JP3045432B2 - Method of forming concave lens-shaped optical element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for press-molding an optical element with a mold by heating and softening an optical material, and more particularly to a method for molding an optical element and a method suitable for molding a concave lens. It relates to an optical material to be used.

[0002]

2. Description of the Related Art Conventionally, the shape of an optical material has been defined as disclosed in JP-A-61-53127 and JP-A-61-6833.
1 and JP-A-63-29547.
In each of the examples, the purpose is to prevent gas accumulation during molding, and the shape of the optical material is devised so that pressing is started from the center of the optical material with respect to the mold, or the optical material is It is characterized by a shape that fits in the mold.

The third example aims at improving the surface transferability. The content of the third example is such that in the process of deforming the optical material during pressing, the side surfaces of the lens before the R surfaces on both sides are sufficiently transferred. When the optical material is touched to the part of the mold, the pressure is dispersed and the surface transferability is deteriorated. Therefore, the relational expression between the press white and the expansion of the diameter is specified for the purpose of preventing the dispersion.

[0004] In addition to these methods, a commonly used method is to prepare optical materials of several shapes selected empirically, and finally determine the shape by actual molding.

More specifically, in the case of a concave lens shape, the pressing pressure at the time of pressing easily escapes to the peripheral portion of the material. For this reason, if the wall pressure of the optical material is too thin, the surface transferability of the outer peripheral portion of the lens becomes insufficient.
Conversely, if the meat pressure is too thick, not only will the press time increase,
It is easy to cause displacement during pressing.

Therefore, it is advantageous to reduce the wall pressure of the optical material within a range in which the surface transferability is guaranteed, and this has conventionally been empirically determined.

The above-mentioned prior art relates to a technique for manufacturing an element by using a mold for restraining the outer peripheral portion of the material. In this case, the material enters a gap between the body mold and the upper and lower molds at the time of molding. As a cause, there has been an inconvenience that the optical element is damaged upon release from the mold.

However, in the above-mentioned conventional example, there is no molding that uses a mold that does not restrict the outer peripheral portion and does not specify the shape of the optical material for improving the surface transfer property. No method was described.
Further, there is no conventional example in which only the thickness of the optical material is specified.

Therefore, in that case, there is no other way but to determine the shape of the optical material empirically by the above-mentioned usual method, and it is necessary to confirm each product individually, which requires a great deal of labor. I needed it. In addition, there is a limit in improving the reliability.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a press molding method having excellent transferability.

[0011]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method for heating and softening a liquid optical material in the form of a droplet, and using a molding die without restricting the outer peripheral portion of the optical material by a body mold or an upper and lower mold. In a method of molding an optical element by press molding an optical element, the thickness of the portion of the optical material corresponding to the maximum thickness portion in the optically effective surface of the molded optical element is at least the maximum thickness of the molded optical element. Molded using an optical material that is
L / D is the maximum diameter of the optical material, and L / D is less than 0 or 5.
The present invention provides a method for forming an optical element having a concave lens shape .

[0012]

[0013]

According to the present invention, when a concave lens-shaped optical element is press-molded, the maximum thickness of the molded optical element in its effective plane (= the thickness of the effective diameter portion) is determined. The corresponding part is at least as thick as
The maximum thickness of the optical material is L and the maximum diameter of the optical material is D
As, by to Rukoto and less than 0,5 the L / D, it is obtained as obtain a sufficient surface transfer of the effective surface.

Hereinafter, the present invention will be described in detail.

FIG. 1 illustrates a press forming state in the present invention. FIG. 1 (A) shows a state before pressing, and FIG. 1 (B) shows a state after pressing is completed. In the drawing, 1 is an upper mold, 2 is a lower mold, 3a is an optical material before molding, and 3b is an optical element after molding.

In this press molding, FIG.
As shown in (B), neither the material 3a nor the optical element 3b has the outer peripheral portions 5a and 5b in contact with the body mold (not shown) or the upper and lower molds. It is a shape that is formed naturally without being constrained.

[0017] Figure 2 shows a disc-shaped optical material before and after press forming (FIG. 2 (A)), and an optical element (FIG. 2 (B)), and FIG. 3 is a longitudinal press-formed droplets of An optical material (FIG. 3A) and an optical element (FIG. 3B) are shown. In the present invention, the optical material in the form of a droplet is shown in FIG.
Optical material,
Obtained by receiving the molten glass flow in a receiving mold
Gob consisting of a lump of glass, a lump of molten glass, or simply glass
Synonymous with the expression gob.

In FIGS. 2 and 3, T1a and T2a denote optical materials 3a and 4a in portions which become the effective diameter of the optical element after molding.
The thickness dimension of T1b, T2b is deformed after molding,
Thickness dimensions (maximum thickness) of portions that become effective diameters of the optical elements 3b and 4b, and Y1 and Y2 are respective effective diameter dimensions.

Further, material 3a, 4a is the maximum diameter thereof is D, and if the maximum thickness and L, L / D is a less than 0.5 since the positional deviation during the press there is a large Kunar tendency
It is necessary to.

When L / D exceeds 0 and 5, misalignment tends to occur during press forming and the press forming time is prolonged. In the case of a columnar material, the outer peripheral portion of the side surface is usually rough. The surface remains as it is, and when it is press-molded, the rough side surface easily enters the effective optical surface, and this surface roughness may become a problem after molding.

