JP5296345B2 - Optical glass - Google Patents

Abstract

The invention provides a phosphate glass, which is suitable for manufacturing a non-spherical die mold, a glass pre-forming blank, and the like due to low dispersivity, low glass transition temperature (Tg) and low average coefficient of linear expansion (alpha). An optical glass is characterized in that the optical glass contains P2O5, B2O3, BaO, Al2O3 and La2O3 as necessary components, on the basis of weight percent of an oxide, the total content of Al2O3 and La2O3 is 1 to 10 percent, the value of the Al2O3 content/ the La2O3 content ranges from 0.05 to 8.0, and the water resisting property RW of the glass measured by a measuring method (powder method) for chemical durability of the optical glass by JOGIS06<-1999> is level 1 to 3.

Description

Since the present invention has low dispersibility and has a low glass transition temperature (Tg) and an average linear expansion coefficient (α), phosphoric acid is suitable for producing an aspherical mold press and a glass preform thereof. It relates to salt glass. In particular, the present invention contains P ₂ O ₅ , B ₂ O ₃ , Al ₂ O ₃ , BaO, Li ₂ O, and since the liquidus temperature is low, the temperature load on the manufacturing apparatus is small and extremely stable production is achieved. It relates to the possible optical glass.

In recent years, the tendency to reduce the weight and size of optical elements such as lenses by reducing the number of lenses using aspherical lenses has been increasing. However, if an aspherical surface is to be obtained by conventional grinding and polishing processes, a costly and complicated work process is required. Therefore, a method has been developed in which a preform material obtained from a gob or glass block is directly molded into a lens with a precision machined mold. The lens thus obtained does not need to be polished, and as a result, can be produced at a low cost and with a short delivery time.

The above-described molding method is called mold press molding, and has been actively researched and developed as a manufacturing method for obtaining fine shapes and aspherical shapes with high accuracy. In mold press molding, glass that softens at a lower temperature, specifically, glass having a glass transition temperature (Tg) of 550 ° C. or lower, more preferably 530 ° C. or lower, has been demanded from the heat resistance of the mold used. In recent years, due to the necessity for optical design, there is an increasing demand for glass materials that can be mold press-molded even for optical glasses having low dispersibility, especially optical glasses having an Abbe number exceeding 50.

Many optical glasses having low dispersibility that are the object of the present invention have been disclosed.
Japanese Patent Application Laid-Open No. 2000-34132 discloses an optical glass containing P ₂ O ₅ , Al ₂ O ₃ , and BaO as main components. However, since this glass contains a large amount of the Ba component, it has poor acid resistance and is not practical.
JP-A-2004-168593, JP-A-2004-262703, JP-A-2005-220289, and JP-A-10-158027 disclose optical glass containing P as a main component. Since the expansion coefficient is large and the liquidus temperature is high, it is not advantageous in glass production.
Japanese Patent Application Laid-Open No. 2005-53749 discloses an optical glass mainly composed of P ₂ O ₅ , B ₂ O ₃ , Al ₂ O ₃ , ZnO, CaO, Li ₂ O, but contains a large amount of alkali components. Therefore, water resistance and acid resistance are not sufficient. Furthermore, it has a large linear expansion coefficient, and is not suitable for a mold press.
Japanese Patent Application Laid-Open No. 2-124743 discloses an optical glass containing P ₂ O ₅ and ZnO as main components. However, since the P component is contained in a large amount, it has a large linear expansion coefficient and is not suitable for a mold press.
Japanese Patent Application Laid-Open No. 7-196336 discloses an optical glass containing P ₂ O ₅ , BaO, and MgO as main components. However, since the Mg component is contained in a large amount, the liquidus temperature is high and the product is stably produced. Is difficult.
In JP-A-11-139845, an optical glass containing P ₂ O ₅ , BaO, ZnO, Li ₂ O as main components is disclosed, but contains components such as rare earth oxides, Nb, Ta, W, The partial dispersion becomes large, which is not preferable as the desired glass in the present invention.
In JP-A-11-355135, or contain lead, or the liquidus temperature is high, it is difficult to produce stably, the undesirable JP 2002-211949 also from an environmental point of _view, P _{2 O} 5, An optical glass having B ₂ O ₃ , Al ₂ O ₃ , and BaO as main components is disclosed. However, since the content of the Al component is large, cracking and chipping defects are likely to occur when the glass is cooled.
Japanese Patent Application Laid-Open No. 2006-52119 discloses an optical glass containing P ₂ O ₅ , B ₂ O ₃ , and MgO as main components. It is difficult to produce.
JP 2000-34132 A JP 2004-168593 A JP 2004-262703 A JP 2005-200269 A JP-A-10-158027 JP 2005-53749 A JP-A-2-124743 JP-A-7-196336 JP-A-11-139845 JP-A-11-355135 JP 2002-211949 A JP 2006-52119 A

As described above, the known phosphate glass optical glass can realize low dispersibility relatively easily, but has disadvantages such as a high coefficient of linear expansion or low chemical durability. It was difficult to put it into practical use as an element.

