GB1595656A - Luminescent substances - Google Patents
Luminescent substances Download PDFInfo
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- GB1595656A GB1595656A GB19925/78A GB1992578A GB1595656A GB 1595656 A GB1595656 A GB 1595656A GB 19925/78 A GB19925/78 A GB 19925/78A GB 1992578 A GB1992578 A GB 1992578A GB 1595656 A GB1595656 A GB 1595656A
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- 239000000126 substance Substances 0.000 title claims description 168
- 238000000034 method Methods 0.000 claims description 24
- 238000000295 emission spectrum Methods 0.000 claims description 19
- CMIHHWBVHJVIGI-UHFFFAOYSA-N gadolinium(III) oxide Inorganic materials [O-2].[O-2].[O-2].[Gd+3].[Gd+3] CMIHHWBVHJVIGI-UHFFFAOYSA-N 0.000 claims description 19
- 229910000421 cerium(III) oxide Inorganic materials 0.000 claims description 17
- MRELNEQAGSRDBK-UHFFFAOYSA-N lanthanum oxide Inorganic materials [O-2].[O-2].[O-2].[La+3].[La+3] MRELNEQAGSRDBK-UHFFFAOYSA-N 0.000 claims description 17
- 239000007858 starting material Substances 0.000 claims description 16
- KTUFCUMIWABKDW-UHFFFAOYSA-N oxo(oxolanthaniooxy)lanthanum Chemical compound O=[La]O[La]=O KTUFCUMIWABKDW-UHFFFAOYSA-N 0.000 claims description 15
- MNNHAPBLZZVQHP-UHFFFAOYSA-N diammonium hydrogen phosphate Chemical compound [NH4+].[NH4+].OP([O-])([O-])=O MNNHAPBLZZVQHP-UHFFFAOYSA-N 0.000 claims description 14
- 229910000388 diammonium phosphate Inorganic materials 0.000 claims description 14
- 235000019838 diammonium phosphate Nutrition 0.000 claims description 14
- CETPSERCERDGAM-UHFFFAOYSA-N ceric oxide Chemical compound O=[Ce]=O CETPSERCERDGAM-UHFFFAOYSA-N 0.000 claims description 12
- 229910000422 cerium(IV) oxide Inorganic materials 0.000 claims description 12
- 238000010438 heat treatment Methods 0.000 claims description 12
- 229910052753 mercury Inorganic materials 0.000 claims description 11
- RUDFQVOCFDJEEF-UHFFFAOYSA-N yttrium(III) oxide Inorganic materials [O-2].[O-2].[O-2].[Y+3].[Y+3] RUDFQVOCFDJEEF-UHFFFAOYSA-N 0.000 claims description 11
- NLQFUUYNQFMIJW-UHFFFAOYSA-N dysprosium(III) oxide Inorganic materials O=[Dy]O[Dy]=O NLQFUUYNQFMIJW-UHFFFAOYSA-N 0.000 claims description 10
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 claims description 10
- BWHMMNNQKKPAPP-UHFFFAOYSA-L potassium carbonate Chemical compound [K+].[K+].[O-]C([O-])=O BWHMMNNQKKPAPP-UHFFFAOYSA-L 0.000 claims description 10
- HYXGAEYDKFCVMU-UHFFFAOYSA-N scandium(III) oxide Inorganic materials O=[Sc]O[Sc]=O HYXGAEYDKFCVMU-UHFFFAOYSA-N 0.000 claims description 10
- 239000000203 mixture Substances 0.000 claims description 9
- 229910000027 potassium carbonate Inorganic materials 0.000 claims description 5
- 235000015320 potassium carbonate Nutrition 0.000 claims description 5
- KOPBYBDAPCDYFK-UHFFFAOYSA-N Cs2O Inorganic materials [O-2].[Cs+].[Cs+] KOPBYBDAPCDYFK-UHFFFAOYSA-N 0.000 claims description 3
- KKCBUQHMOMHUOY-UHFFFAOYSA-N Na2O Inorganic materials [O-2].[Na+].[Na+] KKCBUQHMOMHUOY-UHFFFAOYSA-N 0.000 claims description 3
- AKUNKIJLSDQFLS-UHFFFAOYSA-M dicesium;hydroxide Chemical compound [OH-].[Cs+].[Cs+] AKUNKIJLSDQFLS-UHFFFAOYSA-M 0.000 claims description 3
- 230000004907 flux Effects 0.000 claims description 3
- 230000004048 modification Effects 0.000 claims description 3
- 238000012986 modification Methods 0.000 claims description 3
- 229910001953 rubidium(I) oxide Inorganic materials 0.000 claims description 3
- 101100283604 Caenorhabditis elegans pigk-1 gene Proteins 0.000 claims description 2
- 150000002484 inorganic compounds Chemical class 0.000 claims description 2
- 229910010272 inorganic material Inorganic materials 0.000 claims description 2
- 238000002844 melting Methods 0.000 claims description 2
- 230000008018 melting Effects 0.000 claims description 2
- 150000002894 organic compounds Chemical class 0.000 claims description 2
- 239000002243 precursor Substances 0.000 claims description 2
- 238000002360 preparation method Methods 0.000 claims 2
- 238000001035 drying Methods 0.000 claims 1
- 238000011065 in-situ storage Methods 0.000 claims 1
- 150000002730 mercury Chemical class 0.000 claims 1
- 238000002156 mixing Methods 0.000 claims 1
- 229910019142 PO4 Inorganic materials 0.000 description 35
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 22
- 150000001875 compounds Chemical class 0.000 description 19
- 229910052771 Terbium Inorganic materials 0.000 description 18
- 229910052684 Cerium Inorganic materials 0.000 description 16
- GZCRRIHWUXGPOV-UHFFFAOYSA-N terbium atom Chemical compound [Tb] GZCRRIHWUXGPOV-UHFFFAOYSA-N 0.000 description 16
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 description 14
- 229910000029 sodium carbonate Inorganic materials 0.000 description 11
- 235000017550 sodium carbonate Nutrition 0.000 description 11
- 239000000843 powder Substances 0.000 description 10
- 229910052688 Gadolinium Inorganic materials 0.000 description 9
- 238000000695 excitation spectrum Methods 0.000 description 9
- 230000005855 radiation Effects 0.000 description 9
- 239000012190 activator Substances 0.000 description 7
- 229910052692 Dysprosium Inorganic materials 0.000 description 6
- 239000011230 binding agent Substances 0.000 description 6
- UIWYJDYFSGRHKR-UHFFFAOYSA-N gadolinium atom Chemical compound [Gd] UIWYJDYFSGRHKR-UHFFFAOYSA-N 0.000 description 6
- 238000010586 diagram Methods 0.000 description 5
