JP2006190537A - Cold-cathode fluorescent lamp and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cold-cathode fluorescent lamp and a liquid crystal display using the same with consumption power reduced and life elongated. <P>SOLUTION: The cold-cathode fluorescent lamp equipped with a phosphor layer 9 formed on an inner wall of a glass tube 10, inside of which a rare gas and mercury are sealed, and at both ends of the glass tube 10, lead-in wires 11 are airtightly sealed. Each tip part of the lead-in wires 11 is connected to an electrode 12. A carbon film made of carbon nano-wall 13 is formed on the surface of the electrode 12. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a cold cathode fluorescent lamp and a liquid crystal display device using the same.

  The cold cathode fluorescent lamp CCFL (Cold Cathode Fluorescent Lamp) has a simple structure and is easy to miniaturize (capillary) and has a long life, so it is used for backlights of liquid crystal display devices (for example, , See Patent Document 1).

  FIG. 4 is a cross-sectional view showing a schematic configuration of such a cold cathode fluorescent lamp.

  A rare gas such as neon or argon and mercury are enclosed in the glass tube 10, and a phosphor layer 9 that emits light by ultraviolet rays is provided on the inner wall surface. A pair of lead wires 11 are sealed at both ends of the glass tube 10 so as to face each other, and an electrode 12 is provided at the tip of each lead wire 11.

  Such a cold cathode fluorescent lamp has a high cathode fall voltage (lamp voltage) and a large electrode loss. Therefore, in order to reduce the electrode loss and reduce the power consumption, a cesium compound such as cesium oxide is formed on the surface of the electrode. Is applied to lower the discharge start voltage.

  However, cesium compounds are vulnerable to sputtering, and when the cesium compound is sputtered from the electrode surface while the fluorescent lamp is lit, the cathode fall voltage increases, electrode loss increases, and cold cathode fluorescence increases. There is a problem that the power consumption of the lamp increases.

In addition, since the mercury enclosed in the glass tube is consumed by the sputtering, there is a problem that the life of the cold cathode fluorescent lamp is shortened.
JP 2004-163887 A

  Accordingly, a main problem to be solved by the present invention is to provide a cold cathode fluorescent lamp that reduces power consumption and extends its life, and a liquid crystal display device using the same.

  The cold cathode fluorescent lamp of the present invention is a cold cathode fluorescent lamp comprising a glass tube and a pair of electrodes enclosed in the glass tube, wherein a carbon film is formed on the surface of the electrode.

  The carbon film is preferably made of carbon nanowalls or carbon nanotubes, and the electrode is preferably made of nickel, iron, chromium or an alloy thereof.

  The carbon film is preferably formed by a CVD method.

  According to such a configuration, a carbon film having a low work function such as carbon nanowall and a low sputtering rate is formed on the electrode surface, so that the cathode fall voltage can be reduced to reduce power consumption and sputtering. It is possible to extend the life by suppressing the above.

  Further, the liquid crystal display device of the present invention includes the cold cathode fluorescent lamp according to the present invention as a backlight.

  Therefore, power consumption can be reduced and the life can be extended.

  According to the present invention, since a carbon film having a low work function such as carbon nanowall and a low sputtering rate is formed on the electrode surface, the cathode fall voltage can be reduced to reduce power consumption, Sputtering can be suppressed and the life can be extended.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic cross-sectional view of a main part of a backlight type liquid crystal display device according to one embodiment of the present invention.

  The liquid crystal display device of this embodiment includes a flat liquid crystal panel 1 and an edge light type backlight unit 2 on the back side thereof.

  The liquid crystal panel 1 is configured by sealing a liquid crystal layer between a pair of substrates.

  The backlight unit 2 includes a cold cathode fluorescent lamp 3 according to the present invention, a reflector 4 that reflects light from the cold cathode fluorescent lamp 3, and light emitted from the cold cathode fluorescent lamp 3 as a diffusion sheet 5 and a prism. A light guide plate 7 that leads to the liquid crystal panel 1 through the sheet 6 and a reflection plate 8 disposed on the back side of the light guide plate 7 are provided, and the light from the cold cathode fluorescent lamp 3 is efficiently transmitted to the liquid crystal panel 1. It is comprised so that it can irradiate.

  FIG. 2 is a cross-sectional view of the cold cathode fluorescent lamp 3 of FIG.

  The cold cathode fluorescent lamp 3 of this embodiment includes a glass tube 10 in which a rare gas such as an argon gas and mercury are enclosed, and a phosphor layer 9 that emits light by ultraviolet rays is provided on the inner wall. The glass tube 10 has a tube diameter (inner diameter) of, for example, about 1.2 to 4.8 mm, and a tube length of, for example, about 40 to 800 mm.

  At both ends of the glass tube 10, lead wires 11 connected to a lamp lighting circuit (not shown) pass in the axial direction and are hermetically sealed, respectively. An electrode 12 is provided.

  The electrode 12 is formed in a columnar shape, for example, and is welded and electrically connected to the lead-in wire 11.

  In this embodiment, the electrode 12 has a diameter of, for example, about 0.7 to 2.1 mm, and a length of, for example, about 2 to 6 mm.

