JP2017167231A - Replica optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a replica optical element with which it is possible to reduce the occurrence of stray light.SOLUTION: Provided is a replica optical element 10 fabricated by a manufacturing method that includes a mold release agent film formation step of forming a groove-shaped mold release agent film 43 on the groove surface of a mold plate 30, a metal film formation step of forming a groove-shaped metal film 44 on the mold release agent film 43, a bonding step of closely adhering the metal film 44 and the underside of a glass substrate 11 via adhesive resin, and a reflection type optical element fabrication step of fabricating a replica optical element 10' having an adhesive resin layer 12 and the metal film 44 adhered to the glass substrate 11 by removing the glass substrate 11 form the mold plate 30. A vertical refractive index R satisfies expression (1), where nis a refractive index of glass to a line d and nis a refractive index of the adhesive resin to the line d.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a replica optical element used in various optical instruments such as a spectrophotometer, and more particularly to a replica diffraction grating that is mounted with a fixed installation angle in a spectrograph.

  Conventionally, when mass-producing diffraction gratings, a manufacturing method (White & Fraser replica method) in which a replica diffraction grating is produced from a master diffraction grating has been employed (see, for example, Patent Document 1).

  In the “White & Fraser replica method”, a master diffraction grating is formed by first depositing a metal such as aluminum on the upper surface of a master substrate (glass substrate) to form a master metal thin film and forming a grating groove in the master metal thin film. To do. Next, using this master diffraction grating as a matrix, forming a thin oil film (release agent film) on the upper surface of the grating surface (master metal thin film), forming a replica metal thin film on the upper surface of the oil film by vacuum deposition, A replica metal thin film having a lattice groove shape is formed. Next, a replica substrate (glass substrate) is bonded to the upper surface of the replica metal thin film via an adhesive, and after the adhesive is cured, the replica substrate is removed from the mother die. Thereby, the replica metal thin film formed on the upper surface of the oil film moves to the replica substrate, and a replica reflection type diffraction grating is obtained.

Furthermore, a replica transmission diffraction grating can be obtained by performing wet etching using sodium hydroxide (caustic soda) or the like to dissolve the replica metal thin film.
Such replica reflection diffraction gratings and replica transmission diffraction gratings are mainly used in spectrographs.

Japanese Patent Laid-Open No. 7-261010

  By the way, when analyzing a sample in the spectral mode of a spectroscope, the monochromatic light wavelength-separated by a replica transmission diffraction grating is incident on the sample and the degree of absorption is measured. When light of a wavelength, that is, stray light is mixed, it becomes noise and causes a decrease in analysis sensitivity and analysis accuracy. Such stray light is not a problem when the wavelength of light to be handled is relatively long, specifically, in the case of infrared light or visible light. In particular, when the wavelength to be handled is reduced, for example, soft X-rays or the like. It was a problem when performing spectroscopy.

In order to solve the above-mentioned problems, the present inventors have conducted intensive studies on a replica optical element that can reduce the generation of stray light.
Here, the refractive index n ₁ of the glass “BK7 (a kind of synthetic quartz)” of the replica substrate is 1.518 (d line), and the refractive index n ₂ of the adhesive resin is 1.56 (d line). Reflected at the interface between the replica substrate and the adhesive resin layer, reflected and scattered light is emitted in the same direction as the regular diffracted light and becomes stray light. From these facts, it was found that stray light becomes a problem when the vertical reflectance R with respect to the d-line is 2 × 10 ⁻⁴ .

  Further, for the purpose of improving the adhesion between the replica substrate and the adhesive, in order to widen the adhesion area, a surface on which the adhesive is applied to the replica substrate is formed as a micro uneven surface. However, this slit surface causes stray light. Therefore, it was found that stray light becomes a problem when the surface roughness S is 14 μmRms.

That is, the replica optical element of the present invention forms a release agent film forming step of forming a groove-shaped release agent film on the groove surface of the template, and forms a groove-shaped metal film on the release agent film. A metal film forming step, an adhesion step in which the upper surface of the metal film and the lower surface of the glass substrate are brought into close contact with each other through an adhesive resin, and removing the glass substrate from the mold plate, whereby the adhesive resin layer and the glass substrate a replica optical element produced by the production method comprising a reflective optical element fabricating step of fabricating a replica optical element which a metal film is bonded, the refractive index at the d-line of the glass and n _1, for the adhesive When the refractive index of the resin with respect to the d-line is n ₂ , the vertical reflectance R satisfies the following formula (1).
R = (n ₁ −n ₂ ) ² / (n ₁ + n ₂ ) ² ≦ 1.0 × 10 ⁻⁵ (1)

  In the present invention, the case where the vertical direction is reversed and used in the reverse direction is also included.

  As described above, according to the replica optical element of the present invention, when the vertical reflectance R satisfies Expression (1), reflected light and scattered light are reduced, and stray light can be reduced. This also improves the analysis accuracy and sensitivity when used in a spectroscope, and contributes to a significant improvement in analysis accuracy particularly in a short wavelength region such as soft X-rays.

(Means and effects for solving other problems)
In the replica optical element of the present invention, the surface roughness S of the lower surface of the glass substrate may satisfy the following formula (2).
S ≦ 1.0 (nmRms) (2)
According to the replica optical element of the present invention, when the surface roughness S satisfies the expression (2), reflected light and scattered light are further reduced, and stray light can be reduced.

In the replica optical element of the present invention, the adhesive resin may contain a coupling agent.
According to the replica optical element of the present invention, the adhesive resin is mixed with, for example, a coupling agent typified by a silane coupling agent that improves the bonding between the organic component and the inorganic component. Even if the surface is not a ground surface but a glossy surface, high adhesiveness can be secured, and the metal film can be firmly attached to the replica substrate.

In the replica optics of the present invention, a coupling agent is applied to the lower surface of the glass substrate before the upper surface of the metal film and the lower surface of the glass substrate are brought into close contact with each other through the adhesive resin in the bonding step. There may be.
According to the replica optical element of the present invention, the coupling agent is applied to the adhesive surface of the replica substrate which is a glossy surface, and the adhesive resin is applied or deposited thereon, thereby improving the adhesiveness of the coupling agent. Thus, the metal film can be firmly attached to the replica substrate.

In the replica optical element of the present invention, the metal film is removed from the replica reflective optical element, so that the replica transmissive optical element including the adhesive resin layer having a groove surface and the glass substrate can be used. Good.
Furthermore, in the replica optical element of the present invention, the template may be a master diffraction grating or a negative diffraction grating, and the replica optical element may be a replica diffraction grating.

Sectional drawing which shows an example of the replica transmission type diffraction grating which concerns on this invention. Explanatory drawing of the manufacturing method of the replica transmission type diffraction grating which concerns on this invention. Explanatory drawing of the manufacturing method of the replica transmission type diffraction grating which concerns on this invention. Explanatory drawing of the manufacturing method of the replica transmission type diffraction grating which concerns on this invention. Explanatory drawing of the manufacturing method of the replica transmission type diffraction grating which concerns on this invention. Sectional drawing which shows an example of a master diffraction grating. The graph which shows the relationship between the wavelength of diffracted light, and light intensity. The graph which shows absolute diffraction efficiency.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the embodiments described below, and includes various modes without departing from the spirit of the present invention.

FIG. 1 is a cross-sectional view showing an example of a replica transmission diffraction grating according to the present invention.
The replica transmission diffraction grating 10 includes a replica substrate 11 and an adhesive resin layer 12.

