JP2009073707A - Production method for optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a production method whereby a production cost of an optical element can largely be reduced by enabling an inexpensive member such that conventionally used for plastic molding to use for precision press molding. <P>SOLUTION: The production method for an optical element is characterized by forming a glass preform essentially containing a TeO<SB>2</SB>component and/or a Bi<SB>2</SB>O<SB>3</SB>component by precision press molding using a mold made of surface film-formed steel (including stainless steel) and/or a copper alloy. Wherein the surface film suitably contains at least one selected from the group consisting of Ni, Cr and Co, together with either or both of P and B. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a method for manufacturing an optical element having an optical constant having a high need in the optical field at a low cost.

In recent years, in the field of optical devices such as digital cameras and projectors, downsizing and weight reduction have been demanded, and accordingly, downsizing of optical elements and reduction of the number of lenses used have become issues.

In general, the lenses constituting the optical system generally include a spherical lens and an aspheric lens. Many spherical lenses are manufactured by cold working (grinding / polishing, etc.) a glass material or by cold working a glass molded product obtained by reheat press molding. On the other hand, an aspherical lens is formed by press-molding a heat-softened spherical, elliptical, or flat preform with a mold having a high-precision molding surface, and using the shape of the high-precision molding surface of the mold as a preform material. The mainstream is a method obtained by transfer, that is, manufactured by precision press molding.

When a glass molded product such as an aspheric lens is obtained by precision press molding, the heat-softened preform is pressed in a high-temperature environment in order to transfer the high-precision molding surface of the mold to the glass preform. It is necessary. Therefore, the mold used at that time is also exposed to a high temperature, and a high pressing pressure is applied to the mold. As a result, when the preform is heated and softened and pressed, the release film provided on the molding surface of the mold is often damaged, and the high-precision molding surface of the mold cannot be maintained. Also, the mold itself is easily damaged. In such a case, the mold must be replaced, and as a result, the number of mold replacements increases, and low cost and mass production cannot be realized. Therefore, the glass used as the preform material for precision press molding suppresses the above-mentioned damage, maintains the high-precision molding surface of the mold for a long time, and enables precision press molding with low press pressure. In view of the above, it is desired to have a glass transition temperature (Tg) as low as possible.

Usually, molds used for precision press molding of optical glass materials are made of carbide, cermet, silicon carbide, crystallized glass materials such as tungsten carbide because they have high heat resistance and high strength. .

Further, a surface film (release film) is provided on the molding surface in order to prevent the mold and glass from being fused, to improve the mold release property and to extend the life of the mold. Various films are known as surface films, such as platinum, iridium, rhenium, palladium, osmium, and other precious metal films, diamond-like carbon (DLC), tetrahedral amorphous carbon (TAC), and other carbon films, chromium nitride, and nitride. Nitride films such as titanium are well known.

Furthermore, in order to prevent deterioration of the mold film due to oxidation, precision press molding is often performed in a non-oxidizing atmosphere.

As described above, in general, in order to precisely press the optical glass, special parts and conditions are often required, and there is a problem that the cost increases accordingly.

In particular, cemented carbide molds such as tungsten carbide, which have been used as precision press molding molds for optical glass, have extremely high material hardness. Need to be formed. However, even the diamond grindstone itself may be worn out, and it is difficult to form an aspherical shape with high precision, for example, and a very long processing time and labor are required to satisfy the precision required for the optical element.

A metal material such as steel, particularly stainless steel, is known as a material that is easy to cut without using the time-consuming polishing process, and that enables high-accuracy mold machining to be relatively simple. This mold is mainly used as a mold material for injection molding of a plastic lens, and is recognized as a relatively inexpensive material. However, stainless steel and the like are easily deformed at a temperature required for press molding of glass, for example, at a high temperature of 400 ° C. or higher, and when a stainless steel mold is repeatedly used at a high temperature of 400 ° C. or higher, the mold surface becomes rough due to oxidation and brittleness. Therefore, it has been considered inappropriate to use as a mold for precision press molding. In addition, the stainless steel mold may not have sufficient hardness to press-mold glass, and may be deformed when the glass is pressed at a high temperature.

Thus, in order to perform precision press molding of optical glass using an inexpensive member used in plastic lens molding, there are many problems in terms of equipment and material, and it has not been put into practical use at all.

By the way, in the optical glass market, there is an increasing need for high refractive index glass having a refractive index (nd) of about 2.0 in order to make the optical system compact. The glass in this region is very often used as an aspherical lens, and various studies have been made to reduce the cost of manufacturing such a lens.

For example, Japanese Patent Application Laid-Open No. 2003-48723 (Patent Document 1) describes a press forming method for a glass material containing Te.
JP 2003-48723 A

However, in the process described in Patent Document 1, since glass is press-molded with a tungsten carbide or ceramic mold, the material of the mold and its processing require a very high cost, and the accuracy required for the optical element It takes a very long time and labor to process to satisfy the requirements.

