JP2003066895A - Plasma display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma display device which can realize long service life and small power consumption by making it possible to drive the device with a low source voltage nearly as high as a discharge maintaining voltage. SOLUTION: The plasma address type liquid crystal display device selects liquid crystal cells by rows through plasma discharging has an inductor L connected between an output terminal O of each row of a plasma driving circuit 12 and a discharge electrode 25 and when the plasma driving circuit 12 outputs a select pulse, a resonance circuit is formed of a capacity component between the inductor L and discharge electrode 25; and a voltage which is nearly twice as high as a source voltage Vcc is momentarily applied as a discharge start voltage between an anode electrode A and a cathode electrode K of the discharge electrode 25 by initial undershooting by its resonance and then the source voltage Vcc is applied thereafter as a discharge maintaining voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma display device in which display cells including discharge channels are arranged in a matrix and each of the display cells is addressed by plasma discharge.

[0002]

2. Description of the Related Art A plasma display device has a display layer and a plasma layer which are integrated with each other, and each of the display cells arranged in a matrix is driven by plasma discharge while addressing the display. There is a system in which a display layer and a plasma layer are separately provided, and addressing is performed by plasma discharge on the plasma layer side, while display driving is performed on the display layer side. The former method is PDP (Plasma Di
It is called a splay panel). The latter method is, for example, a PALC (Plasm) using a liquid crystal cell as a display cell.
There is a plasma-addressed liquid crystal display device called "a Addressed Liquid Crystal".

This plasma addressed liquid crystal display device (P
ALC) has a plasma discharge characteristic that is higher than a voltage (hereinafter, referred to as “discharge maintaining voltage”) for maintaining a discharge state (hereinafter, referred to as “discharge starting voltage”).
It is necessary to start the discharge at. In other words, once the discharge is started by the application of the discharge start voltage, the discharge state can be maintained without continuously applying the discharge start voltage. Therefore, it is only necessary to apply the discharge sustaining voltage lower than the discharge start voltage. .

Further, the discharge sustaining voltage is almost constant over time, whereas the discharge starting voltage is the surface of electrodes (cathode electrode and anode electrode provided in the discharge channel) for performing plasma discharge. Depending on the condition, it tends to increase with time. So considering this,
The discharge starting voltage needs to be set to a higher voltage with a further allowance.

On the other hand, the cathode electrode is sputtered by the discharge, and the electrode material becomes ions and adheres to the glass surface between the display cell (liquid crystal cell), which lowers the transmittance of the glass and leads to deterioration in brightness. It is a factor that determines the life of the plasma addressed liquid crystal display device. The larger the discharge current, the more intense this spatter. Therefore, it is important to make the discharge current as small as possible in order to extend the life of the plasma addressed liquid crystal display device.

[0006]

However, as described above, in order to generate stable discharge including changes over time, it is necessary to drive at a high voltage start voltage, and as a result, it is necessary to drive more than necessary. Since driving is performed by supplying a discharge current, the life of the plasma addressed liquid crystal display device is shortened.

Further, applying a high voltage over the entire on period (all selection period) of the selected line (selected row) may lead to arc discharge which causes a defect in the display of the plasma addressed liquid crystal display device. Get higher Therefore, in consideration of the balance with stable discharge, the margin of setting the discharge voltage is small, and it is difficult to set the margin at present. In addition, higher voltage than required,
Driving with a large current also results in unnecessary power consumption.

The present invention has been made in view of the above problems, and an object of the present invention is to extend the life and reduce the power consumption by making it possible to drive the power supply voltage as low as the discharge sustaining voltage. It is to provide a plasma display device that enables the above.

[0009]

In a plasma display device according to the present invention, a power supply voltage is applied to a display unit in which display cells including discharge channels are arranged in a matrix and a discharge electrode formed in the discharge channels. Drive means for scanning while sequentially applying a selection pulse having a peak value of the voltage value of, and a discharge start voltage of a voltage value larger than that based on the power supply voltage at the start of driving of each row in synchronization with the scanning by the drive means. And a discharge starting voltage generating means for generating and applying to the discharge electrode.

In the plasma display device having the above structure, the driving means selectively drives each discharge channel by sequentially applying the selection pulse having the peak value of the power supply voltage to the discharge electrodes. At the start of driving (at the start of discharging), the discharge starting voltage generating means generates a discharge starting voltage having a voltage value higher than that based on the power supply voltage and applies it to the discharge electrode. As a result, the discharge is started by the discharge start voltage having a voltage value higher than the power supply voltage, and then the power supply voltage is applied as the discharge sustaining voltage to maintain the discharge state.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing the overall configuration of a plasma addressed liquid crystal display device according to an embodiment of the present invention.

As is apparent from FIG. 1, the plasma addressed liquid crystal display device according to this embodiment has a PALC display unit 11, a plasma driving circuit (scanning circuit) 12, an inductor circuit 13, and liquid crystal driving circuits 14A and 14B. It is composed. The PALC display unit 11 includes a liquid crystal layer in which pixels using, for example, liquid crystal cells as display cells are arranged in a matrix, and a plasma layer that selects each pixel of the liquid crystal layer in a row unit by plasma discharge. It has a structure.

An example of a specific structure of the PALC display section 11 is shown in a sectional view in FIG. As shown in the figure, the PALC display unit 11 according to this example includes a liquid crystal layer 21 that is a display layer,
Plasma layer 22 and intermediate sheet layer 23 interposed therebetween
It has a flat panel structure consisting of The intermediate sheet layer 23 is made of, for example, an extremely thin plate glass having a thickness of about 50 μm, and is called a microsheet.

The plasma layer 22 has a lower glass substrate (transparent insulating substrate) 24 which is arranged with a predetermined gap with respect to the intermediate sheet layer 23, and between the intermediate sheet layer 23 and the glass substrate 24. A dischargeable gas is enclosed in the void. On the inner surface of the lower glass substrate 24, a plasma discharge electrode (hereinafter, simply referred to as “discharge electrode”) 25 including an anode electrode A and a cathode electrode K is formed in a stripe shape. The discharge electrode 25 is formed on the flat glass substrate 24 by a known screen printing method or the like. Therefore, the productivity and workability in forming the discharge electrode 25 are excellent.

Further, between the lower glass substrate 24 and the intermediate sheet layer 23, in the case of this example, between the central portion of each of the anode electrodes A and the intermediate sheet layer 23, the cathode electrode K is formed.
The partition walls 26 are formed so as to partition each one. The partition wall 26 defines a discharge channel 27 by dividing a space in which a dischargeable gas is enclosed. Partition 2
6 is also formed by a screen printing method, for example. The top of the partition wall 26 is in contact with one surface of the intermediate sheet layer 23.

In the discharge channel 27 surrounded by the pair of adjacent barrier ribs 26, the anode electrode A
By applying a predetermined voltage from the outside between the cathode electrode K and the cathode electrode K, a discharge is generated between the anode electrode A and the cathode electrode K. The intermediate sheet layer 23 and the lower glass substrate 24 are bonded to each other by a glass frit or the like.

On the other hand, the liquid crystal layer 21 is formed by using a transparent upper glass substrate (transparent insulating substrate) 28. The glass substrate 28 is bonded to the other surface side of the intermediate sheet layer 23 with a predetermined gap and a sealing material 29 or the like. Then, the intermediate sheet layer 23 and the upper glass substrate 2
A liquid crystal 30 as an electro-optical substance is sealed in a gap between the liquid crystal 8 and the liquid crystal display device 8.

