JP2003335549A - Optical glass, preform for high precision press-forming, and optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical glass and a preform for high precision press- forming, which permit a good high precision press-forming by inhibiting the reaction of Nb, W and Ti contents of easily reducible components having a high refractive index and high dispersion, with a release membrane on the high precision press mold, and to provide an optical element made of the optical glass having the characteristics of a high refractive index (n<SB>d</SB>≥1.65) and a high dispersion (ν<SB>d</SB>≤35). <P>SOLUTION: The optical glass has a refractive index n<SB>d</SB>of 1.65 or more, an Abbe number υ<SB>d</SB>of 35 or less and a flexure point Ts of 570°C or lower, and has as the essential components at least one kind of an oxide selected from the group consisting of P<SB>2</SB>O<SB>5</SB>, SiO<SB>2</SB>and B<SB>2</SB>O<SB>3</SB>, and also contains from more than 0 mole % to less than 35 mole % of the total sum amount of Nb<SB>2</SB>O<SB>5</SB>, WO<SB>3</SB>and TiO<SB>2</SB>and does not substantially contain Ge, Te and Pb. The preform for high precision press-forming and the optical element comprise the above optical glass. The optical element is obtained by high precision press-forming the above preform. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention basically relates to P ₂ O _5- (N
b ₂ O ₅ , WO ₃ , TiO ₂ ), B ₂ O _3- (Nb ₂ O ₅ , WO ₃ , TiO ₂ ), SiO ₂
-(Nb ₂ O ₅ , WO ₃ , TiO ₂ ), P ₂ O ₅ -SiO _2- (Nb ₂ O ₅ , WO ₃ , TiO 2
₂ ), P ₂ O ₅ -B ₂ O _3- (Nb ₂ O ₅ , WO ₃ , TiO ₂ ), and B ₂ O ₃ -SiO ₂
-(Nb ₂ O ₅ , WO ₃ , TiO ₂ ) -based, the glass has a deformation point temperature (Ts) of 570 ° C or less, and the total content of high refractive index and high dispersion components is less than 35%. The present invention relates to an optical glass useful for press molding. Further, the optical glass according to the present invention,
The present invention relates to an optical glass for precision press molding for producing an optical element such as an ultraprecision aspherical lens that does not require grinding or polishing after precision press molding.

[0002]

2. Description of the Related Art In recent years, with the advent of digital cameras, the high integration and high functionality of devices that use optical systems are rapidly advancing, and the demand for higher precision, lighter weight and smaller size of optical systems is increasing. In order to fulfill this requirement,
Optical designs using aspherical lenses are becoming mainstream. Therefore, in order to stably supply a large amount of aspherical lenses using high-performance glass at low cost, precision press molding technology that directly forms an optical functional surface by press molding and does not require grinding and polishing steps ( Also called molding technology)
, And the demand for optical glass suitable for molding having high functionality (for example, high refractive index / low dispersion / high refractive index / high dispersion) is increasing year by year.

In precision press molding of glass, a glass molding preform (also referred to as a preform) is pressure-molded at a high temperature using a molding die having a cavity of a predetermined shape to obtain a final product shape or a shape very close to the shape. And a method for obtaining a glass molded product having surface accuracy. According to the precision press molding, a molded product having a desired shape can be manufactured with high productivity. Therefore, various optical glass parts such as spherical lenses, aspherical lenses, and diffraction gratings are currently manufactured by precision press molding. Of course,
In order to obtain optical glass parts by precision press molding, it is necessary to pressure mold the glass molding preform as described above, so the mold used for pressing is exposed to high temperature and high pressure is applied. Is added. Therefore, regarding the gob preform for glass molding, from the viewpoint of suppressing damage to the mold itself or the release film provided on the inner surface of the mold due to the high temperature environment of press molding, the glass component and the mold It is desired to suppress the reactivity with the surface and lower the glass transition temperature T _g and the yield point temperature T _s as much as possible.

Conventionally, high refractive index and high dispersion (nd> 1.65 and ν
d <35) As an optical glass having an optical constant, SiO ₂ , P
Glasses containing ₂ O ₅ , B ₂ O ₃ , TiO ₂ , Nb ₂ O ₅ , TiO _{2 and the} like as essential components are known. (For example, Japanese Patent Laid-Open No. 2001-58845)

However, the conventional optical glass for precision press molding is focused on high refractive index and high dispersion, and although it is very useful in the design of the optical system, Nb ₂ O, which is a component that is easily reduced, is used. ₅ , TiO ₂ , WO ₃ and the temperature at which the glass can be pressed, that is, the temperature around the deformation point Ts + 60 ° C, lacks balance, and the surface of the lens is foamed, hardened, or radiatively damaged when pressed. Of components that are easily reduced in glass
Nb, W, and Ti react with the surface of the pressing die in the pressable temperature range and damage the release film, which is problematic as mold pressing glass. No glass material for a mold press having such optical characteristics has solved the manufacturing problem. Further, in the case of a glass containing a large amount of TiO ₂ , there are problems such as coloring of the glass, deterioration of meltability and stability.

