JPS6011357B2 - How to apply a sustain pulse to an image display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for applying a sustain pulse to an image display device using an EL element, and is characterized by generating a timing pulse that widens the pulse width of the sustain pulse.

Generally, when an EL is used as a display element, a matrix type electrode arrangement as shown in FIG. 1 is adopted.

In Figure 1, 1 is a glass plate, 2 is a transparent electrode arranged in a lattice pattern, 3 is a dielectric material such as Y or the like, 4 is a light layer such as ZnS doped with Mn, etc., and 3' is the same as 3. The dielectric material 5 is a back electrode made of aluminum or the like and arranged perpendicular to the electrode 2. In an element with such a structure, the transparent electrode group 2
When an appropriate alternating current is applied to one of the electrodes and one of the back electrode group 5, only the portion where these electrodes intersect will emit light. This corresponds to one picture element on the screen. FIGS. 2a, b, and c show the relationship between the applied voltage and the luminance when a bipolar pulse is applied to one line element of a matrix type EL element.

Initially, when a sustain pulse of amplitude ±Vs is applied at timing L and t2 as shown in FIG. 2a, the luminance of light emission is Bs as shown in FIGS. 2b and c. Next, when a write pulse of amplitude Vw is applied at timing t3, light is instantaneously emitted at a brightness of Bw', and when a sustain pulse of amplitude Vs is applied at timing from t4 to t8, the light emission brightness becomes Bw. Next, t9-t, . When the erasing pulse of the amplitude value VE is applied at the timing of , the luminance becomes Bs again. There is a history characteristic between the luminance of light emission and the applied voltage as shown in FIG. 2b. When displaying a moving image using an EL panel having the above characteristics, various timing pulses (maintenance, erase, write, selection pulses, etc.) are generated based on the horizontal synchronization signal of the television.

A standard television signal has 262 .
Five scanning lines are included, and depending on the number of electrodes in the matrix pulse, a scanning line is taken out every other textbook, the video signal is sampled, and a write pulse modulated according to the level of the video signal is generated. Just apply it to the matrix panel. For example, in a matrix panel with 160 electrodes in the vertical scanning direction, if writing is performed in a cross-sequential and interlaced manner, in the first field, writing is performed on the 80 odd-numbered electrodes of the matrix panel, and in another field. It is sufficient to write to 80 even-numbered electrodes. Since the number of scanning lines containing video signals in one field is approximately 240, it is sufficient to extract one out of every three scanning lines.

The written signal is erased by an erase pulse before the next write pulse is applied. Now, for example, as shown in Figure 3,
Video signal sampling period (SPL) and write selection pulse application period (SEL) based on horizontal synchronization signal Hp
When the signals are generated, the negative voltage sustaining pulse P8M and the positive voltage sustaining pulse PsP are applied at time Ts.

Since the total time of the write selection pulse width Tw and Ts is three horizontal scanning periods (approximately 190 msec), if approximately 100 msec is taken as Tw, only 90 msec of Ts remains. Therefore, the sustain pulse width becomes narrower. If the sustain pulse width is narrow, the memory width will be reduced and the luminance of light emission after application of the write pulse will be reduced, which is undesirable. Note that the reason why the sustain pulses PsM and PsP are applied successively here is to reduce the unevenness in luminance caused by the transient characteristics of EL. Further, the reason why sustain pulses are applied every 29 times to the horizontal synchronizing signal HP is as follows.

It is well known that light emission brightness and memory vary greatly depending on the pulse width, pulse frequency, etc. applied to an EL element.

In other words, an EL element cannot be operated at high brightness and with a large memory width unless a sustaining pulse is applied with an appropriate period and an appropriate pulse width. In the above example, it takes 262.5 lines x 63.5 Sec = 16.7 to write one field of the standard television signal.
sec.

