JP2008285396A - Method for producing optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical element production method capable markedly reducing its production cost by making it possible to perform the precision press molding of a glass having a refractive index (nd) of 1.5-1.75 and an Abbes's number (νd) of 50-70 and therefore having a very large demand for optical elements by using an inexpensive member such as one used in conventional plastic molding. <P>SOLUTION: The production method for optical elements comprises performing the precision press molding of a glass preform by using a molding die made of an iron steel (including stainless steel) and/or a copper alloy covered with a surface film having a Vickers hardness of 400 (HV) or higher and a thickness of 1 μm or thicker. <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 aspherical 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 heat-softened and pressed, the mold 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 noble metal films, diamond-like carbon (DLC), tetrahedral amorphous carbon (TAC), etc. carbon films, chromium nitride, nitriding 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.

Thus, in general, in order to press the optical glass precisely, 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 high-precision processing, for example, formation of an aspherical shape is difficult, and it takes a very long time and effort to satisfy the accuracy required for the optical element.

A metal material such as steel, particularly stainless steel, is known as a material that can be easily 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 plastic lenses and is recognized as a relatively inexpensive material. However, stainless steel and the like are easily deformed at a temperature required for glass press molding, for example, 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 die surface becomes rough and becomes brittle. Therefore, it is not suitable as a mold for precision press molding. In addition, the stainless steel mold may not have sufficient hardness to press-mold the glass, and may be deformed when the glass is pressed at a high temperature.

Thus, performing precision press molding of optical glass using an inexpensive member such as that used in plastic lens molding is impractical in terms of equipment and materials, and has not been put into practical use at all.

By the way, in the optical glass market, there is a very high need for a high refractive index and low dispersion glass having a refractive index (nd) of 1.50 to 1.75 and an Abbe number (νd) of about 50 to 70. 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.

Patent Document 1 discloses a phosphate optical glass having a refractive index of 1.52 to 1.7, an Abbe number of 42 to 70, a glass transition temperature (Tg) of 370 ° C. or less, and containing no lead or fluorine. The step of pressing the sheet with a mold made of stainless steel is described.
JP 2004-217513 A

However, in the process described in Patent Document 1, since the glass is press-molded with a stainless steel mold, the hardness of the stainless steel cannot withstand the load during pressing, and the mold molding surface deforms in a few shots. Resulting in. Therefore, a great improvement is required for practical use.

The present inventor has solved the problems of the prior art, and uses a glass having a refractive index (nd) of 1.5 to 1.75 and an Abbe number (νd) of 50 to 70, which is extremely demanding as an optical element. We have now found a manufacturing method that significantly reduces the manufacturing cost of optical elements by enabling precision press molding using inexpensive members such as those used for molding.

That is, the present inventor has low thermal characteristics (glass transition point, yield point, etc.) that can be pressed with stainless steel and the like, and an optical glass preform whose composition is adjusted to have a high demand optical constant, 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 preform pressing.

The first configuration of the present invention uses a steel (including stainless steel) and / or copper alloy forming mold on which a surface film having a hardness of 400 (HV) or more and a thickness of 1 μm or more is formed, and a glass preform is precisely formed. An optical element manufacturing method comprising press molding.

The second configuration of the present invention is the manufacturing method according to the first configuration in which the surface film is composed of at least one selected from the group consisting of Ni, Cr, and Co, and any one or both of P and B. is there.

In the third configuration of the present invention, the ratio of the total amount (mass%) of Ni, Cr and Co to the total amount (mass%) of P and B in the surface film is in the range of 85:15 to 98: 2. It is a manufacturing method of the said structure 2 characterized by having.

The 4th structure of this invention is a manufacturing method of the said structures 1-3 characterized by shape | molding at 400 degrees C or less.

According to a fifth configuration of the present invention, the glass preform has a refractive index (nd) of 1.50 to 1.75, an Abbe number (νd) of 50 to 70, and a glass transition point (Tg) of 350 ° C. or less. _P 2 _O 5, ZnO in an object reference, that is the configuration 1-4 manufacturing method characterized by consisting of optical glass to essential free of BaO and _Sb 2 _{O 3} component.

According to a sixth configuration of the present invention, the glass preform is made of an optical glass whose mass percentage is based on an oxide and whose total content of Nb ₂ O ₅ , WO ₃ and Bi ₂ O ₃ components is less than 3%. It is a manufacturing method of the said structure 5 characterized by the above-mentioned.

