JP2003089533A - Molding die for glass lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the durability of a molding die and the yield of a product (lens) by preventing a work (glass) from stacking to the molding die of a glass lens and preventing the molding face of the die from being damaged for a long time. SOLUTION: A transparent carbon film 2 having >=95 at.% carbon content and 3,000 to 7,000 Knoop hardness is formed on the surface of the die base material 1. The transparent carbon film 2 contains no hydrogen, has a small content of a graphite component and has a long life.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass lens molding die having improved durability and molding yield.

[0002]

2. Description of the Related Art Glass lenses used in various optical instruments are manufactured by molding molten glass in a mold. The temperature during molding depends on the glass material, but is generally 400 to 7
It is 00 ° C. Since the temperature is relatively high, there are problems such as oxidation and corrosion, and a method of performing molding in an inert gas atmosphere has been adopted.

Particularly, in a mold used for molding, there is a problem that glass adheres to the surface to cause defective molding, or the flow of molten glass on the mold surface is poor and wrinkles are formed on the lens surface. Further, since the mold material is a steel material (stainless steel or the like) having a relatively low hardness, the surface is frequently worn and deformed.

In order to solve such problems, there is a method in which a lubricant is applied to the surface of the mold to enhance the mold releasability and fluidity. But,
Since the object to be processed is a lens that requires a mirror surface, this method has problems such as clouding of the surface and is difficult to apply.

There is also a method of making the die material harder and having a high oxidation / corrosion resistance and cemented carbide or ceramics, but no significant improvement in releasability is seen, and on the other hand, the cost is greatly increased, so that it is not often applied. It has not been. Similarly, surface treatment such as Cr plating or TiN coating is also less effective for the cost.

Among these, the method of coating the diamond-like carbon film is effective for improving the releasability. Such carbon films are described in, for example, JP-A-61-281030, JP-A-6-345461, JP-A-7-314259, and JP-A-11-157852. In addition to glass lens applications, JP-A-2-26842 and JP-A-4-34
4211, JP-A-9-194227, and JP-A-9-183.
No. 622 discloses a method of applying a diamond-like carbon film.

However, the diamond-like carbon film has poor adhesion to the base material and is extremely difficult to put into practical use. For example, Japanese Patent Application Laid-Open No. 4-344211 proposes a measure for improving adhesion by using a Mo intermediate layer, and Japanese Patent Application Laid-Open No. 11-157852 proposes a nitride or carbide intermediate layer. Also,
JP-A-7-314259 proposes an improvement by a cleaning method of a substrate, and JP-A-9-194227 and JP-A-9-183622 propose an example of substrate surface modification by ion implantation.

[0008]

Various methods have been studied in this way, but in reality, a diamond-like carbon film having sufficient durability has not been obtained. Immediately after the start of use, the yield of the lens formed with good releasability was high, but immediately the glass was fixed to the mold, and the yield was reduced.

The present invention covers the molding surface of a glass lens molding die with a film which is more stable and durable than the conventional carbon film to reduce the sticking of the glass to the surface of the die, thereby smoothing the glass. The objective is to maintain stable molding for a long period of time and to improve the molding yield.

[0010]

In order to solve the above problems, in the present invention, the molding surface of the mold has a carbon content of 95 at% or more and a Knoop hardness of 3000 or more and 700 or more.
Cover with a transparent carbon film of 0 or less. The transparent carbon film may be provided only on a part of the molding surface, that is, on a portion where the glass is likely to adhere.

It was found that the durability of the conventional diamond-like carbon film is not sufficient not only because of the adhesion but also because the film itself has poor durability. That is, since the diamond-like carbon film generally contains a graphite component, when used at high temperature, graphitization proceeds from the already existing graphite structure as a starting point, and the film becomes weak and peels.

The transparent carbon film used in the present invention does not have the problem. Such a transparent carbon film is a high-hardness amorphous carbon film, and when it is coated on a metal, it exhibits an interference color due to its transparency even if the film thickness exceeds 1 μm. The transparent carbon film will be defined in detail below.

The film made of carbon includes a diamond film, a graphite film, a diamond-like carbon film and the like. The transparent carbon film is a special film contained in a material system generally called diamond-like carbon.

