JP4280660B2 - Lighting device - Google Patents

Description

  The present invention relates to an illuminating device including multiple fluorescent lamps used in a liquid crystal display, a liquid crystal TV, an instrument display panel, and the like.

  Conventionally, a direct type backlight using a plurality of straight tube fluorescent lamps as described in JP-A-2002-132193 is known. However, in recent years, with the increase in the screen size of liquid crystal displays and liquid crystal TVs, it has been required to increase the size of the backlight. To cope with this, the number of straight fluorescent lamps used as a light source has increased. The problems of large power consumption and cost increase are emerging.

  Therefore, a long lamp is manufactured, and a bent tube fluorescent lamp 10 such as a C tube or a U tube is manufactured by bending it at the center or at an arbitrary position, so that the back of the configuration shown in FIGS. A light has been developed. In the backlight using the conventional curved tube fluorescent lamp 10 as a light source, an electrode side rubber holder 13 is provided on one side 12A of the frame 11, and a power supply side electrode 14 is provided on the electrode side rubber holder 13, whereby each electrode of the curved tube fluorescent lamp 10 is provided. And a holding holder 16 for holding the bent portion 15 of each curved tube fluorescent lamp 10 is arranged on the other side 12B, and the bent portion 15 of the fluorescent lamp 10 is held by this.

  The inverter 17 as a power source in such a backlight has a simple structure in which it is arranged on the back surface side of the reflection case 18 on the lamp electrode side 12A in consideration of the wiring of the power supply wire. The reflection case 18 is made of a metal plate having good thermal conductivity such as aluminum, aluminum alloy, and stainless steel. Reference numeral 19 denotes a transformer of the inverter 17.

  However, in recent years, in the development of products for liquid crystal displays and liquid crystal TVs, development engineers are required to design products that can save energy and reduce costs as well as increasing the screen size (upsizing). As a design to answer this, backlights using multiple short pitch bent tubes have become the mainstream, but there are the following technical problems with respect to size increase.

In the case of the backlight having the structure as shown in FIGS. 13 and 14, if it is less than 17 inches, the temperature distribution is relatively uniform, and the temperature difference and luminance difference in the tube axis direction (left and right direction in FIGS. It is not noticeable, but it is rarely regarded as a problem. However, as shown in FIGS. 15 to 18, when the size increases to 17 inches or more, the lamp applied voltage increases due to the increase in the lamp length as well as the high temperature at the lamp electrode portion which is the main heat generation source. Leakage current near the high voltage due to stray capacitance between the lamp and the unit increased, and because of the increase in inverter power accompanying the increase in lamp power, it was placed behind the reflective case 18 on the lamp electrode side due to the problem of the power supply cable. The amount of heat generated in the inverter 17 increases, and as a result, the temperature difference in the tube axis direction in the unit and lamp effective range increases, and the temperature difference in the tube axis direction due to this temperature difference and leakage current increases. Growing up is becoming a problem. In addition, since the occurrence of temperature difference decreases at the lower right temperature, the lamp wall temperature of the normally lit lamp decreases due to the dimming of the lamp or the change in ambient temperature, and this decrease in the tube wall temperature is caused. This may cause movement and unevenness of mercury contained in the lamp, which may shorten the life of the fluorescent lamp.
JP 2002-132193 A

  The present invention has been made in view of the above-described conventional technical problems, and is in a lighting apparatus using a plurality of curved fluorescent lamps such as a C tube or a U tube, and serves as a light source. The electrodes are alternately arranged, and the inverter is arranged at a position corresponding to the direct back side of the electrode feeding portion of each fluorescent lamp in the reflection case, thereby reducing the tube wall temperature difference in the lamp tube axial direction and the panel surface direction, And it aims at providing the illuminating device which can reduce the brightness | luminance difference on a board surface.

  In the lighting device of the first aspect of the present invention, a phosphor film is formed on the inner wall of a glass lamp tube, and one or more kinds of rare gases or mercury and one or more kinds of rare gases are sealed inside the glass lamp tube, The lead wire is hermetically sealed at both ends of the lamp tube, an electrode is connected to the end portion of the lead wire inside the glass lamp tube, a power supply lead wire is connected to the outer end portion of the lead wire, and A plurality of fluorescent lamps each having a glass lamp tube formed of a C tube or a U tube bent tube are provided, and the fluorescent lamps of the plurality of bent tubes are heated so that their electrode end sides and bent end sides are alternately arranged. Arranged on the front side of the reflective case with good conductivity, and each inverter for supplying a high voltage to each of the plurality of fluorescent lamps is located on the back side of the reflective case, directly behind the electrode part of each fluorescent lamp It is a thing.

