JPS6328286B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrochromic (hereinafter abbreviated as EC) display device that utilizes electrochromism, which is a reversible coloring or luminescence phenomenon of substances due to electrical action, and particularly relates to a reflective type display device. It provides a good display background in an EC display device and also allows the device to be made thinner.

An EC display device is usually mainly composed of a display electrode, a counter electrode, and an electrolyte, and the EC substance is provided as a thin film on a transparent conductive layer as part of the display electrode, or is used by being dissolved in the electrolyte. . As EC substances, inorganic EC substances such as tungsten oxide, molybdenum oxide, and silver iodide, and organic EC substances such as viologen compounds are known. In addition, the electrolyte solution is one in which an electrolyte such as a mixture of sulfuric acid and glycerin, lithium perchlorate, or potassium bromide is dissolved in water or a solvent such as propylene carbonate, cellosolve acetate, carbitol acetate, or γ-butyrolactone. used.

There are two types of EC display devices: transmissive and reflective.
In general, reflective devices are being considered that provide a certain background and display using a colored EC substance. Dispersed and mixed into the electrolyte. By mixing such a white substance, it is possible to provide a display background with a large contrast in the colored state of the EC substance and to hide the counter electrode, etc., but the dispersed and mixed substances can be dispersed during long-term use. The concentration often becomes non-uniform due to precipitation or aggregation, which poses a problem in the practical application of EC display devices.

Furthermore, there are limits to the type and amount of substances that can be dispersed and mixed in this method, and it becomes necessary to thicken the electrolyte layer in order to apply it to an actual device. In order to solve these problems, it has been proposed to provide a porous material as an electrolyte-impregnated layer as a display background, but the hiding power of the base is insufficient and the electrical resistance of the electrolyte layer increases. Because of the excessive amount of the display background, it is still difficult to find a display background that is sufficiently satisfactory for practical use.

The present invention provides an apparatus in which a porous body that holds a pigment as an electrolyte-impregnated layer is provided between a display electrode and a counter electrode, in which the porous body has fibers and nodes interconnected by the fibers. The porous body has a microstructure having an average pore diameter of 0.1 to 50 μm, the proportion of the porous space in the porous body is 30% by volume or more, and at least pigment is contained in the porous space. The present invention proposes an EC display device characterized in that the proportion of the pigment in the porous space is 1 to 50% by volume, and has an unprecedentedly good display background.

In the present invention, the porous body is provided as an electrolyte-impregnated layer between the display electrode and the counter electrode, and its purpose is to retain the pigment in the porous space to hide the base and provide a colored display background. It is something that has.
Therefore, the characteristics of the porous material are that it has a pore size that can hold the pigment, and that even if the necessary amount of pigment for the display background is held in the porous space, the increase in electrical resistance of the electrolyte layer is minimized. It is necessary to have sufficient porosity to allow for The pore size of the porous material is required to be larger than the particle size of the pigment, but
On the other hand, if it becomes too large, it will become visible to the naked eye, causing a problem with the uniformity of the display background. From this point of view, when using general pigments such as those described below, the average pore diameter of the porous body is 0.1.
It has been found that it is appropriate that the proportion of the porous space in the porous body is 30% by volume or more. The material of the porous body is not particularly limited as long as it is not eroded by the electrolytic solution, but the most suitable examples include polytetrafluoroethylene, polypropylene, and polyethylene. In particular, those materials made into porous bodies with fine pore diameters by stretching not only satisfy the above-mentioned characteristics of pore diameter and porosity, but also have good adhesion to display surfaces due to their flexibility. It was found that the pigment retention property due to its microstructure is extremely excellent.

Methods for producing these porous bodies are known, but
An overview will be given using polytetrafluoroethylene as an example. The polytetrafluoroethylene porous material can basically be produced by the method described in Japanese Patent Publication No. 13560/1973. First, a liquid lubricant is mixed with unsintered polytetrafluoroethylene powder, extruded,
Form into a desired shape by rolling or the like. The liquid lubricant is removed from the molded product by extraction, heat evaporation, etc., or the molded product is stretched in at least one direction without removing it. When the stretched structure is heated to a temperature of about 327° C. or higher, which is the sintering temperature, while preventing heat shrinkage, and then sintered and fixed, a polytetrafluoroethylene porous body with improved strength can be obtained. This porous material has a microstructure consisting of very thin fibers and nodules interconnected by the fibers, and the diameter and length of the fibers, the size of the nodules, and their number are determined by drawing and sintering. Pore sizes and porosity suitable for the present invention can be easily obtained since they can be varied depending on conditions. Further, when a porous body having such a microstructure is used, the pigment is retained in the microstructure, and this point is also suitable for the present invention.

In the present invention, the pigment is held within the porous space of the porous body to provide a display background,
At the same time, it has the role of improving the wettability of the porous body to the electrolytic solution. Examples of pigments are:
Titanium white, zinc white, lead white, lithopone, titanium yellow,
Powders of ultramarine, navy blue, cobalt blue, vermilion, cadmium red, Bengara, iron black, silica, alumina, talc, gypsum, calcium carbonate, barium sulfate, carbon black, iron, copper, lead, tin, aluminum, etc., various organic materials Examples include pigments. These pigments can be used singly or in combination, and if necessary, dyes, fluorescent agents, etc. can be added to enhance the effect as a display background.

