JPH04131831A - Electrochromic display element - Google Patents

Abstract

PURPOSE:To obtain bright display colors and to improve a driving life by packing a soln. consisting of an org. electrochromic material, an electrolyte and a solvent of the weight equal to or lower than the total weight of the org. electrochromic material and the electrolyte between electrodes. CONSTITUTION:The soln. 4 consisting of the org. electrochromic material, the electrolyte and the solvent of the weight equal to or lower than the total weight of the org. electrochromic material and the electrolyte is provided between the electrodes 2. Coloration is obtd. if lead wires are taken out of the electrodes of such ECD element and are connected to a power source or circuit, etc., and a voltage is impressed thereto. The ECD element does not contain or contains slightly the solvent in this way and, therefore, the bright display colors and the excellent driving life are obtd. even if the thickness of the cell sealed with the EC soln. is small.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an electrochromic display element (hereinafter referred to as an ECD element) that utilizes the electrochromic phenomenon in which the color of a substance changes reversibly through oxidation and reduction reactions caused by the application of voltage. (abbreviated)).

(Prior Art) Conventionally, electrocomic materials (hereinafter referred to as EC materials) for ECD elements include inorganic transition metal oxides such as tungsten oxide, and organic materials include viologen derivatives, Quinone compounds and the like are known. Although ECD elements using inorganic EC substances generally have an excellent driving life, they have the disadvantage that there are few types of display colors and the color tone is dark.

On the other hand, ECD elements using organic EC substances generally display a wide variety of colors, are clear, and have a large extinction coefficient. Further, compared to metal oxides, they have the advantage of being easier to manufacture large-area ECD elements at low cost, have good processability, and can be coated. However, since organic EC substances are colored by radicals, side reactions are likely to occur and reversibility may be poor. In order to overcome this drawback, several methods such as polymerization have recently been investigated.

In the case of organic ECD elements, there are many solution types in which the EC substance and electrolyte are dissolved in a considerable amount (10 to 1,000 times) of a solvent, and a polar solvent is used as the solvent, but the liquid from the display cell is Leakage, decomposition reactions depending on the solvent used,
Due to the decomposition reaction that occurs between the EC substance and the solvent, the operating life is often short.

When using a polymer as an EC substance, for example, in an ECD element using a polymer membrane for the display electrode, it is thought that using an electrolyte solution will have a better driving life.
Leakage from cells is common.

Furthermore, various attempts have been made to make the electrolyte solution solid or semi-solid, but these efforts slow down the response and do not improve the driving life.

(Problems to be Solved by the Invention) An organic ECD element that exhibits stable reversibility as an ECD element, displays clear colors, and has an excellent driving life has not yet been found. Therefore, it is desired to develop a practical ECD element that is an organic ECD with clear display colors and has an excellent driving life.

(Means for Solving the Problems) The present inventors have studied practical cells with excellent drive life for organic ECD elements that exhibit clear display colors.
The present invention has now been completed.

That is, in the device of the present invention, a solution consisting of an organic electrochromic substance, an electrolyte, and a solvent whose weight is equal to or less than the total amount of the organic electrochromic substance and the electrolyte is filled between the electrodes. This is a characteristic electrochromig display element.

The amount of solvent used in the ECD device of the present invention is very small compared to the amount of solvent used in a normal solution-type ECD device, and is equal in weight or less to the total amount of organic EC substance and electrolyte. If the EC substance used is liquid at room temperature, a solvent may not be used. This is because Rizan uses a smaller amount of solvent than usual or does not use it at all, even if a large amount of solvent is used, the display characteristics remain the same, and in some cases, the coloring may deteriorate on the contrary. Although the appropriate amount varies depending on the compatibility with the EC substance and electrolyte used, it is generally preferably 115 or less of the total amount of the EC substance and electrolyte. Examples of the solvent used include N,N-dimethylformamide, N,N
-dimethylacetamide, N-methylpyrrolidone, dimethylsulfoxide, acetonitrile, propylene carbonate, γ-butyrolactone, 1,2-digloloethane, dichloronaphthalene, etc., and one or more of these are used.

