JP2017007895A - Optical device molding method, molding tool and glass material for molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress defect occurrence while extending life of a molding tool in an optical device molding method.SOLUTION: The optical device molding method for forming an optical device by press-molding a heated glass material by a molding tool with a release film comprising a metal film on a surface, includes: arranging a mold release including a fine graphite at least on either of the surface of the release film or the surface of the glass material (step S1, S2); press-molding by the molding tool by heating the glass material after arranging the mold release (step S3); and removing the fine graphite from the surface of the glass material by heating the press-molded glass material in oxygen atmosphere (step S4).SELECTED DRAWING: Figure 5

Description

  The present invention relates to an optical element molding method, a mold, and a glass material for molding.

Conventionally, as a method for manufacturing an optical element such as a lens, it is known to press-mold a glass material with a mold. Molds used for glass press molding have a release film on the mold surface in close contact with the glass.
In press molding of glass, it is also known that a release agent is interposed between a mold and a glass material. For example, Patent Document 1 describes a glass optical element molding method in which carbon soot as a release agent is sprayed onto a glass gob before the glass gob is dropped onto a mold.
In Patent Document 1, soot in a combustion flame of acetylene gas is used as carbon-based soot. Patent Document 1 describes soot in a combustion flame of a hydrocarbon gas such as methane, butane, propane, or an alcohol-based gas containing carbon atoms as another carbon-based soot.
Furthermore, Patent Document 1 describes that the release agent may be a fine powder obtained by misting a liquid carbon-based organic material.

JP-A-6-305740

However, the conventional optical element molding method has the following problems.
When a highly accurate molding surface is required as in an optical element, sufficient mold release may not be obtained if the mold release film is only a metal film. In a mold in which the release film is a metal film, a release agent is used in combination.
The mold release agent uses an organic compound. The organic compound includes C (carbon atom), H (hydrogen atom), O (oxygen atom), N (nitrogen atom), S (sulfur atom) and the like. A mold release agent improves mold release property, when the thermal decomposition thing of an organic compound adheres to glass and a mold surface.
However, when an organic compound is thermally decomposed, low molecular weight substances such as water, carbon dioxide gas, and molecular fragment components are also generated. These low molecular weight substances are easily vaporized by heating during molding. However, the vaporized material is trapped between the glass and the mold.
As a result, the vaporized material may deform the softened glass. For example, when the vaporized substance forms a fine hole on the glass surface, the optical element is clouded.
Furthermore, unbonded electrons exist in the fragment component of the molecule generated when the organic compound is thermally decomposed. When a fragment component of a molecule having unbonded electrons reacts with glass, it may cause coloring, bubbles, fusion, etc. on the glass surface.

A mold having a release film made of a carbon film can obtain good mold release properties without using a mold release agent. However, the carbon film itself is consumed by repeating the molding. For this reason, there is a problem that the carbon film has a short lifetime.
In the technique described in Patent Document 1, a mold release agent made of carbon-based soot is supplied every time molding is performed. For this reason, a certain mold release performance can be maintained.
However, since carbon-based soot is formed in a combustion flame of organic compounds such as hydrocarbons and alcohols, it has an active component as an organic matter decomposition product. Further, carbon-based soot is composed of secondary particles in which minute primary particles are aggregated. For example, the diameter of the primary particles is several tens nm to several hundreds nm. On the other hand, the diameter of the secondary particles is a few μm at the minimum and is a size exceeding 10 μm at the maximum.
Carbon-based soot having such a particle size tends to remain on the glass surface after molding. Residual carbon-based soot tends to cause poor appearance of the molded product due to the reaction of the active component as the organic decomposition product with glass.
On the other hand, even if carbon-based soot is removed from the glass surface, a depression corresponding to the carbon soot particle size is generated on the glass surface after removal. There is a problem that this dent causes a spider of a molded product.

  The present invention has been made in view of the above problems, and provides an optical element molding method, a molding die, and a molding glass material capable of suppressing the occurrence of defects and extending the lifetime of the molding die. The purpose is to do.

  In order to solve the above-mentioned problems, the optical element molding method according to the first aspect of the present invention is an optical element obtained by press-molding a heated glass material with a molding die having a release film made of a metal film on the surface. An optical element molding method for forming a mold, wherein a mold release agent containing refined graphite is disposed on at least one of a surface of the mold release film and a surface of the glass material, and the mold release agent is disposed Then, the glass material is heated and press-molded by the molding die, and the press-molded glass material is heated in an oxidizing atmosphere, and the refined graphite is applied to the surface of the glass material. Removing from.

  In the optical element molding method, the coating liquid in which the fine graphite is dispersed in a liquid is applied to at least one of the surface of the release film and the surface of the glass material, and the applied coating The mold release agent may be disposed on at least one of the surface of the release film and the surface of the glass material by drying the liquid.

  In the optical element molding method, the annealed glass material may be heated in an oxidizing atmosphere to remove the refined graphite from the surface of the glass material.

  In the optical element molding method, the refined graphite may have a thickness of 30 nm or less.

  The mold according to the second aspect of the present invention includes a mold surface for molding the outer shape of the optical element, a mold release film formed on the surface of the mold surface and made of a metal film, and disposed on the surface of the mold release film. And a release agent containing refined graphite.

  In the above mold, the refined graphite may have a thickness of 30 nm or less.

  The molding glass material according to the third aspect of the present invention is a molding glass material for forming an optical element by press molding, and has a mold release agent containing refined graphite on the surface.

  In the molding glass material, the refined graphite may have a thickness of 30 nm or less.

  According to the optical element molding method, the molding die, and the molding glass material of the present invention, it is possible to suppress the occurrence of defects and extend the lifetime of the molding die.

