TWI641572B - Glass, glass materials for stamping, optical component blanks, and optical components - Google Patents

Abstract

Provided is an oxide glass glass expressed by mass%, and a total content of B ₂ O ₃ and SiO ₂ is 15 to 35 mass%, and La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O _{3 ,} and Yb ₂ O ₃ The total content is 45 to 65 mass%, but the Yb ₂ O ₃ content is 3% by mass or less, the ZrO ₂ content is 3 to 11% by mass, the Ta ₂ O ₅ content is 5% by mass or less, and the B ₂ O ₃ content is B. The mass ratio of the total content of ₂ O ₃ and SiO ₂ is 0.4 to 0.900, and the total content of B ₂ O ₃ and SiO _{2 is} the total content of La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ and Yb ₂ O ₃ . The mass ratio is 0.42~0.53, and the mass ratio of Y ₂ O ₃ content to the total content of La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ and Yb ₂ O _{3 is} 0.05-0.45, and the content of Gd ₂ O _{3 is} La. The mass ratio of ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ and Yb ₂ O ₃ is 0 to 0.05, and the Nb ₂ O ₅ content is for Nb ₂ O ₅ , TiO ₂ , Ta ₂ O ₅ and WO ₃ The mass ratio of the total content is 0.5 to 1, the refractive index nd is in the range of 1.800 to 1.850, and the Abbe number vd is 41.5 to 44.

Description

Glass, glass materials for stamping, optical component blanks, and optical components

The present invention relates to a glass, a glass material for press molding, an optical element blank, and an optical element.

As a glass having a high refractive index and a low dispersion (high refractive index low dispersion glass), for example, Patent Documents 1 to 18 describe a glass having a refractive index nd in the range of 1.800 to 1.850 and an Abbe number vd of 41.5 to 44. .

[Previous Technical Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2002-12443

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2003-267748

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2005-281124

[Patent Document 4] Japanese Patent Laid-Open Publication No. 2005-298262

[Patent Document 5] Japanese Laid-Open Patent Publication No. 55-121925

[Patent Document 6] Japanese Patent Laid-Open Publication No. 2009-203083

[Patent Document 7] JP-A-54-090218

[Patent Document 8] Japanese Laid-Open Patent Publication No. 56-160340

[Patent Document 9] Japanese Patent Laid-Open Publication No. 2009-167080

[Patent Document 10] Japanese Patent Laid-Open Publication No. 2009-167081

[Patent Document 11] Japanese Patent Laid-Open Publication No. 2009-298646

[Patent Document 12] Japanese Patent Laid-Open Publication No. 2010-111527

[Patent Document 13] Japanese Patent Laid-Open Publication No. 2010-111528

[Patent Document 14] Japanese Patent Laid-Open Publication No. 2010-111530

[Patent Document 15] Japanese Laid-Open Patent Publication No. SHO 57-056344

[Patent Document 16] Japanese Laid-Open Patent Publication No. 61-163138

[Patent Document 17] Japanese Patent Laid-Open Publication No. 2002-284542

[Patent Document 18] Japanese Patent Laid-Open Publication No. 2007-269584

A glass having a refractive index nd in the range of 1.800 to 1.850 and an Abbe number vd of 41.5 to 44 is a useful material for an optical element for correcting chromatic aberration, high functionalization of an optical system, and miniaturization. In the following, the refractive index system is set to have a refractive index nd of d-ray (wavelength of 氦 587.56 nm) unless otherwise specified. Further, the Abbe number is set as vd unless otherwise specified. As is conventionally known, when the refractive indices of the F-ray (the wavelength of hydrogen: 486.13 nm) and the C-ray (hydrogen 656.27 nm) are nF and nC, respectively, it is defined as vd=(nd-1)/(nF-nC).

In order to further improve the usefulness of the high refractive index low dispersion glass having the refractive index and the Abbe number in the above range, it is desirable to satisfy the following matters.

Must be able to supply steadily. Therefore, it is preferable to reduce the ratio of Gd and Ta which are rare and expensive elements, and the elements which are insufficiently supplied to the market in recent years, in the glass composition. On the other hand, the glass system described in Patent Document 7 contains a large amount of Ta. Further, the glass described in Patent Documents 8 to 14 The glass and the glass having the refractive index and the Abbe number in the above range described in Patent Document 17 contain a large amount of Gd.

The proportion of Yb in the glass composition must be low. This is based on the following reasons.

The Yb system has absorption in the near infrared rays. Therefore, a glass containing a large amount of Yb (for example, the glass described in Patent Document 16) is not suitable for applications requiring high transmittance from a visible region to near infrared rays, such as a surveillance camera, an infrared camera, or a vehicle. A material for an optical element such as a lens of a camera. Further, Yb is a heavy rare earth element, and as a component of glass, the atomic weight is large, and the specific gravity of glass is increased. When the specific gravity of the glass increases, the lens becomes heavier. As a result, when such a lens is incorporated into an autofocus type camera lens, power consumption increases and battery consumption becomes intense. In view of the above, it is preferable to reduce the proportion of Yb in the glass composition.

Must have excellent thermal stability. Because of the low heat stability of the glass, the glass has a tendency to show transparency in the process of manufacturing the glass. However, according to the study of the present inventors, for example, the glass system described in Patent Document 6 is inferior in thermal stability.

In view of the above circumstances, an aspect of the present invention provides a glass having a refractive index nd in the range of 1.800 to 1.850 and an Abbe number vd in the range of 41.5 to 44, and a proportion of Gd, Ta, and Yb in reducing the glass composition. At the same time, it has excellent thermal stability.

Further, in one aspect, the glass is also expected to further satisfy one or more of the following matters.

Must be able to control the long wave at the light absorption end of the short wavelength side of the glass Long. This is based on the following reasons.

In order to correct chromatic aberration, a method of manufacturing a cemented lens by bonding a plurality of lenses each having a glass having different optical characteristics and bonding the lenses is known. In the process of manufacturing the cemented lens, in order to bond the lenses, an ultraviolet curing type adhesive is usually used. The details are as follows. An ultraviolet curable adhesive is applied to the surface between the bonded lenses, and the lens is bonded. At this time, the external hardening type adhesive usually forms a very thin coating layer between the lenses. Next, the coating layer is irradiated with ultraviolet rays through a lens to cure the ultraviolet curable adhesive. Therefore, when the transmittance of the ultraviolet light of the lens is low, the ultraviolet light having a sufficient amount of light does not pass through the lens and reaches the coating layer, resulting in insufficient curing. Or hardening takes a long time. Further, when the lens is subsequently fixed to the lens barrel or the like using an ultraviolet curable adhesive, similarly, when the ultraviolet transmittance of the lens is low, curing is insufficient or hardening takes a long time.

Therefore, in order to obtain a glass having a transmittance characteristic suitable for the production of an optical system, it is necessary to increase the transmittance of the ultraviolet region of the glass, in other words, it is preferable to suppress the long wavelength of the light absorption end on the short-wavelength side of the glass.

However, according to the study of the inventors of the present invention, for example, the glass of the patent document 5 has a light absorption end on the short-wavelength side of the glass and a low transmittance in the ultraviolet region. Further, in the glass composition of the conventional high refractive index low-dispersion glass, when the content of Gd and Ta is reduced, and the high refractive index, low dispersion property, and thermal stability are simultaneously maintained, the light absorption end of the short-wavelength side of the glass is The wavelength is long and the transmittance of ultraviolet rays is greatly lowered.

Must be suitable for machining. The details are as follows. As a method of obtaining an optical element from glass, in addition to a precision press molding method (for example, refer to Patent Documents 1 to 4), an optical element blank is formed from glass and the optical element blank is formed. The material is subjected to machining such as grinding processing and polishing processing to finish the optical element. In such machining, when the glass is easily broken, the manufacturing yield is lowered. Generally, the glass transition temperature for precision press forming is low, but the glass having a low glass transition temperature tends to be easily broken by machining. Therefore, in order to become a glass suitable for machining, it is preferable to further improve the glass for precision press forming and the glass transition temperature.

One aspect of the present invention relates to a glass of an oxide glass (hereinafter referred to as "glass 1"), which is expressed by mass%, and the total content of B ₂ O ₃ and SiO ₂ is 15 to 35 mass%. The total content of La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ and Yb ₂ O ₃ is 45 to 65% by mass, but the Yb ₂ O ₃ content is 3% by mass or less, and the ZrO ₂ content is 3 to 11% by mass. The content of Ta ₂ O ₅ is 5% by mass or less, and the mass ratio of B ₂ O ₃ content to the total content of B ₂ O ₃ and SiO ₂ (B ₂ O ₃ /(B ₂ O ₃ + SiO ₂ )) is 0.4~ a mass ratio of the total content of 0.900, B ₂ O ₃ and SiO _{2 to} the total content of La ₂ O ₂ , Y ₃ O ₃ , Gd ₂ O ₃ and Yb ₂ O ₃ ((B ₂ O ₃ + SiO ₂ ) / ( La ₂ O ₃ +Y ₂ O ₃ +Gd ₂ O ₃ +Yb ₂ O ₃ )) is 0.42 to 0.53, and Y ₂ O ₃ content is La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ and Yb ₂ O ₃ mass ratio of total content (Y ₂ O ₃ /(La ₂ O ₃ +Y ₂ O ₃ +Gd ₂ O ₃ +Yb ₂ O ₃ ) is 0.05 to 0.45, and Gd ₂ O ₃ content is La ₂ O ₃ , Y The mass ratio of the total content of ₂ O ₃ , Gd ₂ O ₃ and Yb ₂ O ₃ (Gd ₂ O ₃ /(La ₂ O ₃ +Y ₂ O ₃ +Gd ₂ O ₃ +Yb ₂ O ₃ )) is 0~ 0.05,, TiO ₂ mass content of Nb ₂ O ₅ Nb ₂ O _5, the total content of Ta ₂ O ₅ and WO ₃ is _{(Nb 2 O 5 / (Nb} 2 O 5 + TiO 2 + Ta 2 O 5 + WO 3)) is 0.5 to 1, a refractive index nd in a range of 1.800 ~ 1.850, and the Abbe number vd of 41.5 to 44.

Further, an aspect of the present invention relates to a glass of an oxide glass (hereinafter referred to as "glass 2"), which is represented by a cation %, and a total content of B ³⁺ and Si ⁴⁺ is 45 to 65%. The total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ is 25 to 35%, but the content of Yb ³⁺ is less than 2%, the content of Zr ⁴⁺ is 2 to 8%, and the content of Ta ⁵⁺ is 3% or less, the cation ratio (B ³⁺ /(B ³⁺ +Si ⁴⁺ )) of the B ³⁺ content to the total content of B ³⁺ and Si ⁴⁺ is 0.65 or more and less than 0.94, and B ³⁺ and Si ^{4 . +} cation ratio of the total content of the total contents of La ³⁺ , Y ³⁺ , Gd ^{3+ ,} and Yb ³⁺ ((B ³⁺ + Si ⁴⁺ ) / (La ³⁺ + Y ³⁺ + Gd ³⁺ + Yb ³⁺ )) is a cation ratio of 1.65 to 2.60, Y ³⁺ content to the total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ (Y ³⁺ /(La ³⁺ +Y ³⁺ + Gd ³⁺ +Yb ³⁺ )) is a cation ratio of 0.05 to 0.45, Gd ³⁺ content to the total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ (Gd ³⁺ /(La ³⁺ + Y ³⁺ +Gd ³⁺ +Yb ³⁺ )) is a cation ratio of 0 to 0.05, the total content of Nb ⁵⁺ to Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ (Nb ⁵⁺ /( Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ )) is 0.4 to 1, the refractive index nd is in the range of 1.800 to 1.850, and the Abbe number vd is 41.5 to 44.

The glass 1 is a glass having a refractive index nd and an Abbe number vd in the above range, and contains various components of Gd ₂ O ₃ (that is, La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ , and Yb ₂ O ₃ ). The total content is in the above range, and the above-mentioned mass ratio in which the Gd ₂ O ₃ content is set as a molecule and the total content of the above various components is set as a denominator is satisfied. Therefore, the proportion of Gd in the glass composition can be reduced. Further, the content of Ta ₂ O _{5 and the} content of Yb ₂ O ₃ are each as described above, and the ratio of Ta and Yb in the glass composition can also be reduced. In the composition in which the Gd, Ta, and Yb ratios are reduced as described above, by adjusting the composition satisfying the above content, the total content, and the mass ratio, high thermal stability can be achieved (transparency does not easily disappear). nature). Further, it is also possible to suppress the long wavelength of the light absorption end on the short-wavelength side and the high glass transition temperature (Tg) (higher temperature of the glass transition temperature).

The glass 2 has a refractive index nd and an Abbe number vd in the above range, and the total content of the various components including Gd ³⁺ (that is, La ³⁺ , Y ³⁺ , Gd ³⁺ , and Yb ³⁺ ) is the above. In the range, the above cation ratio in which the Gd ³⁺ content is set as a molecule and the total content of the above various components is set as a denominator is satisfied. Therefore, the proportion of Gd in the glass composition can be reduced. Further, the Ta ⁵⁺ content and the Yb ³⁺ content are each as described above, and the ratio of Ta and Yb in the glass composition can also be reduced. In the composition in which the Gd, Ta, and Yb ratios are reduced as described above, the composition can satisfy the above content, the total content, and the cation ratio, thereby achieving high thermal stability (a property in which transparency does not easily disappear). . Further, it is also possible to suppress the long wavelength of the light absorption end on the short-wavelength side and the high glass transition temperature (Tg) (higher temperature of the glass transition temperature).

