JP6904111B2 - Discharge lamp - Google Patents

Description

Embodiments of the present invention relate to discharge lamps.

Conventionally, an ultraviolet irradiation device used for an exposure process of a semiconductor, a drying process of an ultraviolet ink or an ultraviolet paint, a curing process of a resin, or the like is known. The ultraviolet irradiation device includes a discharge lamp that emits light when an electrode provided in the arc tube discharges.

JP-A-2009-259790

However, there is room for improvement in the conventional discharge lamp in terms of improving the stability of discharge. Specifically, due to the characteristics of the power supply that supplies the current, when switching the polarity of the electrodes, there is a period during which the current is temporarily suspended, and if this period is long, the discharge cannot be maintained and the lamp may turn off. there were.

Further, in recent years, the diameter of the electrode tends to increase as the output of the discharge lamp increases. If the diameter of the electrode is increased, the discharge cannot be maintained in the standby mode in which the power to be supplied is reduced, and the lamp may be turned off.

An object of the present invention to be solved is to provide a discharge lamp capable of improving the stability of discharge.

The discharge lamp according to the embodiment includes an arc tube and an electrode. The electrode discharges in the arc tube. Further, the ratio of the current density of the electrode to the ratio of the rest period of the current accompanying the switching of the polarity of the electrode in the half cycle of the current supplied to the discharge lamp is 0.3 or more.

According to the present invention, the stability of discharge can be improved.

It is sectional drawing of the discharge lamp which concerns on embodiment. It is a figure which shows the lighting waveform of the discharge lamp which concerns on embodiment. It is a figure which shows the relationship between the current rest period, the current density and the extinguishing of a discharge lamp which concerns on embodiment. It is a figure which shows the relationship between the electrode diameter, the current and the blackening of a discharge lamp which concerns on embodiment. It is a figure which shows the relationship of the electrode diameter, the current and the current density which concerns on embodiment.

The discharge lamp according to the embodiment described below includes an arc tube and an electrode. The electrode discharges in the arc tube. Further, the ratio of the current density of the electrode to the ratio of the rest period of the current accompanying the switching of the polarity of the electrode in the half cycle of the current supplied to the discharge lamp is 0.3 or more.

Further, in the discharge lamp according to the embodiment described below, a current having a current density of 1.5 A / mm ² or more and 15 A / mm ² or less is supplied to the discharge lamp.

Further, in the discharge lamp according to the embodiment described below, the discharge lamp is lit in the normal lighting mode and the standby mode in which the current value supplied is lower than that in the normal lighting mode. Further, in the normal lighting mode, the discharge lamp is ^{supplied with a current having a current density of 15 A / mm 2} or less, and in the standby mode, a current having a current density of 1.5 A / mm ² or more is supplied.

Further, in the discharge lamp according to the embodiment described below, a rectangular wave current is supplied to the discharge lamp.

Hereinafter, the discharge lamp according to the embodiment will be described with reference to the drawings. In the embodiment, the same parts are designated by the same reference numerals, and duplicate description is omitted.

(Embodiment)
First, a configuration example of the discharge lamp 1 according to the embodiment will be described with reference to FIG. FIG. 1 is a cross-sectional view of the discharge lamp 1 according to the embodiment.

The discharge lamp 1 shown in FIG. 1 is used as a light source that emits ultraviolet rays in, for example, an ultraviolet irradiation device. Further, the ultraviolet irradiation device is used in a step requiring a photochemical reaction by ultraviolet rays, such as a semiconductor exposure step, a drying step of an ultraviolet curable ink or an ultraviolet curable paint, and a curing step of an ultraviolet curable resin.

Further, the discharge lamp 1 is a so-called high-intensity discharge lamp (HID: High Intensity Discharge lamp) such as a mercury lamp or a metal halide lamp. As shown in FIG. 1, the discharge lamp 1 according to the embodiment includes an arc tube 2, an electrode 3, a base member 4, and a lead wire 5.

The arc tube 2 is formed in a cylindrical shape by quartz glass having transmitted light, and has a discharge space 2a inside. Noble gases such as argon and xenon and mercury are sealed in the discharge space 2a, and in addition to these, metal halides such as iron, tin and iodine are sealed.

Further, for example, a columnar sealing portion 2b is formed at both ends of the arc tube 2. The sealing portion 2b seals a part of the electrode 3, a part of the conducting wire 6, and the metal foil 7. The lead wire 6 electrically connects the lead wire 5 and the metal foil 7, which will be described later. The metal foil 7 is made of molybdenum or the like.

The electrodes 3 are provided at both ends of the arc tube 2 so as to face each other, and discharge in the discharge space 2a of the arc tube 2. The electrode 3 has an electrode shaft 31 and a coil 32. The electrode shaft 31 is, for example, a metal member containing tungsten, one end of which is arranged in the discharge space 2a of the arc tube 2, and the other end of which is connected to the metal foil 7 and sealed by the sealing portion 2b. Has been done.

The coil 32 is provided in the discharge space 2a and is wound around the electrode shaft 31. Further, the coil 32 is wound around a portion of the electrode shaft 31 other than the tip portion 31a. As a result, the electric discharge is performed only at the tip portion 31a of the electrode shaft 31. That is, the portion of the electrode shaft 31 around which the coil 32 is wound is not discharged. As a result, the temperature rise of the electrode 3 can be suppressed.

The base member 4 is formed in a bottomed cylindrical shape, for example, and is joined to the sealing portion 2b of the arc tube 2 by filling the inside with an adhesive member, for example. The lead wire 5 is arranged outside the arc tube 2, one end of which is connected to the lead wire 6 and the other end of which is connected to the lighting circuit 100. The lead wire 5 and the lead wire 6 are connected via, for example, a connecting portion 4a formed by welding.

The lighting circuit 100 supplies a current to the electrode 3. Specifically, the lighting circuit 100 is connected to a power supply unit (not shown) and supplies an alternating current supplied from the power supply unit to the electrode 3 via the lead wire 5. Further, the lighting circuit 100 has a normal lighting mode and a standby mode. In other words, the discharge lamp 1 is lit in the normal lighting mode and the standby mode.

The normal lighting mode is, for example, a mode used at the timing when the light of the discharge lamp 1 is irradiated to an object to be irradiated (not shown), and is a mode in which the light is lit with a relatively high power. The standby mode is, for example, a mode used in a section between a plurality of irradiated objects flowing on a conveyor, and is a mode in which lighting is performed with a relatively low electric power. That is, in the standby mode, the supplied current value is smaller than that in the normal lighting mode. The details of the normal lighting mode and the standby mode will be described later.

Next, the lighting waveform of the discharge lamp 1 will be described with reference to FIG. FIG. 2 is a diagram showing a lighting waveform according to the embodiment. FIG. 2 shows the waveform of the alternating current supplied by the lighting circuit 100 to the electrode 3 of the discharge lamp 1.

As shown in FIG. 2, the lighting circuit 100 supplies a square wave current. In other words, a rectangular wave current is supplied to the discharge lamp 1. As shown in FIG. 2, the current value supplied to the discharge lamp 1 by the lighting circuit 100 changes to “+ A” and “−A” with the passage of time. The current of the square wave fluctuates between "+ A" and "-A" with the current value being zero. That is, the polarity of the electrode 3 is switched according to the fluctuation of the applied current. The current supplied by the lighting circuit 100 to the discharge lamp 1, in other words, the current supplied to the discharge lamp 1 is not limited to a square wave, and if it is a high frequency, it may be a sine wave, a triangular wave, a sawtooth wave, or the like. May be good.

Further, the period in which the current value returns to zero again after passing through "+ A" and "-A" starting from zero is one lighting cycle. Specifically, one lighting cycle includes a lighting half cycle that returns from zero to zero via "+ A" and a lighting half cycle W1 that returns from zero to zero via "-A".

Further, the lighting half cycle W1 includes a current pause period W2. In other words, the current supplied by the lighting circuit 100 to the discharge lamp 1 has a current pause period W2 at a predetermined ratio with respect to a half cycle of the current (lighting half cycle W1). The current pause period W2 is a current pause section associated with the switching of the polarity of the electrode 3. During the current suspension period W2, since the current value is zero, the discharge is also stopped. Since the current suspension period W2 is a very short time, it seems to the naked eye that the discharge lamp 1 continues to light even if the discharge is stopped.

Here, the current pause period W2 has a different length depending on the quality of the circuit in the power supply unit (not shown). In general, the higher the quality of the circuit that supplies power from the power supply unit to the lighting circuit 100, the shorter the current pause period W2, and the lower the quality of the circuit, the longer the current pause period W2. That is, when connected to a power supply unit having a low circuit quality, the current suspension period W2 becomes long, so that the stability of discharge becomes low and the lamp may go out.

In addition, in recent years, as the output of the discharge lamp 1 has increased, the diameter of the electrode 3 has tended to increase. When the diameter of the electrode 3 is increased, the discharge cannot be maintained in a mode such as a standby mode in which the supply power is reduced, and the lamp may be turned off. As described above, it is desired to improve the stability of the discharge in the discharge lamp 1.

Therefore, the discharge lamp 1 according to the embodiment is supplied with a current in which the ratio of the current density to the ratio of the current rest period W2 in the lighting half cycle W1 is 0.3 or more. This point will be described with reference to FIG.

FIG. 3 is a diagram showing the relationship between the current pause period W2, the current density, and the extinguishing of the discharge lamp 1 according to the embodiment. The current density is calculated by the current effective value (A) / electrode tip surface area (mm ^2). The electrode tip surface area is calculated by: electrode tip surface area = radius × radius × π using the radius of the tip portion 31a in the electrode 3. That is, the circular area of the tip portion 31a is calculated as the surface area of the electrode tip.

The table shown in FIG. 3 includes items such as "current density / X", "number of extinctions during 1000 hours of lighting", and "occurrence rate of extinction". “Current density / X” indicates the ratio of the current density to the ratio (X) of the current pause period W2 in the lighting half cycle W1.

The "number of extinguished lamps during 1000 hours of lighting" indicates the number of extinguished lamps 1 out of 10 discharge lamps 1. The "disappearance occurrence rate" is a percentage of the "number of extinctions during 1000 hours of lighting".

For example, when "current density / X" is "1.0", it means that the number of extinguished discharge lamps 1 is 0, that is, the extinction rate is 0%. On the other hand, in the example shown in FIG. 3, when the "current density / X" is "0.2", the number of extinguished discharge lamps 1 is 10, that is, the extinction rate is 100%.

That is, as shown in FIG. 3, the lighting circuit 100 preferably supplies a current having a "current density / X" of 0.3 or more. Thereby, the stability of the discharge in the discharge lamp 1 can be improved. Further, more preferably, the lighting circuit 100 supplies a current having a "current density / X" of 0.4 or more. Thereby, the stability of the discharge can be further improved.

Next, the relationship between the radius of the electrode 3, the current value, and the blackening of the discharge lamp 1 will be described with reference to FIGS. 4 and 5. FIG. 4 is a diagram showing the relationship between the electrode diameter, the current, and the blackening of the discharge lamp 1 according to the embodiment. FIG. 5 is a diagram showing the relationship between the electrode diameter, the current, and the current density according to the embodiment. Blackening is a phenomenon that occurs when substances constituting the electrode 3 are scattered and adhere to the arc tube 2 due to a load due to electric discharge.

FIG. 4 shows the result of evaluating the blackening state of the discharge lamp 1 after 1000 hours of lighting in three stages. “○” indicates a state in which almost no blackening occurs, “Δ” indicates a state in which a part is blackened, and “×” indicates a state in which the material is significantly blackened. Further, FIG. 5 shows the current density at the time of such evaluation. In addition, in FIG. 4 and FIG. 5, it is assumed that “current density / X” (see FIG. 3) is 0.3 or more.

