JPH0624991B2 - Mold for press molding of optical glass element - Google Patents

Description

TECHNICAL FIELD The present invention relates to the pressing of an optical glass element used for molding a high-precision optical glass element that does not require a polishing step after press molding in the production of optical glass elements such as lenses and prisms. The present invention relates to a molding die.

2. Description of the Related Art In recent years, optical glass lenses are in the direction of aspherical surface that can achieve both simplification of the lens structure of optical equipment and weight reduction of the lens portion at the same time. In manufacturing this aspherical lens, it is difficult to process and mass-produce it by a conventional polishing method which is a manufacturing method of an optical lens, and a direct press molding method is regarded as promising.

This direct press molding method involves overheating and pressing an optical glass object on an aspherical mold that has been finished to the desired surface quality and surface accuracy, or the optical glass object that has been preheated. It is a method for producing an optical glass lens by subjecting a shaped article to heat and pressure molding and without the need for subsequent polishing steps. (For example, Japanese Examined Patent Publication No. 54-38126) Problems to be Solved by the Invention However, in the production of the above optical glass lens, the optical glass lens obtained by press molding needs to have excellent image forming performance, Particularly in the case of an aspherical lens, it is required to have very high surface accuracy. Therefore, as a mold for molding the optical glass element, the chemical action on the optical glass at a high temperature is minimal, scratches on the press surface of the mold, and less susceptible to scratch damage,
It is necessary to have properties such that high surface accuracy does not change due to press molding.

Various materials have been investigated for this purpose, but the conventional mold materials do not fully satisfy the necessary conditions such as difficult reactivity with optical glass, oxidation resistance, high temperature and high strength, and releasability. .

For example, the glassy carbon disclosed in Japanese Patent Laid-Open No. 47-11277 has relatively good reactivity with optical glass or releasability, but is easily oxidized, has low impact strength, and has thermal conductivity. There are drawbacks such as low degree.

In addition, stainless steel materials such as 13 chrome steel are subject to problems such as oxidation at high temperatures and fusion with optical glass and poor mold release from optical glass.

Means for Solving the Problems In order to solve the above problems, the present invention provides a method for precision molding by heating and pressing optical glass, wherein at least one element of fluorine, chlorine and bromine is used for press molding. The present invention provides a press molding die in which ions are injected into a press molding surface.

Action As a result of research, the inventors have found that in the method of precision molding by heating and pressing optical glass, press molding in which at least one element of fluorine, chlorine and bromine is ion-implanted into the press molding surface of the press molding die. By using the mold
Even if press-molding an optical glass such as borosilicate glass, barium borosilicate glass, lanthanum glass, or lead glass with a press-molding die that is heated to a high temperature, it is released smoothly without fusion to the press-molding die. In addition, they found that the optical characteristics of the press-molded optical glass element were also very excellent.

When at least one element of fluorine, chlorine, and bromine is ion-implanted into the press-molding surface of the press-molding die, fluorinated compounds, chlorinated compounds, and brominated compounds are formed on the surface of the press-molded surface. Since the surface energy is lowered, the optical glass and the press-molded surface are less likely to be fused and the mold is released very smoothly. Furthermore, compared to the conventional method of applying a release agent to the press molding surface, the release agent does not remain on the pressed optical glass element, the release agent does not need to be applied many times, and the release effect is semi-permanent. It has a characteristic that it lasts.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

(Example 1) FIG. 1 is a perspective view of an upper die 1 and a lower die 2 of a press molding die used in the present invention. Both upper and lower molds 1 and 2,
Using a cylindrical material of austenitic steel (SUS 310),
The upper die 1 is provided with a concave molding surface 4 having a radius of curvature of 46 mm and a plurality of V-shaped notches 3 on its periphery, and the lower die 2 has a radius of curvature of 2
A 00 mm concave molding surface 5 was formed. These forming surfaces 4 and 5 were lapped with ultrafine diamond powder, and the maximum surface roughness (Rmax) was about 1 hour in about 1 hour.
I made it a 00 Å mirror surface. Ions were implanted into the surfaces of the molding surfaces 4 and 5 which became mirror surfaces under the conditions shown in Table 1 to obtain a molding upper mold 1 and a molding lower mold 2.

FIG. 2 shows that the heaters 6 and 7 are respectively wound around the outer diameter surfaces of the above glass press molding dies 1 and 2, and they are attached to the upper and lower plungers 8 and 9 of the press, and the entire device is covered with a cover 10. It is a partial fracture surface of a press molding apparatus. In the same figure, 30% by weight of silica (SiO ₂ ), 50% by weight of barium oxide (BaO), 15% by weight of boric acid (B ₂ O ₃ ), and the balance of borosilicate glass barium silicate 11 is a raw material supply. It is gripped by the jig 12, heated to 780 ° C by the preheating furnace 13, and then heated at a temperature of 730 ° C between the glass press molding dies 1 and 2 at a pressing pressure of 40 kg / cm ^2. Then
After cooling to about 600 ° C with the upper and lower molds as it is, a force (pressure 10kg / cm ² ) to separate the molding die and the molding lens from each other is applied to release the mold, and the temperature when the molding die and the molding lens are separated from each other. Was set to the mold release temperature, and the molded lens was taken out from the outlet 14.

After the glass press molding was performed 1000 times by such a process, the surface roughness (Rma) of the molding surfaces 4 and 5 of the mold was measured.
x) and minute Vickers hardness (Hv) and the surface condition of the molded glass lens were observed. From Table 1, the molded lens release temperature is about 580 ° C, which is about the conventional release temperature.
The temperature was increased by 50 ° C, and the molding cycle could be shortened by about 1 minute. Surface roughness (Rmax) of the molding surfaces 4 and 5 of the press mold after 1000 times of glass press molding
Was about 90Å, and the molding surface had no surface roughness. The micro Vickers hardness of the molding die was around 1200, which was extremely high, and no fine scratch was generated. The surface precision of the molded optical glass lens is within 2 Newton rings, within 1/5 ass, and surface roughness is 0.01.
The optical performance was extremely excellent.

(Example 2) A cemented carbide (WC) was processed into the same shape as in Example 1, the molding surfaces 4 and 5 were lapped with ultrafine diamond powder, and the maximum surface roughness (Rmax) was obtained in about 1 hour. Is about 100Å
I made it a mirror surface. The platinum-iridium-osmium alloy (Pt
-Ir-Os) was coated, and then ion implantation was performed under the conditions shown in Table 2 in the same manner as in Example 1 to obtain an upper mold 1 and a lower mold 2 for molding an optical glass element. .

In the same manner as in Example 1, 10 weight percent of silica (SiO ₂ ), 25 weight percent of barium oxide (BaO),
30% by weight of boric acid (B ₂ O ₃ ), 20% by weight of lanthanum oxide (La ₂ O ₃ ), the balance of lanthanum optical glass consisting of trace components, preheating temperature 750 ° C., molding temperature 710 ° C., pressing pressure 40 kg / Press molding is performed under the conditions of cm ² and press time of 1 minute, and the molding lens is cooled to 650 ° C together with the upper and lower molds, and the mold releasing force (pressure 10 kg
/ Cm ² ) was added and the mold was released at a mold release temperature of about 620 ° C., and the molded lens was taken out from the take-out port 13.

After the glass press molding was performed 1000 times by such a process, the surface roughness (Rma) of the molding surfaces 4 and 5 of the mold was measured.
x) and minute Vickers hardness (Hv) and the surface condition of the molded glass lens were observed.

From Table 2, the molded lens release temperature was about 620 ° C, which was about 40 ° C higher than the conventional release temperature. The surface roughness (Rmax) of the molding surfaces 4 and 5 of the press-molding die after 1000 times of glass press molding was about 90Å, and the molding surface was not roughened. The micro Vickers hardness of the molding die was about 1000, which was extremely high, and no fine scratch was generated. The surface precision of the molded optical glass lens was within 2 Newton rings, within 1/5 of asbestos, and surface roughness was 0.01 μm, and its optical performance was extremely excellent.

EFFECTS OF THE INVENTION As described above, according to the present invention, the mold release property, the oxidation resistance, the corrosion resistance, the hardness, etc. of the press molding die are significantly larger than those of the conventional press molding die of the optical glass element. As a result, optical glass such as barium borosilicate optical glass or lanthanum-based optical glass with a press forming temperature of more than 700 ° C can be press-formed with extremely high precision, and the releasability is greatly improved. Has been shortened and the productivity of optical glass elements has been greatly improved.

With a long-lasting molding die that does not deteriorate even after 1000 press moldings, the number of molding die replacements is greatly reduced, enabling mass production of highly accurate optical glass elements, improving productivity and manufacturing. It has a significant effect on cost reduction.

Although the present invention does not particularly define a molding die, as a die material, austenitic steel (SUS 310) and cemented carbide (WC) are used as materials excellent in oxidation resistance, heat resistance, workability and high temperature strength. ) Is coated with a thin film of platinum-iridium-osmium alloy (Pt-Ir-Os) as a molding die. The present invention is not limited to the above examples, for example, martensitic stainless steel, austenitic steel, tungsten alloy, Ni-based alloy, cemented carbide, cermet, molybdenum, tungsten, tantalum, etc. can be used. Even if a molding die coated with a thin film of a noble metal, a nitride such as aluminum nitride, titanium nitride, or tantalum nitride, a heat resistant metal such as nickel, chromium, cobalt, or tantalum is used as a base material of these mold materials, the present invention The same effect as can be obtained.

The ion implantation energy is preferably 30 to 300 KeV, and the ion implantation amount is preferably 1 × 10 ^{17 to} 5 × 10 ¹⁹ IONS / cm ² , and the molding die surface is outside the range of the above ion implantation. And the optical glass element is apt to cause problems such as coloring.

[Brief description of drawings]

FIG. 1 is a perspective view of a glass press molding die used in the present invention, and FIG. 2 is a partially cutaway perspective view of a plunger portion of a press device to which the molding die of FIG. 1 is attached. 1 ... Upper mold, 2 ... Lower mold, 3 ... Notches 4,5 ... Molding surface, 6,7 ... Heating device, 8,9 ... Plunger, 10 ...
… Canopy, 11 …… Optical glass soul, 12 …… Raw material supply jig,
13 …… Preheating furnace, 14 …… Outlet port.

Claims (1)

[Claims] 1. A press molding die for an optical glass element in which at least one element selected from fluorine, chlorine and bromine is ion-implanted into the press molding surface of the press molding die.