JP2005206430A - Mold press machine and manufacturing method of optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently manufacture an optical element which has high eccentric precision and is free from contamination with particles by imparting high durability and slidability to the sliding parts of the upper die, the lower die and the cylinder die. <P>SOLUTION: The mold press machine is provided with an upper die 10 and a lower die 20 at least one of which is movable up and down and a cylinder die 30 which slidably guides the upper die 10 and/or the lower die 20. At least parts of the sliding parts of the upper die 10 and the lower die and/or the cylinder die 30 are surface-treated by high speed blasting of a solid surface treatment agent. Carbon or molybdenum disulfide is preferably used for the surface treatment agent. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a mold press molding apparatus for press molding an optical element such as a lens and a prism, and a method for manufacturing the optical element.

  As a method of manufacturing such an optical element, a molding material softened by heating, for example, a glass preform, is pressed between an upper mold and a lower mold that are precisely processed based on the shape of the optical element to be obtained. A method for producing an optical element by molding is known.

  For example, a molding die has been proposed in which a hydrogenated amorphous carbon film is formed by coating at least a body mold or a sliding portion of a mold member by a microwave plasma CVD method or the like (for example, see Patent Document 1). According to such a mold, it is said that good slidability can be ensured even at high temperatures, the oxidation of the sliding surface can be suppressed by the carbon film, and the number of times of maintenance of the sliding surface can be reduced. .

Japanese Patent Laid-Open No. 7-2534

  However, the carbon film formed by the microwave plasma CVD method or the like described in Patent Document 1 is poor in integration with the substrate, and therefore is continuously pressed while repeating thermal expansion and contraction and mechanical friction between the molds. When it is applied to the sliding surface of a molding die that performs the above, it not only peels and lowers the slidability, but the peeled particles may contaminate the optical element or cause surface defects.

In addition, since the carbon film is relatively quickly consumed, there is a problem in that the sliding performance is lowered and the clearance of the sliding portion is increased with time as the number of presses is increased.
Further, in the film forming method described above, since it is necessary to control the film thickness while monitoring it, it takes time to form the film, and it is difficult to form a film on the inner peripheral surface of the barrel mold.

  By the way, optical elements, such as lenses, are frequently used in imaging devices, optical pickups, and the like, and the required accuracy such as decentering accuracy has become extremely high as the number of pixels and recording density have increased. The decentering accuracy of the optical element is determined by the shift distance (decenter) between the axis of the mold that molds the first surface of the optical function surface of the optical element and the axis of the mold that molds the second surface, the axis of the first surface, and the second axis. It depends on the tilt with respect to the axis of the surface (see FIG. 4). For example, in a lens applied to a digital imaging device having a large number of pixels and a high-density optical pickup optical device, molding conditions are required in which the tilt is suppressed within 2 minutes.

  A mold press molding apparatus used for manufacturing an optical element is usually configured to include an upper mold and a lower mold, at least one of which can move up and down, and a body mold that slides and guides the upper mold and / or the lower mold. Yes. In such a mold press molding apparatus, if the clearance of the sliding part (the part where the molds are in sliding contact with each other) is increased, decentering and tilting increase, and the optical performance of the molded optical element deteriorates. When molding an optical element that requires high accuracy, it is necessary to extremely reduce the clearance of the sliding portion. For example, it is necessary to make the clearance of the sliding part 10 μm or less.

However, if the clearance of the sliding part is made extremely small, not only will the bite occur during sliding, but the mold material will wear due to friction, and the particles generated by the abrasion will contaminate the optical element. Occurs. Further, when continuous pressing is performed under such conditions, the clearance gradually increases due to wear, and the eccentricity accuracy deteriorates with time.
In order to reduce the friction and wear of the sliding part, it is conceivable to use a known lubricant. However, since the molding temperature of the optical element is about 500 to 800 ° C., if the lubricant is dispersed in grease or oil, or if an organic solvent is used, it will be decomposed by heat and contaminate the optical element. Not applicable.