The present invention solves the above problems and, while imparting high refractive index and high dispersion characteristics, the contents of Nb, W, and Ti of high refractive index and high dispersion components which are easily reduced and the precision press mold. An object of the present invention is to provide an optical glass and a precision press-molding preform that enable good precision press-molding by suppressing a reaction with a release film.

Another object of the present invention is to provide an optical element made of an optical glass having a high refractive index (n _d ≥1.65) and a high dispersion (ν _d ≤35).

[0008]

[Means for Solving the Problems] The present invention for solving the above problems is as follows. (1) The refractive index nd is 1.65 or more, the Abbe number νd is 35 or less, the yield point Ts is 570 ° C. or less, and P ₂ O ₅ , SiO
_In an optical glass containing at least one oxide selected from the group consisting of ₂ and B ₂ O ₃ as an essential component, Nb ₂ O ₅ ,
WO ₃ and TiO ₂ in a total amount of more than 0 mol% and 35 mol%
An optical glass comprising less than and substantially free of Ge, Te, and Pb. (2) In a glass precision press-molding preform that is heated and softened to be precision press-molded by a press mold, the refractive index nd is 1.65 or more, the Abbe number νd is 35 or less, and the yield point Ts is 570 ° C or less. Yes, P ₂ O ₅ , SiO
₂ and B ₂ O _3, at least one oxide selected from the group consisting of ₂ and B ₂ O ₃ is contained as an essential component, and Nb ₂ O ₅ , WO ₃ , and TiO ₂ are contained in a total amount of more than 0 mol% and less than 35 mol%, and Ge , T
A press for precision press molding, characterized by comprising an optical glass substantially free of e and Pb, and used for precision press molding with a press mold having a carbon-containing thin film formed on the molding surface. Reform. (3) The refractive index nd is 1.65 or more, the Abbe number νd is 35 or less, the yield point Ts is 570 ° C. or less, and P ₂ O ₅ , SiO
₂ and B ₂ O _3, at least one oxide selected from the group consisting of ₂ and B ₂ O ₃ is contained as an essential component, and Nb ₂ O ₅ , WO ₃ , and TiO ₂ are contained in a total amount of more than 0 mol% and less than 35 mol%, and Ge , T
A preform for precision press molding, wherein a thin film is formed on the surface of optical glass that does not substantially contain e and Pb. (4) The preform for precision press molding according to (3), wherein the thin film is a carbon-containing thin film. (5) WO when the optical glass is displayed in mol%
_When the numerical value of the content of ₃ is Cw and the numerical value of the yield point when expressed in ° C is Ts, the relational expression Ts + (7 × Cw)
≦ 610 (2)-
The precision press molding preform according to any one of (4). (6) The optical glass, in mol% display, is P ₂ O ₅ 15 to 40%, SiO _{20 to} 10%, B ₂ O ₃ 0 to 20%, Al ₂ O ₃ 0 to 5%, Li ₂ O. 5 to 30%, Na ₂ O 0 to 30%, ZnO 0 to 20%, BaO 0 to 20%, Nb ₂ O ₅ 2 to 30%, WO ₃ 2 to 15%, TiO _{2 0 to} 15%, (however, , Nb ₂ O ₅ + WO ₃ + TiO ₂ = 10% or more and less than 35%),
The precision press molding preform according to any one of (2) to (5), wherein the total amount of the above components is 95% or more. (7) An optical element obtained by precision press molding the preform according to any one of (2) to (6).

