JP6165414B2 - Flash lamp for ultraviolet radiation - Google Patents

Description

  The present invention relates to a flash lamp for ultraviolet radiation used as a light source for ultraviolet sterilization by light pulses.

  Conventionally, as a light source for ultraviolet sterilization, ultraviolet light (hereinafter referred to as “sterilization line”) having a wavelength of about 254 nm that is effective for sterilization. As a flash lamp for emitting ultraviolet rays, a lamp in which xenon is sealed inside an arc tube made of heat-resistant glass is known (for example, see Patent Document 1). Such a flash lamp for ultraviolet radiation has a structure in which electrodes are arranged opposite to each other at both ends of a glass arc tube formed into a cylindrical shape by heat-resistant glass that transmits ultraviolet rays and filled with a rare gas xenon gas. An external trigger electrode or a proximity conductor is provided along the longitudinal direction outside the arc tube. The electrodes arranged at both ends of the arc tube are composed of an anode electrode and a cathode electrode, and at least the cathode electrode is made of a sintered body obtained by compression-molding tungsten powder and an electron radioactive substance and firing it at a high temperature. Then, the electron-emitting radioactive material of the electrode made of this sintered body is included in the electrode for improving the starting characteristics of the lamp, and since the starting characteristics are improved, the sintered body constituting the electrode Usually, it is known to contain 20 to 30% by weight.

  The flash lamp for ultraviolet radiation configured in this way uses a glass arc tube, supplies energy stored in the capacitor of the lighting circuit to each electrode, and emits light by applying a trigger voltage, thereby sterilizing effect 200-300 nm short wavelength ultraviolet rays with the following characteristics are strongly emitted.

JP 2011-76825 A (paragraph number “0023”)

  On the other hand, in recent years, it has come to be provided with such an ultraviolet radiation flash lamp in a device used by a patient at home. For example, in a medical device for sterilizing or sterilizing a medical device such as a catheter tube at home, such a flash lamp for ultraviolet radiation is used. However, since it is used at home, it is preferable that it is small and has high mechanical strength in order to ensure safety and security in handling. Therefore, it is conceivable to use an arc tube made of a light-transmitting ceramic that is resistant to impact for such a flash lamp. That is, it is possible to provide a sintered electrode formed by compressing and molding tungsten powder and an electron-emitting material at a high temperature on at least the cathode side of the translucent ceramic arc tube, and enclosing xenon as a luminous gas in the arc tube. Conceivable.

  However, in such a small lamp, when 20-30% by weight of an electron-emitting material is included in the sintered body constituting the electrode as in the conventional case, the lamp is made of the sintered body due to repeated flash lighting. As the temperature of the sintered electrode rises, the electron radioactive material evaporates, and when the electron radioactive material is released from the electrode by sputtering due to ion collision during discharge, the sintered electrode is worn out, and the sintered electrode is damaged. There was a problem that the tungsten and the electron-emitting material contained adhered to the inner wall of the surrounding arc tube and the arc tube became black or clouded. Such blackening and cloudiness of the arc tube reduced the sterilization line illuminance in the lamp, causing a problem that a sufficient sterilization effect could not be obtained at any time in the future.

  In particular, if the weight ratio of the electron-emitting material is increased with emphasis on the starting performance, the mechanical strength of the sintered electrode made of a sintered body becomes weak, the heat capacity at the electrode decreases, and the electron-emitting material evaporates and sputters. When wear of the sintered electrode proceeds due to the phenomenon, the purity of the xenon enclosed in the arc tube is reduced due to evaporation and scattering of the substances, thereby causing a problem that startability is lowered. Furthermore, there is a case where so-called self-discharge occurs, in which discharge starts between the electrodes before the trigger voltage is applied. In such self-discharge, since charging is not completed to the rated value, there arises a problem that flash lighting is performed in a state of insufficient energy.

  On the other hand, if the weight ratio of the electron radioactive material is excessively reduced in order to reduce the evaporation amount of the electron radioactive material contained in the sintered electrode, normal electron emission cannot be performed, the starting performance is reduced, and the trigger voltage is reduced. A start error occurs when the lamp is not lit even when applied. For this reason, in the sintered electrode used in this small flash lamp, the weight ratio of the electron radioactive material contained therein is set to an optimum value to prevent start-up errors and self-discharge in the ultraviolet radiation flash lamp. However, it is necessary to increase the illuminance maintenance rate.

