JP2000327344A - Method for producing mold for molding optical element and mold for molding optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a mold which is used for molding an optical element, has a good mold release property and a small frictional coefficient, and is scarcely worn. SOLUTION: This method for producing a mold for molding an optical element comprises a process for injecting at least oxygen ion into the surface of a chromium-containing mold substrate or into a thin film which is formed on the mold substrate and consists mainly of chromium, and a subsequent process for thermally treating the mold substrate in an atmosphere containing oxygen. The produced chromium oxide is stable, has small crystals, thereby has a small frictional coefficient, and is scarcely worn.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art In recent years, a relatively small-diameter glass lens has been directly press-molded using a molding die.
Materials such as ceramics and cemented carbide are used as the material of the molding die used for this molding, and a precious metal film, a carbon-based film, and various types of nitride films are formed on the molding surface made of these materials as a releasable wear resistant film. Films, various oxide films, various carbonized films, etc. are formed. This prevents fusion of the molded glass lens and improves the durability of the mold.

For example, Japanese Patent Publication No. 3-61616 discloses a mold having good releasability and a long life by forming a compound mainly composed of chromium and nitrogen on a molding surface. Have been. Further, Japanese Patent Publication No. 4-74292 discloses chromium oxide, chromium oxycarbide, chromium oxynitride,
It is disclosed that by forming a molding surface with a sintered body of a chromium-containing substance such as chromium oxycarbonitride, a molding surface having an excellent lubricating effect on glass and having poor affinity for glass is provided. Japanese Patent Publication No. 45458/1992 discloses that dichromium trioxide is formed on the outermost layer by heating an optical element mold having a molding surface made of chromium and nitrogen in an oxidizable atmosphere. It is disclosed that a mold having good mold releasability and high hardness can be obtained.

[0004]

However, in the above-mentioned conventional mold for molding an optical element, there is a growing need for a lens system which requires high-precision image quality in recent years, and an increase in the precision of a single lens. Thus, the moldability, durability, and economy have not been sufficiently satisfied. In particular, in the current situation where the use environment of the optical element molding die is severe due to the advancement of molding conditions, and the demand for the optical element molding die is also high, the above-described conventional optical element molding die is
There are problems such as insufficient transferability of the mold, easy roughening of the molding surface, rapid deterioration, and short durability.

The present invention has been made in view of such problems of the prior art, and has a high transfer property capable of coping with a high surface precision of an optical element. An object of the present invention is to provide a mold for molding an optical element which has good properties and can extend the life, and a method for producing the same.

[0006]

To achieve the above object, a method for manufacturing an optical element molding die according to the first aspect of the present invention comprises:
A step of ion-implanting at least oxygen into the surface of the mold base containing chromium or a thin film containing chromium as a main component formed on the mold base, and after this ion implantation, the mold base is placed in an atmosphere containing oxygen. And a step of performing a heat treatment.

[0007] In ion implantation, ions are accelerated to forcibly add an element to the surface, and chromium oxide can be generated by ion implantation of oxygen into a chromium compound. That is, when oxygen ions are implanted into the surface of the chromium compound, chromium is excited by collision and recoil between chromium and oxygen ions, so that chromium oxide can be synthesized. In addition, it has been found that ion implantation into metal can cause supersaturation beyond the solid solubility limit because elements are forcibly added to the surface, enabling the formation of materials with properties not seen in the past. Become. Furthermore, the size of the crystal grains on the outermost surface is fine, and chromium oxide can be formed with a smooth surface.

The use of the chromium oxide formed by the ion implantation as a mold for forming an optical element was examined. At least oxygen was ion-implanted into a chromium-containing compound, and then heat treatment was performed in an oxygen-containing atmosphere. Thus, it was confirmed that the chromium oxide had characteristics different from those of chromium oxide obtained by coating and chromium oxide obtained by simple thermal oxidation of a chromium compound. In other words, the chromium oxide that has been heat-treated in an atmosphere containing oxygen has a lower friction coefficient on the surface and a lower wear amount than chromium oxide obtained by coating or chromium oxide obtained by simple thermal oxidation of a chromium compound. It has the property of decreasing. Moreover, even if the chromium oxide formed by ion implantation is heat-treated in an atmosphere containing oxygen, the crystal grains on the surface do not grow and the structure remains fine.

FIG. 6A is an electron micrograph of the surface of chromium oxide formed by heat treatment in an air atmosphere after implantation of oxygen ions, and FIG. 6B is a surface of chromium oxide formed only by ion implantation. (C) is an electron micrograph of the surface of chromium oxide formed only by heat treatment in an air atmosphere. As is clear from the comparison between (A) and (B), even when the heat treatment is performed in the air atmosphere, the crystal grains on the surface remain fine without growing. Further, as is clear from the comparison between (A) and (C), the crystal grains are finer than the surface formed only by heating.

FIG. 7 shows the results of a friction test performed using a ball-on-disk, in which (A) is obtained by implanting oxygen ions into a chromium compound and then heat-treated in an atmosphere containing oxygen, and (B) shows only ion implantation. (C) is the result of each of the chromium oxide surfaces obtained by simply thermally oxidizing the chromium compound. As a test ball, an alumina ball having a diameter of 4 inches was used, and a diameter of 10 mm was changed to 5.23 cm / sec under a load of 2N.
The coefficient of friction was measured by moving at a speed of c. As shown in (A), after the oxygen ions are implanted into the chromium compound, the surface that has been heat-treated in an atmosphere containing oxygen has a number of rotations of two.
No wear was observed even after exceeding 000 rotations, and the coefficient of friction was a small value of 0.304. On the other hand, the surface (C) of chromium oxide obtained by simply heat-treating the chromium compound and the surface (B) of chromium oxide obtained only by ion implantation were both rotated at 2,000 times. Where it is less, the base metal is worn down. Further, the coefficient of friction also shows an extremely large value as compared with (A).

