JP2005056707A - Cold-cathode fluorescent lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent deterioration of a peripheral member caused by an ultraviolet ray leaking to the outside by improving the composition of a glass lamp vessel 12 to extend a service life. <P>SOLUTION: This cold-cathode fluorescent lamp 11 is so structured that a phosphor layer 50 is formed on an inside wall surface of the glass lamp vessel 12; mercury and a rare gas 50 is enclosed in the lamp vessel; and a pair of electrodes 20 are sealed at both ends of the lamp vessel. An appropriate quantity of CeO2 is included in borosilicate glass of a material of the lamp vessel 12 to reduce the amount of an ultraviolet ray radiated to the outside from the lamp. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an example cathode fluorescent lamp used as, for example, a liquid crystal backlight light source or a light source for small illumination.

  FIG. 5 shows a conventional cold cathode fluorescent lamp 15. The cold cathode fluorescent lamp 15 has a phosphor layer 50 formed on the inner wall surface of the glass lamp vessel 10, and mercury and a rare gas are enclosed in the lamp vessel 10 as a filler 60. In this structure, a pair of electrodes 20 is sealed. Lead wires 30 are led out of the lamp vessel 10 from the electrodes 20 at both ends.

The material of the glass lamp vessel 10 is borosilicate glass having a thermal expansion coefficient of 43 to 55 × 10 ⁻⁷ / ° C. for sealing Kovar or tungsten.

  The light emission principle of the cold cathode fluorescent lamp 15 having such a structure is that a voltage is applied between the electrodes 20 to generate a discharge in the glass lamp vessel 10 and excite mercury enclosed in the lamp vessel 10. Ultraviolet rays are generated, and the phosphors in the phosphor layer 50 are excited by the ultraviolet rays to generate visible light, which is emitted outside the lamp vessel 10.

  The conventional cold cathode fluorescent lamp 15 shown in FIG. 5 has a problem in that peripheral members such as a light guide plate are likely to be deteriorated by irradiation of ultraviolet rays leaking from the lamp vessel 10.

  As a countermeasure for preventing such leakage of ultraviolet rays, a cold cathode fluorescent lamp 16 having a configuration shown in FIG. 6 has been proposed. The proposed cold cathode fluorescent lamp 16 is obtained by forming a protective film 80 between the phosphor layer 50 and the inner peripheral surface of the glass lamp vessel 10 with respect to the configuration of the conventional example shown in FIG. is there. The protective film 80 is made of aluminum oxide, yttrium oxide, zinc oxide, cerium oxide, or the like.

  However, in the conventionally proposed cold cathode fluorescent lamp 16 shown in FIG. 6, the manufacturing process becomes complicated by forming the protective film, and the yield deteriorates due to variations in the film thickness of the protective film. However, there is a problem that the manufacturing cost becomes high.

  The present invention has been made in view of the above-described conventional technical problems, and by improving the composition of the glass lamp vessel, it is possible to prevent deterioration of peripheral members due to ultraviolet rays leaking to the outside. An object is to provide a cathode fluorescent lamp.

The invention of claim 1 is a cold cathode fluorescent lamp in which a phosphor layer is formed on the inner wall surface of a glass lamp vessel, mercury and a rare gas are enclosed in the lamp vessel, and a pair of electrodes are sealed at both ends of the lamp vessel. In the lamp, CeO ₂ is contained in borosilicate glass which is a material of the glass lamp vessel.

According to a second aspect of the invention, in the cold cathode fluorescent lamp of the first aspect, the CeO ₂ content is 1.5% to 2.5% of the borosilicate glass.

  According to the present invention, it is possible to prevent deterioration of peripheral members due to ultraviolet rays leaking to the outside by improving the composition of the glass lamp vessel, and as a result, the plate surface luminance factor when incorporated in a backlight or the like is improved. The life can be extended.

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

  FIG. 1 shows a cold cathode fluorescent lamp 11 according to a first embodiment of the present invention. In the cold cathode fluorescent lamp 11 of this embodiment, a phosphor layer 50 is formed on the inner wall surface of a glass lamp vessel 12, and a mixed gas of mercury and Ne—Ar is enclosed as a filler 60 in the lamp vessel 12, In this structure, a pair of electrodes 20 are sealed at both ends of the lamp vessel 10. Lead wires 30 are led out of the lamp vessel 12 from the electrodes 20 at both ends.

The material of the glass lamp vessel 12 contains CeO ₂ in a predetermined ratio with respect to the same borosilicate glass as in the past. The CeO ₂ content is 1.5% to 2.5% of the borosilicate glass. If the content is lower than 1.5%, no significant effect appears. On the other hand, if the content exceeds 2.5%, the visible light transmittance is lowered, and the luminous flux of the lamp is lowered.

  The light emission principle of the cold cathode fluorescent lamp 11 having such a configuration is the same as that of the conventional example. By applying a voltage between the electrodes 20, a discharge is generated in the glass lamp container 12 and enclosed in the lamp container 12. Mercury is excited to generate ultraviolet rays, and the ultraviolet rays are used to excite the phosphor of the phosphor layer 50 to generate visible light, which is emitted outside the lamp vessel 12.

[Example]
Example products of the present invention were provided with electrodes having an outer diameter of 1.7 mm and an electrode length of 4.0 mm at both ends inside a tubular glass lamp vessel having an outer diameter of 2.6 mm, an inner diameter of 2.0 mm, and a glass tube length of 300 mm. Is. A three-wavelength phosphor having a thickness of 20 μm was formed as a phosphor layer on the inner wall surface of the tubular glass lamp vessel. Further, a mixed gas of Ne—Ar (composition ratio: Ne / Ar = 90 mol% / 10 mol%) as a filler was enclosed at an enclosure pressure of 8 kPa, and 3 mg of mercury was also enclosed.

Then, in the embodiment product of the present invention as a material of the glass lamp vessel, it was used which contains a CeO ₂ 2.0% borosilicate glass.

[Comparative example]
As a comparative example, a conventional product having the configuration shown in FIG. 5 was used. The dimensions, fillers, and specifications of the phosphor layer are the same as in the example product. However, the material of the glass lamp vessel is 100% borosilicate glass and does not contain CeO2.

  About the example product of this invention, and the conventional example product which is a comparative example, the characteristic of lighting time and plate | board surface brightness maintenance factor was measured. The result was shown in FIG. From this, it was proved that the example product of the present invention has improved the plate surface luminance maintenance rate compared with the conventional product. This is because the deterioration of the peripheral members due to the ultraviolet rays generated from the lamp is improved.

  Next, a cold cathode fluorescent lamp according to a second embodiment of the present invention will be described. The cold cathode fluorescent lamp 13 of the second embodiment shown in FIG. 3 is characterized by a protective layer 81 formed on the inner peripheral wall of the tubular glass lamp vessel 10.

  In recent years, a cold cathode fluorescent lamp 15 as shown in FIG. 5 has been adopted as a backlight of a liquid crystal display such as a television and a monitor. When this cold cathode fluorescent lamp 15 is used at a low current, Since the heat generation is low, as shown in the graph of FIG. 7, it is used in a temperature state where the luminous efficiency does not rise to the optimum temperature. In addition, at present, in order to improve the efficiency of the cold cathode fluorescent lamp, the electrode 20 is formed of a material such as Mo, Ta, and W having a low cathode fall voltage. As a result, the heat generation of the electrode 17 is further reduced. It has become temperature. Therefore, in order to optimize the luminous efficiency, it is necessary to increase the lamp tube wall temperature.

  The cold cathode fluorescent lamp 13 of the second embodiment of the present invention shown in FIG. 3 is characterized by a structure suitable for raising the lamp tube wall temperature, and is different from the configuration of the conventional example shown in FIG. Then, instead of the protective film 80, a silica alumina based ceramic protective film 81 is used, the ceramic protective film 81 is formed on the inner wall surface of the glass lamp vessel 10, and the phosphor layer 70 is formed on the inner peripheral surface thereof. It is. In FIG. 3, elements common to the example cathode fluorescent lamp shown in FIGS. 5 and 6 are denoted by the same reference numerals.

  Thus, by forming the silica-aluminum-based ceramic protective film 81 on the inner wall surface of the tubular glass lamp vessel 10, it is possible to reduce the heat radiation generated by the electrode 20 to the outside of the tube and raise the tube temperature. The luminous efficiency can be improved.

  Specifically, as an embodiment of the present invention, a glass tube outer diameter φ4.0 mm, an inner diameter φ3.0 mm, and a glass tube length 300 mm made of borosilicate glass are used as electrodes, an electrode outer diameter φ2.4 mm, An electrode having an electrode length of 4.0 mm was prepared. A silica-alumina ceramic protective film was formed on the inner wall surface of the tubular glass lamp vessel, and a phosphor layer was formed on the inner peripheral surface. The phosphor layer is a three-wavelength phosphor, and its thickness is 20 μm. Further, a mixed gas of Ne—Ar (composition ratio: Ne / Ar = 90 mol% / 10 mol%) as a filler was enclosed at an enclosure pressure of 8 kPa, and 3 mg of mercury was also enclosed.

  As a comparative example, a conventional product having the configuration shown in FIG. 5 was used. This conventional example product has the same dimensions, fillers, and phosphor layer specifications as the example product, but the ceramic protective film is not formed on the inner wall surface of the tubular glass lamp vessel as in the example product of the present invention. A phosphor layer is directly formed.

  FIG. 4 shows the results of measurement of the relationship between the lamp current and the brightness of the example product of the present invention and the conventional product. From this result, it can be seen that in the case of the example product of the present invention, the same emission luminance can be obtained with the lamp current lower than that of the conventional product. In other words, the luminous efficiency of the example product of the present invention is improved as compared with the conventional product.

1 is an axial sectional view of a cold cathode fluorescent lamp according to a first embodiment of the present invention. The graph of the result of having measured the relationship between lighting time and a plate | board surface luminance maintenance factor about the Example product of the 1st Embodiment of this invention, and the conventional example product which is a comparative example. The axial direction sectional drawing of the cold cathode fluorescent lamp of the 2nd Embodiment of this invention. The graph of the result of having measured the relationship between a lamp current and a brightness | luminance about the Example product of the 2nd Embodiment of this invention, and the conventional example product which is a comparative example. The axial direction sectional drawing of the cold cathode fluorescent lamp of a prior art example. FIG. 6 is an axial sectional view of another conventional cold cathode fluorescent lamp. The graph which shows the relationship between the lamp tube wall temperature and luminous efficiency of a common cold cathode fluorescent lamp.

Explanation of symbols

11 Cold Cathode Fluorescent Lamp 12 Glass Lamp Container 20 Electrode 30 Lead-in Line 50 Phosphor Layer 60 Filler

Claims (2)

In a cold cathode fluorescent lamp in which a phosphor layer is formed on the inner wall surface of a glass lamp vessel, mercury and a rare gas are enclosed in the lamp vessel, and a pair of electrodes are sealed at both ends of the lamp vessel.
A cold cathode fluorescent lamp characterized in that CeO ₂ is contained in borosilicate glass which is a material of the glass lamp container. The cold cathode fluorescent lamp according to claim 1, wherein the CeO ₂ content is 1.5% to 2.5% of the borosilicate glass.

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