JP2019012613A - Discharge lamp - Google Patents

Abstract

To provide a discharge lamp capable of improving discharge stability.SOLUTION: A discharge lamp according to an embodiment includes an arc tube and an electrode. The electrode discharges in the arc tube. In the discharge lamp, a ratio of the current density of the electrode to a proportion of a pause period of a current accompanying switching of the polarity of the electrode in the half period of the current supplied to the discharge lamp is 0.3 or more.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to a discharge lamp.

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

JP 2009-259790 A

  However, the conventional discharge lamp has room for improvement in terms of improving discharge stability. Specifically, due to the characteristics of the power supply that supplies the current, there is a period in which the current temporarily stops when the polarity of the electrode is switched, and if this period becomes longer, the discharge cannot be maintained and the lamp may turn off. there were.

  Furthermore, in recent years, the electrode tends to become thicker as the output of the discharge lamp increases. When 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 extinguished.

  An object of the present invention 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 switching of the polarity of the electrode in a half cycle of the current supplied to the discharge lamp is 0.3 or more.

  According to the present invention, discharge stability 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 electric current rest period concerning embodiment, a current density, and the extinction of a discharge lamp. It is a figure which shows the relationship between the electrode diameter which concerns on embodiment, an electric current, and blackening of the discharge lamp. It is a figure which shows the relationship between the electrode diameter which concerns on embodiment, an electric current, and current density.

  A discharge lamp according to an embodiment described below includes an arc tube and an electrode. The electrode discharges in the arc tube. Further, the ratio of the electrode current density 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.

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

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. The discharge lamp is supplied with a current having a current density of 15 A / mm ² or less in the normal lighting mode, and supplied with a current having a current density of 1.5 A / mm ² or more in the standby mode.

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

  Hereinafter, a discharge lamp according to an embodiment will be described with reference to the drawings. In the embodiment, the same parts are denoted by the same reference numerals, and redundant 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 a discharge lamp 1 according to an embodiment.

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

  The discharge lamp 1 is a so-called high intensity discharge lamp (HID) 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 cap 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. The discharge space 2a is filled with a rare gas such as argon or xenon, or mercury, and in addition, a metal halide such as iron, tin, or iodine is sealed therein.

  Moreover, the cylindrical sealing part 2b is formed in the both ends of the arc tube 2, for example. The sealing part 2 b seals a part of the electrode 3, a part of the conducting wire 6, and the metal foil 7. The conducting wire 6 electrically connects a lead wire 5 and a metal foil 7 described later. The metal foil 7 is made of molybdenum or the like.

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

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

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

  The lighting circuit 100 supplies 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. 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 that is used at a timing when the light of the discharge lamp 1 is irradiated to an object to be irradiated (not shown), and is a mode that is lit with relatively high power. The standby mode is, for example, a mode that is used in a section between a plurality of irradiated objects that flow on the conveyor, and is a mode that lights up with relatively low power. That is, the supplied current value is smaller in the standby mode than in the normal lighting mode. 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 illustrating a lighting waveform according to the embodiment. In FIG. 2, the waveform of the alternating current that the lighting circuit 100 supplies to the electrode 3 of the discharge lamp 1 is shown.

  As shown in FIG. 2, the lighting circuit 100 supplies a rectangular 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” over time. The square-wave current varies between “+ A” and “−A” with the current value centered at zero. That is, the polarity of the electrode 3 is switched according to the fluctuation of the current. Note that the current supplied to the discharge lamp 1 by the lighting circuit 100, in other words, the current supplied to the discharge lamp 1 is not limited to a rectangular wave, and may be a sine wave, a triangular wave, a sawtooth wave, or the like if the frequency is high. Also good.

  In addition, a period in which the current value returns to zero after passing through “+ A” and “−A” with zero as the starting point is one lighting cycle. Specifically, one lighting cycle includes a lighting half cycle that returns from zero through “+ A” to zero and a lighting half cycle W1 that returns from zero through “−A” to zero.

  The lighting half cycle W1 includes a current pause period W2. In other words, the current supplied from the lighting circuit 100 to the discharge lamp 1 includes the current rest period W2 at a predetermined ratio with respect to the half cycle of the current (lighting half cycle W1). The current pause period W2 is a current pause period associated with the switching of the polarity of the electrode 3. During the current pause period W2, since the current value is zero, the discharge is also stopped. It should be noted that since the current rest period W2 is very short, the discharge lamp 1 seems to continue to be lit by the naked eye even when the discharge is stopped.

  Here, the length of the current pause period W2 varies 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 circuit quality, the longer the current pause period W2. That is, when connected to a power supply unit with low circuit quality, the current pause period W2 becomes longer, so that the discharge stability is lowered and the lamp may be turned off.