  The lighting device of the invention of claim 2 forms a phosphor film on the inner wall of the glass lamp tube, encloses one or more kinds of rare gas, or mercury and one or more kinds of rare gas inside the glass lamp tube, Closes both ends of the glass lamp tube, arranges external electrodes on the outer surfaces of both ends of the glass lamp tube, and comprises a plurality of fluorescent lamps in which the glass lamp tube is formed as a curved tube of a C tube or a U tube, The fluorescent lamps of the multiple lamps are arranged on the front side of the reflection case so that the electrode end sides and the bent end sides are alternately arranged, and each of the inverters that supplies a high voltage to each of the multiple lamp fluorescent lamps In the back side of the reflective case, the fluorescent lamp is disposed at a position directly behind the electrode portion of each fluorescent lamp.

  According to a third aspect of the present invention, in the illuminating device of the first or second aspect, the size of the illumination surface is 17 inches or more, and the lamp effective light emission length is 350 mm or more.

  According to a fourth aspect of the present invention, in the illuminating device according to the first to third aspects, the coldest tube wall temperature of each fluorescent lamp is maintained at 50 ° C. or higher even at the lower limit of the operating temperature range.

  According to the present invention, fluorescent lamps having a plurality of lamps are arranged so that the electrode end sides and the bent end sides thereof are alternately arranged, and the electrode feeding portion of each fluorescent lamp is provided in a reflective case having good thermal conductivity. By placing the inverter at a position corresponding to the back side of the tube, the difference in tube wall temperature in the lamp tube axis direction and the panel surface direction can be reduced, and the difference in brightness on the panel surface can be reduced. Lighting with uniform brightness is possible as the light, and the life of the lamp can be extended.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 1 and 2 show a backlight according to an embodiment of the present invention. The backlight of the present embodiment is a backlight that uses a plurality of fluorescent lamps 10 of a C tube or a U tube, and the plurality of fluorescent lamps 10 on the apparatus side are connected to their electrode side end portions 10A. By arranging the inverters 17 on the back side of the reflective case 18 on the electrode feeding side at the positions directly behind the respective electrode positions, the curved portion side end portions 10B are arranged in parallel so as to alternate with each other. Since the case is formed of a metal plate such as aluminum, aluminum alloy, or stainless steel having good thermal conductivity, there is a difference in the tube wall temperature difference between the lamp axis direction and the backlight horizontal direction on the entire plate surface of the reflection case 18. As a result, the luminance difference on the surface of the backlight board can be reduced. The backlight of this embodiment can also be used in the presence of a temperature difference, so that the tube wall temperature in the backlight can be soaked to 50 ° C or higher. It can be done. In FIG. 1 and FIG. 2, components common to those in the conventional example shown in FIG. 13 and FIG. Reference numeral 20 denotes a rubber holder for holding the end of each fluorescent lamp 10.

  As shown in FIG. 3, the curved tube fluorescent lamp 10 used in the present embodiment forms a phosphor film 102 on the inner wall of the glass lamp tube 101, and one or more kinds of rare gases, Alternatively, mercury and at least one kind of rare gas 103 are sealed, both ends of the glass lamp tube 101 are closed, external electrodes 104 are arranged on the outer surfaces of both ends of the glass lamp tube 101, and the glass lamp tube 101 is a C tube. Or it is the fluorescent lamp formed in the curved pipe of U tube.

  As shown in FIG. 4, the fluorescent lamp 10 has a phosphor film 112 formed on the inner wall of a glass lamp tube 111, and one or more kinds of rare gases or mercury and one or more kinds of gases are formed inside the glass lamp tube 111. A rare gas 113 is sealed, the introduction line 114 is hermetically sealed at both ends of the glass lamp tube 111, an electrode 115 is connected to the end of the introduction line 114 inside the glass lamp tube 111, and the outside of the glass lamp tube 111. A fluorescent lamp in which a power supply lead wire 116 is connected to the end of the lead-in wire 114 and the glass lamp tube 111 is formed as a curved tube of a C tube or a U tube can also be used.

  As described with reference to FIGS. 13 and 14, the backlight in which the conventional fluorescent lamps 10 having a plurality of lamps (C tube and U tube) are arranged is shown in the graphs of FIGS. 15 and 16. However, as the backlight size increases, the temperature difference and the brightness difference in the axial direction of the panel tube tend to increase.

  The cause of this temperature difference is (i) heat generation of the lamp electrode, (ii) influence of heat generation and arrangement of the inverter, and (iii) leakage current due to stray capacitance between the lamp and the backlight unit. Power consumption differs, and (iv) heat dissipation effect by holding a lamp such as a holder can be obtained.

  The above factor (i) is due to the fact that the amount of heat generated at the positive column per unit length is very small compared to the amount of heat generated at the electrode portion of the lamp. The reason for (ii) is that the power loss becomes heat quantity due to the power factor of the inverter. This is because the amount of heat generated by the inverter increases due to the increase in lamp power as the lamp length increases, so the temperature difference in the tube axis direction increases due to the heat generated by the inverter placed behind the reflective case. This is to encourage. The reason of (iii) is that the lamp is lit by applying high frequency and high voltage with alternating current, so that current leakage occurs due to the stray capacitance between the lamp and the unit tube, and the current flows from the high pressure part to the low pressure part in the tube axis direction. This is due to the consumption of electric power taking account of leakage. The reason for (iv) is that the bent side of a bent tube lamp is generally held by a holder or the like.However, due to the factor (i), the temperature is low and further heat dissipation by the holder or the like occurs. The conventional backlight structure shown in FIGS. 13 and 14 is caused by a temperature difference in the tube axis direction. Regarding this factor, the longer the backlight size, the longer the lamp used, and in order to maintain the lighting, it is necessary to apply a high voltage. It tends to grow.

  The cause of the difference in luminance in the tube axis direction is (v) the relationship between mercury temperature and ultraviolet light emission efficiency as shown in the graph of FIG. 11, and (vi) current leakage due to stray capacitance between the lamp and the unit. This is because the lamp is lit at a current value of (rated current + leakage current) until the current leaks at the high-pressure portion in the tube axis direction due to the occurrence.

  Because of the above-mentioned problem factors, the improvement of the backlight according to one embodiment of the present invention shown in FIGS. 1 and 2 is focused on reducing the tube wall temperature difference due to the backlight. is there. In the backlight of the present embodiment shown in FIGS. 1 and 2 and the backlight of the conventional example shown in FIGS. 13 and 14, the lamp arrangement is C tube 6 lamps. The number of lamps varies depending on the length (number of inches) and application (for high brightness, high definition, etc.).

  In the backlight structure of the present embodiment shown in FIG. 1 and FIG. 2, the influence of heat generated by the electrode side end portion 10A as a heat generation source and the inverter 17 is structurally uniform in the tube axis direction. Therefore, the temperature is almost the same on both sides of the backlight. As shown in the graphs of FIGS. 5 and 6, not only the temperature difference in the tube axis direction is reduced as a whole, but also the brightness difference in the tube axis direction is reduced. can do. That is, as described above, since the reflective case 18 is formed of a material having good thermal conductivity (aluminum, aluminum alloy, stainless steel, etc.), the temperature of the coldest portion of the plate surface of the reflective case 18 is raised. Is acting on. Further, from the graph of the tube wall temperature difference and luminance difference between the present embodiment A and the conventional example B shown in FIGS. 7 and 8, the present embodiment A also improves the temperature difference and the luminance difference depending on the backlight size. Is possible. Furthermore, from the graphs of the difference in tube wall temperature by size and the difference in board surface brightness by size between the present embodiment A and the conventional example B shown in FIGS. 9 and 10, the effective light emission length with respect to the backlight size in the present embodiment A It is possible to improve the temperature difference and the luminance difference by replacing with. In particular, such an effect of improving the temperature difference and the brightness difference is conspicuous for backlights having an effective light emission length of 350 mm or more for medium- and large-screen liquid crystal displays, liquid crystal TVs and fluorescent lamps of 17 inches or more.

  In general, in a fluorescent lamp, mercury in a glass lamp tube easily moves due to the asymmetry of the lamp waveform at the time of lighting and the difference in tube wall temperature. For example, if there is a location where the temperature is locally low, mercury is concentrated in that location. On the other hand, a portion with a low mercury density occurs in a portion where the temperature is high, and in this portion, a pink discharge occurs at the beginning of lighting or a phenomenon in which the rise of luminance occurs slowly. Will be generated. In particular, in a backlight, a portion holding a lamp always has a heat dissipation effect, and therefore, mercury tends to be biased to a holding portion of a positive column portion having a temperature lower than that of an electrode.

  In this way, mercury has a tendency to diffuse depending on temperature (diffusion coefficient), but even if there is a heat radiating part such as a holding part in a state where it is lit by a backlight, the coldest part of the holding part is If it is 50 degreeC or more, as shown in the graph of FIG. 12, even if mercury is biased, a brightness | luminance rise will become quick with a diffusion coefficient, and pink discharge will not generate | occur | produce. In this way, it is preferable to perform the thermal design so that the lamp tube wall temperature is 50 ° C. or higher at a location where the temperature of the lamp tube can be the coldest part.

  As described above, in the backlight of this embodiment, the temperature difference in the tube axis direction can be reduced by raising the temperature of the coldest part of the lamp and the device, and the brightness difference in the tube axis direction of the lamp and the device can be reduced. Can be reduced. In addition, it is possible to provide a backlight device that can suppress the occurrence of pink discharge of the lamp and achieve a strong lamp usage even when dimming is used or the ambient temperature changes.

The front view of the backlight of one embodiment of this invention. The rear view of the backlight of the said embodiment. The front view which fractures | ruptures partially the curved tube fluorescent lamp used in the said embodiment. The front view which fractures | ruptures partially the other curved tube fluorescent lamp which can be used by the said embodiment. The graph which shows the pipe wall temperature distribution of the pipe-axis direction in the said embodiment. The graph which shows the luminance distribution of the pipe-axis direction in the said embodiment. The graph which compared the pipe wall temperature according to size in a prior art example and the said embodiment. The graph which compared the board surface brightness according to size in a prior art example and the said embodiment. The graph which compared the tube wall temperature according to lamp length in a prior art example and the said embodiment. The graph which compared the board surface brightness according to lamp length in a prior art example and the said embodiment. The graph which shows the relationship between the temperature of mercury of a fluorescent lamp, and ultraviolet-ray luminous efficiency. The graph which shows the relationship between the tube wall temperature of a fluorescent lamp, and a pink discharge distance. The front view of the backlight of a prior art example. The rear view of the backlight of a prior art example. The graph which shows the tube wall temperature according to size in the backlight of a prior art example. The graph which shows the board surface brightness according to size in the backlight of a prior art example. The graph which shows the pipe wall temperature distribution of the pipe-axis direction in the backlight of a prior art example. The graph which shows the luminance distribution of the tube-axis direction in the backlight of a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Curved tube fluorescent lamp 10A Electrode side edge part 10B Curved part side edge part 11 Frame 17 Inverter 18 Reflective case 19 Transformer 20A, 20B Rubber holder

Claims (4)

A phosphor film is formed on the inner wall of the glass lamp tube, and one or more kinds of rare gases, or mercury and one or more kinds of rare gases are sealed inside the glass lamp tube, and the introduction lines are hermetically sealed at both ends of the glass lamp tube. Sealing, connecting an electrode to the end of the lead-in wire inside the glass lamp tube, connecting a power supply lead to the outer end of the lead-in wire, and connecting the glass lamp tube to a C-tube or U-tube A plurality of fluorescent lamps formed on a curved pipe,
The fluorescent lamps of the curved lamps of the plurality of lamps are arranged on the front side of the reflective case having good thermal conductivity so that the electrode end side and the bent end side are alternately arranged,
Each of the inverters for supplying a high voltage to each of the plurality of fluorescent lamps is arranged at a position directly behind the electrode portion of each fluorescent lamp on the back side of the reflecting case. A phosphor film is formed on the inner wall of the glass lamp tube, and one or more kinds of rare gases or mercury and one or more kinds of rare gases are sealed inside the glass lamp tube, and both ends of the glass lamp tube are closed. A plurality of fluorescent lamps in which external electrodes are arranged on the outer surfaces of both ends of the glass lamp tube, and the glass lamp tube is formed as a curved tube of a C tube or a U tube;
The fluorescent lamps of the curved lamps of the plurality of lamps are arranged on the front side of the reflective case so that the electrode end side and the bent end side are alternately arranged,
Each of the inverters for supplying a high voltage to each of the plurality of fluorescent lamps is arranged at a position directly behind the electrode portion of each fluorescent lamp on the back side of the reflecting case.   The illumination device according to claim 1 or 2, wherein the size of the illumination surface is 17 inches or more and the effective light emission length of the lamp is 350 mm or more. The lighting device according to any one of claims 1 to 3, wherein the coldest tube wall temperature of each fluorescent lamp is maintained at 50 ° C or higher even at the lower limit of the operating temperature range.

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