JP3576661B2 - Rare gas discharge lamp - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a rare gas discharge lamp, and more particularly to an improvement in an axial light distribution characteristic of a rare gas discharge lamp applied to an original irradiating device in OA equipment such as a facsimile, an image scanner, and a copying machine.
[0002]
[Prior art]
Generally, as shown in FIG. 7, for example, a document irradiating device irradiates a document surface P with radiation light from a discharge lamp 1 and receives reflected light from the document surface P by a line sensor S composed of a CCD element. It is configured as follows.
[0003]
The discharge lamp applied to this device is required to be turned on immediately according to the operating state of the device, and to have the light amount reach a predetermined light amount or more, for example, about 100% in a very short time. Are proposed.
[0004]
In the figure, a rare gas discharge lamp 1 is formed on a straight tube-shaped glass bulb (envelope) 2 having both ends sealed and a tube diameter of, for example, about 5 to 10 mm, and an inner surface of the glass bulb 2. The light emitting layer 3 is made of a phosphor, and a pair of strip-shaped external electrodes 4 and 5 formed on the outer peripheral surface of the glass bulb 2 at appropriate intervals along the longitudinal direction thereof. A rare gas containing, for example, xenon gas as a main component is sealed in a sealed space in the valve. In addition, the envelope 2 can be formed of ceramics or the like in addition to a glass bulb. In addition, as the rare gas, krypton, neon, helium, or the like can be used in addition to xenon. You can also.
[0005]
In the rare gas discharge lamp 1, when a high-frequency high voltage (for example, 2500 Vp-p at 25 KHz) is applied to the external electrodes 4 and 5, a discharge of xenon gas occurs, and the light emitting layer 3 is formed by an excitation line (147 nm) of xenon gas. It emits light when excited, and light is emitted from the light emitting portion 2a between the external electrodes 4 and 5. In particular, since the discharge lamp 1 does not use mercury, it has a feature that the light quantity rises sharply after lighting and reaches almost 100% almost simultaneously with lighting.
[0006]
Therefore, when the rare gas discharge lamp 1 is arranged in the original irradiating apparatus shown in FIG. 7 such that the light emitting portion 2a faces the original surface P and the distance from the original surface P is about 6 to 10 mm. In the illuminance distribution on the document surface P, as shown by the solid line A in FIG. 9, the light quantity at the central portion of the main portion of the light emitting portion 2a is large and decreases toward the end. Therefore, the light distribution pattern is made uniform by shading correction using a baffle plate or the like. For this reason, the reading quality of the original can be improved.
[0007]
[Problems to be solved by the invention]
By the way, although the rare gas discharge lamp 1 has the feature that the rising of the light amount after lighting is steep as described above, the light amount sharply decreases in about one minute after lighting, for example, and then gradually decreases. , Tend to shift to a stable state in about 5 minutes after lighting.
[0008]
This tendency becomes more pronounced as the tube diameter and the input power of the glass bulb increase, particularly at the center of the glass bulb as compared to the end. For example, when the tube diameter is 6 mm, the decrease in the amount of light is about 4% at the end of the glass bulb and about 5 to 6% at the center, while when the tube diameter is 8 mm, the decrease in the center is about 10%. To increase. This is because, in this discharge lamp, the glass bulb 2, the light-emitting layer 3, and the xenon gas exist between the external electrodes 4 and 5, and the volume resistivity and the dielectric constant of the glass bulb 2 change depending on the temperature. It is considered that the impedance changes and the light quantity also changes.
[0009]
For example, when the rare gas discharge lamp 1 having a tube diameter of 8 mm and a total length of 300 mm of the glass bulb 2 was operated with a power consumption of 11 W including the inverter lighting device, the illuminance distribution immediately after lighting was shown by a solid line A in FIG. However, 5 minutes after the stable state was reached, the decrease in the amount of light at the central portion became large as indicated by the dotted line B in FIG. In particular, the decrease in the amount of light was 4% at the end, but was 10% at the center.
[0010]
In the document irradiating apparatus shown in FIG. 7, the illuminance distribution (light distribution pattern) two seconds after the rare gas discharge lamp 1 is turned on is stored. The correction is performed based on the data. For this reason, the reading accuracy of the document can be maintained at a high accuracy.
[0011]
However, as described above, the illuminance distribution in the axial direction of the discharge lamp is as shown by the characteristic A in FIG. 9 immediately after lighting, but after the transition to the stable state, as shown by the characteristic B in FIG. Becomes large and becomes non-uniform. Therefore, even if the A-characteristic immediately after lighting is stored as basic data, it is not possible to correct the decrease in the amount of light in the central portion because the light distribution pattern is broken at the time of transition to the stable state. . For this reason, there is a problem that the reading accuracy of the document in a portion corresponding to the central portion is impaired.
