JP2015147720A - optical glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel optical glass having optical characteristics of high refractive index and low dispersion.SOLUTION: An optical glass contains 40-99.9% Nb+Tain terms of cation%, and 0.1-60% rare earth element ion (excluding the case of 40% Nband 60% La), and further contains Fas anion.

Description

  The present invention relates to an optical glass.

  In recent years, there has been an increasing demand for higher performance of video lenses such as video cameras, general cameras, and cameras attached to mobile phones. Specifically, in order to reduce the size of the lens optical system and to improve the image quality and magnification while suppressing the chromatic aberration of light, the optical glass has high refractive index and low dispersion (high Abbe number) optical characteristics. There is an increasing demand for it.

In order to achieve the above optical characteristics, B ₂ O ₃ —ZnO—La ₂ O ₃ based glass and Bi based glass have been proposed (see, for example, Patent Documents 1 and 2).

JP 2002-362938 JP 2007-106625 A

Although _{B 2 O 3 -ZnO-La 2} O 3 based glass described in Patent Document 1 has a low dispersion property, a high refractive index characteristic are insufficient. There is a tendency for devitrification to occur when an attempt is made to further increase the refractive index of B ₂ O ₃ —ZnO—La ₂ O ₃ glass. On the other hand, Bi-based glass described in Patent Document 2 has a high refractive index characteristic exceeding 2, but has high dispersion, and it is difficult to achieve reduction of chromatic aberration. When trying to achieve low dispersion with Bi-based glass, the refractive index tends to decrease, and it is difficult to maintain high refractive index characteristics.

  In view of the above, an object of the present invention is to provide a novel optical glass having high refractive index and low dispersion optical characteristics.

The optical glass of the present invention has a cation% of Nb ⁵⁺ + Ta ⁵⁺ 40 to 99.9% and rare earth element ions 0.1 to 60% (provided that Nb ⁵⁺ 40% and La ³⁺ 60% containing the excluding), F ^- as the anion, characterized in that it contains.

In the optical glass of the present invention, the total amount of Nb ⁵⁺ , Ta ⁵⁺ and rare earth element ions is preferably 80 cation% or more.

In the optical glass of the present invention, the rare earth element ion is preferably at least one selected from La ³⁺ , Gd ³⁺ , Y ³⁺ , Yb ³⁺ and Ce ⁴⁺ .

In the optical glass of the present invention, it is preferable to contain 0.1% or more of F ^{− in} anion%.

  In the optical glass of the present invention, the refractive index (nd) is preferably 1.85 to 2.5 and the Abbe number (νd) is preferably 30 to 70.

  According to the present invention, it is possible to provide a novel optical glass having high refractive index and low dispersion optical characteristics.

It is typical sectional drawing which shows one Embodiment of the apparatus for manufacturing the optical glass of this invention.

The optical glass of the present invention has a cation% of Nb ⁵⁺ + Ta ⁵⁺ 40 to 99.9% and rare earth element ions 0.1 to 60% (provided that Nb ⁵⁺ 40% and La ³⁺ 60% containing the excluding), F ^- as the anion, characterized in that it contains. The reason for limiting the content of each component in this way will be described below.

Nb ⁵⁺ and Ta ⁵⁺ are components that increase the refractive index. The content of Nb ⁵⁺ + Ta ⁵⁺ is cation%, which is 40 to 99.9%, preferably 40.1 to 95%, and more preferably 41 to 90%. By containing Nb ⁵⁺ + Ta ⁵⁺ in such a large amount, it is possible to achieve optical characteristics with a very high refractive index (for example, nd is 1.85, or more than 2). From the viewpoint of reducing the raw material cost, it is preferable to use Nb ⁵⁺ .

  Rare earth element ions are components for ensuring the stability of glass and improving devitrification resistance and weather resistance. Moreover, there exists an effect which suppresses the raise of a softening point. Furthermore, there is an effect of increasing the refractive index. The content of rare earth element ions is cation%, 0.1 to 60%, preferably 1 to 50%, more preferably 10 to 45%, and more preferably 20 to 40%. Further preferred. By regulating the content of rare earth element ions within the above range, a glass having excellent devitrification resistance and weather resistance and a low softening point can be easily obtained.

