JPS6328285B2 - - 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 used as a part of the display electrode, either by being provided in the form of a thin film on a transparent conductive layer, or 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.
The electrolyte used is a mixture of sulfuric acid and glycerin, lithium perchlorate, potassium bromide, or other electrolyte dissolved in water or a solvent such as propylene carbonate, cellosolve acetate, carbitol acetate, or γ-butyrolactone. It will be done.

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 body as an electrolyte-impregnated layer and use it as a display background. White porous bodies made of ceramic or resin are used as the porous body, but ceramics have poor adhesion to the display surface, and other porous bodies also have insufficient hiding power for the base, etc. I have not been able to find anything that is fully satisfactory as a display background. The present invention has been achieved by providing a porous body, which is obtained by impregnating a pigment dispersion into a porous body by the action of ultrasonic waves, and retaining the pigment in the porous space as an electrolyte-impregnated layer. The purpose is to submit an EC display device with a good display background.

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.

An example of a porous body suitable for the purpose of the present invention is a porous body having fine pores formed by stretching a resin.

Suitable materials include polytetrafluoroethylene, polypropylene, and polyethylene. Methods for producing these porous bodies are well known, and will be briefly described using polytetrafluoroethylene as an example. Polytetrafluoroethylene porous material is
Basically, it can be produced by the method described in Japanese Patent Publication No. 42-13560. First, a liquid lubricant is mixed with unsintered polytetrafluoroethylene powder, and the mixture is molded into a desired shape by extrusion, 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 axial direction without being removed. Sintering temperature of 327℃ with heat shrinkage prevented
When the stretched structure is sintered and fixed by heating to the above temperature, 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. Since they can be changed depending on the conditions, the pore diameter and porosity of the resulting porous body can also be determined freely. When used in an EC display device, which is the object of the present invention, the average pore diameter of the porous body is 0.1 to 50 μm, preferably 1 to 20 μm, and the volume fraction occupied by porous spaces in the porous body is 30 μm.
~90%, preferably 50 to 90%, was suitable as an electrolyte-impregnated layer with little increase in electrical resistance. Although the thickness of the porous body can be freely selected, a thickness of 1 mm or less is usually used.

This porous material is unsuitable as a display background because it becomes transparent or translucent when impregnated with an electrolyte when it does not hold pigment. Therefore, it is necessary to retain the pigment in some way, but with the common method of directly mixing the pigment into the resin, the pigment is not evenly dispersed in the resin, and the amount of mixing is often limited. . In particular, it is extremely difficult to mix a pigment into the polytetrafluoroethylene, polypropylene, or polyethylene mentioned above from the beginning and then stretch the mixture to form a porous body that uniformly retains the pigment. Therefore, as a result of various studies on methods for retaining pigments within the porous space of a porous body, it was found that a pigment dispersion was impregnated into a porous body by the action of ultrasonic waves. I found it to be optimal. 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. When a porous body is immersed in the porous body and ultrasonic waves are applied at the same time, the pigment enters into the porous space of the porous body. This method is particularly effective when the porous body has a microstructure consisting of fibers and nodules interconnected by the fibers, as described above, and the pigment is retained in the microstructure. Become. For this purpose, the particle size of the pigment needs to be smaller than the pore size of the porous body. It has been found that in order to retain more pigment in the porous spaces of the porous body, it is sufficient to repeat the impregnation and drying of the pigment dispersion by the action of ultrasonic waves.
Although the volume percentage occupied by the pigment in the porous space varies depending on the type of pigment, a porous body suitable for the purpose of the present invention usually has a volume ratio of 1 to 50%. The amount of this pigment is determined by the base hiding power and degree of coloration required as a display background. When using a liquid with high surface tension (such as water) that does not show wettability to the material of the porous body as a dispersion medium for the pigment, the porous body is preliminarily prepared by the method described in Japanese Patent Publication No. 1985-8505. Filling the porous space with a liquid that exhibits wettability,
It can then be replaced with the required liquid. In the case of porous bodies made of polytetrafluoroethylene, polypropylene, and polyethylene, liquids with low surface tension such as methanol, ethanol, isopropyl alcohol, acetone, methyl ethyl ketone, hexane, and aqueous surfactant solutions are used as pigment dispersion media. It is possible to impregnate without pretreatment.

