JP2009198974A - Display element and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display element and a display device capable of performing color display with high picture quality. <P>SOLUTION: The display element 10 includes a display electrode 11, a counter electrode 12 provided opposing to the display electrode 11, a medium 13 containing an electrolyte disposed between the display electrode 11 and the counter electrode 12, and a display layer 14 provided in the counter electrode 12 side of the display electrode 11, and is characterized in that: the medium 13 and the display layer 14 contain at least one of organic electrochromic compounds 13a, 14a, respectively, that can reversibly develop colors and decolorize by an oxidation-reduction reaction; and the organic electrochromic compound 13a develops a color different from that of the organic electrochromic compound 14a and is different in at least one factor among the threshold of a voltage allowing color development, the threshold of a voltage allowing decolorizing, a charge amount necessary until a color is developed to a prescribed density, and a charge amount necessary until a color is eliminated to a prescribed density. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a display element and a display device.

  In recent years, electronic paper has been known as an electronic medium that replaces paper. Necessary characteristics of electronic paper include a reflective display element, high white reflectance, high contrast ratio, high-definition display, display memory effect, and low voltage drive , Thin and light, and inexpensive. In particular, white reflectance and contrast ratio equivalent to those of paper are required as display characteristics. Furthermore, there is a great demand for electronic paper capable of color display.

  As such electronic paper, for example, a medium in which a color filter is formed on a reflective liquid crystal element is known. However, since a polarizing plate is used, light utilization efficiency is low and white reflectance is low. Furthermore, since black cannot be displayed, the contrast ratio is also low.

  In addition, an electrophoretic element based on the principle of moving charged white particles and black particles by an electric field is known, but it is practically difficult to completely invert white particles and black particles, and high white reflectance, It is difficult to satisfy a high contrast ratio at the same time.

  On the other hand, an electrochromic element using an electrochromic compound that reversibly oxidizes or reduces when a voltage is applied, and develops or decolors, is a reflective display element, has a high white reflectance, and is suitable for display. It has a memory effect and can be driven at a low voltage.

  Patent Document 1 includes a first electrode, a second electrode, an electrolyte, and an electron donor disposed on a transparent or translucent substrate, and redox coloring between the first and second electrodes. An electrochromic device having a nanoporous-nanocrystalline film with a semiconducting metal oxide is disclosed.

  Patent Document 2 discloses that in an electrochromic device having two planar electrodes facing each other, and at least one of the electrodes has a layer made of transparent conductive fine particles on a facing surface, the fine particles A configuration carrying an electrochromic dye is disclosed.

  Further, in Patent Document 3, an electrochromic element having an electrochromic element in which an electrolyte layer is interposed between a substrate in which a semiconductor nanoporous layer is formed on at least one surface of two conductive substrates, at least one of which is transparent. In a chromic device, a configuration in which at least one electrochromic dye is supported on a semiconductor nanoporous layer is disclosed.

However, such an electrochromic device (element) has a high white reflectance as compared with a liquid crystal element and an electrophoretic element, and even if a color filter is provided, a certain degree of white reflectance can be secured. Color display of image quality is difficult.
Special table 2001-510590 gazette JP 2002-328401 A JP 2004-151265 A

  The present invention has been made in view of the above-described problems of the related art, and an object of the present invention is to provide a display element and a display device capable of high-quality color display.

  The invention according to claim 1 is a display electrode, a counter electrode provided to face the display electrode, a medium including an electrolyte disposed between the display electrode and the counter electrode, and the display A display element having a display layer provided on the counter electrode side of an electrode, wherein the medium and the display layer are each made of a chromogenic substance capable of reversibly developing and decoloring by an oxidation-reduction reaction. The color-forming substance contained in the medium containing at least one color develops a color different from that of the color-developing substance contained in the display layer, and also has a threshold voltage that can be developed and a voltage that can be erased. And at least one of a charge amount necessary for color development to a predetermined density and a charge amount necessary for decoloration to a predetermined density are different.

  According to a second aspect of the present invention, in the display element according to the first aspect, the display layer includes a unit display layer containing a kind of color-developing substance that can be reversibly developed and decolored by an oxidation-reduction reaction. Two or more layers are laminated, and the chromophoric substance contained in one layer of the unit display layer develops a color different from that of the chromogenic substance contained in the other layer of the unit display layer and causes color development. At least one of a threshold voltage that can be erased, a threshold voltage that can be decolored, an amount of charge required to develop a color to a predetermined density, and an amount of charge necessary to be erased to a predetermined density It is characterized by being different.

  A third aspect of the present invention is the multicolor display element according to the first or second aspect, wherein the medium is composed of two or more structural units separated by a partition wall.

  According to a fourth aspect of the present invention, in the display element according to any one of the first to third aspects, the color-developing substance contained in the medium and the display layer can develop a color on the display electrode. It further has a color filter that transmits light of a color different from a different color.

  According to a fifth aspect of the present invention, in the display element according to any one of the first to fourth aspects, the color-developing substance contained in the display layer is an organic electrochromic compound, and is also conductive or semiconductive. It is characterized in that it is supported on the conductive particles.

  A sixth aspect of the present invention is a display device in which the display element according to any one of the first to fifth aspects is formed on a substrate, and has means for driving the display element. And

  According to the present invention, it is possible to provide a display element and a display device capable of high-quality color display.

  Next, the best mode for carrying out the present invention will be described with reference to the drawings.

  The display element of the present invention includes a display electrode, a counter electrode provided opposite to the display electrode, a medium including an electrolyte disposed between the display electrode and the counter electrode, and a counter electrode side of the display electrode. The display layer and the medium each have a provided display layer, and each of the display layer and the medium includes one or more color forming materials that can reversibly develop and decolor by oxidation-reduction reactions. At this time, the color-forming substance contained in the medium develops a color different from that of the color-forming substance contained in the display layer, a voltage threshold that can be developed, a voltage threshold that can be erased, At least one of the charge amount required until the color is developed to a predetermined density and the charge amount necessary to be erased to the predetermined density are different. Thereby, a display element capable of high-quality color display is obtained.

  Although it does not specifically limit as a color development substance, An electrochromic compound, a conductive polymer, a metal, its salt, etc. are mentioned.

  Examples of the inorganic electrochromic compound include tungsten oxide, molybdenum oxide, iridium oxide, and titanium oxide.

  Although it does not specifically limit as an organic electrochromic compound, 1-Ethyl-1 '-(2-phosphoethyl) -4,4'-bipyridinium dichloride, 1-p-cyanophenyl-1'-(2-phosphonoethyl) -4, 4′-bipyridinium dichloride, Bis (2-phosphorylethyl) -4,4′-bipyridinium dichloride, 1-Ethyl-1′-acetic acid-4, 4′-bipyridinium dichloride 2-viologen [compound 2- [2] 4- (dimethylylamino) -5-carbophenyl] ethyl] -3,3-dimethyllinolin [2,1-b] oxazolidine, 2- [2- [4- (dimethylamino) -5-carbophenyl] -1,3-butadienyl] -3,3-dimethylolino [2,1-b] oxazolidine, 2- [ Styryl compounds such as 2- [4- (dimethylamino) phenyl] -1,3-butadienyl] -3,3-dimethyl-5-sulfonyllinolin [2,1-b] oxazolidine; (2-Phenothiazin-10-yl-) ethyl) -phosphonic acid, 3-Phenothiazin-10-yl-propionic acid, 3-Phenothiazin-10-yl-methanesu fonic acid phenothiazines, etc., and the like.

  Examples of the conductive polymer include polypyrrole, polythiophene, and polyaniline.

  Examples of the metal or a salt thereof include metals such as silver, bismuth, zinc, and copper, or salts thereof.

  In the present invention, the color-developing substance contained in the display layer is an organic electrochromic compound, and is preferably supported on conductive or semiconductive particles, on the surface of the conductive or semiconductive particles. It is particularly preferred that it is adsorbed. At this time, the organic electrochromic compound preferably has an acidic group such as a phosphonic acid group, a carboxylic acid group, a sulfonic acid group, and a salicylic acid group in order to be adsorbed on the surface of the conductive or semiconductive particles. Having a phosphonic acid group is particularly preferred because of its strong adsorption ability. The organic electrochromic compound may be bonded to the surface of conductive or semiconductive particles using a silane coupling agent or the like.

  The conductive or semiconductive particles are not particularly limited as long as they can support an organic electrochromic compound. However, titanium oxide, zinc oxide, tin oxide, alumina, zirconia, ceria, silica, yttria, boronia, magnesia, Strontium titanate, potassium titanate, barium titanate, calcium titanate, calcia, ferrite, hafnia, tungsten trioxide, iron oxide, copper oxide, nickel oxide, cobalt oxide, barium oxide, strontium oxide, vanadium oxide, barium titanate , Aluminosilicate, calcium phosphate, aluminosilicate, and the like, and two or more of them may be used in combination. Among these, titanium oxide, zinc oxide, tin oxide, alumina, zirconia, zirconia, iron oxide, magnesium oxide, indium oxide, and tungsten oxide are preferable, and titanium oxide is particularly preferable from the viewpoint of electrical characteristics and physical characteristics.

  The conductive or semiconductive particles usually have a particle size of about 5 nm to 50 nm.

  Such an organic electrochromic compound is colored or decolored by the movement of electric charge from the display electrode through conductive or semiconductive particles. For this reason, color development or decoloring can be performed efficiently, and power consumption can be reduced. Moreover, the organic electrochromic compound can develop various colors by changing the molecular structure.

  FIG. 1 shows a first example of the display element of the present invention. The display element 10 includes a display electrode 11, a counter electrode 12 provided to face the display electrode 11, and a medium 13 including an electrolyte disposed between the display electrode 11 and the counter electrode 12. Further, the display layer 14 is provided on the surface of the display electrode 11 on the counter electrode 12 side, and the white reflective layer 15 is provided on the surface of the counter electrode 12 on the display electrode 11 side. The counter electrode 12 is bonded via a spacer 16. At this time, the medium 13 and the display layer 14 include organic electrochromic compounds 13a and 14a, respectively, and the organic electrochromic compound 14a is supported on conductive or semiconductive particles 14b. The organic electrochromic compounds 13a and 14a develop cyan (C) and magenta (M), respectively.

  The spacer 16 is not particularly limited, but can be formed using a photolithography method, a screen printing method, or the like.

  Hereinafter, a method for controlling the color development and / or decoloration of the organic electrochromic compounds 13a and 14a will be described.

The thresholds of the voltages at which the organic electrochromic compounds 13a and 14a can be developed are set to Vc (E ₁₃ ) and Vc (E ₁₄ ), respectively, and the organic electrochromic compounds 13a and 14a are developed to a predetermined density. The required charge amounts are Qc (E ₁₃ ) and Qc (E ₁₄ ), respectively, and the equations 0 <Vc (E ₁₄ ) <Vc (E ₁₃ ), 0 <Qc (E ₁₃ ) <Qc (E ₁₄ )
When the condition is satisfied, the organic electrochromic compounds 13a and 14a can be colored as follows.

Specifically, when a voltage of Vc (E ₁₄ ) or more and less than Vc (E ₁₃ ) is applied between the display electrode 11 and the counter electrode 12 and a charge amount of Qc (E ₁₄ ) or more is supplied, the organic electro The chromic compound 14a develops color at a predetermined density. At this time, since a voltage lower than Vc (E ₁₃ ) is applied, the organic electrochromic compound 13a does not develop color.

Further, when a voltage equal to or higher than Vc (E ₁₃ ) is applied between the display electrode 11 and the counter electrode 12 and a charge amount equal to or higher than Qc (E ₁₃ ) and lower than Qc (E ₁₄ ) is supplied, the organic electrochromic compound 13a Develops to a predetermined density. At this time, since a voltage equal to or higher than Vc (E ₁₃ ) is applied, the coloring reaction of the organic electrochromic compounds 13a and 14a proceeds simultaneously, but in order to supply a charge amount less than Qc (E ₁₄ ), the organic electrochromic compound 14a does not color at a predetermined density. Furthermore, if Qc (E ₁₄ ) is sufficiently larger than Qc (E ₁₃ ), the organic electrochromic compound 14a hardly develops color, and substantially only the organic electrochromic compound 13a develops color.

