JPS5933545B2 - Moldable fluoromarminophosphate glass - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to glasses that can be molded or otherwise formed under pressure at temperatures below about 350°C.

Japanese Patent Application No. 55-139728 (Japanese Unexamined Patent Publication No. 56-59641) previously filed by the present applicant shows a low transition temperature (Tg) and does not require aqueous phase treatment (
Alkali metal oxide-alkaline earth metal oxide-fluoride tetraphosphate system (R
20-RO-F-P205) are disclosed.

This glass has a base composition of approximately 15-40% R20, 0-20% RO and 25-55% P2O5 in weight percent based on oxides calculated from the batch, with the exception that R20 O to 45% Li2O,
0 to 20% Na2O and 0 to 10% RO, 0 to 10% MgO, 0 to 15% CaO, 10 to 20% SrO and O to 20% B
The final glass contains approximately 0.3 to 3% by weight of F, as determined by analysis.

20% or less PbO, 7% or less La2 as optional components
03 and up to 12% ZnO are mentioned.

It is stated that it is preferred that Al2O3 is not present.

25% if the P2O5 content is less than 30%
Up to B2O3 may be included.

If the P2O5 content is at least 45%, B
The 2O3 content must be below 5%.

The total amount of optional components other than RO and B2O3 must be 25% or less, and the total amount of optional components other than RO must be less than 35%.

Although phosphate glass compositions containing +L fluoride are well known in the glass art, they generally suffer from two undesirable properties, namely relatively low chemical durability and formation of It is also stated that it exhibits the property of being susceptible to devitrification during processing.

Many fluoride-containing phosphate glasses have poor weather resistance.

That is, glass is easily attacked by the surrounding environment.

The main objects of the present invention are that the glass can be formed by mold or otherwise at temperatures below about 350°C under pressure, and that it has good glass stability (resistance to devitrification during formation and processing). The object of the present invention is to provide a fluoride-containing glass that exhibits good chemical durability and weather resistance.

Another object of the invention is to provide a fluoride-containing phosphate glass as described above which is particularly suitable for optical applications such as ophthalmic lenses.

The inventors believe that the above objective is approximately 30 to 75% P2O5, 3 to 25% R20, 0 to 60% pBO, 0 to 40
% ROlo to 40% ZnO 10 to 30% Cd
013 to 20% Al2O3 and more than 3%24
(However, R20 consists of 0 to 20% Li2O, 0 to 20% Na2O, 0 to 20% of 20.0 to 10% Rb2O, and O to 10% C.
820, RO is 0-15% MgO, O-40% CaO, 10-40% SrO and O-4
Consisting of 0% BaO, PbO+RO+ZnO+CdO
is 0 to 60%), F:Al atomic ratio (atomic
cratio ) is at least 0.75 but about 5
It has been found that the following can be achieved by a glass composition.

The above-mentioned Japanese Patent Application No. 55-139728 discloses that it is preferable that Al2O3 is not present in the glass since it significantly increases the transition temperature (Tg) of the glass.

However, the present inventors have found that when the glass contains a large amount of fluoride, that is, more than 3% in the analysis value of the final glass, the Tg of the glass does not increase significantly even when Al2O3 is included in the glass. I found it.

When Al2O3 is included in the glass, A120s performs three important functions in the glass:

First of all, Al2O3 increases the solubility of fluoride in the glass system.

Second, A I203 suppresses liquid immiscibility that causes phase separation in glasses.

And thirdly, Al2O3 significantly increases the weather resistance and chemical durability of the glass.

Fluoride is an essential component of the glass of the present invention.

This is because fluoride lowers the Tg of phosphate-based glasses, making them more easily moldable.

However, as the fluoride concentration increases, the weatherability and chemical durability of the glass decreases rapidly.

The invention is therefore based on the combined use of Al2O3 and F to give glasses a low transition temperature and good weather and chemical resistance.

Although A 1203 and F must be present in significant amounts in the glass composition, the atomic ratio of fluorine to aluminum is also very important in balancing the Tg and chemical durability of the glass.