According to an aspect of the present invention, it is possible to provide a glass which has high refractive index and low dispersion characteristics which are useful in an optical system and which can be stably supplied and which has excellent thermal stability. Moreover, according to an aspect of the present invention, it is possible to provide a glass material for press molding composed of the above glass, and an optical element blank. Materials, and optical components.

Fig. 1 shows a spectral transmittance curve of a thickness of 10.0 mm of glass A to be described later.

Fig. 2 is a graph showing a light transmittance curve of a thickness of 10.0 mm of glass B to be described later.

The glass composition of the present invention can be quantified by a method such as ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry). The analysis value obtained by ICP-AES is, for example, a measurement error of about ±5% of the analysis value. Further, in the present specification and the present invention, the content of the component is 0% or not or not, which means that the component is not substantially contained, and the content of the component is not more than the level of the impurity.

Hereinafter, the numerical range is described in the case where the (better) lower limit and the (more) good upper limit are shown in the table. In the table, the numerical value described below is better, and the numerical value described at the bottom is the best. In addition, unless otherwise stated, the (lower) lower limit means that the above-described value is (more) good, and the (more) good upper limit means that the value described below is (more) good. The numerical values described in the (better) lower limit of the table can be arbitrarily combined with the numerical values described in the (better) upper limit, and the numerical range can be defined.

[glass]

The glass 1 and the glass 2 according to an aspect of the present invention have the above glass composition, the refractive index nd is in the range of 1.800 to 1.850, and the Abbe number vd is an oxide glass of 41.5 to 44. Hereinafter, the glass 1 and the glass 2 will be described in detail.

<glass composition of glass 1>

In the present invention, the glass composition of the glass 1 is represented by an oxide standard. Here, the "glass composition based on the oxide" is a glass composition obtained by converting the glass raw material into a state in which all of the glass raw material is decomposed during melting and present as an oxide in the glass. In addition, unless otherwise specified, the glass composition of the glass 1 is represented by the mass (mass %, mass ratio).

A network structure forming component of B ₂ O ₃ or SiO ₂ -based glass. When the B ₂ O ₃ and the total content of SiO ₂ (B ₂ O ₃ + SiO ₂₎ is 15%, the thermal stability of the glass can be suppressed to enhance the crystallized glass manufacturing. On the other hand, when the total content of B ₂ O ₃ and SiO ₂ is 35% or less, since the refractive index nd can be suppressed from decreasing (decreasing), it is possible to produce a glass having the above optical characteristics, that is, the refractive index nd is 1.800 to 1.850. At the same time, the Abbe number vd is in the range of 41.5~44. Therefore, the total content of B ₂ O ₃ and SiO ₂ in the glass 1 is set to be in the range of 15 to 35. The lower limit of the total content of B ₂ O ₃ and SiO ₂ and the good upper limit are as shown in the following table.

The ratio of the content of each component of B ₂ O ₃ and SiO ₂ in the network structure forming component of the glass affects the thermal stability, the meltability, the moldability, the chemical durability, the weather resistance, the machinability, and the like of the glass. Although B ₂ O ₃ is more excellent in improving the meltability than SiO ₂ , it is easily volatilized at the time of melting. On the other hand, SiO ₂ has an effect of improving the chemical durability, weather resistance, machinability, or glass viscosity of the glass at the time of melting.

In general, a high refractive index low-dispersion glass containing a rare earth element such as B ₂ O _{3 or} La ₂ O _{3 is} low in viscosity when molten. However, when the viscosity of the glass at the time of melting is low, the thermal stability is lowered (it becomes easy to crystallize). The crystallization in the production of glass is more stable than crystallization, and is generated by crystallization in which the ions constituting the glass move in the glass and are arranged in a crystal structure. Therefore, by adjusting the ratio of the content of each component of B ₂ O ₃ and SiO ₂ so that the viscosity at the time of melting becomes high, the ions are not easily arranged in a crystal structure, and the crystallization of the glass can be further suppressed. And improve the thermal stability of the glass.

When the molten glass flows into the casting mold and is formed, when the viscosity of the molten glass is low, the surface portion of the glass which has flowed into the casting mold is still caught in the molten glass and becomes streaks, resulting in glass. Optical homogeneity is low. Among the high refractive index low-dispersion glass containing a rare earth element, the glass which is excellent in moldability corresponds to a glass having a relatively high viscosity when a molten glass is poured into a casting mold.

When the mass ratio of the B ₂ O ₃ content to the total content of B ₂ O ₃ and SiO ₂ (B ₂ O ₃ /(B ₂ O ₃ + SiO ₂ )) is 0.900 or less, the viscosity at the time of melting can be suppressed from being lowered. Thereby, the thermal stability of the glass can be improved, or the volatilization during melting can be suppressed.

Volatilization during melting causes a change in the glass composition and an increase in the characteristic variation. Moreover, as a result, it is difficult to form an optically homogeneous glass. Therefore, from the viewpoint of the glass having a small variation in mass production composition and characteristics, it is possible to suppress volatilization during melting by setting the mass ratio (B ₂ O ₃ /(B ₂ O ₃ + SiO ₂ )) to 0.900 or less. good. Further, when the mass ratio (B ₂ O ₃ /(B ₂ O ₃ + SiO ₂ )) is 0.900 or less, chemical durability, weather resistance, and machinability of the glass can be suppressed. In contrast, the glass composition described in the above-mentioned Patent Document 15 (JP-A-57-056344) has a B ₂ O ₃ content of 28 to 30% by mass and a SiO ₂ content of 1 to 3% by mass (refer to the patent literature). 15 patent application scope). The mass ratio (B ₂ O ₃ /(B ₂ O ₃ + SiO ₂ )) calculated from the content of the components is a large value of 0.903 to 0.968.

On the other hand, when the mass ratio (B ₂ O ₃ /(B ₂ O ₃ + SiO ₂ )) is 0.4 or more, the melting of the glass raw material at the time of melting can be prevented, so that the meltability can be improved.

From the above, the glass 1 has a mass ratio (B ₂ O ₃ /(B ₂ O ₃ + SiO ₂ )) in the range of 0.4 to 0.900. The lower limit of the mass ratio of the glass 1 (B ₂ O ₃ /(B ₂ O ₃ + SiO ₂ )) and the favorable upper limit are as shown in the following table.

For each of the content of B ₂ O _{3 and} the content of SiO ₂ , a good lower limit and a good upper limit are obtained from the improvement of thermal stability, meltability, moldability, chemical durability, weather resistance, mechanical processing, and the like of the glass. Displayed in the table below.

The La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ and Yb ₂ O ₃ systems have a function of increasing the refractive index while suppressing the decrease in the Abbe number. Moreover, these components also have the effect of improving the chemical durability of the glass, improving the weather resistance, and increasing the glass transition temperature. When the total content of La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ and Yb ₂ O ₃ (La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ ) is 45% or more, Since the refractive index can be suppressed from decreasing, it is possible to produce a glass having the above optical characteristics. Moreover, it is possible to suppress the chemical durability and the weather resistance of the glass from being lowered. Further, when the glass transition temperature is low, when the glass is machined (cut, cut, ground, polished, etc.), the glass is easily broken (machineability is low), but La ₂ O ₃ , Y ₂ O ₃ , Gd _When the total content of ₂ O ₃ and Yb ₂ O ₃ is 45% or more, the glass transition temperature can be suppressed from being lowered, so that the machinability can be improved. On the other hand, when the total content of La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ and Yb ₂ O ₃ is 65% or less, since the thermal stability of the glass can be improved, crystallization at the time of glass production can be suppressed. And reducing the melting of the raw material when the glass is melted. Therefore, in the glass 1, the total content of La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ and Yb ₂ O _{3 is} in the range of 45 to 65%. The lower limit of the total content of the total content of La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ and Yb ₂ O ₃ and the favorable upper limit are shown in the following table.

The ZrO ₂ system has a function of increasing the refractive index, and has an effect of improving the thermal stability of the glass by containing an appropriate amount. Further, the ZrO ₂ system increases the glass transition temperature and also has an effect that the glass is not easily broken during machining. In order to obtain such effects favorably, the content of ZrO ₂ in the glass 1 is set to 3% or more. On the other hand, when the content of ZrO ₂ is 11% or less, since the thermal stability of the glass can be improved, it is possible to suppress the occurrence of crystallization during the production of the glass and the occurrence of the unmelted residue in the glass melting. Therefore, the content of ZrO ₂ in the glass 1 is set to be in the range of 3 to 11%. The lower limit of the good ZrO ₂ content and the good upper limit are shown in the following table.

As described above, the Ta ₂ O ₅ system is preferably a component which is preferably reduced in the proportion of the glass composition from the viewpoint of stably supplying the glass. Further, the Ta ₂ O ₅ system has a function of increasing the refractive index, and also has a component which increases the specific gravity of the glass and lowers the meltability. Therefore, the content of Ta ₂ O ₅ in the glass 1 is set to 5% or less. The lower limit of the content of Ta ₂ O ₅ and the upper limit of goodness are shown in the following table.

In order to improve the thermal stability of the glass and suppress the increase in the specific gravity, in order to achieve the above optical characteristics, the total content of B ₂ O ₃ and SiO ₂ in the glass 1 is La ₂ O ₃ , Y ₂ O ₃ , The mass ratio of the total content of Gd ₂ O ₃ and Yb ₂ O ₃ ((B ₂ O ₃ + SiO ₂ ) / (La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ )) is set to Range of 0.42~0.53. When the mass ratio ((B ₂ O ₃ + SiO ₂ ) / (La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ )) is 0.42 or more, since the thermal stability of the glass can be improved, It is possible to suppress the disappearance of transparency of the glass. Moreover, it is also possible to suppress an increase in the specific gravity of the glass. When the specific gravity of the glass increases, the optical element manufactured using the glass becomes heavy. As a result, the optical system incorporating the optical element becomes heavier. For example, when a heavier optical component is incorporated into an autofocus camera, power consumption when driving autofocus increases and the battery is quickly consumed. From the viewpoint of reducing the weight of the optical element produced by using the glass and the optical system in which the optical element is incorporated, it is preferable to suppress an increase in the specific gravity of the glass. On the other hand, when the mass ratio ((B ₂ O ₃ + SiO ₂ ) / (La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ )) is 0.53 or less, the above optical characteristics can be achieved. . Further, from the viewpoint of improving the chemical durability of the glass and the high glass transition temperature (Tg), the mass ratio ((B ₂ O ₃ + SiO ₂ ) / (La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O) ₃ + Yb ₂ O ₃ )) is preferably 0.53 or less. The lower limit and the good upper limit of the mass ratio ((B ₂ O ₃ + SiO ₂ ) / (La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ ))) are shown in the following table.

Among the La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ and Yb ₂ O ₃ , Yb ₂ O ₃ is a component which is preferable in proportion to the glass composition, based on the reasons described above. Therefore, in the glass 1, the Yb ₂ O ₃ content is set to 3% or less. A good lower limit and a good upper limit of the Yb ₂ O ₃ content are shown in the following table.

The Y ₂ O ₃ system does not significantly reduce the light transmittance in the near-infrared region, but has a function of improving the thermal stability of the glass. Further, in terms of suppressing an increase in the specific gravity of the glass, since the atomic weight is small, it is a preferable component. However, when the content of Y ₂ O ₃ is too large, the thermal stability of the glass is remarkably low and crystallization is likely to occur. Moreover, the meltability is low. In the case of glass which is improved in thermal stability without significantly lowering the light transmittance in the near-infrared region and suppressing an increase in specific gravity and having the above optical characteristics, in the glass 1, the content of Y ₂ O _{3 is} Mass ratio of the total content of La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ and Yb ₂ O ₃ (Y ₂ O ₃ /(La ₂ O ₃ +Y ₂ O ₃ +Gd ₂ O ₃ +Yb ₂ O ₃ )) is set to a range of 0.05 to 0.45. The lower limit of the good mass ratio (Y ₂ O ₃ /(La ₂ O ₃ +Y ₂ O ₃ +Gd ₂ O ₃ +Yb ₂ O ₃ )) and the upper limit of goodness are shown in the following table.

For the reasons already described above, Gd ₂ O ₃ is preferably a component which reduces the proportion of the glass composition. Further, the Gd system is a heavy rare earth element similarly to Yb, and as a component of glass, the atomic weight is large and the specific gravity of the glass is increased. In this regard, Gd is also reduced in proportion to the proportion of glass composition. In the glass 1, the content of Gd ₂ O ₃ is determined by the total content of La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ and Yb ₂ O ₃ , and the Gd ₂ O ₃ content of the total content. .

In the glass 1, from the high refractive index low-dispersion glass having the above optical characteristics, and the glass having a small specific gravity as the high refractive index low-dispersion glass, the Gd ₂ O ₃ content is La Mass ratio of the total content of ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ and Yb ₂ O ₃ (Gd ₂ O ₃ /(La ₂ O ₃ +Y ₂ O ₃ +Gd ₂ O ₃ +Yb ₂ O ₃ )) Set to a range of 0 to 0.05. The lower limit of the good mass ratio (Gd ₂ O ₃ /(La ₂ O ₃ +Y ₂ O ₃ +Gd ₂ O ₃ +Yb ₂ O ₃ )) and the upper limit of goodness are shown in the following table.

