FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
AND
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2005
COMPLETE SPECIFICATION (See section 10 and rule 13)
TITLE OF THE INVENTION
LAMPS EXHIBITING ENHANCED COLOR RENDITION.
APPLICANTS :
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTOR(S):
Ramakrishnan Sankar of Crompton Greaves Limited, Advanced Materials and Process Technology Centre, CG Global R&D Centre, Kanjur Marg (E), Mumbai, Maharashtra, India; and Kumaraswamy Konamki Kanakadriah and Kudrya Prashant of Crompton Greaves Ltd, Baroda Lamp Works, Village Kural, Padra Jambusar Road, Padra Taluka, Vadodara-391430, Gujarat, India; all Indian Nationals.
PREAMBLE TO THE DESCRIPTION:
The following specification particularly describes the nature of this invention and the manner in which it is to be performed:

Technical Field:
This invention relates to Metal Halide Lamps as well as Mercury Vapor Lamps.
Particular, this invention relates to Metal Halide Lamps as well as Mercury Vapor Lamps exhibiting enhanced color rendition and at the same time being stable and having increased operating life.
More particularly, this invention relates to powder blends for coating inner surface of outer envelope of Metal Halide Lamps as well as Mercury Vapor Lamps thereby exhibiting enhance color rendition and at the same being time stable and having increased shelf life.
Background and Prior Art:
A Mercury Vapor Lamp is a gas discnarge lamp that uses marcury :m -an excited state to produce light. The arc discharge is generally confined to a small fused quartz arc tube mounted within a larger borosilicate glass bulb. The outer bulb may be clear or coated with a phosphor; in either case, the outer bulb provides thermal insulation, protection from ultraviolet radiation, and a convenient mounting for the fused quartz arc tube.
When a mercury vapor lamp is first turned on, it will produce a dark blue glow because only a small amount of the mercury is ionized and me gas pressure in the arc tube is very low, so much of the light is produced in the ultraviolet mercury bands. As the main arc strikes and the gas heats up and increases in pressure, the light shifts into the visible range and the high gas pressure causes the mercury emission bands to broaden somewhat, producing a light that appears more nearly white to the human eye, although it is still not a continuous spectrum. Even at full intensity, the light from a Mercury Vapor Lamp with no phosphor is distinctly bluish in color.
A closely-related lamp design to Mercury Vapor Lamp is called a Metal Halide Lamp which uses various compounds in an amalgas with the mercury. Metal Halide Lamps consist of an arc tube (also called a discharge tube or "burner") within an outer envelope, or bulb. The arc tube may De made of either quartz or ceramic and contains a starting gas (usually argon), mercury, and metal halide

salts. Traditional quartz metal halide arc tubes are similar in shape to mercury vapor arc tubes, but they operate at higher temperatures and pressures.
Mercury Halide Lamps start when their ballast supplies a starting voltage higher than those normally supplied to the lamp electrodes through a gas mixture in the arc tube. The gas in the metal halide arc tube must be ionized before current can flow and start the lamp. In addition to supplying the correct starting voltage, the ballast also regulates the lamp starting current and lamp operating current.
As pressure and temperature increase, the materials within the arc tube vaporize and emit light and ultraviolet (UV) radiation. A bulb (also called "outer jacket" or "outer envelope"), usually made of borosilicate glass, provides a stable thermal environment for the arc tube, contains an inert atmosphere that keeps the components of the arc tube from oxidizing at high temperatures, and reduces the amount of UV radiation that the lamp emits.
The illuminance of the Metal Halide Lamp and quality of light depends upon the intensity of discharge tube. The discharge tube having correlated color temperature of 5500 K gives white light but it is normally not stable and durable. The discharge tube having correlated temperature of 4200 K is stable however it gives yellowish light. In the case of Mercury Vapor Lamps, the discharge tube of 5500 K is found to perform better but the color properties need to be improved to that of day light.
Some Metal Halide Lamps have a coated finish on the inner side of the outer envelope of the bulb that diffuses the light. Often a phosphor coat is used to both diffuse the light and change the lamp's color properties.
US Patent No. 3,670,194 discloses a two-component blend phosphor coating on the inner surface of the outer envelope. One of the phosphor blend components provides an emission in the shorter wavelength region of the visible spectrum peaking at from 440 nm to 470 nm, such as, strontium chloroapatite activated by divalent europium, and the other phosphor blend component provides an emission in the longer wavelength region of visible spectrum peaking at from 605 nm to 630 nm such as, yttrium phosphate vanadate activated by trivalent europium.
US Patent No. 3,825,792 discloses a coating on the inner surface of the outer envelope comprising a phosphor mixture of europium activated yttrium phosphate vanadate or yttrium vanadate and manganese activated magnesium fluorogermanate or magnesium-arsenate.

