JP5627214B2 - Mold and its manufacturing method - Google Patents

Description

  The present invention mainly relates to a molding die used when manufacturing an optical element made of glass such as a lens or a prism by press molding of a glass material, and a manufacturing method thereof.

  The technology for manufacturing a lens by press molding of a glass material without the need for a glass polishing process eliminates the complicated process required in conventional manufacturing, and makes it possible to manufacture the lens easily and inexpensively.

  Properties required for such a mold material used for press molding of a glass optical element include excellent hardness, heat resistance, releasability, and mirror finish.

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

  To give some examples, in a metal mold using a cemented carbide as a base material, first, metal nitride (TiN, TiAlN, AlN, TaN, or ZrN), metal carbide (TiC, ZrC, or Cr2C3) are used. Or a metal boride (ZrB2, NbB2, or TaB2).

  Next, Patent Document 1 discloses a molding die in which a metal film made of a group of platinum group metal, tungsten, rhenium, and tantalum or an alloy film containing the metal as a main component is coated on a portion to be a molding surface (transfer surface). Proposed.

  Patent Document 2 proposes a molding die in which a TiAlN film is formed as a coating by sputtering and carbon ions are implanted.

  Patent Document 3 describes a tetrahedral amorphous carbon film (taC film) and a hydrogenated tetrahedral amorphous carbon film (aC: H film) as coatings.

Japanese Patent Laid-Open No. 03-242334 Japanese Patent Application Laid-Open No. 06-263459 Japanese Patent Application Laid-Open No. 2004-075529

  In general, a mold using an aC: H film, a hard carbon film, and a taC film has an advantage in that the mold and the glass are easily releasable and hardly cause fusion with the glass.

  However, the adhesion between the mold and the film is generally low, and when the molding operation is repeated several hundred times or more, the film is partially peeled off, and the molded product may not have sufficient molding performance. There was a problem with durability.

  Furthermore, with the miniaturization of digital cameras and the like, high-refractive-index glass press molding has been desired. In general, since a high refractive index glass has a molding temperature as high as 650 ° C. or higher, a molding die using an aC: H film or a hard carbon film generally has a problem in durability.

  Further, when the surface of the molding die is a carbon-based film, it is necessary to repeatedly form the carbon-based film by removing the carbon film with oxygen plasma or the like.

  The first object of the invention according to the present application is to prevent the release layer from peeling even if the glass material is repeatedly press-molded at a high temperature of 650 ° C. or higher.

  The second object of the invention according to the present application is to repeatedly reproduce the release layer and use it for molding.

  In order to solve these problems, in the present invention, in a molding die having a molding surface as a part of a base material, a layer made of titanium metal, a layer made of titanium aluminum nitride, and silicon carbide are formed on the molding surface. There is provided a molding die characterized in that a layer and a layer made of tetrahedral amorphous carbon are sequentially laminated.

  According to the present invention, it is possible to form a molding die with good surface roughness, which has good adhesion and durability of the release layer at high temperatures, and can be used repeatedly by regenerating the release layer. An optical element made of high refractive index glass can be provided at a significant cost reduction.

It is a schematic diagram of a molding die showing an embodiment of the present invention. It is a schematic diagram of a sputtering device showing an embodiment of the present invention. It is a schematic diagram of the PSII film-forming method apparatus which shows embodiment of this invention. It is a schematic diagram of the FCVA film-forming method apparatus which shows embodiment of this invention.

Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.
Here, the typical cross section of the molding die of this invention is shown in FIG. The film provided on the molding surface (hereinafter referred to as the transfer surface) is drawn with an increased thickness for the sake of explanation.

  In FIG. 1, 11 is a cemented carbide containing tungsten carbide (WC) as a main component, and has a transfer surface for molding an optical element.

  Although FIG. 1 shows a convex lens molding die, the present invention is not limited to the shape, but includes a concave lens molding die, an aspherical lens molding die, a cylindrical lens molding die, and the like. The shape is not limited.

  Reference numeral 12 denotes an underlayer formed of titanium metal (Ti). Since a material having good mold releasability between the mold and glass generally has low adhesion to the mold, it is provided on the mold through another film. This underlayer is provided together with an intermediate layer described below for leveling the surface of a molding die made of cemented carbide and further forming an underlayer for forming another film.

Reference numeral 13 denotes an intermediate layer formed of titanium aluminum nitride (TiAlN).
Reference numeral 14 denotes an adhesion layer made of silicon carbide (SiC) formed by a plasma source ion implantation method (Plasma-Source-Ion-Implatation, hereinafter referred to as PSII method). The adhesion layer is in close contact with the transfer surface of the molding die through the base layer and the intermediate layer, and is also in close contact with the release layer provided on the adhesion layer, so that the release layer is peeled off from the molding die. It is provided to prevent this.

  Reference numeral 15 denotes a release layer made of tetrahedral amorphous carbon (taC) formed by a filtered arc cathodic vacuum arc method (FCVA method). This release layer is provided to press and mold the glass optical element after the press so that the mold and the optical element are separated from each other without fusing the glass and the mold.

The above layers are sequentially laminated on the mold base material.
FIG. 2 is a schematic cross-sectional view of a sputtering film forming apparatus for forming an underlayer and an intermediate layer. A mold base material 22 is installed in the vacuum chamber 21, and the mold base material 22 rotates on the target by a rotating shaft 23. The temperature is detected with a thermocouple 26, heated to 300 ° C. with a heater 27 such as a halogen lamp, and the ultimate vacuum in the chamber is evacuated to 1 × 10 ⁻³ Pa or less.

  Next, argon gas is introduced, the mold base material 22 is rotated, high frequency is applied to the metal titanium target (Ti) 24 from an RF high frequency power source (not shown) through a matching box, and the target is sputtered. A metal titanium (Ti) layer is formed in a thickness of 0.1 to 0.5 μm.

  Argon gas and nitrogen gas are introduced, the mold base material 22 is rotated, and a high frequency is applied to the metal titanium (Ti) target 24 and the metal aluminum (Al) target 25 from an RF high frequency power source (not shown) through a matching box. Sputter the target.

  At that time, a high frequency is applied to the mold base 23 from the RF high frequency power supply 28 through the rotating shaft 23 through a matching box (not shown) to form a TiAlN layer 13 having a thickness of 0.2 to 5 μm.

The composition ratio of Ti and Al is achieved by changing the power of each high frequency applied to the target.
The composition ratio of Ti and Al is preferably 0.3 to 0.7.

  Further, although the sputtering method has been described as the film formation method for the base layer and the intermediate layer, a known CVD or ion plating method is also possible, and the film formation apparatus is not limited to the above film formation apparatus.

  FIG. 3 is a schematic view showing a film forming apparatus of a plasma source ion implantation method (PSII method). A vacuum chamber 31 and an ion source 32 are connected to a valve (not shown), a gas flow regulator, a pressure regulator, and a gas cylinder, and can ionize a carbon-containing gas using a heated filament and an electric field. .

Reference numeral 33 denotes a power source for applying a bias to the substrate holder.
34 schematically shows an ion beam, and 35 is a mold base material having an underlayer and an intermediate layer formed on the surface. In FIG. 3, a mold base material having a concave transfer surface is illustrated for explanation.

Reference numeral 36 denotes a gas exhaust port to which a valve, a turbo molecular pump, and a rotary pump (not shown) are connected. Reference numeral 37 denotes a base material holder which can fix the mold material.
In addition, the film-forming apparatus used by this invention is not limited to the said apparatus at all.

Next, a SiC film forming method using a PSII apparatus will be described.
The mold base material 35 is installed in the vacuum chamber 31 and heated to 300 ° C. with a heater such as a halogen lamp (not shown), and the ultimate vacuum in the chamber is exhausted to 1 × 10 ⁻⁵ Pa or less.

