JP4562041B2 - Optical glass, glass gob for press molding, and optical element - Google Patents

Description

  The present invention relates to an optical glass, a glass gob for press molding, and an optical element. More specifically, the present invention relates to an optical glass having a high refractive index and reduced coloring, and a glass gob for press molding and an optical element made of the optical glass.

In recent years, with the widespread use of digital cameras, the demand for small lenses is increasing. A high refractive index glass is suitable as an optical glass material for producing such a small lens. However, the conventional glass has the disadvantages that the refractive index is increased and the tendency to color is increased. In particular, in the case of a digital camera, since a CCD is used as an image pickup device, there is a problem in that the blue sensitivity on the short wavelength side among the three primary colors is attenuated when viewed as the whole image pickup apparatus. Further, there is a glass described in Patent Document 1 as a high-refractive-index low-dispersion optical Glass used for this kind of application, the glass has a problem that must be used expensive HfO _2.

JP-A-53-4023

  Under such circumstances, an object of the present invention is to provide an optical glass having a high refractive index and reduced coloring, and a glass gob for press molding and an optical element made of the optical glass. .

  As a result of intensive studies to achieve the above object, the present inventor has found that the object can be achieved by using an optical glass having a specific composition, and the present invention has been completed based on this finding. It was.

That is, the present invention
(1) By weight%, B ₂ O ₃ is ₂ to 45%, SiO ₂ is 0 to 30% (however, the content of B ₂ O ₃ > SiO ₂ content), and La ₂ O ₃ is 10 to 50 %, TiO ₂ 0-30%, ZnO 0-15%, ZrO ₂ 0-15%, Nb ₂ O ₅ 0-35%, BaO 0-35%, SrO 0-5%, CaO From 0% to less than 8%, MgO from 0% to less than 13% (however, the total content of BaO, SrO, CaO and MgO is 0 to 40%), Gd ₂ O ₃ is 0 to
20%, Y ₂ O _{3 from 0} to 15%, Ta ₂ O ₅ from 0 to 18%, WO ₃ from 0% to less than 0.5%, Na ₂ O, K ₂ O and Li ₂ O in total 0 % To less than 1.5%, GeO ₂ 0 to 10%, Bi ₂ O ₃ 0 to 20%, Yb ₂ O ₃ 0 to 10%, Al ₂ O ₃ 0 to 10%, Sb ₂ O ₃ An optical glass comprising 0% or more and less than 2% and SnO _{2 in an amount} of 0 to 1%,
(2) The optical glass according to (1), wherein the refractive index (nd) is 1.8 to 2.1 and the Abbe number (νd) is 20 to 40,
(3) A glass gob for press molding comprising the optical glass as described in (1) or (2) above, and heated and softened for use in press molding, and (4) (1) or ( An optical element comprising the optical glass according to item 2),
Is to provide.

According to the present invention, an optical glass having a high refractive index and reduced coloring can be provided.
Further, according to the present invention, it is possible to provide a glass gob for press molding for producing an optical element made of optical glass having a high refractive index and reduced coloring by press molding.
Furthermore, according to the present invention, an optical element made of optical glass having a high refractive index and reduced coloring can be provided.

The optical glass of the present invention is expressed by weight%, ₂ to 45% of B ₂ O ₃ , 0 to 30% of SiO ₂ (however, the content of B ₂ O ₃ > SiO ₂ content), La ₂ O ₃ 10 to 50%, TiO ₂ 0 to 30%, ZnO 0 to 15%, ZrO _{2 0} to 15%, Nb ₂ O _{5 0} to 35%, BaO 0 to 35%, SrO 0 to 5%, CaO 0% or more and less than 8%, MgO 0% or more and less than 13% (however, the total content of BaO, SrO, CaO and MgO is 0 to 40%), Gd ₂ O ₃ is 0 to 20%, Y ₂ O _{3 is 0} to 15%, Ta ₂ O ₅ is 0 to 18%, WO ₃ is 0% or more and less than 0.5%, and Na ₂ O, K ₂ O, and Li ₂ O are 0% or more in total 1 less than .5%, the GeO ₂ 0%, the _Bi 2 _{O 3} 0 to 20%, the _Yb 2 _{O 3} 0%, the _Al 2 _{O 3} 0 10%, is intended _Sb 2 _{O 3} less than 2% 0% or more and containing SnO ₂ 0 to 1%.

According to the optical glass, a high transmittance can be obtained in the visible light region, and in particular, a high transmittance can be obtained in a short wavelength region in the visible region.
Further, a more stable glass can be obtained when the refractive index (nd) is 1.8 to 2.1 and the Abbe number (νd) is 20 to 40.

