JP5729550B2 - Optical glass - Google Patents

Description

  The present invention relates to an optical glass. Specifically, the present invention relates to an optical glass suitable for an optical pickup lens of various optical disk systems, a video camera, a photographing lens of a general camera, and the like.

  Optical pickup lenses for CD, MD, DVD, and other various optical disk systems, video cameras, and photographing lenses for general cameras are generally manufactured as follows.

  First, molten glass is dropped from the tip of a nozzle to produce a droplet glass (droplet molding), and if necessary, grinding, polishing, and washing are performed to produce a preform glass. Alternatively, the molten glass is rapidly cast to produce a glass ingot, which is then ground, polished and washed to produce a preform glass. Subsequently, the preform glass is heated and softened, and pressure-molded with a precision-processed mold, and the surface shape of the mold is transferred to the glass to produce a lens. Such a molding method is generally called a mold press molding method (or a precision press molding method).

  When adopting a mold press molding method, a glass having a glass transition point as low as possible (for example, 600 ° C. or lower) is required to precisely mold press mold a lens while suppressing deterioration of the mold. Various glasses have been proposed.

  In general, in order to produce an optical glass having a low glass transition point, it is necessary to add many components that cause a decrease in refractive index, weather resistance or chemical durability, such as alkali components. Therefore, bismuth-based glass and phosphate-based glass have been proposed as glasses that can achieve a low glass transition point even if the amount of alkali component added is small (see, for example, Patent Documents 1 to 3). ).

JP 2007-106625 A JP 2001-048574 A JP-A-10-297936

Patent Document 1 describes Bi ₂ O ₃ —B ₂ O ₃ —SiO ₂ -based glass having a low glass transition point around 400 ° C., but glass containing a large amount of Bi ₂ O ₃ is yellow. It is easy to color and it is difficult to obtain high transmittance. Patent Documents 2 and 3 describe P-Sn-O-F glass and SnO-PbO-P ₂ O ₅ glass as glasses having a low glass transition point of 300 ° C or lower. Since these glasses contain harmful fluorine components and lead components as essential components, they are not environmentally preferable.

  Therefore, the present invention includes (1) no environmentally undesirable components, (2) easy to achieve a low glass transition point, (3) easy to achieve high refractive index characteristics, and (4) visible light transmittance. It is an object to provide an optical glass that can satisfy all the requirements of excellent, (5) excellent devitrification resistance during mold press molding, and (6) excellent weather resistance and chemical durability. To do.

  As a result of various studies, the present inventors have found that the above problems can be solved by a glass having a specific composition containing a large amount of SnO as a main component, and propose the present invention.

That is, the present invention contains SnO 43.5 to 90%, P ₂ O ₅ + B ₂ O ₃ + SiO ₂ 0.1 to 56.5% in mol% as a glass composition, and a lead component, arsenic It is related with the optical glass characterized by not containing a component and a fluorine component substantially.

  Since the optical glass of the present invention contains SnO in a large amount of 43.5 to 90% in the glass composition, it is easy to achieve high refractive index characteristics and is excellent in weather resistance and chemical durability. . Furthermore, a devitrified substance that hinders transparency is hardly generated during mold press molding.

The optical glass of the present invention contains 0.1 to 56.5% of P ₂ O ₅ , B ₂ O ₃ and SiO ₂ in addition to SnO, so that coloring is difficult to occur and visible. Excellent transmittance in the UV or near UV range. Furthermore, the optical glass of the present invention is an environmentally preferable glass because it contains substantially no harmful components such as a lead component, an arsenic component and a fluorine component.

  In the present invention, “substantially containing no lead component, arsenic component and fluorine component” means that these components are not intentionally added to the glass, and even unavoidable impurities are completely eliminated. It doesn't mean that. Objectively, it means that the content of these components including impurities is less than 0.1% by mass.

Second, the optical glass of the present invention preferably has a P ₂ O ₅ content of 0.1 to 56.5%.

  According to the said structure, it becomes easy to obtain the glass which has a low glass transition point.

