KR20110030325A - Short-arc type discharge lamp - Google Patents

Abstract

PURPOSE: A short arc discharge lamp is provided to maintain the discharge brightness by forming the concave part having the anode inner wall surface, the anode bottom surface, and the circular edge. CONSTITUTION: An anode has a concave part formed on the anode central axis of the anode tip surface. A concave part(30) is formed by being depressed inwardly from the both ends of the anode. An anode inner wall surface(30A) is formed by being depressed inwardly from the front end of the anode. An anode bottom surface(30B) is formed by being extended to the anode inner wall surface.

Description

Short arc type discharge lamp {SHORT-ARC TYPE DISCHARGE LAMP}

This invention relates to a short arc type discharge lamp (henceforth a "discharge lamp"), and especially relates to the anode structure of a short arc type discharge lamp.

The conventional discharge lamp is equipped with the light emitting tube made of quartz glass which the center part expanded, and the anode and cathode arrange | positioned facing the inside of the bulging part of this light emitting tube. The positive electrode has a flat tip surface at the tip opposite to the negative electrode. The negative electrode is formed in a conical shape in which the tip opposite to the positive electrode gradually narrows toward the tip. When the discharge lamp is energized, electrons emitted from the cathode collide with the gas in the lamp to generate charged particles. The charged particles repeatedly impinge, and a substance, such as mercury, encapsulated inside the light emitting tube is in a plasma state, and an arc is formed between the anodes.

The electrons in the plasma flow to the anode side and collide with the tip surface of the anode. Since the tip surface of the anode subjected to the collision of electrons is flat, the electric field strength of the center portion of the anode becomes stronger than that of the peripheral portion, and the electric current flows into the center portion of the anode by being attracted by the strong electric field, and the anode center portion becomes hot and evaporates and is consumed. Known.

In this way, when the anode is consumed, a problem occurs that the evaporated anode constituent material adheres to the inner wall of the light emitting tube and blackens the inner wall surface of the light emitting tube. As the blackening of the inner wall surface of the light emitting tube proceeds, the radiation flux from the discharge lamp decreases, and the required irradiation illuminance on the irradiation surface is insufficient. Therefore, the discharge lamp needs to be replaced with a new lamp.

Therefore, measures for obtaining a high irradiance retention rate have been conventionally studied by suppressing the increase in the temperature of the anode at the time of lighting the discharge lamp and slowing down the consumption of the anode and the blackening of the inner wall surface of the light emitting tube. there was.

Patent Literature 1 discloses an anode in which a porous layer is formed by sintering a mixture made of tungsten carbide (WC), tantalum carbide (TaC), and tungsten (W) on a side surface excluding the tip portion of the anode. Since the porous layer has good adhesion to the base material, it is possible to appropriately suppress the temperature rise of the anode, reduce the consumption of the anode and reduce the blackening of the inner wall surface of the light emitting tube, and it is described that the life of the discharge lamp can be extended. .

In addition, in patent documents 2, 3, and 4, the recessed part 81 is provided in the front-end | tip of the anode 80 which opposes the cathode 90 as shown in FIG. This recessed part 81 is formed so that the intensity | strength of the electric field which generate | occur | produces at the point which receives the electron discharge | emitted from the cathode 90 is close. According to these documents, the current density distribution on the surface of the anode 80 is dispersed, the consumption of the anode 80 is reduced, and the progress of blackening of the inner wall surface of the light emitting tube is delayed, whereby high radiation intensity is obtained. It is supposed that the retention rate can be obtained and the life of the discharge lamp can be extended.

The techniques disclosed in each of these patent documents 1 to 4 have all focused on extending the life of the discharge lamp, that is, increasing the irradiance retention.

In general, however, the discharge lamp used for the exposure apparatus needs to have a high irradiance retention, but in addition, a high emission luminance, that is, a high emission flux is also required.

Therefore, the present inventors have investigated to provide a discharge lamp having a high radiation luminance, that is, a high radiation rate, in addition to the high irradiance retention rate that the lamp has had so far, and applied for a patent as Japanese Patent Application No. 2009-154651 before this application. Done.