Next, the composition range will be described in detail. Hereinafter, the content of each component is expressed by weight%.
B ₂ O ₃ is a component effective as a network-forming oxide in the glass and for reducing the temperature of the meltability and flow viscosity of the glass, and requires 2% or more. However, if it exceeds 45%, the refractive index decreases, so B ₂ O ₃ is set to ₂ to 45%. Preferably it is 3 to 24%, more preferably 5 to 18%.

SiO ₂ fulfills the function of maintaining devitrification resistance in the glass. When SiO ₂ is introduced, it functions as a glass network forming component. However, if it exceeds 30%, the solubility deteriorates and it becomes difficult to produce stably, so the amount of SiO ₂ is made 0 to 30%. A preferred amount is 0 to 18%, and a more preferred amount is 1 to 18%.
Further, when the content of B ₂ O ₃ is less than or equal to the content of SiO ₂ , the glass is likely to be colored and the solubility and devitrification resistance are deteriorated, so the amount of B ₂ O ₃ is reduced to SiO 2. More than the amount of ₂ .

La ₂ O ₃ is an essential component for obtaining a high refractive index and low dispersion glass. If it is less than 10%, the refractive index is lowered, and if it is more than 50%, the devitrification resistance is lowered. It becomes difficult to obtain possible glass. Therefore, the introduction amount of La ₂ O ₃ is 10 to 50%. Preferably, it is 18 to 47%, more preferably 25 to 47%.

TiO ₂ is a component for improving chemical durability and devitrification resistance while adjusting optical characteristics such as refractive index and Abbe number. 0 to 30% is necessary, 0 to 26% is preferable, 1 to 26% is more preferable, and 8 to 26% is more preferable.

ZnO is a component having the effects of imparting high refractive index and low dispersion (small refractive index wavelength dependency) to glass, improving devitrification resistance, and reducing the temperature of viscous flow. However, when the introduction amount exceeds 15%, the devitrification becomes strong, and it becomes difficult to obtain a glass that can be stably manufactured. Therefore, ZnO is set to 0 to 15%. Preferably it is 0 to 12%. When ZnO is added in an appropriate amount, the rise of the short wavelength end of the spectral transmittance becomes steep, so it is more preferable to add more than 0% and 5% or less, more preferably 0.5 to 5%. It is even more preferable to add 5%.

ZrO ₂ is a component that provides a high refractive index, and has the effect of improving devitrification resistance when added in a small amount. However, if it exceeds 15%, the devitrification resistance decreases, and the solubility also deteriorates. Therefore, ZrO _{2 is set} to 0 to 15%. Preferably it is 0 to 10%, more preferably 1 to 10%.

Nb ₂ O ₅ is a component for imparting a high refractive index and also has an effect of improving devitrification resistance. The introduction amount is suitably 0 to 35%. If it exceeds 35%, the absorption in the short wavelength region becomes strong, and there is a strong tendency to cause coloring. Preferably it is 0-30%, More preferably, it is 1-30%, More preferably, it is 1-20%, More preferably, it is 1-15%.

BaO, SrO, CaO, and MgO have an effect of promoting defoaming by using carbonate or nitrate as a glass raw material.
BaO has an effect of improving coloring by addition of 0 to 35%. However, if it exceeds 35%, devitrification resistance deteriorates. Preferably it is 0-32%, More preferably, it is 1-32%, More preferably, it is 1-25%.

  SrO can be added at 0 to 5% by substitution with BaO. Similarly, 0% or more and less than 8% of CaO and 0% or more and less than 13% of MgO can be added. SrO is preferably 0% or more and less than 1% from the viewpoint of improving the devitrification resistance when the glass is reheated and molded. In particular, when the refractive index (nd) is 1.8 to 1.86, it is better to pay attention to the decrease in devitrification resistance. When the refractive index (nd) is 1.8 to 1.86, SrO is 0%. When the above is less than 1% and the refractive index (nd) is more than 1.86 to 2.1, SrO is preferably 0 to 5%. Further, when the refractive index (nd) is 1.8 to 2.1, it is more preferable that SrO is 0 to 0.8%.

  Further, if the total content of BaO, SrO, CaO, and MgO exceeds 40%, the devitrification resistance decreases, and it becomes difficult to obtain a glass that can be stably produced. Therefore, the total content of BaO, SrO, CaO, and MgO 0 to 40%.

Gd ₂ O ₃ can be added up to 20% by substitution with La ₂ O ₃ , but if it exceeds 20%, devitrification resistance deteriorates, and it becomes difficult to obtain a glass that can be stably produced. Therefore, the content of Gd ₂ O ₃ is set to 0 to 20%. Preferably, it is 0 to 10%.

