TWI663137B - Glass, glass materials for press molding, blanks for optical elements, and optical elements - Google Patents

Abstract

The present invention relates to a glass. The present invention provides a glass having a refractive index nd ranging from 1.75 to 1.80 and an Abbe number νd ranging from 47 to 52, which can be stably supplied and can achieve a high manufacturing yield. The glass contains at least La ₂ O ₃ , Y ₂ O ₃ , ZrO ₂ , ZnO, Nb ₂ O ₅ , and one or both selected from B ₂ O ₃ and SiO _{2. It} is expressed in mass%, and B ₂ O The total content of ₃ and SiO ₂ is 28 ~ 38%, the total content of La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ and Yb ₂ O ₃ is 48 ~ 60%, and the content of Gd ₂ O ₃ is less than 3 %, Yb ₂ O ₃ content is less than 2%, ZrO ₂ content is 2 to 14%, WO ₃ content is less than 1%, the total content of MgO, CaO, SrO, and BaO is less than 5%, and the mass ratio (( La ₂ O ₃ + Y ₂ O ₃ ) / (La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ )) is 0.94 or more, ((La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ ) / (B ₂ O ₃ + SiO ₂ )) is 1.9 or less, (Nb ₂ O ₅ / (La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ + Nb ₂ O ₅ + TiO ₂ + WO ₃ )) is 0.003 or more, (ZnO / (ZrO ₂ + Nb ₂ O ₅ + Ta ₂ O ₅ )) is 0.2 to 1.4, and (ZnO / Y ₂ O ₃ ) is 0.30 Above, ((Li ₂ O + ZnO) / (La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ + ZrO ₂ + Nb ₂ O ₅ + Ta ₂ O ₅ )) is 0.11 or less, The range of nd is 1.75 to 1.80, and the range of νd is 47 to 52.

Description

Glass, glass materials for press molding, blanks for optical elements, and optical elements

The invention relates to a glass, a glass material for press molding, an optical element blank and an optical element. Specifically, it relates to glass having a refractive index nd in a range of 1.75 to 1.80 and an Abbe number νd in a range of 47 to 52, and a glass material for press molding composed of the glass, an optical element blank, and an optical element.

As an optical element material constituting an optical system such as a camera optical system such as a camera lens and a projection optical system such as a projector, a high refractive index having a refractive index nd ranging from 1.75 to 1.80 and an Abbe number νd ranging from 47 to 52, Low dispersion optical glass. For example, Patent Documents 1 to 10 describe such a high refractive index and low dispersion optical glass. In addition, unless otherwise specified below, the refractive index and the Abbe number refer to the refractive index nd with respect to the d line and the Abbe number νd with respect to the d line.

(Prior technical literature) (Patent Literature)

Patent Document 1: Japanese Patent Application Laid-Open No. 61-219738.

Patent Document 2: Japanese Patent Application Laid-Open No. 2004-231501.

Patent document 3: WO2013 / 034082.

Patent Document 4: Japanese Patent Application Laid-Open No. 59-195553.

Patent Document 5: Japanese Patent Application Laid-Open No. 55-116641.

Patent Document 6: Japanese Patent Application Laid-Open No. 56-041850.

Patent Document 7: Japanese Patent Application Laid-Open No. 2005-239544.

Patent Document 8: Japanese Patent Application Laid-Open No. 2007-269584.

Patent Document 9: Japanese Patent Application Laid-Open No. 2008-222479.

Patent Document 10: US2009 / 0088310A1.

Among the glass components, the rare earth oxide can increase the refractive index without significantly increasing the dispersion (without substantially reducing the Abbe number), and is therefore a useful component for producing high refractive index and low dispersion glass. Therefore, each of the optical glasses described in Patent Documents 1 to 3 contains one or more rare earth oxides. In particular, the rare earth oxide Gd ₂ O ₃ as capable of imparting a high refractive index, low dispersion and suppressing coloration of the glass composition known to the public, for example, discloses Gd containing 3.0 mass% in Patent Document ₁₂ O ₃ optical glass. However, Gd compounds used to make optical glass containing Gd ₂ O ₃ are heavy rare-earth metal compounds, and are particularly expensive among rare-earth compounds. They are, for example, four times more expensive than La and Y compounds, which are also rare-earth compounds. Circulation. Therefore, in order to supply high-refractive-index, low-dispersion optical glass inexpensively and stably, it is desirable to reduce the content of Gd ₂ O ₃ .

On the other hand, an example of Patent Document 3 discloses an optical glass that does not include Gd ₂ O ₃ . However, according to the study by the present inventors, the optical glass described in Patent Document 3 has a problem that the manufacturing yield is low. This is due to the following reasons. In the optical glass described in Patent Document 3, when the glass is melted, the raw material is not completely melted, and a part of the raw material remains in the glass. The raw materials remaining in the glass in this manner are called unmelted materials. Since optical glass is required to have high homogeneity, a portion of the manufactured glass containing unmelted materials becomes defective and has to be discarded, and the manufacturing yield is reduced.

According to the study by the present inventors, the same problems as described above also exist in the optical glass described in Patent Documents 4, 6 to 10.

In addition, according to the study by the present inventors, the optical glass described in Patent Document 5 has a problem that the manufacturing yield is low. This is due to easy crystallization during glass manufacturing.

As described above, for the high-refractive-index, low-dispersion optical glass with a refractive index nd ranging from 1.75 to 1.80 and an Abbe number νd ranging from 47 to 52 in the prior art, it is required to further stabilize the supply and manufacture yield. improve.

An object of one embodiment of the present invention is to provide a glass having a refractive index nd ranging from 1.75 to 1.80 and an Abbe number νd ranging from 47 to 52, which can be stably supplied and can achieve high manufacturing yield.

An embodiment of the present invention relates to a glass including at least La ₂ O ₃ , Y ₂ O ₃ , ZrO ₂ , ZnO, Nb ₂ O ₅ , and one or both selected from B ₂ O ₃ and SiO ₂ , Expressed in mass%, the total content of B ₂ O ₃ and SiO ₂ is 28 ~ 38%, the total content of La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ and Yb ₂ O ₃ is 48 ~ 60%, Gd ₂ O ₃ content is less than 3%, Yb ₂ O ₃ content is less than 2%, ZrO ₂ content is 2 to 14%, WO ₃ content is less than 1%, and the total content of MgO, CaO, SrO and BaO It is 5% or less, the mass ratio ((La ₂ O ₃ + Y ₂ O ₃ ) / (La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ )) is 0.94 or more, and the mass ratio (( La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ ) / (B ₂ O ₃ + SiO ₂ )) is 1.9 or less, and the mass ratio (Nb ₂ O ₅ / (La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ + Nb ₂ O ₅ + TiO ₂ + WO ₃ )) is 0.003 or more, and the mass ratio (ZnO / (ZrO ₂ + Nb ₂ O ₅ + Ta ₂ O ₅ )) 0.2 ~ 1.4, mass ratio (ZnO / Y ₂ O ₃ ) is 0.30 or more, mass ratio ((Li ₂ O + ZnO) / (La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ + ZrO ₂ + Nb ₂ O ₅ + Ta ₂ O ₅ )) is 0.11 or less, the refractive index nd ranges from 1.75 to 1.80, and the Abbe number ranges νd from 47 to 52.

