JP3149149B2 - Optical element molding die - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold used for manufacturing 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 The technology of manufacturing a lens by press molding a glass material without the need for a polishing step eliminates the complicated steps required in conventional lens manufacturing.
A lens can be manufactured easily and inexpensively, and in recent years, it has been used for manufacturing not only a lens but also an optical element made of a prism or other glass.

The properties required of a mold used for press molding of such glass optical elements include excellent hardness, heat resistance, releasability, mirror workability, and the like. Conventionally, many proposals have been made for this type of mold material, such as metals, ceramics, and materials coated with them. If some examples are given,
No. 51112 discloses 13Cr martensitic steel, and JP-A-52-45613 discloses SiC and Si ₃ N _4.
However, Japanese Patent Application Laid-Open No. 60-246230 discloses a material in which a hard metal is coated with a noble metal.
No. 1 discloses a material obtained by coating a cemented carbide with an oxynitride, and Japanese Unexamined Patent Publication Nos. 61-183134, 61-281030 and 1-301864 disclose a diamond thin film. Alternatively, a material coated with a diamond-like carbon film is proposed in JP-A-64-83529, in which a material coated with a hard carbon film is proposed. Japanese Patent Publication No. 2-31012 proposes forming a carbon film of 50 to 5000 ° on either a lens or a mold.

[0004]

However, 13Cr martensitic steel has the disadvantage that it is easily oxidized, and at high temperatures Fe diffuses into the glass and the glass is colored. Also, SiC, S
Although i ₃ N ₄ is generally considered to be hardly oxidized, it also oxidizes at a high temperature and a SiO ₂ film is formed on the surface, so that the i ₃ N ₄ fuses with glass to form AlN, SiAlO.
Similarly, films such as N and AlON are fused. Further, these films have a drawback that the workability of the mold itself is extremely poor due to high hardness. On the other hand, a material coated with a noble metal does not easily fuse, but has a disadvantage that it is very soft and easily scratched and easily deformed. A diamond thin film, a diamond-like carbon film (hereinafter referred to as a DLC film),
A mold using a hydrogenated amorphous carbon film (hereinafter referred to as aC: H film) or a hard carbon film has good mold-releasing property and does not cause fusion of the glass, but the molding operation is performed several hundred times. If the above steps are repeated, the film may be partially peeled off, and the molded product may not have sufficient molding performance.

The following can be considered as the cause. Each of the above films has a very large compressive stress, and peeling, cracks, etc. occur as a result of stress release accompanying rapid heating and rapid cooling in the molding process. Similarly, a similar phenomenon occurs due to a difference in thermal expansion coefficient between the mold base material and the film and a thermal stress caused by a thermal cycle. Depending on the mold base material, a film may not be formed partially depending on the surface condition,
The film thickness may be small. For example, WC-Co, SiC,
In a sintered body of Si ₃ N ₄ , SiAlON or the like, a loss of grains and a bore during sintering are inevitable, and a hole of several μm or more is present on the formed polished surface. When a film is formed on a surface having no intermediate layer between such a mold base material and a molding surface, no film is formed in these holes or the film becomes extremely thin. Accordingly, the adhesive strength and mechanical strength of the film in such a portion are significantly reduced, and thus the film tends to be a starting point of peeling or cracking. An alloy is formed by diffusion between the sintering aid in the sintered body represented by Co of WC-Co and the above-mentioned film. Such a portion causes fusion of the glass at the time of molding and reacts with components contained in the glass to produce a precipitate, thereby causing deterioration in durability. As described above, an optical element molding die excellent in moldability, durability, and economy has not been realized.

According to Japanese Patent Publication No. 2-31012, if the film thickness is less than 50 °, the film becomes non-uniform, so that the effect of forming the carbon film is reduced. If the angle is 50 to 5000, no problem occurs. However, the carbon film in the embodiment of the present invention has a weak adhesion to the substrate, or peels off during the molding process due to a large compressive stress.
As a result, fusion of the glass at the peeling portion and poor appearance of the molded product are caused, and a practical mold having excellent durability has not been provided.

