JP3271082B2 - 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 and a plasma cell. More specifically, the present invention relates to a plasma addressed display device using a transmission type liquid crystal cell or the like as an electro-optical cell. More specifically, the present invention relates to an electrode structure in a plasma cell related to improvement of an aperture ratio of a transmission type display device.

[0002]

2. Description of the Related Art Conventionally, as means for achieving high resolution and high contrast in a matrix type liquid crystal display device using a liquid crystal cell as an electro-optical cell, a switching element such as a thin film transistor is provided for each pixel. Is generally known. 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 transmission type 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 transmission type liquid crystal cell 101 and a plasma cell 102 and a common transparent intermediate plate 103 interposed therebetween. The plasma cell 102 is formed using a transparent glass substrate 104, and a plurality of parallel grooves 105 are provided on the surface thereof. The groove 105 extends, for example, in the row direction of the matrix. Each groove 105 is hermetically sealed by the intermediate plate 103 and constitutes a separately separated plasma chamber 106. An ionizable gas is sealed in the sealed plasma chamber 106. The convex portions 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. A pair of parallel plasma electrodes 108 and 109 are provided at the bottom of each groove 105. 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 configured using a transparent substrate 110. The transparent substrate 110 is disposed opposite the transparent intermediate plate 103 with a predetermined gap therebetween, and the gap is filled with a liquid crystal layer 111. Further, a signal electrode 112 made of a transparent conductive material is formed on the inner surface of the transparent substrate 110. The signal electrode 112 is orthogonal to the plasma chamber 106 and serves as a column drive unit. A matrix of pixels is defined at the intersection of the column drive unit and the row scan 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 driving voltage 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 a driving voltage is applied to each pixel while the plasma sampling switch is turned on, sampling and holding are performed and the transmittance of the pixel can be controlled. Even after the plasma sampling switch is turned off, the analog drive voltage is held in the pixel as it is.

[0006]

By the way, it is considered that a display device using discharge plasma as described above can be easily made larger in area than a display device using a semiconductor device. Leaves various problems. For example, forming the groove 105 for forming the plasma chamber 106 on the substrate 104 made of glass or the like involves considerable difficulty in manufacturing, and particularly, it is extremely difficult to form the groove 105 at high density. . In addition, it is necessary to form the discharge plasma electrodes 108 and 109 in the grooves 105, respectively, but the etching process for this is complicated, and it is also difficult to maintain the interval between the pair of electrodes 108 and 109 with high accuracy.

In view of the problems or problems of the prior art, the applicant has filed a previously filed patent application No. 477/1991.
No. 84 proposes a transmission type plasma addressed display device which is easy to manufacture and suitable for large screen and high definition. The structure of the previously proposed device will be briefly described with reference to FIG. 9 to facilitate understanding of the present invention. This device comprises a first transparent substrate 202 having a plurality of transparent signal electrodes 201 parallel to each other on one main surface, and a signal electrode 20 on one main surface.
And a second transparent substrate 204 having a plurality of opaque plasma electrodes 203 substantially orthogonal to each other and substantially parallel to each other. The plasma electrode 203 is made of a thick printed film or the like and is optically opaque, so that the amount of light incident on the device is partially blocked. These pair of transparent substrates are used as the signal electrodes 201.
And the plasma electrode 203 are arranged parallel to each other so as to face each other. A liquid crystal layer 205 is interposed so as to be in contact with the signal electrode 201 provided on the upper substrate 202. The liquid crystal layer 205 is separated from the lower transparent substrate 204 by a transparent intermediate plate 206. An ionizable gas is sealed between the intermediate plate 206 and the lower substrate 204 to form a discharge region. This discharge region is formed, for example, by a partition wall 207 made of an opaque insulating film formed by a printing method.
Is divided by In the structure shown in FIG.
Since the plasma electrode is formed on a flat substrate, the patterning process is simplified, which is suitable for increasing the screen size and increasing the definition.

However, despite the fact that the flat panel display structure shown in FIG. 9 is of a transmission type, the plasma electrode 203 is made of an opaque thick-film conductive material. There is a problem that sufficient image brightness cannot be obtained at the cost of sacrificing. As the pitch of the plasma electrodes is reduced for higher definition of the image, the aperture ratio becomes more remarkable. In order to improve the aperture ratio, a measure for making the electrode stripe pattern width extremely smaller than the electrode pitch can be considered. However, when the electrodes are made thinner, particularly when the screen is enlarged, the electrode span is extended, so that the voltage drop becomes remarkable and the uniformity of the discharge region is lost. It is also conceivable that the stripe pattern of each plasma electrode is made of a transparent conductive material. However, a transparent conductive material such as ITO has a higher resistivity than a normal opaque thick film conductive material, causing a problem of voltage drop, and has poor durability against plasma.

