JP2008293924A - Lighting device and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lighting device and a liquid crystal display equipped with it, capable of aiming at elongation of life of a hot cathode fluorescent lamp, without being affected by variation of the hot cathode fluorescent lamp and a driving circuit. <P>SOLUTION: The lighting device 1 monitors light emission by end glow in the vicinity of a filament electrode 32 by a photosensor 3 during preheating of the filament electrode 32. When light emission is detected in the vicinity of the filament electrode 32, a first driving circuit control signal is outputted to a control circuit 7 from a detecting part 4. The control circuit 7, when the first driving circuit control signal is inputted, changes a driving mode of a driving circuit 5 irrespective of the preheating time of the filament electrode 32, impresses startup voltage on a hot cathode fluorescent lamp 2 to light on the same 2. With this, life of the hot cathode fluorescent lamp 2 is prevented from being shortened by the end glow of the filament electrode 32 during the preheating. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an illumination device capable of extending the life of a hot cathode fluorescent lamp without being affected by variations in electrode characteristics of a hot cathode fluorescent lamp and circuit characteristics of a drive circuit, and a liquid crystal display device including the same.

  The backlight is used as a light source for displaying an image on a liquid crystal display panel (hereinafter referred to as an LCD panel) such as a liquid crystal TV, a liquid crystal display, and a liquid crystal monitor, and serves to supply light to the entire surface of the LCD panel. have. Light emitting elements used for such backlights include fluorescent lamps such as hot cathode fluorescent lamps (HCFL elements) and cold cathode fluorescent lamps (CCFL elements), LED elements, and the like. .

  The hot cathode fluorescent lamp is superior to other light emitting elements in terms of luminous efficiency, and is widely used because high luminance light can be obtained at a relatively low voltage. In the conventional hot cathode fluorescent lamp, a filament electrode is provided inside both ends of a cylindrical glass tube coated with a phosphor on the inner wall surface, and an electron-emitting material such as BaO, CaO, and SrO is provided on the filament electrode. Is retained.

  The hot cathode fluorescent lamp emits light according to the following principle. First, before starting the lighting of the hot cathode fluorescent lamp, current is passed through the filament electrode to preheat. Thereby, thermoelectrons are emitted from the emitter into the glass tube. The thermoelectrons emitted from the emitter increase as the temperature of the filament electrode increases. The filament electrode is preheated until sufficient thermoelectrons are emitted to generate an arc discharge between the filament electrodes. And after preheating, a high voltage is applied between the filament electrodes provided inside the both ends of the glass tube. Thereby, thermoelectrons are attracted to the anode, arc discharge is generated, and ultraviolet rays are radiated when colliding with mercury enclosed inside. Ultraviolet light excites the phosphor coated on the inner wall surface of the glass tube and emits visible light unique to the phosphor.

  Thus, in the hot cathode fluorescent lamp, preheating of the filament electrode is indispensable. However, if the filament electrode is preheated too much, there is a problem that end glow occurs and the life of the lamp is shortened. Therefore, it has been proposed to control the preheating of the filament electrode before the start of lighting of the hot cathode fluorescent lamp so that the end glow does not occur. As such a technique, for example, a technique disclosed in Patent Document 1 can be cited. Here, the fluorescent lamp device of Patent Document 1 will be specifically described with reference to FIGS. The fluorescent lamp device of Patent Document 1 includes a lighting circuit shown in FIG. Specifically, the lighting circuit includes a commercial power source 200, a noise filter 210, a rectifier circuit 220 including a full-wave rectifier, a smoothing circuit 230 including a smoothing capacitor, a preheating control circuit 240 for controlling a preheating current and a preheating time, and a switching circuit. 250, a DC cut capacitor 260, a choke ballast (L) 270, a resonance capacitor 280, a fluorescent lamp 300, and a filament electrode 320. The lighting circuit emits high frequency power by high frequency oscillation by the choke ballast (L) 270 and the resonance capacitor 280 during lighting, and this high frequency power is supplied to the fluorescent lamp 300.

At the time of starting the lamp, a predetermined preheating current I _f (mA) controlled by the preheating control circuit 240 is applied to the filament electrodes 320 sealed at both ends of the fluorescent lamp 300, and the preheating time (t Seconds). At this time, since the voltage between the two filament electrodes 320 is lower than the discharge start voltage V _s of the lamp, the inside of the discharge space is kept in an insulating state, and the entire current is supplied from the choke ballast (L) 270 to one filament electrode 320. The resonance capacitor 280 and the other filament electrode 320 flow through a closed circuit.

By supplying such a preheating current I _f (mA), the filament electrode 320 is heated to a high temperature, and the emitter applied to these electrodes is heated to a high temperature to emit electrons. When the temperature of the filament electrode 320 reaches the transition temperature necessary for generating arc discharge within the preheating time (t seconds) and sufficient thermoelectrons are emitted, the preheating time (t seconds). After the lapse of time, the switching circuit 250 acts to generate a starting voltage, and this starting voltage is applied between the filament electrodes 320 (discharge starting voltage V _s ). Thereby, arc discharge occurs between the filament electrodes 320.

Here, the preheating current I _f (mA) is the minimum current I _f1 (mA) that flows until the temperature of the filament electrode 320 reaches the arc transition temperature necessary for the occurrence of arc discharge. When the minimum current for generating an end glow after reaching the transition temperature is I _f2 (mA),
I _f1 ≦ I _f ≦ I _f2 (1)
Is controlled to satisfy.

Further, in order to prevent the occurrence of the end glow, the preheating control circuit 240 controls the preheating time t with a timer so that the filament electrode 320 reaches the arc transition temperature or more and before the end glow is generated. , thereby generating an arc discharge by applying a discharge starting voltage V _s.

More specifically, in Patent Document 1, a filament electrode 320 having an arc transition temperature of 800 ° C. is used. The filament electrode 320, when the preheating current _{I f} is 400 mA, the electrode temperature _{T f} no matter how long preheating time t A - but does not reach the click transition temperature, when the preheating current _{I f} is 600 mA, preheating When the time t is about 2.0 seconds and the preheating current _If is 700 mA, the arc transition temperature is reached when the preheating time t is about 1.0 seconds (see FIG. 17B). ).

Further, it is shown that no end glow occurs even when the preheating current _If is any of 400 mA, 600 mA, and 700 mA (see FIG. 17A).
JP 7-85981 A (published March 31, 1995)

  The fluorescent lamp device disclosed in Patent Document 1 will be briefly described in its circuit configuration. As shown in FIG. 18, based on a signal from the timer circuit 290, the preheating control circuit 240 includes a switching circuit 250. The current applied to the light lamp 300 is controlled. With such a configuration, the end glow in the hot cathode fluorescent lamp can be reduced to some extent. However, the fluorescent lamp device of Patent Document 1 is effective only when the electrode characteristics of the filament electrode 320 of the fluorescent lamp 300 to be mounted are always constant.

  Further, in the case of a fluorescent lamp device including a plurality of fluorescent lamps 300, the electrode characteristics of the filament electrodes 320 of all the fluorescent lamps 300 must be uniform and the circuit characteristics of the drive circuit must be uniform. is there. However, in the hot cathode fluorescent lamp that is put into practical use, there are variations in the electrode characteristics of the filament electrode and the circuit characteristics of the drive circuit. Therefore, as in Patent Document 1, if the preheating current and the preheating time of the filament electrode are only set and managed uniformly, there is a possibility that the preheating level of the filament electrode varies in practice and an end glow occurs. .

  More specifically, the variation in the electrode characteristics of the filament electrode will be described. As described in Patent Document 1, the numerical values of the diameter and coil pitch of the wire constituting the filament electrode 320 of the fluorescent lamp 300 vary. is there. This causes variations in electrode characteristics. Furthermore, the emitter is applied to the filament electrode 320, but the amount of the emitter applied and the condition of the emitter applied to the filament also cause variations in the electrode characteristics of the filament electrode 320. Specifically, when the filament electrode 320 is preheated and the emitter is heated, the impedance of the emitter itself changes. Therefore, even when the same preheating current is applied, the temperature of the filament electrode 320 varies. Thus, when the temperature of the filament electrode 320 varies, the discharge capacity of the filament electrode 320 varies during arc discharge. Therefore, the preheating current of the filament electrode 320 varies greatly for each filament as shown in FIG.

  Further, the variation in the circuit characteristics of the drive circuit will be described more specifically. FIG. 19 is based on the L value of the choke ballast 270, the variation in the capacitor capacity of the resonance capacitor 280, the variation in the CR time constant that determines the preheating time, and the like. As shown, the applied current varies approximately ± 5% from the design value.

  Accordingly, when the optimum range of the preheating current is wide and includes variations in the applied current of the drive circuit as in the lamp 201 and the lamp 202 shown in FIG. 19, the end glow can be prevented to some extent even in the prior art. it can. However, when the optimum range of the preheating current is out of the range of variation in the applied current of the drive circuit as in the lamp 203, or when the optimum range of the preheating current is narrow as in the lamp 204 and the lamp 205, Depending on the variation in the applied current of the drive circuit, there is a possibility that an end glow will occur due to a deviation from the optimum range of the preheating current.

  Therefore, as in Cited Document 1, simply managing the preheating current and preheating time of the filament electrode uniformly does not cope with variations in the characteristics of the filament electrode and the drive circuit described above. Long life cannot be achieved sufficiently. Furthermore, regarding the occurrence of the end glow, there is a variation between the hot cathode fluorescent lamps. As a result, there arises a problem that the variation in the life of each hot cathode fluorescent lamp is also increased. Therefore, development of a technology that can cope with variations in the characteristics of the filament electrode and the drive circuit and can further extend the life of the hot cathode fluorescent lamp is demanded.

  The present invention has been made in view of the above-mentioned problems, and its object is not to be affected by variations in electrode characteristics of the hot cathode fluorescent lamp and circuit characteristics of the drive circuit, and to extend the life of the hot cathode fluorescent lamp. An object of the present invention is to provide a lighting device that can be used, and a liquid crystal display device including the same.

