JP4199022B2 - Cold cathode fluorescent lamp - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cold cathode fluorescent lamp, and more particularly, to a cold cathode fluorescent lamp with improved performance.
[0002]
[Prior art]
For example, liquid crystal display devices such as a liquid crystal display, a word processor, and a personal computer are required to have high performance, a small size, and a long life as the application is expanded or spread. In response to such a demand, a cold cathode fluorescent lamp (cold cathode low-pressure discharge lamp) as a backlight light source is inevitably required to have a higher level of performance.
[0003]
FIG. 3 is a cross-sectional view showing a schematic configuration of a cold cathode fluorescent lamp that has been conventionally used as a backlight light source. That is, a glass tube (glass bulb) 2 in which a phosphor layer 1 that emits light by stimulation with ultraviolet rays is provided on an inner wall surface and a rare gas such as neon or argon and mercury are enclosed as a discharge medium, and both ends of the glass tube 2 And a pair of discharge electrodes 4a sealed in the glass tube 1 that are electrically connected to opposite ends of the introduction wires 3a and 3b, respectively. , 4b.
[0004]
Here, the glass tube 2 has an inner diameter of about 1.2 to 4.8 mm and a length of about 40 to 800 mm. Further, in the glass tube 2, 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.
[0005]
Further, in the above-described configuration, the discharge electrodes 4a and 4b are, for example, cylindrical bodies (for example, nickel cylinders) 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. ) And an emitter layer coated and baked on the outer surface of the side wall of the cylindrical body. The electrodes 4a and 4b are electrically connected to the outer bottom surface of the cylindrical body, which is a component, by electrically connecting the distal ends of the pair of lead-in wires 3a and 3b introduced and sealed by spot welding or the like. It is fixed to the joint.
[0006]
That is, a configuration is adopted in which one electrode is grounded via the lead-in wires 3a and 3b and the other is on the high voltage side, and a required voltage is applied to the discharge electrodes 4a and 4b so that the electrodes 4a and 4b function as discharge electrodes. Note that the emitter layer is generally formed of a material mainly composed of an electron-emitting substance such as a barium compound, an yttrium compound, a lanthanum compound, or a cesium compound. When a required voltage is applied to the pair of discharge electrodes 4a and 4b carrying the emitter layer via the lead-in wires 3a and 3b, the discharge is easily started and ultraviolet rays are radiated. 1 is converted into visible light and functions as a cold cathode fluorescent lamp.
[0007]
[Problems to be solved by the invention]
By the way, when the cold cathode fluorescent lamp is incorporated in a backlight unit, for example, the cold cathode fluorescent lamp is started in the dark, and at this time, the discharge may be delayed by several seconds. This start-up characteristic problem is usually placed in the dark, so in the backlight of liquid crystal display devices where the occurrence of a discharge delay is an important issue (due to the reduction of initial electrons), this is due to the addition of lamp life. It raises various problems.
[0008]
As a countermeasure against this discharge delay, normally, aging lighting is performed at a high current to forcibly blacken the spatter. However, the forced sputter blackening promotes the consumption or shortening of the life of the electrodes 4a and 4b, and also reduces the light emission efficiency or the light emission luminance.
[0009]
In order to avoid or reduce the blackening problem, it is also known that the electrodes 4a and 4b carry an emitter (metal oxide for preventing discharge delay) such as cesium oxide and perform aging lighting with a low current. Yes. It is also known that the metal oxide for preventing the discharge delay is added and mixed in the phosphor layer by about several percent by weight. That is, when a metal oxide for preventing discharge delay such as cesium oxide is applied to the discharge electrodes 4a and 4b, the lamp voltage is lowered by the work function of the metal oxide for preventing discharge delay. This is because that.
