturing glass optical elements and the like by press molding and a manufacturing method thereof.

[0002]

2. Description of the Related Art Recently, a method of manufacturing a glass optical element such as a lens or a prism by press-molding a glass material which has been softened by heating has been rapidly developed.
On the molding surface of the mold used in this press molding,
Usually, a release film is formed for the purpose of preventing fusion of glass to a molding die and protecting the molding die processed with high precision. Therefore, the release film has good adhesion to the mold,
Film characteristics such as releasability from glass, oxidation resistance, smoothness, and high hardness are required.

In response to these requirements, it has been proposed to form a release film made of various materials on the surface of a mold base made of metal, ceramics or the like. For example, Japanese Patent Publication No. 3-61617 discloses an optical element molding die in which the surface of a mold base made of ceramic is coated with silicon carbide (SiC), and boron nitride is coated thereon. Japanese Patent Laid-Open No. 3-61615 proposes to apply to an optical element molding die in which a thin film in which cBN and aBN are mixed is formed. In addition, in JP-A-2-120245 and JP-A-2-243523, an intermediate layer made of a carbide or a nitride is formed on the surface of a substrate, and a hard carbon film or a diamond film is coated thereon. An optical element molding die has been proposed.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In the above prior art, the release film made of carbon or diamond is
It is suitable for press molding of lead-free glass materials such as BK7 and has a molding durability of 1000 times or more.
However, in press molding of a glass material containing lead such as SF6, the lead in the glass component is reduced by the carbon of the carbon film or the diamond film, and a very small amount is deposited on the surface of the molded glass optical element. It becomes cloudy and reduces the surface roughness. Further, the deposited lead causes countless scratches on the surface of the release film, which significantly deteriorates the durability of the release film.

On the other hand, the release film of BN is suitable for press molding of a glass material containing no B such as SF6, and has a molding durability of 1000 times or more. However, in a glass material containing B such as BK7, the boron oxide layer formed on the surface of the BN film reacts with the glass. Then, the adhesion of the glass lowers the surface roughness of the release film, which significantly deteriorates the durability.

[0006]

According to the present invention, as a result of repeated studies on the types of release films in order to solve the above-mentioned problems in the prior art, diamond is formed by forming the release film from carbon nitride. The inventors of the present invention have found that they have high hardness equal to or higher than that, and that they have no problem in molding lead-containing glass, and thus reached the present invention.

Further, as a method for producing the above-mentioned molding die, a reaction gas composed of a nitrogen-containing gas and a carbon-containing gas is introduced into a reaction chamber in which the die substrate is installed, and the die substrate is heated to a temperature of 300 to 1000 ° C. While heating to
By irradiating the surface of the mold substrate with an ultraviolet laser beam,
Or reacting the nitrogen-containing gas and the carbon-containing gas to form a release film containing carbon nitride on the mold substrate surface,
Alternatively, carbon or a substance containing carbon is evaporated from a vapor deposition source to deposit carbon on the surface of the mold substrate, and at the same time, the surface of the mold substrate is irradiated with nitrogen ions or nitrogen-containing ions to separate the surface of the mold substrate from carbon nitride. It is characterized by forming a mold film.

The present invention will be described in detail below. According to the present invention, a hard material made of carbon nitride is formed as a glass release film on the glass molding surface of the glass molding die. What is carbon nitride?
A compound represented by the general formula CxNy, in which x is in the range of 1 to 6 and y is in the range of 1 to 8, and a typical compound is C ₃ N ₄
It has been known. The release film made of carbon nitride is 0.1
It is desirable to be formed with a thickness of ˜5 μm.

On the other hand, the mold base in the glass molding mold of the present invention is made of silicon carbide, silicon nitride, cemented carbide, or Cr ₂ O.
It is composed of ₃ etc., and its surface roughness is the average surface roughness Ra.
Is preferably 1 μm or less, and when the surface roughness increases, the adhesion to the carbon nitride film decreases and the hardness of the carbon nitride film decreases.

