JP2006234857A - Display element, display method, and display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display element easily performing halftone display, in an element constitution of a display using an electrochromic display element. <P>SOLUTION: The display element is provided with a display electrode; a counter electrode provided opposite to the display electrode with an interval; and an electrolyte between both electrodes, and has a display layer containing an electrochromic composition wherein an organic electrochromic compound is carried in conductive or semiconductive fine particles on the surface on the counter electrode side of the display electrode. The element is characterized in that an insulating or semiconductive substance adheres to the surface of a part of the conductive or the semiconductive fine particles in the display layer. The display method and the display apparatus are also provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a display element, and more particularly to an element configuration of a display using an electrochromic display element.

  Electronic paper has been actively developed as an electronic medium to replace paper. The characteristics required for electronic paper compared to conventional displays such as CRTs and liquid crystal displays are reflective display elements, high white reflectance, high contrast ratio, high definition display, display It has a memory effect, can be driven at a low voltage, is thin and light, and is inexpensive. In particular, white reflectance and contrast ratio equivalent to those of paper are required as display characteristics, and it is not easy to develop a display device having these characteristics. Examples of electronic paper technologies that have been proposed so far include reflective liquid crystal elements, electrophoretic elements, and toner electrophoretic elements, all of which have a low white reflectance.

  Electrochromism is a phenomenon in which a reversible color change or a reversible color change occurs when a voltage is applied. An EC display element utilizing the coloring / decoloring of an electrochromic (hereinafter sometimes abbreviated as EC) compound that causes such a phenomenon is a reflective display element, and can have a high white reflectance. It is listed as a candidate for electronic paper because it is effective and can be driven at a low voltage. Patent Document 1, Patent Document 2, Patent Document 3, and Patent Document 4 report an EC device in which an organic EC compound is supported on the surface of semiconductive fine particles such as titanium oxide. It is known that this EC element can be colored and decolored very efficiently due to the surface area effect of semiconducting fine particles, and has high repeated durability. In the EC element, the applied charge amount is controlled by adjusting the voltage application time, and a halftone can be displayed. However, it is difficult to control the amount of applied charge, and there is a problem that multi-level halftone display is difficult.

Special table 2001-510590 gazette JP 2002-328401 A JP 2004-151265 A Japanese Patent Application No. 2004-265054

  The present invention has been made in view of the above-described state of the art and problems, and provides a display element that can easily perform halftone display.

  The display element of the present invention is characterized in that a display electrode, a counter electrode provided opposite to the display electrode at a distance from each other, an electrolyte between both electrodes, and an organic electrochromic material on conductive or semiconductive fine particles. In a display device having a display layer containing an electrochromic composition carrying a compound on the surface on the counter electrode side of the display electrode, a part of the conductivity in the display layer, or an insulating or semiconductor on the surface of semiconductive fine particles It is that a sex substance has adhered.

  As a result of intensive studies by the present inventors, when using fine particles having an insulating or semiconducting substance adhered to the surface, the voltage value for causing the display element to develop color as compared to using fine particles not attached. Were almost the same, but it was found that the voltage value for decoloring was different by about 4V. Therefore, a display medium and display that can easily display halftones by simultaneously using fine particles with insulating or semiconducting material attached to the surface and fine particles not attached to the surface and controlling both the applied voltage value and the applied time. The method has been found and the present invention has been achieved.

That is, the present invention has the following configuration.
(1) A display electrode, a counter electrode provided opposite to the display electrode, and an electrolyte between the two electrodes, and an electrochromic compound having an organic electrochromic compound supported on conductive or semiconductive fine particles In a display element having a display layer containing a composition on the surface on the counter electrode side of the display electrode, an insulating or semiconducting substance adheres to the surface of a part of the conductive or semiconductive fine particles in the display layer. A display element.
(2) Conductive with insulating or semiconducting material attached to the surface, or a layer containing an electrochromic composition in which an organic electrochromic compound is supported on semiconducting fine particles, and insulating or semiconducting material attached to the surface The display element according to (1), wherein a display layer is formed by laminating a layer containing an electrochromic composition in which an organic electrochromic compound is supported on conductive or semiconductive fine particles that are not formed.

(3) The display element according to (1) or (2), wherein the insulating or semiconducting substance attached to the conductive or semiconductive fine particles is a metal oxide compound.
(4) The display element according to any one of (1) to (3), wherein the insulating or semiconducting substance attached to the conductive or semiconductive fine particles is aluminum oxide.
(5) The display element according to any one of (1) to (4), wherein a plurality of types of organic electrochromic compounds are supported.
(6) The display element according to any one of (1) to (5), wherein the display layer is formed in an arbitrary pattern.
(7) The display element according to any one of (1) to (6), wherein a white reflective layer is provided between a display electrode having a display layer and a counter electrode.

(8) The display element according to any one of (1) to (7), wherein the electrolyte contains fine pigment particles.
(9) The display element according to any one of (1) to (8), wherein a drive element is formed on the display electrode substrate or the counter electrode substrate.
(10) The display element according to any one of the above (1) to (9) is sufficiently applied with a voltage necessary for color development to cause the display layer to develop a high density, and then applied to the surface. Conductive or non-insulating or semiconducting substances are not attached to the electrochromic composition in which an organic electrochromic compound is supported on semiconducting fine particles, and the voltage necessary for decoloring and the insulating or semiconducting substance on the surface Decreasing the color density of the color-developing part by applying a voltage necessary for erasing the electrochromic composition carrying the organic electrochromic compound on the adhering conductive or semiconducting fine particles for an arbitrary period of time. A display method characterized by displaying halftones.
(11) A display device using the display element and the display method according to any one of (1) to (10).

A configuration example of the display element of the present invention is shown in FIG. 1 and will be described below. However, the configuration of the display element of the present invention is not limited to FIG.
The EC composition contained in the display layer is composed of an electroconductive or semiconductive fine particle and an organic EC compound having an insulating or semiconducting substance attached to the surface, and an electroconductive or nonconductive or semiconducting substance attached to the surface. EC composition composed of conductive or semiconductive fine particles and an organic EC compound. Here, as the conductive or semiconductive fine particles, fine particles having a particle diameter of about 5 nm to 50 nm made of titanium oxide, zinc oxide, tin oxide or the like are desirable. These materials have conductivity and semiconducting properties, and can exchange charges with the electrode and the organic EC compound. Further, by forming a fine particle layer having a particle size of about 5 nm to 50 nm, it is possible to have a very large specific surface area with respect to a smooth electrode surface, and charge can be efficiently transferred. Furthermore, since a transparent film can be formed, there is a great advantage as a display element.

  Examples of the insulating or semiconducting substance attached to the surface include metal oxides such as aluminum oxide, silicon oxide, and zirconium oxide, and organic compounds such as polymer films. Among these, surface treatment with metal oxides is actually used for the purpose of controlling the dispersibility of particles and is useful as an easy surface treatment method. In addition, in the display medium of the present invention, when conductive or semiconductive fine particles are bonded to the electrode surface by sintering, a strong and conductive display layer can be formed. Therefore, surface treatment with metal oxides rather than organic compounds is possible. Is more effective. In addition, as a result of examination of fine particles surface-treated with various metal oxides by the present inventors, a display element using fine particles surface-treated with aluminum oxide or aluminum oxide / zirconium oxide has the most difference in decoloring voltage. I found it big. It seems to be caused by the high insulating property of aluminum oxide.

  Examples of the organic EC compound include a viologen compound, a styryl compound, a phenothiazine compound, and the like, but it is desirable to use a viologen compound because it has a reduction coloring property and can develop many colors depending on a molecular structure. Moreover, it is necessary to have an adsorption site in order to carry on the fine particle surface. As the adsorption site, acidic structures such as phosphonic acid, carboxylic acid, sulfonic acid, and salicylic acid are good. In particular, the phosphonic acid structure is the most useful structure because of its strong adsorption ability.

