JPH0443549A - Cold cathode fluorescent lamp device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Field of Application) The present invention is a cold cathode fluorescent lamp device in which blackening at the tube end can be reduced even when the lamp is lit in an abnormal glow discharge region. be.

(Prior art) Cold cathode fluorescent lamps, which utilize the so-called γ effect in which ions collide with electrodes and eject electrons, have a long lifespan and are therefore used as light sources for copying machines and facsimile machines, or as backlights for liquid crystal display devices. ing. However, since this type of cold cathode fluorescent lamp has a high cathode fall voltage, sputtering of the electrode material, that is, the material constituting the electrode occurs, and blackening of the tube end progresses during the life of the lamp. Cathode drop voltage of cold cathode fluorescent lamp (
vk) depends on the electrode current density (jk) and the sealed gas pressure (p).1. It increases as jc/p2 increases. Therefore, to suppress spatter and reduce blackening, j+c/p
” to be as small as possible so that vk is low.

Filled gas pressure, electrode area (the total area of the electrode that takes part in discharge), lamp current, etc. were determined based on the degree of blackening in the life test, and the lamp and its lighting circuit were designed as a set. .

However, such a cold cathode fluorescent lamp has a lifespan of 10,000 hours or more, and it takes a long time to determine whether the lamp is at a level that can withstand practical use. Therefore,
The jk/p'' region is close to normal glow discharge where the cathode drop voltage is relatively low and there is little blackening due to sputtering, that is, the jk/p'' region where the cathode drop voltage Vk hardly changes even if the current is changed.
It is recommended that the electrode be used in the p" region ('89. Illuminating Engineering Society of Japan Tokyo Chapter Conference 4). In this report, the electrode is made of nickel (Ni), and a rare gas mainly composed of argon (Ar) is used in the mercury In the case of a cold cathode fluorescent lamp device sealed with
Torr”).
The reason why nickel is used for the electrode is that it is superior overall in terms of price, workability, gas release characteristics, sputtering rate, etc.

(Problem to be solved by the invention) However, recent technological advances in liquid crystal display devices have been remarkable, and in response to this, there has been an increasing demand for thinner backlights, higher brightness, and improved luminous efficiency. . In order to satisfy these demands, it is necessary to make cold cathode fluorescent lamps thinner, have larger currents, and lower gas pressures. However, in this case, because the lamp is operated in the jit/p'' region where abnormal glow discharge has progressed considerably, blackening of the tube end of the lamp progresses quickly. so as not to affect the brightness characteristics of the backlight.
There is a need for a design in which the end portion of the tube is enlarged so that even if the dead space at the end of the tube, that is, the portion becomes black due to being located outside the range of the liquid crystal display device, illumination will not be affected. However, this means that the backlight utilization rate (
effective light emitting area/total backlight area). For the reasons described above, it has been difficult to satisfy all of the requirements of making the backlight smaller, thinner, brighter, and more luminous.

Therefore, the problem of the present invention is to
To provide a cold cathode fluorescent lamp device which can reduce the dead space at the tube end when used for backlighting by setting operating conditions so that blackening at the tube end is reduced even when the lamp is lit in the k/p'' region. .

[Structure of the invention]

(Means for Solving the Problems) The present invention provides a cold cathode fluorescent lamp device in which the current density of the electrodes of the lamp is jk (mA/aj), the cathode drop voltage is V+c (V), and the pressure of the enclosed noble gas is p (Tor).
r), when the average distance between the electrode and the bulb wall is d(c■).

jk-■, /P-d≦0.3 (W/Torr”d) and jk/p”≧1,0XIO-” (mA/cd4
The blackening of the tube wall is reduced by lighting the tube under conditions that satisfy the following conditions.

(Function) The amount of sputtered electrode material is proportional to the energy amount of ions that bombarded the electrode, jk'Vi+, and the time rate for the sputtered electrode material to reach the tube wall, or the product of migration resistance and distance p.
- inversely proportional to d. therefore.

If 9.v/P-d is within the practical limit for blackening, discharge may be performed in the abnormal glow discharge region jk/p''≧1.OX 10-''.

It can withstand long-term lighting and has a long life with little blackening of the tube wall.

〔Example〕

The details of the present invention will be explained below with reference to the illustrated embodiments. In the six figures, (1) is a cold cathode fluorescent lamp, and (2) is this lamp (
1) is a lighting circuit that lights up, and (3) is this lighting circuit that lights up (2).
) and the cold cathode fluorescent lamp (1).

The above cold cathode fluorescent lamp (1) is a glass straight tube bulb (
11) are closed at both ends with stems (12), (12), and lead wires (13), (1) are passed through these stems (12).
3) are equipped with nickel electrodes (14), (14).

Argon is sealed together with mercury inside the bulb (11). Note that a fluorescent film is formed on the inner surface of the bulb (11), but it is omitted in the drawing. Next, the dimensions and composition of each part of the present cold cathode fluorescent lamp (1) are shown.

Inner diameter D of bulb (11) 6-10 mm Electrode (1
4), (14) Distance L2-4 am Argon sealing pressure 5-40 Torr Next, the function of the cold cathode fluorescent lamp device of this embodiment, particularly the function of reducing tube end blackening, will be explained.

When the lighting device (2) is activated, the picture electrode (14),
(14) During this time, a discharge occurs and emits ultraviolet rays, which excites a fluorescent film (not shown) to emit visible light.

Therefore, the inventor of the present invention considered that the tube end blackening of a cold cathode fluorescent lamp occurs in the following manner.

First step: Accelerated ions in the cathode fall zone collide with the electrode, resulting in sputtering of the electrode material.

Second step: The sputtered electrode material diffuses through the rare gas sealed in the tube and adheres to the tube wall.

Third step: As deposits accumulate, they appear as blackening.

Considering the above, the lamp design parameters that affect the first step are the electrode current density jk and the cathode drop voltage vk, and the lamp design parameters that affect the second step are the filled gas pressure p and the average between the electrode and tube wall. The distance is d. In addition, in the third step, if the rate at which the electrode material is deposited on the tube wall is expressed by the light absorption rate μ, the degree of blackening is expressed by exp (−μt). A simple consideration suggests that μ is a function of 9·Vk/P−d.

Here, jk''Vit represents the energy impacting the electrode and is related to the amount of sputtering. Also, p-d represents the time rate at which the sputtered electrode material reaches the tube wall.

Therefore, by taking the tube diameter D, the filled gas pressure P, and the electrode current density jk as parameters, μtjk−vk is calculated for the nickel electrode.
/P-d was investigated. The range of parameters is the tube inner diameter of 4 to 10 mm, the sealed gas pressure p of 5 to 40 Torr,
The electrode current density jh is 5 to 20 s+A/al. Therefore, the converted current density is 0.003≦jk/p”≦0.8
(Synonym A/at・Torr"). Also, the electrode (1
4) uses a flat plate of 5 x 10 x 0.3 + im, and the distance between the electrodes is 2 to 2 to measure only the cathode drop voltage
The score was 4-1.

The brightness (I) after lighting this test lamp for 5 hr, 10 hr and 20 hr was measured, and the light absorption rate μ
A forced test was conducted in an abnormal glow region to find out. The test results are shown in Figure 2, where the horizontal axis shows the lighting time in units of hr, and the vertical axis shows Qゎ (I/I.), that is, the initial brightness factor. Curve (A) is the natural logarithm of the ratio of brightness during lighting to when jh"Vh/p-d is small, and curve (B) is when jk"Vk/P"d is large. The respective Q-I/Io curves of -μt are shown.

Next, FIG. 3 shows the relationship between 9·V/P-d and μ.

In the figure, the horizontal axis is Qog (jk-vk/P-d) and the vertical axis is Qogμ. The curve (C) is a blackening curve, and the chain line is the limit of blackening that does not pose a problem in practical use. From these figures, the light absorption rate μ is a function of jk-vk/P-d, and Q
It can be seen that ogμ is proportional to QOg(, jt'Vk/p−d). In addition, when examining the degree of blackening (dashed line in Figure 3) that does not actually cause problems when used, it is found that jk-vk/P
It was found that -d corresponds to 0.3 (V/Torr·c!Ir).

Next, similar experiments were conducted by changing the shape of the electrodes to parallel plates, cylinders, etc., but the jk・V, /pd
The upper limit was the same. Therefore, jk V, defined by the lamp design parameters jk, vk, p, d,
If the quantity /p-d is designed to be 0.3 (V/Torr-aj) or less, the abnormal glow discharge region jk/p''
≧1. OX I O-” (mA/ aJ ・chorr
” ), it is possible to keep darkening low over a long period of time, and it is also possible to easily predict the degree of blackening progress in response to changes in parameters.

Although the above experiments were conducted on nickel electrodes, the same results could be obtained with nickel-based materials such as iron-nickel alloys, and nickel with other materials other than iron, such as aluminum (AQ), zirconium, etc. (Zr
), titanium nitride (TiN), or the like, the same upper limit can be given to jk'Vb/ρ·d.

Therefore, the lamp device according to the present invention has (1) jb/
p'≧l, OXl 0-2(s+A/cj ・
(2) jit"i+/P"≦0.3(V/Torr-
I decided to turn it on with aJ). As a result, blackening can be suppressed over a long period of time even though it is used in an abnormal glow discharge area, and it is possible to achieve thinner backlights, improved utilization rates, higher brightness, and improved luminous efficiency. It's now possible.

Note that the discharge gas is not limited to argon alone, and a small amount of helium, neon, or krypton may be mixed with argon.

〔Effect of the invention〕

As described above, the cold cathode fluorescent lamp device of the present invention has electrodes mainly made of nickel sealed at both ends of the tube-shaped bulb.
A cold cathode fluorescent lamp containing a rare gas mainly composed of argon and mercury, and a current density of the electrodes of jib (■A/c
d), the cathode drop voltage is Vk (v), the pressure of the enclosed noble gas is p (Torr), and the average distance between the electrode and the bulb wall is d(
c■) When jk-vk/p-d≦0.3 (w/Torr-a#)
js+/p"≧1.0X10-" (mA/aJ4or
The cold cathode fluorescent lamp is configured with a device that lights up the cold cathode fluorescent lamp under conditions that satisfy the following conditions, so even if it is used in an abnormal glow discharge area, it has the advantage that there is little blackening of the tube wall even when the lamp is turned on for a long period of time. , suitable for backlights of liquid crystal display devices.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of an embodiment of the cold cathode fluorescent lamp device of the present invention, Fig. 2 is a graph showing changes in brightness depending on lighting time, and Fig. 3 is a graph showing changes in brightness due to lighting time. It is a graph showing the relationship with practical limits. (1)...cold cathode fluorescent lamp, (11)...bulb, (12)...stem, (14)...electrode, (2)
lighting circuit. (3)...Stabilizer agent Patent attorney Dai Hu Dian Fubu Sui

Claims (1)

[Scope of Claims] A cold cathode fluorescent lamp consisting of a tube-shaped bulb whose ends are sealed with electrodes mainly made of nickel and filled with a rare gas mainly made of argon and mercury, and a device for lighting the same. , the current density of the above electrode is j_k (mA/cm^2)
, the cathode drop voltage is V_k (V), and the enclosed rare gas pressure is p(
Torr), and the average distance between the electrode and the bulb wall is d
(cm), j_k・V_k/p・d≦0.3(V/Torr・cm
^3) And j_k/p^2≧1.0×10^-^2(
A cold cathode fluorescent lamp device characterized in that it is lit under conditions that satisfy mA/cm^2・Torr^2).