Y ₂ O ₃ and Yb ₂ O ₃ can also be added at 0 to 15% and 0 to 10%, respectively, by substitution with La ₂ O ₃ . However, when these amounts are exceeded, the devitrification resistance deteriorates, and it becomes difficult to obtain a glass that can be stably produced. A preferable range is 0 to 4% for Y ₂ O _{3 and} 0 to 4% for Yb ₂ O ₃ . A more preferable range of Y ₂ O ₃ is 0 to 1.5%.

Ta ₂ O ₅ is a component for imparting a high refractive index and low dispersion characteristics, and is useful when making the glass low dispersion. However, if it exceeds 18%, the solubility deteriorates. Therefore, 0 to 18% is appropriate for the content of Ta ₂ O ₅ .

WO ₃ is a component that improves devitrification resistance by addition of a small amount, but when it is 0.5% or more, the absorption in the short wavelength region of the glass becomes strong and the tendency to cause coloring is strong. Therefore, the amount of WO ₃ is set to 0% or more and less than 0.5%. 0 to 0.4% is preferable.

Na ₂ O, K ₂ O, and Li ₂ O are effective components for reducing the glass transition temperature (Tg). In particular, Li ₂ O is extremely effective. However, since the devitrification resistance and the refractive index are greatly reduced, the total content of Na ₂ O, K ₂ O, and Li ₂ O is set to 0% or more and less than 1.5%.

GeO ₂ has the same effect as SiO ₂ and can be added up to 10%. However, if it exceeds 10%, the devitrification resistance decreases. Accordingly, the appropriate amount of GeO ₂ is 0 to 10%. However, in the glass, the desired properties without addition of GeO _2, it is possible to obtain a property, it is preferred not to introduce an expensive GeO _2.

Bi ₂ O ₃ has the effect of lowering the glass transition temperature (Tg) when added in a small amount, but when it exceeds 20%, the devitrification resistance is lowered and coloration occurs. Therefore, the amount of Bi ₂ O ₃ is suitably 0 to 20%.

Al ₂ O ₃ may have an effect of improving devitrification resistance with a small amount of addition, but at the same time the refractive index is lowered, so the addition amount is 0 to 10%.
Ga ₂ O ₃ and In ₂ O ₃ can also be added up to about 10%. However, devitrification resistance may be deteriorated by addition, and since it is an expensive raw material, Ga ₂ O ₃ and In It is desirable not to introduce ₂ O ₃ .

In addition to the above components, Sb ₂ O ₃ and SnO ₂ that are generally used as fining agents can be added. The addition amount of Sb ₂ O ₃ is 0% or more and less than 2%, and the addition amount of SnO is 0 to 1%.
However, it is desirable not to add As ₂ O ₃ having a strong action as a clarifier because it is toxic.

Other things that should not be introduced include lead and its compounds, radioactive materials such as U and Th. In addition, from the viewpoint of reducing the coloring of the glass, introduction of substances that cause coloring such as Cu, Cr, V, Fe, Ni, and Co should be avoided. Also, addition of Te, Se, Cd should be avoided.
In addition, although the optical glass described in the above-mentioned patent document 1 uses expensive HfO ₂ as an essential component, a desired optical glass can be obtained without using HfO ₂ in the present invention.
In the above description, a composition range obtained by arbitrarily combining the ranges shown as the preferred contents of each component is preferable for obtaining the required glass.

  In the optical glass of the present invention, preferable refractive index (nd) and Abbe number (νd) ranges are 1.8 to 2.1 for refractive index (nd) and 20 to 40 for Abbe number (νd). A more preferable Abbe number (νd) is in the range of 20 to 39. Moreover, a more preferable refractive index (nd) is 1.81-2.1, More preferably, it is 1.85-2.1.

The transmittance characteristics of the optical glass of the present invention will be described. The transmittance is quantitatively evaluated as follows. First, a plate-like glass having a thickness of 10 mm ± 0.1 mm is prepared by polishing both surfaces of the optical glass in parallel with each other. Light is incident on the polished surface of the plate glass from the vertical direction, and the spectral transmittance including the surface reflection loss is measured in the wavelength range of 280 nm to 700 nm. A wavelength at which the spectral transmittance is 70% is λ ₇₀ , and a wavelength at which the spectral transmittance is 5% is λ ₅ . It is preferable that λ ₇₀ and λ ₅ have only one wavelength in the wavelength range of 280 nm to 700 nm. It is desirable that the spectral transmittance is 5% or more in the entire region of λ _{5 to 700} nm, and the spectral transmittance is 70% or more in the entire region of λ _{70 to 700} nm.