- 230000005284 excitation Effects 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 230000003595 spectral effect Effects 0.000 description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 4
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 4
- 238000009826 distribution Methods 0.000 description 4
- KBQHZAAAGSGFKK-UHFFFAOYSA-N dysprosium atom Chemical compound [Dy] KBQHZAAAGSGFKK-UHFFFAOYSA-N 0.000 description 4
- 238000001228 spectrum Methods 0.000 description 4
- -1 Tb2O3 Inorganic materials 0.000 description 3
- 238000002441 X-ray diffraction Methods 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
- 235000021317 phosphate Nutrition 0.000 description 3
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 2
- 239000004698 Polyethylene Substances 0.000 description 2
- 229910052786 argon Inorganic materials 0.000 description 2
- 244000309464 bull Species 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 238000004020 luminiscence type Methods 0.000 description 2
- 238000010587 phase diagram Methods 0.000 description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 2
- 150000003013 phosphoric acid derivatives Chemical class 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 229920000573 polyethylene Polymers 0.000 description 2
- OTYBMLCTZGSZBG-UHFFFAOYSA-L potassium sulfate Chemical compound [K+].[K+].[O-]S([O-])(=O)=O OTYBMLCTZGSZBG-UHFFFAOYSA-L 0.000 description 2
- 229910052939 potassium sulfate Inorganic materials 0.000 description 2
- 238000010791 quenching Methods 0.000 description 2
- 230000000171 quenching effect Effects 0.000 description 2
- 229910052761 rare earth metal Inorganic materials 0.000 description 2
- 239000000020 Nitrocellulose Substances 0.000 description 1
- 239000004111 Potassium silicate Substances 0.000 description 1
- 239000004115 Sodium Silicate Substances 0.000 description 1
- 150000001242 acetic acid derivatives Chemical class 0.000 description 1
- 229910052783 alkali metal Inorganic materials 0.000 description 1
- 150000001340 alkali metals Chemical class 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 239000012736 aqueous medium Substances 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910052792 caesium Inorganic materials 0.000 description 1
- 150000004649 carbonic acid derivatives Chemical class 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000000975 co-precipitation Methods 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000012926 crystallographic analysis Methods 0.000 description 1
- 150000004679 hydroxides Chemical class 0.000 description 1
- 239000011872 intimate mixture Substances 0.000 description 1
- 229910052746 lanthanum Inorganic materials 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 150000002823 nitrates Chemical class 0.000 description 1
- 229920001220 nitrocellulos Polymers 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 150000003891 oxalate salts Chemical class 0.000 description 1
- 125000004430 oxygen atom Chemical group O* 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- 125000004437 phosphorous atom Chemical group 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 229920003229 poly(methyl methacrylate) Polymers 0.000 description 1
- 239000004926 polymethyl methacrylate Substances 0.000 description 1
- 229920000915 polyvinyl chloride Polymers 0.000 description 1
- 239000004800 polyvinyl chloride Substances 0.000 description 1
- 229910052700 potassium Inorganic materials 0.000 description 1
- NNHHDJVEYQHLHG-UHFFFAOYSA-N potassium silicate Chemical compound [K+].[K+].[O-][Si]([O-])=O NNHHDJVEYQHLHG-UHFFFAOYSA-N 0.000 description 1
- 229910052913 potassium silicate Inorganic materials 0.000 description 1
- 235000019353 potassium silicate Nutrition 0.000 description 1
- 150000002910 rare earth metals Chemical class 0.000 description 1
- 229910052701 rubidium Inorganic materials 0.000 description 1
- WPFGFHJALYCVMO-UHFFFAOYSA-L rubidium carbonate Chemical compound [Rb+].[Rb+].[O-]C([O-])=O WPFGFHJALYCVMO-UHFFFAOYSA-L 0.000 description 1
- 229910000026 rubidium carbonate Inorganic materials 0.000 description 1
- 229910052706 scandium Inorganic materials 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical compound [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 description 1
- 229910052911 sodium silicate Inorganic materials 0.000 description 1
- 238000003746 solid phase reaction Methods 0.000 description 1
- 238000010671 solid-state reaction Methods 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 229910052727 yttrium Inorganic materials 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
- C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
- C09K11/77—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals
- C09K11/7709—Phosphates
Landscapes
- Chemical & Material Sciences (AREA)
- Inorganic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Luminescent Compositions (AREA)
Description
(54) LUMINESCENT SUBSTANCES
(71) We, RHONE-POULENC INDUSTRIES, a French body corporate, of 22 Avenue Montaigne, 75-Paris 8eme, France, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The invention relates to new luminescent substances.
Numerous luminescent substances are known which when activated by, for example, rare earth elements, produce valuable emissions. There is need for substances which, when they are suitably excited, exhibit a very intense emission.
