JPH11248907A - Metal mold for molding microoptical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the metal mold which has no wrinkle formed nearby an indentation for an element by specifying the Vickers hardness of a cavity surface. SOLUTION: Many element identations 3b are formed on the cavity surface 3a of a metal mold body 3 by indentation machining. The indentation machining is carried out by pressing an indenter made of, for example, diamond against the cavity surface 3a with specific pressure. The cavity surface 3a is formed by forming an electroless nickel plating layer 5 on the metal mold base material 4. The Vickers hardness of this electroless plating layer 5 is >=500 Hv. The thickness W of the plating layer 5 is about three times as large as the indentation depth H of the indenter. A nonferrous material such as aluminum alloy and copper alloy is used for a metal mold base material 4. The surface of the plating layer 5 is polished into the cavity surface 3a in a mirror surface state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a micro-optical element molding die for molding a micro-optical element.

[0002]

2. Description of the Related Art Conventionally, as a micro optical element, for example, a convex lens, a concave lens, a prism and the like are known.
In addition, as a method of manufacturing a micro-optical element array in which a large number of such micro-optical elements are arranged, injection molding, compression molding, and injection molding are performed by using a mold having an inverted shape of the micro-optical element array formed on a cavity surface. A method of molding a resin by molding or the like is known.

On the other hand, as a method of forming an inverted shape of a micro optical element on a cavity surface of a mold, cutting, indentation, and the like are known. In the above-mentioned micro optical element array, it is necessary to form inverted shapes of a large number of optical elements on the cavity surface.

As shown in FIG. 6, such an indentation process presses, for example, an indenter 2 made of diamond on a cavity surface 1a of a mold body 1 at a predetermined pressure, and applies a micro-optical element to the cavity surface 1a. This is performed by forming an element impression 1b having an inverted shape of the above.

[0005]

However, conventionally,
When the element indentation 1b is formed on the cavity surface 1a by such indentation processing, there is a problem that wrinkles 1c are generated near the element indentation 1b as shown in FIG.

The inventor of the present invention has conducted intensive studies in order to solve such a conventional problem. As a result, wrinkles 1c are generated near the element indentations 1b.
When pressed to a, a part of the material of the portion where the indenter 2 is pressed plastically flows laterally and protrudes in the vicinity of the element indentation 1b as shown in FIG. 8, and a wrinkle 1c is formed by the protrusion 1d. I found that.

It has been found that the size of the protrusion 1d generated near the element indentation 1b due to such indentation processing decreases as the hardness of the cavity surface 1a increases. The present invention has been made based on such knowledge, and an object of the present invention is to provide a mold for molding a micro optical element in which wrinkles are not generated in the vicinity of an element indentation.

[0008]

According to a first aspect of the present invention, there is provided a mold for forming a micro optical element, wherein a plurality of element indentations for forming a micro optical element are formed on a cavity surface of a mold body. In the device molding die, the surface of the cavity surface may have a Vickers hardness of 500 Hv or more.

According to a second aspect of the present invention, there is provided a mold for molding a micro optical element according to the first aspect, wherein the cavity surface has a Vickers hardness of 85.
It is characterized by having a hardness of 0 Hv or less.

(Function) In the mold for molding a micro optical element of the first aspect, the surface of the cavity surface has a Vickers hardness of:
When the indenter is pressed against the cavity surface, a part of the material of the portion pressed against the indenter is suppressed from laterally plastically flowing when the indenter is pressed against the cavity surface, and a protruding portion is formed near the indentation for the element. Will not be done.

According to the second aspect of the present invention, the surface of the cavity surface has a Vickers hardness of 850H.
v or less, and wear of the indenter due to indentation is prevented.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 and 2 show a first embodiment of a mold for molding a micro-optical element according to the present invention. This mold comprises a micro-optical element array formed by arranging a large number of micro-optical elements. Used for injection molding of resin. In this mold, a large number of element impressions 3b are formed on the cavity surface 3a of the mold body 3 by indentation processing.

The shape of the element impressions 3b is an inverted shape of the micro optical element. In this embodiment, the cavity surface 3 a of the mold body 3 is formed by forming an electroless nickel plating layer 5 on a mold base material 4. The Vickers hardness of the electroless nickel plating layer 5 is, for example, 500 Hv.

The mold for forming a micro optical element is manufactured, for example, as described below. First, a predetermined electroless nickel plating is applied to the surface of the mold base material 4 to form an electroless nickel plating layer 5. The thickness W of the electroless nickel plating layer 5 is about three times the indentation depth H of the indenter described later.

In this embodiment, a non-ferrous metal material such as an aluminum alloy or a copper alloy is used for the mold base material 4.
The surface of the electroless nickel plating layer 5 is polished, for example, to be a mirror-like cavity surface 3a. Next, in this embodiment, the element indentations 3b are formed on the electroless nickel plating layer 5 by the indentation processing shown in FIG.

