JP2006219365A - Glass - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide glass capable of being used for various optical members such as various prisms, various lenses, a light pick-up lens, and a lens of eye glasses, etc., and for various optical substrates such as reflective plates, diffusion plates, polarizing plates, a cover glass, etc. <P>SOLUTION: This glass has optical constants in the range of not lower than 1.79 refractive index (nd) and not lower than 27 Abbe number (νd), and has a specific gravity (D) of not lower than 3.20, and causes no devitrification in the interior of the glass in the reheating test. This glass has a rating of class 1 of the chemical durability (powder method acid resistance: RA) by the powder method. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention provides various optical members such as various prisms, various lenses, optical pickup lenses, and spectacle lenses having a refractive index (nd) of 1.79 or more and an Abbe number (νd) of 27 or more; The present invention relates to a glass used for various optical substrates such as a plate, a diffusion plate, a polarizing plate and a cover glass, in particular, an optical glass, for example, a SiO ₂ —TiO ₂ —La ₂ O ₃ optical glass.

  In recent years, the characteristics of optical elements related to IT equipment such as digital still cameras, digital video cameras, TV cameras for high-definition photography, and projectors have improved, and the refractive index and refractive index wavelength of lens materials, as typified by chromatic aberration, have been developed. Various optical design possibilities have been proposed to improve the optical characteristics of optical equipment due to dispersion, but there is a problem that lens materials (optical glass) for realizing the optical design are not supplied. is there. Therefore, in the conventional product, the optical characteristics must be sacrificed, or in order to realize the characteristics, complicated lens shape processing is performed, or the lens configuration is complicated (increase in the number of lenses). There have been sacrifices in terms of characteristics, productivity, and manufacturing costs, such as realizing optical characteristics. The reason why the optical glass having a refractive index nd of 1.79 or more and an Abbe number νd of around 30 is not supplied is as follows. (1) The optical glass is devitrified (with transparency) by reheating as in the reheat press step. (2) The chemical durability is poor and special management is necessary for the handling of the material after polishing. (3) The glass specific gravity is large and the weight of the final product becomes heavy. , Etc. can be considered.

As an optical glass having a refractive index nd of 1.79 or more and an Abbe number νd of 27 or more, SiO ₂ —B ₂ O ₃ —La ₂ as disclosed in JP-A-59-50048 is used. _{O 3 -Nb 2 O 5 -ZrO 2} -TiO 2 -RO system (R is an alkaline earth metal element) or an optical glass, as disclosed in JP-a-2002-87841, SiO ₂ -TiO ₂ —Nb ₂ O ₅ —R ₂ O-based (R is an alkali metal element) optical glass, SiO ₂ —B ₂ O ₃ —CaO—TiO ₂ —Nb ₂ as disclosed in JP-A-3-5340 An O ₅ optical glass, an SiO ₂ —B ₂ O ₃ —La ₂ O ₃ —TiO ₂ —Nb ₂ O ₅ optical glass disclosed in JP-A-2004-18371, and the like are known.

  The optical glass disclosed in JP-A-59-50048 satisfies the optical constant, but has a large glass specific gravity, which increases the lens weight, which is not preferable in practice. In addition, for example, when a lens is to be manufactured by reheat pressing, a special reheating condition is required because the glass has a strong tendency to devitrify. Therefore, there is a concern that the lens cannot be manufactured in the reheat press process and must be manufactured by cold work with low efficiency.

  In the optical glass disclosed in Japanese Patent Application Laid-Open No. 2002-87841, the Abbe number related to the wavelength dispersion of the refractive index is less than 27, and the optical glass in this region has been supplied conventionally, so that the optical design is free. From the viewpoint of expanding the degree, it is not enough. In addition, because it contains a large amount of alkali metal oxides, it has a strong tendency to devitrify the glass in the reheat press process. There is concern about deterioration of durability.

The optical glasses disclosed in JP-A-3-5340 and JP-A-2004-18371 are borosilicate-lanthanum oxide optical glasses, but these glasses having a high boric acid content are chemically Since durability (particularly water resistance and acid resistance) is insufficient, care must be taken in handling the material after polishing into a desired shape such as a lens shape or a prism shape, which may cause a deterioration in productivity.
JP 59-50048 JP Japanese Patent Laid-Open No. 2002-87841 Japanese Patent Laid-Open No. 3-5340 JP 2004-18371 A

  An object of the present invention is to provide an optical constant having a refractive index (nd) of 1.79 or more and an Abbe number (νd) of 27 or more, which can increase the degree of freedom in optical design, and is reheated. Glass and optical elements that do not cause milky whiteness and devitrification inside the glass and are excellent in chemical durability even in a manufacturing method in which the shape is created through a reheating process such as pressing. It is to provide at a low manufacturing cost.

As a result of intensive studies and research in order to achieve the above-mentioned goal, the present inventor, in a SiO ₂ —TiO ₂ —La ₂ O ₃ based optical glass having a specific composition, like PbO and As ₂ O ₃ Realizes the desired optical constant without using environmental pollutants, and in the reheating test assuming reheat press, the glass interior does not become milky or devitrified, and the glass raw material and glass melting process and processing Through the process, it was found that desired optical glass and glass products can be supplied at a low production cost, and the present invention has been made.

  The first configuration of the present invention is a glass having an optical constant having a refractive index (nd) of 1.79 or more, an Abbe number (νd) of 27 or more, and a specific gravity (D) of 3.20 or more. And it is this glass characterized by the inside of glass not devitrifying in a reheating test.

  The second constitution of the present invention is the glass of the constitution 1 whose chemical durability by the powder method (powder method acid resistance: RA) is class 1.

A third configuration of the present _invention, glass containing _{SiO 2, TiO 2, La 2} O 3, and component configurations to meet the component content ratio _{B 2 O 3 / SiO 2 =} 0~0.5 in mass% When the refractive index (nd) is 1.79 or more, the Abbe number (νd) is an optical constant in the range of 27 to 35, the refractive index (nd) is Y, and the glass specific gravity is X, This glass satisfies the relationship of Y ≧ 0.175X + 1.137.

According to a fourth configuration of the present invention, in the glass of configuration 3, ΣR ₂ O is 0.1% to less than 15% by mass, and the glass is reheated to 150 ° C. above the glass transition temperature (Tg). It is a glass characterized in that the inside of the glass does not become milky white or devitrified even when kept at high temperature for 30 minutes.

  The 5th structure of this invention is glass of the said structures 1-4, Comprising: Specific gravity (D) is 3.20-4.10.

A sixth configuration of the present invention is the glass according to any one of the above configurations 1 to 5, wherein the component content ratio of mass% (BaO + SrO) / (TiO ₂ + Nb ₂ O ₅ ) <0.80. Glass.

A seventh configuration of the present invention is the glass according to any one of the above configurations 1 to 6, wherein a component content ratio of mass% (SiO ₂ + Al ₂ O ₃ ) / ΣR ₂ O> 2.2 is characterized. Glass.

Eighth aspect of the present invention is a glass according to the configuration 1~7, SiO ₂ 30.0 ~ 48.0% by mol%
TiO ₂ 3.0-25.0%
La ₂ O ₃ 0.5 to 15.0%
It is glass containing.

The ninth configuration of the present invention has an optical constant in the range of refractive index (nd) of 1.79 to 1.88 and Abbe number (νd) of 27 to 35, and is mol%.
SiO ₂ 30.0 ~ 48.0%
TiO ₂ 3.0-25.0%
Nb ₂ O ₅ 0.5 to 15.0%
La ₂ O ₃ 0.5 to 15.0%
ZrO ₂ 0.5 to 10.0%
_{R 2 O (R = Li,} Na, K, Cs) 0.5 ~ 25.0%
Li ₂ O 0.0-23.0% and / or Na ₂ O 0.0-15.0% and / or K ₂ O 0.0-8.0% and / or Cs ₂ O 0.0 ~ 5.0%
And RO (R = Mg, Ca, Sr, Ba) 1.0 to 35.0%
MgO 0.0 to 7.0% and / or CaO 0.0 to 30.0% and / or SrO 0.0 to 8.0% and / or BaO 0.0 to 20% and / or MgO + CaO 0.0-31.0%
And B ₂ O ₃ 0.0 to 10.0%
Al ₂ O ₃ 0.0 to 3.0% and / or ZnO 0.0 to 10.0% and / or WO ₃ 0.0 to 5.0% and / or Bi ₂ O ₃ 0.0 to 3. 0% and / or Gd ₂ O ₃ 0.0 ~ 3.0% and / or Y ₂ O ₃ 0.0 ~ 3.0% and / or Ta ₂ O ₅ 0.0 ~ 3.0% and / or Yb ₂ O ₃ 0.0-2.0% and / or Lu ₂ O ₃ 0.0-2.0% and / or TeO ₂ 0.0-2.0% and / or Sb ₂ O ₃ 0.0 ~ 0.5%
A total amount of 0 to 10% as F of a fluoride substituted with one or more oxides of one or more of the above metal elements, and containing B ₂ O ₃ / SiO It is glass of the said structures 1-8 which is ₂ = 0-0.5.

A tenth configuration of the present invention has an optical constant in the range of a refractive index (nd) of 1.79 to 1.88 and an Abbe number (νd) of 27 to 35, and is represented by mass%.
SiO ₂ 20.0 ~ 35.0%
TiO ₂ 1.0 to less than 21.0% Nb ₂ O ₅ 1.0 to less than 25% La ₂ O ₃ 5.0 to less than 25% ZrO ₂ 1.0 to 12.0%
_{R 2 O (R = Li,} Na, K, Cs) as less than _{0.1 ~ 15.0%, Li 2 O} 0.0 ~ 10.0% and / or Na ₂ O 0.0 ~ 7.0% less than K ₂ O 0.0 ~ 5.0% and / or Cs ₂ O 0.0 ~ 5.0%
And RO (R = Mg, Ca, Sr, Ba) 3.0 to less than 30%, MgO 0.0 to 5.0% and / or CaO 0.0 to less than 15.0% SrO 0.0 to 10 0.0% and / or BaO 0.0 to less than 25%, but MgO + CaO 0.0 to less than 16.0% and B ₂ O ₃ 0.0 to less than 6.0%
Al ₂ O ₃ 0.0 to less than 1.0% and / or ZnO 0.0 to 10.0% and / or WO ₃ 0.0 to 5.0% and / or Bi ₂ O ₃ 0.0 to 5 0.0% and / or Gd ₂ O ₃ 0.0 to 10.0% and / or Y ₂ O ₃ 0.0 to 10.0% and / or Ta ₂ O ₅ 0.0 to 10.0% and / or Or Yb ₂ O ₃ 0.0-5.0% and / or Lu ₂ O ₃ 0.0-5.0% and / or TeO ₂ 0.0-3.0% and / or Sb ₂ O ₃ 0. 0 to 2.0%
A total amount of 0 to 5% as F of a fluoride substituted with one or more oxides of one or more of the above metal elements, and containing B ₂ O ₃ / SiO It is glass of the said structures 1-9 which is ₂ = 0-0.5.

Eleventh aspect of the present invention is a glass of the structure 10, a glass of _B less than 2 _O 3 0 to 2.0% in mass%.

A twelfth configuration of the present invention is the glass of the above configurations 1 to 11, and is a glass containing Na ₂ O 0 to less than 3.0% by mass%.

  The thirteenth configuration of the present invention is an optical element such as a lens / prism using the glass of the above configurations 1-12 as a base material.

  The 14th structure of this invention is optical elements, such as a lens and a prism, produced by reheat press processing the glass of the said structures 1-12.

  A fifteenth configuration of the present invention is an optical substrate material such as a reflection plate, a diffusion plate, or a wavelength separation plate using the glass of the above configurations 1 to 12 as a base material.

  A sixteenth configuration of the present invention is an optical apparatus such as a camera / projector using the optical element and the optical substrate material made of the glass of the above configurations 1-12.

  A seventeenth configuration of the present invention is a precision press-molding preform made of the glass of the above configurations 1-12.

  According to the present invention, a reheating process typified by reheat pressing can be easily applied, which has an optical constant of a refractive index (nd) of 1.79 or more and an Abbe number (νd) of 27 or more. In addition, optical glass with excellent chemical durability can be produced at a low manufacturing cost, so optical design with a high degree of freedom is possible, and optical elements such as lenses, prisms and reflectors with excellent characteristics, and The optical equipment used can be supplied.

  The glass having the structure 1 has an effect of expanding the degree of freedom in optical design. Conventionally, complicated lens shape processing represented by aspheric processing and chromatic aberration that has been reduced by increasing the number of lenses can be reduced to a complicated shape or lens. There is an effect that it can be effectively reduced without increasing the number of sheets, and a reheating treatment represented by reheat press processing can be easily performed, so that the manufacturing cost of the optical element can be reduced. Here, in the “reheating test”, a glass sample made into a prism with a width and thickness of 15 mm and a length of 30 mm is placed on a refractory and placed in an electric furnace to be reheated. The temperature was raised to (near the temperature at which the glass softens to a press-processable viscosity), kept at that temperature for a certain period of time, then cooled to room temperature, taken out of the furnace, and the two opposing surfaces were polished so that the inside could be observed A glass sample is visually observed. In this test, “the glass does not devitrify” means that reheat press processing is easy and is an essential characteristic of the present invention. Assuming the reheat press process, the higher the set temperature of the reheat test, the lower the glass viscosity, so the press pressure can be reduced, but the durability of the press mold is significantly deteriorated. It is preferable to evaluate from + 50 ° C. to + 250 ° C. and the heat retention time from 5 minutes to 30 minutes based on the glass transition point.

  The reason why the chemical durability (powder acid resistance: RA) is class 1 in the optical glass having the constitution 2 is limited as a constituent requirement is, for example, weak acidity in the optical glass polishing surface and the optical element cleaning step. This is to obtain characteristics that hardly change even when an acidic solution is used.

The reason why the constituent components are limited in the optical glass of Configuration 3 is as follows. In order to obtain an optical glass having a refractive index (nd) of 1.79 or more and an Abbe number (νd) in the range of 27 to 35, at least a SiO ₂ component, a high refractive index and a low specific gravity are realized as a glass former. It is necessary to contain a TiO ₂ component that has the effect of increasing the refractive index and a La ₂ O ₃ component that has a high refractive index and an effect of increasing the Abbe number.

The ratio of B ₂ O ₃ / SiO ₂ is an important factor as a criterion for judging the chemical durability of glass. When B ₂ O ₃ is contained in a large amount, the chemical durability is remarkably deteriorated and the devitrification property due to reheating tends to be deteriorated. Therefore, in the glass of the present invention, this ratio is 0.5 or less. More preferably, it is 0.45 or less, and most preferably 0.4 or less.

  When the refractive index (nd) is Y and the glass specific gravity is X, a glass satisfying Y ≧ 0.175X + 1.137 indicates a low specific gravity while having a high refractive index. In general, as the glass specific gravity increases, the refractive index tends to be higher. For example, in an application that is used by a human being, such as a TV camera or a digital camera, it is preferable that the product (equipment) is light. Further, even in applications that are not held in the hand, in a glass having a large glass specific gravity, mechanical stress is applied to the inside of the glass due to the glass's own weight, which may cause birefringence and may deteriorate product characteristics. By satisfying this relational expression, the weight of the product (equipment) can be reduced, and it is possible to realize desirable product characteristics by reducing the birefringence due to the glass weight. In the third configuration of the present invention, it is required to satisfy the relational expression of Y ≧ 0.175X + 1.137 in consideration of the relationship between the low specific gravity and the high refractive index of the glass.

In the optical glass of Configuration 4, the total amount (ΣR ₂ O) of R ₂ O (R = Li, Na, K, Cs) is preferably 0.1% to less than 15% by mass%. The R ₂ O component is an indispensable component because it has the effect of increasing the meltability of the glass and lowering the viscosity and glass transition point of the glass melt during molding. If the total amount is too small, the meltability of the glass is poor and more heat energy is required during production, resulting in a high production cost. However, if the total amount is too large, the desired optical constant range will be reduced. Not only can it not be realized, but the chemical durability of the optical glass obtained is remarkably deteriorated. In addition, in the process of reheating the glass such as a reheat press, milk white and devitrification occur inside the glass. Therefore, the total amount of R ₂ O (ΣR ₂ O) is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and most preferably 0.5% by mass. It is preferably contained at an upper limit of 15.0% by mass, more preferably 14.0% by mass, and most preferably 13.0% by mass.

  In addition, in the reheating test, the property that milk white and devitrification does not occur inside the glass even if it is kept for 30 minutes in a temperature range that is 150 ° C higher than the glass transition point (Tg) is inexpensive and is produced. This is a necessary characteristic for realizing a good optical element manufacturing.

  In the optical glass having the constitution 5, the specific gravity is 3 in order to reduce the product weight of the optical device equipped with the lens / prism using the optical glass of the present invention and to reduce the birefringence due to the glass's own weight. .20 to 4.10.

In the optical glass having the constitution 6, the mass content ratio (BaO + SrO) / (TiO ₂ + Nb ₂ O ₅ ) is an important factor for realizing a low specific gravity while having a high refractive index. BaO and SrO have the effect of increasing the glass specific gravity when added excessively. On the other hand, TiO ₂ and Nb ₂ O ₅ have the effect of realizing a high refractive index while having a low specific gravity. In the present invention, in order to realize a desired optical constant and satisfy the relationship of Y ≧ 0.175X + 1.137, (BaO + SrO) / (TiO ₂ + Nb ₂ O ₅ ) is less than 0.80. Preferably, it is 0.78 or less, and most preferably 0.76 or less.

In the optical glass having the constitution 7, the mass content ratio (SiO ₂ + Al ₂ O ₃ ) / ΣR ₂ O is a criterion for devitrification and chemical durability in the glass by a reheating test of the glass. Used as SiO ₂ and Al ₂ O ₃ are glass forming components, and are devitrification preventing components and chemical durability improving components inside the glass by the reheating test. On the other hand, when R ₂ O is contained in a large amount, it tends to cause devitrification inside the glass by a reheating test, and is a component that significantly deteriorates chemical durability. If this ratio is large, devitrification does not occur and chemical durability is improved by the reheating test of the glass. Therefore, in the present invention, (SiO ₂ + Al ₂ O ₃ ) / ΣR ₂ O is preferably larger than 2.2, more preferably 2.3 or more, and most preferably 2.5 or more.

  In the optical glasses having the configurations 8, 9 and 10, the reason why the content ratio of the constituent components is limited is as follows.

SiO ₂ is an indispensable component as a glass-forming oxide, but if it is less than 30.0 mol% and / or less than 20.0 mass%, a stable glass cannot be formed, and a transparent glass cannot be obtained. Moreover, when it exceeds 48.0 mol% and / or 35.0 mass%, the high refractive index of nd = 1.79 or more cannot be realized. Accordingly, the content of SiO ₂ is preferably 30.0 mol% and / or 20.0% by mass or more, more preferably 30.5 mol% and / or 21.0% by mass or more, and most preferably 31 The lower limit is 0.0 mol% and / or 23.0 mass%, preferably 48.0 mol% and / or 35.0 mass%, more preferably 47.5 mol% and / or 34.0 mass%, most preferably 47. 0.0 mol% and / or 33.0 mass% is contained as an upper limit. The SiO ₂ component can be contained in any raw material form, but is preferably introduced in the form of an oxide (SiO ₂ ), K ₂ SiF ₆ , or Na ₂ SiF ₆ .

TiO ₂ is an essential component for obtaining a low specific gravity and a high refractive index. If it is less than 3.0 mol% and / or 1.0% by mass, the desired refractive index cannot be obtained, but if it contains more than 25.0 mol% and / or 21.0% by mass, the dispersion becomes too large, and the Abbe Not only can the medium dispersion of number = 27 or more not be maintained, but the coloring of the glass becomes remarkable, and high transmittance cannot be realized. Therefore, the content of TiO ₂ is preferably 3.0 mol% and / or 1.0 mass% or more, more preferably 4.0 mol% and / or 3.0 mass% or more, and most preferably 5 mol%. 0.0 mol% and / or 5.0 mass% is the lower limit, preferably 25.0 mol% and / or 21.0 mass%, more preferably 24.5 mol% and / or 20.5 mass%, most preferably 24 0.0 mol% and / or 20.0 mass% is contained as an upper limit. The TiO ₂ component can be contained in any raw material form, but is preferably introduced in the form of an oxide (TiO ₂ ).

Nb ₂ O ₅ is an indispensable component for obtaining a low specific gravity and a high refractive index, like TiO ₂ . If it is less than 0.5 mol% and / or 1.0% by mass, the desired refractive index cannot be obtained, but if it is contained more than 15.0 mol% and / or 18.0% by mass, the dispersion becomes too large and Abbe The medium dispersion of number = 27 or more cannot be maintained. Therefore, the content of Nb ₂ O ₅ is preferably 0.5 mol% and / or 1.0 mass% or more, more preferably 0.8 mol% and / or 3.0 mass% or more, and most preferably 1.0 mol% and / or 5.0 mass% is the lower limit, preferably 15.0 mol% and / or 25.0 mass%, more preferably 14.5 mol% and / or 23.0 mass%, most preferably Is contained at an upper limit of 14.0 mol% and / or 18.0 mass%. The Nb ₂ O ₅ component can be contained in any raw material form, but is preferably introduced in the form of an oxide (Nb ₂ O ₅ ).

La ₂ O ₃ has an effect of reducing dispersion while having a high refractive index, and is an indispensable component for realizing an Abbe number = 27 to 35. If it is 0.5 mol% and / or 5.0 mass% or less, high refractive index and medium dispersion cannot be realized, but if it exceeds 15.0 mol% and / or 16.0 mass%, the meltability is deteriorated. Instead, the specific gravity increases. Therefore, the content of La ₂ O ₃ is preferably more than 0.5 mol% and / or 5.0 mass%, more preferably 0.8 mol% and / or 5.5 mass% or more, most preferably 1.0 mol% and / or 6.0 mass% as the lower limit, preferably 15.0 mol% and / or 25.0 mass%, more preferably 14.5 mol% and / or 20.0 mass%, most Preferably it contains 14.0 mol% and / or 16.0 mass% as an upper limit. The La ₂ O ₃ component can be contained in any raw material form, but preferably, oxide (La ₂ O ₃ ), nitrate and nitrate hydrate (La (NO ₃ ) ₃ XH ₂ O (X is It is preferably introduced in the form of any integer)).

ZrO ₂ is indispensable because it increases the stability of the glass and suppresses devitrification in the process of cooling from the time of melting, and also increases the chemical durability of the obtained glass. It is an ingredient. If it is less than 0.5 mol% and / or 1.0 mass%, the stability of the glass cannot be sufficiently increased, but if it exceeds 10.0 mol% and / or 12.0 mass%, the meltability deteriorates. A homogeneous glass cannot be obtained. Therefore, the content of ZrO ₂ is preferably 0.5 mol% and / or 1.0 mass% or more, more preferably 0.8 mol% and / or 1.5 mass% or more, most preferably 1 0.0 mol% and / or 2.0 mass% is the lower limit, preferably 10.0 mol% and / or 12.0 mass%, more preferably 9.5 mol% and / or 11.0 mass%, most preferably 9 0.0 mol% and / or 10.0 mass% is contained as an upper limit. The ZrO ₂ component can be contained in any raw material form, but is preferably introduced in the form of an oxide (ZrO ₂ ).

R ₂ O (R = Li, Na, K, Cs) is an indispensable component because it increases the meltability of the glass and lowers the viscosity and glass transition point of the glass melt during molding. If the total amount is too small, the meltability of the glass is poor, and more heat energy is required during production, resulting in higher production costs. However, if the total amount is too large, the desired optical constant range is reached. Not only cannot it be realized, but the chemical durability of the obtained glass is remarkably deteriorated. In addition, in the process of reheating the glass such as a reheat press, milk white and devitrification occur in the glass. Therefore, the total content of R ₂ O is preferably 0.5 mol% and / or 0.1 mass% or more, more preferably 0.8 mol% and / or 0.3 mass% or more, and most preferably Has a lower limit of 1.0 mol% and / or 0.5 mass%, preferably 25.0 mol% and / or 15.0 mass%, more preferably 24.5 mol% and / or 14.0 mass%, most preferably Is contained at an upper limit of 24.0 mol% and / or 13.0 mass%.

Hereinafter, the effect and preferable content rate of each component of R ₂ O will be described.
Li ₂ O is a component that most improves the meltability of the glass among the R ₂ O components, and therefore can be arbitrarily added depending on the difficulty of the meltability of the composition. However, if it is excessively contained, not only a high refractive index cannot be realized, but also a problem of milk white or crystal precipitation occurs in the reheating (reheating) step of the obtained glass, so the upper limit is 23.0 mol% and / or 10 It is preferably 0.0% by mass, more preferably 22.0% by mol and / or 9.0% by mass, and most preferably 21.0% by mol and / or 8.0% by mass. The Li ₂ O component can be contained in any raw material form, but is preferably introduced in the form of carbonate (Li ₂ CO ₃ ) or nitrate (LiNO ₃ ).

Na ₂ O has a high effect of improving the meltability of the glass like Li ₂ O, and can be arbitrarily added depending on the difficulty of the meltability of the composition. However, if it is contained excessively, dispersion at a high refractive index cannot be realized, and chemical durability is deteriorated. Therefore, the upper limit is preferably 15.0 mol% and / or 7.0 mass%, more preferably 14.0 mol% and / or 6.5 mass%, most preferably 13.0 mol% and / or 6 0.0% by mass. The Na ₂ O component is carbonate (Na ₂ CO ₃ ), nitrate (NaNO ₃ ), fluoride (NaF), Na ₂ SiF ₆ , Na ₃ AlF ₆ , NaCl, Na ₂ SO ₄ , Na ₂ B ₄ O _7. Na ₂ H ₂ Sb ₂ O ₇ · 5H ₂ O can be contained, but it is preferably introduced in the form of carbonate, nitrate or sulfate.

K ₂ O can be arbitrarily added because the refractive index and the Abbe number can be adjusted while adjusting the meltability of the glass. However, when it is excessively contained, not only high refractive index medium dispersion can be realized, but also the specific gravity increases. Therefore, the upper limit is preferably 8.0 mol% and / or 5.0 mass%, more preferably 7.0 mol% and / or 4.5 mass%, most preferably 6.0 mol% and / or 4.0 mass%. % By mass. The K ₂ O component can be contained in the form of carbonate (K ₂ CO ₃ ), nitrate (KNO ₃ ), fluoride (KF), K ₂ SiF ₆ , K ₂ TIF ₆ / H ₂ O, KI. However, it is preferable to introduce in the form of carbonate or nitrate.

Cs ₂ O can be arbitrarily added since the refractive index and the Abbe number can be adjusted while adjusting the meltability of the glass similarly to K ₂ O. However, when it is excessively contained, not only high refractive index medium dispersion can be realized, but also the specific gravity increases. Therefore, the upper limit is preferably 5.0 mol% and / or 5.0 mass%, more preferably 4.5 mol% and / or 4.5 mass%, most preferably 4.0 mol% and / or 4.0. % By mass. The Cs ₂ O component can be contained in any raw material form, but is preferably introduced in the form of carbonate (Cs ₂ CO) or nitrate (Cs ₂ NO ₃ ).

  RO (Mg, Ca, Sr, Ba) is an indispensable component because an effect of reducing the dispersion while increasing the refractive index can be obtained. However, if the total amount is too small, the desired high refractive index and medium dispersion cannot be realized, but if the total amount is too large, the chemical durability deteriorates and the specific gravity increases. Therefore, the total content of RO is preferably 1.0 mol% and / or 3.0 mass% or more, more preferably 3.0 mol% and / or 4.0 mass% or more, and most preferably 5 mol%. The lower limit is 0.0 mol% and / or 5.0 mass%, preferably 35.0 mol% and / or 30.0 mass%, more preferably 33.0 mol% and / or 27.0 mass%, most preferably 31. 0.0 mol% and / or 25.0 mass% is contained as an upper limit.

Hereinafter, the effect and preferable content of each component of RO will be described.
MgO has the effect of lowering the specific gravity of the glass product while maintaining the optical constant, but if it is excessively contained, the glass becomes unstable and crystals are produced during cooling. Accordingly, the upper limit is preferably 7.0 mol% and / or 5.0 mass%, more preferably 6.0 mol% and / or 4.0 mass%, most preferably 5.0 mol% and / or 3 mass%. 0.0% by mass. The MgO component can be contained in any raw material form, but is preferably introduced in the form of an oxide (MgO), carbonate (MgCO ₃ ), or hydroxide (Mg (OH) ₂ ).

CaO has the effect of lowering the specific gravity of the glass product and reducing the dispersion, but it is not preferable because it makes it difficult to achieve a high refractive index when contained in excess. Therefore, the upper limit is preferably 30.0 mol% and / or 15.0 mass%, more preferably 29.0 mol% and / or 14.8 mass%, most preferably 28.0 mol% and / or 14 0.5% by mass. The CaO component can be contained in any raw material form, but is preferably introduced in the form of carbonate (CaCO ₃ ) or fluoride (CaF ₂ ).

  The total amount of MgO and CaO is preferably up to 31.0 mol% and / or 16.0 mass%. Addition beyond that is not preferable because a desired optical constant cannot be realized. Therefore, in the present invention, the upper limit is more preferably 30.5 mol% and / or 15.5 mass%, and most preferably 30.0 mol% and / or 15.0 mass%.

SrO is a component that can obtain the effect of increasing the refractive index among the RO components, but if contained excessively, the specific gravity of the glass is increased, which is not preferable. Therefore, the upper limit is preferably 8.0 mol% and / or 10.0 mass%, more preferably 7.5 mol% and / or 9.0 mass%, most preferably 7.0 mol% and / or 8 mass%. 0.0% by mass. The SrO component can be contained in any raw material form, but is preferably introduced in the form of nitrate (Sr (NO ₃ ) ₂ ) or fluoride (SrF ₂ ).

BaO has the highest effect of increasing the refractive index among the RO components, and can therefore be contained in the glass of the present invention. However, excessive addition is not preferable because the specific gravity of the glass is remarkably increased. Therefore, the upper limit is preferably 20.0 mol% and / or 25.0 mass%, more preferably 19.0 mol% and / or 24.0 mass%, most preferably 18.0 mol% and / or 23. 0.0% by mass. The BaO component can be contained in an arbitrary raw material form, but is introduced in the form of carbonate (BaCO ₃ ), nitrate (Ba (NO ₃ ) ₂ ), sulfate (BaSO ₄ ), fluoride (BaF ₂ ). It is preferable to do.

B ₂ O ₃ is a kind of glass-forming oxide, and by adding an appropriate amount, an effect of improving the meltability of the glass can be obtained, so that B ₂ O ₃ can be arbitrarily contained. However, if it is excessively contained, not only the chemical durability is remarkably deteriorated, but also in the reheat process of the obtained glass, a problem of milk white or crystal precipitation occurs, so the upper limit is 10.0 mol% and / or 6.0 mass% is preferable, More preferably, it is 6.0 mol% and / or 2.0 mass%, Most preferably, it is not containing at all. The B ₂ O ₃ component can be contained in the raw material form of H ₃ BO ₃ , Na ₂ B ₄ O ₇ , Na ₂ B ₄ O ₇ · 10H ₂ O, but introduced in the form of H ₃ BO _3. Is preferred.

