JP3307272B2 - Discharge lamp and video projector using this discharge lamp - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp and a video projector using the discharge lamp.

[0002]

2. Description of the Related Art As a light source for a video projector such as a liquid crystal projector, a so-called short arc discharge lamp, in which the distance between electrodes is short and close to a point light source, is used to improve the light use efficiency of an optical system.

[0003] Among discharge lamps, metal halide lamps are:
Since the color characteristics of the light source can be easily controlled by manipulating the type and composition of the metal halide sealed in the arc tube, it is widely used as a light source for liquid crystal projectors and the like.

[0004] Such a metal halide lamp, usually, the arc tube made of quartz glass, mercury iodide, dysprosium with an inert gas (DyI _3), metal halides such as iodide neodymium (NdI ₃₎ It is enclosed.

[0005]

During lighting, since the temperature of the arc tube becomes high, the halide reacts with quartz glass, which is the material of the arc tube, to crystallize the quartz and cause a phenomenon called devitrification, or the electrode material. Scatters, blackening occurs in the arc tube. For this reason, the transmittance of the arc tube decreases,
Light is absorbed and diffused in the devitrified or blackened portion, and furthermore, in such a state, the light use efficiency in the optical system is reduced, and the illuminance on the screen is reduced.
In addition, since light is absorbed on the surface of the arc tube wall, the temperature of the arc tube wall rises, increasing the lamp voltage and exceeding the softening point of the quartz glass of the arc tube material.

In general, the higher the temperature and the higher the halide concentration, the more the devitrification proceeds, and these phenomena appear remarkably after about 500 hours of lighting, and the illuminance maintenance rate becomes less than 50% after 1000 hours of lighting. However, it has been difficult to realize a lamp having a long life.

An object of the present invention is to provide a discharge lamp capable of preventing a decrease in illuminance by preventing the occurrence of devitrification and blackening, and an image projector using the discharge lamp.

[0008]

SUMMARY OF THE INVENTION A discharge lamp according to the present invention has a light emitting portion having a pair of electrodes disposed therein, and includes a starting gas, mercury and gadolinium iodide (metal halide) in the light emitting portion. GdI ₃ ), lutetium iodide (LuI ₃ ),
A luminous bulb made of quartz glass in which cesium iodide (CsI) is sealed, wherein the amount of CsI in the metal halide is m (wt%), and a vertical direction of the luminous portion in which the pair of electrodes are arranged horizontally Is the maximum diameter of a (mm) and the maximum horizontal diameter of the light emitting unit is b (mm), 1.0 ≦ b / a ≦ 2.46−0.03 × m, and m ≧
12 and the lamp power is 250W.
The electrode consists of an electrode rod and a coil,
When the distance from the electrode to the tip of the electrode is c (mm)
Has a configuration satisfying 0.70 ≦ c ≦ 1.25 .

As a result, it is possible to obtain an excellent discharge lamp capable of suppressing a decrease in illuminance at the beginning of the life.

The video projector according to the present invention has a configuration in which the discharge lamp is provided on a concave reflecting mirror having a reflecting surface that is a paraboloid or an ellipsoid.

As a result, it is possible to provide a video projector having an excellent center illuminance maintenance ratio.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A 250 W metal halide lamp according to a first embodiment of the present invention is, as shown in FIG.
It has a pair of electrodes 4 inside and Ar as a starting gas.
Gas and mercury along with iodides GdI ₃ , LuI ₃ , CsI
However, for example, when CsI is 26 wt%, GdI ₃ is 42
wt%, LuI ₃ is 32 wt%, and a spheroidal light emitting section 2 in which a total of 2.8 mg of metal halide is sealed.
And a luminous tube 1 made of quartz glass having a luminous portion 2 and sealing portions 3 provided at both ends of the luminous portion 2. An electrode 4 is connected to one end of the sealing portion 3 and an external lead wire 5 is connected to the other end.
Is connected to the light emitting portion 2
It is sealed so as to be located inside. The pair of electrodes 4
The distance AL between the electrodes is 4 mm. The electrode 4 is
As shown in FIG. 2, it is composed of a tungsten electrode rod 7 and a tungsten coil 8, and the coil 8 is provided at the tip of the electrode rod 7.

A thermal insulation film 11 containing zirconium oxide is applied to the sealing portion 3 of the arc tube 1.

One sealing portion 3 is provided with a base 9 made of ceramic, and an external lead wire 5 extends from the base 9. A power supply line 10 is connected to an external lead wire 5 derived from the other sealing portion 3.

The thickness of the light emitting section 2 is 1.2 mm. The light emitting unit 2 is a light emitting unit 2 when the electrodes 4 are arranged horizontally.
Is the maximum diameter in the vertical direction, and b is the maximum diameter in the horizontal direction of the light emitting unit 2. For example, when b / a = 1.6, a = 1
1.2 mm, b = 17.4 mm and the internal volume is about 1.2
cc.