This patent application is as follows. By providing the concave portion composed of the anode inner wall surface, the flat anode inner bottom surface, and the annular edge portion at the anode front end surface, the distance between each point of the recess portion and the electrode of the cathode is changed, so that the electric field is formed at the position of the anode central axis and the position of the annular edge portion. A peak of intensity occurs, and the peak of the field intensity at the position of the center axis of the anode serves to maintain the radiance of the discharge lamp, and the peak of the field intensity at the position of the annular edge attracts the electrons so that the current density of this portion is increased. By raising, the concentration of local currents in some regions on the positive electrode end face is alleviated, which serves to suppress the consumption of the positive electrode.

Below, the content of the said patent application is demonstrated in detail based on FIG.

1 is a cross-sectional view showing an outline of the configuration of a discharge lamp.

The discharge lamp 10 is provided with the light emitting tube comprised from the light emitting part 11 formed in the substantially spherical shape, and the sealing part 12A and 12B of the straight tube shape continuous to both ends of the light emitting part 11, respectively. The light emitting tube is integrally formed with, for example, quartz glass. Sealing parts 12A and 12B are attached with caps 13A and 13B for power feeding each having a cylindrical shape.

In the discharge space S formed inside the light emitting tube, the cathode 2 and the anode 3 are disposed opposite to each other on the anode central axis L, and a light emitting material is sealed.

The light emitting substance is at least one of quenon gas, argon gas and krypton gas, and mercury is encapsulated. As the light emitting material, only one of these rare gases and mercury may be sealed.

The cathode 2 has a cylindrical body portion 2A which is held in the sealing portion 12A and faces the discharge space S, and a tip portion 2B which is formed in a conical shape in which the outer diameter gradually narrows toward the tip portion following the body portion 2A is tungsten. It is formed integrally by such as.

The anode 3 is formed of a cylindrical body portion 3A and truncated conical portions 3B and 3C which are formed on each of the front end side and the rear end side of the trunk part 3A, for example, integrally formed of tungsten. A rod-shaped lead portion (not shown) having a smaller diameter than the trunk portion 3A is integrally connected to the truncated cone portion 3C on the rear end side, and the lead portion is held by the sealing portion 12B.

The positive electrode 3 has a total length of 30 to 100 mm, a diameter of the fuselage part 3A of 20 to 40 mm, a tip diameter of the tip of the truncated cone 3B to 5 to 20 mm, and a diameter of the rear end of the truncated cone 3B to 20 to 40 mm. The distance between electrodes between the cathode 2 and the anode 3 is 3 to 40 mm.

FIG. 2A is an enlarged cross-sectional view of a cross section including the anode central axis L. FIG. FIG.2 (b) is a front view which looked at the anode front end surface from the direction of the arrow B shown to FIG.2 (a).

The anode 3 has a truncated conical portion 3B that gradually decreases in outer diameter toward the distal end. An anode distal end surface 3D is formed at the distal end of the conical distal end portion 3B, and a concave portion 30 is formed on the anode central axis L of the distal end surface 3D. ) Is formed.

When the shape of the recessed part 30 is demonstrated, this recessed part 30 is formed in connection with the anode inner wall surface 30A which is a wall formed in the circumferential direction recessed from the anode front end surface 3D, and formed in connection with the said anode inner wall surface 30A, A ring formed in the circumferential direction spaced apart from the central axis of the anode L in the radial direction at the boundary between the anode inner bottom surface 30B, which is a flat wall, and is formed in a radial direction perpendicular to L, and the anode front end surface 3D and the anode inner wall surface 30A. It has the edge part 30C, and the recessed part 30 which consists of these three structures is formed indented toward the inner side of the anode 3 from the anode front end surface 3D.

Since the recessed part 30 is such a shape, the cross-section containing the anode central axis L is rectangular shape, ie, cylindrical shape. The concave portion 30 is not limited to a cylindrical shape, and may have a rotary truncated cone shape.

In the discharge lamp using the anode having such a shape, when a high voltage is applied between the cathode and the anode, an arc is formed between the electrodes.

