JP3350967B2 - Plasma address electro-optical device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma addressed electro-optical device having a two-layer structure of an electro-optical cell such as a liquid crystal cell and a plasma cell. More specifically, the present invention relates to a discharge stabilization technique for a plasma cell.

[0002]

2. Description of the Related Art Conventionally, as means for increasing the resolution and contrast of a matrix type electro-optical device such as a liquid crystal display device using a liquid crystal cell, a switching element such as a thin film transistor is provided for each pixel. Are generally known in a line-by-line manner (so-called active matrix addressing method). However, in this case, it is necessary to provide a large number of semiconductor elements such as thin film transistors on the substrate, and there is a disadvantage that the production yield is deteriorated particularly when the area is increased.

Therefore, as a means for solving this disadvantage,
Buzak et al. In Japanese Patent Application Laid-Open No. 1-217396 propose a method in which a plasma switch is used in place of a switching element composed of a thin film transistor or the like. Less than,
A configuration of a plasma addressed display device that drives a liquid crystal cell using a switch based on plasma discharge will be briefly described. As shown in FIG. 8, this device has a laminated flat panel structure including a liquid crystal cell 101, a plasma cell 102, and a partition plate 103 interposed therebetween. The plasma cell 102 is formed using a glass substrate 104, and has a plurality of grooves 105 on the surface thereof. The groove 105 extends, for example, in the row direction of the matrix. Each groove 105 is hermetically sealed by a partition plate 103 and constitutes a separately separated plasma chamber 106. The plasma chamber 106 is filled with an ionizable gas. The protruding ridges 107 separating the adjacent grooves 105 serve as partitions for separating the individual plasma chambers 106 and also serve as gap spacers for the respective plasma chambers 106. At the bottom of each groove 105, a pair of parallel plasma electrodes 108 and 109 is provided. The pair of electrodes function as an anode and a cathode, and ionize gas in the plasma chamber 106 to generate discharge plasma. Such a discharge region is a unit of row scanning.

On the other hand, the liquid crystal cell 101 is constituted by using a glass substrate 110. The glass substrate 110 is arranged to face the partition plate 103 with a predetermined gap therebetween, and the gap is filled with a liquid crystal layer 111. The signal electrode 11 made of a transparent conductive material is provided on the inner surface of the glass substrate 110.
2 are formed. The signal electrode 112 is orthogonal to the plasma chamber 106 and is a unit of a column signal. A matrix of pixels is defined at the intersection of the column signal unit and the row scanning unit.

In a display device having such a configuration,
The display driving is performed by switching and scanning the plasma chamber 106 in which the plasma discharge is performed line-sequentially and applying an analog image signal to the signal electrode 112 on the liquid crystal cell side in synchronization with the scanning. When a plasma discharge is generated in the plasma chamber 106, the inside thereof becomes substantially uniformly at the anode potential, and pixel selection for each row is performed. That is, the plasma chamber 106 functions as a sampling switch. When an image signal is applied to each pixel in a state where the plasma sampling switch is turned on, sampling and holding are performed, and lighting or extinguishing of the pixel can be controlled. Even after the plasma sampling switch is turned off, the analog image signal is held in the pixel as it is.

[0006]

In order to stably perform the line sequential driving of the plasma addressing device, it is necessary to make the discharge current flowing in each row scanning unit uniform. However, in practice, the discharge current is not constant due to variations in accuracy in the shape and size of the plasma electrode, the distance between the pair of plasma electrodes, and the like. The discharge current also varies depending on the surface condition of the plasma electrode. In particular, when the screen size of the plasma addressed display device is increased, the total length of the plasma electrode becomes longer and a voltage drop occurs, so that the variation in the discharge current or the discharge start voltage becomes remarkable. When there is such a variation, a drive voltage set in advance must be applied in order to reliably activate all the row scanning units or the discharge channels with a constant power supply voltage. Therefore, there is a problem that an excessive discharge current flows in a certain scanning unit and the life of the plasma electrode is deteriorated. On the other hand, there is a problem that a plasma discharge cannot be generated in a row scanning unit in which a discharge starting voltage is abnormally high, which causes a malfunction.

[0007]

SUMMARY OF THE INVENTION In view of the above-mentioned problems in the prior art, the present invention provides a driving method for stabilizing discharge characteristics over all row scanning units of a plasma addressed electro-optical device. With the goal. The following measures were taken to achieve this purpose. That is, an electro-optical cell having a column signal unit, a plasma cell having a row scanning unit and stacked on the electro-optical cell, a horizontal signal circuit for supplying an electric signal to the column signal unit, and an individual row scanning unit A vertical scanning circuit for applying a driving voltage in a line-sequential manner between a pair of plasma electrodes included in the plasma addressing electro-optical device, wherein the vertical scanning circuit is applied to each row scanning unit in order to equalize plasma discharge in each row scanning unit. A discharge stabilizing means for controlling the drive voltage.