  In order to solve the above problems, the present inventor has conducted extensive research, and as a result of the composition within the specific range, has low dispersion, low liquidus temperature, good chemical durability, The present inventors have found that an optical glass having a low expansion coefficient can be obtained, and have reached the present invention.

The first configuration of the present invention contains P ₂ O ₅ , B ₂ O ₃ , BaO, Al ₂ O ₃ and La ₂ O ₃ as essential components, and the Al ₂ O ₃ component in mass% based on the oxide and The total content of La ₂ O ₃ components is 1 to 10%, and the value of (Al ₂ O ₃ component content) / (La ₂ O ₃ component content) is in the range of 0.05 to 8.0. , and the optical glass water resistance RW glass measured by Japanese optical glass industrial standard JOGIS06 ^-1999 "chemical durability of the measurement method of the optical glass (powder method)" is characterized by a grade 1-3 It is.

The second composition of the present invention is more than 5% B ₂ O ₃ and 15% or less by mass% based on oxide.
Each component in the range of more than Al ₂ O ₃ 0% and less than 5%, and La ₂ O ₃ more than 0% and less than 5%,
It is the optical glass of the said structure 1 whose average linear expansion coefficient ((alpha)) in 100-300 degreeC is 100-123 [ ^10-7 degreeC- ¹ ].

The third configuration of the present invention is 30% to 60% P ₂ O ₅ and 0.1% to 3% Li ₂ O by mass% based on oxide.
Containing each component in the range of
The optical glass having the above constitution 1 or 2 having a glass transition temperature (Tg) of 550 ° C. or lower.

The 4th composition of the present invention is the mass% of an oxide basis,
P ₂ O ₅ 30~60%,
B ₂ O ₃ exceeding 5% and 15% or less,
Al ₂ O ₃ 0.1-3.0%,
55% exceeded 30% BaO less, and _Li 2 O 0.1 to 3%, and SrO 0 to 15%, and / or CaO 0 to 15%, and / or MgO 0 to 15%, and / or ZnO 0 35%, and / or _Na 2 O 0 to 3%, and / or _K 2 O 0 to 3%
It is an optical glass in any one of the said structures 1-3 containing each component of the range.

The fifth configuration of the present invention is a mass% based on oxide,
ZrO ₂ 0 to less than 6%, and / or TiO ₂ 0 to 3%, and / or Nb ₂ O ₅ 0 to 3%, and / or Ta ₂ O ₅ 0 to 3%, and / or WO ₃ 0 to 3 % And / or Bi ₂ O ₃ 0 to 3% and / or Sb ₂ O ₃ 0 to 1%
The optical glass according to any one of claims 1 to 4, comprising each component in the range of (1) to (5).

The sixth configuration of the present invention is any one of the above-described configurations 1 to 5 characterized in that the Al ₂ O ₃ component is contained in a range of 0.1 to less than 1.0% by mass% based on oxide. Optical glass.

A seventh constitution of the present invention is the optical glass according to any one of the constitutions 1 to 6, wherein the optical glass contains a CaO component in a range of 0.1 to 10% by mass% based on an oxide.

According to an eighth aspect of the present invention, there is provided the optical glass according to any one of the first to seventh aspects, wherein the MgO component is contained in a range of 0 to less than 2.0% by mass% based on an oxide. .

The ninth constitution of the present invention is the optical glass according to any one of the constitutions 1 to 8, characterized in that the ZnO component is contained in a range of 1.0 to less than 6.0% by mass% based on oxide. It is.

Tenth aspect of the invention, in mass percent on the oxide _{basis, La 2 O 3, Gd 2} O 3, Y 2 O 3 and _Lu 2 _{O 3} the total amount of the components 0.1 to 5.0% The optical glass according to any one of the above constitutions 1 to 9, wherein each component is contained so that

The eleventh configuration of the present invention is any one of the above-mentioned configurations 1 to 10 characterized in that the Li ₂ O component is contained in a range of 0.1 to less than 1.0% in terms of mass% based on oxide. Optical glass.

A twelfth configuration of the present invention is the optical glass of any one of the above configurations 1 to 11 that does not contain an F component.

A thirteenth configuration of the present invention is the optical glass according to any one of the above configurations 1 to 12, wherein the liquidus temperature is 1000 ° C. or lower.

A fourteenth configuration of the present invention is the optical glass according to any one of the above configurations 1 to 13 having a refractive index of 1.50 to 1.70 and an Abbe number of 59 to 70.