  An object of the present invention is to provide a flash lamp for ultraviolet radiation capable of increasing its illuminance maintenance rate while preventing start-up errors and self-discharge.

In the present invention, a sintered electrode formed by compression molding of tungsten powder and an electron-emitting substance and firing at a high temperature is provided on at least the cathode side or both ends of the cylindrical translucent ceramic arc tube. Xenon is enclosed as a luminescent gas in the light-emitting ceramic arc tube, and when the internal cross-sectional area of the cylindrical light-transmitting ceramic arc tube is D and the peak current during light emission is Ip, (Ip / D) is 30 A / mm ^2. It is a flash lamp for ultraviolet radiation that is used with a peak current supplied .

The characteristic configuration is that the inner diameter of the cylindrical translucent ceramic arc tube is 4 mm , the electron-emitting material is barium oxide, calcium oxide, or barium-calcium oxide, and the electron emission in the sintered electrode. The weight ratio of the substance is 5% to 15%.

  In the flash lamp for ultraviolet radiation according to the present invention, since the weight ratio of the electron radioactive material in the sintered electrode is 5% to 15%, no start-up error and self-discharge occur, and the heat capacity of the sintered electrode is increased. Since the mechanical strength is increased and the lamp is intermittently flashed, it is possible to prevent evaporation of the electron radioactive material in the sintered electrode when the lamp is intermittently lit, and scattering of tungsten and the electron radioactive material due to the sputtering phenomenon. As a result, wear of the sintered electrode can be reduced as compared with the prior art. Therefore, according to the flash lamp for ultraviolet radiation of the present invention, it is possible to suppress the blackening or cloudiness of the arc tube, while increasing the illuminance maintenance rate while preventing start-up errors and self-discharge.

It is sectional drawing of the flash lamp of embodiment of this invention. It is a figure which shows the lighting state of the flash lamp used for this invention Example. It is a figure which shows the relationship between the weight ratio of the electron radioactive substance of the flash lamp in the Example, and an illumination intensity maintenance factor. It is a figure which shows the relationship between the weight ratio of the electron radioactive substance of the flash lamp in the Example, and a starting error generation rate. It is a figure which shows the relationship between Ip / D of the flash lamp in the Example, and a starting failure rate. It is a figure which shows the relationship between Ip / D of the flash lamp in the Example, and a ultraviolet radiation intensity maintenance factor.

  Next, the best mode for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 shows a flash lamp 10 for ultraviolet radiation according to the present invention. The flash lamp 10 includes a tube-type arc tube 11 made of a translucent ceramic in which xenon gas is sealed, and a pair of electrodes 12 and 22 disposed opposite to both ends of the translucent ceramic arc tube 11. Is provided. The arc tube 11 is made of a ceramic having a high ultraviolet transmittance and formed into a cylindrical shape having a circular cross section with an inner diameter of 8 mm or less.

  The reason why the inner diameter of the tubular arc tube 11 made of translucent ceramic is 8 mm or less is to clarify that the subject of the present invention is a small flash lamp 10 for ultraviolet radiation. The inner diameter of the tube 11 is preferably 5 mm or less, and more preferably 4 mm or less. The tubular arc tube 11 made of translucent ceramic is used to obtain a small ultraviolet radiation flash lamp 10 with high mechanical strength. That is, when the translucent ceramic arc tube 11 is used, the mechanical strength can be increased as compared with a conventionally used glass arc tube. In addition, mass productivity is increased in the end sealing process, and the required high dimensional system is also met. For this reason, it is possible to obtain a small ultraviolet radiation flash lamp 10 having high mechanical strength.

  The pair of electrodes 12 and 22 disposed at both ends of the arc tube 11 includes a cathode electrode 12 and an anode electrode 22. Both the cathode electrode 12 and the anode electrode 22 are sintered electrodes formed by compression-molding tungsten powder and an electron-emitting material and firing them at a high temperature. That is, this sintered electrode is composed of a sintered body obtained by firing a pressure-molded body formed by compression molding a mixture of tungsten particles and electron-emitting material particles at about 1400 to 1600 ° C. Here, examples of the electron-emitting substance include barium and calcium oxides.