Furthermore, when a voltage equal to or higher than Vc (E ₁₃ ) is applied between the display electrode 11 and the counter electrode 12 and a charge amount equal to or higher than Qc (E ₁₄ ) is supplied, the organic electrochromic compounds 13 a and 14 a are each predetermined. Color develops in density. Also, supplied to between the display electrode 11 and the counter electrode 12 applies a voltage of less than Vc _{(E 14)} or Vc _{(E 13),} the _{Qc (E 14) -Qc (E} 13) or more charge quantity When applying a voltage equal to or higher than Vc (E ₁₃ ) and supplying a charge amount equal to or higher than Qc (E ₁₃ ), the organic electrochromic compounds 13a and 14a each develop a color at a predetermined density.

Thus, the formulas 0 <Vc (E ₁₄ ) <Vc (E ₁₃ ), 0 <Qc (E ₁₃ ) <Qc (E ₁₄ )
The method for controlling the color development of the organic electrochromic compounds 13a and 14a satisfying the above has been described. However, the formulas Vc (E ₁₃ ) <Vc (E ₁₄ ) <0, Qc (E ₁₄ ) <Qc (E ₁₃ ) <0
The color development of the organic electrochromic compounds 13a and 14a satisfying the above can be controlled in the same manner.

Further, the thresholds of voltages at which the organic electrochromic compounds 13a and 14a can be decolored are Vd (E ₁₃ ) and Vd (E ₁₄ ), respectively, and the organic electrochromic compounds 13a and 14a are decolored to a predetermined concentration, respectively. The amount of charge necessary until the calculation is Qd (E ₁₃ ) and Qd (E ₁₄ ), respectively, and the expressions Vd (E ₁₃ ) <Vd (E ₁₄ ) <0, Qd (E ₁₄ ) <Qd (E ₁₃ ) < 0
When satisfy | filling, the organic electrochromic compounds 13a and 14a can be decolored as follows.

Specifically, when a voltage higher than Vd (E ₁₃ ) and lower than or equal to Vd (E ₁₄ ) is applied between the display electrode 11 and the counter electrode 12, and a charge amount equal to or lower than Qd (E ₁₄ ) is supplied, The organic electrochromic compound 14a is decolored to a predetermined concentration. At this time, since a voltage higher than Vd (E ₁₃ ) is applied, the organic electrochromic compound 13a is not decolored.

Further, when a voltage equal to or lower than Vd (E ₁₃ ) is applied between the display electrode 11 and the counter electrode 12 and a charge amount larger than Qd (E ₁₄ ) and lower than Qd (E ₁₃ ) is supplied, organic electrochromic Compound 13a decolorizes to a predetermined concentration. At this time, since a voltage equal to or lower than Vd (E ₁₃ ) is applied, the decolorization reaction of the organic electrochromic compounds 13a and 14a proceeds simultaneously. However, in order to supply a charge amount larger than Qd (E ₁₄ ), the organic electrochromic Compound 14a does not decolorize to a predetermined concentration. Furthermore, if Qd (E ₁₄ ) is sufficiently smaller than Qd (E ₁₃ ), the organic electrochromic compound 14a is hardly decolored, and only the organic electrochromic compound 13a is substantially decolored.

Further, when a voltage equal to or lower than Vd (E ₁₃ ) is applied between the display electrode 11 and the counter electrode 12 and a charge amount equal to or higher than Qd (E ₁₄ ) is supplied, the organic electrochromic compounds 13a and 14a are each set to a predetermined value. Decolorize to density. In addition, a voltage greater than Vd (E ₁₃ ) and less than Vd (E ₁₄ ) is applied between the display electrode 11 and the counter electrode 12, and a charge amount less than Qd (E ₁₄ ) −Qd (E ₁₃ ) is applied. When combined with supplying and applying a voltage larger than Vd (E ₁₃ ) and supplying a charge amount equal to or less than Qd (E ₁₃ ), the organic electrochromic compounds 13a and 14a are decolored to a predetermined concentration, respectively. .

Thus, the formulas Vd (E ₁₃ ) <Vd (E ₁₄ ) <0, Qd (E ₁₄ ) <Qd (E ₁₃ ) <0
The method for controlling the decolorization of the organic electrochromic compounds 13a and 14a satisfying the above has been described. However, the formula 0 <Vd (E ₁₄ ) <Vd (E ₁₃ ), 0 <Qd (E ₁₃ ) <Qd (E ₁₄ )
The decoloring of the organic electrochromic compounds 13a and 14a satisfying the above can be controlled in the same manner.

Since the redox reaction takes place near the surface of the display layer 14, when the organic electrochromic compound 13 a contained in the medium 13 is colored and decolored, the organic electrochromic compound 13 a reaches the vicinity of the surface of the display layer 14. It is necessary to move by diffusion. For this reason, | Vc (E ₁₃ ) | and | Vd (E ₁₃ ) | are larger than those in the case where the organic electrochromic compound 13 a is included in the display layer 14. Further, efficiency of organic electrochromic compound 13a is diffused the move, vary greatly depending on the viscosity of the medium 13 can be the type of the medium 13, to adjust the Vc _{(E 13)} and Vd _{(E 13).} Therefore, it becomes easy to control the coloring and / or decoloring of the display element 10. Note that the display device having the display element 10 displays an image using a circuit that drives the display element 10, but the circuit can be simplified as the control of color development and / or decoloration is easier.

  The medium 13 is not particularly limited, but an organic solvent such as acetonitrile, propylene carbonate, N-methylpyrrolidone, dimethyl sulfoxide, polyethylene glycol, etc., lithium perchlorate, lithium borofluoride, tetrabutylammonium perchlorate, hexafluoroborate Examples include electrolytes in which electrolytes such as tetrabutylammonium and tetrabutylammonium butylborate are dissolved; solid systems such as perfluorosulfonic acid polymer membranes; ionic liquids and the like.

  The display electrode 11 is not particularly limited, and examples thereof include glass or a plastic film on which a transparent conductive thin film such as ITO, FTO, or ZnO is formed. A plastic film is preferable because a lightweight and flexible display device can be manufactured. .

  Although it does not specifically limit as the counter electrode 12, Glass or a plastic film in which conductive thin films, such as ITO, FTO, and ZnO; Conductive thin films, such as zinc and platinum, were formed is mentioned. In addition, when using the glass or plastic film in which the transparent conductive thin film was formed, when conductive particles having a large specific surface area such as tin oxide or ITO are formed, charges can be efficiently transferred.

  The white reflective layer 15 is formed by applying white pigment particles dispersed in a resin. Although it does not specifically limit as a white pigment particle, Metal oxides, such as a titanium oxide, an aluminum oxide, a zinc oxide, a silicon oxide, a cesium oxide, an yttrium oxide, are mentioned.

