JPH05124824A - Stock for optical element and method for molding optical element - Google Patents

Abstract

PURPOSE:To provide stock for an optical element and to mold an optical element having excellent appearance, shape and accuracy. CONSTITUTION:Columnar stock 1 for an optical element with a groove 1A in a lateral face is used. When this stock 1 is molded, molding pressure is made zero or once reduced during molding. Since the stock with a groove is used, an optical element having satisfactory appearance and shape is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element molding method and an optical element material used for molding the optical element, and particularly to obtain an optical element excellent in shape accuracy and surface accuracy, which is inexpensive and suitable for mass production. To do.

[0002]

2. Description of the Related Art In recent years, optical elements such as lenses and prisms are molded by placing the optical element material in a mold and heating and pressing it instead of manufacturing the optical element material such as glass by polishing. Many methods have been proposed. In order to accurately control the weight of the optical element material, its shape is preferably a cylindrical shape that is the easiest to pre-process and is inexpensive.

Generally, when an optical element is manufactured by press molding, an optical element material is preheated to near the glass softening point. Next, when the mold is closed, the preheated optical element material is supplied between the upper mold and the lower mold that are processed to have almost the same shape as the finished optical element, and pressure molding is performed at a predetermined temperature. I am doing it.

A method for forming a cylindrical glass material is described in, for example, Japanese Patent Application Laid-Open No. 60-246231. Hereinafter, a conventional molding method will be described with reference to the drawings. In the conventional molding method, as shown in FIG. 5, the corner portion 19 of the material 2 is deformed first, and the portion in contact with the upper die 15 and the lower die 16 becomes familiar, so that a closed space 20 is formed. Once a closed space is created, there is a closed space until the completion of molding,
The processed surface of the mold is not sufficiently transferred to the material, resulting in a defective optical element.

Next, a conventional method for preventing such untransferred defects will be described with reference to FIG. The lower die 16 is fixed to the base 16B via the connecting rod 16A, and the upper die 15 is attached to the piston rod 15B via the connecting rod 15A. The optical element material 2 is first heated to a molding temperature by a heater. When the desired forming temperature is reached, the upper die 15 is lowered by the hydraulic cylinder and comes into contact with the material.

After that, the upper die vibrates and presses up and down, which is performed by using, for example, a servo pulser. For example, the vibration pressure is applied up to 90% of the total pressure stroke, and the remaining 10% is molded by steady pressure. When the full pressurization stroke is reached, the power supply is stopped, the temperature is lowered to the desired temperature, the mold is opened, and the optical element is taken out after cooling.

As described above, the shape of the optical element material is preferably as simple as possible from the viewpoint of the manufacturing process or the processing cost of the material. For example, a bar processed into a predetermined glass material outer diameter by centerless processing has a predetermined width. There is a cylindrical body cut in.

[0008]

However, when molding is performed using such a material, the molding temperature is non-uniform, or when the optical element material is inserted into the mold and is displaced from the center, the molded optical element is formed. Burr is likely to occur at the end of the
There was a problem that chips tend to occur starting from Bali.

[0009]

In order to solve the above problems, in the optical element material of the present invention, a groove is provided in a part of the cylindrical portion of the optical element material having a cylindrical shape, or a notch is formed in the cylindrical portion. It is provided.

Further, the optical element and the method for molding an optical element of the present invention include inserting the above-mentioned optical element material between a molding die composed of a first die and a second die, heating and softening it and pressurizing it. It is what is molded.

[0011]

By using the optical element material and the optical element molding method as described above, it is possible to prevent burrs and chips from occurring at the end of the optical element after molding.

[0012]

EXAMPLES Examples will be described below with reference to FIGS. 1 to 3. In FIG. 1, the molding apparatus embodying the molding method of the present invention eliminates the axial misalignment between the upper mold 2 and the lower mold 3. And a barrel mold 4 adjusted to an arbitrary height so as to have a predetermined optical element thickness, and includes an upper mold 2, a lower mold 3, and a barrel mold 4.
In the space surrounded by, the optical element material 1 is vertically supplied so that both end surfaces are in contact with the upper and lower dies.

The upper heater block 5 is connected to a cylinder rod 7 so that a desired pressure can be applied to the upper mold 2 via the upper heater block 5 by an air cylinder. The shape transfer surface of the molding die is processed into the surface shape of the optical element.

The optical element material is a cylindrical body as shown in FIG. 3 (a), which is an optical glass SF-8 having a diameter of 7 mm and a length of 8 mm.
(Glass transition temperature 420 ° C., yield temperature 454 ° C., softening temperature 551 ° C., linear expansion coefficient 90 ° C. to 300 ° C. 90 × 10
^-7 / ° C). Also, from the length of 8 mm, 2 from both end surfaces
A groove 1A having a depth of 0.5 mm is provided in the inner portion except for mm. That is, the volume is somewhat smaller than that of a conventional optical element material without groove processing.

After the optical element material 1 is put into the molds 2 and 3, the upper heater block 5 is brought into contact with the upper mold 2. The upper heater block 5 and the lower heater block 6 need to be heated to a temperature at which the glass material can be sufficiently deformed with respect to the pressing force of the mold, but if the temperature is too high, the lens will not satisfy the performance, so the yield temperature of the material It is better to set between the softening temperature and the softening temperature. In this embodiment, the temperature of the upper heater block and the lower heater block is 5
It was set to 30 ° C. When the temperature of the optical element material reaches 530 ° C., the viscosity of the optical element material is 10 ¹⁰ poise.

Next, the upper heater block 5 presses the material through the upper mold. The pressure at this time is preferably 2 kg / mm ² or more. During molding, the molding pressure is once set to zero and then repressurized. When the body mold 4 and the upper mold 2 come into close contact with each other, the temperatures of the upper heater block 5 and the lower heater block 6 are gradually lowered. Four
When the temperature reaches 00 ° C., the pressing is terminated and the upper heater block 5 is raised. Subsequently, the mold is taken out, and after cooling to room temperature, the mold is opened and the optical element is taken out.

FIG. 2 shows the molded optical element. The area of both end surfaces of the optical element material used in this example is the same as the case of using the conventional cylindrical optical element material,
The optical performance can be exactly the same. On the other hand, the volume of the glass material is slightly smaller than that of the conventional optical element material because the groove is provided on the side surface. Therefore, the volume is sufficiently smaller than the volume of the mold cavity surrounded by the upper and lower molds and the body mold.
No burrs or chips are generated at the end E of the optical element shown in FIG. In this embodiment, the optical element material is shown in FIG.
Although the grooved one shown in FIG. 3 was used, the same effect can be obtained by using a grooved part in the cylindrical portion as shown in FIG.

When the optical element material shown in FIG. 3 is cut from a glass rod into a predetermined length by cutting, the productivity is improved and an extremely smooth optical surface is obtained.

[0019]

EFFECTS OF THE INVENTION Since the present invention is a molding method using the optical element material described above, the following effects can be obtained. It is possible to obtain an optical element that maintains the same optical performance as that of an optical element material formed of a conventional columnar optical element material and has no burr or chip at the end.

[Brief description of drawings]

FIG. 1 is a sectional view of a molding apparatus embodying a molding method of the present invention.

FIG. 2 is a side view of an optical element molded by the molding apparatus.

FIG. 3 is a perspective view of an optical element material used for molding by the molding apparatus.

FIG. 4 is a sectional view of a conventional molding device.

FIG. 5 shows a molding state using a conventional optical element material,
Cross section of the main part of the mold

[Explanation of symbols]

 1 Optical element material 2 Upper mold 3 Lower mold 4 Body 5 Upper heater block 6 Lower heater block 7 Cylinder lot

Claims (3)

[Claims] 1. An optical element material which is put between a molding die composed of a first die and a second die and is heated and softened by the die, wherein a groove or a notch is formed in a part of a cylindrical portion. Optical element material characterized by the provision of. 2. The optical element material according to claim 1, wherein the end face has a split cross section. 3. A method of molding an optical element, wherein an optical element material is inserted between a molding die composed of a first die and a second die, and is softened by heating and pressure-molded to obtain an optical element. 3. The method for molding an optical element, wherein the optical element material according to claim 1 or 2 is charged into the mold, and the molding pressure is once reduced or zeroed and then repressurized during molding. ..