JP3765774B2 - External electrode fluorescent lamp - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an external electrode type fluorescent lamp having an electrode outside a glass tube.
[0002]
[Prior art]
At least first to third thermosensitive coloring layers that develop different colors are laminated, and the lower the thermosensitive coloring layer, the lower the thermal sensitivity, and the first thermosensitive coloring layer on the uppermost layer on the surface side and the second below There is a color thermal printer that uses a color thermal recording paper to which fixing property by ultraviolet rays in a specific wavelength range is applied to each of the thermal color developing layers, so that a full color print can be obtained. In this color thermal printer, while the color thermal recording paper is reciprocally conveyed along the sub-scanning direction, the thermal head arranged along the main scanning direction is pressed to perform thermal recording on each thermal coloring layer, and each thermal recording layer is subjected to thermal recording. After thermal recording on the coloring layer, the fixing unit is used to irradiate ultraviolet rays so that the upper thermal coloring layer does not develop color during thermal recording on the lower thermal coloring layer.
[0003]
The use of an external electrode type fluorescent lamp 101 shown in FIG. 10 as a light source of the fixing device is being studied. As is well known, the external electrode type fluorescent lamp 101 is used as a document reading light source such as a facsimile or a scanner. The external electrode type fluorescent lamp 101 includes a transparent glass tube 102 enclosing a discharge medium and a pair of electrodes 103 a and 103 b provided outside the glass tube 102.
[0004]
The glass tube 102 has a substantially cylindrical shape, and a rare gas such as xenon gas is used as a discharge medium sealed therein. Each of the electrodes 103a and 103b is formed, for example, by forming an aluminum foil into a strip shape, and the longitudinal direction extends in the tube axis direction. Each electrode 103a, 103b is affixed on the outer peripheral surface of the glass tube 102, and is arrange | positioned in the position which mutually opposes. A fluorescent film 104 formed by applying a phosphor is provided on the inner peripheral surface of the glass tube 102.
[0005]
When a voltage is applied to the electrodes 103a and 103b, a discharge is generated between the electrodes 103a and 103b. When discharge occurs, the xenon gas is excited by thermoelectrons, and light having a peak wavelength near 172 nm is generated. When this light hits the phosphor film 24, the phosphor is excited to emit light, and light having a wavelength corresponding to the type of phosphor is emitted.
[0006]
The fluorescent film 24 is removed from a part of the inner peripheral surface of the glass tube 102 corresponding to a portion where the electrodes 103a and 103b on the outer peripheral surface are not attached. This portion constitutes an aperture 106 for emitting the light emitted from the phosphor to the outside of the tube. When the irradiation area is increased, as shown in FIG. 10C, the position of the electrodes 103a, 103b is shifted in the circumferential direction to widen the aperture angle R, thereby increasing the area of the aperture 106.
[0007]
[Problems to be solved by the invention]
By the way, in order to increase the luminous efficiency of the external electrode type fluorescent lamp, it is preferable to generate a discharge evenly in each part of the electrodes 103a and 103b to eliminate unevenness of light emission distribution (light emission unevenness) in the fluorescent film 104. However, the discharge tends to concentrate on a portion where the electric field is strong. This tendency becomes particularly prominent when the gas pressure or power is increased in order to increase the illuminance.
[0008]
Since the glass tube 102 has a circular cross section, the facing electrodes 103a and 103b are each curved in the width direction. Therefore, the interval between the electrodes 103a and 103b differs depending on each part in the width direction. That is, the gap is wide near the center of the electrode, and the gap is narrowed toward the end. Since the electric field is inversely proportional to the interval between the electrodes, the electric field is strong at a portion where the interval is narrow and weak at a portion where the interval is wide.
[0009]
As described above, in the external electrode fluorescent lamp having a circular tube cross section, the electric field is not uniform in the cross-sectional direction of the glass tube. There was a problem that the illumination could not be increased well. In particular, when the aperture angle is widened, there is a problem because the bias of the electric field distribution is further increased.
