JPS6035052B2 - Manufacturing method of electrochromic display device - Google Patents

Description

Detailed Description of the Invention <Overview> The present invention relates to an electrochromic display device (hereinafter referred to as an ECD) using a substance whose optical absorption characteristics in the visible light region reversibly change between two states upon application of an electric current. (hereinafter referred to as EC material), in particular, a method for manufacturing an ECD having a sandwich structure using a tungsten oxide (hereinafter referred to as W03) thin film obtained by vapor deposition or sputtering as an electrochromic material (hereinafter referred to as EC material) and an electrolyte as an ion source. .

Prior art> There are many electrochromic materials, which have two types of optical absorption characteristics in the visible light region, transparent and colored, and can reversibly select between these two states using electrical energy. (U.
S. Pat. No. 2319765, Talmey or U.S. S. Pat. No. 3521941Debet
al).

Furthermore, it is already known that these EC materials can be patterned and two different optical properties can be reversibly selected through electrical control to display arbitrary characters, symbols, patterns, etc. (U.S.
．． Pat. No. 1068744 or the patent by Debetal mentioned above). The cell structure of ECD is a liquid type (U.S. Pat. No. 3283656) in which a colored substance is dissolved in a liquid, that is, an electrolyte.
esetal), an inorganic insulating film type (Deb patent mentioned above), or a solid electrolyte type (U.S. patent).
S. Pat. No. 3712710 Castemone
However, since the present invention relates to a type that uses an electrolyte as an ion supply source, this will be referred to as an electrolyte type hereinafter, and only this type will be described.

Various basic configurations of electrolyte type ECD cells have been proposed.

As the EC substance, the above-mentioned Talmey or Deb
Although many films are known as described in patents such as et al., it has been reported that amorphous tungsten oxide thin film (hereinafter referred to as W03 film) or amorphous molybdenum oxide film 03 exhibits particularly good characteristics. (U.S. Pat.
No. 3708220M. D. Maye etal, Japanese Patent Publication No. 47-18983). As a display electrode using a W03 film, a cell structure of a 7-segment numeric display ECD using an As24-doped Sn02 film is shown (
U. S. Pat. No. 3827784R. D. Gig
iaetal).

Alternatively, an insulating layer is provided to protect the edge portion of the display EC material layer (U.S. Pat. No. 3836229E).
ricSamer) or one that covers the extraction part made of a transparent conductive film with an insulating film (J. Bminink, P.
ro. SMm. Sept. 29-30, 1975atB
row clause veriRes) has been proposed. As a counter electrode structure, a structure in which an EC material layer is provided on graphite or stainless steel has already been proposed (US Pat. NO. 3819252R.○.G
Igia et al or U. S. Pat. No.
3840287Witzke. etal JP-A-50-5
089). The structure that provides the background for the display is one that disperses pigment in the electrolyte to make it optically opaque (the above-mentioned R
．． D. Gigiaetal patent) or insert a plate that allows ions to pass through but is optically opaque (U
．． S. Pat. No. 3892472R. D. Gigi
There is a). The basic configuration of the electrolyte type rainbow CO has been described above, and now the electrolyte most closely related to the present invention will be described. Regarding electrolytes, U. S. Pat. No. 3
704057L. C. The following is described in the technique. ■0.1-12.0M/1 sulfuric acid aqueous solution @ sulfuric acid in propylene carbonate or acetonitrile, or dimethylformamide or other organic solvent solution Public organic strong acid, such as 2-toluenesulfonic acid in propylene carbonate or organic solvent Solution@The electrolyte is an alkali or salt of an alkaline metal or a rare earth metal, such as lithium perchlorate, lithium nitrate, lithium chloride, or lithium sulfate, and the solvent is acetonitrile or propylene carbonate. Furthermore, the aforementioned U. S. Pat. No.
3708220M. D. Meyetsetal states: polyvinyl alcohol or
Semi-solid sulfuric acid using polyacrylamide, ethylene glycol, sodium carbosyl silicate, etc. as a gelling agent, especially polyvinyl alcohol and sulfuric acid, shows good properties, and this gel can also be used to adjust the viscosity and vapor pressure. Add dimethylformamide, acetonitrile, propionitrile, butyrolactone or glycerin to the solution. Also, U. S. Ser. No. 411
53 (1970), DJ. &reGetal proposes a semi-solid electrolyte consisting of a mixture of lithium stearate grease, 2-toluenesulfonic acid, its Li or Na salt, and propylene carbonate.
Although the above-mentioned electrolytes are already known, they have the following problems.