The above-mentioned embodiment relates to a glass having a refractive index and an Abbe number within the above range, and can reduce the content of Gd ₂ O ₃ while satisfying the above-mentioned content and mass ratio, thereby suppressing the generation of unmelted substances and Crystallization during glass manufacturing.

According to one embodiment of the present invention, it is possible to provide glass with a small Gd ₂ O ₃ content, stable supply, and high manufacturing yield. Furthermore, according to one embodiment of the present invention, it is possible to provide a glass material for press molding composed of the glass, an optical element blank, and an optical element.

FIG. 1 is a photograph of the glass evaluated in Comparative Example 2. FIG.

FIG. 2 is a photograph of the glass evaluated in Comparative Example 3. FIG.

FIG. 3 is a photograph of a glass having a composition of No. 12 in Table 1 described below, which is evaluated by the same method as Comparative Examples 2 and 3.

[glass]

A glass according to an embodiment of the present invention is a glass having the above-mentioned glass composition, a refractive index nd ranging from 1.75 to 1.80, and an Abbe number νd ranging from 47 to 52. The details of the glass are described below.

<Glass composition>

In the present invention, the glass composition of glass is expressed on the basis of an oxide. Here, the "glass composition based on oxides" means that all glass raw materials are decomposed when they are melted, and that they are present as oxides in the glass to be converted to obtain a glass composition. In addition, unless otherwise specified, the glass composition is expressed on the basis of mass (mass%, mass ratio).

The glass composition in the present invention can be quantified by a method such as ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry). The analysis value obtained by ICP-AES may include an error of approximately ± 5% of the analysis value. In addition, in the present specification and the present invention, the content of the constituent component is 0%, or the inclusion or non-introduction means that the constituent component is not substantially contained, and means that the content of the constituent component is equal to or less than the impurity level.

Hereinafter, the glass composition of the said glass is demonstrated in more detail.

Both B ₂ O ₃ and SiO ₂ are components forming a network of glass. By the total content of B ₂ O ₃ and SiO ₂ content, i.e., B ₂ O ₃ and the total content of SiO ₂ (B ₂ O ₃ + SiO ₂₎ is set to 28%, thermally stable glass can be improved in the Sex. The glass having high thermal stability can suppress crystallization (devitrification) during glass production. When the total content of B ₂ O ₃ and SiO ₂ is 38% or less, the refractive index can be increased. Therefore, the range of the total content of B ₂ O ₃ and SiO ₂ is set to 28 to 38%. A preferable lower limit of the total content of B ₂ O ₃ and SiO ₂ is 29%, a more preferable lower limit is 30%, a preferable upper limit of the total content of B ₂ O ₃ and SiO ₂ is 36%, and a more preferable upper limit is 35%.

B ₂ O ₃ is a component that functions to improve the thermal stability and meltability of glass. By improving the melting property, there is no residual melting of the glass raw material, and a homogeneous glass can be obtained. In order to obtain such an effect, a preferable lower limit of the content of B ₂ O ₃ is 25%, and a more preferable lower limit is 28%. On the other hand, when the content of B ₂ O ₃ is increased, the refractive index tends to decrease. In order to obtain desired optical characteristics while maintaining the thermal stability of the glass, a preferable upper limit of the content of B ₂ O ₃ is 36%, and a more preferable upper limit is 33%.

SiO ₂ is a component effective for improving the thermal stability and chemical resistance of glass and adjusting the viscosity when molding molten glass. In order to obtain such an effect, a preferable lower limit of the content of SiO ₂ is 1%, and a more preferable lower limit is 1.5%. On the other hand, when the content of SiO ₂ increases, the refractive index tends to decrease, and the meltability of the glass also tends to decrease. It also shows a tendency for the glass transition temperature to rise excessively. In order to obtain the desired optical characteristics while maintaining the thermal stability and melting properties of the glass, a preferable upper limit of the content of SiO ₂ is 5%, and a more preferable upper limit is 4%.

La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ , and Yb ₂ O ₃ are all components having the effect of increasing the refractive index without increasing the dispersion (without reducing the Abbe number). If the _{La 2 O 3, Y 2 O} 3, Gd total and the content of each component of Yb ₂ O ₃ is ₂ O _3, i.e., _{La 2 O 3, Y 2 O} 3, Gd total ₂ O ₃ and Yb ₂ O ₃ is When the content (La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ ) is 48% or more, desired optical characteristics can be obtained. On the other hand, if the total content of La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ and Yb ₂ O ₃ is 60% or less, the thermal stability of the glass can be improved, and the loss of glass during glass production can be suppressed. through. In addition, it is possible to improve the melting property and suppress the unmelted matter of the raw materials remaining in the glass. In addition, it is possible to suppress an excessive increase in the glass transition temperature. Therefore, the range of the total content of La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O _3, and Yb ₂ O ₃ is set to 48 to 60%. The lower limit of the total content of La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ and Yb ₂ O ₃ is 50%, and the more preferable lower limit is 52%. The preferable upper limit of the total content of La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ and Yb ₂ O ₃ is 58%, and the more preferable upper limit is 56%.

Among La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O _3, and Yb ₂ O ₃ , La ₂ O ₃ is a component that does not easily reduce the thermal stability of glass even if it is contained in a relatively large amount. Therefore, the above-mentioned glass contains La ₂ O ₃ and Y ₂ O _{3 in order to} maintain the thermal stability of the glass while suppressing the contents of Gd ₂ O ₃ and Yb ₂ O ₃ while obtaining desired optical characteristics. In order to maintain the thermal stability of the glass while achieving the desired optical characteristics, the total content of La ₂ O ₃ and Y ₂ O ₃ (La ₂ O ₃ + Y ₂ O ₃ ) is compared with La ₂ O ₃ and Y ₂ O ₃ , mass ratio of total content of Gd ₂ O ₃ and Yb ₂ O ₃ ((La ₂ O ₃ + Y ₂ O ₃ ) / (La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ )) Is set to 0.94 or more. In order to reduce the content of Gd ₂ O ₃ and Yb ₂ O ₃ while maintaining the thermal stability of the glass and obtaining the required optical characteristics, the mass ratio ((La ₂ O ₃ + Y ₂ O ₃ ) / (La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ )) is 0.96 or more, and more preferably 0.98 or more.

In order to maintain the thermal stability of the glass and obtain desired optical characteristics, the mass ratio (La ₂ O ₃ / (La ₂ O ₃ + Y ₂ O ₃ )) is preferably 0.9 or less. In order to maintain the thermal stability of the glass and obtain the desired optical characteristics, the better upper limit of the mass ratio (La ₂ O ₃ / (La ₂ O ₃ + Y ₂ O ₃ )) is 0.85, the lower limit is preferably 0.70, and the lower limit is better. Is 0.75.

