JP2785903B2 - Mold for optical element molding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding die used for producing an optical element made of glass such as a lens and a prism by press molding a glass material.

[0002]

2. Description of the Related Art A technique of manufacturing a lens by pressing a glass material without a polishing step eliminates complicated steps required in the conventional manufacturing of a lens, and manufactures a lens simply and inexpensively. Make it possible,
Today, it is used not only for manufacturing lenses but also optical elements made of prisms and other glasses.

[0003] The performance required of a mold used for press molding of such a glass optical element includes scratch resistance,
It is excellent in heat resistance, mold release property, mirror workability, and thermophysical properties suitable for molding.

Conventionally, many proposals have been made for this type of mold material, such as metals, alloys, ceramics, and materials coated with them.

[0005] To give some examples, Japanese Patent Application Laid-Open
No. 51112 discloses 13Cr martensitic steel,
JP-A-52-45613 discloses SiC and Si ₃
N ₄ is in the JP 60-246230 material forming the noble metal cemented carbide have been proposed.

Japanese Unexamined Patent Publication (Kokai) No. 61-136928 discloses that a composite base material composed of metal and ceramic contains nitride, carbide,
A material in which a noble metal is formed via an intermediate layer of an oxide and a metal has been proposed.

[0007] Japanese Patent Application Laid-Open No. 60-81032 proposes a mold material of glassy carbon, silicon carbide, silicon nitride, and sialon.

Further, in accordance with recent advances in thin film technology, Japanese Patent Application Laid-Open No. 61-183134 proposes forming a diamond or diamond-like carbon film on a cemented carbide to form a forming die.

[0009]

However, the 13Cr martensitic steel disclosed in Japanese Patent Application Laid-Open No. 49-51112 is excellent in workability, but has a high scratch resistance,
Since the heat resistance and the releasability are insufficient, it cannot be said to be a good mold material.

[0010] SiC and Si ₃ N ₄ disclosed in JP-A-52-45613 are excellent in scratch resistance and heat resistance, but have problems in workability and mold release properties.

The glassy carbon disclosed in Japanese Patent Application Laid-Open No. 60-81032 is excellent in terms of mold release properties, but has problems in terms of specularity and strength of the material.

As described above, a single mold material cannot sufficiently satisfy the performance required as a glass mold, and as disclosed in Japanese Patent Application Laid-Open No. 60-246230. The releasability, which is insufficient for the cemented carbide material, is compensated for by the surface treatment of the noble metal, but it needs to be improved in terms of scratch resistance.

Further, a diamond or diamond-like carbon film is formed on a cemented carbide disclosed in Japanese Patent Application Laid-Open No. 61-183134 to improve the scratch resistance without impairing the releasability. However, the diamond film has a large surface roughness, and there is a problem that mirror polishing is required after the film formation and the mirror polishing is difficult.On the other hand, the diamond-like carbon film has a film quality change and There is a drawback that a stress change is caused and abrasion resistance is reduced and adhesion to a mold base material is reduced.

[0014]

According to the present invention, as the performance required of the mold material, the mirror workability and the thermophysical property suitable for molding have the performance in the mold base material selected in consideration of the molding process. In terms of abrasion resistance and mold release properties, a layer of a composition in which carbon is mixed with at least one of nitrides and oxides (including hydrogen) is formed on the mold base material. By doing so, a good mold as a whole is obtained.

That is, for example, in the present invention, the change in film quality and the change in stress at a high temperature of a diamond-like carbon film can be achieved by forming a film having a composition in which carbon and highly stable oxide and nitride are mixed. Was reduced.

Since the required mold release performance differs depending on the molding process, the mixture composition ratio is determined according to the purpose.

[0017]

[Example 1]

FIG. 1 shows a first embodiment of the present invention, in which 1 is a cemented carbide as a mold base material, and 6 is one of a nitride and an oxide formed on a molding surface of the mold base material 1. This is a thin film having a composition in which the above and carbon are mixed.

Next, a method for manufacturing the optical element molding die having the above-described configuration will be described.

A cemented carbide as a mold base material was processed into a predetermined mold shape, and the formed surface was mirror-polished to a surface roughness of 0.02 μm to obtain a mold base material 1.

