CN108715512B

CN108715512B - Glass, glass material for press molding, optical element blank, and optical element

Info

Publication number: CN108715512B
Application number: CN201810784796.2A
Authority: CN
Inventors: 根岸智明
Original assignee: Hoya Corp
Current assignee: Hoya Corp
Priority date: 2015-01-13
Filing date: 2016-01-13
Publication date: 2021-05-04
Anticipated expiration: 2036-01-13
Also published as: JP2023085359A; CN108715512A; WO2016114274A1; JP6291598B2; JP2018104283A; JP7250106B2; TWI671270B; CN107207320A; JP2021008397A; TWI641572B; CN107207320B; JP6812382B2; JPWO2016114274A1; JP7003198B2; JP2022050507A; JP7514351B2; TW201904900A; TW201641456A

Abstract

The present invention relates to a glass, a glass material for press molding, an optical element blank and an optical element, wherein the glass is oxide glass, and B is expressed by mass%₂O₃And SiO₂The total content of (A) is 15-35 mass%, La₂O₃、Y₂O₃、Gd₂O₃And Yb₂O₃In which Yb is 45 to 65 mass% in total₂O₃ZrO in an amount of 3 mass% or less₂A content of 3 to 11 mass% of Ta₂O₅The content is 5 mass% or less, B₂O₃Content relative to B₂O₃And SiO₂The mass ratio of the total content of (B) is 0.4 to 0.900, B₂O₃And SiO₂The total content of (A) to La₂O₃、Y₂O₃、Gd₂O₃And Yb₂O₃The mass ratio of the total content of (A) is 0.42 to 0.53, Y₂O₃Content relative to La₂O₃、Y₂O₃、Gd₂O₃And Yb₂O₃The total content of (A) is 0.05-0.45 by mass, Gd₂O₃Content relative to La₂O₃、Y₂O₃、Gd₂O₃And Yb₂O₃In a mass ratio of 0 to 0.05, Nb₂O₅Content relative to Nb₂O₅、TiO₂、Ta₂O₅And WO₃The mass ratio of the total content of (A) is 0.5 to 1, the range of refractive index nd is 1.800 to 1.850, and the range of Abbe number vd is 41.5 to 44.

Description

Glass, glass material for press molding, optical element blank, and optical element

The present application is a divisional application of the invention patent application having application number 201680005396.6, which was filed 2016, 1, 13, and entitled "glass, glass material for press molding, optical element blank, and optical element".

Cross reference to related applications

This application claims priority to Japanese patent application No. 2015-004542 and Japanese patent application No. 2015-004544 applied on 1/13/2015, the entire contents of which are specifically incorporated herein by reference as publications.

Technical Field

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

Background

As glasses having a high refractive index and low dispersion (high refractive index and low dispersion glasses), for example, patent documents 1 to 18 describe glasses having a refractive index nd in the range of 1.800 to 1.850 and an abbe number vd in the range of 41.5 to 44. Patent documents 1 to 18 are incorporated herein by reference in their entirety.

Patent document 1: japanese patent laid-open publication No. 2002-12443;

patent document 2: japanese patent laid-open publication No. 2003-267748;

patent document 3: japanese patent laid-open publication No. 2005-281124;

patent document 4: japanese patent laid-open publication No. 2005-298262;

patent document 5: japanese patent laid-open publication No. 55-121925;

patent document 6: japanese patent laid-open No. 2009-203083;

patent document 7: japanese patent laid-open publication No. Sho 54-090218;

patent document 8: japanese patent laid-open No. 56-160340;

patent document 9: japanese patent laid-open publication No. 2009-167080;

patent document 10: japanese patent laid-open publication No. 2009-167081;

patent document 11: japanese laid-open patent publication No. 2009-298646;

patent document 12: japanese patent laid-open publication No. 2010-111527;

patent document 13: japanese patent laid-open publication No. 2010-111528;

patent document 14: japanese patent laid-open publication No. 2010-111530;

patent document 15: japanese patent laid-open publication No. 57-056344;

patent document 16: japanese patent laid-open publication No. 61-163138;

patent document 17: japanese patent laid-open publication No. 2002-284542;

patent document 18: japanese patent laid-open publication No. 2007-269584.

Disclosure of Invention

The glass having a refractive index nd in the range of 1.800 to 1.850 and an Abbe number vd in the range of 41.5 to 44 is useful as a material for optical elements for correcting chromatic aberration, and for making an optical system highly functional and compact. Hereinafter, unless otherwise specified, the refractive index refers to a refractive index nd of a d-line (wavelength of helium 587.56 nm). The abbe number refers to ν d unless otherwise specified. As is well known, vd is defined as (nd-1)/(nF-nC) when the refractive indices of the F line (wavelength of hydrogen 486.13nm) and the C line (wavelength of hydrogen 656.27nm) are nF and nC, respectively.

In order to further improve the usefulness of the high-refractive-index low-dispersion glass having a refractive index and an abbe number in the above ranges, it is preferable to satisfy the following points.

The supply can be stabilized. Therefore, it is preferable to reduce the ratio of Gd and Ta, which are elements having high rare values and are not supplied enough to meet the market demand in recent years, in the glass composition. In contrast, the glass described in patent document 7 contains a large amount of Ta. Further, the glasses described in patent documents 8 to 14 and the glasses having the refractive index and abbe number in the above ranges described in patent document 17 contain a large amount of Gd.

The ratio of Yb in the glass composition is low. This is due to the following reason.

Yb has absorption in the near infrared region. Therefore, a glass containing a large amount of Yb (for example, a glass described in patent document 16) is not suitable for applications requiring a high transmittance in a range from a visible region to a near-infrared region, for example, materials for optical elements such as lenses of monitoring cameras, infrared cameras, and vehicle-mounted cameras. Yb is a heavy rare earth element, and as a component of glass, Yb has a large atomic weight and increases the specific gravity of glass. When the specific gravity of the glass increases, the lens becomes heavy. As a result, when such a lens is attached to an autofocus lens, power consumption becomes large and battery consumption becomes severe. From the above points, it is preferable to reduce the ratio of Yb in the glass composition.

The thermal stability is excellent. Glasses with low thermal stability may show a tendency to devitrify during the process of making the glass. However, according to the study of the present inventors, for example, the glass described in patent document 6 has poor thermal stability.

In view of the above, one embodiment of the present invention provides a glass having a refractive index nd in the range of 1.800 to 1.850 and an abbe number ν d in the range of 41.5 to 44, in which the ratio of Gd, Ta, and Yb in the glass composition is reduced, and which has excellent thermal stability.

In one embodiment, the glass further preferably satisfies 1 or more of the following points.

The wavelength of the short-wavelength side light absorption edge of the glass is suppressed from increasing. This is due to the following reason.

In order to correct chromatic aberration, the following methods are known: a plurality of lenses were produced using glasses having different optical characteristics, and the lenses were laminated to produce a cemented lens. In the process of manufacturing cemented lenses, an ultraviolet curing adhesive is generally used in order to bond the lenses to each other. The details are as follows. An ultraviolet-curable adhesive is applied to the surfaces to be bonded to each other, and the lenses are bonded to each other. In this case, 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-curable adhesive. Therefore, when the transmittance of ultraviolet rays of the lens is low, ultraviolet rays of insufficient light amount pass through the lens and reach the coating layer, resulting in insufficient curing. Alternatively, curing takes a long time. Further, in the case where a lens is bonded and fixed to a lens barrel or the like using an ultraviolet curing adhesive, similarly, when the ultraviolet transmittance of the lens is low, curing is insufficient or it takes a long time to cure.

Therefore, in order to produce a glass having transmittance characteristics suitable for the production of an optical system, it is preferable to increase the transmittance of the glass in the ultraviolet region, in other words, to suppress the wavelength of the short-wavelength light absorption edge of the glass from increasing.

However, according to the study of the present inventors, for example, in the glass described in patent document 5, the light absorption edge on the short wavelength side of the glass becomes longer in wavelength, and the transmittance in the ultraviolet region is lowered. In addition, in the glass composition of conventional high-refractive-index low-dispersion glass, when the content of Gd and Ta is intended to be reduced while maintaining the high-refractive-index low-dispersion property and the thermal stability, the light absorption edge on the short wavelength side of the glass tends to be longer and the transmittance of ultraviolet rays tends to be significantly reduced.

Is suitable for mechanical processing. The details are as follows. As a method for obtaining an optical element from glass, in addition to a precision press molding method (see, for example, patent documents 1 to 4), there is a method in which an optical element blank is molded from glass, and the optical element blank is subjected to machining such as grinding and polishing to be processed into an optical element. If the glass is easily broken by such machining, the manufacturing yield is lowered. Generally, glass for precision press molding has a low glass transition temperature, but glass having a low glass transition temperature tends to be easily broken during machining. Therefore, in order to produce a glass suitable for machining, it is preferable to set the glass transition temperature higher than that of a glass for precision press molding.

One embodiment of the present invention relates to a glass (hereinafter referred to as "glass 1") which is an oxide glass and is represented by mass%,

B₂O₃and SiO₂The total content of (B) is 15 to 35% by mass,

La₂O₃、Y₂O₃、Gd₂O₃and Yb₂O₃In which Yb is 45 to 65 mass% in total₂O₃The content is 3% by mass or less,

ZrO₂the content is 3 to 11% by mass,

Ta₂O₅the content is 5(ii) at most by mass percent,

B₂O₃content relative to B₂O₃And SiO₂The mass ratio of the total content of (A), (B)₂O₃/(B₂O₃+SiO₂) ) is 0.4 to 0.900,

B₂O₃and SiO₂The total content of (A) to La₂O₃、Y₂O₃、Gd₂O₃And Yb₂O₃(B) the mass ratio of the total content of (A)₂O₃+SiO₂)/(La₂O₃+Y₂O₃+Gd₂O₃+Yb₂O₃) ) is 0.42 to 0.53,

Y₂O₃content relative to La₂O₃、Y₂O₃、Gd₂O₃And Yb₂O₃The mass ratio of the total content of (A), (B), (C), (D), (E), (₂O₃/(La₂O₃+Y₂O₃+Gd₂O₃+Yb₂O₃) ) is 0.05 to 0.45,

Gd₂O₃content relative to La₂O₃、Y₂O₃、Gd₂O₃And Yb₂O₃The mass ratio of the total content of (b) (Gd)₂O₃/(La₂O₃+Y₂O₃+Gd₂O₃+Yb₂O₃) ) is 0 to 0.05,

Nb₂O₅content relative to Nb₂O₅、TiO₂、Ta₂O₅And WO₃Mass ratio of the total content of (B)/(B)₂O₅/(Nb₂O₅+TiO₂+Ta₂O₅+WO₃) ) is 0.5 to 1,

the refractive index nd is in the range of 1.800 to 1.850, and the Abbe number vd is in the range of 41.5 to 44.

One embodiment of the present invention relates to a glass (hereinafter referred to as "glass 2") which is an oxide glass and is expressed in terms of cation%,

B³⁺and Si⁴⁺The total content of (A) is 45 to 65%,

La³⁺、Y³⁺、Gd³⁺and Yb³⁺Is 25 to 35% in total, but Yb³⁺The content is less than 2 percent,

Zr⁴⁺the content of the organic acid is 2-8%,

Ta⁵⁺the content of the organic acid is less than 3 percent,

B³⁺content relative to B³⁺And Si⁴⁺The cation ratio (B) of the total content³⁺/(B³⁺+Si⁴⁺) ) 0.65 or more and less than 0.94,

B³⁺and Si⁴⁺The total content of (A) to La³⁺、Y³⁺、Gd³⁺And Yb³⁺Cation ratio of the total content of ((B)³⁺+Si⁴ ⁺)/(La³⁺+Y³⁺+Gd³⁺+Yb³⁺) ) is 1.65 to 2.60,

Y³⁺content relative to La³⁺、Y³⁺、Gd³⁺And Yb³⁺Cation ratio (Y) of the total content of³⁺/(La³⁺+Y³⁺+Gd³⁺+Yb³ ⁺) ) is 0.05 to 0.45,

Gd³⁺content relative to La³⁺、Y³⁺、Gd³⁺And Yb³⁺The cation ratio (Gd) of the total content of³⁺/(La³⁺+Y³⁺+Gd³⁺+Yb³⁺) ) is 0 to 0.05,

Nb⁵⁺content relative to Nb⁵⁺、Ti⁴⁺、Ta⁵⁺And W⁶⁺Cation ratio (Nb) of the total content⁵⁺/(Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺) ) is 0.4 to 1,

The glass 1 is a glass having a refractive index nd and an Abbe's number vd in the above-mentioned ranges, and contains Gd₂O₃Each component (i.e., La) of₂O₃、Y₂O₃、Gd₂O₃、Yb₂O₃) In the above range, Gd is added₂O₃The content is defined as a numerator, and the total content of the above-mentioned components is defined as a denominator. Therefore, the proportion of Gd occupancy in the glass composition decreases. Further, Ta₂O₅Content and Yb₂O₃The contents are respectively as described above, and the ratio of Ta and Yb occupied in the glass composition is also reduced. The glass can achieve high thermal stability (property of being less susceptible to devitrification) by adjusting the composition to satisfy the above content, total content and mass ratio in the composition in which the proportion of Gd, Ta and Yb is reduced. Further, the wavelength of the short-wavelength light absorption edge can be suppressed from increasing, and a high glass transition temperature (Tg) (an increase in the glass transition temperature) can be achieved.

The glass 2 is a glass having a refractive index nd and an Abbe's number vd in the above-mentioned ranges, and contains Gd³⁺Each component (i.e., La) of³ ⁺、Y³⁺、Gd³⁺、Yb³⁺) In the above range, Gd is added³⁺The cation ratio in which the content is a numerator and the total content of the above-mentioned components is a denominator. Therefore, the proportion of Gd occupancy in the glass composition decreases. Further, Ta⁵⁺Content and Yb³⁺The contents are respectively as described above, and the ratio of Ta and Yb occupied in the glass composition is also reduced. The glass can achieve high thermal stability (property of being less susceptible to devitrification) by adjusting the composition to satisfy the content, the total content, and the cation ratio described above in the composition in which the proportion of Gd, Ta, and Yb is reduced. Further, the wavelength of the short-wavelength light absorption edge can be suppressed from increasing, and a high glass transition temperature (Tg) (an increase in the glass transition temperature) can be achieved.

According to one embodiment of the present invention, a glass having high refractive index and low dispersion characteristics useful in an optical system, capable of being stably supplied, and excellent in thermal stability can be provided. Further, according to an aspect of the present invention, a glass material for press molding, an optical element blank, and an optical element, each of which is made of the above glass, can be provided.

Drawings

FIG. 1 shows a spectral transmittance curve of a glass A having a thickness of 10.0mm, which will be described later.

FIG. 2 shows a spectral transmittance curve of glass B having a thickness of 10.0mm, which will be described later.