  The present invention has been considered in view of the above circumstances, and by providing excellent durability and slidability to sliding parts such as an upper mold, a lower mold, and a trunk mold, the eccentric accuracy is high, and An object of the present invention is to provide a mold press molding apparatus and an optical element manufacturing method capable of efficiently producing optical elements free from contamination by particles.

  In order to achieve the above object, a mold press molding apparatus of the present invention includes a mold press including an upper mold and a lower mold, at least one of which can move up and down, and a body mold that slides and guides the upper mold and / or the lower mold. In the molding apparatus, at least a part of the sliding portion of the upper mold, the lower mold, and / or the barrel mold is subjected to a surface treatment performed by spraying a solid surface treatment material at a high speed.

  If comprised in this way, the outstanding durability and sliding property can be provided to sliding parts, such as an upper mold | type, a lower mold | type, and a trunk | drum type | mold. In particular, when a surface treatment is performed on a solid surface treatment material by high-speed injection, at least a part of the particles of the solid surface treatment material sprayed at a high speed onto the substrate serving as a sliding portion are incorporated into the substrate surface and integrated with the substrate. Therefore, good slidability can be maintained over a long period of time without being peeled off during continuous press molding of optical elements or being consumed at an early stage, such as a carbon film formed by microwave plasma CVD. Can do.

Thereby, it is possible to efficiently produce an optical element with high eccentricity accuracy and free from contamination by particles. In particular, even high-precision optical elements that require a clearance of 10 μm or less for sliding parts can realize stable mold press production, and can be molded even with a clearance of 1 μm or less, which is the sliding limit. Become. Further, since the tilt of the optical element to be obtained is 1 minute or less, and further 30 seconds or less, stable production is possible even when the sliding part is long.
Further, the above-described surface treatment method does not need to be controlled while monitoring the film thickness, unlike the microwave plasma CVD method, and has an advantage that the treatment can be performed on the inner peripheral surface of the body.

In the mold press molding apparatus of the present invention, the solid surface treatment material includes at least one of carbon, molybdenum disulfide, or boron nitride.
If comprised in this way, favorable slidability can be provided to said sliding site | part with the graphite structure which carbon has, and the layered crystal structure which molybdenum disulfide and boron nitride have.
The average particle diameter of the solid surface treatment material is 15 to 25 μm for graphite (carbon), 10 to 15 μm for molybdenum disulfide, and 12 to 18 μm for h-BN (boron nitride). preferable. When this particle size is used, the kinetic energy given to the solid surface treatment material at the time of jetting is in an appropriate range, and the solid surface treatment material is easily taken into the substrate surface, so that the solid surface treatment material is detached and consumed during sliding. It is suppressed and suitable for obtaining the effects of the present invention.

Moreover, the mold press molding apparatus of this invention sets the surface roughness of the said sliding part as 0.05-10 micrometers.
With this configuration, when the solid surface treatment material is sprayed onto the substrate surface, the solid surface treatment material is easily taken into the substrate surface, so that the durability and slidability of the sliding portion can be improved.

Moreover, the mold press molding apparatus of this invention has the clearance of the said sliding part as 0.1-10 micrometers.
If comprised in this way, an optical element with high eccentricity precision can be shape | molded efficiently. Furthermore, if the sliding part is made long, it becomes possible to produce an optical element under a condition that the molding tilt is 1 minute or less, and further 30 seconds or less.

In the mold press molding apparatus of the present invention, the sliding portion is made of a ceramic having polycrystal.
If comprised in this way, since the solid surface treatment material sprayed on the base | substrate surface will become easy to be taken in by the base | substrate surface, durability and sliding property of a sliding site | part can be improved.

  The optical element manufacturing method of the present invention includes an upper mold, a lower mold, and / or a trunk mold in which carbon, molybdenum disulfide, or boron nitride is subjected to high-speed jetting on at least a part of a sliding portion and surface treatment is performed. An optical element manufacturing method using a mold press molding apparatus including: a molding material is supplied to the mold press molding apparatus, and at least one of the upper mold and the lower mold is moved up and down in a non-oxidizing atmosphere. This is a method for performing molding.

