JP4424496B2 - Light source device - Google Patents

Description

  The present invention relates to a light source device, and more particularly, to a light source device using a rare gas fluorescent lamp used for a backlight or the like of a liquid crystal display device.

2. Description of the Related Art Conventionally, a cold cathode fluorescent lamp in which electrodes are disposed opposite to each other in a glass tube is used as a backlight light source such as a liquid crystal television.
Usually, a small amount of mercury is contained in the cold cathode fluorescent lamp. In recent years, from the viewpoint of consideration of environmental protection, development of a new light source for backlight that does not contain mercury is being promoted instead of a cold cathode fluorescent lamp. As one of the methods, application of a rare gas fluorescent lamp that emits a phosphor by ultraviolet light emission by rare gas discharge as disclosed in JP-A-11-249603 has been studied.

  However, the luminous efficiency of rare gas fluorescent lamps is lower than that of cold cathode fluorescent lamps, and when used as a backlight for liquid crystal televisions, there is a problem of increasing power consumption. ing. As a conventionally known rare gas fluorescent lamp, there is a fluorescent lamp used as a reading light source for OA equipment.

FIG. 1 is a view showing a rare gas fluorescent lamp in which a pair of external electrodes are arranged on the outer surface of a glass tube filled with such a rare gas containing xenon gas, and FIG. FIG. 1B is a perspective view of a rare gas fluorescent lamp, and FIG. 1B is a cross-sectional view showing a cross section perpendicular to the tube axis of the glass tube of the fluorescent lamp.
In these figures, 1 is a rare gas fluorescent lamp, 2 glass tubes, 3 and 3 ′ are a pair of external electrodes provided on the outer surface of the glass tube 2, and 4 is a fluorescence applied to the inner surface of the glass tube 2. A substance 5 is a lighting circuit for applying a high-frequency voltage between the external electrodes 3 and 3.

  Japanese Patent Application Laid-Open No. 6-163006 shows that luminous efficiency is improved when a rare gas fluorescent lamp is lit with a rectangular wave voltage.

FIG. 2 is a diagram showing an example of a light source device using a rare gas fluorescent lamp according to the prior art.
In the figure, 6 is an output transformer of the lighting circuit 5, Ce is a stray capacitance of the output transformer 6 and wiring, the range surrounded by a dotted line of the rare gas fluorescent lamp 1 is an equivalent circuit of the rare gas fluorescent lamp 1, and Cg is The capacitance of the glass tube 2 between the external electrodes 3 and 3 ′, Cd is the capacitance of the discharge gap in the glass tube 2, Rd is the resistance of the discharge plasma, and the magnitude thereof is periodically within the lighting cycle. Change.

JP-A-11-249603 JP-A-6-163006

  Incidentally, in the rare gas fluorescent lamp 1 as shown in FIG. 1, in order to increase the ratio of the effective light emission area from the glass tube 2, it is conceivable to make the electrodes of the external electrodes 3 and 3 'thinner. However, when the rectangular electrodes are lit by reducing the electrode area of the external electrodes 3 and 3 ′, there is a problem in that the light distribution is not uniform due to partial non-lighting in the tube axis direction of the rare gas fluorescent lamp 1.

3 and 4 are diagrams showing rectangular wave voltages applied to the rare gas fluorescent lamp 1 in the light source device of the rare gas fluorescent lamp as shown in FIG.
As the electrode areas of the external electrodes 3 and 3 ′ are reduced, the sag a of the rectangular wave voltage waveform increases as shown in FIG. The voltage waveform portion indicated by b in FIG. 3 is considered to be a part of the resonance waveform due to the inductance, stray capacitance Ce, capacitance Cg, and capacitance Cd of the output transformer 6 of the lighting circuit 5. When the resonance frequency of the resonance waveform is sufficiently smaller than the lighting frequency of the lamp, the waveform becomes d as shown by the solid line in FIG. 4, but the lamp capacitances Cg and Cd are small, and the resonance waveform is turned on at the resonance frequency. When the frequency is close, the waveform e is as shown by the dotted line in FIG. 4 and the sag is increased.

  In FIG. 3, the magnitude c of the steep voltage change of the rectangular wave lighting waveform is related to the lamp input power and the discharge stability. As the sag increases, the magnitude c of the steep voltage change decreases. Therefore, the lamp input power is reduced, the discharge becomes unstable, and partial lighting occurs.