  FIG. 2 shows a second example of the display element of the present invention. In FIG. 2, the same components as those in FIG. The display element 20 includes a display electrode 11, a counter electrode 12 provided to face the display electrode 11, and a medium 13 including an electrolyte disposed between the display electrode 11 and the counter electrode 12. Further, display layers 14 and 21 are laminated on the surface of the display electrode 11 on the counter electrode 12 side, and a white reflective layer 15 is provided on the surface of the counter electrode 12 on the display electrode 11 side. The electrode 11 and the counter electrode 12 are bonded via a spacer 16. At this time, the medium 13 and the display layers 14 and 21 include organic electrochromic compounds 13a, 14a, and 21a, respectively, and the organic electrochromic compounds 14a and 21a are supported by conductive or semiconductive particles 14b and 21b, respectively. ing. The organic electrochromic compounds 13a, 14a, and 21a develop cyan (C), magenta (M), and yellow (Y), respectively. Thereby, the display element 20 can perform multi-color display. Note that multi-color display can be similarly performed by using red, green, and blue instead of yellow, magenta, and cyan.

In addition, the threshold value of the voltage at which the organic electrochromic compound 21a can be colored is Vc (E ₂₁ ), and the charge amount required until the organic electrochromic compound 21a is colored to a predetermined concentration is Qc (E ₂₁ ). 0 <Vc (E ₁₄ ) <Vc (E ₂₁ ) <Vc (E ₁₃ )
0 <Qc (E ₁₃ ) <Qc (E ₂₁ ) <Qc (E ₁₄ )
Or the formula Vc (E ₁₃ ) <Vc (E ₂₁ ) <Vc (E ₁₄ ) <0
Qc (E ₁₄ ) <Qc (E ₂₁ ) <Qc (E ₁₃ ) <0
When the condition is satisfied, the color development of the organic electrochromic compounds 13a, 14a, and 21a can be controlled in the same manner as the display element 10.

In addition, the threshold value of the voltage at which the organic electrochromic compound 21a can be decolored is Vd (E ₂₁ ), and the charge amount required until the organic electrochromic compound 21a is decolored to a predetermined concentration is Qd (E ₂₁ ) And the formula Vd (E ₁₃ ) <Vd (E ₂₁ ) <Vd (E ₁₄ ) <0
Qd (E ₁₄ ) <Qd (E ₂₁ ) <Qd (E ₁₃ ) <0
Or the formula 0 <Vd (E ₁₄ ) <Vd (E ₂₁ ) <Vd (E ₁₃ )
0 <Qd (E ₁₃ ) <Qd (E ₂₁ ) <Qd (E ₁₄ )
When the condition is satisfied, the decolorization of the organic electrochromic compounds 13a, 14a and 21a can be controlled in the same manner as the display element 10.

  FIG. 3 shows a third example of the display element of the present invention. In FIG. 3, the same components as those in FIGS. 1 and 2 are denoted by the same reference numerals, and description thereof is omitted. The display element 30 includes a display electrode 11, a counter electrode 12 provided to face the display electrode 11, and a medium 13 including an electrolyte disposed between the display electrode 11 and the counter electrode 12. Further, display layers 14 and 21 are laminated on the surface of the display electrode 11 on the counter electrode 12 side, and a white reflective layer 15 is provided on the surface of the counter electrode 12 on the display electrode 11 side. At this time, the display electrode 11 and the counter electrode 12 are formed for each pixel on the substrates 31 and 32, respectively, separated by the spacer 16. Further, the substrates 31 and 32 are bonded via the spacer 16. That is, the display element 30 includes a structural unit in which the display electrode 11, the counter electrode 12, the medium 13, the display layer 14, the white reflective layer 15, and the display layer 21 are separated by the spacer 16 for each pixel. In addition, the medium 13 and the display layers 14 and 21 include organic electrochromic compounds 13a, 14a, and 21a, respectively, and the organic electrochromic compounds 14a and 21a are supported on conductive or semiconductive particles 14b and 21b, respectively. Yes. The organic electrochromic compounds 13a, 14a, and 21a develop cyan (C), magenta (M), and yellow (Y), respectively.

  A display device having the display element 30 can display an image by a circuit that drives the display element 30 applying a predetermined voltage for each pixel. At this time, the organic electrochromic compound 13a diffuses and moves in the medium 13 and develops and decolors in the vicinity of the display layer 21. However, the organic electrochromic compound 13a diffuses and moves to an adjacent pixel by the partition wall 31 to generate image blur. Can be prevented.

  FIG. 4 shows a fourth example of the display element of the present invention. In FIG. 4, the same components as those in FIGS. 1, 2, and 3 are denoted by the same reference numerals and description thereof is omitted. The display element 40 includes a display electrode 11, a counter electrode 12 provided to face the display electrode 11, and a medium 13 including an electrolyte disposed between the display electrode 11 and the counter electrode 12. A display layer 14 is provided on the surface of the display electrode 11 on the counter electrode 12 side, and a white reflective layer 15 is provided on the surface of the counter electrode 12 on the display electrode 11 side. At this time, the display electrode 11 and the counter electrode 12 are formed on the substrates 31 and 32, respectively, separated by the spacer 16. Further, the substrates 31 and 32 are bonded via the spacer 16. That is, the display element 40 includes a structural unit in which the display electrode 11, the counter electrode 12, the medium 13, the display layer 14, and the white reflective layer 15 are separated by the spacer 16. Further, a color filter 41 is provided on the surface of the substrate 31 on which the display electrode 11 is not formed, and a combination of colors that the color filter 41 transmits and colors that the display layer 14 and the medium 13 develop [1]. , [2] and [3] (see Table 1) are arranged in parallel.

