JPH09129187A - Excimer light emitting tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an excimer light emitting tube in which dispersion among the tubes and the dispersion of characteristics is small in discharge start and discharge termination voltage characteristics by coating with a dielectric substance the surfaces of first and second electrodes provided inside of fluorescent lamp. SOLUTION: Internal electrodes 3 are inserted into the inside of a glass bulb 2, the vessel of a display fluorescent lamp, from the low end front of the glass bulb 2, and an external electrode 4 is provided on the peripheral face of te glass bulb 2. Glass coatings 15 as dielectrics are applied to the whole surfaces of the internal electrodes 3, and the low ends of the glass coatings 15 are connected to the glass bulb 2. In the case in which two internal electrodes 3 are arranged in the glass bulb 2, and one is set to work as an external electrode, dielectric 18 are provided on the first and the second internal electrodes. Thereby, the waterproofing and the insulating of the electrode 4 are facilitated. Also it is possible to obtain an effect increasing a light amount.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a fluorescent lamp for display suitable as a light emitting element used in a large-sized image display device, an electronic bulletin board, etc., particularly in a color image display device.

[0002]

2. Description of the Related Art A fluorescent lamp for display used in a large-sized image display device is disclosed in, for example, Japanese Patent Laid-Open No. 5-190152 (hereinafter referred to as excimer arc tube).
There is. This is shown in FIGS. FIG. 7 is an external view of a conventional excimer arc tube, and FIG. 8 is a sectional view thereof.

FIG. 9 is an enlarged view of the internal electrode 3 provided inside the excimer arc tube of FIG. 7 for explaining the problems in the conventional light emitting operation.

7 to 10, reference numeral 1 is a conventional display fluorescent lamp, and 2 is a container constituting the display fluorescent lamp 1.
For example, it is a right cylindrical glass bulb having a diameter of 3 mm and a length of 10 mm. From the lower end surface of the glass bulb 2, the internal electrode 3
Is inserted inside the glass bulb 2, an outer electrode 4 is provided on the outer peripheral surface of the glass bulb 2, and the inner electrode 3 and the outer electrode 4 are connected to a power source 6 by lead wires 5a and 5b.

A phosphor layer 7 is formed on almost the entire inner wall of the glass bulb 2 excluding the upper end surface, and the upper end surface of the glass bulb 2 serves as a light output portion 8 having a light transmitting property. The glass bulb 2 contains 200T of xenon, which is a rare gas.
About orr is included.

The operation of the display fluorescent lamp (hereinafter also referred to as a lamp) 1 having the above structure will be described. Power supply 6 to internal electrode 3
When a voltage is applied between the external electrode 4 and the external electrode 4, a voltage is applied to the rare gas / xenon in the lamp through the glass that is a dielectric substance, and a discharge occurs. The ultraviolet rays generated at that time are the phosphor layer 7
Are converted into specific visible light determined by the phosphor.

Since the phosphor itself is white, the visible light generated from the phosphor is almost totally reflected by the phosphor layer 7 formed on the inner wall of the glass bulb 2 and returns to the inside of the glass bulb 2. Since this visible light is output and radiated to the outside of the glass bulb 2 from the light output portion 8 having a light-transmitting property, a high-luminance light emitting element can be obtained.

The power supply 6 is an AC power supply. The current flows only immediately after the polarity of the applied voltage is reversed, and otherwise the current is stopped by the accumulation of charges on the inner surface of the glass bulb. Therefore, a pulsed current flows through the lamp.

When the internal discharge state is observed in detail, as shown in FIG. 9, the entire inner surface of the lamp facing the outer electrode 4 is covered with the substantially uniform blue-violet light 13, and the inner electrode 3 It can be seen that many thin thread-shaped discharges 11 connecting the external electrodes 4 are generated.

On the side of the internal electrode 3, this thin thread-shaped discharge 11 is generated from the tip of the minute projection 10 on the electrode surface shown in FIG. There are innumerable such projections, and the surface of the projections 10 is heated by an electric current at the moment when electric discharge occurs, and spatters (electrode metal melts and scatters), so that the projections 10 are deformed or disappear.

As a result, the discharge is not stable at the same position and always moves on the surface of the internal electrode 3.