Detailed Description

The glass composition of the present invention can be quantified by, for example, ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry) or the like. The analysis value obtained by ICP-AES may include a measurement error of about. + -. 5% of the analysis value, for example. In the present specification and the present invention, the content of a constituent of 0% is not included or not introduced, meaning that the constituent is not substantially included, and means that the content of the constituent is not more than the impurity level.

Hereinafter, the following tables may show the (more) preferable lower limit and the (more) preferable upper limit of the numerical range. In the table, the lower numerical value is more preferable, and the lowest numerical value is most preferable. Unless otherwise specified, the lower limit of (more) preferably means a value not less than the specified value (more preferably), and the upper limit of (more) preferably means a value not more than the specified value (more preferably). The numerical value range can be defined by arbitrarily combining the numerical values described in the column of the (more) preferred lower limit and the numerical values described in the column of the (more) preferred upper limit in the table.

[ glass ]

The glass 1 and the glass 2 of one embodiment of the present invention are oxide glasses having the above glass composition, a refractive index nd in the range of 1.800 to 1.850, and an Abbe number ν d in the range of 41.5 to 44. The 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 the glass 1 is represented by an oxide standard. The "oxide-based glass composition" herein means a glass composition obtained by decomposing all glass raw materials at the time of melting and proceeding as a substance existing as an oxide in the glass. Unless otherwise specified, the glass composition of the glass 1 is represented by mass (mass%, mass ratio).

B₂O₃、SiO₂Is a network forming component of the glass. When B is present₂O₃And SiO₂Total content (B) of₂O₃+SiO₂) If the content is 15% or more, the thermal stability of the glass can be improved, and crystallization of the glass during production can be suppressed. On the other hand, when B₂O₃And SiO₂When the total content of (b) is 35% or less, the decrease in refractive index nd can be suppressed, and therefore, a glass having the above optical properties, that is, a glass having a refractive index nd in the range of 1.800 to 1.850 and an Abbe number ν d in the range of 41.5 to 44 can be produced. Thus, B in glass 1₂O₃And SiO₂The total content of (a) is set to 15 to 35%. B is₂O₃And SiO₂The preferable lower limit and the preferable upper limit of the total content of (a) are shown in the following table.

[ TABLE 1]

B as a network-forming component of glass₂O₃And SiO₂The content ratio of each component (a) has an influence on the thermal stability, melting property, moldability, chemical durability, weather resistance, machinability and the like of the glass. B is₂O₃Compared with SiO₂The effect of improving the meltability is more excellent, but the composition is easily volatilized at the time of melting. In contrast, SiO₂Has the effects of improving the chemical durability, weather resistance and machinability of the glass and improving the viscosity of the glass during melting.

Usually, in the presence of B₂O₃And La₂O₃The high-refractive index low-dispersion glass containing a rare earth element has low viscosity during melting. However, when the viscosity of the glass at the time of melting is low, thermal stability is lowered (crystallization becomes easy). Regarding crystallization in glass production, the state of crystallization is more stable than the amorphous state (amorphous state) in which ions constituting the glass are present in the glassMove to align in a manner to have a crystal structure. Thus, by pair B₂O₃And SiO₂The content ratio of each component (a) is adjusted so as to increase the viscosity at the time of melting, whereby the ions are less likely to be aligned so as to have a crystal structure, crystallization of the glass is further suppressed, and the thermal stability of the glass is improved.

When the viscosity of the molten glass is low when the molten glass is poured into a mold for molding, the solidified surface portion of the glass poured into the mold is caught in the glass still in a molten state and streaks occur, and the optical homogeneity of the glass is lowered. The glass having excellent moldability corresponds to a glass having a relatively high viscosity when a glass in a molten state is poured into a mold in a high-refractive-index low-dispersion glass containing a rare earth element.

When B is present₂O₃Content relative to B₂O₃And SiO₂The mass ratio of the total content of (A), (B)₂O₃/(B₂O₃+SiO₂) 0.900 or less), the viscosity at the time of melting can be suppressed from decreasing, whereby the thermal stability of the glass can be improved and volatilization at the time of melting can be suppressed. Volatilization during melting causes a change in glass composition and a change in characteristics to be large. As a result, it is difficult to mold an optically homogeneous glass. Therefore, from the viewpoint of mass production of glass with little variation in composition and characteristics, it is preferable that the mass ratio (B) can be set to be low₂O₃/(B₂O₃+SiO₂) 0.900 or less to suppress volatilization during melting. Further, when the mass ratio (B)₂O₃/(B₂O₃+SiO₂) 0.900 or less, the deterioration of the chemical durability, weather resistance and machinability of the glass can be suppressed. On the other hand, in the glass composition described in the above-mentioned patent document 15 (Japanese patent laid-open No. 57-056344), B is₂O₃28-30 mass% of SiO₂The content of (b) is 1 to 3% by mass (see the claims of patent document 15). Mass ratio (B) calculated from the contents of these components₂O₃/(B₂O₃+SiO₂) ) is 0.903 to 0.968.

On the other hand, when the mass ratio (B)₂O₃/(B₂O₃+SiO₂) 0.4 or more), the meltability can be improved because the glass raw material can be prevented from remaining molten during melting.

From the above point of view, in the glass 1, the mass ratio (B) is set₂O₃/(B₂O₃+SiO₂) 0.4 to 0.900. Mass ratio in glass 1 (B)₂O₃/(B₂O₃+SiO₂) Preferred lower limits and preferred upper limits of) are shown in the following table.

[ TABLE 2]

From the viewpoint of improving the thermal stability, melting property, moldability, chemical durability, weather resistance, machinability and the like of the glass, B is used₂O₃Content of (A), SiO₂The contents of (b), the respective preferred lower limits and the preferred upper limits are shown in the following table.

[ TABLE 3]

[ TABLE 4]

La₂O₃、Y₂O₃、Gd₂O₃And Yb₂O₃Is a component having an action of increasing the refractive index while suppressing a decrease in the abbe number. In addition, these components also have the effect of improving the chemical durability and weather resistance of the glass and increasing the glass transition temperature.

When La₂O₃、Y₂O₃、Gd₂O₃And Yb₂O₃Total content of (La)₂O₃+Y₂O₃+Gd₂O₃+Yb₂O₃) When the refractive index is 45% or more, the decrease in refractive index can be suppressed, and therefore, glass having the above optical properties can be produced. Further, the glass can be inhibited from being deteriorated in chemical durability and weather resistance. In addition, when the glass transition temperature is lowered, the glass becomes easily broken (lowered in machinability) when the glass is machined (cut, ground, polished, etc.), but when La is used₂O₃、Y₂O₃、Gd₂O₃And Yb₂O₃When the total content of (b) is 45% or more, the decrease in glass transition temperature can be suppressed, and therefore the machinability can be improved. On the other hand, when La₂O₃、Y₂O₃、Gd₂O₃And Yb₂O₃When the total content of (b) is 65% or less, the thermal stability of the glass can be improved, and therefore, crystallization in the production of the glass can be suppressed, and the residual amount of the raw material in melting the glass can be reduced. Thus, in glass 1, La₂O₃、Y₂O₃、Gd₂O₃And Yb₂O₃The total content of (C) is set to 45-65%. La₂O₃、Y₂O₃、Gd₂O₃And Yb₂O₃The preferable lower limit and the preferable upper limit of the total content of (a) are shown in the following table.

[ TABLE 5]

ZrO₂Is a component having an action of increasing the refractive index, and has an action of improving the thermal stability of the glass by being contained in an appropriate amount. Furthermore, ZrO₂Also, the glass transition temperature is increased, and the glass is not easily broken when machining is performed. To obtain these effects well, glass is usedIn 1, ZrO is reacted with₂The content of (B) is 3% or more. On the other hand, when ZrO₂When the content of (b) is 11% or less, the thermal stability of the glass can be improved, and therefore, crystallization during glass production and generation of a melt residue during glass melting can be suppressed. Thus, ZrO in the glass 1₂The content of (C) is set to 3 to 11%. ZrO (ZrO)₂The preferred lower limit and the preferred upper limit of the content are shown in the following table.

[ TABLE 6]

As described above, Ta is preferable from the viewpoint of stable supply of glass₂O₅Is preferably a component that reduces the proportion of the glass composition. Further, Ta₂O₅The component is a component having an action of increasing the refractive index, but is also a component that increases the specific gravity of the glass and decreases the meltability. Thus, Ta in glass 1₂O₅The content is 5% or less. Ta₂O₅The preferred lower limit and the preferred upper limit of the content of (b) are shown in the following table.

[ TABLE 7]

In order to improve the thermal stability of the glass and suppress the increase in specific gravity and to realize the above-mentioned optical properties, in the glass 1, B is added₂O₃And SiO₂The total content of (A) to La₂O₃、Y₂O₃、Gd₂O₃And Yb₂O₃(B) the mass ratio of the total content of (A)₂O₃+SiO₂)/(La₂O₃+Y₂O₃+Gd₂O₃+Yb₂O₃) 0.42 to 0.53. When mass ratio ((B)₂O₃+SiO₂)/(La₂O₃+Y₂O₃+Gd₂O₃+Yb₂O₃) 0.42 or more), the thermal stability of the glass can be improved, and therefore devitrification of the glass can be suppressed. In addition, an increase in the specific gravity of the glass can also be suppressed. When the specific gravity of glass increases, an optical element made using the glass becomes heavy. As a result, the optical system in which the optical element is mounted becomes heavy. For example, when a heavy optical element is mounted in an auto-focus camera, power consumption increases when auto-focus is driven, and a battery is rapidly consumed. From the viewpoint of weight reduction of an optical element produced using the glass and an optical system in which the optical element is mounted, it is preferable that an increase in the specific gravity of the glass be suppressed. On the other hand, when the mass ratio ((B)₂O₃+SiO₂)/(La₂O₃+Y₂O₃+Gd₂O₃+Yb₂O₃) 0.53 or less), the above optical characteristics can be achieved. Further, the mass ratio ((B) is also preferable from the viewpoint of improvement in chemical durability of the glass and increase in glass transition temperature (Tg)₂O₃+SiO₂)/(La₂O₃+Y₂O₃+Gd₂O₃+Yb₂O₃) ) 0.53 or less. Mass ratio ((B)₂O₃+SiO₂)/(La₂O₃+Y₂O₃+Gd₂O₃+Yb₂O₃) Preferred lower limits and preferred upper limits of) are shown in the following table.

[ TABLE 8 ]

In La₂O₃、Y₂O₃、Gd₂O₃And Yb₂O₃In (1), Y is determined according to the above-mentioned reason₂O₃Is preferably a component that reduces the proportion of the glass composition. Thus, in glass 1, Y is₂O₃The content is 3% or less. Y is₂O₃The preferred lower limit and the preferred upper limit of the content are shown in the following table。

[ TABLE 9 ]

Y₂O₃Is a component that exerts an effect of improving the thermal stability of the glass without greatly reducing the light transmittance in the near infrared region. Further, since the atomic weight is small, Y is₂O₃Is a preferable component for suppressing the increase in the specific gravity of the glass. However, when Y is₂O₃When the content of (b) is too large, the thermal stability of the glass is remarkably lowered and crystallization is easy. In addition, the meltability is reduced. In order to produce a glass having the above optical properties, in which the thermal stability is improved and the increase in specific gravity is suppressed without greatly decreasing the light transmittance in the near infrared region, Y is added to the glass 1₂O₃Content relative to La₂O₃、Y₂O₃、Gd₂O₃And Yb₂O₃The mass ratio of the total content of (A), (B), (C), (D), (E), (₂O₃/(La₂O₃+Y₂O₃+Gd₂O₃+Yb₂O₃) 0.05 to 0.45 in the range of). Mass ratio (Y)₂O₃/(La₂O₃+Y₂O₃+Gd₂O₃+Yb₂O₃) Preferred lower limits and preferred upper limits of) are shown in the following table.

[ TABLE 10 ]

For the reasons described above, Gd₂O₃Is preferably a component that reduces the proportion of the glass composition. In addition, Gd is a heavy rare earth element similarly to Yb, and Gd has a large atomic weight as a component of glass, and the specific gravity of glass increases. From this point of view, it is also preferable to reduce the proportion of Gd occupied in the glass composition.

In glass 1, Gd₂O₃According to the content of La₂O₃、Y₂O₃、Gd₂O₃And Yb₂O₃And Gd is contained in the total amount of₂O₃The content is determined. In the glass 1, Gd is used from the viewpoint of stably supplying a high-refractivity low-dispersion glass having the above-mentioned optical properties, and further from the viewpoint of producing a glass having a small specific gravity as the high-refractivity low-dispersion glass₂O₃Content relative to La₂O₃、Y₂O₃、Gd₂O₃And Yb₂O₃The mass ratio of the total content of (b) (Gd)₂O₃/(La₂O₃+Y₂O₃+Gd₂O₃+Yb₂O₃) 0 to 0.05). Mass ratio (Gd)₂O₃/(La₂O₃+Y₂O₃+Gd₂O₃+Yb₂O₃) Preferred lower limits and preferred upper limits of) are shown in the following table.

[ TABLE 11 ]

From the viewpoint of providing a high-refractive-index, low-dispersion glass by not greatly lowering the light transmittance in the near infrared region, improving the thermal stability and suppressing the increase in specific gravity₂O₃Is a useful ingredient. Therefore, in the glass 1, La is preferably used₂O₃Content relative to La₂O₃、Y₂O₃、Gd₂O₃And Yb₂O₃The mass ratio of the total content of (A) to (B) (La)₂O₃/(La₂O₃+Y₂O₃+Gd₂O₃+Yb₂O₃) 0.55 to 0.95 is selected as the range of (A) to (B). Mass ratio (La)₂O₃/(La₂O₃+Y₂O₃+Gd₂O₃+Yb₂O₃) More preferred of (1))The lower limit and more preferred upper limit of (b) are shown in the following table.

[ TABLE 12 ]

La₂O₃、Y₂O₃、Gd₂O₃The preferable lower limit and the preferable upper limit of the content of each component (a) are shown in the following table.

[ TABLE 13 ]

[ TABLE 14 ]

[ TABLE 15 ]

Nb₂O₅、TiO₂、Ta₂O₅And WO₃Is a component having an action of increasing the refractive index, and has an action of improving the thermal stability of the glass by being contained in an appropriate amount. From the viewpoint of further improving the thermal stability of the glass while achieving the above-mentioned optical characteristics, Nb is preferable₂O₅、TiO₂、Ta₂O₅And WO₃Total content of (Nb)₂O₅+TiO₂+Ta₂O₅+WO₃) The range of (1) is 3-15%. Nb₂O₅、TiO₂、Ta₂O₅And WO₃The more preferable lower limit and the more preferable upper limit of the total content of (b) are shown in the following table.

