JPH02173728A - Active device - Google Patents

Abstract

PURPOSE:To obtain images which are bright and are high in contrast by providing a ferroelectric substance layer and coupling layer on an insulated substrate and forming electrodes on the coupling layer. CONSTITUTION:Electrodes 13 consisting of ITO are provided on the insulated substrate 12 consisting of a glass substrate and the ferroelectric substance layer 14 consisting of the copolymer of vinylidene fluoride and trifluoroethylene is provided on the electrodes 13. The coupling layer 18 consisting of a titanate coupling agent is provided on the ferroelectric substance layer 14 and the electrodes 15 consisting of Al are provided on the coupling layer 18. The coupling layer 18 increases the adhesive strength between the electrodes 15 and the ferroelectric substance layer 14. The images which are bright and high in contrast are obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an active device for driving pixels of an active matrix display and a printer engine of a printer.

[Conventional technology 1 Conventionally, SID (Society For Inf.
display), 1986
Symposium Digest P296-2
Active devices such as those described in 97 were known. The outline is shown in Figure 2. Gate electrode 2 formed on glass substrate l, gate insulation Il! 3. Channel amorphous 5i10, source and drain region 1
1.6. A lower base iA in which one pixel electrode 7 is connected to a thin film transistor consisting of source and drain electrodes 5 and 4.
An active device is known in which a liquid crystal C is held between an upper substrate B having an electrode 8 formed on a glass substrate 9.

[Problems to be Solved by the Invention] However, conventional active devices have had the following problems. That is, the image information applied to the source electrode 5 is transmitted to the liquid crystal C held between the pixel electrode 7 and the electrode 8 through the channel amorphous St 10 whose on/off is controlled by the gate electrode 2. It is held as a charge of C. However, LCD C
The charge decreases over time due to the leakage of the liquid crystal itself and the leakage current of thin film transistors (which means that image information is lost over time. Therefore, clear, high-contrast images It was difficult to obtain.

SUMMARY OF THE INVENTION The present invention is intended to solve these conventional problems, and an object of the present invention is to provide an active device that provides clear, high-contrast images.

[Means for Solving the Problems 1] The active device of the present invention includes a ferroelectric layer formed on an insulating substrate, a coupling layer formed on the ferroelectric layer, and a coupling layer formed on the coupling layer. It is characterized by being equipped with an electrode.

[Example] An example of the present invention will be described based on the drawings. Figure 1 (a
) and (b) are a sectional view and a top view of the first active device of the present invention, and FIG. 1(a) is a sectional view taken along line AB in FIG. 1(b). An electrode 13 made of ITO is provided on an insulating substrate 12 made of a glass substrate, and a copolymer of vinylidene fluoride (hereinafter abbreviated as VDF) and trifluoroethylene (hereinafter abbreviated as TrFE) is provided on the electrode 13. A ferroelectric layer 14 consisting of
A coupling layer 18 made of a titanate coupling agent is provided thereon, and Aε
An electrode 15 consisting of is provided. Coupling layer 1
8 increases the adhesion strength between the electrode 15 and the ferroelectric layer 14, and at the same time improves the reliability of the first active device of the present invention.

In FIGS. 1(a) and 1(b), the titanate coupling agent used as the coupling layer 18 has a structure such as or, for example, but any titanate coupling agent can be used. The structure is not limited to the above two structures, and a silane coupling agent or an aluminum coupling agent may be used instead of the titanate coupling agent.

The above-mentioned various coupling agents are coated onto the ferroelectric layer 14 (for example, by diluting with a solvent such as isopropyl alcohol to adjust the viscosity) by a spin cord method or a dipping method, and are then dried. After that, the electrode 15 may be formed immediately so that the coupling agent does not react with moisture in the air, or the coupling agent may be sufficiently reacted with moisture (for example, after being placed in water). The electrode 15 may be formed after drying).

The thickness of the coupling layer 18 may be the thickness of one molecular layer of the coupling agent, or may be the thickness of multiple molecules. It does not need to be formed, and may be formed using two or more types of coupling agents.

Furthermore, the material used for the coupling layer 18 does not need to be limited to a coupling agent (for example, inorganic materials such as SiOx, siloxane, polyimide, epoxy resin, acrylic, etc., organic materials, or synthetic materials thereof can be used in one or two layers). Alternatively, these materials may be mixed with a coupling agent, or coated with a coupling agent, or vice versa, or sandwiched between two layers of coupling agents. May be used.

The surface shape of the coupling layer 18 may be flat with no irregularities, or may have irregularities of, for example, several hundred to several thousand angstroms to improve the adhesion of the electrodes 15.

In FIGS. 1(a) and 1(b), the material used for the electrodes 13 and 15 is not limited to ITO and Aff; examples include other transparent electrodes, metals, semiconductors, silicides, superconducting materials, and conductive materials. Insulating substrate 12, which may be formed using a polymer
The material used for this need not be limited to glass, and may be inorganic materials such as ceramics or organic materials such as plastics.

Fig. 1(a), (BaT as ferroelectric layer 3 in bJ)
Perovskite ferroelectrics such as iOs, PbTiOs, WOs, Rothsiel salt, deuterium Rothsiel salt,
Rochelle salt-based ferroelectrics such as tartrate, KDP, phosphate, arsenate, potassium dihydrogen phosphate, dihydrogen phosphate, alkaline ferroelectrics such as potassium, G
Guanidine-based ferroelectrics such as ASH and TGS, potassium niobate, glycine sulfate, ammonium sulfate, sodium nitrite, potassium hexacyanoferrate (yellow blood salt), antimony iodide sulfide, or Li TaO
2, Amorphous ferroelectric materials such as PbT i Ox, PLZT
, PZT, vinylidene fluoride and its copolymers, copolymers of vinylidene fluoride and tetrafluoroethylene, etc., copolymers of vinylidene cyanide and vinyl acetate, and other polymeric ferroelectrics, B i+ Tis (Lm , Fe-B
-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 ferroelectrics, or a composite with a paraelectric substance may be used.
Inorganic ferroelectric materials such as T IB Oa are characterized by large residual polarization and fast switching speed, and amorphous ferroelectric materials are characterized by the ease of obtaining a uniform ferroelectric layer over a large area. Since ferroelectric materials are obtained by the spin-coding method, they have the characteristic that they can be obtained uniformly over a large area at low cost. Also.

Most ferroelectric materials have stable A degree characteristics because there is almost no change in dielectric constant or residual polarization at actual operating temperatures.

In FIGS. 1(a) and 1(b), from the insulating substrate 12 side,
Electrode 15, ferroelectric layer 14, coupling layer 18. The positions of electrode 13 and electrodes 13 and 15 may be reversed.

FIG. 3 shows a cross-sectional view of a liquid crystal panel using the active device of the tube 1 of the present invention, an insulating substrate 1 made of a glass substrate.
Electrode 13 made of ITO provided above, VDF and Tr
Ferroelectric layer 14 made of a copolymer with FE. Coupling layer 18 made of titanate coupling agent, AI2
An electrode 1 made of ITO provided on an insulating substrate 16 made of a glass substrate and a base iD made of an electrode 15 made of
This is a liquid crystal panel in which a liquid crystal F is held between opposing substrates E consisting of 7.

In FIG. 3, since the electrode 13 forms a pixel electrode, the coupling N18 can be used as an alignment film for liquid crystal. It also cuts the DC voltage applied to the liquid crystal. It also functions as a DC voltage cutting film. Therefore, a liquid crystal panel using the active device of the present invention tube 1 is
Since there is no need to add a special process to form a liquid crystal alignment film or a DC voltage cut film, it can be formed in a short process with a high yield, and has great industrial value. Furthermore, since the coupling layer 18 is located between the liquid crystal F and the ferroelectric layer 14, impurities in the ferroelectric layer 14 may dissolve into the liquid crystal F, deteriorating the characteristics of the liquid crystal F, or It also has the function of a protective film that prevents the reliability from decreasing or vice versa from deteriorating the characteristics of the ferroelectric layer 14 . Further, the function of the protective film is to prevent impurities in the insulating substrate 12 from being mixed into the liquid crystal F.

Therefore, it becomes possible to use inexpensive insulating substrates that could not be used in liquid crystal panels due to impurity problems, and in this respect as well, the industrial value is enormous.

In FIG. 3, the material 4 used for the insulating substrate 16 and the electrode 17 is not limited to glass or Aff (the insulating substrate 1
2. The same material as used for the electrode 13 may be used.

In Figure 3, instead of liquid crystal F, materials that have an electro-optical effect, EL materials, gases, electrochromic materials, etc. that change the transmittance of light by an electric field, materials that change the light emitting/non-emitting state, and materials that change the color A variable material or the like may also be used.

FIG. 4 shows a top view of a part of an active matrix panel using the active device of the tube 1 of the present invention. An electrode 13 made of ITo is placed on an insulating substrate 12 made of a glass substrate.
, a ferroelectric layer made of a copolymer of VDF and TrFE,
A coupling layer made of a titanate-based force/knobling agent, a substrate made of an electrode 15 made of Aρ, and an electrode 17 made of ITO provided on an insulating substrate made of a glass substrate.
The liquid crystal is held between opposing substrates formed by.

Electrodes 15 and 17 on both substrates are arranged in a matrix.

