JP5948071B2 - Optical element molding die, optical element manufacturing method, and optical element molding die manufacturing method - Google Patents

Description

  The present invention relates to an optical element molding die, an optical element manufacturing method, and an optical element molding die manufacturing method.

Conventionally, in an optical element molding die, a release film may be formed on a mirror surface formed in a shape that conforms to the surface shape of a molded product in order to improve mold release properties. It is also known to form a release film via an intermediate layer in order to improve the adhesion strength between the release film and the main body member and improve the durability of the release film.
For example, in the field of an optical element molding die for press molding a glass optical element, as shown in Patent Document 1, when a cemented carbide having tungsten carbide (WC) as a main component is used as a mold base material, An underlayer formed of titanium metal (Ti), an intermediate layer formed of titanium aluminum nitride (TiAlN), an adhesion layer formed of silicon carbide (SiC) formed by a plasma source ion implantation method, and A mold for optical element molding in which a release layer of tetrahedral amorphous carbon (taC) formed by a filtered arc cathodic vacuum arc method (FCVA method) is sequentially laminated on a mold base material has been proposed. Yes.

JP 2010-159174 A

However, the conventional optical element molding die as described above has the following problems.
The material used for the intermediate layer needs to be a material having good adhesion to both the main body member and the release film, but since there are few choices for such an intermediate layer, it should be used for the main body member or the release film. The choice of materials that can be made was narrow.
For example, in the press molding of a glass optical element, a good intermediate layer material has been found when the main body member is a cemented carbide, whereas the mold release film has a good mold releasability. However, this intermediate layer may not have good adhesion to the sintered body of the silicon carbide body member. For this reason, for example, in order to use a silicon carbide sintered body for the main body member and use a similar release film, an intermediate layer suitable for silicon carbide is required.
Such an intermediate layer has a problem that the number of processes increases and the manufacturing time increases because the film configuration is more complicated than the conventional intermediate layer. Moreover, there is a problem that the number of processes is likely to cause problems such as film peeling and foreign matter mixing.

  The present invention has been made in view of the above problems, and an optical element molding die and an optical that can improve the adhesion between the release film and the main body member without complicating the film configuration. It aims at providing the manufacturing method of the element shaping die.

In order to solve the above problems, an optical element molding die of the present invention, the surface portion formed in a shape along the surface shape of the molded article, and more grain growth, the surface roughness is the maximum height (R _Z ) And a molding surface that is laminated on the surface portion of the main body member via the projections and depressions and is in close contact with the molding material so as to be releasable. And a release film to be configured.

Further, in the optical element molding die of the present invention, the uneven portion has a surface roughness of a maximum height (R _Z ) of 0. It can be 2 μm or more and 1 μm or less.

  In the optical element molding die of the present invention, the release film can be a multilayer film including at least a lowermost layer laminated on the uneven portion and an outermost layer forming the molding surface. is there.

  In the optical element molding die of the present invention, the surface portion and the concavo-convex portion of the main body member can be made of silicon carbide.

  The method for producing an optical element of the present invention is a method for obtaining the molded product by molding the molding material using the mold for molding an optical element molding of the present invention.

The method for producing an optical element molding die of the present invention includes a mirror surface forming step for forming a mirror surface having a shape along the surface shape of a molded product on a surface portion of a main body member, and grain growth on the mirror surface to form a surface on the mirror surface. A grain growth step for forming an uneven portion having a roughness of a maximum height (R _Z ) of 0.1 μm or more and 2 μm or less, and a separation film for forming a release film on the surface portion of the main body member via the uneven portion. And a mold film forming step.

  According to the optical element molding die of the present invention and the method for manufacturing the optical element molding die, an uneven portion due to grain growth is formed on the surface portion of the main body member, and a release film is formed through the uneven portion. There is an effect that the adhesion between the release film and the main body member can be improved without complicating the film configuration.

It is typical sectional drawing which shows an example of the optical element shaping | molding die of the 1st Embodiment of this invention. FIG. 2 is a schematic partial enlarged view of an A (B) portion in FIG. 1 and schematic partial enlarged views of a C portion and a D portion of the partial sectional view. It is a typical fragmentary sectional view which shows an example of the film structure of the mold release film used for the optical element shaping | molding die of the 1st Embodiment of this invention. It is a flowchart which shows the process flow of the manufacturing method of the optical element shaping | molding die of the 1st Embodiment of this invention. It is typical process explanatory drawing of the mirror surface formation process of the manufacturing method of the optical element shaping | molding die of the 1st Embodiment of this invention, and a grain growth process. It is a typical sectional view showing the principal part of the optical element fabrication die of a 2nd embodiment of the present invention, and a typical partial enlarged view of the J section. It is a typical sectional view showing the principal part of the optical element fabrication die of the modification of the 1st and 2nd embodiments of the present invention, and the typical partial enlarged view of the K section.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. In all the drawings, even if the embodiments are different, the same or corresponding members are denoted by the same reference numerals, and common description is omitted.

