JP2004231501A - Optical glass and optical element produced from it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide optical glass whose refractive index is high, whose dispersion is low, whose Tg and T<SB>L</SB>values are low and which is suitable for a precise press-forming. <P>SOLUTION: The optical glass contains B<SB>2</SB>O<SB>3</SB>of 27-34 wt%, Li<SB>2</SB>O of 0.2-2 wt%, ZnO of 7-15 wt%, ZrO<SB>2</SB>of 5-10 wt%, La<SB>2</SB>O<SB>3</SB>of 35-53 wt%, Y<SB>2</SB>O<SB>3</SB>of 8-15 wt%, Gd<SB>2</SB>O<SB>3</SB>of 0-1 wt% (including 0 and not including 1 wt%), Ta<SB>2</SB>O<SB>5</SB>of 0-1 wt% (including 0), Nb<SB>2</SB>O<SB>5</SB>of 0-1 wt% (including 0), Bi<SB>2</SB>O<SB>3</SB>of 0-1 wt% (including 0), WO<SB>3</SB>of 0-1 wt% (including 0) and SiO<SB>2</SB>of 0-5 wt% (including 0) (wherin, La<SB>2</SB>O<SB>3</SB>+Y<SB>2</SB>O<SB>3</SB>+Gd<SB>2</SB>O<SB>3</SB>is 45-54 wt%;and Ta<SB>2</SB>O<SB>5</SB>+Nb<SB>2</SB>O<SB>5</SB>+Bi<SB>2</SB>O<SB>3</SB>+WO<SB>3</SB>is 0.5-3 wt%). <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００３２】
【表２】

【００３３】
表１から明らかなように、実施例１〜１０の光学ガラスは高屈折率（１．７６６〜１．７７０）、低分散（アッベ数：４９．４〜４９．８）であった。またガラス転移温度（Ｔｇ）が６３９℃以下、液相温度（Ｔ_Ｌ）が１０３０℃以下と精密プレス成形に適したものであった。
【００３４】
これに対し、ＺｎＯとＹ_２Ｏ_３の含有量が少ない比較例１の光学ガラスは、Ｔｇ及びＴ_Ｌが６４４℃及び１１００℃と高く精密プレス成形に適さないものであった。また、Ｌｉ_２Ｏを３．０％と多く含有した比較例２の光学ガラスは溶融中に失透した。ＺｎＯ及びＴａ_２Ｏ_５を２０．０％及び５．０％と多く含有した比較例３の光学ガラスは屈折率が所期の値に達しなかった。比較例３と同様にＺｎＯが２０．０％と多く、さらにＹ_２Ｏ_３を含有せずＬａ_２Ｏ_３とＹ_２Ｏ_３の総量の少ない比較例４の光学ガラスは、屈折率が所期の値に達せずまたＴ_Ｌも高かった。そして、Ｇｄ_２Ｏ_５を３６．４％と多量に含有させた比較例５の光学ガラスは、Ｔ_Ｌが１０８０℃と高く精密プレス成形に適さないものであった。
【００３５】
【発明の効果】
本発明の光学ガラスでは、Ｂ_２Ｏ_３、Ｌｉ_２Ｏ、ＺｎＯ、ＺｒＯ_２、Ｌａ_２Ｏ_３、Ｙ_２Ｏ_３、Ｇｄ_２Ｏ、Ｔａ_２Ｏ_５、Ｎｂ_２Ｏ_５、Ｂｉ_２Ｏ_３、ＷＯ_３、ＳｉＯ_２の各ガラス成分を特定量含有させることにより、高屈折率・低分散（ｎ_ｄ：１．７６６以上，ν_ｄ：４９．０以上）が達成でき、しかも低Ｔｇ及び低Ｔ_Ｌ（Ｔｇ：６４０℃以下，Ｔ_Ｌ：１０３０℃以下）とすることができ優れた精密プレス成形性が得られる。
【００３６】
また本発明の光学素子は、前記光学ガラスを精密プレス成形することにより作製するので、生産効率が高く低コスト化が図れる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical glass and an optical element produced therefrom, and more particularly to an optical glass suitable for precision press molding and having a high refractive index, low dispersion, a relatively low glass transition temperature and a liquidus temperature, and an optical glass produced therefrom. Optical element.
