JPH022512A - Active device, active matrix display, and driving method for active matrix display - Google Patents

Abstract

PURPOSE:To obtain a sharp, high-contrast image by providing a 1st electrode on an insulating substrate, a ferroelectric layer on the 1st electrode, and a 2nd electrode on the ferroelectric layer. CONSTITUTION:The film thickness dF of 1st and 2nd electrodes 13 and 15 is smaller than intervals (x), (y) and (z) between the 1st and 2nd electrodes 13 and 14 parallel to the insulating substrate 12. Therefore, when a voltage is applied between the 1st and 2nd electrodes 13 and 15 to invert the self- polarization of the ferroelectric layer 14 sandwiched between both electrodes 13 and 15, the voltage is so set that the polarization in the dF direction of the short distance between both electrodes 13 and 15 is inverted and not inverted in the (x), (y), and (z) directions. Thus, the dF, (x), (y), (z), and voltage are set then only a beta area operates as an active layer and the self-polarization of the ferroelectric layer 14 in the (x), (y), and (z) directions is not inverted. Consequently, the sharp, high-contrast image is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an active device for driving a pixel used in an active matrix display or a blink printer engine, and a method for driving an active matrix display.

[Summary of the Invention] The present invention provides a clear, high-contrast image at low cost by using an active device, an active matrix display, and an active matrix display driving method using an active device including a ferroelectric material as an active layer. It was donated.

[Conventional technology] Conventionally, SID (Society For Inf.
Ormation Display) 19ss Sy
mposium Digest P, 296-29
Active devices such as those described in 7 were known. The outline thereof is shown in FIG. 2. A gate electrode 2, a gate insulating layer 3, a channel amorphous layer 10, source and drain regions 11, 6,
An active device in which a liquid crystal C is held between a lower substrate G in which a pixel electrode 7 is connected to a thin film transistor consisting of source and drain electrodes 5 and 4, and an upper substrate H in which an electrode 8 is formed on a glass substrate 9. was known.

[Lesson L that the invention attempts to solve! ] However, conventional active devices have the following drawbacks. That is, the pixel information, that is, the data potential applied to the source electrode 5 is applied to the channel amorphous Si 1 whose ON/OFF state is controlled by the gate electrode.
0 to the liquid crystal C held between the pixel electrode 7 and the pixel electrode 8, and the data voltage is held as the amount of charge on the liquid crystal C. However, the charge on the liquid crystal C decreases over time due to leakage current from thin film transistors. That means the data voltage is lost over time. Therefore, it has been difficult to obtain clear, high-contrast images. In addition, conventional active devices have complex structures and require complex and long manufacturing processes, resulting in low yields, high costs, and difficulty in providing uniform characteristics over a large area. there were. Furthermore, active matrix displays using conventional active devices also have similar problems.

The present invention is intended to solve these conventional problems, and aims to provide clear, high-contrast images, with a simple process, high yield, and low cost.
An object of the present invention is to provide an active device and an active matrix display having uniform characteristics over a large area.

[Means for Solving the Problems 1] The active device of the present invention includes a first electrode formed on an insulating substrate, a ferroelectric layer provided so as to cover the first electrode and the insulating substrate, It is characterized by comprising a second electrode provided on the ferroelectric layer so as to overlap with the first electrode.

The active device of the present invention includes a first electrode provided on an insulating substrate, a ferroelectric layer formed on the first 1f pole, and a second electrode having the same shape as the ferroelectric layer. It is characterized by

The active device of the present invention includes a first electrode and a second electrode formed on an insulating substrate, and a first electrode and a second electrode formed on an insulating substrate.
It is characterized by comprising an island-shaped ferroelectric layer provided so as to connect the electrodes.

The active device of the present invention includes a ferroelectric layer provided to cover an insulating substrate, a first electrode and a second electrode provided on the ferroelectric layer or between the insulating substrate and the ferroelectric layer. It is characterized by being equipped with the following electrodes.

The active device of the present invention is characterized by comprising an electrode provided on an insulating substrate and a ferroelectric layer provided on the electrode.

The active device of the present invention includes a ferroelectric layer provided on an insulating substrate, a contact hole provided in the ferroelectric layer, and a contact hole provided in the ferroelectric layer, connected through the contact hole, and provided with the ferroelectric material sandwiched therebetween. A first electrode B and a second electrode are provided, and a first electrode A is provided in the same plane as the first electrode B.

The active device of the present invention includes a first electrode A and a second electrode B provided on an insulating substrate, and an island-shaped strong electrode provided to connect the first electrode A and the first electrode B. a dielectric layer, a second electrode provided in contact with the first electrode B;
It is characterized by being equipped with the following electrodes.

In the active device of the present invention, the film thickness of the first electrode or the second electrode or the first electrode A or the first electrode B provided between the insulating substrate and the ferroelectric layer is the same as that of the ferroelectric layer. It is characterized by being thinner than the film thickness.

The active matrix display of the present invention is characterized in that the active devices described in item 1, item 2, item 3, item 4, item 5, item 6, or item 7 are arranged in a matrix. .

The method for driving an active matrix display of the present invention is as follows: (1) The active matrix display in which the active devices of the present invention are arranged in a matrix and a material having an electro-optic effect is held is driven by each selected line of a group of selected lines within one field period. In an active matrix display driving method in which a selection voltage ±V0 is sequentially applied to a group of data lines, and a data voltage ±v1 is applied to a data line group,
Absolute value 1■ of the difference between 0 and data voltage ±v1. -V1 | is.

The active matrix display driving method of the present invention is characterized in that the active matrix display driving method of the present invention is characterized in that the active matrix display of the present invention is arranged in a matrix and a material having an electro-optic effect is held. A method for driving a display is characterized in that a voltage higher than a coercive electric field is applied to one ferroelectric layer during a certain period immediately before the start of a display operation.

[Function] The function of the active device of the present invention is shown in Fig. 3(a) and (
The hysteresis curve of the zero ferroelectric material explained using b), (c), and (d) is shown in Fig. 3(a).
The middle Pr is called residual polarization, which is the surface charge density that remains on the ferroelectric surface after the electric field applied to the ferroelectric material is cut off, and this surface charge density is known to have memory properties. The arrangement of spontaneous polarization in this state is shown in Figure 3(b).
There is a positive surface charge on the ferroelectric surface where the arrow is pointing,
A negative surface charge is held on the back side. When a sufficiently large electric field is applied from the outside to reverse the spontaneous polarization, the spontaneous polarization is reversed and takes on the arrangement shown in FIG. 3(c). At this time, the polarity of the charges held on the ferroelectric surface is reversed. Further, when a coercive electric field is applied and the ferroelectric material is a non-single crystal, the state in which each spontaneous polarization is randomly arranged vertically is maintained even after the electric field is turned off. At this time, the surface charge of the ferroelectric material becomes zero.

When connecting a liquid crystal etc. in series or parallel with a ferroelectric material,
A voltage proportional to the surface charge density of the ferroelectric can be applied to the liquid crystal. The voltage is an alternating voltage whose polarity changes by rotating the spontaneous polarization, and the voltage can be controlled by changing the amount of surface charge density λ. Voltage controllability is better when the ferroelectric material is non-single crystal.

Furthermore, since the voltage applied to a liquid crystal or the like originates from the surface charge, the active device of the present invention using a ferroelectric material having a memory property for the surface charge will not lose data voltage due to leakage current of the device itself.

[Example] Examples of the present invention will be described below based on the drawings. FIGS. 1(a) and 1(b) show the configuration of a first active device according to the present invention, FIG. 1(b) is a top view, and FIG.
a) is a sectional view taken along line 8-B in FIG. A first electrode 13 made of ITO provided on an insulating substrate 12 made of a glass substrate, and vinylidene fluoride (hereinafter abbreviated as VDF) and trifluoroethylene (hereinafter abbreviated as TrFE) provided on the first electrode 13. The structure includes a ferroelectric layer 14 made of a copolymer of Cr and a second electrode 15 made of Cr provided on the ferroelectric layer 14.

Two photo steps are required to form the active device of the tube 1 of the present invention.

In FIGS. 1(a) and (b), the first and second electrodes 13
．． The thickness d2 of the ferroelectric layer No. 15 is the same as that of the first and second electrodes 1.
The distances x, y, and z in the parallel direction to the insulating substrate 12 are set shorter than 3.15. Therefore, a voltage is applied between the first and second electrodes 13 and 15, and between the two electrodes 13.1
When reversing the spontaneous polarization of the ferroelectric material IJ14 sandwiched between the first and second electrodes 13 and 15,
, it becomes possible to set the voltage so that the polarization is reversed in the x, y, and z directions but not in the x, y, and z directions. In this way, by setting dr,
, only the β region in (b). β as active layer
When only the area moves, the following effects occur. First, since the spontaneous polarization of the ferroelectric layer in the x, y, and z directions in FIGS. 1(a) and 1(b) is not reversed, when the active device of the present invention is used in a liquid crystal display, etc. Crosstalk does not occur and high quality display can be obtained. Second, x, y, z
Since the capacitance generated in the d2 direction can be smaller than the capacitance in the d2 direction, the total capacitance formed by the ferroelectric layer becomes smaller. As will be described later, this has great effects in improving the display quality of a liquid crystal display using the active device of the present invention, such as reducing drive voltage and preventing crosstalk.

Since the copolymer of VDF and TrFE used for the ferroelectric layer 14 exists in a liquid state dissolved in a solvent such as dioxane or methyl ethyl ketone, it can be uniformly formed over a large area by a spin cord method. This shows that a uniform active device can be easily formed over a large area, that is, a display that displays uniformly over a large area can be realized. A ferroelectric layer made of a copolymer of VDF and TrFE is obtained by forming it by a spin code method and then firing it. The copolymer of VDF and TrFE is colorless and transparent at least in a thin film state, so when applied to light-receiving displays such as liquid crystals, especially transmitted-light displays, it has high light transmittance and brightness (low visibility). An excellent display can be achieved.

Further, the thickness d2 of the ferroelectric layer 14 made of a copolymer of VDF and TrFE is set to be thicker than the thickness dM of the first electrode. After coating with spin code method, insulating substrate 1
2 is held horizontally for several tens of seconds to several minutes to flatten the surface of the ferroelectric layer 14. VDF to be dissolved in the solvent at this time
By adjusting the amount of and TrFE (viscosity adjustment) and optimizing the rotation speed and time of the spin coater, it is easy to
A ferroelectric layer 14 that satisfies the relationship dll and has a uniform thickness and quality can be formed. This has the tremendous effect of forming an active device that is uniform over a large area and has small variations.
Since the raw material of the ferroelectric layer 14 is a liquid, the process of coating and forming the ferroelectric layer 14 can flatten the unevenness formed by the first electrode 13 and make the surface of the ferroelectric layer 14 almost flat. . Since the second electrode 15 is formed on a flat surface, it has a good difference shape, and a line breakage occurs at the difference, or a high electric field is applied to the ferroelectric material 14 at the difference, causing dielectric breakdown. This is not the case, and a highly reliable active device can be obtained. It is preferable that the 110 thickness of the first electrode 13 is 100 to 3000 mm thick, and the thickness of the ferroelectric layer is 1000 to 3000 mm thicker than the first electrode.

Furthermore, the active device configured as shown in FIGS. 1(a) and 1(b) can increase the tolerance for alignment errors in the photo process between the first electrode 13 and the second electrode 15.

FIG. 4 shows a cross-sectional view of a liquid crystal panel using the first active device of the present invention, in which a first electrode 13 made of ITO, a VDF and a Tr
Between a substrate consisting of a ferroelectric IJ14 made of a copolymer with FE and a second electrode 15 made of Cr, and a counter substrate E formed of an electrode 17 made of ITO on an insulating substrate 16 made of a glass substrate. This is a liquid crystal panel that holds liquid crystal F.

In Figure 4, materials that change light transmittance depending on an electric field, materials that change light emitting and non-emitting states, materials that change color, etc., are shown in Figure 4. It may be used instead of liquid crystal F.

A liquid crystal panel using the active device of the present invention is an active type liquid crystal panel. Therefore, the active device of the present invention is particularly effective when the liquid crystal used is a non-ferroelectric liquid crystal such as TN, guest host, STN, or NTN, which does not have a memory effect itself.

FIG. 5 shows a top view of a part of the first active matrix display according to the present invention using the first active device of the present invention. It can be obtained by arranging the A substrate consisting of a first electrode 13 made of ITO formed on an insulating substrate made of a glass substrate, a ferroelectric layer, and a second electrode 15 made of Cr; Electrode 1 consisting of
A ferroelectric material F is held on a first electrode 13 that moves once as a six pixel electrode in which the electrodes of the substrate and the counter substrate are arranged in a matrix.
J14 overlaps, but since the copolymer of VDF and TrFE is colorless and transparent, it constitutes a bright, clear, and highly visible display.

Ferroelectric F! 14 has a polarization effect, so example ^
For example, if a rubbing method such as rotational rubbing is used, it can be used as an alignment film for liquid crystal. Unlike conventional active devices, it is possible to align liquid crystals without adding special materials such as polyimide or processes to form an alignment film. Therefore, it is an active device with a simplified process, high throughput, low cost, and high yield. In addition, the properties of the ferroelectric layer 14 are not adversely affected during alignment treatment steps such as rubbing, and the ferroelectric material 7114 also serves as an insulating film that blocks the DC voltage applied to the liquid crystal. There is. In this way, the active matrix display of tube 1 of the present invention does not require any special process to form an alignment film or an insulating film that blocks DC voltage.
It is a low cost, high fraction active matrix display.

As the alignment film of the counter substrate, an organic film such as polyimide, S
An iO obliquely deposited film may also be used.

As the gap agent, a cylindrical or spherical one made of plastic or glass material, or a scallop is used.

The first electrode 13, the second electrode 15, the electrode 17, and the ferroelectric layer 14 constituting the active device of the tube 1 of the present invention and the active matrix display of the tube 1 of the present invention using the active device are manufactured by sputtering, CVD, etc. , PVD method, vapor deposition method,
Can be formed by printing methods such as plating method, spin code method, offset printing, and screen printing, roll coating method, cast film method, dipping method, coating method, sol-gel method, hydrolysis precipitation method, spray method, LB method, etc. .

Ferroelectric layer 14, insulating substrate 12, first electrode 13, second
A coupling layer made of a surfactant, a silane coupling agent, or the like may be provided at the interface with the electrode 15 to increase adhesion strength.

Since the active device of the tube 1 of the present invention can be formed by the spin code method, it has uniform characteristics over a large area. Therefore, the active matrix display of the tube 1 of the present invention can display uniform images over a large area.

The materials used for the first electrode 13, second electrode 15, and electrode 17 constituting the active device of the tube 1 of the present invention and the active matrix display of the tube 1 of the present invention using the active device are not limited to ITO and Cr. , other metals, transparent electrodes such as SnO□, semiconductors, silicides, conductive polymers, conductive paints, and conductive materials such as superconducting materials may be used. The material to be used is not limited to glass, and may be inorganic materials such as ceramics, or organic materials such as plastic, acrylic, or vinyl fluoride, especially when a thin inorganic or organic material is used as the insulating substrate 12.16. , a flexible liquid crystal panel can be obtained.

The thickness of the glass substrate used as the insulating substrate 12 has nothing to do with the device characteristics of the active device of the present invention, so the insulating substrate 12 can be made thicker and stronger or thinner (lighter) without impairing the device characteristics. The thickness of the insulating substrate 12 can be freely selected.

The material used for the ferroelectric layer 14 used in the active device of the cylinder 1 of the present invention is not limited to the copolymer of VDF and TrFE, and may be other ferroelectric materials, such as B a
Peropskite ferroelectrics such as TiOs, PbTiOs, WOs, Rochelle salt ferroelectrics such as Rochelle salt, deuterium Rochelle salt, tartrate, KDP, phosphate, arsenate, potassium dihydrogen phosphate,
Dihydrogen phosphate alkaline ferroelectrics such as potassium dihydrogen phosphate.

Guanidine-based ferroelectrics such as GASH and TGS, potassium niobate, glycine sulfate, ammonium sulfate, sodium nitrite, potassium hexacyanoferrate (yellow blood salt), antimony iodide sulfide, or LiN
Amorphous ferroelectrics such as b Os, Li TaOz, Pb Ti Os, polyvinylidene fluoride and its copolymers, VDF and TrFE (tetrafluoroethylene)
B i4. TI3.012. FeB
-0 series, electret, etc. may be used in a single crystal or non-single crystal form, or a composite of two or more types of ferroelectric materials, or a composite with a paraelectric material may be used.
Inorganic ferroelectric materials such as aTiOs are characterized by large residual polarization and fast switching speed, while amorphous ferroelectric materials are characterized by the ease of obtaining a uniform ferroelectric layer over a large area. Since the body is obtained using the spin code method, it has the characteristic that it can be obtained uniformly over a large area at low cost. In addition, most ferroelectric materials have a
Temperature characteristics are stable because there is almost no change in dielectric constant or residual polarization.

In addition, a copolymer of VDF and TrFE is a colorless and transparent ferroelectric material, but dyes are added to a copolymer of VDF and TrFE or other materials to make a ferroelectric material that is not colorless and transparent. Alternatively, a ferroelectric material that is not colorless and transparent may be used as the ferroelectric layer 14 without adding anything. If a ferroelectric layer that is not colorless and transparent is used, pinholes etc. in the ferroelectric layer 14 may be detected by visual inspection. 0 ferroelectric layer 1 that can be discovered
4 acts as the active layer of the active device, so
Defects such as pinholes become active device defects. Therefore, defects such as pinholes greatly affect the yield of active matrix panels.

If pinholes can be detected through visual inspection, it will have a significant effect on improving yield, and at the same time, defective panels can be detected early and subsequent steps can be omitted. Therefore, using a ferroelectric layer that is not colorless and transparent is highly effective in providing a high-yield, inexpensive active matrix panel.

Dyes added to ferroelectric F114 include natural dyes such as ancient purple, curcumin, alizarin, calcumin, carminic acid, cochineal, and indigo, alizarin, indigo,
Synthetic dyes such as aniline, naphthalene, anthracene,
Direct dyes, basic dyes, mordant dyes, vat dyes, sulfur dyes, oxidation dyes, cold dyes, etc. are used. Further, other than the dye, anything may be added to the ferroelectric FJ 14 as long as it makes the first ferroelectric layer 14 not colorless and transparent.

Further, a material in which a ferroelectric material is held in an organic material such as polyimide may be used as the ferroelectric layer 14. The ferroelectric material used here is the ferroelectric material described above. The shape of these ferroelectric materials may be any shape such as spherical, cylindrical, conical, polyhedral, rod-like, etc.

Instead of polyimide in the ferroelectric layer 14, synthetic resins such as phenol resin, urea resin, polyamide resin, silicon resin/resin, vinyl resin, polyethylene resin, styrene resin, acrylic IB+ resin, nylon, vinyl, pine tar, Any organic material such as balsam, copal, amber, shellac, natural resin, rubber, fiber, organic insulating material, etc. may be used. For example, ferroelectric material containing BaT i Os in polyimide. Body layer 14 can be formed using simple and inexpensive equipment such as a spin cord method.

If the ferroelectric layer 14 is made only of BaTiOs, an expensive vacuum device is required to form it using a sputtering method or the like. In addition, by controlling the content of BaTiOs in polyimide, we can arbitrarily control the dielectric constant, light transmittance, remanent polarization, coercive electric field, rotation speed of spontaneous polarization, etc. of 1 ferroelectric material. It becomes possible to set. In FIGS. 1(a), (b), 4, and 5, the first electrode 13 forms a pixel electrode;
A ferroelectric layer 14 is provided so as to overlap with the first electrode 13, and the light passing through the first electrode 13 also passes through the ferroelectric layer 14.The ferroelectric layer 14 has a light transmittance. The higher the value, the higher the utilization of light and the brighter the display.
Being able to control the light transmittance of the ferroelectric layer by changing the content of T i O 3 has a great effect in obtaining a high light utilization rate and a bright display. Furthermore, since a voltage proportional to the residual polarization of the ferroelectric layer is applied to the liquid crystal, the residual polarization of the ferroelectric layer can be controlled by controlling the content of B a Ti Os in polyimide. This shows that the electric field produced by the ferroelectric layer can be controlled from the material side of the ferroelectric layer.These results greatly expand the degree of freedom in the design of active matrix displays, and are extremely effective in expanding the fields and range of applications of these displays. .

A ferroelectric material subjected to a poling process may be used as the ferroelectric layer 14. FIG. 6 shows hysteresis curves of the ferroelectric layer 14 before and after the poling process.Residual polarization Pr, Pr before and after the poling process 'is clearly p, '<
p, +, and has a large residual polarization and a clear coercive electric field after the poling process. Having a large residual polarization increases the voltage applied to the liquid crystal, and having a clear coercive electric field can reduce crosstalk in active matrix displays. It can be seen from FIG. 6 that in the ferroelectric layer 14 before the poling process, a larger electric field is required in order to reverse the spontaneous polarization. A large voltage is required to generate a large electric field. This creates problems such as the need for a special high-voltage circuit and increased power consumption (although these problems can be resolved by performing polling processing).

Furthermore, the poling process is particularly essential in active devices using ferroelectric layers that do not exhibit ferroelectricity unless the poling process is performed.

In order to perform the poling treatment on the ferroelectric layer 14, the method shown in FIG.
Using the first electrode 13 and second electrode 15 in a) and (b) as electrodes, an electric field of about ~400 KV/Cm is applied to the ferroelectric layer 14 at 80° C., at this time, The electric field applied to the ferroelectric layer 14 may be other than ~400 KV/cm, and the temperature, electric field application time, and atmosphere are not limited, or the voltage between the second electrode 15 and the electrode 17 in FIG. may be applied to perform polling processing.

The poling treatment may be performed by heating. As the poling treatment, one or both of the thermal electret method and the polarization inversion method may be used.

7(a) and 7(b) show the structure of the first active device of the present invention in which an alignment film is formed, FIG. 7(b) is a top view, and FIG. 7(a) is a top view, and FIG. 7(b) is a top view. It is a sectional view taken along AB. On the first active device of the present invention shown in FIGS. 1(a) and (b),
and an oriented JI119 made of polyimide.

VDF and TrFE used as ferroelectric layer 14
Since the copolymer is an organic substance, the solvent for polyimide (usually α-butyllactone, N
, N-dimethylacetamide), so it retains 111
If there is no 1m1B, the ferroelectric layer 1 will be
When the protective film 18 made of SiO2 is used, SiOx acts as a protective film and prevents the ferroelectric layer 14 from eluting and disappearing, since SiOx is insoluble in the polyimide solvent. be able to.

The protective film 18 is not limited to Sin, but may also be made of SiN.
Inorganic materials such as x, 5iON, and Si, organic materials such as Teflon, shellac, glass, etc. may be used, and the formation methods include spuck method, vapor deposition, spin code method, and CVD.
method, roll method, dipping method, printing method, coating method, etc. In addition, silicon compounds [RnS i (OH) 4-
The method of forming a 5iOi film by dissolving 5iOi in an illuminating solvent such as alcohol or ester and then heating it can easily form a uniform 5iOi film over a large area, so it is suitable for large area flat displays. This method is particularly effective as a method for forming active devices.

Further, the alignment film is not limited to polyimide, and may be an obliquely vaporized SiO film or other organic materials.

Figures 8(a), (b), (c), and (d) show the circuits per pixel of the active matrix display shown in Figure 5, and explain the basic operating principle per pixel. The capacitors of the eight ferroelectric layers 14 and the liquid crystal 21 are connected in series. In FIG. 8(a), a positive voltage sufficient to reverse the spontaneous polarization in the ferroelectric layer 14 is applied to the G terminal within the selection period of a certain field, so that almost all of the spontaneous polarization points downward. It shows the state of being. In this way, the write operation is completed by aligning the spontaneous polarization in one direction. After this, the G terminal is kept at ground potential as shown in FIG. 3(b). This is a holding state, that is, a non-selection period state. In the holding state, the ferroelectric layer 14 has −3,·p, (Sr: area of the ferroelectric layer 14, P: remanent polarization of the ferroelectric layer 14; remanent polarization is the polarization applied to the ferroelectric material) Even after the voltage is turned off, the surface charge is retained on the ferroelectric surface with a memory property due to spontaneous polarization), and the free charge distribution between the liquid crystal 21 and the ferroelectric layer 14 is ffi+QLc.

The liquid crystal 21 has Q Lc = Ct, cV LC, and the voltages vF, V applied to the ferroelectric layer 14 and the liquid crystal 21
Since LC is equal, Qr=-Sr-P, +QLC=CFVF ■Q L
c= −Ct, eV t, c
■vF=■Lc ■QLC
: Amount of charge held by the liquid crystal 21 CLc: Capacity of the liquid crystal 21 Q7: Amount of charge held by the ferroelectric material ff1114 C2: Capacitance of the ferroelectric layer 14, which is given by (1), (2), and (2).

In this way, the voltage shown by the formula (2) is maintained in the liquid crystal 21 during the non-selection period.

(2) From the formula, the voltage vt and e applied to the liquid crystal 21 is P.

Since it is proportional to , the ferroelectric FJ1 is
Increasing P of 4 has a tremendous effect in obtaining an active device with a large writing ability to the liquid crystal 21.

In addition, since P is known to have memory properties, there is no leakage current caused by the ferroelectric layer 14, and the active device has a large write capacity and no leakage current, exhibiting good VLC retention characteristics. provides sharp, high-contrast images.

In the next field, as shown in Figure 8(C), a negative voltage is applied to the G terminal within the selection period, and the spontaneous polarization is reversed.
It is shown facing upward. During the subsequent non-selection period, the voltage and charge are maintained as shown in FIG. 8(d), and voltages and charges having polarities opposite to those of equations (1), (2), and 0 are applied to the liquid crystal 21 and the ferroelectric material r614 and are maintained.

(2) As is clear from the formula, VLC is proportional to Pt. Therefore, ±■. VL (can be controlled by changing the size of and Pr value. Particularly when the ferroelectric layer 14 is lined with a non-monocrystalline ferroelectric material, especially a polycrystalline ferroelectric material, , Pr can be easily controlled. This is ±Va
This shows that gradation display of the liquid crystal 21 is possible by changing the size of . Also, if Pr is zero or Pr gives VLc smaller than the threshold voltage of the liquid crystal,
By selecting the value of vo, erasing operations are possible.

When Pr is zero, Vt and c=O from equation (2). In this way, the writing and erasing states of the liquid crystal 21 can be arbitrarily controlled by adjusting the magnitude of ±Va.

In an actual active matrix display, a data voltage (1) is applied from the ground terminal in FIG. 8 during a non-selection period, and is applied to the liquid crystal 21. In order to suppress noise, it is preferable that CLe/CF be large, and preferably small (both 1 or more, preferably 10 or more).

Also, among the voltages ±vo applied to the G terminal within one selection period, a larger voltage is desirable because it is used to invert the polarization of the ferroelectric layer 14, that is, to perform a write operation.
t/Cr is preferably larger, and is at least 1 or more,
It is desirable that it be 10 or more if possible.

FIG. 9 shows an equivalent circuit of the active matrix display shown in FIG.
2, A3, and A4 form a selection line group, and the second electrode 15 of the substrate forms a data line group as B1, B2, and B3. Each pixel is formed by serially coupling a liquid crystal 21 and a ferroelectric layer 14. Here, the electrodes 17 may be used as a data line group, and the first electrodes 15 may be used as a selection line group.

Fig. 10 shows the driving method of the equivalent circuit of the active matrix panel shown in Fig. 9. Fig. 10 and A1 of Fig. 9
．． A2, A3, A4 and Bl, B2, B3 correspond to each other. A1, A2, A3. A4 selects pixels to write data in the horizontal direction, and B1, B2, and B3 send data voltages to each pixel. ■. is the selection voltage, and ■ is the data voltage. CLL)C, almost all of the voltage applied between the selection line and the data line is applied to the ferroelectric layer 14.

Now, consider a case where AI is selected in a certain field. The series connection between the ferroelectric layer 14 of the pixel and the liquid crystal 21 in which data corresponding to ON and OFF of the liquid crystal 21 is written is VCON)=v0+■1 V (OFF)=V, respectively. −■ voltage is applied. Also, for the series combination of both lines that are not selected.

■(Not selected) = ±V.

voltage is applied. At this time, V (ON), V
(OFF) is B6, EC and V (ON
)≧drE−V(OFF)=dFEc. Here, d is the thickness of the ferroelectric layer. At this time, the spontaneous polarization of the ferroelectric layer of the selected pixel and the unselected pixel are respectively shown in FIG.
) and (d), voltages corresponding to the respective residual polarizations are applied to the liquid crystal, and the liquid crystal takes on and off states.

When the selection period of Al ends, A2 and A3 are sequentially selected in the order, and data is written to each pixel (0) When the selection period ends, a non-selection period begins.

When selecting Al again after one field period has passed,
In the ferroelectric layer 14 of the pixel corresponding to ON and OFF, V (ON) = -V DV, <-d FE.

V C0FF) =-V, +V, =-d,
A voltage of EC is applied, and a voltage of ■(non-selection)=±V is applied to the ferroelectric layer of the unselected line. At this time, the spontaneous polarization of the ferroelectric layer of the selected pixel and the unselected pixel becomes as shown in FIG. 3(C) and (d), respectively, and an electric field corresponding to the respective residual polarization is applied to the liquid crystal. , the liquid crystal is in on and off states, and AC driving is performed with a two-field cycle. Here, V(OFF) does not necessarily have to be -d-Ec, and even at other voltages, the light transmittance of the liquid crystal is -d r E
A voltage other than -d r E e may be set to V (OFF) as long as it is not significantly different from when c is applied.

In the first method of driving an active device of the present invention, Vo, ■, is determined as follows.
The driving method for this active device uses the driving method shown in FIG. 10. The ferroelectric layer 14 is made of a copolymer of VDF, T, and FE, and the reversal speed of spontaneous polarization is strongly dependent on the electric field. , coercive electric field (~50 M V/m)
In an electric field of
．． If it is difficult to operate the panel using a coercive electric field because it is too slow than 7 ms ec), Vo, 1 is determined as follows.

As shown in FIG. 11, the spontaneous polarization reversal speed S of the copolymer of VDF, T, and FE is strongly present in the electric field applied to the copolymer, and the coercive electric field (~50 MV/m )'cs is ~1 SeC.

FIG. 12 shows the dependence of the electric displacement in the copolymer over time on the applied electric field strength. Here δD
/δlog(τ) indicates that the spontaneous polarization has been reversed by about half at the time of the peak, and at the time corresponding to the right base of each peak, the spontaneous polarization is almost completely reversed at that time. It shows that it has been reversed. Here, the voltage of V(OFF) is adjusted so that the peak position of the graph of δD/δlog(t) matches the time length of the selection period, and the time length of the selection period and δD/δ1og(t,
) so that the right hem of the graph matches V (ON)
In other words, with V (ON) determined in this way, almost all of the spontaneous polarization is reversed within the selection period, so the voltage determined by the formula is applied to the liquid crystal, and the data is is written. Also, V
(OFF), the spontaneous polarization in the ferroelectric layer is reversed by about half within the selection period, so the spontaneous polarization in the ferroelectric layer is v(ON).
Since it is smaller than that determined by , a smaller voltage is applied to the liquid crystal than when it is (ON).

In this case, data can be erased even if the spontaneous polarization is not exactly half reversed, and ■(erasure) can be expressed as δD/δlog(
It is not necessarily necessary to match the peak of

The voltage applied to the ferroelectric layer 14 during the selection period is V (
Ec in both the ON) and V (OFF) states.
, dr, that is, the liquid crystal is turned on and off by satisfying the following conditions. Here, Ec and d- are the coercive electric field and film thickness of the ferroelectric layer 14.

During the holding period, ±V1 is applied to the ferroelectric layer, but care is taken to prevent spontaneous polarization reversal during the field period.
, from Figures 11 and 12, that is,
±■, the reversal speed of spontaneous polarization when applied should be slower than the l field period.

Furthermore, gradation display can be performed as follows. If a data voltage V smaller than the data voltage V1 is used, the voltage ■ (gray scale) at the time of selection for gray scale display is: ■ (gray scale) 1 = V, +V! I<IV (ON) IV (gradation) 1=V o + V * I > I V (OF F )
Therefore, the amount of reversal of spontaneous polarization within the selection period is V (
ON) (7) Time is low, V (OFF) (7) B
! It's more than that. Then, the residual polarization P, takes the intermediate value of Pr when V (ON) and V (OFF) are applied.
Since IVLC is proportional to P, VLe is determined according to Pr. Gradation display is possible in this way, and ■
It is possible to display as many gradations as there are potential types.

Instead of applying only one of V (ON) and V (OFF) + 7) within the selection period, apply both,
Gradation display is also possible by changing the application time distribution of both.

Further, as shown in FIG. 10, if the common potentials αl and α2 are changed by V and −V for each field, the maximum voltage used becomes vo+vl, and the maximum voltage can be lowered. Therefore, since there is no need to use a special high-voltage circuit, inexpensive general-purpose circuit components can be used, and an active matrix display using an inexpensive drive circuit can be provided. Also, at this time, the common voltage a
1. The difference in α2 is not necessarily ■. -vl does not have to be.

In Fig. 10, the common potential αl is set for each field.
, α2 was changed, but it was changed every selection period,
Alternatively, the common potential may be changed every selection period of a plurality of numbers, so that there are pixels in which the polarity of the voltage written to the liquid crystal 21 is different in one screen within 1|field.

A method of driving the active matrix display of the tube 2 of the present invention will be described below. When the spontaneous polarization reversal speed S of the copolymer of VDF, T, and FE is left in a state where no voltage is applied, it shows a change as shown in FIG. 13 with respect to the elapsed time tw after the poling process, that is, tS increases with tw, and if tS becomes longer than the selection period, display as an active matrix display becomes impossible8 For example,
Assuming 400 scanning lines and estimating using Figure 13, the selection period is 1 | field period (~16.7 m
5ec) divided by the number of scanning lines, approximately 40
It becomes μsec. From FIG. 13, when tw is about 5 minutes, -cS becomes 40 μsec. Therefore, it becomes impossible to display after 5 minutes have passed after the polling process. However, even if the voltage is continued to be applied after the polling process, there is no increase in S.

FIG. 14 shows a second method of driving an active matrix display of the present invention.

As shown in FIG. 14, these problems can be solved by providing an initialization period immediately before the start of display recommendation. During the initialization period, a voltage of ±(V o +V + ) is applied to all pixels, and a polling process using an electric field is performed. Here, vo+vl is the thickness d of the ferroelectric layer so that a larger electric field than the coercive electric field E is applied to the ferroelectric layer. +V is selected. Since spontaneous polarization is reversed by applying an electric field higher than the coercive electric field, efficient poling processing is performed. In this way, by applying an electric field higher than the coercive electric field to the ferroelectric layer immediately before the start of the display operation and returning it to the state immediately after the poling process, it is possible to reduce the deterioration in display image quality caused by the increase in τS over time. It is possible to always obtain a clear, high-contrast display image.

In FIG. 14, the voltage applied during the initialization period may be any voltage and is not limited to ±(VO+V+). Also, during the initialization period, the ferroelectric layer almost recovers to the state immediately after the first poling process. ±(V O+
Although the voltage V l ) was applied for l positive and negative cycles, the number of cycles of the applied voltage may be any number and is not limited to one.

The absolute value of the voltage applied to the scanning line and data line during the initialization period does not have to be a single value, such as Ivo+v+l. A value may also be used.

15(a) and 15(b) show other configurations of the first active device according to the present invention, FIG. 15(b) is a top view, and FIG. 15(a) is a top view of the first active device according to the present invention. FIG. 8 is a sectional view taken along line 8-B. A first electrode 13 made of Cr is provided on an insulating substrate 12 made of a glass substrate, and a ferroelectric layer 1 made of a copolymer of VDF, T, and FE is provided on the first electrode 13.
4 is provided, and the ferroelectric F! A second electrode 15 made of ITO is provided on the electrode 14 . First electrode 13
In this structure, the ferroelectric layer 14 sandwiched between the second electrode 15 and the second electrode 15 acts as an active layer of the active device. Therefore, voltage can be applied efficiently to the liquid crystal.