[ TABLE 16 ]

ZnO has an action of promoting melting of glass raw materials at the time of melting glass, that is, an action of improving meltability. In addition, the glass transition temperature is also lowered by adjusting the refractive index and the abbe number. From the viewpoint of improving the meltability, the ZnO content is preferably divided by B₂O₃And SiO₂The value obtained by the total content of (A), (B) or (C), i.e., the mass ratio (ZnO/(B)₂O₃+SiO₂) ) is 0.04 or more. On the other hand, the mass ratio (ZnO/(B) is preferable from the viewpoint of suppressing the decrease in abbe number (high dispersion) and realizing the above optical characteristics₂O₃+SiO₂) ) is 0.4 or less. Further, the mass ratio (ZnO/(B) is also preferable from the viewpoint of improving the thermal stability of the glass and increasing the glass transition temperature (Tg)₂O₃+SiO₂) ) is 0.4 or less. Therefore, the content of ZnO is preferably B in terms of mass ratio₂O₃And SiO₂0.04 to 0.4 times of the total content of (A), (B), i.e., the mass ratio (ZnO/(B)₂O₃+SiO₂) 0.04 to 0.4. Mass ratio (ZnO/(B)₂O₃+SiO₂) The more preferable lower limit and the preferable upper limit of) are shown in the following table.

[ TABLE 17 ]

From the viewpoint of improving the melting property, thermal stability, moldability, machinability, etc. of the glass and realizing the above optical characteristics, the preferable lower limit and the preferable upper limit of the ZnO content are shown in the following table.

[ TABLE 18 ]

The optical properties described above are realized while the coloring degree λ described later is suppressed5 to improve the ultraviolet transmittance of the glass, B is preferably added₂O₃And SiO₂The total content of (B) relative to Nb₂O₅、TiO₂、Ta₂O₅And WO₃(B) the mass ratio of the total content of (A)₂O₃+SiO₂)/(Nb₂O₅+TiO₂+Ta₂O₅+WO₃) 2.65 to 10. In addition, from the viewpoint of improving the thermal stability of the glass, it is also preferable to set the mass ratio ((B)₂O₃+SiO₂)/(Nb₂O₅+TiO₂+Ta₂O₅+WO₃) 2.65 or more. Mass ratio ((B)₂O₃+SiO₂)/(Nb₂O₅+TiO₂+Ta₂O₅+WO₃) The more preferable lower limit and the more preferable upper limit of) are shown in the following table.

[ TABLE 19 ]

About Nb₂O₅、TiO₂、Ta₂O₅And WO₃When the glass composition is contained in an appropriate amount, the thermal stability of the glass can be improved.

When TiO is contained in these components₂When the content (b) is increased, the transmittance of the glass in the visible region tends to be decreased, and the coloring of the glass tends to be increased.

Ta₂O₅The function of (c) is as described above.

For WO₃When the content is increased, the transmittance of the glass in the visible region tends to be lowered, the glass tends to be colored more, and the specific gravity tends to be increased.

In contrast, Nb₂O₅Has the effects of increasing the specific gravity and coloring of glass, preventing the increase of manufacturing cost, increasing the refractive index, and improving the thermal stability of glass. Therefore, in order to effectively use Nb in glass 1₂O₅Excellent effects of,Effect of adding Nb₂O₅Relative to the content of Nb₂O₅、TiO₂、Ta₂O₅And WO₃Mass ratio of the total content of (B)/(B)₂O₅/(Nb₂O₅+TiO₂+Ta₂O₅+WO₃) 0.5 to 1. From the viewpoint of reducing the coloring degree λ 5 and promoting curing of the ultraviolet-curable adhesive by ultraviolet irradiation, it is preferable to increase the mass ratio (Nb)₂O₅/(Nb₂O₅+TiO₂+Ta₂O₅+WO₃)). Mass ratio (Nb)₂O₅/(Nb₂O₅+TiO₂+Ta₂O₅+WO₃) The more preferable lower limit and the more preferable upper limit of) are shown in the following table.

[ TABLE 20 ]

With respect to Ta₂O₅For the reasons described above, it is not preferable to positively introduce glass. Therefore, for Nb₂O₅Relative to the content in Nb₂O₅、TiO₂、Ta₂O₅And WO₃Middle exclusion of Ta₂O₅Post Nb₂O₅、TiO₂And WO₃Mass ratio of the total content of (B)/(B)₂O₅/(Nb₂O₅+TiO₂+WO₃) Preferred ranges of the compounds) are described. The mass ratio (Nb) is preferred for producing glass having excellent thermal stability and reduced coloring₂O₅/(Nb₂O₅+TiO₂+WO₃) 0.50 to 1. Mass ratio (Nb)₂O₅/(Nb₂O₅+TiO₂+WO₃) The more preferable lower limit and the more preferable upper limit of) are shown in the following table.

[ TABLE 21 ]

From the viewpoint of improving the meltability, the content of ZnO is preferably relative to Nb₂O₅、TiO₂、Ta₂O₅And WO₃The mass ratio of the total content of (1) (ZnO/(Nb))₂O₅+TiO₂+Ta₂O₅+WO₃) ) is 0.1 or more. In addition, in the case of a glass having a low melting property, when the melting temperature of the glass is increased so as not to leave a residue of the glass raw material after melting and the melting time is prolonged, the coloring of the glass tends to increase. This is presumably because, when the melting temperature is increased and the melting time is prolonged when glass is melted in a melting crucible made of a noble metal such as platinum, the noble metal constituting the crucible is melted into the molten glass, light absorption by noble metal ions occurs, and the coloring of the glass, particularly the value of λ 5, increases. On the other hand, when it is intended to improve the meltability by adjusting the content of other glass components, the thermal stability may be lowered, and it may be difficult to obtain a homogeneous glass having the above-mentioned optical characteristics. Therefore, in order to improve the meltability of the glass, the mass ratio (ZnO/(Nb) is also preferably set from the viewpoint of suppressing coloring of the glass₂O₅+TiO₂+Ta₂O₅+WO₃) ) is 0.1 or more. In addition, from the viewpoint of further improving the thermal stability of the glass, suppressing the lowering of the glass transition temperature (the improvement of machinability caused by this), and improving the chemical durability, the mass ratio (ZnO/(Nb) is preferable₂O₅+TiO₂+Ta₂O₅+WO₃) ) is 3 or less. Mass ratio (ZnO/(Nb)₂O₅+TiO₂+Ta₂O₅+WO₃) The more preferable lower limit and the more preferable upper limit of) are shown in the following table.

[ TABLE 22 ]

For Nb₂O₅Content (wt.)、TiO₂Content, WO₃The preferred lower limit and the preferred upper limit of each content are shown in the following table.

[ TABLE 23 ]

[ TABLE 24 ]

[ TABLE 25 ]

From the viewpoints of further improving the thermal stability of the glass, suppressing the lowering of the glass transition temperature (improvement of machinability caused by the lowering), and improving the chemical durability and weather resistance, Li is preferable₂The O content is 1% or less. Li₂The preferred lower limit and the preferred upper limit of the O content are shown in the following table.

[ TABLE 26 ]

Na₂O、K₂O、Rb₂O、Cs₂O has an effect of improving the meltability of the glass, but when the content of these is increased, the thermal stability, chemical durability, weather resistance, and machinability of the glass tend to be reduced. Therefore, Na is preferred₂O、K₂O、Rb₂O、Cs₂The lower limit and the upper limit of each content of O are shown in the following tables, respectively.

[ TABLE 27 ]

[ TABLE 28 ]

[ TABLE 29 ]

[ TABLE 30 ]

Rb₂O、Cs₂O is an expensive component, with Li₂O、Na₂O、K₂O is a component unsuitable for general-purpose glasses. Therefore, Li is preferable from the viewpoint of improving the meltability of the glass while maintaining the thermal stability, chemical durability, weather resistance and machinability of the glass₂O、Na₂O and K₂Total content of O (Li)₂O+Na₂O+K₂O) are set as shown in the following table.

[ TABLE 31 ]

MgO, CaO, SrO and BaO are all components having an effect of improving the meltability of the glass. However, when the content of these components is increased, the thermal stability of the glass is lowered, showing a tendency to devitrify. Therefore, the contents of these components are preferably set to the lower limit or more and the upper limit or less shown in the following table.

[ TABLE 32 ]

[ TABLE 33 ]

[ TABLE 34 ]

[ TABLE 35 ]

From the viewpoint of further improving the thermal stability of the glass, the total content of MgO, CaO, SrO and BaO (MgO + CaO + SrO + BaO) is preferably not less than the lower limit and not more than the upper limit shown in the following table.

[ TABLE 36 ]

Al₂O₃Is a component having an effect of improving the chemical durability and weather resistance of the glass. However, when Al is used₂O₃When the content of (b) is increased, the refractive index tends to be lowered, the thermal stability of the glass tends to be lowered, and the meltability tends to be lowered. In view of the above, Al₂O₃The content is preferably not less than the lower limit and not more than the upper limit shown in the following table.

[ TABLE 37 ]

Ga₂O₃、In₂O₃、Sc₂O₃、HfO₂Both have the effect of increasing the refractive index nd. However, these components are expensive and are not essential components in view of obtaining the glass 1. Thus, Ga₂O₃、In₂O₃、Sc₂O₃、HfO₂The content of (b) is preferably not less than the lower limit and not more than the upper limit shown in the following table.

[ TABLE 38 ]

[ TABLE 39 ]

[ TABLE 40 ]

[ TABLE 41 ]

Lu₂O₃Has the effect of increasing the refractive index nd, but is also a component that increases the specific gravity of the glass. In addition, it is also an expensive component. From the above aspects, Lu₂O₃The preferred lower limit and the preferred upper limit of the content of (b) are shown in the following table.

[ TABLE 42 ]

GeO₂Has an effect of increasing the refractive index nd, but is an extremely expensive component among glass components generally used. GeO from the viewpoint of reducing the production cost of glass₂The preferred lower limit and the preferred upper limit of the content are shown in the following table.

[ TABLE 43 ]

Bi₂O₃Is a component that increases the refractive index nd and lowers the Abbe number. Further, it is also a component which easily increases the coloring of the glass. From the viewpoint of producing a glass having the above-mentioned optical properties and little coloration, Bi₂O₃The preferred lower limit and the preferred upper limit of the content are shown in the following table.

[ TABLE 44 ]

In view of satisfactorily obtaining the various actions and effects described above, the total content (total content) of the glass components described above is preferably more than 95%, more preferably more than 98%, still more preferably more than 99%, and still more preferably more than 99.5%.

In the glass components other than the above-mentioned glass components, P₂O₅The refractive index is lowered, and the thermal stability of the glass is also lowered, but if the amount is extremely small, the thermal stability of the glass may be improved. P for producing a glass having the above optical characteristics and excellent thermal stability₂O₅The preferred lower limit and the preferred upper limit of the content are shown in the following table.

[ TABLE 45 ]

TeO₂Is a component for increasing the refractive index, but is also a component having toxicity, so it is preferable to reduce TeO₂The content of (a). TeO₂The preferred lower limit and the preferred upper limit of the content are shown in the following table.

[ TABLE 46 ]

In addition, it is described in the above tables that the content of the component having the (more) preferable lower limit or 0% is also preferably 0%. The same applies to the total content of the plurality of components.

Pb, As, Cd, Tl, Be, Se are toxic individually. Therefore, it is preferable that these elements are not contained, that is, not introduced into the glass as a glass component.

U, Th and Ra are radioactive elements. Therefore, it is preferable that these elements are not contained, that is, not introduced into the glass as a glass component.

V, Cr, Mn, Fe, Co, Ni, Cu, Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm, Ce or the like increases the coloration of the glass or becomes a source of fluorescence, and is not preferable as an element to be contained in the glass for optical elements. Therefore, it is preferable that these elements are not contained, that is, not introduced into the glass as a glass component.

Sb and Sn are elements that can be added arbitrarily and function as clarifiers.

The amount of Sb added is converted into Sb₂O₃Oxide-based glass composition of Sb₂O₃The amount of Sb added is preferably in the range of 0 to 0.11% by mass, more preferably in the range of 0.01 to 0.08% by mass, and still more preferably in the range of 0.02 to 0.05% by mass, based on 100% by mass of the total content of the other glass components. Here, the "oxide-based glass composition" refers to a glass composition obtained by decomposing all glass raw materials at the time of melting and converting the glass raw materials into substances existing as oxides in the glass. Sb in the glass compositions shown in the tables₂O₃The content is also a content calculated by the above-mentioned method.

The amount of Sn added is converted into SnO₂SnO in oxide-based glass composition₂The addition amount of Sn is preferably in the range of 0 to 1.0% by mass, more preferably in the range of 0 to 0.5% by mass, even more preferably in the range of 0 to 0.2% by mass, and even more preferably in the range of 0 to 0.2% by mass, when the total content of the other glass components is 100% by massFurther preferably 0 mass%.

< glass composition of glass 2 >

In the present invention, the glass composition of the glass 2 is expressed in cation% for the cation component. As is well known, the cation% is a percentage in which the total content of all the cation components contained in the glass is 100%.

With respect to cationic components, e.g. like B³⁺、Si⁴⁺、La³⁺Thus representing the valence of the cationic component (e.g., B)³⁺Valence of +3, Si⁴⁺Valence of +4, La³⁺Valence of +3) is a value determined conventionally, and B, Si, La are represented as B on an oxide basis₂O₃、SiO₂、La₂O₃The same is true. For expression A on an oxide basis_mO_n(A represents a cation, O represents oxygen, and m and n are integers determined by a stoichiometric method), and the cation A is represented by A^s+Here, s is 2 n/m. Therefore, for example, in the analysis and quantification of the glass composition, the valence number of the cationic component may not be analyzed, and hereinafter, unless otherwise specified, the content of the cationic component and the total amount (total content) of the plurality of cationic components may be expressed as% of cations. Further, in the expression of cation%, the ratio of the contents of the cation components (including the total content of the plurality of cation components) is referred to as a cation ratio.

B³⁺、Si⁴⁺Is a network forming component of the glass. When B is present³⁺And Si⁴⁺Total content (B) of³⁺+Si⁴⁺) When the content is 45% or more, the thermal stability of the glass can be improved, and crystallization of the glass during production can be suppressed. On the other hand, when B³⁺And Si⁴⁺When the total content of (b) is 65% or less, the decrease in refractive index can be suppressed, and therefore, a glass having the above optical properties, that is, a glass having a refractive index nd in the range of 1.800 to 1.850 and an Abbe's number vd in the range of 41.5 to 44 can be produced. Thus, B in glass 2³⁺And Si⁴⁺The total content of (C) is set to 45-65%. B is³⁺And Si⁴⁺The preferable lower limit and the preferable upper limit of the total content of (a) are shown in the following table.

[ TABLE 47 ]

B as a network-forming component of glass³⁺And Si⁴⁺The content ratio of each component (a) has an influence on the thermal stability, melting property, moldability, chemical durability, weather resistance, machinability and the like of the glass. B is³⁺The effect ratio of improving meltability of Si⁴⁺More excellent, but easily volatilized when melted. In contrast, Si⁴⁺Has the effects of improving the chemical durability, weather resistance and machinability of the glass and improving the viscosity of the glass during melting.