However, in this example, in order to operate with high brightness and a large memory width, it was necessary to apply a sustain pulse at least every 1.587 seconds, which is 29 times the horizontal synchronization signal HP. Corresponds to solids. In other words, it would be very convenient if high brightness and memory width could be achieved by applying one pair of sustain pulses to each field, but as mentioned above, even in the middle of writing one screen within one field, it would be very convenient to apply one pair of sustain pulses to each field. It may be necessary to apply sustain pulses to the entire screen (approximately 10 times in this example). At this time, a problem arises in that a sufficient sustain pulse width cannot be obtained. The present invention provides an effective solution to the above-mentioned problems, and aims to increase the memory width, luminance, etc. by widening the sustaining pulse width, thereby obtaining a good image.

One embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 4 is a timing chart showing one embodiment of the present invention.

In order to widen the sustain pulse, as shown in FIG. 4, the period for applying the sustain pulse is widened by one horizontal scanning period every two periods of the horizontal synchronizing signal HP.

In this way, the sustain pulse application period becomes Ts',
It increases by 63.5 seconds compared to Ts. When the sustain pulse width is widened, the memory width increases and the luminance becomes high, so that a good image can be obtained. SPL
By setting the period for applying the sustain pulse, the timing at which the signal is generated is set at a ratio of 1 horizontal scanning period to 4 horizontal scanning periods for one of the 8 vertical electrodes, but compared to the normal 3 horizontal scanning periods. There is not much difference compared to the ratio of one horizontal scanning period to the horizontal scanning period, and when we actually produced a prototype and displayed it, the image did not appear discontinuous. The timing pulse as shown in Fig. 4 is obtained by counting the horizontal synchronizing signal HP with a 25-decimal counter and using the output of the counter.
It is sufficient to extract timing signals such as SPL, SEL, PsM, and PsP. For example, the SPL signal is the 1st, 4th, 7th, 10th, 13th, 16th, 19th, 22nd, S
EL signals are 2, 5, 8, 11, 14, 17, 20, 23
It can be caused by phlegmon. PsM signal is counter 2
The PsP signal may be generated from the fourth output, and the PsP signal may be generated at the falling edge of the PsM signal. FIG. 5 shows a block diagram of the configuration of an image display device adopting the method of the present invention.

A composite video signal input from the input terminal 6 is separated into a video signal 8 and horizontal and vertical synchronizing signals 9 by a signal separation circuit 7. The video signal 8 is further extracted by a signal processing circuit 10 using sampling pulses sequentially in time, and after converting the analog signal into a digital signal, this is held for a certain period of time in a holding circuit 11, and then the horizontal drive circuit 12 outputs an EL signal. Applied to the horizontal electrodes of the panel, ~Hm. 13
1 is a clock pulse generation circuit, and the signal from this circuit is combined with horizontal and vertical synchronization signals 9 in 14 timing pulse generation circuits to generate timing control signals for each circuit.

15 is a selection pulse timing signal generation circuit, 16 is an erase pulse timing signal generation circuit, and the selection and erase pulses are synthesized in the matrix circuit 18 and applied to the vertical drive circuit 19.

17 is a sustain pulse timing signal generation circuit employing the method of the present invention, and an output signal is applied to the vertical drive circuit 19.

The vertical drive circuit output is the vertical electrode group V, ~Vn of the EL panel.
is applied to As described above, according to the present invention, since the sustaining pulse width is widened, the memory width is increased, the luminance is also increased, and a good image can be obtained.

[BRIEF DESCRIPTION OF THE DRAWINGS] Figures 1a and b are partially cutaway needle-view and cross-sectional views of an EL with a matrix structure, and Figures 2a, b, and c are waveforms applied to the EL and luminance of the EL. A diagram showing the relationship with the applied voltage and a diagram showing the luminance of EL, FIG. 3 is a timing chart when the sustain pulse width becomes narrower, FIG. 4 is a timing chart when the sustain pulse width is widened, and FIG. The figure is a configuration block diagram of an image display device adopting the method of the present invention. Figure 1 Figure 5 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. In an image display device using an EL element that has a history characteristic between applied voltage and luminance, a video signal is sampled for each of multiple horizontal synchronization signals, and write pulses based on the sampled video signal are line-sequentially generated. At the same time, when applying a sustain pulse in the middle of the line sequential writing, the horizontal synchronization period for the sampling is increased only at the time of application, and a period is set for widening the pulse width of the sustain pulse. A method for applying a sustain pulse to an image display device, characterized in that: