阅读说明：本技术 光学玻璃及光学元件 (Optical glass and optical element ) 是由 佐佐木创 桑谷俊伍 于 2021-05-13 设计创作，主要内容包括：本发明提供折射率及硬度高的光学玻璃,其以质量基准计,SiO-(2)含量为3.00％以上且20.00％以下、TiO-(2)含量为20.00％以上且40.00％以下、Nb-(2)O-(5)含量为3.00％以上且15.00％以下、La-(2)O-(3)含量为20.00％以上且50.00％以下、ZrO-(2)含量为3.00％以上且15.00％以下,质量比(B-(2)O-(3)/La-(2)O-(3))为0.070以下,质量比(B-(2)O-(3)/SiO-(2))为0.700以下,质量比((TiO-(2)+Nb-(2)O-(5))/(SiO-(2)+B-(2)O-(3)))为2.00以上,并且质量比((ZnO+La-(2)O-(3)+Gd-(2)O-(3)+Y-(2)O-(3)+ZrO-(2)+Nb-(2)O-(5)+TiO-(2))/(SiO-(2)+B-(2)O-(3)))为7.00以上。(The present invention provides an optical glass having a high refractive index and high hardness, which is SiO on a mass basis 2 TiO with a content of 3.00-20.00% 2 A content of 20.00% to 40.00%, Nb 2 O 5 La in an amount of 3.00% to 15.00% 2 O 3 ZrO in an amount of 20.00% to 50.00% 2 The content is 3.00-15.00% by mass (B) 2 O 3 /La 2 O 3 ) Is less than 0.070, and has a mass ratio (B) 2 O 3 /SiO 2 ) Is 0.700 or less in mass ratio ((TiO) 2 +Nb 2 O 5 )/(SiO 2 +B 2 O 3 ) 2.00 or more and a mass ratio ((ZnO + La)) 2 O 3 +Gd 2 O 3 +Y 2 O 3 +ZrO 2 +Nb 2 O 5 +TiO 2 )/(SiO 2 +B 2 O 3 ) ) 7.00 or more.)

1. An optical glass in which, on a mass basis,

SiO₂the content is 3.00% or more and 20.00% or less,

TiO₂the content is 20.00% or more and 40.00% or less,

Nb₂O₅the content is 3.00% or more and 15.00% or less,

La₂O₃the content is 20.00% or more and 50.00% or less,

ZrO₂the content is 3.00% or more and 15.00% or less,

B₂O₃content relative to La₂O₃Mass ratio of contents (B)₂O₃/La₂O₃) Is less than 0.070, and the content of the coating is less than 0.070,

B₂O₃content relative to SiO₂Mass ratio of contents (B)₂O₃/SiO₂) Is a content of not more than 0.700%,

TiO₂and Nb₂O₅In total relative to SiO₂And B₂O₃(mass ratio of total content of ((TiO))₂+Nb₂O₅)/(SiO₂+B₂O₃) ) is not less than 2.00 a,

and ZnO, La₂O₃、Gd₂O₃、Y₂O₃、ZrO₂、Nb₂O₅And TiO₂In total relative to SiO₂And B₂O₃(mass ratio of total content of ((ZnO + La))₂O₃+Gd₂O₃+Y₂O₃+ZrO₂+Nb₂O₅+TiO₂)/(SiO₂+B₂O₃) ) 7.00 or more.

2. The optical glass according to claim 1,

SiO₂in a content relative to TiO₂Mass ratio of contents (SiO)₂/TiO₂) Is more than 0.280And 0.430 or less.

3. The optical glass according to claim 1 or 2,

La₂O₃、Gd₂O₃and Y₂O₃Total content of (La)₂O₃+Gd₂O₃+Y₂O₃) Is 40.00 mass% or more and 55.00 mass% or less.

4. The optical glass according to any one of claims 1 to 3, wherein the refractive index nd is 2.000 or more.

5. The optical glass according to any one of claims 1 to 4, which has a Vickers hardness Hv of 780kgf mm^-2The above.

6. The optical glass according to any one of claims 1 to 5, wherein Abbe number ν d is 22.00 or more.

7. An optical element formed of the optical glass as defined in any one of claims 1 to 6.

Technical Field

The present invention relates to an optical glass and an optical element.

Background

An optical glass having a high refractive index is disclosed in, for example, patent document 1.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2019-116408

Disclosure of Invention

Problems to be solved by the invention

An optical glass having a high refractive index can be formed into a cemented lens by combining a lens formed of the glass with another lens formed of a glass having a different dispersion property, for example, thereby compensating for chromatic aberration and achieving miniaturization of an optical system. Therefore, the optical glass is useful as a material for an optical element constituting a projection optical system such as an imaging optical system and a projector.

The physical properties desired for the optical glass include high hardness. High-hardness optical glass is preferable from the viewpoint of improving the yield because it has excellent machinability and is less likely to cause cracks, fractures, and the like in machining such as polishing and grinding.

In view of the above, an object of one embodiment of the present invention is to provide an optical glass having a high refractive index and high hardness.