Further, carbon nitride has a coefficient of thermal expansion of 3 to 5 ×.
Although it is a compound of 10 ⁻⁶ / ° C., when the difference in thermal expansion between the mold base and the mold base is large, when an intermediate layer made of carbon or silicon is formed between the mold base and the mold release film made of carbon nitride, the difference in thermal expansion becomes. It is possible to prevent the release film from being peeled off due to such reasons. For example, when a silicon carbide sintered body is selected as the mold base, silicon nitride may be formed as the intermediate layer.

Next, a method for manufacturing the glass forming mold of the present invention will be described. FIG. 1 shows a schematic view of a photo-CVD apparatus which is an embodiment of the manufacturing method according to the present invention. Figure 1
Inside, 1 is a glass molding die substrate, 2 is a reaction chamber, and 3 is a heater.

According to the present invention, the mold base 1 comprises a heater 3
And is irradiated with laser light from the ultraviolet laser device 4 through the laser light introduction window 5 onto the surface of the die substrate 1. There, a reaction gas composed of a carbon-containing gas and a nitrogen-containing gas is introduced into the reaction chamber 2 together with a carrier gas. The reaction gas introduced into the reaction chamber is excited on the surface of the mold substrate by heating and irradiation with laser light, the carbon-containing gas and the nitrogen-containing gas are decomposed, carbon atoms and nitrogen atoms are generated, and carbon nitride is formed by these bonds. Is generated,
Precipitates on the surface of the mold substrate.

As a film forming condition at this time, the mold base 1 is 30
It is heated to 0 to 1000 ° C., and the pressure in the reaction chamber 2 is set to 0.1 to 200 torr. If the temperature of the mold substrate at this time deviates from the above range, carbon nitride will not be generated. Further, as the carbon-containing gas used in the film formation, CH ₄ , C ₂ H ₄ , C ₂ H ₆ , C ₃ H ₈ and C are used.
₄ H ₁₀ , CO ₂ , CO and the like, and as the nitrogen-containing gas, N ₂ , NH ₃ , N ₂ H _4, etc. are used, but CH ₃ NH ₄ , NH containing both carbon and nitrogen is used.
(CH ₃ ) ₂ , N ₂ H ₂ (CH ₃ ) ₂ and N (C
When H ₃ ) ₃ or the like is used, it is possible to combine both carbon-containing gas and nitrogen-containing gas with one type of gas. The amounts of carbon and nitrogen in these reaction gases are controlled so that C: N = 1 to 10:10 to 1.

Next, an ion beam sputtering method will be described as another method of manufacturing the glass molding die of the present invention.
FIG. 2 is a schematic layout of the ion beam sputtering apparatus.
In the figure, 11 is a mold substrate, 12 is a target, 13 is an ion beam sputtering ion source, and 14 is an ion irradiation ion source. According to this apparatus, carbon or a carbon-containing substance such as graphite, CrC, TiC, TaC, or polyimide resin is installed as the target 12, and an ion beam such as Ar or Xe is irradiated from the ion source 13 for ion beam sputtering. Then, graphite is evaporated from the target and deposited on the surface of the mold base 11. At the same time, by irradiating the ions of a mixed gas of a nitrogen-containing gas and a carrier gas made of an inert gas such as argon from the ion source 14 for ion irradiation, carbon ions and nitrogen ions are bonded on the surface of the mold substrate. Carbon nitride is produced.

The pressure in the reaction chamber at this time is 10 ^-4 ~
The substrate temperature is set to 10 to ⁶ torr, the temperature of the substrate is set to 25 to 500 ° C., and the energy of the ions to be applied to the die substrate is set to 0.1 to 40 keV. Further, the C / N ratio of carbon nitride can be easily controlled by controlling the vapor deposition rate and the ion beam irradiation amount.