A fifteenth configuration of the present invention is the optical glass according to any one of the above configurations 1 to 14, wherein a value Δθg, F indicating anomalous dispersion is 0.0001 or more.

The sixteenth configuration of the present invention is the optical glass according to any one of the above configurations 1 to 14, wherein the value Δθg, F indicating anomalous dispersion is 0.0038 or more.

A seventeenth configuration of the present invention is the optical component according to any one of the first to sixteenth embodiments, which contains substantially no Nb, Bi, and W components and has an internal transmittance of 0.97 or more for a light beam having a wavelength of 400 nm. It is glass.

The eighteenth configuration of the present invention is a glass press material for mold press molding made of the optical glass of any one of the above configurations 1 to 17.

A nineteenth configuration of the present invention is an optical element made of the optical glass of any one of the above configurations 1 to 18.

A twentieth configuration of the present invention is an optical element obtained by mold press molding the glass preform material for mold press molding according to the above configuration 18.

The optical glass of the present invention has low dispersibility, is suitable for mold press molding, and can be stably produced because of its low liquidus temperature. Further, since the optical glass of the present invention has a low viscosity and a low liquidus temperature as described above, the temperature setting in the melting step and the subsequent molding step can be made relatively low. That is, the optical glass of the present invention is useful as an environmentally friendly material that has a very low environmental load because it has a low temperature load on the apparatus and has good productivity and energy-saving production. .

The reason why the composition range of mass% on the basis of oxide in each component of the optical glass shown in the present invention is limited as described above will be described below.

In this specification, “oxide standard” means that oxides, phosphates, nitrates, and the like used as raw materials for the glass constituents of the present invention are all decomposed and changed into oxides when melted. The composition represents the content of each component contained in the glass when the total weight of the generated oxide is 100% by mass.

Further, in the present specification, “substantially does not contain” means that it is not contained artificially unless it is mixed as an impurity.

The P ₂ O ₅ component is a glass-forming oxide, and is an essential component that lowers the liquidus temperature and lowers the glass transition temperature (Tg). However, if the amount is too small, the above effect tends to be insufficient, and if the amount is too large, the glass tends to be milky, and the chemical durability tends to decrease or the linear expansion coefficient (α) tends to increase. Therefore, the upper limit is preferably 30%, more preferably 42%, and most preferably more than 45%, preferably 60%, more preferably 55%, and most preferably less than 50%.

In the optical glass of the present invention containing the P ₂ O ₅ component, the B ₂ O ₃ component is an essential component having an effect of suppressing an increase in average linear expansion coefficient or preventing opacification. However, if the amount is too small, the above effect tends to be insufficient, and if the amount is too large, the chemical durability tends to deteriorate and the glass tends to be colored. Therefore, it preferably contains more than 5.0%, more preferably 6.0%, most preferably more than 7.0%, preferably 15%, more preferably 13%, most preferably 10%. contains.

The Al ₂ O ₃ component is an essential component that is extremely effective in improving the chemical durability of glass. However, if the amount is too large, the liquidus temperature is likely to be increased, and the average linear expansion coefficient of the glass is increased, so that cracks due to thermal stress generated during cooling are likely to occur. Therefore, the lower limit is preferably 0.1%, more preferably 0.2%, and most preferably 0.4%. However, even if it is less than 0.1%, if it exceeds 0%, the desired glass can be produced in the present invention. Further, the upper limit is preferably less than 5.0%, more preferably 3.0%, and most preferably less than 1.0%.

The BaO component is an essential component that has the effect of lowering the liquidus temperature, and is also effective in adjusting the optical constant. However, if the amount is too small, the above effect tends to be insufficient, and if the amount is too large, the chemical durability tends to decrease, or the average linear expansion coefficient may become too large. Therefore, it preferably contains more than 30%, more preferably 32%, most preferably 34% as the lower limit, preferably 55%, more preferably 50%, most preferably 40%.

The La ₂ O ₃ component is an essential component that is effective for increasing the Abbe number and improving the chemical durability. If the amount is too large, the liquidus temperature tends to rise, which may hinder stable production. Accordingly, the lower limit is preferably 0.1%, more preferably 1.0%, and most preferably 1.5%, preferably less than 5.0%, more preferably 4.0%, most preferably 3.0%. % As the upper limit. In addition, even if it is less than 0.1%, if it exceeds 0%, a desired glass can be produced by the present invention.