[0007]

According to the present invention, there is provided a mold having a mixing base comprising carbon and at least one element constituting an intermediate layer formed on a mold base material through an intermediate layer of an oxynitride film. This is a solution to the problem.

That is, the present invention relates to an optical element molding die used for press molding an optical element made of glass.
An intermediate layer of an oxynitride film is formed on at least the molding surface of the mold base material, and the surface of the intermediate layer is composed of carbon and at least one of the elements constituting the intermediate layer, and the carbon atom concentration increases toward the surface. An optical element molding die, characterized in that it is a mixing layer in which the mixing layer increases and decreases toward the intermediate layer side, and the other atomic concentration decreases toward the surface and increases toward the intermediate layer side.

Hereinafter, the present invention will be described in detail. The material used as the mold base material in the present invention is WC, S
iC, TiC, TaC, BN, TiN, AlN, Si ₃
N ₄ , SiO ₂ , Al ₂ O ₃ , ZrO ₂ , W, Ta, M
o, Cermet, SiAlON, Mullite, WC-Co
It is selected from alloys and the like.

However, high-temperature, high-strength mold base materials are often made of sintered bodies such as ceramics and carbides, and have pores formed during the dropping and sintering of crystal grains. Resulting in. Therefore, a poreless intermediate layer that can maintain the performance of the optical element between the mold base material and the molding surface is indispensable.
In addition, since the intermediate layer is subjected to high temperature and high pressure during molding of the optical element, high temperature resistance, high strength, oxidation resistance, and high hardness are required. In the present invention, this problem is solved by using an oxynitride film for the intermediate layer.

Although a highly durable mold material can be obtained by forming an oxynitride film on the molding surface, when an optical element is actually molded, glass is fused to the mold side.

Therefore, the adhesion between the mold and the glass, which can prevent fusion and maintain the surface accuracy of the optical element on the mold surface, and the mold releasing action on the mold to facilitate the mold and glass release. It is necessary to realize a mold surface to be held. Since carbon has low adhesion to glass, carbon has long been used in glass molds. In the glass mold, the above-mentioned hard and smooth carbon film is formed on the molding surface of the mold base material by utilizing the properties of carbon and glass.

As the carbon film, diamond film, DLC
Although a film, an aC: H film, and a hard carbon film are mentioned, there is a problem that a diamond film requires a mirror finish because it is polycrystalline and has a rough surface. On the other hand, an amorphous DLC film, a
-C: The H film and the hard carbon film have a large internal stress and lack thermal stability in a high-temperature region where glass is formed, and a problem occurs that the adhesion strength between the mold base material and the film decreases as the number of times of forming increases. . That is, the problem of the carbon film as the mold surface material in the glass mold mainly relates to the adhesion strength between the mold base material and the film. In this regard, the conventional problem can be solved by forming the molding surface as a mixing layer composed of carbon and at least one element constituting the intermediate layer formed on the mold base material or the mold base material surface.
This mixing layer has extremely good adhesion since carbon is mixed (atomically mixed) with the mold base material or the intermediate layer material which is an oxynitride film formed on the mold base material. In the state of the mixing layer, the concentration of carbon atoms increases toward the surface and decreases toward the base material, while the concentration of atoms other than carbon decreases toward the surface and increases toward the base material. ing. FIG. 1A schematically shows this state, and FIG. 1B is an image diagram of the state. In FIG. 1A, the horizontal axis represents the depth from the surface toward the mold base material, and the position at the depth of 0 is the surface. On the other hand, the vertical axis represents the atomic concentration.

Further, the effect of mixing the carbon film and the oxynitride film can be obtained by a surface transfer which cannot be obtained by the good mold release property of only the carbon film. In other words, the mixture of the oxynitride having a high adhesion and the carbon film can realize an appropriate adhesion that provides excellent surface accuracy.