The present invention relates to a luminescent substance which exhibits an ortho-rhombic or monoclinic crystalline structure; this subtance consists of a double phosphate of an alkali metal and a rare earth metal, having a structure derived form that of the p-form of the compound K2SO4 (see G. GAULTIER and
G. PANNETIER, Bull. Soc. Chim. Fr. 1968, page 105) or derived from that of the compound K3Nd(PO4)2 (see HYP. HONG and S.R. CHINN, Mat. Res.Bull. 11, 1976 page 421), in which the phosphorus atoms form isolated tetrahedra with the oxygen atoms which surround them. the luminescent substance of the present invention is a tenary compound the composition of which can be represented by the phase AaBbCC in an ABC ternary phase diagram, in which:
A represents at least one of the oxides 3/2 Na2O, 3/2 K2O, 3/2 Rb2O and 3/2
Cs2O,
B represents at least one of the oxides l/2Ce203, I/2Gd203, l/2Tb203 and l/2Dy2O3 and, optionally in addition l/2La2O3, l/2Y2O3 and l/2Sc203,and
C represents the oxide P2Os.
The ABC ternary phase diagram, as shown in Figure 1 of the accompanying drawings, is in the form of an equilateral triangle with apices A, B, and C; all the compounds formed from the oxides A, B and C can be represented by a point of the diagram. Thus, a compound, or a mixture of compounds, on the diagram which has a given content of the oxides A, B and C, can be represented by the formula (A)a(B)b(C)c in which each of a, b, and c which may be the same or different represents any positive integers except for the values of a, b, and c which correspond to the pairs
a b a b (--=1/2, 4/3) and (-- 1/3. --=1/2); b b b c of course, the relative proportions of constituents A, B, and C must be such that the compound possesses the desired luminescent properties.
By a "ternary phase" or a "ternary compound" as used herein is meant that the phase or the compound contains at least one oxide of each of the groups A, B and C.
In the abovementioned formula, the preferred luminescent substances of the invention are those in which a 1, b= I and c=l.
The luminescent substances of the invention are activated by at least one of cerium, gadolinium, terbium and dysprosium. (The activators Ce, Gd, Tb and Dy form part of the oxide B.) The concentration of these activators can be such that the oxide B consists wholly of the oxide of the activator or is diluted, within its phase, by at least one of the oxides selected from La203, Y203 and Sc203 and possibly (optically inactive) Gd203. The concentration of the activator should be at least such that the substance emits a luminescence; in a large number of cases, significant luminescence is observed even if the oxide concentration of at least one of the activators Ce203, Tb2O3, Gd203 and Dy203 is as low as 1% relative to that of the oxides B which are considered optically inactive, that is to say La203, Y203 and
Sc203 and possibly Gd203.
The preferred luminescent substances of the invention correspond to the general formula M3Ln(PO4)2, in which
M is at least one of Na, K, Rb and Cs and
Ln is at least one of Ce, Tb, Gd, Dy, optionally with at least one of La, Y and
Sc.
When the luminescent substances of the invention are suitably excited by ultraviolet rays or cathode rays or X-rays, they exhibit the emission of the element used as the activator. Thus, luminescent screens or luminescent tubes provided with such substances can be suitable for a very large number of applications, especially for mercury vapour discharge lamps cathode ray tubes and devices for converting X-rays to visible rays, or X-rays to U.V rays, or U.V. rays to visible rays, or U.V. rays to other U.V. rays.
A particularly valuable group of luminescent substances according to the invention are those in which the oxide B consists entirely or partially of Ce203. The substances activated by means of cerium in accordance with the invention exhibit an emission which is located in the ultraviolet.
Virtually the whole of the radiation emitted depends on the crystalline structure, the nature of A and the cerium content. The radiation is generally located at wavelengths of about 3,200 A. The width of the band at half-height is generally about 600 A. The phosphates activated by means of cerium can advantageously be used in discharge !amps, especially in low pressure mercury vapour discharge lamps used, for example, for photochemical applications such as reproduction.
Another particularly valuable group of luminescent substances according to the invention consists of compounds in which the oxide B consists entirely or partially of Gd203. When activated by means of gadolinium, the substances of the invention, on excitation by ultraviolet rays, exhibit the characteristic emission of gadolinium. The spectral distribution of the radiation emitted by these substances generally consists of a sharp emission peak located at about 3,130 A, having a width at half-height, of about 10 A. These substances are particularly applicable to document-marking processes.
A third particularly valuable group of luminescent substances according to the invention consists of compounds in which the oxide B consists entirely or partially of Tb203. When excited by ultraviolet rays, the substances activated by means of terbium exhibit the characteristic emission of terbium. The spectral distribution of the radiation emitted by these substances generally consists of several sharp emission peaks, of which the highest peak is located at about 5,450 A and has a width at half-height of about 100 A. These substances are in particular applicable to devices which employ the conversion of X-rays to visible rays, for example in the field of radiology.
A fourth particularly valuable group of luminescent substances according to the invention consists of compounds in which the oxide B consists entirely or partially of one of the pairs of oxides (Ce203, Tb203) or (Ce203, Dy203) or (Gd2 03, Tb203). In these substances, the ratios
Ce Ce Gd and Tb Dy Tb can vary within wide limits depending on the spectral energy distribution which is desired.
The substances activated simultaneously with the aid of cerium and of terbium can be employed as high performance luminescent substances, in particular in low pressure mercury vapour discharge lamps used for lighting purposes. It has in fact been found that such substances provide very high luminous flux when excited by ultraviolet rays, especially when excited by radiation resulting from a discharge in low pressure mercury vapour. The spectral distribution of the radiation emitted by these substances can in particular correspond to that of the characteristic emission of terbium, which consists of a very high and narrow emission peak (width, at halfheight, about 100 A) at about 5,450 A, and alongside this, several weaker secondary emission peaks. A transfer of energy from cerium and terbium takes place.Thus, in the case of cerium and terbium concentration for which the ratio Ce/Tb is from 1 to 3, this transfer is usually virtually complete and efficient, as can be seen from the terbium emission output which, is in this case particularly intense. These substances activated by means of cerium and of terbium can be used in combination with other luminescent substances in order to correct the colour of the radiation emitted, for example by a mercury vapour discharge; a correction of this colour by an additional radiation in the yellowish-green spectral region (5,450
A) can be effected by the said substances. In the field of lighting, in particular, a correction is required in a large number of cases and is employed in practice in fluorescent tubes.