Means for solving the problems

One embodiment of the present invention relates to an optical glass in which SiO is present on a mass basis₂TiO with a content of 3.00-20.00%₂A content of 20.00% to 40.00%, Nb₂O₅La in an amount of 3.00% to 15.00%₂O₃ZrO in an amount of 20.00% to 50.00%₂The content is more than 3.00% and less than 15.00%, B₂O₃Content relative to La₂O₃Mass ratio of contents (B)₂O₃/La₂O₃) Is less than 0.070, B₂O₃Content relative to SiO₂Mass ratio of contents (B)₂O₃/SiO₂) Less than 0.700, TiO₂And Nb₂O₅In total relative to SiO₂And B₂O₃(mass ratio of total content of ((TiO))₂+Nb₂O₅)/(SiO₂+B₂O₃) 2.00 or more and ZnO, La₂O₃、Gd₂O₃、Y₂O₃、ZrO₂、Nb₂O₅And TiO₂In total relative to SiO₂And B₂O₃(mass ratio of total content of ((ZnO + La))₂O₃+Gd₂O₃+Y₂O₃+ZrO₂+Nb₂O₅+TiO₂)/(SiO₂+B₂O₃) ) 7.00 or more.

The optical glass has the glass composition. Thus, the optical glass may be an optical glass having a high refractive index and high hardness.

ADVANTAGEOUS EFFECTS OF INVENTION

According to one embodiment of the present invention, an optical glass having a high refractive index and high hardness can be provided. Further, according to an embodiment of the present invention, an optical element formed of the optical glass can be provided.

Detailed Description

[ optical glass ]

< glass composition >

In the present invention and the present specification, the glass composition is expressed by an oxide-based glass composition. Here, the "oxide-based glass composition" refers to a glass composition obtained by converting all glass raw materials into substances present in the form of oxides in glass through decomposition at the time of melting. Unless otherwise specified, the glass composition is represented by mass basis (mass%, mass ratio).

The glass composition in the present invention and the present specification can be determined by a method such as ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry). Quantitative analysis was performed on each element using ICP-AES. Then, the analysis values were converted to oxide representation. The analytical value by ICP-AES may sometimes contain a measurement error of about ± 5% of the analytical value, for example. Therefore, the value expressed by the oxide converted from the analysis value may similarly include an error of about ± 5%.

In the present invention and the present specification, the content of a constituent component of 0.00%, or the absence or absence of the constituent component means that the constituent component is not substantially contained, the content of the constituent component is not more than the impurity level, and the not more than the impurity level means, for example, less than 0.01%.

Hereinafter, the glass composition of the optical glass will be described in more detail.

SiO₂Is a component forming the network of the glass. SiO from the viewpoint of improving the stability of the glass₂The content is 3.00% or more, preferably 4.00% or more, and more preferably 5.00% or more, 6.00% or more, and 7.00% or more in this order. In addition, from the viewpoint of improving the stability of the glass, SiO₂The content is 20.00% or less, preferably 19.00% or less, more preferably 18.00% or less, 17.00% or less, 16.00% or less, 15.00% or less, 14.00% or less, 13.00% or less, and 12.00% or less in this order.

TiO₂And Nb₂O₅All of them are components (high refractive index components) which exhibit an action of increasing the refractive index.

From the viewpoint of increasing the refractive index, TiO₂The content is 20.00% or more, preferably 21.00% or more, and more preferably 22.00% or more, 23.00% or more, and 24.00% or more in this order. In addition, TiO is considered to improve the stability of the glass₂The content is 40.00% or less, preferably 39.00% or less, and more preferably 38.00% or less, 37.00% or less, 36.00% or less, 35.00% or less, 34.00% or less, 33.00% or less, 32.00% or less, 31.00% or less, 30.00% or less, and 29.00% or less in this order.

Nb from the viewpoint of increasing the refractive index₂O₅The content is 3.00% or more, preferably 4.00% or more, and more preferably 5.00% or more, 6.00% or more, and 7.00% or more in this order. Further, from the viewpoint of improving the stability of the glass, Nb is₂O₅The content is 15.00% or less, preferably 14.00% or less, and more preferably 13.00% or less, 12.00% or less, 11.00% or less, 10.00% or less, and 9.00% or less in this order.

La₂O₃Is a component having an effect of increasing the refractive index without increasing the dispersion (without decreasing the abbe number). From high refractive index and low dispersionFrom the viewpoint of conversion, La₂O₃The content is 20.00% or more, preferably 22.00% or more, and more preferably 24.00% or more, 26.00% or more, 28.00% or more, 30.00% or more, 32.00% or more, 34.00% or more, 36.00% or more, and 38.00% or more in this order. In addition, La is considered to improve the stability of the glass₂O₃The content is 50.00% or less, preferably 48.00% or less, more preferably 46.00% or less, and 44.00% or less in this order.

ZrO from the viewpoint of improving the stability of the glass₂The content is 3.00% or more and 15.00% or less. ZrO (ZrO)₂The content is preferably 4.00% or more, more preferably 5.00% or more. In addition, ZrO₂The content is preferably 13.00% or less, more preferably 11.00% or less, and further preferably 9.00% or less.