Diamond-like carbon is a very broad concept material. Diamond like carbon (Diamond like carbon;
DLC), as well as amorphous carbon (a-C, a-
C: H), i-C (eye carbon), hard carbon (hard)
Also called carbon). The structure is an amorphous structure partially having an sp3 structure, the constituent element is carbon only or a hydrogenated carbon film containing hydrogen, and the maximum hydrogen content is 50 at% or more. Knoop hardness is
It is often defined in a wide range of 800 to 8000.
Generally, a graphite component is contained in the film and the film thickness is 0.5.
If it exceeds μm, the color changes from brown to black or gray.

The transparent carbon film according to the present invention is an amorphous carbon film which does not particularly contain hydrogen, has a small graphite component, and has a high transparency among the diamond-like carbons thus widely defined.

Specifically, the constituent element is only carbon, except for impurities that are unavoidable due to the synthetic method. Considering the presence of impurities, 95 at% or more is carbon. Impurities are most often hydrogen and oxygen derived from water, and may be mixed with nitrogen derived from residual gas. Further, a small amount of metal components such as iron inside the film forming apparatus may enter. Since it is mainly synthesized using solid carbon as a raw material, a trace amount of impurities are also contained in the solid carbon raw material. Excluding oxygen, hydrogen, and nitrogen derived from water and air, the analysis shows that 99.5 at% or more is carbon.

The fact that the graphite component is small means that it is specifically transparent and that the Knoop hardness is 3000 or more and 700 or more.
It is defined as being 0 or less. Its transparency is 0.6μ
Interference color is exhibited even at a film thickness of m or more. The standard of the average transmittance of visible light at a film thickness of 1 μm is 30% or more. A Knoop hardness of 3000 or more and 7000 or less is a material having a high hardness among diamond-like carbon films. With dynamic hardness, about 3000kgf (29419.95N) / m
m ² or more, 7,000 kgf (68646.55N) / m
m ² or less.

Since such a transparent carbon film does not easily react with ordinary glass and is excellent in lubricity, when this is applied to a glass lens molding die, the molded glass is easily released from the mold and the yield is improved. . Also, damage to the mold is reduced. This is because the graphite component contained in the film is small and graphitization starting from the already existing graphite phase does not proceed easily, so that the life of the film is extended and such characteristics last extremely long.

About the carbon content of this transparent carbon film 95
The reason why it is specified to be at% or higher is that graphitization from an element other than carbon as the starting point tends to proceed below this range. Desirably, it is composed of only carbon.

Regarding the Knoop hardness, a hardness of 3,000 or less results in a film having a large amount of graphite components, and thus is set to a higher value. The Knoop hardness of 4000 or more is desirable.
Here, the Knoop hardness refers to the surface value of the mold molding surface measured with the smallest load that can be measured with a pushing load of 5 g or more. The reason why the load is not limited to a fixed value is that when the film thickness is large or the hardness is particularly high, the measurement cannot be performed with a low load.

The transparent carbon film is a material different from diamond. Diamond is crystalline and has a Vickers hardness of about 9000 or more. In electron beam diffraction or X-ray diffraction, a diffraction image reflecting the diamond structure is obtained from diamond, but a halo pattern reflecting the amorphous is obtained from the transparent carbon film. In Raman spectroscopic analysis, narrow peak is observed corresponding to the diamond structure in the vicinity of 1333 cm ^-1 in the diamond, the transparent carbon film, a broad peak of a few tens to 2 hundred cm ^-1 in the vicinity of 1350 cm ^-1 and around 1550 cm ^-1 The structure is shown. The refractive index of diamond is about 2.4, but that of transparent carbon film is 2.0-
It takes a value between 2.3. The synthesis temperature of the thin film is 700 ° C. or higher for diamond, generally 800 to 1000 ° C. or higher, but 350 ° C. or lower for the transparent carbon film. For the synthesis of diamond, a large amount of about 99% hydrogen gas is introduced into about 1% hydrocarbon gas such as methane for synthesis. This is because a large amount of atomic hydrogen is generated and the amorphous component in the synthesized film is reacted with the atomic hydrogen to be removed. Solid carbon is used as a raw material for the synthesis of the transparent carbon film.

As the base material of the mold, a steel material such as carbon steel for machine structure, alloy steel, tool steel, stainless steel, cast steel, or cemented carbide can be applied. Ceramics such as silicon nitride, silicon carbide and zirconia may be used as part of the mold.

A plating layer or a thermal spray layer may be formed on the surface of the base material.

The plating layer may be composed mainly of Ni or Cr. In addition, cemented carbide, oxide ceramics such as stellite and zirconia can be applied to the sprayed layer. Since these plating and thermal spray layers are hard and chemically stable, they have the effect of further prolonging the life of the transparent carbon film coated thereon.

The hardness of the surface of the mold before coating with the transparent carbon film is variously selected depending on the purpose of use and environment, but it is preferable to select a material that can obtain high hardness within a possible range. In concrete hardness, Hv350 or more (HRC about 35 or more), and if possible Hv600 or more (HRC about 5
5 or more) is preferable.

For example, as the steel material, carbon steel, tool steel, carburized hardened steel, nitrided steel, etc. may be adopted. Conventionally, these materials were difficult to apply to glass molding dies in terms of oxidation resistance and corrosion resistance, but these problems were eliminated by coating with a chemically stable transparent carbon film. Of these materials, those having a hardness of Hv 350 or higher are relatively inexpensive and easily obtained.

In addition to steel materials, cemented carbide that greatly exceeds Hv1000 is most suitable. When it is required to reduce the weight of the mold itself, ceramics such as silicon nitride, silicon carbide, zirconia, and alumina are preferably used. The hardness of these ceramics is Hv 1000 or more. Since the life is markedly improved, it is a material that can be recommended as the base material if it is reasonable in terms of cost.

By applying the present invention, a life prolonging effect can be seen even in a base material having a hardness of Hv350 or less. For example, Vickers hardness of Hv160 to 270 (Brinell hardness of about HB150 to 250, Rockwell hardness of about HRC5 to 25) is used for stainless steel, which has excellent oxidation resistance and corrosion resistance. Although it has the lower hardness among steel materials, it has been frequently used in lens molding dies since it has excellent corrosion resistance. Because the hardness is low,
Although it was disadvantageous in terms of life, durability is improved by coating the surface with a transparent carbon film.

Aluminum alloys also have extremely low hardness, but a certain life can be secured by coating with a hard carbon film. The hardness of the applied aluminum alloy is preferably Vickers hardness of 85 or more (Brinell hardness of about HB80 or more), and preferably 100 or more (Brinell hardness of about HB95 or more). In order to increase the hardness of the surface, it is effective that the above-mentioned plating layer or thermal spraying layer is applied to the surface.

The transparent carbon film covering the mold has a density of 2.
8 g / cm³Above 3.3g / cm ³To be
desirable.

The density of diamond is 3.52 g / c
The density of m ³ and graphite is 2.25 g / cm ³ . The diamond-like carbon film has a wide value in this range. The transparent carbon film of the present invention preferably has a value higher than that of diamond. Below 2.8 g / cm ³ ,
It shows that it contains components other than carbon, such as hydrogen, and that it contains a large amount of graphite. It has low hardness and low heat resistance. Further, the carbon film having a density of 3.3 g / cm ³ or more becomes a film containing diamond crystals, and the surface roughness becomes large. A more desirable density is 3.0 g / cm ³ or more.

The transparent carbon film of the present invention is transparent because it contains a small amount of graphite as described above, and exhibits an interference color when coated with the base material. In general, diamond-like carbon has a large amount of graphite component in the film and changes from brown to black.

When the amount of the graphite component is large, graphitization tends to proceed from the graphite crystal as a starting point. On the contrary, a transparent carbon film having a small amount of a graphite component and exhibiting an interference color does not easily progress to a graphitization process and has a long life.

Further, if a transparent carbon film exhibiting an interference color is previously coated, there is a merit that when the transparent carbon film is graphitized due to the influence of temperature or the like, the color is changed and the condition of the film can be visually grasped. .

The color tone of the interference color can be various colors such as red, light, yellow, green, blue, purple, an intermediate color thereof, and a state in which these are mixed. The color tone is not essential because it changes depending on the film thickness, the refractive index, and the viewing angle, and any color may be used. Further, it may be a transparent interference color, or black, brown, or a grayish interference color.

When converting the transparency of the transparent carbon film into the transmittance, it is preferable that the visible light transmittance at a film thickness of 1 μm is 30% or more.

Regarding the film thickness, 0.05 μm or more and 5 μm
m or less is preferable.

When the lower limit is 0.05 μm or less, the coating is vulnerable to external force from the high-pressure glass that is about to be solidified, and the coating is easily damaged. It is preferably 0.3 μm or more. If the upper limit is 5.0 μm or more, the internal stress of the film itself is high, and the film tends to peel off. In a generally used range, it may be 2.0 μm or less.

It is desirable that the surface of the transparent carbon film, which is the molding surface, be as smooth as possible. Specifically, the surface roughness is preferably Ra 0.001 μm or more and 0.05 μm or less.

For a film having a surface roughness Ra of 0.001 μm or less, it is practically difficult to process the base material itself. Also, R
When a is 0.05 μm or more, the surface roughness of the lens surface after processing is deteriorated. However, there is no problem if the surface roughness of the surface becomes 0.05 μm or less by performing a treatment such as polishing after coating the transparent carbon film. A more preferable surface roughness is Ra
It is 0.02 μm or less.

For reference, when Rz is 0.003 μm or more and 0.05 μm or less (preferably 0.06 μm or less), and Rmax is 0.05 μm or more and 0.25 μm or less (preferably 0.1 μm or less) as a standard. Good.

As the method for producing the transparent carbon film, an ion plating method, a sputtering method, a laser ablation method or the like can be applied.

These methods are based on 100% graphite, etc.
In principle, the carbon concentration of the synthesized transparent carbon film is 10 because the material consisting of% carbon component can be used as the raw material.
It can be 0 at%.

The ion plating method includes a solid carbon source as a raw material, a combination of electron beam evaporation and various excitation sources, an HCD (holocathode) ion plating method, and a cathode arc ion plating method. The sputtering method also uses magnetron sputtering, DC sputtering, pulse DC sputtering, non-equilibrium magnetron sputtering, etc., using a solid carbon source as a raw material. The laser ablation method is a method of vaporizing solid carbon by laser irradiation to form a film on a substrate. You may use these methods in combination as needed. When importance is attached to the smoothness of the surface, it is preferable to use a deflection magnetic field so that coarse particles are not taken into the film.

In either method, the film is formed at a substrate temperature of 450 ° C. or lower. It is different from crystalline diamond that is synthesized at a high temperature of 700 ° C or higher. It is desirable to perform the treatment at a low temperature in order to avoid the deformation of the substrate, the decrease in hardness, etc., and it is desirable that the temperature be 250 ° C. or less, or the tempering temperature of the substrate or less.

The transparent carbon film is formed of B, Al, S between the base material and the base material.
i, Ge, Ti, V, Cr, Zr, Nb, Mo, Hf,
Adhesion can be improved by providing an intermediate layer made of Ta, W, or at least one of these carbides, nitrides, and carbonitrides.

These metals or metal compounds are considered to be effective in improving the adhesion strength because they have a high affinity for both the base material and the transparent carbon film.

The thickness of the intermediate layer formed between the base material and the transparent carbon film is preferably 0.5 nm or more and 5 nm or less.

If the thickness is 0.5 nm or less, the surface of the base material cannot be covered by one atomic layer or more. Regarding the upper limit, the adhesion is improved even if it is 5 nm or more, but if a thick layer is used, peeling due to fatigue occurs in the intermediate layer portion as the number of times the mold is used increases, so a thin layer of 5 nm or less is preferable, and more preferably 1 nm. Less than is better.

In the intermediate layer between the base material and the transparent carbon film, at least the base material side is (1) the base material,
(2) B, Al, Si, Ge, Ti, V, Cr, Zr,
By forming a mixed layer of (1) and (2), which is composed of one or more kinds of substances selected from Nb, Mo, Hf, Ta and W, the adhesiveness is remarkably improved.

It is considered that the adhesiveness between the base material and the intermediate layer and between the base material and the transparent carbon film becomes stronger by using the mixed layer having a thickness.

The thickness of the mixed layer is 0.5 nm or more and 5
nm or less is preferable.

If the thickness is 0.5 nm or less, a mixed layer of one atomic layer or more cannot be formed in the thickness direction. Regarding the upper limit, the effect can be obtained by forming a mixed layer of 5 nm or more, but the method becomes complicated and expensive equipment is required. Therefore, it is preferably 5 nm or less.

As described above, in the present invention, the structure between the base material and the transparent carbon film may be as follows. That is, from the base material side: -Base material-> intermediate layer-> transparent carbon film / base material-> mixed layer of base material and intermediate layer material-> intermediate layer material-> transparent carbon film / base material-> base material and intermediate layer Mixed layer with materials → transparent carbon film, etc.

