JPH04254829A - Active device - Google Patents

Abstract

PURPOSE:To obtain an active device which has less secular change in element output. CONSTITUTION:An active device is so constructed that the first electrode 2, the second electrode 3, a powerful dielectric layer and the third electrode 5 are provided in sequence on an insulation board 1 formed of a glass substrate. An active layer is the powerful dielectric layer 4 in a region where it is sandwiched between the first and third electrodes 2, 5. The first electrode is made of material capable to adhere to the powerful dielectric layer 4. It is thus possible to prevent the separation of the powerful dielectric layer 4 from the first electrode 2 and lessen a secular change in element output.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention applies a voltage to a liquid crystal, and relates to a liquid crystal device.

0002

2. Description of the Related Art Conventionally, as shown in FIG. 2, a transparent electrode 6 made of ITO is provided on an insulating substrate 1 made of a glass substrate. An active device is known in which a ferroelectric layer 4 made of a polymer is provided and a wiring electrode 7 is provided so as to partially cover a transparent electrode 6 through the ferroelectric layer 4 .

0003

However, in the conventional technology, the adhesion between the ITO and the ferroelectric layer was poor, and peeling occurred there when the active device was operated. Therefore, there is a problem in that the element output of the active device changes significantly over time.

The present invention is intended to solve these conventional problems, and an object thereof is to provide an active device in which the change in element output over time is small.

[0005]

[Means for Solving the Problems] The active device of the present invention includes a first island-shaped electrode provided on an insulating substrate, a second electrode connected to the first electrode and provided in an island-like shape, and at least A ferroelectric layer provided to cover a portion of the first electrode, and a third electrode provided to cover at least a portion of the first electrode via the ferroelectric layer. It is characterized by

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an active device according to the present invention. FIG. 1(a) is a top view, and FIG. 1(b) is a top view.
is a cross-sectional view taken along line A-A in the figure. An island-shaped first electrode 2 made of Cr is provided on an insulating substrate 1 made of a glass substrate. A second electrode 3 made of ITO and arranged in an island shape is connected to the first electrode 2 . A ferroelectric layer 4 made of a VDF/TrFE (vinylidene fluoride/trifluoroethylene) copolymer is provided on the first and second electrodes 2 and 3 so as to cover the entire surface of the insulating substrate 1. A third electrode 5 is provided on the ferroelectric layer 4 so as to partially cover the first electrode 2 with the ferroelectric layer 4 in between. The active layer of the active device includes the first and second electrodes 2
, 3 in a sandwich-like manner.

[0007] At the connection portion between the first and second electrodes 2 and 3, the second electrode 3 is provided so as to cover the entire first electrode 2 and a portion thereof is present on the insulating substrate 1. . This improves the adhesion between the first and second electrodes 2 and 3, making it possible to reduce connection resistance.

The active device of the present invention operates by inverting the spontaneous polarization in the ferroelectric layer 4, which is an active layer, with an externally applied voltage to obtain an element output. Since the ferroelectric layer 4 also has piezoelectricity, the ferroelectric layer 4
vibrates. This vibration tends to cause peeling between the electrodes that are in contact with the ferroelectric layer 4. This is particularly noticeable between the electrodes and the insulating substrate 1 side, which is the fixed end of the vibration. If peeling occurs, sufficient voltage will not be applied to the ferroelectric layer 4, making it impossible for the device to operate satisfactorily. This causes a change over time in which the element output decreases over time. This change over time becomes particularly large when the electrode on the insulating substrate side is made of ITO. This is a ferroelectric material and ITO
This is because the adhesion between the two is weak. Therefore, in this example, the change over time was significantly reduced by using the first electrode 2 made of Cr, which has stronger adhesion to the ferroelectric material than ITO. When ITO was used, the device output was halved after operating the device for 3 hours, but by using the first electrode 2 made of Cr, the reduction in device output could be suppressed to 10%. Furthermore, this will reduce the lifespan of a liquid crystal element using the active device of the present invention to be described later.
I was able to extend it from 0 hours to 3000 hours.

