JPH0398249A - Metallic vapor discharge lamp - Google Patents

Abstract

PURPOSE:To improve bonding force of a heat insulating film to a luminescent tube bulb for preventing the heat insulating film from peeling by a method wherein the heat insulating film is formed of mixture powder of metal oxide mainly containing at least one of zirconia, alumina and silica with finer particles of the same kind of metal oxide blended. CONSTITUTION:A luminescent tube 3 is covered by heat insulating films 10, 10 respectively on both the ends which are to be most cooled parts during lighting. The heat insulating films 10, 10 are composed of metal oxide powder mainly containing at least one of zirconia, alumina and silica while boric anhydride and metal oxide of finer particles than the above metal oxide are blended as binding agent. The metal oxide to be main components of the above heat insulating films 10, 10 is 2 to 3mum in average particle diameter while fine particles of metal oxide as binding agent is composed of at least one of zirconia, alumina and silica which is approximately 0.02 to 0.03mum in diameter, wherein the fine particles are blended into the above main metal oxide by 1 to 20wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a metal vapor discharge lamp in which a heat insulating film made of a metal oxide is formed at the end of an arc tube.

(Prior Art) Metal vapor discharge lamps, such as metal halide lamps, contain metal halides, light-emitting metals, etc. as luminescent metals in a quartz glass arc tube.
The arc tube is filled with mercury and a rare gas and housed in an outer tube filled with nitrogen gas, for example, to form a double tube structure.

In such a metal vapor discharge lamp, the vapor pressure of the metal halide in the discharge space is influenced by the temperature of the coldest part of the arc tube during lighting, and therefore the luminous efficiency is greatly affected.

For this reason, measures have been taken to increase the temperature of the coldest part of the arc tube, and a typical example is to cover the end of the arc tube with a heat insulating film.

Conventionally, as the above-mentioned heat-retaining film, a metal oxide mainly composed of at least one of zirconia, alumina, and silica has been used, which has excellent heat resistance and has reaction resistance against arc tube bulbs. This metal oxide is powdered and suspended in an aqueous solution, and this aqueous solution is applied to the end of the arc tube.
By drying and firing this, the end of the arc tube is coated as a heat-retaining film.

(Problems to be Solved by the Invention) However, the above-mentioned conventional heat insulation film made of metal oxide has a problem of low strength.

That is, in the conventional case, the average particle size of metal oxide powder is 2
The average particle size of the metal oxide powder is approximately 3 μm, that is, several μm, and if only the metal oxide powder has such an average particle size, the bonding force to the arc tube bulb and the bonding force between the metal oxide powders to each other are weak, and the metal oxide powders tend to peel off easily.

The present invention has been made based on the above circumstances, and provides a metal vapor discharge lamp in which peeling of the heat insulating film is prevented by increasing the bonding force of the heat insulating film to the arc tube bulb and the binding force between metal oxide powders. This is what I am trying to do.

[Structure of the Invention] (Means for Solving the Problem) The present invention forms a heat insulating film made of metal oxide powder containing at least one of zirconia, alumina, and silica as a main component at the end of an arc tube. In a metal vapor discharge lamp in which the average particle size of the metal oxide is several μM, zirconia or alumina having an average particle size of 1/10 or less than the above average particle size is added to the metal oxide powder. , 1 to 20% by weight of metal oxide fine particles consisting of at least one kind of silica.
It is characterized by being mixed at a ratio of

(Function) According to the present invention, 1 to 2 fine particles of metal oxide with an average particle size of 0.1 μm or less are added to a metal oxide with an average particle size of several μm.
Since they are mixed at a ratio of 0% by weight, the fine particles of metal oxide fill the gaps between the large particles of metal oxide, increasing the contact area with the arc tube bulb, strengthening the bonding force with the arc tube bulb, and strengthening the metal oxide particles. The frictional force between the oxide powders increases and the binding force between the powders can be increased. Therefore, the mechanical strength of the heat-retaining film as a whole is improved.