  The cathode electrode 12 and the anode electrode 22 made of this sintered electrode are sealed at both ends of the translucent ceramic arc tube 11 via the niobium tubes 13 and 23. Then, xenon is enclosed in the translucent ceramic arc tube 11 as a luminescent gas. FIG. 1 is a cross-sectional view of a flash lamp 10 for ultraviolet radiation according to the present invention. Tube end walls 14 and 24 for sealing both ends of the light-emitting tube 11 are frit on both ends of the translucent ceramic arc tube 11. It is bonded via a special inorganic adhesive. The niobium tubes 13 and 23 are bonded to the centers of the tube end walls 14 and 24 through the tube end walls 14 and 24, and the niobium tubes 13 and 23 are bonded to the ends of the niobium tubes 13 and 23 inside the arc tube 11. 22 is fixed via tungsten core rods 13a and 23a welded to the end portions of the niobium tubes 13 and 23. In this manner, the cathode electrode 12 and the anode electrode 22 that are sintered electrodes are provided to face both ends of the arc tube 11.

  Xenon is sealed by first sealing one end of the niobium tube 13 or 23 outside the translucent ceramic arc tube 11 by plasma welding, and then the niobium tube 13 on the unsealed side or A xenon gas having a pressure of 40 kPa is injected into the arc tube 11 from the end of 23, and the end is sealed by plasma welding.

  The niobium tubes 13 and 23 led out from both ends of the arc tube 11 become terminals electrically connected to the cathode electrode 12 and the anode electrode 22, and the terminals composed of the niobium tubes 13 and 23 are the lighting circuit 40 (FIG. 2). ) Can be connected. As shown in FIG. 2, a proximity conductor 16 made of a conductive material such as tungsten is formed on the outer surface of the translucent ceramic arc tube 11 by extending in the longitudinal direction and baked. The proximity conductor 16 made of this conductive material. Is formed on the outer surface of the arc tube 11. In this way, the ultraviolet radiation flash lamp 10 is manufactured.

In the lamp thus obtained, the flash lamp for ultraviolet radiation according to the present invention has (Ip / D) of 25 A, where D is the internal sectional area of the arc tube 11 and Ip is the peak current during light emission. / Mm ² to 35 A / mm ² . Here, (Ip / D) is set to 25 A / mm ² or more in order to reduce the frequency of occurrence of a start error. That is, when (Ip / D) is less than 25 A / mm ² , since the peak current per unit area is small, the temperature of the electrode does not rise at the time of starting, so the probability of causing a starting error increases.

On the other hand, the reason why (Ip / D) is set to 35 A / mm ² or less is to suppress blackening or white turbidity of the arc tube 11 in the vicinity of the cathode electrode 12 and to prevent the ultraviolet intensity from decreasing in the future. is there. That is, if (Ip / D) exceeds 35 A / mm ² , the temperature of the sintered electrode made of the sintered body rises due to repeated lighting of the flash lamp 10 for ultraviolet radiation, and spattering due to discharge. As a result, the sintered electrode 12 constituting the cathode electrode is worn out, and tungsten and an electron radioactive substance contained in the sintered electrode 12 adhere to the inner wall of the surrounding arc tube 11 to blacken or cloud the arc tube 11. This is because the ultraviolet radiation in the flash lamp 10 for ultraviolet radiation will decrease in the future due to the blackening and cloudiness.

  Further, the ultraviolet radiation flash lamp 10 of the present invention is characterized in that the weight ratio of the electron-emitting material of the sintered electrode 12 constituting the cathode electrode is 5% to 15%. The reason why the weight ratio of the electron radioactive substance in the sintered electrode 12 is set to 5% or more is to reduce the frequency of occurrence of start-up errors. That is, when the weight ratio of the electron radioactive material in the sintered electrode 12 is less than 5%, the absolute amount of the electron radioactive material used for improving the startability is insufficient, and the start performance of the flash lamp 10 for ultraviolet radiation is insufficient. This is because the probability of occurrence of a start error that decreases and the ultraviolet radiation flash lamp 10 does not light normally even when the trigger voltage is applied increases.

