JPH0625001B2 - Method for producing crystallized glass article - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a crystallized glass article, and more particularly to a method for strengthening a crystallized glass for producing a crystallized glass material having high strength and less variation.

[Conventional technology]

Crystallized glass, like glass, does not contain any pores, has a wide range of expansion coefficient from negative expansion coefficient to positive high expansion coefficient, depending on the type of precipitated crystal phase, high heat resistance, high elasticity, high strength, It has various excellent properties such as high hardness, and by taking advantage of these properties, it has been put to practical use in various fields such as heat-resistant tableware, cooker top plates, and reflector mirror blanks.

Recently, crystallized glass has been used for various substrate materials and structural materials,
Alternatively, in the case of a material having transparency equivalent to that of glass, it is increasingly used as a transparent material for windows or covers of various devices in place of glass.

Among those applications, crystal glass is often used after grinding and polishing in applications where dimensional accuracy, flatness, or transparency that does not distort images when transparent is required. In addition, when high strength is required in addition to them, there are not a few cases in which they are used after being chemically strengthened after grinding and polishing.

Crystallized glass requires a longer processing time than glass because it has a lower processing speed than glass, but the same steps as glass, that is, grinding with a diamond grinder, lapping agent such as SiC or alumina, polishing with CeO ₂ slurry, etc. Is possible.

[Problems to be solved by the invention]

However, in general, crystallized glass has higher hardness and higher water resistance than glass, so that not only the processing speed is small and the time required to obtain a mirror surface is long, but it is visually judged that it is a mirror surface. Even after polishing, invisible minute scratches or latent scratches are likely to remain on the surface. In this way, the latent scratches are likely to remain in the crystallized glass, and when a mirror-finished product is etched with dilute hydrofluoric acid or the like, invisible minute scratches are enlarged and visually confirmed. This can be confirmed. Remaining latent scratches such as these lead to a decrease in strength in unreinforced products, and in the case of chemically strengthened products, when the depth of scratches is shallower than the depth of the surface compressive stress layer, the effect on strength is small. On the other hand, if the depth of scratches is deeper than the depth of the surface compressive stress layer, the effect of strengthening cannot be obtained, resulting in the occurrence of low-strength products such as crystallized glass before strengthening and significant variations in strength, which is not preferable for practical use. .

Therefore, in the case of a crystallized glass article that is chemically strengthened after grinding and polishing, in order to prevent the occurrence of low-strength products due to residual latent scratches and significant variations in strength, the polishing time should be the same as that for ordinary glass. Double to 1 in some cases
In order to increase the length to 0 times or more, or to shorten this polishing time, in the ordinary glass grinding / polishing process, the transition from grinding with the No. 1000 lapping agent to the polishing process is performed.
After grinding with No. 1000 lapping agent, it is necessary to add grinding particles with finer grain size, for example, No. 1500 to 2000 lapping agents. However, these grinding
A significant change in the polishing process causes a significant increase in processing cost and is not preferable in practice.

[Means for solving problems]

For the present invention to solve the above problems, the crystallized glass was subjected to SiO ₂ coating on the surface prior to chemical strengthening, SiO ₂ in the surface layer coating the bottom of the crystallized glass article through subsequent to the surface of the SiO ₂ film At least a part of the alkali metal ions is replaced with alkali ions having a large ionic radius in the molten salt.

And as a method of SiO ₂ coating formed by contacting the crystallized glass and silica supersaturated solution of hydrosilicofluoric acid it is characterized by using a means of precipitating SiO ₂ film on the surface.

The present invention particularly exhibits its effect on the production of a crystallized glass article requiring a mirror surface, and the final surface state of the surface polishing of the crystallized glass performed in that case is judged to be insufficiently polished by the usual method. It does not matter even if it is in the state of being struck (the state in which latent scratches remain).