Another application; which is very advantageous for substances activated by means of cerium and of terbium in accordance with the invention, especially the substances for which the energy transfer of cerium to terbium takes place virtually completely, consists in using them in low pressure mercury vapour discharge lamps employed for reproducticn processes, for example xerography. For this purpose, it is necessary to have an efficient luminescent structure which emits in a narrow band in the green part of the spectrum.Thus, compared to the compounds currently used in xerography, the substances activated by means of cerium and of terbium in accordance with the invention exhibit the advantage of having an emission which is substantially shifted towards the red (5,450 A in place of 5,150 A), which makes it possible to improve the reproduction of information recorded in blue; furthermore, the optical performance of these substances is virtually independent of the number and frequency of the excitation operations to which they are subjected.
The transfer of energy in the base lattices of the substances of the invention is also possible between cerium and dysprosium. The substances activated by means of cerium and of dysprosium in accordance with the invention are efficient luminescent substances which can exhibit a maximum emission at about 5,760 A and which can advantageously be applied to low pressure mercury vapour discharge lamps.
The transfer in the substances according to the invention is also possible between gadolinium and terbium. The substances activated simultaneously by gadolinium and terbium in accordance with the invention are usually efficient luminescent substances which can exhibit the characteristic emission of terbium, which consists of several emission peaks, the most intense being located about 5,450 A, and which can advantageously be applied as a luminescent substance for cathode ray tubes and in devices for converting X-rays to visible rays to U.V. rays.
The substances according to the invention can be prepared in accordance with conventional processes for the synthesis of luminescent substances. In general, they can be obtained by a solid state reaction. For this purpose, a mixture of the starting substances is heated at least once, for example for a period of one hour to several days, to a temperature which is approximately between 500"C and the melting point of the compound to be formed, the heating being carried out in the presence or absence of a flux.
The upper heating limit is in practice about 1,200"C, this represents an advantage since luminescent substances currently used for the same applications generally require a significantly higher temperature for their production.
In the case of compounds activated solely by dysprosium and by gadolinium, heating can generally be effected in any type of atmosphere. In the case of compounds activated by cerium and/or terbium, it is necessary to carry out the last heating in a slightly reducing atmosphere in order to convert these activators completely to the trivalent state.
As starting substances it is possible to use the required metal oxides, directly or to use organic or inorganic compounds capable of forming these oxides by heating, such as the carbonates, oxalates, hydroxides, acetates, nitrates or phosphates of the said materials.
In order to obtain a luminescent substance according to the invention, it is advantageous to start from an intimate mixture, at the appropriate concentrations, of all the compounds, in a finely divided state.
There is also a possibility of preparing the compounds of the invention by coprecipitation from solutions of the precursors of the desired oxides, for example in an aqueous medium.
Depending on their desired application, the substances of the present invention can be finely ground and, if desired, mixed with other luminescent materials to obtain products which emit in accordance with the desired characteristics. As is currently the practice, for example, the substances of the present invention can be finely ground and mixed with conventional organic and inorganic binders, luminescent materials and, usually, a solvent for the binder, to give compositions which lend themselves easily to shaping into sheets, films, coatings and other luminescent articles of various shapes.As examples of these binders there may be mentioned organic polymeric binders such as nitrocellulose, polymethyl methacrylate, polyvinyl chloride, polyethylene and chlorosulphonated polyethylene, inorganic binders, such as sodium silicate and potassium silicate, and other binders which are substantially transparent and do not appreciably absorb the radiation employed.
The following Examples further illustrate the present invention. The data mentioned below are given in the accompanying drawings in which: Figure 1 represents the diagram of the ABC ternary phase, described above.
Figure 2 shows the emission spectrum of the luminescent substances described in Example 1, in particular that of [Na3CeO70TBO3o(po4)2]* This emission spectrum also applies to the substances according to the invention given in Examples 2, 3, 4, 5, 11 and 12.
Figure 3 shows the excitation spectrum of the luminescent substances described in Example 1. The excitation spectrum also applies to the substances given in Examples 2, 3, 4, 5, 8 and 9.
Figure 4 shows the emission spectrum of the luminescent substances according to the invention described in Example 6, in particular that of 1Rb3Ce0,6Tb0.3(PO4)2l.
Figure 5 shows the emission spectrum of the luminescent substances according to the invention described in Example 9, in particular that of [Na3LaO 35CeO 6s(Po4)2] Figure 6 shows the excitation spectrum of the luminescent substances according to the invention described in Example 6, in particular that of [Rb3Ce065Tb035(PO4)2l.
Figure 7 shows the emission spectrum of the luminescent substances according to the invention described in Example 10, in particular that of lNa3L.5Gd00(PO4)21.
Figure 8 shows the emission spectrum of the luminescent substances according to the invention described in Example 13, in particular that of lK3La0.65Ce0.36(PO4)21.
Figure 9 shows the emission spectrum of the luminescent substances according to the invention described in Example 14, in particular that of [K3Ce0.65Tb0.35(PO4)2].
It should be noted that the various spectra given also apply to each group of substances exemplified, regardless of the values of x or y in the general formulae.
Furthermore, in all the Figures 2 to 9, the abscissa represents wavelengths expressed in angstroms and the ordinate axis represents the energy (intensity of excitation or of emission of the substance arbitrary units).
