JP2789602B2 - Active matrix device and driving method thereof - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an active matrix device used for a display device such as a liquid crystal display and a driving method thereof.

[Summary of the Invention] The present invention relates to an active element, an active matrix substrate, an active matrix device, and a method for driving the same, which are provided with a ferroelectric as an active layer, and can provide a clear and high-contrast image at low cost.

[Prior art] Conventionally, SID (Society For Information Display) 1986
Active elements such as those described in Symposium Digest pp. 296-297 were known. As shown in FIG. 2, a lower substrate G formed on a glass substrate 1 and including a gate electrode 2, a source region 11, a drain region 6, a source electrode 5, and a drain electrode 4, and a glass are shown in FIG. The liquid crystal C is held between the substrate 9 and the upper substrate H on which the electrodes 8 are formed.

[Problems to be Solved by the Invention] However, the conventional active element has the following problems. That is, the image information applied to the source electrode 5, that is, the data potential, is turned on and off by the gate electrode.
The data voltage is transmitted to the liquid crystal C held between the pixel electrode 7 and the pixel electrode 8 through 10, and the data voltage is held as the charge amount of the liquid crystal C. However, the charge of the liquid crystal C decreases with time due to a leak current of the thin film transistor and the like. That means that the data voltage is lost over time. Therefore, it has been difficult to obtain a clear and high-contrast image. In addition, the conventional active element has a complicated structure and requires a complicated and long manufacturing process, so that it is difficult to provide uniform yield characteristics over a large area with a low yield, a high cost, and the like. Met. Further, conventional active matrix substrates and active matrix devices using active elements have the same problem.

Therefore, the present invention is to solve such a conventional problem, with a high yield in a simple process, at a low cost,
An object of the present invention is to provide a clear and high-contrast image active matrix device having uniform characteristics over a large area and a driving method thereof.

[Means for Solving the Problems] An active matrix device of the present invention comprises: (1) an active matrix substrate and a counter substrate, wherein an electro-optical material is sandwiched between the active matrix substrate and the counter substrate. An active matrix device, wherein the active matrix substrate has a first electrode, a second electrode disposed so as not to overlap with the first electrode, and the first electrode and the first electrode. An active matrix device, comprising: an island-shaped ferroelectric layer disposed on an upper surface or a lower surface of the first electrode and the second electrode so as to be in contact with both of the second electrodes.

(2) An active matrix device including an active matrix substrate and a counter substrate, wherein an electro-optical material is sandwiched between the active matrix substrate and the counter substrate, wherein the active matrix substrate is provided on a substrate. A plurality of linear first electrodes, a plurality of second electrodes arranged so as not to overlap the first electrodes, and an upper surface or a lower surface of the first electrodes and the second electrodes And a planar distance between the first electrode and the second electrode in a portion close to the first electrode and the second electrode, Either the planar distance between the second electrode and another adjacent first electrode or the planar distance between the second electrode and another adjacent second electrode. Acte that is shorter than Breakfast matrix device.

(3) An active matrix device including an active matrix substrate and a counter substrate, wherein an electro-optical material is sandwiched between the active matrix substrate and the counter substrate, wherein the active matrix substrate is provided on a substrate. A first electrode, a second electrode disposed so as not to overlap with the first electrode, and a ferroelectric layer disposed on an upper surface or a lower surface of the first electrode and the second electrode. A conductive layer disposed on the lower surface or the upper surface of the ferroelectric layer and connected to the first electrode through a contact hole provided in the ferroelectric layer. Matrix device.

(4) An active matrix device including an active matrix substrate and a counter substrate, wherein an electro-optical material is sandwiched between the active matrix substrate and the counter substrate, wherein the active matrix substrate is provided on a substrate. A first electrode, a second electrode disposed so as not to overlap the first electrode, and the first electrode disposed on an upper surface or a lower surface of the first electrode and the second electrode. The second
And a conductive layer disposed on the upper or lower surface of the first electrode so as to be in contact with the first electrode. An active matrix device.

In addition, a driving method of an active matrix device according to the present invention includes: (5) a method including: a pair of substrates; and an electro-optical material sandwiched between the pair of substrates. Data line group, a scanning line group including a plurality of scanning lines provided on the other substrate, and an active element and the electro-optical material connected in series between the data line and the scanning line. An active matrix, comprising: a plurality of pixels; wherein the active element includes a first electrode and a second electrode, and a ferroelectric layer disposed between the first electrode and the second electrode. In the driving method of the device, when a selection voltage ± V ₀ is sequentially applied to the selection line within one field period and a data voltage ± V ₁ is applied to the data line, the selection voltage ± V ₀ and the data voltage ± V the absolute value of the difference between the V ₁ | V ₀ -V ₁ But, And applying a voltage to the ferroelectric layer such that an electric field higher than the coercive electric field is applied to the ferroelectric layer for a certain period after the start of the display operation.

Here, E _C : coercive electric field of the ferroelectric layer d _F : layer thickness of the ferroelectric layer C _F : capacitance of the ferroelectric layer per pixel C _LC : of the electro-optical material per pixel Capacity.

[Operation] The principle of the active element used in the active matrix device of the present invention will be described with reference to FIG.

FIG. 3A shows the hysteresis curve of the ferroelectric. In FIG. 3 (a), _Pr is the remnant polarization, which is the surface charge density remaining on the ferroelectric surface after cutting off the electric field applied to the ferroelectric, and the surface charge density has a memory property. It has been known. The arrangement of the spontaneous polarization in this state is
It is shown in FIG. A positive surface charge on the ferroelectric surface,
A negative surface charge is held on the back surface. When an electric field large enough to reverse the spontaneous polarization is applied from the outside, the spontaneous polarization reverses, and the array is arranged as shown in FIG. 3 (c), and the polarity of the electric charge held on the ferroelectric surface is changed. Reverse. Also, when a coercive electric field EC is applied to the ferroelectric layer, the spontaneous electrodes are randomly arranged vertically as shown in FIG.

When an electro-optical material such as a liquid crystal is connected in series or in parallel with the ferroelectric, a voltage proportional to the surface charge density of the ferroelectric can be applied to the electro-optical material. The voltage is an AC voltage whose polarity changes by rotating spontaneous polarization, and can be controlled by changing the amount of surface charge density. The voltage controllability is better if the ferroelectric is a non-single crystal.

In addition, the origin of the voltage applied to the electro-optical material such as liquid crystal is the surface charge, and the active matrix device of the present invention uses a ferroelectric material having a memory property for the surface charge, so the device itself has There is no loss of the data voltage due to the leakage current.

EXAMPLES Examples and reference examples of the present invention will be described below with reference to the drawings.

Reference Example 1 FIG. 1 shows a reference example of the active element of the present invention.
1 (b) is a top view, and FIG. 1 (a) is A in FIG.
It is sectional drawing in -B.

A first electrode 13 made of ITO is formed on an insulating substrate 12 formed of a glass substrate, and vinylidene fluoride (hereinafter, abbreviated as VDF) and trifluoroethylene (hereinafter, T) are formed on the first electrode 13.
abbreviated as rFE) and a ferroelectric layer 14,
A second electrode 15 made of Cr is provided on the ferroelectric layer 14.

In this example, two photo steps are required to form the active element and the active matrix substrate.
In the active element configured as shown in FIG. 1, the tolerance of the alignment error in the photo step between the first electrode 13 and the second electrode 15 can be increased.

In Figure 1, the layer thickness d _F of the ferroelectric layer 14, the distance x of the insulating substrate and the direction parallel to the first electrode 13 second electrode 15, y, z
It is provided smaller than. Therefore, when a voltage sufficient to reverse the spontaneous polarization is applied between the first electrode 13 and the second electrode 15, the distance between the first electrode and the second electrode is minimized. Invert spontaneous polarization only in _F direction,
The setting can be made so that the spontaneous polarization does not reverse in the x, y, and z directions. When the voltage is set in this manner, only the β region of the ferroelectric layer sandwiched between the first electrode and the second electrode functions as the active layer.

When only the β region works as the active layer, the following effects occur. First, since the spontaneous polarization of the ferroelectric layer in the x, y, and z directions does not reverse, when the active element of the present invention is used in a display device or the like, no crosstalk occurs and a high-quality display is obtained. be able to. Second the x, y, capacitance generated z-direction, can be made smaller than the capacitance of d _F direction, the capacity of the total of the ferroelectric layer is formed is reduced. This has a great effect on improving the display quality of the display device using the active element of the present invention, such as lowering the driving voltage and preventing crosstalk, as described later.

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 spin coating. . This indicates that a uniform active element can be easily formed over a large area, that is, an active matrix device capable of performing a uniform display over a large screen can be realized.

After applying the above-mentioned liquid by spin coating, the insulating substrate 12 is held horizontally and left for several tens of seconds to several minutes to flatten the surface, and then baked, thereby forming a strong material comprising a copolymer of VDF and TrFE. A dielectric layer is obtained. Since the copolymer of VDF and TrFE is colorless and transparent at least in a thin film state, when applied to a light-receiving display device such as a liquid crystal device, in particular, a transmissive display device, it has a high light transmittance and is bright and visible. Display with excellent characteristics can be realized.

Further, the thickness of the ferroelectric layer 14 is provided to be larger than the thickness of the first electrode 13. Therefore, the unevenness formed by the first electrode 13 can be flattened, the surface of the ferroelectric layer 14 can be made almost flat, and the second electrode 15 is formed on the flat surface. Therefore, disconnection at the step portion can be prevented, and the ferroelectric layer 14 at the step portion can be prevented.
A high electric field is not applied to the device, and dielectric breakdown does not occur, and a highly reliable active element can be obtained. The thickness of the ferroelectric layer 14 can be easily adjusted by adjusting the amount of VDF and TrFE dissolved in the solvent described above (adjusting the viscosity) or optimizing the rotation speed and time of the spin coater. It is possible to obtain a ferroelectric layer which can be larger than the thickness and which has a uniform thickness and film quality. The thickness of the first electrode 13 is preferably 100 to 3000 mm, and the thickness of the ferroelectric layer is preferably 1000 to 3000 mm thicker than the first electrode.

FIG. 4 is a cross-sectional view of a configuration example of an active matrix device using the active matrix substrate of FIG. 1, and FIG. 5 is a top view of a part of the active matrix device shown in FIG. This is a liquid crystal device in which a liquid crystal F is held between an active matrix substrate D shown in FIG. 1 and a counter substrate E in which a counter electrode made of ITO is formed on an insulating substrate 16 made of a glass substrate. The first that works as a pixel electrode
Although the ferroelectric layer 14 is overlaid on the electrode 13, as described above, the copolymer of VDF and TrFE is colorless and transparent, so that a bright, clear, and highly visible display device is formed. I have.

The first electrode 13, second electrode 15, counter electrode 17, and ferroelectric layer 14 are formed by sputtering, CVD, PVD, vapor deposition, plating,
Spin coating method, printing method such as offset printing and screen printing, roll coating method, cast film method, dipping method, coating method, sol-gel method, hydrolysis precipitation method,
It can be formed by a spray method, an LB method or the like.

The material used for the first electrode 13, the second electrode 15, and the counter electrode 17 does not need to be limited to ITO or Cr, but may be other metals, transparent electrodes such as SnO ₂ , semiconductors, silicides, and conductive polymers. Alternatively, a conductive substance such as a conductive paint or a superconductive material may be used.

Similarly, the material of the insulating substrates 12 and 16 is not limited to glass, but may be an inorganic material such as ceramic, or an organic material such as plastic, acrylic, or vinyl fluoride. When thin substrates are used as the insulating substrates 12 and 16, a flexible active matrix device can be obtained. Since the thickness of the insulating substrate 12 is irrelevant to the characteristics of the active element of the present invention, the thickness of the insulating substrate 12 can be freely selected, such as by making the insulating substrate 12 thicker, stronger, or thinner without losing the element characteristics.

The material used for the ferroelectric layer 14 need not be limited to a copolymer of VDF and TrFE, but may be other ferroelectric materials, for example, Ba.
Perovskite-type ferroelectrics such as TiO ₃ , PbTiO ₃ , WO _{3 and the} like, Rochelle salt ferroelectrics such as Rochelle salt, deuterium Rochelle salt, tartrate, KDP, phosphate, arsenate, potassium dihydrogen phosphate, etc. Alkali dihydrogen phosphate ferroelectric, GA
Guanidine ferroelectrics such as SH and TGS, potassium niobate, glycine sulfate, ammonium sulfate, sodium nitrite, potassium hexacyanoferrate (II) (yellow blood salt), antimony iodide sulfide, LiNbO ₃ , LiTaO ₃ , PbTiO Amorphous ferroelectrics such as ₃ , polyvinylidene fluoride and its copolymers, copolymers of polyvinylidene fluoride with VDF, TrFE, etc., copolymers of vinylidene cyanide and vinyl acetate, vinylidene cyanide and VDF, A single crystal or non-single crystal of a polymer ferroelectric such as a copolymer with TrFE or the like, Bi ₄ , Ti ₃ , O ₁₂ , Fe—BO, or electret may be used.

Inorganic ferroelectrics such as BaTiO ₃ have large remanent polarization and fast switching speed. Also, amorphous ferroelectrics
It is easy to obtain a uniform ferroelectric layer over a large area. Further, the organic ferroelectric can be formed uniformly at a low cost at a large area by using a spin coating method. Most ferroelectrics have a stable temperature characteristic because there is almost no change in dielectric constant or remanent polarization at an actual operating temperature.

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, and its shape may be any of a sphere, a cylinder, a cone, a polyhedron, and a rod. In this case, instead of polyimide, synthetic resin such as phenol resin, urea resin, polyamide resin, silicon resin, vinyl resin, polyethylene resin, styrene resin, acrylic resin, nylon, vinyl, etc.
Natural resins such as Matsuyani, balsam, copal, amber, shellac, etc., rubber, fibers, organic insulating materials and the like may be used.

For example, a ferroelectric layer holding BaTiO ₃ in polyimide
14 can be easily formed by a spin coating method or the like and can be formed using an inexpensive apparatus. On the other hand, in order to form the ferroelectric layer 14 using only BaTiO ₃ , an expensive vacuum apparatus is required because a sputtering method or the like is used.

Further, by controlling the content of BaTiO _{3 in} the polyimide, the dielectric constant of the ferroelectric layer 14, light transmittance, remanent polarization as a ferroelectric, coercive electric field, spontaneous polarization rotation speed, etc. It can be set. FIG. 1, FIG.
In FIG. 5 and FIG. 5, the first electrode 13 forms a pixel electrode, and the ferroelectric layer 14 is provided on the first electrode 13 so as to overlap. Therefore, light passing through the first electrode 13 also passes through the ferroelectric layer 14. The higher the light transmittance of the ferroelectric layer 14, the higher the light utilization and the brighter the display. Will be done. The fact that the light transmittance of the ferroelectric layer 14 can be controlled by changing the content of BaTiO _{3 in} the polyimide has a great effect in obtaining a bright display with high light utilization. Also, since a voltage proportional to the remanent polarization of the ferroelectric layer is applied to the liquid crystal,
The fact that the remanent polarization of the ferroelectric layer 14 can be controlled by the content of BaTiO _{3 in} the polyimide indicates that the electric field applied to the liquid crystal can be controlled from the material side of the ferroelectric layer. These greatly expand the degree of freedom in designing the active matrix device, and are extremely effective in expanding the application field and range of the control display.

A colorless and transparent ferroelectric substance to which a dye is added, or a ferroelectric material that is not colorless and transparent may be used as the ferroelectric layer 14. When a colorless and transparent ferroelectric layer is used, pinholes and the like in the ferroelectric layer can be found by visual inspection. Ferroelectric layer
Since 14 functions as an active layer of an active element, defects such as pinholes greatly affect the yield of the active matrix substrate and the active matrix device. If a pinhole can be found by the appearance inspection, it is possible to find a pinhole early, at the same time as having a great effect on improving the yield, and to omit the subsequent steps. Therefore, an inexpensive active matrix device with a high yield can be provided by using a ferroelectric layer that is not colorless and transparent.

Materials added to the ferroelectric include natural dyes such as ancient purple, curcumin, alizarin, carthamin, carminic acid, cochineal, indigo, aniline, naphthalene,
Synthetic dyes such as anthracene, direct dyes, basic dyes,
Mordant dyes, vat dyes, sulfur dyes, oxidation dyes, cold dyes, and the like are used. In addition, other than the dye, the ferroelectric layer 14 may be used.
May be added to make the colorless and transparent state.

The ferroelectric layer 14 may be made of a material subjected to a polink treatment. FIG. 6 shows the ferroelectric layer 14 before and after the poling process.
3 shows a hysteresis curve. P _r ⁰ and P _r ¹ indicate remanent polarization before and after the poling process, respectively. From the figure, the remanent polarization increases by performing the polling process,
Further, it can be seen that there is a clear coercive electric field. By having a large remanent polarization, the voltage that can be applied to the liquid crystal increases, and by having a clear coercive electric field, crosstalk of the active matrix display can be reduced. Also,
In the ferroelectric layer 14 before the poling process, a larger electric field is required to reverse the spontaneous polarization. In order to generate a large electric field, a large voltage is required. For this reason, there arises a problem that a special high withstand voltage circuit is required and power consumption is increased. However, the problem can be solved by performing a polling process.

Further, there is also a material that exhibits ferroelectricity by performing a poling process. When such a material is used as the ferroelectric layer 14, a poling process is indispensable.

To perform the poling process on the ferroelectric layer 14, for example,
Using the first electrode 13 and the second electrode 15 in FIG. 1 as electrodes, an electric field of about 400 kV / cm may be applied to the ferroelectric layer 14 at 80 ° C. for 1 H. The electric field applied to the ferroelectric layer 14 is ~ 400 kV /
The temperature, the electric field application time, and the atmosphere are not limited. Further, a poling process may be performed by applying a voltage between the second electrode 15 and the counter electrode 17 in FIG.

The poling treatment can be performed by heating. In this case, there is a method using one or both of the thermal electret method and the polarization inversion method.

Since the ferroelectric layer 14 has a polarization effect, it can be used as a liquid crystal alignment film when subjected to a surface treatment such as rotary rubbing. In this case, unlike a conventional active matrix substrate, a special material or process such as polyimide is not required for forming an alignment film, so that the process can be simplified, and the active matrix substrate can be manufactured with high throughput, low cost, and high yield. Can be provided.

Thus, the active matrix substrate of the present invention
There is no need to form an alignment film or an insulating film for cutting off a DC voltage by using a special process, and the film can be formed at low cost and high yield.

A coupling layer made of a surfactant, a silane coupling agent, or the like is provided at the interface between the ferroelectric layer 14 and the insulating substrate 12, the first electrode 13, and the second electrode 15 to increase the adhesion strength. good.

As the alignment film formed on the opposite substrate, an organic film such as polyimide or an obliquely deposited silicon oxide film may be used.

As the gap material, a cylindrical or spherical material using a plastic or glass material, or a scallop is used.

In FIG. 4, a material having an electro-optic effect, that is, a material that changes light transmittance by an electric field, such as an EL material, a gas, an electrochromic material, a material that changes a light emitting-non-light emitting state, and a material that changes color LCD F
It may be used instead of.

Since this example is an active matrix device, it is particularly effective to use a liquid crystal such as TN, guest host, STN, or NTN, which does not have a memory effect, or a non-ferroelectric liquid crystal.

Embodiment 1 FIG. 8 shows an equivalent circuit per pixel of an active matrix device to which the driving method of the present invention is applied, and explains a basic operation principle per pixel. The ferroelectric layer and the capacitance of the liquid crystal are connected in series. FIG. 8 (a) shows that a positive voltage sufficient to invert the spontaneous polarization of the ferroelectric layer is applied to the G terminal during the selection period of a certain field, and the spontaneous polarization of the ferroelectric layer almost completely falls below. It shows a state where it is facing. Thus, the write operation is completed by aligning the spontaneous polarization in one direction.

Thereafter, the G terminal is kept at the ground potential as shown in FIG. 8 (b). This is the holding state, that is, the state of the non-selection period. In the holding state, the amount of charge held by the ferroelectric layer is −S _F · P _r (S _F : area of the ferroelectric layer,
P _r : remanent polarization of the ferroelectric layer) and the amount of free charge distribution between the liquid crystal and the ferroelectric layer + _QLC . The amount of charge Q _LC held by the liquid crystal is C _LC・ V _LC (C _LC : liquid crystal capacity,
V _LC : voltage applied to the liquid crystal). Further, since the voltage V _F applied to the ferroelectric layer is equal to the voltage V _LC applied to the liquid crystal, Q _F = −S _F · P _r + Q _LC = C _F · V _F Q _LC = −C _LC · V _LC V _F = V _LC Q _LC : charge of liquid crystal C _LC : capacity of liquid crystal Q _F : charge of ferroelectric layer C _F : capacity of ferroelectric layer Becomes

As described above, the voltage indicated by the equation is held in the liquid crystal during the non-selection period.

In the next field, as shown in FIG.
This shows a state in which a negative voltage is applied to the terminal within the selection period, the spontaneous polarization is inverted, and the terminal faces upward. During the subsequent non-selection period, the charges are held as shown in FIG.
, A voltage and a charge of the opposite polarity are applied and held to the liquid crystal and the ferroelectric layer.

The equation, since the voltage VLC applied to the liquid crystal is proportional to P _r, increasing the residual polarization P _r of the ferroelectric layer by the polling process described above is, for obtaining a large active element of the writing ability of the liquid crystal With great effect. Also, as described above, since _Pr has a memory property,
There is no leakage current due to the device. Therefore, by using the active element of the present invention, it is possible to provide an active matrix device with a clear image and high contrast.

Also, from the equation, by changing the magnitude of the voltage ± V _G applied to the G terminal, by changing the P _r value, it can be seen that it is possible to control the V _LC. When the ferroelectric layer 14 is formed of a non-single-crystal, particularly a polycrystalline ferroelectric, _Pr
Is easy to control. This also the size change of ± V _G, show that it is possible to gradation display.

Further, by changing the magnitude of ± V _G, V _LC is zero, or by changing the value of P _r as small Ku becomes than the threshold voltage of the liquid crystal, it is possible to erase operations. The state of writing and erasing on the liquid crystal can be arbitrarily controlled depending on the magnitude of ± _VLC .

In actual active matrix device, a non-selection period Figure 8 (a), is applied data voltages V ₁ from the ground terminal in (c), the liquid crystal, , That is, noise is applied. In order to suppress noise, it is preferable that C _LC / C _F is large, and it is desirable that C _LC / C _F be at least 1 or more, preferably 10 or more.

Also, of the voltage ± V _G applied to the G terminal in the selection period, the ferroelectric layer 14 is Is applied. Since this voltage is for reversing the spontaneous polarization, that is, for performing the writing operation, it is desirable that the voltage is higher. For this reason, it is preferable that C _LC / C _F be large, and it is desirable that it be at least 1 or more, preferably 10 or more.

FIG. 9 shows an equivalent circuit of the active matrix device. The counter electrode 17 of the counter substrate forms a selection line group as A ₁ , A ₂ , A ₃ , A ₄ , and the second electrode 15 forms a data line group as B ₁ , B ₂ , B ₃ I have. Each pixel consists of a liquid crystal 21 and a ferroelectric layer
It is formed by series connection with 14. Where the counter electrode
17 may be used as a data line group and the first electrode 15 may be used as a selection line group.

FIG. 10 shows drive waveforms of the active matrix device shown in FIG. A ₁ , A ₂ , A ₃ , A ₄ and B ₁ , B ₂ , B ₃ in FIGS. 10 and 9 correspond to each other. A _1, A _2, with A _3, A ₄ selects a pixel to write data in the horizontal direction, and sends the data voltage to each pixel in _{B 1, B 2, B 3} . V ₀ is selected voltage, V ₁ is the data voltage. If C _LC »C _F, the voltage applied between the selection lines and the data lines are applied almost all ferroelectric layer 14.

Now, in some fields, the case where A ₁ is selected. V (ON) = V ₀ + V ₁ ≧ d _F · E ₀ V (OFF) = The serial coupling between the ferroelectric layer 14 of the pixel where the data corresponding to the turning on and off of the liquid crystal 21 is written and the liquid crystal 21 respectively. A voltage of V ₀ −V ₁ = d _F · E _C is applied. In addition, a voltage of V (unselected) = ± V ₁ is applied to the series connection of both unselected lines. d _F is the layer thickness of a portion of the ferroelectric layer 14 that functions as an active layer. At this time, the spontaneous polarization of the ferroelectric layer 14 of the turned-on pixel and the turned-off pixel is as shown in FIGS. 3 (b) and 3 (d), respectively, and a voltage corresponding to each remanent polarization is applied to the liquid crystal. The liquid crystal is turned on and off.

When the selection period of A ₁ is completed, is sequentially selected in the order of A _2, A _3, go data is written to each pixel. When the selection period ends, a non-selection period starts.

One field period has elapsed, when selecting the A ₁ again, turned, the ferroelectric layer 14 of the pixels corresponding to off, V (ON) = - V 0 -V 1 ≦ -d F · E 0 V (OFF) = − V ₀ + V ₁ ≦ −d The voltage of _F · E _C is applied, and the voltage of V (unselected) = ± V ₁ is applied to the ferroelectric layer of the non-selected line. . At this time,
The spontaneous polarization of the ferroelectric layer of the OFF pixel is as shown in FIGS. 3 (c) and 3 (d), respectively. An electric field corresponding to each remanent polarization is applied to the liquid crystal, and the liquid crystal turns on and off. , And the AC drive is performed in a two-field cycle.

From the formulas, V (ON) and V (OFF) are E ₀ and E in FIG.
_C and, | V (ON) | ≧ d F · E 0 | V (OFF) | has the ≧ d _F · E _C becomes relevant, the voltage value of V (OFF) necessarily d _F · E _C need not be, unless those much different when the liquid crystal light transmittance was applied d _F · E _C, or in other voltage values.

According to the driving method of the active matrix device of the present invention, the voltage applied to the ferroelectric layer during the selection period is V (ON), V (ON).
(OFF) greater than d _F · E _C in either state, ie, Is satisfied.

Here, the values of V (ON) and V (OFF) may be specifically determined as follows.

FIG. 11 shows the time change δ of the electric displacement D in the copolymer.
9 shows the dependence of D / δlog (t) on the applied electric field intensity. Here, each peak of δD / δlog (t) indicates that the spontaneous polarization has been inverted by about half at the time when the peak is present, and the time corresponding to the skirt on the right side of each peak indicates that the spontaneous polarization is at that time. It shows that it was almost completely inverted. Here, the length of the selection period and δD / δlog (t)
The value of V (OFF) is set so that the peak position of the graph of FIG. 7 matches, and the value of V (ON) is set so that the time length of the selection period and the skirt on the right side of the graph of δD / δlog (t) match. You only have to decide. When V (ON) determined in this way is applied to the ferroelectric layer 14, the spontaneous polarization is almost completely inverted within the selection period, and a voltage determined by the equation is applied to the liquid crystal, thereby writing data. When V (OFF) determined in this way is applied to the ferroelectric layer 14, the spontaneous polarization is inverted by about half during the selection period, and the spontaneous polarization in the ferroelectric layer is determined by V (ON). Smaller than that, V (ON)
Is applied to the liquid crystal.

The data can be erased even if the spontaneous polarization is not reversed exactly in half, and it is not always necessary to adjust V (erasure) to the peak of δD / δlog (τ).

± V ₁ is applied to the ferroelectric layer during the non-selection period, that is, the holding period.
Is applied, ± V ₁ may be selected from FIG. 11 so that the inversion of spontaneous polarization does not occur in one field period. That is, the inversion speed of spontaneous polarization at ± V ₁ applied, it may be slower than one field period.

The gradation display uses a small data voltage V ₂ than the data voltage V _1, it can be carried out as follows.

Voltage during selection for gradation display V (gradation) is, | V _{(gradation) | = | V 0 + V} 2 | <| V (ON) | | V ( gradation) | = | V ₀ -V ₂ |> | V (OFF) |, and the amount of reversal of spontaneous polarization during the selection period is V (O
It is less than at N) and more than at V (OFF).
Residual polarization P _r at this time takes a value between P _r upon application V (ON) and V a (OFF). Voltage V _LC applied to liquid crystal
Is proportional to P _r, it is possible to apply a voltage V _LC in accordance with P _r. Therefore, it is gradation display by the same number as the number of types of potential V _2.

It is also possible to perform gradation display by applying not only one of V (ON) and V (OFF) but also applying both and changing the application time distribution during the selection period.

Further, as shown in FIG. 10, when the common potentials α ₁ and α ₂ are changed by V ₀ −V ₁ every field, the maximum voltage to be used becomes V ₀ + V ₁ and the maximum voltage can be reduced. . In this case, there is no need to use a special high-voltage circuit,
Since an inexpensive general-purpose circuit component can be used, an inexpensive active matrix device can be provided. At this time, the difference between the common voltages α ₁ and α ₂ does not necessarily need to be V ₀ −V ₁ .

In FIG. 10, the command potentials α ₁ and α ₂ are changed for each field. However, the command potentials may be changed for each selection period or the common potential may be changed for a plurality of selection periods. LCD 21 on one screen in the field
May be present with pixels having different polarities of voltages written to the pixels.

Further, a driving method of the active matrix device of the present invention will be described below with reference to FIGS. VDF and TrF
The reversal speed τ _S of the spontaneous polarization of the copolymer of E can be calculated as the elapsed time tw
In contrast, changes as shown in FIG. 12 are shown. That is, τ _S is
increases with t _w, τ _S is becomes longer than the selection period, will not function as an active matrix device. For example, assuming the number of scanning lines is 400 and estimating using FIG. 12, the selection period is one field period (-16.7 msec).
Divided by the number of scanning lines, which is about 40 μsec. From FIG. 13, t _w is tau _S when about 5 minutes is 40 .mu.sec. Therefore, five minutes after the polling process, the device does not function as an active matrix device. However, if the voltage is continuously applied after the polling process, τ _S
There is no increase phenomenon.

As shown in FIG. 13, these problems can be solved by providing an initialization period immediately before the start of the display operation. During the initialization period, a voltage of ± (V ₀ + V ₁ ) is applied to all the pixels, and a polling process using an electric field is performed. Where V ₀
+ V ₁ is selected so that an electric field larger than the coercive electric field E _C is applied to the ferroelectric layer. Since the inversion of spontaneous polarization is performed by applying an electric field equal to or higher than the coercive electric field, efficient polling processing is performed. As described above, by applying an electric field equal to or higher than the coercive electric field to the ferroelectric layer immediately before the start of the display operation and returning to the state immediately after the poling process, the display image quality is not degraded due to an increase with time of τ _S , A clear and high-contrast display image can always be obtained.

In FIG. 13, the voltage applied during the initialization period is ±
It is not limited to (V ₀ + V ₁ ). Further, the initialization period is performed until the ferroelectric layer almost recovers to the state immediately after the first polling process, and there is no particular time limitation. Further, here, ± (V ₀ + V ₁ ) during the initialization period
Is applied for one positive and negative cycle, but 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 the data line during the initialization period does not need to be a single value like | V ₀ + V ₁ |
Two or more values may be used, or a voltage value that changes with time may be used.

Reference Example 2 FIG. 7 shows a second reference example of the present invention. FIG. 7 (b) is a top view, FIG. 7 (a) is a cross-sectional view taken along the line AB in FIG. 7 (b). A protective film 18 made of SiO ₂ and an alignment film 19 made of polyimide are provided on the active matrix substrate shown in FIG.

Since the copolymer of VDF and TrFE used as the ferroelectric layer 14 is an organic substance, it is soluble in the polyimide solvent (usually α-butyl lactone, N, N-dimethylacetamide) used as the alignment film 19 Without the protective film 18, the ferroelectric layer 14 elutes and disappears when the alignment film 19 is formed. Since SiO ₂ is insoluble in the polyimide solvent, Si 2
If the protective film 18 made of O ₂ is used, elution of the ferroelectric layer 14
Loss can be prevented.

The material of the protective film 18 need not be limited to SiO ₂ , but may be SiN _x , Si
An inorganic material such as ON or Si, an organic material such as Teflon, shellac, glass, or the like may be used. The formation method includes a sputtering method, a vapor deposition, a spin coating method, a CVD method, a roll coating method, a dipping method, a printing method, a coating method, and the like. Further, after applying a solution of a silicon compound [R _n Si (OH) _4-n ] in an organic solvent such as an alcohol and an ester, heating is performed.
A method of forming a SiO ₂ film, for easy uniform SiO ₂ film is formed on a large area, as an active element forming method for a flat display having a large area is particularly effective.

In addition, the material of the alignment film 19 is not limited to polyimide, and an obliquely deposited SiO ₂ film or another organic material may be used.

Reference Example 3 FIG. 14 shows a third reference example of the present invention. FIG. 14 (b) is a top view, and FIG. 14 (a) is a cross-sectional view taken along a line AB in FIG. 14 (b).

A first electrode 13 made of Cr is provided on an insulating substrate 12 made of a glass substrate, and a ferroelectric layer 14 made of a copolymer of VDF and TrFE is provided on the first electrode 13. On the body layer 14, a second electrode 15 made of ITO is provided.
The ferroelectric layer 14 sandwiched between the first electrode 13 and the second electrode 15 functions as an active layer of an active element. With this structure, since the ferroelectric layer 14 does not exist on the second electrode 15 constituting the pixel electrode, a voltage can be efficiently applied to the liquid crystal.

Reference Example 4 FIG. 15 shows a fourth reference example of the present invention. FIG. 15 (b) is a top view, and FIG. 15 (a) is a cross-sectional view taken along a line AB in FIG. 15 (b).

The first made of ITO on the insulating substrate 12 made of a glass substrate
VDF and TrF are provided on the first electrode 13.
Ferroelectric layer 14 made of copolymer with E and second made of Cr
Are provided in the same shape. The portion of the ferroelectric layer 14 sandwiched between the first electrode 13 and the second electrode 15 functions as an active layer of the active element.

When the active element and the active matrix substrate shown in FIG. 15 are used in place of the active element and the active matrix substrate shown in FIG. 1, and the active matrix device shown in FIGS. Effects occur. In FIG. 15, the pixel electrode is constituted by the first electrode 13 in a region not in contact with the ferroelectric layer 14. Since there is no ferroelectric layer 14 above and below the pixel electrode,
The change in the amount of light transmitted through the liquid crystal panel is determined only by the electro-optic effect of the liquid crystal. Since there is no change in the amount of transmitted light due to the ferroelectric layer 14, the contrast is high and a clear image can be obtained.

Embodiment 2 FIG. 16 shows an embodiment of an active matrix substrate constituting an active matrix device of the present invention. FIG. 16 (b) is a top view of the vicinity of the active element portion, and FIG.
FIG. 4B is a cross-sectional view taken along a line AB in FIG.

An island-shaped ferroelectric layer 14 made of a copolymer of VDF and TrFE, and a ferroelectric layer 14 are formed on an insulating substrate 12 made of a glass substrate.
A first electrode 13 made of Cr is provided thereon, and a second electrode 1 made of ITO is formed so as to cover a part of the ferroelectric layer 14.
5 are provided. That is, the ferroelectric layer 14 is provided so as to connect the first electrode 13 and the second electrode 15.

With such a structure, the first electrode 13 and the second electrode 15
Are not overlapped in the vertical direction, so that two electrodes are not short-circuited due to a defect in the ferroelectric layer 14. Therefore,
In principle, a defect of the active element due to a short circuit, that is, a pixel defect can be removed. This has a tremendous effect on providing clear and high quality display quality.

Embodiment 3 FIG. 17 shows an embodiment of an active matrix substrate constituting an active matrix device of the present invention as a configuration similar to FIG. FIG. 17 (b) is a top view of the vicinity of the active element portion, and FIG. 17 (a) is a cross-sectional view taken along a line AB in FIG. 17 (b).

The first substrate made of Cr is placed on the insulating substrate 12 made of a glass substrate.
Is provided with a second electrode 15 made of ITO and an island-shaped ferroelectric layer 1 made of a copolymer of VDF and TrFE.
4 is provided to connect the first electrode 13 and the second electrode 15.

When forming the active element and the active matrix substrate shown in FIGS. 16 and 17, if different materials are used for the first electrode 13 and the second electrode 15, three photo steps are required. If used, only two photo steps are required.

Since the active element shown in FIGS. 16 and 17 is provided in a direction parallel to the insulating substrate 12, the active element has a large layer thickness and therefore has a small capacitance. Now, the parameters W, L, d _{F of} the active element portion shown in FIGS. 16 and 17 and the relative permittivity ε of the ferroelectric layer are shown.
_F and the parameters x and y of the pixel portion, the layer thickness d of the liquid crystal, and the relative permittivity ε _LC of the liquid crystal are respectively W = 10 μm, L = 1 μm, d _F
= 10 μm, ε _F = 10, and x = 90 μm, y = 100 μm, d = 7
If μm, ε _LC = 10, the ratio of the capacitance C _{F of the} active element to the capacitance C _LC of the pixel is And C _F ≪C _LC . Therefore, most of the voltage applied to the series connection of the ferroelectric layer and the pixel is applied to the ferroelectric layer. Since the active element of the present invention operates by controlling the arrangement electric field of the spontaneous polarization of the ferroelectric layer 14, the condition of C _F ≪C _LC is such that the electrode voltage decreases, the switching speed increases, or the crosstalk decreases. It is effective for reduction and has a tremendous effect for obtaining a clear and high-contrast display.

Embodiment 4 FIG. 18 shows an embodiment of an active matrix substrate constituting an active matrix device of the present invention. FIG. 18 (b) is a top view of the vicinity of the active element portion, and FIG. 18 (a) is a cross-sectional view taken along a line AB in FIG. 18 (b).

A ferroelectric layer 14 made of a copolymer of VDF and TrFE is provided on an insulating substrate 12 made of a glass substrate, and a first electrode 13 made of Cr and ITO are formed on the ferroelectric layer 14. A second electrode 15 is provided. The ferroelectric layer 14 between the first electrode 13 and the second electrode 15 works as an active layer.

Embodiment 5 FIG. 19 shows an embodiment of an active matrix substrate constituting an active matrix device of the present invention as a configuration similar to FIG. FIG. 19 (b) is a top view of the vicinity of the active element portion, and FIG.
It is sectional drawing in B. Insulating substrate made of glass substrate
On 12, a first electrode 13 made of Cr and a second electrode 15 made of ITO are provided. First electrode 13 and second electrode 15
On top, a ferroelectric layer 14 made of a copolymer of VDF and TrFE is provided. With this configuration, since the ferroelectric layer 14 is formed after the formation of the first electrode 13 and the second electrode 15, no damage occurs to the ferroelectric layer 14.

When the active element and the active matrix substrate shown in FIGS. 17 and 18 are formed, if the same material is used for the first electrode 13 and the second electrode 15 and they are formed in the same step, the photo step only needs to be performed once.

In the active element shown in FIGS.
As in the case of the active element shown in FIG. 16, the first electrode 13 and the second electrode 15 do not overlap in the vertical direction, so that a defect due to a short circuit does not occur.

The active element shown in FIGS. 17 and 18 uses the ferroelectric layer 14 in a direction parallel to the insulating substrate 12, so that the active elements shown in FIGS.
Like the active element shown in the figure, the layer thickness is large and therefore has a small capacitance.

FIG. 20 shows a top view of a part of an embodiment of the active matrix device of the present invention using the active matrix substrate shown in FIGS. VDF and TrFE on glass substrate
An active matrix substrate on which a ferroelectric layer 14 made of a copolymer of the following, a first electrode 13 made of Cr, and a second electrode 15 made of ITO are formed, and a counter electrode 17 made of ITO is formed on a glass substrate. Liquid crystals are held between the formed opposing substrates, and pixels composed of electrodes of the substrate and the opposing substrate are arranged in a matrix.

In FIG. 20, since a> t, b> t, and the inversion of the spontaneous polarization at a, b is provided,
No vertical or horizontal crosstalk occurs.

Embodiment 6 FIG. 21 shows an embodiment of an active matrix substrate constituting an active matrix device of the present invention. FIG. 21 (b) is a top view of the vicinity of the active element portion, and FIG. 21 (a) is a cross-sectional view taken along a line AB in FIG. 21 (b).

A ferroelectric layer 14 made of a copolymer of VDF and TrFE is provided on an insulating substrate 12 made of a glass substrate, and a first electrode 13 made of Cr and a first electrode 13 made of ITO are formed on the ferroelectric layer 14. 2
Electrodes 15 are provided. A part of the first electrode 13 is
The ferroelectric layer 14 between the protrusion and the second electrode 15 functions as an active layer of an active element. With such a configuration, the capacitance of the active element is substantially reduced. In FIG. 21 (b), the layer thickness t ₂ of the thickness t and the non-active layer of the active layer has a t _2> t the relationship. Therefore, the first electrode as shown in FIGS.
The capacitance of the ferroelectric layer 14 is smaller than in a configuration in which the ferroelectric layer 14 between the electrode 13 and the second electrode 15 all functions as an active layer.

Further, the first electrode 13 of the active element shown in FIG.
A protruding portion may be formed on the base member to provide a configuration as in this embodiment.

Embodiment 7 FIG. 23 shows an embodiment of an active matrix substrate constituting an active matrix device of the present invention. FIG. 23 (b) is a top view of the vicinity of the active element portion, and FIG. 23 (a) is a cross-sectional view taken along a line AB in FIG. 23 (b).

The first made of ITO on the insulating substrate 12 made of a glass substrate
Electrode 13, second electrode 15, and ferroelectric layer 1 made of a copolymer of VDF and TrFE on first electrode 13 and second electrode 15.
4. A conductor layer 20 made of Cr is provided so as to be connected to the first electrode 13 via a contact hole provided in the ferroelectric layer 14.

In FIG. 23, in the order of the conductor layer 20, the ferroelectric layer 14, the first electrode 13 and the second electrode 15 on the insulating substrate 12, that is, the first electrode 13 and the second electrode 15 The configuration of the conductor layer 15 may be reversed.

Embodiment 8 FIG. 24 shows an embodiment of the active matrix substrate constituting the active matrix device of the present invention. FIG. 24 (b) is a top view of the vicinity of the active element portion, and FIG. 24 (a) is a cross-sectional view taken along a line AB in FIG. 24 (b).

The first made of ITO on the insulating substrate 12 made of a glass substrate
Electrode 13 and second electrode 15, the first electrode 13 and second electrode
A ferroelectric layer 14 made of a copolymer of VDF and TrFE on the electrode 15 of the first electrode 15, and from Cr so as to be connected to the first electrode 13 through a contact hole provided in the ferroelectric layer 14. The conductive layer 20 is provided. In the active element shown in FIG. 24, since the first electrode 13 has a two-layer structure in which the first electrode 13 is connected to the conductor layer 20 via a contact hole having a large area, a reduction in wiring resistance can be realized.

The active element shown in FIG. 24 may be configured by reversing the positional relationship between the first electrode 13 and the second electrode 15 and the conductor layer 20, similarly to the active element shown in FIG.

Embodiment 9 FIG. 25 shows an embodiment of an active matrix substrate constituting an active matrix device of the present invention. FIG. 25 (b) is a top view of the vicinity of the active element portion, and FIG. 25 (a) is a cross-sectional view taken along a line AB in FIG. 25 (b).

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 an IT is formed on the ferroelectric layer 14.
A first electrode 13 and a second electrode 15 made of O are provided, and a conductor layer 20 is provided so as to be in contact with the first electrode 13.

In the active matrix substrate of the present embodiment, the ferroelectric layer 14, the first electrode 13, the second electrode 15, and the conductor layer 20
Need not necessarily be formed in this order, but may be formed in any order.

In the configuration of the present embodiment, the first electrode 13 is formed to be long in the longitudinal direction of the conductor layer 20 and has a two-layer structure with the conductor layer 20, so that the wiring resistance can be reduced. .

23 to 25, since the first electrode 13 and the second electrode 15 are formed in the same step, the distance between the first electrode 13 and the second electrode 15 is , Regardless of the expansion and contraction of the insulating substrate 12, the alignment error of the mask, and the like. This is because the first electrode 13 and the second electrode 15
When the same voltage is applied between the two electrodes, the same electric field is applied to the ferroelectric substance existing between the two electrodes. The fact that the distance between the first electrode 13 and the second electrode 15 is kept constant has a great effect on forming a uniform active element over a large area with good reproducibility.

In the active element shown in FIGS. 23 to 25, similarly to the active element shown in FIG. 21, the ferroelectric layer 14 between the projection of the first electrode 13 and the second electrode 15 has an active layer. Work as

Further, in the configuration shown in FIGS. 23 to 25, the projecting portion may not be formed.

Reference Example 5 FIG. 22 shows a fifth reference example of the present invention. FIG. 22 (b) is a top view, and FIG. 22 (a) is a view of A in FIG.
It is sectional drawing in -B.

Electrode 2 made of ITO on insulating substrate 12 made of glass substrate
2, a ferroelectric layer 14 made of a copolymer of VDF and TrFE is provided on the electrode 22.

The number of photo steps required to form the active matrix substrate of this embodiment is one. Since the area of the electrode 22 is large and the surface resistance is reduced, the wiring delay due to the electrode 22 can be reduced. This has a great effect in obtaining a uniform and clear display over the entire display surface.

[Others] First electrode 13, second electrode 15, conductor layer 20, electrode 22, insulating substrate 1 used in active elements of Examples 2 to 9
2. As the material and forming method used for the ferroelectric layer 14, the same material and forming method as described with reference to FIG. 1 may be used.

In the active elements shown in FIGS. 14, 19, 22, 23 and 24,
The ferroelectric layer 14 may be used as an alignment film. Ferroelectric layer
Reference numeral 14 also serves as an insulating film for cutting off a DC voltage applied to the liquid crystal. Further, as described with reference to FIG. 1, the thickness of the ferroelectric layer 14 is set to the first electrode 13, the second electrode 15, and the conductor layer 20 provided between the insulating substrate 12 and the ferroelectric layer 14. Alternatively, the electrode 22 may be thicker than the film thickness.

An active matrix device as shown in FIG. 20 may be formed using the active matrix substrate on which the active elements of Examples 2 to 9 are formed. At this time, a protective film as shown in FIG. 7 is formed on the active matrix substrate.
18, an alignment film 19 may be formed.

The active element having the configuration shown in FIGS. 1, 14, 15, and 22 has a relatively large capacitance because the length of the ferroelectric layer 14 in the thickness direction is a layer thickness. Is applied with a large electric field. Therefore, the configuration shown in FIGS. 1, 14, 15, and 22 is particularly effective when an organic ferroelectric material having a small relative dielectric constant and a large coercive electric field is used.

The active element having the configuration shown in FIGS. 16 to 19, 21, and 23 to 25 has a small capacitance because the length of the ferroelectric layer 14 in the in-plane direction of the insulating substrate 12 is small, but the ferroelectric It is difficult to apply an electric field to the body layer 14. Therefore, the configurations shown in FIGS. 16 to 19, 21, and 23 to 25 are particularly effective when using an inorganic ferroelectric material having a large relative dielectric constant and a small coercive electric field.

The active matrix driving method described in the first embodiment can be applied to the active matrix device using the active matrix substrate described in the second to ninth embodiments.

[Effects of the Invention] According to the present invention, in an active matrix device using a ferroelectric layer, the first electrode and the second electrode do not overlap in a plane, so that the occurrence of defects due to short-circuit of both electrodes is prevented. This is advantageous in that the quality of a large-area active matrix device can be made high and stable.

Further, according to the driving method of the active matrix device of the present invention, since the poling process of the ferroelectric layer is performed by the electric field after the start of the display operation, a clear and high-contrast display image can be always obtained. Things.

[Brief description of the drawings]

FIG. 1 is a top view (a) and a sectional view (b) showing a reference example of the present invention. FIG. 2 is a sectional view of a conventional active element. FIG. 3 is a diagram showing a hysteresis curve (a) of a ferroelectric substance and arrangements (b) to (d) of spontaneous polarization. FIG. 4 is a sectional view showing a reference example of the present invention. FIG. 5 is a top view of a part of the active matrix device shown in FIG. FIG. 6 is a diagram showing hysteresis curves of a ferroelectric before and after a poling process. FIG. 7 is a top view (a) and a sectional view (b) showing a reference example of the present invention. FIG. 8 is an equivalent circuit diagram per pixel of the active matrix device of the present invention. FIG. 9 is an equivalent circuit diagram of the active matrix device of the present invention. FIG. 10 is a diagram showing driving waveforms of the active matrix device shown in FIG. FIG. 11 is a diagram showing the applied electric field strength dependence of the time change δD / δlog (t) of the electric displacement D of the copolymer of VDF and TrFE. FIG. 12 is a diagram showing the relationship between the reversal speed of the copolymer of VDF and TrFE and the elapsed time after the poling process. FIG. 13 is a diagram showing a driving method of the active matrix device of the present invention. FIG. 14 is a top view (a) and a sectional view (b) showing a reference example of the present invention. FIG. 15 is a top view (a) and a sectional view (b) showing a reference example of the present invention. FIG. 16 is a top view (a) and a sectional view (b) showing an embodiment of an active element constituting the active matrix device of the present invention. FIG. 17 is a top view (a) and a sectional view (b) showing an embodiment of an active element constituting the active matrix device of the present invention. FIG. 18 is a top view (a) and a sectional view (b) showing an embodiment of an active element constituting the active matrix device of the present invention. FIG. 19 is a top view (a) and a sectional view (b) showing an embodiment of an active element constituting the active matrix device of the present invention. FIG. 20 is a top view of a part of an embodiment of the active matrix device of the present invention using the active elements shown in FIGS. FIG. 21 is a top view (a) and a sectional view (b) showing an embodiment of an active element constituting the active matrix device of the present invention. FIG. 22 is a top view (a) and a sectional view (b) showing a reference example of the present invention. FIG. 23 is a top view (a) and a sectional view (b) showing an embodiment of an active element constituting the active matrix device of the present invention. FIG. 24 is a top view (a) and a sectional view (b) showing an embodiment of an active element constituting the active matrix device of the present invention. FIG. 25 is a top view (a) and a sectional view (b) showing an embodiment of an active element constituting the active matrix device of the present invention. DESCRIPTION OF SYMBOLS 1 ... Glass substrate 2 ... Gate electrode 3 ... Gate insulating film 4 ... Drain electrode 5 ... Source electrode 6 ... Drain region 7 ... Pixel electrode 8 ... Electrode 9 ... Glass substrate 10 ... Channel amorphous Si 11 Source region 12 Insulating substrate 13 First electrode 14 Ferroelectric layer 15 Second electrode 16 Insulating substrate 17 Counter electrode 18 Protective film 19 Alignment film 20 Conductor layer 21 Liquid crystal 22 Electrode C Liquid crystal D Active matrix substrate E Counter substrate F Liquid crystal G Lower substrate H Upper substrate

Claims (5)

(57) [Claims] 1. An active matrix device comprising an active matrix substrate and a counter substrate, wherein an electro-optical material is sandwiched between the active matrix substrate and the counter substrate. A first electrode, a second electrode disposed so as not to overlap with the first electrode, and the first electrode so as to be in contact with both the first electrode and the second electrode. And an island-shaped ferroelectric layer disposed on the upper or lower surface of the second electrode. 2. An active matrix device comprising: an active matrix substrate; and a counter substrate, wherein an electro-optical material is sandwiched between the active matrix substrate and the counter substrate. A plurality of linear first electrodes, a plurality of second electrodes arranged so as not to overlap the first electrodes, and upper or lower surfaces of the first electrodes and the second electrodes And a planar distance between the first electrode and the second electrode in a portion where the first electrode and the second electrode are close to each other, A planar distance between the second electrode and another first electrode disposed adjacent to the second electrode and a planar distance between the second electrode and another second electrode disposed adjacent to the second electrode Characterized by being shorter than any of Active matrix device. 3. An active matrix device comprising: an active matrix substrate; and a counter substrate, wherein an electro-optical material is sandwiched between the active matrix substrate and the counter substrate. A first electrode, a second electrode disposed so as not to overlap the first electrode, and a ferroelectric substance disposed on an upper surface or a lower surface of the first electrode and the second electrode And a conductive layer disposed on the lower surface or the upper surface of the ferroelectric layer and connected to the first electrode via a contact hole provided in the ferroelectric layer. Active matrix device. 4. An active matrix device comprising an active matrix substrate and a counter substrate, wherein an electro-optical material is sandwiched between the active matrix substrate and the counter substrate, wherein the active matrix substrate is a substrate. A first electrode, a second electrode disposed so as not to overlap the first electrode, and a first electrode disposed on an upper surface or a lower surface of the first electrode and the second electrode. An island-shaped ferroelectric layer in contact with both the electrode and the second electrode; and a conductor layer arranged on the upper or lower surface of the first electrode so as to be in contact with the first electrode. An active matrix device characterized by the above-mentioned. 5. A data line group comprising a plurality of data lines provided on one substrate, comprising a pair of substrates and an electro-optical material sandwiched between the pair of substrates, and provided on the other substrate. A scanning line group including a plurality of scanning lines, and a plurality of pixels including an active element and the electro-optical material connected in series between the data line and the scanning line,
The active element includes a first electrode and a second electrode;
In a method for driving an active matrix device including a ferroelectric layer disposed between the first electrode and the second electrode, a selection voltage ± V ₀ is sequentially applied to the selection line within one field period. applied to, when applying a data voltage ± V ₁ to the data line, the absolute value of the difference between the selection voltage ± V ₀ and the data voltage ± V ₁ |
V ₀ −V ₁ | And applying a voltage to the ferroelectric layer such that an electric field higher than the coercive electric field is applied to the ferroelectric layer for a certain period after the start of the display operation. Here, E _C : coercive electric field of the ferroelectric layer d _F : layer thickness of the ferroelectric layer C _F : capacitance of the ferroelectric layer per pixel C _LC : of the electro-optical material per pixel Capacity.