The biggest problem among these problems is the solubility of the W03 membrane in the electrolytic solution and the deterioration of properties such as devitrification. Sulfuric acid or an organic acid as an electrolyte dissolved in about 7 hours in a dissolution resistance test at a high temperature of 80 q○, regardless of the system using any of the above-mentioned solvents.

Furthermore, the hydrogen overvoltage of protons is about 1.5 V in an aqueous solution system, and there is not much difference from this value even when an organic solvent is used, so there is a restriction that the voltage that can be applied must be 1.5 V or less. . For these reasons, electrolytes using acids are inappropriate. Although the above-mentioned problems can be solved by using an alkali metal, an alkali metal, or a rare metal salt as an electrolyte, a new problem arises regarding solubility in a solvent over a wide temperature range. Two of these electrolytes, lithium or sodium
, 3 are suitable as electrolytes. The aforementioned U. S
．． Pat. NO. Regarding the acetonitrile solution of lithium perchlorate (hereinafter referred to as LiCI04) in No. 3704057, the solvent acetonitrile has a boiling point of 79 oo, so it has a fatal drawback as a consumer display element material. In addition, the system of LiCI04 and propylene carbonate has a temperature range of -49.2 to 241.7°C, which is no problem, but this material has poor high temperature stability and has the above-mentioned 80qo
In the high temperature storage test, thermal decomposition occurs and the liquid turns yellow, and the W03 film also devitrifies. For the propylene carbonate system, the substances described in this specification other than perchlorate as an electrolyte had insufficient solubility and could not provide the electrical conductivity required for ECO'. The aforementioned U. S. Pat. NO. Even when the electrolytic solution in 3708220 is gelled with PVA etc., the results of the high temperature storage test at 80°C are the same as above, and the gelation is W0.
The dissolution resistance of the three films could not be completely improved. Furthermore, stearic acid grease systems have a problem of poor response characteristics due to their low electrical conductivity.

The above-mentioned solubility problem of the W03 membrane is solved by saturating the electrolyte with WQ in advance (U.S. Pat. No. 3819252R.D.
．． Gigia), but it is unrealistic because display elements for consumer use are considered to have to withstand temperature rises and falls over a wide temperature range.

In other words, it seems unreasonable to think that only W03, which has been dissolved in advance, repeats precipitation and dissolution when moving from a low temperature to a high temperature. As described above, in the W03 ECD manufacturing method that has already been published, the electrolytic solution and the W03 film formation method that provide a stable display element are not known.

These problems can be almost solved by the method of the present application filed on April 4, 1972, as "Electrochromic Display Device." However, even in the method of the above patent, when considering mass production in an actual manufacturing factory, the response characteristics vary, making it difficult to manufacture W03 ECD with good yield and high reliability.

The present invention solves all of these drawbacks by controlling the environmental conditions during the manufacturing process of W03/ECD. Below is W03・ECD by the inventors
The manufacturing and research progress will be described, and the advantages and examples of the present invention will be described, as well as the disadvantages of the conventional example will be pointed out. <Description of the Present Invention> First, the cell structure of the electrolyte type ECD used in the present invention will be described.

Figure 1 is a bird track diagram showing an exploded view of the EC cell;
A cross-sectional view on the earth plane and a simple basic electric circuit diagram are shown in the figure. 1 and 2, 1 and 2 are glass substrates (commercially available as thin glass), 3 is a display material layer (EC material is the aforementioned U.S. Pat. No. 35
21941 (shown here is a W03 film fabricated by a vapor deposition method that exhibits the most desirable characteristics according to the present invention, which will be described later); 4 is a display electrode lead-out portion (S
The film was fabricated using an electron beam deposition method as an ln203 film doped with n02. (Resistance is about 200/mouth)
, 5 is an electrolyte and a counter electrode masking agent (15Vo in various electrolytes)
1% to 20vol% of AI203 powder, which is commercially available as a low-grain polishing powder, such as Mellor's 0.3mu CR-, was mixed. ), 6 is the EC layer of the counter electrode (a layer that facilitates the transfer of charges at the interface, and the same material as the display material layer 3 was used), and 7 is the counter electrode extension part (transparent). Although it is not necessary, the aforementioned ln203 film was also used.)
, 8 is a sealing part and spacer (using a glass plate with a thickness of 1 and commercially available epoxy adhesive. For example, R-2401-HC-160 manufactured by Somar Industries), 9 is an insulating film (protection of the ln203 film on the extension part) ), 1 reference electrode (the same ln203 film as the extraction part 7 was used), 11 is a high input impedance linear amplifier, and 12 is a battery. , 13, 14
is a switch. 15 is an electrolyte injection port and a glass plate for sealing.

