JP3486908B2 - Low pressure mercury vapor discharge lamp - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-pressure mercury vapor discharge lamp, and relates to measures for preventing blackening of a phosphor coating.

[0002]

2. Description of the Related Art A low-pressure mercury vapor discharge lamp, that is, a fluorescent lamp is used for general lighting, various OA equipment,
It is used as a pixel light source for huge screens, as a backlight for liquid crystal displays, as a compact lamp that replaces light bulbs, and because it has higher luminous efficiency than incandescent bulbs, it is often used as a power-saving light source.

In such a low-pressure mercury vapor discharge lamp, a phosphor coating is provided on the inner surface of a bulb made of a glass tube, and the bulb is filled with a mixed gas containing mercury and one or more rare gases. , Is configured to generate a positive column discharge in this mixed gas.

The above discharge is usually maintained by supplying electrode energy to the gas mixture via two electrodes.
This discharge mainly produces ultraviolet rays of the mercury resonance line,
Most of them have wavelengths of 185 nm and 254 nm, and this ultraviolet ray is converted into irradiation of long wavelength light by the phosphor coating formed on the inner surface of the bulb.

This wavelength depends on the type of the fluorescent substance, and wavelengths ranging from near ultraviolet to visible to near infrared have been obtained. A well-known phosphor is a calcium halophosphate phosphor (composition is Ca 5 (PO ₄ ). (FC
1): Sb, Mn) are used, and recently, in order to improve the color rendering properties, the case of using a three-wavelength emission type phosphor coating film has been increasing. As the three-wavelength emission type phosphor, for example, a rare earth phosphor is used. The red phosphor is Y ₂ O ₃ : Eu (red), and the blue phosphor is BaMgO ₂ Al ₁₆ O _27. : Eu and the green phosphor are (La, Ce, Tb). (P, Si) O _{4 and} are composed by mixing these three kinds of phosphor powders.

However, when such a fluorescent lamp is lit for 1000 hours or more, blackening occurs at the end of the bulb. When blackening occurs, not only is the appearance deteriorated and unsightly, but there is also the problem that the luminous flux is reduced because it absorbs or blocks visible light.

The cause of such blackening is that an electron emitting substance such as barium oxide BaO applied to the electrode is subjected to electron impact to evaporate and fly, and adhere to the valve wall near the electrode to turn black. And CO as an impure gas existing in the vicinity of the electrode is subjected to electron or ion bombardment to form C and O.
Is decomposed into oxygen, and the oxygen O in it decomposes with mercury Hg to form mercury oxide HgO, which is a relatively cold part of the valve wall.
That is, it is known that the Faraday is deposited in the dark part (called an end band). HgO is
It is also known that the more the lighting time passes, the more it increases, and the higher the load type lamp, the more it increases.

[0008] By the way, the inventors of the present invention have noticed that in a fluorescent lamp, there is a difference in the degree of occurrence of blackening depending on the type of fluorescent body, and investigated the relationship between the type of fluorescent body and the blackening phenomenon. As a result of experiments and analysis, it was found that the charging tendency of the phosphor and the charging tendency of HgO are closely related to the occurrence of blackening.

That is, when the charging tendency of HgO in the bulb was examined, it was found that HgO was located on the plus side. In contrast, halophosphate phosphors and 3
Examining the charging tendency of the wavelength emission-type phosphors, also Izure these phosphors, a negative side than CuO in the electronegativity characteristics of metal ions Figure 2, however T
It was found to be on the plus side of a ₂ O ₅ . That is,
The charging tendency of HgO is relatively on the positive side, while the charging tendency of the phosphor is on the negative side. Therefore, as a result of mutual attraction of substances of opposite polarities due to electrostatic force, HgO It is expected to deposit on the phosphor coating.

Therefore, the applicant of the present invention has proposed a lamp using a phosphor powder in which the surface of the phosphor film has a positive charging tendency, that is, a charging tendency more positive than that of CuO. Japanese Patent Application No. 3-247660 and Japanese Patent Application No. 3
-249858). In such a case, HgO, which has a positive charging tendency, and HgO, which has a similar charging tendency to the positive side, are electrostatically repulsed with each other. The amount of deposits on the surface is reduced, which is effective in preventing blackening.

[0011]

However, according to the observation made by the present inventors, the lamp in which the charging tendency of the phosphor is controlled to the plus side of the charging tendency of copper causes a blackening phenomenon as compared with the conventional case. It is recognized that the effect of reduction is great, but there is a limit to such effect, and blackening occurs in a few% of the lamps.

As a result of studying this point, it is found that even in a lamp in which the charging tendency of the phosphor is controlled to be on the plus side of the charging tendency of copper, blackening occurs when the amount of floating mercury is large in the discharge space. Has become clear. That is, in the conventional lamp, liquid mercury is weighed using a measuring instrument, and the liquid mercury is directly enclosed in the bulb. However, in the case of such an enclosed form of mercury, since the amount of enclosed mercury varies, conventionally, there was a tendency to preliminarily enclose excess mercury so as to exceed the lower limit of the variation. As a result, excess mercury will be present in the bulb, which will evaporate and float, and this excess floating mercury will combine with oxygen O decomposed from carbon etc. to form mercury oxide HgO, which will be fluorescence. It is thought to adhere to the body coat. That is, it is considered that the presence of excess mercury facilitates the production of HgO, and thus facilitates the occurrence of blackening.

The present invention has been made based on such a prediction, and an object of the present invention is to provide a low-pressure mercury vapor discharge lamp in which generation of HgO is reduced to prevent blackening and to prevent reduction in luminous flux. Is what you are trying to do.

[0014]

According to the present invention, in a low pressure mercury vapor discharge lamp in which a phosphor coating is formed on the inner surface of a bulb and mercury and a rare gas are enclosed in the bulb, the phosphor coating is Fluorescent particles when in contact with copper
It is characterized in that the charging sequence of the child itself is on the positive side and that the mercury enclosed in the bulb is enclosed in the form of amalgam.

[0015]

According to the present invention, since the charging tendency of the phosphor film is set to the positive side with respect to copper, HgO, which also has the same charging tendency to the positive side, repels electrostatically.
Since O is separated from the phosphor coating, the deposition of HgO on the phosphor coating is reduced, which is effective in preventing blackening. In addition, since mercury is enclosed in the form of an amalgam, excess mercury does not exist in the bulb, and excess floating mercury is reduced, so that HgO is less likely to be generated and it can play a major role in preventing blackening.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on an embodiment shown in the drawings.

FIG. 1A shows a straight tube fluorescent lamp, and 1 is a glass bulb. Flare stems 2 and 2 are hermetically sealed at both ends of the valve 1, and a pair of lead wires 3 ...

A hot cathode made of tungsten or the like, that is, filaments 4 and 4 are bridged between the lead wires 3 and 3 of both the stems 2 and 2. Although not shown, the filaments 4 and 4 are coated with an electron emitting substance such as BaO, SrO, or CaO.

On the inner surface of the bulb 1, a phosphor coating 5 is formed.
Are formed. This phosphor coating 5 uses a three-wavelength emitting rare earth phosphor, such as Y ₂ O ₃ : Eu (red) for a red phosphor and BaM for a blue phosphor.
For gO ₂ Al ₁₆ O ₂₇ : Eu and the green phosphor, (L
a, Ce, Tb) · ( P, Si) O 4 is used, it is constructed by mixing these three phosphor powder.

As shown in FIG. 1B, these phosphors have an electrification tendency as compared with that of copper by depositing an oxide powder, for example, MgO powder, on the surface of the phosphor powder 10. It has been changed to the side.

That is, the red-based phosphor Y2O3: E
u, the blue-based phosphor BaMgO ₂ A ₁₆ O ₂₇ : Eu is M
gO and green phosphor (La, Ce, Tb)
By depositing MgO powder in the range of 0.01 to 3.0% by weight with respect to the phosphor, the charge amount of each of (P, Si) O ₄ is higher than that of copper oxide CuO shown in FIG. It is controlled to be on the plus (+) side. Similar performance can be obtained by using one kind of metal oxide selected from the oxides of Ca, Sr, Ba, and Zn instead of Mg.

The valve 1 is filled with a predetermined amount of mercury and a rare gas such as argon. In this case, mercury in the form of an amalgam 6 is housed in an exhaust thin tube 7 connected to the stem 2, and this thin tube 7 communicates with the discharge space of the bulb 1 via a communication hole 8. Amalgam 6 is an alloy of mercury and indium In. The operation of the fluorescent lamp having such a configuration will be described together with the experimental results.

FIG. 3 shows the relationship between the charging tendency of the phosphor and the amount of HgO adhered. The charging tendency of the phosphor is measured by a direct comparison method with a metal plate.
From FIG. 3, it can be understood that the amount of HgO attached decreases as the charging tendency of the phosphor increases toward the positive side.
That is, in the figure, the region (a) is Zn ₂ SiO _2.
In the case of ₄ : Mn, the region (b) is the case of a calcium halophosphate phosphor, the region (c) is the case of a conventional three-wavelength-emitting type rare earth phosphor without electrification, and (d) In the case of the three-wavelength emission type rare earth phosphor of the present example, which has been subjected to electrification and electrification treatment, the regions of (a) and (b) indicate, respectively, and the deposition amount of HgO decreases from (a) to (d). In the case of the three-wavelength emitting rare earth phosphor of the example (d), the charging tendency is on the plus side of copper Cu, and H
It can be seen that the amount of gO attached is significantly reduced.

FIG. 4 shows the relationship between the amount of HgO attached and the rate of decrease in luminous flux. From the figure, the greater the amount of HgO deposited, the greater the degree of decrease in luminous flux. This is due to the effect of absorbing and blocking visible light due to blackening of the light body. Therefore, the phosphor shown in FIG.
From (d) to (d), the attached amount of HgO decreases, and thus the reduction rate of the luminous flux decreases.