  On the other hand, setting the weight ratio of the electron-emitting material of the sintered electrode 12 constituting the cathode electrode to 15% or less suppresses the blackening or white turbidity of the arc tube 11 and prevents the intensity of ultraviolet rays from decreasing. Because. That is, when the weight ratio of the electron-emitting substance in the sintered electrode 12 exceeds 15%, the heat capacity is lowered, the temperature of the sintered electrode 12 made of the sintered body is increased, and the sintered electrode is sputtered by discharge. 12 is accelerated, and the tungsten and the electron radioactive substance contained in the sintered electrode 12 blacken or cloud the surrounding arc tube 11, and this blackening or cloudiness reduces the ultraviolet radiation in the flash lamp 10 for ultraviolet radiation. It is because it makes it. And the probability that discharge starts between the sintered electrodes 12 and 22 before applying the trigger voltage, that is, so-called self-discharge increases. Further, when the wear of the sintered electrode 12 progresses in this way, the wear of the sintered electrode 12 lowers the purity of the xenon enclosed in the arc tube 11 and there is a problem that the startability is lowered.

  In the ultraviolet radiation flash lamp 10 configured as described above, the weight ratio of the electron radioactive material of the sintered electrode 12 constituting the cathode electrode is set to 5% to 15%, which may cause a start-up error and self-discharge. In addition, since the heat capacity of the sintered electrode 12 is increased and the mechanical strength is increased, the evaporation of the electron radioactive material in the sintered electrode 12 when the lamp is intermittently flashed, and tungsten and The scattering of the electron radioactive material can be prevented, and thereby the wear of the sintered electrode 12 can be reduced as compared with the prior art. Therefore, according to the flash lamp 10 for ultraviolet radiation of the present invention, blackening or white turbidity of the arc tube 11 is suppressed, while it is possible to increase the illuminance maintenance rate while preventing start-up errors and self-discharge. .

  In the above-described embodiment, the case where the sintered electrodes 12 and 22 are provided at both ends of the translucent ceramic arc tube 11 via the niobium tubes 13 and 23 has been described. The niobium tubes 13 and 23 may not be used as long as they are provided at both ends of the conductive ceramic arc tube 11.

  In the above-described embodiment, the case where the sintered electrode formed by compression molding the tungsten powder and the electron radioactive substance and firing at high temperature is used for both the cathode electrode 12 and the anode electrode 22 is described. As long as a sintered electrode is used as the cathode electrode 12, it is not always necessary to use a sintered electrode for the anode electrode 22. For example, if the volume is larger than that of the cathode electrode 12, a coiled or cylindrical body made of tungsten may be used as the anode electrode 22.

  Next, examples of the present invention will be described together with comparative examples.

<Example 1>
A flash lamp 10 for ultraviolet radiation as shown in FIG. 1 was manufactured. That is, a translucent ceramic arc tube 11 made of alumina having an inner diameter d of 4 mm and a length L of 34.6 mm, and a cathode electrode 12 disposed opposite to both ends of the arc tube 11, The flash lamp 10 for ultraviolet radiation comprising the anode electrode 22 was manufactured. As the cathode electrode 12 and the anode electrode 22, sintered electrodes 12 and 22 formed by compression-molding tungsten powder and an electron radioactive substance and firing at a high temperature were used. The sintered electrodes 12 and 22 have a cylindrical shape with a diameter φ of 1.9 mm and a length p of 2.2 mm, and the weight ratio of the electron radioactive material in the sintered electrodes 12 and 22 is 5%. It was. Such sintered electrodes 12 and 22 were sealed so as to face each other at both ends in the translucent ceramic arc tube 11 through niobium tubes 13 and 23 so that the distance n was 18.5 mm.

  Then, after sealing one end of the niobium tube 13 or 23 outside the translucent ceramic arc tube 11 by plasma welding, light is emitted from the end of the non-sealed niobium tube 13 or 23. Xenon gas having a pressure of 40 kPa was injected into the tube 11 and the end thereof was sealed by plasma welding. Then, as shown in FIG. 2, a proximity conductor 16 made of a conductive material such as tungsten was stretched in the longitudinal direction and baked on the outer surface of the translucent ceramic arc tube 11. 100 such ultraviolet flashing flash lamps 10 were produced, and these 100 ultraviolet emitting flash lamps 10 were taken as Example 1.

<Example 2>
100 flash lamps 10 for ultraviolet radiation shown in FIG. 1 are manufactured by the same material and the same procedure as in Example 1 except that the weight ratio of the electron-emitting materials in the sintered electrodes 12 and 22 is 10%. did. The 100 ultraviolet radiation flash lamps 10 were set as Example 2.

<Example 3>
100 flash lamps 10 for ultraviolet radiation shown in FIG. 1 are produced by the same material and the same procedure as in Example 1 except that the weight ratio of the electron radioactive substance in the sintered electrodes 12 and 22 is 15%. did. The 100 ultraviolet radiation flash lamps 10 were taken as Example 3.

<Comparative Example 1>
100 flash lamps 10 for ultraviolet radiation shown in FIG. 1 are produced by the same material and the same procedure as in Example 1 except that the weight ratio of the electron-emitting substances in the sintered electrodes 12 and 22 is 20%. did. The 100 ultraviolet radiation flash lamps 10 were used as Comparative Example 1.

<Comparative example 2>
100 flash lamps 10 for ultraviolet radiation shown in FIG. 1 are produced by the same material and the same procedure as in Example 1 except that the weight ratio of the electron-emitting materials in the sintered electrodes 12 and 22 is 30%. did. The 100 ultraviolet radiation flash lamps 10 were used as Comparative Example 2.

<Comparative Example 3>
100 flash lamps 10 for ultraviolet radiation shown in FIG. 1 are produced by the same material and the same procedure as in Example 1 except that the weight ratio of the electron-emitting materials in the sintered electrodes 12 and 22 is 40%. did. The 100 ultraviolet radiation flash lamps 10 were used as Comparative Example 3.

<Comparative Example 4>
100 flash lamps 10 for ultraviolet radiation shown in FIG. 1 are produced by the same material and the same procedure as in Example 1 except that the weight ratio of the electron-emitting materials in the sintered electrodes 12 and 22 is 50%. did. The 100 ultraviolet radiation flash lamps 10 were used as Comparative Example 4.

<Comparative test 1 and result 1>
The ultraviolet radiation flash lamps 10 in Examples 1 to 3 and Comparative Examples 1 to 4 were intermittently flash-lit using the lighting circuit 40 shown in FIG. The lighting circuit 40 for causing the ultraviolet radiation flash lamp 10 to emit light has a structure in which a discharge capacitor 41 for instantaneously discharging charges to the ultraviolet radiation flash lamp 10 and a trigger circuit 42 for applying a trigger voltage are connected in parallel. It is what constitutes.

The lighting condition of the ultraviolet radiation flash lamp 10 was such that the peak current during light emission was 380 A, and flashing was performed 400 times in 17 seconds and then resting for 4 minutes in order. Here, since the inner diameter d of the arc tube 11 is 4 mm, the internal cross-sectional area D of the arc tube 11 is 12.56 mm ² . Since the peak current Ip during light emission is at 380A, at 30A / mm ² is in the range from of 35A / mm ² is 25A / mm ² without (Ip / D), in Examples 1-3 and Comparative Examples 1-4 The flash lamp 10 for ultraviolet radiation was turned on intermittently. Each of the ultraviolet radiation flash lamps 10 is turned on by supplying a charging voltage stored in the discharge capacitor 41 to the sintered electrodes 12 and 22 via the niobium tubes 13 and 23 and a trigger voltage from the trigger circuit 42. This lighting was repeated 300,000 times.

  In all of the ultraviolet radiation flash lamps 10 in Examples 1 to 3 and Comparative Examples 1 to 4, the illuminance at the first lighting and at the 300,000th lighting was measured. The illuminance was measured using an illuminometer capable of measuring ultraviolet rays having a wavelength of 254 nm, and the illuminance was measured for ultraviolet rays having a wavelength of 254 nm, which is effective for sterilization. Then, in all of the ultraviolet radiation flash lamps 10 in Examples 1 to 3 and Comparative Examples 1 to 4, the illuminance at the time of 300,000 lighting when the illuminance at the time of the first lighting was set to 100 was obtained. The illuminance at the time of lighting of the 300,000th time obtained in this way was defined as “254 nm illuminance maintenance rate (%)”, and “254 nm illuminance maintenance rate illuminance (%) of the obtained Examples 1 to 3 and Comparative Examples 1 to 4 was obtained. ) "Is shown in FIG.