  In order to solve the above-described problems, a lighting device according to the present invention applies a light source having a filament electrode that emits thermoelectrons, a first drive mode for preheating the filament electrode, and a voltage for arc discharge of the light source. A drive unit capable of driving the light source in at least two drive modes of the second drive mode, a control unit for controlling switching between the first drive mode and the second drive mode, and the filament electrode being predetermined A first sensor that detects light emitted from the vicinity of the filament electrode when preheated to a temperature equal to or higher than the temperature of the filament, and detects the intensity of the light detected by the first sensor, and the intensity of the light exceeds a predetermined value. And a first detection means for outputting a first signal to the control means, wherein the control means is configured to drive the drive means based on the first signal. It is characterized in that switching from the first drive mode to the second driving mode.

  According to the said structure, the said drive means preheats the filament electrode of the said light source by driving in a 1st drive mode. At this time, when the filament electrode is preheated to a predetermined temperature or higher, light is emitted from the vicinity of the filament electrode. This phenomenon is called end glow. End glow means that the filament electrode is excessively preheated for some reason during preheating (excessive heating, excessive preheating), and electrons are ejected from the emitter applied to the filament electrode, and the surrounding rare gas and mercury are excited by the electrons. This is a phenomenon in which light is emitted in the vicinity of the filament electrode.

  The first sensor detects light emitted in the vicinity of the filament electrode when the filament electrode is preheated to a predetermined temperature or more, in other words, when an end glow is generated. When the first sensor detects light emission in the vicinity of the filament electrode, the first detection means detects the intensity of light detected by the first sensor. When the light intensity is equal to or greater than a predetermined value, the first signal is output to the control means. The control means switches the drive mode of the drive means from the first drive mode to the second drive mode based on the first signal transmitted from the first detection means. Thereby, the drive means applies a voltage for arcing the light source to the light source. As a result, the light source can be arced and lit. That is, according to the above configuration, even if an end glow occurs due to excessive preheating of the filament electrode during preheating of the filament electrode, the drive mode of the drive means is immediately changed from the first drive mode to the second drive mode. The light source can be turned on by switching to the drive mode. Therefore, excessive emitter scattering can be prevented and the life of the light source can be extended without being affected by variations in the electrode characteristics of the light source and the circuit characteristics of the driving means. Furthermore, since the excessive scattering of the emitter due to the end glow is suppressed to the minimum, the variation in the life of each light source can be reduced.

  The light source preferably has the filament electrode inside both ends of a cylindrical glass tube, and the inner wall surface of the glass tube is preferably coated with a phosphor except in the vicinity of the filament electrode.

  According to the said structure, the fluorescent substance is not apply | coated to the inner wall face of the glass tube of the said light source in the vicinity of the said filament electrode. Light emission in the vicinity of the filament electrode when the end glow occurs is easily absorbed by the glass tube coated with the phosphor. However, according to the above configuration, the light emission in the vicinity of the filament electrode when the end glow occurs can pass through the region of the glass tube where the phosphor is not applied without being absorbed by the glass tube. Therefore, the optical sensor can more accurately detect light emission in the vicinity of the filament electrode when the end glow occurs. That is, according to the above configuration, the detection sensitivity of the end glow is further improved, so that excessive emitter scattering can be more effectively prevented, and the life of the light source can be further extended. Furthermore, the variation in the life of each light source can be further reduced.

  The first sensor preferably detects light having a wavelength of 400 nm to 445 nm.

  The light emission in the vicinity of the filament electrode when the end glow is generated is mainly due to the excitation of mercury enclosed in the light source. The emission spectrum of mercury has emission peaks at wavelengths of 405 nm and 436 nm. Therefore, according to the said structure, the light emission by the mercury enclosed in the said light source being excited at the time of end glow generation | occurrence | production can be detected reliably. Therefore, since the detection sensitivity of the end glow is further improved, excessive emitter scattering can be more effectively prevented, and the life of the light source can be further extended. Furthermore, the variation in the life of each light source can be further reduced.

  Furthermore, it is preferable that the first sensor detects at least one of light having a wavelength of 400 nm to 410 nm and light having a wavelength of 430 nm to 445 nm.

  As described above, the spectrum of light emission due to excitation of mercury enclosed in the light source when the end glow occurs has emission peaks at wavelengths of 405 nm and 436 nm. Therefore, according to the said structure, at least one light can be reliably detected among light emission with a wavelength of 405 nm and light emission with a wavelength of 436 nm. Therefore, the detection sensitivity of the end glow can be further improved, and the detection accuracy can be improved. Therefore, excessive emitter scattering can be prevented more reliably, and the life of the light source can be further extended. Furthermore, the variation in lifetime for each light source can be further reduced.

  The first detection means preferably outputs the first signal only when the drive mode of the drive means is the first drive mode.

  When the end glow occurs, as described above, bluish light emission having emission peaks at wavelengths of 405 nm and 436 nm occurs. On the other hand, when the light source is normally lit, in other words, when the light source is arc-discharged, bluish light emission occurs around the cathode portion. According to the above configuration, the first detection means outputs the first signal only when the drive mode of the drive means is the first drive mode. In other words, when the drive mode of the drive means is the second drive mode, the first detection means does not output the first signal. When the light source arcs, light is emitted around the cathode portion when the driving mode of the driving means is the second driving mode. Therefore, according to the above configuration, even if the light sensor detects light emission generated around the cathode portion when the light source performs arc discharge, the first detection unit does not output the first signal. . Therefore, it is possible to prevent the lighting device from malfunctioning due to light emission generated around the cathode portion when the light source performs arc discharge.

  In order to solve the above-described problem, the lighting device according to the present invention measures the preheating time of the filament electrode when the driving means is driven in the first driving mode, and indicates that a predetermined preheating time has elapsed. And a time measuring means for outputting a second signal to the control means, wherein the control means drives the drive means based on the first input signal of the first signal and the second signal. It is preferable to switch the mode from the first drive mode to the second drive mode.

  According to the above configuration, when the filament electrode of the light source is preheated by driving the drive unit in the first drive mode, the time measuring unit measures the preheat time of the filament electrode. Then, when a predetermined preheating time has elapsed, the time measuring means outputs the second signal indicating that to the control means. The control means switches the drive mode of the drive means from the first drive mode to the second drive mode based on the first input signal of the first signal and the second signal. Thereby, the drive means applies a voltage for arcing the light source to the light source. As a result, the light source can be arced and lit.

  That is, according to the above configuration, after preheating the filament electrode for a predetermined time, the light source can be turned on, and even if the filament electrode is excessively preheated within a predetermined time and an end glow occurs, Immediately, it is possible to switch to the mode in which the light source is turned on. Therefore, excessive scattering of the emitter can be prevented and the life of the light source can be further extended without being affected by variations in the electrode characteristics of the light source and the circuit characteristics of the driving means. Furthermore, since the excessive emitter scattering due to the end glow is suppressed to the minimum, the variation in the life of each light source can be further reduced.

  In order to solve the above-described problem, the lighting device according to the present invention is based on a second sensor that detects heat radiated from the vicinity of the filament electrode, and the vicinity of the filament electrode based on the heat detected by the second sensor. And a second detection means for outputting a third signal to the control means when the temperature is equal to or higher than a predetermined value, wherein the control means includes the first signal and the second signal. Independently, it is preferable to control the driving means based on the third signal.

  When the emitter that is the emission source of the thermoelectrons is depleted, the light source cannot emit thermoelectrons from the filament electrode. Even in such a state, if the driving circuit is still driven and a voltage capable of sustaining discharge is continuously applied to the light source, the tube wall temperature around the filament electrode rises and eventually reaches 200. May be higher than ℃. According to the above configuration, the second sensor detects heat radiated from the vicinity of the filament electrode. When the second sensor detects heat radiated from the vicinity of the filament electrode, the second detection means detects the temperature in the vicinity of the filament electrode based on the heat detected by the second sensor. When the temperature is equal to or higher than a predetermined value, a third signal is output to the control means. The control means controls the driving means based on the third signal independently of the first signal and the second signal. In other words, according to the above configuration, an overvoltage and an overcurrent are applied to the light source, and an abnormality of the light source is detected by detecting generated heat (particularly, abnormal heat generation in the filament electrode), via the driving unit. Thus, the driving of the light source can be controlled. Therefore, end glow can be prevented to extend the life of the light source, and ignition due to abnormal heat generation of the light source and damage to peripheral members due to abnormal heat generation of the light source can be prevented.

  The control means preferably stops the driving means based on the third signal.

  According to the above configuration, when the temperature in the vicinity of the filament electrode reaches a predetermined value or more, the control unit stops the driving unit based on the third signal. Thereby, the abnormal heat generation of the light source can be stopped. Therefore, ignition due to abnormal heat generation of the light source and damage to peripheral members due to abnormal heat generation of the light source can be prevented more reliably.

  The second sensor preferably detects light in the infrared region.

  According to the said structure, the said 2nd sensor can detect the heat | fever radiated | emitted from the vicinity of the said filament electrode as infrared rays. Therefore, the precision of the arrangement position of the second sensor can be relaxed. Therefore, the manufacturing yield of the lighting device according to the present invention can be improved.

  Furthermore, according to the said structure, since the said 2nd sensor detects infrared rays, it can detect rapidly the heat | fever radiated | emitted from the vicinity of the said filament electrode. Therefore, the abnormality of the light source can be detected more quickly, and ignition due to abnormal heat generation of the light source and damage to peripheral members due to abnormal heat generation of the light source can be prevented more reliably.

  Further, the second sensor preferably detects light having a wavelength of 700 nm to 1000 nm.

  A sensor that detects light (infrared rays) having a wavelength of 700 nm to 1000 nm is versatile and relatively inexpensive as used in a remote control of home appliances such as a television. Therefore, according to the said structure, the manufacturing cost of the illuminating device concerning this invention can be reduced.

  In the illumination device according to the present invention, it is preferable that the light source is fixed on a substrate via a connector means, and the first sensor is disposed on the substrate.