The replica substrate 11 has six surfaces including upper and lower surfaces and front, rear, left and right side surfaces, and has a flat plate shape having a thickness of 11 mm, front and rear 60 mm, and left and right 60 mm, for example.
The surface roughness S of the upper surface of the replica substrate is preferably 1.0 (nmRms) or less, and more preferably 0.5 (nmRms) or less. Moreover, it is preferable that an AR coat (center wavelength: 400 nm) such as MgF ₂ having a predetermined thickness (for example, 70 nm) is applied to the lower surface of the replica substrate.

  The adhesive resin layer 12 is formed on the upper surface of the replica substrate 11, and the upper surface (lattice surface) of the adhesive resin layer 12 is a lattice groove (for example, a sawtooth shape having a groove number of 200 / mm and a blaze angle of 8.6 °). Is formed.

Examples of the material of the replica substrate include quartz glass, low-expansion crystal glass such as Zerodur (registered trademark: manufactured by SCHOTT), BK7, PYREX (registered trademark) glass, and soda glass. It is done.
Examples of the material for the adhesive resin layer include thermosetting resins such as urea resins, melamine resins, phenol resins, and epoxy resins, and ultraviolet curable resins.
In the present invention, when the refractive index with respect to the d-line of the material of the replica substrate 11 is n ₁ and the refractive index with respect to the d-line of the adhesive resin 12 is n ₂ , the vertical reflectance R is expressed by the equation (1). You will be satisfied.
R = (n ₁ −n ₂ ) ² / (n ₁ + n ₂ ) ² ≦ 1.0 × 10 ⁻⁵ (1)
That is, the vertical reflectance R is particularly preferably 1.0 × 10 ⁻⁵ or less and 4 × 10 ⁻⁷ or less.

  Here, an example of a manufacturing method of the replica transmission type diffraction grating 10 according to the present invention will be described with reference to FIG. The manufacturing method includes a master diffraction grating preparation step (A-1), a release agent film formation step (B-1), a negative metal film formation step (B-2), and an adhesion step (B-3). , Negative diffraction grating preparation step (B-4), release agent film formation step (C-1), replica metal film formation step (C-2), adhesion step (C-3), reflection diffraction Including a grating fabrication step (C-4) and a transmission diffraction grating fabrication step (C-5).

(A-1) Master diffraction grating preparation step First, the master diffraction grating 20 is prepared. FIG. 3 is a cross-sectional view showing an example of a master diffraction grating. The master diffraction grating 20 includes a master substrate 21 and a master metal thin film 22.
The master substrate 21 has six surfaces including an upper surface (lattice surface), a lower surface, and front, back, left, and right side surfaces. On the upper surface of the master substrate 21, lattice grooves (for example, 200 grooves / mm, blaze angle 8.6 °). (Sawtooth shape).
Examples of the material of the master substrate include quartz glass, low-expansion crystal glass such as zerodur, BK7, pyrex glass, soda glass, and the like, similar to the replica substrate.

The master metal thin film 22 is formed on the upper surface (lattice surface) of the master substrate 21 so as to have a predetermined thickness. That is, the master metal thin film 22 has a lattice groove shape.
The predetermined thickness of the master metal thin film is preferably 0.1 μm or more and 2 μm or less. Examples of the material of the master metal thin film include aluminum, gold, platinum, chromium, nichrome, nickel, and the like.

  An example of a manufacturing method of such a master diffraction grating 20 will be described. First, OFPR (registered trademark) 5000 is used as a photoresist (photosensitive resist film) on a glass substrate (float glass) 21 having a size of 60 mm × 60 mm × 11 mm. (Tokyo Ohka Kogyo Co., Ltd.) is coated with a thickness of 0.4 μm, and a resist pattern of lattice grooves (density: 200 lines / mm) is exposed on this photoresist by a holographic exposure method (laser wavelength: 441.6 nm). Then, after immersing in a developer for an appropriate time, a resist pattern is formed. Next, sawtooth-shaped lattice grooves having a blaze angle of 8.6 ° are formed by anisotropic ion beam etching using the resist pattern as a mask. Next, a master metal thin film 22 having a thickness of 0.2 μm is formed on the lattice grooves by vacuum deposition. In this way, the master diffraction grating 20 is completed. The engraving may be mechanical engraving using a diffraction grating engraving apparatus or engraving using ion beam etching.

(B-1) Release agent film forming step (see FIG. 2A)
An oil film (release agent film) 41 is formed on the grating surface of the master diffraction grating 20 so as to have a predetermined thickness.
Examples of the method for forming the oil film include a vacuum vapor deposition method. When using the vacuum vapor deposition method, the film is formed uniformly on the lattice plane while maintaining a certain distance from the vapor deposition source. For example, it is preferable to perform revolution rotation or planet rotation (revolution rotation + rotation rotation). The predetermined thickness of the oil film is preferably 4 nm or more and 10 nm or less, and examples of the material of the oil film include silicone oil.

(B-2) Negative metal film forming step (see FIG. 2B)
A negative metal thin film 42 is formed on the oil film 41 so as to have a predetermined thickness. That is, the negative metal thin film 42 has a lattice groove shape.
Examples of the method for forming the negative metal thin film include the vacuum deposition method described above. The predetermined thickness of the negative metal thin film is preferably 0.1 μm or more and 2 μm or less. Examples of the material of the negative metal thin film include aluminum, gold, platinum, chromium, nichrome, nickel, and the like. It is done.

(B-3) Adhesion Step A flat blue plate 31 is prepared, and an adhesive resin is applied to the lower surface of the blue plate 31 to form an adhesive resin layer 32 ′ (see FIG. 2C). Next, the blue plate 31 is pressed against the negative metal thin film 42 through the adhesive resin layer 32 ′ with an appropriate pressure (see FIG. 2D). At this time, the adhesive resin layer 32 ′ spreads so as to fill the lattice grooves having a sawtooth cross section of the negative metal thin film 42, thereby forming the adhesive resin layer 32 having a lattice groove shape on the lower surface. Next, it is housed in a baking furnace and cured by applying heat at 60 ° C. for about 24 hours or by irradiating the adhesive resin layer 32 with ultraviolet rays.
The surface roughness S of the lower surface of the blue plate is preferably a ground surface, and examples of the material of the adhesive resin layer include thermosetting resins such as urea resin, melamine resin, phenol resin, and epoxy resin. And ultraviolet curable resin.

(B-4) Negative diffraction grating manufacturing process (see FIG. 2 (e))
When the blue plate 31 is removed upward from the master diffraction grating 20, the negative metal thin film 42 and the adhesive resin layer 32 are removed together with the blue plate 31 with the oil film (release agent film) 41 as a boundary. The oil film 41 remaining on the lower surface of the negative metal thin film 42 is removed by washing with a fluorine-based solvent (AK-255: manufactured by Asahi Glass Co., Ltd.) or the like.
As a result, the negative diffraction grating 30 in which the adhesive resin layer 32 and the negative metal thin film 42 are bonded to the blue plate 31 is produced.

(C-1) Release agent film forming step (see FIG. 2 (f))
An oil film (release agent film) 43 is formed on the grating surface of the negative diffraction grating 30 so as to have a predetermined thickness.
Examples of the method for forming the oil film include the vacuum deposition method described above. The predetermined thickness of the oil film is preferably 4 nm or more and 10 nm or less, and examples of the material of the oil film include silicone oil.

(C-2) Replica metal film forming step (see FIG. 2G)
A replica metal thin film 44 is formed on the oil film 43 so as to have a predetermined thickness. That is, the replica metal thin film 44 has a lattice groove shape.
Examples of the method for forming the replica metal thin film include the vacuum evaporation method described above. The predetermined thickness of the replica metal thin film is preferably 0.1 μm or more and 2 μm or less, and examples of the material of the replica metal thin film include aluminum, gold, platinum, chromium, nichrome, nickel, and the like. It is done.

