Patent Application
20070222388
1. Field of the Invention
The present invention relates to a flat fluorescent lamp and a method for driving the same, and more particularly, to a flat fluorescent lamp that provides an area light source with high light uniformity and a method for driving the same.
2. Description of the Related Art
Along with the continuous development of modern video technology, the liquid crystal display (LCD) device has been widely used as a display screen in the consumer electronic apparatus such as the mobile phones, the notebook computers (a.k.a. the laptop computers), the personal computers (PC) and the personal digital assistants (PDA). However, since the liquid crystal display panel of the LCD device does not emit light, a backlight module has to be installed under the liquid crystal display panel to provide a light source required by the liquid crystal display panel, such that the liquid crystal display panel can display an image on the screen. The main backlight module used in the current market includes the flat fluorescent lamp (FFL), the cold cathode fluorescent lamp (CCFL) and the light emitting diode (LED). Wherein, since the flat fluorescent lamp (FFL) is advantageous in its characteristics of lower price and smaller space, it has been widely applied in the LCD device.
A conventional method for driving the flat fluorescent lamp 100 includes first providing a driving voltage to the bottom electrodes 140 and the top electrodes 150, such that a discharge electric field E is generated between each pair of the corresponding bottom electrodes 140 and top electrodes 150, and the discharge gas 130 is then dissociated and converted into plasma by the discharge electric field E. Then, while the excited state electrons in each ion of the plasma are back to their ground state, an ultraviolet radiation is emitted. When the ultraviolet radiation emitted by the plasma emits on the fluorescent material 170, the fluorescent material 170 is excited and emits light.
It is to be noted that in the conventional technique, since the discharge electric field E is mainly distributed between each pair of the corresponding salient bottom electrodes 140 and top electrodes 150, the portion above the bottom electrodes 140 and top electrodes 150 of the area light source formed by the flat fluorescent lamp 100 is obviously brighter. In other words, the area light source formed by the conventional flat fluorescent lamp 100 has a distinct light area and dark area, thus the light uniformity of such area light source is rather poor. In addition, in order to improve the light uniformity of the area light source, a diffusion film with a lower transparency is required, which affects the luminance of the area light source. Moreover, when an area light source with a higher luminance is required, the driving voltage of the flat fluorescent lamp 100 needs to be greatly increased, which easily damages the flat fluorescent lamp.
Therefore, it is an object of the present invention to provide a flat fluorescent lamp that provides an area light source with a better light uniformity.
It is another object of the present invention to provide a method for driving the flat fluorescent lamp so as to improve the light uniformity of the flat fluorescent lamp.
It is yet another object of the present invention to provide a method for driving the flat fluorescent lamp so as to increase the lifespan of the flat fluorescent lamp.
In order to achieve the objects mentioned above and others, the present invention provides a flat fluorescent lamp. The flat fluorescent lamp comprises a chamber, a discharge gas, a fluorescent material, a plurality of first electrode sets, a plurality of second electrode sets and a dielectric layer. Wherein, the discharge gas is disposed inside the chamber, and the chamber has a first inner wall and a second inner wall facing oppositely with each other. The fluorescent material is disposed on the first inner wall and the second inner wall. The first electrode sets are disposed on the first inner wall, and the second electrode sets aligned with the first electrode sets are disposed on the second inner wall. The dielectric layer overlies the first and second electrode sets. In addition, each first electrode set comprises two first electrodes and a second electrode disposed between these two first electrodes. Each second electrode set comprises two third electrodes and a fourth electrode disposed between these two third electrodes. Moreover, a first light-emitting area and a second light-emitting area are formed in each pair of the corresponding first and second electrode sets, and the projections of the first and second light-emitting areas on the first inner wall are not overlaid or just partially overlaid.
In an embodiment of the present invention, each first electrode set further comprises a plurality of first salient points disposed on a first side of the second electrode and a plurality of second salient points disposed on a second side of the second electrode, wherein the first salient points and the second salient points are interleavedly disposed. In addition, each second electrode set further comprises a plurality of third salient points that is disposed on the third electrode on the first side of the second electrode and a plurality of fourth salient points that is disposed on the third electrode on the second side of the second electrode. Moreover, in each pair of the corresponding first and second electrode sets, the first light-emitting area is formed between the first and second salient points and the first electrode, and the second light-emitting area is formed between the third and fourth salient points and the second electrode.
As described above, in each pair of the corresponding first and second electrode sets, the projections of the third salient points on the first inner wall align with the second salient points, and the projections of the fourth salient points on the first inner wall align with the first salient points. In addition, the flat fluorescent lamp further comprises a first inverter and a second inverter. The first inverter has a first contact and a second contact in which each has an opposite electric phase. Wherein, the first contact is electrically connected to the second electrode, and the second contact is electrically connected to the first electrode. The second inverter has a third contact and a fourth contact in which each has an opposite electric phase. Wherein, the third contact is electrically connected to the third electrode, and the fourth contact is electrically connected to the second electrode.
In an embodiment of the present invention, each first electrode set further comprises a plurality of first salient points disposed on a first side of the second electrode and a plurality of second salient points disposed on a second side of the second electrode, wherein the first salient points and the second salient points are interleavedly disposed. In addition, each second electrode set further comprises a plurality of third salient points disposed on a first side of the third electrode and a plurality of fourth salient points disposed on a second side of the third electrode, wherein the third salient points and the fourth salient points are interleavedly disposed. Moreover, in each pair of the corresponding first and second electrode sets, the first light-emitting area is formed between the first and second salient points and the first electrode, and the second light-emitting area is formed between the third and fourth salient points and the first electrode.
As described above, in each pair of the corresponding first and second electrode sets, the projections of the third salient points on the first inner wall align with the second salient points, and the projections of the fourth salient points on the first inner wall align with the first salient points. In addition, the flat fluorescent lamp further comprises a first inverter and a second inverter. The first inverter has a first contact and a second contact in which each has an opposite electric phase. Wherein, the first contact is electrically connected to the second electrode, and the second contact is electrically connected to the first electrode. The second inverter has a third contact and a fourth contact in which each has an opposite electric phase. Wherein, the third contact is electrically connected to the fourth electrode, and the fourth contact is electrically connected to the first electrode.
In an embodiment of the present invention, each first electrode set further comprises a plurality of first salient points disposed on a first side of the second electrode and a plurality of second salient points disposed on a second side of the second electrode, wherein the first salient points and the second salient points are interleavedly disposed. In addition, each second electrode set further comprises a plurality of third salient points that is disposed on the third electrode on the first side of the second electrode and a plurality of fourth salient points that is disposed on the third electrode on the second side of the second electrode. Moreover, in each pair of the corresponding first and second electrode sets, the first light-emitting area is formed between the first and second salient points and the first electrode, and the second light-emitting area is formed between the third and fourth salient points and the fourth electrode.
As described above, in each pair of the corresponding first and second electrode sets, the projections of the third salient points on the first inner wall align with the second salient points, and the projections of the fourth salient points on the first inner wall align with the first salient points. In addition, the flat fluorescent lamp further comprises a first inverter and a second inverter. The first inverter has a first contact and a second contact in which each has an opposite electric phase. Wherein, the first contact is electrically connected to the second electrode, and the second contact is electrically connected to the first electrode. The second inverter has a third contact and a fourth contact in which each has an opposite electric phase. Wherein, the third contact is electrically connected to the third electrode, and the fourth contact is electrically connected to the fourth electrode.
In an embodiment of the present invention, the chamber mentioned above comprises a first substrate, a second substrate, and a frame disposed between the first substrate and the second substrate. Wherein, the surface of the first substrate opposite to the second substrate is regarded as the first inner wall, and the surface of the second substrate opposite to the first substrate is regarded as the second inner wall.
In an embodiment of the present invention, the chamber mentioned above further comprises a plurality of spacers, and the spacers are disposed inside the frame for forming a plurality of discharge rooms. Wherein, a first electrode set and a second electrode set disposed oppositely are disposed in each of the discharge rooms.
