JPH095509A - Formation of master disk for curved diffraction grating - Google Patents

Abstract

PURPOSE: To provide a method for forming a master disk of a curved diffraction grating used in the case of forming diffraction gratings on a curved surface. CONSTITUTION: The master disk of the curved diffraction gratings is formed by a stage for templating the diffraction gratings formed on a flat planar mother substrate with a film-like flexible material and a stage for sticking the film of the flexible material transferred with the diffraction gratings to a master substrate having the curved surface. In this case, the curved surface of the master substrate 4 is formed as a spherical surface 4a and the mother substrate 1 formed with the diffraction gratings 1a expressed by pitch T=T0 /(1+ε) when the elongation rate of the flexible material in the case of sticking the mother substrate to the spherical surface 4a is defined as ε and the pitch of the desired diffraction gratings as T0 is used. The master disk having the precise curved diffraction gratings 2a free from distortions is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a master for a curved diffraction grating for forming a diffraction grating on a curved surface such as a concave mirror.

[0002]

2. Description of the Related Art In recent years, a component in which a diffraction grating is formed on a concave mirror has been adopted for a spectrometer because it can simplify an optical system. This part is raised from the master disk and is efficiently reproduced by injection molding. Conventionally, as disclosed in JP-A-62-30201,
The photoresist pattern is obtained by exposing and then developing interference fringes on a spherical substrate coated with a photoresist by an aspherical interference exposure method using an aspherical wave as an interference exposure wavefront. And, as shown in the Tsushima product catalog,
The sawtooth diffraction grating is processed on the spherical surface by ion-beam etching the substrate from an oblique direction.

[0003]

However, the above-mentioned conventional method requires a complicated and large-scale apparatus called an interference exposure device, and when the interference fringes are exposed to generate an interference fringe of a desired pattern, it is possible to deal with it. Complex interferometric optics are required, and pattern restrictions will also occur depending on their feasibility. Further, in order to stabilize the interference fringes, extremely precise environmental management such as air flow, temperature, and vibration is required.

The present invention has been made in view of the above problems of the prior art, and is a master for a curved diffraction grating for forming a diffraction grating on a curved surface with a simple device and without requiring strict environmental management. The purpose is to provide a method.

[0005]

Means for Solving the Problems In order to solve the above problems, the present invention is configured as follows. According to a first aspect of the present invention, a step of forming a shape of a diffraction grating whose pitch spreads outward from the center on a flat mother substrate, and a step of shaping the shape of the diffraction grating with a film-shaped flexible material. Then, a master of a curved diffraction grating was prepared by a step of sticking a film-like flexible material having the shape of the diffraction grating on the curved surface of a master substrate having a curved surface made of a spherical surface.

According to a second aspect of the present invention, in the first aspect, when the flexible substrate is attached to the spherical surface of the master substrate, the elongation percentage of the flexible material at an arbitrary distance from the center position of the spherical surface is ε,
When the pitch of the desired diffraction grating is T ₀ , T = T ₀ /
It was decided to use a mother substrate on which a diffraction grating having a pitch represented by (1 + ε) was formed.

According to a third aspect of the present invention, there is provided a step of forming a shape of a diffraction grating formed on a flat mother substrate with a film-shaped flexible material, and a step of forming a film of the flexible material on which the diffraction grating is transferred. In the step of sticking to a curved master substrate and creating a master for a curved diffraction grating, as a master substrate, the curved surface makes the ratio of stretching of the flexible material film at the central portion and the outer peripheral portion of the master substrate constant. A master of a curved diffraction grating was prepared by using the substrate having the aspherical surface.

[0008]

According to the constitutions of claims 1 and 2, the following actions can be obtained. First of all, since the method of forming the diffraction grating on the flat mother substrate is taken first, forming the diffraction grating directly on the flat mother substrate does not require a particularly difficult technique and is more difficult than the conventional semiconductor process. The diffraction grating can be easily formed on a flat surface by a known method that is generalized in the above. Next, this diffraction grating is transferred to a thin film of a flexible material to obtain a stretchable and contractible film on which the diffraction grating is formed. Therefore, since the thin film of the flexible material can expand and contract even when the diffraction grating of the mother substrate is transferred in a flat state, the thin film of the flexible material can be attached on the curved surface of the master substrate. Therefore, it is possible to obtain a master of a curved diffraction grating by combining the conventional techniques.

