GB2325927A

GB2325927A - Grey and bronze glass compositions for absorbing uv

Info

Publication number: GB2325927A
Application number: GB9711736A
Authority: GB
Inventors: John Buckett; Kenneth Melvin Fyles
Original assignee: Pilkington PLC
Current assignee: Pilkington Group Ltd
Priority date: 1997-06-07
Filing date: 1997-06-07
Publication date: 1998-12-09
Also published as: GB9711736D0

Abstract

A neutral or grey glass composition comprising a base composition and a colorant portion, the latter comprising 0.4 weight% to 1.0 weight% V 2 O 5 in combination with at least one of Co 3 O 4 and Nd 2 O 3 or at least one of MnO 2 and Er 2 O 3 in specified amounts to produce a glass having a light transmission of at least 35% and an ultraviolet radiation transmission of less than 20% when measured according to the Parry-Moon system. Alternatively, a bronze glass composition comprises 0.4 weight% to 1.0 weight% V 2 O 5 in combination with at least 0.05 weight% Fe 2 O 3 and at least 10 ppm (optical) selenium. In either case, other colorants may be added to the composition to modify the colour of the glass.

Description

Ultra-Violet Absorbing Glasses The present invention relates to ultra-violet radiation absorbing glasses. More particularly, the present invention relates to ultra-violet radiation absorbing glasses containing vanadium oxide primarily, but not essentially, capable of being made by the float process.

The transmission of ultra-violet radiation through glass has been acknowledged as a problem for a relatively long time. Such radiation is known to degrade certain fabrics. It is also known to cause colours to fade. Such properties are clearly detrirnental in the case of, for example, goods such as clothing displayed in shop windows, the interior furnishings of vehicles and works of art. More recently, the dangers to health of prolonged exposure to certain types of ultra-violet radiation have been well documented Accordingly, there have been attempts made to limit the ultra-violet transmission of glass. Thus, for example, it is well known that the addition of cerium oxide and/or titanium oxide to the glass composition will reduce the ultra-violet transmission of the glass being manufactured. However, in order to achieve very low transmission values, of the order of 2% measured according to ISO-9050,less than approximately 20% calculated according to the Parry-Moon Rectangular Rule,in a glass having a 6 mm path length would necessitate more than 1% by weight of the glass composition being cerium and/or titanium oxide.

These materials, particularly cerium oxide, are extremely expensive and, accordingly, such solution is undesirable from a commercial viewpoint.

Furthermore, cerium has very broad absorption bands in the ultra-violet region of the electromagnetic spectrum, which bands extend into the visible portion of the spectrum. At the high levels of cerium and/or titanium oxides which would be necessary to achieve the desired ultra-violet transmission characteristics, the effect of this is to provide glasses which are brown or amber in colour. Such coloration is not aesthetically pleasing and is undesirable from a commercial point of view.

An alternative way of reducing the ultra-violet transmission of glasses is to add iron oxide to the components from which the glass is formed. The iron oxide is in the form of ferric oxide (FeO). However, the addition of iron to the components is well known to cause the glass produced to have a yellow or green tint. As the level of iron is increased, the coloration becomes less and less aesthetically pleasing. To achieve an ultra-violet transmission of less than 1%, the mixture of components from which the glass is made would need to contain over 1% Fe2O3 by weight. This produces an undesirable dark green coloration.

As an alternative to cerium and/or titanium, vanadium has been suggested.

Vanadium, in its pentavelent state, is an effective ultra-violet radiation absorption materiaL It also has the advantage of being cheaper to use than cerium or titanium. However, like iron, vanadium gives rise to aesthetically unacceptable yellow or green colorations when used in large amounts.

In European Patent Specification No. EP-A-507985, there are described glasses suitable for production by the float process which contain 0.1 to 0.3% by weight vanadium.

Cobalt oxide, in an amount of 3 to 7 ppm by weight, is also present. It is believed that the minimum ultra-violet transmission of such glasses, measured according to ISO 9050, is of the order of 2.5% (approximately 22% Parry-Moon). No mention is made of the possibility of using larger amounts of vanadium to reduce such transmission to very much lower levels (of the order of 1%). We suspect that this is due to the fact that it is well known that the green or yellow colour produced by vanadium is notoriously difficult to decolorise.

