JP5850384B2 - Glass - Google Patents

Description

  The present invention relates to a glass excellent in transmittance in the visible region and suitable for various applications.

  Optical lenses for CD, MD, DVD, and other optical disc systems, imaging lenses for digital cameras, video cameras, camera-equipped mobile phones, and other lenses such as transmission / reception lenses used for optical communications are aspherical lenses. Is widely used. These lens glass materials are required to have high transmittance and low dispersion (high Abbe number) optical characteristics in the visible range. For example, in order to reduce the thickness of a camera or the like, optical characteristics having a refractive index nd of 1.5 to 1.9 and an Abbe number νd of 20 to 60 are required.

These glasses are generally produced by melting raw material batches and undergoing a refining process. Here, like _Sb 2 _O 3, SnO ₂ and CeO ₂ are used as a fining agent for floating the specks bubbles remaining in the molten glass in the refining process (e.g., see Patent Document 1 or 2).

JP 2007-176748 A JP 2007-169086 A

Among the above fining agents, Sb ₂ O ₃ in particular has a large environmental load, and its use is being restricted in recent years. However, when the content of Sb ₂ O ₃ is reduced, there is a problem that the visible region transmittance of the obtained glass is greatly reduced.

Accordingly, an object of the present invention is to provide a Sb ₂ content of O _3, even when limited to less than the reference value, high glass capable of maintaining the visible transmittance is fining agent.

As a result of various studies, the present inventors have found that the decrease in the visible region transmittance when the Sb ₂ O ₃ content in the glass is reduced is caused by the decrease in the transmittance particularly near the wavelength of 360 nm. I found it. Accordingly, the present inventors have found that the above-mentioned problems can be solved by limiting the difference in transmittance between wavelengths of 800 nm and 360 nm in glass to a specific range or less, and propose the present invention.

That is, the present invention is, in terms of mass%, _SiO 2 21% or _{more, Al 2 O 3 1~10%,} B 2 O 3 1~35%, BaO 3~25%, Li 2 O 2~12%, Sb 2 O ₃ less than 0.1%, Fe ₂ O ₃ 5-50 ppm, the total content of Pt and Rh is 1 ppm to 20 ppm and the refractive index nd is 1.55 to less than 1.71 (Pt ²⁺ content) / (total Pt content) ≦ 0.8, and the difference ΔT between the transmittance T _{800 at 800} nm and the transmittance T ₃₆₀ at ₃₆₀ nm is 15% or less. This relates to a glass (hereinafter referred to as “first form”).

Since the glass of the present invention has a content of Sb ₂ O ₃ that is a fining agent of less than 0.1%, the environmental load is small, and the difference ΔT between the transmittance T _{800 at 800} nm and the transmittance T ₃₆₀ at ₃₆₀ nm is By limiting to 15% or less, the visible region transmittance is improved. Therefore, the glass of the present invention is particularly suitable as a lens glass material.

In the present invention, the transmittance refers to a measured value at a thickness of 10 mm.
The glass of the present invention satisfies Pt ²⁺ content / total Pt content ≦ 0.8 on a mass basis.
When the content of Sb ₂ O ₃ , which is a fining agent, is reduced, the visible range transmittance of the obtained glass is greatly reduced because of Pt ²⁺ and Pt ²⁺ out of Pt ions and Rh ions eluted and mixed from the melting apparatus. And investigation by the inventors have revealed that Rh ³⁺ is the cause. This point is specifically explained as follows.
Pt ions and Rh ions can be in an oxidized or reduced state depending on other elements present in the solution. The redox reaction of Pt ions and Rh ions is represented by the following formula (1).
M ^{(A + n) +} + n / 2O ²⁻ Ｍ M ^{A +} + n / 4O ₂ (1)
Here, M represents Pt or Rh. In addition, A = 2 or 3, and n = 1 or 2. M ^{(A + n) +} in the formula represents the oxidation state of M, and M ^{A +} represents the reduction state of M. Pt and Rh have different absorption wavelengths in the oxidized state and the reduced state. Therefore, the redox state of Pt and Rh affects the transmittance of the glass obtained. Specifically, Pt ⁴⁺ and Rh ⁴⁺ in the oxidized state each absorb in the ultraviolet region and do not affect the visible region transmittance. On the other hand, Pt ²⁺ and Rh ³⁺ in the reduced state show absorption in the visible range and lower the visible range transmittance.
In particular, since melting tools used for glass melting often contain Pt, Pt ²⁺ in glass is often a problem. Therefore, in the present invention, by limiting the ratio of the Pt ²⁺ content so that (Pt ²⁺ content) / (total Pt content) ≦ 0.8 on the mass basis, the visible region transmittance is excellent. Glass can be used.
The glass of the present invention contains 5 to 50 ppm of Fe ₂ O ₃ .
The redox properties of Pt ions and Rh ions in glass may be greatly influenced by Fe ₂ O ₃ functioning as an oxidizing agent added to the glass raw material. Fe ₂ O ₃ functions as an oxidant by changing the valence of the metal element, and also functions as a fining agent by releasing oxygen itself when the valence of the metal element changes. Fe ₂ O ₃ releases oxygen when the valence of Fe changes from trivalent to divalent. In the present invention, by adding the content of Fe ₂ O _{3 in} the above range, Pt ions and Rh ions can be changed to oxidation states Pt ⁴⁺ and Rh ⁴⁺ to improve the visible region transmittance. It is also possible to ensure a good clarification effect.
As described above, the decrease in the visible transmittance is caused by Pt ²⁺ and Rh ³⁺ . Here, if the content of Pt and Rh is reduced to 20 ppm or less, the content of Pt ²⁺ and Rh ³⁺ can be reduced as a result, and a glass excellent in visible region transmittance can be obtained.

