JPS61242922A - Pressing mold for optical glass element - Google Patents

Abstract

PURPOSE:A pressing mold having shape precision of high accuracy, producible without requiring precision processing after a film formation, having hardly wear of diamond bite during cutting processing, obtained by coating a silicon parent material with a thin film consisting of a specific material. CONSTITUTION:Silicon is used as a parent material and any of a platinum alloy film (alloy film consisting of one or more of Ir, Os, Rh, Pd, Ru and Re and Pt), a diamond thin film and a diamond carbon film is formed on the parent material to give the titled mold. Since silicon having improved precision processing properties is used as the parent material for pressing mold, water of diamond bite is hardly recognized during cutting processing.s A precision processing process after the formation of the platinum alloy film can be eliminated and simultaneously a pressing mold having a higher shape precision can be produced than a case where a conventional zirconia, tungsten carbide, etc. is used as the parent material.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to press-molding of optical glass elements used in press-molding high-precision optical glass elements that do not require a polishing step after press-molding. It is related to usage patterns.

2. Description of the Related Art In order to directly mold a high-precision optical glass element by pressing, it is required that the quality of image formation be good. For this reason, the mold material must be chemically inert to the glass at high temperatures, the glass pressing surface of the mold must be sufficiently hard and resistant to damage such as scratches, and it must also be able to withstand high temperatures. The mold does not undergo plastic deformation when pressed, has excellent heat resistance and thermal shock resistance, and has good workability.
It is necessary to be able to perform ultra-precision machining, and molds that relatively satisfy these properties are, for example, made of tungsten carbide (WC), cermet, or zirconia (
A press-forming mold for an optical glass element constructed by forming a platinum-based alloy film on these base materials using ZrO□),
Press forming mold using silicon carbide (SiC) or silicon nitride (SIJ4)
-45613) etc. have been proposed.

Problems to be Solved by the Invention However, in the case of conventional mold materials such as silicon carbide and silicon nitride, their hardness is extremely high, making it difficult to process the glass press surface into a spherical or aspherical shape with high precision. It was very difficult to do so. Moreover.

These materials are all sintered types, so
Since it contains a third component as a sintering aid for the purpose of improving its sinterability, it is relatively easy to react with glass elements containing lead or alkali elements.

When press forming is repeated, the reaction between the mold and the glass element progresses, and the glass adheres to the mold, making it impossible to mold a highly accurate optical glass element with good image formation quality. In addition, in the case of a mold made of tungsten carbide, cermet, or zirconia as a base material and a platinum-based alloy film formed on these base materials, the base material is first processed into a shape close to the desired shape by grinding, and then By forming a platinum-based alloy film on the base material and cutting it using a diamond cutting tool,
Platinum-based alloy films are shaved and precisely processed into desired shapes to create press molds for optical glass elements. However, when cutting the platinum-based alloy film, the diamond cutting tool was severely worn, and only a few press molds could be cut with a single cutting tool with high precision.

Means for Solving the Problems In order to solve the above problems, the press molding mold for the optical glass element of the present invention uses silicon (Si) as a base material,
The structure is such that a platinum-based alloy film, a diamond thin film, or a diamond-like carbon film is formed on this base material.

Effects According to the above configuration, since silicon, which has excellent precision machinability, is used as the base material of the press molding die for the optical glass element, the wear of the diamond cutting tool during cutting can be almost ignored.

In addition, a platinum-based alloy film, a diamond thin film, or a diamond-like carbon film is formed on a silicon base material that has been precisely processed into the desired shape to a thickness that does not impair the shape accuracy, resulting in improved image formation quality. It has become possible to press-form optical glass elements with high precision and good quality. In addition, by using silicon as the base material, it is possible to omit the precision machining process after forming the platinum alloy film, and at the same time, it is possible to achieve higher shape accuracy than when using zirconia, tungsten carbide, or cermet as the base material. It is now possible to create molds for press molding. On the other hand, it has become possible to extend the life of the diamond tool.

Example The present invention will be explained in detail below.

Silicon with a diameter of 20 m+a and a thickness of 6 mm was processed with high precision as a base material for a pair of press molding molds consisting of an upper mold and a lower mold with a concave shape of a radius of curvature of 46 II m and a radius of 200 + a +++. In this way, base materials for 10 pairs of press molding molds were prepared, but the diamond bit used for cutting was not worn at all. Next, a platinum-based alloy film (with at least one metal element selected from the group consisting of iridium, osmium, rhodium, palladium, ruthenium, and rhenium) with a thickness of approximately 1 to 2 μm is applied to these cut surfaces by sputtering. An alloy film consisting of platinum and platinum was formed.