Gd ₂ O ₃ has the effect of reducing the transmittance on the short wavelength side of the visible light region of glass. In addition, it has the effect of increasing the specific gravity of glass. Furthermore, as compared with La ₂ O ₃ and Y ₂ O ₃ , the supply amount of the raw material compound of Gd ₂ O ₃ is reduced, and the raw material price is increased as described above. Therefore, in order to increase the transmittance of the short-wavelength side of the visible light region of the glass, suppress the increase in specific gravity, and suppress the increase in the production cost of the glass, the content of Gd ₂ O ₃ is less than 3% (less than 3.0 %). That is, the range of the Gd ₂ O ₃ content is 0 to 3%. The preferable range of the Gd ₂ O ₃ content is 2% or less, the more preferable range is 1% or less, and the more preferable range is 0.5% or less. The glass may not contain Gd ₂ O ₃ even if the Gd ₂ O ₃ content is zero.

As described above, Yb ₂ O ₃ is an expensive component of a raw material compound in a rare earth oxide. In addition, glass has a function of absorbing near-infrared rays. Therefore, in order to suppress the increase in the production cost of glass and improve the transmittance of near infrared rays, the content of Yb ₂ O ₃ is set to less than 2%. The preferred range of the content of Yb ₂ O ₃ is 0% or more and less than 1%, a more preferable range is 0 to 0.9%, a more preferable range is 0 to 0.5%, and a more preferable range is 0% or more and less than At 0.1%, the Yb ₂ O ₃ content can also be set to 0%.

As a network-forming component of glass, B ₂ O ₃ , SiO ₂ has a function of maintaining thermal stability. On the other hand, when a large amount of La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ , and Yb ₂ O ₃ are contained, which are effective components for obtaining high refractive index and low dispersion characteristics, the thermal stability of the glass is deteriorated, and the glass may be deteriorated. Become volatile. Therefore, in order to maintain the thermal stability of glass well, in the above glass, the total content of La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ and Yb ₂ O ₃ is divided by the content of B ₂ O ₃ and SiO ₂ The value of the total content, that is, the mass ratio ((La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ ) / (B ₂ O ₃ + SiO ₂ )) is set to 1.9 or less. The preferred upper limit of the mass ratio ((La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ ) / (B ₂ O ₃ + SiO ₂ )) is 1.8, and the more preferred upper limit is 1.7. The lower limit is 1.45, and the more preferable lower limit is 1.55.

ZrO ₂ is a component effective for improving the thermal stability of glass while increasing the refractive index. When the content of ZrO _{2 is} in the range of 2% to 14%, good thermal stability can be obtained. In addition, by setting the content of ZrO ₂ to 14% or less, low dispersion characteristics can also be obtained. Therefore, in the above glass, the content of ZrO ₂ is set to 2 to 14%. A preferred lower limit of the content of ZrO ₂ is 3%, a more preferred lower limit is 4%, a preferred upper limit is 12%, and a more preferred upper limit is 10%.

Nb ₂ O ₅ is an essential component that exerts the effect of increasing the refractive index while maintaining the thermal stability of the glass. In order to obtain the desired optical characteristics while maintaining the thermal stability of the glass, the content of Nb ₂ O ₅ is divided by La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ , Yb ₂ O ₃ , Nb ₂ O ₅ , The total content of TiO ₂ and WO ₃ (La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ + Nb ₂ O ₅ + TiO ₂ + WO ₃ ), that is, the mass ratio (Nb ₂ O ₅ / (La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ + Nb ₂ O ₅ + TiO ₂ + WO ₃ )) is set to 0.003 or more. In order to maintain thermal stability, the mass ratio (Nb ₂ O ₅ / (La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ + Nb ₂ O ₅ + TiO ₂ + WO ₃ )) is preferred. The lower limit is 0.005, and the more preferable lower limit is 0.01. In order to obtain the desired optical characteristics while maintaining the thermal stability of the glass, the mass ratio (Nb ₂ O ₅ / (La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ + Nb ₂ O ₅ + The preferable upper limit of TiO ₂ + WO ₃ )) is 0.04, and the more preferable upper limit is 0.03.

A preferable range of the Nb ₂ O ₅ content is as follows. In order to improve the thermal stability of the glass, a preferable lower limit of the content of Nb ₂ O ₅ is 0.3%, and a more preferable lower limit is 0.6%. In addition, in order to maintain the thermal stability of the glass and suppress coloration, a preferable upper limit of the content of Nb ₂ O ₅ is 2%, and a more preferable upper limit is 1.5%.

Ta ₂ O ₅ is a component having an effect of improving the thermal stability of glass. However, it is also a particularly expensive component among the high refractive index components, and exerts a function of increasing the specific gravity of glass. When the content of Ta ₂ O ₅ is increased, the glass tends to be colored. Therefore, in order to more stably supply the glass by suppressing the production cost of the glass, and to suppress the increase in specific gravity and coloring, the content of Ta ₂ O ₅ is preferably in the range of 0 to 3%, and more preferably in the range of 0 to 2%. The content of Ta ₂ O ₅ can also be set to 0%.

TiO ₂ is also a component that functions to increase the refractive index of glass. In order to obtain the desired optical characteristics while maintaining the thermal stability of the glass, the preferred range of the content of TiO ₂ is 0 to 2%, the more preferred range is 0 to 1%, and it can also be 0%.

WO ₃ is a component having an effect of increasing the refractive index. However, since a large amount of glass containing WO _{3 has} a longer wavelength on the short-wavelength light absorption margin, the transmittance of ultraviolet rays decreases. On the other hand, when an optical element is fixed to a lens barrel or the like, an ultraviolet curing adhesive is usually used, and the adhesive is usually irradiated with ultraviolet rays through the optical element. In addition, in a case where an optical element is used to obtain a cemented lens by cementing the optical elements (lenses) with each other, the cementation of the lenses with each other is generally performed as follows. First, an ultraviolet curable adhesive is applied to the bonding surfaces of the lenses, and the lenses are bonded to each other. Thereafter, the adhesive is irradiated with ultraviolet rays through a lens to cure the adhesive. Here, when the ultraviolet transmittance of the glass constituting the lens is low, curing of the adhesive takes time or becomes difficult. Therefore, as the glass, it is desirable to use glass having a shorter wavelength of light absorption margin on the short wavelength side of the spectral transmittance. In this regard, if the content of WO ₃ is less than 1%, it is possible to avoid a significant decrease in ultraviolet transmittance due to a long wavelength of light absorption margin on the short wavelength side of the spectral transmittance of glass. Therefore, in the above glass, the content of WO ₃ is set to less than 1%. That is, in the glass, WO ₃ content of 0% or more and less than 1%. The content of WO _{3 is} preferably 0.5% or less, and may be set to 0%.

ZnO is an essential component that is effective for improving meltability, suppressing an excessive increase in glass transition temperature, and adjusting optical characteristics. The content of ZnO is determined as follows based on the total content of ZrO ₂ , Nb ₂ O _5, and Ta ₂ O ₅ (ZrO ₂ + Nb ₂ O ₅ + Ta ₂ O ₅ ), and the content of Y ₂ O ₃ .

