JPH02148558A - Metal halide lamp - Google Patents

Abstract

PURPOSE:To reduce the quantity of ultraviolet without reducing transmittance of visible light or using special glass for an outer tube by providing a glass tube enclosing a light emission tube contained in an outer tube, and providing a coating having a UV absorbing property on the surface of the glass tube. CONSTITUTION:A light emitting tube 1 is contained in an outer tube 2 of rigid glass. The light emitting tube 1 is enclosed by a quartz glass tube 3 having a coating 4 of titanium dioxide having a UV absorbing property formed on the outer surface. Ultraviolet radiated from the light emitting tube is thus absorbed, and ultraviolet from the lamp can be reduced. The temperature of the glass tube is not increased to more than 700 deg.C even while lighting, so reduction of transmission of visible light by whitening of the coating will not occur.

Description

[Detailed description of the invention] Industrial applications The present invention relates to metal halide lamps.

Conventional technology Metal halide lamps are characterized by high efficiency and high color rendering properties due to the light emitted from the metal sealed inside the arc tube, and are attracting attention as lamps that can replace the conventionally widely used mercury lamps. , as they become more compact, they are increasingly being used for indoor lighting such as store lighting.

Problems to be Solved by the Invention When metal halide lamps are used for store lighting, particularly spotlights, etc., there is a problem in that the irradiated object changes color due to the influence of ultraviolet rays irradiated from the lamp.

For this reason, when metal halide lamps are used in spotlights and the like, there are restrictions such as requiring the equipment to be equipped with a front glass for absorbing ultraviolet rays.

2. Description of the Related Art In order to prevent ultraviolet rays emitted from metal halide lamps, discharge lamps are known in which a metal oxide film having ultraviolet absorbing properties is formed on the inner or outer surface of an arc tube. Furthermore, as disclosed in Japanese Patent Application Laid-Open No. 52-23881, a metal halide lamp is already known in which a metal oxide film having ultraviolet absorbing properties is formed on the inner surface of the outer bulb.

However, in the former case, the temperature of the arc tube of the metal halide lamp reaches over 800°C while it is lit.
The metal oxide film becomes cloudy and the transmittance of visible light decreases. In the latter case, the hard glass used for the outer tube usually has a strain point of 490°C, so it is not possible to use a material with a temperature of 500°C or higher for baking of the metal oxide film, The tubes had to be made of expensive special glass.

The present invention was made to solve these problems, and provides a metal halide lamp that reduces the amount of ultraviolet rays without reducing the transmittance of visible light or using special glass for the outer bulb. It is.

Means for Solving the Problem In order to solve this problem, the metal halide lamp of the present invention is provided with a glass tube surrounding the arc tube housed in the outer bulb, and a coating having ultraviolet absorption properties is applied to the surface of the glass tube. That is what we have in place.

The UV-absorbing coating of the glass tube surrounding the arc tube absorbs the ultraviolet light emitted from the arc tube, reducing the amount of ultraviolet light emitted from the lamp. Further, since the temperature of the glass tube does not rise above 700° C. even when the lamp is on, there is no reduction in visible light transmittance due to clouding of the coating.

Embodiment FIG. 1 shows a 70W metal halide lamp according to an embodiment of the present invention. In FIG. 1, an arc tube 1 made of quartz glass with an inner diameter of 9 contains argon 20 as a starting gas.
In addition to 0 torr and mercury 13+u, Na I 1.1m
rsTf! I 0.3mg5 Tm 130,
7 mg % DY r 30 , 7 mg NH
o I 30 , 7 mg of metal halide is encapsulated. The arc tube 1 is housed within an outer tube 2 made of hard glass. The arc tube 1 has titanium dioxide (
T i 02) Surrounded by a quartz glass cylinder 3 on which a coating 4 is formed.

In FIG. 1, 5 indicates a getter and 6 indicates a cap.

Next, an example of the process of applying the T i 02 film to the glass cylinder 3 will be described.

(1) A glass cylinder with one end sealed is immersed in a solution of a Ti metal compound in an ethanol-based solvent, and then pulled up at a constant speed to adhere the metal compound.

(2) Evaporate the solvent at a temperature of 200°C.

(3) Metal oxides are formed by thermal decomposition at a temperature of 500°C.

(4) Deposition by crystallization at a temperature of 700°C.

(5) Cut the glass tube to a predetermined length.

If the thickness of the Ti(h coating exceeds 400 m), absorption of ultraviolet rays will be poor, and if it is less than 3 μm, the transmittance of visible light will decrease, so a range of 3 μm to 40 nm is appropriate.

In this way, the ultraviolet irradiance of a metal halide lamp using a quartz glass tube coated with a TiO2 coating and a metal halide lamp using a quartz glass tube without a coating was measured in the measurement wavelength range of 275 to 380 nm at a distance of 1 m from the lamp. I measured 50μW for the lamp without coating.
/cwt UV irradiance, whereas TiO2
It was observed that in the metal halide lamp of the example of the present invention coated with a film, this was reduced to 1/10 to 5 μW/add.

Moreover, the metal halide lamp of the embodiment of the present invention has a 6000
Even after lighting for hours, no clouding of the film occurred, and a luminous flux maintenance rate of 80% or more was obtained.

In the above embodiments, the coating was applied to the outer surface of the glass cylinder, but the same effect can be obtained by applying the coating to the inner surface or both the outer and inner surfaces.

As described in detail, according to the present invention, since the surface of the glass tube surrounding the arc tube has a coating having ultraviolet absorption properties, it can be used without reducing the transmittance of visible light. A metal halide lamp capable of reducing the amount of ultraviolet rays without using special glass for the outer bulb can be provided at low cost.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway front view of a metal halide lamp which is an embodiment of the present invention. 1... Arc tube, 2... Outer tube, 3...
...Glass tube, 4...Coating with ultraviolet absorption properties.

Claims (1)

[Claims] The light emitting tube includes a light emitting tube having a pair of main electrodes and mercury, a rare gas, and a metal halide sealed therein, an outer tube housing the light emitting tube therein, and a glass tube surrounding the light emitting tube. A metal halide lamp whose glass tube has a coating on its surface that has ultraviolet absorption properties.