The composition of the platinum alloy film used at this time is shown in Table 1 below.

(Left below) On the other hand, as yet another sample, a diamond thin film and a diamond-like carbon thin film were each formed on the highly precisely processed silicon base material using an ion beam sputtering method.

The shape accuracy and surface roughness of the press molding mold created as described above are shown in Table 2 below, along with the shape accuracy and surface roughness of the mold created using tungsten carbide, zirconia, or cermet as a base material. Note that λ = 633n
Measured in m.

From Table 2 above, it is clear that the shape accuracy of the mold made of silicon as the base material is excellent.

The drawing is a configuration diagram of a pair of upper and lower press molding molds prepared as described above installed in a press machine, where 1 is an upper mold, 2 is a lower mold, 3 is a heater for the upper mold, and 4 is a lower mold. 5 is a piston cylinder for the upper mold, 6 is a piston cylinder for the lower mold, 7 is a supply glass lump, 8 is a jig for supplying the glass lump, 9 is an outlet for taking out the press-molded optical glass element, 10 is a preheating furnace for the supplied glass mass 7, 1
1 is a cover.

The press working process will be explained below. Lead oxide (P
Supply glass element block 7 made of lead oxide optical glass made of 70% by weight bO), 27% by weight silica (Sin2), and the remainder processed into a spherical shape with a radius of 10 mm.
is heated in the supply glass preheating furnace 10, and then heated to 520°C.
It was placed on the lower mold 2 of the upper and lower molds 1 and 2 held at
The temperature of Step 2 is cooled to 300° C. to produce an optical glass element press-molded so that both sides are convex, and the optical glass element is taken out from the outlet 9, thereby completing the press-molding process of the optical glass element. After repeating the above process 500 times, the upper and lower molds 1 and 2 used were removed from the press machine.

The surface condition of the mold and the pressed surface of the pressed optical glass element were observed and evaluated using a scanning electron microscope.

As described above, press experiments were repeatedly conducted using a press molding die in which silicon was used as a base material and a platinum alloy film, a diamond thin film, or a diamond-like carbon film was formed on this precision-machined base material. What was thought to be a particular problem in this experiment was the problem of adhesion between the silicon base material and the formed thin film, and the problem of the heat resistance strength of the silicon base material, but even after 500 press experiments, the above No problems occurred. Also, regarding surface roughness and scratches caused by pressing the thin film, the diamond thin film and diamond-like carbon film did not change from before the pressing experiment. On the other hand, the platinum-based alloy film could be easily inferred from the experimental results of press-forming dies constructed by selecting tungsten carbide, zirconia, or cermet as the base material and forming a platinum-based alloy film on these base materials. As shown, no surface roughness of the thin film occurred in any of the samples. As mentioned above, even when using a press molding mold that uses silicon as the base material, it is possible to produce optical glass elements with higher precision than when using a mold that has a base material such as tungsten carbide, which has good image formation quality. It was possible to press mold.

In addition, although a concave press molding mold was used in the above example, the shape of the mold surface is not limited to such a shape, and the present invention is also applicable to the shape of an optical glass element such as a prism. Of course it is a thing.

Effects of the Invention As described above, according to the present invention, silicone, which has excellent workability and heat resistance, is selected as the base material of the press molding die,
After processing this silicon base material with high precision, a platinum-based alloy film, diamond thin film, or diamond-like carbon film is formed to a thickness that does not impair the shape accuracy of the pressed surface. A precision processing step after forming by sputtering can be omitted. It also reduces wear on the diamond bit used during precision machining.

Can be processed to a higher degree of shape accuracy. Therefore, it has become possible to mass-produce high-precision optical glass elements with good image forming quality at low cost.

[Brief explanation of drawings]

The drawing is a configuration diagram of a state in which a press-molding mold for an optical glass element according to an embodiment of the present invention is installed in a press machine. 1... Upper mold, 2... Lower mold

Claims (1)

[Scope of Claims] 1. A mold for press-molding an optical glass element, which uses silicon (Si) as a base material and has either a platinum alloy film, a diamond thin film, or a diamond-like carbon film formed on the base material. 2. The platinum-based alloy film is made of at least one metal selected from the group consisting of iridium (Ir), osmium (Os), rhodium (Rh), palladium (Pd), ruthenium (Ru), and rhenium (Re). Elements and platinum (Pt
) A mold for press-molding an optical glass element according to claim 1, which is an alloy film comprising: