JP2014001120A - Optical glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide optical glass that has desired optical characteristics and also has excellent transmittance.SOLUTION: The optical glass contains, as a glass composition, SiO0.1-40%, TaO0.1%-35%, NbO39.5-70% (not including 70%), TiO0-15% and NaO+KO+LiO 0.1-40%, in mass%, and does not substantially contain a lead component, an arsenic component, and a fluorine component.

Description

  The present invention relates to an optical glass suitable as an optical lens or optical communication lens of a digital camera or a video camera.

  In recent years, higher performance of digital cameras and video cameras, specifically, miniaturization, higher magnification, higher definition, and the like have been promoted. In order to achieve such high performance, glass for optical lenses used in digital cameras and video cameras is often required to have characteristics such as high refractive index, high dispersion, and extraordinary dispersion.

As a glass that satisfies the above characteristics, for example, a SiO ₂ —TiO ₂ —Nb ₂ O ₅ glass having a refractive index (nd) of 1.75 or more and an Abbe number (νd) of 30 or less has been proposed (for example, patents). Reference 1). This glass is suitable as a lens for optical communication in addition to the optical lens of a digital camera or a video camera by utilizing characteristics such as a high refractive index and high weather resistance.

JP 2009-203134 A

Although the conventional SiO ₂ —TiO ₂ —Nb ₂ O ₅ glass has desired optical properties, it has a problem of low transmittance and hinders use as an optical lens.

  In view of the above problems, an object of the present invention is to provide an optical glass having desired optical characteristics and good transmittance.

In the present invention, as a glass composition, SiO ₂ 0.1 to 40%, Ta ₂ O ₅ 0.1% to 35%, Nb ₂ O ₅ 39.5 to 70% (provided that 70% is included). Optical glass characterized by containing 0 to 15% of TiO ₂ and 0.1 to 40% of Na ₂ O + K ₂ O + Li ₂ O and substantially not containing a lead component, an arsenic component and a fluorine component. About.

As a result of the investigation by the present inventors, the main cause of the decrease in transmittance in the SiO ₂ —TiO ₂ —Nb ₂ O ₅ glass is that a large amount of TiO ₂ which is a component for increasing the refractive index and dispersion is contained. I found out that there is. Therefore, SiO ₂ —Nb ₂ O ₅ —Ta ₂ O ₅ —R containing a large amount of Nb ₂ O ₅ and Ta ₂ O _5, which are also components that increase the refractive index and dispersion, while reducing the content of TiO ₂ as much as possible. _{It has been found that 2} O (R is Li, Na or K) -based glass can achieve high transmittance while achieving high refractive index and high dispersion optical characteristics. In addition, the weather resistance is also good, and it is difficult for the physical properties to deteriorate and the surface to deteriorate during the manufacturing process and use of the product. Furthermore, by containing Ta ₂ O ₅ as an essential component, it is possible to obtain a glass excellent in anomalous dispersion (ie, having a low partial dispersion ratio).

Secondly, the optical glass of the present invention, further, as a glass composition, in mass%, the MgO + SrO + BaO + ZnO + ZrO 2 preferably contains 0 to 10%.

Thirdly, the optical glass of the present invention, further, as a glass composition, in _mass%, preferably contains ₂ O 3 0% and _Al 2 _O 3 0~10% B.

Fourthly, the optical glass of the present invention further includes, as a glass composition, La ₂ O ₃ + Gd ₂ O ₃ + Bi ₂ O ₃ + Y ₂ O ₃ + Yb ₂ O ₃ + TeO ₂ + GeO ₂ in a mass percentage of 0 to 10%. It is preferable to contain.

Fifth, the optical glass of the present invention, a mass _ratio, is preferably TiO 2 / _Ta 2 _{O 5} is 0.1 to 150.

Sixth, the optical glass of the present invention preferably has a mass ratio of Nb ₂ O ₅ / Ta ₂ O ₅ of 1.5 to 700.

Seventh, the optical glass of the present invention, a mass _ratio, is preferably TiO 2 / _Nb 2 _{O 5} is 0 to 0.35.

Eighth, the optical glass of the present invention, the mass _ratio, it is preferable SiO 2 / _Ta 2 _{O 5} is 0.1 to 300.

  Ninth, the optical glass of the present invention preferably has a refractive index of 1.7 to 1.95 and an Abbe number of 15 to 35.

  Tenth, the optical glass of the present invention preferably has a partial dispersion ratio of 0.63 or less.