これにより、それぞれ媒体１３及び表示層１４に含まれる有機エレクトロクロミック化合物１３ａ及び１４ａの発色及び消色による色表現範囲を広くすることができる。このとき、［１］、［２］及び［３］を合わせて１ピクセルとしている。なお、カラーフィルター４１が導電性を有する場合は、基板３１の表示電極１１が形成されていない側の面の代わりに、基板３１の表示電極１１が形成されている側の面にカラーフィルター４１が設けられていてもよい。さらに、媒体１３及び表示層１４は、それぞれ有機エレクトロクロミック化合物１３ａ及び１４ａを含み、有機エレクトロクロミック化合物１４ａは、導電性又は半導性の粒子１４ｂに担持されている。

Thereby, the color expression range by the coloring and decoloring of the organic electrochromic compounds 13a and 14a included in the medium 13 and the display layer 14 can be widened. At this time, [1], [2] and [3] are combined into one pixel. When the color filter 41 has conductivity, the color filter 41 is provided on the surface of the substrate 31 on which the display electrode 11 is formed instead of the surface of the substrate 31 on which the display electrode 11 is not formed. It may be provided. Furthermore, the medium 13 and the display layer 14 include organic electrochromic compounds 13a and 14a, respectively, and the organic electrochromic compound 14a is supported on conductive or semiconductive particles 14b.

  In the image display device of the present invention, the display element is formed on the substrate and has a means for driving the display element. However, the drive element for driving the display element is preferably formed on the substrate. Thereby, the display element can be actively driven. As the driving element, for example, a thin film transistor (TFT) can be used.

  Next, a method for driving the pixel by the driving element will be described with reference to FIG. First, a voltage is applied from the gradation signal line 51 to the source electrode S of the pixel switching TFT 52 in accordance with the gradation of the pixel 50. Next, an ON / OFF signal voltage is sequentially applied to each line from the scanning line 53 to the gate electrode G of the pixel switching TFT 52, and after scanning of the image is completed, scanning of the next image is started. In addition, when respond | corresponding to a moving image, it is preferable that this space | interval is 50 Hz or more (1/50 second or less). At this time, when the ON signal voltage is applied from the scanning line 53 to the gate electrode G of the pixel switching TFT 52, a current flows from the source electrode S to the drain electrode D, and the voltage is applied to the gate electrode G of the pixel driving TFT 54. Applied. As a result, a current flows from the current supply line 55 to the pixel 50 through the source electrode S and the drain electrode D of the pixel driving TFT 54, and the pixel 50 is colored or decolored.

  Lithium perchlorate (electrolyte) is added to a 50 mM propylene carbonate solution of 1,1′-diundecyl-4,4′-bipyridinium dichloride (organic electrochromic compound 1) to a concentration of 0.2 M to prepare an electrolytic solution. did.

  Tungsten oxide (inorganic electrochromic compound) was vapor-deposited on a glass substrate on which an ITO electrode (display electrode) was formed by using a vacuum vapor deposition method to form a display layer having a thickness of 200 nm.

On the other hand, a dispersion obtained by dispersing 5 g of titanium oxide particles having an average primary particle size of 300 nm and 1 g of polyethylene in 10 ml of tetrahydrofuran was used as a zinc plate (counter electrode) having a thickness of 0.2 mm.
A white reflective layer having a thickness of 5 μm was formed by spin coating on the top. The white reflective layer exhibited the same white color as paper.

  The glass substrate on which the display electrode and the display layer are laminated and the counter electrode on which the white reflective layer is formed are pasted with an adhesive via a spacer having a film thickness of 75 μm so that the display layer and the white reflective layer are opposed to each other. After being combined, an electrolytic solution was injected and sealed to produce a display cell.

  The display cell was white, and the reflectance was measured to show a high value of 65%. The reflectance was measured by irradiating diffused light using a spectrocolorimeter.

Next, when the display electrode is connected to the negative electrode and the counter electrode is connected to the positive electrode, a voltage of 0.7 V is applied and a charge of ²⁰ mC / cm ² is supplied, the display layer is colored and the display cell turns blue. It was. Here, when a voltage of −1.0 V was sufficiently applied, the display layer was decolored and the display cell became white.

Further, when the display electrode is connected to the negative electrode, the counter electrode is connected to the positive electrode, a voltage of 4.0 V is applied, and an electric charge of 50 mC / cm ² is supplied, the display layer and the electrolytic solution are colored, and the display cell is black. Became. Here, when a voltage of −4.0 V was sufficiently applied, the display layer and the electrolytic solution were decolored, and the display cell became white.

Further, when the display electrode is connected to the negative electrode, the counter electrode is connected to the positive electrode, a voltage of 4.0 V is applied, and a charge of 50 mC / cm ² is supplied, the display layer and the electrolytic solution are colored, and the display cell is black. Became. Here, when a voltage of -1.0 V was applied for a short time, the display layer disappeared and the display cell turned purple. Furthermore, when a voltage of −4.0 V was sufficiently applied, the electrolyte solution was decolored and the display cell became white.

  A display cell was produced in the same manner as in Example 1 except that silver iodide (metal salt) was used in place of the organic electrochromic compound 1. The display cell was white, and the reflectance was measured to show a high value of 65%.

Next, when the display electrode is connected to the negative electrode and the counter electrode is connected to the positive electrode, a voltage of 0.7 V is applied and a charge of ²⁰ mC / cm ² is supplied, the display layer is colored and the display cell turns blue. It was.

Further, when the display electrode is connected to the negative electrode, the counter electrode is connected to the positive electrode, a voltage of 3.0 V is applied, and a charge of 40 mC / cm ² is supplied, the display layer and the electrolytic solution are colored, and the display cell is dark. It turned black. Here, when a voltage of -1.0 V was applied for a short time, the display layer was decolored and the display cell was black. Furthermore, when a voltage of −3.0 V was sufficiently applied, the electrolyte solution was decolored and the display cell became white.

  A 20 wt% aqueous dispersion of semiconducting titanium oxide particles having an average primary particle size of 6 nm (manufactured by Teika) was spin-coated on a glass substrate on which a tin oxide electrode (display electrode) was formed, and 450 ° C. Was sintered for 1 hour to form a particle layer having a thickness of 2 μm. Next, the display electrode on which the particle layer is formed is immersed in a 0.04M aqueous solution of Bis (2-phosphonoethyl) -4,4′-bipyridinium dichloride (organic electrochromic compound 2), and the surface of the particles is organically immersed. The electrochromic compound 2 was adsorbed to form a display layer.

  A display cell was produced in the same manner as in Example 1 except that the glass substrate on which the obtained display electrode and display layer were laminated was used. The display cell was white, and the reflectance was measured to show a high value of 65%.

Next, when the display electrode is connected to the negative electrode, the counter electrode is connected to the positive electrode, a voltage of 1.5 V is applied and a charge of 10 mC / cm ² is supplied, the display layer is colored and the display cell turns blue. It was.