By doing so, the surface treatment that jets the solid surface treatment material at a high speed gives excellent durability and slidability to the sliding parts such as the upper mold, the lower mold, and the trunk mold. In addition, an optical element free from contamination by particles can be efficiently produced.
Moreover, since press molding is performed in a non-oxidizing atmosphere, oxidation and decomposition of carbon, molybdenum disulfide, or boron nitride can be suppressed even at high temperatures, and good durability and slidability can be maintained. .
Note that it is possible to perform surface treatment by high-speed jetting for each predetermined press shot, and in this way, it is possible to always manufacture an optical element while maintaining good eccentricity accuracy.

Further, in the method of manufacturing an optical element of the present invention, the surface treatment applied to at least a part of the sliding portion is a surface treatment in which molybdenum disulfide is jetted at high speed, and the press molding in the mold press molding apparatus includes: In the atmosphere, the method is performed at a molding temperature of 500 ° C. or higher.
In this way, it becomes possible to surface-treat the sliding portion using molybdenum disulfide having the property of thermally decomposing at about 400 ° C. in an oxidizing atmosphere and sublimating at about 500 ° C. The above problem can also be prevented in the production of an optical element using a glass material that needs to be molded at a high temperature.

As described above, according to the present invention, excellent durability and slidability are imparted to the sliding parts such as the upper mold, the lower mold, and the trunk mold, so that the eccentric accuracy is high and the contamination by particles. It is possible to efficiently produce an optical element without the above.
Moreover, according to the surface treatment method used in the present invention, the material, particle size, and jetting of the solid surface treatment material can be controlled without monitoring while controlling the film thickness, such as the microwave plasma CVD method and the hot filament CVD method. By simply selecting the speed, it is possible to form a sliding surface that is excellent in durability and slidability.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In the following, the present invention will be described along with an embodiment in which the present invention is applied to a glass optical element manufacturing apparatus, but the present invention is not limited to this embodiment. The present invention can also be applied to manufacturing parts other than glass and resin optical elements.

[Mold press molding equipment]
FIG. 1 is a schematic longitudinal sectional view of a mold press molding apparatus according to the present invention.
As shown in this figure, the mold press molding apparatus includes an upper mold 10 and a lower mold 20 at least one of which can move up and down, and a body mold 30 that slides and guides the upper mold 10 and / or the lower mold 20. It is configured.

The upper mold 10 and the lower mold 20 are opened in order to press-mold the preform (glass material) 40 between the upper mold 10 and the lower mold 20 or when the preform 40 is supplied or the molded product is taken out. In order to do so, it can move up and down. The lower surface of the upper mold 10 forms a molding surface 13, and the upper surface of the lower mold 20 forms a molding surface 23.
The body mold 30 is formed so as to slidably guide (position regulation) the upper mold 10 and the lower mold 20 on the inner peripheral surface thereof.

  When press-molding a high-precision optical element using the above-described mold press molding apparatus, it is required to maintain smooth sliding while extremely reducing the clearance of the sliding portion where the molds are in sliding contact with each other. . In the present invention, in order to satisfy such a requirement, a surface treatment is performed on the upper mold 10, the lower mold 20, and / or at least a part of the sliding portion of the body mold 30 to inject a solid surface treatment material at a high speed, Excellent durability and slidability are imparted to the sliding part.

  Specifically, the above surface treatment can be performed on the outer peripheral surface 11 of the upper mold 10, the outer peripheral surface 21 of the lower mold 20, the inner peripheral surface 31 of the trunk mold 30, and the like. However, when surface treatment is performed on the outer peripheral surface 11 of the upper mold 10 and the outer peripheral surface 21 of the lower mold 20, it is necessary to prevent contamination and damage due to injection to the precision processed molding surfaces 13 and 23. It is convenient and preferable to apply a surface treatment to the inner peripheral surface 31 of the mold 30.

