JP2005183269A - Cold cathode fluorescent lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cold cathode fluorescent lamp in which an intermediate electrode is prepared to eliminate the defect of unstable discharge due to current leakage from the lamp when a long-sized fluorescent lamp is used in a high frequency region of a low current region and to make it possible to discharge stably. <P>SOLUTION: A plurality of discharge paths are prepared by putting an intermediate electrode 19 in a glass tube 11 in the middle of electrodes 13 and 14 sealed at both ends of the glass tube 11. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a cold cathode fluorescent lamp used as a light source such as a liquid crystal display, an instrument display panel, or a signboard illumination.

  Conventionally, cold cathode fluorescent lamps are frequently used as backlights for liquid crystal displays, instrument display panels, notebook personal computers, and the like.

  As shown in FIG. 5, the cold cathode fluorescent lamp has a cylindrical glass tube 51 formed in a cylindrical shape, and the inner wall surface of the glass tube 51 is fluorescent with a thickness of about 20 to 30 μm. A body coat 52 is applied. A pair of electrodes 53 having the same material and the same surface area are disposed at both ends of the glass tube 51, and one end of an introduction wire 54 is connected to the electrode 53.

  The lead-in wire 54 is fixed to the sealing portions 56 at both ends of the glass tube 51 by a sealing material 55 made of frit glass or the like, and the other end is led out of the glass tube 51. Inside such a glass tube 51, a mixture of at least one kind of rare gas such as argon, neon, xenon and mercury is sealed as a discharge medium 57 to constitute a cold cathode fluorescent lamp.

  In the cold cathode fluorescent lamp configured in this way, an AC power source that generates a positive and negative symmetrical AC voltage is connected between the pair of electrodes 53, and the AC voltage excites mercury to generate ultraviolet rays. By irradiating the phosphor film 52, it is converted into visible light and emitted to the outside as illumination light with a sufficient amount of light.

  When such a cold cathode fluorescent lamp is configured as a backlight of a notebook computer, a fluorescent lamp having a length of about 300 mm and a current capacity of 6 mA or more is mainstream, whereas it is used for a television receiver. In this case, a fluorescent lamp having a current capacity of about 500 mm and a current capacity of about 5 mA or less is usually configured as a long fluorescent lamp of about 1,000 mm in a 40-inch class.

  However, when such a long fluorescent lamp is lit in a low current region, particularly at a high frequency, the fluorescent lamp having a length of 1,000 mm has a starting voltage of 1,500 V or more, a stable discharge voltage of 2, A voltage of 000 V or more is required, and for this reason, a high-power inverter is required.

  Furthermore, since the lamp voltage is 1,500 V or more, there is a problem that when the lamp is lit particularly in a high frequency region with a lamp current of 6 mA or less, current leakage from the lamp tends to occur and the discharge operation becomes unstable.

  In addition, FIG. 6 shows the result of investigating the lighting possible region when the lighting frequency and the lamp current are changed using a fluorescent lamp of 4φ × 1,000 mm as the fluorescent lamp. In the figure, a circled area indicates that lighting is possible, and a crossed area indicates that lighting is not possible. As can be seen from FIG. 6, since the lamp voltage is high, there is a lot of lamp current leakage, which makes it difficult to light in a high frequency region, particularly in a low current region.

  The present invention has been made to cope with such a problem. Even in a long cold cathode fluorescent lamp, by providing an intermediate electrode in the middle of both end electrodes, a stable discharge can be achieved even in a low current high frequency region. An object of the present invention is to provide a cold cathode fluorescent lamp particularly suitable for a long type.

  In the present invention, as a first means for solving the above-described problems, a discharge medium is sealed inside a cylindrical glass tube, and arranged at both ends inside the glass tube via lead wires communicating with the outside. In the cold cathode fluorescent lamp having a pair of electrodes, an intermediate electrode disposed inside the glass tube between the pair of electrodes is provided.

  As a second means for solving the above-mentioned problems, the present invention is characterized in that the intermediate electrode is connected to an introduction line that penetrates the side wall of the opposing glass tube and communicates with the outside. .

  As a third means for solving the above-mentioned problems, the present invention is characterized in that the glass tube is bent and the intermediate electrode is arranged at the bent portion.

  According to the present invention, since at least one intermediate electrode is disposed between a pair of electrodes disposed at both ends of the glass tube, it is possible to light even in a low current / high frequency region and to stabilize the discharge operation. Thus, a cold cathode fluorescent lamp that can be performed can be provided.

  Hereinafter, embodiments of a cold cathode fluorescent lamp according to the present invention will be described in detail with reference to the drawings.

