WO2006092981A1 - Fluorescent display tube - Google Patents

Abstract

[PROBLEMS] In a fluorescent display tube, the lighting of a filament can be limited to such a level as not to pose a display quality problem despite a dark surrounding and a low luminance, and power consumption can be reduced. [MEANS OF SOLVING PROBLEMS] A fluorescent display tube (1) comprising an airtight container (2), an anode (3) formed on the inner surface of the container (2), a light emitting surface (4) formed on the surface of the anode (3) and having a fluorescent material, and a filament-like cathode (5) provided to extend in the container (2) and applied with a voltage, wherein an electron emission amount changing means for changing the electron emission amount from the filament-like cathode (5) is further provided. The filament-like cathode (5) includes a high-luminance-use film-like cathode (5a) and a low-luminance-use film-like cathode (5b) that provide mutually different electron emission amounts when the same voltage is applied, and the electron emission amount changing means includes a filament switching unit (6) that applies a voltage to either one of the high-luminance-use film-like cathode (5a) and the low-luminance-use film-like cathode (5b) and switches between the filament-like cathode (5) elements to be applied.

Description

 Specification

 Fluorescent display tube

 Technical field

 The present invention relates to a fluorescent display tube in which a light emitting surface having an anode and a phosphor and a filamentary cathode as an electron source are housed and arranged in an airtight container.

 Background art

 [0002] Fluorescent display tubes are often used as display devices for stereo devices and in-vehicle devices. The fluorescent display tube includes an anode disposed in an airtight container, a light emitting surface having a phosphor on the anode surface, a filamentary cathode stretched inside the hermetic container, and an anode and a filamentous cathode inside the hermetic container. It consists of a grid installed in The filamentary cathode generates heat when it is energized by applying a voltage, and emits electrons at that time. The emitted electrons are attracted to the positive potential applied to the anode and the grid and collide with the light emitting surface. When electrons collide with the light emitting surface, the fluorescent display tube is displayed by emitting light from the collision part.

[0003] When a fluorescent display tube is used in a dark place such as at night, the luminance may need to be changed. As a method of changing the luminance of the fluorescent display tube, Patent Document 1 describes changing the luminance by changing the duty ratio of the voltage applied to the anode.

[0004] Further, as a method of reducing the power consumption of the fluorescent display tube, Patent Document 1 discloses a method of stopping power supply to a filamentary cathode in a portion where display is not performed during standby.

 Patent Document 1: Japanese Patent Laid-Open No. 2001-22324

 Disclosure of the invention

 Problems to be solved by the invention

[0005] In the fluorescent display tube described in Patent Document 1, the luminance change is controlled on the anode side, and the filamentary cathode is always used with a constant voltage applied. When used with a drop, the filamentary cathode heated to a high temperature looks red, which may deteriorate the display quality. In particular, when the display location is limited, such as displaying only the clock when the device is on standby, the filamentary cathode at the location that is not displayed may stand out and cause display quality problems. [0006] In addition, as described above, it is difficult to reduce the power consumption of the fluorescent display tube in the filamentous cathode because a certain voltage must be applied even if the luminance is lowered. Even if the power consumption is reduced by the method described in Patent Document 1 that allows only a part of the display means to be displayed during standby, no measures have been taken for the light emission of the filament cathode at low brightness. The above-described deterioration in display quality cannot be solved.

 [0007] Therefore, an object of the present invention is to provide a fluorescent display device in which, for example, lighting of a filament is suppressed to a level that does not cause a problem in display quality even at low luminance, and further, power consumption at low luminance is reduced. is there.

 Means for solving the problem

[0008] The invention of claim 1 includes an airtight container, an anode formed on an inner surface of the airtight container, a light emitting surface formed on the anode surface and having a phosphor, and is stretched in the airtight container. And a fluorescent display tube having a filamentary cathode to which a voltage is applied,

 An electron emission amount changing means is provided for changing the electron emission amount of the filament cathode when changing the light emission luminance of the light emitting surface.

 Brief Description of Drawings

FIG. 1 is a plan view of a fluorescent display tube according to a first embodiment of the present invention.

 FIG. 2 is a cross-sectional view taken along the line AA in FIG.

 FIG. 3 is a plan view of a fluorescent display tube according to a second embodiment of the present invention.

 FIG. 4 is a plan view of a fluorescent display tube using a transformer with a center tap according to a third embodiment of the present invention.

 FIG. 5 is a plan view of a fluorescent display tube using a center-tapless transformer according to a third embodiment of the present invention.

 FIG. 6 is a plan view of a fluorescent display tube according to a fourth embodiment of the present invention.