Third, the optical glass of the present invention preferably has a molar ratio of SnO / (P ₂ O ₅ + B ₂ O ₃ + SiO ₂ ) of 1.2 or more.

  According to the said structure, it becomes easy to obtain the glass which has a high refractive index characteristic and was excellent in weather resistance and chemical durability.

  Fourthly, it is preferable that the optical glass of the present invention further contains 0 to 30% of CaO + SrO + BaO + MgO + ZnO in terms of mol% as a glass composition.

  According to the said structure, it becomes easy to obtain the glass excellent in devitrification resistance.

Fifth, the optical glass of the present invention preferably further contains 0 to 30% of Li ₂ O + Na ₂ O + K ₂ O as a glass composition in mol%.

  According to the said structure, the glass transition point is low and it becomes easy to obtain the glass excellent in devitrification resistance.

Sixthly, it is preferable that the optical glass of the present invention further contains 0 to 10% of Al ₂ O ₃ + Zr ₂ O as a glass composition in mol%.

  According to the said structure, it becomes easy to obtain the glass excellent in weather resistance and chemical durability.

Seventh, the optical glass of the present invention further has a glass composition of mol%, La ₂ O ₃ + Gd ₂ O ₃ + Ta ₂ O ₅ + WO ₃ + Nb ₂ O ₅ + TiO ₂ + Y ₂ O ₃ + Yb ₂ O ₃ + GeO. _{2 + Bi 2 O 3 + TeO} 2 that preferably contains 0-30%.

  According to the said structure, it becomes easy to obtain the glass which has a desired refractive index and Abbe number.

Eighth, in the optical glass of the present invention, the contents of Fe ₂ O ₃ , NiO and CoO are each preferably 1000 ppm or less.

Since Fe ₂ O ₃ , NiO and CoO are components that cause a decrease in transmittance, limiting the content of these components to the above range makes it easy to obtain a glass with high transmittance.

Ninthly, in the optical glass of the present invention, the content of Sb ₂ O ₃ is preferably 1000 ppm or less.

Since Sb ₂ O ₃ is a component that decreases devitrification resistance, limiting the content of the component to the above range makes it easy to obtain a glass having excellent devitrification resistance.

  Tenth, the optical glass of the present invention preferably has a glass transition point of 500 ° C. or lower.

  According to this configuration, mold press molding can be performed at a low temperature, and it is possible to suppress problems such as mold oxidation, mold contamination due to volatilization of glass components, and further, glass and mold fusion. it can.

  Eleventh, the optical glass of the present invention preferably has a refractive index of 1.55 or more and an Abbe number of 40 or less.

  Twelfth, in the optical glass of the present invention, the relational expression of the Abbe number (νd) and the partial dispersion ratio (θg, F) is in the range of (θg, F) ≦ −0.0047 × (νd) +0.76. It has an optical constant of

  In an optical device, generally, chromatic aberration is corrected by using a combination of an optical lens made of glass with low dispersion and large partial dispersion and an optical lens made of glass with high dispersion and small partial dispersion. In the optical glass of the present invention, when the Abbe number and the partial dispersion ratio satisfy the above relationship, it becomes easy to achieve optical characteristics with high dispersion and small partial dispersion, and an optical device excellent in chromatic aberration can be easily manufactured. .

Thirteenth, the optical glass of the present invention preferably has a glass coloring degree λ ₇₀ of less than 500 nm.

When the glass coloring degree λ ₇₀ satisfies the above range, it is possible to obtain a glass excellent in transmittance in the visible region or near ultraviolet region and suitable for optical elements such as various optical lenses. In the present invention, “coloring degree λ ₇₀ ” refers to a wavelength at which the transmittance is 70% in the transmittance curve.

  Fourteenth, the optical glass of the present invention is preferably used for mold press molding.

  Fifteenth, the present invention relates to an optical element using any one of the above optical glasses.

The optical glass of the present invention contains, as a glass composition, mol%, SnO 43.5 to 90%, P ₂ O ₅ + B ₂ O ₃ + SiO ₂ 0.1 to 56.5%, and a lead component, It is characterized by containing substantially no arsenic component or fluorine component.

  Below, the reason which specified content of each component as mentioned above is demonstrated. Unless otherwise specified, “%” means “mol%” in the following description of component contents.

  SnO is an essential component for achieving high refractive index and high dispersion optical characteristics and improving chemical durability, and also has an effect of reducing the partial dispersion ratio (θg, F). The SnO content is preferably 43.5 to 90%, 45 to 88%, 50 to 86%, 60 to 85%, particularly 67.5 to 83%. When the content of SnO is too small, it becomes difficult to achieve high refractive index characteristics, and the weather resistance and chemical durability tend to decrease. On the other hand, when there is too much content of SnO, there exists a tendency for devitrification resistance to fall.

P ₂ O ₅ , B ₂ O ₃ and SiO ₂ are components constituting the skeleton of the glass. Moreover, it is a component which raises the transmittance | permeability of glass, can suppress the transmittance | permeability fall near ultraviolet region, or can shift an absorption edge to the low wavelength side. In particular, in the case of a glass having a high refractive index, the effect of improving the transmittance due to these components is easily obtained. It also has the effect of suppressing devitrification. The total content of P ₂ O ₅ , B ₂ O ₃ and SiO ₂ is 0.1 to 56.5%, 10 to 50%, 15 to 47.5%, 20 to 45%, particularly 25 to 37 in total. % Is preferred. If the content of these components is too small, the above-described effects are hardly obtained. On the other hand, if the content is too large, the content of SnO ₂ becomes relatively small, and the refractive index tends to decrease.

_A preferable content of each component of the _{P 2 O 5, B 2 O} 3 and SiO ₂ are as follows.

The content of P ₂ O ₅ is 0 to 56.5%, 0.1 to 56.5%, 1 to 50%, 3 to 47.5%, 4 to 45%, 5 to 40%, particularly 10 to 37. % Is preferred. When the content of P ₂ O ₅ is too large, the refractive index tends to decrease. Further, weather resistance and chemical durability are likely to be lowered. Note that by adding P ₂ O ₅ aggressively glass low glass transition temperature can be easily obtained.

The content of B ₂ O ₃ is 0 to 56.5%, 0.1 to 56.5%, 1 to 50%, 3 to 47.5%, 4 to 45%, 5 to 40%, particularly 10 to 37. % Is preferred. If the B ₂ O ₃ content is too large, the refractive index tends to decrease. Further, weather resistance and chemical durability are likely to be lowered.

The content of SiO ₂ is 0 to 56.5%, 0.1 to 56.5%, 1 to 50%, 3 to 47.5%, 4 to 45%, 5 to 40%, particularly 10 to 37%. Preferably there is. When the content of SiO ₂ is too large, the refractive index tends to decrease. Further, striae and bubbles due to undissolved may remain in the glass, and the required quality as lens glass may not be satisfied.

In the present invention, in order to obtain a glass excellent in weather resistance and chemical durability, SnO / (P ₂ O ₅ + B ₂ O ₃ + SiO ₂ ) is 1.2 or more, 1.5 or more, 2 by mass ratio. As described above, 2.05 or more, particularly 2.4 or more is preferable. The upper limit is not particularly limited. However, if the ratio is too large, SnO ₂ is likely to precipitate as scum. Therefore, it is preferably 9 or less, 7 or less, particularly 5 or less.

  The optical glass of the present invention can contain the following components in addition to the above components.

  Alkaline earth metal oxides (RO) such as CaO, SrO and BaO, and MgO and ZnO are components that act as fluxes. By adding these components, the refractive index is greatly reduced or the Abbe number Will not rise significantly. Moreover, there exists an effect which improves a weather resistance, suppresses the elution of the glass component in various washing | cleaning solutions, such as polishing washing water, and suppresses the quality change of the glass surface in a hot and humid state. However, if the content of these components is too large, the liquidus temperature rises (liquidus viscosity decreases), and devitrified substances are likely to precipitate during the melting or molding process, which tends to narrow the working range. is there. As a result, it becomes difficult to mass-produce glass. Therefore, the total content of CaO, SrO, BaO, MgO and ZnO is preferably 0 to 30%, 0 to 20%, 0 to 10%, and particularly preferably 0.1 to 10%.