[First Embodiment]
An optical element molding die according to the first embodiment of the present invention will be described.
FIG. 1 is a schematic cross-sectional view showing an example of an optical element molding die according to the first embodiment of the present invention. FIG. 2A is a schematic partial enlarged view of a portion A (B) in FIG. 2B and 2C are schematic partial enlarged views of a C part and a D part in FIG. 2A, respectively. FIG. 3 is a schematic partial cross-sectional view showing an example of a film configuration of a release film used in the optical element molding die according to the first embodiment of the present invention.

The mold for molding an optical element according to the present embodiment constitutes a part of a mold assembly for manufacturing a glass optical element such as a lens by pressing a glass material, and the shape of the optical surface of the optical element. A molding surface for transferring the material to the glass material.
The type of the optical element is not particularly limited as long as it is made of glass. For example, an appropriate type such as a lens, a prism, a mirror, a filter, or a substrate can be adopted. When the optical element has a curvature, it may be convex or concave.
Hereinafter, as an example of an optical element, an example in the case of molding a meniscus lens (not shown) having a convex lens surface and a concave lens surface will be described.

A mold assembly 1 for molding the lens includes a lower mold 2 (optical element molding mold), an upper mold 3 (optical element molding mold), and a body mold 4 as shown in FIG.
The lower die 2 is a substantially columnar member having a cylindrical side surface 2b. A flange portion 2c protruding from the side surface 2b in the outer peripheral direction is formed at one axial end portion (lower side in FIG. 1). A molding surface 2a having a concave shape that transfers the shape of the convex lens surface to the glass material is formed at the other end (upper side in FIG. 1).

The side surface 2b and the flange portion 2c are formed by the surface of the substrate 2A formed of a material having high hardness and good heat resistance.
As a material of the base material 2A, for example, a sintered body of silicon carbide (SiC) can be employed.

On the other end side in the axial direction of the substrate 2A, as shown in FIG. 2 (a), the molding surface 2a of the along formed as a concave surface of the substrate on S _2A-shaped, the specular layer 2B, releasing The film 2C is laminated in this order, and the molding surface 2a is constituted by the outermost surface of the release film 2C.

Mirror forming layer 2B, as well as to smooth the uneven shape of the substrate surface S _2A, the surface portion in contact with the release film 2C, the two-dot chain line in specular s ₂ along the shape of the molding surface 2a _(FIG. 2 (b) After forming (see FIG. _2B ), an uneven portion S _2B (see FIG. _2B ) for improving the adhesion to the release film 2C is formed.
Uneven portion S _2B is a concavo-convex shape formed by grain growth specular s ₂ constituting the surface portion of the mirror layer 2B.
As the size of the concavo-convex portion of the concavo-convex portion _S2B, an appropriate concavo-convex amount can be employed in which the adhesion strength of the release film 2C is good and the surface accuracy of the molding surface 2a is not more than an allowable value.
Depending on the molded article the lens surface surface accuracy required to, for example, if the lens used in the camera, as the magnitude of a suitable unevenness, the maximum height R _Z of the surface roughness (JIS B 0601-2001) is, Examples thereof include 0.1 μm or more and 2 μm or less.
R _Z is, for 0.1μm smaller than, less likely anchor effect is obtained for the release film 2C, the adhesion strength is lowered. The crystal is coarsened, when R _Z exceeds 2, the surface area is reduced, the anchor effect will be reduced, adhesion between the release film becomes insufficient. Moreover, the surface unevenness | corrugation is too large, the surface accuracy of the molding surface 2a will deteriorate, and the surface accuracy of the convex lens surface of the molded product to which the shape of the molding surface 2a will be transferred will deteriorate.
Therefore, _{R Z} is, 0.1 [mu] m or more, and more preferably a narrower range in the range of 2 [mu] m. For example, R _Z is more preferably in the range of 0.2 μm or more and 1 μm or less.