For example, as the F:Al atomic ratio decreases, chemical durability improves, but transition temperature increases.

Conversely, as the F:Al atomic ratio increases, the transition temperature decreases, but the chemical durability deteriorates, and when the F:Al atomic ratio becomes 5, the chemical resistance of the glass becomes extremely low.

Experiments have shown that a constant F:Al atomic ratio means the same transition temperature and the same chemical durability in the glasses of the invention.

Such phenomena are not unknown in the field of glass technology.

An example of such a phenomenon is the so-called mixed alkali effect, in which alkali metal oxides are manipulated to reduce the glass viscosity and at the same time improve the chemical durability of the glass.

A to increase the chemical durability and transition temperature of glass
The effect of l2O3 is well known, and the opposite effect of fluoride to Al2O3 is also well known.

However, when appropriate amounts of these two components are used together, the same effect as the mixed alkali effect described above can be obtained.

When the F2Al atomic ratio increases to about 5 or more, the durability of the glass appears to decrease significantly.

This is thought to be caused by liquid immiscibility.

The solubility of fluoride in glasses that do not contain Al2O3 is low, and the amount of fluoride retained in the glass is believed to be the amount of fluoride that binds to modified cations.

The reason why the solubility of fluoride increases in Al2O3-containing glasses is because aluminum easily changes from a coordination number of 4 to a coordination number of 6 and behaves as a modified cation, which causes a large number of anions to be incorporated into the glass structure. It is theorized that small amounts of compatible metal oxides such as 3La203, WO3, MoO3 and Nd2O3 (where two F-ions replace one O-2 ion) are included in the glass to improve the refractive index and other may change the physical properties of the glass.

However, the total amount of such additives should not exceed about 10% by weight.

In fact, the glasses of the present invention are divided into two groups: glasses consisting only of the R20-Al□03-F-R20, system composition and glasses containing RO, PbO1ZnO and CdO in the above composition.
Experiments have shown that glasses can be categorized as containing significant amounts, for example about 5%, of at least one modified oxide such as.

The former quaternary glass generally exhibits a refractive index of about 1.45 to 1.5, and the optimum combination of good chemical durability, low Tg and good glass stability is achieved when the Al2O3 and F contents are about 15 to 20% and more than 15% but less than 24%.

On the other hand, in addition to the above four-component composition, RO, PbO1
When modified oxides such as ZnO and CdO are included in significant amounts, the optimum combination of properties is obtained with Al2O3 and F contents of about 3 to 15% and greater than 3% and less than 15%, respectively. The refractive index of the glass is generally between about 1.5 and 1.7.

In the prior art described below, the glass composition is generally reported as a batch raw material.

As stated in the above-mentioned Japanese Patent Application No. 139,728/1982, and as described below, the volatilization of fluoride during melting can be as high as 90%.

Therefore, if chemical analysis values of the glass are not provided, the fluoride content can only be estimated.

Although the present invention allows up to 50% of the amount of fluoride in the batch to be included in the glass when at least 3% by weight Al2O3 is included in the alkali metal phosphate base glass composition, the resulting glass is relatively Based on the discovery that it exhibits good chemical durability.

Therefore, the glass contained up to approximately 24% by weight of fluoride by analysis.

Since Al2O3 increases the transition temperature of the glass, the fluoride content must be greater than 3% by weight in order to keep the transition temperature below 350°C.

US Patent No. 2,430,539 discloses titanium fluorophosphate glasses useful for optical applications.

TiO2 is included in the composition to increase chemical durability.

This glass has the formula AF TiO2-M(POy)z.

Here, AF represents an alkali metal fluoride, and M(PO
y)z represents an aluminum or beryllium phosphate, generally a meta- or orthophosphate.

Analytical values for glass are not shown.

Examples include 55.5 to 77 mol% of NaF or KF, 19.8 mol% or less of TiO2, and 15 to 2
5 mol% A I (PO3) s or 40 to 4
4.5 mol% AlPO4 is mentioned.