  According to the said structure, since the said light source is fixed on a board | substrate via a connector means, even if the said light source is comprised with the cylindrical glass tube, it can fix reliably. Moreover, according to the said structure, the said 1st sensor is arrange | positioned on the board | substrate with which the said light source is fixed. That is, the substrate plays two roles of fixing the light source and fixing the first sensor. Therefore, the members constituting the lighting device of the present invention can be reduced.

  Further, in the configuration including the second sensor, it is preferable that the light source is fixed on the substrate via the connector means, and the first sensor and the second sensor are disposed on the substrate.

  According to the said structure, since the said light source is fixed on a board | substrate via a connector means, even if the said light source is comprised with the cylindrical glass tube, it can fix reliably. Moreover, according to the said structure, both the said 1st sensor and the 2nd sensor are arrange | positioned on the board | substrate with which the said light source is fixed. That is, the substrate plays three roles: fixing the light source, fixing the first sensor, and fixing the second sensor. Therefore, the members constituting the illumination device of the present invention can be further reduced.

  In order to solve the above-described problems, a liquid crystal display device according to the present invention includes a back light source including any one of the illumination devices according to the present invention, and an image display unit using liquid crystal.

  According to the said structure, the lifetime improvement of the light source of the said back light source provided in the liquid crystal display device can be achieved.

  The back light source preferably includes the lighting device and a surface light source unit that converts a plurality of linear light sources emitted from the lighting device into a uniform surface light source.

  According to the above configuration, the surface light source means can convert a plurality of linear light sources emitted from the illumination device into a uniform surface light source, so that the performance as a liquid crystal display device can be improved.

  As described above, the lighting device according to the present invention monitors light emission by the end glow in the filament electrode during preheating of the filament electrode of the light source. For this reason, immediately after the occurrence of end glow during preheating of the filament electrode, preheating of the filament electrode can be terminated, a high voltage can be applied to the light source, and the light source can be turned on. Therefore, there is an effect that it is possible to prevent excessive emitter scattering due to the end glow and to extend the life of the light source without being affected by variations in the electrode characteristics of the light source and the circuit characteristics of the drive circuit. Furthermore, since the excessive scattering of the emitter due to the end glow is suppressed to the minimum, it is possible to reduce the variation in the life of each light source.

[Embodiment 1]
One embodiment of the present invention is described below with reference to FIGS. 1 to 9, but the present invention is not limited to this.

  As shown in FIG. 1, a lighting device 1 according to the present embodiment includes a hot cathode fluorescent lamp 2 (light source), an optical sensor 3 (first sensor), a detection unit 4 (first detection means), and a drive circuit. 5 (driving means) and a control circuit 7 (control means). The detection unit 4 includes a sensor circuit 8 and a determination circuit 9. The drive circuit 5 includes a switching circuit 21 and a series LC resonance circuit 22. Moreover, the illuminating device 1 may further be provided with the timer circuit 24 (time measurement means), as shown in FIG.

  The illuminating device 1 of this embodiment is suitably used as a backlight for displaying an image on a liquid crystal display panel such as a liquid crystal TV, a liquid crystal display, or a liquid crystal monitor.

  The hot cathode fluorescent lamp 2 includes a glass tube 6 and two filament electrodes 32. The glass tube 6 has a cylindrical shape, and an RGB three-wavelength phosphor is applied to the inner wall surface. Inside the both ends of the glass tube 6, a coiled filament electrode 32 coated with an electron radioactive substance is provided. Therefore, the filament electrode 32 can emit thermoelectrons by heating.

  Moreover, the opening part of the both ends of the glass tube 6 is block | closed with the nozzle | cap | die 41 etc. which are shown in FIG. 9, for example, and rare gas, such as mercury and argon, is enclosed in the glass tube 6. FIG. In addition, as the electron-emitting substance, an alkaline earth metal oxide such as Ba, Ca, or Sr, an alkaline earth metal tungstate, or the like is preferably used.

  As shown in FIG. 5, the hot cathode fluorescent lamp 2 preferably has a transparent portion 16 to which no phosphor is applied in the vicinity of the filament electrode 32 at both ends of the glass tube 6. Thereby, at least a part of the filament electrode 32 provided at each of both ends of the hot cathode fluorescent lamp 2 can be seen through. Therefore, by arranging the optical sensor 3 in the vicinity of the transparent portion 16, the optical sensor 3 can detect the light from the filament electrode 32 without passing through the phosphor. In FIG. 9, the transparent portion 16 is provided on the entire circumference of the inner wall surface of the glass tube 6, but the present invention is not limited to this, and may be provided only in a portion close to the optical sensor 3. That is, when the fluorescent material is applied to the entire inner wall surface of the glass tube 6 of the hot cathode fluorescent lamp 2, the light emitted from the filament electrode 32 is absorbed by the fluorescent material. What is necessary is just to provide so that the light discharge | released from 32 can reach | attain the optical sensor 3 without passing through a fluorescent substance.

  Since the vicinity of the filament electrode 32 is not an effective light emission region of the hot cathode fluorescent lamp 2, even if the transparent portion 16 is provided, the emission luminance of the hot cathode fluorescent lamp 2 is hardly affected.

  The diameter and length of the wire constituting the filament electrode 32, the coil pitch, the number of turns, etc. are not particularly limited, and can be set arbitrarily.

  Further, the hot cathode fluorescent lamp 2 may be configured such that a film-like ultraviolet absorption filter (not shown) is attached to the transparent portion 16. In order for the hot cathode fluorescent lamp 2 to emit light, a discharge is caused by the filament electrode 32, and ultraviolet rays emitted by the discharge excite the phosphor applied to the inner wall surface of the glass tube 6. Emits visible light. However, for example, when a peripheral member made of resin or the like is provided around the lighting device 1 of the present embodiment, the peripheral member deteriorates when the peripheral member is irradiated with ultraviolet rays. Therefore, by attaching an ultraviolet absorption filter to the transparent portion 16, it becomes possible to absorb ultraviolet rays emitted from the hot cathode fluorescent lamp 2 by the ultraviolet absorption filter, and from the resin or the like around the illumination device 1 of the present embodiment. Even when the formed peripheral member is provided, deterioration of the peripheral member can be prevented.

  The ultraviolet absorption filter is not particularly limited as long as the ultraviolet ray emitted from the filament electrode 32 is prevented from being emitted outside the hot cathode fluorescent lamp 2.

  The drive circuit 5 is for driving the hot cathode fluorescent lamp 2 and is controlled by the control circuit 7. The drive circuit 5 drives the hot cathode fluorescent lamp 2 in at least two drive modes: a first drive mode for preheating the filament electrode 32 and a second drive mode for applying a voltage for arc discharge of the hot cathode fluorescent lamp 2. be able to.

  As the drive circuit 5, an inverter circuit such as a series LC oscillation circuit using a half-bridge switching circuit is preferably used. Here, the drive circuit 5 will be described more specifically. The drive circuit 5 includes a switching circuit 21 composed of two FETs and a series LC resonance circuit 22. A direct current voltage is applied to the drive circuit 5, but a direct current voltage formed through a noise filter, a rectifier circuit, and a smoothing capacitor may be applied to a commercial power source such as AC 100 V (not shown), or a direct current voltage may be applied directly. May be.

  When the DC voltage is applied to the drive circuit 5, the high-frequency voltage is controlled by the half-bridge switching circuit 21 composed of transistors, and the high-frequency voltage is applied to the series LC resonance circuit 22. The equivalent circuit of the series LC resonance circuit 22 changes as shown in FIGS. 2A and 2B before and after the hot cathode fluorescent lamp 2 is turned on. That is, before the hot cathode fluorescent lamp 2 is turned on, and when the filament electrode 32 is preheated and when the hot cathode fluorescent lamp 2 is arc-discharged, as shown in FIG. . Therefore, the frequency-voltage characteristics have resonance characteristics as shown in FIG. Therefore, the voltage applied to both ends of the hot cathode fluorescent lamp 2 (voltage V in FIG. 2C) can be changed by changing the frequency.

2 If will be described more specifically with reference to (c), for example, during the preheating of the filament electrode 32, in other words, when the frequency of the first drive mode and f _1, to both ends of the hot cathode fluorescent lamp 2 V A voltage of ₁ is applied. This voltage causes a current to flow through the filament electrode 32. At this time, the LC constant is set so that a filament current that can effectively preheat the filament electrode 32 flows at a voltage that does not cause the hot cathode fluorescent lamp 2 to glow discharge.

Then, when the start of turn-on of the hot cathode fluorescent lamp 2, in other words, a hot cathode fluorescent lamp 2 to the second drive mode to arc discharge, changes the frequency f _2. Accordingly, the voltage of both ends of the hot cathode fluorescent lamp 2 V ₂ is applied, as shown in FIG. 2 (c), so that the high voltage is applied. Therefore, arc discharge can be generated in the hot cathode fluorescent lamp 2 and the hot cathode fluorescent lamp 2 can be turned on.

  On the other hand, when the hot cathode fluorescent lamp 2 is turned on, the hot cathode fluorescent lamp 2 becomes a resistance load, and thus an equivalent circuit as shown in FIG. Therefore, the characteristic deviates from the resonance circuit and has a low gain characteristic as shown in FIG. Thus, the current value applied to both ends of the hot cathode fluorescent lamp 2 at the time of lighting is determined by the voltage and frequency applied to the hot cathode fluorescent lamp 2 using the drive circuit 5.

  In the present embodiment, such an inverter circuit is provided as the drive circuit 5, but the present invention is not limited to this, and any conventionally known drive circuit can be used.

  The timer circuit 24 measures the preheating time of the filament electrode 32 when the driving circuit 5 is driven in the first driving mode, and outputs a second driving circuit control signal indicating that the predetermined preheating time has passed. 7 is output. The predetermined preheating time is not particularly limited, and may be set according to the characteristics of the filament electrode 32 of the hot cathode fluorescent lamp 2. Further, the specific configuration of the timer circuit 24 is not limited, and a second driving circuit control signal that indicates the time when a preheating current is passed through the filament electrode 32 and a predetermined preheating time has elapsed is measured. Can be used as long as it can output. The timer circuit 24 has an arbitrary configuration as described above.