  A gas containing silicon and carbon, such as HDMS (hexaethyldisilazane), TEOS (Tetraethyl orthosilicate), or the like, is introduced and ionized with 32 ion sources.

  The die base material 35 is rotated, and a pulsed direct current of 1 to 8 kV is applied to a 33 base material holder by a power source for applying a bias to form a SiC layer of 10 to 100 nm.

In addition, although the CVD method has been described as the film forming method, a known sputtering or ion plating method is also possible, and the film forming apparatus is not limited to the above film forming apparatus.
FIG. 4 is a schematic cross-sectional view of an FCVA film forming apparatus for forming a taC film.

Next, a method of forming taC will be described below.
The mold base material 42 is installed in the vacuum chamber 41, and the ultimate vacuum in the chamber is evacuated to 1 × 10 ⁻⁵ Pa or less.

  A carbon plasma is generated in an arc plasma generation chamber 45 by a vacuum arc power source 46, carbon ions are extracted by a filter 44, and the mold base material 42 is irradiated with the carbon ions.

  When the mold base material 42 is irradiated with carbon ions, a pulsed DC power supply 43 is used to apply −500 to 5 KV to the mold base material to form a taC layer of 50 to 1000 nm.

  In the embodiment of the present invention, the film forming apparatus of the PSII method and the film forming apparatus of the FCVA method are formed using different apparatuses, for the sake of easy understanding.

In general, it is desirable to form a film using a film forming apparatus equipped with a PSII film forming apparatus and an FCVA film forming apparatus in the same chamber from the viewpoint of adhesion and contamination reduction.
However, the effect of the present invention is not impaired even if the films are formed by separate film forming apparatuses.

FIG. 1 shows a schematic sectional view of a molding die according to the present invention.
First, a 300 nm Ti layer 12 and a 700 nm TiAlN layer 13 were formed on the cemented carbide 11 containing WC as a main component on the molding surface side using the sputtering apparatus shown in FIG.

  Next, the mold base material was placed in a plasma source ion implantation method (PSII method) film forming apparatus shown in FIG. 3, and a SiC layer 14 was formed to a thickness of 60 nm.

  Finally, the mold base material was placed in the FCVA film forming apparatus shown in FIG. 4, and the taC layer 14 was formed to a thickness of 200 nm. Since the taC layer was formed by the FCVA method, it was possible to form a high quality film that was homogeneous throughout the film and had good adhesion to the SiC layer.

Next, an optical lens was molded by 800 shots using this molding die.
Molded glass was shelf silicate glass containing rare earth (Tg: 610 ° C., refractive index: 1.86), and the molding conditions were a nitrogen atmosphere and a press temperature of 680 ° C. During molding, the mold release property between the mold and the molded optical element was good.

  Further, when the mold surface after molding was observed with a scanning electron microscope, film peeling, generation of cracks, and fusion of glass were not observed, and the mold surface property was good.

  Therefore, even if the glass material was repeatedly press-molded at a high temperature of 650 ° C. or higher, it was possible to prevent the release layer from peeling off.

  The molded glass lens also had good surface roughness with no glass breakage.

  Further, the SiC and taC layers were removed from the molding die used for molding using an oxygen ashing apparatus, and the TiAlN surface was washed with diamond paste. There was no particularly large defect on the TiAlN surface.

  Then, SiC and taC layers were again formed on this mold, and molding was performed under the same conditions, but the same results as in the first time were obtained. Table 1 below shows the composition and film thickness for each layer formed on the mold base material.

(Comparative Example 1)
In Example 1, a molding die was manufactured in the same manner except that TiN was formed instead of TiAlN as the intermediate layer.

  Using this molding die, an optical lens was molded in the same manner as in Example 1. However, a part of the taC layer was peeled off at 550 shots.