According to this ion beam sputtering method, the ions can be embedded in the substrate surface by relatively increasing the deposition rate and the ion energy at the time of ion irradiation before the carbon nitride is generated. A mixed layer of a substrate component and a film component can be formed between the substrate and the release film, and by forming a carbon nitride film on such an intermediate layer, the adhesion strength of the carbon nitride release film to the mold substrate can be improved. Can be improved.

Furthermore, before the carbon nitride film is formed, 2K
By irradiating the substrate only with an ion beam of about eV, it is possible to remove the dirt attached to the surface of the mold substrate.

According to the above ion beam sputtering method, in addition to the above structure, a metal carbide as a target,
When metal nitride or organic resin is used and carbon nitride is produced and vapor-deposited at the same time, carbon nitride and metal carbide,
It is also possible to form a composite film with a metal nitride or a metal carbonitride.

[0019]

[Function] This carbon nitride is a compound in which a carbon atom and a nitrogen atom are strongly chemically bonded.
00 kg / mm ² or more, 5000 kg / mm in some cases
It has the same hardness as ^two or more diamond films. According to the present invention, by forming such carbon nitride as a release film on the glass molding surface, scratches are unlikely to be formed during press molding as in the case of forming a diamond film, and excellent durability can be imparted. . Moreover, according to such a structure, carbon in the film is strongly bonded to nitrogen, and since the reducing action on glass is extremely small compared to diamond, the optical glass containing lead that could not be conventionally formed is It enables press molding.

[0020]

EXAMPLES Examples of the present invention will be described below. Example 1 A SiC (silicon carbide) sintered body was used as the mold base 1 of the glass optical element molding die, and a SiC film was formed as a base layer in advance to a thickness of several 100 μm on the molding surface by the CVD method.
The surface of the SiC film was mirror-finished so that Ra = 1 nm or less. This substrate 1 is attached to the reaction chamber 2 of the photo CVD apparatus of FIG.
Was set to, and after being evacuated by the vacuum pump 6, it was heated to 550 ° C. by the heater 3. The reaction gas 7 of C ₂ H ₂ gas, CH ₄ gas, NH ₃ gas, and H ₂ gas was introduced into the reaction chamber 2. Then, the surface of the mold substrate 1 was irradiated with the ultraviolet laser 4 from outside the reaction chamber through the mirror 8 and the laser light introduction window 5. Hydrogen gas 10 as a laser introduction window protective gas is caused to flow through the laser light introduction window 5 at a flow rate of 20 SCCM,
Further, the exhaust gas at the time of evacuation was processed by the exhaust gas processing facility 9.

In the above photo-CVD method, as shown in Table 1, the conditions for transporting the raw material gas were changed to form a dense and flat film. Identification of crystal phase by X-ray diffraction measurement, film composition by AES, Knoop hardness and SF6
Perform press molding durability test with (lead-containing glass), measure the number of times until the surface of the pressed glass becomes cloudy,
The results are shown in Table 1.

[0022]

[Table 1]

As a result of the measurement, a crystal phase of carbon nitride was detected in all the films. Further, as shown in Table 1, all of them have high hardness, and no lead precipitation is observed even in press molding of lead-containing glass, and both press durability performances of 1000 times or more are obtained, and Was excellent in releasability.

Example 2 A cemented carbide was used as a glass molding die substrate, and this was used as shown in FIG.
It was installed in the ion beam sputtering apparatus of. Graphite was set on the target 12 and the reaction chamber was evacuated to 10 ^-6 torr or less. The target 12 is irradiated with Ar ion beam from the ion source 13 for ion beam sputtering, and the mold substrate 1
Graphite is deposited on the surface of No. 1 at a deposition rate of about 1 nm / min, and at the same time Ar / N ₂ =
Ions of a mixed gas of 0.3 are irradiated at an acceleration voltage of 40 keV, the mixing time is changed as shown in Table 2, and
-Various thicknesses of the carbon intermediate layer were formed.

