JP3497597B2 - UV fluorescent lamp - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultraviolet fluorescent lamp for emitting ultraviolet light, and to an improvement in ultraviolet light emission efficiency and start-up characteristics. [0002] Ultraviolet fluorescent lamps have a wavelength of 300 nm to 400 nm.
It is a fluorescent lamp having a near-ultraviolet emission wavelength such as nm, and can be used for identification and inspection of substances that react to ultraviolet light. An example of a document describing such an ultraviolet fluorescent lamp is “Lighting Engineering of the Institute of Electrical Engineers of Japan,” No. 85, published by the Institute of Electrical Engineers of Japan on November 20, 1986.
There is a page. [0003] The present inventor has applied the present invention to a reading apparatus utilizing ultraviolet light emission, and therefore has a high ultraviolet output efficiency and a good output rising characteristic even at a low ambient temperature. A comparatively small ultraviolet fluorescent lamp was studied. A so-called rare gas discharge lamp that does not use mercury as a phosphor excitation source, for example, a xenon fluorescent lamp that uses an emission wavelength near 147 nm as a phosphor excitation source, is a UV-emitting phosphor SrB ₄ O ₇ : Eu or Ba.
Since the excitation wavelength of Si ₂ O ₅ : Pb or the like is around 230 to 260 nm (the emission wavelength of the phosphor is approximately 300 to 4 nm).
00 nm), at the time of steady discharge or when the discharge is saturated, practical UV output efficiency for such an UV reader cannot be obtained. A rare gas fluorescent tube using xenon gas was prototyped with a filling pressure of 8 to 40 KPa. However, when the ultraviolet output of the tube wall was a saturated output, only 0.12 mW / cm ² could be obtained. . This is about 1/6 of 0.7 mW / cm ² which is the minimum output required for the reading light source, and is not practical. Therefore, in order to improve the ultraviolet light emission efficiency,
Mercury was sealed as an excitation source of the phosphor. When the mercury is sealed, the phosphor can be efficiently excited by ultraviolet rays of 253.7 nm generated by electric discharge, thereby increasing the luminous efficiency of ultraviolet rays having a wavelength of about 300 to 400 nm. However, it is clear that when mercury is enclosed, the vapor pressure in the tube has a temperature dependency, and the rise characteristics are not negligibly deteriorated. This is because the mercury vapor pressure in the lamp is remarkably reduced in a low-temperature atmosphere such as 0 ° C., and the probability of excitation and emission of mercury at the start of discharge is small. Although the mercury vapor pressure gradually increases due to the heat generated by the discharge, the ultraviolet output also increases. However, when the ambient temperature is as low as 0 ° C., it takes a considerable amount of time to reach a thermal equilibrium state. That is, the required rise characteristics cannot be obtained. Therefore, it has been found that it is necessary to promote the temperature rise inside the bulb at the start of discharge. At this time, in the case of a relatively small reading device that is driven by a battery, a heater is installed outside or inside the ultraviolet fluorescent lamp to heat it, and even if it is intended to improve the start-up characteristics, it naturally has a power supply capability. There is a limit. Further, it has been clarified that a small enough amount of heat is not generated by a small ultraviolet fluorescent lamp having a small tube power, so that a necessary and sufficient start-up characteristic cannot be obtained unless measures are taken in the structure of the discharge lamp itself. An object of the present invention is to improve the rising characteristics of an ultraviolet discharge lamp in which mercury vapor is sealed in a container together with a rare gas at a low temperature. SUMMARY OF THE INVENTION The present inventor has applied the present invention to a relatively small-sized reading apparatus utilizing ultraviolet light emission. 4.8mm or less, total length 50mm
In the following, as a result of intensive studies on an ultraviolet discharge lamp having a discharge power of 2 W or less, in order to make it possible to read light such as ink that emits visible light with ultraviolet light emitted from an ultraviolet fluorescent lamp with a light receiving element such as a phototransistor, The output of the irradiating ultraviolet fluorescent lamp is approximately 0.7 mW / c at the tube wall.