FIG. 5 shows the relationship between the amount of mercury sealed in the bulb, the tendency of the phosphor to be charged, and the amount of HgO adhered. As can be seen from this figure, the amount of HgO attached decreases as the amount of mercury enclosed decreases. Therefore, it can be understood that if the amount of excess mercury in the bulb is reduced as much as possible, the amount of HgO generated is reduced, and the amount of HgO adhering to the phosphor is naturally reduced, which is effective in preventing blackening.

Therefore, as shown in the embodiment as a mercury enclosing form, when the amalgam 6 is used, excess mercury in the bulb 1 is collected in the thin tube 7 and adsorbed to the amalgam 6 during lighting and extinguishing. Therefore, the generation of floating mercury can be suppressed. Therefore, the generation of HgO is reduced, the amount of HgO adhering to the phosphor is reduced as shown by the broken line in FIG. 5, and the occurrence of blackening can be greatly reduced.

That is, even if the phosphor is treated so that the charging tendency of the phosphor is on the positive side, the reduction of blackening is limited only by this treatment. However, if mercury is enclosed in the form of amalgam 6, the bulb is mercury as a surplus in the 1 than suppress the generation of HgO and amalgam 6 is adsorbed, further beyond the limit, it is possible to greatly reduce the occurrence of blackening.

It should be noted that in the above-mentioned embodiment, the phosphor is 3
The case where the wavelength emission type phosphor is used has been described, but the phosphor is a calcium halophosphate phosphor (composition Ca5
(PO ₄ ). (FCl): Sb, Mn) may be used. Also in the case of the calcium halophosphate phosphor, by attaching MgO powder to the phosphor powder, the charging tendency can be changed to the positive side as compared with copper. Also in this case, the same performance can be obtained by using one kind of metal oxide selected from the oxides of Ca, Sr, Ba, and Zn instead of Mg.

It is effective that these oxides are deposited in the range of 0.01 to 3.0% by weight with respect to the phosphor. In other words, the amount of metal oxide is a very important factor for controlling the charging tendency of the phosphor, and when the amount of the adhered metal exceeds 3.0% by weight, the emission output of each phosphor remarkably decreases. . On the other hand, when the adhesion amount is less than 0.01% by weight, the effect of adhering the metal oxide, that is, the effect of changing the charging tendency is not remarkable. Further, the present invention can be applied to other lamps such as a ring type lamp and a compact bent type lamp in addition to the straight tube fluorescent lamp.

[0030]

As described above, according to the present invention, since the phosphor film has a charging tendency toward the positive side with respect to copper, it also electrostatically repels HgO which also has a charging tendency toward the positive side. The HgO becomes more consistent and separates from the phosphor coating, reducing the deposition of HgO on the phosphor coating,
It is effective in preventing blackening. In addition, since mercury is enclosed in the form of an amalgam, excess mercury does not exist in the bulb, and excess floating mercury is reduced, so that HgO is less likely to be generated, which greatly contributes to blackening prevention. Therefore, the luminous flux maintenance factor is improved and the life characteristics are improved.

[Brief description of drawings]

1 shows an embodiment of the present invention, FIG. 1A is a sectional view of a straight tube fluorescent lamp, and FIG. 1B is a schematic view showing a state in which MgO powder is adhered to the surface of phosphor powder. .

FIG. 2 is a diagram showing the relationship between electronegativity of metal ions and the amount of charge.

FIG. 3 is a graph showing the relationship between the charging tendency of a phosphor and the amount of HgO attached.

FIG. 4 is a diagram showing the relationship between the amount of HgO attached and the luminous flux reduction rate.

FIG. 5: Encapsulated mercury amount, phosphor charging tendency, and HgO
The figure which shows the relationship with the adhesion amount of.

[Explanation of symbols]

1 ... Valve, 2 ... Stem, 3 ... Lead wire, 4 ... Electrode, 5
... Fluorescent film, 6 ... Amalgam, 7 ... Capillary, 10 ... Fluorescent material, 20 ... MgO powder.

Claims (3)

(57) [Claims] 1. A phosphor coating is formed on the inner surface of the bulb,
In a low-pressure mercury vapor discharge lamp in which mercury and a noble gas are enclosed in this bulb, the phosphor coating is composed of phosphor particles in which the phosphor itself has a positive charging sequence when in contact with copper.
The low-pressure mercury vapor discharge lamp is characterized in that the mercury enclosed in the bulb is in the form of an amalgam. 2. The phosphor coating comprises depositing particles of at least one oxide selected from the group consisting of Mg 2 O 3 , CaO, SrO, BaO and ZnO on the surface of the phosphor particles. The low-pressure mercury vapor discharge lamp according to claim 1, wherein the charging order of the phosphor particles themselves is on the positive side when the fluorescent particles themselves come into contact with the lamp. 3. The low-pressure mercury vapor discharge lamp according to claim 1, wherein the phosphor coating is composed of three-wavelength emission type rare earth phosphor particles .