From the viewpoint of increasing the refractive index and reducing the dispersion, B₂O₃Relative to La₂O₃Mass ratio of contents (B)₂O₃/La₂O₃) Is 0.070 or less, preferably 0.069 or less, more preferably 0.068 or less, 0.067 or less, 0.066 or less, 0.065 or less, 0.064 or less, 0.063 or less, 0.062 or less, 0.061 or less, or 0.060 or less. Mass ratio (B)₂O₃/La₂O₃) It may be 0.000 or more than 0.000, and from the viewpoint of improving the stability of the glass, it is preferably 0.010 or more, and more preferably 0.015 or more, 0.018 or more, 0.020 or more, and 0.022 or more in this order.

From the viewpoint of increasing the hardness of the glass, B₂O₃Content relative to SiO₂Mass ratio of contents (B)₂O₃/SiO₂) Is 0.700 or less. In addition, the mass ratio (B) is also preferable from the viewpoint of improvement in glass stability and increase in refractive index₂O₃/SiO₂) Is 0.700 or less. Mass ratio (B)₂O₃/SiO₂) Preferably 0.600 or less, more preferably 0.500 or less and 0.400 or less. Mass ratio (B)₂O₃/SiO₂) May be 0.000 or more than 0.000 from the viewpoint of improving the stability of the glassIn view of this, it is preferably 0.050 or more, and more preferably 0.070 or more and 0.100 or more in this order.

From the viewpoint of increasing the refractive index, TiO₂And Nb₂O₅In total relative to SiO₂And B₂O₃(mass ratio of total content of ((TiO))₂+Nb₂O₅)/(SiO₂+B₂O₃) ) is 2.00 or more, preferably 2.50 or more, more preferably 3.00 or more. Further, from the viewpoint of improving the stability of the glass, the mass ratio ((TiO)₂+Nb₂O₅)/(SiO₂+B₂O₃) Preferably 4.50 or less, more preferably 4.25 or less, 4.00 or less, and 3.75 or less.

From the viewpoint of increasing the refractive index, ZnO and La₂O₃、Gd₂O₃、Y₂O₃、ZrO₂、Nb₂O₅And TiO₂In total relative to SiO₂And B₂O₃(mass ratio of total content of ((ZnO + La))₂O₃+Gd₂O₃+Y₂O₃+ZrO₂+Nb₂O₅+TiO₂)/(SiO₂+B₂O₃) ) is 7.00 or more, preferably 7.20 or more, more preferably 7.40 or more, 7.60 or more, 7.80 or more, 8.00 or more in this order. Further, from the viewpoint of improving the stability of the glass, the mass ratio ((ZnO + La)₂O₃+Gd₂O₃+Y₂O₃+ZrO₂+Nb₂O₅+TiO₂)/(SiO₂+B₂O₃) Preferably 10.00 or less, more preferably 9.80 or less, 9.60 or less, and 9.40 or less.

Hereinafter, the glass composition of the optical glass will be described in more detail.

B₂O₃The content of the component that improves the stability and meltability of the glass may be 0.00% or more, more than 0.00%, 0.50% or more, or 1.00% or more. In addition, the stability of the glass is maintained, and the refractive index and the hardness are further improvedFrom the viewpoint of (A), B₂O₃The content is preferably 5.00% or less, more preferably 4.50% or less, and more preferably 4.00% or less, 3.50% or less, and 3.00% or less in this order.

ZnO is a component effective for adjusting dispersion (abbe number), and also a component having an action of improving the meltability of glass, and the content thereof may be 0.00% or more, more than 0.00%, 0.50% or more, or 1.00% or more. From the viewpoint of maintaining the stability of the glass and further improving the refractive index, the ZnO content is preferably 3.00% or less, and more preferably 2.50% or less, 2.00% or less, and 1.50% or less in this order.

Gd₂O₃、Y₂O₃And Yb₂O₃Are components having the effect of increasing the refractive index without increasing the dispersion (without decreasing the abbe number).

Gd₂O₃The content may be 0.00% or more than 0.00%, preferably 0.50% or more, more preferably 1.00% or more, 2.00% or more, 3.00% or more, 4.00% or more, 5.00% or more, and 6.00% or more in this order. In addition, Gd₂O₃Is a component for increasing the specific gravity of the glass component, and is also an expensive component. From these viewpoints, Gd₂O₃The content is preferably 10.00% or less, and more preferably 9.00% or less, 8.00% or less, and 7.00% or less in this order.

Y₂O₃The content may be 0.00% or more, more than 0.00%, 0.10% or more, 0.20% or more, 0.30% or more, or 0.40% or more. From the viewpoint of further improving the stability of the glass, Y is₂O₃The content is preferably 3.00% or less, and more preferably 2.50% or less, 2.00% or less, 1.50% or less, 1.00% or less, and 0.50% or less in this order.

Yb₂O₃The content may be 0.00% or more, more than 0.00%, 0.10% or more, 0.20% or more, 0.30% or more, or 0.40% or more. From the viewpoint of suppressing the increase in specific gravity of the glass, Yb₂O₃The content is preferably 3.00% or less, or 2.50% or less, 2.00% or less, 1.50% or less, 1.00% or less,The order of 0.50% or less is more preferable.