m ² or more, and 0.7
It has been found that there is no practical problem if an ultraviolet output of mW / cm ² or more is obtained. That is, since the rising characteristic of the ultraviolet light emission at the start of discharge has at least 0.14 mW / cm ² / sec at 0 ° C., the ability as an ultraviolet light emission source optimal for a relatively small reader using ultraviolet light emission can be obtained. Can be obtained. In order to satisfy the above rising characteristics, the present inventor has made a number of prototypes of an ultraviolet discharge lamp for a reading light source and obtained the characteristics of each in various experiments which will be described later. I found a relationship. According to this, there is an optimum value for the sealed gas pressure in terms of the rising characteristics at a low temperature such as 0 ° C.
As the filling gas pressure becomes lower than the optimum value, the impedance of the discharge tube decreases, the heat generated by the discharge decreases, and the evaporation of mercury is not promoted. It is thought to go. When the filling gas pressure is higher than the optimum value, the thermal resistance of the filling gas increases (the molecular weight of the filling gas increases), and the time until the discharge tube reaches thermal saturation increases. Therefore, the evaporation of mercury is not promoted, and the ultraviolet output in the transition period is reduced. According to the experiment, the rising characteristic of ultraviolet light emission at the start of discharge at 0 ° C. was 0.14 mW / cm ² / sec.
It has been found that the charged gas pressure of the mercury vapor and the rare gas needs to be in the range of 6 to 13 kPa to obtain c or more. Further, as a result of the above experiment, it has been found that there is also a close relationship between the thickness of the container constituting the ultraviolet fluorescent lamp and the rising characteristics. In other words, when the inner diameter of the container is the same and the wall thickness is changed, there is no substantial difference in the ultraviolet output in the output stable state several minutes after the start of lighting, but in the transition period within several tens of seconds from the start of lighting. In the case of, there was a remarkable difference in the rising characteristics due to the difference in heat capacity of the container caused by the difference in wall thickness. This is because the calorific value per unit time is determined by the inner diameter of the ultraviolet fluorescent lamp, the sealed gas pressure, the discharge current, and the like, and the ultraviolet output is stabilized when it reaches a thermal equilibrium with the ambient temperature after the start of lighting, Irrespective of the thickness of the container, if the inner diameter of the container is the same, the ultraviolet output at the time of stability should be the same. However, until the thermal equilibrium state is reached, a large amount of heat is required to bring the container having a large thickness and a large heat capacity to the same temperature. If the calorific value per unit time is the same, the time required to reach the same temperature is shorter as the thickness of the container is smaller. According to the experiment, the rising characteristic of ultraviolet light emission at the start of discharge at 0 ° C. was 0.14.
The relation between the inner diameter (φ) of the container and the thickness (t) of the container for obtaining mW / cm ² / sec or more is t (φ + t) ≦
It was found that it was necessary to satisfy 1.11.
For example, according to this relationship, when the inner diameter of the container is 2 mm,
Its wall thickness should be 0.45 mm. According to the above-mentioned means, the rising characteristic of ultraviolet light emission at the start of discharge is at least 0.14 at 0.degree.