The mold base material 1 is cleaned and set in a substrate holder of a vapor deposition apparatus capable of performing a dual vapor deposition, and is set to 1 × 10 ⁻⁵ Torr.
After evacuating to a vacuum, high-purity carbon and TiO ₂ were vapor-deposited from each evaporation source. A film 6 having a thickness of about 80 nm was formed using a quartz crystal film thickness meter to form a molding die 10. The composition of the film obtained at this time is changed by changing the emission current of the electron gun, and based on the results of the evaluation of the molding and the measurement of the adhesion between the mold and the glass, the composition ratio of carbon and Ti for good molding is determined. It is necessary to select the emission current value so that

Table 1 shows the relationship between the composition ratio of carbon and Ti and the mold releasability of the mold and the glass. The composition ratio is an atom% ratio.

[0022]

A composition ratio of C / Ti to about 11.0 is good for mold release, but is unfavorable as a surface of a molding die because abrasion resistance is lowered due to a change in film quality.

Next, an example in which a glass lens is press-molded by the optical element molding die according to the present invention will be described in detail.

FIG. 3 shows a lens molding apparatus used.

In FIG. 3, reference numeral 21 denotes a vacuum chamber main body, 22 denotes a lid thereof, 23 denotes an upper die for molding an optical element, 24 denotes a lower die thereof, 25 denotes an upper die holder for holding an upper die, and 26 denotes an upper die holder. 27, a mold holder, 28, a heater, 29, a raising rod for raising the lower die, 30 is an air cylinder for operating the raising rod, 31 is an oil rotary pump, 32, 33, 34 are valves, 35 Is an inert gas inflow valve, 36 is a valve,
Reference numeral 37 denotes a leak pipe, 38 denotes a valve, 39 denotes a temperature sensor, 40 denotes a water cooling pipe, and 41 denotes a base for supporting a vacuum tank.

The steps for manufacturing the lens will now be described. Flint optical glass SF14 (manufactured by OHARA, transition point Tg = 4
A glass material having a spherical shape (85 ° C., softening point Sp = 586 ° C.) adjusted to a predetermined amount is put into the cavity of the mold.

After the mold into which the glass material has been put is placed in the apparatus, the lid 22 of the vacuum chamber 21 is closed, water is passed through the water cooling pipe 40, and current is passed through the heater 28. At this time, the nitrogen gas valves 36 and 38 are closed and the exhaust system valves 32 and 3 are closed.
3, 34 are also closed. The oil rotary pump 31 is always rotating.

Open the valve 32 and start exhausting. 10 ^-2 To
When the pressure becomes rr or less, the valve 32 is closed, the valve 36 is opened, and nitrogen gas is introduced from the cylinder into the vacuum chamber. When the temperature reaches a predetermined temperature, the air cylinder 30 is operated to 10 kg /
Press for 5 minutes at a pressure of cm ² . After the pressure was removed, the cooling rate was -5 ° C./min until the temperature was below the dislocation point, and then cooling was performed at a rate of -20 ° C./min or more. The air is introduced into the vacuum chamber 21 by opening the leak valve 33.
Then, the lid 22 is opened, the upper mold retainer is removed, and the molded product is taken out.

As described above, a lens was formed using the flint optical glass SF14.

Embodiment 2 FIG. 2 shows a second embodiment of the present invention, in which 1 is a cemented carbide as a mold base material, and 3 is a nitride formed on a molding surface of the mold base material 1. 6, an intermediate layer composed of at least one of carbides and oxides, and a thin film 6 formed on the intermediate layer 3 and having a composition in which at least one of nitrides and oxides is mixed with carbon. is there.

Next, a method for manufacturing the optical element molding die having the above configuration will be described.

A cemented carbide as a mold base material was processed into a predetermined mold shape, and the formed surface was mirror-polished to a surface roughness of 0.02 μm or less to obtain a mold base material 1.

The mold base material 1 is cleaned, set on a substrate holder of an ion plating apparatus equipped with an ion gun capable of applying a high acceleration voltage, evacuated to 1 × 10 ⁻⁵ Torr, and then Ar gas is introduced into the ion gun. Was introduced and discharged, and an acceleration voltage of 1 kV was applied to perform ion sputter cleaning on the molding surface.

