JP5915976B2 - Long arc discharge lamp and light irradiation device - Google Patents

Description

  The present invention relates to a long arc type discharge lamp and a light irradiation apparatus, and more particularly to a long arc type discharge lamp having a reflective film on the outer surface of an arc tube and a light irradiation apparatus including the same.

  Conventionally, in the printing industry and the electronics industry, as an ultraviolet light source for photochemical reaction equipment used for drying ink and paint, curing resin, or for exposing a liquid crystal substrate for a semiconductor substrate or a liquid crystal display. Long-arc discharge lamps such as mercury lamps and metal halide lamps are used as the ultraviolet light source of the exposure apparatus used.

A long arc type discharge lamp 1 used in a conventional light irradiation apparatus will be described with reference to FIG.
Sealing portions 3 are formed at both ends of the arc tube 2, and a pair of electrodes 4 and 4 are disposed in the arc tube 2.
The rear end portion 4a of the electrode 4 is cut so that the upper and lower portions have a flat surface shape, and has a substantially prismatic shape.
A flat spacer glass 5 made of quartz glass is embedded in the sealing portion 3, and a pair of (two) metal foils 6 a and 6 b are arranged on the upper and lower surfaces so as to sandwich the spacer glass 5. An external lead 8 is connected to the rear ends of the metal foils 6a and 6b.
A glass holding cylinder 7 is disposed in the sealing portion 3, and the electrode 4 is inserted through the holding cylinder 7, thereby supporting the electrode 4.
A base 9 is attached to the rear end of the sealing portion 3, and when the lamp 1 is incorporated into the light irradiation device, the base 9 is attached to a lamp support (not shown).

In addition, a strip-shaped reflective film 10 is formed on the entire outer surface of the arc tube 2 so as to reflect the light traveling upward of the arc tube 2 and irradiate the irradiated object below. .
This reflective film 10 is mainly composed of silica particles from the viewpoint of heat resistance, and is composed of alumina particles or a mixture of silica particles and alumina particles, and is elongated on the outer surface of the arc tube 2. It is provided in a band shape.
In the long arc type discharge lamp having the above configuration, a metal such as mercury, iron, or gallium is enclosed in the arc tube 2 in order to radiate ultraviolet rays satisfactorily.

The structure of the light irradiation apparatus using such a long arc type discharge lamp is known in Japanese Patent Application Laid-Open No. 2008-130302 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2012-198997 (Patent Document 2). The structure is shown in FIG.
FIG. 3A is an explanatory diagram of a state where the reflection mirror is opened.
FIG. 3B is an explanatory diagram of a state in which the reflection mirror is closed.
The light irradiation device 20 includes a bowl-shaped reflection mirror 21 surrounding the metal halide lamp 1, and has a reflection surface 22 made of a dielectric multilayer film or the like on its inner surface.
The reflection mirror 21 has a top opening 21a and a front opening 21b, and can be opened and closed. The top opening 21a is arranged corresponding to the cooling air exhaust port 23. Then, as shown in FIG. 3A, the front opening 21b is opened during the steady lighting mode in which the processing object is irradiated with ultraviolet rays, and during the standby lighting mode such as replacement of the processing object, the front opening 21b is opened. As shown, the reflecting mirror 20 rotates to close the front opening 21b. In the standby lighting mode, the input power to the lamp is reduced from the viewpoint of power saving.

At the time of steady lighting shown in FIG. 3A, cooling air is flowed from below the reflecting mirror 21, passes around the lamp 1, cools it, and flows out from the top opening 21a through the exhaust port 23.
In the standby lighting mode shown in FIG. 3B, the lamp is lit at a low power lower than the rated power. At this time, the front opening 21b of the reflecting mirror 21 may be closed. The reflection mirror 21 is heated. In order to protect the dielectric multilayer film constituting the reflection surface 22 of the reflection mirror 21, it is necessary to cool the dielectric multilayer film, and the cooling air is not stopped and the ventilation is maintained.

As described above, as much power saving as possible is required in the production line, and the discharge lamp is sufficiently used during work non-processing periods such as when the work is replaced (while maintaining the lighting state of the discharge lamp in preparation for re-lighting). A standby lighting mode is employed in which the lamp is lit at low power.
As a result, the discharge lamp enters a state in which the power value is largely switched in a short time such as a work processing period and a non-processing period of several tens of seconds, and changes between a high temperature state and a low temperature state in a short cycle.
Here, taking an example of power during steady lighting and power during standby lighting (power saving lighting), the power per unit length in the effective light emission length is 280 W / cm during steady lighting, and standby lighting. 80 W / cm at hour.

  As described above, the high power and the low power are frequently switched, and the difference in height between the power and the conventional power is increased, so that the thermal stress becomes more conspicuous at the interface between the arc tube and the reflective film. As the lighting time elapses, there is a problem that the reflective film peels off.

JP 2008-130302 A JP 2012-198997 A

In view of the above-described problems of the prior art, the present invention has a pair of electrodes opposed to each other in the arc tube and encapsulates a metal as a luminescent material, and mainly comprises silica particles on the outer surface of the arc tube. In a long arc type discharge lamp in which a strip-shaped reflective film is formed over the entire light emission length, the reflective film may be peeled off or peeled off even when the discharge lamp is turned on frequently by switching between high power and low power. It is to provide a long arc discharge lamp with no high reliability.
Another problem is that in the light irradiation device using the long arc type discharge lamp and having a bowl-shaped reflection mirror, the light emitted toward the opening of the reflection mirror is also used without being wasted by the reflection film. In addition, it is an object of the present invention to provide a highly reliable light irradiation device in which even when the discharge lamp is turned on by frequently switching between high power and low power, the reflective film does not peel off or peel off.

In order to solve the above-described problems, the long arc discharge lamp according to the present invention has an OH group content of 50 ppm to 300 ppm on the tube wall of the arc tube, and an OH group content of the reflective film is 100 ppm or more. Features.
Further, the light irradiation apparatus according to the present invention uses the long arc type discharge lamp, has a reflecting surface surrounding the discharge lamp, and has a bowl-shaped reflecting mirror provided with an opening corresponding to an upper portion of the discharge lamp. It is characterized by comprising.

According to the long arc type discharge lamp of the present invention, since both the reflective film and the arc tube contain OH groups even when the discharge lamp is frequently switched between high power and low power, At this interface, the OH groups are dehydrated and condensed to obtain a strong adhesion, and even under severe lighting conditions, the film can be lit for a long time without peeling off or cracking.
In addition, since the OH group of the arc tube is 50 ppm or more, there is sufficient OH group binding to the reflection film, and sufficient bonding with the reflection film is obtained. The amount of OH released from the tube into the discharge space does not become excessive, and the situation of electrode oxidation can be avoided.
Since the OH group content of the reflective film is 100 ppm or more, the dehydration condensation reaction between the OH groups of the arc tube and the reflective film also contributes to the bonding between the silica particles, and the reflective film itself becomes strong and peels off. It becomes difficult.

  Further, according to the light irradiation device provided with the long arc type discharge lamp and the bowl-shaped reflection mirror, the light emitted from the discharge lamp toward the opening is wasted while maintaining the cooling structure of the mirror opening. Without being able to contribute to the illuminance improvement on the irradiated surface, and even if the discharge lamp is turned on frequently by switching between high power and low power, the reflective film does not peel off and peel off, A highly reliable light irradiation device can be provided.

The partial cross section figure of the arc tube in the long arc type discharge lamp of this invention. Sectional drawing of the conventional long arc type discharge lamp. The whole light irradiation apparatus sectional drawing.

The overall structure of the long arc type discharge lamp in the present invention is the same as that shown in FIG. 2, and the metal sealed as the luminescent material in the arc tube 2 is, for example, mercury (Hg), iron (Fe), It is a metal such as gallium (Ga), and one or more of them may be mixed.
The reflective film 10 is mainly composed of silica particles, and preferably includes silica particles in a proportion of more than 50%.

  As shown in FIG. 1A, the silica particles constituting the reflective film 10 contain OH groups. As a means for containing an OH group, for example, a method of producing silica by a wet method such as a precipitation method, a gel method, or a sol-gel method can be suitably employed. Of course, in the silica produced by the dry method, for example, a reflective film having an OH group can be formed by using a silica-based alkoxide solution as a binder. The shape and diameter of the fine particles are not particularly specified as long as they function as a reflective layer. However, since the reflection mechanism of the fine particle film is reflected on the surface of each fine particle, the fine particle is as dense as possible. More layers are preferred. For example, the shape of the silica fine particles is a spherical shape, a flat shape, or the like, and the average particle diameter is preferably about 0.1 to 10 μm.

Further, the quartz glass constituting the arc tube 2 also contains OH groups. The OH group is contained, for example, by a method of melting quartz powder using an oxyhydrogen flame (flame fused quartz) or heating to a high temperature in a state where a valve is exposed to the atmosphere.
In this way, by adding the OH group to the arc tube 2, as shown in FIG. 1B, the OH group of the arc tube 2 and the OH group of the silica fine particles constituting the reflective film 10 are A dehydration condensation reaction occurs, and the adhesion of the reflective film 10 to the arc tube 2 can be increased.

The OH group content in the arc tube 2 is preferably 50 to 300 ppm. When it becomes 50 ppm or less, the OH group that can be bonded decreases, and the adhesion strength of the reflective film 10 decreases. On the other hand, if it exceeds 300 ppm, the amount of OH released from the arc tube 2 into the discharge space increases, and oxidation of the tungsten electrode in the discharge space occurs, thereby promoting melting. Thereby, tungsten adheres to the arc tube and causes a decrease in illuminance.
The content of OH groups in the reflective film 10 is preferably large, and these can increase the bonding force with the arc tube 2 and the bonding force between the fine particles.

  As described above, according to the short arc type discharge lamp according to the present invention, by adding OH groups to both the reflective film and the arc tube, the OH groups are subjected to a dehydration condensation reaction at the interface, so that it is stronger. Adhesion can be obtained.

An experiment was conducted to demonstrate the effect of the present invention.
<Experimental example>
Using reflective films and arc tubes having different OH group contents, the emission length (distance between a pair of electrodes) is 250 mm, the inner diameter of the arc tube is 22 mm, and the outer diameter is 26 mm. The amount of mercury enclosed in each arc tube A long arc type mercury lamp in which 58 mg of mercury, 2.5 mg of mercury iodide and 1 kPa of argon are sealed is manufactured. It was applied and dried for 10 hours to form a film.
These lamps were turned on for a total of 1000 hours in a lighting mode in which the input per arc length of 1 cm was changed alternately at 80 W and 280 W for 30 seconds, and the appearance of the reflective film was observed.

The results are shown in the table below.

As can be seen from the above table, when the number of OH groups in the arc tube and the reflection film is small, the bonding force is weak, and the reflection film is peeled off under severe lighting conditions with high input and input change. On the other hand, when many OH groups were contained, the reflective film did not peel off even under severe lighting conditions.
In Comparative Example 3, film peeling did not occur, but the amount of OH groups contained in the arc tube was too large, causing devitrification of the arc tube, resulting in a significant decrease in illuminance.

DESCRIPTION OF SYMBOLS 1 Long arc type discharge lamp 2 Arc tube 3 Sealing part 4 Electrode 5 Spacer glass 6a, 6b Metal foil 7 Holding cylinder 8 External lead 9 Base 10 Reflective film 20 Light irradiation device 21 Reflection mirror 21a Top opening 21b Front opening 22 Reflecting surface 23 Cooling air exhaust port

Claims (2)

A pair of electrodes are arranged oppositely in a long quartz glass arc tube, and a metal is enclosed as a luminescent material,
In a long arc discharge lamp in which a band-shaped reflective film mainly composed of silica particles is formed on the entire outer surface of the arc tube over the entire emission length,
The OH group content of the tube wall of the arc tube is 50 ppm to 300 ppm,
The long arc type discharge lamp, wherein the reflective film has an OH group content of 100 ppm or more. The long arc discharge lamp of claim 1;
A bowl-shaped reflecting mirror having a reflecting surface surrounding the long arc type discharge lamp and having an opening corresponding to the upper part of the long arc type discharge lamp;
The light irradiation apparatus characterized by comprising.

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