In an embodiment of the present invention, the chamber mentioned above further comprises a reflective layer disposed on the first inner wall, and the reflective layer is overlaid by the fluorescent material.
In an embodiment of the present invention, the first, the second, the third and the fourth electrodes are stripe type electrodes.
The present invention further provides a method for driving a flat fluorescent lamp, and the method is suitable for driving the flat fluorescent lamp mentioned above. With such method, the first light-emitting area and the second light-emitting area of the flat fluorescent lamp emit light interleavedly, and the light emitting frequency of the first light-emitting area and the second light-emitting area is between 10 kHz and 500 kHz.
In an embodiment of the present invention, the light emitting frequency of the first light-emitting area and the second light-emitting area is between 40 kHz and 80 kHz.
The present invention further provides a method for driving a flat fluorescent lamp, and the method is suitable for driving the flat fluorescent lamp mentioned above. In the driving method, the first light-emitting area emits light only when the flat fluorescent lamp is turned on at the nth time, and the second light-emitting area emits light only when the flat fluorescent lamp is turned on at the mth time, where n is an odd number, and m is an even number.
The present invention further provides a flat fluorescent lamp comprising a chamber having a first inner wall and a second inner wall facing oppositely with each other, a fluorescent material disposed on the first inner wall and the second inner wall, a plurality of first electrodes and a plurality of second electrodes disposed on the first inner wall, a plurality of third electrodes and a plurality of fourth electrodes disposed on the second inner wall, a plurality of first salient points disposed on the side walls of the first electrodes and the second electrodes, and a plurality of second salient points disposed on the side walls of the third electrodes and the fourth electrodes. Wherein, the first electrodes and the second electrodes are alternately disposed, the third electrodes are disposed opposite to the first electrodes, and the fourth electrodes are disposed opposite to the second electrodes. The first salient points and the second salient points face to the different directions. Moreover, a first light-emitting area is formed between the first salient points and the corresponding first electrodes and second electrodes opposite to the first salient points. A second light-emitting area is formed between the second salient points and the corresponding third electrodes and fourth electrodes opposite to the second salient points, or between the second salient points and the corresponding first electrodes and second electrodes opposite to the second salient points. The first light-emitting area and the second light-emitting area are not overlaid or just partially overlaid.
In an embodiment of the present invention, the projection of the first salient points and the second salient points on the first inner wall are alternately arranged.
In the flat fluorescent lamp of the present invention, since the projections of the first light-emitting area and the second light-emitting area on the first inner wall are not overlaid or just partially overlaid. Accordingly, the first light-emitting area and the second light-emitting area emit light interleavedly, such that the light uniformity of the area light source is improved and the lifespan of the flat fluorescent lamp is increased.
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention, and together with the description, serve to explain the principles of the invention.
The present invention is to control the discharge electric field generated between each pair of the corresponding first and second electrode sets in the chamber, such that a first light-emitting area and a second light-emitting area are formed in each pair of the corresponding first and second electrode sets, and the projections of the first and second light-emitting areas on the first inner wall in the chamber are not overlaid or just partially overlaid. The detail description is as following.
In the first embodiment, the discharge gas is an inert gas such as Xe, Ne, or Ar, and the dielectric layer is made of a ceramic material. In addition, the chamber 210 comprises a first substrate 212, a second substrate 214 and a frame 216 disposed between the first substrate 212 and the second substrate 214. Wherein, the surface of the first substrate 212 opposite to the second substrate 214 is regarded as the first inner wall 211, and the surface of the second substrate 214 opposite to the first substrate 212 is regarded as the second inner wall 213.
The chamber 210 further comprises a plurality of spacers 270 disposed inside the frame 216 for forming a plurality of discharge rooms. Wherein, a first electrode set 240 and a second electrode set 250 disposed oppositely are disposed in each discharge space. In addition, a reflective layer 280 is disposed on the first inner wall 211 of the chamber 210, and the reflective layer 280 is overlaid by the fluorescent material 230. Here, the reflective layer 280 is made of a white ceramic material such as TiO2 or SiO2. Such material is used to reflect the light emitted by the fluorescent material 230, such that the light emerges from the first substrate 214.