[0035] Thereafter, N ₂ gas, a TiN film is approximately 2μm deposited to form an intermediate layer 3 by introducing up to 5 × 10 ^-4 Torr by activated reactive evaporation, and subsequently CH ₄ in the ion gun
Discharge was performed by introducing a gas, and an accelerating voltage of 2 kV was applied to form a film 6 having a composition of a mixture of carbon and TiN of about 80 nm, thereby forming a mold 20.

The releasability of the molding die of this embodiment is the same as that of Embodiment 1, but has the effect of increasing the surface strength and the chemical stability of the cemented carbide base material.

This effect can also be achieved by removing and regenerating the thin film 6 having a composition in which one or more of the outermost surface nitride or oxide and carbon are mixed.

Further, although the film of this example contains some hydrogen, no adverse effect was observed in actual molding.

[0039]

As described above, an optical element is formed by using a molding die having a layer of a composition in which at least one of nitride and oxide and carbon (including hydrogen) are mixed on the molding surface. By molding, it is possible to obtain a molded article having a good appearance while maintaining a stable release property, and has an effect of reducing costs by improving the operation rate of the molding apparatus and improving the yield rate.

The nitrides and oxides mixed with carbon are composed of B, Al, Si, Ti, V, Cr, Z
In the case of r, Nb, Hf, and Ta, although there are some differences,
Since a highly stable nitride or oxide is formed, a highly stable molding surface layer is obtained as a molding die.

The mold base material is cemented carbide, cermet, sintered S
Materials having different thermophysical properties, such as i ₃ N ₄ , sintered SiC (including surface CVD SiC coating), and stainless steel, can be selected as the optimum material in accordance with the shape of the forming optical element and the forming process, and a highly accurate optical element can be obtained.

As the composition of the molding surface layer, carbon and nitride,
By making the composition mixed with the oxide, the problem of film peeling during molding was eliminated.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a configuration of a molding die embodying the present invention.

FIG. 2 is a schematic view showing a configuration of another molding die embodying the present invention.

FIG. 3 is a cross-sectional view showing a lens molding apparatus using the optical element molding die of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mold base material 3 Intermediate layer 6 Molding surface layer 10 Molding mold provided with molding surface layer 20 Molding mold having molding surface layer on intermediate layer 21 Vacuum tank body 22 Lid 23 Upper mold 24 Lower mold 25 Upper mold Holder 26 Body type 27 Type holder 28 Heater 29 Lift rod 30 Air cylinder 31 Oil rotary pump 32, 33, 34 Valve 35 Inflow pipe 36 Valve 37 Outflow pipe 38 Valve 39 Temperature sensor 40 Water cooling pipe 41

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasushi Taniguchi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Keiji Hirabayashi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (56) References JP-A-5-24865 (JP, A) JP-A-7-17728 (JP, A) JP-A-6-263461 (JP, A) JP-A-5-294642 (JP, A) A) JP-A-60-81032 (JP, A) JP-A-49-51112 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C03B 11/00 C03B 11/08 C03B 40 / 02

Claims (5)

(57) [Claims] 1. An optical element molding comprising a layer having a composition in which at least one of nitrides and oxides and carbon are mixed on at least a molding surface of a mold base material processed into a predetermined shape. Type. 2. The composition ratio of carbon to a metal element contained in at least one of nitrides and oxides is atom%.
The mold for molding an optical element according to claim 1, wherein the ratio of carbon / metal is 2 to 10 in a ratio. 3. The nitride and oxide constituent metal elements are B, Al, Si, Ti, V, Cr, Zr, Nb, H
2. The mold for molding an optical element according to claim 1, wherein the mold is at least one of f, Ta and W. 4. The optical element molding die according to claim 1, wherein the die base material is a cemented carbide, cermet, sintered Si ₃ N ₄ , sintered SiC or stainless steel. 5. A method according to claim 1, wherein said mold base material and one or more of nitrides and oxides are mixed with a layer having a composition in which carbon is mixed.
Having a composition of one or more of carbides and oxides,
And an intermediate layer in which the constituent metal elements of the nitride, carbide and oxide are at least one of B, Si, Ti, V, Cr, Zr, Nb, Hf, Ta and W.
The mold for molding an optical element according to the above.