Usually, in the presence of B³⁺And La³⁺And the like, the rare earth element glass having a high refractive index and a low dispersion has a low viscosity when melted. However, when the viscosity of the glass at the time of melting is low, thermal stability is lowered (crystallization becomes easy). With respect to crystallization in glass production, the state of crystallization is more stable than the amorphous state (amorphous state), which occurs by ions constituting the glass moving in the glass and being arranged so as to have a crystal structure. Thus, by pair B³⁺And Si⁴⁺The content ratio of each component (a) is adjusted so as to increase the viscosity at the time of melting, whereby the ions are less likely to be aligned so as to have a crystal structure, crystallization of the glass is further suppressed, and the thermal stability of the glass is further improved.

If B is present³⁺Relative to B³⁺And Si⁴⁺The cation ratio (B) of the total content³⁺/(B³⁺+Si⁴⁺) Less than 0.94), the viscosity at the time of melting can be suppressed from decreasing, whereby the thermal stability of the glass can be improved and volatilization at the time of melting can be suppressed. Volatilization during melting causes a change in glass composition and a change in characteristics to be large. As a result, it is difficult to mold an optically homogeneous glass. Therefore, from the viewpoint of mass production of glass with little variation in composition and characteristics, it is preferable that the cation ratio (B) can be adjusted³⁺/(B³⁺+Si⁴⁺) Less than 0.94) to suppress volatilization during melting. Further, when the cation ratio is (B)³⁺/(B³⁺+Si⁴ ⁺) When the glass composition is less than 0.94), the glass can be inhibited from being deteriorated in chemical durability, weather resistance and machinability. On the other hand, in the glass composition described in the above-mentioned patent document 15 (Japanese patent laid-open No. 57-056344), B is₂O₃28-30 mass% of SiO₂The content of (b) is 1 to 3% by mass (see the claims of patent document 15). Cation ratio (B) calculated from the contents of these components³⁺/(B³⁺+Si⁴⁺) ) is 0.942 to 0.981.

On the other hand, when the cation ratio (B)³⁺/(B³⁺+Si⁴⁺) 0.65 or more), the meltability can be improved because the glass raw material can be prevented from remaining molten during melting.

From the above point of view, in the glass 2, the cation ratio (B) is set³⁺/(B³⁺+Si⁴⁺) ) is set to 0.65 or more and less than 0.94. Cation ratio (B) in glass 2³⁺/(B³⁺+Si⁴⁺) Preferred lower limits and preferred upper limits of) are shown in the following table.

[ TABLE 48 ]

Improve the thermal stability, melting property, forming property, chemical durability, weather resistance and mechanical property of the glassFrom the viewpoint of working or the like, for B³⁺Content of (A), Si⁴⁺The respective preferred lower limits and preferred upper limits of the contents of (a) are shown in the following table.

[ TABLE 49 ]

[ TABLE 50 ]

La³⁺、Y³⁺、Gd³⁺And Yb³⁺Is a component having an action of increasing the refractive index while suppressing a decrease in the abbe number. In addition, these components also have the effect of improving the chemical durability and weather resistance of the glass and increasing the glass transition temperature.

When La³⁺、Y³⁺、Gd³⁺And Yb³⁺Total content of (La)³⁺+Y³⁺+Gd³⁺+Yb³⁺) When the content is 25% or more, the decrease in refractive index can be suppressed, and therefore, glass having the above-mentioned optical properties can be produced. Further, the glass can be inhibited from being deteriorated in chemical durability and weather resistance. In addition, when the glass transition temperature is lowered, the glass becomes easily broken (lowered in machinability) when the glass is machined (cut, ground, polished, etc.), but when La is used³⁺、Y³⁺、Gd³⁺And Yb³⁺When the total content of (b) is 25% or more, the decrease in glass transition temperature can be suppressed, and therefore, the machinability can be improved. On the other hand, when La³⁺、Y³⁺、Gd³⁺And Yb³⁺When the total content of (b) is 35% or less, the thermal stability of the glass can be improved, and therefore, crystallization in the production of the glass can be suppressed, and the residual amount of molten raw material in the melting of the glass can be reduced. Thus, in the glass 2, La³⁺、Y³⁺、Gd³ ⁺And Yb³⁺The total content of (a) is set to 25 to 35%.La³⁺、Y³⁺、Gd³⁺And Yb³⁺The preferable lower limit and the preferable upper limit of the total content of (a) are shown in the following table.

[ TABLE 51 ]

Zr⁴⁺Is a component having an action of increasing the refractive index, and has an action of improving the thermal stability of the glass by being contained in an appropriate amount. In addition, Zr⁴⁺Also, the glass transition temperature is increased, and the glass is not easily broken during machining. In order to obtain these effects well, in the glass 2, Zr is added⁴⁺The content of (B) is set to 2% or more. On the other hand, when Zr⁴⁺When the content of (b) is 8% or less, the thermal stability of the glass can be improved, and therefore, crystallization during glass production and generation of a melt residue during glass melting can be suppressed. Thus, Zr in glass 2⁴⁺The content of (C) is set to 2 to 8%. Zr⁴⁺The preferred lower limit and the preferred upper limit of the content are shown in the following table.

[ TABLE 52 ]

As described above, Ta is preferable from the viewpoint of stable supply of glass⁵⁺Is preferably a component that reduces the proportion of the glass composition. Further, Ta⁵⁺The component is a component having an action of increasing the refractive index, but is also a component that increases the specific gravity of the glass and decreases the meltability. Thus, Ta in glass 2⁵⁺The content is 3% or less. Ta⁵⁺The preferred lower limit and the preferred upper limit of the content of (b) are shown in the following table.

[ TABLE 53 ]

In order to improve the thermal stability of the glass and suppress the increase in specific gravity and to realize the above-mentioned optical properties, in the glass 2, B is added³⁺And Si⁴⁺The total content of (A) to La³⁺、Y³⁺、Gd³⁺And Yb³⁺Cation ratio of the total content of ((B)³⁺+Si⁴ ⁺)/(La³⁺+Y³⁺+Gd³⁺+Yb³⁺) ) is in the range of 1.65 to 2.60. When cation ratio ((B)³⁺+Si⁴⁺)/(La³⁺+Y³⁺+Gd³⁺+Yb³⁺) 1.65 or more), the thermal stability of the glass can be improved, and therefore devitrification of the glass can be suppressed. In addition, an increase in the specific gravity of the glass can also be suppressed. When the specific gravity of glass increases, an optical element made using the glass becomes heavy. As a result, the optical system in which the optical element is mounted becomes heavy. For example, when a heavy optical element is mounted in an auto-focus camera, power consumption increases when auto-focus is driven, and a battery is rapidly consumed. From the viewpoint of weight reduction of an optical element produced using the glass and an optical system in which the optical element is mounted, it is preferable that an increase in the specific gravity of the glass be suppressed. On the other hand, when the cation ratio ((B)³⁺+Si⁴⁺)/(La³⁺+Y³⁺+Gd³⁺+Yb³⁺) 2.60 or less), the above optical characteristics can be achieved. Further, from the viewpoint of improving the chemical durability of the glass and increasing the glass transition temperature (Tg), the cation ratio ((B) is preferred³⁺+Si⁴⁺)/(La³⁺+Y³⁺+Gd³⁺+Yb³⁺) ) is 2.60 or less. Cation ratio ((B)³⁺+Si⁴⁺)/(La³⁺+Y³⁺+Gd³⁺+Yb³⁺) Preferred lower limits and preferred upper limits of) are shown in the following table.

[ TABLE 54 ]

For the reasons described above, La³⁺、Y³⁺、Gd³⁺And Yb³⁺Medium, Yb³⁺Is preferably a component that reduces the proportion of the glass composition. Thus, in glass 2, Yb³⁺The content was set to be less than 2%. Yb of³⁺The preferred lower limit and the preferred upper limit of the content are shown in the following table.

[ TABLE 55 ]

Y³⁺Is a component that exerts an effect of improving the thermal stability of the glass without greatly reducing the light transmittance in the near infrared region. Further, since the atomic weight is small, Y is³⁺Is a preferable component in terms of suppressing an increase in the specific gravity of the glass. However, when Y is³⁺When the content of (b) is too large, the thermal stability of the glass is remarkably lowered and crystallization is easy. In addition, the meltability is reduced. From the viewpoint of producing a glass having the above-mentioned optical properties, which has improved thermal stability and in which the increase in specific gravity is suppressed without significantly decreasing the light transmittance in the near infrared region, it is preferable to add Y to the glass 2³⁺Relative to La³⁺、Y³⁺、Gd³⁺And Yb³⁺Cation ratio (Y) of the total content of³⁺/(La³⁺+Y³⁺+Gd³⁺+Yb³⁺) 0.05 to 0.45 in the range of). Cation ratio (Y)³⁺/(La³⁺+Y³⁺+Gd³⁺+Yb³⁺) Preferred lower limits and preferred upper limits of) are shown in the following table.

[ TABLE 56 ]

For the reasons described above, Gd³⁺Is preferably a component that reduces the proportion of the glass composition. In addition, Gd is a heavy rare earth element similarly to Yb, and Gd has a large atomic weight as a component of glass, and the specific gravity of glass increases. From this point of view, it is also preferable to reduce the proportion of Gd occupied in the glass composition.

In glass 2, Gd³⁺According to the content of La³⁺、Y³⁺、Gd³⁺And Yb³⁺And Gd is contained in the total amount of³⁺The content is determined. Gd is added to the glass having the above optical properties from the viewpoint of stably supplying the glass having a high refractive index and a low dispersion, and further from the viewpoint of producing a glass having a low specific gravity as the glass having a high refractive index and a low dispersion³⁺Content relative to La³⁺、Y³⁺、Gd³⁺And Yb³⁺The cation ratio (Gd) of the total content of³⁺/(La³⁺+Y³⁺+Gd³⁺+Yb³⁺) 0 to 0.05). Cation ratio (Gd)³⁺/(La³⁺+Y³⁺+Gd³⁺+Yb³⁺) Preferred lower limits and preferred upper limits of) are shown in the following table.

[ TABLE 57 ]

From the viewpoint of providing a high-refractive-index, low-dispersion glass by not greatly lowering the light transmittance in the near infrared region, improving the thermal stability and suppressing the increase in specific gravity³⁺Is a useful ingredient. Therefore, in the glass 2, La is preferably used³ ⁺Content relative to La³⁺、Y³⁺、Gd³⁺And Yb³⁺Cation ratio (La) of the total content of³⁺/(La³⁺+Y³⁺+Gd³⁺+Yb³⁺) 0.55 to 0.95 is selected as the range of (A) to (B). Cation ratio (La)³⁺/(La³⁺+Y³⁺+Gd³⁺+Yb³⁺) The more preferable lower limit and the more preferable upper limit of) are shown in the following table.

[ TABLE 58 ]

La³⁺、Y³⁺、Gd³⁺The content of each component (a) is preferableThe lower limits and preferred upper limits of (b) are shown in the following table.

[ TABLE 59 ]

[ TABLE 60 ]

[ TABLE 61 ]

Nb⁵⁺、Ti⁴⁺、Ta⁵⁺And W⁶⁺Is a component having an action of increasing the refractive index, and has an action of improving the thermal stability of the glass by being contained in an appropriate amount. From the viewpoint of further improving the thermal stability of the glass while achieving the above-mentioned optical characteristics, Nb is preferable⁵⁺、Ti⁴⁺、Ta⁵⁺And W⁶⁺Total content of (Nb)⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺) The range of (1) is 2 to 10%. Nb⁵ ⁺、Ti⁴⁺、Ta⁵⁺And W⁶⁺The more preferable lower limit and the more preferable upper limit of the total content of (b) are shown in the following table.

[ TABLE 62 ]

Zn²⁺Has an action of promoting melting of glass raw materials at the time of melting glass, that is, an action of improving meltability. In addition, the glass transition temperature is also lowered by adjusting the refractive index and abbe number. From the viewpoint of improving the meltability, Zn is preferred²⁺Content divided by B³⁺And Si⁴⁺The value obtained by the total content of (A), (B), (C) and (C), that is, the cation ratio (Zn)²⁺/(B³⁺+Si⁴⁺) ) is 0.01 or more. On the other hand, the cation ratio (Zn) is preferred from the viewpoint of suppressing the decrease in Abbe number (high dispersion) and realizing the above optical properties²⁺/(B³⁺+Si⁴⁺) ) 0.22 or less. Further, the cation ratio (Zn) is also preferable from the viewpoint of improving the thermal stability and increasing the glass transition temperature (Tg) of the glass²⁺/(B³⁺+Si⁴⁺) ) 0.22 or less. Therefore, Zn is preferably added²⁺The content of (A) is set as B in the cation ratio³⁺And Si⁴⁺0.01 to 0.22 times of the total content of (A), i.e., the cation ratio (Zn)²⁺/(B³⁺+Si⁴⁺) 0.01 to 0.22. Cation ratio (Zn)²⁺/(B³⁺+Si⁴⁺) The more preferable lower limit and the preferable upper limit of) are shown in the following table.

[ TABLE 63 ]

From the viewpoint of improving the melting property, thermal stability, moldability, machinability, etc. of the glass to realize the above-mentioned optical properties, Zn²⁺The preferred lower limit and the preferred upper limit of the content are shown in the following table.

[ TABLE 64 ]

In order to improve the ultraviolet transmittance of the glass by suppressing an increase in the coloring degree λ 5 described later while achieving the above optical properties, B is preferable³⁺And Si⁴⁺The total content of (B) relative to Nb⁵⁺、Ti⁴⁺、Ta⁵⁺And W⁶⁺Cation ratio of the total content of ((B)³⁺+Si⁴⁺)/(Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺) ) is set to be 9.0 to 32. In addition, from the viewpoint of improving the thermal stability of the glass, it is also preferable to set the cation ratio ((B)³⁺+Si⁴⁺)/(Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺) ) is 9.0 or more. Cation ratio ((B)³⁺+Si⁴⁺)/(Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺) The more preferable lower limit and the more preferable upper limit of) are shown in the following table.

[ TABLE 65 ]

About Nb⁵⁺、Ti⁴⁺、Ta⁵⁺And W⁶⁺When the glass composition is contained in an appropriate amount, the thermal stability of the glass can be improved.

When Ti is contained in these components⁴⁺When the content (b) is increased, the transmittance of the glass in the visible region tends to be decreased, and the coloring of the glass tends to be increased.

Ta⁵⁺The function of (c) is as described above.

For W⁶⁺When the content is increased, the transmittance of the glass in the visible region tends to be lowered, the glass tends to be colored more, and the specific gravity tends to be increased.

In contrast, Nb⁵⁺Has the effects of increasing the specific gravity and coloring of glass, preventing the increase of manufacturing cost, increasing the refractive index, and improving the thermal stability of glass. Therefore, in order to effectively use Nb in the glass 2⁵⁺Excellent action and effect of (2) Nb⁵⁺Relative to the content of Nb⁵⁺、Ti⁴⁺、Ta⁵⁺And W⁶⁺Cation ratio (Nb) of the total content⁵⁺/(Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺) ) is set to 0.4 to 1. From the viewpoint of reducing the coloring degree λ 5 and promoting curing of the ultraviolet-curable adhesive by ultraviolet irradiation, it is preferable to increase the cation ratio (Nb)⁵⁺/(Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺)). Cation ratio (Nb)⁵⁺/(Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶ ⁺) The more preferable lower limit and the more preferable upper limit of) are shown in the following table.

[ TABLE 66 ]

With respect to Ta⁵⁺For the reasons described above, it is not preferable to positively introduce glass. Therefore, for Nb⁵⁺Relative to the content in Nb⁵⁺、Ti⁴⁺、Ta⁵⁺And W⁶⁺Middle exclusion of Ta⁵⁺Post Nb⁵⁺、Ti⁴⁺And W⁶⁺Cation ratio (Nb) of the total content⁵⁺/(Nb⁵⁺+Ti⁴⁺+W⁶⁺) Preferred ranges of the compounds) are described. The cation ratio (Nb) is preferred for producing glass having excellent thermal stability and reduced coloring⁵⁺/(Nb⁵⁺+Ti⁴⁺+W⁶⁺) 0.4 to 1. Cation ratio (Nb)⁵⁺/(Nb⁵⁺+Ti⁴⁺+W⁶⁺) The more preferable lower limit and the more preferable upper limit of) are shown in the following table.

[ TABLE 67 ]

From the viewpoint of improving the meltability, Zn is preferred²⁺Content relative to Nb⁵⁺、Ti⁴⁺、Ta⁵⁺And W⁶⁺Cation ratio (Zn) of the total content of²⁺/(Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺) ) is 0.1 or more. In addition, in the case of a glass having a low melting property, when the melting temperature of the glass is increased so as not to leave a residue of the glass raw material after melting and the melting time is prolonged, the coloring of the glass tends to increase. This is presumably because, when the melting temperature is increased and the melting time is prolonged when glass is melted in a melting crucible made of a noble metal such as platinum, the noble metal constituting the crucible is melted into the molten glass, light absorption by noble metal ions occurs, and the coloring of the glass, particularly the value of λ 5, increases. On the other hand, when it is intended to improve the meltability by adjusting the content of other glass components,thermal stability may be lowered, and it may be difficult to obtain homogeneous glass having the above optical characteristics. Therefore, in order to improve the meltability of the glass, it is also preferable to use a cation ratio (Zn) in order to suppress coloring of the glass²⁺/(Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺) ) is 0.1 or more. In addition, from the viewpoint of further improving the thermal stability of the glass, suppressing the lowering of the glass transition temperature (the improvement of machinability caused by this), and improving the chemical durability, it is preferable to use the cation ratio (Zn)²⁺/(Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺) ) is 5 or less. Cation ratio (Zn)²⁺/(Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺) The more preferable lower limit and the more preferable upper limit of) are shown in the following table.

[ TABLE 68 ]

For Nb⁵⁺Content of Ti⁴⁺Content, W⁶⁺The preferred lower limit and the preferred upper limit of each content are shown in the following table.

[ TABLE 69 ]

[ TABLE 70 ]

[ TABLE 71 ]

Further improves the thermal stability of the glass, suppresses the lowering of the glass transition temperature (thereby improving the machinability), and improves the chemical durabilityFrom the viewpoint of weather resistance, Li is preferred⁺The content is 3% or less. Li⁺The preferred lower limit and the preferred upper limit of the content are shown in the following table.

[ TABLE 72 ]

Na⁺、K⁺、Rb⁺、Cs⁺All have an effect of improving the meltability of the glass, but when the content of these is increased, the thermal stability, chemical durability, weather resistance and machinability of the glass tend to be reduced. Therefore, Na is preferred⁺、K⁺、Rb⁺、Cs⁺The lower limit and the upper limit of each content are shown in the following table.

[ TABLE 73 ]

[ TABLE 74 ]

[ TABLE 75 ]

[ TABLE 76 ]

Rb⁺、Cs⁺Is an expensive component, with Li⁺、Na⁺、K⁺In contrast, it is a composition unsuitable for general-purpose glasses. Therefore, the melting of the glass is improved while maintaining the thermal stability, chemical durability, weather resistance and machinability of the glassFrom the viewpoint of properties, Li is preferred⁺、Na⁺、K⁺Total content of (Li)⁺+Na⁺+K⁺) The lower limit and the upper limit of (d) are shown in the following tables, respectively.

[ TABLE 77 ]

Mg²⁺、Ca²⁺、Sr²⁺、Ba²⁺All of them are components having an effect of improving the meltability of the glass. However, when the content of these components is increased, the thermal stability of the glass is lowered, showing a tendency to devitrify. Therefore, the contents of these components are preferably set to the lower limit or more and the upper limit or less shown in the following table.

[ TABLE 78 ]

[ TABLE 79 ]

[ TABLE 80 ]

[ TABLE 81 ]

Further, from the viewpoint of further improving the thermal stability of the glass, Mg²⁺、Ca²⁺、Sr²⁺And Ba²⁺Total content (Mg) of²⁺+Ca²⁺+Sr²⁺+Ba²⁺) Preferably, the lower limit or more and the upper limit or less are shown in the following table.

[ TABLE 82 ]

Al³⁺Is a component having an effect of improving the chemical durability and weather resistance of the glass. However, when Al is used³⁺When the content of (b) is increased, the refractive index tends to be lowered, the thermal stability of the glass tends to be lowered, and the meltability tends to be lowered. In view of the above, Al³⁺The content is preferably not less than the lower limit and not more than the upper limit shown in the following table.

[ TABLE 83 ]

Ga³⁺、In³⁺、Sc³⁺、Hf⁴⁺All have the function of improving the refractive index. However, these components are expensive and are not essential components in view of obtaining the glass 2. Thus, Ga³⁺、In³⁺、Sc³⁺、Hf⁴⁺The content of (b) is preferably not less than the lower limit and not more than the upper limit shown in the following table.

[ TABLE 84 ]

[ TABLE 85 ]

[ TABLE 86 ]

[ TABLE 87 ]

Lu³⁺Has the effect of increasing the refractive index, but also increases the specific gravity of the glass. In addition, it is also an expensive component. From the above aspects, Lu³⁺The preferred lower limit and the preferred upper limit of the content of (b) are shown in the following table.

[ TABLE 88 ]

Ge⁴⁺Has an effect of increasing the refractive index, but is an extremely expensive component among glass components generally used. From the viewpoint of reducing the production cost of glass, Ge⁴⁺The preferred lower limit and the preferred upper limit of the content are shown in the following table.

[ TABLE 89 ]

Bi³⁺Is a component that increases the refractive index and decreases the abbe number. Further, it is also a component which easily increases the coloring of the glass. From the viewpoint of producing a glass having the above-mentioned optical properties and little coloration, Bi³⁺The preferred lower limit and the preferred upper limit of the content are shown in the following table.

[ TABLE 90 ]

In view of satisfactorily obtaining the various actions and effects described above, the total content (total content) of the respective contents of the cationic components described above is preferably more than 95%, more preferably more than 98%, still more preferably more than 99%, and still more preferably more than 99.5%.

In addition to the cationic components described aboveIn the cationic component of (A), P⁵⁺The refractive index is lowered, and the thermal stability of the glass is also lowered, but if the amount is extremely small, the thermal stability of the glass may be improved. P for producing a glass having the above optical characteristics and excellent thermal stability⁵⁺The preferred lower limit and the preferred upper limit of the content are shown in the following table.

[ TABLE 91 ]

Te⁴⁺Is a component for increasing the refractive index, but is also a component having toxicity, so it is preferable to reduce Te⁴⁺The content of (a). Te (Te)⁴⁺The preferred lower limit and the preferred upper limit of the content are shown in the following table.

[ TABLE 92 ]

The amount of Sb added is converted into Sb₂O₃Oxide-based glass composition of Sb₂O₃The amount of Sb added is preferably in the range of 0 to 0.11% by mass, more preferably in the range of 0.01 to 0.08% by mass, and still more preferably in the range of 0.02 to 0.05% by mass, based on 100% by mass of the total content of the other glass components. Here, the "oxide-based glass composition" refers to a glass composition obtained by decomposing all glass raw materials at the time of melting and converting the glass raw materials into substances existing as oxides in the glass. Sb of glass composition shown in the following Table₂O₃The content is also a content calculated by the above-mentioned method.

The amount of Sn added is converted into SnO₂SnO in oxide-based glass composition₂The addition amount of Sn is preferably in the range of 0 to 1.0% by mass, more preferably in the range of 0 to 0.5% by mass, even more preferably in the range of 0 to 0.2% by mass, and even more preferably 0% by mass, when the total content of the other glass components is 100% by mass.

The cationic component is explained above. Next, the anion component will be explained.

Since the glass 2 is an oxide glass, it contains O as an anionic component^2-。O^2-The content of (b) is preferably in the range of 98 to 100 anions, more preferably in the range of 99 to 100 anions, still more preferably in the range of 99.5 to 100 anions, and still more preferably 100 anions.

As O^2-Other anionic component, for example, F^-、Cl^-、Br^-、I^-. However, F^-、Cl^-、Br^-、I^-They are easily volatilized in the melting of glass. Volatilization of these components tends to cause variation in glass characteristics, decrease in glass homogeneity, and increase in consumption of melting equipment. Therefore, F is preferably added^-、Cl^-、Br^-And I^-Is suppressed to a total of O minus 100 anion%^2-Amount of (b).

As is well known, the anion% is a percentage in which the total content of all anion components contained in the glass is 100%.

< glass characteristics >

Next, the glass properties common to glass 1 and glass 2 will be described. The glass described below refers 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 vd in the range of 41.5 to 44.

Glass having a refractive index of 1.800 or more is suitable as a material for optical elements such as lenses having a large refractive power. On the other hand, when the refractive index is higher than 1.850, the abbe number tends to decrease, the thermal stability of the glass tends to decrease, and the coloring tends to increase. Preferred lower and upper limits of the refractive index are shown in the following table.

[ TABLE 93 ]

Glass having an abbe number of 41.5 or more is effective as a material for an optical element in correcting chromatic aberration. On the other hand, when the abbe number is larger than 44, the refractive index tends to decrease, and the thermal stability of the glass tends to decrease. The preferred lower limit and the preferred upper limit of the abbe number are shown in the following table.

[ TABLE 94 ]

(partial Dispersion characteristics)

From the viewpoint of correcting chromatic aberration, the glass is preferably a glass having a small relative dispersion when the abbe number is fixed.

Here, F is expressed as (ng-nF)/(nF-nC) using the refractive indices ng, nF and nC of g line (wavelength of mercury 435.84nm), F line and C line, respectively, for the partial dispersion Pg.

From the viewpoint of providing a glass suitable for the chromatic aberration correction of a high order, preferred lower limits and preferred upper limits of the relative partial dispersions Pg, F of the above glasses are shown in the following table.

[ TABLE 95 ]

(glass transition temperature)

From the viewpoint of improving machinability, the glass transition temperature of the glass is preferably 640 ℃ or higher. By setting the glass transition temperature to 640 ℃ or higher, the glass can be made less likely to be damaged when the glass is subjected to machining such as cutting, polishing, or the like.

On the other hand, when the glass transition temperature is set too high, the glass must be annealed at a high temperature, and the annealing furnace is significantly consumed. In addition, when glass is molded, it is necessary to mold the glass at a high temperature, and thus the consumption of a mold used for molding becomes significant.

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

[ TABLE 96 ]

(light transmittance of glass)

The light transmittance of the glass can be evaluated by the coloring degree λ 5, specifically, by suppressing the wavelength increase of the light absorption edge on the short wavelength side. The coloring degree λ 5 is a wavelength at which the spectral transmittance (including surface reflection loss) of glass having a thickness of 10mm from the ultraviolet region to the visible region becomes 5%. λ 5 in the examples described later is a value measured in a wavelength region of 250 to 700 nm. The spectral transmittance is, for example, more specifically, a spectral transmittance obtained by emitting light from a direction perpendicular to the optically polished surface using a glass sample having parallel flat surfaces optically polished to a thickness of 10.0 ± 0.1mm, that is, an intensity ratio Iout/Iin when the intensity of light emitted to the glass sample is Iin and the intensity of light transmitted through the glass sample is Iout.

From the coloring degree λ 5, the absorption edge on the short wavelength side of the spectral transmittance can be quantitatively evaluated. As described above, when lenses are bonded to each other with an ultraviolet-curable adhesive to produce a cemented lens, the adhesive is cured by irradiating the adhesive with ultraviolet rays through an optical element. In view of efficiently curing the ultraviolet-curable adhesive, it is preferable that the absorption edge on the short wavelength side of the spectral transmittance is in the short wavelength region. As an index for quantitatively evaluating the absorption edge on the short wavelength side, the coloring degree λ 5 can be used. The above glass can show λ 5 of preferably 335nm or less, more preferably 332nm or less, still more preferably 330nm or less, still more preferably 328nm or less, and still more preferably 326nm or less by the above-described composition adjustment. As an example, the lower limit of λ 5 can be set to 315nm, but is not particularly limited as the lower limit is more preferable.

On the other hand, an index of the coloring degree of glass is a coloring degree λ 70.λ 70 is the wavelength at which the spectral transmittance measured by the method described for λ 5 is 70%. From the viewpoint of producing a glass with less coloration, λ 70 is preferably in the range of 420nm or less, more preferably in the range of 400nm or less, still more preferably in the range of 390nm or less, and still more preferably in the range of 380nm or less. The lower limit of λ 70 is set to 340nm, but the lower the value, the more preferable, is not particularly limited.

Further, as an index of the coloring degree of the glass, the coloring degree λ 80 may be mentioned. λ 80 is a wavelength at which the spectral transmittance measured by the method described for λ 5 is 80%. From the viewpoint of producing a glass with less coloration, λ 80 is preferably 480nm or less, more preferably 460nm or less, still more preferably 440nm or less, and still more preferably 420nm or less. The lower limit of λ 80 is set to 350nm, but the lower limit is more preferable and is not particularly limited.

(specific gravity of glass)

In an optical element (lens) constituting an optical system, refractive power is determined by the refractive index of glass constituting the lens and the curvature of an optical functional surface (surface on which light rays to be controlled enter and exit) of the lens. When the curvature of the optically functional surface is to be increased, the thickness of the lens is also increased. As a result, the lens becomes heavy. On the other hand, if glass having a high refractive index is used, a large refractive power can be obtained without increasing the curvature of the optically functional surface.

Thus, if the refractive index can be increased while suppressing an increase in the specific gravity of the glass, the optical element having a fixed refractive power can be reduced in weight.

Regarding the action of the refractive index nd on the refractive power, the ratio of the specific gravity d of the glass to the value (nd-1) obtained by subtracting the refractive index 1 in vacuum from the refractive index nd of the glass can be used as an index for reducing the weight of the optical element. That is, d/(nd-1) is used as an index for reducing the weight of the optical element, and the weight of the lens can be reduced by reducing this value.