The present inventor has solved the problems of the prior art and seems to use glass having an nd of 1.9 or more and an Abbe number (νd) of 15 or more, which are in increasing demand as an optical element, in conventional plastic molding. We have now found a manufacturing method that significantly reduces the manufacturing cost of optical elements by enabling precision press molding using inexpensive members.

That is, the inventor of the present invention describes thermal properties (glass transition point, yield point, etc.) that can be pressed with stainless steel and the like, an optical glass preform whose composition is adjusted to have a large demand for optical constants, and the preform. They have found a method that can be mass-produced at a very low cost by precision press-molding by combining a mold material and a mold film suitable for reforming.

The first configuration of the present invention is a glass containing a TeO ₂ and / or Bi ₂ O ₃ component essentially using a steel (including stainless steel) and / or copper alloy mold having a surface film formed thereon. A method of manufacturing an optical element, wherein a preform is precision press-molded.

The second configuration of the present invention is characterized in that the surface film contains “one or more selected from the group consisting of Ni, Cr and Co” and “any one or both of P and B”. It is the manufacturing method of the said structure 1.

According to a third configuration of the present invention, in the surface film, a ratio of “total amount of Ni, Cr and Co (mass%)” to “total amount of P and B (mass%)” is 85:15 to 15:15. The manufacturing method according to Configuration 2, wherein the ratio is in a range of 99: 1.

A fourth configuration of the present invention is the manufacturing method according to any one of the above configurations 1 to 3, wherein the surface film has a hardness of 200 (Hv) or more and a thickness of 0.5 μm or more.

According to a fifth aspect of the present invention, there is provided the manufacturing method according to any one of the first to fourth aspects, wherein organic powder, carbon-based powder, or ceramic is dispersed in the surface film.

A sixth configuration of the present invention is the manufacturing method according to the fifth configuration, wherein an intermediate layer is provided between the mold and the surface film.

The 7th structure of this invention is a manufacturing method of the said structures 1-6 characterized by shape | molding at 400 degrees C or less.

In an eighth configuration of the present invention, the glass preform has a refractive index (nd) of 1.9 or more and an Abbe number (νd) of 15 or more, and a glass transition point (Tg) of 300 ° C. or less. free of Pb and / or as component, it is a manufacturing method of the structure 1 to 7, characterized in that formed of optical glass characterized by containing TeO ₂ components or more 50 mol%.

According to a ninth configuration of the present invention, the glass preform includes an R ₂ O component (R is one or more selected from the group consisting of Li, Na, K, and Cs), a ZnO component, and a Bi ₂ O ₃ component. It contains a further manufacturing method of the structure 8, characterized in that formed of optical glass containing _Al 2 _{O 3} and / or _Ga 2 _{O 3} component.

In a tenth configuration of the present invention, the glass preform is mol% based on oxide,
TeO ₂ 50-90%,
R ₂ O (R is one or more selected from the group consisting of Li, Na, K, Cs) 5-30%,
ZnO 1-30% and Bi ₂ O ₃ 1-20%
The manufacturing method of the said structure 8 or 9 which consists of optical glass containing each component of these.

According to an eleventh configuration of the present invention, the glass preform contains an Al ₂ O ₃ and / or Ga ₂ O ₃ component in mol% based on an oxide and 0.01 to 3.0 mol% in an outer ratio. It is a manufacturing method of said structure 8-10 characterized by consisting of glass.

A twelfth configuration of the present invention is the manufacturing method according to any of the above configurations 8 to 11, wherein the glass preform is made of an optical glass having powder method water resistance of first grade, second grade, or third grade.

In a thirteenth configuration of the present invention, the glass preform is made of an optical glass in which the total content of B ₂ O ₃ , GeO ₂ and P ₂ O ₅ components is 5 mol% or less based on oxides. It is a manufacturing method of the said structures 8-12.

In the fourteenth aspect of the invention, the glass preform, in the configuration 8-13 manufacturing method of R 2 _O component is characterized by comprising from optical glass consisting of Li 2 _O and / or Na 2 _O component is there.

A fifteenth configuration of the present invention is the manufacturing method according to any of the above configurations 8 to 14, wherein the glass preform is made of an optical glass substantially not containing an F component.

In a sixteenth configuration of the present invention, the glass preform is mol% based on oxide, and SiO ₂ 0 to 10% and / or Li ₂ O 0 to 30% and / or Na ₂ O 0 to O as an optional component. 20% and / or _K 2 O 0 to 15% and / or _Cs 2 O 0% and / or 0% MgO and / or CaO 0 to 20% and / or BaO 0 to 20% and / or SrO 0-20% and / or TiO ₂ 0-10% and / or Nb ₂ O ₅ 0-10% and / or Ta ₂ O ₅ 0-10% and / or WO ₃ 0-10% and / or ZrO ₂ 0 10% and / or _Y 2 _O 3 0% and / or _Yb 2 _O 3 0% and / or _La 2 _O 3 0% and / or _Gd 2 _O 3 0% and / or Sb ₂ O ₃ 0-0.5%
It consists of optical glass containing each of these components, It is a manufacturing method of the said structures 8-15 characterized by the above-mentioned.