A signal electrode Y is formed on the inner surface of the upper glass substrate 28 so as to be orthogonal to the discharge channel 27. That is, the discharge channels 27 are formed in rows,
The signal electrodes Y are wired in rows. Then, liquid crystal cells are formed in a matrix at the intersections of the signal electrodes Y and the discharge channels 27 as pixels. A color filter 31 is further provided on the inner surface of the upper glass substrate 28. In this color filter 31, for example, three primary colors of R (red), G (green), and B (blue) are assigned to each pixel.

The flat panel having the above structure is a transmissive type, and for example, the plasma layer 22 is on the incident side, and the liquid crystal layer 2 is provided.
1 is the emission side. Further, a backlight 32 is arranged on the plasma layer 22 side, specifically, on the outer side of the lower glass substrate 24.

Next, the operating principle of the PALC display unit 11 will be described with reference to FIG. Note that FIG. 3 schematically shows two pixels P, and in order to facilitate understanding,
Only the signal electrodes Y1 and Y2 and one cathode electrode K and one anode electrode A are shown.

Each pixel P has two signal electrodes Y1 and Y.
2, a liquid crystal 30, an intermediate sheet layer 23, and a discharge channel (in FIG. 3, a switch symbol S is used for the reason to be described later) are laminated. Since the discharge channel 27 has conductivity during plasma discharge, it is substantially at the anode potential. In this state, the signal electrode Y
When an image signal is applied to each of 1 and Y2, charges are injected into the liquid crystal 30 and the intermediate sheet layer 23.

When the plasma discharge is completed, the discharge channel 27 returns to the insulating state and becomes a floating potential, and the injected charges are held in each pixel P. In other words, a so-called sample hold operation is performed. That is, the discharge channel 2
Reference numeral 7 functions as a sampling switch provided in each pixel P. Therefore, in FIG.
7 is schematically shown by using a switch symbol S.
On the other hand, the liquid crystal 30 and the intermediate sheet layer 23 held between the signal electrodes Y1 and Y2 and the discharge channel 27 (S) are
Functions as a sampling capacitor.

When the sampling switch S is turned on, the image data is written in the sampling capacitor, and each pixel P is turned on or off according to the signal voltage level. Even after the sampling switch S is turned off, the signal voltage is held in the sampling capacitor, and the active matrix operation of the PALC display unit 11 is performed. The effective voltage actually applied to the liquid crystal 30 is determined by capacity division with the intermediate sheet layer 23.

Referring again to FIG. 1, the plasma drive circuit 12
Is applied to the above-mentioned discharge electrode 25 formed in the discharge channel 27 of the plasma layer 22 while sequentially applying a selection pulse having a peak value of the voltage value of the power supply voltage Vcc (line-sequential scanning). It has a function of discharging the discharge channels 27 row by row. In order to realize this function, the output end of each row of the plasma drive circuit 12 is connected to the discharge electrode 25 of each row of the plasma layer 22 in the PALC display unit 11 via the inductor circuit 13.

FIG. 4 shows an equivalent circuit for one discharge line (one row) of the plasma drive system. In FIG. 4, the plasma drive circuit 12 has a configuration in which the high potential side and the low potential side of the DC power source E are selected by the switches SW1 and SW2.
Further, the inductor circuit 13 is configured to have an inductor L connected between the output end O of each row of the plasma drive circuit 12 and the discharge electrode 25 (for example, the cathode electrode K). In FIG. 4, the resistance R indicates the resistance of the wiring and the switches SW1 and SW2.

In this plasma drive system, the switch S
W1 and the switch SW2 are designed to perform the opposite operations with respect to the on / off operation. That is, when the switch SW1 is on (closed), the switch SW2 is off (open), and when the switch SW1 is off, the switch SW2 is on. When the high potential side is selected by turning on the switch SW1, the same high potential is applied to both the cathode electrode K and the anode electrode A of the discharge electrode 25, and the potentials are the same, so that the cathode electrode K and the anode electrode A are the same.
No discharge occurs between and.