In the optical glass of the present invention, in order to maintain good chemical durability and maintain a low liquidus temperature while maintaining low dispersibility, the inclusion of Al ₂ O ₃ component and La ₂ O ₃ component It is preferable to limit the quantity relationship to a certain range. Specifically, the total content of the Al ₂ O ₃ component and the La ₂ O ₃ component is preferably 1.0% or more, more preferably 1.25% or more, most preferably 1.5% or more, Preferably it is 10.0% or less, more preferably 9% or less, and most preferably 8.0% or less. Furthermore, the ratio of the content of the Al ₂ O ₃ component and the La ₂ O ₃ component, that is, the value of (Al ₂ O ₃ content) / (La ₂ O ₃ content) is preferably 0.05 or more, More preferably, it is 0.09 or more, most preferably 0.1 or more, preferably 8.0 or less, more preferably 7.5 or less, and most preferably 7.0 or less.

The Li ₂ O component is an optional component that has a great effect on lowering the liquidus temperature, lowering the melting temperature, and lowering the glass transition temperature (Tg). However, if the amount is too large, the average linear expansion coefficient increases and the chemical durability tends to deteriorate. Accordingly, the upper limit is preferably 3.0%, more preferably 2.0%, and most preferably less than 1.0%. Although it is possible to obtain the optical glass required by the present invention even if Li ₂ O component is not contained, it is preferably 0.1%, more preferably 0.3%, and most preferably 0.5%. By making it contain exceeding, meltability can be improved easily.

Since the SrO component has the same effect as the BaO component, it is an optional component that can be used by partially replacing the BaO component. However, if the amount is too large, the chemical durability tends to decrease. Accordingly, the upper limit is preferably 15%, more preferably 13%, and most preferably 10%.

The CaO component is an effective optional component that improves the chemical durability and can lower the glass transition temperature while maintaining a low average linear expansion coefficient. However, if the amount is too large, the liquidus temperature tends to increase. Become. Accordingly, the upper limit is preferably 15%, more preferably 10%, and most preferably less than 4%. Although it is possible to obtain the optical glass required by the present invention even if the CaO component is not contained, it is preferably 0.1%, more preferably 1.0%, and most preferably 2.0% as the lower limit. Thus, the above effects can be easily obtained.

Similar to the CaO component, the MgO component is an effective component for improving chemical durability and has the effect of lowering the chromatic dispersion. However, if the amount is too large, the liquidus temperature tends to increase. Accordingly, the upper limit is preferably 15%, more preferably less than 2%, and most preferably substantially no content.

The ZnO component is an effective component for reducing the glass transition temperature (Tg), but if the amount is too large, the liquidus temperature tends to increase. Accordingly, the upper limit is preferably 35%, more preferably less than 6%, and most preferably 5%. Although it is possible to obtain the optical glass required by the present invention even if it does not contain a ZnO component, it is preferable to contain 1.0%, more preferably 2.0%, and most preferably 3.0% as the lower limit. Thus, the glass transition temperature (Tg) can be easily reduced.

Na ₂ O and K ₂ O components are optional components that have the effect of lowering the melting temperature and lowering the glass transition temperature (Tg). However, when the amount is too large, the chemical durability tends to be deteriorated. Therefore, each component preferably contains 3.0%, more preferably 2.0%, and most preferably 1.0% as the upper limit.

The ZrO ₂ component has an effect of improving chemical durability, but if the amount is too large, the liquidus temperature tends to increase. Therefore, it is preferably less than 6.0%, more preferably 3.0%, most preferably 1.0% as the upper limit, and most preferably not substantially contained.

Each component of Nb ₂ O ₅ , WO ₃ and Ta ₂ O ₅ contributes to the improvement of durability. However, if the amount is too large, there are disadvantages such as an increase in glass transition temperature (Tg) or an increase in liquidus temperature. It tends to occur. Therefore, the total content of each component of Nb ₂ O ₅ , WO ₃ and Ta ₂ O ₅ is preferably 3.0%, more preferably 1.0%, so as to be the upper limit, and substantially contained Most preferably not. Each of Nb ₂ O ₅ , WO ₃ and Ta ₂ O ₅ also preferably contains 3.0%, more preferably 1.0% so as to be the upper limit, and most preferably does not contain substantially.

Bi ₂ O _{3 and} TiO ₂ are effective components for adjusting the refractive index, but if the amount is too large, the glass tends to be colored. Therefore, it is most preferable that each component contains 3.0%, more preferably 1.0% as an upper limit, and substantially does not contain. Also, the total content of Bi ₂ O ₃ and TiO ₂ is preferably 3.0%, more preferably 1.0% as the upper limit, and most preferably not substantially contained.
Incidentally, _Nb 2 _O 5 Of the above _components, Bi ₂ O _3, WO 3 component preferably does not contain particular.

Sb ₂ O ₃ component can be used as a refining agent having a defoaming effect in the glass melting step. Since the optical glass composition of the present invention has good defoaming properties, it is not necessary to add a clarifier. Even when contained, the upper limit is preferably 1.0%, more preferably 0.8%, and most preferably 0.5%.

