JPH1167150A - Discharge device, lighting system, and liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To widen the range of a voltage values and frequencies for a stable operation and a range of modulated light for brightness. SOLUTION: A front plate 10, an insulating board 20 and a side board 30 are sealed integrally and airtightly to constitute a flat closed vessel 1. A first and second discharge electrodes 40, 41 which are in parallel with each other with an inner surface of the front plate 10 are provided. Surfaces of the discharge electrodes 40, 41 are covered by the first dielectric layer 50, phosphor 60 is painted on the inner surface of the insulating board 20 and a discharge gas is filled in a discharge space 70 in the closed vessel 1. A grounded electrode 80 is provided at the center of an outer surface of the insulating board 20, in parallel with the discharge electrodes 40, 41 over the entire length of the discharge space 70.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge device such as a flat discharge device which emits light in a planar manner, for example, information on a television, a game machine, a car navigation system and the like using a display element such as a liquid crystal panel which requires a backlight. The present invention relates to a discharge device, an illumination device using the discharge device, and a liquid crystal display device in an OA device such as a video device or a word processor, or a display system including a light source.

[0002]

2. Description of the Related Art A liquid crystal display device having a liquid crystal panel is widely used as various information video displays such as personal computers and televisions because of its thinness, light weight and low power consumption. For display, a backlight for supplying light from the back of the liquid crystal panel is required. A backlight generally used for a liquid crystal display device is mainly a combination of a small-diameter fluorescent lamp and a light guide made of an acrylic resin, but a flat discharge device (discharge lamp) is also used. I have.

FIG. 10 shows, for example, Japanese Patent Application No. 7-272322.
FIG. 1 is a cross-sectional view showing a conventional flat discharge device described in the specification and the drawings of the above-mentioned publication. As shown in the figure, a light-transmitting front plate 10 made of soda glass or the like, an insulating substrate 20 made of soda glass, ceramic or the like, and a side plate 30 are integrally air-tightly sealed with, for example, low melting point glass (not shown). , A flat closed container 1 is formed. First and second (pair of) discharge electrodes 40 and 41 parallel to each other are provided on the inner surface of the front plate 10 serving as a light emitting surface.
1 is covered with a first dielectric layer 50. Also,
A phosphor 60 is applied to the inner surface of the insulating substrate 20, and a discharge space 70 in the closed vessel 1 is a mercury and a mixed gas such as argon or neon-argon as a starting gas, or xenon, krypton, argon, helium, or neon. Noble gas discharge gas is sealed.

In this flat discharge device, when a high-frequency drive voltage is applied between the discharge electrodes 40 and 41, a discharge is generated in the discharge space 70, and the phosphor 60 is excited by the ultraviolet rays generated by the discharge to emit light. Then, light is radiated outside through the front plate 10.

[0005]

In order to use a flat discharge device as a backlight of a liquid crystal display device,
It is necessary to change the voltage value, frequency, and the like of the drive voltage for dimming. However, in order to use a flat discharge device for a backlight of a liquid crystal display device, it is one of the important conditions that good luminance uniformity of light emission is one of the important conditions. In the case, when the voltage value and frequency of the driving voltage are changed, the voltage value region and the frequency region that operate stably are narrow, so that the discharge becomes unstable during operation, and uneven brightness, flicker, shrinkage of the positive column, etc. This is likely to occur, and as a result, the light emission becomes non-uniform, the degree of uniformity of the luminance may be deteriorated, and the dimming range of the luminance is narrow.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and is a discharge device having a wide range of voltage values and frequencies, a discharge device having a wide dimming range of luminance, a lighting device, and a liquid crystal display device. The purpose is to provide.

[0007]

According to the present invention, there is provided a discharge apparatus having first and second discharge electrodes, the surfaces of which are covered with a first dielectric layer. An earth electrode is provided between the first and second discharge electrodes and in a direction substantially parallel to the first and second discharge electrodes.

Further, a flat closed container is formed by combining a light-transmitting front plate and an insulating substrate, and first and second discharge electrodes are provided on the inner surface of the front plate, and the first and second discharge electrodes are provided. 2
A first dielectric layer is provided to cover the surface of the discharge electrode, a phosphor is applied to the inner surface of the insulating substrate, and a discharge gas is sealed in the closed container; An earth electrode is provided between the first and second discharge electrodes on the outer surface of the substrate or the front plate and in a direction substantially parallel to the first and second discharge electrodes.

In this case, a metal foil is used as the ground electrode, and the ground electrode is bonded to the closed container.

Further, a flat closed container is formed by combining a light-transmitting front plate and an insulating substrate, and first and second discharge electrodes are provided on the inner surface of the front plate, and the first and second discharge electrodes are provided. 2
A first dielectric layer is provided to cover the surface of the discharge electrode, a phosphor is applied to the inner surface of the insulating substrate, and a discharge gas is sealed in the closed container; An earth electrode is provided between the first and second discharge electrodes on the inner surface of the substrate or the front plate and in a direction substantially parallel to the first and second discharge electrodes, and a second electrode is provided covering the surface of the earth electrode. Is provided.

In this case, the second dielectric layer covering the surface of the ground electrode provided on the front plate is made of a transparent material.

In these cases, the width of the ground electrode is set to 0.1.
8 mm or more.

The ground electrode is provided on the insulating substrate at a distance of at least 8.5 mm from the first and second discharge electrodes.

The ground electrode is provided on the front plate at a distance of at least 20 mm from the first and second discharge electrodes.

[0015] A protective layer is provided on the surface of the first dielectric layer.

Further, a transparent conductive film is used as the ground electrode provided on the front plate.

Further, the lighting device is configured to illuminate using the above-described discharge device.

In the liquid crystal display device, the above-described discharge device is used as a backlight.

[0019]

FIG. 1 is a partially cutaway perspective view showing a flat discharge device according to the present invention. As shown in the figure, a front plate 10, an insulating substrate 20, and a side plate 30 are integrally hermetically sealed to form a flat hermetic container 1, and discharge electrodes 40, 41 parallel to each other are formed on the inner surface of the front plate 10. Is provided, the surfaces of the discharge electrodes 40 and 41 are covered with a first dielectric layer 50 provided by a thick film printing method, and the phosphor 60 is applied on the inner surface of the insulating substrate 20. Space 7
0 is filled with a discharge gas. Further, an earth electrode 80 is provided between the discharge electrodes 40 and 41 on the outer surface of the insulating substrate 20, that is, in the center, in parallel with the discharge electrodes 40 and 41 and over the entire length of the discharge space 70.

In this flat discharge device, a drive voltage as shown in FIG. 2 is applied to the discharge electrodes 40 and 41. That is, the rectangular wave voltage V1 with a voltage of -V _h shown to the discharge electrode 40 in FIGS. 2 (a) is applied, to the discharge electrode 41 2
A rectangular wave voltage V2 whose phase is shifted by a half cycle from the rectangular wave voltage V1 shown in FIG. Further, the earth electrode 80 is kept at the earth potential. By such a driving method, a discharge is generated in the discharge space 70, the phosphor 60 is excited by the ultraviolet light generated by the discharge, emits light, and the light is emitted to the outside through the front plate 10.

In such a flat discharge device, since the ground electrode 80 is provided on the outer surface of the insulating substrate 20, a discharge having good stability and uniformity is generated in the discharge space 70. The body 60 is stably excited to emit light. Therefore, the range of the voltage values and frequencies of the rectangular wave voltages V1 and V2 that operate stably is widened.
1, Even if the voltage value and frequency of V2 are greatly changed, the discharge does not become unstable during operation, and uneven brightness, flicker, shrinkage of the positive column, etc. hardly occur, and light emission becomes uniform. Since the luminance uniformity is good, the luminance dimming range is widened. Moreover, since the discharge does not become unstable during operation, the life is extended. Further, since the dielectric layer 50 is provided by the thick film printing method, the dielectric layer 50 can be provided easily.