Here, the maximum height R _Z, the portion withdrawn by reference length from a cross-sectional curve (hereinafter, referred to as extraction portion) when sandwiching the extracted portion in two straight lines parallel to the average line of the cross-section the distance between the two straight lines It is measured in the direction of the vertical magnification of the curve, and the value is expressed in micrometer units (μm).

The material of the specular layer 2B is a material easy close contact with irregularities capable smoothing a substrate surface S _2A of the substrate surface S _2A, if it is possible to form the uneven portion S _2B by grain growth, especially It is not limited.
As a method for forming the mirror surface forming layer 2B, an appropriate film forming method, for example, a sputtering method, a molecular beam epitaxial method, a chemical vapor deposition method (CVD method), or the like may be employed depending on the material of the mirror surface forming layer 2B. it can.

The release film 2C can adopt an appropriate layer configuration of an appropriate material as long as the outermost layer is a material having a good releasability from the glass material used for molding. The layer configuration may be, for example, a single layer configuration or a multilayer configuration.
In general, when the substrate is made of a cemented carbide whose main component is tungsten carbide (WC), the structure of the release film suitable for the sintered body of SiC does not have good adhesion strength. In the embodiment, since the concavo-convex portion _S2B is formed in the mirror surface forming layer 2B, a release film in the case of using such a cemented carbide as a base material is also suitable. As described above, the unevenness S _2B of the present embodiment improves the adhesion strength even if it is a well-known release film configuration in which good adhesion strength cannot be obtained only by forming it on the mirror surface of a conventional base material. can do. Therefore, the release film 2C is not limited to the release film for cemented carbide, but other known release films are also suitable.
In the present embodiment, a film configuration suitable for such a cemented carbide is employed as an example of the release film 2C.
That is, as shown in FIG. 3, the film configuration of the release film 2C is from the uneven portion S2B of the mirror surface forming layer _2B to the base layer 5 (lowermost layer), the metal layer 6, the nitride layer 7, and the surface layer 8. (Outermost layer) are laminated in this order.
As a method for forming the release film 2C, for example, an evaporation method, a sputtering method, a CVD method, or the like can be used, but an ion beam sputtering method is particularly preferable from the viewpoint of the film density and the purity of the film composition.

The underlayer 5 is a layered portion that covers and adheres to the concavo-convex portion _S2B , and is formed in an amorphous state from at least one material of tungsten (W) and tungsten carbide (WC).
The metal layer 6 is a layered portion made of a material having good adhesion strength with the base layer 5 and made of at least one metal material of chromium (Cr), titanium (Ti), and molybdenum (Mo).
The nitride layer 7 is a layered portion made of a material having good adhesion strength with the metal layer 6 and is made of a nitride containing at least one element of Cr, Ti, and Mo.
The surface layer 8 is a layered portion made of a material that has good adhesion strength with the nitride layer 7 and has good releasability from the glass material used for molding.
Since the surface of the surface layer 8 constitutes the molding surface 2a, it is a mirror surface with a small surface roughness. For example, the arithmetic average roughness _Ra is 0.005 μm or less.
Examples of suitable materials for the surface layer 8 include noble metals. Particularly suitable materials include at least one element selected from the group consisting of platinum (Pt), palladium (Pd), iridium (Ir), osmium (Os), ruthenium (Ru), and rhenium (Re). Examples thereof include an element, an alloy containing at least one element in the element group, and a compound containing at least one element in the element group.

Outermost in the structure of such a release film 2C, the base layer 5 constitutes the bottom layer is laminated to the uneven portion S _2B of the mirror forming layer 2B, the surface layer 8, which forms a molding surface 2a Is configured.

Examples of particularly suitable film configurations of the release film 2C include the following film configurations.
When the underlayer 5 is made of WC, the metal layer 6 is made of Cr, and the nitride layer 7 is made of CrN, or these are the main components, the surface layer 8 is made of an alloy of Pt and Ir, Ir and Re. An alloy or a metal made of Pt is particularly suitable.
Further, when the underlayer 5 is made of WC, the metal layer 6 is made of Ti, and the nitride layer 7 is made of TiN, or these are the main components, the surface layer 8 is made of an alloy of Pt and Ir, Ir and An alloy with Re and a metal made of Pt are particularly suitable.