It is the typical front view and top view which show an example of the optical element manufactured by the optical element shaping | molding method of embodiment of this invention. 1 is a schematic cross-sectional view of a mold and a mold assembly according to an embodiment of the present invention. It is typical sectional drawing of the shaping | molding die of embodiment of this invention. It is typical sectional drawing of the glass material for shaping | molding of embodiment of this invention. It is a flowchart which shows the flow of the optical element shaping | molding method of embodiment of this invention. It is typical process explanatory drawing of the mold release agent application | coating process of the optical element shaping | molding method of embodiment of this invention. It is typical process explanatory drawing of the mold release agent application | coating process of the optical element shaping | molding method of embodiment of this invention. It is a flowchart which shows the flow of the shaping | molding process of the optical element shaping | molding method of embodiment of this invention. It is typical sectional drawing which shows the structural example of the shaping | molding apparatus used for the optical element shaping | molding method of embodiment of this invention. It is typical process explanatory drawing of the shaping | molding process of the optical element shaping | molding method of embodiment of this invention. It is typical process explanatory drawing of the shaping | molding process of the optical element shaping | molding method of embodiment of this invention. It is a schematic diagram explaining the effect | action of the mold release agent used for the optical element shaping | molding method of embodiment of this invention. It is typical process explanatory drawing of the molded article heating process of the optical element shaping | molding method of embodiment of this invention.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
First, an optical element molded by the optical element molding method of the embodiment of the present invention and a molding die used for molding will be described.
FIGS. 1A and 1B are a schematic front view and a plan view showing an example of an optical element molded by the optical element molding method according to the embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of a mold and a mold assembly according to an embodiment of the present invention. FIG. 3 is a schematic cross-sectional view of a mold according to an embodiment of the present invention. FIG. 4 is a schematic cross-sectional view of a glass material for molding according to an embodiment of the present invention.
Since each drawing is a schematic diagram, dimensions and shapes are exaggerated (the same applies to other drawings).

The optical element molded by the optical element molding method of the present embodiment is not particularly limited as long as it is an optical element that press-molds a glass material to form an outer shape. For example, an appropriate type of optical element such as a lens, a prism, a mirror, a filter, or a substrate can be used, and the surface of the optically effective area may have a curvature or a plane that has no curvature. Also good. Moreover, when it has a curvature, a convex surface or a concave surface may be sufficient.
Hereinafter, as an example of an optical element molded by the optical element molding method of the present embodiment, an example in which the lens 1 (optical element) shown in FIGS. 1A and 1B is molded will be described.

The lens 1 is a single biconvex lens formed of glass, and includes a convex lens surface 1a and a convex lens surface 1b. The lens 1 has a flange portion 1c having a circular outer shape on the outer periphery of the convex lens surfaces 1a and 1b.
The convex lens surfaces 1 a and 1 b are processed to have a surface shape and surface accuracy based on the design specifications of the lens 1. The convex lens surfaces 1a and 1b can be coated with a film coat such as an antireflection film coat or a protective film coat as necessary.

  The lens 1 is molded by the optical element molding method of the present embodiment using a molding die 2 and a glass preform 6 (molding glass material) as shown in FIG.

  The molding die 2 includes a lower die 3, an upper die 4, and a body die 5, and each of these center axes is arranged so as to be coaxial with the center axis P. Hereinafter, the central axis of each member constituting the mold 2 is referred to as a central axis P.

The lower mold 3 is formed of a substantially columnar member having a cylindrical side surface 3d having an outer diameter slightly larger than the outer diameter of the lens 1. The lower mold 3 has a lens surface molding surface 3a (mold surface), a flat surface molding surface 3b (mold surface) on one end portion (upper end portion in FIG. 2) in the axial direction along the central axis P. Is formed.
The lens surface molding surface 3a is a concave molding surface that transfers the shape of the convex lens surface 1b.
The flat portion molding surface 3b is a flat molding surface that transfers the shape of the flange portion 1c adjacent to the convex lens surface 1b.
A flange portion 3e is formed at the other end portion of the lower mold 3 in the axial direction. The flange portion 3 e extends from the side surface 3 d of the lower mold 3 to the outside in the radial direction perpendicular to the central axis P. The other end surface in the axial direction of the flange portion 3e (the lower end surface in FIG. 2) constitutes a lower surface 3f perpendicular to the central axis P.

The base material of the lower mold 3 is made of a material having high hardness and good heat resistance, such as a cemented carbide mainly composed of tungsten carbide (WC), silicon carbide, or carbon.
The lens surface molding surface 3a and the flat surface molding surface 3b are formed by processing such a base material into the shape of the convex lens surface 1b and the planar shape, respectively, and then forming a thin film containing a noble metal as a release film. Is done.
The mold release film used for the lens surface molding surface 3a and the flat surface molding surface 3b is a precious metal that hardly causes a chemical reaction during molding with glass components so that the mold release property of the outermost surface that comes into contact with the glass during molding is good. It is a metal film containing an element. Hereinafter, the lens surface molding surface 3a and the flat surface molding surface 3b may be collectively referred to as a release film portion 3m (release film).
As the noble metal element contained in the release film part 3m, an appropriate noble metal element can be adopted. For example, the release film part 3m is made of platinum (Pt), gold (Au), iridium (Ir), rhenium (Re), silver (Ag), osmium (Os), tantalum (Ta), and palladium (Pd). You may use the structure containing 1 or more types of at least 1 type of selected elements or these elements.
Examples of the method for forming the release film portion 3m include RF sputtering, magnetron sputtering, and ion beam sputtering.

In this embodiment, as shown in FIG. 3, the mold release agent 9 is arrange | positioned on the surface of the mold release film | membrane part 3m before shaping | molding is started.
The mold release agent 9 contains refined graphite.
In this embodiment, the mold release agent 9 is arrange | positioned in the mold release film part 3m by apply | coating the coating liquid which disperse | distributed the refined graphite in the liquid to the surface of the mold release film part 3m, and drying.

Graphite is a hexagonal crystal in which layered bodies each having one atomic layer formed of a six-membered ring in which carbon is covalently bonded are stacked. Each layer of graphite is bonded by van der Waals forces. The substance from which the layered body of one atomic layer constituting graphite is exfoliated is called graphene.
Since graphite has such a crystal structure, it tends to slip between the layered bodies.
The graphite used for the release agent 9 is pressed to the glass preform 6 at the time of press molding to a size that does not cause a defective appearance or optical characteristics of the lens 1 even if a depression is formed on the glass preform 6. Refine. In this embodiment, as will be described later, since the release agent 9 is applied by spraying, the graphite used for the release agent 9 needs to be refined to a size that allows spray application.

In the present embodiment, the thickness of the graphite layered body in the release agent 9 in the stacking direction is 30 nm or less.
The size of the layered body when the layered body of graphite is viewed in the stacking direction may be about 10 μm × 10 μm or less. The size of the layered body may be 5 μm × 5 μm or less, or 1 μm × 1 μm or less.
When the graphite is in such a flake shape, a stable adhesion posture with respect to the release film portion 3m is a posture in which the normal direction of the release film portion 3m substantially coincides with the stacking direction of the layered bodies. As a result, the amount of protrusion from the release film part 3m is also about the thickness of the refined graphite.
The graphite layer may be thinner. For example, the layer thickness of the graphite layered body may be 10 nm or less, or 5 nm or less.
Since graphene has a thickness equivalent to one layer of carbon atoms, the refined graphite used for the release agent 9 may include graphene. Furthermore, the refined graphite used for the release agent 9 may be composed only of graphene.

Graphene oxide is a compound in which part of graphene is substituted with a functional group containing oxygen by oxidation of part of graphene. The main part of graphene oxide is a six-membered ring of carbon. Graphene oxide as a whole consists of a two-dimensional layered body that is substantially the same as graphene. Since graphene oxide does not have a crystal structure, it is a very thin layered body like graphene.
Since graphene oxide has a functional group containing oxygen, it has hydrophilicity. For this reason, graphene oxide is easily dispersed in a liquid.
The release agent 9 may include graphene oxide.

As shown in FIG. 2, the upper die 4 is made of a substantially columnar member having a cylindrical side surface 4 d having the same outer diameter as the side surface 3 d of the lower die 3. The upper mold 4 has a lens surface molding surface 4a (mold surface) and a flat surface molding surface 4b (mold surface) at one end (the lower end in FIG. 2) in the axial direction along the central axis P. And are formed.
The lens surface molding surface 4a is a concave molding surface that transfers the shape of the convex lens surface 1a.
The flat surface molding surface 4b is a flat molding surface that transfers the shape of the flange portion 1c adjacent to the convex lens surface 1a.
A flange portion 4e is formed at the other end portion of the upper mold 4 in the axial direction. The flange portion 4 e extends from the side surface 4 d of the upper mold 4 to the outside in the radial direction perpendicular to the central axis P. The other end face in the axial direction of the flange portion 4e (the upper end face in FIG. 2) constitutes an upper face 4f perpendicular to the central axis P.

  After forming the outer shape of the upper mold 4 with the same material as the base material of the lower mold 3, the lens surface molding surface 4 a and the flat surface molding surface 4 b are formed by forming a release film similar to the lower mold 3. doing. Hereinafter, the lens surface molding surface 4a and the flat surface molding surface 4b may be collectively referred to as a release film portion 4m (release film).

  In this embodiment, as shown in FIG. 3, the mold release agent 9 is arrange | positioned in the release film part 4m by the time it starts shaping | molding. The release agent 9 can be disposed on the release film part 4m in the same manner as the release film part 3m of the lower mold 3.

As shown in FIG. 2, the body mold 5 is a cylindrical member having a side surface 3d of the lower mold 3 and an inner peripheral surface 5a on which the side surface 4d of the upper mold 4 is slidably fitted. The lower surface 5b and the upper surface 5c which are both ends in the axial direction of the body mold 5 are formed by planes orthogonal to the central axis P of the inner peripheral surface 5a.
The axial length of the body mold 5 (the distance from the lower surface 5b to the upper surface 5c) is shorter than the distance between the flange portions 3e and 4e in the assembled state of the molding die 2 described later.
With such a configuration, the body die 5 holds the lower die 3 and the upper die 4 in a coaxial positional relationship while performing glass molding, and guides the upper die 4 to be movable along the central axis P. it can.
In the present embodiment, the body mold 5 is not a molding surface that molds the side surface of the flange portion 1c, and thus can be made of an appropriate metal material or ceramic having heat resistance against the molding temperature. In the present embodiment, a cemented carbide having high hardness and good heat resistance is employed as an example.

The molding die 2 has a barrel die 5 fitted on the side surface 3d of the lower die 3, and a glass preform 6 (glass material for molding) that is weighed to a mass necessary for molding is disposed on the lens surface molding surface 3a. The upper die 4 is inserted from above the barrel die 5 and assembled. A configuration in which the glass preform 6 is assembled to the mold 2 is referred to as a mold assembly 7.
In the mold assembly 7, the glass preform 6 is accommodated in a molding space S surrounded by the lens surface molding surfaces 3 a and 4 a, the flat surface molding surfaces 3 b and 4 b, and the body mold 5.
The molding space S communicates with the outside through a gap between the lower mold 3 and the upper mold 4 and the trunk mold 5, or a through hole (not shown) provided in the trunk mold 5 in some cases.
The mold assembly 7 is disposed in a molding apparatus to be described later and used for molding the lens 1.

As shown in FIG. 4, the glass preform 6 includes a glass molded body 6A and a release agent 6B applied to the surface 6a of the glass molded body 6A.
The glass molded body 6 </ b> A is a massive member obtained by molding a glass material used for the lens 1 into an appropriate shape. The molding means of the glass molded body 6A may be molding, or may be machining such as cutting and polishing.
The shape of the glass molded body 6A is drawn in a spherical shape as an example in FIG. However, the shape of the glass molded body 6 </ b> A is not limited to a spherical shape as long as it can be press-molded by the mold 2. The shape of the glass molded body 6A may be, for example, a disk shape, a spheroid shape, or a similar shape to the lens 1 in addition to the spherical shape.

The release agent 6 </ b> B, like the release agent 9, contains refined graphite. In the present embodiment, the release agent 6B is formed by applying and drying a coating liquid in which fine graphite is dispersed in a liquid on the surface 6a of the glass molded body 6A.
The configuration of the release agent 6B may be different from that of the release agent 9, but in the present embodiment, for example, the configuration is the same as that of the release agent 9.

Next, the optical element shaping | molding method of this embodiment is demonstrated.
FIG. 5 is a flowchart showing a flow of the optical element molding method according to the embodiment of the present invention. 6 and 7 are schematic process explanatory views of a release agent coating process of the optical element molding method according to the embodiment of the present invention. FIG. 8 is a flowchart showing the flow of the molding process of the optical element molding method according to the embodiment of the present invention. FIG. 9 is a schematic cross-sectional view illustrating a configuration example of a molding apparatus used in the optical element molding method according to the embodiment of the present invention. FIG. 10 is a schematic process explanatory diagram of the molding process of the optical element molding method according to the embodiment of the present invention. FIG. 11 is a schematic process explanatory diagram of a molding process of the optical element molding method according to the embodiment of the present invention. FIG. 12 is a schematic diagram for explaining the action of the release agent used in the optical element molding method according to the embodiment of the present invention. FIG. 13 is a schematic process explanatory diagram of a molded article heating process of the optical element molding method according to the embodiment of the present invention.

