JPH0589841A - Low pressure mercury vapor discharge lamp - Google Patents

Abstract

PURPOSE:To prevent generation of end band blackening in a Faraday darkness. CONSTITUTION:A fluophor film 5 is formed over the inner surface of a bulb 1, in which mercury and rare gas are encapsulated to form a mercury vapor discharge lamp of low pressure type, wherein a film 6 of an oxide whose charging tendency lies further to the plus side than the electronegativity of Cu, is formed over the surface of the fluophor film 5 at the bulb end corresponding to a Faraday darkness. Because the charging tendency of the oxide film is plus and the fluophor film and HgO repulse each other electrostatically, HgO deposition is prevented, and end band blackening is eliminated.

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 a measure for preventing blackening at the end of a bulb.

[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 light 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, most of which is 1
It has wavelengths of 85 nm and 254 nm, and this ultraviolet ray
It is converted to longer wavelength radiation by the phosphor coating formed on the inner surface of the bulb.

This wavelength depends on the kind of the phosphor, and wavelengths from near ultraviolet to visible to near infrared have been obtained. The phosphor that are well known in the art, halo phosphate phosphor (composition _{Ca5 (PO 4) · (FCl} ): Sb,
Mn) is used. Further, the above-mentioned valve is not limited to a straight pipe type, but may be circular, U-shaped, saddle-shaped, etc. Recently, miniaturization has progressed and the number of complicated shapes has increased.

[0006]

However, when such a fluorescent lamp is lit for 1000 hours or more,
Some 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 scatter and adhere to the valve wall near the electrode to be blackened. And CO as an impure gas existing in the vicinity of the electrodes is bombarded with electrons or ions and C and O
Is decomposed into oxygen, and oxygen O in the oxygen is combined 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 dark part is deposited (called an end band). As a phosphor,
When the above halophosphate phosphor is used, an end band tends to be generated particularly easily.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a low-pressure mercury vapor discharge lamp capable of preventing end band blackening which occurs at the end of a bulb. To do.

[0009]

The first aspect of the present invention is 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, which corresponds to a Faraday dark portion. On the surface of the phosphor coating at the end of the bulb, an oxide coating having a charging tendency on the positive side of the electronegativity of copper Cu is formed.

A second aspect of the present invention is 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 photoconductor coating is made by attaching oxide particles to the surface of the phosphor particles and having a particle size of 44 to 74 μm.
It is characterized in that the charging order per 1 g of the fluorescent substance is controlled to be on the plus side of the electronegativity of copper when the m is brought into contact with the reduced iron powder.

[0011]

When the present inventors examined the charging tendency of HgO in the bulb, they found that it was located on the plus side, as is clear from FIG. Therefore, when the charging tendency of the halophosphate phosphor is examined, as can be seen from the experiment described later, CuO in the electronegativity characteristic of the metal ion in FIG.
It was found to be on the minus side, but on the plus side of TaO. That is, the charging tendency of HgO is relatively on the positive side, whereas the charging tendency of the halophosphate phosphor is on the negative side. Therefore, substances having opposite charging characteristics have electrostatic forces. Due to this, HgO is deposited on the phosphor coating near the Faraday dark part.

Therefore, if the surface of the phosphor coating near the Faraday dark part is controlled so that the charging tendency is on the positive side, that is, the charging tendency is on the positive side of CuO, they repel each other electrostatically. HgO deposition is reduced,
End band blackening can be prevented.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on an embodiment shown in FIGS. The drawing shows a straight tube fluorescent lamp, 1 being a glass bulb. Both ends of the valve 1 are airtightly closed by flare stems 2 and 2, and a pair of lead wires 3 ...

A hot cathode made of tungsten or the like, that is, filaments 4 and 4, are laid over the respective lead wires 3 and 3 of both the stems 2 and 2. The filaments 4, 4
Although not shown, an electron emitting material such as barium oxide BaO is applied to the.

On the inner surface of the bulb 1, a phosphor coating 5 is formed.
Are formed. This phosphor coating 5 is a halophosphate phosphor, such as a calcium halophosphate phosphor (Ca
5 (PO ₄ ). (FCl): Sb, Mn) is used. Oxide films 6, 6 are formed on the surface of the phosphor coating 5 in a band shape at the location where the Faraday dark portion of the end of the bulb 1 is generated, that is, near the filaments 4, 4.

The oxide films 6, 6 are oxide films having a positive charging tendency, for example, Mg0, CaO, SrO, BaO, Z.
It is at least one selected from nO, and a Mg0 film is formed in this embodiment.

According to this structure, since the Mg0 film 6 is formed at the Faraday dark portion, HgO generated in the bulb 1 is prevented from depositing on the Faraday dark portion, and the end band blackening can be prevented. it can.

That is, as is clear from the electronegativity of FIG. 2, HgO has a relatively positive charge tendency, whereas the Mg0 film 6 formed in the Faraday dark part also has a positive charge tendency. It is in. For this reason, the two become positive each other, and electrostatically repel each other, so that HgO is not attracted to the phosphor film 5 in the Faraday dark portion, and the end band blackening does not occur at this portion. The charging tendency, as is generally known, is indicated by the amount of charged electric charge when contacting with reduced iron powder having a particle diameter of 44 to 74 μm. The present inventors confirmed the above blackening prevention by experiments.

That is, in the following experimental example, the state of occurrence of blackening of the end band after the FL20W fluorescent lamp was lit for 7,500 hours was examined. In the blackening evaluation, a score of 10 indicates no occurrence of blackening, and the frequency of occurrence of blackening increases in the order of 9, 7, 7 ... ..

Experimental Example 1 Calcium halophosphate phosphor (Ca5
In the conventional case where (PO ₄ ) · (FCl): Sb, Mn) is used and the surface treatment of the portion corresponding to the Faraday dark portion is not performed, the charging tendency is on the negative side of CuO.
The evaluation of occurrence of end band blackening after lighting for 00 hours is a score of 3.

Experimental Example 2 As a phosphor, a calcium halophosphate phosphor (Ca5
In the case of the present invention in which (PO ₄ ) · (FCl): Sb, Mn) is used and the MgO film 6 is formed on the surface of the portion corresponding to the Faraday dark portion, the charging tendency is on the plus side of CuO, and the charging tendency is 7500 hours. The evaluation of the occurrence of blackening of the end band after lighting is 9 points.

Experimental Example 3 As a phosphor, calcium halophosphate phosphor (Ca5
In the case of the present invention in which (PO ₄ ) · (FCl): Sb, Mn) is used and the ZnO film 6 is formed on the surface of the portion corresponding to the Faraday dark portion, the charging tendency is on the plus side of CuO, and it is 7500 hours The evaluation of the occurrence of blackening of the end band after lighting is 9 points.

As is apparent from the above experiments, in the conventional case, the oxide film 6 was not provided, so that the blackening rate of the end band was high. However, as in the present invention, MgO or Zn was used.
When the O film 6 is formed, the degree of occurrence of blackening in the end band is low, and the effect of preventing blackening is confirmed. Next, FIG.
Shows a second embodiment of the present invention.

In the case of this embodiment, the calcium halophosphate phosphor coatings 8 and 8 whose charging tendency is controlled to be positive are formed over the end side of the bulb rather than the location of the Faraday dark portion, and other locations. Formed a coating 5 of a conventional calcium halophosphate phosphor.

In order to prepare a calcium halophosphate phosphor whose charge tendency is controlled to be positive, as shown in FIG. 3 (B), M is added to powder 10 of calcium halophosphate phosphor.
The powder 20 of gO may be attached. MgO powder 20
It is advisable to adhere the phosphor powder 10 to about 0.01 to 3.0% by weight.

According to this structure, the phosphor coatings 8 and 8 formed on the tube end side of the Faraday dark portion.
Has a positive charge charge tendency by adhering Mg0 powder, and thus electrostatically repels HgO, which has a positive charge charge tendency, and HgO is not adsorbed to the Faraday dark part. Blackening is prevented from occurring. The present invention can be applied to a straight tube type, a ring type, a compact bent type lamp and the like.

[0027]

As described above, each of the present inventions,
Since the electronegativity of the phosphor film near the Faraday dark part is set to be on the plus side of copper, the phosphor film and H
HgO and gO come to repel each other electrostatically.
Deposition is prevented, and blackening of the end band can be prevented. Therefore, the appearance is improved and the luminous flux maintenance factor is improved.

[Brief description of drawings]

FIG. 1 is a sectional view of a fluorescent lamp showing a first embodiment of the present invention.

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

FIG. 3 shows a second embodiment of the present invention, in which (A) is a sectional view of a fluorescent lamp and (B) is M on the surface of the phosphor powder.
The schematic diagram which shows the state which attached the gO powder.

[Explanation of symbols]

1 ... Valve, 2 ... Stem, 3 ... Lead wire, 4 ... Electrode, 5
... phosphor film, 6 ... MgO film, 10 ... phosphor, 20
... MgO powder.

Claims (4)

[Claims] 1. A fluorescent film is formed on the inner surface of the bulb,
In a low-pressure mercury vapor discharge lamp in which mercury and a rare gas are enclosed in this bulb, the surface of the phosphor film at the end of the bulb, which corresponds to the Faraday dark part, has an electrification tendency on the positive side of the electronegativity of copper. A low-pressure mercury vapor discharge lamp, which is characterized in that a film of a material is formed. 2. A fluorescent film is formed on the inner surface of the bulb,
In a low-pressure mercury vapor discharge lamp in which mercury and a rare gas are enclosed in this bulb, the phosphor coating on the end of the bulb, which corresponds to the Faraday dark part, has a particle size of oxide particles attached to the surface of the phosphor particles. Fluorescent substance 1g when contacting with reduced iron powder of 44-74 μm
A low-pressure mercury vapor discharge lamp characterized in that the charging order per hit is controlled to be on the plus side of the electronegativity of copper. 3. The oxide is Mg0, CaO, Sr.
The low-pressure mercury vapor discharge lamp according to claim 1 or 2, wherein the low-pressure mercury vapor discharge lamp is at least one selected from O, BaO, and ZnO. 4. The low-pressure mercury vapor discharge lamp according to claim 1, wherein the phosphor is a halophosphate phosphor.