  In addition, preferable content of each component is as follows.

  CaO is an effective component for improving weather resistance, and is particularly effective in improving water resistance and alkali resistance. However, when the content is too large, it becomes easy to color. Therefore, the content of CaO is preferably 0 to 30%, 0 to 20%, particularly preferably 0.1 to 10%.

  SrO is a component that increases the refractive index. Moreover, compared with CaO, the effect of improving weather resistance, such as water resistance and alkali resistance, is high. Therefore, it becomes easy to obtain glass excellent in weather resistance by positively containing SrO. However, when the content is too large, it becomes easy to color. Therefore, the content of SrO is preferably 0 to 30%, 0 to 20%, particularly preferably 0.1 to 10%.

  BaO has a smaller increase in liquidus temperature than CaO, and is highly effective in improving water resistance and alkali resistance. However, when there is too much the content, it will become easy to color. Therefore, the content of BaO is preferably 0 to 30%, 0 to 20%, particularly preferably 0.1 to 10%.

  MgO is a component that increases the refractive index. Moreover, compared with CaO, the effect of improving weather resistance, such as water resistance and alkali resistance, is high. Therefore, it becomes easy to obtain a glass excellent in weather resistance by positively containing MgO. However, when there is too much the content, it will become easy to color. Therefore, the content of MgO is preferably 0 to 30%, 0 to 20%, particularly preferably 0.1 to 10%.

  ZnO is a component capable of reducing the viscosity without substantially reducing the refractive index. Therefore, the glass transition point can be lowered to obtain glass that is difficult to fuse with the mold. It also has the effect of improving weather resistance. Furthermore, since the tendency to devitrification is not strong compared to CaO, SrO, BaO and MgO, a homogeneous glass can be obtained even if contained in a large amount. ZnO is also a component that makes it difficult to color the glass. The content of ZnO is preferably 0 to 30%, 0 to 20%, particularly preferably 0.1 to 10%. If the ZnO content is too large, the weather resistance tends to decrease. Moreover, it becomes difficult to obtain high refractive index and high dispersion optical characteristics.

Li ₂ O is a component that has the greatest effect of lowering the softening point among alkali metal oxides, and has a small increase in liquidus temperature. In addition, there is an effect of reducing the partial dispersion ratio. Furthermore, the refractive index can be improved by substituting with B ₂ O ₃ , SiO ₂ or Al ₂ O ₃ . However, since Li ₂ O has a strong phase separation property, if its content is too large, the liquidus temperature rises and devitrified substances are likely to precipitate, which may reduce workability. In addition, Li ₂ O tends to reduce chemical durability and easily reduce transmittance. Therefore, the content of Li ₂ O is preferably 0 to 30%, 0 to 20%, particularly preferably 0.1 to 10%.

Na ₂ O has the effect of lowering the softening point, like Li ₂ O. _Further, by replacing the _{B 2 O 3, SiO 2,} Al 2 O 3, it is possible to improve the refractive index. In addition, there is an effect of reducing the partial dispersion ratio. However, if the content is too large, the refractive index tends to decrease significantly, or the generation of striae tends to be promoted. Moreover, liquidus temperature rises and a devitrification thing precipitates easily in glass. Therefore, the content of Na ₂ O is preferably 0 to 30%, 0 to 20%, particularly preferably 0.1 to 10%.

K ₂ O also has the effect of lowering the softening point, like Li ₂ O. _Further, by replacing the _{B 2 O 3, SiO 2,} Al 2 O 3, it is possible to improve the refractive index. It also has the effect of reducing the partial dispersion ratio. However, when there is too much the content, there exists a tendency for a refractive index to fall significantly or for a weather resistance to fall. Moreover, liquidus temperature rises and a devitrification thing precipitates easily in glass. Therefore, the content of K ₂ O is preferably 0 to 30%, 0 to 20%, particularly preferably 0.1 to 10%.

