JP7250106B2 - Glass, glass material for press molding, optical element blanks, and optical elements - Google Patents

Description

[Cross reference to related application]
This application claims priority to Japanese Patent Application No. 2015-004542 and Japanese Patent Application No. 2015-004544 filed on January 13, 2015, the entire descriptions of which are specifically incorporated herein as disclosure.

TECHNICAL FIELD The present invention relates to glass, glass material for press molding, optical element blanks, and optical elements.

Glass having a refractive index nd in the range of 1.800 to 1.850 and an Abbe number νd in the range of 41.5 to 44 as a glass having a high refractive index and low dispersion (high refractive index low dispersion glass) are described, for example, in Patent Documents 1 to 18. The entire disclosures of Patent Documents 1-18 are specifically incorporated herein by reference.

Patent Document 1: JP-A-2002-12443 Patent Document 2: JP-A-2003-267748 Patent Document 3: JP-A-2005-281124 Patent Document 4: JP-A-2005-298262 Patent Document 5: JP-A Patent Document 6: JP-A-2009-203083 Patent Document 7: JP-A-54-090218 Patent Document 8: JP-A-56-160340 Patent Document 9: JP-A-2009-167080 Patent Document 10: JP 2009-167081 Patent Document 11: JP 2009-298646 Patent Document 12: JP 2010-111527 Patent Document 13: JP 2010-111528 Patent Document 14: JP-A-2010-111530 Patent Document 15: JP-A-57-056344 Patent Document 16: JP-A-61-163138 Patent Document 17: JP-A-2002-284542 Patent Document 18: JP-A-2007- 269584 publication

A glass having a refractive index nd in the range of 1.800 to 1.850 and an Abbe number νd in the range of 41.5 to 44 is useful for correcting chromatic aberration, improving the functionality of an optical system, and making it compact. It is a material for optical elements. In the following, unless otherwise specified, the refractive index refers to the refractive index nd at the d-line (helium wavelength 587.56 nm). The Abbe number is νd unless otherwise specified. As is well known, νd is given by νd=(nd−1)/(nF− nC).

High-refractive-index, low-dispersion glass having a refractive index and Abbe number within the above ranges is desired to satisfy the following points in order to further enhance its usefulness.

Stable supply is possible. For this purpose, it is desirable to reduce the ratio of Gd and Ta, which are elements with a high scarcity value and whose supply has been insufficient in recent years against demand in the market, in the glass composition. On the other hand, the glass described in Patent Document 7 contains a large amount of Ta. Further, the glass described in Patent Documents 8 to 14 and the glass described in Patent Document 17 having a refractive index and an Abbe number within the above ranges contain a large amount of Gd.

The proportion of Yb in the glass composition is low. This is for the following reasons.
Yb has absorption in the near-infrared region. Therefore, the glass containing a large amount of Yb (for example, the glass described in Patent Document 16) is used for applications that require high transmittance from the visible range to the near-infrared range, such as surveillance cameras, night vision cameras, vehicle camera lenses, etc. is not suitable as a material for optical elements of Yb belongs to the heavy rare earth elements, has a large atomic weight as a component of glass, and increases the specific gravity of glass. As the specific gravity of the glass increases, the lens becomes heavier. As a result, when such a lens is incorporated into an autofocus camera lens, power consumption increases and the battery drains rapidly. From the above points, it is desirable to reduce the proportion of Yb in the glass composition.

Excellent thermal stability. This is because glass with low thermal stability tends to devitrify during the glass manufacturing process. However, according to the studies of the present inventors, for example, the glass described in Patent Document 6 is inferior in thermal stability.

In view of the above points, in one aspect of the present invention, the refractive index nd is in the range of 1.800 to 1.850, the Abbe number νd is in the range of 41.5 to 44, and the glass composition contains Gd, Provided is a glass in which the proportions of Ta and Yb are reduced and which is excellent in thermal stability.

In one aspect, it is also desirable that the glass further satisfies one or more of the following points.

Suppressing the lengthening of the light absorption edge on the short wavelength side of the glass. This is for the following reasons.
A known method for correcting chromatic aberration is to make a plurality of lenses using glass having different optical properties, and then bond these lenses together to make a cemented lens. In the process of making a cemented lens, an ultraviolet curable adhesive is usually used to bond the lenses together. Details are as follows. Apply an ultraviolet curable adhesive to the surfaces where the lenses are to be bonded together, and then bond the lenses together. At this time, an extremely thin coating layer of the ultraviolet curable adhesive is usually formed between the lenses. Next, the coating layer is irradiated with ultraviolet rays through a lens to cure the ultraviolet curing adhesive. Therefore, if the UV transmittance of the lens is low, a sufficient amount of UV light does not reach the coating layer through the lens, resulting in insufficient curing. Or it takes a long time to harden. Also, when a lens is fixed to a lens barrel or the like using an ultraviolet curable adhesive, if the ultraviolet transmittance of the lens is low, curing may be insufficient or may take a long time. It takes time.
Therefore, in order to obtain a glass having a transmittance characteristic suitable for manufacturing an optical system, the transmittance of the glass in the ultraviolet region must be increased. should be suppressed.
However, according to the study of the present inventor, for example, in the glass described in Patent Document 5, the light absorption edge on the short wavelength side of the glass has a longer wavelength, and the transmittance in the ultraviolet region has decreased. In addition, in the glass composition of conventional high refractive index low dispersion glass, when trying to maintain both high refractive index low dispersion characteristics and thermal stability while reducing the content of Gd and Ta, the short wavelength side of the glass There was a tendency for the light absorption edge to be longer in wavelength and the transmittance of ultraviolet rays to be greatly reduced.

Be suitable for machining. Details are as follows. As a method of obtaining an optical element from glass, in addition to the precision press molding method (see, for example, Patent Documents 1 to 4), an optical element blank is molded from glass, and the optical element blank is subjected to mechanical processing such as grinding and polishing. There is also a method of finishing the optical element by performing If the glass is susceptible to breakage during such machining, the manufacturing yield will be reduced. In general, glass for precision press molding has a low glass transition temperature, but glass with a low glass transition temperature tends to break easily during machining. Therefore, in order to make the glass suitable for machining, it is desirable to make the glass transition temperature higher than the glass for precision press molding.

One aspect of the present invention is expressed in mass %,
The total content of B ₂ O ₃ and SiO ₂ is 15 to 35% by 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, provided that the Yb ₂ O ₃ content is 3% by mass or less;
a ZrO ₂ content of 3 to 11% by weight,
Ta ₂ O ₅ content is 5% by mass or less,
mass ratio of B ₂ O ₃ content to 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;
Mass ratio of the total _{content of B2O3 and SiO2 to the total content of La2O3, Y2O3 , Gd2O3 and Yb2O3 ( ( B2O3 + SiO2 ) / ( La 2} O ₃ +Y ₂ O ₃ +Gd ₂ O ₃ +Yb ₂ O ₃ )) is 0.42 to 0.53;
Mass _ratio of _Y2O3 content to _{total content of La2O3} , _{Y2O3 , Gd2O3} and _Yb2O3 ( _{Y2O3 / ( La2O3 + Y2O3} + _Gd2 O ₃ +Yb ₂ O ₃ )) is 0.05 to 0.45;
Mass ratio of _{Gd2O3 content to total content of La2O3 , Y2O3} , _Gd2O3 and _Yb2O3 ( _{Gd2O3 /} ( _La2O3 + _{Y2O3 + Gd2} O ₃ +Yb ₂ O ₃ )) is 0 to 0.05;
Mass ratio _{of Nb2O5} content to total content _{of Nb2O5} , _TiO2 , _Ta2O5 and _{WO3 ( Nb2O5} /( _Nb2O5 + _{TiO2 + Ta2O5 + WO3} ) ₎ is 0.5 to 1,
and an oxide glass having a refractive index nd in the range of 1.800 to 1.850 and an Abbe number νd of 41.5 to 44 (hereinafter referred to as “glass 1”),
Regarding.

In addition, in one aspect of the present invention, in cation % display,
a total content of B ³⁺ and Si ⁴⁺ of 45 to 65%;
the total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ is 25-35%, provided that the Yb ³⁺ content is less than 2%;
a Zr ⁴⁺ content of 2-8%,
Ta ⁵⁺ content is 3% or less,
a cation ratio of the B ³⁺ content to the total B ³⁺ and Si ⁴⁺ content (B ³⁺ /(B ³⁺ +Si ⁴⁺ )) of 0.65 or more and less than 0.94;
Cation ratio of the total content of B ³⁺ and Si ⁴⁺ to the total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ ((B ³⁺ +Si ⁴⁺ )/(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )) is 1.65 to 2.60,
The cation ratio of the 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 0 .05 to 0.45,
The cation ratio of the 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 0 ~0.05,
The cation ratio of the Nb ⁵⁺ content to the total content of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ (Nb ⁵⁺ /(Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )) is 0 .4-1,
and an oxide glass having a refractive index nd in the range of 1.800 to 1.850 and an Abbe number νd of 41.5 to 44 (hereinafter referred to as “glass 2”),
Regarding.

The glass 1 is glass having a refractive index nd and an Abbe number νd within the above ranges, and contains various components including Gd ₂ O ₃ (that is, La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ , Yb ₂ O ₃ ) satisfies the above mass ratio in which the content of Gd ₂ O ₃ is the numerator and the total content of the various components is the denominator. Therefore, the proportion of Gd in the glass composition is reduced. Furthermore, the Ta ₂ O ₅ content and the Yb ₂ O ₃ content are as described above, respectively, and the proportions of Ta and Yb in the glass composition are also reduced. The above glass has high thermal stability by adjusting the composition to satisfy the above-mentioned content, total content and mass ratio in the composition in which the ratio of Gd, Ta and Yb is reduced in this way. property (property of being resistant to devitrification) can be realized. Furthermore, it is possible to suppress the lengthening of the light absorption edge on the short wavelength side and increase the glass transition temperature (Tg) (increase the glass transition temperature).

Glass 2 is glass having a refractive index nd and an Abbe number νd within the above ranges, and the total content of various components including Gd ³⁺ (that is, La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ ) satisfies the above cation ratio within the above range, with the Gd ³⁺ content as the numerator and the total content of the above various components as the denominator. Therefore, the proportion of Gd in the glass composition is reduced. Furthermore, the Ta ⁵⁺ content and the Yb ³⁺ content are as described above, respectively, and the proportions of Ta and Yb in the glass composition are also reduced. The above glass has high thermal stability by adjusting the composition to satisfy the above-mentioned content, total content and cation ratio in the composition in which the ratio of Gd, Ta and Yb is reduced. property (property of being resistant to devitrification) can be realized. Furthermore, it is possible to suppress the lengthening of the light absorption edge on the short wavelength side and increase the glass transition temperature (Tg) (increase the glass transition temperature).

According to one aspect of the present invention, it is possible to provide a glass that has high refractive index and low dispersion properties useful in optical systems, can be stably supplied, and has excellent thermal stability. Furthermore, according to one aspect of the present invention, it is possible to provide a press-molding glass material, an optical element blank, and an optical element made of the glass described above.

A spectral transmittance curve at a thickness of 10.0 mm of the later-described glass A is shown. A spectral transmittance curve for glass B having a thickness of 10.0 mm, which will be described later, is shown.

The glass composition in the present invention can be quantified by a method such as ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry). Analytical values obtained by ICP-AES may contain measurement errors of about ±5% of the analytical values, for example. In addition, in the present specification and the present invention, the content of a component is 0%, or it does not contain or is not introduced means that this component is substantially not included, and the content of this component is at the impurity level It means that it is below the degree.

In the following, (more) preferable lower limits and (more) preferable upper limits of numerical ranges may be shown and described in tables. In the table, the lower the value, the more preferable, and the lowest value is the most preferable. Further, unless otherwise specified, the (more) preferable lower limit means that it is (more) preferable that it is at least the stated value, and the (more) preferable upper limit means that it is less than or equal to the stated value. It means something that is (more) preferable. Numerical ranges can be defined by arbitrarily combining the numerical values described in the (more) preferable lower limit column and the numerical values described in the (more) preferable upper limit column in the table.

[Glass]
The glass 1 and the glass 2 according to one aspect of the present invention have the above glass composition, a refractive index nd in the range of 1.800 to 1.850, and an Abbe number νd of 41.5 to 44. It is a material glass. Details of the glass 1 and the glass 2 will be described below.

<Glass Composition of Glass 1>
In the present invention, the glass composition of glass 1 is indicated on the basis of oxides. Here, the term "glass composition based on oxides" refers to a glass composition obtained by conversion assuming that the glass raw materials are all decomposed during melting and exist as oxides in the glass. In addition, unless otherwise specified, the glass composition of the glass 1 is indicated on a mass basis (% by mass, mass ratio).

B ₂ O ₃ and SiO ₂ are network forming components of glass. When the total content of B ₂ O ₃ and SiO ₂ (B ₂ O ₃ +SiO ₂ ) is 15% or more, the thermal stability of the glass is improved and crystallization of the glass during production can be suppressed. can. On the other hand, when the total content of B ₂ O ₃ and SiO ₂ is 35% or less, a decrease in the refractive index nd can be suppressed. It is possible to produce a glass having an Abbe number νd in the range of 41.5 to 44 while being in the range of 0.800 to 1.850. Therefore, the total content of B ₂ O ₃ and SiO ₂ in the glass 1 should be in the range of 15-35%. A preferable lower limit and preferable upper limit of the total content of B ₂ O ₃ and SiO ₂ are as shown in the table below.

The content ratio of each component of B ₂ O ₃ and SiO ₂ , which are network forming components of glass, depends on the thermal stability, meltability, moldability, chemical durability, weather resistance, machinability, etc. of the glass. influence. B ₂ O ₃ is superior to SiO ₂ in improving meltability, but is easily volatilized during melting. On the other hand, SiO ₂ works to improve the chemical durability, weather resistance and machinability of the glass, and to increase the viscosity of the glass during melting.
In general, a high-refractive-index, low-dispersion glass containing rare earth elements such as B ₂ O ₃ and La ₂ O ₃ has a low viscosity when melted. However, if the viscosity of the glass when melted is low, the thermal stability is lowered (easily crystallized). Crystallization during glass production is more stable in a crystalline state than in an amorphous state (amorphous state), and occurs when the ions that make up the glass move through the glass and are arranged to have a crystal structure. Therefore, by adjusting the content ratio of each component of B ₂ O ₃ and SiO ₂ so as to increase the viscosity at the time of melting, it becomes difficult for the ions to be arranged in a crystal structure, and the glass crystals are formed. It is possible to further suppress the quenching and improve the thermal stability of the glass.
When molten glass is poured into a mold for molding, if the viscosity of the molten glass is low, the solidified surface of the glass poured into the mold is caught in the glass that is still in a molten state, forming striae. homogeneity is reduced. A glass with excellent formability corresponds to a glass having a relatively high viscosity when poured into a mold in a molten state, among high refractive index and low dispersion glasses containing rare earth elements.
If 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 It is possible to suppress the decrease, thereby improving the thermal stability of the glass and suppressing volatilization during melting. Volatilization at the time of melting causes fluctuations in glass composition and properties. And as a result, it is difficult to form optically homogeneous glass. Therefore, it is preferable from the viewpoint of mass production of glass with little variation in composition and properties that the mass ratio (B ₂ O ₃ /(B ₂ O ₃ +SiO ₂ )) is set to 0.900 or less to suppress volatilization during melting. Furthermore, if the mass ratio ( _B2O3 /( _B2O3 + _SiO2 )) _is 0.900 or less, it is possible to suppress deterioration in the chemical durability, weather resistance _, and machinability of the glass. On the other hand, in the glass composition described in the aforementioned Patent Document 15 (JP-A-57-056344), the B ₂ O ₃ content is 28 to 30% by mass, and the SiO ₂ content is 1 to 3%. % by mass (see the claims of Patent Document 15). The mass ratio (B ₂ O ₃ /(B ₂ O ₃ +SiO ₂ )) calculated from the contents of these components is a large value of 0.903 to 0.968.
On the other hand, if the mass ratio (B ₂ O ₃ /(B ₂ O ₃ +SiO ₂ )) is 0.4 or more, it is possible to prevent the frit from remaining unmelted during melting, thereby improving the meltability. can.
From the above points, in the glass 1, the mass ratio (B ₂ O ₃ /(B ₂ O ₃ +SiO ₂ )) is set in the range of 0.4 to 0.900. A preferable lower limit and a preferable _{upper limit} of the mass ratio ( _B2O3 /( _B2O3 + _SiO2 )) in the glass 1 are as shown in the table below.

For each of the B ₂ O ₃ content and the SiO ₂ content, preferred lower limits and preferred from the viewpoint of improving the thermal stability, meltability, moldability, chemical durability, weather resistance, machinability, etc. of the glass The upper limits are shown in the table below.

La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ and Yb ₂ O ₃ are components that increase the refractive index while suppressing the decrease in Abbe's number. These components also work to improve the chemical durability and weatherability of the glass and to raise 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, the refraction Since it is possible to suppress the decrease in the refractive index, it is possible to produce a glass having the above-described optical properties. Furthermore, it is possible to suppress the deterioration of the chemical durability and weather resistance of the glass. Note that when the glass transition temperature is lowered, the glass is more likely to be damaged (decreased machinability) when the glass is mechanically processed (cutting, cutting, grinding, polishing, etc.), but La ₂ O ₃ and Y ₂ When the total content of O ₃ , Gd ₂ O ₃ and Yb ₂ O ₃ is 45% or more, the decrease in glass transition temperature can be suppressed, and machinability can be improved. On the other hand, if 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, the thermal stability of the glass can be enhanced. It is also possible to suppress crystallization during melting and to reduce unmelted raw materials when melting the glass. Therefore, in 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 45-65%. Preferred lower and preferred upper limits _{for the total content of La2O3, Y2O3, Gd2O3 and Yb2O3 are shown in the table below} .

ZrO ₂ is a component that works to increase the refractive index, and also works to improve the thermal stability of the glass when contained in an appropriate amount. ZrO ₂ also has the function of increasing the glass transition temperature and making the glass less likely to break during mechanical processing. In order to satisfactorily obtain these effects, the glass 1 has a ZrO ₂ content of 3% or more. On the other hand, if the ZrO ₂ content is 11% or less, the thermal stability of the glass can be improved, so that crystallization during glass production and unmelted residue during glass melting can be suppressed. . Therefore, the content of ZrO ₂ in the glass 1 should be in the range of 3 to 11%. A preferred lower limit and preferred upper limit for the ZrO ₂ content are shown in the table below.

As described above, Ta ₂ O ₅ is a component whose proportion in the glass composition is desirably reduced from the viewpoint of stable supply of glass. Ta ₂ O ₅ is a component that works to increase the refractive index, but it also increases the specific gravity of the glass and reduces the meltability. Therefore, the Ta ₂ O ₅ content in the glass 1 should be 5% or less. A preferred lower limit and preferred upper limit for the Ta ₂ O ₅ content are shown in the table below.

In order to improve the thermal stability of the glass and suppress the increase in specific gravity while realizing the above optical properties, the glass 1 contains La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ and Yb ₂ O _{3 .} The mass _ratio of the total content of _B2O3 and _{SiO2 to the total content of ((B2O3 + SiO2 ) /} ( _{La2O3 + Y2O3} + _Gd2O3 + _Yb2O3 )) is set to ₀ 0.42 to 0.53. If the mass ratio (( _B2O3 + _SiO2 )/( _{La2O3 + Y2O3} + _Gd2O3 + _{Yb2O3 )} ) is 0.42 or more, the thermal _{stability of} the glass is _improved . Therefore, devitrification of the glass can be suppressed. Also, it is possible to suppress an increase in the specific gravity of the glass. As the specific gravity of the glass increases, the weight of the optical element manufactured using this glass increases. As a result, an optical system incorporating this optical element becomes heavy. For example, if a heavy optical element is incorporated in an autofocus camera, power consumption increases when the autofocus is driven, and the battery is quickly exhausted. Being able to suppress an increase in the specific gravity of the glass is preferable from the viewpoint of reducing the weight of an optical element manufactured using this glass and an optical system incorporating this optical element. On the other hand, if 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. can be done. In addition, the fact that the mass ratio (( _{B2O3 + SiO2} ) _/ ( _{La2O3 + Y2O3 + Gd2O3} + _Yb2O3 )) is 0.53 or less is effective for the chemical durability of the glass _. It is also preferable from the viewpoint of improvement and increase in glass transition temperature (Tg). Preferred lower and preferred _upper limits _of the mass ratio ( _{( B2O3 + SiO2} )/( _{La2O3 + Y2O3} + _Gd2O3 + _Yb2O3 )) are shown in the table below.

Among La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ and Yb ₂ O ₃ , Yb ₂ O ₃ is a component whose proportion in the glass composition should be reduced for the reason described above. . Therefore, in Glass 1, the Yb ₂ O ₃ content is set to 3% or less. A preferred lower limit and preferred upper limit for the Yb ₂ O ₃ content are shown in the table below.

Y ₂ O ₃ is a component that works to improve the thermal stability of the glass without significantly lowering the light transmittance in the near-infrared region. Moreover, since its atomic weight is small, it is a preferable component for suppressing an increase in the specific gravity of the glass. However, if the Y ₂ O ₃ content is too high, the thermal stability of the glass will be significantly reduced, and crystallization will tend to occur. Also, the meltability is lowered. In glass 1, La ₂ O ₃ is used to produce a glass having the above-described optical properties by suppressing an increase in specific gravity while improving thermal stability without significantly reducing light transmittance in the near-infrared region. , the mass ratio of _{the Y2O3} content _{to the total} content _{of Y2O3 , Gd2O3} and _Yb2O3 ( _{Y2O3 /} ( _{La2O3 + Y2O3} + _Gd2O3 + _Yb2 O ₃ )) is in the range of 0.05 to 0.45. Preferred lower and preferred upper limits of the mass ratio (Y ₂ O ₃ /(La ₂ O ₃ +Y ₂ O ₃ +Gd ₂ O ₃ +Yb ₂ O ₃ )) are shown in the table below.

Gd ₂ O ₃ is a component whose proportion in the glass composition should be reduced for the reasons described above. Gd, like Yb, belongs to heavy rare earth elements, has a large atomic weight as a component of glass, and increases the specific gravity of glass. From this point of view as well, it is desirable to reduce the proportion of Gd in the glass composition.
In glass 1, the content _{of Gd2O3} is _determined by the total content _{of La2O3} , _{Y2O3 , Gd2O3 and Yb2O3 and the content of Gd2O3 with respect to this} total content _. determined. In the glass 1, La ₂ O ₃ and Y ₂ O are used in order to stably supply a high refractive index, low dispersion glass having the above-described optical properties, and in order to produce a glass having a small specific gravity as a high refractive index, low dispersion glass. ₃ , mass ratio of _Gd2O3 content to total content _{of Gd2O3 and Yb2O3 ( Gd2O3 /} ( _{La2O3 + Y2O3 + Gd2O3 + Yb2O3} ) ₎ is in the range of 0 to 0.05. Preferred lower and preferred upper limits _of the mass ratio ( _{Gd2O3 /} ( _{La2O3 + Y2O3 + Gd2O3 + Yb2O3} )) are shown in the table below.

La ₂ O ₃ does not significantly lower the light transmittance in the near-infrared region, improves thermal stability, suppresses an increase in specific gravity, and is useful for providing a high refractive index and low dispersion glass. ingredients. Therefore, in glass 1, the mass ratio of the La 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 (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 more preferable lower limit and the more preferable upper _{limit of the} mass ratio ( _La2O3 /( _{La2O3 + Y2O3} + _{Gd2O3 + Yb2O3} )) are shown in the table below.

The preferred lower and preferred upper limits of the content of each of La ₂ O ₃ , Y ₂ O ₃ and Gd ₂ O ₃ are shown in the table below.

Nb ₂ O ₅ , TiO ₂ , Ta ₂ O ₅ and WO ₃ are components that work to increase the refractive index, and also work to improve the thermal stability of the glass when contained in appropriate amounts. The total content of Nb ₂ O ₅ , TiO ₂ , Ta ₂ O ₅ and WO ₃ (Nb ₂ O ₅ +TiO ₂ +Ta ₂ O ₅ +WO ₃ ) is in the range of 3 to 15%. It is preferable in terms of further improving the thermal stability of the glass while realizing it. A more preferable lower limit and a more preferable upper limit of the total content of Nb ₂ O ₅ , TiO ₂ , Ta ₂ O ₅ and WO ₃ are shown in the table below.