Second, the glass of the present invention, in _{mass%, SiO 2 21~60%, C} aO 0~15%, S rO 0~15%, N a 2 O 0~10%, K 2 O 0~10 %, Li ₂ O + Na ₂ O + K ₂ O 3-15%, ZrO ₂ 0-10%, La ₂ O ₃ 0-20%, Gd ₂ O ₃ 0-15 % .

Thirdly, the present invention provides, as another form, in mass%, _SiO 2 of less than 21% (not including _{0%), B 2 O 3} 8~23%, ZnO 6~40%, ZrO 2 2~10 %, La ₂ O ₃ 20-40%, Gd ₂ O ₃ 4-16%, Nb ₂ O ₅ 1-10%, Ta ₂ O ₅ 3-25%, Li ₂ O 0.1-5%, Sb ₂ O ₃ less than _{0.1%, Fe 2 O 3 5~} 50 ppm, the content of Pt and Rh are contained composition of 1ppm or 20ppm or less in total, the refractive index nd of at 1.71 or more glass mass (Pt ²⁺ content) / (total Pt content) ≦ 0.8 on the basis, and the difference ΔT between the transmittance T _{800 at 800} nm and the transmittance T ₃₆₀ at ₃₆₀ nm is 20% or less. It relates to glass (hereinafter referred to as “second form”).

Fourthly , the glass of the present invention preferably has a total content of metal oxides functioning as an oxidizing agent on a mass basis, more than the total content of Pt and Rh.

In the glass, when the content of the metal oxide functioning as an oxidizing agent increases, the equilibrium state of the above formula (1) is biased to the left, and the oxidized states Pt ⁴⁺ and Rh ⁴⁺ increase. As a result of studies by the present inventors, when the total content of metal oxides functioning as an oxidant is larger than the total content of Pt and Rh on a mass basis, a glass having particularly good visible range transmittance is obtained. I found out that

Fifth , the glass of the present invention is preferably an optical glass.

  By applying the glass of the present invention to an optical glass, the effects of the present invention can be enjoyed accurately.

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

As described above, since Sb ₂ O ₃ is an environmental load substance, its content is limited. Further, in the case of mold press molding applications, Sb ₂ O ₃ has been found to cause white turbidity on the glass surface, and it is preferable to limit the use as much as possible. In the present invention, because it limits the content of Sb ₂ O ₃ within the above range, a glass suitable for press molding applications.

Glass sample No. in an Example. It is a graph which shows the transmittance | permeability curve of 1-4. Glass sample No. in an Example. It is a graph which shows the transmittance | permeability curve of 5 and 6.

The glass of the first form of the present invention is characterized in that it contains 21% by mass or more of SiO ₂ in the composition and has a refractive index nd of less than 1.71. On the other hand, the glass of the second embodiment of the present invention is characterized by containing SiO ₂ in an amount of less than 21 mass% (not including 0%) in the composition and having a refractive index nd of 1.71 or more.

In these two forms, the content of Sb ₂ O ₃ is limited to less than 0.1%. When the content of Sb ₂ O ₃ is 0.1% or more, it is not preferable in terms of the environment, and when used for mold press molding, the glass surface may become cloudy. The content of Sb ₂ O ₃ is preferably 0.01% (100 ppm) or less, particularly less than 0.0005% (5 ppm). On the other hand, as will be described later, Sb ₂ O ₃ also has a function as an oxidant that changes Pt ions and Rh ions to an oxidized state and a function as a clarifier. Therefore, when it is intended to be sufficiently exhibited these features, _Sb 2 _{O 3} and 1ppm or more preferably it contains particularly 10ppm or more.