  When the above-mentioned surface treatment is performed, the solid surface treatment material sprayed at a high speed onto the substrate serving as the sliding part is incorporated into the substrate by at least part of the particles being incorporated into the substrate surface. As in the case of a carbon film formed by coating or the like, good slidability can be ensured over a long period of time without being peeled off during continuous press molding of an optical element or being consumed at an early stage.

  Carbon, molybdenum disulfide, or boron nitride can be used as the solid surface treatment material. All of these bring about an excellent lubricating effect. Of these, carbon preferably has a graphite structure. This is because the graphite structure imparts excellent slipperiness to the substrate surface. Molybdenum disulfide can also give excellent slipperiness to the substrate surface due to the layered crystal structure. In the case of boron nitride, h-BN is preferable. This is because h-BN imparts excellent slipperiness to the substrate surface due to the same crystal structure as described above.

  Among these, graphite is suitable as a solid surface treatment material in the molding apparatus of the present invention that performs press molding at a high temperature because it is excellent in heat resistance. On the other hand, since molybdenum disulfide has a higher specific gravity than graphite, it has a high probability of colliding with the substrate surface with sufficient kinetic energy at the time of injection, and at least a part of the particles being taken into the substrate surface. From this point, molybdenum disulfide is used as a preferable solid surface treatment material.

  The average particle diameter of the solid surface treatment material is preferably 15 to 25 μm in the case of graphite, 10 to 15 μm in the case of molybdenum disulfide, and 12 to 18 μm in the case of h-BN. When this particle size is used, the kinetic energy of the solid surface treatment material at the time of jetting falls within an appropriate range and is easily taken into the surface of the substrate, so that separation and wear during sliding can be suppressed.

  When the solid surface treatment material is jetted at a high speed, it is not necessary to disperse the solid surface treatment material in oil or grease or dissolve it in an organic solvent. Along with the compressed air or an inert gas such as nitrogen, it can be injected using a known injection device. The injection speed is preferably 50 to 150 m / s.

  When such a surface treatment is performed, the solid surface treatment material reaches the surface of the substrate with sufficient kinetic energy, and at least a part, preferably most of the solid surface treatment material is taken into a gap between crystals constituting the surface of the substrate, or the substrate. Is taken into the interior from between the atoms constituting the. Thus, in order for the solid surface treatment material to be taken into the substrate side, the surface of the substrate is preferably a rough surface in a predetermined range. That is, the surface roughness of the substrate is 0.05 to 10 μm in Ra, preferably 0.1 to 5 μm.

  For example, if the substrate is ceramic, a surface state in which the solid surface treatment material is taken into the crystal gaps (for example, grain boundaries) is preferable, and a polycrystalline one is particularly preferable. A preferable method for producing the ceramic constituting the substrate is by sintering. This is because the chemical vapor deposition method or the like may cause the surface to be too dense and smooth, making it difficult to obtain the effects of the present invention.

In the present invention, an upper mold and a lower mold having a molding surface that is precisely shaped based on the shape of the optical element to be molded are prepared. As the mold base material of the molding surface portion, known materials (SiC, Si ₃ N ₄ , WC, TiC, TaC, BN, TiN, ZrO 2, cermet, stainless steel, etc.) can be used. In particular, SiC, Si ₃ N ₄ , and WC are preferable because they can withstand high molding temperatures and are dense and can be precisely machined.
Incidentally, the sliding parts of the present invention, the upper die, in the case of providing at least a portion of the lower mold, the sliding portion is polycrystalline SiC, it is preferable that the Si ₃ N ₄ or WC. For example, a dense layer may be deposited by a CVD method or the like in the vicinity of the molding surface of the mold base material of the above-described material by sintering. The body mold can be selected from the same materials.

  When the surface of the substrate is smooth, the solid surface treatment material is difficult to be taken in, and therefore it is preferable to perform a roughening treatment in advance. For example, when the substrate is a metal or the like, if the surface is a mirror surface, the solid surface treatment material is difficult to be taken in, so it is preferable to perform a roughening treatment such as blasting or chemical etching in advance. In the blast method, the abrasive is collided with the workpiece at a high speed together with the compressed air. In chemical etching, the surface can be roughened by surface treatment with phosphoric acid, strong acid, strong alkali, or the like.