The La ₂ O ₃ is a useful component in that the light transmittance in the near-infrared region is not greatly improved, and the thermal stability is improved while suppressing an increase in specific gravity and providing a high refractive index low-dispersion glass. Thus, the glass 1, based mass the total content of the La ₂ O ₃ content of _{La 2 O 3, Y 2 O} 3, Gd 2 O 3 and Yb ₂ O ₃ ratio _{(La 2 O 3 / (La} 2 O ₃ +Y ₂ O ₃ +Gd ₂ O ₃ +Yb ₂ O ₃ )) is preferably in the range of 0.55 to 0.95. The lower limit and the good upper limit of the mass ratio (La ₂ O ₃ /(La ₂ O ₃ +Y ₂ O ₃ +Gd ₂ O ₃ +Yb ₂ O ₃ )) are shown in the following table.

The lower limit of the content of each component of La ₂ O ₃ , Y ₂ O ₃ , and Gd ₂ O ₃ and the favorable upper limit are shown in the following table.

Nb ₂ O ₅ , TiO ₂ , Ta ₂ O ₅ and WO ₃ have a function of increasing the refractive index, and by containing an appropriate amount, also have an effect of improving the thermal stability of the glass. The total content of Nb ₂ O ₅ , TiO ₂ , Ta ₂ O ₅ and WO ₃ in terms of achieving the above optical properties while further improving the thermal stability of the glass (Nb ₂ O ₃ + TiO ₂ + Ta ₂ O ₅ + WO ₃ ) is preferably in the range of 3 to 15%. The lower limit and the good upper limit of the total content of the total contents of Nb ₂ O ₅ , TiO ₂ , Ta ₂ O ₅ and WO ₃ are shown in the following table.

When the glass is melted, the ZnO system has an effect of promoting the melting of the glass raw material, that is, improving the meltability. Further, it has an effect of adjusting the refractive index and the Abbe number or lowering the glass transition temperature. In order to improve the meltability, the value of the ZnO content divided by the total content of B ₂ O ₃ and SiO ₂ , that is, the mass ratio (ZnO/(B ₂ O ₃ + SiO ₂ )) is preferably 0.04 or more. On the other hand, in order to suppress the decrease in the Abbe number (high dispersion) and to achieve the above optical characteristics, the mass ratio (ZnO/(B ₂ O ₃ + SiO ₂ )) is preferably 0.4 or less. Further, in order to improve the thermal stability of the glass and the high glass transition temperature (Tg), the mass ratio (ZnO/(B ₂ O ₃ + SiO ₂ )) is preferably 0.4 or less. Therefore, the content of ZnO is set to be 0.04 to 0.4 times the total content of B ₂ O ₃ and SiO ₂ by mass ratio, that is, the mass ratio (ZnO/(B ₂ O ₃ + SiO ₂ )) is set. It is better to make 0.04~0.4. A good lower limit and a good upper limit of the mass ratio (ZnO/(B ₂ O ₃ + SiO ₂ )) are shown in the following table.

The lower limit of the favorable ZnO content and the favorable upper limit are as shown in the following table in order to achieve the above-mentioned optical characteristics in order to improve the meltability, heat stability, moldability, and machinability of the glass.

The total content of Nb ₂ O ₅ , TiO ₂ , Ta ₂ O ₅ and WO ₃ is adjusted to B ₂ O ₃ and SiO in order to achieve the above optical characteristics while suppressing an increase in the degree of coloration λ5 described later and increasing the ultraviolet transmittance of the glass. mass of the total content of better than _{2 ((B 2 O 3 + SiO} 2) / (Nb 2 O 5 + TiO 2 + Ta 2 O 5 + WO 3)), based in the range of 2.65 to 10 is set. Further, in terms of improving the thermal stability of the glass, the mass ratio ((B ₂ O ₃ + SiO ₂ ) / (Nb ₂ O ₅ + TiO ₂ + Ta ₂ O ₅ + WO ₃ )) is also set to 2.65. The above is better. The lower limit and the good upper limit of the mass ratio ((B ₂ O ₃ + SiO ₂ ) / (Nb ₂ O ₅ + TiO ₂ + Ta ₂ O ₅ + WO ₃ ))) are shown in the following table.

It has an effect of improving the thermal stability of the glass by appropriately containing Nb ₂ O ₅ , TiO ₂ , Ta ₂ O ₅ and WO ₃ .

Among these components, when the content of TiO ₂ is increased, the transmittance in the visible region of the glass is lowered and the coloration of the glass tends to increase.

The action against Ta ₂ O ₅ is as described above. In the case of WO ₃ , when the content is increased, the transmittance of the visible region of the glass is lowered and the coloration of the glass tends to increase, and the specific gravity tends to increase.

On the other hand, Nb ₂ O ₅ does not easily increase the specific gravity, coloration, and production cost of glass, and has an effect of increasing the refractive index and improving the thermal stability of the glass. Thus, the glass 1, in order to utilize Nb excellent ₂ O ₅ of action, the effect of Nb ₂ O ₅ content of Nb ₂ O _{5, 2} mass of the total content of Ta ₂ O ₅ and WO ₃ is TiO, ratio (Nb ₂ O ₅ /(Nb ₂ O ₅ +TiO ₂ +Ta ₂ O ₅ +WO ₃ )) is set to a range of 0.5 to 1. In order to lower the degree of coloring λ5 and promote the hardening of the ultraviolet curable type adhesive by ultraviolet irradiation, the mass ratio (Nb ₂ O ₅ /(Nb ₂ O ₅ +TiO ₂ +Ta ₂ O ₅ +WO _{3 ) is obtained.} )) Increase is better. The lower limit and a more preferable upper limit of the mass ratio (Nb ₂ O ₅ /(Nb ₂ O ₅ +TiO ₂ +Ta ₂ O ₅ +WO ₃ )) are shown in the following table.

For the reasons already described above, the Ta ₂ O ₅ system is not suitable for positive introduction into glass. Thus, among the described _{3 Nb 2 O 5, TiO 2,} Ta 2 O 5, and WO, the content of Nb ₂ O ₅ to the total content of Nb in addition to other than the _{2 O 5 Ta 2 O 5,} TiO 2 and WO ₃ is A preferred range of the mass ratio (Nb ₂ O ₅ /(Nb ₂ O ₅ +TiO ₂ +WO ₃ )). In order to produce a glass having excellent thermal stability and less coloration, the mass ratio (Nb ₂ O ₅ /(Nb ₂ O ₅ +TiO ₂ +WO ₃ )) is preferably in the range of 0.50 to 1. The lower limit and the more favorable upper limit of the mass ratio (Nb ₂ O ₅ /(Nb ₂ O ₅ +TiO ₂ +WO ₃ )) are shown in the following table.

From the viewpoint of improving the meltability, the mass ratio of the ZnO content to the total content of Nb ₂ O ₅ , TiO ₂ , Ta ₂ O ₅ and WO ₃ (ZnO/(Nb ₂ O ₅ +TiO ₂ +Ta ₂ O ₅ + It is preferable that WO ₃ )) is set to 0.1 or more. Further, in the case of a glass having low meltability, in order to increase the melting temperature of the glass and increase the melting time in order to prevent the glass raw material from being melted and remaining, the glass coloring tends to increase. When the glass is melted in a molten crucible made of a noble metal such as platinum, it is presumed that when the melting temperature is increased or the melting time is increased, the noble metal constituting the crucible is melted into the molten glass, and the light is absorbed by the noble metal ions to cause the glass to be colored, particularly The value of λ5 increases. On the other hand, when the meltability is to be improved by adjusting the content of other glass components, there is a case where the thermal stability is lowered or it is difficult to obtain a homogeneous glass having the above optical characteristics. Therefore, in order to improve the meltability of the glass, it is also preferable to set the mass ratio (ZnO/(Nb ₂ O ₅ + TiO ₂ + Ta ₂ O ₅ + WO ₃ )) to 0.1 or more in suppressing the coloration of the glass. Further, from the viewpoint of further improving the thermal stability of the glass, suppressing the low glass transition temperature, improving the machinability, and improving the chemical durability, the mass ratio (ZnO/(Nb ₂ O ₅ + TiO ₂ + Ta ₂ O) is used. ₅ +WO ₃ )) It is better to set it to 3 or less. The lower limit and the good upper limit of the mass ratio (ZnO/(Nb ₂ O ₅ + TiO ₂ + Ta ₂ O ₅ + WO ₃ )) are shown in the following table.

The lower limit and the good upper limit are shown in the following table for each of the Nb ₂ O ₅ content, the TiO ₂ content, and the WO ₃ content.

From the viewpoint of further improving the thermal stability of the glass, the Li ₂ O content is preferably 1 or less from the viewpoint of suppressing the deterioration of the glass transition temperature, improving the machinability, and improving chemical durability and weather resistance. The lower limit and the good upper limit of the favorable Li ₂ O content are shown in the following table.

Any of Na ₂ O, K ₂ O, Rb ₂ O, and Cs ₂ O has an effect of improving the meltability of the glass. When the content is increased, the thermal stability, chemical durability, weather resistance, and mechanical processing of the glass are increased. Sex lines show a tendency to be low. Therefore, the lower limit and the upper limit of the respective contents of Na ₂ O, K ₂ O, Rb ₂ O, and Cs ₂ O are preferably set as shown in the following table.

Rb ₂ O and Cs ₂ O are expensive components, and are less suitable for general-purpose glass components than Li ₂ O, Na ₂ O, and K ₂ O. Therefore, in order to maintain the thermal stability, chemical durability, weather resistance, and machinability of the glass while improving the meltability of the glass, the total content of Li ₂ O, Na ₂ O, and K ₂ O (Li ₂ O+Na) The lower limit and the upper limit of ₂ O+K ₂ O) are preferably set as shown in the following table.

Any of MgO, CaO, SrO, and BaO has a function of improving the meltability of the glass. However, when the content of these components is too large, the thermal stability of the glass is low and the transparency tends to disappear. Therefore, it is preferable that each content of each of these components is set to the lower limit or more shown below, and it is preferable to set it as an upper limit or less.

In addition, the total content of MgO, CaO, SrO, and BaO (MgO+CaO+SrO+BaO) is preferably at least the lower limit of the following table, and is preferably set to an upper limit or less. good.

The Al ₂ O ₃ system improves the chemical durability and weather resistance of the glass. However, when the content of Al ₂ O ₃ is increased, the refractive index tends to be lowered, the thermal stability of the glass tends to be low, and the meltability is low. The tendency. In consideration of the above, the content of Al ₂ O ₃ is preferably at least the lower limit shown in the following table, and preferably not more than the upper limit.

Any of Ga ₂ O ₃ , In ₂ O ₃ , Sc ₂ O ₃ , and HfO ₂ has an effect of increasing the refractive index nd. However, these components are expensive and are not essential components for obtaining the glass 1. Therefore, the content of each of Ga ₂ O ₃ , In ₂ O ₃ , Sc ₂ O ₃ , and HfO ₂ is preferably at least the lower limit shown in the following table, and is preferably equal to or less than the upper limit.

The Lu ₂ O ₃ system has an effect of increasing the refractive index nd and is also a component for increasing the specific gravity of the glass. Also, it is an expensive ingredient. In view of the above, the lower limit of the content of Lu ₂ O ₃ and the good upper limit are as shown in the following table.

The GeO ₂ system has an effect of increasing the refractive index nd, but is a particularly expensive component among the glass components which are generally used. In terms of reducing the manufacturing cost of the glass, the lower limit of the GeO ₂ content and the good upper limit are as shown in the following table.

The Bi ₂ O ₃ system is a component which lowers the Abbe number while increasing the refractive index nd. Further, it is also a component which tends to increase the coloration of the glass. From the viewpoint of producing a glass having the above-described optical characteristics and having less coloration, the lower limit of the favorable content of Bi ₂ O ₃ and the favorable upper limit are as shown in the following table.

Get the various effects described above. In view of the effect, the total content (total content) of each of the glass components described above is preferably more than 95%, more preferably more than 98%, more preferably more than 99%, and even more preferably more than 99.5%. .

Among the glass components described above, P ₂ O ₅ is a component which lowers the refractive index, and is a component which lowers the thermal stability of the glass. However, when a small amount is introduced, the thermal stability is improved. In order to produce a glass having excellent thermal stability while having the above optical characteristics, a good lower limit and a good upper limit of the P ₂ O ₅ content are as shown in the following table.

TeO ₂ is a component that increases the refractive index, but since it is toxic, it is preferable to reduce the content of TeO ₂ . A good lower limit and a good upper limit of the TeO ₂ content are shown in the following table.

Further, in each of the above tables, a (better) lower limit or a component of 0% is described, and the content is preferably 0%. The same is true for the total content of the plurality of components.

Each of Pb, As, Cd, Tl, Be, and Se is toxic. Therefore, it is preferred that the elements are not contained, that is, the elements are not introduced into the glass as the glass component.

Any of the U, Th, and Ra systems is a radioactive element. Therefore, it is preferred that the elements are not contained, that is, the elements are not introduced into the glass as the glass component.

V, Cr, Mn, Fe, Co, Ni, Cu, Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm, and Ce increase the coloration of the glass and become a source of fluorescence. It is not preferable to make the element for the optical element glass. Therefore, it is preferred that the elements are not contained, that is, the elements are not introduced into the glass as the glass component.

