JPH0615184B2 - Method for producing die for press-molding optical element - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a press-molding die for mass-producing high-precision micro-machined optical elements by press molding.

Conventional technology To directly press and mold high precision optical elements,
The mold material must be stable at high temperatures, have excellent oxidation resistance, be inert to glass or plastic, and have excellent mechanical strength so that the shape accuracy does not collapse when pressed. On the other hand, It must have excellent workability.

As a mold material satisfying the above-mentioned conditions necessary for a press molding mold for an optical element to some extent, JP-A-59-99 has been proposed.
A mold is used in which a cemented carbide described in 059 is used as a base material, a press surface of the base material is machined into a desired shape, and the surface is covered with a noble metal layer as a protective film.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, the conventional mold material has very excellent mechanical strength,
Furthermore, since it is chemically very stable, there is a limit in performing mechanical processing directly or by wet etching. In addition, molds of the same shape can be highly accurately and reproducibly
It is very difficult to fabricate a large amount, and it takes a lot of production time and cost.

In view of the above problems, in the present invention, by directly performing fine processing on the protective film on the surface of the mold by a physical method, it is possible to form a highly accurate optical element with good optical performance by the direct press molding method. For easy press molding, and
It is intended for mass production.

Means for Solving the Problems In order to solve the above problems, in the present invention, it is difficult to react with an optical element, as a mold having heat resistance and excellent mechanical strength,
WC-based cemented carbide or TiN
A cermet containing TiC, Cr ₃ C ₂ or Al ₂ O ₃ as a main component was used, and Pt, Pd, Ir and R were used on the press surface.
Using h, Os, Ru, Re, W, and ta, which are formed by coating an alloy thin film containing at least one or more kinds of metals as a protective film, the surface of the protective film is directly micromachined by a physical method. By performing the above, it is possible to easily and in large quantity manufacture a press-molding die for enabling press molding of an optical element having good optical performance and high precision.

Operation The present invention produces a press-molding die for an optical element that has been subjected to microfabrication by the above-described method, and by using this die, a high-precision optical element having good optical performance is directly pressed to form a large amount of the optical element. It is possible to do.

Embodiment Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

First, as a first example, an example in which the present invention is applied to manufacture an aspherical glass lens will be described.

First, a cemented carbide containing WC with a diameter of 20 mm and a thickness of 6 mm as a main component is used as a base material, and the base material has a radius of curvature of 46 mm.
Was processed into a mold having a concave press surface. The press surface of this mold was mirror-polished using ultrafine diamond abrasive grains. Next, a Pt—Ta alloy thin film having a thickness of 5 μm was coated as a protective film on the mirror surface by a sputtering method to prepare a spherical press-molding die. FIG. 1 shows a cross-sectional structural diagram of the unprocessed press-molding die thus constructed. In FIG. 1, 11 is a base material and 12 is a protective film.

UV curable bisazide compound resin is applied to the surface of the spherical press molding die, and a desired aspherical surface is applied to the transparent plastic semi-finished product with a radius of 46 mm, and the release agent is applied. The coated master was placed, and the shaft was aligned and fixed. A schematic diagram in this state is shown in FIG. In FIG. 2, reference numeral 21 is an ultraviolet-curable bisazide compound resin, and 22 is an aspherical surface-processed transparent master.

Next, ultraviolet rays are irradiated from the back surface of the master until the resin is hardened, the master is removed after the resin is hardened, and an aspherical resin layer is formed on the surface of an unprocessed spherical press-molding die.

This mold is set in a dry etching device, and anisotropic etching is uniformly performed on the surface of the cured bisazide compound-based resin layer, and the mold is taken out after the entire resin layer is etched. The surface of the mold thus manufactured reflects the surface shape of the resin layer. That is, when the etching rate of the resin layer and the protective film is the same, the surface shape of the protective film after etching becomes the same as the surface shape of the resin layer, and when the etching rates of the resin layer and the protective film are different, the etching rate The surface shape depends on the ratio. A cross-sectional view of this aspherical press-molding die is shown in FIG. In FIG. 3, 31 is a spherical base material, and 32 is a protective film whose surface is processed into an aspherical shape.

The mold manufactured by this method has good reproducibility, and a large number of molds having the same shape can be manufactured.

This mold is set as the upper and lower molds in the press molding machine shown in FIG. In FIG. 4, 41 is a fixed block for the upper die, 42 is a heater for the upper die, 43-a is the upper die, 4
4-a is a shaped glass element, 45-a is a lower die, 46 is a lower die heater, 47 is a lower die fixed block, 48 is an upper die thermocouple, 49 is a lower die thermocouple, and 410 is Plunger 411 is a positioning sensor, 412 is a stopper, and 413 is a cover.

Next, lead oxide (PbO) 70% by weight, silica (SiO)
A glass element 44-a obtained by processing an oxidative optical glass consisting of 27% by weight and the balance trace components into a spherical shape having a radius of 10 mm.
Is placed on the upper and lower molds 43-a and 45-a, and the upper mold 43-a is placed on the lower mold 45-a.
The temperature is raised to ℃, pressed in a nitrogen atmosphere with a pressing pressure of about 40 kg / cm ² and held for 2 minutes, then the upper and lower molds are cooled to 300 ° C. in that state, and press-formed aspherical glass. The lens is taken out, and the step of press molding the aspherical glass lens is completed. By repeating the above steps, the upper and lower molds 43-
a and 45-a were removed from the press molding machine, the state of the press surface was observed with an optical microscope, and the surface roughness (RMS value, Å) of the press surface at that time was measured to evaluate the mold accuracy of each. .

The results of the press test are shown in Table 1. In the mold made here, like sample Nos. 1 and 2, 10000
Even after pressing twice, the surface roughness (RMS value)
It can be seen that there is almost no roughness at 12.1Å and 12.4Å, and the mold shape has not changed.

As described above, according to the present invention, it becomes possible to easily manufacture a high-precision aspherical surface press-molding die in a large amount, and by using this mold, a high-precision aspherical glass lens is directly press-molded. It became possible to mold a large amount with.

Next, as a second example, the pitch is 0.1 mm and the step is 0.
An example carried out for producing a diffraction grating having a sawtooth surface shape of 5 μm will be described.

Using a cemented carbide plate having a thickness of 7 mm and a size of 5 cm and containing WC as a main component as a base material, the pressed surface was mirror-polished using ultrafine diamond abrasive grains. Then, a Pt-Rh-W alloy thin film having a thickness of 4 [mu] m was coated as a protective film on the mirror surface by an ion plating method to prepare a planar press-molding die.

A mold release agent is applied on the surface of the above-mentioned flat-shaped press-molding die coated with a UV-curable bisazito compound-based resin, and the surface of the plastic plate has a pitch of 0.1 mm.
Then, a master processed into a sawtooth surface shape having a step of 0.5 μm is placed, and ultraviolet rays are irradiated from the back surface of the master until the bisazide compound resin is cured, and the master is removed.

This mold is set in a dry etching apparatus, and the cured bisazide compound-based resin layer is uniformly anisotropically etched from the surface, and the mold is taken out after the entire resin layer is etched. In this way, a saw tooth-like fine processing was applied to the surface, and a cross-sectional view of the mold is shown in FIG. In FIG. 5, reference numeral 51 is a base material, and 52 is a protective film processed into a sawtooth shape. With this mold as the upper mold and the flat mold as the lower mold, the mold was set in the press molding machine shown in FIG. 4, and as in the first embodiment, 70% by weight of PbO, 27% by weight of SiO and the rest were Lead oxide optical glass consisting of trace components with a thickness of 2 mm,
The glass element 44-b processed into a flat plate of 5 cm square is placed on the upper and lower molds 43-b and 45-b lower mold 45-b, and the upper mold 43-b is placed thereon, and the temperature is raised to 520 ° C. Warm and press in a nitrogen atmosphere with a pressing pressure of about 40 kg / cm ² and hold for 2 minutes, then cool the upper and lower molds to 300 ° C. in that state, and take out the press-formed diffraction grating, The process of pressing the diffraction grating is completed.