<Comparative test 2 and result 2>
In 100 each of the ultraviolet radiation flash lamps 10 in Examples 1 to 3 and Comparative Examples 1 to 4, the flash lighting up to the 300,000th time is the same as the comparative test 1, and subsequently the same as the comparative test 1 up to the first million times. The flash was turned on under the lighting conditions of the above, and start-up errors in these ultraviolet radiation flash lamps 10 were monitored. Then, the number of start errors was measured, and the average value of the measured number of start errors was divided by the total number of repetitions of 1 million times to obtain a start error occurrence rate (ppm). The “starting error occurrence rate (ppm)” of Examples 1 to 3 and Comparative Examples 1 to 4 thus obtained is shown in FIG.

<Comparative test 3 and result 3>
In each of 100 of the ultraviolet radiation flash lamps 10 in Examples 1 to 3 and Comparative Examples 1 to 4, discharge started before applying the trigger voltage simultaneously with 1 million flash lightings performed in Comparative Test 2. The number of lightings at which so-called self-discharge occurs first was measured visually.

  As a result, in each of 100 of the ultraviolet radiation flash lamps 10 in Examples 1 to 3 and Comparative Examples 1 and 2, even if lighting is repeated until reaching 1 million times, any ultraviolet radiation flash lamp 10 Also, no self-discharge was confirmed.

  On the other hand, in Comparative Example 3 in which 40% by weight of the electron-emitting material was included in the sintered electrode 12 as the cathode electrode, self-discharge was confirmed in the lighting per 400,000 times from the first light emission. And after that, self-discharge was confirmed sporadically.

  Further, in Comparative Example 4 in which 50% by weight of the electron-emitting material is included in the sintered electrode 12 which is the cathode electrode, self-discharge is caused in the lighting per 200,000 times from the first light emission during the comparative test 1. confirmed. And after that, self-discharge was confirmed sporadically.

<Evaluation 1>
As is apparent from FIG. 3 showing the results of Comparative Test 1, in Examples 1 to 3, in which 5 to 15% by weight of an electron-emitting material is contained in the sintered electrode 12 as the cathode electrode, the illuminance thereof is all It can be seen that the maintenance rate exceeds 60%, indicating a relatively high value. On the other hand, in Comparative Examples 1-4 in which the sintered electrode 12 that is the cathode electrode contains 20% by weight or more of the electron-emitting material, the illuminance maintenance rate is higher than that of Examples 1-3. It can be seen that there are cases where the illuminance maintenance ratio does not reach 60%. In the flash lamp 10 for ultraviolet radiation of Comparative Examples 1 to 4, the sintered electrode 12 is worn by sputtering due to discharge, and the arc tube 11 is blackened or clouded due to scattering of the tungsten and the electron radioactive material. This is considered to be due to the progress of UV transmittance.

  Further, as apparent from FIG. 4 showing the result of the comparative test 2, in Examples 1 to 3 in which the sintered electrode 12 as the cathode electrode contains 5 to 15% by weight of the electron-emitting material, a start error is caused. It can be seen that the occurrence rate is extremely low. On the other hand, in Comparative Examples 1 to 4 in which the sintered electrode 12 that is the cathode electrode contains 20% by weight or more of the electron radioactive material, the starting error increases as the weight ratio of the electron radioactive material increases. It can be seen that the incidence of In the flash lamp 10 for ultraviolet radiation of Comparative Examples 1 to 4, as the weight ratio of the electron radioactive substance is increased, the sintered electrode 12 is worn out by the evaporation of the electron radioactive substance in the sintered electrode 12 or by sputtering due to discharge. At that time, with the scattering of the tungsten and the electron radioactive substance, the impure gas and moisture adsorbed on the sintered electrode 12 at the time of manufacture are released, and the purity of the xenon enclosed in the arc tube 11 is lowered. Therefore, it is considered that the startability is lowered.