Here, when the curved surface of the master substrate is a spherical surface, when the flexible material thin film 11 in which the diffraction grating 10a formed on the mother substrate 10 shown in FIG. As shown in FIG. 2 (b), the diffraction grating 11a formed on the flexible material thin film 11 attached to the master substrate is distorted so that the pitch of the central portion is wider than that of the outer peripheral portion. The cause of this distortion is that, when the flexible material thin film 11 is attached to the spherical surface of the master substrate, the thin film 11 is stretched along the spherical surface of the master substrate at different rates between the center and the outer periphery of the spherical surface. FIG. 3 is a diagram geometrically showing the difference in the ratio of the thin film 11 stretched on the spherical surface 4a of the master substrate 4, FIG. 3 (a) is a perspective view of the master substrate 4, and FIG. 3 (b) is FIG. The arc X of a) is shown. That is, the thin film 11 is stretched along the large arc O at the center of the spherical surface 4a, and is stretched along the arc X smaller than the arc O at the distance x from the center, and the pitch of the diffraction grating 11a depends on the stretched amount. Each spreads. As a result, in the diffraction grating 11a, as shown in FIG. 2B, distortion occurs in which the central pitch is wide and the outer peripheral pitch is narrow.

Therefore, as shown in FIG. 1 (a), if the diffraction grating 1a of the mother substrate 1 is formed so that the pitch of the central portion of the diffraction grating before the attachment is narrowed beforehand,
As shown in (b), when the film of the flexible material 2 having the diffraction grating 2a obtained by patterning the diffraction grating 1a is attached to the curved surface 4a of the master substrate 4, the central portion of the curved surface 4a of the master substrate 4 is There is no difference in the pitch of the diffraction grating 2a from the outer peripheral portion, and distortion of the diffraction grating 2a can be eliminated.

Specifically, as shown in FIG. 3 (a), a distance x from the center o of the large arc O and the chord of the arc O (bottom of the arc, the same applies hereinafter) at the center of the spherical surface 4a of the master substrate 4.
Consider a small arc X parallel to the arc O at the position. Assuming that the length of the chord of the arc O is D, the length of the chord of the small arc X D _X
Becomes like the formula (1). Further, when the radius of curvature of the spherical surface 4a (arc O) is R, the radius R _X of the arc X centered on the center O _X of the small arc _X is given by equation (2), and the half angle of the center angle of the arc X is Where α is α, the length L of the arc X is expressed by equation (3). On the other hand, since the original length L ₀ of the planar flexible material film attached to the portion of the arc _X is the same as the chord length D _X of the arc X, it is represented by the formula (1), The elongation rate ε when the material film is attached to the spherical surface 4a of the master substrate 4 is given by the equation (4).
become that way. Therefore, the master substrate 4 having the spherical surface 4a
With respect to the pitch T _{0 of the} diffraction grating required on the curved surface 4a at the position of the above-mentioned arbitrary distance x from the center O of T, the pitch T of the diffraction grating formed on the flat mother substrate at the distance x is T ( x) = T ₀ / (1 + ε (x)). The above formulas (1) to (4) are shown below.

[0012]

[Equation 1]

According to the structure of claim 3, the following actions can be obtained. When a flexible material film is attached to the curved surface of the master substrate, if the curved surface of the master substrate is spherical, the ratio ε (x) at which the film is stretched is different between the central portion and the outer peripheral portion of the master substrate. Although distortion will occur in the diffraction grating, ε (x) =
By using an aspherical curved surface that is constant, distortion of the diffraction grating on the master substrate can be eliminated.

