FR2778398A1 - CROWN GLASSES AND FLINT LANTHANE AND LEAD FREE GLASSES - Google Patents

Abstract

The present invention relates to lanthanum and lead-free crown glasses and flint glasses, whose refractive index is from 1.66 to 1.76 and whose Abbe number is from 46 to 57. These glasses have the composition following, in oxides and in weight percentages: SiO2 1 - 9; B2O3 29-43.5; La2 O3 27 - 40; CaO 5.5 - 10; SrO 0 - 3.5; MgO 0 - 4.5; ZnO 3.5 - 10; TiO2 0.1 - 3.5; ZrO2 3.5 - 9.

Description

Crown and lead-free lantern and flint glasses

  The invention relates to crown glasses and lead-free lanthanum flint glasses, the refractive index nd being equal to

  1.66 to 1.76 and the number of Abbe vd is from 46 to 57.

  Since we are currently questioning the use of

  posers of PbO and As203 glasses because they are pollutants for the environment, the manufacturers of optical instruments need glasses which do not contain PbO, nor, preferably,

  of As203, but which retain interesting optical properties.

  If you just replace lead oxide with one or more

  In various components, it is generally not possible to find the desired optical and technical properties of the glass, due to PbO. Instead of doing this, it is essential to make profound modifications to glass compositions, or even to develop

  completely new glass compositions.

  The prior art can be considered to be in particular

  link consisting of the documents referred to below and where are described lead-free glasses whose optical indices have

  values located in the ranges indicated above or in the

  hands close to these intervals, but with very different

disadvantages.

  In document DE-B1 061 976, a base glass belonging to the B203-SiO2-La203 system and having a high La203 content is described, as well as glasses obtained by adding, to this base glass, oxide of aluminum and / or yttrium oxide and oxides of certain metals, in particular alkaline earth metal oxides, zirconium oxide, zinc oxide and / or cadmium oxide, or

  glasses which have only low levels of B203, but only

  when there is A1203, Y203 and other additives. These glasses are very expensive due to the nature of their components, and it is difficult to melt them or their resistance to devitrification is

not satisfactory.

  In GB patent 1,136,239, an electric lamp is described.

  troluminescence o there is a glass which comprises an oxide of a rare earth metal, a glass forming oxide and an oxide of a divalent metal, and in which the phosphor is incorporated. The components

  are possible, including additional adjuvants,

  breux and their proportions vary in very wide intervals. But these glasses do not offer the high level performance that is required

optical glasses.

  Document JP-A-55/121925 (1980) discloses dense lanthanum flint glasses, that is to say glasses with high refractive index and low Abbe number, which contain ZnO and SrO and / or BaO as oxides of divalent metals. In addition, MgO and small amounts of CaO can be added. SiO2 is also only an optional component. These glasses, whose optical situations (situations in the diagram of the optical coordinates nd and Vd) are different from those which one wishes to achieve in

  the present invention do not exhibit good resistance either.

devitrification.

  In German patent No. 22 65 703 (C2), optical glasses belonging to the B203-Gd203-La203 system are disclosed. To resist devitrification well, these glasses must contain at least 2% by weight of Gd203, and they can contain up to 50% by weight. The presence of this expensive component in proportions also

  important increases the price of these glasses enormously.

  In document JP-A-62/100449 (1987), there are disclosed glasses where it is necessary to provide up to 2% by weight of Sb203. But when we use this component in such proportions, it is essential

  strengthen, during production operations, the pre-

  bail taken to protect the personnel concerned, and on the other hand, the transmission power of the glasses decreases a lot. In addition, these

  glasses must contain Li2O, which increases their propensity

devitrification.

  Likewise, the glasses described in document JP-A-60/221338 (1985) necessarily contain Li2O. It is also essential to incorporate therein, in addition to La203, up to 20% by weight of Y203, a very expensive component, in order to vary the refractive index. Glasses with a high ZnO content described in document JP-B-54/6243

  (1979) also contain Y203.

  In the glasses described in document JP-A-53/4023 (1978), it is mandatory to use HfO2. But this component, used instead

  La20O3, also greatly increases the price of these glasses.

