JP6173224B2 - Optical glass - Google Patents

Description

  The present invention relates to an optical glass, and more particularly to an optical glass having high refractive index and low dispersion optical characteristics.

  In recent years, with the reduction in size and weight of optical systems used in cameras, microscopes, endoscopes, etc., the higher the refractive index and the lower dispersion (high Abbe number) as the optical characteristics of glass used in optical lenses. Is required.

In order to make the glass have a higher refractive index and lower dispersion, the content of SiO ₂ and B ₂ O ₃ which are glass network components is reduced, and La ₂ O ₃ , Gd ₂ O ₃ , Ta ₂ O _5, etc. It is necessary to contain a large amount of rare earth oxide. In this case, however, vitrification becomes difficult. This is because optical glass is generally manufactured by melting and cooling the raw material in a melting vessel such as a crucible, and in a glass system with few network components, crystallization proceeds from the contact interface with the melting vessel. It is easy to do.

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 solidification method (a containerless floating 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. For example, in Patent Document 1, a glass containing only TiO ₂ and BaO as a glass composition is produced by a containerless solidification method.

Japanese Patent No. 4789086

The glass described in Patent Document 1 contains a large amount of TiO ₂ . Although TiO ₂ has a large effect of increasing the refractive index, it is difficult to obtain low dispersion characteristics because it significantly reduces the Abbe number.

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

The optical glass of the present invention is mol%, Gd ₂ O ₃ 14 to 45% (excluding 14%), La ₂ O ₃ 0 to 50%, and SiO ₂ + B ₂ O ₃ 0 to 50% ( However, 0% and 50% are not included).

The optical glass of the present invention, further, in _{mol%, ZrO 2 0~25%, Al} 2 O 3 0~25%, Nb 2 O 5 0~30%, Ta 2 O 5 0~30%, Y 2 O ₃ 0-30%, or _preferably contains a GeO 2 0-30%.

In the optical glass of the present invention, Gd ₂ O ₃ + La ₂ O ₃ is preferably 15 mol% or more.

  The optical glass of the present invention preferably has a refractive index (nd) of 1.8 to 2.05 and an Abbe number (νd) of 20 to 47.

  The optical glass manufacturing method of the present invention is a method for manufacturing any one of the above optical glasses, wherein the glass raw material is heated in a state where the glass raw material is suspended and held above the molding surface of the mold. It is characterized by comprising a step of obtaining a glass material by cooling the molten glass after melting and obtaining the molten glass.

  According to the present invention, it is possible to provide a novel optical glass having a high refractive index and low dispersion 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 is mol%, Gd ₂ O ₃ 14 to 45% (excluding 14%), La ₂ O ₃ 0 to 50%, and SiO ₂ + B ₂ O ₃ 0 to 50% ( However, 0% and 50% are not included). The reason for limiting the glass composition range in this way will be described below. Hereinafter, unless otherwise specified, “%” indicates “mol%”.

Gd ₂ O ₃ is a component that increases the refractive index without substantially reducing the Abbe number. It also has the effect of improving weather resistance. The content of Gd ₂ O ₃ is 14 to 45% (excluding 14%), preferably 14.5 to 30%, more preferably 14.5 to 25%. If the content of Gd ₂ O ₃ is too small, it becomes difficult to obtain a desired refractive index or Abbe number. On the other hand, if the content of _Gd 2 _{O 3} is too large, it is difficult to vitrify.

La ₂ O ₃ is a component that increases the refractive index without substantially reducing the Abbe number. It also has the effect of improving weather resistance. The content of La ₂ O ₃ is 0 to 50%, preferably 10 to 45%, more preferably 15 to 40%. When the content of La ₂ O ₃ is too large, it is difficult to vitrify.

In order to obtain a desired refractive index and Abbe number, Gd ₂ O ₃ + La ₂ O ₃ is preferably 15% or more, and more preferably 20% or more.

SiO ₂ and B ₂ O ₃ are components that become a glass skeleton and widen the vitrification range. By using the containerless solidification method, crystallization starting from the interface between the molten glass and the molten container can be prevented, but the glass diameter is particularly large (for example, a diameter of 5 mm or more) in a composition that is extremely difficult to vitrify. It takes time to cool down to the inside, and crystallization tends to occur. Since the optical glass of the present invention contains a predetermined amount of SiO ₂ and B ₂ O ₃ , vitrification is facilitated, and a large size glass can be obtained. The content of SiO ₂ + B ₂ O ₃ is 0 to 50% (however, 0% and 50% are not included), preferably 10 to 45%, more preferably 20 to 40%. When SiO ₂ + _B 2 _{O 3} is too small, the effect is difficult to obtain. On the other hand, when the content of SiO 2 ₊ B ₂ O ₃ is too large, the refractive index is hardly desired optical characteristics can be obtained by reduction.