Sb and Sn can be arbitrarily added as a function of a clarifying agent. element.

The amount of addition of Sb is converted to Sb ₂ O ₃ and the composition of the glass based on the oxide is set to 0 to 0.11% by mass when the total content of the glass components other than Sb ₂ O ₃ is 100% by mass. The range is preferably from 0.01 to 0.08% by mass, more preferably from 0.02 to 0.05% by mass. Here, the "oxide-based glass composition" is a glass composition obtained by converting a glass raw material into a state in which all of the glass raw material is decomposed and present as an oxide in the glass. The content calculated by the above method is also used for the Sb ₂ O ₃ content of the glass composition shown in the table to be described later.

Sn is added in an amount, based on the composition in terms of SnO ₂ based on oxides and glass, the total content of the glass component other than the SnO ₂ is 100% by mass, so as to be the range of 0 to 1.0% by mass preferably to be 0 The range of 0.5% by mass is preferable, the range of 0 to 0.2% by mass is more preferably, and the content of 0% by mass is more preferably.

<glass composition of glass 2>

In the present invention, the glass composition of the glass 2 is described as a cationic component with respect to the cationic component. The cation % is a percentage of 100% of the total content of all the cationic components contained in the glass as is conventional.

The cation component is represented by, for example, B ³⁺ , Si ⁴⁺ , and La ³⁺ , and the valence of the cation component (for example, the valence of B ^{3+ is +3} , and the valence of Si ⁴⁺ is +4, The valence of La ³⁺ is +3) is a value determined by convention, and is similar to B, Si, and La described as B ₂ O ₃ , SiO ₂ , and La ₂ O _{3 on the} basis of oxide. The cation A is described as A ^s+ as a component of A _m O _n (A is a cation, O is an oxygen, and m is an integer determined by stoichiometry) on the basis of an oxide. Here, s=2n/m. Therefore, for example, when the glass composition is analyzed and quantified, the valence of the cationic component may not be analyzed. In the following, the total content (total content) of the content of the cationic component and the content of the plurality of cationic components is represented by the cationic percentage, unless otherwise specified. Further, the ratio of the cation % means that the ratio of the content of the cation components (including the total content of the plurality of cation components) is referred to as a cation ratio.

A network structure forming component of B ³⁺ and Si ⁴⁺ glass. When the total content of B ³⁺ and Si ⁴⁺ (B ³⁺ + Si ⁴⁺ ) is 45% or more, the thermal stability of the glass is improved, and crystallization of the glass during production can be suppressed. On the other hand, when the total content of B ³⁺ and Si ⁴⁺ is 65% or less, since the refractive index can be suppressed from decreasing, it is possible to produce a glass having the above optical characteristics, that is, the refractive index nd is in the range of 1.800 to 1.850. At the same time, the Abbe number ν d is a glass in the range of 41.5 to 44. Therefore, the total content of B ³⁺ and Si ⁴⁺ in the glass 2 is in the range of 45 to 65%. The lower limit and the good upper limit of the total content of B ³⁺ and Si ⁴⁺ are as shown in the following table.

The ratio of the content of each of the components of B ³⁺ and Si ^{4 +} of the network structure forming component of the glass affects the thermal stability, the meltability, the formability, the chemical durability, the weather resistance, the machinability, and the like of the glass. Compared with Si ⁴⁺ , B ³⁺ is excellent in improving the meltability, but is easily volatilized during melting. On the other hand, Si ⁴⁺ has an effect of improving the chemical durability, weather resistance, and machinability of glass, or improving the viscosity of glass during melting.

In general, a high refractive index low-dispersion glass containing a rare earth element such as B ^{3+ or} La ^{3+ is} low in viscosity when molten. However, when the viscosity of the glass at the time of melting is low, the thermal stability is lowered (it becomes easy to crystallize). The crystallization during the production of the glass is caused by the fact that the crystallization is more stable than the amorphous state, and the ions constituting the glass move in the glass and are arranged in such a manner as to have a crystal structure. Therefore, by adjusting the ratio of the contents of the respective components of B ³⁺ and Si ^{4 +} so that the viscosity at the time of melting becomes high, the ions are not easily arranged in a crystal structure, and the crystallization of the glass can be further suppressed. Improve the thermal stability of the glass.

When the molten glass flows into the casting mold and is formed, when the viscosity of the molten glass is low, the surface portion of the glass which has flowed into the casting mold is still caught in the molten glass and becomes streaks, resulting in glass. Optical homogeneity is low. Among the high refractive index low-dispersion glass containing a rare earth element, the glass which is excellent in moldability corresponds to a glass having a relatively high viscosity when a molten glass is poured into a casting mold.

B ³⁺ content of B ³⁺ cations and the total content of Si ⁴⁺ ratio of ^{(B 3+ / (B 3+ +} Si 4+)) is less than 0.94, when the melt viscosity can be suppressed low, thereby capable of The thermal stability of the glass is improved and the volatilization at the time of melting is suppressed. The volatilization at the time of melting is a cause of an increase in the composition change of the glass and a change in characteristics. Further, as a result, it is difficult to form an optically homogeneous glass. Therefore, from the viewpoint of the glass having a small mass composition and a small variation in characteristics, it is preferable to set the cation ratio (B ³⁺ /(B ³⁺ +Si ⁴⁺ )) to less than 0.94 to suppress volatilization during melting. Further, when the cation ratio (B ³⁺ /(B ³⁺ +Si ⁴⁺ )) is less than 0.94, chemical durability, weather resistance, and machinability of the glass can be suppressed. In contrast, the glass composition described in the above-mentioned Patent Document 15 (JP-A-57-056344) has a B ₂ O ₃ content of 28 to 30% by mass and a SiO ₂ content of 1 to 3% by mass. (Refer to the patent application scope of Patent Document 15). The cation ratio (B ³⁺ /(B ³⁺ +Si ⁴⁺ )) calculated from the content of these components is a large value of 0.942 to 0.981.

On the other hand, when the cation ratio (B ³⁺ /(B ³⁺ +Si ⁴⁺ )) is 0.65 or more, the melting of the glass raw material at the time of melting can be prevented, so that the meltability can be improved.

From the above, in the glass 2, the cation ratio (B ³⁺ /(B ³⁺ +Si ⁴⁺ )) is set to 0.65 or more and less than 0.94. The lower limit and a good upper limit of the cation ratio (B ³⁺ /(B ³⁺ +Si ⁴⁺ )) of the glass 2 are as shown in the following table.

For each of the content of B ^{3+ and} the content of Si ⁴⁺ , a good lower limit and a good upper limit are obtained in terms of improving the thermal stability, meltability, moldability, chemical durability, weather resistance, mechanical processing, and the like of the glass. Displayed in the table below.

La ³⁺ , Y ³⁺ , Gd ^{3+ ,} and Yb ³⁺ are components having an effect of suppressing the Abbe number and increasing the refractive index. Moreover, these components also have the effect of improving the chemical durability and weather resistance of the glass and increasing the glass transition temperature.

When the total content of La ³⁺ , Y ³⁺ , Gd ^{3+ ,} and Yb ³⁺ (La ³⁺ + Y ³⁺ + Gd ³⁺ + Yb ³⁺ ) is 25% or more, since the refractive index can be suppressed from decreasing, it is possible to A glass having the above optical characteristics is produced. Moreover, it is also possible to suppress the chemical durability and the weather resistance of the glass from being lowered. Further, when the glass transition temperature is low, when the glass is machined (cut, cut, ground, polished, etc.), the glass is easily broken (machineability is low), but La ³⁺ , Y ³⁺ , Gd ^{3 When} the total content of ⁺ and Yb ³⁺ is 25% or more, since the glass transition temperature can be suppressed from being lowered, the machinability can be improved. On the other hand, when the total content of La ³⁺ , Y ³⁺ , Gd ^{3+ ,} and Yb ³⁺ is 35% or less, since the thermal stability of the glass can be improved, crystallization during production of the glass can be suppressed, and The melting of the raw material when the glass melts remains. Therefore, in the glass 2, the total content of La ³⁺ , Y ³⁺ , Gd ^{3+ ,} and Yb ^{3+ is} in the range of 25 to 35%. The lower limit and the good upper limit of the total content of the total contents of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ are shown in the following table.

Zr ⁴⁺ is a component which increases the refractive index and, by containing an appropriate amount, also has an effect of improving the thermal stability of the glass. Further, Zr ⁴⁺ also has an effect of increasing the glass transition temperature and not easily breaking the glass during machining. In order to obtain such effects favorably, in the glass 2, the content of Zr ⁴⁺ is set to 2% or more. On the other hand, when the content of Zr ⁴⁺ is 8% or less, since the thermal stability of the glass can be improved, it is possible to suppress the crystallization during the production of the glass and the melting residue during the glass melting. Therefore, the content of Zr ⁴⁺ in the glass 2 is in the range of 2 to 8%. A good lower limit and a good upper limit of the Zr ⁴⁺ content are shown in the following table.

As described above, the Ta ⁵⁺ system is preferably a component which reduces the proportion of the glass composition from the viewpoint of stably supplying the glass. Further, Ta ⁵⁺ is a component having an effect of increasing the refractive index, but is also a component which increases the specific gravity of the glass and lowers the meltability. Therefore, the Ta ⁵⁺ content of the glass 2 is set to 3% or less. The lower limit of the content of Ta ⁵⁺ and the upper limit of goodness are shown in the following table.

In order to improve the thermal stability of the glass and suppress the increase in specific gravity and achieve the above optical characteristics, in the glass 2, the total content of B ³⁺ and Si ⁴⁺ is La ³⁺ , Y ³⁺ , Gd ³⁺ and total content of Yb ³⁺ cation ratio of ^{((B 3+ + Si 4+)} / (La 3+ + Y 3+ + Gd 3+ + Yb 3+)) is set in the range of 1.65 to 2.60. When the cation ratio ((B ³⁺ +Si ⁴⁺ )/(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ ))) is 1.65 or more, since the thermal stability of the glass can be improved, the glass can be suppressed. The transparency disappears. Moreover, it is also possible to suppress an increase in the specific gravity of the glass. When the specific gravity of the glass increases, the optical element manufactured using the glass becomes heavy. As a result, the optical system incorporating the optical element becomes heavier. For example, when a heavier optical component is incorporated into an autofocus camera, power consumption when driving autofocus increases and the battery is quickly consumed. From the viewpoint of reducing the weight of the optical element produced by using the glass and the optical system in which the optical element is incorporated, it is preferable to suppress an increase in the specific gravity of the glass. On the other hand, when the cation ratio ((B ³⁺ + Si ⁴⁺ ) / (La ³⁺ + Y ³⁺ + Gd ³⁺ + Yb ³⁺ ))) is 2.60 or less, the above optical characteristics can be achieved. Further, from the viewpoint of improving the chemical durability of the glass and the high glass transition temperature (Tg), the cation ratio ((B ³⁺ + Si ⁴⁺ ) / (La ³⁺ + Y ³⁺ + Gd ³⁺ + Yb) ³⁺ )) is also better than 2.60. The lower limit and the good upper limit of the cation ratio ((B ³⁺ + Si ⁴⁺ ) / (La ³⁺ + Y ³⁺ + Gd ³⁺ + Yb ³⁺ ))) are shown in the following table.

Among La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ , Yb ³⁺ is a component which is preferable in proportion to the glass composition, based on the reasons described above. Therefore, in the glass 2, the Yb ³⁺ content is set to be less than 2%. The lower limit and the good upper limit of the good Yb ³⁺ content are shown in the following table.

Y ³⁺ is a component that does not greatly reduce the light transmittance in the near-infrared region and improves the thermal stability of the glass. Further, since the atomic weight is small, it is a preferable component in terms of suppressing an increase in the specific gravity of the glass. However, when the Y ³⁺ content is too much, the thermal stability of the glass is remarkably low and it is easy to crystallize. Moreover, the meltability is low. While improving the thermal stability, the light transmittance in the near-infrared region is not greatly lowered, and the content of Y ³⁺ is increased in the glass 2 from the case where the specific gravity is increased and the optical properties having the above optical characteristics are produced. The cation ratio (Y ³⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )) to the total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ is set to 0.05 to 0.45 The scope. The lower limit of the good cation ratio (Y ³⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )) and the upper limit of goodness are shown in the following table.

For the reasons already described above, Gd ³⁺ is a component which is preferable in proportion to the glass composition. Further, the Gd system is a heavy rare earth element similarly to Yb, and as a glass component, the atomic weight is large and the specific gravity of the glass is increased. In this regard, Gd is preferred to reduce the proportion of glass composition.

In the glass 2, the content of Gd ³⁺ is determined according to the total content of La ³⁺ , Y ³⁺ , Gd ^{3+ ,} and Yb ³⁺ , and the Gd ³⁺ content. In the glass 2, a high refractive index low-dispersion glass having the above-described optical characteristics is stably supplied, and from a glass having a small specific gravity, as a high refractive index low-dispersion glass, a Gd ³⁺ content is applied to La. The cation ratio (Gd ³⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )) of the total content of ³⁺ , Y ³⁺ , Gd ^{3+ ,} and Yb ³⁺ is set to a range of 0 to 0.05. . The lower limit of the good cation ratio (Gd ³⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )) and the upper limit of goodness are shown in the following table.

The La ³⁺ system does not cause a large drop in light transmittance in the near-infrared region and improves thermal stability, and at the same time, it can suppress an increase in specific gravity, and is a useful component for providing a high refractive index low-dispersion glass. Thus, the glass 2, the total content based cationic content of La ³⁺ La ^3+, Y ^3+, Gd3 and Yb ³⁺ ratio ^{(La 3+ / (La 3+ +} Y 3+ + Gd 3+ + Yb ³⁺ )) is preferably in the range of 0.55 to 0.95. The lower limit of the good cation ratio (La ³⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )) and the upper limit of goodness are shown in the following table.

The lower limit of the content of each component of La ³⁺ , Y ³⁺ , and Gd ³⁺ and the favorable upper limit are shown in the following table.

Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ are components which increase the refractive index, and have an effect of improving the thermal stability of the glass by containing an appropriate amount. The total content of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ in terms of achieving the above optical properties while further improving the thermal stability of the glass (Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ ) is preferably in the range of 2 to 10%. The lower limit and the good upper limit of the total content of the total contents of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ are shown in the following table.

When the glass is melted, the Zn ²⁺ system has an effect of promoting the melting of the glass raw material, that is, it has an effect of improving the meltability. Moreover, it also has the effect of adjusting the refractive index and the Abbe number, or lowering the glass transition temperature. In terms of improving the meltability, the value of the Zn ²⁺ content divided by the total content of B ³⁺ and Si ⁴⁺ , that is, the cation ratio (Zn ²⁺ /(B ³⁺ +Si ⁴⁺ )), is 0.01. The above is better. On the other hand, in order to suppress the Abbe number decrease (high dispersion) and achieve the above optical characteristics, the cation ratio (Zn ²⁺ /(B ³⁺ +Si ⁴⁺ )) is preferably 0.22 or less. Further, in order to improve the thermal stability of the glass and the high glass transition temperature (Tg), the cation ratio (Zn ²⁺ /(B ³⁺ +Si ⁴⁺ )) is preferably 0.22 or less. Accordingly, in order to train the cation ratio of Zn content ²⁺ B ³⁺ is set to 0.22 and 0.01 times the total content of Si ^4+, i.e., the cation ratio ^{(Zn 2+ / (B 3+ +} Si 4+) ) It is better to set it to 0.01~0.22. The lower limit of the good cation ratio (Zn ²⁺ /(B ³⁺ +Si ⁴⁺ )) and the upper limit of goodness are shown in the following table.

From the viewpoint of achieving the above optical characteristics and improving the meltability, heat stability, moldability, machinability, and the like of the glass, the lower limit of the favorable content of Zn ²⁺ and the favorable upper limit are as shown in the following table.

The total content of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ is proportional to B ³⁺ and Si ^{4 in order} to achieve the above optical characteristics while suppressing an increase in the chromaticity λ5 to be described later and increasing the ultraviolet transmittance of the glass. ⁺ cation total content ratio ^{((B 3+ + Si 4+)} / (Nb 5+ + Ti 4+ + Ta 5+ + W 6+)), is set to line 32 in the range of preferably 9.0 ~. Further, in terms of improving the thermal stability of the glass, the cation ratio ((B ³⁺ + Si ⁴⁺ )/(Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ )) is also set to 9.0. The above is better. A good lower limit and a good upper limit of the cation ratio ((B ³⁺ + Si ⁴⁺ ) / (Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ ))) are shown in the following table.

Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ have an effect of improving the thermal stability of the glass by making it appropriate.

Among these components, when the content of Ti ⁴⁺ is increased, the transmittance of the visible region of the glass is lowered and the coloration of the glass tends to increase.

The effect on Ta ⁵⁺ is as described above.

When W ^{6+ is} increased in content, the transmittance of the visible region of the glass tends to decrease and the coloration of the glass tends to increase, and the specific gravity tends to increase.

On the other hand, Nb ⁵⁺ does not easily increase the specific gravity, coloring, and manufacturing cost of the glass, and has an effect of increasing the refractive index and improving the thermal stability of the glass. Thus the glass 2, in order to utilize the excellent effect of Nb ^5+, effects, based on the content of Nb ⁵⁺ Nb ^5+, Ti ^4+, Ta ⁵⁺ cation and the total content of W ⁶⁺ ratio (Nb ⁵⁺ /(Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )) is set to a range of 0.4 to 1. The cation ratio (Nb ⁵⁺ /(Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ )) is increased by decreasing the degree of coloring λ5 and promoting the hardening of the ultraviolet curable adhesive by ultraviolet irradiation. Great. The lower limit of the good cation ratio (Nb ⁵⁺ /(Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )) and the upper limit of goodness are shown in the following table.

For the reasons already described above, it is preferred that Ta ⁵⁺ is introduced into the glass without being actively introduced. Therefore, for among Nb ^5+, Ti ^4+, Ta ⁵⁺ and W ^6+, the content of Nb ⁵⁺ on the outside except for Nb ^{5+ 5+} Ta, a total cation content of Ti ⁴⁺ and W ⁶⁺ of A preferred range of the ratio (Nb ⁵⁺ /(Nb ⁵⁺ +Ti ⁴⁺ +W ⁶⁺ )) will be described. In order to produce a glass having excellent thermal stability and less coloration, the cation ratio (Nb ⁵⁺ /(Nb ⁵⁺ + Ti ⁴⁺ + W ⁶⁺ )) is preferably in the range of 0.4 to 1. A good lower limit and a good upper limit of the cation ratio (Nb ⁵⁺ /(Nb ⁵⁺ +Ti ⁴⁺ +W ⁶⁺ )) are shown in the following table.

From the viewpoint enhance meltability, the total content of Zn ²⁺ cation content of Nb ^5+, Ti ^4+, Ta ^5+, and W ⁶⁺ ratio ^{(Zn 2+ / (Nb 5+ +} Ti 4+ + Ta ⁵⁺ + W ⁶⁺ )) is preferably set to 0.1 or more. Further, in the case of a glass having a low meltability, when the melting temperature of the glass is increased to prevent the glass raw material from being melted or when the melting time is increased, the glass coloring tends to increase. It is presumed that, for example, when the glass is melted in a molten crucible made of a noble metal such as platinum, when the melting temperature is increased or the melting time is increased, the noble metal constituting the crucible is melted into the molten glass, and the glass is colored due to light absorption by the noble metal ions. It is the value of λ5 increases. On the other hand, when the meltability is improved by adjusting the content of other glass components, there is a case where the thermal stability is lowered or it is difficult to obtain a homogeneous glass having the above optical characteristics. Therefore, in order to suppress the glass meltability, it is also preferable to set the cation ratio (Zn ²⁺ /(Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ )) to 0.1 or more in suppressing the coloration of the glass. Further, from the viewpoint of further improving the thermal stability of the glass and suppressing the decrease in the glass transition temperature (by thereby improving the machinability) and improving the chemical durability, the cation ratio (Zn ²⁺ /(Nb ^{5 ) is used. +} +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )) It is preferable to set it to 5 or less. The lower limit and the good upper limit of the cation ratio (Zn ²⁺ /(Nb ⁵⁺ + Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )) are shown in the following table.

The lower limit and the good upper limit are shown in the following table for each of the Nb ⁵⁺ content, the Ti ⁴⁺ content, and the W ⁶⁺ content.

The Li ⁺ content is more preferably 3% or less from the viewpoint of improving the thermal stability of the glass, suppressing the glass transition temperature from being lowered (by thereby improving the machinability), and improving chemical durability and weather resistance. A good lower limit and a more favorable upper limit of the Li ⁺ content are shown in the following table.

Any of Na ⁺ , K ⁺ , Rb ⁺ , and Cs ⁺ has an effect of improving the meltability of the glass. However, when the content is increased, the thermal stability, chemical durability, weather resistance, and machinability of the glass are shown. The tendency to be low. Therefore, the lower limit and the upper limit of the respective contents of Na ⁺ , K ⁺ , Rb ⁺ and Cs ⁺ are preferably set as shown in the following table.

Rb ⁺ and Cs ⁺ are expensive components, and are less suitable for general glass components than Li ⁺ , Na ⁺ , and K ⁺ . Therefore, in order to improve the glass meltability, the total content of Li ⁺ , Na ⁺ and K ⁺ (Li ⁺ +Na ⁺ +K ^{+ ) is} maintained while maintaining the glass thermal stability, chemical durability, weather resistance, and machinability. The lower limit and the upper limit of each are preferably as shown in the following table.

Any of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , and Ba ²⁺ has a function of improving the glass meltability. However, when the content of these components is increased, the thermal stability of the glass tends to be low and the transparency tends to disappear. Therefore, it is preferable that each content of the components is set to be equal to or lower than the lower limit shown below, and it is preferably equal to or less than the upper limit.

Further, in terms of further improving the thermal stability of the glass, the total content of Mg ²⁺ , Ca ²⁺ , Sr ^{2+ ,} and Ba ²⁺ (Mg ²⁺ + Ca ²⁺ + Sr ²⁺ + Ba ²⁺ ) is It is preferable to set it as the lower limit or more shown in the following table, and it is preferable to set it as an upper limit or less.

Al ³⁺ is a component having an effect of improving the chemical durability and weather resistance of the glass. However, when the content of Al ³⁺ is increased, the tendency of the refractive index to be lowered, the thermal stability of the glass tends to be lowered, and the meltability tends to be low. In view of the above, the Al ³⁺ content is preferably at least the lower limit shown in the following table, and preferably at most the lower limit.

Any of Ga ³⁺ , In ³⁺ , Sc ³⁺ , and Hf ⁴⁺ has an effect of increasing the refractive index. However, these components are expensive and are not essential components for obtaining the glass 2. Therefore, the content of each of Ga ³⁺ , In ³⁺ , Sc ³⁺ , and Hf ⁴⁺ is preferably at least the lower limit shown in the following table, and is preferably equal to or less than the upper limit.

Lu ³⁺ has the effect of increasing the refractive index, but is also a component that increases the specific gravity of the glass. Also, it is an expensive ingredient. From the above, the lower limit of the content of Lu ³⁺ and the good upper limit are as shown in the following table.

The Ge ⁴⁺ system has an effect of increasing the refractive index, but is a particularly expensive component among the glass components generally used. In terms of reducing the manufacturing cost of the glass, the lower limit of the Ge ⁴⁺ content and the good upper limit are as shown in the following table.

Bi ³⁺ is a component that lowers the Abbe number while increasing the refractive index. Moreover, it is also a component which makes a glass easy to color. For the glass having the above optical characteristics and having less coloration, the lower limit of the Bi ³⁺ content and the upper limit of goodness are as shown in the following table.

Good to get the various effects described above. The effect is that the total content (total content) of the above-described cationic component is preferably more than 95%, more preferably more than 98%, more preferably more than 99%, and even more preferably more than 99.5%. .

Among the cation components other than the above-mentioned cationic component, P ⁵⁺ is a component which ^lowers the refractive index, and is a component which lowers the thermal stability of the glass. However, when a small amount is introduced, the thermal stability of the glass is improved. situation. In order to produce a glass having excellent thermal stability while having the above optical characteristics, a good lower limit and a good upper limit of the P ⁵⁺ content are as shown in the following table.

Te ⁴⁺ is a component that increases the refractive index, but it is preferable to reduce the content of Te ⁴⁺ because it is toxic. The lower limit of the Te ⁴⁺ content and the good upper limit are as shown in the following table.

Further, in each of the above tables, a (better) lower limit or a component of 0% is described, and the content thereof is preferably 0%. The total content of the plurality of components is also the same.

Each of Pb, As, Cd, Tl, Be, and Se is toxic. Therefore, it is preferred that the elements are not contained, that is, the elements are not introduced into the glass as the glass component.

Any of the U, Th, and Ra systems are radioactive elements. Therefore, it is preferred that the elements are not contained, that is, the elements are not introduced into the glass as the glass component.

V, Cr, Mn, Fe, Co, Ni, Cu, Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm, and Ce, which increase the coloration of the glass and become a source of fluorescence. It is not preferable as an element contained in the glass for an optical element. Therefore, it is preferred that the elements are not contained, that is, the elements are not introduced into the glass as the glass component.

Sb and Sn are elements which can be arbitrarily added as a function of a clarifying agent.

The amount of addition of Sb is converted to Sb ₂ O ₃ and the composition of the glass based on the oxide is set to 0 to 0.11% by mass when the total content of the glass components other than Sb ₂ O ₃ is 100% by mass. The range is preferably from 0.01 to 0.08% by mass, more preferably from 0.02 to 0.05% by mass. Here, the "oxide-based glass composition" is a glass composition obtained by converting a glass raw material into a state in which all of the glass raw material is decomposed and present as an oxide in the glass. The content calculated by the above method is also used for the Sb ₂ O ₃ content of the glass composition shown in the table to be described later.

Sn is added in an amount, based on the composition in terms of SnO ₂ based on oxides and glass, the total content of the glass component other than the SnO ₂ is 100% by mass, so as to be the range of 0 to 1.0% by mass preferably to be 0 The range of 0.5% by mass is preferable, the range of 0 to 0.2% by mass is more preferably, and the content of 0% by mass is more preferably.

The cationic component has been described above. Next, the anion component will be described.

Since the glass 2 is an oxide glass, it contains O ^2- as an anion component. The content of O ^2- is preferably in the range of 98 to 100 anionic %, preferably in the range of 99 to 100 anionic %, more preferably 99.5 to 100 anionic %, and even more preferably 100 anionic %.