In the anode 3 shown in FIG. 2, the anode has a flat anode inner bottom 30B which is recessed toward the inner side of the anode rather than the anode front end surface 3D, and the electric field strength increases as the anode inner bottom 30B approaches the anode central axis L. As shown in FIG. Moreover, since the annular edge part 30C is provided in the position spaced apart radially outward from the anode central axis L, the electric field strength becomes high also in the said position.

As described above, the anode 3 is in a state where the electric field strength is high at the positions of both the anode central axis L and the annular edge portion 30C, so that electrons emitted from the cathode 2 are applied to each of the anode central axis L and the annular edge portion 3OC. Since it is dispersed and attracted, the amount of electrons attracted to the anode central axis L is reduced.

The peak of the electric field intensity at the position of the anode central axis L of the anode inner bottom surface 30B acts to maintain the brightness of the discharge lamp, and the peak of the electric field intensity at the position of the annular edge portion attracts electrons to increase the current in this portion. As a result, local concentration of current at the anode end surface is alleviated, thereby acting to suppress consumption of the anode.

FIG. 8 shows a discharge lamp (hereinafter referred to as "lamp 1") having the anode shown in FIG. 2 having a concave portion composed of the anode inner wall surface, the planar anode bottom surface and the annular edge portion described above, and the electric field strength described above. The simulation results of the electric field intensity distribution in the arc are shown for each of the discharge lamps (hereinafter referred to as "lamp 2") provided with the anode shown in FIG. 7 having an adjacent recess. 8 represents the electric field strength, the horizontal axis represents the distance from the anode center axis L, the solid line represents the electric field strength of the anode of lamp 1, and the broken line represents the electric field strength of the anode of lamp 2.

In the anode of the lamp 1, as shown by the solid line of FIG. 8, the sharp peak of the electric field intensity is shown in the position of the anode center axis L and the position corresponding to the annular edge part 30C of the recessed part 30, and the anode center axis L It is assumed that electrons in the arc concentrate on the annular edge portion 30C. On the other hand, since the peak is not seen at the anode of the lamp 2, the ratio of the electric current attracted to the edge portion 82 of the recess 81 is small.

Thus, since the lamp 1 has the flat anode inner bottom surface 30B, the current density of the center axis L of the anode is moderately high to the extent that the anode is not consumed, and the radiation luminance is high, and the gap is spaced outward from the radial direction of the center axis L of the anode. By having the annular edge portion 30C formed so that the current is distributed to the annular edge portion 30C, local concentration of the current to the anode central axis L is alleviated, and consumption of the anode can be suppressed, so that a high irradiance retention can be achieved.

Therefore, the lamp 1 can be made to have a high irradiance maintenance ratio while maintaining the luminance of radiation compared to the lamp 2.

The above is the content of Japanese Patent Application No. 2009-154651.

Japanese Patent No. 3598475 (Japanese Patent Application Laid-Open No. 09-115479) Japanese Patent No. 3136511 (Japanese Patent Application Laid-open No. Hei 10-283988) Japanese Patent No. 404198 (Japanese Unexamined Patent Publication No. 2003-234083) Japanese Patent No. 4132879 (JP-A-2003-257365)

The discharge lamp of the lamp 1 described above and disclosed in Japanese Patent Application No. 2009-154651 also did not sufficiently satisfy the requirements required for the light source used for the exposure apparatus.

That is, even in a discharge lamp having a high emission luminance, in a discharge lamp having a low irradiance retention rate, the inner wall surface of the light emitting tube becomes black in a short time, so that the required radiation flux from the lamp cannot be obtained in a short time, and thus the lamp life is short and the discharge lamp is short. Need to be replaced frequently. In addition to the complexity of the replacement operation, this is a time when the exposure time (down time) of the exposure apparatus accompanying the replacement, the time until the exposure apparatus after the lamp is turned back to the normal temperature, etc. cannot be used for exposure, There exists a problem of becoming an exposure apparatus with low productivity.