That is, according to the present invention, by providing a gradient mixing layer of the above-mentioned carbon and oxynitride film on a mold base material, glass fusion is prevented, and a good mold release and high durability optical element molding is performed. It is to provide a mold.

[0016]

【Example】

[Example 1 (SiAlON, C) mixing layer, Si
AlON Intermediate Layer] FIGS. 2 and 3 show one embodiment of the optical element molding die according to the present invention. 2 shows a state before press molding of the optical element, and FIG. 3 shows a state after molding of the optical element. In FIG. 2, 1 is a mold base material, 2 is a molding surface for molding a glass material, 3 is a mixing layer, 4 is an intermediate layer,
5 is a glass material, and 6 in FIG. 3 is an optical element. As shown in FIG. 2, an optical element 6 such as a lens is formed by press-molding a glass material 5 placed between molds.

Next, the optical element molding die of the present invention will be described in detail. After processing carbide (WC-Ti) as a mold base material into a predetermined shape, a SiAlON film is formed as an intermediate layer between the molding surface and the mold base material by a plasma CVD method, and then the molding surface is Rmax = 0.02 μm. A mirror-polished product was prepared.

After thoroughly cleaning this mold, the I shown in FIG.
It was installed in a BD (Ion Beam Deposition) device. In the figure, 15 is a vacuum chamber, 7 is an ion beam device, 8 is an ionization chamber, 9 is a gas inlet, 10 is an ion beam extraction grid, 11 is an ion beam, 12 is a mold base material, 13 is a substrate holder and a heater, 14 Indicates an exhaust port. First, 35 sccm of Ar gas is introduced into the ionization chamber from the gas inlet and ionized, and then an ion beam is extracted by applying a voltage of 500 V to the ion beam extraction grid, and the mold base material is irradiated for 5 minutes to clean the molding surface. Was done. _{Then, CH 4: 15sccm, H 2} : 30s
ccm into the ionization chamber and gas pressure 3.5 × 10 ^-4 T
At orr, an ion beam was irradiated at an acceleration voltage of 10 kV onto the drawing surface to form a 35 nm mixing layer. At this time, the ion beam current was 30 mA, the current density was 2 mA / cm ² , and the substrate temperature was 300 ° C. The mixing layer of the analysis sample prepared under the same conditions was used for AES (Aug
er Electron Spectroscopy)
FIG. 5 shows the results of the analysis in the depth direction. As is clear from FIG. 5, the thickness of the mixing layer is 35 nm,
Decreases from 100% on the surface side toward the mold base material side. On the other hand, the concentration of Si atoms increases from 0% on the surface side toward the mold base material side. That is, FIG. 5 shows the profile of the C and Si concentrations in the depth direction. The thickness of the mixing layer is, as defined above, the thickness from the depth of 100% of the variation where the C concentration changes from a maximum to a minimum before and after the mold base material interface, from the depth to the surface.

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. FIG.
Inside, 51 is a vacuum chamber main body, 52 is a lid thereof, 53 is an upper die for molding an optical element, 54 is a lower die thereof, 55 is an upper die holder for pressing the upper die, 56 is a trunk die, and 57 is a die. A mold holder, 58 a heater, 59 a push-up bar for pushing up the lower mold, 60 an air cylinder for operating the push-up bar,
61 is an oil rotary pump, 62, 63, 64 are valves, 65
Denotes an inert gas inflow pipe, 61 denotes a valve, 67 denotes a leak valve, 68 denotes a valve, 69 denotes a temperature sensor, 70 denotes a water cooling pipe, and 71 denotes a base supporting a vacuum tank.

The steps for fabricating the lens will now be described.