The ground electrode 80 can be provided very easily by bonding a metal foil (ribbon) of, for example, aluminum or the like, so that the manufacturing cost hardly increases. Further, if a metal foil (metal tape) with an adhesive is used, the ground electrode 80 can be more easily provided. The dielectric layer 50 has its surface covered with a protective layer (not shown) made of, for example, MgO, so that the operating voltage can be reduced and the sputtering can be reduced. Obtainable.

FIG. 3 is a graph showing a stable operation region of the driving voltage of the flat discharge device as shown in FIG. 1. This graph shows that the width of the ground electrode 80 provided at the center of the insulating substrate 20 is 3 mm, the light emission is The size of the surface is 115 mm × 88 mm, mercury and argon are sealed at 2.66 kPa, and the pulse widths of the rectangular wave voltages V1 and V2 are constant at 5 μs, and the voltage values of the rectangular wave voltages V1 and V2 and It shows the result of examining the operation region where the discharge is stabilized by changing the frequency. The region a shows the stable operation region when the ground electrode 80 is provided, and the region b shows the result when the ground electrode 80 is not provided. Shows the stable operation area. As is clear from this graph, when the ground electrode 80 is provided, the stable operation area can be greatly expanded as compared with the case where the ground electrode is not provided. That is, when the earth electrode is not provided, the stable operation frequency range is 15 to 30 kHz, but when the earth electrode 80 is provided, the stable operation frequency range is 10 to 3 kHz.
It can be expanded up to 5 kHz. That is, when the earth electrode 80 is provided, the stable operation frequency range can be expanded by 5 kHz each in the upper and lower directions as compared with the case where the earth electrode is not provided. Further, when the ground electrode 80 is provided, it can operate at a substantially constant low voltage value over the entire operating frequency. Note that, in this graph, the upper limit of the voltage value is 800 V, which cannot be tested due to the withstand voltage of the circuit elements constituting the drive circuit, and the measurement at a higher voltage value was not performed. However, for example, when the frequency of the rectangular wave voltages V1 and V2 is 30 kHz, the upper limit stable operation voltage is high, and when the ground electrode 80 is provided, the stable operation voltage value range is clearly increased vertically. is there. As described above, by adding the ground electrode 80 to the flat plate type discharge device, the discharge can be stabilized in a wide voltage value range and frequency range, and the light emission luminance increases in proportion to the voltage value and the frequency. Therefore, the dimming range of the luminance can be expanded almost twice. Further, the earth electrode 80 is kept at the earth potential, and almost no current flows through the earth electrode 80 during operation. Therefore, even if the earth electrode 80 is provided, power consumption does not increase.

FIG. 4 is a graph showing the relationship between the width of the ground electrode 80 and the minimum stable operating voltage of the flat plate discharge device as shown in FIG. This is the same as the case of the graph shown in FIG. 3, except that the discharge is not stable unless added. As is apparent from this graph, when the width of the ground electrode 80 is set to 0.8 mm or more, the discharge becomes stable when the rectangular wave voltages V1 and V2 having a voltage value equal to or more than a predetermined value are applied. Also, the minimum stable operation voltage decreases as the width of the ground electrode 80 increases, and when the width of the ground electrode 80 becomes 3 mm or more, the minimum stable operation voltage becomes substantially constant. Therefore, the width of the ground electrode 80 is set to 0.8 mm.
In this case, the dimming range of the luminance can be reliably widened.

FIG. 5 is a graph showing the relationship between the distance L ₁ between the discharge electrode 40 and the ground electrode 80 as shown in FIG. 1 and the minimum stable operating voltage.
Is 76 mm inside and the width of the ground electrode 80 is 3 mm
The ground electrode 80 is provided on the outer surface of the insulating substrate 20, and the operating conditions are the same as those in the case of the graph shown in FIG. 4. The frequency of the rectangular wave voltages V1 and V2 is 32 kHz and the pulse width is 5 μs. Is the case. As is apparent from this graph, will release gradually the ground electrode 80 from the discharge electrode 40, the distance L ₁ is equal to or greater than 8.5 mm, the rectangular wave voltage V1 with a voltage value higher than a predetermined value, V2
, The discharge becomes stable. In this case, the minimum stable operation voltage is almost constant at about 500V. However, the distance L
₁ is less than 8.5 mm, that is, the ground electrode 80
Is closer to the discharge electrode 40 than 8.5 mm, stable discharge cannot be obtained even when the voltage condition is changed. Further, the distance L ₁ is more than 64.5 mm, i.e. the distance between the ground electrode 80 and the discharge electrode 41 is less than 8.5 mm, no stable discharge can be obtained even by changing the voltage conditions. Therefore, the ground electrode 80 is 8.5 m from the discharge electrodes 40 and 41.
When the insulating substrate 20 is provided at a distance of m or more, a wide stable operation region can be obtained, and light emission with good uniformity can be obtained.
The dimming range of the luminance can be reliably widened.

FIG. 6 is a sectional view showing another flat-plate type discharge device according to the present invention. As shown in the figure, a ground electrode 81 is provided at the center of the inner surface of the insulating substrate 20 in parallel with the discharge electrodes 40 and 41 and over the entire length of the discharge space 70 so that the ground electrode 81 is not exposed to the discharge space 70. In addition, the ground electrode 81 is covered with the second dielectric layer 51, and the phosphor 60 is applied to the surfaces of the insulating substrate 20 and the dielectric layer 51.

In this flat discharge device, the relationship between the distance between the discharge electrode 40 and the ground electrode 81 and the minimum stable operating voltage is the same as that of the flat discharge device shown in FIG. Therefore, the earth electrode 81 is connected to the discharge electrodes 40 and 41.
When provided on the insulating substrate 20 at a distance of 8.5 mm or more from the substrate, a wide stable operation region can be obtained, and light emission with good uniformity can be obtained, so that the dimming range of luminance can be surely widened.

In this embodiment, only the ground electrode 81 is covered with the dielectric layer 51.
May be covered with a second dielectric layer.

FIG. 7 is a sectional view showing another flat discharge device according to the present invention. As shown in FIG.
1 is covered with a first dielectric layer 52, and a ground electrode 82 made of a transparent conductive film such as an ITO film or a Nesa film is formed at the center of the outer surface of the front plate 10 in parallel with the discharge electrodes 40 and 41 and discharge. It is provided over the entire length of the space 70.

In this flat discharge device, the front plate 1
Since the ground electrode 82 made of a transparent conductive film is provided on the outer surface of the reference numeral 0, the brightness is not reduced by the ground electrode 82, and the brightness uniformity is good.

FIG. 8 is a graph showing the relationship between the distance L ₂ between the discharge electrode 40 and the ground electrode 82 and the stable operation voltage as shown in FIG. 7, and this graph shows that the inner distance between the discharge electrodes 40 and 41 is 76 mm. The width of the ground electrode 82 is 3 mm, the operating conditions are the same as those of the graph shown in FIG. 4, the frequency of the rectangular wave voltages V1 and V2 is 32 kHz, and the pulse width is 5 kHz.
μs. As is apparent from this graph, will release gradually the ground electrode 82 from the discharge electrode 40, the distance L ₂ is equal to or greater than 20 mm, uniform by applying a square wave voltage V1, V2 having the predetermined value or more voltage values Although stable discharge occurs, if the distance L ₂ is less than 20mm is not stable discharge is obtained even by changing the voltage conditions. The distance L ₂ is more than 53 mm, i.e. when the ground electrode 82 is less than 20mm from the discharge electrode 41, also by changing the voltage condition discharge becomes unstable. Therefore, the ground electrode 82 is connected to the discharge electrodes 40 and 41
When provided on the front panel 10 at a distance of 0 mm or more, the dimming range of luminance can be reliably widened.

FIG. 9 is a sectional view showing another flat discharge device according to the present invention. As shown in the figure, for example, an insulating substrate 21 integrated with a side plate, that is, a box-shaped container formed by thermoforming a glass plate, and a front plate 10 are hermetically sealed to form a flat closed container 2. Discharge electrode 4 of front plate 10
An earth electrode 83 made of a transparent conductive film such as an ITO film or a Nesa film is provided between the first and second discharge electrodes 70 and 41 in parallel with the discharge electrodes 40 and 41 and over the entire length of the discharge space 70. The discharge electrodes 40 and 41 and the ground electrode 83 are covered with the dielectric layer 53 also serving as the first and second dielectric layers, and the phosphor 60 is also applied to the surface of the dielectric layer 53.