Further, in FIG. 1, an adhesive layer may be provided between the first electrode 2 and the ferroelectric layer 4. This adhesive layer may be provided at least in the region where the active layer is to be formed. For example, it may be provided over the entire surface of the insulating substrate 1 including the first and second electrodes 2 and 3. This adhesion layer is used to enhance the adhesion between the first electrode 2 and the ferroelectric layer 4. For example, a silane coupling material can be used. This is I
It adheres more strongly to Cr used as the first electrode 2 than TO. Therefore, the adhesion between the ferroelectric layer 4 and the first electrode 2 is strong, and the change in the device output over time is reduced. This made it possible to increase the lifespan of the liquid crystal element to 30,000 hours. Here, it is not necessary to limit the silane coupling material to be used for the adhesion layer; other coupling materials or PMM may be used.
Organic materials such as A, acrylic, and epoxy may also be used. Of course, a mixed material of an organic material and a coupling material may also be used. In addition, these materials have a strong adhesion with ITO of Cr.
weak compared to

In FIG. 1, a second electrode 3 is placed on an insulating substrate 1.
may be provided, and then the first electrode 2 may be provided. In that case, the first electrode 2
covers the second electrode 3, and a portion thereof is present on the insulating substrate 1.

In FIG. 1, the insulating substrate 1 used is not limited to a glass substrate, and other substrates such as an organic insulating substrate may also be used. It is not necessary to limit the material used for the first electrode 2 to Cr; Au, Ag, Ti, Ta, Al, Mo
Transparent electrodes such as metals such as metals, semiconductors such as Si, silicides, polymer conductors, superconductors, and ZnO may also be used. No matter which material is used, the adhesion to the ferroelectric layer 4 is stronger than that of ITO. The material used for the second electrode 3 is not limited to ITO, and other transparent electrodes or materials that can be used for the first electrode 2 may be used. VDF is used for ferroelectric material 4
/TrFE copolymer, organic ferroelectric materials such as copolymers of vinylidene fluoride and tetrafluoroethylene, copolymers of vinylidene cyanide and vinyl acetate, polyvinylidene fluoride, or inorganic materials such as BaTiO3. A ferroelectric material may also be used. Al is used for the third electrode 5.
There is no need to limit the material to the material used for the first electrode 2.

In FIG. 1, the ferroelectric layer 4 is connected to the insulating substrate 1.
Although the third electrode 5 is formed on the entire upper surface, the ferroelectric layer 4 may be etched and removed using the third electrode 5 as a mask. Of course, what is removed is the region of the ferroelectric layer 4 that is not held sandwiched between the ferroelectric layer 4 and the insulating substrate 1. Then, the ferroelectric layer 4 may be partially or completely removed in the thickness direction.

FIG. 3 shows a liquid crystal element using the active device of the present invention. FIG. 3(a) is a top view, and FIG. 3(b) is a sectional view taken along line A-A in FIG. 3(a). A first electrode 2 made of Cr is disposed on an insulating substrate 1 made of a glass substrate.
, a second electrode 3 made of ITO, a ferroelectric layer 4 made of a copolymer of VDF and TrFE, and a third electrode 5 made of Al. This is a liquid crystal element in which liquid crystal is held between opposing substrates consisting of a opposing electrode 9 made of ITO on a substrate 8.

In FIG. 3, the materials used for the insulating substrate 8 and the counter electrode 9 are not limited to glass substrates and ITO, and the same materials as the insulating substrate 1 and the second electrode 3 in FIG. 1 may be used. Further, what is held between the element substrate and the counter substrate is not limited to liquid crystal, and it is also possible to use a material whose light transmittance and light emitting/non-emitting state can be controlled by voltage.

[0015]

As explained above, the active device of the present invention has a small change in element output over time.

[Brief explanation of the drawing]

FIG. 1 shows an active device of the invention.

FIG. 2 shows a conventional active device.

FIG. 3 is a diagram showing a liquid crystal element using the active device of the present invention.

[Explanation of symbols]

1 Insulating substrate 2 First electrode 3 Second electrode 4 Ferroelectric layer 5 Third electrode 6 Transparent electrode 7 Wiring electrode 8 Insulating substrate 9 Counter electrode

Claims (1)

[Claims] Claims: 1. A first island-shaped electrode provided on an insulating substrate; a second electrode connected to the first electrode and provided in an island shape; covering at least a portion of the first electrode; What is claimed is: 1. An active device comprising: a ferroelectric layer provided as shown in FIG.