  In addition, in recent years, as the output of the discharge lamp 1 increases, the electrode 3 tends to have a larger diameter. When the diameter of the electrode 3 is increased, the discharge cannot be maintained in the mode in which the supplied power is reduced, such as the standby mode, and the lamp may be extinguished. Thus, it is desired to improve the discharge stability in the discharge lamp 1.

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

FIG. 3 is a diagram illustrating a relationship between the current pause period W2, the current density, and the extinction 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 using the radius of the tip 31a of the electrode 3 as follows: electrode tip surface area = radius × radius × π. That is, the circular area of the tip 31a is calculated as the electrode tip surface area.

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

  “Number of extinctions during 1000 hours of lighting” indicates the number of 10 discharge lamps 1 that have disappeared. 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”, zero discharge lamps 1 are extinguished, that is, the extinction rate is 0%. On the other hand, in the example shown in FIG. 3, when “Current density / X” is “0.2”, 10 discharge lamps 1 have disappeared, that is, the extinction rate is 100%.

  That is, as shown in FIG. 3, it is preferable that the lighting circuit 100 supply a current with “current density / X” being 0.3 or more. Thereby, the stability of the discharge in the discharge lamp 1 can be improved. More preferably, the lighting circuit 100 supplies a current with “current density / X” being 0.4 or more. Thereby, the stability of 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 illustrating the relationship between the electrode diameter, current, and blackening of the discharge lamp 1 according to the embodiment. FIG. 5 is a diagram illustrating a relationship among 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 scatter and adhere to the arc tube 2 with a load due to discharge.

  FIG. 4 shows the result of evaluating the blackened state of the discharge lamp 1 after lighting for 1000 hours in three stages. “◯” indicates a state in which the film is hardly blackened, “Δ” indicates a partially blackened state, and “x” indicates a state in which the blackened remarkably. Moreover, in FIG. 5, the current density in the case of this evaluation is shown. In FIGS. 4 and 5, “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 that is not blackened. 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. 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. Thereby, the lifetime of the discharge lamp 1 can be further extended.

More specifically, the lighting circuit 100 supplies a current with a current density of 15 A / mm ² or less in the normal lighting mode, and a current with 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 supplied with a current having a current density of 1.5 A / mm ² or more in the standby mode. Is done.

  Referring to the results shown in FIG. 5, when the “electrode diameter” is 1.5 mm and the “current” in the normal lighting mode is set to 15 A, the discharge lamp 1 can be used even if the “current” in the standby mode is reduced to 4 A. A good state can be maintained without blackening. In FIG. 5, since “current density / X” (see FIG. 3) is 0.3 or more, the discharge lamp 1 does not disappear.

  That is, it is possible to improve both the stability of discharge and extend the life of the discharge lamp 1. In addition, 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 the arc tube 2 and the electrode 3. The electrode 3 discharges in the arc tube 2. In addition, the ratio of the current density of the electrode 3 to the ratio of the current rest period (current rest period W2) associated with the switching of the polarity of the electrode 3 in the half cycle (lighting half period W1) of the current supplied to the discharge lamp 1 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 apparatus has been described. However, the discharge lamp 1 is not limited to the discharge lamp 1 of the ultraviolet irradiation apparatus, and any discharge lamp may be used as long as it is a discharge lamp that discharges between electrodes. May be.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example 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 spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 Discharge lamp 2 Arc tube 2a Discharge space 2b Sealing part 3 Electrode 4 Cap member 5 Lead wire 6 Conductor 7 Metal foil 31 Electrode shaft 32 Coil 100 Lighting circuit W1 Lighting half cycle W2 Current rest period

Claims (4)

A discharge lamp comprising: an arc tube; and an electrode for discharging within the arc tube;
A discharge lamp in which a ratio of a current density of the electrode to a ratio of a rest period of the current accompanying switching of polarity of the electrode in a half cycle of a current supplied to the discharge lamp is 0.3 or more. The discharge lamp includes
The discharge lamp according to claim 1, wherein the current is supplied such that the current density is 1.5 A / mm ² or more and 15 A / mm ² or less. The discharge lamp is
It is lit in the normal lighting mode and the standby mode in which the current value supplied is lower than the normal lighting mode,
The current at which the current density is 15 A / mm ² or less is supplied in the normal lighting mode, and the current at which the current density is 1.5 A / mm ² or more is supplied in the standby mode. Item 3. A discharge lamp according to Item 2. The discharge lamp includes
The discharge lamp according to claim 1, wherein the rectangular wave current is supplied.

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