JPH03112046A - Ultraviolet irradiation unit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION CObject of the Invention] (Industrial Application Field) The present invention relates to an ultraviolet irradiation device used as a light source for photochemical reactions and the like.

(Prior Art) Photochemical reaction devices using ultraviolet light sources are used in various fields, such as photoCVD (Che+w1cal).
It is widely used in semiconductor manufacturing, including the synthesis of SF thin films by the V apor Deposition method, photo-curing of resists, photo-ashing, photo-cleaning, etc., and its application fields are rapidly expanding.

In these fields, a light source that efficiently irradiates short-wavelength ultraviolet light is desired, and for this reason, low-pressure mercury ultraviolet discharge lamps are preferably used.

This type of low-pressure mercury ultraviolet discharge lamp has an arc tube made of quartz glass or the like that transmits ultraviolet rays, and electrodes are sealed at both ends of the arc tube, and mercury and a rare gas are sealed inside the arc tube, so that the mercury-based vapor is kept at a low pressure. The lamp efficiently emits light in the short wavelength ultraviolet region including the mercury resonance line 254no+ by discharging the lamp.

Incidentally, in recent years, there has been an increasing demand for dimming of the ultraviolet irradiation device itself used as such a light source.

Generally, when attempting to dim a discharge lamp, a method is adopted in which the lamp current is increased or decreased.

Even in the above-mentioned low-pressure mercury ultraviolet discharge lamp, it is not impossible to control the light by increasing or decreasing the lamp current.

(Problems to be Solved by the Invention) However, in the case of the above-mentioned low-pressure mercury ultraviolet discharge lamp, the current density is relatively large, at several A/c-.

Therefore, when the lamp current is increased, the current density further increases, the amount of mercury excitation increases, the ground state mercury atom density decreases, and the occupation density of 63P1, which is the excited species, decreases accordingly. As a result, the UV radiation efficiency is significantly reduced,
Therefore, it becomes difficult to obtain a sufficient dimming effect.

Moreover, reducing the lamp current causes problems such as turning off and making the discharge unstable, while increasing the lamp current not only causes a significant drop in the ultraviolet radiation efficiency mentioned above, but also causes the electrodes to overheat and emit light. There is also a defect that causes early blackening of the tube.

Therefore, the conventional techniques are insufficient for controlling the light with a sufficient difference in an ultraviolet irradiation device using a low-pressure mercury ultraviolet discharge lamp.

The present invention has been made to solve the above-mentioned problems, and aims to provide an ultraviolet irradiation device that can be easily adjusted without causing problems such as a decrease in ultraviolet radiation efficiency, fading, or blackening. It is something.

[Structure of the Invention] (Means for Solving the Problems) The present invention connects a part of the arc tube to a cooling device, and cools the arc tube to its maximum temperature by forcibly cooling the part of the arc tube with the cooling device. The lamp is characterized in that the temperature is controlled so that, at the same lamp voltage, different values of ultraviolet light output are generated depending on whether the temperature of the coldest part is high or low.

(Function) The present inventors have found that when various conditions such as the inner diameter of the arc tube, rare gas pressure, and current density are changed in a low-pressure mercury ultraviolet discharge lamp, at the same lamp voltage (however, the lamp power factor changes slightly). It has been found that two different ultraviolet outputs can be obtained. For example, there are cases where the fourth output is at point A and cases where the fourth output is at point B. Therefore, if this is used, dimming can be performed without changing the lamp voltage or lamp current.

Therefore, in the present invention, since the lowest cooling temperature of the arc tube is controlled using a cooling device, the lowest cooling temperature can be increased,
The internal pressure of the arc tube can be made different by lowering the pressure, thereby making it possible to use the ultraviolet light output at point A and point B.

(Example) The present invention will be described below based on a first example shown in FIG.

In the figure, reference numeral 1 denotes a low-pressure mercury ultraviolet discharge lamp, and the discharge lamp 1 is composed of a discharge vessel or arc tube 2 made of quartz glass with high ultraviolet transmittance. This luminous tube 2
is U-shaped, and a stem 3.3 is hermetically welded to both ends of the arc tube 2. These stems 3.3
An anode 4 and a cathode 5 are respectively attached via power supply lines 6.7.

This arc tube 1 contains a predetermined amount of mercury or amalgam,
It is filled with argon gas for starting.

Such a low-pressure mercury ultraviolet discharge lamp 1 is configured such that when discharging the anode 4 of one stem 2 and the cathode 5 of the other stem 2, and when discharging between the anode 4 of the other stem 2 and the cathode 5 of the other stem 2, respectively.
The discharge is continued by alternately repeating the discharge with the cathode 5.

In such a discharge, mercury-based vapor is discharged under a low pressure state, and light in the short wavelength ultraviolet region including the mercury resonance line of 254 nm is emitted.

A cooling device 1o is attached to the end of the discharge lamp 1.

The cooling device 10 includes, for example, a metal cooling block 11 that surrounds the end of the discharge lamp 1.
1 has a water jacket 12 through which cooling water flows.
It is formed.

This water jacket 12 is connected to a variable speed pump 14 and a heat exchanger 15 via a pipe 13, and the variable speed pump 14 and heat exchanger 15 are connected to a cooling water tank 16.
is familiar with

When the variable speed pump 14 is operated, cooling water is sent from the cooling water tank 16 to the water jacket 12 via the vibrator 13, and the cooling water in the water jacket 12 is sent to the heat exchanger 1.
5 and is returned to the cooling water tank 16.

In such a cooling device 10, when the variable speed pump 14 is operated at a predetermined flow rate, a corresponding amount of cooling water is flowed into the water jacket 12. Therefore, the end of the low-pressure mercury ultraviolet discharge lamp 1 exchanges heat with the cooling block 11, so that it is forcedly cooled.

When the operating speed of the variable speed pump 14 is controlled to reduce the flow rate of cooling water, the flow of cooling water in the water jacket 12 is also small, so the performance for forcedly cooling the end of the low pressure mercury ultraviolet discharge lamp 1 is low.

Therefore, in this case, the temperature of the coldest part at the end of the low-pressure mercury ultraviolet discharge lamp 1 is relatively high, and the lamp is lit with a relatively high mercury vapor pressure during lighting.

In this case, as shown by point A in the characteristics of FIG. 4, lighting is performed with a large ultraviolet output.

Furthermore, when the operating speed of the variable speed pump 14 is controlled to increase the flow rate of cooling water, the flow rate of cooling water in the water jacket 12 also increases, and the performance for forcedly cooling the end of the low-pressure mercury ultraviolet discharge lamp 1 increases. Therefore, in this case, the temperature of the coldest part at the end of the low-pressure mercury ultraviolet discharge lamp 1 is made relatively low, and the mercury vapor pressure during lighting is kept low, and lighting is performed.

This allows for dimming.

In this case, as shown by point B in the characteristics of Fig. 4, the ultraviolet output is small, and the case where the ultraviolet output is large (point A) and the case where the ultraviolet output is small (point B) are as follows. Since the lamp voltage is the same in both cases, and therefore there is no variation in lamp current, there is no significant reduction in UV radiation efficiency, preventing fading, unstable discharge, or premature blackening of the arc tube. .

In addition, the inner diameter of the arc tube 2 is 25 cm, and the luminous length is 107501 cm.
In a U-shaped low-pressure mercury ultraviolet discharge lamp with a rated human power of 500 W, mercury is 100 a + g, argon gas is Q, 3 to
rr sealed and the temperature of the coldest part is 50℃, the fourth
The ultraviolet output at point A in the figure can be obtained, and the temperature at the coldest part can be reduced by 3.
When the temperature is 0°C, the ultraviolet output at point B in Figure 4 is obtained,
The lamp voltage for each of these was 80V.

Note that the present invention is not limited to the above embodiments.

That is, the structure of the lamp is not limited to the U-shape, and is not limited to having an anode and a cathode at both ends and lighting alternately.

Even in the case of a cooling device, as in the second embodiment shown in FIG.
2 may be driven, and the cooling block 23 may be cooled by cooling the refrigerant by the fan 22. Alternatively, the cooling block 30 may be connected to the tap water pipe 31 as in the third embodiment shown in FIG. However, the cooling performance may be changed by controlling the flow rate with the flow rate adjustment valve 32.

Of course, it is also possible to use the cooling device only when lighting at low temperatures, without using equivalent cooling when lighting at high temperatures.

[Effects of the Invention] As explained above, according to the present invention, the temperature of the coldest part of the arc tube is controlled using a cooling device, and the internal pressure of the arc tube is adjusted by increasing or decreasing the temperature of the coldest part. This allows the UV output to be used in two ways without changing the lamp voltage. This allows for dimming. When the UV output is high and when the UV output is low, the lamp voltage is the same, so there is no fluctuation in the lamp current, so the UV radiation efficiency will not be significantly reduced, and there will be no fading or discharge. instability or early blackening of the arc tube.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an ultraviolet irradiation device showing a first embodiment of the present invention, FIG. 2 is a configuration diagram of an ultraviolet irradiation device showing a second embodiment of the invention, and FIG. FIG. 4 is a diagram showing the configuration of the ultraviolet irradiation device according to the third embodiment, and FIG. 4 is a characteristic diagram showing the relationship between the ultraviolet output and the lamp voltage. 1...Low pressure mercury ultraviolet discharge lamp, 2...Earth tube, 3.
... Stem, 4... Anode, 5... Cathode, 10...
Cooling device, 11... Cooling block, 12... Water jacket, 14... Variable speed pump.

Claims (1)

[Scope of Claims] In an ultraviolet irradiation device that uses an arc tube as a light source in which electrodes are sealed and mercury and rare gases are sealed, a portion of the arc tube is connected to a cooling device, and the cooling device cools the arc tube. The temperature of the coldest part of the arc tube is controlled by forced cooling, and different values of ultraviolet output are generated when the temperature of this coldest part is high and low at the same lamp voltage. Characteristic ultraviolet irradiation device.