JP3722025B2 - Flat discharge light source - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flat discharge light source such as a discharge device that emits light in a flat form, for example, a video camera, a digital camera, a television, a game machine, a car navigation system, or the like that uses a display element that requires a backlight such as a liquid crystal panel. The present invention relates to a flat discharge light source, an illuminating device using the flat discharge light source, and a liquid crystal display device in an OA device such as a word processor or a display system incorporating a light source.
[0002]
[Prior art]
Since the liquid crystal panel is thin and lightweight and has low power consumption, it is widely used as various information video displays such as portable devices such as video cameras, personal computers and televisions. However, the liquid crystal itself is not a light emitting element, and a backlight for supplying light from the back surface of the liquid crystal panel is necessary for display. Usually used backlights are made by combining a cold cathode fluorescent lamp filled with mercury and a rare gas and a light guide made of acrylic resin to emit light in a planar shape, but flat discharge lamps are also used. Yes.
[0003]
FIG. 6 is a cross-sectional view of a conventional flat discharge light source (flat plate light source) described in, for example, Japanese Patent Application Laid-Open No. 62-195848. As shown in the figure, a light-transmitting front plate 2 made of soda glass or the like, a back plate 3 and a side plate 4 are hermetically sealed together to form a sealed container 1 having a flat discharge space 8. ing. A phosphor is applied to the inner surface of the front plate 2 serving as a light emitting surface, and a plurality of discharge electrodes 9 parallel to each other are provided on the inner surface of the rear plate 3, and further on the surface of the discharge electrode 9 in the discharge space. An insulating layer and a dielectric layer are formed. The discharge space 8 is filled with mercury and a rare gas such as argon as a starting gas.
[0004]
As shown in FIG. 7, the planar discharge light source according to this structure applies an AC voltage from the AC power source 10 to the plurality of electrodes 9 so that the polarities of the mutual electrode potentials are different from each other. A mercury discharge is generated, whereby the phosphor is excited to emit light and is emitted to the outside through the front plate 2.
[0005]
[Problems to be solved by the invention]
A conventional flat discharge light source is provided with a plurality of discharge electrodes, and AC discharge is performed between adjacent electrodes. In the discharge with this configuration, since the interval between the adjacent electrodes is short, the ultraviolet light that causes the phosphor to emit light is emitted from a negative glow, which has a problem of poor luminous efficiency. When a positive column is generated to improve efficiency, the conventional structure and voltage application method may cause the discharge to be shifted or contracted, resulting in a problem that the entire surface does not emit light uniformly. In addition, when the phosphor is excited and emitted by ultraviolet rays generated by mercury discharge, the luminous efficiency is relatively good. However, since mercury vapor is used, there is a problem that characteristics such as light output and voltage change greatly depending on temperature. In particular, when the temperature is lowered, there is a problem that the brightness is lowered and the starting voltage is increased and the life is shortened.
[0006]
Furthermore, since a flat discharge light source having a large area is damaged at atmospheric pressure unless the glass plate thickness of the flat container is increased, columns and ribs are provided in the discharge space to reduce the thickness and weight. However, if there are the above-mentioned pillars and ribs in the discharge path, the discharge contracts, and there is a problem that the flat discharge cannot be obtained because the discharge is not uniformly distributed over the entire discharge space.
[0007]
SUMMARY OF THE INVENTION An object of the present invention is to provide a flat discharge light source which has a flat, small, high luminance, high efficiency and uniform flat emission with little change in luminance from the start.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, a flat discharge light source according to the present invention comprises a sealed container having a flat discharge space with a translucent front plate and a back plate positioned substantially parallel to each other. In a planar discharge light source in which a plurality of pairs of discharge electrodes are provided on the inner surface, a dielectric layer is provided to cover the surface of the discharge electrodes, and a discharge gas is sealed inside the sealed container, the plurality of pairs of discharge electrodes are adjacent to each other. The same voltage is applied to the electrodes and discharged. Moreover, a support | pillar and a rib are provided between the electrodes which adjoin the said several pairs of discharge electrode. Further, the interval between each pair of the plurality of discharge electrodes is substantially the same, and the interval is configured to have a length that generates a positive column during discharge. In addition, a phosphor is applied to the inner surface of the closed container, the struts, and the surfaces of the ribs. The discharge electrode is provided over substantially the entire length of the side of the discharge space. The discharge electrode is divided into a plurality of pieces. A transparent conductive film is used as the discharge electrode. A protective film is provided on the surface of the dielectric layer. Further, xenon or a mixture of xenon and other rare gas is used as the discharge gas.
