JP2009176440A - Rare gas fluorescent lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rare gas fluorescent lamp enabled to have a distribution of luminance in a tube axis direction of a luminous tube, without raising an input power. <P>SOLUTION: The rare gas fluorescent lamp is provided with a phosphor layer 2 over a whole inner face of the straight-tube luminous tube 1 with rare gas sealed in and a pair of strip-shaped outer electrodes 3 extended in a tube axis direction at an outside face of the luminous tube 1. A conductor 4, provided at an outer face of the luminous tube 1 not electrically connected with the outer electrode 3, is formed extended toward the tube axis direction separated from and in parallel with the outer electrode 3. Further, the conductor 4 is formed at a center part in a tube axis direction of the luminous tube 1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a light source of a backlight device of a liquid crystal display device or a signboard illumination device, and more particularly to an external electrode type rare gas fluorescent lamp.

Conventionally, a lamp used in a backlight device such as a liquid crystal display device has a rare gas sealed in an arc tube made of an elongated glass tube, and an inner surface is coated with a phosphor, and is formed on the outer surface of the arc tube. A voltage is applied to the pair of strip-shaped external electrodes to generate excimer discharge in the arc tube, and the phosphor is excited with ultraviolet rays to obtain visible light.
Such a rare gas fluorescent lamp has an advantage that it does not use mercury, has a small environmental load, and is quick to start.

FIG. 6A is a schematic view of a conventional rare gas fluorescent lamp, and FIG. 6B is a cross-sectional view in a direction perpendicular to the tube axis.
The rare gas fluorescent lamp has a phosphor layer 2 formed on the inner surface of a straight tube arc tube 1 over the entire circumference, and has a pair of strip-like external electrodes 3 extending in the tube axis direction on the outer surface of the arc tube 1. is doing.
In the arc tube 1, for example, xenon is sealed as a rare gas, and by applying a high frequency high voltage between the external electrodes 3, ultraviolet rays are generated by the discharge generated in the arc tube 1, and phosphors are irradiated with ultraviolet rays. To emit visible light.
JP 2007-134059 A

In recent years, as represented by liquid crystal televisions, the screen size of liquid crystals has been increasing, and recently, there are liquid crystal screens exceeding 50 inches.
In such a liquid crystal screen, a rare gas fluorescent lamp used as a backlight has a total length exceeding 1.2 m.

  When such a rare gas fluorescent lamp is used as a light source for a liquid crystal backlight, there are the following problems.

In such a rare gas fluorescent lamp, the luminance is substantially uniform in the tube axis direction of the lamp, and the luminance distribution on the liquid crystal screen is also substantially uniform.
However, when viewing the LCD screen, the brightness of the central part of the LCD screen is increased from the peripheral part to make the screen look more natural to human eyes, except when the entire LCD screen has a uniform brightness. May show.

  In order to achieve this latter case, the rare gas fluorescent lamp must have a higher luminance at the central portion in the tube axis direction and lower luminance at both ends compared to the central portion, as shown in FIG. Noble gas fluorescent lamps having the structure shown are known.

In this rare gas fluorescent lamp, the external electrode 3 has a structure in which the electrode width is wide at the center and the electrode width is narrow on both sides.
8A is a cross-sectional view taken along the line AA in FIG. 7, and FIG. 8B is a cross-sectional view taken along the line BB in FIG.
As shown in FIGS. 8A and 8B, in FIG. 8A, the formation range of the external electrode 3 on the outer surface of the arc tube 1 is on the outer surface of the arc tube 1 shown in FIG. 8B. Therefore, the amount of current flowing in the discharge space corresponding to the portion where the formation range of the external electrode 3 is widened can be increased.
For this reason, the ultraviolet light output is increased and the luminance is higher at the central portion in the tube axis direction where the width of the external electrode 3 is wider than at both ends.

However, even if the brightness in the tube axis direction can be raised compared to both ends, the amount of current increases in the discharge space where the width of the external electrode 3 is wide, so the increased current causes the gas temperature of the entire discharge space to increase. A rising phenomenon occurs.
When the gas temperature in the discharge space rises, the amount of ultraviolet light generated decreases, and the luminance in the tube axis direction of the rare gas fluorescent lamp maintains a high distribution in the center compared to both ends, but the entire lamp Absolute efficiency is reduced.
As a result, in order to increase the luminance at the central portion in the tube axis direction of the rare gas fluorescent lamp, the amount of ultraviolet rays generated is increased by increasing the input power at the central portion in the tube axis direction.
That is, by changing the width of the external electrode, the brightness can be increased or decreased in the tube axis direction of the rare gas fluorescent lamp, but the input power is increased in order to obtain the required brightness at the center in the tube axis direction. There was a problem.

