JPH05135741A - Ultraviolet generator - Google Patents

Abstract

PURPOSE:To provide a ultraviolet generator capable of preventing the reduction of the ultraviolet intensity generated when the current density is increased. CONSTITUTION:A low-pressure mercury vapor discharge lamp 1 formed with a luminescence section into a noncircular cross section, sealed with mercury and rare gas, and made of quartz glass is provided. A lighting device 10 having the lamp current density per cross section of a luminescence section of 0.5A/cm<2> or above and feeding a rectangular wave current or high-frequency power of 10kHz or above is provided for the discharge lamp 1. A lighting device having the lamp current density per cross section of the luminescence section of 0.5-4A/cm<2> and feeding a rectangular wave current is also provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultraviolet ray generator used as a light source for a low pressure mercury vapor discharge lamp, for example, for ultraviolet chemical reaction.

[0002]

2. Description of the Related Art A low-pressure mercury vapor discharge lamp in which electrodes are sealed at both ends of an arc tube made of quartz glass or the like which transmits ultraviolet rays, and mercury and a rare gas are enclosed in the arc tube,
For example, an ultraviolet ray generator that emits ultraviolet rays mainly composed of the resonance lines 185 nm and 254 nm of mercury by supplying commercial power to generate a discharge in the arc tube to ionize and excite mercury atoms is known. , Used in photochemical reactors, etc.

That is, the above-mentioned ultraviolet ray generator is, for example, a photo-CVD (Chemical Vapor Depos).
It is essential for semiconductor manufacturing such as synthesis of Si thin film by photoionization method, photo-curing of resist and photo-ashing or photo-cleaning, and water purification, sterilization treatment, food sterilization treatment, etc. It is also widely used for irradiating short wavelength ultraviolet rays.

More specifically, the ultraviolet ray generator developed today is equipped with a low pressure mercury vapor discharge lamp as shown in FIG. 6 and a lighting device as shown in FIG. The arc tube of the low-pressure mercury vapor discharge lamp shown in the figure is provided with a hot cathode and an anode at both ends of a cylindrical quartz glass, and mercury and a rare gas such as argon are sealed inside.

Further, the contacts a and b in the figure of the lighting device constituted by a transformer and a current limiting inductance are connected to a commercial power source, and c, d and e and f are respectively connected to hot cathodes of discharge lamps g and h. By connecting each of them to the anode, the hot cathode always generates heat and becomes ready to emit thermoelectrons, and the emitted electrons are accelerated by the electric field and the cathode on one side, the anode on the other side and the cathode on the other side. The discharge is alternately repeated between the positive electrode and the positive electrode on the one side according to the frequency of the commercial power source, and ultraviolet rays are emitted.

If the low-pressure mercury vapor discharge lamp is turned on by the AC power source as described above, the so-called catalysis phenomenon in which mercury ions are biased toward the cathode side can be suppressed.

[0007]

By the way, as shown in FIG. 8, when the lamp current supplied to the low-pressure mercury vapor discharge lamp is increased in order to improve the ultraviolet ray output emitted from the ultraviolet ray generator as described above. It was also confirmed that, when the current density was low, the ultraviolet intensity increased with the increase of the discharge current, but when the current density was further increased, the ultraviolet intensity sharply decreased.

The reason for this has not been completely clarified, but it is presumed that mercury atoms are excessively ionized with an increase in current density, and the number of excited atoms contributing to light emission is insufficient. Especially when the discharge current is a sine wave as described above,
At the intermediate phase angle of each half cycle, the current value increases, and it is considered that the shortage of excited atoms is further promoted.

It is possible to increase the mercury vapor pressure in order to make up for this shortage of excited atoms. However, in this case, the ultraviolet rays are self-absorbed by the mercury vapor in the arc and the intensity of the ultraviolet rays does not increase. was there.

Further, this kind of ultraviolet ray generator is often used in combination with a cooling device for cooling the coldest part of the arc tube to about 40 ° C. Therefore, in practice, the ultraviolet ray generator has the highest temperature. It is necessary to make the lamp efficiency and the intensity of radiated ultraviolet rays maximum when the cold part temperature is near this cooling temperature.

However, when the current density is increased, the temperature of the coldest part of the arc tube which gives the maximum ultraviolet ray output shifts to the high temperature side as the lamp current increases. When cooled, the efficiency of the arc tube was lowered, and it was difficult to obtain the necessary ultraviolet intensity.

The present invention has been made under these circumstances, and an object of the present invention is to provide an ultraviolet ray generator capable of preventing a decrease in ultraviolet ray intensity which occurs when the current density is increased. It is a thing.

[Constitution of Invention]

[0014]

In order to solve the above-mentioned problems, in the ultraviolet generator according to the present invention, the light emitting portion has a non-circular cross-sectional shape, and the quartz glass is filled with mercury and a rare gas. A low-pressure mercury vapor discharge lamp and a lighting device for the low-pressure mercury vapor discharge lamp, which has a lamp current density per cross-sectional area of the light emitting portion of 0.5 A / cm 2 or more and which supplies a rectangular wave current. It is characterized by having.

In the ultraviolet generator according to the second aspect of the present invention, the light emitting portion has a non-circular cross-sectional shape, and a low-pressure mercury vapor discharge lamp made of quartz glass in which mercury and a rare gas are sealed, and the low-pressure mercury. The vapor discharge lamp has a lamp current density of 0.5 A / cm 2 or more per cross-sectional area of the light emitting portion, and a lighting device for supplying high frequency power of 10 KHz or more. ..

Further, in the ultraviolet generator according to the third aspect of the present invention, a low-pressure mercury vapor discharge lamp made of quartz glass in which mercury and a rare gas are sealed, and a cross-sectional area of a light-emitting portion for the low-pressure mercury vapor discharge lamp. Lamp current density of 0.5A
/ Cm @ 2 to 4 A / cm @ 2 and a lighting device for supplying a rectangular wave current.

[0017]

According to the invention described in claim 1 and claim 2, since the light emitting portion of the low-pressure mercury vapor discharge lamp has a non-circular cross-sectional shape, the optical thickness of the mercury vapor layer is reduced. Then, while suppressing self-absorption by mercury vapor,
By turning on the high frequency power of 10 KHz or more or the rectangular wave current, the excited atoms can be filled without increasing the mercury vapor pressure as in the case of the sine wave, so that the ultraviolet intensity decreases even if the current density is increased. It is thought that it does not.

Further, according to the third aspect of the present invention, since the proper range of the lamp current density is defined, it is unlikely that the optimum coldest part temperature of the low-pressure mercury vapor discharge lamp is raised, and therefore the normal cooling is performed. Even when used in combination with a device, it is possible to improve the ultraviolet intensity.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic view showing an embodiment of an ultraviolet ray generator according to the present invention. As shown in FIG.
Low-pressure mercury vapor discharge lamp 1 arc tube 2 bent into a substantially U shape
Stems are sealed at both ends of the positive electrode 3, and an anode 3 and a hot cathode 4 are supported by the stem, respectively. Each anode 3 is arranged in front of the hot cathode 4 in the discharge space. The anode 3 is formed by a circular coil, a cylinder or an annular plate, and the hot cathode 4 is formed by a filament coil.

Here, if the anode 3 and the cathode 4 are sealed at both ends of the arc tube 2 as described above, the cathode 4 can be miniaturized to reduce the loss due to heat dissipation when the discharge current is increased, On the other hand, the anode 3 can be made large to promote heat dissipation.

The arc tube 2 has a non-circular cross section, for example, a substantially flat square shape as shown in FIG. 2, and the ratio X / Y of the short side X to the long side Y is 0.2 to. It is formed to about 0.8. In this embodiment, the short side X is 15 mm and the long side Y is
Is 30 mm, and the cross-sectional area of this arc tube is about 4.5 cm 2.

Inside the arc tube 2, 0.5 to 13 Pa is provided.
And a rare gas such as argon of 13 to 267 Pa are enclosed.

The low-pressure mercury vapor discharge lamp configured as described above is connected to the AC power supply 11 via the lighting device 10. The lighting device 10 includes a rectifying / smoothing circuit 12 and a power FE.
A rectangular wave inverter circuit 13 including T is provided. The rectangular wave inverter circuit 13 is provided with variable resistors 14 and 15 for frequency adjustment and current adjustment. By adjusting these, a discharge current as shown in FIG. 1.56 in terms of the lamp current density per cross-sectional area of the light emitting part of the vapor discharge lamp
It is configured to supply a square wave current of A / cm @ 2 to the low pressure mercury vapor discharge lamp.

The AC power supply 11 is, for example, a 200 V commercial power supply, and the power supply 11 is connected to the heater transformers 16 and 16 in addition to the rectifying / smoothing circuit 12 and the rectangular wave inverter circuit 13 described above. ..

The heater transformers 16 and 16 are connected to the cathodes 4 and 4, respectively. Therefore, the cathodes 4 and 4 are hot cathodes that constantly generate heat and emit thermoelectrons.

The operation of the ultraviolet ray generator having the above structure will be described below.

When the low-pressure mercury vapor discharge lamp 1 is connected to the power source through the lighting device 10, since the cathodes 4 and 4 are connected to the AC power source 11 via the heater transformers 16 and 16, these cathodes 4 and 4 are always connected. It generates heat and emits thermoelectrons.

Then, the rectifying / smoothing circuit 12 and the rectangular wave inverter circuit 13 convert the sine wave of the power source into the above-mentioned rectangular wave, and the rectangular wave currents are variable resistors 14 and 15 for frequency adjustment and current adjustment. And is supplied between the anodes 3 and 3 and the cathodes 4 and 4.

Therefore, in the low-pressure mercury vapor discharge lamp, a rectangular wave half-wave rectification current is passed between the anode 3 on one end side and the cathode 4 on the other end side, and a discharge occurs between them, A reverse half-wave rectified current flows between the anode 3 on the other end side and the cathode 4 on the one end side, and each time the polarity is reversed, each anode and cathode repeats discharge to maintain lighting.

Due to such discharge, the mercury-based vapor is excited at a low pressure, and the mercury resonance lines 185 nm and 25
It emits light in the short wavelength ultraviolet region including 4 nm.

When the ultraviolet intensity of the ultraviolet generator as described above was measured with various current densities, the results shown in FIG. 4 were obtained. From the figure, the ultraviolet emission of this embodiment shown by the solid line B was obtained. The device has a current density of 0.5 A /
In the area of cm2 or more, the ultraviolet intensity is higher than that of the conventional ultraviolet generator (broken line A), and especially 1.6 A / cm
In the case of a current density of 2 or more, the ultraviolet intensity of the conventional ultraviolet generator is remarkably reduced, but the ultraviolet intensity of the present embodiment does not decrease, and the ultraviolet intensity remarkably increases as the current density increases. I was able to confirm that.

Although the reason for this has not been completely clarified, since the light emitting portion of the low-pressure mercury vapor discharge lamp has a non-circular cross-sectional shape, the optical thickness of the mercury vapor layer is reduced and the mercury vapor self-exists. By suppressing the absorption and by lighting with a square wave current, it is possible to fill the excited atoms without increasing the mercury vapor pressure as in the case of a sine wave, so the ultraviolet intensity decreases even if the current density is increased. I guess it won't.

In the low-pressure mercury vapor discharge lamp of the present embodiment in which the light emitting portion has a flat cross section, the ratio of the short side to the long side of the cross section is 0.2 to 0. It is preferable to satisfy the range of 8.

That is, if it exceeds 0.8, the effect of suppressing self-absorption by mercury vapor is reduced, which is not preferable, and if it is less than 0.2, the discharge of the low-pressure mercury vapor discharge lamp is not possible. It is not preferable because it tends to be non-uniform and uneven light emission tends to occur.

In the above embodiments, the rectangular wave current is supplied, but the rectangular wave current is supplied even when high frequency power of 10 KHz or more is supplied to the low pressure mercury vapor discharge lamp. The same effect as the supplied example was obtained.

That is, even when a high-frequency power of 10 KHz or more is supplied, the excited atoms can be filled without increasing the mercury vapor pressure as in the case of a sine wave, so that the ultraviolet intensity decreases even if the current density is increased. It is speculated that it will not occur.

That is, the high-frequency current microscopically has a current fluctuation similar to that of an ordinary commercial power source, but since the fluctuation cycle is extremely short, it is possible to generate an excited atom without increasing the mercury vapor pressure. It is speculated that the above can be sufficiently satisfied.

In the above embodiments, the description has been made of the case in which the anode and the cathode are sealed at both ends of the arc tube, but the present embodiment is also applied to the arc tube in which a pair of electrodes are sealed at both ends of the arc tube. It has been confirmed that it has the same effect as the example.

Furthermore, in the above embodiment, the arc tube having a U-shape is described in detail, but the arc tube may be formed in other shapes besides the straight tube arc tube. .. Further, the cross-sectional shape of the light emitting portion of the low-pressure mercury vapor discharge lamp is not limited to the flat shape described in the examples, but may be formed in another non-circular shape so as to reduce the optical thickness of the mercury vapor layer. Is also good.

Next, the inventor of the present invention uses a low-pressure mercury vapor discharge lamp having a circular cross-section in the light-emitting section, and uses the current density and the ultraviolet ray intensity of the rectangular wave current to the arc tube and the coldest of the low-pressure mercury vapor discharge lamp. When various experiments were conducted on the relationship with the temperature of the part, the results shown in FIG. 5 were obtained.

That is, when the lamp current density exceeds 4 A / cm 2, the coldest part temperature at which the intensity of ultraviolet rays becomes maximum shifts to the high temperature side, and when used in combination with a normal cooling device, this optimum maximum temperature is obtained. It was found that the lamp efficiency and the ultraviolet intensity were reduced because the temperature was outside the cold region temperature range.

The lamp current density is 0.5 A / cm 2
If it is less than 100%, the absolute UV intensity will decrease,
Not preferable.

Therefore, from the above results, if the low-pressure mercury vapor discharge lamp is lit with the rectangular wave of the lamp current of 0.5 A / cm 2 to 4 A / cm 2, it can be used in combination with the ordinary cooling device. The coldest part of the arc tube is maintained in a temperature range where the lamp efficiency and the intensity of radiated ultraviolet rays are maximized, which is practically preferable.

[0045]

According to the present invention, since the light emitting portion of the low-pressure mercury vapor discharge lamp has a non-circular cross-sectional shape, the optical thickness of the mercury vapor layer is reduced, and self-absorption by mercury vapor can be suppressed. By activating with high-frequency power of 10 KHz or more or rectangular wave current, excited atoms can be filled without increasing mercury vapor pressure. Therefore, even if the current density is increased, the intensity of ultraviolet rays does not decrease. An ultraviolet generator having improved strength can be provided.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of an ultraviolet ray generator according to the present invention.

FIG. 2 is a drawing showing a cross-sectional shape of a light emitting portion of the low-pressure mercury vapor discharge lamp in FIG.

FIG. 3 is a drawing showing a rectangular wave current waveform supplied to a low-pressure mercury vapor discharge lamp.

FIG. 4 is an experimental result showing a change in ultraviolet intensity of the ultraviolet generator according to the present invention.

FIG. 5 is an experimental result showing a change in ultraviolet intensity of the ultraviolet generator according to the present invention.

FIG. 6 is a drawing showing an example of a low-pressure mercury vapor discharge lamp applied to a conventional ultraviolet generator.

FIG. 7 is a view showing an example of a lighting device applied to a conventional ultraviolet ray generating device.

FIG. 8 is a drawing showing changes in ultraviolet intensity of a conventional ultraviolet generator.

[Explanation of symbols]

1 ... Low-pressure mercury vapor discharge lamp 2 ... Arc tube
3 ... Anode 4 ... Cathode 10 ... Lighting device
11 ・ ・ AC power supply 12 ・ ・ Rectifying and smoothing circuit 13 ・ ・ Square wave inverter circuit 14,15 ・ Variable resistor 16 ・ ・ Heater transformer

Front Page Continuation (72) Inventor Shinichi Oshima 1-4-2-4 Mita, Minato-ku, Tokyo Toshiba Lighting & Technology Corporation

Claims (3)

[Claims] 1. A low-pressure mercury vapor discharge lamp made of quartz glass in which a cross-sectional shape of a light-emitting portion is formed into a non-circular shape and in which mercury and a rare gas are sealed, and a disconnection of the light-emitting portion with respect to the low-pressure mercury vapor discharge lamp. The lamp current density per area is 0.5 A / cm2 or more,
An ultraviolet ray generating device comprising: a lighting device that supplies a rectangular wave current. 2. A low-pressure mercury vapor discharge lamp made of quartz glass in which a cross-sectional shape of a light-emitting portion is formed into a non-circular shape and in which mercury and a rare gas are sealed, and a disconnection of the light-emitting portion with respect to the low-pressure mercury vapor discharge lamp. The lamp current density per area is 0.5 A / cm2 or more,
And a lighting device that supplies high-frequency power of 10 KHz or higher. 3. A low-pressure mercury vapor discharge lamp made of quartz glass in which mercury and a rare gas are sealed, and a lamp current density per cross-sectional area of the light emitting portion of the low-pressure mercury vapor discharge lamp is 0.5 A / cm2. To 4 A / c
a lighting device of m2 and supplying a rectangular wave current,
An ultraviolet ray generator characterized by comprising: