JPH10212133A - Lead-free dense or very dense optical barium crown glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain lead-free dense or very dense optical barium crown glass having very satisfactory chemical resistance, very high crystallization stability, a refractive index of 1.60-1.65 and an Abbe's number of 49-60. SOLUTION: This glass has an oxide compsn. consisting of, by weight, 38-45% SiO2 , 5-10% B2 O3 , 29-42% BaO, 0-10% ZnO, 0-5% CaO (35%<=BaO+ZnO+ CaO<=50%), 1-5% TiO2 , 0.5-3% ZrO2 [0.84<=(SiO2 +TiO2 +ZrO2 )/(BaO+ZnO+ CaO)<=1.35], 0-2.5% La2 O3 , 1-3.5% Al2 O3 (2.5%<=La2 O3 +Al2 O3 <=3.5%), 0-2% Na2 O and 0-6% K2 O (0%<=Na2 O+K2 O<=7%). It may contain a usual amt. of a refining gent if necessary.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to the present invention in the range of 1.60 to 1.6.
It relates to a lead-free dense to extremely dense optical barium crown glass having a refractive index n _{d of} 5 and an Abbe number ν _{d of} 49-60.

[0002]

_2. Description of the Related Art In recent years, glass components PbO and As ₂ O ₃
Is a controversial pollutant, so some manufacturers of consumer products and optics do not contain PbO,
It has come up with a person furthermore attempts to convert to the use of only glass containing no As ₂ O _3. Therefore, such glasses with specific optical properties must be commercially available. In the production of lightweight glass members, that is, low-density glass, it is also desirable not to mix PbO. Simply by replacing lead oxide with one or more components, the optical and glass technical properties will be Pb
Due to the influence of O, it is generally difficult to reproduce such desired properties. So, instead,
New developments or extensive changes in glass composition are required.

Various specifications have already been disclosed in the patent literature, and various lead-free glasses having the above optical values have been disclosed. However, these glasses have significant disadvantages. For example, JP-A-60-221338 describes a glass mainly composed of Y ₂ O ₃ , La ₂ O ₃ , B ₂ O ₃ and Li ₂ O. For example, SiO ₂ is merely an arbitrary component. Absent. Y ₂ O ₃ content up to 20% by weight,
The La ₂ O ₃ content is up to 52% by weight, which makes the glass expensive and uneconomical for continuous production processes. In some cases very B
_The high ₂ O ₃ content (up to 50% by weight) and the presence of Li ₂ O, however, make the glass less chemically resistant, which makes subsequent processing more difficult and It also limits their use. The same applies to Japanese Patent Application Laid-Open Nos. 53-92816 and 54-1.
The same applies to the Li ₂ O-containing glass described in No. 59428. Li ₂ O reduces the crystallization stability of the glass.
Glass described in JP-A-3-5341 has also require the addition of Li ₂ O, it contains a La ₂ O ₃ addition at a relatively high rate.

A similar situation (disadvantage) for La ₂ O ₃ and Y ₂ O _{3 is} true for Nb ₂ O ₅ . This oxide increases the price of the glass batch and thus significantly increases the production costs. It is the German patent DE 14
It is a critical component of the glass described in JP-A-96-524 and JP-A-6-107425. DE 149
The glass described in U.S. 6,524,524 has a significantly higher refractive index (1.
65 or more). In the glass described in JP-A-6-107425, the optical values vary over a wide range. In these glasses, Nb ₂ O ₅ is used in some cases to improve the significant adverse effects on chemical resistance and crystallization stability which are caused by very high alkali metal oxide contents (up to 30% by weight). Is required. The glass proposed in JP-A-5-17176 requires SrO and contains this component in an amount up to 20% by weight. The effect on the optical properties of SrO is
Although similar to that of BaO and CaO, it is advantageous for economical production to eliminate SrO because BaO and CaO can be added to the glass with fairly inexpensive raw materials.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and aims at good melting and processing characteristics, good chemical resistance, and the like. , The viscosity at the upper limit of devitrification is 1,000 dPa
・ High crystallization stability such as s or more,
It is to provide a lead-free dense or extremely dense optical barium crown glass having a refractive index n _d of 1.60 to 1.65 and an Abbe number ν _{d of} 49 to 60.

[0006]

According to a basic aspect of the present invention, there is provided, according to a basic aspect of the present invention, the following composition: 38 to 45% by weight of SiO _{2 and} 5 to 10% by weight of B ₂ O _{3 on} an oxide basis. %, BaO 29 to 42 wt%, ZnO 0 wt%, CaO 0 to 5 wt%, BaO + ZnO + CaO 35~50 wt%, TiO ₂ 1 to 5 wt%, ZrO ₂ 0.5 to 3 wt%, (SiO _{2 + TiO 2 + ZrO 2)} / (BaO + ZnO + CaO) 0.84 ~1.35, La 2 O 3 0~2.5 wt%, Al ₂ O ₃ 1~3.5 _{wt%, La 2 O 3 + Al} 2 O 3 2.5-3.5 wt%, Na ₂ O 0 to 2 wt%, K ₂ O Less than six _{weight%, Na 2 O + K 2} O 0~7 has a weight%, of conventional amounts if desired refining And a refractive index n _{d of} 1.60 to 1.65. 9 ~
A lead-free dense or ultra-dense optical barium crown glass having an Abbe number ν _{d of} 60 is provided.

[0007]

Glass DETAILED DESCRIPTION OF THE INVENTION The present invention comprises a glass former SiO ₂ of 38 to 45 wt%. When the SiO ₂ content is lower than the above range, the crystallization stability and the transition temperature of the glass are lowered, and when it is high, the melting property of the glass is impaired and the refractive index is lowered. Another glass former is B ₂ O
₃ and is present in an amount of 5-10% by weight. This minimum content is necessary to ensure proper melting of the glass. The maximum content should not be exceeded because beyond this the desired refractive index cannot be obtained and the chemical resistance is adversely affected.

[0008] The glass also comprises 29 to 42% by weight of BaO.
It contains. When the content of BaO is less than the above range,
A predetermined Abbe number cannot be obtained, while a content higher than the above range increases the devitrification tendency. To improve crystallization stability and chemical resistance, the glass may also contain up to 5% by weight of CaO and up to 10% by weight of ZnO. However, the total amount of BaO, ZnO and CaO is 35 to
It should be in the range of 50% by weight, otherwise the crystallization stability and chemical resistance are again adversely affected. It is particularly preferred to limit this total to a maximum of 49% by weight. To obtain the desired optical value, the glass should be 1-5% by weight
Containing ZrO ₂ in an amount of TiO ₂ and 0.5 to 3% by weight.

In addition to the absolute amounts of the individual components, an essential feature of the present invention is the weight ratio of the total amount of SiO ₂ , TiO ₂ and ZrO _{2 to} the total amount of BaO, ZnO and CaO, (SiO
₂ + TiO ₂ + ZrO ₂ ) / (BaO + ZnO + Ca
O). This ratio is crucial for the very good chemical resistance of the novel glasses of the invention, from 0.84 to
Must be in the range of 1.35. When the weight ratio is less than 0.84, chemical resistance, particularly acid resistance, is reduced. The novel glasses according to the invention are therefore very acid-resistant (see Examples 7 and 9: acid resistance = 1.0). In contrast, a commercially available ultra-dense barium crown glass SSK2 having a comparable basic glass composition but containing PbO and having a value of the above ratio of 0.81, is a relatively low acid-resistant acid-resistant material. Belongs to sex class 51.3. On the other hand, when the above ratio exceeds 1.35, the melting property of the glass decreases.
This can be compensated for by increasing the content of B ₂ O ₃ and Na ₂ O and / or K ₂ O, but as a result of increasing their content, first of all, the crystallization stability is impaired,
Second, the desired optical properties are difficult to achieve except to accommodate other disadvantages. It is particularly preferred that the upper limit of the ratio be limited to 1.34.

The glass also contains from 1 to 3.5% by weight of Al ₂ O ₃ . A low content of this component is necessary both for good crystallization stability of the glass and also for good chemical resistance. On the other hand, if it exceeds the above maximum content, the meltability decreases. Further, the glass contains 2.5% by weight of La ₂ O _3.
The following amounts can be included, which also improves the chemical resistance. However, the content of this component is 2.5% by weight.
When it exceeds, the glass becomes difficult to melt, and when the expensive component La ₂ O ₃ is excessively contained, the glass becomes unnecessarily expensive. For these reasons, the total amount of La ₂ O ₃ and Al ₂ O ₃ is less than 3.5% by weight,
It should be more than that. This total amount is particularly preferably 2.
7 to 3.4% by weight.