In order to retain these pigments in the porous spaces of the porous body, the porous body may be impregnated with a pigment dispersion. The pigment dispersion used is one in which the pigment is dispersed in a liquid that has wettability with respect to the material of the porous body. In the case of porous bodies made of hydrophobic materials such as polytetrafluoroethylene, polypropylene, and polyethylene, methanol, ethanol, isopropyl alcohol, acetone,
A liquid with low surface tension such as methyl ethyl ketone, hexane, or an aqueous surfactant solution may be used. When using a liquid with a high surface tension (such as water) that does not show wettability to the material of the porous body as a dispersion medium for pigments, it is necessary to prepare the porous body in advance by the method described in Japanese Patent Publication No. 1985-8505. The porous spaces of the substrate can be filled with a wetting liquid and then replaced with the required liquid. The amount of pigment retained in the porous material must be at least the amount necessary to hide the base and provide appropriate coloring as a display background, but if the amount is large enough to fill the porous spaces of the porous material, The increase in electrical resistance of the electrolyte layer becomes excessive, and the purpose of the present invention cannot be achieved. Furthermore, when using a porous body made of a hydrophobic material, it is also necessary to retain an amount of pigment in excess of that required to impart wettability to the electrolytic solution. From this point of view, it has been found that when using the above-mentioned general pigments, it is appropriate that the pigment occupy 1 to 50% by volume in the porous space. In particular, when the pigment contains titanium oxide in an amount of 50% by volume or more, it is appropriate that the pigment occupies 2 to 25% by volume in the porous space.

Although the shape of the porous body of the present invention is not particularly limited, generally a sheet-like body is often used. The thickness of the sheet-like porous material is
The normal range is about 0.03 to 2 mm, but when using a porous body with a thickness within this range, the amount of pigment expressed in terms of the amount per unit area of the porous body is 3 ml or more per 1 m ² of area. was found to be the amount necessary to provide a good display background.

The porous body of the present invention uniformly retains pigments necessary as a display background within its porous space, and in particular, polytetrafluoroethylene, polypropylene,
In the case of porous bodies made of polyethylene,
Due to its good chemical resistance, it has excellent resistance to electrolytes, and even when used in an electrolyte layer, the increase in electrical resistance is small, so this porous material can be used as an electrolyte-impregnated layer for EC. The display device is capable of displaying clear images against an unprecedented display background. Furthermore, when the porous body is made of a resin such as polytetrafluoroethylene, polypropylene, or polyethylene, it is flexible and has good adhesion to the display electrode surface. In addition, if the thickness of the porous body is made extremely thin, for example, 0.1 mm or less, it will have a great effect as a display background, and the layer thickness of the electrolyte used by impregnating this porous body can also be made that thinner. Therefore, the amount of electrolytic solution is small, and the increase in electrical resistance of the electrolytic solution layer is also small, which is advantageous from an economic point of view. The advantage of being able to reduce the thickness also leads to a reduction in the overall thickness of the device, and the EC display device of the present invention is particularly useful as a display device that requires reduction in size and weight.

Taking advantage of these features, the EC display device of the present invention can be used in watches, electronic desktop calculators, measuring instruments, control panels,
It can be used for display parts such as road signs and information boards.

Examples are shown below, but the scope of the present invention is not limited thereto.

Example 1 Titanium white pigment Taipek CR-90 (manufactured by Ishihara Sangyo Co., Ltd., titanium oxide
90% content) was added and dispersed and mixed. Average pore size made from polytetrafluoroethylene
A porous membrane Fluoropore FP-1000 (manufactured by Sumitomo Electric Industries, Ltd.) sheet having a diameter of 10.0 μm, a porosity of 87%, and a thickness of 0.1 mm was impregnated with the above dispersion, washed with water, and then heated and dried. This impregnation,
The sheet-like porous material obtained by repeating the water washing and drying operations two more times retained the titanium white pigment in the porous space, and the proportion of the pigment in the porous space was 15% by volume. .

This sheet-like porous material holding the pigment is incorporated into the electrolyte layer of an EC display device that uses tungsten oxide as the EC substance, and a solution of lithium perchlorate dissolved in γ-butyrolactone at a concentration of 1.0M is used as the electrolyte. Impregnated. In this EC display device, the increase in electrical resistance of the electrolyte layer due to the inclusion of a porous body is only a few percent, and when a voltage is applied in the display direction, the display is colored against a white background. It was an unprecedentedly clear display.

Example 2 Titanium yellow pigment Taipei Yellow as pigment
Using TY-70 (manufactured by Ishihara Sangyo, containing 78% titanium oxide), a polytetrafluoroethylene material with an average pore diameter of 5.0μ was prepared in the same manner as in Example 1.
A porous membrane Fluoropore FT-500 (manufactured by Sumitomo Electric Industries, Ltd.) sheet having a porosity of 80% and a thickness of 0.38 mm was treated to obtain a sheet-like porous body in which titanium yellow pigment was retained in the porous spaces. In this porous body, the proportion of pigment in the porous space was 6% by volume. An EC display device in which this porous body was incorporated into the electrolyte layer was displayed on a yellow background, giving the same good results as in Example 1.

Claims (1)

[Claims] 1. In an apparatus in which a porous body for retaining pigment as an electrolyte-impregnated layer is provided between a display electrode and a counter electrode,
The porous body has a microstructure composed of fibers and nodes interconnected by the fibers, the average pore diameter of the porous body is 0.1 to 50 μm, and the proportion of porous spaces in the porous body is 30% by volume or more, at least a pigment is retained in the porous space, and the proportion of the pigment in the porous space is 1 to 50% by volume. 2. The electrochromic display device according to claim 1, wherein the porous body is in the form of a sheet with a thickness of 0.03 to 2 mm and retains 3 ml or more of pigment per 1 m ² of area. 3. The pigment contains 50% by volume or more of titanium oxide,
Claim 1, characterized in that the proportion of the pigment in the porous space is 2 to 25% by volume.
The electromic display device described in Section 1. 4. The electrochromic display device according to claim 1, wherein the material of the porous body is polytetrafluoroethylene. 5. The electrochromic display device according to claim 1, wherein the material of the porous body is polypropylene or polyethylene.