In an optical glass having such a transmittance characteristic, by reducing the wavelengths of λ ₇₀ and λ ₅ , high transmittance is exhibited over a wide range in the visible region.
In the present invention, optical glass with λ ₇₀ of 460 nm or less is preferable, optical glass with 450 nm or less is more preferable, and optical glass with 440 nm or less is more preferable. Further, from the viewpoint of imparting various properties including the refractive index and the Abbe number to the glass, λ ₇₀ is set to 350-4.
The range is preferably 60 nm, more preferably 350 to 450 nm, and even more preferably 350 to 440 nm.

In the present invention, an optical glass with λ ₅ of 400 nm or less is preferable, and an optical glass with 390 nm or less is more preferable. Moreover, it is more preferable to set λ ₅ in the range of 300 to 390 nm from the viewpoint of imparting various properties including the refractive index and Abbe number to the glass.
Furthermore, optical glass in which λ ₇₀ and λ ₅ simultaneously satisfy the above range is more preferable.
Since λ ₇₀ and λ ₅ (especially λ ₇₀ ) are likely to change depending on the melting conditions of the glass, it should be noted that λ ₇₀ and λ ₅ have shorter wavelengths when setting the melting temperature and melting time of the glass. is there. Also, impurities that cause coloring should be reduced as much as possible.

Here, a more preferable composition range, optical constant, and λ ₇₀ range are exemplified.
(Optical glass 1)
B ₂ O ₃ and 2-45%, a SiO ₂ 0 to 30% _(although, B 2 _{O 3} content> SiO ₂ content), _La 2 _{O 3} 10 to 50% of TiO ₂ 0 to 30% ZnO 0-15%, ZrO ₂ 0-15%, Nb ₂ O ₅ 0-35%, BaO 0-35%, SrO 0-5%, CaO 0% or more and less than 8%, MgO 0% or more and less than 13% (however, the total content of BaO, SrO, CaO and MgO is 0 to 40%), Gd ₂ O ₃ is 0 to 20%, Y ₂ O ₃ is 0 to 15%, Ta ₂ O ₅ is 0 to 18%, WO ₃ is 0% or more and less than 0.5%, the total content of Na ₂ O, K ₂ O and Li ₂ O is 0% or more and less than 1.5%, GeO ₂ is 0 to 0% 10% _Bi 2 _{O 3} 0-20% and _Yb 2 _{O 3} 0% to _Al 2 _{O 3} 0% to _Sb 2 _{O 3} 0% 2 Below, comprises SnO ₂ 0 to 1%, a refractive index (nd) of a 1.86 super to 2.1, optical glass, wherein a lambda ₇₀ is 460nm or less.

(Optical glass 2)
B ₂ O ₃ and 2-45%, a SiO ₂ 0 to 30% _(although, B 2 _{O 3} content> SiO ₂ content), _La 2 _{O 3} 10 to 50% of TiO ₂ 0 to 30% the ZnO 0 to 15% of _{ZrO 2 0~15%, Nb 2 O} 5 0 to 35% of BaO 0-35%, 2% or more and less than 0% SrO, CaO, 0% or more and less than 8% MgO from 0% to less than 13% (however, the total content of BaO, SrO, CaO and MgO is 0 to 40%), Gd ₂ O ₃ is 0 to 20%, Y ₂ O ₃ is 0 to 15%, Ta ₂ O ₅ is 0 to 18%, WO ₃ is 0% or more and less than 0.5%, the total content of Na ₂ O, K ₂ O and Li ₂ O is 0% or more and less than 1.5%, GeO ₂ 0-10%, a _Bi 2 _{O 3} 0 to 20% of _Yb 2 _{O 3} 0 to 10%, the _Al 2 _{O 3} 0-10%, the _Sb 2 _{O 3} 0 More than 2%, a SnO ₂ containing 0 to 1%, a refractive index (nd) of a 1.8 to 1.86, the optical glass, wherein a lambda ₇₀ is 460nm or less.

(Optical glass 3)
B ₂ O ₃ and 2-45%, a SiO ₂ 0 to 30% _(although, B 2 _{O 3} content> SiO ₂ content), _La 2 _{O 3} 10 to 50% of TiO ₂ 0 to 30% the ZnO 0 to 15% of _{ZrO 2 0~15%, Nb 2 O} 5 0 to 35% of BaO 0-35%, 1% or more and less than 0% SrO, CaO, 0% or more and less than 8% MgO from 0% to less than 13% (however, the total content of BaO, SrO, CaO and MgO is 0 to 40%), Gd ₂ O ₃ is 0 to 20%, Y ₂ O ₃ is 0 to 15%, Ta ₂ O ₅ is 0 to 18%, WO ₃ is 0% or more and less than 0.5%, the total content of Na ₂ O, K ₂ O and Li ₂ O is 0% or more and less than 1.5%, GeO ₂ 0-10%, a _Bi 2 _{O 3} 0 to 20% of _Yb 2 _{O 3} 0 to 10%, the _Al 2 _{O 3} 0-10%, the _Sb 2 _{O 3} 0 More than 2%, a SnO ₂ containing 0 to 1%, a refractive index (nd) of a 1.8-2.1, lambda ₇
An optical glass characterized in that ₀ is 460 nm or less.

