JPH06340432A - Method for molding optical element and optical material to be used in this method - Google Patents

Abstract

PURPOSE:To provide molded goods having an excellent surface transfer characteristic and high reliability by molding an optical element such as concave lens, by using a blank material having the thickness larger than the max. thickness of the optical element after molding at the time of producing the optical element by press molding. CONSTITUTION:The optical blank material 3a is softened by heating and is press molded in molds, by which the optical element 3b (concave lens, etc.) is obtd. The molds consist of a mold or a top and bottom forces and the element 3b is obtd. by press molding in a manner as not to restrain the outer peripheral part of the blank material 3a. The blank material having the thickness of the part of the blank material 3a corresponding to the max. thickness part T1b within the optically effective surface of the molded optical element 3b larger than the max. thickness of at least the molded optical element 3b is used for the blank material 3a.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, Japanese Patent Laid-Open Nos. 61-53127 and 61-6833 have been used to define the shape of optical materials.
1 and JP-A-63-295447, the former 2
In each of the two examples, the purpose was to prevent gas accumulation during molding, and the shape of the optical material was devised so that pressing started from the center of the optical material with respect to the molding die, or the optical material worked well. The feature is that the shape fits in the mold.

The third example is intended to improve the surface transferability, and the content thereof is a side surface before the R surfaces on both sides of the lens are sufficiently transferred during the deformation process of the optical material during pressing. When an optical material is touched on the mold part, the pressure is dispersed and the surface transfer property is deteriorated. Therefore, in order to prevent this, the relational expression between the press silo and the diameter spread is defined.

In addition to these methods, as a method usually performed, optical materials having several kinds of shapes selected empirically were prepared, and the shapes were finally determined by actually molding.

To explain this in a little more detail, particularly in the case of a concave lens shape, the pressing pressure at the time of pressing tends to escape to the peripheral portion of the material. Therefore, if the optical pressure of the optical material is too thin, the surface transferability of the lens outer peripheral portion becomes insufficient.
On the contrary, if the meat pressure is too thick, not only the pressing time will increase,
It is easy to cause misalignment during pressing.

Therefore, it is advantageous to reduce the wall pressure of the optical material within the range where the surface transferability is guaranteed, which has been empirically sought in the past.

The above-mentioned conventional example relates to a technique for manufacturing an element by using a die for restraining the outer peripheral portion of the material. In this case, the material enters the gap between the body die and the upper and lower dies during the forming, As a cause, there is an inconvenience such as damage to the optical element during release.

However, in the above-mentioned conventional example, there is no molding in which a mold whose outer peripheral portion is not constrained is used and the shape of the optical material for improving the surface transfer property is regulated, and further molding is performed using it. There was no mention of the method.
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 than to empirically determine the shape of the optical material by the above-mentioned commonly used method, which requires confirmation for each individual product, which requires a great deal of labor. I needed it. In addition, there is a limit in improving the reliability.

[0010]

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]

In order to achieve the above object, the present invention is to soften an optical material by heating and press the optical element by a molding die without restraining the outer peripheral portion of the optical material by a barrel die or an upper die. In the method of molding an optical element to be molded, an optical material in which 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 or more. The optical material includes a maximum thickness of not more than the maximum diameter of the optical material, and the optical element is a concave lens.

Further, the present invention is an optical material used in the above molding method.

[0013]

According to the present invention, when a concave lens-shaped optical element is press-molded, the maximum thickness of the optical element after molding (= the thickness of the effective diameter portion) is By molding using an optical material in which the portion corresponding to it is at least the thickness thereof, it is possible to obtain sufficient surface transferability within the effective surface.

The present invention will be described in detail below.

FIG. 1 illustrates the press-molded state of the present invention. FIG. 1 (A) shows the state before the pressing and FIG. 1 (B) shows the state after the completion of the pressing. In the figure, 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, as shown in FIG.
As shown in (B), the outer peripheral portions 5a and 5b of neither the material 3a nor the optical element 3b are in contact with the body mold (not shown) or the upper and lower molds, so that the outer peripheral portions are the body mold and the upper and lower molds. It becomes a shape that is formed naturally without being restricted by.

FIG. 2 shows the disc-shaped optical material (FIG. 2 (A)) and the optical element (FIG. 2 (B)) before and after press molding, and FIG. 3 shows the droplet-shaped optical material before and after press molding. The material (FIG. 3 (A)) and the optical element (FIG. 3 (B)) are shown.

In FIGS. 2 and 3, T1a and T2a are optical materials 3a and 4a of a portion which becomes the effective diameter of the optical element after molding.
The wall thickness of T1b, T2b is deformed after molding,
The thicknesses (maximum thicknesses) of the optical elements 3b and 4b, which are the effective diameters, are Y1 and Y2, respectively.