Since the proportion of Gd, Ta, and Yb occupied by the glass, which causes an increase in specific gravity, is small, the specific gravity can be reduced while the glass has a high refractive index and low dispersion. Therefore, the glass can have a d/(nd-1) of, for example, 5.70 or less. However, when d/(nd-1) is excessively decreased, the thermal stability of the glass tends to be lowered. Therefore, d/(nd-1) is preferably set to 5.00 or more. More preferred lower limits and more preferred upper limits of d/(nd-1) are shown in the following tables.

[ TABLE 97 ]

Further, preferable lower limits and preferable upper limits of the specific weight d of the glass are shown in the following table. From the viewpoint of reducing the weight of an optical element made of this glass, the specific gravity d is preferably not more than the upper limit shown in the following table. In addition, from the viewpoint of further improving the thermal stability of the glass, it is preferable to set the specific gravity to be not less than the lower limit shown in the following table.

[ TABLE 98 ]

(liquidus temperature)

The liquidus temperature is one of the indicators of the thermal stability of glass. From the viewpoint of suppressing crystallization and devitrification during glass production, the liquidus temperature LT is preferably 1300 ℃ or lower, more preferably 1250 ℃ or lower, still more preferably 1200 ℃ or lower, and still more preferably 1150 ℃ or lower. The lower limit of the liquidus temperature LT is 1100 ℃ or higher as an example, but a low temperature is preferable and is not particularly limited.

The glass (glass 1 and glass 2) according to one embodiment of the present invention described above is a high-refractive-index low-dispersion glass, and is useful as a glass material for optical elements. Further, by performing the above-described composition adjustment, the glass can be homogenized and the coloring can be reduced. In addition, the glass is easy to mold and machine. Therefore, the glass is suitable as an optical glass.

< method for producing glass >

The glass can be obtained by: oxides, carbonates, sulfates, nitrates, hydroxides, and the like as raw materials are weighed and blended so as to obtain a target glass composition, and are sufficiently mixed to prepare a mixed batch, and the mixed batch is heated and melted in a melting vessel, and is defoamed and stirred to prepare a homogeneous and foam-free molten glass, and the molten glass is molded. Specifically, the polymer can be produced by a known melting method. The glass is a high-refractive-index low-dispersion glass having the above optical properties and is excellent in thermal stability, and therefore can be stably produced by a known melting method or a known molding method.

[ glass Material for Press Molding, optical element blank, and methods for producing these ]

Another embodiment of the present invention relates to:

a glass material for press molding formed of the above glass 1 or glass 2;

an optical element blank formed of the above glass 1 or glass 2;

according to another aspect of the present invention, there is provided:

a method for producing a glass material for press molding, which comprises a step of molding the glass 1 or 2 into a glass material for press molding;

a method for producing an optical element blank, which comprises a step of producing an optical element blank by press-molding the glass material for press molding using a press-molding die;

a method for producing an optical element blank, comprising the step of molding the glass 1 or 2 into an optical element blank.

Since the glass material for press molding and the optical element blank are made of the above-described glass 1 or glass 2, it is obvious that the glass material for press molding and the optical element blank also correspond to the above-described glass.

The optical element blank is an optical element base material having a shape similar to the shape of the target optical element, in which a polishing margin (a surface layer removed by polishing) is added to the shape of the optical element, and a polishing margin (a surface layer removed by polishing) is added as necessary. The optical element is completed by polishing the surface of the optical element blank, or by grinding and polishing. In one embodiment, an optical element blank can be produced by a method of press molding a molten glass obtained by melting the above glass in an appropriate amount (referred to as a direct press method). In another embodiment, an optical element blank can be produced by solidifying and further processing a molten glass obtained by melting an appropriate amount of the above glass.

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

The press molding of the glass material for press molding can be performed by a known method of pressing a glass material for press molding which is softened by heating with a press mold. Both heating and press forming can be carried out in the atmosphere. The stress inside the glass can be reduced by annealing after press forming, thereby obtaining a homogeneous optical element blank.

The glass material for press molding includes a glass material for press molding which is supplied as it is to a glass gob for press molding called press molding used for press molding for producing an optical element blank, and a glass material for press molding which is supplied to the press molding through the glass gob for press molding by applying mechanical processing such as cutting, grinding, polishing, etc. As a cutting method, there is a method of forming a groove in a portion to be cut on the front surface of a glass plate by a method called scribing, applying a local pressure to the groove portion from the back surface of the groove surface to cut the glass plate at the groove portion; a method of cutting a glass plate with a cutting blade, and the like. The polishing and buffing methods include known processing methods such as barrel buffing.

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

[ optical element and method for producing the same ]

Another embodiment of the invention relates to

An optical element formed of the above glass 1 or glass 2.

The optical element is manufactured using the glass 1 or the glass 2. In the optical element, one or more coating films such as a multilayer film such as an antireflection film may be formed on the glass surface.

Since the optical element is made of the above glass 1 or glass 2, it is obvious that the optical element corresponds to the above glass. When a coating film is formed on the glass surface of the optical element, the portion of the glass other than the coating film corresponds to the above-described glass.

Further, according to one aspect of the present invention,

also provided is a method for manufacturing an optical element, which comprises a step of polishing at least the optical element blank to form an optical element.

In the above-described method for producing an optical element, a known method may be used for polishing and buffing, and an optical element having high internal quality and high surface quality can be obtained by sufficiently cleaning the surface of the optical element after processing, drying the surface, and the like. In this manner, an optical element made of the above glass can be obtained. Examples of the optical element include various lenses such as a spherical lens, an aspherical lens, and a microlens, and a prism.

Further, an optical element formed of the above glass 1 or glass 2 is also suitable as a lens constituting a cemented optical element. Examples of the cemented optical element include a cemented optical element (cemented lens) obtained by cementing lenses to each other, and a cemented optical element obtained by cementing a lens and a prism. For example, the cemented optical element may be made by: the bonded surfaces of the 2 optical elements to be bonded are precisely processed (for example, spherical surface polishing) so that the shapes thereof are inverted, an ultraviolet-curable adhesive is applied to the bonded surfaces, the bonded surfaces are bonded to each other, and then the adhesive on the bonded surfaces is irradiated with ultraviolet light through the optical elements to cure the adhesive. In order to produce the cemented optical element in this way, the above glass is preferable. By preparing a plurality of cemented optical elements using a plurality of types of glasses having different abbe numbers and cementing them, an element suitable for correction of chromatic aberration can be prepared.

As a result of quantitative analysis of the glass composition, the glass component may be expressed on an oxide basis, and the content of the glass component may be expressed in mass%. The composition expressed in mass% based on the oxide can be converted into a composition expressed in cation% and anion% by the following method, for example.

For example, an oxide formed from a cation A and oxygen is represented as A_mO_n. m and n are each an integer determined by the stoichiometric method. For example, in B³⁺In the case of (A) is represented by B on an oxide basis₂O₃M is 2, n is 3; in Si⁴⁺In the case of (A) is represented by SiO₂，m＝1、n＝2。

First, A is expressed by mass%_mO_nIs divided by A_mO_nAnd further multiplied by m. This value is set to P. Then, P is added to the total of all the cationic components. When the total value of P is Σ P, the value obtained by normalizing the value of P of each cationic component so that Σ P is 100% is a represented by cationic%^s+The content of (a). Here, s is 2 n/m.

In addition, for minor amounts of additives, such as Sb²O³Such a clarifying agent may not be contained in Σ P. In this case, the content of Sb is converted into Sb as described above₂O₃The content (mass%) of (c) may be added. That is, Sb will be removed₂O₃The total content of the glass components (a) is 100 mass%, and Sb is₂O₃The content of (b) is expressed as a value relative to 100 mass%.

The above molecular weight may be calculated, for example, by rounding the 4 th position after the decimal point to the 3 rd position after the decimal point. In addition, for example, oxide A_mO_nThe molecular weight of (A) is the sum of a value m times the atomic weight of the element A and a value n times the atomic weight of oxygen. The molecular weights expressed on an oxide basis for some of the glass components and additives are shown in the table below.

[ TABLE 99 ]

Oxide compound	Molecular weight	Oxide compound	Molecular weight
				B₂O₃	69.621	Cs₂O	281.810
SiO₂	60.084	ZnO	81.389
				La₂O₃	325.809	MgO	40.304
Y₂O₃	225.810	CaO	56.077
				Gd₂O₃	362.498	SrO	81.389
Yb₂O₃	394.084	BaO	153.326
				Nb₂O₅	265.810	Al₂O₃	101.961
TiO₂	79.882	Ga₂O₃	187.444
				WO₃	231.839	In₂O₃	277.634
Ta₂O₅	441.893	Sc₂O₃	137.910
				Bi₂O₃	465.959	HfO₂	210.489
ZrO₂	123.223	Lu₂O₃	397.932
				Li₂O	29.882	GeO₂	104.629
Na₂O	61.979	P₂O₅	141.945
				K₂O	94.196	TeO₂	159.599
Rb₂O	186.935	Sb₂O₃	291.518

Examples

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

(example 1)

In order to obtain glasses having compositions shown in the following table, compounds such as oxides and boric acid as raw materials were weighed and mixed sufficiently to prepare batch raw materials.

The batch of raw materials are placed into a platinum crucible, and are heated to 1350-1450 ℃ together with the crucible, and the glass is melted and clarified after 2-3 hours. After homogenizing molten glass by stirring, the molten glass is cast into a preheated molding die, left to cool to a temperature near the glass transition temperature, and immediately placed into an annealing furnace together with the molding die. Then, annealing was performed for about 1 hour in the vicinity of the glass transition temperature. After the annealing, the resultant was left to cool to room temperature in an annealing furnace.

The glass thus produced was observed, and no crystal precipitation, bubbles, streaks, and melting residue of the raw material were observed. This enables the production of glass having high homogeneity.

In Table 100 (tables 100-1 to 100-7), Nos. 1 to 33 are glass 1, and in Table 101 (tables 101-1 to 101-6), Nos. 1 to 33 are glass 2.

The glass properties of the obtained glass were measured by the following methods. The measurement results are shown in the following table.

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

The glass obtained by cooling at a cooling rate of-30 ℃/hr was measured for refractive indices nd, nF, nC, and ng according to the refractometry method standardized by the Japan optical glass Industrial Association. Abbe number vd is calculated using the measured values of refractive indices nd, nF, and nC.

(2) Glass transition temperature Tg

The temperature was measured at a temperature rising rate of 10 ℃ per minute using a Differential Scanning Calorimetry (DSC).

(3) Specific gravity of

The measurement was carried out by the Archimedes method.

(4) The coloring degree is lambda 5, lambda 70, lambda 80

Using a glass sample having a thickness of 10 ± 0.1mm with 2 optically polished planes facing each other, light of intensity Iin was incident from the perpendicular direction to the polished plane by a spectrophotometer, and the intensity Iout of light transmitted through the glass sample was measured, and the spectral transmittance Iout/Iin was calculated, with the wavelength of 5% spectral transmittance being λ 5, the wavelength of 70% spectral transmittance being λ 70, and the wavelength of 80% spectral transmittance being λ 80.

(5) Relative partial dispersion Pg, F

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

(6) Liquidus temperature

The glass was placed in a furnace heated to a predetermined temperature, held for 2 hours, cooled, and then the inside of the glass was observed with an optical microscope of 100 magnifications, and the liquidus temperature was determined depending on the presence or absence of crystals.

[ Table 100-1]

[ Table 100-2]

[ tables 100-3]

[ tables 100-4]

[ tables 100-5]

[ tables 100-6]

[ tables 100 to 7]

[ Table 101-1]

[ Table 101-2]

[ tables 101-3]

[ tables 101-4]

[ tables 101-5]

[ tables 101-6]

(example 2)

Using the various glasses obtained in example 1, a glass gob for press molding (glass gob) was produced. The glass block was heated and softened in the atmosphere, and press-molded with a press molding die to prepare a lens blank (optical element blank). The produced lens blank was taken out of the press mold, annealed, and subjected to machining including polishing, thereby producing a spherical lens formed of each glass produced in example 1.

(example 3)

A desired amount of the molten glass produced in example 1 was obtained, press-molded with a press molding die while the obtained glass was in a softened state, and cooled to produce a lens blank (optical element blank). The produced lens blank was taken out of the press mold, annealed, and subjected to machining including polishing, thereby producing a spherical lens formed of each glass produced in example 1.

(example 4)

A glass block (optical element blank) obtained by solidifying the molten glass produced in example 1 was annealed and subjected to machining including polishing, thereby producing a spherical lens formed of each glass produced in example 1.

(example 5)

The spherical lenses manufactured in examples 2 to 4 were bonded to spherical lenses made of other types of glass to manufacture cemented lenses. The cemented surface of the spherical lenses manufactured in examples 2 to 4 was a convex spherical surface, and the cemented surface of the spherical lens formed of another type of optical glass was a concave spherical surface. The 2 bonding surfaces are formed so that the absolute values of the radii of curvature are equal to each other. An ultraviolet-curable adhesive for optical element bonding was applied to the bonding surfaces, and 2 bonding surfaces for lenses were bonded to each other. Thereafter, the adhesive applied to the bonding surface was irradiated with ultraviolet rays through the spherical lenses manufactured in examples 2 to 4, and the adhesive was cured.

Cemented lenses were produced as described above. The cemented lens has a sufficiently high cemented strength and a sufficient degree of optical performance.

(investigation of the influence of Yb on the transmittance in the near Infrared region)

Glass having a composition shown in table 102 below (hereinafter referred to as "glass a") and glass having a composition shown in table 103 below (hereinafter referred to as "glass B") were respectively melted and molded, and processed into a plate shape. These glass plates have 2 opposing flat surfaces. The 2 planes are parallel to each other and optically polished. The spacing of the 2 planes is 10.0 mm.

Using this glass plate, the spectral transmittance was measured. The light was incident perpendicularly on the above-mentioned 2 opposing planes, and the spectral transmittance of the glass plate was obtained by calculating the ratio of the intensity of the incident light incident on the glass plate to the intensity of the transmitted light transmitted through the glass plate (intensity of transmitted light/intensity of incident light) while scanning the wavelength. The spectral transmittance curves of these 2 glasses, having a thickness of 10.0mm, are shown in FIGS. 1 and 2 (FIG. 1: glass A, FIG. 2: glass B), respectively.

[ TABLE 102 ]

< glass A >

	Mass%	Cation%
			B₂O₃	26.16	57.85
SiO₂	3.62	4.64
			La₂O₃	45.53	21.5
Y₂O₃	12.9	8.79
			Yb₂O₃	0.1	0.04
ZrO₂	7.9	4.94
			TiO₂	0.1	0.1
Nb₂O₅	3.69	2.14
			Total up to	100	100
Sb₂O₃	0.02	0.02% by mass

[ TABLE 103 ]

< glass B >

	Mass%	Cation%
			B₂O₃	10.97	33.75
SiO₂	1.17	2.09
			La₂O₃	25.78	16.94
Gd₂O₃	0.85	0.50
			Yb₂O₃	3.68	2.00
ZrO₂	2.7	2.35
			ZnO	14.2	18.69
TiO₂	1.49	2.00
			Nb₂O₅	9.74	7.85
Ta₂O₅	10.73	5.2
			WO₃	18.69	8.63
Total up to	100	100

The glass B does not contain Y in the glass composition expressed by mass percent₂O₃Thus it is the mass ratio (Y)₂O₃/(La₂O₃+Y₂O₃+Gd₂O₃+Yb₂O₃) Glass outside the above range. Further, since the glass B does not contain Y in the glass composition expressed by cation%³⁺Thus it is the cation ratio (Y)³⁺/(La³⁺+Y³⁺+Gd³⁺+Yb³⁺) Glass outside the above range. Therefore, glass B does not correspond to glass 1 and glass 2 described above as one embodiment of the present invention, but the increase or decrease in the absorption in the near infrared region depending on the Yb content is not dependent on the presence or absence of Y₂O₃And Y³⁺. Therefore, the effect of Yb on the transmittance in the near-infrared region can be confirmed by comparing glass a and glass B.