Crown optical glass (SK1 manufactured by OHARA)
2) is adjusted to a predetermined amount, the spherical glass material is placed in a cavity of a mold, and this is placed in a molding apparatus.
After the mold into which the glass material has been put is placed in the apparatus, the lid 52 of the vacuum chamber 51 is closed, water is supplied to the water-cooled pipe 70, and current is supplied to the heater 58. At this time, the nitrogen gas valve 66
And 68 are closed, and the exhaust system valves 62, 63 and 64 are also closed. The oil rotary pump 61 is always rotating. When the pressure becomes 10 ^-2 Torr or less after opening the valve 62 and starting the evacuation, the valve 62 is closed, the valve 66 is opened, and nitrogen gas is introduced from the cylinder into the vacuum chamber. When the temperature reaches a predetermined temperature, activate the air cylinder 60 to 150 kg / cm
Press for 1 minute at pressure of ² . After the pressure is released, the cooling rate is -5 ° C./min until the temperature falls below the transition point, and then the cooling rate is -20 ° C./min or more.
When the temperature drops below ℃, the valve 66 is closed and the leak valve 6
3 is opened and air is introduced into the vacuum chamber 51. Then, the lid 52 is opened, the upper mold retainer is removed, and the molded product is taken out. As described above, the lens 6 shown in FIG. 3 was formed using the crown-based optical glass SK12 (softening point Sp = 672, transition point Tg = 500).

The molding surface of the mold member and the surface roughness of the molded optical element after molding 3,000 times by the above-described pressing process, and the releasability between the mold member and the molded optical element are good. Was. In particular, when the molding surface of the mold member was observed with an optical microscope or a scanning electron microscope (SEM), no defects such as scratches and cracks, no reaction components of glass components, and no fusion of glass were observed.

Example 2 (Ti--O--N, C) Mixing Layer, Ti--O--N Intermediate Layer!
-Ti) is processed into a predetermined shape, and then, as an intermediate layer between the molding surface and the mold base material by ion plating, Ti-
After forming the ON-N film, a mirror-finished product having an Rmax of 0.02 μm was produced.

Hereinafter, the molding surface Ti was formed in the same manner as in Example 1.
A mold having a mixing layer of an -ON intermediate layer and a carbon film was formed, and a molding experiment similar to that of Example 1 was performed using the mold.

As a result, the molding surface of the mold member after molding 3000 times, the surface roughness of the molded optical element, and the releasability between the mold member and the molded optical element were good.
In particular, when the molding surface of the mold member was observed with an optical microscope or a scanning electron microscope (SEM), no defects such as scratches or cracks, reaction precipitates of glass components, and fusion of glass were observed.

Example 3 (Ta-ON, C) Mixing Layer, Ta-ON Middle Layer!
-Ti) is processed into a predetermined shape, and then Ta- is formed as an intermediate layer between the molding surface and the mold base material by an ion plating method.
After forming the ON-N film, a mirror-finished product having an Rmax of 0.02 μm was produced.

Hereinafter, the molding surface Ta is produced in the same manner as in Example 1.
A mold having a mixing layer of an -ON intermediate layer and a carbon film was formed, and a molding experiment similar to that of Example 1 was performed using the mold.

As a result, the molding surface of the mold member after molding 3000 times, the surface roughness of the molded optical element, and the releasability between the mold member and the molded optical element were good.
In particular, when the molding surface of the mold member was observed with an optical microscope or a scanning electron microscope (SEM), no defects such as scratches or cracks, reaction precipitates of glass components, and fusion of glass were observed.

Example 4 (Al--O--N, C) Mixing Layer, Al--O--N Intermediate Layer
-Ti) is processed into a predetermined shape, and then Al-O-N is formed as an intermediate layer between the molding surface and the mold base material by a plasma CVD method.
After forming the film, a mirror-finished product with Rmax = 0.02 μm was produced.

Hereinafter, the molding surface Al was formed in the same manner as in Example 1.
A mold having a mixing layer of an -ON intermediate layer and a carbon film was formed, and a molding experiment similar to that of Example 1 was performed using the mold.