The glass of the first embodiment of the present invention is characterized in that a difference ΔT between a transmittance T _{800 at 800} nm and a transmittance T ₃₆₀ at ₃₆₀ nm is 15% or less. When ΔT is greater than 15%, the visible region transmittance is inferior, making it unsuitable for various optical lens applications. ΔT is more preferably 10% or less.

The glass of the second embodiment of the present invention is characterized in that a difference ΔT between a transmittance T _{800 at 800} nm and a transmittance T ₃₆₀ at ₃₆₀ nm is 20% or less. When ΔT is larger than 20%, the visible light transmittance is inferior, making it unsuitable for various optical lens applications. ΔT is more preferably 18% or less.

The glass of the second embodiment of the present invention limits SiO ₂ to less than 21% in order to increase the refractive index, and may contain Nb ₂ O ₅ or WO ₃ . Therefore, the transmittance in the visible region tends to be low. Such a glass having a low transmittance in the visible region is relatively less susceptible to a decrease in transmittance due to absorption of Pt ²⁺ . However, for example, by suppressing the absorption of Pt ²⁺ , the difference ΔT between the transmittance T _{800 at 800} nm and the transmittance T ₃₆₀ at ₃₆₀ nm can be reduced to 20% or less, and the glass is particularly suitable as a glass material for lenses. be able to.

In the present invention, the ratio of (Pt ²⁺ content) / (total Pt content) on the mass basis is preferably 0.8 or less, 0.5 or less, and particularly preferably 0.3 or less. When the ratio exceeds 0.8, the visible light transmittance tends to decrease.

In the present invention, the total content of Pt and Rh is preferably 20 ppm or less and 10 ppm or less. When the total amount of Pt and Rh exceeds 20 ppm, the contents of Pt ²⁺ and Rh ³⁺ increase, and the visible region transmittance tends to decrease. The lower limit is not particularly limited, but the effect of the present invention can be easily enjoyed particularly when the total amount of Pt and Rh is 1 ppm or more. As described above, since melting equipment used for glass melting often contains Pt, when the content of Rh can be ignored, the content of Pt alone preferably satisfies these ranges. .

  In the glass of the present invention, it is preferable to add a metal oxide that functions as an oxidizing agent in order to change Pt ions and Rh ions into an oxidized state. As the metal oxide that functions as an oxidant, a metal oxide that changes its valence and functions as an oxidant is applicable. Specific examples include oxides such as Sb, Fe, Ce, and Sn.

The content of the metal oxide that functions as an oxidant is preferably 1 to less than 200 ppm, 5 to 100 ppm, particularly 10 to 50 ppm. When the metal oxide functioning as an oxidizing agent is less than 1 ppm, the Pt ²⁺ and Rh ³⁺ content in the glass tends to increase, and the visible region transmittance tends to decrease. On the other hand, if the metal oxide functioning as an oxidizing agent exceeds 200 ppm, it may cause coloring (Fe ₂ O ₃ , CeO ₂ ), or cause cloudiness on the glass surface when molded by press (Sb ₂ O ₃ , SnO ₂ ).

Among metal oxides functioning as an oxidizing agent, Sb ₂ O ₃ and Fe ₂ O ₃ have a strong oxidizing power against Pt and Rh. Therefore, by adding these, it becomes possible to effectively reduce the contents of Pt ²⁺ and Rh ³⁺ and to improve the visible region transmittance.

Incidentally, _Fe 2 _{O 3} is the absorption of Fe itself is near 300 nm, if the content too much leads to a decrease in visible transmittance. Therefore, the content of Fe ₂ O ₃ is preferably 100 ppm or less, particularly preferably 50 ppm or less.

In order to sufficiently reduce the content of Pt ²⁺ and Rh ³⁺ , particularly in order to make the ratio of (Pt ²⁺ content) / (total Pt content) 0.8 or less, a metal oxide that functions as an oxidizing agent It is preferable that the content of is larger than the total amount of Pt and Rh. Specifically, the ratio of (amount of metal oxide functioning as an oxidizing agent) / (total amount of Pt and Rh) is preferably more than 1, 2 or more, particularly 5 or more.

Although the contents of Pt ²⁺ and Rh ³⁺ can be adjusted by the melting temperature and the annealing temperature, it is difficult to sufficiently reduce the contents of Pt ²⁺ and Rh ³⁺ by these methods. Further, when the melting temperature is changed, devitrification and inhomogeneity are likely to occur, so that mass productivity may be reduced.

If the glass of the present invention is a low softening point glass that can be used for mold press molding, it can be clarified sufficiently even if the Sb ₂ O ₃ content is less than 0.1%. In the present invention, the low softening point glass specifically refers to a glass having a glass transition point of 650 ° C. or lower, particularly 630 ° C. or lower.

Of the first embodiment of the glass of the invention, as particularly preferred, in _{mass%, SiO 2 21~60%, B} 2 O 3 1~35%, CaO 0~15%, BaO 0~25%, SrO _{0~15%, Li 2 O 2~12%} , Na 2 O 0~10%, K 2 O 0~10%, Li 2 O + Na 2 O + K 2 O 3~15%, ZrO 2 0~10%, La 2 Glass containing O ₃ 0-20%, Gd ₂ O ₃ 0-15%, Sb ₂ O ₃ less than 0.1% (glass composition A) may be mentioned. According to the composition, an optical constant having a refractive index nd of less than 1.55 to 1.71 and an Abbe number νd of 30 or more is easily achieved.

Further, in the second embodiment of the glass of the present invention, as particularly preferred, in _mass%, SiO 2 of less than _{3~21%, B 2 O 3 8~23} %, 0~40% ZnO, ZrO 2 2~ 10%, La ₂ O ₃ 20-46%, Gd ₂ O ₃ 0-16%, Nb ₂ O ₅ 0-10%, Ta ₂ O ₅ 0-25%, Sb ₂ O ₃ less than 0.1% composition Glass containing glass (glass composition B). According to the composition, it is easy to achieve an optical constant having a refractive index nd of 1.71 to 1.90 and an Abbe number νd of 20 or more.

The reason for limiting each composition range is shown below. In the following description, “%” means “% by mass” unless otherwise specified. The reason for limiting Sb ₂ O ₃ is as described above, and is omitted in the following description.

(Glass composition A)
SiO ₂ is a component constituting a glass skeleton, and is a component having a large effect of increasing the Abbe number after B ₂ O ₃ . It also has the effect of improving weather resistance. The content of SiO ₂ is preferably 21 to 60%, 25 to 60%, 33 to 55%, particularly preferably 42 to 55%. When the content of SiO ₂ is less than 21%, the weather resistance and acid resistance tend to deteriorate. When the content of SiO ₂ is more than 60%, the refractive index tends to decrease and the softening point tends to increase.

B ₂ O ₃ is a component that increases the Abbe number. In order to obtain an Abbe number of 30 or more, the content of B ₂ O ₃ is preferably 1 to 35%, 3 to 14%, particularly preferably 3 to 11%. In particular, in order to obtain an Abbe number of 55 to 65, the content of B ₂ O ₃ is preferably 12 to 30%. When the content of B ₂ O ₃ is more than 35%, the acid resistance tends to decrease.

  CaO has a great effect of lowering the softening point next to alkali metal oxides, and is a component that can improve weather resistance and acid resistance by substitution with alkali metal oxides. It also has the effect of increasing the refractive index. However, if contained in a large amount, the glass surface is likely to be altered when exposed to a high temperature and humidity environment for a long period of time. Therefore, the content of CaO is preferably 0 to 15%, 0 to 10%, particularly preferably 0.5 to 10%.

  BaO is a component that improves weatherability, increases the refractive index, and lowers the liquidus temperature to improve workability. However, if contained in a large amount, the glass surface is likely to be altered when exposed to a high temperature and humidity environment for a long period of time. Therefore, the content of BaO is preferably 0 to 25%, 3 to 25%, particularly 3 to 12%.

  SrO, like BaO, is a component that improves weatherability, raises the refractive index, and lowers the liquidus temperature to improve workability. However, if contained in a large amount, the glass surface is likely to be altered when exposed to a high temperature and humidity environment for a long period of time. Therefore, the content of SrO is preferably 0 to 15%, particularly preferably 0.1 to 10%.

Li ₂ O is added as an essential component because it has an effect of lowering the melting temperature and softening point and improving workability. The content of Li ₂ O is preferably 2 to 12%, particularly preferably 3 to 10%. When the content of Li ₂ O is less than 2%, the melting temperature tends to increase. On the other hand, when the content of Li ₂ O is more than 12%, the phase separation becomes strong, the liquidus temperature tends to be high, and the workability tends to be lowered.

Na ₂ O, like Li ₂ O, has the effect of lowering the melting temperature and softening point and improving workability. However, when the content is too large, volatiles is often formed during glass melting with B _{2 O} 3 _{-Na 2 O,} tends to promote the formation of striae. Therefore, the content of Na ₂ O is preferably 0 to 10%, particularly preferably 0.1 to 5%.

K ₂ O, like Li ₂ O, has the effect of lowering the melting temperature and softening point and improving workability. However, when the content is too large, volatiles is often formed during glass melting with B _{2 O} 3 _{-K 2 O,} tends to promote the formation of striae. Therefore, the content of K ₂ O is preferably 0 to 10%, particularly preferably 0.1 to 5%.

The total amount of Li ₂ O, Na ₂ O and K ₂ O is 3 to 15%, preferably 3 to 12%. If the total amount of these components is more than 15%, the glass surface tends to be altered in the cleaning process. In addition, the liquidus temperature rises and the working temperature range becomes narrow, which may adversely affect mass productivity. On the other hand, when the total amount of these components is less than 3%, the softening point tends to be high and workability tends to be lowered.

ZrO ₂ is a component that increases the refractive index and improves the weather resistance. However, if it is contained excessively, the Abbe number tends to decrease and the tendency to devitrification increases, making it difficult to obtain a homogeneous glass. Therefore, the content of ZrO ₂ is preferably 0 to 10%, particularly preferably 0 to 5.

La ₂ O ₃ has the effect of increasing the refractive index without decreasing the Abbe number. However, when it contains excessively, the tendency to devitrification will become strong and it will become difficult to obtain homogeneous glass. Therefore, the content of La ₂ O ₃ is preferably 0 to 20%, 3 to 20%, particularly preferably 7.5 to 15%. In addition, in the case of a glass containing a total amount of alkaline earth metal oxides (MgO, CaO, BaO, SrO) of 23% or more, the addition of La ₂ O ₃ increases the tendency to devitrify, so that La ₂ O ₃ The upper limit of the content is preferably 2.5%.

Gd ₂ O ₃ also has the effect of increasing the refractive index without reducing the Abbe number, like La ₂ O ₃ . However, when it contains excessively, the tendency to devitrification will become strong. Therefore, the content of Gd ₂ O ₃ is preferably 0 to 15%, particularly preferably 0.1 to 10%.

In the glass composition A, in addition to the above components, Al ₂ O ₃ , MgO, TiO ₂ , Nb ₂ O _{5 and the} like can be added for the purpose of adjusting optical constants and improving weather resistance.

Al ₂ O ₃ is a component constituting a glass skeleton together with SiO ₂ and has an effect of improving weather resistance. Furthermore, by adding Al ₂ O _3, it can be the alkali component in the glass can be effectively suppressed eluting in water. However, when the content of Al ₂ O ₃ increases, the refractive index tends to decrease and the softening point tends to increase. Therefore, the content of Al ₂ O ₃ is preferably 0 to 10%, 0 to 8%, particularly preferably 1 to 5%.

  MgO is a component that increases the weather resistance and the refractive index. However, if contained excessively, the phase separation tendency becomes strong and the liquidus temperature tends to increase. Therefore, the content of MgO is preferably 0 to 5%, 0 to 4%, particularly preferably 0.1 to 3%.

TiO ₂ is a component that increases the refractive index and improves the weather resistance. However, when it contains excessively, it will become easy to color glass. Therefore, the content of TiO ₂ is preferably 0 to 1%, particularly preferably 0.1 to 0.4%.

Nb ₂ O ₅ is an effective component for increasing the refractive index, but has a problem that the Abbe number is significantly reduced. Therefore, the content of Nb ₂ O ₅ is preferably 0 to 15%, particularly preferably 0.1 to 10%.

In the glass composition A, Bi ₂ O ₃ and P ₂ O ₅ can be added as appropriate.

Bi ₂ O ₃ is a component that increases the refractive index. However, since the glass tends to be colored when excessively contained, the content is preferably 5% or less.

P ₂ O ₅ is a component that lowers the liquidus temperature. However, since it will become easy to phase-divide glass when it contains excessively, and the surface tends to become cloudy in a washing | cleaning process, the content is preferable to be 5% or less.

(Glass composition B)
SiO ₂ is a component constituting a glass skeleton, and has an effect of suppressing devitrification and improving weather resistance. It also has the effect of increasing the Abbe number. The content of SiO ₂ is preferably less than 3 to 21%, 3 to 20%, 3.5 to 16%, particularly preferably 3.5 to 10%. When the content of SiO ₂ is less than 3%, the glass becomes unstable and the devitrification resistance is deteriorated, and the weather resistance such as acid resistance and water resistance tends to deteriorate while phase separation occurs. On the other hand, when the content of SiO ₂ is 21% or more, the refractive index tends to decrease or the softening point tends to increase.