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have conducted intensive studies to achieve the above object, and as a result, introduced such that the refractive index (nd) is 1.65 or more and the Abbe number (νd) is 35 or less. Reaction of Nb, W, and Ti with high refractive index and high dispersion with the mold release film formed on the molding surface of the press mold, or improvement of mold releasing effect and sliding between the mold surface and glass during pressing. It was found that the reaction between the thin film formed on the surface of the press-molding preform and the glass was mainly a function of the press temperature in order to improve the temperature. When the content of Nb, W, and Ti is high, if the press temperature, that is, the yield point temperature (Ts) of the glass is kept low, the reaction between the mold release film of the press mold and the glass due to these high refractive index imparting components It won't happen. Or, the yield point temperature Ts
It was found that the higher the value, the smaller the content of the high refractive index and high dispersion component should be. The same applies to the reaction between the thin film provided on the surface of the preform and the glass.
Especially in phosphoric acid type glass, the influence of W is the largest, and
_When the content of ₃ is large, unless the yield point temperature is suppressed to a certain level or less according to the content of WO ₃ , it is possible to perform precision press molding of optical elements such as lenses while preventing glass foaming and radiation damage. However, we found that if the yield point temperature is kept below 500 ° C, optical elements such as aspherical lenses can be satisfactorily precision press-molded even if WO ₃ is added up to about 15 mol%.

In the optical glass of the present invention, Ge
O₂, TeO₂, PbO is glass that is very easily reduced
Since these are minutes, these components are excluded. In addition, G
eO ₂Is expensive and TeO₂, PbO an environmental problem?
Should be excluded. Eliminating the glass here
It means that it is not used as a raw material, and is impure.
Use glass raw materials with a low content of these ingredients.
It is desirable to use.

Nb ₂ O ₅ , WO ₃ , and
In a phosphate-based, silicate-based, borate-based, and mixed phosphate-silicate-borate-based glass containing at least one of TiO ₂ , the yield point temperature is 550 ° C. or lower, and The total content C _{H of} high refractive index and high dispersion component (Nb ₂ O ₅ + TiO ₂ + WO ₃ ) is less than 35 mol%, the refractive index of the glass is 1.65 or more, and the Abbe number is 35 or less. The present invention relates to a high-refractive-index, high-dispersion optical glass for precision press molding. In addition, in the phosphate-based, silicate-based, borate-based, and mixed phosphate-silicate-borate-based glasses containing WO ₃ as a high-refractive index / high-dispersion component, the glass yields The point temperature Ts (℃) and the WO ₃ content C _W (mol%) are Ts + 7 C _W ≦ 610
The present invention relates to a high-refractive-index, high-dispersion optical glass for precision presses, which is in a region satisfying the relationship of, WO ₃ is 2 to 15 mol% or less, a refractive index is 1.65 or more, and an Abbe number is 35 or less. The range P ₂ O ₅ As the glass is 15 to 40% and Li ₂ O
Is preferably in the range of 5 to 30%. Furthermore, mol%
In _{view, P 2 O 5 = 15~40%} , SiO 2 = 0~10%, B 2 O 3 = 0~20%, A
_{l 2 O 3 = 0~5%,} Li 2 O = 5~30%, Na 2 O = 0~30%, ZnO = 0~20
%, BaO = 0~20%, Nb 2 O 5 = 2~30%, WO 3 = 2~15%, TiO 2 = 0~1
It is preferable that it contains 5% (however, Nb ₂ O ₅ + WO ₃ + TiO ₂ = 10% or more and less than 35%), and the total amount of the above components is 95% or more. The optical glass for precision press molding of the present invention will be described below. Hereinafter, the content of each component will be represented by mol% unless otherwise specified.

In the optical glass of the present invention, the yield point temperature is 57
It is limited to 0 ° C. or lower and the total content of Nb ₂ O ₅ , TiO ₂ and WO ₃ is limited to less than 35 mol%. The reason is,
If the yield point temperature is higher than 570 ° C, the pressing temperature is too high and defects such as foaming, radial scratches, and spots remain on the surface of the lens during pressing, making it difficult to produce high-quality lenses. is there. Therefore, it is necessary to keep the yield point temperature below 570 ° C. The temperature is more preferably 550 ° C or lower, still more preferably 540 ° C or lower. Also, Nb ₂ O ₅ , T
Unless the total amount of iO ₂ and WO ₃ is suppressed to less than 35%, Nb, W, and Ti, which are components that are particularly easily reduced in glass, react with the surface of the pressing mold in the temperature range where they can be pressed and release the mold. It is not suitable as a glass for precision press because it may damage the film and may cause the glass to be colored due to too much of the above components that are easily reduced. It is more preferably 32% or less.