A preferred range of the content of each of SiO ₂ and _B 2 _{O 3} is as follows.

The content of SiO ₂ is preferably 0 to 50% (but not including 50%), more preferably 0 to 40%, and still more preferably 2 to 40%. Note that SiO ₂ also has an effect of improving weather resistance.

The content of B ₂ O ₃ is preferably 0 to 50% (but not including 50%), more preferably 10 to 45%, and still more preferably 20 to 40%.

In addition to the above components, the optical glass of the present invention can contain ZrO ₂ , Al ₂ O ₃ , Nb ₂ O ₅ , Ta ₂ O ₅ , Y ₂ O ₃ or GeO ₂ . By introducing these components, a glass having a desired refractive index and Abbe number can be easily produced.

ZrO ₂ is a component that increases the refractive index without substantially reducing the Abbe number. Moreover, since a glass skeleton is formed as an intermediate oxide, there is an effect of widening the vitrification range. Furthermore, there is an effect of improving chemical durability. However, vitrification becomes difficult when a large amount of ZrO ₂ is contained. Therefore, the content of ZrO ₂ is preferably 0 to 25%, more preferably 0.5 to 23%, and further preferably 2 to 20%.

Al ₂ O ₃ is a component that forms a glass skeleton as an intermediate oxide and widens the vitrification range. It also has the effect of improving chemical durability. However, when a large amount of Al ₂ O ₃ is contained, the refractive index and the Abbe number decrease, and it becomes difficult to obtain desired optical characteristics. Therefore, the content of Al ₂ O ₃ is preferably 0 to 25%, more preferably 0.1 to 20%, and still more preferably 1 to 15%.

Nb ₂ O ₅ is a component having a large effect of increasing the refractive index, and also has an effect of widening the vitrification range. However, since Nb ₂ O ₅ tends to lower the Abbe number, if its content is too large, it becomes difficult to obtain desired optical characteristics. Therefore, the content of Nb ₂ O ₅ is preferably 0 to 30%, more preferably 1 to 25%, and still more preferably 1 to 20%.

Ta ₂ O ₅ is a component that increases the refractive index. It also has the effect of increasing chemical durability. However, when Ta ₂ O ₅ is contained in a large amount, the Abbe number decreases, and it becomes difficult to obtain desired optical characteristics. In addition, raw material costs tend to be high. Therefore, the content of Ta ₂ O ₅ is preferably 0 to 30%, more preferably 1 to 20%, and still more preferably 5 to 15%.

Y ₂ O ₃ is a component that increases the refractive index without substantially reducing the Abbe number. However, when a large amount of Y ₂ O ₃ is contained, vitrification becomes difficult. Therefore, the content of Y ₂ O ₃ is preferably 0 to 30%, more preferably 1 to 20%, and further preferably 2 to 10%.

GeO ₂ is a component that increases the refractive index and has the effect of expanding the vitrification range. However, if GeO ₂ is contained in a large amount, the Abbe number decreases, and it becomes difficult to obtain desired optical characteristics. In addition, raw material costs tend to be high. Therefore, the GeO ₂ content is preferably 0 to 30%, more preferably 0 to 15%, and still more preferably 0 to 5%.

  In addition to the above components, the optical glass of the present invention may contain the following components.

WO ₃ has the effect of increasing the refractive index. Moreover, since a glass skeleton is formed as an intermediate oxide, there is an effect of widening the vitrification range. However, when a large amount of WO ₃ is contained, the Abbe number decreases, and it becomes difficult to obtain desired optical characteristics. Therefore, the content of WO ₃ is preferably 0 to 10%, more preferably 0.5 to 5%, and still more preferably 1 to 3.5%.

Yb ₂ O ₃ is a component that increases the refractive index without substantially reducing the Abbe number. However, vitrification becomes difficult when Yb ₂ O ₃ is contained in a large amount. In addition, raw material costs tend to be high. Therefore, the content of Yb ₂ O ₃ is preferably 0 to 15%, more preferably 1 to 10%, and further preferably 2 to 8%.

TiO ₂ is a component that has a large effect of increasing the refractive index. However, since the Abbe number is likely to be lowered, if the content is too large, it becomes difficult to obtain desired optical characteristics. Therefore, the content of TiO ₂ is preferably 0 to 10%, more preferably 1 to 5%.

SnO ₂ is a component having a large effect of increasing the refractive index. However, since the Abbe number is likely to be lowered, if the content is too large, it becomes difficult to obtain desired optical characteristics. Therefore, the content of SnO ₂ is preferably 0 to 10%, more preferably 1 to 5%.

P ₂ O ₅ is a component constituting a glass skeleton and has an effect of extending the vitrification range. However, when a large amount of P ₂ O ₅ is contained, phase separation is facilitated. Therefore, the content of P ₂ O ₅ is preferably 0 to 10%, more preferably 0 to 3%.

