JP2003347081A - Lighting circuit for dielectric barrier discharge lamp and illuminating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lighting circuit for a dielectric barrier discharge lamp capable of obtaining ultraviolet ray having high luminous efficiency and a narrow wavelength region by suppressing glow discharge of filler gas by cold cathode discharge of an internal electrode, and an illuminating device having excellent wavelength conversion efficiency of a phosphor film using the lighting circuit and high luminance. <P>SOLUTION: Maximum values of the amplitude of voltage of a negative region for ground voltage when connecting a high pressure output of the lighting circuit of the dielectric barrier discharge lamp to the internal electrode of the dielectric barrier discharge lamp and a positive region when connecting the high pressure output to an external electrode of the dielectric barrier discharge lamp, respectively, are below starting voltage of the cold cathode discharge of the internal electrode. <P>COPYRIGHT: (C)2004,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light source for a backlight of a liquid crystal display device used for, for example, a personal computer, a car navigation system, a liquid crystal television, a scanner, or a light source for generating ultraviolet light for sterilization or processing by ultraviolet light. The present invention relates to a dielectric barrier discharge lamp and an illuminating device used as a device.

[0002]

2. Description of the Related Art Conventionally, fluorescent lamps and ultraviolet lamps which do not use mercury which is a harmful substance and have little adverse effect on the environment and whose light output and discharge voltage are hardly influenced by ambient temperature are disclosed in, for example, JP-A-2001-2001. 1436
An internal electrode is provided at one end of the discharge lamp as shown at 62,
A dielectric barrier discharge lamp having an external electrode on the outer surface of a glass tube has been developed.

FIG. 8 is a configuration diagram of a general dielectric barrier discharge lamp. Reference numeral 1 denotes a glass tube filled with, for example, xenon gas, which itself is a dielectric for causing a dielectric barrier discharge. Reference numeral 2 denotes a phosphor coating formed on the inner surface of the glass tube 1 so that the discharge lamp functions as a fluorescent lamp. Reference numeral 3 denotes an internal electrode sealed at one end of the glass tube 1, and a conductive terminal 4 to the outside of the tube is connected to the internal electrode 3 by welding or the like. Reference numeral 5 denotes an external electrode formed by winding a conductive wire or the like around the outer periphery of the glass tube 1.

The above-mentioned dielectric barrier discharge lamp is disclosed in
As shown by reference numeral 230091, for example, lighting is performed by applying a high-frequency voltage having a voltage waveform as shown in FIG. 10 between the internal electrode 3 and the external electrode 5 by a lighting circuit as shown in FIG.

[0005]

However, when the dielectric barrier discharge lamp having the above-described structure is lit with a voltage waveform as shown in FIG. Since a body barrier discharge occurs, it is possible to efficiently generate excimer of the filled gas and efficiently generate ultraviolet rays corresponding to the energy level when the gas deviates and returns to the ground state. Since the cold cathode discharge start voltage of the electrode 3 is lower than the dielectric barrier discharge start voltage in principle, the absolute value of the voltage exceeds the cold cathode discharge start voltage of the internal electrode 3 in the cycle in which the voltage waveform becomes negative, Glow discharge occurs.

The discharge electrons generated by the cold cathode glow discharge ionize or excite a gas such as xenon sealed in the glass tube 1, while the atoms excited by the cold cathode glow discharge are excited by the dielectric barrier discharge. Unlike an atom to be excimer, it is not excited to an energy level at which an excimer molecule is easily formed, so that it is not possible to obtain an ultraviolet ray having a wavelength required for excimer emission which is originally required.
Therefore, the conversion efficiency is reduced at the time of wavelength conversion in the phosphor coating 2, and the overall luminous efficiency is reduced. Conversely, the time required for the ground state required for the cycle of excimer generation is reduced, which is a factor that hinders the generation of excimer molecules.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and suppresses the generation of glow discharge by preventing unnecessary cold cathode discharge from occurring in internal electrodes.
By enabling efficient dielectric barrier discharge, the luminous efficiency is improved.

[0008]

According to a first aspect of the present invention, there is provided a glass tube in which xenon, a rare gas such as argon or krypton, or a mixed gas thereof is sealed. A dielectric barrier discharge lamp having an internal electrode that is led out and sealed with a conductive terminal to the outside, and an external electrode on a part of the outer peripheral surface of the glass tube to cause a dielectric barrier discharge using the glass tube as a dielectric. A high voltage output of an output transformer of a lighting circuit for lighting the dielectric barrier discharge lamp is connected to the internal electrode, the other is grounded and connected to the external electrode of the dielectric barrier discharge lamp, and a rectangular wave or the like is connected. The lighting circuit of the dielectric barrier discharge lamp driven by the AC waveform has a maximum value of the voltage amplitude in a region where the lighting waveform is negative with respect to the ground potential of the lighting circuit of the dielectric barrier discharge lamp. Characterized in that the starting voltage (breakdown voltage) of the cold cathode discharge of the internal electrodes or less.

According to a second aspect of the present invention, in the first aspect, a high voltage output of a lighting circuit of the dielectric barrier discharge lamp is connected to the external electrode of the dielectric barrier discharge lamp, and the other is grounded. And the maximum value of the amplitude of the voltage in a region where the lighting waveform is positive with respect to the ground voltage of the lighting circuit of the dielectric barrier discharge lamp is equal to or less than the cold cathode discharge starting voltage of the internal electrode. It is characterized by being.

According to a third aspect of the present invention, there is provided a lighting apparatus including the lighting circuit of the dielectric barrier discharge lamp according to the first or second aspect.

A fourth aspect of the present invention is characterized in that, in the third aspect of the present invention, a phosphor coating is formed on the inner surface of the glass tube of the dielectric barrier discharge lamp.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1, 2, 3, 4, 5, 6, and 7. FIG.

(Embodiment 1) FIG. 1 is a block diagram showing a lighting circuit of a dielectric barrier discharge lamp according to a first or a second embodiment of the present invention. It is a block diagram showing a configuration, and is a dielectric barrier discharge lamp in which a portion (b) is lit. The dielectric barrier discharge lamp to be turned on here may be a straight tube as shown in FIG. 8, or may be any shape, such as an L-shape, or a so-called flat plate. Here, as the dielectric barrier discharge lamp shown in (b), in the configuration shown in FIG. 12. Wind a Ni conductor and use xenon gas as a rare gas as a discharge medium.
A case where 3 kPa is used will be described.
The high voltage output terminal 10 of the transformer 7 is connected to the internal electrode 3 and the external electrode 5 is grounded.

In the dielectric-barrier discharge lamp of the first embodiment, when a positive-period voltage is applied to the internal electrode 3, electric charges are charged on the surface of the glass tube 1 serving as a dielectric with the external electrode 5 as a ground. The starting voltage at which the dielectric barrier discharge occurs was about 1.5 kV, and when a negative cycle voltage was applied to the internal electrode 3, the voltage at which glow discharge was started using the internal electrode 3 as a cold cathode was about −1 kV. .

FIG. 2 shows an example of the lighting circuit according to claim 1 shown in FIG. Here, 6 is a switching element composed of a transistor or FET, and 7 is a transformer for boosting. In this lighting circuit, the power supply terminal 8
An arbitrary power supply voltage is applied between the ground and the ground, and the oscillation circuit 9
The switching element 6 is turned on / off by a signal from the switch. The frequency of the signal from the oscillation circuit 9 is set to an arbitrary value of 20 kHz to 80 kHz suitable for lighting the dielectric barrier discharge lamp of the first embodiment, and the duty ratio is an arbitrary value between 1% and 50%. I take the.

At this time, a square wave as shown in FIG. 3 should ideally be output to the high voltage output terminal 10 of the transformer due to the step-up of the transformer 7, but the impedance and the impedance of the dielectric barrier discharge lamp should be reduced. Kickback is generated by the resonance of the discharge tube, and a quasi-rectangular wave having distortion as shown in FIG. 4 and having asymmetrical positive and negative peak voltages is applied to the discharge tube.

Here, the power supply voltage or the step-up ratio of the transformer is controlled. The maximum voltage 11 in the positive cycle of the output waveform shown in FIG. 4 is 1.5 kV or more, and the minimum voltage 12 in the negative cycle is -1 kV. By doing so, it was confirmed that excimer emission due to dielectric barrier discharge was efficiently generated while suppressing cold cathode discharge in the internal electrode 3.

Further, in the fluorescent lamp in which a phosphor film effective for 176 nm, which is the excimer emission wavelength peak of xenon, is formed on the inner surface of the glass tube 1 of the dielectric barrier discharge lamp of the first embodiment. It was confirmed that light was emitted with high luminance with respect to the voltage waveform.

(Embodiment 2) A case where the same dielectric barrier discharge lamp as in Embodiment 1 is lit by another lighting circuit will be described.

FIG. 5 shows another example of the lighting circuit shown in FIG. Here, 6 is a switching element composed of a transistor or FET, and 13 is a transformer for boosting. The primary winding 14 of the transformer 13 is divided into an arbitrary number of turns as shown in FIG. 5, and one of the windings is grounded via a diode 15. Instead of the diode 15, a transistor or FET that turns on and off in opposite phase in synchronization with the switching element 6 may be used. In this drive circuit, an arbitrary power supply voltage is applied between the power supply terminal 8 and the ground, and the switching element 6 is turned on / off by a signal from the oscillation circuit 9.

The frequency of the signal from the oscillation circuit 9 is the same as that of the first embodiment.
20 KHz suitable for lighting a dielectric barrier discharge lamp as in
It is set to any value from z to 80 kHz, and its duty ratio takes any value between 1% and 50%.

At this time, a square wave as shown in FIG. 3 should ideally be output to the high voltage output terminal 10 of the transformer due to the step-up of the transformer 13, but the impedance and the impedance of the dielectric barrier discharge lamp are reduced. Kickback is generated by the resonance of the discharge tube, and a quasi-rectangular wave having distortion as shown in FIG. 4 and having asymmetrical positive and negative peak voltages is applied to the discharge tube. Here, the divided primary winding 14 and diode 15
Of the primary winding 1 in the form to cancel kickback
Since the current flows through 4, the minimum voltage 16 in the negative cycle can be increased as shown in FIG.

By doing so, the maximum voltage 17 in the positive cycle of the output waveform is maintained high while the minimum voltage 1 in the negative cycle is maintained.
6 can be suppressed higher than -1 kV, so that higher power can be applied to the dielectric barrier discharge than in the first embodiment while suppressing the cold cathode discharge of the internal electrode 3, and further, the light output Can be improved.

(Embodiment 3) An example of a lighting circuit according to the second aspect of the present invention is a lighting circuit as shown in FIG. Here, 6, 1
Reference numeral 8 denotes a switching element formed of a transistor or an FET, and 13 denotes a transformer for boosting. The block diagram of the lighting device of the dielectric barrier discharge lamp is shown in FIG. 1, but the high voltage output terminal 10 of the transformer 13 is connected to the external electrode 5 and the internal electrode 3 is grounded.

In this dielectric barrier discharge lamp,
When a negative cycle voltage is applied to the external electrode 5, the internal electrode 3
The surface of the glass tube 1 serving as a dielectric is charged with the ground as a ground, and a starting voltage at which a dielectric barrier discharge occurs is about -1.5 kV. When a positive-period voltage is applied to the external electrode 5, The voltage for starting glow discharge using the electrode 3 as a cold cathode was about 1 kV.

In this lighting circuit, an arbitrary power supply voltage is applied between the power supply terminal 8 and the ground, and the switching element 6 is turned on / off by a signal from the oscillation circuit 9. A signal having a phase opposite to that of the signal input from the oscillation circuit 9 to the switching element 6 is input to the switching element 18, and current is alternately applied to the divided primary windings 14 of the transformer 13 by zero-volt switching. Here, for the sake of explanation, of the primary winding, the side corresponding to the switching element 6 is referred to as a primary winding 19, and the side corresponding to the switching element 18 is referred to as a primary winding 20. When the switching element 6 is turned on and a current flows through the primary winding 19, the output waveform of the transformer 13 has a positive period. When the switching element 18 is turned on and a current flows through the primary winding 20, the output of the transformer 13 is output. The winding direction is determined so that the waveform has a negative period.

The frequency of the signal from the oscillation circuit 8 is the same as that of the first embodiment.
20 KHz suitable for lighting a dielectric barrier discharge lamp as in
It is set to any value from z to 80 kHz, and its duty ratio takes any value between 1% and 50%.

At this time, if the number of turns of the primary winding 19 and the primary winding 20 of the transformer 13 is made different so that the primary winding 19 becomes 1.5 times or more the primary winding 20, Due to the difference in the step-up ratio resulting from the difference in the turns ratio between the primary winding and the secondary winding, the peak of the negative cycle of the output voltage from the transformer 13 becomes 1.5 times or more larger than the peak of the positive cycle. .

Here, the power supply voltage is adjusted so that the maximum positive-period voltage applied to the dielectric barrier discharge lamp is 1 kV or less, so that the cold cathode discharge at the internal electrode 3 is suppressed and the minimum negative-period voltage is maintained. Since the voltage can be reduced to -1.5 kV or less, excimer light emission by dielectric barrier discharge can be efficiently generated.

Next, FIG. 11 shows an illuminating device provided with any one of the first, second and third embodiments. In such a lighting device, light emitted from the dielectric barrier discharge lamp 26 is incident on the side surface of the light-transmitting light guide 21 made of a resin material,
After being reflected by the light reflecting plate 22 having a light reflecting surface made of a metal or a resin material and arranged below the light guide, light is incident again, and the light diffusing plate 23 and the prism are further arranged above the light guide. The light direction is controlled by the light control member of the sheet 24, and light is emitted from above. Reference numeral 25 denotes a light reflector that reflects light emitted from the dielectric barrier discharge lamp and makes the light efficiently enter the light guide.

[0031]

According to the first and second aspects of the present invention, when the dielectric barrier discharge lamp having the internal electrode is driven, the internal electrode has been an obstacle to the generation of excimer molecules due to the dielectric barrier discharge. It is possible to provide a lighting circuit of a dielectric barrier discharge lamp which can suppress the glow discharge of the sealing gas due to the cold cathode discharge of the above and can obtain a higher luminous efficiency and an ultraviolet ray having a narrow wavelength range.

In the lighting device using the lighting device of the dielectric barrier discharge lamp, when the dielectric barrier discharge lamp having the internal electrodes is driven, it is a factor that hinders the generation of excimer molecules by the conventional dielectric barrier discharge. It is possible to suppress the glow discharge of the filling gas due to the cold cathode discharge of the internal electrode, which has a higher luminous efficiency and can obtain ultraviolet light with a narrow wavelength range. The discharge lamp can provide a higher-luminance illuminating device in which the wavelength conversion efficiency of the phosphor film is good.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a lighting circuit of a dielectric barrier discharge lamp according to an embodiment of the present invention.

FIG. 2 is a circuit diagram illustrating an example of a lighting circuit block according to the first embodiment of the present invention.

FIG. 3 is an ideal output waveform diagram of the lighting circuit of FIG. 2;

FIG. 4 is a lighting voltage waveform diagram for lighting the dielectric barrier discharge lamp according to the first embodiment of the present invention.

FIG. 5 is a circuit diagram illustrating an example of a lighting circuit block according to a second embodiment of the present invention.

FIG. 6 is a lighting voltage waveform diagram for lighting a dielectric barrier discharge lamp according to a second embodiment of the present invention.

FIG. 7 is a lighting voltage waveform diagram for lighting a dielectric barrier discharge lamp according to a third embodiment of the present invention.

FIG. 8 is a configuration diagram showing a general dielectric barrier discharge lamp.

FIG. 9 is a block diagram showing an example of a lighting circuit of a conventional dielectric barrier discharge lamp.

FIG. 10 is a lighting voltage waveform diagram for lighting a conventional dielectric barrier discharge lamp.

FIG. 11 is a schematic sectional view of a lighting device of the present invention.

[Description of Signs] 1 Glass tube 2 Phosphor coating 3 Internal electrode 4 Conductive terminal 5 External electrode 6 Switching element 7 Transformer 8 Power supply terminal 9 Oscillation circuit 10 High voltage output terminal 11 Maximum voltage of positive cycle of output waveform 12 Negative of output waveform The minimum voltage of the cycle 13 The transformer 14 The primary winding 15 The diode 16 The minimum voltage of the negative cycle of the output waveform 17 The maximum voltage of the positive cycle of the output waveform 18 The switching element 19 The primary divided corresponding to the switching element 6 of the primary winding 14 Winding 20 Primary winding 21 of primary winding 14 divided corresponding to switching element 18 Light guide 22 Light reflector 23 Light diffuser 24 Prism sheet 25 Light reflector 26 Dielectric barrier discharge lamp

Claims (4)

[Claims] 1. An internal electrode which is sealed at least at one end of a glass tube in which a rare gas such as xenon, or argon or krypton, or a mixed gas thereof is enclosed. In a dielectric barrier discharge lamp having an external electrode that generates a dielectric barrier discharge using a glass tube as a dielectric on a part of the outer peripheral surface of the dielectric tube, a high-voltage output of an output transformer of a lighting circuit for lighting the dielectric barrier discharge lamp is used. The lighting circuit of the dielectric barrier discharge lamp, which is connected to the internal electrode and grounded to the other electrode of the dielectric barrier discharge lamp and connected to the external electrode of the dielectric barrier discharge lamp and is lit by an AC waveform such as a rectangular wave, comprises: The maximum value of the voltage amplitude in a region where the lighting waveform is negative with respect to the ground potential of the lighting circuit of the discharge lamp is equal to or less than the cold cathode discharge start voltage (discharge breakdown voltage) of the internal electrode. Lighting circuit of a dielectric barrier discharge lamp according to claim. 2. The dielectric barrier discharge lamp, wherein a high-voltage output of a lighting circuit of the dielectric barrier discharge lamp is connected to the external electrode of the dielectric barrier discharge lamp, and the other is grounded and connected to the internal electrode. The maximum value of the amplitude of the voltage in a region where the lighting waveform is positive with respect to the ground voltage of the lighting circuit of (i) is not more than the starting voltage of the cold cathode discharge of the internal electrode. Lighting circuit for body barrier discharge lamp. 3. A lighting device comprising the lighting circuit of the dielectric barrier discharge lamp according to claim 1. 4. A phosphor coating is formed on the inner surface of the glass tube of the dielectric barrier discharge lamp.
The lighting device according to claim 1.