  As described above, it is desirable that the external electrodes 3 and 3 ′ disposed on the outer surface of the glass tube 2 block light and reduce the area of the external electrodes 3 and 3 ′ as much as possible in order to reduce the light output. However, the capacitances Cg and Cd are reduced in proportion to the reduction in the area of the external electrodes 3 and 3 ′. As a result, as described above, the sag is increased and partial lighting occurs.

  Specifically, in a rare gas fluorescent lamp having a light emission length (external electrode length) of 800 mm, out of a pair of external electrodes 3, 3 ′ disposed on the outer surface of the glass tube, one external electrode 3 (or one) When the area of 3 ′) was 8% or more of the surface area outside the glass tube, it was normally lit, but when the area was less than that, the discharge became unstable and partial lighting did not occur.

  In view of the above problems, an object of the present invention is to improve the light emission efficiency of a rare gas fluorescent lamp used as a backlight of a liquid crystal television or the like, and to reduce power consumption when used as a backlight. An object of the present invention is to provide a light source device that is made possible.

The present invention employs the following means in order to solve the above problems.
The first means includes a straight glass tube enclosing a rare gas therein, a pair of external electrodes extending in the tube axis direction on the outer surface of the glass tube, and a fluorescent material applied to the inner surface of the glass tube. In a light source device that is lit by applying a rectangular wave voltage to a rare gas fluorescent lamp comprising: a plurality of the rare gas fluorescent lamps are arranged in parallel with respect to at least one output transformer , and the tube axis direction of the external electrode The ratio of the surface area of the one external electrode to the external surface area of the glass tube over the entire circumference of the glass tube is W (%), and the total length of the external electrode in the tube axis direction is L (m) The light source device satisfies the relationship of (0.8 / L) × (8 / N) ≦ W <(0.8 / L) × 8, where N is the number of parallel lines. .

Second means, Oite the first hand stage, among the rare gas sealed inside the glass tube, with a light source and wherein the partial pressure of xenon is 6.6kPa to 31.9kPa is there.

According to the first aspect of the present invention, a straight glass tube enclosing a rare gas therein, a pair of external electrodes extending in the tube axis direction on the outer surface of the glass tube, and coating on the inner surface of the glass tube A plurality of rare gas fluorescent lamps arranged in parallel with respect to at least one output transformer in a light source device that is lit by applying a rectangular wave voltage to a rare gas fluorescent lamp comprising The ratio of the surface area of the one external electrode to the external surface area of the glass tube over the entire circumference of the glass tube in the total length in the tube axis direction of the electrode is W (%), and the total length of the external electrode in the tube axis direction is Since L (m) and N (lines) in parallel, the relationship of (0.8 / L) × (8 / N) ≦ W <(0.8 / L) × 8 is satisfied . Without causing partial lighting of the rare gas fluorescent lamp in the tube axis direction, The area of the external electrode can be reduced, the light beam blocked by the external electrode is reduced, and the light emission efficiency can be increased. Furthermore, the starting characteristics can be improved as the number of parallel rare gas fluorescent lamps increases.

According to the second aspect of the present invention, since the partial pressure of xenon is set in the range of 6.6 kPa to 31.9 kPa among the rare gases sealed inside the glass tube, the brightness as the backlight of the liquid crystal Can be obtained sufficiently, and a light source device with good luminous efficiency can be obtained.

An embodiment of the present invention will be described with reference to FIGS. 1 and 5.
FIG. 5 is a diagram showing an outline of the light source device according to the invention of the present embodiment.
In the figure, 1... N is a plurality of rare gas fluorescent lamps connected in parallel to at least one output transformer 6 of the lighting circuit 5, and the other configurations are denoted by the same reference numerals shown in FIG. Since it corresponds to the configuration, the description is omitted.

  1 and 5, the light source device of the present embodiment includes a straight glass tube 2 in which a rare gas is enclosed, and a pair of external electrodes 3 and 3 ′ extending in the tube axis direction of the outer surface of the glass tube 2. And a noble gas fluorescent lamp 1... N having a fluorescent material 4 applied to the inner surface of the glass tube 2 to be lit by applying a rectangular wave voltage, and at least one output of the lighting circuit 5 A plurality of rare gas fluorescent lamps 1... N are arranged in parallel with respect to the transformer 6, and the surface area of the outer surface corresponding to the region where the pair of external electrodes 3, 3 ′ of the glass tube 2 is disposed is 1. The ratio of the surface area of the two external electrodes 3 (or 3 ′) is to be gradually decreased with respect to the case where a single lamp is used as the number of rare gas fluorescent lamps in parallel increases.