If the value of the ZnO content divided by the total content of ZrO ₂ , Nb ₂ O ₅ and Ta ₂ O ₅ , that is, the mass ratio (ZnO / (ZrO ₂ + Nb ₂ O ₅ + Ta ₂ O ₅ )) is 0.2 or more, then Since the melting property can be improved, it is possible to prevent the raw material from remaining molten (unmelted material remaining) and the homogeneity of the glass is significantly reduced. In addition, if the mass ratio (ZnO / (ZrO ₂ + Nb ₂ O ₅ + Ta ₂ O ₅ )) is 0.2 or more, it is possible to prevent the tendency of the moldability of the display glass from deteriorating because the glass transition temperature becomes too high. It is also possible to obtain the required optical characteristics while maintaining the thermal stability of the glass. The unmelted material derived from the raw material is a material that should be vitrified with other components to become a glass component, but is not vitrified and remains in the glass as an impurity. Therefore, in glass in which a large amount of unmelted matter is generated, the content of a specific component becomes smaller than a target value. As a result, the characteristics of the produced glass deviated from the target value. When the melting temperature of the glass is excessively increased in order to completely melt the raw materials, platinum constituting the melting vessel may be dissolved into the glass melt as ions to increase the color of the glass, or may be mixed into the glass melt as a solid to make The homogeneity of the glass is reduced. Furthermore, certain components such as boron B, which are volatile when the glass is melted, are volatilized from the glass melt, and the characteristics of the glass produced may change over time, or optically unevenness called streaks may occur in the formed glass section. The same phenomenon occurs when the melting temperature of glass is excessively increased to prevent crystallization during glass melting.

Therefore, in order to prevent the above-mentioned phenomenon from occurring, it is preferable to maintain the melting property and thermal stability of the glass well from the viewpoint of stable production of high-quality glass.

When the mass ratio (ZnO / (ZrO ₂ + Nb ₂ O ₅ + Ta ₂ O ₅ )) is 1.4 or less, the required optical characteristics can be obtained while maintaining thermal stability. In addition, it is possible to obtain glass having good processability such as grinding and polishing.

From the above, in the above glass, the range of the mass ratio (ZnO / (ZrO ₂ + Nb ₂ O ₅ + Ta ₂ O ₅ )) is set to 0.2 to 1.4. The preferred lower limit of the mass ratio (ZnO / (ZrO ₂ + Nb ₂ O ₅ + Ta ₂ O ₅ )) is 0.3, the more preferred lower limit is 0.4, the preferred upper limit is 1.1, and the preferred upper limit is 0.9.

By adjusting the total content of ZrO ₂ , Nb ₂ O ₅ , and Ta ₂ O ₅ , the thermal stability of the glass can be improved. The improvement of thermal stability can also reduce the liquidus temperature. Compared with La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ , and Yb ₂ O ₃ , which are also high refractive index components, ZrO ₂ , Nb ₂ O ₅ , and Ta ₂ O ₅ are easier to make as the content increases. High dispersion (easy to reduce Abbe number) component of glass. In order to achieve the desired optical characteristics while maintaining the thermal stability of the glass, the lower limit of the total content of ZrO ₂ , Nb ₂ O ₅ , and Ta ₂ O ₅ (ZrO ₂ + Nb ₂ O ₅ + Ta ₂ O ₅ ) is 3%, with a better lower limit of 4%, and a better lower limit of 5%, a better upper limit of 14%, a better upper limit of 12%, and an even higher limit of 10%.

In order to improve the melting and thermal stability of glass and achieve the desired optical characteristics, the preferred range of the content of ZnO is 2-9%. A preferred lower limit of the ZnO content is 3%, a more preferred lower limit is 4%, a preferred upper limit is 7%, and a more preferred upper limit is 6%.

When the value of the ZnO content divided by the Y ₂ O ₃ content, that is, the mass ratio (ZnO / Y ₂ O ₃ ) is set to 0.30 or more, the melting property of the glass can be improved, and thus the raw material can be prevented from remaining. In addition, it is also possible to prevent the glass transition temperature from being excessively increased to deteriorate the moldability of the glass. Therefore, in the above glass, the mass ratio (ZnO / Y ₂ O ₃ ) is set to 0.30 or more. The preferable lower limit of the mass ratio (ZnO / Y ₂ O ₃ ) is 0.35, and the more preferable lower limit is 0.40.

However, in glass characteristics, the glass transition temperature is a physical property value of a glass corresponding to moldability and processability. When the glass transition temperature is too high, the glass must be formed at a high temperature. Therefore, exposing the molding die to a high temperature for a long period of time may cause significant thermal aging of the molding die. On the other hand, although the moldability can be improved when the glass transition temperature is low, the workability when grinding or polishing glass shows a tendency to deteriorate. For example, the optical glass described in the aforementioned Patent Document 2 has a low glass transition temperature, and the workability when grinding or polishing the glass is not good. In order to balance moldability and processability, it is desirable to appropriately maintain the content of ZnO and Li ₂ O that have the effect of reducing the glass transition temperature and La ₂ O ₃ , Y ₂ O ₃ and that have the effect of increasing the glass transition temperature. The balance of the contents of Gd ₂ O ₃ , Yb ₂ O ₃ , ZrO ₂ , Nb ₂ O ₅ , and Ta ₂ O ₅ . Therefore, the total of the Li ₂ O content and the ZnO content (Li ₂ O + ZnO) is divided by La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ , Yb ₂ O ₃ , ZrO ₂ , Nb ₂ O ₅ , Ta The total content of ₂ O ₅ (La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ + ZrO ₂ + Nb ₂ O ₅ + Ta ₂ O ₅ ), that is, the mass ratio ((Li ₂ O + ZnO) / (La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ + ZrO ₂ + Nb ₂ O ₅ + Ta ₂ O ₅ )) is set to 0.11 or less. By setting the above-mentioned mass ratio to 0.11 or less, it is possible to prevent the glass transition temperature from being excessively lowered to deteriorate the processability. Mass upper limit ((Li ₂ O + ZnO) / (La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ + ZrO ₂ + Nb ₂ O ₅ + Ta ₂ O ₅ )) It is 0.10, and a more preferable upper limit is 0.09. On the other hand, in order to maintain the moldability of the glass, the mass ratio ((Li ₂ O + ZnO) / (La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ + ZrO ₂ + Nb ₂ O ₅ + Ta ₂ O ₅ )) has a preferable lower limit of 0.04, and a more preferable lower limit of 0.06.

Although MgO, CaO, SrO, and BaO have the effect of improving the meltability of glass, the refractive index decreases when the total content of each component of MgO, CaO, SrO, and BaO (MgO + CaO + SrO + BaO) exceeds 5%. It becomes difficult to obtain desired optical characteristics, and the thermal stability of the glass tends to decrease. Therefore, in the above glass, the total content of MgO, CaO, SrO, and BaO (MgO + CaO + SrO + BaO) ranges from 0 to 5%. More preferably, the range of the total content is set to 0 to 3%, more preferably 0 to 1%, or 0%.

F significantly increases the volatility of the glass during melting. For this reason, the optical characteristics of a glass with a large amount of F are liable to fluctuate, streaks are likely to occur, and homogeneity is liable to decrease. In order to obtain a glass with high homogeneity and stable optical characteristics, the content of F is preferably less than 0.1%, and more preferably 0.05% or less. The content of F may be set to 0%.

The rare earth component can maintain the thermal stability of the glass even if it contains La ₂ O _{3 in a} large amount. Therefore, the above glass contains La ₂ O ₃ as an essential component. As the content of La ₂ O ₃ increases, the thermal stability of the glass tends to decrease. Therefore, the range of the content of La ₂ O ₃ is preferably 35 to 55%. The more preferable lower limit of the content of La ₂ O ₃ is 38%, the more preferable lower limit is 40%, the more preferable upper limit is 50%, and the more preferable upper limit is 48%.

Y ₂ O ₃ is a component that exhibits an effect of improving the thermal stability of glass by containing it in an appropriate amount. In order to obtain such an effect, the glass contains Y ₂ O ₃ as an essential component. The content of Y ₂ O ₃ is preferably 5% or more. On the other hand, in order to maintain the thermal stability of the glass, it is preferable to set the content of Y ₂ O ₃ to 15% or less, more preferably 14% or less, still more preferably 13% or less, and still more preferably less than 12%. A more preferable lower limit of the content of Y ₂ O ₃ is 7%, and a more preferable lower limit is 8%.

Li ₂ O, Na ₂ O, K ₂ O, and Cs ₂ O have the effect of improving the meltability of glass. In order to obtain a desired refractive index and good thermal stability, it is preferable to add the total content of each component of Li ₂ O, Na ₂ O, K ₂ O, and Cs ₂ O (Li ₂ O + Na ₂ O + K ₂ The range of O + Cs ₂ O) is set to 0 to 5%, a more preferable range is 0 to 3%, and a more preferable range is 0 to 1%, and it can also be set to 0%.

GeO ₂ is a network-forming oxide, that is, a network-forming component of glass, and also plays a role in increasing the refractive index. Therefore, it is a component which can raise the refractive index while maintaining the thermal stability of glass. However, since GeO ₂ is a very expensive component, it is a component whose content is desired to be controlled. The GeO ₂ content is preferably in the range of 0 to 3%, more preferably in the range of 0 to 1%, more preferably in the range of 0 to 0.5%, and still more preferably in the range of 0 to 0.1%. The content of GeO ₂ can be made 0%.

Bi ₂ O ₃ plays a role of increasing the refractive index and improving the thermal stability of glass. When Bi ₂ O ₃ is contained excessively, the absorption margin on the short wavelength side of the spectral transmittance is shortened. Therefore, the preferred range of the content of Bi ₂ O ₃ is 0 to 3%, and the more preferred range is 0. ~ 1%, a more preferred range is 0 ~ 0.5%, and a more preferred range is 0 ~ 0.1%. The content of Bi ₂ O ₃ can also be set to 0%.

When Al ₂ O ₃ is present in a small amount, it improves the thermal stability and chemical durability of the glass. However, excessive introduction of Al ₂ O ₃ tends to increase the liquidus temperature and deteriorate the thermal stability. From the above point of view, the preferred range of the content of Al ₂ O ₃ is 0 ~ 3%, the more preferred range is 0 ~ 1%, the more preferred range is 0 ~ 0.5%, and the more preferred range is 0 ~ 0.1%. The content of Al ₂ O ₃ can also be set to 0%.

Sb ₂ O ₃ can be added as a clarifying agent. Although a small amount of Sb ₂ O ₃ also suppresses the decrease in light transmittance caused by the incorporation of impurities such as Fe, but when the amount of Sb ₂ O ₃ is excessively added, Light absorption shows a tendency for the coloration of glass to increase. From the above point of view, the preferable range of the addition amount of Sb ₂ O ₃ is 0 to 0.1%, the more preferable range is 0 to 0.06%, and the more preferable range is 0 to 0.04%. Further additional content of Sb ₂ O ₃ means the total content of the glass component other than Sb ₂ O ₃ is 100 mass% content of Sb ₂ O ₃ is expressed in mass%.

SnO ₂ can also be added as a fining agent. When the added amount exceeds 0.5%, the glass will be colored, or when remolding such as heating and softening the glass for press molding, Sn will become the starting point of crystal nuclei and devitrification tends to occur. Therefore, it is preferable to set the range of the externally added amount of SnO ₂ to 0 to 0.5%, a more preferable range is 0 to 0.3%, and it is more preferable not to add. The added content of SnO ₂ means the content of SnO ₂ expressed as mass% when the total content of glass components other than SnO ₂ is 100% by mass.

The glass can achieve high refractive index and low dispersion optical characteristics while maintaining the thermal stability of the glass, and does not need to contain components such as Lu and Hf. Since Lu and Hf are also expensive components, it is preferable to control the contents of Lu ₂ O ₃ and HfO ₂ to 0 to 3%, more preferably to 0 to 1%, and more preferably to 0. ~ 0.5%, and even more preferably, it is controlled to less than 0.1%, and it is particularly preferable not to introduce Lu ₂ O ₃ and HfO _{2 respectively} .

In addition, considering the environmental impact, the above glass is preferably substantially Does not contain Pb. The fact that Pb is not substantially included means that it is converted into PbO, and the content of PbO is less than 0.05%, and may be 0%.

In addition, it is preferable not to introduce As, U, Th, and Cd that affect the environment.

Since Te also affects the environment, it is preferable not to introduce a large amount of Te. The preferable range of the content of TeO ₂ is 0 to 1%, the more preferable range is 0 to 0.5%, and the more preferable range is 0 to 0.1%, and TeO ₂ may not be contained.

Furthermore, in order to take advantage of the excellent light transmittance of glass, it is preferable not to introduce substances such as Cu, Cr, V, Fe, Ni, Co, etc., which are the main causes of coloring.

The glass is a high-refractive-index, low-dispersion glass, which can be a glass with little coloration, and is suitable as an optical glass.

The glass composition of the said glass was demonstrated above. Next, the glass characteristics of the said glass are demonstrated.

<Glass Characteristics>

(Refractive index nd, Abbe number νd)

From the viewpoint of usefulness as an optical element material constituting an optical system such as a photographing optical system, a projection optical system, and the like, specifically, correction of chromatic aberration, and high functionalization of the optical system, the refractive index nd of the glass ranges from 1.75 to 1.80. The lower limit of the refractive index nd is preferably 1.76, and more preferably 1.765. The upper limit of the refractive index nd is preferably 1.79, and more preferably 1.785.

In addition, from the same viewpoint, the range of the Abbe number νd of the glass is 47 to 52. The lower limit of the Abbe number νd is preferably 48, and more preferably 49. The upper limit of the Abbe number νd is preferably 51, and more preferably 50.

