JP3673624B2 - Emitter, electrode, cold cathode fluorescent lamp and lighting device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cold cathode fluorescent lamp provided with an electrode having an emitter material and an illumination device using the lamp.
[0002]
[Prior art]
Cold cathode fluorescent lamps incorporated in backlights such as liquid crystal displays have become smaller in size as the backlights become smaller. For example, the tube diameter of the cold cathode fluorescent lamp is 4 mm or less, particularly 2.5 mm, and the electrode is often made of a metal such as nickel (Ni) or tungsten (W).
[0003]
On the other hand, the use of carrying a backlight is rapidly increasing, and in such a use, the cold cathode fluorescent lamp is driven by a battery. Accordingly, cold cathode fluorescent lamps are required to have lower power consumption and longer life.
[0004]
The electrode of the cold cathode fluorescent lamp has a long electrode life because it is a metal as described above. However, since electrons are generally extracted by field emission, power consumption accounts for a large proportion of electrode loss that does not contribute to light emission.
[0005]
Recently, in order to reduce this electrode loss, a technique for attaching an emitter material to an electrode has been disclosed. For example, a sintered body in which tungsten (W) and lanthanum boride (LaB ₆ ) are mixed and covered with an aluminum (Al) sleeve (Japanese Patent Laid-Open No. 7-153422), or titanium (Ti) in a cylindrical shape -Using an electrode in which mercury (Hg) and lanthanum boride (LaB ₆ ) are applied to the outer periphery (Japanese Patent Laid-Open No. 7-21979). Since these electrodes use an emitter material, the work function is lower than that of an electrode made of only a metal such as nickel (Ni), the cathode fall voltage is lowered, and the electrode loss is reduced.
[0006]
[Problems to be solved by the invention]
However, it has been found that lanthanum boride (LaB ₆ ) reacts with mercury (Hg) during lighting to form amalgam. This amalgamation of mercury (Hg) reduces the amount of mercury (Hg) present as vapor in the lamp, and reduces the amount of ultraviolet (185 nm, 254 nm) radiation that is the mercury (Hg) emission line obtained by discharge. Resulting in.
[0007]
That is, the ratio of the discharge by the rare gas increases due to the exhaustion of mercury (Hg), and not only the emission color is affected by the emission of the rare gas but also the visible light emitted from the phosphor by the excitation of ultraviolet rays. Since the amount of light is also reduced, there is a problem that the brightness of the cold cathode fluorescent lamp is remarkably lowered and the service life is reached early.
[0008]
The present invention has been made to solve the above-described problems, and an object thereof is to provide a cold cathode fluorescent lamp that reduces electrode loss and improves the lamp life and an illumination device using the lamp.
[0009]
[Means for Solving the Problems]
The emitter of claim 1 is made of 50-80 wt % of at least one powder of barium aluminate (BaAl ₂ O ₄ ) or lithium aluminate (LiAlO ₂ ), and a conductive metal powder that is not easily amalgamated. The main component is a mixture of 20 to 50 wt % .
[0010]
In the present claims and the following claims, the definition of each constituent element can be selected from the following description, and a well-known configuration can be appropriately selected for a configuration that is not particularly described.
[0011]
Emitter barium aluminate (BaAl ₂ O ₄₎ or at least the one powder 50 to 80 wt%, 20 to 50 wt powder of amalgamation hard conductive metal of the lithium aluminate (LiAlO ₂₎ % As a main component, and is attached to the electrode by a plasma spraying method or a known coating means.
[0012]
The operation of claim 1 will be described. The emitter is attached to, for example, an electrode of a cold cathode fluorescent lamp , and discharge of electrons from the emitter causes discharge in the hermetic container (bulb) , and mercury atoms enclosed in the hermetic container (bulb) are ionized and excited by the discharge. Then, ultraviolet rays are emitted from mercury, and the ultraviolet rays are converted into visible light by the phosphor layer and emitted to the outside of the bulb.
[0013]
Relatively large number of electrons are emitted from the deposited barium aluminate electrode (BaAl ₂ O ₄₎ or lithium aluminate (LiAlO _2), Ru can be reduced cathode fall voltage. Conductive metals that are difficult to amalgamate are mixed to increase the conductivity of the emitter, but it is difficult for mercury (Hg) to react with mercury (Hg), so that mercury (Hg) in the container (valve) is consumed at the electrode part. Almost all of them are lost, and the lifetime due to the reduced mercury content is less likely to occur.
Moreover, the mixing ratio of the conductive metal which is not easily amalgamated is 20 to 50 wt %. If a predetermined amount is contained, barium aluminate (BaAl ₂ O ₄ ) Or lithium aluminate (LiAlO ₂₎ ) Barium aluminate (BaAl ₂₎ O ₄ ) And lithium aluminate (LiAlO ₂₎ ) May be mixed.
If the mixing ratio of the conductive metals is less than 20 wt %, the conductivity of the emitter material is impaired and the cathode fall voltage increases. If it exceeds 50 wt %, barium aluminate (BaAl _2). O ₄ ) Or lithium aluminate (LiAlO ₂₎ ), The amount of initial electron emission from the large amount cannot be expected, so that the cathode fall voltage also increases.
Further, if the mixing ratio of conductive metals is less than 20 wt %, the ratio of barium (Ba) or lithium (Li) in the emitter, which is relatively easy to react with mercury (Hg), increases, so that lanthanum boride ( LaB ₆ ) Is not as much as mercury (Hg) consumption, which is also not preferable because it leads to a reduction in the amount of mercury (Hg).
According to various experiments, the most effective mixing ratio of the conductive metal was 30 to 40 wt % on the operating characteristics of the cold cathode fluorescent lamp .
[0014]
According to a second aspect of the present invention, in the emitter of the first aspect, the conductive metal which is not easily amalgamated is at least one of the group consisting of manganese (Mn), tungsten (W), nickel (Ni), chromium (Cr) or molybdenum (Mo). It is a type.
[0015]
The emitter is mixed with a metal selected from the above group, but may contain a substance other than the above group as long as the effects of the present invention are not impaired.
[0016]
In consideration of lamp characteristics, manufacturability, cost, etc., it is preferable to use manganese (Mn) as a conductive metal that does not amalgamate among the above groups.
[0022]
A third aspect of the present invention provides the emitter according to the first or second aspect, wherein the primary particle size of the conductive metal is 1 to 10 μm, and barium aluminate (BaAl ₂ O ₄ ) or lithium aluminate (LiAlO ₂ ). The diameter is 1 to 8 μm.
[0023]
According to the emitter of Claim 3, by selecting the optimum particle size of the material, manufacturability is Takama Rutotomoni, adhesion strength of the emitter is improved. Furthermore, the cathode fall voltage can be effectively reduced.
[0024]
An electrode according to claim 4 is characterized in that the emitter according to any one of claims 1 to 3 is attached.
[0025]
According to a fifth aspect of the present invention, in the electrode of the fourth aspect , the emitter is attached to a conductor, and the conductor is attached to a main part of the electrode.
[0026]
According to the electrode of claim 5 , it is not necessary to attach the emitter directly to the electrode, and the emitter can be easily attached to the electrode.
[0027]
For example, the emitter may be attached to a large conductor first, and then the conductor may be cut to a desired size and attached to the electrode.
[0028]
The emitter may be attached directly to the surface of the electrode or indirectly through a conductor attached to the electrode.
[0029]
The electrical conductor is attached for electrical connection to the electrode or lead.
[0030]
The electrode is formed in a sleeve shape or a plate shape with a conductive metal such as nickel (Ni), but the shape is arbitrary. Further, a getter made of aluminum (Al) -zirconium (Zr) and a mercury discharge structure made of titanium (Ti) -mercury (Hg) may be housed in the electrode. Product name) "may be used.
[0031]
The connection between the electrode and the lead wire is made by a known means such as electric welding or laser welding.
[0032]
According to a sixth aspect of the present invention, in the electrode of the fourth or fifth aspect, the emitter is attached to the electrode or the conductor by plasma spraying.
According to plasma spraying, the material powder is in an inert gas atmosphere such as argon (Ar) gas until it is sprayed onto the metal substrate, and the surface of the material powder melts and adheres to the substrate and binds to each other. The process becomes simple and the generation of impure gas can be reduced.
The cold cathode fluorescent lamp according to claim 7 is a tubular translucent airtight container having a phosphor layer formed on its inner surface; a discharge medium composed of mercury and a rare gas enclosed in the container; and introduced into the end of the container A pair of lead wires formed thereon; and an electrode according to any one of claims 4 to 6 attached to the lead wires.
[0033]
Vessel (bulb) is formed of a translucent material such as glass or ceramics, and the cross-sectional shape thereof may be a circular, elliptical or oval. The outer shape may be a straight tube shape, an L shape, a U shape, a W shape, a ring shape, or the like.
[0034]
The phosphor layer is excited by ultraviolet rays of mercury emission lines and emits visible light, and a known composition may be used. In addition to those that emit visible light, ultraviolet rays having a wavelength of 300 to 400 nm may be emitted.
[0035]
The discharge medium is composed of mercury and a rare gas such as argon or neon, and is enclosed in a bulb by a known means.
[0036]
The emitter may be attached to only one of the pair of electrodes, or may be attached to both.
[0037]
According to an eighth aspect of the present invention, there is provided an illuminating device comprising: the cold cathode fluorescent lamp according to the seventh aspect; and an apparatus main body to which the lamp is mounted.
[0038]
Examples of the illuminating device include, but are not limited to, a liquid crystal backlight, an in-vehicle instrument, an indicator lamp, a guide lamp, and the like.
[0039]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to the drawings.
[0040]
FIG. 1 is a sectional view showing a cold cathode fluorescent lamp A of the first embodiment.
[0041]
Reference numeral 1 denotes a glass translucent container (bulb) having a phosphor layer 2 formed on the inner surface. The container 1 has a tube outer diameter of 3 mm, and a pair of electrodes 3 and 3 ′ having a trade name “GEMEDIS” manufactured by SAES are sealed at both ends via lead wires 4 and 4 ′.
[0042]
The electrodes 3 and 3 ′ have a getter made of aluminum (Al) -zirconium (Zr) and a mercury discharge structure made of titanium (Ti) -mercury (Hg) in a nickel (Ni) sleeve having an outer diameter of 1 mm and a length of 5 mm. Is housed.
[0043]
Argon (Ar) gas is sealed in the container 1 at a pressure of 80 Torr. Thereafter, mercury (Hg) is released into the container 1 by high-frequency induction heating of the electrodes 3 and 3 ′.
[0044]
The emitter 5 is a mixture of 33 wt% manganese (Mn) as a conductive metal and 67 wt% barium aluminate (BaAl ₂ O ₄ ) on the outer surfaces of the pair of electrodes 3 and 3 ′. Argon (Ar) is used as a carrier. It is deposited by plasma spraying as a gas. At this time, the primary particle size of manganese (Mn) is 1 to 10 μm, and the primary particle size of barium aluminate (BaAl ₂ O ₄ ) is 1 to 8 μm.
[0045]
FIG. 2 is a graph showing the results of measuring the change in cathode fall voltage when the mixing ratio of manganese (Mn) in the emitter 5 of this cold cathode fluorescent lamp is changed.
[0046]
When the mixing ratio of manganese (Mn) exceeds 50 wt%, the cathode fall voltage increases and takes a value of around 110V. If it is 50 wt% or less, the cathode fall voltage is about the same as that of a conventionally used emitter in which lanthanum boride (LaB ₆ ) and barium aluminate (BaAl ₂ O ₄ ) are mixed, and the mixing ratio of manganese (Mn) is 30 wt%. When 78%, 78V was indicated.
[0047]
When the mixing ratio of manganese (Mn) was less than 20 wt%, the conductivity of the emitter 5 was lowered, and the cathode fall voltage was also increased to 90 V or higher. When the content was less than 20 wt%, the emitter 5 was scattered by sputtering and adhered to the inner wall surface of the container.
[0048]
Further, a mixture of lanthanum boride (LaB ₆ ) and barium aluminate (BaAl ₂ O ₄ ) as an emitter on the electrode was prepared as a cold cathode fluorescent lamp of a comparative example, and a lamp current of 10 mA together with the fluorescent lamp of this embodiment. Was lit.
[0049]
Then, the luminance of the electrode of the fluorescent lamp of the comparative example was remarkably lowered after 3000 hours. When this electrode was observed with SEM (electron micrograph), it was confirmed that the electrode surface was covered with amalgam of mercury (Hg), lanthanum (La) and barium (Ba), and the emitter was hardly scattered. It was done.
[0050]
On the other hand, the fluorescent lamp of this embodiment did not cause the phenomenon as in the comparative example even after several thousand hours had elapsed. This is because the amalgam of mercury (Hg) and barium (Ba) is slightly formed on the surface when extinguished, but it is thought that Hg is released into the discharge space by turning on the lamp. .
[0051]
Instead of barium aluminate (BaAl ₂ O ₄ ) as an emitter, a mixture of barium aluminate (BaAl ₂ O ₄ ) and lithium aluminate (LiAlO ₂ ) or lithium aluminate (LiAlO ₂ ) alone with manganese When the emitter mixed with (Mn) was measured as described above, substantially the same characteristics were obtained.
[0052]
In addition to plasma spraying, manganese (Mn) and barium aluminate (BaAl ₂ O ₄ ) are mixed in a glass-based binder to form a film on the metal surface. In this method, heating is required to decompose the binder and the binder, and a lot of gas may be emitted. Therefore, plasma spraying is preferable for depositing the emitter. It is.
[0053]
Also, according to plasma spraying, the material powder is in an inert gas atmosphere such as argon (Ar) gas until it is sprayed onto the metal substrate, and the surface of the material powder melts and adheres to the substrate so that the powders are bonded together. Also, there are advantages that the manufacturing process is simplified and that a decrease in luminance due to impure gas can be avoided.
[0054]
FIG. 3 is a partially enlarged perspective view showing the electrodes of the cold cathode fluorescent lamp of the second embodiment. 3a is the same getter and mercury discharge structure as in the first embodiment.
[0055]
A plate-like conductor 6 made of nickel (Ni) is attached to the outer surface of the electrode 3 so as to stick together. An emitter 5 similar to that of the first embodiment is attached to the outer surface of the conductor 6.
[0056]
The conductor 6 is formed by first attaching the emitter 5 to a larger conductor and then cutting the conductor 6 to a desired size. The conductor 6 may be attached so as to be electrically connected to the lead wire.
[0057]
The shape of the conductor 6 is not limited to a plate shape, and may be a rod shape, a cylindrical shape, a coil shape, or the like.
[0058]
FIG. 4 is a schematic sectional view showing a liquid crystal display device B according to the third embodiment. The liquid crystal display device B has a thin box-like case body 13 having an irradiation opening 12 on the front surface, and a backlight unit 14 serving as an illumination device is accommodated in the case body 13. This backlight unit 14 has a cold cathode fluorescent lamp A, and in the vicinity of the cold cathode fluorescent lamp A, a film-like reflective surface 15 on which silver is deposited and also serves as an adjacent conductor so as to enclose the container 1 is provided. The light guide plate 16 made of acrylic resin is disposed in the irradiation direction of the reflecting surface 15.
[0059]
The light guide plate 16 is positioned to face the opening 12 of the case body 13. In addition, a planar reflecting plate 18 is disposed on the back side of the light guide plate 6, and a light control means 22 configured by a diffusion plate 20 and a light collecting plate 21 between the light guide plate 16 and the case body 3. Is arranged. A liquid crystal unit 24 as display means is disposed on the front side of the opening 12 of the case body 13.
[0060]
According to this embodiment, since the cathode fall voltage is reduced, the temperature of the container in the vicinity of the electrode 3 can be reduced, and the effect of simplifying the material or structure of the cold cathode fluorescent lamp A housing portion can be expected. Further, in the case of a fluorescent lamp for a liquid crystal backlight of a portable information device in which the cold cathode fluorescent lamp A is driven by a battery, it is possible to provide suitable characteristics due to power saving associated with a reduction in lamp voltage.
[0061]
FIG. 5 is an exploded perspective view showing a flat fluorescent lamp C according to the fourth embodiment.
[0062]
The container 1 includes an upper glass 31, a lower glass 32, and a frame glass 33 that hermetically closes the peripheral portions of the glasses 31 and 32.
[0063]
A phosphor layer is formed on the inner surface of the upper glass 31, and a rare gas such as mercury (Hg) and argon (Ar) is sealed inside the container 1 at a predetermined pressure.
[0064]
A pair of plate-like electrodes 3, 3 ′ are disposed at both ends in the longitudinal direction of the container 1, and these electrodes 3, 3 ′ are connected to lead wires that are airtightly led out from the frame glass 33. Yes.
[0065]
An emitter made of 30 wt% manganese (Mn) and 70 wt% barium aluminate (BaAl ₂ O ₄ ) is attached to the surface of the pair of electrodes 3 and 3 ′ facing each other by plasma spraying.
[0066]
The size of the flat lamp C is about 3 inches, and is used for the backlight of a viewfinder of a video camera, for example.
[0067]
According to this embodiment, if the brightness is the same as that of a conventional electrode without an emitter, the power consumption of 0.3 to 0.15 W can be reduced, and the lamp life can be greatly improved.
[0068]
【The invention's effect】
According to the present invention, an emitter composed mainly of at least one of barium aluminate (BaAl ₂ O ₄ ) and lithium aluminate (LiAlO ₂ ) and a conductive metal that hardly amalgamates is attached to the electrode of the cold cathode fluorescent lamp. As a result, a relatively large amount of initial electrons are emitted from the electrode, the cathode fall voltage is reduced, and mercury (Hg) in the container is hardly consumed at the electrode portion, and the lamp life is reduced by reducing the amount of mercury. Can be improved.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a cold cathode fluorescent lamp according to a first embodiment of the present invention.
FIG. 2 is a graph showing the results of measuring the change in cathode fall voltage when the mixing ratio of the emitters of the cold cathode fluorescent lamp is changed.
FIG. 3 is a partially enlarged perspective view showing electrodes of a cold cathode fluorescent lamp according to a second embodiment of the present invention.
FIG. 4 is a schematic cross-sectional view showing a liquid crystal display device according to a third embodiment of the present invention.
FIG. 5 is an exploded perspective view showing a flat fluorescent lamp according to a fourth embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Translucent airtight container (bulb) , 2 ... Phosphor layer, 3, 3 '... Electrode, 4, 4 ... Lead wire, 5 ... Emitter, 6 ... Conductor, 14 ... Illuminating device, A ... Cold cathode fluorescence lamp,

Claims (8)

50 to 80 wt % of at least one powder of barium aluminate (BaAl ₂ O ₄ ) or lithium aluminate (LiAlO ₂ ) and 20 to 50 wt % of a conductive metal powder that is difficult to amalgamate. Emitter characterized by having a mixture as a main component. 2. The conductive metal which is not easily amalgamated is at least one selected from the group consisting of manganese (Mn), tungsten (W), nickel (Ni), chromium (Cr) or molybdenum (Mo). Emitter. The primary particle size of the conductive metal is 1-10 μm, barium aluminate (BaAl ₂ O ₄ ) Or lithium aluminate (LiAlO ₂₎ 3) The emitter according to claim 1 or 2, wherein the primary particle diameter of 1) to 8 [mu] m . 4. An electrode to which the emitter according to claim 1 is attached. 5. The electrode according to claim 4 , wherein the emitter is attached to a conductor, and the conductor is attached to a main portion of the electrode. 6. The electrode according to claim 4 , wherein the emitter is attached to the electrode or the conductor by plasma spraying. A tubular translucent airtight container having a phosphor layer formed on the inner surface;
A discharge medium comprising mercury and a rare gas enclosed in the container;
A pair of lead wires introduced into the container end ;
An electrode as claimed in any one of claims 4 to 6 attached to the lead;
A cold cathode fluorescent lamp comprising: A cold cathode fluorescent lamp according to claim 7;
The device body to which this lamp is mounted;
An illumination device comprising:

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