These intermediate layers or mixed layers can be formed by any of plasma CVD method, ion plating method, sputtering method and laser ablation method. These are preferably synthesized by a method that is easy to combine with the method for synthesizing a transparent carbon film. Further, a plurality of methods may be combined and used. Particularly preferred is the cathodic arc ion plating method. In the case of forming the mixed layer, a method of setting a bias voltage applied to the substrate to be high can be applied. For example, -400V or more, -30kV
The voltage in the following range can be applied.

When higher performance is required, even a transparent carbon film having an excellent releasability may cause adhesion of glass because very minute irregularities on the surface may cause sticking of glass, so it is important to eliminate it. Therefore, it is more effective to coat the surface of the transparent carbon film and then smooth the surface by mechanical polishing or the like.

Particularly, the effect is remarkable when the film thickness is made relatively thick in consideration of the life, or when the transparent carbon film is formed by the cathode arc ion plating method or the laser ablation method in which coarse particles are easily taken in. is there.

The surface roughness processing methods include buffing, brush polishing and barrel polishing. The main purpose is to make a minute acute angle an obtuse angle, rather than simply reducing the roughness.

The surface roughness after polishing is Ra0.00 as a guide.
01 μm or more and 0.05 μm or less, more preferably Ra
0.02 μm or less is preferable.

When a transparent carbon film is synthesized using a solid carbon raw material having a 100% carbon content, coarse particles are often contained in the film, as compared with a method using a hydrocarbon gas as a raw material. Regarding these particles, it is desirable that the density of particles having a size of 0.2 μm or more observed on the surface of the transparent carbon film is 20,000 particles / mm ² or less.

If the number is 20,000 / mm ² or more, the defective rate of the lens after molding becomes large. 20,000 pieces / mm ² immediately after film formation
If it exceeds, it is desirable to polish the surface as described above.

The glass lens molding die of the present invention is particularly effective when it is molded in an inert gas, but it has a longer life in the atmosphere as compared with conventional products.

[0063]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 to 3 are sectional views of the essential parts of a mold according to the present invention. FIG. 1 shows a base material of a mold, and a surface of the base material which is a molding surface is covered with a transparent carbon film 2 which characterizes the present invention. The above-mentioned plating layer or thermal spray layer 3 (FIG. 2) may be provided between the base material 1 and the transparent carbon film 2. In addition, an intermediate layer 4 (FIG. 3) that enhances the adhesion of the transparent carbon film 2 may be provided. Furthermore, the surface of the lower surface of the base material to which the film 2 is attached or the surface of the film 2 may be polished and finished as needed.

A more detailed embodiment will be described below.

[0065]

Example 1 A carbon film synthesized on a cemented carbide substrate by various methods was heat-treated to compare changes in the film.

For the film formation, an RF plasma CVD method, an ionization vapor deposition method, a hollow cathode (HCD) plasma CVD method,
Non-equilibrium magnetron sputtering method, cathodic arc ion plating method and laser ablation method were applied.

In the RF plasma CVD method, methane gas was applied as a raw material. A high frequency of 13.56 MHz was applied to the substrate to generate RF plasma, the raw material gas was decomposed, and a film was formed on the substrate.

In the ionization vapor deposition method, methane was used as a raw material. A methane plasma was generated by an ionization source and was irradiated on the substrate to form a film.

In the non-equilibrium magnetron sputtering method (UBM method), a solid carbon target or a solid carbon and silicon target was applied as a raw material. Argon gas or a mixed gas of argon and methane was introduced into the atmosphere, and a negative DC voltage was applied to the target to cause discharge. Sputtered from the target surface,
Carbon ions activated in plasma reacted with carbon ions and hydrocarbon ions in the plasma atmosphere on the substrate to form a film.

In the cathode arc ion plating method, a solid carbon target was applied as a raw material. A negative potential was applied to the target to generate an arc discharge, and the energy was used to evaporate the carbon on the surface into a plasma and form a film on the substrate.

In the laser ablation method, a solid carbon target was applied as a raw material. The target was irradiated with laser to vaporize the carbon on the surface into plasma by using the energy, and a film was formed on the substrate.

After the test, the sample was kept in a nitrogen gas atmosphere at 600 ° C. for 2 hours to compare the hardness and appearance before and after the test.

The results are shown in Table 1. The transparent carbon film exhibiting the interference color showed no change in hardness before and after the test. on the other hand,
The diamond-like carbon film containing a brown or black graphite component had a decreased hardness after the test, or the film was completely lost or powdered. It is considered that the presence or absence of the graphite component greatly affected the heat resistance.

