CA1061102A - Luminescent screen - Google Patents
Luminescent screenInfo
- Publication number
- CA1061102A CA1061102A CA219,522A CA219522A CA1061102A CA 1061102 A CA1061102 A CA 1061102A CA 219522 A CA219522 A CA 219522A CA 1061102 A CA1061102 A CA 1061102A
- Authority
- CA
- Canada
- Prior art keywords
- luminescent
- alkaline earth
- strontium
- aluminates
- formula
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
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
- C09K11/7715—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals containing cerium
- C09K11/7721—Aluminates
Landscapes
- Chemical & Material Sciences (AREA)
- Inorganic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Luminescent Compositions (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE:
A luminescent cerium-activated alkaline earth aluminate defined by the formula Me1-x-yCexAyAl12019+0.5(x-y), where Me represents at least one of the alkaline earth metals strontium and calcium and A represents at least one of the alkali metals sodium, potassium and rubidium, in which up to 25 mol % of aluminium may be replaced by gallium and in which 0.005?x?0.30 and 0?y?0.30.
A luminescent cerium-activated alkaline earth aluminate defined by the formula Me1-x-yCexAyAl12019+0.5(x-y), where Me represents at least one of the alkaline earth metals strontium and calcium and A represents at least one of the alkali metals sodium, potassium and rubidium, in which up to 25 mol % of aluminium may be replaced by gallium and in which 0.005?x?0.30 and 0?y?0.30.
Description
PHN. 7352.
The invention relates to a lum mescent screen provided with a luminescent alkaline earth aluminate.
EbrthermDre, the invention relates to a mercNry vapour discharge lam~ provided with such a luminescent screen, and to the luminescent alumlnate itself.
A luminescent cerium aluminate defined by the form~la Ce203.n~1203, where n has a value of between 8 and 13 is kncwn from United Kingdo.m Pate~ Specification 1,191,014. This aluminate has a crystal structure cor-respanding to the structure of ~-alumina (for example, Na~111017). The known alumina~e may be excited by ultra-violet radiation and has a light blue emission whose spectral distribu ;on consists of a broad band (half-value width approximately 100 nm) with a mQximum at approximately 460 nm.
The alkaline earth aluminates defined by the formula M~112019~ where M represents o~e or more of the elements calcium, strontium and barium, have a hexag~nal crystal structure which is analogous bo that of magneto, plumbite (for exa~ple, BaFel2019). Activation of these hexagonal aluminates by manganesè is known from the bcok by F.A. Kr~ger ("Some Aspects of the Luminescence of Solids", 1948) and yields materials efficiently lumines-cing upon electron excitation. ~pon excitation by ultra-violet radiation efficiently luminescent materials are obtained if the hexagonal aluminates are activated by bivalent europium.
The invention relates to a lum mescent screen provided with a luminescent alkaline earth aluminate.
EbrthermDre, the invention relates to a mercNry vapour discharge lam~ provided with such a luminescent screen, and to the luminescent alumlnate itself.
A luminescent cerium aluminate defined by the form~la Ce203.n~1203, where n has a value of between 8 and 13 is kncwn from United Kingdo.m Pate~ Specification 1,191,014. This aluminate has a crystal structure cor-respanding to the structure of ~-alumina (for example, Na~111017). The known alumina~e may be excited by ultra-violet radiation and has a light blue emission whose spectral distribu ;on consists of a broad band (half-value width approximately 100 nm) with a mQximum at approximately 460 nm.
The alkaline earth aluminates defined by the formula M~112019~ where M represents o~e or more of the elements calcium, strontium and barium, have a hexag~nal crystal structure which is analogous bo that of magneto, plumbite (for exa~ple, BaFel2019). Activation of these hexagonal aluminates by manganesè is known from the bcok by F.A. Kr~ger ("Some Aspects of the Luminescence of Solids", 1948) and yields materials efficiently lumines-cing upon electron excitation. ~pon excitation by ultra-violet radiation efficiently luminescent materials are obtained if the hexagonal aluminates are activated by bivalent europium.
-2--~ PHN 7352 ~L~3~L3L~
The object of the invention is to provide nove1 luminescent materials having an emission in the ultraviolet part of the spectrum.
A luminescent screen according to the invention is provided with a luminescent alkaline earth aluminate and is characterized in that the aluminate is activated by cerium and is defined by the formula Mel x_yCexAyAll2019~0 5(x y)~ where Me represents at least one of the alkaline earth metals strontium and calcium and A represents at least one of the alkali metals sodium, potassium and rubidium, in which up to 25 mol % of aluminium may be replaced by gallium and in which 0.005 ~ x ' 0.30 and 0 -~ y -~- 0.30.