In this flat discharge device, the closed container 2 is constituted by the insulating substrate 21 integrated with the side plate and the front plate 10, so that the assembly is simplified and the manufacturing cost is reduced. Further, since the ground electrode 83 is covered with the dielectric layer 53 made of a light-transmitting material,
The brightness does not decrease. In this flat discharge device, the same experimental results as those shown in FIG. 8 were obtained. Therefore, the earth electrode 83 is connected to the discharge electrodes 40 and 41.
When provided on the front plate 10 at a distance of 20 mm or more from the
The dimming range of the luminance can be reliably widened.

If the lighting device is configured to be illuminated by using the flat discharge device shown in FIGS. 1, 6, 7, and 9, the dimming range of the luminance is widened and the life is extended. become longer.

Also, in the liquid crystal display device, if the flat discharge device shown in FIGS. 1, 6, 7 and 9 is used as a backlight, the dimming range of the luminance can be widened,
The life of the backlight is extended.

In the above-described embodiment, a flat discharge device has been described, but the present invention can be applied to other discharge devices. In the above-described embodiment, the ground electrodes 80 to 83 are provided in parallel with the discharge electrodes 40 and 41. However, the ground electrode is substantially parallel to the first and second discharge electrodes, that is, the ground electrodes are first and second. It may be provided with a slight inclination with respect to the two discharge electrodes. Further, in the above embodiment, the first and second discharge electrodes 40 and 41 are provided, but a discharge electrode other than the discharge electrodes 40 and 41 may be provided.

[0037]

In the discharge device according to the present invention, the range of the voltage value and the frequency at which the operation is stable is widened.

Further, a flat closed container is formed by combining a light-transmitting front plate and an insulating substrate, and first and second discharge electrodes are provided on the inner surface of the front plate. A first dielectric layer is provided to cover the surface of the discharge electrode, a phosphor is applied to the inner surface of the insulating substrate, and a discharge gas is sealed in the closed container. Between the first and second discharge electrodes on the outer surface and between the first and second discharge electrodes.
When the ground electrode is provided in a direction substantially parallel to the discharge electrode, the range of the voltage value and the frequency at which the operation is stable is widened, so that the dimming range of the luminance is widened.

When a ground electrode made of metal foil is used and the ground electrode is adhered to a closed container,
Since the ground electrode can be easily provided, the manufacturing cost hardly increases.

Further, a flat closed container is formed by combining a light-transmitting front plate and an insulating substrate, and first and second discharge electrodes are provided on the inner surface of the front plate, and the first and second discharge electrodes are provided. A first dielectric layer is provided to cover the surface of the discharge electrode, a phosphor is applied to the inner surface of the insulating substrate, and a discharge gas is sealed in the closed container. Between the first and second discharge electrodes on the inner surface and between the first and second discharge electrodes.
When the ground electrode is provided in a direction substantially parallel to the discharge electrode of
Since the voltage range and frequency range for stable operation are widened,
The dimming range of the luminance is widened.

When the second dielectric layer covering the surface of the ground electrode provided on the front plate is made of a light-transmitting material, the luminance does not decrease and the luminance uniformity is good. It is.

When the width of the ground electrode is set to 0.8 mm or more, the dimming range of the luminance can be surely widened.

When the ground electrode is provided on the insulating substrate at a distance of 8.5 mm or more from the first and second discharge electrodes,
The dimming range of the luminance can be reliably widened.

Further, when the ground electrode is provided on the front plate at a distance of at least 20 mm from the first and second discharge electrodes, the dimming range of the luminance can be reliably widened.

When a protective layer is provided on the surface of the first dielectric layer, the operating voltage can be reduced and sputtering can be reduced, and the life can be extended.

When a transparent conductive film is used as the ground electrode provided on the front plate, the luminance uniformity is good.

Further, in the illumination device and the liquid crystal display device according to the present invention, the dimming range of the luminance is widened.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view showing a flat discharge device according to the present invention.

FIG. 2 is a driving voltage waveform diagram of the flat discharge device shown in FIG.

FIG. 3 is a graph showing a stable operation region of a driving voltage of a flat discharge device.

FIG. 4 is a graph showing a relationship between a width of a ground electrode and a minimum stable operation voltage.

5 is a graph showing the relationship between the distance L ₁ and the lowest stable operating voltage of the discharge electrode and the ground electrode.

FIG. 6 is a sectional view showing another flat discharge device according to the present invention.

FIG. 7 is a cross-sectional view illustrating another flat discharge device according to the present invention.

FIG. 8 is a graph showing a relationship between a distance L ₂ between a discharge electrode and a ground electrode and a minimum stable operation voltage.

FIG. 9 is a cross-sectional view showing another flat discharge device according to the present invention.

FIG. 10 is a cross-sectional view showing a conventional flat discharge device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Closed container 2 ... Closed container 10 ... Front plate 20 ... Insulated substrate 21 ... Insulated substrate 40 ... 1st discharge electrode 41 ... 2nd discharge electrode 50 ... 1st dielectric layer 51 ... 2nd dielectric layer 52 first dielectric layer 53 dielectric layer 60 phosphor 80 earth electrode 81 earth electrode 82 earth electrode 83 earth electrode

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masashi Tsuchiya 888 Fujibashi, Ome-shi, Tokyo Heating Lighting Division, Hitachi, Ltd.

Claims (12)

[Claims] 1. A discharge device having first and second discharge electrodes whose surfaces are covered with a first dielectric layer, between the first and second discharge electrodes and between the first and second discharge electrodes. A ground electrode provided in a direction substantially parallel to the discharge electrode. 2. A flat closed container is formed by combining a light-transmitting front plate and an insulating substrate, and first and second discharge electrodes are provided on the inner surface of the front plate, and the first and second discharge electrodes are provided. A first dielectric layer covering the surface of the second discharge electrode, a phosphor applied to the inner surface of the insulating substrate, and a discharge gas sealed in the closed container; A discharge device, wherein an earth electrode is provided between the first and second discharge electrodes on an outer surface of an insulating substrate or the front plate and in a direction substantially parallel to the first and second discharge electrodes. 3. The discharge device according to claim 2, wherein the earth electrode is made of a metal foil, and the earth electrode is adhered to the closed container. 4. A flat hermetic container is formed by combining a light-transmitting front plate and an insulating substrate, and first and second discharge electrodes are provided on the inner surface of the front plate, and the first and second discharge electrodes are provided. A first dielectric layer covering the surface of the second discharge electrode, a phosphor applied to the inner surface of the insulating substrate, and a discharge gas sealed in the closed container; An earth electrode is provided between the first and second discharge electrodes on the inner surface of the insulating substrate or the front plate and in a direction substantially parallel to the first and second discharge electrodes, and covers the surface of the earth electrode. A discharge device provided with two dielectric layers. 5. The discharge device according to claim 4, wherein the second dielectric layer covering the surface of the ground electrode provided on the front plate is made of a light-transmitting material. . 6. The discharge device according to claim 2, wherein the width of the ground electrode is 0.8 mm or more. 7. The discharge device according to claim 2, wherein said ground electrode is provided on said insulating substrate at a distance of at least 8.5 mm from said first and second discharge electrodes. 8. The discharge device according to claim 2, wherein said ground electrode is provided on said front plate at a distance of at least 20 mm from said first and second discharge electrodes. 9. The discharge device according to claim 1, wherein a protective layer is provided on a surface of said first dielectric layer. 10. The discharge device according to claim 2, wherein said earth electrode provided on said front plate is made of a transparent conductive film. 11. An illuminating device configured to illuminate using the discharge device according to claim 2. Description: 12. A liquid crystal display device using the discharge device according to claim 2 as a backlight.