(C-3) Adhesion Step A replica substrate 11 is prepared, the upper surface of the replica substrate 11 is polished to a predetermined surface roughness S, washed with a fluorine-based solvent, etc., and then an adhesive resin is applied to the upper surface of the replica substrate 11 Thus, an adhesive resin layer 12 ′ is formed (see FIG. 2H).
Examples of the polishing method for the upper surface of the replica substrate include double-sided lapping polishing.

At this time, before applying the adhesive resin to the upper surface of the replica substrate 11, it is preferable to add a coupling agent to the adhesive resin or apply the coupling agent to the upper surface of the replica substrate 11.
The coupling agent functions as a binder between an organic material and an inorganic material, and examples thereof include a silane coupling agent. Specific examples of the silane coupling agent include 3-glycidoxypropyltrimethoxy. Silane (“KBM-403”, manufactured by Shin-Etsu Chemical Co., Ltd.) and the like are useful.

  Then, the replica substrate 11 is pressed against the replica metal thin film 44 through the adhesive resin layer 12 ′ with an appropriate pressure (see FIG. 2I). At this time, the adhesive resin layer 12 ′ spreads so as to fill the lattice grooves having a sawtooth cross section of the replica metal thin film 44, thereby forming the adhesive resin layer 12 having a lattice groove shape on the upper surface. Next, it is placed in a baking furnace and cured by applying heat at 60 ° C. for about 24 hours or by irradiating the adhesive resin layer 12 with ultraviolet rays.

(C-4) Reflective diffraction grating manufacturing process (see FIG. 2 (j))
When the replica substrate 11 is removed downward from the negative diffraction grating 30, the replica metal thin film 44 and the adhesive resin layer 12 are removed together with the replica substrate 11 with the oil film (release agent film) 44 as a boundary. The oil film 43 remaining on the upper surface of the replica metal thin film 44 is removed by washing with a fluorine-based solvent or the like.
As a result, a replica reflective diffraction grating 10 ′ in which the adhesive resin layer 12 and the replica metal thin film 44 are bonded to the replica substrate 11 is manufactured.

(C-5) Transmission diffraction grating manufacturing process The replica reflection diffraction grating 10 'is immersed in a sodium hydroxide (caustic soda) solution to dissolve the replica metal thin film 44, and then taken out from the caustic soda solution and washed with pure water. Dry using a spinner or the like. Thereby, the replica transmission type diffraction grating 10 (refer FIG. 1) which consists of the replica board | substrate 11 and the adhesive resin layer 12 which has a grating | lattice surface can be produced.

  As described above, according to the replica transmission diffraction grating 10 according to the present invention, when the vertical reflectance R satisfies the expression (1), reflected light and scattered light are reduced, and stray light can be reduced. .

<Other embodiments>
The present invention can also be applied to, for example, an aspheric optical replica element, a spherical optical replica element, a planar optical replica element, and the like.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

<Example 1>
In the manufacturing method described above, surface roughness S is 1 nm RMS, thickness 11mm refractive index _{n 1} material is 1.562 (d line), front and rear 60mm, replica substrate of a flat shape of the left and right 60mm "N-SK11 with use of (SCHOTT Co.) ", of using the adhesive resin whose refractive index _{n 2} of the adhesive resin is 1.56 (d line), the number of grooves 200 present / mm, the blaze angle 8.6 ° serrated A replica transmission diffraction grating according to Example 1 having a shaped grating surface was produced. The vertical reflectance R is 4 × 10 ⁻⁷ .

<Example 2>
A replica transmission diffraction grating according to Example 2 was fabricated in the same manner as in Example 1 except that a replica substrate having a surface roughness S of 14 μmRms was used instead of the replica substrate having a surface roughness S of 1 nmRms. . The vertical reflectance R is 4 × 10 ⁻⁷ .