Examples of the rare earth element ^{ions, La 3+, Gd 3+, Y} 3+, Yb 3+, Ce 4+, Sc 3+, Pr 3+, Nd 3+, Pm 3+, Sm 3+, Eu 3+, Tb 3+, Dy 3+, Ho 3+, Er 3+ , Tm ³⁺ , Lu ^{3+ and the} like. Among these, La ³⁺ , Gd ³⁺ , Y ³⁺ , Yb ³⁺ or Ce ⁴⁺ is preferable because it is easy to stabilize the glass, and La ³⁺ is more preferable.

From the viewpoint of obtaining high refractive index and low dispersion optical characteristics, the total amount of Nb ⁵⁺ , Ta ⁵⁺ and rare earth element ions is preferably 80% or more and 85% or more in terms of cation%. Is more preferably 90% or more, and particularly preferably 95% or more.

F ⁻ is a component for achieving low dispersion (high Abbe number). It also has the effect of improving the transmittance in the ultraviolet region and lowering the glass transition point. In order to obtain the effect, the content of F ⁻ in anion% is preferably 0.1% or more, more preferably 1% or more, further preferably 10% or more, 20 % Or more is particularly preferable. The upper limit is not particularly limited, but if the content of F ⁻ is too large, it tends to evaporate during melting, and it tends to be difficult to obtain a glass stably. Is preferably 50% or less, more preferably 45% or less, and particularly preferably 40% or less.

The optical glass of the present invention can contain various components in addition to the above components as long as the effects of the present invention are not impaired. For example, Si ⁴⁺ , B ³⁺ , Al ³⁺ , P ⁵⁺ , Zn ²⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ or Ba ²⁺ can be contained as a component for facilitating vitrification. Note that Si ⁴⁺ , B ³⁺ , and Al ³⁺ tend to lower the refractive index, and therefore the content thereof needs to be adjusted so that desired optical characteristics can be obtained. Ti ⁴⁺ or Sn ⁴⁺ can be contained as a component for increasing the refractive index. Zr ⁴⁺ , W ⁶⁺ or Ge ⁴⁺ can be contained as a component for increasing the refractive index or facilitating vitrification. Li ⁺ , Na ⁺ , K ⁺ or Cs ⁺ can be contained as a component that lowers the melting temperature. Sb ³⁺ can be included as a fining agent. The total content of these components is preferably 0 to 20 cation%, more preferably 0 to 15 cation%, and still more preferably 0 to 10 cation%.

In addition, it is preferable not to contain Pb <^2+> from an environmental viewpoint.

  The refractive index (nd) of the optical glass of the present invention is preferably 1.85 or more, more preferably 1.9 or more, further preferably 1.95 or more, and preferably 2 or more. Particularly preferred is 2.05 or more. When optical glass is used as a lens, the higher the refractive index, the thinner the lens, which is advantageous for downsizing the optical device. However, if the refractive index is too high, the glass tends to become unstable. Therefore, considering the stability of the glass, the upper limit of the refractive index is preferably 2.5 or less, more preferably 2.3 or less, and even more preferably 2.2 or less.

  The optical glass of the present invention preferably has an Abbe number (νd) of 30 or more, more preferably 35 or more, further preferably 40 or more, and particularly preferably 50 or more. A higher Abbe number is preferable because the wavelength dispersion of the refractive index becomes smaller. However, if the Abbe number is too high, the refractive index is lowered or the glass tends to be unstable. Therefore, in consideration of maintaining high refractive index characteristics and glass stability, the upper limit of the Abbe number is preferably 70 or less, more preferably 65 or less, and even more preferably 60 or less.

In addition, since the optical glass of the present invention contains a large amount of Nb ⁵⁺ , Ta ⁵⁺ and rare earth element ions, vitrification is difficult by a general melting method using a melting container such as a crucible. This is because crystallization of the molten glass tends to proceed starting from the contact interface with the melting vessel. This tendency becomes prominent particularly when the content of glass skeleton-forming components such as Si ⁴⁺ , B ³⁺ and Al ³⁺ is small.

  Even if the composition is difficult to vitrify, it can be vitrified by eliminating contact at the interface with the melting vessel. As such a method, a containerless floating method (a containerless solidification method) in which a raw material is melted and cooled in a suspended state is known. When this method is used, since the molten glass hardly comes into contact with the melting vessel, crystallization starting from the interface with the melting vessel can be prevented, and vitrification becomes possible. Therefore, the optical glass of the present invention is preferably produced by a containerless floating method.

