JPS6227115B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an image display device that applies electrochemical coloring/decoloring phenomenon, and particularly to an image display cell that is the main body of the display section thereof. In general, a certain element is colored when it is energized, and the color is erased (i.e., it returns to its original color) by energization with the polarity opposite to that of the energization, heating, or a combination of these operations. In other words, reversible coloring/decoloring development depending on electrical polarity is called electrochromy phenomenon. The mechanism that causes the electrochromy phenomenon is not necessarily single, but in many cases it is considered to be a so-called redox reaction between an electrolyte and a color-forming substance.
In this case, the electrolyte and the color-forming substance are not necessarily distinguished from each other in terms of materials. In some cases, the same substance can be a color-forming substance and an electrolyte at the same time. In addition, from another perspective, it is considered that the light absorption characteristics change due to the injection of injected electrons into the color center, as in the case of the photochromy phenomenon, and in reality, the electrochromy phenomenon is the result of a combination of these two phenomena. It is understood that this is occurring. Since the electrochromy phenomenon electrically changes the original color of a material, the combination of colors is diverse. Also, whether a material can transmit light, reflect light, or scatter light is not determined by the properties of the material itself, but rather by the method of forming the layers. It has the property of being able to form either type. In addition to these configurations and the above-mentioned diversity, there are also materials that have a memory property in which the colored state persists after coloring or development occurs until it is erased, and there are also materials whose color tone changes in response to the applied voltage value. Since various applications can be considered, research has been actively conducted in recent years, mainly in the field of image display. Among these, a phenomenon based on the electrolysis of a substance by an electric current, that is, the redox reaction of a substance, is particularly called electrochemical microsm, and the technical object of the present invention is applied devices related to such a phenomenon. be. The characteristics of image display devices that apply electrochemical microscopy are that they are so-called passive displays, have low driving voltage, have memory characteristics, have good contrast, have a wide viewing angle, and are colorful. It has advantageous characteristics compared to liquid crystal display elements and LED display elements that have been put into practical use. However, in such devices, the problem of device life remains the most important issue in the process of putting them into practical use. In other words, when the writing → memory → erasing cycle is repeated, coloring failures on the electrodes, erasing failures, generation of yellow precipitates, coloring unevenness, color tone changes, etc. occur, and these failures affect the performance of the display element. This significantly shortens the lifespan and is a major obstacle to commercialization. At present, no clear solution to this problem has been proposed. Incidentally, the main cause is estimated to be electrode contamination, which is caused by impurities contained in the electrochemical coloring/decolorizing substance, chemical change products of the electrochemical coloring/decolorizing substance, and the cell container. It is said that factors such as impurities and incompatibility of the drive system are intricately intertwined. Therefore, the main purpose of the present invention is to write → memory →
An object of the present invention is to provide an image display cell whose durability against repeated erasing cycles is dramatically improved. That is, in the present invention, improvements have been made particularly regarding the electrically responsive coloring/decoloring medium, and the electrically responsive coloring/decoloring medium is provided in a cell container that is provided with at least a working electrode and a counter electrode. The present invention provides an image display cell containing an electroresponsive coloring/decoloring medium, which is characterized in that the electroresponsive coloring/decolorizing medium contains an amphoteric surfactant. Display devices based on electrochemical microscopy use a light-transmissive or reflective working electrode, a counter electrode, and the redox state of the counter electrode changes reversibly when a current passes through it, which can be detected by the appearance of the working electrode. It is known to use cells containing electrochemical color-chromic substances capable of effecting color changes, and electroresponsive color-bleaching media consisting of electrolytes and their solvents. Both electrodes and the electrolyte are housed in a suitable housing with means for viewing the working electrode. The electrochemical color-developing material in such a device is capable of accepting or donating electrons, thereby converting it into a radical ion with high absorbance, usually in the visible region of the spectrum, and at the same time, this radical ion