The pigment-retaining porous body obtained in this way uniformly retains the pigment required as a display background within its porous space. In the case of a porous body, it has good chemical resistance and therefore has excellent resistance to electrolytes, and even when used in an electrolyte layer, the increase in electrical resistance is small, so this porous body is The EC display device using an electrolyte-impregnated layer enables clear display 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. Furthermore, even if the thickness of the porous body is extremely thin, for example, 0.1 mm or less, the effect as a display background is great, and the layer thickness of the electrolyte used by impregnating this porous body can also be made that thinner. Therefore, the amount of electrolyte required is small, and the electrical resistance of the electrolyte layer is also low, which is economically advantageous. 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 for display parts of watches, electronic desktop calculators, measuring instruments, control panels, road signs, information boards, and the like.

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

Example 1 150 g of titanium white pigment Taipeiku CR-90 (manufactured by Ishihara Sangyo) was added to 1 part of isopropyl alcohol and dispersed and mixed. This dispersion liquid was placed in a metal container and placed on an ultrasonic vibrator with a frequency of 28 KHz and an output of 1200 W. Polytetrafluoroethylene material is added to the dispersion liquid while applying ultrasonic waves.
A porous membrane Fluoropore FP-1000 (manufactured by Sumitomo Electric) sheet with an average pore diameter of 10.0 μm, a porosity of 86%, and a thickness of 0.1 mm was used.
It was immersed for 15 seconds, washed with water, and then heated and dried. Next, the upper and lower surfaces of the sheet were turned over, and the same operations of impregnation by ultrasonic waves, washing with water, and drying as described above were repeated.
The sheet-like porous material obtained had a titanium white pigment retained in the porous space at a volume percentage of 12%.

The sheet-like porous material holding this pigment was incorporated into the electrolyte layer of an EC display device using tungsten oxide as the EC material, and lithium perchlorate was added to a concentration of 1.0M.
- A solution dissolved in butyrolactone was impregnated as an electrolyte. 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 appears blue on a white background. It was an unprecedentedly clear display.

Furthermore, when a porous material obtained by adding a small amount of fluorescent agent together with a white pigment was incorporated into an EC display device, the whiteness of the display background was even more excellent due to its whitening effect.

Example 2 Titanium yellow pigment Taipei Yellow as pigment
By the same operation as in Example 1 using TY-70 (manufactured by Ishihara Sangyo), a material made of polytetrafluoroethylene, average pore diameter 5.0 μm, porosity 82%, thickness
A 0.35 mm porous membrane Fluoropore FT-500 (manufactured by Sumitomo Electric Industries, Ltd.) sheet was treated to obtain a sheet-like porous body in which titanium yellow pigment was retained at a volume percentage of 7% within the porous space. The porous body incorporated into the electrolyte layer of the EC display device is displayed on a yellow background, and is shown in Example 1.
gave similar good results.

Claims (1)

[Claims] 1. In an apparatus in which a porous body is provided as an electrolyte-impregnated layer between a display electrode and a counter electrode, the porous body
1. An electrochromic display device characterized in that it is a porous body obtained by impregnating a pigment dispersion with the action of ultrasonic waves and retaining pigment in porous spaces. 2. An electrochromic display device according to claim 1, wherein the porous body has a microstructure consisting of fibers and nodules interconnected by the fibers. 3. The electrochromic display device according to claim 1, wherein the material of the porous body is polytetrafluoroethylene. 4. The electrochromic display device according to claim 1, wherein the material of the porous body is polypropylene or polyethylene. 5. The electrochromic display device according to claim 1, wherein the porous body has an average pore diameter of 0.1 to 50 μm, and the pigment has a particle diameter smaller than the average pore diameter. 6 The volume fraction occupied by porous space in the porous body is
2. The electrochromic display device according to claim 1, wherein the volume fraction occupied by the pigment in the porous space is 1 to 50%.