JP2007087901A - Flat discharge lamp lighting system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flat discharge lamp lighting system capable of preventing fusion of a dielectric layer and a glass container separating an electrode and a discharge medium due to extreme temperature rise of an electrode part while shortening rise time of luminance in early stages of lighting in the flat discharge lamp of a barrier discharge system. <P>SOLUTION: This flat discharge lamp lighting system detects the temperature of the electrodes 6a, 6b of the flat discharge lamp L, and controls to continuously or gradually reduce tube power supplied to the lamp according to the rise of the electrode temperature in start of lighting. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a flat discharge lamp lighting system.

  Conventionally, a flat discharge lamp described in Japanese Patent Application Laid-Open No. 11-204080 (Patent Document 1) is known as a backlight light source or illumination device for a liquid crystal display. As shown in FIG. 1A of Patent Document 1, the conventional flat discharge lamp includes a translucent front plate 20 made of soda glass and a rear substrate made of soda glass, ceramic, or the like. 10 and the side plate 30 are integrally hermetically sealed with, for example, a low melting point glass to constitute a flat discharge vessel. A pair of discharge electrodes 40 and 41 parallel to each other are provided on the inner surface of the front plate 20, and the surfaces of the discharge electrodes 40 and 41 are covered with a dielectric layer 50 provided by a thick film printing method or the like. A fluorescent material 60 is applied to the inner surface of 10, and mercury or a rare gas discharge gas is sealed in the discharge space 70 of the sealed container.

  In this conventional flat discharge lamp, by applying a high-frequency voltage between the discharge electrodes 40 and 41, a discharge is generated in the discharge space 70, and the phosphor 60 is caused by ultraviolet rays generated from mercury as a discharge medium by the discharge. The light is excited and emitted, and the light is emitted to the outside through the front plate 20.

  The brightness of a flat discharge lamp enclosing mercury as this type of discharge medium is greatly influenced by the vapor pressure of the enclosed mercury, that is, the tube wall temperature of the lamp. The lamp tube wall temperature at which the luminous efficiency of the lamp is maximized is 40 ° C. to 60 ° C., and the lamp efficiency is lowered whether it is higher or lower.

  On the other hand, as a general characteristic, a flat discharge lamp requires a considerable time for the tube wall temperature to reach a constant operating temperature because the glass material constituting the discharge vessel has a large heat capacity. As a result, the rise of luminance is slow at the beginning of lighting, and there is a problem that it takes a considerable time to reach a predetermined brightness.

  In order to solve this problem, FIG. 1B of Patent Document 1 is provided with a heating means 80 on the outer surface of the discharge vessel, and the sealed vessel is heated at the start to increase the glass tube wall temperature. A technique for improving the rising characteristic of luminance by promoting the above is disclosed. However, in this prior art, in the case of using a heater as the heating means 80, a heater and a heater control circuit are necessary, and many parts other than the discharge lighting must be mounted, resulting in a significant increase in apparatus cost. There was an inevitable problem.

  Japanese Patent Laying-Open No. 9-288262 (Patent Document 2) discloses an improvement in luminance rise characteristics of a liquid crystal display using a cold cathode discharge lamp in which a discharge medium containing mercury is enclosed, although the shape of the lamp is different. Describes the following technologies. As shown in FIG. 2 of Patent Document 2, the inverter circuit 10 converts the DC voltage 90 supplied from the constant voltage circuit 9 into AC having a predetermined frequency, and supplies the voltage to the lamp. The thermistor 4 is installed on the outer wall of the glass tube at the center of the positive column of the cold cathode fluorescent lamp, and outputs a thermistor output voltage 40 corresponding to the lamp temperature. The temperature control unit 7 outputs a control DC voltage 72 corresponding to the thermistor output voltage 40 to the luminance control unit 8. The luminance control unit 8 outputs to the inverter circuit 10 an adjustment signal 80 having a duty ratio corresponding to the control DC voltage 72 and the user set value at that time. The inverter circuit 10 adjusts the duty ratio of the AC voltage supplied to the lamp by turning ON / OFF the input of the DC voltage 90 according to the adjustment signal 80. As a result, as shown in FIG. 3 of Patent Document 2, the lamp is turned on while controlling the duty ratio of the voltage in accordance with the tube wall temperature of the lamp. In this conventional example, when the temperature of the lamp at the beginning of lighting is low, the duty ratio is increased to increase the input power to the lamp to promote the heat generation of the lamp, and the duty ratio is decreased as the lamp temperature rises. Control to do.

However, in the case of a flat discharge lamp of the barrier discharge type in which the electrode and the discharge medium are blocked by a dielectric layer or a glass container, the following problems occur when the above lighting system is applied. In other words, in the case of a barrier discharge type flat discharge lamp, if the temperature of the electrode part is extremely increased, the dielectric layer or glass container that separates the electrode and the discharge medium may be melted. It is necessary to keep below the specified value. However, as in the lighting system shown in FIGS. 2 and 3 of Patent Document 2, when the temperature detection part is the positive column part of the lamp, the temperature of the electrode part cannot be detected. In this case, the temperature of the electrode part rises, and there is a possibility that the dielectric layer separating the discharge medium and the glass container are melted. In particular, when the size of the lamp is increased, the rate of increase in the tube wall temperature at the center of the lamp becomes very slow relative to the rate of increase in the tube wall temperature at the electrode portion, and the degree of risk increases.
Japanese Patent Laid-Open No. 11-204080 Japanese Patent Laid-Open No. 9-288262

  The present invention has been made in view of the above-described conventional technical problems, and in a flat discharge lamp of a barrier discharge type configured to cut off an electrode and a discharge medium with a dielectric layer or a glass container, the luminance at the initial stage of lighting is provided. An object of the present invention is to provide a flat type discharge lamp lighting system capable of shortening the rise time and preventing the dielectric layer and the glass container separating the electrode and the discharge medium from being melted due to excessive temperature rise of the electrode part. To do.

  In the flat discharge lamp lighting system according to the first aspect of the present invention, a translucent front substrate and a rear substrate are disposed so as to face each other, and the discharge between the two plates is hermetically sealed. A flat discharge lamp in which a medium is enclosed and at least one pair of electrodes is provided outside or inside the planar discharge vessel so as not to contact the discharge medium, and the temperature of the electrode of the flat discharge lamp is set directly or A temperature detection means for indirectly detecting; a control circuit for generating a control signal for designating a power value to be applied to the flat discharge lamp based on a temperature detected by the temperature detection means; and a power value according to the control signal The voltage supply circuit continuously or stepwise supplies the tube power supplied to the flat discharge lamp as the electrode temperature increases at the start of lighting of the flat discharge lamp. Decrease And it is characterized in that the control.

  According to a second aspect of the present invention, in the flat discharge lamp lighting system according to the first aspect, the voltage supply circuit lowers the amplitude value of the voltage applied to the flat discharge lamp so that the electrode temperature at the start of lighting is reduced. The tube power supplied to the flat discharge lamp is reduced continuously or stepwise according to the rise in the pressure.

  According to a third aspect of the present invention, in the flat discharge lamp lighting system according to the first aspect, the voltage supply circuit lowers the frequency of the voltage applied to the flat discharge lamp, thereby reducing the electrode temperature at the start of lighting. The tube power supplied to the flat type discharge lamp is decreased continuously or stepwise as it rises.

  According to a fourth aspect of the present invention, in the planar discharge lamp lighting system according to the first aspect, the voltage supply circuit performs PWM lighting in which an ON period and an OFF period are provided for a voltage applied to the planar discharge lamp, By reducing the ratio, the tube power supplied to the flat discharge lamp is decreased continuously or stepwise as the electrode temperature rises at the start of lighting.

  According to a fifth aspect of the present invention, in the flat discharge lamp lighting system according to the first to fourth aspects, the voltage supply circuit is configured so that the electrode temperature does not exceed a predetermined value at the start of lighting of the flat discharge lamp. The tube electric power supplied to the discharge lamp is controlled to decrease continuously or stepwise.

  According to a sixth aspect of the present invention, in the flat discharge lamp lighting system according to the first to fifth aspects, the voltage supply circuit supplies a voltage having a substantially sinusoidal waveform to the flat discharge lamp.

  According to the present invention, at the start of lighting of the flat discharge lamp by the voltage supply circuit, the tube power supplied to the flat discharge lamp is controlled to decrease continuously or stepwise according to the increase of the electrode temperature. It is possible to provide a flat discharge lamp lighting system capable of shortening the rise time of the brightness and preventing the dielectric layer and the glass container separating the electrode and the discharge medium from being melted due to excessive temperature rise of the electrode section.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  The structure of a flat discharge lamp of the barrier discharge system to which the flat discharge lamp lighting system of one embodiment of the present invention is applied is shown in FIGS. A front substrate 1 made of a light-transmitting glass plate and a rear substrate 2 integrally formed with a side wall portion 3 and a spacer 5 are arranged facing each other at a substantially constant interval, and the peripheral portion is made of frit glass 7. A flat discharge vessel is formed by sealing. Inside the flat discharge vessel, one of mercury vapor, xenon, krypton, argon, neon, and helium as a discharge medium is used alone or in combination of two or more, and the sealed pressure is from several kPa to several hundred kPa. Enclosed. An example of the enclosed gas is a mixed gas of mercury vapor, argon, and neon, and the ratio of neon to argon gas is 50:50 to 99: 1 when priority is given to luminous efficiency and low voltage starting of the lamp. When the composition ratio is increased and priority is given to the rising speed of light emission, the composition ratio is increased from 1:99 to 50:50 and argon. The gas pressure is in the range of 1 Torr to 700 Torr, and is preferably set in the range of 20 to 100 Torr from the viewpoint of low voltage startability, luminous efficiency, and lifetime.

  On the outer surface of the front substrate 1, an external electrode 6a for applying a high voltage and an external electrode 6b for applying a low voltage are arranged along the end of the discharge vessel so as not to come into contact with the discharge medium. In the case of this example, the external electrodes 6a and 6b and the discharge medium are blocked by the front substrate 1 itself, but may be blocked using a dielectric layer. In this example, both electrodes 6a and 6b are shielded from the discharge medium, but one electrode may be an internal electrode and only the other electrode may be shielded from the discharge medium. In this example, the external electrodes 6 a and 6 b are provided only on the front substrate 1. However, the external electrodes 6 a and 6 b are formed only on the rear substrate 2 or formed on both the front substrate 1 and the rear substrate 2. The structure which forms in the side surface which joins the structure which carries out, the front substrate 1, the back substrate 2, and the front substrate 1 and the back substrate 2 can also be taken.

  As a method of forming the electrodes 6a and 6b, a method of forming a conductive tape such as aluminum on a discharge vessel through a conductive adhesive, or a conductive paste in which a metal powder such as silver, a solvent, and a binder are mixed. Is applied to the surface of the discharge vessel by screen printing, dispenser application or dipping, followed by drying and baking, and solder containing at least one or more of tin, indium, bismuth, lead, zinc, antimony or silver For example, a method in which a material melted by heating is applied to the surface of the discharge vessel by a dispenser or immersion while applying ultrasonic vibration can be employed. Furthermore, in order to improve the adhesiveness between the electrode layer and the discharge vessel, a method can be used in which the surface of the discharge vessel at the position where the electrodes 6a and 6b are formed is roughened by, for example, sandblasting.

  The external electrodes 6a and 6b can have various shapes such as a convex shape toward each discharge space 8 separated by a spacer, in addition to the strip shape shown in the figure. 1 to 3 show a pair of electrodes, a plurality of pairs of electrodes may be used.

  The elongated spacers 5 formed integrally with the rear substrate 2 are arranged at a predetermined interval, keep the distance between the front substrate 1 and the rear substrate 2 constant, and also a lamp caused by a difference in internal and external pressures of the discharge vessel. Prevent damage due to implosion. The spacer 5 is disposed in a direction perpendicular to the electrodes 6a and 6b, and divides the electrodes 6a and 6b into a plurality of discharge regions. In addition to the trapezoidal cross section shown in the figure, the spacer 5 can have an arbitrary shape such as a wave shape as shown in FIG. 4A or a semi-elliptical shape as shown in FIG. Moreover, as shown in FIG.4 (c), it can also be set as the structure which made the front substrate 1 and the back substrate 2 flat plate shape, and provided the spacer 5 separately. In this example, the rear substrate 2 is integrally formed by thermal processing. However, as shown in FIGS. 4D and 4E, the front substrate 1 is thermally processed to form a flat rear substrate 2. A configuration in which the front substrate 1 and the rear substrate 2 are bonded together by thermal processing as illustrated in FIG.

  The size of the discharge space 8 divided by the spacer 5 is set according to the required lamp starting voltage, tube voltage, and light quantity. For example, the discharge space 8 has a width W of 0.5 to 30 mm. The height H of the space is set in the range of 0.5 to 6 mm. In each example of FIG. 4, the case where all the discharge spaces 8 have the same cross-sectional area is illustrated, but the cross-sectional area of the discharge space may be different depending on the location.

  A phosphor layer 4 is formed inside each of the front substrate 1, the back substrate 2, and the spacer 5. The phosphor layer 4 converts ultraviolet rays radiated from the discharge medium by discharge into visible light. The phosphor layer 4 uses phosphors used in general illumination, cold cathode discharge lamps, and PDPs, and is coated with several kinds of phosphors having different emission colors. In addition, the fluorescent substance layer 4 can also be comprised by apply | coating the fluorescent substance of a different luminescent color separately in stripe shape or dot shape. The phosphor layer 4 of the front substrate 1 on the light extraction side has, for example, an average particle size (primary particle size) of about 2.5 μm or more in order to transmit the phosphor light from the back substrate 2 side without loss. The phosphor particles are formed as thin as 5 to 15 μm. On the other hand, the phosphor layer 4 of the back substrate 2 from which light is not extracted has a thickness of 30 to 100 μm, for example, with a phosphor particle having an average particle size of about 2.5 μm or less in order to guide much light to the front substrate 1 side. The thickness is increased to increase the reflection luminance.

  Although not shown, in the substrate on which the electrodes 6a and 6b are formed, the stage where the phosphor layer is located inside the substrate at the position where the electrode is formed, the phosphor layer is sputtered by discharge, and gas is consumed. In order to increase the speed, a configuration in which no phosphor layer is provided on the inner side of the substrate where the electrodes 6a and 6b are provided is also common.

  Between the back substrate 2 and the phosphor layer 4, a fine metal oxide reflective layer can be formed. Further, a metal oxide layer such as titanium oxide, aluminum oxide or yttrium oxide is formed between the front substrate 1 and the rear substrate 2 and the phosphor layer 4 to prevent mercury from moving to the glass surface. It is also possible to absorb ultraviolet rays generated from discharge. In this example, the phosphor layer 4 is provided on the inner surfaces of both the glass substrates 1 and 2, but either one of the phosphor layers may be omitted. Further, depending on the use of the lamp, it is possible to omit the phosphor layers 4 of the front substrate 1 and the rear substrate 2 and directly use visible light emitted from the discharge medium.

  FIG. 5 shows a flat discharge lamp lighting system for lighting the flat discharge lamp L having the above configuration. In the vicinity of the electrode 6a, for example, an electrode temperature detector 11 such as a thermistor is installed to indirectly detect the temperature of the electrode 6a. This electrode temperature detector 11 holds in advance a correlation equation obtained by measuring its output and the actual temperature of the electrode portion, and by applying the measured value of its own device to the correlation equation, the electrode portion The actual temperature is determined and output to the control circuit 12 as the electrode portion temperature.

  Based on the temperature information output from the electrode temperature detector 11, the control circuit 12 determines the power to be input to the lamp based on the relationship between the electrode temperature and the input power shown in FIG. 6, and designates the power value. The signal to be output is output to the voltage supply circuit 13. In the relationship of FIG. 6, the higher the electrode temperature, the lower the electric power to be applied, and the closer to the limit temperature at which the dielectric layer separating the electrode and the discharge vessel and the glass vessel melt, the electric power value. Consideration is made so as not to reach the limit temperature by increasing the attenuation rate of the.

  The voltage supply circuit 13 converts a driving voltage such as a direct current voltage into a voltage applied to the lamp L such as a sine wave alternating current, and at the same time, according to a signal designating a power value output from the control circuit 12. The power supplied to the lamp L is adjusted.

  An example of the control is shown in FIG. In the initial stage of lighting (STEP 1), when the electrode temperature is low, the power supplied to the electrodes 6a and 6b of the lamp L is increased to promote the heat generation of the lamp L, and as the lamp temperature rises, the lamp is turned on The tube power value to be controlled is decreased stepwise as in STEP 2 and STEP 3 so as to keep the luminance constant. As a result, the rise time of luminance can be shortened compared to the case where constant power is applied. Further, by continuously performing the power change control, it is possible to reduce flickering of light emission at the time of power switching.

As a means to reduce tube power at the start of lighting,
(I) a method of reducing the amplitude value of the voltage applied to the lamp L, as shown in FIGS.
(Ii) a method of lowering the frequency of the voltage applied to the lamp L, as shown in FIGS.
(Iii) A method of providing an ON period and an OFF period for the voltage applied to the lamp L and reducing the ratio of the ON period as shown in FIGS.
Can be taken. In addition, these methods (i) to (iii) can be used in combination of two or three. Further, by making the applied voltage a sine wave, it is possible to reduce the occurrence of noise due to the harmonics.

  According to the planar discharge lamp lighting system of the present embodiment, the dielectric layer and the glass container that reduce the rise time of the luminance at the beginning of lighting and separate the electrode and the discharge medium due to the excessive temperature rise of the electrode portion are provided. Melting can be prevented.

  (Second Embodiment) A flat discharge lamp lighting system according to a second embodiment of the present invention will be described with reference to FIG. In the present embodiment, a flat discharge lamp L similar to that of the first embodiment shown in FIGS. 1 to 3 is used as a backlight light source B / L and is lit.

  The casing of the backlight B / L is composed of a front frame 21a and a back frame 21b. The lamp L is disposed at a distance of 0.1 mm to 5.0 mm from the bottom surface of the back case 21b, and is fixed by fixing members 22a and 22b. In order to further improve the uniformity of light emission of the lamp L, the transmittance is 40% or more at an interval of about 0.1 mm to 30 mm on the front substrate side (the upper surface side in FIG. 11B) of the lamp L. A diffusion plate 23 is arranged. Furthermore, when improving the uniformity and brightness of light emission, a diffusion sheet, a light collecting sheet, and a polarization reflection sheet are disposed on the upper surface of the diffusion plate 23. In the vicinity of the electrode 6a, for example, a temperature detector 8 such as a thermistor is installed via a fixing member 22a to indirectly detect the temperature of the electrode 6a.

Also in this embodiment, the voltage application circuit for the electrodes 6a and 6b is the same as that in the first embodiment, and the voltage application method is also the same as that in the first embodiment. Thus, as a backlight lighting system, a dielectric layer that shortens the rise time of the initial brightness of the flat discharge lamp L that is the light source and separates the electrode and the discharge medium due to excessive temperature rise of the electrode portion And the glass container can be prevented from melting.

1 is a perspective view of a flat discharge lamp that is turned on by the flat discharge lamp lighting system according to the first embodiment of the present invention. The partially broken perspective view seen from the upper side of the flat discharge lamp of FIG. The partially broken perspective view seen from the lower side of the flat type discharge lamp of FIG. Sectional drawing of the modification group of the planar discharge lamp of FIG. 1 is a block diagram of a flat discharge lamp lighting system according to a first embodiment of the present invention. The graph which shows the relationship between the electrode part temperature and input tube electric power of the flat type discharge lamp shown in FIG. The characteristic graph of the electric power control by the flat type discharge lamp lighting system of the 1st Embodiment of this invention. The tube voltage waveform figure in the example of control which controls a voltage amplitude by the flat type discharge lamp lighting system of the 1st Embodiment of this invention. The tube voltage waveform figure in the control example which controls a voltage frequency by the flat type discharge lamp lighting system of the 1st Embodiment of this invention. The tube voltage waveform figure in the example of control which controls a voltage application period with the planar discharge lamp lighting system of the 1st Embodiment of this invention. The front view and sectional drawing of the backlight which apply the flat type discharge lamp lighting system of the 2nd Embodiment of this invention.

Explanation of symbols

L Flat discharge lamp 1 Front substrate 2 Rear substrate 6a, 6b External electrode 11 Electrode temperature detector 12 Control circuit 13 Voltage supply circuit

Claims (6)

A translucent front substrate and a rear substrate are arranged to face each other, and a discharge medium is sealed inside a planar discharge vessel in which the interior between both plates is hermetically sealed, and the outside or inside of the planar discharge vessel A flat discharge lamp provided with at least one pair of electrodes so as not to contact the discharge medium;
Temperature detecting means for directly or indirectly detecting the temperature of the electrode of the flat discharge lamp;
A control circuit for generating a control signal for designating a power value to be applied to the flat discharge lamp based on a detected temperature of the temperature detecting means;
A voltage supply circuit for supplying a power value according to the control signal,
The voltage supply circuit performs control to reduce the tube power supplied to the planar discharge lamp continuously or stepwise as the electrode temperature rises at the start of lighting of the planar discharge lamp. Type discharge lamp lighting system.   The voltage supply circuit reduces the amplitude value of the voltage applied to the flat discharge lamp, thereby continuously or stepwise supplying tube power supplied to the flat discharge lamp as the electrode temperature increases at the start of lighting. The flat discharge lamp lighting system according to claim 1, wherein the flat discharge lamp lighting system is reduced.   The voltage supply circuit lowers the frequency of the voltage applied to the flat discharge lamp, thereby continuously or stepwise supplying tube power supplied to the flat discharge lamp as the electrode temperature rises at the start of lighting. The flat discharge lamp lighting system according to claim 1, wherein the flat discharge lamp lighting system is reduced.   The voltage supply circuit performs PWM lighting in which an ON period and an OFF period are provided in a voltage applied to the flat discharge lamp, and reduces the ratio of the ON period, thereby reducing the flat surface according to an increase in the electrode temperature at the start of the lighting. 2. The flat discharge lamp lighting system according to claim 1, wherein the tube power supplied to the flat discharge lamp is reduced continuously or stepwise.   The voltage supply circuit performs control to continuously or stepwise decrease the tube power supplied to the planar discharge lamp so that the electrode temperature does not exceed a predetermined value at the start of lighting of the planar discharge lamp. The flat discharge lamp lighting system according to any one of claims 1 to 4. 6. The flat discharge lamp lighting system according to claim 1, wherein the voltage supply circuit supplies a voltage having a substantially sinusoidal waveform to the flat discharge lamp.

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