The anions present in the medium are combined to form a medium-insoluble colored body on the working electrode. Its general structure is as shown in FIG. 1, in which a working electrode 1 and a counter electrode 2 are arranged in a cell 3 made of glass or the like, and both electrodes are connected to a power source 4. Inside the cell 3, an electrically responsive colored medium is enclosed. Next, the driving method of such a device is as follows. That is, first, the writing to the working electrode occurs when a DC voltage is applied from the outside so that the working electrode becomes negative and the counter electrode becomes positive, and second, the memory effect (the working electrode) that occurs when the external voltage is turned off and the circuit is opened. Thirdly, the writing on the working electrode is reversed, and the writing on the working electrode is applied externally so that the working polarity is positive and the opposite electrode is negative. There are three driving steps called erasing. Note that writing may be performed with the working electrode side facing positive. Figure 2 shows a typical drive pulse application method, with 5 indicating a write step and 6
7 represents a memory step and 7 represents an erase step. The present invention provides an improved electroresponsive coloring medium in an image display device applying electrochemometry as described above. That is, by incorporating an amphoteric surfactant into such a medium, the display life could be dramatically extended. Hereinafter, the constituent materials of the image display cell of the present invention will be explained in detail. As the electrode material, chemically stable metals such as platinum and palladium gold, or metal compounds such as tin oxide and indium oxide can be preferably used. Selection of these materials or arrangement within the cell can be made arbitrarily according to the specifications of the device. The electroresponsive coloring/decoloring medium is mainly composed of an electrochemical coloring/decolorizing substance (redox-reactive organic substance can also be seen) and an electrolyte, and is obtained by further adding an amphoteric surfactant. Note that these are usually used after being dissolved in a solvent such as water. The electrochemical coloring/discoloring substance used in the present invention is not particularly limited, and may include a wide range of redox-reactive organic substances. For example, as pyridinium compounds having a quaternary ammonium salt structure, 1,1'-dimethyl-4,4'-bipyridinium.
dibromide 1,1'-diethyl-4,4'-bipyridinium.
dibromide 1,1'-diheptyl-4,4'-bipyridinium dibromide 1,1'-dibenzyl-4,4'-bipyridinium dibromide N・N′-di(p-cyanophenyl)-4・4′-
Bipyridinium dichloride 2,2'-(diethyl)bipyridinium dichloride N・N'-diethyl-2,7-diazapyrenium dichloride N-benzyl-4-cyano-bipyridinium-
Bromide Also used as a redox indicator Safranin T Neutral Red Indigo monosulfonic acid Diphenyl amine Diphenyl amine-P-sulfonic acid P-nitro diphenyl amine Diphenyl amine-2,3'-dicarboxylic acid Diphenyl amine-2,2'-dicarboxylic acid etc. can be mentioned. Next, regarding the electrolyte, potassium bromide, potassium chloride and the like are typical, but ferrous ammonium sulfate and the like can also be used as a good electrolyte. Water is generally used as a solvent, but depending on the type of electrochemical coloring/decolorizing substance,
Water and methyl alcohol, dimethyl foam,
A mixed solvent with an organic solvent such as an amide may also be used. Particularly important components in the present invention are commonly referred to as amphoteric surfactants. Although there are a large number of compounds that are generally classified as amphoteric surfactants, preferred amphoteric surfactants for the present invention are compounds represented by the following general formula. (However, in the formula, R represents an alkyl group having 31 or less carbon atoms, R ₁ and R ₂ each represent hydrogen or an alkyl group or hydroxyalkyl group having 5 or less carbon atoms, and n is 15
It is an integer below. ),