A thermostatic chamber (Nuvai Biltolabo) was used to control the environmental conditions (temperature and humidity). EC mentioned here
In the cell, the substrate 1, the electrode extension part 4, the protective film 9, and the display material layer 3 are all configured to be optically transparent.
When viewed from the left in FIG. 2, the counter electrode hiding layer 5 (white) can be seen.

Then, by turning the polarity switch 13 to the positive position and turning the switch 14 to ON', an electric field is applied to the ECD, and the display section 3 is colored blue. Conversely, when an electric field is applied to the ECD by turning the polarity selection switch 13 negative and turning the switch 14 ON, the display section 3 returns to transparency. Here E
The reason why constant potential drive was used as the CD drive method is as follows. In an electrolyte type ECD, coloring and decoloring operations are performed by a potential difference at the interface between the electrolyte and the display electrode, and the response speed largely depends on this potential difference. Therefore, in order to more accurately grasp the response characteristics due to the combination of electrolyte and EC material, we used the aforementioned driving method that can maintain the potential difference at the display electrode interface constant at an arbitrary value. As mentioned above, the present invention utilizes the aforementioned patent filed by the applicant,
This is supplemented by controlling the atmosphere to which the W03 film is exposed, thereby providing a method for producing W03/ECD with high yield and high reliability.

Therefore, the manufacturing conditions and characteristic measurement method of W03 ECD used in the present invention will be described. Table 1 Experimental conditions Environmental conditions considered to occur under general air conditioning conditions, i.e., temperature 20% and humidity 45-50%.
, 55 to 60%, and 65 to 70%, the response characteristics of W03 ECD manufactured under three environmental conditions (the cell manufacturing conditions were described above) were measured using the measurement method listed in Table 1.
The distribution is shown as a histogram in FIG. 3 for writing and in FIG. 4 for erasing.

In Figure 3, 010 indicates humidity of 45 to 50%, △-△ indicates humidity of 55 to 60%, low mouth indicates humidity of 65 to 70%, measurement conditions are 2000, and contrast ratio is 59 m.
The applied voltage for writing is 1.0 V with respect to the reference electrode ln203, and the applied voltage for erasing is -1.5 V with respect to the reference electrode ln203. In each case, the histogram has a class interval of 10 hSec, and those that exhibit characteristics for 1 second or more are classified as one class (class center 105 hSec).
They are summarized in c).

From FIG. 3 and FIG. 4, it can be seen that the histogram of the response characteristics largely depends on the parameters that are environmental conditions. It can be seen that this tendency is remarkable in erasure. For example, high temperature 6
In the distribution in the range of 5 to 70%, 31% of the erase times are 1 second or more, and some of them have a characteristic of 1 hour. If we assume that both writing and erasing are 40 hSec or less, then writing is 66% and erasing is 5.
The yield was 4%, and the yield as W03・ECD was 36
We can only expect about %. However, the histogram at low humidity of 45% shows an almost normal distribution,
It can be seen that it is hardly affected by environmental conditions, especially humidity. In this case, the arithmetic average of writing time is 25 hours.
Sec, the standard deviation is 12 hSec, and the same machine as before has 4 dishes h
If less than Sec is considered a good product, the yield is 88%, and erasing times longer than 1 second, which were observed when the humidity was 65 to 70%, were not observed at all, and the arithmetic average was 17 hSe.
c, the standard deviation is also 17 hSec, and if you use the criteria for determining good and bad mentioned above, the yield is 94%, so W03・EC
As D, a yield of 88% or more can be expected, indicating that controlling environmental conditions is effective. Further, the relative humidity was fixed at 55-60%, the temperature at that time was taken as a parameter, and the results of measurements similar to those described above are shown in Figures 5 and 6.
As shown in the figure.