Further, the shape of the crystallized glass article is not limited to the plate-like rod shape, and any shape that can be brought into contact with a silica supersaturated solution of hydrofluoric acid can be used. The silica supersaturated solution of hydrosilicofluoric acid used is prepared by shifting the equilibrium conditions of the silica hydrofluoric acid saturated solution by a method of adding additives such as H ₃ BO ₃ and Al (OH) _3. can do. The hydrosilicofluoric acid solution used is preferably one having a concentration of 0.5 to 3.0 mol / l in order to obtain a good deposition rate. When boric acid (H ₃ BO ₃ ) is used as an additive,
It is preferred to add 2.0 × 10 ^-2 mol or more to 1 part of the hydrosilicofluoric acid aqueous solution having a concentration of 3.0 mol / in order to obtain a good precipitation rate.

The silica supersaturated solution of hydrosilicofluoric acid is brought into contact with the crystallized glass by a commonly used method such as a spraying method, a coating method or a dipping method, but the reaction time until the intended deposited film is obtained is relatively long. Contacting using the dipping method is preferred as it takes time.

The SiO ₂ film deposited on the crystallized glass substance is preferably a film having a thickness of 50 to 200 nm, which has a remarkable deposition effect and has good productivity.

After that, the crystallized glass is ion-exchanged through the SiO ₂ coating and strengthened (commonly called chemical strengthening). As the chemical strengthening method, a usual strengthening method can be used.

[Work]

The present invention is believed to operate as follows. That is, when crystallized glass with latent scratches on its surface is contacted with a hydrosilicofluoric acid silica supersaturated aqueous solution, SiO ₂ is precipitated with the surface as a nucleation site, and the surface is coated with a SiO ₂ film. It At this time, since the hydrosilicofluoric acid aqueous solution which is the source of SiO ₂ has a low viscosity, it penetrates into the minute latent scratches of the crystallized glass caused by grinding and polishing. Therefore, the precipitation of SiO ₂ also occurs inside the latent scratch, and as a result, the latent scratch is filled with SiO ₂ and its influence on the strength is substantially not recognized.

Examples of the SiO ₂ coating method include a method using an alkyl silicate, a method using a silane gas, and the like in addition to the method according to the present invention. However, even if subjected to SiO ₂ coated by these methods, SiO ₂ obtained film a certain size of SiO ₂
The particles are deposited on the surface, and not only the effect that the SiO ₂ obtained by the method of the present invention does not fill the tip of the latent scratch, but the SiO ₂ film obtained by these methods is chemically strengthened, for example, 450. Molten KNO ₃ at ~ 480 ° C
If it is immersed for 8 to 40 hours, it becomes cloudy or peels off if it is remarkable, and it cannot withstand chemical strengthening.

Also, such SiO ₂ films are expected to interfere with chemical strengthening, which requires migration of alkali metal ions through the SiO ₂ film. However, in a high temperature where chemical strengthening treatment is performed, for example, in a temperature range of 450 to 480 ° C., the Si is immersed in a pure KNO ₃ melt under the condition of Si.
The migration rate of alkali metal ions in the O ₂ film is relatively high, and its interfering effect on the chemical strengthening process is relatively low, filling latent scratches and preventing their influence on the strength, and preventing the generation of low strength products. It works very effectively in reducing variability.

Hereinafter, the present invention will be described in more detail based on examples.