[Formula] (However, in the formula, R ₁ and R ₂ each represent an alkyl group having 31 or less carbon atoms, and X is sodium or potassium or (However, R ₃ , R ₄ and R ₅ each represent hydrogen, an alkyl group or a hydroxyalkyl group having 5 or less carbon atoms.) where n is an integer of 15 or less. ), (However, in the formula, R ₁ , R ₂ , and R ₃ each represent an alkyl group having 31 or less carbon atoms, and n is an integer of 15 or less.) (However, in the formula, R represents an alkyl group having 31 or less carbon atoms, and X is sodium or potassium or (However, R ₁ , R ₂ and R ₃ each represent hydrogen, an alkyl group or a hydroxyalkyl group having 5 or less carbon atoms.) where n is an integer of 15 or less. (However, in the formula, R represents an alkyl group having 31 or less carbon atoms, and R ₁ , R ₂ , and R ₃ each represent hydrogen or an alkyl group or hydroxyalkyl group having 5 or less carbon atoms.) (However, in the formula, R represents an alkyl group having 31 or less carbon atoms, or R ₁ and R ₂ each represent an alkyl group having 5 or less carbon atoms, or an alkylene group in which R ₁ and R ₂ form a nitrogen-containing ring) ( _R3 represents a hydrogen atom or a methyl group, X represents an oxygen atom, and n is an integer of 15 or less.) (However, in the formula, R represents an alkyl group having 31 or less carbon atoms, R ₁ and R ₂ each represent an alkyl group having 5 or less carbon atoms, and n is an integer of 15 or less.) (However, in the formula, R represents an alkyl group having 31 or less carbon atoms, and X is hydrogen or an alkyl group having 5 or less carbon atoms,
Or the formula −(CH ₂ ) ₂ −NH−R ₁ (However, R ₁ has a carbon number of 31
The substituents represented by the following alkyl groups are shown below. ), (However, in the formula, R represents an alkyl group having 31 or less carbon atoms, R ₁ represents an alkyl group having 10 or less carbon atoms, or a hydroxyalkyl group, and n is an integer of 15 or less.) It is shown as follows. Amphoteric surfactant Note that the amphoteric surfactants used in the present invention are not limited to the above-mentioned compounds. Also, among the above, general formula The amphoteric surfactants represented by are particularly preferred from the viewpoint of action and effect. Furthermore, in the present invention, it is of course possible to use two or more types of amphoteric surfactants in combination. The amphoteric surfactants listed above may be used in a weight percentage of 0.0001% to 1% based on an electroresponsive coloring/decolorizing medium consisting of an electrochemical coloring/decolorizing substance, an electrolyte, an aqueous medium, or a mixed solvent of water and an organic solvent. %,Preferably
It is effective to use it in the range of 0.0005 to 0.1%. However, since the amount added varies depending on the type and amount of the coloring/decoloring medium to be used, the above range of the amount added is not absolute. Furthermore, the effect of adding the amphoteric surfactant of the present invention is remarkable. This effect facilitates the cycle of electrochemically depositing and then dissolving the coloring/dissolving substance on the electrode, which is the essential mechanism of electrochemicomism, and further improves the repeatability characteristics to a large extent. For the specific effect of adding amphoteric surfactant, please write →
It is possible to prevent the accumulation of unnecessary precipitates on the electrode that occurs when the number of repetitions of memory → erase is increased, and by adding the amphoteric surfactant of the present invention, display operation can be prevented. It is possible to dramatically extend the cycle life of the product from several tens of times to several hundred times that of conventional products. Note that specific effects of the present invention will be explained in more detail in Examples. Example A counter electrode was placed in a glass cell. A tin oxide transparent electrode with a resistance value of 15 Ω/cm ² was used as the working electrode and the counter electrode, and the electrode size was 2 × 3 each.
(mm). Also, the distance between both electrodes is 2mm.
And so. In this cell, electrochemical coloring/decolorizing substance, electrolyte,
It contained a composition consisting of an amphoteric surfactant and a solvent. Note that specific examples of the electrochemical coloring/decoloring substance and the amphoteric surfactant are as shown in the table below, and various combinations were tested. Incidentally, the concentration of the electrochemical coloring/discoloring substance was 0.1 mol%, the amphoteric surfactant concentration was 0.005 wt%, and KBr was used as the electrolyte, and it was 0.3 mol%. Water was used as the solvent. For the various cells obtained above, -2V (2sec) → Ov (0.5sec) → 2V (2sec) using a DC power supply.