Nothing is said about PbO, RO or ZnO.

U.S. Pat. No. 2,496,824 discloses fluoroiron phosphate glasses.

It is stated that this glass is suitable for optical applications because it has little coloration.

The composition of this glass is 20% by weight calculated from the batch.
40% NaF, 22-40% LiF, 2-15% Fe2O3 and 55-76% A! (P.O.
3) Consists of 2.

No analysis of the glass is given, no PbO, RO or ZnO are used as components, and the alkali metal content is much higher than allowed by the present invention.

US Pat. No. 2,481,700 discloses fluorophosphate glasses useful for optical applications.

This glass has the formula AF-MF2-R, where A
F represents a fluoride selected from the group consisting of LiF, NaF and KF, and ■゛2 represents MgF2, CAF2, SrF
2, BaF2 and ZnF2, and R represents one or both of aluminum phosphate and beryllium phosphate.

AF constitutes 7 to 54% by weight of the composition, ゛2 constitutes O to 58% by weight, and R constitutes 30 to 90% by weight.

The atomic ratio of fluorine and phosphorus in the glass batch is between 0.23 and 2.
The range is 9.

No analysis of the glass is given, no RO, PbO or ZnO are used as components, and no specific ratios of aluminum and fluoride components are taught.

Note that for the latter, Al2O3 is used merely as an optional component.

U.S. Pat. No. 3,281,254 states that approximately 15% by weight
aluminum metaphosphate, 16-23.8%
% alkali metal metaphosphate, 23.8-41% alkaline earth metal metaphosphate and 1-21% PbF.
Glasses useful for optical applications are disclosed having a batch composition consisting of a fluoride selected from the group consisting of: 2, LiF, KHF2, Zn5iF6, BaF2 and MgF2.

Again, no analytical values are given to indicate the fluoride content in the final glass, nor is there even any suggestion of maintaining a specific ratio of aluminum and fluoride components.

U.S. Pat. No. 3,656,976 discloses fluorophosphate glasses suitable for optical applications.

This glass has 15-40% PO2, 5,0,5-21% BOl, 5% cations calculated from the batch.
．． 0.7 to 40% alkali metal fluoride, 10 to 6
It consists of 0% alkaline earth metal fluoride and 10-25% AlF3, with a B:P ratio less than 0.7.

Fluoride analysis of the final glass is not shown and B2O3
is used as an essential component rather than an optional component, and it is not required to maintain a specific ratio of the fluoride component and aluminum component.

No. 3,954,484 discloses alkaline earth metal aluminofluorophosphate glasses having a refractive index greater than 1.57, an Abbe number less than 70, and a relatively large positive local anomalous dispersion.

No fluoride analysis of the final glass is reported, no alkali metal oxides are included in the composition, and no specific atomic ratio of fluoride and aluminum components is required.

Table 1 below shows several glass batches melted on a laboratory scale, expressed in parts by weight of the batch raw material actually used, and illustrates the parameters of the invention.

Reagent grade batch raw materials were used for this melting to avoid abnormal reactions or phenomena due to impurities in the raw materials.

Particularly preferred batch feed phosphate compounds were alkali metal and alkaline earth metal meta and orthophosphates.

AI(PO3)3, Pb(PO3)2 and Zn3(
PO4)2 was found to be effective in obtaining good glass quality.

P2O, is hygroscopic, cannot be easily ball milled, and volatilizes rapidly in the early stages of melting, but can be used as a batch feedstock.

Ammonium phosphate appears to be unsuitable as a batch feedstock.

This is because although ammonium phosphate can be ball milled, it volatilizes very easily during the early stages of melting.

Additionally, ammonium phosphate is a reducing agent and therefore Pb
It cannot be used in combination with easily reducible metal oxides such as O.

Each compound shown in Table 1 is merely an example, and other compounds may of course be used in place of these compounds.

