JP2596378B2 - Solid state display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device comprising a thin layer of a polymer of a five-membered heterocyclic compound and an electrode pair sandwiching the thin layer, and more particularly to a solid display device having a high response speed and excellent durability. .

[0002]

2. Description of the Related Art In recent years, technical innovation has progressed in the field of functional organic materials, and polyacetylene, polyparaphenylene,
A conductive polymer obtained by adding an electron-donating or electron-accepting compound as a dopant to an electron conjugated polymer such as polypyrrole, polythiophene, or polyaniline has been developed, and has been put to practical use as an electrode material or a conductive thin film. this house,
Heterocyclic five-membered cyclic compound polymers such as polypyrrole and polythiophene can be easily formed into thin films by methods such as electrolytic polymerization,
It is known that the absorption spectrum changes due to the change of the electronic state by electrochemically doping and undoping, and a display device using this is also proposed (Kando et al., Japanese Journal of Japan). Applied Physics (JJ Appl. Phys.),
22, L412, 1983). However, this type of display device has a low response speed because the change in absorption spectrum is controlled by doping and undoping, which are electrochemical oxidation-reduction reactions, and has a complicated device configuration that does not leak due to the use of an electrolyte solution. I needed to. Also,
Although this type of display element may use a solid electrolyte, it is expected that the response speed will be lower than that using an electrolyte because the movement speed of electrolyte ions is low in the solid electrolyte. It is difficult to use as an element. As a display element utilizing an electrochemical oxidation-reduction reaction, an optical device integrated with a field effect transistor (Japanese Patent Application Laid-Open Nos. 64-37538 and 1-37538) has been proposed. .

[0003] As a conventional display element similar to the present invention,
By applying a voltage to both ends of a vertically long organic molecular layer that is regularly arranged, an electronic polarization is caused in the organic molecular layer, thereby changing the electronic structure of the organic molecule. There has been proposed a field-effect display characterized by using a change as a display principle (Japanese Patent Application Laid-Open No. 57-191621). However, it is considered that the absorption spectrum is hardly changed by the low electric field electron polarization that can be controlled without changing the arrangement of the organic molecular layer, and it is considered that there are few or very special organic molecules that can be used. In fact, the proposal of the field effect display does not show a specific example of a vertically long organic molecule.

Further, as a display element using a conductive polymer, an electroluminescent element in which an organic compound such as a conductive polymer and another material are joined has been proposed. The display principle utilizes a phenomenon in which light is emitted when injected holes recombine.

[0005]

As described above, the response speed of a display element utilizing an electrochemical oxidation-reduction reaction using a conventional electron conjugated compound polymer such as a five-membered heterocyclic compound polymer is high. However, it was difficult to achieve a simple element configuration having excellent durability.

The present invention has been made to solve these problems, and an object of the present invention is to provide a solid-state display device having a high response speed and excellent durability.

[0007]

Means for Solving the Problems The present inventors have conducted various studies to solve the above-mentioned problems. As a result, the solid-state display device includes a thin layer of the five-membered heterocyclic compound polymer and an electrode pair sandwiching the thin layer, wherein the five-membered heterocyclic compound polymer is plane-oriented, and voltage is applied. It has been found that a solid-state display device characterized in that it is a compound whose absorption spectrum changes with a change in conformation caused by the above has a high response speed and excellent durability, and has led to the present invention.

That is, the present invention is characterized in that the conformation of the polymer of a five-membered heterocyclic compound is changed by an electric field to change the absorption spectrum.

In the present invention, the polymer of a five-membered heterocyclic compound or a derivative thereof is pyrrole, thiophene, furan,
Selenophene, a polymer having a basic skeleton such as tellurophen or a derivative thereof, and among them, a copolymer of the heteropentacyclic compound and a heteropentacyclic polymer having a substituent is preferable. Polythiophene or its derivative as a basic skeleton is preferable from the viewpoint of stability and ease of production. In the present invention, the derivative of the polymer of the five-membered heterocyclic compound is not particularly limited as long as the basic skeleton is a derivative having a five-membered heterocyclic compound.
Examples of such a compound include a compound in which an alkyl group, an alkenyl group, an alkoxy group, a phenyl group, a cyano group, a halogen, and the like are added to the above five-membered heterocyclic compound.

The method for synthesizing the polymer of the five-membered heterocyclic compound or its derivative used in the present invention is not particularly limited.
Examples include a method of oxidatively polymerizing one or two or more heteropentacyclic compounds or derivatives thereof as a monomer with an oxidizing agent, and a method of electrolytic oxidative polymerization in an electrolytic solution. Also, the method for forming the thin layer is not particularly limited, and the polymer synthesized by the above method may be dedoped and cast in a solvent, or the thin layer synthesized by electrolytic polymerization may be dedoped. It can be used as it is.

In the present invention, plane orientation means that the main chain of the polymer of the five-membered heterocyclic compound is not distributed isotropically, but the number along the electrode surface is smaller than that in the vertical direction. This can be confirmed by an X-ray diffraction pattern, a polarized infrared absorption spectrum, or the like.

