JP5956790B2 - Discharge lamp - Google Patents

Description

  The present invention relates to a discharge lamp not containing mercury as a discharge medium for light emission.

  As a light source for a vehicular lamp, a discharge lamp that emits excitation light from a discharge medium excited by discharge generated between a pair of electrodes is known. Conventionally, this type of discharge lamp has used mercury as a discharge medium. However, since mercury is an environmentally hazardous substance, a mercury-free discharge lamp that does not use mercury is required, and various developments and improvements have been attempted.

  For example, Patent Document 1 discloses that a metal halide is enclosed in a sealed glass bulb (main discharge space) in which a discharge medium is enclosed in order to obtain a characteristic equivalent to that of a discharge lamp containing mercury even in a discharge lamp that does not use mercury. Furthermore, it has been proposed that the sealing pressure of the sealed glass sphere be within a predetermined range.

JP 2003-168391 A

  However, even with the proposal of Patent Document 1, there is still room for improvement with respect to a decrease in the starting voltage. For example, the sealing pressure in the main discharge space of a mercury-free discharge lamp is set higher than the sealing pressure in the main discharge space of a conventional mercury-containing discharge lamp. For this reason, the molecular density in the main discharge space is high and the mean free path of electrons is shortened, so that the voltage (starting voltage) necessary for causing dielectric breakdown between the electrodes becomes high. When the starting voltage is high, the power source (ballast power source) of the discharge lamp increases, and in the worst case, the discharge lamp may not light up.

  In view of this, the present inventors have studied to provide a conductive film on a part of the outer peripheral surface of the pinch seal portion in order to reduce the starting voltage. It was considered that the conductive film generates ultraviolet rays by dielectric barrier discharge and makes the ultraviolet rays enter the main discharge space, thereby increasing the energy state of the main discharge space and easily causing dielectric breakdown in the main discharge space.

By the way, in the state where the arc tube is cooled and the energy state of the main discharge space is low, such as when the lamp is turned on immediately after the vehicle engine is started, the start-up voltage decreases when the coating area of the conductive film is large. For this reason, in order to make a starting voltage 20 kV or less, it is preferable that the coating area of a conductive film shall be 4 mm < ² > or more in consideration of the variation at the time of creation of the conductive film.

However, on the other hand, the present inventors have found that when the arc tube is already warmed, such as when the discharge lamp is turned on again, the starting voltage does not decrease even if dielectric barrier discharge occurs. Rather, the present inventors have found that if the formation area of the conductive film is increased, electrons for causing dielectric breakdown in the main discharge space are taken by the conductive film, resulting in an increase in starting voltage. It was. From this point of view, in order to keep the starting voltage at 20 kV or less even when the discharge lamp is turned on again, it is preferable to set the coating area of the conductive film to 4 mm ² or less in consideration of variations in the formation of the conductive film.

That is, it has been found that the conductive film must be strictly controlled to about 4 mm ² in order to set the starting voltage of the discharge lamp to 20 kV or less regardless of the arc tube temperature. However, it is difficult and costly to form the conductive film accurately so that the area of the conductive film is about 4 mm ² .

  Accordingly, an object of the present invention is to provide a discharge lamp in which the starting voltage is always 20 kV or less even if the area of the conductive film varies.

According to the present invention, in order to achieve the above object,
An arc tube having a main discharge space sealed at both ends by a pair of pinch seals;
A shroud tube that surrounds the arc tube across an auxiliary discharge space;
A plug that supports one end of the shroud tube;
With the end portions facing each other in the main discharge space, the plug-side electrode unit and the anti-plug-side electrode unit covered with the pinch seal portion,
An external lead electrically connected to the anti-plug side electrode unit and extending outside the shroud tube along the shroud tube to the plug;
The main discharge space is hermetically sealed with a first discharge medium having a sealing pressure not containing mercury of 10 atm or more,
A second discharge medium not containing mercury is hermetically sealed in the auxiliary discharge space;
The plug-side electrode unit is electrically connected to the plug;
A conductive film having a concavo-convex surface is provided on the outer peripheral surface of the pinch seal portion covering the plug-side electrode unit at a position facing the external lead via the auxiliary discharge space,
The conductive film is formed to 4 mm ² or more and 16 mm ² or less,
A part of the outer peripheral surface of the pinch seal portion formed of an irregular curved surface is exposed from the uneven surface of the conductive film,
The discharge lamp is provided in which the area of the exposed portion of the outer peripheral surface of the pinch seal portion is 40% or less with respect to the area of the conductive film.

  According to the present invention, in the above discharge lamp, the surface roughness Rmax of the uneven surface of the conductive film may be 1 μm or more and 5 μm or less.

  According to the present invention, in the above discharge lamp, the film thickness of the conductive film may be 5 μm or less.

  According to the present invention, in the above discharge lamp, the conductive film preferably contains tin oxide in an amount of 40 wt% to 90 wt%.

  According to the present invention, in the above discharge lamp, the conductive film preferably contains 10 wt% or more and 60 wt% or less of inorganic glass.

According to the present invention, in the above discharge lamp,
An arc tube having a main discharge space sealed at both ends by a pair of pinch seals;
A shroud tube that surrounds the arc tube across an auxiliary discharge space;
A plug that supports one end of the shroud tube;
With the end portions facing each other in the main discharge space, the plug-side electrode unit and the anti-plug-side electrode unit covered with the pinch seal portion,
An external lead electrically connected to the anti-plug side electrode unit and extending outside the shroud tube along the shroud tube to the plug,
Forming the pinch seal portion formed of an irregular curved surface obtained by subjecting heated glass to flow deformation using a pressing jig;
A conductive film having a concavo-convex surface and an area of 4 mm ² or more and 16 mm ² or less at a position facing the external lead through the auxiliary discharge space on the outer peripheral surface of the pinch seal portion covering the plug side electrode unit. And forming a process,
A part of the outer peripheral surface of the pinch seal portion formed of an irregular curved surface is exposed from the uneven surface of the conductive film,
There is provided a method for manufacturing a discharge lamp, wherein the conductive film is formed so that an area of an exposed portion of the outer peripheral surface of the pinch seal portion from the conductive film is 40% or less with respect to an area of the conductive film. The

Moreover, according to the present invention, in the method for manufacturing the discharge lamp,
The conductive film having the uneven surface may be formed by applying a conductive paste using a stamp.

According to the present invention, in the above discharge lamp,
You may apply | coat the said electrically conductive paste to the said outer peripheral surface of the said pinch seal part using the said stamp whose dimension of the direction which cross | intersects the sequence direction of a pair of said pinch seal part is larger than the said pinch seal part.

According to the discharge lamp of the present invention, by providing the conductive film, it is possible to reduce the starting voltage when the arc tube is cooled. In addition, since the conductive film has an uneven surface so that a part of the outer peripheral surface of the pinch seal part is exposed moderately, even if the conductive film is formed large, even if the arc tube is warmed, electrons are more than necessary. Is not taken by the conductive film. For this reason, discharge can be efficiently generated between the plug-side electrode unit and the anti-plug-side electrode unit, and an increase in starting voltage can be suppressed. Thereby, even if the formation area of the conductive film varies within the range of 4 mm ² or more and 16 mm ² or less, it is possible to provide a discharge lamp having a starting voltage of 20 kV or less regardless of the temperature of the arc tube.

Further, according to the method for manufacturing a discharge lamp according to the present invention, since the conductive film is formed so as to have an appropriate uneven surface, the arc tube can be formed by forming the formation area in the range of 4 mm ^{2 to} 16 mm ^2. Therefore, it is possible to provide a discharge lamp with a starting voltage of 20 kV or less regardless of the temperature at a low cost.

It is a longitudinal cross-sectional view of the discharge lamp which concerns on embodiment of this invention. It is a principal part enlarged view of FIG. It is an enlarged view of the pinch seal part provided with the electrically conductive film. It is an expanded sectional view of an electrically conductive film. It is a graph which shows the relationship between the formation area of a electrically conductive film, and a starting voltage in the discharge lamp which concerns on a reference example. It is a graph which shows the relationship between the formation area of a electrically conductive film, and a starting voltage in the discharge lamp which concerns on embodiment of this invention. It is a longitudinal cross-sectional view which shows the manufacturing process of the discharge lamp shown in FIG. It is a longitudinal cross-sectional view which shows the manufacturing process of the discharge lamp shown in FIG. It is a longitudinal cross-sectional view which shows the manufacturing process of the discharge lamp shown in FIG. FIG. 2 is an upper cross-sectional view showing a manufacturing process of the discharge lamp shown in FIG. It is a longitudinal cross-sectional view which shows the manufacturing process of the discharge lamp shown in FIG.

  Hereinafter, a discharge lamp according to an embodiment of the present invention will be described with reference to the drawings.

(Overall structure)
FIG. 1 is a longitudinal sectional view of a discharge lamp according to an embodiment of the present invention. The discharge lamp is used, for example, as a light source for a vehicle headlamp.

  The discharge lamp shown in FIG. 1 includes an arc tube 10 having a main discharge space 11, a shroud tube 20 that surrounds the arc tube 10, a plug 30 that supports one end of the shroud tube 20, and a main discharge space 11. A plug-side electrode unit 40A, an anti-plug-side electrode unit 40B, and an external lead 50 electrically connected to the anti-plug-side electrode unit 40B. Yes.

  The arc tube 10 is a cylindrical transparent glass tube extending in the longitudinal direction. In addition, a main discharge space 11 swelled in a spheroid shape is defined at the center in the longitudinal direction of the arc tube 10. The main discharge space 11 is a space sealed by pinch seal portions 12A and 12B at both ends in the longitudinal direction, and a first discharge medium is hermetically sealed therein. The main discharge space 11 has an inner diameter of 2.5 to 3.0 mm, a distance between the pinch seal portions 12A and 12B of 7 to 8 mm, and a volume of 20 to 25 μl. The longitudinal direction is the direction in which the pinch seal portions 12A, 12B are arranged, and means the left-right direction in FIGS.

  Further, the plug side electrode unit 40A is provided on the plug side pinch seal part 12A of the arc tube 10, and the anti plug side electrode unit 40B is provided on the anti plug side pinch seal part 12B. Hereinafter, when the plug-side electrode unit 40A and the anti-plug-side electrode unit 40B are referred to without particular distinction, they are referred to as electrode units 40A and 40B.

  FIG. 2 is an enlarged view of a main part of FIG. As shown in FIG. 2, each of the electrode units 40A and 40B has discharge electrodes 41A and 41B whose end portions face each other in the main discharge space 11, lead wires 43A and 43B whose end portions protrude from the arc tube 10, Metal foils 42A and 42B are provided for electrically connecting the discharge electrodes 41A and 41B and the lead wires 43A and 43B, respectively. The discharge electrodes 41A and 41B can be formed of tungsten doped with 0.1% to 0.5% tria, for example. Moreover, the separation distance between the ends of the discharge electrodes 41A and 41B is set to, for example, 4.0 to 4.4 mm.

  Since the discharge electrodes 41A and 41B are heated and thermally expanded by the discharge in the main discharge space 11 while the discharge lamp is lit, the lead wires 43A and 43B are provided at positions separated from the discharge electrodes 41A and 41B. Even if the discharge electrodes 41A and 41B expand and contract due to thermal expansion, the metal foils 42A and 42B made of molybdenum or tungsten can reliably maintain electrical contact with the lead wires 43A and 43B.

  A coil 44 formed with a wire diameter of 0.05 mm, a coil pitch of 0.35 mm, and a coil length of 4.0 mm is wound around the discharge electrodes 41A and 41B inside the pinch seal portions 12A and 12B. The coil 44 prevents the pinch seal portions 12A and 12B from being damaged due to the difference in thermal expansion coefficient between the glass pinch seal portions 12A and 12B and the metal electrode units 40A and 40B.

The shroud tube 20 is a glass tube having a diameter larger than that of the main discharge space 11. For example, a glass tube having an outer diameter of 9.0 mm and an inner diameter of 7.0 mm can be used. The shroud tube 20 is formed of quartz glass doped with TiO ₂ , CeO ₂ or the like and having an ultraviolet shielding effect. Thereby, ultraviolet rays harmful to the human body emitted from the main discharge space 11 are prevented from being emitted to the outside.

  The shroud tube 20 is welded near both ends of the plug-side and anti-plug-side pinch seal portions 12A and 12B and integrated with the arc tube 10, and the auxiliary discharge space 21 is provided between the arc tube 10 and the shroud tube 20. Is defined. The auxiliary discharge space 21 is hermetically sealed with the second discharge medium.

  The external lead 50 is a conductive member that extends outside the shroud tube 20 along the shroud tube 20 to the plug 30. The external lead 50 is formed of a substantially L-shaped metal wire, the end on the short side is electrically connected to the lead wire 43B of the anti-plug side electrode unit 40B, and the end on the long side is the inside of the plug 30. Has been inserted.

  The plug 30 is an insulating member that supports the shroud tube 20 by holding the plug-side end portion of the shroud tube 20. Each plug 30 includes a connection terminal connected to a ballast power source, and the lead wire 43A of the plug-side electrode unit 40A and the external lead 50 are electrically connected to each.

In addition, a conductive conductive film 45 is provided on the outer peripheral surface of the pinch seal portion 12A that covers the plug-side electrode unit 40A at a position facing the external lead 50 through the auxiliary discharge space 21. It is sufficient that the conductive film 45 has conductivity sufficient to cause dielectric barrier discharge, and does not need to be a good conductor that conducts electricity in a general sense. The conductive film 45 is formed to have a formation area of 4 mm ² or more and 16 mm ² or less.

  FIG. 3 is an enlarged view of the pinch seal portion 12A provided with the conductive film 45. In particular, the surface of the conductive film 45 is shown by a micrograph. FIG. 4 is an enlarged cross-sectional view of the conductive film 45. As shown in FIGS. 3 and 4, the surface of the conductive film 45 is an uneven surface, and a part of the outer peripheral surface of the pinch seal portion 12 </ b> A under the conductive film 45 is exposed. The total area of the exposed portion 12Aa on the outer peripheral surface of the pinch seal portion 12A is 40% or less with respect to the entire area where the conductive film 45 is formed. Further, the surface roughness Rmax of the conductive film 45 is preferably 1 μm or more and 5 μm or less.

  Since the outer peripheral surface of the pinch seal portion 12A on which the conductive film 45 is formed is formed by pressing a pressing jig against softened glass, as will be described later, an irregular curved surface in which minute irregularities are smoothly continuous. It has become. Since the conductive film 45 is formed on the irregular curved surface of the pinch seal portion 12A, the conductive film 45 is formed in a shape having an uneven surface, so that a part of the outer peripheral surface of the pinch seal portion 12A is easily exposed from the conductive film 45.

  Further, the conductive film 45 is formed so that the film thickness is 5 μm or less even in the thickest region. When the thickness of the conductive film 45 is larger than 5 μm, the outer peripheral surface of the pinch seal portion 12A is difficult to be exposed, and the starting voltage in a state where the arc tube 10 described later is warmed is not easily lowered. The conductive film 45 is preferably formed so that the film thickness of the thickest portion is 1 μm or more. Even in the thickest part, the conductive film 45 having a film thickness of less than 1 μm does not function as an electrode for dielectric barrier discharge because the conductive film 45 is too thin, and the starting voltage of the discharge lamp cannot be lowered.

The first discharge medium enclosed in the main discharge space 11 is a discharge medium that does not contain mercury, has a main light emitting metal halide in addition to Xe as a starting rare gas, and further includes a buffer metal halide. Is preferred. The main light emitting metal halide, for example sodium, such as NaI and _ScI 3, ScBr ₃ - scandium-based halide. The buffer metal halide is at least one selected from halides of Al, Bi, Cr, Cs, Fe, Ga, In, Mg, Ni, Nd, Sb, Sn, Tb, Tl, Ti, Li, and Zn. In particular, it is preferable to contain ZnI and InI.

  By sealing Xe as the starting rare gas in the main discharge space 11 with a sealing pressure of 15 atm or more, the rate at which electrons emitted from the electrode units 40A and 40B collide with the rare gas molecules during discharge increases. Thereby, the inside of the main discharge space 11 at the time of lighting becomes high temperature, the vapor pressure of the main light emitting metal halide is increased, and a high tube voltage is obtained. Therefore, high tube power can be obtained without increasing the tube current, and a discharge lamp with high luminous efficiency can be obtained. In order to prevent the starting voltage from becoming too high, it is preferable to set the Xe sealing pressure to 20 atm or less.

  In addition, the main light emitting metal halide is excited by discharge and emits excitation light having a color close to the emission color of mercury to increase the amount of light emission in the visible light region, and in the visible light region due to the absence of mercury. Compensates for a decrease in light intensity. About 0.3 mg of the main light emitting metal halide and buffer metal halide are preferably contained in the 24 μl main discharge space 11.

The second discharge medium sealed in the auxiliary discharge space 21 is a medium that generates a dielectric barrier discharge between the conductive film 45 and the external lead 50. Examples of the second discharge medium include N ₂ gas, a mixed gas of N ₂ and Ar, and a mixed gas of N ₂ and Xe that can cause dielectric barrier discharge efficiently. The second discharge medium is preferably enclosed in the auxiliary discharge space 21 at an enclosure pressure of about 0.1 atm.

<Action>
The operation of the discharge lamp configured as described above will be described.
First, when a high voltage is applied to the plug-side electrode unit 40A by a ballast power source (not shown), the glass pinch seal portion 12A between the plug-side electrode unit 40A and the conductive film 45 is polarized, and the conductive film 45 is They are charged positively or negatively. At this time, when the potential difference generated between the conductive film 45 and the external lead 50 becomes equal to or higher than the dielectric breakdown voltage of the auxiliary discharge space 21, dielectric barrier discharge occurs in the auxiliary discharge space 21.

  When the dielectric barrier discharge occurs in the auxiliary discharge space 21, the second discharge medium enclosed in the auxiliary discharge space 21 is excited, and excitation light is generated. By making the excitation light generated in the auxiliary discharge space 21 enter the main discharge space 11, the energy state of the first discharge medium in the main discharge space 11 is increased, and discharge is easily generated in the main discharge space 11.

  Subsequently, dielectric breakdown is caused in the first discharge medium whose energy state is increased by the discharge electrodes 41A and 41B, discharge occurs in the discharge electrodes 41A and 41B, excitation light is generated from the first discharge medium excited by the discharge, and the discharge The lamp can be turned on. Thus, by providing the conductive film 45, the energy state of the first discharge medium can be increased and the starting voltage of the discharge lamp can be reduced.

  Further, since the plug-side electrode unit 40A is connected to an external power supply, a high voltage is first applied when the external power supply is turned on. Since the conductive film 45 is provided on the outer peripheral surface of the pinch seal portion 12A that covers the plug-side electrode unit 40A, the conductive film 45 is quickly charged from the time when the external power source is turned on to cause dielectric barrier discharge. Can do. That is, the time required until the discharge lamp is turned on can be shortened.

  Further, since the conductive film 45 is provided on the outer peripheral surface of the pinch seal portion 12A on the plug side on the surface facing the external lead 50 through the auxiliary discharge space 21, the dielectric barrier discharge is performed toward the external lead 50. It can be easily generated.

  The inventors of the present invention can reduce the starting voltage by the conductive film 45 as described above when lighting the discharge lamp while the arc tube 10 is cold. It has been found that the starting voltage is increased by the conductive film 45 when the discharge lamp is lit while the arc tube is warmed up, such as when the lamp is turned on again.

FIG. 5 is a graph showing the relationship between the formation area of the conductive film having a flat surface and the starting voltage in the discharge lamp according to the reference example. The horizontal axis represents the formation area [mm ² ] of the conductive film, and the vertical axis represents the starting voltage [kV]. In FIG. 5, unlike the above-described conductive film 45, a discharge lamp having a conductive film having a flat surface in which unevenness is not formed on the surface and the pinch seal portion is not exposed was evaluated.

  Plot a1 shows the relationship between the starting voltage and the formation area of the conductive film when the arc tube is cold (the arc tube is 20 ° C.). Plot a shows the relationship between the maximum value of the starting voltage and the formation area of the conductive film when the formation area of the conductive film varies by 3σ (the variation is three times the standard deviation) with the arc tube cooled. Show.

  The plot b1 shows the relationship between the starting voltage and the formation area of the conductive film when the arc tube is warmed (the arc tube temperature is 600 ° C.). Plot b shows the relationship between the maximum value of the starting voltage and the conductive film formation area when the formation area of the conductive film varies by 3σ (the variation is three times the standard deviation) with the arc tube heated. .

  As shown in plot a and plot a1, the starting voltage decreases as the conductive film formation area increases. Therefore, it is possible to confirm the effect of enhancing the energy state in the arc tube and assisting the initial discharge by the conductive film described above. It was.

  On the other hand, plot b and plot b1 indicate that the starting voltage increases as the conductive film formation area increases. In the state where the arc tube is warmed, the energy state of the arc tube is high in the first place, so that the discharge with the discharge electrode is easy. However, when a conductive film is formed around the arc tube, electrons originally concentrated on the discharge electrode are also distributed to the conductive film. That is, since the number of electrons in the discharge electrode is reduced, it is difficult for discharge to occur between the discharge electrodes. FIG. 6 shows that this effect becomes more prominent as the conductive film formation area increases.

Further, considering the plot a1 and the plot b1, in order to set the starting voltage to 20 kV or less, it is necessary to manage the formation area of the conductive film very strictly to about 4 mm ² . For this reason, in the case where the conductive film is provided in the pinch seal portion in order to reduce the starting voltage, it is necessary to manage the dimensional error of the conductive film at the time of manufacture with high accuracy, and the present invention increases the cost. Noticed.

Here, the present inventors have found that the starting voltage in a state where the arc tube 10 is warmed can be reduced by making the surface of the conductive film 45 an uneven surface as described above.
FIG. 6 is a graph showing the relationship between the formation area of the conductive film 45 and the starting voltage in the discharge lamp according to the present embodiment.

  A plot c1 in FIG. 6 shows the relationship between the starting voltage and the formation area of the conductive film 45 when the arc tube is cold (the arc tube is 20 ° C.). Plot c shows the maximum value of the starting voltage and the formation area of the conductive film 45 in a state where the formation area of the conductive film 45 varies by 3σ (the variation is three times the standard deviation) with the arc tube cooled. Show the relationship.

  The plot d1 in FIG. 6 shows a state in which the arc tube 10 is warmed (the arc tube temperature is 600 ° C.) when the exposed area of the pinch seal portion 12C as the base layer is 40% of the formation area of the conductive film 45. The relationship between the starting voltage and the conductive film 45 is shown. The plot d shows the maximum value of the starting voltage and the formation area of the conductive film 45 when the formation area of the conductive film 45 varies by 3σ (the variation is three times the standard deviation) in a state where the arc tube 10 is warmed. The relationship is shown.

In the state where the arc tube 10 is warmed, the starting voltage is generally reduced in the plots d and d1 of FIG. 6 compared to the plots b and b1 of FIG. For this reason, even if the formation area of the conductive film 45 is designed to be about 16 mm ² in a state where the arc tube 10 is warmed, the starting voltage can be stably reduced to 20 kV or less regardless of manufacturing errors. Therefore, in consideration of plots c and d, it is confirmed that the starting voltage can be reduced to 20 kV or less regardless of the temperature of the arc tube 10 even if the formation area of the conductive film 45 is set to a wide range of 4 mm ^{2 to} 16 mm ^2. It was done.

That is, since the surface of the conductive film 45 is an uneven surface, it is not necessary to make the formation area of the conductive film 45 as strict as about 4 mm ² in order to make the starting voltage 20 kV or less. For this reason, the formation cost of the electrically conductive film 45 can be reduced, and the discharge lamp which can be lighted with the starting voltage of 20 kV or less reliably at low cost irrespective of the temperature of an arc tube can be provided.

  In the example of FIG. 6, the case where the exposed area of the pinch seal portion 12C is 40% of the formation area of the conductive film 45 is taken as an example. However, the exposed area of the pinch seal portion 12C is less than 40%. Even when the arc tube 10 was used, the starting voltage when the arc tube 10 was warmed could be 20 kV or less, and the starting voltage could be 20 kV or less even if the formation area of the conductive film 45 varied.

  If the exposed area of the pinch seal portion 12C is larger than 40% of the formation area of the conductive film 45, the conductive region contributing to the discharge in the conductive film 45 is reduced. For this reason, dielectric barrier discharge cannot be generated from the conductive film 45 in a state where the arc tube 10 is cooled, and the starting voltage of the discharge lamp cannot be reduced.

<Manufacturing method>
Next, a method for manufacturing the above-described discharge lamp will be described with reference to FIGS.

  First, as shown in the longitudinal sectional view of FIG. 7, a glass tube 110 is prepared as an arc tube 10 having a bulging portion 111 that becomes a main discharge space 11 and straight portions 112A and 112B that become pinch seal portions 12A and 12B. To do. Next, the plug side electrode unit 40A in which the discharge electrode 41A, the metal foil 42A, the lead wire 43A, and the coil 44 are integrated is inserted from one end of the opening of the glass tube 110 to a predetermined position.

  When the plug-side electrode unit 40A is inserted to a predetermined position, as shown in FIG. 8, while the one straight portion 112A is heated by the burner 120 or the like, the pressing surface 131 of the pressing jig 130 is pressed against the straight portion 112A. 112A is pinch-sealed. Thereby, the pinch seal part 12A which covers the plug side electrode unit 40A is formed. At this time, minute cracks are generated around the coil 44. When the discharge lamp is turned on, the minute cracks expand and contract to absorb the difference in thermal expansion between the glass arc tube 10 and the electrode units 40A and 40B, thereby preventing the arc tube 10 from being damaged.

  Further, when the pinch seal portion 12A is formed, the glass tube 110 heated and softened by the burner 120 is pressed by the pressing jig 130, and the glass tube 110 is fluidly deformed. For this reason, the outer peripheral surface of the pinch seal portion 12A is formed into an irregular curved surface in which minute irregularities are smoothly continuous.

  Next, the non-plug side electrode unit 40B in which the discharge electrode 41B, the metal foil 42B, the lead wire 43B, and the coil 44 are integrated is inserted from the other end of the opening of the glass tube 110 to a predetermined position in the glass tube 110. . In addition, in order to remove moisture in the glass tube 110 and moisture attached to the electrode units 40A and 40B, the glass tube 110 into which the electrode units 40A and 40B are inserted is heated to 500 to 800 ° C., and the glass tube The inside of 110 is evacuated and heat dehydration is performed.

When the moisture in the glass tube 110 is removed, the pellet P made of the above-mentioned main light emitting metal halide or buffer metal halide having an outer diameter of about 0.5 mm is not yet pinched and sealed on the side opposite to the plug. The portion 112B is introduced into the bulging portion 111. When the pellet P is inserted, the insertion position of the anti-plug side electrode unit 40B is finely adjusted so that the end portion thereof is opposed to the end portion of the plug side electrode unit 40A in the bulging portion 111. The pellet P is charged with 0.3 mg containing NaI, ScI ₃ , ScBr ₃ , InI, and ZnI ₂ at a ratio of 58: 12.8: 20: 0.2: 9, for example.

  Next, as shown in FIG. 9, while pressing the inside of the glass tube 110 and supplying Xe gas, the straight portion 112B on the side not yet pinch-sealed is heated with a burner 120 or the like, and a flat pressing surface The pinch seal portion 12B that covers the anti-plug side electrode unit 40B is formed by pressurizing and pinch-sealing. At this time, the linear portion 112B is heated while cooling the bulging portion 111 so that the pellet P is not vaporized and scattered outside. Further, the Xe gas sealing pressure is, for example, 15.5 atm.

FIG. 10 is a top view of the glass tube 110 showing a process of forming the conductive film 45 by the stamp 140. After pinching the straight portions 112A and 112B, as shown in FIG. 10, a stamp 140 is formed on one surface of the outer peripheral surface of the pinch seal portion 12A covering the plug side electrode unit 40A (the upper surface of the pinch seal portion 12A in FIG. 9). The conductive paste is applied so that the conductive film 45 having a formation area of 4 mm ² or more and 16 mm ² or less and a thickness of 5 μm or less is formed. For example, the stamp 140 having a stamp surface of 5 to 20 mm ² can be used.

  The conductive paste is a paste containing a conductive material, an inorganic binder, and an organic binder. The conductive paste has appropriate fluidity and viscosity so that the conductive paste attached to the stamp surface of the stamp 140 is transferred to the outer peripheral surface of the pinch seal portion 12A.

  Further, the conductive paste applied to the outer peripheral surface of the pinch seal portion 12A is heated by the burner 120 or the like, the organic binder is evaporated, the inorganic binder is melted and solidified, and the conductive film 45 is formed on the outer peripheral surface of the pinch seal portion 12A. To do. In addition, since the conductive film 45 is formed by stamp printing, the cross-sectional shape of the conductive film 45 is a cross-sectional shape and both ends in the width direction are tapered.

  At this time, for example, by using a stamp 140 having a stamp surface on which minute irregularities such as a mesh shape are formed, the conductive paste is mottled on the outer peripheral surface of the pinch seal portion 12A. Thereby, the conductive film 45 having an uneven surface is formed in which the pinch seal portion 12A is exposed from the conductive film 45 in the region where the conductive paste has not adhered. In addition, by selecting the stamp 140 having an appropriately sized uneven surface, the conductive film 45 in which the area of the exposed portion of the pinch seal portion 12A is 40% or less of the formation area of the conductive film 45 is formed. be able to.

  Further, the conductive paste is pressed against the irregular curved surface of the pinch seal portion 12A by the stamp 140, and the conductive film 45 is formed. For this reason, the conductive paste pressed against the convex part of the pinch seal part 12A moves to the concave part of the pinch seal part 12A, the film thickness of the conductive film 45 becomes uneven, and a part of the convex part of the pinch seal part 12A is The conductive film 45 may be exposed. This also forms a conductive film 45 having an uneven surface and a portion of the pinch seal portion 12A exposed. As a result, a conductive film 45 having a non-uniform film thickness is formed in which a region where the pinch seal portion 12A is exposed and a region where the thickness is formed to be about 5 μm are mixed.

  Next, as shown in FIG. 11, the arc tube 10 is inserted into the shroud tube 20, the vicinity of both ends in the longitudinal direction of the arc tube 10 is welded to the shroud tube 20, and the arc tube 10 and the shroud tube 20 are integrated.

  At this time, after the shroud tube 20 and the arc tube 10 are welded and integrated at one end (for example, the end on the plug side), the auxiliary discharge space 21 is evacuated, and the auxiliary discharge space 21 is made into the second discharge medium. The shroud tube 20 and the arc tube 10 are welded and integrated at the other end portion (for example, the end portion on the anti-plug side). As the second discharge medium, for example, nitrogen gas is sealed in the auxiliary discharge space 21 at a sealing pressure of 0.1 atm.

  Next, the lead wire 43B of the anti-plug side electrode unit 40B protruding from the arc tube 10 and the external lead 50 are electrically connected, and the plug side end of the shroud tube 20 is attached to the plug 30. At this time, the shroud tube 20 is attached to the plug 30 so that the conductive film 45 faces the external lead 50 through the auxiliary discharge space 21. Further, the lead wire 43A and the external lead 50 are inserted into the plug 30 so that the lead wire 43A and the external lead 50 of the plug-side electrode unit 40A are electrically connected to the external power source, and the discharge lamp shown in FIG. create.

  According to the method for manufacturing a discharge lamp according to this embodiment, the conductive film 45 can be easily formed on the outer peripheral surface of the pinch seal portion 12A by using the stamp 140 formed in a desired shape. In addition, since the conductive film 45 having an uneven surface is formed, it is not necessary to strictly manage the formation area of the conductive film 45. For this reason, a discharge lamp whose starting voltage is always 20 kV can be provided at low cost regardless of the temperature.

  When the conductive film 45 is formed, as shown in FIG. 10, the dimension (width dimension) of the stamp 140 in the direction intersecting the arrangement direction of the pair of pinch seal portions 12A and 12B is It is preferably larger than the width dimension. By applying the conductive paste to the arc tube 10 with the stamp 140 and forming the conductive film 45, the displacement of the conductive film 45 and the variation in the size of the conductive film 45 are suppressed. The starting voltage of the discharge lamp can be stably reduced.

  The conductive paste is a mixture of a conductive material, an inorganic binder, and an organic binder as described above. The conductive paste has sufficient conductivity to cause dielectric barrier discharge after being formed as the conductive film 45, and the stamp. The material is not particularly limited as long as the fluidity and viscosity necessary for application by 140 can be secured, but it is preferable to select the material as follows.

As the conductive material, tin oxide (SnO ₂ ), indium tin oxide (ITO), or titanium oxide (TiO ₂ ) can be suitably used. This is because these materials are metal oxides, so that they are less likely to be oxidized, there is little change in electrical conductivity with time, and electrical characteristics are hardly changed even when exposed to high temperatures when the discharge lamp is turned on.

  Moreover, it is preferable that inorganic glass is included as an inorganic binder. By including inorganic glass in the conductive film 45, the adhesion to the glass arc tube 10 can be improved, and the temperature during lighting can be increased by bringing the thermal expansion coefficient between the conductive film 45 and the arc tube 10 closer. It is possible to prevent the conductive film 45 from being peeled off from the arc tube 10 even by the rise.

  Next, as shown in Tables 1 and 2, discharge lamps were created using the conductive pastes of Examples 1 to 4 and Comparative Examples 1 and 2 having different compositions, and whether or not the effect of reducing the starting voltage was recognized, And the adhesiveness with respect to the arc tube 10 of the electrically conductive film 45 was evaluated. In Tables 1 and 2, the solvent removal means a composition ratio of the conductive material, the inorganic binder, and the organic binder excluding the solvent. The term “organic removal” refers to the composition ratio of the conductive material and the inorganic binder contained in the conductive film 45 in a state assembled as a discharge lamp excluding the solvent and the organic binder. In addition, O indicates that the starting voltage reduction effect or adhesion is good, Δ indicates that the starting voltage reduction effect or adhesion is recognized although it is insufficient, and X indicates that the starting voltage reduction effect or adhesion is recognized. Indicates no.

  As shown in Tables 1 and 2, the conductive film 45 preferably contains 40 wt% or more and 90 wt% or less of tin oxide at a composition ratio excluding the solvent and the organic binder. When the content of tin oxide was less than 40%, the conductivity of the conductive film 45 was insufficient, and the effect of reducing the starting voltage was not sufficiently obtained. When the content of tin oxide is more than 90 wt%, the amount of inorganic glass or binder is insufficient, and the conductive film 45 is easily peeled from the pinch seal portion 12A.

  The conductive film 45 preferably contains 10 wt% or more and 60 wt% or less of inorganic glass at a composition ratio excluding the solvent and the organic binder. When the content of the inorganic glass is less than 10 wt%, it is difficult to align the thermal expansion coefficient of the conductive film 45 with the thermal expansion coefficient of the pinch seal portion 12A made of glass, and the conductive film 45 is easily peeled from the pinch seal portion 12A. Moreover, when there is more content of inorganic glass than 60 wt%, it will be difficult to ensure the electroconductivity of the electrically conductive film 45, and the fall effect of a starting voltage will not fully be acquired.

  Further, the ratio M: I of the amount M of tin oxide which is a conductive material and the amount I of inorganic glass which is an inorganic binder is preferably 2: 3 to 9: 1. When there is more conductive material than this ratio, the adhesiveness of the conductive film 45 to the pinch seal portion 12A is not sufficient, and when there is more inorganic glass than this ratio, the conductive film 45 effectively causes dielectric barrier discharge. Can't cause.

  Table 3 shows the baking time under the condition of baking temperature 700 ° C. for Examples 1 and 2 and Comparative Examples 1 and 2 in Table 1 described above in order to investigate the correlation between the baking time and the starting voltage. Discharge lamps were prepared with different [seconds], and the starting voltage [kV] at the time of lighting was measured. In Table 3, “-” indicates that the discharge lamp was not lit.

  From Table 3, the baking time is preferably set to 10 seconds or more and 15 seconds or less. If the baking temperature is set in the range of 650 ° C. to 750 ° C., the organic binder can be efficiently evaporated.

  When the baking time is 5 seconds, the starting voltage of the discharge lamp is as high as 23 to 25 kV, and the effect of reducing the starting voltage is not sufficient. This is because the baking time is insufficient, so that the organic binder component contained in the conductive paste remains in the conductive film 45 and the gas derived from the organic binder is released into the auxiliary discharge space 21 when the discharge lamp is turned on. As a result, the dielectric breakdown voltage of the auxiliary discharge space 21 is increased and the dielectric barrier discharge is not efficiently caused. As a result, the starting voltage of the discharge lamp is increased.

  Actually, carbon dioxide, methane, oxygen, etc. that are considered to be derived from the organic binder were confirmed from the auxiliary discharge space 21 of the discharge lamp having a baking time of 5 seconds. In other words, in order to reduce the starting voltage, the gas derived from the organic binder in the auxiliary discharge space 21 is preferably set to 0.01 atm or less.

  In addition, when the baking time is too long as 20 seconds, it is considered that the tin oxide, which is a conductive material, is scattered by heat, and the conductive film 45 does not exhibit conductivity, so that the discharge lamp does not light. It is done.

  As mentioned above, although this invention was demonstrated using the embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications and improvements can be made to the above-described embodiment.

  For example, in the above-described example, the paste is applied to the mesh-shaped stamp surface, and this is transferred to the outer peripheral surface of the pinch seal portion 12A to form the conductive film 45. However, the conductive paste 45 is impregnated. The conductive film 45 may be formed by pressing the ribbon on the outer peripheral surface with a stamp.

10: Arc tube, 11: Main discharge space, 12: Pinch seal part, 20: Shroud tube, 21: Auxiliary discharge space, 30: Plug, 40A: Plug side electrode unit, 40B: Anti plug side electrode unit, 41A, 41B : Discharge electrode, 42A, 42B: metal foil, 43A, 43B: lead wire, 44: coil, 45: conductive film, 50: external lead, 110: glass tube, 111: bulging part, 112A, 112B: straight part, 120: burner, 130: pressing means, 131: pressing surface, 140: stamp, P: pellet

Claims (4)

An arc tube having a main discharge space sealed at both ends by a pair of pinch seals;
A shroud tube that surrounds the arc tube across an auxiliary discharge space;
A plug that supports one end of the shroud tube;
With the end portions facing each other in the main discharge space, the plug-side electrode unit and the anti-plug-side electrode unit covered with the pinch seal portion,
An external lead electrically connected to the anti-plug side electrode unit and extending outside the shroud tube along the shroud tube to the plug;
The main discharge space is hermetically sealed with a first discharge medium having a sealing pressure not containing mercury of 10 atm or more,
A second discharge medium not containing mercury is hermetically sealed in the auxiliary discharge space;
The plug-side electrode unit is electrically connected to the plug;
A conductive film having a concavo-convex surface is provided on the outer peripheral surface of the pinch seal portion covering the plug-side electrode unit at a position facing the external lead via the auxiliary discharge space,
The conductive film is formed to 4 mm ² or more and 16 mm ² or less,
A part of the outer peripheral surface of the pinch seal portion formed of an irregular curved surface is exposed from the uneven surface of the conductive film,
Area of the exposed portion of the outer peripheral surface of the pinch seal portion is state, and are less than 40% of the area of the conductive film,
The discharge lamp has a surface roughness Rmax of the uneven surface of the conductive film of 1 μm or more and 5 μm or less . The discharge lamp according to claim 1 , wherein the conductive film has a thickness of 5 μm or less. The discharge lamp according to claim 1 or 2 , wherein the conductive film contains 40 wt% or more and 90 wt% or less of tin oxide. The discharge lamp according to any one of claims 1 to 3 , wherein the conductive film contains 10 wt% or more and 60 wt% or less of inorganic glass.