JP3667414B2 - Cold cathode low pressure discharge lamp - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cold cathode low pressure discharge lamp, and more particularly to a cold cathode low pressure discharge lamp which is small and light in weight and has improved luminance.
[0002]
[Prior art]
Liquid crystal display devices have been widely put into practical use as display units for word processors, personal computers, liquid crystal televisions, and the like, and their use tends to further expand. Liquid crystal display devices tend to be required to have structures and functions that can be used for a wide variety of applications, and light sources for liquid crystal backlights are desired to be smaller and lighter and have higher brightness.
[0003]
By the way, a cold cathode fluorescent lamp (cold cathode low pressure discharge lamp) is generally used as a light source for a liquid crystal backlight, and FIG. Such cold cathode fluorescent lamps are provided. That is, the phosphor layer 1 that emits light by stimulation with ultraviolet rays is provided on the inner wall surface, and a glass tube (glass bulb) 2 that seals a rare gas, and a pair of cold tubes respectively sealed at both ends of the glass tube 2. One end is connected to the pair of cold cathodes 3, 3 ′, and the other end side is composed of lead wires 4, 4 ′ sealed from the glass tube 2. If necessary, an ultraviolet reflecting layer may be interposed between the inner wall surface of the glass tube 2 and the phosphor layer 1.
[0004]
This type of cold cathode fluorescent lamp has secondary electrons from each cold cathode 3, 3 ′ by ions in the initial plasma generated by energizing each cold cathode 3, 3 ′ via lead-in lines 4, 4 ′. Is discharged, and discharge starts in the glass tube 2. Then, ultraviolet rays are radiated by the resonance transition of mercury atoms excited by the discharge energy accompanying the start of discharge, and the ultraviolet rays are converted into visible light by the phosphor layer 1 on the inner wall surface of the glass tube 2 to emit visible light. It functions as an electric light. In addition, when an ultraviolet reflecting layer is interposed, in the visible light conversion by the phosphor layer 1, the ultraviolet light transmitted through the phosphor layer 1 is reflected by the ultraviolet reflecting layer and returned to the phosphor layer 1 again to be visible light. Since it is converted, the utilization efficiency of ultraviolet rays increases, and as a result, the luminous efficiency can be increased.
[0005]
[Problems to be solved by the invention]
However, with regard to cold cathode fluorescent lamps as light sources for liquid crystal backlights, as described above, the trend in the market for thin, lightweight, high-brightness, and long-life backlight units is important. Along with this, the light source (lamp) to be incorporated is desired to be further reduced in weight, size and brightness. However, as described above, even when an ultraviolet reflecting layer is interposed between the inner wall surface of the glass bulb 2 and the phosphor layer 1, there is still a problem in terms of increasing the brightness. That is, the path of light emitted from the cold cathode fluorescent lamp can be broadly divided into two directions, and the light directed toward the wall of the glass tube 2 is used as it is, but the light directed toward the central axis of the glass tube 2 is enclosed. There is a problem that the desired high luminance cannot be obtained because the visible light that is lost due to absorption by gas or the like and as a result the visible light emitted from the phosphor layer is not sufficiently utilized.
[0006]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a cold cathode low pressure discharge lamp that is small, lightweight, and has high brightness, which can reduce the thickness and weight of a backlight unit.
[0007]
[Means for Solving the Problems]
The invention of claim 1 is a cold cathode low pressure discharge lamp having a phosphor layer provided on the inner wall surface and having a rare gas sealed therein, and a pair of cold cathodes sealed at both ends of the glass tube. The cold cathode low-pressure discharge lamp is characterized in that a visible light reflecting film having a thickness of 100 to 200 nm that reflects ultraviolet light is formed and disposed on the inner wall surface of the phosphor layer .
[0008]
That is, the cold cathode low-pressure discharge lamp according to the present invention is obtained by forming a visible light reflecting layer (thin film) that transmits ultraviolet light on a phosphor layer disposed on the inner wall surface of a light emitting glass tube. By adopting such a configuration, the phosphor layer absorbs the ultraviolet rays emitted by the discharge medium excited by the discharge energy, and the visible light emitted by the excitation accompanying the ultraviolet absorption is enclosed in the light emitting glass tube. The main point is to further improve the utilization efficiency of visible light emitted by avoiding / reducing absorption by gas.
[0009]
In the present invention, the ultraviolet ray transmissive and visible light reflecting film disposed in a laminated manner on the inner wall surface (discharge path surface side) of the phosphor layer is formed into a thin film using, for example, alumina, silica, zinc oxide or the like as a material. In addition, the formation of the visible light reflecting film may be performed by applying and firing a fine particle dispersion of the material, or a solution of a metal salt or an organometallic compound on the formed phosphor layer surface, The film thickness at this time may generally be about 100 to 200 nm.
[0010]
In the present invention, if necessary, a structure in which a phosphor layer is provided on the inner wall surface of the light-emitting glass tube through an ultraviolet reflecting layer that transmits visible light and reflects ultraviolet rays can be used. That is, in the structure in which a visible light reflecting film is disposed on the inner wall surface of the phosphor layer, when an ultraviolet reflecting layer that reflects ultraviolet light while transmitting visible light is interposed as an underlayer of the phosphor layer, the phosphor by ultraviolet light The luminous efficiency of visible light in the layer is also improved. Here, in order to increase the reflectivity of the ultraviolet light having the wavelength λ emitted by the excitation of the discharge medium, a multilayer ultraviolet reflective layer is desirable. That is, it is desirable that the thickness of each of the material layer having a high refractive index and the material layer having a low refractive index be set to λ / 4n to form a laminate type (n is the refractive index of each material).
[0011]
As described above, when the ultraviolet reflecting layer is additionally provided, the efficiency of light emission of the cold cathode low pressure discharge lamp is enhanced. That is, the phosphor in the phosphor layer is excited, and the ultraviolet rays that are converted into the required visible light are reflected by the reflective layer and contribute to the excitation of the phosphor again, so that more efficient visible light conversion is achieved, The luminous efficiency is greatly improved.
[0012]
By adopting the configuration as described above, it is possible to improve the light emission luminance and the light emission efficiency. Therefore, when the same light emission intensity and luminance are expected, the cold cathode low pressure discharge lamp can be reduced in size and weight. Also become. In other words, the cold cathode is designed to increase the efficiency of light emission and reduce the size and weight through efficient use of visible light emitted from phosphors by visible light reflection (absorption and loss of visible light) and excellent durability. A low pressure discharge lamp is provided.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment will be described with reference to FIG.
[0014]
FIG. 1 is a sectional view showing an example of the configuration of the main part of a cold cathode low pressure discharge lamp. In FIG. 1, 5 is a glass tube having an outer diameter of 3.0 mm and an inner diameter of 2.0 mm, in which a phosphor layer 6 that emits light by stimulation with ultraviolet rays is provided on the inner wall surface and encapsulating a discharge medium such as rare gas or mercury, A reflective film 8 and 8 ′, which is formed on the surface of the phosphor layer 6 and is UV-transparent and reflects visible light, is a pair of cold cathodes sealed at both ends of the glass tube 5, 9. , 9 ′ are lead wires connected at one end to the cold cathodes 8, 8 ′ and led at the other end from the glass tube 5. Here, the visible light reflecting film 7 is formed by, for example, applying an ethyl silicate solution of ethyl silicate to the phosphor layer 6 surface, air-drying, and applying and air-drying each time at a temperature of about 600 ° C. for about 15 minutes. It is formed by firing.
[0015]
When the cold cathode fluorescent lamp is energized to the cold cathodes 8 and 8 'via the lead wires 9 and 9', secondary electrons are generated from the cold cathodes 8 and 8 'by the ions in the initial plasma generated by the energization. And discharge is started in the glass tube 5. And the discharge energy accompanying this discharge start radiates | emits an ultraviolet-ray by the resonance excitation of the mercury atom which is a discharge medium (encapsulated gas). The emitted ultraviolet rays are absorbed and excited by the phosphor layer 6 on the inner wall surface of the glass tube 5 and converted into visible light, thereby contributing to light emission. And the visible light radiated | emitted to the tube wall side of the fluorescent lamp (glass tube 5) permeate | transmits a tube wall, and is radiated | emitted out of a fluorescent lamp.
[0016]
On the other hand, the visible light radiated in the axial direction of the fluorescent lamp (glass tube 5) is reflected to the tube wall side by the visible light reflecting film 7 arranged on the surface of the phosphor layer 6 as a layered enemy, so that the tube wall is covered. It is transmitted and emitted outside the fluorescent lamp. That is, the visible light reflecting film 7 exhibits good visible light conversion without affecting the ultraviolet absorption and excitation of the phosphor layer 6, while suppressing and preventing the absorption of converted visible light by the discharge medium and the like. Since it promotes visible light emission outside the lamp, it functions as a cold cathode discharge lamp with high emission luminance (emission intensity) while being small and lightweight.
[0017]
When the above-mentioned cold cathode low-pressure discharge lamps were subjected to lighting tests at room temperature and with a lamp current of 5 mA, the cathode fall voltage was about 100 V r · m · s. Compared to the cathode low-pressure discharge lamp, it was improved by about 5%.
[0018]
The present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the invention. For example, the structure of the cold cathode and the phosphor in the phosphor layer are not particularly limited.
[0019]
【The invention's effect】
According to the cold cathode low pressure discharge lamp according to the present invention, since the utilization efficiency of visible light emitted by the absorption and conversion of ultraviolet rays is improved, the emission intensity of the cold cathode low pressure discharge lamp can be easily increased. Also, compactness can be achieved. That is, visible light that is radiated to the positive column region and does not contribute to light emission due to absorption or loss in this region is significantly suppressed, prevented, or reduced by the visible light reflection film, and thus emitted from the phosphor layer. The use efficiency of visible light will increase, and the brightness of the cold cathode low pressure discharge lamp will be greatly improved.
[0020]
On the one hand, this significant improvement in emission brightness enables reduction in power consumption of cold cathode low pressure discharge lamps and reduction in size and weight of cold cathode low pressure discharge lamps. For example, the realization of small and high-quality liquid crystal display devices Also contributes.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a configuration example of a main part of a cold cathode low pressure discharge lamp according to the present invention.
FIG. 2 is a cross-sectional view showing a main configuration of a conventional cold cathode low pressure discharge lamp.
[Explanation of symbols]
1, 6... Phosphor layer 2, 5... Glass tube 3, 3 ', 8, 8' ... Cold cathode 4, 4 ', 9, 9'. Reflective film

Claims (1)

  A cold cathode low pressure discharge lamp having a phosphor layer provided on an inner wall surface and having a rare gas sealed therein, and a pair of cold cathodes sealed at both ends of the glass tube, respectively, A cold cathode low-pressure discharge lamp characterized in that a visible light reflecting film having a thickness of 100 to 200 nm that reflects ultraviolet light is formed and disposed on the inner wall surface of the cathode.

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