Further, when the display electrode is connected to the negative electrode, the counter electrode is connected to the positive electrode, a voltage of 3.0 V is applied, and a charge of 40 mC / cm ² is supplied, the display layer and the electrolytic solution are colored, and the display cell is black. Became. Here, when a voltage of -1.0 V was applied for a short time, the display layer disappeared and the display cell turned purple. Furthermore, when a voltage of −4.0 V was sufficiently applied, the electrolyte solution was decolored and the display cell became white.

  A display cell was produced in the same manner as in Example 3 except that silver iodide (metal salt) was used in place of the organic electrochromic compound 1. The display cell was white, and the reflectance was measured to show a high value of 65%.

Next, when the display electrode was connected to the negative electrode and the counter electrode was connected to the positive electrode, a voltage of 1.5 V was applied and a charge of 10 mC / cm ² was supplied, the display layer was colored and the display cell turned blue .

Further, when the display electrode is connected to the negative electrode, the counter electrode is connected to the positive electrode, a voltage of 3.0 V is applied, and a charge of 40 mC / cm ² is supplied, both the display layer and the electrolytic solution are colored, It turned dark black. Here, when a voltage of -1.0 V was applied for a short time, the display layer was decolored and the display cell was black. Furthermore, when a voltage of −4.0 V was sufficiently applied, the electrolyte solution was decolored and the display cell became white.

  On the glass substrate on which the ITO electrode (display electrode) was formed, tungsten oxide (inorganic electrochromic compound) was vapor-deposited using a vacuum vapor deposition method to form a unit display layer 1 having a thickness of 200 nm. A 20 wt% aqueous dispersion of semiconducting titanium oxide particles having an average primary particle size of 6 nm (manufactured by Teika) was spin-coated on the glass substrate on which the unit display layer 1 was formed, and the mixture was heated at 450 ° C. for 1 hour. Sintering was performed to form a particle layer having a thickness of 2 μm. Next, the display electrode on which the particle layer is formed is immersed in a 0.04M aqueous solution of 1-p-cyanophenyl-1 ′-(2-phosphoyneethyl) -4,4′-bipyridinium dichloride (organic electrochromic compound 3). Thus, the organic electrochromic compound 3 was adsorbed on the surface of the particles, and the unit display layer 2 was formed.

  A display cell was produced in the same manner as in Example 1 except that the glass substrate on which the obtained display electrodes and display layers (unit display layers 1 and 2) were laminated was used. The display cell was white, and the reflectance was measured to show a high value of 65%.

Next, when the display electrode is connected to the negative electrode and the counter electrode is connected to the positive electrode, a voltage of 0.7 V is applied and a charge of ²⁰ mC / cm ² is supplied, the unit display layer 1 develops color and the display cell turns blue. became.

Further, when the display electrode is connected to the negative electrode, the counter electrode is connected to the positive electrode, a voltage of 1.5 V is applied, and a charge of 30 mC / cm ² is supplied, the unit display layers 1 and 2 are colored, and the display cell is It became dark blue. Here, when a voltage of -1.0 V was applied for a short time, the unit display layer 1 was decolored and the display cell became green. Furthermore, when a voltage of −2.0 V was sufficiently applied, the unit display layer 2 was decolored and the display cell became white.

Next, when the display electrode is connected to the negative electrode, the counter electrode is connected to the positive electrode, a voltage of 4.0 V is applied, and a charge of 50 mC / cm ² is supplied, the unit display layers 1 and 2 and the electrolytic solution develop color. The display cell turned black. Here, when a voltage of −2.0 V was applied for a short time, the unit display layers 1 and 2 were decolored, and the display cell became purple. Furthermore, when a voltage of −4.0 V was sufficiently applied, the electrolyte solution was decolored and the display cell became white.

In addition, when the display electrode is connected to the negative electrode, the counter electrode is connected to the positive electrode, a voltage of 4.0 V is applied, and a charge of 50 mC / cm ² is supplied, the unit display layers 1 and 2 and the electrolyte color, The display cell turned black. Here, when a voltage of -1.0 V was applied for a short time, the unit display layer 1 was decolored and the display cell became dark purple. Furthermore, when a voltage of −4.0 V was sufficiently applied, the unit display layer 2 and the electrolytic solution were decolored, and the display cell became white.

  Organic electrochromic compound 2 having a concentration of 50 mM in a 20 wt% isopropanol dispersion of semiconducting titanium oxide particles (manufactured by Teika) having an average primary particle size of 6 nm coated with insulating alumina / zirconia on the surface. Was added, and the mixture was stirred to adsorb the organic electrochromic compound on the surface of the particles to prepare a coating solution.

  A 20 wt% aqueous dispersion of semiconducting titanium oxide particles having an average primary particle size of 6 nm (manufactured by Teika) was spin-coated on a glass substrate on which a tin oxide electrode (display electrode) was formed, and 450 ° C. Was sintered for 1 hour to form a particle layer having a thickness of 2 μm. Next, the display electrode on which the particle layer was formed was immersed in a 0.04M aqueous solution of the organic electrochromic compound 3, and the organic electrochromic compound 3 was adsorbed on the surface of the particle to form the unit display layer 1. Further, the coating liquid was spin-coated on the unit display layer 1 and dried at 100 ° C. for 1 hour to form a unit display layer 2 having a thickness of 2 μm.

  A display cell was produced in the same manner as in Example 1 except that the glass substrate on which the obtained display electrodes and display layers (unit display layers 1 and 2) were laminated was used. The display cell was white, and the reflectance was measured to show a high value of 65%.

Next, when the display electrode is connected to the negative electrode and the counter electrode is connected to the positive electrode, a voltage of 1.2 V is applied and a charge of 10 mC / cm ² is supplied, the unit display layer 1 develops color and the display cell turns green. became.

Further, when the display electrode is connected to the negative electrode, the counter electrode is connected to the positive electrode, a voltage of 1.5 V is applied and a charge of 30 mC / cm ² is supplied, the unit display layers 1 and 2 are colored, and the display cell is dark blue. It became a color. Here, when a voltage of −0.5 V was applied for a short time, the unit display layer 1 was decolored and the display cell turned blue. Furthermore, when a voltage of −2.0 V was sufficiently applied, the unit display layer 2 was decolored and the display cell became white.