As described above, the flat fluorescent lamp 200 further comprises a first inverter 290a and a second inverter 290b. The first inverter 290a has a first contact 292 and a second contact 294 in which each has an opposite electric phase. Wherein, the first contact 292 is electrically connected to the second electrode 244, and the second contact 294 is electrically connected to the first electrodes 242a, 242b. The second inverter 290b has a third contact 296 and a fourth contact 298 in which each has an opposite electric phase. Wherein, the third contact 296 is electrically connected to the third electrodes 252a, 252b, and the fourth contact 298 is electrically connected to the second electrode 244.
When the first inverter 290a provides a driving voltage to the first electrodes 242a, 242b and the second electrode 244, in each pair of the corresponding first electrode set 240 and the second electrode set 250, a first discharge electric field E1 is generated between the first electrodes 242a, 242b and the second electrode 244, such that a first light-emitting area A1 is formed between the first salient points 245 and the first electrode 242a and between the second salient point 245 and the first electrode 242b. In addition, when the second inverter 290b provides a driving voltage to the third electrodes 252a, 252b and the second electrode 244, in each pair of the corresponding first electrode set 240 and the second electrode set 250, a second discharge electric field E2 is generated between the third electrodes 252a, 252b and the second electrode 244, such that a second light-emitting area A2 is formed between the third salient points 255 and the second electrode 244 and between the fourth salient points 256 and the second electrode 244.
It is to be noted that in each pair of the corresponding first electrode set 240 and the second electrode set 250, when the projections of the third salient points 255 on the first inner wall 211 align with the second salient points 246, and the projections of the fourth salient points 256 on the first inner wall 211 align with the first salient points 245, the projections of the first light-emitting area A1 and the second light-emitting area A2 on the first inner wall 211 are not overlaid. In addition, the first light-emitting area A1 can compensate the area not covered by the second light-emitting area A2, and the second light-emitting area A2 can compensate the area not covered by the first light-emitting area A1.
In order to have the first light-emitting area A1 and the second light-emitting area A2 compensated by each other, the present invention especially provides a method for driving the flat fluorescent lamp. The driving method is having the first light-emitting area A1 and the second light-emitting area A2 of the flat fluorescent lamp 200 emit light interleavedly. In the embodiment, the first inverter 290a and the second inverter 290b are interleavedly driven, such that the first light-emitting area A1 and the second light-emitting area A2 of the flat fluorescent lamp 200 emit light interleavedly. In addition, the light emitting frequency of the first light-emitting area A1 and the second light-emitting area A2 must be higher than the range human eyes can recognize, such as between 10 kHz and 500 kHz, the better is between 40 kHz and 80 kHz, such that the image of the object can be temporarily stilled in human eyes. Since the projections of the first light-emitting area A1 and the second light-emitting area A2 on the first inner wall 211 are not completely overlaid, the areas not covered can be compensated by each other. Accordingly, the flat fluorescent lamp 200 of the present embodiment can provide an area light source with a better light uniformity.
As described above, since the flat fluorescent lamp 200 can provide an area light source with a better light uniformity, the diffusion film with a higher transparency can be used and in some cases it is not even needed, such that the affect of the diffusion film to the luminance of the area light source is decreased. In addition, comparing to the conventional flat fluorescent lamp 100, if an area light source with the same luminance is required, the driving voltage output from the first inverter 290a and the second inverter 290b of the flat fluorescent lamp 200 of the present embodiment is lower, such that the present embodiment can avoid the flat fluorescent lamp 200 being damaged due to an over high driving voltage. Moreover, since the first light-emitting area A1 and the second light-emitting area A2 are disposed at different locations, the light emitting positions of the fluorescent material 230 are not the same, which increases the lifespan of the flat fluorescent lamp 200.
It is to be noted that the present invention further provides a method for driving a flat fluorescent lamp. In the driving method, the first light-emitting area A1 emits light only when the flat fluorescent lamp 200 is turned on at the nth time, and the second light-emitting area A2 emits light only when the flat fluorescent lamp 200 is turned on at the mth time, where n is an odd number, and m is an even number. With such method, the fluorescent material 230 on different locations in the flat fluorescent lamp 200 emits light interleavedly, such that the lifespan of the flat fluorescent lamp 200 is increased.