  The display layer of this display element is made by mixing or laminating conductive or semiconducting fine particles having an insulating or semiconducting substance adhering to the surface and conductive or semiconducting fine particles having no insulating or semiconducting substance adhering to the surface. It is prepared by supporting an organic EC compound. Here, a voltage (denoted as E1) at which the organic EC compound carried on the fine particles subjected to the surface treatment is decolored and a voltage (denoted as E2) at which the organic EC compound carried on the fine particles not subjected to the surface treatment are decolored. Is different. In this case, when the voltage value E2 is applied, only the organic EC compound carried on the fine particles not subjected to the surface treatment is erased. Further, when the voltage value E1 is applied, both organic EC compounds are decolored. Therefore, first, the organic EC compound is brought into a colored state by applying a coloring voltage, and then it can be erased to half the color density by applying the voltage value E2 for an arbitrary time. Next, by applying the voltage value E1 for an arbitrary time, it is possible to display from half the color density to complete decoloring. When only the fine particles not subjected to the surface treatment of the prior art are used, the halftone must be controlled only by the application time of the voltage value E2, so that the display of the halftone becomes very easy by using the display method of the present invention. .

  As the structure of the display layer, mixing each particle makes it possible to make a single layer, which simplifies the manufacturing process. On the other hand, the hydrophilicity of the particles often differs depending on whether or not the surface treatment is performed. It is difficult to prepare a coating solution in which is uniformly dispersed. In the laminated structure, the dispersion condition can be changed for each particle, so that the coating liquid can be easily prepared.

  Another feature of the display element of the present invention is that a plurality of types of organic EC compounds are supported on conductive or semiconductive fine particles. Organic EC compounds such as viologen compounds can produce various colors depending on their molecular structure. Since the display element of the present invention can easily carry a plurality of types of compounds, for example, a deep purple color (substantially black) can be developed by simultaneously carrying a blue color developing compound and a red color developing compound. Advantages include increased color variations and the ability to display black with high visibility.

  Another feature of the display element of the present invention is that the display layer made of the EC composition is formed in an arbitrary pattern. In the display element of the present invention, even when a display layer is provided on the entire surface of a substrate with a transparent electrode, only a part of the color can be developed by applying a voltage, but since the charge is slightly diffused, the color is developed. The image may be slightly blurred. Therefore, by patterning the display layer with high definition for each pixel in advance, blurring of the image due to charge diffusion can be prevented, and a sharp color image can be obtained.

  Another feature of the display element of the present invention is that a white reflective layer is provided. Since the display layer of the display element of the present invention causes a reversible color change between a transparent state and a colored state, when it is a reflective display element, the whiteness of the element is determined by the characteristics of the white reflective layer. If a white reflective layer in which white particles are dispersed in a resin or the like is used, the reflective layer can be easily produced and a high white reflectance similar to paper can be obtained.

  As another method for obtaining a high white reflectance, there is a method in which pigment fine particles are dispersed in an electrolytic solution. The pigment fine particles are dispersed in advance in the electrolytic solution and then injected into the display element. In this method, since no resin for fixing the pigment fine particles is required, the conductivity in the element is good and the element can be driven at a low voltage. As the pigment fine particles, particles made of a general metal oxide can be applied as described above, and specific examples include titanium oxide, aluminum oxide, zinc oxide, silicon oxide, cesium oxide, yttrium oxide and the like.

  Another feature of the display element of the present invention is that it can be driven actively. Control using an active drive element is indispensable for high-definition display on an A4 size screen. In the reflective display element of the present invention, active driving can be easily performed by providing an active driving element on the counter electrode.

