JPS634189B2 - - Google Patents

Description

Detailed Description of the Invention At present, an image display element is a display element that obtains an image by scanning an electron beam, and a large number of electrodes are arranged orthogonally on both the front and back surfaces, and the points where the electrodes on both sides intersect emit, transmit, or reflect light. There are display elements that obtain a desired image. Examples of the former include CRTs, and examples of the latter include electroluminescent panels (hereinafter abbreviated as ELP), plasma display panels (hereinafter abbreviated as PDP), liquid crystal panels, and others. The present invention uses these latter elements and also has a memory function.
This was done regarding ELP.

When multiplexed still images are sent from the sending side and you select the desired one,
When trying to obtain an image display device suitable for extracting only one desired image on the receiver side from a video signal that changes from moment to moment, displaying it stationary for a certain period of time, and then returning to the moving image again, the following message appears. In addition to the device, a storage device for storing at least one frame of the desired image is required, which makes the device very complicated and expensive. In this respect, according to the present invention, since the display element itself has a memory function, the above-mentioned external storage device is unnecessary, and the device has the advantage of being extremely simple and low-cost.

A specific example using ELP will be explained below.

First, the characteristics of ELP will be explained. As shown in FIG. 1, transparent electrodes 2 are arranged in stripes on a glass substrate 1. On top of this, a dielectric material 3 such as Y ₂ O ₃ , a fluorescent layer 4 such as Mn-doped ZnS, and a dielectric material 3' same as above are formed into a three-layer structure by vapor deposition. Electrodes 5 perpendicular to electrodes 2 are arranged in a striped pattern. With such a structure, one of the first electrode group 2 and the second
When a suitable alternating current voltage is applied to one of the electrode groups 5, only a small area sandwiched between the two electrodes will emit light, and this corresponds to one pixel on the screen.

FIG. 2 shows, as an example, the relationship between a voltage waveform a applied to a picture element and a light emission waveform b. Furthermore, the EL with the structure shown in Figure 1 has superior characteristics in terms of brightness, lifespan, and stability compared to conventional distributed EL elements, but the individual picture elements have new characteristics with regard to brightness and stability. During the applied voltage, a history phenomenon as shown in FIG. 3b is exhibited. To explain this characteristic according to Fig. 3, when a pulse of voltage amplitude V ₁ is first applied as shown in Fig. 3 a, the brightness will change as shown in Fig. 3 b and c.
It is at the level of B ₁ as shown. Here, V ₁ satisfies V ₁ >V _th , where V _th is the emission threshold voltage. When a write voltage V ₂ is applied to this, the brightness increases all at once to B ₃
After that, even if the voltage value is returned to the maintenance voltage _V1 again, the brightness settles to _B2 , which is higher than _B1 . When the erase voltage _V3 is applied to this, the brightness level decreases rapidly, and when it is returned to the sustaining voltage _V1 again, the brightness settles to _B1 . These temporal relationships are shown by making the symbols t ₁ , t _{3 .} . . , t ₂₁ attached to FIG. 3a correspond to the positions of the same symbols in FIG. 3c. As shown by the thin line in FIG. 3b, this overlapping phenomenon can take any small loop depending on the amplitude and pulse width (not shown) of the write voltage. That is, it is also possible to display halftones. A major feature of the ELP, which is not found in other display elements, is that once a write voltage is applied, each picture element continues to emit light without losing the gradation given to it by the sustain pulse. The above voltages vary depending on the composition, film thickness, and applied waveform, but in a prototype example, V _th = 200 V, V ₁ = 210 V, V ₂ = 210 to 280 V,
V ₃ =190V.

Matrix type with (m×n) electrodes
FIG. 4 shows a block diagram of the structure of the image display device of the present invention using ELP. That is, when displaying a moving image such as on a TV, a composite video signal is input from a signal input terminal 6 and is separated into a video signal 8 and a synchronization signal (horizontal, vertical) 9 by a separation circuit 7. Furthermore, video signal 8
The signal processing circuit 10 samples m points within one horizontal scanning period, and the holding circuit 11 holds the signal level. When all m points have been sampled, the write modulation voltage is simultaneously applied to the electrode groups H ₁ , H ₂ , ..., H _n through the gate circuit 16 and output drive circuit 17 according to the signal level that was being held. Supplied. Also, the vertical electrode group V _i (i=1, 2,...,
n) are sequentially selected by the gate circuit 18, and a voltage is supplied from the output drive circuit 19. These methods are well known as so-called line sequential methods. Further, these write signals, vertical electrode selection signals, and signals supplied from the erase pulse generating circuit 14 and the light emission sustaining pulse generating circuit 15 are all controlled by the timing control circuit 13 for both the horizontal and vertical electrodes. The timing control circuit 13 is composed of logic elements and receives the synchronization signal 9 and the clock of the clock pulse generator 12.