Gd ₂ O ₃ , Y ₂ O ₃ and Lu ₂ O ₃ components are effective components for improving the chemical durability of glass when used together with La ₂ O ₃ components, but La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O _3, and Lu ₂ O _{3 As the} total content of the _three components, if the amount is too large, the liquidus temperature tends to increase. Therefore, the total content of La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ and Lu ₂ O ₃ components is preferably 5.0%, more preferably 4.0%, most preferably 3.0% Each component is contained so as to be the upper limit. Moreover, even if it does not contain Gd ₂ O ₃ , Y ₂ O ₃ and Lu ₂ O ₃ components, it is possible to obtain the optical glass required by the present invention, but La ₂ O ₃ , Gd ₂ O ₃ , Y _2. Each component (Gd ₂ O ₃ , Gd ₂ O ₃ , so that the total content of O ₃ and Lu ₂ O ₃ is preferably 0.1%, more preferably 1.0%, and most preferably 1.5%. By containing Y ₂ O ₃ and / or Lu ₂ O ₃ component), not only the chemical durability of the glass can be improved, but also the stability at the time of melting can be improved.

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

The F component is a component that has an effect of lowering the glass transition temperature (Tg) and adjusting the dispersion performance. However, when the preform is molded, the F component volatilizes from the glass surface and may adhere to the preform or mold, causing a problem with the lens. In addition, there are problems such as a large change in refractive index due to volatilization and a tendency to deteriorate chemical durability, which is not suitable for stable production. Accordingly, the upper limit is preferably 3.0%, more preferably less than 1.0%, and most preferably not substantially contained.

Further, the Cs ₂ O component may be added for the purpose of adjusting the optical constant. However, since it is an expensive raw material, it is preferable that the Cs ₂ O component is not substantially contained when an inexpensive glass is to be obtained.

The TeO ₂ component may be added for the purpose of increasing the refractive index and lowering the Tg. However, when mold pressing is performed, the lens surface due to volatilization may be spoiled. , Preferably not substantially contained

  In addition, transition metal components such as V, Cr, Mn, Fe, Co, Ni, Cu, and Mo, excluding Ti, are colored because they have absorption at a specific wavelength in the visible range even when added in small amounts. End up. Accordingly, the optical glass using a wavelength in the visible region should not be substantially contained.

  Further, Pb and Th components may be added for the purpose of increasing the refractive index and improving the stability as glass. In addition, Cd and Tl components may be added for the purpose of lowering Tg. Further, the As component may be added for the purpose of clarifying and homogenizing the glass. However, Pb, Th, Cd, Tl, and As components have tended to refrain from being used as harmful chemicals in recent years. Not only for glass manufacturing processes but also for processing processes and disposal after commercialization, Should be added because of the necessary measures.

The glass composition of the present invention cannot be expressed directly in the description of mol% because the composition range is expressed by mass%, but exists in the glass composition satisfying various properties required in the present invention. The composition expressed by mol% of each oxide generally takes the following values. In addition, the value in the following mol% is for reference only, and does not limit the range in each aspect of the present invention.
P ₂ O ₅ 35~50 mol%,
B ₂ O ₃ 5~20 mol%,
Al ₂ O ₃ 0.1~3.5 mol%,
BaO 25-35 mol%,
Li ₂ O 0~10 mol%,
SrO 0-15 mol%,
CaO 0-20 mol%,
MgO 0-30 mol%,
ZnO 0-30 mol%,
La ₂ O ₃ 0~1 mol%,
Na ₂ O 0~3 mol%,
K ₂ O 0~2 mol%,

Next, the physical property regarding the optical glass of this invention is demonstrated.

Glass and optical elements are desired to have good chemical durability. When the glass has poor durability, lens fogging, called burn, occurs on the polished surface of the lens or the free surface in the preform state. Usually, such glass requires strict temperature and humidity management, which tends to increase costs.

Specifically, Japanese Optical Glass Industrial Standard; the JOGIS06- ¹⁹⁹⁹ chemical durability of the measurement method of the optical glass (powder method), also powder method water resistance weight loss rate, preferably class 1-3, more preferably Is class 1-2, most preferably class 1.
In addition, the weight loss rate of acid resistance of the powder method is less than 2.2, more preferably less than 2.0, and most preferably less than 1.8.

The glass material used as the mold press glass preferably has a lower glass transition temperature (Tg), and is particularly useful in the current mold press mold technology if it is 550 ° C. or less. In order to extend the life of the mold and thus reduce the press temperature, the upper limit is preferably 550 ° C, more preferably 540 ° C, and most preferably 530 ° C.
For the same reason, the upper limit of the yield point (At) is preferably 650 ° C, more preferably 630 ° C, and most preferably 610 ° C.

In the process of obtaining a lens shape from a glass substrate by press-molding optical glass using a mold, a temperature gradient may be generated inside and outside the lens during the cooling process. At this time, if the average coefficient of linear expansion is large, depressions (so-called sinks) are likely to occur in the obtained lens, and cracking is likely to occur particularly when trying to obtain a thin lens. In addition, problems such as cracks and sink marks in the cooling process may occur during the preform molding process. Therefore, the average linear expansion coefficient α at 100 to 300 ° C. is preferably 123 × 10 ⁻⁷ / ° C., more preferably 121 × 10 ⁻⁷ / ° C., and most preferably 116 × 10 ⁻⁷ / ° C. The lower limit is preferably 100 × 10 ⁻⁷ / ° C., more preferably 102 × 10 ⁻⁷ / ° C., and most preferably 104 × 10 ⁻⁷ / ° C.

In the optical glass, the liquid phase temperature is preferably set to 1000 ° C. or lower, more preferably 980 ° C. or lower, most preferably 950 ° C. or lower in order to realize stable production and improve yield by a manufacturing method described later.

As described above, the optical glass of the present invention can be used as a preform material for press molding, or the molten glass can be directly pressed. When used as a preform material, the production method and mold press molding method are not particularly limited, and known production methods and molding methods can be used. As a method for manufacturing a preform material, for example, a glass press product manufacturing apparatus described in JP-A-06-157051 and a manufacturing method thereof, and an optical glass manufacturing method and manufacturing apparatus described in JP-A-11-157849 are known. Technology can be used.

As described above, not only a method for producing a preform material directly from molten glass, but also a lens shape may be obtained by cold working from a plate material, and after an approximate shape is obtained by cold working, mold pressing is performed. You may obtain the optical element which is a final product.

The optical glass of the present invention is used in combination with a glass having a small Abbe number containing components such as Ti and Nb, so that the Abbe number is large due to a request in optical design for effectively reducing chromatic aberration. Is preferred. The larger the Abbe number, the greater the effect. However, when considering the composition, if the Abbe number is too large, the liquidus temperature tends to rise, and it becomes difficult to stably produce the glass. Accordingly, the lower limit is preferably 59, more preferably 60, and most preferably 61, preferably 70, more preferably 69, and most preferably 68.

In order to reduce the thickness of the lens and reduce the thickness of the optical element, it is advantageous that the refractive index is large. In mold press molding, the smaller the radius of curvature of the lens, the more difficult it becomes to mass-produce. Therefore, if the material has a high refractive index, the radius of curvature can be increased accordingly, contributing to the improvement of molding accuracy in molding. To do. However, when the refractive index is to be increased in considering the composition, it is difficult to maintain the internal transmittance and the Abbe number in a desired range. Accordingly, the lower limit is preferably 1.50, more preferably 1.52, and most preferably 1.55, preferably 1.70, more preferably 1.67, and most preferably 1.65.

Further, the glass of the present invention is required to have a larger Δθg, F value indicating anomalous dispersion than other glasses. This is because it is very useful for correcting a so-called secondary spectrum. The lower limit is preferably 0.0001, more preferably 0.0005, and most preferably 0.001. Note that it is particularly preferable to exceed 0.0038. When the glass of the present invention has such a value of Δθg, F, it is possible to improve the chromatic aberration in the blue region.

The value of Δθg, F indicating anomalous dispersion is calculated by the method described on page 64 of OHARA Optical Glass Catalog (OHARA OPTICAL GLASS: issued in August 2005). That is, the partial dispersion ratio (θg, F) is obtained by the following formula, the partial dispersion ratio (θg, F) is taken on the vertical axis, the Abbe number (νd) is taken on the horizontal axis, and plotted on the θg, F−νd coordinates. . Based on two types of optical glasses having normal dispersion ratio (θg, F) and Abbe number (νd) shown in Table 1 below as normal optical glasses that do not exhibit anomalous dispersion, NSL7 and PBM2 manufactured by OHARA INC. The coordinates (θg, F, νd) of the two types of optical glass are connected by a straight line, and the difference between the ordinates (Δθg, F) is the same for the same νd. The dispersion ratio was biased, that is, a value indicating anomalous dispersion. When the values of Δθg and F calculated in this way are positive, that is, when the glass coordinates (Δθg, F, νd) are located above the straight line, the glass has positive anomalous dispersion. doing.

θg, F = (ng−nF) / (nF−nc)

Since the optical glass of the present invention is extremely excellent in light transmittance, it can be used for an objective lens of an optical pickup for recording and reproducing information. In particular, since the internal transmittance in the ultraviolet region is also good, it can be used for optical devices using various wavelengths in the wavelength range of 400 nm to 900 nm. In particular, in order to use a wavelength in the vicinity of 400 nm, the internal transmittance is preferably 0.97 or more, more preferably 0.98 or more, and most preferably 0.99 or more with respect to a light beam of 400 nm.

