KR20080084731A - Cold cathode fluorescent lamp - Google Patents

Abstract

A cold cathode fluorescent lamp is provided to obtain high sputtering resistance by forming electrodes including nickel and tungsten or molybdenum. A fluorescent material layer(4) is formed on an inner surface of a light transmitting tube(2) for storing rare gas and mercury. Both ends of the light transmitting tube are sealed with sealing members. A plurality of electrodes(7) are formed around both ends of the inside of the light transmitting tube. A plurality of lead lines(9) are connected to the electrodes and penetrate the sealing member. Each of the electrodes includes nickel as a main element. Each of the electrodes includes tungsten within a range of 0.4-6.5 weight percent and molybdenum within a range of 3-35 weight percent.

Description

Cold Cathode Fluorescent Lamps {COLD CATHODE FLUORESCENT LAMP}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to cold cathode fluorescent lamps, and more particularly to cold cathode fluorescent lamps that extend their lifetime by improving sputtering resistance of electrodes.

This application is based on Japanese Patent Application No. 2007-66817, filed March 15, 2007, which claims the benefit of priority, and all of the contents of this patent application are incorporated herein by reference.

Cold cathode fluorescent lamps have excellent characteristics such as high brightness, high color rendering characteristics, long lifespan, and low power consumption, so that the backlight of liquid crystal display devices used for television receivers, computers, light sources for image readings such as facsimile machines, copiers, etc. It is frequently used in eraser light sources and various display devices. In this type of cold cathode fluorescent lamp, voltage is applied to the electrodes provided near both ends of a light transmitting tube, such as a glass tube, and a small amount of gas and mercury in the inside of the light tube is preserved by airtightness. The existing electrons collide with the rare gas, and the rare gas is ionized. The ionized rare gas collides with the electrons and secondary electrons are released, thereby causing a glow discharge. Mercury is excited as the discharge electrons collide to emit ultraviolet light. Fluorescent materials absorb ultraviolet light and emit fluorescence.

As an electrode of such a cold cathode fluorescent lamp, a pair of cup-shaped electrodes are used, and these electrodes are provided near both ends in the interior of the floodlight tube so that the cup-shaped openings face each other. Cup-shaped electrodes can reduce tube voltage and power consumption. These electrodes are made of nickel, since their melting temperature is as low as about 1200 ° C, they can be easily processed, have excellent sputtering resistance to ions such as mercury and rare gases, and are commonly used in Kovar, which is commonly used in sealing members and the like. This is because good welding is ensured, and also durability is achieved upon application of 4 to 5 kPa. However, the cold-cathode fluorescent lamps used in the backlight of the recent large-sized television screens and high-brightness liquid crystal display devices need to be durable against currents of less than 5 mA. For this reason, electrodes made of high melting point sintered metals such as molybdenum and niobium having good sputtering resistance under large loads are used instead of nickel electrodes.

For example, one or more kinds of metal particles selected from the group consisting of niobium, molybdenum, tantalum and tungsten are bonded to each other and a porous bond having continuous projections and depressions of 0.1 to 5 탆 on the surface. A cold cathode fluorescent lamp in which an electrode member is formed of a material has been reported (Japanese Patent Laid-Open No. 2006-156151). In addition, cold cathode electrodes made of a sintered body of a single metal material such as tungsten, niobium, tantalum, molybdenum and rhenium, or an alloy of these metals having an average particle diameter not larger than 100 μm have been reported (Japanese Patent Laid-Open No. 2004-). 178875).

However, on the other hand, electrodes made of these high melting point sintered metals have a problem of deterioration of the lead wire which occurs when welding the lead wite and a problem of deterioration of the sealing member which occurs when sealing both ends of the floodlight tube. . In addition, these electrode materials are expensive compared to nickel, difficult to form electrodes, and require consumables such as jigs in this regard, which makes the electrodes very expensive. Therefore, the appearance of nickel electrodes with good sputtering resistance under large loads is expected. Nickel-molybdenum alloy electrodes containing 6 to 35% molybdenum have been reported (Japanese Patent Laid-Open No. 2006-12505). However, in the case of a nickel-molybdenum alloy electrode, when a high current of more than 10 mA is applied, the interface portions of the crystal grains are oxidized by a small amount of oxygen, so that sputtering resistance is drastically reduced.

We have already developed an electrode with improved sputtering resistance formed of a base material containing nickel or a nickel alloy and dispersed in yttrium. However, applying a high current of more than 10 mA to this electrode increases the heat generation of the electrode and reduces the sputtering resistance.

It is an object of the present invention to make the surface area less prone to oxidation at the time of manufacture, and to have a cold sputtered electrode which has excellent sputtering resistance, long life and low cost and can be easily manufactured even when a high amperage current is applied to the electrode. It is to provide a cathode fluorescent lamp.

As a result of the present inventor's dedication to research, he applied a high current exceeding 10 mA when the electrodes of a cold cathode fluorescent lamp were formed of a material containing nickel as a main component and a given amount of tungsten or further containing molybdenum. Even when the electrodes of the cold cathode fluorescent lamps have a good sputtering resistance, the knowledge that can extend the life of the cold cathode fluorescent lamp. The present inventors were able to complete the present invention based on this knowledge.

That is, the present invention provides a light emitting tube, wherein a layer of fluorescent material is provided on the inner wall surface of the light emitting tube, rare gas and mercury are preserved in the inside of the light emitting tube, and both ends of the light emitting tube are hermetically sealed with a sealing member; Electrodes provided near the both ends in the interior of the floodlight tube; And a lead wire connected to these electrodes and provided to penetrate the sealing member. In this cold cathode fluorescent lamp, the electrode contains nickel as the main component and contains tungsten in the range of not less than 0.4 wt% and not more than 6.5 wt%.

The cold cathode fluorescent lamp of the present invention has a light emitting tube provided with a layer of fluorescent material on the inner wall surface of the light emitting tube, rare gas and mercury are preserved inside the light emitting tube, and both ends of the light emitting tube are hermetically sealed with a sealing member. ; Electrodes provided near the both ends in the interior of the floodlight tube; And a lead wire connected to these electrodes and provided to penetrate the sealing member. In this cold cathode fluorescent lamp, the electrode contains nickel as the main component and contains tungsten in the range of not less than 0.4 wt% and not more than 6.5 wt%.

From the results, it is clear that the electrode used in the cold cathode fluorescent lamp of the present invention has excellent sputtering resistance, and the cold cathode fluorescent lamp of the present invention has excellent durability.

The cold-cathode fluorescent lamp of this invention which extended life by improving the sputtering resistance of an electrode is a light source which reads the image of backlights, a facsimile, etc. of a liquid crystal display device used for a television receiver, a computer, etc., the erasing light source of a copier, and various displays. It is useful because it can be advantageously applied to the device.

In the cold cathode fluorescent lamp of the present invention, the surface area of the electrodes is less easily oxidized during manufacturing, and has excellent sputtering resistance even when a high amperage current is applied to the electrodes. Cold cathode fluorescent lamps have a long lifetime and can be easily manufactured at low cost.

The cold cathode fluorescent lamp of the present invention has a light emitting tube provided with a layer of fluorescent material on the inner wall surface of the light emitting tube, rare gas and mercury are preserved inside the light emitting tube, and both ends of the light emitting tube are hermetically sealed with a sealing member. ; Electrodes provided near the both ends in the interior of the floodlight tube; And a lead wire connected to these electrodes and provided to penetrate the sealing member. In this cold cathode fluorescent lamp, the electrode contains nickel as the main component and contains tungsten in the range of not less than 0.4 wt% and not more than 6.5 wt%.

As the floodlight tube used in the cold cathode fluorescent lamp of the present invention, any material, for example, silicate glass, borosilicate glass, zinc boro, as long as the floodlight tube is made of a material which allows visible light emitted from the fluorescent material layer to pass through Those made of glass such as silicate glass, lead glass and soda glass can be used. Any type of light transmitting tube such as a straight tube and a curved tube can be used. A light transmitting tube having any tube diameter may be used, examples of the tube diameters include 1.5 to 6.0 mm. The thickness of the light transmitting tube may be selected as necessary according to the purpose of use, and the thickness of the light transmitting tube is preferably 0.15 to 0.60 mm if the diameter of the tube is in the above-described range.

A layer of fluorescent material is provided over almost the entire surface of the inner wall surface of the floodlight tube. The fluorescent material layer contains a fluorescent material, which will be described later, is excited by ultraviolet light emitted by mercury to emit fluorescence. Such fluorescent materials that emit visible light of a desired wavelength may be selected according to the purpose of use, and specific examples thereof include halphosphate fluorescent materials and rare earth fluorescent materials. Moreover, white light can be emitted by containing these fluorescent substances suitably. The thickness of the fluorescent material layer is preferably not smaller than 11 mu m but not larger than 28 mu m.

Mercury and rare gases selected from argon, xenon, neon and the like are sealed in the floodlight tube. The discharge electrons generated in the floodlight collide with the mercury atoms, and the mercury atoms generate 253.7 nm-containing ultraviolet light that excites the fluorescent material. Examples of the vapor pressure of mercury to be introduced include 1 to 10 Pa, and examples of the rare gas pressure include 5000 Pa to 11000 Pa when the cold cathode fluorescent lamp is turned on.

The electrodes provided at both ends of the interior of the light emitting tube contain nickel as a main component and contain tungsten in the range of not less than 0.4 mass% and not more than 6.5 mass%. Nickel as a main component can constitute the entire electrode except tungsten. The electrode containing nickel as a main component can suppress the deterioration of the lead wire when connecting the lead wire to the electrode, and can suppress the deterioration of the sealing member when both ends of the floodlight tube are hermetically sealed with the sealing member. The electrode containing has excellent forming power.

Tungsten contained in the electrode prevents the electrode from being sputtered by the collision of ionized rare gas and mercury, thereby providing excellent sputtering resistance to the electrode. In addition, even if traces of oxygen remaining in the electrode during manufacture oxidize the interface portions of the crystal grains, tungsten contained in the electrode can enhance the bonding of the interface of the crystal grains to further improve sputtering resistance. The tungsten content in the electrode is not less than 0.4 wt%, but not more than 6.5 wt%. If the tungsten content is in this range, the electrode has excellent sputtering resistance to ionized rare gas and mercury even when a current of more than 10 mA is applied, thereby extending the life of the cold cathode fluorescent lamp.

It is preferable that the molybdenum contained in the above-mentioned electrode exists in the range which is not less than 3 mass% and not more than 35 mass%. If molybdenum is within this range, an alloy of tungsten, molybdenum and nickel is formed, so that sputtering resistance is further improved. If the electrode contains molybdenum within this range, the electrode has excellent sputtering resistance even when applying a current exceeding 10 mA, thereby extending the life of the cold cathode fluorescent lamp.

In addition, it is preferable that the above-mentioned electrode contains yttrium in the range which is not less than 0.05 mass% and is not more than 1.10 mass%. By containing yttrium in this range, crystal grains of nickel in the electrode can be formed in a fine state having, for example, an average particle diameter not larger than 25 μm. And, the fine crystal particles in the electrode can make the bond between the particles strong, significantly preventing the electrode from being sputtered by the ions and mercury of the rare gas.

It is preferable that the cobalt or iron content in the electrode is not more than 0.5% by mass, respectively. If each of the cobalt or iron content is not more than 0.5% by mass, these components do not interfere with the operation of yttrium to refine the crystal grains of nickel, so that the crystal grains of nickel in the electrode are finely formed, resulting in sputtering resistance of the electrode. Further improve.

The average particle diameter of the crystal grains can be found from the particle diameter obtained by a comparative method comprising observing the surface of the electrode etched with acid under an optical microscope. Specifically, this average particle diameter is described in "An Introduction to Metallic Materials and Structures" (pp. 189 to 193) published and edited by The Japan Society for Heat Treatment (JSHT) and published by KK Taiga Shuppan. It can be found by using the method according to the method. By comparing the magnification of the optical microscope with a magnification of 100 times, the circle of the actual field of view having a diameter of 0.8 mm, and the circle of the photoprint having the diameter of 80 mm, and the standard diagram to determine the number of equivalent particle size And an average particle diameter are obtained. For example, a particle diameter of 25 μm is precisely located at 7.5, which is halfway between particle size numbers 7 and 8, so that an average value of the particle diameters can be obtained.

Since the tube voltage and power consumption can be reduced by the cup shape of the above-mentioned electrode, it is preferable to form a pair of electrodes in the vicinity of both ends in the inside of the floodlight tube so that the cup-shaped holes face each other. In making cup-shaped electrodes, one may also employ a method that involves cutting out members from the plate-shaped ingot and joining these members. In addition, the plate-shaped ingot can be cut out into a circle shape and the center of the circle can be hammered out into a cup shape to easily form an electrode. In addition, the cup is formed by cutting a material wire to a desired length, tapping the cut face in the axial direction to form a concave, and forming a concave into a cup shape. A shaped electrode can be easily formed. The shape of the cup, which may be appropriately selected depending on the inner diameter of the floodlight and the output of the lamp, may be, for example, an outer diameter of 1.05 to 2.75 mm and a length of 3 to 8 mm.

Lead wires are connected to the aforementioned electrodes to connect the electrodes to an external power source. The lead wire may be installed so that one end of the lead wire is dissolved and coupled to the bottom surface of the electrode and the other end of the lead wire passes through a sealing member for sealing the ends of the light emitting tube. The lead wire preferably has heat resistance to prevent the lead wire from deteriorating due to the heat performed when the sealing member is joined to the floodlight tube. In addition, it is possible to use a Kovar wire having a double structure in which Kovar is coated with a core wire made of copper so that the heat of the electrodes can be efficiently radiated to the outside of the floodlight tube during the use of the lamp.

A sealing member for hermetically sealing both ends of the above-described light emitting tube for storing rare gas and mercury is provided to penetrate the above-described lead wire and has a function of fixing the electrode through the lead wire. For example, bead glass, Kovar, etc. are used as a sealing member.

Between the fluorescent material layer of the floodlight tube and the surface of the inner wall, the cold cathode fluorescent lamp of the present invention suppresses the leakage of ultraviolet rays or the like emitted from mercury to the outside of the floodlight tube or the degradation of the floodlight tube due to mercury or the like. It may have a protective layer. The protective layer can be formed using, for example, metal oxides such as yttrium oxide, aluminum oxide and cerium oxide.

As a method of forming the cold cathode fluorescent lamp described above, yttrium is mixed with a melt of nickel and tungsten, or a melt of nickel, molybdenum and tungsten, and an ingot or material wire made of an alloy of these components is prepared. . Electrodes with microcrystalline particles are formed using such ingots or material wires.

As a method of manufacturing an electrode, specifically, the metal containing nickel which comprises the electrode mentioned above as a main component is dissolved. Regarding the dissolution temperature, it is preferable to perform dissolution at a temperature near the dissolution temperature of nickel, since this makes it possible to obtain an electrode having fine crystal grains.

The melt is then poured into ingots to form a mold and cast into ingots of nickel alloys containing these metals. Ingots are also plastically processed by hot rolling and cold rolling to form ingots, for example, sheet thicknesses of 0.1 to 0.2 mm or material wire diameters of 1 to 2.6 mm. can do. After the hot rolling and the inner rolling, the ingot is annealed to reduce internal stress deformation and improve spreadability. Then, surface grinding is performed. By subjecting the material wire to press forming or header processing, an electrode having a microcrystalline structure and a cup shape can be obtained. The lead wire is fused to the electrode thus obtained.

In forming the fluorescent material layer on the inner wall of the floodlight tube, a dispersion liquid in which the above-described fluorescent substance is dispersed in a solvent is prepared, and the inner wall surface of the floodlight tube made of glass or the like is coated with the dispersion liquid to a predetermined thickness. As the coating method, a method such as immersion or spraying can be adopted. The coated film is dried to form a layer of fluorescent material. Thereafter, the electrons are arranged at the end of the floodlight tube and the ends of the floodlight tube are hermetically sealed with a sealing member through which the lead wire is to pass. Mercury and rare gases can be introduced into the floodlight tube.

The backlight of the liquid crystal panel shown in FIG. 1 can be taken as an example of the cold cathode fluorescent lamp of the present invention. In the cold cathode fluorescent lamp 1 shown in the schematic cross-sectional view of FIG. 1, both ends of the glass tube 2 made of borosilicate glass are hermetically sealed with bead glass 3. The outer diameter of the glass tube 2 is in the range of 1.5 to 6.0 mm, preferably in the range of 1.5 to 5.0 mm. On the inner wall surface of the glass tube 2 a layer of fluorescent material 4 is provided substantially along the entire glass tube length. The pressure in the interior space 5 of the glass tube 2 is reduced to a few tenths of the atmospheric pressure and introduces a certain amount of rare gas and mercury into this space. As shown in the enlarged perspective view of FIG. 2, at both ends of the glass tube 2, cup-shaped holes 10 are opposed to each other and cup-shaped electrodes 7 each having the above-described chemical composition are arranged. . Each lead wire 9 is provided such that one end thereof is connected to the lower end face 8 of the electrode 7 and the other end penetrates through the bead glass 3 and is drawn out of the glass tube 2.

Since the cold cathode fluorescent lamp 1 described above has an electrode containing nickel as a main component, a predetermined amount of tungsten and, if necessary, a predetermined amount of molybdenum and yttrium and having a fine structure of crystal grains, the cold cathode fluorescent lamp is significantly improved. Has sputtering resistance and long lifespan.

The invention is described in more detail below with reference to exemplary embodiments.

Example 1

71.4 mass% nickel, 3.3 mass% tungsten, 25.0 mass% molybdenum; And a starting material having a chemical composition consisting of a total of 0.3 mass% of incident incident impurities such as carbon, silicon, copper, sulfur and magnesium at a temperature not lower than the melting point of nickel. This lysate was poured into molds and cooled at room temperature. Thereafter, hot rolling and cold rolling were repeated to produce a rolled material having a thickness of about 0.2 mm. The rolled material was annealed and press molded after surface polishing to produce a cup-shaped electrode with an outer diameter of 1.7 mm and a length of 5 mm. Kovar wire having a 0.8 mm bore was welded to the bottom surface of the electrode, each obtained as a 1-piece member.

The average crystal grain diameter of nickel of the electrodes was measured by a comparison method. The average diameter of the crystal grains of nickel was 20 mu m.

A dispersion liquid containing fluorescent material was applied to the inner wall surface of the glass tube having a bore of 2.0 mm in a thickness of about 18 mu m. The electrodes to which the Kovar wires were fused bonded were arranged at the ends in the glass tube so that the holes of the electrodes faced each other, and both ends of the glass tube were sealed by glass beads through which the Kovar wire penetrated. Thereafter, mercury and rare gases were introduced to prepare a cold cathode fluorescent lamp.

In the case of the obtained cold cathode fluorescent lamp, after the lamp was ignited with a tube current of 10 mA, it was observed from the wear amount of the cup-shaped portion whether or not the sputtering resistance was good. Sputtering resistance was evaluated from the amount of wear of the cup-shaped portion of the electrodes based on the following criteria. The results are shown in Table 1.

T: The wear of the cup-shaped portion is observed to be very slight.

0: Even though wear of the cup-shaped portion was observed, a cold cathode fluorescent lamp can be used sufficiently.

<: Wear of the cup-shaped portion is observed, which is an important site for use.

X: The wear of a cup-shaped part is severe, and a cold cathode fluorescent lamp cannot be used.

Example 2

A cold cathode fluorescent lamp was manufactured in the same manner as in Example 1, except that the chemical composition of the starting material was changed with respect to the chemical composition shown in Table 1. Sputtering tolerance of the obtained cold cathode fluorescent lamp was evaluated. The results are shown in Table 1.

Example 3

A cold cathode fluorescent lamp was manufactured in the same manner as in Example 1, except that the chemical composition of the starting material was changed with respect to the chemical composition shown in Table 1. Sputtering tolerance of the obtained cold cathode fluorescent lamp was evaluated. The results are shown in Table 1.

[Example 4]

A cold cathode fluorescent lamp was manufactured in the same manner as in Example 1, except that the chemical composition of the starting material was changed with respect to the chemical composition shown in Table 1. Sputtering tolerance of the obtained cold cathode fluorescent lamp was evaluated. The results are shown in Table 1.

[Comparative Example]

A cold cathode fluorescent lamp was manufactured in the same manner as in Example 1, except that the chemical composition of the starting material was changed with respect to the chemical composition shown in Table 1. Sputtering tolerance of the obtained cold cathode fluorescent lamp was evaluated. The results are shown in Table 1.

From the results, it is clear that the electrode used in the cold cathode fluorescent lamp of the present invention has excellent sputtering resistance, and the cold cathode fluorescent lamp of the present invention has excellent durability.

The cold-cathode fluorescent lamp of this invention which extended life by improving the sputtering resistance of an electrode is a light source which reads the image of backlights, a facsimile, etc. of a liquid crystal display device used for a television receiver, a computer, etc., the erasing light source of a copier, and various displays. It is useful because it can be advantageously applied to the device.

In the cold cathode fluorescent lamp of the present invention, the surface area of the electrodes is less easily oxidized during manufacturing, and has excellent sputtering resistance even when a high amperage current is applied to the electrodes. Cold cathode fluorescent lamps have a long lifetime and can be easily manufactured at low cost.

1 is a schematic cross-sectional view of an example of a cold cathode fluorescent lamp of the present invention.

FIG. 2 is a schematic perspective view of one example of the electrode shown in FIG. 1. FIG.

<Explanation of symbols for main parts of the drawings>

1: cold cathode fluorescent lamp

2: glass tube

3: bead glass

4: fluorescent material layer

5: interior space

7: electrode

8: bottom surface

9: lead wire

10: hole

Claims (3)

As a cold cathode fluorescent lamp, A floodlight tube provided with a layer of fluorescent material on the inner surface, the rare gas and mercury being preserved therein, and both ends sealed with a sealing member, Electrodes provided near both ends in the interior of the floodlight tube, and Lead wires connected to the electrodes and provided to penetrate the sealing member Including; And the electrode contains nickel as a main component, and contains tungsten within a range not less than 0.4 mass% and not more than 6.5 mass%. The method of claim 1, And the electrode contains molybdenum in a range of no more than 3% by mass and no more than 35% by mass. The method according to claim 1 or 2, Wherein said electrode contains yttrium in the range of not less than 0.05% by mass and not more than 1.10% by mass, and the content of cobalt or iron is not more than 0.5% by mass, respectively.

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