The organic EC substance used in the present invention is preferably liquid at room temperature, and may be a solid substance that dissolves well in a small amount of solvent and similarly becomes liquid. Specifically, dibutyl terephthalate, dibutyl terephthalate, tetrabutyl pyromellitate, dibutyl dimethyl pyromellitate, hexabutyl mellitate, 3.3°, 4.4'-tetrahexyl biphenyltetracarboxylate, 3.3',4 .4'-Biphenyltetracarboxylic acid diethyl dibutyl, 2,3,5
．． Tetrabutyl 6-pyridinetetracarboxylate and the like.

Examples of the electrolyte used in the present invention include tetrahexylammonium chloride, tetrabutylammonium bromide, tetrahexylammonium iodide, n-dodecyltribromide, methylammonium, tetrabutylammonium perchlorate, and tetrafluoroborate. etc., and one or more of these are used. This electrolyte is usually used in a range of 0.1 to 50 when the weight of the EC substance used is 100. Although it varies depending on the characteristics of the EC substance and solvent used and the required display characteristics, a value of 0.5 to 5 is particularly good, being economical, easy to dissolve, and sufficiently colored.

The ECD element of the present invention will be explained below.

A typical ECD element is one in which an EC substance and a supporting electrolyte are dissolved in a solvent to form a solution, which is sealed in a cell as shown in FIG. 1, for example. In Figure 1, 0) is a transparent substrate, and (2) is a transparent electrode. Usually, the transparent substrate (
A transparent conductive glass or the like in which 1) and transparent 1ii(2) are integrated is used.

(3) is a spacer, which is usually made of polyester, polyimide, Teflon, or the like. (4) is a solution containing an EC substance and a supporting electrolyte. Electrode spacing is ○, O○ 5~1m
m, and a background body may be inserted between the electrodes.

A porous white plate made of ceramic or the like is used as the background.

The ECD element of the present invention also has the same structure as above.

The ECD element of the present invention is prepared by filling a cell as shown in FIG. 1 with an EC solution in which an EC substance or the like is dissolved. Coloring can be obtained by taking out lead wires from the electrodes of this ECD element, connecting them to a power source or circuit, and applying voltage. EC of the present invention
Since the D element has no solvent or only a small amount of solvent, it has the characteristics of clear display colors and excellent driving life even if the cell containing the EC solution has a small thickness. Furthermore, there is almost no need to worry about liquid leakage, which has traditionally been the biggest problem.

(Example) Hereinafter, the present invention will be explained in more detail with reference to Examples. In addition, parts in the examples represent parts by weight.

Example 1 Two parts of tetrahexylammonium bromide were dissolved in 98 parts of tetrabutyl pyromellitate, and the resulting solution was sealed in an empty cell shown in FIG. 1 to obtain an ECD element of the present invention. When a voltage was applied between the electrodes of this element using a DC power supply, a bright red coloring was obtained at 2.7V. When the voltage application was stopped, the color disappeared and returned to colorless. When this was measured with a spectrophotometer, λmax at the time of coloring was 530 ram.

The driving life was 1° or more. Moreover, no liquid leakage from the cell was observed at this time.

Examples 2 to 4 ECD elements having the compositions shown in Table 1 were prepared in the same manner as in Example 1, and the same measurements as in Example 1 were performed. The results are shown in Table 1.

Comparative Example 1 3.1 parts of dimethyl pyromellitate and 1.85 i of tetrabutylammonium iodide were dissolved in X-methylpyrrolidone to make 100 parts, and an EC solution was prepared.

Using this EC solution, an ECD element was prepared in the same manner as in Example 1, and the driving life was measured. However, after 10" cycles, the liquid leakage became severe and the colored portion was reduced to half of the initial value.

(Effects of the Invention) According to the present invention, an ECD element with clear display colors, excellent driving life, and no leakage was obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a general ECD element cell. 1. Transparent substrate 2. Transparent electrode 3. Spacer 4. Solution containing EC substance and supporting electrolyte Patent applicant
Nippon Carlit Co., Ltd.

Claims (1)

[Claims] An electrochromic display element characterized in that a solution consisting of an organic electrochromic substance, an electrolyte, and a solvent whose weight is equal to or less than the total amount of the organic electrochromic substance and the electrolyte is filled between the electrodes.