  The upper die 3 is a substantially columnar member having a cylindrical side surface 3b having the same outer diameter as that of the side surface 2b of the lower die 2, and protrudes from the side surface 3b to the outer circumferential direction at one axial end (upper side in FIG. 1). A flange 3c is formed, and a molding surface 3a having a convex shape for transferring the shape of the concave lens surface of the optical element to the glass material is formed at the other end in the axial direction (lower side in FIG. 1).

The side surface 3b and the flange portion 3c are formed by the surface of the base material 3A made of the same material as that of the lower mold 2.
On the other end side in the axial direction of the base material 3A, as shown in FIG. 2A, on the base material surface _S3A formed as a concave surface along the shape of the molding surface 3a, the mirror surface forming layer 3B, the mold release The film 3C is laminated in this order, and the molding surface 3a is constituted by the outermost surface of the release film 3C.
The mirror surface forming layer 3B has the same configuration as the mirror surface forming layer 2B of the lower mold 2 and is formed of the same material. For this reason, the mirror surface forming layer 3 </ b> B has the concavo-convex portion S _<b > 3 </ b> _B similar to the concavo-convex portion S _{<b> 2 </ b> B.}
The release film 3C has the same configuration as the release film 2C and is formed of the same material. For this reason, the release film 3C is formed so as to cover the mirror surface forming layer 3B via the uneven portion _S3B .

  With such a configuration, in the lower mold 2, the base material 2 </ b> A and the mirror surface forming layer 2 </ b> B constitute a main body member. In the upper mold 3, the base material 3 </ b> A and the mirror surface forming layer 3 </ b> B constitute a main body member.

As shown in FIG. 1, the body mold 4 has an inner peripheral surface 4 a having an inner diameter equal to the outer diameter of the side surface 2 b of the lower mold 2 and the outer diameter of the side surface 3 b of the upper mold 3, and the side surface 2 b of the lower mold 2. , And the side surface 3b of the upper mold 3 are cylindrical members that are slidably fitted in the axial direction.
As a result, one end portion (lower side in FIG. 1) of the body die 4 is fitted to the lower die 2 in a state where the one end portion (lower side in FIG. 1) is engaged with the flange portion 2c of the lower die 2, and the other end portion (upper side in FIG. The upper mold 3 can be removably inserted with the molding surface 3a facing the molding surface 2a.
Thus, in the state where the lower mold 2 and the upper mold 3 are inserted at both ends of the body mold 4, a molding space is formed between the molding surfaces 2a and 3a facing each other.
Silicon carbide and cemented carbide can be used as the material of the trunk mold 4.

Next, the manufacturing method of the lower mold 2 and the upper mold 3 in the mold assembly 1 having such a configuration will be described focusing on the manufacturing process relating to the formation of the molding surfaces 2a and 3a.
Moreover, these manufacturing processes are the same except for the difference in the outer shape of the lower mold 2 and the upper mold 3, and the description of the manufacturing process relating to the formation of the molding surface 2a is the same as the manufacturing process relating to the formation of the molding surface 3a. Applicable to. Therefore, hereinafter, an example in which the molding surface 2a is formed on the lower mold 2 will be described.
FIG. 4 is a flowchart showing a process flow of the method for manufacturing an optical element molding die according to the first embodiment of the present invention. 5 (a-1) and 5 (b-1) are schematic process explanatory views of a mirror surface forming process of the method for manufacturing an optical element molding die according to the first embodiment of the present invention. FIGS. 5A-2 and 5B-2 are schematic partial enlarged views of the E part and the F part in FIGS. 5A-1 and 5B-1, respectively. FIGS. 5C-1 and 5D-1 are schematic process explanatory views of a grain growth process of the method for manufacturing an optical element molding die according to the first embodiment of the present invention. FIGS. 5C-2 and 5D-2 are schematic partial enlarged views of the G and H portions in FIGS. 5C-1 and 5D-1, respectively.

  As shown in FIG. 4, the method for manufacturing an optical element molding die according to this embodiment includes a mirror surface forming step S1, a grain growth step S2, and a release film forming step S3.

First, the mirror surface forming step S1 is performed. This step is a step of forming a mirror surface having a shape along the surface shape of the molded product on the mirror surface forming layer 2B which is the surface portion of the main body member.
In the present embodiment, first, the substrate 2A is formed by sintering SiC particles. The base material surface S2A of the base material _2A is formed in a shape substantially conforming to the surface shape of the molded product. As schematically shown in FIGS. 5 (a-1) and (a-2), SiC is sintered. in the body, the grain size of the sintered particles, for example, because having a size such as 5 m to 10 m, the remaining irregularities of the same degree to the substrate surface S _2A, it is impossible to form a mirror surface.
Therefore, FIG. 5 (b-1), ( b-2) in as shown schematically, on the substrate surface _{S 2A,} for example, to form a SiC layer 2B ₁ by CVD. The SiC constituting the SiC layer 2B ₁ is β-SiC.

