JP2005251425A - Cold cathode fluorescent lamp and backlight unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cold cathode fluorescent lamp capable of reducing ultraviolet-ray emission amount for long period and preventing a peripheral member from ultraviolet-ray deterioration caused by the ultraviolet-ray emission when utilized as a backlight unit. <P>SOLUTION: The cold cathode fluorescent lamp 12 is structured by forming a phosphor film 2 on its inner surface, sealing a discharging media in a glass bulb 1, sealing both end parts of the glass bulb so that electrodes 3 face each other, and by forming coating film 12 composed of a polymer compound containing benzotriazole group ultraviolet-ray absorber and cesium oxide on outer surface of the glass bulb. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a cold cathode fluorescent lamp and a backlight unit.

  Conventionally, a cold cathode fluorescent lamp 10 used as a backlight light source of a liquid crystal display device or a light source of a small illumination device has a phosphor film 2 formed on the inner wall surface of a glass bulb 1 made of borosilicate as shown in FIG. The discharge medium is enclosed in the glass bulb 1, and the electrodes 3 are sealed so as to be opposed to each other at both ends of the glass bulb 1, respectively. The electrode 3 is integrally joined to the lead-in wire 4 and is attached together with the lead-in wire 4 by covering the end of the glass bulb 1 with the bead glass 5 and heating and sealing the bead glass 5 to the end of the glass bulb 1. It is what was done.

  In such a conventional cold cathode fluorescent lamp 10, borosilicate glass having a thermal expansion coefficient of 43 to 55 × 10 −7 / ° C. sealed with kovar or tungsten is used for the glass bulb 1. The light emission principle is that a discharge medium enclosed in the glass bulb 1 is discharged by applying a high voltage between the opposing electrodes 3 and 3 through the discharge space in the glass bulb 1 at both ends of the glass bulb 1. Among them, mercury is excited to emit ultraviolet rays, and the ultraviolet rays are applied to the phosphor coating 2 formed on the inner wall surface of the glass bulb 1 to emit visible light.

  Such a cold cathode fluorescent lamp 10 emits a large amount of ultraviolet rays when emitting light. Therefore, for example, when it is incorporated in a backlight unit as a backlight light source, a large amount of ultraviolet rays emitted from the cold cathode fluorescent lamp 10 are continuously irradiated to peripheral members such as a light guide plate that is a member constituting the backlight unit. There is a problem in that the peripheral member is deteriorated in a short period of time by ultraviolet rays due to the lighting.

  In order to solve such a conventional technical problem, a cold cathode fluorescent lamp 11 having a configuration shown in FIG. 7 has also been proposed. In the cold cathode fluorescent lamp 11 shown in FIG. 7, the internal structure of the glass bulb 1 is the same as that shown in FIG. A polymer compound film 6 containing an absorbent is formed.

  However, even in the cold cathode fluorescent lamp 11 in which a coating film of a polymer compound containing such a benzotriazole-based ultraviolet absorber is formed on the outer peripheral surface of the glass bulb, the coating film 6 of the polymer compound is rapidly deteriorated, and ultraviolet There was still a problem that the absorption capacity deteriorated with time and ultraviolet rays began to be gradually emitted while the lamp was lit, and the light guide plate constituting the backlight unit was deteriorated by ultraviolet irradiation.

  The present invention has been made in view of the above-described conventional technical problems, and can reduce the amount of ultraviolet rays emitted over a long period of time. It aims at providing the cold cathode fluorescent lamp which can suppress degradation.

  Another object of the present invention is to provide a backlight unit that incorporates such a cold-cathode fluorescent lamp and has little deterioration with time of peripheral members due to ultraviolet emission, and can be used for a long time without replacing the members.

  In the cold cathode fluorescent lamp according to the first aspect of the present invention, a phosphor film is formed on the inner wall surface of the glass bulb, a discharge medium is enclosed in the glass bulb, and electrodes are opposed to each other at both ends of the glass bulb. It is sealed, and a coating film of a polymer compound containing a benzotriazole ultraviolet absorber and cerium oxide is formed on the entire outer surface of the glass bulb.

  According to a second aspect of the present invention, in the cold cathode fluorescent lamp of the first aspect, the coating of the polymer compound has a thickness of 30 μm or less.