  Eleventh, in the optical glass of the present invention, the partial dispersion ratio (θg, F) and the Abbe number (νd) satisfy the relational expression (θg, F) <− 0.0041 × (νd) +0.7190. It is preferable.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the optical glass which has a desired optical characteristic and favorable transmittance | permeability.

For each sample of Examples and Comparative Examples, the relationship between the partial dispersion ratio (θg, F) and the Abbe number (νd) and the formula (θg, F) = − 0.0041 × (νd) +0.7190 It is a graph to show.

  The reason why the content of each component in the optical glass of the present invention is limited as described above will be described below. Unless otherwise specified, “%” in the following description means “% by mass”.

SiO ₂ is a component that forms a glass skeleton. Moreover, there exists an effect which improves a weather resistance, and especially the effect which suppresses that components, such as an alkali metal oxide in glass, elute selectively to water is high. Furthermore, it has the effect of reducing liquidus temperature and suppressing devitrification. The content of SiO ₂ is 0.1 to 40%, preferably 0.1 to 37.5%, more preferably 2.5 to 35%, and still more preferably 5 to 30%. If the content of SiO ₂ is too small, the above effect is difficult to obtain. On the other hand, when the content of SiO ₂ is too large, meltability is lowered, and striae and bubbles due to undissolution are likely to remain in the glass, which may not satisfy the required quality as lens glass.

Ta ₂ O ₅ is a component for achieving a high refractive index and a high dispersion, and is a component having a high effect of reducing the partial dispersion ratio. Furthermore, among the components that can achieve a high refractive index, it is a component that is relatively difficult to raise the liquidus temperature (devitrification hardly occurs). The content of Ta ₂ O ₅ is 0.1 to 35%, preferably 0.5 to 33%, more preferably 1 to 32%, and still more preferably 2 to 31%. When the content of Ta ₂ O ₅ is too small, the effect is difficult to obtain. On the other hand, if the content of Ta ₂ O ₅ is too large, the liquidus temperature rises and crystals containing Ta ₂ O ₅ as a main component tend to precipitate, and vitrification tends to be difficult.

Nb ₂ O ₅ is a component for achieving high refractive index and high dispersion, and also has an effect of reducing the partial dispersion ratio. The content of Nb ₂ O ₅ is 39.5 to 70% (excluding 70%), preferably 40 to 65%, more preferably 41 to 60%, and still more preferably 42 to 57.5%. When the content of Nb ₂ O ₅ is too small, the effect is difficult to obtain. On the other hand, if the content of Nb ₂ O ₅ is too large, the liquidus temperature rises and crystals containing Nb ₂ O ₅ as a main component tend to precipitate, and vitrification tends to be difficult.

TiO ₂ is a component for achieving high refractive index and high dispersion, and also has the effect of reducing the partial dispersion ratio. Moreover, there exists an effect which suppresses coloring of the glass by ultraviolet light. However, when there is too much the content, there exists a tendency for devitrification resistance to fall and vitrification to become difficult. In addition, the visible region transmittance is likely to decrease. In view of the above, the content of TiO ₂ is 0 to 15%, preferably 0.1 to 12.5%, more preferably 0.5 to 10%, and particularly 1 to 8.5%.

In the optical glass of the present invention, in order to achieve a low partial dispersion ratio, it is preferable to appropriately adjust the content ratio of TiO ₂ and Ta ₂ O ₅ . Specifically, the mass _ratio, TiO 2 / _Ta 2 _{O 5} is preferably 0.1 to 150, more preferably from 0.5 to 125, more preferably 1-100. If the ratio is too small, it becomes difficult to obtain desired optical characteristics or devitrification tends to occur. On the other hand, when the ratio is too large, it is difficult to obtain a low partial dispersion ratio.

In the optical glass of the present invention, in order to achieve a low partial dispersion ratio, it is preferable to appropriately adjust the content ratio of Nb ₂ O ₅ and Ta ₂ O ₅ . Specifically, Nb ₂ O ₅ / Ta ₂ O ₅ is preferably 1.5 to 700, more preferably 2 to 500, and still more preferably 2.5 to 300 in terms of mass ratio. If the ratio is too small, it becomes difficult to obtain desired optical characteristics or devitrification tends to occur. On the other hand, when the ratio is too large, it is difficult to obtain a low partial dispersion ratio.

In the optical glass of the present invention, in order to achieve a low partial dispersion ratio, it is preferable to appropriately adjust the content ratio of TiO ₂ and Nb ₂ O ₅ . Specifically, the mass _ratio, TiO 2 / _Nb 2 _{O 5} is preferably from 0 to 0.35, more preferably 0 to 0.3, more preferably from 0.1 to 0.25. When the ratio is too large, it is difficult to obtain a low partial dispersion ratio. In addition, it is difficult to obtain high refractive index and high dispersion optical characteristics.

In the optical glass of the present invention, in order to achieve a low partial dispersion ratio, it is preferable to appropriately adjust the ratio of the content of SiO ₂ and Ta ₂ O ₅ . Specifically, in terms of mass ratio, SiO ₂ / Ta ₂ O ₅ is preferably 0.1 to 300, more preferably 0.5 to 200, and still more preferably 1 to 150. If the ratio is too small, it becomes difficult to obtain desired optical characteristics or devitrification tends to occur. On the other hand, when the ratio is too large, it is difficult to obtain a low partial dispersion ratio.

Li ₂ O, Na ₂ O and K ₂ O are components that lower the partial dispersion ratio. Moreover, there exists an effect which makes a softening point fall or vitrification becomes easy. The content of Li ₂ O + Na ₂ O + K ₂ O is 0.1 to 40%, preferably 0.5 to 37.5%, more preferably 1 to 35%, still more preferably 1.5 to 32.5%. Especially preferably, it is 2 to 30%. When _{Li 2 O + Na 2 O +} K 2 O content is too small, the effect is difficult to obtain. On the other _hand, when the _{Li 2 O + Na 2 O +} K 2 O content is too large, chemical durability tends to decrease. Moreover, it becomes difficult to obtain high refractive index and high dispersion optical characteristics.

_The content of each component of Li 2 O, Na ₂ O and _{K 2} O, 0 to 40%, respectively, preferably from 0.1 to 37.5%, more preferably from 0.5 to 35%, More preferably, it is 1-32.5%, Most preferably, it is 1.5-30%.

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

P ₂ O ₅ is a component that forms a glass skeleton, and has an effect of suppressing devitrification and improving weather resistance. It also has the effect of increasing the Abbe number. However, when the content of P ₂ O ₅ is too large, rather weather resistance tends to decrease. Moreover, there exists a tendency for a refractive index to fall or for the softening point to rise and to make mold press molding at a low temperature difficult. Furthermore, the partial dispersion ratio tends to increase unduly. Therefore, the content of P ₂ O ₅ is preferably 0 to 10%, more preferably 0 to 5%.

Since MgO, SrO, BaO, ZnO, and ZrO ₂ form a glass skeleton as an intermediate oxide, there is an effect of improving devitrification resistance or improving chemical durability. However, since these components increase the partial dispersion ratio, if the content is too large, it becomes difficult to obtain desired optical characteristics. Therefore, the content of MgO + SrO + BaO + ZnO + ZrO ₂ is preferably 0 to 10%, more preferably 0 to 8%, still more preferably 0.1 to 7%, and particularly preferably 0.5 to 6.5%.

La ₂ O ₃ , Gd ₂ O ₃ , Bi ₂ O ₃ , Y ₂ O ₃ , Yb ₂ O ₃ , TeO ₂ and GeO ₂ are components that increase the refractive index. However, since these components increase the partial dispersion ratio, if the content is too large, it becomes difficult to obtain desired optical characteristics. Therefore, the content of La ₂ O ₃ + Gd ₂ O ₃ + Bi ₂ O ₃ + Y ₂ O ₃ + Yb ₂ O ₃ + TeO ₂ + GeO ₂ is preferably 0 to 10%, more preferably 0 to 9%, and even more preferably 0. 0.1 to 8%, particularly preferably 0.5 to 5%.

WO ₃ is a component for achieving high refractive index and high dispersion, and also has an effect of reducing the partial dispersion ratio. Moreover, coloring by ultraviolet light can be suppressed. However, when there is too much the content, devitrification resistance will fall and vitrification will become difficult, and there exists a tendency for ultraviolet region transmittance | permeability to fall. In addition, the affinity with the press mold is increased, and the glass tends to be easily fused with the mold during mold press molding. Therefore, the content of WO ₃ is preferably 0 to 30%, more preferably 0.1 to 29%, still more preferably 0.5 to 28%, and particularly preferably 1 to 27.5%.

B ₂ O ₃ is a component capable of forming a glass skeleton similarly to SiO ₂ . Moreover, there exists an effect which improves a weather resistance, and especially the effect which suppresses that the component in glass selectively elutes to water is high. The content of B ₂ O ₃ is preferably 0 to 10%, more preferably 0.1 to 5%. When the content of B ₂ O ₃ is too large, the partial dispersion ratio tends to increase. Moreover, it becomes difficult to obtain high refractive index and high dispersion optical characteristics.