In order to obtain mW / cm ² / sec, the gas pressure of the mercury vapor and the rare gas is set in the range of 6 to 13 kPa, and the relationship between the inner diameter (φ) of the container and the thickness (t) of the container is represented by t (φ + t). )
By setting ≦ 1.11, it is possible to improve the ultraviolet light emission efficiency as compared with the conventional mercury non-encapsulated so-called rare gas fluorescent lamp, and also to improve the rising characteristics at low temperatures. The means focuses on the essential components of the fluorescent lamp itself, such as the sealed gas pressure and the wall thickness of the container, and does not require overloading at the time of lighting. Since it does not need to be externally mounted, it is suitable for an ultraviolet fluorescent lamp which is applied to a relatively small reader utilizing ultraviolet light emission and which is turned on by battery driving. FIG. 1 shows an ultraviolet fluorescent lamp according to an embodiment of the present invention. The ultraviolet fluorescent lamp according to the present embodiment is applied to a relatively small reader using ultraviolet light emission, and is lit by driving a battery. Is 50m
m and mercury vapor are sealed together with a rare gas in a cylindrical glass container 1 having a phosphor 4 on the inner surface, and a discharge electrode is provided at the tip of each lead wire 2 introduced from both ends of the container 1 from outside. 3 is provided, and the discharge power is set to 2 W or less. The rare gas is a simple gas such as xenon, neon, or argon, or a mixed gas thereof. The phosphor is S
rB ₄ O ₇ : Eu or BaSi ₂ O ₅ : Pb. When the ultraviolet fluorescent lamp according to the present embodiment is a so-called black light fluorescent lamp, the container is made of an ultraviolet transmitting glass that blocks visible light. The ultraviolet fluorescent lamp of this embodiment is a non-preheating type cold cathode discharge lamp as is apparent from the structure thereof. The discharge electrode can be arranged outside the container. One typical specification of the ultraviolet fluorescent lamp of this embodiment is as follows. Pipe outer diameter: φ2.9 (mm) Pipe inner diameter: φ2.0 (m
m) Tube length: 22 mm Phosphor: SrB ₄ O ₇ : Eu Filling gas: Neon gas 10 KPa and mercury vapor tube current: 7 mArms Tube voltage: 180 Vrms
Tube power: 1.3 W UV output: 0.8 mW / cm ² at the tube wall 5 seconds after the start of discharge at an ambient temperature of 0 ° C. When mercury vapor is sealed in an ultraviolet fluorescent lamp, the mercury spectrum generated by the discharge 253.
The phosphor is excited by the ultraviolet ray of 7 nm, and the excitation of the phosphor becomes more active than the discharge of the rare gas alone, whereby the luminous efficiency of the ultraviolet ray having a wavelength of about 300 to 400 nm can be increased. At this time, the rising characteristics at a low temperature are such that the tube wall output of ultraviolet light satisfies 0.7 mW / cm ² or more within 5 seconds from the start of lighting at 0 ° C. In other words, the rising characteristic of the ultraviolet light emission at the start of the discharge is at least 0.14 m at 0 ° C.
W / cm ² / sec is satisfied. In order to satisfy such a rising characteristic, the filling gas pressure of the mercury vapor and the rare gas is set to 6 to 13 kPa. Furthermore, the inner diameter of the container (φ)
And the thickness (t) of the container is t (φ + t) ≦ 1.11
It is said. FIG. 2 shows the tendency obtained from the results of various experiments conducted to obtain the optimum range of the gas pressure of the mercury vapor and the rare gas. The ultraviolet fluorescent lamp used in the experiment has an outer diameter of 2.5 mm (thickness 0.39 mm) to 4.8 mm.
(Wall thickness 0.8 mm), total length 25 mm to 50 mm, and power consumption 0.5 W to 2 W. Each of the charged gases is a neon gas and a trace amount of mercury vapor. In an atmosphere of 0 ° C., the ultraviolet output per unit time (m) in a unit area from the start of discharge to the stable discharge of each ultraviolet discharge lamp.
W). As a result, the sealed gas pressure for satisfying the rising characteristics was in the range of 6 to 13 kPa. FIG. 3 shows the tendency obtained from the results of various experiments conducted to obtain the optimum range of the wall thickness with respect to the inner diameter of the container. The ultraviolet fluorescent lamp used in the experiment has an inner diameter of 2 mm, a total length of 25 mm, a power consumption of 0.6 W, and various thicknesses of the container in the range of 0.2 mm to 0.7 mm. Each sealed gas is a neon gas and a trace amount of mercury vapor, which is set to 10 kPa, and in an atmosphere of 0 ° C., an ultraviolet output per unit time in a unit area from discharge start to stable discharge for each ultraviolet discharge lamp ( mW). As a result, it was found that the thickness for satisfying the rising characteristics was 0.45 mm or less. Further, when the same experiment was performed by changing the inner diameter of the container to 3 mm, the ultraviolet output per unit time was reduced as a whole by the increase in the inner diameter. Has a tendency to be made thinner than in FIG. Taking these experimental results into consideration, the results shown in FIG. 3 are used as representative values, and the satisfactory relationship between the inner diameter and the wall thickness of the container is defined as t (φ + t) ≦ 1.