In addition, the third contact 296 of the second inverter 290b in the flat fluorescent lamp 200a is electrically connected to the fourth electrode 254, and the fourth contact 298 is electrically connected to the first electrodes 242a, 242b. Moreover, in a preferred embodiment of the present invention, in each pair of the corresponding first electrode set 240 and the second electrode set 250, the projections of the third salient points 255 on the first inner wall 211 align with the second salient points 246, and the projections of the fourth salient points 256 on the first inner wall 211 align with the first salient points 245.
When the second inverter 290b provides a driving voltage to the first electrodes 242a, 242b and the fourth electrode 254, in each pair of the corresponding first electrode set 240 and the second electrode set 250, a second discharge electric field E2 is generated between the first electrodes 242a, 242b and the fourth electrode 254, such that a second light-emitting area A2 is formed between the third salient points 255 and the first electrode 242a and between the fourth salient points 256 and the first electrode 242b.
When the second inverter 290b provides a driving voltage to the third electrodes 252a, 252b and the fourth electrode 254, in each pair of the corresponding first electrode set 240 and the second electrode set 250, a second discharge electric field E2 is generated between the third electrodes 252a, 252b and the fourth electrode 254, such that a second light-emitting area A2 is formed between the third salient points 255 and the fourth electrode 254 and between the fourth salient points 256 and the fourth electrode 254.
It is to be noted that those two methods for driving the flat fluorescent lamp described in the first embodiment can also be used to drive the flat fluorescent lamp 200a, 200b of the second embodiment and the third embodiment. Moreover, the advantages of the flat fluorescent lamp 200a, 200b of the second embodiment and the third embodiment are similar to the flat fluorescent lamp 200 of the first embodiment; please refer to the description in the first embodiment for the details.
In the flat fluorescent lamp 300, the projection of the first salient points 362 and the second salient points 364 on the first inner wall 312 are alternately arranged. A reflective layer 380 is disposed on the first inner wall 312 of the chamber 310, and the reflective layer 380 is overlaid by the fluorescent material 330. Further, the first salient points 362 are driven to discharge to the first electrodes 342 and second electrodes 344 opposite to the first salient points 362, such that the first light-emitting area A1 emits light. The second salient points 364 are driven to discharge to the third electrodes 352 and fourth electrodes 354 opposite to the second salient points 364, such that the second light-emitting area A2 emits light.
It is to be noted that those two methods for driving the flat fluorescent lamp described in the first embodiment can also be used to drive the flat fluorescent lamp 200, 200a of the fourth embodiment and the fifth embodiment. Moreover, the advantages of the flat fluorescent lamp 300, 300a of the fourth embodiment and the fifth embodiment are similar to the flat fluorescent lamp 200 of the first embodiment.
In summary, the flat fluorescent lamp and the methods for driving the same provided by the present invention at least have the following advantages:
1. Since the projections of the first light-emitting area and the second light-emitting area on the first inner wall are not overlaid or just partially overlaid, such that the first light-emitting area and the second light-emitting area emit light interleavedly and the light uniformity of the area light source is improved.
2. Since the light emitting positions of the fluorescent material are not the same, the lifespan of the flat fluorescent lamp is increased.
3. Comparing to the conventional technique, under the condition of the same luminance provided by the area light source, since the driving voltage of the flat fluorescent lamp in the present invention is lower, the problem of the flat fluorescent lamp being damaged due to the over high driving voltage is eliminated.
4. Since the flat fluorescent lamp of the present invention can provide an area light source with a better light uniformity, the diffusion film with a higher transparency can be used and in some cases it is not even needed, such that the influence of the diffusion film to the luminance of the area light source is decreased.
Although the invention has been described with reference to a particular embodiment thereof, it will be apparent to one of the ordinary skills in the art that modifications to the described embodiment may be made without departing from the spirit of the invention. Accordingly, the scope of the invention will be defined by the attached claims not by the above detailed description.