Al ₂ O ₃ is a kind of glass-forming oxide, and has an effect of remarkably improving the chemical durability of glass by adding an appropriate amount. However, if it is contained excessively, the devitrification stability of the glass is remarkably deteriorated, so that it is difficult to obtain a glass having no foreign matter inside. Therefore, the upper limit is preferably 3.0 mol% and / or 1.0 mass%, more preferably 2.5 mol% and / or 0.8 mass%, most preferably 2.0 mol% and / or 0.5 mass%. % By mass. The Al ₂ O ₃ component can be contained in any raw material form, but can be introduced in the form of oxide (Al ₂ O ₃ ), hydroxide (Al (OH) ₃ ), and Na ₃ AlF _6. preferable.

ZnO can be arbitrarily added because it has the effects of improving the meltability of the glass and obtaining a high refractive index. However, when it is contained excessively, a problem of milky white or crystal precipitation is induced during the reheating process of the obtained glass. Therefore, the upper limit is preferably 10.0 mol% and / or 10.0 mass%, more preferably 9.0 mol% and / or 8.0 mass%, most preferably 8.0 mol% and / or 6 0.0% by mass. The ZnO component can be contained in any raw material form, but is preferably introduced in the form of oxide (ZnO) or fluoride (ZnF ₂ ).

WO ₃ can be arbitrarily contained since it has the effects of improving the meltability of the glass and suppressing the occurrence of devitrification when cooling the melt and obtaining a high refractive index. However, if excessively contained, the dispersion becomes too large, and not only the desired Abbe number cannot be realized, but also the coloring of the glass becomes remarkable, so the upper limit is 5.0 mol% and / or 5.0 mass%. Preferably, it is 4.5 mol% and / or 4.5 mass%, most preferably 4.0 mol% and / or 4.0 mass%. The WO ₃ component can be contained in any raw material form, but is preferably introduced in the form of an oxide (WO ₃ ).

Bi ₂ O ₃ , as in WO ₃ , improves the glass meltability, suppresses devitrification when cooling the melt, and has the effect of obtaining a high refractive index. Can do. However, if excessively contained, the dispersion becomes too large, and not only the desired Abbe number cannot be realized, but also the coloration of the glass becomes remarkable, so the upper limit is 3.0 mol% and / or 5.0 mass%. Preferably, it is 2.5 mol% and / or 4.5 mass%, most preferably 2.0 mol% and / or 4.0 mass%. The Bi ₂ O ₃ component can be contained in any raw material form, but is preferably introduced in the form of an oxide (Bi ₂ O ₃ ).

Gd ₂ O ₃ and Y ₂ O ₃ can realize a high refractive index and small dispersion similarly to La ₂ O _3, and thus can be arbitrarily contained. However, when it is contained excessively, the stability of the glass is remarkably lowered, and it becomes difficult to obtain a glass having no foreign matter inside. The upper limit is preferably 3.0 mol% and / or 10.0 mass%, more preferably 2.8 mol% and / or 9.0 mass%, most preferably 2.5 mol% and / or 8.0 mass%, respectively. %. The Gd ₂ O ₃ component and the Y ₂ O ₃ component can be contained in any raw material form, but are in the form of oxides (Gd ₂ O ₃ and Y ₂ O ₃ ) or fluorides (GdF ₃ and YF ₃ ). It is preferable to introduce by.

Ta ₂ O ₅ can be arbitrarily added because it can achieve a high refractive index and can suppress the occurrence of devitrification when the glass melt is cooled. However, when 3.0 mol% and / or 10.0 mass% or more is added, dispersion becomes too large, and it is difficult to produce at low cost because the raw material is expensive. Therefore, the upper limit is preferably 3.0 mol% and / or 10.0 mass%, more preferably 2.8 mol% and / or 9.0 mass%, and most preferably 2.5 mol% and / or 8 mass%. 0.0% by mass. The Ta ₂ O ₅ component can be contained in any raw material form, but is preferably introduced in the form of an oxide (Ta ₂ O ₅ ).

Yb ₂ O ₃ and Lu ₂ O ₃ can be arbitrarily added because they have an effect of obtaining a high refractive index. However, if it is contained excessively, the stability of the glass deteriorates, and it becomes difficult to obtain a glass having no foreign matter inside, and it is difficult to produce it at low cost because the raw material is expensive. Therefore, the upper limit is preferably 2.0 mol% and / or 5.0 mass%, more preferably 1.8 mol% and / or 4.0 mass%, most preferably 1.5 mol% and / or 3 mass%. 0.0% by mass. The Yb ₂ O ₃ component and the Lu ₂ O ₃ component can be contained in any raw material form, but are preferably introduced in the form of oxides (Yb ₂ O ₃ and Lu ₂ O ₃ ).

TeO ₂ can realize a high refractive index and can be arbitrarily contained since an effect of promoting clarification of the glass melt can be obtained by adding an appropriate amount. Since the glass is colored when excessively contained, the upper limit is preferably 2.0 mol% and / or 3.0 mass%, more preferably 1.8 mol% and / or 2.0 mass%, most preferably 1.5 mol% and / or 1.0 mass%. The TeO ₂ component can be contained in any raw material form, but is preferably introduced in the form of an oxide (TeO ₂ ).

Sb ₂ O ₃ can be arbitrarily added because an effect of promoting clarification and defoaming of the glass melt can be obtained by adding an appropriate amount. However, if it is contained excessively, it causes excessive foaming and leads to deterioration of the internal quality of the product, and it also has an adverse effect on metals (including alloys) with high heat resistance such as platinum in melting equipment. Therefore, the upper limit is preferably 0.5 mol% and / or 2.0 mass%, more preferably 0.4 mol% and / or 1.5 mass%, most preferably 0.3 mol% and / or 1.0 mass%. %. The Sb ₂ O ₃ component can be contained in any raw material form, but is introduced in the form of oxides (Sb ₂ O ₃ and Sb ₂ O ₅ ) or Na ₂ H ₂ Sb ₂ O ₇ · 5H ₂ O. It is preferable.