  It is one of the aims of the present invention to propose optical glasses, flint or crown, with lanthanum and lead-free, whose refractive index nd is equivalent to 1.66 to 1.76 and the number d'Abbe vd is worth 46 to 57, which behaves well during melting and lend themselves well to implementation, and whose manufacture is inexpensive. These glasses must also have a satisfactory resistance to devitrification. This object is achieved with crown glasses and lead-free flint lanthanum glasses, whose refractive indices nd are worth

  1.66 to 1.76 and whose Abbe vd numbers are from 46 to 57. The com-

  position of these glasses is as follows, in oxides and in weight percentages (Composition A): SiO2 1 - 9

B203 29 - 43.5

  La203 27 - 40 CaO 5.5- 10 SrO 0- 3.5 MgO 0 - 4.5 ZnO 3.5 - 10 TiO2 0.1 3.5 ZrO2 3.5 - 9

  If desired, refining agents can be added to them,

usual tities.

  The glasses of the invention contain from 29 to 43.5% by weight, and preferably at most 43% by weight, of the glass-forming oxide that is B203. If they contained more, their resistance to chemicals would be reduced. Their minimum content of B203 is high enough so that they can contain only a fairly low proportion, from 1 to 9% by weight, of the glass-forming oxide that is SiO2. The fact that the SiO2 content is also low has firstly advantageous effects on the melting conditions of the vitrifiable mixture: the melting point of this mixture is lowered, and the duration of the melting is reduced. Second, it facilitates the introduction of large amounts of oxide

lanthanum.

  This is because the glasses of the invention indeed contain from 27 to 40% by weight, and preferably from 29 to 40% by weight, of La203. Since the lanthanum oxide content is within this range, it

  is easier to achieve the desired optical situation, and in particular

  bind, to obtain glasses having both a moderate Abbe number and a high refractive index. In addition, La203 increases the power

  of transmission of the glasses, as well as their resistance to devitrification

  tion. But if the proportion of La203 was even higher, this would only have the effect of giving values of nd and vd different from

  those we seek, as well as increase without counter

  part of the cost of the batch composition.

  The glasses of the invention contain from 0.1 to 3.5% by weight, and preferably from 0.1 to 3% by weight, of TiO2, as well as from 3.5 to 9% by weight, and preferably from 4 to 9% by weight, of ZrO2. Used in these proportions, these two components improve the resistance of the glasses

  chemical agents. So not only do they facilitate the incorporation

  tion of B203 in the high contents mentioned above, but furthermore, which is surprising, they make the glasses more resistant to alkalis and acids than are the usual lead glasses which

have the same optical situation.

  The glasses of the invention contain from 3.5 to 10% by weight,

  and preferably from 4 to 10% by weight, of ZnO. Used in these proportions

  tions, this component has the effect of giving glasses which resist

  better at coloring and who are less inclined to devitrify.

  It is true that, if the proportions of TiO2, ZrO2 and ZnO were increased beyond the maximum values indicated above for each of these components, this would have an even positive effect on the devitrification behavior, in other words, that would cause a further increase in the resistance to devitrification, but on the other hand it would lead to a deterioration of the melting conditions

of the batch.

  Instead, in order to obtain glasses very resistant to devitrification without practically having to worry about the melting conditions of the vitrifiable mixture, there are introduced, according to the invention, from 5.5 to 10% by weight, and preferably 5.5 to 9.5% by weight of CaO. Yes

  this component was found in a lower proportion, the glasses

  would decrease their resistance to devitrification, but if it were

  in a larger proportion, it is their resistance to chemical agents

which would weaken.

  To further improve their resistance to devitri-

  Fication, we can put in the glasses of the invention up to 3.5% by weight, and preferably up to 3% by weight, of SrO, as well as up to 4.5% by weight, and preferably up to 4% by weight, of MgO. If these respective maximum proportions were exceeded, it is again

  the resistance of the glasses to the chemical agents which would suffer from it.

  According to a particular embodiment, lanthanum crown glasses of the invention or lanthanum flint glasses of the invention contain at least 35% by weight of La203, but they contain neither SrO nor MgO, and contain relatively little of ZnO and CaO, ie at most 6% and 7.5% by weight, respectively. Consequently, the glasses of this set preferably contain, in oxides and in weight percentages: SiO2 1 - 9

B203 29 - 43

  La203 35 - 40 CaO 5.5 - 7.5 ZnO 4- 6 TiO2 0.1 - 3 ZrO2 4- 9 The refractive index nd of these glasses is 1.69 to 1.76 and their

number of Abbe vd is from 46 to 54.