〔Example〕

Example 1 SiO ₂ 65.0, Al ₂ O ₃ 22.5, Li ₂ O 4.5, Na ₂ O in wt%
1.0, TiO ₂ 2.0, ZrO ₂ 2.5, P ₂ O ₅ 1.5, As ₂
A glass made of O ₃ 1.0 was heated to 850 ° C. at 5 ° C./min and held at 850 ° C. for 4 hours to obtain a transparent crystallized glass containing β-quartz solid solution as a main precipitated crystal phase. This is cut with a diamond saw into rods of about 5 mm square and 50 mm long, and 40
After grinding with No. 0 SiC and No. 1000 alumina lapping agent, 4 surfaces of 5 mm in width and 50 mm in height were polished with CeO ₂ slurry. After about 15 minutes each, the scratches generated in the grinding process disappeared visually, and the surface was judged to be a mirror surface. The rod-shaped samples thus obtained were divided into five groups, and one group was immersed for 16 hours in a treatment solution prepared by adding 0.5 mol / H ₃ BO _{3 30} CC to 200 CC of a 2 mol / silica hydrofluoric acid saturated silica solution. As a result, a SiO ₂ film having a thickness of about 150 nm was formed on the surface. For comparison, two of the remaining three groups were made of SiO ₂
The crystallized glass is soaked in an ethanol solution of tetraethyl silicate having a concentration of 5% in terms of, then pulled up, dried and baked at 500 ° C. for 30 minutes. Monosilane 5
%, N ₂ 95% mixed gas is sprayed on the substrate heated to 500 ° C. The surface was coated with a SiO ₂ film having a thickness of about 120 nm. In this way, the SiO ₂
The coated 3 groups and the 2 groups as-grinded / polished were subjected to chemical strengthening treatment by immersing them in a KNO ₃ bath at 450 ° C for 24 hours. After that, a group of those subjected to the chemical strengthening treatment as they were in the grinding / polishing process was immersed in the above-mentioned silica supersaturated solution of hydrofluoric acid to deposit a SiO ₂ film having a thickness of about 150 nm on the crystallized glass.

Then, three-point bending test was performed on the above-mentioned five kinds of samples to measure the strength. The results are shown in Table 1.

The reinforced product of the present invention has a slightly lower strength as compared with the product without SiO ₂ coating, but the difference is slight, and the minimum value of the strength is considerably high, and the variation is about 1
Remarkably low as / 3. Also formed by the method of the present invention.
The SiO ₂ film did not show any change by the chemical strengthening treatment. On the other hand, SiO ₂ formed by dipping and CVD in the previous period
The film undergoes alteration or delamination due to chemical strengthening treatment,
Further, the effect of reducing the variation in strength is not recognized.

Example 2 A glass having the same composition as in Example 1 was heated to 1150 ° C. at 5 ° C./min and held at 1150 ° C. for 2 hours to give a white opaque crystallized glass containing β-spodumene solid solution as the main precipitated crystals. From the crystallized glass thus obtained, a rod-shaped polished sample having a length of about 5 mm and a length of 50 mm was prepared in the same manner as in Example 1. This rod-shaped polished sample was divided into two groups, one group of 200CC 2m
ol / 0.5 mol of 30CC to saturated silica hydrofluoric acid solution
After dipping in a treatment solution containing HBO ₃ aqueous solution for 16 hours and coating the surface with a SiO ₂ film with a thickness of about 150 nm, the other group was left as ground and polished, and KNO _{3 at} 450 ° C was used. After being immersed in a bath for 24 hours for chemical strengthening treatment, its strength was measured by three-point bending. The results are shown in Table 2.

[Effects of the Invention] According to the present invention, in a crystallized glass article that has been chemically strengthened after grinding / polishing in a process similar to glass, it is possible to prevent generation of low-strength products due to residual latent scratches and significant variation in strength. . Further, although the above-mentioned examples were carried out on the crystallized glass containing β-quartz and β-spodumene, the method for producing the crystallized glass article according to the present invention is not limited to the crystallized glass but for any crystallized glass. Applicable.

Claims (1)

[Claims] 1. A crystallized glass article containing an alkali metal ion whose surface is covered with SiO ₂ is brought into contact with a molten salt containing an alkali ion having a larger ionic radius than that of the alkali metal ion contained in the glass to form a SiO ₂ surface. What is claimed is: 1. A method for producing a crystallized glass article, wherein at least a part of alkali metal ions on the surface of the crystallized glass article through a coating is replaced with alkali ions having a large ionic radius in a molten salt. _{2. A} method for producing a crystallized glass article, characterized in that the coating is formed by contacting with a silica supersaturated solution of hydrofluoric acid.