FIGS. 16(a) and 16(b) show the configuration of the second active device according to the present invention, FIG. 16(b) is a top view,
Figure (a) is a sectional view taken along line AB in figure (b). A first electrode 13 made of ITO is provided on an insulating substrate 12 made of a glass substrate, and a ferroelectric material 1'! made of a copolymer of VDF, T, and FE is provided on the first electrode 13.
14 and a second electrode 15 made of Cr are provided in the same shape. The portion of the ferroelectric layer 14 where the first and second 1 are sandwiched between the poles 13 and 15 acts as an active layer of an active device (see FIGS. 16(a) and 16(b)).
When the active device shown in FIG. 1 is used instead of the active device shown in FIGS. 1(a) and 1(b) to construct the active matrix display shown in FIG. 4.5, the following effects occur. Figure 16(a),(b)
In the pixel electrode, there is no ferroelectric material FJ14 having an electro-optic effect on both the upper and lower sides of one pixel electrode formed by the first electrode 13 in a region not in contact with the ferroelectric layer 14, so that light passing through the liquid crystal panel is not present. Since there is no change in the amount of transmitted light due to the zero ferroelectric FJ14, which is determined only by the electro-optic effect of the liquid crystal, a clear image with high contrast can be obtained.

The configuration of the third active device of the present invention is shown in FIG.
) and (b), FIG. 17(b) is a top view, and FIG.
) is a sectional view taken along line A-B in FIG. An island-shaped ferroelectric layer 14 made of a copolymer of VDF, T, and FE is provided on an insulating substrate 12 made of a glass substrate.
A first electrode 13 made of Cr is provided on the ferroelectric layer 14, and the ferroelectric 1! A second electrode 15 made of ITo is provided to cover a portion of F 14.

That is, the ferroelectric layer 14 is provided so as to connect the first and second electrodes 13.15. With this structure, the first and second electrodes 13,15 do not overlap in the vertical direction, so there is no short circuit between the two electrodes due to defects in the first ferroelectric layer 14.

Therefore, defects in active devices due to short circuits,
That is, pixel defects can be removed in principle. This has a tremendous effect in providing clear and high-quality display quality.

Other configurations of the active device of the tube 3 of the present invention are shown in FIGS. 18(a) and 18(b), FIG. 18(b) is a top view, and FIG. 18(a) is a top view, and FIG. 18(b) is A-B. FIG. A first electrode 13 made of Cr and a second electrode 15 made of ITO are provided on an insulating substrate 12 made of a glass substrate, and an island-shaped ferroelectric material made of a copolymer of VDF, T, and FE is provided. A layer 14 is provided connecting the first and second electrodes 13.15.

In Figures 17.18 (a) and (b), the first and second
If different materials are used for the electrodes 13 and 15, three photo steps are required, but if the same material is used, the active device of the tube 3 of the present invention can be formed in two photo steps.

Since the active devices shown in FIGS. 17.18 (a) and (b) are provided parallel to the insulating substrate 12, they are thick, that is, have small capacitance.
As shown in Figure 8, the capacitance width W of the ferroelectric layer 14 is W=tOμm, the length dr=LLLm, and the thickness L=l.
0 μm, dielectric constant EF = IO1 Width x = 90 μm, length y = 100 μm, thickness d = 7 μm, and relative permittivity εLc = 10 of a pixel composed of liquid crystal, capacitance C of the ferroelectric layer and pixel
F, the ratio of CLC is.

Fwdr and CF (CLL. Therefore, most of the voltage applied to the series connection of the ferroelectric layer and the pixel is applied to the ferroelectric layer. Under these conditions, the active device of the present invention operates by controlling the arrangement electric field of the spontaneous polarization of the ferroelectric layer 14, so it is effective for lowering the power supply voltage, increasing switching speed, reducing crosstalk, etc., and displaying clear and high contrast images. It has a tremendous effect on obtaining.

19(a) and 19(b) show the configuration of the active device of the cylinder 4 of the present invention, FIG. 19(b) is a top view, and FIG. 19(a) is a top view, and FIG. FIG. A ferroelectric layer 14 made of a copolymer of VDF, T, and FE is provided on an insulating substrate 12 made of a glass substrate.
A first electrode 13 made of Cr and an IT on the ferroelectric layer 14
In the fourth active device of the present invention, in which a second electrode 15 made of O is provided, the ferroelectric layer 14 between the first and second electrodes 13.15 acts as an active layer.

20(a) and 20(b) show other configurations of the active device of the tube 4 of the present invention, FIG. 20(b) is a top view, and FIG. 20(a) is a top view, and FIG. It is a sectional view at -B. A first electrode 13 made of Cr and a second electrode 15 made of ITO are provided on an insulating substrate 12 made of a glass substrate. VDF and T on the first electrode 13 and the second electrode
, and a ferroelectric layer 14 made of a copolymer with FE. Further, since the ferroelectric layer 14 is formed after the first and second electrodes 13.15 are formed, no damage occurs to the ferroelectric layer 14.

The active device of the cylinder 4 according to the present invention is great if the first and second electrodes 13 and 15 are made of the same material and formed in the same process! * indicates the 1 process, and if they are not formed in the same process, they can be formed in the 2 photo process.

The active device of the cylinder 4 of the present invention uses the ferroelectric layer 14 in a direction parallel to the insulating substrate 12, so it has a large thickness, that is, a small capacitance, like the third active device.

FIG. 21 shows a top view of a part of an active matrix display using the active device of tube 4 of the present invention, and shows a ferroelectric layer made of a copolymer of VDF, T, and FE formed on a glass substrate. , a first electrode 13 made of Cr
, a liquid crystal is held between a substrate consisting of a second electrode 15 made of ITO and a counter substrate formed of an electrode 17 made of ITO on an insulating substrate made of a glass substrate, and the substrate,
Pixels made up of respective electrodes on the counter substrate are arranged in a matrix.

In FIG. 21, Ct b>t and the arrangement is such that no reversal of spontaneous polarization occurs in a and b, so no crosstalk occurs in the vertical and horizontal directions.

Also in the active device of the cylinder 4 of the present invention, since the first and second electrodes 13.15 do not overlap in the vertical direction,
No defects occur due to short circuits.

22(a) and 22(b) show other configurations of the active device of the cylinder 4 of the present invention, FIG. 22(b) is a top view, and FIG. 22(a) is a top view, and FIG. It is a sectional view at -B. VDF, T, and F are placed on an insulating substrate 12 made of a glass substrate.
A ferroelectric layer 14 made of a copolymer with E is provided, and a first electrode 13 made of Cr and a second electrode 15 made of ITO are provided on the ferroelectric layer 14. 1st
A part of the electrode 13 protrudes toward the second electrode 15, and the ferroelectric layer 14 between this protrusion and the second electrode 15
acts as the active layer of the active device (with such a configuration, the capacitance of the ferroelectric layer 14 between the first and second electrodes 13.15 becomes substantially smaller.
), the distance t, t2 between the first and second electrodes of the active layer and the non-active layer satisfies t2>t. Therefore, Fig. 20 (a
), (b), the capacitance of the ferroelectric material N14 is smaller than the structure in which the ferroelectric layer 14 between the first and second electrodes 13, 15 all functions as an active layer.

Further, a structure in which a protrusion is formed on the first electrode 13 as shown in FIGS. 22(a) and (b) using the active device of the tube 4 of the present invention shown in FIGS. 20(a) and (b) You can also do it.

23(a) and 23(b) show the configuration of the active device of the tube 5 of the present invention, FIG. 23(b) is a top view, and FIG. 23(a) is a top view, and FIG. FIG. A first layer made of ITO is placed on an insulating substrate 12 made of a glass substrate.
VDF and T are provided on the electrode 23.
, and a ferroelectric layer 14 made of a copolymer with FE. In the eighth active device, the first electrode 13 also serves as the second electrode 15.