From the viewpoint of further increasing the refractive index and from the viewpoint of reducing the dispersion, La₂O₃、Gd₂O₃And Y₂O₃And the total content (La)₂O₃+Gd₂O₃+Y₂O₃) Preferably 35.00% or more, more preferably 37.50% or more, 40.00% or more, 42.50% or more, and 45.00% or more in this order. The total content (La) is determined from the viewpoint of improving the stability of the glass₂O₃+Gd₂O₃+Y₂O₃) Preferably 60.00% or less, more preferably 57.50% or less, 55.00% or less, 52.5% or less, and 50.00% or less.

SiO from the viewpoint of improving the stability of the glass₂In a content relative to TiO₂Mass ratio of contents (SiO)₂/TiO₂) Preferably 0.270 or more, more preferably 0.280 or more, 0.290 or more, and 0.300 or more. Mass ratio (SiO) from the viewpoint of further increasing the refractive index₂/TiO₂) Preferably 0.460 or less, and more preferably 0.450 or less, 0.440 or less, 0.430 or less, and 0.420 or less.

WO₃The content may be 0.00% or more than 0.00%. Containing a large amount of WO₃Since the light absorption edge on the shorter wavelength side of the spectral transmittance of the glass (2) has a longer wavelength, the transmittance of ultraviolet rays is remarkably low. On the other hand, in an optical system such as an imaging optical system such as a camera lens or a projection optical system such as a projector, optical elements (lenses) formed of optical glasses having different optical characteristics may be joined to each other in order to correct chromatic aberration. A cemented lens in which lenses are cemented to each other is generally manufactured as follows. First, an ultraviolet-curable adhesive is applied to the bonding surfaces of the lenses to bond the lenses to each other, and then the adhesive is cured by irradiating ultraviolet light through the lenses. Here, if the ultraviolet transmittance of the optical glass constituting the lens is low, it takes time to cure the adhesive or curing becomes difficult, and therefore, it is desirable as the optical glass used for the above optical systemAn optical glass having absorption characteristics suitable for the production of a cemented lens, in which the wavelength of the light absorption edge on the short wavelength side of the spectral transmittance is shortened, is desired. According to this, WO₃The content is preferably 2.00% or less, more preferably 1.50% or less, 1.00% or less, 0.50% or less, and 0.10% or less in this order, and still more preferably 0.00%.

Ta₂O₅The content may be 0.00% or more than 0.00%. Ta₂O₅Is an expensive component among the high refractive index components, and is also a component for increasing the specific gravity of the glass. Therefore, from the viewpoint of suppressing the production cost of glass to supply glass more stably and suppressing the increase in specific gravity, Ta₂O₅The content is preferably 5.00% or less, more preferably 4.00% or less, 3.00% or less, 2.00% or less, 1.00% or less, 0.50% or less, and 0.10% or less in this order, and still more preferably 0.00%.

Li₂O、Na₂O、K₂O、Cs₂O has an effect of improving the meltability of the glass, but when introduced in a large amount, the refractive index may be lowered and the stability of the glass may be lowered. Thus, Li₂O、Na₂O、K₂O and Cs₂The total content of O is preferably 5.00% or less, more preferably 2.00% or less, 1.00% or less, and 0.80% or less in this order, and may be 0.00%.

MgO, CaO, SrO and BaO have an effect of improving the meltability of the glass, but when they are introduced in a large amount, the refractive index may be lowered and the stability of the glass may be lowered. Therefore, the total content of MgO, CaO, SrO, and BaO is preferably 0.00% or more and 5.00% or less, more preferably 2.00% or less, 1.00% or less, and 0.80% or less in this order, and may be 0.00%.

GeO₂Is a component forming a network and also plays a role of increasing the refractive index, and therefore, is a component capable of increasing the refractive index while maintaining the stability of the glass. However, GeO₂It is also a very expensive component, and therefore, it is also a component whose content is desired to be controlled. GeO₂The content is preferably 0.00% or more and 2.00% or less, more preferably 1.00% or less and 0.80% or less in this order, and alsoMay be 0.00%.

Bi₂O₃The effect of improving the refractive index and also improving the stability of the glass is exerted. From the viewpoint of further shortening the absorption edge on the short wavelength side of the spectral transmittance, Bi₂O₃The content is preferably 0.00% or more and 2.00% or less, more preferably 1.00% or less and 0.80% or less in this order, and may be 0.00%.

Al₂O₃The content is preferably 0.00% or more and 2.00% or less, more preferably 1.00% or less and 0.80% or less in this order, and may be 0.00%. Al (Al)₂O₃The component is a component which can exert an effect of improving the stability and chemical durability of the glass by introducing a small amount of the component.

Sb₂O₃Is an ingredient that can be added as a clarifying agent. The effect of suppressing the decrease in light transmittance due to the incorporation of impurities such as Fe can be exhibited by adding a small amount of Sb₂O₃The amount of (3) is added, the coloring of the glass tends to increase. Thus, Sb₂O₃The amount of (b) is preferably 0.00% or more and 0.10% or less, more preferably 0.00% or more and 0.05% or less, and further preferably 0.00% or more and 0.03% or less in terms of an addition ratio. Sb based on addition ratio₂O₃The content is defined as₂O₃Sb in mass% when the total content of the other glass components is 100 mass%₂O₃The content of (a).