[0074]

Example 2 A lens was molded by coating a carbon film on the molding surface of a glass lens molding die. The base material of the mold, the coated carbon film, the intermediate layer, the mixed layer and the performance during molding are summarized in Tables 2 (a) to 2 (c).

The mold is made of various materials such as tool steel SKD61, stainless steel SUS304, aluminum alloy A2014, cemented carbide, silicon carbide, and Cr-plated aluminum alloy A2014.

The hardness of each base material is represented by Vickers hardness, and if necessary, the Rockwell hardness C scale or Brinell hardness is also shown.

The surface of the base material before forming the carbon film was Ra0.00.
It is mirror-finished to 08 μm.

The carbon film was synthesized by RF plasma CVD method, microwave plasma CVD method, non-equilibrium magnetron sputtering method, cathode arc ion plating method and laser ablation method.

In the microwave plasma CVD method, methane and hydrogen were used as raw materials. Microwave plasma was generated with a microwave of 2.45 GHz to decompose the source gas and form a film on the base material. The other manufacturing method is in accordance with the first embodiment. In either method, the base material temperature during film formation was set in the range of 150 to 250 ° C.

The thickness of the carbon film is 0.03 μm to 6 μm
Controlled up to the range. As for the surface roughness, not only the roughness as obtained after the film formation but also the one partially polished was prepared. The color tone is determined by visual color tone on the molding surface,
Those with an interference color were marked as transparent.

The intermediate layer or the mixed layer was prepared with or without. The materials applied in this example are germanium, titanium, titanium carbide, chromium, and silicon.

Those having an intermediate layer or a mixed layer were synthesized by the following methods.

In the cathodic arc ion plating method, titanium carbide, chromium, or titanium was deposited. The raw materials are solid titanium or solid chromium target and methane,
Argon or the like was applied. A negative potential was applied to the target to generate arc discharge, and the energy of the target evaporated the elements on the surface of the target into plasma, which was reacted on the base material to form a film.

In the nonequilibrium magnetron sputtering method (UBM method), germanium and silicon were synthesized. A solid silicon or germanium target was applied to the raw material. Argon was introduced into the atmosphere, and a negative DC voltage was applied to the target to generate discharge. The target surface was sputtered to form a film on the substrate.

In the laser ablation method, titanium was formed into a film. A titanium target was applied as a raw material. The target was irradiated with a laser to evaporate titanium into plasma and form a film on the base material.

Silicon was formed by the magnetron sputtering method. Using a silicon target as a raw material,
A film was deposited on the base material by magnetron sputtering.

The film thickness was in the range of 0.3 nm to 10 nm.

The performance was evaluated by actually molding a glass lens. The evaluation items are service life and non-defective product rate.

The life is shown as a relative value when the number of shots at which the mold made of uncoated SKD61 material cannot be used is 1.

The non-defective rate is shown as an average value until the life of each mold.

The results show that the performance is significantly improved by coating the carbon film, as shown in Table 2. In this embodiment, a life of at least 5 times and a life of at least 20 times is obtained. It can be seen that the life of the transparent carbon film of the invention is significantly longer than that of diamond-like carbon containing a black or brown graphite component.

The rate of non-defective products was about 95% without coating, but improved to 95-99.5%. It was confirmed that the defects due to the glass adhered to the mold surface and the wrinkles due to the poor flow of the glass on the mold surface, which were conventionally seen, were significantly reduced.

[0093]

Example 3 A glass lens molding die was coated with TiN or a carbon film to mold a lens. Table 3 summarizes the mold base material, the coated carbon film, the intermediate layer, and the molded lens surface grade.

The mold was made of tool steel SKD11 as a base material.
The forming surface of the die base material before forming the carbon film is Ra 0.002 μ
m has been subjected to ultra-mirror finishing.

The carbon film and the intermediate layer were synthesized by the method according to Example 2. Some coatings were brushed or buffed. The mold surface before lens molding was observed and the particle density of 0.2 μm or larger was estimated.

The surface condition of the lens molded by the above coated mold was classified into 5 grades. The higher the number, the higher the grade. The lower the particle density, the higher the surface grade of the molded lens.

[0097]

[Table 1]

[0098]

[Table 2 (a)]

[0099]

[Table 2 (b)]

[0100]

[Table 2 (c)]

[0101]

[Table 3]

[0102]

As described above, in the glass lens molding die of the present invention, the transparent carbon film, which does not contain hydrogen and the content of the graphite component is restricted, is provided on the molding surface. The defective product rate due to poor flowability of the product is reduced, and the molding yield is improved.