In a seventeenth configuration of the present invention, the glass preform is made of an optical glass in which the total content of Y ₂ O ₃ , Yb ₂ O ₃ , La ₂ O ₃ and Gd ₂ O ₃ components is less than 10 mol%. It is a manufacturing method of the said structures 8-16 characterized by the above-mentioned.

According to the manufacturing method of the present invention, a member that can be used for plastic molding can be mass-produced at a low cost because an optical element having a high refractive index region, which has very high needs, can be used.

Hereinafter, the production method of the present invention will be described.

(Molding mold)
The mold used in the production method of the present invention is not particularly limited as long as it is not deformed at the molding temperature applied when precision press molding is performed, but a glass preform which is a molded body to be described later In view of the gist of the present invention in which Tg is 350 ° C. or less and it is desired to reduce the production cost as much as possible, it is preferable to use an inexpensive mold that can be used for molding a plastic lens or the like.

The mold material used in the manufacturing method of the present invention does not require a high cost method such as grinding and / or polishing with a diamond grindstone, and can form a surface shape with high accuracy by inexpensive grinding. preferable. Specifically, it is preferable to use a mold material mainly composed of steel (including stainless steel) and / or copper alloy, more preferably steel (including stainless steel), and most preferably stainless steel. Used as mold material.

Here, what is used as steel includes, for example, steel, castings, and special steels, and in particular, stainless steel includes martensitic stainless steel, ferritic stainless steel, austenitic stainless steel, and precipitation hardening stainless steel. Moreover, what is used as a copper alloy can use the well-known alloy which has copper as a main component.

The mold according to the present invention has a predetermined mold in order to extend the life of the mold by improving the mold release by protecting the mold material from oxidation and wear due to heat and pressure loads during precision press molding of glass. It is preferable to form a surface film. Here, in order to precision press-mold the glass preform used in the present invention, a material having a hardness of preferably 200 Hv or higher, more preferably 250 Hv or higher, and most preferably 300 Hv or higher is used as the surface film.

The Vickers hardness in the present invention is a value measured according to JIS Z 2244, with a sample load of 9.807 mN.

The thickness of the surface film is not particularly limited as long as the base material can be protected from various loads during precision pressing and is not fused to the preform. However, when the surface of the molded film deteriorates by performing many presses, it is preferable to have a thickness that allows a new molded surface to be easily formed by grinding again. By realizing such a simple film regeneration, it is possible to omit complicated processes and contribute to cost reduction of the entire manufacturing process. From such a viewpoint, the surface film has a thickness of 0.5 μm or more, more preferably 1 μm or more, and most preferably 5 μm or more.

In order to form a film having the hardness, heat resistance, releasability, and thickness as described above, “one or more selected from the group consisting of Ni, Cr, Co” and “P” , B, or both ”is preferably included. The (Ni, Cr, Co)-(P, B) surface film is a very good film even in consideration of chemical reactivity with the constituents of the preform described later.

In the (Ni, Cr, Co)-(P, B) surface film, if the content of Ni, Cr, Co is too large, the corrosion resistance is lowered and the life of the film tends to be shortened. If the amount is too large, the hardness is lowered and deformation tends to occur. Therefore, the ratio of “total amount of Ni, Cr, and Co (mass%)” and “total amount of P and B (mass%)” is considered in consideration of chemical reactivity with TeO ₂ -based optical glass. Preferably, it is adjusted to a range of 85:15 to 99: 1, more preferably 86:14 to 98: 2, and most preferably 87:13 to 97: 3.

The formation of the surface film of the mold is not particularly limited, but known methods such as ion plating method, sputtering method, dry etching method, vapor deposition method, plasma CVD method, PVD method, electrolytic or electroless plating method, etc. It is preferred to use the method. The electroless plating method is particularly preferable.

In order to improve the corrosion resistance and / or releasability of the film, known additives may be dispersed in the film. For example, organic powders such as polytetrafluoroethylene, carbon-based powders such as carbon black, and ceramics such as SiC can be dispersed. In that case, in order to improve the adhesion between the mold and the surface film, it is preferable to provide an intermediate layer of a known film mainly composed of Ni, Cr, Co or the like.

The hardness of the molded film formed by the above method can be improved by a heat treatment after the film formation. The heat treatment is not intended to use a special method and can be performed by a known method.

In the present invention, other films can be used or used in combination as a multilayer film. However, for known films such as white metal films, iron, aluminum and copper, the preform of the present invention is formed. Therefore, the hardness of the carbon-based film such as diamond-like carbon film (DLC) or tetrahedral amorphous carbon film (TAC) is difficult to achieve a predetermined value or more. It is difficult to use as a surface film of a mold used in the manufacturing method.