  The optical sensor 3 detects light emitted from the filament electrode 32 or the vicinity thereof. That is, light in the vicinity of the filament electrode 32 is detected. More specifically, when the filament electrode 32 is preheated to a predetermined temperature or more and an end glow is generated, light emitted from the filament electrode 32 or the vicinity thereof is detected. The optical sensor 3 is provided for each filament electrode 32.

  End glow is a phenomenon in which electrons are emitted from the emitter due to excessive preheating of the filament electrode (excessive heating of the filament electrode), and the surrounding rare gas or mercury is excited by the electrons, and light is emitted in the vicinity of the filament electrode. The light emission is mainly due to the excitation of mercury enclosed in the hot cathode fluorescent lamp 2. As shown in FIG. 3, the emitted light has emission wavelength peaks at 405 nm and 436 nm. That is, the light emission has a light emission wavelength peak from the low-wavelength side in the visible light region to the green-yellow side where human eye visibility is high. Therefore, the optical sensor 3 may be any sensor that can detect light in the visible light region, but preferably can detect light having a wavelength of 400 nm to 445 nm.

  Specifically, as the optical sensor 3, any optical sensor having any material or structure can be used as long as it has a light receiving sensitivity in the visible light region. For example, a PN photodiode, a PIN photodiode, an avalanche photodiode, a Schottky photodiode, a phototransistor, or the like can be used. The light receiving sensitivity of the PN photodiode varies depending on the material. For example, as shown in FIG. 4, when GaP, GaAsP, and Si are used as the material of the optical sensor 3, the light receiving sensitivity with respect to light of each wavelength is different. Si photodiodes made of Si generally have a wide wavelength range for light reception sensitivity, exhibiting maximum light reception sensitivity for light near 900 nm, and the maximum sensitivity wavelength in the visible light region is the length of the visible light region. On the wavelength side. The sensitivity wavelength in the visible light region is about 420 nm to about 780 nm. However, normally, when the filament electrode 32 is preheated, no light emission phenomenon occurs. Therefore, by providing an amplifier (signal amplification circuit) such as an operational amplifier in the detection unit 4 and amplifying a light signal, the light emission can be detected even if the light emission at the time of occurrence of end glow is weak.

  In general, a hot cathode fluorescent lamp coated with a white light emitting phosphor has a light emission wavelength peak in the vicinity of 555 nm with high visibility. Therefore, it is more preferable that the optical sensor 3 can specifically detect light having a wavelength of 400 nm to 440 nm. Thereby, the optical sensor 3 can detect the light at the time of lighting of the hot cathode fluorescent lamp 2, and can prevent malfunctioning. Specifically, as shown in FIG. 4, the maximum sensitivity wavelength of a GaP photodiode made of GaP is around 410 nm. Therefore, according to the GaP photodiode, light having a wavelength of 400 nm to 445 nm can be specifically detected. Note that any optical sensor having a maximum sensitivity wavelength of around 400 nm is not limited to a GaP photodiode, and any structure and any type of optical sensor can be used because the same effect can be obtained.

  Further, the optical sensor 3 is provided with a plurality of optical filters (not shown) so as to pass light having a wavelength of 400 nm to 445 nm in the previous stage, and the light emitted from the filament electrode 32 is passed through the optical filter. You may let it pass. Accordingly, only light having a wavelength of 400 nm to 445 nm among the light emitted from the filament electrode 32 passes and reaches the optical sensor 3. As a result, the optical sensor 3 can detect only light having a wavelength of 400 nm to 445 nm. Therefore, the optical sensor 3 can detect the light when the hot cathode fluorescent lamp 2 is turned on and prevent malfunction.

  Further, the optical sensor 3 is specific to (a) light having a wavelength of 400 nm to 410 nm, (b) light having a wavelength of 430 nm to 445 nm, or (c) light having a wavelength of 400 nm to 410 nm and light having a wavelength of 430 nm to 445 nm. It may be one that can be detected automatically. In addition, this is because, in the front stage of the optical sensor 3, (a) light having a wavelength of 400 nm to 410 nm, (b) light having a wavelength of 430 nm to 445 nm, or (c) light having a wavelength of 400 nm to 410 nm and 430 nm to 445 nm You may implement | achieve by providing the optical filter which lets the light of a wavelength pass. As a result, the optical sensor 3 receives (a) light having a wavelength of 400 nm to 410 nm, (b) light having a wavelength of 430 nm to 445 nm, or (c) light having a wavelength of 400 nm to 410 nm and light having a wavelength of 430 nm to 445 nm. It can be detected with high sensitivity. Therefore, the emission spectrum emitted from the filament electrode 32 during the end glow and the emission spectrum emitted from the phosphor emitted when the hot cathode fluorescent lamp 2 is turned on can be distinguished. It can be effectively prevented. In addition, the sensing sensitivity of the optical sensor 3 can be further improved. The optical filter is not particularly limited as long as it has a spectral characteristic for dispersing light so as to improve the light receiving sensitivity of the optical sensor 3 in the wavelength range.

  In the embodiment in which the optical filter is provided in front of the optical sensor 3, the light is split by the optical film and only light having a specific wavelength reaches the optical sensor 3. Therefore, the sensitivity wavelength range of the optical sensor 3 is not particularly limited. That is, the material of the optical sensor 3 is not limited, and for example, GaP, GaAsP, Ge, or InGaAs / InP can be used. Further, the structure of the optical sensor 3 is not limited, and for example, a PIN photodiode, an avalanche photodiode, a Schottky photodiode, or a phototransistor can be used.

  As the optical sensor 3 moves away from the filament electrode 32, the intensity of the detected light having a wavelength in the visible light region decreases. Therefore, in the vicinity of the filament electrode 32 at both ends of the hot cathode fluorescent lamp 2, more specifically, It is disposed in the vicinity of the transparent portion 16 provided in the cathode fluorescent lamp 2. Further, from the viewpoint of improving sensitivity and preventing malfunction, the glass tube 6 is preferably disposed at a position closer to the tube wall. Specifically, when the light receiving portion of the optical sensor 3 passes through the center of the filament electrode 32 and an arbitrary perpendicular to the tube wall of the glass tube 6 is 0 degree, it is within a range of ± 20 ° from the center. And it is preferable that the distance from the outer wall surface of the glass tube 6 is provided within 0 mm-5 mm.

  Furthermore, it is preferable that the optical sensor 3 is fixed so that the relative positional relationship with the filament electrode 32 does not fluctuate. According to such a configuration, fluctuations in sensor output can be prevented, so that light emission at or near the filament electrode 32 can be accurately detected. Specifically, for example, the photosensor 3 is mounted on the outer wall surface of the glass tube 6 of the hot cathode fluorescent lamp 2 or is held by a photosensor holder in a space outside the hot cathode fluorescent lamp 2. It is preferable to arrange.

  The arrangement position of the optical sensor 3 is not limited to the above-described one, and the optical sensor 3 may be arranged at any position as long as the light emitted from the filament electrode 32 or the vicinity thereof can be detected even if it is not in the vicinity of the filament electrode 32. May be. For example, it is possible to detect light emitted from the filament electrode 32 or the vicinity thereof even at the center of the glass tube 6.

  The detection unit 4 detects the intensity of the light based on the intensity of the light detected by the optical sensor 3. When the intensity of the light is equal to or greater than a predetermined value, the detection unit 4 outputs a first drive circuit control signal (first signal). Output to the control circuit 7. More specifically, the detection unit 4 includes a sensor circuit 8 and a determination circuit 9. The sensor circuit 8 converts the light detected by the optical sensor 3 into an electrical signal, and the electrical signal is subsequently transmitted to the determination circuit 9. The magnitude of the electrical signal corresponds to the magnitude of the light intensity detected by the optical sensor 3. Therefore, the determination circuit 9 can detect the intensity of light in the vicinity of the filament electrode 32 based on the intensity of the electrical signal transmitted from the sensor circuit 8.

  The determination circuit 9 outputs the first drive circuit control signal if the detected light intensity is equal to or greater than the predetermined value, and does not output the first drive circuit control signal if the detected light intensity is smaller than the predetermined value. Although the specific numerical value of the predetermined value is not particularly limited, specifically, for example, a value lower than the minimum intensity of light emission when an end glow occurs, and the maximum light emission when no end glow occurs. What is necessary is just to set to the value higher than the electric signal strength showing an intensity | strength.

  The determination circuit 9 may be configured to detect the intensity of light in the vicinity of the filament electrode 32 from the difference in light emission intensity from the vicinity of the filament electrode 32 when the end glow is generated and when it is not generated.

  As shown in FIG. 5, the sensor circuit 8 may include an amplifier such as an operational amplifier and amplify the electric signal. Thereby, even if the light radiated | emitted from the filament electrode 32 is weak, this light can be detected.

  More specifically, a circuit that generates a pulse of about 5 V, a circuit that switches from a low level output of 0 V to a high level output of 5 V, or the like is preferably used as the determination circuit 9. For example, as shown in FIG. 6, when the filament electrode 32 is preheated, that is, when the drive circuit 5 is driven in the first drive mode, end glow occurs (in other words, light emission from the filament electrode 32). Switching from Low level output to High level output. As a result, the first drive circuit control signal is output to the control circuit 7. That is, in this case, the High level output becomes the first drive circuit control signal.