  FIG. 1 shows a schematic cross-sectional view of a production apparatus for producing a glass material by a containerless floating method. Below, the manufacturing apparatus of a glass material is demonstrated, referring FIG. The glass material manufacturing apparatus 1 includes a mold 10. The mold 10 also serves as a melting container. The molding die 10 has a molding surface 10a. The molding die 10 has a plurality of gas ejection holes 10b that are open on the molding surface 10a. The gas ejection hole 10b is connected to a gas supply mechanism 11 such as a gas cylinder. Gas is supplied from the gas supply mechanism 11 to the molding surface 10a via the gas ejection hole 10b. The type of gas is not particularly limited. The gas may be, for example, air or oxygen, or an inert gas such as nitrogen gas, argon gas, or helium gas.

  When manufacturing a glass material using the manufacturing apparatus 1, first, the glass raw material lump 12 is arrange | positioned on the molding surface 10a. As the glass raw material block 12, for example, a raw material powder integrated by press molding or the like, a sintered body obtained by integrating the raw material powder by press molding or the like, and a composition equivalent to the target glass composition are used. For example, an aggregate of crystals.

  Next, the glass raw material block 12 is floated on the molding surface 10a by ejecting gas from the gas ejection holes 10b. That is, the glass raw material block 12 is held in a state where it is not in contact with the molding surface 10a. In this state, the glass material block 12 is irradiated with laser light from the laser irradiation device 13. Thereby, the glass raw material lump 12 is heated and melted to be vitrified to obtain molten glass. Thereafter, the glass material can be obtained by cooling the molten glass. In the step of heating and melting the glass raw material lump 12 and the step of cooling until the temperature of the molten glass and further the glass material becomes at least the softening point or less, at least gas ejection is continued, and the glass raw material lump 12 and the molten glass Furthermore, it is preferable to suppress contact between the glass material and the molding surface 10a. In addition to the method of irradiating with laser light, the method of heating and melting may be radiant heating.

  EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited to these Examples.

  Tables 1 to 7 show examples of the present invention (sample Nos. 1 to 28 and 30 to 63) and comparative examples (samples No. 29 and 64), respectively.

Each sample was produced as follows. First, the raw material powder was weighed and mixed so as to have each glass composition, and then calcined at a temperature of about 1000 ° C. to sinter the raw material powder. A raw material lump having a desired volume was cut out from the sintered body. Using the obtained raw material lump, a glass material was produced by a containerless floating method using an apparatus according to FIG. As a heat source, a CO ₂ laser with an output of 100 W was used, and the raw material lump was heated to 1000 to 2500 ° C. and dissolved.

  The obtained sample was measured for refractive index (nd) and Abbe number (νd). The results are shown in Tables 1-3.

  The refractive index (nd) is indicated by a measured value for the d-line (587.6 nm) of a helium lamp.

  Abbe number (νd) uses the refractive index of d-line and the refractive index of F-line (486.1 nm) and C-line (656.3 nm) of hydrogen lamp, and Abbe number (νd) = {(nd−1) / (NF-nC)}.

  As is apparent from the table, No. 1 as an example of the present invention. Samples 1 to 28 and 30 to 63 have a high refractive index and low dispersion optical characteristics such as a refractive index (nd) of 1.869 to 2.298 and an Abbe number (νd) of 31.0 to 75.4. Had. On the other hand, No. which is a comparative example. The samples 29 and 64 both had a high refractive index of 2.152, but the Abbe number was as low as 24.9.

  The optical glass of the present invention is suitable as an optical glass used for an optical lens such as a photographing lens for a video camera or a general camera.

1: Glass material manufacturing apparatus 10: Mold 10a: Molding surface 10b: Gas ejection hole 11: Gas supply mechanism 12: Glass raw material block 13: Laser beam irradiation apparatus

Claims (5)

Cation%, Nb ⁵⁺ + Ta ⁵⁺ 40-99.9% and rare earth element ions 0.1-60% (except Nb ⁵⁺ 40% and La ³⁺ 60%), An optical glass containing F ⁻ as an anion. 2. The optical glass according to claim 1, wherein the total amount of Nb ⁵⁺ , Ta ⁵⁺ and rare earth element ions is 80 cation% or more. The optical glass according to claim 1, wherein the rare earth element ion is at least one selected from La ³⁺ , Gd ³⁺ , Y ³⁺ , Yb ^3+, and Ce ⁴⁺ . The optical glass according to claim 1, wherein the optical glass contains 0.1% or more of F ^{− in} anion%. The optical glass according to any one of claims 1 to 4, wherein the refractive index (nd) is 1.85 to 2.5, and the Abbe number (νd) is 30 to 70.

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