(Optical glass 4)
B ₂ O ₃ and 2-45%, a SiO ₂ 0 to 30% _(although, B 2 _{O 3} content> SiO ₂ content), _La 2 _{O 3} 10 to 50% of TiO ₂ 0 to 30% ZnO 0-15%, ZrO ₂ 0-15%, Nb ₂ O ₅ 0-35%, BaO 0-35%, SrO 0-0.8%, CaO 0-7%, MgO 0-12% (however, the total content of BaO, SrO, CaO and MgO is 0-40%), Gd ₂ O ₃ is 0-20%, Y ₂ O ₃ is 0-15%, Ta ₂ O ₅ 0 to 18%, WO _{3 0} to 0.4%, the total content of Na ₂ O, K ₂ O and Li ₂ O is 0 to 1.2%, GeO ₂ is 0 to 10%, Bi ₂ O ₃ 0-20% and _Yb 2 _{O 3} 0% to _Al 2 _{O 3} 0% to _Sb 2 _{O 3} 0 to 1.8% include SnO ₂ 0 to 1% An optical glass characterized in that λ ₇₀ is 460 nm or less.

(Optical glass 5)
B ₂ O ₃ and 2-45%, a SiO ₂ 0 to 30% _(although, B 2 _{O 3} content> SiO ₂ content), _La 2 _{O 3} 10 to 50% of TiO ₂ 0 to 30% the ZnO 0 to 15% of _{ZrO 2 0~15%, Nb 2 O} 5 0 to 35% of BaO 0-35%, 1% or more and less than 0% SrO, CaO, 0% or more and less than 8% MgO is 0% or more and less than 13% (however, the total content of BaO, SrO, CaO and MgO is 0 to 40%), Gd ₂ O ₃ is 0 to 20%, and Y ₂ O ₃ is 0% or more and 2%. Less than 0%, Ta ₂ O ₅ from 0 to 18%, WO ₃ from 0% to less than 0.5%, the total content of Na ₂ O, K ₂ O and Li ₂ O from 0% to less than 1.5%, GeO ₂ 0-10% of _Bi 2 _{O 3} 0 to 20% of _Yb 2 _{O 3} 0-10%, the _Al 2 _{O 3} 0-10%, _Sb 2 O Less than 2% 0% or more, optical glass characterized in that it comprises a SnO ₂ 0 to 1%.

(Optical glass 6)
In the optical glass 5, B ₂ O ₃ is ₃ to 24% and SiO ₂ is 0 to 18% (however, the weight ratio of the content of B ₂ O ₃ / the content of SiO ₂ is 1.1 or more, or SiO ₂ is not contained), La ₂ O ₃ is 18 to 47%, TiO ₂ is 0 to 26%, ZnO is 0 to 12%, ZrO ₂ is 0 to 10%, Nb ₂ O ₅ is 0 to 30%, Optical glass containing 0 to 32% BaO, 0 to 10% Gd ₂ O ₃ and 0 to 4% Yb ₂ O ₃ .

(Optical glass 7)
Optical glass containing 1 to 5% of ZnO in the optical glass 5 or the optical glass 6.

(Optical glass 8)
In the optical glass of any one of the optical glasses 1 to 7, B ₂ O ₃ , SiO ₂ , La ₂ O ₃ , ZnO, ZrO ₂ , Nb ₂ O ₅ , TiO ₂ , BaO, CaO, SrO, Gd ₂ O ₃ , Y ₂ O ₃ , Ta ₂ O ₅ , WO ₃ , Na ₂ O, K ₂ O, Li ₂ O, GeO ₂ , Yb ₂ O ₃ , Sb ₂ O ₃ , SnO ₂ total content is 99% or more , More preferably 100% optical glass.

(Optical glass 9)
In the optical glass 8, the total content of B ₂ O ₃ , SiO ₂ , La ₂ O ₃ , ZnO, ZrO ₂ , Nb ₂ O ₅ , TiO ₂ , BaO, Sb ₂ O ₃ is 99% or more, more preferably 100% optical glass.