  The optical element molding method of this embodiment is a method of executing steps S1 to S5 shown in FIG. 5 according to the flow shown in FIG.

In steps S1 and S2, a release agent coating process and a drying process are performed. Steps S1 and S2 are steps including disposing a release agent containing refined graphite on at least one of the surface of the release film and the surface of the glass material.
In the release agent coating step in the present embodiment, a release agent dispersion liquid L (coating liquid) in which the components of the release agent are dispersed in a liquid is prepared. It is applied to the release film portions 3m and 4m of the mold 4 and the surface 6a of the glass molded body 6A. The release agent dispersion L is adjusted before step S1.
In the drying process in the present embodiment, the applied release agent dispersion L is dried.
Steps S <b> 1 and S <b> 2 may be performed simultaneously on the lower mold 3, the upper mold 4, and the glass molded body 6 </ b> A that are the respective objects, or may be performed for each object.
When steps S1 and S2 are executed for each object, the execution timing may be different.

In order to produce the release agent dispersion L, first, at least one of graphite refinement and graphene constituting the release agent 9 (6B) is formed.
The refined graphite is formed by mechanically refining graphite so that the layer thickness of the refined product is 30 nm or less. What is necessary is just to make it the magnitude | size when it sees in the layer thickness direction of the refinement | purification of a graphite to be 10 micrometers x 10 micrometers or less.
The size of the refined product viewed from the thickness direction may be 5 μm × 5 μm or less, or 1 μm × 1 μm or less.
The graphite refinement produced in this manner may contain graphene alone.
In the case of graphene, since the layer thickness is one atom, 5 nm or less is satisfied. The size of the graphene viewed from the thickness direction may be the same as that of the refined graphite. For example, when it exceeds 10 μm × 10 μm, it may be appropriately crushed to be 10 μm × 10 μm or less, 5 μm × 5 μm or less, or 1 μm × 1 μm or less.
Next, at least one of the formed graphite refinement and graphene is mixed in pure water, and ultrasonic vibration is applied to disperse the refined product in pure water. When the refined matter is dispersed, the liquid excluding the precipitate is separated as the release agent dispersion liquid L.

The concentration of the release agent 9 (6B) in the release agent dispersion liquid L is set so that the amount of the release agent 9 (6B) adhering to the coating surface does not become excessive. When there is too little quantity of the mold release agent 9 (6B), mold release property will fall. If the amount of the release agent 9 (6B) is too large, an overlap of the release agent 9 (6B) adhering to the coated surface occurs, and the mold release agent 9 (6B) has an unacceptable depth on the surface of the glass material during molding. There is a possibility of generating a depression. As an example of the allowable amount of the depression, 30 nm or less can be mentioned.
For example, the concentration of the release agent 9 (6B) in the release agent dispersion L in which the amount of the release agent 9 (6B) adhering to the coated surface does not become excessive is 0.001% or more and 0.1% or less. And it is sufficient.

First, steps S1 and S2 for the release film portion 3m (4m) will be described.
Examples of means for applying the release agent dispersion L to the release film portion 3m (4m) in Step S1 include a spray method, an inkjet method, a dip method, and a spin coat method.
In this embodiment, the spray method is adopted as an example.
In order to apply the release agent dispersion liquid L by the spray method, as shown in FIG. 6, the release agent dispersion liquid L is pressurized and directed from the spray nozzle 8 toward the release film portion 3m (4m). Let spray. The release agent dispersion liquid L sprayed from the spray nozzle 8 becomes fine droplets and adheres to the release film portion 3m (4m).
When the release agent dispersion L can be applied to the entire release film portion 3m (4m), the injection of the release agent dispersion L is stopped.
For example, when the diameter of the release film portion 3 m (4 m) is 15 mm, it is preferable that the concentration of the release agent in the release agent dispersion L is 0.001%, and the coating is applied in the range of about 0.1 mL to 0.3 mL. is there.
Thus, step S1 is completed.

In step S2, the release agent dispersion L applied to the release film part 3m (4m) is dried.
Examples of the drying method include a method of applying warm air to the application part, a method of heating the lower mold 3 (upper mold 4), and the like.
When the liquid in the release agent dispersion L evaporates, the release agent 9 remains on the release film portion 3m (4m).
In this way, as schematically shown in FIG. 3, the release agent 9 can be arranged in layers on the release film portion 3m (4m).
This is the end of step S2.

Next, steps S1 and S2 for the surface 6a of the glass molded body 6A will be described.
Examples of means for applying the release agent dispersion L to the glass molded body 6A in Step S1 include a spray method, an ink jet method, a dip method, and a spin coat method.
In this embodiment, the spray method is adopted as an example.
In order to apply the release agent dispersion L by the spray method, as shown in FIG. 7, the release agent dispersion L is pressurized and sprayed from the spray nozzle 8 toward the glass molded body 6A. The release agent dispersion liquid L sprayed from the spray nozzle 8 becomes fine droplets and adheres to the surface 6a.
When the release agent dispersion liquid L can be applied to the entire surface 6a, the injection of the release agent dispersion liquid L is stopped.
Thus, step S1 is completed.

In step S2, the release agent dispersion L applied to the surface 6a is dried.
Examples of the drying method include a method of applying warm air to the application part, a method of heating the glass molded body 6A, and the like.
When the liquid in the release agent dispersion L evaporates, the release agent 6B remains on the surface 6a.
Thus, as schematically shown in FIG. 4, the release agent 6 </ b> B can be arranged in layers on the release film portion 3 m (4 m).
This is the end of step S2.

When each step S2 described above is completed, step S3 shown in FIG. 5 is performed.
Step S3 is a molding process including heating the glass material and press molding with a molding die after disposing the release agent.
In the present embodiment, step S3 executes steps S11 to S15 shown in FIG. 8 along the flow shown in FIG.

In step S11, the mold assembly 7 shown in FIG. 1 is formed.
First, the glass preform 6 is disposed on the release film portion 3 m of the lower mold 3, and the body mold 5 is fitted on the side surface 3 d of the lower mold 3. Thereafter, the side surface 4d of the upper mold 4 is inserted into the inner peripheral surface 5a on the inner peripheral surface 5a of the body mold 5, and the glass preform 6 is sandwiched between the lens surface molding surfaces 3a and 4a.
Above, step S11 is complete | finished.

Steps S12 to S14 are performed using the molding apparatus 100 shown in FIG.
Before describing steps S12 to S14, the configuration of the molding apparatus 100 will be described.
As shown in FIG. 9, the molding apparatus 100 heats, pressurizes, and cools a glass preform 6 (not shown) disposed inside the mold 2 to transfer the shape of the molding surface in the mold 2. Device.
As shown in FIG. 9, the molding apparatus 100 includes a molding chamber 17 provided on the side with an opening 17 a for carrying in the molding die 2 and an opening 17 b for carrying out the molding die 2, and an interior of the molding chamber 17. A heating stage 10A, a press stage 10B, and a cooling stage 10C are provided.
Shutters 18a and 18b are installed in the openings 17a and 17b, respectively, so that they can be opened and closed. When the shutters 18a and 18b are closed, the molding chamber 17 is sealed.

The molding chamber 17 is provided with a evacuation conduit 15 for evacuating the molding chamber 17 and an inert gas inflow passage 16 for supplying the inert gas G into the molding chamber 17. .
The end (not shown) of the evacuation duct 15 opposite to the molding chamber 17 is connected to a vacuum pump (not shown).
The end (not shown) of the inert gas inflow path 16 opposite to the molding chamber 17 is connected to an inert gas supply source (not shown).
As the inert gas G, a gas that is not oxidized and does not cause a chemical reaction with the mold 2 and the glass preform 6 at a temperature equal to or lower than the maximum temperature during molding, for example, a gas such as nitrogen gas or argon gas is employed. be able to. In this embodiment, the inert gas G employs nitrogen gas as an example.

In the present embodiment, the molding chamber 17 is sealed when the shutters 18a and 18b are closed. For this reason, after performing evacuation through the evacuation conduit 15 in this sealed state, the inert gas G is introduced from the inert gas inflow passage 16 to fill the inside of the molding chamber 17 with the inert gas G. And can be replaced with a non-oxidizing atmosphere.
However, the molding chamber 17 can be a semi-sealed structure. In this case, the inert gas G is constantly supplied into the molding chamber 17 to keep the molding chamber 17 at a positive pressure, thereby suppressing the inflow of external air and maintaining the inner inert gas atmosphere. be able to. In this case, the evacuation conduit 15 and a vacuum pump (not shown) can be omitted.

Inside the molding chamber 17, a heating stage 10 </ b> A, a press stage 10 </ b> B, and a cooling stage 10 </ b> C are arranged close to each other in this order on a path from the opening 17 a to the opening 17 b.
The heating stage 10 </ b> A is a device portion that heats the mold 2 and the glass preform 6 in the mold 2.
The press stage 10B is an apparatus part that heats the glass preform 6 heated by the heating stage 10A to a temperature at which the glass preform 6 can be molded and then press-molds it.
The cooling stage 10C is an apparatus portion that cools the glass preform 6 to which the shape of the lens 1 is imparted by press molding.

In the present embodiment, the heating stage 10A, the press stage 10B, and the cooling stage 10C have the same apparatus configuration, and include press plates 11 and 12 and an air cylinder 13, respectively.
The press plate 11 is a disk-shaped member that supports the lower mold 3 of the mold 2 from below and heats the lower mold 3. The press plate 11 has a built-in heater.
The press plate 12 is a disk-like member that is disposed to face the upper side of the press plate 11 and that heats the upper die 4 by contacting the upper die 4 from above. The press plate 12 has a built-in heater.
The air cylinder 13 is a device portion that raises and lowers the press plate 12 and pressurizes the mold 2 from above when lowered. The air cylinder 13 is attached to the upper part of the molding chamber 17 so as to advance and retreat inside the molding chamber 17.

  Hereinafter, when it is necessary to distinguish whether the press plates 11 and 12 and the air cylinder 13 belong to any one of the heating stage 10A, the press stage 10B, and the cooling stage 10C, the suffixes A and B are added to the reference numerals of the respective stages. , C to distinguish. For example, press plates 11 and 12 and air cylinder 13 of heating stage 10A are represented as press plates 11A and 12A and air cylinder 13A, respectively.

The temperature of each press plate 11, 12 can be controlled independently.
The upper surfaces of the press plates 11 are aligned in the horizontal direction, and the mold 2 can be slid in the horizontal direction.
The raising / lowering operation and pressure of each air cylinder 13 can be independently controlled.

Further, inside the molding chamber 17, the molding die 2 moves on the respective press plates 11 of the heating stage 10 </ b> A, the press stage 10 </ b> B, and the cooling stage 10 </ b> C from the opening 17 a toward the opening 17 b. A conveying means is provided.
As the transfer means, for example, a robot arm or the like can be employed.

In step S <b> 12, the mold assembly 7 is heated by the molding apparatus 100.
First, the atmosphere in the molding chamber 17 of the molding apparatus 100 is replaced with the inert gas G before the molding die assembly 7 is carried in.
Specifically, vacuuming is performed from the evacuation duct 15 while the openings 17a and 17b are closed by the shutters 18a and 18b, respectively, and the pressure is reduced to about 100 Pa or less. Thereafter, an inert gas G is introduced from the inert gas inflow path 16 to form a non-oxidizing atmosphere in the molding chamber 17 that is slightly positive compared to the atmospheric pressure. As a non-oxidizing atmosphere of this embodiment, oxygen concentration should just be 10 ppm or less, for example.
In this state, the shutter 18a is opened, and the mold assembly 7 is carried in from the opening 17a. When the mold assembly 7 is carried into the molding apparatus 100, the mold assembly 7 is moved onto the press plate 11A of the heating stage 10A by a conveying means (not shown). Thereafter, the shutter 18a is closed.

When the mold assembly 7 moves onto the press plate 11A, as shown in FIG. 10, the air cylinder 13A is driven, and the mold assembly 7 is sandwiched in the direction along the central axis P by the press plates 11A and 12A.
The press plates 11 </ b> A and 12 </ b> A are heated in advance with a heater and heated to a temperature at which the glass preform 6 is softened.
When the mold assembly 7 is sandwiched between the press plates 11A and 12A, the lower mold 3 and the upper mold 4 are heated by heat conduction from the press plates 11A and 12A. As a result, the glass preform 6 sandwiched between the lower mold 3 and the upper mold 4 is also heated. In the heating stage 10A, the temperature of the glass preform 6 is raised to the vicinity of the molding temperature.
Above, step S12 is complete | finished.

Next, step S13 is performed. In this step, the mold assembly 7 is pressurized by the molding apparatus 100 under heating.
When the glass preform 6 is heated to a temperature slightly lower than the molding temperature, the air cylinder 13A is raised to release the clamping of the molding die assembly 7, and the molding die assembly is conveyed by a conveying means (not shown). 7 is moved to the press stage 10B.
In the press stage 10B, the press plates 11B and 12B are heated in advance so as to reach the molding temperature.
A particularly preferable temperature as the molding temperature of the glass preform 6 is a temperature in the vicinity of the middle between the yield point and the softening point. The molding temperature is set according to the type of the glass molded body 6 </ b> A of the glass preform 6. The molding temperature of the glass material that can be used for the glass molded body 6A is, for example, about 490 ° C. or more and 810 ° C. or less.

When the mold assembly 7 moves onto the press plate 11B, as shown in FIG. 10, the air cylinder 13B is driven, and the mold assembly 7 is clamped in the direction along the central axis P by the press plates 11B and 12B.
In this state, the mold 2 and the glass preform 6 are heated until the temperature of the glass preform 6 reaches the molding temperature.
When the glass preform 6 is heated to the molding temperature, the air cylinder 13B is driven and the press plate 12B is lowered as shown in FIG. The press plate 12B pressurizes the mold 2 from above and pushes down the upper mold 4.
The glass preform 6 in the molding space S is sandwiched and pressed between the lens surface molding surface 3a and the flat surface molding surface 3b, and the lens surface molding surface 4a and the flat surface molding surface 4b. The glass preform 6 is deformed along the shapes of the lens surface molding surface 3a and the flat surface molding surface 3b, and the lens surface molding surface 4a and the flat surface molding surface 4b.

When the press plate 12B is pushed down until the distance between the lens surface molding surfaces 3a and 4b becomes the distance between the lens surfaces of the lens 1, the air cylinder 13B is stopped.
As a result, the deformed glass preform 6 comes into close contact with the lens surface molding surface 3a and the flat surface molding surface 3b, and the lens surface molding surface 4a and the flat surface molding surface 4b. Each shape of the lens surface molding surface 3a and the flat surface molding surface 3b and the lens surface molding surface 4a and the flat surface molding surface 4b is transferred to the surface of the deformed glass preform 6. The glass preform 6 is formed into the shape of the lens 1.

When the shape of the glass preform 6 is stabilized, the air cylinder 13B is raised to release the pressurization and clamping of the mold assembly 7, and the mold assembly 7 is moved to the cooling stage 10C by a conveying means (not shown). Moving.
Above, step S13 is complete | finished.

The operation of the release agents 6B and 9 in step S13 will be described.
In steps S12 and S13, the inside of the molding chamber 17 is in a non-oxidizing atmosphere by replacing oxygen with the inert gas G. For this reason, even if heating is performed in steps S12 and S13, the release agent 6B on the glass molded body 6A and the release agent 9 on the release film portions 3m and 4m are not oxidized. As a result, as shown in FIG. 12A, before the pressurization of the mold assembly 7 is started, the glass molded body 6A and the release film portion 3m (4m) face each other with the release agents 6B and 9 interposed therebetween. doing.

When the pressurization of the mold assembly 7 proceeds, the release agents 6B and 9 are sandwiched between the glass molded body 6A and the release film portion 3m (4m) as shown in FIG. 12 (b). Since the glass molded body 6A is softened by being heated, it moves relative to the release film part 3m (4m) along the surface of the release film part 3m (4m) according to the applied pressure.
Therefore, the release agents 6B and 9 are subjected to shear in a direction along the surface of the release film part 3m (4m).

The release agents 6B and 9 include finely divided graphite which is a flaky layered body. For this reason, as schematically shown in FIGS. 12 (a) and 12 (b), the individual layered bodies of the release agents 6B and 9 have a layer thickness direction of the glass molded body 6A and the release film portion 3m (4m). ) Is aligned on the surface of the glass molded body 6A and the release film part 3m (4m) in a posture that is aligned with the normal direction of the surface.
As a result, the layered bodies of the release agents 6B and 9 sandwiched between the glass molded body 6A and the release film part 3m (4m) are normal to the surface of the glass molded body 6A and the release film part 3m (4m). Pressed in the direction. The release agents 6B and 9 facing each other are stacked in the respective layer thickness directions.
As described above, the release agents 6B and 9 to be pressurized constitute a laminated body in which the layer thickness direction and the lamination direction are aligned as a whole.

When such a laminate is sheared in a direction perpendicular to the lamination direction, slip occurs in the direction of the shearing force. Therefore, the release agents 6B and 9 act as a lubricant between the glass molded body 6A and the release film part 3m (4m).
Therefore, the frictional force between the glass molded body 6A and the release film portion 3m (4m) is reduced, and the relative movement is performed smoothly. For this reason, the distortion at the time of a deformation | transformation of the glass molded object 6A is also suppressed.
Furthermore, since the laminated body by the release agents 6B and 9 also undergoes shear deformation as a whole, even if the opposing layered bodies are in close contact with each other, when shear deformation proceeds, the layer thickness as the laminated body is leveled. That is, since the release agents 6B and 9 do not aggregate and become granular, they do not protrude toward the softened glass molded body 6A.
Even if an isolated layered body bites into the glass molded body 6A due to application variation of the release agent dispersion L or the like, the glass molded body 6A cannot be forced as the lens 1 because the layered body itself is a thin layer. The concave portion is not transferred.

  Furthermore, the release agents 6B and 9 are excellent in thermal conductivity due to the six-membered ring structure of carbon atoms common to the layered body. For this reason, heat conduction is promoted by the release agents 6B and 9 being interposed between the release film part 3m (4m) and the glass molded body 6A.