Moreover, even if it is a discharge lamp with a high irradiance retention, if the radiation luminance of ultraviolet light is small, the exposure amount required for exposure will not be enough, and as a result, exposure time will become long and it will become a exposure apparatus with low productivity.

As described above, in the exposure step, shortening of the exposure time, that is, increase in throughput is required. In order to contribute to the shortening of the exposure time and to the improvement of the productivity of the exposure process, the discharge lamp is also required to have a large amount of "accumulated radiation amount", which is the total emission amount of ultraviolet light emitted during the constant lighting time.

Therefore, in view of the above problems, the present invention is a short arc type discharge lamp used in an exposure apparatus, which can be made to have a high irradiance maintaining rate while maintaining radiation luminance, and furthermore, to a lamp having a large amount of "accumulated radiation amount". It aims at providing the discharge lamp which improves the productivity of an exposure apparatus by this.

Here, consider the relationship between the accumulated radiation amount, the radiation luminance and the radiation flux.

If the radiation luminance distribution of the arc is B, the " radiation flux radiated from the arc " L is obtained by integrating the radiation luminance distribution B into the area ds and solid angle dΩ as shown in the following equation (1). Is saved.

Since taking out through a "radiation in which the radiation from the arc of the lighting initial" L ₀ is the arc tube, when the transmissivity of "any time, radiation in which the radiation from the lamp post" L ₁ is, the arc tube is T, the following expression As shown in (2), the product is expressed by the product of the radiation flux L ₀ and the transmittance T.

This transmittance T is largely due to blackening or scattering of light due to evaporation from the anode or the like attached to the light emitting tube with time, so that the irradiance retention ratio η (t) (%) expressed as a function of the lighting time is shown. It can be approximated by substitution. Thus, "in the radiation emitted from the lamp" at time t L ₁ (t) is

.

Since the "integrated radiation amount φ", which is the total radiation amount of ultraviolet rays, is represented by the time integration of the "radiation flux radiated from the lamp" L ₁ (t) at time t, it becomes as shown by following formula (4).

Here, the irradiance retention η (t) is closely related to the deposition of the evaporate on the inner surface of the light emitting tube and can be approximated by a simple exponential function, so that the irradiance retention after lighting t ₀ hours to η (t ₀ )%. Then, the attenuation constant can be expressed by the following equation (5).

Therefore, when Formula (4) is used, the accumulated radiation amount φ after t ₀ hours of lighting is further expressed as in Formula (6).

From this equation (6), it can be seen that the integrated radiation amount φ can be calculated using the "radiation flux radiated from the arc in the initial stage of lighting" L ₀ and the irradiance retention rate η (t ₀ ) after t ₀ time elapses. have.

In the following, when calculating the integrated radiation amount φ, this "radiation flux radiated from the arc of the initial stage of lighting" L ₀ and the irradiance retention η (t ₀ ) after t ₀ time elapse are used.

The short arc type discharge lamp of Claim 1,

A short arc type discharge lamp in which an anode and a cathode are disposed to face each other in a light emitting tube, and an arc is generated by applying a voltage between the anode and the cathode.

The anode has a recess formed on the center axis of the anode of the anode front end surface,

The concave portion includes a positive electrode inner wall surface formed in the circumferential direction recessed from the positive electrode tip surface, an inner bottom surface of the positive electrode formed on a surface extending from the positive electrode inner wall surface and extending in a radial direction with respect to the positive electrode central axis, and from the positive electrode central axis. It is composed of an annular corner portion formed in the circumferential direction at the boundary between the positive electrode tip surface and the positive electrode inner wall surface spaced apart in the radial direction, and the concave portion consisting of these three configurations is recessed toward the inner side of the electrode from the positive electrode tip surface. It is

When the index indicating the size of the arc is set to D0 and the diameter of the concave portion is set to D1 (mm), the ratio D1 / D0 satisfies 0.25 ≦ D1 / D0 ≦ 1.2.

In addition, the indicator D0 which shows the magnitude | size of the said arc is prescribed | regulated by the following formula.