SnO₂However, when the addition amount exceeds 1.00%, the glass is colored, and when the glass is heated, softened, and subjected to reshaping such as press molding, Sn becomes a starting point of crystal nucleus formation and tends to devitrify. Thus, it is preferable to use SnO in an external scale₂The amount of (b) is 0.00% or more and 1.00% or less, more preferably 0.00% or more and 0.50% or less, and particularly preferably not added. SnO based on external ratio₂The content is that SnO₂SnO expressed in mass% when the total content of other glass components is 100 mass%₂The content of (a).

The optical glass can be produced without containing such components as Lu and Hf. Lu and Hf are expensive components, and therefore, Lu is preferably used₂O₃、HfO₂The content of (b) is controlled to 0.00% or more and 2.00% or less, more preferably 0.00% or more and 1.00% or less, still more preferably 0.00% or more and 0.80% or less, still more preferably 0.00% or more and 0.10% or less, and particularly preferably no introduction of Lu₂O₃Without introducing HfO₂。

In consideration of environmental influences, it is preferable that As, Pb, U, Th, Te, and Cd are not introduced.

In addition, from the viewpoint of exhibiting excellent light transmittance of the glass, it is preferable not to introduce a substance which causes coloring such as Cu, Cr, V, Fe, Ni, and Co.

F is a component that significantly increases the volatility of the glass during melting and causes a reduction in the stability and homogeneity of the optical properties of the glass. The content of F can be defined as a content (unit: mass%) in an additive ratio of the oxide-based F element to the total content of 100 mass% of the glass composition, which is determined as described above. In the above optical glass, the content of F thus defined is preferably less than 0.10%, more preferably less than 0.08%, and further preferably less than 0.05%. The content of F may be 0.00% or more, or may be 0.00%.

< Property of glass >

(refractive index nd)

The optical glass may be a glass having a high refractive index. The refractive index nd of the optical glass is preferably 2.000 or more, and more preferably 2.020 or more, 2.040 or more, and 2.060 or more in this order. The refractive index nd of the optical glass may be, for example, 2.160 or less, 2.150 or less, 2.140 or less, or 2.130 or less. In the present invention and the present specification, "refractive index" means "refractive index nd".

(Abbe number vd)

The abbe number ν d is a value indicating a property related to dispersibility, and ν d ═ d (nd-1)/(nF-nC) is expressed by using refractive indices nd, nF, and nC of a d line, an F line, and a C line. From the viewpoint of usefulness as a material for optical elements, the abbe number ν d of the above optical glass is preferably 21.00 or more, and more preferably 21.50 or more, 22.00 or more, 22.25 or more, 22.50 or more, 23.00 or more, 23.50 or more, 24.00 or more, 24.50 or more, and 25.00 or more in this order.

(Vickers hardness Hv)

The optical glass may be a high-hardness glass. As an index of hardness, vickers hardness Hv may be mentioned. The vickers hardness Hv in the present invention and the present specification is based on JIS Z2244: 2009 is a value obtained by the method described in the following examples.

The Vickers hardness Hv of the optical glass is preferably 780kgf mm^-2Above, in 790kgf mm^-2Above, 800kgf mm^-2Above 810kgf mm^-2The above sequence is more preferred. The Vickers hardness Hv of the optical glass may be, for example, 910kgf mm^-2Hereinafter, 900kgf mm^-2Hereinafter, or 890kgf mm^-2Hereinafter, the upper limit of the vickers hardness Hv of the optical glass is not particularly limited, since it is preferable from the viewpoint of suppressing the occurrence of cracks, fractures, and the like in the machining when the value of the vickers hardness Hv is large.

(specific gravity)

In an optical element constituting an optical system, refractive power is determined by the refractive index of glass constituting the optical element and the curvature of an optically functional surface (a surface on which light to be controlled enters and exits) of the optical element. If it is desired to increase the curvature of the optically functional surface, the thickness of the optical element is also increased. As a result, the optical element 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, the weight of the optical element having a certain refractive power can be reduced as long as the increase in the specific gravity of the glass can be suppressed and the refractive index can be increased.

From the above viewpoint, the specific gravity of the optical glass is preferably 5.20 or less, and more preferably 5.15 or less and 5.10 or less in this order. The lower the specific gravity, the more preferable from the viewpoint of weight reduction of the optical element, and therefore, the lower limit of the specific gravity of the optical glass is not particularly limited. In one embodiment, the specific gravity may be 4.75 or more, 4.80 or more, or 4.85 or more.