More specifically, the discharge stabilizing means includes a memory for storing previously measured discharge characteristic data for each row scanning unit, and a discharge stabilizing means based on the discharge characteristic data read out in synchronization with line-sequential scanning. And a regulator for supplying the adjusted drive voltage. Alternatively, in another specific mode, the discharge stabilizing means includes a constant-voltage power supply for supplying a constant drive voltage of a predetermined level, and a correction drive voltage whose level fluctuates according to a regular change in discharge characteristics of each row scan unit. It consists of a combination with a power supply for correction to be superimposed. The correction power supply outputs, for example, a correction drive voltage whose polarity is inverted for each row scanning unit and whose amplitude increases from the center row scanning unit to the peripheral row scanning unit.

[0009]

According to the present invention, the drive voltage is controlled according to the discharge characteristics of each row scanning unit. For example, when a row scanning unit having a relatively high discharge current is selected, a relatively low driving voltage is supplied between a pair of corresponding plasma electrodes. On the other hand, when a row scanning unit having a relatively low discharge current is selected, a relatively high driving voltage is supplied to a corresponding pair of plasma electrodes. In this way, variations in the discharge characteristics existing between the row scanning units are made uniform, and stable driving can be performed. It is possible to prevent an excessive discharge current from repeatedly flowing in a specific row scanning unit, and to suppress deterioration in the life of the plasma electrode. Alternatively, it is possible to prevent a plasma discharge from occurring in a specific row scanning unit, thereby suppressing malfunction. As means for stabilizing such discharge, a digital control method and an analog control method can be considered.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic circuit diagram showing one embodiment of a plasma addressed electro-optical device according to the present invention. In this embodiment, the plasma discharge is made uniform by digital control. As shown, the device has a structure in which an electro-optical cell having column signal units D1, D2, D3, and D4 and a plasma cell having row scanning units are stacked. Each row scanning unit includes a pair of plasma electrodes (A1,
K1), (A2, K2), (A3, K3), (A4, K
4). A represents an anode and K represents a cathode. In this embodiment, all the anodes A
1, A2, A3 and A4 are commonly grounded. A matrix of pixels P is provided at the intersection of a column signal unit and a row scanning unit.
Is defined. A plurality of column signal units D1, D2, D3, D
Reference numeral 4 is connected to the horizontal signal circuit 1 via a buffer and receives supply of an electric signal. The horizontal signal circuit 1 outputs an electric signal Vsig for each column signal according to the horizontal synchronization signal HD. On the other hand, a plurality of cathode electrodes K1, K2, K
3 and K4 are connected to the vertical scanning circuit 2. The vertical scanning circuit 2 applies a driving voltage line-sequentially between a pair of plasma electrodes included in each row scanning unit. That is, the vertical scanning circuit 2 includes a shift register 3 for line selection, and the individual cathodes K via the switching transistors 4 according to the vertical synchronizing signal VD and the horizontal synchronizing signal HD.
1, K2, K3, and K4 are selected in a line-sequential manner. Further, a discharge stabilizing unit 5 is provided, and controls the drive voltage for each row scanning unit in order to equalize the plasma discharge in each row scanning unit. Specifically, the discharge stabilizing means 5 includes a memory (ROM) 6 for storing previously measured discharge characteristic data for each row scan unit, and a discharge characteristic read out in synchronization with line-sequential scanning. And a regulator for supplying a drive voltage adjusted based on the data. More specifically, the counter 7 outputs an address signal in response to the horizontal synchronization signal HD, and accesses the memory 6. The discharge characteristic data read from the memory 6 is supplied to the base terminal of the control transistor 9 via the D / A converter 8. The control transistor 9 is connected to a power supply 10 and adjusts a drive voltage applied to each of the cathodes K1, K2, K3, K4 according to the discharge characteristic data. Therefore, the D / A converter 8, the control transistor 9, and the power supply 10 constitute the above-described regulator. In the present embodiment, the discharge characteristic data stored in the memory 6 is written as voltage data to be applied to each row scanning unit. In other words, voltage data is written in advance such that the discharge intensity in each row scanning unit is constant. This voltage data can be set based on actual measurement.