The yield point temperature is 570 ° C. or lower,
Further, Ts + 7C _W ≦ 610, and WO ₃ is preferably 2 to 15 mol%, more preferably Ts + 6C _W ≦ 590 while satisfying the above relationship. If the deformation point temperature is higher than 570 ° C, the pressing temperature is too high and defects such as foaming, radial scratches, and spots remain on the surface of the lens when pressing, so that a good quality lens cannot be manufactured. Therefore, it is necessary to keep the yield point temperature below 570 ° C. The temperature is more preferably 550 ° C or lower, still more preferably 540 ° C or lower. Also, when Ts + 7C _W > 610, _W , which is a component that is particularly easily reduced in this glass, tends to react with the surface of the pressing die in the temperature range where pressing is possible and easily damage the release film. Therefore, it is preferable to satisfy Ts + 7C _W ≦ 610, and it is more preferable to satisfy Ts + 6C _W ≦ 590 while satisfying the above relationship. Further, WO ₃ content becomes less than 2 mol%, WO ₃ is too small likelihood is increased that a sag temperature Ts> 570 ° C., and even worse the stability of the glass. Therefore Ts
It is more preferable that the content of WO _{3 be} 2% or more while keeping + 7C _W ≦ 610. However, on the other hand, when the WO ₃ content exceeds 15 mol%, the glass may be colored due to too much WO ₃ , so while maintaining Ts + 7C _W ≦ 610, the WO ₃ content is 15%. % Or less is preferable. More preferably in the above range Ts + 6C _W ≦ 590, and the content of WO ₃
It is in the range of 2 to 12%. More preferably, Ts + 6C _W ≤580
And

The preferred glass containing P ₂ O ₅ as an essential component of the present invention is P ₂ O ₅ : 17-37, expressed in mol%.
%, SiO ₂ : 0-8%, B ₂ O ₃ : 1-15%, Al ₂ O ₃ = 0-4%, Nb ₂
O ₅ : 5-25%, WO ₃ : 2-12%, TiO ₂ : 0-12%, but Nb
₂ O ₅ + WO ₃ + TiO ₂ : 15-35%, BaO: 0-18%, ZnO: 0-18
%, SrO: 0-10%, but BaO + ZnO + SrO <25%, Li
₂ O: 5-25%, Na ₂ O: 3-25%, K ₂ O: 0-8%, provided that Li ₂
O + Na ₂ O + K ₂ O: 45% or less, Sb ₂ O ₃ : 0-1%, As ₂ O ₃ : 0-1
% Component, and the total composition is at least
95%, refractive index nd is 1.65 or more, Abbe number νd is 35 or less,
An optical glass having a deformation point temperature of 570 ° C or lower, preferably 550 ° C or lower, and more preferably 540 ° C or lower. The role of each component in the optical glass for precision press molding containing P ₂ O ₅ will be described below.

P ₂ O ₅ is a glass network-structured product and is an essential component for imparting stability to glass production. However, when the content of P ₂ O ₅ exceeds 40%, the glass transition temperature and the yield point temperature of the glass increase, the refractive index decreases, and the Abbe number increases, whereas when it is less than 15%, Since the devitrification tendency of the glass becomes strong and the glass becomes unstable, the content of P ₂ O ₅ is set in the range of 15-40%. More preferably, it is in the range of 17-37%.

B ₂ O ₃ is an important component of this glass,
It is a very effective ingredient for improving the meltability of glass and homogenizing glass, and at the same time, it changes the bonding property of OH inside the glass by introducing a small amount of B ₂ O ₃ and does not cause the glass to foam during pressing. It is an effective ingredient. However, if B ₂ O ₃ is introduced in an amount of more than 20%, the glass in which a large amount of Nb ₂ O ₅ is introduced to maintain a high refractive index becomes very unstable. Is preferred. More preferably 1
It is in the range of -15%.

Similar to P ₂ O ₅ , SiO ₂ is a component that acts as a glass network structure-forming product and contributes to the improvement of the durability and stability of the glass and the improvement of the viscosity of the glass at the liquidus temperature.
However, if more than 10% of SiO ₂ is introduced into a glass in which a large amount of high refractive index components such as WO ₃ and Nb ₂ O ₅ are introduced, the glass is likely to be crystallized, the refractive index is greatly lowered, and the glass is melted. Since the yield point temperature and the liquidus temperature become high, the introduction amount is preferably suppressed to 10% or less. It is more preferably 8% or less.

Nb ₂ O ₅ is an essential component of this glass, and Pb
It is a component that plays a very important role, which is indispensable for giving glass properties such as high refractive index and high dispersion without using bO. However, if the amount introduced exceeds 30%, the transition temperature and the yield point temperature of the glass are increased, the stability is deteriorated, and the high temperature solubility is deteriorated, while the glass tends to be foamed or colored during precision pressing. On the other hand, the introduction amount is
If it is 2% or less, the refractive index of the glass is lowered and the dispersion is also small. Therefore, the content of Nb ₂ O ₅ is preferably in the range of 2-30%. It is preferably in the range of 5-25%.