(degree of coloration. lamda.5)

The light transmittance of the glass, specifically, the suppression of the wavelength increase of the light absorption edge on the short wavelength side can be evaluated by the coloring degree λ 5 and/or the coloring degree λ 70. The coloring degree λ 5 is a wavelength at which the spectral transmittance (including surface reflection loss) of a glass having a thickness of 10mm from an ultraviolet region to a visible region reaches 5%. The coloring degree λ 70 is a wavelength at which the spectral transmittance (including surface reflection loss) of a glass having a thickness of 10mm from the ultraviolet region to the visible region reaches 70%. λ 5 and λ 70 shown in examples described later are values measured in a wavelength region of 250 to 700 nm. More specifically, the spectral transmittance is a spectral transmittance obtained by using a glass sample polished to a thickness of 10.0 ± 0.1mm and having mutually parallel flat surfaces and by causing light to enter the polished surface from a direction perpendicular thereto, that is, Iout/Iin when the intensity of light entering the glass sample is Iin and the intensity of light transmitted through the glass sample is Iout.

The absorption edge on the short wavelength side of the spectral transmittance can be quantitatively evaluated from the coloring degree λ 5 and/or λ 70. When lenses are bonded to each other with an ultraviolet-curable adhesive in order to produce a bonded lens, for example, the following operations may be performed: the adhesive is irradiated with ultraviolet rays through the optical element to cure the adhesive. From the viewpoint 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 and/or λ 70 can be used. The optical glass preferably exhibits λ 5 of 420nm or less. λ 5 is preferably 415nm or less, 410nm or less, 405nm or less, 400nm or less, and 395nm or less in this order. The optical glass preferably exhibits a λ 70 of 600nm or less. λ 70 is preferably 595nm or less, 590nm or less, 585nm or less, 580nm or less, or 575nm or less in this order. The lower λ 5 and λ 70 are preferable, and the lower limit thereof is not particularly limited.

(glass transition temperature Tg)

From the viewpoint of machinability, the glass transition temperature Tg of the optical glass is preferably 640.0 ℃ or higher, more preferably 650.0 ℃ or higher, and still more preferably 660.0 ℃ or higher. Glass having a high glass transition temperature is preferred because it tends to be less likely to be broken when the glass is subjected to mechanical processing such as cutting, grinding, polishing, etc. On the other hand, from the viewpoint of reducing the burden on the annealing furnace and the molding die, the glass transition temperature Tg is preferably 850.0 ℃ or lower, and more preferably 840.0 ℃ or lower, 830.0 ℃ or lower, 820.0 ℃ or lower, and 810.0 ℃ or lower in this order.

(Tx－Tg)

The glass stability can be determined by using the difference between the crystallization temperature Tx and the glass transition temperature Tg (Tx-Tg) as an index of resistance to devitrification when the glass that has been once solidified is reheated. The devitrification resistance is considered to be more excellent as the difference (Tx-Tg) between the crystallization temperature Tx and the glass transition temperature Tg is larger.

The glass transition temperature Tg and the crystallization temperature Tx are determined as follows. In the differential scanning calorimetry, if the temperature of a glass sample is raised, an endothermic behavior accompanying the change in specific heat, that is, an endothermic peak, appears, and when the temperature is further raised, an exothermic peak appears. In the differential scanning calorimetry analysis, a differential scanning calorimetry curve (DSC curve) is obtained in which the horizontal axis represents the temperature and the vertical axis represents the amount corresponding to the endothermic heat release of the sample. In this graph, the glass transition temperature Tg is defined as the intersection of the base line and a tangent line from the base line to a point at which the slope becomes maximum when the endothermic peak appears, and the crystallization temperature Tx is defined as the intersection of the base line and a tangent line at a point at which the slope becomes maximum when the exothermic peak appears. The glass transition temperature Tg and the crystallization temperature Tx can be measured as follows: the glass was sufficiently crushed in a mortar or the like, and the temperature was raised at a rate of 10 ℃ per minute using a differential scanning calorimeter as a sample.

In the reheat press forming method of heating and softening a glass raw material to form the glass raw material into a desired shape, the glass raw material is heated to a high temperature higher than the glass transition temperature. Since devitrification occurs when the temperature of the glass during forming reaches the crystallization temperature range, a glass having a small (Tx-Tg) tends to be disadvantageous in preventing devitrification and forming. On the other hand, glass having a large (Tx-Tg) value tends to be advantageously shaped by reheating and softening without devitrification.

For the above reasons, the difference (Tx-Tg) between the crystallization temperature Tx and the glass transition temperature Tg is preferably 80.0 ℃ or higher, and more preferably 90.0 ℃ or higher, 100.0 ℃ or higher, 110.0 ℃ or higher, and 120.0 ℃ or higher in this order. (Tx-Tg) may be, for example, 300.0 ℃ or lower, 280.0 ℃ or lower, 260.0 ℃ or lower, 240.0 ℃ or lower, 220.0 ℃ or lower, or 200.0 ℃ or lower, or may be higher than the values exemplified here.

From the viewpoint of crystallization resistance, the crystallization temperature Tx is preferably 850.0 ℃ or higher, and more preferably 860.0 ℃ or higher, 870.0 ℃ or higher, and 880.0 ℃ or higher in this order.

(partial Dispersion characteristics)

From the viewpoint of chromatic aberration correction, the optical glass is preferably a glass having small dispersion in the relative region when the abbe number ν d is fixed.