[0014]

【Example】

[First Embodiment] A first embodiment of the present invention will be described with reference to FIG. FIG. 4 is a cross-sectional view showing the process of this embodiment, and FIG.
Is a process of molding the diffraction grating of the mother substrate into silicon rubber,
FIG. 4B shows a step of sticking silicone rubber to the master substrate, and FIG. 4C shows a state where silicone rubber is stuck to the spherical surface of the master substrate.

First, as shown in FIG. 4 (a), the shape of the blazed grating 1a formed on the flat mother substrate 1 is molded with a silicone rubber 2 made of a flexible material. Next, as shown in FIG. 4 (b), after the lattice 2a transferred from the mother substrate 1 faces upward, the film of the silicone rubber 2 is attached to the upper end surface of the sleeve 3, and then as shown in FIG. 4 (c). , The master substrate 4 is inserted from the bottom of the sleeve 3, and the spherical surface 4a of the master substrate 4 is moved so as to come into contact with the back surface of the silicon rubber 2 (the side opposite to the surface on which the lattice 2a is provided). Is attached along the convex spherical surface 4a of the master substrate 4 to form the blazed grating 5 on the convex spherical surface 4a of the master substrate 4.

In this embodiment, as the master substrate 4, a case where a diffraction grating is formed on a convex spherical surface having a radius of curvature of 82 mm and a diameter of 40 mm will be described. In this case, the elongation rate ε of the silicon rubber 2 calculated from the dimensions of the master substrate 4 is about 1% at the center of the master substrate 4 as shown in FIG. 5, and decreases toward the outer periphery. Therefore, using the value of the elongation rate ε obtained from the graph of FIG. 5, as shown in FIG. 6, the pitch of the diffraction grating 1a on the mother substrate 1 is set to T ( x) = T ₀ /
The distribution represented by (1 + ε (x)) was given. The mother substrate 1 may be formed by drawing a diffraction grating pattern on a glass plate by a known technique such as photolithography.

In this embodiment, when the mother substrate 1 on which the diffraction grating 1a is formed in consideration of the elongation of the silicon rubber 2 film is used, the diffraction grating 1a is separated from the mother substrate 1.
When the film of the silicon rubber 2 on which the pattern is copied is attached to the spherical surface 4a of the master substrate 4, the deformation of the diffraction grating 2a due to the expansion of the film of the silicon rubber 2 is offset.

According to this embodiment, it is possible to form a distortion-free diffraction grating on the spherical surface 4a of the master substrate 4 with a simple apparatus as described above. Therefore, it is possible to produce a precise curved diffraction grating by using this as a master and forming a molding die by an electroforming method.

[Second Embodiment] A second embodiment of the present invention will be described with reference to FIGS. 7 and 8. FIG. 7 is a perspective view showing a partial cross section of the master substrate used in this embodiment, and FIG. 8 is a perspective view showing a silicon rubber film in which a diffraction grating stuck to the curved surface of the master substrate is modeled.

In this embodiment, a flat plate on which parallel and equidistant diffraction gratings are formed is used as a mother substrate, and a master substrate 7 having a convex aspherical surface 7a is used.
As shown in FIG. 7, the shape of the aspherical surface 7a of the master substrate 7 has a cross section parallel to the central axis of the master substrate 7 and the aspherical surface 7a.
With respect to the length L of the line of intersection with the line L and the length L ₀ of the line of intersection (chord) between the cross section and the bottom surface of the aspherical surface 7a, a ratio L / L ₀ thereof is constant in any cross section. To use. The other steps are the same as in the first embodiment.

In this embodiment, a film of silicon rubber 8 having a diffraction grating 8a obtained by patterning a diffraction grating pattern from a flat mother substrate (not shown) is formed on the master substrate 7 having the aspherical surface 7a (see FIG. 8) is attached,
Since the elongation rate ε of the film is ε = (L / L ₀ ) −1 = constant, the elongation of the film of the silicon rubber 8 depends on the master substrate 7
Is constant on any part of the aspherical surface 7a.

According to this embodiment, the diffraction grating 8a formed on the film of the silicon rubber 8 is formed on the aspherical surface 7a of the master substrate 7.
Even if the diffraction grating 8a is attached to the substrate, no strain is generated in the diffraction grating 8a. Therefore, also in this embodiment, it is possible to produce a precise master of a curved diffraction grating with a simple device.

[0023]

According to the present invention, the following effects can be obtained. According to the method of claims 1 and 2, when a film-shaped flexible material having a diffraction grating formed thereon is attached to the curved surface of the master substrate, diffraction is performed at a pitch according to the rate at which the flexible material is stretched. Since the grating pattern is formed on a flat mother substrate and this diffraction grating is molded with a flexible material, it is possible to create a precise curved diffraction grating master without distortion with a simple device. .

According to the third aspect of the present invention, the curved surface of the master substrate is formed into an aspherical surface so that the ratio of the stretched film of the flexible material between the central portion and the outer peripheral portion thereof becomes constant. Diffraction grating formed on a flat-plate mother substrate that is molded with a flexible material can be made into a parallel diffraction grating pattern, and a simple curved disc diffraction grating master can be created with a simple device. You can

[Brief description of drawings]

1A and 1B are conceptual diagrams illustrating the present invention, FIG. 1A is a perspective view showing a mother substrate, and FIG. 1B is a perspective view showing a master of a curved diffraction grating.

2A is a plan view showing a mother substrate on which parallel diffraction gratings are formed, and FIG. 2B is a flexible material having a diffraction grating formed from the mother substrate of FIG. 2A. FIG. 6 is a plan view showing a state in which the film of FIG.

FIG. 3 is a diagram for explaining the operation of the present invention.
3A is a perspective view showing a master substrate, and FIG. 3B is an arc X.
FIG.

FIG. 4 is a cross-sectional view showing the process of Embodiment 1 of the present invention.
4A is a step of molding the diffraction grating of the mother substrate on silicon rubber, FIG. 4B is a step of attaching the silicon rubber to the master substrate, and FIG. 4C is a step of attaching the silicon rubber to the spherical surface of the master substrate. It shows the state.

FIG. 5 is a diagram showing an elongation rate of silicon rubber stuck on the spherical surface of the master substrate used in Example 1 of the present invention.

6 is a diagram showing pitches of diffraction gratings formed on a mother substrate based on FIG.

FIG. 7 is a perspective view showing a partial cross section of a master substrate used in Example 2 of the present invention.

FIG. 8 is a perspective view showing a silicone rubber modeled with a diffraction grating used in Example 2 of the present invention.

[Explanation of symbols]

 1 Mother Substrate 1a Diffraction Grating 2 Silicon Rubber 2a Diffraction Grating 4 Master Substrate 5 Diffraction Grating 4a Spherical 7 Master Substrate 7a Aspherical Surface 8 Silicon Rubber 8a Diffraction Grating

Claims (3)

[Claims] 1. A step of forming a shape of a diffraction grating whose pitch spreads outward from the center on a flat mother substrate, a step of shaping the shape of the diffraction grating with a film-like flexible material, A method of producing a master for a curved diffraction grating, comprising a step of sticking a film-shaped flexible material having a shape of the diffraction grating onto the curved surface of a master substrate having a curved surface made of a spherical surface. 2. When affixed to a spherical surface of a master substrate, where the elongation percentage of the flexible material at an arbitrary distance from the center position of the spherical surface is ε and the desired pitch of the diffraction grating is T ₀ , T = The method for producing a master for a curved diffraction grating according to claim 1, wherein a mother substrate having a diffraction grating with a pitch represented by T ₀ / (1 + ε) is used. 3. A step of molding the shape of a diffraction grating formed on a flat mother substrate with a film-shaped flexible material, and a film of the flexible material to which the diffraction grating is transferred is formed on a curved master substrate. In the step of sticking and making a master of a curved diffraction grating, as the master substrate, the curved surface has an aspherical surface in which the ratio of stretching of the flexible material film is constant between the central portion and the outer peripheral portion of the master substrate. A method for producing a master for a curved diffraction grating, characterized by using a substrate.