[0009]
In this case, a rectangular wave or a pulse voltage is applied to the discharge electrode to cause high frequency discharge.
[0010]
The flat discharge light source of the present invention is suitable as a backlight of a liquid crystal display device, but is also effective as a light source for illumination.
[0011]
FIG. 8 is a view for explaining the invention described in claim 1. This figure is a combination of FIG. 1 and FIG. An electrode 5a at one end, a pair of electrodes (5b, 5b), (5a, 5a),..., (5b, 5b), and an electrode 5a at the other end are provided. A common voltage V1 (for example, a rectangular wave voltage is applied) is applied to the electrode 5a, and a common voltage V2 (for example, a rectangular wave voltage is applied) having a phase different from that of the electrode 5b. . Reference numeral 1 denotes a discharge vessel. Other symbols (1a, 1b), (2a, 2b), and (3a, 3b) are marked on parts of the electrodes 5a and 5b. The invention of claim 1 shows that discharge occurs at least between the electrodes 1b-2a and between the electrodes 2b-3a. An ellipse dotted line indicates an electrode pair in which discharge occurs. The discharge itself can occur widely in the longitudinal direction between the electrodes, and this is shown in the embodiment of the present invention.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a sectional perspective view showing an embodiment of a flat discharge light source according to the present invention. As shown in the figure, a translucent front plate 2 made of soda glass or the like, and a back plate 3 and side plates 4 made of soda glass or the like are integrated so as to be substantially parallel with, for example, low-melting glass (not shown). A hermetic container 1 having a flat discharge space 8 is hermetically sealed. A phosphor 7 is applied to the inner surface of the front plate 2 and the inner surface of the side plate 4 that serve as the light emitting surface. The back plate 3 is provided with a total of eight discharge electrodes 5 a and 5 b that are substantially parallel to each other, and a dielectric layer 6 is formed on the surface of the discharge electrodes 5 a and 5 b in the discharge space 8. The width of the discharge electrodes 5a and 5b is, for example, 1 mm, and the adjacent discharge electrodes 5a-5a and 5b-
The interval between the electrodes 5b is 1 mm, and the electrode interval between the pair of discharge electrodes 5a and 5b is 40 mm, and the phosphor 7 is applied between them. For example, a mixed gas of xenon, neon, and argon is sealed in the discharge space 8.
[0013]
In the driving method of the flat discharge light source according to the present embodiment, a rectangular wave voltage or a pulse voltage is applied to the discharge electrodes 5a and 5b for discharge.
[0014]
FIG. 2 is a diagram showing an example of an electrode connection diagram and a rectangular driving voltage waveform. For example, a rectangular wave or a substantially rectangular wave voltage 11 having a voltage of Vs and −Vs around 0 V is applied to the discharge electrode 5a. Then, by applying a rectangular wave or a substantially rectangular wave voltage 12 having the same frequency and opposite polarity to 11 to the discharge electrode 5b to cause discharge, a rare gas discharge is generated in the discharge space 8, and xenon The phosphor 7 is excited by the ultraviolet rays radiated from the light and emits light, and is emitted to the outside through the front plate 2.
The rectangular wave voltage may be applied to both electrodes 5a and 5b as in the above-described embodiment, or may be applied to one of the discharge electrodes to be discharged.
FIG. 3 is a diagram showing another driving waveform. For example, −Vh is applied to the electrode 5a.
A voltage 11 having a voltage pulse of 5 is applied, and the other electrode 5b is applied with a voltage 12 having the same voltage pulse as 11 and a voltage pulse -Vh having a half-cycle phase shift to cause discharge. If the relationship between the pulse width W1 and the pause period W2 is W1 <W2, the pulse voltage with a pause period is driven, and if the same time width is used, the rectangular wave drive is performed. The frequency can be used from 10 kHz to 100 kHz.
[0015]
The planar discharge light source according to the present invention has a plurality of pairs of discharge electrodes, but the same voltage is applied to another pair of discharge electrodes that are adjacent to each other. No false discharge occurs. Each pair of discharge electrodes 5a and 5b has substantially the same interval, and the interval is made long enough to generate a positive column so that a positive column is always generated when a discharge occurs. is there. A positive column is generated when the electrode interval is 10 mm or more, although it depends on the pressure of the sealed gas. Since the phosphor is excited to emit light by this positive column, it has a feature that flat light emission with high luminance, high luminous efficiency and good uniformity can be obtained. Furthermore, since a xenon mixed gas is used as the sealing gas, there is almost no change in characteristics with respect to a change in ambient temperature, and light is emitted at a constant brightness immediately after lighting at both low and high temperatures.
[0016]
In the flat discharge light source according to the present invention, the number of discharge electrode pairs may be increased or decreased according to the size of the light emitting surface, and the light emission area can be increased without increasing the applied voltage by increasing the number of discharge electrode pairs. Suitable for flat discharge light source for large area.
Although the length of the discharge electrodes 5a and 5b is substantially the same as the entire length of one side of the discharge space 8 in the above embodiment, the length is not limited to this and may be a little shorter or longer than the side of the discharge space. It may be formed. Further, when the light emitting surface is increased, the discharge electrode becomes longer. However, when the light emitting surface is too long, the electrode area is increased, the discharge current is increased, and the current capacity of the drive circuit is increased. If the current capacity of the drive circuit increases, problems such as heat dissipation and high costs will arise. In this case, if the discharge electrode is divided into an appropriate number, the current per electrode will decrease, so the circuit will be reduced. Small and low cost.
As the discharge electrodes 5a and 5b, a transparent conductive film such as an ITO film or a nesa film may be used. Further, by covering the surface of the dielectric layer 6 with a protective layer (not shown) such as MgO, the operating voltage can be reduced and the sputtering can be reduced, and a long-life planar discharge light source can be obtained.
FIG. 4 is a sectional perspective view showing another embodiment of the flat discharge light source according to the present invention. The flat discharge light source of this structure uses the back plate 3 on which three pairs of discharge electrodes are formed as a light emitting surface, and forms a discharge space 8 with a shallow dish-like container 13 made by molding with soda glass, for example. A support column 14 having the same height as the discharge space is provided in the discharge space 8. The support column 14 is positioned between the discharge electrodes 5a-5a, 5b-5b adjacent to each other, and a phosphor is applied to the surface. A light diffusing plate 15 is provided on the outer surface of the back plate 3 so as to eliminate unevenness of light emission due to the shadows of the discharge electrodes 5a and 5b and the pillars 14 and to obtain a substantially uniform light emitting surface.
As in this embodiment, when the distance between the discharge electrodes is long, the back plate on which the discharge electrodes are formed can also be used as the light emitting surface, so that a planar discharge light source that emits light from both sides can be obtained. The pressure of the rare gas sealed in the discharge space 8 is usually 1/3 to 1/10 atm. If the glass plate thickness is not increased when the size is increased, the sealed container 1 is destroyed due to the pressure difference from the atmospheric pressure. End up. If the back plate 3 and the glass plate of the container 13 are made thicker to withstand the differential pressure, they become very heavy and thicker like a cathode ray tube of a television.
The flat discharge light source in the present embodiment keeps the height of the discharge space 8 substantially constant by the support 14 provided in the discharge space 8 and can receive the external pressure in a distributed manner. However, it can withstand the stress caused by the differential pressure from atmospheric pressure. For this reason, even if the flat discharge light source is enlarged, it can be made thin and light without being damaged. Further, since there is no support in the discharge path, there is an advantage that stable flat light emission can be obtained without causing contraction of discharge or non-uniform discharge.
The support column may be provided integrally with the shallow dish container 13 or may be provided separately from the shallow dish container 13. Further, the intervals may be regular or irregular. The shape of the support column 14 is preferably a cone that narrows toward the light emitting surface, but may be a columnar shape or a spherical shape. Further, it may be any shape such as a circle, a square, or a cross.
[0017]
FIG. 5 is a cross-sectional perspective view showing another embodiment of the flat discharge light source according to the present invention. The planar discharge light source of this structure is provided with ribs 16 between the discharge electrodes 5a-5a adjacent to each other in the central portion of the discharge space 8 in addition to the structure shown in FIG. A phosphor is applied. The shape is trapezoidal but may be square. The function and effect of the rib 16 are the same as those of the column 14 of the embodiment shown in FIG.
In the above embodiment, the ribs 16 are short at the center of the discharge space at an appropriate interval, but may be provided between the discharge electrodes 5a-5a and 5b-5b. Further, the length may be provided approximately the same as the length of the discharge space 8.
