JP2686118B2 - Glass optical element molding method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a glass optical element molding method for molding a glass optical element by pressurizing a glass material that has been softened by heating so as to be pressure-moldable.

[Conventional technology]

It is known, for example, from Japanese Examined Patent Publication (Kokoku) No. 55-116245 to obtain a glass optical element by molding a glass material which has been softened by heating into a desired shape while deforming it by a heating press. By the way, when the glass optical element is obtained by the hot pressing means, it is necessary that the releasability between the glass and the molding die is good, and in particular, the strict surface shape and surface characteristics required for the optical lens for image formation are satisfied. For this reason, the releasability over the entire molding surface of the molding die is important. This mold releasability depends largely on the glass leakage property due to the material of the molding die.

As a molding die having good releasability, the patent applicant has disclosed in Japanese Patent Laid-Open No.
The technology disclosed in Japanese Patent Publication No. 87423 has been disclosed. That is, in the molding die described in this publication, the molding surface of the optical element is made of a chemical substance containing chromium and nitrogen as main components. This molding die is generally obtained by forming a coating film containing chromium and nitrogen as the main components on the molding surface by ion plating or other PVD method, and the mold releasability is disclosed as a prior art. It is good compared to the
When used for molding, if the product is in a new state or after long-term use and after removing the deposits on the mold surface by polishing, etc., glass fusion will initially occur due to deformation of the glass material during molding. There were cases (the same applies to other conventional examples).

This particularly occurs when the pressure is increased in order to shorten the pressure holding time in the molding process and improve the productivity.

The present invention was created with attention to such problems, and particularly continuous press molding using a molding die after removing new or adhered substances (that is, continuously pressing a large number of pieces). It is an object of the present invention to provide a method for molding a glass optical element, which makes it possible to prevent fusion of a glass material in molding.

[Means for solving the problem]

The present invention, before continuous pressure molding, at least one of the molding conditions of the mold temperature, the pressing force and the pressing time during the continuous pressure molding is appropriately preliminarily pressure molded as a molding condition having a low numerical value, Then, it is subjected to continuous pressure molding, and further, for example, a heavy flint type glass material is used at the time of this preliminary pressure molding. Glass component (especially Pb
A very thin film consisting of (O etc.) is formed on the mold surface to prevent fusion of the glass material to the mold surface during continuous pressure molding, and especially the activity after removing the new condition and removing the adhered substances. It is effective for pressure molding using a molding die having a modified mold surface. This means that a film consisting of glass components is formed on the molding surface of the molding die before continuous pressure molding, and then many glass materials are continuously pressure-molded by this molding die To obtain the optical element of.

Further, when the glass material used for the preliminary pressure molding is a heavy flint type glass, it is possible to efficiently form a coating film of the above glass component. This is because heavy flint glass has a high PbO content, and an extremely thin coating film formed on the mold surface due to PbO precipitated from the glass is efficiently generated.

〔Example〕

1 and 2 show a molding apparatus using the method for molding a glass optical element according to the present invention.

In the figure, 1 denotes an upper mold, 2 denotes a lower mold, and the upper mold 1 and the lower mold 2 are controlled to a predetermined temperature by a temperature-controlled heater (not shown), and the upper mold 1 is an upper plate. The lower die 2 is fixed to the lower die 2 through the lower plate 11 and is movably held in the vertical direction (direction of arrow A) by a drive source (eg, cylinder) not shown. Are arranged to match each other.

Further, the upper and lower molds 1 and 2 are surrounded by a quartz glass tube 7, and a non-oxidizing gas such as nitrogen gas, an inert gas or a reducing gas is provided inside the quartz glass tube 7 by an atmosphere gas supply device 9. The non-oxidizing gas is supplied so that the high temperature portions of the upper and lower molds 1 and 2 are not oxidized. Further, the upper plate 10 and the lower plate 11 are connected to each other by members (not shown), and the positional relationship between them is constant.