Next, when the display electrode is connected to the negative electrode, the counter electrode is connected to the positive electrode, a voltage of 4.0 V is applied, and a charge of 50 mC / cm ² is supplied, the unit display layers 1 and 2 and the electrolyte color, The display cell turned black. Here, when a voltage of −2.0 V was applied for a short time, the unit display layers 1 and 2 were decolored, and the display cell became purple. Furthermore, when a voltage of −4.0 V was sufficiently applied, the electrolyte solution was decolored and the display cell became white.

In addition, when the display electrode is connected to the negative electrode, the counter electrode is connected to the positive electrode, a voltage of 4.0 V is applied, and a charge of 50 mC / cm ² is supplied, the unit display layers 1 and 2 and the electrolytic solution develop a color and display. The cell turned black. Here, when a voltage of −0.5 V was applied for a short time, the unit display layer 1 was decolored and the display cell became dark purple. Furthermore, when a voltage of −4.0 V was sufficiently applied, the unit display layer 2 and the electrolytic solution were decolored, and the display cell became white.

  Lithium perchlorate (electrolyte) was added to a 50 mM propylene carbonate solution of the organic electrochromic compound 1 to a concentration of 0.2 M to prepare an electrolytic solution.

  Three 2.7 cm × 5 mm tin oxide electrodes were formed on a 3 cm × 2.5 cm glass substrate through a space having a width of 1 mm, and zinc was deposited on the tin oxide electrode to form a counter electrode. . A dispersion obtained by dispersing 5 g of titanium oxide particles having an average primary particle size of 300 nm and 1 g of polyethylene in 10 ml of tetrahydrofuran was spin-coated on a glass substrate on which a counter electrode was formed, and a white reflective layer having a thickness of 5 μm was formed. Formed.

  Three 2.7 cm × 5 mm tin oxide electrodes (display electrodes) were formed on a 3 cm × 2.5 cm glass substrate through a space having a width of 1 mm. Next, a 20 wt% aqueous dispersion of semiconducting titanium oxide particles having an average primary particle size of 6 nm (manufactured by Teika) is spin-coated on a glass substrate on which display electrodes are formed, and the temperature is 1 at 450 ° C. Sintering was performed for a time to form a particle layer having a thickness of 2 μm. Further, after the photosensitive photoresist is applied on the glass substrate on which the particle layer is formed so as to have a thickness of 20 μm, the film thickness is increased in a region where the display electrode is not formed by using a photolithography method. A 20 μm spacer was formed. Next, the glass substrate on which the spacer was formed was immersed in a 0.04M aqueous solution of the organic electrochromic compound 2, and the organic electrochromic compound 2 was adsorbed on the surface of the particles to form a display layer. Further, after adding an electrolyte solution to the region surrounded by the spacer, the display electrode and the counter electrode are opposed to each other with the glass substrate on which the display electrode and the display layer are stacked and the glass substrate on which the counter electrode and the white reflective layer are stacked. At the same time, the display cells were manufactured by pasting and sealing with an adhesive so as to overlap.

  The display cell was white, and the reflectance was measured to show a high value of 60%.

Next, the display electrode is connected to the negative electrode, the counter electrode is connected to the positive electrode, a voltage of 1.2 V is applied, and a charge of 10 mC / cm ² is supplied. Turned blue.

Further, when the display electrode is connected to the negative electrode, the counter electrode is connected to the positive electrode, a voltage of 4.0 V is applied, and a charge of 50 mC / cm ² is supplied, the display layer and the electrolytic solution on the display electrode are colored, The display cell became dark purple, but no blurring of the image was seen. Here, when a voltage of -1.0 V was applied for a short time, the display layer on the display electrode disappeared and the display cell turned purple, but no blur of the image was seen. Furthermore, when a voltage of −4.0 V was sufficiently applied, the electrolyte solution was decolored and the display cell became white.

  Three 2.7 cm × 5 mm tin oxide electrodes (display electrodes) were formed on a 3 cm × 2.5 cm glass substrate through a space having a width of 1 mm. Next, a 20 wt% aqueous dispersion of semiconducting titanium oxide particles having an average primary particle size of 6 nm (manufactured by Teika) is spin-coated on a glass substrate on which display electrodes are formed, and the temperature is 1 at 450 ° C. Sintering was performed for a time to form a particle layer having a thickness of 2 μm. Furthermore, the glass substrate in which the particle layer was formed was immersed in 0.04M aqueous solution of the organic electrochromic compound 2, and the organic electrochromic compound 2 was made to adsorb | suck to the surface of particle | grains, and the display layer was formed.

  The obtained glass substrate on which the display electrode and the display layer are laminated and the counter electrode on which the counter electrode and the white reflective layer are laminated are provided with a spacer having a film thickness of 20 μm so that the display electrode and the counter electrode face each other and overlap. Thus, a display cell was produced in the same manner as in Example 7 except that after bonding with an adhesive, the electrolyte was injected and sealed.

  The display cell was white, and the reflectance was measured to show a high value of 65%.

Next, the display electrode is connected to the negative electrode, the counter electrode is connected to the positive electrode, a voltage of 1.2 V is applied, and a charge of 10 mC / cm ² is supplied. Turned blue.

Further, when the display electrode is connected to the negative electrode, the counter electrode is connected to the positive electrode, a voltage of 4.0 V is applied, and a charge of 50 mC / cm ² is supplied, the display layer and the electrolytic solution on the display electrode are colored, The display cell became dark purple, but a slight blur was seen in the heel part of the image. Here, when a voltage of -1.0 V was applied for a short time, the display layer on the display electrode was decolored and the display cell turned purple, but slight blur was seen in the wrinkled part of the image. Furthermore, when a voltage of −4.0 V was sufficiently applied, the electrolyte solution was decolored and the display cell became white.

  Lithium perchlorate (electrolyte) was added to each 50 mM propylene carbonate solution of the organic electrochromic compounds 1, 2 and 3 so as to have a concentration of 0.2 M to prepare electrolytic solutions 1, 2 and 3, respectively.

  Twenty 2.7 cm × 1 mm tin oxide electrodes were formed on a 3 cm × 2.5 cm glass substrate through a space having a width of 0.1 mm, and zinc was vapor-deposited on the tin oxide electrode. Formed. A dispersion in which 5 g of titanium oxide particles having an average primary particle size of 300 nm and 1 g of polyethylene are dispersed in 10 ml of tetrahydrofuran is spin-coated on a glass substrate on which zinc has been deposited to form a white reflective layer having a thickness of 5 μm. did.