<Comparative Example 1>
Surface roughness S is 1 nm RMS, the refractive index _{n 1} of the material is in place the replica substrate to be 1.562 (d line), surface roughness S is 14MyumRms, refractive index _{n 1} of the material is 1.518 (d line) A replica transmission diffraction grating according to Comparative Example 1 was fabricated in the same manner as in Example 1 except that the replica substrate “BK7” to be used was used. The vertical reflectance R is 2 × 10 ⁻⁴ .

<Evaluation 1> Intensity of Diffracted Light Light was applied to the lower surface of the replica transmission type diffraction gratings according to Examples 1 and 2 and Comparative Example 1, and diffracted light emitted from the upper surface was detected. FIG. 4 is a graph showing the relationship between the wavelength of diffracted light and the light intensity.
As shown in FIG. 4, the diffracted light by the replica transmission type diffraction grating according to Comparative Example 1 has a large amount of stray light, but the diffracted light by the replica transmission type diffraction grating according to Examples 1 and 2 is stray light. There is almost no sharpness. That is, in the replica transmission type diffraction gratings according to Examples 1 and 2, stray light was suppressed to about 1/10 as compared with the replica transmission type diffraction grating according to Comparative Example 1.

<Evaluation 2> Absolute diffraction efficiency (Diffraction light intensity ratio of order 1 with respect to incident light intensity)
The lower surface of the replica transmission type diffraction grating according to Examples 1 and 2 and Comparative Example 1 was irradiated with light, and diffracted light emitted from the upper surface was detected. FIG. 5 is a graph showing the absolute diffraction efficiency.
As shown in FIG. 5, the absolute diffraction efficiency increased in the order of the replica transmission diffraction grating according to Comparative Example 1, the replica transmission diffraction grating according to Example 2, and the replica transmission diffraction grating according to Example 1. That is, the absolute transmission efficiency of the replica transmission diffraction gratings according to Examples 1 and 2 was improved by about 10% compared with the replica transmission diffraction grating according to Comparative Example 1.

  The present invention can be suitably used for a replica optical element or the like used in various optical devices such as a spectrophotometer.

DESCRIPTION OF SYMBOLS 10 Replica transmission type diffraction grating 10 'Replica reflection type diffraction grating 11 Replica substrate (glass substrate)
12 Adhesive resin layer 20 Master diffraction grating 30 Negative diffraction grating (template)
41 Oil film (release agent film)
43 Oil film (release agent film)
44 Replica metal thin film (metal film)

Claims (6)

A release agent film forming step of forming a groove-shaped release agent film on the groove surface of the template,
A metal film forming step of forming a groove-shaped metal film on the release agent film;
An adhesion step in which the upper surface of the metal film and the lower surface of the glass substrate are in close contact with each other through an adhesive resin;
A replica manufactured by a manufacturing method including a reflective optical element manufacturing step of manufacturing a replica optical element in which an adhesive resin layer and the metal film are bonded to the glass substrate by removing the glass substrate from the template An optical element,
The vertical reflectivity R satisfies the following formula (1) when the refractive index for the d-line of the glass is n ₁ and the refractive index for the d-line of the adhesive resin is n _2. Optical element.
R = (n ₁ −n ₂ ) ² / (n ₁ + n ₂ ) ² ≦ 1.0 × 10 ⁻⁵ (1) The replica optical element according to claim 1, wherein the surface roughness S of the lower surface of the glass substrate satisfies the following formula (2).
S ≦ 1.0 (nmRms) (2)   The replica optical element according to claim 2, wherein the adhesive resin contains a coupling agent.   3. In the bonding step, a coupling agent is applied to the lower surface of the glass substrate before the upper surface of the metal film and the lower surface of the glass substrate are brought into close contact with each other through the bonding resin. The replica optical element described in 1.   The replica reflective optical element comprising the adhesive resin layer having a groove surface and the glass substrate by removing the metal film from the replica reflective optical element. Item 5. The replica optical element according to any one of items 4 to 5. The template is a master diffraction grating or a negative diffraction grating,
The replica optical element according to claim 1, wherein the replica optical element is a replica diffraction grating.

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