A luminescent aluminate according to the invention has the same crystal structure as the above-mentioned hexagonal aluminates. It was found that upon activation of the strontium and/or calcium aluminates by cerium luminescent materials are obtained which luminesce very efficiently in a band (half-value width approximately 50 nm) with a maximum at 300-320 nm when excited by ultraviolet radiation, particularly short-wave ultraviolet radiation.
It was found that aluminium in these aluminates may be replaced by gallium while maintaining the crystal structure.
Ho~ever, not more than 25 mol % o~ Al203 is replaced by Ga203 in the luminescent aluminates according to the invention, because larger quantities of Ga203 yield materials having too low luminous fluxes for practical uses. Materials having a very low luminous flux are obtained when barium is chosen for the element denoted by Me. Therefore strontium and/or calcium ~L~6~L'~t~
is used for Me in the materials according to the invention, while small quantities of barium (for example, up to 10 at %) may be admitted. These small quantities of barium do not yield any extra advantage and are preferably not used.
Cerium used as an activator replaces part of the alkaline earth metals denoted by Me. The cerium content x may be chosen within the above-mentioned limits. For values of x of less than 0.005 materials having a too low luminous flux are obtained and for values of x of more than 0.30 materials are obtained whose emission is located beyond the desired part of the spectrum, namely at larger wavelengths.
As is apparent from the above-mentioned general formula, a further part of the alkaline earth metal may be replaced by one or more of the alkali metals sodium, potassium and rubidium denoted by A in the luminescent aluminates according to the invention. The hexagonal crystal structure is then maintained. Partial replacement of bivalent Me by univalent A has the advantage that a charge compensation is obtained which is generally desirable when Me is partially replaced by trivalent ions (trivalent cerium in the case of the materials according to the invention). A ~ull charge com-pensation is obtained when the content A is equal or sub-stantially equal to the content Ce. Materials according to the invention in which x is substantially equal to y are there-fore generally preferred.
The highest luminous fluxes are obtained with luminescent aluminates according to the invention in which the alkaline earth metal Me is strontium.
3L0~ 3 The luminescent aluminates according to the invention may be advantageously used in mercury vapour discharge lamps, both of the high-pressure and the low-pressure type. Such mercury vapour discharge lamps are used in equipment for influencing photochemical processes, for example, equipment for lacquer hardening or for generating erythemal radiation.
When used in combination with high-pressure mercury vapour discharge lamps it is a special advantage that the luminescent aluminates according to the invention have a very satis-factory temperature dependence of the luminous flux, because these materials are then brought to relatively high tempera-tures. It was found that at 500C the aluminates according to the invention may still have 100% of the luminous flux at room temperature. In high-pressure mercury vapour discharge lamps, for example, for irradiators or sun lamps, the materials according to the invention can efFiciently convert the 254 nm resonant radiation emitted by these lamps in addition to the 365 nm radiation into erythema radiation. When used in low-pressure mercury vapour discharge lamps aluminates according to the invention for w~ich y=0 are sometimes preferred, because alkali-containing materials are known to give rise to a relatively strong decline in the luminous flux during the lifetime of these lamps.
The luminescent aluminates according to the invention may be prepared by generally known methods. For example, it is possible to obtain the aluminates by heating a mixture of the composite oxides at a high temperature, for example, 1200-1700C. Instead of the oxides it is alternatively possible to use compounds yielding these oxides at an elevated temperature in the starting mixture (for example9 carbonates and hydroxides). This heat treatment is preferably performed in two or more stages with the first heat treatment taking place in air5 optionally at a relatively low temperature (for example, at 800C) so as to firstly decompose the hydroxides possibly used. To increase the reaction speed, part of aluminium or part of the alkaline earth metal Me may be added as fluoride to the firing mixture.
The invention will now be described in greater detail with reference to an example, a number of measurements on examples of luminescent aluminates according to the invention, and a drawing.
In the drawing Fig. 1 ~iagrammatically shows a low-pressure mercury vapour discharge lamp having a luminescent screen according to the invention, and Fig. 2 shows the spectral energy distribution of the emitted radiation of a ; luminescent aluminate according to the invention.
Example.
A mixture is made of 14.00 g SrC03 0.86 g Ce~2 93.20 9 Al(OH)3 0.70 9 A1F3.3H20 This mixture is heated in air in a furnace at 800C for 1 hour.
After cooling the product obtained is ground and sieved and subsequently heated in a weakly reducing atmosphere at a tempera-ture of 1500C for 1 hour. After cooling, grinding and sieving the reaction product defined by the formula SrO 95CeO 05A1120 19 025 is ready for use. The aluminate thus obtained is found to have a quantum efFiciency of approximately 70% when excited by short-wave ultraviolet radiation (254 nm). The emitted radiation consists of a band having its maximum at 303 nm and a half-value width of approx;mately 50 nm.
Analogously as in the above-mentioned example, a number of aluminates according to the invention is obtained in which sodium in the form of sodium carbonate is added to the firing mixture so as to obtain the charge compensation desired ~or replacement of Me2+ by Ce3+. Measurements were performed on the materials thus obtained and their results are summari~ed in the Table below. The Table states for each example the formula, the absorptlon of the exciting radiation (254 nm) in % under A, the hal~-value width of the emission band (in nm) under Hwb, and the location of the maximum of the emission band (nm) under A max TABLE
Example Formula A Hwb Am.x _ in % (nm) (nm) 1 CaO 8CeO lNaO.lA112l9 ; 84 50 318 2 CaO gCeQosNao.OsA112019 76 50 318
The object of the invention is to provide nove1 luminescent materials having an emission in the ultraviolet part of the spectrum.
A luminescent screen according to the invention is provided with a luminescent alkaline earth aluminate and is characterized in that the aluminate is activated by cerium and is defined by the formula Mel x_yCexAyAll2019~0 5(x y)~ where Me represents at least one of the alkaline earth metals strontium and calcium and A represents at least one of the alkali metals sodium, potassium and rubidium, in which up to 25 mol % of aluminium may be replaced by gallium and in which 0.005 ~ x ' 0.30 and 0 -~ y -~- 0.30.
A luminescent aluminate according to the invention has the same crystal structure as the above-mentioned hexagonal aluminates. It was found that upon activation of the strontium and/or calcium aluminates by cerium luminescent materials are obtained which luminesce very efficiently in a band (half-value width approximately 50 nm) with a maximum at 300-320 nm when excited by ultraviolet radiation, particularly short-wave ultraviolet radiation.
It was found that aluminium in these aluminates may be replaced by gallium while maintaining the crystal structure.
Ho~ever, not more than 25 mol % o~ Al203 is replaced by Ga203 in the luminescent aluminates according to the invention, because larger quantities of Ga203 yield materials having too low luminous fluxes for practical uses. Materials having a very low luminous flux are obtained when barium is chosen for the element denoted by Me. Therefore strontium and/or calcium ~L~6~L'~t~
is used for Me in the materials according to the invention, while small quantities of barium (for example, up to 10 at %) may be admitted. These small quantities of barium do not yield any extra advantage and are preferably not used.
Cerium used as an activator replaces part of the alkaline earth metals denoted by Me. The cerium content x may be chosen within the above-mentioned limits. For values of x of less than 0.005 materials having a too low luminous flux are obtained and for values of x of more than 0.30 materials are obtained whose emission is located beyond the desired part of the spectrum, namely at larger wavelengths.
As is apparent from the above-mentioned general formula, a further part of the alkaline earth metal may be replaced by one or more of the alkali metals sodium, potassium and rubidium denoted by A in the luminescent aluminates according to the invention. The hexagonal crystal structure is then maintained. Partial replacement of bivalent Me by univalent A has the advantage that a charge compensation is obtained which is generally desirable when Me is partially replaced by trivalent ions (trivalent cerium in the case of the materials according to the invention). A ~ull charge com-pensation is obtained when the content A is equal or sub-stantially equal to the content Ce. Materials according to the invention in which x is substantially equal to y are there-fore generally preferred.
The highest luminous fluxes are obtained with luminescent aluminates according to the invention in which the alkaline earth metal Me is strontium.
3L0~ 3 The luminescent aluminates according to the invention may be advantageously used in mercury vapour discharge lamps, both of the high-pressure and the low-pressure type. Such mercury vapour discharge lamps are used in equipment for influencing photochemical processes, for example, equipment for lacquer hardening or for generating erythemal radiation.
When used in combination with high-pressure mercury vapour discharge lamps it is a special advantage that the luminescent aluminates according to the invention have a very satis-factory temperature dependence of the luminous flux, because these materials are then brought to relatively high tempera-tures. It was found that at 500C the aluminates according to the invention may still have 100% of the luminous flux at room temperature. In high-pressure mercury vapour discharge lamps, for example, for irradiators or sun lamps, the materials according to the invention can efFiciently convert the 254 nm resonant radiation emitted by these lamps in addition to the 365 nm radiation into erythema radiation. When used in low-pressure mercury vapour discharge lamps aluminates according to the invention for w~ich y=0 are sometimes preferred, because alkali-containing materials are known to give rise to a relatively strong decline in the luminous flux during the lifetime of these lamps.
The luminescent aluminates according to the invention may be prepared by generally known methods. For example, it is possible to obtain the aluminates by heating a mixture of the composite oxides at a high temperature, for example, 1200-1700C. Instead of the oxides it is alternatively possible to use compounds yielding these oxides at an elevated temperature in the starting mixture (for example9 carbonates and hydroxides). This heat treatment is preferably performed in two or more stages with the first heat treatment taking place in air5 optionally at a relatively low temperature (for example, at 800C) so as to firstly decompose the hydroxides possibly used. To increase the reaction speed, part of aluminium or part of the alkaline earth metal Me may be added as fluoride to the firing mixture.
The invention will now be described in greater detail with reference to an example, a number of measurements on examples of luminescent aluminates according to the invention, and a drawing.
In the drawing Fig. 1 ~iagrammatically shows a low-pressure mercury vapour discharge lamp having a luminescent screen according to the invention, and Fig. 2 shows the spectral energy distribution of the emitted radiation of a ; luminescent aluminate according to the invention.
Example.
A mixture is made of 14.00 g SrC03 0.86 g Ce~2 93.20 9 Al(OH)3 0.70 9 A1F3.3H20 This mixture is heated in air in a furnace at 800C for 1 hour.
After cooling the product obtained is ground and sieved and subsequently heated in a weakly reducing atmosphere at a tempera-ture of 1500C for 1 hour. After cooling, grinding and sieving the reaction product defined by the formula SrO 95CeO 05A1120 19 025 is ready for use. The aluminate thus obtained is found to have a quantum efFiciency of approximately 70% when excited by short-wave ultraviolet radiation (254 nm). The emitted radiation consists of a band having its maximum at 303 nm and a half-value width of approx;mately 50 nm.
Analogously as in the above-mentioned example, a number of aluminates according to the invention is obtained in which sodium in the form of sodium carbonate is added to the firing mixture so as to obtain the charge compensation desired ~or replacement of Me2+ by Ce3+. Measurements were performed on the materials thus obtained and their results are summari~ed in the Table below. The Table states for each example the formula, the absorptlon of the exciting radiation (254 nm) in % under A, the hal~-value width of the emission band (in nm) under Hwb, and the location of the maximum of the emission band (nm) under A max TABLE
Example Formula A Hwb Am.x _ in % (nm) (nm) 1 CaO 8CeO lNaO.lA112l9 ; 84 50 318 2 CaO gCeQosNao.OsA112019 76 50 318
3 SrO 8CeO lNao.lA112l9 81 50 303
4 SrO gCeO osNao.o5All2ol9 73 45 303 CaO 6Ceo.2Nao.2A112l9 39 50 318 ~ PHN 7352 -Fig. 1 shows a low-pressure mercury vapour discharge lamp having an envelope 1. Electrodes 2 and 3 between which the discharge is maintained are placed at the ends of the lamp.
The inner side of the envelope 1 is coated with a luminescent coatins 4 comprising a luminescent aluminate according to the invention. The luminescent coating may be provided by one of the conventional methods on the envelope 1.
Fig. 2 shows in a graph the spectral energy dis-tribution of the luminescent aluminate obtained in accordance with the abovementioned example upon excitation by 254 nm radiation. The wavelength ~ is plotted in nm on the horizontal axisi the emitted radiation energy E per constant wavelength interval is plotted in arbitrary units on the vertical axis.
The peak height of the emission band of this material is found to be 2.2 times as high as that of the NBS standard 1027 (a luminescent magnesium tungstate).
The inner side of the envelope 1 is coated with a luminescent coatins 4 comprising a luminescent aluminate according to the invention. The luminescent coating may be provided by one of the conventional methods on the envelope 1.
Fig. 2 shows in a graph the spectral energy dis-tribution of the luminescent aluminate obtained in accordance with the abovementioned example upon excitation by 254 nm radiation. The wavelength ~ is plotted in nm on the horizontal axisi the emitted radiation energy E per constant wavelength interval is plotted in arbitrary units on the vertical axis.
The peak height of the emission band of this material is found to be 2.2 times as high as that of the NBS standard 1027 (a luminescent magnesium tungstate).
Claims (4)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A luminescent screen provided with a luminescent alkaline earth aluminate, characterized in that the alumi-nate is activated by cerium and is defined by the formula Me1-x-yCexAyAl12019+0.5(x-y), where Me represents at least one of the alkaline earth metals strontium and calcium and A represents at least one of the alkali metals sodium, pot assium and rubidium, in which up to 25 mol % of aluminium may be replaced by gallium and in which 0.005 ? x ? 0.30 and 0 ? y ? 0.30.
2. A luminescent screen as claimed in Claim 1, charac-terized in that x is substantially equal to y.
3. A luminescent screen as claimed in Claim 1 or 2, characterized in that Me is strontium.
4. A luminescent cerium-activated alkaline earth aluminate defined by the formula Me1-x-yCexAyAl12019+0.5(x-y), where Me represents at least one of the alkaline earth metals strontium and calcium and A represents at least one of the alkali metals sodium, potassium and rubidium, in which up to 25 mol % of aluminium may be replaced by gallium and in which 0.005 ? x ? 0.30 and 0 ? y ? 0.30.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL7401935A NL7401935A (en) | 1974-02-13 | 1974-02-13 | LUMINESCENT SCREEN. |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1061102A true CA1061102A (en) | 1979-08-28 |
Family
ID=19820735
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA219,522A Expired CA1061102A (en) | 1974-02-13 | 1975-02-06 | Luminescent screen |
Country Status (9)
| Country | Link |
|---|---|
| JP (1) | JPS5743114B2 (en) |
| AT (1) | AT353356B (en) |
| BE (1) | BE825415A (en) |
| CA (1) | CA1061102A (en) |
| DE (1) | DE2503904C2 (en) |
| FR (1) | FR2260611B1 (en) |
| GB (1) | GB1476902A (en) |
| NL (1) | NL7401935A (en) |
| SE (1) | SE7501449L (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2707894A1 (en) * | 1977-02-24 | 1978-08-31 | Kosmedico Vertrieb Kosmetische | UV-lamp with narrow emission spectrum - esp. for the treatment of psoriasis |
| NL184712C (en) * | 1979-07-03 | 1989-10-02 | Philips Nv | LOW-PRESSURE MERCURY DISCHARGE LAMP. |
| NL7905162A (en) * | 1979-07-03 | 1981-01-06 | Philips Nv | LOW-PRESSURE MERCURY DISCHARGE LAMP. |
| US4246630A (en) * | 1979-12-19 | 1981-01-20 | Gte Products Corporation | Ultraviolet emitting Ce alkaline earth aluminate lamp phosphors and lamps utilizing same |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1191014A (en) * | 1967-05-10 | 1970-05-06 | Thorn Lighting Ltd | Phosphor |
-
1974
- 1974-02-13 NL NL7401935A patent/NL7401935A/en not_active Application Discontinuation
-
1975
- 1975-01-31 DE DE2503904A patent/DE2503904C2/en not_active Expired
- 1975-02-06 CA CA219,522A patent/CA1061102A/en not_active Expired
- 1975-02-10 AT AT98175A patent/AT353356B/en not_active IP Right Cessation
- 1975-02-10 SE SE7501449A patent/SE7501449L/xx unknown
- 1975-02-10 GB GB548675A patent/GB1476902A/en not_active Expired
- 1975-02-11 BE BE153260A patent/BE825415A/en unknown
- 1975-02-13 FR FR7504505A patent/FR2260611B1/fr not_active Expired
- 1975-02-13 JP JP50017526A patent/JPS5743114B2/ja not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| NL7401935A (en) | 1975-08-15 |
| DE2503904A1 (en) | 1975-08-14 |
| BE825415A (en) | 1975-08-11 |
| ATA98175A (en) | 1979-04-15 |
| SE7501449L (en) | 1975-08-14 |
| GB1476902A (en) | 1977-06-16 |
| FR2260611A1 (en) | 1975-09-05 |
| DE2503904C2 (en) | 1983-06-09 |
| JPS5743114B2 (en) | 1982-09-13 |
| AT353356B (en) | 1979-11-12 |
| JPS50115682A (en) | 1975-09-10 |
| FR2260611B1 (en) | 1978-10-27 |
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