Furthermore, the fluorescent spectra of the luminescent substances given were recorded at ambient temperature under ultraviolet excitation.
Example I
We have prepared the luminescent substances corresponding to the formula [Na3Ce1~xTbx(PO4)2] for various values of x, with x between 0 and 1.
For the compound of the formula Na3Ce0,0TbO3o(po4)2 the following oxides were used, in the proportions indicated below
Starting compounds Quantities employed
Na2CO3 1.272 g
(NH4)2HPO4 2. 113g CeO2 0.9640 g Tb4O7 0.4486 g
The mixture of oxides, in the form of powders, was introduced into a platinum crucible and the whole was heated to 9000C for 10 hours.
The quenched product was again ground and this powder was then heated to 1,200"C for 12 hours, in an alumina boat, under a stream of argon doped with 10% of hydrogen. Subsequently, the material was cooled in the same stream of Ar/H2.
The duration of this cooling was of the order of 6 hours. When the temperature of the product was of the order of 70"C, the product was ground. The powder obtained was sieved so as to obtain particles of which the size is approximately between 20 and 40y.
Crystallographic analysis was used to establish that the white product obtained had a structure derived from that of the p-form of K2SO4.
TABLE I
d in h k I I in % 6057 021 60 4.63 023,004 30 4.14 121 30 3.857 024,122 20 3.495 040,123 35 3.264 025 20 3.037 043 15 2.782 125 100 2.662 200,106 60 2.463 221 15 2.308 046- 35 2.236 127 20 2.117 240 20 2.077 162 15 2.061 242 15 2.015 163 20 1.994 206 35 1.996 029 20 1.922 244 35 1.740 208 20 The fluorescent spectrum of the orthophosphate thus prepared is characterised at ambient temperature, under ultraviolet excitation, by 4 lines of approximate width 200 A, of which the intensity maxima are located at 4,880, 5,425, 5,820 and 6,210 A. The most intense of these lines is that with the intensity maximum at 5,425 A (Figure 2).
The excitation spectrum is given in Figure 3.
The above Table (I) gives the values of d (the lattice distances expressed in A) and the intensities I (expressed as a percentage) and the Miller indices hkl deduced from the X-ray diffraction diagrams of the substance in question.
Example 2
The substances corresponding to the formula [Na3Lay-x-yCexTby(PO4)2] were prepared for different values of x and y.
For the substance of the formula [Na,La,,Ce,,Tb,,(P0,),1, the following oxides were used in the proportions indicated below:
Starting compounds Quantities employed
Na2CO3 1.272 g
(NH4)2HPO4 2.113g CeO2 0.6885 g Tb4O7 0.5982g La2O3 0.1303 g
Thereafter, the procedure described in Example 1 was followed.
The emission and excitation spectra observed for the substances as well as their crystallographic characteristics correspond to those given for the substances of Example 1.
Example 3
The substances corresponding to the formula [Na3-xKxCe1-yTby(PO4)2] were prepared for different values of x and y, x being between 0 and 3 and y between 0 and 1.
For the substance of the formula [Na2.7K0.3Ce0.80Tb0.40(PO4)2] the following oxides were used in the proportions indicated below:
Starting compounds Quantities employed
Na2CO3 1.145 g
K2CO3 0.1656 g
(NH4)2HPO4 2.113g CeO2 0.8622 g Tb4O7 0.5982 g
Thereafter the procedure described in Example 1 was followed.
The emission and excitation spectra observed for these substances correspond to those given for the substances of Example 1.
It should be noted that depending on the value of x the X-ray diffraction diagram of the substances corresponding to the above formula can exhibit the characteristics of the structure of the substances of Examples 1 and/or 6.
Example 4
The substances corresponding to the formula [Na3Y1-x-yCexTby(PO4)2] were prepared for different values of x and y.
For the substance of the formula [Na3Y0.1Ce0.8Tb0.4(PO4)2], the following oxides were used in the proportions indicated below:
Starting compounds Quantities employed Na2CO3 1.272 g
(NH4)2HPO4 2.113 g Y203 0.0903 g
CeO2 0.826 g
Tb4O7 0.449g
Thereafter the procedure described in Example 1 was followed.
The emission and excitation spectra observed for these substances as well as their radiocrystallographic characteristics correspond to those given for the substances of Example 1.
Example 5
The substances corresponding to the formula [Na3Gd1-x-yCexTby(PO4)2] were prepared for different values of x and y.
For the substance of the formula [Na3Gd0,1Ce0,8Tb0,3(PO4)2], the following oxides were used in the proportions indicated below:
Starting compounds Quantities employed Na2CO3 1.272 g (NH4)2HPO4 2.113g Gd2O3 0.145 g
CeO2 0.826 g Tb4O7 0.449 g
Thereafter the procedure described in Example 1 was followed.
The emission and excitation spectra observed for these substances as well as their crystallographic characteristics correspond to those given for the substances of Example l.
Example 6
We have prepared the substances corresponding to the formula [Rb3Ce1-xTbx(PO4)2], x being between 0 and l.
For the substance of the formula [Rb3C30.6sTb0,35(PO4)2], the following oxides were used in the proportions indicated below:
Starting compounds Quantities employed
Rb2CO3 2.772 g
(NH4)2HPO4 2.113g CeO2 0.895 g Tb4O7 0.5234 g
The mixture of oxides, in the form of powders, was introduced into an alumina crucible and the whole was heated to 9000C for 10 hours.
The quenched product was again ground and this powder was then heated to 1,050"C for twelve hours, in an alumina boat, under a stream of argon doped with 10% of hydrogen. After this heating period of twelve hours, the material is cooled in the same stream of Ar/H2. The duration of cooling is of the order of 6 hours but can be reduced since the quenching of the product does not alter its luminescent properties.
