JPH0212752A - Fluorescent lamp - Google Patents

Abstract

PURPOSE:To speed up the starting time and to stabilize the operation even in a low current by making the gas sealing pressure and the tube inner diameter to satisfy a specific relation. CONSTITUTION:When the sealed gas pressure in a lamp is made pTorr, and the inner diameter of a tube is made dcm, in a hot cathode type fluorescent lamp of less than 50mA of lamp current, the lamp is composed to satisfy the relation pd>=13. As a result, the temperature of the cathode bright point can be raised sufficiently to obtain a necessary thermion radiation, regardless of the size of the wire diameter of the coil wire composing the hot cathode. Consequently, the transition to the arc discharge is carried out easily, the arc discharge can be stabilized, an unstable lighting is eliminated, the blackening of the tube end is reduced, and a short service life resulting from a shortage of emitter is also eliminated.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention provides a compact fluorescent lamp that is operated with a lamp current of 50 mA or less, which quickly transitions from glow discharge to arc discharge upon starting. , and the arc discharge can be maintained stably during operation.

(Prior Art) Fluorescent lamps are widely used as high-efficiency light sources for general lighting, and this is largely due to the invention of the hot cathode.In other words, by adopting the hot cathode, the lamp voltage can be lowered and This is because it has become possible to easily light the lamp with a voltage of ~200V. Also, by using a hot cathode.

It is also important to note that electrode fall loss has been reduced and the luminous efficiency of the lamp has been improved.

Nowadays, the application of fluorescent lamps is not limited to general lighting, but is also expanding to office equipment (OA equipment), and compact fluorescent lamps are also used in backlights of LCD televisions and the like. However, in order to take advantage of the small size and light weight of LCD televisions, portable types that can be powered by dry batteries have become mainstream. In this case, since it is desirable that the power consumption of the backlight is low, the fluorescent lamp is of a hot cathode type, and the lamp current is set to 10 to 30 mA.

In order to easily start and stably operate such a small, low-current fluorescent lamp, it is necessary to form a stable cathode bright spot on the hot cathode to stably maintain the arc. Therefore, the temperature of the cathode bright spot settles at a point where the heat loss due to radiation and conduction is balanced against the heating effect of the ionic current flowing in during the cathode cycle and the electron current flowing in during the anode cycle, which maintains the arc discharge. The thermionic current required for this purpose and the radiation loss that lowers the temperature of the bright spot are determined by the size and temperature of the cathode bright spot, but it is better to make the bright spot smaller and raise the temperature to obtain the same thermionic current. Radiation loss can be kept small. That is, the electrode can be heated more effectively by increasing the temperature of the bright spot and reducing the size of the bright spot. For this purpose, it is effective to reduce the wire diameter of the filament constituting the hot cathode as the lamp current becomes smaller.

For this reason, in the conventional design of hot cathodes for fluorescent lamps, the coil wire diameter for the lamp current is approximately the same, and if a coil with a wire diameter calculated according to this design standard is used, 113 The point temperature is 1000
It falls within the range of ~1o5oC.

(11 Problems to be Solved by the Invention) When designing a hot cathode coil for a small fluorescent lamp with a lamp current of 50 A or less by applying the design standards for hot cathodes for fluorescent lamps described above, the tungsten wire of the coil The diameter is 8th
As shown in the figure, when the conventional design standard is extrapolated to 50 mA or less, the wire diameter of the coil becomes negative around 50 to 70 mA. In reality, it would be smaller than IMG because it would be as thin as possible. Here, MG is a unit expressing the wire diameter of a thin metal wire, and refers to the weight of the thin metal wire per 200 cm in length expressed in sweetfish.

Such thin tungsten wires are not only difficult to manufacture and process, but the resulting coils also have weak mechanical strength, so not only do they require extreme care when handling them, but if they are made too large, they may deform under their own weight. Therefore, it is difficult to increase the size of the electrode, and therefore the emitter cannot be sufficiently deposited, making it difficult to extend the absolute life of the electrode.

