Electroluminescent display device having uniform display element column luminosity
First Claim
1. An EL display device comprising:
- an EL display panel having an electroluminescing layer interposed between a plurality of scan electrodes and a plurality of data electrodes, a plurality of EL elements being formed at locations where said scan electrodes and said data electrodes intersect;
first voltage applying means for sequentially applying a voltage pulse to said plurality of scan electrodes; and
second voltage applying means for selectively applying a display voltage to said plurality of data electrodes;
wherein said plurality of EL elements are for emitting light by application of said voltage pulse and said display voltage; and
said first voltage applying means is for applying said voltage pulse to said plurality of scan electrodes by charging said plurality of EL elements during a charging period and holding a charging voltage thereof for a holding period, for detecting a number of EL elements which are to emit light by application of said voltage pulse and said display voltage, and for varying said charging period in accordance with said number of detected EL elements;
said first voltage applying means is further for holding said charging voltage by causing said plurality of scan electrodes to go to high impedance.
1 Assignment
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Accused Products
Abstract
To eliminate uneven luminance between columns, and along with this, to eliminate uneven luminance also among EL elements in several columns in an EL display device for performing matrix display, in a matrix type EL display device in which a scan voltage is sequentially applied to scan electrodes and EL elements are caused to electroluminesce by this scan voltage and a data voltage, a pulse width of the scan voltage is kept uniform, and together with this, a charging period for the EL elements is varied in accordance with a number of light emitting pixels in a line scanned and driven to eliminate uneven luminance between columns. Additionally, a holding period for holding a charging voltage is provided to alleviate differences in terminal voltages among the EL elements due to wiring resistance delay and to eliminate uneven luminance among the EL elements.
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Citations
19 Claims
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1. An EL display device comprising:
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an EL display panel having an electroluminescing layer interposed between a plurality of scan electrodes and a plurality of data electrodes, a plurality of EL elements being formed at locations where said scan electrodes and said data electrodes intersect; first voltage applying means for sequentially applying a voltage pulse to said plurality of scan electrodes; and second voltage applying means for selectively applying a display voltage to said plurality of data electrodes; wherein said plurality of EL elements are for emitting light by application of said voltage pulse and said display voltage; and said first voltage applying means is for applying said voltage pulse to said plurality of scan electrodes by charging said plurality of EL elements during a charging period and holding a charging voltage thereof for a holding period, for detecting a number of EL elements which are to emit light by application of said voltage pulse and said display voltage, and for varying said charging period in accordance with said number of detected EL elements; said first voltage applying means is further for holding said charging voltage by causing said plurality of scan electrodes to go to high impedance. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 13, 16)
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9. An EL display device comprising:
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an EL display panel having an electroluminescing layer interposed between a plurality of scan electrodes and a plurality of data electrodes, a plurality of EL elements being formed at locations where said scan electrodes and said data electrodes intersect; first voltage applying means for sequentially applying a voltage pulse to said plurality of scan electrodes; and second voltage applying means for selectively applying a display voltage to said plurality of data electrodes; wherein said plurality of EL elements are for emitting light by application of said voltage pulse and said display voltage; and said first voltage applying means is for applying said voltage pulse to said plurality of scan electrodes by charging said plurality of EL elements during a charging period and holding a charging voltage thereof for a holding period, for detecting a number of EL elements which are to emit light by application of said voltage pulse and said display voltage, and for changing a charging charge quantity in a case where said charging is performed in accordance with said number of detected EL elements; said first voltage applying means is further for holding said charging voltage by causing said plurality of scan electrodes to go to high impedance. - View Dependent Claims (14, 17)
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10. An EL display device comprising:
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an EL display panel having an electroluminescing layer interposed between a plurality of scan electrodes and a plurality of data electrodes, a plurality of EL elements being formed where said scan electrodes and said data electrodes intersect; means for driving said scan electrodes to sequentially apply a scan voltage to said plurality of scan electrodes; and means for driving data electrodes to selectively apply a data voltage to said plurality of data electrodes; wherein said plurality of EL elements are for emitting light by application of said scan voltage and said data voltage; said scan electrode driving means is for applying a scan voltage of uniform pulse width to said plurality of scan electrodes by charging said plurality of EL elements during a charging period and holding a charging voltage thereof for a holding period, for detecting a number of EL elements which are to emit light by application of said scan voltage and said data voltage, and for varying said charging period in accordance with said number of detected EL elements; said scan electrode driving means is further for holding said charging voltage by causing said plurality of scan electrodes to go to high impedance. - View Dependent Claims (15, 18)
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11. An EL display device comprising:
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an EL display panel having an electroluminescing layer interposed between a plurality of scan electrodes and a plurality of data electrodes, a plurality of EL element being formed at locations where said scan electrodes and said data electrodes intersect; first voltage applying means for sequentially applying a voltage pulse to said plurality of scan electrodes; and second voltage applying means for selectively applying a display voltage to said plurality of data electrodes; said first voltage applying means includes a first switch for opening and closing a path between a constant voltage source and said scan electrodes, and a second switch for opening and closing a path between a voltage point differing from said constant voltage source and said scan electrodes, and said EL elements are actuated by connecting said constant voltage source and said scan electrodes during a period from operation of said first switch until operation of said second switch in a negative field operation of said first voltage applying means and during a period from operation of said second switch until operation of said first switch in a positive field operation of said first voltage applying means; and said first voltage applying means is for detecting a number of EL elements which are to emit light by application of said voltage pulse and said display voltage, and is for controlling an actuation timing of said first switch and said second switch in accordance with said number of detected EL elements. - View Dependent Claims (12)
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19. An EL device comprising:
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an EL display panel having an electroluminescing layer interposed between a plurality of scan electrodes and a plurality of data electrodes, a plurality of EL elements being formed at locations where said scan electrodes and said data electrodes intersect; first voltage applying means for sequentially applying a voltage pulse to said plurality of scan electrodes by inputting electric current; and second voltage applying means for selectively applying a display voltage to said plurality of data electrodes by inputting electric current; wherein said plurality of EL elements are for emitting light by application of said voltage pulse and said display voltage; and said first voltage applying means is for applying said voltage pulse to said plurality of scan electrodes by charging said plurality of EL elements during a charging period, and then stopping the electric current input to the plurality of scan electrodes and holding a charging voltage thereof for a holding period, for detecting a number of EL elements which are to emit light by application of said voltage pulse and said display voltage, and for varying said charging period in accordance with said number of detected EL elements.
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Specification