Each batch of raw materials was blended, tumble mixed to help obtain a homogeneous melt, and then placed in either a 96% silica crucible or an aluminium crucible.

The crucible used is 5i02 or Al2O as shown in Table 1.
3.

Although the batches shown in Table 1 represent laboratory scale melts, it is of course possible to carry out larger melts in pots or continuous melt tanks for commercial production.

The crucible is placed in a furnace at approximately 900°C, and the batch is approximately 30°C.
melted for minutes.

The resulting melt was then poured into a steel mold, approx.
A glass plate measuring inches by 6 inches by 1/2 inch was obtained.

The glass plate was immediately transferred to an annealer at a temperature of about 25° C. above the Tg of the glass.

Each glass in Table 1 was chemically analyzed for fluoride and alumina by methods commonly used in the glass art.

The measured values are shown in Table 2 below, and for F a comparison of the amount of fluoride in the batch expressed in weight % as well as the analysis of fluoride in the final glass expressed in weight % i.e. Residue percentage (%) is also shown.

Table 2 also shows the F:Al atomic ratio.

Table 2 also shows the values of various physical properties determined by conventional methods.

The refractive index (nD) is measured by the Betzke line method and the transition temperature (T
g) was determined by scanning differential calorimetry and the density was determined using a modified Westphal hydrometer.

The chemical durability of glass is 10% by weight HC at room temperature.
I by immersion in aqueous solution for 10 minutes and by immersing the glass in boiling water for 1 hour.

The weight loss of glass is expressed as vty/crA,
N, C, means almost no weight loss.

Typically, a batch melted in an A1□03 crucible has 96
%SiO2 retained more fluoride in the final glass than the batch melted in the crucible.

This is presumably because the molten batch reacts with 5i02 in the crucible to produce highly volatile SiF2.

Al2O3 amount in batch and Al2O in final glass
Comparison of the three analyzes revealed that the batches melted in the Al2O3 crucible took about 1-2% of Al2O3 from the crucible.

Surprising results were found regarding fluoride retention in batches melted in open crucibles.

That is, glasses melted in open crucibles had higher fluoride retention than glasses melted in covered crucibles.

It is theorized that this is because more water remains in the melt when the crucible is capped, resulting in the production of more volatile HF.

However, P2O5 and other relatively volatile compounds are more easily lost from the molten glass when melted in an open crucible.

The fluoride residual percentage shown in Table 2 was calculated from the fluoride concentration analysis value in the final glass and the fluoride concentration in the batch.

However, the accuracy of this calculation is not sufficient.

This is because other volatile products are not taken into account.

A complete chemical analysis is necessary to obtain sufficiently high values of precision.

All or almost all of the P2O5 is anhydrous P2O
Preferably, the batches such as those obtained from 5 and alkali metal metaphosphates are melted in an aluminium crucible.

This is because such batches melt rapidly and exhibit high fluoride retention.

When lead metaphosphate and barium metaphosphate are used as batch raw materials, melting takes time and considerable foaming occurs.

As is clear from Table 2 above, the F:Al atomic ratio influences the transition temperature exhibited by the glass.

Therefore, in general, the smaller the atomic ratio, the higher the transition temperature.

The concentration of fluoride in the glass is also very important regarding the transition temperature.

The glasses of Examples 9 and 11 of Table 1 containing analytically 2.11% and 1.37% fluoride, respectively, were 35%
Shows a Tg higher than 0°C.

Table 3 below shows 105 to 101 for five types of glass.
This figure shows the results of parallel plate viscosity measurements carried out over a range of 0 poise.

Table 3 shows the difference between softening point (Tsp) and Tg, analytical value of Al2O3, analytical value of F, and F: Al for each glass.
Atomic ratios are indicated.

In Table 3, Glass A is Table 1, Glass Example 5 of Table 2,
B is the same as Example 6, C is the same as Example 1, and D is the same as Example 9.

A large difference between Tsp-Tg means that the slope of the viscosity curve is gentle, and conversely, a small difference between Tsp-Tg means that the slope of the viscosity curve is steep.