However, if a coil is designed using a thick tungsten thin wire that deviates from the above-mentioned design standards, the resulting hot cathode will have a large cathode bright spot, making it impossible to obtain the necessary bright spot temperature. Current may not be obtained, and the transition from glow discharge to arc discharge may not be smooth when starting, or even if the lamp is turned on, the arc discharge may be unstable, causing it to reverse to glow discharge or go out. In severe cases, it may not be possible to switch to arc discharge upon starting, and the glow discharge may continue for a long time.

In this way, if the emitter blinks frequently or the glow discharge takes a long time, the emitter may scatter a lot, resulting in early blackening or premature wear, resulting in shortened lifespan, or premature disconnection of the coil.

Therefore, an object of the present invention is to improve a small hot cathode fluorescent lamp with a lamp current of 50 mA or less so that it can start quickly and operate stably even at a low current.

[Structure of the invention]

(Means for Solving the Problem) The present invention has been made to stabilize the operation of a hot cathode fluorescent lamp with a lamp current of 50 A or less. The size of the cathode bright spot is limited regardless of the wire diameter of the hot cathode coil, and its temperature is is made sufficiently high to obtain the necessary thermionic emission. In addition to the conditions stated in the first claim, the second claim provides that the fine wire of the hot cathode coil is made to be 2MG or more, without impairing the effect of the first claim. The wire diameter is increased, thereby making it easier to manufacture the coil material and forming the coil, prevent mechanical deformation of the coil, and increase the amount of emitter coating.

(Function) Through research conducted by the present inventors, it was discovered that the size of the cathode bright spot is also determined by the product of pd. As a result of further research, we found that if the relationship Pd≧13 is satisfied, even in small fluorescent lamps with a lamp current of 50 μA or less, the size of the cathode bright spot can be controlled regardless of the wire diameter of the coil. They discovered that they could make it small enough and raise its temperature high enough to obtain the required thermionic emission. Also, this research shows that
If the above relationship pct≧13 is satisfied, the wire diameter of the coil thin wire can be made sufficiently large without impairing the effects of the present invention.
It was discovered that the mechanical strength of the coil can be increased and the coil dimensions can be increased.

In addition, in a hot cathode fluorescent lamp with a lamp current exceeding 50 mA, even if the conditions of the present invention are not met, the temperature of the cathode bright spot becomes high and the necessary thermionic emission can be obtained, so the effect of the present invention is remarkable. It doesn't show up.

(Example) In the fluorescent lamp of the example, the present inventor has developed a sealed gas pressure (p
) and tube diameter (d) were varied to investigate the correlation with lighting conditions. First, if we calculate the approximate number of example fluorescent lamps,
The inner diameter d of the lamp tube is varied from 3 to 7 mm, the filled gas is argon, and the sealed pressure p is varied from 5 to 50 Torr, and the cathode is made of 3.7 MG tungsten thin wire formed into a double coil, barium, An emitter made of three component oxides of calcium and strontium was deposited, and the lighting method was such that a high frequency voltage of 33 KH2 was applied between both electrodes and started directly without preheating.

First, the relationship between the glow discharge power (ω) and the lighting time (time from energization to the start of arc discharge) (τ) when the tube inner diameter is fixed at 7 m and the filled gas pressure is varied and started. Energy amount of glow discharge (ε) and lighting time (
τ) was investigated, and this is shown in FIGS. 1 and 2. In Figure 1, the horizontal axis shows the above-mentioned ω factor as a relative value, and the vertical axis shows 1/τ in units of 5ee-'. 20
ω and 1/τ when set to Torr and 40 Torr
Showing the correlation with. In addition, in Figure 2, the horizontal axis shows ip in relative value units, and the vertical axis shows 1/τ in Be(:'' units), and the four curves show p at 5 Torr and 10 Torr.
, 20 Torr, and 40 Torr, which show the correlation between if and 1/τ, as is clear from Fig. 1 and Fig. 2, increasing the filled gas pressure p facilitates the transition from glow discharge to arc discharge. It was found that not only this, but also that the reversal from arc discharge to glow discharge became difficult, and stable arc discharge was formed. This was also supported by life tests. The results are shown in FIG.

In the figure, the horizontal axis shows the lighting time as a relative value, and the vertical axis shows the residual rate in %.
5 curve is taken in units of 5 To
rr, 10Torr, 20Torr and 40Torr
As is clear from Figure 3, which shows the life characteristics when the temperature is set to The higher the gas pressure, the longer the life, and in particular, in the case of 40 Torr, the life was several thousand hours. The reason for this is that the higher the filled gas pressure is, the more stable the arc discharge is, and therefore the time for glow discharge and the power consumption during it are shorter, so there is less scattering and wear and tear of the emitter, and there is less chance of premature disconnection of the coil. Conceivable. Furthermore, as has been said in the past, increasing the gas pressure has the effect of reducing emitter evaporation.

Furthermore, similar tests were conducted on tubes with inner diameters of 31 and 5 ml, and both showed similar trends. However, some differences were observed depending on the pipe inner diameter.

Next, the sealed gas pressure was fixed at 30 Torr, and the pipe inner diameter (
We investigated the relationship between glow discharge power (ω) and lighting time (τ) and the relationship between glow discharge energy (ε) and lighting time (τ) when starting with various changes in d). , this is shown in FIGS. 4 and 5. In Figure 4, the above-mentioned ω is taken as a relative value on the horizontal axis, and 1/τ is taken as 5ec-' in the vertical and horizontal directions.
The three curves are taken in units of 3 + m, the inner diameter of the pipe,
The correlation between ω9 and l/τ in the case of 5IIn and 7m is shown. In addition, in Figure 5, the horizontal axis shows ε′ leakage as a relative value,
The vertical axis shows 1/τ in units of 5ec-', and the three curves show the correlation between εt and 1/τ when d is 3m+, 5IIIl, and 7m. As is clear from Figures 4 and 5, increasing the tube inner diameter d not only facilitates the transition from glow discharge to arc discharge, but also makes it difficult to reverse from arc discharge to glow discharge, resulting in a stable arc. It was found that a discharge was formed. This was also supported by life tests. This result is shown in Figure 6.
In the figure, the horizontal axis shows the lighting time as a relative value, and the vertical axis shows the residual rate in %.
The curve is taken in units of 31.5 + no.
As is clear from Figure 6, which shows the life characteristics when the tube is set to It has a lifespan of several thousand hours. The reason for this is thought to be that the larger the inner diameter of the tube, the more stable the arc discharge is, and therefore the time for glow discharge and the power consumption during it are shorter, and therefore there is less scattering and wear of the emitter, and there is less early disconnection of the coil. In addition, the sealed gas pressure is 10T.
Similar results were obtained when the pressure was set to 20 Torr, 20 Torr, and 40 Torr.

Taken together, these experimental results show that increasing the filler gas pressure and increasing the tube inner diameter stabilize arc discharge in the same way, and as a result, similarly reduce tube end blackening and increase long tube length. It is clear that longevity is obtained. From this, it can be inferred that increasing the sealed gas pressure and increasing the pipe inner diameter have a synergistic effect. Therefore, the inventor took the product of the sealed gas pressure p and the pipe inner diameter d, and
We investigated the correlation between this product and lifespan. The results are shown in FIG. In the figure, the horizontal axis shows pxa in Torr-cm, and the vertical axis shows absolute life as a relative value.

The solid line indicates the pipe inner diameter of 0.71, the chain line indicates 0.501, and the dashed line indicates 0.
．． The correlations in the case of 3011 are shown respectively. As is clear from this figure, the curves have extremely similar shapes for all pipe inner diameters, and for all curves, p
The shape of the curve clearly differs when X d = 13 Torr-cm, and the lifetime rapidly shortens at p For example, it can be seen that the arc discharge is stable and a long life can be obtained.If this is expressed numerically, for example, when the tube inner diameter is 0.71,
The pressure of the filled gas may be set to 19 Torr or higher, and if the pipe inner diameter is 0.5 am, the pressure of the filled gas may be set to 26 Torr or higher.

In this case, the wire diameter of the coil constituting the hot cathode has nothing to do with conventional design standards; for example, even if a thin tungsten wire with a diameter larger than the conventional design standard is used, or conversely, However, the above effect remains unchanged.

Therefore, the relationship between the lamp current and the wire diameter of the thin coil wire in the above-mentioned fluorescent lamp is shown in a graph in FIG. In the figure, the horizontal axis shows the lamp current in units of yaA, and the vertical axis shows the diameter of the thin coil wire in units of MG, and the straight line indicates the above-mentioned design criteria. From this figure, according to the conventional design standard,
When the lamp current becomes 70a+A or less, the diameter of the thin coil wire must be made very thin, and it becomes indistinguishable from the horizontal line in the figure. However, as mentioned above, pXd≧13T of the present invention
If the condition of orr-01 is followed, it is not necessarily necessary to follow the design standard, so if the lamp current is small, it is possible to make the coil thin wire diameter larger than the design standard to provide the necessary mechanical strength. According to experiments, the coil wire diameter is 2M.
If it is G or more, the strength necessary for manufacturing thin wires, forming coils, and forming hot cathodes can be obtained, and the length of the coil can be increased. Moreover, even in this case, since the temperature of the cathode bright spot is sufficiently high, the necessary thermionic emission can be obtained, the transition to arc discharge is easy, and the formed arc discharge is stable, and according to the design standards. It is the same as when

In the present invention, if the lamp current exceeds 30+mA, the amount of ions and electrons flowing into the hot cathode will be sufficiently large, and the cathode will shine even if the above-mentioned condition of pct≧13Torr・1 is not satisfied. The temperature at the point becomes higher, the necessary thermionic radiation is obtained, the transition to arc discharge and the stability of arc discharge are obtained, and the thickness of the thin coil wire is also increased to obtain sufficient mechanical strength. The effect of the invention is not significant. Therefore, in the present invention, the lamp current is limited to 50 mA or less.

Furthermore, in the present invention, 1. The coil constituting the hot cathode is not limited to the above-mentioned double coil type, but can also be applied to, for example, a single coil or triple coil type, and the coil thin wire is not limited to the above-mentioned tungsten wire, but also a molybdenum wire, Other high melting point metal wires such as tungsten-molybdenum alloy wires may also be used.

〔Effect of the invention〕

Thus, the fluorescent lamp of the present invention has a lamp current of 50
The arc discharge is stabilized in a hot cathode type that operates at less than mA.
By satisfying pct≧13, where Torr and tube inner diameter are dai, the temperature of the cathode bright spot can be raised sufficiently regardless of the diameter of the coil thin wire that constitutes the hot cathode, and the necessary thermionic emission can be achieved. As a result, it is possible to easily transition to arc discharge and stabilize arc discharge, eliminating unstable lighting, reducing tube end blackening, and reducing the risk of coil breakage. , and also solved the problem of short life due to lack of emitters. Furthermore, in addition to the first condition of the above-mentioned claim, the second claim is that the hot cathode coil is made of a thin wire of 2 MG or more, so that the mechanical strength of the thin wire is improved, and the manufacturing of the thin wire, coil forming, etc. The process of forming a hot cathode has become easier.

[Brief explanation of the drawing]

The figures show the reasons for the limitations in the fluorescent lamp of the present invention. Figures 1 and 2 are graphs showing the relationship between the filled gas pressure and the starting characteristics when the tube inner diameter is kept constant, and Figure 3 is a graph showing the relationship between the filled gas pressure and the starting characteristics when the tube inner diameter is kept constant. Graph showing the relationship between gas pressure and lamp life, 4th
Figure 5 and Figure 5 are graphs showing the relationship between the tube inner diameter and starting characteristics when the filled gas pressure is kept constant, Figure 6 is a graph showing the relationship between the tube inner diameter and service life, and Figure 7 is the filled gas pressure. FIG. 8 is a graph showing the effect of the product of 2 and the tube inner diameter on the life span. FIG. 8 is a graph showing the relationship between the conventional design standard and the wire diameter limitation of the present invention in the relationship between the lamp current and the coil thin wire diameter. Agent Patent Attorney Norihiro Ogo Husband and father 1L of electricity I 7”5 (nememe;ri “i=jro”)
Fig. Fig. 7b One length t energy key (η1 letter) 1) Fig. 5 Tomotake opening (5th JT42i) xct (7orrC^) Fig. )

Claims (2)

[Claims] (1) A hot cathode fluorescent lamp operated at a lamp current of 50 mA or less, which satisfies pd≧13, where the sealed gas pressure is pTorr and the tube inner diameter is dcm. (2) The fluorescent lamp according to claim 1, wherein the hot cathode is formed by forming a thin wire of 2 MG or more into a coil.