The lamp of the present embodiment is lit by an AC lighting method, the lamp voltage is about 60 V and the lamp power consumption is 2
50W.

A concave reflecting mirror 12 made of glass having a parabolic reflecting surface is fixed to one sealing portion 3 of the arc tube with cement 13.

FIG. 3 shows a screen center illuminance maintenance rate at 1000 h when b / a of the metal halide lamp of this embodiment is changed. Note that the screen center illuminance maintenance ratio is a change in illuminance at the center of the screen when projected on a 40-inch screen. In addition, as a lighting experiment, a cycle of turning on for 5.5 hours and turning off lights for 0.5 hours was repeatedly performed.

As is apparent from FIG. 3, it is necessary to make b / a larger than 1.0 in order to maintain the center illuminance maintenance ratio (indicated by a straight line A in FIG. 3) at 50% or more. .
By making b / a larger than 1.0, the temperature distribution of the arc tube wall changes, and the devitrification does not spread from directly above the arc tube, but rather from the upper side of the heat insulating film above the arc tube. Therefore, devitrification of the arc tube on the base insulator side having high light use efficiency is delayed. Therefore, the service life can be extended.
However, if the value of b / a is too large, the enclosed metal halide accumulates near the tube end of the arc tube, and the emission generated from metal atoms (Gd, Lu) other than mercury decreases, and the emission of mercury decreases. Will be strong. If the emission of mercury is too strong, the screen turns green, which is not preferable.

The emission intensity from atoms other than mercury is 5
The emission intensity of 445 nm with respect to the emission intensity of 45 nm (B
/ G), and FIG. 3 shows Cs occupying metal halides.
I amount m is 9 wt%, 12 wt%, 26 wt%, 32 wt%
% And 40 wt%, the change of the B / G ratio with the change of b / a of the lamp was shown. As is clear from FIG. 3, it can be seen that the emission of Gd and Lu increases by decreasing the amount m of CsI in the metal halide. Therefore, by decreasing the CsI amount m in the metal halide, the emission of Gd and Lu increases, the emission of mercury atoms can be prevented from being enhanced, and the B / G ratio improves. In FIG. 3, the mark * indicates m = 9 wt%,
The mark indicates m = 12 wt%, the mark □ indicates m = 26 wt%, the mark △ indicates m = 32 wt%, and the mark × indicates m = 40 wt%.

FIG. 4 shows that when B / G is 25% or more, the color on the screen is in a preferable state.
B / G ratio is 25% when I amount m and b / a are changed.
Or not. Note that in FIG.
% And less than 25%. As is clear from FIG. 4, in order to make the B / G ratio 25% or more,
B / a and Cs so as to fall within the shaded region in FIG.
It is necessary to set the I amount m. That is, in order for the central illuminance maintenance ratio at 1000 h to be 50% or more and the B / G to be 25% or more, 1.0 ≦ b / a ≦ 2.46−0.03 m
It is preferable that Also, the CsI amount m is 12 wt%
If it is smaller, the arc becomes too thin and flickers occur. Therefore, it is preferable that m ≧ 12.

Next, a second embodiment will be described.
The arc tube configuration is the same as that of the first embodiment. Here, a coil 8 is attached to a tungsten electrode rod 7 having a diameter d of 0.80 mm at a distance c (mm) from the tip of the electrode rod 7. Here, the interval c is defined as an electrode protrusion length. The coil 8 is formed by winding a tungsten wire having a diameter of 0.2 mm and has two layers. In the first layer, the wire is wound 11 times, and in the second layer, the wire is wound 5 times on the first layer. The electrode rod length is 13 mm. In this embodiment, the CsI amount m is 26 wt%. Input power is 250W
It is. Table 1 shows the screen center illuminance maintenance ratio of the lamp when the electrode protrusion length c was changed.

[0023]

[Table 1]

As is evident from Table 1, when the electrode protrusion length c is long (c> 1.25 mm), the deterioration of the electrode becomes severe due to the small heat capacity of the electrode tip, and the decrease in the illuminance maintenance rate at the center of the screen is large. Become. As the electrode protrusion length c is reduced, the screen center illuminance maintenance ratio increases. However, if it is extremely short (c <0.70 mm), the bright spot of the arc normally generated at the tip of the tungsten electrode rod during discharge shifts to the coil. In such a state, the scattering amount of tungsten, which is the material of the coil, increases, and blackening of the arc tube is promoted. Also, it is not good because it causes flickering. From this, the electrode protrusion length c (mm)
Is preferably set to 0.70 ≦ c ≦ 1.25.

Next, a third embodiment will be described.
The configuration of the arc tube is the same as in the first embodiment. The electrode protrusion length c was 0.75 mm, and the CsI amount m was 26 wt%. The lamp input power is 250W. Electrode rod diameter d
Was changed, and the illuminance maintenance rate at the center of the screen was examined. FIG. 5 shows the results of measurement of the relationship between the screen center illuminance maintenance factor and the diameter of the electrode bar at 1000 h.

As is apparent from FIG. 5, the diameter d of the electrode rod
When (mm) was smaller than 0.70, it was found that the center illuminance maintenance ratio at 1000 h was less than 50%, the amount of evaporation of the electrode material was increased, and blackening of the arc tube was promoted. When the diameter d (mm) of the electrode rod exceeded 0.90, the center illuminance maintenance rate at 1000 h was less than 50%, and blackening of the arc tube due to spatter at the time of startup was found to increase. Therefore, 5 hours at 1000h
In order to obtain a center illuminance maintenance ratio of 0% or more, it is preferable that the diameter d (mm) of the electrode rod be 0.70 ≦ d ≦ 0.90.

Next, a metal halide lamp having a reflecting mirror as shown in the first embodiment will be described for a liquid crystal projector.

In the present embodiment, as shown in FIG.
Light source unit 14 showing the metal halide lamp according to the embodiment
Light emitted from the liquid crystal panel is condensed by a field lens 15 and irradiated on a liquid crystal panel 16, and an optical image formed by the liquid crystal panel is enlarged and projected on a screen 18 by a projection lens 17. FIG. 7 shows a change in the screen center illuminance maintenance ratio in this optical system.

As is clear from FIG. 7, it can be seen that the central illuminance maintenance ratio is improved by increasing b / a.

[0030]

As described above, according to the structure of the present invention, it is possible to provide an excellent discharge lamp capable of suppressing a decrease in illuminance at the beginning of its life, and to use the discharge lamp to provide a central illuminance. An image projector with an excellent maintenance rate can be provided.

[Brief description of the drawings]

FIG. 1 is a partial sectional view of a metal halide lamp according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of the same electrode rod.

FIG. 3 is a graph showing the relationship between the amount of CsI and the amount of m in the metal halide when the b / a is changed.
Figure showing the screen center illuminance maintenance rate at h and B / G at 0h

FIG. 4 is a diagram showing the relationship between the CsI amount m and b / a.

FIG. 5 is a diagram showing a relationship between a screen center illuminance maintenance factor and a diameter of an electrode bar at 1000 h.

FIG. 6 is a schematic diagram of a liquid crystal projector.

FIG. 7 is a diagram showing a change in a screen center illuminance maintenance ratio when used as a light source of a liquid crystal projector.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Arc tube 2 Light emission part 3 Sealing part 4 Electrode 5 External lead wire 6 Molybdenum foil 7 Electrode rod 8 Coil 9 Cap 10 Power supply line 11 Heat insulation film 12 Reflector 13 Cement 14 Light source part 15 Field lens 16 Liquid crystal panel 17 Projection lens 18 screen

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-7-130333 (JP, A) JP-A-5-135739 (JP, A) JP-A-8-96748 (JP, A) JP-A-9-1997 82276 (JP, A) JP-A-6-13030 (JP, A) JP-A-7-99036 (JP, A) JP-A-8-55604 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01J 61/88 H01J 61/10-61/33

Claims (4)

(57) [Claims] 1. A light-emitting portion having a pair of electrodes disposed therein, and gadolinium iodide (GdI ₃ ) and lutetium iodide (LuI ₃ ) as a starting gas, mercury, and a metal halide in the light-emitting portion. A luminous tube made of quartz glass in which cesium iodide (CsI) is sealed, wherein the amount of CsI in the metal halide is m (wt%), and the luminous portion is vertically arranged with the pair of electrodes arranged horizontally. The maximum diameter in the direction
(Mm) and the maximum horizontal diameter of the light emitting unit is b
(Mm), 1.0 ≦ b / a ≦ 2.46-0.
03 × m and m ≧ 12, and lamp
At a power of 250 W, the electrodes consist of an electrode rod and a coil.
And the distance from the coil tip to the electrode rod tip is c
(Mm), satisfying 0.70 ≦ c ≦ 1.25
A discharge lamp. 2. The lamp is lit so that the electrode is horizontal,
The discharge lamp according to claim 1, wherein the discharge lamp is to be used in an AC lighting system. The diameter d of wherein prior Symbol electrode rod (mm) 0.70
Claim 1 or, characterized by satisfying the ≦ d ≦ 0.90
A discharge lamp according to claim 2 . Wherein images of the discharge lamp according to any one of claims 1 to 3, characterized in that provided in the concave reflector having a reflective surface which is parabolic or ellipsoidal Projector.