ZnO has a function of promoting the melting of raw materials of the glass when the glass is melted, that is, a function of improving the meltability. It also has the function of adjusting the refractive index and Abbe's number and lowering the glass transition temperature. The value obtained by dividing the ZnO content by the total content of B ₂ O ₃ and SiO ₂ , that is, the mass ratio (ZnO/(B ₂ O ₃ +SiO ₂ )) of 0.04 or more indicates meltability. Good for improvement. On the other hand, a mass ratio (ZnO/(B ₂ O ₃ +SiO ₂ )) of 0.4 or less is preferable for suppressing a decrease in the Abbe's number (high dispersion) and realizing the above optical properties. Further, the mass ratio (ZnO/(B ₂ O ₃ +SiO ₂ )) of 0.4 or less is preferable in terms of improving the thermal stability of the glass and increasing the glass transition temperature (Tg). Therefore, the content of ZnO should be 0.04 to 0.4 times the total content of B ₂ O ₃ and SiO ₂ in mass ratio, that is, the mass ratio (ZnO/(B ₂ O ₃ +SiO ₂ )) is preferably 0.04 to 0.4. A more preferable lower limit and a more preferable upper limit of the mass ratio (ZnO/(B ₂ O ₃ +SiO ₂ )) are shown in the table below.

From the viewpoint of improving the meltability, thermal stability, moldability, machinability, etc. of the glass and realizing the above optical properties, the preferable lower and preferable upper limits of the ZnO content are as shown in the table below.

Mass _ratio of the total content of _B2O3 and _SiO2 to _{the total} content of _{Nb2O5 , TiO2} , _Ta2O5 and _WO3 ( _{( B2O3} + _SiO2 )/( _Nb2O5 +TiO ₂ + Ta ₂ O ₅ + WO ₃ )) is in the range of 2.65 to 10 in order to suppress an increase in the degree of coloring λ5 described later and increase the UV transmittance of the glass while realizing the above optical characteristics. is preferred. Also, in terms of improving the thermal stability of the glass, it is also possible _to set the mass ratio (( _B2O3 + _SiO2 )/( _Nb2O5 + _{TiO2 + Ta2O5} + _{WO3 )} ) to 2.65 or more. preferable. A more preferred lower limit and a more preferred 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 table below.

Nb ₂ O ₅ , TiO ₂ , Ta ₂ O ₅ and WO ₃ work to improve the thermal stability of the glass when included in appropriate amounts.
Among these components, when the content of TiO ₂ increases, the transmittance of the glass in the visible region tends to decrease and the coloration of the glass tends to increase.
The action of Ta ₂ O ₅ is as described above.
When the content of _WO3 increases, the transmittance of the glass in the visible region tends to decrease, the coloration of the glass tends to increase, and the specific gravity tends to increase.
On the other hand, Nb ₂ O ₅ hardly increases the specific gravity, coloration, and manufacturing cost of the glass, and has the function of increasing the refractive index and improving the thermal stability of the glass. Therefore, in glass 1, in order to take advantage of the excellent action and effect of Nb ₂ O ₅ , the mass of the content of Nb ₂ O ₅ with respect to the total content of Nb ₂ O ₅ , TiO ₂ , Ta ₂ O ₅ and WO ₃ The ratio (Nb ₂ O ₅ /(Nb ₂ O ₅ +TiO ₂ +Ta ₂ O ₅ +WO ₃ )) is in the range of 0.5-1. The mass ratio (Nb ₂ O ₅ /(Nb ₂ O ₅ +TiO ₂ +Ta ₂ O ₅ +WO ₃ )) is increased in order to reduce the degree of coloring λ5 and accelerate the curing of the UV-curable adhesive by UV irradiation. is preferred. _A more preferable lower limit and _a more preferable upper limit of the mass ratio ( _Nb2O5 /( _Nb2O5 + _TiO2 + _Ta2O5 + _WO3 )) are shown in the table _below .

Ta ₂ O ₅ is not preferred to be actively introduced into the glass for the reasons described above. Therefore, among Nb ₂ O ₅ , TiO ₂ , Ta ₂ O ₅ and WO ₃ , the content of Nb ₂ O ₅ with respect to the total content of Nb ₂ O ₅ excluding Ta ₂ O ₅ , TiO ₂ and WO ₃ A preferred range of the _mass ratio of ( _Nb2O5 /( _Nb2O5 + _{TiO2 + WO3} )) will be described. The mass ratio (Nb ₂ O ₅ /(Nb ₂ O ₅ +TiO ₂ +WO ₃ )) should be in the range of 0.50 to 1 in order to produce a glass with excellent thermal stability and little coloration. is preferred. A more preferred lower limit and a more preferred upper limit of the mass ratio (Nb ₂ O ₅ /(Nb ₂ O ₅ +TiO ₂ +WO ₃ )) are shown in the table below.

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 )) improves meltability. From the viewpoint of, it is preferable to set it to 0.1 or more. In the case of low-melting glass, if the melting temperature of the glass is increased or the melting time is lengthened in order to prevent unmelted glass raw materials, the coloration of the glass tends to increase. This is because, for example, when glass is melted in a melting crucible made of a precious metal such as platinum, if the melting temperature is increased or the melting time is prolonged, the precious metal that constitutes the crucible will melt into the molten glass, and the precious metal ions will absorb light. This is presumed to be due to the coloration of the glass, especially the increase in the value of λ5. On the other hand, if the meltability is improved by adjusting the contents of other glass components, the thermal stability may decrease, or it may become difficult to obtain a homogeneous glass having the above optical properties. Therefore, in order to improve the meltability of the glass, it is 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 terms of suppressing the coloring of the glass. . In addition, from the viewpoint of further improving the thermal stability of the glass, suppressing a decrease in the glass transition temperature (improving the machinability thereby), and improving the chemical durability, the mass ratio (ZnO/(Nb ₂ O ₅ +TiO ₂ +Ta ₂ O ₅ +WO ₃ )) is preferably 3 or less. A more preferable lower limit and a more preferable upper limit _of the mass ratio (ZnO/( _{Nb2O5 + TiO2} + _Ta2O5 + _WO3 )) are shown in the table below.

Preferred lower and preferred upper limits for each of the Nb ₂ O ₅ content, TiO ₂ content, and WO ₃ content are shown in the table below.

The Li ₂ O content is 1% from the viewpoint of further improving the thermal stability of the glass, suppressing the decrease in the glass transition temperature (improving the machinability thereby), and improving the chemical durability and weather resistance. It is preferable to: A preferred lower limit and a more preferred upper limit for the Li ₂ O content are shown in the table below.

Na ₂ O, K ₂ O, Rb ₂ O, and Cs ₂ O all work to improve the meltability of the glass. Tendency to decrease in toughness, weather resistance and machinability. Therefore, the lower and upper limits of the contents of Na ₂ O, K ₂ O, Rb ₂ O and Cs ₂ O are preferably as shown in the table below.

Rb ₂ O and Cs ₂ O are expensive components and, compared with Li ₂ O, Na ₂ O and K ₂ O, are components that are not suitable for general-purpose glass. Therefore, from the viewpoint of improving the meltability of the glass while maintaining the thermal stability, chemical durability, weather resistance and machinability of the glass, the total content of Li ₂ O, Na ₂ O and K ₂ O is The lower and upper limits of (Li ₂ O+Na ₂ O+K ₂ O) are preferably as shown in the table below.

MgO, CaO, SrO, and BaO are all components that work to improve the meltability of glass. However, when the content of these components increases, the thermal stability of the glass decreases and the glass tends to devitrify. Therefore, the content of each of these components is preferably not less than the lower limit shown below, and preferably not more than the upper limit.

In order to further improve the thermal stability of the glass, the total content of MgO, CaO, SrO and BaO (MgO + CaO + SrO + BaO) is preferably at least the lower limit shown in the table below, preferably at most the upper limit. .

Al ₂ O ₃ is a component that works to improve the chemical durability and weather resistance of glass. However, when the content of Al ₂ O ₃ increases, the refractive index tends to decrease, the thermal stability of the glass tends to decrease, and the meltability tends to decrease. Considering the above points, the Al ₂ O ₃ content is preferably at least the lower limit shown in the table below, and preferably at most the upper limit.

Ga ₂ O ₃ , In ₂ O ₃ , Sc ₂ O ₃ and HfO ₂ all have the function of increasing the refractive index nd. However, these components are expensive and are not essential components for obtaining the glass 1 . Therefore, the contents of Ga ₂ O ₃ , In ₂ O ₃ , Sc ₂ O ₃ and HfO ₂ are preferably at least the lower limits shown in the table below, and preferably at most the upper limits.

Lu ₂ O ₃ has the function of increasing the refractive index nd, but is also a component that increases the specific gravity of the glass. It is also an expensive ingredient. From the above points, the preferred lower limit and preferred upper limit of the Lu ₂ O ₃ content are as shown in the table below.

GeO ₂ has the function of increasing the refractive index nd, but it is by far the most expensive component among commonly used glass components. From the viewpoint of reducing the manufacturing cost of glass, the preferred lower limit and preferred upper limit of the GeO ₂ content are as shown in the table below.

Bi ₂ O ₃ is a component that increases the refractive index nd and lowers the Abbe number. It is also a component that tends to increase the coloration of glass. The lower and preferred upper limits of the Bi ₂ O ₃ content are shown in the table below in order to produce a glass having the above optical properties and less coloring.

In order to satisfactorily obtain the various functions and effects described above, the total content (total content) of the respective glass components described above is preferably greater than 95%, more preferably greater than 98%. More preferably, more than 99% is even more preferable, and more than 99.5% is even more preferable.

Among the glass components other than those described above, P ₂ O ₅ is a component that lowers the refractive index and lowers the thermal stability of the glass. May improve stability. The preferred lower and upper limits of the P ₂ O ₅ content for producing a glass having the above optical properties and excellent thermal stability are as shown in the table below.

TeO ₂ is a component that increases the refractive index, but is a toxic component, so it is preferable to reduce the content of TeO ₂ . A preferred lower limit and preferred upper limit for the TeO ₂ content are as shown in the table below.

In each of the above tables, the content of the (more) preferred lower limit or 0% is preferably 0%. The same applies to the total content of multiple components.

Pb, As, Cd, Tl, Be and Se each have toxicity. Therefore, it is preferable not to contain these elements, that is, not to introduce these elements into the glass as glass components.
All of U, Th, and Ra are radioactive elements. Therefore, it is preferable not to contain these elements, that is, not to introduce these elements into the glass as glass components.
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 or become a source of fluorescence. , is not preferable as an element to be contained in glass for optical elements. Therefore, it is preferable not to contain these elements, that is, not to introduce these elements into the glass as glass components.

Sb and Sn are arbitrarily added elements that function as refining agents.
The amount of Sb added is converted to Sb ₂ O ₃ , and is 0 to 0.11% by mass when the total content of glass components other than Sb ₂ O ₃ is 100% by mass in the oxide-based glass composition. It is preferably in the range, more preferably in the range of 0.01 to 0.08% by mass, and even more preferably in the range of 0.02 to 0.05% by mass. Here, the term "glass composition based on oxides" refers to a glass composition obtained by conversion assuming that the glass raw materials are all decomposed during melting and exist as oxides in the glass. The Sb ₂ O ₃ content in the glass composition shown in the table below is also the content calculated by the above method.
The amount of Sn to be added should be in the range of 0 to 1.0% by mass in terms of SnO ₂ , when the total content of glass components other than SnO ₂ is 100% by mass in the oxide-based glass composition. , more preferably in the range of 0 to 0.5% by mass, still more preferably in the range of 0 to 0.2% by mass, and even more preferably 0% by mass.

<Glass Composition of Glass 2>
In the present invention, the glass composition of the glass 2 is represented by cation % with respect to cationic components. As is well known, the cation % is a percentage based on the total content of all cationic components contained in the glass as 100%.
The cation components are indicated, for example, as B ³⁺ , Si ⁴⁺ , La ³⁺ , and the valences of the cation components (for example, the valence of B ³⁺ is +3, the valence of Si ⁴⁺ is +4 , the valence of La ³⁺ is +3) is a value determined by convention, and is the same as B, Si, and La being expressed as B ₂ O ₃ , SiO ₂ , and La ₂ O ₃ based on oxides. . For a component denoted A _m O _n (A represents a cation, O represents oxygen, and m and n are stoichiometrically determined integers) on an oxide basis, the cation A is denoted A ^s+ be done. where s=2n/m. Therefore, for example, when analyzing and quantifying the glass composition, it is not necessary to analyze the valence of the cationic component. Hereinafter, unless otherwise specified, the content of a cationic component and the total content of a plurality of types of cationic components (total content) are expressed in terms of cation %. Furthermore, in terms of cation %, the ratio of the contents of cationic components (including the total content of a plurality of cationic components) is referred to as the cationic ratio.