B ₂ O ₃ is a component that constitutes the glass skeleton, and is also a component that maximizes the Abbe number. The content of B ₂ O ₃ is 8 to 23%, preferably 8.5 to 20%, more preferably 9 to 15%. When B ₂ O ₃ is less than 8%, it becomes difficult to obtain a high Abbe number. On the other hand, when the content of B ₂ O ₃ is more than 23%, a devitrified material formed of B ₂ O ₃ and La ₂ O ₃ is easily generated during glass molding, and the refractive index is lowered and the weather resistance is reduced. There is a tendency to get worse.

  ZnO is a component that increases the refractive index, and when added in a large amount, high refractive index and low dispersion can be achieved. It also has the effect of improving weather resistance. In addition, since ZnO is not so strong in devitrification as an alkaline earth metal component, homogeneous glass can be obtained even if it is contained in a large amount. Furthermore, since it has the effect of reducing the glass viscosity, the glass transition point can be lowered, and a glass that is difficult to fuse with the mold can be obtained. The content of ZnO is preferably 0 to 40%, 6 to 40%, 8.5 to 30%, 10 to 25%, particularly preferably 15 to 21%. If the ZnO content is more than 40%, the weather resistance tends to deteriorate.

ZrO ₂ is a component that increases the refractive index without decreasing the Abbe number. In addition, since a glass skeleton is formed as an intermediate oxide, the effect of improving devitrification resistance (suppression of devitrified substances formed by B ₂ O ₃ and La ₂ O ₃ ) and improving chemical durability. There is also. However, when the content of ZrO ₂ increases, the glass transition point increases, mold press formability deteriorates, and at the same time, a devitrified material containing ZrO ₂ as a main component tends to precipitate. Therefore, the content of ZrO ₂ is preferably 2 to 10%, 3 to 8%, particularly 4 to 8%.

La ₂ O ₃ is a component that increases the refractive index without decreasing the Abbe number. The content of La ₂ O ₃ is preferably 20 to 46%, 25 to 45%, 30 to 45%, 31 to 42%, 32 to 40%, particularly preferably 32 to 37%. When the content of La ₂ O ₃ is less than 20%, it is difficult to obtain a sufficiently high refractive index. On the other hand, when the content of La ₂ O ₃ is more than 46%, a devitrified material formed by B ₂ O ₃ and La ₂ O ₃ is easily generated during glass molding, and the devitrification resistance tends to deteriorate. There is.

Gd ₂ O ₃ is a component that increases the refractive index. Further, there is the effect of improving the devitrification resistance (B ₂ O ₃ and La ₂ O ₃ in devitrification suppression formed), a component capable of expanding the working temperature range. On the other hand, when it is contained in a large amount, the phase separation tendency of the glass becomes strong, and it becomes difficult to obtain a homogeneous glass. _Further, B ₂ O _3, the _La 2 _{O 3} and _Ta 2 _{O 5} composition system _{comprising, B 2 O 3, La 2} O 3 and _Ta 2 _{O 5} devitrification formed by precipitation on the glass surface (surface Devitrification). Therefore, the content of Gd ₂ O ₃ is preferably 0 to 16%, 4 to 16%, particularly preferably 5 to 12%. Although the Abbe number tends to decrease when Gd ₂ O ₃ is added, the Abbe number decreases compared to other components that reduce the Abbe number (for example, Ta ₂ O ₅ , WO ₃ , TiO _2, etc.). The rate is low.

Nb ₂ O ₅ is a component having a large increase in refractive index with respect to a decrease in Abbe number, and is an effective component for obtaining high refractive index and low dispersion optical characteristics. Further, the glass containing a large amount of Ta ₂ O ₅ has a function of improving devitrification resistance (suppression of devitrified substances formed of La ₂ O ₃ , Ta ₂ O ₅ and B ₂ O ₃ ). The content of Nb ₂ O ₅ is preferably 0 to 10%, particularly preferably 1 to 10%. When the content of Nb ₂ O ₅ exceeds 10%, surface devitrification tends to occur. If Nb ₂ O ₅ is contained in an amount of 1% or more, a refractive index of 1.71 or more can be easily obtained.