According to claims 1 and 10, an EC composition in which an organic EC compound is supported on conductive or semiconductive fine particles having an insulating or semiconducting substance adhered to the surface and no insulating or semiconducting substance adhering to the surface By having a display layer containing an EC composition in which an organic EC compound is supported on conductive or semiconductive fine particles, a display element capable of expressing a multi-level halftone can be provided.
According to the second aspect, it is easier to prepare a dispersion when the display layer has a laminated structure, and a display element capable of expressing a multi-level halftone can be provided at a low cost.
According to the third aspect, by using a metal oxide compound as the insulating or semiconducting substance, the surface treatment of the fine particles can be facilitated, and a display element capable of expressing multi-level halftone can be provided at low cost.

According to the fourth aspect, by using aluminum oxide as the insulating or semiconducting substance, it is possible to provide a display element that can easily perform multi-level halftone at low cost.
According to the fifth aspect, by using a plurality of types of organic EC compounds, it is possible to provide a display element capable of increasing display color variations and displaying black with high visibility.
According to the sixth aspect, since the display layer is formed in an arbitrary pattern, it is possible to provide a display element capable of displaying high-definition image quality.
According to the seventh aspect, by providing the white reflective layer between the display electrode having the display layer and the counter electrode, a display element having a high white reflectance can be provided.
According to the eighth aspect, it is possible to provide a display element that can be driven at a low voltage by providing pigment fine particles in the electrolyte.
According to the ninth aspect, by forming the drive element, the display element can be actively driven, and a large area and high definition display can be handled.
According to the eleventh aspect of the present invention, it is possible to provide a reflective display that can easily perform multi-level halftones.

Hereinafter, the present invention will be described based on examples.
Example 1
As conductive or semiconducting fine particles to which an insulating or semiconducting substance is attached, titanium oxide fine particles (manufactured by Teika Co., Ltd.) (hereinafter abbreviated as TiO1) having a primary particle diameter of 6 nm treated with aluminum oxide / zirconium oxide are used. It was. In addition, as the conductive or semiconductive fine particles to which no insulating or semiconducting substance is attached, titanium oxide fine particles (manufactured by TEIKA CORPORATION) (hereinafter abbreviated as TiO2) having a primary particle size of 6 nm were used.
Further, 1-Ethyl-1 ′-(2-phosphonoethyl) -4,4′-bipyridinium dichloride (hereinafter abbreviated as EPBp) was used as the organic EC compound.

The display electrode was produced as follows. Apply a 20 wt% toluene dispersion of TiO1 to a thickness of about 2 μm by spin coating on a part of the glass substrate (area 1 cm ² ) with a tin oxide transparent electrode film on the entire surface, and baked at 450 ° C. for 1 hour. I concluded. Next, a 20 wt% aqueous dispersion of TiO 2 was applied by spin coating to a thickness of about 2 μm and sintered at 450 ° C. for 1 hour.
EPBp was dissolved in water to prepare a 0.04M solution, and the display substrate was immersed in this aqueous solution to adsorb EPBp on the surface of each fine particle.

The counter electrode is formed by spin coating on a glass substrate with a tin oxide transparent electrode film on the entire surface of a 20 wt% aqueous dispersion of tin oxide particles (manufactured by Mitsubishi Materials Corporation) with a primary particle size of 30 nm so that the thickness is about 2 μm. It was produced by applying to sinter and sintering at 450 ° C. for 1 hour.
The display electrode and the counter electrode were bonded together via a 75 μm spacer to produce a cell. Displayed by dispersing 35 wt% of titanium oxide particles (Ishihara Sangyo Co., Ltd.) with a primary particle size of 300 nm in a solution of 0.2 M perchloric acid chloride in propylene carbonate, preparing an electrolyte solution, and sealing it in a cell. An element was produced.

Example 2
When the white reflectance was measured without applying a voltage, it showed a high value of about 60%. This measurement was performed by irradiating diffused light using a spectrocolorimeter.
Example 3
When the display electrode was connected to the negative electrode, the counter electrode was connected to the positive electrode, and a voltage of 3.0 V was applied for 1 second, only a portion where the fine particle layer of the display electrode was colored reddish purple. This color is attributed to the development of EPBp. When a voltage of −4.0 V was applied for 1 second, the reddish purple color disappeared and became white again.
Example 4
When the display electrode was connected to the negative electrode, the counter electrode was connected to the positive electrode, and a voltage of 3.0 V was applied for 1 second, only a portion where the fine particle layer of the display electrode was colored reddish purple. Next, when a voltage of -1.5 V was applied for 1 second, the reddish purple color became lighter and the color density became about half. Further, when a voltage of -4.0 V was applied for 1 second, all the remaining colors were erased and became white.

Example 5
When the display electrode was connected to the negative electrode, the counter electrode was connected to the positive electrode, and a voltage of 3.0 V was applied for 1 second, only a portion where the fine particle layer of the display electrode was colored reddish purple. Next, when a voltage of -1.5 V was applied for 1 second, the reddish purple color became lighter and the color density became about half. Further, when a voltage of -4.0 V was applied for 1 second, all the remaining colors were erased and became white.
Example 6
When the display electrode was connected to the negative electrode, the counter electrode was connected to the positive electrode, and a voltage of 3.0 V was applied for 1 second, only a portion where the fine particle layer of the display electrode was colored reddish purple. Next, when a voltage of -1.5 V was applied for 0.5 seconds, the reddish purple color became lighter and the color density became about 3/4. Further, when a voltage of -4.0 V was applied for 0.5 seconds, the color density became about 1/4 of the initial color development state.

It is explanatory drawing of an example of the display apparatus of this invention.

Claims (11)

An electrochromic composition comprising a display electrode, a counter electrode provided opposite to the display electrode at an interval, an electrolyte between both electrodes, and an organic electrochromic compound supported on conductive or semiconductive fine particles In the display element having the display layer including the display electrode on the surface on the counter electrode side, an insulating or semiconducting substance is attached to the surface of a part of the conductive or semiconductive fine particles in the display layer. A characteristic display element. Conductive with an insulating or semiconducting substance on the surface, or a layer containing an electrochromic composition in which an organic electrochromic compound is supported on semiconducting fine particles, and an insulating or semiconducting substance on the surface The display element according to claim 1, wherein the display layer is formed by laminating a layer containing an electrochromic composition in which an organic electrochromic compound is supported on non-conductive or semiconductive fine particles. The display element according to claim 1, wherein the insulating or semiconducting substance attached to the conductive or semiconductive fine particles is a metal oxide compound. The display element according to claim 1, wherein the insulating or semiconducting substance attached to the conductive or semiconductive fine particles is aluminum oxide. The display element according to claim 1, wherein a plurality of types of organic electrochromic compounds are supported. The display element according to any one of claims 1 to 5, wherein the display layer is formed in an arbitrary pattern. The display element according to claim 1, wherein a white reflective layer is provided between the display electrode having the display layer and the counter electrode. The display element according to claim 1, wherein the electrolyte contains fine pigment particles. The display element according to claim 1, wherein a drive element is formed on the display electrode substrate or the counter electrode substrate. An insulating or semiconducting substance on the surface of the display element according to any one of claims 1 to 9, wherein the display layer is colored at a high concentration by sufficiently applying a voltage necessary for color development. Conductivity not adhering to the surface, or voltage necessary for decoloring an electrochromic composition in which an organic electrochromic compound is supported on semiconductive fine particles, and conductivity having an insulating or semiconducting material on the surface Alternatively, a halftone is displayed by reducing the color density of the colored portion by applying a voltage necessary for erasing the electrochromic composition in which the organic electrochromic compound is supported on the semiconductor fine particles for each arbitrary time. A display method characterized by that. A display device comprising the display element and the display method according to claim 1.

Images