WO ₃ is an important component in this glass, and is the most effective component that can give a glass having a low melting point and a high refractive index and high dispersion without using PbO. Like the alkali metal oxide, WO ₃ has a function of lowering the glass transition temperature and the yield point temperature, and also has an effect of increasing the refractive index. However, if too much WO ₃ is introduced, for example, if the introduction amount exceeds 15%, the glass tends to be colored, while the high temperature viscosity of the glass also becomes low, making it difficult to make a glass preform for precision press. On the other hand, if it is less than 2%, the transition temperature and the yield point temperature of the glass become high, and the glass tends to foam during precision pressing. Therefore, the content is preferably in the range of 2-15%. The range is more preferably 2-12%.

TiO ₂ has the effect of increasing the refractive index of the glass and improving the devitrification stability, but if its content exceeds 15%, the devitrification stability of the glass deteriorates sharply and the yield point temperature is lowered. Also, the liquidus temperature rises sharply, and the glass tends to be colored during precision pressing, so the amount introduced is limited to 15% or less. It is preferably 12% or less. When the total amount of Nb ₂ O ₅ , WO ₃ and TiO ₂ is 35% or more, the characteristics of high refractive index and high dispersion can be obtained, but the melted glass is colored and the devitrification stability is deteriorated. If the total amount is less than 10%, the desired optical properties such as refractive index and dispersion cannot be obtained, so
The total amount of Nb ₂ O ₅ , WO ₃ and TiO ₂ is in the range of 10% or more and less than 35%. Further, it is preferably 15% or more and less than 35%, more preferably 16-34%, further preferably 16-33%, particularly preferably 16-32%.

BaO is an essential component for increasing the refractive index of glass, improving devitrification stability, and lowering the liquidus temperature. Especially when a large amount of WO ₃ is introduced, the effect of suppressing the coloring of the glass and increasing the devitrification stability is large by introducing BaO. However, when a large amount of BaO introduced exceeds 20%, not only the glass becomes thermally unstable but also the yield point temperature rises, so the amount of BaO introduced is preferably 20% or less. More preferably, it is in the range of 0-18%.

ZnO is a component introduced to enhance the refractive index and dispersion of glass, and the introduction of a small amount of ZnO also has the effect of lowering the transition temperature, yield point temperature or liquidus temperature of glass.
However, if a large amount is introduced, the devitrification stability of the glass may be significantly deteriorated and the liquidus temperature may be increased on the contrary. Therefore, the introduction amount is preferably 20% or less. It is more preferably 18% or less.

Alkali metal oxides such as Li ₂ O, Na ₂ O, and K ₂ O all improve the devitrification resistance of the glass, lower the yield point temperature and liquidus temperature, and melt the glass at high temperatures. It is a component introduced to improve the sex. Therefore, Li ₂ O
% Or more is preferably introduced. However, if more than 30% of Li ₂ O and Na ₂ O are introduced, respectively, or if Li ₂ O, Na ₂ O,
And when the total amount of K ₂ O exceeds 45%, not only the stability of the glass deteriorates, but also the desired high refractive index
Since it becomes difficult to obtain high dispersion characteristics, it is preferable that the introduced amounts of Li ₂ O and Na ₂ O be 30% or less. The amount of K ₂ O introduced is preferably 15% or less. More preferably, Li ₂ O is in the range of 5-25%, Na ₂ O is in the range of 3-25%, and K ₂ O is in the range of 0-8%. The total amount of Li ₂ O, Na ₂ O, and K ₂ O is preferably 45% or less.

Al ₂ O _3, which is an optional component, is very effective in improving the viscosity at the liquidus temperature of the glass and the durability of the glass by adding an appropriate amount, but Al ₂ O ₃ is introduced in excess of 5%. Then, the glass becomes difficult to melt, and the yield point temperature and the liquidus temperature also increase, so that the amount of introduction thereof is preferably 5% or less. It is preferably 4% or less.

As ₂ O ₃ and Sb ₂ O ₃ are effective as a fining agent for glass. However, in both cases, if added in excess of 1%, the glass tends to foam during precision pressing, so the amount introduced is 1% or less. In addition, SiO ₂ , La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O
Components such as ₃ , ZrO ₂ , Ta ₂ O ₅ , CaO, MgO, and Cs ₂ O can be introduced up to 5% as long as the object of the present invention is not impaired, but more consistent with the above object. From the viewpoint of obtaining good quality glass, it is preferable not to introduce the above components. Also,
Since Bi ₂ O ₃ tends to color the glass, it is desirable that the proportion of Bi ₂ O ₃ in the glass composition is 4% or less by weight, and it is more desirable not to introduce it.