When the maximum diameters of the materials 3a and 4a are D and the maximum thickness is L, the maximum thickness is preferably less than or equal to the maximum diameter. That is, L / D ≦ 1 is preferable. In particular, in the case of a convex lens, L / D is preferably 1 or less in consideration of the pressing time and the ease of positioning the material, and in the case of a concave lens, the positional deviation during pressing is large, so it is less than 0.5. Is desirable.

When L / D> 1, misalignment is likely to occur during press molding and the press molding time becomes long.
Also, in the case of cylindrical material, the outer peripheral surface of the side surface is usually a rough surface, and if this is pressed, the rough side surface easily enters the effective optical surface, and this surface roughness is a problem even after molding. May be.

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

[0022]

【Example】

(Examples 1 and 2) A biconcave lens was manufactured using the press die and the material shown in FIGS. The product shape is 16 mm in outer diameter,
The effective diameter Y1 was Φ15 mm, both surfaces were R30, and the effective diameter portion thickness T1b was 3 mm. The glass material was BAL42. The optical material 3a has a constant volume, a diameter D, and a thickness T.
Four types of disc shapes having different 1a were prepared. Table 1 shows the results of molding using these with a mold temperature of 620 ° C. and a pressing pressure of 3000N. “Effective transfer surface Y” in Table 1 is the diameter of a portion within one habit when a molded product is evaluated, and “judgment” is that the effective transfer surface Y has a product effective diameter Y1 or more. The ones were evaluated as ◯ and those less than were evaluated as x. For example, when the optical material has a thickness T1a of 2.0 mm, the effective transfer surface Y is Φ12.0 mm, and the outer peripheral portion has a sufficient thickness.
Since the surface transfer is defective and the product effective diameter Y1 = Φ15.0 mm is not satisfied, the judgment is “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 is 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. 3 (b) has an outer diameter of Φ26 mm, an effective diameter Y2 of Φ25 mm, one surface has a concave R15, the other surface has a convex R55, and an effective diameter portion has a wall thickness T.
2b was 7.5 mm, and a concave meniscus lens having a glass material of BAL42 was molded.

As the optical material 4a to be used, a droplet-shaped material shown in FIG. 3 (A) was prepared in which the thickness T2a of the portion which becomes the effective diameter of the optical element after molding is 8 mm. It should be noted that it is possible to roughly calculate which portion of the optical material 4a will become the effective diameter portion of the optical element after molding, but this time, it was dealt with by marking the optical material 4a and actually molding. .

When this optical material 4a was used and molded under the same conditions as in Examples 1 and 2, a molded product with a surface accuracy within one habit was obtained within the product effective diameter Y2. .

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

In the above embodiment, the glass press molding was described, but the material is not particularly specified.
For example, it may be applied to plastic or the like.

Further, in the above embodiment, the concave lens shape which seems to be particularly effective is described, but the shape is not limited, and if the shape is such that the pressing pressure easily escapes to a portion other than the pressing surface, it may be a convex lens shape. Alternatively, it may have a shape other than a lens.

[0030]

As described above, the present invention is particularly preferable in the case of press-molding an optical element having a concave lens shape. However, in the portion having the maximum wall thickness in the effective surface of the optical element after molding. On the other hand, by molding using an optical material whose corresponding portion is at least thicker than that, it was determined that sufficient surface transferability within the effective surface could be obtained, and molding was performed according to that dimension. In addition, it is possible to easily obtain a molded product having high surface transferability without trial and error due to experience as in the past, and it is possible to improve both accuracy and economical efficiency.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a state where press molding is carried out in carrying out the present invention, FIG. 1 (A) shows before pressing, and FIG. 1 (B) shows after pressing.

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

FIG. 3 is an optical material used for implementing the present invention (FIG. 3 (A))
FIG. 5 is an explanatory diagram showing another example of the optical material after molding (FIG. 3 (B)).

[Explanation of symbols]

1 Upper mold 2 Lower mold 3a, 4a Optical material 3b, 4b Optical element T1a, T2a Thickness of the optical material of the portion that becomes the effective diameter of the optical element after molding T1b, T2b Thickness of the effective diameter portion of the optical element Y1 , Y2 Effective diameter dimension L Maximum thickness of optical material D Maximum diameter of optical material

Front Page Continuation (72) Inventor Masayuki Tomita 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Masashi Majuge 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. Within

Claims (4)

[Claims] 1. A method for molding an optical element, which comprises softening an optical material by heating and press-molding the optical element with a molding die without restraining the outer peripheral portion of the optical material with a barrel die or an upper die and a lower die. A molding method of an optical element, characterized in that molding is performed using an optical material in which the thickness of the portion of the optical material corresponding to the maximum thickness portion in the optically effective surface is at least not less than the maximum thickness of the molded optical element. . 2. The molding method according to claim 1, wherein the maximum thickness of the optical material is not more than the maximum diameter of the optical material. 3. The molding method according to claim 1, wherein the optical element is a concave lens. 4. An optical material used in the molding method according to claim 1.