The powder obtained is sieved so as to obtain particles of size between about 20 and 49cm.
Radiocrystallographic analysis was used to show that the white product obtained was the phase [Rb3CeO esTbo 35(PO4)2] which is isotypical with [K3Nd(O4)2l.
Table (II) below shows the values of d [expressed in angströms] and the intensities (I expressed as a percentage) measured by X-ray diffraction, of the luminescent powder thus obtained.
TABLE II
d in A h k I I in % '7.68 001 60 4:92 110,200 10 4.1'5 111 15 4.07 201 5 3.85 002 10 3.57 102 20 3.32 211 26 3.193 012 10 3.030 112,3'01 100 2.861 020 30 2.803 120 35 2.673 021 5 2.490 103 40 2.344' 221 20 2.230 122 10 2.139' 320 10 2.074 222 20 2.000 303 10 1.928 412 25 1.874 123,r04 15 1.797 204 20 The emission and excitation spectra of the luminescent substances thus prepared are given in Figures 4 and 6 respectively.
It should be noted that the radiocrystallographic characteristics mentioned above are also those of the substances cited in Examples 13 and 14 below, as well as those of Example 3 if x has a sufficiently high value.
Example 7
We have prepared the substances corresponding to the formula [Na3La1~xDyx(PO4)2] for different values of x.
For the substance of the formula [Na3La0Dy01(PO4)2l, the following oxides were used in the proportions indicated below:
Starting compounds Quantities employed
Na2CO3 1.272 g
(NH4)2HPO4 2.113g La2O3 1.173 g Dy2O3 0.1492 g
The mixture of oxides, in the form of powders, was introduced into an alumina crucible and the whole was heated to 9000C for 10 hours.
The quenched product was again ground and this powder was then heated at I ,0500C in air for twelve hours. Cooling can be effected over the course of several hours or by quenching. The powder obtained is sieved so as to obtain particles of size between about 20 and 40y.
The crystallographic characteristics of the substances thus prepared correspond to those given for the substances of Example 1.
Example 8
We have prepared the substances corresponding to the formula [Na3Ce,~xDyx(PO4)2] for different values of x.
For the substance of the formula [Na3Ce0.9Dy0.1(PO4)2], the following oxides were used in the proportions indicated below:
Starting compounds Quantities employed
Na2CO3 1.272 g (NH4)2HPO4 2.113g CeO2 1.239 g Dy2O3 0.1492 g
Thereafter the procedure described in Example 6 was followed.
The crystallographic characteristics of the substances thus prepared correspond to those given for the substances of Example 1.
Example 9
We have prepared the substances corresponding to the formula [Na3Lat~xCex(PO4)2] for different values of x, x being between 0.001 and 1.
For the substance of the formula lNa2La035Ce065(PO4)21, the following oxides were used in the proportions indicated below:
Starting compounds Quantities employed
Na2CO3 2.162g
(NH4)2HPO4 3.592 g
CeO2 1.521 g La2O3 0.7752g
Thereafter the procedure described in Example 6 was followed.
The crystallographic characteristics of the substances thus prepared correspond to those given for the substances of Example 1.
Example 10
We have prepared the substances corresponding to the formula [Na3La,~xGdx(PO4)2] for different values of x, x being between 0.001 and 1.
For the substance of the formula [Na3La050Gd0(PO4)2], the following oxides were used in the proportions indicated below:
Starting compounds Quantities employed
Na2CO3 1.272 g (NH4)2HPO4 2.1132 g La2O3 0.6516 g Gd2O3 0.725g
Thereafter the procedure described in Example 7 was followed.
The emission spectrum of the luminescent substances thus prepared is given in
Figure 7. The crystallographic characteristics of the substances thus prepared correspond to those given for the substances of Example 1.
Example 11
We have prepared the substances corresponding to the formula [Na,La,~,Tb,(PO,),] for different values of x, x being between 0.0001 and 1.
For the substance of the formula [Na3La0.50Tb0.50(PO4)2], the following oxides were used in the proportions indicated below:
Starting compounds Quantities employed
Na2CO3 1.272 g
(NH4)2HPO4 2.1132 g La2O3 0.6516 g
Tb4O7 0.7477g
Thereafter the procedure described in Example 1 was followed.
The emission spectrum of the luminescent substances thus prepared is similar to that given in Figure 2. The crystallographic characteristics of the substances thus prepared correspond to those given for the substances of Example 1.
Example 12
We have prepared the substances corresponding to the formula [Na3Gd,~xTbx(PO4)2] for different values of x, x being between 0 and 1.
For the substance of the formula [Na3Gd00Tb050(PO4)2l, the following oxides were used in the proportions indicated below:
Starting compounds Quantities employed
Na2CO3 1.272 g
(NH4)2HPO4 2.1132 g Gd2O3 0.725 g Tb4O7 0.7477g
Thereafter the procedure described in Example 1 was followed.
The emission spectra of the luminescent substances thus prepared are those given in Figures 2 and/or 7, depending on the value of x.
The crystallographic characteristics of the substances thus prepared correspond to those given for the substances of Example 1.
Example 13
We have prepared the substances corresponding to the formula [K3La,~xCex(PO4)2)] for different values of x, x being between 0.001 and 1.
For the substance of the formula lK3La065Ce035(PO4)2], the following oxides were used in the proportions indicated below:
Starting compounds Quantities employed
K2CO3 1.658 g
(NH4)HPO4 2.1132 g La2O3 0.4561 g
CeO2 0.895 g
Thereafter the procedure described in Example 6 was followed.
The emission spectrum of the luminescent substances thus prepared is given in
Figure 8. The crystallographic characteristics of the luminescent substances thus prepared correspond to those given for the substances of Example 6.
Example 14
We have prepared the substances corresponding to the formula [K3Ce,~xTbx(Po4)2] for different values of x, x being between 0 and 1.
For the substance of the formula [K3Ce0.65Tb0.35(PO4)2], the following oxides were used in the proportions indicated below:
Starting compounds Quantities employed
K2CO3 1.658 g
(NH4)2HPO4 2.1132g
CeO2 0.895 g
Tb4O7 0.5234g
Thereafter the procedure described in Example 6 was followed.
The emission spectrum of the luminescent substances thus prepared is given in
Figure 9.
The crystallographic characteristics of the substances thus prepared
correspond to those given for the substances of Example 6.
WHAT WE CLAIM IS:
1. A luminescent substance having the formula: (A)8(B)b(C)C in which
A represents at least one of the oxides 3/2 Na2O, 3/2 K2O, 3/2 Rb2O and 3/2
Cs2O,
B represents at least one of the oxides 1/2 Ce2O3, 1/2 Gd2O3, 1/2 Tb2O3 and 1/2
Dy203,
C represents the oxide P2Os and each of a, b, and c which may be the same or
different, is a positive integer with the proviso that a, b, and c cannot be such that a 1 b 4 a 1 b 1 ~ = ~ and - = ~ , or = and- = - b 2 c 3 b 3 c 2 2. A luminescent substance according to claim 1 in which a = 1, b = l and c = 1.
3. A modification of a luminescent substance according to claim 1 or 2, in which B represents at least one of a first group of oxides namely 1/2 Ce2O3, 1/2
Gd203, 1/2 Tb2O3, and 1/2 Dy2O3 in combination with at least one of a second group of oxides namely 1/2 La2O3, 1/2 Y203 and 1/2 Sc2O3.
4. A luminescent substances according to claim 3, in which the concentration of the first group of oxides, the group consisting of at least one of the oxides Ce203, Tb2O3, is at least 1% relative to that of the second group of oxides.
**WARNING** end of DESC field may overlap start of CLMS **.
Claims (34)
1. A luminescent substance having the formula: (A)8(B)b(C)C in which
A represents at least one of the oxides 3/
2 Na2O, 3/2 K2O, 3/2 Rb2O and 3/2
Cs2O,
B represents at least one of the oxides 1/2 Ce2O3, 1/2 Gd2O3, 1/2 Tb2O3 and 1/2
Dy203,
C represents the oxide P2Os and each of a, b, and c which may be the same or
different, is a positive integer with the proviso that a, b, and c cannot be such that a 1 b 4 a 1 b 1 ~ = ~ and - = ~ , or = and- = - b 2 c 3 b 3 c 2 2. A luminescent substance according to claim 1 in which a = 1, b = l and c = 1.
3. A modification of a luminescent substance according to claim 1 or 2, in which B represents at least one of a first group of oxides namely 1/2 Ce2O3, 1/2
Gd203, 1/2 Tb2O3, and 1/2 Dy2O3 in combination with at least one of a second group of oxides namely 1/2 La2O3, 1/2 Y203 and 1/2 Sc2O3.
4. A luminescent substances according to claim 3, in which the concentration of the first group of oxides, the group consisting of at least one of the oxides Ce203, Tb2O3, is at least 1% relative to that of the second group of oxides.
5. A luminescent substance according to claim l or 2, in which B represents 1/2
Ce2O3 and 1/2 Tb2O3.
6. A luminescent substance according to claim 3 or 4, in which B represents 1/2 Ce2O3 and 1/2 Tb2O3 and at least one of the oxides 1/2 La2O3, 1/2 Y2O3, 1/2 Sc2O3 and 1/2 Gd2O3.
7. A luminescent substance according to claim 5 or 6, in which the ratio
Ce - is from I to 3.
Tb
8. A luminescent substance according to claim 1 or 2, in which B represents 1/2 Gd2O3 and 1/2 Tb2O3.
9. A luminescent substance according to claim 3 or 4, in which B represents 1/2 Gd2O3 and 1/2 Tb2O3 and at least one of the oxides 1/2 La2O3, 1/2 Y203 and 1/2 Sc2O3.
10. A luminescent substance according to claim 1 or 2, in which B represents 1/2 Ce2O3 and 1/2 Dy2O3.
11. A luminescent substance according to claim 3 or 4, in which B represents 1/2 Ce2O3 and 1/2 Dy2O3 and at least one of the oxides 1/2 La2O3, 1/2 Y2O3, 1/2 Gd2O3 and 1/2 Sc2O3.
12. A luminescent substance according to claim 1 or 2, in which B represents 1/2 Ce2O3.
13. A luminescent substance according to claim 3 or 4, in which B represents 1/2 Ce2O3 and at least one of the oxides 1/2 La2O3, 1/2 Y2O3, 1/2 Sc2O3 and 1/2 Gd2O3.
14. A luminescent substance according to claim 1 or 2, in which B represents 1/2 Gd2O3.
15. A luminescent substance according to claim 3 or 4, in that B represents 1/2 Gd2O3 and at least one of the oxides 1/2 La2O3, 1/2 Y203 and 1/2 Sc2O3.
16. A luminescent substance according to claim 1 or 2, in which B represents 1/2 Tb2O3.
17. A luminescent substance according to claim 3 or 4, in which B represents
1/2 Tb2O3 and at least one of the oxides 1/2 La2O3, 1/2 Y2O3, 1/2 Gd2O3 and 1/2 Sc2O3.
18. A luminescent substance according to claim 1 or 3, specifically identified herein.
19. Process for the preparation of a luminescent substance as claimed in any one of the preceding claims, which comprises mixing the oxides corresponding to
A, B and C, respectively, heating the resulting mixture at least once to a temperature from 500"C to the melting point of the substance to be formed, optionally in the presence of a flux.
20. Process according to claim 19 in which the said heating is below 12000C.
21. A modification of a process according to claim 19 or 20, in which the oxides are formed in situ by heating organic or inorganic compounds capable of forming said oxides on heating.
