JPH02135322A - Electrochromic display element - Google Patents

Abstract

PURPOSE:To improve the cycle life of the electrochromic display element by working and forming an insulating protective film to such a shape with which the vapor deposited particles of an electrochromic material are liable to infiltrate. CONSTITUTION:The end part of the insulating protective film 3 is formed to the suitable shape to allow the easier infiltration of the vapor deposited particles of the electrochromic material. The similar effect is obtd. as well even if the end of the insulating protective film 3 is formed to a staircase shape. The part where the film thickness is small is gradually eliminated if the grade is confined to <=1,700/1,000 (about 60 deg. elevation angle) in case of forming a grade. The part where the film thickness is small is substantially eliminated if the grade is confined to <=600/1,000 (about 30 deg. elevation angle). The uniformity of the thickness of the electrochromic film 5 is assured by eliminating the part where the film thickness is partly small. The long-term cycle life is obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to improvements in electrochromic display elements.

[Conventional technology]

FIG. 1 shows an example of the basic cell structure of an electrochromic display element. In the figure, 1 is a transparent glass plate, and display electrodes 2 made of transparent conductive films and insulating protective films 3 are provided on the surface of this transparent glass plate 1 in a predetermined pattern consisting of a plurality of display segments. 4 is formed. Tungsten oxide (W○, ) or molybdenum oxide (Mo
The electrochromic film 5 made of O3) etc.
The display electrode 6 is formed with a film thickness of 0.00 to 10,000. The thicker the electrochromic film 5 is, the higher the coloring density becomes, but since some residue remains when erasing the color, 5,000 to 6,000 people are usually used.

7 is a counter electrode substrate, and a counter electrode material layer 9 is provided on the surface of this counter electrode substrate 7 with a counter electrode 8 interposed therebetween.
is formed. The display electrode substrate 4 and the counter electrode substrate 7 are arranged facing each other with their respective processed surfaces inward through a spacer 11 made of synthetic resin or glass, and are filled with an organic solvent such as propylene carbonate or gamma-butyrolactone inside. It is filled with an electrolytic solution 12 in which a lithium salt such as lithium chlorate or lithium borofluoride is dissolved.

The display electrode 2 is made of indium-tin composite oxide (IT
It is made of a transparent conductive material such as
It is formed to a thickness of about ,000 to 5,000 people. When the display electrode 2 and the electrolyte 12 come into contact, an electrochemical reaction occurs not only in the electrochromic film but also in the display mold 2 during IJJ of the device, causing deterioration of not only the display electrode 2 but also the electrolyte 12. To prevent this, an insulating protective film 3 such as silicon dioxide (SiO2) or magnesium fluoride (MgF) is applied to the display electrode 2 as a protective film.
The thickness is approximately 0 to 10,000 people.

For pattern formation of the insulating protective film 3, a photolithography method is usually used which allows sharp edges to be formed. However, if there is a gap at the interface between the electrochromic film 5 and the insulating protective film 3, there is a problem that the display electrode 2 and the electrolyte 12 come into contact with each other. Various measures have been taken to eliminate this gap. For example, as shown in FIG. 2(A), the insulating protective film 2o is formed continuously so as not to overlap with the electrochromic film 19 (Japanese Patent Application Laid-Open No. 52-38947), as shown in FIG. 2(B). As shown in FIG.
Methods have been proposed, such as overlapping. However, none of these methods were sufficiently effective. That is, in the method disclosed in Japanese Patent Application Laid-Open No. 52-38947, the insulating protective film 20 and the electrochromic film 19 appear to be continuous from a macroscopic perspective, but when the interface between the two is closely observed with an electron microscope, it is found that the insulating protective film 20 and the electrochromic film 19 are continuous. A narrow gap of about 1 to 1 μm may occur, or the electrochromic film 19 may slightly overlap the insulating protective film 20, and the insulating protective film 2o and the electrochromic film 19 should be continuously formed with good reproducibility. It is very flexible, and if there is even a slight gap, if the element is cycled over tens of blades or hundreds of gals, it will gradually deteriorate and eventually malfunction will occur.

In the case of FIG. 2(B), the insulating protective film 20 overlaps the electrochromic film 19, so the portion of the electrochromic film 19 below the insulating protective film 20 does not come into direct contact with the electrolytic solution. There is a drawback that the decoloring reaction is slow and one-color unevenness occurs, resulting in a decrease in display quality. On the other hand, the second
The method of overlapping the end portion of the electrothalomic film 19 on the insulating protective film 20 shown in FIG. 3(C) can improve the cycle life without deteriorating the display quality.

