JPH06171964A - Method for forming optical element - Google Patents

Abstract

PURPOSE:To prevent the generation of sink marks by glass blank material softened by heating while pressurizing the parts near the outer peripheries of the upper and lower forming surfaces thereof with respectively different shrinking forces by using a master die varying in coefft. of thermal expansion in a pressing direction. CONSTITUTION:The glass blank material 8 softened by heating is transported between a punch 1 and a die 2 by a transporting arm 9 and the die 2 is risen to fit an ejector ring 3 and a transporting jig 7. The centers of the die 2 and the glass blank material 8 are then aligned and the glass blank material 8 is pressed by the punch 1 and the die 2. The upper part of the glass blank material 8 is formed to the inside diameter of an upper inside diameter ring 5 and the lower part thereof to the outside diameter equal to the inside diameter of the lower inside diameter ring 6. The shrinkage factor is larger in the lower inside diameter ring 6 than in the upper inside diameter ring 5, the compressive force acting on the glass blank material 8 is larger on the lower inside diameter ring 6 than the upper inside diameter ring 5. As a result, the glass flows into the gap parts between the glass blank material 8 and the punch 1 and the die 2. The punch 2 descends after the forming and the formed optical element 10 free from the sink marks is recovered by the transporting arm 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for molding an optical element for press-molding a glass material that has been softened by heating.

[0002]

2. Description of the Related Art Conventionally, as a molding method of an optical element for press-molding a glass material which has been softened by heating, for example, Japanese Patent Laid-Open No. Sho 64-64 has been proposed.
There is an invention described in JP-A-24028. According to the above invention, after the glass material is held in the elastically deformable barrel die and pressed by the die, the optical element is cooled while being held in the barrel die. By using the elastically deformable barrel mold, since it absorbs and weakens the compression force of the molded lens caused by the difference in the coefficient of thermal expansion between the barrel mold and the optical element during the cooling process, the molded lens can be recovered without damage, It is possible to control the pressure on the side surface of the optical element without using a pressing die.

[0003]

However, in the above-mentioned prior art, since the barrel shape is formed of a single material, when the shapes of the upper and lower surfaces (lens surfaces) of the optical element are greatly different, There is a problem in that the pressure applied on the lower surface is equalized, and as a result, an optical element having a good molding surface and a molding surface with a sink mark is molded.

Therefore, the present invention was developed in view of the above problems in the prior art. Even when the shapes of the upper and lower surfaces of an optical element are greatly different, a simple mechanism (structure) is used to reduce the sink marks on both the upper and lower surfaces. An object of the present invention is to provide an optical element molding method that does not occur.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides an optical element molding method for press-molding a glass material that has been softened by heating with an upper mold and a lower mold of the glass material using a barrel mold having a different linear expansion coefficient in the pressing direction. This is a method of molding while pressing the vicinity of the outer periphery of the surface with different contracting forces.

[0006]

According to the present invention, even when the shapes of the upper and lower surfaces of the optical element are largely different, the pressure applied from the side surface of each portion of the optical element can be set to an appropriate value.

[0007]

[Embodiment 1] FIG. 1 is a sectional view of an essential part of an apparatus used in this embodiment. Reference numerals 1 and 2 denote an upper mold and a lower mold, which are arranged to face each other on the same axis. The upper mold 1 is fixed and the lower mold 2 is held so as to be vertically movable. A push-up ring 3 is concentrically and integrally attached to the outer surface of the lower mold 2. Upper and lower mold 1,
In both cases, the molding surfaces 1a and 2a are formed in a convex shape (the optical element to be molded is concave), and the molding surface 2a is formed to have a smaller radius of curvature than the molding surface 1a.

The barrel die 4 is composed of an upper inner diameter ring 5, a lower inner diameter ring 6 and a carrying jig 7 on which the upper and lower inner diameter rings 5, 6 are placed. The upper and lower inner diameter rings 5, 6 have a cylindrical shape and their inner diameters are formed slightly larger than the outer diameter of the glass material 8.
It is formed so that it can be placed stably without tilting inside.

The upper inner ring 5 is made of a heat-resistant alloy (coefficient of linear expansion 1
(3.4 × 10 ⁻⁶ / ° C.), the lower inner diameter ring 6 is S
It is formed with US310S (linear expansion coefficient 18 × 10 ⁻⁶ / ° C.), and is formed so that the linear expansion coefficient of the lower inner diameter ring 6 is larger than the linear expansion coefficient of the upper inner diameter ring 5. Further, the transfer jig 7 has a smaller linear expansion coefficient than the upper and lower inner diameter rings 5 and 6, and a tungsten alloy (having a linear expansion coefficient of 4.5 × 10 ⁻⁶ / ° C.). Reference numeral 9 denotes a transfer arm that transfers the barrel mold 4 on which the glass material 8 is placed between the upper and lower molds 1 and 2.

In the present embodiment, BSL7 (coefficient of linear expansion 8.6 × 1) is used as the glass material 8 by the apparatus having the above-mentioned structure.
0 ^-6 / ° C.) was molded using. First, the glass material 8 placed and held on the body mold 4 is heated to about 80 by a heating means (not shown).
After heating to 0 ° C., it is conveyed between the upper and lower molds 1 and 2 by the conveying arm 9. At this time, the upper and lower inner diameter rings 5, 6 have a larger linear expansion coefficient than the glass material 8, and the clearance between the upper and lower inner diameter rings 5, 6 and the glass material 8 increases due to the difference in the linear expansion coefficient.

Next, the lower mold 2 is raised and the push-up ring 3 is moved.
And the transfer jig 7 are fitted to each other to align the center of the lower mold 2 and the center of the transfer jig 7, that is, the center of the lower mold 2 and the center of the lens material 8, and thereby to form the upper mold 1 and the lower mold 2. The glass material 8 is press-molded with. When the glass material 8 is pressed, the upper part has an inner diameter of the upper inner diameter ring 5 and the lower part has an outer diameter equal to the inner diameter of the lower inner diameter ring 6.

During the press molding, the temperatures of the glass material 8 and the barrel die 4 drop, and the respective members shrink accordingly. At this time, the contraction rate of the upper inner diameter ring 5 is larger than the contraction rate of the glass material 8, and a compressive force acts on the glass material 8 from the upper inner diameter ring 5. Similarly, the contraction rate of the lower inner diameter ring 6 is also larger than that of the glass material 8, and a compressive force acts on the glass material 8 from the lower inner diameter ring 6.

The compressive force acting on the glass material 8 is smaller in the lower inner diameter ring 6 than in the upper inner diameter ring 5, so that the lower inner diameter is smaller than the compressive force acting on the glass material 8 from the upper inner diameter ring 5. The compressive force acting on the glass material 8 from the ring 6 becomes larger. The glass material 8 also tries to shrink in the thickness direction, but due to the above-mentioned compressive force, the glass flows into the void portion (the portion where the sink mark occurs) between the glass material 8 and the upper and lower molds 1, 2. The flow amount of glass is larger on the lower mold 2 side compressed by the lower inner diameter ring 6.

After molding, the lower mold 2 is lowered, and the molded optical element 10 is recovered by the transfer arm 9 to a recovery place (not shown). The upper and lower inner diameter rings 5, 6 and the transfer jig 7 may be heat-resistant coated with TiN or the like.

According to the present embodiment, the sink marks generated as the glass contracts during the press molding are compensated by flowing the glass from the outer periphery by the compressive force due to the contraction of the barrel mold, and the compensation amount thereof. Since the linear expansion coefficient of the barrel shape is changed according to the amount of sink marks and the compression force is controlled to be different, it is possible to surely prevent sink marks and obtain an optical element having good surface accuracy.

[0016]

Second Embodiment FIG. 2 is a side view of the upper and lower inner diameter rings used in this embodiment. The present embodiment is different in that the upper and lower inner diameter rings 5 and 6 in the first embodiment are eliminated, and instead, the upper and lower inner diameter rings 21 and 22 having the slit portions 23 are used, and other configurations are the same. The description of the configuration is omitted.

The upper and lower inner diameter rings 5 in the first embodiment
The shape of 6 was a simple cylindrical ring. In this case, removal of the ring from the optical element after molding involves processing such as cutting and centering, and when the difference in the linear expansion coefficient between the glass and the upper and lower inner diameter rings is increased, a part of the optical element suddenly undergoes strong compression. When released from the force, cracks and the like may occur.

Therefore, in this embodiment, as a measure against the case where there is no material that makes the difference in linear expansion coefficient between the glass and the upper and lower inner diameter rings 21 and 22 appropriate, a slit portion 23 is formed in the upper and lower inner diameter rings 21 and 22. By providing it, it is possible to simplify the work such as cutting at the time of taking out, and even if the difference in linear expansion coefficient between the glass and the upper and lower inner diameter rings 21 and 22 is large, the compressing force is slightly released by the slitting portion 23. Prevents cracking due to sudden release from compression force. Moreover, it is possible to prevent sink marks by an appropriate compression force.
The following is the same operation / effect as in the first embodiment.
The description of the effect is omitted.

The upper and lower inner diameter rings 21 in the embodiment,
The slitting portion 23 provided in 22 is not limited to one location, but may be provided in several locations as needed.

[0020]

[Embodiment 3] FIG. 3 is a cross-sectional view of an essential part of an apparatus used in this embodiment. The present embodiment is an example in which the upper inner diameter ring 5 in the first embodiment is omitted, the other configurations are the same, and the same reference numerals are given and the description of the configuration is omitted.

As in the present embodiment, when one surface of the glass material 31 can have good surface accuracy without causing the glass to flow by the compression force of the barrel mold 4, only the lower inner diameter ring 6 is used. The inner diameter ring can be omitted. Hereinafter, the operation and effect are similar to those of the first embodiment, and the description of the operation and effect will be omitted.

The lower inner diameter ring 6 in this embodiment is
Even with the cylindrical lower inner diameter ring 6 of the first embodiment,
Alternatively, the lower inner diameter ring 22 provided with the slit portion 23 of the second embodiment may be used. When the lower inner diameter ring 22 provided with the slit portion 23 is used, the same effect as that of the second embodiment can be obtained.

[0023]

As described above, according to the optical element molding method of the present invention, even if the shapes of the upper and lower surfaces of the optical element are significantly different, good surface accuracy without sink marks is obtained on the upper and lower surfaces. An optical element having the same can be molded.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of essential parts showing a first embodiment.

FIG. 2 is a side view showing a second embodiment.

FIG. 3 is a cross-sectional view of essential parts showing a third embodiment.

[Explanation of symbols]

 1 Upper mold 2 Lower mold 3 Push-up ring 4 Body 5 Upper inner ring 6 Lower inner ring 7 Transfer jig 8 Glass material 9 Transfer arm 10 Optical element

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigeya Sugada 2-43-2 Hatagaya, Shibuya-ku, Tokyo Inside Olympus Optical Co., Ltd.

Claims (1)

[Claims] 1. An optical element molding method for press-molding a heat-softened glass material with upper and lower molds, wherein different shrinkage forces are applied to the outer periphery of the upper and lower molding surfaces of the glass material by using barrel molds having different linear expansion coefficients in the pressing direction. A method for molding an optical element, which comprises molding while applying pressure.