Here, F is expressed as (ng-nF)/(nF-nc) using the refractive indices ng, nF, nc for the g-line, F-line, and c-line, respectively, with respect to the partial dispersion Pg. From the viewpoint of providing a glass suitable for chromatic aberration correction of a high order, the relative partial dispersion Pg, F of the optical glass is preferably 0.550 or more, more preferably 0.575 or more, and preferably 0.715 or less, more preferably 0.690 or less.

< method for producing optical glass >

The optical glass can be obtained as follows: oxides, carbonates, sulfates, nitrates, hydroxides, and the like as raw materials are weighed and mixed so as to obtain a target glass composition, and sufficiently mixed to prepare a mixed batch, and the mixed batch is heated, melted, defoamed, and stirred in a melting vessel to prepare a homogeneous and bubble-free molten glass, and the homogeneous and bubble-free molten glass is molded to obtain an optical glass. Specifically, the resin composition can be produced by a known melting 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 optical glass;

an optical element blank comprising the above optical glass.

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

a method for producing a glass material for press molding, comprising: a step of molding the optical glass into a glass material for press molding;

a method for manufacturing an optical element blank, comprising: a step of press-molding the glass material for press-molding optical glass using a press-molding die to produce an optical element blank;

a method for manufacturing an optical element blank, comprising: and a step of forming the optical glass into an optical element blank.

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

In another aspect, the optical element blank may 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 softened state by heating with a press molding die. The heating and the press molding can be performed in the air. By annealing after press forming, strain in the glass is reduced, and a homogeneous optical element blank can be obtained.

The glass material for press molding includes a material called a glass gob for press molding (glass gob) which is used for press molding for producing an optical element blank as it is, and a material which is subjected to mechanical processing such as cutting, grinding, polishing, etc., is subjected to a glass gob for press molding, and is then subjected to press molding. As the cutting method, the following methods are included: a method in which a groove is formed in a portion to be cut of a surface of a glass sheet by a method called scribing, and a local pressure is applied to the portion of the groove from a back surface of one surface on which the groove is formed, thereby cutting the glass sheet at the portion of the groove; a method of cutting a glass plate with a cutter blade, and the like. Further, as a grinding and polishing method, barrel polishing and the like can be given.

The glass material for press molding can be produced, for example, by casting molten glass into a mold and molding the glass into a glass plate, and cutting the glass plate into a plurality of glass sheets. Alternatively, a glass gob for press molding may be produced by molding a suitable amount of molten glass. The optical element blank may be produced by heating and softening a press-molding glass gob, and press-molding the heated and softened glass gob. A method of manufacturing an optical element blank by reheating, softening, and press-molding glass is called a reheat press method (reheat press method) as compared with a direct press method.

[ optical element and method for producing the same ]

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

The optical element is produced using the optical glass. In the optical element, one or more coating layers such as a multilayer film of an antireflection film or the like may be formed on the glass surface.

Further, according to an aspect of the present invention, there is provided a method for manufacturing an optical element, the method including: and (d) grinding and/or polishing the optical element blank to produce an optical element.

In the above-described method for manufacturing an optical element, mechanical processing such as grinding and polishing can be performed by a known method, and an optical element having high internal quality and surface quality can be obtained by sufficiently cleaning and drying the surface of the optical element after the processing. Thus, 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 optical glass is also suitably used as a lens constituting a joined optical element. Examples of the bonded optical element include an element in which lenses are bonded to each other (bonded lens), an element in which a lens and a prism are bonded to each other, and the like. For example, the bonded optical element can be made by: the joint surfaces of 2 optical elements to be joined are precisely processed (for example, spherical surface polishing) so that their shapes are inverted, an ultraviolet-curable adhesive for joining lenses is applied, the lenses are bonded, and then ultraviolet rays are irradiated through the lenses to cure the adhesive, thereby producing joined optical elements. The glass is preferably used for producing the bonded optical element in this manner. A plurality of optical elements to be bonded can be manufactured by using a plurality of kinds of glasses having different Abbe numbers ν d, respectively, and bonded to each other, thereby manufacturing an element suitable for correction of chromatic aberration.

Examples

The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the embodiments shown in the examples.

(example 1)

The materials for introducing the respective components were weighed and mixed thoroughly so as to have glass compositions shown in the following table, using nitrates, sulfates, carbonates, hydroxides, oxides, boric acids, and the like corresponding thereto, respectively, as the materials.

The prepared raw materials were put into a platinum crucible, and heated and melted. After the melting, the molten glass was poured into a mold, naturally cooled to a temperature around the glass transition temperature, immediately placed in an annealing furnace, annealed within the glass transition temperature range for about 1 hour, and naturally cooled to room temperature in the furnace, whereby each of the optical glasses shown in table 1 (table 1-1 to table 1-3) was obtained.

The following table shows various physical properties of the optical glass thus obtained.

The physical properties of the optical glass were measured by the following methods.

< evaluation of physical Properties of optical glass >

(1) Refractive index nd, Abbe number vd

The glass obtained by cooling at a cooling rate of-30 ℃ per hour was measured for refractive index nd and Abbe number ν d by a refractive index measurement method standardized by the Japan optical glass industry Association.

