JPH0721984A - Flat light source - Google Patents

Abstract

PURPOSE:To obtain a light source which has a high safety to electric shock, a low discharge starting voltage and a low discharge maintaining voltage, a high brightness, and a high efficiency, by laminating to form a transparent electrode membrane, a translucent dielectric membrane, and a phosphor membrane, on a front side substrate and a rear side substrate opposing each other, respectively. CONSTITUTION:To a front side substrate 1 opposing to a rear side substrate 2 at a specific interval, a transparent electrode membrane 6, a translucent dielectric membrane 8, and a phosphor membrane 5 are laminated and formed. The same membranes are laminated and formed also to the rear side substrate 2, and almost all the electrode parts are in an envelope, so as to increase the safety against an electric shock. And by forming the dielectric membrane and the transparent electric membrane on the surface, the material membrane thickness of the dielectric membrane can be selected freely. Consequently, the light can be emitted at a high brightness and a high efficiency in an optimum condition, as well as the impedance in the discharge space can be regulated, and the discharge starting voltage and the discharge maintaining voltage can be lowered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin flat plate type fluorescent lamp used for a backlight of a liquid crystal display, interior lighting or the like.

[0002]

2. Description of the Related Art FIG. 6 shows, for example, Japanese Patent Laid-Open No. 3-225743.
FIG. 7 is a cross-sectional view of a conventional flat plate rare gas discharge lamp disclosed in Japanese Patent Publication No. In the space between the front substrate 1 and the rear substrate 2, spacers 3 made of glass beads of uniform small diameter are dispersed and arranged, the periphery of which is sealed by a low-melting glass 4, and a xenon gas is mainly contained inside. A rare gas as a component is enclosed. A phosphor film 5 is deposited on the inner surface of the rear substrate 2, and electrodes 6 and 7 made of a transparent conductive film and a metal film tape are formed on the outer surfaces of both substrates 1 and 2, respectively. In the rare gas discharge lamp having such a structure, when a high frequency voltage is applied between the electrodes 6 and 7, a discharge of the rare gas is generated in the discharge lamp, whereby the phosphor film 5 is excited and emits light, and the transparent electrode 6 A uniform radiated light is emitted through.

[0003]

In the conventional flat plate type light source as described above, when a high voltage is applied between the upper and lower electrodes, the electrodes are formed on the outer surface of the glass, which causes a safety problem such as electric shock. was there. In addition, because there is a structural limit to controlling the material and thickness of the glass substrate sandwiched between the electrode and the discharge space, it is not possible to freely select the material and thickness, and therefore the glass substrate tends to have high impedance It becomes difficult to apply a voltage and inject energy into the space, and the discharge starting voltage and the discharge sustaining voltage become high.
There is also a problem that it is difficult to optimize the light emitting conditions.

The present invention has been made in order to solve the above problems, and an object thereof is to obtain a safe flat plate type light source without danger of electric shock, and to lower the discharge start voltage and the sustain voltage. The purpose of the present invention is to obtain a high-luminance and high-efficiency flat panel light source by reducing the load on the lighting circuit and causing light to be emitted under optimum conditions.

[0005]

In the flat plate type light source according to the present invention, translucent front and rear substrates are arranged to face each other, and a translucent electrode is provided on the inner surface of the front and rear substrates. A transparent dielectric, a phosphor on the top surface of one or both of the front and rear substrates to cover the transparent electrodes, and hermetically seal the discharge gas, and apply a high-frequency voltage between the electrodes. To do so.

Alternatively, two substrates, one of which has a light-transmitting property, are arranged so as to face each other, and a light-transmitting electrode is formed inside the substrate having the light-transmitting property. The electrode is covered with a translucent dielectric, a metal electrode is formed on the inner surface of the other substrate, the metal electrode is covered with a second dielectric, and a phosphor is provided on at least one of the dielectrics. A high frequency voltage is applied between the electrodes.

The second dielectric is made of a low melting point glass containing PbO as a main component and TiO ₂ added thereto.

Further, the translucent electrode is made of a transparent high resistance conductive material, and a metal member is arranged in the peripheral portion.

A metal mesh or a grid metal is used as the translucent electrode.

[0010]

In the flat type light source configured as described above, light is emitted from either or both surfaces, and the electrodes are formed inside the substrate, so there is no danger of electric shock.
Further, since the degree of freedom in selecting the dielectric is large, the impedance other than the discharge space can be freely changed.

Further, since a material having a high reflectance is used for the dielectric, the amount of light emitted to the outside of the substrate can be increased.

Further, by providing a metal electrode around the high resistance electrode in a shape surrounding the high resistance electrode, it is possible to reduce the resistance of the high resistance electrode region.

When a metal mesh or a grid metal is used as the electrode, the area involved in the discharge is reduced, so that the power consumption can be reduced.