FIGS. 5(a) and 5(b) show the active device of the tube 2 of the present invention, FIG. 5(b) is a top view, and FIG. 5(a) is a sectional view taken along line A-H in the same figure. . An electrode 13 made of ITO 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 electrode 13.
A coupling layer 18 made of a titanate-based coupling agent is provided on the coupling layer 18.
A ferroelectric layer 14 and a coupling layer 18, on which an electrode 15 is provided. The electrodes 15 are formed in the same shape.

In FIGS. 5(a) and 5(b), the coupling layer 18 does not necessarily have to have the same shape as the electrode 15, but may be provided to cover the insulating substrate 12 and the electrode 13 as in the first active device. Also good. In this case, the ferroelectric layer 14 and the electrode 15 may be formed in the same shape or may be formed in different shapes.

FIGS. 6(a) and 6(b) show the active device of the cylinder 3 of the present invention, FIG. 6(b) is a top view, and FIG. FIG. 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 coupling layer 18 made of a titanate coupling agent is provided on the ferroelectric layer 14. An electrode 13 made of ITO and an electrode 15 made of Ar1 are provided on the coupling layer 18.

In FIGS. 6(a) and 6(b), it is not necessarily necessary to provide the coupling layer 18 on the entire surface of the ferroelectric layer 14, and the coupling layer 18 in the area not in contact with the electrode 13.15 is removed. You can also set it as

FIGS. 7(a) and 7(b) show the active device of the cylinder 4 of the present invention, FIG. 7(b) is a top view, and FIG. FIG. A ferroelectric layer 14 made of a copolymer of VDF and TrFE is provided in an island shape on an insulating substrate 12 made of a glass substrate, and a titanate cup is formed to cover the ferroelectric layer 14 and the insulating substrate 12. A coupling layer 18 made of a ring agent is provided, and an electrode 13 made of ITO and an electrode 15 made of Ar1 are placed on the coupling layer 18.
The ferroelectric layer 14 is provided so as to partially overlap with the ferroelectric layer 14 via the ferroelectric layer 8 .

In the active device of the present invention cylinder 4.

The coupling layer 18 does not necessarily need to be provided also in the region in contact with the insulating substrate 12, and at least the ferroelectric layer 14
It suffices if it is provided in a region sandwiched between the electrodes 13 and 15.

In the active devices according to the invention cylinders 2 to 4, the coupling layer 18 is used to increase the adhesion strength between the ferroelectric layer 14 and the electrode 13 or the electrode 15, as in the active device according to the invention cylinder 1. When the active devices of the present invention cylinders 2 to 4 are used in a liquid crystal panel, the coupling layer 18 is a liquid crystal alignment film, a DC voltage cut film, and a protective film, as in the case of using the active device of the present invention cylinder 1. It also has the function of a membrane.

Insulating substrate 121 ferroelectric layer 14 used in active devices of cylinders 2 to 4 of the present invention. The materials used for the electrodes 13, 15 and the coupling layer 18 may be the same as those used for the active device of the cylinder 1 of the present invention.

The active devices of the tubes 2 to 4 of the present invention may be used instead of the active devices of the tube 1 of the present invention to form a liquid crystal panel or an active matrix panel shown in FIGS. 2 and 3.

The active devices of cylinders 1 to 4 of the present invention drive the liquid crystal using the residual polarization of a ferroelectric material that has memory properties, and the active devices themselves have no leakage current (the active devices provide clear, high-contrast images). It is a device.

(Effects of the Invention) The active device of the present invention is a highly reliable active device and provides a clear and high-contrast coupling layer image.

[Brief explanation of the drawing]

FIGS. 1(a) and (b) are cross-sectional views and top views of the first active device of the present invention, FIG. 2 is a diagram showing a conventional active device, and FIG. 3 is a diagram showing the first active device of the present invention. 4 is a top view of a part of an active device using the first active device of the present invention, and FIGS. 5(a) and 5(b) are a cross-sectional view of the liquid crystal panel used. 6(a) and (b) are sectional views and top views of the third active device of the present invention, and FIGS. 7(a) and (b) are the fourth active device of the present invention. FIG. 2 is a cross-sectional view and a top view of an active device. Applicant Seiko Epson Co., Ltd. Agent Patent Attorney Masatoshi Kamiyanagi (and 1 other person) 12...
Insulating substrate 13...electrode 14...ferroelectric layer 15...electrode<a) (b) Figure 1 (lt) (shi) Figure 5 (Figure 2)

Claims (1)

[Claims] An active device comprising: a ferroelectric layer formed on an insulating substrate; a coupling layer formed on the ferroelectric layer; and an electrode formed on the coupling layer.