The chromium oxide obtained by the ion implantation is subjected to a heat treatment in an atmosphere containing oxygen, whereby the amorphous chromium on the implantation surface is recrystallized. Usually, in the oxidation of chromium by thermal oxidation, chromium that cannot be completely oxidized exists as metal chromium and also exists as an unstable oxide. However, on the surface of chromium oxide obtained by ion implantation, the amount of oxygen is supersaturated with respect to the amount of chromium, so chromium is sufficiently oxidized by heating, and the surface becomes chromium oxide. It is the most stable dichromium trioxide. Therefore, stable and stable chromium oxide without defects is formed on the surface.

Further, the chromium bond on the surface is broken by ion implantation to form a fine crystal surface (amorphous surface). By subjecting this to a heat treatment in an atmosphere containing oxygen, oxidation proceeds while fine crystals remain, and fine oxides can be formed.

When chromium oxide obtained by ion implantation is subjected to heat treatment in an oxygen-free atmosphere, for example, an inert gas atmosphere such as a nitrogen atmosphere or an argon atmosphere, unstable oxides or metallic chromium Is slightly contained. Further, in a heat treatment in a vacuum atmosphere, release of oxygen from the surface becomes remarkable. Therefore, heat treatment in an atmosphere containing oxygen is desirable.

As described above, a surface having a small friction coefficient and a very small amount of wear can be obtained by performing a heat treatment in an atmosphere containing oxygen after ion-implanting at least oxygen into a compound containing chromium. . Then, by using this surface for a mold for molding an optical element, it is possible to obtain a molded surface having a small friction coefficient and an extremely small amount of wear.

According to the first aspect of the present invention, at least oxygen is ion-implanted into the chromium-based thin film formed on the mold base, and thereafter, a heat treatment can be performed in an atmosphere containing oxygen.

For example, a thin film containing chromium as a main component is formed on a molding surface of a high thermal conductivity mold substrate having physical properties required for an optical element molding die, and oxygen is ion-implanted into the surface. By performing a heat treatment thereafter, it becomes possible to obtain an optical element molding die having a surface having a high thermal conductivity, a small wear coefficient of the molding surface, and an extremely small amount of wear. Thus, by selecting the material of the mold base while considering the physical properties of the mold for molding the optical element,
It has various characteristics, a small coefficient of wear, and a surface characteristic with a very small amount of wear.

According to a second aspect of the present invention, in the first aspect, the heat treatment is performed within a temperature range of 400 to 700 ° C.

In the present invention, at least oxygen ions are implanted into the surface of a chromium-containing mold base or a thin film containing chromium as a main component formed on the mold base, and thereafter, a heat treatment is performed to form a molding surface. Although it is formed, the conditions of the heat treatment are limited to a temperature range of 400 ° C. to 700 ° C. Usually, the temperature at which chromium is thermally oxidized is about 550 ° C. in the air atmosphere. However, chromium oxide formed by implantation of oxygen ions exists in a state where the amount of oxygen is supersaturated with respect to the amount of chromium. In addition, since the bond is broken by ion implantation into the surface or the thin film, recrystallization proceeds even at a relatively low temperature as compared with normal thermal oxidation.

For this reason, if the temperature is 400 ° C. or higher, recrystallization can be performed. At a temperature lower than this, recrystallization of the oxide on the surface becomes difficult. In addition, when heat treatment is performed at a temperature of 700 ° C. or more, the crystal grows rapidly after recrystallization of the oxide, so that the effect of amorphization by ion implantation is lost. A similar surface or thin film is formed, and the crystal becomes large, so that no effect can be obtained on the friction coefficient and the wear amount. Therefore, the temperature of the heat treatment in the oxygen atmosphere is preferably in a temperature range of 400 ° C to 700 ° C. More preferably, it is a temperature range of 450 ° C to 650 ° C, and still more preferably, a temperature range of 500 ° C to 600 ° C.

[0020] The invention of claim 3 is the invention of claim 1 or 2, wherein the mold base is an alloy, ceramic or cermet containing chromium as a main component.

In the present invention, at least oxygen is ion-implanted into a mold base made of an alloy containing chromium as a main component, a ceramic, and a cermet, and then a heat treatment is performed in an atmosphere containing oxygen to form a chromium oxide layer. Therefore, the bonding of the surface of the mold base made of an alloy containing chromium, ceramic, and cermet is broken, resulting in a fine crystal surface (amorphous surface). This is heat-treated in an atmosphere containing oxygen to recrystallize it and oxidation proceeds as fine crystals, so that a fine oxide can be formed.

Further, in the present invention, since ions are directly implanted into the mold base, a simple processing step of simply implanting oxygen ions into the base and performing a heat treatment is provided. In addition, a strong chromium oxide layer can be formed by the ion implantation effect.

The invention of claim 4 is the invention according to any one of claims 1 to 3, wherein the formation of the thin film containing the mold base material chromium as a main component and the formation of at least oxygen ions And simultaneously or alternately.

Such a film is formed by a dynamic ion mixing process. In the dynamic ion mixing process, vacuum deposition and ion implantation are performed simultaneously, and an element is forcibly added to the surface during the deposition. As a result, a mixed layer of the mold base, the injection element, and the film forming element is formed on the surface. Due to the forced addition of ions, the mixed layer becomes a mixed layer of the base element, the implanted element, and the film forming element near the mold base, and becomes a mixture of the implanted element and the film formed element near the surface. In such a dynamic ion mixing process, there is no clear interface between the mixed layer and the mold substrate.