Examples of the anion component other than O ²⁻ are F ⁻ , Cl ⁻ , Br ⁻ , and I ⁻ . However, any of F ^- , Cl ^- , Br ^- , and I ^- is easily volatilized in the melting of the glass. Due to the volatilization of these components, there is a tendency that the glass characteristics are changed, the homogeneity of the glass is lowered, or the consumption of the melting equipment becomes remarkable. Therefore, it is preferable to suppress the total content of F ^- , Cl ^- , Br ^- and I ^{- to} the amount obtained by subtracting the content of O ^2- from 100 anions %.

Further, the anionic % is conventionally obtained by setting the total content of all the anionic components contained in the glass to a percentage of 100%.

<glass characteristics>

Next, the common glass characteristics of the glass 1 and the glass 2 will be described. The glass described below means glass 1 and glass 2.

(Optical properties of glass)

The refractive index nd of the above glass is in the range of 1.800 to 1.850, and the Abbe number ν d is 41.5 to 44.

A glass having a refractive index of 1.800 or more is suitable as a material for an optical element such as a lens having a large refractive power. On the other hand, when the refractive index is higher than 1.850, the Abbe number is decreased, or the thermal stability of the glass tends to be lowered, and the coloring tends to increase. The lower limit of the good refractive index and the upper limit of goodness are shown in the following table.

A glass having an Abbe number of 41.5 or more is used as an optical element material effective for correcting chromatic aberration. On the other hand, when the Abbe number is more than 44, there is a tendency that the refractive index is decreased or the thermal stability of the glass is lowered. The lower limit of the good Abbe number and the good upper limit are shown in the following table.

(partial dispersion characteristics)

From the viewpoint of chromatic aberration correction, in the case where the above-mentioned glass system has an Abbe number, it is preferable to use a glass having a small partial dispersion ratio.

Here, the partial dispersion ratio Pg, F is expressed by (g-nF)/(nF-nC) in the respective refractive indices ng, nF, and n of the g-ray (the wavelength of mercury is 435.84 nm), the F-ray, and the C-ray.

In order to provide a glass suitable for high-order chromatic aberration correction, the lower limit and the good upper limit of the partial dispersion ratio Pg, F of the above glass are shown in the following table.

(glass transition temperature)

From the viewpoint of improving the machined part, the glass transition temperature of the above glass is preferably 640 C or more. When the glass transition temperature is 640 ° C or higher, the glass can be machined during cutting, cutting, grinding, polishing, etc. Glass is not easy to break.

On the other hand, excessively increasing the glass transition temperature requires annealing the glass at a high temperature, so that the annealing furnace is significantly consumed. Further, when the glass is molded, it is necessary to perform molding at a relatively high temperature, so that the consumption of the mold used for molding becomes remarkable.

From the viewpoint of improving the machinability and reducing the burden on the annealing furnace and the molding die, the lower limit of the glass transition temperature and the favorable upper limit are as shown in the following table.

(light transmission of glass)

The light transmittance of the glass, in particular, can suppress the long wavelength of the light absorption end on the short wavelength side, and can be evaluated by the degree of coloring λ5. The degree of coloration λ5 is a wavelength at which the light transmittance (including surface reflection loss) of the glass having a thickness of 10 mm is 5% from the ultraviolet region to the visible region. Λ5 shown in the examples described later is a value measured in a wavelength region of 250 to 700 nm. The spectral transmittance is, for example, more specifically, a glass sample having a thickness of 10.0 ± 0.1 mm and optically polished with planes parallel to each other, and a spectroscopic light obtained by incident light to the surface of the optically polished surface. The transmittance is also set such that the intensity of the light incident on the glass sample is Iin, and the intensity of the light transmitted through the glass sample is set as the intensity ratio Iout/Iin when Iout.

According to the degree of coloring λ5, the absorption end on the short-wavelength side of the spectral transmittance can be quantitatively evaluated. As described above, in order to manufacture a cemented lens, an ultraviolet curing type is used, and then, when the lenses are joined to each other, the adhesive is irradiated with ultraviolet rays by an optical element to cure the adhesive. In order to efficiently perform the curing of the ultraviolet curable adhesive, the absorption end on the short wavelength side of the spectral transmittance is preferably in a shorter wavelength region. The coloring degree λ5 can be used as a quantitative evaluation of the absorption end on the short-wavelength side. The glass is preferably 335 nm or less, preferably 332 nm or less, more preferably 330 nm or less, still more preferably 328 nm or less, still more preferably λ nm or less λ5 by adjusting the composition described above. As an example, the lower limit of λ5 can set 315 nm as a standard and is preferably as low as possible, and is not particularly limited.

On the other hand, as a coloring index of glass, the coloring degree λ70 is mentioned. Λ70 is a wavelength at which the spectral transmittance measured by the method described in λ5 is 70%. In the case of a glass which is less colored, the range of λ70 is preferably 420 nm or less, more preferably 400 mm or less, still more preferably 390 nm or less, and still more preferably 380 nm or less. The lower limit of λ70 is 340 nm, and the lower the better, the other is not particularly limited.

Moreover, as a coloring index of glass, the coloring degree λ80 is also mentioned. Λ80 is a wavelength at which the spectral transmittance measured by the method described in λ5 is 80%. In the case of a glass which is less colored, the range of λ80 is preferably 480 nm or less, preferably 460 mm or less, more preferably 440 nm or less, and still more preferably 420 nm or less. The lower limit standard of λ80 is 350 nm, and the lower the better, the other is not particularly limited.

(specific gravity of glass)

The optical element (lens) constituting the optical system determines the refractive power in accordance with the refractive index of the glass constituting the lens and the curvature of the optical functional surface of the lens (the surface on which the light to be controlled is incident and emitted). When the curvature of the optical functional surface is to be increased, the thickness of the lens is also increased. As a result, the lens becomes heavier. On the other hand, using a glass having a high refractive index can obtain a large refractive power without increasing the curvature of the optical functional surface.

From the above, as long as the refractive index can be increased while suppressing an increase in the specific gravity of the glass, the optical element having a certain refractive power can be made lighter.

The contribution of the refractive index nd to the refractive power can be obtained as a lighter optical element by using the ratio of the glass specific gravity d to the value (nd-1) obtained by subtracting the refractive index 1 of the vacuum from the refractive index nd of the glass. Quantitative indicators. In other words, d/(nd-1) is used as an index for reducing the weight of the optical element, and by reducing the value, it is possible to reduce the weight of the optical element.

Since the Gd, Ta, and Yb ratios which increase the specific gravity of the glass system are small, the glass has a high refractive index and low dispersion glass, but can be made low in specific gravity. Therefore, the d/(nd-1) of the above glass can be, for example, 5.70 or less. However, when d/(nd-1) is excessively reduced, the thermal stability of the glass tends to be low. Therefore, d/(nd-1) is preferably 5.00 or more. The lower limit of good d/(nd-1) and the upper limit of goodness are shown in the following table.

Further, the lower limit of the specific gravity d of the glass and the favorable upper limit are shown in the following table. From the viewpoint of weight reduction of the optical element composed of the glass, it is preferable that the specific gravity d is equal to or higher than the upper limit shown in the following table. Moreover, in order to further improve the thermal stability of the glass, it is preferable that the specific gravity is at least the lower limit shown in the following table.

(liquidus temperature)

The liquidus temperature is one of the thermal stability indicators of glass. The liquidus temperature LT is preferably 1300 ° C or lower, preferably 1250 ° C or lower, more preferably 1200 ° C or less, and even more preferably 1150 ° C or less, in order to suppress crystallization and transparency disappearance in the production of glass. . The lower limit of the liquidus temperature LT is preferably 1100 ° C or more as an example, and is preferably lower, but is not particularly limited.

From the aspect of the invention described above, such glass (glass 1 and glass 2) is a high refractive index low dispersion glass, and is useful as a glass material for optical elements. Moreover, the glass can also be homogenized and reduced in coloration by the composition adjustment described above. Further, the above-mentioned glass system is easy to mold and easy to machine. Therefore, the above glass is suitable as an optical glass.

<Method of Manufacturing Glass>

The glass system can be obtained by mixing, blending, and sufficiently mixing an oxide, a carbonate, a sulfate, a nitrate, a water oxide or the like of a raw material into a mixed batch so as to obtain a target glass composition, and melting it. The inside of the vessel is heated, melted, degreased, and stirred to obtain a molten glass which is homogeneous and does not contain bubbles, and can be obtained by molding it. Specifically, it can be produced by a conventional melting method. Although the glass has a high refractive index low-dispersion glass having the above optical characteristics, it is excellent in thermal stability, and can be stably produced by a conventional melting method or molding method.

[Glass material for press molding, optical element blank, and manufacturing method thereof]

Another aspect of the present invention relates to a glass material for press forming comprising the glass 1 or the glass 2 described above, and an optical element blank comprising the glass 1 or the glass 2 described above.

According to another aspect of the present invention, there is provided a method for producing a glass material for press molding comprising the step of molding the glass 1 or the glass 2 described above into a glass material for press molding, and the glass for press molding described above is provided A method for producing an optical element blank in which a material is formed by press forming using a press molding die to produce an optical element blank, and a method of producing an optical element blank including the step of forming the glass 1 or the glass 2 described above into an optical element blank.

Since the glass material for press molding and the optical element blank are manufactured using the above-described glass 1 or glass 2, it goes without saying that the glass material for press molding and the optical element blank correspond to the above-mentioned glass.

The optical element blank is approximated to the shape of the target optical element, and a grinding allowance (a surface layer removed by polishing) is added in accordance with the shape of the optical element, and a grinding allowance is added as necessary. The optical element base material obtained by the degree of surface layer removed by grinding. The optical element can be finished by grinding the surface of the optical element blank or by grinding and grinding. In one aspect, a method of press forming a molten glass obtained by appropriately melting the glass (referred to as a direct press method) can produce an optical element blank. In another aspect, the molten glass obtained by appropriately melting the glass can be cured and further processed to produce an optical element blank.

Further, in another aspect, a glass material for press forming is produced, and an optical element blank can be produced by press-molding the produced glass material for press forming.

The press forming of the glass material for press molding can be performed by a conventional method of pressing a glass material for press forming in a state of being softened by heating using a press forming die. Heating and stamping can be carried out simultaneously in the atmosphere. A uniform optical element blank can be obtained by reducing the strain inside the glass by annealing after press forming.

The glass material for press forming includes a glass gob for press forming which is used for press forming for manufacturing an optical element blank in a direct state, and includes cutting, grinding, and grinding. The machine is machined and provided with a glass block for press forming to provide a stamper. As a cutting method, a method called glass scribing is used to form a groove on a portion of the surface of the glass plate to be cut, and a partial pressure is applied to a portion of the groove from the back surface on which the groove is formed, and the glass plate is applied. a method of cutting in a portion of a trench; and using a cut Cutting the blade to cut the glass plate, etc. Further, as a grinding and polishing method, a conventional processing technique such as barrel polishing can be mentioned.

The glass material for press molding can be produced, for example, by molding a molten glass into a cast glass sheet in a casting mold, cutting the glass sheet into a plurality of glass sheets, or performing barrel polishing on the plurality of glass sheets. Alternatively, an appropriate amount of molten glass can be molded to produce a glass block for press forming. It is also possible to manufacture an optical element blank by reheating, softening, and press-molding a glass block for press forming. The method of producing an optical element blank by reheating, softening, and press-molding a glass is called a reheating press method with respect to a direct press method.

[Optical element and its manufacturing method]

Another aspect of the present invention relates to an optical element comprising the above-described glass 1 or glass 2.

The optical element described above is produced by using the above-described glass 1 or glass 2. One or more layers of a multilayer film such as an antireflection film may be formed on the glass surface of the optical element.

Since the optical element is manufactured from the above-described glass 1 or glass 2, it goes without saying that it corresponds to the above-mentioned glass. Further, when coating is formed on the glass surface of the optical element, the glass portion other than the coating corresponds to the above-described glass.

Moreover, according to an aspect of the present invention, a method of manufacturing an optical element comprising the step of manufacturing an optical element by polishing at least the optical element blank described above is provided.

In the above method for producing an optical element, a conventional method may be applied to the grinding and polishing, and the surface of the optical element is sufficiently washed and dried by the processing. Dry, and can obtain optical components with high internal quality and high surface quality. In this way, an optical element composed of the above glass can be obtained. As the optical element, various lenses such as a spherical lens, an aspherical lens, and a microlens, and the like can be exemplified.

Further, an optical element composed of the above-described glass 1 or glass 2 is also suitable as a constituent bonding optical element. As the bonding optical element, a case in which a lens is joined to each other (joining lens), a lens and a cymbal are joined, and the like can be exemplified. For example, in the bonding optical element, the bonding surface of the two types of bonding optical elements is precisely processed (for example, spherical polishing processing) so that the shape is reversed, and the ultraviolet curing adhesive is applied to the bonding surface. After the bonding surfaces are bonded to each other, the adhesive of the bonding surface is irradiated with ultraviolet rays by an optical element to cure the adhesive. In order to manufacture the bonded optical element in this manner, the above glass is preferred. A plurality of optical elements that are joined by using a plurality of glass sheets having different Abbe numbers can be used as suitable elements for correcting chromatic aberration by bonding.

As a result of quantitative analysis of the glass composition, the glass component is represented by an oxide standard and the content of the glass component is represented by mass%. The composition represented by the oxide standard in terms of the mass % can be converted into a composition represented by the cation % and the anion % by the following method, for example.

For example, an oxide composed of a cation A and oxygen is described as A _m O _n . m and n are each an integer determined stoichiometrically. For example, B ³⁺ is described as B ₂ O ₃ according to the oxide standard, and becomes m=2 and n=3, and Si ⁴⁺ is SiO ₂ and becomes m=1 and n=2.

First, the content of A _m O _n expressed by mass % is divided by the molecular weight of AmOn, and multiplied by m. Set this value to P. Then, P is totaled for all of the cationic components. When the total P value is Σ P, the value of the P value of each cation component is normalized so that Σ P becomes 100%, and the content is A ^s+ expressed by the cation %. Here, s is 2n/m.

Further, a small amount of an additive such as a clarifier of Sb ₂ O ₃ may not be contained in Σ P. In this case, the content of Sb may be set to a content (% by mass) in a ratio other than the above Sb ₂ O ₃ . In other words, the total content of the glass components other than the content of Sb ₂ O ₃ is set to 100% by mass, and the content of Sb ₂ O ₃ is represented by a value of 100% by mass.

In addition, the above-mentioned molecular weight may be calculated by rounding off the fourth decimal place and using the value indicated by the third decimal place or less. Further, for example, the molecular weight of the oxide AmOn is a total of a value obtained by multiplying the atomic weight m of the element A by a value n times the atomic weight of oxygen. The molecular weights described in terms of oxides for several kinds of glass components and additives are shown in the following table.

[Examples]

Hereinafter, the present invention will be further described based on examples. However, the present invention is not limited to the embodiment shown in the embodiment.

(Example 1)

In order to obtain a glass having the composition shown in the table below, a compound such as an oxide or a boric acid is weighed as a raw material, and sufficiently mixed and mixed to prepare a batch raw material. The batch of raw materials was placed in a platinum crucible, heated together with hydrazine to a temperature of 1350 to 1450 ° C, and the glass was melted and clarified in 2 to 3 hours. After the molten glass was stirred and homogenized, the molten glass was cast, and after the preheated forming mold was allowed to cool to near the glass transition temperature, the glass was placed in the annealing furnace together with the forming mold. Subsequently, annealing was carried out for about 1 hour near the glass transition temperature. After annealing, it is allowed to cool to room temperature in an annealing furnace. When the glass produced in this manner was observed, crystal precipitation, bubbles, streaks, and melting of the raw material were not observed. By doing so, it is possible to produce a glass having high homogeneity. No. 1 to 33 in Table 100 (Tables 100-1 to 100-7) are glass 1, and Nos. 1 to 33 in Table 101 (Tables 101-1 to 101-6) are glass 2.

The glass characteristics of the obtained glass were measured using the method shown below. The measurement results are shown in the following table.

(1) Refractive index nd, nF, nC, ng, Abbe number ν d

The refractive index nd, nF, nC, and ng were measured using a refractive index measurement method of the Japan Optical Glass Industry Association standard for the glass obtained by cooling at a temperature drop rate of -30 ° C / hour. The Abbe's number ν d was calculated using the respective measured values of the refractive indices nd, nF, and nC.

(2) Glass transition temperature Tg

Use a differential scanning calorimetric analyzer (DSC) and set the heating rate to The measurement was carried out at 10 ° C / min.

(3) Specific gravity

Determined using the Archimedes method.

(4) Coloring degree λ5, λ70, λ80

A glass sample having a thickness of 10 ± 0.1 mm having two optically polished planes opposed to each other was used, and a light having a intensity Iin incident from the surface to be polished was perpendicularly measured using a spectrophotometer, and the light after the transmission of the glass sample was measured. The intensity Iout is calculated, and the spectral transmittance Iout/Iin is calculated, the wavelength at which the spectral transmittance is 5% is set to λ5, the wavelength at which the spectral transmittance is 70% is set to λ70, and the wavelength at which the spectral transmittance is 80% is set as λ80. .

(5) Partial dispersion ratio Pg, F

Calculated from the values of nF, nC, and ng measured in the above (1).

(6) liquid phase temperature

The glass was added to a furnace heated to a predetermined temperature and held for 2 hours. After cooling, the inside of the glass was observed using a 100-fold optical microscope and the liquidus temperature was determined from the presence or absence of crystallization.

(Example 2)

A glass block (glass frit) for press forming was produced using the various glasses obtained in Example 1. The glass block was heated and softened in the atmosphere, and a lens blank (optical element blank) was produced by press forming using a press forming die. The lens blank thus obtained was taken out from a molding die, and subjected to mechanical processing including annealing and polishing to obtain a spherical lens composed of various glasses produced in Example 1.

(Example 3)

The molten glass produced in Example 1 was obtained by a press molding die and cooled to obtain a lens blank (optical element blank) while the obtained glass was in a softened state. The lens blank thus obtained was taken out from a press molding die, annealed, and subjected to mechanical processing including polishing to prepare a spherical lens composed of various glasses produced in Example 1.

(Example 4)

The glass block (optical element blank) produced by curing the molten glass produced in Example 1 was subjected to mechanical processing including polishing to obtain a spherical lens composed of various glasses produced in Example 1.

(Example 5)

The spherical lenses manufactured in Examples 2 to 4 were bonded to a spherical lens composed of other types of glass to form a cemented lens. The joint surface of the spherical lens manufactured in Examples 2 to 4 was a convex spherical surface, and the joint surface of the spherical lens composed of the other kind of optical glass was a concave spherical surface. The two types of joint surfaces are manufactured such that the absolute values of the curvature radii of each other are equal. The ultraviolet-curable adhesive for bonding an optical element was applied to the joint surface, and the two lenses were bonded to each other between the joint surfaces. Subsequently, by the spherical lenses manufactured in Examples 2 to 4, the coating was applied to the joint surface. The agent is irradiated with ultraviolet rays to cure the adhesive.

The cemented lens was produced as described above. The bonding strength of the bonded lens is a level that is sufficiently high and the optical performance is also sufficient.

(Study on the effect of Yb on the transmittance in the near-infrared region)

The glass having the composition shown in Table 102 (hereinafter referred to as "glass A") and the glass having the composition shown in Table 103 (hereinafter referred to as "glass B") are melted, molded, and processed. Plate shape. The glass sheets have two planes facing each other. The two planes are parallel to each other and optically ground. The interval between the two planes is set to 10.0 mm.

This glass plate was used and the spectral transmittance was measured. The light is incident perpendicularly to the two opposing planes, and the ratio of the intensity of the incident light incident on the glass plate to the intensity of the transmitted light transmitted through the glass plate (the intensity of the transmitted light/the intensity of the incident light) is calculated while scanning the wavelength. A spectral transmittance curve of the glass plate was obtained. The spectral transmittance curves of the thicknesses of the two types of glass of 10.0 mm are shown in Fig. 1 and Fig. 2 (Fig. 1 : glass A, Fig. 2: glass B).

Glass B is a glass composition represented by mass %, and since it does not contain Y ₂ O ₃ , it is a mass ratio (Y ₂ O ₃ /(La ₂ O ₃ +Y ₂ O ₃ +Gd ₂ O ₃ +Yb ₂ O ₃ )) is a glass outside the aforementioned range. Further, since glass B is a glass composition represented by cation %, since it does not contain Y ³⁺ , the cation ratio (Y ³⁺ /La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ ) is outside the above range. Glass. Therefore, the glass B does not conform to the glass 1 and the glass 2 of the present invention which has been described above, but the absorption in the near-infrared region is increased or decreased according to the content of the Yb content, instead of the Y ₂ O ₃ and Y ³⁺ Whether there is. Therefore, the influence of Yb on the transmittance of near-infrared rays can be confirmed by the comparison of the glass A and the glass B. As shown in Fig. 1, the glass composition containing 0.1% by mass of Yb ₂ O _{3 in the} mass % and the glass composition containing 0.04 cationic % of Yb ^{3+ in} the cationic % is due to the wavelength of 950 nm. The light absorption of the center Yb causes the transmittance in the vicinity to decrease.

Further, as shown in Fig. 2, the glass composition represented by mass % contains 3.68 mass% of Yb ₂ O ₃ , and the glass composition represented by the cation contains 2.00 cationic % of Yb ³⁺ glass B because of the wavelength of 960 nm. The light absorption of the Yb as a center in the vicinity causes the transmittance in the vicinity to be greatly lowered.

As described above, as the content of Yb increases, the transmittance in the near-infrared region of the glass is greatly lowered, and it is not suitable as a glass Yb-based material which is required to have a high transmittance from the visible region to the near-infrared region.

(Comparative Example 1)

The glass of Example 4 of Patent Document 6 (JP-A-2009-203083) was reproduced, but crystallization was produced in the production of glass. This is considered to be due to the fact that the glass composition represented by mass% of the glass has a mass ratio (B ₂ O ₃ /(B ₂ O ₃ +SiO ₂ )) of 1, and a cation of the glass composition represented by the cation. The ratio (B ³⁺ /(B ³⁺ +Si ⁴⁺ )) is 1, so the thermal stability is low.

(Comparative Example 2)

The glass of Example 28 (hereinafter referred to as "glass C") of Patent Document 5 (JP-A-55-121925) was reproduced, and when λ5 was measured by the above method, it was 348 nm.

A spherical lens is made using glass C. Then, the convex spherical surface of the spherical lens and the concave spherical surface of the spherical lens composed of the optical glass of the other type are used as a bonding surface, and an ultraviolet curing adhesive for optical element bonding is applied, and an attempt is made in the same manner as in the fifth embodiment. Engage the lens. However, when the ultraviolet curable adhesive applied to the joint surface is irradiated with ultraviolet rays by a lens composed of the glass C, since the ultraviolet light transmittance of the glass C is low, the adhesive cannot be sufficiently cured.

(Comparative Example 3)

In the glass of Example 7 of Patent Document 17 (JP-A-2002-28452), the mass ratio (Gd ₂ O ₃ /(La ₂ O ₃ +Y ₂ O ₃十 Gd ₂ O ₃ +Yb ₂ O ₃ ) is 0.09, mass ratio (B ₂ O ₃ /(B ₂ O ₃ + SiO ₂ )) was 0.92. For this glass, it was verified that the content of components other than La ₂ O ₃ , Y ₂ O ₃ , and Gd ₂ O ₃ was constant. Further, when a part or all of Gd ₂ O ₃ is substituted with La ₂ O ₃ and Y ₂ O ₃ , the glass thermal stability changes.

First, the glass composition based on the oxide is made to contain 5.15 mass% of Gd ₂ O ₃ to 0%, and the Gd ₂ O ₃ content reduction amount of 5.15 mass% according to the content of La ₂ O ₃ and Y ₂ O ₃ . The contents are each assigned to La ₂ O ₃ and Y ₂ O ₃ . Specifically, it is 4.09 mass% calculated from 5.15 mass% × ((content of La ₂ O ₃ / (content of content of La ₂ O ₃ and content of Y ₂ O ₃ ))) from Gd ₂ O _{3 is} substituted into La ₂ O ₃ , and 1.06 mass is calculated from 5.15 mass% × ((content of Y ₂ O ₃ / (content of La ₂ O ₃ and total content of Y ₂ O ₃ )) from Gd ₂ O _{3 is} substituted into Y ₂ O ₃ . This composition is described below as "composition a".

Next, the amount of Gd ₂ O ₃ containing 5.15 mass% was reduced to 3% by mass, and the amount of reduction of Gd ₂ O ₃ content was 2.15 mass%, and each was distributed to La ₂ according to the content of La ₂ O _{3 and} the content of Y ₂ O ₃ . O ₃ and Y ₂ O ₃ . Specifically, it is 1.11% by mass calculated from 2.15 mass% × ((content of La ₂ O ₃ / (content of La ₂ O ₃ and total content of Y ₂ O ₃ ))) from Gd ₂ O ₃ In the case of substitution of La ₂ O ₃ , 5.14 mass% × ((the content of Y ₂ O ₃ / (the total content of La ₂ O _{3 and} the content of Y ₂ O ₃ ))) was calculated from Gd ₂ by 0.44 mass%. O _{3 is} substituted into Y ₂ O ₃ . This composition is described below as "composition b".

The composition, "composition a" and "composition b" of the seventh embodiment of Patent Document 17 are shown in Table 104.

When the glass is produced by the method described in the examples of Patent Document 17 using 150 g of the glass having the compositions a and b, the peripheral portion of the glass which is formed by flowing the molten glass into the casting mold, that is, by contact with the casting mold On the other hand, in the quenched portion, crystal precipitation was not observed, but in the central portion of the glass, that is, in the portion where the cooling rate was small compared to the peripheral portion, many crystals were precipitated. Further, when the glass of the above-described examples was produced by the same method, it was not limited to the peripheral portion of the glass, and crystal precipitation was not observed throughout the entire portion.

As a result of the above, it is considered that the mass ratio (B ₂ O ₃ /(B ₂ O ₃ + SiO ₂ )) is larger than the glass composition in the range described above, and when the Gd ₂ O ₃ content is lowered, the thermal stability is considered to be low. The result.