D0 = 1.4 + 2.5 (P-1.6) ^0.5

Where P is the lamp power (kW)

The short arc type discharge lamp of Claim 2,

The short arc type discharge lamp of Claim 1 whose depth of the said recessed part is 0.1 mm-0.5 mm, It is characterized by the above-mentioned.

In the short arc discharge lamp of the present invention, the anode is formed with a recess on the anode central axis of the anode front end surface, and the recess is spaced apart radially outward from the anode inner wall surface, the flat anode inner bottom surface, and the anode central axis. By providing one annular corner part, the lamp | ramp of the radiation luminance is maintained and a high irradiance maintenance ratio can be obtained.

In addition, the value D1 / D0 of the index D0 indicating the size of the arc formed between the anode and the cathode and the diameter D1 (mm) of the concave portion provided in the anode satisfies the relationship of 0.25≤D1 / D0≤1.2, It is possible to obtain a lamp with a high accumulated radiation amount.

In addition, when the depth of the concave portion of the anode is 0.1 mm to 0.5 mm, both the radiance and the irradiance retention can be reliably increased.

1 is a cross-sectional view showing an example of the configuration of a discharge lamp.
2 is an explanatory diagram of an anode applied to a discharge lamp.
3 is a cross-sectional view showing an arc state formed between a cathode and an anode when the discharge lamp is turned on.
FIG. 4 shows a profile of the emission luminance distribution of ultraviolet light having a wavelength of 365 nm emitted from the arc shown in FIG. 3.
5 is a graph showing the relationship between the "indicator indicating the size of arc" D0 and the lamp power P;
FIG. 6 is a graph showing the relationship between the relative integrated radiation amount and the value D1 / D0 of the ratio of the “index indicating arc size” D0 and the diameter D1 of the recessed portion.
7 is a cross-sectional view showing the electrode structure of a conventional short arc type discharge lamp.
8 is a diagram illustrating electric field intensity distribution.

EMBODIMENT OF THE INVENTION Hereinafter, the discharge lamp of this invention is demonstrated using drawing.

Since the structure of a discharge lamp is the same as that of the above-mentioned description and the content of FIGS. 1 and 2, it abbreviate | omits by referring description of this part.

When a high voltage is applied between the cathode 2 and the anode 3 of the discharge lamp 10, dielectric breakdown occurs between the anodes, and an arc AR is formed between the cathodes 2 and 3. The conceptual diagram of the arc AR is shown in FIG. The arc AR expands or contracts about the anode central axis L depending on the lamp power P (kW). That is, as the lamp power becomes larger, the arc AR becomes wider and larger, and as the lamp power becomes smaller, the arc AR contracts and becomes smaller. If the size of the concave portion 30 is constant, the arc AR may spread beyond the annular edge portion 30C of the concave portion 30 to the anode tip surface 3D, and may remain inside the annular edge portion 30C of the concave portion 30. There is also.

From the relationship between the size of the recessed portion 30 and the arc AR, the value D1 / D0 of the ratio of the size D1 of the recessed portion 30 to the size D0 of the arc AR is obtained. When the value of this ratio, that is, the extent to which the arc AR covers the recessed part 30, is changed, the effect of an annular edge part 30C attracting a part of electric current by an electric field is shown. This affects the flow of electrons generated between the electrodes, causing the radiation amount to fluctuate.

Therefore, the value D1 / D0 of the ratio of the size of the recessed portion 30 to the size of the arc AR is closely related to the above-described "integrated radiation dose", and the optimum range of the integrated radiation dose can be found as a function of D1 / D0. I think it can. Here, the size D1 of the concave portion is a value used for an index indicating the extent to which the arc is covered, and since it is necessary to contrast the size of the arc with this D1, the diameter of the concave portion, that is, the diameter of the annular edge portion, is used. do.

Next, how to specify the size of the arc is examined.

An arc refers to the area | region which the enclosure made into plasma, and it is difficult to measure and specify the magnitude | size.