  Twenty 2.7 cm × 1 mm tin oxide electrodes (display electrodes) were formed on a 3 cm × 2.5 cm glass substrate through a space having a width of 0.1 mm. Next, a 20% by weight aqueous dispersion of semiconducting titanium oxide particles having an average primary particle size of 6 nm (manufactured by Teika) was applied onto the display electrode by ink jetting and sintered at 450 ° C. for 1 hour to obtain a film thickness. Formed a 2 μm particle layer. Furthermore, after applying the photosensitive photoresist on the glass substrate on which the particle layer was formed so as to have a thickness of 20 μm, a spacer was formed in a region where the display electrode was not formed by using a photolithography method. . Next, each methanol solution of the organic electrochromic compounds 1, 2 and 3 was sequentially applied to the particle layer surrounded by the spacer, and then dried at 120 ° C. for 1 hour, and the organic electrochromic compound 1, 2 and 3 were adsorbed to form a display layer. Further, after adding electrolytic solutions 2, 3 and 1 to the region where the display layer containing organic electrochromic compounds 1, 2 and 3 is formed, respectively, a glass substrate on which the display electrode and the display layer are laminated, and a counter electrode And the glass substrate on which the white reflective layer was laminated was bonded and sealed with an adhesive so that the display electrode and the counter electrode faced each other and overlapped. Furthermore, an RGB color filter (manufactured by Kyodo Printing Co., Ltd.) was attached to the surface of the glass substrate on which the display electrode was formed, on which the display electrode was not formed, to produce a display cell. At this time, it adjusted so that the area | region in which the display layer containing the organic electrochromic compounds 1, 2, and 3 was formed might become the green part (G), red part (R), and blue part (B) of a color filter, respectively. .

  The display cell was white, and the reflectance was measured to show a high value of 48%.

Next, the display electrode corresponding to R of the color filter was connected to the negative electrode, the counter electrode was connected to the positive electrode, a voltage of 1.5 V was applied, and a charge of 10 mC / cm ² was supplied. Furthermore, after connecting the display electrode corresponding to G of the color filter to the negative electrode, applying a voltage of 4.0 V, supplying a charge of 50 mC / cm ² , and then applying a voltage of −1.0 V for a short time, The display cell turned blue. In addition, when the sensory test regarding the color appearance was performed, 45 out of 50 people were satisfied with blue. Here, when the display electrode corresponding to R and G of the color filter was connected to the negative electrode, the counter electrode was connected to the positive electrode, and a voltage of −4.0 V was sufficiently applied, the display cell turned white.

Further, the display electrode corresponding to G of the color filter was connected to the negative electrode, the counter electrode was connected to the positive electrode, a voltage of 1.5 V was applied, and a charge of 10 mC / cm ² was supplied. Furthermore, after connecting the display electrode corresponding to B of the color filter to the negative electrode, applying a voltage of 4.0 V, supplying a charge of 50 mC / cm ² , and then applying a voltage of −1.0 V for a short time, The display cell turned red. In addition, when the sensory test regarding the color appearance was performed, 47 out of 50 people were satisfied with red. Here, when the display electrode corresponding to B and G of the color filter was connected to the negative electrode, the counter electrode was connected to the positive electrode, and a voltage of −3.0 V was sufficiently applied, the display cell turned white.

Further, the display electrode corresponding to B of the color filter was connected to the negative electrode, the counter electrode was connected to the positive electrode, a voltage of 1.5 V was applied, and a charge of 10 mC / cm ² was supplied. Furthermore, after connecting the display electrode corresponding to R of the color filter to the negative electrode, applying a voltage of 4.0 V, supplying a charge of 50 mC / cm ² , and then applying a voltage of −1.0 V for a short time, The display cell turned green. In addition, when the sensory test regarding the color appearance was performed, 43 out of 50 people were satisfied with green. Here, when the display electrode corresponding to B and R of the color filter was connected to the negative electrode, the counter electrode was connected to the positive electrode, and a voltage of −4.0 V was sufficiently applied, the display cell turned white.

It is sectional drawing which shows the 1st example of the display element of this invention. It is sectional drawing which shows the 2nd example of the display element of this invention. It is sectional drawing which shows the 3rd example of the display element of this invention. It is sectional drawing which shows the 4th example of the display element of this invention. It is a wiring diagram explaining the method by which a drive element drives a pixel.

Explanation of symbols

10, 20, 30, 40 Display element 11 Display electrode 12 Counter electrode 13 Medium 13a Organic electrochromic compound 14 Display layer 14a Organic electrochromic compound 14b Conductive or semiconductive particles 15 White reflective layer 16 Spacer 21 Display layer 21a Organic Electrochromic compound 21b Conductive or semiconductive particles 31, 32 Substrate 41 Color filter

Claims (6)

A display electrode; a counter electrode provided opposite to the display electrode; a medium including an electrolyte disposed between the display electrode and the counter electrode; and the display electrode provided on the counter electrode side. A display element having a display layer,
The medium and the display layer each include one or more color forming substances that can reversibly develop and decolor by oxidation-reduction reactions,
The chromogenic substance contained in the medium develops a color different from that of the chromogenic substance contained in the display layer, a voltage threshold that can be developed, a voltage threshold that can be erased, a predetermined threshold A display element characterized in that at least one of a charge amount necessary for color development at a predetermined density and a charge amount necessary for decoloration to a predetermined density are different. The display layer is formed by laminating two or more unit display layers containing one kind of chromogenic material that can be reversibly developed and decolored by an oxidation-reduction reaction,
The chromogenic substance contained in one layer of the unit display layer develops a color different from that of the chromogenic substance contained in the other layers of the unit display layer, and the threshold voltage and extinction that can be developed. The threshold value of a voltage that can be colored, at least one of a charge amount necessary for color development to a predetermined density and a charge amount necessary for decoloring to a predetermined density are different from each other. The display element according to 1.   The display element according to claim 1, wherein the medium is composed of two or more structural units separated by a partition wall.   The color filter which transmits the light of the color different from the color which the color development substance contained in the said medium and the said display layer can color on the said display electrode is further characterized by the above-mentioned. The display element according to any one of the above.   The color-developing substance contained in the display layer is an organic electrochromic compound and is supported on conductive or semiconductive particles. Display element. A display device in which the display element according to any one of claims 1 to 5 is formed on a substrate,
A display device comprising means for driving the display element.

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