 FIG. 7 is a waveform diagram showing a change in duty ratio at high luminance and low luminance in the fourth embodiment.

 Explanation of symbols

[0010] 1 Fluorescent display tube 4 Light emitting surface

 5 Filament cathode

 6 Filament switching part (electron emission amount changing means, switching means)

 9 DC voltage regulator (Electron emission amount changing means)

 10 AC voltage regulator (electron emission amount changing means)

 11 Transformer (Electron emission amount change means)

 12 Duty ratio control unit (Electron emission amount changing means, means for changing the ratio of time for applying voltage per unit time)

 BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of the present invention will be described. A fluorescent display tube according to an embodiment of the present invention includes an airtight container, an anode formed on an inner surface of the airtight container, a light emitting surface formed on the anode surface and having a phosphor, and the airtight container. An electron emission amount changing means for changing the electron emission amount of the filamentary cathode when changing the light emission luminance of the light emitting surface. Prepare. In this way, by changing the amount of electron emission from the filamentary cathode in accordance with the change in brightness, the current flowing through the filamentary cathode can be reduced at low brightness, so the temperature of the filamentous cathode decreases. However, the filamentary cathode emits red light. In addition, since the current flowing through the filament cathode is reduced, the power consumption of the fluorescent display tube can be reduced.

 [0012] Further, the filament cathode includes a high-luminance filament cathode having different electron emission amounts when the applied voltage is the same, and a low-luminance filament cathode, and the electron emission amount changing means includes: And a switching means for applying a voltage to one of the high luminance filament cathode and the low luminance filament cathode and switching the filament cathode to be applied.

[0013] In addition, all the filamentary cathodes have the same amount of electron emission when the applied voltage is the same, and the electron emission amount changing means changes the voltage value applied to the filamentous cathode. Thus, a voltage regulator for changing the electron emission amount may be provided. [0014] Further, all the filamentary cathodes have the same amount of electron emission when the applied voltage is the same, and the electron emission amount changing means applies a voltage per unit time to the filamentary cathode. There may be provided means for changing the ratio of the time to perform.

 Example 1

 As shown in FIG. 1 and FIG. 2, a fluorescent display tube 1 useful for the first embodiment of the present invention includes an airtight container 2, an anode 3 housed in the airtight container 2, and a light emitting surface 4. A filament-shaped cathode 5, a grid 8, and a filament switching section 6 as a switching means which is an electron emission amount changing means.

 The airtight container 2 is a container in which glass plates are assembled in a box shape and the inside is in a vacuum state, and the display surface is a transparent glass plate. The anode 3 is a conductor electrode formed on a glass substrate facing the display surface of the hermetic container 2, and in this embodiment, rectangular electrodes are arranged at predetermined intervals. The anodes 3 are electrically insulated from each other and connected to circuit wiring (not shown) formed on the glass substrate, and a voltage is applied through the circuit wiring.

 The light emitting surface 4 is formed of a known phosphor on the surface of the anode 3 and emits light when electrons emitted from the filamentary cathode 5 and attracted to the anode 3 collide. The filamentary cathode 5 is stretched in the hermetic container 2 so that a plurality of filament cathodes 5 are parallel to each other so as to overlap the light emitting surface 4 in the longitudinal direction of the hermetic container 2. The filamentary cathode 5 is mainly coated with tungsten oxide wire such as barium, strontium, calcium, etc., and both ends are connected to the filament power supply 7 and energized by applying voltage to generate heat. To emit electrons. The grid 8 is provided between the anode 3 and the filamentary cathode 5 in the hermetic container 2 and is formed by forming a conductive metal in a mesh shape. The grid 8 is electrically insulated from the anode 3, and a voltage is applied through a circuit wiring (not shown) formed on the glass substrate.

[0018] In this embodiment, the filamentous cathode 5 has two types of filamentous cathodes 5; a high-luminance filamentary cathode 5a and a low-luminance filamentary cathode 5b that emit different amounts of electrons when the same voltage is applied. Is provided. The filamentary cathode 5a for high brightness and the filamentous cathode 5b for low brightness are alternately stretched in the airtight container 2 so as not to overlap each other. The same voltage is applied to the filament cathode 5b for low brightness as the filament cathode 5a for high brightness. In this case, the current flowing is reduced, so that the temperature is lowered and the amount of emitted electrons is reduced.

 [0019] The filament switching unit 6 is a switching switch that selects which of the high-luminance filament-like cathode 5a and the low-luminance filament-like cathode 5b is to be applied with a voltage. Switch manually. The filament switching section 6 applies a voltage to one of the filament cathode 5a for high brightness and the filament cathode 5b for low brightness, and applies the voltage to the filament cathode 5a for low brightness and the filament cathode 5b for low brightness. The amount of electron emission from the filamentary cathode 5 is changed by switching. The filament power supply 7 is a power supply that applies a voltage for causing the filamentary negative electrode 5 to generate heat and emitting electrons, and is a DC power supply in this embodiment.

[0020] Next, the operation of the fluorescent electron tube 1 of the present embodiment having such a constitutional force will be described.

[0021] First, a description will be given of the case of using at high luminance during the daytime or in a bright room. At this time, the filament switching unit 6 is switched so that the voltage of the filament power source 7 is applied to the high-luminance filament cathode 5a. A positive potential is applied to anode 3 and grid 8 from a separate power source that can change the duty ratio (not shown), and the luminance of fluorescent display tube 1 is changed by changing the duty ratio. . In the case of high brightness, the time during which voltage is applied to anode 3 and grid 8 per unit time is lengthened. That is, the luminance of the fluorescent display tube 1 is increased by setting the duty ratio of the voltage applied to the anode 3 and the grid 8 to be large.

 When a voltage is applied to the high-intensity filamentary cathode 5a, the high-intensity filamentous cathode 5a is energized and generates heat. When the high-luminance filamentary cathode 5a generates heat, it begins to emit electrons. The emitted electrons are attracted to the grid 8 and the anode 3 to which a positive potential is applied. The light emitting surface 4 formed on the surface of the anode 3 emits light when electrons attracted to the anode 3 collide. The fluorescent display tube 1 is displayed by this light emission.

[0023] When a display is performed using the high-luminance filamentary cathode 5a, a large amount of current flows through the high-luminance filamentary cathode 5a in order to emit a large amount of electrons. As a result, the high-luminance filamentary cathode 5a itself emits red light. However, since the brightness of the fluorescent display tube 1 is increased, the filamentous cathode for high brightness 5 The light emission of a is rare. In addition, since the periphery of the fluorescent display tube 1 is bright, the light emission from the high-luminance filament cathode 5a is not noticeable.

 [0024] Next, the case of using at low luminance at night or in a dark room will be described. At this time, the filament switching unit 6 is switched so that the voltage of the filament power supply 7 is applied to the low-luminance filament-like cathode 5b. In the case of low luminance, the time during which voltage is applied per unit time is shortened from another power source that can change the duty ratio (not shown) to the anode 3 and the grid 8. That is, the luminance of the fluorescent display tube 1 is lowered by setting the duty ratio of the voltage applied to the anode 3 and the grid 8 to be small.

 [0025] When the low-luminance filamentary cathode 5b is used, similarly to the case where the high-luminance filamentary cathode 5a is used, the electrons emitted by the heat generation of the low-luminance filamentary cathode 5b are positive potentials. Is attracted to the grid 8 and anode 3 to which is applied. The light emitting surface 4 formed on the surface of the anode 3 emits light when electrons attracted to the anode 3 collide. The fluorescent display tube 1 is displayed by this light emission.

 [0026] When displaying with the low-brightness filamentary cathode 5b, when the same voltage is applied, the amount of electron emission is reduced by reducing the current flowing from the high-brightness filamentous cathode 5a. The amount of heat generation is also reduced, and the filament-like cathode 5b for low brightness becomes cold, so the light emission of the filament cathode 5b for low brightness is lower than that of the filament cathode 5a for high brightness. The light emission is conspicuous.

 [0027] According to the present embodiment, the filament-like cathode 5a and the filament-like cathode 5b for low brightness are prepared for high brightness and low brightness, respectively, so that the filament cathode is used even at low brightness. 5 is less noticeable, and the current flowing through the filamentary cathode 5 is also reduced, so that the power consumption of the fluorescent display tube 1 at low brightness can be reduced.

 In this embodiment, the switch for manually switching the filament switching unit 6 is used as a switch, however, in conjunction with the duty ratio of the voltage value applied to the anode 3 and the grid 8 for changing the luminance. The filamentous cathode 5a for high brightness and the filamentous cathode 5b for low brightness may be switched. Further, as the filament power source 7, a power AC power source using a DC power source or a PWM power source may be used.

Example 2 Next, a second embodiment of the present invention will be described with reference to FIG. The same parts as those in the first embodiment described above are denoted by the same reference numerals and description thereof is omitted.

 [0030] In this embodiment, all the filamentary cathodes 5 have the same amount of electron emission when the applied voltage is the same. A DC voltage regulator 9 is provided as means for changing the amount of emitted electrons. The DC voltage regulator 9 changes the electron emission amount of the filament cathode 5 by changing the voltage value applied to both ends of the filament cathode 5.

