Electric lamp and discharge devices – With luminescent solid or liquid material – With gaseous discharge medium
Patent
1983-02-16
1986-01-21
Cooper, Jack
Electric lamp and discharge devices
With luminescent solid or liquid material
With gaseous discharge medium
2523014R, 2523014F, 2523014P, H01J 163
Patent
active
045659486
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an improvement in a fluorescent lamp.
BACKGROUND ART
The three peak emission system is known as one of the methods for improving color rendering properties of a fluorescent lamp without impairing its efficacy. In other words, it is known to use three types of phosphors which have light emission spectra with peaks in the vicinities of 450 nm, 540 nm and 610 nm, respectively, and with relatively narrow half value width.
Phosphors which may be conveniently used by the above-mentioned three peak emission system may include a europium activated divalent strontium.calcium chlorophosphate phosphor as a blue-emitting phosphor having a peak of the spectrum in the vicinity of 450 nm, a cerium and terbium activated yttrium silicate phosphor as a green-emitting phosphor having a peak of the spectrum in the vicinity of 540 nm, and a europium activated yttrium oxide phosphor as a red-emitting phosphor having a peak of the spectrum in the vicinity of 610 nm.
When the lamp ambient temperature becomes low, the starting voltage of the lamp generally becomes high. Therefore, when a lamp is used in a cold area or at a position where it is subject to cool temperatures, the starting voltage is an important problem. When the starting voltage becomes higher than the commercial supply voltage, the lamp cannot be turned on. In a general fluorescent lamp, the practical starting voltage must be a voltage about 10% lower than the commercial supply voltage for the purpose of preventing non-starting of the lamp if the lamp ambient temperature is 21.degree. C. Therefore, when the commercial voltage is 100 V, the practical starting voltage must be 90 V or lower.
In a fluorescent lamp of the three wavelength method which uses as blue, green and red-emitting phosphors a europium activated divalent strontium.calcium chlorophosphate, a cerium and terbium activated yttrium silicate phosphor, and a europium activated yttrium oxide phosphor, the starting voltage becomes high and frequently exceeds 90 V, thus limiting the installation location of the lamp.
DISCLOSURE OF INVENTION
The applicant of the present invention has succeeded in synthesizing a novel blue-emitting phosphor (to be referred to as phosphor I hereinafter) in which the light output is 30% improved over that of a divalent europium activated strontium.calcium chlorophosphate phosphor, and which is covered by Japanese Patent Application No. 55-183939.
The phosphor I is a divalent europium activated haloborophosphate blue phosphor and has the general formula: barium; X is at least one of chlorine, fluorine, and bromine; and 2.7.ltoreq.x.ltoreq.3.3, 0.50.ltoreq.y.ltoreq.1.5, 0.10.ltoreq.a.ltoreq.0.50, 0.01.ltoreq.b.ltoreq.0.50, and 0.001.ltoreq.p.ltoreq.0.20.
The applicant of the present invention has also succeeded in synthesizing a novel green-emitting phosphor (to be referred to as phosphor II hereinafter) in which the decrease in the light output after some ON time is improved over that of a cerium and terbium activated yttrium silicate green-emitting phosphor and in which the light output itself is also significantly improved.
The phosphor II is a cerium and terbium activated silicophosphate green-emitting phosphor having the general formula: O.sub.5.rSiO.sub.2 least one alkaline metal; and 0<c, 0<d, 5.times.10.sup.-2 .gtoreq.e.gtoreq.1.times.10.sup.-5, 0<c+d+3e<1, 0<q, and 0<r.
The peak wavelength of the spectrum of the phosphor I is in the vicinity of 452 nm, while that of the phosphor II is in the vicinity of 543 nm. When these phosphors are used as the fluorescent lamp of the three wavelength type, that is, for example, at least one of the phosphor I and divalent europium activated chlorophosphate is used as the blue-emitting phosphate, the phosphor II is used as the green-emitting phosphor, and a europium activated yttrium oxide phosphor represented by the general formula (Y, Eu).sub.2 O.sub.3 is used as the red-emitting phosphor, the starting voltage of the fluorescent lamp is found to be lowered. The
REFERENCES:
patent: 3481884 (1969-12-01), Palilla et al.
patent: 4151443 (1979-04-01), Van den Boom et al.
patent: 4208611 (1980-06-01), Watanabe et al.
Asada Masao
Kimura Yoshio
Sugano Satoshi
Terashima Kenji
Cooper Jack
Tokyo Shibaura Denki Kabushiki Kaisha
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