FIG. 5 shows a barrel-shaped carrier on which the optical glass material 3 and the glass optical element after press molding are placed and transported. The barrel-shaped carrier is supported by the barrel-shaped carrier transporting arm 4 and predetermined by a temperature control device (not shown). It is transferred into the heating furnace 6 which can be set to the temperature of 1 and is conveyed between the upper and lower molds 1 and 2.

Next, a method of molding a glass optical element with this molding apparatus will be described.

First, the optical glass material 3 is placed in the barrel-shaped carrier 5 and is transported into the heating furnace 6 by the barrel-shaped carrier transporting arm 4 until the material 3 can be molded by the upper and lower heaters 6a, 6a. Heat softening treatment (up to near the softening temperature).
Next, the arm 4 is operated to return the barrel-shaped carrier 5 to the original position (that is, a position where the center of the barrel-shaped carrier 5 and the axis a coincide with each other is set in advance, and this position is used as a reference. Since the transfer arm 4 is operated as the origin position, the position is returned to this origin position, and after the optical glass material 3 placed on the barrel mold carrier 5 is positioned between the upper mold 1 and the lower mold 2. Then, the lower mold 2 is vertically moved upward, and the optical glass material 3 is pressed by the molding surface 1a of the upper mold 1 and the molding surface 2a of the lower mold 2 to obtain an optical element. After optical element press molding,
The lower die 2 is vertically moved downward to be released from the mold, and the optical element mounted on the barrel carrier 5 is moved by the barrel carrier transfer arm 4 in an annealing furnace (not shown) provided on the opposite side of the heating furnace 6. It is conveyed and cooled, and after cooling, the optical element is taken out from the carrier 5. The optical element is transferred to the annealing furnace by moving (that is, transferring) the cylinder-shaped carrier transfer arm 4 from the cylinder-shaped carrier transfer arm 4 to another transfer arm after the press molding. In some cases.

The upper mold 1 and the lower mold 2 are formed by processing a metal base material made of stainless steel into a shape corresponding to a desired final product, and mirror-polishing the molded side surface to a thickness by ion plating.
The molded surfaces 1a and 2b are formed by applying CrN coatings 1b and 2b of 1.5 μm, and the CrN coatings 1b and 2b contain CrN of 95 mol% or more and impurities such as carbon, silicon and sodium.

Prior to continuous pressure molding of a glass optical material by such a method, an appropriate number of glass materials (glass materials of the same kind or different kinds as the glass optical material) are prepress-molded by upper and lower molds, A thin coating film consisting of a trace amount of glass component deposited from the above is formed on the molding surface, and then continuously pressure-molded by this molding die. Table 1 shows the first to fourth examples. The molding conditions of the pre-press molding are summarized and listed for easy understanding. In Table 1, "shape of molded product / glass type" indicates a molded product obtained by continuous pressure molding and preliminary pressure molding, and continuous compression without pre-press molding under the pressure conditions shown in Table 1. Upon molding, fusion occurred at the initial stage of continuous pressure molding.

First to fourth embodiments will be described. In Table 1, LLF6 is a flint glass having a glass component of the SiO ₂ —PbO—R ₂ O series and a relatively small amount of PbO, and D is the outer diameter, t
Indicates the maximum wall thickness, and R _A and R _B indicate the radii of curvature of the upper and lower surfaces.

(First Example) The first example is a method in which only the numerical value of the mold temperature is lowered among the pressure molding conditions of the mold temperature, the pressing force, and the pressing time at the time of continuous pressure molding. That is, after 5 shots of pre-molding at a mold temperature of 420 ° C, which is 20 ° C lower than 440 ° C in the molding conditions during continuous pressure molding, a pressing force of 500 kgf and a pressure holding time of 17 s.
A molded product is obtained by continuous pressure molding under a pressure condition of ec and a mold temperature of 440 ° C.

Thus, it was confirmed that a continuous molded product was obtained by continuous pressure molding, and a stable molded product was obtained without fusion even in the initial stage of pressing.