The above steps were repeated, and at the end of the 10,000th press, the die 43-b was removed from the press molding machine, and the state of the press surface was observed with an optical microscope for evaluation. As a result, it was found that the mold surface shape was not deformed and the mold surface was not roughened, and high-precision mass production of diffraction gratings was possible.

In order to explain the present invention, a cemented carbide containing WC as a main component is used as the base material of the press-molding die in the first and second embodiments, and a Pt-Ta alloy thin film or Pt- is used as the protective film. Although a mold coated with a Rh-W alloy thin film has been taken as an example, a cermet containing TiN, TiC, Cr ₃ C ₂ or Al ₂ O ₃ as a main component is used as a base material instead of the cemented carbide containing WC as a main component. And press Pt,
Even if a mold constituted by coating an alloy thin film containing at least one kind of metal among Pd, Ir, Rh, Os, Ru, Re, W, and Ta is used, a high precision is obtained by the same method. Needless to say, it becomes possible to easily manufacture a large number of press-molding molds for optical elements, and by using this mold, it is possible to directly mold a large amount of high-precision optical elements by direct press-molding.

Further, in order to explain the present invention, plastic is used as the master in the first and second embodiments, but any material can be used as long as it is a material that transmits light of a wavelength that cures the photosensitive resin. Needless to say.

Furthermore, in order to explain the present invention, an ultraviolet-curable bisazide compound-based resin was used as the photosensitive resin in the first and second examples, but a resin that is cured by light having a wavelength in another region is used. However, it goes without saying that the same effect can be obtained.

EFFECTS OF THE INVENTION As described above, in the present invention, in producing a press-molding die for an optical element, the photosensitive resin applied to the surface of the press-forming die for the unprocessed optical element was subjected to fine processing on the surface. By irradiating light from the back side of the transparent master, the surface shape of the master is transferred, the entire surface is physically etched uniformly, and the surface of the press mold of the optical element is finely processed to achieve high accuracy. A press-molding die for an optical element can be easily manufactured in a large amount, and by using this die, a high-precision optical element can be directly formed in a large amount by press molding.

[Brief description of drawings]

1, 2, 3, and 5 are schematic views of a cross section of a press-molding die for an optical element of the present invention, and FIGS. 4 (a) and 4 (b) are presses for the optical element in the embodiment. It is a schematic diagram of a press molding machine incorporating a molding die. 11 ... Base material, 12 ... Protective film.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location B21D 37/20 B 7425-4E B29L 11:00 4F

Claims (3)

[Claims] 1. A surface shape of a master is transferred by irradiating a photosensitive resin applied on the surface of a press mold of an unprocessed optical element with light from the back side of a transparent master having a finely processed surface. After that, the entire surface is uniformly physically etched, and the surface of the mold is subjected to fine processing, so that a mold for press-molding an optical element is manufactured. 2. The press for an optical element according to claim 1, wherein the master is a transparent master having a surface of resin or glass which is finely processed by machining or physical and chemical etching. A method for producing a molding die. 3. A press-molding die whose base material is a cemented carbide containing tungsten carbide (WC) as a main component, or titanium nitride (TiN), titanium carbide (TiC), and chromium carbide (Cr ₃ C). ₂ ) or a cermet containing alumina (Al ₂ O ₃ ) as a main component is used, and platinum (Pt), palladium (Pd), iridium (Ir), rhodium (Rh), osmium (O) is used on the press surface.
s), ruthenium (Ru), rhenium (Re), tungsten (W), and tantalum (Ta) are coated with an alloy thin film containing at least one metal. A method for producing a press molding die for an optical element according to the item (1).