(Comparative Example 4)

The glass of Example 7 of Patent Document 17 (JP-A-2002-284542) has a cation ratio (Gd ³⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )) of 0.08, a cation ratio (B ³⁺ /(B ³⁺ +Si ⁴⁺ )) was 0.95. The glass was subjected to verification to determine the content of components other than La ³⁺ , Y ³⁺ , and Gd ³⁺ , and the glass thermal stability when a part or all of Gd ³⁺ was substituted into La ³⁺ and Y ³⁺ . The change.

First, containing 2.31% of Gd ³⁺ cations to 0%, reduces the amount of Gd ³⁺ content is 2.31% according to the content of the cation content of Y ³⁺ and La ³⁺ being assigned to each of Y ³⁺ and La ^3+. Specifically, 1.68 cationic % calculated by 2.31 cation % × ((the content of La ³⁺ / (the total content of La ^{3+ and} the content of Y ³⁺ )) is replaced by Gd ³⁺ La ^{3+ is} replaced by Gd ³⁺ to Y ³⁺ by 2.31 cation % × ((the content of Y ³⁺ / (the total content of La ^{3+ and} the content of Y ³⁺ )). The composition is described below as "composition c".

Next, Gd ³⁺ containing 2.31 cationic % was reduced to 1.5 cationic %, and the amount of reduction of Gd ³⁺ content of 0.81 cationic % was assigned to La ³⁺ and Y ³ according to the content of La ^{3+ and} the content of Y ³⁺ . ⁺ . Specifically, 0.53 cation % calculated as 0.81 cation % × ((the content of La ³⁺ / (the total content of La ^{3+ and} the content of Y ³⁺ )) is substituted into La ³⁺ , and The 0.22 cation % calculated by the method of 0.81 cation % × ((the content of Y ³⁺ / (the total content of La ^{3+ and} the content of Y ³⁺ )) is substituted with Y ³⁺ . This composition is described below as " Composition d".

The composition, "composition c" and "composition d" of Example 7 of Patent Document 17 are shown in Table 105.

When the glass is produced by the method described in the examples of Patent Document 17, 150 g of the glass having the composition c and d is used, and the molten glass is poured into the casting mold and molded into the peripheral portion of the glass, that is, by contact with the casting mold. On the other hand, in the quenched portion, crystal precipitation was not observed, but in the central portion of the glass, that is, in the portion where the cooling rate was small compared to the peripheral portion, many crystals were precipitated. Further, when the glass of the above-described examples was produced by the same method, it was not limited to the peripheral portion of the glass, and crystal precipitation was not observed throughout the entire portion. As a result of the above, it is considered that when the cation ratio (B ³⁺ /(B ³⁺ +Si ⁴⁺ )) is larger than the glass composition in the range described above, when the Gd ³⁺ content is lowered, the thermal stability is lowered. .

Finally, combine the various aspects described above.

According to one aspect, it is possible to provide a glass of an oxide glass (glass 1) expressed by mass%, and a total content of B ₂ O ₃ and SiO ₂ is 15 to 35 mass%, La ₂ O ₃ , Y ₂ O ₃ , the total content of Gd ₂ O ₃ and Yb ₂ O ₃ is 45 to 65 mass%, but the Yb ₂ O ₃ content is 3% by mass or less, the ZrO ₂ content is 3 to 11% by mass, and the Ta ₂ O ₃ content is 5 mass% or less, the mass ratio of B ₂ O ₃ content to the total content of B ₂ O ₃ and SiO ₂ (B ₂ O ₃ /(B ₂ O ₃ + SiO ₂ )) is 0.4 to 0.900, B ₂ O ₃ and Mass ratio of the total content of SiO _{2 to} the total content of La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ and Yb ₂ O ₃ (B ₂ O ₃ + SiO ₂ ) / (La ₂ O ₃ + Y ₂ O _{3 + Gd 2 O 3 + Yb} 2 O 3) is 0.42 ~ 0.53, Y ₂ O ₃ content of _{La 2 O 3, Y 2 O} 3, Gd 2 O 3 and Yb ₂ O ₃ to the total mass content ratio (Y ₂ O ₃ /(La ₂ O ₃ +Y ₂ O ₃ +Gd ₂ O ₃ +Yb ₂ O ₃ )) is 0.05-0.45, and the Gd ₂ O ₃ content is La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O The mass ratio of the total content of ₃ and Yb ₂ O ₃ (Gd ₂ O ₃ /(La ₂ O ₃ +Y ₂ O ₃ +Gd ₂ O ₃ +Yb ₂ O ₃ )) is 0 to 0.05, and the Nb ₂ O ₅ content Mass ratio of total content of Nb ₂ O ₅ , TiO ₂ , Ta ₂ O ₅ and WO ₃ (Nb ₂ O ₅ /(Nb ₂ O ₅ + TiO ₂ + Ta ₂ O ₅ + WO ₃ )) is 0.5 to 1, the refractive index nd is in the range of 1.800 to 1.850, and the Abbe number ν d is 41.5 to 44.

According to one aspect, it is possible to provide a glass of an oxide glass (glass 2) which is represented by a cation %, and a total content of B ³⁺ and Si ⁴⁺ is 45 to 65%, La ³⁺ , Y ³⁺ , Gd The total content of ³⁺ and Yb ³⁺ is 25~35%, but the content of Yb ³⁺ is less than 2%, the content of Zr ⁴⁺ is 2~8%, the content of Ta ⁵⁺ is 3% or less, and the content of B ^{3+ is} B. ³⁺ cations and the total content of Si ⁴⁺ ratio ^{(B 3+ / (B 3+ +} Si 4+)) is 0.65 or more and less than 0.94, B ³⁺ and Si ⁴⁺ to the total content of La ^3+, Y The cation ratio ((B ³⁺ +Si ⁴⁺ )/(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ ))) of the total content of ³⁺ , Gd ³⁺ and Yb ³⁺ is 1.65 to 2.60, the content of Y ³⁺ La ^3+, Y ^3+, Gd ³⁺ cations and the total content of Yb ³⁺ ratio ^{(Y 3+ / (La 3+ +} Y 3+ + Gd 3+ + Yb 3+) 0.05 to 0.45, the total content of Gd ³⁺ cation content of La ^3+, Y ^3+, Gd ³⁺ and Yb ³⁺ ratio ^{(Gd 3+ / (La 3+ +} Y 3+ + Gd 3+ + Yb 3+ ) is a cation ratio of 0 to 0.05, the total content of Nb ⁵⁺ to Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ (Nb ⁵⁺ /(Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ )) is 0.4 to 1, the refractive index nd is in the range of 1.800 to 1.850, and the Abbe number ν d is 41.5 to 44.

The glass 1 and the glass 2 have a refractive index nd and an Abbe number ν d in the above range, and are high refractive index low-dispersion optical glasses which are useful as materials for optical elements constituting the optical system. The above-mentioned glass is a glass which is reduced in the contents of Gd, Ta and Yb, and is a glass which can exhibit high thermal stability.

In one aspect, from the viewpoint of improving the meltability, further improving the thermal stability of the glass, and suppressing the glass transition temperature to be lowered (in order to improve the machinability), the glass 1 series mass ratio is improved from the viewpoint of improving chemical durability. (ZnO/(Nb ₂ O ₅ + TiO ₂ + Ta ₂ O ₅ + WO ₃ )) is preferably in the range of 0.1 to 3.

In one aspect, the glass 2 cation ratio is improved from the viewpoint of improving the meltability, further improving the thermal stability of the glass, suppressing the glass transition temperature from being lowered (by thereby improving the machinability), and improving the chemical durability. The range of Zn ²⁺ /(Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )) is preferably from 0.1 to 5.

In one aspect, it is preferable that the glass 1 and the glass 2 suppress the long wavelength of the light absorption end on the short-wavelength side of the glass so that the degree of coloration λ5 becomes 335 nm or less.

In one aspect, from the viewpoint of making it possible to reduce the weight of the optical element having a certain refractive power, it is preferable that the specific gravity d of the glass 1 and the glass 2 and the refractive index nd satisfy the above formula (A).

In one aspect, the glass transition temperature of the glass 1 and the glass 2 is preferably 640 ° C or higher from the viewpoint of improving machinability.

From the glass 1 or the glass 2 described above, a glass material for press molding, an optical element blank, and an optical element can be produced. That is, according to another aspect, it is possible to provide a glass material for press molding composed of glass 1 or glass 2, an optical element blank, and an optical element.

Moreover, according to another aspect, it is also possible to provide a method of producing a glass material for press molding including the step of molding the glass 1 or the glass 2 into a glass material for press molding.

Further, according to another aspect, it is possible to provide a method of producing an optical element blank including a step of producing an optical element blank by press-molding the glass material for press forming using a press molding die.

Further, according to another aspect, it is also possible to provide a method of producing an optical element blank including the step of forming the glass 1 or the glass 2 into an optical element blank.

Further, according to another aspect, it is also possible to provide a method of manufacturing an optical element including the step of producing an optical element by polishing at least the optical element blank.

It is to be understood that the embodiments disclosed herein are all illustrative and not restrictive. The scope of the present invention is defined by the scope of the claims and the scope of the claims

For example, by adjusting the composition described in the above description of the glass composition disclosed in the above examples, such a glass can be obtained in one aspect of the present invention.

Further, of course, it is possible to arbitrarily combine two or more items as exemplified or described in the specification as a preferable range.

Further, a certain glass also has a condition equivalent to both the glass 1 and the glass 2.

[Industry use possibility]

The invention is useful in the field of manufacture of various optical components.

Claims (15)

A glass which is an oxide glass, and the content of each component of the glass is expressed by mass%, and the total content of B ₂ O ₃ and SiO ₂ is 21 to 32% by mass, La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O The total content of ₃ and Yb ₂ O ₃ is 50 to 63% by mass, but the Yb ₂ O ₃ content is 1.0% by mass or less, the ZrO ₂ content is 4 to 10% by mass, and the Ta ₂ O ₅ content is 2% by mass or less. The total content of ₂ O, Na ₂ O and K ₂ O is 0 to 2.0% by mass, and the total content of Nb ₂ O ₅ , TiO ₂ , Ta ₂ O ₅ and WO ₃ is 4 to 14% by mass, and B ₂ O ₃ content the quality of B ₂ O ₃ and the total content of SiO ₂ ratio _{(B 2 O 3 / (B} 2 O 3 + SiO 2)) is from 0.6 to 0.900, the total content of B ₂ O ₃ and SiO ₂ to La ₂ O ₃ Mass ratio of the total content of Y ₂ O ₃ , Gd ₂ O ₃ and Yb ₂ O ₃ ((B ₂ O ₃ + SiO ₂ ) / (La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃₎₎ is 0.42 ~ 0.53, Y ₂ O ₃ content of _{La 2 O 3, Y 2 O} 3, Gd 2 O 3 and Yb ₂ O ₃ the total mass content ratio _{(Y 2 O 3 / (La} 2 O 3 +Y ₂ O ₃ +Gd ₂ O ₃ +Yb ₂ O ₃ ) is 0.10 to 0.30, and the total content of Gd ₂ O _{3 is} La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ and Yb ₂ O ₃ . mass ratio of _{(Gd 2 O 3 / (La} 2 O 3 + Y 2 O 3 + Gd 2 O 3 + Yb 2 O 3)) 0 ~ 0.05, Nb ₂ O ₅ content of Nb ₂ O _5, TiO _2, mass of the total content of Ta ₂ O ₅ and WO ₃ ratio _{(Nb 2 O 5 / (Nb} 2 O 5 + TiO 2 + Ta 2 O 5 +WO ₃ )) is 0.95~1, the refractive index nd is in the range of 1.800~1.850, and the Abbe number νd is 41.5~44. The glass according to claim 1, wherein the content of B ₂ O ₃ is 17% by mass or more. The glass according to claim 1, wherein the B ₂ O ₃ content is 23% by mass or less. The glass according to claim 2, wherein the B ₂ O ₃ content is 23% by mass or less. The glass according to any one of claims 1 to 4, further comprising ZnO, wherein the mass ratio of ZnO content to the total content of Nb ₂ O ₅ , TiO ₂ , Ta ₂ O ₅ and WO ₃ (ZnO/( Nb ₂ O ₅ +TiO ₂ +Ta ₂ O ₅ +WO ₃ )) is in the range of 0.20 to 1.5. The glass according to claim 5, wherein the mass ratio of the ZnO content to the total content of Nb ₂ O ₅ , TiO ₂ , Ta ₂ O ₅ and WO ₃ (ZnO/(Nb ₂ O ₅ + TiO ₂ + Ta) ₂ O ₅ +WO ₃ )) is in the range of 0.20 to 0.500. The glass of any one of claims 1 to 4, which does not contain Pb. The glass according to any one of claims 1 to 4, wherein the refractive index nd is in the range of 1.810 to 1.850. The glass of claim 8 is characterized in that the refractive index nd is in the range of 1.820 to 1.850. The glass according to any one of claims 1 to 4, wherein the degree of coloration λ5 is 335 nm or less. The glass according to any one of claims 1 to 4, wherein the specific gravity d and the refractive index nd satisfy the following formula (A): d / (nd - 1) ≦ 5.70 (A). The glass according to any one of claims 1 to 4, wherein the glass transition temperature is 640 ° C or higher. A glass material for press forming is composed of the glass according to any one of claims 1 to 12. An optical element blank comprising the glass of any one of claims 1 to 12. An optical component comprising the glass of any one of claims 1 to 12.