JP3266659B2 - Mold for molding optical element and method for molding optical element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold for molding an optical element having at least one microlens having a concave surface on a plane or an arbitrary curved surface, and a method for molding the optical element using the mold.

[0002]

2. Description of the Related Art Conventionally, an optical element made of a glass material or the like has been manufactured by a polishing process. However, recently, the optical element material is softened by heating and pressed between a pair of a molding die and a body die. A direct press (glass molding method) for manufacturing an optical element by molding is being adopted.
The molding die used for this glass molding method is a material obtained by finishing a molding material (WC, ceramics, etc.) into an aspherical shape with the desired shape accuracy and surface accuracy, and improves oxidation resistance and wet resistance. Protective film (for example, Pt-Rh based:
JP-B-63-95128).

[0003] Even when mass-producing an optical element having one or more small concave microlenses on its surface, it is desired to mold between the dies as described above, but a small convex surface is formed on the molding surface of the mold. Very difficult and requires a lot of effort.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art, and to provide a mold capable of mass-producing an optical element having at least one small concave microlens on its surface without forming a minute convex surface on the mold surface. An object of the present invention is to provide a method for molding a mold and an optical element.

[0005]

SUMMARY OF THE INVENTION The present invention has achieved the above object by providing a hole having a specific depth and diameter from the side opposite to the molding surface of a mold. That is, a mold for molding an optical element having one or more concave microlenses on a flat surface or an arbitrary curved surface according to the present invention has a hole having the same diameter as the desired microlens diameter on the back surface with respect to the molding surface. It is characterized in that a desired number of microlenses are provided with holes whose tip ends are 1.5 mm or less from the molding surface and do not penetrate the molding surface.

Further, in the method of molding an optical element according to the present invention, an upper and / or lower mold is used as an upper mold and / or a lower mold when molding an optical element having at least one microlens having a concave surface on a plane or an arbitrary curved surface. Using a mold, heat the optical element material and the mold, after softening the optical element material,
It is characterized by being molded by a molding die.

In the present invention, the base material of the mold is not particularly limited, and various types can be used. For example, stainless steel, various heat-resistant alloys, various ceramics, tungsten carbide, silicon carbide, nitrided One made of silicon or the like can be used. These base materials are ground into a flat surface or a desired curved surface by ultra-precision processing, and then the surfaces thereof are polished using a diamond paste abrasive or the like so that the surface roughness becomes R _max = 0.02 μm or less. A coating is provided on the surface of the base material for the purpose of improving oxidation resistance and wet resistance. The coating is provided by a known method such as a sputtering method, an ion plating method, and a chemical vapor deposition (CVD) method, using a noble metal, a noble metal alloy, a ceramic, or a mixture of a noble metal and a ceramic.

As described above, the molding die of the present invention has the same diameter as the desired microlens on the back surface with respect to the molding surface, and the tip of the hole is 1.5 mm or less from the molding surface and penetrates the molding surface. Not having holes of depth. The mechanism by which this mold can be used to mold an optical element having a concave microlens has not been completely elucidated, but when the mold is heated, the tip of the hole, that is, the thickness of the mold, is reduced. It is considered that the thin portion expands more than the other portions and deforms into a mold having a convex surface, and the optical element material in contact therewith is molded into an optical element having a concave microlens.

The shape of the microlens on the optical element formed by the present invention depends on the shape of the tip of the hole from the back surface, the thickness between the tip of the hole and the molding surface, the molding temperature, the pressure, and the like. Further, as the optical element material, not only various optical glasses but also resins can be used. Further, as a molding method, not only press molding but also various methods such as injection molding and hot sag molding can be applied.

[0010]

Next, the present invention will be described in detail by way of examples with reference to the drawings, but the present invention is not limited to these examples. FIG. 1 is a perspective view of a molding die showing one embodiment of the present invention, and FIG. 2 is a sectional view of the molding die shown in FIG. 1 and 2, a molding die 1 has a coating 3 on a molding surface 2 thereof.
And a plurality of holes 4 are provided on the molding surface 2 from the back surface. The hole 4 has the same diameter as the desired microlens, its tip is 1.5 mm or less from the molding surface, and has a depth not penetrating the molding surface.

