JPH1148355A - Optical element with fine uneven pattern, its manufacture, molding die for optical element with fine uneven pattern and manufacture of molding die - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a final shape after the formation of a protecting coat to assume a fine uneven pattern intended for an objective pattern by fabricating a protecting coat into a different shape from the fine uneven pattern intended for an objective pattern so that the final uneven pattern after the formation of the protecting coat becomes the objective uneven pattern. SOLUTION: A fine uneven pattern 12 to be formed on a base material 11 is of a different shape from an ideal shape 13i so that the fine uneven pattern 12 after the formation of a protecting coat becomes an ideal shape 13i, considering the non- uniformity of the thickness of the protecting coat 13 to be formed on the fine uneven pattern 12. More precisely, the fine uneven pattern 12 has a deep root part 12c compared to the ideal shape 13i with a serrated cross section. When deciding the shape of the fine uneven pattern 12, the protecting coat is actually formed as a preliminary experiment using parameters such as the ideal shape 13i, the property of the protecting coat 13 (platinum sputtered coat, reflection preventive coat, hard coat, etc.), and coat thickness, to compare the shape before the formation of the protecting coat with the shape after the formation of the coat.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an optical element having a fine concavo-convex pattern such as a diffraction pattern, a method of manufacturing the same,
The present invention relates to a mold for molding such an optical element and a method for manufacturing the same.

[0002]

2. Description of the Related Art For example, a plastic or glass lens having a diffractive shape is coated with a protective film such as an antireflection film or a hard coat on a fine diffraction pattern. In a mold for molding such a lens, a protective film made of, for example, platinum or the like for preventing oxidation is formed on a similar fine diffraction pattern. However, the thickness of these protective films will vary depending on the location of the fine irregularities in the diffraction pattern, and even if the irregularities before the protective film is formed are processed into the desired diffraction pattern,
The final shape does not become the desired diffraction pattern. This is because the depth and pitch of the unevenness of the diffraction pattern (on the order of μm) and the thickness of the protective film (on the order of several tens of nm to several μm)
This is because there is no large difference between them, and that the protective film does not easily adhere to the steep surface of the saw-toothed irregularities. This problem can be solved to some extent by making the thickness of the protective film thinner, but thinning has a limit in maintaining the quality of the lens or the mold.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical element and a molding die for forming a protective film on a fine uneven pattern, wherein the final shape after forming the protective film is an optical element (molding mold) having a desired fine uneven pattern. ) And a method for producing the same.

[0004]

SUMMARY OF THE INVENTION The present invention is based on the fact that the thickness of a protective film formed on a fine uneven pattern is determined by the shape of the uneven pattern, the film forming conditions and the like, and can be predicted in advance. In an optical element (mold for an optical element) having a concave-convex pattern and forming a protective film on the concave-convex pattern, the concave-convex pattern is not appropriate when the protective film is formed on the concave-convex pattern. In view of the uniformity, the surface is processed into a shape different from the target concavo-convex pattern so that the final concavo-convex shape after the formation of the protective film becomes a target concavo-convex pattern. The fine uneven pattern is, for example, a diffraction pattern, but may be another fine uneven pattern. Of course, any planar shape such as concentric or parallel may be used. Further, the present invention is more effective when the cross-sectional shape of the fine concavo-convex pattern is a shape having a nearly vertical steep surface such as a sawtooth shape or a rectangular wave shape.

Further, the method of the present invention is a method for manufacturing an optical element (mold for optical element) having a fine concavo-convex pattern and forming a protective film on the concavo-convex pattern. In consideration of the non-uniformity of the film thickness when the protective film is formed, the final concave-convex shape after forming the protective film is different from the target concave-convex pattern so as to be the target concave-convex pattern. It is characterized in that it is formed in a shape, and a protective film is formed on this uneven pattern.

[0006] The conditions for forming the protective film are determined so that the final concave-convex shape after forming the protective film becomes the target concave-convex pattern by a preliminary experiment in which at least the shape of the fine concave-convex pattern and the film material are used as parameters. be able to.
More specifically, the conditions for forming the protective film include, for example, the step amount of the fine uneven pattern, the thickness of the protective film formed on this uneven pattern, and the final fineness of the formed protective film. The ratio can be determined in consideration of the relationship of the enlargement ratio ∝ (film thickness / step amount) between the amount of step difference of the uneven pattern and the amount of step difference.

[0007]

FIG. 1 shows an example of the shape (principle) of an optical element (mold for optical element) of the present invention, and FIG. 2 shows an example of a conventional shape for comparison. 2, the fine uneven pattern 2 is formed on the surface of the substrate 1 of the optical element (mold for optical element). The concavo-convex pattern 2 has a desired ideal shape. When the protective film 3 is formed on the concave / convex pattern 2, the final shape thereof is different from the ideal shape 3i due to the unevenness of the film thickness of the protective film 3.

On the other hand, in the example of FIG. 1, the fine uneven pattern 12 formed on the base material 11 is formed in consideration of the nonuniformity of the thickness of the protective film 13 formed on the fine uneven pattern 12. Thus, the shape after forming the protective film 13 is the ideal shape 13
The shape is different from the ideal shape 13i so as to be i. More specifically, in the fine concavo-convex pattern 12, the depth of the valley portion 12c is made deeper than the ideal shape 13i of the sawtooth cross section.

In determining the shape of the fine concavo-convex pattern 12, as a preliminary experiment, the ideal shape 13i, the properties of the protective film 13 (platinum sputtered film, antireflection film, hard coat film, etc.), film thickness, etc. are used as parameters. A film is actually formed, and the shape before and after the film formation is compared to measure the film formation unevenness. For example, when cutting the diffraction surface of a glass mold, the base material is cut into a shape that takes into account the correction amount for the unevenness of film formation of the protective film predicted from preliminary experiments. If a film is formed on the diffraction surface processed in this manner, the final shape after the film formation becomes the target fine unevenness due to unevenness generated during the film formation.

FIGS. 3 to 5 show examples of specific preliminary experiments for determining film forming conditions. A base material 20 made of stainless steel was cut into an approximate aspherical shape 21, and an electroless Ni plating layer 22 was formed thereon. The plating layer 22 is cut with a single-crystal diamond tool into a diffraction-shaped surface 23 having fine irregularities in the shape of a cross section of a spur gear (helicoid?) Having a step amount of 1 μm. A platinum protective film 24 for improving heat resistance, oxidation resistance, and wet resistance was formed under a condition of forming a 1 μm-thick film. After measuring the shape after cutting and coating,
Diffraction shape is enlarged by 10% at the convex part after cutting to 1.1 μm
(FIG. 4). The recess is not enlarged. Similarly, when the protective film 24 was formed under a film forming condition of a thickness of 0.3 μm, the peak became a shape enlarged by 0.3%. Further, when the step amount of the diffraction shape surface 23 is 2 μm, the protective film 2
As a result, when the film No. 4 was formed under the film forming condition of 1 μm, the convex portion was 2.1 μm and the film thickness was 1.1 μm with respect to the concave portion.

From these preliminary experiments, the enlargement ratio K of the step amount is calculated.
It was found that K = (film thickness / step amount) × 10 (step amount + step amount × K / 100) = final step amount (FIG. 5).

Considering this, the final step amount is 1 μm.
When m and the thickness of the recess are 1 μm, it can be seen that the step formed on the plating layer 22 may be 0.9 μm. The plating layer 22 is processed under these conditions, and the protection film 24 is
When the film was formed under the film forming condition of m, a mold having a target final step amount of 1 μm could be formed.

As another example of the preliminary experiment,
It is a shape obtained by roughly reducing the diffraction shape with a step size of μm.
The plating layer 22 was cut, and then the actual shape was measured.
The step amount at this time was 0.92 μm. In order to make the final step amount after film formation 1 μm, from the above equation,
The film thickness is 0.8 μm. Then, when the film forming conditions (power and time) were adjusted so that the thickness became 0.8 μm in the concave portion, the protective film 24 was formed.
Was able to create a mold.

The above is an example of a preliminary experiment in the case where the cross-sectional shape of the diffraction pattern formed on the plating layer 22 is a spur gear shape (helicoid shape). The relationship between the shape of the surface 23 and the thickness of the protective film 24 can be found.

[0015]

According to the present invention, in an optical element and a mold for forming a protective film on a fine concave-convex pattern, an optical element having a final fine concave-convex pattern after forming the protective film ( Mold) is obtained.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing an example of the shape (principle) of an optical element having a protective film according to the present invention and a mold for an optical element.