In Figures 5 and 6, 0-0 indicates 2000, △-△ 2500, and low □ indicates the case of 30pm.The measurement conditions are humidity of 55-60%, contrast ratio (59Mm) of 3
:1, write voltage is 1.0 with respect to reference electrode ln203
V, the erase voltage is 1.5V with respect to the reference electrode ln203. When the temperature is 20°C, the writing time is 90%, the erasing time is 99%, and the yield as W03/ECD is expected to be 89% or more based on the above-mentioned criteria for determining good/defective products. can. On the other hand, in the case of 2500, the writing time is 8
4%, and the erasure time is 94%, so a yield of 79% or more can be expected as W03 ECD. However, 3000
In this case, it is 50% for writing and 71% for erasing, so W03
・As ECD, only a yield of about 36% can be expected. From the results shown in FIGS. 5 and 6, it can be said that controlling only the relative humidity as an environmental condition during the production of W03 ECD is insufficient. Therefore, we will consider the vapor pressure of water in the air, or absolute humidity, as a parameter. The maximum absolute humidity 14 skin Hg (relative humidity 25oo
, 60%) and the temperature was kept constant at 3000°C (relative humidity 3000°, 45%). The above experimental results are shown in the histogram of FIG. Figure 7a shows the case of writing, and Figure 7b shows the case of erasing.The horizontal axis shows the writing time (in seconds) and the erasing time (in seconds), and the vertical axis shows the frequency (in the unit of seconds). pcs). The measurement conditions were 30°C, humidity 40-45%, contrast ratio (59m) 3:1, write voltage 1.0V with respect to the reference electrode, and erase voltage -1.5V with respect to the reference electrode. . According to FIG. 7, the yield is 85% in writing time and 87% in erasing time, so W03.
A yield of 74% or more can be expected as ECD, and W03・E
It can be seen that the environmental conditions for manufacturing CDs are suitable.
Taking all of the above into consideration, if the environmental conditions during the manufacture of W03/ECD are determined to satisfy both the relative humidity of 60% and the absolute humidity of 14 willow Hg and below, the writing time and erasing time will be as shown in the table below. 40 skin Sec. under the driving conditions described in 1. In the criteria for determining good and defective products, the following are considered good products: 75
% or higher yield can be expected.

This limited environmental condition, in other words, the desirable environmental condition when manufacturing W03/ECD is shown in the shaded area in FIG. The horizontal axis in Figure 8 is temperature (°C), and the vertical axis is water vapor pressure (skin H
g), and the curve shows the line at 60% relative humidity. The environmental conditions during the manufacturing of W03/ECD as described above,
In particular, the causes of the influence of humidity on the response characteristics in ECD are not so obvious, but are thought to be as follows.

0. F. According to Schirmer et al., there is a close relationship between the crystallization of the W03 film and the electro-optical properties of the W03 film.
It has been reported that as the crystallization of the three films progresses, the response speed of the electro-optical properties slows down.

(J. Electrochem Soc. 124■, 7
49, (1977)) Furthermore, when a W03 film produced in a high temperature environment is observed with a scanning electron microscope, cracks in the order of several degrees are observed in the W03 film. Considering these things, it seems that the humidity in the air promotes the crystallization of the W03 film.
Moreover, as a result, cracks occur in the W03 film, and the electric field cannot be applied to this thin film as expected.
This is thought to cause deterioration of the electro-optic effect characteristics of the three films. However, since the above hypothesis is a simple speculation, more detailed experiments are required to understand this mechanism. <
Effects of the present invention> As described above, by introducing the atmosphere to which the W03 film is exposed, mainly humidity, as a parameter to the manufacturing conditions of W03/ECD, high yields of W03 can be achieved.
03・ECD can be manufactured, and the effect of the present invention is great.

[Brief explanation of the drawing]

Figure 1 is an exploded view of the ECD, Figure 2 is a cross-sectional view of Ero from Figure 1 and a simple electrical circuit diagram, and Figure 3 is W
03・Histogram (expressed as a percentage) of response characteristics (writing time) using atmospheric humidity during ECD manufacturing as a parameter,
Figure 4 is a histogram (shown as a percentage) of response characteristics (erasure time) with humidity as a parameter, and Figure 5 is W0.
3. Histogram of write time (expressed as a percentage) using temperature during ECD manufacturing as a parameter. Figure 6 is a histogram of erase time (expressed as a percentage) under similar conditions. Figure 7 is W03 manufactured under high temperature and low humidity.・The histogram of ECD response characteristics (shown in actual measured numbers), Figure 8 shows the relationship between temperature and water vapor pressure. 3 is an EC material layer, 4 is a transparent conductive film, 5 is an electrolytic solution, 6 is a counter electrode EC layer, 7 is a conductive film layer, and 10 is a reference electrode. Figure 3 Figure 2 Child figure Figure 5 Figure a Figure 6 Figure A

Claims (1)

[Claims] 1. In the manufacturing process of an electrochromic display device using a tungsten oxide vapor deposited film as an electrochromic material and an electrolytic solution as an ion supply source, the relative humidity of the atmosphere to which the tungsten oxide vapor deposited film is exposed is set to 60%.
% or less and absolute humidity is controlled and set to 14 mmHg or less.