JP2007059199A - Discharge lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge lamp such as a cold-cathode fluorescent lamp capable of suppressing blackening of a glass bulb due to sputtering even if an emitter-impregnated sintered metal is used for an electrode head, high in light emission efficiency and having a long service life. <P>SOLUTION: When it is assumed that the inside diameter of a cylindrical cup part-shaped part 4 and an axial length of an area which is formed on the opening side of the cylindrical cup part 4 without impregnating the emitter are R and L, respectively, the electrode head 3 of this discharge lamp 11 is so formed as to satisfy a relationship of L>R. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a discharge lamp such as a cold cathode fluorescent lamp using an electrode head made of a porous sintered metal and used for a backlight light source such as a display.

  In many cases, a small fluorescent lamp (electrode head fluorescent lamp), which is a discharge lamp, is used as a light source for an original reading unit in a liquid crystal backlight or an OA device such as a copying machine, a facsimile machine, or a scanner. These OA devices are required to have high performance, high efficiency, multiple functions, downsizing, long life, and the like with the expansion and spread of applications. In response to such demands, fluorescent lamps serving as backlight light sources are inevitably required to have improved performance such as higher efficiency, longer life, and smaller size.

  16 (a) and 16 (b) show a schematic configuration of a cold cathode fluorescent lamp conventionally used as a backlight light source. FIG. 16 (a) is a side sectional view of the whole, and FIG. ) Is an enlarged side sectional view of the electrode head sealing region. 16 (a) and 16 (b), a glass bulb 31 is provided with a phosphor layer 32 that emits light upon stimulation by ultraviolet rays on its inner wall surface, and is encapsulated with a rare gas such as neon or argon and mercury as a discharge medium. Yes. A pair of lead wires 33 and 33 are provided at both ends of the glass bulb 31 so as to be sealed and introduced. Electrode heads (cold cathode heads) 34 and 34 that are electrically connected to the lead wires 33 and 33 are disposed at the leading ends of the lead wires 33 and 33 inside the glass bulb 1, respectively.

The glass bulb 31 has an inner diameter of about 1.2 to 4.8 mm and a length of about 40 to 800 mm. Further, inside the glass bulb 31, for example, mercury of about 0.5 to 2.0 mg / cm ³ and rare gas of about 60 to 150 Torr are enclosed as a discharge medium.

  The electrode head 34 includes a cylindrical body (for example, a nickel cylindrical body) 34a having an inner diameter of about 0.6 to 1.7 mm, a thickness of about 0.1 to 0.2 mm, and a length of about 2 to 3 mm. A cylindrical member 34a is composed of a central member 34b having an outer surface coated and baked with an emitter material (electron emitting material).

  Then, the electrode head 34 and the lead wire 33 are joined by inserting and fitting the tip end portions of the pair of lead wires 33 sealed and introduced into the reduced diameter portion of the cylindrical body 34a, which is a constituent member. Are electrically connected by means such as welding by irradiation (for example, see Patent Document 1), brazing using Mo (molybten) -Ru (ruthenium) as a brazing material (for example, see Patent Document 2), and It is fixed mechanically.

  That is, a required voltage is applied to the electrode heads 34 and 34 via the lead wires 33 and 33 to cause the electrode heads 34 and 34 to function as discharge electrodes. The central member 34b is for increasing the emission of thermoelectrons and obtaining a long life, and is generally a material mainly composed of an electron-emitting substance (emitter substance) such as a barium compound, an yttrium compound, or a lanthanum compound. It is formed with. With these configurations, when a pair of electrode heads 34, 34 carrying the emitter layer 34b is energized through the lead wires 33, 33, ultraviolet rays are emitted, and the ultraviolet rays are converted into visible light by the phosphor layer 32, Functions as a cold cathode fluorescent lamp.

  In addition, in order to prevent the emitter material of the electrode head from scattering during lighting (during discharge) and depleting as the usage time elapses, the emitter is applied to the electrode head formed of porous sintered metal provided with pores. A structure impregnated with a substance is also disclosed.

For example, as shown in FIG. 17, the electrode head 43 made of a sintered body (sintered metal) inside the glass bulb 40 is formed in a cylindrical shape, and a hollow portion 45 formed in the center is formed. Has been. The tip of the hollow portion 45 is opened toward the discharge space 2. The tip of the electrode shaft 41 is inserted and fixed at the rear end of the hollow portion 45. The tip of the electrode shaft 41 is inserted into the hollow portion 45 of the electrode head 43 in a range that is half or less of the entire length of the hollow portion 45 in the axial direction. (For example, see Patent Document 3)
As the sintered electrode, a refractory metal such as tungsten (W), titanium (Ti), nickel (Ni), niobium (Nb) or the like is used alone or in combination. Since this type of high melting point metal sintered electrode has a large number of pores (air holes) formed throughout, an emitter that can be held by the electrode is made possible by impregnating a large number of pores with an emitter material. Even if the amount of the material increases and the emitter material disappears on the surface of the electrode, the emitter held in the internal vacancies supplies and replenishes the surface, so that the emitter material works well for a long time. Can be maintained.

In addition, the sintered metal made of a refractory metal has a nodule shape such as a columnar shape, so that the volume of the electrode increases and the heat capacity also increases. Can be prevented. Thereby, early blackening of the bulb of the fluorescent lamp can be prevented. (For example, see Patent Document 3)
JP 2003-272520 A (paragraph numbers 0025 to 0026) JP 2000-2158844 A (paragraph number 0028) JP-A-6-52828 (paragraph number 0016, paragraph numbers 0004 to 0005)

  An emitter-impregnated sintered electrode (electrode head) in which an emitter material is impregnated into a sintered metal electrode head as described above, in principle, can reduce the voltage of the fluorescent lamp, and thus consumes less power. , Has the advantage of high luminous efficiency. However, when the actually manufactured fluorescent lamp is continuously lit, blackening occurs in the glass bulb near the electrode in several hundred hours, resulting in a problem that the luminous efficiency is lowered.

  Usually, sintered metal has low melting point materials such as nickel (Ni), iron (Fe) and copper (Cu) as well as high melting point materials such as tungsten (W) and molybdenum (Mo) in order to create voids. Is manufactured using. Low melting point materials generally have the property of being easily sputtered. In a fluorescent lamp, spatter is generated mainly by collision of ions during lighting (during discharge). At that time, it is considered that the sputtered material adheres to the glass bulb in the vicinity of the electrode and blackening occurs in the glass bulb. When blackening occurs in the glass bulb, there arises a problem that the light emission efficiency of the fluorescent lamp is lowered due to hindering the light emission of the phosphor. Therefore, development of means for preventing the sputtered material from sticking to the glass bulb is desired.

  The present invention has been made based on these circumstances. Even when a sintered metal impregnated with an emitter is used for the electrode head, blackening of the glass bulb due to sputtering is suppressed, and the cooling efficiency is high and the lifetime is long. It aims at providing discharge lamps, such as a cathode fluorescent lamp.

According to the present invention, a phosphor bulb is provided on the inner wall surface, and a rare gas and mercury are sealed, and the lead wires sealed at both ends of the glass bulb are fixed to the glass bulb. Discharge including a pair of electrode heads formed in a cylindrical cup shape disposed inside and made of a porous metal sintered body in which a hole in a predetermined region on the bottom side of the cylindrical cup-shaped portion is impregnated with an emitter material A lamp,
In the electrode head, when the inner diameter of the cylindrical cup-shaped portion is R, and the axial length of the region not impregnated with the emitter formed on the opening side of the cylindrical cup-shaped portion is L, L> R A discharge lamp characterized by the relationship.

  Further, according to the present invention, the electrode head is mounted with a disk-shaped mica having a passage hole at the center or a disk made of insulating ceramic at the opening of the cylindrical cup-shaped part. A discharge lamp characterized by

Further, according to the present invention, the glass bulb is provided with a phosphor layer provided on the inner wall surface and sealed with a rare gas and mercury, and the lead bulb sealed at both ends of the glass bulb. A discharge lamp comprising a pair of electrode heads made of a porous sintered metal body in the shape of a cylindrical cup disposed inside and having a hole portion impregnated with an emitter material,
The electrode head is a discharge lamp characterized in that at least one of the side surface of the opening, the inlet portion and the outer peripheral surface of the cylindrical cup-shaped portion is coated with a non-conductive coating or a ceramic material.

  According to the present invention, even when an emitter-impregnated sintered metal is used for the electrode head, a discharge lamp such as a cold cathode fluorescent lamp having a high luminous efficiency and a long lifetime is suppressed by suppressing the blackening of the glass bulb by sputtering. Can be realized.

  The best mode for carrying out the present invention will be described below with reference to the drawings. 2 and the subsequent drawings, the same reference numerals are assigned to the same functional portions as those in FIG. In addition, the individual description is omitted to avoid duplication.

  The inventor turned on a fluorescent lamp equipped with an electrode head using a sintered metal impregnated with an emitter material in order to solve the problem of blackening in the vicinity of the electrode of the glass bulb of the fluorescent lamp (discharge lamp). The state of the inside discharge state was observed in detail. as a result. It was determined that the blackening of the glass bulb was due to sputtering of the electrode head. That is, when the discharge start point is deep in the inner diameter portion of the cylindrical cup of the electrode head, the glass bulb in the vicinity of the electrode head is less blackened. On the other hand, it was confirmed that the blackening in the vicinity of the electrode head became severe when the discharge origin was in the shallow part of the inner diameter part of the cylindrical cup part.

  Hereinafter, the electron density distribution during the discharge of the fluorescent lamp will be described. FIG. 1 is an explanatory diagram of an image of an electron density distribution high region in an electron density distribution during an ideal discharge in a fluorescent lamp. Ideally, the electron density distribution high region 5a is shown in relation to the cross section of the electrode head. During the discharge, the deep portion of the inner diameter portion 4a of the cylindrical cup-shaped portion 4 of the cylindrical cup-shaped electrode head 3 in which the lead wire 1 is fixed to one end side and the other end side is opened 2 (the opposite side to the opening 2) ) (Starting point P1), and the electron density distribution high region 5a gradually spreads outward from the opening 2.

  On the other hand, FIG. 2 is an explanatory diagram when the glass bulb (not shown) is blackened in a short time, and the electron density distribution high region when the discharge origin is in the shallow part (near the opening 2) of the inner diameter part 4a. The image of 5b is shown by the relationship with the cross section of the electrode head 3. FIG. In this case, the discharge occurs at the shallow portion of the inner diameter portion 4 a of the electrode head 3 (starting point P <b> 2), and the electron density distribution high region 5 b spreads rapidly outside the electrode head 3.

  FIG. 3 is an explanatory diagram when a glass bulb (not shown) in the vicinity of the electrode head 3 is blackened in a short time. An image in the case where there is a discharge starting point on the outer periphery of the electrode head 3 is shown in FIG. The relationship between the region 5c and the cross section of the electrode head 3 is shown. In this case, since the discharge starting point P3 is generated outside the electrode head 3, the electron density distribution high region 5c spreads at a stretch toward the nearby glass bulb.

  From these facts, it is effective for suppressing the blackening of the glass bulb to make the discharge starting point Pn as deep as possible (bottom side) of the inner diameter portion 4a of the cylindrical cup-shaped portion 4 of the electrode head 3. It can be seen that it is.

  Further, even when the discharge starting point P2 is generated in the shallow portion of the inner diameter portion 4a of the electrode head 3, as shown in the schematic diagram of FIG. 4, the sputtering on the glass bulb in the vicinity of the electrode head 3 becomes intense. In order to prevent this, it is possible to cover the opening 2 of the inner diameter portion 4a with a ceramic material lid 7 having a hole 6 smaller than the inner diameter of the inner diameter portion 4a of the cylindrical cup-shaped portion 4 of the electrode head 3. It was also confirmed that it is effective for the gentle formation of the high region 5n.

  However, when the opening 2 of the inner diameter portion 4a is covered, the joining of the sintered metal electrode head 3 and the ceramic material lid 7 cannot be directly welded in terms of material. The ceramic lid 7 is held as shown in the schematic diagram of the structure of the electrode head 3 as shown in a) an external front view, (b) a front view of the B1-B2 cross section, and (c) an external side view. In order to do this, the metal fitting 8 is used as an auxiliary part. However, the inventor has also found a solution to be described later regarding means for fixing the ceramic lid 7 without using auxiliary parts.

  Hereinafter, the fluorescent lamp of the present invention based on these findings will be described.

  FIG. 6 is a partially cutaway side view of a fluorescent lamp showing an example of the present invention.

  An example of a fluorescent lamp which is a discharge lamp is a fluorescent lamp 11 having a straight tube shape and a lamp current of 30 mA or less. A tubular glass bulb 12 made of soft glass or hard glass has an outer diameter of 4 mm and a thickness of 0.5 mm, for example. The lead wires 13 are hermetically sealed at the respective sealing portions formed at both ends of the glass bulb 12. The electrode head 3 of the cylindrical cup-shaped portion 4 is fixed to the tip of the lead wire 13 inside the glass bulb 12.

  Further, on the inner wall surface of the glass bulb 12, for example, a three-wavelength phosphor coating 10 in which phosphors having light emitting regions of blue, green, and red are mixed is formed by coating. After exhausting, a mixed rare gas of about 90 volume% Xe (xenon) -about 10 volume% He (helium), such as mercury Hg or a rare gas, is sealed at about 100 Torr.

  When the fluorescent lamp 11 having such a configuration is connected to a normal high-frequency lighting circuit (not shown) and energized, the electron radioactive substance existing on the tip surface of the electrode head 3 emits electrons, and both electrode heads 3, Discharge between 5. Then, a rare gas such as Xe emits light and emits ultraviolet light, and this ultraviolet light is received and excited by the phosphor coating 7 on the inner wall surface of the glass bulb 12 to emit predetermined visible light to the outside of the glass bulb 12.

  Next, the electrode head 3 will be described. The electrode head 3 uses a porous sintered metal of a sparse metal sintered body having pores (not shown) having a porosity of 30% or more. In the pores, an electron emitting property is used as a thermionic emission source. Substance (emitter substance) is impregnated. The electrode head 3 is entirely formed in a cylindrical cup-shaped portion 4 having a cylindrical cup shape, and the shape of the hollow cathode can be obtained by this shape.

  Since the porous sintered metal electrode head 3 contains a large amount of emitter material (electron-emitting material, not shown) in the vacancies, the consumption of the emitter material due to the elapse of the lighting time will occur on the surface of the electrode head 3. The electrode head 3 is gradually moved from the surface side to the inside of the electrode head 3 and supplied from the inside of the electrode head 3, so that the discharge can be sustained for a long period of time and the life can be extended.

  Moreover, as shown in FIG. 7A, an external front view, FIG. 7B a front view of the A1-A2 cross section, and FIG. 7C an external side view, the emitter material impregnated region 14 in the electrode head 3 is an electrode head. 3 is a predetermined region on the bottom side of the cylindrical cup-shaped portion 4, the inner diameter is R, and the axial length of the region 15 not impregnated with the emitter material formed on the opening side of the cylindrical cup-shaped portion 4 is When L, L> R is formed.

  FIG. 8 is a schematic diagram showing the state of discharge in this relationship. Since the discharge starting point P4 occurs at the end of the emitter material impregnated region 14, the tip (shallow portion) of the electrode head 3 does not become the starting point of the discharge, and the discharge starting point P4 is the inner diameter portion 4a of the electrode head 3. The electron density distribution high region 5d that is formed inside the tip (shallow part) of the first electrode spreads outward gently. Therefore, blackening of the glass bulb 12 in the vicinity of the electrode head 3 due to sputtering corresponding to the high electron density distribution region 5d can be reliably suppressed.

  In addition, as a porous sintered metal used for the electrode head 3, for example, nickel (Ni), tungsten (W), or molybdenum (Mo) is used. Further, non-conductors may be mixed as long as the conductivity of the electrode head 3 is not impaired.

  In addition, the composition material of the porous sintered metal includes Nb (niobium), Ru (ruthenium), Hf (hafnium), Ta (tantalum), Re (rhenium), Os (osmium) as a refractory metal group. Moreover, Mg (magnesium), Al (aluminum), Si (silicon), Zr (zirconium), etc. can be used as a metal group having a reducing action.

  As the electron-emitting substance (emitter substance), a simple substance or a compound such as Ca (calcium), Sr (strontium), Ba (barium), or Ra (radium) of the alkaline earth metal group can be used. .

  Further, on the inner wall surface of the glass bulb 12, for example, a three-wavelength phosphor film in which phosphors having light emitting regions of blue, green, and red are mixed is formed. Inside the glass bulb 12, mercury Hg or rare gas is formed. For example, a mixed rare gas of about 90% by volume of Xe (xenon) -about 10% by volume of He (helium) is sealed at about 100 Torr.

  The material of the glass bulb 12 may be soft glass such as lead glass or soda lime glass, or hard glass such as aluminosilicate glass, and the shape is not limited to a straight tube shape, but is U-shaped or W-shaped. A glass bulb 12 having a bent shape or the like, or a glass bulb 12 in which a plurality of straight tubular tubes are connected to form a discharge path in series may be used. Further, the rare gas sealed in the lamp is not limited to Xe (xenon) -He (helium), but may be a gas in which Xe (xenon) is mixed with Ar (argon), Ne (neon), Kr (krypton), or the like. Also, the mixing ratio and the sealing pressure may be appropriately determined according to the lamp characteristics.

  Next, each example of the present invention will be described.

  In each of the following embodiments, the overall structure and material of the fluorescent lamp 11 are the same as those described above, and therefore description thereof will be omitted to avoid duplication, and only the electrode head 3 will be described.

Example 1
FIG. 9 (a) shows an external front view, FIG. 9 (b) shows a front view of the A3-A4 cross section, and FIG. 9 (c) shows an external side view. A mica or insulating ceramic disc 17 having a passage hole 16 formed in the center is attached to the tip of the opening 2 of the inner diameter portion 4a of the electrode head 3, and the outer periphery thereof is held by a pressing member 18 with an inner diameter of the electrode head 3. It is fixed to the part 4a.

  FIG. 10 is a schematic diagram of the discharge state in this case. The discharge starting point P5 is formed in the vicinity of the shallow portion of the inner diameter portion 4a of the electrode head 3, but the electron density distribution high region 5e is mica or insulating. Since it spreads outside the electrode head 3 through the passage hole 16 of the ceramic disc 17, the spattering of the sputters toward the 12 wall surfaces of the glass valve corresponding to the high electron density distribution region 5 is suppressed in the vicinity of the electrode head 3. Thus, blackening of the glass bulb 12 can be suppressed.

(Example 2)
FIG. 11 (a) shows an external front view, FIG. 11 (b) shows an A5-A6 cross-sectional front view, and FIG. 11 (c) shows an external side view. Furthermore, when the emitter material-impregnated region 14 in the electrode head 3 is R, the inner diameter of the cylindrical cup portion shape of the electrode head 3 is R, and the axial length of the region 15 not impregnated with the emitter material is L, L The relationship of> R is taken into consideration.

  Therefore, the discharge starting point P is formed deeper than the shallow portion of the inner diameter portion 4a of the electrode head 3, and the high electron density distribution region 5 is a passage hole 16 of the disc 17 of mica or insulating ceramics. Since it spreads outside the electrode head 3 through the gap, spattering of the spatter in the direction of the wall surface of the glass bulb 12 is suppressed in the vicinity of the electrode head 3, and the blackening of the glass bulb 12 can be further suppressed.

(Example 3)
As shown in the front sectional view of FIG. 12 (Example 3), the outer surface of the electrode head 3 made of a porous sintered metal containing an emitter material as a whole and the opening 2 of the inner diameter portion 4a are made of non-conductive material such as ceramic. The non-conductive coating 19 is formed by spraying the thermal spray material. Since the discharge starting point P6 does not occur at the location of the formed nonconductive film 19, the image of the discharge electron density distribution high region 5d spreads at a position away from the electrode head 3.

（実施例４）
図１３に正面断面図を示したように（実施例３）では、全体にエミッタ物質を含有した多孔質焼結金属による電極ヘッド３の端面部と内径部位４ａの開口２にセラミック等の不導体の溶射材料を溶射して、不導体被膜１９を形成する。この場合も、形成された不導体被膜１９の箇所には放電の起点Ｐ７が生じないので、放電の電子密度分布のイメージは電極ヘッド３から離間した位置で広がるようになる。 As a result of lighting the fluorescent lamp 11 actually manufactured, as shown in Table 1, conventionally, there were 17 defects out of 50 of the fluorescent lamp 11, but in Example 3, the discharge starting point P is Since it did not occur on the outer periphery or the tip of the electrode head 3, it was confirmed that there were no defects and that there were no.

Example 4
As shown in the front sectional view of FIG. 13 (Example 3), a non-conductor such as a ceramic is formed on the end face portion of the electrode head 3 and the opening 2 of the inner diameter portion 4a by the porous sintered metal containing the emitter material as a whole. The non-conductive coating 19 is formed by spraying the thermal spray material. Also in this case, since the discharge starting point P7 does not occur in the formed portion of the non-conductive coating 19, the image of the discharge electron density distribution spreads at a position away from the electrode head 3.

  As a result of actually turning on the fluorescent lamp 11 manufactured, as shown in Table 1, there were 17 defects in the conventional 50 lamps as shown in Table 1. In Example 4, the starting point P of the discharge is the electrode head 3. It was confirmed that there were only two defects because it did not occur on the outer periphery or the tip of the.

(Example 5)
FIG. 14A shows an external front view, FIG. 14B shows an A7-A8 cross-sectional front view, and FIG. 14C shows an external side view. When the electrode head 3 is sintered into the opening 2 of the inner diameter portion 4a of the electrode head 3 made of a sintered metal, a ceramic material lid 7a is fitted by utilizing the fact that the inner diameter portion 4a becomes smaller. It is fixed. The ceramic lid 7a has a vent hole 16a in the center.

  FIGS. 15A to 15C are schematic views showing manufacturing process diagrams of (Example 5). The electrode head 3 is formed by solidifying the metal powder together with the binder so that the inner diameter of the cylindrical cup-shaped portion 4 is slightly larger than a desired size. On the other hand, since the outer diameter of the ceramic insertion portion that becomes the lid 7a is φ2.0 mm, the inner diameter φ2.1 mm of the cylindrical cup-shaped portion 4 of the sintered body before sintering is set. The ceramic lid 7a has a passage hole 6a at the center.

  First, as shown in FIG. 15A, the lead wire 1 and the ceramic lid 7a are inserted before sintering. Next, as shown in FIG. 15B, heating and sintering are performed in a heating furnace 20. At this time, since the sintered body of the electrode head 3 expands, the inner diameter portion 4a of the cylindrical cup-shaped portion 4 contracts and the lead wire 1 and the ceramic lid 7a are fastened and fixed. As shown in FIG. 15 (c), the lid 7 a is fixed to the cylindrical cup-shaped portion 4 even if it is removed from the heating furnace.

  According to this method, the ceramic lid 7a can be easily and reliably fixed to the electrode head 3 which is a sintered metal body, and the number of parts can be reduced.

Explanatory drawing of the image of the electron density distribution high area | region in the electron density distribution in the case of the ideal discharge in a fluorescent lamp. Explanatory drawing in case a glass bulb turns black in a short time. Explanatory drawing in case a glass bulb turns black in a short time. Schematic diagram of measures when the glass bulb turns black in a short time. (A) is the external appearance front view of the countermeasure when a glass bulb is blackened in a short time, (b) is the cross-sectional front view, (c) is the external appearance side view. The partially cutaway side view of the fluorescent lamp which shows an example of this invention. (A) Front view of appearance of electrode head of discharge lamp of the present invention, (b) is a sectional front view thereof, and (c) is a side view of its appearance. The schematic diagram which showed the mode of discharge by the electrode head of the discharge lamp of this invention. It is explanatory drawing of the Example of the electrode head of the discharge lamp of this invention, (a) is an external appearance front view, (b) is a cross-sectional front view, (c) is an external appearance side view. The schematic diagram of the discharge state of the Example of the electrode head of the discharge lamp of this invention. It is explanatory drawing of the Example of the electrode head of the discharge lamp of this invention, (a) is an external appearance front view, (b) is a cross-sectional front view, (c) is an external appearance side view. Explanatory drawing by front sectional drawing of the Example of the electrode head of the discharge lamp of this invention. Explanatory drawing by front sectional drawing of the Example of the electrode head of the discharge lamp of this invention. It is explanatory drawing of the Example of the electrode head of the discharge lamp of this invention, (a) is an external appearance front view, (b) is a cross-sectional front view, (c) is an external appearance side view. (A)-(c) is a manufacturing-process figure of the Example of the electrode head of the discharge lamp of this invention. (A) And (b) is a schematic block diagram of the cold cathode fluorescent lamp conventionally used as a light source for backlights. The block diagram of the electrode head of the conventional fluorescent lamp.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Lead wire, 2 ... Opening, 3 ... Electrode head, 4 ... Cylindrical cup-shaped part 4a ... Inner diameter part, 5 ... Electron density work distribution area, 7 ... Cover, 8 ... Holding metal fitting, 11 ... Fluorescent lamp, 12 ... Glass Valve, 14 ... Emitter material impregnation region, 17 ... Disc, 18 ... Non-conductive coating

Claims (3)

A glass bulb in which a phosphor layer is provided on the inner wall surface and in which rare gas and mercury are enclosed, and a cylinder that is fixed to lead wires sealed at both ends of the glass bulb and disposed inside the glass bulb A discharge lamp comprising a pair of electrode heads made of a porous metal sintered body having a cup shape and impregnating an emitter material in a hole in a predetermined region on the bottom side of the cylindrical cup-shaped part,
In the electrode head, when the inner diameter of the cylindrical cup-shaped portion is R, and the axial length of the region not impregnated with the emitter formed on the opening side of the cylindrical cup-shaped portion is L, L> R A discharge lamp characterized by the relationship.   2. The electrode head according to claim 1, wherein a disk-shaped mica having a through-hole formed in a central part or a disk made of insulating ceramic is attached to an opening of the cylindrical cup-shaped part. The discharge lamp described in. A glass bulb in which a phosphor layer is provided on the inner wall surface and in which rare gas and mercury are enclosed, and a cylinder that is fixed to lead wires sealed at both ends of the glass bulb and disposed inside the glass bulb A discharge lamp comprising a pair of electrode heads made of a porous metal sintered body having a cup shape and impregnated with an emitter substance in a hole,
In the electrode head, at least one of the side surface of the opening, the inlet portion, and the outer peripheral surface of the cylindrical cup-shaped portion is coated with a non-conductive coating or sprayed with a ceramic material.

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