Hereinafter, the state in which a moving image is displayed is called dynamic mode (hereinafter abbreviated as DM), and the state in which only one image is displayed for a certain period of time, that is, a still image state, is called static mode (hereinafter abbreviated as SM). I'll decide. In order to further facilitate understanding, hereafter (3×
Assuming the matrix of 3) - one frame consists of 3 horizontal scanning periods (3H) and is sampled at 3 time points per each horizontal scanning period, the 5th
The system of the present invention will be explained with reference to the drawings. FIG. 5 shows DM; dynamic mode SM; static mode H; horizontal scanning period F; frame W; writing period S; light emission sustaining period E; and erasing period.

First of all, in DM, as mentioned above, it is a line sequential method, so
The signal level sampled at each point during each horizontal scanning period is held in a holding circuit, and may be held at the end of the horizontal scanning period or partially at the next horizontal scanning period, depending on the signal level at each sampling point. Each picture element is simultaneously written and emitted. As shown in Figure 2, if a pulse with the opposite polarity is applied after the write pulse, that picture element emits light, but if it is only fired once per horizontal scanning period as in the conventional method, the light emission will attenuate. . Generally, the time constant of this decay is much smaller than the frame period. In the method according to the present invention, after writing, emission sustaining pulses, that is, reverse polarity pulses are applied alternately, so that emission continues until the next pixel signal arrives. Of course, this light emission must be erased before writing the next frame signal of the same picture element. From the above explanation, it can be easily understood that the display device of this type exhibits high brightness because each picture element in both DM and SM emits light for most of the frame period. So this
Assume that the SM conversion command S1 is issued at an arbitrary point in the DM. (FIG. 5 S1) This command is immediately sent to the timing control circuit 1 from the terminal 20 as shown in FIG.
given to 3. This command may be given by the viewer switching a mode changeover switch while viewing the image, or by being set by hardware within the receiver. However, the actual mode switching from DM to SM is not performed from the moment the command is given, but from the beginning of the frame following the frame to which the command is given, as shown in FIG. When SM is reached, the write pulse and erase pulse are stopped and only the sustain pulse is supplied to the horizontal and vertical electrode groups. Therefore, from then on, the image of the frame immediately before the mode is switched will be displayed in a still state. When switching to DM again at a certain point in SM (represented by S2 in Fig. 5), a command is also given from the terminal 20 in Fig. 4, but the mode is switched from SM to DM immediately after the command is given. Instead of switching to DM from the beginning of the next frame. Once switched, the write pulse and erase pulse are again supplied to each electrode as described above, and a moving image of the sent video signal is displayed.

FIG. 6 also shows a time chart of voltage waveforms applied to each electrode and picture element as a specific example of the above-described method in a (3×3) matrix. Here, V _h1 , V _h2 , V _h3 , V _v1 , V _v2 , and V _v3 are the voltages applied to the electrodes H ₁ , H ₂ , H ₃ , V ₁ , V ₂ , and V ₃ respectively, and V _h1 and V _v1 The voltage waveforms applied to the picture elements 1, 1 and the corresponding light emission waveforms are also shown. In addition, A is a write signal whose pulse amplitude is changed according to each sampling signal, B is a light emission sustaining pulse, C is an erasing pulse, and D is a vertical electrode selection pulse. Furthermore, if the emission sustaining voltage V _S is selected to be a voltage slightly larger than the emission threshold voltage V _th in Figure 3b, and the erasing voltage V _E is selected to be a voltage slightly lower than V _th , the voltage pulse applied to each picture element in Figure 6 will be Of these, pulses with amplitude V _S /2 and amplitude V _E /
It can be considered that the second pulse and the pulse of amplitude V _W do not contribute to light emission or erasure. As shown in FIG. 6, even when switching from DM to SM, the light emission level is maintained by the maintenance pulse control.

In addition to FIG. 6, FIG. 7 shows an example of applied waveforms. Each signal in FIG. 7 is the same as in FIG. 6. Furthermore, the relationships among V _S , V _E , and V _th are the same as in FIG. 6. However, in the application method in this case, unlike in FIG. 6, the voltage applied to the picture element does not have the levels of V _S /2 and V _E /2.

Next, for comparison with the ELP of the present invention, an Illinois-type PDP, which is known as a PDP with a memory function, will be described. matrix type
FIG. 8 shows the relationship between the voltage waveform (solid line 21) applied to a minute area where orthogonal electrode groups intersect, that is, a picture element, and the light emission waveform in a PDP. A dotted line 22 indicates a wall voltage, which will be described later. A is a write pulse, B is a sustain pulse, and C is an erase pulse. Since the electrode group is covered with an insulator, when a voltage A with an amplitude of V ₁ that exceeds the discharge starting voltage is applied to the picture element, the picture element discharges, and the resulting charged particles are attracted to the inner wall surface. Generate wall voltage. Due to the effect of this wall voltage, even if the amplitude V _S is less than the discharge start voltage, discharge and light emission can be performed by simply adding a pulse train B of the opposite polarity. Discharge and light emission occur at the moment a reverse polarity pulse is applied, as shown in FIG. Furthermore, when a pulse V with an amplitude V ₂ smaller than the emission sustaining voltage is applied to this, the wall voltage disappears, and thereafter, even with the sustaining pulse L, no discharge or light emission occurs. As mentioned above, the Illinois type PDP can obtain a memory function by utilizing the history characteristics in which the discharge starting voltage and the discharge sustaining voltage are different. However, in this case, unlike the above-mentioned ELP, it is difficult to display multiple gradations based solely on the amplitude and pulse width of the write voltage. When looking at the time interval, the brightness is proportional to the number of light emissions performed during that time, that is, the number of sustain pulses once written. Therefore, one pixel is made up of multiple cells, and each cell is weighted by the number of times it emits light, and the gradation is obtained by combining them.Also, the number of times of light emission is increased/decreased in a time-division manner, and the gradation is created by combining them. Until now, time-sharing methods and the like have been proposed to obtain .

As explained in detail above, the present invention allows still images to be extracted and obtained from images on the sending side without an external storage device by operation on the receiver side. Furthermore, it can be used for determining cross-play, taking photographs, and if a reading function is added, it can also be used for copying. Further, even when used in still image broadcasting, as a computer terminal display device, or as a data transmission display device, the system of the present invention is useful in simplifying attached equipment and reducing line usage time, and the practical value of the system of the present invention is extremely large.

[Brief explanation of the drawing]

FIG. 1 shows an example of a display panel used in the present invention.
A is a partially cutaway perspective view, and b is a sectional view. Figures 2 and 3 are diagrams explaining the display panel, where Figure 2a is a voltage waveform diagram, b is a light emission waveform diagram, and Figure 3a
is a voltage waveform diagram, b is a characteristic curve diagram, and c is a light emission waveform diagram. FIG. 4 is a block circuit diagram of one embodiment of the present invention, and FIG. 5 is a time chart of the embodiment. FIG. 6 and FIG. 7 are time relationship diagrams explaining applied pulses, respectively. FIG. 8 is an explanatory diagram for explaining the operation of the PDP. 6: Input signal terminal, 7: Separation circuit, 8: Video signal, 9: Synchronization signal, 10: Signal processing circuit, 11:
Signal level holding circuit, 12: Clock pulse generator, 13: Timing control circuit, 14: Erasing pulse generation circuit, 15: Emission sustaining pulse generation circuit, 1
6, 18: gate circuit, 17, 19: output drive circuit.

Claims (1)

[Scope of Claims] 1. A light-emitting layer that emits EL light upon application of an AC pulse voltage is interposed between matrix electrodes consisting of first and second electrode groups arranged in parallel in directions crossing each other, and A light-emitting picture element is formed at the intersection of the electrodes, and the change in light emission brightness during the step-down process from the high voltage side is higher than the change in light-emission brightness during the step-up process of the pulse voltage applied via the matrix electrode. In an image display device equipped with a memory function based on historical characteristics maintained in a state, a moving image corresponding to a video signal is displayed by applying a sustain pulse whose emission brightness has a different voltage value during a step-up process and a step-down step. a first image display function to selectively apply a write pulse having a voltage value that causes high-intensity light emission during the boosting process to the matrix electrode in response to a synchronization signal, and then apply the sustain pulse based on the memory function. A second step of switching and displaying the moving image into a still image independent from the video signal by
a video display function, and displaying a moving image corresponding to the video signal by applying an erase pulse having a voltage value below a threshold of light emission to the light emitting pixels of the still image and then applying the sustain pulse. An image display device further comprising a switching means for switching from the second video display function to the first video display function.