_{Incidentally,} Li 2 O, the total content of Na ₂ O and _{K 2} O 0 to 30%, and preferably 0-20%, in particular 0.1% to 10%. When there is too much total amount of these components, it will become easy to devitrify and there exists a tendency for chemical durability to fall. Moreover, it becomes difficult to obtain desired optical characteristics. Furthermore, it causes a decrease in transmittance.

Al ₂ O ₃ is a component that can form a glass skeleton together with SiO ₂ and B ₂ O ₃ . Further, there is the effect of improving the weather resistance, in particular, greater the effect of suppressing the of component such as _{P 2 O 5, B 2 O} 3 or alkali metal oxides in the glass is selectively eluted into water. The content of Al ₂ O ₃ is preferably 0 to 10%, particularly preferably 0.1 to 5%. When the content of Al ₂ O ₃ is too large, it tends to be devitrified. In addition, the melting temperature becomes high, and striae and bubbles due to undissolved tend to remain in the glass. As a result, there is a possibility that the required quality as lens glass may not be satisfied. Moreover, the transmittance tends to decrease.

Since ZrO ₂ forms a glass skeleton as an intermediate oxide, it has an effect of improving weather resistance. In particular, the effect of suppressing the selective elution of components such as P ₂ O ₅ , B ₂ O ₃ or alkali metal oxide in the glass into water is great. The content of ZrO ₂ is preferably 0 to 10%, particularly preferably 0.1 to 5%. When the content of ZrO ₂ is too large, it tends to be devitrified. In addition, the melting temperature becomes high, and striae and bubbles due to undissolved tend to remain in the glass. As a result, there is a possibility that the required quality as lens glass may not be satisfied. In addition, the transmittance tends to be low.

In order to obtain a glass excellent in weather resistance and chemical durability, Al ₂ O ₃ + ZrO ₂ is preferably 0 to 10%, particularly preferably 0.1 to 5%.

La ₂ O ₃ is a component that improves the refractive index without substantially reducing the transmittance. To obtain the effect, the content of _La 2 _{O 3} is 0.1% or more, and particularly preferably 1% or more. However, when the content is too large, the devitrification resistance is lowered, and at the same time, a highly dispersed glass is hardly obtained. Therefore, the upper limit of the content of La ₂ O ₃ is preferably 30% or less, 20% or less, and particularly preferably 10% or less.

Gd ₂ O ₃ is a component that improves the refractive index without lowering the transmittance as in La ₂ O ₃ . To obtain the effect, the content of _Gd 2 _{O 3} is 0.1% or more, and particularly preferably 1% or more. However, when the content is too large, the devitrification resistance is lowered, and at the same time, a highly dispersed glass is hardly obtained. Therefore, the upper limit of the content of Gd ₂ O ₃ is preferably 30% or less, 20% or less, and particularly preferably 10% or less.

Ta ₂ O ₅ has the effect of increasing the refractive index and dispersion without substantially reducing the transmittance. To obtain the effect, the content of _Ta 2 _{O 5} is 0.1% or more, and particularly preferably 1% or more. However, when there is too much the content, devitrification resistance will fall easily. Therefore, the upper limit of the content of Ta ₂ O ₅ is preferably 30% or less, 20% or less, and particularly preferably 10% or less.

WO ₃ has the effect of increasing the refractive index and dispersion without substantially reducing the transmittance. To obtain the effect, the content of WO ₃ is 0.1% or more, and particularly preferably 1% or more. However, when there is too much the content, devitrification resistance will fall easily. Therefore, the upper limit of the content of WO ₃ is preferably 30% or less, 20% or less, and particularly preferably 10% or less.

