JP3178259B2 - Electrodeless 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 an electrodeless discharge lamp which has no electrodes inside a bulb and excites and emits a discharge gas inside the bulb by an external high-frequency electromagnetic field.

[0002]

2. Description of the Related Art In recent years, electrodeless fluorescent lamps have been put to practical use. In this lamp, a high-frequency current is applied to an induction coil disposed close to a bulb in which a discharge gas is sealed, and the discharge gas in the bulb is excited and emits light by an induced electromagnetic field generated.

FIG. 8 shows an example of this. An induction coil 2 arranged close to a bulb 1 filled with argon and mercury at a pressure of several Torr is applied to a 13.56 MHz output from a high frequency power supply (not shown). A high-frequency current is applied to excite the mercury atoms in the bulb 1 with an induced electromagnetic field to emit ultraviolet light of 254 nm. The ultraviolet light is applied to the phosphor 4 applied to the inner surface of the bulb 1 to emit visible light. It is an electrodeless fluorescent lamp that was obtained.

In FIG. 8, reference numeral 5 denotes an apparatus main body made of a conductor, which houses the high-frequency power supply and the like and removes radiation noise generated from a lamp and a high-frequency power supply. Numeral 6 denotes an electromagnetic shielding means constituted by a conductive mesh, which transmits the irradiation light from the lamp and prevents noise from leaking from the irradiation surface.

[0005] Since this electrodeless fluorescent lamp has no electrodes in the bulb 1, there is no fear of the electrodes being cut, and the lamp has a long life. Another feature is that the shape of the lamp can be freely designed.

[0006]

When mercury vapor is used as the discharge gas, the lamp characteristics are regulated by the mercury vapor pressure in the bulb, and the mercury vapor pressure is determined by the temperature of the coldest point of the lamp. Is well known.
In a low-pressure discharge lamp using mercury vapor, the maximum luminous efficiency is reached when the temperature at the coldest point is about 40 ° C., and the luminous efficiency decreases at low temperatures.

The high-power radiator disclosed in Japanese Patent Application Laid-Open No. 2-7353 is sealed by so-called dielectric barrier discharge using external electrodes 12 and 13 via a dielectric 11, as shown in FIG. Gases that form excimers are disclosed as gases. In such a high-power radiator, when the gas forming the enclosed excimer is a halogen gas, the halogen gas is deteriorated early and the light output is reduced. Further, in such a form of dielectric barrier discharge, it is difficult to obtain a discharge with a high current density, so that power loss occurs in the external electrodes and the dielectric portion, and power cannot be efficiently supplied to plasma.

The present invention has been made in view of the above problems, and has as its object to provide an electrodeless discharge lamp having excellent temperature characteristics and a long life.

[0009]

According to a first aspect of the present invention, there is provided an electrodeless discharge lamp, wherein a discharge gas filled in a bulb is formed of at least one kind of metal halide and at least one kind of metal halide. 3. The method according to claim 2, wherein the metal halide is disposed at a place where the metal halide is at a bulb temperature (during discharge) lower than its evaporation temperature. Wherein the chloride is a metal chloride, metal bromide or metal iodide.

The invention according to claim 3 is characterized in that the bulb has a shape having a small tube portion smaller in diameter than the main discharge portion, and the metal halide is arranged in the small tube portion. In the invention according to claim 4, the valve temperature control means is provided near the place where the metal halide is disposed, and the valve temperature is controlled by the valve temperature control means to be lower than the evaporation temperature of the metal halide. The invention according to claim 5 is characterized in that a phosphor for converting ultraviolet light into visible light is disposed near the bulb.

[0011]

According to the first aspect of the present invention, since the metal halide is disposed at a place where the valve temperature is lower than the evaporation temperature, the metal halide does not evaporate during discharge, and free halogen and rare gas are removed. An excimer is formed, and excited light emission is generated from the excimer. When excimer gas is used, there is no output fluctuation due to temperature. In addition, since excimer gas is sealed in the form of a metal halide unlike direct sealing, even when the halogen gas is deteriorated, free halogen is supplied from the metal halide so that the life of the halogen gas is long. Therefore, the ultraviolet light source has excellent temperature characteristics and a long life. Further, if the metal halide is a metal chloride as in the second aspect of the invention, an excimer of a rare gas and chlorine is generated, ultraviolet rays having a specific wavelength are emitted, and the metal halide is converted to a metal bromide. An excimer of a rare gas and bromine is generated to emit ultraviolet rays of a specific wavelength. If the metal halide is a metal iodide, an excimer of a rare gas and iodine is generated to emit ultraviolet rays of a specific wavelength.

According to the third aspect of the invention, the bulb has a shape having a small tube portion smaller in diameter than the main discharge portion, and the metal halide is disposed in the small tube portion. The temperature of the thin tube portion becomes the lowest in the bulb, and the metal halide is less likely to evaporate.

According to the fourth aspect of the present invention, the temperature control means is provided such that the place where the metal halide is disposed is equal to or lower than the evaporation temperature of the metal halide.
The metal halide does not evaporate even at a high input such that the entire valve is at or above the metal halide evaporation temperature.

According to the fifth aspect of the present invention, since the phosphor for converting ultraviolet light into visible light is disposed near the bulb, the output of visible light does not change even if the ambient temperature changes.

[0015]

【Example】

(Embodiment 1) FIG. 1 shows a first embodiment according to the present invention. In the drawing, reference numeral 1 denotes a valve made of a light-transmitting material.
The bulb 1 is filled with a rare gas and a metal halide as a discharge gas. In this embodiment, 100 Torr of Xe (xenon) is sealed as a rare gas, and 16 mg of LiI (lithium iodide) is sealed as a metal halide.
Xe is sealed in a gas state, and LiI is sealed in a solid state. Note that other rare gas such as Ne may be added as a buffer gas in addition to Xe.

LiI is a solid at room temperature, but is partially separated into metal (Li) and iodine (I). Iodine exists alone as a gas in the form of I ₂ . The iodine separated from this LiI is referred to herein as free iodine.

Reference numeral 2 denotes an induction coil wound around the outer periphery of the valve 1. In this embodiment, the winding is wound three turns. However, the number of turns is not particularly limited. Good.

Reference numeral 3 denotes a high-frequency power supply for supplying a high-frequency current to the induction coil 2. The high frequency power supply 3 has an oscillation frequency of 13.5
Continuous oscillation is performed at 6 MHz.

When a high-frequency current generated by a high-frequency power supply 3 is applied to the induction coil 2 of the electrodeless discharge lamp thus configured, an alternating magnetic field is generated around the induction coil 2.
Further, an induced electric field is generated in a form interlinking with the alternating magnetic field. This induction electric field is a closed electric field along the coil 2, and the plasma is maintained in the bulb 1 by the induction electric field. In the plasma, electrons receive energy from the electric field and collide with the filling gas, causing various excitations,
Although phenomena such as ionization and bonding occur, the bond between Xe and I is allowed only in an excited state, and generates an excited molecule generally called an excimer. When the excimer dissociates, it emits ultraviolet light at a wavelength of 254 nm.

As is known from excimer lasers, halogen gas (here, iodine) has a very high reactivity and immediately bonds with other substances, making it difficult to efficiently generate excimers. Normally, in an excimer laser device, the life is obtained by frequently supplying a halogen gas from the outside, but this is not possible in a sealed device such as an excimer lamp.

According to the present invention, the life is greatly extended by storing a large amount of halogen in the form of a compound with a metal in the lamp. That is, the degraded iodine is supplied from the metal halide.

The vapor pressures of Xe and I ₂ are not affected by the ambient temperature, and the output does not fluctuate due to the ambient temperature as in a lamp filled with mercury. Therefore, the ultraviolet light source has excellent temperature characteristics and a long life. FIG. 2 is a characteristic diagram showing an emission spectrum according to the present embodiment.

The excimer-forming gas is not limited to the gas according to the above-described embodiment, but the excimer-forming gas shown in Table 1 may be filled according to the intended use. The base metal of the metal halide at the time of encapsulation may be selected as needed as long as it is a solid combination at room temperature.

[0024]

[Table 1]

(Embodiment 2) FIG. 3 shows a second embodiment according to the present invention. The difference from Embodiment 1 is that the bulb 1 has a spherical main discharge portion 1a and a main discharge portion 1a. It is composed of a thin tube portion 1b having a smaller diameter than the diameter, and LiI, which is a metal halide, is disposed in the thin tube portion 1b. The description is omitted by appending a symbol.

With this configuration, the temperature of the thin tube portion 1b is the lowest during the operation of the lamp (during lighting), and therefore, the metal halide LiI can be kept relatively low. When the lamp input power is increased, the temperature becomes extremely high without the thin tube portion 1b, and LiI may evaporate. When LiI evaporates, metal emission of Li occurs, or the supply amount of I becomes excessive, which causes inconvenience in excimer generation. However, in the case of this embodiment,
The temperature of LiI, which is a metal halide, can be adjusted to be low by the thin tube portion 1b, and the above problem can be solved. The temperature of the metal halide can be adjusted by changing the length of the thin tube portion 1b as necessary.

FIG. 4 shows a vapor pressure curve of the metal halide. For example, in the case of LiI, the temperature of the thin tube portion 1b is set to 800
It can be seen that it is sufficient to keep the temperature below K.

(Embodiment 3) FIG. 5 shows a third embodiment according to the present invention. The difference from Embodiment 1 is that the temperature control device 7 controls a part of the valve 1 by a temperature control device 7. Since the means 8 is provided and the metal halide is arranged near the temperature control means 8, the other configuration is the same as that of the first embodiment.