The low melting point, high refractive index and high dispersion optical lens of the present invention
As a raw material for lath, P₂O_FiveAbout H ₃PO_Four, Metallin
Acid salts, diphosphorus pentoxide, etc., B₂O₃About H₃BO₃, B₂O₃Na
For other ingredients, carbonates, nitrates, oxides
And the like can be used as appropriate. These ingredients
Weigh it to a prescribed ratio and mix it to make a blended raw material.
Put into a melting furnace heated to 00-1250 ℃, melt, clarify, stir
Then, homogenize it, then cast it in the mold and slowly cool it.
A low melting point, high refractive index and high dispersion optical glass of the present invention can be obtained.
You can The above optical glass has a refractive index of 1.65 or more
(Nd) and an Abbe number (νd) of 35% or less. Refractive index
The more preferable range of (nd) is less than 1.83.

The optical product of the present invention can be obtained by precision pressing the above-mentioned high refractive index and high dispersion optical glass of the present invention. As the method and apparatus for precision pressing, known ones can be used, and the conditions can be appropriately selected in consideration of the composition and physical properties of the glass. More preferred optical products are
It is an aspherical lens obtained by precision-pressing an aspherical surface of the low melting point optical glass of the present invention. The precision press molding can be performed using a pressing device as shown in FIG. 1, for example. The apparatus shown in FIG. 1 is a quartz tube in which a heater 12 is wound around an outer periphery of a support die 10 provided on a support rod 9 on which a forming die including an upper die 1, a lower die 2 and a guide die 3 is placed. It is provided in 11. High refractive index of the present invention
Glass preform 4 made of high-dispersion optical glass
Can be, for example, a spherical object having a diameter of about 2-20 mm or an elliptic spherical object. The size of a spherical object or an oval spherical object,
The weight is appropriately determined in consideration of the size of the final product. It is desirable to form a thin film on the surface of the preform to improve releasability and slip between the glass and the mold during press molding. Examples of such a thin film include a carbon film, a hydrogenated carbon film, and a self-assembled film.

After the glass to be molded 4 is placed between the lower mold 2 and the upper mold 1, the heater 12 is energized to heat the inside of the quartz tube 11. The temperature inside the mold is controlled by the thermocouple 14 inserted inside the lower mold 2. The heating temperature is a temperature at which the viscosity of the glass to be molded 4 is suitable for precision pressing, for example, about 10 ^7.6 poise. After reaching a predetermined temperature, the push rod 13 is lowered to push the upper mold 1 from above to press the glass to be molded 4 in the molding mold. The pressure and time of the press can be appropriately determined in consideration of the viscosity of glass and the like. For example, the pressure can be in the range 50-150 kg / cm ² and the time can be 10-300 seconds. After the pressing, the optical product of the present invention can be obtained by gradually cooling to the glass transition temperature, then rapidly cooling to room temperature, and taking out the molded product from the molding die.

It is preferable to provide a carbon-containing thin film on the molding surfaces of the upper mold 1 and the lower mold 2 (surfaces transferred to glass by press molding) in order to obtain good mold releasability. Is more preferably a film containing carbon as a main component. Here, the main component is a component contained most in the film. Examples of such a film include a carbon film and a hydrogenated carbon film. The carbon-containing thin film acts as a release film provided on the mold forming surface, and has an effect of suppressing the occurrence of scratches on the surface of the precision press-formed product.
However, when precision press-molding a glass containing a high-refractivity high-dispersion component that is easily reduced, such as Nb ₂ O ₅ , TiO ₂ , and WO ₃ , the glass easily damages the carbon-containing thin film, resulting in carbon-containing The releasability and scratch control effect of the thin film are likely to be impaired. In the case of the above-mentioned optical glass or preform, even if precision press molding is performed using a mold in which the carbon-containing thin film is used for the molding surface, damage to the carbon-containing thin film is suppressed and prevented. It is possible to perform precision press molding without impairing the moldability and scratch control effect.
As a result, the occurrence of scratches on the surface of the precision press-formed product can be significantly reduced and prevented.

[0030]

EXAMPLES The present invention will be further described below with reference to examples. Table 1 shows the compositions of the glasses of Examples 1 to 15, and Table 2 shows their characteristic values (refractive index (nd), Abbe number (νd), glass transition temperature (Tg), yield point temperature (Ts), and Liquidus temperature (LT)) is shown. The glass of the present invention uses the corresponding oxides, fluorides, hydroxides, carbonates, and nitrates as raw materials for the respective components, and weighs them so that the composition ratio of each example in Table 1 is obtained after vitrification. Then, after thoroughly mixing, it was put into a platinum crucible and melted in an electric furnace in a temperature range of 1050 to 1200 ° C., homogenized by stirring, clarified, and cast into a mold preheated to an appropriate temperature. After that, the glass is cooled to the transition temperature of the glass, immediately annealed, and gradually cooled to room temperature. The composition of the obtained glass is also the same as the value shown in Table 1.

[0031]

[Table 1]

The refractive index (n
d), Abbe number (νd), glass transition temperature (Tg), yield point temperature
(Ts), liquidus temperature (LT), and glass viscosity at the liquidus temperature were measured as follows. These results are shown in Table 2.
Shown in.

[0033]

[Table 2]

The liquidus temperature of each glass containing P ₂ O ₅ of Examples 1 to 13 is 970 ° C. or lower, which shows that the glass has excellent devitrification resistance. Thus, the liquidus temperature is 97
Since the temperature is 0 ° C. or less, good preform molding can be performed without devitrifying the glass even when the precision press molding preform is molded directly from the molten glass.

(1) Refractive index (nd) and Abbe's number (νd) The optical glass obtained was measured at a slow cooling rate of -30 ° C / h. (2) Transition temperature (Tg) and yield point temperature (Ts) The rate of temperature rise was set to 4 by the thermomechanical analyzer of Rigaku Denki Co.
It was measured at ° C / min. (3) Liquid phase temperature (LT) 400 to 1150 ℃ held in a devitrification test furnace with a temperature gradient for 1 hour, observe the presence or absence of crystals with a microscope with a magnification of 80 times,
The liquidus temperature was measured.

Next, the refined and homogenized molten glass from which the glasses of Examples 1 to 15 were obtained was dropped from a nozzle made of a platinum alloy, and precision press molding was performed using a constant weight of the glasses of Examples 1 to 15. A preform for use was produced. Then, a hydrogenated carbon film was formed on the surface of each of these preforms, and aspherical lens was obtained by performing aspherical surface precision press molding using the pressing device shown in FIG. The details are as follows. After placing a preform made of the glass of the above-mentioned embodiment in the form of a sphere having a diameter of 2-30 mm between the lower mold 2 and the upper mold 1 made of SiC having a carbon film on the molding surface
The inside of the quartz tube 11 was heated to energize the heater 12 in a nitrogen atmosphere. The temperature inside the forming die is set to a temperature at which the deformation point temperature of glass is +20 to 60 ° C, and while maintaining the same temperature, the push rod 13 is lowered and the upper die 1 is pushed to press the preform in the forming die. did. Press pressure is 8M
Pa, press time was 30 seconds, after which the pressure of the press was released and the glass transition temperature was maintained in the state where the aspherical press-molded glass molding was in contact with the lower mold 2 and the upper mold 1. The glass molded into the aspherical lens was taken out from the molding die by gradually cooling to a temperature of -30 ° C and then rapidly cooling to room temperature.

The aspherical lenses obtained by precision press molding using the glass preforms of Examples 1 to 12 are lenses with extremely high precision and are required as optical elements without grinding or polishing. It had an optical functional surface (a surface used for transmitting, reflecting, or refracting light rays when used as an optical element). Further, the surface of the lens had no defects such as scratches, bubbles and cloudiness, and the performance as a lens was extremely good. Further, no damage was observed on the release film of the press mold used for precision press molding. It should be noted that these examples are included in the scope and preferred scope of the present invention shown in FIGS. A self-assembled film made of a Si-containing organic material may be formed and used on the surface of the preform instead of the carbon film or the hydrogenated carbon film.

As a result of precision press molding using the glass preforms of Examples 13 to 15, the accuracy of the obtained aspherical lens was sufficient, but scratches and bubbles were formed on the lens surface. It was also recognized that defects such as This glass falls within the scope of the present invention as shown in FIG. 1 but is slightly out of the preferred range shown in FIG. 2 or does not contain P ₂ O ₅ . Further, when precision press molding was performed using the glasses of Comparative Examples 1 to 4 not included in the present invention, defects such as scratches and bubbles were found on the surface of the obtained lens. In addition, the release film of the mold used for the press was also damaged. As described above, it was confirmed that the present invention is effective in preventing scratches and foaming on the surface of the molded article, and preventing damage to the release film of the press mold.