Since the F component has the effect of increasing the meltability of the glass and the effect of increasing the Abbe number, the F as the fluoride of F substituted for one or more of the above-mentioned metal elements or two or more oxides. It is possible to add 10 mol% and / or 5.0 mass% in total amount as an upper limit. However, when it is added more than necessary, not only the desired optical constant cannot be realized, but also the internal quality of the glass is deteriorated and the glass inside the glass is devitrified by the reheating test. Therefore, the upper limit is preferably 10 mol% and / or 5.0 mass%, more preferably 9.0 mol% and / or 4.5 mass%, most preferably 8.0 mol% and / or 4.0 mass%. It is. In the introduction of the various oxides described above, the F component is introduced into the glass when the raw material form is introduced as a fluoride.
In the present specification, the notation representing the fluorine compound “the total amount of fluorides substituted with one or more oxides of one or more of each metal element as F” means the glass constitution of the present invention. Assuming that oxides, composite salts, metal fluorides, etc. used as raw materials for components are all decomposed and changed to oxides when melted, in the case of mass% notation, the actual mass with respect to the total mass of the generated oxide The mass of F atoms contained is expressed as a percentage by mass, and in the case of mol%, the number of moles of F atoms actually contained relative to the total number of moles of the generated oxide is expressed as a mole percentage. is there.

The P ₂ O ₅ component may be added as long as it does not impair the effects of the present invention. However, the addition of the P ₂ O ₅ component tends to promote devitrification inside the glass due to reheating. Is preferably 10.0 mol% and / or 5.0 mass%. Most preferably, it does not contain. The P ₂ O ₅ component can be contained in any raw material form, but it is preferably introduced in the form of Al (PO ₃ ) ₃ , Ba (PO ₃ ) ₃ , BPO ₄ , H ₃ PO ₄ .

Furthermore, in the present invention, lead and / or PbO and As ₂ O ₃ are preferably 0.01 mol% and / or 0.01 mass%, more preferably 0.005 mol% and / or 0.005 mass%. The upper limit is set, and most preferably it is not contained at all except for inevitable mixing. SnO ₂ and SnO are preferably 0.01 mol% and / or 0.01 mass%, more preferably 0.005 mol% and / or 0.005 mass%, and most preferably none.

  Each transition metal component such as V, Cr, Mn, Fe, Co, Ni, Cu, Ag, and Mo, excluding Ti, is colored even when contained in a small amount by combining them individually or in combination. In order to cause absorption at the wavelength of the optical glass, it is preferable that the optical glass using the wavelength in the visible region does not substantially contain. Furthermore, each component of Pb, Th, Cd, Tl, As, Os, Be, and Se has tended to be refrained from being used as a harmful chemical material in recent years. Therefore, it is preferable not to include it substantially when the environmental impact is important.

In the optical glass of constitution 11, by limiting the content of B ₂ O ₃ to 0 to less than 0% by mass%, the effect of preventing devitrification and improving the chemical durability in the reheating test can be obtained. can get.

In the optical glass of composition 12, the effect of improving chemical durability can be obtained by limiting the content of Na ₂ O to 0 to less than 3.0% by mass.

As described in Structures 13-17, the glass of Structures 1-12 is useful as a base material for producing optical substrate materials such as optical elements such as lenses and prisms, reflectors, diffusers, and wavelength separators. Yes, when they are produced by precision press molding, they are suitable as a preform material.

  Next, examples of the present invention will be described. In all the tables below, the glass component content is all expressed in mass%.

  To obtain an optical glass having a refractive index (nd) of 1.79 or more and an Abbe number (νd) of 27 or more in Tables 1 to 7 and the glass interior is not devitrified in a reheating test. The composition of the preferred examples (Nos. 1 to 34) and the refractive index (nd), Abbe number (νd), powder method acid resistance RA, specific gravity (D), and reheat test pass / fail of the obtained glass are shown. .

  Tables 8 and 9 show various physical properties and evaluation results of known optical glass comparative examples (No. A to J). Here, Comparative Examples A to D show Examples 2, 35, 39, and 40 of JP-A-59-50048 described above. Comparative Examples E to G show Examples 16, 34, and 41 of JP-A No. 2002-87841. Comparative examples H and I show Examples 1 and 7 of JP-A-3-5340. Comparative Example J shows Example 4 of Japanese Patent Application Laid-Open No. 2004-18371.

Powder Method acid resistance (RA), based on the Japanese Optical Glass Industrial Standard "chemical durability of the measurement method of the optical glass (Powder Method)" JOGIS06- ^1999, crushed the resulting glass to particle size 425～600Myuemu, Take the crushed glass sample in a specific gravity gram, put it in a platinum basket, put the platinum basket in a quartz glass round bottom flask containing 0.01N nitric acid aqueous solution, treat in a boiling water bath for 60 minutes, When the weight loss rate (%) of the glass sample is calculated, when the weight loss rate is less than 0.05%, it is class 1, when the weight loss rate is less than 0.05 to 0.10%, it is class 2, and the weight loss rate is 0. The case of less than 10 to 0.25% is classified as class 3, and the smaller the number of classes, the better the acid resistance of the glass.

In the reheating test, a glass sample made of a prism having a width and thickness of 15 mm and a length of 30 mm is placed on a refractory and placed in an electric furnace to be reheated. After raising the temperature to 150 ° C. higher than the transition temperature (Tg), keeping the temperature at that temperature for 30 minutes, lowering the temperature to room temperature, taking it out of the furnace, and visually observing a glass sample with two opposite surfaces polished so that the inside can be observed The reheating test results are shown by observing the glass with milky white and devitrification not clear and colorless and transparent, with ◯ and with milk white or devitrification x.
In addition, the glass transition temperature of the optical glass of this invention used for the following Example is in the range of 550-700 degreeC.

  The glasses of the examples of the present invention described in Tables 1 to 7 are all in a predetermined ratio using ordinary optical glass raw materials such as oxides, carbonates, nitrates, fluorine compounds, hydroxides, and metaphosphate compounds. After weighing and mixing, put into a platinum crucible, etc., melt for 3 to 4 hours at a temperature of 1200 to 1400 ° C. according to the difficulty of melting the glass composition, homogenize with stirring, and then lower the temperature to an appropriate temperature. It was obtained by casting into a mold or the like and gradually cooling.

  As shown in Tables 1-7, all of the preferred embodiments of the present invention achieve the desired optical constant while being excellent in chemical durability and are not devitrified even when a reheating test is performed. I understood. On the other hand, in Comparative Examples shown in Tables 8 and 9, Comparative Examples A to D and Comparative Example J have a large glass specific gravity, do not satisfy the relational expression of Y ≧ 0.175X + 1.137, and from the viewpoint of reducing the product weight. It was inferior. Moreover, Comparative Example B and EG confirmed devitrification inside the glass by the reheating test, and it turned out that reheat press processing is difficult. Further, Comparative Examples H to J had acid resistances of 2 and 3, and the chemical durability was poor.