In a seventh configuration of the present invention, the glass preform contains three or more alkali metal oxides on an oxide basis, and the RO component (R is selected from the group consisting of Ba, Ca, Mg, Sr and Zn). The production method according to any one of the constitutions 5 and 6, wherein the ratio of the content of the ZnO component to the total content of at least one kind of the optical glass is 0.2 or more.

In an eighth configuration of the present invention, the glass preform is an oxide-based mass% as an essential component.
P ₂ O ₅ 40~55%
BaO 20-40%
ZnO 5-20% and Sb ₂ O ₃ 0.1-10%
It is a manufacturing method of the said structures 5-7 which consists of optical glass containing this.

According to a ninth configuration of the present invention, the glass preform is further in mass% based on an oxide,
Li ₂ O 1-5%
Na ₂ O 1 to 10% and _K 2 O 1~10%,
And SiO ₂ 0-2% and / or B ₂ O ₃ 0-3% and / or Al ₂ O ₃ 0-3% and / or Y ₂ O ₃ 0-3% and / or La ₂ O ₃ 0-1 .5% and / or Gd ₂ O ₃ 0 to 1.3% and / or TiO ₂ 0 to 5% and / or Ta ₂ O ₅ 0 to 10% and / or MgO 0 to 5% and / or CaO 0 5% and / or SrO 0 to 5% and / or _ZrO 2 0 to 3%
It consists of optical glass containing each component of the range of this, It is a manufacturing method of the said structures 5-8 characterized by the above-mentioned.

According to a tenth configuration of the present invention, the glass preform is made of an optical glass whose mass percentage is based on oxide and whose total content of SiO ₂ , B ₂ O ₃ and Al ₂ O ₃ components is 1% or less. It is a manufacturing method of the said structures 5-9 characterized by the above-mentioned.

According to the manufacturing method of the present invention, since a member that can be used for plastic molding can be used for an optical element in a high refractive index and low dispersion region, which is in great demand, it can be mass-produced at low cost.

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 the glass transition temperature (Tg) is 350 ° C. or less and it is desired to reduce the manufacturing 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 method that causes high costs such as polishing with a diamond grindstone, and is preferably one that can form a surface shape with high accuracy by inexpensive grinding. Specifically, it is preferable to use a mold material mainly composed of steel (including stainless steel) and / or a copper alloy, more preferably steel (including stainless steel), and most preferably stainless steel. Use as

Here, what is used as steel includes, for example, steel, casting, and special steel, 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 hardness and heat-resistant temperature in order to protect the mold material from pressure load and heat load during precision press molding of glass, extend the life of the mold, and improve releasability. It is preferable to form a surface film having Here, in order to precision press-mold the glass preform used in the present invention, a material having a hardness of preferably 400 HV or higher, more preferably 500 HV or higher, and most preferably 600 HV or higher is used as the surface film. As for heat resistance, a material that does not deform or deteriorate at 400 ° C., more preferably 420 ° C., and most preferably 450 ° C. is used.
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 1 μm or more, more preferably 5 μm or more, and most preferably 10 μm or more.

In order to form a film having the above-described hardness, heat resistance, and thickness, as a constituent component of the film, one or more selected from the group consisting of Ni, Cr, and Co, and any one of P and B Or it is preferred to use both. The (Ni, Cr, Co)-(P, B) surface film is a very good film even in consideration of chemical reactivity with the components of the preform described later.

In the (Ni, Cr, Co)-(P, B) surface film, the ratio of the total amount (% by mass) of Cr, Ni and Co to the total amount (% by mass) of B and P is phosphoric acid type. It is an important factor that determines various physical properties when pressing optical glass. Here, 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 content of P, B is too large, the hardness is lowered and the film is likely to be deformed. Therefore, the ratio of the total amount (% by mass) of Ni, Cr, Ni and Co to the total amount (% by mass) of P and B is preferably 85:15 to 98: 2, more preferably 86:14 to 97: 3, most preferably in the range of 87:13 to 95: 5.

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, ceramics such as carbon black and SiC can be dispersed. In that case, you may provide the intermediate | middle layer by the well-known film | membrane which has Ni, Cr, Co, etc. as a main component.

