JPH06212478A - Production of electroforming mold - Google Patents

Abstract

PURPOSE:To improve the position accuracy at the front side and the rear side by forming a master having right relative positions of shapes of front and rear surfaces, simultaneously electroforming at front and rear surfaces of the master and then simultaneously processing outer peripherys of front and rear electroforming parts. CONSTITUTION:Electroformings are simultaneously executed at the front and rear surfaces of the master 1. Formed electroformings 2, 3 are formed in a condition holding the position relations between front and rear surfaces of the master 1. Outer peripherys 2a, 3a of respective electroformings 2, 3 are simultaneously processed by an end mill 4, etc., in a condition in which electroformings 2, 3 are attached to the master 1. Thus the outer periphery 2a of the front electroforming 2 accords with the outer periphery 3a of the rear electroforming 3 with accuracy. Thus a pair of molds having accurate position relations between the front and rear surfaces are obtained. Consequently, processing of hole for positioning, etc., is unnecessary.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an electroforming mold.

[0002]

2. Description of the Related Art Conventionally, a method of manufacturing a mold for an optical element by electroforming has been known. Usually, an optical element has two surfaces, an entrance surface and an exit surface, each of which has a specific shape. In order to ensure the performance of the optical element, the optical axis or the relative position of the entrance surface and the exit surface must match. Therefore, when the optical element is molded by the molding die, the positions (optical axes) of the respective molding dies for molding the entrance surface and the exit surface must match.

As a conventional technique for ensuring the positional accuracy of the electroforming mold, for example, there is the invention disclosed in Japanese Patent Publication No. 62-30905. In the above invention, a positioning hole is formed in the master separately from the Fresnel portion, and a guide is passed through the hole to be used for positioning.

[0004]

However, in Japanese Patent Publication No. 62-30905, it is necessary to form positioning holes on both sides of the master. However, the Fresnel processing and the hole processing need to be performed by different processing machines, and a relatively large positional deviation is inevitable due to work setting or the like. Since this positional deviation error occurs in the processing of the front and back sides,
Relative displacement when combined as a molding die results in the addition of two processing errors, and sometimes a large displacement of 10 micron order occurs. This positional deviation is a large enough amount to reduce the performance as an optical element.

Further, the positioning hole is originally unnecessary as an optical element, and it is an extra step to process the positioning hole to ensure the accuracy of the mold.

Further, let us consider a case where the molding die described in the above publication is used as a nest and is provided for an injection molding machine and used for injection molding. At this time, a die for injection as shown in FIG. 23 is used. Generally, the molds include mold plates 41, which are arranged to face each other.
The template plates 41, 42 are provided with insertion holes 41a, 42a facing each other. Then, a pair of inserts (molding dies) 43, 44 are inserted into the insertion holes 41a, 42a for injection molding.

Since the insertion holes 41a and 42a are preliminarily positioned with respect to each other, both the inserts 43 and 44 are positioned with respect to each other by being inserted into the insertion holes 41a and 42a. However, both nests 43,44
If the correlation (positional relationship) between the molding surface and the outer diameter of each of them does not match between the inserts 43 and 44, the molded product is compared with the desired molded product shape. Accurate molding cannot be performed because the front and back surfaces are misaligned.

That is, one of the nests 43 (or 44)
The relationship between the molding surface and the outer diameter of the other insert 44
(Or 43) As long as the positional relationship between the molding surface and the outer diameter does not match, even if the positional relationships between the insertion holes 41a, 42a are exactly the same, both the nests 43,
The molding surfaces of 44 do not coincide with each other. Therefore, after forming the molds by the method described in the above publication, it is necessary to machine the outer diameters of both molds so that the positional relationship between the molding surface and the outer diameters of both molds coincides with each other.

However, due to the processing precision in the outer diameter processing, an error occurs in the positional relationship between the molding surfaces of both molds and the outer diameter. Due to this error, even if those molds are provided in the injection molding machine, it is very difficult to exactly match the front and back of the desired molded product.

Therefore, the present invention was developed in view of the above-mentioned drawbacks of the prior art, and an object of the present invention is to provide a method for producing an electroforming mold in which the front and back surfaces of a desired molded product have good positional accuracy.

[0011]

According to the present invention, when manufacturing an electroforming mold for molding an optical element having a front surface and a back surface each having a specific shape, a master in which the relative positions of the shapes on each surface are formed correctly. The method is a method of simultaneously electroforming the front and back surfaces of the master, and then simultaneously processing the outer peripheries of the formed front and back electroformed portions.

1 to 4 are conceptual views showing the manufacturing process of the present invention. First, a master-1 is formed in which the relative positions of the shapes on the front and back surfaces are correct (see FIG. 1).
When the electroforming is simultaneously performed on the front and back surfaces of the above, the formed electroformed materials 2 and 3 are formed in a state where the positional relationship between the front and back surfaces of the master-1 is maintained (see FIG. 2). Next, the outer circumferences 2a and 3a of the electroformed pieces 2 and 3 are simultaneously processed by the end mill 4 etc. with the electroformed pieces 2 and 3 attached to the master-1 (see FIG. 3). Thereby, the outer peripheries 2a and 3a of the front electroformed 2 and the back electroformed 3 exactly match. Therefore, the positional relationship between the front electroforming mold 5 and the back electroforming mold 6 thus formed is the same as that of the front and back surfaces of the master-1 (see FIG. 4).

By the way, although the displacement of the front and back surfaces of the master-1 is caused by an error in the shape processing of the master-1, since it is only an error that occurs in one step, the error amount can be suppressed to a small value of the micron order. it can. Therefore, a pair of electroforming molds 5 and 6 in which the positions of the front and back surfaces are accurately aligned can be obtained.
Further, it is not necessary to process a positioning hole or the like, and the number of steps can be minimized.

[0014]

Embodiment 1 FIGS. 5 to 12 are process diagrams showing this embodiment. First, the phase type diffraction grating pattern 12a is formed on one surface (front surface) 11a of the glass flat plate 11 by photolithography (see FIG. 5).

Subsequently, a positive photoresist 13 is applied to the other surface (back surface) 11b of the glass flat plate 11 and prebaked, and then a photomask 1 of another diffraction grating pattern is formed.
4 is aligned with the position of the phase type diffraction grating pattern 12a previously formed so as to be a desired position. Since the alignment is performed by observing the position of the phase type diffraction grating pattern 12a already processed by the optical microscope, the alignment can be performed with an accuracy of 2 μm or less (see FIG. 6).

After the steps of exposure, development, post baking, etching, and photoresist stripping, the front and back surfaces 11a, 1a, 1
1b includes phase type diffraction grating patterns 12a and 12b, respectively.
A glass flat plate 11 having The positional accuracy of the front and back patterns 12a and 12b on the glass flat plate 11 is determined by the alignment accuracy of the photomask 14, and is 2 μm or less (see FIG. 7).

The obtained glass flat plate 11 is adhered and fixed to the jig 15, and the front and back surfaces 11 of the glass flat plate 11 are vacuum-deposited.
Nickel 16 is formed on the a and 11b by 1000Å (Fig. 8)
reference). After film formation, nickel electroforming 17 is performed on the front and back surfaces 11a and 11b of the glass plate 11 using the nickel 16 as an electrode (see FIG. 9).

After electroforming 17, the outer surface (upper and lower surfaces) is smoothed by a milling machine (see FIG. 10). Then, the outer periphery of the electroformed 17 is simultaneously processed on the front and back sides.
During processing, the electroforming 17 is performed while pressing from both sides so as not to come off from the glass flat plate 11 (see FIG. 11). After that, the electrocasting 17 is separated from the glass flat plate 11 to obtain a pair of electroforming molds 18 and 19 whose front and back positions are matched with each other with high accuracy (see FIG. 12).

According to this embodiment, a molding die for a phase type diffraction grating with good positional accuracy can be obtained by electroforming. Further, the molding die obtained in this example is inserted into the injection molding machine shown in FIG. 23, and a molded product having a desired shape is molded by injection molding. Here, it is assumed that the insertion holes of the injection molding machine are exactly aligned. According to this embodiment, the insertion holes of the injection molding machine are exactly aligned with each other, and the outer circumferences of both molding dies (nests) and the molding surface are aligned with each other. The front and back surfaces of the molded product formed by the above-mentioned molding are exactly the same.

[0020]

Embodiment 2 FIGS. 13 to 18 are process drawings showing this embodiment. In this embodiment, a PMMA disc 21 is attached to a jig and chucked on a precision lathe, and Fresnel 22 is attached to one surface.
Cut a. Then, the reference outer periphery 23a is coaxially cut (see FIG. 13). Next, remove the chaku and remove the reference circumference 23.
A is re-chucked again, and the aspherical surface 22b is cut on the other surface (see FIG. 14). At this time, the Fresnel 22a and the reference outer circumference 23a are exactly coaxial, and the aspherical surface 22b is also formed by the same processing machine, so that the error in the concentricity between the Fresnel 22a and the aspherical surface 22b is suppressed to 3 μm or less.

After that, 1000 L of gold 24 is deposited on the Fresnel 22a and the aspherical surface 22b of the disk 21 by vacuum vapor deposition (see FIG. 15). Subsequently, nickel electroforming 25 is performed on the disk 21 using the gold 24 as a cathode (see FIG. 16).