  The solid surface treatment material taken into the substrate by such surface treatment modifies the surface layer up to a depth of about 100 to several hundreds of nanometers on the substrate surface. The closer the surface of the modified surface layer is, the higher the concentration of the solid surface treatment material becomes. This modified layer has high durability, withstands repeated sliding performed in a continuous press, and suppresses generation of particles. For example, good slidability was exhibited in thousands of continuous presses.

  In addition, it is preferable to provide a release film on the molding surfaces 13 and 23 of the upper mold 10 and the lower mold 20 to promote the mold release. As the release film, diamond-like carbon film (DLC), hydrogenated diamond-like carbon film (DLC: H), tetrahedral amorphous carbon film (ta-C), hydrogenated tetrahedral amorphous carbon film (ta-C) : H), amorphous carbon film (a-C), hydrogenated amorphous carbon film (aC: H), carbon-based films such as carbon films containing nitrogen, platinum (Pt), palladium (Pd), iridium ( An alloy film containing at least one metal selected from Ir), rhodium (Rh), osmium (Os), ruthenium (Ru), rhenium (Re), tungsten (W), and tantalum (Ta) can be used.

  Further, the release film is formed on the molding surfaces 13 and 23 by DC-plasma CVD method, RF-plasma CVD method, microwave plasma CVD method, ECR-plasma CVD method, photo-CVD method, laser CVD method, etc. Techniques such as ionized vapor deposition such as plasma CVD and ion plating, sputtering, ion plating, vapor deposition, and FCA (Filtered Cathodic Arc) can be used.

[Method for Manufacturing Optical Element]
Next, a method for manufacturing an optical element using the mold press molding apparatus will be described.
As a molding material used for molding an optical element, for example, a preformed glass preform can be used. The glass preform is formed into a predetermined volume and shape by melting and solidifying or cold working glass in advance. It is preferable to provide a film having a release function on the surface of the glass preform prior to press molding. Such films include carbon films, hydrocarbon films, self-assembled films (films formed by self-aligning and organizing organic substances having specific functional groups in the molecule on the surface of glass preforms), etc. Is given.

In the molding step, a glass preform heated and softened to a viscosity suitable for molding is press-molded by applying an appropriate load between the upper mold and the lower mold, and the molding surface is transferred. While maintaining the load or reducing the load, the molded optical element and the mold are kept in close contact, for example, after cooling to a temperature equal to or less than 10 ¹² dPa · s in terms of glass viscosity, Separate the mold from the lower mold and release. The mold release temperature is preferably equivalent to 10 ^12.5 to 10 ^15.0 dPa · s, more preferably 10 ¹³ to 10 ^15.0 dPa · s in terms of glass viscosity. And after mold release, an optical element is taken out.

After placing the glass preform between the upper and lower molds, the temperature is raised to a predetermined temperature (for example, a temperature corresponding to a glass viscosity of 10 ⁷ to 10 ⁹ dPa · s) together with the mold, and then pressed. You may shape | mold (henceforth molding method 1), or the shaping | molding which heated the glass preform heated to predetermined temperature (For example, the temperature equivalent to 10 < ⁶ > -10 < ⁹ > dPa * s by glass viscosity) out of a type | mold. It may be supplied to a mold and press-molded (hereinafter, molding method 2). In the latter case, the molding material heated outside the mold is supplied to a molding mold heated to a lower temperature (for example, a glass viscosity equivalent to 10 ⁸ to 10 ¹² dPa · s), and the upper and lower molds are immediately It can be made close and press-molded under load.

