JPS5918713B2 - electroluminescence display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention ιL generally relates to a display device, ie, a data storage device consisting of a matrix of electroluminescent cells.

More particularly, the present invention relates to a novel apparatus for selectively brightening particular cells in a matrix while minimizing the brightness of all unselected cells. A special phenomenon occurs when gas cells are used as electroluminescent sources. When an electric field of sufficient magnitude is applied to a gas electroluminescent cell, ionization of the gas (air discharge) occurs within the cell, resulting in a positive charge on the dielectric covering the cathode. Meanwhile, electrons accumulate on the dielectric covering the anode. Charges stored on the walls are trapped due to the capacitive coupling exerted by the cell walls and electrodes. Because positive ions accumulate on the walls of the cathode and electrons accumulate on the walls of the anode, the wall charge is opposite in polarity to the electric field that induced the gas discharge. Therefore, after discharge, the total voltage applied to the cell will be the algebraic sum of the voltage supplied to the cell plus the voltage due to the wall charge. The gas discharge that occurs within the cell continues until the wall charge reaches a point where the supplied voltage can no longer support ionization, at which point the cell is turned off. In order to ignite the cell again by using the same magnitude of supply voltage, it is necessary to change the polarity of the supply voltage. Since the wall charge is trapped within the cell, the wall charge is always opposite to the charge that initiated the gas discharge. The main problem with the use of gas cells in display matrices is the firing of non-selected cells due to the fact that voltage is supplied to one end of the non-selected cells. Prior art systems for using electroluminescent cells in an X-Y display matrix & ζ Raymond J. Rodgers (RaymOndJ.ROger
No. 3,343,128 entitled "Electroluminescent Panel Driver Circuit" by S).

The prior art system described above uses a device to provide inhibit pulses to unselected rows of the matrix.

As a result of this, a potential difference occurs at the intersection of the unselected row and the selected column, and this &ζ is not sufficient to fire the cell intervening at the particular intersection. The approach requires complex circuitry. Another form of control is the Half-Select mode, in which half of the required voltage is supplied to one end of the gas cell and the other half to the other end, whereby the selected effectively supplying full voltage to the cell.

This method also requires complex circuitry.

This is because each end of the cell must float to half the total voltage required to ignite the cell. Another prior art patent is William L. U.S. Patent No. 3,636,405 entitled "Split Electrode Gas Cell" by William L. Cotter.
No., where each cell of the matrix is provided with a segmented anode.

A supporting voltage is provided from one of the cathode and anode. Selective application of a positive pulse to one anode and a negative pulse to the other anode causes the cell to ignite.

The extra structure required within the cells increases the cost of each cell, thereby offsetting the benefits obtained with this method.

Another prior art device is the William E. Coleman (W.
illamE. No. 3,614,769 entitled "All-Select-Semi-Select Plasma Display Driver Circuit" by Coleman et al., the problem of firing non-selected cells is partially solved.

The device of this patent operates by alternately connecting selected rows to a firing voltage and a reference voltage, such as ground, while alternately connecting selected columns to a reference voltage and a firing voltage. The driving technique described above limits the firing of unselected cells, causing them to fire only twice during each cycle of scanning all columns. Even though this ignition occurs only twice during the cycle of scanning all columns, it can still be observed in a dark room, as if reducing the purity of the selected cell. The present invention completely solves this problem of visual detection of unselected cells. In one embodiment of the invention, a display device is provided in which a matrix is formed using crossed rows and columns of conductors and a plurality of electroluminescent cells connecting the rows and columns at their crossing points. provided.

Power & ζ provided to ignite the cell.

A first device is provided for periodically connecting the selected column with a power supply at a fixed frequency. Another device is provided for periodically connecting the selected row and all non-selected columns with the power supply at a fixed frequency, the frequencies being out of phase; The luminescence of unselected cells is minimized to a level that is undetectable to humans. In a second embodiment of the invention, the first device for cycling connects the selected column circuitry with a power supply at a fixed frequency;
Meanwhile, all unselected columns are connected to a reference potential, such as ground.