  This is because, when a plurality of rare gas fluorescent lamps 1... N are connected to one output transformer 6, a plurality of individual rare gas fluorescent lamps with respect to the entire area of the plurality of glass tubes. This is because it has been found that there is a region where stable discharge can be obtained when the ratio of the integrated area of one external electrode is defined within a predetermined range.

  Specifically, the ratio of the surface area of one external electrode 3 (or 3 ′) to the area of the outer surface corresponding to the region where the pair of external electrodes 3 and 3 ′ of the glass tube 2 are disposed is W ( %), The relationship of (8 / N) ≦ W <8 is preferably satisfied.

  That is, in one rare gas fluorescent lamp, the area of the external electrode 3 (or 3 ′) on one side of the pair of external electrodes 3 and 3 ′ disposed on the outer surface of the glass tube 2 is the glass tube 2. If it is 8% or more of the outer surface area, normal lighting is possible. In other words, in the light source device shown in FIG. 5, the capacitances Cg and Cd are N times larger, so that the external electrode 3 (or 3 ′) on one side is 8 / N% or more of the outer surface area of the glass tube. If it is large, normal lighting is possible.

Next, an embodiment of the present invention will be described with reference to FIG. 1 and FIGS.
The configuration of the rare gas fluorescent lamp used here is the same as that shown in FIG. 1. Three types of glass tube diameters of φ6.2, φ8.0, and φ10.0 are used, and the sealed gas is Xe: Ne. = 8: 2 mixed gas, Xe partial pressure is 26.6 kPa. The external electrodes 3 and 3 ′ were aluminum tapes having a width of 1 mm or more, and screen pastes were used for those having a width of less than 1 mm. The lamp emission length (external electrode length) is 800 mm.

FIG. 6 is a diagram showing the configuration of the light source device used in this embodiment.
In the figure, 7 is a switching element, 8 is a switching element drive circuit, and 9 is a DC power source. Other configurations correspond to the configurations of the same reference numerals shown in FIG.
In this light source device, N rare gas fluorescent lamps are connected in parallel to at least one output transformer 6 provided in a lighting circuit 5 that outputs a rectangular wave voltage, and power is supplied from a DC power source 9 for switching. A rectangular wave voltage is applied to each rare gas fluorescent lamp 1... N via the output transformer 6 by periodically switching the switching element 7 such as an FET in the element driving circuit 8. The output-side inductance of the output transformer 6 is approximately 200 mH. Increasing the inductance of the output transformer 6 can also suppress the sag of the voltage waveform and stabilize the discharge, but the size of the output transformer 6 becomes large and mounting becomes difficult, which is not realistic.

  FIG. 7 is a diagram showing types of rectangular wave voltage waveforms applied to the rare gas fluorescent lamp. FIG. 7A is a rectangular wave voltage waveform in which positive and negative rectangular wave voltages are repeated every half cycle. It is used for the light source device of the example. In addition, a rectangular wave voltage waveform having a pause period between positive and negative rectangular wave voltages as shown in FIG. 7 (b), a rectangular wave voltage waveform composed of positive rectangular wave voltages as shown in FIG. 7 (c), As shown in FIG. 7D, it is also possible to use a rectangular wave voltage waveform having a pause period after every positive and negative rectangular wave voltage. It is possible to turn on the lamp by applying these rectangular wave voltages to the rare gas fluorescent lamps 1.

FIG. 8 is a diagram showing the relationship between the one-side external electrode / surface area outside the glass tube and the lighting state with respect to the number N of lamps in parallel when the glass tube diameter is 8.0. Here, the outer surface area of the glass tube refers to the outer surface area corresponding to the region where the pair of external electrodes of the glass tube is disposed, in other words, the total length of the glass tube in the tube axis direction of the external electrode. It is the outer surface area over the entire circumference. ○ is a condition for normal lighting, and x is a condition for partial non-lighting.
As shown in the figure, it can be seen that as the number of parallel lamps N 1 is increased, normal lighting is possible even when the external electrode area is reduced. The solid line in the figure indicates that the external electrode area ratio is 8
/ N% is a line connecting points. It can be seen that normal lighting is possible when the area ratio of the external electrodes is equal to or larger than the size represented by the solid line.

