JPS6146407B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for molding a press lens that has high shape accuracy and high surface roughness without the need for polishing after press molding. BACKGROUND ART Conventionally, as a method for manufacturing press lenses, for example, Japanese Patent Application Laid-open No. 47-27216 discloses a method in which the temperature of a mold is kept constant above the transition point and below the softening point, and fluid glass is placed inside the mold. A method is described in which the molded glass is placed in the glass, pressure-molded, maintained in this state until the temperature distribution of the molded glass becomes uniform, and then taken out and molded into a glass lens. Manufacturing lenses using this method eliminates the need for grinding and polishing processes, which can lead to significant cost reductions.
The time required for molding is extremely long, and the glass is constantly in contact with the mold during this time, so the mold is exposed to high temperatures for a long time. In addition, instead of fluid glass, preforms (glass without shear marks manufactured by a specified molding method, glass of a specified weight obtained by cutting from plate glass or glass rod, etc.) are heated and softened by induction heating. A method is also known in which the above-mentioned pressing step is performed after the above-mentioned pressing step. Problems to be Solved by the Invention However, in the conventional press lens molding method, the heat capacity of the preform or molten glass is large, and the mold is also heated at the same time as the preform is heated, resulting in the mold becoming hot and causing oxidation of the mold surface. There were problems in that it caused deterioration (rough skin), worsened the surface roughness of the mold surface, and worsened the mold releasability of the glass. Means for Solving the Problems The present invention has been made to solve these problems, and it is a press lens molding method using a mold containing an upper mold, a lower mold, and a ring-shaped body mold. In the method, a preform is placed on a ring-shaped body mold,
After heating and softening the preform by irradiating the main surface of the preform with laser light,
This press lens molding method is characterized in that a preform is transferred together with a ring-shaped body mold between an upper mold and a lower mold, and press-molded between the upper mold and the lower mold. A preferred embodiment is a press lens molding method characterized in that the laser beam is a carbon dioxide laser. Effects In the press lens molding method of the present invention, the preform is placed on a ring-shaped barrel mold immediately before press molding and heated by laser beam irradiation, so that the upper mold and the lower mold are heated in conjunction with the above-mentioned heating of the preform. never be done. Further, the heating method is heating by irradiation with laser light, and since the laser light is hardly absorbed by the surface of the ring-shaped body, the temperature of the ring-shaped body increases only slightly. In addition, when using a carbon dioxide laser, since the wavelength is around 10.6 μm, the energy of the laser light is absorbed near the main surface of the preform and converted into thermal energy, so the laser light can be efficiently used near the main surface of the preform. It can be heated and softened, and the heat capacity of the entire glass preform can be kept low, so it is possible to reduce the temperature rise of the upper mold, lower mold, and ring-shaped body mold that are in contact with the glass preform during press molding. . Example Preform 1 made of heavy flint optical glass SF11 (glass transition temperature 435°C) was
An example in which press molding is performed after heating and softening using a laser beam 3 (preferably a carbon dioxide gas laser) of about μm will be described in detail. First, the preform 1 is placed on the holding portion 2' of the ring-shaped body mold 2. The ring-shaped cylinder mold 2 carrying the preform 1 is moved into an electric furnace maintained at a temperature higher than the glass transition temperature and moved to a laser beam irradiation position, and as shown in FIG. 2, both main surfaces of the preform 1 are exposed to the laser beam 3. irradiated and heated. The ring-shaped body mold 2 is inserted together with the preform 1 into a cylindrical sleeve 6 that guides the upper mold 4 and the lower mold 5, and is then transferred between the upper mold 4 and the lower mold 5. 5, press molding is performed at a predetermined pressure. Note that the upper mold 4, the lower mold 5, and the sleeve 6 are held in advance at a certain temperature higher than the glass transition temperature. The table shows the laser light irradiation conditions, the preform surface temperature (glass temperature) and ring-shaped body temperature after laser light irradiation.

[Table] As shown in the table, it can be seen that while the glass surface temperature of the preform 1 is sufficiently increased by laser beam irradiation, the temperature of the ring-shaped body is hardly increased. Further, since the upper mold and the lower mold are not irradiated with laser light, the temperature of these molds does not rise.
This made it possible to prevent damage to the mold due to heat, that is, oxidation (roughness) of the mold surface. In addition, the effect of preventing glass from fusing to the mold during pressing was also observed by preventing rough skin. Effects As explained above, according to the present invention, the preform is heated by laser beam irradiation on the ring-shaped body mold,
Since the upper and lower molds are not irradiated with this laser light, it is possible to prevent the temperature of the upper and lower molds from rising, and by using a laser light with a wavelength of around 10.6 μm, the above-mentioned temperature can be prevented during press molding. Since the temperature rise of the upper mold, lower mold, and ring-shaped body mold that were in contact with the preform could be reduced, roughening of the mold surface (deterioration due to oxidation of the mold surface) could be prevented.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a preform according to an embodiment of the present invention placed on a ring-shaped body mold, FIG. 2 is a cross-sectional view showing the state of the preform according to the embodiment when it is heated, and FIG. 3 is a cross-sectional view of the preform according to the embodiment. FIG. 2 is a cross-sectional view showing the relationship between a mold and a preform during press molding. 1... Preform, 2... Ring-shaped body type,
2'... Holding part, 3... Laser light, 4... Upper mold,
5...Lower mold, 6...Sleeve.

Claims (1)

[Claims] 1. A press lens molding method using a mold containing an upper mold, a lower mold, and a ring-shaped body mold, in which a preform is placed on the ring-shaped body mold, and a laser beam is applied to the main surface of this form. After the preform is heated and softened by irradiation with , the preform is transferred together with the ring-shaped body mold between an upper mold and a lower mold, and press-molded by the upper mold and the lower mold. How to mold press lenses. 2. The press lens molding method according to claim 1, wherein the laser beam is a carbon dioxide laser.