[0014]

【Example】

Example 1. FIG. 1 is a cross-sectional view showing an embodiment of the present invention, in which 1 and 2 are transparent front and rear substrates which are opposed to each other and are made of glass, and 4 is a low-melting glass or the like for sealing the space between the glass substrates. Side wall as a complete enclosure,
Reference numeral 5 is a phosphor that emits ultraviolet rays in the vacuum ultraviolet region. 6 and 7 are transparent electrode films such as ITO, and 8 and 9 are transparent dielectric films formed by screen printing or vapor deposition. The transparent electrode films 6 and 7 have a lead-out portion (not shown) to the outside of the envelope. A metal film is formed on the surface of the extracted portion by printing or the like, and lead wires are connected by wire bonding or soldering. Reference numeral 10 denotes a discharge space in which, for example, several tens to several hundreds Torr of Xe gas is sealed.

Next, the operation of this embodiment will be described.
When a voltage is alternately applied between the transparent electrode films 6 and 7 facing each other, an electric field is applied to the discharge space 10 via the dielectric films 8 and 9 on the electrodes. At this time, the dielectric film is much smaller than the distance between the substrates defined as the discharge space, and its dielectric constant can be made larger than that of the plate glass, so that a strong electric field is generated in the discharge space. As a result, an AC discharge between the substrates occurs at a relatively low voltage. In the case of an electric field that rises rapidly in a pulse shape, this discharge is approximately 1
The discharge does not continue until the next pulse is applied, which is completed within μsec. When Xe gas is used by this discharge, excimer Xe ₂ ^* is generated and ultraviolet rays in the vacuum ultraviolet region are emitted during the transition to the ground state. The ultraviolet rays emitted from the excimer are not usually absorbed by the discharge gas molecules themselves, so the self-absorption phenomenon does not occur.
The phosphor films 5 on the surfaces of the front substrate 1 and the rear substrate 2 can be reached without attenuation. The phosphor is excited by ultraviolet rays to emit light, and is extracted as visible light through the front substrate 1 and the rear substrate 2.

Example 2. FIG. 2 shows another embodiment of a flat-type light source using the same principle as that of Example 1, in which a transparent electrode is not used on the inner surface of the rear substrate 2 and a thin film or metal film formed by vapor deposition of metal is used. A metal electrode film 11 such as a thick film formed by a printing method is used, and a dielectric film 9 is formed on the metal electrode film 11. Therefore, since the translucency of the rear substrate 2 is lost, the rear substrate 2 itself does not need to be a translucent material. The operation is almost the same as that of the first embodiment, but the light emission is obtained only from the front substrate 1 and not from the rear substrate 2. Therefore, the phosphor 5 on the rear substrate side
In order to efficiently extract the light emitted from the front substrate side as well,
Usually, the phosphor film on the rear substrate side is formed thicker than the phosphor film on the front substrate side. In this, the phosphor layer is formed in such an amount that the emission of ultraviolet light is sufficiently saturated. Further, since the fluorescent substance film is usually white, the light emitted from the fluorescent substance film 5 on the substrate is transmitted from the front substrate 1 and is reflected by the fluorescent substance film on the rear substrate 2 toward the front substrate 1 again. , The brightness can be synergistically increased.

Embodiment 3. When a metal film is used as the electrode of the back substrate, a method of making the dielectric film white or a glossy surface can be considered in order to increase the reflectance inside the back substrate. To form a white dielectric film by printing, for example, TiO is added to a composite low melting point glass system containing PbO as a main component.
It is conceivable that it is added to ₂ , and a visible light reflectance of 80% or more can be obtained. As a result, visible light can be efficiently emitted to the outside through the front substrate, so that high-luminance and high-efficiency light emission can be performed.

Example 4. Figure 3 shows ITO formed on the substrate
FIG. 6 is a cross-sectional view and a front view showing a method in which the outer periphery of the transparent electrode films 6 and 7 is covered with a metal film electrode. Since the outer peripheral electrode 14 does not transmit light, the transparent electrode portion inside the outer peripheral electrode 14 serves as a light emitting region. Since a thin film of ITO usually has a sheet resistance of 10 Ω / □ or more, when the extraction electrode is taken out from a part of the film, the potential drop in the region far from the extraction portion becomes remarkable, and uneven discharge is likely to occur. By covering with the outer peripheral electrode 14, even if the extraction electrode is taken out from a part of the film, the electric potential becomes constant at least on the outer periphery, so that the unevenness of discharge can be alleviated. Therefore, the discharge can be stabilized and the power consumption can be reduced.

Example 5. In FIG. 4, a transparent electrode is not used on the inner surface of the front substrate 1, and the diameter of the metal is 15 to 200 μm.
Mesh electrode 1 formed by weaving thin wire rods in length and width
2 is disposed inside the front substrate 1, a translucent dielectric material is coated, and a phosphor layer is further formed.
The external connection to the metallic mesh is made by Dumet wire (for example, Nikola, product number 561387) or 42-6 alloy (for example, Nippon Metal Industry Co., Ltd., product number NAS42-6) inside the envelope. Are connected by wire bonding, soldering or the like, drawn out through the sealing layer, and connected to lead wires by soldering or the like. The electrode on the rear substrate side uses the metal electrode film 11 as in the second embodiment.
The operation is the same as that of the second embodiment, except that the light emitted from the phosphor 5 is emitted in a form of leaking from the so-called opening space of the woven mesh. The discharge in this system is performed by the electrode 11 on the back side and the mesh electrode 12 on the front side.
Strictly speaking, it does not occur in the opening space because it occurs between the and, but the unevenness of light emission can be macroscopically eliminated by using a mesh having fine meshes depending on the application. Further, when the mesh electrode is used, the area involved in the discharge is smaller than that when the transparent electrode is used, so that there is an advantage that the power consumption is reduced. Further, in FIG. 3, the dielectric film is formed on the upper layer of the metal mesh electrode 12, but if the dielectric film is attached to the surface of the wire rod of the metal mesh in advance and the mesh-shaped dielectric electrode is used. Good. At this time, the phosphor may be formed on the surface of the mesh electrode, or the mesh electrode may be arranged on the phosphor film formed on the front substrate. Further, a metal mesh may also be used for the electrode on the rear substrate side, and a transparent rear substrate or a transparent dielectric film may be used.

Example 6. FIG. 5 is a front substrate in which a metal electrode film is previously patterned in a grid pattern in the flat plate light source as described in the above embodiment, instead of using a mesh woven of thin metal wires as electrodes. A method of forming a transparent dielectric layer is shown in FIG. Therefore,
The operation is the same as the above-mentioned embodiment. The use of the grid electrode also has the advantage of reducing power consumption during discharge. To form the grid-shaped electrode pattern 13, a photolithography method of exposing a UV-sensitive material to a uniform film formed by a method such as screen printing or vapor deposition and patterning it by wet etching, and a grid-shaped pattern directly on a glass substrate. There is a way to print.

[0021]

Since the present invention is constructed as described above, it has the following effects.

Since most of the electrode portions are inside the envelope, safety problems such as electric shock can be reduced.

By forming the dielectric on the surface of the electrode, the material and thickness of the dielectric can be freely selected.
Since the impedance other than the discharge space can be adjusted, the discharge start voltage and the discharge sustaining voltage can be lowered,
Further, since the light can be emitted under the optimum conditions, high brightness and high efficiency light emission can be performed.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 is a sectional view showing Embodiment 2 of the present invention.

3A and 3B are a sectional view and a front view showing a fourth embodiment of the present invention.

FIG. 4 is a sectional view showing Embodiment 5 of the present invention.

FIG. 5 is a sectional view showing Embodiment 6 of the present invention.

FIG. 6 is a cross-sectional view showing a conventional flat plate light source.

[Explanation of symbols]

 1 Front Substrate 2 Rear Substrate 3 Spacer 4 Sidewall 5 Phosphor Film 6 Transparent Electrode Film (Front Substrate) 7 Transparent Electrode Film (Back Substrate) 8 Dielectric Film (Front Substrate) 9 Dielectric Film (Back Substrate) 10 Discharge Space 11 Metal electrode film 12 Mesh electrode 13 Lattice electrode pattern 14 Peripheral electrode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Goroku Kobayashi 2-14-40 Ofuna, Kamakura City Mitsubishi Electric Co., Ltd. Life Systems Research Institute (72) Inventor Masao Kano 2-14-40 Ofuna, Kamakura-shi Mitsubishi Electric Living Systems Research Institute, Inc. (72) Inventor Takeo Nishikatsu 2-14-40 Ofuna, Kamakura City Mitsubishi Electric Corporation Living Systems Research Institute

Claims (5)

[Claims] 1. A container comprising a translucent front substrate, a translucent rear substrate, and a side wall facing each other and having a discharge gas sealed therein, wherein an inner surface of the front substrate and an inner surface of the rear substrate are provided. A plate type light source characterized in that a transparent electrode is formed, both of the electrodes are covered with a transparent dielectric, a phosphor is provided on the dielectric, and a high-frequency voltage is applied between the electrodes. . 2. A container comprising two substrates, one of which has a light-transmitting property and facing each other, and a side wall, in which a discharge gas is sealed, and the light-transmitting property is provided on the inner surface of the light-transmitting substrate. Electrode is formed, the translucent electrode is covered with a translucent dielectric, a metal electrode is formed on the inner surface of the other substrate, and the metal electrode is covered with a second dielectric. A flat-type light source characterized in that a phosphor is provided on at least one of an optical dielectric and the second dielectric, and a high-frequency voltage is applied between the electrodes. 3. The second dielectric covering the electrode formed on the inner surface of the other substrate is a low melting point glass containing PbO as a main component and TiO ₂ added thereto. The flat type light source according to claim 2. 4. The flat-type light source according to claim 1, wherein the translucent electrode is made of a conductive material having a high resistance, and a metal member is arranged in a peripheral portion of the transparent electrode. 5. The flat-type light source according to claim 1, wherein the translucent electrode is made of a metal mesh or a grid metal.