According to the present invention, oxygen ions are implanted by using the dynamic ion mixing process while depositing a thin film containing Cr as a main component on the molding surface.
That is, an inert ion such as a nitrogen ion is implanted into the base material surface to start the Cr film formation. After that, oxygen ions are implanted, and various conditions are set in addition to the amount of oxygen implanted so as to obtain a desired chromium oxide content or more. The reason why the inert ions are first implanted into the surface of the substrate is to prevent the substrate from being oxidized by oxygen ions. The ions are good. On the other hand, if oxygen ions are implanted first, there is a possibility that the film will be peeled off from the portion after film formation. Further, by implanting inert ions first, a portion that becomes a nucleus for growth of a thin film to be deposited is easily formed, and the adhesion of the film is improved.

The chromium oxide film formed by the dynamic ion mixing process is also heat-treated in an atmosphere containing oxygen, so that oxygen is ion-implanted into a compound containing chromium, and then heat-treated in an atmosphere containing oxygen. As in the case of the above, the surface has a small coefficient of friction and an extremely small amount of wear. Therefore, according to this method, it is possible to form a thick layer having a characteristic of a small wear coefficient and a very small wear amount. Normally, the search for ions to enter by ion implantation is several hundred to several thousand Angstroms, but by performing this dynamic ion mixing process, even if the thickness is several μm, a layer having the above-described characteristics can be obtained. Obtainable. The chromium oxide formed by the dynamic ion mixing method can supersaturate oxygen, so that the entire film formed is the same as when oxygen ion implantation is performed on chromium. Then, by performing a heat treatment in an atmosphere containing oxygen, the entire film has a small wear coefficient and a very small wear amount.

According to a fifth aspect of the present invention, there is provided a mold for molding an optical element, which is produced by the production method according to any one of the first to fourth aspects and has a chromium oxide layer on a molding surface.

Chromium oxide has a large standard formation energy and is a negative value, and it is difficult to form a compound with other elements. For this reason, mold release failure called seizure of the molten glass during molding is unlikely to occur. Further, chromium oxide is a sublimable substance, and thus has a releasability.

When the optical element is molded in an atmosphere containing oxygen by the molding surface of chromium oxide, the outermost surface layer is in a state where chromium oxide is always formed by heating, and no seizure occurs for the above-mentioned reason. In addition, the sublimation of chromium oxide generates a gas gap between the molding surface and the glass, thereby further improving the releasability. By gradually sublimating the outermost layer of the molding surface, the releasing effect can be continued.

The mold for forming an optical element of the present invention contains oxygen, after ion-implanting at least oxygen into a compound containing chromium, in addition to the above-described specific mold releasability as a mold for forming a chromium oxide optical element. By performing the heat treatment in an atmosphere, it is possible to impart surface characteristics with a small friction coefficient and a very small wear amount. When this surface is used as a molding surface of a mold for molding an optical element, the frictional resistance between the mold and the glass is reduced due to its low friction coefficient, and the glass can be sufficiently filled to the shape of the outer peripheral portion of the mold. Further, since the amount of wear on the surface is extremely small, the wear on the molding surface due to molding is extremely small.

[0031]

(Embodiment 1) FIG. 1 shows the configuration of an apparatus used in a method of manufacturing an optical element molding die. The holder 2 is provided in the vacuum container 6, and the holder 2 holds the mold base 1 of the optical element molding die. In addition, holder 2
Is attached to a cooling plate (not shown) and is cooled by cooling water supplied to the cooling plate.

An ion source 3 for irradiating ions 8 is provided at a position facing the mold base 1 in the vacuum vessel 6. The ion source 3 is in communication with an inlet 4 for introducing ionized ion gas. The inlet 4 is connected to an ionizer not shown. In the vicinity of the mold base 1, an ion current measuring device 5 for measuring the number of irradiated ions is arranged. Further, the vacuum container 6
Is reduced to a predetermined pressure by a vacuum pump 7.

In this embodiment, an optical element molding die is manufactured using tungsten carbide as the mold substrate 1. First, the mold substrate 1 made of tungsten carbide is processed into a concave shape having a predetermined radius of curvature (70 mm), and the molding surface is formed using diamond abrasives or the like to have a maximum surface roughness (Rmax) of 0.
Mirror polishing is performed so that the thickness becomes 03 μm or less. afterwards,
A chromium nitride film is formed. This film formation was performed by magnetron sputtering. First, a Cr film was formed as an intermediate layer by 2000 Å, and then a chromium nitride film was formed by 6000 Å.

Next, the mold substrate 1 thus obtained is held in the holder 2 in the vacuum vessel 6, and in this state, the inside of the vacuum vessel 6 is evacuated using the vacuum pump 7, and 6 × 10
High vacuum of ^-4 Pa or less.

Then, ions 8 are irradiated from the ion source 3 to the molding surface of the mold base 1. In this embodiment,
Pure oxygen is introduced into the ionization device by 1 to 5 SCCM, and plasma is generated to ionize. Further, the ionized material is mass-separated to a desired ion ratio, and is introduced into the ion source 3 through the inlet 4. The energy during acceleration of the irradiated oxygen ions is 30 KeV,
The ion beam current density is 35 μA / cm ² . The ion irradiation amount is 1 × 10 ¹⁸ ions / cm ² .
The method of the ion source is not limited to the method used in this embodiment, but may be a Kaufman type, a bucket type, or the like.

In this embodiment, it is desirable that the acceleration energy of the irradiated ions is in the range of 5 to 200 KeV.
More preferably, it is in the range of 15 to 100 KeV.
When the acceleration energy is 5 KeV or less, the processed surface is excessively damaged due to the etching effect, and the formed film thickness becomes thin, and the chromium oxide layer formed on the surface becomes too thin, resulting in a good effect. Is not preferred because it is no longer possible to obtain On the other hand, when the acceleration energy is 200 KeV or more, the treated surface is heated, which affects the mold substrate 1, which is not preferable.

