JP2001322130A - Method for manufacturing diffraction optical element and method for manufacturing mold to be used for manufacturing the element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a diffraction optical element of a high diffraction efficiency wherein a round part and a fine surface roughness which are left as unprocessed, do not exist substantially, and a blaze shape wherein a flatness of a slant face part is good, is provided. SOLUTION: In a method for manufacturing a diffraction optical element having a required shape, a process for manufacturing a master mold 1 of a deeper shape than a shape corresponding to a required shape; a process for forming a processing layer 3 on a substrate 2 which is substantially transparent in a wavelength band by using a material which is more easy to processed than the substrate 2 is; a process for forming the processing layer 3 by using the manufactured master mold 1; a process for processing by removing a projected part end face R3 of the formed processing layer 3 to shape corresponding to the required shape; and a process for forming a surface shape of the processing layer 3 to the substrate 2 approximatively in a depth direction by etching the processing layer 3 and the substrate 2, are provided.

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 a diffractive optical element having a structure such as a relief type grating on the surface and a method for manufacturing a mold used for manufacturing the diffractive optical element.

[0002]

2. Description of the Related Art In recent years, diffractive optical elements and Fresnel lenses have attracted attention due to demands for higher performance and smaller and lighter optical systems. Diffractive optical elements having a relief-type grating structure are useful because a high diffraction efficiency can be obtained by blazing, ie, sawtoothing the groove cross-sectional shape. Conventionally, as a method for manufacturing a diffractive optical element, the following is known.

(Conventional example a) A method of applying a resist on a substrate, performing exposure and development treatments to form a predetermined pattern on the resist, and then transferring the pattern shape of the resist to the substrate by dry etching. (Conventional example b) After applying a resist on a substrate, performing a process of exposing and developing to form a predetermined pattern on the resist and performing etching or deposition.
A method of forming an approximate blazed shape on a substrate by changing masks repeatedly (binary method). (Conventional example c) A method of directly processing a grating groove on a substrate using a focused ion beam. (Conventional example d) A method in which a grating groove is directly formed on a substrate using a ruling engine type machine or a lathe. (Conventional Example E) For example, as disclosed in JP-A-10-232306, a mold manufactured by cutting with a cutting machine and a quartz substrate coated with a polymer film on one side are placed in a press machine. Set, raise the temperature, press-mold to transfer the mold shape to the polymer film, and then form a blazed shape by reactive ion etching of the quartz substrate having the polymer film with the transferred mold shape. Method.

[0004]

However, in the method of manufacturing the diffractive optical element of the prior art (a), the remaining film thickness of the resist is
Because it has the property that it does not change linearly with exposure dose, for example, when creating a blazed shape by electron beam exposure on the resist surface, the exposure dose must be precisely controlled according to the characteristics of the resist. For this purpose, it is necessary to precisely control the intensity or line width of the electron beam in the electron beam exposure apparatus. For this reason, there is a problem that the apparatus becomes complicated and expensive, and it is difficult to draw a large area. Furthermore, since the pattern shape may deviate from the design value in the fine pattern part due to scattering or proximity effect of electron beam, far ultraviolet ray, ultraviolet ray, etc. in the resist used for exposure, the diffractive optical element is efficiently and accurately manufactured. There is a problem that it becomes difficult to do.

In a conventional method for manufacturing a diffractive optical element,
Since a desired blaze shape can be obtained only as a shape approximating a stepped shape, there is a problem that diffraction efficiency is reduced.

In the conventional method for manufacturing a diffractive optical element of the prior art C,
Since the spot diameter of the focused ion beam is as small as about 0.1 μm, fine processing is possible. On the other hand, it is affected by the instability of the ion source and the penetration depth is shallow, so The desired depth may not be obtained. In addition, since the processing speed of the ion beam is low, there is a problem that processing takes a very long time.

In the conventional method of manufacturing a diffractive optical element,
For example, when glass is used as the material of the diffractive optical element, the tool for directly processing the glass has significant wear,
Due to the poor processing efficiency, a large amount of cost and an enormous amount of time are required to produce a diffraction grating having a practical area. For this reason, this method has a problem that the material of the substrate is substantially limited to a material such as metal which is easy to process.

[0008] In the conventional method for manufacturing a diffractive optical element according to E,
In the finishing stage of the die manufacturing process, a desired blazed shape is obtained by cutting with a tool, and the accuracy of the blazed shape depends on the accuracy of the tool to be used. That is, depending on the size of the nose radius R of the tool tip used for processing, an R portion as an unprocessed portion is formed at the bottom of the blazed shape obtained by cutting, or fine surface roughness remains, and There is a problem that the diffraction efficiency is deteriorated because they are transferred to the blaze shape of the diffractive optical element molded by using the mold and finally the precision as a molded product is deteriorated.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention according to claim 1 or 3 is to substantially eliminate the presence of an unprocessed R portion or fine surface roughness. And the flatness of the slope has a good blaze shape,
An object of the present invention is to provide a method for manufacturing a diffractive optical element for obtaining a diffractive optical element having high diffraction efficiency.

An object of the present invention according to claim 2 or 4 is to have a blazed shape in which substantially no unprocessed R portion or fine surface roughness is present and the flatness of the slope portion is good.
An object of the present invention is to provide a method of manufacturing a mold used for manufacturing a diffractive optical element, which can obtain a diffractive optical element having high diffraction efficiency.

[0011]

According to a first aspect of the present invention, there is provided a method of manufacturing a diffractive optical element having a desired shape, wherein the master has a shape deeper than a shape corresponding to the desired shape. A step of manufacturing a mold, and a step of forming a processed layer on a substrate that is substantially transparent in a wavelength band to be used by using a material that is easier to process than the substrate, and using the manufactured master mold. A step of forming the processed layer, a step of removing the end face of the convex portion of the formed processed layer to a shape corresponding to a desired shape, and etching the processed layer and the substrate to form a surface shape of the processed layer. Is formed on the substrate similarly in the depth direction.

According to a second aspect of the present invention, there is provided a method of manufacturing a mold having a desired shape used for manufacturing a diffractive optical element, wherein a step of manufacturing a master mold having a shape deeper than a shape corresponding to the desired shape is provided. Forming a processed layer on a mold substrate using a material that is easier to process than the mold substrate; forming the processed layer using the manufactured master mold; and forming the processed layer. Removing the end face of the convex portion to a shape corresponding to a desired shape, and etching the processing layer and the mold substrate, so that the surface shape of the processing layer is similar to the depth direction on the mold substrate. Forming.

According to a third aspect of the present invention, there is provided a method of manufacturing a diffractive optical element having a desired shape, the method comprising: Pressing a glass material made of a low-melting glass heated and softened by using the mold to obtain a diffractive optical element substrate having a boundary surface of a desired shape; and forming a thermoplastic resin on the boundary surface of the diffractive optical element substrate. Press-molding and integrating the resin to obtain a diffractive optical element having a two-layer structure.

According to a fourth aspect of the present invention, there is provided a method of manufacturing a mold having a desired shape used for manufacturing a diffractive optical element, comprising the steps of manufacturing a master mold having a shape deeper than a shape corresponding to the desired shape. Forming a working layer constituting at least one surface of the intermediate mold using a master mold, removing the end face of the convex portion of the formed working layer to a shape corresponding to a desired shape; And electroforming to transfer the shape of the mold to obtain a mold.

In the method of manufacturing a diffractive optical element according to the first aspect of the present invention, the end face of the convex portion of the processing layer on the substrate formed by the master die formed into a shape deeper than the shape corresponding to the desired shape is formed. Remove to the shape corresponding to the shape,
By etching the processing layer and the substrate, the processing layer disappears and the surface shape of the processing layer is formed on the substrate in a similar manner in the depth direction to obtain a diffractive optical element having a desired surface shape.

According to a second aspect of the present invention, there is provided a method of manufacturing a mold for use in manufacturing a diffractive optical element, comprising: forming a projection of a processing layer on a mold substrate formed by a master mold having a shape deeper than a shape corresponding to a desired shape; The end surface is removed to a shape corresponding to the desired shape, and the processed layer and the mold substrate are etched to remove the processed layer, and the surface shape of the processed layer on the mold substrate is similar to the depth direction. Then, a mold having a molding surface of a desired shape is obtained.

According to a third aspect of the invention, there is provided a method for manufacturing a diffractive optical element, wherein a mold is manufactured by the method for manufacturing a mold used for manufacturing a diffractive optical element according to the second aspect, and the mold is heated and softened. Obtain a diffractive optical element substrate having a boundary surface of a desired shape by press-molding a glass material made of a low-melting glass that has been formed, and press-molding and integrating a thermoplastic resin on the boundary surface of the diffractive optical element substrate, A two-layer diffractive optical element is obtained.

According to a fourth aspect of the present invention, in the method of manufacturing a mold used for manufacturing a diffractive optical element, at least one surface of an intermediate mold is formed using a master mold having a shape deeper than a shape corresponding to a desired shape. Forming a layer, removing the convex end face of the formed processing layer to a shape corresponding to a desired shape,
Electroforming is performed to transfer the surface shape of the intermediate processing layer to obtain a mold having a molding surface of a desired shape.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The outline of the invention according to claim 1 will be described. A working layer made of, for example, resin, which is easy to machine, is formed on a substrate, such as glass, which is substantially transparent in the wavelength band to be used and is difficult to machine. Separately from this, a master mold used for forming a working layer is manufactured, and at this time, an unprocessed portion which is estimated to remain at the bottom of the concave portion due to the size of a nose radius R of a tool tip used for manufacturing is eliminated. Work deeper than desired. Next, the processed layer is formed using a master mold. The blazed shape of the processed layer obtained by this process is a transcript of the blazed shape of the master mold as it is.
The shape concave portion is formed as the surface roughness of the blazed shape of the processing layer or the R-shaped convex portion at the corner of the tip.

Next, a removal process such as a cutting process or a grinding process is performed on the blazed convex portion of the processed layer,
A desired blaze shape is obtained by removing the R shape and the surface roughness at the tip corner. For this reason, the accuracy of the blaze shape is not affected by the size of the nose radius R of the tool tip used for machining the master die, and high accuracy can be maintained. Next, the processed layer and the substrate are eroded by an etching method selected from dry etching such as plasma etching and reactive etching, wet etching, and the like, so that the processed layer disappears and the surface shape of the processed layer is changed in the depth direction. Is transferred to the substrate in a similar manner. For this reason, it is more accurate than machining,
It becomes possible to manufacture a diffractive optical element having a desired shape.
In order to form the shape of the surface of the processed layer on the substrate, reactive ion etching with high anisotropy is desirable.