The slope of the viscosity curve in the above viscosity range does not appear to be directly related to the fluoride concentration or the F/AI atomic ratio.

However, the slope appears to follow the Al2O3 content.

That is, the smaller the amount of A1□03, the steeper the slope of the curve.

This is believed to be because the AI+3 cation captures one alkali metal cation, thereby hardening the glass in this viscoelastic flow region.

As shown in Table 4 below, two test methods were used to evaluate the weatherability of the glasses of the present invention.

The first test method is what is called a shot test in the field of optical glass technology.

The second test method was recently developed by Corning and is believed to be the more detailed test method.

Approximately 2 inches x 2 inches x 1/4 in both tests
An inch polished square glass plate was used as a sample.

In the shot test, a polished glass plate is exposed to a saturated steam atmosphere in which the temperature varies between 40°C and 50°C over a 1 hour period.

Condensation (no flow) occurs on the test sample surface for approximately 15 minutes in each hourly cycle.

30. After 100 and 180 hours of exposure, the samples are removed from the test chamber and classified by making diffuse light measurements.

That is, the portion of the transmitted visible light that is scattered and diffused by the exposed surface is used as a measure of the degree of weather resistance.

Glass is evaluated according to the classification below.

Crust: There is almost no erosion after 7 hours.

Class 4: Significant corrosion is observed after 30 hours.

Class 2 and 3: Erosion class between class 1 and class 4.

No further subdivision. In the Corning Weathering Test, polished glass plates are exposed to a constant humidity atmosphere with a relative humidity of 98% and an air temperature of 50°C.

Three identical samples are used, one of which is visually inspected, cleaned, and then re-examined every three or four days; another one is examined on the same schedule but once every two weeks. It is only cleaned once.

The remaining one will be inspected periodically but will not be cleaned until the end of the test one month later, at which time it will be cleaned.

The glass is then classified by visual inspection as follows:

Class A: No spots or cloudiness are observed when inspected under a strong parallel light source.

Class B: Only a few spots or slight cloudiness is observed when inspected under the same lighting conditions as Class A.

Class C: Many spots or significant cloudiness are observed when inspected under the same lighting conditions as Class A.

Class D: Spots or haze are observed under normal ambient lighting.

Class E: Significant product accumulation is observed (test will be terminated).

The Corning Weathering Test was conducted for the period shown in Table 4, and the glass was not cleaned during the test period.

Classes A to E refer to the same visual appearance as above.

For comparison, a similar weather resistance test was conducted on the most preferred glass of Japanese Patent Application No. 55-139728.

This glass has an analytical value of 48% P2O5, 2,09% Li2O, 4,0% by weight based on oxides.
It consists of 8% Na2O, 23.8% pbo, 21.43% BaO and 0.56% F.

This glass failed after 4 hours of exposure in the Corning Weathering Test.

As is clear from Table 4 above, weather resistance does not strictly follow trends in transition temperature or F:A1 atomic ratio.

This is due to the unequal comparison of glasses containing large amounts of Al2O3.

This is because, as mentioned above, AI+3 cations have the ability to scavenge alkali metal cations, thereby increasing the chemical durability of the glass.

The effect of divalent cations on the fluorophosphate glass of the present invention was evaluated.

Properties of direct interest were Tg, chemical durability, refractive index and fluoride retention.

The divalent cations used were Mg1Ca, Sr, Ba, and C.
d, Pb and Zn.

Three types of glass compositions were selected as basic materials for evaluation.

The composition of these glasses, expressed in parts by weight based on oxides calculated from the batch, is as follows.

In addition, the composition table below also shows the F:Al calculated from the batch.
F determined from the atomic ratio and analytical values of these components:
The Al atomic ratio is also shown.

In each composition used in the experiment, the BaO in the base composition was replaced with other divalent metals, and the other batch components were kept relatively constant in molar content.

Much of the melting was done in a platinum crucible with an interference fit platinum lid.