  A backlight unit according to a third aspect of the invention is characterized in that the cold cathode fluorescent lamp of the first or second aspect is used as a backlight light source for a liquid crystal screen.

  According to the cold cathode fluorescent lamp of the present invention, the coating of a polymer compound containing a benzotriazole-based ultraviolet absorber and cerium oxide is formed on the entire outer surface of the glass bulb, so that the ultraviolet light generated when the lamp is lit is benzotriazole. Can be absorbed by a coating of a polymer compound containing an ultraviolet absorber and cerium oxide, and the absorption performance can be maintained over a long period of time, and as a result, the UV cut performance during lighting can be maintained over a long period of time. Therefore, when used as a backlight light source of a liquid crystal display device or a light source of the illuminating device, deterioration of the peripheral members over time due to ultraviolet rays does not occur over a long period of time.

  Further, according to the backlight unit of the present invention, a cold cathode fluorescent lamp in which a coating of a polymer compound containing a benzotriazole-based ultraviolet absorber and cerium oxide is formed on the entire outer surface of the glass bulb is used as a backlight light source. Accordingly, since the cold cathode fluorescent lamp maintains the ultraviolet ray cutting performance for a long period of time, it is less likely to deteriorate with time due to the ultraviolet irradiation of the light guide plate and other peripheral members, and can be used for a long period of time without replacing the member.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows the structure of a cold cathode fluorescent lamp according to one embodiment of the present invention. In the cold cathode fluorescent lamp 12 of the present embodiment, the phosphor coating 2 is formed on the inner wall surface of the glass bulb 1 made of borosilicate, as in the conventional example shown in FIGS. The discharge medium is sealed, and the electrodes 3 are sealed so as to face each other at both ends of the glass bulb 1. The electrode 3 is integrally joined with the lead-in wire 4, covered with a bead glass 5, and attached to the end of the glass bulb 1 by heating and sealing the bead glass 5 together with the lead-in wire 4. Is.

  The cold cathode fluorescent lamp 12 having such a structure is discharged by applying a high voltage between the opposing electrodes 3 and 3 through the discharge space in the glass bulb 1 at both ends of the glass bulb 1 as in the conventional example. The mercury in the discharge medium enclosed in the glass bulb 1 is excited to emit ultraviolet rays, and the ultraviolet rays are applied to the phosphor coating 2 formed on the inner wall surface of the glass bulb 1 to emit visible light. And become a light source.

  The ultraviolet rays generated during the light emission are absorbed by the polymer compound film 60 on the outer surface of the glass bulb 1 and cut so as not to be emitted outside. As a result, when the cold cathode fluorescent lamp 12 of the present embodiment is used as a backlight light source of a liquid crystal display device, the amount of ultraviolet light irradiated to the light guide plate and other peripheral members is small, and deterioration over time can be suppressed. . Moreover, in the cold cathode fluorescent lamp 12 of the present embodiment, the polymer compound film 60 for absorbing ultraviolet rays uses a material containing a benzotriazole-based ultraviolet absorbent and cerium oxide. It can be maintained for a longer period than the triazole-based ultraviolet absorber alone, and when incorporated in a backlight unit or other lighting device, the life of the device can be extended.

  In the present embodiment, the amount of cerium oxide added to the benzotriazole-based ultraviolet absorber in the polymer compound coating 60 is preferably 1 to 2%. This is because if the content of cerium oxide exceeds 2%, the dispersibility becomes poor, and if it is 1% or less, there is no effect of prolonging the life.

  Moreover, the film thickness of the polymer compound film 60 and the experimental results are the graphs shown in FIG. In this case, the amount of cerium oxide added is 2%, and the glass bulb 1 has an outer diameter of 2.6 mm, an inner diameter of 2.0 mm, and an electrode outer diameter of 1.7 mm. The discharge medium is a rare gas mixed gas of mercury and Ne—Ar.

  As shown in the graph of FIG. 2, the polymer compound film 60 of the present invention has a high UV absorption effect even when the film thickness is 1 μm. When the film thickness is 30 μm, the initial luminance factor is when there is no film. Compared to 5%, it was 95%. From this experimental result, it is preferable that the film thickness of the polymer compound film 60 is preferably 1 μm to 30 μm when the decrease in the initial luminance rate is set to 5% in order to improve the performance of ultraviolet ray cutting while maintaining the initial luminance rate. I understood.

  Next, a backlight unit according to a second embodiment of the present invention will be described with reference to FIG. The backlight unit of the present embodiment is characterized by using the cold cathode fluorescent lamp 12 of the first embodiment as a backlight light source. The liquid crystal screen, the reflector, the light guide plate, and the like are all the same as those used in the past, and the fluorescent lamp is constructed by replacing the first embodiment with the conventional fluorescent lamp. is there.

  The backlight unit of the present embodiment is an edge type, and a reflector 22 having a U-shaped groove or a U-shaped groove along the edge of the acrylic light guide plate 21 is opened so that the groove faces the edge of the light guide plate 21. Further, two cold cathode fluorescent lamps 12 are inserted into the reflector 22 in parallel as light sources. Further, a reflective sheet 24 is applied to the rear surface side of the light guide plate 21, and a light diffusion sheet 25 and a light collecting sheet 26 are disposed on the front surface side.

  As described above, in the backlight unit according to the second embodiment, the cold cathode fluorescent lamp 12 according to the first embodiment is used as a backlight light source. Has the advantage that it can be used for a long time.

  Next, a backlight unit according to a third embodiment of the present invention will be described with reference to FIG. This backlight unit is of a direct type backlight system, and has a structure in which a plurality of cold cathode fluorescent lamps 12 are accommodated in a reflective case 201 as light sources and are reinforced by a back frame 202 and a front frame 203. In the reflection case 201, a reflector sheet or plate material having a light reflecting action, or a resin molded product is accommodated so as to be close to or in contact with the back surface of the lamp 12.

  Even in the backlight unit having such a configuration, the use of the cold cathode fluorescent lamp 12 of the first embodiment as a backlight light source reduces the amount of emitted ultraviolet rays, so that the reflector sheet, the plate material and other peripheral members are made of ultraviolet rays. The degree of deterioration is small, and there is an advantage that it can be used for a long time.

  FIG. 5 shows a cold cathode fluorescent lamp 12 according to an embodiment of the present invention, a lamp 10 not provided with the conventional polymer compound coating 6 shown in FIG. 6, and a conventional benzotriazole ultraviolet absorber shown in FIG. The result of having measured the plate | board surface luminance rate of the backlight unit for liquid crystal display devices which uses each of the single polymer compound film 6 and the lamp | ramp 11 which provided in the outer surface of the glass bulb 1 as a light source is shown.

  As shown in this graph, when a conventional product that does not take measures against ultraviolet rays is used as a light source, the luminance rate is reduced to 50% at 3000 hours, and when a conventional product that takes measures against ultraviolet rays is used as a light source, 4000 is used. While the luminance factor of 50% was divided when the time elapsed, in the case of the product of the present invention, the plate surface luminance factor could be maintained at 50% or more even after the lapse of 5000 hours.

1 is a cross-sectional view in which a part of the cold cathode fluorescent lamp of the first embodiment of the present invention is cut away. The graph of the measurement result of the brightness | luminance according to the film thickness of a polymer compound film in the said embodiment, and an ultraviolet cut rate. The disassembled perspective view of the backlight unit of the edge light system of the 2nd Embodiment of this invention. The exploded perspective view of the direct-type backlight type backlight unit of the 3rd Embodiment of this invention. The graph of the brightness maintenance factor characteristic of the backlight unit of the said embodiment. Sectional drawing of the cold cathode fluorescent lamp of a prior art example. Sectional drawing of the cold cathode fluorescent lamp of another conventional example.

Explanation of symbols

1 Glass Bulb 2 Phosphor Film 3 Electrode 12 Cold Cathode Fluorescent Lamp 60 Polymer Compound Film

Claims (3)

A phosphor film is formed on the inner wall surface of the glass bulb,
A discharge medium is enclosed in the glass bulb,
The electrodes are sealed so that the electrodes face each other at both ends of the glass bulb,
A cold cathode fluorescent lamp, wherein a coating of a polymer compound containing a benzotriazole-based ultraviolet absorber and cerium oxide is formed on the entire outer surface of the glass bulb.   2. The cold cathode fluorescent lamp according to claim 1, wherein the polymer compound film has a thickness of 30 [mu] m or less. A backlight unit comprising the cold cathode fluorescent lamp according to claim 1 or 2 as a backlight light source for a liquid crystal screen.

Images