[0012]
SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a rare gas discharge lamp which can maintain a relatively uniform light distribution pattern in the axial direction even if the amount of light varies with elapsed lighting time with a simple configuration. is there.
[0013]
[Means for Solving the Problems]
Therefore, in order to achieve the above-described object, the present invention arranges a pair of strip-shaped external electrodes on the outer peripheral surface of an envelope having a light emitting layer on the inner surface and separates a rare gas into the envelope. In a rare gas discharge lamp having a light emitting portion sealed therein , the interval between one side edge adjacent to each other on the light emitting portion side of the external electrode is made substantially constant over the entire length, and the distance between the other side edge is reduced. Are provided with portions having different intervals, and the width of the central portion is made narrower than that of the end portion.
[0014]
The second aspect of the present invention spaced apart a pair of strip-like external electrodes on the outer peripheral surface of the envelope with a luminescent layer on an inner surface, and a rare gas enclosed in the envelope, light In a rare gas discharge lamp having an emission portion, the interval between one side edge adjacent to each other on the light emission portion side of the external electrode is made substantially constant over the entire length, and an end portion between the other side edge is formed. A differently shaped portion different from the interval is provided , and the end of the external electrode and the side edge of the deformed portion are formed by a straight line substantially parallel to the axial direction. It is characterized by being narrow .
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of the present invention will be described with reference to FIGS. The same parts as those of the conventional example shown in FIGS. 7 and 8 are denoted by the same reference numerals, and detailed description thereof will be omitted. The feature of the present invention is that the width of the central portion in the axial direction of the pair of external electrodes 4 and 5 arranged on the outer peripheral surface of the rare gas discharge lamp 1 is narrower than the end portion.
[0017]
The external electrodes 4 and 5 have one side edges 4a and 5a formed linearly, and the other side edges 4b and 5b are inclined such that the width of the central portion decreases from the end to the central portion. Is formed. As a result, deformed portions 4A and 5A whose central portions are narrower in width than the end portions are formed in the external electrodes 4 and 5.
[0018]
The external electrodes 4 and 5 are made of a non-translucent metal member having excellent conductivity such as aluminum, copper, and silver, and have an adhesive layer formed on one surface. ing. Then, it is fixed and arranged on the outer peripheral surface of the glass bulb 2 using this adhesive layer.
[0019]
According to this embodiment, since the widths of the central portions of the external electrodes 4 and 5 are formed narrower than the end portions, the amount of current flowing between the external electrodes is smaller at the central portion than at the end portions. The temperature rise due to the lighting operation is suppressed. Therefore, the rate of decrease in the amount of light at the center can be suppressed to the same degree as the rate of decrease at the ends.
[0020]
Moreover, the light distribution pattern in the axial direction of the light emitting portion 2a is relatively flattened (uniform) over the whole as shown by the C-characteristic shown by the two-dot chain line in FIG. ) Is done. Therefore, the light distribution pattern in the axial direction immediately after lighting and after shifting to the stable state can be kept substantially constant. For this reason, even if the light amount fluctuates, it can be dealt with by correction by the document irradiation device, and sufficient reading accuracy can be obtained.
[0021]
FIG. 4 shows another embodiment of the present invention, in which the external electrodes 4 and 5 are formed to have the same width by a fixed length in the axial direction from both ends, and the portion closer to the center than that has a width. Are formed.
[0022]
According to this embodiment, since the end portions of the external electrodes 4 and 5 and the deformed portions 4B and 5B are formed substantially in a straight line, the external electrodes 4 and 5 can be easily formed and the working efficiency can be improved.
[0023]
FIG. 5 shows a different embodiment of the present invention, in which external electrodes 5 (4) have respective side edges 5a, 5b from both ends toward the center so that the width of the center decreases. (4a, 4b) is formed in an inclined shape. The external electrode 5 (4) has a deformed portion 5C (4C) as a whole.
[0024]
FIG. 6 shows still another embodiment of the present invention, and the basic configuration is the same as that shown in FIGS. The difference is that the outer peripheral surface of the glass bulb 2 is covered with an insulating member 6. As the insulating member 6, a protective tube made of a heat-shrinkable resin such as polyethylene terephthalate (PET) resin is preferable. This protection tube (6) can also be applied to the embodiment shown in FIGS.
[0025]
In addition, the present invention is not limited to the above-described embodiment at all, and for example, the external electrodes can be set in an appropriate form according to the light distribution characteristics in the axial direction. Further, when the external electrodes are arranged on the outer peripheral surface of the envelope, the external electrodes having a desired shape are attached to the translucent sheet in advance so as to be separated from each other. Can be streamlined. Further, the light emitting layer in the envelope may be formed on the entire inner surface, may be formed so as to form an aperture portion, or may be combined with the light reflecting layer.
[0026]
【Example】
Next, an experimental example will be described. In the rare gas discharge lamp 1 shown in FIGS. 1 and 2, a pair of external electrodes 4 and 5 made of aluminum foil are provided on the outer peripheral surface of a glass bulb made of lead glass having a tube diameter of 8 mm and a total length of 300 mm over substantially the entire length. And glue. The external electrodes 4 and 5 have a width of 8 mm at both ends and a width of 6 mm at the center, and the other side edges 4b and 5b are formed to be inclined from the end to the center. An illuminometer was arranged at a position 8 mm apart from the light emitting portion 2a of the discharge lamp in the normal direction, and the optical characteristics were measured. The total power consumption including the lighting device was 11 W.
[0027]
The initial illuminance at the center of the light emitting portion 2a was approximately 11000 (Lx), and the illuminance after lighting for 5 minutes was 10,560 (Lx). Further, the reduction rate of the light quantity at the end and the center was almost 4%. Further, the light distribution pattern in the axial direction of the light emitting portion 2a was almost flat over the whole as shown by the C characteristic shown in FIG. In the conventional example in which the width of the external electrode was 8 mm over the entire length, the illuminance after lighting for 5 minutes was 10,000 (Lx), and the reduction rate of the light amount was 4% at the end and 10% at the center. .
[0028]
【The invention's effect】
As described above, according to the present invention, since the width of the central portion of the external electrode is formed narrower than the end portion, the amount of current flowing between the external electrodes is smaller at the central portion than at the end portion. In addition, a rise in temperature due to the lighting operation can be suppressed. Therefore, the rate of decrease in the amount of light at the center can be suppressed to approximately the same as the rate of decrease at the ends.
[0029]
In addition, the light distribution pattern in the axial direction of the light emitting portion is relatively uniform over the whole due to the decrease in the amount of light at the central portion. Therefore, the light distribution pattern in the axial direction immediately after lighting and after shifting to the stable state can be kept substantially constant. For this reason, even if the light amount fluctuates, it can be dealt with by correction by the document irradiation device, and sufficient reading accuracy can be obtained.
[Brief description of the drawings]
FIG. 1 is a side view showing one embodiment of the present invention.
FIG. 2 is a longitudinal sectional view of a central portion of FIG.
FIG. 3 is a development view of FIG. 1;
FIG. 4 is a side view showing another embodiment of the present invention.
FIG. 5 is a side view showing a different embodiment of the present invention.
FIG. 6 is a side view showing still another embodiment of the present invention.
FIG. 7 is a schematic view of a conventional document irradiation apparatus.
FIG. 8 is a cross-sectional view of a discharge lamp used in a conventional document irradiation apparatus.
FIG. 9 is a diagram showing an illuminance distribution in an axial direction.
[Explanation of symbols]
1 rare gas discharge lamp 2 envelope (glass bulb)
2a Light emitting portion 3 Light emitting layer 4, 5 External electrode 4a, 5a One side edge 4b, 5b The other side edge 4A-4C, 5A-5C Deformed portion 6 Insulating member

Claims (2)

In a rare gas discharge lamp having a light emitting portion, a pair of band-shaped external electrodes are arranged at a distance on an outer peripheral surface of an envelope having a light emitting layer on an inner surface, and a rare gas is sealed in the envelope. The interval between one side edge adjacent to each other on the light emitting portion side of the external electrode is made substantially constant over the entire length, a portion having a different interval is provided between the other side edges, and the width of the central portion is reduced to the end portion. A rare gas discharge lamp characterized by being narrower than that of the above. In a rare gas discharge lamp having a light emitting portion, a pair of band-shaped external electrodes are arranged at a distance on an outer peripheral surface of an envelope having a light emitting layer on an inner surface, and a rare gas is sealed in the envelope. The interval between one side edge adjacent to each other on the light emitting portion side of the external electrode is made substantially constant over the entire length, and a deformed portion different from the interval at the end portion is provided between the other side edges , The end portion of the electrode and the side edge of the deformed portion are constituted by straight lines substantially parallel to the axial direction, and the width of the central portion, which is the deformed portion, is narrower than that of the end portion. Electric lights.

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