  The determination circuit 9 may output the first drive circuit control signal to the control circuit 7 whenever the electrical signal input from the sensor circuit 8 is equal to or greater than a predetermined value, but the drive mode of the drive circuit 5 is the first. It is preferable that the first drive circuit control signal is output only in the one drive mode. Thereby, it is possible to prevent the optical sensor 3 from malfunctioning due to the emission wavelength of glow discharge when the hot cathode fluorescent lamp 2 is normally lit. This point will be described in more detail. The end glow is a light emission phenomenon from the bluish filament electrode 32. Even when the hot cathode fluorescent lamp 2 is normally lit, it emits bluish light around the cathode portion. More specifically, in the vicinity of the cathode of the discharge lamp, there are states called Aston dark part, cathode glow, cathode dark part, negative glow, Faraday dark part, and positive column, while in the vicinity of the anode, states called anode glow and anode dark part. There is. The combination of both is the discharge state of the discharge lamp. Among these, in the cathode glow or negative glow part, positive ions approaching the cathode and electrons from the cathode are combined to emit bluish light (nitrogen and oxygen) when returning to the ground state. This light may cause the optical sensor 3 to malfunction. However, according to the configuration in which the first drive circuit control signal is output only when the drive mode of the drive circuit 5 is the first drive mode, when the hot cathode fluorescent lamp 2 is arc-discharged, the detection circuit 4 controls the control circuit. 7 does not output the first drive circuit control signal, it is possible to prevent the optical sensor 3 from malfunctioning due to the emission wavelength of glow discharge when the hot cathode fluorescent lamp 2 is normally lit. In other words, it is possible to prevent the lighting device 1 from malfunctioning due to light emission by glow discharge when the hot cathode fluorescent lamp 2 is normally lit.

  As a specific circuit configuration, for example, as shown in FIG. 7, the logical product of the sensor output and the High signal generated at the time of preheating is taken and returned to the drive circuit 5, and only when both are High, the drive circuit 5 A start pulse may be applied to the.

  The control circuit 7 is for controlling the operation of the drive circuit 5 based on the first drive circuit control signal (first signal) transmitted from the detection unit 4. Specifically, when the first drive circuit control signal (first signal) transmitted from the detection unit 4 is input to the control circuit 7, the series LC resonance circuit 22 is connected via the switching circuit 21 of the drive circuit 5. Change the oscillation frequency. Thereby, the drive mode of the drive circuit 5 is switched from the first drive mode to the second drive mode.

  In the configuration in which the lighting device 1 includes the timer circuit 24, the control circuit 7 controls the first drive circuit control signal (first signal) transmitted from the detection unit 4 or the second drive circuit control transmitted from the timer circuit 24. Of the signals (second signal), the operation of the drive circuit 5 is controlled based on the previously input signal. Specifically, either the first drive circuit control signal (first signal) transmitted from the detection unit 4 or the second drive circuit control signal (second signal) transmitted from the timer circuit 24 is first. When input to the control circuit 7, the oscillation frequency of the series LC resonance circuit 22 is changed via the switching circuit 21 of the drive circuit 5. Thereby, the drive mode of the drive circuit 5 is switched from the first drive mode to the second drive mode.

  Thus, by switching the drive mode of the drive circuit 5 from the first drive mode to the second drive mode, a high voltage is applied across the hot cathode fluorescent lamp 2 from the state in which the filament electrode 32 is preheated. The state is switched, arc discharge is generated in the hot cathode fluorescent lamp 2, and the hot cathode fluorescent lamp 2 is turned on.

  The means for the control circuit 7 to change the oscillation frequency of the series LC resonance circuit 22 is not particularly limited. Specifically, for example, the first drive circuit control signal or the second drive circuit control is detected from the detection unit 4. When a signal is input, the switching circuit 21 is switched on and off, and the voltage supplied to the series LC resonance circuit 22 is controlled to change the oscillation frequency of the series LC resonance circuit 22.

  Control of the drive circuit 5 by the control circuit 7 will be described in more detail with reference to FIG. Here, a configuration including the timer circuit 24 will be described as an example. As shown in FIG. 8, when the lighting device 1 is turned on, a preheating voltage for preheating the filament electrode 32 is applied to the filament electrode 32. During this time, the timer circuit 24 measures the preheating time of the filament electrode 32, and the optical sensor 3 monitors whether or not the filament electrode 32 emits light. If the filament electrode 32 does not emit light within a predetermined preheating time, a second drive circuit control signal is output from the timer circuit 24 to the control circuit 7. The control circuit 7 changes the oscillation frequency of the series LC resonance circuit 22 of the drive circuit 5 with the input of the second drive circuit control signal as a cue. As a result, the drive circuit 5 applies a starting voltage to the hot cathode fluorescent lamp 2 to generate arc discharge. Therefore, the hot cathode fluorescent lamp 2 is turned on.

  On the other hand, when the optical sensor 3 detects light emission from the filament electrode 32 during preheating of the filament electrode 32, a first drive circuit control signal is output from the detection unit 4 to the control circuit 7. When the first drive circuit control signal is input, the control circuit 7 changes the oscillation frequency of the series LC resonance circuit 22 of the drive circuit 5 regardless of whether the second drive circuit control signal is input. As a result, the driving circuit 5 is applied with a starting voltage to the hot cathode fluorescent lamp 2 to generate arc discharge. Therefore, the hot cathode fluorescent lamp 2 is lit.

  Since the illuminating device 1 according to the present embodiment has the above-described configuration, even if there are variations in the electrode characteristics of the hot cathode fluorescent lamp 2 and the circuit characteristics of the drive circuit 5, all the hot cathode fluorescent lamps 2 are connected to the end. Without generating glow, the filament electrode 32 is preheated, and after completion of preheating, a high voltage can be applied immediately to turn on the hot cathode fluorescent lamp 2. Therefore, excessive scattering of the emitter can be prevented, and the life of the hot cathode fluorescent lamp 2 can be extended. Furthermore, the variation in the lifetime between the lamps of the hot cathode fluorescent lamp 2 can be reduced.

  Heretofore, the lighting device 1 according to the present embodiment has been described in detail focusing on the circuit configuration, in other words, the control method. The illuminating device 1 should just be provided with the circuit structure as mentioned above, and the specific structure is not specifically limited. Here, a preferred embodiment of the structure of the illumination device 1 will be specifically described with reference to FIGS. 9 (a) and 9 (b).

  The lighting device 1 has a structure in which the hot cathode fluorescent lamp 2 is fixed on a substrate 40, as shown in FIGS. 9 (a) and 9 (b). More specifically, as shown in FIG. 9A, both ends of the hot cathode fluorescent lamp 2 are covered with a base 41, and a terminal 42 for connecting the filament electrode 32 to the drive circuit 5 protrudes to the outside. . The terminal 42 can be configured by, for example, a connector such as a socket for connecting to the drive circuit 5.

  On the other hand, the lamp connector 43 (connector means), the optical sensor 3 and the sensor circuit 8 are disposed on the substrate 40. By connecting the lamp connector 43 and the terminal 42, the hot cathode fluorescent lamp 2 is fixed on the substrate 40, and the filament electrode 32 and the drive circuit 5 are connected. Further, the arrangement position of the photosensor 3 on the substrate 40 is such that when the hot cathode fluorescent lamp 2 is fixed on the substrate 40 as shown in FIG. Is arranged so that the optical sensor 3 is located in the vicinity. In other words, when the hot cathode fluorescent lamp 2 is fixed to the substrate 40, the photosensor 3 is fixed at a position where the filament electrode 32 of the hot cathode fluorescent lamp 2 can be seen.

  9A and 9B, the drive circuit 5 is not illustrated, but the drive circuit 5 may also be disposed on the same substrate 40. Further, the drive circuit 5 may be arranged on another board and connected by a connector.

  According to the configuration having the above structure, problems such as the wiring of the terminal 42 of the hot cathode fluorescent lamp 2 and the alignment of the optical sensor 3 on the mechanism surface can be easily solved.

[Embodiment 2]
Another embodiment of the present invention will be described below with reference to FIGS. For convenience of explanation, members having the same functions as those used in the first embodiment are denoted by the same member numbers, and description thereof is omitted.

  As shown in FIG. 10, the illumination device 11 according to the present embodiment further includes an infrared sensor 13 (second sensor) and a detection unit having sensitivity in the infrared region as compared to the illumination device 1 described in the first embodiment. 14 (second detection means). Further, instead of the control circuit 7, a control circuit 17 (control means) is provided.

  The infrared sensor 13 detects heat radiated from the vicinity of the filament electrode 32 when abnormal heat generation occurs in the hot cathode fluorescent lamp 2. The hot cathode fluorescent lamp cannot emit thermal electrons when the emitter, which is an electron emission source, is depleted. This is the life of the hot cathode fluorescent lamp. In such a state, it is necessary to stop driving the inverter circuit. Therefore, a general lighting device includes a circuit for detecting emitter depletion. In addition, in the illuminating device concerning this invention, although such a circuit is not illustrated, it cannot be overemphasized that such a circuit may be provided.

  However, the above circuit may not always detect emitter depletion. In that case, even though the emitter is depleted, a voltage that can still maintain the arc discharge continues to be applied across the hot cathode fluorescent lamp. Thereby, secondary electrons are emitted from the material of the filament itself, for example, tungsten, and the filament is cut by sputtering or the like by ion bombardment. Even when the filament is cut, it is still possible to discharge, for example, between the cut filament end and the metal guide wire holding the filament wire, or the conductive layer of the emitter or tungsten scattered on the glass tube wall or stem. Is maintained, the tube wall temperature around the electrodes can be as high as 200 ° C., and in some cases, even a glass can be melted. The infrared sensor 13 detects abnormal heat generation in such a hot cathode fluorescent lamp 2.

  Here, the heat generated by the filament electrode 32 when the hot cathode fluorescent lamp 2 is normal and abnormal will be described with reference to FIGS. 11A and 11B and FIG. FIG. 11A is a diagram showing the tube wall temperature in the vicinity of the filament electrode 32 of the glass tube 6 when the hot cathode fluorescent lamp 2 is normal, and FIG. 11B is a diagram when the hot cathode fluorescent lamp 2 is abnormal. It is a figure which shows the tube wall temperature in the filament electrode 32 vicinity of the glass tube 6 in FIG.