Reference numeral 14 in FIG. 10 shows an example of voltage and current characteristics of this type of fluorescent lamp for display. The horizontal axis of the figure shows the voltage value applied between the external electrode 4 and the internal electrode 3, and the vertical axis shows the value of the current flowing between the internal electrode 3 and the external electrode 4. The voltage is AC.

Conventionally, since metal is used for the internal electrode, when the internal electrode portion is enlarged, minute protrusions are present on the metal surface as shown in FIG. 9, and therefore discharge is likely to be concentrated on this protrusion portion. There was a drawback.

Once the concentration of the discharge occurs, the metal in that portion is heated to evaporate and generate sputtering, which stains the surface of the phosphor to reduce the brightness and changes in the shape of the fine projections due to sputtering, etc. change,
In the short term, it was easy to cause instability of the brightness due to the change in the position of the filamentous discharge.

Further, it is known that the discharge tube has a discharge start voltage and a discharge end voltage (also referred to as a minimum sustain voltage) at which the voltage is lowered once the discharge is started and the discharge is not maintained, as shown in FIG. However, when a large number of discharge tubes are arranged in a display device, the difference between these two voltages must be as large as possible and the voltages of the individual elements must be the same.

However, even if the position of the shape (thickness, length) of the internal electrode is strictly controlled, it is difficult to control the minute projections on the electrode surface and the end portion, so that a large number of light emitting elements having uniform characteristics are manufactured. Is difficult, or even if the characteristics are selected, the characteristics of the display device are deteriorated because the characteristics change with the display time due to the characteristics change due to the above reasons and become uneven.

[0017]

Since the conventional excimer arc tube is constructed as described above, it is not possible to obtain one having uniform characteristics. The characteristics are not stable. There was a problem that the discharge was not stable. That is, even if the shape (thickness, length) and position of the internal electrode can be strictly controlled, it is impossible to control the minute protrusions on the surface of the internal electrode. Even when only the uniform display lamps are used, there is a problem in that the characteristics of the display as a whole are not uniform and the display quality is deteriorated due to a difference in the characteristics over time.

[0018]

In the fluorescent lamp for display according to the first invention, the surfaces of the first and second electrodes provided inside the lamp are coated with a dielectric.

The display fluorescent lamp according to the second invention is the first
Alternatively, in addition to the means of the second invention, the dielectric covers the discharge surfaces of all the electrodes inside the glass bulb.

The display fluorescent lamp according to the third invention uses glass or ceramic as a dielectric in addition to the means of the first and second inventions.

The display fluorescent lamp according to the fourth invention is the fourth.
In addition to the means of the invention, the glass coating or the ceramic layer has a layer for reflecting external light on the surface or the inner surface thereof.

The display fluorescent lamp according to the fifth invention is the fourth fluorescent lamp.
In addition to the means of the invention of 1, the phosphor layer is provided on the surface or the inner surface of the glass coating layer.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. Embodiments according to the first and third inventions of the present invention are shown in FIGS. 1 is a view showing the structure, FIG. 2 is a cross-sectional view, and FIG. 3 is an enlarged view for explaining the details of the internal electrodes in FIG. FIG. 4 is an electrical characteristic diagram.

In FIGS. 1 to 3, 100 is a display fluorescent lamp according to the present invention, and 2 is a container that constitutes the display fluorescent lamp 100, for example, a straight cylindrical glass bulb having a diameter of 3 mm and a length of 10 mm. . The inner electrode 3 is inserted into the glass bulb 2 from the lower end surface of the glass bulb 2, and the outer electrode 4 is provided on the outer peripheral surface of the glass bulb 2. The inner electrode 3 and the outer electrode 4 are connected to the lead wires 5a and It is connected to the power supply 6 by 5b.

A phosphor layer 7 is formed on almost the entire inner wall of the glass bulb 2 excluding the upper end surface, and the upper end surface of the glass bulb 2 has a light transmitting property and serves as a light output portion 8. Xenon, which is a rare gas, is 200To inside the glass bulb 2.
About rr is enclosed. Reference numeral 15 is a glass coating covering the entire surface of the internal electrode 3, and its thickness is 0.0
It is about 1 to 0.1 mm. The lower end of the glass coating 15 is connected to the glass bulb 2.

Although the glass coating 15 and the surface of the internal electrode 3 are in close contact with each other, there may be a very small gap.

The material of the glass used for the glass coating 15 may be the same as that of the glass bulb 2, but it is suitable that the coefficient of thermal expansion thereof is close to that of the internal electrode 3 since the temperature becomes high due to the emitted heat. There is. The color of the glass used for the glass coating 15 is not particularly limited.

The operation of the display fluorescent lamp (hereinafter also referred to as a lamp) 100 having the above structure will be described. When a voltage is applied between the inner electrode 3 and the outer electrode 4 from the power source 6, a voltage is applied to the rare gas / xenon in the lamp through the glass of the glass bulb 2 and the glass of the glass coating 15 which are dielectrics, and a discharge is generated. Occur. The ultraviolet light generated at that time excites the phosphor layer 7 and is converted into a specific visible light determined by the phosphor.

Since the phosphor itself is white, the visible light generated from the phosphor is almost totally reflected by the phosphor layer 7 formed on the inner wall of the glass bulb 2 and returns to the inside of the glass bulb 2. Since this visible light is output and radiated to the outside of the glass bulb 2 only from the light output portion 8 having a light-transmitting property, a high-luminance light emitting element can be obtained.

The current flows only immediately after the polarity of the applied voltage is reversed, and otherwise the current is stopped by the accumulation of charges on the inner surface of the glass bulb. Therefore, a pulsed current flows through the lamp.

When the internal discharge state is observed in detail, as shown in FIG. 3, the entire inner surface of the lamp facing the outer electrode 4 is covered with the substantially uniform bluish-violet light 13, and the inner electrode 3 and The thin thread-like discharge connecting the external electrodes 4 is smaller than that in the case of FIG. 9, and is a mist-like discharge.

The position of the discharge is stable, and as shown in FIG.
It is rare to say that it often moves as in the case of.

As a result of the presence of the glass coating 15 on the surface of the internal electrode 3, once discharge occurs, the charge is accumulated in the coating of the discharged part, so that the discharge is stopped and the charge is not discharged. This is because the discharge is moved to a portion where is not accumulated and the discharge is generated in a wide range on the electrode, so that the discharge is not concentrated.

Reference numeral 16 in FIG. 4 shows an example of voltage and current characteristics of the fluorescent lamp for display according to the present invention. The horizontal axis of the figure is the voltage value applied between the external electrode 4 and the internal electrode 3,
The vertical axis represents the value of the current flowing between the inner electrode 3 and the outer electrode 4. The voltage is AC.

Compared to the conventional characteristic 14, the difference between the discharge start voltage and the discharge end voltage (minimum sustain voltage) is large.

It is considered that this is because the surface of the internal electrode is coated with the dielectric material 15, which is an insulator, so that electrons, ions, etc. in the space near the internal electrode do not disappear.

Further, although not shown in the figure, the individual difference of the display fluorescent lamp 100 is small. That is, variations in characteristics are reduced.

This is because the surface of the internal electrode 4 is apparently smooth due to the glass coating 15, and the presence of the large protrusions 10 prevents the characteristics thereof from being extremely changed.

In FIG. 1 or 2, the external electrode 4 may have the same structure as the internal electrode 3, and both electrodes may be provided side by side inside the glass bulb 2. With such a structure, waterproofing and insulation of the external electrodes can be facilitated.

Although not shown in the figure, the electrode penetrating portion of the glass bulb 2 of FIG. 2 has a so-called hermetic seal structure, so that the glass is covered up to near the tip of the internal electrode 3.

The internal electrode 3 is the first electrode. The external electrode 4 is the second electrode regardless of whether it is outside or inside the glass bulb 2.

Embodiment 2. FIG. 5 shows a cross-sectional view of an excimer arc tube according to another embodiment of the first and second inventions of the present invention. In the figure, reference numeral 18 denotes a cylindrical dielectric material which is covered with the internal electrode 3. This may be glass, ceramic, quartz, mica, or cement-like insulator that withstands heat and ultraviolet rays, does not generate gas, etc., and can be made into an extremely thin pipe-like structure. .

