JPH05105460A - Mold for molding optical element - Google Patents

Abstract

PURPOSE:To provide the subject mold causing no exfoliation of a film and no melt sticking of glass. CONSTITUTION:A nitrided layer 2 is formed by ion implantation in the surface layer of the substrate 1 of a mold made of a cemented carbide, ceramics, etc., and a chromium nitride film 3 is formed by ion implantation on the nitrided layer 2. Since N ions in the nitrided layer 2 bond to N ions in the chromium nitride film 3, the adhesion of the film 3 is improved and the exfoliation of the film 3 is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element molding die for molding a lens or the like by hot pressing.

[0002]

2. Description of the Related Art A mold for molding an optical element by a hot press is required to have good releasability and high adhesion of a film coated on a mold base material. This is because if the latter has low adhesion, film peeling occurs, glass is fused to the peeled portion, the releasability decreases, and the life of the mold is lost.

As a mold for molding such an optical element, JP-A-63-123822 is conventionally known.
In this optical element molding die, a Cr simple substance film is formed on the surface of a metal mold base made of stainless steel, a Cr-N type film is formed on the Cr simple substance film, and further on the Cr-N type film. Cr
-It has a three-layer structure in which a C-based film is formed.

[0004]

In the conventional molding die, the first layer of Cr on the die base material made of stainless steel is used.
A single film is formed by vacuum vapor deposition. This Cr simple substance film is formed as the first layer of a mold base made of a cemented carbide based on tungsten carbide (WC) or ceramics such as silicon carbide (SiC), and continuously molded at a mold temperature of 600 ° C. or higher. When done, oxidation of the Cr single film causes Cr
Form an oxide. However, this Cr oxide is a porous film with expanded crystal grains and has a large thermal expansion coefficient. Therefore, when a thermal shock and a tensile force are applied at the time of mold release, a peeling force pulling the film acts, so that the bond as the film is broken and minute peeling occurs. As a result, the glass comes into contact with the film exfoliation portion of the molding surface, resulting in micro-baking, which causes crater-like surface defects in the molded optical element. Since the appearance defects of the molded product frequently occur in this way, the appearance yield is lowered, which is a problem.

The present invention has been made in view of the above conventional problems, and provides a long-life optical element molding die in which the coating film has high adhesion to the die base material and does not cause glass seizure. The purpose is to do.

[0006]

In the optical element molding die of the present invention, a nitride layer is formed by ion implantation inside the surface layer of a mold base material, and a chromium nitride film is formed on the nitride layer by ion implantation film formation. Are laminated.

In the above structure, by implanting N ions, the oxide layer formed on the surface of the die base material made of cemented carbide or ceramics is modified, and the nitride layer containing the oxide in the crystal structure is modified. Can be formed. Since this nitride layer assists the adhesion of the nitride film made of chromium nitride coated thereon, the diffusion action of N ions, that is, the N ions in the nitride layer and the N ions in the nitride film are ion-bonded. Therefore, the ion particles of the nitride film grow so as to bite into the nitride layer. After that, when an ion implantation film forming method, that is, a high-acceleration N ₂ implantation ion is bombarded against the coating material, thereby forming a film with ionized particles sputtered at a high speed, the nitride film formed has a binding energy effect. It grows on the nitride layer. Then, the nitride layer and the nitride film formed by the ion implantation film formation method enable the film formation with extremely improved adhesion.

[0008]

First Embodiment FIGS. 1 to 3 show a first embodiment of the present invention. As shown in FIG. 1, the optical element molding die of this embodiment has a die base material 1 made of cemented carbide and a film-forming base surface 1A of the die base material 1.
The surface of the modified layer 2 is modified, and the nitrided film 3 made of chromium nitride coated on the modified layer 2 is formed. The molding base surface 1A of the mold base material 1 is ground and polished so that the surface roughness Rmax is 0.06 μm or less.