  According to another particular embodiment, glasses of the invention contain SrO and / or MgO, and more precisely, at least 0.1% by weight of (SrO + MgO). These glasses have the advantage, compared to glasses without SrO or MgO, of opposing a little resistance

  better at devitrification and to be less dense.

  Within this set of glasses, the glasses that contain

  of SrO, but do not contain MgO constitute a first va-

  particular riant of realization of the invention. What differentiates them from glasses without SrO, but containing MgO, which are described below, is that they have a lower density and a lower coefficient of thermal expansion. Their composition, in oxides and in weight percentages, is preferably as follows: SiO2 2.5 - 4.5 better still 2.5 - 4 B203 35 (better,> 35) - 42 better still 37 - 40 La203 31 - 40 better still 32 - 38 CaO 6- 8 better still 7 - 8 SrO 0.1 - 2 better still 0.5 - 1.5 ZnO 4.5 - 7.5 better still 5 - 7 TiO2 0.5 - 2.5 better still 1 - 2.5 ZrO2 5 - 9 better still 6 - 7 The refractive index nd of these glasses is worth from 1.69 to 1.75 and their number of Abbe vd is worth from 48 to 54. In the case glasses presenting

  preferred compositions, these optical coordinates are respectively

  from 1.70 to 1.72 and from 48 to 51.

  Glasses that contain MgO, but do not contain

  of SrO, mentioned above, constitute a second partial variant

  of the invention. Their composition, in oxides and in weight percentages, is preferably the following SiO2 5 (better,> 5) - 7.5

B203 30 - 39

  La203 30- 39 CaO 6- 8 MgO 1 - 3 ZnO 6 - 9 TiO2 0.5 - 2.5 ZrO2 5- 8 The refractive index nd of these glasses is 1.69 to 1.75 and their number d 'Abbe vd is worth from 48 to 54. Among the glasses of the invention, of composition already indicated

  (Composition A), there are two other groups of very integrated glasses

  substances, which are distinguished by their TiO2 content.

  In the first of these groups, there are glasses which contain-

  are MgO and have a TiO2 content near the top of the

  global valley already mentioned, i.e. glasses whose composition

  tion, in oxides and in weight percentages, is as follows: SiO2 3.5 4.5

B203 41 - 43

  La203 27 - 31 CaO 8 - 10 MgO 3.5 - 4.5 ZnO 3.5 - 4.5 TiO2 2.5 - 3.5 ZrO2 3.5 - 4.5 The refractive index nd of these glasses is from 1.68 to 1.70 and their

number of Abbe vd is from 49 to 51.

  In the second of these groups are gathered glasses which contain MgO and SrO, but whose TiO2 content is relatively low. Their composition, in oxides and in weight percentages, is as follows SiO2 3.5 - 4.5

B203 41 - 43

  La203 27- 31 CaO 8.5 - 9.5 SrO 2.5 - 3.5 MgO 3.5 - 4.5 ZnO 3.5 - 4.5 TiO2 0.1 - 1 ZrO2 3.5 - 4.5 These are lanthanum crown glasses whose refractive index nd is

  from 1.66 to 1.69 and whose number of Abbe vd is from 54 to 56.

  In order to improve the quality of the glass obtained, one or more known refining agents may be added to the batch mixture, in the amounts usually sufficient to effect the refining of the glass. This is how we can obtain a glass whose internal appearance is then particularly good, in particular as regards the absence of bubbles.

and sons.

  If it is not As203 that is used as a

  swims, but for example Sb203, preferably in a proportion of up to 0.3% by weight, which is possible without the glass obtained losing its quality, the lead-free glasses of the invention do not

  will not contain arsenic either.

  The present invention therefore makes it possible to produce glasses which, while having the desired optical properties, do not contain oxides of alkali metals, nor of BaO, A1203, Nb2O5, Y203 or Ta203, apart from the usual impurities. This has various advantages, for example with regard to behavior during melting or

  resistance to devitrification, as well as with regard to the cost of pro-

  duction of these glasses, which is weak.

  The new glasses of the invention bring the advantages

shown in the following.

  These glasses do not contain PbO, and in a pre-

  a real achievement, they also do not contain As203. In comparison

  because of conventional glasses containing PbO and being in the same range of optical coordinates, they are "longer", which means that they are suitable for work in a wider range

of temperature.