 Next, the operation of this embodiment will be described. When the fluorescent display tube 1 is applied to the anode 3 and the grid 8 and the duty ratio of the squeezed voltage is changed to switch the high luminance power to low luminance, the voltage value applied to both ends of the filamentary cathode 5 is changed. Change to lower. Then, since the current flowing through the filamentous cathode 5 is reduced, the amount of electrons emitted is also reduced. As a result, the filament-like cathode 5 becomes low temperature, and the light emission of the filament-like cathode 5 also decreases.

 [0032] According to the present embodiment, by changing the voltage value applied to the filamentary cathode 5, the light emission of the filamentous cathode 5 is less noticeable even at low brightness, and the current flowing through the filamentous cathode 5 is also reduced. Therefore, the power consumption of the fluorescent display tube 1 at low luminance can be reduced. Also, two types of filamentous cathodes 5 for high luminance and low luminance are prepared, and the configuration becomes simpler than switching them.

 Example 3

 Next, a third embodiment of the present invention will be described with reference to FIGS. 4 and 5. The same parts as those in the first embodiment described above are denoted by the same reference numerals and description thereof is omitted.

 In this embodiment, all filament-like cathodes 5 have the same amount of electron emission when the applied voltage is the same. An AC voltage regulator 10 and a transformer 11 are provided as means for changing the amount of emitted electrons. The AC voltage regulator 10 and the transformer 11 change the electron emission amount of the filament cathode 5 by changing the voltage value applied to both ends of the filament cathode 5. Note that the transformer 11 shown in FIG. 5 may be a transformer having a center tap with no center tap in FIG.

Next, the operation of this embodiment will be described. When the duty ratio of the voltage applied to the anode 3 and the grid 8 is changed to switch the brightness of the fluorescent display tube 1 to high luminance or low luminance, the voltage value output from the AC voltage regulator 10 is changed. Lower. Output from AC voltage regulator 10 Since the voltage value is applied to both ends of the filamentary cathode 5 via the transformer 11, if the voltage value output from the AC voltage regulator 10 is lowered, the filament cathode 5 via the transformer 11 is reduced. The voltage value applied to both ends also decreases. Then, since the current flowing through the filamentary cathode 5 is reduced, the amount of electrons emitted is also reduced. As a result, the filamentary cathode 5 becomes low temperature, and the light emission of the filamentous cathode 5 is also reduced.

 [0036] According to the present embodiment, by changing the voltage value applied to the filamentary cathode 5, light emission of the filamentous cathode 5 is less noticeable even at low luminance, and the current flowing through the filamentous cathode 5 is also small. Therefore, it is possible to reduce the power consumption of the fluorescent display tube 1 when the luminance is low. In addition, two types of filamentary cathodes 5 for high luminance and low luminance are prepared, and the configuration becomes simpler than switching them.

 In Examples 2 and 3, the output voltage changing method of the DC voltage regulator 9 and the AC voltage regulator 10 is not limited to manual operation, and a voltage is applied to the anode 3 and the grid 8 that change the luminance. The voltage value may be changed in conjunction with the duty ratio of the power supply.

 Example 4

 Next, a fourth embodiment of the present invention will be described with reference to FIG. 6 and FIG. The same parts as those in the first embodiment described above are denoted by the same reference numerals and description thereof is omitted.

 In this embodiment, all filament-like cathodes 5 have the same amount of electron emission when the applied voltage is the same. A duty ratio control unit 12 is provided as an electron emission amount changing means. The duty ratio control unit 12 changes the duty ratio of the voltage applied to both ends of the filamentary cathode 5 by changing the ratio of the time for applying the voltage per unit time of the filament power supply 7 to change the electron emission amount. Make a change.

Next, the operation of the present embodiment will be described. When the duty ratio of the voltage applied to the anode 3 and the grid 8 is changed to switch the high luminance power to low luminance, the duty ratio control unit 12 uses the filament shape control unit 12 Set the duty ratio of the voltage applied to cathode 5 to a low value. For example, as shown in Fig. 7, when the duty ratio during a certain period T is set to S and the voltage is applied to the filamentary cathode 5 when the brightness is high, and the brightness is lower than this, the duty ratio If S is set smaller than that at high brightness and the duty ratio is set, the current flowing through the filamentary cathode 5 per period T decreases, and electrons are emitted. The amount is reduced and the calorific value is also reduced. As a result, the filamentary cathode 5 becomes low temperature, and the light emission of the filamentous cathode 5 is also reduced.

[0041] According to the present embodiment, by changing the voltage applied to the filamentary cathode 5, light emission of the filamentous cathode 5 is less noticeable even at low luminance, and the current flowing through the filamentous cathode 5 is also reduced. Therefore, it is possible to reduce the power consumption of the fluorescent display tube 1 when the luminance is low.

 In the present embodiment, the duty change method of the duty ratio control unit 12 is not limited to manual operation, and is changed in conjunction with the duty ratio of the power source that applies voltage to the anode 3 and the grid 8 that change the luminance. It ’s okay.

 [0043] Further, in Examples 1 to 4 described above, the force that forms the anode 3 and the light emitting surface 4 in a rectangular shape is not limited thereto, and can be formed in any shape such as letters and symbols, and the shape can be displayed. . In addition, by forming a large number of dots and selectively applying a positive potential to each dot-shaped anode 3, it is possible to display not only characters and symbols but also various displays such as figures by combining the dots. .

 Further, in Examples 1 to 4 above, the luminance was changed by changing the duty ratio of the voltage applied to the anode 3 and the grid 8. The voltage applied to the anode 3 and the grid 8. The duty ratio may be constant, and the electron emission amount may be changed only by changing the electron emission amount of the filament cathode 5 by means for changing the amount of electron emission. That is, the amount of electrons colliding with the light emitting surface 4 is not changed by controlling the amount of electrons attracted by the anode 3 and the grid 8 but by changing the amount of electrons generated on the filamentary cathode 5 side. The brightness may be changed by changing the light emission frequency.

 [0045] According to the embodiment described above, the following fluorescent display tube 1 is obtained.

 (Supplementary note 1) An airtight container 2, an anode 3 formed on the inner surface of the airtight container 2, a light emitting surface 4 formed on the surface of the anode 3 and having a phosphor, and the airtight container 2 In a fluorescent display tube 1 having a filamentary cathode 5 that is stretched and to which a voltage is applied, the electron emission amount of the filamentous cathode 5 is changed when the emission luminance of the light emitting surface 4 is changed. 1. Fluorescent display tube having discharge amount changing means 1.

(Supplementary note 2) As the filamentous cathode 5, when the applied voltage is the same, the amount of electron emission is mutually different. A filamentous cathode 5a for high brightness and a filamentous cathode 5b for low brightness, and the electron emission amount changing means includes the filamentary cathode 5a for high brightness and the filamentous cathode 5b for low brightness. The fluorescent display tube 1 according to appendix 1, further comprising a filament switching unit 6 for applying a voltage to either one and switching the filament cathode 5 to be applied.

 (Appendix 3) All the filamentary cathodes 5 have the same amount of electron emission when the applied voltage is the same, and the voltage value applied to the filamentous cathode 5 by the electron emission amount changing means The fluorescent display tube 1 according to appendix 1, characterized in that it comprises either a DC voltage regulator 9 or an AC voltage regulator 10 and a transformer 11 that change the amount of electron emission by changing

 (Appendix 4) All the filamentary cathodes have the same amount of electron emission when the applied voltage is the same, and the electron emission amount changing means includes a duty ratio control unit 12. The fluorescent display tube 1 according to appendix 1.

[0050] It should be noted that the present invention is not limited to the above-described embodiment as long as means for changing the amount of electrons emitted from the filamentary cathode 5 as the electron source according to the emission luminance of the fluorescent display tube 1 is provided. Applicable.

Claims

The scope of the claims  [1] An airtight container, an anode formed on an inner surface of the airtight container, and an anode surface And a fluorescent display tube comprising a light emitting surface having a phosphor, and a filamentary cathode that is stretched in the hermetic container and to which a voltage is applied,  A fluorescent display tube, comprising: an electron emission amount changing means for changing an electron emission amount of the filament cathode when changing the light emission luminance of the light emitting surface.  [2] The filament cathode includes a high-luminance filament cathode having different electron emission amounts when the applied voltage is the same, and a low-luminance filament cathode.  The electron emission amount changing means includes switching means for applying a voltage to one of the high-luminance filament cathode and the low-luminance filament cathode and switching the filament cathode to be applied. The fluorescent display tube according to claim 1, wherein:  [3] All the filamentary cathodes have the same amount of electron emission when the applied voltage is the same.  2. The fluorescent display tube according to claim 1, wherein the electron emission amount changing means includes a voltage regulator that changes an electron emission amount by changing a voltage value applied to the filamentary cathode.  [4] All the filamentary cathodes have the same amount of electron emission when the applied voltage is the same,  2. The fluorescent display tube according to claim 1, wherein the electron emission amount changing means includes means for changing a ratio of time for applying a voltage per unit time to the filamentary cathode.