Next, the outer surface of the electroformed 25 is smoothed by a milling machine (see FIG. 17). Subsequently, outer peripheral processing is performed on both sides simultaneously (see FIG. 18). After that, the electroformed mold 25 is separated from the circular plate 21 to obtain a pair of electroformed molds whose front and back positions are matched with each other with high accuracy.

According to this embodiment, since the master is the PMMA, the master can be cut together with the outer peripheral processing, and a die smaller than the master can be obtained in a small number of steps.

[0024]

Third Embodiment FIGS. 19 to 22 are process drawings showing the present embodiment. In this embodiment, a brass plate 31 is attached to a jig 32 and chucked on a precision lathe, and the Fresnel lenses 31a and 31b are formed on the front and back surfaces of the plate 31 using the same method as in the second embodiment.
Are formed by cutting (see FIG. 19). Next, nickel electroforming 33 is performed on the front and back surfaces of the brass plate 31 as a cathode (see FIG. 20).

After performing the electroforming 33, the outer surface of the electroforming 33 is smoothed by a milling machine (see FIG. 21). Subsequently, outer peripheral processing is performed on both sides simultaneously (see FIG. 22). After this, by separating the electroformed 33 from the brass plate 31,
A pair of electroforming molds whose front and back positions are accurately matched are obtained.

According to the present embodiment, since the master is brass, precision machining by cutting can be performed, electroforming can be directly performed, and further, it is possible to perform machining together with electroforming at the time of outer peripheral machining, thereby reducing the number of steps. .

[0027]

As described above, according to the method for manufacturing an electroforming mold according to the present invention, it is possible to obtain an electroforming mold having good front and back positional accuracy by a simple method.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing the present invention.

FIG. 2 is a conceptual diagram showing the present invention.

FIG. 3 is a conceptual diagram showing the present invention.

FIG. 4 is a conceptual diagram showing the present invention.

FIG. 5 is a process diagram showing Example 1.

FIG. 6 is a process diagram showing Example 1.

FIG. 7 is a process drawing showing the first embodiment.

FIG. 8 is a process drawing showing the first embodiment.

FIG. 9 is a process drawing showing Example 1.

FIG. 10 is a process chart showing Example 1.

FIG. 12 is a process diagram showing Example 1.

FIG. 13 is a process diagram showing a second embodiment.

FIG. 14 is a process diagram showing a second embodiment.

FIG. 15 is a process diagram showing a second embodiment.

FIG. 16 is a process drawing showing Example 2.

FIG. 17 is a process diagram showing a second embodiment.

FIG. 18 is a process diagram showing a second embodiment.

FIG. 19 is a process drawing showing Example 3;

FIG. 20 is a process diagram showing a third embodiment.

FIG. 21 is a process drawing showing Example 3;

FIG. 22 is a process drawing showing Example 3;

FIG. 23 is a cross-sectional view showing a conventional example.

[Explanation of symbols]

 1 Master 2,3 Electroforming 4 End mill 5,6 Electroforming

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[Procedure amendment]

[Submission date] July 22, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Added

[Correction content]

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing the present invention.

FIG. 2 is a conceptual diagram showing the present invention.

FIG. 3 is a conceptual diagram showing the present invention.

FIG. 4 is a conceptual diagram showing the present invention.

FIG. 5 is a process diagram showing Example 1.

FIG. 6 is a process diagram showing Example 1.

FIG. 7 is a process drawing showing the first embodiment.

FIG. 8 is a process drawing showing the first embodiment.

FIG. 9 is a process drawing showing Example 1.

FIG. 10 is a process chart showing Example 1.

FIG. 11 is a process chart showing Example 1.

FIG. 12 is a process diagram showing Example 1.

FIG. 13 is a process diagram showing a second embodiment.

FIG. 14 is a process diagram showing a second embodiment.

FIG. 15 is a process diagram showing a second embodiment.

FIG. 16 is a process drawing showing Example 2.

FIG. 17 is a process diagram showing a second embodiment.

FIG. 18 is a process diagram showing a second embodiment.

FIG. 19 is a process drawing showing Example 3;

FIG. 20 is a process diagram showing a third embodiment.

FIG. 21 is a process drawing showing Example 3;

FIG. 22 is a process drawing showing Example 3;

FIG. 23 is a cross-sectional view showing a conventional example.

Claims (1)

[Claims] 1. When manufacturing an electroforming mold for molding an optical element, each having a front surface and a back surface of a specific shape, a master is formed in which the relative positions of the shapes on the front and back surfaces are correct, and the front and back surfaces of the master are simultaneously charged. A method for producing an electroforming mold, which comprises simultaneously processing the outer circumferences of the formed front and back electroformed parts after casting.