JPH08102288A - Cold cathode fluorescent discharge tube - Google Patents

Abstract

PURPOSE: To downsize a device, and to reduce the power consumption, and to improve the luminous efficiency by specifying the inner diameter of an outer case, and using the mixture gas, which is composed of neon at the specified % and argon at the residual %, as the sealing gas, and setting the sealing pressure thereof in a range at the predetermined kPa. CONSTITUTION: In the case where the inner diameter of an outer case 1 is changed, in a cold cathode fluorescent discharge tube at 1.2W, in which the simple substance of AR is sealed at, for example, 5320Pass, downsize of the inner diameter to the range at 1.5-3.5mm is remarkably effective in a point of luminous efficiency. The mixture gas, which is composed of Ne at 60-99.9% and AR at the residual %, is sealed in the cold cathode fluorescent discharge tube at 6-18kPass of sealing pressure. At this stage, in the case where the inner diameter of the tube is enlarged, power consumption is increased, and the maximum efficiency can not be obtained. In the case where Ne at 60% or less is included, characteristic as the cold cathode fluorescent discharge tube can not be obtained. Inner diameter at 1.5-3.5mm is thereby appropriate for downsize of the tube, and the mixture gas, which is composed of Ne at 60-99% and Ar at the residual %, is sealed at 6-18kPa.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cold cathode fluorescent discharge tube used for a backlight of a liquid crystal display device.

[0002]

2. Description of the Related Art Conventionally, a cold cathode fluorescent discharge tube has been used as a light source for illumination such as a backlight of a liquid crystal display device, and various structures are known.

For example, in Japanese Unexamined Patent Publication No. 63-292558, the discharge electrode is formed of a base metal having a plurality of holes opened in the discharge direction, and at least one of the plurality of holes is more than other holes. Is disclosed so that an arc spot is easily formed, the discharge state is stable and favorable, and the luminous efficiency is also favorable. As a specific example of the glass including an enclosed gas, an outer diameter of 8 mm is disclosed. A bulb containing 5 mg of mercury and 20 torr (2.7 kPass) of argon is disclosed.

Further, in Japanese Patent Laid-Open No. 2-7345, an insulating layer and a protective layer are provided on nickel plate-shaped electrodes facing each other with a lead serving as a discharge electrode interposed therebetween to lower the starting voltage and the discharge sustaining voltage. As a specific example including a sealed gas, a glass bulb having a tube diameter of 8 mm contains 10% of a rare gas of neon / argon 0.1%.
It is disclosed that ~ 50 torr and a few mg of mercury are enclosed.

[0005]

As described above, various cold cathode fluorescent discharge tubes are well known.

On the other hand, in recent years, there has been a demand for further thinning, weight reduction, and low power consumption of illumination light sources such as backlights. In order to meet such demand, the cold cathode fluorescent discharge tube also consumes less power. There is a strong demand for higher power efficiency and higher efficiency.

Factors such as the tube diameter, the composition and structure of the electrode and the phosphor, the type and pressure of the enclosed gas, and the pressure can be considered as design factors for reducing the power consumption of the cold cathode fluorescent discharge tube as described above. .

Here, when the conventional cold cathode fluorescent discharge tubes described above are respectively made to correspond to the above-mentioned respective factors, all the conventional examples are characterized by their discharge electrodes and other factors. Has not been studied in particular, and the low power consumption of the cold cathode fluorescent discharge tube is still considered,
There is room for improvement.

That is, looking at the cold cathode fluorescent discharge tube disclosed as a specific example in each of the above-mentioned conventional examples, the tube diameter is about 8 mm, and the enclosed gas and its enclosed pressure are argon simple substance or neon / argon 0. .1%
It is only disclosed to use the noble gas of 10 to 50 torr.

Therefore, it has been impossible to expect more than the conventionally well-known results with respect to the reduction of power consumption and the improvement of efficiency based on the factors of the tube diameter or the enclosed gas and the enclosed pressure.

The present invention has been made in consideration of the above points, and is a cold cathode fluorescent lamp which realizes low power consumption and high efficiency of light emission based on factors such as the tube diameter or the enclosed gas and its enclosed pressure. It is intended to provide a discharge tube.

[0012]

A cold cathode fluorescent discharge tube according to the present invention has a discharge electrode sealed at both ends and a fluorescent material coated on the inner surface of the outer diameter of 1.5 to 3.5 mm. It is configured by enclosing a mixed gas of 60 to 99.9% neon and the balance of argon at an enclosing pressure of 6 to 18 kPass in the enclosure.

[0013]

Since the cold cathode fluorescent discharge tube according to the present invention has an inner diameter of 1.5 to 3.5 mm as described above, the power consumption thereof is lower than that of the conventionally known cold cathode fluorescent discharge tube. The emission efficiency can be improved because the filling gas is a mixed gas of 60 to 99.9% neon and the balance argon and the filling pressure is in the range of 6 to 18 kPass.