  In the method of feeding the preform heated outside the mold to the heated upper and lower molds (molding method 2), the preform heated outside the mold is fed between the heated upper and lower molds, and then the preform is fed. It is necessary to immediately close the upper and lower molds by regulating the position of the upper and lower molds so as not to lower the temperature of the reform (the trunk mold is also heated to the upper or lower mold temperature or a temperature close thereto). Conventionally, in order to smoothly perform position regulation and sliding of the thermally expanded upper and lower molds in the body mold at such a high temperature, it has been difficult to extremely reduce the clearance of the sliding part.

  However, at least a part of the sliding portion in the upper mold, the lower mold, and / or the barrel mold is subjected to a surface treatment that jets carbon, molybdenum disulfide, or boron nitride at a high speed, and then press-molded. Even when the clearance of the sliding portion was 10 μm or less, it was possible to perform continuous pressing. As a result, an optical element with sufficiently high eccentricity accuracy (for example, within 2 minutes of tilt) could be formed.

  In addition, in the method (molding method 1) in which the preform is placed between the upper and lower molds, heated and heated together with the mold, and then press-molded (molding method 1), the upper and lower molds and the body mold are assembled before thermal expansion. Therefore, the clearance of the sliding portion could be 5 μm or less. As a result, an optical element (for example, tilt within 60 seconds) with higher decentration accuracy can be obtained.

Furthermore, in the method for manufacturing an optical element in the present invention, the molding atmosphere in the molding process is a non-oxidizing atmosphere. For example, nitrogen gas or a mixed atmosphere of nitrogen gas and hydrogen gas can be used. Thereby, the oxidation and decomposition | disassembly of the solid surface treatment material given to the sliding site | part of the shaping | molding die were able to be suppressed.
In particular, among the solid surface treatment materials of the present invention, molybdenum disulfide is thermally decomposed near 400 ° C. and sublimates near 500 ° C. in an oxidizing atmosphere, so it is applied to a molding apparatus that performs molding at a high temperature of 500 ° C. or higher. However, it was considered impossible to do this, but as a result of investigations by the inventors, press molding was performed in a non-oxidizing atmosphere using a surface treated by high-speed injection of molybdenum disulfide on the sliding part of the mold. As a result, the surface treatment was not impaired even at a high temperature of 500 ° C. or higher, and press molding could be performed satisfactorily.

Needless to say, the present invention is not limited to the embodiment. For example, the surface treatment of the present invention can also be applied to the following mold press molding apparatus.
This mold press molding apparatus includes forced release means for releasing a molded body attached to the molding surface of the upper mold or the lower mold, and the forced mold release means is provided on the outer peripheral surface of the upper mold or the outer peripheral surface of the lower mold. A mold press molding apparatus that moves relative to an upper mold or a lower mold by sliding with at least a part, wherein the forced release means, the upper mold, and / or at least a part of a sliding part of the lower mold In addition, a surface treatment is performed in which carbon, molybdenum disulfide, or boron nitride is jetted at a high speed.

  In other words, in the above-described mold press molding apparatus, when the molded optical element is released, if sticking occurs on the molding surface of the upper mold or the lower mold, an automatic take-out is hindered. Forced mold release means is provided to reliably release the mold from the molding surface. This forced mold release means is provided near the outer periphery of the upper mold or the lower mold, and when the upper and lower molds are separated after press molding, the optical element is released from the upper mold or the lower mold and dropped onto the lower mold. . At this time, the forced release means moves relative to the molding surface of the upper mold or the lower mold by sliding with the outer periphery of the upper mold or the lower mold. When the surface treatment of the present invention is applied to the moving part, the operation of the forced mold release means becomes smooth, and it is possible to reliably perform mold release and automatic removal of the optical element.

[Examples and Comparative Examples]
Next, examples and comparative examples of the present invention will be described with reference to FIGS.
FIG. 2 is a table showing the implementation conditions and results of Examples 1 to 3 and Comparative Example, and FIG. 3 is a table showing the implementation conditions and results of Examples 4 to 7.
However, in these figures, the number of stoppage of biting is the number of stoppages due to biting when the press is performed 5000 times in the same mold, and the appearance failure due to particles is the number of stoppages when 5000 presses are performed in the same mold. Appearance defect rate due to particles (○: defect rate is less than 0.5%, Δ: defect rate is 0.5% to 2%, x: defect rate is over 2%), eccentric performance is 5000 press-formed products 10 shows the decentration performance of 10 optical elements selected at random.

[Example 1]
As a molding material, a glass preform made of borate optical glass A (glass transition temperature (Tg) is 520 ° C., yield point (Ts) is 560 ° C.) was used to mold a biconvex lens. As the upper and lower molds, a polycrystalline SiC molding surface produced by a CVD method is mirror-polished to Rmax = 18 nm (AFM measurement), and then a DLC: H film (hydrogen) is formed on the molding surface using an ion plating film forming apparatus. A diamond-like carbon film) was used. The body mold was processed from a SiC sintered body so that the clearance between the upper and lower molds and the sliding portion was 3 μm.

  Carbon (graphite) particles (average particle diameter: 20 μm) were sprayed at a speed of 100 m / s onto the sliding part of the inner surface of the body mold. The surface roughness was 0.5 μm in Ra. As a result of observing the ejection surface with an optical microscope and an electron microscope (SEM), it was confirmed that carbon particles were embedded in the SiC substrate.

Using these barrel molds and upper and lower molds, mold pressing was performed in a press chamber in a nitrogen gas atmosphere. That is, a preform was placed between the upper and lower molds, heated to 610 ° C., and pressurized with a pressure of 150 kg / cm ² for 1 minute. After releasing the pressure, the cooling rate is reduced to 480 ° C. at −50 ° C./min. After that, cooling is performed at a rate of −100 ° C./min or more, and the temperature of the press-molded product is lowered to 200 ° C. or less. The molded product was taken out.

As a result of continuous press molding up to 5,000 press shots with the same mold, there is no sliding failure such as biting, and there are no appearance defects such as spots (dot-like appearance defects) due to particles on the surface of the molded lens. I couldn't.
Further, when the upper and lower molds and the body mold were observed after press molding, no defects based on sliding failure such as rubbing were found. Moreover, as a result of observing the ejection surface with an optical microscope and an electron microscope (SEM), it was confirmed that the carbon component embedded in the SiC base material remained.

Furthermore, when 10 were randomly selected from the 5000 biconvex lenses produced by the mold press method and the tilt was evaluated from the aspherical eccentricity of these 10 biconvex lenses, the tilt was 45 seconds at maximum. .
The decentering accuracy (tilt) of the aspheric lens was converted from the obtained aspheric decenter using a known aspheric decenter measuring device (Olympus ASDM: measurement resolution 30 seconds or more).

[Comparative example]
When the press molding was started with the same mold without injecting the carbon particles to the upper and lower molds and the barrel mold, the biting part occurred at about 150 shots, and about 400 shots were generated. As a result, appearance defects such as pots due to rubbing particles occurred.
Pressing was performed with the same mold up to 1000 shots, but biting stop occurred seven times during the process. Further, the appearance defect rate of 1000 biconvex lenses molded by press reached 24%.
Further, when the outer periphery of the upper and lower molds and the inner surface of the barrel mold were observed after press molding, both of the sliding parts were rubbed.

[Example 2]
A convex meniscus lens was molded using a preform composed of borosilicate optical glass B (glass transition temperature (Tg) 500 ° C., yield point (Ts) 540 ° C.). WC materials were used as the upper and lower molds and the trunk mold. The upper and lower molds used were those in which the molding surface was mirror-polished to Rmax = 22 nm (AFM measurement), and then a DLC film (diamond-like carbon film) was formed on the molding surface using a sputtering method deposition apparatus. The body mold used was processed to have a clearance of 7 μm from the sliding part with the upper and lower molds.

MoS ₂ particles (particle size: 12 μm) were sprayed at a speed of 100 m / s onto the sliding part of the upper and lower mold outer periphery and the sliding part of the inner surface of the body mold. The surface roughness of the sliding surface of the WC material was Ra 0.5 μm.
As a result of observing the ejection surface with an optical microscope and an electron microscope (SEM), it was confirmed that MoS ₂ particles were embedded in the WC substrate.