The SiC particles by CVD have a particle size that is significantly smaller than that of sintered particles, for example, about 10 nm to 300 nm. For this reason, the surface s ₁ of the mirror surface forming layer 2B ₁ has an uneven shape corresponding to the unevenness of the substrate surface S _2A , but can be smoothed by polishing.
Therefore, FIG. 5 (c-1), as shown in (c-2), and polished surfaces s _1, mirror layer 2B having a mirror surface s ₂ of a shape along the surface shape of the molded article on the outermost surface ₂ is formed. The surface roughness of the mirror surface s ₂ is preferably 0.005 μm or less in terms of _Ra .
This completes the mirror surface forming step S1.

Next, a grain growth step S2 is performed. This step is a step of forming a concave-convex portion S _2B mirror s ₂ by grain growth specular s _2.
That is, the lower mold 2 in a state where the mirror surface s ₂ is formed is placed in an electric furnace filled with an inert gas such as nitrogen gas (N ₂ ) to form a non-oxidizing atmosphere and heated.
When β-SiC is heated, it grows as α-SiC. For this reason, the crystal grows in various directions from the mirror surface s ₂ to form the concavo-convex portion S _2B having a concavo-convex shape in which minute protrusions gather (see FIGS. 5D-1 and 5D-2).

Grain growth has been known to occur during the SiC material fabrication process. In particular, when the crystal grain size is enlarged to several tens of μm or more, it is called abnormal crystal grain growth, and the homogeneity and physical properties of the material are impaired. Therefore, grain growth is suppressed as much as possible.
As a result of extensive research, the present inventor achieved an anchor effect when forming a release film by controlling this grain growth, and an uneven portion S _{2B in a} range where the specularity of the molding surface can be secured. The present inventors have found a suitable range of the present invention and have arrived at the present invention.
That is, by setting the heating temperature and the heating time within suitable ranges, the adhesion strength to the release film 2C formed in the release film forming step S3 becomes good, and the surface accuracy of the outermost surface of the release film 2C is good. The concavo-convex part _S2B having the size of the concavo-convex shape can be formed.

Here, in the case where the surface roughness of the mirror surface s ₂ of the mirror surface forming layer 2B ₂ is 0.005 μm in R _Z , an example of the result of experimenting the change in surface roughness depending on the combination of the heating temperature and the heating time is as follows: Shown in Table 1.

As shown in Table 1 above, in the case of SiC, when the heating temperature is in the range of 1600 ° C. to 2400 ° C., the surface roughness is R _Z by appropriately setting the heating time between 0.5 hours and 3 hours. , 0.07 μm to 10 μm.
That is, the growth rate of grain growth because the heating temperature is slow enough low, be set as appropriate combinations of the heating temperature and the heating time, it is possible to obtain a constant R _Z without grain growth progresses excessively.
By multiplying an appropriate heating time at the above temperature range, without the possible cause abnormal grain growth, the preferred range 0.1μm~2μm or _{R Z} of the concave-convex portion _{S 2B,} a more preferred range 0.2μm~1μm realized Is possible.
Moreover, since the molding temperature in the glass press molding is, for example, 400 ° C. to 800 ° C., which is sufficiently lower than the heating temperature in this step, SiC does not grow during the molding of the optical element. For this reason, even if press molding is repeated, the surface accuracy of the surface shape of the molding surface 2a is maintained.

When the preset heating time has elapsed, heating is stopped, and after cooling, the lower mold 2 is taken out of the electric furnace.
This is the end of the grain growth step S2.

Even if the material of the mirror layer 2B is different, in advance, by the magnitude of the heating temperature and the heating time and the R _Z, previously examined by experiments in the same manner, sets the suitable heating temperature and heating conditions Condition Is possible.

Next, a release film forming step S3 is performed. This step is a step of forming the release film 2C on the surface portion of the main body member via the uneven portion _S2B .
In the present embodiment, as shown in FIG. 3, the base layer 5, the metal layer 6, the nitride layer 7, and the surface layer 8 are sequentially formed in this order on the concavo-convex portion S _2B . Film formation is performed by ion beam sputtering.
When the surface roughness _{R a} of the surface layer 8 is larger than 0.005μm, the surface was mirror-polished, smaller than 0.005μm and _{R a.}
Thus, the release film forming step S3 is completed.
In this way, the lower mold 2 is manufactured.

According to the lower die 2 of the present embodiment, the surface portion of the substrate 2A, to form a mirror layer 2B having a concave-convex portion S _2B, are formed the mold release film 2C through the uneven portion S _2B Therefore, the adhesion of the release film 2C can be improved. For this reason, the durability of the release film 2C of the lower mold 2 can be improved.
Further, as the release film 2C, for example, the configuration of the release film in the case where the base material is a cemented carbide, which is widely used in the past, is good even when the base material is a sintered body of SiC. High adhesion strength. For this reason, the adhesiveness between the release film 2C and the main body member can be improved without complicating the film configuration of the release film.

[Second Embodiment]
An optical element molding die according to the second embodiment of the present invention will be described.
Fig.6 (a) is typical sectional drawing which shows the principal part of the optical element shaping | molding die of the 2nd Embodiment of this invention. FIG. 6B is a schematic partial enlarged view of a portion J in FIG.

As shown in FIG. 1, a mold assembly 11 of this embodiment is replaced with a lower mold 12 (for optical element molding) instead of the lower mold 2 and the upper mold 3 of the mold assembly 11 of the first embodiment. Mold) and upper mold 13 (optical element molding mold).
As shown in FIG. 6A, the lower mold 12 (upper mold 13) is obtained by deleting the mirror surface forming layer 2B (3B) of the lower mold 2 (upper mold 3) of the first embodiment. For this reason, in this embodiment, base material 2A (3A) comprises a main body member.
Hereinafter, a description will be given centering on differences from the first embodiment.

Lower die 12 of the present embodiment (upper die 13) can form a mirror surface s _{12 (the} surface portion of the body member, see the two-dot chain lines in FIG. 6 (b)) on the surface of the substrate 2A (3A) In addition, this is an embodiment in which the uneven portion S ₁₂ (S ₁₃ ) can be formed by grain growth from the mirror surface s ₁₂ .
Examples of the material of the base material 2A (3A) include cemented carbide, cermet, silicon nitride, aluminum nitride, and boron nitride.

The lower mold 12 (upper mold 13) of the present embodiment can be manufactured in substantially the same manner as in the first embodiment. Hereinafter, as in the first embodiment, an example in which the lower mold 12 is manufactured will be described.
Mirror forming step S1 of this embodiment is a step of forming a mirror surface s ₂ of a shape along the surface shape of the molded article on the surface of the substrate 2A. The particle size of the WC particles constituting the cemented carbide is, for example, 0.5 μm to 1.5 μm, which is smaller than the sintered particles of SiC. For this reason, after forming the outer shape of the base material 2A by sintering, the mirror surface s ₂ having _a surface roughness _Ra of about 0.005 μm or less is formed by polishing the surface along the surface shape of the molded product. be able to.
This completes the mirror surface forming step S1.

Next, the grain growth step S2 of this embodiment is performed. This step is a step of forming a concave-convex portion S ₁₂ mirror s ₂ by grain growth specular s _2.
That is, the lower mold 12 in a state where the mirror surface s ₂ is formed is put in an electric furnace in a non-oxidizing atmosphere and heat-treated at a preset heating temperature and heating time to grow grains from the mirror surface s ₂ .
This is the end of the grain growth step S2.

Release film forming process S3 is a step of forming a release film 2C through the uneven portion S ₁₂ on the surface portion of the substrate 2A. The release film 2C can be formed in the same manner as in the first embodiment.
In this way, the lower mold 12 of this embodiment can be manufactured.

Lower die 12 of the present embodiment, forming the direct uneven portion S ₁₂ on the surface of the substrate 2A, it is possible to simplify the manufacturing process as compared with the first embodiment.

In the description of each of the embodiments described above, the optical element molding die is a mold for manufacturing an optical element, and has been described as an example in the case of having a molding surface that transfers the shape of the optical surface of the optical element. The molding surface that forms the shape of the molded product other than the optical surface can be configured similarly.
The optical element molding die can produce an appropriate molded product that requires a molding surface with good surface accuracy.

  In the description of the first embodiment, the base material 2A and the mirror surface forming layer 2B have been described as an example of the case where the base material 2A and the mirror surface forming layer 2B are made of the same kind of material. Different types of materials can be combined as long as they can adhere well to each other.