As shown in FIGS. 4 and 5, when the current density is 1.5 A / mm ² or more and 15 A / mm ² or less, the discharge lamp 1 is in a good state without blackening. That is, the life of the discharge lamp 1 can be extended by setting the current density supplied to the discharge lamp 1 to 1.5 A / mm ² or more and 15 A / mm ^{2 or less.} Further, more preferably, the current density supplied to the discharge lamp 1 is 2.0 A / mm ² or more and 8.5 A / mm ² or less. As a result, the life of the discharge lamp 1 can be further extended.

More specifically, the lighting circuit 100 supplies a current having a current density of 15 A / mm ² or less in the normal lighting mode, and a current having a current density of 1.5 A / mm ² or more in the standby mode. Supply. In other words, the discharge lamp 1 ^{is supplied with a current having a current density of 15 A / mm 2} or less in the normal lighting mode, and a current having a current density of 1.5 A / mm ² or more in the standby mode. Will be done.

When referring to the result shown in FIG. 5, when the "electrode diameter" is 1.5 mm and the "current" in the normal lighting mode is 15 A, the discharge lamp 1 even if the "current" in the standby mode is reduced to 4 A. Can be maintained in good condition without blackening. Further, in FIG. 5, since the “current density / X” (see FIG. 3) is 0.3 or more, the discharge lamp 1 does not go out.

That is, it is possible to improve the stability of the discharge and extend the life of the discharge lamp 1. Moreover, since stable discharge can be performed even in the standby mode, power saving can be realized.

As described above, the discharge lamp 1 according to the embodiment includes a light emitting tube 2 and an electrode 3. The electrode 3 discharges in the arc tube 2. Further, the ratio of the current density of the electrode 3 to the ratio of the current pause period (current pause period W2) accompanying the switching of the polarity of the electrode 3 in the half cycle of the current supplied to the discharge lamp 1 (lighting half cycle W1) is 0. .3 or more. Thereby, the stability of the discharge in the discharge lamp 1 can be improved.

In the above-described embodiment, the discharge lamp 1 used in the ultraviolet irradiation device has been described, but the discharge lamp 1 is not limited to the discharge lamp 1 of the ultraviolet irradiation device, and any discharge lamp that discharges between electrodes can be used. You may.

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, as well as in the scope of the invention described in the claims and the equivalent scope thereof.

1 Discharge lamp 2 Light emitting tube 2a Discharge space 2b Sealing part 3 Electrode 4 Mouthpiece member 5 Lead wire 6 Conductor wire 7 Metal leaf 31 Electrode shaft 32 Coil 100 Lighting circuit W1 Lighting half cycle W2 Current pause period

Claims (4)

A discharge lamp comprising an arc tube and an electrode for discharging in the arc tube;
Ri der ratio of 0.3 or more current density of the electrode with respect to the proportion of idle period of the current due to the switching of the polarity of the electrodes in the half period of the current supplied to the discharge lamp,
The current density is
It is a value obtained by dividing the effective value of the current by the surface area of the tip of the electrode, and the range of the value is 0.8 A / mm ² or more and 19.1 A / mm ² or less.
The current is
With the passage of time, there is a first half cycle in which the current value returns from zero to zero via a positive amplitude, and a second half cycle in which the current value returns from zero to zero via a negative amplitude. And
A discharge lamp having the rest period in which the current value becomes zero between the first half cycle and the second half cycle. The discharge lamp has
The discharge lamp according to claim 1, wherein the current is supplied so that the current density is 1.5 A / mm ² or more and 15 A / mm ^{2 or less.} The discharge lamp
It is lit in the normal lighting mode and the standby mode in which the current value supplied is lower than that of the normal lighting mode.
In the normal lighting mode, the current having a current density of 15 A / mm ² or less is supplied, and in the standby mode, the current having a current density of 1.5 A / mm ² or more is supplied. Item 2. The discharge lamp according to Item 2. The discharge lamp has
The discharge lamp according to any one of claims 1 to 3, wherein the current of a square wave is supplied.

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