  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 together as a multilayer film, but for known films such as white metal films, iron, aluminum, copper, etc., in order to mold the preform of the present invention. Is used in the manufacturing method of the present invention because its hardness tends to be insufficient, and the thickness of a carbon-based film such as diamond-like carbon film (DLC) or tetrahedral amorphous carbon film (TAC) is difficult to exceed a predetermined value. It is difficult to use as a surface film of a forming mold.

(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 up 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 by a glass viscosity. In addition, by supplying a preform heated to a high temperature and immediately press-molding it, the adhesion between the mold and the glass can be shortened and the molding surface of the mold can be transferred to the preform. According to this, 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 Φ5 to 20 mm. . Thereafter, the mold and the glass preform are cooled, and when the temperature is preferably equal to or lower than the glass transition point (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 of the present invention preferably has a refractive index (nd) of 1.50 to 1.75 and an Abbe number (νd) of 50 to 70 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 the glass transition point (Tg) often exceeds 400 ° C. Inexpensive materials such as stainless steel could not be used, and there was a problem that costs increased. The optical glass of the present invention is required to have a lower transition point (Tg) than those known, and is preferably 350 ° C. or lower, more preferably 340 ° C. or lower, most preferably 330 ° C. or lower. Is preferred.

In particular, in the present invention, the use of a mold using a material such as steel (including stainless steel) on which a (Ni, Cr, Co)-(P, B) surface film is formed is intended. In consideration of compatibility with the film, it is preferably made of an optical glass mainly composed of P ₂ O ₅ , ZnO, BaO and Sb ₂ O ₃ on the basis of oxide.

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, in the present specification, unless otherwise specified, all the glass composition contents are expressed in mass% based on oxides.

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

The P ₂ O ₅ component is an essential essential component for forming glass, but if the amount is small, the devitrification resistance is likely to be deteriorated, and if it is too large, the chemical durability is likely to be lowered. Accordingly, the lower limit is preferably 40%, more preferably 42%, and most preferably 44%, preferably 55%, more preferably 53%, and most preferably 51%.

The BaO component is an essential essential component for adjusting the optical constant. However, if the amount is too small, the effect is not sufficient. If the amount is too large, it is difficult to obtain a desired glass transition temperature. Accordingly, the lower limit is preferably 20%, more preferably 22%, and most preferably 24%, preferably 40%, more preferably 38%, and most preferably 36%.

The ZnO component has the effect of lowering the glass transition temperature, and is an important essential component that can be added to adjust the optical constant. However, if the amount is too small, the effect is not sufficient. Durability tends to deteriorate. Therefore, the lower limit is preferably 5%, more preferably 7%, and most preferably 9%, preferably 20%, more preferably 17%, in order to maintain the chemical durability and the desired Abbe number. In particular, the content is preferably 14% or less.

The Sb ₂ O ₃ component is an essential component not only for defoaming but also for adjusting the optical constant, but if its amount is too small, its effect is difficult to be exhibited, and if it is too large, the desired glass transition is achieved. Temperature is difficult to obtain. Accordingly, the upper limit is preferably 0.1%, more preferably 1.0%, and most preferably 1.5%, preferably 10%, more preferably 7%, and most preferably 5%.

The Li ₂ O component is an important component having the effect of lowering the glass transition temperature. However, if the amount is too small, the effect is difficult to obtain, and if it is too large, the devitrification resistance is likely to rapidly decrease. Accordingly, the lower limit is preferably 1%, more preferably 1.3%, and most preferably 1.5%, preferably 5%, more preferably 4%, and most preferably 3%.

The Na ₂ O component is an important component having the effect of lowering the glass transition temperature. However, if the amount is too small, the effect is difficult to obtain, and if it is too large, the devitrification resistance is likely to rapidly decrease. Accordingly, the lower limit is preferably 1%, more preferably 1.5%, and most preferably 2%, preferably 10%, more preferably 8%, and most preferably 7%.

The K ₂ O component is an important component having the effect of lowering the glass transition temperature. However, if the amount is too small, the effect is difficult to obtain, and if it is too large, the devitrification resistance tends to be rapidly lowered. Accordingly, the lower limit is preferably 1%, more preferably 1.5%, and most preferably 2%, preferably 10%, more preferably 8%, and most preferably 7%.

In the present invention, it is known that the inclusion of three or more alkali metal oxides has better glass stability and better devitrification resistance than the composition containing one or two alkali metal oxides. Therefore, in order to produce a stable and high yield in the production process, it is preferable to contain three or more alkali metal oxides.

The B ₂ O ₃ component is a component that can be added to improve devitrification resistance. However, if the amount is too large, it becomes difficult to obtain a desired glass transition temperature. Therefore, the upper limit is preferably 3%, more preferably 2.5%, and most preferably 1%.

The SiO ₂ component can be added to adjust the optical constant, but if the amount is too large, it becomes difficult to obtain a desired glass transition temperature. Therefore, the upper limit is preferably 2%, more preferably 1.5%, and most preferably 1%.

The Al ₂ O ₃ component is a component that can be added to improve chemical durability, but if the amount is too large, it becomes difficult to obtain a desired glass transition temperature. Therefore, the upper limit is preferably 3%, more preferably 2.5%, and most preferably 2%.

Even if the total content of the B ₂ O ₃ , SiO _2, and Al ₂ O ₃ components becomes too large, the glass transition point tends to increase, making it difficult to obtain the desired glass. Accordingly, the total content of these components is 1% or less, more preferably 0.9% or less, and most preferably 0.8% or less.

The Y ₂ O ₃ component can be added to adjust the optical constant, but if the amount is too large, the devitrification resistance deteriorates and it becomes difficult to obtain a desired glass transition temperature. Therefore, the upper limit is preferably 3%, more preferably 2.5%, and most preferably 2%.

La ₂ O ₃ component has the effect of improving chemical durability in a relatively small amount, and can be added to adjust the optical constant, but in P ₂ O ₅ glass, the devitrification resistance deteriorates rapidly. It is also an easy-to-use component. Accordingly, the upper limit is preferably 1.5%, more preferably 1.3%, and most preferably 1%.

The Gd ₂ O ₃ component has an effect of improving chemical durability and can be added for the adjustment of the optical constant. However, even in the P ₂ O ₅ glass, it is a component that easily deteriorates devitrification resistance. is there. Therefore, the upper limit is preferably 1.3%, more preferably 1%, and most preferably 0.8%.

The TiO ₂ component can be added to adjust the optical constant, but if the amount is too large, it becomes difficult to obtain the desired glass transition temperature. Therefore, the upper limit is preferably 5%, more preferably 4%, and most preferably 3%.

The Ta ₂ O ₅ component can be added to adjust the optical constant, but if the amount is too large, it becomes difficult to obtain the desired glass transition temperature. Therefore, the upper limit is preferably 10%, more preferably 8%, and most preferably 7%.

Each component of MgO, CaO, and SrO can be added to adjust the optical constant, but if the amount is too large, it becomes difficult to obtain a desired glass transition temperature. Accordingly, each of these components is preferably 5%, more preferably 4.7%, and most preferably 4.5%.

Among them, particularly in the glass mainly composed of P ₂ O ₅ , BaO, and ZnO as in the present invention, the glass transition temperature (Tg) is remarkably increased when the content of MgO is particularly high among alkaline earth metal oxides. Cheap. Therefore, the upper limit of the content of MgO is particularly preferably 1%.

In addition, when stably producing a glass having a Tg of 350 ° C. or lower, the RO component (R is one or more selected from the group consisting of Ba, Ca, Mg, Sr and Zn) is added to the total content. It is preferable that the content ratio of the ZnO component is 0.2 or more, more preferably 0.21 or more, and most preferably 0.22 or more. By maintaining the composition within this limit, it is easy to lower the glass transition temperature while maintaining stability.

The ZrO ₂ component has an effect of improving chemical durability and can be added to adjust the optical constant. However, if the amount is too large, the devitrification resistance is likely to rapidly decrease. Therefore, the upper limit is preferably 3%, more preferably 2%, and most preferably 1.5%.

Nb ₂ O ₅ , Bi ₂ O _3, and WO ₃ components can be added to increase the refractive index, but on the other hand, they easily cause a decrease in transmittance, and the transmittance on the short wavelength side is rapidly deteriorated. It is a component that becomes a factor. Therefore, in the optical glass of the present invention. The total of these components should be less than 3%, more preferably 1% or less, and most preferably not contained.

Since the lead compound has a problem that it is a component that is easily fused to the mold during precision press molding and has a large environmental load, it should not be contained in the optical glass of the present invention.