Although the present invention has been described in detail for the purpose of illustration, this embodiment is only for the purpose of illustration, and many modifications can be made by those skilled in the art without departing from the spirit and scope of the present invention. Will be understood.

Claims (17)

A glass having an optical constant of a refractive index (nd) of 1.79 or more, an Abbe number (νd) of 27 or more, and a specific gravity (D) of 3.20 or more. The glass is characterized by not devitrifying. The glass according to claim 1, which has a chemical durability (powder method acid resistance: RA) of class 1 by a powder method. SiO ₂ , TiO ₂ , La ₂ O ₃ , and a glass having a component composition satisfying the component content ratio B ₂ O ₃ / SiO ₂ = 0 to 0.5 in mass%, and having a refractive index (nd) Has an optical constant in the range of 1.79 or more, Abbe number (νd) in the range of 27 to 35, refractive index (nd) is Y, and glass specific gravity is X, the relationship of Y ≧ 0.175X + 1.137 The glass satisfying The glass according to claim 3, wherein ΣR ₂ O is 0.1% to less than 15% by mass, and the glass is reheated and kept at a temperature range of 150 ° C. higher than the glass transition temperature (Tg) for 30 minutes. Even if the inside of the glass is not milky white or devitrified, it is a glass. The glass according to any one of claims 1 to 4, wherein the specific gravity (D) is 3.20 to 4.10. A glass according to any one of claims 1 to 5, component content ratio of the _{mass% (BaO + SrO) / (} TiO 2 + Nb 2 O 5) < Glass, which is a 0.80. The glass according to claim 1, wherein a component content ratio of mass% (SiO ₂ + Al ₂ O ₃ ) / ΣR ₂ O> 2.2. A glass according to any one of claims 1~7, SiO ₂ 30.0 ~ 48.0% by mol%
TiO ₂ 3.0-25.0%
La ₂ O ₃ 0.5 to 15.0%
Glass containing It has an optical constant in the range of refractive index (nd) 1.79 to 1.88 and Abbe number (νd) 27 to 35, in mol%,
SiO ₂ 30.0 ~ 48.0%
TiO ₂ 3.0-25.0%
Nb ₂ O ₅ 0.5 to 15.0%
La ₂ O ₃ 0.5 to 15.0%
ZrO ₂ 0.5 to 10.0%
_{R 2 O (R = Li,} Na, K, Cs) 0.5 ~ 25.0%
Li ₂ O 0.0-23.0% and / or Na ₂ O 0.0-15.0% and / or K ₂ O 0.0-8.0% and / or Cs ₂ O 0.0 ~ 5.0%
And RO (R = Mg, Ca, Sr, Ba) 1.0 to 35.0%
MgO 0.0 to 7.0% and / or CaO 0.0 to 30.0% and / or SrO 0.0 to 8.0% and / or BaO 0.0 to 20% and / or MgO + CaO 0.0-31.0%
And B ₂ O ₃ 0.0 to 10.0%
Al ₂ O ₃ 0.0 to 3.0% and / or ZnO 0.0 to 10.0% and / or WO ₃ 0.0 to 5.0% and / or Bi ₂ O ₃ 0.0 to 3. 0% and / or Gd ₂ O ₃ 0.0 ~ 3.0% and / or Y ₂ O ₃ 0.0 ~ 3.0% and / or Ta ₂ O ₅ 0.0 ~ 3.0% and / or Yb ₂ O ₃ 0.0-2.0% and / or Lu ₂ O ₃ 0.0-2.0% and / or TeO ₂ 0.0-2.0% and / or Sb ₂ O ₃ 0.0 ~ 0.5%
A total amount of 0 to 10% as F of a fluoride substituted with one or more oxides of one or more of the above metal elements, and containing B ₂ O ₃ / SiO ₂ = 0 to 0.5, The glass according to any one of claims 1 to 8. It has an optical constant in the range of refractive index (nd) 1.79 to 1.88 and Abbe number (νd) 27 to 35.
SiO ₂ 20.0 ~ 35.0%
TiO ₂ 1.0 to less than 21.0% Nb ₂ O ₅ 1.0 to less than 25% La ₂ O ₃ 5.0 to less than 25% ZrO ₂ 1.0 to 12.0%
_{R 2 O (R = Li,} Na, K, Cs) as less than _{0.1 ~ 15.0%, Li 2 O} 0.0 ~ 10.0% and / or Na ₂ O 0.0 ~ 7.0% Less than
K ₂ O 0.0 ~ 5.0% and / or Cs ₂ O 0.0 ~ 5.0%
And RO (R = Mg, Ca, Sr, Ba) 3.0 to less than 30%, MgO 0.0 to 5.0% and / or CaO 0.0 to less than 15.0% SrO 0.0 to 10 0.0% and / or BaO 0.0 to less than 25%, but MgO + CaO 0.0 to less than 16.0% and B ₂ O ₃ 0.0 to less than 6.0%
Al ₂ O ₃ 0.0 to less than 1.0% and / or ZnO 0.0 to 10.0% and / or WO ₃ 0.0 to 5.0% and / or Bi ₂ O ₃ 0.0 to 5 0.0% and / or Gd ₂ O ₃ 0.0 to 10.0% and / or Y ₂ O ₃ 0.0 to 10.0% and / or Ta ₂ O ₅ 0.0 to 10.0% and / or Or Yb ₂ O ₃ 0.0-5.0% and / or Lu ₂ O ₃ 0.0-5.0% and / or TeO ₂ 0.0-3.0% and / or Sb ₂ O ₃ 0. 0 to 2.0%
A total amount of 0 to 5% as F of a fluoride substituted with one or more oxides of one or more of the above metal elements, and containing B ₂ O ₃ / SiO ₂ It is = 0-0.5, The glass of any one of Claims 1-9. A glass according to claim 1~10, _B 2 _O 3 0~2.0% less glass mass%. A glass according to claim 1 to 11, _Na 2 O 0 to 3.0% less than the glass in mass%. An optical element such as a lens / prism using the glass according to any one of claims 1 to 12 as a base material. An optical element such as a lens or a prism, which is produced by reheat press processing the glass according to any one of claims 1 to 12. Optical board materials, such as a reflecting plate, a diffuser plate, and a wavelength separation plate, using the glass according to any one of claims 1 to 12 as a base material. An optical device such as a camera / projector using the optical element and the optical substrate material made of the glass according to claim 1. A precision press-molding preform made of the glass according to claim 1.