  The tube wall temperature in the vicinity of the filament electrode 32 of the glass tube 6 when the hot cathode fluorescent lamp 2 is normal is, for example, that the configuration of the hot cathode fluorescent lamp 2 is an ambient temperature of 25 ° C., a tube diameter of 15.5 mm, and a tube length of 820 mm. When the hot cathode fluorescent lamp 2 is driven at a current of 135 mA and a filament current of 250 mA, the temperature is around 70 ° C. as shown in FIG. When the hot cathode fluorescent lamp 2 is abnormal, the tube wall temperature in the vicinity of the filament electrode 32 of the glass tube 6 becomes a high temperature of 150 ° C. or more as shown in FIG.

  Next, the relationship between the tube wall temperature in the vicinity of the filament electrode 32 of the hot cathode fluorescent lamp 2 and the infrared radiation intensity will be described with reference to FIG. FIG. 12 shows that when the tube wall temperature of the hot cathode fluorescent lamp 2 is 0 ° C., 25 ° C., 50 ° C., 75 ° C., 100 ° C., 150 ° C., 200 ° C., the infrared radiation intensity at 200 ° C. is 100%. It is a graph which shows the relative radiant intensity of the infrared rays in each temperature at the time.

  The spectral distribution of the tube wall temperature and the emitted infrared rays shown in FIG. 12 is calculated by the following formula based on Planck's radiation law. However, the infrared absorption of glass is ignored.

(Where E is the radiant energy density (W / m ² ), λ is the wavelength (m), T is the absolute temperature (K), C1 is Planck's first radiation constant = 3.7415 × 10 ⁻¹⁵ (W / m ² ), C2 represents Planck's second radial constant = 1.43879 × 10 ⁻² (m / K).)
As shown in FIG. 12, the peak of the radiation intensity at each temperature is included in the wavelength range of about 4 μm to about 10 μm. That is, the intensity of infrared rays emitted at each temperature is high in a wavelength range of about 4 μm to about 10 μm.

  Therefore, the infrared sensor 13 is not limited as long as it detects invisible light in a long wavelength region, in other words, infrared rays, but it is preferable to use an infrared sensor having a wavelength of about 0.7 μm to about 10 μm. . More specifically, an embodiment using a sensor having a detection wavelength of about 4 μm to about 10 μm can be given. When the detection wavelength of the infrared sensor 13 is about 4 μm to about 10 μm, the amount of infrared rays emitted increases, so that malfunction due to noise or the like can be ignored. Moreover, since the contrast amount of the amount of infrared rays between the normal state and the abnormal state of the hot cathode fluorescent lamp 2 is nearly double, it can be accurately detected whether or not the hot cathode fluorescent lamp 2 is abnormal. More specifically, for example, in order to detect that the heat generation temperature is 150 ° C. or higher, it is preferable to use an infrared sensor capable of detecting a wavelength of about 5 μm with high sensitivity. Thereby, the abnormality of the hot cathode fluorescent lamp 2 can be detected with high sensitivity.

  As another preferred embodiment, it is preferable to use an infrared sensor capable of detecting infrared rays having a wavelength of 700 nm to 1000 nm, more preferably about 800 nm. In general, an infrared sensor having a high sensitivity wavelength of several μm is expensive. On the other hand, the high-sensitivity wavelength infrared sensor is used, for example, in a remote control of home appliances such as a television. Therefore, the infrared sensor having the high sensitivity wavelength is versatile and inexpensive. Therefore, the manufacturing cost of the illumination device 11 according to the present embodiment can be reduced. However, when an infrared sensor having a high sensitivity wavelength in the near infrared region is used, the amount of near infrared rays emitted from the filament electrode 32 is small, and malfunction due to noise or the like is likely to occur. Therefore, it is preferable to amplify near infrared rays detected by the infrared sensor 13 using an amplifier such as an operational amplifier.

  Examples of the material of the infrared sensor include, but are not limited to, PtSi and InSb. For example, when detecting a wavelength of around 5 μm, if there is sensitivity around 5 μm, even if the sensor output is weak, it can be detected by amplification with an operational amplifier or the like, so if it has sensitivity around 5 μm, An infrared sensor of any material can be used. Also, the structure of the infrared sensor is not particularly limited. For example, a photodiode or a phototransistor can be used.

  Further, in the case of an infrared sensor having a high sensitivity wavelength in the near-infrared wavelength region of 700 nm to 1000 nm, for example, a PN type photodiode made of Si and a combination of an IR filter can be used. The IR filter may be any filter that cuts visible light and transmits near-infrared rays of approximately 700 nm or more. For example, a filter composed of a methacrylic resin can be used. In addition, if it is a sensor which can detect the near infrared rays of wavelength 700nm-1000nm, it will not be limited to said material and structure.

  The arrangement position of the infrared sensor 13 is not particularly limited, but it is preferable that the infrared sensor 13 is close to the filament electrode 32 because the detected infrared radiation intensity decreases as the distance from the filament electrode 32 increases. Further, since the infrared light emitted from the filament electrode 32 is easily absorbed by the phosphor applied to the inner wall surface of the glass tube 6 of the hot cathode fluorescent lamp 2, the infrared sensor 13 includes a transparent portion provided on the glass tube 6. More preferably, it is arranged in the vicinity of 16. Specifically, when the light receiving portion of the infrared sensor 13 passes through the center of the filament electrode 32 and an arbitrary perpendicular to the tube wall of the glass tube 6 is 0 °, the range is within ± 20 ° from the center. And it is preferable that the distance from the outer wall surface of the glass tube 6 is provided within 0 mm-5 mm. For example, the infrared sensor 13 can be mounted on the outer wall surface of the glass tube 6 of the hot cathode fluorescent lamp 2 or can be disposed in a space outside the hot cathode fluorescent lamp 2 by a photosensor holding stand. . The arrangement position of the infrared sensor 13 is not limited to this, and the infrared sensor 13 may be arranged at any position as long as the infrared ray emitted from the filament electrode 32 can be detected, even if it is not near the filament electrode 32.

  Moreover, the optical sensor 3 and the infrared sensor 13 are arrange | positioned so that the detection of light may not be prevented mutually. In FIG. 10, the infrared sensor 13 is disposed in the vicinity of the optical sensor 3, but the positional relationship between them is not limited to this. For example, one of the optical sensor 3 and the infrared sensor 13 may be disposed in the vicinity of the filament electrode 32 and the other may be disposed in the center of the glass tube 6.

  The detection unit 14 detects the temperature in the vicinity of the filament electrode 32 based on the intensity of infrared rays detected by the infrared sensor 13, and when the temperature is equal to or higher than a predetermined value, the third drive circuit control signal (third signal). Is output to the control circuit 17. More specifically, the detection unit 14 includes a sensor circuit 18 and a determination circuit 19. The sensor circuit 18 converts the infrared light detected by the infrared sensor 13 into an electrical signal, which is subsequently transmitted to the determination circuit 19.

  Here, as shown in FIGS. 11A and 11B, the wall temperature in the vicinity of the filament electrode 32 is different when the hot cathode fluorescent lamp 2 is normal and abnormal. Further, as shown in FIG. 12, the intensity of infrared rays emitted from the vicinity of the filament electrode 32 varies depending on the amount of heat generated by the filament electrode 32. More specifically, as the tube wall temperature of the hot cathode fluorescent lamp 2 rises, the infrared radiation intensity emitted from the vicinity of the filament electrode 32 increases. That is, the magnitude of the electrical signal corresponds to the magnitude of the infrared intensity detected by the infrared sensor 13, and further corresponds to the temperature level in the vicinity of the filament electrode 32. Therefore, the determination circuit 19 can detect the temperature in the vicinity of the filament electrode 32 based on the intensity of the electrical signal transmitted from the sensor circuit 18.

  The determination circuit 19 outputs a third drive circuit control signal if the detected temperature is equal to or higher than a predetermined value, and does not output a third drive circuit control signal if the detected temperature is smaller than the predetermined value. Although the specific numerical value of the predetermined value is not particularly limited, specifically, for example, when detecting 150 ° C. as an abnormal temperature, the vicinity of the filament electrode 2 when the hot cathode fluorescent lamp 2 is normally lit is used. A temperature that is higher than the temperature and lower than 150 ° C. may be set as the predetermined value.

  Further, the determination circuit 19 uses the temperature difference generated by the filament electrode 32 when the hot cathode fluorescent lamp 2 is normal and abnormal to determine the difference in infrared radiation intensity between when the hot cathode fluorescent lamp 2 is normal and abnormal. It can also be set as the structure which detects the temperature of the vicinity of the said filament electrode by measuring.

  As shown in FIG. 10, the sensor circuit 18 may include an amplifier (signal amplification circuit) such as an operational amplifier and amplify the electric signal. Thereby, even if the infrared rays radiated from the filament electrode 32 are weak, the infrared rays can be detected.

  More specifically, a circuit that generates a pulse of about 5 V, a circuit that switches from a low level output of 0 V to a high level output of 5 V, or the like is preferably used as the determination circuit 19.

  Based on the first drive circuit control signal (first signal) transmitted from the detection unit 4 or the second drive circuit control signal (second signal) transmitted from the timer circuit 24, the control circuit 17. In addition to controlling the operation, the operation of the drive circuit 5 is controlled based on the third drive circuit control signal (third signal) transmitted from the detection unit 14. Since the control of the operation of the drive circuit 5 based on the first drive circuit control signal and the second drive circuit control signal (second signal) is the same as in the first embodiment, the description thereof is omitted here.

  The control circuit 17 further causes the drive circuit 5 to stop driving the hot cathode fluorescent lamp 2 when the infrared sensor 13 detects that the filament electrode 32 has generated heat. The embodiment is not limited to the embodiment in which the driving of the hot cathode fluorescent lamp 2 is stopped, and the embodiment in which the hot cathode fluorescent lamp 2 is temporarily stopped or the output is reduced according to the heat generation temperature in the filament electrode 32 detected by the infrared sensor 13. You can also

  The means for the control circuit 17 to control the drive circuit 5 based on the third drive circuit control signal is not particularly limited. Specifically, for example, the third drive circuit control signal is transmitted to the control circuit 17. When inputted, the driving of the hot cathode fluorescent lamp 2 can be controlled by switching the ON / OFF of the switching circuit 21 and controlling the voltage supplied to the series LC resonance circuit 22. Further, the driving of the hot cathode fluorescent lamp 2 can be controlled by adjusting the power supply to the control circuit 17.

  The specific circuit configuration of the control circuit 17 is not particularly limited. For example, a circuit that generates a pulse of about 5V, a circuit that switches from a low level output of 0V to a high level output of 5V, and the like. Preferably used.

  Thus, since the illuminating device 11 according to the present embodiment includes the infrared sensor 13 in addition to the optical sensor 3, the end glow is prevented and the lamp life is extended, and the end-of-life heat generation is achieved. The phenomenon can be prevented.

  In addition, although the illuminating device 11 concerning this embodiment is provided with the infrared sensor 13 in order to detect the heat | fever which overvoltage and overcurrent were applied to the hot cathode fluorescent lamp 2 and generate | occur | produced, it replaces with the infrared sensor 13. A temperature sensor such as a thermocouple can be bonded to the wall of the glass tube 6. However, a temperature sensor such as a thermocouple may cause a problem of contact with the glass tube 6 and a problem of a slow reaction rate. Further, there are cases where the temperature sensor cannot always be arranged at a position that fits the heat generating part. Therefore, as described above, it is more preferable to use the infrared sensor 13 in order to detect the generated heat when an overvoltage and an overcurrent are applied to the hot cathode fluorescent lamp 2. Furthermore, a configuration including a temperature sensor and an infrared sensor 13 is also possible.

  In the illumination device 11 according to the present embodiment, when the control circuit 17 transmits a signal for stopping the driving of the hot cathode fluorescent lamp 2 to the drive circuit 5 as the third drive circuit control signal, the hot cathode fluorescent lamp 2 is abnormal. A signal generation unit (not shown) for generating an alarm signal for notifying the outside that the occurrence of the occurrence of the failure or the stop of the driving of the hot cathode fluorescent lamp 2 may be further provided.

  The alarm signal indicates that the illumination device 11 is abnormal when the illumination device 11 of the present embodiment is provided in an external device, for example, when the illumination device 11 is provided in a liquid crystal display device. By displaying on the display device, it is possible to notify the user of the liquid crystal display device that an abnormality has occurred in the illumination device 11. As a result, when an abnormality occurs in the hot cathode fluorescent lamp 2, it is possible to deal with it immediately, and the influence of the heat generated by the filament electrode 32 on the peripheral members and the like provided around the lighting device 11. Can be suppressed.

[Embodiment 3]
Another embodiment of the present invention will be described below with reference to FIGS. For convenience of explanation, members having the same functions as those used in Embodiments 1 and 2 are given the same member numbers, and explanations thereof are omitted.

  As shown in FIG. 13, the liquid crystal display device 101 according to the present embodiment includes a surface light source device 102 (back light source) including a plurality of illumination devices 1 according to the present embodiment, an optical sheet 103 (surface light source means), and the like. The liquid crystal display panel 104 (image display means). In FIG. 13, for the sake of simplicity, the surface light source device 102 has a configuration including four illumination devices 1, but the number of illumination devices 1 is not limited thereto.

  In the liquid crystal display device 101, a plurality of illumination devices 1 are provided in parallel in the surface light source device 102, and the optical sheet 103 and the liquid crystal display panel 104 are laminated in this order on the upper surface of the surface light source device 102. That is, the surface light source device 102 functions as a backlight in the liquid crystal display device 101. The optical sheet 103 converts a plurality of linear light sources emitted from the lighting device 1 into uniform surface light sources.

  In each of the plurality of lighting devices 1 provided in the surface light source device 102, the light sensor 3 is provided in the vicinity of the filament electrode 32 of the hot cathode fluorescent lamp 2 of the lighting device 1, and each light sensor 3 has one control circuit. 7 is connected. The control circuit 7 is connected to one drive circuit 5, and the drive circuit 5 controls driving of the hot cathode fluorescent lamps 2 of all the lighting devices 1 provided in the surface light source device 102.

  As the liquid crystal display panel 104, for example, an active matrix color liquid crystal panel using TFTs is preferably used. The surface light source device 102 of the liquid crystal display device 101 according to the present embodiment is a direct type backlight device as shown in FIGS. 13 and 14, but the present invention is not limited to this, and the surface light source is not limited thereto. The device 102 may be an edge type backlight device using a light guide plate and an optical sheet. That is, the illumination device 1 can be applied to an edge type backlight device using a light guide plate and an optical sheet.

  Further, as shown in FIG. 14, the hot cathode fluorescent lamp 2 of the illuminating device 1 in the liquid crystal display device 101 is held by a lamp holding base 105, and the optical sensor 3 is mounted on the lamp holding base 105. May be. As the lamp holder 105, for example, a resin housing having a socket into which the filament electrode 32 portion of the hot cathode fluorescent lamp 2 is inserted, a printed board on which the socket is mounted, and the like are preferably used. The hot cathode fluorescent lamp 2 and the drive circuit 5 are connected via a lamp holder 105.

  Since the hot cathode fluorescent lamp 2 is composed of a cylindrical glass tube 6, it is generally held using a holding table or the like. The photosensor 3 is provided on the outer wall surface of the glass tube 6 of the hot cathode fluorescent lamp 2 or in a space outside the hot cathode fluorescent lamp 2, and when provided in a space outside the hot cathode fluorescent lamp 2. It is held using an optical sensor holding stand or the like.

  Therefore, by holding the hot cathode fluorescent lamp 2 on the lamp holding base 105 and mounting the optical sensor 3, the holding base for holding the hot cathode fluorescent lamp 2 and the optical sensor holding base can be shared. It becomes possible to reduce the members constituting the illumination device 1 of the present embodiment. Further, since the optical sensor 3 can be installed in the vicinity of the filament electrode 32, an abnormality occurring in the hot cathode fluorescent lamp 2 can be detected with high sensitivity.

  In the third embodiment, the configuration in which the surface light source device 102 includes the illumination device 1 has been described. However, it goes without saying that the configuration in which the surface light source device 102 includes the illumination device 11 and the configuration in which the surface light source 102 includes the certification device 1 and the illumination device 11 in combination are also included in the present invention.

  As mentioned above, although embodiment of the illuminating device and liquid crystal display device concerning this invention was described in detail, the illuminating device concerning this invention can also be paraphrased as follows. In other words, the lighting device according to the present invention includes a fluorescent tube having a filament electrode that emits thermoelectrons, and preheating the filament electrode for a time determined by a timer, and then applying a starting voltage to the fluorescent tube to shift to arc discharge. In the illuminating device constituted by the driving circuit, the phosphor of the fluorescent tube is applied so that at least a part of the filament electrode can be seen through, and the light for detecting the intensity of the light emitted from the transparent part is detected. If the output of the sensor and the light sensor reaches a predetermined level, it can be said that the lighting device immediately shifts to the start mode of the fluorescent tube regardless of the time set by the timer.

  It can also be said that the photosensor preferably has high sensitivity on the short wavelength side in the visible light region. In particular, it can be said that the high-sensitivity wavelength of the optical sensor is preferably 400 nm to 410 nm, 430 nm to 445 nm, or both. Furthermore, it can be said that the output of the optical sensor is preferably effective until the preheating period.

  In addition, the optical sensor of the illumination device according to the present invention preferably includes a first sensor having high sensitivity on the short wavelength side in the visible light region and a second sensor having sensitivity in the infrared region. it can. In that case, the high sensitivity wavelength of the first sensor is preferably 400 nm to 410 nm, or 430 nm to 445 nm, or both, and the high sensitivity wavelength of the second sensor is preferably 700 nm to 1000 nm.

  In the display device according to the present invention, it can also be said that the sensor and the connector of the fluorescent tube are preferably on the same substrate.

  On the other hand, the liquid crystal display device according to the present invention can also be described as follows. That is, the liquid crystal display device according to the present invention is an image display device using liquid crystal by combining the illumination device according to the present invention and a surface light source means for converting the plurality of linear light sources into a uniform surface light source. It can also be referred to as a liquid crystal display device using a back light source.

  The present invention is not limited to the configurations described above, and various modifications can be made within the scope of the claims, and the technical means disclosed in different embodiments are appropriately combined. The obtained embodiment is also included in the technical scope of the present invention.

  The present invention will be described more specifically based on Examples and Comparative Examples and FIG. 15, but the present invention is not limited to this. Those skilled in the art can make various changes, modifications, and alterations without departing from the scope of the present invention.

[Example 1]
Using a commercially available hot cathode fluorescent lamp (tube diameter: 15.5 mm, tube length: 820 mm), the correlation between the occurrence timing of end glow and the blackening level at the end of the lamp tube was examined.

  In the experiment, a current of 280 mA was applied to the filament of the hot cathode fluorescent lamp for 1.5 seconds, and then a voltage of 800 V was applied to both ends of the lamp for 100 μsecond, thereby lighting the hot cathode fluorescent lamp. After lighting, the lamp current was 300 mA and the filament current was 180 mA.

  Under the above conditions, a flashing experiment was repeated for 8 hot-cathode fluorescent lamps that were turned on for 10 seconds and turned off for 10 seconds. The occurrence timing of end glow (a light-emitting phenomenon of bluish light) that can be visually recognized, and the lamp tube end The blackening level was observed. As a result, it was confirmed that, after the power was turned on and preheating was started, the lamps that became the end glow early were blackened quickly, and the lamps that were slow to become the end glow were slow blackened. It was also confirmed that the lamps that could not recognize the end glow were not blackened.

  Furthermore, when the lighting experiment was repeated, the lamp with a high blackening level was not lit due to filament breakage after about 500,000 times. On the other hand, the lamp with a low blackening level continued to be lit and the blackening did not progress.

  From the above results, it was clarified that by preventing end glow, the progress of blackening can be prevented and the life of the hot cathode fluorescent lamp can be extended.

  Next, in order to prevent the occurrence of the end glow, the light emitted from the hot cathode fluorescent lamp when the end glow occurred was examined.