In order to improve the meltability, the glass may further comprise Na ₂ O in an amount of up to ₂ % by weight and K in an amount of up to 6% by weight.
_It may contain ₂ O. However, the total amount of K ₂ O and Na ₂ O should not exceed 7% by weight, otherwise chemical resistance and crystallization stability will be reduced. Li ₂ O should be completely removed. The total amount of Na ₂ O and K ₂ O, particularly preferably from 0 to 6.4 wt%. On the one hand the total amount of SiO ₂ and B ₂ O ₃ , on the other hand La ₂ O ₃ , Al ₂ O ₃ ,
The balanced content of the total amount of K ₂ O and Na ₂ O results in excellent crystallization stability of the glass. For example, in a preferred embodiment of the present invention, SiO ₂ + B ₂ O ₃
The total amount in the range of 45 to 50 wt%, at the same _{time, La 2 O 3 + Al 2} O 3 + Na 2 O + K 2 the total amount of O should not exceed 10 wt%. Thereby, the crystallization stability of the glass is particularly excellent.

[0012] Within the ranges specified in the basic aspect of the present invention are those glasses of the preferred composition range which exhibit particularly good melting and processing properties due to a balanced combination of glass components. This is the following composition range on an oxide basis. SiO ₂ 38-43 wt%, B ₂ O ₃ 5~9 wt%, BaO 29-40 wt%, ZnO 0 to 9 wt%, CaO 0 to 5 wt%, TiO ₂ 1 to 5 wt%, ZrO ₂ 0 .5～3 wt%, La ₂ O ₃ 0~2.5 wt%, Al ₂ O ₃ 1~3.5 wt%, Na ₂ O 0 to 2 wt%, K ₂ O 0-5.5 wt% BaO ₂ + ZnO + CaO 35 to 50% by weight, La ₂ O ₃ + Al ₂ O ₃ 2.5 to 3.5% by weight, Na ₂ O + K ₂ O 0 to 7% by weight, (SiO ₂ + TiO ₂ + ZrO ₂ ) / (BaO + ZnO + CaO) ) 0.84 to 1.35. These glasses are extremely dense barium crown glasses having a refractive index n _d of 1.60 to 1.63 and an Abbe number ν _{d of} 49.5 to 54.

To further improve the glass quality, one or more fining agents known per se can be added in customary amounts to the batch (mixture) for fining the glass. This gives a glass with particularly good "internal" quality without bubbles and streaks. If the fining agent used is not As ₂ O ₃ , but instead Sb ₂ O _3, which can be added without impairing the glass quality, is used, then the novel lead-free glass according to the invention is It is also arsenic-free. In a further preferred embodiment of the present invention, the glass comprises the following fining agent: Sb ₂ O ₃ + F
^- 0.1 to 0.5 wt%, however, Sb ₂ O ₃ is 0
At 0.5% by weight, F ^- contains 0-0.5% by weight, which results in excellent internal glass quality. F ^- is added, for example, as KF.

[0014]

The novel glass composition range according to the present invention is as follows:
There is thus provided another group of lead-free dense to ultra-dense barium crown glasses having the optical properties described above. These glasses have the following advantages. The glass has very good chemical resistance (which is critical for subsequent processing such as grinding and polishing, and for potential uses of the glass), very high crystallization stability (which is relatively Large melting equipment, such as an optical tank, allows glass production) and good "internal" glass quality. Also, glass can be produced at low cost, in part because there is no need to use some expensive components. Glass is P
The absence of bO is important not only for the aforementioned environmental protection reasons, but also for the advantageous effects obtained by reducing the density of the glasses and raising their transition temperature. A further advantage is that the glasses according to the invention not only do not contain PbO, but also in a preferred embodiment do not contain As ₂ O ₃ .

[0015]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but it is needless to say that the present invention is not limited to the following examples.

Examples 1 to 9 The novel glasses of the nine examples of the present invention within the preferred composition range were prepared from conventional raw materials. Table 1 shows an example of the melting (Example 9).

[Table 1] The properties of the glass obtained by this melting example are shown in Example 9 in Table 2 below.