It was derived that it was 11. This is for the following reason. That is, the calorific value per unit time is determined by the inner diameter of the UV-prone lamp, the sealed gas pressure, the discharge current, and the like, and the UV output becomes stable when the temperature reaches the thermal equilibrium with the ambient temperature after the start of lighting. Irrespective of the wall thickness, if the inner diameter of the container is the same, the ultraviolet output at the time of stability should be the same. On the other hand, until the thermal equilibrium state is reached, a large amount of heat is required to bring the container having a large thickness and a large heat capacity to the same temperature. If the calorific value per unit time is the same, the time required to reach the same temperature is shorter as the thickness of the container is smaller. Further, if the inside diameter is large, the amount of ultraviolet light emission per unit time per unit area decreases, so that it is necessary to reduce the thickness accordingly. Based on this, it was concluded that the cross-sectional area of the container was desirably not more than the cross-sectional area of the container having an inner diameter of 2 mm and a wall thickness of 0.45 mm, and derived the above relationship. Although the invention made by the inventor has been specifically described based on the embodiments, it is needless to say that the present invention is not limited thereto and can be variously modified without departing from the gist thereof. No. For example,
In the above embodiment, both the thickness of the container and the pressure of the filled gas are set as the optimum ranges. However, it is possible to realize the desired start-up characteristics at a low temperature by setting only one of the ranges as the optimum range. According to the present invention, the rising characteristic of ultraviolet light emission at the start of discharge is at least 0.14 at 0 ° C.
mW / cm ² / sec. For this purpose, the gas pressure of the mercury vapor and the rare gas is set in the range of 6 to 13 kPa, and the relationship between the inner diameter (φ) of the container and the thickness (t) of the container is t.
By setting (φ + t) ≦ 1.11, it is possible to improve the ultraviolet light emission efficiency as compared with the conventional mercury non-encapsulated so-called noble gas fluorescent lamp and to improve the startup characteristics at low temperatures. it can. Furthermore, these means focus on the essential components of the fluorescent lamp itself, such as the sealed gas pressure and the wall thickness of the container, and do not require an overload at the time of lighting, and require special circuit means and members. Since there is no need to externally attach the fluorescent lamp to the fluorescent lamp, the present invention can be applied to a relatively small reader using ultraviolet light emission and can be an ultraviolet fluorescent lamp most suitable for being driven by a battery.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional view of an ultraviolet fluorescent lamp according to one embodiment of the present invention. FIG. 2 is an explanatory diagram showing a tendency obtained from various experimental results performed to obtain an optimum range of gas pressures of mercury vapor and a rare gas. FIG. 3 is an explanatory diagram showing a tendency obtained from various experimental results performed to obtain an optimum range of a thickness with respect to an inner diameter of a container. [Description of Signs] 1 container 2 lead wire 3 discharge electrode 4 phosphor

Claims (1)

(57) [Claims] (1) An ultraviolet fluorescent lamp applied to an ultraviolet reader.
A light lamp having an outer diameter of 4.8 mm or less and a total length of 50
mm or less, a mercury vapor is sealed together with a rare gas in a container having a phosphor on the inner surface, and a pair of discharge electrodes is provided inside or outside the container. The discharge power is 2 W or less. The rising characteristic is at least 0.14 mW / cm ² / sec at 0 ° C., 6 to 13 kPa of rare gas is enclosed together with mercury vapor, and the inner diameter (φ) of the container and the thickness of the container ( t) is t
An ultraviolet fluorescent lamp having a relationship of (φ + t) ≦ 1.11 .