B ³⁺ and Si ⁴⁺ are network-forming components of 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. can. On the other hand, when the total content of B ³⁺ and Si ⁴⁺ is 65% or less, the decrease in the refractive index can be suppressed. It is possible to produce a glass having an Abbe number νd in the range of 41.5 to 44 while being in the range of 800 to 1.850. Therefore, the total content of B ³⁺ and Si ⁴⁺ in the glass 2 should be in the range of 45-65%. A preferable lower limit and preferable upper limit of the total content of B ³⁺ and Si ⁴⁺ are as shown in the table below.

The content ratio of each component of B ³⁺ and Si ⁴⁺ , which are the network forming components of glass, depends on the thermal stability, meltability, formability, chemical durability, weather resistance, machinability, etc. of the glass. influence. B ³⁺ works better than Si ⁴⁺ in improving meltability, but it is easily volatilized during melting. On the other hand, Si ⁴⁺ works to improve the chemical durability, weather resistance and machinability of the glass, and to increase the viscosity of the glass during melting.
In general, a high-refractive-index, low-dispersion glass containing rare earth elements such as B ³⁺ and La ³⁺ has a low viscosity when melted. However, if the viscosity of the glass when melted is low, the thermal stability is lowered (easily crystallized). Crystallization during glass production is more stable in a crystalline state than in an amorphous state (amorphous state), and occurs when the ions that make up the glass move through the glass and are arranged to have a crystal structure. Therefore, by adjusting the content ratio of each component of B ³⁺ and Si ⁴⁺ so as to increase the viscosity at the time of melting, the above-mentioned ions are made difficult to be arranged in a crystal structure, and the crystal of the glass is formed. It is possible to further suppress the quenching and improve the thermal stability of the glass.
When molten glass is poured into a mold for molding, if the viscosity of the molten glass is low, the solidified surface of the glass poured into the mold is caught in the glass that is still in a molten state, forming striae. homogeneity is reduced. A glass with excellent formability corresponds to a glass having a relatively high viscosity when poured into a mold in a molten state, among high refractive index and low dispersion glasses containing rare earth elements.
If the cation ratio of the content of B ³⁺ to the total content of B ³⁺ and Si ⁴⁺ (B ³⁺ /(B ³⁺ +Si ⁴⁺ )) is less than 0.94, the viscosity will not decrease during melting. This can improve the thermal stability of the glass and suppress volatilization during melting. Volatilization at the time of melting causes fluctuations in glass composition and properties. And as a result, it is difficult to form optically homogeneous glass. Therefore, it is preferable from the viewpoint of mass production of glass with little variation in composition and properties that the cation ratio (B ³⁺ /(B ³⁺ +Si ⁴⁺ )) is less than 0.94 so that volatilization during melting can be suppressed. Furthermore, when the cation ratio (B ³⁺ /(B ³⁺ +Si ⁴⁺ )) is less than 0.94, deterioration in chemical durability, weather resistance and machinability of the glass can be suppressed. On the other hand, in the glass composition described in the aforementioned Patent Document 15 (JP-A-57-056344), the B ₂ O ₃ content is 28 to 30% by mass, and the SiO ₂ content is 1 to 3%. % by mass (see the claims of Patent Document 15). The cation ratio (B ³⁺ /(B ³⁺ +Si ⁴⁺ )) calculated from the contents of these components is a large value of 0.942 to 0.981.
On the other hand, if the cation ratio (B ³⁺ /(B ³⁺ +Si ⁴⁺ )) is 0.65 or more, it is possible to prevent unmelted glass raw materials during melting, so that the meltability can be improved. .
From the above points, 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 preferred lower and preferred upper limits of the cation ratio (B ³⁺ /(B ³⁺ +Si ⁴⁺ )) in glass 2 are as shown in the table below.

For each of the B ³⁺ content and the Si ⁴⁺ content, preferred lower limits and preferred from the viewpoint of improving the thermal stability, meltability, moldability, chemical durability, weather resistance, machinability, etc. of the glass The upper limits are shown in the table below.

La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ are components that work to increase the refractive index while suppressing the decrease in Abbe's number. These components also work to improve the chemical durability and weatherability of the glass and to raise 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, the decrease in refractive index can be suppressed. Therefore, it is possible to produce a glass having the optical properties described above. Furthermore, it is possible to suppress the deterioration of the chemical durability and weather resistance of the glass. Note that when the glass transition temperature is lowered, the glass is more likely to be damaged (decreased machinability) when the glass is mechanically processed (cutting, cutting, grinding, polishing, etc.), but La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ is 25% or more, the decrease in the glass transition temperature can be suppressed, and the machinability can be improved. On the other hand, if the total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ is 35% or less, the thermal stability of the glass can be enhanced, so crystallization during glass production can be suppressed, and unmelted raw materials can be reduced when the glass is melted. Therefore, in glass 2, the total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ should be in the range of 25-35%. Preferred lower and preferred upper limits for the total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ are shown in the table below.

Zr ⁴⁺ is a component that works to increase the refractive index, and also works to improve the thermal stability of the glass when contained in an appropriate amount. Zr ⁴⁺ also has the function of increasing the glass transition temperature and making the glass less likely to break during mechanical processing. In order to satisfactorily obtain these effects, the glass 2 has a Zr ⁴⁺ content of 2% or more. On the other hand, if the Zr ⁴⁺ content is 8% or less, the thermal stability of the glass can be improved, so crystallization during glass production and unmelted residue during glass melting can be suppressed. can. Therefore, the content of Zr ⁴⁺ in the glass 2 should be in the range of 2 to 8%. Preferred lower and preferred upper limits for the Zr ⁴⁺ content are shown in the table below.

As described above, Ta ⁵⁺ is a component whose proportion in the glass composition is desirably reduced from the viewpoint of stable supply of glass. Ta ⁵⁺ is a component that works to increase the refractive index, but it is also a component that increases the specific gravity of the glass and reduces the meltability. Therefore, the Ta ⁵⁺ content in the glass 2 should be 3% or less. A preferred lower limit and preferred upper limit for the Ta ⁵⁺ content are shown in the table below.

In order to improve the thermal stability of the glass and suppress the increase in the specific gravity while realizing the above optical properties, the total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ in the glass 2 cation ratio ((B ³⁺ +Si ⁴⁺ )/(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )) of the total content ^of B ³⁺ and Si 4+ to Range. If the cation ratio ((B ³⁺ +Si ⁴⁺ )/(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )) is 1.65 or more, the thermal stability of the glass can be improved. Devitrification of glass can be suppressed. Also, it is possible to suppress an increase in the specific gravity of the glass. As the specific gravity of the glass increases, the weight of the optical element manufactured using this glass increases. As a result, an optical system incorporating this optical element becomes heavy. For example, if a heavy optical element is incorporated in an autofocus camera, power consumption increases when the autofocus is driven, and the battery is quickly exhausted. Being able to suppress an increase in the specific gravity of the glass is preferable from the viewpoint of reducing the weight of an optical element manufactured using this glass and an optical system incorporating this optical element. On the other hand, if the cation ratio ((B ³⁺ +Si ⁴⁺ )/(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )) is 2.60 or less, the above optical properties can be achieved. In addition, the cation ratio ((B ³⁺ +Si ⁴⁺ )/(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )) of 2.60 or less contributes to the improvement of the chemical durability of the glass, It is also preferable from the viewpoint of increasing the transition temperature (Tg). The preferred lower and preferred upper limits of the cation ratio ((B ³⁺ +Si ⁴⁺ )/(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )) are shown in the table below.

Among La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ , Yb ³⁺ is a component whose proportion in the glass composition should be reduced for the reasons described above. Therefore, in glass 2, the Yb ³⁺ content is set to less than 2%. A preferred lower limit and preferred upper limit for the Yb ³⁺ content are shown in the table below.

Y ³⁺ is a component that works to improve the thermal stability of the glass without significantly lowering the light transmittance in the near-infrared region. Moreover, since its atomic weight is small, it is a preferable component for suppressing an increase in the specific gravity of the glass. However, if the Y ³⁺ content is too high, the thermal stability of the glass will be significantly reduced, and crystallization will tend to occur. Also, the meltability is lowered. In glass 2, La ³⁺ , The cation ratio of the content of Y ³⁺ to the total content of Y ³⁺ , Gd ³⁺ and Yb ³⁺ (Y ³⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )) was 0.05. ∼0.45. The preferred lower and preferred upper limits of the cation ratio (Y ³⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )) are shown in the table below.

Gd ³⁺ is a component whose proportion in the glass composition should be reduced for the reasons described above. Gd, like Yb, belongs to heavy rare earth elements, has a large atomic weight as a component of glass, and increases the specific gravity of glass. From this point of view as well, it is desirable to reduce the proportion of Gd in the glass composition.
In Glass 2, the Gd ³⁺ content is determined by the total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ and the Gd ³⁺ content relative to this total content. For the glass 2, La ³⁺ , Y ³⁺ , The cation ratio of the Gd ³⁺ content to the total content of Gd ³⁺ and Yb ³⁺ (Gd ³⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )) is in the range of 0 to 0.05. . The preferred lower and preferred upper limits of the cation ratio (Gd ³⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )) are shown in the table below.

La ³⁺ does not significantly reduce the light transmittance in the near-infrared region, improves thermal stability, suppresses an increase in specific gravity, and is useful for providing a high refractive index and low dispersion glass. is an ingredient. Therefore, in glass 2, the cation ratio of the La ³⁺ content to the total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ (La ³⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ^{3 +} )) is preferably in the range of 0.55 to 0.95. A more preferable lower limit and a more preferable upper limit of the cation ratio (La ³⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )) are shown in the table below.

Preferred lower and preferred upper limits for the content of each of La ³⁺ , Y ³⁺ and Gd ³⁺ are shown in the table below.

Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ are components that work to increase the refractive index, and also work to improve the thermal stability of the glass when contained in appropriate amounts. The total content of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ (Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ ) is in the range of 2 to 10%. It is preferable in terms of further improving the thermal stability of the glass while realizing it. A more preferable lower limit and a more preferable upper limit of the total content of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ are shown in the table below.

Zn ²⁺ has a function of promoting the melting of the raw materials of the glass when the glass is melted, that is, a function of improving the meltability. It also has the function of adjusting the refractive index and Abbe's number and lowering the glass transition temperature. The value obtained by dividing the Zn ²⁺ content by the total content of B ³⁺ and Si ⁴⁺ , that is, the cation ratio (Zn ²⁺ /(B ³⁺ +Si ⁴⁺ )) is 0.01 or more. , is preferred for improving the meltability. On the other hand, a cation ratio (Zn ²⁺ /(B ³⁺ +Si ⁴⁺ )) of 0.22 or less is preferable for suppressing a decrease in the Abbe number (high dispersion) and realizing the above optical properties. . A cation ratio (Zn ²⁺ /(B ³⁺ +Si ⁴⁺ )) of 0.22 or less is also preferable for improving the thermal stability of the glass and increasing the glass transition temperature (Tg). Therefore, the content of Zn ²⁺ should be 0.01 to 0.22 times the total content of B ³⁺ and Si ⁴⁺ in terms of cation ratio, that is, the cation ratio (Zn ²⁺ /(B ^{3 +} +Si ⁴⁺ )) is preferably 0.01 to 0.22. A more preferable lower limit and a more preferable upper limit of the cation ratio (Zn ²⁺ /(B ³⁺ +Si ⁴⁺ )) are shown in the table below.

From the viewpoint of improving the meltability, thermal stability, formability, machinability, etc. of the glass and realizing the above optical properties, the preferable lower and preferable upper limits of the Zn ²⁺ content are as shown in the table below. be.

Cation ratio of the total content of B ³⁺ and Si ⁴⁺ to the total content of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ ((B ³⁺ +Si ⁴⁺ )/(Nb ⁵⁺ +Ti ^{4 +} +Ta ⁵⁺ +W ⁶⁺ )) is in the range of 9.0 to 32 in order to suppress an increase in the degree of coloring λ5 described later and increase the ultraviolet transmittance of the glass while realizing the above optical characteristics. is preferred. Also, in terms of improving the thermal stability of the glass, it is also possible to set the cation ratio ((B ³⁺ +Si ⁴⁺ )/(Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )) to 9.0 or more. preferable. A more preferable lower limit and a more preferable upper limit of the cation ratio ((B ³⁺ +Si ⁴⁺ )/(Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )) are shown in the table below.

Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ work to improve the thermal stability of the glass when contained in appropriate amounts.
Among these components, when the content of Ti ⁴⁺ increases, the transmittance of the glass in the visible region tends to decrease and the coloration of the glass tends to increase.
The action of Ta ⁵⁺ is as described above.
As for W ⁶⁺ , when its content increases, the transmittance of the glass in the visible region tends to decrease, the coloration of the glass tends to increase, and the specific gravity tends to increase.
On the other hand, Nb ⁵⁺ hardly increases the specific gravity, coloration, and manufacturing cost of the glass, and has the function of increasing the refractive index and improving the thermal stability of the glass. Therefore, in glass 2, in order to take advantage of the excellent action and effect of Nb ⁵⁺ , the cation ratio of the content of Nb ⁵⁺ to the total content of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ ( Nb ⁵⁺ /(Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )) is in the range of 0.4-1. The cation ratio (Nb ⁵⁺ /(Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )) should be increased in order to reduce the degree of coloring λ5 and accelerate the curing of the UV-curable adhesive by UV irradiation. is preferred. A more preferable lower limit and a more preferable upper limit of the cation ratio (Nb ⁵⁺ /(Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )) are shown in the table below.

Ta ⁵⁺ is not preferable to be actively introduced into the glass for the reasons described above. Therefore, among Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ , the content of Nb ⁵⁺ with respect to the total content of Nb ⁵⁺ excluding Ta ⁵⁺ , Ti ⁴⁺ and W ⁶⁺ A preferred range of the cation ratio (Nb ⁵⁺ /(Nb ⁵⁺ +Ti ⁴⁺ +W ⁶⁺ )) will be explained. The cation ratio (Nb ⁵⁺ /(Nb ⁵⁺ +Ti ⁴⁺ +W ⁶⁺ )) should be in the range of 0.4 to 1 in order to produce a glass with excellent thermal stability and low coloration. is preferred. A more preferable lower limit and a more preferable upper limit of the cation ratio (Nb ⁵⁺ /(Nb ⁵⁺ +Ti ⁴⁺ +W ⁶⁺ )) are shown in the table below.

The cation ratio of the Zn ²⁺ content to the total content of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ (Zn ²⁺ /(Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )) is From the viewpoint of improving meltability, it is preferably 0.1 or more. In the case of low-melting glass, if the melting temperature of the glass is increased or the melting time is lengthened in order to prevent unmelted glass raw materials, the coloration of the glass tends to increase. This is because, for example, when glass is melted in a melting crucible made of a precious metal such as platinum, if the melting temperature is increased or the melting time is prolonged, the precious metal that constitutes the crucible will melt into the molten glass, and the precious metal ions will absorb light. This is presumed to be due to the coloration of the glass, especially the increase in the value of λ5. On the other hand, if the meltability is improved by adjusting the contents of other glass components, the thermal stability may decrease, or it may become difficult to obtain a homogeneous glass having the above optical properties. Therefore, in order to improve the meltability of the glass, setting the cation ratio (Zn ²⁺ /(Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )) to 0.1 or more is effective in suppressing coloration of the glass. But preferred. From the viewpoint of further improving the thermal stability of the glass, suppressing the decrease in the glass transition temperature (improving the machinability thereby), and improving the chemical durability, the cation ratio (Zn ²⁺ /(Nb ^{5 +} +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )) is preferably 5 or less. A more preferable lower limit and a more preferable upper limit of the cation ratio (Zn ²⁺ /(Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )) are shown in the table below.

Preferred lower limits and preferred upper limits for each of the Nb ⁵⁺ content, Ti ⁴⁺ content, and W ⁶⁺ content are shown in the table below.

The Li ⁺ content is 3% or less from the viewpoint of further improving the thermal stability of the glass, suppressing the decrease in the glass transition temperature (improving the machinability by this), and improving the chemical durability and weather resistance. It is preferable to A preferred lower limit and a more preferred upper limit for the Li ⁺ content are shown in the table below.

Na ⁺ , K ⁺ , Rb ⁺ , and Cs ⁺ all work to improve the meltability of the glass. , the machinability tends to decrease. Therefore, the lower and upper limits of each content of Na ⁺ , K ⁺ , Rb ⁺ , and Cs ⁺ are preferably as shown in the table below.

Rb ⁺ and Cs ⁺ are expensive components and, compared to Li ⁺ , Na ⁺ and K ⁺ , they are not suitable for general-purpose glass. Therefore, the total content of Li ⁺ , Na ⁺ and K ⁺ (Li ⁺ +Na ⁺ +K ⁺ ) is preferably as shown in the table below.

Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ are all components that work to improve the meltability of the glass. However, when the content of these components increases, the thermal stability of the glass decreases and the glass tends to devitrify. Therefore, the content of each of these components is preferably not less than the lower limit shown below, and preferably not more than the upper limit.

In order to further improve 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 preferably at least the lower limit shown in the table below, and preferably at most the upper limit.

Al ³⁺ is a component that works to improve the chemical durability and weather resistance of glass. However, when the content of Al ³⁺ increases, the refractive index tends to decrease, the thermal stability of the glass tends to decrease, and the meltability tends to decrease. Considering the above points, the Al ³⁺ content is preferably equal to or higher than the lower limit shown in the table below, and preferably equal to or lower than the upper limit.

Ga ³⁺ , In ³⁺ , Sc ³⁺ , and Hf ⁴⁺ all work to increase the refractive index. However, these components are expensive and are not essential components for obtaining the glass 2 . Therefore, each content of Ga ³⁺ , In ³⁺ , Sc ³⁺ and Hf ⁴⁺ is preferably at least the lower limit shown in the table below, and preferably at most the upper limit.

Lu ³⁺ has the function of increasing the refractive index, but is also a component that increases the specific gravity of the glass. It is also an expensive ingredient. From the above points, the preferred lower limit and preferred upper limit of the Lu ³⁺ content are as shown in the table below.

Ge ⁴⁺ has the function of increasing the refractive index, but it is by far the most expensive component among commonly used glass components. From the viewpoint of reducing the manufacturing cost of glass, the preferred lower and upper limits of the Ge ⁴⁺ content are as shown in the table below.

Bi ³⁺ is a component that increases the refractive index and lowers the Abbe number. It is also a component that tends to increase the coloration of glass. The lower and preferred upper limits of the Bi ³⁺ content are shown in the table below in order to produce a glass having the above optical properties and less coloring.

In order to satisfactorily obtain the various functions and effects described above, the total content of the cationic components described above (total content) is preferably greater than 95%, and preferably greater than 98%. More preferably, more than 99% is even more preferable, and more than 99.5% is even more preferable.

Among the cationic components other than the cationic components described above, P ⁵⁺ is a component that lowers the refractive index and lowers the thermal stability of the glass. May improve thermal stability. The preferred lower limit and preferred upper limit of the P ⁵⁺ content for producing a glass having the above-described optical properties and excellent thermal stability are as shown in the table below.

Although Te ⁴⁺ is a component that increases the refractive index, it is a toxic component, so it is preferable to reduce the content of Te ⁴⁺ . A preferred lower limit and preferred upper limit for the Te ⁴⁺ content are as shown in the table below.

In each of the above tables, the content of the (more) preferred lower limit or 0% is preferably 0%. The same applies to the total content of multiple components.

Pb, As, Cd, Tl, Be and Se each have toxicity. Therefore, it is preferable not to contain these elements, that is, not to introduce these elements into the glass as glass components.
All of U, Th, and Ra are radioactive elements. Therefore, it is preferable not to contain these elements, that is, not to introduce these elements into the glass as glass components.
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 or become a source of fluorescence. , is not preferable as an element to be contained in glass for optical elements. Therefore, it is preferable not to contain these elements, that is, not to introduce these elements into the glass as glass components.

Sb and Sn are arbitrarily added elements that function as refining agents.
The amount of Sb added is converted to Sb ₂ O ₃ , and is 0 to 0.11% by mass when the total content of glass components other than Sb ₂ O ₃ is 100% by mass in the oxide-based glass composition. It is preferably in the range, more preferably in the range of 0.01 to 0.08% by mass, and even more preferably in the range of 0.02 to 0.05% by mass. Here, the term "glass composition based on oxides" refers to a glass composition obtained by conversion assuming that the glass raw materials are all decomposed during melting and exist as oxides in the glass. The Sb ₂ O ₃ content in the glass composition shown in the table below is also the content calculated by the above method.
The amount of Sn to be added should be in the range of 0 to 1.0% by mass in terms of SnO ₂ , when the total content of glass components other than SnO ₂ is 100% by mass in the oxide-based glass composition. , more preferably in the range of 0 to 0.5% by mass, still more preferably in the range of 0 to 0.2% by mass, and even more preferably 0% by mass.

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

Since the glass 2 is oxide glass, it contains O ²⁻ as an anion component. The content of O ^2- is preferably in the range of 98 to 100 anion%, more preferably in the range of 99 to 100 anion%, even more preferably in the range of 99.5 to 100 anion%, and 100 Anion % is more preferred.
Examples of anion components other than O ^2- include F ⁻ , Cl ⁻ , Br ⁻ and I ⁻ . However, F ⁻ , Cl ⁻ , Br ⁻ and I ⁻ are all easily volatilized during melting of the glass. Volatilization of these components tends to change the properties of the glass, reduce the homogeneity of the glass, and significantly wear out the melting equipment. Therefore, it is preferable to limit the total content of F ⁻ , Cl ⁻ , Br ⁻ and I ⁻ to 100 anion % minus the content of O ²⁻ .
Incidentally, as is well known, the anion % is a percentage based on the total content of all anion components contained in the glass being 100%.

<Glass characteristics>
Next, glass properties common to glass 1 and glass 2 will be described. The glasses mentioned below shall refer to glass 1 and glass 2.

(Optical properties of glass)
The glass has a refractive index nd in the range of 1.800 to 1.850 and an Abbe number νd in the range of 41.5 to 44.

Glass with a refractive index of 1.800 or more is suitable as a material for optical elements such as lenses with a large refractive power. On the other hand, if the refractive index is higher than 1.850, the Abbe number tends to decrease, the thermal stability of the glass tends to decrease, and coloring tends to increase. A preferred lower limit and preferred upper limit of the refractive index are shown in the table below.

A glass with an Abbe number of 41.5 or more is effective for correcting chromatic aberration as a material for optical elements. On the other hand, when the Abbe number is greater than 44, the refractive index tends to decrease and the thermal stability of the glass tends to deteriorate. A preferred lower limit and preferred upper limit for the Abbe number are shown in the table below.

(Partial dispersion characteristics)
From the viewpoint of correction of chromatic aberration, it is preferable that the glass has a small partial dispersion ratio when the Abbe number is fixed.
Here, the partial dispersion ratio Pg, F is (ng−nF)/(nF−nC ).
From the viewpoint of providing a glass suitable for high-order chromatic aberration correction, the preferable lower and preferable upper limits of the partial dispersion ratio Pg,F of the glass are as shown in the table below.

(Glass-transition temperature)
From the viewpoint of improving machinability, the glass preferably has a glass transition temperature of 640° C. or higher. By setting the glass transition temperature to 640° C. or higher, it is possible to make the glass less likely to be damaged during mechanical processing of the glass such as cutting, cutting, grinding and polishing.
On the other hand, if the glass transition temperature is too high, the glass must be annealed at a high temperature, resulting in significant consumption of the annealing furnace. In addition, when molding glass, molding must be performed at a high temperature, and the consumption of the mold used for molding becomes significant.
More preferable lower and preferable upper limits of the glass transition temperature are as shown in the table below from the viewpoint of improving machinability and reducing the load on the annealing furnace and mold.

(Light transmittance of glass)
The light transmittance of the glass, more specifically, the fact that the light absorption edge on the short wavelength side is suppressed from becoming longer in wavelength can be evaluated by the degree of coloring λ5. The coloring degree λ5 is the wavelength at which the spectral transmittance (including surface reflection loss) of 10 mm-thick glass is 5% from the ultraviolet region to the visible region. λ5 shown in Examples below is a value measured in a wavelength range of 250 to 700 nm. Spectral transmittance is, for example, more specifically, a glass sample having planes parallel to each other and optically polished to a thickness of 10.0±0.1 mm. i.e., the intensity ratio Iout/Iin where Iin is the intensity of light incident on the glass sample and Iout is the intensity of light transmitted through the glass sample.
According to the coloring degree λ5, the absorption edge on the short wavelength side of the spectral transmittance can be quantitatively evaluated. As described above, when lenses are bonded together with an ultraviolet-curing adhesive to produce a cemented lens, the adhesive is cured by irradiating the adhesive with ultraviolet rays through an optical element. It is preferable that the absorption edge on the short wavelength side of the spectral transmittance is in a short wavelength region in order to efficiently cure the ultraviolet curable adhesive. As an index for quantitatively evaluating the absorption edge on the short wavelength side, the degree of coloring λ5 can be used. The above-described glass can exhibit a λ5 of preferably 335 nm or less, more preferably 332 nm or less, even more preferably 330 nm or less, still more preferably 328 nm or less, and even more preferably 326 nm or less by adjusting the composition as described above. As an example, the lower limit of λ5 can be 315 nm, but it is not particularly limited as the lower the better.