FIG. 9 is a diagram showing the relationship between the one-side external electrode / surface area outside the glass tube and the lighting state with respect to the lamp parallel number N in the case of the glass tube diameter φ6.2. As in the case of FIG. 8, the glass tube outer surface area refers to the area of the outer surface corresponding to the region where the pair of external electrodes of the glass tube is disposed. ○ is a condition for normal lighting, and x is a condition for partial non-lighting.
As shown in the figure, it can be seen that as the number N of lamps in parallel increases, normal lighting is possible even when the external electrode area is reduced. The solid line in the figure is a line connecting points when the external electrode area ratio is 8 / N%. It can be seen that normal lighting is possible when the area ratio of the external electrodes is equal to or larger than the size represented by the solid line.

FIG. 10 is a diagram showing the relationship between the one-side external electrode / glass tube outer surface area with respect to the lamp parallel number N and the lighting state in the case of the glass tube diameter φ10.0. As in the case of FIG. 8, the glass tube outer surface area refers to the area of the outer surface corresponding to the region where the pair of external electrodes of the glass tube is disposed. ○ is a condition for normal lighting, and x is a condition for partial non-lighting.
As shown in the figure, it can be seen that as the number N of lamps in parallel increases, normal lighting is possible even when the external electrode area is reduced. The solid line in the figure is a line connecting points when the external electrode area ratio is 8 / N%. It can be seen that normal lighting is possible when the area ratio of the external electrodes is equal to or larger than the size represented by the solid line.

FIG. 11 is a graph showing the relationship between the number of parallel lamps N and the relative starting voltage when the size of the external surface area on one side / glass tube is 2.0%, 4.0%, and 8.0%. . Here, when the number of lamps in parallel is 5, the starting voltage is 100%, and the glass tube outer diameter is φ8.0.
As shown in the figure, the larger the lamp parallel number N, the more the starting voltage tends to decrease. Therefore, increasing the lamp parallel number N not only suppresses partial non-lighting but also improves startability. It can be seen that there is also an effect.

FIG. 12 is a diagram showing a relationship between relative luminous efficiency with respect to Xe partial pressure. Here, the size of the external surface area on one side / glass tube is 8.0%, the outer diameter of the glass tube is φ8.0, the number of parallel lamps is 5, the luminous efficiency is the total luminous flux / input power, and 26.6 kPa. In this case, the luminous efficiency is set to 100%.
As shown in the figure, the light emission efficiency tends to increase as the Xe partial pressure increases, but it tends to be saturated after 31.9 kPa. As the Xe partial pressure increases, the lamp startability is adversely affected. Therefore, it is meaningless to increase the Xe partial pressure more than necessary. Therefore, it is desirable that the Xe partial pressure has an upper limit of 31.9 kPa. Further, the lower limit of the Xe partial pressure is 6.6 kPa, and if it is less than that, the brightness becomes insufficient as the backlight of the liquid crystal.

FIG. 13 is a diagram showing the relationship between the one-side external electrode / outside surface area of the glass tube and the lighting state with respect to the number N of lamps in parallel when the length of the external electrode in the tube axis direction is 0.5 m. Here, the glass tube diameter is φ8.0.
As shown in the figure, when the length of the external electrode in the tube axis direction is 0.5 m, compared with the case where the length of the external electrode in the tube axis direction of FIG. X) The ratio of the external electrode area is large, and the magnitude of 8 / N%, which is the lower limit of normal lighting when the length of the external electrode in the tube axis direction is 0.8 m (dotted line in the figure) It exceeds. This is because the capacitance of the lamp is proportional to the length of the external electrode in the tube axis direction, and the capacitance is approximately 0.5 / 0 compared to the case where the length of the external electrode in the tube axis direction is 0.8 m. This is thought to be due to a reduction of 8 times. The solid line in the figure shows the capacitance due to the change of the length of the external electrode in the tube axis direction to the lower limit of 8 / N% during normal lighting when the length of the external electrode in the tube axis direction is 0.8 m. The length is corrected by multiplying the reciprocal of the rate of change (0.8 / 0.5).

  As can be seen from the figure, normal lighting is possible when the ratio of the area of the external electrode is not less than the size represented by the solid line. By performing the length correction in this way, even when the length of the external electrode in the tube axis direction is different from 0.8 m, the outer surface area corresponding to the region where the pair of external electrodes of the glass tube is disposed. When the ratio of the surface area of one external electrode to W is% (%), the total length of the rare gas fluorescent lamp is L (m), and the parallel number is N (lines), the threshold is (0.8 / L) X (8 / N) ≦ W <(0.8 / L) × 8.

FIG. 14 is a diagram for explaining the effect of improving brightness by reducing the external electrode area ratio.
In the figure, reference numeral 10 denotes a rare gas fluorescent lamp whose tube axis is arranged in parallel in the direction perpendicular to the paper surface, 11 is a reflection mirror, and 12 is a diffusion plate.
As shown in the figure, eight rare gas fluorescent lamps 10 are arranged, two lighting circuits (not shown) are used, and four rare gas fluorescent lamps 10 are connected in parallel. The outer surface area on one side / glass tube is 8% and 4%, the lamp tube diameter is φ8.0, and the length of the external electrode in the tube axis direction is 0.8m. As a result of comparing the brightness on the surface of the diffusion plate 12 with the same power, the 4% is brighter by 7% than the 8% external electrode / glass tube surface area. It was confirmed.

It is a figure which shows the noble gas fluorescent lamp which provided a pair of external electrode on the outer surface of a glass tube. It is a figure which shows an example of the light source device using the noble gas fluorescent lamp concerning a prior art. It is a figure which shows the rectangular wave voltage applied to a noble gas fluorescent lamp in the light source device of the noble gas fluorescent lamp as shown in FIG. It is a figure which shows the rectangular wave voltage applied to a noble gas fluorescent lamp in the light source device of the noble gas fluorescent lamp as shown in FIG. It is a figure which shows the outline | summary of the light source device which concerns on this invention. It is a figure which shows the structure of the light source device used in the Example. It is a figure which shows the kind of rectangular wave voltage waveform applied to a noble gas fluorescent lamp. It is a figure which shows the relationship and lighting state of the one side external electrode / glass tube external surface area with respect to the lamp parallel number N in the case of glass tube diameter φ8.0. It is a figure which shows the relationship between the one side external electrode / glass tube external surface area with respect to the lamp parallel number N, and a lighting state in the case of glass tube diameter (phi) 6.2. It is a figure which shows the relationship and lighting state of the one side external electrode / glass tube external surface area with respect to the lamp parallel number N in the case of glass tube diameter φ10.0. It is a figure which shows the relationship with the relative starting voltage with respect to the lamp parallel number N when the magnitude | size of the one-side external electrode / glass tube outer surface area is 2.0%, 4.0%, and 8.0%. It is a figure which shows the relationship with the relative luminous efficiency with respect to Xe partial pressure. It is a figure which shows the relationship between the one side external electrode / glass-tube outer surface area and a lighting state with respect to the number N of lamp parallel, when the length of the external electrode in the tube axis direction is 0.5 m. It is a figure for demonstrating the improvement effect of the brightness by making an external electrode area ratio small.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Noble gas fluorescent lamp 1 ... N Noble gas fluorescent lamp 2 Glass tube 3, 3 'External electrode 4 Fluorescent substance 5 Lighting circuit 6 Output transformer 7 Switching element 8 Switching element drive circuit 9 DC power supply 10 Noble gas fluorescent lamp 11 Reflection Mirror 12 Diffusion plate Ce Floating capacitance Cg of output transformer, wiring, etc. Capacitance of glass tube between external electrodes Cd Capacitance of discharge gap in glass tube Rd Resistance of discharge plasma

Claims (2)

A rare gas comprising: a straight tubular glass tube filled with a rare gas; a pair of external electrodes extending in the tube axis direction on the outer surface of the glass tube; and a fluorescent material applied to the inner surface of the glass tube. In a light source device that is lit by applying a rectangular wave voltage to a fluorescent lamp,
A plurality of the rare gas fluorescent lamps are arranged in parallel with respect to at least one output transformer, and the one external portion with respect to the outer surface area of the glass tube over the entire circumference of the glass tube in the entire length in the tube axis direction of the external electrode. When the ratio of the surface area of the electrode is W (%), the total length of the external electrode in the tube axis direction is L (m), and the parallel number is N (number), (0.8 / L) × (8 /N)≦W<(0.8/L)×8 satisfying the relationship . 2. The light source device according to claim 1 , wherein a partial pressure of xenon is 6.6 kPa to 31.9 kPa among rare gases sealed in the glass tube .

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