[0010]
An object of the present invention is to provide an external electrode fluorescent lamp with high luminous efficiency.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, an external electrode fluorescent lamp according to the present invention includes a substantially cylindrical glass tube in which a discharge medium is sealed, a phosphor coated on the inner peripheral surface of the glass tube, and the glass tube. In an external electrode fluorescent lamp comprising a pair of electrodes that are provided on the outer peripheral surface of the glass tube and arranged at positions substantially opposite to each other across the glass tube, and whose longitudinal direction extends in the tube axis direction of the glass tube, The resistance value in each part in the width direction of each electrode is changed so that the magnitude of the current generated between the electrodes after the start of discharge becomes uniform in the cross-sectional direction of the glass tube.
[0012]
Another external electrode fluorescent lamp of the present invention is provided outside the glass tube, a substantially cylindrical glass tube in which a discharge medium is sealed, a phosphor applied to the inner peripheral surface of the glass tube, and the glass tube. In an external electrode type fluorescent lamp that is arranged at a position substantially opposite to each other with the glass tube interposed therebetween and whose longitudinal direction extends in the tube axis direction of the glass tube, the strength of the electric field between the electrodes is The dielectric constant between the electrodes is substantially uniform in the width direction of each electrode so as to be uniform in the cross-sectional direction of the glass tube.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
The color thermal printer 2 shown in FIG. 1 performs thermal recording of a full-color image and optical fixing of the color thermal recording paper 3 that has been thermal-recorded while reciprocating the color thermal recording paper 3 in the forward direction and in the opposite direction. I do.
[0014]
As is well known, the color thermosensitive recording paper 3 has a cyan thermosensitive coloring layer, a magenta thermosensitive coloring layer, and a yellow thermosensitive coloring layer sequentially provided on a support. The yellow thermosensitive coloring layer, which is the uppermost layer, has the highest thermal sensitivity and develops yellow with a small amount of heat energy. The cyan thermosensitive coloring layer, which is the lowermost layer, has the lowest thermal sensitivity and develops cyan with large heat energy. The yellow thermosensitive coloring layer loses its coloring ability when irradiated with yellow fixing light, which is blue-violet light having a peak wavelength of about 420 nm. The magenta thermosensitive coloring layer develops magenta with intermediate heat energy between the yellow thermosensitive coloring layer and the cyan thermosensitive coloring layer, and has a coloring ability when irradiated with magenta fixing light having a peak wavelength near 365 nm. Disappear. For example, a black thermosensitive coloring layer may be provided on the color thermosensitive recording paper 3 to form a four-layer structure.
[0015]
A thermal head 6 and a platen roller 7 that supports the color thermal recording paper 3 are disposed on the conveyance path of the color thermal recording paper 3 so as to face the thermal head 6. As is well known, the thermal head 6 includes a heating element array 6a in which a large number of heating elements are arranged in a line along the main scanning direction. Each heating element generates thermal energy corresponding to the density of the pixel and thermally records an image of each color of yellow, magenta, and cyan on each thermosensitive coloring layer.
[0016]
On the downstream side of the thermal head 6 in the forward direction, a conveyance roller pair 8 and yellow and magenta light fixing devices 9 and 11 are arranged. The conveyance roller pair 8 nips the fed color thermal recording paper 3 and conveys it in the sub-scanning direction. The conveyance roller pair 8 is driven to rotate by the conveyance motor 12.
[0017]
During this conveyance, the color thermal recording paper 3 passes through the thermal head 6 and the optical fixing devices 9 and 11, and thermal recording and optical fixing are performed. The color thermal recording paper 3 that has been subjected to thermal recording and light fixing is cut into a predetermined size by a cutter (not shown) and discharged out of the color thermal printer 2.
[0018]
As the transport motor 12, for example, a pulse motor that rotates by a predetermined amount according to the number of applied drive pulses is used. The conveyance amount of the color thermal recording paper 3 is controlled by counting the number of drive pulses applied to the conveyance motor 12.