French Patent Publication No. 2,229,139 discloses a high-pressure Metal Vapor Lamp carrying a phosphor coating on the inner surface of the outer envelope. The coating comprises red-emitting yttrium vanadate phosphate phosphor activated with trivalent europium with the addition of a non-fluorescent yellow pigment-reaction product of NiO and Ti 02.
Japanese Patent No. 43-20514 discloses a high-pressure metal discharge lamp having electrode vessels containing an addition of 2 to 3 iodine compounds, for example, iodides of sodium, thallium and indium.
GB 2054261 discloses metal halide high-intensity discharge lamp with a luminescent coating on the inner surface which consists of a mixture of predetermined amounts of strontium chloroapatite phosphor activated by divalent europium and yttrium vanadate phosphate phosphor activated by trivalent europium in predetermined relative weight proportions.
One of the drawbacks of the Metal Halide Lamps is that they usually have shorter hours of life rating. Another drawback of the Metal Halide Lamp is that it gives yellowish light. Yet another drawback of the Metal Halide Lamp is that the overall performance and illuminance output of the lamp totally depends upon the intensity of discharge tube. To overcome the above-mentioned drawback there is a need to develop efficient coating composition for the lamp.
Objects:
An object of the invention is to provide an improved Metal Halide Lamp or a Mercury Vapor Lamp for exhibiting enhanced color rendition where inner side of the outer envelope of the lamp is coated with powder blend comprising either YV04:Eu3+; or (Sr, Mg) P04: Sn2+; or A1203; or Y203; or Y203:Eu3+; or (LaCe)P04: Tb3+; or BaMgAl10O17:Eu2+; or CeMgAln019:T or combination thereof thereby to achieve white illuminace.
b3+Another object of the invention is to provide the improved Metal Halide Lamp or a Mercury Vapor Lamp for exhibiting enhanced color rendition where inner side of the outer envelope of the lamp is coated with the powder blend comprising either YV04:Eu3+; or (Sr, Mg) P04:Sn2+; or Al203; or Y203; or Y203:Eu3+; or (LaCe)P04:Tb3+; or BaMgAl]0Oi7:Eu2+; or CeMgAln0i9:Tb3+ or combination thereof which achieves the correlated color temperature of 5500 K with discharge

tube having correlated color temperature of 4200K thereby improving the lamp's color properties , brightness, durability and cost-effectiveness.
Another object of the invention is to provide an improved Metal Halide Lamp or a Mercury Vapor Lamp for exhibiting enhanced color rendition where inner side of the outer envelope of the lamp is coated with the Powder blend comprising either YV04:Eu3+; or (Sr, Mg) P04:Sn2+; or A1203; or Y203; or Y203:Eu3+; or (LaCe)P04 :Tb +; orBaMgAl10Oi7:Eu2+; or CeMgAl019:Tb3+ or combination thereof which is stable up t0 temperatures of at least 800° C in air.
Another object of the invention is to provide an improved Metal Halide Lamp or a Mercury Vapor Lamp for exhibiting enhanced color rendition where inner side of the outer envelope of the lamp is coated with the Powder blend comprising either YV04: EU3+; or (Sr, Mg) P04:Sn2+; or A1203; or Y203; or Y203:Eu3+; or (LaCe)P04 '•Tb J or BaMgAl10O17:Eu2+; or CeMgA11 iO19:Tb3+ or combination thereof which is stable in air as well as during lamp operation, and which shows increase in lamp life and better co/or properties.
Yet another object of the invention is to provide an improved Metal Halide Lamp or a Mercury Vapor Lamp where inner side of the outer envelope of the lamp is coated with the powder blend comprising either YV04: Eu3+; or (Sr, Mg) P04:Sn2+; or A1203; or y203; or Y203:Eu3+; or (LaCe)P04 :TD3+; or BaMgAl,oO,7:Eu2+; or CeMgAli,o]9:Tb3+ or combination thereof where the powder blend coating is cost effective.
Yet another object of the invention is to provide an improved Metal Halide Lamp or a Mercury Vapor Lamp in which the above disadvantages are substantially eliminated,

Detailed Description :
According to the invention there are provided, lamps for exhibiting enhanced color rendition where inner side of the outer envelope of the lamp is coated with the powder blend comprising either
a. YV04:Eu3+;or
b. (Sr,Mg)P04:Sn2+;or
c. AI2O3; or
d. Y203; or
e. Y203:Eu3+; or
f. (LaCe)P04 :Tb3+; or
g. BaMgAl|0O17:Eu2+; or
h. CeMgAl] |0)9:Tb3+ or combination thereof.
In one of the embodiment of the invention, the inner side of the outer envelope the lamp is coated with powder blends comprising YVCV Eu and AI203 in the ratio of 90 to 10: 10 to 90.
In another embodiment of the invention, the inner side of the outer envelope of the lamp is coated with powder blend comprising (Sr, Mg) P04:Sn2+ and A1203 in the ratio of 90 to 10: 10 to 90.
In yet another embodiment of the invention, the inner side of the outer envelope of the lamp is coated with powder blend comprising Y2 03:Eu3+; (LaCe)P04 :Tb3+; and BaMgAl]0Oi7:Eu2+ in the ratio of 5 to 50: 5 to 50: 90 to 50.
In yet another embodiment of the invention, the inner side of the outer envelope of the lamp is coated with powder blend comprising Y203:Eu3+; CeMgAli,019:Tb3+; and BaMgAl10O17:Eu2+ in the ratio of 5 to 50: 5 to 50: 90 to 50.
The powder blend of the invention is either in the form of slurry, suspension or powder.

The slurry or suspension of powder blend of the invention is prepared by mixing either YV04: Eu3+; or (Sr, Mg) PQ4:Sn2+; 0r A1203; or Y203; or Y203:Eu3+; or (LaCe)P04 :Tb3+; or BaMgAl(0O`17:Eu2+; or CeMgAlirO9:Tb3+ or combination thereof with butyl acetate, nitro cellulose Cotton, butanol and Aare in the range of 0.8 to 1.4 and viscosity in the range 15 lon C. The specific gravity of slurry / suspento 25 sec.sion of the powder blend
The dry powder blends of the powders of the invention are prepared by mixing either YV04: Eu3+; or (Sr, Mg) P04:Sn2+; orAl2 03; or Y203; or Y203:Eu3+; or (LaCe)P04 :Tb3+; or BaMgAIi0Oi7:Eu2+; or CeMgAlnOi9:Tb3+ or combination thereof.
The lamps are coated with suspension or slurry prepared form the powder blends according to the invention by using conventional coating process such as suspension dry coating, etc. The lamps are also coated with the dry powder blend of the powders according to the invention by electrostatic coating method after suitable modification of zeta potential of the powders.
The lamps coated with powder blends of the invention are tested for Lumen, Color Temperature, operating life (i.e. durability) and stability in terms of Lumen degradation over a period of time of lamp operation and found that they are stable over 5000 hour and more without much of lumen depreciation (< 10 %).
The correlated color temperature of the powder blend of the invention is in the range of 5400 K to 6500 K and light obtained is similar to daylight i.e. cool white light. The powder blend of the invention can be excited by UV light in the range of 250nm to 370nm, preferably 254nm, 320 nm and 365 nm. The UV range generated is completely converted into visible light. The powder blends of the invention are found to be stable at temperature < 800° C in air.

The use of powder blend of the invention has correlated color temperature in the range of 5400 K to 6500 r temperature of 4200K in Metal Halide Lamps; thereby making the lK irrespective of using lower intensity discharge tube having correlated coloamps coated with the powder blends of the invention cost-effective. Thus, the lamps coated with the powder blend of the invention gives high luminance even with low intensity discharge tube. The lamps with the powder blends are also stable in brightness for long operating hours and thus have longer life-time i.e. durability. Thus, the powder blends of the invention are cost-effective, stable and durable with increased operating life of the lamps.
The following experimental examples are illustrative of the invention but not limitative of the scope thereof:
Example 1:
100 gm of Nitro Cellulose Cotton (binder) was soaked in 1 liter of Butylene acetate for about 12 hours in a ceramic jar and the jar was closed with a lid tightly. The closed jar was placed in a ball mill roller for 24 hours with 0.5 to 1.0 inch ceramic pebbles. To this jar, 1kg of A1203 powder, 40 ml of butanol, and 10 gm of Alon C were added. The lid was tightened to jar and jar was placed on the ball mill roller for milling for 6hours. The suspension formed was further stirred. To this suspension, 1 liter of Butyl acetate was added and the suspension was stirred for 15 minutes. Specific gravity of the suspension is 1.0 and viscosity is 20 sec.
All four wattage Metal Halide Lamps have been made by coating the inner surface of the outer envelope of the lamps with the above prepared suspension of A1203 The lamps have discharge tube with the correlated color temperate 4200 K. The lamps prepared as above are tested for luminance and the results obtained are given in table 1 :

Table 1
No. MHL Type VLO ILO WL0 LmO LmlOO X Y Color
T(K)
1 MHL70E 84.9 0.93
4 73 5850 5032 0.337 0.452 4300
2 MHL250E 96.7 2.85 8 259 25463 24611 0.379 0.40 4200
3 MHL250E 95.8 2.85 8 257 25338 24079
4 MHL400E 106.3 4.06 4 405 45792 46473 0.37 0.40 4400
5 MHL400E 107.1 4.14 2 417 46240 48270
According to the results obtained, it is found that A1203 absorbs UV light. There is slight enhancement in correlated color temperature. Its performance is found to be as per standard requirement. However, it is found to be durable up to 5000 hr of operation and more. It reduces the cost as only A1203 is being used for powder blend.
Example_2:
100 gm ofNitro Cellulose Cotton (binder) was soaked in 1 liter of Butylene acetate for about 12 hours in a ceramic jar and the jar was closed with lid tightly. The closed jar was placed in a ball mill roller for 24 hours with 0.5 to 1.0 inch ceramic pebbles. To this jar, 1kg of blend of YV04:Eu3+ and A1203 in the ratio 75:25 , 40 ml of butanol, and 10 gm of Alon C were added. The lid was tightened to jar and

jar was placed on the ball mill roller for milling for 6 hours. The suspension formed was further stirred. To this suspension, 1 liter of Butyl acetate was added and the suspension was stirred for 15 minutes. Specific gravity of the suspension is 1.0 and viscosity is 20 sec.
All four wattage Metal Halide Lamps have been made by coating the inner surface of the outer envelope of the lamps with the above prepared suspension of blend of YV04:Eu3+ and AI2O3 in the ratio 75:25. The lamps have discharge tube with the Correlated color temperate of 4200 K. The lamps made as above are tested for brightness and the results obtained are given in table 2 :

OHR Readin g (SV-MH = 75:25)
Lamp No Type Voltag e Curr ent Watta
ge Lume n X Y
1 MHL250 E 97.5 2.79
7 258 21551 0.406 0.417
2 MHL250
E 98.2 2.81 3 260 23581 0.405 0.417
3 MHL250 E 94.2 2.85 6 254 22555 0.392 0.413
4 MHL250 E 97.0 2.81
5 257 21853 0.397 0.415
5 MHL250 E 92.0 2.87 7 252 20401 0.391 0.413
6 MHL250 E 95.3 2.83 9 255 22007 0.396 0.412

1Q0HRS Reading
Lamp
No Type Volta Curr ent Watta ge Lume n X Y
1 MHL25 OE 94.5 2.889 256 18945 0.406 0.417
2 MHL25 OE 95.8 2.862 255 19762 0.405 0.417
3 MHL25 OE 93.2 2.895 252 19692 0.392 0.413
4 MHL25 OE 95.Q 2.896 256 18118 0.397 0.415
5 MHL25 OE 91.1 2.913 248 18566 0.391 0.413
6 MHL25 OE 94.6 2.876 255 18926 0.396 0.412
500HRS Reading
Lamp No Type Volta Curre nt Watta ge Lume
n % Lume
n Drop X Y
1 MHL 250E 97.7 2.856 257 17336 8.49% 0.40 6 0.417
2 MHL 250E 96.6 2.840 253 18125 8.28% 0.40 5 0.417
3 MHL 250E 93.9 2.867 250 17076 13.28
% 0.39
2 0.413

4 MHL 250E 96.0 2.866 255 16249 10.32 % 0.39
7 0.415
5 MHL 250E 92.7 2.906 250 16700 10.05 % 0.39 1 0.413
6 MHL 250E 96.1 2.874 256 17940 5.21% 0.39 6 0.412
According to the results obtained, it is found that blend convert some of the available UV inside the lamp into visible light. There is enhancement in red light output and hence in brightness. There is slight improvement in correlated color temperature. Its performance is found to be improved as compared to standard requirement. It is observed that the lamps performed best throughout 5000 hours. It also reduces the cost.
Example 3;
100 gm ofNitro Cellulose Cotton (binder) was soaked in 1 liter of Butylene acetate for about 12 hours in a ceramic jar and the jar was closed with lid tightly. The closed jar was placed in a ball mill roller for 24 hours with 0.5 to 1.0 inch ceramic pebbles. To this jar, 1kg of blend of Blend of Y203: Eu3+ (Eu3+ in Y203 at the Y-site ranges from 0.001 - 0.5), LaCeP04: Tb3+ (Tb3+ in LaCeP04 at the Ba-site ranges from 0.001 - 0.2, and BaMgAl10O17: Eu2+ (Eu2+ in BaMgAl10O17at the La-site ranges from 0.001 - 0.4) in the ratio 10:10:80 (hereinafter referred as RGB daylight phosphor), 40 ml of butanol, and 10 gm of Alon C were added. The lid was tightened to jar and jar was placed on the ball mill roller for milling for 6 hours. The suspension formed was further stirred. To this suspension, 1 liter of Butyl acetate was added and the suspension was stirred for 15 minutes. Specific gravity of the suspension is 1.0 and viscosity is 20 sec.

All four wattage Mercury Vapor Lamps (MVL) have been made by coating the above prepared suspension of Blend of RGB daylight phosphor and are tested for luminance upto 1075 hours and the results obtained are given in table 3:
All four wattage Metal Halide Lamps (MHL) have been made by coating the inner surface of the outer envelope of the lamps with the above prepared suspension of RGB daylight phosphor.. The lamps have discharge tube with the correlated color temperate 4200 K. The lamps prepared as above are tested for luminance and the results obtained are given in table 4:
Table 3 : RGB daylight phosphor (6500 K) of lamp 250W for MVLS

0 hour reading of MVLs with RGB powder blend
Lamp
No Voltage Current Wattage Lumen
3 140.4 1.837 237 13759
4 132.3 1.991 241 14099
5 140.3 1.875 242 14024
100 hour reading of MVLs with RGB powder blend
Lamp
No Voltage Current Wattage Lumen
3 141.7 1.77 228 12300
4 134.9 1.868 229 13003
5 140 1.791 230 12600

Lamp
No Voltage Current Wattage Lumen
3 141 1.805 232 11811
4 134.6 1.892 233 12356
5 141.9 1.767 225 12049

Table 4 : RGB davlisht phosphor blend for 250W MHLS

250W MHLs with RGB powder blend
Lamp No Voltage Current Wattage Lumen
Ohour reading Lumen (100 hr)
1 92,6 2.868 250 23179 21133
2 89.1 2.902 243 21897 20113
3 91.5 2.869 249 22580 21100
4 92.1 2.853 248 23160 21500.

Thus the light obtained is white light similar to day light which is cooler to eyes. It has higher brightness and higher correlated color temperature of 5500 K due to color mixing of light emitted by the discharge tube as well as the powder blend coated on the inner walls of the outer envelope than our normal MHLs produced in the line. The lamps are stable over long duration up to 5000 hr. The powder blends

are excited by short and long wavelength UV (240 to 370 nm). Same suspension has been used for both MVL and MHL and hence it helps to eliminate separate coating process for MVL and MHL. It increases brightness as well as light output as coating converts maximum UV light in to visible light. Because of the particular combination, it increases whiteness of the light similar to day light. The correlated color temperature in the case of Metal Halide Lamps is 5500 K and in the case of Mercury Vapor Lamps it is 6200K.

We claim:
1. Lamps for exhibiting enhanced color rendition where inner side of the outer envelope of the lamp is coated with the powder blend comprising either
a. YV04:Eu3+;or
b. (Sr, Mg) P04:Sn2+; or
c. AI203; or
d. Y203; or
e. Y203:Eu3+; or
f. (LaCe)P04 :Tb3+; or
g. BaMgAl10O17:Eu2+; or
h. CeMgAlnO19:Tb or combination thereof.
2. The lamps as claimed in claim 1, wherein the inner side of the outer envelope of the lamp is coated with powder blend comprising YVO4: Eu3+ and A1203 in the ratio of 90 to 10 : 10 to 90.
3. The lamps as claimed in claim 1, wherein the inner side of the outer envelope of the lamp is coated with powder blend comprising (Sr, Mg) P04:Sn2+ and AI203 in the ratio of 90 to 10 : 10 to 90.
4. The lamps as claimed in claim 1, wherein the inner side of the outer envelope of the lamp is coated with powder blend comprising Y203:Eu3+; (LaCe)P04 :Tb3+; and BaMgAl10O17:Eu2+ in the ratio of 5 to 50: 5 to 50: 90 to 50.

5. The lamps as claimed in claim 1, wherein the inner side of the outer envelope of the lamp is coated with powder blend comprising Y2O3:Eu3+; CeMgAlnO19:Tb3+; and BaMgAl10O17:Eu2+ in the ratio of 5 to 50: 5 to 50: 90 to 50.
6. The lamps claimed as any of the preceding claims wherein the powder blend gives correlative color temperature ranging from 5200K to 6500 K.
7. The lamps claimed as any of the preceding claims wherein the powder blend is stable at temperature up to 800°C in air.
8. The lamps claimed as any of the preceding claims wherein the powder blend is excited efficiently by UV light ranges from 250nm to 370 nm.
9. The lamps claimed as any of the preceding claims wherein the powder blend is in the form of slurry, suspension or dry powder.