(Optical glass 10)
In the optical glass 9, the optical glass containing any component of B ₂ O ₃ , SiO ₂ , La ₂ O ₃ , ZnO, ZrO ₂ , Nb ₂ O ₅ , TiO ₂ , and BaO.

(Optical glass 11)
In any of the optical glass of the optical glass 1 to 11, an optical glass containing TiO _2. Here, the Nb ₂ O ₅ content / TiO ₂ content is preferably 0 to 7, and more preferably 0 to 6. By doing in this way, glass with less coloring can be obtained.

  By providing the above transmittance characteristics, the transmittance in the short wavelength region in the visible light region is high, so that it is possible to easily construct an imaging optical system having a good color balance. In particular, it is suitable for the material of an optical element, such as a lens, constituting an imaging optical system for a solid-state imaging element.

  Next, the liquidus temperature of the optical glass of the present invention will be described. In the optical glass of the present invention, a preferable liquidus temperature is 1250 ° C. or lower, more preferably 1200 ° C. or lower. In view of the stability of the glass, those having no liquidus temperature are preferred, but the liquidus temperature is more preferably 900 to 1200 ° C. from the viewpoint of imparting the above properties to the glass.

  Next, the glass gob for press molding of the present invention and the manufacturing method thereof will be described. A glass gob for press molding is a glass molded body for heating and softening to be used for press molding, and is sometimes called a press molding preform, and the weight and shape are appropriately determined depending on the target press molded product. . The glass gob for press molding of the present invention is made of the above optical glass. Therefore, the various properties of the glass gob for press molding reflect the various properties of the optical glass of the present invention.

  In the method for producing a glass gob for press molding, a glass gob for press molding made of optical glass is produced by molding molten glass. First, a glass raw material is prepared so as to obtain the optical glass of the present invention, and melted, clarified, and homogenized to make a homogeneous molten glass that does not contain undissolved materials, bubbles, and foreign matters. Next, the molten glass flows out from an outflow pipe made of platinum alloy or the like. Consider the conditions such as the temperature of the outflow pipe so that the glass does not devitrify during the outflow. The molten glass flowing out is cast into a receiving mold or mold and formed into a predetermined shape. The method suitable for the said shaping | molding is illustrated below.

  First, the first forming method is a method in which a plurality of receiving molds are sequentially carried under the outflow pipe, a molten glass lump having a predetermined weight is received by the mold, and cooled while forming the glass lump. In this method, the tip of the flowing molten glass flow is supported by the receiving mold, and the receiving mold is rapidly lowered at a timing at which a molten glass lump having a desired weight can be separated. If it does so, supply to the receiving mold of molten glass cannot catch up, a molten glass flow will separate on the way, and a molten glass lump of predetermined weight can be received with a receiving mold. By doing in this way, glass shaping | molding can be performed, without leaving the cutting trace which arises when a molten glass flow is cut | disconnected with a cutting blade. According to this first molding method, a glass lump that is slightly heavier than the weight of one press-molding glass gob or slightly above the weight can be formed.

  When a glass lump having a weight equivalent to one press-molding glass gob is formed, this glass lump can be used as a press-molding glass gob. In this case, the glass lump is preferably cooled at a speed that does not break.

When molding a glass lump that is heavier than the weight of one glass gob for press molding, the glass lump is annealed to reduce distortion, and then machined to finish the weight for one glass gob for press molding. The glass gob for press molding is used. According to this method, it is possible to provide a glass gob for press molding that can be used for molding optical elements of various sizes by previously forming a glass lump and adjusting the weight by machining according to demand. Can do. In addition, barrel polishing is preferable as the machining.
Further, when the press-molding glass gob is used for precision press-molding, a press-molding glass gob produced without machining the glass lump is suitable.

  Next, in the second forming method, molten glass is cast at a constant speed into a mold having a substantially horizontal bottom surface and a pair of side walls opposed in parallel across the bottom surface. The cast molten glass spreads in the mold with a uniform thickness and is formed into a glass plate having a width determined by the distance between the pair of side walls. The formed glass plate is pulled out in the horizontal direction from the opening of the mold in accordance with the molten glass supply speed so as to obtain a plate having a uniform thickness and width. The glass plate thus obtained is annealed to reduce strain and then cut into a required size. The glass piece obtained in this way is called a cut piece, but the cut piece is chamfered as necessary or machined to match the weight of the glass gob for press molding. In addition, barrel polishing is preferable for machining for chamfering the cut piece and adjusting the weight.

  In this manner, a glass gob for press molding made of the optical glass of the present invention having a predetermined weight can be obtained. Note that the glass gob for press molding may be formed with a release film for facilitating release during press molding, or may be coated with a powder release agent, if necessary. If a release agent is used, the release agent is transferred to glass, which is not preferable for precision press molding.