(Precision press molding conditions)
In the method of the present invention, the preform is pressure molded in a mold. The method of pressure molding is appropriately selected in consideration of the composition and physical properties of the glass, but it is preferable that the preform is supplied into a mold and pressure-molded in a heat-softened state.

For example, after a preform is supplied between a pair of upper and lower molds, both the mold and the preform are heated to a temperature corresponding to 10 ⁸ to 10 ¹² poise in terms of glass viscosity. By softening by heating and pressure molding this, the molding surface of the mold is transferred to the preform to obtain a glass molded body. In this molding method, after the mold and the preform are heated in an isothermal state, the preform is pressure-molded, and then the mold and the glass molded body are cooled. For this reason, sink marks do not occur in the glass molded body and good surface accuracy can be obtained, but the mold is easily damaged because the temperature of the mold is high and the adhesion time with the glass is long.

Therefore, the pair of upper mold and lower mold is heated to a temperature corresponding to 10 ⁸ to 10 ¹² poise in advance in terms of glass viscosity, and heated between the upper mold and the lower mold to a temperature equivalent to the upper mold and the lower mold. From the upper mold and the lower mold between a pair of upper mold and lower mold that have been heated to a temperature corresponding to 10 ⁸ to 10 ¹² poise in advance. In addition, by supplying a preform heated to a high temperature and immediately press-molding it, the molding die and the glass can be brought into close contact with each other in a short time, and the molding surface of the molding die can be transferred to the preform. According to this method, damage to the surface film can be reduced.

When the preform used in the present invention described below is used, the molding temperature is preferably set to 400 ° C. or lower, more preferably 390 ° C. or lower, and most preferably 380 ° C. or lower.

The atmosphere during press molding is preferably a non-oxidizing atmosphere in order to reduce deterioration of the surface film of the mold. As the non-oxidizing atmosphere, an inert gas such as argon or nitrogen, a reducing gas such as hydrogen, or a mixed gas thereof can be used. Preferably, nitrogen gas or nitrogen gas mixed with a small amount of hydrogen gas is used. Can be used.

The applied pressure and time can be appropriately determined in consideration of the viscosity of the glass. For example, the pressure can be increased for about 30 to 300 seconds at a pressure of 4 to 20 MPa using a stainless steel mold having an inner diameter of 5 to 20 mm. . Thereafter, the mold and the glass preform are cooled, and when the temperature is preferably equal to or lower than Tg, the mold is released and the molded glass molded body is taken out. Cooling of the molded product after pressing may be performed by releasing the pressurizing load, or may be cooled while pressing.

(Preform for precision press molding)
Next, the precision press molding preform to be pressed in the manufacturing method of the present invention will be described.

The optical glass used in the production method of the present invention preferably has an nd of 1.9 or more and νd of 15 or more from the viewpoint of optical design. Conventionally, glass of various compositions has been used to realize this optical constant, but all of them satisfy the optical constant, but many have a Tg exceeding 400 ° C., and are inexpensive such as stainless steel in precision press molding. There was a problem that the material could not be used and the cost increased. The optical glass of the present invention is required to have a lower Tg than those known, so that it is preferably 350 ° C. or lower, more preferably 330 ° C. or lower, and most preferably 300 ° C. or lower.

Furthermore, since it is difficult to use as an optical glass if the chemical durability is poor, in consideration of applying the optical glass of the present invention to a lens preform material, the Japan Optical Glass Industry Association Standard; JOGIS06-1999 It is desirable that the evaluation by the water resistance of the powder method specified is preferably 1-3 grades, more preferably 1-2 grades, and most preferably grade 1.

Moreover, as a composition of the optical glass satisfying the optical constant, Tg, durability and the like, it is preferable that TeO ₂ and Bi ₂ O ₃ are the main components on the basis of oxide. The composition has extremely good reactivity even in consideration of compatibility with the (Ni, Cr, Co)-(P, B) surface film and mold material in the present production method.

The reason why the composition range of each component is limited as described above in the optical glass of the present invention will be described below. Hereinafter, unless otherwise specified, in the present specification, the glass composition content is all expressed in mol% based on oxide.

In this specification, “oxide reference” means that the oxide, nitrate, etc. used as a raw material for glass constituents are all decomposed and changed into oxides when melted. It is the composition which described each component contained in glass by making the sum total 100 mol%.

The TeO ₂ component is a component having an effect of forming a glass, and is essential in the present invention. However, if the amount is too small, it becomes difficult to vitrify, and if it is excessively contained, there is a disadvantage that the glass tends to be unstable. Accordingly, in the present invention, the lower limit is preferably 50%, more preferably 55%, and most preferably 60%, preferably 90%, more preferably 85%, and most preferably 80%.

The R ₂ O component (R is one or more selected from the group consisting of Li, Na, K, and Cs) is an optional component that facilitates vitrification of the TeO ₂ component and has an effect of keeping Tg low. It is a useful component in the invention. However, if the amount is too small, it tends to be insufficient for forming glass, and if it is contained excessively, there is a disadvantage that the refractive index tends to decrease and devitrification tends to increase. Therefore, in the present invention, the total content of R ₂ O components is preferably 5%, more preferably 7%, most preferably 10% as the lower limit, preferably 30%, more preferably 27%, most preferably 25%. % Is the upper limit.

Next, each component of R ₂ O will be described.

The Li ₂ O component is an optional component that facilitates vitrification of the TeO ₂ component and has an effect of keeping Tg low. However, if contained excessively, there are disadvantages that the refractive index tends to decrease and devitrification tends to increase. The Li ₂ O component content in the present invention may be 0%, but is preferably 1%, more preferably 3%, most preferably 5% as a lower limit, preferably 30%, more preferably 27%, most preferably The upper limit is 25%.

The Na ₂ O component is an optional component that facilitates vitrification of the TeO ₂ component and has an effect of keeping Tg low. However, if it is excessively contained, there is a disadvantage that the refractive index tends to decrease and devitrification tends to increase. The Na ₂ O component content in the present invention is preferably 20%, more preferably 17%, and most preferably 15%.

The K ₂ O component is an optional component that facilitates vitrification of the TeO ₂ component and has an effect of keeping Tg low. However, if it is excessively contained, there is a disadvantage that the refractive index tends to decrease and devitrification tends to increase. In the present invention, the K ₂ O component content is preferably 15%, more preferably 13%, and most preferably 10%.

The Cs ₂ O component is an optional component that has an effect of facilitating the vitrification of the TeO ₂ component. However, if it is excessively contained, there is a disadvantage that the refractive index tends to decrease and devitrification tends to increase. In the present invention, the upper limit of the Cs ₂ O component is preferably 10%, more preferably 5%, and most preferably 3%.

R ₂ O preferably contains one or both of Li ₂ O and Na ₂ O components. This is because the other R ₂ O components are relatively less likely to be significantly devitrified than Li ₂ O and Na ₂ O components.

The ZnO component is an optional component having an effect of facilitating vitrification of the TeO ₂ component, and is a useful component in the present invention. However, if the amount is too small, the glass tends to be unstable, and there is a disadvantage that devitrification tends to increase even if it is contained in excess, or that the refractive index is lowered and Tg tends to be high. Therefore, 0% may be used in the present invention, but preferably 1%, more preferably 2%, most preferably 3% is the lower limit, preferably 30%, more preferably 27%, and most preferably 25%. To do.

The Bi ₂ O ₃ component has an effect of facilitating the vitrification of the TeO ₂ component and increasing the refractive index, and is an optional component useful in the invention. However, if the amount is too small, the glass tends to be unstable, and devitrification tends to increase even if it is contained in excess, and Tg tends to be high. Therefore, in the present invention, 0% may be used, but preferably 1%, more preferably 2%, most preferably 3% is the lower limit, preferably 20%, more preferably 17%, and most preferably 15%. To do.

Both the Al ₂ O ₃ and Ga ₂ O ₃ components are optional components that have an effect of suppressing the devitrification of glass, and preferably contain either one or both. However, if the amount is too small, the effect of suppressing devitrification tends to be insufficient, and even if contained in excess, devitrification tends to increase, and the disadvantage is that the refractive index tends to decrease and Tg increases. is there. Therefore, in the present invention, the total content of Al ₂ O ₃ and Ga ₂ O ₃ components is preferably 0.01%, more preferably 0.05%, and most preferably 0.1% as the lower limit, The upper limit is preferably 3.0%, more preferably 2.0%, and most preferably 1.0%.

Note that "outer percentage" during Honma specification, in the case where the total content of the oxide components other than _Al 2 _{O 3} and _Ga 2 _{O 3} component assuming 100%, _Al 2 _{O 3} and _Ga 2 O The relative mol% of the _three components is meant.

For each component, the upper limit of the Al ₂ O ₃ component is preferably 2.0%, more preferably 1.5%, and most preferably 1.0%. Ga ₂ O ₃ preferably has an upper limit of 2.0%, more preferably 1.5%, and most preferably 1.0%.

By the way, the TeO ₂ component can act as a glass-forming oxide in the optical glass of the present invention, but it is very difficult to vitrify by itself. Therefore, it is preferable to include at least one or more of the above-described components (that is, one or both of R ₂ O, ZnO and Bi ₂ O ₃ components, and Al ₂ O ₃ and Ga ₂ O ₃ components). Further, by containing the TeO ₂ component and the components at the same time, better stability, solubility, chemical durability, easily obtain a glass having a performance as an optical glass.

Since the B ₂ O ₃ , GeO ₂ and P ₂ O ₅ components are components that lower the refractive index and increase the Tg, the total amount is preferably 5%, more preferably 3%, most preferably 1%. The upper limit. However, it does not matter if none is contained.

For each component of B ₂ O ₃ , GeO ₂ and P ₂ O ₅ , the upper limit is preferably 5%, more preferably 3%, and most preferably 1%.