  The glasses of the invention resist chemical agents well, and in particular, they resist alkalies very well. Therefore,

  compared to conventional glasses containing lead and of the same situa-

  they have both better resistance to

  (for example, glass # 8 - see Table 2 in the examples -

  has an acid resistance marked 52.0, instead of 52.3 for an equivalent glass containing lead) and better resistance to alkalis (for example, glass n 8 has resistance to alkalis

  noted 1.0, instead of 1.2 for an equivalent glass containing lead).

  The high resistance of these glasses to chemical agents is very important for their subsequent mechanical treatment, for example for grinding and polishing operations.

  These glasses also have a high resistance to devitrification.

  cation, which makes it possible to manufacture them in fairly large glass-melting equipment, for example in a basin furnace. We can get an idea of the resistance of a glass to devitrification according to its

  upper devitrification limit or according to its viscosity at this time

  temperature. For continuous production, this must be greater than or equal to 100 Pa.s. The new glasses of the invention meet this criterion. The glasses of the invention are easy to melt and process, and their density, less than or equal to 4.0 g / cm3, is

relatively small.

Examples

  Eight examples of new inventive glasses were made.

  tion, from usual raw materials.

  In Table 2 are indicated, for each of the glasses fa-

  brick, its composition, in percentages by weight and in oxides, its refractive index nd, its Abbe number vd, its density p in g / cm3, its coefficient of thermal expansion o20 / 300 in 10-6.K-1 ,

  and its glass transition temperature Tv in C.

  We make these new glasses as follows. All

  first, we weigh the raw materials used, which are preferably

  carbonates and oxides, and the refining agent is added, then all of these components are mixed well. This mixture is melted at a temperature of about 1200 to 1360 C, then it is refined and

  homogenizes it well. The casting temperature is from 1000 to 1080 C.

  Table 1 gives an example of a batch.

Table 1

  Example of vitrifiable mixture (quantities calculated for 100 kg of glass) Oxide% by weight Material First initial weight (kg) SiO2 0 SiO2 1.0 SiO20

B203 42.9 H3BO3 76.23

  CaO 5.5 CaCO3 9.75 TiO2 0.1 TiO2 0.10 ZnO 5.00 ZnO 5.01 Zr02 5.4 ZrO2 5.51 La203 40.0 La203 40.08 Sb203 0.10 Sb203 0.10

  The properties of the glass obtained from this vitrified mixture

  ble are indicated below in Table 2: this is Example 1.

  86'9 18't, 98 'úL'9 L8'9 66'9 9S'LO' 9 (1.901) ooI / oz.o 0Oú / OZn ZZ9 úIL úIL bú9 ZS9 b'ú9 S19 9b, 9 (Do) AI z OL'ú 00'ú ZO'ú 6ú'ú 88'ú Iv'ú OL'ú 99'ú (um-,) d 91'OS O'O OZ'V8t 'O úb'9 6ú'55 Lb- I 8L'E5 PS Z81L'I 160L'I b'tL'I 8689'1 18tL'I ZSL9 '980L'1 úúOL'I Pu oz OZ O O l'0 l'0 l'0 l' 0 l'0 l'O [OzqS ú'tú I'Sú Z'5ú 0'6Z O'Ot 0'6Z 0'6Z O'Ot, '0Ze s'9' 9 19 'it,' 8 0 '69 ', SZ b'l S'l S'Z O'ú 0'ú 1'0 l'0 l'0 ZOi0 S'L 6' 6'S 0't '' t, 0't O'OI 0 O1 OUZ 1I O 'Z - - Ob - Ot, 0'b O - OY - 0'I 0'l - 0'ú 0 oú - OiS' L 'L' L 0'6 'S 0'6 0'6 S' OeD 9'b'ú 8'8ú 8'8ú O'úb 6'6Z 6'Zb 0'6Z 6'Zib úOZ

  Z'9 L'ú 6'Z 6'ú 0'6 6'ú 6'8 O'I ZO S O

  8 L 9 b 'ú Z I oiduoxa SOJOA SOZ op s919udoid lo sopXxo uo lo xnm9puod soilruoa: nod uo SOMIOA op suo! L. sodmuoD Z nolqeL

Claims (12)