Ta ₂ O ₅ has the effect of increasing the refractive index, chemical durability, and devitrification resistance (suppression of devitrification formed by B ₂ O ₃ and La ₂ O ₃ ). Further, it is a component with a large increase in refractive index with respect to a decrease in Abbe number, and is an effective component for obtaining optical characteristics of high refraction and low dispersion. The content of Ta ₂ O ₅ is particularly preferably 0 to 25%, 3 to 22.5%, 7 to 18%, or 10 to 18%. When the content of Ta ₂ O ₅ is less than 3%, it becomes difficult to obtain a high refractive index, particularly a refractive index of 1.71 or more. On the other hand, if the content of Ta ₂ O ₅ is more than 25%, the Abbe number decreases, and it becomes difficult to obtain desired optical characteristics. In addition, a devitrified material formed by La ₂ O ₃ , Gd ₂ O ₃ , Ta ₂ O ₅ and B ₂ O ₃ is precipitated, and the liquidus temperature is likely to rise. Further, the cost is increased, which is not preferable from an economic viewpoint.

In the glass composition B, as a component other than the above, for example, an alkali metal oxide such as WO ₃ , TiO ₂ , or LiO ₂ can be appropriately added.

WO ₃ and TiO ₂ have the effect of increasing the refractive index, but the increase in the refractive index with respect to the decrease in the Abbe number is small compared to ZnO, Ta ₂ O ₅ , and Nb ₂ O ₅ . Accordingly, if added in a large amount, it becomes difficult to maintain a high refractive index and low dispersion, and therefore, it is necessary to use it while taking into consideration the balance with other components. An alkali metal oxide such as Li ₂ O is a component for lowering the softening point.

WO ₃ has the effect of increasing the refractive index and also has the effect of improving devitrification resistance because it forms a glass skeleton as an intermediate oxide. The content of WO ₃ is preferably 0 to 10%, 0 to 5%, 0 to 3%, 0 to 2.5%, particularly preferably 0.1 to 1.5%. If the WO ₃ is more than 10%, the Abbe number decreases, and it becomes difficult to obtain desired optical characteristics. In addition, the transmittance in the short wavelength region may be reduced.

TiO ₂ has the effect of increasing the refractive index and also improving the devitrification resistance. The content of TiO ₂ is preferably 0 to 20%, 0 to 5%, 0 to 2.5%, particularly preferably 0.1 to 2.5%. When the content of TiO ₂ is more than 20%, the Abbe number decreases and it becomes difficult to obtain desired optical characteristics. Further, the transmittance in a short wavelength region (for example, 390 to 440 nm) is lowered, which may hinder use as a short wavelength lens.

In particular, from the viewpoint of suppressing a decrease in transmittance in the short wavelength region, the total amount of WO ₃ + TiO ₂ is preferably 10% or less, particularly 5% or less.

Li ₂ O has the greatest effect of lowering the softening point among alkali metal oxides. However, since Li ₂ O has a strong phase separation property, when it is excessively contained, a devitrified material containing B ₂ O ₃ and La ₂ O ₃ as main components is precipitated, and the liquid phase temperature becomes high and the workability may be deteriorated. There is. In addition, the volatile matter generated during mold press molding increases, or it becomes easy to fuse with a mold, and mold press molding tends to be difficult. Therefore, the content of Li ₂ O is preferably 0 to 5%, 0 to 3%, or 0.1 to 1.5%.

In addition, it is preferable not to contain substantially the lead component (PbO), the arsenic component (As ₂ O ₃ ), and the F component (F ₂ ) in both the glass composition A and the glass composition B for environmental reasons. Here, “substantially not containing” means that these components are not intentionally added, and does not exclude contamination at the impurity level. Specifically, it means that these components are each less than 0.1%.

  Next, the manufacturing method of optical components, such as a lens using the glass of this invention, is demonstrated.

  First, a glass material prepared to have a desired composition is melted in a melting container. The melting temperature is preferably 1150 to 1400 ° C. If the melting time is too short, clarification may be insufficient. Therefore, it is preferably 2 hours or more, particularly 3 hours or more. However, from the viewpoint of preventing glass coloring due to the penetration of Pt and Rh, the melting time is preferably within 8 hours, particularly within 5 hours.

  If the depth of the glass melt in the melting vessel is too shallow, the productivity will deteriorate, so it is preferably 30 mm or more, particularly 50 mm or more. On the other hand, if it is too deep, it takes time for the fine bubbles generated in the molten glass to float, so 1 m or less, particularly 0.5 m or less is preferable.

  Subsequently, the molten glass is formed into a preform having a size that can be mold-pressed, and the preform is subjected to mold-press molding while being heated, and processed into a desired shape. Thereafter, it is washed and dried to obtain an optical component.

  The preform may be produced by cutting out and polishing into a predetermined shape from a plate-like or lump-like glass piece, and after cooling and shaping by dropping a molten glass continuously by a predetermined amount, It is preferable to use a droplet forming method in which grinding, polishing, and cleaning are performed because they can be easily manufactured.