  Recently, a display device represented by a liquid crystal television has a strong demand for power saving, and the input power cannot be increased.

  The present invention has been made to solve such a problem, and its object is to provide a rare gas capable of having a luminance distribution in the tube axis direction of the arc tube without increasing the input power. It is to provide a fluorescent lamp.

  The rare gas fluorescent lamp according to claim 1 has a pair of fluorescent layers on the inner surface of a straight tubular arc tube filled with a rare gas and extending in the tube axis direction on the outer surface of the arc tube. In a rare gas fluorescent lamp having a strip-shaped external electrode, a conductor that is not electrically connected to the external electrode is provided on the outer surface of the arc tube, and the conductor is separated from the external electrode. And extending in the tube axis direction in parallel.

  The rare gas fluorescent lamp according to claim 2 is the rare gas fluorescent lamp according to claim 1, and in particular, the conductor is formed in a central portion of the arc tube in the tube axis direction. And

The rare gas fluorescent lamp of the present invention has a pair of strip-shaped external electrodes extending in the tube axis direction on the outer surface of the arc tube, and a conductor not electrically connected to the external electrode is provided on the outer surface of the arc tube. Since the conductor is formed so as to extend in the tube axis direction in parallel with the external electrode, the inner surface portion of the arc tube facing the external electrode when a high frequency high voltage is applied to the external electrode Then, charges are accumulated in both portions of the inner surface portion of the arc tube facing the conductor, and the charges in the inner surface portions are released by reversing the polarity of the external electrodes, so that the discharge in the discharge space can be expanded. And since the external electrode and the conductor are not electrically connected, the discharge in the discharge space where the conductor is located spreads without changing the input power, and the discharge current density per unit volume in the discharge space is reduced. The gas temperature in the discharge space can be lowered, and the amount of ultraviolet rays generated in the discharge space can be increased. Therefore, the luminance of the rare gas fluorescent lamp in the portion where the conductor is formed is increased, and a luminance distribution can be provided in the tube axis direction of the arc tube.
Thus, in the rare gas fluorescent lamp of the present invention, it is possible to have a luminance distribution in the tube axis direction of the arc tube without changing the input power, and in particular, the luminance in the tube axis direction of the arc tube is compared with the central portion. If both ends are lowered, it is possible to make the appearance of the screen look more natural when viewed by human eyes in a display device that is required to save power, such as a liquid crystal television.

  Further, by forming the conductor at the central portion in the tube axis direction of the arc tube, the luminance of the central portion in the tube axis direction of the arc tube can be made higher than the luminance at both ends.

Hereinafter, the discharge lamp of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic perspective view of a rare gas fluorescent lamp of the present invention, and FIG. 2 is a cross-sectional view of the rare gas fluorescent lamp taken along the line AA in FIG.

  The arc tube 1 of the rare gas fluorescent lamp is made of translucent glass, and examples thereof include soda lime glass, aluminosilicate glass, borosilicate glass, and barium glass. A pair of strip-shaped external electrodes 3 are arranged on the outer surface of the arc tube 1 so as to extend in the tube axis direction of the arc tube 1. These external electrodes 3 are arranged so as to face each other in the cross-sectional view perpendicular to the tube axis shown in FIG.

The external electrode 3 is not particularly limited as long as it is a conductive material. For example, gold, silver, nickel, carbon, gold palladium, silver palladium, platinum, or the like can be suitably used. This is realized by sticking a tape-like metal to the outer surface of the tube 1 or screen-printing and baking a silver conductive paste.
The external electrode 3 has a width of 0.5 mm and a length of 1150 mm.

  A conductor 4 that is not electrically connected to the external electrode 3 is provided on the outer surface of the arc tube 1. The conductor 4 is the same member as the external electrode 3, and, for example, gold, silver, nickel, carbon, gold palladium, silver palladium, platinum, or the like can be suitably used on the outer surface of the arc tube 1. This is realized by attaching a tape-like metal or screen printing and baking a silver conductive paste.

The conductor 4 is formed so as to be spaced apart from the external electrode 3 and extending in the tube axis direction in parallel. As shown in FIG. 2, the conductor 4 is centered on each external electrode 3 and both sides thereof. In other words, four conductors 4 are arranged on the outer surface of the arc tube 1.
Although not shown in FIGS. 1 and 2, the external electrode 3 and the conductor 4 are each made of a glassy protective layer so that dielectric breakdown does not occur between the external electrode 3 and the conductor 4. It protects by covering the surface.

The conductor 4 is formed at the central portion of the arc tube 1 in the tube axis direction.
The conductor 4 has a width of 0.5 mm and a length of 500 mm.
The distance between the external electrode 3 and the conductor 4 is 1.5 mm, for example.

For example, Xe (xenon) gas or a mixed gas of a rare gas containing Xe is sealed in the arc tube 1 in a total sealing pressure range of 5 to 50 kPa.
When a high frequency voltage is applied to the external electrode 3 from a lighting power source (not shown), a discharge is generated with the arc tube 1 as a dielectric interposed between the external electrodes 3, and this discharge causes excimer molecular light emission (ultraviolet light) by xenon. ) Occurs.

A phosphor layer 2 is formed on the inner surface of the arc tube over the entire circumference. As for the phosphor, a red phosphor is a europium activated yttrium oxide phosphor (Y ₂ O ₃ : Eu) or (Y, Gd) BO ₃ : Eu, and a green phosphor is a cerium terbium activated lanthanum phosphate phosphor (LaPO). ₄ : Ce, Tb), and the blue phosphor is a europium-activated barium magnesium aluminate phosphor (BaMgAl ₁₀ O ₁₇ : Eu).

  In such a rare gas fluorescent lamp, when a high frequency voltage is applied to the external electrode 3 from the lighting power source, ultraviolet light having a wavelength of 172 nm is generated in the arc tube 1, and this ultraviolet light irradiates the phosphor in the phosphor layer 2. Excited, and visible light is emitted.

Next, the discharge phenomenon of the rare gas fluorescent lamp of the present invention having a conductor will be described.
FIG. 3 is an explanatory diagram schematically showing a discharge state in the cross-sectional view shown in FIG.
As shown in FIG. 3, when a conductor 4 that is not electrically connected to the external electrode 3 is disposed near the external electrode 3, the arc tube 1 that faces the conductor 4 in the internal space of the arc tube 1. The electric discharge is attracted to the inner surface portion.

In the case of high-frequency lighting, this mechanism is not only for the inner surface portion of the arc tube 1 facing the one external electrode 3 but also for the one external electrode 3 when the polarity of the one external electrode 3 is negative. A certain amount of electric charge also accumulates on the inner surface portion of the arc tube 1 facing the conductor 4 arranged in the vicinity of.
Then, when the polarity of the one external electrode 3 is switched to the plus side, the inner surface portion of the arc tube 1 facing the one external electrode 3 and the inner surface of the arc tube 1 facing the conductor 4 The charge accumulated in the part is released.
Therefore, only the inner surface portion of the arc tube 1 facing the one external electrode 3 has a narrow charge accumulation range and the discharge is difficult to spread, but the inner surface portion of the arc tube 1 facing the conductor 4 also has a charge. When these charges are released, the discharge spreads.

  Even if the conductor 4 is provided, the conductor 4 is not electrically connected to the external electrode 3 and is in an insulating state, so that the voltage applied to the external electrode 3 is provided with the conductor 4. Since the applied voltage does not change, the amount of current flowing in the discharge space does not change.

  As a result, the amount of current flowing in the discharge space is the same as when the conductor 4 is not provided, but by providing the conductor 4, the discharge in the discharge space can be expanded, and the amount per unit volume in the discharge space can be increased. The discharge current density can be lowered, and the gas temperature in the discharge space through which the current flows can be lowered.

And if the gas temperature of discharge space falls, the generation amount of an ultraviolet-ray will increase.
Therefore, by providing the conductor 4, even if the applied voltage is not changed, that is, the input power is not changed, the generation amount of ultraviolet rays is increased and the luminance of the rare gas fluorescent lamp in the portion where the discharge is expanded is increased. be able to.
In the rare gas fluorescent lamp shown in FIG. 1, the luminance of the rare gas fluorescent lamp in the portion where the conductor 4 is formed is increased, and the luminance of the central portion in the tube axis direction of the arc tube 1 is higher than both ends. .