This indentation is formed by pressing an indenter 6 made of, for example, diamond on the cavity surface 3a with a predetermined pressure. In the micro-optical element molding die configured as described above, since the Vickers hardness of the surface of the cavity surface 3a was set to a hardness of 500 Hv or more, the indenter 6 was pressed when the indenter 6 was pressed against the cavity surface 3a. Part of the material of the portion is prevented from plastically flowing laterally, and no protruding portion is formed in the vicinity of the indentation 3b for the element. As a result, there is no micro wrinkle near the indentation 3b for the element. An optical element molding die can be easily and reliably provided.

That is, in the conventional mold for forming a micro optical element, a copper alloy or a martensitic stainless steel is usually used in order to maintain a long life of the indenter 6 in indentation processing. In the case of a series stainless steel, the Vickers hardness is about 300 to 400 Hv, and at such hardness, as shown in FIG. The protruding portion C was formed near the element indentation B formed on the surface A.

However, in the above-described mold for molding a micro optical element, the Vickers hardness of the surface of the cavity surface 3a is set to a hardness of 500 Hv or more. Part of the material of the portion is prevented from plastically flowing laterally, and the formation of the protruding portion in the vicinity of the element impressions 3b is almost completely eliminated.

In FIG. 4, when the Vickers hardness of the cavity surface A is changed from 340 Hv to 450 Hv,
The protrusion becomes smaller from C to C1, and at 550Hv,
You can see that it is almost completely gone. In the above-described mold for molding a micro optical element, the Vickers hardness of the surface of the cavity surface 3a is set to a hardness of 850 Hv or less. An element can be formed.

That is, for example, on a mat surface of a reticle used for focusing of a single-lens reflex camera, for example,
Approximately 2.2 million microlenses with a sphere R of 30 μm are arranged in a range of 25 mm × 35 mm. And when manufacturing such a cavity of the reticle molding die,
When an indentation process is performed on a mold base material having a Vickers hardness exceeding 850 Hv using a diamond indenter having a tip ball R of 30 μm, about 2.2 million device indentations are completed at the end of processing.
The tip ball R of the diamond indenter is worn, for example,
R23 μm to R28 μm, making it difficult to manufacture a uniform microlens array.

However, in the above-described mold for forming a micro-optical element, the Vickers hardness of the surface of the cavity surface 3a is set to a hardness of 850 Hv or less. A high microlens array can be formed. FIG.
7 shows a second embodiment of a mold for molding a micro optical element of the present invention. In this embodiment, the material of the mold body 7 is martensitic stainless steel, and the base material is hardened by heat treatment. Hardness is 56 in Vickers hardness
0Hv.

The mirror-finished cavity surface 7a is formed by polishing the surface of the base material. The cavity surface 7a is formed with an element indentation 7b by indentation processing.
Are formed. In this embodiment, in the indentation processing, a spherical diamond indenter having a tip of R100 μm was used, and the element indentation 7b having the inverted shape of the convex lens was formed by this processing.

In this embodiment, the same effects as in the first embodiment can be obtained. In the above-described embodiment, an example in which diamond is used for the indenter 6 has been described, but the present invention is not limited to this.
For example, an indenter made of a cemented carbide, ceramic or the like can be used.

[0025]

As described above, in the mold for molding a micro-optical element according to the first aspect, the Vickers hardness of the surface of the cavity surface is set to a hardness of 500 Hv or more. A part of the material of the portion where the indenter is pressed is suppressed from plastically flowing laterally, and a protrusion is not formed near the element indentation. As a result, wrinkles are generated near the element indentation. It is possible to easily and reliably provide a mold for molding a micro optical element.

According to the second aspect of the present invention, the Vickers hardness of the cavity surface is 850H.
Since the hardness is not more than v, wear of the indenter due to indentation processing can be prevented, and a highly accurate micro optical element can be formed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an element indentation portion of a first embodiment of a micro-optical element molding die according to the present invention.

FIG. 2 is a front view showing a mold on which a large number of element indentations of FIG. 1 are formed.

FIG. 3 is an explanatory view showing a state in which an indentation for an element is formed in the mold for molding a micro optical element in FIG. 1;

FIG. 4 is an explanatory view showing a relationship between hardness of a cavity surface and a size of a protrusion formed near an element impression.

FIG. 5 is a cross-sectional view illustrating a second embodiment of a micro-optical element molding die according to the present invention.

FIG. 6 is an explanatory view showing a state in which an indentation for an element is formed in a conventional mold for molding a micro optical element.

FIG. 7 is an explanatory view showing wrinkles formed in the vicinity of an element impression in a conventional micro-optical element molding die.

FIG. 8 is an explanatory view showing a protruding portion formed in the vicinity of an element indentation of a conventional mold for molding a micro optical element.

[Explanation of symbols]

 3,7 Mold main body 3a, 7a Cavity surface 3b, 7b Device indentation 6 Indenter

Claims (2)

[Claims] 1. A micro-optical element molding die in which a large number of element indentations for molding a micro-optical element are formed on a cavity surface of a mold main body, wherein the Vickers hardness of the surface of the cavity surface is 500H
A mold for molding a micro optical element, which has a hardness of not less than v. 2. The mold for molding a micro optical element according to claim 1, wherein the surface of the cavity surface has a Vickers hardness of 850H.
A mold for molding a micro optical element, which has a hardness of not more than v.