  ZnO, MgO, CaO, SrO and BaO have the effect of increasing the stability and chemical durability of the glass. However, if the content is too large, the refractive index is lowered, making it difficult to obtain desired optical characteristics. Therefore, the content of these components is preferably 0 to 10%, more preferably 1 to 5%, respectively.

Li ₂ O, Na ₂ O, K ₂ O and Cs ₂ O have the effect of lowering the melting temperature, but since the refractive index tends to decrease, the total amount is preferably 0 to 10%, and 0 to 5 % Is more preferable.

Sb ₂ O ₃ can be added as a fining agent. However, the content of Sb ₂ O ₃ is preferably 0.1% or less, and more preferably not contained, in order to avoid coloring or in consideration of environmental aspects.

  PbO is preferably not contained from the environmental viewpoint.

  The refractive index of the optical glass of the present invention is preferably 1.8 or more, more preferably 1.83 or more, and further preferably 1.9 or more. For example, when the optical glass of the present invention is used as a lens, the lens can be made thinner as the refractive index is increased, which is advantageous for downsizing the optical device. The upper limit of the refractive index is preferably 2.05 or less, more preferably 2 or less in consideration of the stability of the glass.

  The Abbe number of the optical glass of the present invention is preferably 20 or more, more preferably 30 or more, and still more preferably 35 or more. A higher Abbe number is preferable because the wavelength dispersion of the refractive index becomes smaller, but the upper limit is preferably 45 or less, and more preferably 43 or less, from the viewpoint of maintaining high refractive index characteristics and glass stability.

  The optical glass of the present invention can be produced, for example, by a containerless solidification method. FIG. 1 is a schematic cross-sectional view of a production apparatus for producing a glass material by a containerless solidification method.

  As shown in FIG. 1, 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 4 show examples of the present invention and comparative examples, respectively.

  Each sample was prepared as follows. First, a raw material prepared so as to have a glass composition shown in the table was press-molded, and sintered at 1250 to 1400 ° C. for 12 hours to produce a glass raw material lump. Alternatively, a raw material prepared so as to have the glass composition shown in the table is melted at 1450 to 1580 ° C. for 30 minutes in an alumina or platinum crucible, and the molten glass is poured into a carbon plate shape (not vitrified). ) Was produced.

Next, the glass raw material lump was coarsely pulverized in a mortar to obtain small pieces of 0.1 to 0.5 g. A glass material (about 2 to 8 mm in diameter) was produced by a containerless solidification method using an apparatus according to FIG. A 100 W CO ₂ laser oscillator was used as the heat source. Moreover, oxygen gas was used as gas for suspending a raw material lump, and it supplied with the flow rate of 1-15 L / min.

  About the obtained glass material, refractive index (nd) and Abbe number ((nu) d) were measured. The results are shown in Tables 1-4.

  The refractive index (nd) is obtained by bonding a glass material on a 5 mm thick soda plate substrate, performing right-angle polishing, and using KPR-2000 (manufactured by Shimadzu Corporation) with respect to the d-line (587.6 nm) of a helium lamp. Evaluation was made using measured values.

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

  As shown in Tables 1 to 4, the glasses of Examples 1 to 21 had a high refractive index of 1.85709 to 2.01051, and an Abbe number of 30.86 to 44.27.

  On the other hand, Comparative Examples 1 and 2 were not vitrified. In Comparative Examples 3 and 4, the refractive index was as low as 1.773331 or less. In Comparative Example 5, the refractive index was as high as 2.01422, but the Abbe number was as low as 19.42.

  The optical glass of the present invention is suitable for optical lenses used in cameras, microscopes, endoscopes and the like.

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 (4)

Gd ₂ O ₃ 14 to 45% (excluding 14%), La ₂ O _{30 to} 34.4 % , Gd ₂ O ₃ + La ₂ O ₃ 36.0 to 53.3 mol%, _{S iO 2 + B 2 O 3} 20 ~50% ( not including the free and 50%) containing _P 2 _O 5 0 to 3% and 0% ZnO,
An optical glass having a refractive index (nd) of 1.85709 to 2.05 and an Abbe number (νd) of 20 to 43 . Furthermore, in _{mol%, ZrO 2 0~25%, Al} 2 O 3 0~25%, Nb 2 O 5 0~30%, Ta 2 O 5 0~30%, Y 2 O 3 0~30%, or The optical glass according to claim 1, further comprising 0-30% GeO ₂ . The optical glass according to claim 1 or 2, wherein the diameter is 5 mm or more. It is a method for manufacturing the optical glass as described in any one of Claims 1-3, Comprising :
A step of obtaining a glass material by cooling the molten glass after obtaining the molten glass by heating and melting the glass raw material in a state where the glass raw material is suspended and held above the molding surface of the mold; A method for producing optical glass.

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