With this configuration, the temperature of the metal halide can be kept below the evaporation temperature even when the lamp input power is high. Here, the temperature control means 8 may be, for example, a heat sink or a Peltier element.

(Embodiment 4) FIG. 6 shows a fourth embodiment according to the present invention. The difference from the first embodiment is that the fluorescent material 4 is applied to the inner surface of the bulb 1. With this configuration, the ultraviolet light generated inside the bulb 1 is converted into visible light by the phosphor 4. Therefore, even when the ambient temperature changes, there is no change in the visible light output.

In the above embodiment, the phosphor 4 is applied to the inner surface of the bulb 1. However, the present invention is not limited to this. For example, the outer surface of the bulb 1 may be slightly separated from the bulb 1 as shown in FIG. The phosphor 4 may be arranged at the place.

[0032]

According to the first aspect of the present invention, at least one kind of metal halide and at least one kind of rare gas are sealed in the bulb, and the metal halide is discharged during the discharge of the sealed gas. Since the metal halide is arranged at a place where the valve temperature is lower than the evaporation temperature of
During discharge, a rare gas halide excimer is generated, and a stable ultraviolet output can be obtained without being affected by changes in the ambient temperature. Further, since the excimer gas is sealed in the form of a metal halide unlike the case where the excimer gas is directly sealed, a halogen gas is supplied from the metal halide even when the halogen gas is deteriorated, so that a long-life excimer light source is obtained.

According to the second aspect of the present invention, since the metal halide is a metal chloride, metal bromide or metal iodide, an excimer of a rare gas and chlorine or an excimer of a rare gas and bromine or an excimer of a rare gas and bromine is used. Are produced, and an ultraviolet output of each specific wavelength is obtained.

According to the third aspect of the present invention, the bulb has a shape having a small tube portion smaller in diameter than the main discharge portion, and the metal halide is disposed in the small tube portion. The temperature of the thin tube portion is the lowest in the bulb, the metal halide is less likely to evaporate, and a stable excimer emission output can be obtained even when the input power is high and the bulb temperature rises.

According to the fourth aspect of the present invention, the temperature control means is provided such that the place where the metal halide is disposed is lower than the evaporation temperature of the metal halide.
Even at the time of high input such that the entire bulb becomes equal to or higher than the evaporation temperature of the metal halide, the metal halide does not evaporate, and a stable excimer light emission output is obtained.

According to the fifth aspect of the present invention, since the phosphor for converting ultraviolet light into visible light is disposed near the bulb, a visible light source that does not vary in output even when the ambient temperature varies can be obtained.

[Brief description of the drawings]

FIGS. 1A and 1B show a first embodiment of the present invention, in which FIG. 1A is a simplified perspective view, and FIG.

FIG. 2 is a characteristic diagram showing an emission spectrum according to the first example of the present invention.

FIG. 3 is a simplified sectional view showing a second embodiment of the present invention.

FIG. 4 is a vapor pressure curve diagram of a metal and a metal halide.

FIG. 5 is a simplified sectional view showing a third embodiment of the present invention.

FIG. 6 is a simplified sectional view showing a fourth embodiment of the present invention.

FIG. 7 is a simplified sectional view showing a fifth embodiment of the present invention.

FIG. 8 is a perspective view showing a conventional example.

FIG. 9 is a simplified sectional view showing a different conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bulb 1a Main discharge part 1b Thin tube part 2 Induction coil 2 3 High frequency power supply 4 Phosphor 7 Temperature control device 8 Temperature control means

Continuation of front page (58) Fields investigated (Int. Cl. ⁷ , DB name) H01J 65/04 F21S 2/00

Claims (5)

(57) [Claims] 1. A high-frequency current is supplied from a high-frequency power supply to an induction coil disposed outside a bulb made of a light-transmitting material in which a discharge gas is sealed, and a high-frequency electromagnetic field is applied to the discharge gas sealed in the bulb. In the electrodeless discharge lamp that excites and emits the discharge gas, the discharge gas sealed in the bulb is composed of at least one kind of metal halide and at least one kind of rare gas, and the metal halide is An electrodeless discharge lamp, which is disposed at a place where the bulb temperature (during discharge) is lower than the evaporation temperature. 2. The electrodeless discharge lamp according to claim 1, wherein the metal halide is one of a metal chloride, a metal bromide and a metal iodide. 3. The valve according to claim 1, wherein the bulb has a shape having a small tube portion having a diameter smaller than that of the main discharge portion, and the metal halide is arranged in the small tube portion. Item 2. An electrodeless discharge lamp according to Item 2. 4. A valve temperature control means is provided near a place where said metal halide is disposed, and the valve temperature is controlled by said valve temperature control means to be lower than an evaporation temperature of said metal halide. The electrodeless discharge lamp according to any one of claims 1 to 3. 5. The electrodeless discharge lamp according to claim 1, wherein a phosphor for converting ultraviolet light into visible light is disposed near the bulb.