Al ₂ O ₃ is a component capable of forming a glass skeleton similarly to SiO ₂ . Moreover, there exists an effect which improves a weather resistance, and especially the effect which suppresses that the component in glass selectively elutes to water is high. Moreover, there exists an effect which suppresses devitrification by adding a small amount. The content of Al ₂ O ₃ is preferably 0 to 10%, more preferably 0.1 to 5%. When the content of Al ₂ O ₃ is too large, it tends to be devitrified. Further, the meltability is lowered, and striae and bubbles remain in the glass, which may not satisfy the required quality as lens glass.

As a fining agent, for example, Sb ₂ O ₃ , SnO ₂ , CeO ₂ , NO ₃ or SO ₃ can be contained. Sb ₂ O ₃ also has an effect of improving the visible region transmittance if it is a trace amount. However, since there is a possibility that undesired coloring may occur if the content of the clarifier is too large, the content of these components is preferably 1% or less.

A lead component (for example, PbO), an arsenic component (for example, As ₂ O ₃ ), and a fluorine component (for example, F ₂ ) have a large environmental load, and there is a concern about coloring to glass, so that they are not substantially contained ( Specifically, each is less than 0.1%).

When the optical glass of the present invention is used as a lens, the thickness can be reduced as the refractive index is increased, which is advantageous in reducing the size of the optical device. Therefore, the refractive index (nd) of the optical glass of the present invention is preferably 1.7 or more, more preferably 1.75 or more, further preferably 1.775 or more, particularly preferably 1.785 or more, and most preferably 1. .8 or more. On the other hand, in order to improve the refractive index, it is necessary to contain many components that make the glass unstable, such as Nb ₂ O ₅ , so it is necessary to define the upper limit of the refractive index in consideration of the stability of the glass. is there. Specifically, the refractive index of the optical glass of the present invention is preferably 1.95 or less, more preferably 1.9 or less.

  The Abbe number of the optical glass of the present invention is preferably 35 or less, more preferably 30 or less, still more preferably 26 or less, and particularly preferably 24 or less. A lower Abbe number is advantageous in terms of optical design in reducing chromatic aberration in combination with other lenses, but on the other hand, the refractive index tends to decrease and the glass tends to become unstable. Therefore, the Abbe number of the optical glass of the present invention is preferably 20 or more, more preferably 21 or more, and further preferably 22 or more.

  In order to correct chromatic aberration in an optical device, it is common to use a combination of a low dispersion glass and a high dispersion glass. Here, it is known that chromatic aberration can be corrected more effectively by using a glass having a small partial dispersion ratio as the high dispersion glass. Therefore, the partial dispersion ratio (θg, F) of the optical glass of the present invention is preferably 0.63 or less, more preferably 0.62 or less, and further preferably 0.615 or less.

  In addition to the characteristics already described, the optical glass of the present invention preferably satisfies a low glass transition point. Thereby, fusion with a mold at the time of mold press molding can be suppressed, and mass productivity can be improved. In addition, the lower the glass transition point, the less the glass component volatilizes during mold press molding, and the less likely it is that problems such as a reduction in molding accuracy or deterioration or contamination of the mold occur. Specifically, the glass transition point of the optical glass of the present invention is preferably 700 ° C. or lower, more preferably 650 ° C. or lower.

The optical glass of the present invention preferably has a low degree of coloring λ ₇₀ . Thereby, the transmittance in the visible region and the near ultraviolet region is increased, and the color correction is reduced, which is suitable for optical elements such as various optical lenses. Specifically, the color glass λ ₇₀ of the optical glass of the present invention is preferably less than 480 nm, more preferably 470 nm or less, and further preferably 460 nm or less.

“Coloring degree λ ₇₀ ” refers to the shortest wavelength at which the transmittance shows 70% in the transmittance curve.

  Next, a method for producing an optical lens using the optical glass of the present invention and used for a digital camera or a video camera will be described.

  First, a glass material prepared so as to have a desired composition is melted. Next, molten glass is dropped from the tip of the nozzle and shaped into droplets (droplet shaping) to obtain a glass material. After the obtained glass material is polished or molded without being polished, an optical lens having a predetermined shape is obtained. Instead of performing droplet forming, it is also possible to adopt a method in which molten glass is formed into an ingot shape, a glass material cut into an appropriate size is polished, and then mold press molding is performed.

  Optical lenses made from the optical glass of the present invention can also be used as lens caps assembled with metal parts.