[0019]
The yellow light fixing unit 9 includes a yellow fixing lamp 14 and a reflector 17, and the magenta light fixing unit 11 includes a magenta fixing lamp 16 and a reflector 18. The yellow fixing lamp 14 is a fixing light source that emits yellow fixing light, and the magenta fixing lamp 16 is a fixing light source that emits magenta fixing light. The fixing lamps 14 and 16 are arranged so that the longitudinal direction is along the main scanning direction.
[0020]
The reflectors 17 and 18 are arranged around the fixing lamps 14 and 16, and reflect the light emitted from the fixing lamps 14 and 16 toward the color thermal recording paper 3, and from the fixing lamps 14 and 16. The emitted light is prevented from leaking to the unrecorded area of the color thermal recording paper 3.
[0021]
As each of the fixing lamps 14 and 16, an external electrode type fluorescent lamp is used. As shown in FIG. 2, the external electrode fluorescent lamp 20 includes a glass tube 21 in which a discharge medium is sealed, and a pair of electrodes 22 a and 22 b provided outside the glass tube 21. Holders 23 are attached to both ends of the glass tube 21.
[0022]
A fluorescent film 24 made of a phosphor is formed on the inner peripheral surface of the glass tube 21. When a voltage is applied to each of the electrodes 22a and 22b, the glass tube 21 that is a dielectric is polarized, and a discharge is generated in the glass tube 21. When the thermal electrons collide with the xenon gas by the discharge, the xenon gas is excited and light having a peak wavelength of about 172 nm is emitted. When this light hits the fluorescent film 24, the fluorescent film 24 emits light in a wavelength region corresponding to the type of phosphor. The yellow fixing lamp 14 uses a phosphor that emits yellow fixing light, and the magenta fixing lamp 16 uses a phosphor that emits magenta fixing light.
[0023]
There is a region where the fluorescent film 24 is not applied on the inner peripheral surface of the glass tube 21, and this region constitutes an aperture 26 for transmitting each fixing light to the outside of the glass tube 21. The fixing lamps 14 and 16 are arranged so that the aperture 26 faces the recording surface of the color thermosensitive recording paper 3.
[0024]
As each electrode 22a, 22b, strip-shaped aluminum foil is used, for example. Each electrode 22a, 22b is affixed on the outer peripheral surface of the glass tube 21 so that the longitudinal direction is substantially parallel to the tube axis. Each electrode 22a, 22b is disposed at a position facing each other with the glass tube 21 in between.
[0025]
As shown in FIG. 3 (B), the cross-sectional shape of the glass tube 21 is circular, and each electrode 22a, 22b is affixed on the outer peripheral surface of the glass tube 21, so the distance between the electrodes 22a, 22b. L differs at each position in the width direction of each electrode 22a, 22b. That is, the distance between the portions of the electrodes 22a and 22b is the widest distance Lxc in the vicinity of the center xc and becomes narrower toward the end. The strength of the electric field when a voltage is applied to each electrode 22a, 22b is determined according to the dielectric constant between each electrode 22a, 22b and the distance L between them. Accordingly, if the dielectric constant at each part of each electrode 22a, 22b is constant, the electric field is weaker as the distance L is wider and stronger as it is narrower. The electric field distribution E (x) in FIG. 3C shows the electric field distribution in each part of the electrodes 22a and 22b in the width direction (hereinafter referred to as X direction).
[0026]
Since the discharge tends to concentrate on a portion where the electric field is strong, it concentrates on both ends of each electrode 22a, 22b. This tendency becomes stronger when the gas pressure is increased or the power is increased to increase the illuminance. When the discharge is concentrated, the light emission distribution of the fluorescent film 24 is also biased, so that the light emission efficiency is lowered. In order to increase the light emission efficiency, it is preferable to uniformly generate a discharge in each part of each electrode 22a, 22b to eliminate the light emission unevenness of the fluorescent film 24.
[0027]
Therefore, in the external electrode fluorescent lamp 20, by changing the thickness T of each electrode 22a, 22b along the width direction, the current C after the start of discharge generated between each electrode 22a, 22b is changed to the glass tube 21. It is made uniform in the cross-sectional direction. Thereby, the light emission unevenness of the fluorescent film 24 is reduced, so that the light emission efficiency is improved.
