JP2002132193A - Light installation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lighting installation which may be made thinner in thickness in spite of use of cold cathode fluorescent tubes of the light installation in which signboards for advertisement, various kinds of films, etc., to be used for illumination are used and is long in life and is free of illumination unevenness which having high brightness. SOLUTION: This lighting installation is constituted to illuminate an object for illumination from its rear with the transmitted light from the cold cathode fluorescent tubes 2 having electrodes at each of both ends in the axial direction of the tubes by impressing high-frequency voltages from inverter circuits to the fluorescent tubes 2. A plurality of the fluorescent tubes 2 are disposed in nearly parallel to each other and circuit boards 14 formed with the inverter circuits are disposed at each one-side end of a plurality of the fluorescent tubes 2 or near the same and the high-frequency output side output terminals Vo of the inverter circuits are connected to the electrodes disposed to each one-side end of the fluorescent tubes 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illuminating device which can be suitably used for illuminating an advertising signboard, as a backlight for various films such as an X-ray film or a photographic film, or as a backlight for a liquid crystal display device. is there.

[0002]

2. Description of the Related Art A hot-cathode fluorescent tube, which is widely used in a general lighting apparatus, is heated by applying a low-frequency voltage between a pair of filament electrodes provided at both ends of a tube axis, thereby being heated by thermoelectrons. When the thermoelectrons collide with the mercury atoms sealed in the tube, the mercury atoms are excited and emit ultraviolet rays, and the ultraviolet rays impinge on the phosphor applied on the inner wall of the tube, thereby causing the outer tube to emit light. R (Red), G (Gr
een) and B (Blue) visible light.

[0003] On the other hand, cold cathode fluorescent tubes have various electrode structures such as an electrolytic emission type, a metal-insulator-metal type, and a diode type. Instead, a high-frequency high voltage is applied between a pair of electrodes at both ends in the tube axis direction via a lead wire to start discharge and emit electrons. Since the cold cathode fluorescent tube is not consumed by heat like the filament electrode of the hot cathode fluorescent tube, the life of the cold cathode fluorescent tube is, for example, 3,00% of that of the hot cathode fluorescent tube.
It is much longer at 10,000 to 50,000 hours compared to 0 to 10,000 hours. In addition, cold cathode fluorescent tubes are 30,000-65,000 cd / m
It is suitable for downsizing and weight reduction of applied equipment that incorporates it because it has a very high luminance of ² and is currently limited to illumination of originals for image scanners and digital copiers and backlighting of LCD monitors. Used for certain applications.

Incidentally, cold cathode fluorescent tubes generally have a problem that the total light amount is small because the tube diameter is small.
In the backlight of the LCD monitor, 100 cd / m ²
Therefore, by adopting a so-called side irradiation method (for example, Japanese Patent Application Laid-Open No. H10-186138), a compact lighting device can be obtained. But,
For lighting equipment for advertising signboards and various films,
Since the brightness of the object to be illuminated needs to be 2,000 cd / m ² or more, and preferably 4,000 cd / m ² or more, a side illumination method such as a liquid crystal monitor cannot be used at all. Therefore, in a lighting device for a billboard for advertisement or a lighting device for various films, similarly to a lighting device using a conventional hot-cathode fluorescent tube, a plurality of cold-cathode fluorescent tubes are arranged on the back surface of an object to be illuminated. There is a need to.

[0005]

However, since the cold cathode fluorescent tube has considerably higher brightness than the hot cathode fluorescent tube, when a plurality of cold cathode fluorescent tubes are provided as described above, the cold cathode fluorescent tube is passed through the diffusion plate. Illumination unevenness such that the arrangement state can be visually observed easily occurs. In order to reduce such illumination unevenness, it is necessary to arrange the cold cathode fluorescent tubes at a relatively large distance from the illumination target, but in such a configuration, the depth of the illumination device is reduced. Since a large space must be provided in the direction, not only does the entire device become large, but also the light intensity is insufficient.Therefore, it is necessary to increase the number of cold cathode fluorescent tubes to be arranged at a small arrangement pitch. come. Therefore, conventionally, even if a lighting device requiring a brightness of 2,000 cd / m ² or more is configured using a cold cathode fluorescent tube, the device itself does not become thin, and the number of cold cathode fluorescent tubes used is small. It has been recognized that the merits of using cold cathode fluorescent tubes are small because of the increase.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and is intended to be used for lighting a billboard for advertisement, various films, and the like, and to make it possible to reduce the thickness while using a cold cathode fluorescent tube. It is an object of the present invention to provide a lighting device which has high brightness, has a long service life, and has no uneven lighting.

[0007]

In order to achieve the above object, a lighting device according to the present invention is provided by applying a high-frequency voltage from an inverter circuit to a cold cathode fluorescent tube having electrodes at both ends in the tube axis direction. Illuminating the illumination target from behind with the transmitted light from the fluorescent tubes, arranging a plurality of the fluorescent tubes substantially in parallel with each other, and connecting the circuit board on which the inverter circuit is formed to the plurality of the fluorescent tubes. The fluorescent lamp is disposed at or near one end of the fluorescent tube, and a high-frequency output side output terminal of the inverter circuit is connected to an electrode provided at the one end of the fluorescent tube.

In this illuminating device, a plurality of cold cathode fluorescent tubes are arranged in parallel, so that an illuminating object requiring a brightness of 2,000 cd / m ² or more, such as an advertising signboard or various films, is used. It can be suitably used for lighting. Further, since the high-frequency output side output terminal of the inverter circuit on the circuit board disposed at or near the end of the fluorescent tube is connected to the electrode provided at one end of the fluorescent tube, a high-frequency voltage is applied to the fluorescent tube. The length of the high voltage side lead wire can be reduced as much as possible, and each high voltage side lead wire from each of two adjacent inverter circuit boards is wired in a long distance and in parallel. Therefore, as described later, each fluorescent tube can emit light with the same brightness.

In a preferred embodiment of the present invention, the fluorescent tubes are arranged in an aligned state with the ends of the plurality of fluorescent tubes aligned. As a result, the high-voltage side lead wires for connecting the high-frequency output side output terminal of the inverter circuit and one electrode of the fluorescent tube have the same length on opposite sides on both sides of the fluorescent tube. Or less.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. 1 to 3, the lighting apparatus has a plurality (four in this embodiment) of cold cathode fluorescent tubes (hereinafter, simply referred to as “fluorescent tubes”) 2.
These fluorescent tubes 2 are arranged on a bottom plate (case) 1 in parallel with each other. The frame-shaped side reflector 3 has a shielding function, and is formed in a frame shape so as to surround portions of each fluorescent tube 2 excluding the tube ends on both sides. A diffusion plate 4 made of a translucent member is placed on the upper end of the side reflection plate 3 in FIG. The upper cover frame (case) 7 is placed and fixed on the peripheral edge of the bottom plate 1 so as to cover the peripheral edge of the diffusion plate 4 and the side reflector 3. Thereby, the diffusion plate 4 is sandwiched between the side reflection plate 3 and the upper cover frame 7.

In FIG. 1, a pair of rail-shaped tube holders 8 and 9 are fixed to the bottom plate 1 in the vicinity of both ends in the longitudinal direction so as to be parallel and opposed to each other. Each fluorescent tube 2 has a holding groove 8a formed in both tube holders 8 and 9,
Both ends are fitted into 9a and positioned and held. Both ends of each fluorescent tube 2 are fixed between the tube holders 8 and 9 and the holding member 11 via the cushion member 10. The fluorescent tubes 2 are respectively inserted into the substantially inverted U-shaped escape grooves 3a formed at the lower end of the side reflection plate 3. Reference numeral 12 denotes a fixing screw.

As shown in FIG. 3, a space 13 surrounded by a bottom plate 1, a side reflector 3 and an upper cover frame 7 is provided at both ends of the fluorescent tube 2 in the longitudinal direction.
Are formed respectively. In the present embodiment, the space 13 is effectively used so as not to be a dead space. That is, in both the spaces,
Four inverter circuit boards 14 provided for each of the four fluorescent tubes 2 are accommodated two by two, whereby each of the two inverter circuit boards 14 occupies the space 1.
3, it is possible to dispose it at a position close to the end of the fluorescent tube 2. Inverter circuit board 14
Is formed with an inverter circuit for applying a high-frequency high voltage to the fluorescent tube 2.

Further, a high-frequency high-voltage high-voltage side lead wire 21 connected to the inverter circuit board 14 and the fluorescent tube 2 is provided.
It is shielded by the side reflector 3, the bottom plate (case) 1, and the upper cover (case) 7 so that the electromagnetic noise generated from (described later) does not affect the outside. Thus, generation of electromagnetic noise toward the outside of the lighting device can be prevented. Note that each of the two inverter circuit boards 1
Reference numerals 4 are vertically arranged in parallel with each other and are supported by a support member (not shown). In this embodiment, the inverter circuit board 14 is provided for each fluorescent tube 2, but a plurality of inverter circuits may be formed on one circuit board.

FIG. 4 is an electric circuit diagram showing an inverter circuit formed on the inverter circuit board 14. As shown in FIG. In this figure, this inverter circuit has input terminals Vi, G
When a DC voltage is applied from a DC power supply (not shown) between ND and ND, a base current flows through the first switching transistor Q1 via the resistor R1, and the transistor Q1
Is turned on. As a result, the current from the input terminal Vi flows to the primary winding T1 of the transformer T via the coil L in the direction of arrow A from its midpoint, and then to the earth ground via the first switching transistor Q1. . At this time, a current flows through the resistor R2 in the sensor winding T3 wound on the primary side of the transformer T by being induced by the current flowing in the primary winding T1. Therefore, the first switching transistor Q1 is turned off when the base voltage decreases, and at the same time,
Since the base voltage of the second switching transistor Q2 rises, the transistor Q2 switches to the ON state.

When the transistor Q2 is turned on, the current flowing through the coil L flows through the primary winding T1 of the transformer T in the direction of the arrow B from the middle point thereof, and then flows into the second switching transistor Q2. To earth ground via At this time, since the sensor winding T3 of the transformer T is induced in the reverse direction by the current flowing in the direction of the arrow B in the primary winding T1, the base voltage of the first switching transistor Q1 rises again, and the transistor Q1 turns on. Switch to state. At the same time,
Since the base voltage of the second switching transistor Q2 drops, the transistor Q2 switches to the off state.

Therefore, the current flowing through the coil flows into the primary winding T1 of the transformer T from the middle point in the direction of arrow A, and then flows to the earth ground via the first switching transistor Q1. After that,
The same operation as described above is repeated at regular intervals. The capacitor C1 prevents the back electromotive force generated in the primary winding T1 of the transformer T from being applied between the input terminals Vi and GND.

As described above, in the primary winding T1 of the transformer T, the direction of the current flowing through the windings on both sides with respect to the middle point changes at a constant period, so that the secondary winding T2 of the transformer T
Is induced so that an electromotive force is generated alternately in the opposite direction at the fixed period, and a high-frequency high voltage is generated between both output terminals Vo and GND, and this high-frequency high voltage is generated between both electrodes of the fluorescent tube 2. Applied. Note that the capacitor C2 is for sharpening the waveform of the high-frequency high voltage.

In this inverter circuit, the input terminals Vi,
When a DC voltage of 5 V was actually applied to GND, the open output voltage between the output terminals Vo and GND was about 1,300 V, and the lighting frequency of the fluorescent tube 2 was 65 kHz. The output voltage can be controlled to an arbitrary value by changing the voltage applied between the input terminals Vi and GND by operating the volume of a DC power supply or the like. Thereby, the brightness of the lighting device can be easily adjusted.