A method for forming an optical element using the above-described mold will be described with reference to FIGS. FIG. 3 is a schematic explanatory view showing a state of a molding part using the molding die of the present invention shown in FIG. 1 as an upper mold before press molding of an optical element material, and FIG. FIG. 4 is a schematic explanatory diagram showing the state of FIG.
The molding die 1 is attached to the upper cylinder 5, the optical element material 11 is set on the lower die 6, and the molding part is heated by the heater 8. The heating temperature is measured by the thermocouple 10. At a high temperature, an inert gas, for example, a nitrogen gas can be supplied from the atmosphere gas supply port 13 into the atmosphere seal box 9 in order to prevent deterioration of the mold member due to oxidation. Reference numeral 7 denotes a spacer for adjusting the thickness of the optical element.

When the optical element material 11 is softened, the upper cylinder 5 is lowered, and the optical element material 11 is pressed at a desired pressure to be molded. Thereafter, the temperature is gradually cooled, and when the temperature of the molded portion becomes lower than the glass transition point of the optical element material 11, the pressure is removed, and the upper cylinder 5 is raised to take out the molded product 12. FIG. 5 shows a sectional view of the obtained molded product 12. This can be cut to the required size and used for various applications.

Example 1 A molding die was made of SUS304 stainless steel as a base material, and the molding surface was ground and polished until the surface roughness became 0.02 μm or less. The molding surface was coated with a platinum-gold alloy film to a thickness of 1 μm. Holes 4 having the same diameter (diameter: 1 mm) as the desired microlenses were formed on the back surface of the mold at intervals of 2 mm at a depth of 0.5 mm from the tip to the molding surface. The shape of the tip of the hole was a spherical surface having a radius of curvature of 0.5 mm.

The mold thus prepared is mounted on an upper cylinder, and an optical glass SFS as an optical element material is placed on a lower mold made of the same material as the upper mold but having no holes.
01 (manufactured by Ohara Optical Glass) was set. The molded part was heated with a heater, and when the temperature reached 440 ° C., the upper cylinder was lowered to press-mold the optical element material. Thereafter, it was cooled, and when the temperature was lower than 380 ° C., the cylinder was raised and the molded product was taken out. The obtained molded product was an optical element having concave lenses with a diameter of 1 mm and a radius of curvature of 0.5 mm on the surface at intervals of 2 mm.

In the above embodiment, the mold of the present invention was used only for the upper mold. However, when the mold of the present invention was used for both the upper mold and the lower mold, the optical element having microlenses on both surfaces was used. Can be manufactured.

[0016]

The molding die of the present invention can be easily and inexpensively manufactured because it is not necessary to form a minute convex surface on the surface of the molding die. Further, by using the mold of the present invention, an optical element having one or more small concave microlenses on its surface can be easily mass-produced.

[Brief description of the drawings]

FIG. 1 is a perspective view of a mold showing one embodiment of the present invention.

FIG. 2 is a cross-sectional view of the mold of FIG.

FIG. 3 is a schematic explanatory view showing a state of a molded portion before press molding of an optical element material.

FIG. 4 is a schematic explanatory view showing a state of a molding portion during press molding of an optical element material.

FIG. 5 is a cross-sectional view of a press-formed product.

[Explanation of symbols]

 Reference Signs List 1 molding die 2 molding surface 3 coating 4 hole 5 upper cylinder 6 lower die 7 thickness adjusting spacer 8 heater 9 atmosphere seal box 10 thermocouple 11 optical element material 12 molded product

Continuation of the front page (56) References JP-A-2-111635 (JP, A) JP-A-1-188436 (JP, A) JP-A-69-195912 (JP, A) JP-A-62-278136 (JP) JP-A-2-133326 (JP, A) JP-A-2-149436 (JP, A) JP-A-4-175228 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB Name) C03B 11/00-11/16

Claims (3)

(57) [Claims] 1. A molding die for molding an optical element having one or more concave microlenses on a flat surface or an arbitrary curved surface, wherein the molding surface has a back surface having the same diameter as a desired microlens diameter. A molding die for molding an optical element, wherein a desired number of microlenses are provided with holes whose tip ends are not more than 1.5 mm from the molding surface and do not penetrate the molding surface. 2. In molding an optical element having one or more concave microlenses on a flat surface or an arbitrary curved surface, the molding die according to claim 1 is used as an upper die and / or a lower die.
A method for molding an optical element, comprising heating an optical element material and a mold to soften the optical element material, and then molding with a mold. 3. The method for molding an optical element according to claim 2, wherein the molding is performed by a press molding method, an injection molding method or a hot sag molding method.