An additional device for cycling is to circuit the selected rows,
Connect to the power supply at a fixed frequency out of phase, while all Q unselected rows are connected to the power supply. The above sequence of connections to selected and unselected rows and columns of power supplies Q ensures that selected cells fire while unselected cells do not fire. SUMMARY OF THE INVENTION Accordingly, a first object of the present invention is to provide an improved display matrix in which only the electroluminescent cells selected by row and column selection are visibly lit. Another object of the invention is to provide an apparatus for selecting individual cells of a display matrix to emit light without causing any of the unselected cells to visibly emit light.

It is a further object of the present invention to provide an improved display device.

These objects and others of the invention will become more apparent when considered in conjunction with the following description and drawings, in which like numerals indicate like parts and are part of the invention.

FIG. 1 shows a gas discharge type electroluminescent cell that can be used in the present invention.

Cell 10 consists of two glass elements 11 and 12,
They are joined together to form chamber 13.

A gas 14, such as neon, is inserted into the chamber under pressure. Electrodes 15 and 16 are placed on either side of chamber 13.
Terminals A and B are connected to electrodes and supply a potential to the gas. When a potential of sufficient magnitude is applied to terminals A and B, a discharge occurs within gas 14. Electrons and ions created by the discharge attach to the anode and cathode sides of the glass element, respectively, and create wall charges. The wall charge voltage has the opposite polarity to the supply voltage that caused the discharge.
Once the wall charge reaches a certain level, the cell can no longer continue discharging and the cell turns off. Another discharge occurs due to the reversal of the supply voltage. This discharge occurs because the wall charge is directly applied to the reversely supplied voltage. For efficiency, the voltage level of the alternately applied signals can be reduced to such a low value that when applied to the wall charge, it causes a discharge. By continuously reversing the supplied voltage, the cell can be continuously illuminated (illuminated). By keeping the alternating frequency high enough, the cells appear to the human eye to be glowing continuously. Generally, the alternating frequency is kept substantially above about 60 cycles/second. In this embodiment of the device, the voltage supplied to the cell was approximately 250 volts, and the neon, nitrogen, and argon mixture was at a pressure of 200 mm Hg. For ease of manufacture and use, the cell of Figure 1 has been modified to include multiple electrodes, with a group of electrodes called row electrodes placed on one side of the cell. , the group of electrodes placed on the other side are called column electrodes.

FIG. 2 schematically shows a cross-sectional view of a ζ cell, in which one column is shown as being common to four rows.

Four rows are used merely as an example; more or fewer rows or columns can be used if desired.

Figures 3a and 3b & ζ Continuous 2 used in the present invention
Figure 1 shows two phase clock signals.

The signal shown corresponds to only one time slot T1 and is the same for all remaining time slots. The +V potential is large enough to cause the cell to emit light if the wall charge is not reversed. One phase of the clock signal is called φ1 and the out-of-phase signal is called φ2. Instead of a digital clock, an analog quadrature signal can be used. First scheme (Scheme) to block visible light emission of unselected cells
The first scheme will be easier to understand if FIG. 2 is considered in conjunction with the waveforms of FIGS. 4A-4E to explain.

In FIG. 4A, the voltages applied to column 1 during one scan cycle are shown. The above cycle is T1-T8
It consists of eight time slots designated as
Each time slot is usually assigned to a particular column, so the arrangement of FIG. 4 is used for a total of eight columns, although only one is shown for simplicity. This technique is applicable to any number of columns or rows. Therefore T
1 is assigned to column 1, T2 is assigned to column 2, and so on. When column 1 is selected in its corresponding time slot, a clocked signal φ1 is applied to the column conductor.
At all other unselected times, the voltage on the column conductor is φ2. Whenever any zero row is selected, a clocked signal φ2 is applied to the row conductor. Otherwise, the voltage remains positive. There are four possible states for selecting and deselecting rows.

Each state is explained in the following cases. Case 1. Row 1
is never selected. Since row 1 is never selected, the voltage applied to row 1 is +V.

The first pulse φ1 or φ- on the column side fires the unfired cell once, depositing a positive charge on the column side and a negative charge on the row 1 side of the cell inner wall. The polarity of these wall charges is such that it is opposite to the electric field applied during the time that pulses φ1 and φ2 are applied to the column side, so that the cell never fires again. case. row 2
If this column is not selected at the Q selection time (T1), but is selected at some other times (eg T4 and T7). In this case, the cell fires once on the first pulse φ1 or φ2 on the column side when row 2 is at +V.

The wall charge created by this firing is always in opposition to the electric field applied to the cell, except when row 2 is selected. When row 2 is selected in some other column, the voltage applied on both sides of this cell is in phase with the wall charge and the wall charge is not destroyed. This cell therefore remains charged and prevents further Q firing during the remaining period. case. Row 3 is selected during the selection time (T1) of this column and never selected during the times of other columns.

In this case, the selected cell starts firing with the first pulse φ1 or φ2 occurring during the selection time (T1) and fires alternately. After completion of the selection time, the cell 11ζ is left with a positive charge on the row side and a negative charge on the column side of its inner wall.

The first pulse φ2 on the column side after the selected time
This causes the cell to ignite, which reverses the polarity of the charge on the inner wall of the cell.
Prevents the cell from firing any further at times other than the selected time. However, because of the polarity of this charge, the cell skips firing on the first φ1 pulse at the next selected time. The total number of times the selected cell fires therefore remains unchanged. case. Row 4 is the selection time of this column (
T1) are selected during some or all other column times (e.g. T3-T5 and T7).

As in the case, the cells fire alternately during the selected time.

The last φ2 pulse at the selected time leaves a positive charge on the row side of the cell inner wall. If this row is selected by all other columns, the polarity of this charge will not be broken and the cell will fire in the opposite direction with the first φ1 pulse at the selected time. However, if this row is not selected in any one column, the cell will be
fires once, but skips firing at the next selected time. Therefore, the total number of times a selected cell fires remains unchanged. From these four cases, we can see that, regardless of the data type, i.e. the mode of row selection, unselected cells fire only once during the data display time; while selected cells fire only once; It is clear that they are the same.

In some applications of the first approach using MOS devices, there will be significant delays in the signals passing through the different MOS paths.

When these signals are used late to control the switches, they can cause undesirable overlap in the switch off-on times. When using the first method, non-selected cells are visibly fired due to undesirable overlap. Therefore, the second
The scheme is described in conjunction with the waveforms of FIGS. 5A-5E.
The only difference between this second method and the first method is the column voltage. During selected times the voltage is still pulsed φ1, but at all other times the voltage is at 0 or ground. Let us again explain four cases corresponding to the states of the row signals. Case 1. If row 1 is never selected.

When a row is not selected, ie, there is no data on the row line, the voltage is +V.

The first pulse φ1 on the column side fires the unfired (uncharged) cell and deposits a positive charge on the column side and a negative charge on the row side of the cell inner wall. The electric field created by this charge! Electric field applied at other times and 11
? It has become active, so this cell will never fire again. case. Although row 2 is not selected during column 10 selection time (T1), other column times (e.g. T4 and T
7) if selected.

In this case, the cell fires only once when pulse φ1 is applied to column 1.

The electric field created by this wall charge is opposite to the applied electric field except when pulse φ2 is applied to the row side. Note that when pulse φ2 is applied to the row side, either there is no applied electric field, or the applied electric field is opposite to the wall charge electric field. The cell cannot fire in the absence of an applied electric field unless the voltage due to the wall charge exceeds the firing voltage (X,) so the cell remains charged and cannot fire any further during the remaining time. to prevent case. If row 3 is chosen during the selection time in column 1, but never in other columns.

During the selection time in column 1, the cells fire alternately, and after the selection time,
The cell fires once again when column 1 is installed.

As a result, the inner walls of the cell remain attached with a wall charge that opposes the applied electric field for the remainder of the cycle, thus preventing the cell from firing any further.
However, due to the polarity of the wall charge, the cell will fire on the first φ1 pulse on the column side at its beginning in the next cycle.
It skips once and then fires alternately. Therefore, the total number of times a cell fires remains unchanged. case. row 4 is column 1
are selected during the selection time of , and are selected during the selection time of some other columns as well.

As in the previous case, the first ground pulse after the chosen time deposits a negative charge on the row side and a positive charge on the column side of the cell inner walls.

When this row is also selected in some other column, the electric field due to the wall charges never adds to the applied electric field and the cell never fires during the remainder of the scan cycle. As in the previous case, the cell skips firing once at the chosen time, and the number of times the chosen cell fires remains unchanged. Again from above, regardless of the type of data on the row side, i.e. the row selection mode, unselected cells fire only once during the entire cycle of displaying data, whereas all selected cells fire only once during the entire cycle of displaying data. It is clear that the cells fire the same number of times each cell.

Therefore, the brightness of all selected cells is similar throughout the matrix. Now, if we look at Figure 6, we see that the 4th
A first embodiment of the first type of switching technique shown in Figures A-4E is shown.

Matrix 20 includes a plurality of row conductors 22 that intersect with a plurality of column conductors 21, with an electroluminescent cell connecting each of the intersecting rows and columns at their junction points. Switch 26 in the first row! ζ Each row has a common point (
(earth) and the positive terminal of the power supply 24.

The other terminals of the power supply 24 are connected to a common point. Two-phase signal generator 29Gζ Two signals φ whose phases are separated by 90
1 and φ2.

Other phase relationships may be used as long as overlapping conditions are avoided. Row selector 28 sends a signal φ2 to the corresponding one of row select switches 27a, 27b, 27c and 27d in column 26. The selected switch switches at the frequency of signal φ2, thereby connecting the selected rows alternately to the +V source and to the common point. Switches that are not selected remain in the +V position. ” The second row switch 23 includes row selection switches 25a, 25b, 25c and 2
5d, these switches connect each column to the common point +
It serves to connect alternately with the V source.

Column selector 30 has two-phase clock generator 2 as input.
9 receives the φ1 and φ2 signals.

When a column is selected, the φ1 signal is supplied to the switch connected to the selected column, while all selected
is supplied with the φ2 signal. The selected column (in this case, the column handled by switch 25d) is supplied with the waveform shown in FIG. 4A, while the selected row is supplied with the waveform shown in FIG. 4D. Supplied. FIG. 7 shows a first embodiment of the second scheme in which the column selector 31 has its output conductor attached to the corresponding switch line designated A, B, C or D. This replaces the column selector 30 in FIG.

Column selector 31 receives signal φ1 and supplies this signal to any selected column. All unselected columns are held in a common or ground position. The switches in the first and second rows are shown as having mechanical arms.

It will be apparent to those skilled in the art that electronic switches can be used to achieve faster processing speeds. Turning now to FIG. 8, a second embodiment of the first scheme is shown, in which the matrix 20 is shown to consist of seven row conductors 22 and eight column conductors 21. .
One end of each column and row conductor &ζ impedance device 32
is connected to the positive terminal +V of the two-terminal supply source 24. Electroluminescent cells 10 interconnect the column and row conductors at each crossover point. A first column 40 of driver switches 43 serves to connect the selected row to the negative terminal of source 24.

Each switch 43 in column 40 is an NPN transistor whose collector is connected to the opposite end of the row conductor from the end connected to the impedance device and whose emitter is connected to the negative terminal of source 24. and its base is connected to one of the outputs of the binary to seven row decoder 44. In operation, a positive signal at the base of transistor 43 turns it on and connects the selected row in the circuit with source 24. The same column 41 of driver switches is also provided for column selection.

For row selection, input data is provided by buffer circuit 46 to data timing control block 45.

