JPH0455135B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a mold for press-molding glass, and particularly to a mold for obtaining a high-precision glass molded body that does not require polishing after press-molding. [Prior Art] As a mold for obtaining a glass molded body by press molding, a mold using silicon carbide or silicon nitride (see JP-A-52-45613) is known. Recently, a coating film of a noble metal alloy made of platinum and other noble metal elements is formed as a surface layer on a substrate mainly composed of tungsten carbide (see Japanese Patent Application Laid-Open No. 60-246230), and a substrate made of silicon. A coating film in which a noble metal alloy consisting of platinum and other noble metal elements is formed as a surface layer has been proposed (see Japanese Patent Application Laid-open No. 242922/1983). [Problems to be solved by the invention] However, the mold made of silicon nitride or silicon carbide disclosed in JP-A No. 52-45613 tends to form an oxidized layer on its extreme surface, so it cannot be used with glass during press molding. It had the disadvantage of being easily fused. Furthermore, the mold disclosed in JP-A No. 60-246230, in which a platinum-based noble metal alloy layer is formed as a surface layer on a tungsten carbide base, is made by molding optical glass at high temperatures for a long period of time. However, tungsten carbide, which is the base material, is oxidized, resulting in a decrease in surface precision, the noble metal alloy layer is likely to peel off, and the molded glass body does not have good releasability during molding. Furthermore, in the mold disclosed in JP-A-61-242922, the platinum-based noble metal alloy film provided as a surface layer on the silicon substrate has poor adhesion to silicon, and the thermal expansion coefficient between the two is large. Due to the difference, the precious metal alloy film easily peels off from the silicon substrate after several press moldings.
In addition, a surface layer made of only a combination of platinum and precious metals such as iridium, osmium, rhodium, palladium, and ruthenium had the disadvantage that the mold release properties of the glass molded product during press molding were not very good. Therefore, an object of the present invention is to eliminate the above-mentioned drawbacks of the prior art molds, and to improve the adhesion between the base and the surface layer.
It is an object of the present invention to provide a mold for a glass molded body that satisfies all of the releasability requirements of a glass molded body at the same time. [Means for Solving the Problems] The present invention has been made to achieve the above object, and the mold for a glass molded article of the present invention includes a base and a surface layer, and the surface layer has a weight of 10 to 90 wt. % platinum and 5-40wt% nickel and/or chromium and 5%
It is characterized by being composed of at least three types of materials containing ~70 wt% silicon carbide. The present invention will be explained in detail below. The mold for a glass molded article of the present invention includes a base and a surface layer provided on the base. First, the base material is not particularly limited as long as it satisfies the hardness, strength, heat resistance, etc. generally required for a base, and examples include silicon carbide, tungsten carbide, silicon, silicon nitride, cermet, etc. is available. As described later, a substrate made of these materials is processed precisely and then coated with a surface layer of 0.03 to 10 μm, or processed into an approximate shape and coated with a surface layer of 3 to 50 μm, and then coated with a surface layer of 3 to 50 μm. By precision processing and finishing, the mold of the present invention can be obtained. When silicon is used as a base and a surface layer containing platinum is provided on the silicon base, not only is the adhesion between the base and the surface layer insufficient, but also the silicon on the base reacts with the platinum in the surface layer. , causing rough skin on the surface. Therefore, when silicon is used as the base, it is essential to provide an intervening layer of silicon carbide between this and the surface layer. Further, when tungsten carbide is used as the base, adhesion between the base and the intermediate layer is improved by providing an intervening layer of silicon carbide.
An intervening layer may also be provided in the case of silicon nitride, cermet, etc. On the other hand, when using silicon carbide as a base, if the silicon carbide is a sintered body, if the sintered body is coated with a silicon carbide CVD layer, the sintered body is coated with a silicon carbide CVD layer.
In some cases, a sputtering layer of silicon carbide is coated, and all of these are collectively referred to as a base. In the mold of the present invention, a surface layer is provided on the base or intervening layer, and the surface layer has a
It is composed of at least three materials including 90 wt% platinum, 5-40 wt% nickel and/or chromium, and 5-70 wt% silicon carbide. The present inventors discovered that while conventional surface layers made of noble metal alloys such as platinum and iridium do not have very good mold release properties of glass molded bodies during press molding,
It has been found that the surface layer of the present invention containing platinum and nickel and/or chromium and silicon carbide has significantly improved mold releasability. Since the surface layer of the present invention contains silicon carbide as an essential component along with the above-mentioned platinum, nickel, and/or chromium, it also has the advantage that the surface layer has increased hardness and is less prone to scratches. When the base is made of silicon carbide, the surface layer also contains silicon carbide, so the base and the surface layer have excellent affinity and adhesion and do not separate. In addition, when the base is made of tungsten carbide, since the tungsten carbide of the base and the silicon carbide in the surface layer are both carbides, a corresponding degree of affinity is guaranteed, and adhesion is ensured without any practical problems. is ensured. Furthermore, since the surface layer contains silicon carbide, there is little diffusion of cobalt, which is a binder in the base tungsten carbide. Adhesion between the tungsten carbide base and the surface layer and non-diffusion of cobalt, which is a binder for tungsten carbide, are further improved by providing an intervening layer of silicon carbide between the tungsten carbide base and the surface layer. Further, when the base is silicon, it is essential to provide an intervening layer of silicon carbide between the base and the surface layer, thereby sufficiently ensuring adhesion between the base and the surface layer. When the base is silicon, without the above intervening layer, the silicon of the base will react with the platinum in the surface layer, causing surface roughening, but due to the presence of the intervening layer of silicon carbide, the interaction between silicon and platinum will occur. Prevents surface roughness caused by reactions. In the surface layer of the present invention, the composition range of essential components is 10 to 90 wt% platinum, 5 to 40 wt% nickel and/or chromium, and 5 to 40 wt% silicon carbide.
Although it is limited to 70wt%, the composition range of each essential component is determined by taking into account the releasability of the glass molded body during press molding, the adhesion of the surface layer to the base (non-peelability), the hardness of the surface layer, etc. The decision was made in consideration of the Note that when using tungsten carbide containing cobalt as a binder as the base and not providing an intervening layer of silicon carbide, the amount of silicon carbide in the surface layer is adjusted to prevent cobalt from diffusing into the surface layer. It is preferable to use a slightly larger number than when an intervening layer is provided. In addition to the above platinum and nickel and/or chromium and silicon carbide, rhodium, iridium,
By adding palladium, gold, etc., it becomes possible to withstand even higher temperature press molding. The surface layer is preferably formed by a sputtering method or the like. In forming the surface layer by the sputtering method, targets for each substance constituting the surface layer may be prepared individually, or an alloy target consisting of a silicon carbide target and a plurality of metals may be prepared. The thickness of the surface layer is preferably 3 to 50 μm when using silicon nitride, silicon carbide, tungsten carbide, etc. as the base material and performing high-precision aspherical processing after forming the surface layer. . In addition, when providing a surface layer after precision processing a silicon carbide or tungsten carbide substrate, the thickness is 10 μm.
Below, it is particularly preferable to set it to 0.03 to 10 μm. When silicon is used as the base material and subjected to highly accurate aspherical cutting using a diamond cutting tool, the surface layer may have a thickness of 0.03 to 10 μm. In addition, when the final shape is spherical, the base material may be mirror-finished, the surface layer may be coated to a thickness of 0.03 to 10 μm, and this may be used as the final surface. [Example] The present invention will be further explained below with reference to Examples, but the present invention is not limited to these Examples. A cross-sectional view showing the structure of a press molding machine housing a mold is shown in FIG. The mold is composed of an upper mold 1, a lower mold 2, and a guide mold 3. The upper mold 1 and the lower mold 2 are slidably housed in the guide mold 3, and the upper mold 1 and the lower mold 2 are A glass gob 4 to be formed is set in between. In this example, the guide mold 3 is made of silicon carbide, has an outer diameter of 26 mm, an inner diameter of 14 mm, and a height of 40 mm.
The processed material was used as it was without providing a surface layer. In addition, the outer diameter of upper mold 1 and lower mold 2 is 14 mm.
The height was approximately 20 mm, and a number of materials such as tungsten carbide, silicon carbide, and silicon were prepared, one end surface was finely ground into a concave shape, and this was used as the base. In this example, both tungsten carbide substrates were prepared, one without and one with a silicon carbide intervening layer between it and the surface layer. In addition, a silicon substrate having a silicon carbide intervening layer between the surface layer and the surface layer was prepared. Next, on these bases, platinum, nickel and/or
Alternatively, various molds of the present invention were obtained by forming a surface layer consisting of chromium and silicon carbide or a surface layer consisting of platinum and nickel and/or chromium, silicon carbide and another metal (rhodium, iridium, palladium or gold). For comparison, the base is silicon carbide,
A mold whose surface layer contains platinum and nickel but does not contain silicon carbide (Comparative Experiment No. 5c),
The base is silicon carbide and the surface layer contains platinum but does not contain silicon carbide, nickel or chromium (Comparative Experiment No. 12c, 12c') and the base is silicon with silicon carbide between it and the surface layer. A mold without the intervening layer (Comparative Experiment Example No. 25c) was prepared and subjected to a comparative experiment. Table 1 shows the material of the base of these molds, the substance and thickness of the intervening layer, and the composition and thickness of the surface layer. Below, the key points of the method for manufacturing the various molds shown in Table 1 will be explained. Experimental Examples Nos. 1 to 24 and Comparative Experimental Examples No. 5c, 12c, 12c' These are examples of spherical molds in which the base is silicon carbide or tungsten carbide. When making this mold, the base was mirror-finished into a spherical surface,
A surface layer was formed by a sputtering method. Experimental Example No. 25 and Comparative Experimental Example No. 25c These are examples of aspherical molds whose base is silicon. The base was precision cut into an aspherical surface using single-crystal diamond bide, and then, in the case of Experimental Example No. 25, an intervening layer of silicon carbide was provided, and in the case of Comparative Experimental Example No. 25c, this was The mold was completed by immediately forming a surface layer without forming a surface layer. Next, an example of press molding using the mold thus produced will be described with reference to FIG. 1.
First, in a mold consisting of an upper mold 1, a lower mold 2, and a guide mold 3, glass compositions of wt% SiO ₂ 27.8, Na ₂ O 1.8,
A spherical glass lump 4 with a diameter of 10 mm made of optical glass (transition temperature 435°C) consisting of K ₂ O 1.2, PbO 65.2, Al ₂ O ₃ 2.0, and TiO ₂ 2.0 is placed on the support rod 9. A heater 12 placed through a support stand 10 and wrapped around the outer periphery of a quartz tube 11 in an N ₂ atmosphere,
The glass gob 4 to be formed is heated together with the mold, and the push rod 13 is lowered to heat it at 500°C and under a pressure of 80Kg/ ^cm2.
Pressed for 30 seconds. After that, the pressure is released, and the press-molded glass molded body is slowly cooled to the above transition temperature while in contact with the upper mold 1 and the lower mold 2,
The glass molded body was then rapidly cooled to around room temperature and taken out from the mold. Using the molds of Experimental Examples No. 1 to 25, respectively
As a result of repeating press molding 1000 times, in all experimental examples, the glass molded product had good mold releasability, no chemical reaction was observed on the contact surface with the mold, and the surface roughness was less than 100 ÅR _nax . The transparency was also good. In addition, no peeling of the surface layer occurred in any of the molds, and the surface precision and mirror finish were maintained. The surface layer also had high hardness and was resistant to scratches. On the other hand, in Experiment No. 5, the mold of Comparative Experiment 5c, in which the amount of silicon carbide (10%) was reduced to zero and the amount of nickel was increased from 20% to 30%, was press-molded 100 times. Peeling of the surface layer was observed at the time of completion. Furthermore, although the amount of platinum is the same, the molds of Comparative Experiments No. 12c and 12c' are different from the mold of Experiment No. 12 in that they do not contain silicon carbide and contain rhodium or iridium instead of chromium. The mold releasability was extremely poor from the time of initial press molding. In addition, the mold of Comparative Experiment No. 25c, which differs from the mold of Experiment No. 25 only in that no intervening layer of silicon carbide was formed, had a markedly rough surface (surface roughness of 500 ÅR _nax ). Although the surface layer of the mold was slightly oxidized in the above-mentioned experimental example, it was found that this had no effect on the releasability or surface roughness of the glass molded product during press molding. In all of the above examples, SiO ₂ −Na ₂ O with a pressing temperature of around 500°C was used as the glass to be formed.
_-K2O -PbO- _{Al2O3 -TiO2 glass} was used, but the glass to be formed is not limited to this. For the glass to be formed, the pressing temperature, that is, the temperature at which the glass viscosity is approximately 10 ⁸ −10 ¹⁰ poise, is
The temperature is preferably 650°C or lower.