Further, since the durability of the transparent carbon film is improved and the molding surface is protected by the film for a long period of time,
Less damage to the mold.

In the case where the hard plating layer or the thermal spray layer is provided on the surface of the base material, the surface hardness of the molding surface is increased and the life of the die is further extended. Further, in the case where the intermediate layer which enhances the adhesiveness of the film is provided between the base material and the transparent carbon film, the life reduction due to the peeling of the transparent carbon film is prevented.

In addition, when the surface of the base material or the surface of the transparent carbon film is polished, the releasability of the glass and the surface properties of the molded lens are improved.

Further, when the transparent carbon film exhibits an interference color, there is also an advantage that the change in the film property can be visually recognized by the change in the color of the film.

[Brief description of drawings]

FIG. 1 is a partially cutaway front view showing an example of a mold of the present invention.

FIG. 2 is a partially cutaway front view showing an example in which a plating layer or a thermal spray layer is provided.

FIG. 3 is a partially cutaway front view showing an example in which an intermediate layer is provided.

[Explanation of symbols]

1 base material 2 Transparent carbon film 3 Plating layer or sprayed layer 4 Middle class

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yoshiharu Utsumi             Sumitomo Electric Co., Ltd. 1-1-1 Koyo Kita, Itami City             Business Itami Manufacturing Co., Ltd.

Claims (16)

[Claims] 1. A transparent carbon film is coated on at least a part of the molding surface, and the transparent carbon film contains 95 at% or more of carbon and has a Knoop hardness of 3,000 or more and 7,000 or less. Glass lens molding die. 2. The glass lens molding die according to claim 1, wherein the base material is made of steel, alloy steel, cemented carbide, or ceramics. 3. The glass lens molding die according to claim 1, wherein a hard plating layer or a thermal spray layer is formed on the surface of the base material, and a transparent carbon film is coated on the hard plating layer or the thermal spray layer. 4. The glass lens molding die according to claim 1, 2 or 3, wherein the surface of the die covered with the transparent carbon film has a Vickers hardness of 350 or more. 5. The density of the transparent carbon film is 2.8 g / cm.³Since
Top 3.3g / cm ³Any of claims 1 to 4 below
The glass lens molding die according to claim 1. 6. The glass lens molding die according to claim 1, wherein the coated transparent carbon film exhibits an interference color. 7. A transparent carbon film having a thickness of 0.05 μm or more,
The glass lens molding die according to any one of claims 1 to 6, which has a thickness of 5 µm or less. 8. The glass lens molding die according to claim 1, wherein a molding surface made of a transparent carbon film has a surface roughness Ra of 0.001 μm or more and 0.05 μm or less. 9. The glass lens molding die according to claim 1, wherein the transparent carbon film is a film formed by any one of an ion plating method, a sputtering method, and a laser ablation method. . 10. B, A between the base material and the transparent carbon film
l, Si, Ge, Ti, V, Cr, Zr, Nb, Mo,
The glass lens molding die according to any one of claims 1 to 9, which has an intermediate layer made of Hf, Ta, W, or one or more kinds of substances selected from these carbides, nitrides, and carbonitrides. . 11. The intermediate layer has a thickness of 0.5 nm or more,
The glass lens molding die according to claim 1, which has a thickness of 5 nm or less. 12. An intermediate layer is provided between the base material and the transparent carbon film, and at least the base material side of the intermediate layer is the base material and B, A.
l, Si, Ge, Ti, V, Cr, Zr, Nb, Mo,
The glass lens molding die according to any one of claims 1 to 11, which is a mixed layer composed of one or more substances selected from Hf, Ta and W. 13. The mixed layer has a thickness of 0.5 nm or more and 5 or more.
The glass lens molding die according to any one of claims 1 to 12, having a thickness of not more than nm. 14. The intermediate layer or the mixed layer is formed by any one of a plasma CVD method, an ion plating method, a sputtering method, and a laser ablation method. The glass lens molding die described. 15. The glass lens molding die according to claim 1, wherein the surface of the transparent carbon film is smoothed by machining. 16. A particle density of 20,000 particles having a major axis of 0.2 μm or more observed on the surface of the transparent carbon film /
The glass lens molding die according to any one of claims 1 to 15, which has a size of ² mm ² or less.