Nb ₂ O ₅ has the effect of increasing the refractive index and dispersion without substantially reducing the transmittance. To obtain the effect, the content of _Nb 2 _{O 5} is 0.1% or more, and particularly preferably 1% or more. However, when there is too much the content, devitrification resistance will fall easily. Therefore, the upper limit of the content of Nb ₂ O ₅ is preferably 30% or less, 20% or less, and particularly preferably 10% or less.

TiO ₂ is a component that has an effect of increasing the refractive index and dispersion. Moreover, it is a component effective in improving devitrification resistance as compared with Nb ₂ O ₅ and WO ₃ . To obtain the effect, the content of TiO ₂ is 0.1% or more, and particularly preferably 1% or more. However, if the content is too large, the transmittance tends to decrease. In particular, when a large amount of Fe component is contained in the glass as an impurity (for example, 20 ppm or more), the transmittance tends to be significantly reduced. Further, the devitrification resistance is likely to be lowered. Therefore, the content of TiO ₂ is preferably 30% or less, 20% or less, and particularly preferably 10% or less.

Y ₂ O ₃ has the effect of increasing the refractive index and dispersion without substantially reducing the transmittance. To obtain the _effect, the content of Y 2 _{O 3} is 0.1% or more, and particularly preferably 1% or more. However, when there is too much the content, devitrification resistance will fall easily. Therefore, the upper limit of the content of Y ₂ O ₃ is preferably 30% or less, 20% or less, and particularly preferably 10% or less.

Yb ₂ O ₃ has the effect of increasing the refractive index and dispersion without substantially reducing the transmittance. To obtain the effect, the content of _Yb 2 _{O 3} is 0.1% or more, and particularly preferably 1% or more. However, when there is too much the content, devitrification resistance will fall easily. Therefore, the upper limit of the content of Yb ₂ O ₃ is preferably 30% or less, 20% or less, and particularly preferably 10% or less.

GeO ₂ has the effect of increasing the refractive index and dispersion without substantially reducing the transmittance. To obtain the effect, the content of GeO ₂ is 0.1% or more, and particularly preferably 1% or more. However, when there is too much the content, devitrification resistance will fall easily. Therefore, the upper limit of the GeO ₂ content is preferably 30% or less, 20% or less, and particularly preferably 10% or less.

Bi ₂ O ₃ has the effect of increasing the refractive index and dispersion without substantially reducing the transmittance. To obtain the effect, the content of _Bi 2 _{O 3} is 0.1% or more, and particularly preferably 1% or more. However, when there is too much the content, devitrification resistance will fall easily. Therefore, the content of Bi ₂ O ₃ is preferably 30% or less, 20% or less, and particularly preferably 10% or less.

TeO ₂ has the effect of increasing the refractive index and dispersion without substantially reducing the transmittance. In addition, there is an effect of reducing the partial dispersion ratio. To obtain the effect, the content of TeO ₂ is 0.1% or more, and particularly preferably 1% or more. However, when there is too much the content, devitrification resistance will fall easily. Therefore, the upper limit of the TeO ₂ content is preferably 30% or less, 20% or less, and particularly preferably 10% or less.

In order to obtain a glass having a desired refractive index and Abbe number, La ₂ O ₃ + Gd ₂ O ₃ + Ta ₂ O ₅ + WO ₃ + Nb ₂ O ₅ + TiO ₂ + Y ₂ O ₃ + Yb ₂ O ₃ + GeO ₂ + Bi ₂ O ₃ + TeO ₂ is preferably 0.1% or more, particularly preferably 1% or more. However, if the total amount of these components is too large, the devitrification resistance tends to decrease, so the upper limit is preferably 30% or less, 20% or less, and particularly preferably 10% or less.

Fe ₂ O ₃ , NiO and CoO are components that reduce the transmittance. Therefore, the content of these components is preferably 1000 ppm or less.

  In addition, since the rare earth components of Ce, Pr, Nd, Eu, Tb, and Er may also decrease the transmittance, the content of these components is preferably 1000 ppm or less in terms of oxide.