Next, a specific structural example of the plasma addressed electro-optical device according to the present invention will be described with reference to FIG. This device has a structure in which a liquid crystal cell 11, a plasma cell 12, and a partition plate 13 interposed therebetween are laminated.
The partition plate 13 needs to be as thin as possible to drive the liquid crystal cell 11, and is made of, for example, a thin glass plate having a thickness of about 50 μm. The liquid crystal cell 11 is a glass substrate 14
, And a plurality of column signal units D made of a transparent conductive film patterned in a stripe shape are formed on the inner main surface thereof. The substrate 14 is connected to the partition plate 13 with a predetermined gap using a spacer 15.
The gap is filled with a liquid crystal layer 16 which is an electro-optical material layer. This gap size is usually about 5 μm and needs to be kept uniform over the entire display surface. The liquid crystal layer 16 is in contact with the column signal unit D and the partition plate 13. In this embodiment, a liquid crystal is used as the electro-optical material, but the present invention is not limited to this, and other fluid materials can be used. Although the present embodiment relates to a plasma addressed display device, the present invention is not limited to this, but can be widely applied to a plasma addressed electro-optical device such as an optical modulation device.

On the other hand, the plasma cell 12 is constituted by using a lower glass substrate 17. A plasma electrode 18 is formed on the inner main surface of the glass substrate 17. The plasma electrodes 18 alternately function as an anode A and a cathode K to generate a plasma discharge. The plasma electrodes 18 are arranged along the row direction so as to cross the column signal units D. A partition wall 19 is formed along the plasma electrode 18. The partition wall 19 uniformly defines the gap of the plasma cell 12. A low-melting glass 20 is provided along the periphery of the glass substrate 17, and the partition plate 1
3 and the glass substrate 17 are bonded together. An airtightly sealed plasma chamber 21 is formed between the two. An ionizable gas is sealed inside the plasma chamber 21. The gas type can be selected from, for example, helium, neon, argon, xenon, or a mixed gas thereof. The plasma chamber 21 is divided by the partition walls 19 or the ribs described above, and each constitutes a row scanning unit.

When a predetermined voltage is applied between a pair of adjacent plasma electrodes 18, ie, anode A and cathode K, the enclosed gas is selectively ionized to form a discharge region 22 in which ion gas is localized. . This discharge area 22
Is substantially limited by the partition wall 19 and is a row scanning unit. Each pixel is located at the intersection of the row scanning unit and the column signal unit D. In the present invention, the driving voltage applied between the pair of plasma electrodes is controlled in accordance with the discharge characteristics of each row scanning unit, so that the plasma discharge intensity is constant over the entire screen.

Next, an embodiment in which the discharge stabilizing means is realized by using an analog method will be described below. before that,
With reference to FIGS. 3 to 5, a description will be given of a typical aspect of variation in discharge characteristics between row scanning units of the plasma addressed electro-optical device shown in FIG. FIG. 3 is a schematic diagram showing an arrangement relationship between the plasma electrode 18 and the partition wall 19. The plasma electrodes 18 and the partition walls 19 are both formed by a screen printing method, and have the same arrangement pitch in design. However, actually, the arrangement pitch includes an error, and the two do not perfectly match. Generally, the plasma electrode 18 and the partition wall 19 are aligned at the center of the screen. For example, when the arrangement pitch of the partition wall 19 is larger than the arrangement pitch of the plasma electrodes 18, the plasma electrode 18 faces the upper end side and the lower end side of the screen. Accordingly, the partition wall 19 relatively shifts outward. Incidentally, the plasma electrode 18 alternately functions as an anode A and a cathode K, and each row scanning unit S
Is defined. For convenience of explanation, a number is given to each scanning unit. With reference to the row scanning unit located at the center, a positive number that increases toward the lower end is assigned, and a negative number is assigned to the upper end. Similarly, positive and negative numbers are assigned to the anode A and the cathode K, respectively.

Generally, the plasma discharge characteristics depend on the exposed area of the cathode electrode. FIG. 4 is a graph showing the distribution of the exposed area of the cathode electrode in the vertical direction of the screen. Odd-numbered row scanning units (−S1, + S1, +
Focusing on S3), as the pitch shifts from the upper end to the lower end, the cathode electrode (− in FIG.
(K1, + K1, + K2) are large. Conversely, even-numbered row scanning units (-S2, ± S in FIG. 3)
Focusing on (0, + S2), the exposed area of the cathode electrode (−K2, −K1, + K1 in FIG. 3) increases on the upper end side, and decreases on the lower end side.

[0016] As a general property of plasma discharge between the discharge current cathode electrode exposed area Ru proportional relationship there. What slave, is supplied a constant driving voltage line-sequentially to all the row scanning unit, a plasma discharge current distribution as shown in FIG. 5 is obtained. In other words, for the odd-numbered scanning units, the discharge current increases from the upper end to the lower end of the screen. Conversely, in the scanning unit of the even-numbered row, the discharge current decreases from the upper end to the lower end. As described above, in the conventional method in which a constant drive voltage is applied, a variation in discharge current occurs between row scanning units, and deterioration proceeds in a plasma electrode in which an excessive current flows. Conversely, a row scan unit in which plasma discharge is not easily generated may not be generated.

Therefore, in the present invention, the plasma drive intensity is made uniform by applying a correction drive voltage having a phase opposite to that of the discharge current distribution shown in FIG. FIG. 6 shows the waveform of the corrected drive voltage. In this waveform, the polarity is inverted for each row scanning unit, that is, for each horizontal cycle (1H), and the amplitude increases from the center row scanning unit to the peripheral row scanning unit in one vertical cycle (1V). .

FIG. 7 shows an example of a vertical scanning circuit configured to realize line-sequential application of the correction drive voltage shown in FIG. The vertical scanning circuit includes a constant voltage power supply 31 for supplying a predetermined level of a constant driving voltage. Further, a correction power supply 32 for outputting a correction drive voltage whose level fluctuates according to a regular discharge characteristic change in each row scanning unit is connected in series, and the correction drive voltage having a waveform as shown in FIG. Superimposed on the voltage. The anode is commonly grounded to the positive electrode side of the constant-voltage power supply 31, and the individual cathodes are connected via a switching transistor 33 to a correction power supply 32.
It is connected to the. The switching transistor 33 is line-sequentially selected by the vertical shift register 34, and synchronously samples a periodically changing drive voltage on which the constant drive voltage and the correction drive voltage are superimposed.

In this embodiment, the optimum correction drive voltage waveform is set according to the relative pitch shift between the plasma electrode and the partition shown in FIG. Actually, the above-described aspect of the pitch shift differs for each individual device, but in any case, it exhibits an aspect of a regular change. Therefore, by appropriately setting the amplitude and phase of the correction driving voltage in accordance with the aspect of this change, it is possible to realize a uniform plasma discharge in accordance with the actual pitch shift.

[0020]

As described above, according to the present invention, the discharge stabilizing means for controlling the drive voltage for each row scan unit is provided in order to equalize the plasma discharge in each row scan unit. There is an effect that malfunction such as misfire can be effectively prevented. Further, it is not necessary to apply an excessive drive voltage to a scan unit in which discharge is easy, and there is an effect that deterioration of the plasma electrode can be effectively prevented.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of a plasma addressed electro-optical device according to the present invention.

FIG. 2 is a schematic sectional view showing a structural example of a plasma addressed electro-optical device according to the present invention.

FIG. 3 is an explanatory diagram showing a relative arrangement pitch shift between a plasma electrode and a partition.

FIG. 4 is a graph showing a relationship between a vertical position of a screen in units of row scanning and an exposed area of a cathode electrode.

FIG. 5 is a graph showing a discharge current distribution for each row scanning unit.

FIG. 6 is a schematic diagram showing a correction drive voltage waveform.

FIG. 7 is a circuit diagram showing a vertical scanning circuit according to another embodiment of the present invention.

FIG. 8 is a perspective view showing an example of a conventional plasma addressed electro-optical device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Horizontal signal circuit 2 Vertical scanning circuit 3 Shift register for line selection 4 Switching transistor 5 Discharge stabilization means 6 Memory 7 Counter 8 D / A converter 9 Control transistor 10 Power supply

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G09G 3/28 G09G 3/36 G09G 3/20 G02F 1/1333 H04N 5/66 101

Claims (4)

(57) [Claims] An electro-optical cell having a column signal unit, a plasma cell having a row scanning unit stacked on the electro-optical cell, a horizontal signal circuit for supplying an electric signal to the column signal unit, A vertical scanning circuit for applying a drive voltage in a line-sequential manner between a pair of plasma electrodes included in a row scanning unit, wherein the vertical scanning circuit is used to equalize plasma discharge in each row scanning unit. A plasma addressed electro-optical device comprising a discharge stabilizing means for controlling a driving voltage for each row scanning unit. 2. The discharge stabilizing means according to claim 1, wherein said discharge stabilizing means is a memory for storing previously measured discharge characteristic data for each row scanning unit, and is adjusted based on said discharge characteristic data read out in synchronization with line-sequential scanning. 2. The plasma addressed electro-optical device according to claim 1, further comprising a regulator for supplying a driving voltage. 3. The discharge stabilizing means superimposes a constant-voltage power supply for supplying a constant driving voltage of a predetermined level and a correction driving voltage whose level fluctuates in accordance with a regular change in discharge characteristics of each row scanning unit. 2. The plasma addressed electro-optical device according to claim 1, comprising a combination with a correction power supply. 4. The correction power supply outputs a correction drive voltage whose polarity is inverted for each row scanning unit and whose amplitude increases from a central row scanning unit to a peripheral row scanning unit. The plasma addressed electro-optical device according to claim 3.