On the other hand, as an index of the degree of coloring of glass, the degree of coloring λ70 can be mentioned. λ70 is the wavelength at which the spectral transmittance measured by the method described for λ5 is 70%. From the viewpoint of making the glass less colored, λ70 is preferably 420 nm or less, more preferably 400 nm or less, still more preferably 390 nm or less, and still more preferably 380 nm or less. Although the lower limit of λ70 is 340 nm, it is not particularly limited as the lower the better.
Further, as an index of the degree of coloring of glass, the degree of coloring λ80 is also exemplified. λ80 is the wavelength at which the spectral transmittance measured by the method described for λ5 is 80%. From the viewpoint of making the glass less colored, λ80 is preferably 480 nm or less, more preferably 460 nm or less, still more preferably 440 nm or less, and still more preferably 420 nm or less. Although the lower limit of λ80 is 350 nm, it is not particularly limited as the lower the better.

(Specific gravity of glass)
In an optical element (lens) that constitutes an optical system, the refractive power is determined by the refractive index of the glass that constitutes the lens and the curvature of the optically functional surface of the lens (the surface on which light rays to be controlled enter and exit). Increasing the curvature of the optically functional surface also increases the thickness of the lens. As a result, the lens becomes heavy. On the other hand, if glass with a high refractive index is used, a large refractive power can be obtained without increasing the curvature of the optically functional surface.
As described above, if the refractive index can be increased while suppressing an increase in the specific gravity of the glass, it becomes possible to reduce the weight of the optical element having a constant refractive power.
Regarding the contribution of the refractive index nd to the refractive power, the ratio of the specific gravity d of the glass to the value (nd-1) obtained by subtracting 1, which is the refractive index in a vacuum, from the refractive index nd of the glass, yields It can be used as an index for weight reduction. That is, d/(nd−1) is used as an index for reducing the weight of the optical element, and by reducing this value, the weight of the lens can be reduced.
Since the above glass has a low proportion of Gd, Ta, and Yb, which cause an increase in specific gravity, it is possible to reduce the specific gravity of the glass while maintaining a high refractive index and low dispersion. Therefore, d/(nd-1) of the glass can be, for example, 5.70 or less. However, excessive reduction of d/(nd-1) tends to lower the thermal stability of the glass. Therefore, d/(nd-1) is preferably 5.00 or more. A more preferable lower limit and a more preferable upper limit of d/(nd-1) are shown in the table below.

Furthermore, the preferred lower limit and preferred upper limit of the specific gravity d of the glass are shown in the table below. It is preferable to make the specific gravity d equal to or higher than the upper limit shown in the table below from the viewpoint of reducing the weight of the optical element made of this glass. Further, it is preferable to make the specific gravity equal to or higher than the lower limit shown in the table below in order to further improve the thermal stability of the glass.

(Liquidus temperature)
One of the indexes of the thermal stability of glass is the liquidus temperature. From the viewpoint of suppressing crystallization and devitrification during glass production, the liquidus temperature LT is preferably 1300° C. or lower, more preferably 1250° C. or lower, and still more preferably 1200° C. or lower. °C or less is even more preferable. The lower limit of the liquidus temperature LT is, for example, 1100° C. or higher, but it is preferably low and is not particularly limited.

The glasses (glass 1 and glass 2) according to one aspect of the present invention described above are high-refractive-index, low-dispersion glasses, and are useful as glass materials for optical elements. Further, the composition adjustment described above enables homogenization and reduction of coloration of the glass. In addition, the glass is easy to mold and easy to mechanically process. Therefore, the above glass is suitable as an optical glass.

<Glass manufacturing method>
In order to obtain the desired glass composition, the above glass is prepared by weighing and blending raw materials such as oxides, carbonates, sulfates, nitrates, hydroxides, etc., and thoroughly mixing them to form a mixed batch, which is then placed in a melting vessel. It can be obtained by heating, melting, defoaming, and stirring to form a homogeneous and bubble-free molten glass, which is then molded. Specifically, it can be produced using a known melting method. Although the above glass is a high refractive index and low dispersion glass having the above optical properties, it has excellent thermal stability, so that it can be stably produced using a known melting method and molding method.

[Glass material for press molding, optical element blank, and manufacturing method thereof]
Another aspect of the present invention is
A press-molding glass material comprising glass 1 or glass 2 described above;
an optical element blank made of glass 1 or glass 2 described above;
Regarding.

According to another aspect of the invention,
A method for producing a press-molding glass material, comprising the step of forming the above glass 1 or glass 2 into a press-molding glass material;
A method for producing an optical element blank, comprising a step of producing an optical element blank by press-molding the above glass material for press molding using a press mold;
A method for manufacturing an optical element blank, comprising a step of molding the above glass 1 or glass 2 into an optical element blank;
is also provided.
Since the press-molding glass material and the optical element blank are made of the glass 1 or glass 2 described above, the press-molding glass material and the optical element blank naturally correspond to the glass described above.

The optical element blank is similar to the shape of the target optical element, and is polished to the shape of the optical element (surface layer to be removed by polishing), and if necessary, is ground (to be removed by grinding). surface layer) is added to the optical element base material. The optical element is finished by polishing the surface of the optical element blank, or by grinding and polishing. In one aspect, an optical element blank can be produced by a method of press-molding a molten glass obtained by melting an appropriate amount of the glass (referred to as a direct press method). In another aspect, an optical element blank can also be produced by solidifying the molten glass obtained by melting an appropriate amount of the above glass and further processing the molten glass.

In another aspect, an optical element blank can be produced by producing a press-molding glass material and press-molding the produced press-molding glass material.

The press-molding glass material for press-molding can be press-molded by a known method of pressing the glass material for press-molding that has been softened by heating with a press mold. Both heating and press molding can be performed in the atmosphere. A homogeneous optical element blank can be obtained by annealing after press molding to reduce the strain inside the glass.

Glass materials for press molding include glass gobs for press molding, which are used as they are for press molding to produce optical element blanks, and glass gobs for press molding that are subjected to machining such as cutting, grinding, and polishing. Also includes those subjected to press molding through. As a cutting method, grooves are formed in the part of the surface of the glass plate to be cut by a method called scribing. There are methods such as breaking a plate and cutting a glass plate with a cutting blade. Further, the grinding and polishing methods include well-known processing methods such as barrel polishing.

The glass material for press molding is produced, for example, by casting molten glass in a mold to form a glass plate, cutting the glass plate into a plurality of glass pieces, or by barrel polishing the plurality of glass pieces. can be done. Alternatively, a glass gob for press molding can be produced by molding an appropriate amount of molten glass. An optical element blank can also be produced by reheating, softening, and press-molding a press-molding glass gob. A method of manufacturing an optical element blank by reheating, softening, and press-molding glass is called a reheat press method as opposed to the direct press method.

[Optical element and its manufacturing method]
Another aspect of the present invention is
An optical element made of glass 1 or glass 2 described above.
The optical element is manufactured using the glass 1 or glass 2 described above. In the optical element, the glass surface may be coated with one or more layers such as a multilayer film such as an antireflection film.
Since the optical element is made of glass 1 or glass 2 described above, it naturally corresponds to the glass described above. Further, when a coating is formed on the glass surface of the optical element, the portion of the glass excluding the coating corresponds to the glass described above.

Further, according to one aspect of the present invention,
A method for manufacturing an optical element, comprising a step of manufacturing an optical element by at least polishing the optical element blank described above;
is also provided.

In the above optical element manufacturing method, known methods may be applied for grinding and polishing, and an optical element with high internal quality and surface quality can be obtained by sufficiently washing and drying the optical element surface after processing. can. Thus, an optical element made of the above glass can be obtained. Examples of optical elements include various lenses such as spherical lenses, aspherical lenses, and microlenses, and prisms.

Further, the optical element made of glass 1 or glass 2 is also suitable as a lens constituting a cemented optical element. Examples of cemented optical elements include cemented lenses (cemented lenses) and cemented lenses and prisms. For example, to make a cemented optical element, the bonding surfaces of two optical elements to be bonded are precisely processed (for example, spherically polished) so that their shapes are reversed, and an ultraviolet curable adhesive is applied to the bonding surfaces. can be produced by bonding the bonding surfaces together and then irradiating the adhesive on the bonding surfaces with ultraviolet rays through an optical element to cure the adhesive. The glasses described above are preferred for producing cemented optical elements in this manner. A plurality of optical elements to be cemented can be manufactured using a plurality of types of glass having different Abbe's numbers, respectively, and bonded together to form an element suitable for correcting chromatic aberration.

As a result of the quantitative analysis of the glass composition, the glass components are expressed on the basis of oxides, and the contents of the glass components are expressed in mass %. The composition represented by % by mass based on the oxide can be converted into a composition represented by % of cation and % of anion, for example, by the following method.
For example, an oxide consisting of cation A and oxygen is represented as A _m O _n . m and n are stoichiometrically determined integers. For example, for B ³⁺ , the notation based on the oxide standard is B ₂ O ₃ , m=2, n=3, and for Si ⁴⁺ , SiO ₂ , m=1, n=2.
First, the content of A _m O _n expressed in mass % is divided by the molecular weight of A _m O _n and then multiplied by m. Let P be this value. Then sum P for all of the cationic components. Assuming that the total value of P is ΣP, the value obtained by standardizing the P value of each cationic component so that ΣP is 100% is the content of As ⁺ in cation %. where s is 2n/m.
Note that trace amounts of additives, such as clarifiers such as Sb ₂ O ₃ , may not be included in ΣP. In that case, the content of Sb may be the content (% by mass) of Sb ₂ O ₃ converted to Sb 2 O 3 as described above. That is, the total content of the glass components excluding the content of Sb ₂ O ₃ is 100% by mass, and the content of Sb ₂ O ₃ is expressed as a value relative to 100% by mass.
Further, the above molecular weight may be calculated using, for example, a value displayed up to the third decimal place after rounding off to the fourth decimal place. For example, the molecular weight of the oxide A _m O _n is the sum of the atomic weight of the element A multiplied by m and the atomic weight of oxygen multiplied by n. The following table shows the molecular weights of some glass components and additives in terms of oxide standards.

The present invention will be further described below based on examples. However, the present invention is not limited to the embodiments shown in the examples.

(Example 1)
Compounds such as oxides and boric acid as raw materials were weighed and sufficiently mixed to prepare a batch raw material so as to obtain a glass having the composition shown in the table below.
This batch raw material was placed in a platinum crucible and heated together with the crucible to a temperature of 1350 to 1450° C. for 2 to 3 hours to melt and refine the glass. After the molten glass was stirred and homogenized, the molten glass was poured into a preheated mold, allowed to cool to near the glass transition temperature, and immediately placed in an annealing furnace together with the mold. It was then annealed around the glass transition temperature for about 1 hour. After annealing, it was allowed to cool to room temperature in an annealing furnace.
Observation of the glass produced in this manner revealed no deposition of crystals, bubbles, striae, or unmelted raw materials. In this way, a highly homogeneous glass could be produced.
No. in Table 100 (Tables 100-1 to 100-7). 1 to 33 are glass 1, No. in Table 101 (Tables 101-1 to 101-6). 1 to 33 are glass 2.

The glass properties of the obtained glass were measured by the methods described below. The measurement results are shown in the table below.
(1) Refractive indices nd, nF, nC, ng, Abbe number νd
The refractive indices nd, nF, nC, and ng of the glass obtained by cooling at a cooling rate of −30° C./hour were measured according to the refractive index measurement method specified by the Japan Optical Glass Industry Association. The Abbe number νd was calculated using the measured values of the refractive indices nd, nF, and nC.
(2) Glass transition temperature Tg
Measurement was performed using a differential scanning calorimeter (DSC) at a heating rate of 10°C/min.
(3) Specific gravity Measured by the Archimedes method.
(4) Coloring degree λ5, λ70, λ80
Using a glass sample with a thickness of 10 ± 0.1 mm having two optically polished planes facing each other, a spectrophotometer is used to irradiate light with an intensity Iin from the direction perpendicular to the polished surface, and the glass sample The intensity Iout of the light transmitted through is measured, and the spectral transmittance Iout/Iin is calculated. % is defined as λ80.
(5) Partial dispersion ratio Pg,F
It was calculated from the values of nF, nC and ng measured in (1) above.
(6) Liquidus temperature The glass was placed in a furnace heated to a predetermined temperature and held for 2 hours. After cooling, the inside of the glass was observed with an optical microscope at a magnification of 100, and the liquidus temperature was determined from the presence or absence of crystals.

(Example 2)
Various types of glass obtained in Example 1 were used to produce glass gobs for press molding (glass gobs). This glass mass was heated and softened in the air, and press-molded with a press mold to produce a lens blank (optical element blank). The produced lens blank was removed from the press mold, annealed, and machined including polishing to produce spherical lenses made of the various glasses produced in Example 1.

(Example 3)
A desired amount of the molten glass produced in Example 1 was obtained, and while the obtained glass was in a softened state, it was press-molded with a press mold and cooled to produce a lens blank (optical element blank). The produced lens blank was removed from the press mold, annealed, and machined including polishing to produce spherical lenses made of the various glasses produced in Example 1.

(Example 4)
A glass mass (optical element blank) produced by solidifying the molten glass produced in Example 1 was annealed and subjected to machining including polishing to produce spherical lenses made of the various glasses produced in Example 1.

(Example 5)
The spherical lenses produced in Examples 2 to 4 were adhered to spherical lenses made of other types of glass to produce cemented lenses. The cemented surfaces of the spherical lenses produced in Examples 2 to 4 were convex spherical surfaces, and the cemented surfaces of the spherical lenses made of other types of optical glass were concave spherical surfaces. The above two joint surfaces were produced so that the absolute values of the radii of curvature were equal to each other. An ultraviolet curable adhesive for bonding optical elements was applied to the bonding surfaces, and the two lenses were bonded between the bonding surfaces. After that, the adhesive applied to the bonding surfaces was irradiated with ultraviolet rays through the spherical lenses produced in Examples 2 to 4, and the adhesive was solidified.
A cemented lens was produced as described above. The bonding strength of the cemented lens was sufficiently high, and the optical performance was at a sufficient level.

(Examination of the influence of Yb on transmittance in the near-infrared region)
A glass having a composition shown in Table 102 below (hereinafter referred to as "glass A") and a glass having a composition shown in Table 103 (hereinafter referred to as "glass B") were melted and molded. , processed into plates. These glass plates have two planes facing each other. The two planes are parallel to each other and optically polished. The distance between the two planes was 10.0 mm.
Using such a glass plate, the spectral transmittance was measured. Light is vertically incident on the above two opposing planes, and while scanning the wavelength, the ratio of the intensity of the incident light incident on the glass plate to the intensity of the transmitted light that has passed through the glass plate (intensity of transmitted light / incident light intensity) was calculated to obtain a spectral transmittance curve of the glass plate. The spectral transmittance curves at a thickness of 10.0 mm for these two types of glass are shown in FIGS. 1 and 2, respectively (FIG. 1: glass A, FIG. 2: glass B).

Glass B does not contain _Y2O3 in _{the glass composition} expressed in mass %, so the mass ratio ( _{Y2O3 /} ( _{La2O3 + Y2O3} + _Gd2O3 + _Yb2O3 )) is the same as the above- _mentioned This glass is out of range. Further, since the glass B does not contain Y ³⁺ in the glass composition expressed in cation %, the cation ratio (Y ³⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )) is outside the above range. is glass. Therefore, the glass B does not correspond to either the glass 1 or the glass 2 according to one aspect of the present _invention described above _. and the presence or absence of Y ³⁺ . Therefore, by comparing the glass A and the glass B, it is possible to confirm the influence of Yb on the transmittance in the near-infrared region.
As shown in FIG. 1, glass A containing 0.1% by mass of Yb ₂ O ₃ in the glass composition expressed in mass % and containing 0.04 cation % Yb ³⁺ in the glass composition expressed in cation %, Due to the light absorption of Yb around the wavelength of 950 nm, the transmittance around this region is reduced.
Further, as shown in FIG. 2, glass B containing 3.68 mass % of Yb ₂ O ₃ in the glass composition expressed in mass % and containing 2.00 cation % of Yb ³⁺ in the glass composition expressed in cation %. , the light absorption of Yb centered around a wavelength of 960 nm significantly reduces the transmittance in this vicinity.
Thus, as the content of Yb increases, the transmittance of the glass in the near-infrared region decreases significantly. Glass containing a lot of is not suitable.

(Comparative example 1)
An attempt was made to reproduce the glass of Example 4 of Patent Document 6 (Japanese Unexamined Patent Application Publication No. 2009-203083), but crystallization occurred during the production of the glass. This is because this glass has a mass ratio (B ₂ O ₃ /(B ₂ O ₃ +SiO ₂ )) of 1 in the glass composition expressed in mass %, and a cation ratio (B ³⁺ / (B ³⁺ +Si ⁴⁺ )) is 1, so the thermal stability is considered to be low.

(Comparative example 2)
The glass of Example 28 of Patent Document 5 (Japanese Patent Application Laid-Open No. 55-121925) (hereinafter referred to as "glass C") was reproduced, and λ5 was measured by the above method to be 348 nm.
Glass C was used to produce a spherical lens. Next, using the convex spherical surface of this spherical lens and the concave spherical surface of a spherical lens made of another kind of optical glass as a bonding surface, an ultraviolet curable adhesive for bonding optical elements is applied, as in Example 5. We attempted to fabricate a cemented lens. However, when the ultraviolet curable adhesive applied to the joint surface was irradiated with ultraviolet rays through a lens made of glass C, the adhesive could not be sufficiently cured due to the low ultraviolet transmittance of glass C.

(Comparative Example 3)
The glass of Example 7 of Patent Document 17 (JP-A-2002-284542) has a mass ratio (Gd ₂ O ₃ /(La ₂ O ₃ +Y ₂ O ₃ +Gd ₂ O ₃ +Yb ₂ O ₃ )) of 0.0. 09, _and the mass ratio ( _B2O3 /( _B2O3 + _SiO2 )) is 0.92 _. In this glass, the contents of components other than La ₂ O ₃ , Y ₂ O ₃ and Gd ₂ O ₃ were kept constant, and part or all of Gd ₂ O ₃ was replaced with La ₂ O ₃ and Y ₂ O ₃ . We verified the change in the thermal stability of the glass.
First, as an oxide-based glass composition, 5.15% by mass of Gd ₂ O ₃ is assumed to be 0%, and the decrease in Gd ₂ O ₃ content of 5.15% by mass is defined as the La ₂ O ₃ content. _{and Y 2} O _{3 content respectively} . Specifically, 4. calculated as 5.15% by mass×((La ₂ O ₃ content/(Total content of La ₂ O ₃ content and Y ₂ O ₃ content))). 09% by mass of Gd ₂ O ₃ is replaced with La ₂ O ₃ , 5.15% by mass × ((content of Y ₂ O ₃ /(content of La ₂ O ₃ and total content of Y ₂ O ₃ )) was replaced by Y ₂ O ₃ from Gd ₂ O _3. This composition is hereinafter referred to as “composition a”.
Next, the Gd ₂ O ₃ contained in 5.15% by mass is reduced to 3% by mass, and the decrease in Gd ₂ O ₃ content of 2.15% by mass is the content of La ₂ O ₃ and Y ₂ O ₃ was distributed to La ₂ O ₃ and Y ₂ O ₃ respectively according to the content of 3. Specifically, 1.71% by mass calculated as 2.15% by mass × ((content of La ₂ O ₃ /(total content of La ₂ O ₃ content and Y ₂ O ₃ content))) is replaced by La ₂ O ₃ from Gd ₂ O ₃ , 5.15% by mass × ((content of Y ₂ O ₃ /(total content of La ₂ O ₃ content and Y ₂ O ₃ content)) 0.44% by mass calculated as , was replaced with Y ₂ O ₃ from Gd ₂ O _3. This composition is hereinafter referred to as "composition b".
Table 104 shows the compositions of Example 7 of Patent Document 17, "Composition a" and "Composition b".

Using 150 g of glass having compositions a and b, glass was produced according to the method described in Examples of Patent Document 17, and the peripheral portion of the glass formed by pouring the molten glass into a mold, that is, the contact with the mold Crystal precipitation was not observed in the quenched portion, but a large number of crystals precipitated in the central portion of the glass, that is, in the portion where the cooling speed was lower than that in the peripheral portion. When the glass of the example described above was produced by the same method, precipitation of crystals was not observed not only in the peripheral portion of the glass but also over the entire surface of the glass.
The above results show that in a glass composition in which the mass ratio (B ₂ O ₃ /(B ₂ O ₃ +SiO ₂ )) exceeds the range described above, thermal stability decreases as the Gd ₂ O ₃ content decreases. This result is considered to indicate that

(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 and a cation ratio ( B ³⁺ /(B ³⁺ +Si ⁴⁺ )) is 0.95. Regarding this glass, the contents of components other than La ³⁺ , Y ³⁺ , and Gd ³⁺ are fixed, and part or all of Gd ³⁺ is replaced with La ³⁺ and Y ³⁺ , the heat of the glass We verified the change in stability.
First, the Gd ³⁺ content of 2.31 cation % was assumed to be 0%, and the decrease in the Gd ³⁺ content of 2.31 cation % was determined according to the La ³⁺ content and the Y ³⁺ content. It was distributed between La ³⁺ and Y ³⁺ . Specifically, 1.68 cation % calculated as 2.31 cation % x ((La ³⁺ content/(total content of La ³⁺ content and Y ³⁺ content)) is substituted for La ³⁺ from Gd ³⁺ , and 0.31 cation % x ((content of Y ³⁺ /(content of La ³⁺ and total content of Y ³⁺ ))). 63 cation % were replaced by Y ³⁺ for Gd ³⁺ , and this composition is referred to below as "composition c".
Next, the amount of Gd ³⁺ contained in 2.31 cation % was reduced to 1.5 cation %, and the decrease in the Gd ³⁺ content of 0.81 cation % was changed to the La ³⁺ content and the Y ³⁺ content. It was distributed to La ³⁺ and Y ³⁺ according to the content. Specifically, ^0.59 cation % calculated as 0.81 cation % × ((La ³⁺ content/(Total content of La ³⁺ content and Y ³⁺ content)) is ⁺ and ^0.22 cation% calculated as 0.81 cation% × ((content of Y ³⁺ /(total content of La ³⁺ and Y ³⁺ )) ⁺ This composition is hereinafter referred to as “composition d”.
Table 105 shows the compositions of Example 7 of Patent Document 17, "Composition c" and "Composition d".

Using 150 g of glass having compositions c and d, glass was produced according to the method described in the example of Patent Document 17, and the periphery of the glass formed by pouring molten glass into a mold, that is, the contact with the mold Crystal precipitation was not observed in the quenched portion, but a large number of crystals precipitated in the central portion of the glass, that is, in the portion where the cooling speed was lower than that in the peripheral portion. When the glass of the example described above was produced by the same method, precipitation of crystals was not observed not only in the peripheral portion of the glass but also over the entire surface of the glass.
The above results show that in glass compositions in which the cation ratio (B ³⁺ /(B ³⁺ +Si ⁴⁺ )) exceeds the range described above, thermal stability decreases as the Gd ³⁺ content decreases. It is considered that the result shows

Finally, each aspect described above is summarized.

According to one aspect, the total content of B ₂ O ₃ and SiO ₂ is 15 to 35% by mass, La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ and Yb ₂ O ₃ in terms of % by mass. provided that the Yb ₂ O ₃ content is 3 mass % or less, the ZrO ₂ content is 3 to 11 mass %, the Ta ₂ O ₅ content is 5 mass % or less, Mass ratio of B ₂ O ₃ content to 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, La ₂ O ₃ , the mass ratio of the total content of B ₂ O ₃ and SiO ₂ to 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 _to 0.53, Y 2 O 3 with respect to the total content _of La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ and Yb ₂ O ₃ Content mass ratio (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, La ₂ O ₃ , Y ₂ O ₃ , Gd mass ratio of Gd ₂ O ₃ content to total content of 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 to 0.05, mass ratio of _{Nb2O5 content} to total content _{of Nb2O5 , TiO2} , _Ta2O5 and _{WO3 ( Nb2O5} /( _{Nb2O5 + TiO2 + Ta2O5} +WO ₃ )) of 0.5 to 1, a refractive index nd of 1.800 to 1.850, and an Abbe number νd of 41.5 to 44 (glass 1 ) can be provided.

According to one embodiment, the total content of B ³⁺ and Si ⁴⁺ is 45 to 65%, and the total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ is 25-35% with a Yb ³⁺ content of less than 2%, a Zr ⁴⁺ content of 2-8%, a Ta ⁵⁺ content of 3% or less, the sum of B ³⁺ and Si ⁴⁺ The cation ratio of the B ³⁺ content to the content (B ³⁺ /(B ³⁺ +Si ⁴⁺ )) is 0.65 or more and less than 0.94, La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ cation ratio ((B ³⁺ +Si ⁴⁺ )/(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )) of the total content of B ³⁺ and Si ⁴⁺ to the total content of 2.60, the cation ratio of the 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 0.05 to 0.45, and the cation ratio of the 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 0 to 0.05, and the cation ratio of the Nb ⁵⁺ content to the total content of 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 νd is 41.5 to 44 A glass (Glass 2) that is a material glass can be provided.

Glass 1 and glass 2 are high-refractive-index, low-dispersion optical glasses that have a refractive index nd and an Abbe number νd within the above ranges and are useful as materials for optical elements constituting an optical system. The glass is a glass with reduced Gd, Ta and Yb contents and can exhibit high thermal stability.

In one aspect, the glass 1 has improved meltability, further improved thermal stability of the glass, suppressed decrease in glass transition temperature (improved machinability due to this), improved chemical durability, The mass ratio (ZnO/(Nb ₂ O ₅ +TiO ₂ +Ta ₂ O ₅ +WO ₃ )) is preferably in the range of 0.1-3.

In one aspect, the glass 2 has improved meltability, further improved thermal stability of glass, suppressed decrease in glass transition temperature (improved machinability thereby), improved chemical durability, The cation ratio (Zn ²⁺ /(Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )) is preferably in the range of 0.1-5.

In one aspect, it is preferable that the glass 1 and the glass 2 suppress the lengthening of the light absorption edge on the short wavelength side of the glass so that the degree of coloring λ5 is 335 nm or less.

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

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

A glass material for press molding, an optical element blank, and an optical element can be produced from the glass 1 or glass 2 described above. That is, according to another aspect, a press-molding glass material, an optical element blank, and an optical element made of glass 1 or glass 2 are provided.

Further, according to another aspect, there is also provided a method of manufacturing a press-molding glass material comprising a step of forming the glass 1 or the glass 2 into a press-molding glass material.

According to still another aspect, there is also provided a method for producing an optical element blank, comprising a step of producing an optical element blank by press-molding the glass material for press-molding using a press-molding die.

According to yet another aspect, there is also provided a method of manufacturing an optical element blank comprising forming glass 1 or glass 2 into an optical element blank.

According to yet another aspect, there is also provided a method of manufacturing an optical element, comprising fabricating an optical element by at least polishing the optical element blank.

It should be considered that the embodiments disclosed this time are illustrative in all respects and not restrictive. The scope of the present invention is indicated by the scope of the claims rather than the above description, and is intended to include all modifications within the meaning and range of equivalents of the scope of the claims.
For example, the glass according to one aspect of the present invention can be obtained by adjusting the composition described in the specification with respect to the glass composition exemplified above.
In addition, it is of course possible to arbitrarily combine two or more of the matters described as examples or preferred ranges in the specification.
Also, a certain glass may correspond to both glass 1 and glass 2.

INDUSTRIAL APPLICABILITY The present invention is useful in the field of manufacturing various optical elements.

Claims (11)

In cation % display,
B. ³⁺ and Si ⁴⁺ with a total content of 45 to 65%,
La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ The total content of 25 to 35%, provided that Yb ³⁺ The content is less than 2%,
La ³⁺ content is 23.6% or less,
Zr ⁴⁺ content of 2 to 8%,
Ta ⁵⁺ content is 3% or less,
B. ³⁺ content of 46% or more,
P. ⁵⁺ content is 5% or less,
B. ³⁺ and Si ⁴⁺ B for the total content with ³⁺ Cation ratio of content (B ³⁺ /(B ³⁺ + Si ⁴⁺ )) is 0.65 or more and less than 0.94,
La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ B for the total content of ³⁺ and Si ⁴⁺ and the cation ratio of the total content ((B ³⁺ + Si ⁴⁺ )/(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )) is 1.65 to 2.60,
La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ Y for the total content of ³⁺ The cation ratio of the content (Y ³⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )) is 0.05 to 0.45,
La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ Gd for the total content of ³⁺ Cation ratio of content (Gd ³⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )) is 0 to 0.05,
Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ Nb for the total content of ⁵⁺ Cation ratio of content (Nb ⁵⁺ /(Nb ⁵⁺ + Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )) is 0.4 to 1,
Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ B for the total content of ³⁺ and Si ⁴⁺ The cation ratio of the total content of ((B ³⁺ + Si ⁴⁺ )/(Nb ⁵⁺ + Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )) is 32 or less,
Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ Zn for the total content of ²⁺ Cation ratio of content (Zn ²⁺ /(Nb ⁵⁺ + Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )) is 0.800 or less,
is an oxide glass having a glass transition temperature of 671° C. or higher, a refractive index nd in the range of 1.800 to 1.850, and an Abbe number νd of 41.5 to 44. In cation % display,
B. ³⁺ and Si ⁴⁺ with a total content of 45 to 65%,
La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ The total content of 25 to 35%, provided that Yb ³⁺ The content is less than 2%,
La ³⁺ content is 23.6% or less,
Zr ⁴⁺ content of 2 to 8%,
Ta ⁵⁺ content is 3% or less,
B. ³⁺ content of 46% or more,
P. ⁵⁺ content is 5% or less,
B. ³⁺ and Si ⁴⁺ B for the total content with ³⁺ Cation ratio of content (B ³⁺ /(B ³⁺ + Si ⁴⁺ )) is 0.65 or more and less than 0.94,
La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ B for the total content of ³⁺ and Si ⁴⁺ and the cation ratio of the total content ((B ³⁺ + Si ⁴⁺ )/(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )) is 1.65 to 2.60,
La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ Y for the total content of ³⁺ The cation ratio of the content (Y ³⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )) is 0.05 to 0.45,
La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ Gd for the total content of ³⁺ Cation ratio of content (Gd ³⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )) is 0 to 0.05,
Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ Nb for the total content of ⁵⁺ Cation ratio of content (Nb ⁵⁺ /(Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ +W ⁶⁺ )) is 0.4 to 1,
Li ⁺ , Na ⁺ and K ⁺ The total content of 5% or less,
Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ Zn for the total content of ²⁺ Cation ratio of content (Zn ²⁺ /(Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ +W ⁶⁺ )) is 0.800 or less,
is an oxide glass having a glass transition temperature of 671° C. or higher, a refractive index nd in the range of 1.800 to 1.850, and an Abbe number νd of 41.5 to 44. Si ⁴⁺ 3. The glass according to claim 1, wherein the content is 9 cation % or less. In mass % display,
The total content of B ₂ O ₃ and SiO ₂ is 15 to 35% by mass, and 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, provided that , Yb ₂ O ₃ content is 3% by mass or less,
La ₂ O ₃ content is 45.8% or less,
a ZrO ₂ content of 3 to 11% by weight,
Ta ₂ O ₅ content is 5% by mass or less,
B ₂ O ₃ content content is 19% or more,
P ₂ O ₅ content is 5% or less,
mass ratio of B ₂ O ₃ content to 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;
Mass ratio of the total content of _{B2O3 and SiO2} to the _total content of _La2O3 , _{Y2O3 , Gd2O3 and Yb2O3} (( _B2O3 + _SiO2 ) _/ ( _{La 2} O ₃ +Y ₂ O ₃ +Gd ₂ O ₃ +Yb ₂ O ₃ )) is 0.42 to 0.53;
Mass ratio of _{Y2O3 content to total content of La2O3} , _Y2O3 , _Gd2O3 and _Yb2O3 ( _{Y2O3 / ( La2O3 + Y2O3} + _Gd2 O ₃ +Yb ₂ O ₃ )) is 0.05 to 0.45;
Mass ratio of _{Gd2O3 content to total content of La2O3 , Y2O3} , _Gd2O3 and _Yb2O3 ( _{Gd2O3 /} ( _La2O3 + _{Y2O3 + Gd2} O ₃ +Yb ₂ O ₃ )) is 0 to 0.05;
Mass ratio _{of Nb2O5} content to total content _{of Nb2O5} , _TiO2 , _Ta2O5 and _{WO3 ( Nb2O5} /( _Nb2O5 + _{TiO2 + Ta2O5 + WO3} ) ₎ is 0.5 to 1,
_{Mass ratio} of the total content of B2O3 _and SiO2 to _{the total content} of Nb2O5 _{, TiO2} , _Ta2O5 and _WO3 ( ( _{B2O3 +} SiO2 ₎ / ( Nb2O5 ₊ TiO ₂ + Ta ₂ O ₅ + WO ₃ )) is 10 or less,
mass ratio of ZnO content to total content of _Nb2O5 , _TiO2 , _Ta2O5 and WO3 ( ZnO / _{( Nb2O5 + TiO2} +Ta2O5 _{+ WO3} ) ) is _0.500 or _{less ;}
and an oxide glass having a glass transition temperature of 671° C. or higher, a refractive index nd in the range of 1.800 to 1.850, and an Abbe number νd of 41.5 to 44. In mass % display,
B. ₂ O. ₃ and SiO ₂ with a total content of 15 to 35% by mass, La ₂ O. ₃ , Y ₂ O. ₃ , Gd ₂ O. ₃ and Yb ₂ O. ₃ The total content of 45 to 65% by mass, provided that Yb ₂ O. ₃ The content is 3% by mass or less,
La ₂ O. ₃ content is 45.8% or less,
ZrO ₂ a content of 3 to 11% by mass,
Ta ₂ O. _Five content is 5% by mass or less,
B. ₂ O. ₃ Content content is 19% or more,
P. ₂ O. _Five content is 5% or less,
B. ₂ O. ₃ and SiO ₂ B for the total content with ₂ O. ₃ Content mass ratio (B ₂ O. ₃ /(B ₂ O. ₃ + SiO ₂ )) is 0.4 to 0.900,
La ₂ O. ₃ , Y ₂ O. ₃ , Gd ₂ O. ₃ and Yb ₂ O. ₃ B for the total content of ₂ O. ₃ and SiO ₂ The mass ratio of the total content of ((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,
La ₂ O. ₃ , Y ₂ O. ₃ , Gd ₂ O. ₃ and Yb ₂ O. ₃ Y for the total content of ₂ O. ₃ Content mass ratio (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,
La ₂ O. ₃ , Y ₂ O. ₃ , Gd ₂ O. ₃ and Yb ₂ O. ₃ Gd for the total content of ₂ O. ₃ Content mass ratio (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,
Nb ₂ O. _Five , TiO ₂ , Ta ₂ O. _Five and WO ₃ Nb for the total content of ₂ O. _Five Content mass ratio (Nb ₂ O. _Five /(Nb ₂ O. _Five +TiO ₂ +Ta ₂ O. _Five +WO ₃ )) is 0.5 to 1,
Li ₂ O, Na ₂ O and K ₂ The total content of O is 2.0% or less,
Nb ₂ O. _Five , TiO ₂ , Ta ₂ O. _Five and WO ₃ The mass ratio of ZnO content to the total content of (ZnO/(Nb ₂ O. _Five +TiO ₂ +Ta ₂ O. _Five +WO ₃ )) is 0.500 or less,
is an oxide glass having a glass transition temperature of 671° C. or higher, a refractive index nd in the range of 1.800 to 1.850, and an Abbe number νd of 41.5 to 44. SiO ₂ 6. The glass according to claim 4 or 5, having a content of 7.0% by mass or less. 7. The glass according to any one of claims 1 to 6, which has a coloring degree λ5 of 335 nm or less. The specific gravity d and the refractive index nd are represented by the following formula (A):
d/(nd−1)≦5.70 (A)
The glass according to any one of claims 1 to 7 , which satisfies A press-molding glass material comprising the glass according to any one of claims 1 to 8 . An optical element blank made of the glass according to any one of claims 1 to 8 . An optical element made of the glass according to any one of claims 1 to 8 .

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