JP3888123B2 - Flat light source and flat light source system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flat light source such as a discharge device that emits light in a planar shape, a flat light source such as a backlight of a liquid crystal panel, and a flat illumination light source.
[0002]
[Prior art]
Since the liquid crystal panel is thin and lightweight and has low power consumption, it is widely used as a portable device such as a video camera, and various information video devices such as a personal computer and a television. 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. Conventionally used backlights are mainly a combination of a cold cathode fluorescent lamp filled with mercury and a rare gas and a light guide made of acrylic resin, but as a backlight for portable liquid crystal display devices, low power is required. The flat plate type light source is also used.
[0003]
For example, a conventional flat light source described in Japanese Patent Application Laid-Open No. 2000-149869 is composed of a sealed container having a discharge space having a flat cross section and having a phosphor coated on the inner surface thereof. A pair of discharge electrodes whose surfaces are covered with a dielectric are provided, and a mixed gas of xenon and argon is sealed in the discharge space. In the flat light source having this structure, a rare gas discharge is generated in the discharge space by applying a high frequency voltage between the electrodes, whereby the phosphor is excited to emit light and radiate outside.
[0004]
[Problems to be solved by the invention]
When a conventional flat light source is increased in size, the distance between the electrodes becomes longer, and a large high-frequency voltage must be applied in order to start discharge, and a large and expensive power source is required.
[0005]
In addition, with a conventional flat light source, it is difficult to achieve a discharge state that spreads uniformly in the discharge space immediately after starting by simply applying a high-frequency voltage. Especially when it is necessary to increase the input power to the lamp in order to increase the brightness, if a large amount of power is applied immediately after start-up, the contracted discharge is almost certainly generated, and the discharge state can be spread uniformly. There wasn't.
[0006]
Conventionally, in order to start and light a flat light source stably, the high voltage DC power source is often driven by pulse lighting with a relatively small duty through a switching element. When a conventional flat light source is lit with an inverter power supply having a large duty, it is difficult to obtain a discharge state that spreads uniformly in the discharge space immediately after starting.
[0007]
[Means for Solving the Problems]
In order to solve the above problems, in the present invention, a plurality of strip-shaped auxiliary conductors are installed so as to be orthogonal to the electrodes. By installing this auxiliary conductor, first, a discharge is started between the electrode and the auxiliary conductor, and this shifts to a discharge between the electrodes, so that the discharge is started at a low voltage and the start is facilitated. In addition, since it is configured to cover the entire surface of the flat light source with a plurality of strip-shaped auxiliary conductors arranged in parallel, the discharge starts evenly at each location, the discharge does not shrink, and spreads from the start to the entire surface. It can be discharged.
[0008]
A flashing test was repeatedly performed on a flat light source having no auxiliary conductor, a flat light source having one auxiliary conductor on the entire surface, and a flat light source in which the pitch P of a plurality of strip-shaped auxiliary conductors was changed. At this time, conditions other than the auxiliary conductor are the same. As a result, when there is no auxiliary conductor, when the entire surface is made of one auxiliary conductor, the discharge is mostly contracted, or even in the case of a plurality of strip-shaped auxiliary conductors under the condition of no discharge As a result, it was confirmed that the rate of normal starting increases as the discharge spreads throughout. Furthermore, it was found that when the pitch P was 10 mm or less, the rate of normal discharge start was significantly increased. For this reason, in order to make the effect remarkable in the present invention, the plurality of auxiliary conductors are installed so as to have a pitch of 10 mm or less.
[0009]
In the present invention, the distance between the inner surface of the discharge space and the auxiliary conductor is 5 mm or less. If the distance between the inner surface of the discharge space and the auxiliary conductor is increased, the effect of limiting the discharge progress direction at the start by the auxiliary conductor is weakened, and as a result, the discharge is easily contracted. For this reason, in this invention, the effect can be exhibited notably by comprising so that the space | interval of discharge space inner surface and an auxiliary conductor may be 5 mm or less.
[0010]
In the present invention, the auxiliary conductor is attached so as to contact the back surface of the discharge vessel. Generally, the auxiliary conductor is installed in the discharge vessel with a complicated configuration, but can be installed easily and inexpensively by installing it on the outer surface of the vessel.