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

  Tables 1 to 3 show examples (samples Nos. 1 to 22) and comparative examples (samples Nos. 23 to 27) of the present invention.

Each sample was prepared as follows. First, glass raw materials were prepared so as to have each composition shown in the table, and were melted at 1500 ° C. for 2 hours using a platinum crucible. The obtained molten glass was poured onto a carbon plate, and after annealing, a sample suitable for each measurement was produced.

The obtained sample refractive index (nd), Abbe number ([nu] d), were measured partial dispersion ratio ([theta] g, F) and coloring degree lambda _70. The results are shown in Tables 1-3. FIG. 1 shows the relationship between the partial dispersion ratio (θg, F) and the Abbe number (νd) and the formula (θg, F) = − 0.0041 × (νd) +0.7190. In FIG. 1-22 and ■ are No. 24-26 data are shown.

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

  The Abbe number uses the refractive index of the d-line of the helium lamp and the refractive index 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)}.

  The partial dispersion ratio uses the refractive index values of the F-line, C-line and g-line (435.8 nm) of the hydrogen lamp, and the partial dispersion ratio (θg, F) = {(ng−nF) / (nF−nC) } Was calculated from the following formula.

The coloring degree λ ₇₀ was obtained by measuring the transmittance in the wavelength range of 200 to 800 nm at intervals of 0.5 nm for an optically polished sample having a thickness of 10 mm ± 0.1 mm using a spectrophotometer. The evaluation was made based on the shortest wavelength indicating 70% transmittance in the transmittance curve.

As is apparent from Tables 1 to 3, No. 1 is an example of the present invention. Samples 1 to 22 are vitrified without devitrification, have a refractive index of 1.7992 to 1.8891, an Abbe number of 23.2 to 27.3, and a partial dispersion ratio of 0.5995 to 0.6180. The coloring degree λ ₇₀ was 435 to 469 nm and had desired optical characteristics.

On the other hand, No. which is a comparative example. Samples 23 and 27 did not vitrify. No. Each of the samples 24 to 26 had a high partial dispersion ratio of 0.6305 or more, and a coloring degree λ ₇₀ of 480 to 540 nm, which was inferior in transmittance.

  The optical glass of the present invention is an optical pickup lens for CD, MD, DVD, and other various optical disk systems, a video camera, a digital camera, and other general camera photographing lenses and light as glass materials for mold press molding and polishing. Suitable for communication lenses and the like.

Claims (11)

As a glass composition, SiO ₂ 0.1 to 40%, Ta ₂ O ₅ 0.1% to 35%, Nb ₂ O ₅ 39.5 to 70% (however, 70% is not included), TiO _{2 by} mass% An optical glass containing _{20 to} 15% and Na ₂ O + K ₂ O + Li ₂ O 0.1 to 40%, and substantially free of a lead component, an arsenic component, and a fluorine component. Further, as a glass composition, in mass%, MgO + SrO + BaO + ZnO + optical glass according to claim 1, ZrO ₂ and characterized in that it contains 0 to 10%. Further, as a glass composition,% by _mass, B ₂ O 3 0% and _Al 2 _O 3 0% optical glass according to claim 1 or 2, characterized in that it contains. Furthermore, the glass composition contains 0 to 10% of La ₂ O ₃ + Gd ₂ O ₃ + Bi ₂ O ₃ + Y ₂ O ₃ + Yb ₂ O ₃ + TeO ₂ + GeO ₂ by mass%. 4. The optical glass according to any one of 3. A mass _ratio, the optical glass according to any one of claims 1 to 4, characterized in that TiO 2 / _Ta 2 _{O 5} is 0.1 to 150. A mass _{ratio, Nb 2 O 5 / Ta 2} O 5 optical glass according to any one of claims 1-5, characterized in that it is 1.5 to 700. A mass _ratio, the optical glass according to any one of claims 1 to 6, wherein the TiO 2 / _Nb 2 _{O 5} is 0 to 0.35. The optical glass according to claim 1, wherein SiO ₂ / Ta ₂ O ₅ is 0.1 to 300 in terms of mass ratio.   The optical glass according to any one of claims 1 to 8, wherein a refractive index is 1.7 to 1.95 and an Abbe number is 15 to 35.   A partial dispersion ratio is 0.63 or less, Optical glass as described in any one of Claims 1-9 characterized by the above-mentioned.   The partial dispersion ratio (θg, F) and the Abbe number (νd) satisfy a relational expression of (θg, F) <− 0.0041 × (νd) +0.7190. Optical glass as described in any one of Claims.