For glasses containing lead and cadmium, porcelain crucibles, aluminium crucibles, glass carbon crucibles, and VYCOR1 crucibles were used.

These crucibles also had Vycor or porcelain lids.

Table 5 below shows three groups of glass batches expressed in parts by weight based on oxides calculated from the batches.

In each batch, the sum of each component is 100 or nearly 100, so that in practice each value may be considered to be expressed in % by weight.

Fluoride is simply designated as fluoride (F) since it is not known which cation it is bound to.

Divalent cations were added as metaphosphates, except for cadmium and zinc, which were added as orthophosphates.

Each batch of raw materials was formulated and tumble mixed to obtain a homogeneous melt, and then filled into a crucible.

The crucibles used are shown in Table 5.

The crucible is placed in a furnace at 1000°C, and the temperature is approximately 1
It took 0 minutes.

The resulting melt was poured onto a graphite block and quenched into a glass slab.

The glass slab has a Tg of about 15 to 40
It was annealed by being kept in a furnace at 100°C for 2 hours and then cooled at furnace speed.

In Table 5, glasses of groups A, B and C are based on glasses A, B and C above, respectively.

The fluoride content of the glasses was determined by conventional chemical analysis methods.

The percent fluoride remaining between the amount of fluoride in the batch feed and the amount of fluoride analyzed from the final glass is shown in Table 6 below.

The F:Al atomic ratio also has a refractive index (nD) measured by the Becke line method.
) and the transition temperature (Tg ) determined by scanning differential calorimetry are shown in Table 6.

Weathering tests were carried out in a humidity chamber where the air temperature and relative humidity were kept constant at 50° C. and 98%, respectively.

A small piece of the glass slab was placed on a nichrome wire screen.

After 8 days in the humidity chamber, the samples were removed from the humidity chamber and visually graded for surface changes.

There were six grades ranging from A, where no change was observed, to F, where significant erosion was observed.

To test the water resistance of the glass, a portion of the slab was cut out and each side was sanded with 320 silicon carbide abrasive paper to give it a uniform abrasion.

The sample was then weighed and its external dimensions carefully measured.

The sample was placed on a nichrome wire screen, the screen was placed in a beaker, 100 ml of 75°C deionized water was added to the beaker, and then the beaker was placed in a constant temperature water bath at 95°C.

After about 15 minutes, the contents of the beaker reach a constant temperature (~90°C)
reached.

The beaker was kept in the water bath for an additional hour, after which the sample was removed from the beaker, washed, and air-dried overnight.

After weighing the sample, the weight loss per unit surface area (~/c
yst) was determined.

The results are also shown in Table 6. Several conclusions can be drawn from Tables 5 and 6 above.

Group A glasses with F:Al atomic ratios in the smallest batches showed higher fluorine retention than the other two groups of glasses, and among Group A glasses Sr
The glass containing O showed the highest fluorine residual rate.

Group A glasses showed the best durability but at the same time a high transition temperature.

Group B glasses exhibited the lowest fluorine retention and lowest transition temperatures of the three groups of glasses.

Regarding the effect of individual divalent cations on the fluorine residual rate, it is clear from Tables 5 and 6 that alkaline earth metals (Ba, Sr, Mg and Ca) have a higher effect than Cd, Zn and PB. The residual rate was given.

Sr gives the highest residual rate, followed by Ca, Ba and M
The order was g.

Of the remaining three divalent metal ions, Cd appeared to produce the highest fluorine retention, and pb appeared to produce the lowest fluorine retention.

As the F:A1 atomic ratio in the batch increases (the fluorine residual rate decreases).

Furthermore, as the molar content of divalent metal cations increases, the fluorine residual rate increases.

Batches melted in platinum crucibles appeared to exhibit higher fluorine retention than batches melted in crucibles made of other materials.

As is clear from Tables 5 and 6, as the concentration of divalent metal increases, the amount of fluorine retained in the glass generally increases.