[0011]
Further, the present invention is configured to have a function of cutting off the current at the time of steady lighting near the center of the starting auxiliary conductor. As a result, there is no current flowing through the auxiliary conductor during steady lighting, so that there is no reduction in luminance, and a stable and high luminance flat light source can be realized.
[0012]
In the present invention, an MgO film is formed on the surface of the discharge space and above the pair of electrodes. When the MgO film is formed, the discharge current easily flows, so that the start can be facilitated. However, there is a drawback that the discharge is easily contracted. Therefore, the improvement of normal discharge startability by the configuration using the auxiliary electrode of the present invention is remarkably effective in preventing the contraction of the discharge due to the MgO film, particularly when applied to the flat light source on which the MgO film is formed. is there.
[0013]
In the present invention, a light source system is constituted by the flat light source of the present invention and the inverter power supply. Conventionally, the driving power source of a flat plate light source is often pulsed with a relatively low duty through a switching element from a high voltage power source. The improvement of normal discharge startability by the configuration using the auxiliary electrode of the present invention is particularly effective in a system including an inverter power supply.
[0014]
Further, in the present invention, when the power is turned on, a small electric power is applied to start the discharge, and then the electric power is increased so that steady lighting is performed. Thereby, generation | occurrence | production of contraction discharge can be prevented now.
[0015]
In addition, the voltage pulse applied in the present invention is configured to start application from a pulse height that does not substantially start a discharge when the power is turned on, and then gradually increases the pulse height. Thereby, generation | occurrence | production of contraction discharge can be prevented effectively.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an embodiment of a flat light source according to the present invention. (A) shows an overall configuration, (b) shows an AA ′ section, and (c) shows a BB ′ section. Reference numeral 1 denotes a plate-like front plate, and 2 denotes a thin plate-like back plate, both of which are made of soda glass. The front plate 1 and the back plate 2 are sealed with a sealing glass 3 to form a sealed structure. A mixed gas of Xe, Ne, and Ar is sealed in the container. Reference numerals 4 and 5 denote a pair of electrodes, which are printed on the inner surface of the front plate 1. Further, a thick dielectric film 6 and MgO film 7 are printed on the electrodes 4 and 5, and the electrodes 4 and 5 are not exposed inside the container. A phosphor 8 is applied to the inner surfaces of the front plate 1 and the back plate 2.
[0017]
A plurality of strip-shaped auxiliary conductors 9 are formed on the outer surface of the back plate 2. Here, the thickness from the bottom of the back plate to the phosphor surface, and therefore the distance d between the auxiliary conductor and the discharge space is 2 mm in this embodiment. The pitch P of the auxiliary conductors formed in parallel is 5 mm. The auxiliary conductor is made of Cu or Al.
[0018]
The operation of this embodiment is as follows. When a voltage is applied between the electrodes 4 and 5, an electric circuit is formed between the electrode 4 and the auxiliary conductor facing the electrode 4, and between the auxiliary conductor and the electrode 5 and the auxiliary conductor facing the electrode 5. And is started by discharging through this electric circuit. After starting, the discharge extends in the direction of the auxiliary conductor, and finally progresses to a discharge only in the discharge space that does not pass through the auxiliary conductor. Since the plurality of auxiliary conductors are installed in parallel, the discharge corresponding to each auxiliary conductor extends in the direction of the auxiliary conductor, so that a discharge is formed while spreading uniformly as a whole. On the other hand, when the entire back surface is covered with a single conductor or the pitch of the auxiliary conductors is long, the discharge contracts because it becomes easier to move in the lateral direction during discharge formation. As shown in this embodiment, according to the configuration of the present invention, it is possible to provide a flat light source and a flat light source system that can easily start discharge and can be easily lit with normal discharge.
[0019]
In the structure of FIG. 1, for example, the container may be a plate glass-like front plate and a back plate, and another side glass plate may be used on the side surface and these may be sealed. Further, it is not always essential to form the MgO film 6 on the electrode. Alternatively, the auxiliary conductor 9 may be formed on the inner surface of the back plate 2 and the upper portion thereof may be covered with a dielectric thick film printing. Alternatively, a plurality of auxiliary conductors 9 may be printed and integrated on another plastic thin plate, and may be brought into close contact with the back surface of the back plate. The auxiliary conductor 9 may be made of a transparent conductor such as Ag or ITO. Alternatively, one end side of the auxiliary conductor 9 may be short-circuited to each other to form a comb-shaped auxiliary conductor. The enclosure may be Hg and Ar gas.
[0020]
Further, the first gist of the present invention is the configuration thereof and is not limited to the numerical value (size) in FIG. However, among the configurations of the present invention, the most effective is when the pitch P of the auxiliary conductor is 10 mm or less and the distance d to the discharge space is 5 mm or less.
[0021]
As a modification of FIG. 1, another embodiment of a flat light source is shown in FIG. In the embodiment of FIG. 2, wave-like protrusions are provided on the inner surface (discharge space side) of the back plate 2 at regular intervals in a direction orthogonal to the pair of electrodes. A plurality of strip-shaped auxiliary conductors 9 are provided on the bottom of the back plate 2 at positions facing the troughs of the wavy projections. In the present embodiment, the provision of the protrusions makes it easier for the discharge at start-up to progress toward the auxiliary conductor, and thus toward the counter electrode, and the effect of preventing contracted discharge is increased. Moreover, the phosphor coating area is increased and the luminance is increased.
[0022]
FIG. 3 shows another embodiment of the flat light source according to the present invention, and is a plan view and a side view as seen from the back side. In the present embodiment, the auxiliary conductor is divided into two at the center and is composed of 10a and 10b. The auxiliary conductors 10a and 10b are connected via the switching element 11 between them. A plurality of auxiliary conductors having such a configuration are arranged in parallel. The switching element 11 is controlled by a signal from a power source (not shown) so that the switching element 11 is turned on at the start and turned off at the steady state. A specific example of the switching element 11 is a photorelay in which two FETs having input signals coupled by a photocoupler are connected in series in the opposite direction and plastic molded.
[0023]
As a result, the control signal side and the auxiliary conductor can be ON / OFF controlled at the central portion of the auxiliary conductor while being electrically insulated. Further, instead of the switching element, for example, only a resistor for limiting the current may be used, but in this case, a small amount of current flows even during steady state.
[0024]
FIG. 4 shows another embodiment of the flat light source according to the present invention, and is a plan view and a side view as seen from the back side. In FIG. 4, a part of the back plate 2 is notched, and a part of the phosphor applied to the inner surface of the front plate 1 is notched. In this embodiment, a pair of electrodes 4 and 5 and an auxiliary conductor 12 are formed on the inner surface of the front plate 1. Examples of the forming method include a method using silver paste printing. The pair of electrodes 4 and 5 and the auxiliary conductor 12 are in the same plane, and there are a plurality of auxiliary conductors 12 in the direction perpendicular to the longitudinal direction of the electrodes 5 and 6 between the electrodes 4 and 5, as shown in FIG. They are arranged in parallel. Further, both the electrodes 4 and 5 and the auxiliary conductor 12 are covered with a dielectric 6, and a phosphor 8 is applied on the dielectric 6.
[0025]
In this embodiment, light is extracted to the back plate side. If the auxiliary conductor 12 is made of a transparent conductive film such as an ITO film, light can be extracted to the front plate side or both sides.
[0026]
Another embodiment of the present invention will be described in detail with reference to FIG. FIG. 5 shows an embodiment of a flat light source system according to the present invention. In the figure, 20 is a flat light source, 30 is a DC power supply unit, and 31 is an inverter unit. The inverter unit 31 includes a control unit 32, a starting voltage adjustment unit 33, a high-frequency transformer 34, and FETs 35 and 36. The voltage adjustment unit 33 at the time of start-up includes a three-terminal regulator 37, a resistor 38, and an electrolytic capacitor 39.
[0027]
The operation of the flat light source system of this embodiment is as follows. When a voltage is applied from the DC power supply unit 30, the control unit 32 immediately starts to operate, and alternately turns on and off the FETs 35 and 36 at a predetermined frequency. Consider the output voltage V1 of the voltage adjusting unit 33 at the start. When a voltage is applied from the DC power supply unit 30, it is 0 immediately after the voltage of the electrolytic capacitor 39 is applied, so that V 1 is a predetermined output voltage of the three-terminal regulator 37. Thereafter, the electrolytic capacitor 39 is charged through the resistor 38, whereby the voltage V1 gradually rises, and is set to become a steady voltage after 0.5 seconds, for example. A high-frequency rectangular high voltage is applied to the flat light source 20 via the high-frequency transformer 34.
[0028]
The voltage V1 (equal to the input voltage of the high-frequency transformer 34) is set so that the high-frequency voltage applied to the flat light source 20 immediately after starting is slightly lower than the voltage at which discharge is started. Thereafter, since the voltage applied to the flat light source 20 gradually increases, the discharge is started, and further rises to a steady-state voltage, increasing the input power and stabilizing at high brightness. In this embodiment, the discharge is started with a small electric power, and then the electric power is increased and the lamp is steadily lit, so that the occurrence of contracted discharge can be prevented.
[0029]
As a modified example of FIG. 5, the voltage adjusting unit 33 at the time of starting can be simply replaced with a resistor. At this time, a time constant circuit is constituted by the electrolytic capacitor on the primary side of the high-frequency transformer 34, and a time delay occurs in increasing the voltage to the steady state voltage.
[0030]
【The invention's effect】
According to the present invention, even when a flat light source with a large shape and a flat light source with large input power are used, it is possible to effectively prevent the problem that the discharge contracts and does not spread over the entire discharge space at the time of starting. A stable, high-brightness, large-area flat light source or light source system can be easily realized.
[Brief description of the drawings]
FIG. 1 is a perspective view and a cross-sectional view of a flat light source according to an embodiment of the present invention.
FIG. 2 is a cross-sectional perspective view showing another embodiment of a flat light source according to the present invention.
FIGS. 3A and 3B are a plan view and a cross-sectional view showing another embodiment of the flat light source according to the present invention. FIGS.
4A and 4B are a plan view and a cross-sectional view showing another embodiment of the flat light source according to the present invention.
FIG. 5 is a block diagram showing a configuration of a flat light source system according to an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Front plate, 2 ... Back plate, 3 ... Frit glass, 4, 5 ... Electrode, 6 ... Dielectric film, 7 ... MgO film, 8 ... Phosphor, 9, 10a, 10b, 12 ... Auxiliary conductor, 11 ... Switching element, 20 ... Flat light source, 30 ... DC power supply, 31 ... Inverter, 32 ... Control, 33 ... Voltage regulator at start-up, 37 ... Three-terminal regulator.

Claims (9)

A flat discharge vessel having at least one side of translucency, a phosphor is applied to the inner surface of the discharge space, and a mixed gas of two or more kinds of rare gases containing Xe in the discharge space or Hg and a rare gas the mixture is sealed in a plate type light source having a pair of electrodes disposed parallel to the inner surface of the discharge vessel is not exposed to the discharge space, in a direction perpendicular to the pair of electrodes, the discharge is not exposed to the discharge space A flat light source characterized in that a plurality of parallel auxiliary conductors are provided so as to cover the entire surface of the container . 2. The flat light source according to claim 1, wherein a plurality of auxiliary conductors are installed at a pitch of 10 mm or less. 2. The flat light source according to claim 1, wherein a distance between the inner surface of the discharge space and the auxiliary conductor is 5 mm or less. 2. The flat light source according to claim 1, wherein the auxiliary conductor is attached so as to contact the back surface of the discharge vessel. 2. The flat light source according to claim 1, wherein the auxiliary conductor has a function of conducting at the time of starting lighting and cutting off or reducing a current at the time of steady lighting near the substantially center. 6. The flat light source according to claim 1, wherein an MgO film is formed at a portion covering at least the pair of electrodes on the surface of the discharge space. 7. A flat light source system, comprising: the flat light source according to claim 1; and an inverter power source for turning on the flat light source. In flat-plate type light source system according to claim 7, flat type light source system, characterized in that the power-on of the power source to discharge started by applying a small power, thereafter steadily lit with increasing power. In flat-plate type light source system according to claim 7, flat type, characterized in that at power-on of the power source is started application from the minimum pulse voltage necessary for discharge start-up, thereafter the pulse voltage is gradually increased steadily lit Light source system.

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