  In the description of each of the above embodiments, an example in which the grain growth process is performed by performing a heat treatment using an electric furnace has been described. However, the heat treatment is not limited to heating of the electric furnace, and appropriate energy application is performed. Means can be employed. For example, the grains may be grown by applying energy by ion beam, plasma, laser irradiation or the like.

In the description of each of the above embodiments, the grain growth step S2 is performed in an electric furnace, and the release film forming step S3 is performed using a dedicated film forming apparatus. When the mold is moved to the film forming apparatus after the grain growth step S2, foreign matter such as floating organic matter may adhere to the grain-grown molding surface. In such a case, there is a risk of impairing the adhesion between the molding surface in which grains have grown due to foreign matter and the release film.
By using an apparatus capable of continuously performing the grain growth step S2 and the release film forming step S3, it is possible to avoid the above obstacles.
In addition, by performing the process continuously, a release film is formed immediately after the grain growth, so that the release film is formed on the surface activated by the grain growth and the adhesion force is further increased. Can be expected.

In the description of each embodiment described above, the film structure of the release film 2C is also the body member is a sintered body of SiC, away for the cemented carbide substrate by the intervention of an uneven portion S _2B In order to show that a mold film can be provided, an example in the case of a four-layer structure in which the base layer 5, the metal layer 6, the nitride layer 7, and the surface layer 8 are laminated in this order has been described.
According to such a configuration, even when the material of the surface portion of the main body member is other than the cemented carbide, the conventional release film for the cemented carbide substrate and the manufacturing process for forming the release film are not changed. Can be used as is. For this reason, the adhesive strength with the surface part of the main body member of the optical element molding die can be improved without changing the release film. Thereby, there exists an advantage that it becomes easy to selectively use only the base material of a main body member, for example to a cemented carbide alloy and SiC.
However, such a film configuration of the release film is an example, and the release film can have an appropriate film configuration as needed. That is, the film configuration of each of the above embodiments has a configuration of the surface layer 8 being the outermost layer and the base layer 5, the metal layer 6, and the nitride layer 7 being other intermediate layers. As the material and layer structure (combination and order of layers), an appropriate material and layer structure can be adopted according to the material of the outermost layer and the required adhesion strength.
For example, some of these intermediate layers may be deleted, each may be provided with a plurality of different materials and compositions, another different intermediate layer may be inserted, or the layer stacking order may be changed. Good.
Further, at least a part of the intermediate layer of the release film may be a material gradient layer in which the material composition changes in the layer thickness direction.
The release film may be a single layer in which the same material is uniformly distributed, or may be a single layer formed of a material gradient layer.

Here, a modified example of the film configuration of such a release film will be described.
FIG. 7 is a schematic cross-sectional view showing a main part of an optical element molding die according to a modification of the first and second embodiments of the present invention, and a schematic partial enlarged view of the K part.
As shown in FIG. 7A, in the lower mold 20 of this modification, an intermediate layer 21 is inserted between the release film 2C and the mirror surface forming layer 2B in the lower mold 2 of the first embodiment. Or a film configuration in which an intermediate layer 21 is inserted between the mold release film 2C and the base material 2A in the lower mold 12 of the second embodiment. A release film 20C is provided.
In these modifications, the intermediate layer 21 constitutes a part of the intermediate layer in the release film 20 </ b> C together with the base layer 5, the metal layer 6, and the nitride layer 7 constituting the release film 2 </ b> C. For this reason, the underlayer 5 does not constitute the lowermost layer in the release film 20C, and the intermediate layer 21 constitutes the lowermost layer.
According to the intermediate layer 21, the same multilayer film and the release film 2C, the more robust and can be joined to the concave-convex portion S _2B or raised portion S _12.
Examples of the material of the intermediate layer 21 include aluminum (Al), chromium (Cr), tantalum (Ta), hafnium (Hf), zirconium (Zr), niobium (Nb), cobalt (Co), copper ( Cu), titanium (Ti), iron (Fe), nickel (Ni), any metal element group, an alloy containing at least one of the element groups, or the element group A structure containing any of the above compounds or titanium nitride (TiN), titanium carbonitride (TiCN), titanium aluminum nitride (TiAlN), or aluminum nitride chromium (AlCrN) is preferable.
Such a manufacturing method of the lower mold | type 20 is implement | achieved by providing such an intermediate | middle layer formation process between a grain growth process and the said mold release film formation process.