Durability data vary somewhat, but there appears to be more weight loss in the middle than at the ends of the divalent metal concentration range tested.

As expected, the weathering test results generally agree with the water resistance test results, with clearly the best performance being obtained in glasses with lower F:A1 atomic ratios.

However, MgO-containing glasses appear to exhibit better weather resistance than PbO-containing glasses.

Therefore, in order to obtain practical durability and weather resistance in the glass of the present invention, the F:Al atomic ratio must be kept at 5 or less.

In summary, although the durability and weather resistance of the glass of the present invention are inferior to those of soda-lime glass or borosilicate glass, the glass of the present invention has
It is comparable to many optical glasses that have a transition temperature higher than °C.

Furthermore, as described in Japanese Patent Application No. 55-139728, antireflection coatings such as MgF2 are commonly applied to glasses used for optical applications.

Such a coating serves to protect the glass surface from ambient moisture.

Good weather resistance and good moldability, i.e. approx. 325
Glasses with the best optical quality with a Tg of less than or equal to
0-65% P2O3, 0-50% pbo, 0-30% BaO10-3.0% ZnO, 3-2
0% A1□03,O to 10% Li2O,0 to 2
Glass composition consisting of 0% Na2O, O to 20% and more than 3% less than 24% F (with the exception of pb
o+BaO+ZnO is O to 50%, Li2O+
Na2O+20 can be obtained from 3 to 20%).

Claims (1)

Claims: 1. Approximately 30 to 75% P2O6, 3 to 25% R20, analytically expressed in weight percent based on oxides;
0 to 40% ROlo to 60% pbo, o to 4
0% ZnO1O to 30% Cd013 to 20% A
12O3 and more than 3% less than 24% F (where R20 is 0 to 20% Li2O, 0 to 20%
% Na2O, 0-20% 2010-10% Rb2O and 0-10% Cs20, RO
is composed of O to 15% MgO, 10 to 40% CaO, 10 to 40% SrO, and O to 40% BaO, and RO+PbO+ZnO+CdO is 0 to 60%), and the F:A1 atomic ratio is 0.75 to 5. 4 about 350
A glass characterized by having a transition temperature of 0.degree. C. or less and exhibiting good weather resistance. 2 Approximately 30 to 65% P2O5, 0 to 5% pbo, o, analytically expressed in weight percent based on oxides.
10 to 30% BaO13 to 30% ZnO
0% Al2O3, 0-10% Li2O, 0-2
0% Na2Q, 0 to 20% more than 20 and 3% (less than 24% F (but PbO + BaO
+ZnO is O to 50%, L i20 +Na2
0+20 is 3 to 20%), and has a transition temperature of about 325° C. or less.
Glass as described in section. Consisting of 3R20, Al2O3, F and Al2O3,
Al2O3 content is about 15 to 20%, F content is more than 15% and less than 24%, and about 1.45 to 1
．． Glass according to claim 1, characterized in that it has a refractive index of 5. 4 Contains at least 5% of at least one of RO, PbO, ZnO, and CdO, has an Al2O3 content of about 3 to 15%, and has an F content of more than 3%.
1. Glass according to claim 1, characterized in that it has a refractive index of less than 1.0% and about 1.5 to 1.7. 5 P2O5 of approximately 30 to 75%, R20 of 3 to 25%, analytically expressed in weight percent based on oxides;
0 to 40% ROlo to 60% pbo, 0 to 4
0% ZnO10-30% CdO, 3-20% Al2O3, more than 3% less than 24% F, and less than 10% La203, WO2, MoO3 and Nd
2O3 (however, R20 is 0 to 20% Li2O, 0 to 20% Na2O, 0
20.0 to 10% of Rb2O and O
RO consists of O to 10% Cs20, O to 15% MgO, O to 40% CaO, 10 to 40% SrO.
and 0 to 40% BaO, RO+PbO+
(ZnO+CdO is O to 60%), F:Al atomic ratio is 0.75 to 5, has a transition temperature of about 350° C. or less, and exhibits good weather resistance.