Using these barrel molds and upper and lower molds, a mold press was performed in a press chamber that is a nitrogen gas atmosphere. A preform heated to 650 ° C. in advance outside the mold was supplied onto the lower mold surface of the upper and lower molds heated to 600 ° C., and the upper and lower molds were brought close to each other, followed by pressurizing at a pressure of 150 kg / cm ² for 1 minute. . After releasing the pressure, the cooling rate is reduced to 480 ° C. at −50 ° C./min. After that, cooling is performed at a rate of −100 ° C./min or more, and the temperature of the press-molded product is lowered to 200 ° C. or less. The mold was released and the molded product was taken out.

As a result of continuous press molding up to 5000 press shots with the same mold, no sliding failure due to biting occurred, and no appearance defects such as spots due to particles were found on the molded lens surface. Further, when the upper and lower molds and the body mold were observed after press molding, no defects based on sliding failure such as rubbing were found. Moreover, as a result of observing the ejection surface with an optical microscope and an electron microscope (SEM), it was confirmed that the MoS ₂ component embedded in the WC substrate remained.

  Furthermore, when randomly selecting 10 of the 5000 biconvex lenses produced by the mold press method and evaluating the eccentricity of these 10 biconvex lenses, the tilt was 120 seconds at maximum.

[Examples 3 to 6]
Continuously up to 5000 presses with the same mold in the molding apparatus as in Example 1, except that the material of the upper and lower molds and the injection mold, the glass of the preform, etc. were changed as shown in the tables of FIGS. Pressed. As shown in FIGS. 2 and 3, no sliding failure occurred, and no defects such as spots due to particles were observed on the surface of the molded optical element.

  The present invention is applied to a mold press molding apparatus for press molding an optical element such as a lens and a prism, and a method for manufacturing the optical element. In particular, it can be suitably used for the production of optical elements that require high decentering accuracy.

It is a schematic longitudinal cross-sectional view of the mold press molding apparatus which concerns on this invention. It is Table 1 which shows the implementation conditions and result of Examples 1-3 and a comparative example. It is Table 2 which shows the implementation conditions and result of Examples 4-6. It is explanatory drawing of eccentric performance.

Explanation of symbols

10 Upper mold 13 Molding surface 20 Lower mold 23 Molding surface 30 Body mold 40 Preform

Claims (7)

In a mold press molding apparatus including an upper mold and a lower mold, at least one of which can move up and down, and a barrel mold that slide-guides the upper mold and / or the lower mold,
A mold press molding apparatus, wherein a surface treatment is performed by spraying a solid surface treatment material at a high speed onto at least a part of sliding portions of the upper mold, the lower mold, and / or the body mold.   The mold press molding apparatus according to claim 1, wherein the solid surface treatment material includes at least one of carbon, molybdenum disulfide, or boron nitride.   The mold press molding apparatus according to claim 1 or 2, wherein the sliding portion has a surface roughness of 0.05 to 10 µm.   The mold press molding apparatus according to any one of claims 1 to 3, wherein a clearance of the sliding portion is 0.1 to 10 µm.   The mold press molding apparatus according to any one of claims 1 to 4, wherein the sliding portion is a ceramic having a polycrystal. Optics using a mold press molding apparatus including an upper die, a lower die, and / or a barrel die that are subjected to surface treatment by spraying carbon, molybdenum disulfide, or boron nitride at a high speed on at least a part of the sliding portion. A method for manufacturing an element, comprising:
A method of manufacturing an optical element, comprising: supplying a molding material to the mold press molding apparatus, and performing the press molding by vertically moving at least one of the upper mold and the lower mold in a non-oxidizing atmosphere. The surface treatment applied to at least a part of the sliding portion is a surface treatment for spraying molybdenum disulfide at high speed,
The optical element manufacturing method according to claim 6, wherein the press molding in the mold press molding apparatus is performed at a molding temperature of 500 ° C. or higher in a non-oxidizing atmosphere.

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