Thus, for example, the arc is naturally closely related to the current density distribution, and since the current density distribution can be regarded as a form of the arc distribution, it is conceivable to obtain the arc size by measuring the current density distribution. . However, it is difficult to directly and precisely measure this current density distribution, and since this current density distribution is continuously changing, it is difficult to clearly define the arc distribution even by this current density distribution, and it is difficult to specify the arc size. Can't. In this way, it is very difficult or impossible to specify the "arc size" by measuring the "current density distribution".

However, the current density distribution of the arc is closely related to the radiation luminance distribution, and by measuring the "radiation luminance distribution", the "current density distribution" and "arc size" of the arc can be known.

Thus, the radiation luminance distribution is measured.

In the case where the light emitting material is mercury, when a high voltage is applied between the cathode 2 and the anode 3, the electrons emitted from the cathode 2 collide with the atoms of mercury enclosed in the discharge space S, and the valence of mercury It enters an excited state and emits various emitted light when it transitions from an excited state to a lower energy state. The emitted light is passed through a band pass filter passing only a specific wavelength, for example, a wavelength of 365 nm, to obtain luminance distribution of emission. The luminance distribution of the ultraviolet ray with the wavelength of 365 nm is the luminance distribution in the radial direction at an arbitrary point on the electrode central axis L, which is shown in FIG. 4. The profile of this distribution can be approximated by the following formula (7) when the radial luminance is J (r) and the distance from the electrode central axis in the radial direction is r.

Here, J ₀ is the radiation luminance at the center of the arc, and r ₀ is the distance (mm) from the center where the radiation luminance J ₀ at the center attenuates to 1 / e (≒ 0.37). Equation (7) of the radiation luminance distribution indicates that most of the current flowing in the arc is concentrated within a distance of r ₀ from the center of the electrode.

When 2r ₀ obtained by doubling this r ₀ is considered to be a "virtual diameter", this 2r ₀ can be used as an "indicator which shows the magnitude | size of an arc" D0. It should be noted, however, that the actual arc size has spread beyond the value of the "indicator indicating the size of the arc" D0 which is this virtual diameter.

As described above, the "indicator indicating the size of arc" can be obtained from the radiation luminance distribution, but this method involves the complexity of measuring the radiation luminance distribution when it is necessary to obtain the "indicator indicating the size of the arc". . However, as a result of an example study by the author and the like, the radiation luminance distribution is found to have a strong correlation with the lamp input power. Thus, when the relationship between the lamp power and the radiation luminance distribution is obtained in advance, the radiation luminance distribution can be measured when necessary. The complexity can be eliminated, and the "index indicating the magnitude | size of an arc" can be calculated | required from lamp electric power.

The following experiment was performed for the examination which calculates | requires the relationship between this lamp electric power and "the index | index which shows the magnitude | size of an arc" D0.

However, the shape of the arc is affected by the physical shape of the tip of the electrode. When attempting to create the said index using the discharge lamp using the electrode which provided the recessed part in the anode front end surface, an arc will receive different influence from a recessed part for every lamp from which the recessed part differs in size. In this case, the "indicator which shows the magnitude | size of an arc" D0 differs for every lamp and cannot be used as an index of reference. "Indicator which shows the magnitude | size of an arc" Since D0 is an index and a value which should be a reference | standard, it must be an unchanging value which does not change. In order to prevent the arc from being affected by the shape of the tip of the anode, a "indicator representing the size of the arc" D0 was created using a discharge lamp using a very ordinary anode having a flat and no concave portion, and this was used as a reference index.

Therefore, the experimental discharge lamps A1 to A5 used in the experiment for producing the "indicator indicating the size of the arc" D0 used a very ordinary anode that had a flat surface without a concave portion at the anode end surface. Then, five types of experimental discharge lamps A1 to A5 were produced by changing the amount of mercury encapsulated and the distance between the electrodes.

The experimental discharge lamps A1 to A5 are turned on with the lamp power P shown in Table 1, the emission luminance distribution of the arc near the anode is measured, and fitting is carried out according to equation (7) for those emission luminance distributions to obtain r ₀ . , "Indicator representing arc size" D0 was obtained.

Table 1 shows their experimental results.