As shown in FIG. 1, the glass composition represented by mass% contained 0.1 mass% of Yb₂O₃The glass composition represented by cation% contained Yb in an amount of 0.04 cation%³⁺The glass A of (2) has a reduced transmittance in the vicinity of wavelength 950nm due to the absorption of Yb light centered around the wavelength.

Further, as shown in FIG. 2, Yb was contained in an amount of 3.68 mass% in the glass composition expressed by mass%₂O₃The glass composition represented by cation% contained 2.00 cation% of Yb³⁺The glass B of (2) has a significantly reduced transmittance in the vicinity of wavelength 960nm due to light absorption of Yb centered around the vicinity.

Since the transmittance of the glass in the near infrared region is greatly reduced with an increase in the Yb content, glasses containing many Yb are not suitable as glasses for applications requiring high transmittance in the range from the visible region to the near infrared region.

Comparative example 1

An attempt was made to reproduce the glass of example 4 of patent document 6 (jp 2009-203083 a), but crystallization was performed in the glass production process. This is because the glass has a mass ratio (B) in the glass composition expressed by mass%₂O₃/(B₂O₃+SiO₂) Has a cation ratio (B) of 1 in the glass composition expressed by cation%³⁺/(B³⁺+Si⁴⁺) 1 and thus reduced thermal stability.

Comparative example 2

The glass (hereinafter referred to as "glass C") of example 28 of patent document 5 (Japanese patent application laid-open No. Sho 55-121925) was reproduced, and measured by the above-mentioned method to find that λ 5 was 348 nm.

A spherical lens was produced using glass C. Next, an ultraviolet-curable adhesive for optical element bonding was applied using the convex spherical surface of the spherical lens and the concave spherical surface of a spherical lens made of another type of optical glass as bonding surfaces, and an attempt was made to produce a cemented lens in the same manner as in example 5. However, when the ultraviolet-curable adhesive applied to the bonding surface is irradiated with ultraviolet rays through a lens made of glass C, the ultraviolet transmittance of glass C is low, and therefore the adhesive cannot be sufficiently cured.

Comparative example 3

The mass ratio (Gd) of the glass of example 7 in patent document 17 (Japanese unexamined patent publication No. 2002-284542)₂O₃/(La₂O₃+Y₂O₃+Gd₂O₃+Yb₂O₃) 0.09 in mass ratio (B)₂O₃/(B₂O₃+SiO₂) ) was 0.92. For the glass, La₂O₃、Y₂O₃、Gd₂O₃The content of other components is fixed, for₂O₃Is partially or wholly replaced by La₂O₃And Y₂O₃The change in thermal stability of the glass was verified.

First, as an oxide-based glass composition, 5.15 mass% of Gd was contained₂O₃Set to 0%, Gd₂O₃Decrease in content 5.15 mass% based on La₂O₃Content of (A) and Y₂O₃Respectively to La₂O₃And Y₂O₃. Specifically, the amount of La is 5.15 mass% × (La)₂O₃Content of (A)/(La)₂O₃Content of (A) and Y₂O₃Total content of (b)) 4.09 mass% was calculated from Gd₂O₃Substitution to La₂O₃Will be 5.15 mass% × (Y)₂O₃Content of (A)/(La)₂O₃Content of (A) and Y₂O₃Total content of (b)) 1.06 mass% was calculated from Gd₂O₃Substitution by Y₂O₃. Hereinafter, this composition is referred to as "composition a".

Then, 5.15 mass% of Gd was added₂O₃Reduced to 3% by mass, Gd₂O₃The amount of decrease in the content was 2.15 mass% based on La₂O₃Content of (A) and Y₂O₃Respectively to La₂O₃And Y₂O₃. Specifically, the amount of La is 2.15 mass% × (La)₂O₃Content of (A)/(La)₂O₃Content of (A) and Y₂O₃Total content of (b)) 1.71 mass% calculated from Gd₂O₃Substitution to La₂O₃Will be 5.15 mass% × (Y)₂O₃Content of (A)/(La)₂O₃Content of (A) and Y₂O₃Total content of (b)) 0.44 mass% calculated from Gd₂O₃Substitution by Y₂O₃. Hereinafter, this composition is referred to as "composition b".

The composition, "composition a" and "composition b" of example 7 of patent document 17 are shown in table 104.

[ TABLE 104 ]

(unit: mass%, mass ratio)

Glass was produced by the method described in the example of patent document 17 using 150g of glass having compositions a and b, and no crystal was precipitated in the peripheral portion of the glass molded by pouring molten glass into a mold, that is, in the portion rapidly cooled by contact with the mold, but a large amount of crystals were precipitated in the central portion of the glass, that is, in the portion where the cooling rate was lower than that in the peripheral portion. In addition, when the glass of the above-described examples was produced by the same method, the precipitation of crystals was not observed in the entire range, not limited to the peripheral portion of the glass.

The above results are considered to be expressed in the mass ratio (B)₂O₃/(B₂O₃+SiO₂) Gd is added to the glass composition in an amount exceeding the above-mentioned range₂O₃The thermal stability is reduced as the content is reduced.

Comparative example 4

The cation ratio (Gd) of the glass of example 7 in patent document 17 (Japanese unexamined patent publication No. 2002-284542)³⁺/(La³⁺+Y³⁺+Gd³⁺+Yb³⁺) 0.08, cation ratio (B)³⁺/(B³⁺+Si⁴⁺) ) was 0.95. For the glass, La³⁺、Y³⁺、Gd³⁺The content of other components is fixed, for³⁺Is partially or wholly replaced by La³⁺And Y³⁺The change in thermal stability of the glass was verified.

First, 2.31 cation% Gd will be contained³⁺Set to 0%, Gd³⁺Reduction of content 2.31 cation% according to La³⁺Content of (A) and Y³⁺Respectively to La³⁺And Y³⁺. Specifically, the cation ratio is 2.31% × ((La)³⁺Content of (A)/(La)³⁺Content of (A) and Y³⁺Total content of (b)) 1.68 cation% calculated from Gd³⁺Substitution to La³⁺Will be 2.31 cation% × ((Y)³⁺Content of (A)/(La)³⁺Content of (A) and Y³⁺Total content of (b)) 0.63 cation% calculated from Gd³⁺Substitution by Y³⁺. Hereinafter, this composition is referred to as "composition c".

Then, Gd containing 2.31 cation%³⁺Reduced to 1.5 cation% to reduce Gd³⁺Reduction of content 0.81 cation% according to La³⁺Content of (A) and Y³⁺Respectively to La³⁺And Y³⁺. Specifically, the cation% x (((La) is 0.81³⁺Content of (A)/(La)³⁺Content of (A) and Y³⁺Total content of (d)) 0.59 cation% was replaced with La³⁺Will be 0.81 cation% × ((Y)³⁺Content of (A)/(La)³⁺Content of (A) and Y³⁺Total content of (b)) is replaced by Y³⁺. Hereinafter, this composition is referred to as "composition d".

The composition, "composition c" and "composition d" of example 7 of patent document 17 are shown in table 105.

[ TABLE 105 ]

(unit: cation%, cation ratio)

Glass was produced by the method described in the example of patent document 17 using 150g of glass having compositions c and d, and no crystal was precipitated in the peripheral portion of the glass molded by pouring molten glass into a mold, that is, in the portion rapidly cooled by contact with the mold, but a large amount of crystals were precipitated in the central portion of the glass, that is, in the portion where the cooling rate was lower than that in the peripheral portion. In addition, when the glass of the above-described examples was produced by the same method, the precipitation of crystals was not observed in the entire range, not limited to the peripheral portion of the glass.

The above results are considered to be expressed in the cation ratio (C) ((C))B³⁺/(B³⁺+Si⁴⁺) Gd is added to the glass composition in an amount exceeding the above-mentioned range³⁺The thermal stability is reduced as the content is reduced.

Finally, the above-described respective modes are summarized.

According to one embodiment, there can be provided a glass (glass 1) which is an oxide glass and B represents B in mass%₂O₃And SiO₂The total content of (A) is 15-35 mass%, La₂O₃、Y₂O₃、Gd₂O₃And Yb₂O₃The total content of (B) is 45 to 65 mass%, however, Yb₂O₃ZrO in an amount of 3 mass% or less₂A content of 3 to 11 mass% of Ta₂O₅The content is 5 mass% or less, B₂O₃Content relative to B₂O₃And SiO₂The mass ratio of the total content of (A), (B)₂O₃/(B₂O₃+SiO₂) B) is 0.4 to 0.900, B₂O₃And SiO₂The total content of (A) to La₂O₃、Y₂O₃、Gd₂O₃And Yb₂O₃(B) the mass ratio of the total content of (A)₂O₃+SiO₂)/(La₂O₃+Y₂O₃+Gd₂O₃+Yb₂O₃) 0.42 to 0.53, Y)₂O₃Content relative to La₂O₃、Y₂O₃、Gd₂O₃And Yb₂O₃The mass ratio of the total content of (A), (B), (C), (D), (E), (₂O₃/(La₂O₃+Y₂O₃+Gd₂O₃+Yb₂O₃) 0.05 to 0.45) of Gd₂O₃Content relative to La₂O₃、Y₂O₃、Gd₂O₃And Yb₂O₃The mass ratio of the total content of (b) (Gd)₂O₃/(La₂O₃+Y₂O₃+Gd₂O₃+Yb₂O₃) 0 to 0.05) of Nb₂O₅Content relative to Nb₂O₅、TiO₂、Ta₂O₅And WO₃Mass ratio of the total content of (B)/(B)₂O₅/(Nb₂O₅+TiO₂+Ta₂O₅+WO₃) 0.5 to 1, a refractive index nd in the range of 1.800 to 1.850, and an Abbe number vd in the range of 41.5 to 44.

According to one embodiment, there can be provided a glass (glass 2) which is an oxide glass and B represents cation%³⁺And Si⁴⁺The total content of La is 45-65%³⁺、Y³⁺、Gd³⁺And Yb³⁺Is 25 to 35% in total, but Yb³⁺Content less than 2%, Zr⁴⁺2-8% of Ta⁵⁺Content is less than 3%, B³⁺Content relative to B³⁺And Si⁴⁺The cation ratio (B) of the total content³⁺/(B³⁺+Si⁴⁺) B) is 0.65 or more and less than 0.94, B³⁺And Si⁴⁺The total content of (A) to La³⁺、Y³⁺、Gd³⁺And Yb³⁺Cation ratio of the total content of ((B)³⁺+Si⁴⁺)/(La³⁺+Y³⁺+Gd³⁺+Yb³⁺) ) is 1.65 to 2.60, Y³⁺Content relative to La³⁺、Y³⁺、Gd³⁺And Yb³⁺Cation ratio (Y) of the total content of³⁺/(La³⁺+Y³⁺+Gd³⁺+Yb³⁺) 0.05 to 0.45) of Gd³⁺Content relative to La³⁺、Y³⁺、Gd³⁺And Yb³⁺The cation ratio (Gd) of the total content of³⁺/(La³⁺+Y³⁺+Gd³⁺+Yb³⁺) 0 to 0.05) of Nb⁵⁺Content relative to Nb⁵⁺、Ti⁴⁺、Ta⁵⁺And W⁶⁺Cation ratio (Nb) of the total content⁵⁺/(Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺) 0.4 to 1, a refractive index nd in the range of 1.800 to 1.850, and an Abbe number vd in the range of 41.5 to 44.

The glass 1 and the glass 2 are high-refractive-index low-dispersion optical glasses having refractive indices nd and abbe numbers ν d in the above ranges, which are useful as materials for optical elements constituting optical systems. The above glass is a glass having reduced Gd, Ta and Yb contents and capable of showing high thermal stability.

In one embodiment, the glass 1 is preferably used in a mass ratio (ZnO/(Nb)) from the viewpoints of improving meltability, further improving thermal stability of the glass, suppressing a decrease in glass transition temperature (improving machinability due to the decrease), and improving chemical durability₂O₅+TiO₂+Ta₂O₅+WO₃) 0.1 to 3 or less.

In one embodiment, the glass 2 is preferably a cation ratio (Zn) from the viewpoints of improving meltability, further improving thermal stability of the glass, suppressing a decrease in glass transition temperature (improving machinability due to this), and improving chemical durability²⁺/(Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺) 0.1 to 5 or less.

In one embodiment, it is preferable that the glass 1 and the glass 2 be made such that the coloring degree λ 5 is 335nm or less by suppressing the wavelength of the short wavelength side light absorption edge of the glass from increasing.

In one embodiment, the specific gravity d and the refractive index nd preferably satisfy the above formula (a) in terms of making it possible to reduce the weight of an optical element having a fixed refractive power, for the glass 1 and the glass 2.

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

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

Further, according to another embodiment, there is provided a method for producing a glass material for press molding, including a step of molding the glass 1 or the glass 2 into a glass material for press molding.

Further, according to another aspect, there is provided a method for manufacturing an optical element blank, including a step of manufacturing an optical element blank by press-molding the above-described glass material for press-molding using a press-molding die.

Further, according to another aspect, there is provided a method for manufacturing an optical element blank including a step of molding the glass 1 or the glass 2 into the optical element blank.

Further, according to another aspect, there is provided a method for manufacturing an optical element including a step of manufacturing an optical element by polishing at least the optical element blank.

The embodiments disclosed herein are illustrative in all respects and should not be construed as being limiting. The scope of the present invention is defined by the scope of the claims rather than the description above, and is intended to include meanings equivalent to the scope of the claims and all modifications within the scope.

For example, a glass according to an embodiment of the present invention can be obtained by adjusting the composition described in the specification for the above-described exemplary glass composition.

It is to be understood that 2 or more of the items shown in the specification or described as preferable ranges may be arbitrarily combined.

In addition, there are cases where a certain glass corresponds to both glass 1 and glass 2.