FIG. 2 is a schematic cross-sectional view showing the shape of an optical element having a conventional protective film and a molding die for an optical element, which are shown for comparison.

FIG. 3 is a cross-sectional view showing an example of a process of forming a fine uneven pattern and a protective film on a molding die base material.

FIG. 4 is a schematic cross-sectional view showing a relationship between a fine uneven pattern and a protective film formed thereon.

FIG. 5 shows an example of a relationship between a step amount of a fine concavo-convex pattern, a film thickness of a protective film formed on this concavo-convex pattern, and an enlarged amount of a step of a final fine concavo-convex pattern on which a protective film is formed. It is a figure shown by the graph shown.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Substrate 12 Fine uneven pattern 13 Protective film 13i Ideal shape 20 Base material 21 Aspherical shape 22 Plating layer 23 Diffractive shape surface 24 Protective film

Claims (10)

[Claims] 1. An optical element having a fine concavo-convex pattern and forming a protective film on the concavo-convex pattern, wherein the concave-convex pattern has a film thickness when the protective film is formed on the concavo-convex pattern. In consideration of uniformity, a fine uneven pattern characterized by having a shape different from the target uneven pattern so that the final uneven shape after forming the protective film becomes the target uneven pattern. Optical element. 2. The optical element according to claim 1, wherein the fine concavo-convex pattern is a diffraction pattern. 3. A method for manufacturing an optical element having a fine concavo-convex pattern and forming a protective film on the concavo-convex pattern, comprising: forming a film when the protective film is formed on the concavo-convex pattern. In consideration of the non-uniformity of the thickness, the final concave-convex shape after forming the protective film is formed into a shape different from the target concave-convex pattern so that the final concave-convex pattern becomes the target concave-convex pattern. And a method of manufacturing an optical element having a fine concavo-convex pattern, wherein the protective film is formed. 4. The manufacturing method according to claim 3, wherein the conditions for forming the protective film include:
A method of manufacturing an optical element in which a final unevenness after forming a protective film is determined to be a target unevenness pattern by a preliminary experiment performed using a film material as a parameter. 5. The film forming conditions of the protective film according to claim 4, wherein the step amount of the fine uneven pattern, the thickness of the protective film formed on the uneven pattern, and the final thickness of the formed protective film. A method for manufacturing an optical element, which is determined in consideration of a relationship of an enlargement ratio ∝ (film thickness / amount of a step) between a stepped amount of a fine fine uneven pattern and an amount of an enlarged step. 6. A mold for an optical element having a fine uneven pattern corresponding to a molded optical element, and a protective film formed on the uneven pattern, wherein the uneven pattern is formed on the uneven pattern. In consideration of the non-uniformity of the film thickness when the protective film is formed, a shape different from the target uneven pattern such that the final uneven shape after forming the protective film is the desired uneven pattern. A mold for an optical element having a fine concavo-convex pattern. 7. An optical element molding die according to claim 6, wherein the fine uneven pattern is a diffraction pattern. 8. A method of manufacturing a mold for an optical element, comprising a concave / convex pattern corresponding to a fine concave / convex pattern of a molded optical element, and a protective film formed on the concave / convex pattern. In consideration of the non-uniformity of the film thickness when the protective film is formed on the concave / convex pattern, the target concave / convex pattern is formed so that the final concave / convex shape after forming the protective film becomes the target concave / convex pattern. A method for producing a mold for an optical element having a fine uneven pattern, wherein the mold is formed in a shape different from the pattern, and the protective film is formed on the uneven pattern. 9. The manufacturing method according to claim 8, wherein the conditions for forming the protective film include:
A method of manufacturing a mold for an optical element, wherein a final uneven shape after forming a protective film is determined to be a target uneven pattern by a preliminary experiment in which a film material is used as a parameter. 10. The manufacturing method according to claim 9, wherein the film forming conditions of the protective film include: a film forming condition of the protective film; a step amount of the fine unevenness pattern; The optics is determined by considering that there is a relationship of magnification ∝ (film thickness / step difference) between the film thickness and the step enlargement amount of the final fine uneven pattern on which the protective film is formed. A method for manufacturing a molding die for an element.