[0009]

SUMMARY OF THE INVENTION In view of the problems or problems of the above-mentioned plasma addressing transmission type display device according to the above proposal, the present invention improves the aperture ratio without impairing the conductivity and durability of the plasma electrode. For the purpose. In order to achieve such an object, a measure has been taken in which the anode and the cathode of the plasma electrode have different structures. Specifically, a transparent conductive film is formed in a planar shape on the inner surface of the plasma cell substrate so as to include a plurality of discharge regions or scanning units, and this is used as an anode, and the transparent conductive film is formed via an insulating film. A striped cathode was formed on the film.
This transparent conductive film may be formed continuously over the entire surface of the substrate so as to include all scanning units. Further, a partition may be provided on the cathode to partition the plasma chamber into scanning units.
Further, according to another aspect of the present invention, the first cell has a flat structure in which a first cell and a second cell are stacked, and the first cell includes:
A first substrate having a plurality of first electrodes disposed substantially parallel to each other on the inner main surface, and an electro-optical material layer disposed between the first substrate and the second cell; The second cell includes a second substrate having a plurality of second electrodes substantially orthogonal to the first electrode and arranged substantially in parallel with each other on the inner main surface, the second substrate and the first substrate. A plasma addressing electro-optical device comprising a plasma chamber disposed between cells and filled with an ionizable gas, wherein the second electrode comprises an anode and a cathode, and the anode is disposed on a second substrate. A transparent conductive film formed in a planar shape including a plurality of scanning units, the transparent conductive film is divided into a plurality of regions, and the cathode is formed of a stripe-shaped conductive film, and is formed in one region. The cathode that belongs to Characterized in that the over de are commonly connected.

[0010]

According to the present invention, the anode is formed of a transparent conductive film. Therefore, the amount of incident light increases by that amount, and the aperture ratio can be improved. Since the anode is formed not in an individually separated stripe pattern but in a planar shape, the electric resistance can be suppressed to a relatively low level even with a transparent conductive material, and the adverse effect of a voltage drop can be suppressed. In addition, the anode is less susceptible to damage from plasma than the cathode, and can sufficiently withstand a transparent conductive material. On the other hand, the cathode is formed in a stripe shape on this transparent conductive film via an insulating film. It is made of a usual opaque conductive material to ensure sufficient conductivity and durability. When a plasma discharge is generated, a negative voltage is applied to the cathode and the cathode is irradiated with plasma cation particles. Therefore, the cathode needs higher durability than the anode, and it is not preferable to use a transparent conductive film such as ITO.

[0011]

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 sectional view showing one embodiment of a transmission type plasma addressed display device according to the present invention. It shows a shape cut along the column direction, that is, the signal electrode direction. This device has a transmission type flat panel structure in which a liquid crystal cell 1 and a plasma cell 2 and a common intermediate plate 3 made of a transparent dielectric sheet interposed therebetween are laminated. The liquid crystal cell 1 is formed using a first substrate, for example, a glass substrate 4, and a plurality of first electrodes, ie, signal electrodes D, made of a transparent conductive film such as ITO are formed in parallel on the inner main surface thereof. ing. The glass substrate 4 is bonded to the intermediate plate 3 with a predetermined gap using a spacer 5. The gap is filled with a liquid crystal layer 6 which is an electro-optical material layer. In the present embodiment, a fluid electro-optic material is used, but it is not necessarily limited to this. For example, an electro-optic crystal plate can be used. In this case, the intermediate plate 3 can be removed. 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 a transmission type optical modulator.

On the other hand, the plasma cell 2 is constituted by using a second substrate, for example, a glass substrate 7. On the inner main surface of the substrate 7, a second electrode orthogonal to the signal electrode D, that is, a plasma electrode 8 is formed. The plasma electrode 8 is divided into two types, an anode A and a cathode K, which are alternately arranged, and each has a different structure. Anode A is glass substrate 7
And a transparent conductive film 9 made of sheet-like ITO or the like formed over the entire surface of the substrate. The portions of the transparent conductive film 9 exposed in a stripe shape define the individual anodes A. On the other hand, the cathode K is made of a stripe-shaped thick opaque conductive film formed on the transparent conductive film 9 via the insulating film 10. A partition 11 made of an insulating layer is formed in the row direction along the cathode K. The upper end of the partition 11 is the intermediate plate 3
And also serves as a spacer. The glass substrate 7 is bonded to the intermediate plate 3 using a sealing material 12. An airtightly sealed plasma chamber 13 is formed between the two. The plasma chamber 13 is divided by the partition wall 11 and individually constitutes a discharge region serving as a row scanning unit.
Each discharge region communicates with each other via a peripheral portion of the plasma cell 2. An ionizable gas is sealed in the airtight plasma chamber 13. The gas type can be selected from, for example, helium, neon, argon, or a mixed gas thereof.