(Example) An example of the present invention will be described below based on FIG.

The drawing shows a metal halide lamp, in which reference numeral 1 denotes an outer tube made of hard or soft glass, which is shaped like a spindle and has a base 2 attached to one end thereof.

Note that the outer tube 1 is filled with nitrogen gas.

An arc tube 3 is housed within the outer tube 1. The arc tube 3 has a bulb made of quartz glass sealed with a predetermined amount of metal halide, mercury, and rare gas, and main electrodes 5, 5 are sealed in crushed sealing parts 4, 4 formed at both ends, respectively. There is. Note that an auxiliary electrode 6 is sealed in one of the crushing sealing parts 4 in proximity to one of the main electrodes 5 .

The arc tube 3 has crushed sealing portions 4.4 formed at both ends supported by lamp holders 7.7, and these lamp holders 7.7 are fixed to support wires 8 which also serve as lead wires.

The auxiliary electrode 6 is connected to the support wire 8 via an auxiliary resistor 9, and the other main electrode 5 is also connected to the support wire 8.

One main electrode 5 is connected to the shell of the base 2, and the support wire 8 is connected to the eyelet terminal of the base 2.

5 The arc tube 3 is provided with a heat insulating film 10.1 at least at the end which becomes the coldest part during lighting, at both ends in this embodiment.
0 is coated. These heat insulating films 10.10 are applied to the outer surface of the arc tube 3 from the crushing sealing parts 4, 4 to approximately the main electrode 5.
．． It is formed over the area up to the tip of the 5.

Such a heat-retaining film 10.10 is made of a metal oxide powder containing at least one of zirconia, alumina, and silica as a main component, and contains boric anhydride as a binder and finer particles than the metal oxide. Contains metal oxides.

The metal oxide that forms the main body of the heat retaining film 10 has an average particle size of 2
The thickness is several micrometers, approximately 3 to 3 micrometers, and the boric anhydride is mixed in an amount of 2 to 8% by weight based on the metal oxide. Furthermore, the fine particle metal oxide as a binder has an average particle size of 1/10 or less than the average particle size of the main metal oxide, such as zirconia or alumina with a size of about 0.02 to 0.03 μm. , silica, and these fine particles are mixed in a proportion of 1 to 620% by weight based on the main metal oxide.

In addition, to explain how to make the heat insulation film 1o using these materials, alumina (AI203) with an average particle size of about 2 to 3 μm and anhydrous Boric acid (B2 03
) was mixed in an amount of 4.0% by weight based on the above alumina, and further alumina sol was added thereto.

Alumina sol is made by kneading fine powder of alumina (AI203) in water. For example, 0.02
A mixture of 30% by weight of fine alumina powder of about 0.03 μm is used.

Such alumina sol contains 10.0% by weight of alumina having an average particle size of about 2 to 3 μm, and therefore, substantially, the alumina fine powder contains 3.0% by weight of the large alumina particles. be done.

The reason why fine alumina powder is mixed in the form of alumina sol is that even if large alumina particles and fine alumina powder are added to an aqueous solution at the same time and mixed together, they will not be evenly dispersed and mixed because they have different particle sizes. On the other hand, if the alumina fine powder is prepared in advance in the form of an alumina sol and mixed, the dispersibility is good and the mixture is evenly mixed.

Such a solvent is applied to the end of the arc tube 3, dried, and fired at 600 to 900°C, for example, 700°C.

As a result, heat insulating films 10, 10 are formed at the ends of the arc tube 3.

In such a structure, anhydrous boric acid mixed with alumina at a ratio of 4.0% by weight bears the bonding force of the heat insulating film 10 to the arc tube bulb 3, that is, the heat insulating film 10
and increases the interfacial adhesion of the arc tube bulb 3.

In addition, the fine alumina powder mixed with 3.0% by weight is
It enters between the large particles of alumina, which is the main component, and fills the gaps, increasing the contact area of the heat insulating film 10 with the arc tube bulb 3, and thus, together with the boric anhydride, the interface between the heat insulating film 10 and the arc tube bulb 3 is formed. Increase your wearing power.

