JPH0480080B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a cleaning liquid used for cleaning a mold for press-molding a glass lens. [Prior Art] In recent years, optical glass components, especially optical glass lenses, have been trending toward aspheric surfaces that can simultaneously simplify the structure of a lens system of an optical device and reduce the weight of the lens portion. To manufacture this aspherical lens,
The polishing method, which is a conventional optical lens manufacturing method, has difficulty in processing and mass production, and direct press molding is considered promising. This direct press molding method involves heating a lump of optical glass and then press-molding it on a mold that has been finished to the desired surface quality and precision, or pressing a lump of optical glass that has been heated in advance. This is a method of manufacturing optical lenses by molding and press-molding without requiring post-processes such as polishing or polishing. In order to obtain an optical lens using this method, a mold with the desired high shape accuracy and an optical mirror finish is of course required, but on the molding surface of the mold,
If glass dust or other foreign matter adheres to the lens, the desired lens cannot be obtained, so in such a case, it is necessary to promptly remove the adhered substance. For this purpose, Japanese Patent Application Laid-Open No. 61-72633 discloses a method in which non-oxidizing gas is blown onto the molding surface of the mold after press molding to blow away glass debris and foreign matter on the molding surface. ing. [Problems to be Solved by the Invention] With the conventional cleaning method described above, glass debris and foreign matter adhering to the molding surface may not be removed and may remain on the molding surface, and this method cleans glass more reliably than gas blowing. A method for removing debris and foreign matter was desired. Accordingly, an object of the present invention is to provide a cleaning liquid that can easily remove glass debris adhering to the molding surface of a mold, foreign matter such as attached or deposited lead, and other stains, and can clean the molding surface. It's about doing. [Means for Solving the Problems] The present invention has been made to achieve the above object, and the cleaning liquid for glass lens molds of the present invention contains an acidic ammonium fluoride saturated aqueous solution as an essential component, Furthermore, it is a liquid containing concentrated nitric acid and/or water as an essential component in some cases, and is a liquid containing acidic ammonium fluoride saturated aqueous solution/(acidic ammonium fluoride saturated aqueous solution +
The ratio of (concentrated nitric acid) is 50% by volume or more, and the ratio of (acidic ammonium fluoride saturated aqueous solution + concentrated nitric acid) / (acidic ammonium fluoride saturated aqueous solution + concentrated nitric acid + water) is 10
It is characterized by a capacity of % or more. Here, the acidic ammonium fluoride saturated aqueous solution is
670g of acidic ammonium fluoride in 1 part of water at room temperature
It refers to the dissolved liquid (the amount of acidic ammonium fluoride dissolved to obtain a saturated aqueous solution varies depending on the temperature). Also, concentrated nitric acid contains 63% by weight of _HNO3 .
It is an aqueous solution with a specific gravity of 1.38, and is equivalent to commercially available concentrated nitric acid. In addition to these main components, sulfuric acid, hydrochloric acid, acetic acid, hydrofluoric acid, etc. may be added, but it is preferable not to use hydrofluoric acid since it is dangerous if it adheres to the skin. By using the cleaning liquid of the present invention, glass debris adhering to a mold can be easily dissolved and removed regardless of the type of glass. In addition, SF optical glass
Because it contains a large amount of PbO, reduced particles tend to adhere to and accumulate on the mold during molding, but these can also be easily removed. The material of the mold to be cleaned with the cleaning solution of the present invention is silicon carbide, a mixture of silicon carbide and carbon,
These include silicon nitride, titanium boride, precious metals (platinum, rhodium, gold, etc.), tungsten carbide, stainless steel and many other materials. Depending on the material, the mixing ratio of the components in the cleaning solution can be changed arbitrarily, but if the ratio of acidic ammonium fluoride saturated aqueous solution/(acidic ammonium fluoride saturated aqueous solution + concentrated nitric acid) is less than 50% by volume, cobalt may be removed. It is not preferable to use sintered tungsten carbide or stainless steel as the binder because they are easily corroded. In addition, if the ratio of (acidic ammonium fluoride saturated aqueous solution + concentrated nitric acid)/(acidic ammonium fluoride saturated aqueous solution + concentrated nitric acid + water) is less than 10% by volume, it will be difficult to remove glass debris that has adhered to the mold by pressing. This is not preferred because it takes time. By applying the cleaning liquid of the present invention to the part of the mold where glass debris etc. have adhered and leaving it for a while,
Glass debris etc. can be removed without damaging the mold, and the mold can then be used again by wiping it with acetone. Also, by immersing the mold in the cleaning solution,
It is even better to perform ultrasonic cleaning, and then pass through an automatic ultrasonic cleaning process normally used for cleaning optical lenses so that no stains or the like remain. [Examples] Hereinafter, the present invention will be further explained with reference to Examples.
The present invention is not limited to the following examples. As the cleaning liquid of the present invention, 10 of No. 1 to 10 in Table 1 are listed.