(2) Vickers hardness Hv

Glass samples having a thickness of 10 ± 0.1mm with 2 flat surfaces facing each other and optically polished were measured under the conditions of a test force of 0.3kgf (2.942N) and a holding time of 15 seconds, based on the measurement method described in japanese industrial standard JIS Z2244: 2009. The measurement was performed 5 times, and the arithmetic mean of the obtained measurement values was used as the vickers hardness v of the glass to be measured.

(3) Glass transition temperature Tg and crystallization temperature Tx

The glass was sufficiently crushed in a mortar, and a glass transition temperature Tg and a crystallization temperature Tx were measured as a sample using a differential scanning calorimetry analyzer (DSC3300SA) manufactured by NETZSCH corporation, with a temperature rise rate of 10 ℃/min.

(4) Specific gravity of

The specific gravity was measured by the archimedes method.

(5) The degree of coloration is λ 5, λ 70

Using a glass sample having a thickness of 10 ± 0.1mm and having 2 optically polished planes opposed to each other, the intensity Iout of light transmitted through the glass sample was measured by a spectrophotometer by entering light of intensity Iin from a direction perpendicular to the polished planes, and the spectral transmittance Iout/Iin was calculated, where λ 5 is a wavelength at which the spectral transmittance becomes 5% and λ 70 is a wavelength at which the spectral transmittance becomes 70%.

(6) Relative partial dispersion Pg, F

The glass obtained by cooling at a cooling rate of-30 ℃/h was measured for refractive indices nF, nc, and ng by a refractometry method standardized by the Japan optical glass Industrial Association, and relative partial dispersions Pg and F were calculated from the measurement results.

(example 2)

Using the various glasses obtained in example 1, a press-molding glass gob (glass gob) was produced. The glass gob was heated and softened in the air, and press-molded with a press mold to produce a lens blank (optical element blank). The produced lens blank was taken out of the press molding die, 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 press-molded with a press mold 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) produced 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 produced in examples 2 to 4 were bonded to spherical lenses made of other types of glass, to produce cemented lenses. The spherical lenses manufactured in examples 2 to 4 had convex bonding surfaces, and the spherical lenses made of other types of glass had concave bonding surfaces. The 2 joint surfaces were prepared so that the absolute values of the radii of curvature were equal to each other. An ultraviolet-curable adhesive for bonding an optical element was applied to the bonding surface, and 2 lenses were bonded to each other at the bonding surface. Then, the adhesive coated on the bonding surface was irradiated with ultraviolet rays through the spherical lens manufactured in examples 2 to 4, and the adhesive was solidified.

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

Finally, the above-described embodiments are summarized.

According to one aspect, there is provided an optical glass in which SiO is present on a mass basis₂TiO with a content of 3.00-20.00%₂A content of 20.00% to 40.00%, Nb₂O₅La in an amount of 3.00% to 15.00%₂O₃ZrO in an amount of 20.00% to 50.00%₂The content is more than 3.00% and less than 15.00%, B₂O₃Content relative to La₂O₃Mass ratio of contents (B)₂O₃/La₂O₃) Is less than 0.070, B₂O₃Content relative to SiO₂Mass ratio of contents (B)₂O₃/SiO₂) Less than 0.700, TiO₂And Nb₂O₅In total relative to SiO₂And B₂O₃(mass ratio of total content of ((TiO))₂+Nb₂O₅)/(SiO₂+B₂O₃) 2.00 or more and ZnO, La₂O₃、Gd₂O₃、Y₂O₃、ZrO₂、Nb₂O₅And TiO₂In total relative to SiO₂And B₂O₃(mass ratio of total content of ((ZnO + La))₂O₃+Gd₂O₃+Y₂O₃+ZrO₂+Nb₂O₅+TiO₂)/(SiO₂+B₂O₃) ) 7.00 or more.

The optical glass may be an optical glass having a high refractive index and high hardness.

In one embodiment, the optical glass contains SiO₂In a content relative to TiO₂Mass ratio of contents (SiO)₂/TiO₂) May be 0.280 or more and 0.430 or less.

In one embodiment, La of the optical glass₂O₃、Gd₂O₃And Y₂O₃Total content of (La)₂O₃+Gd₂O₃+Y₂O₃) The content may be 40.00% or more and 55.00% or less.

In one embodiment, the refractive index nd of the optical glass may be 2.000 or more.

In one embodiment, the Vickers hardness Hv of the optical glass may be 780kgf mm^-2The above.

In one embodiment, the abbe number ν d of the optical glass may be 22.00 or more.

According to one aspect, there is provided an optical element formed of the above optical glass.

It should be understood that the embodiments disclosed herein are all exemplary and not limiting. The scope of the invention is indicated by the appended claims, rather than the foregoing description, and all changes that come within the meaning and range of equivalency of the claims are intended to be embraced therein.

For example, the optical glass according to one embodiment of the present invention can be obtained by adjusting the composition described in the description of the glass composition exemplified above.

It is needless to say that 2 or more of the items exemplified in the description or described as the preferable ranges may be arbitrarily combined.