(Second Example) In the second example, after prepress molding as in the first example,
Continuous press-molding, the pre-pressurizing condition is 300 kgf, which is 200 kgf lower than the pressurizing force of 500 kgf in the continuous press-molding, and pre-pressurized to have the same effect as the first embodiment. I was able to confirm.

(Third Embodiment) The third embodiment is an example in which only the pressure holding time is 8 seconds as the preliminary pressure molding condition (17 seconds in continuous pressure molding, therefore, 9 seconds are reduced), and the same effect as the first embodiment is obtained. I was able to confirm.

(Fourth Embodiment) The point different from the first embodiment is that the pre-pressing molding conditions are a mold temperature of 420 ° C. (20 ° C. decrease), a pressing force of 300 kgf (200 kgf decrease), and a preliminary molding number of 10 shots. Therefore, the same effect as that of the first embodiment was confirmed.

(Fifth Example) Table 2 shows an example in which the glass type of the glass material used for the preliminary pressure molding is SF7 of the heavy flint type optical glass. The pre-press molding conditions were set such that the mold temperature, the pressure, and the pressure holding time were sufficiently reduced as in the first embodiment so that fusion did not occur. It was confirmed that the number of pre-press molding shots was 2 and stable molding could be performed without fusion during continuous pressure molding. Heavy flint glass has a high PbO content, and the very thin coating film generated on the mold surface due to PbO precipitated from the glass is efficiently generated, so the number of pre-press molding shots can be reduced. The cost can be reduced by reducing the number of processes.

Note as shown in Comparative Example in Table 2 in the preliminary pressing condition glass type BaLF3 (glass of the glass component is _{SiO 2 -PbO-BaO-R 2} O series), mold temperature 460 ° C., pressure 400kgf and pressure After holding for 15 seconds and setting the number of pre-press molding to 2 shots,
When continuous pressure molding was carried out in the same manner as in the fifth embodiment under the conditions of continuous pressure molding and glass type and the like, fusion occurred at the initial stage of continuous molding. When pressure molding was performed, fusion did not occur.

[Effects of the Invention] According to the present invention, a thin coating film is formed on the molding surface of the molding die by preliminary pressure molding, the thin coating film consisting of a small amount of glass component precipitated from the glass material. Since continuous pressure molding is used, it is possible to prevent fusion of the glass material to the molding surface, which tends to occur at the initial stage of continuous pressure molding, and therefore stable molding can be continuously performed, especially when the molding surface is It is effective when it is in a new state or when using a molding die after removing the adhered substances. Also, by using heavy flint glass as the glass material used for pre-press molding, pre-press molding Economical because the number of shots can be reduced.

[Brief description of the drawings]

The drawings show a glass optical element molding apparatus using the method of the present invention. FIG. 1 is a schematic view, and FIG. 2 is a cross-sectional view showing a state in which a glass material is pressed by upper and lower molds. 1 …… Upper mold 2 …… Lower mold 3 …… Optical glass material 6 …… Heating furnace

Claims (3)

(57) [Claims] 1. A method for molding a glass optical element, wherein a glass material is softened by heating and pressure-molded by a molding die to obtain a large number of optical elements continuously, wherein a glass is formed on a molding surface of the molding die. A method for molding a glass optical element, comprising forming a coating film comprising the components, and thereafter, pressure-molding the glass material with the molding die to continuously mold a large number of optical elements. 2. A method for molding a glass optical element, wherein a glass material is softened by heating and pressure-molded by a molding die to obtain a large number of optical elements continuously, before continuous pressure molding. A glass material is pre-press-molded in the molding die, with at least one of molding conditions of mold temperature, pressure, and pressing time at the time of continuous pressure molding being a molding condition having a low numerical value. A film consisting of the glass component deposited from this glass material is formed on the molding surface of the molding die, and then the glass material is pressure-molded by this molding die to continuously mold a large number of optical elements. A method for molding a glass optical element, comprising: 3. The method for molding a glass optical element according to claim 2, wherein the glass material to be pre-press-molded is a glass material containing PbO.