[0028]
FIG. 3A is a cross-sectional view of the electrodes 22 a and 22 b before being attached to the glass tube 21. Each electrode 22a, 22b has the thickest thickness Txc at the position xc near the center, and becomes narrower toward the end than that. When the thickness T of the electrode changes, the resistance R also changes according to the thickness. That is, the greater the thickness T, the smaller the resistance, and the thinner the thickness T, the greater the resistance. FIG. 4C shows a resistance distribution R (x) in each part in the width direction of each electrode 22a, 22b and a voltage distribution V (X) after the start of discharge.
[0029]
As described above, the discharge tends to concentrate on the portion where the electric field E is strong. Therefore, by providing each electrode 22a, 22b with a resistance distribution R (x) as shown in FIG. 4 (c), the voltage V after the start of discharge is low at the portion where the electric field E is strong, while the electric field E The voltage V after the start of the discharge is made high at the part where is low. Thereby, as shown in FIG. 4A, the magnitude of the discharge current C after the start of discharge can be made uniform in the cross-sectional direction of the glass tube 21.
[0030]
Hereinafter, the operation of the above configuration will be described. When printing is started, first, the color thermal recording paper 3 is fed to the conveyance path. When the leading edge of the color thermal recording paper 3 reaches the conveying roller pair 8, it is nipped by the conveying roller pair 8 and conveyed. During this conveyance, first, a yellow image is thermally recorded on the yellow thermosensitive coloring layer by the thermal head 6. During this thermal recording, the yellow fixing lamp 14 is turned on, and the yellow thermosensitive coloring layer is optically fixed sequentially from the recorded portion of the color thermosensitive recording paper 3.
[0031]
Each electrode 22a, 22b of the external electrode type fluorescent lamp 20 changes the resistance value in each part in the width direction by changing the thickness T according to the electric field distribution E (x) shown in FIG. Yes. Therefore, the voltage V after the discharge is low in the portion where the electric field E where the discharge is concentrated is strong, and the voltage V is high in the portion where the electric field E is weak. Therefore, the discharge current C is large in the cross-sectional direction of the glass tube 21. Becomes uniform. For this reason, since the light emission unevenness of the fluorescent film 24 is reduced, it can be lit with high light emission efficiency.
[0032]
When the thermal recording and photofixing of the yellow thermosensitive coloring layer is completed, the color thermosensitive recording paper 3 is once rewound in the reverse direction and then conveyed again in the forward direction to start thermal recording of the magenta thermosensitive coloring layer. . During this recording, the magenta fixing lamp 16 is turned on, and the heat-recorded portions are sequentially sent to the magenta light fixing device 11 to perform magenta light fixing. Similar to the yellow fixing lamp 14, the magenta fixing lamp 16 uses the external electrode fluorescent lamp 20, and therefore can be lit with high luminous efficiency.
[0033]
When magenta thermal recording and light fixing are completed, the color thermal recording paper 3 is once rewound and then a cyan image is thermally recorded. The printed recording paper 3 on which the full color image is recorded is discharged out of the printer.
[0034]
In the above embodiment, the unevenness of the emission of the fluorescent film is reduced by changing the resistance value by changing the thickness in the width direction of the electrode according to the electric field distribution between the electrodes and making the current uniform after the start of discharge. As described in the example, the electric field distribution between the electrodes may be made uniform to reduce the light emission unevenness of the fluorescent film.
[0035]
In the external electrode fluorescent lamp 40 shown in FIG. 5, an electric field compensation member 43 is provided between the glass tube 21 and the electrodes 42a and 42b. The electric field compensation member 43 is a dielectric different from the glass tube 21 and is a dielectric constant adjusting member for making the dielectric constant ε of each part in the width direction of each electrode 42a, 42b uniform. By providing the electric field compensation member 43, the dielectric constant distribution ε (x) between the electrodes 42a and 42b becomes substantially uniform, and as shown in FIG. 5C, the electric field distribution E (X) of the glass tube 21 in the X direction. x) can also be made substantially uniform. Since the electric field distribution E (x) is uniform, the discharge does not concentrate in part.