About F component, since it is a component which makes devitrification increase easily, Preferably it is 5%, More preferably, it is 2%, Most preferably, it does not contain. The F content in the present invention is calculated as F atoms based on 100 mol% of the oxide reference composition based on the total amount of F in which a part or all of the oxide constituting the glass of the present invention is fluoride-substituted. This is expressed in mol%.

Since the SiO ₂ component is a component that has the effect of improving devitrification, it can be optionally contained in the present invention. However, if it is contained excessively, devitrification tends to increase, and the refractive index tends to decrease and Tg tends to be high. Therefore, in the present invention, the upper limit is preferably 10%, more preferably 5%, and most preferably 2%.

Since the MgO component is a component that has an effect of improving devitrification, it can be optionally contained in the present invention. However, if it is contained excessively, devitrification tends to increase, and the refractive index tends to decrease and Tg tends to be high. Therefore, in the present invention, the upper limit is preferably 10%, more preferably 5%, and most preferably 2%.

Since the CaO component is a component having an effect of improving devitrification, it can be arbitrarily contained in the present invention. However, if it is contained excessively, devitrification tends to increase, and the refractive index tends to decrease and Tg tends to be high. Therefore, in the present invention, the upper limit is preferably 20%, more preferably 7%, and most preferably 5%.

Since the BaO component has an effect of improving devitrification, it can be optionally contained in the present invention. However, if it is contained excessively, devitrification tends to increase, and the refractive index tends to decrease and Tg tends to be high. Therefore, in the present invention, the upper limit is preferably 20%, more preferably 7%, and most preferably 5%.

Since the SrO component is an ingredient that has an effect of improving devitrification, it can be optionally contained in the present invention. However, if it is contained excessively, devitrification tends to increase, and the refractive index tends to decrease and Tg tends to be high. Therefore, in the present invention, the upper limit is preferably 20%, more preferably 7%, and most preferably 5%.

Since the TiO ₂ component is a component that has an effect of increasing the refractive index, it can be optionally contained in the present invention. However, when it contains excessively, devitrification will increase easily and there exists a disadvantage that Tg tends to become high. Therefore, in the present invention, the upper limit is preferably 10%, more preferably 7%, and most preferably 5%.

The Nb ₂ O ₅ component is a component that has the effect of increasing the refractive index, and therefore can be optionally contained in the present invention. However, when it contains excessively, devitrification will increase easily and there exists a disadvantage that Tg tends to become high. Therefore, in the present invention, the upper limit is preferably 10%, more preferably 7%, and most preferably 5%.

The Ta ₂ O ₅ component is a component that has the effect of increasing the refractive index, and therefore can be optionally contained in the present invention. However, when it contains excessively, devitrification will increase easily and there exists a disadvantage that Tg tends to become high. Therefore, in the present invention, the upper limit is preferably 10%, more preferably 7%, and most preferably 5%.

Since the WO ₃ component is a component that has an effect of increasing the refractive index, it can be optionally contained in the present invention. However, when it contains excessively, devitrification will increase easily and there exists a disadvantage that Tg tends to become high. Therefore, in the present invention, the upper limit is preferably 10%, more preferably 7%, and most preferably 5%.

The ZrO ₂ component is a component having an effect of improving chemical durability, and therefore can be arbitrarily contained in the present invention. However, when it contains excessively, devitrification will increase easily and there exists a disadvantage that Tg tends to become high. Therefore, in the present invention, the upper limit is preferably 10%, more preferably 5%, and most preferably 2%.

The Y ₂ O ₃ component is a component having an effect of improving chemical durability, and therefore can be optionally contained in the present invention. However, when it contains excessively, devitrification will increase easily and there exists a disadvantage that Tg tends to become high. Therefore, in the present invention, the upper limit is preferably 10%, more preferably 7%, and most preferably 5%.

The Yb ₂ O ₃ component is a component that has the effect of increasing the refractive index, and therefore can be optionally contained in the present invention. However, when it contains excessively, devitrification will increase easily and there exists a disadvantage that Tg tends to become high. Therefore, in the present invention, the upper limit is preferably 10%, more preferably 7%, and most preferably 5%.

The La ₂ O ₃ component is a component that has the effect of increasing the refractive index, and therefore can be optionally contained in the present invention. However, when it contains excessively, devitrification will increase easily and there exists a disadvantage that Tg tends to become high. Therefore, in the present invention, the upper limit is preferably 10%, more preferably 7%, and most preferably 5%.

Since the Gd ₂ O ₃ component is a component that has an effect of increasing the refractive index, it can be optionally contained in the present invention. However, when it contains excessively, devitrification will increase easily and there exists a disadvantage that Tg tends to become high. Therefore, in the present invention, the upper limit is preferably 10%, more preferably 7%, and most preferably 5%.

