Patent Application
20100156297
This application claims priority to and the benefit of Korean Patent Application No. 10-2008-0129664, filed Dec. 18, 2008, the disclosure of which is incorporated herein by reference in its entirety.
1. Field of the Invention
The present invention relates to a color variable field emission device, and more particularly, to a field emission device having a simple structure and capable of adjusting emission intensity of red, green and blue light, respectively, to readily change emission colors.
2. Discussion of Related Art
Generally, in a triode-type field emission device, when a gate electrode induces electron emission from a field emitter formed on a cathode electrode, the emitted electrons collide with a fluorescent layer formed on an anode electrode, so that cathode luminescence of the fluorescent layer causes light to be generated.
However, the conventional triode-type field emission device necessarily applies a high-voltage pulse as high as several to several tens of volts to the gate electrode in order to adjust brightness. Accordingly, the device requires a separate pulse driving high-voltage power supply for applying such a high-voltage pulse, which results in a complicated drive circuit and increased manufacturing costs.
In addition, while the conventional triode-type field emission device is easily applied to a general field emission display (FED), its structure is somewhat complicated to be applied to a field emission lamp.
The present invention is directed to a field emission device having a simple structure and capable of readily changing emission colors of light by individually adjusting emission intensity of red, green and blue light.
One aspect of the present invention provides a color variable field emission device including: a cathode substrate and an anode substrate that are disposed to face each other with a predetermined distance therebetween; first, second and third cathode electrode blocks formed on the cathode substrate to be electrically separated from each other; first, second and third field emitter blocks formed on the first, second and third cathode electrode blocks, respectively, in predetermined patterns; an anode electrode formed on the anode substrate; red, green and blue fluorescent layers formed on the anode electrode to correspond to the first, second and third field emitter blocks, respectively, in predetermined patterns; a gate electrode disposed between the cathode substrate and the anode substrate to induce electron emission from each of the field emitter blocks; and a plurality of current switching circuits electrically connected to each of the cathode electrode blocks to individually control current that flows into each of the cathode electrode blocks.
When the current that is applied to each of the cathode electrode blocks is individually adjusted through the current switching circuits with a predetermined voltage applied to the anode electrode and the gate electrode over time, the amount of electrons emitted from the first, second and third field emitters formed on the cathode electrode blocks, respectively, may be adjusted, so that emission intensity of light emitted from the red, green and blue fluorescent layers may be individually adjusted.
The current switching circuit may include a current switching device electrically connected to each cathode electrode block to adjust current that flows into the corresponding cathode electrode block, and a pulse generator providing the current switching device with a control pulse signal that repeats a high level and a low level within a range of 0 to 5 V.
When the control pulse signal that repeats a high level and a low level is applied to the current switching device with a predetermined voltage applied to the anode electrode and the gate electrode over time, the current switching device may be turned on only during the high level of the control pulse signal, so that current flows into the cathode electrode block connected to the current switching device. Also, the current switching device may be turned off during the low level of the control pulse signal, so that current may be prevented from flowing into the cathode electrode block connected to the current switching device.
The above and other features and advantages of the present invention will become more apparent to those of ordinary skill in the art by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:
The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. This invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein.
A color variable field emission device according to the present invention will be described in detail with reference to the accompanying drawings.
Referring to
Here, the sequence of the red fluorescent layer 170a, the green fluorescent layer 170b, and the blue fluorescent layer 170c may be changed, and field emitter blocks that are formed to correspond to the red, green and blue fluorescent layers 170a to 170c, respectively, are referred to as first to third field emitter blocks 130a to 130c for the sake of simplicity.
When electrons are emitted from the first to third field emitter blocks 130a, 130b and 130c due to a DC voltage applied to the gate electrode 140, the emitted electrons are accelerated by the DC voltage applied to the anode electrode 160 to collide with the red, green and blue fluorescent layers 170a to 170c, so that red, green and blue light emission occurs.
At this time, when an amount of current that flows from each of the cathode electrode blocks 120a, 120b and 120c is adjusted using the current switching circuits 190a, 190b and 190c serially connected to the cathode electrode blocks 120a, 120b and 120c, respectively, the amount of electrons emitted from the first to third field emitter blocks 130a, 130b and 130c is adjusted, respectively, and as a result, emission intensity of red, green and blue light emitted from the red, green and blue fluorescent layers 170a to 170c is adjusted as well.
Constitutions and operations of the current switching circuits 190a, 190b and 190c will be described below in detail.
Referring to
Here, the control pulse signal has a voltage value of a high or low level within a range of 0 to 5 V.