In the optical glass of the present invention, it is preferable that the optical element made of the optical glass of the present invention is mounted on a precision instrument, so that the specific gravity is preferably low.

Where ng is the refractive index of the glass with respect to the spectral line having a light source of mercury and a wavelength of 435.835 nm, nF is the refractive index of the glass with respect to the spectral line having a light source of hydrogen and a wavelength of 486.13 nm, and nc is the It means the refractive index of glass with respect to a spectral line having a wavelength of 656.27 nm with hydrogen, and (nF-nc) is called main dispersion.

Composition of Examples and Reference Examples (No. 1 to No. 34) of the optical glass according to the present invention, Example 2 described in JP-A No. 2004-262703, and Example 1 described in JP-A No. 2004-168593 As a comparative example (No. A and No. B), the optical constants (nd, νd), glass transition temperature (Tg), yield point At, average linear expansion coefficient α at 100 to 300 ° C., internal transmittance, The results are shown in Tables 2 to 6, 8, and 9 together with the liquidus temperature, powder method water resistance (RW), and specific gravity. The anomalous dispersibility is shown in Table 7.

In addition, the glass of the Example concerning this invention and the reference examples (No.1-No.34) is made so that normal optical glass materials, such as an oxide, carbonate, phosphate, and nitrate, may become a predetermined ratio. After weighing and mixing, put into a platinum crucible, etc., melt and degas at a temperature of 900 to 1200 ° C. for 2 to 4 hours, stir and homogenize, and lower the temperature after stirring. It is possible to obtain a glass having excellent homogeneity by melting at low temperature by casting from a metal mold into a mold or the like and gradually cooling.

The value of the grade indicating the powder method water resistance "RW" is the Japanese Optical Glass Industrial Standard; the JOGIS06- ¹⁹⁹⁹ chemical durability of the measurement method of the optical glass (powder method), was determined as follows. The glass was pulverized to a particle size of 420 to 590 μm, respectively, and the obtained glass powder sample was placed in a specific gravity gram in a platinum elution basket. Next, the elution basket containing the glass powder sample was placed in a quartz glass round bottom flask containing 80 ml of pure water having a pH of 6.5 to 7.5 and treated in a boiling water bath for 60 minutes. The elution basket was taken out from the round bottom flask and was graded as follows based on the initial mass of the glass powder sample and the weight loss rate (% by weight) calculated from the weight loss. That is, when the weight loss rate (% by weight) is less than 0.05%, the grade is grade 1, 0.05 to less than 0.10% is grade 2, and 0.10 to less than 0.25% is grade 3, Less than 0.25 to 0.60% was grade 4, and less than 0.60 to 1.10% was grade 5.

The average linear expansion coefficient α (100 to 300 ° C.) was determined as an average linear expansion coefficient at 100 to 300 ° C. according to Japan Optical Glass Industry Standard JOGIS08-2003 “Measurement Method of Thermal Expansion of Optical Glass”.

The liquidus temperature is measured by holding a transparent glass sample in a temperature gradient furnace with a temperature gradient of 850 ° C. to 1000 ° C. for 30 minutes and observing the presence or absence of crystals with a microscope at a magnification of 100 times. did. Among the samples in which crystals were observed within the above temperature range, the highest temperature was defined as the liquidus temperature. In addition, the transparent glass material used used the glass piece which used the glass piece grind | pulverized to the size of 1-2 mm, put it on a platinum plate at equal intervals, and put it in the temperature gradient furnace.

The internal transmittance was determined by measuring the light transmittance at a wavelength of 400 nm according to Japan Optical Glass Industry Association Standard JOGIS 17-1982 “Measurement Method of Internal Transmittance of Optical Glass”. However, measurement was performed using 10 mm and 50 mm facing polished samples.

The specific gravity was measured according to Japan Optical Glass Industry Association Standard JOGIS05-1975 “Method for Measuring Specific Gravity of Optical Glass”.

As can be seen from Tables 2 to 6, the glasses (No. 1 to No. 34) of the examples of the present invention all have a desired range of refractive index (nd), Abbe number (νd), and internal transmittance. ing.
Further, regarding the glass of the example of the present invention, the water resistance class of the powder method was “3” or less, and the chemical durability was good. In addition, the liquidus temperature is low and stable production is possible.
Moreover, the value which can be utilized for mold press molding was shown for both the average linear expansion coefficient and the glass transition temperature.
Moreover, all the glass of the Example of this invention had desired anomalous dispersibility.

Next, mold press molding was performed using the preform of the product of the present invention. The pressing conditions are appropriately set depending on the shape, but are generally performed under the following conditions. In a situation where the press mold is heated to the yield point (At) + 10 ° C to the yield point (At) + 20 ° C, the press pressure is 10 to 20MPa and the press time is 30 to 250 seconds. After the molding was cooled to around 200 ° C., it was removed from the mold. The obtained molded article had good transferability, and no defects were observed when observed with a stereomicroscope 50 ×.

Since all of the above glasses have high chemical durability and low liquidus temperature while maintaining a desired refractive index, good productivity can be expected.

Comparative Example No. The glass of A and B does not satisfy the composition range required in the present invention, does not satisfy the average linear expansion coefficient required in the glass of the present invention, and is not suitable for a mold press. It was.

Claims (19)

% By mass based on oxide,
P ₂ O ₅ 30~60%
B ₂ O ₃ exceeding 5% and 15% or less,
BaO more than 30% and 55% or less,
Li ₂ O 0.1-3%,
Containing each component in the range of
Al ₂ O ₃ and La ₂ O ₃ are contained as essential components, and the total content of the Al ₂ O ₃ component and the La ₂ O ₃ component is 1 to 10% by mass% based on the oxide, and (Al ₂ O _The value of (content of ₃ components) / (content of La ₂ O ₃ components) is in the range of 0.05 to 8.0 ( excluding CeO ₂ ) , Japan Optical Glass Industry Standard JOGIS06 ^-1999 “Optical Glass” chemical durability of the measurement method (powder method) "Ri water resistance RW is grade 1-3 der glass measured by, press molding a glass transition temperature (Tg), characterized in that at 550 ° C. or less of use optical glass. In mass% of oxide basis
Containing A l ₂ O ₃ less than 5% greater than 0%, and _La 2 _O 3 each ingredient in the range of less than 5% greater than 0%
2. The optical glass according to claim 1, wherein an average linear expansion coefficient (α) at 100 to 300 ° C. is 100 to 123 [10 −7 ° C.−1]. % By mass based on oxide,
Al ₂ O ₃ 0.1-3.0%,
BaO over 30% and up to 55% and SrO 0-15% and / or CaO 0-15% and / or MgO 0-15% and / or ZnO 0-35% and / or Na ₂ O 0 to 3%, and / or _K 2 O 0 to 3%
The optical glass according to claim 1, which contains each component in the range of 5 above . % By mass based on oxide,
ZrO ₂ 0 to less than 6% and / or TiO ₂ 0 to 3% and / or Nb ₂ O ₅ 0 to 3% and / or Ta ₂ O ₅ 0 to 3% and / or WO ₃ 0 to 3 % And / or Bi ₂ O ₃ 0-3% and / or Sb ₂ O ₃ 0-1%
The optical glass according to any one of claims 1 to 3 , comprising each component in the range of (1). % By mass on the oxide basis, the optical glass according to any one of claims 1 to 4, the _Al 2 _{O 3} component, characterized in that it contains in a range of less than 0.1% to 1.0%. The optical glass according to any one of claims 1 to 5 , wherein the CaO component is contained in a range of 0.1 to 10% by mass% based on an oxide. The optical glass according to any one of claims 1 to 6 , wherein the optical glass contains a MgO component in a range of 0 to less than 2.0% by mass% based on an oxide. The optical glass according to any one of claims 1 to 7 , wherein the optical glass contains ZnO component in a range of 1.0 to less than 6.0% by mass% based on an oxide. % By mass based on oxide,
Each component is contained so that the total content of La ₂ O ₃ , Gd ₂ O- ₃ , Y ₂ O ₃ and Lu ₂ O ₃ components is 0.1 to 5.0%. Item 10. The optical glass according to any one of Items 1 to 8 . % By mass on the oxide basis, the optical glass according to any one of claims 1 to 9, characterized in that it contains _Li 2 O ingredient in the range of less than 0.1% to 1.0%. The optical glass according to any one of claims 1 to 10 , which does not contain an F component. The optical glass according to any one of claims 1 to 11, the liquid phase temperature is equal to or is 1000 ° C. or less. The optical glass according to any one of claims 1 to 12 , which has a refractive index of 1.50 to 1.70 and an Abbe number of 59 to 70. Anomalous dispersion are shown values Derutashitag, optical glass according to any one of claims 1 to 13, F is equal to or is 0.0001 or more. Anomalous dispersion are shown values Derutashitag, optical glass according to any one of claims 1 to 1 3, characterized in that F is 0.0038 or more. The optical glass according to any one of claims 1 to 15 , wherein the optical glass contains substantially no Nb, Bi, and W components and has an internal transmittance of 0.97 or more for light having a wavelength of 400 nm. Press molding glass preform formed of the optical glass according to any one of claims 1-16. An optical element formed of the optical glass according to claim 1-16. An optical element obtained by mold press molding the glass preform material for mold press molding according to claim 17 .