  On the other hand, if the weight ratio of the electron-emitting substance is reduced in order to suppress the evaporation amount of the electron-emitting substance in the sintered electrode 12 as the cathode electrode, it is considered that the starting performance of the flash lamp 10 for ultraviolet radiation decreases. Even in Example 1 in which the sintered electrode 12 as the cathode electrode contains 5 wt% of the electron-emitting material, no start-up error has occurred. For this reason, in the cathode electrode 12 used in the relatively small ultraviolet radiation flash lamp 10 of the present invention, even if the weight ratio of the electron radioactive material contained therein is reduced to 5% by weight, it is for ultraviolet radiation. It can be seen that the starting error in the flash lamp 10 can be avoided.

  Further, as is apparent from the results of Comparative Test 3, in Examples 1 to 3, in which 5 to 15% by weight of the electron-emitting material is included in the sintered electrode 12 that is the cathode electrode, until 1 million times is reached. No self-discharge has been confirmed even after repeated flash lighting. Further, in Comparative Examples 1 and 2 in which 20% by weight and 30% by weight of the electron-emitting material are included in the sintered electrode 12 as the cathode electrode, self-discharge is confirmed even if the flash lighting is repeated until reaching 1 million times. It has not been. On the other hand, in Comparative Example 3 in which 40% by weight of the electron-emitting material is included in the sintered electrode 12 as the cathode electrode, self-discharge is started in the lighting for the 400,000th time. In Comparative Example 4 in which 50% by weight of the electron-emitting material is included in a certain sintered electrode 12, self-discharge is started in the lighting for the 200,000th time. This indicates that when the weight ratio of the electron-emitting substance is increased, the probability of self-discharge occurring at an early stage is high. In other words, it is considered that the heat capacity of the electrode 12 is decreased and the temperature of the sintered electrode 12 is increased, and that the startability is improved due to excessive presence of the electron radioactive substance on the surface or inside of the electrode. .

  From the above evaluation, the ultraviolet radiation flash lamp 10 of the present invention in which 5-15% by weight of the electron radioactive material is contained in the sintered electrode 12 as the cathode electrode, while preventing start-up errors and self-discharge. It can be seen that the illuminance maintenance rate can be increased as compared with the prior art.

<Comparative test 4 and result 4>
In the comparative test 3, 100 flash lamps 10 for ultraviolet radiation in Example 2 which have been turned on a total of 1 million times are divided into 9 groups of 10 groups, and the lighting circuit 40 shown in FIG. The flash was turned on again and again under the same lighting conditions. The peak current during light emission at this time was different for each group. That is, the peak current during light emission in each group is different from 130A, 190A, 250A, 300A, 380A, 440A, 510A, 570A and 630A, and light is emitted by 12.56 mm ² which is the internal cross-sectional area D of the arc tube 11. The value obtained by dividing the peak current Ip (Ip / D) is 10 A / mm ² , 15 A / mm ² , 20 A / mm ² , 25 A / mm ² , 30 A / mm ² , 35 A / mm ² , 40 A / mm ² , 45 A / mm ² and 50 A / mm ² , the flash lamps 10 for ultraviolet radiation of each group were intermittently flashed again. This light emission was newly repeated 300,000 times, and the number of start errors in the ultraviolet radiation flash lamp 10 was visually measured. The average value of the measured number of start errors was divided by 300,000, which is the average of the total number of repeated light emissions, to obtain a start failure rate (ppm). FIG. 5 shows the “starting failure rate (ppm)” in Example 1 obtained as described above.

<Comparative test 5 and result 5>
At the time of the new flash lighting of 300,000 times performed in the comparative test 4, the “ultraviolet radiation intensity maintenance rate (%)” was measured at the same time. That is, in the comparative test 4, in each of the 10 ultraviolet radiation flash lamps 10 divided into 9 groups, at the first lighting time of 1,000,000 times and at the end after 300,000 times lighting time is further performed. The illuminance at the time of lighting was measured. The illuminance was measured using an illuminometer capable of measuring ultraviolet rays having a wavelength of 254 nm, and the illuminance was measured for ultraviolet rays having a wavelength of 254 nm, which is effective for sterilization. Then, when the average of the illuminance at the time of the first lighting of 1,000,000 times, which is the first time of each group, is set to 100, the value at the average value of the illuminance at the time of lighting which is the last after the lighting of 300,000 times is made. Asked. FIG. 6 shows the “ultraviolet radiation intensity maintenance rate (%)” in Example 3 obtained in this manner.