One photo process is necessary to construct the active device of the tube 5 of the present invention. Since the electrode 23 has a large area and is shaped to reduce sheet resistance, wiring delay due to the electrode 23 can be reduced. This has a tremendous effect in forming a high-quality, clear active matrix liquid crystal panel that is uniform within the display surface.

24(a) and 24(b) show the configuration of the active device of the tube 6 of the present invention, FIG. 24(b) is a top view, and FIG. 24(a) is a top view, and FIG. FIG. A first layer made of ITO is placed on an insulating substrate 12 made of a glass substrate.
electrode A22, first electrode B20. the first electrode A;
A ferroelectric F! made of a copolymer of VDF, T, and FE on B22.20. 14. A second electrode 15 made of Cr is provided so as to be connected to the first electrode B20 through a contact hole provided in the ferroelectric FJ14. In FIGS. 24(a) and 24(b), the insulating substrate 1
2, in the order of second electrode 15, ferroelectric layer 14, first electrode A, B22.20, that is, first electrode A,
The positional relationship between B22.20 and the second electrode 15 may be reversed.

25(a) and 25(b) show other configurations of the active device of the tube 6 of the present invention, FIG. 25(b) is a top view, and FIG. 25(a) is a top view, and FIG. It is a sectional view at -B. A first electrode A22 made of ITO, a first electrode B20 on an insulating substrate 12 made of a glass substrate, and a ferroelectric made of a copolymer of VDF, T, and FE on the first electrodes A and B22.20. A second electrode 15 made of Cr is provided so as to be connected to the first electrode B20 through a contact hole provided in the body layer 14 and the ferroelectric layer 14. In the active device shown in FIGS. 25(a) and 25(b), the first electrode B20 has a two-layer structure connected to the second electrode 15 via a contact hole with a large area. Wiring resistance can be reduced.

The active devices shown in FIGS. 25(a) and 25(b) also have the same positional relationship between the first electrodes A and B 22.20 and the second electrode 15 as in the active devices shown in FIGS. You may also use it in reverse.

26(a) and 26(b) show the configuration of the active device of the tube 7 of the present invention, FIG. 26(b) is a top view, and FIG. 26(a) is a top view, and FIG. FIG. A ferroelectric layer 14 made of a copolymer of VDF and TrFE is formed on an insulating substrate 12 made of a glass substrate, and the ferroelectric HI
3, a first electrode A22 made of ITO, a second electrode B
In the seventh active device of the present invention, a ferroelectric layer 1 is provided on an insulating substrate, and a second electrode 15 is provided in contact with the first electrode B20.
4. The first electrodes A, B, 22.20 and the second electrode 15 do not need to be formed in this order, and may be formed in any order. Wiring resistance can be reduced by forming the electrode B20 long in the longitudinal direction of the second electrode 15 and forming a two-layer structure with the second electrode 15.

In Figures 24.25.26 (a) and (b), the first
Since the electrode A22 and the second electrode B20 are formed in the same process, the distance between the first electrodes A, B, and 22.20 is always constant regardless of expansion and contraction of the insulating substrate 12, mask alignment error, etc. It is maintained. This is the electrode A of 24.25.26
, B22.20, the same electric field is applied to the ferroelectric material existing between the two electrodes. As shown in Figure 3(a), the reversal of the spontaneous polarization of the first ferroelectric is determined by the electric field applied to the ferroelectric, so the distance between the first electrodes A, B, 22.20 is kept constant. Maintaining the same value has a great effect on uniformly forming the first active device of the present invention over a large area with good reproducibility.

In the active devices shown in FIGS. 24 to 26 (a) and (b), the protrusion of the first electrode B20 and the first electrode A22 are similar to those shown in FIGS. 22 (a) and (b). The ferroelectric layer 14 between the two functions as an active layer, and there is no need to form a protrusion.

The first tube used in the active device of tubes 2 to 7 of the present invention
The materials used for the electrode 13, the second electrode 15, the insulating substrate 12, and the ferroelectric layer 14, and the same material as that used in the active device of the present invention tube 1 as the forming method,
Similarly, the formation method may be changed to the first electrodes A, B, 22.2o, and the first and second electrodes 1 of the first active device.
The same materials and forming method as in 3.15 may be used.

15.20.23.24.25 Also in the active device shown in FIGS. 15(a) and 25(b), the ferroelectric layer 14 may be used as an alignment film.8 The ferroelectric layer 14 is applied to the liquid crystal. It also serves as an insulator that cuts off DC voltage.

The active devices of tubes 2 to 7 of the present invention are used in place of the active devices of tube 1 of the present invention to form a liquid crystal panel as shown in FIG. 4.5, an active matrix display of tubes 2 to 7 of the present invention. Also, in that case, the 7th
Protective film 18, orientation 11 as shown in Figures (a) and (b)
Similarly, the film thickness of the ferroelectric layer 14 may be determined by the thickness of the first electrode 13, the second electrode 15, the electrode 23, and the first electrode provided between the insulating substrate 12 and the ferroelectric layer 14. Electrode A2
2. The film thickness may be greater than that of the first electrode B20.

The active device of cylinders 1 to 3 of the present invention is a ferroelectric layer 14.
Although the capacitance is relatively large because the ferroelectric layer 14 has a thin film thickness, a large electric field is applied to the ferroelectric layer 14. Therefore, it is particularly effective when using an organic ferroelectric material with a small dielectric constant and a large coercive electric field.

The active device of the present invention tubes 4 to 7.91|O is a ferroelectric F! Since the length in the in-plane direction of the insulating substrate 12 of 14 is used as the thickness, the capacitance is small, but the ferroelectric layer 14
It is difficult to apply a large electric field to , so it is particularly effective when using an inorganic ferroelectric material with a large dielectric constant and a small coercive electric field.

Also in the active matrix display using the active devices according to the second to seventh aspects of the present invention.

The driving method used for the first active device can be applied.

[Effect of the invention] The present invention will be explained in detail below.

(1) Since the active device of the present invention uses a ferroelectric layer that has a memory property of 1 surface charge as the active layer, there is no leakage current of the device itself, and the retention property is very excellent, resulting in sharp images. High contrast images can be provided.

(2) The ferroelectric layer, which is the active layer of the active device of the present invention, is formed by an extremely simple method called the spin code method, and the thickness of the ferroelectric layer over a large area is It is an active device with uniform characteristics over a large area because it has the characteristics of uniform film quality. Therefore, it is an active device that can display uniform images over a large area.

(3) The number of photo steps required to form the active device of the present invention is very small, 1 to 3 times, and the ferroelectric layer, which is the active layer, is formed by an extremely simple process called the spin code method. It is a low-cost active device with high fractionation.

(4) Since the active device of the present invention uses a ferroelectric layer provided in parallel within the upper surface of an insulating substrate, there are no defects due to short circuits in the ferroelectric layer, and the capacitance is small.

(5) The ferroelectric layer of the active device of the present invention is formed by a spin code method and has a thickness that is thicker than that of the electrode between the ferroelectric layer and the insulating substrate. It is a highly reliable active device with good performance and high yield.

(6) The active matrix display of the present invention includes:
Since there is no need to use a special process to form an alignment film or an insulating film for blocking DC voltage, the cost is low and the yield is high.