A film was formed. After that, Ar / N ₂ = 0.
While irradiating the ions of the mixed gas of 3 at an accelerating voltage of 10 keV, the deposition rate was controlled so that the C / N composition ratio was about 0.75, and a carbon nitride film was formed to a thickness of about 300 nm. . Then, Knoop hardness was measured for a plurality of films having different mixing treatment times, and shown in Table 2.

[0026]

[Table 2]

According to Table 2, the hardness of the carbon nitride film was improved by performing the mixing treatment. It is considered that this is because the adhesiveness of the release film to the mold substrate is increased.

Further, when forming a film under the same conditions as above, the influence of the type of substrate and the surface roughness of its surface was investigated. The film forming conditions of carbon nitride were the same as those of sample No. 4 in Table 2.

At this time, the relationship between the surface roughness of the mold substrate, the Knoop hardness, and the number of times of endurance in the glass forming endurance test (the number of times of press molding of the optical material containing lead such as SF6) was examined, and the results are shown in Table 3. It was

[0030]

[Table 3]

According to Table 3, the surface roughness Ra of the substrate is about 1.
When the thickness is 00 nm or less, a good mixing effect was obtained, and a film having good releasability was obtained. The release film was a high-hardness carbon nitride thin film having a Knoop hardness of 3000 to 4000 kg / mm ² , and was excellent in molding durability of 1000 times or more.

Example 3 Using the same equipment as in Example 2, graphite, CrC, TiC,
One kind or two kinds were selected from the five kinds of TaC and polyimide resin, and this was used as a target for ion beam sputtering, and irradiation ions and their ion energies were set to the conditions shown in Table 4 to form a film. Other film forming conditions are the same as those of Sample No. 12 in Table 3. The crystal phase in the film is identified by X-ray diffraction measurement on the obtained film,
Further, the Knoop hardness and the number of times of press molding durability were measured. The results are shown in Table 4.

[0033]

[Table 4]

As is apparent from Table 4, a film made of carbon nitride or a composite film made of carbon nitride and metal carbonitride was produced, and each of these films had a Knoop hardness of 3
It was found that the release film had a high hardness of 000 to 4000 kg / mm ² and an excellent durability of 1000 times or more in glass molding.

[0035]

As described in detail above, according to the present invention,
By forming a hard film containing carbon nitride as a release film on the glass molding surface, excellent press durability can be imparted. Moreover, even when press-molding an optical material containing lead such as SF6, since it does not chemically react with lead, it is possible to press-mold an optical glass containing lead without lead precipitation.

[Brief description of drawings]

FIG. 1 is a schematic view of a film forming apparatus by a photo CVD method according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of a film forming apparatus by an ion beam sputtering method in an example of the present invention.

[Explanation of symbols]

 1, 11 type substrate 2 reaction chamber 3 heater 4 ultraviolet laser 12 target 13 ion source for ion beam sputtering 14 ion source for ion irradiation

Claims (3)

[Claims] 1. A mold for glass molding, wherein a mold-releasing film containing carbon nitride is formed on the glass molding surface of a mold base. 2. A reaction gas comprising a nitrogen-containing gas and a carbon-containing gas is introduced into the reaction chamber in which the mold substrate is installed, and the mold substrate is heated to a temperature of 300 to 1000 ° C. By irradiating with an ultraviolet laser beam, the nitrogen-containing gas and the carbon-containing gas are caused to react with each other, and a mold release film containing carbon nitride is formed on the surface of the mold substrate. . 3. Carbon or a substance containing carbon is evaporated from a vapor deposition source to vapor deposit carbon on the surface of the mold substrate, and at the same time,
A method for producing a glass molding die, which comprises irradiating the surface of the die substrate with nitrogen ions or nitrogen-containing ions to form a release film containing carbon nitride on the surface of the die substrate.