As for the shape of the side surface, centering may be performed after molding, if necessary.

[0022]

EXAMPLES (Examples 1 and 2 and Comparative Examples 1 and 2 ) A biconcave lens was manufactured using the press dies and materials shown in FIGS. Product shape is outer diameter Φ16mm, effective diameter Y1 is Φ1
5 mm, both sides were R30, and the thickness T1b of the effective diameter portion was 3 mm. The glass material was BAL42. As the optical material 3a, four kinds of disk-shaped materials having a constant volume and different diameters D and thicknesses T1a were prepared. Table 1 shows the results of molding using these at a mold temperature of 620 ° C. and a pressing pressure of 3000 N.
It was shown to. As a comparative example, the thickness of the optical material used was
For example, when the thickness of the formed optical element is less than the maximum thickness,
That is, an example of adopting the condition of T1a less than 3 mm of T1b is as follows.
Indicated. "Effective transfer surface Y" in Table 1 is a value obtained by measuring the diameter of a portion within one habit when the molded article is evaluated, and "Judgment" means that the effective transfer surface Y is equal to or more than the product effective diameter Y1. The sample was evaluated as ○ and the sample less than X. For example, in Comparative Example 1,
As shown, when the optical material is molded with an optical material having a thickness T1a of 2.0 mm, the effective transfer surface Y is Φ12.0 mm, and although the outer peripheral portion has a sufficient thickness,
Since the surface transfer was poor and did not satisfy the product effective diameter Y1 = Φ15.0 mm, the judgment was “x”.

[0023]

[Table 1] From Table 1, if the thickness T1a of the optical material is 3.0 mm or more, which is the same as the thickness T1b of the effective diameter portion of the molded product, the effective transfer surface Y becomes Φ15.0 mm or more, and the product effective diameter Y1 = Φ15.
It can be seen that 0 mm is satisfied.

(Embodiment 3) The product shape shown in FIG. 3B has an outer diameter of 26 mm, an effective diameter Y2 of 25 mm, a concave surface R15 on one surface, a convex surface R55 on the other surface, and a thickness T of the effective diameter portion.
2b was 7.5 mm, and the glass material formed a concave meniscus lens of BAL42.

As the optical material 4a to be used, a droplet-shaped material having a thickness T2a of 8 mm at a portion which becomes an effective diameter of the optical element after molding was prepared as shown in FIG. 3A. Although it is possible to roughly predict which part of the optical material 4a will become the effective diameter of the optical element after molding by calculation, in this case, a measure was taken by engraving the optical material 4a and actually performing the molding. .

Using this optical material 4a, molding was performed under the same conditions as in Examples 1 and 2 above. As a result, a molded product with a surface accuracy within one habit within the product effective diameter Y2 could be obtained. .

The optical material 4 having a thickness T2a of 7 mm
When a was used, a sufficient thickness of the outer peripheral portion of the molded product from Φ24 mm was secured, but sufficient surface transferability was not obtained.

In the above embodiment, the press forming of glass was described, but the material is not particularly specified.
For example, you may apply to plastic etc.

In the above embodiment, the concave lens shape which is considered to be particularly effective has been described. However, the shape is not limited. Or a shape other than a lens.

[0030]

As described above, the present invention is particularly preferable when an optical element having a concave lens shape is press-molded. However, the optical element after molding has a maximum thickness in the effective plane of the optical element. contrast, those portions corresponding thereto molded using the optical material is at least the thickness or
The maximum thickness of the optical material and the maximum diameter of the optical material
D and L / D less than 0 and 5 determine that sufficient surface transferability in the effective plane can be obtained, and molding is performed based on the dimensions. It is possible to easily obtain a molded product having high surface transferability without error, and to improve both accuracy and economic efficiency.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory view showing a state in which press molding is performed in practicing the present invention. FIG. 1A shows a state before pressing, and FIG.

FIG. 2 is an optical material used for implementing the present invention (FIG. 2A).
FIG. 3 is an explanatory view showing an example of an optical material after molding (FIG. 2B).

FIG. 3 is an optical material used in the embodiment of the present invention (FIG. 3A)
It is explanatory drawing which shows the other example of the optical material (FIG.3 (B)) after shaping | molding.

[Explanation of symbols]

Reference Signs List 1 upper mold 2 lower mold 3a, 4a optical material 3b, 4b optical element T1a, T2a thickness dimension of optical material at a portion which becomes effective diameter of optical element after molding T1b, T2b thickness dimension of effective diameter portion of optical element Y1 , Y2 Effective diameter dimension L Maximum thickness of optical material D Maximum diameter of optical material

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masayuki Tomita 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Masashi Maegashi 3-30-2 Shimomaruko, Ota-ku, Tokyo (56) References JP-A-2-208228 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C03B 11/08 C03B 11/00

Claims (1)

(57) [Claims] In a method for forming an optical element, an optical element in the form of a droplet is heated and softened, and the optical element is press-molded by a molding die without restraining an outer peripheral portion of the optical material by a barrel mold or an upper and lower mold. and it is intended thickness of the portion of the optical material corresponding to the maximum wall thickness portion is formed using an optical material is greater than or equal to the maximum thickness of the optical element at least formed in the optically effective plane of the optical element and the optical material Maximum wall thickness
Is L and the maximum diameter of the optical material is D, and L / D is 0,5
A method for molding an optical element having a concave lens shape, wherein the optical element is full .