The tip of the dielectric 18 need not be closed but may be open as long as it is sufficiently longer than the tip of the internal electrode 3 and does not cause discharge. In short, it is provided so as to cover the discharge surface of the surface of the electrode.

Although the dielectric 18 and the glass bulb 2 may be adhered to each other, they need not be adhered as long as they are physically held.

In the figure, the external electrode 4 of FIG. 1 is also shown to be provided inside the glass bulb 2 and to have two internal electrodes 3, but one of them electrically functions as an external electrode. is there.

The dielectric 18 is provided at the portion where discharge occurs in all the electrodes provided inside the glass bulb 2.

Embodiment 3 An embodiment of the arc tube according to the fifth invention is shown in FIG. FIG. 6 is a cross-sectional view showing a state in which the dielectric coating 19 of the internal electrodes is applied.
Reference numeral 19 is a glass coating having a light reflecting film on the surface or the inner surface thereof, and 20 is a light reflecting film provided on the surface of the dielectric coating.

The ultraviolet rays generated from the discharge and the light emitted from the fluorescent material 7 are reflected by the reflective film 20, so that the excimer arc tube has an effect of increasing the light output.

This reflective film is made of, for example, titanium oxide (TiO 2).
₂ ), magnesium oxide (MgO), or the like having a high reflectance is preferable, and even if a phosphor is applied instead of the reflective film, the same effect can be expected because the reflectance of the phosphor itself is high, and light emission is further improved. There is an effect that the optical output is increased by increasing the number of parts.

[0050]

The excimer arc tubes according to the first, second, and third aspects of the present invention have a small individual difference in discharge start and discharge end voltage characteristics and a small characteristic variation. Therefore, when a large number of arc tubes are combined as a display, The display quality is improved.

The excimer arc tube according to the first aspect of the present invention has the effect of further facilitating waterproofing and insulation of the external electrodes.

The excimer arc tubes according to the fourth and fifth inventions have the effect of increasing the amount of light in addition to the effect of the third invention.

[Brief description of the drawings]

FIG. 1 is a diagram showing a structure of an excimer arc tube according to Embodiment 1 of the present invention.

FIG. 2 is a sectional view of the excimer arc tube of FIG.

FIG. 3 is a detailed view of internal electrodes of the excimer arc tube of FIG.

FIG. 4 is a diagram showing electrical characteristics of the excimer arc tube of FIG.

FIG. 5 is a sectional view of an excimer arc tube according to Embodiment 2 of the present invention.

FIG. 6 is a detailed view showing an internal electrode structure of an excimer arc tube according to Embodiment 3 of the present invention.

FIG. 7 is a diagram showing a structure of a conventional excimer arc tube.

8 is a sectional view of the excimer arc tube of FIG.

9 is a diagram illustrating details of internal electrodes of the excimer arc tube of FIG. 7. FIG.

FIG. 10 is a diagram showing electrical characteristics of the excimer arc tube of FIG.

[Explanation of symbols]

2 Glass bulb 3 Internal electrode 4 External electrode 7 Phosphor layer 8 Light output part 10 Protrusions 15 Glass coating 16 Voltage-current characteristics 18 Cylindrical dielectric 19 Glass coating 20 Light reflection layer 100 Fluorescent lamp for display

Claims (5)

[Claims] 1. A rare gas is enclosed in a glass bulb,
An excimer arc tube in which a phosphor layer is formed on an inner surface and a voltage is applied between first and second electrodes provided inside the excimer arc tube so that the phosphor layer emits light. An excimer arc tube characterized in that both electrodes have a dielectric coating layer on their surfaces. 2. The excimer arc tube according to claim 1, wherein the dielectric coating layer covers the discharge surfaces of all the electrodes provided inside the glass bulb. 3. The excimer arc tube according to claim 1, wherein the dielectric material forming the coating layer is glass or ceramic. 4. The excimer arc tube according to claim 3, wherein the glass coating layer is made of glass or ceramic having a light reflection layer for reflecting light on the surface or the inner surface thereof. 5. The excimer arc tube according to claim 3, wherein the glass coating layer is made of glass having a phosphor layer on its surface or inner surface.