[0036]
Further, since the thickness T of each electrode 42a, 42b is constant (Txc = Tx1), the resistance distribution R (x) in the width direction of each electrode 42a, 42b and the voltage distribution V (x) after the start of discharge are uniform. is there. Therefore, the current distribution C (x) becomes uniform, and the light emission unevenness of the fluorescent film 24 is reduced.
[0037]
In this example, by providing the electric field compensation member 43, the dielectric constant distribution ε (x) between the electrodes 42a and 42b is made substantially uniform, but it is slight as it goes from the position xc to the position x1. The thickness of the glass tube 21 increases. Therefore, strictly speaking, the dielectric constant distribution ε (x) does not become uniform, and the electric field E becomes weaker toward the end position x1.
[0038]
Therefore, when it is desired to make the dielectric constant distribution ε (x) uniform with higher accuracy, the ends of the electrodes 42a and 42b are curved in consideration of the change in the dielectric constant ε due to the thickness change of the glass tube 21. It is good to let them close. That is, in the portion where the thickness of the glass tube 21 is increased, the thickness of the electric field compensation member 43 is reduced and the ends of the electrodes 42a and 42b are brought closer to each other. Thereby, the electric field distribution E (x) becomes more uniform, and the concentration of discharge is further prevented.
[0039]
FIG. 6 is an example in which the thickness of the glass tube 51 is changed along the X direction to make the dielectric constant distribution ε (x) between the electrodes 52a and 52b uniform. Each electrode 52a, 52b is affixed on the outer peripheral surface of the glass tube 51. Therefore, the interval near the end is narrower than the center position xc. Corresponding to the change in the interval, the glass tube 51 is formed so that the thickness G increases from the center position xc toward the end, that is, Gxc <Gx1. Thereby, the dielectric constant distribution ε (x) between the electrodes 52a and 52b becomes uniform, and the electric field distribution E (x) becomes uniform.
[0040]
Moreover, in the said embodiment, although the strip-shaped electrode was used and demonstrated in the example arrange | positioned according to the longitudinal direction in the tube-axis direction of a glass tube, the waveform and comb-shaped electrodes 61 and 62, as shown in FIG. 63 may be used. The electrode 61 shown in FIG. 7A is formed in a waveform along the tube axis direction. Each of the electrodes 62 and 63 shown in FIGS. 7B and 7C has a comb shape in which a plurality of rectangular or triangular tongue pieces 62b and 63b are formed on the trunk portions 62a and 63a extending in the tube axis direction. It has a shape.
[0041]
As the area of the electrode increases, the portion where the discharge concentrates tends to fluctuate. The fluctuation of the discharge becomes remarkable in the longitudinal direction (tube axis direction) when strip-shaped electrodes are used. By forming the electrodes 61 to 63 in a corrugated shape or a comb shape, the portion where the discharge is generated is limited, so that the fluctuation of the discharge in the tube axis direction can be prevented. In addition to the corrugated and comb-shaped electrodes, various electrodes such as a strip-shaped electrode provided with a large number of holes can be considered as electrodes for preventing the fluctuation of the discharge in the tube axis direction. Any of these may be used.
[0042]
Further, when the electrode 61 or the electrode 62 is used in place of the electrodes 22a and 22b shown in FIGS. 3 and 4, in order to change the resistance value in each part in the width direction, similarly to the electrodes 22a and 22b. It is necessary to change the thickness along the X direction. FIG. 8 shows a cross-sectional view when the electrode 62 has a thickness change, its resistance distribution R (x), and voltage distribution V (x) after the start of discharge. By providing such a resistance distribution R (x) by changing the thickness, a current distribution C (x) after the start of discharge is generated according to the electric field distribution E (x). Unevenness is reduced.
[0043]
On the other hand, as shown in FIG. 9, when a comb-shaped electrode 63 having a triangular tongue 63b is used instead of the electrodes 22a and 22b, the thickness of the electrode 63 may be constant. In other words, since the tongue 63b of the electrode 63 has a triangular shape, the resistance value at each site in the width direction varies depending on the shape. That is, in the vicinity of the center, since the base of the triangle is located, the area is large and the resistance value is small. On the other hand, since the apex of the triangle is located on the end side, the area is small and the resistance value is large. Thus, since the resistance value changes depending on the shape, it is not necessary to change the thickness.
