TWI500067B - Discharge lamp - Google Patents

Description

Discharge lamp

The present invention relates to an electrodeless discharge lamp such as an excimer lamp or an external electrode type fluorescent lamp that discharges light by dielectric barrier discharge or capacitive coupling type high-frequency discharge, and more particularly The electrode of the lamp is constructed.

In the double-tube type excimer lamp, the light-emitting portion is formed by two coaxial tubes of a long axis, and high-pressure gas is sealed in the light-emitting tube, and the inner surface of the inner tube and the outer surface of the outer tube are axially arranged along the axial direction. Set a pair of electrodes. Then, light emission is discharged by applying a high-frequency voltage of several thousand volts between the electrodes (for example, refer to Patent Document 1).

Further, in a discharge lamp having a single-tube structure such as an external electrode type fluorescent lamp, a strip-shaped electrode covered with a dielectric is disposed along an axial direction inside the discharge tube, and is disposed in the discharge tube. Discharge luminescence is performed between external electrodes on the outer surface (refer to Patent Document 2).

[First technical literature]

[Patent Literature]

[Patent Document 1] JP-A-6-275242

[Patent Document 2] Japanese Patent Publication No. 11-283579

In a conventional discharge lamp, the electrode inside the discharge tube is cylindrical or thin, and its cross-sectional shape is circular or rectangular. With such a cross-sectional shape, in order to discharge between the electrode in the dielectric and the electrode located outside the discharge tube, very large electric power is required, and the lighting of the lamp is started slowly.

If a large amount of power is supplied to the lamp, the difference in thermal expansion between the dielectric covering the electrode and the electrode makes the electrode easily peel off from the dielectric, and the electrode material is oxidized due to exposure of the electrode material to the discharge space.

The discharge lamp of the present invention is a discharge lamp that emits light by dielectric barrier discharge or capacitive coupling type high-frequency discharge, etc., and has: a discharge tube sealed with a discharge gas; at least one strip electrode disposed at the above Inside the discharge vessel; and at least one dielectric covering the electrodes. The strip electrode such as a foil electrode is buried in the dielectric and is not exposed to the discharge space. The gas enclosed in the discharge space is arbitrary, and a rare gas monomer or a halogen monomer such as chlorine or a mixed gas of a halogen and a rare gas may be enclosed.

In the present invention, the thickness of at least one of the two edges of the electrode along the longitudinal direction is thinner than the central portion of the electrode. Thereby, an electric field concentration effect occurs at the edge portion of the thin electrode, and the electric field strength is enhanced. As a result, a discharge will still occur between the electrodes at a relatively low input voltage.

It is also possible to cover a plurality of electrodes together with one dielectric material, or to cover the respective electrodes with different dielectric materials. It is preferable that the thickness of both edges of the strip electrode is thinner than the thickness of the central portion of the electrode, and the lighting startability is improved at both ends of the electrode.

As the shape of the electrode, various shapes which are sharpened toward the edge and sharpened at the tip end can be applied, but it is preferable that the blade shape is a shape which is smoothly pointed toward the edge portion. Thereby, the cross-section of the edge portion is linear in the axial direction, and the discharge starting voltage can be further lowered. Further, it is difficult to form a gap at the boundary portion with the coated dielectric by the blade shape, and peeling or the like is less likely to occur.

For the electrode configuration, one side of the electrode may be disposed outside the discharge tube, or the electrode may be formed only inside the discharge tube. For example, a plurality of strip electrodes having the same polarity are disposed in the discharge tube, and electrodes are disposed outside the discharge tube. In this case, in consideration of emitting uniform light from the entire discharge tube, a plurality of strip electrodes may be disposed in a state in which their width directions are parallel to each other. Alternatively, a plurality of strip electrodes may be disposed at a position symmetrical with respect to the discharge tube axis.

On the other hand, a plurality of strip electrodes having different polarities can be disposed in the discharge tube. In this case, it is conceivable that the plurality of strip electrodes are arranged to be uniformly distributed from the entire discharge tube, and the plurality of strip electrodes may be disposed at a position symmetrical with respect to the discharge tube axis. Further, by making the width directions of the plurality of strip electrodes the same direction, that is, parallel to each other, overall radiation is also achieved.

For example, in the case where an electrode lamp is disposed outside the discharge tube, in order to increase the electric field strength with the electrode edge portion, the strip electrode may be coaxially disposed in the discharge tube to have a width direction of the electrode and a radial direction inside the discharge tube. Consistent. Thereby, the electric field intensity in the extending direction of the edge portion of the electrode is maximized, and the lighting starting voltage can be depressed.

The material of the electrode can be formed from a highly conductive metal or alloy. The thickness of the electrode is preferably set in consideration of current capacity, expansion coefficient, and the like, and is set, for example, in the range of any value of 20 μm to 50 μm. Further, the width of the electrode is preferably set in consideration of the current capacity, and is preferably set in the range of, for example, 1.2 mm to 10 mm.

The thickness of the tube wall of the discharge tube should have a thickness that prevents deterioration of the discharge tube by excimer light, and should be equal to or less than the thickness at which the discharge start voltage and the lighting maintenance voltage are not increased. For example, the wall thickness of the discharge tube is set in the range of 0.8 mm to 1.5 mm. The inner diameter of the discharge tube is preferably such that the illuminance is insufficient due to the short discharge distance, and the discharge is not unstable due to the long discharge distance. For example, it is set in the range of 8 mm to 20 mm.

The dielectric material may be composed of, for example, a columnar dielectric having a circular cross section, and is preferably composed of an insulating material having a thermal expansion coefficient close to that of the electrode at the use temperature. Further, the thickness of the dielectric material is preferably in the range of 0.1 mm to 2 mm in consideration of maintaining the insulating property and preventing the discharge starting voltage from increasing.

The discharge distance between the other electrode having a different polarity from the electrode and the electrode is determined in accordance with the type of the discharge gas, the applied voltage, and the like. In order to prevent the discharge space from being narrow, the illuminance is insufficient, and on the other hand, in order to prevent the discharge from being unstable due to the long discharge distance, the discharge distance can be set in the range of 3 mm to 10 mm.

When the width of the strip electrode is w and the inner diameter of the discharge tube is d, it is preferable that the ratio satisfies "1.6 ≦d/w ≦ 13.4". If the value of d/w is less than 1.6, the area of the foil occupied by the discharge vessel becomes larger, and the discharge distance becomes shorter, and the strip electrode shields the discharge light and causes insufficient illuminance. When the value of d/w is larger than 13.4, the width of the strip electrode is small, and overheating occurs due to an overcurrent, and the discharge distance becomes long and the discharge becomes unstable.

According to the present invention, it is possible to provide a discharge lamp which can improve the startability of the lighting and maintain the illuminance for a long time.

[Best form for implementing the invention]

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

Fig. 1 is a schematic plan view of a discharge lamp of a first embodiment. Fig. 2 is a cross-sectional view taken along line II-II of Fig. 1.

The discharge lamp 10 of the excimer lamp is a discharge tube 20 having a circular cross section made of a dielectric material such as quartz glass; and a rare gas such as helium or the like, or a mixture of the above-mentioned rare gases is enclosed in the discharge tube 20. The gas acts as a discharge gas. The sealing pressure of the discharge gas is set to, for example, 5 kPa to 150 kPa.

Inside the discharge tube 20, a single foil electrode 30 extending in a strip shape along the tube axis C is disposed. The foil electrode 30 is covered with a columnar dielectric 50 having a substantially circular cross section, and is embedded in the dielectric 50 without being exposed to the discharge space.

The foil electrode 30 is coaxially disposed at the center of the dielectric 50 in a state in which the center of the dielectric 50 is aligned in the width direction. Further, the dielectric material 50 is disposed coaxially with the discharge tube 20. Therefore, the foil electrode 30 is disposed at a position coaxial with the discharge tube 20, and is disposed at a position symmetrical with respect to the tube axis C.

As will be described later, the edge portions 30K1, 30K2 are two edges along the tube axis direction of the foil electrode 30, and the edge portions 30K1, 30K2 are formed in a blade shape. Therefore, the thickness of the foil electrode 30 is thinner and thinner from the center toward the edge in the width direction, and the cross-sectional shape of the electrode is a shape in which the tip end is tapered. In the second drawing, the width direction of the foil electrode 30 is set to the Y direction, and the direction (thickness direction) orthogonal thereto is defined as the X direction.

The external electrode 40 provided on the outer surface of the discharge tube 20 has a configuration in which a plurality of electrode portions are formed in a mesh shape, and is spirally formed along the tube axis C and arranged in parallel at predetermined intervals. The power supply line 70 connected to the end of the foil electrode 30 is connected to a power supply unit (not shown) provided outside, and supplies electric power to the discharge lamp 10 via the power supply line 70.

The polarities of the foil electrode 30 and the external electrode 40 are defined as an anode and a cathode, respectively. Once the discharge lamp 10 is supplied with a voltage of several thousand volts, a dielectric barrier discharge occurs between the foil electrode 30 and the external electrode 40, and excimer light of a predetermined spectrum (for example, 172 nm) is emitted.

The axial length of the discharge tube 20 is set to be 100 mm to 250 mm. On the other hand, the wall thickness of the discharge tube 20 is set to be 0.8 mm to 1.5 mm in order to prevent deterioration of the discharge tube caused by excimer light and to suppress an increase in discharge starting voltage. In addition, the inner diameter of the discharge tube 20 is set to be 8 mm to 20 mm in order to prevent the discharge distance from being unstable and the discharge distance to be short and the illuminance to be insufficient.

The thickness of the foil electrode 30 is set to be 20 μm to 50 μm in consideration of electrode capacity, ease of manufacture, and the like, and prevention of peeling due to thermal expansion. In addition, the width of the foil is set to 1.2 mm to 10 mm in consideration of the electrode capacity, the ease of manufacture, and the like, in order to prevent the discharge of the electrode due to the enlargement of the electrode area. The electrode material is molybdenum or an alloy containing molybdenum or the like.

The dielectric material 50 is composed of a dielectric material (SiO ₂ or the like) which is as close as possible to the thermal expansion coefficient of the electrode. The thickness of the dielectric material 50 is set to be 0.1 mm to 2 mm in consideration of the limit of maintaining the insulating property and preventing the rise of the discharge starting voltage.

The discharge distance is the distance between the dielectric material 50 and the inner diameter of the discharge tube 20, and is set to be 3 mm to 10 mm in consideration of prevention of insufficient illuminance and stability of discharge. In addition, when the width of the foil electrode 30 is w and the inner diameter of the discharge tube is d, the electrode width and the inner diameter of the discharge tube are set in accordance with the following conditional expression.

1.6≦d/w≦13.4 ...(1)

Fig. 3 is an enlarged cross-sectional view showing the vicinity of the electrode edge portion of Fig. 2; However, the dimensions and relative positional relationship of the electrodes, dielectrics, and discharge tubes are different from those in the first drawing.

As described above, the edge portions 30K1, 30K2 of the foil electrode 30 have a blade shape. The foil electrode 30 is sharpened toward the edge from the center in the width direction, and its edge thickness is thinner than the thickness T of the center portion in the width direction, and the edge 30T1 has a sharp shape. The edge portion 30K2 (not shown) has the same shape.

With such an electrode shape, electric field concentration occurs at the edge 30T1. That is, the region where the electric field strength is near the edge 30T1 (refer to the broken line E) becomes maximum, and this region is narrow due to the sharp shape of the edge 30T1. This is because in the conventional cross-sectional rectangle where the edge portion is not sharp, electric field concentration occurs, that is, the electric potential gradient becomes large across the entire planar portion of the edge; however, in the present embodiment, the edge 30T1 is essentially a line extending along the axial direction, and only electric field concentration occurs at the edge.

Further, the foil electrode 30 is disposed coaxially with the dielectric 50 and the discharge tube 20, and has a width direction along the radial direction. Therefore, the distance (discharge distance) between the edge portions 30K1, 30K2 of the foil electrode 30 and the inner surface of the discharge tube 20 is equal. Therefore, light having a good overall balance is emitted from the discharge tube 20.

Figure 4 is a diagram showing the process of the discharge lamp.

The power supply line 80 is connected to the foil electrode 70 by resistance welding, and is inserted into the glass tube 60 which becomes a dielectric film material. After the electrode 70 is inserted, the inside of the tube is evacuated, and then the dielectric film material 60 is heated from the outside to be welded to the foil electrode 70 (step (1)). Alternatively, the step of coating the dielectric may be substituted.

At the position of the glass tube corresponding to the edge portion of the electrode, a so-called bead-shaped encapsulating portion 85 of a ring-shaped shape is formed (step (2)). Then, a discharge tube 90 such as quartz glass provided with an exhaust pipe at one end and an insertion port at the other end is formed (step (3)). The electrode 70 is inserted into the discharge tube 90, and the insertion port of the discharge tube 70 is welded to the bead-shaped encapsulation portion 85 (step 4).

While heating the entire body, the vacuum was evacuated through the exhaust pipe of the discharge tube 90 to remove impurities. Then, after the discharge gas is sealed, the exhaust pipe is sealed, and the discharge electrode 95 is disposed on the outer surface of the discharge tube 90 (step (5)).

As described above, according to the present embodiment, the foil electrode 30 covered with the dielectric 50 inside the discharge tube 20 is disposed along the tube axis C. Further, the external electrodes 40 having different polarities are disposed on the outer surface of the discharge tube 20. Then, the edge portions 30K1, 30K2 of the foil electrode 30 are formed in a blade shape.

Since the edge portion of the electrode is sharp, the electric field strength is locally increased at the edge portion of the electrode, and the discharge at the start of the lighting is generated at a low voltage. The edge of the electrode is the role of the trigger that acts as the start of the discharge, and the illumination is maintained even if the lamp is turned on for a long time.

In addition, since the edge portion of the electrode is smoothly sharpened at the front end, it is not easy to create a gap between the electrode and the dielectric, and even if the electrode is not exposed to the discharge space due to the thermal expansion at the time of lighting, it is protected from oxidation.

Next, a discharge lamp of the second embodiment will be described using FIG. In the second embodiment, two foil electrodes having mutually different polarities are disposed inside the discharge tube.

Fig. 5 is a schematic cross-sectional view showing a discharge lamp in the second embodiment.

The discharge lamp 100 has two foil electrodes 130A and 130B inside the discharge tube 120, which are covered by the column dielectrics 150A and 150B, respectively. The foil electrodes 130A and 130B have mutually different polarities. Here, the foil electrode 130A is an anode and the foil electrode 130B is a cathode.

Further, the foil electrodes 130A and 130B are disposed at positions symmetrical with respect to the tube axis C, and are both parallel to the Y axis in the width direction. Both edge portions of the foil electrodes 130A and 130B have a blade shape as in the first embodiment. With such an electrode arrangement, discharge luminescence symmetric with respect to the discharge tube 20 is generated, and light is emitted from the entire discharge tube 20.

Fig. 6 is a schematic cross-sectional view showing a discharge lamp of a third embodiment. In the third embodiment, a plurality of foil electrodes are disposed in the discharge tube.

In the discharge lamp 200, in the discharge tube 210, nine foil electrodes are arranged along the X and Y axes to embed dielectric materials 220A to 220C. The width direction of each foil electrode is toward the Y-axis direction. External electrodes 250 having different polarities are disposed on the outer surface of the discharge tube 210. With such a symmetrical arrangement of the electrodes, light is uniformly emitted from the entire discharge tube.

Fig. 7 is a view showing a discharge lamp of a fourth embodiment. The discharge lamp 300 has three foil electrode embedding dielectrics 320 in the discharge tube 310, which are arranged in a row. External electrodes 350 having different polarities are disposed on both sides of the discharge lamp 300 having a rectangular cross section. With such an electrode arrangement, light is irradiated from the lower side of the discharge tube.

The dielectric material may have a shape other than a circular cross section. For example, the foil electrode may be coated in a form that is coaxial with the foil electrode. The edge portion of the electrode is not limited to the shape of the blade, and may be a shape in which the thickness is thinner than the central portion in the width direction, and the electric field is concentrated. Alternatively, the front end of the electrode edge portion having only one side may be sharpened. Further, the shape of the electrode is a zigzag shape in which the width is not uniform, the center position of the dielectric is not aligned with the center position of the foil electrode, and the like, and the position at which the electric field concentration is generated may be set. In addition, the spiral electrode which is a spiral shape in the axial direction of the torsion electrode foil of the discharge tube may be used to disperse the stress in the thickness direction in which the electrode foil and the dielectric are peeled off.

As the discharge method, a relatively low-voltage capacitive coupling type (capacitive type) high-frequency discharge type lamp can be applied instead of the above-described dielectric resistance which can stably generate uniform discharge along the axis of the discharge space. The barrier discharge excimer lamp is, for example, an external electrode type fluorescent lamp used for a scanner light source or the like as a relatively low voltage capacitive coupling type (electrostatic voltage type) high frequency discharge type lamp. In the case of the capacitive coupling type high frequency discharge method, a high voltage can be easily applied by using the final portion of the power supply unit as an LC resonance circuit.

[Examples]

A description will be given of a discharge lamp corresponding to the embodiment of the first embodiment. The axial length of the discharge tube was set to 300 mm, the thickness of the tube wall was set to 1 mm, and the inner diameter was set to 12.8 mm. The dielectric thickness of the circular cross section was set to 1 mm in the direction parallel to the width of the foil electrode, and the foil was The thickness of the electrode was set to 1.5 mm in the parallel direction, and the discharge distance was set to 5 mm. The thickness of the foil electrode was set to 20 μm and the width was set to 1.5 mm. If the inner diameter of the discharge tube is d and the width of the foil electrode is w, the ratio d/w is 8.5.

The Xe gas was sealed as a discharge gas, and a lighting test was performed under an applied voltage of 6.5 kV and a gas pressure of 47 kPa. When the lighting operation of the lamp that emits light in the spectrum of 172 nm continues for 2,500 hours, the illuminance can be maintained at 90%.

10. . . Discharge lamp

20. . . Discharge tube

30. . . Foil electrode

30K1. . . Edge

30K2. . . Edge

30T1. . . edge

40. . . External electrode

50. . . Dielectric

60. . . Glass tube (dielectric coating material)

70. . . Foil electrode

80. . . Power supply line

85. . . Bead shape package

90. . . Discharge tube

95. . . Discharge electrode

100. . . Discharge lamp

120. . . Discharge tube

130A. . . Foil electrode

130B. . . Foil electrode

150A. . . Columnar dielectric

150B. . . Columnar dielectric

200. . . Discharge lamp

210. . . Discharge tube

220A. . . Foil electrode embedding dielectric

220B. . . Foil electrode embedding dielectric

220C. . . Foil electrode embedding dielectric

250. . . External electrode

300. . . Discharge lamp

310. . . Discharge tube

320. . . Foil electrode embedding dielectric

350. . . External electrode

C. . . Tube axis

E. . . dotted line

Fig. 1 is a schematic plan view of a discharge lamp of a first embodiment.

Fig. 2 is a cross-sectional view taken along line II-II of Fig. 1.

Fig. 3 is an enlarged cross-sectional view showing the vicinity of the electrode edge portion of Fig. 2;

Figure 4 is a diagram showing the process of the discharge lamp.

Fig. 5 is a schematic cross-sectional view showing a discharge lamp in the second embodiment.

Fig. 6 is a schematic cross-sectional view showing a discharge lamp of a third embodiment.

Fig. 7 is a view showing a discharge lamp of a fourth embodiment.

20. . . Discharge tube

30. . . Foil electrode

30K1. . . Edge

30K2. . . Edge

40. . . External electrode

50. . . Dielectric

C. . . Tube axis

Claims (11)

A discharge lamp having: a discharge tube enclosing a discharge gas; at least one dielectric disposed in the discharge vessel; and at least one strip electrode embedded in the dielectric; wherein: the electrode is along the length The thickness of at least one of the two edges in the side direction is thinner than the central portion of the electrode. The discharge lamp of claim 1, wherein the edge of the strip electrode is in the shape of a knife edge. The discharge lamp according to any one of claims 1 to 2, wherein the strip electrode is coaxially disposed in the discharge tube. The discharge lamp of claim 1, wherein the thickness of both edges of the strip electrode is thinner than the thickness of the central portion of the electrode. The discharge lamp of claim 1, wherein a plurality of strip electrodes having different polarities are disposed in the discharge tube. The discharge lamp according to claim 1, wherein a plurality of strip electrodes having the same polarity are disposed in the discharge tube, and an external electrode having a polarity different from the strip electrodes is disposed outside the discharge tube. The discharge lamp according to any one of claims 5 to 6, wherein the plurality of strip electrodes are disposed at positions symmetrical with respect to the discharge tube axis. The discharge lamp according to any one of claims 5 to 6, wherein the plurality of strip electrodes are disposed in a state in which their width directions are parallel to each other. The discharge lamp of claim 1, wherein the thickness of the strip electrode is in the range of 20 μm to 50 μm, and the width of the strip electrode is set in the range of 1.2 mm to 10 mm. The discharge lamp of claim 1, wherein the tube wall thickness of the discharge tube is set within a range of 0.8 mm to 1.5 mm, and the inner diameter of the discharge tube is set within a range of 8 mm to 20 mm. The thickness of the dielectric is set in the range of 0.1 mm to 2 mm, and the discharge distance is set in the range of 3 mm to 10 mm. The discharge lamp according to any one of claims 9 to 10, wherein when the width of the strip electrode is w and the inner diameter of the discharge tube is d, the following formula is satisfied: 1.6≦d/w ≦ 13.4.