[0018]
【The invention's effect】
According to the embodiment of the present invention, the characteristics are not changed at the ambient temperature, and there is an effect that the planar light emission having high luminance, high light emission efficiency and good stability is maintained. In addition, even if the area is increased, the thickness and weight can be reduced, and there is an effect that lighting can be performed without using a high voltage circuit. When the flat discharge light source according to the embodiment of the present invention is used as, for example, a backlight light source of a liquid crystal display device, a flat backlight having a high luminance and a long life can be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional perspective view of a flat discharge light source according to the present invention.
FIG. 2 is a connection diagram and driving voltage waveform of a planar discharge light source.
FIG. 3 is another drive voltage waveform of the planar discharge light source.
FIG. 4 is a cross-sectional perspective view of another planar discharge light source according to the present invention.
FIG. 5 is a cross-sectional perspective view of another planar discharge light source according to the present invention.
FIG. 6 is a perspective view showing a conventional flat discharge light source.
FIG. 7 is a conventional circuit connection diagram.
FIG. 8 is a diagram for explaining how to apply a voltage to be applied to each electrode of the planar light source according to the embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Sealed container, 2 ... Front plate, 3 ... Back plate, 4 ... Side plate, 5a, 5b, 9 ... Discharge electrode, 6 ... Dielectric, 7 ... Phosphor, 8 ... Discharge space, 10 ... AC power supply, 11, DESCRIPTION OF SYMBOLS 12 ... Drive voltage waveform, 13 ... Shallow dish container, 14 ... Support | pillar, 15 ... Light diffusing plate, 16 ... Rib.

Claims (12)

The first, second and third non-crossing electrode pairs (1a, 1b, 2a, 2b, and 2) are formed on the inner surface of one of the discharge vessels having a cubic shape or a rectangular parallelepiped shape and having a discharge space therein. 3a, 3b) are provided at predetermined intervals, a dielectric layer is provided to cover the surface of the electrode, a discharge gas is sealed in the discharge vessel, and the first and third A voltage having a first potential is applied to the electrode pairs (1a, 1b and 3a, 3b), and a second potential different from the first potential is applied to the second electrode pair (2a, 2b). By applying a voltage, the electrode (1b) closer to the second electrode pair in the first electrode pair and the electrode closer to the first electrode pair in the second electrode pair ( and between the second electrode pair side electrode closer to the third electrode pair of the 2a) and (2b) Serial discharge is configured to occur between the third electrode to said second electrode pair near the side electrode of the (3a), a distance between the first electrode pair and the second pair of electrodes And the distance between the second electrode pair and the third electrode pair is substantially equal, and the distance between the first electrode pair and the second electrode pair is such that a positive column is generated during discharge. A flat discharge light source characterized in that the distance between the second electrode pair and the third electrode pair is such that a positive column is generated during discharge. . The flat discharge light source according to claim 1, wherein a phosphor film is provided on one glass surface of the discharge vessel, and visible light can be emitted from the surface. 2. The flat discharge light source according to claim 1, wherein struts or ribs are provided between adjacent electrodes of the plurality of pairs of discharge electrodes. The struts or ribs for supporting the discharge space of the discharge vessel is provided, the inner surface of the discharge vessel, the plane discharge light source according to claim 1, characterized in that a phosphor film on the struts or ribs. A planar shape of one surface of the discharge vessel is a rectangle, and the discharge electrode is provided on the one surface and extending over the entire length from one end of the short side or the long side to the other end. The flat discharge light source according to any one of claims 1 to 4 , wherein the flat discharge light source is provided. Planar discharge light source according to any one of claims 1 to 5, characterized in that a transparent conductive film as the discharge electrodes. The planar discharge light source according to any one of claims 1 to 6 , wherein a protective film is provided on a surface of the dielectric layer. The flat discharge light source according to any one of claims 1 to 7 , wherein xenon or xenon and another rare gas are sealed in the discharge space as a discharge gas. Planar discharge light source according to any one of claims 1 to 8, characterized in that Ru to perform the high-frequency discharge by applying a square wave or a pulse voltage to the discharge electrode. The flat discharge light source according to any one of claims 1 to 9 , wherein a light diffusion plate is provided on an outer surface of the sealed container. Lighting equipment, characterized in that configured to illuminate with a flat discharge light source according to any one of claims 1 to 10. A liquid crystal display device using the flat discharge light source according to any one of claims 1 to 10 as a backlight.

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