[0044]
In the above embodiment, the external electrode type fluorescent lamp of the present invention is described as an example of using as a fixing light source of a thermal printer. However, the present invention is not limited to this, for example, a document such as a scanner, a fax machine, or a laser printer. It can be applied to a light source for reading.
[0045]
【The invention's effect】
As described above in detail, the external electrode fluorescent lamp of the present invention is provided outside the glass tube with a substantially cylindrical glass tube in which a discharge medium is enclosed and phosphor is applied to the inner peripheral surface, In an external electrode type fluorescent lamp that is arranged at a position substantially opposite to each other with a glass tube interposed therebetween and whose longitudinal direction extends in the tube axis direction of the glass tube, an electric current after the start of discharge generated between the electrodes The resistance value at each part in the width direction of each electrode is changed so that the size of the electrode becomes uniform in the cross-sectional direction of the glass tube, and the electric field strength between the electrodes is uniform in the cross-sectional direction of the glass tube Thus, since the dielectric constant between the electrodes is made substantially uniform in the width direction of the electrodes, the light emission unevenness of the phosphor can be reduced. Thereby, luminous efficiency improves.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a color thermal printer.
FIG. 2 is a perspective view of an external electrode fluorescent lamp.
FIG. 3 is a cross-sectional view of an external electrode type fluorescent lamp.
FIG. 4 is an explanatory diagram of electrode resistance distribution and voltage distribution;
FIG. 5 is an explanatory diagram of an external electrode type fluorescent lamp in which the dielectric constant between electrodes is made uniform using an electric field compensation member.
FIG. 6 is an explanatory diagram of an external electrode type fluorescent lamp in which the thickness of a glass tube is changed to make the dielectric constant between electrodes uniform.
FIG. 7 is a plan view of corrugated and comb-shaped electrodes along the tube axis direction.
FIG. 8 is an explanatory diagram of resistance distribution and voltage distribution of a comb-shaped electrode having a rectangular tongue piece.
FIG. 9 is an explanatory diagram of resistance distribution and voltage distribution of a comb-shaped electrode having a triangular tongue piece.
FIG. 10 is an explanatory diagram of a conventional external electrode type lamp.
[Explanation of symbols]
2 Color thermal printer 3 Color thermal recording paper 9 Yellow light fixing device 10 Magenta light fixing device 14 Yellow fixing lamp 16 Magenta fixing lamp 20, 40, 50 External electrode type fluorescent lamps 22a, 22b, 42a, 42b, 52a, 52b , 61, 62, 63 Electrode 21, 51 Glass tube 24 Fluorescent film 26 Aperture

Claims (2)

A substantially cylindrical glass tube in which a discharge medium is enclosed, a phosphor applied to the inner peripheral surface of the glass tube, and a position provided on the outer peripheral surface of the glass tube and substantially opposed to each other with the glass tube interposed therebetween. In the external electrode fluorescent lamp comprising a pair of electrodes whose longitudinal direction extends in the tube axis direction of the glass tube,
An external electrode type characterized in that the resistance value in each part in the width direction of each electrode is changed so that the magnitude of the current generated between each electrode after the start of discharge becomes uniform in the cross-sectional direction of the glass tube Fluorescent lamp. A substantially cylindrical glass tube in which a discharge medium is enclosed, a phosphor applied to the inner peripheral surface of the glass tube, and provided outside the glass tube, and disposed at substantially opposite positions across the glass tube. And in the external electrode type fluorescent lamp consisting of a pair of electrodes whose longitudinal direction extends in the tube axis direction of the glass tube,
An external electrode fluorescent lamp characterized in that the dielectric constant between the electrodes is made substantially uniform in the width direction of each electrode so that the electric field strength between the electrodes becomes uniform in the cross-sectional direction of the glass tube.

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