According to the present invention, an electrode is attached to both surfaces of a thin layer of a polymer of a five-membered heterocyclic compound or a derivative thereof formed as described above as it is or through an insulator layer, and an electric field is applied to the five-membered heterocyclic compound. The absorption spectrum is controlled by changing the conformation of the cyclic compound polymer. Therefore, it is considered that the display element of the present invention is solid and has a high response speed, unlike the conventional display element utilizing an electrochemical oxidation-reduction reaction. Conventionally, a field effect display utilizing an absorption spectrum change due to the polarization of organic molecules has been proposed, but this principle and element configuration are significantly different from the display element of the present invention. In particular, in a field effect display, it is considered that there are few or few compounds whose absorption spectrum actually changes according to this principle. Further, the present invention is different from the organic electroluminescent device in both display principle and effect.

In the present invention, the thickness of the thin layer of the polymer of the five-membered heterocyclic compound is not particularly limited. However, in order to use the five-membered heterocyclic polymer as a color former, if it is too thin, the display becomes unclear. Therefore, the thickness is preferably 0.1 μm or more. If the thin layer of the polymer of the five-membered heterocyclic compound is too thick, the electric field that causes discoloration increases, so that the driving voltage is preferably 20 μm or less in order to keep the driving voltage at 20 V or less.

The type of electrode used in the present invention is not particularly limited as long as it is conductive, and gold, silver, platinum, copper,
Various alloys such as nickel, aluminum, and indium / tin oxide can be used. However, in order to function as a display element, at least one electrode is made of a thin film of metal having a large light transmittance of 1000 Å or less or an indium / tin oxide. It is preferably an object. The electric field strength is not particularly limited, but is preferably 1 kV / cm or more from the viewpoint of display effect.

When an electric field is applied to the display device of the present invention, for example, when a copolymer of thiophene and octylthiophene (copolymerization ratio 30:70) is used as a derivative of a five-membered heterocyclic compound, an absorption peak at 505 nm is obtained. Shift to 515 nm. Therefore, in the present invention, an image can be displayed by using an appropriate pixel electrode. In the present invention, the driving method of the pixel electrode is not particularly limited, and a conventionally known method can be used. The display element of the present invention can be displayed by light transmitted by a backlight similarly to a conventional liquid crystal display element,
It can also be displayed with reflected light.

Since the display element of the present invention utilizes a change in hue due to a conformational change of the polymer of the five-membered heterocyclic compound, the display element has a high response speed and a five-membered heterocyclic polymer or a color-forming layer. By reducing the thickness of the derivative, low-voltage driving is possible. Further, compared to the conventional liquid crystal display device, there is no need to use a polarizing plate or the like, so that a wide viewing angle is obtained.

[0017]

Hereinafter, the present invention will be described with reference to Examples.
The present invention is not limited to the following examples unless it exceeds the gist.

(Example 1) A copolymer of thiophene and 3-octylthiophene having a copolymerization ratio of 30:70 synthesized by oxidative cationic polymerization using thiophene and 3-octylthiophene as monomers was dedoped and extracted with chloroform. Thus, a 10% by weight solution was prepared. This solution was dropped onto a clean glass substrate on which a conductive film of indium / tin oxide was formed, and a thin film having a thickness of 1 μm was formed by spin coating. Further, a gold electrode layer was formed on the copolymer layer of thiophene and 3-octylthiophene by a vacuum evaporation method, and a voltage of 20 V was applied to the indium / tin oxide conductive layer and the gold electrode layer. As shown, the absorption peak at 505 nm shifted to 515 nm, and the absorption spectrum changed.

The thin film formed by the spin coating method was partially peeled off and irradiated with X-rays in the direction of the film thickness, and the diffraction pattern was measured. As a result, a broad amorphous property was observed around 2θ = 18 to 22 °. A diffraction peak was observed, and the ratio of the diffraction intensity in the meridian direction to the diffraction intensity in the equator direction when the film surface was in the equator direction was 0.7, indicating a deviation in the diffraction pattern. When the diffraction pattern was measured by irradiating the film surface with X-rays perpendicularly, no deviation of the diffraction pattern was observed. This confirmed that the thin film was plane-oriented.

Example 2 3-Methylthiophene and 3-methylthiophene
Octylthiophene as monomer, copolymerization ratio 30: 7
A copolymer of 3-methylthiophene and 3-octylthiophene was prepared, a thin film was formed in the same manner as in Example 1, and an electrode layer was attached. When a voltage of 20 V was applied to this electrode layer, the absorption spectrum changed. Figure 1
Shown in

When the X-ray diffraction pattern of the thin film formed in this embodiment was measured in the same manner as in Embodiment 1, when the X-ray was irradiated from the film thickness direction, the deviation of the diffraction pattern was observed. No deviation of the diffraction pattern was observed in the film surface direction. This confirmed that the thin film was plane-oriented.

[0022]

As described above, according to the present invention, a solid-state display device having a high response speed and excellent durability can be provided, and the effect is large.

[Brief description of the drawings]

FIG. 1 is a diagram showing a change in an absorption spectrum due to application of a voltage.

[Explanation of symbols]

 None

Claims (3)

(57) [Claims] 1. A solid display device comprising a thin layer of a five-membered heterocyclic compound polymer and an electrode pair sandwiching the thin layer, wherein the five-membered heterocyclic compound polymer is plane-oriented, and A solid-state display device, which is a compound whose absorption spectrum changes with a change in conformation due to voltage application. 2. The solid display according to claim 1, wherein the five-membered heterocyclic compound polymer is a copolymer of a five-membered heterocyclic compound and a five-membered heterocyclic compound having a substituent. element. 3. The solid-state display device according to claim 1, wherein the five-membered heterocyclic compound is thiophene or a thiophene derivative.