  Furthermore, the mold used for the molding was removed from the SiC and diamond-like carbon layers using an oxygen ashing device, and the TiN surface was washed with diamond paste, but scratches were generated on the TiN surface. It was not possible to regenerate the mold by forming SiC and taC layers again on the intermediate layer. Therefore, it was found that it is desirable to form TiAlN as an intermediate layer after the Ti layer as the underlayer.

(Comparative Example 2)
In Example 1, instead of the taC layer by the FCVA method, an SiC layer as an adhesion layer was formed, and subsequently, an aromatic hydrocarbon gas such as toluene was introduced into the film forming apparatus of the PSII method, and the release layer A molding die was produced in the same manner except that a diamond-like carbon layer having a thickness of 200 nm was formed.

  Next, using this molding die, an optical lens was molded in the same manner as in Example 1. However, a large number of fine diamond-like carbon layers were peeled off after 300 shots.

Furthermore, the SiC and diamond-like carbon layers were removed from the mold used for molding using an oxygen ashing device, and the TiAlN surface was cleaned with diamond paste, but scratches were generated on the TiAlN surface. It was impossible to regenerate the mold by forming SiC and taC layers again on the TiAlN layer as the intermediate layer. Therefore, it was found that a taC layer formed by the FCVA method is good for the release layer formed over the SiC layer as the adhesion layer.

(Comparative Example 3)
Ti superimposed on the mold base material in the base layer, TiAlN the intermediate layer, SiC adhesion layer, the optical element molding die of Comparative Example 2 were successively provided with a diamond-like carbon layer on the release layer, an intermediate layer TiAlN In place of the layer , a molding die was similarly manufactured except that a TiN layer was used in order to suppress peeling.

  Using this molding die, an optical lens was molded in the same manner as in Example 1. However, a large amount of peeling of the diamond-like carbon layer occurred in 200 shots.

Furthermore, the mold used for molding was removed from the SiC and diamond-like carbon layers using an oxygen ashing device, and the TiN surface was cleaned with diamond paste, but scratches were generated on the TiN surface. It was impossible to regenerate the mold by forming SiC and taC layers again on the intermediate layer.

  It is suitably used for a molding die used when manufacturing an optical element made of glass such as a lens or a prism by press molding of a glass material.

34 schematically showing an ion beam 35 mold base material 36 gas exhaust port 37 base material holder

Claims (7)

  In a molding die having a molding surface as a part of a base material, a layer composed of titanium metal, a layer composed of titanium aluminum nitride, a layer composed of silicon carbide, and a layer composed of tetrahedral amorphous carbon are sequentially laminated on the molding surface. A molding die characterized by being made. The metal titanium layer has a thickness of 0.1 to 5 μm, the titanium aluminum nitride layer has a thickness of 0.2 to 5 μm, and the silicon carbide layer has a thickness of 10 to 100 nm. The molding die according to claim 1, wherein the thickness of the layer made of tetrahedral amorphous carbon is 50 to 100 nm. The molding die according to claim 1, wherein a ratio of titanium to aluminum in the layer made of titanium aluminum nitride is 0.3 to 0.7.   In the method of manufacturing a molding die having a molding surface as a part of a base material, a layer made of metallic titanium, a layer made of titanium aluminum nitride, a layer made of silicon carbide, a layer made of tetrahedral amorphous carbon on the molding surface A method of manufacturing a molding die characterized by sequentially forming films. The metal titanium layer has a thickness of 0.1 to 5 μm, the titanium aluminum nitride layer has a thickness of 0.2 to 5 μm, and the silicon carbide layer has a thickness of 10 to 100 nm. The thickness of the layer made of tetrahedral amorphous carbon is 50 to 100 nm, and the method for producing a molding die according to claim 4.   The method for producing a molding die according to claim 4 or 5, wherein the tetrahedral amorphous carbon film is formed by a filtered arc cathodic vacuum arc method.   The method for manufacturing a molding die according to claim 6, wherein the silicon carbide film is formed by a plasma source ion implantation method or a sputtering method.

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