JPS62136746A - Low pressure mercury discharge lamp - Google Patents

Abstract

PURPOSE:To reduce declination of ultraviolet rays output by preventing dispersing scatter of electronic radiant substance by means of a metal enclosure so as to prevent a mercury compound generated in response thereto from being stuck to a discharge passage tube. CONSTITUTION:Synthetic quartz allowing rays up to the class of far ultraviolet rays to be transmitted through itself is used in the positive optical column part of a quartz tube 1 for a discharge lamp serving as the luminous part of a low pressure mercury discharge lamp, and both ends thereof are enclosed inside a negative electrode enclosing insulator tube 2 which is larger than the quartz tube 1 by means of a stem 5 to which a hot negative electrode 3 is connected. In addition, a metal enclosure 8 having a window 10 provided thereon is disposed in the periphery of the hot negative electrode 3. This enclosure 8 and the hot negative electrode 3 are supported by a column 9 in an electrically insulated state. A part of said enclosure 8 is made of getter material and after degassing the inside of the tube by means of high frequency heating by the enclosure 8, sealing process is applied to any desired simple substance such as mercury, Ar, Ne, or a mixed gas consisting of some of them is charged under desired pressure. Thus, any electronic radiant substance may be prevented from being stuck to a discharge passage tube as the result of scattering so that any declination of X-ray output may be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a low-pressure mercury discharge lamp, and particularly to a cathode enclosure suitable for preventing a decrease in ultraviolet fidelity.

[Background of the invention]

Conventionally, as shown in US Pat. No. 3,778,662, in order to reduce the consumption of the electron emitting material of the cathode,
However, in order to prevent the scattering of electron emitting substances, the front and sides of the hot cathode are actively covered and surrounded, and the scattered oxygen and Hg compounds are removed from the discharge. No consideration was given to preventing the light from diffusing into the light and reducing the optical output.

[Purpose of the invention]

The object of the present invention is to prevent the decomposition and scattering of the electron emitting material that is coated on the hot cathode by using a metal enclosure. An object of the present invention is to provide a low-pressure mercury discharge lamp which prevents the adhesion of ultraviolet rays and reduces a decrease in ultraviolet output.

[Summary of the invention]

The decrease in the output of ultraviolet rays is caused by the reaction of the decomposed oxygen of the electron emitting material in the electrode with the mercury in the tube, producing mercury oxide, which adheres to the tube wall and colors it brown, resulting in a decrease in transmittance and at the same time due to the resonance line of mercury. It is presumed that this is due to storage. Therefore, by allowing the decomposed oxygen of the electron emitting substance to adhere to the enclosure without reacting with mercury, a decrease in the output of ultraviolet rays is prevented.

[Embodiments of the invention]

The structure of the discharge lamp of the present invention will be explained with reference to FIG. 1.2.3. The light-emitting part 1, the solar column, is made of synthetic quartz that transmits even deep ultraviolet rays, and the filament 3 is attached to both ends of the solar column.
A tube 22 larger than the optical part 1 is connected to the stem 5.
is sealed with.

The periphery of the filament 3 is marked with an enclosing tube 8 with 10 in front according to the invention, which is similar to the filament 3.
It is supported by pillars 9 in order to be electrically insulated from the other parts. The lamp is heated to degas the entire lamp through an exhaust pipe 7 (not shown), thermally decompose and activate the electron emitting material coated on the filament 3, and is further heated to degas the entire lamp through an exhaust pipe 7 (not shown).
After degassing by high-frequency heating, a desired mercury and a single or mixed gas such as Ar, Ne, or Kr are filled in at a desired filling pressure, and then the exhaust pipe 7 is sealed off to form a lamp. Power for the lamp 7 is input through the hard wire 6.

The discharge vessel was a quartz tube 1 with an inner diameter of 8 mm that can transmit up to far ultraviolet light (160 nm), the part housing the shade 143 and enclosure 8 was a glass tube 2 with an inner diameter of 18 + m, and the distance between the electrodes was 850 fields. An enclosure 8 made of quartz is provided around the cathode 3 as shown in FIG. One with an open side and one without one were made, and after heating and exhausting the inside of the tube, mercury and argon gas were filled in at 2.5 Torr to form a lamp. This was lit for 2000 hours at lamp current IA (5 hours lit 3
0 minute off), then UV output 254nm compared to the initial stage
When comparing the mercury resonance lines of , 85% of the samples did not have the enclosure 8, and 67% did not have the enclosure 8.

In another embodiment, the cylindrical portion of the enclosure as shown in FIG.
254 nm after 2000 hours of the lamp, which was coated with a getter material made of r-AQ metal, and the disk portion with the front window was made of Ta, and the rest was the same as in the previous example.
The initial output was 90%.

〔Effect of the invention〕

According to the present invention, by preventing the scattering of the electron emitting material, it is possible to prevent the adhesion of the water poison compound that is generated by the reaction with the electron emitting material to the discharge tube, which has the effect of greatly reducing the decrease in ultraviolet output. There is.

Furthermore, according to the present invention, the effect can be further enhanced by selecting a material having a getter effect for the metal of the enclosure.

In addition, the selection of how to surround the hot cathode, that is, the relative distance between the four sides and the hot cathode (that is, in Fig. 3, 0≦d
2≦d1. (ω≧dz, Qz≧Ω1°h≧5dz), the effect can be made more reliable.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of a discharge lamp showing a conventional example, Fig. 2 is a cutaway diagram of the main part for explaining the present invention, and Fig. 3 is a silk holder for explaining the present invention in detail. It is an explanatory diagram.

Claims (1)

[Claims] 1. A discharge tube having a hot cathode at both ends and a discharge path between them, the tube having a diameter smaller than that of the tube accommodating the hot cathode, and forming the discharge path. The hot cathode is made of a material that sufficiently transmits far ultraviolet rays, and the hot cathode is covered with a metal enclosure, and the metal enclosure has a window on the side of the discharge path, the side surface of which is completely closed,
A low-pressure mercury discharge lamp characterized in that the side opposite to the discharge path is open. 2. The low-pressure mercury discharge lamp according to item 1, wherein at least a portion of the metal enclosure is made of getter material.