[0039]

According to the present invention, an optical glass having desired optical characteristics and excellent press moldability and capable of preventing defects such as bubbles, scratches and cloudiness on the glass surface during precision press molding, and a precision press. A molding preform can be provided. In addition, according to the present invention, since the liquidus temperature is 970 ° C. or less and it is possible to provide a phosphate optical glass having excellent devitrification resistance, it is possible to directly form a precision press molding preform from a molten glass. It is effective in preventing devitrification of the glass when it is applied. Furthermore, by using the optical glass of the present invention, it is possible to extend the life of the precision press mold material,
Precision press molding can be stably performed.

[Brief description of drawings]

FIG. 1 is a schematic view of a press device used for precision press molding.

FIG. 2 is an evaluation result of a lens obtained by precision press molding, which is shown in the coordinates of the yield point Ts and the TiO ₂ + Nb ₂ O ₅ + WO ₃ content.

FIG. 3 is an evaluation result of the lens obtained by precision press molding, which is shown in the coordinates of the yield point Ts and the WO ₃ content.

Continued front page    F term (reference) 4G062 AA04 BB09 DA01 DA02 DA03                       DB01 DB02 DB03 DC01 DC02                       DC03 DC04 DD04 DD05 DE01                       DE02 DE03 DE04 DF01 EA03                       EA04 EB01 EB02 EB03 EB04                       EC01 ED01 EE01 EF01 EG01                       FA01 FB01 FB02 FB03 FB04                       FC01 FD01 FE01 FF01 FG03                       FG04 FH01 FJ01 FK01 FL01                       GA01 GA10 GB01 GC01 GD01                       GE01 HH01 HH03 HH05 HH07                       HH08 HH09 HH11 HH13 HH15                       HH17 HH20 JJ01 JJ03 JJ05                       JJ07 JJ10 KK01 KK03 KK05                       KK07 KK10 MM02 NN02

Claims (7)

[Claims] 1. A refractive index nd of 1.65 or more and an Abbe number νd
Is 35 or less, the yield point Ts is 570 ° C. or less, P ₂ O ₅ ,
At least one selected from the group consisting of SiO ₂ and B ₂ O _3.
In an optical glass containing a certain kind of oxide as an essential component, Nb
₂ O ₅ , WO ₃ , and TiO ₂ in a total amount of more than 0 mol% and 35
An optical glass comprising less than mol% and substantially free of Ge, Te and Pb. 2. A glass precision press-molding preform that is heated and softened and precision press-molded by a press mold, wherein the refractive index nd is 1.65 or more, the Abbe number νd is 35 or less, and the yield point Ts is 570 ° C. Below, P ₂ O ₅ , SiO ₂ and B ₂ O
_At least one oxide selected from the group consisting of ₃ is contained as an essential component, and Nb ₂ O ₅ , WO ₃ , and TiO ₂ are contained in a total amount of more than 0 mol% and less than 35 mol%, and Ge, Te, and Pb are contained.
A precision press-molding preform, which is made of optical glass substantially free from the above, and is used for precision press-molding by a press mold having a carbon-containing thin film formed on a molding surface. 3. The refractive index nd is 1.65 or more and the Abbe number νd.
Is 35 or less, the yield point Ts is 570 ° C. or less, P ₂ O ₅ ,
At least one selected from the group consisting of SiO ₂ and B ₂ O _3.
Nb ₂ O ₅ , WO ₃ , and T as essential components
iO ₂ in a total amount of more than 0 mol% and less than 35 mol%,
A precision press-molding preform having a thin film formed on the surface of an optical glass that does not substantially contain e, Te, and Pb. 4. The precision press molding preform according to claim 3, wherein the thin film is a carbon-containing thin film. 5. The relational expression Ts + (7 ×), where Cw is the numerical value of the content of WO ₃ in mol% of the optical glass and Ts is the numerical value of the yield point in ° C.
The preform for precision press molding according to any one of claims 2 to 4, wherein Cw) ≦ 610 is satisfied. Wherein said optical glass, by _{mol%, P 2 O 5 15~40%,} SiO 2 0~10%, B 2 O 3 0~20%, Al 2 O 3 0~5%, Li ₂ O 5-30%, Na ₂ O 0-30%, ZnO 0-20%, BaO 0-20%, Nb ₂ O ₅ 2-30%, WO ₃ 2-15%, TiO ₂ 0-15%, (However, Nb ₂ O ₅ + WO ₃ + TiO ₂ = 10% or more and less than 35%) is included,
The preform for precision press molding according to any one of claims 2 to 5, wherein the total amount of the above components is 95% or more. 7. An optical element obtained by precision press-molding the preform according to claim 2. Description: