JP3404494B2 - Discharge lamps and lighting devices - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp used in office equipment such as facsimiles and copiers and display equipment such as televisions, and an illumination device such as a document reading device and a backlight device equipped with the discharge lamp.

[0002]

2. Description of the Related Art In recent years, office equipment such as facsimiles and display equipment such as televisions using a liquid crystal display device have been strongly required to be thin, small and light, and accordingly, bulbs of discharge lamps attached to these equipment are also required. It is recommended to reduce the diameter. For example, a lamp mounted on a facsimile or the like has an outer diameter of about 5.5 mm, which is 10 mm or less.
A long strip of 00 mm is used.

However, it is known that the thinner the bulb diameter of these discharge lamps, the higher the starting voltage at the start of lighting, which makes it difficult to downsize office equipment. Therefore, these discharge lamps are used for these equipment. A starting auxiliary means is attached to the lamp to lower the starting voltage. Also,
In order to obtain a predetermined luminous efficiency and further improvement in startability, these discharge lamps have a voltage and current, the type and amount of rare gas and electron emissive substance to be enclosed, and the amount of mercury to be enclosed as necessary. The optimum design is made from the viewpoint of life.

For example, in a straight tube type fluorescent lamp used as a light source for reading a facsimile, an internal electrode is provided so as to face both ends of a glass bulb, and a glass is used as a start-up assisting means for improving startability. On the outer surface of the bulb, an external electrode made of a conductive material such as copper or carbon powder formed in a strip shape is provided. The external electrode is electrically connected to one of the internal electrodes through an impedance element, and is arranged so as to extend along the outer surface of the valve to a position where its tip end faces the other internal electrode. This external electrode has the same polarity as one of the electrodes.

The sealing parts at both ends of the bulb are made of a synthetic resin made of an electrically insulating material for supporting the lamp on a casing of a facsimile or the like and holding lead wires for supplying power to the electrodes of the lamp. The substantially cylindrical holder is attached via a thermoplastic resin adhesive. Further, the tip portion of the external electrode is arranged so as to extend into the cylindrical holder.

To start the lamp, when a voltage is applied to the internal electrodes at both ends of the bulb, a voltage is also applied to the external electrode connected to one internal electrode, and the other electrode and the external electrode which are in close proximity to each other. As a result of the concentrated electric field, a discharge current flows between the other inner electrode and the outer electrode at a low starting voltage. Then, this discharge current triggers a glow discharge between both internal electrodes, and the discharge resistance between both electrodes is reduced to, for example, about 5 to 10 KΩ and shifts to the main discharge, so that the lamp is discharged within a short time. It is supposed to light up.

This lamp has an advantage that it can be lit in a short time. However, some of these lamps have problems such as smoke and offensive odor after their rated life is exceeded.

[0008]

Therefore, the inventors of the present invention have made various studies on the cause of this problem. As a result, the lamp having the rated life has been exhausted by the electron emissive material formed on the internal electrodes and the like. Although the discharge continues even if there is no radioactive substance, the electrode is overheated due to the reduced heat capacity due to the reduction of the electron radioactive substance. If this overheating continues, the glass bulb near the electrode is also heated, and normally 6
The valve temperature of about 0 ° C is overheated to 150 to 180 ° C.

The temperature rise of the bulb due to this heating melts the adhesive made of the above-mentioned thermoplastic resin that adheres the bulb and the holder, lowers the electrical insulation of the adhesive, and becomes conductive. This deterioration of the electrical insulation of the adhesive causes the external electrodes embedded in the adhesive and the lead wires connected to the internal electrodes to be short-circuited in the holder. The short circuit due to the decrease in the electric resistance of the adhesive causes a rise in temperature and causes odor and smoke.

The present invention has been made in view of the above problems,
To provide a discharge lamp in which a lead wire of the external electrode and the internal electrode are not short-circuited in a holder that also serves as a base even if the electron emissive material of the internal electrode is consumed and the lamp reaches the end of its life, and a lighting device equipped with this lamp. To aim.