Japanese Patent Specification No. JP-A-59-50045 describes a soda-lime glass which contains from 0.05 to 1% V2Os, 0.2 to 0.5% Fe2O3 and 0 to 5% TiO2. It is inevitable that these glasses, depending upon the relative amounts of these three components, will either by yellow-green or green in colour.

British Patent Specification No. 708031 describes glasses for ophthalmic use having a refractive index of 1.523. Such glasses contain 0.2 to 1.2% V205 together with other additives selected from the group consisting of oxides of iron, cobalt, copper, chromium, tin, antimony, arsenic and manganese. The stated intention of such patent is to produce glasses having a pink (amethyst) coloration and, accordingly, manganese is the preferred additive. Similarly, the amount of cobalt oxide is limited to 1 ppm None of the above-mentioned prior art addresses, or even gives any indication, of the problems of providing glasses having an extremely low ultra-violet radiation transmission but having a neutral, grey or bronze coloration. The present invention therefore seeks to provide neutral tinted glasses containing relatively large amounts of vanadium which have an extremely low ultra-violet transmission.

According to the present invention, there is therefore provided a neutral or grey glass composition comprising a base composition and a colorant portion, characterised in that the colorant portion comprises 0.4% to 1.0% V2Os by weight, at least one of Co3O in an amount of at least 10 ppm with Nd203 in an amount of at least 0.2 weight% with the proviso that the following inequation applies: 200 Co304 + Nd203 > 0.2 weight% in glass having, in a thickness of 6 mm an ultra-violet transmission calculated according to Parry-Moon of less than 20% and a visible transmission of at least 35%, the a* and b* colour coordinates of the glasses according to the Cie-Lab system lying within the ranges of -7 to +2 and -3 to +3 respectively.

In a preferred aspect of the invention, the glass may include further colorants selected from the group consisting of: Mono2 0 to 0.3 weight% NiO Oto400ppm Er203 0 to 2 weight% Se 0 to 400 ppm Fe2O3 0 to 0.2 weight% CuO 0 to 0.1 weight% In a further aspect of the present invention, there is provided a bronze glass composition comprising a base glass composition and a colorant portion, characterised in that the colorant portion comprises 0.4% to 1% by weight V205 in combination with at least one of Er203 and MnO2 with the proviso that the following inequation applies: MnO2 + Er203 > 0.25 weight% the glasses having, at a thickness of 6 mm, an ultra-violet radiation transmission of less than 20% when calculated according to the Parry-Moon system and a visible light transmission of at least 35%, the glasses having a* and b* colour coordinates according to the Cie-Lab system of between -1 and +7 and +5 and +25 respectively.

In this aspect of the invention, it is preferred if at least one of the following colorants is additionally present: NiO 0 to 1000 ppm Fe2O3 0 to 0.2 weight% CuO 0 to 0.1 weight% Co3O4 0 to 10 ppm Nd2O3 0 to 0.2 weight% Se 0 to 400 ppm In the case of grey or neutral glasses containing between 0.4% and 0.6% (by weight) V205, it is highly desirable if the following inequation applies: 0.2 weight% < 200 Co304 + Nd203 < 0.7 weight% If between 0.6% and 1% V205 is present, it is preferable if the following inequation applies: 150 Co304 + Nd203 > 0.3 weight% In the case of bronze glasses, it is highly desirable if the following inequation applies: MnO2 + 10 NiO + Er203 > 0.25 weight% If, in such a glass MnO2 is present, it is desirable if at least one colorant selected from the group consisting of NiO and Er203 is present. This is because manganese glasses tend to solarise in ultra-violet light This phenomenon is due to the conversion of colourless Mn2+ to magenta Mnk and vice versa. In such a case, it is desirable to maintain the Mn content as low as practically possible whilst the minimum amounts of the other colorants utilised therewith are as follows: NiO 25 ppm Er2O3 0.1 weight% Erbium oxide is well known to produce a pink coloration in conventional crown glass compositions. When used with at least 0.4% V as in the glasses of the present invention, it is preferable to utilise erbium in combination with at least one of MnO2 or Se. If Er203 and NiO are used as the colorants, it is advantageous to utilise at least 0.3 weight% Er203 to achieve the optimum coloration.

