Compositions – Light transmission modifying compositions – Inorganic crystalline solid
Reexamination Certificate
2001-05-08
2004-05-25
Tucker, Philip C. (Department: 1712)
Compositions
Light transmission modifying compositions
Inorganic crystalline solid
C501S120000, C501S123000, C501S125000, C501S152000, C501S153000
Reexamination Certificate
active
06740262
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a light-transmitting sintered body, light-emitting tube and electric discharge lamp using the same.
2. Prior Art
Sintered bodies represented by ceramics are not transparent and have been considered to be unsuitable as optical materials. In recent years, however, light-transmitting sintered bodies have been developed and used as light-transmitting materials with an excellent heat-resisting properties in such applications as light-emitting tube body, inspection windowpane for high temperature, optical lens, infrared windowpane, substrates for mounting functional devices, high voltage sodium lamps or electronic devices such as the light-emitting tube and the electric discharge lamp, optical memory, optical shutter, scintillator and solid laser.
The light-transmitting sintered bodies that have been known so far include Al
2
O
3
sintered body (Japanese patent application laid open under No. 6-211569), ZnO sintered body (Japanese patent application laid open under No. 55-14757), PLZT sintered body (Japanese patent application laid open under No. 5-139862), Y
3
Al
5
O
12
sintered body (Japanese patent application laid open under No. 6-107456), M
3
Al
15
O
12
sintered body (M is at least one element selected from the group consisting of Er, Tm, Ho, Dy, Lu, Tb; Japanese patent application laid open under No. 11-147757), oxide sintered body containing sintered body containing Al
100-a
M
a
—obtained by heating in oxygen or atmospheric air—as metallic element in the ceramics (M is one or more elements selected from the group consisting of Y, Ce, Nd, Sm, La, Gd, Pr; Japanese patent application laid open under No. 6-56514), MgAl
2
O
4
sintered body (Japanese patent application laid open under No. 6-171930), AlON sintered body (Japanese patent application laid open under No. 7-309667), AlN sintered body (Japanese patent application laid open under No. 5-120909), cubic BN sintered body (Japanese patent application laid open under No. 5-221730), Si
3
N
4
sintered body (Japanese patent application laid open under No. 5-286766), BaF
2
sintered body (Japanese patent application laid open under No. 6-24828), Y
2
O
3
sintered body (Japanese patent application laid open under No. 11-157933), such sintered bodies as aluminum-type oxynitride, hafnium-type oxynitride, zirconium-type oxynitride, titanium-type oxynitride, zirconium-type nitride, hafnium-type nitride (Japanese patent application laid open under No. 9-92206).
In addition, the following light-transmitting sintered bodes are known: SiAlON sintered body, MgO sintered body, BeO sintered body, Gd
2
O
3
sintered body, CaO sintered body, ThO
2
sintered body etc.
Also known are light-transmitting fluorescent in visible or ultraviolet region under an irradiation of ultraviolet light. Among them are Y
3
Al
5
O
12
: Tb
3+
(U.S. Pat. No. 3,767,745) and Y
2
O
3
: Gd
3+
(G. Blasse and B. C. Grambaier; Luminescent Materials, Springer-Verlag, pp. 157-159).
It is understood that the light-transmitting sintered bodies mentioned above include the so-called light-transmitting ceramics.
The above-mentioned light-transmitting sintered bodies are obtained this way: a mixture of sintered body ingredient materials of an aluminum compound, rare earth elements, silicone compound etc. is pressure molded and well sintered by sintering means such as heating.
Furthermore, light-emitting tubes constructed of the above-mentioned light-transmitting sintered bodies and electric discharge lamps and illumination equipment using the light-emitting tubes are known (Japanese patent application laid open under No. 5-266861).
The light-emitting tube formed of the light-transmitting sintered bodies has an enclosure with a pair of electrodes therein which is sealed with inert gas, mercury, halogen gas or the like therein. In the light-emitting tube, a reduced pressure atmosphere or a high pressure atmosphere is maintained. The light-emitting tube made with the above-mentioned light-transmitting sintered bodies is superior to the prior art light-emitting tube made with silicon oxide in heat resistance and corrosion, and permits application of high power. By using the light-emitting tube, therefore, the electric discharge lamp can be raised in luminous flux and illumination equipment can be increased in quantity of light.
In addition, the light-transmitting fluorescent sintered body has a capability to convert ultraviolet rays into visible rays and, it is considered, can be applied as functional light-transmitting sintered body capable of raising the luminous flux emitted from the light-emitting tube by converting into visible rays the ultraviolet rays radiated within the light-emitting tube and capable of controlling the color rendering of the light emitted from the light-emitting tube.
In the prior art, as set forth above, the known materials that can be made into light-transmitting sintered bodies are only the substances with the following compounds as main components: Al
2
O
3
, ZnO, Y
2
O
3
, PLZT, Y
3
Al
5
O
12
; the above-mentioned M
3
Al
15
O
12
; oxides containing the above-mentioned Al
100-a
M
a
—obtained by heating in oxygen or in the atmospheric air—as metallic element in the ceramics; MgAl
2
O
4
, AlON, AlN, cubic BN, Si
3
N
4
, BaF
2
; aluminum-type nitride; hafnium-type nitride, zirconium-type nitride, titanium-type nitride, zirconium-type nitride, hafnium-type nitride; SiAlON, MgO, BeO, Gd
2
O
3
, CaO, ThO
2
etc.
The materials that can be used for the following articles are limited because the purposes of them are different and those articles have to be made with such limited kinds of materials. The articles include a variety of component parts manufactured with light-transmitting sintered bodes such as the light-emitting tube body, inspection windowpane for high temperature, optical lens, infrared windowpane, substrate for mounting functional elements and such electronic devices as the light-emitting tube, electric discharge lamp, optical memory, optical shutter and solid laser.
For this reason, it is impossible to fully meet the performance requirements demanded of those articles, and in addition the manufacturing method and applications are limited.
Furthermore, the light-emitting tubes using the prior art light-transmitting sintered bodies, especially one using Y
3
Al
5
O
12
light-transmitting sintered body presents this problem: the light emitting material (halide) sealed in the light-emitting tube undertakes a chemical reaction, lowering the light transmittance. And a light-emitting tube of a light-transmitting sintered body has been wanted which is made of a material different from the prior art.
Furthermore, the prior art light-emitting tube that makes up the electric discharge lamp and illumination equipment is formed of a non-fluorescent light-transmitting sintered body of non-fluorescent substance that does not emit light when irradiated with ultraviolet rays with a wave-length of not shorter than 100 nm and not longer than 380 nm. The ultraviolet rays that occur within the light-emitting tube merely radiate out and are not converted into visible rays, and therefore are low in luminous flux. Furthermore, even if a light-emitting tube is constructed with a light-transmitting fluorescent sintered body so that it can convert the ultraviolet rays into visible rays, the kinds of available light-transmitting fluorescent sintered bodies are quite limited in number and there is no suitable fluorescent material to choose, and the fluorescent colors of the light-emitting tube are limited to specific ones. The known light-transmitting fluorescent sintered bodies that emit light when irradiated with ultraviolet rays include only those based on Y
3
Al
5
O
12
:Tb
3+
or Y
2
O
3
:Gd
3+
. The light-emitting tube that is made of the light-transmitting fluorescent sintered body has not been put to practical use as general product for manufacturing and other reasons. Y
3
Al
5
O
12
: Tb
3+
, Y
2
O
3
: Gd
3+
etc. are relatively low in light emitt
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