  Hereinafter, the glass of this invention is demonstrated in detail based on an Example.

  Tables 1-3 show examples (Nos. 1-3, 5, 7, 9, 11, 13) and comparative examples (Nos. 4, 6, 8, 10, 12, 14) of the present invention.

  Each sample was produced as follows.

  The glass raw material prepared so that it may become a composition of Tables 1-3 is thrown into a platinum crucible, Sample No. 1 to 10 were melted at 1300 ° C. and Samples 11 to 14 were melted at 1350 ° C. for 2 hours. Next, the molten glass was poured onto a carbon plate, cooled and solidified, and then annealed to obtain a glass sample.

The sample thus obtained was measured for Pt and Rh content, Pt ²⁺ ratio, glass transition point, transmittance, refractive index, and Abbe number. The results are shown in Tables 1-3.

The Pt and Rh contents were measured as follows. First, the ground glass sample was decomposed with a mixed acid (HF, HClO ₄ , HNO ₃ , HCl) and then dried by heating to obtain a salt. Subsequently, nitric acid was added to the obtained salt and analyzed and quantified by an ICP mass spectrometer.

The proportion of Pt ²⁺ was analyzed with EXAFS by irradiating a glass sample with high energy.

  The glass transition point was obtained from the intersection of the low temperature line and the high temperature line in the thermal expansion curve.

The transmittance was measured using a 10 mm thick double-side polished sample. The transmittance T _{800 at 800} nm and the transmittance T ₃₆₀ at ₃₆₀ nm were read from the obtained transmittance curve, and the difference ΔT (= T ₈₀₀ −T ₃₆₀ ) was determined.

  The refractive index and Abbe number were measured by the V block method.

  In FIG. 1-4, the transmittance | permeability curve of the samples 5 and 6 is shown in FIG.

No. which is an example of the present invention. Samples Nos. 1 to 3, 5, 7, 9, 11, and 13 are comparative samples. The (Pt ²⁺ content) / (total Pt content) of 4, 6, 8, 10, 12, and 14 was larger than 0.8, and the transmittance was inferior in the region of wavelengths of about 330 to 400 nm.

  The glass of the present invention is used for optical glass requiring high visible light transmittance, specifically, optical pickup lenses for CD, MD, DVD, and other various optical disk systems, digital cameras, video cameras, camera-equipped mobile phones, etc. It is suitable as a glass material for optical lenses such as an imaging lens, a transmission / reception lens used for optical communication, and the like.

Claims (6)

By mass%, _SiO 2 21% or _{more, Al 2 O 3 1~10%,} B 2 O 3 1~35%, BaO 3~25%, Li 2 O 2~12%, Sb 2 O 3 0.1% Less than, Fe ₂ O ₃ 5-50 ppm, the total content of Pt and Rh contains a composition of 1 ppm or more and 20 ppm or less, and the refractive index nd is 1.55 or more and less than 1.71, (Pt ²⁺ content) / (total Pt content) ≦ 0.8 on the basis, and the difference ΔT between the transmittance T _{800 at 800} nm and the transmittance T ₃₆₀ at ₃₆₀ nm is 15% or less. Glass. By _{mass%, SiO 2 21~60%, CaO} 0~15%, SrO 0~15%, Na 2 O 0~10%, K 2 O 0~10%, Li 2 O + Na 2 O + K 2 O 3~15% _{, ZrO 2 0~10%, La 2} O 3 0~20%, glass according to claim 1, characterized by containing the composition of _Gd 2 O 3 _0~15%. By mass%, _SiO 2 of less than 21% (not including _{0%), B 2 O 3} 8~23%, ZnO 6~40%, ZrO 2 2~10%, La 2 O 3 20~40%, Gd 2 O ₃ 4-16%, Nb ₂ O ₅ 1-10%, Ta ₂ O ₅ 3-25%, Li ₂ O 0.1-5%, Sb ₂ O ₃ less than 0.1%, Fe ₂ O ₃ 5 In a glass having a total content of 50 ppm, Pt and Rh of 1 ppm or more and 20 ppm or less and a refractive index nd of 1.71 or more, (Pt ²⁺ content) / (total Pt Content) ≦ 0.8, and the difference ΔT between the transmittance T _{800 at 800} nm and the transmittance T ₃₆₀ at ₃₆₀ nm is 20% or less.   The glass according to any one of claims 1 to 3, wherein the total content of metal oxides functioning as an oxidizing agent on a mass basis is greater than the total content of Pt and Rh.   It is optical glass, The glass in any one of Claims 1-4 characterized by the above-mentioned.   The glass according to claim 1, which is used for mold press molding.