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

Claims

1. One type of glass, which is an oxide glass,

expressed in mass%, of the total amount of the catalyst,

B₂O₃and SiO₂The total content of (B) is 15 to 35% by mass,

ZrO₂the content is 3 ℃11% by mass of the total amount of the organic solvent,

Ta₂O₅the content is 5% by mass or less,

B₂O₃content relative to B₂O₃And SiO₂The mass ratio of the total content of (A), (B)₂O₃/（B₂O₃+SiO₂) ) is 0.4 to 0.900,

B₂O₃and SiO₂The total content of (A) to La₂O₃、Y₂O₃、Gd₂O₃And Yb₂O₃(B) the mass ratio of the total content of (A)₂O₃+SiO₂）/（La₂O₃+Y₂O₃+Gd₂O₃+Yb₂O₃) ) is 0.42 to 0.53,

Y₂O₃content relative to La₂O₃、Y₂O₃、Gd₂O₃And Yb₂O₃The mass ratio of the total content of (A), (B), (C), (D), (E), (₂O₃/（La₂O₃+Y₂O₃+Gd₂O₃+Yb₂O₃) ) is 0.05 to 0.45,

Gd₂O₃content relative to La₂O₃、Y₂O₃、Gd₂O₃And Yb₂O₃The mass ratio of the total content of (b) (Gd)₂O₃/（La₂O₃+Y₂O₃+Gd₂O₃+Yb₂O₃) ) is 0 to 0.05,

Nb₂O₅content relative to Nb₂O₅、TiO₂、Ta₂O₅And WO₃Mass ratio of the total content of (B)/(B)₂O₅/（Nb₂O₅+TiO₂+Ta₂O₅+WO₃) ) is 0.5 to 1,

content of ZnO to Nb₂O₅、TiO₂、Ta₂O₅And WO₃Mass of the total content ofRatio (ZnO/(Nb)₂O₅+TiO₂+Ta₂O₅+WO₃) ) is not more than 0.500 a,

the refractive index nd is in the range of 1.800 to 1.850, and the Abbe number vd is in the range of 41.5 to 44,

the glass has a glass transition temperature Tg of 671 ℃ or higher.

2. The glass of claim 1, wherein Y is₂O₃The content is 9.7 mass% or more.

3. The glass according to claim 1, wherein the ZnO content is 4.0% by mass or less.

4. The glass of claim 1, wherein B₂O₃The content is 22.1 mass% or less.

5. The glass of claim 1, wherein Yb₂O₃The content is 1.0 mass% or less.

6. The glass of claim 1, wherein Yb₂O₃The content is 0.5 mass% or less.

7. The glass of claim 1, wherein Ta₂O₅The content is 2 mass% or less.

8. The glass of claim 1, wherein Ta₂O₅The content is 0.5 mass% or less.

9. Glass according to claim 1, wherein ZrO₂The content is 4 to 10 mass%.

10. Glass according to claim 1, wherein ZrO₂The content is 7.3 mass% or less.

11. The glass of claim 1, wherein Li₂The O content is 1 mass% or less.

12. The glass of claim 1, wherein Si is₂The O content is 5.2 mass% or less.

13. The glass of claim 1, wherein the La₂O₃The content is 38 to 55 mass%.

14. The glass of claim 1, wherein Gd₂O₃The content is 0 to 1.0 mass%.

15. The glass of claim 1, wherein Nb₂O₅The content is 2 to 15 mass%.

16. The glass of claim 1, wherein the TiO₂The content is 0 to 3.0 mass%.

17. The glass according to claim 1, wherein WO₃The content is 0 to 3.0 mass%.

18. The glass of claim 1, wherein B₂O₃And SiO₂The total content of (B) is 21 to 32 mass%.

19. The glass of claim 1, wherein B₂O₃And SiO₂The total content of (B) is 26.2 mass% or less.

20. The glass of claim 1, wherein the La₂O₃、Y₂O₃、Gd₂O₃And Yb₂O₃The total content of (B) is 50 to 63 mass%.

21. The glass of claim 1, wherein B₂O₃Content relative to B₂O₃And SiO₂The mass ratio of the total content of (A), (B)₂O₃/（B₂O₃+SiO₂) ) is 0.6 to 0.900.

22. The glass of claim 1, wherein the La₂O₃、Y₂O₃、Gd₂O₃And Yb₂O₃The total content of (B) is 58.1 mass% or less.

23. The glass of claim 1, wherein B₂O₃And SiO₂The total content of (A) to La₂O₃、Y₂O₃、Gd₂O₃And Yb₂O₃(B) the mass ratio of the total content of (A)₂O₃+SiO₂）/（La₂O₃+Y₂O₃+Gd₂O₃+Yb₂O₃) 0.475 or less.

24. The glass of claim 1, wherein Y is₂O₃Content relative to La₂O₃、Y₂O₃、Gd₂O₃And Yb₂O₃The mass ratio of the total content of (A), (B), (C), (D), (E), (₂O₃/（La₂O₃+Y₂O₃+Gd₂O₃+Yb₂O₃) 0.10 to 0.30.

25. The glass of claim 1, wherein Y is₂O₃Content relative to La₂O₃、Y₂O₃、Gd₂O₃And Yb₂O₃The mass ratio of the total content of (A), (B), (C), (D), (E), (₂O₃/（La₂O₃+Y₂O₃+Gd₂O₃+Yb₂O₃) ) 0.242 or less.

26. The glass of claim 1, wherein Gd₂O₃Content relative to La₂O₃、Y₂O₃、Gd₂O₃And Yb₂O₃The mass ratio of the total content of (b) (Gd)₂O₃/（La₂O₃+Y₂O₃+Gd₂O₃+Yb₂O₃) ) is 0 to 0.05.

27. The glass of claim 1, wherein Gd₂O₃Content relative to La₂O₃、Y₂O₃、Gd₂O₃And Yb₂O₃The mass ratio of the total content of (b) (Gd)₂O₃/（La₂O₃+Y₂O₃+Gd₂O₃+Yb₂O₃) 0.020 or less.

28. The glass of claim 1, wherein the La₂O₃Content relative to La₂O₃、Y₂O₃、Gd₂O₃And Yb₂O₃The mass ratio of the total content of (A) to (B) (La)₂O₃/（La₂O₃+Y₂O₃+Gd₂O₃+Yb₂O₃) ) is 0.55 to 0.95.

29. The glass of claim 1, wherein Nb₂O₅、TiO₂、Ta₂O₅And WO₃The total content of (B) is 3 to 15 mass%.

30. The glass of claim 1, wherein Nb₂O₅Content relative to Nb₂O₅、TiO₂、Ta₂O₅And WO₃Mass ratio of the total content of (B)/(B)₂O₅/（Nb₂O₅+TiO₂+Ta₂O₅+WO₃) ) is 0.95 to 1.

31. The glass of claim 1, wherein Nb₂O₅Content relative to Nb₂O₅、TiO₂And WO₃Mass ratio of the total content of (B)/(B)₂O₅/（Nb₂O₅+TiO₂+WO₃) 0.5 to 1.

32. The glass of claim 1, wherein the ZnO content is relative to Nb₂O₅、TiO₂、Ta₂O₅And WO₃The mass ratio of the total content of (1) (ZnO/(Nb))₂O₅+TiO₂+Ta₂O₅+WO₃) 0.1 to 0.500.

33. The glass of claim 1, wherein the ZnO content is relative to Nb₂O₅、TiO₂、Ta₂O₅And WO₃The mass ratio of the total content of (1) (ZnO/(Nb))₂O₅+TiO₂+Ta₂O₅+WO₃) ) is 3.6/7.2 or less.

34. The glass of claim 1, wherein B₂O₃And SiO₂The total content of (B) relative to Nb₂O₅、TiO₂、Ta₂O₅And WO₃(B) the mass ratio of the total content of (A)₂O₃+SiO₂）/（Nb₂O₅+TiO₂+Ta₂O₅+WO₃) ) is 25.9/7.7 or less.

35. Glass according to claim 1, wherein the ZnO content is relative to B₂O₃And SiO₂The mass ratio of the total content of (1) (ZnO/(B))₂O₃+SiO₂) ) is 4.0/25.6 or less.

36. The glass of claim 1, wherein Li₂O、Na₂O and K₂The total content of O is 0 to 5.0 mass%.

37. The glass according to claim 1, wherein the total content of MgO, CaO, SrO and BaO is 0 to 20% by mass.

38. The glass according to any one of claims 1 to 37, wherein a coloring degree λ 5 is 335nm or less.

39. The glass of any one of claims 1-37, wherein the specific gravity d and the refractive index nd satisfy the following formula (A): d/(nd-1) is less than or equal to 5.70 … (A).

40. The glass of any one of claims 1-37, wherein the specific gravity is 4.70 or less.

41. The glass of any of claims 1-37, wherein the refractive index nd ranges from 1.830 to 1.839 and the Abbe number vd ranges from 41.7 to 43.2.

42. The glass of any one of claims 1-37, wherein the glass transition temperature is 671-680 ℃.

43. One type of glass, which is an oxide glass,

expressed as a% of cations, is,

B³⁺and Si⁴⁺The total content of (A) is 45 to 65%,

Zr⁴⁺the content of the organic acid is 2-8%,

Ta⁵⁺the content of the organic acid is less than 3 percent,

B³⁺content relative to B³⁺And Si⁴⁺The cation ratio (B) of the total content³⁺/（B³⁺+Si⁴⁺) ) 0.65 or more and less than 0.94,

B³⁺and Si⁴⁺The total content of (A) to La³⁺、Y³⁺、Gd³⁺And Yb³⁺Cation ratio of the total content of ((B)³⁺+Si⁴⁺）/（La³⁺+Y³⁺+Gd³⁺+Yb³⁺) ) is 1.65 to 2.60,

Y³⁺content relative to La³⁺、Y³⁺、Gd³⁺And Yb³⁺Cation ratio (Y) of the total content of³⁺/（La³⁺+Y³⁺+Gd³⁺+Yb³⁺) ) is 0.05 to 0.45,

Gd³⁺content relative to La³⁺、Y³⁺、Gd³⁺And Yb³⁺The cation ratio (Gd) of the total content of³⁺/（La³⁺+Y³⁺+Gd³⁺+Yb³⁺) ) is 0 to 0.05,

Nb⁵⁺content relative to Nb⁵⁺、Ti⁴⁺、Ta⁵⁺And W⁶⁺Cation ratio (Nb) of the total content⁵⁺/（Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺) ) is 0.4 to 1,

Zn²⁺content of (2) and Nb⁵⁺、Ti⁴⁺、Ta⁵⁺And W⁶⁺The mass ratio of the total content of (1) (Zn)²⁺/（Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺) ) is not more than 0.800 (g),

the glass has a glass transition temperature Tg of 671 ℃ or higher.

44. The glass of claim 43, wherein Y is³⁺The content is more than 7.1 cation percent.

45. The glass of claim 43, wherein Zn²⁺In an amount of4.1 cation% or less.

46. The glass of claim 43, wherein B³⁺The content is less than 51.5 cation%.

47. The glass of claim 43, wherein Yb³⁺The content is less than 0.2 cation percent.

48. The glass of claim 43, wherein Ta⁵⁺The content is less than 0.2 cation percent.

49. The glass of claim 43, wherein Zr⁴⁺The content is below 4.9 cation%.

50. The glass of claim 43, wherein Li⁺The content is 3 cation% or less.

51. The glass of claim 43, wherein Si⁴⁺The content is below 7.2 cation%.

52. The glass of claim 43, wherein the La³⁺The content of the cationic surfactant is 15-30 cation%.

53. The glass of claim 43, wherein Gd³⁺The content of the cationic surfactant is 0-0.5 cationic%.

54. The glass of claim 43, wherein Nb is⁵⁺The content is 1-10 cation%.

55. The glass of claim 43, wherein Ti⁴⁺The content of the cationic polymer is 0-3.0 cation%.

56. The glass of claim 43, wherein W is⁶⁺The content of the cationic surfactant is 0-1 cation%.

57. The glass of claim 43, wherein B³⁺And Si⁴⁺The total content of (A) is 57.6 cation% or less.

58. The glass of claim 43, wherein the La³⁺、Y³⁺、Gd³⁺And Yb³⁺The total content of (A) is 32.0 cation% or less.

59. The glass of claim 43, wherein B³⁺And Si⁴⁺The total content of (A) to La³⁺、Y³⁺、Gd³⁺And Yb³⁺Cation ratio of the total content of ((B)³⁺+Si⁴⁺）/（La³⁺+Y³⁺+Gd³⁺+Yb³⁺) ) 1.99 cation% or less.

60. The glass of claim 43, wherein Y is³⁺Content relative to La³⁺、Y³⁺、Gd³⁺And Yb³⁺Cation ratio (Y) of the total content of³⁺/（La³⁺+Y³⁺+Gd³⁺+Yb³⁺) 0.279 cation% or less.

61. The glass of claim 43, wherein Gd³⁺Content relative to La³⁺、Y³⁺、Gd³⁺And Yb³⁺The cation ratio (Gd) of the total content of³⁺/（La³⁺+Y³⁺+Gd³⁺+Yb³⁺) 0.016 cation% or less.

62. The glass of claim 43, wherein the La³⁺Content relative to La³⁺、Y³⁺、Gd³⁺And Yb³⁺Cation ratio (La) of the total content of³⁺/（La³⁺+Y³⁺+Gd³⁺+Yb³⁺) ) is 0.55 to 0.95 cation%.

63. The glass of claim 43, wherein Nb is⁵⁺、Ti⁴⁺、Ta⁵⁺And W⁶⁺The total content of (B) is 2 to 10 cation%.

64. The glass of claim 43, wherein Nb is⁵⁺Content relative to Nb⁵⁺、Ti⁴⁺And W⁶⁺Cation ratio (Nb) of the total content⁵⁺/（Nb⁵⁺+Ti⁴⁺+W⁶⁺) ) is 0.4 to 1.

65. The glass of claim 43, wherein Zn²⁺Content relative to Nb⁵⁺、Ti⁴⁺、Ta⁵⁺And W⁶⁺Cation ratio (Zn) of the total content of²⁺/（Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺) ) is 3.6/4.5 or less.

66. The glass of claim 43, wherein B³⁺And Si⁴⁺The total content of (B) relative to Nb⁵⁺、Ti⁴⁺、Ta⁵⁺And W⁶⁺Cation ratio of the total content of ((B)³⁺+Si⁴⁺）/（Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺) ) is 54.5/4.5 or less.

67. The glass of claim 43, wherein Zn²⁺Content relative to B³⁺And Si⁴⁺Cation ratio Zn of the total content of²⁺/（B³⁺+Si⁴⁺) Is 4.0/56.6 or less.

68. The glass of claim 43, wherein Li⁺、Na⁺、K⁺The total content of (B) is 0 to 5 cation%.

69. The glass of claim 43, wherein Mg²⁺、Ca²⁺、Sr²⁺And Ba²⁺In total content of0 to 10 cation%.

70. The glass of claim 43, wherein the refractive index nd ranges from 1.830 to 1.837, and the Abbe number vd ranges from 41.7 to 43.2.

71. The glass of claim 43, wherein the specific gravity is 4.70 or less.

72. A glass material for press molding, which is formed of the glass according to any one of claims 1 to 71.

73. An optical element blank formed of the glass as defined in any one of claims 1 to 71.

74. An optical element formed from the glass as defined in any one of claims 1 to 71.