Further, as a fining agent, may contain, for example, _Sb 2 _{O 3.} However, Sb ₂ O ₃ also works as an oxidizing agent, and SnO ₂ is likely to be generated as scum. Therefore, the content of Sb ₂ O ₃ is preferably 0 to 1000 ppm, 0 to 100 ppm, particularly 1 to 100 ppm.

Lead components (eg PbO), arsenic components (eg As ₂ O ₃ ) and fluorine components (eg F ₂ ) should be avoided in substantial glass for environmental reasons. Therefore, in the present invention, these components are not substantially contained.

  The refractive index (nd) of the optical glass of the present invention is preferably 1.55 or more, 1.6 or more, 1.65 or more, 1.7 or more, particularly 1.72 or more. The Abbe number (νd) of the optical glass of the present invention is preferably 40 or less, 35 or less, 30 or less, 28 or less, particularly 25 or less. By satisfying these optical characteristics, chromatic dispersion is reduced, and it is suitable as an optical lens for high-performance and small-sized optical devices.

  In the optical glass of the present invention, the Abbe number (νd) and the partial dispersion ratio (θg, F) preferably satisfy the relationship (θg, F) ≦ −0.0047 × νd + 0.76. If the Abbe number and the partial dispersion ratio do not satisfy this relationship, it becomes difficult to achieve high dispersion and low partial dispersion ratio optical characteristics.

The optical glass of the present invention preferably has a coloring degree λ ₇₀ of less than 500 nm, 470 nm or less, particularly 460 nm or less. When the coloring degree λ ₇₀ is too large, the transmittance in the visible region or the near ultraviolet region is inferior, and it tends to be difficult to use for various optical lenses.

  The optical glass of the present invention preferably has a glass transition point of 500 ° C. or lower, 450 ° C. or lower, 425 ° C. or lower, particularly 420 ° C. or lower. If the glass transition point is too high, mold press molding at low temperatures becomes difficult, and problems such as mold oxidation, mold contamination due to volatilization of glass components, and fusion between glass and mold occur. It becomes easy.

  Next, a method for producing an optical element such as an optical pickup lens or a photographing lens using the optical glass of the present invention will be described.

  First, after preparing a glass raw material so that it may become a desired composition, it fuse | melts in a glass melting furnace. Here, it is preferable to select an optimal glass raw material so as to have a predetermined composition to suppress the mixing of impurities or to adjust the glass melting atmosphere. Moreover, what was once vitrified can also be reused as a glass raw material. In particular, the melting atmosphere is preferably neutral or reducing. For example, it becomes easy to obtain a homogeneous glass by melting in an inert atmosphere such as nitrogen or argon. As the glass melting container, a refractory, quartz glass, platinum, gold, glassy carbon or the like can be used.

  Next, molten glass is dropped from the tip of the nozzle to produce droplet glass, and preform glass is obtained. Alternatively, the molten glass is rapidly cast to prepare a glass block, which is then ground, polished and washed to obtain a preform glass.

  Subsequently, the preform glass is put into a precision-worked mold, and pressure molding is performed while heating until it becomes softened, and the surface shape of the mold is transferred to the preform glass (mold press molding). In this way, an optical element such as an optical pickup lens or a photographing lens can be obtained.

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

  Tables 1 to 3 show examples (Nos. 1 to 23) and comparative examples (Nos. 24 to 26) of the present invention.

  Each sample was prepared as follows.

  First, glass raw materials were prepared so as to have the respective compositions shown in the table, and were melted at 1000 to 1250 ° C. for 1 hour using a glassy carbon container in a nitrogen atmosphere. After melting, the glass melt was poured onto a carbon plate, and after annealing, a sample suitable for each measurement was produced.

About the obtained sample, refractive index (nd), Abbe number (νd), partial dispersion ratio (θg, F), glass transition point (Tg), yield point (Tf), coloring degree λ ₇₀ , visible light average transmittance The chromaticity was measured. Moreover, it evaluated about vitrification and a weather resistance. The results are shown in Table 1.