A high-voltage transistor may be used for the current switching device 191, and in such a case, the control pulse signal is input into a gate terminal of the high-voltage transistor, a drain terminal is connected to each of the cathode electrode blocks 120a to 120c, and a source terminal is connected to the ground.
Here, in order to prevent overvoltage from being applied to the current switching device 191, a resistor or a reactance device may be connected to the drain terminal of the current switching device 191 in series. Further, in order to prevent overcurrent from being applied to the current switching device 191, zener diodes or varistors may be connected in parallel between the drain and source terminals of the current switching device 191.
When the control pulse signal repeating a high level and a low level is applied to the current switching device 191 from the pulse generator 193, the corresponding current switching device 191 is turned on only during the high level of the control pulse signal. As a result, current flows into the cathode electrode blocks 120a to 120c connected to the corresponding current switching device 191, and thus electrons are emitted from only the field emitter blocks 130a to 130c on the corresponding cathode electrode blocks 120a to 120c.
During the low level of the control pulse signal, the corresponding current switching device 191 is turned off to prevent current from flowing into the cathode electrode blocks 120a to 120c connected to the corresponding current switching device 191. Accordingly, electron emission from the field emitter blocks 130a to 130c on the corresponding electrode blocks 120a to 120c ceases.
Here, the amount of electrons emitted from each of the field emitter blocks 130a to 130c may be adjusted by means of pulse width modulation (PWM) or pulse amplitude modulation (PAM).
In PWM, an on/off duty cycle is adjusted with a fixed voltage level of the control pulse signal, and in PAM, a voltage level is varied with a fixed on/off duty cycle of the control pulse signal.
That is, the field emission device 100 according to the present invention enables each of the field emitter blocks 130a to 130c to emit a different amount of electrons to be emitted through each of the current switching circuits 190a to 190c. As a result, emission intensities of red, green and blue emitted from the red, green and blue fluorescent layers 170a to 170c can be individually adjusted.
Meanwhile, in order to exhibit uniform brightness over a large area, the red, green and blue fluorescent layers 170a to 170c should emit light with constant emission intensity, a description of which will be provided below.
Referring to
Describing the structure in which the first to third field emitter blocks 130a to 130c are disposed in further detail, the first field emitter block 130a and the third field emitter block 130c are alternately disposed, and the second field emitter block 130b is filled in between the first field emitter block 130a and the third field emitter block 130c.
Therefore, in order for the red, green and blue fluorescent layers 170a to 170c to have the same emission intensity, a width b of the second field emitter block 130b may be formed to be one half of widths a and c of the first and third field emitter blocks 130a and 130c.
Referring to
That is, the red fluorescent layer 170a and the blue fluorescent layer 170c are alternately disposed, and the green fluorescent layer 170b is filled in between the red fluorescent layer 170a and the blue fluorescent layer 170c.
Therefore, in order for the red, green and blue fluorescent layers 170a to 170c to have the same emission intensity, a width b′ of the green fluorescent layer 170b may be formed to be one half of widths a′ and c′ of the red and blue fluorescent layers 170a and 170c.
As illustrated in
At this time, when the amount of current that flows from each of the cathode electrode blocks 120a to 120c is adjusted using the current switching circuits 190a to 190c, the amount of electrons emitted from the field emitter blocks 130a to 130c may be adjusted. As a result, emission intensity of light emitted from the red, green and blue fluorescent layers 170a to 170c is adjusted, so that emission colors of the field emission device can be arbitrarily adjusted.
Meanwhile, in order to effectively mix the three colors of red, green and blue emitted from the red, green and blue fluorescent layers 170a to 170c, a diffusion plate 200 may be additionally disposed over the anode substrate 150.
As illustrated in
In conclusion, in the field emission device 100 according to the present invention, current that flows into each of the cathode electrode blocks 120a to 120c is adjusted according to a very low control pulse signal of 0 to 5 V with a predetermined voltage applied to the anode electrode 160 and the gate electrode 140 over time, so that emission intensities of red, green and blue can be individually adjusted. Accordingly, the present invention simplifies the structure and facilitates adjustment of emission colors without a pulse driving high-voltage power supply compared with a conventional field emission device.
According to the present invention, current that flows into each cathode electrode block is adjusted in a simple manner using a control pulse signal of a low voltage level without a pulse driving high-voltage power supply, and thus emission intensities of red, green and blue can be arbitrarily adjusted, so that emission colors of the field emission device can be readily changed.
In the drawings and specification, there have been disclosed typical exemplary embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation. As for the scope of the invention, it is to be set forth in the following claims. Therefore, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2008-0129664 | Dec 2008 | KR | national |