The rare earth oxide component composed of Y ₂ O ₃ , Yb ₂ O ₃ , La ₂ O ₃ and Gd ₂ O ₃ is an optional component having the effect of improving chemical durability and increasing the refractive index as described above. . However, when these components are contained excessively, devitrification tends to increase and Tg tends to be high. Accordingly, in the present invention, the total amount is preferably 10%, more preferably 7%, and most preferably 5%.

Since the Sb ₂ O ₃ component is a component having an effect of clarification, it can be optionally contained in the present invention. However, when it contains excessively, devitrification will increase easily and there exists a disadvantage that Tg tends to become high. Therefore, in the present invention, the upper limit is preferably 0.5%, more preferably 0.4%, and most preferably 0.3%.

Next, components that should not be contained in the optical glass of the present invention will be described.

Lead compounds are components that are easy to fuse with molds during precision press molding and glass manufacturing, as well as glass processing such as polishing and environmental measures such as glass processing and glass disposal. The optical glass of the present invention should not be contained because it is necessary and has a problem that it is a component with a large environmental load.

Since As ₂ O ₃ , cadmium and thorium components both have harmful effects on the environment and are extremely heavy components of the environment, they should not be contained in the optical glass of the present invention.

Furthermore, in the optical glass of the present invention, coloring components such as V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Eu, Nd, Sm, Tb, Dy, and Er are likely to lower the light transmittance. It is preferable not to contain substantially. Here, “substantially does not contain” means that it is not contained artificially unless it is mixed as an impurity.

The glass composition of the present invention cannot be directly converted to mass% because the composition is expressed in mol%, but is present in the glass composition satisfying various properties required in the present invention. The composition by mass% display of each component to be taken takes the following value in general with an oxide reference | standard composition.
TeO ₂ 40-90%,
R ₂ O (R is one or more selected from the group consisting of Li, Na, K, Cs) 5-30%,
ZnO 1-20%
Bi ₂ O ₃ 1~50% and _Al 2 _{O 3} and / or from 0.005 to 3.0% by outer percentage of _Ga 2 _{O 3} and _{B 2 O} 3, GeO 2 and _P 2 _O 5 _0~5%
SiO ₂ 0-10% and / or Li ₂ O 0-10% and / or Na ₂ O 0-10% and / or K ₂ O 0-10% and / or MgO 0-5% and / or CaO 0 20% and / or BaO 0-20% and / or SrO 0-20% and / or TiO ₂ 0-5% and / or Nb ₂ O ₅ 0-20% and / or Ta ₂ O ₅ 0-25% and WO ₃ 0-15% and / or ZrO ₂ 0-5% and / or Y ₂ O ₃ 0-15% and / or Yb ₂ O ₃ 0-25% and / or La ₂ O ₃ 0-20% And / or Gd ₂ O ₃ 0-10% and / or Sb ₂ O ₃ 0-2%

The present invention will be described in detail by the following examples, but the present invention is not limited thereto.
Example 1
Contains 65% TeO ₂ component, 20% Li ₂ O component, 10% ZnO component, 5% Bi ₂ O ₃ component and 0.2% Al ₂ O ₃ component on an oxide basis. A glass preform made of optical glass was prepared. The preform had a refractive index of 2.03, an Abbe number of 19.1, and a glass transition temperature of 270 ° C. As the shape of the preform, a spherical preform having a diameter of 7.2 mm was used.

This preform was precision press-molded by the following method to produce a biconvex optical lens having an outer diameter of 10 mm and a center wall thickness of 3.3 mm.

A stainless steel mold (equivalent to SUS420J2 and hardness of 580 Hv) manufactured by STAVAX was used as a mold material. This stainless steel mold is ground, and an intermediate layer (Ni: P = 90: 10) made of Ni—P is provided thereon, and then a Ni—P film (Ni: P) containing about 30% by volume of polytetrafluoroethylene particles. P = 90: 10) was formed by electroless plating. The film thickness was 30 μm.

A MO2C machine manufactured by Toshiba Machine Co. was used as a molding machine for precision press molding.

The glass preform was supplied at room temperature into the mold having an inner diameter of 10.4 mm, heated to 297 ° C. in a nitrogen gas atmosphere, and pressurized at a pressure of 20 MPa for 60 seconds. Thereafter, pressurization was continued for 12 seconds at a pressure of 10 MPa while slowly cooling at a cooling rate of −2.2 ° C./s, and when the temperature of the glass molded body dropped to 50 ° C. or lower, the glass molded body was taken out. When this process was used and continuous press molding was performed 1000 times with the same mold, there was no occurrence of cracks or cracks in the glass molded body. Further, no disadvantages such as fusion and cloudiness were generated in the surface film of the mold.

(Example 2)
A Ni—P—B film (Ni: P: B = 98: 1.5: 0.5) was formed on the ground stainless steel mold by an electroless plating method. The other conditions were the same as in Example 1, and when the same mold was continuously pressed 1000 times, there was no occurrence of cracks or cracks in the glass molded body. Further, no disadvantages such as fusion and cloudiness were generated in the surface film of the mold.