(7) When the active matrix display driving method of the present invention is used, the reversal speed of spontaneous polarization is much slower than the selection period (<16.7 m5ec) in an electric field of a coercive electric field, especially in organic ferroelectric layers. In an active matrix display configured using an active device using a dielectric layer, display operation as a display becomes possible.

(8) By using the active matrix display driving method of the present invention, there is no deterioration in display quality due to an increase or decrease in the speed of spontaneous polarization reversal during non-voltage application, and it is possible to always provide clear, high-contrast images. .

[Brief explanation of the drawing]

FIGS. 1(a) and (b) are a sectional view and a top view of the first active device of the present invention, FIG. 2 is a sectional view of a conventional active device, and FIGS. 3(a), (b), ( c) and (d) are diagrams showing the hysteresis curve and spontaneous polarization arrangement of a ferroelectric material, Figure 4 is a cross-sectional view of a liquid crystal panel, Figure 5 is a top view of a part of an active matrix display, and Figure 6. 7(a) and 7(b) are cross-sectional views and top views of the first active device of the present invention in which an alignment film is formed, and FIG. a
) to (d) are equivalent circuit diagrams per pixel of an active matrix display, FIG. 9 is an equivalent circuit diagram of an active matrix display, FIG. 10 is a diagram showing the driving method of the first active matrix display of the present invention, and FIG. Figure 11 shows the relationship between the spontaneous polarization reversal speed and electric field strength of a copolymer of VDF and TrFE, and Figure 12 shows the relationship between VDF and TrFE copolymers.
Figure 13 is a diagram showing the time change of δD/δ10g (t) of a copolymer of VDF and TrFE, and Figure 13 is a diagram showing the relationship between the reversal speed of the copolymer of VDF and TrFE and the elapsed time after poling treatment. FIG. 14 is a diagram showing the driving method of the second active matrix display of the present invention, and FIG. 15 (a
) and (b) are cross-sectional views and top views of other configurations of the active device of the tube 1 of the present invention, and FIGS. 16(a) and (b) are cross-sectional views and top views of the active device of the tube 2 of the present invention. , FIGS. 17(a) and 17(b) are cross-sectional views and top views of the active device of the inventive tube 3, and FIGS. 18(a) and (b) are views of other configurations of the active device of the inventive tube 3. Cross-sectional view, top view, 1st
9(a) and (b) are cross-sectional views and top views of the active device of the inventive tube 4, and FIGS. 20(a) and (b) are cross-sectional views of other configurations of the active device of the inventive tube 4. , top view,
FIG. 21 is a top view of a part of an active matrix display using the active device of tube 4 of the present invention;
2(a) and 23(b) are a sectional view and a top view of other configurations of the active display of the cylinder 4 of the present invention, and FIG. 23(a), (
b) is a sectional view and a top view of the active device of the tube 5 of the present invention, and FIGS. 24(a) and 24(b) are a sectional view and a top view of the active device of the tube 6 of the present invention, and FIG. 25(a) , (b) is a sectional view of another configuration of the active device of the present invention cylinder 6,
The top view and FIGS. 26(a) and 26(b) are a sectional view and a top view of the active device of the tube 7 of the present invention. 1 ・ ・ 2 ・ ・ 3 ・ ・ 4 ・ ・ 5 ・ ・ 6 ・ 7 ・ ・ 8 ・ ・ 9 ・ ・ 10 ・ ・ 11 ・ ・ l 2 ・ ・ 13 ・ ・ l 4 ・ ・ 15 ・ ・ 16 ・ ・17 ・ ・ ・Glass substrate, gate electrode, and gate are out! lIl! - Drain electrode - Source electrode - Train region - Pixel electrode - Electrode - Glass substrate - Channel amorphous Si - Lease region - Insulating substrate - First electrode - Ferroelectric layer - Second electrode - Insulating substrate - Electrode 18 ・ l 9 ・ 20 ・ 21 ・ 22 ・ 23 ・ C・ D ・ E ・ F ・ G ・ H Substrate/LCD/Lower substrate/Upper substrate Applicant Seiko Epson Co., Ltd. Agent Patent Attorney Masayoshi Kamiyanagi (and 1 other person) <'ry) Figure 1 Figure 2 (Phantom computer Figure 3 Figure 6 Figure CL) tb Figure 8 (Ku) ξb) Figure 7 7 I-n11.1 1ρ t〆/ρ' 7- (-;su,) Fig. 13 (Ln (ton ((L) cb) Fig. 17 4L pole (g) of Takuma 1 (IL) and t2 Fig. 20 ζb] (Magazine (a-) (Shin Fig. 24 CL) Item 2 (4, Figure 25)

Claims (11)

[Claims] (1) A first electrode formed on an insulating substrate, a ferroelectric layer provided to cover the first electrode and the insulating substrate, and a ferroelectric layer provided so as to overlap with the first electrode. An active device comprising a second electrode provided on the layer. (2) A first electrode provided on an insulating substrate, a ferroelectric layer formed on the first electrode, and a second electrode having the same shape as the ferroelectric layer. active device. (3) A first electrode and a second electrode formed on an insulating substrate, and an island-shaped ferroelectric layer provided to connect the first electrode and the second electrode. Features an active device. (4) A ferroelectric layer provided to cover an insulating substrate, and a first electrode and a second electrode provided on the ferroelectric layer or between the insulating substrate and the ferroelectric layer. An active device characterized by: (5) An active device comprising an electrode provided on an insulating substrate and a ferroelectric layer provided on the electrode. (6) A ferroelectric layer provided on an insulating substrate, a contact hole provided in the ferroelectric layer, and a first layer connected via the contact hole and provided to sandwich the ferroelectric. An active device comprising an electrode B, a second electrode, and a first electrode A provided in the same plane as the first electrode B. (7) a first electrode A and a second electrode B provided on an insulating substrate; an island-shaped ferroelectric layer provided to connect the first electrode A and the first electrode B; An active device comprising a second electrode provided in contact with the first electrode B. (8) The film thickness of the first electrode or the second electrode or the electrode or the first electrode A or the first electrode B provided between the insulating substrate and the ferroelectric layer is greater than the film thickness of the ferroelectric layer. 8. The active device according to claim 1, or 2, or 3, or 4, or 5, or 6 or 7, characterized in that it is thin. (9) An active matrix display characterized in that the active devices according to item 1, 2, 3, 4, 5, 6, or 7 are arranged in a matrix. (10) The active devices according to item 1 or 2 or 3 or 4 or 5 or 6 or 7 are arranged in a matrix to hold a material having an electro-optic effect. A selection voltage ±V_0 is sequentially applied to each selection line of the selection line group within one field period, and a data voltage ±V_0 is applied to the data line group.
In an active matrix display driving method that applies V_1, the absolute value of the difference between the selection voltage ±V_0 and the data voltage ±V_1 |V_0−V_1| is C_L_
C/(C_L_C+C_F) |V_0-V_1|>E_
C・d_F where E_C: coercive electric field of ferroelectric layer d_F: film thickness of ferroelectric layer C_F: capacitance of ferroelectric layer per pixel C_L_C: capacitance of material with electro-optic effect per pixel A method for driving an active matrix display characterized by satisfying the following. (11) The active devices according to item 1 or 2 or 3 or 4 or 5 or 6 or 7 are arranged in a matrix to hold a material having an electro-optic effect. An active matrix display driving method for driving an active matrix display comprising applying a voltage higher than a coercive electric field to a ferroelectric layer during a certain period immediately before the start of a display operation.