<Evaluation 2>
As is apparent from FIG. 5 showing the result of the comparative test 4, when the value (Ip / D) obtained by dividing the peak current Ip during light emission by the internal cross-sectional area D of the arc tube 11 is 25 A / mm ² or more, It can be seen that the error rate is extremely low. On the other hand, when the value (Ip / D) obtained by dividing the peak current Ip during light emission by the internal cross-sectional area D of the arc tube 11 is less than 25 A / mm ² , as the value (Ip / D) decreases. It can be seen that the occurrence rate of the start error is rising. It is considered that this is because when the value (Ip / D) is less than 25 A / mm ² , the heat capacity increases and the temperature of the electrode does not reach a temperature sufficient for starting at the time of starting. As a result, it can be seen that if the value (Ip / D) is 25 A / mm ² or more, the temperature of the electrode can be raised at the time of starting to avoid a starting error.

Further, as apparent from FIG. 6 showing the result of the comparative test 5, the value (Ip / D) obtained by dividing the peak current Ip during light emission by the internal cross-sectional area D of the arc tube 11 is 35 A / mm ² or less. It can be seen that the ultraviolet radiation intensity maintenance rate is relatively high. On the other hand, when the value (Ip / D) obtained by dividing the peak current Ip during light emission by the internal cross-sectional area D of the arc tube 11 exceeds 35 A / mm ² , the value (Ip / D) increases. It can be seen that the ultraviolet radiation intensity maintenance rate gradually decreases. This is because when the value (Ip / D) exceeds 35 A / mm ² , the temperature of the sintered electrode 12 as the cathode electrode rises due to repeated lighting of the flash lamp 10 for ultraviolet radiation, and also due to discharge. Due to the evaporation of the electron radioactive material in the sintered electrode 12 which is the cathode electrode due to the sputtering and the scattering of tungsten and the electron radioactive material due to the sputtering phenomenon, the sintered electrode 12 is worn out, and the electron radioactive material which is evaporated and scattered is It is considered that the arc tube 11 adheres to the inner wall of the surrounding arc tube 11 and is blackened or clouded, and the blackening and cloudiness reduce the ultraviolet radiation in the flash lamp 10 for ultraviolet radiation. As a result, it can be seen that when the value (Ip / D) is 35 A / mm ² or less, blackening or white turbidity of the arc tube 11 can be suppressed to prevent the intensity of ultraviolet rays from decreasing.

From the above evaluation, it is required that (Ip / D) is 25 A / mm ² to 35 A / mm ² where D is the internal cross-sectional area of the arc tube 11 and Ip is the peak current during light emission. In the ultraviolet radiation flash lamp 10 of the present invention, it can be said that the illuminance maintenance rate can be remarkably increased while reliably preventing start-up errors and self-discharge.

10 Flash lamp for ultraviolet radiation 11 Translucent ceramic arc tube 12, 22 Sintered electrode

Claims (1)

Sintered electrodes (12, 22) formed by compression molding tungsten powder and electron-emitting material and firing at high temperature are provided at least on the cathode side or both ends of the cylindrical translucent ceramic arc tube (11). The cylindrical translucent ceramic arc tube (11) is filled with xenon as a luminescent gas, the internal cross-sectional area of the cylindrical translucent ceramic arc tube (11) is D, and the peak current during light emission is Ip. An ultraviolet radiation flash lamp used by supplying a peak current so that (Ip / D) is 30 A / mm ² ,
The cylindrical translucent ceramic arc tube (11) has an inner diameter (d) of 4 mm ,
The electron-emitting substance is an oxide of barium or an oxide of calcium or an oxide of barium and calcium;
An ultraviolet radiation flash lamp, wherein a weight ratio of the electron-emitting material in the sintered electrodes (12, 22) is 5% to 15%.

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