When the beam current density is 200 μA / cm ² or more, the treated surface becomes rough, so that it is not preferable to use it for the functional surface of a precise molding die. Preferably, the beam current density is 100 μA / cm ² or less.

It is possible to cool the mold base 1 during the ion implantation process by flowing water through the cooling plate of the holder 2 supporting the mold base 1, whereby the mold base during the implantation can be cooled. Thermal deformation of the material 1 can be prevented.

In this embodiment, the chromium nitride film is formed by magnetron sputtering. However, the present invention is not limited to this, and the film may be formed by a PVD method, various CVD methods, plating, or the like.

The optical element molding die obtained as described above was heated at 550 ° C. for 50 minutes using an electric furnace.
The specific method of the heat treatment is as follows. First, the mold for molding an optical element is set in an electric furnace, and the 55
The temperature is raised to 0 ° C., then maintained for 30 minutes, and then cooled naturally in the furnace. The atmosphere at the time of heating has a certain effect even in a vacuum or an inert gas atmosphere,
An atmosphere containing oxygen is favorable for forming an oxide layer on the surface.

The heating temperature was 550 ° C.
What is necessary is just the temperature range of 00 degreeC-700 degreeC. Usually, the temperature at which the thermal oxidation of chromium proceeds is 550 ° C. in the air atmosphere.
Before and after, the chromium oxide formed by the implantation of oxygen ions has a surface in which the amount of oxygen is supersaturated with respect to the amount of chromium, and the surface is broken by ion implantation. In this state, recrystallization proceeds even at a relatively low temperature as compared with normal thermal oxidation. Therefore, if the temperature is 400 ° C. or higher, this recrystallization can be performed. However, if the temperature is 400 ° C. or lower, the recrystallization of the oxide on the surface becomes difficult. On the other hand, when the heat treatment is performed at a temperature of 700 ° C. or more, since the crystal rapidly grows after recrystallization of the oxide, the effect of amorphization by ion implantation disappears, and the surface of ordinary chromium The surface is similar to that of oxide. For this reason, the crystals become large, and good effects cannot be obtained on the friction coefficient and the wear amount.

From the above, the temperature in the heat treatment is set in the temperature range of 400 ° C. to 700 ° C. The temperature of this heat treatment is preferably 450
° C to 650 ° C, more preferably 500 ° C to
The temperature range is 600 ° C. This temperature is the temperature of the surface of the mold, not the temperature of the atmosphere in the furnace. Therefore, the same effect can be obtained even if the heat treatment is performed in a short time by setting the atmosphere temperature in the furnace to a high temperature, and in this case, the effect of the heat treatment is applied only to the outermost surface layer . In order to impart the effect of the heat treatment to all the regions into which oxygen is ion-implanted, it is preferable to perform the heat treatment in a temperature range of 500 ° C. to 600 ° C. for tens of minutes or more.

FIG. 2 shows the structure of the surface of the optical element molding die manufactured as described above. The lowermost layer is tungsten carbide 9, which is a component of the mold base 1, and a chromium film 10 as an intermediate layer formed by magnetron sputtering is present near the surface thereof, and a nitride film formed by magnetron sputtering is formed thereon. There is a chromium film 11.
The chromium oxide layer 12 is formed on the surface layer. The chromium oxide layer 12 is in a state in which oxygen is inclinedly implanted by ion implantation, and is recrystallized as it is by heat treatment, so that it is a strong layer.

In this embodiment, when oxygen ions are implanted into the molding surface, the implantation amount is adjusted by the beam current density and the implantation time of oxygen ions so that oxygen is supersaturated on the surface. . This adjustment is performed by the ion current measuring device 5. As the ion current measuring device 5, a Faraday cup provided with a secondary electron suppressing electrode was used.

According to such a method of manufacturing a mold for forming an optical element, the chromium oxide obtained by ion implantation is subjected to a heat treatment in an atmosphere containing oxygen, so that the amorphous chromium on the implantation surface is regenerated. Crystallized. In the oxidation of chromium by ordinary thermal oxidation, chromium that cannot be oxidized exists not only as metallic chromium but also as an unstable oxide. However, the surface of the chromium oxide obtained by this ion implantation has an excessive amount of oxygen with respect to the amount of chromium, so that the chromium can be sufficiently heated by heat treatment in an atmosphere containing oxygen. Oxidize. Accordingly, dichromium trioxide, which is the most stable chromium oxide, is formed, and stable chromium oxide having no defect is uniformly formed on the surface. Furthermore, since the bonding of chromium on the surface is broken by ion implantation to form a fine crystal surface (amorphous surface), even if this is heat-treated, the crystal growth does not progress, and the fine crystal Oxidation proceeds as it is, and a fine oxide can be formed.

When the coefficient of friction of the surface of the optical element molding die formed by the above method was measured by a ball-on-disk test method, the coefficient of friction was 0.3. Also,
Even when the number of rotations was 25,000, no abrasion was observed on the surface. The test conditions were as follows. Alumina balls having a diameter of 4 inches were used as test balls, and a load of 2 N was applied to the test pieces.
mm was moved at a speed of 5.23 cm / sec to measure the friction coefficient. On the other hand, the chromium oxide surface obtained by simply heat-treating the chromium compound and the chromium oxide surface obtained only by ion implantation both have a rotation frequency of about 2,000 times and reach the mold substrate. It has worn out. Further, the coefficient of friction also showed a large value as compared with the surface of this embodiment.

Next, the glass material SK11 (transition point: 5) was formed using the optical element molding die manufactured according to the above embodiment.
A preform having a temperature of 35 ° C. and a softening point of 630 ° C.) was pressed. The pressing conditions were as follows: after the glass material was softened by heating to 710 ° C., it was conveyed between upper and lower molds, and the mold temperature was 515 ° C. and the press pressure was 25 kg / cm ² . This process was repeated 100,000 times, but no abrasion was observed.

Then, the surface roughness of the molded surface after the pressing was measured, but it was substantially the same as the original. Further, a PV value representing a deviation from a desired design value is 0.
In contrast to 10 μm, the PV value of the molded lens was also 0.10 μm. This is because the flow of the glass material was smooth due to the low friction coefficient of the surface, and the transferability was improved.

When the same molding was performed using an optical element molding die using a chromium oxide layer formed by simple thermal oxidation of chromium on the molding surface, the PV value of the molded lens was 0.23 μm.
Met. Furthermore, when the molding was continued and the mold surface was measured after repeating 30,000 times, the PV value was 0.34 μm.
m, and the vicinity of the center of the molding surface was dented. This is due to wear due to the flow of the glass.

Chromium oxide has a large standard formation energy and is a negative value, and it is difficult to form a compound with other elements.
For this reason, mold release failure called seizure of the molten glass during molding is unlikely to occur. Further, since chromium oxide is a sublimable substance, it has good releasability.

According to such an embodiment, a thin film containing chromium as a main component is formed, and then, after oxygen ions are implanted, heat treatment is performed in an atmosphere containing oxygen to form a chromium oxide on the molding surface. This layer forms a layer, and the surface of chromium oxide obtained by ion implantation exists in a state in which the amount of oxygen is supersaturated with respect to the amount of chromium, and this is heated in an atmosphere containing oxygen. Then, chromium is sufficiently oxidized, and the surface becomes the most stable dichromium trioxide as chromium oxide, and stable chromium oxide having no defect is uniformly formed on the surface. Furthermore, the chromium bond on the surface is broken by ion implantation to form a fine crystal surface (amorphous surface). Even if this is heat-treated, the crystal growth does not progress and the crystal remains fine. As a result, recrystallization and oxidation proceed, and a fine oxide can be formed. By these,
The surface of the mold substrate has a low coefficient of friction and a small amount of wear.

Therefore, the mold for forming an optical element of this embodiment has a surface characteristic with a small friction coefficient and an extremely small wear amount in addition to the releasability as a material of chromium oxide. Such a low coefficient of friction reduces the frictional resistance between the mold and the glass, so that the glass can be sufficiently filled up to the shape of the outer peripheral portion of the mold, and the transferability of the mold shape to the lens is improved.
Further, since the amount of wear on the surface is small, the wear on the molding surface of the mold due to molding is extremely small. As described above, the progress of deterioration due to abrasion of the mold is slowed, and the life of the mold can be extended while maintaining good releasability. In addition, according to the optical element molding die of this embodiment, since the chromium oxide layer is formed only on the molding surface, the characteristics of the mold base material are maintained, and the mold has the releasability that is the surface characteristic. As it is, it has the characteristics that the friction coefficient of the molding surface is small and the amount of wear is extremely small.

(Embodiment 2) FIG. 3 shows an apparatus used for manufacturing an optical element molding die according to this embodiment. A holder 14 is provided in the vacuum vessel 22, and the holder 14 holds a mold base 13 of an optical element molding die. The holder 14 is attached to a cooling plate (not shown) and is cooled by cooling water supplied to the cooling plate.

An ion source 17 for irradiating ions 23 is provided at a position facing the mold base 13 in the vacuum vessel 22. The ion source 17 is in communication with an inlet 18 for introducing ionized ion gas. The inlet 18 is connected to an ionizer not shown. Further, an ion current measuring device 20 for measuring the number of irradiated ions is arranged near the mold base 13.

Below the mold base 13, an evaporation source 15 is arranged. The evaporation source 15 is a substance 16 containing a film forming element.
Is to evaporate. This film formation is monitored by the film thickness monitor 19. The film thickness monitor 19 measures the number of elements formed on the surface of the mold base 13 and the film thickness thereof. The inside of the vacuum container 22 is reduced to a predetermined pressure by the vacuum pump 21.

In this embodiment, an optical element molding die is manufactured by using tungsten carbide as the mold base 13.
First, the mold substrate 13 is ground into a predetermined aspherical shape, and the molding surface is subjected to a maximum surface roughness (R) using diamond abrasive grains or the like.
max) Mirror polishing is performed so as to be 0.15 μm or less. Thereafter, the mold base 13 is held by the holder 14, and in this state, the inside of the vacuum vessel 22 is evacuated by the vacuum pump 21 to a high vacuum of 4 × 10 ⁻⁴ Pa or less.

In this state, first, argon ions are implanted into the molding surface of the mold base 13. That is, 2.4 SCCM of pure argon gas is introduced into the ionization apparatus, ionized by generating plasma, ionized, mass-separated, and argon atom ions are introduced from the ion introduction port 18 to the ion source 17.

The acceleration energy of the irradiated argon ions is 5 KeV, and the beam current density of the ions is 25 μA / cm.
^{2. The} ion irradiation amount was 1 × 10 ¹⁷ ions / cm ² . It should be noted that the ion source 17 is not limited to the method used in this embodiment, but may be a Kaufman type, bucket type, or the like.

After the ion implantation of the argon ions, the material 16 containing chromium was vacuum-deposited on the molding surface of the mold base 13 from the evaporation source 15. Note that the implantation amount of argon ions was 1 × 10 ¹⁷ ions / cm ^2.
After that, the vapor deposition of chromium and the implantation of argon ions are simultaneously performed. Thereby, a mixing layer of tungsten carbide, argon, and chromium of the mold base 13 is formed.

As a film thickness monitor 19, a quartz oscillation type film thickness meter is used.
Angstrom / sec is set, and this vapor deposition is continued until the film thickness becomes 2000 Å.