22. Process according to any one of claims 19 to 21 for preparing a luminescent substance which contains Ce2O3 and/or Tb2O3, in which the or the last heating is effected in a slightly reducing atmosphere.
23. Process for the preparation of a luminescent substance as claimed in any one of claims 1 to 18 which comprises coprecipitating a solution of the precursors of the oxides corresponding to A, B and C respectively and drying resulting mixture and heating it at least once to a temperature of 500"C to 1,2000C.
24. Process according to claim 19 or 23 substantially as hereinbefore described.
25. A luminescent substance according to claim 1 or 3 whenever prepared by a process as claimed in any one of claims 19 to 24.
26. A luminescent screen or tube provided with a luminescent substance as claimed in any one of claims 1 to 18 and 25:
27. A screen or tube according to claim 26 in the form of a mercury vapour
discharge lamp.
28. A low pressure mercury vapour discharge lamp according to claim 27
suitable for reproduction purposes provided with a substance as claimed in claim
12 or 13.
29; A low pressure mercury vapour discharge lamp according to claim 27 suitable for lighting or reproduction purposes provided with a substance as claimed in claim 5 or 6.
30. A low pressure mercury vapour discharge lamp according to claim 27 provided with a substance as claimed in claim 10 or 11.
31. A screen or tube according to claim 26 in the form of a cathode ray tube or a device for converting X-rays to visible rays or X-rays to ultraviolet rays.
32. A screen or tube according to claim 31 provided with a substance as claimed in claim 8 or 9.
33. A screen or tube according to claim 26 in the form of a device for converting ultraviolet rays to visible rays or ultraviolet to other ultraviolet rays.
34. A screen or tube according to claim 33 provided with a substance as claimed in any one of claims 5, 6 and 8 to 17.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR7715229A FR2391260A1 (en) | 1977-05-18 | 1977-05-18 | NEW LUMINESCENT SUBSTANCES FOR SCREENS OR TUBES |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB1595656A true GB1595656A (en) | 1981-08-12 |
Family
ID=9190987
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB19925/78A Expired GB1595656A (en) | 1977-05-18 | 1978-05-16 | Luminescent substances |
Country Status (10)
| Country | Link |
|---|---|
| JP (1) | JPS5413479A (en) |
| BE (1) | BE867186A (en) |
| CA (1) | CA1103914A (en) |
| DE (1) | DE2820889C2 (en) |
| FI (1) | FI781574A (en) |
| FR (1) | FR2391260A1 (en) |
| GB (1) | GB1595656A (en) |
| HU (1) | HU178714B (en) |
| IT (1) | IT1104838B (en) |
| NL (1) | NL7805348A (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5920378A (en) * | 1982-07-26 | 1984-02-02 | Mitsubishi Electric Corp | Fluophor and its use in low-pressure mercury vapor luminescent lamp |
| DE19645035C1 (en) * | 1996-10-31 | 1998-04-30 | Siemens Ag | Multi-color light emitting image display device |
| KR101281830B1 (en) * | 2006-09-26 | 2013-07-03 | 엘지디스플레이 주식회사 | Liquid crystal display having multi-touch sensing function and driving method thereof |
| FR2938526B1 (en) * | 2008-11-20 | 2011-01-07 | Rhodia Operations | CERIUM AND / OR TERBIUM PHOSPHATE, POSSIBLY WITH LANTHANE, LUMINOPHORE FROM THIS PHOSPHATE AND PROCESSES FOR THE PREPARATION THEREOF |
| FR2938525B1 (en) * | 2008-11-20 | 2011-01-07 | Rhodia Operations | CERIUM AND / OR TERBIUM PHOSPHATE, POSSIBLY WITH LANTHANE, LUMINOPHORE FROM THIS PHOSPHATE AND PROCESSES FOR THE PREPARATION THEREOF |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1590705A (en) * | 1968-09-26 | 1970-04-20 | ||
| US4000247A (en) * | 1974-05-27 | 1976-12-28 | Nippon Telegraph And Telephone Public Corporation | Dielectric active medium for lasers |
-
1977
- 1977-05-18 FR FR7715229A patent/FR2391260A1/en active Granted
-
1978
- 1978-05-12 DE DE2820889A patent/DE2820889C2/en not_active Expired
- 1978-05-16 GB GB19925/78A patent/GB1595656A/en not_active Expired
- 1978-05-17 IT IT49417/78A patent/IT1104838B/en active
- 1978-05-17 FI FI781574A patent/FI781574A/en not_active Application Discontinuation
- 1978-05-17 BE BE187791A patent/BE867186A/en not_active IP Right Cessation
- 1978-05-17 CA CA303,592A patent/CA1103914A/en not_active Expired
- 1978-05-17 HU HU78RO983A patent/HU178714B/en not_active IP Right Cessation
- 1978-05-17 NL NL7805348A patent/NL7805348A/en not_active Application Discontinuation
- 1978-05-18 JP JP5833278A patent/JPS5413479A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| FR2391260B1 (en) | 1980-11-28 |
| IT1104838B (en) | 1985-10-28 |
| DE2820889C2 (en) | 1984-10-18 |
| FR2391260A1 (en) | 1978-12-15 |
| JPS5413479A (en) | 1979-01-31 |
| IT7849417A0 (en) | 1978-05-17 |
| HU178714B (en) | 1982-06-28 |
| NL7805348A (en) | 1978-11-21 |
| FI781574A (en) | 1978-11-19 |
| DE2820889A1 (en) | 1978-11-23 |
| CA1103914A (en) | 1981-06-30 |
| BE867186A (en) | 1978-11-17 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PS | Patent sealed [section 19, patents act 1949] | ||
| PCNP | Patent ceased through non-payment of renewal fee |