  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 and the refractive index of the F-line (486.1 nm) of the hydrogen lamp and the C-line (656.3 nm) of the hydrogen lamp, and the Abbe number (νd) = (nd− 1) Calculated from the formula of (nF-nC).

  The partial dispersion ratio was determined by measuring the refractive index nC at the C line (wavelength 656.27 nm), the refractive index nF at the F line (wavelength 486.13 nm), and the refractive index ng at the g line (wavelength 435.835 nm), (θg, F) = (ng−nF) / (nF−nC).

  The glass transition point and yield point were measured with a dilatometer.

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

  The average visible light transmittance was determined by measuring the average transmittance in a wavelength range of 380 to 780 nm using a spectrophotometer for an optically polished glass sample having a thickness of 10 mm ± 0.1 mm.

  The chromaticity was measured using a spectrophotometer on an optically polished glass sample having a thickness of 10 mm ± 0.1 mm.

  In the vitrification, each sample was observed with a microscope, and “◯” was given when no devitrification was observed on the surface or inside, and “X” was given when devitrification was seen.

  As for weather resistance, a high temperature and high humidity tester was used, and after each sample was exposed for 500 hours under conditions of a temperature of 85 ° C. and a humidity of 85%, “○” indicates that there was no change in appearance, and a slight change in gloss was observed. The case was evaluated as “△”, and the case where the gloss was remarkably lost or cracked was evaluated as “x”.

  The optical glass of the present invention is suitable as a glass material for mold press molding used in optical pickup lenses for CD, MD, DVD and other various optical disk systems, video cameras, photographing lenses for general cameras, and the like. Further, it can be used as a glass material for optical communication manufactured by a molding method other than mold press molding.

Claims (13)

As a glass composition, it contains SnO 43.5 to 90%, P ₂ O ₅ + B ₂ O ₃ + SiO ₂ 0.1 to 56.5% in mol%, and substantially contains a lead component, an arsenic component, and a fluorine component. a manner have a contained light Studies glass for press molding, an Abbe's number ([nu] d) and the partial dispersion ratio ([theta] g, F) is, (θg, F) ≦ -0.0047 × (νd) +0. An optical glass characterized by satisfying the relationship of 76 . The optical glass according to claim 1, wherein the content of P ₂ O ₅ is 0.1 to 56.5%. The optical glass according to claim 1, wherein SnO / (P ₂ O ₅ + B ₂ O ₃ + SiO ₂ ) is 1.2 or more in terms of a molar ratio.   Furthermore, 0-30% of CaO + SrO + BaO + MgO + ZnO is contained by mol% as a glass composition, The optical glass in any one of Claims 1-3 characterized by the above-mentioned. Further, as a glass composition, _mol%, the optical glass according to claim 1, the _{Li 2 O + Na 2 O +} K 2 O , characterized in that it contains 0-30%. Further, as a glass composition, _mol%, the optical glass according to claim 1, the Al ₂ O 3 + Zr ₂ O, characterized in that it contains 0 to 10%. Furthermore, as a glass composition, La ₂ O ₃ + Gd ₂ O ₃ + Ta ₂ O ₅ + WO ₃ + Nb ₂ O ₅ + TiO ₂ + Y ₂ O ₃ + Yb ₂ O ₃ + GeO ₂ + Bi ₂ O ₃ + TeO ₂ in a mol% of 0 to 30 The optical glass according to claim 1, wherein the optical glass is contained. The optical glass according to claim 1, wherein the contents of Fe ₂ O ₃ , NiO, and CoO are each 1000 ppm or less. The optical glass according to any one of claims 1 to 8 the content of Sb ₂ O ₃ is equal to or is 1000ppm or less.   10. The optical glass according to claim 1, wherein the glass transition point is 500 ° C. or lower.   The optical glass according to claim 1, having a refractive index of 1.55 or more and an Abbe number of 40 or less. The optical glass according to any one of claims 1 to 11, coloration of lambda ₇₀ of the glass and less than 500 nm. Optical element characterized by using the optical glass according to any one of claims 1 to 12.