Next, an experiment was conducted to examine the change in luminance depending on the presence or absence of a conductor.
In this experiment, not the overall average luminance in the tube axis direction of the arc tube, but the luminance of only the portion where the conductor is provided in the arc tube.
The rare gas fluorescent lamp of the present invention used in this experiment is a rare gas fluorescent lamp having the structure shown in FIGS. 1 and 2, and an arc tube having a phosphor layer inside has an outer diameter of 9.8 mm (inner diameter φ9 mm), The total length is 1170 mm. Inside, a mixed gas of 80% xenon and 20% neon is sealed in 21 kPa (25 ° C conversion), and a silver paste with a width of 0.5 mm and a length of 1150 mm is placed on the outer surface of the arc tube. A fired external electrode is formed, and four conductors made of aluminum tape having a width of 0.5 mm and a length of 500 mm are provided on both sides of the external electrode. The distance between the external electrode and the conductor is 1 mm.
As a comparative lamp, a lamp having the same structure as that of the rare gas fluorescent lamp of the present invention and having only a conductor was prepared.
In this experiment, the input power was changed in the range of 29 W to 37 W in each lamp, and the luminance at each input power was obtained as the luminance efficiency (luminance / input power).
The experimental results are shown in FIG.

From the experimental results shown in FIG. 4, it can be seen that the noble gas fluorescent lamp of the present invention has higher luminance efficiency at all input powers than the comparative lamp not provided with the conductor.
In other words, it was found that when the rare gas fluorescent lamp of the present invention and the comparative lamp were compared with the same input power, the luminance of the rare gas fluorescent lamp of the present invention provided with the conductor was higher.

  Furthermore, in other words, in a rare gas fluorescent lamp having a pair of external electrodes on the outer surface of the arc tube, by providing a conductor that is not electrically connected to the external electrode on the outer surface of the arc tube, the input power is not changed. It has been found that the brightness of the lamp (arc tube) in the portion provided with the conductor is increased.

Next, the luminance portion in the tube axis direction of the rare gas fluorescent lamp of the present invention shown in FIGS. 1 and 2 was measured. This rare gas fluorescent lamp is lit at 33 W.
The measurement results are shown in FIG.
In FIG. 5, the horizontal axis indicates the position of the arc tube in the tube axis direction, the position of the horizontal axis 600 mm is the center point of the arc tube in the tube axis direction, and the conductor is formed at a position of 450 mm to 750 mm. ing.
The vertical axis represents the relative value of the luminance efficiency, with the value having the highest luminance efficiency (luminance / input power) in the tube axis direction of the rare gas fluorescent lamp as 100%.

From the measurement result of FIG. 5, it can be seen that the luminance in the tube axis direction of the arc tube is higher in the portion where the conductor is provided than in the portion where the conductor is not provided.
That is, the luminance at the central portion in the tube axis direction of the rare gas fluorescent lamp is higher than the luminance at both ends, in other words, the luminance at both ends is lower than the luminance at the central portion.
As a result, by incorporating such a rare gas fluorescent lamp in a display device typified by a liquid crystal television, the luminance of the display screen can be lowered at the peripheral portion, and an optimum luminance distribution can be obtained.

  The luminance distribution in the tube axis direction of the rare gas fluorescent lamp can be arbitrarily changed by changing the position where the conductor is provided in the tube axis direction of the arc tube.

It is a schematic perspective view of the rare gas fluorescent lamp of the present invention. It is AA sectional drawing of the noble gas fluorescent lamp shown in FIG. FIG. 3 is an explanatory diagram schematically showing a discharge state in the cross-sectional view shown in FIG. 2. It is experiment data explanatory drawing which investigated the brightness | luminance efficiency of the rare gas fluorescent lamp of this invention, and the comparative rare gas fluorescent lamp. It is measurement result data explanatory drawing which shows the brightness | luminance part of the tube-axis direction of the noble gas fluorescent lamp of this invention. It is the schematic perspective view of the conventional rare gas fluorescent lamp, and sectional drawing of a pipe-axis direction. It is a schematic perspective view of the conventional noble gas fluorescent lamp. 8A is a cross-sectional view taken along the line AA in FIG. 7, and FIG. 8B is a cross-sectional view taken along the line BB in FIG.

Explanation of symbols

1 arc tube 2 phosphor layer 3 external electrode 4 conductor

Claims (2)

In a rare gas fluorescent lamp having a phosphor layer over the entire inner surface of a straight tube arc tube filled with a rare gas and having a pair of strip-like external electrodes extending in the tube axis direction on the outer surface of the arc tube,
A conductor that is not electrically connected to the external electrode is provided on the outer surface of the arc tube,
The noble gas fluorescent lamp, wherein the conductor is formed to extend in the tube axis direction in parallel with the external electrode.   2. The rare gas fluorescent lamp according to claim 1, wherein the conductor is formed in a central portion of the arc tube in the tube axis direction.

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