  Specifically, the emission spectrum of the hot cathode fluorescent lamp used in the blinking experiment when the end glow occurred and the emission spectrum of the phosphor during normal lighting were measured. As a result, as shown in FIG. 15A, the emission spectrum when the end glow occurred had emission peaks at 400 nm to 410 nm and 430 nm to 445 nm. The emission intensity at the emission peak was higher than the emission intensity in the wavelength range of the phosphor during normal lighting (see FIGS. 15A and 15B).

  From this result, an optical sensor having a high sensitivity wavelength range of 400 nm to 410 nm, an optical sensor having a high sensitivity wavelength range of 430 nm to 445 nm, or an optical sensor having a high sensitivity wavelength range of 400 nm to 410 nm and 430 nm to 445 nm. When used as the optical sensor 3 described in the above embodiment, it has been clarified that the detection sensitivity and the malfunction prevention power can be further improved while distinguishing from the emission spectrum from the phosphor during normal lighting.

[Comparative example]
Using a commercially available hot-cathode fluorescent lamp (tube diameter: 15.5 mm, tube length: 820 mm), the variation in the hot-cathode fluorescent lamp was examined for the blackening level at the end of the lamp tube.

  In the experiment, a current of 280 mA was applied to the filament of the hot cathode fluorescent lamp for 1.5 seconds, and then a voltage of 800 V was applied to both ends of the lamp for 100 μsecond, thereby lighting the hot cathode fluorescent lamp. After lighting, the lamp current was 300 mA and the filament current was 180 mA.

  Under the above-mentioned conditions, a blinking experiment was performed in which the eight hot cathode fluorescent lamps were turned on for 10 seconds and turned off for 10 seconds, and whether or not the blackening level at the end of the lamp tube varies from one hot cathode fluorescent lamp to another. Examined. As a result, for some hot cathode fluorescent lamps, the tube wall around the filament electrode started to blacken after the ON / OFF cycle exceeded 20,000 times, and began to blacken as the number of times further increased. Such a hot cathode fluorescent lamp is further blackened as the number of ON / OFF cycles is further increased. On the other hand, hot cathode fluorescent lamps that did not blacken even when the ON / OFF cycle exceeded 20,000 were hardly blackened. That is, it was confirmed that even if the hot cathode fluorescent lamps having the same specifications are driven by the same drive circuit (inverter circuit), a difference in blackening level occurs.

  From this result, it has been found that the lifetime of the hot cathode fluorescent lamp cannot be sufficiently extended by simply controlling the preheating current and the preheating time as in the prior art.

  Note that the present invention is not limited to the configurations described above, and various modifications are possible within the scope of the claims, and technical means disclosed in different embodiments and examples respectively. Embodiments and examples obtained by appropriately combining them are also included in the technical scope of the present invention.

  As described above, in the present invention, during the preheating of the filament electrode for lighting the hot cathode fluorescent lamp, whether or not the end glow is generated is monitored by detecting the light emission from the filament electrode, At the time of occurrence, immediately stop the preheating of the filament electrode and apply a high voltage for lighting the hot cathode fluorescent lamp. Therefore, even if there are variations in the electrode characteristics of the filament electrode and the circuit characteristics of the drive circuit, the life of the hot cathode fluorescent lamp can be further extended. Therefore, the present invention can be widely used in various illumination devices using a hot cathode fluorescent lamp and devices including the illumination device, such as liquid crystal display devices.

FIG. 1 is a block diagram showing a main part of a circuit configuration of an illumination device according to an embodiment of the present invention. 2A and 2B are diagrams showing equivalent circuits before and during lighting of the lighting device according to the embodiment of the present invention, respectively, and FIG. 2C is a circuit of each equivalent circuit. It is a figure which shows a characteristic. FIG. 3 is a diagram showing an emission spectrum of mercury. FIG. 4 is a diagram showing the light receiving sensitivity of each of the PN photodiodes using GaP, GaAsP, and Si. FIG. 5 is a circuit diagram showing the main part of the sensor circuit of the illumination device according to the embodiment of the present invention. FIG. 6 is a diagram showing an outline of the operation of the illumination device according to the embodiment of the present invention. FIG. 7 is a circuit diagram showing an outline of a control circuit of the illumination device according to the embodiment of the present invention. FIG. 8 is a diagram showing a flowchart of the operation of the illumination device according to the embodiment of the present invention. Fig.9 (a) is a top view of the illuminating device concerning one Embodiment of this invention, FIG.9 (b) is a side view. FIG. 10 is a circuit diagram illustrating a main part of two sensor circuits in the case where an illumination device according to an embodiment of the present invention includes an optical sensor and an infrared sensor. FIG. 11 shows that when a hot cathode fluorescent lamp is driven with a lamp current of 135 mA and a filament current of 250 mA when the configuration of the hot cathode fluorescent lamp is an ambient temperature of 25 ° C., a tube diameter of 15.5 mm, a tube length of 820 mm, It is a figure which shows the pipe wall temperature at the time of (a) and abnormality (b). FIG. 12 shows a case where the tube wall temperature of the hot cathode fluorescent lamp is 0 ° C., 25 ° C., 50 ° C., 75 ° C., 100 ° C., 150 ° C., and 200 ° C., and the infrared radiation intensity at 200 ° C. is 100%. It is the figure which represented the relative radiant intensity of the infrared rays in each temperature of this to the graph. FIG. 13 is a cross-sectional view showing a schematic configuration of a liquid crystal display device according to an embodiment of the present invention. 14 is a cross-sectional view in a direction orthogonal to the liquid crystal display device of FIG. FIG. 15 is a diagram showing the results of measuring the spectrum (a) of the luminous body of the hot cathode fluorescent lamp and the emission spectrum (b) when the end glow occurs in the example of the present invention. FIG. 16 is a block diagram showing a circuit configuration of a conventional fluorescent lamp device. FIG. 17 is a diagram showing a preheating current (a) for generating an end glow and a preheating current (b) for heating to the arc transition temperature for a hot cathode fluorescent lamp having an arc transition temperature of 800 ° C. FIG. 18 is a more simplified block diagram of the circuit configuration of the fluorescent lamp device of FIG. FIG. 19 is a diagram illustrating variations in circuit characteristics of a drive circuit and variations in electrode characteristics of a filament of a hot cathode fluorescent lamp in an illumination device using a hot cathode fluorescent lamp.

Explanation of symbols

1 Illumination device (back light source)
2 Hot cathode fluorescent lamp (light source)
3 Optical sensor (first sensor)
4 Detection unit (first detection means)
5 Drive circuit (drive means)
6 Glass tube 7 Control circuit (control means)
8 Sensor Circuit 9 Judgment Circuit 11 Illumination Device 13 Infrared Sensor (Second Sensor)
14 Detection unit (second detection means)
15 Ultraviolet absorption filter 16 Transparent portion 17 Control circuit (control means)
18 sensor circuit 19 judgment circuit 21 switching circuit 22 series LC resonance circuit 24 timer circuit (time measuring means)
32 Filament electrode 40 Substrate 42 Terminal 43 Lamp connector (connector means)
101 Liquid crystal display device 102 Surface light source device (back light source)
103 Optical sheet (surface light source means)
104 Liquid crystal display panel (image display means)

Claims (14)

A light source having a filament electrode that emits thermoelectrons;
Drive means capable of driving the light source in at least two drive modes: a first drive mode for preheating the filament electrode; and a second drive mode for applying a voltage for arcing the light source;
Control means for controlling switching between the first drive mode and the second drive mode;
A first sensor for detecting light emitted from the vicinity of the filament electrode when the filament electrode is preheated to a predetermined temperature or higher;
First intensity detecting means for detecting the intensity of light detected by the first sensor and outputting a first signal to the control means when the intensity of the light is equal to or greater than a predetermined value;
The said control means switches the drive mode of the said drive means from the said 1st drive mode to a 2nd drive mode based on the said 1st signal, The illuminating device characterized by the above-mentioned.   The said light source has the said filament electrode inside the both ends of a cylindrical glass tube, The fluorescent substance is apply | coated to the inner wall surface of this glass tube except the vicinity of the said filament electrode. The lighting device according to 1.   The lighting device according to claim 1, wherein the first sensor detects light having a wavelength of 400 nm to 445 nm.   4. The lighting device according to claim 1, wherein the first sensor detects at least one of light having a wavelength of 400 nm to 410 nm and light having a wavelength of 430 nm to 445 nm. .   5. The illumination according to claim 1, wherein the first detection unit outputs the first signal only when a driving mode of the driving unit is the first driving mode. 6. apparatus. Time measuring means for measuring a preheating time of the filament electrode and outputting a second signal indicating that a predetermined preheating time has elapsed to the control means when the driving means is driven in the first driving mode. In addition,
The control means switches the drive mode of the drive means from the first drive mode to the second drive mode based on the first input signal of the first signal and the second signal. The lighting device according to any one of claims 1 to 5. A second sensor for detecting heat radiated from the vicinity of the filament electrode;
Second detection means for detecting a temperature in the vicinity of the filament electrode based on the heat detected by the second sensor and outputting a third signal to the control means when the temperature is equal to or higher than a predetermined value; Prepared,
The said control means controls the said drive means based on the said 3rd signal independently of the said 1st signal and a 2nd signal, The any one of Claims 1-6 characterized by the above-mentioned. Lighting device.   The lighting device according to claim 7, wherein the control unit stops the driving unit based on the third signal.   The lighting device according to claim 7, wherein the second sensor detects light in an infrared region.   The lighting device according to claim 7, wherein the second sensor detects light having a wavelength of 700 nm to 1000 nm. The light source is fixed on the substrate via the connector means,
The lighting device according to claim 1, wherein the first sensor is disposed on the substrate. The light source is fixed on the substrate via the connector means,
The lighting device according to any one of claims 7 to 10, wherein the first sensor and the second sensor are arranged on the substrate. A back light source comprising the illumination device according to any one of claims 1 to 12,
And an image display means using liquid crystal.   The liquid crystal display device according to claim 13, wherein the back light source includes the illuminating device and a surface light source unit that converts a plurality of linear light sources emitted from the illuminating device into a uniform surface light source.