NiO is generally not used on its own as a colorant in the glasses of the present invention because, in the presence of at least 0.4% V, it increases the yellowness of the glass. It is therefore chiefly used in combination with other colorants to adjust the b* colour coordinate to the desired level.

Of the other possible colorants, selenium may be used in conjunction with iron with the proviso that at least 0.05% Fe203 and at least 10 ppm (optical) Se are presence.

The invention will be further described, by way of illustration only, with reference to the following Examples given in Table I which show glass compositions in accordance with the present invention, together with some comparative Examples.

Table I Example V2O5 Fe2O3 Co3O4 Nd2O3 Se - A Se - R MnO2 NiO ErO3 LT DSHT UV-ISO UV- a* b* PM A 0.2 0.1 7 86 84 4 28 -.25 2.2 B 0.9 66 34 11 29 -12.0 2.5 1 0.4 0.013 88 82 1 18 -4.1 4.5 2 0.5 0.013 86 79 1 14 -5.4 5.8 3 0.6 0.013 86 78 0 12 -5.6 6.7 4 0.4 0.013 10 83 79 1 18 -4.3 2.1 5 0.4 0.013 20 79 77 1 19 -5.1 0.5 6 0.4 0.013 25 77 75 1 19 -5.6 -1.8 7 0.4 0.013 0.3 79 75 1 17 -5.8 1.0 8 0.6 0.013 20 79 76 0 13 -5.8 2.4 9 0.6 0.13 0.3 80 76 0 11 -6.2 3.5 10 0.4 0.05 20 79 77 1 18 -5.2 0.8 11 0.4 0.113 20 78 74 1 18 -6.2 2.2 12 0.4 0.25 20 72 64 1 16 -9.4 5.7 13 0.4 0.013 25 30 16 77 76 1 19 -4.9 -1.4 14 0.4 0.013 25 100 35 78 77 1 19 -4.5 -0.9 15 0.4 0.013 25 100 n/a 79 79 1 19 -4.2 -1.0 16 0.4 0.013 80 300 1.000 45 61 1 16 0.3 -1.2 17 0.4 0.05 21 0.093 77 76 0 16 -4.7 1.8 Example V2O5 Fe2O3 Co3O4 Nd2O3 Se - A Se - R MnO2 NiO Er2O3 LT DSHT UV-ISO UV - a* b* PM 18 0.4 0.013 25 0.200 74 76 0 15 -3.3 2.6 19 0.4 0.013 30 90 72 75 1 18 -4.3 1.8 20 0.4 0.13 14 0.497 78 75 0 17 -2.5 -1.1 21 0.5 0.013 18 0.732 77 76 0 14 -0.5 0.1 22 0.6 0.013 24 0.830 73 73 0 11 -1.0 -0.4 23 0.7 0.013 84 76 0 10 -6.6 7.9 24 0.9 0.013 80 70 0 8 -9.3 11.5 25 1.0 0.013 80 70 0 5 -9.7 13.9 26 0.8 0.013 40 1.200 65 69 0 8 0.3 -1.6 27 0.8 0.013 40 50 1.000 62 66 0 8 -1.2 0.5 28 1.0 0.013 110 300 1.800 35 49 0 5 -1.8 0.8 29 0.4 0.013 0.250 78 78 0 14 -1.0 8.1 30 0.5 0.013 0.500 55 69 0 7 6.4 14.3 31 0.5 0.013 1.000 48 64 0 4 6.6 22.2 32 0.45 0.013 0.180 200 1.000 65 71 0 14 3.8 12.3 33 0.7 0.013 0.180 2.000 72 71 0 7 4.6 8.9 34 0.4 0.19 0.400 1.000 72 69 0 9 0.2 12.1 In Table I, all of the values are given in weight% with the exception of the selenium and the NiO which are given in parts per million (ppm). Se - A represents the selenium added to the composition and Se - R represents the amount of selenium retained in the glass. Examples A and B are comparative Examples only containing no, or only small, amounts of vanadium whilst Examples 1, 2 and 3 are comparative Examples showing that as more vanadium is included in the composition, the Illuminant C light transmission (LT) and the ultraviolet transmission (UV) both decrease. Moreover, these latter three Examples also show that, as more vanadium is added, the colour becomes more yellower and more greener as shown by the b* and a* values respectively.