Next, the relationship between the "index indicating arc size" D0 in Table 1 and the lamp power P (kW) is shown in circles in FIG. 5. The equation of the approximation curve connecting the circles shown in FIG. 5 was obtained, and the following equation (8) was obtained.

From this equation (8), for the lamp of which the lamp power P (kW) is known, the "indicator indicating the arc size" D0 can be obtained without measuring the radiation luminance distribution.

In this way, when the "index indicating arc size" D0 is determined from the lamp power P (kW), as described above, the optimum range of the integrated radiation amount can be found using the ratio value D1 / D0 as a variable. .

Thus, an experiment was performed to determine the accumulated radiation amount using the value D1 / D0 of the ratio between the diameter D1 of the recess and the “indicator indicating the size of the arc” D0 as a variable.

Example 1

When performing an experiment, experimental discharge lamps B1-B10 were produced and prepared. Experimental discharge lamps B1-B10 have the common lamp basic structure shown below.

<Basic Configuration of Lamps B1 to B10>

Depth of the recess of the anode 3: 0.4mm

Mercury level: 25mg / cm ³

Quixenone gas: 2 × 10 ⁵ Pa at room temperature

Distance between electrodes L: 5.5mm

Lamp power P: 7.5kW (constant power)

The anode of each lamp has a concave portion formed at the distal end surface of the anode inner wall surface and the anode inner bottom surface and an annular corner portion, but the size of the concave portion is shown in Table 2 as "index indicating arc size." The value D1 / D0 of the ratio of the diameter D1 (mm) of the recessed part 30 with respect to D0 is made to differ, respectively.

As a comparative example, the comparative discharge lamp X provided with the positive electrode which does not have a recessed part with the value D1 / D0 of 0, ie, was also produced and prepared. The comparative discharge lamp X has the same basic configuration as the experimental discharge lamp B, except that there is no concave portion in the positive electrode end surface.

Since the lamp power of the experimental discharge lamps B1 to B10 and the comparative discharge lamp X is 7.5 kW, the "indicator indicating the size of the arc" D0 can be obtained by substituting p = 7.5 into equation (8), and D0 = 7.5. Is saved.

About the experimental discharge lamp B1-B10 and the comparative discharge lamp X, the irradiance of the ultraviolet light of wavelength 365nm was measured at the time of a lighting initial stage and after 800-hour constant electric power lighting. Let this be experiment a. "Radiation illuminance retention rate (%)" of Table 2 expresses the ratio of the irradiance after lighting for 800 hours with respect to the irradiance of the initial stage of lighting for each lamp%.

In addition, the experimental discharge lamps B1 to B10 and the comparative discharge lamp X are turned on, and for each discharge lamp, the emission luminance of the ultraviolet light having a wavelength of 365 nm at the initial stage of lighting is measured, and according to equation (1), It was obtained in the radiation L ₁ of the light initially by integration. Let this be experiment b. In Table 2, from the result of experiment b, the ratio of the radiant flux of the initial stage of lighting of the experimental discharge lamp B to the radiant flux of the initial stage of lighting of the comparative discharge lamp X is determined, and this relative value is described as "relative radiant flux". have.

"Integrated radiation amount" is calculated | required from Formula (6) using the "radiation roughness retention (%)" and "relative radiation flux" of Table 2. In addition, it represents with the "relative integrated radiation amount" which is a relative value which made the maximum value of the integrated radiation amount 1.

In addition, as can be seen from equation (6), the "radiation flux radiated from the arc of the initial stage of lighting" is required for the calculation of the integrated radiation amount. For the sake of explanation, the relationship between the radiation flux and the "radiation flux emitted from the lamp in the initial stage of lighting" will be described.

In the formula (3), since the time t is 0 in the lighting initial state, T (t) is almost 1 in T (0), and L ₁ (0) = L ₀ . This is the radiant flux at the initial stage of lighting of each lamp, which can be obtained by experiment b, is "radiated flux radiated from the lamp at the beginning of lighting" L ₁ (0), but this radiant flux is actually "radiated flux radiated from the arc at the beginning of lighting". "L ₀ is the same. Thus, "in the radiation emitted from the arc of the initial light" in the expression (6) is L _0, it is found that can be calculated by substituting the value of the radiation L ₁ in the initial lighting of each lamp obtained in experiment b.