(Comparative example)
A carbide die was used as the mold material. A film containing Pt as a main component was formed on this superhard mold by vacuum deposition. The film thickness was 0.5 μm. A MO2C machine manufactured by Toshiba Machine Co. was used as a molding machine for precision press molding. The glass preform was supplied at room temperature into the mold having an inner diameter of 10.4 mm, heated to 327 ° C. in a nitrogen gas atmosphere, and pressurized at a pressure of 10 MPa for 80 seconds. Thereafter, pressurization was continued for 12 seconds at a pressure of 10 MPa while slowly cooling at a cooling rate of −2.2 ° C./s, and when the temperature of the glass molded body dropped to 50 ° C. or lower, the glass molded body was taken out. In this step, the glass was fused to the mold, and repeated molding could not be performed.

Claims (17)

Using a steel (including stainless steel) and / or copper alloy mold with a surface film formed, precision press-molding a glass preform that essentially contains a TeO ₂ component and / or a Bi ₂ O ₃ component. A method for producing an optical element characterized by the above. 2. The method according to claim 1, wherein the surface film contains “one or more selected from the group consisting of Ni, Cr, and Co” and “any one or both of P and B”. The ratio of “total amount (% by mass) of Ni, Cr, and Co” to “total amount (% by mass) of P and B” in the surface film is in the range of 85:15 to 99: 1. The manufacturing method according to claim 1 or 2, characterized by the above. The manufacturing method according to claim 1, wherein the surface film has a hardness of 200 (Hv) or more and a thickness of 0.5 μm or more. The manufacturing method according to claim 1, wherein organic powder, carbon powder, or ceramics is dispersed in the surface film. 6. The method of manufacturing an optical element according to claim 5, wherein an intermediate layer is provided between the mold and the surface film. The manufacturing method according to claim 1, wherein the molding is performed at 400 ° C. or lower. The glass preform has a refractive index (nd) of 1.9 or more, an Abbe number (νd) of 15 or more, a glass transition point (Tg) of 350 ° C. or less, and does not contain Pb and / or As components. The production method according to claim 1, comprising an optical glass containing 50 mol% or more of TeO ₂ component based on oxide. The glass preform contains an R ₂ O component (R is one or more selected from the group consisting of Li, Na, K, and Cs), a ZnO component, a Bi ₂ O ₃ component, and Al ₂ O ₃ and The manufacturing method according to claim 8, wherein the manufacturing method comprises optical glass containing a Ga ₂ O ₃ component. The glass preform is mol% based on oxide,
TeO ₂ 50-90%,
R ₂ O (R is one or more selected from the group consisting of Li, Na, K, Cs) 5-30%,
ZnO 1-30% and Bi ₂ O ₃ 1-20%
The manufacturing method of Claim 8 or 9 which consists of optical glass containing each component of these. Wherein said glass _preform, the Al 2 _{O 3} and / or _Ga 2 _{O 3} component in mol% on an oxide basis, characterized by comprising from optical glass containing 0.01～3.0Mol% by outer percentage The manufacturing method in any one of claim | item 8-10. The manufacturing method according to any one of claims 8 to 11, wherein the glass preform is made of an optical glass having a powder method water resistance specified in JOGIS06-1999 of first grade, second grade, or third grade. Claim wherein the glass _preform, a total of B ₂ O 3, GeO ₂ and _P 2 _{O 5} component content is, in mol% on an oxide basis, characterized by comprising from optical glass or less 5 mol% The manufacturing method in any one of 8-12. The glass preform, method of making any of claims 8 to 13 _{R 2} O component is characterized by comprising from optical glass consisting of Li ₂ O and / or Na ₂ O component. The manufacturing method according to any one of claims 8 to 14, wherein the glass preform is made of an optical glass having an F component content of 5 mol% or less. The glass preform is mol% based on oxide, and as an optional component SiO ₂ 0-10% and / or Li ₂ O 0-30% and / or Na ₂ O 0-20% and / or K ₂ O 0 15% and / or _Cs 2 O 0% and / or 0% MgO and / or CaO 0 to 20% and / or BaO 0 to 20% and / or SrO 0 to 20% and / or TiO ₂ 0-10% and / or _Nb 2 _O 5 0-10% and / or _Ta 2 _O 5 0-10% and / or _WO 3 0 - 10% and / or _ZrO 2 0 - 10% and / or _Y 2 O ₃ 0 to 10% and / or _Yb 2 _O 3 0-10% and / or _La 2 _O 3 0-10% and / or _Gd 2 _O 3 0-10% and / or _Sb 2 _O 3 0 to 0.5 %
It consists of optical glass containing each of these components, The manufacturing method in any one of Claims 8-15 characterized by the above-mentioned. The glass _{preform, Y 2 O 3, Yb 2} O 3, La 2 O 3 and _Gd 2 _{O 3} claims total content of the components is characterized by comprising from optical glass is less than 10 mol%. 8 to 16. The manufacturing method of any one of 16.