Next, the optical element of the present invention will be described. The optical element of the present invention is composed of the optical glass of the present invention described above. Therefore, the optical element of the present invention has various characteristics that the optical glass has. The typical ones have a refractive index (nd) of 1.8 to 2.1 and an Abbe number (νd) of 20 to 40, but they share the same characteristic of high transmittance on the short wavelength side in the visible range. To do. Of the optical elements made of the optical glass, λ ₇₀ and λ ₅ are in the above ranges, exhibit high visible transmittance, and no coloring is observed. According to such an optical element, it is possible to provide an optical element suitable for an optical system of a camera using a solid-state imaging element such as a digital camera, a video camera, or a camera incorporated in a mobile device.

  Examples of the optical element of the present invention include various kinds of lenses such as a spherical lens, an aspherical lens, a microlens, and a lens array, a prism, and a diffraction grating. In addition, you may form optical thin films, such as an antireflection film, a partial reflection film, and a high reflection film, in the optical element of this invention as needed.

  Next, the manufacturing method of the optical element of this invention is demonstrated. The method for producing an optical element of the present invention produces an optical element by heating and softening the press-molding glass gob or the press-molding glass gob produced by the above-described production method, and press-molding using a press mold. .

  The optical element has an optical functional surface having an optical function of refracting, transmitting, diffracting, and reflecting light. Depending on how the optical functional surface is formed, the press molding method can be roughly divided into the following two methods.

  The first method is a method of press-molding a press-molded product that approximates the shape of the target optical element and is larger than the optical element. The formed press-molded product is subjected to grinding and polishing, and the surface of the optical element including the optical functional surface is formed by machining. Since mechanical processing is performed after press molding, it is preferable to reduce the strain by subjecting the press molded product to an annealing treatment from the viewpoint of preventing breakage of the glass during processing. According to this method, the press molding can be performed in the atmosphere, and the powdery mold release agent can also be used.

The second method is called precision press molding, and is precisely processed into a shape obtained by inverting the shape of the target optical element on the molding surface of the press mold, and if necessary, forming a release film, The shape of the molding surface is precisely transferred to a glass gob for press molding that has been heated and softened by press molding. According to this method, the optical functional surface can be formed by press molding without grinding or polishing. However, press molding is performed in a non-oxidizing gas atmosphere such as a nitrogen gas atmosphere.

  In this second method, since the machining of the press-formed product is not essential, the strain may remain as long as the optical effect of the strain does not occur, and the annealing treatment of the press-formed product is omitted. You can also Furthermore, as a method of manufacturing an optical element, a molten glass is supplied to a press mold to form a press-molded product having a shape similar to the optical element, and then it is ground and polished to finish the optical element. There is also.

Since the refractive index (nd) and Abbe number (νd) of the optical element slightly change due to the thermal history in the optical element manufacturing process, an optical element having a precisely defined optical constant is produced. In this case, the glass composition and the thermal history in the manufacturing process may be adjusted in consideration of the changes in the refractive index (nd) and Abbe number (νd).
In this way, it is possible to provide an optical element that has a desired optical constant and excellent transmittance and that is particularly suitable as an optical component of a device on which a solid-state imaging device or the like is mounted.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
Examples 1-11
A raw material batch prepared so as to obtain 100 g of each glass having the composition shown in Table 1 and Table 2 is put in a platinum crucible, melted in a furnace set at 1300 ° C., stirred, clarified, and poured into an iron frame. The glass was kept at a temperature near the glass transition temperature (Tg) for 2 hours and then slowly cooled to obtain an optical glass.

About each optical glass, refractive index (nd), Abbe number ((nu) d), liquidus temperature (LT), (lambda) ₅ , (lambda) ₇₀ was measured as follows. The results are shown in Tables 1 and 2.
(1) Refractive index (nd), Abbe number (νd)
It measured about the optical glass obtained by cooling at the temperature fall rate of 30 degreeC per hour.
(2) Liquidus temperature (LT)
Prepare several platinum crucibles, put 50cm ³ glass into each crucible, put the lid in a furnace set in 10 ° C increments, and hold for 2 hours under different temperature settings Then, after cooling, the inside of the glass was observed with a 100 × microscope and determined from the presence or absence of crystals.
(3) λ ₅ , λ ₇₀
For polishing a sample of 10mm thickness was measured spectral transmittance, determined transmission rate of 5% of the wavelength (nm) of a lambda _5, transmittance of 70% of the wavelength (nm) of obtained as lambda _70.