These cleaning solutions were prepared as follows. That is, add acidic ammonium fluoride little by little into a certain amount of distilled water at room temperature while stirring to prepare a saturated aqueous solution of acidic ammonium fluoride (dissolved amount of acidic ammonium fluoride in 1 part of water: 670 g), and add this as it is. This was the No. 3 cleaning solution of the present invention. In addition, the cleaning liquids No. 1, 2 and 4 to 10 of the present invention are:
It was prepared by adding concentrated nitric acid (JIS special grade 63% by weight liquid, specific gravity 1.38) and/or distilled water in a predetermined volume ratio to the acidic ammonium fluoride saturated aqueous solution obtained above and stirring. For comparison, concentrated nitric acid was prepared as No. 11. Using these cleaning solutions, first, as a preliminary test, the melting rate of glass was investigated, and a surface roughening test of the mold material was conducted. Figure 1 shows an example of the results of examining the relationship between immersion time and weight loss by immersing a polished ball (4.4 mm in diameter, 230 mg in weight) of SF6, an optical glass containing a large amount of lead, in each cleaning solution. Normally, the glass debris that adheres to the mold during press molding is minute, about several μm in size, and is less than 1 mg, so these cleaning solutions can sufficiently dissolve and remove the adhered glass. On the other hand, in order to investigate the surface roughness of the mold material, we used a silicon carbide sintered body coated with silicon carbide using the CVD method and a tungsten carbide sintered body whose binder was mainly cobalt, with a diameter of 17 mm and a thickness of 3 mm.
mirror-polished the flat disk to a surface roughness of 150Å or less,
These were immersed in each cleaning solution for 2 hours at room temperature, and the surface roughness before and after was measured and observed under a microscope. As a result, the molds coated with silicon carbide by the CVD method did not change at all no matter which of the cleaning liquids Nos. 1 to 10 were used. In the case of sintered tungsten carbide, the mold did not change at all when cleaning solutions No. 1 to 8 were used, and the surface roughness worsened by about 10 Å when cleaning solutions No. 9 and No. 10 were used, but this is not practical. It was within a reasonable range. In contrast, liquid No. 11 for comparison had noticeable skin roughness. This is thought to be because cobalt in the bander is corroded by nitric acid. Next, the SF6 polished ball was placed in the mold with the mirror-finished surface and heated at 500°C in an _N2 atmosphere.
The glass was heated to a temperature of 100°C and press-molded, then cooled to room temperature, the molded body was taken out of the mold, new glass was placed in the mold, and press-molded 20 times in the same manner. After that, when I observed the mold surface, I found that
Products coated with silicon carbide using the CVD method are also available.
In the case of the tungsten carbide sintered body, the adhesion of glass debris was also observed under a microscope, and the adhesion of lead components was determined due to the reduction of PbO. This mold was immersed in each cleaning solution No. 1 to No. 10 for 5 minutes, followed by an automatic ultrasonic cleaning process normally used for cleaning optical lenses (water → surfactant solution → water → isopropyl alcohol → When observed under an optical microscope after drying with Freon, no residual foreign matter was observed.
The original mirror surface condition was maintained. Similar tests were conducted on each of the cleaning solutions No. 1 to No. 10, and similar results were obtained for all of them. Also, put a few drops of cleaning liquid on the molded surface, rub it with a cotton swab about 10 times at specified intervals for 5 minutes, then wipe it with water.
Similar results were obtained by wiping with acetone. In the above examples, an acidic ammonium fluoride saturated aqueous solution or a mixture of the acidic ammonium fluoride saturated aqueous solution and concentrated nitric acid and/or water was used, but sulfuric acid, hydrochloric acid, acetic acid, hydrofluoric acid, etc. were further added to this. You may. However, since hydrofluoric acid has an adverse effect on the human body when it comes into contact with the skin, its use should be avoided as much as possible.

[Table] [Effects of the Invention] As described above, the cleaning liquid of the present invention is obtained by using an acidic ammonium fluoride aqueous solution or a mixture of this with concentrated nitric acid and/or water at a predetermined mixing ratio. When the cleaning liquid of the present invention is used to clean a glass lens mold, it can easily remove deposits on the molding surface when manufacturing glass lenses by direct press molding, while preventing danger to the human body. This has the remarkable advantage that it can be removed quickly and that ultra-precision optical glass lenses with good surface quality and shape can be stably manufactured.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the immersion time and the weight loss of the optical glass bulb when the optical glass bulb is immersed in the cleaning solution of the present invention.

Claims (1)

[Claims] 1 A liquid containing an acidic saturated ammonium fluoride aqueous solution as an essential component, and further containing concentrated nitric acid and/or water as an essential component, where the acidic ammonium fluoride saturated aqueous solution/(acidic ammonium fluoride saturated aqueous solution + concentrated nitric acid) A glass characterized in that the ratio of (acidic ammonium fluoride saturated aqueous solution + concentrated nitric acid)/(acidic ammonium fluoride saturated aqueous solution + concentrated nitric acid + water) is at least 10% by volume. Cleaning liquid for lens molds.