An outline of the invention according to claim 2 will be described. A processing layer made of, for example, resin, which is easy to machine, is formed on the mold substrate. Separately from this, a master die used for forming a working layer is manufactured, and at this time, a portion which remains unprocessed is formed at the bottom of the concave portion of the master die depending on a size of a nose radius R of a tool tip used for manufacturing. Not like
Work deeper than desired. Next, in the same manner as in the first aspect, a processed layer is formed using the master mold. Next, the blaze-shaped convex portion of the processed layer is subjected to removal processing such as cutting or grinding, for example, to remove the R shape and surface roughness at the corner of the tip, thereby completing the desired blaze shape. Next, the processed layer and the mold substrate are eroded by an etching method selected from dry etching such as plasma etching and reactive etching, wet etching, and the like, so that the processed layer disappears and the surface shape of the processed layer is reduced. Is similarly transferred to the mold substrate in the depth direction. For this reason, it is possible to manufacture a mold used for manufacturing a diffractive optical element having a desired shape with higher precision than machining.

An outline of the invention according to claim 3 will be described. First, a mold is manufactured according to the second aspect of the present invention. Using this mold, a glass material made of low-melting glass is heated and softened and pressed to manufacture a diffractive optical element substrate. Next, a thermoplastic resin is precision-pressed and integrated with the relief pattern surface of the diffractive optical element substrate to obtain a two-layer diffractive optical element.

An outline of the invention according to claim 4 will be described. A master mold used for forming a working layer is manufactured, and at this time, a nose radius R of a tool tip used for manufacturing the master mold is formed.
In order to prevent a portion that remains unprocessed at the bottom of the concave portion of the master mold depending on the size of the master mold, the work is processed deeper than a desired depth. Next, using this master mold, after forming a working layer that constitutes at least one surface of the intermediate mold, the blaze-shaped convex portion of the working layer is subjected to removal processing such as cutting or grinding to form a tip angle. The desired blaze shape is obtained by removing the R shape and surface roughness of the portion. Next, an electroforming process is performed on the surface of the processed layer that has been finished to the intermediate blazed shape, thereby producing an electroformed mold to which the blazed shape has been transferred. This makes it possible to manufacture a mold used for manufacturing a diffractive optical element having a desired shape with higher precision than machining. Hereinafter, specific embodiments will be described.

(Embodiment 1) FIGS. 1 to 6 show Embodiment 1, FIG. 1 is a sectional view showing a blazed shape of a master type, FIG. 2 is a structural view of a substrate of a diffractive optical element, and FIG. 4 is a diagram showing a molding process, FIG. 4 is a diagram showing an ion etching process, FIG. 5 is a cross-sectional view of a manufactured diffractive optical element, and FIG. 6 is a first-order diffraction efficiency of the diffractive optical elements of Embodiment 1 and Comparative Example 1. 3 is a table showing the wavelength dependence of the graph. This embodiment shows an example of a diffractive lens which is a diffractive optical element.

In FIG. 2, the substrate 4 of the diffractive optical element is
A processing layer 3 is coated on one side of the substrate 2 with a predetermined thickness T.₁Laminated
Has been established. The material of the substrate 2 is sufficient because of the post-process.
High rigidity and workability to etching
, For example, quartz, synthetic quartz, SiO₂System glass, L
iF, MgF₂, CaF₂, BaF₂, Sapphire, K
Br, KI, etc. are desirable, but wavelengths used for other materials
Any substance having sufficient transmittance in the band may be used. on the other hand,
The material of the processing layer 3 is methacrylic resin, polycarbonate
Resin, polysulfone resin, polyphenylene oxide tree
Fat, polymethylpentene resin, polyvinylidene fluoride
It is important that it is a thermoplastic resin such as fat and has a low coefficient of thermal expansion
And has excellent releasability from the master mold 1.
Is desirable. The processing layer 3 is formed by a spin coater
And baking conditions as appropriate.
More suitable hardness for the subsequent process. The thickness of the processing layer 3
Sa T ₁In the molding step described below,
The concave portion of the master mold 1 is set so that the convex portion does not contact the substrate 2.
Depth D₁(See FIG. 1).

Next, referring to FIG. 1, a description will be given of a blazed shape to be formed on the master mold 1 and a process of forming the blazed shape on the processing surface 1a by cutting. The material of the master mold 1 includes materials that are easily machined, for example, A
Metals such as l, P-Ni (electroless nickel), and brass are used. As shown in FIG. 1, the blaze shape as a shape deeper than the shape corresponding to the desired shape substantially reverses the blaze shape of the diffractive optical element (see FIG. 5) as the final product, and has a pitch p ₁ and a depth D. ₁ is several μm to several tens μ
m, the machined surface 1a includes a rising portion 1b, a slope portion composed of a gentle slope portion 1c and a steep slope portion 1d having different angles with respect to the rising portion 1b, a rising portion 1b and a steep slope portion 1d.
Nose radius R of the tip of the cutting tool used for cutting between d and
It consists recess R ₁ Metropolitan THAT formed. The formation of this blazed, extension of the gentle slope portion 1c (dotted line) uses byte having a selected end shape so as not to recess R _1. In this case, the depth D ₁ of the the recess R ₁ bottom surface of is the value obtained by adding a depth d ₁ to the desired height r ₁ of the concave portion R _1.

Next, as shown in FIG.
The step of press-molding the processed layer 3 of the base material 4 using will be described. First, the master mold 1 and the base material 4 are set on a press (not shown) so that the processing surface 1a of the master mold 1 and the processing layer 3 of the base material 4 are opposed to each other. Heat and raise the temperature. This temperature is appropriately adjusted depending on the type of resin used for the processing layer 3. When press forming is performed in this state, a blazed shape obtained by inverting the blazed shape formed on the processed surface 1a of the master mold 1 is transferred to the surface 3a of the processed layer 3. That is, the nose radius R is not formed in the concave portion on the surface 3a of the processing layer 3, and the slope 3d corresponding to the steep slope 1d of the master mold 1 (see FIG. 1).
Leading protrusion R ₃ as protrusion end face is to be formed on the. Here, the pressure molding step may be performed in the air, but is performed in an inert gas atmosphere such as nitrogen or argon because the resin constituting the processing layer 3 may be oxidized and burned to the master mold 1. It is desirable. Master type 1
To silicone resin, fluorine resin, stearates,
By applying a release agent such as waxes, the releasability of the processed layer 3 after press molding may be enhanced. In this case, the release agent is made as thin as possible (preferably 0.2 μm or less), and By uniformly applying, the blazed shape formed on the processing surface 1 a of the master mold 1 can be faithfully transferred to the surface 3 a of the processing layer 3.

Next, after the base material 4 having the pressed working layer 3 is cooled to room temperature, the surface 3a of the working layer 3 is subjected to removal processing to obtain a desired blaze shape. That is,
Subjected to cutting at the same angle as the gentle slope portion 3c to the convex portion R ₃ shown in FIG. 3, by removing the hatched portion, as shown in FIG. 4, the desired height d of the surface shape of the working layer _Thus , a blazed processing layer 3 having the number ₁ is obtained. At this time, in the case where the diffractive optical element to be manufactured is like a diffractive lens having a ring pattern, a cutting machine (not shown) such as a numerical control lathe has a processed layer 3 subjected to press forming as a work. The base material 4 is attached. Then, while rotating the work, a cutting tool (not shown) is moved based on the design data of the diffraction lens to be manufactured, and the processing layer 3 is cut into a desired shape. On the other hand, when manufacturing a diffractive optical element having a linear pattern, for example, a diffractive cylindrical lens, using a cutting machine (not shown) such as a numerically controlled milling machine or a ruling engine type machine,
Move the work up, down, left and right with the tool fixed, or
Alternatively, the work layer 3 is cut into a desired shape by moving the cutting tool up, down, left and right while the work is fixed.

Thereafter, the base material 4 having the cut working layer 3 is set in a reactive ion etching apparatus, and a flow rate of 30 c is applied by an etching gas 5 composed of CF _4.
Anisotropic etching is performed under the conditions of m ³ / min, pressure of 5 Pascal, and power of 100 watts until the processing layer 3 is completely etched and disappears. Thereby, the substrate 2 of the substrate 4
Obtained, as shown in FIG. 5, similar to the height of the blaze shape of the processed layer 3 in the depth direction to form a blazed as desired shape so that the d _4, the diffractive optical element 6 Was.

In the present embodiment, the substrate 2 is made of LaFK55
(Low melting point glass made by Sumita Optical Co., Ltd.) with refractive index n _d
Is 1.694 and Abbe number ν _d is 56.3. At this time, the depth d ₁ of the blazed shape is set to 0.76 μm, and 51
The maximum diffraction efficiency was obtained at a wavelength of 0 nm.
FIG. 6 shows the wavelength dependence of the diffraction efficiency. FIG. 6 shows the wavelength dependence of the diffractive optical element manufactured by the manufacturing method of the present embodiment (Embodiment 1), and FIG. 3 shows the wavelength dependence of the diffractive optical element (Comparative Example 1). As is clear from FIG. 6, the diffractive optical element according to the first embodiment has a diffraction efficiency close to the theoretical diffraction efficiency as compared with the comparative example 1, so that it cannot be avoided in the related art. The reduction in diffraction efficiency due to the unprocessed nose radius R of the blaze shape can be suppressed to a substantially negligible level, and it has been proved that the improvement effect is remarkable.

According to the present embodiment, there is substantially no unprocessed R portion or fine surface roughness, the sloping portion has a good flatness, and the diffraction efficiency is high. A diffractive optical element can be manufactured.

(Embodiment 2) FIGS. 7 to 11 show Embodiment 2, FIG. 7 is a sectional view showing a blazed shape of a master mold, FIG. 8 is a structural view of a mold base material, and FIG. FIG. 10 is a diagram showing a process, FIG. 10 is a diagram showing an ion etching process, and FIG. 11 is a cross-sectional view of the formed molding die. In the present embodiment, a method of manufacturing a molding die for molding a diffractive lens, which is a diffractive optical element, and a method of manufacturing a diffractive optical element using the molding die will be described. In the present embodiment, there are portions similar to those of the method of manufacturing the diffractive optical element of the first embodiment. Therefore, portions different from the first embodiment will be mainly described, and the same portions will be briefly described.