On the other hand, when the low potential side is selected by turning on the switch SW2, the power supply voltage (selection pulse) passes through the inductor L and the cathode electrode K- of the discharge electrode 25.
Since the voltage is applied between the anode electrodes A, discharge occurs between the cathode electrode K and the anode electrode A. By this discharge, the discharge channel 27 of that line has conductivity and functions as the sampling switch S described above, so that the pixels for that one line are selected.

In this selected state, the signal to be displayed from the liquid crystal drive circuit 14A / 14B corresponding to that line is the signal electrode Y of the liquid crystal layer 21 in the PALC display section 11.
(See FIG. 2), the PALC display unit 1
The image is displayed at 1. In this example, the liquid crystal drive circuits 14A, 1 are provided on the upper and lower sides of the PALC display unit 11.
Although the configuration in which 4B is arranged is taken as an example, the liquid crystal drive circuit does not necessarily have to be arranged on both upper and lower sides, and the PALC display unit 1
It is also possible to dispose only on one of the upper and lower sides of 1.

Next, the operation of the inductor L in the inductor circuit 13 will be described. Here, as an example, a 42-inch liquid crystal panel has an XGA (extende
Taking the case of the d graphics array) display standard as an example, the capacitance component between the discharge electrodes 25, that is, between the anode electrode A and the cathode electrode K is about 100 [pF].
When this discharge electrode 25 is driven through the inductor L of about 1 [mH], resonance of about 2 [μs] cycle occurs.

That is, when the selection pulse is applied from the plasma drive circuit 12 to the inductor L, the inductor L forms a resonance circuit with the capacitance component between the discharge electrodes 25. Naturally, the resonance frequency changes depending on the capacitance between the discharge electrodes 25 and the inductance of the inductor L due to the panel structure. In the state where the voltage applied to the inductor L is low and there is no discharge between the discharge electrode poles 25, this resonance continues and is superimposed on the drive waveform. The drive waveform in this case is shown in FIG.
It shows in (A).

On the other hand, the voltage value of the power supply voltage Vcc is set to a value that can maintain the discharge state (discharge maintaining voltage), and a selection pulse for setting the voltage value of the power supply voltage Vcc as a peak value is applied to the inductor L. Then, due to the first undershoot due to resonance, theoretically a voltage close to twice the voltage value of the power supply voltage Vcc is generated. The drive waveform in this case is shown in FIG. Then, when this high voltage is applied between the discharge electrodes 25, discharge occurs between the discharge electrodes 25.

When the discharge starts, the capacitance component between the discharge electrodes 25 changes to a resistance component by being brought into conduction by the discharge, and the impedance between the discharge electrodes 25 sharply decreases, so that the resonance is immediately attenuated. As a result,
As shown in (B), the voltage applied between the discharge electrodes 25 quickly converges to the discharge sustaining voltage, that is, the power supply voltage.

As described above, by connecting the inductor L between the output terminal O of each row of the plasma drive circuit 12 and the discharge electrode 25, when the selection pulse is output from the plasma drive circuit 12, the inductor L is connected. And discharge electrode 25
A resonance circuit is formed by the capacitance component between the discharge electrode 25 and the first undershoot due to the resonance.
Power supply voltage Vcc between the anode electrode A and the cathode electrode K of
Since a voltage nearly twice as high as the discharge start voltage is instantaneously applied, even if the power supply voltage Vcc is a voltage as low as the discharge sustaining voltage, the discharge can be reliably generated.

In other words, it is possible to generate a voltage higher than the power supply voltage Vcc by the action of resonance and apply the generated high voltage as a discharge start voltage between the discharge electrodes 25. Therefore, as the power supply voltage Vcc, Even if the voltage is set as low as the sustaining voltage, it is possible to apply a sufficient voltage required for starting the discharge between the discharge electrodes 25. Further, since it is possible to generate a voltage having a sufficient margin even with respect to the change of the discharge starting voltage with time, it is easy to set the voltage at the time of manufacturing.