[0002]
[Prior art]
In recent years, an aspheric lens has been frequently used in optical devices such as digital cameras in order to reduce the size and weight of the devices. However, it is difficult to process the lens into an aspherical shape by conventional cutting and polishing, and the production cost is inevitably increased. Therefore, a precision press molding method (mold molding method) has attracted attention as a technique that can relatively easily form glass having a difficult-to-process shape such as an aspherical shape. According to this molding method, the steps of polishing and cutting the lens, which were conventionally required, are not required, and the cost can be reduced.
[0003]
However, when molding glass by the precision press molding method, it is necessary to set the temperature of the press die to a temperature close to or higher than the glass transition temperature (hereinafter, sometimes referred to as “Tg”), while the Tg of the glass is The higher the temperature, the more the surface oxidation of the press die and the change in the metal composition occur, and the more severe the deterioration of the die, the shorter the life of the die. As a measure for suppressing mold deterioration, it is conceivable to control the molding atmosphere to an inert atmosphere such as nitrogen, but this leads to an increase in production cost. Therefore, it is desirable that the glass used in the precision press molding method has a Tg as low as possible. Further, from the viewpoint of the moldability of the glass, it is desirable that the liquidus temperature (hereinafter sometimes referred to as “ _TL ”) be low, and that the viscosity of the glass at the liquidus temperature be high.
[0004]
Various optical glasses suitable for such a precision press molding method have been conventionally proposed. For example, Patent Document 1 proposes an optical glass for precision press molding for the purpose of high refractive index, low dispersion, relatively low Tg and _TL .
[0005]
[Patent Document 1]
JP-A-2002-249337 (claims,
[0005]
[0039]
[0006]
[Problems to be solved by the invention]
However, when the present inventor additionally tested the example described in Patent Document 1, the obtained optical glass had a high refractive index and a low dispersion, but had a _TL of 1040 ° C. or higher, which was not yet a satisfactory level. Was.
[0007]
The present invention has been made in view of such conventional problems, the refractive index and it is an object of (n _d) is 1.766 or more and an Abbe's number ([nu _d) is 49.0 or more, the glass transition An object of the present invention is to provide an optical glass having a temperature (T _g ) of 640 ° C. or less and a liquidus temperature (T _L ) of 1030 ° C. or less.
[0008]
Another object of the present invention is to provide an optical element having the above-mentioned refractive index and Abbe number, which can achieve high productivity and low cost.
[0009]
[Means for Solving the Problems]
As a result of intensive studies to achieve the above object, the present inventor has found that one factor that causes an increase in _TL is Gd ₂ O ₃ . Further studies were conducted to determine whether the content of Gd ₂ O ₃ could be reduced. As a result, a glass material other than Gd ₂ O ₃ was optimally combined with the type and content thereof to achieve a high refractive index and a low dispersion, and a relatively high refractive index. The present inventors have experimentally found that an optical glass suitable for precision press molding with low Tg and _TL can be obtained, and have accomplished the present invention. That is, the optical glass of the present invention, in _{wt%, B 2 O 3:} 27~34%, Li 2 O: 0.2~2%, ZnO: 7~15%, ZrO 2: 5~10%, La ₂ O ₃ : 35 to 53%, Y ₂ O ₃ : 8 to 15%, Gd ₂ O ₃ : 0 to 1% (including zero and not including 1%), provided that La ₂ O ₃ + Y ₂ O _{3 + Gd 2 O 3: 45~54%} , Ta 2 O 5: ( including _{zero) 0~1%, Nb 2 O 5} : 0~1% ( including _{zero), Bi 2 O 3: 0~1} % ( including _zero), WO 3: _0~1% (including zero), _{however, Ta 2 O 5 + Nb 2} O 5 + Bi 2 O 3 + WO 3: 0.5~3%, SiO 2: 0~5% ( (Including zero). In the present specification, unless otherwise specified, the following “%” means “wt%”.
[0010]
Here, from the viewpoint of increasing the viscosity of the glass, increasing the refractive index, adjusting the optical constant, and the like, GeO ₂ : 3% or less, TiO ₂ : 1% or less, Al ₂ O ₃ : 3% or less, MgO: 3% hereinafter, CaO: 3% or less, SrO: 3 or less, BaO: 3% or less, _Na 2 O: 1% or _less, K 2 O: even further contain one or more of 1% or less of the glass component Good.
[0011]
Further, according to the present invention, there is provided an optical element characterized in that the optical glass is manufactured by precision press molding. As such an optical element, a lens is preferable.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
The reason why each component of the optical glass of the present invention is limited as described above will be described below. First, B ₂ O ₃ is a main component forming glass, and if the content of B ₂ O ₃ is less than 27%, the glass is apt to be devitrified. On the other hand, if the content exceeds 34%, the desired refractive index cannot be obtained. Therefore, the content was determined to be in the range of 27 to 34%. A more preferred content is in the range of 29-33%.
[0013]
Li ₂ O has an effect of effectively lowering the Tg of the glass, and by including Li ₂ O in an amount of 0.2% or more, it becomes easy to adjust the Tg to 640 ° C. or less. On the other hand, if the content exceeds 2%, the glass tends to rapidly devitrify. In addition, the viscosity becomes small and molding becomes difficult. Therefore, the content is set in the range of 0.2 to 2%. A more preferred content is in the range of 0.2-1%.
[0014]
ZnO has the effect of effectively lowering the Tg of glass, and if its content is less than 7%, the effect cannot be obtained. On the other hand, if the content exceeds 15%, it becomes difficult to obtain the desired refractive index and Abbe number. Therefore, the content is set in the range of 7 to 15%. A more preferred content is in the range of 7.5 to 12%.
[0015]
ZrO ₂ has the effect of stabilizing the glass and lowering the liquidus temperature, but if its content is less than 5%, the effect cannot be obtained sufficiently. On the other hand, if the content exceeds 10%, the glass tends to rapidly devitrify. Therefore, the content is set in the range of 5 to 10%. A more preferred content is in the range of 6-7%.
[0016]
La ₂ O ₃ has an effect of increasing the refractive index, and if the content is less than 35%, the effect cannot be obtained. On the other hand, if the content exceeds 53%, the glass tends to be devitrified. Therefore, the content is set in the range of 35 to 53%. A more preferred content is in the range of 47-52%.
[0017]
Y ₂ O ₃ is inferior to La ₂ O ₃ but has an effect of increasing the refractive index. It also has the effect of stabilizing the glass. If the content is less than 8%, these effects cannot be sufficiently obtained. On the other hand, if the content exceeds 15%, the glass tends to be devitrified. Therefore, the content is set in the range of 8 to 15%. A more preferred range is from 9 to 10%.
[0018]
Although Gd ₂ O ₃ also has the effect of increasing the refractive index, its performance is inferior to La ₂ O ₃ and Y ₂ O ₃ , and the addition of Gd ₂ O ₃ causes an increase in the liquidus temperature. Therefore, the content of Gd ₂ O ₃ was determined to be less than 1%. More preferably, it is substantially not contained.
[0019]
If the total amount of La ₂ O ₃ , Y ₂ O ₃ and Gd ₂ O ₃ is less than 45%, it becomes difficult to obtain the desired optical constant. On the other hand, if the total amount exceeds 54%, the glass tends to be devitrified. Therefore, the total amount is set in the range of 45 to 54%. A more preferred total is in the range of 47-52%.
[0020]
Ta ₂ O ₅ , Nb ₂ O ₅ , Bi ₂ O ₃ , and WO ₃ all have the effect of increasing the refractive index of glass. When the total amount is less than 0.5%, the effect is not sufficiently achieved. I can't get it. On the other hand, if the total amount exceeds 3%, it becomes difficult to obtain the desired Abbe number. Therefore, the total amount is set in the range of 0.5 to 3%. A more preferred total is in the range of 0.5-2.5%. Further, even if Ta ₂ O ₅ , Nb ₂ O ₅ , or WO ₃ is contained in more than 1% of these glass components, the above effect cannot be improved. When Bi ₂ O ₃ is contained in an amount exceeding 1%, the glass is easily colored. Therefore, the content of each of these glass components was determined to be 1% or less.