Referring to FIG. 7, a description will be given of a blazed shape formed on the master mold 11 and a process of forming the blazed shape on the processing surface 11a by cutting. The same material as in the first embodiment is used for the material of the master mold 11. The blaze shape as a shape deeper than the shape corresponding to the desired shape is almost the same as the blaze shape of the diffractive optical element (see FIG. 5) as the final product as shown in FIG.
The pitch p ₂ and the depth D ₂ are both several μm to several tens μm, and the machined surface 11a is composed of a rising part 11b, a gentle slope part 11c and a steep slope part 11d having different angles with respect to the rising part 11b. Slope section consisting of
consists recess R ₁₁ Metropolitan formed by the nose radius R of the tip of bytes used for cutting between the b and the steep slope portion 11d. The blaze in the formation of the shape, extension of the gentle slope portion 11c (dotted line) uses byte having a selected end shape so as not to recess R _11. In this case, the depth _{D 2} from the surface of the recess _{R 11} bottom surface to the height _{r 2} and depth _{d 2} and a value obtained by adding the desired recess _{R 11.}

In FIG. 8, a mold substrate 14 is formed by forming a processing layer 13 on one side of a substrate 12 as a mold substrate to a predetermined thickness T _2.
It is configured by being laminated on. The material of the substrate 12 is required to have a sufficient hardness and heat resistance, such as cemented carbide, Si
C, stainless alloy, Ni, Zn, Al and the like are preferable. On the other hand, the same material as that of the first embodiment is used for the material of the processing layer 13. Conditions of thickness T ₂ of the forming method and processing layer 13 of the working layer 13 is the same as in the first embodiment.

Next, as shown in FIG.
The process of press-molding the processing layer 13 of the mold base material 14 using 1 will be described. First, the master mold 11 and the mold base material 14 are set on a press (not shown) such that the working surface 11a of the master mold 11 and the work layer 13 of the mold base material 14 face each other. The temperature is raised to a temperature at which the material softens. This temperature is appropriately adjusted depending on the type of resin used for the processing layer 13. When press forming is performed in this state, a blazed shape obtained by inverting the blazed shape formed on the processed surface 11a of the master mold 11 is transferred to the surface 13a of the processed layer 13. That is, the surface 13 of the processing layer 13
In FIG. 7A, the nose radius R is not formed in the concave portion, and the slope 13 corresponding to the steep slope 11d of the master mold 11 (see FIG. 7).
protrusions R ₁₃ as protrusion end face is to be formed at the tip of the d. Here, it is desirable that the pressing step be performed in an atmosphere of an inert gas such as nitrogen or argon. The use of the release agent is the same as in the first embodiment.

Next, after cooling the mold base 14 having the press-formed work layer 13 to room temperature, the surface 13a of the work layer 13 is subjected to removal processing to obtain a desired blaze shape. That is, the gentle slope portion 13c to the protrusion _{R 13} shown in FIG. 9
The same angle subjected to cutting and, by removing the hatched portion, as shown in FIG. 10 to obtain the working layer 13 of the blaze shape having a desired height d ₂ of the surface shape of the working layer. At this time, when the diffractive optical element to be manufactured is like a diffractive lens having a ring pattern, and when a diffractive optical element having a linear pattern, for example, a diffractive cylindrical lens is manufactured, each is performed in the same manner as in the first embodiment.

Thereafter, the mold base 14 having the cut working layer 13 is set in a reactive ion etching apparatus, and a flow rate of 30 cm ³ / min, a pressure of 5 Pascal, a power of 100 is applied by an etching gas 15 composed of CF _4. Under the condition of watts, anisotropic etching is performed until the processing layer 13 is completely etched and disappears. As a result, as shown in FIG. 11, the height dimension of the blazed shape of the processing layer 13 is made similar to the depth direction on the substrate 12 of the mold base 14.
_Then , a blaze shape as a desired shape was formed so as to obtain a molding die 16 as a die.

Using the molding die 16 thus obtained, a diffractive optical element is manufactured by plastic injection molding. The diffractive optical element injection-molded using the molding die 16 has substantially no unprocessed R portion similarly to the diffractive optical element obtained by the manufacturing method of the first embodiment. In addition, the diffractive optical element has a blaze shape having a good flatness of the slope portion and a high diffraction efficiency.

The method of manufacturing the diffractive optical element using the molding die 16 is not limited to the injection molding method, but may be, for example, a photopolymer method (2P method). This involves forming an ultraviolet-curable resin (photopolymer) layer on a transparent substrate, pressing a molding die 16 and irradiating ultraviolet rays from the substrate side to cure the ultraviolet-curable resin, thereby forming a diffractive optical element. What you get. Since this method does not require a temperature cycle, compared to the injection molding method, in addition to its effects, (1) the process can be shortened, (2) birefringence and coma are less likely to occur, and (3) molding There is an advantage that the service life of the tool can be extended.

In the molding die manufactured by the manufacturing method of this embodiment, when the material of the die substrate is a cemented carbide or SiC, the diffractive optical element made of glass is pressed. Obtainable. In this case, in addition to the effect of the resin-made diffractive optical element by the injection molding method or the photopolymer method, a diffractive optical element having a long life and good weather resistance can be obtained.

According to the present embodiment, a molding die having a blazed shape having substantially no unprocessed R portion or fine surface roughness and a good flatness of the slope portion is obtained. be able to. Further, by using this molding die, it is possible to accurately and mass-produce a diffractive optical element having high diffraction efficiency even by a conventional manufacturing method.

(Third Embodiment) FIGS. 12 and 13 show a third embodiment. FIG. 12 is a sectional view of a manufactured diffractive optical element having a two-layer structure. FIG. 13 is a third embodiment and a comparative example 2. 6 is a table showing the wavelength dependence of the first-order diffraction efficiency of the diffractive optical element of FIG. In the present embodiment, a method of manufacturing a diffractive optical element having a two-layer structure using a mold for forming a diffractive optical element obtained by the manufacturing method described in Embodiment 2 will be described. The description of the method for manufacturing the molding die described in the second embodiment will be omitted.

First, as shown in FIG. 11, a molding die 16 made of a cemented carbide was obtained by the manufacturing method described in the second embodiment. The depth of the blazed shape of mold 16 _{d 5} was set to 7.7 .mu.m. The depth _{d 5} is 1
2. Material La of substrate 21 as diffractive optical element substrate shown in FIG.
The depth is optimized so that the maximum diffraction efficiency can be obtained at a wavelength of 450 nm for the combination of the material FK55 and the material O-PET of the laminate 22.

Next, using the molding die 16,
Low melting glass base made of LaFK55 as material
The plate 21 (see FIG. 12) is softened by heating and precision pressed.
On one side, the blaze-shaped relief pattern
Was molded into a flat surface on the other side. Next, FIG.
As shown, the thermoplastic resin O-PET (Kanebo Co., Ltd.)
Precision pressing on the relief pattern surface of No. 21 and low melting point glass
And a laminate 22 made of thermoplastic resin.
And two layers having a relief pattern on the boundary surface
A diffractive optical element 23 having the structure was obtained. In addition, the thermoplastic resin O
-Refractive index n of PET _dIs 1.620, Abbe number ν_dIs 2
4.0.

FIG. 13 shows the wavelength dependence of the diffraction efficiency of the diffractive optical element 23 having a two-layer structure. FIG. 13 shows the wavelength dependence of the diffractive optical element 23 manufactured by the manufacturing method of the present embodiment. 3) shows the wavelength-dependent characteristics (Comparative Example 2) of the diffractive optical element 23 manufactured using a mold manufactured by a conventional manufacturing method. As is apparent from FIG. 13, the diffraction optical element according to the third embodiment has a diffraction efficiency close to the theoretical diffraction efficiency as compared with Comparative Example 2, so that it cannot be avoided in the prior art. The reduction in diffraction efficiency due to the unprocessed nose radius R of the blaze shape can be suppressed to a substantially negligible level, and it has been proved that the improvement effect is remarkable. Further, the maximum diffraction efficiency of Comparative Example 2 is 90%, which is lower than 95% of Comparative Example 1 (see FIG. 6), because the depth d of the blazed shape is smaller in Comparative Example 2 than in Comparative Example 1. Because it is about 10 times, the R portion becomes large.

According to the present embodiment, in addition to the effect of the first embodiment, the two-layer diffractive optical element according to the present embodiment has a wavelength dependence of the diffraction efficiency which is higher than that of the first embodiment. Characteristics can be suppressed to a substantially negligible level. Also, the light incident on the diffractive optical element is bent in a specific direction, but the wavelength dependence of the light bending action is complementary between the relief pattern and the surface in contact with the outside (refractive surface). There is also an effect that chromatic aberration is reduced. Furthermore, in a normal refractive element (for example, a lens),
When the surface is contaminated with dust or fingerprints, it is generally difficult to wipe it off.However, since the relief pattern is formed at the interface between the low-melting glass and the thermoplastic resin, the effect of the contamination does not occur, and the anti-contamination effect does not occur. The environment is improved.

(Fourth Embodiment) FIGS. 14 to 17 show a fourth embodiment, FIG. 14 is a view showing a molding step, FIG. 15 is a sectional view of an intermediate mold, and FIG. 16 is a view showing an electroforming process step. FIG.
FIG. 3 is a sectional view of the manufactured electroforming mold. In this embodiment,
A method of manufacturing a molding die for molding a diffractive lens, which is a diffractive optical element, and a method of manufacturing a diffractive optical element using the molding die will be described. In the present embodiment, since there are portions similar to those of the method for manufacturing the diffractive optical element of the first embodiment, portions different from the first embodiment will be mainly described, and similar portions will be briefly described.

Referring to FIG. 14, a description will be given of a blazed shape formed on the master mold 31 and a step of forming the blazed shape on the processing surface 31a by cutting. The same material as in the first embodiment is used for the material of the master mold 11. Blazed as deeper shape than the corresponding shape to the desired shape, as shown in FIG. 14, the blazed shape of the diffractive optical element (see FIG. 5) as a final product substantially inverted, and the pitch p ₃ and depth and _{D 3} are both number μm~
In the case of several tens μm, the processed surface 31a is
And a gentle slope portion 3 having a different angle with respect to the rising portion 31b.
A slope portion consisting 1c and steep slope 31d, consists recess R ₃₁ Metropolitan formed by the nose radius R of the tip of bytes used for cutting between the rising portion 31b and a steep slope portion 31d. In order to form this blaze shape, the gentle slope 3
1c extension of (dotted line) uses byte having a selected end shape so as not to recess R _31. At this time, the depth D ₃ from the bottom surface of the concave portion R ₃₁ is
The height r ₃ of ₃₁ to a value obtained by adding a depth d ₃ of desired.