This is the most suitable method among the above three methods.

Even with this method, there is no problem if the insulating protective film is thin (less than 3,000 layers), but in order to sufficiently protect the display electrodes below, the film thickness is usually between 5,000 and 6,000 layers. On the other hand, as mentioned above, the thickness of the electrochromic film cannot be increased indefinitely from the viewpoint of preventing residual color from being left behind during erasing. Therefore, in such a case, when observing the interface between the formed insulating protective film and the electrochromic film using an electron microscope, it is found that the end portion is overlapped on the insulating protective film 24 by vapor deposition later, as shown in Figure 3. In the electrochromic film 23, depressions are formed at the step portions, and some portions of the film are inevitably thin. This is unavoidable when another film is deposited to a similar thickness on a part of a film with a nearly vertical step.31 On the other hand, on the edge of an electrochromic film, Since the current is concentrated due to the edge effect, if there is a thin part at the edge, the electrochromic film will melt due to multiple cycle driving1, and the part will gradually become thinner, and eventually the display electrode The drawback was that deterioration began due to direct contact between the electrolyte and the electrolyte.

[Problem that the invention seeks to solve]

The object of the present invention is to provide an electrochromic display element that has a long cycle life by devising the shape of the interface between an insulating protective film and an electrochromic film.

[Means to solve the problem]

The present inventors conducted various studies based on the knowledge that it is necessary to ensure the uniformity of the thickness of the electrochromic film in order to achieve this objective, and found that the shape of the edge of the insulating protective film is an important factor. I found that. In other words, M! ! When the electrochromic film is deposited on the soil of the edge protection film so that the edges overlap, if the edge of the insulation protection film is vertical and steep, some of the electrochromic film J It was found that the thickness becomes thinner. It has been found that the reason for this is that particles of the electrochromic substance that fly during vapor deposition do not sufficiently wrap around the shaded portion at the bottom of the insulating protective film.

The present inventors focused on this fact and as a result of intensive studies, in order to ensure the uniformity of the thickness of the electrochromic film, the ends of the Ma protective film should be appropriately shaped as shown in Figure 4 (A). It has been found that the shape can be formed so that the vapor-deposited particles of the electrochromic substance can easily wrap around it. Furthermore, the same effect can be obtained by rounding the corners of the slope as shown in FIG. 4(B) or by forming the edges of the insulating protective film into a stepped shape as shown in FIG. 4(C). I discovered that.

When forming a gradient, set the gradient to 1700/1000 (
When the elevation angle is set to about 60° or less, the thin part of the film is gradually eliminated, preferably 1000/l.

00 (elevation angle approximately 45°) or less, more preferably 600/
When the angle is less than 1000 (elevation angle of about 30°), the thin part of the film almost disappears. However, if the slope is made too small, M
The overlap of the electrochromic film on the AI protective film becomes large, and the coloring/decoloring reaction in that area becomes slow, resulting in a decrease in display quality. Although it is related to the film thickness, the lower limit of the slope is 200/
1000, preferably 300/1000 or more.

Further, when forming the end portion of the insulating protective film in a step-like manner as shown in FIG. 4(C), it is desirable to have multiple steps, but since the processing process becomes complicated, 2 to 3 steps is practical. In that case, if the bottom layer is too thick, it will be the same as in the case of one layer and the effect of making it step-like will be reduced, so the thickness of the bottom layer should be less than half of the total thickness of the absolute protective film and less than 3000 Å. is desirable.

Below, an example of an electrochromic display element according to the present invention will be described in comparison with a conventional example. [Example] Conventional example After forming an ITO film with a thickness of 2,500 mm, which will become the display electrode, by vacuum evaporation and forming it into a predetermined pattern, a SiO film is deposited on the entire surface of this IT○ film as a protective film to a thickness of 5,000 mm. It was provided by a vapor deposition method. Next, a photoresist (product name: 0FPR-800 manufactured by Tokyo Ohka Co., Ltd.) was formed to a thickness of 2 μm on the 5 in 7 film except for the 1 display pattern area and the extraction electrode area. Next, S
The iO2 film was etched with carbon tetrafluoride (CF4) gas, and then the photoresist was retreated with oxygen (O7) gas to form the end shape shown in FIG. The etching time was 3 minutes for CF gas and 5 minutes for 02 gas, and the etching temperature was 80°C. The slope of the end at this time was approximately 5000/1000 (elevation angle approximately 80'). 02 gas pressure IXLO-'torr, substrate temperature 150°C, film formation rate 1
A WO3 film having a thickness of 5,000 layers was vacuum-deposited under conditions of 0 layers per second, and formed into an 8-figure pattern for displaying numbers using a lift-off method to form a display electrode.

On the other hand, fir 45mm, width 160n+m, thickness 1. A layer with a thickness of 400 nm is placed on the entire surface of the counter electrode substrate made of a transparent glass plate of 1 nm.
A counter electrode made of an ITO film was formed by vacuum evaporation, and activated carbon fiber cloth (trade name CH-20, manufactured by Kuraray Co., Ltd.) was applied on top of the counter electrode (trade name PR-10, manufactured by Taikisha Co., Ltd.). A counter electrode material layer was formed by bonding the electrodes together through a heat treatment at 180° C. for 2 hours, thereby forming a counter electrode. Then, the above-mentioned peripheral substrate was placed in such a manner that the WO3 film and the counter electrode material layer faced each other, and titanium dioxide (
A background material made of a mixture of TiO2) powder and polytetrafluoroethylene powder (trade name Boaflon, manufactured by Judenki Kogyo Co., Ltd.) is interposed, and a rectangular shape made of polyester resin with a thickness of 1 mm is placed around the periphery. After placing them facing each other with an annular spacer in between and sealing with epoxy resin adhesive, 1 mol/l of lithium perchlorate is dissolved in propylene carbonate through an electrolyte injection hole made in a part of the spacer. 6 ml of electrolytic solution prepared by adding 0.1% by weight of pure water was injected, and the injection hole was adhesively sealed with an epoxy resin adhesive. Next, lead terminals were attached and a conductive layer was formed by applying silver paste, thereby producing the electrochromic display element shown in FIG. 1.

Example 1 The etching time of the 5in2 film in the conventional example was changed to CF4
Gas: 3 minutes (Fig. 6 (A) → (B)), 02 gas = 5 minutes (Fig. 6 (B) → (C)), CF4 gas: 4 minutes (Fig. 6 (C) → (D) )), 02 gas = 8 minutes (Figure 6 (D) → (
An electrochromic display element was manufactured in the same manner as in the conventional example except for E)). When the substrate manufactured in Example 1 was observed with an electron microscope, the edges of the SiO2 film were found as shown in Figure 6 (E). It became a shape.

The slope was approximately 600/1000.

Example 2 Etching time for 5in2 film in conventional example.

CF, gas: 5 minutes, 02 gas: 10 minutes, CF4 gas: 1
．． An electrochromic display element was produced in the same manner as in the conventional example except that the heating time was 5 minutes and the 02 gas was 8 minutes. Example 2
In the case of Sin, the end shape of the film had a two-step staircase shape as shown in FIG. The thickness of the lower tier was about 2,500 people.

The three types of electrochromic display elements produced as described above are shown in the time chart shown in Figure 8.
At a constant temperature of 5°C, coloring applied voltage knee 1. A cycle life test was conducted under the following conditions: OV, coloring voltage application time: 20.8 seconds, pause time = 58 seconds, decoloring applied voltage: +1.2V, and decoloring voltage application time = 1.2 seconds. This mode mimics the movement of the minute hand on a digital clock.

As a result, the conventional element broke after 260,000 cycles and displayed an abnormal display, but the elements of Examples 1 and 2 did not exhibit any abnormality even after being cycled more than 400,000 times. . Note that the disconnection mentioned here is due to the melting of the edge of the WO1 film, causing the underlying I to break along the edge of the display segment.
The TO film comes into contact with the electrolyte, causing an electrochemical reaction and
This is a phenomenon in which the O film oozes out and conduction between the display segment and the lead electrode portion is lost. Therefore, the display segment in which the disconnection occurs no longer shows any response, which is a fatal abnormality for the display element.

[Effects of inventions and ideas]

As explained above, in the present invention, we focus on the shape of the end of the insulating protective film in contact with the electrochromic film, and process and form the insulating protective film in a shape that allows the deposited particles of the electrochromic substance to easily wrap around. It was possible to significantly improve the cycle life of the display element.