Furthermore, since the fine alumina powder enters between the large alumina particles, the adhesion area between the large alumina particles increases, and the frictional force increases, thereby strengthening the binding force between the powders.

Therefore, problems such as the surface of the heat insulating film 10 peeling off do not occur, and therefore the entire heat insulating film 10 is prevented from peeling off from the arc tube 33, and the mechanical adhesion strength is improved.

In addition, when the strength evaluation of the heat insulation film 10 was measured using a pencil hardness tester, the heat insulation film 10 that did not contain boric anhydride and alumina fine powder was evaluated as B, whereas the strength of the heat insulation film 10 that did not contain boric anhydride and alumina fine powder was evaluated as B. It was confirmed that the thermal insulation film 10 containing the powder had an evaluation of 6H or higher.

Therefore, the fine alumina powder is mixed at a ratio of 1 to 20% by weight with respect to the main metal oxide, and if the fine alumina powder is less than 1% by weight, the heat insulating film 10 will have a negative effect on the arc tube 3. The initial purpose of adding fine alumina powder could not be achieved because sufficient bonding force could not be obtained and it would peel off easily.Also, if the fine alumina powder exceeds 20% by weight, the gaps between large particles of alumina powder would be reduced. As the particles become filled, the powders tend to slip together, and therefore, in this case as well, sufficient bonding force to the arc tube 3 cannot be obtained, and the bonding force between the powders decreases, making them easy to peel off.

Note that boric anhydride works to enhance the bonding force of the heat insulating film 10 to the arc tube bulb 3, that is, to increase the interfacial adhesion between the heat insulating film 10 and the arc tube bulb 3. Although it is preferable that boric anhydride also be present, it is not essential, and boric anhydride may be omitted.

Note that the firing temperature of the heat retaining film 10 is suitably 600 to 900°C; if it is less than 600°C, the heat retaining film 10 will not vitrify, and if it exceeds 900°C, the metal foil of the sealing parts 4, 4 will be oxidized. There is a worry that

Furthermore, the present invention is not limited to metal halide lamps, but can be implemented with any discharge lamp in which a heat insulating film is formed on the arc tube.

Further, in the above embodiment, a case was explained in which a heat insulating film was formed at each end of the arc tube, but the present invention is not limited to this, and it may be applied to a case where a heat insulating film is formed only at one end of the arc tube. In this case, a heat insulating film may be formed at the end of the arc tube that is the coldest part during lighting, for example, in the case of vertical lighting, at the lower end.

[Effects of the Invention] As explained above, according to the present invention, the average particle size is several μ■
Since fine metal oxide particles with an average particle size of 0.1 μm or less are mixed with the metal oxide at a ratio of 1 to 20% by weight, the fine metal oxide particles fill the gaps between the large metal oxide particles. This increases the contact area with the arc tube bulb, strengthens the bonding force with the arc tube bulb, and also increases the contact area of the metal oxide powders with each other, increasing the frictional force and increasing the binding force between the powders. Therefore, the mechanical strength of the heat-retaining film as a whole is improved.

[Brief explanation of drawings]

FIG. 1 is a side view of a metal halide lamp showing an embodiment of the present invention. 11 1... Outer tube, 3... Arc tube, 4... Crushing sealing part,
5... Main electrode, 10... Heat insulation film.

Claims (1)

[Claims] A heat insulating film made of a metal oxide powder containing at least one of zirconia, alumina, and silica as a main component is formed at the end of the arc tube, and the average particle size of the metal oxide is A few μm
In the metal vapor discharge lamp, the metal oxide powder contains 1/10 of the average particle size.
1 to 2 fine particles of a metal oxide made of at least one of zirconia, alumina, and silica having the following average particle size.
A metal vapor discharge lamp characterized by being mixed at a ratio of 0% by weight.