Further, in the case of the resonance circuit formed by the inductor L and the capacitance component between the discharge electrodes 25, when the discharge starts, the impedance between the discharge electrodes 25 sharply decreases,
Since the resonance is immediately attenuated and the voltage applied between the discharge electrodes 25 quickly converges to the power supply voltage Vcc, the high voltage is applied between the discharge electrodes 25 only at the moment when the discharge starts, and the discharge current Can be suppressed to a necessary minimum level. As a result, the deterioration of the transmittance due to the sputtering of the cathode electrode K during discharge can be suppressed, and the life of the device can be extended. At the same time, the power consumption can be suppressed to the necessary minimum and wasteful consumption of the power can be suppressed, so that the power consumption of the device can be reduced.

Further, as is clear from the drive waveform shown in FIG. 5 (A), before the discharge starts, an overshoot also occurs at the rise of the drive waveform at the end of the drive. On the other hand, after the discharge, the state in which the capacitance component between the discharge electrodes 25 is changed to the resistance component continues, and the impedance between the discharge electrodes 25 is low. Therefore, as shown in the drive waveform of FIG. The overshoot does not occur when the drive waveform rises at the end of drive. Therefore, it does not adversely affect the data writing operation to the liquid crystal cell.

In this embodiment, at the start of driving each row in synchronization with the scanning by the plasma drive circuit 12, a discharge start voltage having a voltage value higher than that is generated based on the power supply voltage Vcc and applied to the discharge electrode 25. As a means to do so, the case where the resonance circuit formed by the inductor L and the capacitance component between the discharge electrodes 25 is used has been described as an example, but the means is not limited to this, and the power supply voltage Vcc is not limited to the booster circuit. Any structure may be used as long as it can generate a discharge starting voltage having a voltage value higher than that.

Next, the overall operation of the plasma addressed liquid crystal display device having the above structure will be described with reference to the timing chart of FIG.

In FIG. 1, the plasma driving circuit 12 is
By sequentially outputting the selection pulse (scanning pulse) from the output end of each row, the discharge channel 27 (see FIG. 2) in which plasma discharge is performed is line-sequentially selected and scanned. At this time, since the inductor circuit 13 is inserted between the plasma drive circuit 12 and the PALC display unit 11, the action of the above-described inductor L causes the selection pulse of each selection pulse to be clearly understood from the timing chart of FIG. At the time of falling (at the start of driving), a discharge starting voltage having a voltage value higher than the discharge sustaining voltage which is the power supply voltage Vcc is generated.

By applying this discharge starting voltage between the discharge electrodes 25 in the discharge channel 27, plasma discharge is generated in the discharge channel 27. Then, the inside of the discharge channel 27 is almost uniformly at the potential of the anode electrode A, and pixel selection is performed for each row. That is,
One discharge channel 5 corresponds to one scanning line in the matrix type display device and functions as a sampling switch.

In synchronization with the scanning by the plasma driving circuit 12, image data is supplied from the liquid crystal driving circuits 14A and 14B to each of the signal electrodes Y (see FIG. 2) of the selected row. In this way, the discharge channel 5 of a certain row is plasma-discharged, and image data is supplied to each of the signal electrodes Y in a state where the plasma sampling switch is in a conductive state, thereby controlling the turning on or off of the liquid crystal cell (pixel). Is done. The image data is retained in the pixel as it is even after the plasma sampling switch is turned off. The liquid crystal layer 21 shown in FIG. 2 displays an image by modulating incident light from the backlight 32 into emitted light according to image data.

In the above embodiment, the case where the invention is applied to the plasma addressed liquid crystal display device has been described as an example, but the present invention is not limited to this application example, and the display layer and the plasma layer are integrated. It is also applicable to a PDP in which each of the display cells that are provided in a matrix and are arranged in a matrix are driven for display while being addressed by plasma discharge. In the case of this application example, the plasma drive circuit 12 in FIG. 1 corresponds to the scan electrode drive circuit, and the liquid crystal drive circuit 1
4A and 14B correspond to the data electrode driving circuit, the signal electrode Y in FIG. 2 corresponds to the data electrode, and the cathode electrode K corresponds to the scanning electrode.

[0043]

As described above, according to the present invention,
At the start of driving each row, a discharge start voltage with a voltage value higher than that is generated based on the power supply voltage, and the generated discharge start voltage is applied between the discharge electrodes. Even if the voltage is set to a low value, the discharge can be reliably generated. Further, since a high voltage is applied between the discharge electrodes only at the moment of starting the discharge, the discharge current can be suppressed to the necessary minimum level, and therefore the transmittance deterioration due to the sputtering of the cathode electrode can be prevented. Since the power consumption can be suppressed, the life of the device can be extended, and the power consumption can be suppressed to the necessary minimum and wasteful consumption of the power can be suppressed, so that the power consumption of the device can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of a plasma addressed liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing an example of a specific structure of a PALC display unit.

FIG. 3 is a schematic diagram for explaining an operation principle of a PALC display unit.

FIG. 4 is a diagram showing an equivalent circuit for one discharge line of a plasma drive system.

5A and 5B are waveform diagrams showing drive waveforms applied between discharge electrodes, where FIG. 5A shows a waveform in the case of no discharge and FIG. 5B shows a waveform in the case of discharge.

FIG. 6 is a timing chart showing an example of driving timing of a plasma addressed liquid crystal display device.

[Explanation of symbols]

11 ... PALC display unit, 12 ... Plasma drive circuit, 13
... inductor circuit, 14A, 14B ... liquid crystal drive circuit, 2
1 ... Liquid crystal layer, 22 ... Plasma layer, 23 ... Intermediate sheet layer,
25 ... Plasma discharge electrode, 27 ... Discharge channel, 30 ...
Liquid crystal, A ... Anode electrode, K ... Cathode electrode

Claims (8)

[Claims] 1. A display unit in which display cells including discharge channels are arranged in a matrix, and a selection pulse having a peak value of a power supply voltage is sequentially applied to a discharge electrode formed in the discharge channel. Driving means for scanning while applying, and discharge for applying to the discharge electrodes by generating a discharge starting voltage having a voltage value higher than that based on the power supply voltage at the start of driving of each row in synchronization with the scanning by the driving means. A plasma display device comprising a starting voltage generating means. 2. The discharge starting voltage generating means has an inductor connected between an output end of each row for outputting the selection pulse of the driving means and the discharge electrode, and outputs the scan pulse. 2. The plasma display device according to claim 1, wherein a resonance circuit is formed by the inductor and the capacitance component between the discharge electrodes when the discharge circuit is turned on. 3. The display unit includes a display layer including signal electrodes arranged in columns, and a plasma layer including discharge channels formed in rows, the plasma layer being overlaid on the display layers. The plasma display device according to claim 1, wherein: 4. The discharge starting voltage generating means has an inductor connected between an output end of each row for outputting the selection pulse of the driving means and the discharge electrode, and outputs the scan pulse. 4. The plasma display device according to claim 3, wherein a resonance circuit is formed by the capacitance component between the inductor and the discharge electrode when the discharge circuit is activated. 5. The plasma display device according to claim 4, wherein the inductance of the inductor is set so that the resonance cycle of the resonance circuit is shorter than the row selection period. 6. The plasma display device as claimed in claim 4, wherein the resonance circuit abruptly attenuates resonance due to a change in impedance due to discharge of the discharge channel. 7. The plasma layer is bonded to the display layer via an intermediate sheet layer, and a dischargeable gas is sealed in a gap between the transparent insulating substrate and the intermediate sheet layer. 4. The plasma display device according to claim 3, which is characterized in that. 8. The plasma display device according to claim 7, wherein the display layer is a liquid crystal layer in which liquid crystal is filled in a gap between the transparent insulating substrate and the intermediate sheet layer.