FIG. 2 shows a method of forming the modified layer 2,
N ions 4 are ion-implanted into the molding base surface 1A at an acceleration voltage of 93 keV, an acceleration current of 2 mA, and an implantation amount of 2 × 10 ¹⁷ ions / cm ² . Thereafter, as shown in FIG. 3, the mold base material 1 is inverted, and the molding base surface 1A is coated with a coating material 5 made of chromium.
To face. Then, N ions 4 are applied to the coating material 5 as an accelerating voltage of 92 keV, an accelerating current of 0.5 mA, and an implantation amount of 1 × 10 ^15.
ion implantation at ion / cm ² , and at the same time, Cr-N sputtered particles 6 are grown on the modified layer 2 obtained by modifying the surface of the molding base surface 1A of the mold base material 1 by sputtering.
The CrN film 3 is formed. The thickness of the formed CrN film is d =
1.2 μm, Vickers hardness Hv = 1410k
gf / mm ² (25 gf load), surface roughness Rmax =
It was 0.062, which was not different from that after polishing.

When SF type optical glass was continuously molded for 20000 shots or more using this optical element molding die,
When the surface roughness Rmax was 0.059 μm, no change was observed, and neither film peeling nor micro-image sticking caused by micro-peeling occurred.

Second Embodiment FIGS. 4 to 6 show a second embodiment of the present invention. As shown in FIG. 4, a mold base material 11 made of SiC and a modified layer 1 obtained by modifying the surface of a film-forming base surface 11A of the mold base material 11.
2 and a nitrided coating 13 made of chromium nitride coated on the modified layer 12. The molding base surface 11A of the mold base material 11 is ground and polished so that the surface roughness Rmax is 0.08 μm or less. To form the modified layer 12 of silicon nitride, as shown in FIG. 5, N ions 14 are accelerated on the molding base surface 11A at an acceleration voltage of 96 k.
eV, accelerating current 2.4 mA, injection amount 2 × 10 ¹⁷ ion /
Ion implantation is performed at cm ² . Thereafter, as shown in FIG. 6, the mold base 11 is turned over so that the molding base surface 11A faces the coating material 15 made of chromium, and N ions 14 are accelerated in the coating material 15 at an acceleration voltage of 94 keV and an acceleration current of 0.6 mA. Simultaneously with the ion implantation at a dose of 2 × 10 ¹⁵ ions / cm ² , the CrN film 13 was formed in the same manner as in Example 1. CrN
The thickness of the film 13 is d = 1.1 μm, the Vickers hardness is Hv = 1860 kgf / mm ² , and the surface roughness is Rmax =
It was 0.079, which was not different from that after polishing.

When SF type optical glass was continuously molded for 20000 shots or more using this optical element molding die,
When the surface roughness Rmax was 0.077 μm, no change was observed, no film peeling occurred, and no fine image sticking caused by fine peeling occurred. By using a high frequency sputtering film forming method on a mold base made of SiC, a Cr film as an intermediate layer is applied to the first layer, a Cr-N film is applied on the Cr film, and then C
The molding die of the conventional example in which the Cr-C film was formed on the r-N film was subjected to molding under the same conditions as in the above-mentioned example, and as a result, 1
Micro-peeling of 00 μm or more occurred, micro-seizure of glass occurred, and the molded product also had crater-like defects of 100 μm or more.

[0012]

EFFECTS OF THE INVENTION The present invention forms a nitride layer for assisting adhesion by ion implantation inside the surface of a mold base material such as cemented carbide or ceramics, and further uses a ion implantation film forming method to achieve high adhesion efficiency of chromium nitride. Since the film is grown, the seizure of the glass that occurs on the peeled surface of the film is eliminated and the life of the mold is extended.

[Brief description of drawings]

FIG. 1 is a sectional view of a first embodiment of the present invention.

FIG. 2 is a sectional view of a manufacturing process according to the first embodiment of the present invention.

FIG. 3 is a sectional view of a manufacturing process according to the first embodiment of the present invention.

FIG. 4 is a sectional view of a second embodiment of the present invention.

FIG. 5 is a sectional view of a manufacturing process according to a second embodiment of the present invention.

FIG. 6 is a sectional view of a manufacturing process according to a second embodiment of the present invention.

[Explanation of symbols]

 1 type base material 2 nitride layer 3 chromium nitride film

Claims (1)

[Claims] 1. An optical element molding die, characterized in that a nitride layer is formed inside the surface layer of a mold base material by ion implantation, and a chromium nitride film is laminated on the nitride layer by ion implantation film formation.