Examples 4, 5 and 6 show the effect of adding Co304 to the composition. From these Examples, it can be seen that at least 10 ppm, ideally at least 15 ppm of this cobalt oxide is necessary to neutralise the yellow colour produced by the vanadium to values which we define as being neutral or grey. Example 7 illustrates that a glass containing 0.4% V205 can be neutralised in colour using Nod203 instead of Co304. Erbium oxide (Er203), particularly when used in combination with Co304 or Nd203, is particularly effective for producing grey glasses as shown by Examples 20, 21 and 22. As is well known, grey glasses have colour coordinates (a* and b*) which are both close to zero.

As the amount of vanadium is increased beyond 0.4 weight%, correspondignly more Co304 and/or Nd203 is required to neutralise the colour. Examples 8 and 9 show that at least 20 ppm Co304 or about 0.35 weight% Nd203 are required to cause the colour of the glass to be neutral or grey.

Examples 10 and 11, together with comparative Example 12, show the effect of the presence of iron in the composition. Whilst iron does alter the colour of the glass, making it more green and more yellow, it does improve the infra-red absorbence of the glass as shown by the DSHT figures. We have found that up to 0.2 weight% Fe203 can be included in the composition whilst still making it possible to obtain grey or neutral glasses as defined hereinbefore. In most of the Examples, however, only a minimal amount of iron is present, this being in the form of impurities in the raw materials.

Selenium is often used in conjunction with Co304 to neutralise the blue-green colorations to grey. Examples 13, 14 and 15 show that selenium does have a neutralising effect but that such effect is somewhat limited.

MnOz and or Er203 are the preferred compounds to neutralise the colour insofar as the a* value is concerned. Similarly the b* constitutent is neutralised by using nickel in conjunction with manganese and/or erbium and/or selenium Such neutralisation is exemplified in Examples 16 to 19 inclusive.

To produce grey glasses with colour coordinates of -4 < a* < 2 and -3 < b* < 3, erbium in combination with Co304 or Nd203 is particularly effective and this is shown by Examples 20 to 22 inclusive.

Examples 1 to 22 show glasses containing from 0.4% to 0.6% vanadium. We have found that the amount of vanadium can, in fact, be increased to up to 1%. A problem does arise in that, as more vanadium is added, the glasses tend to turn both greener and yellower as is evidenced by the increase in the numerical values of the -a* and b* colour coordinates in comparative Examples 23 to 25. The advantage of the use of higher quantities of vanadium is the decrease in the transmission of ultra-violet radiation.

To produce both grey and neutral glasses with these higher levels of vanadium, it is usually necessary to utilise at least one of manganese, erbium, selenium or nickel in combination with cobalt and/or selenium. Of these, selenium is the least desirable due to its toxicity, to the difficulty of retaining selenium in the glass and to the colour effects which it produces. Neutral and grey glasses having colour coordinates within the following limits: -7 < a* < 2and-3 < 3 may be produced if the following inequation is maintained: 150 Co304 + Nd203 > 0.3 weight% These requirements are exemplified by Examples 26 to 28 inclusive.

Bronze tinted glasses are generally recognised as having colour coordinates within the following ranges: -1 < a* < 7 and 5 < b* < 25 Examples of bronze glasses are shown in Examples 29 to 34 inclusive. To achieve these tints, erbium oxide and/or manganese oxide are used as the basic colouring agents whilst nickel oxide and cobalt oxide may be used to slightly modify the colour. Whilst manganese oxide is the cheapest and easiest colorant to use to produce bronze glasses, it does have the unfortunate effect of solarising in ultra-violet radiation. To minimise these effects, it is desirable if the manganese oxide content is maintained below about 0.2 weight%.