  The electrode 12 may have a cylindrical shape, a rod shape, a plate shape, a spiral shape, or the like.

  In this embodiment, the electrode 12 is made of nickel, for example, and a carbon nanowall 13 is formed on the surface of the electrode 12.

  The carbon nanowall 13 has a low work function, can lower the cathode fall voltage (lamp voltage), has a low sputtering rate, and suppresses consumption of itself and consumption of mercury enclosed in the glass tube 10. To extend the service life.

  This carbon nanowall 13 is formed as follows using, for example, a DC plasma CVD apparatus.

  FIG. 3 is a diagram showing a DC plasma CVD apparatus. In this DC plasma CVD apparatus, a cathode electrode plate 15 and an anode electrode plate 16 are arranged in a vacuum chamber 14 so as to be opposed to each other in the vertical direction to constitute a parallel plate electrode, and between the anode electrode plate 16 and the cathode electrode plate 15. In this configuration, a DC voltage is applied from a DC power source 17. The vacuum chamber 14 includes an exhaust port 18 to which a vacuum pump (not shown) is connected, and a gas introduction port 19 for introducing a raw material gas.

  The nickel electrode 12 described above is placed on a substrate (not shown) on the cathode electrode plate 15. For example, a mixed gas of hydrogen and methane or a mixed gas of hydrogen and carbon monoxide is used as a raw material gas, and the raw material gas is introduced into the vacuum chamber 14 from the gas inlet 19 and a direct current power source A DC voltage is applied between the anode electrode plate 16 and the cathode electrode plate 15 by 17. As a result, high temperature plasma of about 600 ° C. to 900 ° C. is generated in the vacuum chamber 14, and the electrode 12 is exposed to the high temperature plasma, thereby forming a carbon nanowall on the electrode 12.

  The carbon nanowall is preferably grown to a length of about 2 to 4 μm, for example.

  In the cold cathode fluorescent lamp 3 including the electrode 12 having the carbon nanowall 13 formed on the surface as described above, when an AC voltage is applied between the pair of electrodes 12, electrons are emitted from one electrode 12. Electrons collide with mercury atoms in the glass tube 10 to generate ultraviolet rays. The ultraviolet rays excite the phosphor 9 formed on the inner wall of the glass tube 10 to obtain visible light.

  Next, Table 1 shows the result of comparing the characteristics of the cold cathode fluorescent lamp according to the present invention in which carbon nanowalls are formed on the electrode surface and the conventional cold cathode fluorescent lamp.

この表１において、従来例１は、パソコンのバックライトとして用いられる冷陰極蛍光ランプを、従来例２は、大型液晶のパックライトとして用いられる冷陰極蛍光ランプを、従来例３は、電極表面にセシウム化合物を塗布したものを、それぞれ示している。

In Table 1, Conventional Example 1 is a cold cathode fluorescent lamp used as a backlight of a personal computer, Conventional Example 2 is a cold cathode fluorescent lamp used as a pack light of a large liquid crystal, and Conventional Example 3 is on the electrode surface. Each of the cesium compounds applied is shown.

  As can be seen from Table 1, in the conventional examples 1 to 3, the efficiency is 47 (lm / W), whereas in the example of the present invention, the efficiency is 56 (lm / W), and the efficiency is improved. In the conventional example, the lifetime is 5000 to 40000 (h), whereas in the embodiment of the present invention, the lifetime is 80000 (h).

  As described above, the cold cathode fluorescent lamp according to the present invention can reduce power consumption and increase the efficiency, and is less prone to sputtering and can have a long life.

  In the above-described embodiment, the carbon nanowall is formed. However, the present invention is not limited to the carbon nanowall, and other carbon-based materials such as carbon nanotubes and diamond-like carbon may be formed.

  Further, although the film is formed by DC plasma CVD in the above-described embodiment, it is not limited to DC plasma CVD but may be formed by RF plasma CVD, thermal CVD, microwave plasma CVD, cathodic arc, or the like.

  The present invention is useful as a liquid crystal display device and a backlight thereof.

It is a schematic sectional drawing of the principal part of the liquid crystal display device which concerns on one embodiment of this invention. It is sectional drawing of the cold cathode fluorescent lamp of FIG. It is a schematic block diagram of DC plasma CVD apparatus. It is sectional drawing of the conventional cold cathode fluorescent lamp.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid crystal panel 3 Cold cathode fluorescent lamp 9 Phosphor layer 10 Glass tube 11 Lead-in line 12 Electrode 13 Carbon nanowall

Claims (5)

In a cold cathode fluorescent lamp comprising a glass tube and a pair of electrodes enclosed in the glass tube,
A cold cathode fluorescent lamp, wherein a carbon film is formed on the electrode surface.   The cold cathode fluorescent lamp according to claim 1, wherein the carbon film is made of carbon nanowalls or carbon nanotubes.   The cold cathode fluorescent lamp according to claim 1 or 2, wherein the electrode is made of nickel, iron, chromium, or an alloy thereof.   The cold cathode fluorescent lamp according to claim 1, wherein the carbon film is formed by a CVD method.   A liquid crystal display device comprising the cold cathode fluorescent lamp according to claim 1 as a backlight.

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