(Coloring degree λ5, λ70, λ80)

As described above, when the ultraviolet-ray-curable adhesive is irradiated with ultraviolet rays through the optical element, it is preferable that the short-wavelength absorption margin of the spectral transmittance of the optical element is in the short-wavelength region. As an index for quantitatively evaluating the absorption margin on the short wavelength side, the degree of coloration λ5 can be used. λ5 represents a wavelength at which the spectral transmittance (including the surface reflection loss) of glass having a thickness of 10 mm in the ultraviolet region to the visible region is 5%. Λ5 shown in the examples described later is a value measured in a wavelength region of 280 to 700 nm. The spectral transmittance is, for example, a spectral transmittance obtained by using a glass sample having parallel surfaces polished to a thickness of 10.0 ± 0.1 mm to make light incident from a direction perpendicular to the polished surface, that is, The value of Iout / Iin when the intensity of light incident on the glass sample is Iin and the intensity of light transmitted through the glass sample is Iout.

Based on the coloring degree λ5, the absorption margin on the short wavelength side of the spectral transmittance can be quantitatively evaluated. In order to efficiently cure the ultraviolet curable adhesive, the λ5 of the glass is preferably 335 mm or less, more preferably 325 nm or less, and still more preferably 315 nm or less. The lower limit of λ5 can be set as a target of 300 nm as an example, but as low as possible, it is not particularly limited.

On the other hand, as an index of the coloring degree of glass, the coloring degrees λ70 and λ80 can also be mentioned. λ70 indicates a wavelength at which the spectral transmittance measured by the method described in λ5 is 70%. λ80 indicates a wavelength at which the spectral transmittance measured by the method described in λ5 is 80%. The λ70 of the glass is preferably 380 nm or less, more preferably 370 nm or less, and even more preferably 365 nm or less. The lower limit of λ70 can be set as a target of 340 nm as an example, but as low as possible, it is not particularly limited. The λ80 of the glass is preferably 420 nm or less, more preferably 400 nm or less, and even more preferably 390 nm or less. For the lower limit of λ80, as An example is that 360 nm can be set as a target, but the lower the better, it is not particularly limited.

(Partial dispersion characteristics)

From the viewpoint of chromatic aberration correction, it is preferable that the glass is a glass having a small relative partial dispersion when the Abbe number νd is fixed.

Here, the relative partial dispersions Pg and F are expressed as (ng-nF) / (nF-nc) using the respective refractive indices ng, nF, and nc at the g-line, F-line, and c-line.

In order to provide a glass suitable for high-order chromatic aberration correction, the relative partial dispersion Pg, F of the above glass is preferably in the range of 0.545 to 0.560.

(Glass transition temperature Tg)

When the annealing temperature and the temperature of the glass during press molding become too high, the annealing furnace and the press mold are consumed. In order to reduce the thermal load of the annealing furnace and the press mold, the glass transition temperature Tg is preferably 680 ° C or lower, and more preferably 675 ° C or lower.

When the glass transition temperature Tg is too low, the workability of mechanical processing such as polishing and polishing tends to decrease. Therefore, in order to maintain processability, the glass transition temperature Tg is preferably 645 ° C or higher, and more preferably 650 ° C or higher.

(Liquid phase temperature LT)

The liquidus temperature is one of the indicators of the thermal stability of glass. In order to suppress crystallization and devitrification during glass production, the liquidus temperature LT is preferably 1100 ° C or lower, and more preferably 1080 ° C or lower. The lower limit of the liquidus temperature LT is 1000 ° C. or higher as an example, but a lower temperature is preferred and is not particularly limited.

(proportion)

For example, when using the above glass in a lens with autofocus In the case where the quality of the lens is large, power consumption at the time of focusing increases, and battery consumption increases. One of the means for reducing the weight of a lens is to reduce the specific gravity of glass. The specific gravity of the glass is preferably 4.60 or less, and more preferably 4.50 or less. The lower limit of the specific gravity is naturally determined based on the composition range described above. The lower limit of the specific gravity is set at 4.0.

<Manufacturing method of glass>

The above-mentioned glass can be obtained by weighing, formulating and sufficiently mixing oxides, carbonates, sulfates, nitrates, hydroxides, etc. as raw materials so as to obtain a desired glass composition, and mixing them to form a mixture. The batch material (batch material) is heated, melted, degassed, and stirred in a melting container made of a noble metal such as platinum to form a homogeneous molten glass without bubbles, and molds it. Specifically, it can be produced using a known melting method. Since glass A and B are not only high-refractive-index low-dispersion glass which has the above-mentioned optical characteristics, but also excellent thermal stability, they can be stably manufactured using a known melting method and molding method.

[Glass material for press molding, blank of optical element, and method for manufacturing the same]

Another embodiment of the present invention relates to a glass material for press molding composed of the aforementioned glass, and an optical element blank composed of the aforementioned glass.

According to another embodiment of the present invention, there is also provided a method for manufacturing a glass material for press molding, which includes the step of molding the glass into a glass material for press molding, and a method for manufacturing an optical element blank, comprising: The step of manufacturing the above-mentioned glass material for press molding by using a press-molding die to produce a blank of the optical element; and a method for manufacturing the blank of the optical element, including: Including the step of forming the above-mentioned glass into an optical element blank.

The blank of the optical element refers to the shape of the target optical element. A polishing tolerance (a surface layer removed by polishing) is added to the shape of the optical element, and a grinding tolerance (by polishing) is added as needed. While removing the surface layer) of the optical element base material. The optical element is completed by grinding and polishing the surface of the blank of the optical element. In one embodiment, an optical element blank can be produced by a method (called a direct pressing method) of press-molding a molten glass obtained by appropriately melting the glass. In another embodiment, an optical element blank can also be produced by solidifying a molten glass obtained by appropriately melting the glass.

In addition, in another embodiment, an optical element blank can also 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 the glass material for press molding in a heated and softened state with a press mold. Both heating and pressing can be performed in the atmosphere. By annealing after press molding to reduce the stress in the glass, a homogeneous blank of the optical element can be obtained.

The glass material for press molding is supplied in the original state to a material called a glass gob for press molding, which is used for the press molding of optical element blanks, and includes cutting, grinding, and polishing. It is mechanically processed and supplied to a press-molded material through a glass gob for press molding. As a cutting method, a groove is formed on a portion of a glass plate surface to be cut by a method called scoring, and the groove portion is applied from the back surface of the surface on which the groove is formed. A method of breaking a glass plate in a groove portion by a local pressure; a method of cutting a glass plate by a cutter, and the like. Examples of the grinding and polishing methods include barrel polishing.

The glass material for press molding can be produced by, for example, casting a molten glass into a mold to form a glass plate, and cutting the glass plate into a plurality of glass pieces. In addition, an appropriate amount of molten glass can be formed to produce a glass gob for press molding. An optical element blank can also be produced by reheating and softening the glass frit for press molding and performing press molding. The method of reheating and softening glass and pressing and forming the blank of the optical element is called a reheating and pressing method compared with the direct pressing method.

[Optical element and manufacturing method thereof]

Another embodiment of the present invention relates to an optical element composed of the glass described above.

In addition, according to an embodiment of the present invention, there is also provided a method for manufacturing an optical element, which includes a step of manufacturing the optical element by grinding and / or polishing the blank of the optical element.

In the above-mentioned method for manufacturing an optical element, a known method may be used for polishing and polishing. By sufficiently cleaning and drying the surface of the optical element after processing, an optical element having high internal quality and surface quality can be obtained. In this way, it is possible to obtain an optical element composed of the above-mentioned glass having a refractive index nd in a range of 1.75 to 1.80 and an Abbe number νd in a range of 47 to 52. As an optical element, various lenses, such as a spherical lens, an aspherical lens, and a micro lens, etc. can be illustrated.

In addition, an optical element composed of the above glass is also suitable as a lens constituting a cemented optical element. Examples of the cemented optical element include a lens Elements glued to each other (glue lens), elements glued to the lens and cymbals, etc. For example, a cemented optical element can be produced by precision-processing (such as spherical polishing) the bonded surface of the two bonded optical elements so that their shapes are inverted, and coating the cemented lens. The ultraviolet curing adhesive used is irradiated with ultraviolet rays through a lens after lamination to cure the adhesive. In order to produce a bonded optical element in this manner, glass having the absorption characteristics described above is preferable. A plurality of optical elements to be bonded are produced and bonded using a plurality of types of glass having different Abbe numbers νd, respectively. This makes it possible to be an element suitable for correction of chromatic aberration.

(Example)

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

(Example 1)

In order to obtain a glass having the composition shown in Table 1, carbonates, nitrates, sulfates, hydroxides, oxides, boric acid, and the like are suitably used as raw materials. Each raw material powder is weighed and mixed thoroughly to prepare a blended raw material. The prepared raw materials were added to a platinum crucible, and heated and melted at 1100 to 1400 ° C. for 1 to 3 hours, and then clarified and stirred to obtain a homogeneous molten glass. This molten glass was poured into a preheated mold and quenched, and after maintaining at a temperature near the glass transition temperature for 1 hour, it was slowly cooled to obtain each glass having the composition shown in Table 1. In addition, none of the glasses shown in Table 1 contains F.

No precipitation of crystals was observed in any glass. In addition, it was confirmed that no melting residue (unmelted substance) of the raw material was found in the glass.

The characteristics of each glass were measured by the methods shown below. Shown in Table 1 定 结果。 The result.

(1) Refractive index nd and Abbe number νd

The measurement was performed on glass cooled at a temperature lowering rate of 30 ° C. per hour.

(2) Glass transition temperature Tg

The measurement was performed using a thermomechanical analyzer under the condition of a temperature rise rate of 4 ° C / min.

(3) Liquidus temperature LT

The glass was placed in a furnace heated to a predetermined temperature for 2 hours, and after cooling, the inside of the glass was observed with an optical microscope 100 times, and the liquidus temperature was determined according to the presence or absence of crystals.

(4) Specific gravity

The measurement was performed by the Archimedes method.

(5) Coloring degrees λ5, λ70, λ80

A glass sample having a thickness of 10 ± 0.1 mm with two optically polished planes facing each other was used, and a spectrophotometer was used to incident light of intensity Iin from a direction perpendicular to the polished surface to determine the light transmission through the glass sample. The intensity Iout is used to calculate the spectral transmittance Iout / Iin. The wavelength at which the spectral transmittance is 5% is λ5, the wavelength at which the spectral transmittance is 70% is λ70, and the wavelength at which the spectral transmittance is 80% is λ80.

(6) Relative partial dispersion Pg, F

The refractive indices nF, nc, and ng were measured and calculated from the measurement results.

Evaluation of thermal stability (1)

The glass raw material was prepared so that the glass which has a composition of glass No. 12 was obtained, 150g of each prepared raw material was put in a platinum crucible, and it heated at 1350 degreeC, and melted for 120 minutes, and cooled the molten material and obtained the solidified material. As a result of observation of the cured product, no crystals were precipitated. Furthermore, even when the glass was held at 1100 ° C for 120 minutes, crystals were not precipitated, and the holding temperature was lowered to 1060 ° C to be maintained, and no crystals were precipitated.

The other compositions shown in Table 1 were similarly evaluated, and as a result, no crystals were precipitated.

(Comparative example 1)

In the example of Patent Document 5, for Examples 3, 6, and 7 that do not include Nb ₂ O ₅ , the mass ratio ((La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ ) / (B ₂ O ₃ + SiO ₂ )) was 1.93 in each composition of Example 11, and the cured product obtained by heating and melting at 1350 ° C. for 120 minutes was cooled in the same manner as described above. As a result, Examples 3, A large number of crystals were precipitated at 7 and 11. In Example 6, no precipitation of crystals was observed.

Next, the glass of Example 6 was heated and held at 1100 ° C for 120 minutes, and then cooled to room temperature and observed. As a result, many crystals were found. The same experiment was performed on Examples 3, 7, and 11, and as a result, many crystals were observed.

From the above results, it was confirmed that the glass of the example had better thermal stability than the glass evaluated in Comparative Example 1.

(Comparative example 2)

In the examples of Patent Document 3 1 to 10, to be able to obtain a glass composition having a mass ratio (ZnO / Y ₂ O ₃₎ Maximum Example 8 (mass ratio (ZnO / Y ₂ O ₃₎ 0.28) of Method, the glass raw material was prepared, and 50 g of the prepared material was added to a platinum crucible and melted at 1150 ° C. for 20 minutes.

Thereafter, the melt was quenched together with the crucible, the solidified glass was taken out from the crucible, and the inside of the glass was observed.

FIG. 1 is a photograph of glass (glass taken out from a crucible) evaluated in Comparative Example 2. FIG. It can be clearly seen from FIG. 1 that a number of glass pieces contain a lot of molten residues of raw materials, which are cloudy and lose transparency.

Except that the melting temperature was set to 1200 ° C, glass was produced in the same manner as described above, and as a result, a lot of raw materials remained in the edge portion of the glass taken out from the crucible.

(Comparative example 3)

In order to obtain a glass having a composition of Example 2 of Patent Document 4 in which the mass ratio (ZnO / (ZrO ₂ + Nb ₂ O ₅ + Ta ₂ O ₅ )) is 0.044, a glass raw material was prepared, and 50 g of the mixed material was added to The platinum crucible was melted at 1150 ° C for 20 minutes.

The melt was quenched together with the crucible, the solidified glass was taken out from the crucible, and the inside of the glass was observed.

FIG. 2 is a photograph of a glass (glass taken out from a crucible) evaluated in Comparative Example 3. FIG. It is clear from FIG. 2 that a number of glass pieces contain a lot of raw material residues, which are cloudy and lose transparency.

Evaluation of thermal stability (2)

About the composition of the glass No. 12 of Table 1, the same experiment as Comparative Examples 2 and 3 was performed. That is, 50 g of the prepared raw materials were put into a platinum crucible and melted at 1150 ° C. for 20 minutes. The melt was quenched together with the crucible, and the solidified glass was taken out of the crucible.

FIG. 3 is a photograph of a glass (glass taken out from a crucible) with a composition of No. 12 in Table 1 evaluated by the same method as Comparative Examples 2 and 3 as described above. It can be clearly seen from FIG. 3 that no residual raw materials are found in the glass, and a homogeneous glass can be produced.

Furthermore, even if the melting temperature is lowered to 1130 ° C, no raw material remains, and a homogeneous glass can be obtained.

From the above results, it was confirmed that the glass of the example had better thermal stability than the glass evaluated in Comparative Examples 2 and 3.

(Example 2)

The various glass obtained in Example 1 were used to produce a glass block (glass gob) for press molding. This glass block was heated and softened in the atmosphere, and was pressed and molded with a press-molding die to produce a lens blank (optical element blank). The produced lens blank was taken out from the press molding die, annealed, and subjected to mechanical processing including polishing to produce a spherical lens composed of various glasses produced in Example 1.

(Example 3)

A desired amount of the molten glass produced in Example 1 was press-molded with a press-forming mold to produce a lens blank (optical element blank). The produced lens blank was taken out from the press molding die, annealed, and subjected to mechanical processing including polishing to produce a spherical lens composed of various glasses produced in Example 1.

(Example 4)

The glass block produced by solidifying the molten glass produced in Example 1 was annealed, and the machining including polishing was performed to produce a spherical lens made of various glasses produced in Example 1.

(Example 5)

The spherical lens produced in Examples 2 to 4 was bonded to a spherical lens made of other types of glass to produce a cemented lens. The cemented surface of the spherical lens produced in Examples 2 to 4 is convex, and the cemented surface of the spherical lens made of other types of glass is concave. The two cemented surfaces are produced so that the absolute values of the curvature radii are equal to each other. A UV-curable adhesive for bonding an optical element is coated on the bonding surface, and the two lenses are bonded to each other with the bonding surface. Thereafter, the spherical lens produced in Examples 2 to 4 was used to irradiate the adhesive applied to the adhesive surface with ultraviolet rays to cure the adhesive.

A cemented lens was produced as described above. A cemented lens is a lens having a sufficiently high cementing strength and a sufficient level of optical performance.

Finally, the foregoing methods are summarized.

According to an embodiment, it is possible to provide a glass including at least La ₂ O ₃ , Y ₂ O ₃ , ZrO ₂ , ZnO, Nb ₂ O ₅ , and one or both selected from B ₂ O ₃ and SiO ₂ . In terms of mass%, the total content of B ₂ O ₃ and SiO ₂ is 28 to 38%, and the total content of La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ and Yb ₂ O ₃ is 48 to 60%. , Gd ₂ O ₃ content is less than 3%, Yb ₂ O ₃ content is less than 2%, ZrO ₂ content is 2 to 14%, WO ₃ content is less than 1%, the total of MgO, CaO, SrO and BaO The content is 5% or less, the mass ratio ((La ₂ O ₃ + Y ₂ O ₃ ) / (La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ )) is 0.94 or more, and the mass ratio ( (La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ ) / (B ₂ O ₃ + SiO ₂ )) is 1.9 or less, and the mass ratio (Nb ₂ O ₅ / (La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ + Nb ₂ O ₅ + TiO ₂ + WO ₃ )) is 0.003 or more, and the mass ratio (ZnO / (ZrO ₂ + Nb ₂ O ₅ + Ta ₂ O ₅ ) ) Is 0.2 to 1.4, the mass ratio (ZnO / Y ₂ O ₃ ) is 0.30 or more, and the mass ratio ((Li ₂ O + ZnO) / (La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ + ZrO ₂ + Nb ₂ O ₅ + Ta ₂ O ₅ )) is 0.11 or less, the refractive index nd ranges from 1.75 to 1.80, and the Abbe number νd ranges from 47 to 5 2.

The above-mentioned glass is a glass having a refractive index and an Abbe number within the above-mentioned range, and can be stably supplied because the content of Gd ₂ O _{3 and the} content of Yb ₂ O ₃ are reduced, and by satisfying the above-mentioned content and mass ratio, it is possible to suppress Generation of melts and crystallization during glass manufacturing.

In one embodiment, from the viewpoint of further improving the thermal stability of the glass, the Y ₂ O ₃ content is preferably less than 12% by mass.

In one embodiment, it is preferable that the glass transition temperature of the glass is 645 ° C or higher from the viewpoint of workability such as grinding and polishing.

The glass described above can be used to produce a glass material for press molding, an optical element blank, and an optical element. That is, according to another embodiment, the glass material for press molding which consists of the said glass, an optical element blank, and an optical element are provided.

Moreover, according to another embodiment, the manufacturing method of the glass material for press molding is provided, Comprising: The process of shaping | molding the said glass into the glass material for press molding is provided.

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

According to still another embodiment, a method for manufacturing an optical element blank includes a step of molding the glass into an optical element blank.

According to yet another embodiment, a method for manufacturing an optical element is provided, which includes the step of manufacturing the optical element by grinding and / or polishing the blank of the optical element.

The embodiments disclosed this time are illustrative in all aspects and should be considered non-limiting. The scope of the present invention is not expressed by the above description but by the scope of patent application, and actually includes all changes within the meaning and scope equivalent to the scope of patent application.

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

In addition, it is needless to say that any two or more items described as items exemplified in the specification or preferable ranges can be arbitrarily combined.

Industrial availability

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

Claims (6)

A glass containing at least La ₂ O ₃ , Y ₂ O ₃ , ZrO ₂ , ZnO, Nb ₂ O ₅ , and one or both selected from B ₂ O ₃ and SiO ₂ , expressed in mass%: B ₂ The total content of O ₃ and SiO ₂ is 28 ~ 38%; the total content of La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ and Yb ₂ O ₃ is 48 ~ 60%; the content of Gd ₂ O ₃ is less than 3%; Yb ₂ O ₃ content is less than 2%; ZrO ₂ content is 2 to 14%; WO ₃ content is less than 1%; the total content of MgO, CaO, SrO and BaO is less than 5%; the mass ratio ( (La ₂ O ₃ + Y ₂ O ₃ ) / (La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ )) is 0.94 or more, and the mass ratio ((La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ ) / (B ₂ O ₃ + SiO ₂ )) is 1.9 or less; mass ratio (Nb ₂ O ₅ / (La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ + Nb ₂ O ₅ + TiO ₂ + WO ₃ )) is 0.003 or more; the mass ratio (ZnO / (ZrO ₂ + Nb ₂ O ₅ + Ta ₂ O ₅ )) is 0.2 to 1.4; the mass ratio ( ZnO / Y ₂ O ₃ ) is 0.40 or more; mass ratio ((Li ₂ O + ZnO) / (La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ + ZrO ₂ + Nb ₂ O ₅ + Ta ₂ O ₅ )) is 0.11 or less; the refractive index nd ranges from 1.75 to 1.80, and the Abbe number νd ranges from 47 to 52. The glass according to item 1 of the scope of patent application, wherein the content of Y ₂ O ₃ is less than 12% by mass. The glass according to item 1 or 2 of the scope of patent application, wherein the glass transition temperature is 645 ° C or higher. A glass material for press molding is composed of the glass described in any one of claims 1 to 3 of the scope of patent application. An optical element blank is composed of the glass described in any one of claims 1 to 3 of the scope of patent application. An optical element is composed of the glass described in any one of claims 1 to 3 of the scope of patent application.