JP2003171766A - Silicon carbide coating member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a practical silicon carbide coating member, when used as a constituting material, e.g. for a forming mold for an optical element made of glass, capable of eliminating problems caused by a silicon carbide film therein. <P>SOLUTION: The silicon carbide coating member is obtained by forming a silicon carbide film 2 by chemical vapor deposition on the surface 2a of a substrate 2 formed as a silicon carbide sintered compact. The silicon carbide film 2 has a gradient composition in which the component part of carbon increases as it goes to the film surface, and consists of an adhesion layer 31 having a silicon-rich composition, an intermediate layer 32 having a stoichiometric composition, and a surface layer 33 having a carbon-rich composition. As the carbon-rich composition, e.g. an amorphous carbon composition such as a glassy carbon composition and a pyrolytic carbon composition can be cited. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold for one-mold molding of glass optical elements (lenses, prisms, etc. used in CD drives, laser devices, cameras, microscopes, telescopes, optical fiber devices, etc.). The present invention relates to a silicon carbide coating member suitable for use as various sliding bodies (sealing rings of mechanical seals, bearings, etc.), various optical elements (laser reflecting mirrors, diffraction gratings, etc.), and the like.

[0002]

2. Description of the Related Art A silicon carbide coating member formed by coating a surface of a substrate made of silicon carbide or carbon with a silicon carbide film by chemical vapor deposition has a high hardness of the silicon carbide film.
Since it has excellent wear resistance, heat resistance, chemical resistance, and conductivity, it is particularly suitable for various products and parts that require physical, chemical, electrical / electronic durability on the surface. It can be used and has been practically used in many fields.

For example, conventionally, in order to manufacture a camera lens or the like, in addition to a step of molding a glass material into a predetermined shape, a base polishing step for ensuring the shape and accuracy of the molded article and the surface of the polished article. Many steps were required, such as a finish polishing step for finishing. Therefore, according to such a traditional manufacturing method, it is difficult to manufacture a large amount of lenses and the like at low cost, and it is difficult to obtain an aspherical lens. Therefore, in recent years, not only general-purpose optical elements such as CD pickup lenses but also high-precision optical elements such as aspherical microlenses for optical fiber couplers are being one-molded by a precision press mold. However, a mold made of a silicon carbide coating member is known as a mold for a glass optical element used for such one-mold molding. That is, in this molding die (hereinafter referred to as "conventional mold"), a silicon carbide film is formed on the surface of a mold body made of a silicon carbide sintered material by chemical vapor deposition, and the film surface is polished to form a molding surface. It is a thing.

[0004]

However, although the conventional type is excellent in heat resistance, durability, etc., it has a problem of releasability, and the glass as an optical element material has a surface (molding surface) of the silicon carbide film. However, there is a problem in that stable molding cannot be performed.

Although such a problem is caused by the silicon carbide film, the problem caused by the properties of the silicon carbide film is not limited to the molding die for the glass optical element, but the silicon carbide coating member. It has been pointed out in various products and equipments using the conventional silicon carbide coating member,
The fact is that some functions are not always satisfactory.

The present invention has been made in view of the above circumstances, and eliminates the problems caused by the silicon carbide film which they have when used as a constituent material of a molding die or the like for a glass optical element. It is an object of the present invention to provide a practical silicon carbide coating member that can be used.

[0007]

The present invention provides a silicon carbide coating member comprising a substrate and a silicon carbide film formed by chemical vapor deposition on the surface thereof. It is proposed that the carbon composition has a graded composition in which the carbon component increases toward the film surface in the film thickness direction. That is, it is proposed that the silicon carbide film has a graded composition in which the carbon component gradually increases and the silicon component gradually decreases as the film surface is approached.

Specifically, the surface layer of the silicon carbide film is made to have a carbon-rich composition. Here, the carbon-rich composition is a composition in which the carbon component is greater than the stoichiometric composition forming the chemical equivalence ratio (while the silicon component is less than the stoichiometric composition), and it is a glassy carbon (Glass) composition.
Amorphous carbon compositions such as sy Carbon and amorphous carbon compositions and Pyrolytic carbon (pyrolytic carbon) compositions are included. On the surface of the film having such a carbon-rich composition, the carbon-like property appears more strongly and the silicon-like property is suppressed as compared with the surface of the general silicon carbide film having the stoichiometric composition. It will be. Therefore, the silicon carbide coating member having such a silicon carbide film formed on the surface of the substrate can be suitably used as a constituent member such as a molding die for a glass optical element or a sliding body such as a sealing ring for a mechanical seal. . For example, in a mold for a glass optical element having a film surface as a molding surface, the molding surface contains a large amount of a carbon component which hinders the adhesion (reactivity) with glass and has an adhesion property with glass. Since it does not contain a large amount of silicon components that do not inhibit, the releasability is greatly improved as compared with the conventional type described at the beginning. Further, in the case of the seal ring for the mechanical seal having the film surface as the seal end face, the seal end face has a self-lubricating property which is a carbon property, and the slidability with the mating seal ring is significantly improved. It will be.

On the other hand, the silicon component gradually decreases as it approaches the film surface in the film thickness direction. Especially, when the substrate is made of a silicon carbide material (for example, a silicon carbide sintered material). It is preferable that the adhesion layer of the silicon carbide film to the substrate has a silicon-rich composition in which the silicon component is larger than the stoichiometric composition. By thus forming the adhesive layer with the silicon-rich composition, the adhesion between the silicon carbide film and the base body made of the silicon carbide material is higher than that in the case where the silicon carbide film has the stoichiometric composition.
Greatly improved.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be specifically described below with reference to the drawings.

FIGS. 1 and 2 show a first embodiment. In this embodiment, a glass optical element molding die 1 is constructed using a silicon carbide coating member according to the present invention. Has been done.

That is, the molding die 1 is, as shown in FIG.
The mold body 2 is molded into a predetermined shape (Fig. A), a silicon carbide film 3 is formed on the surface of the mold portion 2a of the mold body 2 by chemical vapor deposition (Fig. B), and the surface of the silicon carbide film 3 is polished. The polishing surface is the molding surface 3a (Fig. C).

As shown in FIG. 1 (A), the die body 2 is made of β-type silicon carbide (or α-type carbonized) obtained by, for example, pressureless sintering, hot press sintering, hot isostatic pressing or the like. A sintered body of silicon (for example, a bulk density of 3.0)
The above is ground into a predetermined shape. It should be noted that the shape of the mold portion 2a is adapted to the final shape obtained by coating the silicon carbide film 3.

The silicon carbide film 3 is formed as shown in FIG.
By chemically vapor-depositing pure β-type silicon carbide (or α-type silicon carbide) in a non-oxidizing atmosphere by a low pressure CVD method or the like, the surface of the mold portion 2a of the mold body 2 is coated and formed.
By controlling the vapor deposition conditions, in particular, the flow rates of the Si source (SiCl ₄ etc.) and C source (C ₃ H ₈ etc.) in the reaction gas,
The molar ratio and the reduction ratio with H ₂ which is a carrier gas are controlled by a mass flow controller so that the amount of silicon components in the film composition gradually decreases and the amount of carbon components gradually increases as the film formation progresses. As a result, as shown in FIG. 2, a film having a graded composition in which the carbon component increases in the film thickness direction toward the film surface is formed.

First, in the initial stage (first stage) of film formation, the surface of the mold body 2 (the mold portion) on which the first layer 31 having a silicon-rich composition containing a silicon component in a larger amount than the chemical equivalent ratio of silicon carbide is the substrate. 2a). In the second step, the second layer 32 having a stoichiometric composition in which the silicon content is decreased and the carbon content is increased is formed on the first layer 31. Then, in the third stage, the silicon component is further decreased and the carbon component is further increased, so that the second layer 32 is formed.
Carbon-rich composition (eg, glassy carbon composition,
A third layer 33 having an amorphous carbon composition such as a pyrolithic carbon composition) is formed, and the film formation is completed.
In FIG. 2, for convenience, each layer 31, 32, 33
Although boundaries between are shown, it should be understood that such boundaries are not apparent.

By the way, the amount of carbon added to the stoichiometric composition of the carbon-rich composition is so small that it cannot be detected by an X-ray diffractometer, but the carbon-rich composition can be confirmed by Raman spectrum spectroscopy using a laser Raman spectroscope or the like. It can be done easily. For example, as shown in FIGS. 5 and 6, the Raman spectra of the glassy carbon composition and the stoichiometric composition are clearly different. That is, in the Raman spectrum of the glassy carbon composition shown in FIG. 5, in addition to Raman line peaks a and b of silicon carbide, Raman line peaks c (around 1360 cm −1) and d (1590 cm) of glassy carbon are obtained.
(Around -1) is prominent. On the other hand, in the Raman spectrum of the stoichiometric composition shown in FIG. 6, only peaks e, f, g and h of silicon carbide appear.

The third layer 33, which is the surface layer of the silicon carbide film 3, is
As shown in FIG. 1 (C), the surface is polished to a desired ultra-smooth surface (for example, surface roughness: about 1 nm RMS, shape accuracy: λ / 4 or less) 3a by an appropriate mechanical processing method. Such surface polishing is performed, for example, by roughening the surface of the silicon carbide film 3 with diamond abrasive grains and then performing precision polishing with diamond abrasive grains. Although the molding die 1 is the upper die, the lower die is also manufactured through the same steps.

In this molding die 1, since the molding surface 3a, which is the polished film surface, has a carbon-rich composition such as a glassy carbon composition and a pyrolithic carbon composition, glass adhesion occurs during molding. It is excellent in releasability without any damage, and it is possible to mass-produce optical elements satisfactorily and with high accuracy. That is, the molding surface 3a
Does not adhere to the glass because it contains a large amount of carbon component that inhibits the reaction with glass and the amount of silicon component that does not inhibit the reaction is very small.

On the other hand, since the adhesive layer 31 as the first layer has a silicon-rich composition, the adhesiveness to the die body 2, which is a silicon carbide sintered material, is higher than that of the stoichiometric composition. And the durability of the mold 1 is improved.

3 and 4 show a second embodiment. In this embodiment, the silicon carbide coating member according to the present invention is used as a sealing ring.

That is, the mechanical seal shown in FIG. 3 is held by a seal ring 4 (hereinafter referred to as a "fixed ring") fixedly held in a seal case 4 and by a rotary shaft 6 so as to be movable in the axial direction and not relatively rotatable. A spring which is interposed between a sealing ring (hereinafter referred to as "rotating ring") 7, a spring retainer 8 fixed to the rotating shaft 6 and the rotating ring 7, and presses the rotating ring 7 toward the fixed ring 5. 9 and the both sealing rings 5,
By the relative rotational sliding contact action of the sealed end surfaces 5a, 7a, which are the opposing end surfaces of 7, the inner peripheral area A, which is the outer peripheral side area of the relative rotational sliding contact portion, and the outer peripheral area (atmosphere area) B, which is the inner peripheral side area, are sealed. It is of an end face contact type.

In such a mechanical seal, the rotary ring 5 is made of a silicon carbide sintered material and the fixed seal ring 5 is used.
Is composed of the silicon carbide coating material according to the present invention. That is, as shown in FIG. 4, the fixed sealing ring 5 has a surface (sealing end surface 5a) of the substrate 10 made of a silicon carbide sintered material.
A silicon carbide film 11 is formed by chemical vapor deposition on the surface of the portion where the film is to be formed, and the film surface is polished to form the sealed end surface 5a.
It is what The silicon carbide film 11 has a composition similar to that of the molding die 1 described above. As shown in FIG. 4, a first layer 111 having a silicon-rich composition is formed on the surface of the base 10 and the first layer 111 is formed. Second layer 11 having a stoichiometric composition
2 to form a carbon-rich composition (for example, an amorphous carbon composition such as a glassy carbon composition or a pyrolithic carbon composition) on the second layer 112.
And the surface of the third layer 113, which is a surface layer, is polished to the sealed end surface 5a.

By the way, as an end-face contact type mechanical seal, generally, one of two sealing rings that make relative rotational sliding contact is made of silicon carbide and the other sealing ring is made of carbon (hereinafter referred to as "C / SiC seal"). ) And both sealing rings are made of silicon carbide (hereinafter “SiC /
"SiC seal") is well known, but C / SiC
In the sealing, the carbon sealing ring, which is softer than silicon carbide, is easily worn, and particularly the slurry fluid containing the solid component cannot be sealed well. On the other hand, SiC / Si
In the C-seal, since the silicon carbide is hard and has excellent wear resistance, and also has excellent thermal, chemical, and mechanical properties, the sealed fluid is a slurry fluid containing solid components, etc. Even under severe sealing conditions, the good sealing function can be achieved. However, since silicon carbide does not have self-lubricating properties like carbon, and is inferior in slidability (lubricity) with the mating sealing ring, SiC / SiC
In the seal, there is a possibility that noise, so-called squeal, may occur between the sealing end faces, or that the sealing end faces may stick (seize).

On the other hand, in the mechanical seal described above, the sealing end surface 5a of the fixed sealing ring 5 has a carbon-rich composition in which carbon-like properties (particularly self-lubricating property) are strongly exhibited, and therefore the general chemical composition is used. Unlike the silicon carbide sealing ring having a stoichiometric composition, the slidability with the mating sealing ring 7 made of silicon carbide is high, and problems such as the SiC / SiC seal do not occur. Of course, there is no problem in C / SiC sealing, and a good sealing function can be exhibited even for a slurry fluid containing a solid component.

Under the sealing conditions in which the C / SiC seal is preferably used, the mating sealing ring 7 can be made of carbon. In this case as well, the sliding performance between the sealing rings 5 and 7 is good. Is significantly improved, and wear of the carbon seal ring and the pristor phenomenon can be more effectively prevented. Alternatively, both the sealing rings 5 and 7 may be made of the silicon carbide coating member according to the present invention.