[0010]
However, in reality, there is a problem that the emitter is consumed due to sputtering during lighting, and the lamp voltage rises during lighting (lamp voltage instability) occurs, which is not a sufficient countermeasure. Moreover, the occurrence of the sputtering causes premature exhaustion of mercury and premature exhaustion of the sealed gas, resulting in a reduction in lamp life. It should be noted that the extreme occurrence of sputtering causes damage to the glass tube 2 due to discharge starting from the sputtering portion. On the other hand, when the metal oxide for preventing delay is a non-light emitting substance, the addition and mixing of the phosphor layer impairs the light emission characteristics of the phosphor layer, resulting in a decrease in luminance and luminous flux.
[0011]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a cold cathode fluorescent lamp suitable for a light source such as a backlight unit while maintaining excellent starting characteristics and high luminance.
[0012]
[Means for Solving the Problems]
The cold cathode fluorescent lamp of the present invention includes a glass tube having a phosphor layer provided on the inner wall surface and sealed with a rare gas and mercury, and a pair of introductions sealed and introduced at opposite ends of the glass tube. A cold cathode fluorescent lamp having a wire and a pair of discharge electrodes which are electrically connected and sealed to the leading ends of the lead-in wires, respectively,
For preventing discharge delay having an average particle size larger than the average particle size of the phosphor forming the phosphor layer on the phosphor layer surface extending from the region facing the high-voltage side discharge electrode in the discharge electrode to the glass tube sealing side A metal oxide layer is provided.
[0013]
Further, the cold cathode fluorescent lamp of the present invention includes a glass tube having a phosphor layer provided on the inner wall surface and filled with a rare gas and mercury, and a pair of oppositely disposed outer peripheral surfaces at both ends in the glass tube. A cold cathode fluorescent lamp having an outer discharge electrode,
For preventing discharge delay having an average particle size larger than the average particle size of the phosphor forming the phosphor layer on the phosphor layer surface extending from the region facing the high-voltage side discharge electrode in the discharge electrode to the glass tube sealing side A metal oxide layer is provided.
[0014]
In the cold cathode fluorescent lamp of the present invention, the metal oxide layer for preventing discharge delay extends from the edge of the phosphor layer toward the glass tube sealing side.
[0015]
In the present invention, a rare gas and mercury are enclosed as a discharge medium in a glass tube, and a cold cathode fluorescent lamp formed by sealing a pair of discharge electrodes facing both ends of the glass tube, or facing both outer peripheral surfaces of the glass tube The cold cathode fluorescent lamp having a pair of outer surface discharge electrodes arranged (arranged) is based on the result of examination of discharge delay countermeasures in the dark. That is, in the discharge electrode of the cold cathode fluorescent lamp, a discharge delay-preventing metal oxide (metal oxide having electron emission property), for example, oxidation is applied from the region facing the high-pressure side discharge electrode to the phosphor layer surface on the glass tube sealing side. It has been found that when a cesium layer is provided, the discharge delay in the dark can be easily improved without causing a decrease in luminance, and the present invention has been achieved.
[0016]
Furthermore, the present inventor, instead of supporting cesium oxide (cesium compound) or the like on the discharge electrode surface, adheres to the phosphor layer surface in the region facing the discharge electrode on the high-voltage side, particularly in the pair of discharge electrodes.・ We carried and examined and evaluated countermeasures for discharge delay in the dark. For example, in the configuration of a cold cathode fluorescent lamp using a glass tube having an outer diameter of 1.8 mm and a length of 200 mm as an arc tube, as shown in FIG. In the body layer 1 surface, the cesium oxide layer 5 was provided on the entire surface on the glass tube 2 sealing side from the region facing the electrode 4a (4b) portion.
[0017]
And about these cold cathode fluorescent lamps, when the discharge delay time in the dark was measured, it was opposite to the high voltage side discharge electrode 4a (4b) on the basis of the glass tube 2 sealing side phosphor layer edge on the high voltage discharge electrode side. It has been found that when the cesium oxide layer 5 is provided on the surface of the phosphor layer 1 in the area to be discharged, the discharge delay (startability) in the dark is greatly improved. Here, the cesium oxide layer 5 on the surface of the phosphor layer 1 in the region facing the high-voltage side discharge electrode 4a (4b) is preferably set and selected as follows.
[0018]
That is, on the tip side of the high-voltage side discharge electrode 4a (4b), the tip of the cesium oxide layer 5 protrudes from 0 to 2 mm, more preferably from about 0 to 1 mm, while on the sealing side of the glass tube 2, at least When covering to the edge of the phosphor layer 1, preferably extending from the edge, a more excellent start-up characteristic is exhibited, while the consumption during lighting is small and the life is extended. In addition, the film thickness (layer thickness) of the cesium compound 5 may be about 5-10 micrometers, and may be formed in the spot shape instead of a uniform layer.
[0019]
Here, as the metal oxide for preventing discharge delay, in addition to cesium compounds (for example, cesium oxide, cesium sulfate, cesium chromate, etc.), for example, metal oxides having a low work function such as alumina, strontium, calcium compounds, etc. Similarly, the lamp voltage can be lowered, and the discharge delay in the dark can be improved. The average particle diameter of the discharge delay preventing metal oxide is preferably larger than the average particle diameter of the phosphor forming the phosphor layer 1. That is, when the average particle diameter of the discharge delay preventing metal oxide is the same as or smaller than the average particle diameter of the phosphor, the discharge delay preventing metal oxide is made of glass by the impact of rare gas or mercury ions during lighting. Since it moves to the tube 2 side and the effect of preventing discharge delay may be reduced, it is desirable to select a particle size larger than the average particle size of the phosphor.
[0020]
In the present invention, the glass tube generally has an inner diameter of about 1.2 to 4.8 mm and a length of about 40 to 800 mm. In the glass tube, for example, 0.5 to 2.5 mg / A mercury gas of about cm ³ and a rare gas of about 60 to 150 Torr such as neon and argon are enclosed.
[0021]
In the present invention, the discharge electrodes sealed at both ends in the glass tube are, for example, tantalum type 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 4 mm. It is composed of a molybdenum-based metal cylinder. The discharge electrode is electrically connected to the outer bottom wall surface of the metal cylindrical body, and the required grounding and voltage application is performed through an introduction line that seals and leads the end of the glass tube. .
[0022]
In the present invention, the outer discharge electrodes arranged on the outer peripheral surfaces of both ends of the glass tube have a wall thickness of 0.1 to 0.1 that has an inner diameter that can be closely and fitly fitted to the glass tube via a conductive layer or the like. It is made of a metal having a length of about 0.2 mm and a length of about 2 to 30 mm, for example, a tape made of Al, Ni, Cu, Fe, SUS, etc., a conductive metal oxide film, or the like. The outer surface discharge electrode is subjected to required grounding and voltage application via an electrically connected lead wire.
[0023]
In the above invention, the metal oxide layer for preventing discharge delay on the phosphor layer on the inner wall surface of one end of the glass tube is formed on the one end side of the glass tube opened in the lamp manufacturing process. Since the neck cleaning of the layer and the neck cleaning of the metal oxide layer for preventing discharge delay can be performed easily and selectively, the required metal oxide layer for preventing discharge delay can be provided with high accuracy, and quality control, etc. This is also advantageous.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment will be described with reference to FIGS. 1 and 2.
[0025]
FIG. 1 is an enlarged cross-sectional view showing a main configuration of a cold cathode fluorescent lamp according to a first embodiment. That is, a phosphor layer 1 that emits light by stimulation with ultraviolet rays is provided on the inner wall surface, and a glass tube 2 in which rare gas and mercury are enclosed, and a pair of seals that are respectively opposed to both ends of the glass tube 2 Lead wires 3a, 3b, discharge electrodes 4a, 4b sealed and joined to the leading ends of the lead wires 3a, 3b, and the discharge electrodes on the high voltage side among the electrodes 4a, 4b (ground side and high voltage side) Based on 4a (4b), the cesium oxide deposited on the surface of the phosphor layer 1 in the region facing the discharge electrode 4a (4b) on the high voltage side by extending 0 to 2.5 mm toward the glass tube 2 sealing side The structure having the layer 5 is adopted.
[0026]
Here, the glass tube 1 has, for example, an outer diameter of 2.6 mm, an inner diameter of 2.0 mm, and a length of 220 mm. For example, mercury of about 2.5 mg / cm ³ and rare gas such as neon and argon of about 80 Torr are enclosed. ing. In this specific example, the cesium oxide layer 5 is provided so as to be aligned with the tip of the high-voltage discharge electrode 4a (4b) (protrusion 0 mm) and extended from the sealing end-side edge. Further, the discharge electrodes 4a and 4b are formed of a nickel metal cylinder having an outer diameter of 1.7 mm and a length of 2.8 mm.
[0027]
Furthermore, the discharge electrodes 4a and 4b are joined to the outer bottom wall surface of the cylindrical body by spot welding or the like, with the leading ends of the lead wires 3a and 3b sealed and led out at both ends of the glass tube 2, respectively. Electrical connection is made along with mechanical fixation. That is, if one of the pair of discharge electrodes 4a and 4b is connected to the ground side and the discharge electrode 4a (4b) is connected to the high voltage side through the lead-in wires 3a and 3b, the current can be easily supplied. Ultraviolet rays are radiated, and the ultraviolet rays are converted into visible light by the phosphor layer 1 to function as a light source having excellent dark characteristics.
[0028]
When the cold cathode fluorescent lamp having the above configuration was subjected to a continuous lighting test under a lamp current condition of 5 mA, the bulb voltage hardly changed even after 10,000 hours had elapsed. In addition, it was confirmed that the luminous flux comparable to that at the beginning of lighting was maintained and exhibited, and the lifetime and luminous efficiency were excellent. That is, the cold cathode fluorescent lamp according to the first example maintains a low work function of cesium oxide and good discharge delay preventing property (emitter property). Therefore, the lamp voltage rise during lighting for a long time is also eliminated, and electrons are efficiently exchanged by the emitter, so that excellent startability and long life are ensured.
[0029]
FIG. 2 is an enlarged cross-sectional view showing the main configuration of the cold cathode fluorescent lamp according to the second embodiment. That is, a phosphor layer 1 that emits light by stimulation with ultraviolet rays is provided on the inner wall surface, and a glass tube 2 in which a rare gas and mercury are enclosed, and opposite both outer peripheral surfaces of the glass tube 2 are arranged in close contact with each other. Of the pair of external discharge electrodes 4a and 4b and the electrodes 4a and 4b (the ground side and the high voltage side), the discharge electrode 4a (4b) on the high voltage side is used as a reference. A structure having a cesium oxide layer 5 which is applied by extending 0 to 2.5 mm toward the glass tube 2 sealing side on the surface of the phosphor layer 1 in the facing region is adopted.
[0030]
Here, the glass tube 1 has, for example, an outer diameter of 2.6 mm, an inner diameter of 2.0 mm, and a length of 220 mm. For example, mercury of about 2.5 mg / cm ³ and rare gas such as neon and argon of about 80 Torr are enclosed. ing. Further, in this specific example, the cesium oxide layer 5 is provided with the tip portion aligned with the tip portion of the high-voltage side discharge electrode 4a (4b) (projecting 0 mm) and extending from the edge on the sealing end side. Yes. Further, the discharge electrodes 4a and 4b are formed in a cylindrical shape with a conductive metal oxide film, a nickel-based thin film or the like.
[0031]
Furthermore, although not shown, the discharge electrodes 4a and 4b are electrically connected by lead wires drawn to both ends of the glass tube 2. In other words, when one of the pair of discharge electrodes 4a and 4b is energized through the lead wire with one of the discharge electrodes 4b (4a) as the ground side and the discharge electrode 4a (4b) as the high-voltage side, Ultraviolet rays are radiated, and the ultraviolet rays are converted into visible light by the phosphor layer 1 to function as a light source having excellent dark characteristics.
[0032]
When the cold cathode fluorescent lamp having the above configuration was subjected to a continuous lighting test under a lamp current condition of 5 mA, the bulb voltage hardly changed even after 10,000 hours had elapsed. In addition, it was confirmed that the luminous flux comparable to that at the beginning of lighting was maintained and exhibited, and the lifetime and luminous efficiency were excellent. That is, the cold cathode fluorescent lamp according to the second embodiment maintains a low work function and good discharge delay prevention (emitter property) of cesium oxide. Therefore, the lamp voltage rise during lighting for a long time is also eliminated, and electrons are efficiently exchanged by the emitter, so that excellent startability and long life are ensured.
[0033]
As can be seen from the above embodiments, the cold cathode fluorescent lamp according to the present invention is provided in the darkness by providing a metal oxide layer for preventing discharge delay on the phosphor layer surface in the region facing the discharge electrode on the high voltage side. Stable startability even when placed. In addition, the ease of discharge is improved by increasing the supporting and forming surface of the metal oxide for preventing discharge delay, but there is no wear during lighting. That is, the lifetime can be extended in combination with the prevention / reduction of sputtering of the metal oxide for preventing discharge delay.
[0034]
The present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the invention. For example, the diameter and length of the glass tube constituting the arc tube, the interval between the discharge electrodes, and the material shape and dimensions of the forensic electrode can be appropriately changed and set. Further, the metal oxide for preventing discharge delay may be a metal oxide other than the cesium compound.
[0035]
【The invention's effect】
According to the present invention described above, since the consumption of cesium oxide and the like is suppressed as compared with a cold cathode fluorescent lamp (conventional example) having a structure in which a cesium compound layer is applied and formed on the discharge electrode, a small size with excellent startability. Thus, a long-life cold cathode fluorescent lamp is provided. That is, the improvement of the sputtering resistance of the cesium oxide layer and the like also prevents the lamp voltage (cathode drop voltage) from increasing during the lifetime and lowers the power and increases the efficiency of the cold cathode fluorescent lamp. Therefore, a cold cathode fluorescent lamp suitable for a liquid crystal backlight requiring a small size, high efficiency, long life and the like is provided.
[Brief description of the drawings]
FIG. 1 is an enlarged cross-sectional view showing a main configuration of a cold cathode fluorescent lamp according to a first embodiment.
FIG. 2 is an enlarged cross-sectional view showing a main configuration of a cold cathode fluorescent lamp according to a second embodiment.
FIG. 3 is a cross-sectional view showing a schematic configuration of a conventional cold cathode fluorescent lamp.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Phosphor layer 2 ... Glass tube 3a, 3b ... Lead-in wire 4a, 4b ... Discharge electrode 5 ... Cesium compound layer

Claims (3)

A glass tube in which a phosphor layer is provided on the inner wall surface and in which rare gas and mercury are enclosed, a pair of introduction lines sealed and introduced opposite to both ends of the glass tube, and opposed tips of the introduction lines A cold cathode fluorescent lamp having a pair of discharge electrodes electrically connected and sealed to each part,
For preventing discharge delay having an average particle size larger than the average particle size of the phosphor forming the phosphor layer on the phosphor layer surface extending from the region facing the high-voltage side discharge electrode in the discharge electrode to the glass tube sealing side A cold cathode fluorescent lamp comprising a metal oxide layer. A cold cathode fluorescent lamp comprising a glass tube provided with a phosphor layer on an inner wall surface and filled with rare gas and mercury, and a pair of outer surface discharge electrodes disposed opposite to the outer peripheral surfaces at both ends in the glass tube. There,
For preventing discharge delay having an average particle size larger than the average particle size of the phosphor forming the phosphor layer on the phosphor layer surface extending from the region facing the high-voltage side discharge electrode in the discharge electrode to the glass tube sealing side A cold cathode fluorescent lamp comprising a metal oxide layer. 3. The cold cathode fluorescent lamp according to claim 1, wherein the discharge delay preventing metal oxide layer extends from the edge of the phosphor layer toward the glass tube sealing side .

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