JP2009238664A - Discharge lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable a discharge lamp to raise illumination intensity and emit light without limitation on a radiation range. <P>SOLUTION: In the short-arc type discharge lamp having a negative electrode 20 and a positive electrode 30, the surface 34 of a tapered positive electrode diameter-contracting section 31 is finished in a mirror surface. A part of light emitted from a luminance spot H in the vicinity of a pointed head face 23 of the negative electrode 20 is reflected by the surface 34, and the reflected light is radiated outside the lamp at a reflective radiation range R<SB>1</SB>at latitudes of 10-30 °. Here, the reflective radiation range R<SB>1</SB>is put in a direct radiation range R<SB>0</SB>. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a discharge lamp that emits light of a specific wavelength, such as a short arc discharge lamp, and more particularly to an electrode structure that adjusts the light distribution of light.

  In the short arc type discharge lamp, the anode and the cathode are held in the vicinity of the arc tube, and by applying a voltage, an arc discharge is generated between the electrodes, and light of a specific wavelength such as ultraviolet light is emitted. The short arc type discharge lamp can be regarded as a point light source because the distance between the electrodes is short, and light with high radiance can be obtained. For example, when used for forming a wiring pattern on a substrate, light emitted outside the lamp is converted into parallel light through a lens, a mirror, and the like, and is irradiated on an object to be irradiated.

In the case of a small short arc lamp, since it is installed beside the irradiated object, uneven illumination occurs due to the shielding of the reflected light by the arc tube and the sealing tube itself, and a uniform light distribution cannot be obtained. Therefore, in order to obtain a uniform light distribution, a method is known in which the thickness near the center of the arc tube is maximized and the thickness is gradually reduced toward the end of the arc tube (see Patent Document 1). . By changing the refractive index according to the location of the arc tube, the emitted light is concentrated near the center of the arc tube having a large thickness, and the light distribution is made uniform.
JP-A-60-70655

  In the lens refraction effect of the arc tube, the radiation direction is limited, and the light distribution of the light generated by the discharge is determined in a limited range. Further, the light blocked by the electrode inside the arc tube is not guided outside the lamp, and the illuminance of the radiated light does not increase. That is, the light generated by the discharge cannot be effectively extracted outside the lamp.

  The discharge lamp of the present invention includes an arc tube and a pair of electrodes (anode and cathode) held in the arc tube and facing each other with a predetermined interval. At least one of the electrodes includes a body portion and a reduced diameter portion whose diameter decreases toward the electrode front end surface where discharge is performed. For example, the body part formed in a substantially cylindrical shape is supported by the electrode support rod. In the present invention, the surface of the reduced diameter portion is a mirror surface. However, the “mirror surface” means a surface having high reflectivity and good image clarity, and a surface on which a clear image can be obtained when an image is projected on the surface. It should be noted that a part of the surface of the reduced diameter portion being a mirror surface is also included in the mirror surface state.

  The light emitted by the discharge between the electrodes is radiated in the radial direction from the light emission center (hereinafter referred to as a bright spot), and a part of the light hits the surface of the reduced diameter portion and is reflected. At this time, the emitted light is reflected according to the approach angle at the time of reflection. As a result, the reflected light is emitted outside the lamp while traveling toward a predetermined range. For example, the reduced diameter portion may be formed in a tapered shape in order to radiate light in a collective range. In the case of emitting ultraviolet light, the surface of the reduced diameter portion may be a mirror surface with respect to light having a wavelength of 300 to 500 nm.

  Since the surface of the reduced diameter part is a mirror surface, the light generated between the electrodes is reflected without being scattered on the surface of the reduced diameter part, and the reflected light is emitted toward the outside of the lamp. The Thus, the light generated by the discharge can be emitted to the outside of the lamp without waste, and the illuminance of the lamp is improved. In addition, since the surface of the reduced diameter portion is inclined with respect to the axial direction, it is possible to reflect the radiated light from the bright spot to the rear side of the electrode, and the light is not restricted by the light distribution distribution. Can radiate.

  Speaking of the light distribution in the range where the radiated light from the discharge between the electrodes can be emitted directly through the arc tube to the outside of the lamp (hereinafter referred to as the direct radiating range), the light distribution is uniform due to the problem of lamp characteristics. Often not distributed. Therefore, in order to prevent a decrease in illuminance in a part of the range, the range of light reflected from the surface of the reduced diameter portion and radiated to the outside of the lamp (hereinafter referred to as reflected radiation range) is included in the direct radiation range. It should be configured. In this case, the size and shape of the reduced diameter portion of the electrode and the inclination angle of the surface of the reduced diameter portion are determined so that the reflected radiation range is directly superimposed on the radiation range.

  In particular, in order to make the light distribution distribution as uniform as possible in the direct radiation range, it is desirable to configure the reflected radiation range so as to overlap a relatively low illuminance range in the direct radiation range. For example, when the surface of the reduced diameter portion is formed on the anode, the reflected radiation range may be determined on the anode side with respect to a reference surface having a bright spot (such as the cathode tip surface). For example, the reflected radiation range on the anode side is set to an angle range of 10 degrees to 30 degrees toward the anode side.

  In order to prevent the electrode from being overheated, it is preferable to form a groove along the circumferential direction with respect to the reduced diameter portion. The electrode temperature decreases due to heat dissipation. When forming a plurality of grooves, in order to prevent scattered light from being scattered inside the grooves, the surface formed between the grooves of the reduced diameter portion is made to be more than the virtual extension surface with respect to the surface on the tip surface side across the grooves. It is good to form on the shaft side.

  ADVANTAGE OF THE INVENTION According to this invention, lamp illumination intensity can be raised and light can be radiated | emitted without restrict | limiting a radiation range.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic external view of a short arc type discharge lamp according to this embodiment.

  The short arc type discharge lamp 10 includes a light emitting tube 12 made of transparent quartz glass, and a cathode 20 and an anode 30 in the light emitting tube 12, and the cathode 20 and the anode 30 are arranged to face each other with a predetermined interval. On both sides of the arc tube 12, quartz glass sealing tubes 13A and 13B facing each other are formed integrally with the arc tube 12, and both ends of the sealing tubes 13A and 13B are closed by caps 14A and 14B. . The discharge lamp 10 is arranged along the vertical direction so that the anode 30 is on the upper side and the cathode 20 is on the lower side.

  Inside the sealing tubes 13A and 13B, conductive electrode support rods 17A and 17B for supporting the metallic cathode 20 and the anode 30 are disposed, and the conductive lead rod 15A is interposed via the metal foils 16A and 16B. , 15B. The sealing tubes 13A and 13B are welded to glass tubes (not shown) provided in the sealing tubes 13A and 13B, whereby the discharge space formed in the arc tube 12 is sealed. Mercury and a rare gas are enclosed in the arc tube 12.

  The lead rods 15A and 15B are connected to an external power source (not shown), and are connected between the cathode 20 and the anode 30 via the lead rods 15A and 15B, the metal foils 16A and 16B, and the electrode support rods 17A and 17B. A voltage is applied to. As a result, arc discharge occurs between the electrodes, and ultraviolet light is radiated out of the arc tube 12.

  FIG. 2 is a schematic external view of the cathode 20 and the anode 30.

  The cathode 20 includes a cylindrical cathode body portion 22 connected to the electrode support rod 17A and a conical cathode diameter-reduced portion 21. A tip surface 23 of the cathode diameter-reduced portion 21 is configured as a discharge surface. On the other hand, the anode 30 is also composed of a cylindrical anode body portion 32 connected to the electrode support rod 17B and a conical anode reduced diameter portion 31, and the tip end surface 33 of the anode reduced diameter portion 31 is configured as a discharge surface. Yes.

  When arc discharge occurs between the tip surface 23 of the cathode reduced diameter portion 21 and the tip surface 33 of the anode reduced diameter portion 31, ultraviolet light is generated by mercury and radiated in all directions. A light emission center (hereinafter referred to as a bright spot) H when the discharge lamp 10 is used as a point light source is defined near the tip surface 23 of the cathode reduced diameter portion 21, and it is considered that ultraviolet light is emitted from the bright spot H. Can do.

The radiation range of the discharge lamp 10 is determined according to the arrangement and size of the cathode 20 and the anode 30 and the distance between the cathode 20 and the anode 30. The reduced diameter portions 21 and 31 of the cathode 20 and the anode 30 are formed in a tapered shape so as to widen the radiation range. Here, the surfaces 23 and 33 of the reduced diameter portions 21 and 31 are directly connected to the boundary of the radiation range R. It is defined as a surface. However, the radiation range in which the radiated light from the bright spot H is not blocked by the cathode 20 and the anode 30 and proceeds to the outside of the lamp as it is is referred to herein as the direct radiation range _R0 .

In the present embodiment, the tip surfaces 23 and 33 of the cathode 20 and the anode 30 are mirror-finished, and the surface 33 of the anode reduced diameter portion 31 is also mirror-finished. That is, the surface 33 of the anode diameter-reduced portion 31 is a surface having a high reflectance and no irregularities, and the light reflected on the surface 33 is not scattered. The radiation range R ₁ of light reflected from the surface 33 of the anode reduced diameter portion 31 and traveling to the outside of the lamp (hereinafter referred to as the reflected radiation range) R ₁ is included in the direct radiation range R ₀ and is near the anode side boundary. To position.

  FIG. 3 is an enlarged schematic cross-sectional view showing the vicinity of the tip surfaces 23 and 33 of the anodes 20 and 30.

The cathode 20 and the anode 30 are coaxially opposed to each other with a distance interval d, and the anode reduced diameter portion 33 has a tapered inclination angle smaller than that of the cathode reduced diameter portion 23. The diameter of the anode body 32 is M, the diameter of the tip 23 of the cathode 23 is D2, the diameter of the tip 33 of the anode 30 is D1, and the inclination angle of the anode reduced diameter 33 is α. Then, the reflected radiation range R ₁ of the light reflected on the surface 33 of the anode reduced diameter portion 31 follows M, D 1, D 2, d, and α. However, the inclination angle α indicates an angle with respect to the distal end surface 33, and the inclination angle α (= arctan (L) according to the diameter M of the anode body portion 32, the diameter D1 of the distal end surface 33, and the axial length L of the reduced diameter portion 31. / ((M-D1) / 2))).

The reflected radiation range R ₀ is set to a latitude range of 10 ° to 30 ° on the anode side, and so as to satisfy this, that is, the reflected light travels toward this range R ₀ . The size and the inclination angle α are determined. However, a plane (horizontal plane) along the tip surface 23 of the cathode 20 is defined as a reference plane (0 degree), and a positive latitude and a negative cathode side are defined from the reference plane to the anode side. What is necessary is just to obtain | require the size, shape, etc. of the anode diameter reducing part 31 by simulation.

For example, the diameter M of the anode body portion 32 is 25 mm, the axial length L of the anode reduced diameter portion 31 is 5 mm, the diameter D1 of the tip surface 33 of the anode 30 is 8 mm, and the diameter D2 of the tip surface of the cathode 20 is 1.3 mm. , by determining the distance d of the distal end surface 23, 33 and 6 mm, the reflected radiation range _{R 1} is defined in the latitudinal direction of 10 degrees to 30 degrees.

  FIG. 4 is a view showing the spectral reflectance of the surface 33 of the anode reduced diameter portion 31. However, since the anode reduced diameter portion 31 has a tapered shape, the spectral reflectance is measured with respect to a small area of the surface 33 in order to prevent the influence of the curvature. Or you may measure the spectral reflectance of the front end surface 33 finished by the same mirror surface degree.

  FIG. 4 shows the spectral reflectance T2 before mirror processing and the spectral reflectance T1 after mirror processing. The surface 30 of the anode reduced diameter portion 31 is mirror-finished by electrolytic polishing or buffing, and the spectral reflectance after mirror finishing is 40% or more for light in any wavelength region. The short arc type discharge lamp 10 often uses g-line (436 nm), h-line (405 nm) and i-line (365 nm), which are mercury emission lines, and the surface 30 has a wavelength region of about 300 to 500 nm. It has a reflectivity of about 44 percent for light.

  FIG. 5 is a diagram showing a light distribution of a discharge lamp using a conventional electrode, that is, an electrode having a reduced diameter portion that is not mirror-finished. FIG. 6 is a view showing a light distribution of the discharge lamp using the electrode according to the present embodiment.

  The light distribution Q shown in FIGS. 5 and 6 is obtained by measuring the irradiance in the vertical direction, that is, in the latitudinal direction among the light emitted in the direction of 360 degrees. Here, the light distribution is measured using an illuminometer having sensitivity near the i-line. The vertical axis represents the illuminance. When the illuminance on the reference plane (± 0 °) is 100%, the illuminance along the latitude is represented by the ratio. The only difference between the conventional discharge lamp in FIG. 5 and the discharge lamp of the present embodiment in FIG. 6 is the surface state of the anode reduced diameter portion.

Figure 5, a comparison of the area defined by reference numeral N in Figure 6, in this embodiment, + 10 ° to 30 ° range on the anode side, i.e. the reflected radiation range R _1, the illuminance is increased. In the discharge lamp of FIG. 5, since the light reflected by the surface of the anode reduced diameter portion is scattered, the illuminance decreases in the latitude range of 10 degrees to 30 degrees on the anode side. On the other hand, in FIG. 6, the illuminance does not decrease much compared to other ranges. This indicates that the light reflected by the surface 34 of the anode reduced diameter portion 32 travels toward a range of 10 to 30 degrees latitude without being scattered. That is, the light distribution as a discharge lamp is a uniform distribution.

  The table shown below represents the measurement results at the representative latitudes in FIGS. As is apparent from the table, the illuminance on the anode side is higher than that of the conventional lamp. In addition, in the latitude range of −50 degrees to +30 degrees, the minimum and maximum range of illuminance in the related art is 70% to 103%, whereas the minimum and maximum range of the present embodiment is 80% to 103%. The light distribution is uniform.

  In addition, also when it measures with the illuminometer which has sensitivity in the vicinity of 250 nm and 420 nm, it is confirmed that the illuminance is high in the range of +10 degrees to 30 degrees.

Thus, according to this embodiment, in the short arc type discharge lamp 10, the surface 34 of the tapered anode reduced diameter portion 31 is finished to be a mirror surface. A part of the light emitted from the bright point H on the tip surface 23 near the cathode 20 is reflected by the surface 34, it is emitted to the lamp outside the reflected radiation range R ₁ of 10 to 30 degrees latitude. The reflected radiation range R ₁ is included in the direct radiation range R ₀ , and the size, shape, and inclination angle of the anode reduced diameter portion 31 so that the reflected radiation range R ₁ is determined in the range of latitude 10 degrees to 30 degrees. α is determined.

Since the surface 34 of the anode reduced-diameter portion 31 is a mirror surface, light reflected on the surface 34 is not scattered, the process proceeds to the reflected radiation range R _1. In particular, the irradiance is improved in the range of latitude +10 degrees to +30 degrees where the illuminance tends to decrease, and the light distribution is made uniform. That is, light can be emitted by making maximum use of light generated by discharge.

  Note that the inclination angle α of the anode diameter-reduced portion 31 is determined so that the reflected light travels in the latitude range of 10 to 30 degrees, but is configured to reflect the emitted light toward the predetermined latitude range. May be. For example, the inclination angle may be determined so that the radiated light travels toward the latitude range where the irradiation illuminance falls relatively in accordance with the light distribution characteristics of the discharge lamp.

  Next, the discharge lamp which is 2nd Embodiment is demonstrated using FIG. In the second embodiment, the anode reduced diameter portion is formed on the concave surface.

  FIG. 7 is a schematic sectional view showing electrodes of a discharge lamp according to the second embodiment. The cathode 120 and the anode 130 of the discharge lamp 100 are disposed opposite to each other, the surface 134 of the anode reduced diameter portion 131 is a concave mirror surface, and the cross-sectional shape is formed in a curved shape. Thereby, the radiation range of the radiated light reflected by the surface 134 becomes narrow. In addition, what is necessary is just to make an anode diameter-reduced part convex shape, when expanding a reflected radiation range.

  Next, the discharge lamp which is 3rd Embodiment is demonstrated using FIG. 8, FIG. In the third embodiment, a groove is formed along the circumferential direction of the anode reduced diameter portion. About another structure, it is the same as 1st Embodiment.

  FIG. 8 is a schematic cross-sectional view of an electrode of a discharge lamp according to the third embodiment. FIG. 9 is an enlarged schematic cross-sectional view of the vicinity of the groove of the anode reduced diameter portion.

  The cathode 220 and the anode 230 of the discharge lamp 200 are disposed to face each other, and a plurality of grooves 235A, 235B, and 235C are formed in the anode reduced diameter portion 231 of the anode 230 along the circumferential direction. The heat radiation effect is generated by the grooves 235A to 235B, and the temperature of the anode 230 is lowered. In FIG. 9, the radiated light is illustrated as parallel light for convenience.