【table】

〔Effect of the invention〕

According to the present invention, by using a substance whose main components are platinum, nickel, and/or chromium and silicon carbide as the surface layer, the releasability of the glass molded body during press molding and the adhesion between the surface layer and the base are improved. (non-peelability) etc. were improved, and the hardness of the surface layer was also improved. Therefore, it was possible to obtain a mold with a long life.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the structure of a press molding machine housing a mold of the present invention. DESCRIPTION OF SYMBOLS 1... Upper mold, 2... Lower mold, 3... Guide mold, 4... Glass lump to be formed, 9... Support rod, 10... Support stand, 11... Quartz tube, 12... Heater, 13... Push rod, 14... Thermocouple .

Claims (1)

[Claims] 1. Comprising a base and a surface layer, where the surface layer is 10 to 90 wt%
A mold for a glass molded article, characterized in that the mold is made of at least three substances including platinum, nickel and/or chromium in an amount of 5 to 40 wt%, and silicon carbide in an amount of 5 to 70 wt%. 2. The mold according to claim 1, wherein the substrate is selected from the group consisting of tungsten carbide, silicon carbide, silicon, silicon nitride and cermet. 3. The mold according to claim 2, wherein an intervening layer of silicon carbide is provided between the base and the surface layer. 4. The mold according to claim 1, wherein the surface layer further contains at least one metal selected from the group consisting of rhodium, iridium, palladium, and gold in addition to platinum and nickel and/or chromium and silicon carbide. .