  In addition, the components described in the above embodiments can be implemented by being appropriately combined or deleted within the scope of the technical idea of the present invention.

Below, the specific Example of the said 1st Embodiment is demonstrated with an evaluation result.
[Example 1]
In the lower mold 2 of Example 1, the main body member is formed of a SiC sintered body, and a SiC film having a thickness of 0.5 mm is formed on the surface of the molded lens along the convex lens surface by CVD (CVD- SiC). By polishing the surface of the CVD-SiC, the surface roughness Ra to form a mirror _{S 2} of about 0.005 .mu.m (mirror formation step S1).
Next, this main body member on which the mirror surface S2 is formed is carried into an electric furnace purged with nitrogen and heat-treated at a heating temperature of 1900 ° C. for 30 minutes to grow SiC on the mirror surface s ₂ so that R _Z is about 0. to form the uneven portion _{S 2B} of .4Myuemu (grain growth step S2).
Then, through the uneven portion _{S 2B,} WC, Cr, sequentially formed CrN, the Ir-Re, the base layer 5, the metal layer 6, a nitride layer 7, to form a surface layer 8. Thereby, the release film 2C was formed (release film forming step S3).

[Example 2]
The lower mold 2 of Example 2 was moved to the ion beam sputtering apparatus after performing the mirror surface forming step S1 and the grain growth step S2 as in Example 1. In the vacuum, the concavo-convex portion S2B was irradiated with an argon ion beam for 5 minutes, and then Ir-Re was deposited to form a release film 2C.
For this reason, the release film 2C in Example 2 is a release film having a single layer structure.

[Comparative example]
As a comparative example, a lower mold in which the grain growth step S2 was omitted in Example 1 was created.

[Evaluation]
The film adhesion of each release film of the optical element molding die of Examples 1 and 2 and Comparative Example was evaluated.
The critical peel strength was measured using a film adhesion measuring machine (CSR-2000 manufactured by Resuka Co., Ltd.) as a measuring machine.
The measured critical peel strength was 130 mN in the comparative example, 200 mN in the example 1, and 240 mN in the example 2.
From these results, in Examples 1 and 2, by having the concavo-convex part S _2B , the critical peel strength of the release film is significantly higher than that of the comparative example having no concavo-convex part. It turns out that the adhesive force with respect to the surface part of the main-body member is improving.

1,11 Mold assembly 2,12 Lower mold (Optical element molding mold)
2A, 3A Base material (main body member)
2B, 3B Mirror surface forming layer (main body member)
2C, 3C Release film 2a, 3a Molding surface 3, 13 Upper mold (optical element molding mold)
4 Body type 5 Underlayer (lowermost layer)
6 Metal layer 7 Nitride layer 8 Surface layer (outermost layer)
21 Middle layer (lowermost layer)
s ₂ , s ₁₂ mirror surface (surface part of main body member)
S _2A , S _3A substrate surface S _2B , S _3B , S ₁₂ , S ₁₃ concavo-convex part S1 mirror surface forming step S2 grain growing step S3 release film forming step

Claims (6)

A surface portion formed in a shape along the surface shape of the molded article, and more grain growth, the surface roughness is the maximum height (R _Z) at 0.1μm or more, body member following uneven portion 2μm is formed When,
A mold release film constituting a molding surface that is laminated on the surface portion of the main body member via the concave and convex portions, and is in close contact with the molding material so that the mold can be released;
An optical element molding die comprising: The uneven portion has a surface roughness, the maximum height _{(R Z),} 0. The optical element molding die according to claim 1, wherein the mold is 2 μm or more and 1 μm or less. 3. The optical element according to claim 1, wherein the release film is a multilayer film including at least a lowermost layer laminated on the uneven portion and an outermost layer forming the molding surface. Mold for molding. The optical element molding die according to any one of claims 1 to 3, wherein the surface portion and the concavo-convex portion of the main body member are made of silicon carbide.   The manufacturing method of the optical element which shape | molds the said molding material using the optical element shaping | molding die of any one of Claims 1-4, and obtains the said molded article. A mirror surface forming step for forming a mirror surface having a shape along the surface shape of the molded product on the surface portion of the main body member;
A grain growth step in which grain growth is performed on the mirror surface to form an uneven portion having a surface roughness of 0.1 μm or more and 2 μm or less at a maximum height (R _Z ) on the mirror surface ;
A release film forming step of forming a release film on the surface portion of the main body member via the uneven portion;
A method for producing an optical element molding die, comprising:

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