It will be readily apparent to those skilled in the art that minor modifications may be made to the glasses of the present invention without departing from the scope thereof.

Thus, for example, the base glass composition may be a standard composition used for producing float glass. Moreover, the glasses of the present invention may be coated, either on-line or off-line anchor may form part of a double glazing unit. They may also be utilised, in conjunction with a suitable interlayer, to form a laminated glass.

Claims

Claims 1. A neutral or grey glass composition comprising a base composition and a colorant portion, characterised in that the colorant portion comprises 0.4 weight% to 1 weight% V2Os in combination with at least one of Co304 in an amount of at least 10 ppm and Nd203 in an amount of at least 0.2 weight% with the proviso that the following inequation applies:

200 Co304 + Nd203 > 0.2 weight% the glass having, in a thickness of 6 mm, an ultra-violet transmission according to Parry-Moon of less than 20% and less than 2% according to ISO-9050 and a visible transmission of at least 35%, the a* and b* coordinates of the glasses according to the Cie-Lab system lying within the ranges of -7 to +2 and -3 to +3 respectively.
2. A composition as claimed in claim 1 additionally comprising at least one of: Mn02 0 to 0.
3 weight% NiO O to 400 ppm Er203 0 to 2 weight% Se Oto400ppm Fe203 0 to 0.2 weight% CuO 0 to 0.1 weight% 3. A bronze glass composition comprising a base glass composition and a colorant portion, characterised in that the colorant portion comprises 0.4 weight% to 1 weight% V205 in combination with at least one of MnO2 and Er203 with the proviso that the following inequation applies: MnO2 + Er203 > 0.25 weight% theglasses having, at a thickness of 6 mm, an ultra-violet transmission of less than 20% when calculated according to the Parry-Moon system and of less than 2% when calculated according to ISO-9050 and a visible transmission of at least 35%, the glasses having a* and b* colour coordinates of between -1 and +7 and +5 and +25 respectively.
4. A composition as claimed in claim 3 additionally including at least one additional colorant selected from the group consisting of: NiO 0 to 1000 ppm F2Os 0 to 0.2 weight% CuO 0 to 0.1 weight% Co304 0 to 10 ppm Nd2O3 0 to 0.2 weight% Se 0 to 400 ppm
5. A composition as claimed in claim 1 or claim 2 containing between 0.4 weight% and 0.
6 weight% V205 and in which the following inequation applies: 0.2 weight% < 200 Co304 + Nd203 < 0.7 weight% 6. A bronze glass composition comprising a base glass composition and a colorant portion, characterised in that the colorant portion comprises 0.4 weight% to 1 weight% V2O5 in combination with at least 0.05 weight% Fe203 and at least 10 ppm (optical) selenium.
7. A composition as claimed in claim 1 or claim 2 containing between 0.6 weight% and 1.0 weight% V205 and in which the following inequation applies:

150 Co304 + Nd203 # 0.3 weight%
8. A composition as claimed in Claim 3 or 4 wherein the following inequation applies: MnO2 + 10 NiO + Er2O3 # 0.25 weight%
9. A composition as claimed in Claim 3,4 or 8 wherein the colorant portion includes MnO2 and at least one of NiO and Er203.
10. A composition as claimed in Claim 9 wherein the maximum amounts of the NiO and Er203 if present are 25 ppm and 0.1 weight% respectively.
11. A composition as claimed in Claim 9 wherein the colorants are Er203 and NiO and the Er203 is present in an amount of at least 0.3 weight%.
12. A grey or neutral glass as claimed in Claim 1 substantially as hereinbefore described with reference to Examples 4 to 11, 13 to 22 and 26 to 28 of the foregoing Examples.
13. A bronze glass as claimed in Claim 1 substantially as hereinbefore described with reference to Examples 29 to 34 of the foregoing Examples.
14. A bronze glass as claimed in Claim 6 substantially as hereinbefore described.