In the embodiment, a dry etching method using a gas is employed, but a wet etching method using an acid or the like may also be employed.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional structure diagram showing an example of the basic element structure of an electrochromic display element, Fig. 2 is a cross-sectional structure diagram of main parts to explain a conventional example, and Fig. 3 shows the structure of the conventional example in detail. FIG. 4 is a sectional view of the main part for explaining the embodiment of the present invention; FIG. 5 is a sectional view of the main part for explaining the conventional example; FIG. 6 is a sectional view of the main part for explaining the conventional example; FIG. 7 is a cross-sectional view of the main part for explaining Example 1, FIG. 7 is a cross-sectional view of main part for explaining Example 2, and FIG. 8 is a time chart of the cycle life test. 1.17.21.25.29.33.37...Transparent glass plate, 2.18.22.26.30.34.3
8...Display electrode, 3.20.24°28.31
．． 35.39...Insulating protective film, 4...
・Display electrode substrate, 5.19.23.27... Electrochromic film, 6... Display electrode, 7...
...Counter electrode substrate, 8...Counter electrode, 9
...Counter electrode material layer, 10...Counter electrode, 11...Spacer, 12...
...Electrolyte, 13 display terminal, 14...
... Opposite electrode lead terminal, 15 ... Conductive layer,
16...Background material. 32.36.40...Photography/Sist Patent Applicant Hitachi Maxell Co., Ltd. Representative Atsushi Nagai 1 Figure 2 (,4) q CB) 1-11 Toru B Monthly Button Sui and 2-11 Display phone section 3--1 Umbrella, blind negative film 4--1 Display base, 5--1 Electrochromic film 6--Display box One opposing electrode 77 of the electrolyte layer 7 in one direction - Electrolyte 13 - Doj Takako 74-m 1 Opposite pole 1 Dohanawa each 7, f--1 Conductive eyebrow 76-1--One view elbow 17--Transparent force glass temporary 18-116 Indicating electrode/d 79- 11 Electrochromi, Rime ZO--Ichikasuke promotion 3rd figure Ibarashi Denkyu Ikzetsuroku promotion 5th figure 3 No ~ - I'm sorry for my relationship with you Lath plate 35 34-----Rawobi display broken o) 36 External protective film photoresist diagram (C) (ρ) Figure 38-11 Display bell 4θ 17 Otresist diagram (E-) Figure body stop Time Decoloring voltage application time Coloring voltage application time

Claims (6)

[Claims] (1) A transparent conductive film formed on the surface of a transparent glass plate,
an electrochromic film partially patterned and formed on the surface of the transparent conductive film; and an insulating film having a thickness of at least 3,000 Å formed on the surface of the transparent conductive film on which the electrochromic film is not formed. 1. An electrochromic display element having a protective film, wherein the thickness of the electrochromic film in the vicinity where the electrochromic film contacts the insulating protective film is approximately equal to or greater than the thickness of the central part. (2) a transparent conductive film formed on the surface of a transparent glass plate;
an electrochromic film partially patterned and formed on the surface of the transparent conductive film; and an insulating film having a thickness of at least 3,000 Å formed on the surface of the transparent conductive film on which the electrochromic film is not formed. An electrochromic display element having a protective film, characterized in that an end portion of the insulating protective film in contact with the electrochromic film is provided with a slope. (3) The electrochromic display element according to claim (2), wherein the slope of the edge of the insulating protective film is in the range of 300/1000 to 1000/1000. (4) Claim (2) or (4) characterized in that the slope corner of the sloped insulating protective film is formed in an arc shape.
3) The electrochromic display element described above. (5) a transparent conductive film formed on the surface of a transparent glass plate;
an electrochromic film partially patterned and formed on the surface of the transparent conductive film; and an insulating film having a thickness of at least 3,000 Å formed on the surface of the transparent conductive film on which the electrochromic film is not formed. An electrochromic display element having a protective film, characterized in that an end portion of the insulating protective film in contact with the electrochromic film is formed in a stepped shape. (6) The thickness of the bottom step of the stepped portion at the end of the insulating protective film is 1/2 or less of the total thickness of the insulating protective film and 3,000 yen
6. The electrochromic display element according to claim 5, wherein the electrochromic display element has a thickness of Å or less.