After that, the pure argon gas introduced into the ionizer is switched to pure oxygen. At this time, the introduction amount of the pure oxygen gas is appropriately adjusted within a range of 1 to 3 SCCM. Further, the ionized material is mass-separated, and oxygen atom ions are selected and implanted. The acceleration energy of the irradiated oxygen ions is 10 KeV, and the beam current density of the ions is 45 μm.
A / cm ² . During this time, chromium deposition and oxygen ion implantation are performed simultaneously by continuing chromium deposition. The deposition rate at this time was set to 6 angstroms / sec while adjusting with the film thickness monitor 19, and the film thickness was set to 1.
It continued until it reached 0000 angstroms. By performing such chromium deposition and oxygen ion implantation at the same time, oxygen can be present in the chromium oxide film in a supersaturated state. It should be noted that when chromium deposition and oxygen ion implantation are performed simultaneously, it is also possible to introduce oxygen into the vacuum vessel 22 so that more oxygen is present.

The optical element molding die thus obtained was heated at 580 ° C. for 80 minutes using an electric furnace. The specific method of the heat treatment is as follows. The mold for forming an optical element is set in an electric furnace, the temperature is raised to 580 ° C. in the air atmosphere over 20 minutes, and then maintained for 60 minutes, and then naturally cooled in the furnace. Is what you do.

FIG. 4 shows the surface of the optical element molding die formed as described above. The lowermost layer is tungsten carbide 24, which is a component of the mold base 1, and there is a chromium film 25 formed thereon after injecting argon in advance. The interface between the mold base 24 and the chromium film 25 is mixed by argon injection, and there is no clear interface.

The reason why argon ions which are inert ions are implanted beforehand on the surface of the mold base 24 is to prevent the surface from being oxidized by oxygen ions due to the effect of cleaning the surface by sputtering. In order to form a mixed diffusion layer of the mold base and the membrane, an inert ion is preferable. On the other hand, if oxygen ions are implanted first, oxidation proceeds from the interface after film formation, and the film is easily peeled. Further, by implanting inert ions first, it becomes easy to form a portion that becomes a nucleus for the growth of a thin film to be deposited, and the adhesion of the film is also improved.

In FIG. 4, a chromium oxide film 26 is formed on the chromium film 25 by heating the chromium oxide film formed by the deposition of chromium and the implantation of oxygen ions. The surface of the chromium oxide obtained by this method has a state in which the stress of the film, which is a characteristic of the film formed by the dynamic mixing method, has been reduced, and has a high density.

When the coefficient of friction on the surface of the optical element molding die formed by the above method was measured by the ball-on-disk test method, the coefficient of friction was 0.32. Even when the number of rotations was 25,000, no wear was observed on the surface. The test conditions were as follows. A 4 inch diameter alumina ball was used as a test ball, and the friction coefficient was measured by moving a diameter of 10 mm at a speed of 5.23 cm / sec under a load of 2N.

As described above, the surface formed in this embodiment has a small friction coefficient and a very small wear amount. Using this optical element molding die, a glass material LaS
A preform of F03 (transition point: 730 ° C., softening point: 808 ° C.) was pressed. Pressing conditions are as follows:
℃, softened by heating, and transported between upper and lower molds.
The temperature was 80 ° C. and the press pressure was 40 kg / cm ² . This press was repeated 50,000 times, but no abrasion was observed.

Then, the surface roughness of the molding surface after the use of the press was measured, but it was substantially the same as the original. Also,
The PV value representing the deviation from the desired design value was 0.10 μm on the surface after the mold processing, and the PV value of the lens after molding was 0.10 μm. This is because the flow of the glass material was smooth due to the low friction coefficient of the surface, and the transferability was improved.

When the same molding was carried out using an optical element molding die using a chromium oxide layer formed by simple thermal oxidation of chromium on the molding surface, the PV value of the molded lens was 0.32 μm.
Met. Furthermore, when the molding was continued and the mold surface was measured after repeating 5000 times, the PV value was 0.3
4 μm, and the vicinity of the center of the molding surface was dented. Thereafter, when the molding was further cascaded, the film was peeled off after a total of 7,500 moldings.

According to such an embodiment, the molding surface of the optical element molding die forms a thin film containing chromium as a main component, and simultaneously or alternately implants oxygen ions to form chromium and oxygen. To form a mixed layer of
It is composed of a chromium oxide layer formed by performing a heat treatment in an atmosphere containing oxygen. In the film formed by the dynamic ion mixing method, the amount of oxygen is supersaturated with respect to the amount of chromium, and chromium is sufficiently oxidized by heating, and the surface is most stable as chromium oxide. It becomes dichromium trioxide, and a stable chromium oxide film without defects is uniform.

The surface of the chromium oxide obtained by the above method has the characteristics that the film stress is reduced and the film density is high, which is characteristic of the film formed by the dynamic ion mixing method. ing. Most of the thin film formed by the dynamic ion mixing method is in a state where oxygen ions are implanted and heat treatment is performed. Therefore, most parts of the thin film have a small coefficient of friction and an extremely small amount of wear.
A layer having this characteristic can be formed thick. Further, since the interface between the mold base material and the film is not clear due to the mixing, film peeling does not occur.

(Embodiment 3) In this embodiment, an optical element molding die was manufactured using the same apparatus and method as in Embodiment 1. Note that, as the mold base 1, a chromium carbide sintered body is used to perform the same ion implantation processing and heating processing as in the first embodiment.

FIG. 5 shows the structure of an optical element molding die according to the third embodiment. Chromium carbide 27 which is a component of the mold base 1
There is a chromium oxide layer 28 formed by implanting oxygen ions and then performing a heat treatment in an atmosphere containing oxygen.