Next, the intermediate mold 33 shown in FIG. 15 will be described. The intermediate mold 33 is a master mold for manufacturing an electroforming mold 35 (see FIG. 16) described later by electroforming. The material of the intermediate mold 33 is made of a thermoplastic resin, and may have any thickness as long as sufficient strength and rigidity are secured. Further, in the present embodiment, a solid thermoplastic resin is used as the base material and the processed layer is used. However, a two-layer base material composed of the substrate and the thermoplastic resin is used, and the thermoplastic resin portion is used as the processed layer. Is also good.

Next, as shown in FIG. 14, a process of press-molding the intermediate mold base material 32 using the master mold 31 will be described. First, the master mold 31 and the intermediate mold base material 32 are placed on a press (not shown) by a processing machine 31 of the master mold 31.
a and the processing layer surface of the intermediate base material 32 are set so as to face each other, and the temperature is raised to a temperature at which the surface softens. This temperature is appropriately adjusted depending on the type of resin used for the intermediate mold base material 32. When press molding is performed in this state, a blazed shape obtained by inverting the blazed shape formed on the processing surface 31a of the master mold 31 is transferred to the surface 32a of the intermediate mold base material 32. That is, the surface 3 of the intermediate mold base material 32
The 2a, nose radius R is not formed in the recess, so that the protrusions R ₃₂ as protrusion end face at the distal end of the inclined surface 32d corresponding to the steep slope portion 31d of the master mold 31 is formed.
Here, it is desirable that the pressing step be performed in an atmosphere of an inert gas such as nitrogen or argon. The use of the release agent is the same as in the first embodiment.

Next, after the press-formed intermediate mold base material 32 having a blazed shape is cooled to room temperature, the surface 32a of the intermediate mold base material 32 is subjected to removal processing to obtain a desired blazed shape. That is, the blaze shape having subjected to the same angle by cutting and gentle slope portion 32c to the protrusion R ₃₂ shown in FIG. 14, by removing the hatched portion, as shown in FIG. 15, the desired height dimension d ₃ The intermediate mold 33 having the surface 33a is obtained. At this time, when the diffractive optical element to be manufactured is like a diffractive lens having a ring pattern, and when a diffractive optical element having a linear pattern, for example, a diffractive cylindrical lens is manufactured, each is performed in the same manner as in the first embodiment.

Next, a conductive metal, for example, nickel is deposited on the surface 33a of the intermediate mold 33 by a method such as sputtering or vapor deposition to form an electrode body. Next, the intermediate mold 33 having the electrode body 34 formed on the surface 33 a is immersed in a nickel plating bath and subjected to an electroforming process for energizing to form a nickel electroforming mold 35. Then, after the nickel electroforming mold 35 is released from the intermediate mold 33, the outer periphery of the nickel electroforming mold 35 is ground. On the surface 35a of the nickel electroformed mold 35 as a mold obtained at this time, together with the electrode body 34,
A blazed shape that is the reverse of the blazed shape formed on the surface 33a of the intermediate mold 33 is formed, and the nickel electroforming mold 35 for obtaining the diffractive optical element is completed.

The method of manufacturing the diffractive optical element using the nickel electroforming mold 35 is the same as that of the second embodiment. The diffractive optical element is made of a thermoplastic resin by the injection molding method, and the ultraviolet curable resin is made by the photopolymer method. Can be obtained respectively.

According to the present embodiment, the molding die having a blazed shape having substantially no unprocessed R portion or fine surface roughness and having a good flatness of the slope portion is etched. It can be obtained without depending on. Further, by using this molding die, it is possible to accurately and mass-produce a diffractive optical element having high diffraction efficiency even by a conventional manufacturing method.

It should be noted that from the specific embodiment described above,
The technical idea of the following configuration is derived. (Supplementary note) (1) A thermoplastic resin is injection-molded using a mold manufactured by the method for manufacturing a mold used for manufacturing the diffractive optical element according to claim 2 or 4, to obtain a diffractive optical element. A method for manufacturing a diffractive optical element.

According to appendix (1), R which remains unprocessed
Parts and fine surface roughness are substantially absent, and the flatness of the slope part has a good blazed shape, and it is possible to accurately and mass-produce a diffractive optical element made of a thermoplastic resin having high diffraction efficiency. it can.

(2) An ultraviolet-curable resin is molded by a photopolymer method using a mold manufactured by the method for manufacturing a mold used for manufacturing a diffractive optical element according to claim 2 or 4, to form a diffractive optical element. A method for manufacturing a diffractive optical element.

According to appendix (2), R which remains unprocessed
To accurately and mass-produce a diffractive optical element made of a UV-curable resin having high diffraction efficiency, having a blazed shape with substantially no flat part or fine surface roughness and good flatness of the slope part. Can be.

(3) An optical glass is formed by press molding using a mold manufactured by the method for manufacturing a mold used for manufacturing a diffractive optical element according to claim 2 to obtain a diffractive optical element. A method for manufacturing a diffractive optical element.

According to appendix (3), R which remains unprocessed
Part and fine surface roughness are substantially absent, and the flatness of the slope part has a good blazed shape, and it is possible to accurately and mass-produce a diffractive optical element made of optical glass having high diffraction efficiency. .

[0061]

According to the first aspect of the present invention, there is substantially no R portion or fine surface roughness left unprocessed, and the sloping portion has a blaze shape with good flatness, A diffractive optical element having high diffraction efficiency can be manufactured.

According to the second aspect of the present invention, there is provided a mold having a blaze shape having substantially no unprocessed R portion or fine surface roughness and a good flatness of the slope portion. be able to. Also, by using this mold,
Even by a conventional manufacturing method, a large number of diffractive optical elements having high diffraction efficiency can be obtained accurately.

According to the third aspect of the invention, in addition to the effect of the first aspect, the wavelength dependence of the diffraction efficiency of the diffractive optical element can be suppressed to a substantially negligible level. Also, the light incident on the diffractive optical element is bent in a specific direction, but the wavelength dependence of the light bending action is complementary between the relief pattern and the surface in contact with the outside (refractive surface). There is also an effect that chromatic aberration is reduced. Furthermore, in a normal refractive element (for example, a lens),
When the surface is contaminated with dust or fingerprints, it is generally difficult to wipe it off.However, since the relief pattern is formed at the interface between the low-melting glass and the thermoplastic resin, the effect of the contamination does not occur, and the anti-contamination effect does not occur. The environment is improved.

According to the fourth aspect of the present invention, there is substantially no unprocessed R portion or fine surface roughness, and a blaze shape having a good flatness of the slope portion. Can be obtained without relying on etching. Further, by using this molding die, it is possible to accurately and mass-produce a diffractive optical element having high diffraction efficiency even by a conventional manufacturing method.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a blaze shape of a master die according to a first embodiment.

FIG. 2 is a configuration diagram of a substrate of the diffractive optical element according to the first embodiment.

FIG. 3 is a diagram showing a molding step according to the first embodiment.

FIG. 4 is a diagram showing an ion etching step of the first embodiment.

FIG. 5 is a cross-sectional view of the manufactured diffractive optical element according to the first embodiment.

FIG. 6 is a table showing the wavelength dependence of the first-order diffraction efficiency of the diffractive optical elements according to the first embodiment and the first comparative example.

FIG. 7 is a cross-sectional view showing a blaze shape of a master die according to the second embodiment.

FIG. 8 is a configuration diagram of a mold base material according to a second embodiment.

FIG. 9 is a diagram showing a molding step according to the second embodiment.

FIG. 10 is a diagram showing an ion etching step of the second embodiment.

FIG. 11 is a sectional view of a molding die manufactured in a second embodiment.

FIG. 12 is a cross-sectional view of a manufactured two-layer diffractive optical element according to the third embodiment.

FIG. 13 is a table showing the wavelength dependence of the first-order diffraction efficiency of the diffractive optical elements according to the third embodiment and the comparative example 2.

FIG. 14 is a diagram showing a molding step according to the fourth embodiment.

FIG. 15 is a sectional view of an intermediate mold according to the fourth embodiment.

FIG. 16 is a diagram showing an electroforming process according to a fourth embodiment.

FIG. 17 is a cross-sectional view of the manufactured electroforming mold according to the fourth embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Master type 2 Substrate 3 Processing layer R ₃ Convex part

 ────────────────────────────────────────────────── ─── Continued on the front page F-term (reference) 2H049 AA03 AA04 AA13 AA14 AA37 AA39 AA40 AA41 AA43 AA44 AA45 AA46 AA51 AA53 AA55 AA61 AA63 AA64 4F202 AA44 AH73 CA11 CB01 CD02 CD12 CD24 4G0AB A01

Claims (4)

[Claims] 1. A method of manufacturing a diffractive optical element having a desired shape, comprising the steps of: manufacturing a master mold having a shape deeper than a shape corresponding to the desired shape; and forming a master mold that is substantially transparent in a wavelength band to be used. A step of forming a processing layer using a material that is easier to process than the substrate, a step of forming the processing layer using the manufactured master mold, and a step of projecting the end face of the formed processing layer. A step of removing the processed layer to a shape corresponding to a desired shape; and a step of forming the surface shape of the processed layer on the substrate in a depth-wise similar manner by etching the processed layer and the substrate. Of manufacturing a diffractive optical element. 2. A method of manufacturing a mold having a desired shape used for manufacturing a diffractive optical element, comprising: a step of manufacturing a master mold having a shape deeper than a shape corresponding to the desired shape; A step of forming a processing layer using a material that is easier to process than a mold substrate, a step of forming the processing layer using the manufactured master mold, and a step of forming a convex end face of the formed processing layer. And removing the work layer and the mold substrate by etching to form a surface shape of the work layer in the mold substrate in a depth direction similar to the shape of the work layer and the mold substrate. A method for manufacturing a mold used for manufacturing a diffractive optical element, characterized by comprising: 3. A method of manufacturing a diffractive optical element having a desired shape, comprising: a step of manufacturing a die by the method of manufacturing a die used for manufacturing a diffractive optical element according to claim 2; A step of obtaining a diffractive optical element substrate having a boundary of a desired shape by pressing and molding a glass material made of a heat-softened low melting point glass, and pressing and molding a thermoplastic resin on the boundary of the diffractive optical element substrate. Obtaining a diffractive optical element having a two-layer structure by integrating them. 4. A method of manufacturing a mold having a desired shape used for manufacturing a diffractive optical element, comprising: a step of manufacturing a master mold having a shape deeper than a shape corresponding to the desired shape; Forming a working layer forming at least one surface of the mold, removing the convex end face of the formed working layer to a shape corresponding to a desired shape, and transferring the shape of the working layer. Casting a mold to obtain a mold. A method of manufacturing a mold for use in manufacturing a diffractive optical element.