[0021]
SiO ₂ has the effect of increasing the viscosity of glass, but if its content exceeds 5%, the glass tends to devitrify. Therefore, the content of SiO ₂ is determined to be 5% or less. A more preferred content is in the range of 1-4%.
[0022]
In the optical glass of the present invention, GeO ₂ : 3% or less, TiO ₂ : 1% or less, Al ₂ O ₃ : 3% or less, MgO: 3% or less, CaO: 3% or less, SrO: 3 or less, BaO : 1% or less, Na ₂ O: 1% or less, K ₂ O: 1% or less.
[0023]
By including GeO ₂ , TiO ₂ , Al ₂ O ₃ , MgO, CaO, SrO, BaO, Na ₂ O, and K ₂ O, the optical constant can be adjusted to a desired range. However, if the content of GeO ₂ and TiO ₂ exceeds 3% and 1%, respectively, the Abbe number decreases, and the desired values may not be obtained. Therefore, the contents of GeO ₂ and TiO ₂ are desirably 3% or less and 1% or less, respectively. On the other hand, when the content of each of Al ₂ O ₃ , MgO, CaO, SrO, and BaO exceeds 3%, and when the content of Na ₂ O, K ₂ O exceeds 1%, the refractive index of the glass increases. It may decrease. Therefore, the content of Al ₂ O ₃ , MgO, CaO, SrO, and BaO is desirably 3% or less, and the content of Na ₂ O, K ₂ O is desirably 1% or less.
[0024]
Further, as a fining agent, one or more of each glass component of As ₂ O ₃ , Sb ₂ O ₃ , and SnO ₂ is contained in a range of 0.5 parts by weight or less based on 100 parts by weight of the total amount of the glass components. You may let it. The content is set to 0.5 part by weight or less because a sufficient clarifying action can be obtained by containing 0.5 part by weight.
[0025]
If necessary, a conventionally known glass component and additive may be added as long as the effects of the present invention are not impaired.
[0026]
The optical element of the present invention is produced by precision press molding the optical glass. As the precision press molding method, there is a precision direct press molding method in which molten glass is dropped from a nozzle into a mold heated to a predetermined temperature and press molded, and a glass softening point in which a preform material is placed on a mold and placed on a mold. The reheat molding method of heating and press molding is mentioned above. According to such a method, polishing and grinding steps are not required, and productivity is improved. Among these, the precision direct press molding method is more preferable as the method for producing the optical element of the present invention.
[0027]
The molding conditions vary depending on the glass component, the shape of the molded product, and the like. Generally, the mold temperature is preferably in the range of 600 to 700 ° C., and particularly preferably a high temperature range close to the glass transition temperature. The pressing time is preferably in the range of several seconds to several tens of seconds, and the higher the pressing time, the higher the precision of molding. The pressing pressure is preferably in the range of 200 kgf / cm ^{2 to} 600 kgf / cm ² , and the higher the pressure, the higher the precision of molding. The viscosity of the glass at the time of molding is preferably in the range of 10 ² to 10 ¹² poise.
[0028]
The optical element of the present invention can be used, for example, as a lens of a digital camera or a collimator lens of a laser beam printer.
[0029]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples. The present invention is not limited to these examples.