As a result, the molding surface of the mold member after 3,000 moldings, the surface roughness of the molded optical element, and the releasability between the mold member and the molded optical element were good.
In particular, when the molding surface of the mold member was observed with an optical microscope or a scanning electron microscope (SEM), no defects such as scratches or cracks, reaction precipitates of glass components, and fusion of glass were observed.

[0032]

As described above, according to the mold for molding an optical element of the present invention, an oxynitride film is interposed between the mold base material and the molding surface, and the molding surface is made of carbon and oxynitride film. By forming a mixing layer comprising at least one or more types of elements constituting the intermediate layer, a mold having a mirror surface with few surface defects that does not cause peeling or cracking of the film during glass molding can be obtained. When a glass optical element is molded using this mold, the mold releasability between the glass and the mold is extremely good, and a molded article having good surface roughness, surface accuracy, transmittance, and shape accuracy can be obtained. Furthermore, an extremely durable optical element molding die which does not cause defects such as film peeling, cracking and scratching even when press molding is repeated for a long time using this mold can be obtained.

Further, by using the mold for molding an optical element obtained by the present invention, it has become possible to realize an improvement in productivity and a reduction in cost.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing the state of atomic mixing of a mixing layer formed on a molding surface of an optical element molding die according to the present invention.

FIG. 2 is a cross-sectional view showing an example of an optical element molding die according to the present invention, showing a state before press molding.

FIG. 3 is a cross-sectional view showing an example of an optical element molding die according to the present invention, showing a state after press molding.

FIG. 4 is a schematic view showing an ion beam mixing apparatus used in an embodiment of the present invention.

FIG. 5 shows AES of a mixing layer in an embodiment of the present invention.
FIG. 3 is a diagram showing a depth profile according to the present invention.

FIG. 6 is a cross-sectional view showing a lens molding apparatus using the optical element molding die according to the present invention, which is a discontinuous molding type.

[Description of Signs] 1 mold base material 2 molding surface 3 mixing layer 4 oxynitride film (intermediate layer) 5 glass material 6 molded lens 7 ion beam device 8 ionization chamber 9 gas inlet 10 ion beam extraction grid 11 ion beam 12 mold base material 13 substrate holder and heater 14 exhaust port 15 vacuum tank 51 vacuum tank 52 vacuum tank lid 53 upper mold 54 lower mold 55 upper mold holder 56 trunk mold 57 mold holder 58 heater 59 push-up rod pushing up lower mold 60 air Cylinder 61 Oil rotary pump 62, 63, 64 Valve 65 Inert gas introduction valve 66 Valve 67 Leak pipe 68 Valve 69 Temperature sensor 70 Water cooling pipe 71 Vacuum tank support

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasushi Taniguchi 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Keiji Hirabayashi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (56) References JP-A-6-72728 (JP, A) JP-A-7-10565 (JP, A) JP-A-5-124825 (JP, A) JP-A-3-208821 (JP, A) A) JP-A-64-83529 (JP, A) JP-A-1-301864 (JP, A) JP-A-61-281030 (JP, A) JP-A-61-183134 (JP, A) JP-A-61-183134 JP-A-246230 (JP, A) JP-A-52-45613 (JP, A) JP-A-49-51112 (JP, A) JP-B-2-31012 (JP, B2) (58) Fields investigated (Int. . ^7, DB name) C03B 11/00 C03B 11/08 C03B 40/02

Claims (1)

(57) [Claims] 1. An optical element molding die used for press molding of an optical element made of glass, wherein an intermediate layer of an oxynitride film is formed on at least a molding surface of the mold base material, and the surface of the intermediate layer is formed of carbon. And at least one or more of the constituent elements of the intermediate layer, and the carbon atom concentration increases toward the surface and decreases toward the intermediate layer, and the other atomic concentrations decrease toward the surface and decreases toward the intermediate layer. A mold for forming an optical element, characterized in that the mixing layer is increasing.