The input data can come from a card reader or a manual key selector, for example. Data timing control circuit 45 and column selector 49 are adapted to receive the same control signals from binary counter 50 and load the desired data into the selected column. Binary counter 50 receives signal φ1 from binary phase generator 29 as its input.

The output of the counter is a repetitive signal that is synchronized to signal φ1. The repeating signal sequence selector causes all the sequences to be sequentially and periodically scanned at a frequency lower than the frequency of the biphasic signal, but greater than the frequency visible to the human eye. When a particular column is selected, the AND circuit 48 outputs the signal φ1
to the selected column driver and signal φ2 to all unselected column drivers. In a similar way, the binary to 7 line decoder! The ζ signal φ2 is applied to the selected row driver while keeping all other driver switches in the off position. The second embodiment of FIG. 8 does not supply the φ2 signal to the AND circuit 48, so that the unselected column drivers remain on and the selected column drivers receive the second phase signal φ1. It can be modified for the second method by making it receive.

While what are considered to be preferred embodiments of the invention have been shown, these are by way of example only and are not intended to be limiting in any way.

The scope of the invention is limited only by the following claims.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a plasma cell that can be used in the present invention. FIG. 2 is a schematic representation of a plurality of cells connected in a common column. FIGS. 3A and 3B are clocked signals selectively provided to a plurality of cells shown in FIG. 2. Figures 4A-4E illustrate the correct provision of clock signals according to the first method of operation. 5th A~5
Figure E shows the correct provision of the clock signal according to the second method of operation. FIG. 6 depicts one embodiment of the invention in block diagram form. FIG. 7 shows sub-blocks that can be replaced with sub-blocks in the block diagram of FIG. FIG. 8 shows another embodiment of the invention in block diagram form. 10...electroluminescence cell, 11,12...glass element,
14...gas, 15,16...electrode,
20...Matrix, 21...Column conductor, 22...Row conductor, 23...Second column switch, 24...Power supply , 26... First column switch, 28... Row selector, 29...
...Two-phase clock generator, 30, 31...
・Column selector, 40...First column of driver switch, 41...8th column driver, 44...
Row decoder, 45...Data timing control circuit, 46...Buffer circuit, 48...
・AND circuit, 49... Column selector, 50...
...Binary counter.

Claims (1)

[Scope of Claims] 1. A plurality of row conductors, a plurality of column conductors forming a matrix together with the plurality of row conductors, and a plurality of electroluminescent conductors connecting each row and each column at their intersection points. a cell having an insulating jacket containing an ionizable medium and at least one pair of insulated electrodes, wherein a voltage level corresponding to an ionization voltage of the medium is applied between the pair of electrodes; the at least one pair of insulated electrodes positioned to ionize the medium, the ionization of the medium resulting in a wall charge on an inner wall surface of the insulating jacket; a luminescent cell, a power supply whose voltage level is sufficient to initially induce luminescence within the cell, and a selected column connected in a circuit to said power supply periodically, at a constant frequency; luminescence of the unselected cells, periodically connecting the selected row and all unselected columns to the power supply at said constant frequency out of phase; An electroluminescent display device having a device for minimizing. 2. a plurality of row conductors, a plurality of column conductors forming a matrix with said plurality of row conductors, and a plurality of electroluminescent cells connecting each row and each column at their intersection points, the ionization an envelope containing a capable medium, and at least one pair of insulated electrodes configured to ionize the medium when a voltage level corresponding to an ionizing voltage of the medium is applied between the pair of electrodes; said plurality of electroluminescent cells having said at least one pair of insulated electrodes disposed therein, wherein said ionization of said medium causes a wall charge to be deposited on an inner wall surface of said insulating jacket; A power supply whose voltage level is initially sufficient to cause luminescence in the cell is connected periodically, at a constant frequency, to form a circuit with the selected column to said power supply, while all selected a device that connects the unselected columns to a reference potential, and periodically connects the selected rows to the power source with said constant frequency shifted in phase, while all unselected rows an electroluminescent display device, comprising: a device for connecting a row to said power supply and minimizing luminescence of unselected cells;