JPH0952721A - Formation of protective film of die - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the durability of a die of non-porous silicon carbide ceramics held on a holder by inducing negative DC potential in this die and chemically depositing a diamond-like carbon film by evaporation on the forming die. SOLUTION: The die 5 of the non-porous silicon carbide ceramics is held on the holder 3 arranged in a vacuum chamber 2. After the inside of this chamber 2 is evacuated to vacuum, gaseous raw materials are introduced and a high-frequency voltage is impressed on the holder 3 from a high-frequency power source 4 to induce the DC voltage of 600 to 1000V. Next, the die 5 is irradiated with the plasma P generated by a plasma generating source 1 to form the protective film consisting of the diamond-like carbon film of a film thickness of 0.02 to 0.1μm on the surface of the die 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a protective film on a molding die for molding a molding object such as a glass press lens.

[0002]

2. Description of the Related Art An optical element made of glass, for example, a prism made of glass, may be molded by using a glass press mold. As a protective film of this molding die, Diamond Like Carbon (DLC; Diamond Like)
Carbon) membrane is used. This diamond-like carbon has an advantage that it has a high effect of preventing attraction even to a lanthanum glass material to which a precious metal-based protective film tends to attract.

[0003]

However, such a diamond-like carbon is a suitable material for a molding die such as cemented carbide (WC) or alumina (Al).
₂ O ₃ ), sialon, etc. have weak adhesion, the diamond-like carbon film is easily peeled off, and as a result, the durability of the molding die is reduced. This is particularly remarkable in a mold having an edge shape (pointed shape) portion, and it is a problem to suppress such a film peeling phenomenon starting from an edge. Porous silicon carbide (SiC) is a type of material that is relatively suitable for the diamond-like carbon film, but in general, porous silicon carbide has a low surface roughness limit even if polished, and an optical mirror surface. I can't get it. For this reason, a CVD-SiC layer (silicon carbide layer formed by a chemical vapor deposition method) is grown on the entire surface or functional surface of the material to take measures such as closing pores (pores) on the surface. This is a cost problem and the degree of freedom in shape is small. Therefore, the present invention has been made to solve the above problems, and an object of the present invention is to provide a method for forming a protective film for a molding die, which can improve the durability of the molding die.

[0004]

In order to achieve the above object, according to the invention of claim 1, a method for forming a protective film on a molding die for forming a protective film on the surface of a molding die for molding an object to be molded. By holding a mold of non-porous silicon carbide ceramic in a holder and applying a high frequency voltage to the holder to induce a negative DC potential, a diamond-like protective film, which is a protective film, is formed by a chemical vapor deposition method. This is achieved by a method for forming a protective film for a molding die in which a carbon film is formed on the molding die.

In the present invention, a non-porous silicon carbide ceramic molding die is used, and by applying a high frequency voltage to the substrate holding the molding die to induce a negative DC potential, Since the diamond-like carbon, which is the protective film, is formed or formed on the mold by the chemical vapor deposition method, the protective film is unlikely to peel off from the mold, and the durability of the mold can be improved.

[0006]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Note that the embodiments described below are preferred specific examples of the present invention,
Although various technically preferable limitations are given, the scope of the present invention is not limited to these modes unless otherwise specified to limit the present invention.

FIG. 1 shows an example of a protective film forming apparatus for carrying out the method for forming a protective film on a mold according to the present invention. The apparatus of FIG. 1 is an apparatus for coating a diamond-like carbon film as a protective film on, for example, a mold for glass press molding. In FIG. 1, the film forming apparatus includes a plasma generation source 1, a vacuum chamber 2, a holder 3, a high frequency power source (also referred to as an RF power source) 4
Etc. The plasma generation source 1 is a device for converting ethylene, which is a raw material gas, into plasma P under ECR conditions, and the plasma P is introduced to the film formation substrate 5 as a reactive group. This ECR (electro-
The cyclotron resonance condition is
It is a resonance between microwaves and molecular vibrations, and it is to create a reactive group by efficiently applying microwave energy to the decomposition of ethylene.

A holder 3 for holding the above-mentioned film forming substrate 5 is housed in the vacuum chamber 2. The holder 3 detachably holds the film formation substrate 5 inside the vacuum chamber 2. Deposition substrate 5 on holder 3
Is at a position facing the plasma generation source 1, and the holder 3
A high-frequency voltage (RF voltage) is applied by the high-frequency power source 4, whereby a negative DC potential is induced in the holder 3 and the film formation substrate 5, and the negative potential is charged. This negative DC potential is preferably 600 V or more and 1000 V or less. If the negative DC potential is less than 600 V, the adhesion of the film will be reduced, which is not preferable.
If the negative DC potential is higher than 1000V, DLC
It is not preferable because the film hardness is lowered and the non-uniformity of film formation is increased.

Next, the film formation substrate 5 of FIG. 1 will be described in more detail with reference to FIG. As shown in FIG. 3, the film formation substrate 5 includes a mounting plate 3a set on the holder 3 and a molding die 20 detachably set on the mounting plate 3a. The molding die 20 is, for example, a mold having projections and depressions for molding an objective lens which is an optical element for an optical disk device or a magneto-optical disk device as a molding target. The holder 3 drives the film forming substrate 5 at a corresponding position of the plasma generation source 1 of FIG.
It has.

Next, referring to FIG. 4, the diamond-like carbon which is a protective film of the molding die 20 is used as the molding die 2 of FIG.
A procedure for forming a film on the 0 molding surface will be described. Referring to FIG. 4, the precision-molded mold 20 as shown in FIG.
Ultrasonic cleaning is performed with an organic solvent (step S1). After ultrasonic cleaning, the mold 20 is attached to a dedicated mounting plate (also referred to as a substrate adapter) 3a shown in FIG. 3, and is placed in a vacuum chamber (also referred to as a film forming chamber) 2 shown in FIG. It is sent by 30 and positioned (step S2). And the atmosphere in the vacuum chamber 2 is 1 × 1
The inside of the vacuum chamber 2 is heated in a state of being evacuated to 0 −4 Pa or less (step S3) (step S3).
4). Then, the argon gas shown in FIG. 2 is introduced into the plasma generation source 1, the plasma P is ignited, and the dirt on the surface of the molding die 20 is removed by etching (step S5).
Then, subsequently, by introducing ethylene gas, the diamond-like carbon film 5 as shown in FIG.
0 is deposited (step S6). And this mold 20
Is taken out from the vacuum chamber 2 of FIG. 1 (step S
7). In this way, the diamond-like carbon film 50 is reliably formed on the surface 20a of the molding die 20 as shown in FIG.

When the plasma P from the plasma generation source 1 is introduced as a reactive group onto the film-forming substrate 5, a diamond-like carbon film grows on the film-forming substrate 5. An example of 50 film forming conditions is shown in FIG. In FIG. 2, the temperature of the film-forming substrate 5 is, for example, 300 ° C., and when the film-forming substrate is a mold of non-porous silicon carbide (SiC), argon discharge is first performed, and then ethylene is used. Discharge.

In this way, the DC potential induced in the holder 3 when the diamond-like carbon film was grown on the film formation substrate 5 was, for example, about 650 to 700V. The thickness of the diamond-like carbon film in this case was about 50 nm. The thickness of the diamond-like carbon film is preferably 0.02 μm or more and 0.1 μm or less. When the film thickness is less than 0.02 μm, the uniformity as a DLC film is deteriorated and the fusion preventing effect is lowered, which is not preferable. On the other hand, if the film thickness exceeds 0.1 μm, peeling is likely to occur due to a decrease in adhesion due to an increase in film stress, which is not preferable. At this time, when the optical element is press-molded by the molding die 20 including the edge portion, 5000 shots (sho
In the forming tests up to t), the diamond-like carbon film 50 did not change, and the durability of the film-forming substrate 5 could be confirmed without peeling from the film-forming substrate 5.

Next, FIG. 5 shows a glass press molding material (molding object) 60 molded by the molding die 20 protected by the diamond-like carbon 50.

As described above, in the embodiment of the present invention, a non-porous silicon carbide ceramic molding die is held, and a high-frequency voltage is applied to the holding holder to induce its DC potential. By chemical vapor deposition method (CVD method)
Thus, the diamond-like carbon film, which is a protective film, can be formed on the mold. Since the forming die is made of non-porous silicon carbide ceramic, the surface of the forming die can be a mirror surface. Therefore, unlike the conventional case where a porous silicon carbide is used as the material of the mold, an optical mirror surface cannot be obtained, and it is not necessary to close the pores on the surface, so that the cost can be reduced. In addition, even if such a non-porous silicon carbide ceramic has a life as a molding die once due to film peeling of diamond-like carbon, etc., after that, this kind of diamond-like carbon is removed by heating in an oxidizing atmosphere, By additionally processing another diamond-like carbon film, the mold can be easily regenerated.

Further, the cost is reduced by adopting a structure capable of correcting the dimensions of the molding die.

By the way, in the above-described embodiment of the present invention, the protective film for the molding die for molding the optical element such as the objective lens for the optical disk is formed, but the present invention is not limited to this, and other fields such as an injection molding die are used. It is also possible to form a protective film on. Further, the invention can be applied to forming a diamond like carbon film on a sliding member such as a capstan or a tape of a video tape recorder, or a cutting tool, and the durability thereof can be improved.

[0017]

As described above, according to the present invention,
The durability of the molding die can be improved.

[Brief description of drawings]

FIG. 1 is a view showing an outline of a film forming apparatus for carrying out a method for forming a protective film for a mold according to the present invention.

FIG. 2 is a diagram showing an example of film forming conditions.

FIG. 3 is a diagram showing an example of a film formation substrate 5.

FIG. 4 is a flowchart showing a film forming procedure.

FIG. 5 is a diagram showing a state where a glass press molding material is molded by a molding die having a diamond-like carbon film formed according to the present invention.

[Explanation of Codes] 3 Holder 20 Mold 50 Diamond-like carbon (protective film) 60 Object

Claims (4)

[Claims] 1. A method for forming a protective film of a molding die for forming a protective film on a surface of a molding die for molding an object to be molded, wherein a non-porous silicon carbide ceramic molding die is held in a holder. Then, a high-frequency voltage is applied to this holder to induce a negative DC potential, and a diamond-like carbon film, which is a protective film, is formed on the mold by a chemical vapor deposition method. Forming method. 2. The negative DC potential is 600 V or more and 1000 V.
The method for forming a protective film for a molding die according to claim 1, wherein: 3. The method for forming a protective film for a mold according to claim 1, wherein the diamond-like carbon film has a thickness of 0.02 μm or more and 0.1 μm or less. 4. The method of forming a protective film for a mold according to claim 1, wherein the mold is mirror-polished.