The present invention is not limited to the above-mentioned respective embodiments, but can be appropriately improved and changed without departing from the basic principle of the present invention.

The silicon carbide-coated member according to the present invention, in addition to the molding die and the sealing ring described above, is a member whose film surface is required to have carbon-like properties (lubricity or slidability), and the amount of silicon components on the film surface. Suitable for use in members that are required to have a small amount, members that are required to have adhesion between a silicon carbide film and a substrate, and the like that may cause problems with a silicon carbide film having a general stoichiometric composition. You can For example, in addition to a sealing ring for a mechanical seal, there is a sliding member such as a bearing member as a member whose film surface is required to have lubricity or slidability.

Further, as a member required to have a small amount of silicon component on the film surface, there are optical elements such as a laser reflecting mirror and a diffraction grating. For example, as a laser reflecting mirror, it is well known that a silicon carbide film is formed by chemical vapor deposition on the surface of a substrate which is a silicon carbide sintered body or a carbon sintered body. When a high-energy beam is applied to the mirror surface obtained by polishing, white turbidity (cloudiness) may occur at the irradiation location, causing a problem such as a decrease in beam reflectance. The cause of such white turbidity mainly lies in the precipitation of silicon, and silicon is deposited in the form of fine droplets at the white turbid portion. However, by setting the surface of the film, which is a mirror surface, to a carbon-rich composition with a small amount of silicon component (for example, an amorphous carbon composition such as a glassy carbon composition or a pyrolithic carbon composition), the problem due to such silicon precipitation can be solved. .

[0029]

As can be easily understood from the above description, according to the silicon carbide coating member of the present invention, the silicon carbide film formed on the substrate is carbonized in the film thickness direction toward the film surface. Since the composition has a graded composition with increasing components (a kind of functionally graded material), characteristics that cannot be obtained with a general silicon carbide film having a stoichiometric composition (for example, a molding die for a glass optical element) And the sliding property of the sealing ring for mechanical seal with the mating sealing ring) can be exhibited, and the problems caused by the silicon carbide film in the molding die, sealing ring, etc. can be solved. , Its performance can be greatly improved.

[Brief description of drawings]

FIG. 1 shows an example in which the present invention is applied to a molding die for a glass optical element, and is a process drawing of the molding die.

FIG. 2 is a detailed view showing an enlarged main part (silicon carbide film) of FIG.

FIG. 3 shows an example in which the present invention is applied to a sealing ring, and is a cross-sectional view of a main part showing an example of a mechanical seal using the sealing ring.

FIG. 4 is a detailed view showing an enlarged main part (sealing end surface of the fixed ring) of FIG.

FIG. 5 is a Raman spectrum diagram of a silicon carbide film having a carbon-rich composition (glassy carbon composition).

FIG. 6 is a Raman spectrum diagram of a silicon carbide film having a stoichiometric composition.

[Explanation of symbols]

1 ... Mold, 2 ... Mold body (base), 2a ... Mold part, 3, 1
DESCRIPTION OF SYMBOLS 1 ... Silicon carbide film, 3a ... Molding surface, 5 ... Fixed ring (sealing ring), 5a ... Sealing end surface, 10 ... Base, 31,111 ... 1st layer (adhesive layer) having a silicon-rich composition, 32, 112 ...
Second layer having stoichiometric composition, 33, 113 ... Third layer having carbon-rich composition (surface layer).

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2K009 BB01 CC01 DD04 EE00                 4K030 AA03 AA06 AA09 AA17 BA37                       CA05 FA10 JA06 JA08 LA11

Claims (5)

[Claims] 1. A silicon carbide coating member comprising a silicon carbide film formed by chemical vapor deposition on the surface of a substrate, wherein the silicon carbide film has a graded composition in which the carbon component increases in the film thickness direction toward the film surface. A silicon carbide coating member characterized by being an eggplant. 2. The silicon carbide coating member according to claim 1, wherein the surface layer of silicon carbide has a carbon-rich composition. 3. The carbonization according to claim 1 or 2, wherein the substrate is made of a silicon carbide material, and the adhesive layer to the substrate in the silicon carbide film has a silicon-rich composition. Silicon coating member. 4. The silicon carbide coating member according to claim 1, which is a molding die for a glass optical element having a surface of a silicon carbide film as a molding surface. 5. The carbonized film according to claim 1, wherein the silicon carbide film is a sealing ring for a mechanical seal in which the surface of the silicon carbide film is a sliding surface with a mating sealing ring. Silicon coating member.