The F component is preferably not contained in order to easily generate striae when making a glass lump from molten glass.

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

Furthermore, it is preferable that the optical glass of the present invention does not contain coloring components such as V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Eu, Nd, Sm, Tb, Dy, and Er. However, the term “not contained” means that it is not contained artificially unless it is mixed as an impurity.

The present invention will be described in detail by the following examples, but the present invention is not limited thereto.
Example 1
Optical glass (Li ₂ containing 48% P ₂ O ₅ component, 30% BaO component, 9% ZnO component, 9% Li ₂ O, Na ₂ O and K ₂ O components in total on oxide basis) A glass preform comprising O, Na ₂ O and K ₂ O in excess of 0%) was prepared. The preform had a refractive index of 1.58, an Abbe number of 59, and a glass transition temperature of 327 ° 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 was ground, and a Ni—P film (Ni: P = 90: 10) was formed thereon by electroless plating. The film thickness was 30 μm.

A Toshiba machine MO2C machine was used as a precision press molding machine.

The glass preform was supplied at room temperature into the mold having an inner diameter of Φ10.4 mm, heated to 387 ° C. in a nitrogen gas atmosphere, and pressurized at a pressure of 14 MPa for 80 seconds. After that, while removing the cooling at a cooling rate of −2.2 ° C./S, pressurization was continued for 27 seconds at a pressure of 5.6 MPa. 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.

Claims (10)

An optical system characterized by precision press-molding a glass preform using a mold made of steel (including stainless steel) and / or copper alloy having a surface film having a hardness of 400 (HV) or more and a thickness of 1 μm or more. Device manufacturing method. 2. The method according to claim 1, wherein the surface film is composed of at least one selected from the group consisting of Ni, Cr, and Co, and any one or both of P and B. The ratio of the total amount (% by mass) of Ni, Cr and Co to the total amount (% by mass) of P and B in the surface film is in the range of 85:15 to 98: 2. 2. Manufacturing method of 2. It shape | molds at 400 degrees C or less, The manufacturing method in any one of Claims 1-3 characterized by the above-mentioned. The glass preform has a refractive index (nd) of 1.50 to 1.75, an Abbe number (νd) of 50 to 70, a glass transition point (Tg) of 350 ° C. or less, and P ₂ O ₅ and ZnO based on oxides. The manufacturing method according to any one of claims 1 to 4, wherein the manufacturing method comprises an optical glass essentially containing the components BaO and Sb ₂ O ₃ . The glass preform,% by mass on the oxide _basis, the claim, characterized in that the total content of Nb ₂ O 5, WO ₃ and _Bi 2 _{O 3} component is made of optical glass is less than 3% 5 Manufacturing method. The glass preform contains three or more alkali metal oxides on an oxide basis, and the total content of RO components (R is one or more selected from the group consisting of Ba, Ca, Mg, Sr and Zn). The method according to claim 5 or 6, wherein the optical glass is made of an optical glass having a ZnO component content ratio of 0.2 or more. The glass preform is an essential component in mass% based on oxide,
P ₂ O ₅ 40~55%
BaO 20-40%
ZnO 5-20% and Sb ₂ O ₃ 0.1-10%
The manufacturing method according to claim 5, comprising optical glass containing The glass preform is further mass% based on oxide,
Li ₂ O 1-5%
Na ₂ O 1 to 10% and _K 2 O 1~10%,
And SiO ₂ 0-2% and / or B ₂ O ₃ 0-3% and / or Al ₂ O ₃ 0-3% and / or Y ₂ O ₃ 0-3% and / or La ₂ O ₃ 0-1 .5% and / or Gd ₂ O ₃ 0 to 1.3% and / or TiO ₂ 0 to 5% and / or Ta ₂ O ₅ 0 to 10% and / or MgO 0 to 5% and / or CaO 0 5% and / or SrO 0 to 5% and / or _ZrO 2 0 to 3%
It consists of optical glass containing each component of the range of these, The manufacturing method in any one of Claims 5-8 characterized by the above-mentioned. The glass preform,% by mass on the oxide _basis, claim, characterized in that the total content of SiO _2, B 2 _{O 3} and _Al 2 _{O 3} component is made of optical glass is not more than 1% 5 9. The production method according to any one of 9 above.