[0014]

FIG. 1 is a front view including a partial cross section showing an embodiment of a cold cathode fluorescent discharge tube according to the present invention.

As is apparent from FIG. 1, the cold cathode fluorescent discharge tube according to the present invention has discharge electrodes 3 and 4 sealed at both ends of an envelope 1 having an inner surface coated with a phosphor 2. .

The discharge electrode 3 is a cathode having a metal cap 5 to which a mercury emission structure 6 for enclosing mercury in the envelope 1 is welded and attached, and the other electrode 4 is provided.
Shows an anode in which a sintered body 7 formed by sintering tungsten, for example, is welded and attached to the metal cap 5.

As the mercury-releasing structure, S. A. E. FIG. S. The element etc. marketed by the company as brand name GEMEDIS can be adopted.

Further, as will be described later in detail, the envelope 1 has a tube inner diameter of 1.5 to 3.5 mm, and contains 60 to 99.9% neon and the remaining argon inside. The mixed gas consisting of is enclosed at an enclosure pressure of 6-18 kPass.

The reasons for designing the tube diameter and the like of the cold cathode fluorescent discharge tube according to the present invention and the results of studying the characteristics will be described in detail below.

In general, since the backlight is lit with a low electric power of several W, it is difficult to supply sufficient electric power to the positive column in the cold cathode fluorescent discharge tube having a large electrode loss, which is the object of the present invention. It is difficult to raise the temperature and it becomes difficult to raise the luminous efficiency to the maximum efficiency.

Therefore, the inventors of the present application have considered a measure for increasing the tube wall load by reducing the tube diameter of the discharge tube in order to improve such inconvenience. The relationship with the luminous efficiency was examined.

The examination was conducted with argon alone in the tube at 5320 Pa.
Luminous flux was measured when the inner diameter of the cold cathode fluorescent discharge tube of 1.2 W sealed with the ss sealing pressure was changed variously.
The results are shown in FIG. 2. As is clear from FIG. 2, the reduction of the tube inner diameter from 1.5 to 3.5 mm with the peak in the range of 2 to 2.5 mm is extremely effective in terms of luminous efficiency. It was confirmed to be effective.

However, it is also known that when the inner diameter of the pipe is reduced, a new problem is caused in terms of life characteristics.

That is, when the inner diameter of the tube is reduced, the blackening phenomenon of the tube end portion due to the sputtering of the electrode becomes remarkable, so that it is extremely difficult to secure the life characteristics, and it is impossible to unnecessarily reduce the inner diameter of the tube.

On the other hand, it is conventionally known that the filling pressure of the filling gas may be increased in order to suppress the above-mentioned sputtering, and the inventors of the present application next examined the relationship between the filling pressure and the luminous efficiency. .

In the study, as disclosed in the above-mentioned conventional example, the inner diameter and the filling pressure of the cold cathode fluorescent discharge tube having a total length of 150 mm and using a simple general argon as the filling gas were varied. In this case, the luminous flux was measured. The results are shown in FIG. 3, and as is clear from FIG. 3, it was confirmed that the luminous efficiency tends to be higher as the filling pressure is lower regardless of the tube diameter. Also, although not shown, it was confirmed that the starting voltage thereof increased as the filling pressure was increased.

That is, if the filling pressure of the filling gas is increased in order to suppress the sputtering, the starting voltage and the luminous efficiency are lowered in the case of argon, so that the filling pressure is increased unnecessarily like the tube diameter. In view of the above points, the minimum inner diameter of the cold cathode fluorescent discharge tube that has been put into practical use is around 5 mm.

Based on the above-mentioned examination results, the inventors of the present application have studied the further miniaturization of the tube inner diameter, various gases and their filling pressures, while ensuring the life characteristics to some extent, and examined the cold cathode fluorescent discharge. The improvement of the efficiency of the pipe was examined.

The results of the examination will be described below. 95% of the inside of the envelope with a tube inner diameter of 2 mm and a total length of 150 mm
Cold cathode fluorescent discharge tube filled with various filling pressures of neon and balance argon, and cold cathode fluorescent discharge tube filled with various filling pressures of 60% neon and balance argon with argon alone And a cold cathode fluorescent discharge tube in which was sealed at various sealing pressures, and the luminous flux thereof was measured.

The results are shown in FIG. 4. As is clear from FIG. 4, in the case of argon alone, the luminous efficiency increases as the filling pressure becomes lower. In other words, in FIG. As described above, it is confirmed that the higher the filling pressure is, the lower the luminous efficiency is. On the contrary, in the case of the mixed gas composed of 95% balance of neon, the luminous efficiency is higher as the filling pressure is higher. did it.

The increase in the luminous efficiency is caused by the filling pressure 10
Almost saturated when kPass is exceeded, that is,
Luminous efficiency is higher than that of argon alone. Filling pressure is 10 kP.
It shows the highest efficiency at ass or higher, and is better than argon alone at a pressure of 6 kPass or higher.

Therefore, in practical use, it is practical to adopt a pressure of 6 kPass or more as the filling pressure on the low-pressure side, and the filling pressure on the high-pressure side is a factor other than the luminous efficiency.
For example, it may be decided in consideration of the cost of the enclosed gas,
Actually, a filling pressure of up to about 18 kPass is appropriate because the above-described effect of increasing the luminous efficiency can be fully enjoyed in practical use. It has also been confirmed that the sealing pressure in the range of 10 to 13 kPass gives the most preferable results in terms of luminous efficiency, cost and the like.

Further, although the life characteristics will not be described in detail, it has been confirmed that no particular problem occurs when the filling pressure is in the range of 6 to 18 kPass.

On the other hand, when the ratio of neon is 60%, as shown in FIG.
As shown in the figure, the luminous efficiency does not significantly increase even if the filling pressure increases, that is, the lower the neon ratio, the lower the luminous efficiency, the higher the starting voltage, and the neon ratio is 60% or more. In the following, the characteristic efficiency of the cold cathode fluorescent discharge tube according to the present invention, in which the luminous efficiency is increased by increasing the filling pressure, which has been described in the case where the ratio of neon is 95%, is not seen, and it is similar to the case of argon alone It has been confirmed that the luminous efficiency decreases when the filling pressure is increased.

Therefore, when considering practical use, it is appropriate that the low ratio side of the neon to argon ratio is 60% or more, and more specifically, the ratio of 90% or more is 95%. It has been confirmed that the decrease in the luminous efficiency of is extremely small, which is preferable.

On the high ratio side of the neon ratio, when the ratio exceeds 95% as exemplified above, the characteristic of FIG. 4 showing the relationship between the filling pressure and the luminous efficiency is hardly changed, and the neon ratio is 99.9%. It has been confirmed that the starting voltage rises when it exceeds the limit. In practical use, for example, the neon ratio may be determined in consideration of conditions such as the cost of the enclosed gas and the starting voltage. Actually, it is 99.9% or less. This is appropriate because the effect of increasing the luminous efficiency described above can be fully enjoyed from a practical standpoint in the neon ratio. In consideration of the above points, it can be confirmed that the neon ratio of 90 to 97% is the neon ratio range in which the most preferable results are obtained in terms of luminous efficiency, cost, etc. in the range of the tube inner diameter described above. There is.

Finally, supplementing the explanation about the inner diameter of the pipe, the larger the inner diameter of the pipe is, the more power is consumed and the maximum efficiency cannot be obtained, and the above neon ratio is 60%.
As in the following cases, it has been confirmed that the characteristic features of the cold cathode fluorescent discharge tube according to the present invention described in FIG. 4 tend not to be seen.

Therefore, as described above, 1.5 to
3.5 mm is suitable, and in particular, as is clear from FIG. 2, downsizing of the tube inner diameter within the range of 2 to 2.5 mm reduces the size of the entire backlight device and improves the luminous efficiency. It has been confirmed that the above is extremely effective, and that the adoption of such a range is most preferable for practical use.

From the above examination results, even when the inner diameter of the envelope of the cold cathode fluorescent discharge tube is made thin, when a mixed gas of argon mainly neon is used as the filling gas, the filling pressure is appropriately set. By doing so, the luminous efficiency is good,
It was confirmed that it is possible to provide a cold cathode fluorescent discharge tube that can also secure life characteristics.

[0040]

In the cold cathode fluorescent discharge tube according to the present invention, the inner diameter of the envelope is set to 1.5 to 3.5 mm, and a mixed gas of 60 to 99.9% neon and the balance argon is used as a filling gas. Moreover, since the filling pressure is set in the range of 6 to 18 kPass, there is an effect that a compact shape, low power consumption, and high luminous efficiency can be realized.

[Brief description of drawings]

FIG. 1 is a front view including a partial cross section showing an embodiment of a cold cathode fluorescent discharge tube according to the present invention.

FIG. 2 is a diagram showing a result of examining a relationship between a tube inner diameter and luminous efficiency.

FIG. 3 is a diagram showing the results of examining the relationship between the filling pressure and the luminous efficiency.

FIG. 4 is a diagram showing the results of measuring the luminous flux of a cold cathode fluorescent discharge tube when different filled gases are filled at various filled pressures.

[Explanation of symbols]

 1 Enclosure 2 Phosphor 3,4 Discharge Electrode 5 Metal Cap 6 Mercury Emitting Structure 7 Sintered Body

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukito Iseki, 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electronics Industrial Co., Ltd.

Claims (1)

[Claims] 1. Neon of 60 to 99.9% is contained in an envelope having a tube inner diameter of 1.5 to 3.5 mm in which a discharge electrode is sealed at both ends and a phosphor is applied to the inner surface. A cold cathode fluorescent discharge tube in which a mixed gas consisting of the balance argon is filled with a filling pressure of 6 to 18 kPass.