表１および表２から、実施例に示す本発明の光学ガラスにおいては、ｎｄが１．８〜２．１、νｄが２０〜４０の範囲にあることが分かる。

From Tables 1 and 2, it can be seen that in the optical glass of the present invention shown in the examples, nd is in the range of 1.8 to 2.1 and νd is in the range of 20 to 40.

Example 12
The clarified and homogenized molten glass from which each glass of Examples 1 to 11 is obtained is melted and poured into a mold with one side wall opened from a platinum pipe at a constant flow rate, and formed into a glass plate having a constant thickness and width. However, the molded glass plate was pulled out from the opening of the mold. The drawn glass plate was annealed in an annealing furnace to reduce strain and obtain a glass plate made of the optical glass of Examples 1 to 11 that was homogeneous, colorless, and contained no foreign matter.
Next, each glass plate was cut into a square shape to obtain a plurality of cut pieces having the same dimensions. Further, a plurality of cut pieces were barrel-polished to match the target weight to obtain a glass gob for press molding.
Separately from the above method, the molten glass flows out of the platinum nozzle at a constant speed, and a number of receiving molds are successively transferred under the nozzle to receive a predetermined weight of molten glass lump one after another. The lump may be formed into a spherical shape or a flattened shape, annealed and then barrel-polished to match the target weight, and may be a glass gob for press molding.

Example 13
A powder mold release agent was applied to the entire surface of each glass gob obtained in Example 12, heated and softened with a heater, and then charged into a press mold having an upper mold and a lower mold. Each lens blank in the shape of a lens was press-molded by pressurizing with.
Subsequently, each lens blank is annealed to remove distortion and adjust to a desired refractive index and Abbe number. Each cooled lens blank was ground and polished to produce a lens. The series of steps was performed in the atmosphere.
Each of the obtained lenses was excellent in transmittance characteristics, and the various characteristics included in the optical glasses of Examples 1 to 11 were also provided in each lens. This lens can be provided with an antireflection film as required.
With such a lens, a good imaging optical system can be configured.

  Since the optical glass of the present invention has a high refractive index and reduced coloring, it can be suitably used for an imaging apparatus such as a digital camera using a CCD as an imaging element.

Claims (13)

In terms of% by weight, B ₂ O ₃ is 2 to 24 %, SiO ₂ is 0 to 30% (however, B ₂ O ₃ content> SiO ₂ content), La ₂ O ₃ is 10 to 50%, TiO ₂ the 3.94 to 30%, the ZnO 0 to 15% of _{ZrO 2 0~15%, Nb 2 O} 5 and 1-35%, 1-35% of BaO, 0 to 5% of SrO, and CaO 0 % or more but less than 8%, the MgO less than 13% 0% (however, BaO, SrO, total content 0-40% of CaO and MgO), a _Gd 2 _{O 3} 0 to _20%, a Y 2 _{O 3} 0 to 15% _Ta 2 _{O 5} and 0 to 18%, of WO ₃ 0.5% or more and less than 0%, Na ₂ O and _{K 2} O and Li less than 1.5% or more 0% ₂ O in total, B i ₂ O ₃ 0-20% and _Yb 2 _{O 3} 0% to _{Al 2 O 3 0~10%, Sb} 2 O 3 0% to 2% Fully and SnO ₂ unrealized 0 to _1%, free of GeO 2, _As 2 _{O 3} and Te, a refractive index (nd) of 1.8741 to 2.1, an Abbe number ([nu] d) 20 to 40, An optical glass comprising a transmittance characteristic in which λ ₇₀ is 460 nm or less . TiO ₂ The optical glass according to claim 1, wherein the content of is 13.4% or less. ZrO ₂ The optical glass according to claim 1, wherein the content of is 1 to 15%. WO ₃ The optical glass according to any one of claims 1 to 3, wherein the content of the glass is 0 to 0.4%. Y ₂ O ₃ The optical glass of any one of Claims 1-4 which does not contain. TiO ₂ Content of 13.4% or less, ZrO ₂ Content of 1-15%, WO ₃ Is 0 to 0.4%, Y ₂ O ₃ The optical glass of Claim 1 which does not contain. Liquid phase temperature is 1250 degrees C or less, The optical glass of any one of Claims 1-6. λ ₅ Is 400 nm or less, The optical glass of any one of Claims 1-7. A glass gob for press molding, comprising the optical glass according to any one of claims 1 to 8 , and subjected to press molding after being heated and softened. A method for manufacturing a press-molded product, wherein the press-molding glass gob according to claim 9 is heated and softened to perform press molding. The manufacturing method of the optical element which produces a press-molded product by the method of Claim 10, and machines the said press-molded product. An optical element comprising the optical glass according to any one of claims 1 to 8 . The optical element according to claim 12, which is any one of a lens, a prism, and a diffraction grating.