[0030]
Examples 1 to 10, Comparative Examples 1 to 5
Glass raw materials were prepared using a general glass raw material such as an oxide raw material and a carbonate so as to have a target composition shown in Table 1, and were sufficiently mixed with powder to obtain a prepared raw material. This is put into a platinum crucible in an electric furnace heated to 1,150 to 1,350 ° C., melted and clarified, stirred and homogenized, cast into a pre-heated iron or carbon mold, gradually cooled, and cooled. Samples were produced. Refractive index at the d-line of the respective samples _{(n d)} and Abbe number ([nu _d), glass transition temperature (Tg), was measured liquidus temperature _{(T L).} In addition, these measurements were performed according to the test method of the Japan Optical Glass Industry Association standard (JOGIS). The Tg was measured using a thermomechanical analyzer “TMA / SS6000” (manufactured by Seiko Instruments Inc.) at a temperature rising rate of 5 ° C./min. The _TL was placed in a devitrification test furnace having a temperature gradient of 500 to 1150 ° C. for 2 hours, taken out, and observed by a microscope for the presence or absence of devitrification. The measurement results are shown in Tables 1 and 2.
[0031]
[Table 1]

[0032]
[Table 2]

[0033]
As is clear from Table 1, the optical glasses of Examples 1 to 10 had a high refractive index (1.766 to 1.770) and a low dispersion (Abbe number: 49.4 to 49.8). Further, the glass transition temperature (Tg) was 639 ° C. or less, and the liquidus temperature (T _L ) was 1030 ° C. or less, which was suitable for precision press molding.
[0034]
On the other hand, the optical glass of Comparative Example 1 having a small content of ZnO and Y ₂ O ₃ had high Tg and _TL of 644 ° C. and 1100 ° C., and was not suitable for precision press molding. Further, the optical glass of Comparative Example 2 containing a large amount of Li ₂ O as 3.0% was devitrified during melting. The refractive index of the optical glass of Comparative Example 3 containing ZnO and Ta ₂ O ₅ as large as 20.0% and 5.0% did not reach the expected value. As in Comparative Example 3, ZnO was as high as 20.0%, and the optical glass of Comparative Example 4 containing no Y ₂ O ₃ and having a small total amount of La ₂ O ₃ and Y ₂ O ₃ had a desired refractive index. And the _TL was also high. The optical glass of Comparative Example 5 containing a large amount of Gd ₂ O ₅ at 36.4% had a _TL of 1080 ° C. and was not suitable for precision press molding.
[0035]
【The invention's effect】
In the optical glass of the present invention, B ₂ O ₃ , Li ₂ O, ZnO, ZrO ₂ , La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O, Ta ₂ O ₅ , Nb ₂ O ₅ , Bi ₂ O ₃ , WO _3, each glass component SiO ₂ by incorporating a specific amount, high refractive index and low dispersion _(n d: 1.766 or more, [nu _d: 49.0 or higher) can be achieved, yet low Tg and low T _L (Tg: 640 ° C. or less, T _L : 1030 ° C. or less), and excellent precision press moldability can be obtained.
[0036]
Further, since the optical element of the present invention is manufactured by precision press-molding the optical glass, the production efficiency is high and the cost can be reduced.

Claims (4)

In wt%,
B ₂ O _3: 27~34%,
Li ₂ O: 0.2~2%,
ZnO: 7 to 15%,
ZrO _2: 5~10%,
La ₂ O ₃ : 35-53%,
Y ₂ O _3: 8~15%,
Gd ₂ O _3: 0~1% (including zero, not including 1%)
However, La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ : 45 to 54%,
Ta ₂ O _5: 0~1% (including zero),
Nb ₂ O _5: 0~1% (including zero),
Bi ₂ O _3: 0~1% (including zero),
WO _3: 0~1% (including zero),
_{However, Ta 2 O 5 + Nb 2} O 5 + Bi 2 O 3 + WO 3: 0.5~3%,
SiO ₂ : 0 to 5% (including zero),
An optical glass characterized by containing the following glass component. In wt%,
GeO ₂ : 3% or less,
TiO ₂ : 1% or less,
Al ₂ O ₃ : 3% or less,
MgO: 3% or less,
CaO: 3% or less,
SrO: 3 or less,
BaO: 3% or less,
Na ₂ O: 1% or less,
K ₂ O: 1% or less,
The optical glass according to claim 1, further comprising one or more of the following glass components. An optical element produced by precision press molding the optical glass according to claim 1 or 2. The optical element according to claim 3, wherein the optical element is a lens.