[0011]

DISCLOSURE OF THE INVENTION The discharge lamp of the present invention comprises:
A glass bulb, a pair of internal electrodes sealed in the sealing portions at both ends of the bulb, lead wires connected to the internal electrodes and led out from the sealing portion, and a bulb on the outer surface of the bulb. An external electrode extending along the axis and connected to one of the internal electrodes via an impedance element, a discharge sustaining medium sealed in the bulb, and a sealing portion at the end of the bulb. In a discharge lamp comprising a holder made of an electric insulator adhered via a thermoplastic resin adhesive, at least one of an external electrode portion or a lead wire portion embedded in the thermoplastic resin adhesive of the holder. Is characterized by forming a thermosetting resin adhesive layer.

Further, a glass bulb, a pair of internal electrodes sealed in the sealing portions on both ends of the bulb, lead wires connected to the internal electrodes and led out from the sealing portion, and the bulb. The external electrode is formed to extend along the bulb axis on the outer surface of the external electrode and is connected to one of the internal electrodes via an impedance element, and is wound so as to cover the extended tip portion of the external electrode. A discharge lamp comprising a protective film, a discharge maintaining medium enclosed in the bulb, and a holder made of an electric insulator adhered to a sealing portion at the end of the bulb via a thermoplastic resin adhesive. In the above, the protective film is made of a polyimide resin.

Further, a glass bulb, a pair of internal electrodes sealed in the sealing portions at both ends of the bulb, lead wires connected to the internal electrodes and led out from the sealing portion, and the bulb. The external electrode is formed to extend along the bulb axis on the outer surface of the external electrode and is connected to one of the internal electrodes via an impedance element, and is wound so as to cover the extended tip portion of the external electrode. A protective film made of a polyimide resin, a discharge maintaining medium enclosed in the bulb, and a holder made of an electric insulator adhered to a sealing portion of the bulb end portion with a thermoplastic resin adhesive are provided. In the above discharge lamp, a thermosetting resin adhesive layer is formed so as to cover at least one of the protective film and the lead wire portion embedded in the thermoplastic resin adhesive of the holder. It is set to.

Further, the protective film for covering the tip portion of the external electrode is characterized in that the external electrode portion is covered with double or more and is wound around the valve.

The protective film covering the tip of the external electrode is characterized in that it extends to the outside of the holder and has a non-formation portion of the thermoplastic resin adhesive.

Further, the illumination device of the present invention is characterized in that the discharge lamp described above is mounted as a light source.

[0017]

[Function] Even if the temperature of the electrode rises abnormally due to the consumption of the electron emissive material, and the thermoplastic resin adhesive formed on the valve portion near the electrode softens and the electrical insulation deteriorates, the external electrode or the sealing portion Since the thermosetting resin adhesive layer that does not soften even when the temperature rises is formed on the lead wire of the internal electrode derived from the above, the external electrode on the outer surface of the valve and the lead wire of the internal electrode may be short-circuited. There is no. In addition, if an electrically insulating film is wound in advance on the portion of the external electrode formed on the outer surface of the bulb, which extends inside the holder, the safety is further enhanced.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of a cold cathode type discharge lamp mounted on a facsimile and used for reading, for example.
2 is an enlarged cross-sectional front view showing the right end portion of the lamp of FIG. 1, FIG. 3 is an enlarged cross-sectional side view of the surface cut along the line XX in FIG. FIG. 2 is an enlarged sectional front view showing a left end portion of the lamp shown in FIG. 1.

This cold cathode type discharge lamp L is, for example, a straight tube type fluorescent lamp L of about 6 W with a power consumption of 10 W or less. This lamp L is a tubular bulb 1 made of soda lime magnesia glass or lead glass having an outer diameter of about 5.5 mm, an inner diameter of about 4.7 mm and a length of about 350 mm.
Lead wires 4a and 4b having cylindrical cold cathode type internal electrodes 3a and 3b formed of nickel (Ni) or the like at their tips are sealed in the sealing portions 1a and 1b at both ends of the above. Although not shown, an electron emissive substance made of an oxide or carbonate of an alkali metal or an alkaline earth metal is attached on the surfaces of the internal electrodes 3a, 3b.

The valve 1 is filled with several tens to 200 torr of xenon (Xe) gas as a rare gas.
Further, the inner surface of the bulb 1 has a width of about 2.
An aperture-shaped fluorescent lamp L is formed in which a phosphor layer 2 having a predetermined light emitting region is formed while leaving a 5 mm slit 2a. On the outer surface of the bulb 1 opposite to the surface where the slits 2a are formed, a conductive member such as copper or carbon powder having a width of about 1 mm is formed in a strip shape and the external electrode 5 is provided. .

Reference numerals 61 and 62 denote holders molded of a synthetic resin material made of an electrically insulating material such as polycarbonate, which serves to hold the valve 1 and lead out the power supply line, as shown in an enlarged view in FIGS. 2 to 4. It consists of a hollow body having a substantially tunnel-shaped cavity 6a acting as a base, a protruding mounting piece 6b also serving as a closing wall on one end side, and a valve 1 on the other end side.
The receiving piece 6c is provided. The holders 61 and 62 are sealed with the sealing portion 1a via the thermoplastic resin adhesive 7 made of polyamide resin or the like filled in the space 6a.
1b is adhered to both ends of the valve 1. In addition,
In the figure, 4x is a lead wire 4a and 4y is a lead wire 4b.
z is a power supply line connected to the external electrode 5 and led out of the holders 61 and 62.

Then, in the holder 61 on the right side shown in FIGS. 2 and 3, and in the vicinity of the holder 61, the external electrode 5 on the outer circumference of the bulb 1 facing the internal electrode 3a at the portion buried in the thermoplastic resin adhesive 7 is shown. A thermosetting resin adhesive layer 81 made of silicon resin or the like is formed to cover the portion.

Similarly to the right side, the left holder 62 side shown in FIG. 4 has a portion of the external electrode 5 buried in the thermoplastic resin adhesive 7 and a feeder line 4z connected to this electrode 5, respectively. A thermosetting resin adhesive layer 83 made of silicone resin is formed covering the exposed portion of the conductor, here from the external electrode 5 to the insulating coating portion of the power supply line 4z, similarly to the above.
This fluorescent lamp L is manufactured by forming the internal electrodes 3 on both ends of the glass bulb 1 in which the fluorescent material layer 2 having the slits 2a is formed.
After the lead wires 4a and 4b provided with a and 3b are sealed and the valve 1 is evacuated and the rare gas is filled, it is hermetically sealed. (The inside of the valve 1 whose one end is sealed may be exhausted first, and the other end may be hermetically sealed after the rare gas is sealed.) Next, a conductive member such as copper or carbon powder is pasted. The shaped material is applied in a strip shape with a width of about 1 mm between the portions of the surface opposite to the surface where the slits 2a of the bulb 1 are formed and facing the internal electrodes 3a and 3b, and dried and baked to form the external electrode 5. Form. Next, the lead wires 4a and 4b extending from the sealing portions 1a and 1b and the power supply wires 4x and 4y are connected by welding, brazing, caulking or the like. Further, the power supply line 4z is connected to the external electrode 5 with a conductive adhesive or the like. Next, the lead wires 4a and 4b extending from the sealing portions 1a and 1b of the valve 1 are bent about 90 degrees with respect to the valve shaft. At this time, pay attention to the extending direction of the slit 2a formed on the inner surface of the valve 1.

Then, the valve 1 facing the internal electrode 3a
The outer electrode 5 portion on the outer periphery, that is, the extending tip portion of the outer electrode 5,
A thermosetting resin adhesive made of a silicone resin or the like is applied to the exposed portions of the respective conductors of the external electrode 5 and the power feeding line 4z and the surface of the adjacent power feeding line insulating coating, etc. The layers 81 and 83 are formed by coating.

Then, the sealing portions 1a and 1b at both ends of the valve 1 are provided.
When the outside of the valve 1 is fitted to the receiving pieces 6c of the holders 61 and 62, the thermoplastic resin adhesive 7 made of polyamide resin or the like is injected into the space 6a. The thermoplastic resin adhesive 7 is dried, heated and baked to hold the holders 61, 6
Adhesion of 2 is over, and thermosetting resin adhesive layers 81, 8 are formed on the surface.
The feed line 4z covered with 3 and the tips of the external electrodes 5 are embedded and fixed in the adhesive 7. (Note that the holders 61 and 62 may not be adhered to the respective sealing portions 1a and 1b at the same time and may be separate, and the thermosetting resin adhesive layers 81 and 83 and the thermoplastic resin adhesive 7 may be separated. May be fired at the same time.) The fluorescent lamp L having such a configuration is lit by, for example, the lighting circuit shown in FIG. In FIG. 9, the inverter lighting circuit 11 converts the direct current of the direct current power supply 12 into a high frequency of several tens of KHz and applies it to the internal electrodes 3a and 3b of the fluorescent lamp L to light the lamp L at a high frequency. 1 in the figure
Reference numerals 3a and 13b denote impedance elements composed of capacitors.

The start of the discharge lamp L completed through the above-described structure and steps is performed by the internal electrodes 3 at both ends of the bulb.
When a voltage is applied to a and 3b, a voltage is also applied to the outer electrode 5 connected to the left inner electrode 3b, and the electric field is concentrated between the right electrode 3a and the outer electrode 5 which are close to each other. As a result, a discharge current flows between the inner electrode 3a on the right side and the outer electrode 5 at a low starting voltage. Then, this discharge current triggers a glow discharge between the internal electrodes 3a and 3b, and the discharge resistance between the electrodes 3a and 3b decreases to, for example, about 5 to 10 KΩ and shifts to the main discharge, which is short. The lamp L lights up in time.

The lamp L reaches the end of its life, and when the electron emissive material decreases in the right inner electrode 3a due to consumption of the electron emissive material, for example, the heat capacity decreases correspondingly and the temperature of the inner electrode 3a rises abnormally. The temperature of the bulb 1 near the electrode 3a reaches a high temperature of about 150 to 180 ° C. Then, the temperature of the thermoplastic resin adhesive 7 that adheres the tip of the external electrode 5, the lead wire 4a, the thermosetting resin adhesive layer 81, and the holder 61 near the end of the bulb 1 also rises.

When the temperature rises, the thermoplastic resin adhesive 7 melts beyond its softening point and its electrical insulation is lowered, but from the silicone resin covering the exposed portion of the conductor surface at the tip of the external electrode 5, etc. The thermosetting resin adhesive layer 81 has a high heat resistance, so that it does not soften and melt, and the electrical insulation does not deteriorate.

Therefore, in the holder 61 on the right side in FIG. 1, the thermoplastic resin adhesive 7 for bonding the holder 61 is used.
Even if it undesirably softens and melts, the electrical insulation between the external electrode 5 and the lead wire 4a having different polarities is maintained to prevent a short circuit, and odor and smoke are generated from the adhesive portion of the holder 61. There is no need to improve safety.

Although the thermosetting resin adhesive layer 81 is formed on the tip side of the external electrode 5 in the holder 61 shown in FIGS. 2 and 3 in the above embodiment, the present invention is not limited to this. The exposed portion of the surface of the conductor or the like to which the lead wire 4a extending from the power supply line 4x is connected, and here, as shown by the dotted line from the end face of the sealing portion 1a to the insulating coating portion of the power supply line 4x. Similar to the above, the thermosetting resin adhesive layer 82 made of silicon resin or the like is formed, or the thermosetting resin adhesive layer is formed on both the tip end side of the external electrode 5 and the side to which the lead wire 4a is connected. 81 and 82 may be formed.

This is because even if the polarities are different, if the thermosetting resin adhesive layer is coated only on one side, the thermoplastic resin adhesive 7 for bonding the holder 61 is undesirably softened. This is because even if the conductor is melted and the electrical insulation property is lowered and the conductor is conducted, a short circuit does not occur as long as the insulation on the other conductor side is maintained.

In the left holder 62 shown in FIG. 4, the thermoplastic resin adhesive 7 is softened and melted due to some cause to lower the electrical insulation property, and a current leaks to the adhesive 7 to cause an external electrode. Since the polarities are the same even if the 5 side and the lead wire 4b side are short-circuited, in principle, there is no particular problem even without the thermosetting resin adhesive layer. However, when the applied voltage between the internal electrode and the external electrode is different, it is necessary to insulate each other. In this case, the external electrode 5 and the power supply line 4z are connected to each other by a conductor or the like. The sealing portion 1 is not limited to the one in which the thermosetting resin adhesive layer 81 is formed to cover the exposed portion of the surface.
The exposed portion of the surface of the conductor or the like, to which the lead wire 4b extending from b and the power supply wire 4y are connected, is covered by the sealing portion 1 in this case.
Even if a thermosetting resin adhesive layer 84 made of silicon resin or the like is formed as shown above from the end face b to the insulating coating portion of the power supply line 4y by a dotted line, or the external electrode 5 side and the lead wire 4b. The thermosetting resin adhesive layers 83 and 84 may be formed on both of the sides connected to.

At this time, on the external electrode 5 side, when the thermoplastic resin adhesive 7 is melted and flows onto the external electrode 5, conduction occurs and a short circuit occurs. Although it is necessary to form the adhesive layers 81 and 83, the thermosetting resin adhesive layers 82 and 84 on the side to which the lead wires 4a and 4b are connected are entirely buried in the thermoplastic resin adhesive 7. May be.

5 and 6 show a second embodiment of the present invention, in which the same parts as those in FIGS. 1 to 4 are designated by the same reference numerals and the description thereof is omitted.

This embodiment differs from the first embodiment in that it is embedded in the thermoplastic resin adhesive 7 in the holder 61 on the right side of FIG. 1 and in the vicinity of the holder 61. A portion that covers at least the outer electrode 5 portion on the outer circumference of the bulb 1 facing the electrode 3a and is housed in at least the holder 61 (up to a position extending outward from the holder 61).
Further, a protective film 9 made of polyimide resin having a thickness of about 60 μm and a width of about 13 mm is wound.

The holder 61 is adhered to the sealing portion 1a at the end of the valve 1 via a thermoplastic resin adhesive 7 made of polyamide resin or the like filled in the space 6a. In the manufacture of the lamp L in this case, the difference from the first embodiment is that the end portion of the bulb 1 on the side of the sealing portion 1a extends beyond the portion accommodated in the holder 61 to the outside. The protective film 9 made of resin is being wound. As described above, the extending position is a range in which the thermoplastic resin adhesive 7 does not flow onto the external electrode 5 when the adhesive 7 is melted. The end of the protective film 9 is fixed with a thermosetting resin adhesive or the like.

Since the thickness of the protective film 9 is thin, it is preferable to wind the double winding 9a or more on the external electrode 5 in terms of strength, electrical insulation and winding strength.

The lamp L shown in the second embodiment reaches the end of its life, and for example, the inner electrode 3a on the right side is reduced in electron emissive material due to consumption of the electron emissive material, and the heat capacity is reduced accordingly. When the temperature of 3a rises abnormally, the temperature of the thermoplastic resin adhesive 7 that adheres the protective film 9 and the holder 61 also rises.

Then, the thermoplastic resin adhesive 7 having a high temperature is softened and melted to lower its electrical insulating property, and the sealing portion 1a
Even if the exposed portion of the conductor such as the lead wire 4a or the power supply wire 4x derived from the conductive material is electrically connected to the thermoplastic resin adhesive 7, the external electrode 5 embedded in the thermoplastic resin adhesive 7 is surrounded by the tip portion thereof. Since the protective film 9 made of polyimide resin having high heat resistance is wound, the molten thermoplastic resin adhesive 7 does not penetrate to the external electrode 5 part and the thermoplastic resin adhesive 7 and the external electrode 5 are Never short circuit.

7 and 8 show a third embodiment of the present invention. In the figure, the same parts as those in FIGS. 1 to 6 are designated by the same reference numerals, and the description thereof will be omitted.

The difference between this embodiment and the first and second embodiments is that in the holder 61 on the right side in FIG. 1 and in the vicinity of the holder 61, the portion is buried in the thermoplastic resin adhesive 7. An example is the same polyimide as above, at least at a portion (to a position extending from the holder 61 to the outside) that covers the outer electrode 5 portion on the outer periphery of the bulb 1 facing the inner electrode 3a and is housed in the holder 61. A protective film 9 made of a resin is wound via a thermosetting resin adhesive layer 85 made of a silicone resin.

The protective film 9 thus wound has a high fixing force because the surface of the valve 1 and the portion 9a where the protective film 9 is laminated are adhered via the adhesive layer 85. However, even if the temperature of the valve 1 rises, the protective film 9 is not peeled off and no gap is formed, so that the softened and melted thermoplastic resin adhesive 7 can be prevented from entering the external electrode 5 portion, and the protective film 9 and the adhesive can be prevented. Layer 85
Has high heat resistance and does not deteriorate.

Therefore, in the holder 61 on the right side of FIG. 1, the thermoplastic resin adhesive 7 around the lead wire 4a led out from the sealing portion 1a is softened and melted, and a current leaks from the lead wire 4a to the adhesive 7. Even so, since the external electrode 5 on the outer surface of the bulb 1 is electrically insulated by the protective film 9 and the thermosetting resin adhesive layer 85, a short circuit between the external electrode 5 having different polarity and the lead wire 4a is prevented. The safety can be improved.

Further, if the double correspondence of the protective film 9 and the thermosetting resin adhesive layer 85 is adopted in this way, even if the electric insulation of one member is lowered, the other of The electrical insulation can be maintained by the member. Since the protective film 9 has a small thickness, it is preferable to wind the double winding 9a or more on the external electrode 5 in terms of strength, electrical insulation and winding strength. Further, the protective film 9 made of a polyimide resin has higher heat resistance than the thermosetting resin adhesive layer 85 made of a silicone resin, and even if the thermosetting resin adhesive layer 85 is deteriorated, the protective film 9 makes a thermoplastic resin. It is possible to prevent the adhesive 7 from entering.

Therefore, the discharge lamp of this embodiment can prevent an electrical short circuit between the external electrode 5 and the lead wire 4a having different polarities in the holders 61 and 62, and smoke or emit due to the temperature rise of the adhesive or the like. No odor is generated.

As shown in FIG. 10, the discharge lamp L shown in the first to third embodiments is incorporated and used as a light source in, for example, a facsimile image reading apparatus.
In FIG. 6, R is a lens, S is an image sensor, and P is a document. Then, the image of the original P irradiated by the lamp L is formed on the image pickup element S via the lens R, and the characters on the original P are read by moving the original P in the arrow direction. I am trying.

The present invention is not limited to the above embodiment. For example, the lamp is not limited to a fluorescent lamp in which a cold cathode type slit filled with a rare gas is formed, and may be another type of discharge lamp such as a fluorescent lamp of another type or an ultraviolet radiation lamp, or mercury as a discharge maintaining medium. It can also be applied to a discharge lamp or the like in which the luminescent substance of (1) is enclosed. Further, the shape of the bulb is not limited to the straight pipe shape, and may be bent into a U-shape, a W-shape, an annular shape, etc. In these cases as well, the external electrode may be arranged along the bent shape of the bulb. Good.

Further, the shape of the holder that also serves as the base is not limited to that of the embodiment, but any shape can be used as long as the end of the valve can be joined to the inside with an adhesive, and the mounting piece is not limited to the shape of the embodiment. It may have a shape and may have no attachment piece. Further, the thermosetting resin adhesive for the heat resistant coating is not limited to the silicone resin adhesive, and may be a phenol resin adhesive, an epoxy resin adhesive, or the like. It does not melt even when heated, the electric resistance value does not decrease, and the external electrode and the lead wire are not short-circuited. Further, the thermoplastic resin adhesive for adhering the holder is not limited to the polyamide resin, and may be a phenol resin adhesive, an epoxy resin adhesive, or the like, and even if these adhesives are used, the same operational effect as described in the embodiment is obtained. Play.

Further, when joining two holders to one lamp, the thermosetting resin adhesive layer is coated on the side where the external electrodes and the internal electrodes of opposite polarities are located (in the embodiment). Only the right side in the drawing) may be used, and the holder on the side of the internal electrode having the same polarity as the external electrode may be a conventional thermoplastic resin adhesive alone.

Although there is a case where a thermosetting resin adhesive having high heat resistance is used for bonding the holder, if a thermosetting resin adhesive is used as a whole, it takes a long time to cure and the productivity is good. Since the cost of the adhesive increases as it disappears, the present invention proposes to mainly use the thermoplastic resin adhesive.

In the embodiment, a protective film made of a polyimide resin is wound around the outer surface of the valve in the vicinity of the end of the external electrode. However, this protective film is not essential.
Similar to the above, only the side where the external electrode and the internal electrode side having a different polarity are located may be provided, and the other side may be wrapped with a protective film having a lower electric insulation than the resin.

The external electrodes are not limited to those of the embodiment,
The powder of another conductive member may be applied and formed, or a metal foil, a metal wire, a mesh metal, or the like may be attached. In addition, it does not matter if a protective coating such as a silicone resin or an epoxy resin is formed on the entire surface of the external electrode.

Further, the internal electrode is not limited to the cold cathode type electrode having the cylindrical shape shown in the figure, and the internal lead wire may be used as it is, or may be formed by processing a metal plate or mesh. Alternatively, it may be provided with a hot cathode type electrode in which a filament is wound in a coil shape.

Further, the electron emissive substance may be formed on the inner surface of the cylindrical electrode when the enclosed gas pressure at which the electron emissive substance is not easily scattered is about 30 to 100 Torr.

Furthermore, the discharge lamp of the present invention is shown in FIG.
In addition to a reading device such as a facsimile, as shown in
Needless to say, it can be widely used as a lighting device by being attached to office equipment such as an exposure device of a copying machine or a liquid crystal display device, a backlight such as a liquid crystal television or a decoration device, or a fixture or lamp for ordinary lighting. .

[0056]

As described in detail above, according to the present invention, the lamp reaches the end of its life, the temperature of the internal electrode rises abnormally due to the consumption of electron emissive material, and the temperature of the bulb near the electrode rises. Even if the temperature of the thermoplastic adhesive adhering to the temperature rises and the electrical insulation deteriorates due to melting, the exposed parts such as conductors are covered with a thermosetting resin adhesive, The electrical insulation from the conductor is maintained, and the external electrode on the outer surface of the valve and the lead wire of the internal electrode led out from the sealing portion are not short-circuited.

If a highly electrically insulating protective film made of polyimide resin is wound around the portion of the external electrode extending into the holder, the electrical insulating property of the adhesive will be lowered due to a temperature rise or the like. However, it is possible to prevent a short circuit between the external electrode and the lead wire of the internal electrode, which have different polarities, and to enhance the safety.

Therefore, this discharge lamp can prevent an electrical short circuit between the bulb and the holder, and does not cause problems such as smoking or odor.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a straight tube type discharge lamp of the present invention.

2 is an enlarged front sectional view of a right end portion of the lamp shown in FIG.

FIG. 3 is a side cross-sectional view showing a portion cut along line XX in FIG.

FIG. 4 is a front sectional view showing, on an enlarged scale, a left end portion of the lamp shown in FIG.

FIG. 5 is an enlarged front sectional view showing a right end portion of a lamp showing a second embodiment of the present invention.

FIG. 6 is a side sectional view showing a portion cut along line YY in FIG.

FIG. 7 is a front sectional view showing an enlarged right end portion of a lamp showing a third embodiment of the present invention.

FIG. 8 is a side sectional view showing a portion cut along line ZZ in FIG.

FIG. 9 is an explanatory diagram showing an embodiment of a discharge lamp lighting circuit of the present invention.

FIG. 10 is a schematic perspective view showing an embodiment of an illumination device according to the present invention incorporated in a facsimile.

[Explanation of symbols]

L: Discharge lamp (fluorescent lamp) 1: Glass bulb 1a, 1b: sealing part 3a, 3b: internal electrodes 4a, 4b: Lead wire 5: External electrode 61, 62: Holder 7: Thermoplastic resin adhesive 81, 82, 83, 84: Thermosetting resin adhesive layer 9: Protective film R: Lens S: Image sensor P: Manuscript

Claims (6)

(57) [Claims] 1. A glass bulb; a pair of internal electrodes sealed in sealing portions on both ends of the bulb; lead wires connected to the internal electrodes and led out from the sealing portion; An external electrode extending along the bulb axis on the outer surface of the bulb and connected to one of the internal electrodes via an impedance element; a discharge sustaining medium sealed in the bulb; In a discharge lamp comprising: a holder made of an electrical insulator, which is adhered to the sealing part of the holder via a thermoplastic resin adhesive; and an external electrode portion embedded in the thermoplastic resin adhesive of the holder or A discharge lamp having a thermosetting resin adhesive layer formed on at least one of the lead wire portions. 2. A glass bulb; a pair of internal electrodes sealed in the sealing portions at both ends of the bulb; lead wires connected to the internal electrodes and led out from the sealing portion; An external electrode formed along the bulb axis on the outer surface of the external electrode and connected to one of the internal electrodes via an impedance element; wound to cover the extended tip of the external electrode. A discharge lamp comprising: a protective film; a discharge sustaining medium enclosed in the bulb; and a holder made of an electric insulator adhered to a sealing portion at the end of the bulb via a thermoplastic resin adhesive. In the discharge lamp, the protective film is made of a polyimide resin. 3. A glass bulb; a pair of internal electrodes sealed in sealing portions at both ends of the bulb; lead wires connected to the internal electrodes and led out from the sealing portion; An external electrode formed along the bulb axis on the outer surface of the external electrode and connected to one of the internal electrodes via an impedance element; wound to cover the extended tip of the external electrode. A protective film made of a polyimide resin; a discharge sustaining medium sealed in the bulb; an electric insulator holder bonded to a sealing portion of the bulb end through a thermoplastic resin adhesive; In the discharge lamp in which the thermosetting resin adhesive layer is formed so as to cover at least one of the protective film or the lead wire portion embedded in the thermoplastic resin adhesive of the holder. Discharge lamp and butterflies. 4. The discharge lamp according to claim 2 , wherein the protective film covering the tip of the external electrode covers the external electrode more than twice and is wound around a bulb. . 5. The protective film covering the tip of the external electrode extends outside the holder and has a non-formation portion of the thermoplastic resin adhesive. Item 5. The discharge lamp according to any one of Items 4. 6. An illuminating device comprising the discharge lamp according to any one of claims 1 to 5 as a light source.