  As shown in FIG. 1, the cold cathode fluorescent lamp according to the present invention has a cylindrical glass tube 11 having an outer diameter of 4.0 mm and an inner diameter of 3.0 mm, for example, formed in a cylindrical or rectangular tube shape. The phosphor tube 12 is deposited on the inner wall surface of the glass tube 11. A pair of cup-shaped electrodes 13 and 14 having an outer diameter of 3.0 mm, for example, made of metal, sintered metal, or the like formed in a cylindrical shape, a plate shape, or a columnar shape are disposed at both inner end portions of the glass tube 11. Has been.

  One end of an introduction line 15 is connected to the ends of the pair of electrodes 13 and 14, respectively, and the introduction line 15 is fixed to the enclosing portions 17 at both ends of the glass tube 11 by a sealing material 16 made of frit glass or the like. The other end is led out of the glass tube 11. Inside the glass tube 11 is sealed a discharge medium 18 made of a mixture of mercury and at least one kind of rare gas such as argon, neon, xenon and the like. An intermediate electrode 19 is disposed inside the glass tube 11 at an intermediate position of the glass tube 11, and the intermediate electrode 19 is connected to an introduction line 20 hermetically penetrating the corresponding side wall of the glass tube 11 to be cold cathode fluorescent light. It constitutes a lamp.

  The cold cathode fluorescent lamp configured in this manner is provided with an AC power source that generates an AC voltage that is symmetrical between positive and negative so that a discharge is generated between the pair of electrodes 13 and 14 and the intermediate electrode through a plurality of discharge paths. And between the intermediate electrode 19 and between the intermediate electrode and the other electrode 14, it is possible to drive efficiently.

  Here, a high voltage of 500 to 2,000 V is applied between the pair of electrodes 13 and 14 from the AC power source through the lead-in line 15 through the lead-in line 15 at a frequency of 20 to 100 kHz, and the intermediate electrode 19 is passed through the lead-in line 20. Grounded. As a result, discharge paths between the electrode 13 and the intermediate electrode 19 and between the intermediate electrode 19 and the electrode 14 are formed in the discharge space, and in order to discharge in these discharge paths, ultraviolet rays are radiated through the two discharge paths, and fluorescence is emitted. It is converted into visible light by the body coating 12. If such a cold cathode fluorescent lamp is employed, it is possible to obtain a sufficient amount of light as a light source such as a backlight.

  Here, as a fluorescent lamp, the fluorescent lamp according to the present invention of 4φ × 1,000 mm was used, and as a result of investigating the lighting possible region when the lighting frequency and the lamp current were changed, as shown in FIG. It turned out that lighting in the area is possible.

  Further, the number of intermediate electrodes 19 is not limited to one as long as it is between a pair of electrodes 13 and 14, but a plurality of, for example, three intermediate electrodes 19 are provided as shown in FIG. Is set to, for example, a ground potential, and an alternating current is provided between the left intermediate electrode 19 and one electrode 13, between the middle intermediate electrode 19 and the left and right intermediate electrodes 19, and between the right intermediate electrode 19 and the electrode 14. By wiring so that electric power is applied, it is possible to form a larger number of discharge paths, which is a preferable form in the case of a long type.

  Furthermore, as shown in FIG. 4, the glass tube 11 is bent and formed into a U-shape or a U-shape, and the intermediate electrode 19 is arranged in the bent portion, thereby forming a long type. This is effective as a measure for reducing the size in the length direction.

  The location and number of the intermediate electrodes 19 can be appropriately changed according to the form to be used, and the bent shape is L-shaped, U-shaped, U-shaped, etc. It can be applied to various forms.

1 is a cross-sectional view showing a first embodiment of a cold cathode fluorescent lamp according to the present invention. Explanatory drawing which shows the lighting possible area | region of the cold cathode fluorescent lamp which concerns on this invention. Sectional drawing which shows 2nd Embodiment of the cold cathode fluorescent lamp which concerns on this invention. Sectional drawing which similarly shows 3rd Embodiment of a cold cathode fluorescent lamp. Sectional drawing which shows the conventional cold cathode fluorescent lamp. Explanatory drawing which shows the lighting possible area | region of the conventional cold cathode fluorescent lamp.

Explanation of symbols

11: Glass tube 12: Phosphor 13: One electrode 14: Other electrode 15: Lead wire 18: Discharge medium 19: Intermediate electrode

Claims (3)

In the cold cathode fluorescent lamp having a pair of electrodes disposed via an introduction line communicating with the outside at both ends inside the glass tube, the discharge medium is sealed inside the cylindrical glass tube,
A cold cathode fluorescent lamp comprising an intermediate electrode disposed inside the glass tube between the pair of electrodes.   2. The cold cathode fluorescent lamp according to claim 1, wherein the intermediate electrode is connected to an introduction line that penetrates through a side wall of the opposing glass tube and communicates with the outside.   The cold cathode fluorescent lamp according to claim 1 or 2, wherein the glass tube is bent and the intermediate electrode is disposed at the bent portion.

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