  The surfaces 234A to 234D of the anode reduced diameter portion 23 formed between the grooves 235A, 235B, and 235C have different surface formation positions. That is, no surface rests on one conical surface. As shown in FIG. 9, the surface of the surface 234 </ b> B is located closer to the electrode axis side than the virtual extension surface T of the surface 234 </ b> C near the tip surface 233. Thereby, the emitted light enters the inside of the groove and the light is prevented from scattering inside the groove, and the surfaces 234A to 234D of the anode reduced diameter portion 231 are effectively used as mirror surfaces. Note that the effect ratio of heat dissipation and reflection may be adjusted by adjusting the groove formation interval.

  Regarding the surface formation of the anode 234, grooves 235A to 235C are formed by a laser or a diamond cutter, and after the grooves are formed, the surface between the grooves is cut at a predetermined position at a predetermined angle. Then, mirror finishing is performed by buffing or electrolytic polishing.

  The anode diameter-reduced portion may be other than a tapered shape or a concave shape, and a plurality of tapered surfaces having different inclination angles may be integrally formed. Alternatively, it may be formed in a bullet shape or a spherical shape. Further, the surface of the reduced diameter portion of the cathode, not the anode, may be mirror-like. As for the specularity of the reduced diameter portion, it is sufficient that the surface state has good reflectivity and image clarity so that light is not scattered. Further, the discharge lamp 10 may be arranged in a direction other than the vertical direction, and may be applied to a discharge lamp other than the short arc type.

It is a schematic external view of the short arc type discharge lamp which is this embodiment. It is a schematic external view of a cathode and an anode. It is the schematic sectional drawing which expanded and showed the front end surface vicinity of the anode. It is the figure which showed the spectral reflectance of the surface of an anode diameter reduction part. It is the figure which showed the light distribution of the discharge lamp using the conventional type electrode. It is the figure which showed the light distribution of the discharge lamp using the electrode by this embodiment. It is the schematic sectional drawing which showed the electrode of the discharge lamp which is 2nd Embodiment. It is a schematic sectional drawing of the electrode of the discharge lamp which is 3rd Embodiment. It is the schematic sectional drawing which expanded the groove vicinity of the extremely reduced diameter part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Discharge lamp 12 Light emission tube 13A, 13B Sealing tube 17A, 17B Electrode support rod 20, 120, 220 Cathode 21 Cathode diameter-reduced part 22 Cathode body part 23 Tip surface 24 Surface 30, 130, 230 Anode 31, 131, 231 Anode Reduced diameter portion 32, anode body portion 33, 133, 233 Tip surface 34, 134, 234A to 234D Surface 235A to 235C Groove H Bright point R ₀ Direct radiation range R ₁ Reflected radiation range α Inclination angle Q Light distribution

Claims (9)

Arc tube,
A pair of electrodes held in the arc tube and facing each other at a predetermined interval;
At least one of the pair of electrodes has a body portion and a reduced diameter portion whose diameter decreases toward an electrode tip surface where discharge is performed,
The discharge lamp characterized in that the surface of the reduced diameter portion is a mirror surface, and light generated between the pair of electrodes is reflected by the surface of the reduced diameter portion and radiated to the outside of the lamp.   The reflected radiation range of the light reflected from the surface of the reduced diameter portion and emitted to the outside of the lamp is included in the direct emission range of the light directly emitted to the outside of the lamp. Discharge lamp.   The discharge lamp according to claim 2, wherein the reflected radiation range overlaps a range having a relatively low illuminance within the direct radiation range. The surface of the reduced diameter portion is formed on the anode,
4. The discharge lamp according to claim 3, wherein the reflected radiation range is determined on the anode side with respect to a reference surface having a bright spot.   The discharge lamp according to claim 4, wherein the reflected radiation range is set to an angle range of 10 degrees to 30 degrees on the anode side with respect to the reference plane.   The discharge lamp according to claim 1, wherein the reduced diameter portion is formed in a tapered shape.   The discharge lamp according to any one of claims 1 to 6, wherein the reduced diameter portion has a groove along a circumferential direction. In the reduced diameter portion, a plurality of grooves are formed at predetermined intervals,
The discharge lamp according to claim 7, wherein a surface formed between the grooves of the reduced diameter portion is formed on an axial side with respect to a virtual extension surface with respect to a surface on a tip surface side across the groove. . 9. The discharge lamp according to claim 1, wherein the surface of the reduced diameter portion is a mirror surface with respect to light having a wavelength of 300 to 500 nm.

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