JP2002237277A - Discharge tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a discharge tube suitable to a backlight for a liquid crystal display device, eliminating the possibility of leaking a ultraviolet ray causing the deterioration of a light diffusion plate. SOLUTION: The discharge tube 1 is constructed by applying a coating of a phosphor for generating a visible light with a waveband of 380 nm or more at a thickness of 30 μm or more on the whole outer periphery face of a ultraviolet discharge tube formed of a ultraviolet transmissive glass 2 to form a phosphor layer 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge tube which can be suitably used for a backlight of a liquid crystal display.

[0002]

2. Description of the Related Art Conventionally, a backlight of a liquid crystal display device is:
A structure in which a discharge tube as a light source is arranged on an end surface of a light diffusion plate made of acrylic resin or the like arranged on the back surface of the liquid crystal unit. As shown in FIG. 5, this discharge tube 20 has a glass layer 21 filled with an ultraviolet radiation gas such as mercury vapor, and a phosphor layer 22 which emits light when excited by ultraviolet light.
Is formed on the inner surface of the tube. 185 nm, 254 nm from the ultraviolet radiation gas by the discharge of the discharge tube
Ultraviolet light having a wavelength of m, 360 nm or the like is generated, and the ultraviolet light excites the phosphor to emit light including visible light, and this light becomes a backlight through a light diffusion plate. Visible light is a wavelength band of about 400 to 750 nm, at most 3
It is light in a wavelength band of 60 to 830 nm.

[0003]

However, in the above-described conventional discharge tube, the phosphor layer cannot be formed thick because of the structure in which the phosphor layer is coated on the inner surface of the glass tube. It has to be as thin as 10 μm at most,
In addition, since both ends of the glass tube are sealed off, the phosphor layers could not be applied to both end portions of the glass tube to be sealed off. For this reason, the light passes through both ends of the glass tube and the thin phosphor layer to reach 185 nm, 254 nm, and 360 nm.
Ultraviolet rays having a wavelength such as nm leaked to a certain extent. The leaked ultraviolet light, particularly ultraviolet light having a wavelength of 290 to 315 nm, causes white turbidity or cracks with time in the acrylic resin or the like as the light diffusion plate, and as a result, the irradiation light of the backlight is attenuated. Was.

Accordingly, an object of the present invention is to provide a discharge tube which can be suitably used for a backlight of a liquid crystal display device in which ultraviolet rays which deteriorate the light diffusion plate do not leak.

[0005]

In order to achieve the above object, a discharge tube according to the present invention is provided with a phosphor which generates visible light of a wavelength band of 380 nm or more over the entire outer peripheral surface of an ultraviolet discharge tube made of ultraviolet transmission glass. It is characterized by being coated to a thickness of 30 μm or more.

[0006] Alternatively, an ultraviolet absorber that transmits visible light is applied to the entire outer peripheral surface of an ultraviolet discharge tube having a glass surface coated with a phosphor.

[0007] The ultraviolet discharge tube is characterized in that it is used for a backlight of a liquid crystal display device.

[0008]

FIG. 1 shows a first embodiment of a discharge tube according to the present invention. A discharge tube 1 uses a glass tube 2 such as a quartz tube which transmits ultraviolet rays, and has mercury vapor sealed therein. With respect to the cold cathode discharge tube, 38
A phosphor layer 3 made of a phosphor that generates visible light in a wavelength band of 0 nm or more is provided.

In the present invention, the wavelength of 380 nm or more is used.
Phosphors that generate visible light in the wavelength band are listed below.
is there. Y (PV) O as red phosphor_Four: Eu, YV
O_Four: Eu, 3.5MgO.0.5MgF_Two・ GeO_Two:
Mg, (SrMg)_Three(PO_Four): Sn, Y_TwoO_Three: Eu,
CaSiO_Three: Pb, Mn and the like. Also green
As the phosphor, Zn_TwoSiO_Four: Mn, (CeTbM
n) MgAl ₁₁O₁₉, LaPO_Four: Ce, Tb, (Ce
Tb) MgAl₁₁O₁₉, Y_TwoSiO_Five: Ce, Tb, etc.
I can do it. Furthermore, blue (SrMg)_TwoP_TwoO₇: Eu,
Sr_TwoP_TwoO₇: Eu, Sr_TwoP_TwoO₇: Sn, Sr_Five(P
O_Four)_ThreeCl: Eu, (SrCaBa)_Five(PO_Four)_ThreeC
1: Eu, BaMg_TwoAl₁₆O₂₇: Eu, CaWO_Four, C
aWO_Four: Pb and the like. These three color phosphors
Can be selected and mixed as appropriate to produce various colors.
It becomes possible.

FIG. 2 is a graph showing Table 1 showing the relationship between the thickness of the phosphor layer and the intensity of ultraviolet light having a wavelength of 254 nm in the discharge tube having the composition of the present invention.
From the above, it can be seen that almost no ultraviolet light leaks.

[0011]

[Table 1]

FIG. 3 shows a second embodiment of the discharge tube according to the present invention. The discharge tube 4 uses the glass tube 5 such as the quartz tube which transmits ultraviolet light of the above-described first embodiment, and contains mercury therein. The phosphor layer 6 is formed on the entire outer peripheral surface of the glass tube 5 of the cold cathode discharge tube in which the vapor is sealed, and the surface of the phosphor layer 6 is coated with an ultraviolet absorber 7 that transmits visible light. The thickness of the phosphor layer 6 of the present embodiment may be 30 μm or less, and the emission of the phosphor may include ultraviolet rays having a wavelength of 380 nm or less. There is no danger of being absorbed and leaking.

(Embodiment 1) A phosphor layer 6 composed of a 30 μm white phosphor film of three colors is provided on the entire outer peripheral surface of a glass tube 5 and an acrylic resin clear (acryl clear 1000, Dai Nippon Paint) is provided thereon. Manufactured by VIOSORV 52
0 (benzotriazole type, manufactured by Kyodo Chemical Co., Ltd.) is coated with an ultraviolet absorbent 7 to which 0.5% is added to have a film thickness of 10 μm. In this cold cathode discharge tube, there is no leakage of ultraviolet light having a wavelength of 320 nm or less that deteriorates the acrylic resin.

(Embodiment 2) A phosphor layer 6 composed of a 35 μm white phosphor film of a mixture of three colors is provided on the entire outer peripheral surface of a glass tube 5 and an acrylic resin clear (Duracron Clear 200, Dainippon Japan) is provided thereon. UV absorber 7 to which 1% of RUMA-93 (benzotriazole type, manufactured by Otsuka Chemical Co., Ltd.) is added to a paint (made of paint) to have a film thickness of 10 μm. In this cold cathode discharge tube, there is no leakage of ultraviolet light having a wavelength of 320 nm or less that deteriorates the acrylic resin.

(Embodiment 3) A phosphor layer 6 composed of a 30 μm white phosphor film of three colors is provided on the entire outer peripheral surface of a glass tube 5 and an acrylic resin clear (acryl clear 1000, Dai Nippon Paint) Manufactured by VIOSORV 93
0 (phenyl acrylate, manufactured by Kyodo Chemical Co., Ltd.) is coated with an ultraviolet absorbent 7 to which 1% is added, and the film thickness is 10 μm. In this cold cathode discharge tube, there is no leakage of ultraviolet light having a wavelength of 320 nm or less that deteriorates the acrylic resin.

(Embodiment 4) A phosphor layer 6 composed of a 30 μm white phosphor film of three colors is provided on the entire outer peripheral surface of a glass tube 5 and an acrylic resin clear (acryl clear 1000, Dai Nippon Paint) is provided thereon. MARK LA-51
(Benzotophenone type, manufactured by Adeka Argus Chemical Co., Ltd.) is coated with an ultraviolet absorber 7 to which 0.5% is added, to give a film thickness of 10 μm. In this cold cathode discharge tube, there is no leakage of ultraviolet light having a wavelength of 320 nm or less that deteriorates the acrylic resin.

The ultraviolet absorbent 7 used in this embodiment is as follows. Salicylate (such as phenyl salicylate) Benzophenone (such as 2-hydroxy-4-methoxybenzophenone) Benzotriazole (such as 2- (2′-hydroxy5′-methylphenyl) benzotriazole) Cyanoacrylate (ethyl 2-cyano-) Or a heat-resistant ultraviolet absorber having a methacryl group introduced into the skeleton of benzotriazole. In particular, a triazole-based ultraviolet absorber is effective for an acrylic resin.

FIG. 4 shows a third embodiment of the discharge tube according to the present invention. This discharge tube 8 is a cold cathode in which a phosphor layer 10 is applied to the inner surface of a glass tube 9 and mercury vapor is sealed inside. With respect to the discharge tube, the ultraviolet absorber 7 of the second embodiment is applied to the entire outer peripheral surface of the glass tube 9.

[0019]

As described above in detail, according to the discharge tube of the present invention, a fluorescent material for generating visible light of a wavelength band of 380 nm or more is provided over the entire outer peripheral surface of the ultraviolet discharge tube made of ultraviolet transmitting glass. By coating to a thickness, the ultraviolet light transmitted through the glass can be absorbed by the phosphor to prevent leakage to the outside, and the adverse effect of the ultraviolet light on the synthetic resin material can be fundamentally prevented.

Alternatively, by applying an ultraviolet absorber that transmits visible light to the entire outer peripheral surface of an ultraviolet discharge tube having a glass surface coated with a phosphor, even if the discharge tube leaks ultraviolet light, the ultraviolet light can be removed. It is possible to appropriately absorb and prevent the adverse effect of the ultraviolet rays on the synthetic resin material.

Further, by using the ultraviolet discharge tube for the backlight of the liquid crystal display device, the ultraviolet discharge tube can be attenuated with time without causing cloudiness or cracks in the acrylic resin or the like as the light diffusion plate used for the backlight. There can be no suitable backlight.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first embodiment of a discharge tube according to the present invention.

FIG. 2 is a graph showing the relationship between the thickness of a phosphor in a discharge tube of the present invention and the intensity of ultraviolet light transmitted therethrough.

FIG. 3 is a front view showing a second embodiment of the discharge tube of the present invention.

FIG. 4 is a front view showing a third embodiment of the discharge tube of the present invention.

FIG. 5 is a sectional view of a conventional discharge tube.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Discharge tube 2 Glass tube 3 Phosphor layer 4 Discharge tube 5 Glass tube 6 Phosphor layer 7 Ultraviolet absorber 8 Discharge tube 9 Glass tube 10 Phosphor layer

Claims (3)

[Claims] 1. A discharge tube characterized in that a fluorescent substance for generating visible light in a wavelength band of 380 nm or more is coated to a thickness of 30 μm or more on the entire outer peripheral surface of an ultraviolet discharge tube made of ultraviolet transmitting glass. 2. A discharge tube characterized in that an ultraviolet absorber that transmits visible light is applied to the entire outer peripheral surface of an ultraviolet discharge tube having a phosphor coated on a glass surface. 3. The discharge tube according to claim 1, wherein the ultraviolet discharge tube is used for a backlight of a liquid crystal display device.