Table 2 also shows the composition of each glass (expressed in terms of% by weight on an oxide basis) and the basic properties such as the refractive index and Abbe number, and for some examples, other properties. The novel glass of the present invention was produced as follows. That is, the raw materials for oxides, preferably carbonates and nitrates, were weighed, and a fining agent Sb ₂ O ₃ was added thereto, followed by sufficient stirring. The glass batch is melted in a continuous melting apparatus for about 1,300-
Melted at 1,350 ° C., then clarified and homogenized well. The glass was formed into the desired dimensions at a casting temperature of 1,220 ° C.

[Table 2]

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Uwe, Kolberg, Germany, 55252 Mainz, Fresselweg 1 (72) Inventor Alvin, Weizel Germany, 55120 Mainz, Vässel 283

Claims (9)

[Claims] 1. Composition based on oxides: 38 to 45% by weight of SiO _2, 5 to 10% by weight of B ₂ O ₃ , 29 to 42% by weight of BaO, 0 to 10% by weight of ZnO, 0 to 5% by weight of CaO , BaO + ZnO + CaO 35~50 wt%, TiO ₂ 1 to 5 wt%, ZrO ₂ 0.5 to 3 _{wt%, (SiO 2 + TiO 2} + ZrO 2) / (BaO + ZnO + CaO) 0.84 ~1.35, La 2 O 3 0 to 2.5 wt%, Al ₂ O ₃ 1~3.5 _{wt%, La 2 O 3 + Al} 2 O 3 2.5~3.5 wt%, Na ₂ O 0~2 wt%, K ₂ O 0-6 _{wt%, Na 2 O + K 2} O 0~7 has a weight%, 1.60 to 1.65 refractive index n _d and characterized in that it contains conventional amounts of fining agent, if necessary 49 ~
A lead-free dense or ultra-dense optical barium crown glass having an Abbe number ν _{d of} 60. _2. The total amount of La ₂ O ₃ , Al ₂ O ₃ , Na ₂ O and K ₂ O is 10% by weight or less, and SiO ₂ and B
₂ O ₃ of the total amount unleaded dense or very dense optical barium crown glass according to claim 1, characterized in that a 45 to 50% by weight. 3. The following composition based on oxides: 38 to 43% by weight of SiO _2, 5 to 9% by weight of B ₂ O ₃ , 29 to 40% by weight of BaO, 0 to 9% by weight of ZnO, 0 to 5% by weight of CaO , TiO ₂ 1 to 5 wt%, ZrO ₂ 0.5 to 3 wt%, La ₂ O ₃ 0~2.5 wt%, Al ₂ O ₃ 1~3.5 wt%, Na ₂ O 0~2 wt % Of K ₂ O 0-5.5% by weight, optionally containing a conventional amount of fining agent, 1.6%
The lead-free dense or ultra-dense optical barium crown glass according to claim 1 or 2, having a refractive index n _d of 0 to 1.63 and an Abbe number ν _{d of} 49.5 to 54. 4. The total amount of BaO, ZnO and CaO is 3
4. The composition according to claim 1, wherein the content is 5 to 49% by weight.
The lead-free dense or ultra-dense optical barium crown glass according to any one of the above. 5. The total amount of La ₂ O ₃ and Al ₂ O ₃ is 2.
The lead-free dense or ultra-dense optical barium crown glass according to any one of claims 1 to 4, wherein the content is 7 to 3.4% by weight. 6. The total amount of Na ₂ O and K ₂ O is from 0 to 6.4.
The lead-free dense or ultra-dense optical barium crown glass according to any one of claims 1 to 5, characterized in that the amount is% by weight. 7. The weight ratio (SiO ₂ + TiO ₂ + ZrO)
₂ ) / (BaO + ZnO + CaO) is 0.84 to 1.3
The lead-free dense or ultra-dense optical barium crown glass according to any one of claims 1 to 6, characterized in that: 8. A fining agent containing 0 to 0.5% by weight of Sb ₂ O ₃ , 0 to 0.5% by weight of F ⁻ , and Sb ₂ O ₃ + F ⁻
The lead-free dense or ultra-dense optical barium crown glass according to any one of claims 1 to 7, which is contained in a total amount of 0.1 to 0.5% by weight. 9. The lead-free dense or ultra-dense optical barium crown glass according to claim 1, which contains no arsenic oxide except for inevitable impurities.