  1. Crown glasses and lead-free lanthanum flint glasses, whose refractive index nd is from 1.66 to 1.76 and whose Abbe vd number is from 46 to 57, characterized by the following composition, oxides and in weight percentages: SiO2 1 - 9 B203 29 - 43.5   La203 27 - 40 CaO 5.5- 10 SrO 0- 3.5 MgO 0 - 4.5 ZnO 3.5- 10 TiO2 0.1 3.5 ZrO2 3.5 - 9   with, if desired, refining agents in the usual quantities.   2. Crown glasses and lantern flint glasses, according to claim 1, characterized by the following composition, in oxides and in weight percentages: SiO2 1- 9 B203 29 - 43.5   La203 29 - 40 CaO 5.5 - 9.5 SrO 0- 3 MgO 0 - 4 ZnO 4-10 TiO2 0.1 - 3 ZrO2 4 - 9   with, if desired, refining agents in the usual quantities.   3. Crown glasses and lantern flint glasses, according to claim 1 or 2, the refractive index nd being from 1.69 to 1.76   and whose number of Abbe vd is from 46 to 54, characterized by the com-   following position, in oxides and in weight percentages: SiO2 1 - 9 B203 29 - 43   La203 35 - 40 CaO 5.5 - 7.5 ZnO 4 - 6 TiO2 0.1 - 3 ZrO2 4 - 9   with, if desired, refining agents in the usual quantities.   4. Crown or flint lanthanum glasses, in accordance with the claim   cation 1 or 2, characterized in that they contain, in total, at least 0.1% by weight of SrO and / or MgO.   5. Crown glasses and lantern flint glasses, according to claim 1, 2 or 4, whose refractive index nd is from 1.69 to 1.75 and whose Abbe vd number is from 48 to 54, characterized by the following composition, in oxides and in weight percentages: SiO2 2.5 - 4.5 B203 35 - 42   La203 31-40 CaO 6 - 8 SrO 0.1 - 2 ZnO 4.5 - 7.5 TiO2 0.5 - 2.5 ZrO2 5- 9   with, if desired, refining agents in the usual quantities.   6. Crown glasses and lanthanum flint glasses, according to claim 5, whose refractive index nd is from 1.70 to 1.72 and   whose number of Abbe vd is 48 to 51, characterized by the composition   next tion, in oxides and in weight percent SiO2 2.5 - 4 B203 37 - 40   La203 32 - 38 CaO 7 - 8 SrO 0.5-1.5 ZnO 5 - 7 TiO2 1 - 2.5 ZrO2 6 - 7 with, if desired, refining agents in the usual amounts. 7. Crown glasses and lantern flint glasses, according to claim 1, 2 or 4, whose refractive index nd is from 1.69 to 1.75 and whose Abbe vd number is from 48 to 54, characterized by the following composition, in oxides and in weight percentages: SiO2 5 - 7.5 B203 30 - 39   La203 30 - 39 CaO 6- 8 MgO 1 - 3 ZnO 6 - 9 TiO2 0.5 - 2.5 ZrO2 5 - 8   with, if desired, refining agents in the usual quantities.   8. Crown glasses and lantern flint glasses, according to claim 1, whose refractive index nd is from 1.68 to 1.70 and   whose number of Abbe Vd is from 49 to 51, characterized by the composition   next tion, in oxides and in weight percent SiO2 3.5 - 4.5 B203 41 - 43   La203 27 - 31 CaO 8-10 MgO 3.5 - 4.5 ZnO 3.5 - 4.5 TiO2 2.5 - 3.5 ZrO2 3.5 - 4.5   with, if desired, refining agents in the usual quantities.   9. Crown glasses and lantern flint glasses, according to claim 1, the refractive index nd being from 1.66 to 1.69 and   whose number of Abbe vd is from 54 to 56, characterized by the composition   following tion, in oxides and in weight percentages: SiO2 3.5 - 4.5 B203 41 - 43   La203 27 - 31 CaO 8.5 - 9.5 SrO 2.5 - 3.5 MgO 3.5 - 4.5 ZnO 3.5 - 4.5 TiO2 0.1 - 1 ZrO2 3.5 - 4.5   with, if desired, refining agents in the usual quantities.   10. Crown glasses and lantern flint glasses, in accordance with   at least one of claims 1 to 9, characterized in that they contain   from 0 to 0.3% by weight of Sb203.   11. Crown glasses and lantern flint glasses, in accordance with   minus one of claims 1 to 10, characterized in that they do not   contain no arsenic oxide, apart from inevitable impurities   wheat. 12. Crown glasses and lantern flint glasses, in accordance with   minus one of claims 1 to 11, characterized in that they do not   contain no niobium oxide, aluminum oxide, barium oxide and alkali metal oxides, apart from the usual impurities.