The driving operation was performed at a potential cycle of . The values shown in the table below are calculated by the amount of time (Write → Memory →
This represents the number of cycles in which the (erase) step is repeated. In addition, 0.0005 per concentration of amphoteric surfactant used.
Almost the same results as in this example were obtained even when cells with varying concentrations in the range of ~0.1 wt% were used. In addition, as a comparative experiment, instead of an amphoteric surfactant,
A comparative image display cell was prepared in exactly the same manner as in the example described above, except that polyoxyethylene hexadecyl ether, which is a nonionic surfactant, was used. The electrochemical coloring/discoloring substances used at this time were 1,1'-dimethyl-4,4'-bipyridinium dibromide (Comparative Example 1) and 1,1'-diethyl-4,4'-bipyridinium dibromide. Comparative experiments were conducted with two types of dibromide (Comparative Example 2). As a result, the number of repeated cycles in Comparative Example 1 was 700 times, and the number of repeated cycles in Comparative Example 2 was 600 times.

【table】

【table】 [Brief explanation of the drawing]

FIG. 1 is a schematic diagram for explaining an example of the configuration of an image display device to which electrochemometry is applied, and FIG. 2 is an explanatory diagram showing an outline of a driving method of an image display cell. 1, 2...electrode, 3...cell, 4...power supply.

Claims (1)

[Claims] 1. A pair of electrodes, at least one of which is transparent, and a redox-reactive organic substance that forms an insoluble colored body on one electrode by passing current between the pair of electrodes. In an image display cell equipped with an electrolyte solution, the electrolyte solution has the following general formula:
At least one of the amphoteric surfactants represented by (1) to (9)
An image display cell characterized by containing seeds. General formula (1) (In the formula, R represents an alkyl group having 31 or less carbon atoms,
R ₁ and R ₂ represent hydrogen, an alkyl group having 5 or less carbon atoms, or a hydroxyalkyl group, and n is an integer of 15 or less. ) (2) (In the formula, R ₁ and R ₂ represent an alkyl group having 31 or less carbon atoms, and X represents sodium, potassium, or [Formula]. However, R ₃ , R ₄ and R ₅ are hydrogen, and Indicates an alkyl group or a hydroxyalkyl group.
n is an integer of 15 or less. ) (3) (In the formula, R ₁ , R ₂ and R ₃ represent an alkyl group having 31 or less carbon atoms, and n is an integer of 15 or less.) (4) (In the formula, R represents an alkyl group having 31 or less carbon atoms,
X represents sodium, potassium or [Formula]. However, R ₁ , R ₂ and R ₃ represent hydrogen, an alkyl group having 5 or less carbon atoms, or a hydroxyalkyl group. n
is an integer less than or equal to 15. ) (Five) (In the formula, R represents an alkyl group having 31 or less carbon atoms,
R ₁ , R ₂ and R ₃ represent hydrogen, an alkyl group having 5 or less carbon atoms, or a hydroxyalkyl group. ) (6) (In the formula, R represents an alkyl group having 31 or less carbon atoms,
R ₁ and R ₂ are alkyl groups having 5 or less carbon atoms, or R ₁ and R ₂
represents an alkylene group forming a nitrogen-containing ring, and R ₃
represents a hydrogen atom or a methyl group, X represents an oxygen atom, and n is an integer of 15 or less. ) (7) (In the formula, R represents an alkyl group having 31 or less carbon atoms,
R ₁ and R ₂ represent an alkyl group having 5 or less carbon atoms, and n
is an integer less than or equal to 15. ) (8) (In the formula, R represents an alkyl group having 31 or less carbon atoms,
X is hydrogen, an alkyl group or formula having 5 or less carbon atoms, -
( _CH2 ) ₂ -NH- _R1 is shown. However, R ₁ is an alkyl group having 31 or less carbon atoms. ) (9) (In the formula, R represents an alkyl group having 31 or less carbon atoms,
R ₁ represents an alkyl group or a hydroxyalkyl group having 10 or less carbon atoms, and n is an integer of 15 or less. )