In the molding surface of the optical element molding die in this embodiment, the bond of chromium carbide is cut by ion implantation of oxygen into chromium carbide. Further, since oxygen is injected into the surface so as to be supersaturated with oxygen, chromium is sufficiently oxidized by heat treatment in an atmosphere containing oxygen. For this reason, the surface becomes the most stable dichromium trioxide as chromium oxide, and a stable chromium oxide film without defects is formed uniformly. In addition, carbon is present on the surface by breaking the bond of chromium carbide, but by heat treatment, carbon on the surface becomes gaseous carbon dioxide and diffuses, and thus does not exist on the surface. Further, even when the crystal on the surface of the sintered body is large, the crystal is refined by ion implantation, so that the surface roughness can be improved.

In this embodiment, chromium carbide is used as the mold base. However, the present invention is not limited to this, and alloys containing chromium as a main component, ceramics, cermets, and the like can also be used.

In such an embodiment, the mold base is formed of a sintered body of chromium carbide, oxygen is injected into the surface thereof, and thereafter, a heat treatment is performed in an atmosphere containing oxygen to form a molding surface. Since it is formed, a mold for forming an optical element can be manufactured quickly and inexpensively without the trouble of forming a film.
In addition, since there is no film on the molding surface in terms of structure, the phenomenon that the film occurs when the optical element is molded does not peel off.

When glass is formed by using such an optical element molding die, the chromium carbide is simply thermally oxidized and compared with an optical element molding die in which a chromium oxide layer is formed on the molding surface. It is possible to obtain 10 to 10 times the durability. In this embodiment, the glass material SK11 (transition point: 53
A preform having a temperature of 5 ° C. and a softening point of 630 ° C.) was pressed. The pressing conditions are as follows: the glass material is heated and softened to 700 ° C., and is conveyed between the upper and lower dies. The pressing temperature is 510 ° C. and the pressing pressure is 10 kg / cm ² . As a result, the durability was five times that of the optical element molding die in which chromium carbide was simply thermally oxidized to form a chromium oxide layer on the molding surface.

The glass material LaSF03 (transition point temperature: 7)
In the press molding of the preform having a temperature of 30 ° C. and a softening point of 808 ° C.), the glass material is heated to 800 ° C., and is conveyed between the upper and lower dies manufactured according to this embodiment.
0 ℃, it was pressed at a press pressure of 15kg / cm ^2. As a result, it was ten times more durable than an optical element molding die in which chromium carbide was simply thermally oxidized to form a chromium oxide layer on the molding surface.

As apparent from the above description, the present invention includes the inventions described in the following additional items.

(Additional Item 1) At least a molding surface is formed by ion-implanting at least oxygen into a surface containing chromium and then performing a heat treatment in an atmosphere containing oxygen. Mold manufacturing method.

In the present invention, at least oxygen is ion-implanted into the surface containing chromium, and thereafter, a heat treatment is performed in an atmosphere containing oxygen to form a molded surface. And a fine oxide can be formed on the molding surface, and a molding surface having a small friction coefficient and an extremely small amount of wear can be obtained. Therefore, in addition to the good releasability of the chromium oxide itself, it is possible to impart to the molded surface a characteristic having a small friction coefficient and an extremely small wear amount.

(Additional Item 2) The condition of the heat treatment is 4
The method for producing an optical element molding die according to claim 1, wherein the temperature is in the range of 00 ° C to 700 ° C.

In the present invention, since the condition of the heat treatment in the atmosphere containing oxygen is in the temperature range of 400 ° C. to 700 ° C., the crystal is not enlarged, the friction coefficient is reduced, and the amount of wear is reduced. Chromium oxide can be recrystallized, which can reduce the amount of chromium oxide.

(Additional Item 3) The compound containing chromium is ion-implanted with at least oxygen and then subjected to a heat treatment in an oxygen-containing atmosphere to form at least a molding surface. A mold for forming an optical element, comprising a chromium oxide layer on a molding surface.

According to the present invention, in addition to the good releasability of chromium oxide itself, since the molding surface has a characteristic of a small friction coefficient and a very small wear amount, the frictional resistance between the mold and the glass is reduced. In addition, the glass is sufficiently filled up to the shape of the outer peripheral portion of the mold, and the transferability of the mold to the lens is improved.
In addition, since the amount of wear on the surface is small, the wear on the molding surface of the mold due to molding is extremely small, and the progress of deterioration due to wear is slowed, and the life of the mold can be extended.

(Additional Item 4) A thin film containing chromium as a main component is formed, and then at least oxygen is ion-implanted, and then heat treatment is performed in an atmosphere containing oxygen.
A method for producing an optical element molding die, wherein at least a molding surface is formed.

According to the present invention, a thin film containing chromium as a main component can be formed on a material having physical properties required for a mold for forming an optical element, and oxygen is ion-implanted on the surface. After that, since the heat treatment is performed, an optical element molding die having a characteristic that the friction coefficient of the molding surface is small and the amount of wear is extremely small in addition to the physical properties required for the optical element molding die can be produced.

(Appendix 5) When the conditions of the heat treatment are 4
Item 4. The method for producing an optical element molding die according to Item 4, wherein the temperature is in the range of 00 ° C to 700 ° C.

According to the present invention, it is possible to recrystallize chromium oxide without enlarging the crystals, reducing the friction coefficient and reducing the amount of wear.

(Supplementary note 6) The production according to Supplementary note 4, wherein at least a molding surface is formed by performing a heat treatment in an atmosphere containing oxygen after at least oxygen is ion-implanted into the thin film containing chromium as a main component. A mold for molding an optical element, which is produced by a method and has a chromium oxide layer on a molding surface.

According to the present invention, since the thin film containing chromium as a main component is provided with a chromium oxide layer formed by performing a heat treatment in an atmosphere containing oxygen after at least ion implantation of oxygen, It has the characteristics of a material, a small coefficient of friction of the molding surface, and a characteristic of extremely small wear.

(Additional Item 7) A thin film containing chromium as a main component is formed, and at least oxygen ions are simultaneously or alternately implanted to form a mixed layer of chromium and oxygen, and then heated in an atmosphere containing oxygen. By performing the processing,
A method for producing an optical element molding die, wherein at least a molding surface is formed.

According to the present invention, a thin film containing chromium as a main component is formed, and at least oxygen ions are simultaneously or alternately implanted to form a mixed layer of chromium and oxygen. , And a layer having characteristics of extremely small abrasion can be formed thickly.

(Appendix 8) When the conditions of the heat treatment are 4
Item 7. The method for producing an optical element molding die according to Item 7, wherein the temperature is in the range of 00 ° C to 700 ° C.

According to the present invention, it is possible to recrystallize chromium oxide without enlarging the crystals, reducing the friction coefficient and reducing the amount of wear.

(Additional Item 9) A thin film containing chromium as a main component is formed, and at least oxygen ions are simultaneously or alternately implanted to form a mixed layer of chromium and oxygen, and then heated in an atmosphere containing oxygen. By performing the processing,
An optical element molding die manufactured by the manufacturing method according to claim 7, wherein at least a molding surface is formed, and the molding surface is provided with a chromium oxide layer.

According to the present invention, the formed chromium oxide layer is thick, the progress of deterioration due to wear of the mold is slowed, and the life of the mold can be extended while maintaining good mold releasability.

(Supplementary item 10) At least oxygen is ion-implanted into a mold base composed of an alloy, a ceramic, and a cermet containing chromium as a main component, and then a heat treatment is performed in an atmosphere containing oxygen to form at least a molding surface. Forming a mold for forming an optical element.

In the present invention, at least oxygen is ion-implanted into a mold base made of an alloy containing chromium as a main component, a ceramic, and a cermet, and then a heat treatment is performed to form a molding surface. Chromium oxide can be formed directly, eliminating the need for a thin film forming step, making it possible to easily form a chromium oxide layer

(Additional Item 11) The conditions of the heat treatment are as follows:
Item 11. The method for producing an optical element molding die according to Item 10, wherein the temperature is in a temperature range of 400 ° C to 700 ° C.

According to the present invention, chromium oxide can be recrystallized without enlarging the crystal, reducing the coefficient of friction and reducing the amount of wear.

(Supplementary Item 12) At least oxygen is ion-implanted into a mold base made of an alloy, ceramic or cermet containing chromium as a main component, and then a heat treatment is performed in an atmosphere containing oxygen to form at least a molding surface. 12. A mold for molding an optical element, which is manufactured by the manufacturing method according to Additional Item 11 and has a chromium oxide layer on a molding surface.

According to the present invention, the mold base is directly formed with a strong surface having a low coefficient of friction and an extremely small amount of abrasion. Can be.

[0104]

According to the first aspect of the present invention, stable chromium oxide having no defect can be uniformly formed on the surface and fine oxide can be formed on the molding surface.
A molded surface having a small coefficient of friction and an extremely small amount of wear can be obtained.

According to the second aspect of the present invention, the crystal of chromium oxide is not enlarged and the coefficient of friction is reduced.
Chromium oxide can be recrystallized, which can reduce the amount of wear.

According to the third aspect of the present invention, chromium oxide can be formed directly on the surface of the mold substrate, and the step of forming a thin film is not required, and the chromium oxide layer can be easily formed.

According to the fourth aspect of the present invention, since a mixed layer of chromium and oxygen is formed on a thin film containing chromium as a main component, the thickness of the layer having characteristics of a small friction coefficient and a very small amount of wear is increased. Can be formed.

According to the fifth aspect of the invention, in addition to the good releasability of chromium oxide itself, the frictional resistance between the mold and the glass is reduced, so that the transferability of the mold shape to the lens is improved.
Moreover, since the amount of wear is small, the life of the mold can be extended.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a manufacturing apparatus used in Embodiment 1 of the present invention.

FIG. 2 is a sectional view of a molding die according to the first embodiment.

FIG. 3 is a sectional view of a manufacturing apparatus used in a second embodiment.

FIG. 4 is a sectional view of a molding die according to a second embodiment.

FIG. 5 is a sectional view of a molding die according to a third embodiment.

FIG. 6A is an electron micrograph of a molding surface of a molding die of the present invention, and FIGS. 6B and 6C are electron micrographs of a molding surface of a conventional molding die.

FIG. 7A is a characteristic diagram of a friction test on a molding surface of a molding die of the present invention, and FIGS. 7B and 7C are characteristic diagrams of a friction test on a molding surface of a conventional molding die.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 13 type base material 9 tungsten carbide 10 chromium film 11 chromium nitride film 12 chromium oxide layer 24 tungsten carbide 25 chromium film 26 chromium oxide film 27 chromium carbide 28 chromium oxide layer

Claims (5)

[Claims] 1. a step of ion-implanting at least oxygen into the surface of a chromium-containing mold substrate or a thin film containing chromium as a main component formed on the mold substrate; A step of performing a heat treatment in an atmosphere containing: a method for producing an optical element molding die. 2. The method according to claim 1, wherein the heat treatment is performed within a temperature range of 400 to 700 ° C. 3. The method of manufacturing an optical element molding die according to claim 1, wherein said mold base is an alloy, ceramic or cermet containing chromium as a main component. 4. The method according to claim 1, wherein when forming the thin film containing chromium base material as a main component, the forming of the thin film and the implantation of at least oxygen ions are performed simultaneously or alternately. A method for producing a mold for molding an optical element according to any of the above items. 5. An optical element molding die produced by the production method according to claim 1, wherein the molding surface is provided with a chromium oxide layer.