The release agents 6B and 9 are chemically stable under heating and pressurization in step S13.
For this reason, as in the case of using a release agent containing an organic compound that is thermally decomposed, a substance that vaporizes or a fragment component of molecules generated during the thermal decomposition is generated, causing defects on the glass surface. There is nothing.
Further, as in the case of using a release agent containing an organic compound that is thermally decomposed, a reaction product of the organic compound, the release film portions 3m and 4m, and the glass molded body 6A adheres to the surface, and seizure occurs. There is no waking.

After step S13, step S14 is performed. In this step, the mold assembly 7 is cooled by the molding apparatus 100.
When the mold assembly 7 moves onto the press plate 11C, as shown in FIG. 11, the air cylinder 13C is driven to lower the press plate 12C. When the press plate 12C is in close contact with the upper surface 4f of the upper mold 4, the lowering of the press plate 12C is stopped. The press plates 11C and 12C sandwich the mold assembly 7 in a direction along the central axis P.
Thereby, heat conduction occurs from the higher temperature mold assembly 7 to the lower temperature press plates 11C and 12C. As a result, cooling of the mold 2 and the glass molded body 6A proceeds.
When the glass molded body 6A is cooled below the strain point and solidified, the air cylinder 13C is driven to raise the press plate 12C. The clamping of the mold assembly 7 is released.
A molded product 26 in a solidified state is formed inside the mold 2.
Then, the shutter 18b is opened, and the mold assembly 7 is unloaded from the opening 17b to the outside of the molding chamber 17 by a conveying means (not shown), and the shutter 18b is closed.
Above, step S14 is complete | finished.

The operation of the molding apparatus 100 in steps S12 to S14 has been described above, focusing on one molding die assembly 7. In the molding apparatus 100, for example, a plurality of molding die assemblies 7 can be sequentially introduced by providing a conveyance tact.
In this case, in the heating stage 10A, the press stage 10B, and the cooling stage 10C in the molding chamber 17, the above processes are repeated for each of the plurality of mold assemblies 7 by repeating the above operation for each conveyance tact. Can be done. Thereby, the molded product 26 can be continuously manufactured using the plurality of mold assemblies 7.

Next, step S15 is performed. In this step, the molded product 26 is taken out.
When the mold assembly 7 is carried out of the molding chamber 17, at least one of the upper mold 4 and the lower mold 3 is pulled out from the body mold 5 to release the molded product 26.
At this time, as schematically shown in FIG. 12C, between the molded product 26 and the release film portion 3m (4m), in the normal direction of each surface and in the direction perpendicular to the normal line, The relative movement in the opposite direction to that during press molding occurs.
The laminate made of the release agents 6B and 9 receives the shearing force in the direction perpendicular to the stacking direction and the pulling force pulled away in the stacking direction, and the release agent 6B ′ on the molded product 26 and the release film portion 3m. (4m) Separated into the release agent 9 ′ above. The release agents 6B ′ and 9 ′ represent that they are different from the components and layer thicknesses of the release agents 6B and 9 before separation. A part of the release agent 9 is mixed with the release agent 6B ′, and a part of the release agent 6B is mixed with the release agent 9 ′.

Thus, also in the relative movement when releasing the molded product 26, the release agents 6B and 9 are interposed between the surface of the molded product 26 and the release film portions 3m and 4m. For this reason, unlike the case where the release agents 6B and 9 are not disposed, the entire surface of the molded product 26 and the release film portions 3m and 4m do not slide in direct contact with each other at the time of release. Even if there is a portion where the surface of the molded product 26 and the release film portions 3m and 4m are in direct contact, the area ratio with respect to the entire surface decreases according to the amount of the release agents 6B and 9. For this reason, according to this embodiment, the surface of the molded product 26 does not adhere to the release film portions 3m and 4m, and the molded product 26 can be released smoothly.
Further, since the release agent 6B ′ adhering to the surface of the molded product 26 is chemically stable, the release agent 6B ′ does not chemically react with the glass component of the molded product 26. For this reason, the surface of the molded product 26 is not altered, and the reaction product is not fixed to the surface of the molded product 26.

When the molded product 26 is removed from the mold 2, step S15 is completed.
Thus, step S3 shown in FIG. 5 is completed.
The molding die 2 for which step S15 has been completed can be reused in order to perform molding using another glass preform 6. At that time, depending on the remaining amount of the release agent 9 ′, the application of the release agent 9 in step S1 may be omitted. Or you may reduce the application quantity of the mold release agent 9 in step S1 depending on the residual quantity of mold release agent 9 '.

As shown in FIG. 5, when step S3 is completed, step S4 is performed. This step is a molded product heating process including heating the molded product 26 and heating it in an oxidizing atmosphere to remove the release agent 6B ′ from the surface of the molded product 26.
In the present embodiment, the heating in step S4 also serves as the annealing treatment.

In the present embodiment, the molded product 26 taken out from the mold 2 is carried into a heating furnace 110 made of, for example, an electric furnace.
The heating furnace 110 includes a mounting table 22 on which the molded product 26 is mounted and a heater 21 that performs heating inside the chamber 20.
The chamber 20 is provided with a pipe line 23 for supplying air into the chamber 20.

After placing the molded product 26 on the mounting table 22, heating by the heater 21 is started. The temperature (heating temperature) in the chamber 20 is a temperature at which the release agent 6B ′ can be oxidized and does not exceed the annealing temperature of the molded product 26. Since the oxidation of carbon proceeds at 400 ° C. or higher, the heating temperature for removing fine graphite may be 400 ° C. or higher.
For example, if the yield point of the glass molded body 6A is a glass material such as 550 ° C, the heating temperature can be 400 ° C. As for the heating time, a time during which all of the release agent 6B ′ remaining on the surface of the molded product 26 can be oxidized is obtained in advance by experiments or the like. The heating time can be, for example, 2 hours.
During the heating, the inside of the chamber 20 maintains an oxidizing atmosphere, so that oxygen is supplied and the oxidizing gas is exhausted from the pipe line 23 as necessary.

By performing such heating, the release agent 6B ′ remaining on the surface of the molded product 26 is oxidized. Since the oxide is a gas such as carbon dioxide, it does not remain on the surface of the molded product 26. In this way, the release agent 6B ′ is removed from the surface of the molded product 26.
When the preset heating time has elapsed, step S4 ends.

Step S5 is performed after step S4. This step is a molded product gradual cooling process in which the molded product 26 is gradually cooled in order to remove distortion of the molded product 26.
In this step, the temperature of the heater 21 is controlled so that the temperature of the molded product 26 in the chamber 20 falls along the cooling curve necessary for the annealing process.
When the cooling to the target cooling temperature is completed, the heating of the heater 21 is stopped and the molded product 26 is carried out of the chamber 20.
Above, step S5 is complete | finished and the optical element shaping | molding method of this embodiment is complete | finished.

The molded product 26 taken out from the heating furnace 110 is subjected to post-processing such as cutting the outer periphery of the lens as necessary to adjust the outer diameter or centering. Further, surface treatment such as antireflection coating is performed as necessary.
In this way, the lens 1 is manufactured.

According to the optical element molding method of the present embodiment, the release agent 6B is arranged on the surface 6a of the glass molded body 6A, and the release film part 3m of the lower mold 3 and the release film part 4m of the upper mold 4 are arranged. A mold release agent 9 is arranged, and the glass molded body 6A is press-molded in a non-oxidizing atmosphere.
At that time, since the release agents 6B and 9 contain fine graphite, the friction between the glass molded body 6A and the release film portions 3m and 4m is reduced. For this reason, pressurization at the time of press molding and mold release of the molded product 26 can be performed smoothly. As a result, the occurrence of defects during press molding and mold release can be suppressed.
Furthermore, the mold release agents 6B and 9 do not cause a chemical reaction during press molding to generate gas or attach a reaction product to the glass molded body 6A and the release film portions 3m and 4m. For this reason, generation | occurrence | production of defects, such as coloring in the surface of the molded article 26, a bubble, a melt | fusion, can be suppressed. Further, it is possible to prevent deterioration due to molding of the release film portions 3m and 4m.

  In the present embodiment, in particular, the layer thickness of the layered bodies constituting the release agents 6B and 9 is set to 30 nm or less. For this reason, even when the layered body is bitten into the molded product 26, the dent generated in the molded product 26 is a minute dent of 30 nm or less. Can be prevented.

After molding, since the release agent 6B ′ adhering to the surface of the molded product 26 is mainly composed of carbon, it can be easily removed only by heating in an oxidizing atmosphere such as an air atmosphere. In this embodiment, it is not necessary to apply a chemical to the molded product 26 in order to remove the release agent 6B ′. For this reason, it can prevent that the reaction material etc. with a chemical | medical agent adhere to the surface of the molded article 26. FIG.
In the present embodiment, the release agent 6B ′ is removed by heating when the molded product 26 is annealed. For this reason, the process for exclusive use for removing mold release agent 6B 'becomes unnecessary, and the lens 1 can be manufactured rapidly.

  As described above, according to the optical element molding method of the present embodiment, the occurrence of defects can be suppressed and the life of the mold can be extended.

  In the description of the above embodiment, the release agents 6B and 9 are dispersed in a liquid when the release agents 6B and 9 are arranged on the glass molded body 6A and the release film portions 3m and 4m. The dispersion liquid L was demonstrated in the example apply | coated to 6A of glass forming bodies and the release film parts 3m and 4m. However, the means for disposing the release agents 6B and 9 on the glass molded body 6A and the release film portions 3m and 4m is not limited to the application of the release agent dispersion L. For example, the release agents 6B and 9 may be disposed as powders by directly spraying or electrostatically adsorbing them onto the glass molded body 6A and the release film portions 3m and 4m.

  In the description of the above-described embodiment, the example in which the release agent is disposed on the surface of the release film and the surface of the glass material has been described. However, the release agent only needs to be interposed between the release film and the glass material during press molding. For this reason, the release agent may be disposed only on either the surface of the release film or the surface of the glass material.

In the description of the above embodiment, the example in which the release agent is removed during the heating in the annealing process has been described. However, the heating in the annealing process and the heating for removing the release agent may be performed at different timings.
In this case, the heating in step S4 in the above embodiment is performed only to remove the release agent. In this case, step S5 does not need to be gradually cooled along the cooling curve necessary for the annealing treatment as long as the temperature at which the molded product is taken out from the heating furnace can be cooled.

As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment and its modification. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit of the present invention.
Further, the present invention is not limited by the above description, and is limited only by the appended claims.

1 Lens (optical element)
2 Mold 3 Lower mold 3a, 4a Lens surface molding surface (mold surface)
3b, 4b Plane surface (mold surface)
3m, 4m release film part (release film)
4 Upper mold 5 Body mold 6 Glass preform (glass material for molding)
6A Glass molded body 6B, 6B ′, 9, 9 ′ Mold release agent 7 Mold assembly 26 Molded product 100 Molding device 110 Heating furnace L Mold release agent dispersion (coating liquid)

Claims (8)

An optical element molding method for forming an optical element by press molding a heated glass material with a mold having a release film made of a metal film on the surface,
Disposing a release agent containing refined graphite on at least one of the surface of the release film and the surface of the glass material;
After placing the mold release agent, heating the glass material and press-molding with the mold;
Heating the pressed glass material in an oxidizing atmosphere to remove the refined graphite from the surface of the glass material;
An optical element molding method comprising: Applying a coating liquid in which the refined graphite is dispersed in a liquid to at least one of the surface of the release film and the surface of the glass material;
Drying the applied coating solution;
By
Disposing the release agent on at least one of the surface of the release film and the surface of the glass material;
The optical element molding method according to claim 1. When annealing the press-molded glass material, the glass material is heated in an oxidizing atmosphere to remove the refined graphite from the surface of the glass material.
The optical element shaping | molding method of Claim 1 or 2. The refined graphite is
The thickness is 30 nm or less,
The optical element shaping | molding method of any one of Claim 1 to 3. A mold surface for shaping the outer shape of the optical element;
A mold release film formed on the surface of the mold surface and made of a metal film;
A mold release agent comprising finely divided graphite disposed on the surface of the mold release film;
A mold. The refined graphite is
The thickness is 30 nm or less,
The mold according to claim 5. A molding glass material for forming an optical element by press molding,
Provided with a mold release agent containing finely divided graphite on the surface,
Glass material for molding. The refined graphite is
The thickness is 30 nm or less,
The glass material for molding according to claim 7.

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