Next, a plan shape of the lower glass substrate 7 will be described with reference to FIG. On the substrate surface, a transparent conductive film 9 made of ITO or the like is formed so as to cover the entire effective screen area. The transparent conductive film 9 is formed by sputtering or vacuum evaporation. Cathodes K arranged in a stripe pattern at a predetermined pitch are provided thereon. The cathode K is formed by printing a conductive paste using a screen mask, for example. The conductive paste is opaque because it contains a large amount of metal powder such as Ni, but has a lower electric resistance than a transparent conductive film such as ITO. Therefore, even if the cathode K is formed in a stripe shape, there is no possibility of causing a voltage drop or the like. Note that an insulating film 10 is interposed to electrically insulate the cathode K from the underlying transparent conductive film 9. This insulating film 10 is also formed by thick film screen printing or the like. On the surface of each cathode K, partition walls 11 are formed along a stripe pattern. This partition 11 is also formed by thick film printing using a screen mask. The portion of the transparent conductive film 9 exposed between the adjacent cathodes K forms the anode A. Unlike the cathode K formed in a stripe shape, the anode A is continuous in a sheet shape. Therefore, even if the anode A is formed of a transparent conductive film having a relatively high resistivity, the problem of voltage drop does not substantially occur. Normal anode A
Are connected to a common ground, the transparent conductive film 9 may be simply connected to the ground level. When a negative voltage is applied line-sequentially to each cathode K, a plasma discharge is generated between the adjacent anodes A. At this time, the cathode K is irradiated with the cation particles contained in the plasma, but is made of a durable material, so that it is not damaged by sputtering or the like. On the other hand, since the anode A is not subjected to the sputtering of the cation particles, even if it is a transparent conductive material, no deterioration occurs. Thus, according to the present invention, at least the anode A can be made transparent, so that the aperture ratio can be improved.

FIG. 3 shows a reference example for comparison. The same components as those of the plasma addressed display device according to the present invention shown in FIG. 1 are denoted by the same reference numerals to facilitate understanding. In this reference example, both the anode A and the cathode K are formed of a transparent conductive film. In this case, the anode A
The anode A is also patterned in stripes to electrically separate the cathode K from the cathode K. However, in such a structure, since the transparent conductive film formed in a stripe shape has a relatively high resistance, the voltage drop becomes remarkable, and a uniform plasma discharge cannot be obtained over the entire scanning unit length. In addition, the transparent conductive film constituting the cathode K is damaged by sputtering and deteriorates.

Next, the operation of the plasma addressed display device shown in FIGS. 1 and 2 will be briefly described with reference to FIG. FIG.
Shows an example of a driving circuit used for a display device.
This drive circuit includes a signal circuit 21, a scanning circuit 22, and a control circuit 23. Signal electrodes D1 to Dm are connected to the signal circuit 21 via a buffer. On the other hand, cathode electrodes K1 to Kn are also connected to the scanning circuit 22 via a buffer. Anode electrode A
1 to An are made of a sheet-like transparent conductive film as described above and are commonly grounded. The cathode electrode is the scanning circuit 2
2, the signal circuit 21 supplies an analog image signal to each signal electrode in synchronization with the scanning. The control circuit 23 controls the synchronization between the signal circuit 21 and the scanning circuit 22. A plasma discharge region is formed along each cathode electrode and between the anode electrodes on both sides thereof to form a row scanning unit. On the other hand, each signal electrode is a column drive unit. A pixel 24 is defined between the two units.

FIG. 5 is a schematic diagram showing two pixels 24 shown in FIG. 4 cut out. Each pixel 24 includes a sampling capacitor composed of the liquid crystal layer 6 sandwiched between the signal electrodes D1 and D2 and the intermediate plate 3, and a series connection of a plasma sampling switch S1. The plasma sampling switch S1 equivalently represents the function of the discharge region. That is, when the discharge region is activated, the inside of the discharge region is almost entirely connected to the anode potential. On the other hand, when the plasma discharge ends, the discharge region becomes a floating potential. An analog image signal is written into the sampling capacitor of each pixel 24 via the sampling switch S1 to perform a so-called sampling hold. The gradational lighting or extinguishing of each pixel 24 can be controlled by the level of the analog image signal.

FIG. 6 shows another embodiment of the plasma addressed electro-optical device according to the present invention. In this example, the transparent conductive film is divided into two on the display screen to form a pair of anode regions AF and AS. Each region includes a plurality of cathodes. Corresponding cathodes are commonly connected across both anode regions. Each cathode K1, K2
Are selected line by line by the scanning circuit 22. On the other hand, the pair of anode regions AF and AS are alternately selected.

FIG. 7 shows selected waveforms of the cathode and the anode. In this example, time-division driving is performed, and in the first half of the field, one anode area AF is selected and set to a voltage suitable for discharge. In the latter half of the subsequent field, the other anode region AS is selected and set to a voltage suitable for discharging. On the other hand, the scanning circuit 22 performs line-sequential operation for each of the cathodes K1, K2, K3.
Is applied with a selection pulse of negative polarity. In this way, line-sequential plasma discharge is performed in one anode region AF in the first half of the field, and line-sequential plasma discharge is similarly performed in the other anode region AS in the second half of the field. In this example, so-called drive multiplexing is performed by using the scanning circuit 22 in a time-division manner.

[0019]

As described above, according to the present invention, in an image display apparatus for addressing a liquid crystal cell by line-sequential plasma discharge, an anode electrode for plasma discharge is formed of a transparent conductive film. The transparent conductive film is patterned in a plane including a plurality of scanning units. The corresponding cathode electrodes are formed in stripes on the transparent conductive film via an insulating layer. With this structure, the transmittance of the display device can be improved, and the image quality, the luminance, and the power consumption can be reduced. In addition, the number of electrodes can be increased by an amount corresponding to the improvement in transmittance, and there is an effect that a significant improvement in resolution is achieved. Furthermore, since it is not necessary to connect the anode electrodes one by one, there is an effect that the mounting process of the device is simplified.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a first embodiment of a plasma addressed electro-optical device according to the present invention.

FIG. 2 is a plan view of the plasma addressed electro-optical device shown in FIG.

FIG. 3 is a schematic sectional view showing a reference example of the plasma addressed electro-optical device.

FIG. 4 is a drive circuit diagram of the plasma addressed electro-optical device shown in FIG.

FIG. 5 is a schematic diagram showing the pixel shown in FIG. 4 cut out.

FIG. 6 is a schematic circuit diagram showing a second embodiment of the plasma addressed electro-optical device according to the present invention.

FIG. 7 is a waveform chart for explaining the operation of the embodiment shown in FIG. 6;

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

FIG. 9 is a schematic cross-sectional view showing a plasma addressed electro-optical device previously developed by the applicant.

[Explanation of symbols]

 Reference Signs List 1 liquid crystal cell 2 plasma cell 3 intermediate plate 4 glass substrate 6 liquid crystal layer 7 glass substrate 8 plasma electrode 9 transparent conductive film 10 insulating film 11 partition 13 plasma chamber A anode K cathode D signal electrode

Claims (4)

(57) [Claims] 1. A flat structure in which a first cell and a second cell are stacked, wherein the first cell has a plurality of first electrodes arranged on an inner main surface substantially in parallel with each other. A first substrate, an electro-optic material layer disposed between the first substrate and the second cell, wherein the second cell is substantially orthogonal to the first electrode and on an inner main surface. A second substrate having a plurality of second electrodes disposed substantially parallel to each other, and a plasma chamber disposed between the second substrate and the first cell and filled with an ionizable gas. In the plasma addressed electro-optical device, the second electrode includes an anode and a cathode, and the anode is formed of a transparent conductive film formed in a plane including a plurality of scanning units on a second substrate; The cathode is formed on the transparent conductive film via an insulating film Plasma addressing electro-optical device characterized by comprising the stripe-shaped conductive film. 2. The method according to claim 1, wherein the transparent conductive film is formed continuously so as to include all scanning units.
The plasma-addressed electro-optical device according to claim 1. 3. The plasma addressed electro-optical device according to claim 1, wherein a partition for dividing a plasma chamber for each scanning unit is formed on the cathode. 4. It has a flat structure in which a first cell and a second cell are stacked, and the first cell has a plurality of first electrodes arranged substantially in parallel on an inner main surface. A first substrate, an electro-optic material layer disposed between the first substrate and the second cell, wherein the second cell is substantially orthogonal to the first electrode and on an inner main surface. A second substrate having a plurality of second electrodes disposed substantially parallel to each other, and a plasma chamber disposed between the second substrate and the first cell and filled with an ionizable gas. In the plasma addressed electro-optical device, the second electrode includes an anode and a cathode, and the anode is formed of a transparent conductive film formed in a plane including a plurality of scan units on a second substrate; The transparent conductive film is divided into a plurality of regions. The plasma addressing electro-optical device is characterized in that the mode is formed of a stripe-shaped conductive film, and a cathode belonging to one region and a cathode belonging to another region are commonly connected.