This lighting device irradiates the object to be illuminated with a brightness of 2,000 cd / m ² or more, such as an advertising sign or various films, with the transmitted light of the plurality of fluorescent tubes 2 from the back side thereof. Are arranged as follows. The fluorescent tube 2 emits light when a high frequency high voltage is applied from the inverter circuit board 14, and light emitted from the upper surface side of the fluorescent tube 2
The diffusion plate 4 is directly irradiated. On the other hand, light emitted from the lower surface side of the fluorescent tube 2 is once reflected by the bottom plate 1 and then irradiates the diffusion plate 4. Light emitted from the side of the fluorescent tube 2 is reflected by the side reflector 3 and irradiates the diffuser 4, or is reflected by the bottom plate 1 and irradiates the diffuser 4.

Incidentally, in order to reduce the thickness of the illuminating device and eliminate uneven illumination while obtaining high brightness, it is necessary to set the following parameters to optimal values. The first parameter is the distance between the fluorescent tube 2 and the diffusion plate 4, and the second parameter
Is the distance between the fluorescent tube 2 and the bottom plate 1, and the third parameter
Is the arrangement pitch of the fluorescent tubes 2. Fluorescent tube 2
Diffuser 4 of the light emitted from
The intensity of the light exiting from is determined by the first parameter. The intensity of the light once reflected by the bottom plate 1 and emitted from the diffusion plate 4 toward the diffusion plate 4 is determined by the second parameter. In order to minimize the desired brightness and uneven lighting, it is necessary to set the first to third parameters to values that have an optimal relationship with each other.

When the illuminating device is constructed, the fluorescent tube 2 has a diameter of 26,000 cd / m ^{2 and} a surface luminance of 26,000 cd / m ^2.
A light diffusion coefficient of 2.6 mm is used as the diffusion plate 4.
The optimum parameter value was determined on the condition that a milky white plate of 0.8 was used and the side reflector 3 had a white painted surface. As a result, the distance between the fluorescent tube 2 and the diffusion plate 4 as the first parameter is 24.5 mm, the distance from the fluorescent tube 2 as the second parameter to the bottom plate 1 is 6 mm, and the distance between the fluorescent tube 2 and the bottom plate 1 is 6 mm.
The optimum value of the arrangement pitch of the fluorescent tubes 2 as a parameter was 34 mm.

In the lighting device configured based on the above parameter values, the maximum luminance on the diffusion plate 4 is 4,350 cd / m ^2.
And the minimum luminance was 4,250 cd / m ² . Therefore, with this lighting device, the illumination unevenness was able to be kept extremely small. In addition, in this lighting device, as can be seen from the above-described parameter values, the distance between the fluorescent tube 2 and the diffusion plate 4 is set as small as possible within a range in which uneven lighting does not occur.
mm, so a reduction in thickness has been achieved.

On the other hand, with respect to the uneven surface luminance of the diffusion plate 4, it is required that there is no variation in the surface luminance of each fluorescent tube 2, and the cause of the variation in the surface luminance is as follows. That is, the output terminals Vo,
If the lengths of the lead wires for connecting the GND and the two electrodes of the fluorescent tube 2 vary, the brightness of each fluorescent tube 2 varies, and the illumination light of the advertising signboard and various films cannot be made uniform. . If the lead wire is longer than a predetermined length, the high-frequency high voltage on the lead wire is attenuated by the influence of the surrounding dielectric material and the like, and the predetermined high-frequency high voltage cannot be applied to the fluorescent tube 2. is there.

FIG. 8 shows the result of an experiment conducted by the present inventors. The length of the high-voltage side lead wire for connecting the high-frequency output side output terminal of the inverter circuit board 14 to the fluorescent tube 2 is shown. FIG. 6 is a characteristic diagram of a relationship between the center of the fluorescent tube 2 and the luminance of the tube surface. As can be seen from this figure, the length of the lead wire connecting the inverter circuit board 14 and the fluorescent tube 2 is 80.
It was found that when the distance was equal to or larger than 1 mm, the luminance gradually began to decrease, and the above-mentioned adverse effects occurred. Further, when the respective lead wires from two adjacent inverter circuit boards 14 to the fluorescent tubes 2 are wired in parallel over a long distance,
As a result, a predetermined high-frequency high voltage is not applied to the fluorescent tube 2, and in this case, the surface brightness of the fluorescent tube 2 varies.

In the above-described embodiment, in order to eliminate variations in the luminance of the tube surface of the fluorescent tubes 2, the relative positions of the respective fluorescent tubes 2 and the inverter circuit board 14 and their connections are configured as shown in FIG. 5 or FIG. ing. In FIG. 5, within the range 17 of the illumination object, the four fluorescent tubes 2 are arranged in parallel at an arrangement pitch of 34 mm determined as the above-mentioned third parameter with the ends thereof aligned. Two inverter circuit boards 14 are arranged at positions close to both ends in the tube axis direction of the above. Each high-frequency output side output terminal Vo of each inverter circuit board 14 is connected to a closer electrode 20 of the electrodes of each fluorescent tube 2 via a high-voltage side lead wire 21. On the other hand, each ground-side output terminal GND of each inverter circuit board 14 is connected to a far electrode 29 of the corresponding fluorescent tube 2 via a lead wire 22. Also,
Each input terminal Vi, GN of each inverter circuit board 14
D is connected to output terminals + B and -B of a DC power supply (not shown) via lead wires 23, respectively.

As described above, the length of each high-voltage side lead wire 21 is because the high-frequency output side output terminal Vo of the inverter circuit board 14 is connected to the closer one of the electrodes of the fluorescent tube 2. In addition, it is possible to make the fluorescent tubes 2 as short as possible, and since the fluorescent tubes 2 are arranged in parallel with their respective ends aligned, the opposing members on both sides have the same length, and both have a predetermined length. It can be less than the length. In addition, the two adjacent inverter circuit boards 14
Are not wired in a parallel state over a long distance. Thereby, each of the fluorescent tubes 2 emits light with the same brightness.

The input terminal GND and the output terminal GND of the inverter circuit board 14 are electrically connected to a conductive member such as the bottom plate 1 via a contact or a lead wire, and the output terminal GND of the inverter circuit board 14 is connected to the conductive terminal. If the electrode 29 on the far side of the fluorescent tube 2 to be connected is electrically connected to a conductive member such as the bottom plate 1 or via a lead wire, a connection between the ground side output terminal GND and the fluorescent tube 2 can be obtained. Lead wires are not required.

In FIG. 6, four fluorescent tubes 2 in the range 17 of the object to be illuminated are arranged in the same manner as in FIG. I have. However, as for each inverter circuit board 14, two pairs arranged in the same direction are arranged in different directions. Each high frequency output side output terminal Vo of each inverter circuit board 14 is connected to the closer electrode 20 of each fluorescent tube 2.
Via a high-voltage side lead wire 21. on the other hand,
Each ground side output terminal G of each inverter circuit board 14
The ND is connected to the corresponding farther electrode 29 of the fluorescent tube 2 via the lead wire 22. Input terminals Vi and GND of each inverter circuit board 14 are connected to output terminals + B and -B of a DC power supply (not shown) via lead wires 23, respectively.

Each fluorescent tube 2 is, as shown in FIG.
They may be arranged in parallel in a staggered arrangement in which the positions are alternately slightly shifted in the opposite direction.

[0030]

As described above, according to the lighting apparatus of the present invention, since a plurality of cold cathode fluorescent lamps are arranged in parallel, 2,000 cd / m ^{2 of} advertising signs, various films and the like can be obtained.
It can be suitably used for illuminating an illumination object requiring the above brightness. In addition, a high-frequency output side output terminal of an inverter circuit on a circuit board disposed at or near the end of the fluorescent tube is connected to an electrode provided at one end of the fluorescent tube, and a high-frequency voltage is applied to the fluorescent tube. Therefore, it is possible to shorten the length of the high-voltage side lead wires as much as possible, and since the high-voltage side leads from each inverter circuit board are not wired in parallel over a long distance. In addition, the brightness of each fluorescent tube becomes uniform. Therefore, bright illumination without unevenness becomes possible.

If the ends of the fluorescent tubes are aligned with each other and a circuit board is arranged at the ends, the dead space can be effectively used, and the size of the lighting device can be reduced.

Further, by arranging the circuit board in a space shielded by the side reflector and the case, it is possible to prevent generation of electromagnetic noise toward the outside of the lighting device.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a lighting device according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of the lighting device, cut along a direction perpendicular to the longitudinal direction.

FIG. 3 is a longitudinal sectional view of the lighting device, cut along a longitudinal direction.

FIG. 4 is an electric circuit diagram showing an inverter circuit used in the lighting device.

FIG. 5 is a layout diagram showing relative positions of each fluorescent tube and each inverter circuit board of the lighting device, and lead wires for connecting these.

FIG. 6 is a layout diagram showing another example of the relative positions of each fluorescent tube and each inverter circuit board of the illumination device and lead wires connecting the fluorescent tubes and the inverter circuit boards to each other;

FIG. 7 is a layout view showing another arrangement of the cold cathode phosphors in the lighting device.

FIG. 8 is a characteristic diagram showing a relationship between the length of a high-voltage side lead wire connecting an inverter circuit and a cold cathode fluorescent tube in the lighting device and the luminance of a tube surface at the center of the fluorescent tube.

[Explanation of symbols]

 1: bottom plate 2: cold cathode fluorescent tube 3: side reflector 4: diffusion plate 7: upper cover frame 13: space 14: inverter circuit board 20: electrode 21: high voltage side lead wire Vo: high frequency output side output terminal

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H091 FA14Z FA32Z FA42Z GA11 LA18 3K014 AA02 DA03 5C096 AA02 AA05 BA01 CB04 CC10 CC22 CE12 CF02 DA01 DC06 FA02 5G435 AA02 AA03 BB15 DD13 EE03 EE04 EE26 FF23

Claims (4)

[Claims] 1. A lighting device for applying a high-frequency voltage from an inverter circuit to a cold cathode fluorescent tube having electrodes at both ends in the tube axis direction, and illuminating an illumination object from the back with light transmitted from said fluorescent tube. Wherein a plurality of the fluorescent tubes are disposed substantially in parallel with each other, and a circuit board on which the inverter circuit is formed is disposed at one end of the plurality of fluorescent tubes or in the vicinity thereof, A lighting device in which a high-frequency output side output terminal of the inverter circuit is connected to an electrode provided at the one end. 2. The diffusion plate according to claim 1, wherein the plurality of fluorescent tubes are aligned so that the ends thereof are aligned with each other, and the fluorescent tubes are aligned and arranged, and a diffusion plate is provided at a position facing a surface on which the plurality of fluorescent tubes are arranged. Is disposed at a predetermined interval from each of the fluorescent tubes, and a circuit board on which the inverter circuit is formed is provided between the end portion of each of the fluorescent tubes and the diffusion plate. A lighting device arranged so as to be orthogonal to the fluorescent tube along an end. 3. The fluorescent tube according to claim 2, wherein the circuit boards are disposed at both ends of the plurality of fluorescent tubes, respectively, and a high-frequency output side output terminal of each inverter circuit of each of the circuit boards is connected to the fluorescent tube. A lighting device in which one of the electrodes, which is closer to the output terminal, is connected via a lead wire. 4. The frame-like side reflector according to claim 2, wherein a frame-like side reflector is disposed so as to surround a tube portion excluding an end of the plurality of fluorescent tubes, and is surrounded by the side reflector and a case. A lighting device in which an end of the fluorescent tube and the circuit board are disposed in a space to be provided, and the side reflector and the case have a shielding function.