Next, Table 2 shows the relationship between the ratio D1 / D0 and the relative integrated radiation amount in FIG. 6.

The vertical axis represents the relative integrated radiation dose, and the horizontal axis represents the ratio D1 / D0.

In the area where the ratio value D1 / D0 is small, the relative integrated radiation amount is almost unchanged, increases from around 0.2, reaches a maximum near 0.65, and then decreases. The value D1 / D0 of the ratio becomes the same as the case where the value D1 / D0 of 0 is near 1.2, and it decreases further after that.

When the recess is not provided at the electrode tip, that is, when the ratio D1 / D0 is 0, the value of the relative integrated radiation amount is 0.959. By setting it as the range exceeding this value of 0.959, it can be set as the discharge lamp with a larger amount of relative integrated radiation than the lamp which has an anode without a recessed part. Therefore, it turns out that the value D1 / D0 of ratio is 0.25-1.2 as the range which is effective as a relative integrated radiation amount.

Moreover, when the value D1 / D0 of ratio is 0.39-1.1, the integrated radiation amount shows a higher value, and a more remarkable effect is acquired and it is preferable.

Moreover, it is preferable that the depth H of the recessed part 30 is 0.1 mm-0.5 mm. The reason for this is as follows.

When the depth H of the concave portion 30 exceeds 0.5 mm, the distance between the electrodes becomes long, so that the lamp voltage rises. Since the short arc type discharge lamp 10 uses a constant power supply as a power source for lighting, when the lamp voltage rises as described above, it is controlled to lower the lamp current supplied between the cathode and the anode, whereby the luminance of radiation is lowered. Done. This decrease in the radiation luminance is remarkable as the depth H of the concave portion 30 becomes deeper.

On the other hand, when the depth H of the concave portion 30 is less than 0.1 mm, the concave portion 30 is substantially eliminated, and the effect of concentration of the electric field strength by the annular edge portion is lost, and a high irradiance maintenance rate cannot be obtained.

Therefore, in order to make the fall of the radiation luminance of a discharge lamp as small as possible and to obtain a high irradiance maintenance ratio, it is preferable to make depth H of the recessed part 30 into 0.1 mm-0.5 mm.

10 Short arc type discharge lamp 11 Light emitting part
12A, 12B Sealing Section 13A, 13B Detention
2 cathode 2A fuselage
2B Tip 3 Anode
3B, 3C truncated 3A fuselage
3D anode tip 30 recess
30A anode inner wall surface 30B anode inner wall surface
30C annular corner AR arc

Claims (2)

A short arc type discharge lamp in which an anode and a cathode are disposed to face each other in a light emitting tube, and an arc is generated by applying a voltage between the anode and the cathode.
The anode has a recess formed on the center axis of the anode of the anode front end surface,
The concave portion includes a positive electrode inner wall surface formed in the circumferential direction recessed from the positive electrode tip surface, an inner bottom surface of the positive electrode formed on a surface extending from the positive electrode inner wall surface and extending in a radial direction with respect to the positive electrode central axis, and from the positive electrode central axis. It is composed of an annular corner portion formed in the circumferential direction at the boundary between the positive electrode tip surface and the positive electrode inner wall surface spaced apart in the radial direction, and the concave portion consisting of these three configurations is recessed toward the inner side of the electrode from the positive electrode tip surface. It is
When the index indicating the arc size is set to D0 and the diameter of the concave portion is set to D1 (mm), the value D1 / D0 of the ratio satisfies 0.25 ≦ D1 / D0 ≦ 1.2. Discharge lamp.
The index D0 indicating the size of the arc is defined by the following formula.
D0 = 1.4 + 2.5 (P-1.6) ^0.5
Where P is the lamp power (kW) The method according to claim 1,
Short arc type discharge lamp, characterized in that the depth of the recess is 0.1mm ~ 0.5mm.

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